Journal of Engineering and Science

Save this PDF as:
 WORD  PNG  TXT  JPG

Ebat: px
Şu sayfadan göstermeyi başlat:

Download "Journal of Engineering and Science"

Transkript

1 Volume: 6 Issue : 2 Year : 2018

2 Volume 6 / Issue 2 Journal of Engineering and Science Editor in Chief (Owned By Academic Perspective) Prof.Dr.Mehmet SARIBIYIK, Sakarya University, Turkey Editors Prof.Dr. Barış Tamer TONGUÇ, Sakarya University, Turkey Assoc. Prof. Dr. Özer UYGUN, Sakarya University, Turkey Assoc. Prof. Dr. Mustafa CAN, Sakarya University, Turkey Asst. Prof. Dr. Hakan ASLAN, Sakarya University, Turkey Members of Advisory Board Prof. Dr. Abdullah Çavuşoğlu, Council of Higher Education, Turkey Prof. Dr. Mehmet Emin AYDIN, University of West of England, England Prof. Dr. Erol ARCAKLIOĞLU, The Scientific and Technological Research Council of Turkey Prof. Dr. Fahrettin ÖZTÜRK, The Petroleum Institute, The United Arab Emirates Prof. Dr. Ahmet TÜRK, Celal Bayar University, Turkey Support Lec. Gökhan ATALI, Sakarya University, Turkey ISSN: Contact Academic Platform

3 Volume 6 / Issue 2 Journal of Engineering and Science Field Editors Dr. Ali SARIBIYIK Dr. Metin YAMAN Dr. Beytullah EREN Dr. Mustafa Zahid YILDIZ Dr. Fatih ÇALIŞKAN Dr. Sinan Serdar ÖZKAN Dr. Halil ARSLAN Dr. Süleyman KALELİ Dr. Mehmet UYSAL Dr. Taki DEMİR Dr. Zafer ALBAYRAK ISSN: Contact Academic Platform

4 Journal of Engineering and Science Contents A Novel Economic Power Flow Solution in Practical Multi-terminal AC-DC Systems using Genetic Algorithm Investigation of Rubber Bushing of Calibration Process On Durability Effect Design of a Tracking Welding Robot Automation System for Manufacturing of Steam and Heating Boilers Subcontractor Company Selection with Multiple Criteria Decision Making: An application in Kırıkkale Effects to System Performance of Different PWM Techniques in Field Oriented Speed Control with back-to-back Converter of PMSG Torsional Loading Behaviors of Slotted Filament Wound Glass Fiber Reinforced Composite Tubes Solar Simulator Design and Production for Solar Collector Test Analysis of Homogeneous Glioblastoma Samples with High-Resolution Genomic Technologies Dynamic phase transition features of the cylindrical nanowire driven by a propagating magnetic field Investigations of Effects of Density and Viscosity of Diesel and Biodiesel Fuels on NOx and other Emission Formations Investigation and thermodynamic Analysis of Geothermal Based Power and Fresh Water Production System Hysteresis properties of a mixed ferromagnetic-ferrimagnetic ternary alloy Estimation of Higher Heating Value of Biomass Using Proximate Analysis Data A Study on Assessing the Importance of Attributes for Breast Cancer Diagnosis Effect of Nanosize Al2O3 Concentration on Tribological Behavior of Ni-Co based Nanocomposite Coatings Designing an Object Tracker Self-Balancing Robot Particle Swarm Optimization Based Stacking Method with an Application to Text Classification An ABC Algorithm Inspired by Boolean Operators for Knapsack and Lot Sizing Problems Effect of Dehydration Treatment on Dissolution of Ulexite in Ammonium Sulfate Solutions Analytical Solutions for Buckling Behavior of Two Directional Functionally Graded Beams Using a Third Order Shear Deformable Beam Theory Synthesis of Novel Thio-Substituted Aminonaphthoquinones Optimization of Solid Particle Erosion by ZrN Coating Applied Fiber Reinforced Composites by Taguchi Method

5 Journal of Engineering and Science İçindekiler A Novel Economic Power Flow Solution in Practical Multi-terminal AC-DC Systems using Genetic Algorithm Titreşim Sönümleme Elemanı Olan Kauçuk Burçta Çaplama İşleminin Ömre Etkisinin Sonlu Elemanlar Analizi ve Deneysel Çalışma İle İncelenmesi Design of a Tracking Welding Robot Automation System for Manufacturing of Steam and Heating Boilers Çok Kriterli Karar Verme Yöntemleriyle Taşeron Firma Seçimi: Kırıkkale İlinde Bir Uygulama Effects to System Performance of Different PWM Techniques in Field Oriented Speed Control with back-to-back Converter of PMSG Torsional Loading Behaviors of Slotted Filament Wound Glass Fiber Reinforced Composite Tubes Güneş Kollektörü Testi için Güneş Simülatör Tasarımı ve İmalatı Homojen Glioblastoma Örneklerinin Yüksek Çözünürlüklü Genetik Teknolojiler ile Analizi Dynamic phase transition features of the cylindrical nanowire driven by a propagating magnetic field Investigations of Effects of Density and Viscosity of Diesel and Biodiesel Fuels on NOx and other Emission Formations Jeotermal Enerji Destekli Güç ve Temiz Su Üretim Sisteminin İncelenmesi ve Termodinamik Analizi Hysteresis properties of a mixed ferromagnetic-ferrimagnetic ternary alloy Kısa Analiz Verileri Kullanılarak Biyokütlenin Üst Isı Değerinin Hesaplanması Meme Kanseri Tanısı İçin Özniteliklerin Öneminin Değerlendirilmesi Üzerine Bir Çalışma Nano Al2O3 Oranının Ni-Co Matrisli Nano Kompozit Kaplamaların Tribolojik Özelliklerine Etkisi Designing an Object Tracker Self-Balancing Robot Particle Swarm Optimization Based Stacking Method with an Application to Text Classification An ABC Algorithm Inspired by Boolean Operators for Knapsack and Lot Sizing Problems Uleksitin Amonyum Sülfat Çözeltilerindeki Çözünürlüğüne Dehidrasyon İşleminin Etkisi Analytical Solutions for Buckling Behavior of Two Directional Functionally Graded Beams Using a Third Order Shear Deformable Beam Theory Synthesis of Novel Thio-Substituted Aminonaphthoquinones Optimization of Solid Particle Erosion by ZrN Coating Applied Fiber Reinforced Composites by Taguchi Method

6 Academic Platform Journal of Engineering and Science 6-2, 01-10, 2018 Academic Platform Journal of Engineering and Science journal homepage: A Novel Economic Power Flow Solution in Practical Multi-terminal AC-DC Systems using Genetic Algorithm * 1 Faruk Yalçın( X), 2 Uğur Arifoğlu( ) 1 Department of Mechatronics Engineering, Faculty of Technology, Sakarya University, Sakarya, TURKEY 2 Department of Electrical-Electronics Engineering, Faculty of Engineering, Sakarya University, Sakarya, TURKEY Received Date: Accepted Date: Abstract This paper presents a novel approach for economic power flow in multi-terminal AC-DC systems. Unlike the similar AC-DC power flow studies, real equivalent circuit for the under load tap changer transformers (ULTCs) of the DC converters are considered in the AC-DC power flow algorithm. So the study provides real accurate results for practical AC-DC applications. Economic power flow solution for minimum generation cost is provided by Genetic Algorithm (GA). The proposed approach is tested on the modified IEEE 14-bus AC-DC test system. The results show that the proposed approach is efficient to reach the global optimum point of minimum generation cost without getting stuck to local minima while satisfying system constraints. Keywords: Economic power flow, AC-DC, multi-terminal, ULTC, genetic algorithm. 1. INTRODUCTION Optimal operation of the electrical power system is very important because of the high generation costs. In power systems, most of the generators operates by fuel force. Fuel costs increase depending on the power requested by the customers. The relationship between the demanded active power and fuel costs are in proportion but not linear. On the other hand, the power systems are generally operated with many generators in a power system. Because of this situation, each generator s active power is very important to obtain total economic generation cost. Minimum generation cost is achieved by economic power flow in power systems [1]. Although the built-up costs of High Voltage Direct Current (HVDC) systems are high, they are more economic than AC transmission lines for longer distances. On the other hand, system consistency and reliability, efficient implementation, efficient conductor intersection, flexible control, no reactive power problem and continuously increasing development in semiconductor technology are the advantages of the HVDC systems [2]. Because of these reasons, researchers are studying on integrated AC-DC systems for a long time. Many methods have been proposed for AC-DC power flow studies. These methods in the literature are divided into two main part: simultaneous method and sequential method. AC and DC power flows are implemented separately and convergence is provided by getting back and forward in sequential method [3]. In simultaneous method, all equations related to AC-DC system are one within other and the equations are solved together [4]. Even though there are many researches for AC-DC power flow, there are not enough studies on optimal power flow of two or multi-terminal AC-DC systems. The existing optimal power flow studies in AC-DC systems are implemented successfully by using numerical optimization methods: quadratic programming, linear programming, mixed-integer nonlinear programming, gradient-restoration algorithm and steepest descent algorithm [5-12]. But on the other hand, there are convergence and getting stuck to local minima problems in these methods [13]. Heuristic methods like artificial bee colony algorithm [14], differential evolution [15], particle swarm optimization [16] and artificial ant colony [17] are developed for the solution of global optimization problems and they are applied to those problems successfully. These mentioned methods are more efficient with respect to accurate and faster Corresponding Author: * 1 Department of Mechatronics Engineering, Faculty of Technology, Sakarya University, Sakarya,TURKEY, Doi: /apjes

7 F YALÇIN Academic Platform Journal of Engineering and Science 6-2, 01-10, 2018 convergence and not getting stuck to local minima than conventional numerical techniques mentioned above. Genetic algorithm (GA) is one of the heuristic techniques mentioned above. It is successfully applied to economic power flow, optimal reactive power flow and optimal active-reactive power flow in AC power systems as well as in other fields [18-19]. In this study, a novel approach is presented for solution of economic power flow in multi-terminal AC-DC systems by using GA. Sequential technique is used for AC-DC power flow problem. The real equivalent circuits of the DC converters ULTCs are considered in the AC-DC power flow algorithm to be valid in practical applications. GA is used for economic power flow solution. On the other hand, the system constraints of the control and state variables are also included into the economic power flow. The proposed approach s accuracy and consistency are tested on the modified IEEE 14-bus AC-DC test system. 2. THE PROPOSED SEQUENTIAL AC-DC POWER FLOW ALGORITHM This section presents the proposed sequential AC-DC power flow algorithm used in economic power flow study. The sequential AC-DC power flow is performed by getting backwards and forwards between the proposed sequential AC and DC power flow algorithms The Illustration Of The Proposed Sequential AC Power Flow Algorithm This section presents the proposed sequential AC power flow algorithm used in this optimal AC-DC power flow study. The AC power flow algorithm is based on Newton- Raphson method and the real equivalent circuit models are considered for DC converters ULTCs as well as the other ULTCs used in AC system in this study. The ULTC s model and the equivalent circuit are given in Fig. 1 [20]. v k i k v t i m v m k t km y km m k 1:t km (a) y km = g km + jb km m i k = - i m tkm im= y km( v m - v t ) v t = v k t km t ( km t km -1) y ( km 1-t km ) y km Fig. 1. ULTC model a) representation of ULTC b) equivalent circuit of ULTC (b) k, m, t km and y km show the bus that ULTC s primary side is connected to, the bus that ULTC s secondary side is connected to, the tap value of ULTC and the admittance of ULTC s windings, respectively in Fig. 1. y = g + jb (1) km km km The series and shunt admittance values of ULTCs depending on the tap values are changed as the tap values of DC converters ULTCs are changed in each sequential DC power flow iteration to achieve DC power balance in the study as shown in Fig. 1. Thus, bus admittance matrix of the AC system must be rebuilt for each new sequential AC power flow algorithm. Only the ULTC s serial winding nb admittance y km is considered in the AC bus admittance y and shunt admittances for bus k and m are matrix bus considered as zero to avoid rebuilding of the AC bus admittance matrix for new ULTCs tap values. Depending on these conditions, p k, q k, p m and q m which are active power flowing from bus k to other buses in AC network, reactive power flowing from bus k to other buses in AC network, active power flowing from bus m to other buses in AC network and reactive power flowing from bus m to other buses in AC network respectively can be defined as follow; 2 2 ( δ δ ) ( δ δ ) ( ) (2) p = v v g cos + b sin + vvt g cos + b sin + v g t 1 g j 1, k k j buskj kj buskj kj k m km buskm km buskm km k buskk km buskm = j km nb 2 2 ( δ δ ) ( δ δ ) ( ) (3) q = v v g sin b cos + vvt g sin b cos + v b + t 1 b j 1, k k j buskj kj buskj kj k m km buskm km buskm km k buskk km buskm = j km nb 2 ( cosδ sinδ ) ( cosδ sinδ ) p = v v g + b + v vt g + b + v g (4) m m j busmj mj busmj mj m k km busmk mk busmk mk m busmm j= 1 j mk, 2

8 F YALÇIN Academic Platform Journal of Engineering and Science 6-2, 01-10, 2018 nb 2 ( sinδ cosδ ) ( sinδ cosδ ) (5) q = v v g b + v vt g b v b where m m j busmj mj busmj mj m k km busmk mk busmk mk m busmm j= 1 j mk, n b, v i, g, bus ij b and δ ij represent the total bus bus ij number of the AC system, i th bus voltage, conductance value of y bus s i th and jth component, the susceptance value of y bus s i th and j th component and the phase angle nb ( cosδ sinδ ) ij ij p = v v g + b i i j bus ij bus ij j= 1 difference between i th and j th bus voltages, respectively. The active and reactive powers flowing from the buses different than the buses k and m that are connected to ULTC to the other buses in AC system are defined as, (6) nb ( sinδ cosδ ) ij ij (7) q = v v g b i i j bus ij bus ij j= 1 The general bus representation for the AC-DC system used in this economic power flow study is given in Fig. 2. In Fig. 2, p gi, q gi, p di, q di, p li, q li, q ci, p i and q i represent the active power of the i th bus generator, the reactive power of the i th bus generator, the active power of the DC converter connected to i th bus, the reactive power of the DC converter connected to i th bus, the active power of the i th bus load, the reactive power of the i th bus load, the reactive power of shunt reactive power supply of the i th bus, the active power flowing from i th bus to other buses in AC system given by (2), (4), (6) and the reactive power flowing from i th bus to other buses in AC system given by (3), (5), (7), respectively. AC transmission lines p i q i p gi q gi i v i δ i p di q di DC transmission lines q p q ci li, li The active and reactive powers of the DC converters are considered as constant loads in the proposed sequential AC power flow algorithm for the buses where the DC converters are connected. Updated active and reactive powers of the DC converters at the end of the sequential where Fig. 2. General bus representation for the proposed AC-DC system ( ) ( ) DC power flow algorithm are transferred to the sequential AC power flow algorithm. Thus, the power equations to be provided in the Newton-Raphson based sequential AC power flow algorithm for general bus representation given in Fig. 2 are given as, g = p + p + p p = 0 i = 2, K n (8) pi i d l g b i i i g = q + q + q q = 0 i = n + 1, K n (9) qi i di li ci g b n g represents the total generator bus number in the system. The tap values of DC converters ULTCs which are power flow algorithm. So, the state and control variables changed in the sequential DC power flow algorithm are for the proposed AC power flow algorithm are given as, considered as control variables during the sequential AC xac = δ2, K, δ nb, vng+ 1, K, v nb (10) uac = pg 2, K, pgng, v1, K, vng, t1k tnt, td K t 1 d nd (11) where t, n t, t d and n td represent the tap value of the ULTC which is not connected to a DC converter, the total number of the ULTCs which are not connected to the DC converters, the tap value of the DC converter s ULTC and the total number of the DC converters ULTCs, respectively The Illustration Of The Proposed Sequential DC Power Flow Algorithm 3

9 F YALÇIN Academic Platform Journal of Engineering and Science 6-2, 01-10, 2018 This section demonstrates the proposed sequential DC power flow algorithm based on the proposed DC power model shown in Fig v di r dij j AC System v k v d δk i di m di δmd i 1:tdi i di i m d φ i m di r c i +ei i DC System Fig. 3. The proposed multi-terminal DC power model e i, and v d i, r c i, t d i, v kd i, i d i, r d ij, v md i, i md i, d kd i, d md i ϕ represent the i th DC converter s open circuit md i direct voltage, the i th DC converter s terminal direct voltage, the i th DC converter s direct current, the i th DC converter s commutation resistance, DC line resistance between the i th and the j th DC converters, the i th DC converter s ULTC tap value, the i th DC converter s ULTC The DC converters open circuit direct voltages are given as, ( ) e = v cosθ i = 1, K, n (12) i mdi i c where n c represents the total number of DC converters in the system. θ i defines α d i and γ d i where the firing angle of the i th DC converter that operates in the rectifier mode and the extinction/recovery angle of the i th DC converter that operates in the inverter mode, respectively. DC converters terminal direct voltages are given as, i i i ( 1,, ) v = e ri i= K n (13) d i c d c The commutation resistance r is positive for the DC converter that operates in the rectifier mode and negative for the DC converter that operates in the inverter mode in (13). The phase angle between the DC converter s ULTC secondary alternative voltage angle and angle of the alternative current flowing from the DC converter s ULTC secondary to DC converter is given as, i i i c i ( i 1,, n ) φ = d ϕ = K (14) md md md c and can also be obtained from, φ mdi v di = arccos = 1,, v mdi ( i n ) K (15) The active and reactive powers of the DC converters can be defined as, c primary alternative voltage, the i th DC converter s ULTC secondary alternative voltage, alternative current flowing from the DC converter s ULTC secondary to DC converter, phase angle of the i th DC converter s ULTC primary alternative voltage, phase angle of the i th DC converter s ULTC secondary alternative voltage and phase angle of alternative current flowing from the i th DC converter s ULTC secondary to DC converter, respectively. i i i ( 1,, ) ( ) p = v i i = K n (16) d d d c q = p tan φ i = 1, K, n (17) di di mdi c The multi-terminal DC system model is shown in Fig. 4. The commutation resistances are not included into the DC bus resistance matrix to avoid rebuilding of the DC bus resistance matrix in each DC algorithm iteration in this model, as the commutation resistance values change their sign in each iteration when the converters are updated from the rectifier mode to the inverter mode or vice versa. If the DC terminal direct voltages are considered as source voltages, the commutation resistances can be ignored in the DC bus resistance matrix and the DC bus resistance matrix is given as, 1 r = y (18) where d bus d bus d bus y represents the DC bus admittance matrix which includes only the admittances of the DC lines. If the 1 st DC converter s terminal direct voltage is considered as reference voltage, the DC converters open circuit direct voltages can be given as, e= v + ri (19) 1 d c d n c ( 2,..., ) (20) e= e ri + ri + r i i= n i 1 c1 d1 ci di dbusij d j c j= 2 According to the DC model shown in Fig. 4, the algebraic sum of the DC converters direct currents must be zero, 4

10 F YALÇIN Academic Platform Journal of Engineering and Science 6-2, 01-10, 2018 n c id = 0 (21) i i= 1 The active powers of all converters except at least one are selected as control variables for economic power flow in the study to achieve most suitable converter active powers and converter types that improve the total generation cost minimization. r c1 e 1 i d1 v d1 r c2 e 2 i d2 v d2 DC Transmission System r cnc e nc i dnc v dnc Fig. 4. The multi-terminal DC system model 2.3. The Illustration Of The Proposed Sequential AC- DC Power Flow Algorithm The proposed sequential AC-DC power flow algorithm is given through the sequential AC and DC power flow algorithms given in section 2.1 and 2.2 in this section. The proposed AC-DC power flow algorithm is shown in detailed in Fig Estimate the active and reactive powers for DC converters. Consider the minimum values for the tap values of the DC converters ULTCs. 2. Execute the proposed sequential AC power flow algorithm given in section Send the active and reactive powers of the DC converters used in the proposed sequential AC power flow algorithm to the proposed sequential DC power flow algorithm. 4. Execute the proposed sequential DC power flow algorithm given in section Is any tap value of the DC converters ULTCs updated to a new value in the DC power flow algorithm? Yes No 5 6 No Yes Are the differences between all of the active and reactive powers of the DC converters used in the AC power flow algorithm and calculated at the end of the DC power flow algorithm smaller than determined error tolerance? Return to the AC power flow algorithm with the updated tap values of the DC converters ULTCs and the calculated active and reactive powers of the DC converters at the end of the DC power flow algorithm The sequential AC-DC power flow algorithm is accomplished. Fig. 5. The proposed AC-DC power flow algorithm 3. THE ECONOMIC POWER FLOW PROBLEM The general optimization formula can be shown below, Minimize f x u (, ) (, ) & (, ) Subjected to g x u h x u (22) where, f( xu, ), g( xu, ), hxu (, ), x and u represent the objective function, the equality constraints, the inequality constraints, the state variables and the control variables, respectively. 5

11 F YALÇIN Academic Platform Journal of Engineering and Science 6-2, 01-10, 2018 The total generators generation cost in AC-DC system can be calculated as follows: where ng 2 f ( xu, ) = a p + b p + c (23) cost gi gi gi gi gi i= 1 a, g i b and coefficients of the generators. g i c represent the generation cost The equality constraints for the AC system, g i p p p p = 0 (24) gi li di i qgi + qsci qli qdi qi = 0 (25) where q sci represents the reactive power of the synchronous condensers. The equality constraints for the DC system, n c idi = 0 (26) i= 1 The equality constraints in (24-26) defined as (, ) g xu are solved in the proposed AC-DC power flow algorithm mentioned before. The inequality constraints for the AC system are given as, p p p (27) min max gi gi gi q q q (28) min max gi gi gi q q q (29) min max sci sci sci v v v (30) min max i i i t t t (31) min max i i i where t i represents the tap values of the tap changers between the AC buses, min and max superscripts represent the lower and upper limits of the associated variables, respectively. The inequality constraints for the DC system, p p p (32) min max di di di v v v (33) min max di di di t t t (34) min max di di di The proposed DC power flow algorithm automatically provides the inequality given in (34). The state variables of the AC-DC system are given as, x= x, x (35) [ ] AC DC where x AC and x DC represent the state variables of the AC and the DC system, respectively. [ δ2,, δ, 1,, ] [,,,,, ] x = K v K v (36) AC nb nl x = i K i v K v (37) DC d1 dnc d1 dnc where δ i and n l represent the AC bus voltage angle and the AC load bus number without synchronous condenser, respectively. The control variables of the AC-DC system, u = [ uac, udc ] (38) where u AC and u DC represent the control variables of the AC and the DC system, respectively. uac = pg 2, K, pgng, v1, K, vng, v1, K, vnsc, t1, K, t nt (39) u [,, DC = pd 2 K pdnc ] (40) where n t and n sc represent the number of the ULTCs between the AC buses and the number of the synchronous condensers in AC system, respectively. It must be noted that there is a difference between (11) and (39), the existing of t di values in (11). As mentioned in section 2.1, in fact, t di values are not part of the AC systems, but they are presented in (11) to show that they are considered in the sequential AC power flow algorithm as control values. The economic power flow in the multi-terminal AC-DC system tries to minimize the total generation cost defined in (23) while providing system constraints in (27-33) defined as (, ) h xu. So, the objective function that is optimized can be given as, ng ng lim lim 1 cost 2 gi gi 3 gi gi i= 1 i= 1 f( xu, ) = c. f + c. p p + c. q q nsc nb nt lim lim lim 4. sci sci 5. i i 6. i i i= 1 i= 1 i= 1 + c q q + c v v + c t t nc nc lim lim 7. di di 8. di di i= 1 i= 1 + c p p + c v v where c i represents the penalty coefficients of the objective function. The variables having lim superscript can be given as, (41) 6

12 F YALÇIN Academic Platform Journal of Engineering and Science 6-2, 01-10, 2018 ( ) ( xu, ),( xu, ) ( xu, ) ( xu, ) min ( ) ( ) ( ) min min ( xu, ),( xu, ) > ( xu, ) lim xu, = xu,, xu, < xu, max max max (42) 4. GA AND ITS APPLICATION FOR ECONOMIC POWER FLOW PROBLEM GA is a kind of heuristic method for searching and optimizing based on evolutionary process. GA is firstly proposed and used for solving optimization problems by Holland in 1975 [21]. GA is based on natural selection. The main stages of natural selection are separated into three parts: human is born, human grows and human dies. The parameters which produce objective function that will be optimized by GA are defined as gens in GA. For the economic power flow solution, these parameters are the control variables defined in (38). The set of the gens is defined as individual in GA. According to the natural selection, the individual represents human. All of the individuals create population. The flow chart of the economic power flow solution in multi-terminal AC-DC system by GA is given in Fig. 6. Main stages of GA can be determined as follows; initial population, fitness scaling, selection, crossover, mutation and optimization criterion [22]. Initial population of the algorithm is defined as, ( 0,1) ( ) ( 1 ) ( 1 ) w = w + rand w w i = K n j = K n (43) ij min, j max, j min, j ind p where n ind, n p, w min, j and w max, j represent the number of the individuals within the population, the number of the parameters of the individuals, the minimum and maximum values of the parameters, respectively. In the fitness scaling stage, the individuals that will be used in selection stage are defined as, fit ave = n ind i= 1 n fit ind i (44) where fit ave and fit i represent the average fitness value of the population and fitness value of the i th individual that equals to objective function defined in (41), respectively. The individuals whose fitness values are better (smaller) than the average fitness value are used in the selection stage. In the selection stage, the parents to be crossed for producing children are selected within the defined individuals. For the selection of the parents within these defined individuals, tournament method is used and can be formulated as, fiti gi = (45) nind fit j= 1 where g i is the weight of the i th individual. The weight of an individual determines the elective probability in this stage and the sum of the weights within population is 1. j n ind gi = 1 (46) i= 1 The number of the individuals for selection of the parents within the population is twice of the children number defined in the beginning of the algorithm. The parents in the same number of the children are selected within these selected individuals. In the crossover stage, the children are produced as new individuals by parents defined in selection stage. These new individuals in the same number of the children are produced through the crossing method. 0 and 1 values in the same number of individual s gen number for crossing are produced randomly. If the value is 0, then gen is taken from father, if the value is 1, then gen is taken from mother and thus the child is produced. Crossing process can be presented as follows: Cross: Mother: a b c d e Father: u w x y z Child: u b c y e In the mutation stage, new individuals are produced to be changed all or some gens of the selected individuals that undergo mutation in the population. The number of the selected individuals is defined in the beginning of the algorithm. These individuals are reproduced to be formed all the gens of the selected individuals within algorithm. So, new individuals in the same number of the selected individuals that undergo mutation are randomly produced by (43). Mutation process increases variety of the population and prevents losing the individuals that provide good solutions. 7

13 F YALÇIN Academic Platform Journal of Engineering and Science 6-2, 01-10, 2018 There are many stopping criterions for optimization that is performed by GA and similar heuristic methods in the literature. In this study, iteration number is selected for stopping the optimization by GA. The stopping iteration number is selected as 100 for the study. GA stops when it reaches the defined maximum iteration number, 100. On the other hand, in this study, system constraints defined (27-33) are included in the optimization stopping criterion so that all of the system constraints are provided at the end of GA. Generate initial population for the control variables in (38) ite = 1 GENERATE NEW POPULATION Execute the AC-DC power flow in Fig. 5 for all individuals of population selection ite = ite + 1 crossover mutation Evaluate the objective function for all individuals of population in (41) NO ite > ite max? YES NO All of the AC-DC system constraints provided for best individuals? YES Total generation cost and all of the control and state variables of the entire AC-DC system for best individuals Result Fig. 6. The proposed flow chart for economic power flow in multi-terminal AC-DC system by GA 5. RESULTS The proposed approach s accuracy and efficiency are tested on the modified IEEE 14-bus AC-DC test system shown in Fig. 7. Total generation cost throughout the proposed GA based optimization algorithm is shown graphically in Fig. 8. Total generation cost obtained with proposed GA based approach and another traditional numerical method, steepest descent algorithm (SDA), are compared in the same test system. In the literature, generally, 100 iterations are performed for heuristic methods. So, 100 iterations application is chosen for the proposed GA for the optimization. The proposed optimization algorithm is performed for 50 optimization trials with different AC-DC system initials. GA approximately has reached to global optimum at about 65th iteration for the best trial. For GA: 20 population sizes, 0.5 crossover rate and 0.1 mutation rate are used. These values used for GA are found at trials. The upper values of the used ones do not change the global optimum for GA. 8

14 F YALÇIN Academic Platform Journal of Engineering and Science 6-2, 01-10, 2018 The situation, using more sizes than the above values, decreased the number of iteration but increased optimization time in order to reach the global optimum. Penalty coefficient values c i used in (41) are found after several trials. For the 50 optimization trials, the worst and the best total generation cost values for GA are $/hour and $/hour, respectively. Error deviation for GA is 1.32%. It is observed that all control and state variables are in their limit values at the end of the optimization G 1 G 3 C SC 2 C3 C2 4 7 G 6 SC Fig. 7. The modified IEEE 14-bus AC-DC test system Fig. 8. Variation of total generation cost against iteration for the proposed approach The proposed approach is better and more reliable than SDA [23] shown in Table 1 for reaching global optimum. Table 1. Comparison of the results for the test system GA SDA [23] Total Generation Cost $/hour $/hour 6. CONCLUSION In this paper, a novel approach is proposed for economic power flow in multi-terminal AC-DC systems. GA is used for the first time in multi-terminal AC-DC system for economic power flow solution in this study. Any AC and DC power flow method can be used without any change in optimization algorithm as the sequential method in AC-DC power flow is used. Unlike the similar studies in the literature, converter active powers are used as control variables for optimization in the entire dc system in this study. Thus, both the most 9

15 F YALÇIN Academic Platform Journal of Engineering and Science 6-2, 01-10, 2018 min max suitable converter active powers ( pdi pdi pdi ) and converter types (rectifier or inverter) are achieved at determined system conditions. Thus, efficiency of the achieving economic generation cost is enhanced. The obtained results have presented that the proposed approach is better and more reliable for reaching global optimum than traditional numerical optimization methods not getting stuck to local minima. The proposed approach have also provided the system constraints for security and healthy system operation. REFERENCES [1].Y.N.V. Kumar, S. Sivanagaraju and V.C. Suresh, Security constrained economic load dispatch in the presence of interline power flow controller using modified BAT algorithm, Ain Shams Engineering Journal, vol. 7, no. 4, pp , December [2].Y.A. Mobarak, Modified load flow analysis for integrated ac/dc power systems, in Proceeding of 12th Int. Middle East Power Syst. Conf. MEPCON, Aswan, Egypt, (2008). [3].J.R. De Silva and C.P. Arnold, A simple improvement to sequential ac/dc power flow algorithms, International Journal of Electrical Power & Energy Systems, vol. 12, no. 3, pp , July [4].U. Arifoglu, Load flow based on newton's method using norton equivalent circuit for ac-dc multiterminal systems, European Transactions on Electrical Power, vol. 9, no. 3, pp , May-June [5].D. Thukaram and G. Yesuratnam, Optimal reactive power dispatch in a large power system with ac-dc and FACTs controllers, IET Generation Transmission & Distribution, vol. 2, no. 1, pp , January [6].D. Thukaram, G. Yesuratnam, and C. Vyjayanthi, Optimal reactive power dispatch based on voltage stability criteria in a large power system with ac/dc and FACTs devices, in Proceeding of IEEE Int. Conf. Power Electro. Drives Energy Syst. PEDES, New Delhi, India, (2006). [7].J. Yu, W. Yan, W. Li and L. Wen, Quadratic models of ac-dc power flow and optimal reactive power flow with HVDC and UPFC controls, Electric Power Systems Research, vol. 78, no. 3, pp , March [8].J. Yu, W. Yan, W. Li, C.Y. Chung and K.P. Wong, An unfixed piecewise-optimal reactive power-flow model and its algorithm for ac-dc systems, IEEE Transactions on Power Systems, vol. 23, no. 1, pp , February [9].U. De Martinis, F. Gagliardi, A. Losi, V. Mangoni and F. Rossi, Optimal load flow for electrical power systems with multiterminal HVDC links, IEE Proceedings Generation Transmission and Distribution, vol. 137, no. 2, pp , March [10].C.N. Lu, S.S. Chen and C.M. Ong, The incorporation of HVDC equations in optimal power flow methods using sequential quadratic programming techniques, IEEE Transactions on Power Systems, vol. 3, no. 3, pp , August [11].H. Ambriz-Perez, E. Acha and C.R. Fuerte-Esquivel, High voltage direct current modelling in optimal power flows, International Journal of Electrical Power & Energy Systems, vol. 30, no. 3, pp , March [12].U. Arifoglu and N. Tarkan, New sequential ac-dc load-flow approach utilizing optimization techniques, European Transactions on Electrical Power, vol. 9, no. 2, pp , March-April [13].K. Ayan and U. Kilic, Artificial bee colony algorithm solution for optimal reactive power flow, Applied Soft Computing, vol. 12, no. 5, pp , May [14].J. Huo, L. Liu and Y. Zhang, An improved multicores parallel artificial Bee colony optimization algorithm for parameters calibration of hydrological model, Future Generation Computer Systems-The International Journal of escience, vol. 81, pp , April [15].L. Wang and L. Li, A coevolutionary differential evolution with harmony search for reliability-redundancy optimization, Expert Systems with Applications, vol. 39, no. 5, pp , April [16].M. Gomez-Gonzalez, A. Lopez and F. Jurado, Optimization of distributed generation systems using a new discrete PSO and OPF, Electric Power Systems Research, vol. 84, no. 1, pp , March [17].O.P. Verma, P. Kumar, M. Hanmandlu and S. Chhabra, High dynamic range optimal fuzzy color image enhancement using artificial ant colony system, Applied Soft Computing, vol. 12, no. 1, pp , January [18].U. Guvenc, B.E. Altun and S. Duman, Optimal power flow using genetic algorithm based on similarity, Energy Education Science and Technology Part A: Energy Science and Research, vol. 29, no. 1, pp. 1-10, April [19].M.S. Kumari and S. Maheswarapu, Enhanced genetic algorithm based computation technique for multiobjective optimal power flow solution, International Journal of Electrical Power & Energy Systems, vol. 32, no. 6, pp , July [20].F. Yalcin and U. Arifoglu, Inserting the tap values of the tap changer transformers into the Jacobian matrix as control variables, Sakarya University Journal of Science, vol. 17, no. 3, pp , December [21].J.H. Holland, Adaptation in Natural and Artificial Systems, Michigan: University of Michigan Press, [22].MATLAB Optimization Toolbox 5 User s Guide (2012) The Math Works, Inc. [23].Ugur Arifoglu, Optimal power flow using sequential power flow approach for an ac-dc power system, Ph. D. thesis, Istanbul Technical University, Istanbul,

16 Academic Platform Journal of Engineering and Science 6-2, 11-18, 2018 Academic Platform Journal of Engineering and Science journal homepage: Titreşim Sönümleme Elemanı Olan Kauçuk Burçta Çaplama İşleminin Ömre Etkisinin Sonlu Elemanlar Analizi ve Deneysel Çalışma İle İncelenmesi * 1 İbrahim Cem ÖNCÜ( ), 2 Aylin DOVA( ) 1 Uludağ Üniversitesi Fen Bilimleri Enstitüsü, Makine Mühendisliği Bölümü, Bursa 1 2 Uludağ Üniversitesi Fen Bilimleri Enstitüsü, Otomotiv Mühendisliği Bölümü, Bursa 2 Geliş Tarihi: Kabul Tarihi: Öz Bu çalışmada süspansiyon sistemi titreşim sönümleme elemanı olan kauçuk metal malzeme çiftinden üretilen bir burçta çaplama işleminin ömre etkisi incelenmiştir. Çaplama işlemi ve statik katılık değişimlerinin tespitinde sonlu elemanlar analizi kullanılmıştır. Doğrusal olmayan analiz modelinin hazırlanmasında ve sonuçların değerlendirilmesinde Msc.Patran 2014 yazılımı, analizin çözümleyicisi olarak ise Msc.Marc 2014 yazılımı kullanılmıştır. Doğrusal olmayan analizde kullanılan malzeme modelinin ve uygulanan metodun doğruluğunu değerlendirmek için üretilen prototipler, analiz koşullarında öncelikle radyal yönde test edilerek sonuçlar karşılaştırılmıştır. Son aşamada ise çaplamanın parça ömrü üzerine etkisinin incelenmesi amacıyla üretilen prototipler ömür testine tabi tutulmuşlardır. Ömür testi sonucunda çaplamasız parçaya göre %1,4 çaplama yapıldığında ömür performansında %35 lik bir iyileşme, % 2,5 değerinde bir çaplama uygulandığında ise ömür performansında %48 lik bir iyileşme sağlanmıştır. Anahtar Kelimeler: Kauçuk Burç, Ömür Analizi, Çaplama, Ömür, Sonlu Elemanlar Analizi Investigation of Rubber Bushing of Calibration Process On Durability Effect * 1 İbrahim Cem ÖNCÜ, 2 Aylin DOVA 1 Uludag University Institute of Science, Department of Mechanical Engineering, Bursa 1 2 Uludag University Institute of Science, Department of Automotive Engineering, Bursa 2 Abstract In this study, the durability effect of a bushing process produced from a pair of rubber metal materials with a railway suspension system vibration damping element is examined.finite element analysis is performed to determine the change of the static stiffness and calibration prosess. The MSC.Patran 2014 sofware is used in the preparation of the nonlinear analysis model and evaluation of the results, MSC.MARC 2014 software is used as an solver. The prototypes which are evaluate the accuracy of the material model used in the nonlinear analysis and the applied method first tested in radial direction analysis conditions and the results are compared. At the last stage, prototypes which are produced for examination the effect of calibration on the part are used for durability test.as a result of this study, the effect of the applied calibration value on the durability is determined. As a result of durability test, first part which has %1,4 calibration ratio, durability performance was improvement by %35, second part which has %2,5 calibration ratio, durability performance was improvement by %48 according to uncalibrated part. Keywords: Rubber Bushing, Durability Analysis, Calibration, Durability, Finite Element Analysis Sorumlu Yazar: Uludağ Üniversitesi Fen Bilimleri Enstitüsü, Makine Mühendisliği Bölümü, Bursa Doi: /apjes

17 İ C ÖNCÜ Academic Platform Journal of Engineering and Science 6-2, 10-18, GİRİŞ Kauçuk-metal burçlar her aracın süspansiyon sisteminde bulunan, titreşim sönümleme elamanı olarak kullanılan hiperelastik malzemelerdir. Yoldan ve aracın hareketli parçalarından gelen titreşim, şok ve darbe gibi etkileri sönümleyerek araç gövdesine iletilmesini engelleyen, sürüş konfor gereksinimini sağlayan en önemli parçalardan biridir. Bir araç üzerinde (otomobil) yaklaşık 50 adet kauçuk burç bulunmaktadır. Kauçuk burçlar otomobillerde olduğu gibi ticari araçlarda, ağır vasıta araçlarda, römorklarda, trenlerde, traktörlerde süspansiyon sistemine sahip bir çok araçta kullanılmaktadır. Süspansiyon elemanlarının birbirlerine ve ana gövdeye bağlantılarında kauçuk burçlar kullanılmaktadır. Burçlar, süspansiyon sistemlerinin dinamik davranışlarının belirlenmesi ve tasarlanması safhasında da anahtar rol üstlenmektedir. Şekil 1 de çeşitli metal kauçuk burç parçaları gösterilmektedir. Şekil 1. Çeşitli kauçuk - metal burçlar Şekil 1 de gösterildiği gibi kauçuk metal burçlar genel itibari ile bir metal iç burç, bir metal dış burç ve bu burçların arasını dolduran kauçuk malzemesinden oluşmaktadır. Kauçuk parçalar vulkanizasyon yöntemi dediğimiz bir yöntem ile, kauçuk preslerinde özel kalıplar içinde üretilmektedir. Şekil 2 de iç burç, dış burç ve onun arasını dolduran kauçuktan oluşan bir kauçuk burç gösterilmektedir. Şekil 2. İç burç, dış burç ve bu burçların arasını dolduran kauçuk malzemesinden oluşan parça Kauçuk malzemelerle ilgili ilgili yapılan literatür araştırmasında sıcaklığın, kauçuk içerisine ilave edilen maddelerin ve çaplama işlemlerinin yapılan parça testlerine etkilerinin incelendiği görülmüştür. Vahapoğlu, V. (2013). Kauçuk mekaniğinde yapılan deneyler konulu çalışmasında kauçuk malzemeler için yapılan tüm deneyleri sınıflandırarak detaylı bir biçimde incelmiştir. Bu çalışmada testler yükleme ve numune şekillerine göre detaylı bir şekilde gruplandırılarak incelenmiştir. Yapılan testlerin geçmişten günümüze ulaşana kadar uğradığı değişikliklere de yer verilmiştir. Çalışmamızda bu testlerden en çok bilinen ve uygulananlarına yer verilmiştir. [1] Erkek, S. (2007). Karbon siyahı / yağ ve karbon siyahı / dolgu maddesi oranının farklı vulkanizasyon sistemlerinde EPDM, NBR ve SBR elastomerlerinin fiziko-mekaniksel özellikleri üzerine etkisi incelenmiştir. Yüksek lisans tezi, Çukurova Üni., Fen Bilimleri Enstitüsü, Kimya Anabilim dalı, Adana [2]. Özgün, R.E. (2010). Kauçuk - metal burçlarda kauçuk sertliği ve çaplama işlemlerinin kopma mukavemetine etkisini araştırmıştır. Yüksek lisans tezi, Uludağ Üni., Fen Bilimleri Enstitüsü, Makine Mühendisliği Anabilim Dalı, Bursa [3]. Soyel, D. (2008). Sonlu elemanlar metodu ile NR / SBR tipi elastomer esaslı malzemelerin davranış modellerinin belirlenmesi konulu çalışmasında malzemenin matematiksel modellenmesi üzerinde durmuştur. Çalışma kapsamında iki tip kauçuk malzeme için mekanik testler gerçekleştirilmiştir. Abaqus sonlu elemanlar yazılımı kullanılarak test verileri ile yazılım içerisinde yer alan malzeme modelleri için hiperelastik malzeme katsayıları hesaplanmıştır. Her bir hiperelastik malzeme modeli için eğriler elde edilmiştir. Bu eğriler test verisini temsil eden eğri ile kıyaslanarak en uygun hiperelastik malzeme modeli belirlenmeye çalışılmıştır [4]. Vahapoğlu (2010) Literatürde, kauçuk türü malzemelerin elastik davranışını modelleyebilmek için bir çok farklı formda şekil değiştirme enerji fonksiyonları önerilmiştir. Teorik olarak önerilen bu şekil değiştirme enerji fonksiyonlarının doğruluğu ise çekme, basma ve kayma deneyleri ile kontrol edilmektedir. Hazırlanan bu çalışmada kauçuk mekaniğinde yapılan deneyler tanımlanmış ve sınıflandırılmıştır. Ayrıca, çalışmada literatürde kauçuk türü malzemeler için yapılan deneysel çalışmalar incelenmiştir [5] Çekme basma ve kesme etkisi altında çalışabilen kauçuk burçların deforme olmaları da bu yükleme türlerine göre değişiklik göstermektedir. Çekme etkisi altında çalışan kauçuk burçlar incelendiğinde uygulanan çeki kuvveti zamanla kauçuk yapısındaki bağların kopmasına sebep olmaktadır. Vulkanizasyon işlemi sırasında metal parçalara iki kat boya sürülür. Bu sürülen boyalardaki kimyasal kauçuktaki kükürt halkaları ile etkileşime girerek kauçuğun metal parçalara yapışmasını sağlamaktadır. Çekme yüklemesi altında çalışan parçalarda bu yapışma zorlanmakta ve yapışma bölgelerinden kopmalar gözlemlenmektedir. Basma yükü altında çalışan parçalarda yapışma zorlanmamaktadır. Bu yüzden parça ömrü çeki yüklemesinde çalışan parçalara göre çok daha yüksek olmaktadır. Parça tasarımında pratik olarak kauçuk 12

18 İ C ÖNCÜ Academic Platform Journal of Engineering and Science 6-2, 10-18, 2018 parçalar için kesme yüklemeleri altında en fazla % birim şekil değişikliği, bası ve çeki yükleri altında en fazla %30 birim şekil değişikliği öngörülebilir [6]. Kauçuk burç üretimi göz önüne alındığında, kalıptan çıkan vulkanize parça soğumaya bırakılır ve bu soğuma esnasında da iç ve dış burca yakın olan bölgelerdeki kauçuk daha geç soğur ve kenarlara doğru çekilir. Bu da kauçuk içerisinde iç gerilmelerin oluşmasına sebeb olmaktadır. Yapılacak olan çalışmada kauçuk burç sürekli olarak bası yüklemesine maruz bırakılacaktır. Bunun için üretilecek olan kauçuk burçlar montaj olacağı yuvadan belirli bir miktarda büyük üretilecek, daha sonra çaplama işlemi dediğimiz dış burç plastik şekil değişimine uğratılarak, dış çap değeri küçültülerek çalışacağı yuvaya montaj edilecektir. Çalışmanın amacı, literatürde çalışması yapılan çaplamanın kopma mukavemetine etkisinin incelenmesi yerine, çaplamanın ömür dayanımındaki etkisi incelenmiştir. Ayrıca müşteri gereksinimlerindeki ömür beklentisini sağlayacak minimum çaplama değerlerinin bulunmasından oluşmaktadır. Şekil 3 de tasarlanan ve üretilen kauçuk burç gösterilmiştir. a. b. Şekil 3 a. Tasarlanan kauçuk burç b. Üretilen kauçuk burç Kauçuk burçlarda çaplama işlemini dıştan merkeze doğru yarı çap boyunca dış metale plastik şekil vererek uygulanmaktadır. Bu çaplama işlemi simetrik olarak kapanan çeneler ile yapılabileceği gibi, konik bir kalıp içerisinden de geçirilerek yapılabilmektedir. Şekil 4 te çaplama işlemini temsil eden görsel bulunmaktadır. dış burç, iç burç ve aralarındaki kauçuk malzemeden meydana gelmektedir. Şekil 5. Çaplama işleminin gerçekleştirileceği parçanın kesit görünümü ve burç boyutları Kauçuk burcu oluşturan parçaların üretiminde kullanılan malzeme bilgileri Tablo 1 de verilmiştir. Kauçuk parça N506-B malzemesinden, iç ve dış burç ise St 37-2 çelik malzemeden üretilmiştir. Tablo 1. Kauçuk Burçta Kullanılan Malzemeler Parça Adı Malzeme Açıklama Kauçuk N506-B NR 70±5 ShA İç Burç DIN 2393 St ** 37-2 NBK Dış Burç DIN 2393 St ** 37-2 NBK Burç yapımında kullanılan metalik malzemeler boru seklinde olup dışta ve içte olmak üzere iki adettir. St37 den üretilen dikişli dış boru her hangi bir ısıl işleme tabi tutulmamıştır. Dış çapı 72,8 mm, et kalınlığı 2,9 mm olan dış boru malzemesinin ve dış çapı 55 mm, et kalınlığı 5,175 mm olan iç ve dış boru malzemesinin mekanik özellikleri Tablo 2 de verilmiştir. Tablo 2. İç ve dış borunun mekanik özellikleri Akma Çekme Uzama (%) Mukavemeti (Mpa) Mukavemeti (Mpa) Şekil 4. Çaplama işlemi görseli 2. MALZEME VE YÖNTEM Kauçuk çaplama işleminin burç ömrüne etkisinin araştırıldığı bu çalışmada kullanılan kauçuk-metal burç boyutları, Şekil 5 de görülmektedir. Görüldüğü gibi burç; Tasarımı ve üretimi yapılan burcun Msc.Patran 2014 programında sonlu elemanlar modeli oluşturulmuştur. Analiz sırasında deformasyonun fazla olmasının beklenildiği bölgelerde mesh yapısının sıklığı arttırılarak hassas sonuçlar elde edilmesi amaçlanılmıştır. Mesh yapısı oluşturulduktan sonra, sınır şartlar ve yüklemeler parça üzerine tanımlanmıştır. Şekil 6 da parçanın mesh yapısı görülmektedir. Bu yapıda iç burç olarak tanımlan metal yapıda hex 8 eleman, dış burçta hex 8 eleman, hex 8 eleman kullanılmıştır. Hex 8 eleman, doğrusal altıyüzlü olarak tanımlanan C3D8RH tipi eleman 13

19 İ C ÖNCÜ Academic Platform Journal of Engineering and Science 6-2, 10-18, 2018 demektir. Şekil 6 da hex 8 elemana ait görsel görülmektedir. Şekil 6. Hex 8 eleman tipi Farklı renkler ile gösterilen iç burç, dış burç ve kauçuğun, analiz programının ara yüzünde sonlu elemanlar modeli oluşturulmuştur. Bu model oluşturulurken deformasyonun ve şekil değişiminin daha yüksek olacağı bölgelere daha sık mesh atılarak analiz kolaylaştırılmış ve oluşacak deformasyonun daha belirgin görülmesi amaçlanmıştır. Eleman boyutu seçimi için farklı boyutlarda elemanlar kullanılmış ve eleman boyutu 1.5 mm den küçük değerlerde sonuçların fazla değişmediği görülerek bu boyut için elemanlar oluşturulmuştur. Şekil 7 de kauçuk burç mesh yapısı ve eksen takımı görülmektedir. kısaltmıştır. Bulunan sonuçlar çeyrek modele ait olacağı için, sonuçların kuvvet biriminin 4 katının alınması gerekmektedir. Çeyrek modelde kesilen yüzeylerden (yz ve yx), düğüm noktalarının hareketleri sınırlandırılmıştır. Ayrıca parçanın montaj yerini simüle edebilmek için dış burcun dış yüzeyinde bulunan düğüm noktaları x,y,z ekseninde hareketleri sınırlandırılmıştır. Radyal hareketi sağlamak üzere ise iç burcun merkezinde yeni bir düğüm elemanı oluşturularak, iç burcun iç yüzeyinde bulunan tüm düğüm noktalarını merkezdeki düğüm elemanı bağlanarak MPC olarak tanımlanan birleştirilmiş düğüm yapısı oluşturulmuştur. Radyal hareket bu düğüm elemanı kullanılarak gerçekleştirilmiştir. Ayrıca dış burç, kauçuk ve iç burç arasında glue (yapışık) kontak tanımlaması yapılmıştır. Bu tanımlama kauçuk burcun üretim yönteminden gelmektedir. Kauçuk burçlar üretilirken iç burca ve dış burca özel bir yapıştırıcı sürülür ve vulkanizasyon esnasında kauçuk bu yapıştırıcı sayesinde iç ve dış burca tutunur. Şekil 9 de kauçuk sınır şartlarının tanımlanmış hali ve MPC oluşturulmuş yapı görülmektedir. Şekil 7. Kauçuk burç mesh yapısı ve eksen takımı Sonlu elemanlar analiz modeli oluşturulurken parçanın simetrik olmasından yararlanılarak radyal hareket ölçümü için çeyrek (1/4) parça modellenmiştir. Şekil 8 de parçanın ¼ modeli görülmektedir. Dış Burç Kauçuk İç Burç Şekil 8. ¼ Kauçuk burç mesh yapısı ¼ kauçuk burç modeli oluşturulurken parça yz ve yx düzlemlerince kesilerek çeyrek model elde edilmiştir. ¼ modelin kullanımı model oluşturma ve çözümleme süresini Şekil 9. Kauçuk burç analizinde sınır şartların tanımlanmış hali 2.1 Malzeme Modeli Oluşturma MPC SEA (Sonlu Elemanlar Analizi) için malzeme verisinin tanımlanması gerekmektedir. Malzeme verisi özel oluşturulan numuneler test edilerek belirlenmiştir. Yapılan testlerde çekme, basma ve kesme malzeme verisi toplamak için numuneler oluşturulmuştur. Bu testlerden elde edilen kuvvet deplasman verileri, daha sonra numenin boyutları dikkate alınarak gerilim gerinim verilerine dönüştürülmüş ve analiz programına yüklenilmiştir. Analiz programında hiperelastik malzeme tanımı için Mooney Rivlin 2 malzeme modeli kullanılmıştır. Bilgisayar programı girmiş olduğumuz gerilim gerinim değerlerini baz alarak malzeme modeli tanımında kullanılacak olan C10 ve C01 katsayılarını otomatik olarak hesaplamaktadır. Şekil 10 da test numuneleri ve boyutları görülmektedir. 14

20 İ C ÖNCÜ Academic Platform Journal of Engineering and Science 6-2, 10-18, I 1 = λ 1 + λ 2 + λ 3 2 I 2 = λ 1 λ λ λ 3 + λ λ 1 2 I 3 = λ 1 λ λ 3 (2a) (2b) (2c) a. b. İzotropik ve mükemmel sıkıştırılamaz bir malzeme için I 3 =1 dir. Gerinme enerjisi potansiyeli (W), uzama oranları ve gerinme invaryantlarının fonksiyonudur. Literatürde birçok hiperelastik malzeme modeli tanımlanmıştır. Bunlardan bazıları; Mooney-Rivlin, Polynomial Form, Neo-Hookean, Ogden, Arruda-Boyce, Gent, Yeoh ve Marlow modelleridir [7]. Elastomer modellerinde kauçuk için genel olarak Mooney-Rivlin hiperelastik malzeme modeli kullanılmasına rağmen doğrusal elastik malzeme modelleri de yakın sonuçlar vermektedir. Mooney-Rivlin malzeme modeli denklem (3) de belirtilmiştir [7]. n W(I 1, I 2 )= ij=0 C ij (I 1 3) i (I 2 3) i (3) Bu denklemde C ij katsayıları belirtmektedir. Mooney- Rivlin modeli %100 gerinmelere kadar çekme testleri için uygun olsa da, bası şeklindeki deformasyonlarda gerinmede olduğu kadar başarılı sonuçlar vermemektedir. 3. BULGULAR 3.1 Radyal Statik Analizler c. Şekil 10. a. Çekme Test Numunesi ve ölçüleri (mm) b. Basma Test Numunesi ve ölçüleri (mm) c. Kesme Test Numunesi ve ölçüleri (mm) Malzeme modelinin bulunmasının diğer bir yolu da matematiksel formüller kullanılmasıdır. Bu denklemlerin oluşturulması hiperelastik malzemelerde şu şekilde olur; Tek eksenli çekme testinde uzamadan sonraki uzunluğun, ilk uzunluğa oranı denklem (1) de gösterildiği gibi uzama oranı (λ) olarak tanımlanır; λ = L/L 0 =ε+1 (1) Hiperelastik bir malzemenin bünye denklemi için gerinme enerjisi potansiyeli kullanılır. Bu tanım için invaryant ve uzama oranı değerleri tanımlanır. İnvaryantlar, koordinat sisteminden bağımsız gerinmeleri ölçmek için kullanılır. Gerinme enerjisi potansiyelinin tanımlanması için üç yönde uzama ( λ 1, λ 2, λ 3 ) oranı tanımlanır. Bu sembollerde λ 1 ve λ 2 düzlemdeki uzamaları temsil ederken, λ 3 ise düzlem dışı uzamayı temsil etmektedir. Üç yöndeki gerinme invaryantları denklem (2a), (2b) ve (2c) deki gibi yazılır [7]. Oluşturulan mesh modeline çaplamalı ve çaplamasız parçaların katılık (stiffness) değerlerinin belirlenebilmesi için, tanımlanan hareket yönünde (radyal yönde) 1 mm yer değiştirme uygulanarak parça üzerinde oluşan kuvvet değerleri kaydedilmiştir. Aynı zamanda parçada meydana gelen strain değerleri kontrol edilerek bu değerlerin uygunluğu teyit edilmiştir. Şekil 11 de çaplamalı ve çaplamasız parçalar için yapılan radyal analiz görselleri verilmiştir. Çaplamalı parçalarda, çaplamasız parçaya göre sıkışmanın daha fazla olduğu Şekil 11 de verilen radyal analiz görsellerinde belirgin olarak farkedilmektedir. Yapılan analizlerde çaplamasız parça (72,8 mm dış burç çapına sahip olan parça), 1 mm çaplamalı parça ve 1,75 mm çaplamalı parça kullanılmıştır. Radyal analiz sonucunda elde edilen kuvvet ve deplasman verileri kullanılarak Şekil 12 de gösterilen SEA radyal katılık grafiği oluşturulmuştur. Şekil 12 da yer alan grafikten de görüleceği üzere çaplama değeri arttıkça parça üzerinden 1 mm deplasmanda toplanan kuvvet değerinin artış gösterdiği görülmektedir. Çaplamanın radyal katılık değerlerini arttırıcı bir etkisi olduğu anlaşılmaktadır. Yapılan SEA analizleri sonucunda çaplamanın radyal katılık değerlerini arttırdığı gözlemlenmiştir ve elde edilen veriler Tablo 3 de görülmektedir. Çaplamasız parçayla karşılaştırıldığında çaplama oranının %1,4 arttırılması parçada yaklaşık 1,5 kat, çaplama oranını %2,5 15

21 İ C ÖNCÜ Academic Platform Journal of Engineering and Science 6-2, 10-18, 2018 arttırılmasında ise yaklaşık 2 kat katılık değerlerinde artışa sebep olmaktadır. a. b. c. a. 72,8 mm (Çaplanmamış parça) b. 1 mm çaplama c. 1 mm çaplamalı parçanın radyal analizi Hareket Yönü 3.2 Radyal Katılık Testleri Radyal katılık testleri Zwick test makinasında Tablo 4 de belirtilen, test hızı, yorulma hızı, yorulma sayısı ve test yükleme noktası gibi test verileri kullanılarak gerçekleştirilmiştir. Bu değerler incelemesini gerçekleştirdiğimiz parçamız için müşteri gereksinimleridir. Burada test hızı statik olarak kabul edilebilecek bir değer belirlenmiştir. Kauçuk gibi elastomer parçalarda test yapılırken mullin etkisinden parçayı arındırmak için 2 kere ön yükleme yapılmış ve 3. yüklemede test verileri kaydedilmiştir. Test yükleme değeri olarak parçanın çalışma ortamında maruz kaldığı yük seçilmiştir. Tablo 3. Test Parametreleri Test hızı 5 mm/min Yorulma hızı 5 mm/min Yorulma sayısı 2 Test yükleme noktası 20 kn d. e. Hareket Yönü Şekil 13 te gerçekleştirilen radyal testler ile ilgili Zwick test düzeneği görülmektedir. Zwick test makinasında montaj yerini simüle eden aparatlar tasarlanmış ve Tablo 4 te verilen test parametreleri kullanılarak kauçuk parçaya ait radyal test gerçekleştirilmiştir. d. 1,75 mm çaplama e. 1,75 mm çaplamalı parçanın radyal analizi Şekil 11. Radyal sonlu elemanlar analizleri Şekil 12. SEA radyal katılık değerleri grafiği Tablo 3. SEA Radyal Katılık Değerleri SEA Radyal Çaplama Katılık Değeri Oranı [N/mm] [%] 72,8 mm çaplamasız ,8 mm (1mm ,40 çaplamalı) 71,05 mm (1,75 mm çaplamalı) ,50 Şekil 11. Radyal katılık testleri Yapılan radyal statik testler sonucunda Tablo 5 te gösterilen değerler bulunmuştur. Radyal statik test sonucunda elde edilen bu değerler, SEA radyal analizleri ile karşılaştırıldığında ortalama %4 lük bir sapma tespit edilmiştir. Bu elde edilen değer elastomer grubu gibi doğrusal olmayan özellik gösteren parçaların analiz-test karşılaştırması için oldukça iyi bir sonuçtur. 16

22 İ C ÖNCÜ Academic Platform Journal of Engineering and Science 6-2, 10-18, 2018 Tablo 5. SEA ve Radyal Katılık Testi Değerlerinin Karşılaştırılması SEA Radyal Katılık Değerleri Test Radyal Katılık Değerleri Sapma Oranı [%] [N/mm] [N/mm] 72,8 mm ,3 çaplamasız 71,8 mm ,2 (1mm çaplamalı) 71,05 mm ,4 (1,75mm çaplamalı) Şekil 14 te radyal test sonucunda elde edilen verilere göre hazırlanmış kuvvet deplasman grafiği görülmektedir. Parçaların testleri Tablo 4 de tanımlanan test parametrelerine göre gerçekleştirilmiştir. 20kN yük altında parçaların deplasman değerleri tespit edilmiştir. Şekil 15. Ömür testleri MTS test sisteminde gerçekleştirilmiştir. Tablo 6. Ömür Testi Parametreleri Yük (Radyal) LW ile 20 kn arasında x- yönünde (Gerilme) İşletme Sürekli kullanım: sıcaklığı (-25 C)+(+70 C) Nadir sıcaklık: (-40 C)+(+80 C) Tablo 7 de her çevrim sonucunda elde edilen katılık değerlerini ve bunların başlangıç durumuna göre değişim değerleri verilmiştir. Çaplamasız parçada çevrim sonucunda %23 lük bir katılık değişimi gözlemlenirken, 1 mm çaplamalı parçada %15, 1,75 mm çaplamalı parçada ise %12 katılık değişimi görülmektedir. Şekil 14. Test radyal katılık değerleri 3.3 Ömür Testleri Çaplama işleminin kauçuk burç parça ömrüne etkisinin incelendiği bu çalışmada ömür testleri Şekil 15 te gösterilen MTS test sistemi kullanılarak yapılmıştır. Yapılan çalışmada 50 kn kapasiteye sahip aktüatörler kullanılmıştır. Tablo 6 da ömür testi için kullanılacak test parametreleri görülmektedir. Bu parametreler parça üzerine araç dinamiğinden gelen yüklemeler kullanılarak bulunmuştur. Kauçuk burç parçası ±20 kn luk dinamik bir yükleme altında çalışmaktadır çevrim ise parçanın bu yükleme altında deforme olmadan çalışması gereken süreci belirtmektedir. Her çevrimde dinamik test durdurulmuş, radyal statik teste tabi tutulmuş ve parçanın test sonucunda elde edilen katılık değerleri kaydedilmiştir. Şekil 16 da çaplamasız, 1 mm çaplamalı ve 1,75 mm çaplamalı parçaya ait çevrim boyunca oluşan katılık değişimleri görülmektedir. Grafikten de görüleceği üzere çaplamasız parça başlangıç durumuna göre % 20 nin üzerinde katılık değişimi göstermektedir. Bu değişim oranı çaplamalı parçalara baktığımızda 1 mm çaplamalı parçada %15, 1,75 mm çaplamalı parçada ise %12 dolaylarındadır. Şekil 16. Parça ömründeki katılık değişimin grafiksel gösterimi 17

23 İ C ÖNCÜ Academic Platform Journal of Engineering and Science 6-2, 10-18, 2018 Çevrim Sayısı Tablo 7. Çevrim Sayısına Karşılık Gelen Katılık Değerleri Değişimi Ø72,8mm Ø72,8mm İçin Ø71,8mm Ø71,8mm İçin Radyal Katılık Başlangıca İçin Radyal Başlangıca Değeri Göre Değişim Katılık Göre Değişim Değeri 17 Ø71,05 İçin Radyal Katılık Değeri Ø71,05mm Başlangıca Değişim İçin Göre (N/mm) (N/mm) (N/mm) (%) (N/mm) , , , , , , , , , , , , , , ,24 12 (%) 4. DEĞERLENDİRME VE SONUÇLAR Yapılan çalışmada SEA statik katılık analizleri ile statik katılık testleri karşılaştırılmıştır. Ortalama %4 lük bir sapma ile SEA analizlerinin doğruluğu sağlanmıştır. Kauçuk gibi elastomerlerin analizlerinde %4 lük bir yakınsana iyi olarak kabul edilmektedir. Kauçuk malzemesinin içeriğinin metalden farklı olması ve birçok değişkenden etkilenmesinden dolayı doğrusal olmayan analizlerde test sonuçları ile analiz sonuçları arasındaki kolerasyonda belirli oranda sapma görülmektedir çevrim sonucunda maksimum %20 katılık değişimi isteği çaplamasız parçada sağlanamazken, çaplama işlemi uygulandıktan sonra sağlanmaya başlanmıştır. Çaplama değeri arttırıldıkça katılık değişimin azaldığı görülmüştür. %2,5 luk çaplama değerindeki katılık değişimi %12 iken, bu değer %1,4 lük çaplama değerinde %15 değerine ulaşmıştır. Parçanın çaplama değerinin arttırılması ile katılık değişimin düştüğü görülmüştür fakat çaplama değeri daha arttırıldığında kauçuk burç için %30 luk gerinim değişimini geçen bir ön gerilme uygulanmış olacaktır. Bu da parçanın çevrimden önce %20 lik katılık değişimini aşacağını ön görmektedir. KAYNAKLAR [1].Vahapoğlu, V. (2013). Kauçuk Mekaniğinde Yapılan Deneyler. Pamukkale Üniversitesi Mühendislik Bilimleri Dergisi, 19(1): [2].Erkek, S Karbon Siyahı/Yağ ve Karbon Siyahı/Dolgu Maddesi Oranının Farklı Vulkanizasyon Sistemlerinde EPDM, NBR ve SBR Elastomerlerinin Fiziko-Mekaniksel Özellikleri Üzerine Etkisi. Yüksek Lisans Tezi, Çukurova Üni., Fen Bilimleri Enstitüsü, Kimya Anabilim Dalı, Adana. [3].Özgün, R.E Kauçuk- Metal Burçlarda Kauçuk Sertliği ve Çaplama işlemlerinin Kopma Mukavemetine Etkisinin Araştırılması. Yüksek Lisans Tezi, Uludağ Üni., Fen Bilimleri Enstitüsü, Makine Mühendisliği Anabilim Dalı, Bursa. [4].Soyel, D Sonlu Elemanlar Metodu ile NR/SBR Tipi Elastomer Esaslı Malzemelerin Davranış Modellerinin Belirlenmesi. Yüksek Lisans Tezi, Sakarya Üni., Fen Bilimleri Enstitüsü, Makine Eğitimi Anabilim Dalı, Sakarya. [5].Vahapoğlu, V. 2010; Kauçuk Türü Malzemeler: Şekil Değiştirme Hızı Etkileri, Pamukkale Üniversitesi Mühendislik Bilimleri Dergisi Cilt 16, Sayı 3, 2010, Sayfa 265 [6].Kenstitu, URL: arastirilmasi/(erişim zamanı; Aralık, 5, 2017) [7].Karen, İ, Kaya, N., Öztürk, F.ve Korkmaz, İ., (2008), Motor Titreşim Takozlarının İstenen Özelliklerde Tasarımı ve Doğrulaması, 4. Otomotiv Teknolojileri Kongresi Otekon 08, 1-4 Haziran 2008, Bursa. 18

24 Academic Platform Journal of Engineering and Science 6-2, 19-24, 2018 Academic Platform Journal of Engineering and Science journal homepage: Design of a Tracking Welding Robot Automation System for Manufacturing of Steam and Heating Boilers * 1 Süleyman Ersöz( ), 1 Ahmet Kürşad Türker( ), 1 Adnan Aktepe( X), 2 İrfan Atabaş( ), 1 Melda Kokoç( ) a Kırıkkale University, Department of Industrial Engineering, 71450, Yahşihan, KIRIKKALE b Kırıkkale University, Department of Computer Engineering, 71450, Yahşihan, KIRIKKALE Received Date: Accepted Date: Abstract For satisfying customers companies want to respond to customer requests on time. At the same time, they expect production process to be completed with low cost and low loss. For this reason, the importance of mechanization and automation in production sector has increased. As a result, companies have begun to give more importance to robotic systems, which are the basic components of automation systems. Despite the likelihood of mistakes caused by physiological and mental states of humans, these systems can perform operations precisely without any variability. In this study, an application was carried out for the automation of welding process of industrial type boilers in different sizes and features. For products of which standard measurements or welding operations are difficult to perform manually, a robotic system was proposed in which measurement and welding operations can be performed automatically. In addition, operators are prevented from exposure to gas and light via the proposed system which enables a safer working condition. Keywords: Automation, Image Processing, Robotic System, Welding Process 1. INTRODUCTION In recent years, developing technology and changing processes of life have forced companies to re-examine business policies, to determine targets that meet the developing conditions and to reach these targets. The most important factors that distinguish companies from their competitors today are that they can adapt to changing conditions and respond to customer demands with flexible organizational structure. Due to changing production and consumption conditions, importance of mechanization and automation in production sector has increased and many companies have begun to give more places to automation systems in production line. One of the basic elements of automation systems is robotic systems. With these systems, operations that require sensibility or power are performed quickly and accurately. It is a process that leaving companies in manufacturing sector from traditional methods based on labour power and then moving to automation systems, requires cost. Some of companies cannot move to automation systems either because of lack of vision, or because they do not want to bear extra costs. One of manufacturing sectors experiencing this problem is steam and hot water boiler sector, where production is still being done using conventional methods. The most critical process in boiler production is welding process. Welding is said to be process of joining two or more pieces of metal in such a way that they are not separated under high temperature [1, 2]. Welding in manufacturing sector is widely carried out by workers. However, there are many negative situations in welding which carried out by human hands. Some of these are: i. Welding operator directly influences welding quality, ii. Welding process is not always the same and continuous quality, iii. There are negative effects on human health, iv. Finding welding specialist is difficult, etc. Today, organizations that use welding connections in their production have realized need to use robotic arm technology in welding operations that enables mass production. In automation sector, there are solutions available for standard production. However, these systems are not suitable for businesses where non-standard products are produced. Corresponding Author: Kırıkkale University, Department of Industrial Engineering, 71450, Yahşihan, KIRIKKALE, Doi: /apjes

25 S ERSÖZ Academic Platform Journal of Engineering and Science 6-2, 19-24, 2018 Determination of points to be welded has different difficulties according to material to be welded. Several methods for 3D scanning have been proposed in literature. Xu et al. [3] extracted the 3D model of objects by integrating 2D classification algorithms via Kinect sensor. Another study that uses the Kinect sensor to perform 3D modelling of industrial products is study of Kahn et al. [4]. Kinect sensor technology which has been used since 2014 cannot produce depth information on reflective surfaces, transparent surfaces, or deep areas. Saygılı et al. [5] filled these empty depth areas with learning algorithms. A limited number of studies about automatic welding systems which used 3D imaging systems have been carried out. In one of these studies prototype capable of 3 axes linear welding was produced [6]. In another study, Qian et al. 7], proposed a method of detecting edges of metal parts using image processing techniques. But, proposed method is not suitable for real-time applications and produces solutions for nonlinear boundaries. Several other studies have been carried out to automate welding operations. In order to control and operate process of GMAW, a neural network based on generalized delta rule was adopted in Yang and et al. [8] s study. In entrance layer of neural network algorithm, width and depth of weld joint were chosen as neurons. Input variables (width and depth of weld joint) were obtained via image information. In output layer, voltage, weld speed and wire feed rate are symbolized as neurons. In Starke, et al. [9] s study, they presented strategies, and research results in applying robot operating system and robot operating system-based solutions. This system was proposed to overcome existing technical gaps via integration of selforganization capabilities and autonomous path planning. In Borovik, et al. [10]'s study, algorithm synthesis for industrial robot control was carried out. Electron -beam projector with plasma emitter was used as operating tool. Parameters of emission power provided melting of additive material were determined. In our study, a prototype which automatically welds by defining coordinates of the welding points of different scales and geometries, was designed and produced. Developed system offers innovative solutions compared to systems produced in automation sector in order to be compatible with different products. In developed system, object to be welded is scanned horizontally, vertically or circularly in 3 dimensions and joints on object are automatically detected using artificial intelligence algorithms. Combining these points with welding is done with a torch integrated into a cartesian robot arm that can move in 5 axes. Following advantages are provided by produced system; Development of automation and integrated software system in production with new welding technology, The ability to respond quickly to the different needs of customers with increased flexibility in production, Providing stability in product quality through intelligent manufacturing technology, Preventing the problems that affect the health of the workers caused by the source, Reducing injuries or deaths which were caused by boiler explosion, by minimizing production faults in pressurized boilers. Programmable robot welding systems are being used effectively in advanced manufacturing sectors for standard production. However, in the manufacturing sector where non-standard production is carried out, welding operations are performed entirely manually by workers. In addition to adverse effects to health of workers, manual welding leads to poor welding quality. It is possible to provide worker safety, and also to automatically perform welding operations with an automation system so that standard and reliable welding operations can be performed. In this study, it was ensured that these adverse conditions were removed. In addition, unique qualities of this study are as follows; In the developed system, imaging system which allows 3D modelling of not only horizontal but also, vertical and circular areas was used. Generated welding automation system is a selfprogrammable structure. In this system, motion capability of torch was increased by using a 5-axis Cartesian arm so that it was not only linear but welded in free-form or circular shapes. Production of such a system which has automated welding capability has been first application for Turkey in this field. Unlike standard automatic welding systems, because this system enables versatile 3D imaging and welding with a 5-axis robot arm, allowing system to automatically weld many products in the manufacturing industry, not just in the boiler. 2. DESIGN OF WELDING AUTOMATION SYSTEM Steps followed when creating the proposed robotic welding system are as shown in in Figure 1. Basic Process steps are explained below. 20

26 S ERSÖZ Academic Platform Journal of Engineering and Science 6-2, 19-24, 2018 Opinions of firms which is expert about design Computer-aided design Simulation Yes Is there any problem? No Manufactured domestic robot arm Image processing software Control software Manufacturing and system integration Software integration and interface development Imaging unit Welding torque Test Fig. 1. Flow Diagram of Proposed System 2.1. Design To create a machine roughly, the stages are i. Imagining machine, ii. Drawing sketch shape, iii. Ensuring that mechanism works, iv. Dimensioning elements, v. Drawing assembly drawings, vi. Making and testing prototype machine. All processes up to production stage are called design [11, 12]. Designer identifies material selection, manufacturing method, dimensions, and tolerances in design phase. This stage requires more technical experience. Knowledge that designer can use, such as stress formulas, material properties, production methods, is required. When a satisfactory design is achieved, analysis is appropriate. If design is good, manufacturing can be done. Often design is insufficient after the prototype production because of unsatisfactory and inadequate material, and is returned to the draft design stage [13, 14, 15]. Since movement system used in the study has a cartesian structure, this system was designed again in the computer environment. It was tried to determine problems that can be encountered after designing system with simulations during designing. For mechanical design of system, collaborations were made with companies specialized in design. Designed system consists of 5 axes. x and y axes are shown in Figure 2. 3rd, 4th, and 5th axes are located on the robot arm. 3rd axis allows robot arm to move up and down, while 4th and 5th axes are used to make arm movements. At the end of axis 5, welding torch is present. Fig. 2. Front view 2.2. Manufacturing and System Integration After the section shown in Figure 2 was manufactured, assembly of robot arm used in this system was carried out as shown in Figure 3. Robot arm used in system was manufactured with local opportunities. An imaging unit was also placed on robot arm along with welding torch. Camera, lens and filter are included in this unit. After the design stage, this design was produced with a company. We also exchanged ideas about design with company working in manufacture of mechanical components. Fig. 3. View after installation 21

27 S ERSÖZ Academic Platform Journal of Engineering and Science 6-2, 19-24, Imaging System Image processing is a different process from "signal processing" which is the process of capturing, measuring and evaluating data, then transforming it into a readable form in another device or transferring it from one electronic environment to another electronic environment [16]. Preprocessing applied to images for image processing reduces the noise (fogging, resolution, and bad view) on the images. For this, low, medium and high level operations are applied to the images. In low level operations, the reality of input and output images is provided by filtering. For medium level operations, splitting and recognition operations are performed for the recognition and classification of objects in images. High-level operations involve analysis of images to recognize objects in images. By analysing images in computer, the image contents of the objects in the images are detailed. Then, image processing is performed with this detailing step [17, 18]. In the study, surface of object to be welded should be scanned and surface structure must be visualized in 3D. There are different methods in literature to extract 3D model. In this study, because of the low cost, a 3D model was extracted with a laser line light and a camera that displays this light shown in Figure 4. Imaging system consists of a linear laser light (635nm), a camera and a near (NIR) ( nm) optical band pass filter to be placed in front of the camera. of object corresponding to this pixel are found by Equation 1-6 [20]. Fig. 5. Determining coordinates of object from camera image [20] ddφφ xx = aaaaaaaaaaaa ( uu rr tttttt(ffffff )) 22 (1) )) (2) ddφφ yy = aaaaaaaaaaaa ( vv rr tttttt(ffffff 22 LL = ( FFFFFF ) 22 (3) ww 22 + hh 22 ZZ = dd cccccc(aaaaaaaaaaaa(uuuu))ssssss(ππ θθ) ssssss((ππ θθ)+φφ+aaaaaaaaaaaa(uuuu)) (4) YY = ZZZZZZ (5) XX = ZZZZZZ (6) During image processing phase, data of image processed by camera is transmitted to data matrix. After transferring to matrix, missing or noisy data in dataset are cleared and transferred to torch. Fig. 4. Drawing of 3D scanner [19] In the 3D imaging system, when the horizontal axis is referenced (Figure 5), the camera was assembled with a horizontal metal plate with φ angle and the laser light source is assembled with a horizontal metal plate with θ angle. The reflection of the laser beam, which occurs on the object, is displayed on the camera by providing that the linear light to fall on the object to be displayed. When coordinates of object relative to camera axis are extracted, camera parameters that are considered are viewing angle, the size of point formed in image, and size of generated image. X, y, z are coordinates desired to determine, d is the distance between camera and light source, u and v are dimensions of pixel, r is the distance from the scanned pixel to imaginary square. Based on position and dimensions of target pixel on captured image, 3D coordinates X, Y, and Z To sum up the imaging process: Imaging system consists of a laser, a camera, a special lens and an industrial computer. Cartesian motion system consists of a module that can move on 5 different axes, a welding machine placed on this module and a panel with all controls of the system. After cartesian motion system was completed, imaging system was integrated. When system is run, imaging system, which is placed on cartesian system, first takes an image of material to be welded. With developed methods, locations to be welded are determined and these places are shown from user panel to operator. An option was added to software so that system can be continued to operate without operator's approval if requested. Then, coordinates of points to be welded are determined. Lastly, these coordinates are sent to prepared cartesian system. Welding process is started with the torch located on the cartesian system Software Integration and Interface Development There are two softwares in system. One of these is image processing software which detects the places to be welded. 22

28 S ERSÖZ Academic Platform Journal of Engineering and Science 6-2, 19-24, 2018 With this software, the locations to be welded and the coordinates of these places were determined. Other software is control software that makes movement of mechanical system. After coordinates of locations to be welded with image processing software were determined these coordinates were sent to control software. In control software, G-codes of coordinates coming from image processing software was extracted and sent to control card of cartesian system. Two systems were integrated with each other thereby entire system is automatically operated. An understandable interface program was also developed to ensure that entire control of system can be controlled by the operator. Thanks to this interface, points to be welded can be seen by the operator before welding is done. If operator selects the "automatic welding" option from interface, system can start automatic welding without operator approval. All transactions made with prepared interface are also recorded. Thus, necessary reporting can be done about operation of system Testing In testing stage system is tried or assessed manually or automatically to determine whether it meets specified requirements or to determine the difference between expected and observed results. After stages of design, manufacturing, imaging, integration and interface development, testing was started. At this stage, operations shown in Figure 7 are performed individually to test system. By testing weld points, control engineer make feedback about it. At this point, which is final stage of test processes in project, control is provided by a Fuzzy Expert System algorithm. System's mobility, image acquisition and related parameters and temperature are inputs of fuzzy expert system. Feedback of quality control engineer about control processes constitutes knowledge base composed of decision rules of fuzzy expert system. System's mobility was tested via interface prepared. Manual operation of welding torch was tested. System was operated under different temperatures, images taken by the camera were examined. System's image taking capability was tested. System was tested for 24 hours without interruption, and it was tested whether there is any deviation in images taken. Parts of boiler were scanned to determine locations of welding spot. Afterwards, it was tested whether these locations were correctly welded or not. System was run on production line of boiler and performance of system in actual production environment is tested. pressure than own pressure. Fig. 7. Operations in testing stage Physical quality control was carried out by filling water or air with 3-4 times more pressure than own pressure. 3. RESULTS AND DISCUSSION In this study, an intelligent welding robot design is developed. The system is based on automated processes for welding operations. With the help of the system developed, welding operations can be conducted automatically which brings many advantages such as flexibility, technological improvement, safer production and better quality products. With developed system, a production company has several advantages in terms of; Flexibility: The company is more flexible than past because now it can reply to customers requirements quickly. Production rate is increased thanks to automation. Technology: System enables workers, especially engineers, to develop new algorithms and to broaden horizon of them. Occupational health and safety: Production is safer in terms of human health. Welding process is completely carried out by robot. Quality: Defects caused by human errors is minimized. Whole system can be monitored automatically. In addition, thanks to 5-axis design system and integration with intelligent imaging system, system can be used not 23

29 S ERSÖZ Academic Platform Journal of Engineering and Science 6-2, 19-24, 2018 only in boiler manufacturing but also in different manufacturing sectors. REFERENCES [1] Yang, S. M., Cho, M. H., Lee, H. Y., Cho, T. D., Weld line detection and process control for welding automation. Measurement Science and Technology, 18 (3), 819, [2] Özkan S.S., Karayel D., Atalı G., Gökbayrak İ., Esnek Algılayıcı Kontrollü Robot El Tasarımı ve Gerçeklenmesi, Akademik Platform Mühendislik ve Fen Bilimleri Dergisi (APJES), 5 (3), 35-40, [3] Xu D., Cai J. Cham T.J., Fu P., Zhang J., Kinect- Based Easy 3D Object Reconstruction, Lecture Notes in Computer Science, 7674, , [4] Kahn S., Bockholt U., Kuijper A., Fellner D. W., Towards precise real-time 3D difference detection for industrial applications, Computers in Industry, 64 (9), , [5] Saygili G., Balim C., Kalkan H., Hendriks E.A., Hierarchical Grid-Based Learning Approach for Recovering Unknown Depths in Kinect Depth Maps, International Conference on Image Analysis and Recognition, Póvoa de Varzim, Portugal, [6] Ersöz, S., Türker, A., K., "İz Süren Kaynak Otomasyonu" (Welding Automation with Tracing), KOSGEB Project, [7] Qian X., Yang L., Lou P., The autonomous detection of sheet metal parts using image Processing, International Journal of Advanced Manufacturing Technology, DOI: /s , [8] Yang, Sang-M., Weld line detection and process control for welding automation", Measurement Science and Technology, 18 (3), 819, [9] Starke, G. et al., "Self-Organization and Self- Coordination in Welding Automation with Collaborating Teams of Industrial Robots", Machines, 4 (4), 23, [10] Borovik, V., "Industrial Robot Automation in Solving Non-Vacuum Electron-Beam Welding Problems", MATEC Web of Conferences, 79, EDP Sciences, [11] Renner, G. Anikó E., "Genetic algorithms in computer aided design." Computer-Aided Design 35 (8), , [12] Boothroyd, G., "Product design for manufacture and assembly", Computer-Aided Design 26 (7), , [13] Regli, William C., Vincent A. C., "Managing digital libraries for computer-aided design", Computer-Aided Design, 32 (2), , [14] Wang, H., et al. "Computer aided fixture design: Recent research and trends", Computer-Aided Design, 42 (12), , [15] Wang, H., Yiming K. R., "Case based reasoning method for computer aided welding fixture design", Computer-Aided Design, 40 (12), , [16] Gonzalez R. C., Woods R. E., "Digital Image Processing", 3th Ed., 1-7, U.S.A., New Jersey, Prentice Hall, [17] Çomak, B., Beycioğlu, A., Başyiğit, C., Kılınçarslan, Ş., "Beton teknolojisinde görüntü işleme tekniklerinin kullanımı", (Use of image processing techniques in concrete technology), In 6th Intenational Advanced Technologies Symposium (IATS 11), [18] Erkan E., Özçalık H.R., Yılmaz Ş., Görüntü İşleme Teknikleri Kullanılarak İnsan Hareketlerini Algılayan Akıllı Güvenlik Sistemi Tasarımı, Akademik Platform Mühendislik ve Fen Bilimleri Dergisi (APJES), 3 (1), 1-6, [19] Kjaer, K. H., Carl-Otto O., "3D laser triangulation for plant phenotyping in challenging environments", Sensors, 15 (6), , [20] "Determining coordinates of object from camera image", Available from: gulation.php, (Access date: )

30 Academic Platform Journal of Engineering and Science 6-2, 25-33, 2018 Academic Platform Journal of Engineering and Science journal homepage: Çok Kriterli Karar Verme Yöntemleriyle Taşeron Firma Seçimi: Kırıkkale İlinde Bir Uygulama 1 Neşet Bedir( ), 2 Hamza Yalçın( ), 3 Emir Hüseyin Özder( ), 4 *Tamer Eren( ) 1 Kırıkkale Üniversitesi, Mühendislik Fakültesi, Endüstri Mühendisliği Bölümü, 2 Kırıkkale Üniversitesi, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü, 3 Başkent Üniversitesi, Ticari Bilimler Fakültesi, Yönetim Bilişim Sistemleri Bölümü, 4 Kırıkkale Üniversitesi, Mühendislik Fakültesi, Endüstri Mühendisliği Bölümü, Geliş Tarihi: Kabul Tarihi: Öz Günümüz piyasalarında firmaların hayatta kalabilmeleri için rekabet etmeleri gerekmektedir. Arz talep dengesinin yön değiştirdiği günümüzde, firmalar, asıl işlerini kendileri yapıp diğer işlerini o alanda çalışan yetkin firmalara bırakmaktadırlar. Bu sayede iş gücü ve malzeme envanterlerini minimum seviyede tutarak fazla işgücü ve stok maliyetlerinden kurtulmaktadırlar. Taşeron işçiler günümüzde birçok şirket tarafından yardımcı işlerde kullanılmaktadır. Bunun başlıca sebebi büyük işletmeler için dış kaynak kullanımı yoluyla esas yaptıkları üretime odaklanmak iken küçük işletmeler için kendi bünyesinde çalıştırdıkları işçilerin sigorta, sosyal imkân, vb. masraflarından kurtularak üzerlerindeki bu yükü atarak daha fazla kâr etmektir. Gayrimenkul ve proje şirketleri de ev satmanın yanında tadilat işleri de yapmaktadır. Bunun için taşeron firma kullanmaktadırlar. Taşeron firma kullanımına en fazla ihtiyaç duyulan sektörlerden birisi de inşaat sektörüdür. Bu amaçla Kırıkkale ilinde faaliyet gösteren bir gayrimenkul ve proje şirketinin anahtar teslim tadilat işi için taşeron firma seçimi problemi ele alınmıştır. Problemin çözümünde çok kriterli karar verme (ÇKKV) yöntemlerinden Analitik Ağ Süreci ve PROMETHEE yöntemlerinden yararlanılmıştır. Taşeron firma seçimine etkiyen kriterlerin ağırlıklarının belirlenmesinde Analitik Ağ Süreci yöntemi kullanılmıştır. Analitik Ağ Süreci yöntemi ile bulunan kriter ağırlıkları kullanılarak PROMETHEE yöntemi ile alternatif firmaların sıralaması yapılmıştır. PROMETHEE I kısmi sıralama sonucuna göre MAK firması diğer alternatiflere tam üstünlük sağlarken, diğer alternatiflerin net sıralaması çıkarılamamaktadır. Bu sebeple PROMETHEE II ile net üstünlükler sıralandığında yine MAK şirketi net üstünlük sağlayarak yapılacak işi almıştır. Anahtar kelimeler: Dış kaynak kullanımı, Analitik Ağ Süreci, PROMETHEE, Çok Kriterli Karar Verme Subcontractor Company Selection with Multiple Criteria Decision Making: An application in Kırıkkale 1 Neşet Bedir, 2 Hamza Yalçın, 3 Emir Hüseyin Özder, 4 *Tamer Eren 1 Kırıkkale University, Faculty of Engineering, Department of Industrial Engineering, 2 Kırıkkale University, Faculty of Engineering, Department of Civil Engineering,, 3 Başkent University, Faculty of Commercial Science, Department of Management Information Systems, 4 Kırıkkale University, Faculty of Engineering, Department of Industrial Engineering, Abstract Competition is necessary for companies to survive in today's markets. To change the direction of supply demand equilibrium nowadays, the firm is authorized to make according to others and to act according to others. On this basis, they keep their labor and material inventories at a minimum level to get rid of labor and inventory costs. Subcontractor workers are now used in many aids for many companies. The main reason for this is the outsourcing principles for large enterprises, the focus is on production, while for small businesses workers themselves employ insurance, social facilities, and so on. to make more profit by getting rid of the costs and throwing this burden on them. Real estate and project companies also do renovation works. It uses a subcontractor Sorumlu Yazar: Kırıkkale Üniversitesi, Mühendislik Fakültesi, Endüstri Mühendisliği Bölümü, Doi: /apjes

31 T EREN Academic Platform Journal of Engineering and Science 6-2, 25-33, 2018 for this. One of the most needed sectors for subcontractor use is the construction sector. For this purpose, the problem of subcontractor selection for a turnkey renovation work of a real estate and project company operating in the province of Kırıkkale has been discussed. It is based on the method of multi-criteria decision making (MCDM) methods and it is benefited from Ağrı Süreci and PROMETHEE methods. The Method of Aperture Process is used. PROMETHEE method was used to rank the companies selected. PROMETHEE According to the result of the partial selection, the MAK firm provides a superiority to the other alternatives, but the net order of the other alternatives can not be obtained. For this reason, when PROMETHEE II is listed as a net superiority, again MAK company has got a net profit and got the job to be done first. Keywords: Outsourcing, ANP, PROMETHEE, Multi-criteria Decision Making 1. GİRİŞ Teknolojik gelişmelerle beraber değişen ekonomi dünyasında işletmeler birbirleriyle sürekli iletişim halindedirler. İşletmeler önceleri yalnızca hammadde, ara ürün, yarı mamul, yedek parça ve sarf malzemeler için dış kaynak kullanırken, günümüzde ürünü direk olarak başka işletmelerden alabilmekte hatta işin tamamı için dış kaynak kullanımı yoluna gidebilmektedirler. Dış kaynak kullanımında işletmeler yapılacak olan işleri uygun taşeron firma aracılıyla yaptıkları takdirde hem zamandan, hem mekândan hem de paradan tasarruf ederler. Özellikle inşaat sektöründe taşeron kullanımı büyük önem teşkil etmektedir. İnşaatın hemen hemen bütün aşamaları taşeron firmalar aracılığıyla taşeron işçiler tarafından yapılmaktadır. Taşeron firma seçimi bu noktada çok kriterli bir problem haline dönüşür. Birden çok kriterin bir arada değerlendirilmesi gereken problemlerin çözümünde çok kriterli karar verme yöntemi kullanılır. Karar verme, karşılaşılan bir sorun karşısında beklentileri en iyi şekilde karşılayacak alternatifi seçme eylemidir. Literatürde en sık rastlanan çok kriterli karar verme problemleri AHP, ANP (Analitik Ağ süreci), TOPSIS, ELECTRE, PROMETHEE (Preference Ranking Organization Method of Enrichment evaluation ) ve VIKOR'dur. Bu çalışmada Kırıkkale de faaliyet gösteren bir müteahhit firmasının anahtar teslim tadilat işlerini yaptırmak için sektördeki taşeron firmalardan hangisi ile çalışacağı belirlenmiştir. Problemin çözümü için çok kriterli karar verme yöntemlerinden ANP, ve PROMETHEE yöntemleri birlikte kullanılmıştır. Öncelikle ANP yöntemi ile seçilecek olan firmaların değerlendirme kriterlerinin ağırlıkları belirlenmiştir. Elde edilen kriter ağırlıkları kullanılarak aday firmaların sıralanması için PROMETHEE yöntemi kullanılmıştır. Çalışmanın planı şu şekildedir. İkinci bölümde taşeron firma seçim problemi tanımlanmıştır. Üçüncü bölümde taşeron firma seçimi ile ilgili literatürde yapılan çalışmalar incelenmiştir. Dördüncü bölümde çok kriterli karar verme yöntemleri anlatılmıştır. Beşinci bölümde taşeron firma seçimi probleminin uygulaması anlatılmıştır. Son bölümde sonuçlar değerlendirilmiştir. 2. TAŞERON FİRMA SEÇİMİ Müteahhitler almış oldukları projeleri yetiştirebilmek için projenin tamamını ya da bir kısmını taşeron firma eliyle yaptırmaktadır. Bu durumda iş yaptırılacak olan firmalar işin gerekliliklerine uygun olarak seçilmelidir. Firmaların seçilmesini etkiyen özellikler doğru belirlenirse yapılan iş istenilen kalitede olur. Bir işin bir bölümünü, esas işi yapan kurum ya da kişiden alarak, o işi yapmaya başlayan kişi, kurum ya da firmaya taşeron adı verilir. Taşeron kavramı yasalarda alt işveren olarak geçmektedir. Taşeron iş yapan firmalarda çalışan işçilere taşeron işçi denir. Taşeron işçiler bir işin esas bölümünde değil de işin asıl yürümesine yardımcı olan yan kollarda görevlendirilebilir. 3. LİTERATÜRDE YER ALAN ÇALIŞMALAR Bu bölümde literatürde taşeron firma seçimi ile ilgili yapılan çalışmalara yer verilmiştir. Hatush ve Skitmore [1] çok katlı bir bina projesisin yapılması için 5 alternatif firmadan hangisinin seçileceğini çok kriterli fayda teorisi kullanarak belirlemişlerdir. Topçu [2] çalışmasında Türk kamu sektöründe müteahhit seçimi için çok amaçlı karar verme modeli önermişlerdir. Önerdikleri modelin uygun yüklenici seçiminde proje sahipleri tarafından karar destek sistemi olarak kullanılmasını amaçlamışlardır. Mulavdic [3], sürdürülebilir gelişim çerçevesinde, konut tipi seçimine ilişkin çalışmasında VIKOR yöntemini uygulamışlardır. Gül [4] çalışmasında dış kaynak kullanımın taşıdığı riskleri imalat sektöründe bir uygulamayla anlatmıştır. Singh ve Tiong [5] yüklenici firma seçimi için bulanık mantıktan faydalanmışlardır. Maliyet, zaman, kalite ve işgücü kriterlerine göre alternatifleri değerlendirerek en uygun yükleniciyi seçmişlerdir. Tzeng vd. [6], yapmış oldukları çalışmada toplu taşımada kullanılacak alternatif yakıtların değerlendirmesinde VIKOR ve TOPSIS yöntemlerini kullanmışlardır. Soner ve Önüt [7] çalışmalarında tedarikçi seçimi için AHP ve ELECTRE yöntemlerini kullanmışlardır. Opricovic [8] su kaynakları planlamasında VIKOR yöntemini kullanmıştır. Chu vd. [9] çalışmalarında bilgi yönetim alanında ortaya çıkan çok kriterli karar verme yöntemlerini değerlendirmişlerdir ve TOPSIS ve VİKOR yönteminin gerçeğe daha yakın sonuçlar verdiğini saptamışlardır. Lixin vd. [10] çalışmalarında 4 farklı alternatif içerisinden iyi lojistik servis sağlayıcının seçimini ANP ve VIKOR yöntemini kullanarak yapmışlardır. 26

32 T EREN Academic Platform Journal of Engineering and Science 6-2, 25-33, 2018 VİKOR yönteminin uygulamada daha kolay olduğunu saptamışlardır. Wua vd. [11] çalışmalarında performans ölçümü amacıyla AHP ve VİKOR yöntemini kullanarak üç bankayı yirmi üç kriter kapsamında bulanık ortamda analiz etmişlerdir. Ertuğrul ve Karakaşoğlu [12] çalışmalarında Ege bölgesindeki banka şubelerinin performansını ölçmek amacıyla VIKOR yöntemini kullanmışlardır. Sanayei vd. [13] çalışmalarında bulanık ortamdaki tedarikçi seçim problemi için VIKOR yöntemini kullanmışlardır. Kaya ve Kahraman [14] yenilenebilir enerji alternatiflerinin seçimi problem için, AHP ve VIKOR yöntemlerini kullanarak bulanık ortamda bir analiz gerçekleştirmişlerdir. Akyüz [15] çalışmasında mobilya parçaları üreten bir firmanın ambalaj tedarikçisi seçim probleminde ÇKKV yöntemlerinden Bulanık VIKOR'u kullanmışlardır. Ravi [16] çalışmasında üçüncü parti lojistik firma seçimi için AHP ve TOPSIS yöntemlerini kullanımıştır. Abbasianjahromi vd. [17] çalışmalarında uluslararası bir müteahhitlik şirketinin karayolu köprü yapımı için kullanacağı taşeron firma seçimi problemini ele almışlardır. Problemin çözümünde çkkv ve bulanık mantık kullanmışlardır. İraz vd. [18] çalışmalarında Konya ilinde faaliyet gösteren KOBİ lerin yenilik yönetimi açısından dış kaynak kullanma eğilimlerini analiz etmişlerdir. Rençber ve Kazan [19] çalışmalarında büyük çaplı bir inşaat projesi için taşeron firma seçimi problemini ele almışlardır. Firma seçerken dikkate alınacak kriterlerin önemi karşılaştırmak ve tekliflerin değerlendirilmesini yapmak için AHP yöntemini kullanmışlardır. Bedir vd. [20] dış kaynak kullanımı için AHP ve PROMETHEE yöntemlerini kullanmışlardır. Kalkan vd. [21] çalışmalarında Ankara Halk Sağlığı Müdürlüğü ne bağlı sağlık kuruluşlarının dış kaynak kullanımının müdürlüğe maliyetlerini tespit etmişlerdir. Görener ve Sabuncuoğlu [22] çalışmalarında yüklenici seçiminde çok kriterli karar verme yöntemlerinde AHP ve TOPSIS yöntemleriyle bir yaklaşım önermişlerdir ve inşaat endüstrisinden örnek bir uygulama yapmışlardır. 4. ÇOK KRİTERLİ KARAR VERME Çok kriterli karar verme, Karar Bilimlerinin bir alt dalıdır. Karar verme sürecini kriterlere göre modelleme ve analiz sürecine dayanır. Literatürde en sık rastlanan çok kriterli karar verme yöntemleri AHP, TOPSIS, VIKOR, ELECTRE ve PROMETHEE' dir [23] ANP Yöntemi Analitik Ağ Prosesi (ANP), Analitik Hiyerarşi Proses (AHP) yönteminden daha genel bir yaklaşım olarak Thomas L. Saaty tarafından geliştirilmiş çok kriterli bir karar verme tekniğidir ve AHP gibi ikili karşılaştırma mantığıyla çalışır [24]. Analitik Ağ Prosesi, faktörler arasındaki ilişkilerin dikkate alınmasını gerektiren karar problemlerinin modellenmesinde kullanılabilecek ve daha etkin sonuçlara ulaşılmasını sağlayacak yöntemdir. ANP yönteminde, bir amaç ve hedefi etkileyen faktörler, birbirlerine olan etkilerine göre gruplandırılmakta ve amaca uygun bir a ğ (network) şeklinde model kurulmaktadır. ANP nin AHP ye göre farklılığı, yukarıdan aşağıya doğru bir hiyerarşik yapı yerine etkileşimli (ağ/network biçiminde) bir hiyerarşik yapı kullanılmasıdır. Ayrıca AHP yönteminde karşılaşılan önemli bir sorun sıra değişimidir. Sıra değişimi; belirli bir faktör kümesine göre belirlenen alternatif önceliklerinin, yeni bir alternatif eklendiğinde veya çıkarıldığında değişmesidir. Bu sorun ANP yönteminde azaltılmıştır [25]. ANP yönteminin adımları; Adım 1: Problemin tanımlanması ve modelin kurulması Adım 2: İkili karşılaştırma matrisinin oluşturulması Adım 3: Matrislerin tutarlılık analizi ve süper matrisin oluşturulması Adım 4: Süper matrisin oluşturulması Adım 5: En iyi alternatifin oluşturulması şeklindedir. ANP yönteminin birçok uygulama alanı bulunmaktadır. Lin vd. [26], Yurdakul [27], Bhattacharya [28] vd. performans ölçümünde, Meade ve Presley [29], Hamurcu ve Eren [30] proje değerlendirmede, Gencer ve Gürpınar [31] tedarikçi seçiminde, Cheng vd. [32], Burnaz ve Topçu [33], Partovi [34], Tuzkaya vd. [35] tesis yeri seçiminde, Özcan vd. [36] güneş enerji santrali seçiminde,özcan vd. [37] enerji yatırımlarının değerlendirilmesinde, Bağ vd. [38] hemşire çizelgeleme probleminin çözümünde, Özder vd. [39] paket program seçiminde ANP yöntemini kullanmışlardır. 4.2 PROMETHEE Yöntemi PROMETHEE Brans [40] tarafından geliştirilmiş bir çoklu karar verme yöntemidir. Yöntem karar noktalarının sırasını, PROMETHEE I (kısmi sıralama) ve PROMETHEE II (tam sıralama) ana aşamalarıyla belirler. PROMETHEE yöntemi karar noktalarının değerlendirme faktörlerine göre ikili kıyaslamalarına dayanır. Ancak diğer çoklu karar verme yöntemlerinden temel farkı, değerlendirme faktörlerinin birbirleri arasında ilişki düzeyini gösteren önem ağırlıklarının yanı sıra, her bir değerlendirme faktörünün kendi iç ilişkisini de dikkate almasıdır. PROMETHEE yöntemi ile birçok alanda uygulanmaktadır. Bedir ve Eren [41] personel seçiminde, Bedir vd. [42] öğrenci seçiminde, Özder vd.[43] akademik personel seçiminde, Bedir vd.[44] lojistik firma seçiminde, Bedir vd. [45] demontaj hattı dengelemede, Taş vd. [46] monoray hat tipinin belirlenmesinde PROMETHEE yöntemini kullanmıştır PROMETHEE yöntemi aşamaları PROMETHEE yöntemi, diğer çok kriterli karar verme metotları ile uygulama ve kapsam açısından karşılaştırıldığında gerçek değerler ile ifade edilebilen çok sayıda kriter için uyarlanabilir basit bir yöntemdir. PROMETHEE yöntemi 7 adımdan oluşmaktadır [41]: Adım 1: Veri matrisinin oluşturulması: w = (w1,w2,,wk) ağırlıkları ile k kriter c= (f1,f2,,fk) tarafından değerlendirilen alternatiflere A = (a,b,c, ) ilişkin veri matrisi, Tablo 1'deki gibi oluşturulur. 27

33 T EREN Academic Platform Journal of Engineering and Science 6-2, 25-33, 2018 Tablo 1. PROMETHEE Veri Matrisi Değerlendirme Faktörleri Karar Noktaları f 1 f 2 f 3 f k A f 1 (A) f 2 (A) f 3 (A) f k (A) B f 1 (B) f 2 (B) f 3 (B) f k (B) C f 1 (C) f 2 (C) f 3 (C) f k (C) Ağırlıklar w i w 1 w 2 w 3 w k Adım 2: Kriterler için tercih fonksiyonların tanımlanması: Yöntemin uygulanmasında kullanılacak 6 farklı tercih fonksiyonu Tablo 2 de gösterilmiştir. Tablo 2. Tercih fonksiyonları Adım 3: Ortak tercih fonksiyonlarının belirlenmesi: Alternatifler için belirlenen ortak tercih fonksiyonlarının şematik gösterimi Şekil 1 de verilmiş olup a ve b alternatifleri için ortak tercih fonksiyonu Eşitlik 4.1 ile belirlenir. P(a,b)={ 0, f(a) f(b) p[f(a) f(b)], f(a) > f(b) } (4.1) a P(c,a) P(a,b) P(b,a) c P(b,c) b Şekil 1. Ortak tercih fonksiyonlarının şematik gösterimi 28

34 T EREN Academic Platform Journal of Engineering and Science 6-2, 25-33, 2018 Adım 4: Tercih indekslerinin belirlenmesi: Ortak tercih fonksiyonlarından hareketle her alternatif çifti için tercih indeksleri belirlenir. Wi (i=1,2,,k) ağırlıklarına sahip olan k kriter tarafından değerlendirilen a ve b alternatiflerinin tercih indeksi Eşitlik 4.2 ile hesaplanır. π(a, b) = k i=1 w i P i (a,b) k i=1 w i (4.2) Adım 5: Alternatifler için pozitif (Φ + ) ve negatif (Φ )üstünlükler belirlenmesi: A alternatifi için pozitif ve negatif üstünlük şematik olarak Şekil 2 de gösterilmiş olup pozitif üstünlük Eşitlik 4.3, negatif üstünlük ise eşitlik 4.4 ile hesaplanır. Φ + (a) = 1 π(a, b) n 1 (4.3) Φ (a) = 1 π(b, a) n 1 (4.4) b c d b c d a Φ + a Φ Şekil 2. a alternatifi için hesaplanan pozitif ve negatif üstünlük Adım 6: PROMETHEE I ile alternatifler için kısmi önceliklerin belirlenmesi: Kısmi öncelikler alternatiflerin birbirlerine göre tercih edilme durumlarının, birbirinden farksız olan alternatiflerin ve birbirleriyle karşılaştırılamayacak olan alternatiflerin belirlenmesini sağlar. Adım 7: PROMETHEE II ile alternatifler için tam önceliklerin belirlenmesi: Eşitlik 4.11 yardımıyla her bir alternatif için tam öncelikler hesaplanır. Hesaplanan tam öncelik değerleri ile bütün alternatifler aynı düzlemde değerlendirerek tam sıralama belirlenir. Φ(a) =Φ + (a) - Φ (a) (4.11) a ve b gibi iki alternatif için hesaplanan tam öncelik değerine bağlı olarak aşağıda verilen kararlar alınır. Φ(a) > Φ(b) ise, a alternatifi daha üstündür, Φ(a) = Φ(b) ise, a ve b alternatifleri farksızdır. 5. ÖRNEK UYGULAMA Problemin akış şeması Şekil 3 te gösterildiği gibidir Problemin Tanımlanması Bu çalışmada Kırıkkale' de faaliyet gösteren bir gayrimenkul ve proje firmasının anahtar teslim tadilat işi için seçeceği taşeron firmanın belirlenmesi amaçlanmıştır Alternatiflerin Belirlenmesi İşi alacak olan alternatif şirketler Ankara'da faaliyet gösteren MAK, MSK, VEFA ve UMUT'dur Kriterlerin Belirlenmesi Müteahhit firma bünyesinde çalışan 1 inşaat mühendisi, 1 endüstri mühendisi ve 1 proje müdürünün değerlendirmesi ve literatürün incelenmesi sonucunda belirlenen kriterler şu şekildedir; Maliyet (M) : Firmaların yapılacak olan iş için standart bir daire için belirledikleri teklifin maliyetini gösterir. Finansal kapasite (FK) :Yapılacak olan işlerin aksamaması açısından firmaların finansal kapasiteleri önemlidir. Bu kriter firmaların sermayelerini göstermektedir. Geçmiş performans (GP) : Aday firmaların piyasada daha önceden yaptıkları işler referans alınarak firma hakkında fikir sahibi olunmasına etkiyen kriterdir. İş gücü (İG) : Aday firmaların mevcut personellerinin işe hakimiyetleri ve personellerin sayılarına göre değişen kriterdir. Güvenlik (G) : Aday firmaların yaptıkları işleri önceden belirledikleri tarihlerde gerçekleştirebilmesi durumu, yapılan işin kalitesi ve uzun süreli ilişkilerdeki faaliyetlerini içeren kriterdir. 29

35 T EREN Academic Platform Journal of Engineering and Science 6-2, 25-33, 2018 Problemin tanımlanması Karar Probleminin Tanımlanası ve Modelin Kurulması Kriterlerin belirlenmesi ANP ile Ağırlıkların elde edilmesi İlişkilerin Belirlenmesi Kriterler Arası İkili Karşılaştırmaların Yapılması ve Öncelik Vektörlerinin Hesaplanması Karşılaştırma Matrislerinin Tutarlılık Analizlerinin Yapılması Veri matrisinin oluşturulması Kriterler için tercih fonksiyonların tanımlanması Ortak tercih fonksiyonlarının belirlenmesi PROMETHEE ile firmaların sıralanması Tercih indekslerinin belirlenmesi Alternatifler için pozitif (Φ + ) ve negatif (Φ )üstünlükler belirlenmesi Sonuçların Değerlendirilmesi PROMETHEE I ile alternatifler için kısmi önceliklerin belirlenmesi PROMETHEE II ile alternatifler için tam önceliklerin belirlenmesi Şekil 3. Problem akış şeması 5.4. Problemin Çözümü ANP yöntemi ile en uygun taşeron firmanın seçimi yapılırken SUPER DESICION programından faydalanılmıştır. ANP yöntemi ile elde edilen kriter ağırlıkları Tablo 3'de gösterilmektedir. Tablo 3 ANP kriter ağırlıkları Kriterler Ağırlık Finansal Kapasite 0,0797 Geçmiş performans 0,1553 Güvenlik 0,3732 İş gücü 0,1834 Maliyet 0,

36 T EREN Academic Platform Journal of Engineering and Science 6-2, 25-33, 2018 PROMETHEE yöntemi ile çözüm yapmak için VİSUAL PROMETHEE programı kullanılmıştır. PROMETHEE yönteminde ANP yönteminden elde edilen Tablo 3'deki ağırlıklar kullanılmıştır. Kriterlerin tamamı maksimizasyondur. PROMETHEE yönteminde kriterler için tercih fonksiyonu uzman görüşü alınarak ve literatürde yer alan benzer çalışmalar incelenerek maliyet için 5. tip, finansal kapasite ve güvenlik için 4. tip, Geçmiş performans ve iş gücü için 3. tip olarak belirlenmiştir. Eşik değerleri q=1 p=2 olacak şekilde işlemler yapılmıştır. PROMETHEE yönteminde çözüme ulaşmak için VISUAL PROMETHEE programında veri girişi Şekil 4 te gösterildiği gibi yapılmıştır. PROMETHEE yöntemi ile elde edilen sıralama Tablo 4' teki gibi elde edilmiştir. Şekil 4. PROMETHEE veri girişi Tablo 4. PROMETHEE sonucu Alternatifler Φ net Φ + Φ MAK 0,8081 0,8081 0,0000 MSK 0,3199 0,5286 0,2088 UMUT -0,5320 0,0000 0,5320 VEFA -0,5960 0,0135 0,6094 PROMETHEE I sonucuna göre MAK hem MSK, UMUT ve VEFA firmalarına göre hem pozitif hem de negatif üstün olduğundan MAK diğer alternatiflerden üstündür. Özellikle güvenlik kriterinde diğer firmalardan olan MAK şirketi finansal kapasitesi diğer alternatiflerden düşük olmasına rağmen bütün kriterler için değerlendirildiğinde en iyi alternatif olmaktadır. Net üstünlükler hesaplandığında PROMETHEE II sonucuna göre sıralama MAK-MSK-UMUT ve VEFA şeklinde belirlenmiştir. 6. SONUÇ Bu çalışmada anahtar teslim tadilat işi için müteahhit firmanın alt yüklenici seçim problemi ele alınmıştır. Problemin çözümünde çok kriterli karar verme yönteminden ANP ve PROMETHEE yöntemleri kullanılmıştır. İleride yapılacak çalışmalarda problemin çözümü için yeni alternatifler eklenebilir. Kriterlerin öncelikleri için hedef programlama ya da bulanık mantık kullanılabilir. Diğer çok kriterli karar verme yöntemleri uygulanarak sonuçları karşılaştırılabilir. KAYNAKLAR [1] Hatush, Z., Skitmore, M., Contractor selection using multicriteria utility theory: an additive model" Building and environment, 33(2), , [2] Topçu, Y.I.. A decision model proposal for construction contractor selection in Turkey, Building and environment, 39(4), , [3] Mulavdic, E., Multi Criteria Optimization of Construction Technology of Residential Building Upon The 31

37 T EREN Academic Platform Journal of Engineering and Science 6-2, 25-33, 2018 Principles of Sustainable Development, Thermal Science, 9(3), 39-52, [4] Gül, H., Dış kaynak kullanma nedenleri ve taşıdığı riskler: imalat sanayiinde bir uygulama, Yönetim ve Ekonomi Araştırmaları Dergisi, 3(4), , [5] Singh, D., Tiong, R.L., A fuzzy decision framework for contractor selection, Journal of Construction Engineering and Management, 131(1), 62-70, [6] Tzeng, G. H., Lin, C. W., Opricovic, S., Multi-criteria analysis of alternative-fuel buses for public transportation, Energy Policy, 33(11), , [7] Soner, S., Önüt, S., Multi-Criteria Supplier Selection: An ELECTRE-AHP Application, Sigma, 4, , [8] Opricovic, S., Multicriteria optimization of civil engineering systems, Faculty of Civil Engineering, Belgrade, 2(1), 5-21, [9] Chu, M.T., Shyu, J., Tzeng, G.-H., Khosla, R., Comparison Among Three Analytical Methods For Knowledge Communities Group Decision Analysis.Expert Systems with Applications, 33(4), , [10] Lixin, D., Ying, L., Zhiguang, Z., Selection of logistics service provider based on analytic network process and VIKOR algorithm. InNetworking, Sensing and Control, ICNSC, IEEE International Conference, , April [11] Wua, H.Y., Tzeng, G.H., Chen, Y.H., A Fuzzy Mcdm Approach For Evaluating Banking Performance Based On Balanced Scorecard, Expert Systems with Applications, 36: , [12] Ertuğrul, İ., Karakaşoğlu, N., Banka şube performanslarının VIKOR yöntemi ile değerlendirilmesi. Endüstri Mühendisliği Dergisi, 20(1), 19-28, [13] Sanayei, A., Mousavi, S. F., Yazdankhah, A., Group decision making process for supplier selection with VIKOR under fuzzy environment. Expert Systems with Applications, 37(1), 24-30, [14] Kaya, T., Kahraman, C., Multicriteria Renewable Energy Planning Using an Integrated Fuzzy VIKOR & AHP Methodology: The Case of Istanbul, Energy, 35: , [15] Akyüz, G., Bulanık VIKOR yöntemi ile tedarikçi seçimi, Atatürk Üniversitesi İktisadi ve İdari Bilimler Dergisi, 26(1), , [16] Ravi, V., Selection of third-party reverse logistics providers for End-ofLife computers using TOPSIS-AHP based approach, International Journal of Logistics Systems and Management, 11(1), 24-37, [17] Abbasianjahromi, H., Rajaie, H., Shakeri, E., A Framework for Subcontractor Selection in the Construction Industry, Journal of Civil Engineering and Management, 19(2), , [18] İraz, R., Çakıcı, A. B., Tekin, İ. Ç., Yenilik yönetimi açısından KOBİ lerde dış kaynak kullanımının araştırılması: Konya ili örneği, Global Journal of Economics and Business Studies, 3(6), 51-68, [19] Rençber, Ö. F., Kazan, H., Büyük Çaplı Projelerde Taşeron Firma Seçiminde Teklif Değerlendirme: Analitik Hiyerarşi Süreci Yöntemi İle Karar Verme, International Journal of Social Science Research, 3 (4), 11-24, [20] Bedir N., Özder E.H., Eren T., The Third Party Logistics Fırm Selection Using Of AHP-PROMETHEE Methods, XIII. International Logistics and Supply Chain Congress 22, Izmir, Turkey, 23 October [21] Kalkan, M., Sökmen, A., Bıyık, Y., Sağlık hizmetlerinde dış kaynak kullanımı: Ankara halk sağlığı müdürlüğü uygulaması, İktisadi ve İdari Bilimler Fakültesi Dergisi, 17(2), 35-56, [22] Görener, A., Sabuncuoglu, O., Bulanık TOPSIS Metodu ile Karar Verme: İnşaat Projelerinde Yüklenici Seçimi (Decision Making Through the Fuzzy TOPSIS Method: Contractor Selection in Construction Projects).International Journal of Research in Business and Social Science, 5(2), 71-82, 2016 [23] Bedir, N., Özder, E. H., Eren, T., Course Selection with AHP & PROMETHEE Methods for Post Graduate Students: An Application in Kirikkale University Graduate School of Natural and Applied Sciences, The 3rd International Conference on Industrial Engineering and Applications (ICIEA) in Hong Kong, during April 28-30, [24] Bağ, N., Özdemir, N. M., Eren, T., 0-1 Hedef Programlama ve ANP Yöntemi ile Hemşire Çizelgeleme Problemi Çözümü, International Journal of Engineering Research and Development, 4(1), 2-6, [25] Timor, M., Analitik Hiyerarşi Prosesi. İstanbul, Türkmen Kitabevi, [26] Lin C.T., Lee C. and Chen W.Y., An Expert System Approach To Assess Service Performance Of Travel İntermediary, Expert Systems with Applications, 36, , (2009). 122 [27] Yurdakul M., Measuring Long-Term Performance Of A Manufacturing Firm Using The Analytic Network Process, International Journal of Production Research, 41(11): , (2003). [28] Bhattacharya, A., Mohapatra, P., Kumar, V., Dey, P. K., Brady, M., Tiwari, M. K., & Nudurupati, S. S. (2014). Green supply chain performance measurement using fuzzy ANPbased balanced scorecard: a collaborative decision-making approach. Production Planning & Control, 25(8), [29] Hamurcu M., Eren T., Bulanık ANP Kullanılarak Raylı Sistem Projelerinin Önceliklendirilmesi Transist 10. Uluslararası Ulaşım Teknolojileri Sempozyumu ve Fuarı, 2-4 Kasım 2017, 89-97, İstanbul, Türkiye. [30] Meade M.L. and Presley A., R&D Project Selection Using The Analytic Network Process, IEEE Transactions on Engineering Management, 49(1): 59-66, [31] Gencer C. and Gürpınar D., Analytic Network Process In Supplier Selection: A Case Study İn An Electronic Firm, Applied Mathematical Modelling, 31, , [32] Cheng, E.W. L., Li, H. ve Y. Ling, The Analytic Network Process Approach to Location Selection: A Shopping Mall Illustration, Construction Innovation, 5, 83-97, [33] Burnaz, S. ve İ. Topcu, A Multiple-Criteria Decision- Making Approach for The Evaluation of Retail Location, Journal of Multi-Criteria Decision Analysis, 14, 67 76, [34] Partovi, F.Y., An Analytic Model for Locating Facilities Strategically, The International Journal of Management Science, 34, 41-55,

38 T EREN Academic Platform Journal of Engineering and Science 6-2, 25-33, 2018 [35] Tuzkaya,G., Önüt, S., Tuzkaya, U.R., Gülsün B., An Analytic Network Process Approach for Locating Undesirable Facilities: An Example from Istanbul, Journal of Environmental Management, 88(4): , [36] Özcan, E.C., Özcan, N.A., Eren, T., CSP Teknolojisine Sahip Güneş Enerjisi Santrallarının Kombine ANP- PROMETHEE Yaklaşımı ile Seçimi, Başkent Üniversitesi, Ticari Bilimler Fakültesi Dergisi, 1 (1), 18-44, [37] Özcan, E.C., Ünlüsoy, S., Eren, T., ANP ve TOPSIS Yöntemleriyle Türkiye'de Yenilenebilir Enerji Yatırım Alternatiflerinin Değerlendirilmesi, Selcuk University Journal of Engineering, Science and Technology, 5 (2), , [38] Bağ N., Özdemir M., Eren T., 0-1 Hedef Programlama ve ANP Yöntemi ile Hemşire Çizelgeleme Problemi Çözümü International Journal of Engineering Research and Development, 4 (1), 2-6, [39] Özder, E., Gür Ş., Eren T., İşletmelerde Yönetimin Etkinliğini Arttırmak İçin ANP Ve TOPSIS Yöntemleri İle Muhasebe Paket Programı Seçimi, The 13th International Accounting Conference, s , İzmir, Turkey, October 20-21, [40] Brans, J.P. L'ingenierie de la decision: Elaboration d'instruments d'aide a la decision. La Methode PROMETHEE. Universite Laval, Colloque d'aide a la Decision, Quebec, Canada, , [41] Bedir, N.,Eren, T., AHP-PROMETHEE Yöntemleri Entegrasyonu ile Personel Seçim Problemi: Perakende Sektöründe Bir Uygulama, Social Sciences Research Journal,4 (4), 46-58, [42] Bedir, N., Özder, E. H., Eren, T., Course Selection with AHP & PROMETHEE Methods for Post Graduate Students: An Application in Kirikkale University Graduate School of Natural and Applied Sciences The 3rd International Conference on Industrial Engineering and Applications (ICIEA 2016) in Hong Kong, during April [43] Özder, E. H., Bedir, N., Eren, T., Academic Staff Selection With Anp & Promethee Method: A Case Study In Turkey International Academic Conference on Engineering, Technology and Innovations (IACETI), Dubai, UAE, March 5th, [44] Bedir N., Özder E.H., Eren T., The Third Party Logistics Fırm Selection Using Of AHP-PROMETHEE Methods, XIII.International Logistics and Supply Chain Congress October 2015, Izmir, Turkey. [45] Bedir, N., Alağaş, H.M., Eren, T., Çok Ölçütlü Karar Verme İle Demontaj Hattı Dengeleme, Uluslararası Mühendislik Araştırma ve Geliştirme Dergisi, 9(1), 11-18, [46] Taş, M., Özlemiş, Ş.N., Hamurcu, M., Eren, T., Ankara da AHP Ve PROMETHEE Yaklaşımıyla Monoray Hat Tipinin Belirlenmesi, Ekonomi, İşletme, Siyaset ve Uluslararası İlişkiler Dergisi, 3 (1): 64-89,

39 Academic Platform Journal of Engineering and Science 6-2, 34-44, 2018 Academic Platform Journal of Engineering and Science journal homepage: Effects to System Performance of Different PWM Techniques in Field Oriented Speed Control with back-to-back Converter of PMSG 1 Naim Suleyman Ting( ), 2 Yakup Sahin( ) 1 Department of Electrical Electronics Engineering, Engineering Faculty of Erzincan Binali Yildirim University, 24100, Erzincan, Turkey 2 Department of Electrical Electronics Engineering, Engineering Faculty of Bitlis Eren University, 13000, Bitlis, Turkey Received Date: Accepted Date: Abstract In this paper, the performance of space vector pulse width modulation (SVPWM), sinusoidal pulse width modulation (SPWM) and hysteresis current control (HCC) techniques used in speed control with back to back converter of permanent magnet synchronous generator (PMSG) used in wind turbines are comparatively analyzed. The comparative analysis includes dynamic response, total harmonic distortion (THD), torque ripple and current ripple. Furthermore, SVPWM and SPWM are compared in terms of the using DC link voltage. Analysis of system is realized with MATLAB/Simulink program. PMSG used in simulations is surface mounted, bipolar and its power is 1.8 kw. Also, the energy of PMSG is transferred to grid with Field Oriented Control (FOC). According to analysis results, it has been observed that SVPWM generally has more effective results than both HCC and SPWM control techniques. Finally, it is observed that SVPWM can produce about 15 percent higher than SPWM in output voltage. Keywords: Field oriented control, motor control, back to back converter, space vector pulse width modulation, hysteresis control. 1. INTRODUCTION The utilization of renewable energy sources is becoming increasingly important in terms of energy efficiency in recent years. Wind energy is one of the renewable energy sources. The wind turbines are designed to convert the wind energy to electrical energy over the world. There is an electric machine operated as generator for making conversion to electricity energy from mechanical energy in the structure of wind turbine. There are two types of commonly used generator which double fed induction generator (DFIG) and permanent magnet synchronous generator (PMSG) [1, 2]. PMSG offers better performance due to higher efficiency and less maintenance because it does not have rotor current. Furthermore, PMSG can be used without a gearbox, which implies a reduction of the weight of the nacelle and reduction of costs [3-16]. The main advantage of PMSG compared to electrical excited synchronous generators is that PMSG does not require any external excitation current. This feature allows to simplify the rotor structure and use a smaller pole pitch. So, the machines can be designed to rotate at rated speeds of r/min with multiple poles, depending on the generator rated power [1]-[4]. Field Oriented Control (FOC) is used for energy transmission to grid from generator. This energy *Corresponding Author: 1 Department of Electrical Electronics Engineering, Engineering Faculty of Erzincan Binali Yildirim University, 24100, Erzincan, Turkey, Doi: /apjes

40 N S TİNG Academic Platform Journal of Engineering and Science 6-2, 34-44, 2018 transmission is carried out a back to back converter. Back to back converter consist of forced commutated two 3 phase inverter and these inverters are connected each other with a DC link capacitor. Back to back converter provides energy transmission to grid by synchronizing generator frequency and grid frequency [4]. In literature, there are many studies about control strategy of grid-connected converter. In [11], space vector pulse width modulation (SVPWM) and hysteresis current control (HCC) techniques are compared in terms of total harmonic distortion (THD) and dynamic response. It claims that SVPWM has better results than HCC. In [17], SVPWM and sinusoidal pulse width modulation (SPWM) techniques are compared in terms of THD. The THD of SVPWM is lower than SPWM according this study. In [18], SVPWM and HCC are compared in terms of DC link voltage profile. It foregrounds the SVPWM due to its performance. In this paper unlike previous studies in the literatures, the effects to system of three different pulse width modulation (PWM) control techniques in the speed control of PMSG used in wind power systems are compared under the same conditions as terms of dynamics response, THD, torque ripple and current ripple. The comparative analysis of these techniques are presented, and also their advantages and disadvantages are introduced. Fig. 1. Schematic of control strategy for generator side converter FOC for generator-side converter and the current loop control diagram is shown Figure Grid-Side Field Oriented Control In the grid-side converter, the aim is to hold constant the DC link voltage and adjust the active power and reactive power delivered to the grid while wind changing and load transients. In the grid-side converter, a PI controller is used to stabilize the DC voltage [5]. In this paper, DC link reference voltage is selected to 450 V dc because it should be higher than the peak value of grid-phase voltage. As shown in Fig. 2, the current of d-axis i sd_ref is set to value of zero to eliminate the reactive power transferred to grid. 2. CONTROL OF SYSTEM 2.1 Generator-Side Field Oriented Control Fig. 2. Schematic of control strategy for grid side converter In generator-side converter, ω ref and ω is compared to maintain generator operating at optimum situation and obtain maximum energy from wind. By this comparison, i sq_ref is determined. At the same time, the current of d- axis i sd_ref is set to value of zero to obtain the maximum torque [5]. 3. MATHEMATICAL MODELING OF PMSG The PMSG is basically an ordinary AC machine with three phase windings distributed in the slots of the stator to create the flux by stator current which is approximately sinusoidal. It uses permanent magnets in 35 2

41 N S TİNG Academic Platform Journal of Engineering and Science 6-2, 34-44, 2018 rotor to produce the air gap magnetic field instead of using electromagnets. The model of PMSG without damper winding has been developed on rotor reference frame using the following assumptions: 1. Saturation is neglected. 2. The induced EMF is sinusoidal. 3. Eddy currents and hysteresis losses are negligible. 4. There are no field current dynamics [6]. The PMSG dynamic equations are expressed in the d-q reference frame. The voltage equations are given by [1] and flux linkage is given by: φφ ssss = LL dd. ii ssss + φ sq = L q.i sq (1) V sq = R s.i sq + dφ sq -ω dt e.φ sd (2) V sd = R s.i sd + dφ sd -ω.φ dt sq P e = 3 2 (V sd.i sd +V sq.i sq ) (3) Substituting eq (1) in (2) and eq. (2) in (3): PP ee = 3 2 RR ss. ii ssss 2 + RR ss. ii ssss LL dd 3 dd ssss 2 dddd + LL qq dd ssss 2 2 ( ω ee. ii qq. ii dd LL dd LL qq + ω ee. φφ mm. ii qq ) (4) dddd + In here,ϕ m is permanent magnet flux, ω e is electrical speed. The first term refers to the power loss in conductors; the second term refers to ratio variation with time of stored energy in magnetic field and finally, the third term refers to energy conversion. The third term also is equal electromagnetic torque because motor shaft power is equal electromechanical power [7]. According to this information, we can use only the third term to calculate electromagnetic torque: 4. CONTROL TECHNIQUES The control technique used to obtain the switching signals is fairly important in terms of applicability and productivity. If there is not a good control system, a large part of the generated power is wasted. In this study, it is compared to impact to system performance of SVPWM, SPWM and HCC control techniques. 4.1 Space Vector Pulse Width Modulation (SVPWM) SVPWM is a digital modulation technique used in power converter for switching of semiconductor devices. This technique purposes to minimize switching losses and obtain desired output current or voltage with minimum THD. This control technique s advantages are: The less switching power loss due to suitable number of switching compared to HCC. More DC bus utilization than SPWM Low harmonic content in output current with proper switching pattern selection [8]. SVPWM is basically based to be defined as separate space vectors of every switching situation in inverter. There are eight switching situation in there phase inverter. As shown in Fig. 3, according as these switching situations, it consists of six active vectors and two zero vectors. Then, it is calculated phase and interphase voltages of every switching situation as Fig. 3. Also, these voltage values are shown in Table I. T e = 3 2 p p (i q.i d (L d -L q )+φ m.i q ) (5) In this study, since surface mounted PMSG is used, d-axis and q-axis inductances are equal each other. Finally, for PMSG used in this study, electromagnetic torque is shown eq (6): T e = 3 p 2 p.φ m.i q (6) Fig. 3. The switching situations of a three phase inverter 363

42 N S TİNG Academic Platform Journal of Engineering and Science 6-2, 34-44, 2018 The basic principle of SVPWM is to supply a reference voltage vector which approximates as closely as possible to the ideal voltage vector by using eight separate voltage vectors produced by inverter. Finally, it is obtained a reference voltage vector rotated in a hexagonal that created by six active vectors and zero vectors. As shown in Fig. 4, it is consist of six sections in hexagonal. In every section, two active vectors and a zero vector is switched and VV ref is produced. Table 1. Phase and interphase voltages according as switching situations θ = tan -1 V β V α (9) By using Clarke transformation, it can be written to VV ref in three phase axis frame. V ref = 2 3 (VV aa. ee jj0 + VV bb. ee jj2ππ 3 + VV cc. ee jj4ππ 3 ) (10) It can be calculated VV ref in every section if it is written to inside equation (8) V abc values. And this reference voltage is expressed a general equation: V = 2 (VV k 3 dddd. ee jj(kk 1)ππ 3 ) k=1, 2, 3, 4, 5, 6 (11) Then, it can be obtained the switching signals in four steps: Step 1: The section where reference voltage is determined. Step 2: The switching durations (T a, T b and T 0 ) are calculated. Step 3: Control voltages (S 1, S 3 ve S 5 ) determining according as optimal switching sequence are calculated. Step 4: Control voltages (S 1, S 3 ve S 5 ) and carrier triangular signal are compared and so, the switching signals are obtained Determination of Sections As shown in Fig. 4, there is a difference of 60 degrees between the vectors. For example, if it is 0 < θ < 60 0,VV ref is first section. Therefore, to know what VV ref is in the section θ should be calculated. Fig. 4. Rotated reference vector in hexagonal By looking to Fig. 4, it can be obtained the following equations: V ref = VV αα + jjjj ββ (7) V ref = V 2 2 α +V β (8) In eq. (9), the functions as arctan and square root need to calculate θ. But these functions slow down the operating speed of Digital Signal Processor (DSP). Therefore in this paper, it is found in a different way since experimental studies were also considered to be made. The algorithm needed to determinate sections is shown in Fig. 5. The following equations are given with regard to the algorithm. x = 3VV αα (12) 37 4

43 N S TİNG Academic Platform Journal of Engineering and Science 6-2, 34-44, 2018 y = VV ββ (13) z = xx (14) Valfa Vbeta x y z Similar operations are performed also for other sections and times are calculated. These calculations are shown in Fig. 8. Vbeta>0 && Valfa>0 && Vbeta<x n=1; elseif Vbeta<0 && Valfa>0 && Vbeta>=z n=6; elseif Determination of Reference Control Voltages Vbeta>0 && Valfa>=0 && Vbeta>=x n=2; elseif Vbeta>0 && Valfa<0 && y<x n=2; elseif Vbeta>0 && Valfa<0 && y>=x n=3; elseif Vbeta<0 && Valfa>0 && Vbeta<z n=5; elseif Vbeta<0 && Valfa<0 && y>=z n=5; elseif Vbeta<0 && Valfa<0 && y<z n=4; Fig. 5. The algorithm developed to determine the sections Determination of Sections The most important factor is to ensure the minimum switching loss while reference control voltages are determined. So, the most suitable switching sequence for each section is determined and thereby it is provided minimum switching power loss and better harmonic performance. The most suitable switching is only possible when just one switch is transmission or cutting in each switching period. After the section of VV ref is determined by looking Fig. 5, the implementation durations of active vectors in the relevant section can be calculated. For example; in order that VV ref is in the first section, VV 1 should be applied until T a time; VV 2 should be applied until T b time; VV 0 and VV 7 should be applied until T o time. The sum of these three times is equal to a switching period (T s ). Active vectors and zero vectors are VV 0 and VV 7 in the first section. And just one switch is active in each switching period as seen from Fig. 7. Therefore, the minimum switching loss is provided with minimum switching number. The most suitable switching sequence for the first section is shown in Fig. 7. According as Fig. 6, it can be written the following equation: V ref. TT ss = V 1. TT aa + V 2. TT bb + V 0. TT V 7. TT 0 2 (15) Fig. 7. The most suitable switching sequence for first Switching Signals section Fig. 6. The switching times in the first section Substituting eq. (11) in (19) for each vector in the first section: TT aa = m b. VV aa 0.5m a. VV ββ (16) TT bb = m a. VV ββ (17) In here, mm aa = 3 TT ss, mm VV bb = 3 dddd 2 TT ss VV dddd Total switching durations is collected by considering the most suitable switching sequence and reference control voltages (S 1, S 3,S 5 ). There are 120 degrees phase differences between these reference voltages and their waveforms are similar to seagull. The algorithm needed to obtain the switching signals is shown in Fig. 8. Owing to this algorithm, the reference control voltages (S 1, S 3 and S 5 ) are obtained as shown in Fig. 9. Then, according 38 5

44 N S TİNG Academic Platform Journal of Engineering and Science 6-2, 34-44, 2018 as principle of PWM, the reference control voltages obtained are compared with a carrier triangle wave. Consequently, the switching signals of semiconductors elements on the back to back converter are obtained. The comparison of reference control voltages and carrier triangle wave obtained is shown Fig Hysteresis Current Control (HCC) Aim of this control is to keep outside the current of converter within a hysteresis band determined. HCC block diagram for one phase in MATLAB/Simulink is shown in Fig. 11. Valfa Vbeta ma mb n Ts n=1 Ta=mb*Valfa-0.5*ma*Vbeta; Tb=ma*Vbeta; Tc=0.5*(Ts-Ta-Tb); S1=Ta+Tb+Tc; S3=Tb+Tc; S5=Tc; elseif n=2 Ta=mb*Valfa+0.5*ma*Vbeta; Tb=-mb*Valfa+0.5*ma*Vbeta; Tc=0.5*(Ts-Ta-Tb); S1=Ta+Tc; S3=Ta+Tb+Tc; S5=Tc; elseif n=3 Tb=-mb*Valfa-0.5*ma*Vbeta; Ta=ma*Vbeta; Tc=0.5*(Ts-Ta-Tb); S1=Tc; S3=Ta+Tb+Tc; S5=Tb+Tc; elseif Fig. 8. The algorithm developed to obtain the switching signals n=6 Ta=-ma*Vbeta; Tb=mb*Valfa-0.5*Ta; Tc=0.5*(Ts-Ta-Tb); S1=Ta+Tb+Tc; S3=Tc; S5=Ta+Tc; elseif n=5 Ta=-mb*Valfa-0.5*ma*Vbeta; Tb=mb*Valfa-0.5*ma*Vbeta; Tc=0.5*(Ts-Ta-Tb); S1=Tb+Tc; S3=Tc; S5=Ta+Tb+Tc; elseif n=4 Tb=-ma*Vbeta; Ta=-mb*Valfa+0.5*ma*Vbeta; Tc=0.5*(Ts-Ta-Tb); S1=Tc; S3=Ta+Tc; S5=Ta+Tb+Tc; Fig. 11. HCC block diagram for one phase in MATLAB/Simulink In here, the measured load currents are compared with the references by using hysteresis comparators. Each comparator determines the switching state of the corresponding inverter leg such that the load currents are forced to remain within the hysteresis band. Based on the band, there are two types of current controllers, namely, fixed band and sinusoidal band hysteresis current controller [10]. Fig. 9. Comparison of reference control voltages and carrier triangle wave Fig. 12. HCC A phase current wave and the first phase arm IGBT control signal Fig. 10. The switching signals for sixth section and the first section Upper band and lower band limits for reference and real currents are determined by hysteresis band for a phase. As shown in Fig. 12, the ripple of real current always is within hysteresis band. If real current reaches or exceeds to upper band, while the element on upper of the first phase arm is turned off (T1=0), the element on upper of 39 6

45 N S TİNG Academic Platform Journal of Engineering and Science 6-2, 34-44, 2018 the first phase arm is turned on (T4=1). Thus, the current is reduced. Conversely, if real current reaches or exceeds to lower band, while the element on upper of the first phase arm is turned on (T1=1), the element on upper of the first phase arm is turned off (T4=0). Thus, the current is increased. This control technique s advantages: The simple control algorithm Dynamic response speed There is no need to information about load parameters [11]. 4.3 Sinusoidal PWM The most popular PWM approach is the sinusoidal PWM. In this method, a triangular (carrier) wave is compared to a sinusoidal wave at the desired fundamental frequency. So, the relative levels of the two signals are used to determine the pulse widths and control the switching of devices in each phase leg of the inverter. Therefore, the pulse width is a sinusoidal function of the angular position [8].In SPWM technique, the generated reference voltages are continuously compared with the triangular carrier wave. When the value of the sine wave is greater than triangular wave, the upper switch of the related phase is switched ON; otherwise the lower switch is switched ON. Due to SPWM technique, the output contains less harmonic content as compared to the square wave inverter. The output contains the high frequency harmonics which depends upon the frequency modulation index. As the frequency modulation index increases the harmonic spectrum shifts towards higher frequency, which can be easily filtered out. To be increased the index also leads to increase in switching frequency. The amplitude of output voltage can be controlled by varying the amplitude of the reference voltage [12]. 5. SIMULATION RESULTS AND DISCUSSION Comparison of SVPWM, SPWM and HCC control techniques used to obtain converter switch signals in speed control of PMSG are analyzed in terms of dynamic response, harmonic content, torque ripple and current ripple with MATLAB/Simulink. The motor parameters used in simulation are given Table I. In HCC, the band width is set to hold constant the switching frequency by 10 khz. Table 2. Pmsg Parameters Nominal Power (P) 1.8 kw Impedence (R s ) Ω q-axis inductance (L q ) 7.31 mh d-axis inductance (L d ) 7.31 mh Magnetizing flux (φφ m ) Wb Torque/Current (T/A) Nm/A Pairs of poles (p p ) 2 Moment of Inertia (J) kg/m 2 Coefficient of Friction (B) 0 The analysis are carried out according to the values of V eff = 155 V, f = 50 Hz, DC link capacitor voltage = 450 V and angular velocity of PMSG = 200 rd/sec. Additionally, the generator are applied to a load torque (T e = 10 Nm) depending on power obtained from wind. All of comparisons are made in the same conditionals as PI parameters, reference angular speed etc. The switching frequency is constant 10 khz in SVPWM and SPWM but it is not constant in HCC. Because the ripple of current changes by depending on band width in HCC. Nevertheless, this three control technique based on a common value can be compared. Hence, in this paper, the setting band with is values because it is provided that the average switching frequency is 10 khz for HCC. It desired that the switching frequency varies nearly between 5 khz - 15 khz in fundamental cycle for 10 khz average switching in HCC. This case can be determined by band with. The average switching frequency can be obtained by 10 khz when band with is Comparison Based on THD The current wave forms are usually discussed for 407

46 N S TİNG Academic Platform Journal of Engineering and Science 6-2, 34-44, 2018 analysis of THD. In this paper, the integrity of system operation is provided and the grid current waveforms are examined for THD. Fig. 13 shows THD analysis at 10 khz switching frequency for the grid currents with SVPWM, SPWM and HCC. THD values can read from Fig in SVPWM. Therefore, HCC technique is more advantageous than the other two techniques in terms of current harmonic content. Besides, these results are quite suitable if it is considered that THD should be less than % 5 in inverter transferred to grid as mentioned in ref [11]. Similar results are observed for the currents of generator in a wind power system. 5.2 Comparison Based on Dynamic Response Speed (a) It is mentioned in ref [11] that dynamic response is required to be as fast as possible. The generator current waveforms obtained with SVPWM, SPWM and HCC by lowering the load torque at 0.6 seconds are showed in Fig. 14. In here, according to motor parameters, Torque/Current value is 1.12 Nm/A. Since torque is 10 Nm in this study, peak value of generator s current must be 8.9 A. (b) As shown in the Fig. 14, in such a case while real current becomes zero time 200 micro-seconds with SVPWM and SPWM technique, it becomes zero time about 70 microseconds. The reason of these results that SVPWM and SPWM control block has three PI controllers but HCC has one PI controller for both generator side control and grid side control. Therefore, it is clear that the use of HCC technique is better than the use of both SVPWM and SPWM in terms of dynamic response. Likewise, similar results are observed for the currents of grid in a wind power system. (c) Fig. 13. THD analysis for (a) SVPWM, (b) SPWM and (c) HCC techniques As shown in Fig.13, THD of the grid currents obtained by using HCC is % 3.61; it is % 4.95 in SPWM and is % Fig. 14. Dynamic response analysis of the generator currents for (a) SVPWM, (b) SPWM and (c) HCC techniques 41 8

47 N S TİNG Academic Platform Journal of Engineering and Science 6-2, 34-44, Comparison Based on Torque Ripple The ripple is an undesirable situation in power systems. The ripple of electromagnetic torque obtained separately by using SVPWM, SPWM and HCC is shown on Fig.15. As results obtained, the torque ripple is about 1.33 in control with HCC and it is about 0.9 in control with SPWM while it is about 0.75 in control with SVPWM. ripple factor. Consequently, Table 3 is formed according as the results obtained. Type of Controlle r Table 3. Comparısıon of Control Technıques Dynamic Curren Torque Respons t THD Ripple e Curren t Ripple SVPWM % 4.68 Slower Lower Lower SPWM % 4.95 Slower Mediu m Medium HCC % 3.61 Faster Higher Higher 5.5 Comparison of SVPWM and SPWM Based on the Use of DC Link Voltage Fig. 15. Torque ripple analysis for (a) SVPWM, (b) SPWM and (c) HCCtechniques 5.4 Comparison Based on the Grid Current Ripple In addition to those described results, the literature research says to have benefited % 15 more from the DC bus with SVPWM control technique compared with SPWM. Also, modulation index to obtain same output voltage is equal 3.V ref /V dc in SVPWM while it is equal V dc /2 in SPWM [13]. In this paper, this result also is obtained. Modulation index (m a ) obtained with SVPWM while output voltage is equal to V is shown Fig. 17. In the same way, m a obtained with SPWM while output voltage is equal to V is shown Fig. 18. It can be examining to grid currents shown in Fig.16 for the current ripple quality between the use of SVPWM, SPWM and HCC techniques. As results obtained, the ripple is about (2BW) in control with HCC and it is about 1.5 in control with SPWM while it is evaluated about 1.15 in control with SVPWM. Fig. 17. Modulation index obtained with SVPWM for V output voltage Fig. 16. The grid currents ripple analysis for (a) SVPWM, (b) SPWM and (c) HCC techniques So, it is clear that the control with SVPWM is more suitable than control with HCC systems in terms of Fig. 18. Modulation index obtained with SPWM for V output voltage 429

48 N S TİNG Academic Platform Journal of Engineering and Science 6-2, 34-44, 2018 As shown in figures, m a is 0.6 in SVPWM while m a is 0.69 in SPWM in case of obtained the same output voltage. The rate of these modulation index is 15 percent. So, it is clear that it has benefited % 15 more from the DC bus with SVPWM control technique compared with SPWM. In other words, it can be commented that these modulation index values in that if modulation indexes are equal for SVPWM and SPWM then it will be produced % 15 more output voltage in SVPWM than in SPWM. 7. CONCLUSIONS In this paper, the performance of system is tested in MATLAB/Simulink by using SVPWM, SPWM and HCC in the control of SMSG. For this, PMSG is connected to grid via a back to back converter and power transfer to grid is provided. It is examined that modulation techniques (HCC, SPWM and SVPWM) used to be obtained switching signals of back to back converter and in terms of some features impact to system of these techniques is researched. By considering all specifications by looking TABLE III and the other results, the use of SVPWM is more suitable than HCC and SPWM for speed control of PMSG. SVPWM uses lower DC link voltage for the given application and reduces the harmonic content of both grid current and generator current. Because of its superior performance characteristics, the space vector modulation technique is widely used in recent years. REFERENCES [1] A. Rolan, A. Luna, G. Vazquez, D. Aguliar, and G. Azevedo, Modelling of a Variable Speed Wind Turbine with a Permanent Magnet Synchronous Generator, IEEE International Symposium on Industrial Electronics,Seoul, pp , 2009 [2] C. Busca, A.I. Stan, T. Stanciu D.I. Stroe, Control of Permanent Magnet Synchronous Generator for Large Wind Turbines, Industrial Electronics Symposiom, Bari 2010, pp [3] M.M. Hussein, M. Orabi, M.E. Ahmed, M.A. Sayed, Simple Sensorless Control Technique of Permanent Magnet Synchronous Generator Wind Turbine, International Conference on Power and Energy, Kuala Lumpur, Malaysia, 2010, pp [4] K. Huang, S. Huang, F. She, B. Luo, L. Cai, A Control Strategy for Direct-drive Permanent Magnet Wind Power Generator Using Back to Back PWM Converter, ICEMS 2008 Conference, Wuhan, pp [5] S. Yang, L. Zhang, Modelling and Control of the PMSG Wind Generation System with A Novel Controller, Third International Conference on Intelligent System Design and Engineering Applications, 2013, pp [6] J. Pradeep, R. Devanathan, Comparative Analysis and Simulation of PWM and SVPWM Inverter Fed Permanent Magnet Synchronuos Motor, ICETEEEM Conference, 2012, India. [7] A. Cimpoer, Encoderless Vector Control of PMSG for Wind Turbine Applications, Master Thesis, Aalborg University Institute of Energy Technology, 2010, Denmark. [8] E. Hendawi, F. Khater, A. Shaltout, Anlysis, Simulation and Implementation of Space Vector Pulse Width Modulation Inverter, 9th WSEAS International Conference [9] K.V. Kumar, P.A. Michael, J.P. John, S.S. Kumar, Simulation and Comparison of SPWM and SVPWM Control for Three Phase Inverter, ARPN Journal of Engineering and Applied Sciences, pp , 2010 [10] A. Nachiappan, K. Sudararajan, V. Malarselvam, Current Controlled Voltage Source Inverter Using Hystresis Controller and PI Controller, EPSCICON Conference, 2012, Kerela

49 N S TİNG Academic Platform Journal of Engineering and Science 6-2, 34-44, 2018 [11] E. İsen, A.F. Bakan, Comparison of SVPWM and HCC Control Techniques in Grid Connected Three Phase Inverters, ELECO 2010, [12] R. Bhosale, J. Shaikh, R. Bindu, Analysis of Inverter Modulation Strategies for Vector Controlled Drives, International Journal of Advances in Electrical and Electronics Engineering, pp [13] B. K. Swamy, P. N. Rao, Simulation of A Space Vector PWM Controller for A Three-Level Voltage-Fed Inverter Motor Drive, International Journal of Advanced Trend in Computer Science and Engineering, 2013, pp [14] H. Shariatpanah, R. Fadaeinedjad, G. Moschopoulos, An investigation of furl control in a direct-drive PMSG Wind Turbine, Telecommunications Energy Conference, 2014, Vancouver Canada. [15] A. Kumar, B. Parasannakumari, E. Varghese, Space Vector PWM and Fractional Controller based Wind Energy Conversion Systems, International Conference on Advances in Green Energy, 2014, Trivandrum. [16] M. R. Abedi, K. Y. Lee, Modelling, Operation and Control of Wind Turbine with Direct Drive PMSG Connected to Power Grid, Pes General Meeting Conference, [17] J. Sabarad, G. H. Kulkarni, Comparative Analysis of SVPWM and SPWM Techniques for Multilevel Inverter, International Conference on Power and Advanced Control Engineering, 2015, pp [18] N. Viswanath, A. K. Kapoor, Performance Estimation of HCC and SVPWM Current Control Techniques on Shunt Active Power Filters, International Conference on Power,Control and Embedded Systems, 2010, pp

50 Academic Platform Journal of Engineering and Science 6-2, 45-54, 2018 Academic Platform Journal of Engineering and Science journal homepage: Torsional Loading Behaviors of Slotted Filament Wound Glass Fiber Reinforced Composite Tubes Abstract *İbrahim Fadıl Soykök( ) * Department of Mechatronics Engineering, H.F.T. Faculty of Technology, Manisa Celal Bayar University, Turgutlu, Manisa, Turkey Received Date: Accepted Date: The stress and strain behaviors of filament wound glass-fiber epoxy based cylindrical tube structures made of two different stacking sequences as [(±45 ) 5 ] and [(0/ 90) 5 ] were numerically investigated under a constant torque value. The exterior surfaces of tubes were deliberately defected by longitudinally extending, rounded end, 0.6 mm deep, 2 mm wide but varying-length slots. Slot-less and full-length-slot structures were also included in the study. During torsional loading, the variations in stresses, strains and twisting angles of the specified thin-walled composite tube models were investigated, comparatively. Additionally, the effects of fiber winding angles and slot lengths on the specified quantities were parametrically examined. A considerable amount of stress accumulation around the slot tip of both type of tube model is measured which constitute a risk of damage progression. At the innermost laminas, slight fluctuations in the maximum stresses are observed in the slot lengths shorter than 140mm, whereas rapid increases are remarkable for exceeded lengths. On the other hand, the maximum stress changes in the outermost layer are quite uneven. From slot-less to full-length-slot, the change in slot dimensions provokes 8.32 and 9.11 % increments in twisting angles in the 45 /-45 angle-ply and 0 /90 cross-ply structures, respectively. Under the same loading condition, [(±45 ) 5 ] stacking sequence gives the structure averagely 0.66 lower total rotation at the specimen tip in comparison to [(0/ 90) 5 ] fiber arrangement. Keywords: Filament winding, Glass-fiber epoxy, Composite tubes, Torsion 1. INTRODUCTION Due to the rapidly expanding use of composite materials especially in aerospace, automotive and marine industries, investigating the multi-axial tensile stresses both numerically and experimentally has become more important since a few decades. Hollow cylindrical components, which are generally designed as carrier bars in vehicle bodies, can meet different challenges, such as bending, torsion and buckling, simultaneously or alternatively. This study will generally be based on a numerical examination of the effect of the torsional moments on the glass-fiber / epoxy tubes produced by filament winding technique. Because of the anisotropic nature of the material, numerous experimental studies have been conducted so far and they have been verified and supported by numerical examinations like the current one. In a study by Meijer and Ellyin [1], multi-axial experimental tests of tubes produced by filament winding method showed that the first faults and fracture occur in the outer shell. The specimens tested for various axial stresses to the internal stress ratios was adjusted to the MTS test system prior to applying axial force and internal pressure simultaneously. Five different failure modes such as spiral cracks, regional leakages and axial collapses were observed on the tubes exposed to aforecited load ratios. Burda et al. [2] studied sintered glass fiber polymer matrix composite bars produced industrially for various applications. Beside these bars, a double console beam specimen is also designed for delamination tests in semi-static mode. During the investigation of the case, the size and shape of the test specimens, the load starting type, and different pre-cracking methods were examined. Perillo et al. [3] reported a complete application procedure which was used to evaluate the performance of the newly developed test methodologies for composite filament wound composites produced from glass-vinilester and carbonepoxy materials which are known as essential for making some aircraft components. In the new method developed for biaxial testing, an arrangement is made to reduce the stress * Corresponding author: Department of Mechatronics Engineering, H.F.T. Faculty of Technology, Manisa Celal Bayar University, Turgutlu, Manisa, Turkey, GSM: Doi: /apjes

51 İ F SOYKÖK Academic Platform Journal of Engineering and Science 6-2, 45-54, 2018 concentration at the sample edges. Furthermore, the amount of void space produced by the newly applied optical method has been evaluated. Martins et al.[4] applied internal pressure to filament wound composite tubes in order to find out burst pressures. Closedend four thin-walled and various wind angle E-glass fiber/epoxy tube models were subjected to pressure loading by employing an alternative damage method. In terms of the leakage and burst failure pressures numerical results performed in ABAQUS and experimental data showed a good agreement. As a follow up study Martins et al.[5] performed progressive failure analysis by using finite element method in order to determine the minimum specimen length for representing infinite tube, to find the optimum wind angle and the influence of diameter and thickness on the tubes subjected to internal pressure. The parametric study has given optimum wing angles of 53.25, 74.5 and 88 degrees for closed, restrained and open-end conditions, respectively. It was also found that the failure pressure changes linearly in accordance with h/r (mean thickness / Radius) ratio. Morozov [6] draws the attention on some manufacturing effects of filament winding process. The study claims that the filament-winding mosaic pattern of the composite layer has not been taken into account in previous studies which could significantly affect the stress and strain fields in the thin-walled composite structure. Actually, this effect has been clearly demonstrated numerically by using particular examples. Hafeez and Almaskari by V shaped cradles at each end. The compliance of behavior with the scaling law of Buckingham Pi theorem was investigated with tests for four different scales. Contrary to the previous findings, semi-circular cradle supported specimens resting on V support have given[7] applied lateral indentation to glass fiber / epoxy filament wound thin walled tubes supported higher loads and bigger damage area for same indentation displacement. The load required for delamination initiation has been found same for both floor supported and V supported specimens. Xing at al. [8] analyzed varying winding angle structures under axial loading, internal and external pressure. First the results related to deformation and stresses of orthotropic layers were obtained, analytically and then they were compared with the numerical data. The usage of multi angle filament-wound composites has been found to increase material utilization and working pressure. Interestingly, it was found that a constant through thickness strength for multi angle wound cylindrical vessel under internal pressure is obtained by applying gradual bigger winding angle outward. Another study conducted by Mertiny et al. [9] maintains also considerable advantages of multi-angle winding technology over pure angle-ply lay-ups. The performances of multi-angle and ± α angle-ply lay-up filament wound structures were compared by assessing experimental results in terms of failure stresses, failure modes and stress-strain curves. Under various loading conditions, multi-angle wound structures exhibited an overall better performance in resisting damage. Krishnan et al. [10] performed a multi-axial cycling loading on glass/epoxy composite tubes with different winding angles. By the aid of a novel test equipment, the tubes with three different winding angles were subjected to five stress ratios from pure axial to pure hoop loading. The results showed a strong relation between optimum winding angle and the ratio of applied stresses. Loading condition is a deterministic factor affecting mechanical response of filament wound composite tubes having diverse winding patterns. As an alternative loading type, Moreno et al. [11] studied external pressure behaviors of cylindrical specimens having stacked layers with coincident patterns in a hyperbaric testing chamber. Buckling pressures and modes of thin walled cylinders were predicted analytically and verified by experimental results. Buckling behavior of cylinders did not seem to be influenced by two chosen winding patterns, whereas, length to diameter ratio and thickness have very expectedly a direct influence on the buckling response. As can be seen in the previous studies, the winding pattern and loading conditions is regarded as the main factors influencing under load behavior and failure response of filament wound composite tubes in design. However if the tube has been damaged somehow, its ability to carry on functioning until replaced or repaired becomes more important. Deep scratches created by a pointed tip are one of the most significant damages which result in stress concentrations triggering a sudden breakage or deformation of the thin walled cylindrical structure. In the present study, the specified scratch damage was tried to be modeled with a rectangular-cross-section wedge slot formed longitudinally on the outer wall of the tubes. The results of two different types of winding e.g. cross-ply (0-90 ) and angle-ply (45 / -45 ) is identified parametrically, while examining the effects of different lengths of slots on stress distribution and angle of distortion. 2. MODEL GEOMETRY, MATERIAL AND LOADING CONDITIONS Consider a thin walled hollow cylindrical tube with the outer and inner diameters of 18 mm and 16 mm, respectively. Through 1 mm thickness in radial direction, the tube has ten orthotropic layers each of which has 0.1 mm thickness. The fiber orientations of each adjacent plies of the tube are different which gives the structure resistance under multiaxial loading. Fiber orientation angle, the angle between fibers and rotation axis is formed as ± θ at each sub-laminate due to the nature of the filament winding process. This angle is automatically adjusted by filament winding device (Fig. 1) by means of controlling the rotation speed of the mandrel and the linear motion rate of the horizontal carrier [12]. 46

52 İ F SOYKÖK Academic Platform Journal of Engineering and Science 6-2, 45-54, 2018 Fig.1 : Schematic illustration of filament winding process (Tele et. al,2016) All of the specimens discussed within the scope of this paper is exposed to a fixed torque of 10 Nm in order to evaluate the actual influence of geometrical defects on the maximum stresses, strains and twist angles. The specimens are of 180 mm length which is an adequate length to extract accurate values of twist angles for each structure geometry. Although D5448/D5448M [13] Standard Test Method for In-plane Shear Properties of Hoop Wound Polymer Matrix Composite Cylinders gives useful definition of clamping fixture to apply torsional moment, the tube s geometrical values is not restricted and not defined for the current specific procedure. Nevertheless, the size and dimensions of the sample has been chosen from among the most encountered in practice. Two different types of stacking sequence that constitute the thin-walled epoxy based glassfiber reinforced tube structure have been studied. One of them is selected as an angle-ply laminate structure having 10 equal-thickness layers of [(±45 ) 5 ] fiber orientations [14]. The latter is a [(0/ 90) 5 ] fiber orientated cross-ply laminate structure manufactured by coating the pre-preg sheets around the mandrel. It is also made of 10 equalthickness laminas. Because filament wound process allows to be produced merely angle-ply laminas, making use of the pre-preg layers is essential for creating a cylindrical structure with fibers oriented at 0 and 90 degrees. In order to model the effects of deep scratches that may have been created by any sharp point during operation and is considered to weaken the structure, 2 mm wide, 0.6 mm deep rectangular cross-section wedge slots were processed on the outer surfaces of the filament wound tubes in the longitudinal direction. This means that a total of six layers inward from the outer surface to the radial direction are affected by the grooving process. Providing that the slot depths and widths stay fixed, the effect of variations in slot lengths on torsional behavior of the tubes made of two alternate layered compositions was investigated parametrically. As listed in Table 1, 18 different types of specimen were defined according to their slot dimensions and corresponding locations. In order to illustrate the slot positioning on the tube geometry, Fig. 2 is given as an example representing the type 6 slotted specimen. It is worth noting that, the type 1 specimen stands for the slotless model for the purpose of defining a perfect and nondamaged specimen. The torsional responses of the two different material designs of non-slot specimens (0 / 90 and 45 / - 45 ) were also examined separately. Fig.2 : Schematic illustration of type 6 specimen with a 0.6 mm slot depth and displayed slot dimensions. Each specimen is 180 mm long and has 16 and 18 mm inner and outer diameter. 47

53 İ F SOYKÖK Academic Platform Journal of Engineering and Science 6-2, 45-54, 2018 Table 1. Specimen types according to slot lengths and slot distance to specimen tips Specimen Type Number Slot length (mm) Slot distance from the tip (mm) Slot tip radius (mm) The finite element models were developed and analyzed according to the given material and geometrical specifications. Glass-fiber and epoxy matrix elastic properties and endurance limits used in the numerical solution can be found in Table 2. Quasi-static torsional loads were applied on to the free ends of the composite tube specimens where other ends are fixed. Table 2. Orthotropic properties of E-glass fiber reinforced epoxy based composite material Density x 10-9 kg/m 3 Young's Modulus in dir. x (MPa) Young's Modulus in dir. y (MPa) Young's Modulus in dir. z (MPa) Poisson's Ratio xy Poisson's Ratio yz Poisson's Ratio xz Shear Modulus xy (MPa) Shear Modulus yz (MPa) Shear Modulus xz (MPa) RESULTS AND DISCUSSION The glass fiber reinforced epoxy tubes with 16 mm inner and 18 mm outer diameter and with a total length of 180 mm was subjected to a 10 Nm static torsional load from one end while the other end is fixed. Finite element models (FEM) were developed to define two types of composite tube structures as [(0/ 90) 5 ] and [(±45 ) 5 ] fiber orientations. The tubes were deliberately defected by longitudinally extending, 0.6 mm deep and 2 mm wide but varying-length slots. An appearance of a meshed geometry relating to the 50 mm long slot with locally refined element sizes is given Fig. 3. The both ends of the slot clearance were rounded at a radius of 1 mm, which is formed by the shape of the milling cutter. Fig.3 : Mesh configuration in the vicinity of the slot for the type 6 specimen 48

54 İ F SOYKÖK Academic Platform Journal of Engineering and Science 6-2, 45-54, 2018 Fig. 4 illustrates equivalent Von-Mises stress distribution on the outermost laminate of the type 6 (see Table 2) epoxy based specimen with [(0/ 90) 5 ] glass fibers during the application of a static load of 10 Nm Torsional Moment. Apparently, maximum stress was measured as around 60 MPa in red colored areas of the outermost layer of the tube structure. Although the most critical region and the highest stress concentration is found to appear on both sides of the slot line near the tip of the tube, it is clear that at least a part of the slot perimeter is also affected by the stress accumulation with about 45 MPa stress level according to the color chart. Thus, the notch effect based on the discontinuity formed by the slot cavity at the outermost layer must also not be ignored. Conversely, remaining parts of the slot vicinity exhibited the lowest stress values with a substantial stress relaxation. Generally, in comparison to those of measured in the outermost lamina, the stresses in innermost lamina have been found as far more severe according to Fig. 5, and reaches to MPa at some points. The maximum stress marker and red areas are located at the extreme end of the tube; however these high stresses are doubtlessly originated by the stress accumulation due to limited load application area. This type of intensifications can be easily eliminated by expanding the load application surface. As for the other regions, the actual stress intensity occurs in the area below the tip of the slot clearance at nearly 60 MPa, which is about 33.3 % higher than that calculated in the slot vicinity but nearly the same as calculated in the most critical region of the outermost layer. Fig.4 : Equivalent Von-Mises stress distribution on the outermost lamina of the type 6 specimen with [0/90/0/90/0/90/0/90/0/90] fiber orientations Fig.5 : Equivalent Von-Mises stress distribution on the innermost layer of the type 6 specimen with [0/90/0/90/0/90/0/90/0/90] fiber orientations 49

55 İ F SOYKÖK Academic Platform Journal of Engineering and Science 6-2, 45-54, 2018 Unlike the [(0/ 90) 5 ] oriented specimen type, the maximum stress intensification at the outermost lamina is seen at a tip of the slot perimeter of the tube with a [(±45 ) 5 ] laminated structure (Fig. 6). The remaining stress accumulations are about the same as observed in [(0/ 90) 5 ] oriented structure in terms of value as well as location. As for the innermost lamina which has not been damaged by milling process, stress concentration below the slot clearance reaches to a level of almost 70 MPa, whereas maximum stress is found to be as MPa exactly in the load application region. Thus, comparing with [(0/ 90) 5 ] laminate, it can be said for [(±45 ) 5 ] fiber oriented structure that, relatively higher stresses are generated by the same torsional load, not only in the circumferential and subjacent areas of slots, but also in the load application zone of the tube specimen. Stress accumulation regions observed at the innermost lamina of [(±45 ) 5 ] filament wound specimen ( Fig. 7) seem to be analogous with the [(0/ 90) 5 ] pre-preg tube specimen except for the stress values. Approximately, % increase in equivalent stress level is measured under slot clearance area when [(±45 ) 5 ] filament wound material is used instead of [(0/ 90) 5 ] laminated structure. Besides this, the maximum stress value detectable at any point also increased by % at the extreme end of the innermost layer of the [(±45 ) 5 ] structure in comparison to that of the [(0/ 90) 5 ] structure. Fig.6 : Equivalent Von-Mises stress distribution on the outermost layer of the type 6 specimen with [45/-45/45/-45/45/-45/45/- 45/45/-45] fiber orientations Fig.7 : Equivalent Von-Mises stress distribution on the innermost layer of the type 6 specimen with [45/-45/45/-45/45/-45/45/- 45/45/-45] fiber orientations 50

56 Stress (MPa) İ F SOYKÖK Academic Platform Journal of Engineering and Science 6-2, 45-54, 2018 Maximum stresses are observed to be also changeable according to slot lengths in axial direction and the variation can be said to be not in a linear manner in outermost layer according to Fig. 8. This unsteadiness in stress increase in case of slot length change is probably caused from the fiber discontinuities in outermost layer which inhold the slot cavity. Considering that slot lengths of 0 and 180 mm represent tubes with slot-less and full length slots, respectively, the changes in maximum stresses of the outermost layer displays a fluctuating course. The slotless geometry of the laminated materials made of both [(±45 ) 5 ] and [(0/ 90) 5 ] stacking sequences, give the same top stress levels, however different state of stresses takes place on outermost lamina of each specific model in the case of the presence of the slot cavity. It is worth noting that the maximum stress measured as MPa at outermost layer of [(0/ 90) 5 ] laminate develops when slot length is 30 mm, whereas the [(±45 ) 5 ] laminated specimen with 170 mm slot length gives the maximum outermost lamina stress as MPa. In other words, the maximum stress levels reaches at an analogous peak point at different slot lengths in both types of structure with dissimilar fiber orientations. Another striking point is that the calculated maximum stress at the outermost layer of the slot-less [(±45 ) 5 ] structure is the same as that of the thoroughly slotted [(±45 ) 5 ] structure. This suggests that discontinuous longitudinal cuts in tubular structures made of [(±45 ) 5 ] fibers are more damaging as compared to continuous shallow cuts. However, it is not right to use the same expression for [(0/ 90) 5 ] prepreg composite tube constructions. Because, when the maximum stress points in this structure are examined, it is obvious that there is a clear difference of 16,193 MPa between the slot-less structure and the thoroughly slotted [(0/ 90) 5 ] structure. Top 45/-45 Top 0/ Slot Length (mm) Fig.8 : Maximum von-mises stress level detected on the outermost layer of the filament wound tubes of different slot lengths As regards the maximum stress variation in the innermost layer (Fig. 9), a regular increase in the maximum stress can be detected as the case changes from slot-less to full-length slotted tube structure (0-180 mm), contrary to the situation on the outermost layer. None the less, the slot-less structures of two different material types ([(±45 ) 5 ] and [(0/ 90) 5 ] ) of stacking sequence give very close values, just as the situation observed in the outermost layer. When switched to the slotted structure, two sort of material model display a marked difference in maximum stresses and the difference gets even larger starting from 140 mm slot length to full length slot. While the top maximum stress between two sorts of material in the outermost layer varies according to the slot lengths as seen in Fig. 8, the innermost layer with the highest maximum stress is continuously the 45 angle lamina, regardless of slot length. In general, it can be acknowledged for both of the material models that, the stress state at the innermost layer changes with respect to the slot length more smoothly than that measured at the outermost layer. The situation proves that the stress state at the innermost lamina which has not been affected by slot damage is more predictable for any length of void defect. 51

57 Strain (mm/mm) Stress (MPa) İ F SOYKÖK Academic Platform Journal of Engineering and Science 6-2, 45-54, 2018 Bottom 45/-45 Bottom.0/ Slot Length (mm) Fig.9 : Maximum von-mises stress level detected on the innermost layer of the filament wound tubes of different slot lengths Maximum strains detected at outermost and innermost lamina are presented in Fig. 10 and Fig. 11, respectively. As a result of 10 Nm torsional moment, the structure with 45 /- 45 oriented fibers has apparently highest maximum strains at the outermost lamina between 30 mm and 120 mm slot lengths, whereas the 0 /90 structure exhibited further amount of deformation under and above the specified range. In both of the structures, it is possible to define three characteristic maximum elastic strain regions separated by 30 and 120 mm vertical lines. Interestingly, values in both structures exhibit an opposite state of maximum stress to each other. This can be attributed that the principal and maximum shear stress axes in pure torsion coincide with the winding directions in both structures. On the other hand, maximum strain levels detected at the innermost lamina of the both structures have also three characteristic regions separated by 20 and 160 mm vertical lines. In the maximum strain levels of the both structures, a rapid increase in the first part of slot lengths (0-20 mm), fluctuations in opposite directions in the second part ( mm), and a more sudden increase in the last part ( mm) are visually detected. The situation gives a clue about which distance from the slot tip to the tube end is starting to be critical in torsion for fiber reinforced plastic tubes made of angle and cross-ply laminates. Top 45/-45 Top 0/90 0,007 0,006 0,005 0,004 0,003 0,002 0, Slot Length (mm) Fig.10 : Maximum strain levels detected on the outermost layer of the filament wound tubes of different slot lengths 52

58 Twist Angle ( ) Strain (mm/mm) İ F SOYKÖK Academic Platform Journal of Engineering and Science 6-2, 45-54, ,012 Bottom 45/-45 Bottom 0/90 0,01 0,008 0,006 0,004 0, Slot Length (mm) Fig.11 : Maximum strain levels detected on the innermost layer of the filament wound tubes of different slot lengths 3,7 Twist Angle 45/-45 Twist Angle 0/90 3,5 3,3 3,1 2,9 2,7 2, Slot Length (mm) Fig.12 : Maximum twisting angles detected on the tip of the of the 18 mm long filament wound tubes of different slot lengths The total rotation angles at the extreme ends of the tubes shown in Fig. 12 are one of the most prominent results of the current study. The first notable point here is that there is a significant difference in rotation angle between the two tube structures that differ in terms of fiber orientation. The difference in twist angle between two structures begins with the slot-less tube and is maintained up to the vertical border representing the full slot specimen. Although it varies for each slot length, there is an average difference of 0.66 between the rotation angles of two separate types of structures for all slot lengths. Another important aspect related with the curves is that the slots longitudinally processed on the outer surfaces of the hollow cylindrical specimens significantly increase the twisting angle in both cases of [(±45 ) 5 ] and [(0/ 90) 5 ] structures despite a slight geometric defect created deliberately. When the situation of the 45 /-45 angle-ply structure is examined, the twist angle measured as 2.72 in the slot-less case increased by 8.32 % up to the case of full-length slot, in association with extended slot length. It is also possible to observe a similar increase when 0 /90 structure is investigated. While the amount of angular deformation at the end of the flawless structure is limited to 3.36, it reached up to 3.67 during the examination of full-length slotted structure, by an 53

59 İ F SOYKÖK Academic Platform Journal of Engineering and Science 6-2, 45-54, 2018 increase of 9.11 %. This can be regarded as an indication of the importance of longitudinal slots in thin-walled cylindrical composite structures and how much the torsion resistance tends to decrease depending on the slot length. 4. CONCLUSION: Torsional loading responses of two types ([(±45 ) 5 ] and [(0/ 90) 5 ]) of hollow thin-walled (1 mm) cylindrical tubes (with 16 mm inner diameter and 180 mm length) were investigated throughout the current numerical examination. The effects of rounded end, 2 mm wide and 0,6 mm deep slots created in longitudinal direction were investigated under 10 Nm constant torsional loading condition for the two specified kind of structure. Based upon the results of the study the following conclusions can be made: While the notch effect based on the discontinuity formed by the slot cavity at the outermost layer is non-negligible at the slot tip, remaining parts of the slot vicinity exhibits a substantial stress relaxation. It may be advisable to reinforce the specified end piece to prevent the risk of progression of the slotlike damage. Although stress accumulation regions observed under slot clearance at the innermost lamina are very similar to each other, [(±45 ) 5 ] filament wound specimen exhibits % higher equivalent stress value than [(0/ 90) 5 ] laminated structure under the same torsional moment which allows developing of a greater load capacity. Maximum stresses are observed to increase as the slot lengths extended in axial direction and the variation can be said to be not in a linear manner in outermost layer which probably caused from the fiber discontinuities. Contrary to the situation on the outermost layer, a regular increase in the maximum stress can be detected in the innermost layer as the case changes from slot-less to full-length slotted tube structure (0-180 mm). Both in innermost and outermost layer, the slotless structures of two different material types ([(±45 ) 5 ] and [(0/ 90) 5 ] ) generate very close maximum stresses. However, two sort of material model display a marked difference in maximum stresses especially for slot lengths longer than 140 mm. The total twisting angles at the extreme ends of the tubes with [(0/ 90) 5 ] stacking sequence are 0.66 greater than those with [(±45 ) 5 ], on average. The twisting angles increase in both structures as the slot lengths are extended. This increase is detected as 8.32 and 9.11 % in the 45 /-45 angleply and 0 /90 cross-ply structures, respectively. REFERENCES [1] G. Meijer, F. Ellyin, A failure envelope for ±60_ filament wound glass fibre reinforced epoxy tubulars, Composites: Part A, vol. 39, pp , [2] I. Burda, AJ. Brunner, M. Barbezat, Mode I fracture testing of pultruded glass fiber reinforced epoxy rods: Test development and influence of precracking method and manufacturing, Engineering Fracture Mechanics, vol. 149, pp , [3] G. Perillo, R. Vacher, F. Grytten, S. Sørbø, V. Delhaye, Material characterisation and failure envelope evaluation of filament wound GFRP and CFRP composite tubes, Polymer Testing, vol. 40, pp , [4] LAL. Martins, FL. Bastian, TA. Netto, Structural and functional failure pressure of filament wound composite tubes, Materials and Design, vol. 36, pp , [5] LAL. Martins, FL. Bastian, TA. Netto, Reviewing some design issues for filament wound composite tubes, Materials and Design, vol. 55, pp , [6] EV. Morozov, The effect of filament-winding mosaic patterns on the strength of thin-walled composite shells, Composite Structures, vol. 76, pp , [7] F. Hafeez, F. Almaskari, Experimental investigation of the scaling laws in laterally indented filament wound tubes supported with V shaped cradles, Composite Structures, vol. 126, pp , [8] J. Xing, P. Geng, T. Yang, Stress and deformation of multiple winding angle hybrid filament-wound thick cylinder under axial loading and internal and external pressure, Composite Structures, vol. 13, pp , [9] P. Mertiny, F. Ellyin, A Hothan, An experimental investigation on the effect of multi-angle filament winding on the strength of tubular composite structures, Composites Science and Technology, vol. 64, pp. 1 9, [10] P. Krishnan, MS. AbdulMajid, M. Afendi, AG. Gibson, HFA Marzuki, Effects of winding angle on the behaviour of glass/epoxy pipes under multiaxial cyclic loading, Materials and Design, vol. 88, pp , [11] HH. Moreno, B. Douchin, F. Collombet, D. Choqueuse, P. Davies, Influence of winding pattern on the mechanical behavior of filament wound composite cylinders under external pressure, Composites Science and Technology, vol. 68, pp , [12] D. Tele, N. Wakhare, R. Bhosale, P. Bharde and S. Nerkar, A Review on Design and Development of Filament Winding Machine for Composite Materials, International Journal of Current Engineering and Technology, vol.6, pp , [13] ASTM D5448/D5448M-11 Standard Test Method for Inplane Shear Properties of Hoop Wound Polymer Matrix Composite Cylinders. [14] ASTM D Standard Practice for Fiber Reinforcement Orientation Codes for Composite Materials1 54

60 Academic Platform Journal of Engineering and Science 6-2, 55-62, 2018 Academic Platform Journal of Engineering and Science journal homepage: Güneş Kollektörü Testi için Güneş Simülatör Tasarımı ve İmalatı * 1 Ahmet ÖZSOY( ), 2 Mustafa GALİP( ) * 1 Süleyman Demirel Üniversitesi, Teknoloji Fakültesi, Enerji Sistemleri Mühendisliği, Isparta 2 Süleyman Demirel Üniversitesi, Fen Bilimleri Enstitüsü, Enerji Sistemleri Mühendisliği Anabilim Dalı, Isparta 1 2 Geliş Tarihi: Kabul Tarihi: Öz Bu çalışmada güneş kollektörlerinin laboratuvar ortamında test edilebilmesi için 140x250 cm büyüklüğünde bir güneş simülatörü oluşturulmuştur. Simülatörde 46 adet 400 W ve 4 adet 1000 W halojen lamba kullanılmış, lambalar dört gruba ayrılarak dimmerlerle ışınım şiddetleri ayarlanmıştır. Simülatörün 100x200 cm lik orta alanında ortalama 1080 W/m 2 ışınım şiddeti sağlanmıştır. Simülatöre sera filesi ile gölgeleme yapılarak ışınım şiddeti 896 W/m 2 ye düşürülmüştür. Hazırlanan simülatörde bir düzlemsel güneş kollektörü 25, 40, 60 ve 80 o C sabit akışkan giriş sıcaklıklarında ve 0.02 kg/s m 2 standart akışkan debisiyle test edilmiştir. Kollektör verimi çalışılan sıcaklık aralığında %72-48 arasında hesaplanmış ve kollektördeki basınç düşümü de 19.4 paskal olarak ölçülmüştür. Tasarımı yapılıp üretimi gerçekleştirilen güneş simülatörüyle, dış ortamın değişken şartlarından bağımsız olarak, düzlemsel veya U-borulu vakum tüplü güneş kollektörleri standarda uygun olarak test edilip, kollektör verim eğrileri oluşturulabilecektir. Anahtar kelimeler: Güneş simülatörü, Güneş kollektörü, TS EN ISO 9806 Solar Simulator Design and Production for Solar Collector Test * 1 Ahmet ÖZSOY, 2 Mustafa GALİP * 1 Süleyman Demirel Üniversitesi, Teknoloji Fakültesi, Enerji Sistemleri Mühendisliği, Isparta 2 Süleyman Demirel Üniversitesi, Fen Bilimleri Enstitüsü, Enerji Sistemleri Mühendisliği Anabilim Dalı, Isparta 1 2 Abstract In this study, a solar simulator with a size of 140x250 cm was established to test the solar collectors in the laboratory. Inside of the simulator, 46 pieces of 400 W and 4 pieces of 1000 W halogen lamps were used. The lamps were divided into four groups and their light intensities were adjusted with dimmers. The simulator provided an average intensity of 1080 W/m 2 radiation from the 100x200 cm central area. Greenhouse shading material was used on the simulator and the average radiation value was reduced to 896 W/m 2. A flat plate solar collector was tested with the prepared simulator. The tests were carried out at 25, 40, 60 and 80 o C constant fluid input temperatures and a standard flow rate of 0.02 kg/s m 2. The efficiency of the tested collector was calculated as 72-48% of the working temperature range and the pressure drop of the collector was measured 19.4 pascal. Independently from the variable environmental conditions, flat plate or U-pipe vacuum tube solar collectors could be tested and their efficiency curves could be generated with the designed and established simulator. Keywords: Solar simulator, Solar collector, TS EN ISO 9806 *Sorumlu Yazar: Süleyman Demirel Üniversitesi, Teknoloji Fakültesi, Enerji Sistemleri Mühendisliği, Isparta, Doi: /apjes

61 A ÖZSOY Academic Platform Journal of Engineering and Science 6-2, 55-62, GİRİŞ Güneş kollektörlerinin dış ortamda, gerçek şartlarda test edilmesinde, dış ortam sıcaklığı ve ışınım şiddeti gibi kollektör verimini doğrudan etkileyen girdilerin sabit olmaması ve zamanla değişmesi nedeniyle sağlıklı veri alınmasında sorunlar yaşanmaktadır. Bu nedenle güneş kollektörlerinin dış ortam şartlarından etkilenmeden sabit şartlarda test edilmesi, laboratuvar ortamında güneş simülatörlerinde yapılmaktadır. Yaygın olarak bilinen ısıl güneş kollektörlerinin test yöntemleri ISO , ISO , ASHRAE ve EN gibi standartlar mevcuttur [1]. TS EN ISO 9806 Güneş kollektörleri, deney metotlar standardına göre iç ortam performans testleri için belirlenmiş kriterler vardır [2]. Bunlar; simülatörde ışınım şiddeti 700 W/m 2 den büyük olmalı, kollektörde birim alan için akışkan debisi 0.02 kg/s.m 2 ve rüzgar hızı da 1-4 m/s olmalıdır. Test boyunca kollektördeki akışkan debisindeki değişim ±%10 dan fazla olmamalı ve simülatör alanı içerisinde ışınım şiddetinde ortalama üzerinden en fazla ±%15 sapma olmalıdır. Literatürdeki güneş simülatörleriyle ilgili çalışmalar incelendiğinde, Shatat vd., [3] oluşturduğu güneş simülatöründe 30 adet 400 W halojen lamba kullanarak, lambalara uygulanan elektriksel gerilimi değiştirip, 150x165 cm lik simülatör alanında W/m 2 arasında ortalama ışınım şiddeti elde etmiştir. Köse [4], 28 adet 400 W halojen lamba ile, 100x200 cm lik simülatör alanında 946 W/m 2 ortalama ışınım şiddeti sağlamış, fakat simülatör alanı içinde standarda uygun homojen bir ışınım dağılımı oluşturamamıştır. Sabahi vd. [5], 2.8x2.7 m ölçülerindeki bir alan için 6 adet 1000 W ve 6 adet de 2000 W olmak üzere 12 adet metal halide lamba kullanarak standarda uygun bir güneş simülatörü tasarımı ve üretimi yapmıştır. Lambalardan 1 m uzaklıkta 790 W/m 2 ortalama ışınım sağlanmıştır. Bir CPC güneş kollektörü hem dış ortamda güneş altında hem de simülatörde test edilmiş, sonuçların benzer olduğunu bildirmiştir. Sopian vd. [6], 45 adet 330 W halojen lamba ile 120x240 cm boyutlarında güneş simülatörü oluşturmuş, lambaları dimmerle kontrol ederek 600 W/m 2 ortalama ışınım sağlamıştır. Literatürde güneş hücreleri ve PV modüllerinin test edilmesine yönelik benzer çalışmalar da mevcuttur [7-8]. Meng vd. [9], 188 adet, 400 W metal halide lambayla 388x450 cm boyutunda güneş simülatörü oluşturmuş ve simülatör alanında W/m 2 ışınım şiddeti sağlanmıştır. Lambalarda 175 cm uzaklıkta 200x230 cm lik alanda 1000 W/m 2 ışınım şiddet elde edilmiş, bu alandaki ışınım dağılımındaki düzensizliğin %4.3 ve toplam alanda da %24.5 olduğu belirtilmiştir. Codd vd. [10], yoğunlaştırmalı güneş güç sistemleri için düşük maliyetli, ışınım şiddeti yüksek bir güneş simülatörü tasarlayıp, üretmiştir. Simülatörde 7 adet 1500 W metal halide lamba kullanılmış, odak merkezinde 61.0 kw/m 2, merkezden 5.1 cm uzaklıkta 56.4 kw/m 2 ışınım şiddeti oluşturulmuştur. Ekmen vd., [11] tarafından da yüksek ışınım şiddetine sahip güneş simülatörlerinin geliştirilmesi için her biri 6 kw lık 7 lambanın kullanıldığı sistemde 1 MW/m 2 ışınım şiddeti sağlanmıştır. Yüksek ışınım yoğunluğuna sahip çalışmalar da literatürde bulunmaktadır [12]. Bu simülatörler odaklamalı ve yüksek sıcaklıkta çalışan güneş enerjisi sistemlerinin test edilmesinde kullanılmaktadır. Fotovoltaik paneller için kullanılacak güneş simülatörlerindeki lambalarla ilgili bir çalışma Esen vd. [13] tarafından yapılmıştır. Çalışma kapsamında karbon ark lambaları, sodyum buharlı lambalar, argon arkı lambaları, kuartz-tungsten halojen lambalar, civa xenon lambalar, ksenon arkı, ksenon flaş lambaları, metal halide lambalar, LED ve süper sürekli lazer ışık kaynakları incelenmiştir. Yine fotovoltaik güneş simülatörlerindeki spektrum ve ölçüm belirsizlikleri Schubert ve Spinner [14] tarafından analiz edilmiştir. Solanki vd, [15], PVT kollektörlerin test edilmesi için 16 adet 500 W lamba ile bir simülatör oluşturmuş, ancak çalışmada simülatör ile ilgili detaylı bilgi verilmemiştir. Güneş simülatörü ile ilgili daha önceki yapılan çalışmalarda simülatörlerle ilgili ışınım şiddetinin dağılımı ve lambaların konumları gibi detaylar verilmemiş, çoğunlukla kullanım amacına yönelik simülatör yapılıp çalışmada kullanılmıştır. Bu çalışmada laboratuvar ortamında güneş kollektörü ısıl performans testi için TS EN ISO 9806 standardına uygun bir güneş simülatörü tasarlanıp üretilmiş ve bir düzlemsel güneş kollektörü test edilmiştir. 2. MATERYAL VE YÖNTEM Bu çalışmada literatürdeki benzerleri de referans alınarak 140x250x150 cm boyutlarında simülatör yapılması planlanmıştır. Lambaların merkezleri arası enine 20 cm ve boyuna da 25 cm olacak şekilde konumlandırılmış ve toplamda 46 adet 119 mm uzunlukta 400 W ve 4 adet 189 mm uzunlukta 1000 W r7s Philips (2900 K) halojen lambalar kullanılmıştır. Literatürdeki çalışmalarda ve ön deneysel ölçümlerde, simülatörün orta kısımlarında oluşan ışınım yoğunluğunu azaltmak için lambalar dört gruba ayrılarak dimmerlerle ışınım şiddetleri ayarlanmıştır. Alınan ilk ışınım ölçümlerinden sonra orta bölgelerde yine yoğunlaşma olduğu görülüp, orta bölümden 4 adet lamba çıkarılarak son durumdaki lamba konumları Şekil 1 deki hale getirilmiştir. Buradaki sarı renkli olarak görünen ilk grup sistemin en iç merkezidir. Bu bölge 6 adet 400 W halojen lambadan oluşmakta ve 5 kw lık dimmer ile kontrol edilmektedir. İkinci grup, ortada kalan lambaları (açık yeşil renkte) kapsar. Bu grup 18 adet 400 W halojen lambadan oluşmakta ve 10 kw lık dimmer ile kontrol edilmektedir. Üçüncü 56

62 A ÖZSOY Academic Platform Journal of Engineering and Science 6-2, 55-62, 2018 grup ise en dıştaki (koyu yeşil) lambalardır. Bu grup 14 adet 400 W halojen lambadan oluşmakta ve 10 kw lık dimmer ile kontrol edilmektedir. Dördüncü grup ise köşelerde bulunan + işaretli grup olup tam güçte (220 V) çalışmaktadır. 1. ve 2. grup 120 V, 3. grup 215 V gerilime ayarlanmıştır. Şekil 1. Simülatördeki lambaların konumları Güneş simülatöründe kullanılan 50 adet halojen lambalar tam güçte 22.4 kw gücünde olup, çalıştıklarında bu lambalardan deney ortamına çok miktarda ısı enerjisi yayılmaktadır. Güneş kollektörleri test edilirken simülatör lambalarından kollektöre doğru oluşan yoğun ısı akısını kollektörden uzaklaştırmak için 6 mm lik temperlenmiş camdan bir perde oluşturulmuştur. Cam perdenin altından ve üstünden birer fan yardımıyla hava akışı sağlanarak lambalarda üretilen ısı simülatörden uzaklaştırılmıştır. Böylece test edilen kollektörün alt ve üst ortamlarının yaklaşık aynı sıcaklıkta olması sağlanmıştır. Şekil 2 de simülatördeki elamanlar arası mesafe şematik olarak verilmiştir. Şekil 2. Simülatörde yükseklik ölçüleri Test ortamındaki ışınım şiddeti yoğunluğunun tespiti için test alanı, 10x12.5 cm ölçülerinde 280 adet alana bölünerek her bir alan için ışınım şiddeti ölçümleri üçer defa tekrarlanarak, ölçülen değerlerin ortalaması alınmıştır. Işınım şiddeti ölçümlerinde Ahlborn FLA613-GS global radyasyon probu kullanılmış olup, bu cihaz ±%10 luk hassasiyetle çalışmaktadır. Şekil 3 te oluşturulan güneş simülatörü görülmektedir. 57

63 A ÖZSOY Academic Platform Journal of Engineering and Science 6-2, 55-62, 2018 Şekil 3. Güneş simülatörünün görünümü Simülatör kullanılarak yapılacak iç ortam kollektör performans testleri, sabit ışınım şiddeti ve akışkan debisinde, kollektöre giren akışkan sıcaklığı değiştirilerek yapılır. Bu amaçla hazırlanan test düzeneği şematik olarak Şekil 4 de görülmektedir. Şekil 4. Kollektör testi için oluşturulan deneysel sistemin şeması Test düzeneğinde kollektöre giren akışkan sıcaklığını istenilen değerde sabit tutmak için 60 lt kapasiteli elektrikli termosifon kullanılmış ve termosifondan alınan suyun sirkülasyonu bir pompa ile sağlanmıştır. Kollektöre giren ve çıkan akışkan sıcaklıkları Pt100 ile ölçülmüştür. Sistemde dolaşan akışkan debisi Krohne rotametre ile ve kollektördeki basınç düşümü de kollektör giriş ve çıkışındaki fark basınç transmitteri (Autrol APT3100) ile 58

64 A ÖZSOY Academic Platform Journal of Engineering and Science 6-2, 55-62, 2018 ölçülmüştür. Kollektörden çıkan akışkan sıcaklığını, istenilen kollektör giriş sıcaklığına yakın bir değere getirmek için plakalı ısı değiştirici kullanılarak depodaki akışkan sıcaklığının sabit bir değerde kalması sağlanmıştır. Test edilen kollektörün alt ve üst ortam sıcaklıkları birer adet K tipi termokupılla ölçülmüş, bu sıcaklıkların ortalaması dış ortam sıcaklığı olarak alınmıştır. Sıcaklık ölçümleri Ahlborn Almemo ile kaydedilmiştir. Bir adet fan, kollektör üzerinde rüzgar etkisi oluşturmak amacıyla kullanılmış, oluşan havanın ortalama hızı Testo ile 1.5 m/s olarak ölçülmüştür. Çizelge 1 de deneysel sistemdeki ölçme cihazlar ve bu cihazların hassasiyetleri verilmiştir. Tablo 1. Kullanılan ölçüm cihazları ve hassasiyetleri Ölçüm cihazı Kullanım amacı Hassasiyeti Pt100 Akışkan sıcaklık ölçümü ± 0.05 K tipi termokupıl Çevre sıcaklığı ölçümü ± 0.05 Krohne hacimsel debimetre Debi ölçümü ± %1.16 Autrol APT3100 Basınç farkı ölçümü ± %0.075 Ahlborn FLA613-GS Işınım şiddeti ölçümü ± %10 Güneş kollektörlerinde verim, alınan enerjinin, kollektör yüzeyine gelen enerjiye oranı şeklinde ifade edilir. Alınan enerji test edilen kollektöre giren akışkanın sıcaklık artışı ile belirlenir. Gelen enerji ise dış ortam şartlarında güneşten, laboratuvar ortamında güneş simülatöründen kollektör alanına gelen enerjidir. Kollektör verimi Eşitlik 1 de verilmiştir. η k = m C p T A I Burada ṁ (kg/s) kütlesel debi, C p (J/kg o C) akışkanın özgül ısısı, ΔT ( o C) akışkanın giriş ve çıkış sıcaklıkları farkı, A (m 2 ) kollektör alanı ve I (W/m 2 ) ışınım şiddetidir. Güneş kollektörlerinin verimi dış ortam sıcaklığı, ışınım şiddeti ve kollektördeki ortalama akışkan sıcaklığı ile değişir. Bu değişim azaltılmış sıcaklık olarak tanımlanmış olup T * ile ifade edilir (Eşitlik 2). T = T k T ç I Burada T k ( o C) kollektördeki ortalama akışkan sıcaklığı ve T ç ( o C) çevre sıcaklığıdır. Ortalama akışkan sıcaklığı, kolektöre giriş ve çıkış sıcaklıklarının, çevre sıcaklığı ise kollektörün üst ve alt kısımlarındaki ortam sıcaklıklarının aritmetik ortalaması olarak alınır. 3. DENEYSEL BULGULAR Çalışma iki bölümden oluşmaktadır. Birinci kısımda güneş simülatöründeki ölçümlerden elde edilen bulgular ve ikinci kısımda kollektör testlerinden elde dilen bulgular incelenmiştir. (1) (2) 3.1. Güneş Simülatörü Işınım Şiddeti Ölçümlerinin Analizi Şekil 1 de verilen lamba konumları ve Şekil 2 deki simülatör tasarımına göre 140x250 cm ölçülerindeki (3.5 m 2 ) alan, 10x12.5 cm lik bölümlere ayrılıp her bir alan için ışınım şiddeti ölçümleri yapılmıştır. Yapılan ölçüm değerlerinin eş yükselti eğrileri şeklinde NetCAD programı ile oluşturulan görünümü Şekil 5 de görülmektedir. Şekil üzerindeki her çizgi üzerindeki değer oradaki ışınım şiddetini göstermektedir. Simülatör alanında ölçülen en küçük değer 633 W/m 2, en büyük değer de 1187 W/m 2 olup, tüm alanın ortalama ışınım şiddeti 987 W/m 2 dir. Ancak ilgili standartta [2] ±%15 sapmaya müsaade edildiğinden standarda uygun değildir. Eş yükselti eğrilerinin dağılımı incelendiğinde simülatör alanının orta kısımlarında ışınım şiddetinde bir yoğunlaşma, kenar kısımlarında ve özellikle köşelerde ise azalma dikkat çekicidir. Bu azalma köşe ve kenarlardaki lambalardan yayılan ışınımın, ölçüm alanının dışına çıkmasından kaynaklanmaktadır. Eğer sadece simülatörün orta kısmındaki çizgilerle işaretlenmiş alan (100x200 cm lik bölüm) dikkate alınırsa, burada ölçülen en yüksek değer 1187 W/m 2 ve en düşük değerde 982 W/m 2 olup, bu alandaki ortalama ışınım şiddeti 1080 W/m 2 dir. Bu bölgedeki ortalama değer ±%8 sapma ile standarda uygundur. Bu çalışmada oluşturulan 3.5 m 2 simülatör alanın %57 si standarda uygun homojenliktedir. Meng vd. [9] oluşturdukları m 2 simülatör alanının sadece %26 sında homojen bir dağılım elde edebilmiştir. 59

65 A ÖZSOY Academic Platform Journal of Engineering and Science 6-2, 55-62, 2018 Şekil 5. Simülatördeki ışınım şiddeti dağılımı Güneş simülatörünün Şekil 5 te çizgi ile işaretli bölge içindeki ortalama ışınım şiddeti 1080 W/m 2 dir. Ancak bu değer, gerçek dış ortam şartlarındaki ışınım şiddetine göre yüksek olduğundan azaltılmasının kollektör verim eğrilerinin oluşturulmasında daha uygun olacağı düşünülmektedir. Bu nedenle halojen lambalardaki kısılma daha da azaltılamadığı için ısı perdesi olarak kullanılan camın altına, seralarda gölgeleme amacıyla kullanılan sera filesi uygulanarak (dimmer gerilimleri 115 V, 115 V ve 210 V da sabit tutularak) ışınım şiddeti azaltılmış ve ışınım ölçümleri tekrarlanmıştır. Yapılan ölçümlerden elde edilen eş yükselti eğrileri Şekil 6 da verilmiştir. Şekil 6. Simülatörde sera filesi uygulaması ile oluşan ışınım şiddeti dağılımı Şekil 6 daki eş yükselti eğrileri incelendiğinde, cam örtü altında tüm alana gölgeleme yapıldığı için karakteristik görünüm Şekil 5 ile aynıdır. Ancak tüm alan için ışınım şiddeti ortalaması ilk uygulamada 987 W/m 2 olmasına rağmen gölgelemeden sonra %17 azalarak 822 W/m 2 ye getirilmiştir. Bu durumda alandaki ışınım şiddeti ölçümlerindeki en yüksek ve düşük değerler sırasıyla 533 ve 988 W/m 2 ölçülmüştür. Elde edilen sonuç, standardın istediği maksimum hatadan yine fazladır. Ancak Şekil 6 daki işaretli alan kullanıldığında, en yüksek 988 W/m 2, en düşük 836 W/m 2 ve ortalama 896 W/m 2 ışınım şiddeti elde edilmiştir. Bu değer maksimum %10 sapmaya karşılık gelmekte olup standarda uygundur. 60

66 A ÖZSOY Academic Platform Journal of Engineering and Science 6-2, 55-62, Düzlemsel Güneş Kollektörü Test Sonuçları Çalışmada 38x196 cm boyutlarında bir düzlemsel kollektör, üretilen güneş simülatörü kullanılarak test edilmiş ve verim grafiği oluşturulmuştur. Deneyler 25, 40, 60 ve 80 o C kollektör giriş suyu sıcaklıklarında ve 0.02 kg/s m 2 standart akışkan debisiyle test edilmiştir. Deneysel çalışmada çevre sıcaklığı o C arasında değişmiştir. Deneylerde kollektöre giren akışkan sıcaklığı istenilen değere ayarlanıp kollektörün kararlı hale gelmesi için en az 60 dakika beklenmiştir. Aynı sıcaklıkta alınan ölçümler tekrarlanırken de her ölçüm arasında bir süre beklenmiştir. Akışkan giriş sıcaklığının her değişiminde aynı prosedür uygulanmıştır. Şekil 7 de deneyler sonucunda oluşturulan kollektör verim eğrisi ve eşitliği verilmiştir r4l r3l Kollektör Verimi (%) r2l r2l r1l y = x r1l T* Şekil 7. Güneş simülatöründe elde edilen düzlemsel kollektör verim eğrisi Test edilen düzlemsel kollektörün verimi çalışılan sıcaklık aralığında %72 ile %48 arasında bulunmuştur. Literatürdeki düzlemsel kollektörlerle ilgili bazı çalışmalarda kollektör verimleri %66-33, %79-46, %65-51 ve %56-44 olarak verilmiştir [3,4,10-12]. Oluşturulan simülatörde gerçekleştirilen deneylerle literatürle uyumlu sonuçlar alındığı görülmektedir. Kollektörün basınç düşümü sıcaklıkla değişmekte olup, ortalama 28 o C akışkan sıcaklığında 64 l/h akışkan debisi için 19.3 Pa olarak ölçülmüştür Hata Analizi Kollektör verim hesabındaki hata analizi Eşitlik 3 ten bulunur. Burada ṁ kütlesel debi ölçümlerini, T sıcaklık ölçümlerini ve I ışınım şiddeti ölçümlerini ifade etmektedir. Toplam hata ölçülen debinin, sıcaklık değerlerinin ve ışınım şiddetinin ölçüm hatalarını kapsamakta olup, Çizelge 1 deki veriler yardımıyla kollektör veriminde maksimum hata %5.24 olarak hesaplanmıştır. W ηη = ηη ṁ ww ṁ 2 + ηη T ww TT 2 + ηη I ww II 2 (3) 4. SONUÇ Çalışmada tasarlanıp üretilen güneş simülatörünün toplam 100x200 cm lik alanında ortalama 1080 W/m 2 ışınım şiddeti sağlanmıştır. Simülatördeki ışınım şiddetini gerçek dış ortam şartlarına yaklaştırmak için yapılan sera filesi ile gölgeleme yapılarak, ortalama ışınım şiddeti 896 W/m 2 değerine düşürülmüştür. Her iki durumda toplam simülatör alanının %57 lik kısmında, ışınım şiddetindeki sapma TS EN ISO 9806 standardında istenen maksimum ±%15 lik sapmanın altında kalmaktadır. Oluşturulan güneş simülatörlü kollektör test düzeneği ile laboratuvar ortamında, değişken atmosferik şartlardan bağımsız olarak kollektör testleri yapılabilir. Ayrıca sisteme eklenmiş olan fark basınç algılayıcıları ile güneş kollektöründeki basınç düşümü, farklı akışkan debileri için belirlenebilir. Simülatördeki ışınım şiddeti lambaların konumlarına ve kollektörün lambalardan olan uzaklığına da bağlıdır. Daha önceki çalışmalarda görüldüğü gibi oluşturulan güneş simülatörü tüm alanında standarda uygun bir homojenlik sağlanması mümkün olmamaktadır. Bu nedenle yapılacak deneylerin standarda uygun homojenliğin sağlandığı bölgede yapılması gerekir. Ayrıca ışınım üreten halojen lambaların ortama yaydığı ısı enerjisinin de bir ısı perdesi ile kollektörü etkilemesi engellenmiş ve bir fanla da ortamdan uzaklaştırılmıştır. Işınım şiddeti dağılımında orta kısımlarda yoğunlaşma, kenarlarda ve özellikle de köşelerde azalma vardır. Dört köşeye 1000 W lık lamba yerleştirilmiş olmasına rağmen yeterli olmadığı görülmüştür. Kenarların orta kısımlarındaki 400 W lık lambaların 1000 W lık lambalarla değiştirilmesi ile bu sorun azaltılabilir. Yapılan deneysel çalışmalarda güneş simülatörünü besleyen elektrik şebekesindeki gerilim değişikliklerinin halojen lambalarda üretilen ışınım şiddetini etkilemekte olduğu görülmüştür. Deneysel çalışmalarda sistem 61

67 A ÖZSOY Academic Platform Journal of Engineering and Science 6-2, 55-62, 2018 gerilimlerindeki değişim pano üzerindeki voltaj göstergesinden takip edilip, değişiklik durumunda gerekli düzeltmeler manuel olarak yapılmıştır. Sistemin elektriksel kararlılığının sağlanması için voltaj regülatörünün kullanılması daha kararlı veriler alınması için uygun olacaktır. Güneş simülatörü ile ilgili daha önceki yapılan çalışmalarda genellikle simülatörlerle ilgili detaylı bilgi verilmemiş, çoğunlukla kullanım amacına yönelik simülatör yapılmıştır. Bu çalışmada ise simülatör tasarımı, lambaların konumları, lambalarla güneş kollektörü arasındaki mesafe, ısı perdesi uygulaması, ışınım şiddetinin azaltılması ve alandaki ışınım şiddetinin dağılımı detaylı olarak verilmiştir. Bu çalışma, bundan sonraki araştırmacılara kendi uygulamalarına yönelik simülatör tasarımında yardımcı olacaktır. TEŞEKKÜR Bu çalışma, Süleyman Demirel Üniversitesi, Bilimsel Araştırma Projeleri Koordinasyon Birimi tarafından YL1-16 numaralı proje çalışması kapsamında desteklenmiştir. Çalışmaya katkılarından dolayı EFEM Mekatronik e de ayrıca teşekkür ederiz. KAYNAKLAR [1] S. Fischer, W. Heidemann, H. Müller-Steinhagen, B. Perers, P. Bergquist, and B. Hellström, Collector test method under quasi-dynamic conditions according to the European Standard EN , Solar Energy 76, , [2] TS EN ISO 9806, Güneş Enerjisi-Güneş kollektörleri- Deney metotlar, [3] M. Shatat, S. Riffat, and F. Agyenim, Experimental testing method for solar light simulator with an attached evacuated solar collector, International Journal of Energy and Environment, 4, 2, , [4] İ.İ. Köse, Düzlemsel güneş kollektörlerinde boru içerisinde kıvrılmış şerit kullanımının ısı transferine etkisinin deneysel incelenmesi, Süleyman Demirel Üniversitesi, Fen Bilimleri Enstitüsü, Yüksek Lisans tezi, Isparta, [5] H. Sabahi, A.A. Tofigh, I.M. Kakhki, and H. Bungypoor-Fard, Design, construction and performance test of an efficient large-scale solar simulator for investigation of solar thermal collectors, Sustainable Energy Technologies and Assessments, 15, 35 41, [6] K. Sopian, Dr. Supranto, W.R.W. Daud, M.Y. Othman, and B. Yatim, Thermal performance of the double-pass solar collector with and without porous media, Renewable Energy, 18, , [7] C. Dominguez, I. Anton, and G. Sala, Solar simulator for concentrator photovoltaic systems, Optics Express, 16, 19, , [8] M.G. Guvenc, C. Gurcan, K. Durgin, and D. MacDonald, Solar simulator and I-V measurement system for large area solar cell testing, Proceedings of the American Society for Engineering Education Annual Conference and Exposition, 3659, [9] Q. Meng, Y. Wang, and L. Zhang, Irradiance characteristics and optimization design of a large-scale solar simulator, Solar Energy, 85, , [10] D.S. Codd, A. Carlson, J. Rees, and A.H. Slocum, A low cost high flux solar simulator, Solar Energy, 84, , [11] B.M. Ekman, G. Brooks, and M. A. Rhamdhani. Development of high flux solar simulators for solar thermal research. Solar Energy Materials and Solar Cells, 141, , [12] A. Galloa, A. Marzo, E. Fuentealba, and E. Alonso, High flux solar simulators for concentrated solar thermal research: A review, Renewable and Sustainable Energy Reviews, 77, , [13] V. Esen, Ş. Sağlam, and B. Oral. Light sources of solar simulators for photovoltaic devices: A review, Renewable and Sustainable Energy Reviews 77, , [14] F. Schubert, and D. Spinner, Solar simulator spectrum and measurement uncertainties, Energy Procedia, 92, , [15] S.C. Solanki, S. Dubey, and A. Tiwari. Indoor simulation and testing of photovoltaic thermal (PV/T) air collectors, Applied Energy 86, ,

68 Academic Platform Journal of Engineering and Science 6-2, 63-71, 2018 Academic Platform Journal of Engineering and Science journal homepage: Öz Homojen Glioblastoma Örneklerinin Yüksek Çözünürlüklü Genetik Teknolojiler ile Analizi Mehmet Baysan( ) İstanbul Şehir Üniversitesi Mühendislik ve Doğa Bilimleri Fakültesi, Bilgisayar Mühendisliği, İstanbul, Geliş Tarihi: Kabul Tarihi: Tümör içi genomik heterojenlik kanserlerde sıkça karşılaşılan bir durumdur. Normal şartlarda her bir hücrede her bir genin iki kopyası vardır ve bazı istisnalar dışında organizmanın farklı hücreleri aynı DNA dizisini taşır. Kanser hücrelerinde ise gerek mutasyonlar sonucu gerekse de DNA silinmeleri ve eklenmeleri sonucu bu düzenli yapı karmaşık ve heterojen bir yapıya dönüşür. Bu genetik heterojenliğin sebebi ve tümör oluşumundaki rolü, genetik veri üretebilme teknolojilerindeki gelişmeler ışığında son zamanlarda çokça çalışılan önemli bir problemdir. Aynı tümörden elde edilmiş yüksek çözünürlüklü homojen numuneler, heterojenliği anlamak için yapılan çalışmalarda büyük önem arz etmektedir. Gerek kanser dokusuna erişimdeki zorluklar, gerekse de finansal limitler böyle yüksek çözünürlüklü veri setlerinin elde edilmesi önünde engel oluşturmaktadır. Glioblastoma multiforme teşhis sonrası ortalama yaşam süresi yaklaşık on beş ay olan, en sık görülen ve en agresif beyin tümörüdür. Bu çalışmada bir glioblastoma hastasından alınan detaylı homojen ve heterojen numuneler kullanılarak elde edilmiş yüksek çözünürlüklü bir veri seti incelenip, yapılan analizler sunulacaktır. Anahtar kelimeler: Kanser, Bioinformatik, Glioblastoma, DNA Dizileme, DNA Kopya Sayısı Analysis of Homogeneous Glioblastoma Samples with High-Resolution Genomic Technologies Abstract Intra-tumor genomic heterogeneity is a common feature in human cancers. Normally, there are two copies of each gene in a cell and all cells of an organism carries the same DNA sequence despite some exceptions. With mutations and copy number changes in cancer, this well-defined structure is impaired and transformed into a chaotic structure. Cause of these transformations and their role in tumor development and maintenance is an important problem of oncology. Recent technological improvements allow generation of high-resolution genomic data which can be utilized to address this problem. Obtaining high-resolution homogeneous samples that are obtained from a single cancer is critical to study intra-tumor genomic heterogeneity. Both experimental and financial limitations create difficulties in obtaining detailed data sets that includes such samples. Gioblastoma multiforme is the most common and most aggressive brain tumor with a median survival of fifteen months post diagnosis. In this manuscript, analysis results of a data set that includes high-resolution homogeneous and heterogeneous samples from a glioblastoma patient will be presented. Keywords: Cancer, Bioinformatics, Glioblastoma, DNA Sequencing, DNA Copy Number 1. GİRİŞ Yaşamı devam ettirecek vücut fonksiyonları ancak dokuların ve dokuları oluşturan hücrelerin birbiri ile uyumlu çalışması ile elde edilebilir. Sağlıklı dokularda gözlemlenen morfolojik ve yapısal düzen bu uyumlu çalışmayı sağlayan temel unsurlardan bir tanesidir. Kanserle birlikte bu düzen kaybolur ve hücreler heterojen ve dağınık bir şekilde görüntülenirler. Bu düzen kaybı * Sorumlu Yazar: İstanbul Şehir Üniversitesi Mühendislik ve Doğa Bilimleri Fakültesi, Bilgisayar Mühendisliği, İstanbul, Doi: /apjes sadece dış görünümde kalmaz. Mutasyonlar sonucu normal şartlarda tüm hücrelerde aynı kalması gereken genetik harita heterojenleşirken özellikle DNA metilasyonu gibi hücre içi fonksiyonları direk etkileyen epigenetik profillerde de heterojenleşme gözlemlenmiştir [1]. Kanser dokusundaki bu heterojenleşme kanser tanısı ve tedavisi adına büyük zorlukları da beraberinde getirmektedir. Tanı için kullanılan biopsiler birçok

69 M BAYSAN Academic Platform Journal of Engineering and Science 6-2, 65-71, 2018 zaman heterojen bir tümörün çok küçük bir kısmını temsil etmektedir ve yanıltıcı olabilmektedir. İşin tedavi boyutunda ise heterojenlik kanser hücreleri için korunma kalkanı olabilmektedir. Uygulanan herhangi bir tedavi kanser hücrelerinin çok büyük bir çoğunluğunu öldürebilse bile heterojen yapıdan dolayı tedaviye dirençli hücreler bulunabilmekte ve bu dayanıklı hücreler kısa zamanda çoğalarak kanserin tekrar etmesi ile neticelenmektedir [2]. Tümör içi heterojenlik tespitleri ve bu konudaki ilk çalışmalar 19. yüzyılda başlamıştır [3]. 20. yüzyılda aynı tümör içindeki farklı klonlara ait farklı hücrelerin gerek metastaz potansiyeli, gerekse de tedaviye dayanıklılık açısından farklı özellikler gösterdiği deneylerle gösterilmiştir [4-7]. Yakın zamanda, tek hücre sıralaması (single cell sequencing) gibi modern genomik teknolojiler kullanılarak göğüs kanseri [8], böbrek kanseri [9], akciğer kanseri [10] gibi temel kanser tiplerinde tümör içi heterojenlik calışmaları yapılmış, özellikle pediatrik tümörler için tümör içi heterojenlik seviyesi ve tümör agresifliği arasında pozitif korelasyon gösterilmiştir [11]. Tümör içi heterojenlik ile ilgili önemli çalışmalar ve bunların tedavi ile ilgili potansiyel etkileri için yakın zamanlı derleme makalelerine [12] başvurulabilir. Glioblastoma multiforme (GBM) en sık teşhis edilen ve en agresif beyin kanseridir. Bu kanserde ameliyat sonrası tümörün tekrar nüks etmesi kaçınılmazdır ve ilk teşhis sonrası kalan yaşam süresi ortalama on beş aydır [13, 14]. GBM dengesiz dağıtılmış nekrotik odaklar, hiperhücresel bölgeleri ve yüksek miktarda damar oluşumu gibi fenotipik özellikler ile daha düşük seviyeli gliomalardan ayrılır ve hastalık ismindeki multiforme nin de işaret ettiği gibi yüksek seviyede morfolojik heterojenlik sergiler [15]. 20. yüzyıldaki genetik çalışmalar bu morfolojik heterojenliğe paralel olarak, tümör içi hücrelerin genetik profillerinin de heterojen olduğunu ortaya koymuştur [16]. 21. yüzyıl ile beraber özellikle insan genomu projesi sonrası genomik veri üretme teknolojileri gelişmiş, bu teknolojilerin GBM tümörlerine uygulanması sonucu yüksek seviyeli tümör içi heterojenlik ortaya konmuştur [17-20]. Bu çalışmalar beyin kanserlerinde yüksek evrelerde daha fazla tümör içi heterojenlik olduğunu göstermiş [21, 22] ve GBM özelinde daha heterojen tümörlerin daha kötü bir seyir izlediğini ifade etmiştir [20]. Tümör içi heterojenlik çalışmaları farklı yaklaşımlarla yapılabilmektedir. Bunlardan ilki yeni nesil yüksek çözünürlüklü sıralama teknolojisinin tümörden alınan tek örnek üzerinde uygulanmasıdır. Bu teknolojiler örnekteki DNA veya RNA`nın küçük parçalara bölünüp ( nükleotid) bu parçaların okunması ve referans genoma yerleştirilip örneğin referans genomla farklılıkların belirlenmesine dayanır. Her bir DNA bölgesi çok defa okunduğu için örnekteki herhangi bir DNA bölgesi heterojense (mesela hücrelerin yarısı referans genomla aynı yarısı farklı ise) bu o bölgedeki okumalara da yansıyacaktır. Bu okuma farkları kullanılarak heterojen bölgeler ve mutlak kopya sayıları (normalde her genin iki kopyası olması gerekir ama kanser dokusunda değişiklikler olabilir) tahmin edilebilir [23-25]. Tek örnek kullanıldığı için nispeten ucuz ve kolay olan bu yöntem birçok çalışmada kullanılmıştır [12, 26]. Fakat elde edilen sonuçların ne kadar doğru olduğu detaylı olarak çalışılamamıştır ve bu durum bizim bu makalede kısmen de olsa cevaplandırmaya çalışacağımız önemli bir eksikliktir. Bir tümörden alınan farklı örnekleri karşılaştırmak heterojenlik konusunda fikir vermek adına kullanışlı alternatif bir yaklaşımdır. Fakat ilk metodda olduğu gibi örneklerin herbiri çok miktarda heterojen hücre içerdiği için elde edilen veri bu hücre profillerinin ortalaması olmaktadır. Dolayısı ile heterojenlik ve mutlak kopya sayıları adına kesin kanaat verememektedir. Alternatif olarak tek bir hücrenin profilini incelemek için tek hücre bazlı sıralama teknolojileri (single cell sequencing) kullanılabilir fakat günümüzde bu teknolojiler (özellikle amplifikasyon işleminden ötürü) güvenilir yüksek çözünürlüklü bilgi verememektedirler. Biz bu çalışmamızda heterojenliği analiz etmek için bir GBM hastasından alınan örneklerden laboratuar ortamında çoğaltılabilen heterojen ve homojen hücre hatlarını kullandık. Homojen hücre hatları, heterojen hücre hatlarından tek hücreler alınarak ve bu tek hücreleri çoğaltarak analiz edebilecek miktara ulaştırılarak oluşturuldu. Böylece aynı heterojen tümör örneğinden elde edilmiş yüksek çözünürlüklü homojen örneklere ulaşıldı. Bu homojen örnekler bize mutlak kopya sayıları ve herhangi bir mutasyonun kopyaların ne kadarında gözlemlendiği hakkında detaylı ve yeni bilgiler sundu. Makalenin geri kalanında önce teorik bir altyapı geliştirip sonra gözlemleri teorik beklentiler ile karşılaştıracağız. 64

70 M BAYSAN Academic Platform Journal of Engineering and Science 6-2, 65-71, MALZEME VE YÖNTEM 2.1 Yeni Nesil Dizileme Verisi Örneklerden elde edilen DNA, Ambry Genetics firmasına gönderildi ve yeni nesil sıralama teknolojisi ile fastq dosyalarına dönüştürüldü. Elde edilen okuma segmentleri insan genomuna(hg19) yerleştirildi ve örnekler için 40x ile 100x arası ortalama okuma derinliği elde edildi. Mutasyonları belirlemek için yaygın olarak kullanılan algoritmaları birleştirerek iki bağımsız sistem(pipeline) geliştirdik ve analizlerimizde sadece iki sistemin de bulduğu mutasyonları kullandık. Birinci sistem okumaları yerleştirme için BWA/GATK ( algoritmalarını ve mutasyon keşfi için Mutect ( algoritmasını kullandı. İkinci sistem okumaları yerleştirme için NovoAlign ( algoritmasını ve mutasyon keşfi için Varscan2( algoritmasını kullandı. Mutasyon oranları ilk metod kullanılarak elde edildi. 2.2 Kopya Sayısı Verisi Kopya sayısı için Affymetrix Human SNP array 6.0 and CytoScan HD array mikrodizi teknolojisi kullanıldı. Hazırlanan DNA (QIAamp DNA kit (Qiagen, Germany) ) mikrodizi üreticisinin tavsiyelerine uygun şekilde hibridize edildi, Affymetrix GeneChip Fluidics Station 450 cihazı kullanılarak renklendirildi ve GeneChip Scanner G cihazı ile okundu. Oluşturulan CEL dosyaları Partek Genomics Suite kullanılarak analiz edildi ve herbir mutasyon için kullanılacak kopya sayısı verileri oluşturuldu. 3. BULGULAR 3.1 Homojen bir örnekte nasıl bir kopya numarası ve mutasyon oranı gözlemlenir? İnsan hücrelerinde birisi anneden birisi babadan gelmek üzere herbir kromozomun (istisnalar hariç) iki kopyası vardır. Kanser hücreleri DNA sında ise kopya sayısı değişimi ve mutasyon olmak üzere iki temel transformasyon gözlemlenir. Normalde iki olan kopya sayısı kromozomun tamamının veya bir bölümünün silinmesi ile bir veya sıfıra düşebilir ya da duplikasyonlar neticesi üç veya daha fazlaya çıkabilir. Genomik teknolojiler ile DNA nın farklı bölgelerine ait kopya sayısı belirlenebilmekte, bizler de bu temel tanımları kullanarak homojen bir örnekteki kopya sayısı profilini simüle edebilmekteyiz. Bu çalışmada da kullandığımız platformlardaki teknik hata paylarını temsil edecek rasgele kaymalar (uniformly distributed random noise) da ekleyerek bu simülasyonları yaptık. Kanserli bir dokuda beklenilen kopya numarası profili Şekil 1A da da gözlemlenebileceği üzere, DNA nın büyük kısmı sağlıklı durum olan iki kopya sayısını muhafaza eder. Ancak silinme veya artma sonucu bazı bölgelerde değişen kopya sayıları farklı katmanlar oluşturur. (A) (B) Şekil 1. Homojen bir tümör örneğine ait (A) simüle edilmiş kopya sayısı verisinin histogramı (B) simüle edilmiş mutasyon oranı verisinin histogramı. Mutasyonlar sonucu tekli nükleotidler (A-G-C-T) değişkenlik gösterir; mesela normal hücrelerdeki A nın tümörde C olması gibi. Mutasyon oranını örnekteki okunan kopyaların ne kadarının mutant olduğu olarak tanımlıyoruz. Mesela iki kopyalı bir DNA bölgesinde bir kopya mutant bir kopya normal ise mutasyon oranı

71 M BAYSAN Academic Platform Journal of Engineering and Science 6-2, 65-71, 2018 dir. Eğer iki kopya da mutant ise mutasyon oranı 1.0 dir. Kanserli homojen bir dokuda beklenilen mutasyon oranı profili Şekil 1B de gözlemlenebilir. Şekilde gözlemlendiği üzere mutasyonların çoğu DNA nın iki kopyasının birinin değişmesi sonucu oluşur ve mutasyon oranı 0.5 bölgesinde kümelenir. Eğer mutasyon olan bölgede tek DNA kopyası varsa (diğeri silindiyse) mutasyon oranı 1.0 olur. Şekil 2. Kopya sayısı ve mutasyon oranı ilişkisini gösteren dağılım grafiği (scatter plot). Her bir daire bir mutasyona işaret eder. X-aksisi kopya sayısını, y-aksisi mutasyona ait oranı gösterir. Çalışmamızın bir sonraki aşamasında kopya sayısı ve mutasyon oranı profillerini birleştirdik. Şekil-2 de her bir mutasyon için x aksisine kopya sayısını, y aksisine mutasyon oranını yerleştirdik. Kopya sayıları homojen bir örnekte tam sayılar olmalıdır. Bu sebepten x aksisinde tam sayılarda katmanlar görüyoruz. Mutasyon oranları bu katmanlar içinde belli bölgelerde kümeleniyor. Mesela kopya sayısı üç olan bölgede sadece bir kopya mutantsa mutasyon oranı 0.33, iki kopya mutantsa mutasyon oranı 0.66, üç kopya da mutantsa mutasyon oranı 1.0 civarında gözlemleniyor. 3.2 Hastadan Elde Edilmiş Kanser Örneğinden Elde Edilen Sonuçlar Simüle edilmiş verilerle günümüz genetik kabüllerine göre oluşturulmuş beklentileri ifade ettikten sonra, bu kısımla birlikte gerçek kanser hücreleri üzerine yaptığımız analizlere geçiyoruz. Bundan bir kaç yıl önce, NIH (National İnstitutes of Health, Bethesda, MD, USA) bünyesindeki bir proje kapsamında bir GBM hastası ölmeye yakın hastaneye yatırıldı ve ölür ölmez tümörün farklı bölgelerinden örnekler alındı [27]. Kanser içi heterojenliği çalışmak için her bir örnekten heterojen ve homojen hücre hatları oluşturuldu ve herbir örnekteki herbir mutasyon için kopya sayısı ve mutasyon oranı verilerini meydana getirildi. Hasta örneklerini incelediğimizde, elde edilen verinin simülasyonlardan oldukça farklı olduğunu görüldü (Şekil 3). Gerek kopya sayısında gerekse de mutasyon oranında birbiri ile ayrılmış net katmanlar görülememesi bize örneğin oldukça heterojen hücre gruplarından oluştuğunu ifade etti. Bunu destekleyen başka bir delil de aralığında gözlemlenen farklı mutasyon oranları oldu. İlk aşamada bu mutasyonları örnek içindeki hücrelerin sadecebir kısmında bulunan heterojen mutasyonlar olarak nitelendirdik. 66

72 M BAYSAN Academic Platform Journal of Engineering and Science 6-2, 65-71, 2018 (A) (B) (C) Şekil 3. Hastadan alınan T6 bölgesi için (A) kopya sayısı ve (B) mutasyon oranı verilerinin histogramları. (C) bu verilerin birleştirilmiş halinin dağılım grafiği (scatter plot). (C) de Herbir işaret bir mutasyona işaret eder. 3.3 Heterojen ve Homojen Hücre Hatları ile İlgili Sonuçlar Bu bölümde hücre hatları ile elde ettiğimiz sonuçları sunacağız. Yukarıda sunulan hasta örneğinden oluşturulan hücre hattını analiz ettiğimizde kopya sayısında 2, 2.5, 3 bölgelerinde bir toplanma (Şekil 4A, 4C) ve birçok homozigot mutasyon (Şekil 4B, 4C) gözlemlendi. Bu sonuçlar hücre hattının hasta tümörüne göre daha homojen olduğuna işaret etti. Öbür yandan özellikle Şekil 4C de net ayrışmalar göremememiz heterojenliğin kısmen muhafaza edildiğini gösteriyordu. (A) (B) (C) Şekil 4. T6 dan oluşturulan hücre hattı için (A) kopya sayısı ve (B) mutasyon oranı verilerinin histogramları. (C) bu verilerin birleştirilmiş halinin dağılım grafiği (scatter plot). (C) de Herbir işaret bir mutasyona işaret eder. Daha önce ifade edildiği gibi oluşturulan hücre hatlarından, tek bir hücre seçilip analiz için gerekli miktara ulaşıncaya kadar çoğaltılıp homojen hücre hatları elde edildi. Bu homojen hücre hatları analiz edildiğinde çok ilginç sonuçlar elde edildi (Şekil 5). Öncelikle kopya sayısında 1.3,2 ve 2.8 civarında üç temel band gözlemlendi. Öncelikle genel kabul çerçevesinde; bu üç bandın 1, 2 veya 3 kopya sayılarına işaret ettiğini düşündük. Fakat mutasyon oranları ile birleştirdiğimizde (Şekil 5C) bu bandların net bir şekilde 2,3 ve 4 kopyaya işaret ettiğini görüldü (1.3 kopya sayısı bandında mutasyon oranları 0.5 ve 1 alanında kümelenmiş, 2 kopya sayısı bandında mutasyon oranları 0.33, 0.66 ve 1 alanında kümelenmiş, 2.8 kopya sayısı bandında mutasyon oranları 0.25, 0.5 ve 1 alanında kümelenmiş). Kullandığımız çiplerde kanser hücreleri ve normal hücrelerden eşit miktarda DNA karşılaştırılarak sonuçlar elde edilmektedir. Ortalama kopya sayısının iki olacağı genel olarak kabul edildiği için bizde simülasyonlarda 67 böyle sonuçlar elde etmiştik. Fakat analiz edilen homojen örnekte ortalama kopya sayısı üç olduğu için bu iki bantta gözlemlendi (mesela analiz ettiğimiz örnekte ortalama kopya 5 olsaydı, gerçekte 5 kopya sayısı olan bölgeler veri üreten algoritmadaki normalizasyon sonucu ortalama 2 ye denk gelecek şekilde kaydırılacak ve 2 bandında gözlemlenecekti). Kopya sayılarının ortalamasının 3 olması, literatüre alternatif ilginç bir sonuçtu buna ek olarak kopya sayılarının 2, 3, ve 4 kopya sayıları arasında birbirine yakın şekilde dağılması kanser hücresinde farklı DNA bölgelerinin kopya sayıları açısından yüksek heterojenlik gösterdiğini ifade etti. Bunlara ek olan farklı bir gözlemse 3 ve 4 kopya sayısı olan bölgelerde mutasyon oranlarının dengeli bir şekilde dağılmadığı oldu. Kopya sayısı 3 olan bölgelerde 0.33 mutasyon oranı 0.66 mutasyon oranına göre daha fazla gözlemlendi. Benzer şekilde kopya sayısı 4 olan bölgelerde 0.25 ve 0.5 mutasyon oranı 0.75 mutasyon oranına göre daha fazla gözlemlendi. Bu gözlemler

73 M BAYSAN Academic Platform Journal of Engineering and Science 6-2, 65-71, 2018 mutasyon taşımayan kopyaların mutasyon taşıyan kopyalara göre daha fazla olduğunu ve muhtemelen mutasyonların negatif bir seçime tabi tutulduğunu gösteriyordu. (A) (B) (C) Şekil 5. T6 dan oluşturulan homojen bir hücre hattı için (A) kopya sayısı ve (B) mutasyon oranı verilerinin histogramları. (C) bu verilerin birleştirilmiş halinin dağılım grafiği (scatter plot). (C) de Herbir işaret bir mutasyona işaret eder. 3.4 K-means Gruplama Homojen hücre hattında görsel olarak teorik profile benzer bir profil elde ettikten sonra, homojen ve heterojen örneklerde k-means gruplaması yaptık. Bu gruplamada amacımız, teorik olarak bildiğimiz grupların veri üzerinden pratikte tespit edilip edilemeyeceği idi. K- means gruplamasında iki farklı veri tipi kullandığımız için şehir bloğu (city block) mesafe ölçümünü tercih ettik. İdeal grup sayısını bulmak için 5-15 aralığındaki tüm sayılarla k-means algoritmasını çalıştırdık ve en az Davies Bouldin skorunu veren grup sayısını tercih ettik. Bu sayı homojen hücre kültürü için 8 (T6MC23, Şekil 6A), heterojen hücre kültürü için 13 (T6poly, Şekil 6B) ve hastadan alınan örnek için 9 (T6T, Şekil 6C) olarak elde edildi. (A) (B) (C) Şekil 6. T6 homojen hücre hattı (A), T6 heterojen hücre hattı (B) ve T6 hasta örneği (C) verileri için k-means gruplaması uygulanmış kopya sayısı ve mutasyon frekansı (oranı) profilleri. Herbir işaret bir mutasyona işaret eder ve mutasyonlar gruplamalara göre renklendirilmiştir. Homojen bir hücre hattı için yukarıdaki gözlemleri yaptıktan sonra, farklı homojen hücre hatlarında bu gözlemlerin geçerli olup olmadığını sorguladık. Şekil 7 de iki homojen hücre hattını karşılaştırdık ve kopya sayısı ve mutasyon oranı profillerinin benzer olduğunu gözlemledik (Şekil 7A,7B). Şekil 7C de aynı iki örnekte ortak görülen mutasyonları çizgiler ile birleştirdik. Bu çizgiler birçok mutasyonun farklı örneklerde farklı bandlarda olduğunu gösterdi. Mutasyonlar sadece silinme ve çoğalma gibi kopya sayısı değişimleri sonucu bant değiştirebilir. Dolayısı ile örnekler arası bu değişimler bu kanser hücrelerinin oldukça dinamik bir DNA kopya sayısı yapısı olduğunu gösterdi. 68

74 M BAYSAN Academic Platform Journal of Engineering and Science 6-2, 65-71, 2018 (A) (B) (C) Şekil 7. T6 dan oluşturulan iki homojen hücre hattı için (A) kopya sayısı ve (B) mutasyon oranı verilerinin histogramları. (C) bu verilerin birleştirilmiş halinin dağılım grafiği (scatter plot). (C) de Herbir işaret bir mutasyona işaret eder ve aynı mutasyonlar çizgi ile birleştirilmiştir. (A) (B) Şekil milyon bazlık DNA pencereleri için ortalama kopya sayıları (A) pencerelerin histogram formatında gösterilmiş hali (B) pencerelerin genomdaki sıraya göre x-ekseninde sıralanmış hali 69

75 M BAYSAN Academic Platform Journal of Engineering and Science 6-2, 65-71, Genel Kopya Sayıları Bu aşamaya kadar mutasyonların sahip olduğu kopya sayıları üzerine yoğunlaştık ve mutlak kopya sayılarını belirledik. Bu bölümde homojen kanser örneğinin genel DNA profilini inceleyeceğiz. Bu amaç doğrultusunda DNA yı her biri 10 milyon bazlık 300 civarında pencereye böldük. Homojen bir örnek (T6MC23) için herbir bölgenin ortalama kopya sayısını elde ettik. Ortalama kopya sayıları da daha önceki analizlerimize benzer şekilde mutlak kopya sayısı 2,3 ve 4 olacak şekilde üç bantta toplandı (Şekil 8A). Buna ek olarak 2,3 ve 4 kopyalı bölgelerin genom içinde heterojen (farklı kopya sayıları birçok kromozomda dağılmış şekilde gözlemleniyor) şekilde dağıldığını gözlemledik (Şekil 8B). 4. DEĞERLENDİRME VE SONUÇ Genetik alanındaki teknolojik gelişmeler sayesinde yüksek çözünürlüklü veriler makul fiyatlarla üretilebiliyor. Bu yeni verilerden faydalı sonuçlar elde edilmesi, ancak verimli analiz metodlarının geliştirilmesi ile mümkün. Analiz metodları dizayn ederken belli önkabuller kullanmamız gerekiyor. Bu önkabullerin seçimi analiz sonuçlarını direk etkileyen önemli bir mesele. Bu seçimler yapılırken, çoğunlukla genetik bilimi literatüründe sıklıkla kullanılan fakat ispatlanmamış temel anlayışlar kullanılıyor. Dolayısıyla, yeni veriler ışığında bu temel anlayışların doğruluğunun test edilmesi, çalışılması gereken önemli bir problem. Kanser hücrelerinde silinme ve duplikasyonlar sıkça gözlemlenen olaylardır. Bununla beraber genel profilde kanser hücrelerinin sağlıklı hücrelerdeki iki kopyalı yapıyı devam ettirdiği kabul edilir ve analizler buna göre yapılır. Genel profilde değişim olabileceğini iddia eden çalışmalar ise değişimin homojen olacağını yani kopya sayısının toptan üçe veya dörde çıkacağı kabulü üzerine çalışırlar. Mesela [28] kanser DNA sının homojen olarak artışı ön kabulü üzerine yapılmış bir çalışmadır. Bu çalışmamızda yeni nesil sıralama teknolojilerini, tek hücreden elde edilmiş homojen kanser örneklerine uyguladık ve oldukça ilginç sonuçlar elde ettik. İncelediğimiz kanser hücrelerinin ortalama üç kopya sayısına sahip olduğunu ve farklı bölgeler arasında büyük heterojenlik olduğunu gözlemledik. GBM lerin genetik yapısı ve genetik stabilitesi, bu tümör için geliştireceğimiz tedaviler için göz önünde bulundurmamız gereken önemli unsurlar ve elde ettiğimiz sonuçlar bu unsurlar adına genel kabulleri değiştirebilecek veriler sunuyor. Gözlemlerimiz detaylı çalıştığımız bir GBM tümörüne dayanmakta. Tümör için oluşturduğumuz farklı homojen hücre hatlarında benzer gözlemler yaptık, dolayısı ile sonuçlarımızın doğruluğuna güveniyoruz. Fakat tüm örnekler tek bir hastadan geldiği için genellemeler yapamıyoruz. Bu genellemeler için farklı tümörlerin analiz edileceği kapsamlı çalışmalar gerekiyor. TEŞEKKÜR Bu çalışmada kullanılan verilerin üretimine ve yapılan analizlere desteklerinden ötürü Tübitak, Avrupa Komisyonu ve Amerikan Ulusal Kanser Enstitüsü (NCI) ne teşekkür ederiz. REFERANSLAR [1] M. Baysan et al., "G-Cimp Status Prediction Of Glioblastoma Samples Using mrna Expression Data," PloS ONE, vol. 7, no. 11, p. e47839, [2] B. E. Johnson et al., "Mutational analysis reveals the origin and therapy-driven evolution of recurrent glioma," Science, vol. 343, no. 6167, pp , [3] T. M. Brown and E. Fee, "Rudolf Carl Virchow: medical scientist, social reformer, role model," American Journal of Public Health, vol. 96, no. 12, p. 2104, [4] S. Makino, "Further evidence favoring the concept of the stem cell in ascites tumors of rats," Annals of the New York Academy of Sciences, vol. 63, no. 5, pp , [5] G. H. Heppner and B. E. Miller, "Tumor heterogeneity: biological implications and therapeutic consequences," Cancer and Metastasis Reviews, vol. 2, no. 1, pp. 5-23, [6] I. J. Fidler and M. L. Kripke, "Metastasis results from preexisting variant cells within a malignant tumor," Science, vol. 197, no. 4306, pp , [7] I. J. Fidler, "Tumor heterogeneity and the biology of cancer invasion and metastasis," Cancer research, vol. 38, no. 9, pp , [8] N. Navin et al., "Tumour evolution inferred by singlecell sequencing," Nature, vol. 472, no. 7341, pp , [9] M. Gerlinger et al., "Genomic architecture and evolution of clear cell renal cell carcinomas defined by multiregion sequencing," Nature genetics, vol. 46, no. 3, pp , [10] J. Zhang et al., "Intratumor heterogeneity in localized lung adenocarcinomas delineated by multiregion sequencing," Science, vol. 346, no. 6206, pp , [11] L. H. Mengelbier et al., "Intratumoral genome diversity parallels progression and predicts outcome in pediatric cancer," Nat Commun, vol. 6, p. 6125, [12] N. McGranahan and C. Swanton, "Biological and Therapeutic Impact of Intratumor Heterogeneity in Cancer Evolution," Cancer cell, vol. 27, no. 1, pp , [13] D. R. Johnson and B. P. O Neill, "Glioblastoma survival in the United States before and during the temozolomide era," Journal of neuro-oncology, vol. 107, no. 2, pp ,

76 M BAYSAN Academic Platform Journal of Engineering and Science 6-2, 65-71, 2018 [14] D. R. Johnson, H. E. Leeper, and J. H. Uhm, "Glioblastoma survival in the United States improved after Food and Drug Administration approval of bevacizumab: A population based analysis," Cancer, vol. 119, no. 19, pp , [15] P. Y. Wen and S. Kesari, "Malignant gliomas in adults," New England Journal of Medicine, vol. 359, no. 5, pp , [16] V. Jung et al., "Evidence of focal genetic microheterogeneity in glioblastoma multiforme by areaspecific CGH on microdissected tumor cells," Journal of Neuropathology & Experimental Neurology, vol. 58, no. 9, pp , [17] M. Snuderl et al., "Mosaic amplification of multiple receptor tyrosine kinase genes in glioblastoma," Cancer cell, vol. 20, no. 6, pp , [18] N. J. Szerlip et al., "Intratumoral heterogeneity of receptor tyrosine kinases EGFR and PDGFRA amplification in glioblastoma defines subpopulations with distinct growth factor response," Proceedings of the National Academy of Sciences, vol. 109, no. 8, pp , [19] A. Sottoriva et al., "Intratumor heterogeneity in human glioblastoma reflects cancer evolutionary dynamics," Proceedings of the National Academy of Sciences, vol. 110, no. 10, pp , [20] A. P. Patel et al., "Single-cell RNA-seq highlights intratumoral heterogeneity in primary glioblastoma," Science, vol. 344, no. 6190, pp , [21] A. L. Vital et al., "Intratumoral patterns of clonal evolution in gliomas," Neurogenetics, vol. 11, no. 2, pp , [22] K. Harada, T. Nishizaki, S. Ozaki, H. Kubota, H. Ito, and K. Sasaki, "Intratumoral cytogenetic heterogeneity detected by comparative genomic hybridization and laser scanning cytometry in human gliomas," Cancer research, vol. 58, no. 20, pp , [23] S. L. Carter et al., "Absolute quantification of somatic DNA alterations in human cancer," Nature biotechnology, vol. 30, no. 5, pp , [24] A. Roth et al., "PyClone: statistical inference of clonal population structure in cancer," Nature methods, vol. 11, no. 4, pp , [25] N. Andor, J. V. Harness, S. Mueller, H. W. Mewes, and C. Petritsch, "EXPANDS: expanding ploidy and allele frequency on nested subpopulations," Bioinformatics, vol. 30, no. 1, pp , [26] L. Ding et al., "Clonal evolution in relapsed acute myeloid leukaemia revealed by whole-genome sequencing," (in eng), Nature, vol. 481, no. 7382, pp , Jan [27] M. Baysan et al., "Detailed longitudinal sampling of glioma stem cells in situ reveals Chr7 gain and Chr10 loss as repeated events in primary tumor formation and recurrence," International journal of cancer, vol. 141, no. 10, pp , [28] T. I. Zack et al., "Pan-cancer patterns of somatic copy number alteration," Nature genetics, vol. 45, no. 10, pp ,

77 Academic Platform Journal of Engineering and Science 6-2, 72-80, 2018 Academic Platform Journal of Engineering and Science journal homepage: Dynamic phase transition features of the cylindrical nanowire driven by a propagating magnetic field *Erol VATANSEVER( ) Department of Physics, Faculty of Science, Dokuz Eylul University, Izmir, Turkey Arrival Date: Accepted Date: Abstract Magnetic response of the spin-1/2 cylindrical nanowire to the propagating magnetic field wave has been investigated by means of Monte Carlo simulation method based on Metropolis algorithm. The obtained microscopic spin configurations suggest that the studied system exhibits two types of dynamical phases depending on the considered values of system parameters: Coherent propagation of spin bands and spin-frozen or pinned phases, as in the case of the conventional bulk systems under the influence of a propagating magnetic field. By benefiting from the temperature dependencies of variances of dynamic order parameter, internal energy and the derivative of dynamic order parameter of the system, dynamic phase diagrams are also obtained in related planes for varying values of the wavelength of the propagating magnetic field. Our simulation results demonstrate that as the strength of the field amplitude is increased, the phase transition points tend to shift to the relatively lower temperature regions. Moreover, it has been observed that dynamic phase boundary line shrinks inward when the value of wavelength of the external field decreases. Keywords: Cylindrical nanowire, propagating magnetic field, Monte Carlo simulation. 1. INTRODUCTION Interacting spin systems driven by a sinusoidal oscillating magnetic field can exhibit distinctive and fascinating dynamic behaviours, which cannot occur for the corresponding equilibrium spin systems. For the first time in Ref. [1], the authors applied their theoretical model to investigate the physics underlying a simple ferromagnet being exposed to a time dependent magnetic field. From their analysis, the authors concluded that amplitude and period of the oscillatory magnetic field play an important role on the dynamic characters of the considered magnetic system. Since then, many theoretical [2-15] and several over a full cycle of the external field. In addition to the consensus in dynamic phase transitions and equilibrium phase transitions, however, there are inconsistencies in the literature, in view of the universality class of the spin systems. For instance, recent detailed Monte Carlo (MC) simulations studies show that there is a clear difference between critical dynamics of the magnetic system with surfaces and its equilibrium case [9]. From their finite-size scaling analysis, the authors found that nonequilibrium surface exponents do not coincide with those of the experimental works [16-20] have been carried to understand the origin of the dynamic phase transitions. Based on the some of the previously published studies, it is possible to say that there is a good consensus between dynamic phase transitions and equilibrium phase transitions. For example, it has been reported that the critical exponents of the two-dimensional kinetic Ising model subjected to a square-wave oscillatory magnetic field are consistent with the universality class of the corresponding equilibrium Ising model [5]. Moreover, it is recommended in these references [12, 15, 17, and 19] that bias field appears to be a conjugate field of the dynamic order parameter, which is time averaged magnetization equilibrium critical surface. Very recently, it is reported both experimentally and theoretically that there are metamagnetic fluctuations in the neighbourhood of dynamic phase transitions, which do not emerge in the thermodynamic behaviour of typical ferromagnets [20]. Keeping these facts mentioned above in mind, it is possible to say that more work is required to understand the origin of dynamic phase transitions of magnetic systems driven by oscillatory magnetic field. *Corresponding Author: Department of Physics, Faculty of Science, Dokuz Eylul University, Izmir, Turkey, Doi: /apjes

78 E VATANSEVER Academic Platform Journal of Engineering and Science 6-2, 72-80, 2018 In addition to the works regarding the influences of an oscillating magnetic field (uniform over space) on the dynamic characteristics of the magnetic systems, some efforts were taken to investigate the dynamic features resulting from standing and/or propagating magnetic field waves [21-24]. It is possible to say that propagating magnetic field wave is an example of spatially and also of temporally changed magnetic field being exposed to a magnetic system. In Ref. [21], the authors applied their theoretical model to elucidate the dynamical modes and nonequilibrium phase transition of the spin-1 Blume-Capel model for two-dimensional square lattice, within the framework of MC simulation. It has been found that, the wavelength of the external field plays an important role in the dynamic nature of the considered system, in addition to the amplitude and period of the field. The system presents two dynamical phases: Propagating spin wave and spin frozen or pinned phases. In another interesting work, the physics behind a simple ferromagnet under the influence of a propagating magnetic field has been discussed in detail [22]. It is shown that dynamic phase boundary constructed in temperature versus applied field amplitude tends to shrink as the strength of the wavelength of the external field decreases. It is clear that particular attention in the works mentioned above has only been devoted to clarifying the physics in the bulk materials. To the best of our knowledge, there is no any attempt to address the same problem for nanoparticles with surfaces, especially for magnetic nanowires, driven by a propagating or (and) standing magnetic field wave(s). Magnetic nanowires are important materials and also potential candidates for applications in advanced nanotechnology including magnetic memory devices [25-26] and biomedical applications [27] due to their own distinctive magnetic properties. For the sake of completeness, we would like to emphasize that nonequilibrium dynamics as well as phase transition characteristics of various types of magnetic nanowire systems under the existence of an oscillating field (uniform over space) have been studied by employing Effective-field theory [28-34] and also MC simulation method [35-36]. From this point of view, we intend to investigate the dynamic behaviours of cylindrical nanowire system being subjected to a propagating magnetic field (variation in spatio-temporal), by utilizing MC simulation method. Our obtained results indicate that the present system exhibits unusual and interesting magnetic dynamics originating from the occurrence of the propagating magnetic field, which have not been observed and discussed so far, in view of the magnetic nanostructures. The outline of the remainder parts of the paper is as follows: In section 2, we present the model and simulation details. The results and discussion are given in section 3, and finally section 4 includes our conclusions. 2. FORMULATION The Hamiltonian of the spin-1/2 cylindrical nanowire (as shown in Fig. 1) driven by a propagating magnetic field can be written as follows: zz HH = JJ SS ii (xx, yy, zz, tt)ss zz jj (xx, yy, zz, tt) h(xx, yy, zz, tt) SS zz ii (xx, yy, zz, tt) (1) iiii ii here SS ii zz (xx, yy, zz, tt) = ±1 is the Ising spin variable at any position xx, yy and zz in the nanowire. JJ (> 0) is the ferromagnetic spin-spin coupling term. The first summation in Eq. [1] is over the nearestneighbor spin couplings while the second one is over all lattice sites in the system. h(xx, yy, zz, tt) represents the propagating magnetic field, which has the following form [21]: h(xx, yy, zz, tt) = h 0 cos(wwww kkkk). (2) For the sake of simplicity, the magnetic field is propagating in the zz direction (long axis of the nanowire). It is obvious that it varies with time and position of the nanowire. Here, h 0, ww and kk refer to the amplitude, angular frequency and wave vector of the external field, and tt is time. Period and wavelength of the magnetic field are ττ = 2ππ/ww and λλ = 2ππ/kk, respectively. It may be noted here that we have fixed the period of the external field as ττ = 100 throughout the study. 73 2

79 E VATANSEVER Academic Platform Journal of Engineering and Science 6-2, 72-80, 2018 Figure 1. Schematic representation of the spin-1/2 Ising cylindrical nanowire with length LL zz and radius rr. By utilizing Metropolis algorithm [37-38], we employ MC simulation to understand the magnetic nature of the cylindrical nanowire system driven by a propagating magnetic field wave. The nanowire system is located on a simple cubic lattice, which has a length of LL zz = 200 (lattice space) and a radius rr = 10 (lattice space). For these selected values of the LL zz and rr, total number of the spins in the system is NN tt = In order to mimic the cylindrical nanowire, we follow the boundary conditions such that it is free in xxxx plane and periodic along the zz direction of the system. The simulation procedure we follow in this study can be briefly summarized as follows. The We have calculated the instantaneous value of the magnetization at time tt as follows: simulation starts from a high temperature kk BB TT/JJ = 5.0 (here, kk BB and TT are Boltzmann constant and absolute temperature, respectively) using random initial configurations, which corresponds to paramagnetic phase. Next, it is slowly cooled down until the temperature reaches to the value of kk BB TT/JJ = 10 2 with a relatively small temperature step kk BB TT/JJ = In each temperature, Monte Carlo steps per site (MCSS) are discarded for thermalization process, and next MCSS are collected to determine the thermal variations of physical quantities used in this study. Numerical data were collected over 20 independent samples. NN tt MM(tt) = 1 NN tt SS ii zz (xx, yy, zz, tt). ii=1 (3) Using MM(tt), dynamic order parameter of the cylindrical nanowire system can be defined as follows: QQ = 1 MM(tt)dddd. (4) ττ In order to detect the dynamic phase transition points of the present system, in addition to the derivative of dynamic order parameter dddd/dddd, we check the variance of the QQ and internal energy (EE), which are defined as follows: and χχ QQ = NN tt ( QQ 2 QQ 2 ), (5) χχ EE = NN tt ( EE 2 EE 2 ), (6) here EE is the internal energy given in Eq. [1] over a full cycle of the propagating magnetic field, which is defined in the following form: EE = 1 ττnn tt HH dddd. (7) 74

80 E VATANSEVER Academic Platform Journal of Engineering and Science 6-2, 72-80, RESULTS AND DISCUSSION The microscopic spin configurations of the present cylindrical nanowire system show that the system demonstrates two different dynamical phases, which sensitively Figure 2. Coherent propagation of spin clusters of up (green dots) and down (red dots) spins, swept by a propagating magnetic field wave. The spin snapshots are taken for two different values of the Monte Carlo simulation time (a) tt = MCSS, (b) tt = MCSS for values of the reduced temperature kk BB TT/JJ = 4.0, amplitude h 0 /JJ = 0.3, wavelength λλ = 100 and period ττ = 100 of the external magnetic field. (c) corresponds to spin snapshot at time tt = MCSS, for the same parameters with (a) and (b), except from considered value of temperature kk BB TT/JJ = 1.5. Depend on the considered values of the system parameters. Two alternate bands of spin values SS = ±1 are found, and they tend to propagate along the long axis of the nanowire (namely along zz axis of nanowire), in the high temperature regions. In Fig. 2, we can see easily the coherent propagation of the spin bands. These spin snapshots are taken for two different values of the MC simulation time (aa) tt = MCSS, (bb) tt = MCSS for values of the reduced temperature kk BB TT/JJ = 4.0 and amplitude h 0 /JJ = 0.3 and wavelength λλ = 100 of the external magnetic field. The cylindrical nanowire includes two full waves for the considered value of λ. Our MC simulation results also suggest that a reduction in the value of temperature destroys the coherent propagating of spin bands of the cylindrical nanowire system, leading to a spin-frozen or pinned phase [21], as shown in Fig. 1(c) which is displayed for value of kk BB TT/JJ = 1.5, with all other parameters of propagating magnetic field remain the same. At the lower temperature regions, ferromagnetic spin-spin coupling dominates against the propagating magnetic field, hence, most of the spins in the nanowire are frozen or pinned to any one value of SS. It is clear that these microscopic behaviors sensitively depend on the studied system parameters. We should note that these types of coherent propagations of spin bands and also spin-frozen phases have been recently observed in bulk materials under the existence of a propagating magnetic field [21-23]. In Figs. 3(a-d), we focus our attention on the effects of the varying field amplitudes on the thermal variations of the dynamic order parameter (QQ), its derivative dddd/dddd, variance of QQ (χχ QQ /NN tt ) and of EE (χχ EE /NN tt ). The curves are depicted for three values of the applied field amplitudes, i.e., h 0 /JJ = 0.1, 0.3 and 0.5 with ττ = 100 and λ = 100. As shown in Fig. 3(a), QQ gradually decreases starting from its saturation value with increasing thermal energy, and it vanishes continuously at the critical temperature. 75

81 E VATANSEVER Academic Platform Journal of Engineering and Science 6-2, 72-80, 2018 Figure 3. Thermal variations of the (a) dynamic order parameter (QQ), (b) dddd/dddd, (c) variance of QQ (χχ QQ /NN tt ) and (d) of EE (χχ EE /NN tt ) for different values of reduced amplitude h 0 /JJ of the external field. The curves are depicted for values of ττ = 100 and λ = 100. Dynamic phase transition point strongly depends on the component of the propagating magnetic field. Our MC findings underline that an increment in value of the applied field amplitude leads to a decrement in the location of phase transition point. At the higher temperature regions, QQ is zero and this corresponds to a phase where the coherent propagation of spin bands exhibit. In the lower temperature regions, the system exhibits dynamically ferromagnetic phase, where QQ is nonzero. As discussed earlier, the microscopic spin snapshots show that the system presents low temperature spin-frozen phase in these regions. Based on these spin configurations of the cylindrical nanowire system, it is possible to say that the system undergoes a dynamical phase transition from a coherent spin propagation phase to a spin-frozen phase, when the temperature is decreased starting from a relatively higher value. For a selected combination of the Hamiltonian parameters, the temperature dependencies of dddd/dddd show a sharp dip while χχ QQ and χχ EE reveal a very sharp peak indicating the existence of a second order phase transition, as depicted in Figs. 3(b-d). These peaks are found to shift to the lower temperature values when the strength of h 0 /JJ is increased. In order to have a better understanding about the influences of the varying values of wavelength of the propagating field on the system, we give the thermal variations of QQ, dddd/dddd, χχ QQ and also χχ EE in Figs. 4(a-d). The curves are given for two values of the wavelengths of the field, i.e., λλ = 50 and 100 with h 0 /JJ = 0.3 and ττ = 100. It is found that dynamic phase transition points depend on the selected value of λλ of the propagating magnetic field wave. 76

82 E VATANSEVER Academic Platform Journal of Engineering and Science 6-2, 72-80, 2018 Figure 4. Temperature dependencies of the (a) QQ, (b) dddd/dddd, (c) χχ QQ /NN tt and (d) χχ EE /NN tt at various values of wavelength λ of the external field. The curves are depicted for values of ττ = 100 and h 0 /JJ = 0.3. As seen in these figures, thermal variations of QQ, dddd/dddd, χχ QQ and χχ EE support that when the value of wavelength of the external field is increased, dynamically ferromagnetic phase region gets wider. It may be noted here that such types of observations originating from the variation of the wavelength of the propagating magnetic field have been found in Ref. [22], where kinetic Ising model on a 2D square lattice is exposed to a propagating magnetic field. In order to elucidate the influences of the applied field amplitude on the dynamic phase transition features of the cylindrical nanowire system, we obtain the phase diagrams in (kk BB TT CC /JJ h 0 /JJ) plane with two values of the wavelength of the propagating magnetic field with ττ = 100, in figure 5. We note that dynamic phase transition points are deduced from the peaks of the thermal variations of dddd/dddd, χχ QQ and χχ EE curves. It is clear from the phase diagrams that when the applied field amplitude is increased, the dynamic phase transition points are shifted to the relatively lower temperature regions. The aforementioned behaviors seem to be independent of the applied field wavelength λλ. On the other hand, dynamic phase boundary line, which separates dynamically ordered phases from disordered phases, shrinks inward when the strength of the λλ of the external field decreases. Recently, magnetic response of the spin-1/2 Ising cylindrical nanowire system to an oscillating magnetic field (uniform over space) has been investigated by means of MC simulation with Metropolis algorithm [35] for the same system parameters with the present study. 77

83 E VATANSEVER Academic Platform Journal of Engineering and Science 6-2, 72-80, 2018 Figure 5. Dynamic phase diagram in the (kk BB TT CC /JJ h 0 /JJ) plane for the cylindrical nanowire system under the presence of a propagating magnetic field. Different symbols correspond to the different values of applied field wavelengths: λλ = 100 (red bullet), and λλ = 50 (blue triangle). Here, green square symbols correspond to the phase transition points of the spin-1/2 cylindrical nanowire system under a time dependent oscillating magnetic field, which is uniform over space [35], for the same system parameters used in this study. Dynamic phase diagrams are given for value of ττ = 100. In order to make a comparison between propagating and oscillating magnetic fields, the results of the reference [35] are added to the Fig. 5 (green squares). It is obvious from the figure that there is no clear distinction between the magnetic field sources for the small values of the applied field amplitudes, in the sense of dynamic phase transition point. However, as the strength of h 0 /JJ is increased, dynamic phase boundaries begin to separate from each other. For considered values of the wavelengths of the propagating magnetic field in this study, our MC simulation findings indicate that phase transition points are always lower than those of the critical points obtained in reference [35], especially at the higher applied field amplitude regions. Note that in Ref. [40], the authors have studied the standing magnetic field effects on the spin-1/2 Ising model using Monte-Carlo simulations. They have also plotted the phase diagram in dynamic transition temperature and field amplitude for varying values of the wavelength. Even though there exists a clear difference between Ref. [40] and the current study, it may possible to compare the obtained phase diagrams. By comparing the Fig. 6 of Ref. [40] with the Fig. 5 of the present study, it is possible to underline that when value of the wavelength is increased, dynamic phase transition temperature tends to shift to the upper transition regions. In addition to the MC simulation studies, there are a few studies regarding the time dependent magnetic field effects on the spin-1/2 cylindirical nanowires, by means of Effective-Field Theory [28-34]. In these studies, external magnetic field is selected to be uniform over space. It is possible to say that there are many similarities between the results in those found in previous studies and the current work. For example, for a fixed value of period of the external field, with increasing value of the applied field amplitude, dynamic phase transition points tend to shift to the lower temperature values. And also, it is possible to break the symmetry due to the applied field period. The aforementioned situations are also valid for both MC simulation and Effective-Field Theory methods. 78

84 E VATANSEVER Academic Platform Journal of Engineering and Science 6-2, 72-80, CONCLUDING REMARKS To conclude, we study the nonequilibrium dynamics and phase transition features of the ferromagnetic spin-1/2 cylindrical nanowire under the existence of a propagating magnetic field. For this investigation, we use Monte Carlo simulation method with single-site update Metropolis algorithm. Based on the obtained results in this study, it is possible to mention that there are two types of dynamical states in the system, depending on the considered system parameters. The results can be summarized as follows: In the higher temperature regions, two alternate bands of spins are found, and they tend to coherently propagate along the long axis of the nanowire. However, a decrement in the value of temperature leads to the occurrence of spinfrozen or spin pinned phase. This phase generally occurs at the relatively lower temperature regions, as in the case of the conventional bulk systems under the influence of a propagating magnetic field [21-23]. Additionally, we give the dynamic phase diagram of the spin-1/2 cylindrical nanowire in (kk BB TT CC /JJ h 0 /JJ) plane for two values of the wavelengths of the propagating magnetic field. Our MC simulation findings clearly indicate that as the strength of the field amplitude is increased, the phase transition points tend to shift to the relatively lower temperature regions. In the sense of wavelength of the field, it is found that dynamic phase boundary line shrinks inward in the related plane when the value of λλ of the external field decreases. We also observed that the dynamic behavior of the present system with a propagating magnetic field exhibits quite different characteristics in comparison with the same system, but only in the presence of a sinusoidal oscillating magnetic field (uniform over space) [35]. Very recently, it has been shown that frequency dispersion of the nanocubic core/shell particle driven by an oscillating field (uniform over space) can be categorized into three groups, as in the case of the conventional bulk systems [11]. Keeping these in mind, it would be interesting to investigate the influences of the propagating magnetic field on the frequency dispersion of dynamic loop area of the present system. From the theoretical perspective, the effects of standing magnetic field on the present system and also on the quenched disordered binary alloy cylindrical nanowire [39] could also be studied. We believe that such types of studies will be beneficial to provide deeper understanding of physics underlying of nanoscale materials driven by a time dependent magnetic field. ACKNOWLEDGEMENTS The author is thankful to Muktish Acharyya from Presidency University for valuable discussions and suggestions. The numerical calculations reported in this paper were performed at TÜBİTAK ULAKBIM (Turkish agency) High Performance and Grid Computing Center (TRUBA Resources). REFERENCES [1] T. Tomè and M.J. de Oliveira, Dynamic phase transition in the kinetic Ising model under a time dependent oscillating magnetic field Phys. Rev. A, vol. 41, pp , [2] W.S. Lo and R.A. Pelcovits, Ising model in a time dependent magnetic field Phys. Rev. A, vol. 42, pp , [3] S.W. Sides, P.A. Rikvold and M.A. Novotny, Phys. Rev. Lett. vol. 81, pp [4] G.M. Buendia and E. Machado, Magnetic behaviour of a mixed Ising ferrimagnetic model in an oscillating magnetic field Phys. Rev. B, vol. 61, pp , [5] G.M. Buendia and P.A. Rikvold, Dynamic phase transition in the two-dimensional kinetic Ising model in an oscillating magnetic field: Universality with respect to the stochastic dynamics Phys. Rev. E, vol. 78, pp [6] B. Chakrabarti and M. Acharyya, Dynamic transitions and hysteresis Rev. Mod. Phys. vol. 71, pp , [7] M. Keskin, O. Canko and Ü. Temizer, Dynamic phase transition in the kinetic spin-1 Blume-Capel model under a time dependent oscillating external field Phys. Rev. E, vol. 72, pp [8] X. Shi, G. Wei and L. Li, Effective-field theory on the kinetic Ising model Phys. Lett. A, vol. 372, pp , [9] H. Park and M. Pleimling, Surface criticality at a dynamic phase transition Phys. Rev. Lett., vol. 109, pp , [10] Y. Yüksel, E. Vatansever and H. Polat, Dynamic phase transition properties and hysteretic behaviour of a ferrimagnetic core-shell nanoparticle in the presence of a time dependent magnetic field J. Phys.: Condens. Matter, vol. 24, pp , [11] E. Vatansever, Monte Carlo simulation of dynamic phase transitions and frequency dispersions of hysteresis curves in core/shell ferrimagnetic cubic nanoparticle Phys. Lett. A, vol. 381, pp , [12] E. Vatansever and H. Polat, Dynamic phase transitions in a ferromagnetic thin film system: A Monte Carlo simulation study Thin Solid Films, vol. 589, pp , [13] M. Acharyya, Nonequilibrium phase transition in the kinetic Ising model: Divergences of fluctuations and responses near the transition point Phys. Rev. E, vol. 56, pp. 1234, [14] M. Acharyya, Nonequilibrium phase transition in the kinetic Ising model: Critical slowing down and the specific-heat singularity Phys. Rev. E, vol. 56, pp. 2407,

85 E VATANSEVER Academic Platform Journal of Engineering and Science 6-2, 72-80, 2018 [15] R.A. Gallardo, O. Idigoras, P. Landeros and A. Berger, Mean field theory of dynamic phase transition in ferromagnets Physica B, vol. 407, pp , [16] Y.-L. He and G.-C. Wang, Observation of dynamic scaling of magnetic hysteresis in ultrathin ferromagnetic Fe/Au(001) films Phys. Rev. Lett. vol. 70, pp , [17] D.T. Robb, Y.H. Xu, O. Hellwig, J. McCord, A. Berger, M.A. Novotny and P.A. Rikvold, Evidence for a dynamic phase transition in [Co/Pt]3 magnetic multilayers Phys. Rev. B., vol. 78, pp [18] J.-S. Suen and J.L. Erskine, Magnetic hysteresis dynamics: Thin p(1x1) Fe films on flat and stepped W(110) Phys. Rev. Lett., vol. 78, pp [19] A. Berger, O. Idigoras and P. Vavassori, Transient behaviour of the dynamically ordered phase in uniaxial cobalt films Phys. Rev. Lett., vol. 111, pp , [20] P. Riego, P. Vavassori and A. Berger, Metamagnetic anomalies near dynamic phase transitions Phys. Rev. Lett., vol. 118, pp [21] M. Acharyya and A. Halder, Blume-Capel ferromagnet driven by propagating and standing magnetic field wave: Dynamical modes and nonequilibrium phase transition J. Magn. Magn. Mater. vol. 426, pp , [22] M. Acharyya, Polarized electromagnetic wave propagation through the ferromagnet: Phase boundary of dynamic phase transition Acta Phys. Pol. B, vol. 45, pp , [23] M. Acharyya, Dynamic symmetry breaking breathing and spreading transitions in ferromagnetic film irradiated by spherical electromagnetic wave J. Magn. Magn. Mater., vol. 354, pp , [24] M. Acharyya, Ising metamagnet driven by propagating magnetic field wave: Nonequilibrium phases and transitions J. Magn. Magn. Mater., vol. 382, pp , [25] M.I. Irshad, F. Ahmad and N.M. Mohamed, A reviews on nanowires as an alternatives high density magnetic storage media AIP Conf. Proc., vol. 1482, pp , [26] Y.P. Ivanov, A. Chuvilin, S. Lopatin and J. Kosel, Modulated magnetic nanowires for controlling domain wall motion: Towards 3D magnetic memories ACS Nano, vol. 10, pp. 5326, [27] Y.P. Ivanov, A. Alfadhel, M. Alnassar, J.E. Perez, M. Vazquez, A. Chuvilin and J. Kosel, Tunable magnetic nanowires for biomedical and harsh environment applications J. Sci. Rep., vol. 6, pp , [28] B. Deviren, E. Kantar and M. Keskin, Dynamic phase transition in cylindrical Ising nanowire under a time dependent oscillating magnetic field J. Magn. Magn. Mater., vol. 324, pp , [29] B. Deviren, M. Ertaş and M. Keskin, Dynamic magnetizations and dynamic phase transitions in a transverse cylindrical Ising nanowire Phys. Scr., vol. 85, pp , [30] E. Kantar, B. Deviren and M. Keskin, Magnetic properties of mixed Ising nanoparticles with core-shell structure Eur. Phys. J. B., vol. 86, pp. 253, [31] M. Ertaş and Y. Kocakaplan, Dynamic behaviors of the hexagonal Ising nanowire Phys. Lett. A, vol. 378, pp , [32] B. Deviren and M. Keskin, Thermal behaviour of dynamic magnetizations, hysteresis loop areas and correlations of a cylindrical Ising nanotube in an oscillating magnetic field within the effective field theory and the Glauber type stochastic dynamic approach Phys. Lett. A, vol. 376, pp , [33] B. Deviren, Y. Sener, M. Keskin, Dynamic magnetic properties of the kinetic cylindrical Ising nanotube Physica A, vol. 392, pp , [34] E. Kantar, M. Ertaş and M. Keskin, Dynamic phase diagrams of a cylindrical nanowire in the presence of a time dependent magnetic field J. Magn. Magn. Mater., vol. 361, pp. 61, [35] Y. Yüksel, Monte Carlo study of magnetization dynamics in uniaxial ferromagnetic nanowires in the presence of oscillating and biased magnetic fields Phys. Rev. E, vol. 91, pp , [36] Y. Yüksel, Dynamic phase transition phenomena and magnetization reversal process in uniaxial ferromagnetic nanowires J. Magn. Magn. Mater., vol. 389, pp , [37] K. Binder, Monte Carlo Methods in Statistical Physics, Springer, Berlin, [38] M.E.J. Newman and G.T. Barkema, Monte Carlo Methods in Statistical Physics, Clarendon Press, Oxford, [39] Z.D. Vatansever and E. Vatansever, Finite temperature magnetic phase transition features of the quenched disordered binary alloy cylindrical nanowire J. Alloys Compd. vol. 701, pp. 288, [40] A. Halder and M. Acharyya, Standing magnetic wave on Ising ferromagnet: Nonequilibrium phase transition J. Magn. Magn. Mater., vol. 420, pp. 290,

86 Academic Platform Journal of Engineering and Science 6-2, 81-85, 2018 Academic Platform Journal of Engineering and Science journal homepage: Investigations of Effects of Density and Viscosity of Diesel and Biodiesel Fuels on NOx and other Emission Formations * 1 Gökhan TÜCCAR( X), 2 Erdi TOSUN( ), 3 Erinç ULUDAMAR( ) (1) Adana Science and Technology University, Faculty of Engineering, Mechanical Engineering Department, Adana, (2) Çukurova University, Faculty of Engineering and Architecture, Mechanical Engineering Department, Adana, (3) Adana Science and Technology University, Faculty of Engineering, Automotive Engineering Department, Adana, Abstract *Corresponding Author: Adana Science and Technology University, Faculty of Engineering, Mechanical Engineering Department, Adana, Doi: /apjes Received Date: Accepted Date: In the present study, effects of fuel properties; such as viscosity and density of different biodiesels on engine exhaust emissions were investigated. Sunflower, corn and canola oils were used as raw materials of biodiesel fuels which were produced via transesterification method. In experiments, pure biodiesels were used as test fuels and diesel was used as reference fuel. The results indicated that viscosity and density of biodiesel fuels went up with a higher proportion of biodiesel. Engine experiments, which were conducted on a Mitsubishi Canter 4D34-2A, four-stroke, four-cylinder diesel engine indicated that carbon monoxide (CO) emission reduced with the utilization of fuels that have higher viscosity and density. On the other hand, carbon dioxide (CO 2 ) and nitrogen oxide (NOx) emission had opposite trend. Both emission values were increased with higher biodiesel ratios. Keywords: Biodiesel, density, emission, viscosity 1. INTRODUCTION Energy demand which is rapidly growing with industrialization, forces developed and developing countries to import crude oil. Dependently, a considerable amount of domestic income is spent on importing of oil. For instance, crude oil consumption in our country climbed above 30 million tons per year in last years and this situation causes external dependency of Turkey to increase up to 70% with regard to energy issue [1]. With energy demand in the rapidly industrialized world, oil consumption is also growing inevitably and it causes oil prices to increase. Furthermore, emission gases released by combustion of petroleum-based fuels constitute greenhouse effect and they cause global warming. It is known that 73% of produced CO 2 is originated from fossil-based fuels nowadays [2]. In addition, it is predicted that petroleum reserves are limited sources and they will be depleted in near future [3-6]. The studies which focus on a search of a candidate to petroleum products revealed that vegetable oils can be used with close performance to diesel fuel in compression ignition engines. Use of biodiesel in diesel engines is firstly suggested by Rudolf Diesel in 1900s but cheap petroleum prices cause a decrease of attention to biodiesel [7]. Nevertheless, the importance of biodiesel has been gradually increasing with energy crises occurred in the 1970s. Nowadays, the most important environmental problem is global warming caused by greenhouse effect. Beside increments in use of coal and petroleum fossil fuels, a decrease of vegetation has an effect of a rapid increase in the amount of CO 2 in the atmosphere. Increasing of chlorofluorocarbons, hydrocarbons, methane, NOx and SOx which are produced by combustion are also accelerating greenhouse effect as well as CO 2. The greenhouse effect cause melting of glaciers and dependently rising of sea levels, warming globally and changes in climate. Reduction of emissions as unburned hydrocarbons (UHC), carbon monoxide (CO) and particulate matter (PM) can be provided with the use of biodiesel. Despite these reductions, there are studies which report an increase, decrease or no change in NOx emissions [8-9]. Zhang and Van Gerpen [10] have explored the use of soybean biodiesel and diesel mixtures on a modified, turbocharged, four-cylinder, direct-injection diesel engine, They discovered that the mixtures provide similar combustion properties compared to diesel fuel. Radwan et al. [11] investigated the effect of equivalence ratio, ignition temperature, ignition pressure, and ignition delay time of jojoba methyl ester. They reported that jojoba methyl ester has a lower ignition delay time, higher ignition temperature

87 G TÜCCAR Academic Platform Journal of Engineering and Science 6-2, 81-85, 2018 and higher ignition pressure [11]. Combustion properties of the waste cooking oil are investigated by Yu et al. [12] on a direct injection diesel engine. Tashtoush et al. [13] have reported the combustion performance of ethyl esters of waste vegetable oil. One of the most important points of avoiding emission formations is understanding of emission formation reasons. Therefore, investigations of effects on emission formation by determination of fuel properties of biodiesel fuels which are used as an alternative to diesel fuel in internal combustion engines are very important. Therefore, the aim of the study is investigation of the effects of biofuel fuel properties obtained from various oils on emissions. 2. MATERIAL AND METHODS 2.1. Biodiesel Production Production of test fuels used in the project was performed in Çukurova University Automotive Engineering Department Fuel Analysis Laboratory. Biodiesel production method used in this study is transesterification. Transesterification is a method that reacting of animal fats or vegetable oils with alcohol and catalyst to form glycerol and ester. The ratio of alcohol to triglyceride must be 3:1 in order to transesterification reaction to being completed stoichiometric. Practically, this ratio must be higher to obtain the maximum amount of product. Various types of catalysts are used to enhance reaction speed and products. The reaction can be catalyzed by alkaline, acids or enzymes. The chemical interaction of reaction was shown in Figure 1. One ester transforms to another ester in the transesterification reaction. Figure 1. Transesterification reaction Methanol which has 20% weight of oil and sodium hydroxide which has 1% weight of oil was mixed in a separate case by using a magnetic mixer and then, this mixture was mixed with oil which was heated up to 65 o C with 600 rpm for one hour and reaction occurred. The temperature was kept at 60 o C during the reaction. Then, the new blend was put in a separating funnel for one day and so, separation of biodiesel from glycerine phase was ensured. Lastly, obtained biodiesel was washed with warm water by three times, it was subjected to filtration process after drying at 105 o C for one hour (Figure 2). Figure 2. Biodiesel production steps 2.2. Measurements of Fuel Properties of Test Fuels Fuel properties were determined in Çukurova University Fuel Analysis Laboratory. Tests were repeated 3 times and mean values of results were calculated. Fuel properties were analysed by, Zeltex ZX 440 NIR petroleum analyzer with an accuracy of ±0.5 for determining cetane number; Tanaka AKV-202 type automatic kinematics viscosity meter with an accuracy of ±0.01 mm 2 /s for determining the viscosity; Kyoto Electronics DA-130 type density meter with an accuracy of ±0.001 g/cm 3 for density measurement, Tanaka APM-7 type flash point analyzer with an accuracy of ±0.5 o C for flash point measurement, IKA-Werke C2000 Calorimeter for heating value measurement Engine Tests The engine used in performance tests is 4 stroke, 4 cylinders diesel engine. Technical specifications are given in Table 1 and schematic representation of the experimental setup is given in Figure 3. Experiments were conducted at full load conditions between the most common engine speed interval from 1200 to 2400 rpm, with an increment of 200 rpm. A hydraulic dynamometer which has a torque range of Nm and speed range of rpm was used to measure engine torque. Before starting the experiment, the engine was operated with the new fuel for sufficient time to clean out the remaining fuel from the previous experiment. Sealing of fuel unit of experimental set-up was checked before every experiment to be able to ensure accurate measurements. Then, the load cell was calibrated. 2 82

88 G TÜCCAR Academic Platform Journal of Engineering and Science 6-2, 81-85, 2018 Table 1. Technical specifications of the test engine Brand Mitsubishi Canter Model 4D34-2A Configuration In line 4 Displacement Diesel Stroke Power Torque Cooling type Weight Sunflower Biodiesel Corn Biodiesel Canola Biodiesel 3907 cc 115 mm rpm rpm Water cooled 325kg Biodiesel Standards (EN 14214) Density (kg/l) Cetane Number >51 Viscosity (mm 2 /s) Heating Value (kj/kg) Flash Point 58.5 >140 > >120 ( o C) Bore 104 mm measurement accuracy of the gas analyzer is ±10 ppm for CO, 1% for CO 2 and ±1 ppm for NOx. 3. RESULTS AND DISCUSSIONS 3.1. Fuel Properties The test results obtained to determine fuel properties of produced biodiesel fuels were given in Table 2. It is specified that all density and viscosity values of biodiesels are in the range of European Biodiesel Standards (EN 14214). Viscosity which is an important property for injection of fuel was measured at 40 o C and compared according to standards. Nevertheless, viscosity values can be very different for biodiesel produced from different oils and produced with different techniques. Higher density generally means higher viscosity. Flow resistance increases with higher viscosity. Cetane number is used for measuring combustion quality in diesel engines. Higher cetane number means the higher self-ignition tendency of fuel. Therefore, cetane number is an important property for diesel fuels. Low cetane numbers of test fuels were recorded. Mixing of test fuels with diesel fuel or usage of cetane improvers as an additive are suggested in order to eliminate this disadvantage. Flash point is the minimum temperature that fuel releases vapor which is needed for ignitable mixture. This property is important for transportation and safety. High flash point means safe fuel. As seen in Table 2, the flash points of test fuels are in safe range. Fuel analysis results 3.2. Emissions There were some differences between emission values of different fuels used as seen in Figure 3, 4 and 5. While biodiesels which have higher density and viscosity values than diesel fuel cause to decrease in CO emission values, there is an increase in CO 2 and NO X emission values. Table 3 shows the amount of increment or decrement percentage of emissions when different biodiesels were used instead of diesel fuel. Table 3. Change in emissions (%) with respect to diesel fuel CO 2 CO NOx Sunflower Canola Corn Figure 3. Schematic representation of the experimental setup TESTO 350 XL gas analyzer was used to measure exhaust emissions. Emission data were collected with the help of a computer program which takes data at intervals of 2 s. The Density is mass per unit volume. If a fuel has higher density than other, it means much more mass is entering into the combustion chamber for the same volume, since new generation diesel injectors which supply fuel into combustion chamber for power generation regulate the amount of fuel by volume, not by mass. Much more fuel entering into cylinder means an increase of emissions. The increment of CO 2 and NOx emission values with biodiesel use can be explained by this reason. 83 3

89 G TÜCCAR Academic Platform Journal of Engineering and Science 6-2, 81-85, 2018 There is a reduction in CO emission with biodiesel usage. Since biodiesel has extra oxygen content, it gives less CO emissions (Figure 3). It is expected that reduction in CO emission due to extra oxygen cause to the conversion of CO to CO 2. The increment in CO 2 emission values can also be explained with the same reason (Figure 4). Biodiesel which has higher density will cause to have more oxygen and mass per unit volume. There are also many articles in the literature that report CO 2 increase and CO reduction with the use of biodiesel [14-17]. Figure 4. CO (ppm) emissions Figure 5. CO 2 (%) emissions Viscosity is an important property of fuel which has effects on NO X formation. NO X formation occurs at temperatures above 1700 K since nitrogen and oxygen molecules are inert up to these temperatures [9]. NOx emission values tend to increase with increasing viscosity and density of the fuel. Since viscosity and density of biodiesel fuels are greater than diesel fuel, fuel leakage during injection is reduced with biodiesel utilization, as a result, increased combustion chamber pressure and advanced injection timing occurs [18]. The increase in NOx formation can be explained by these phenomena. Figure 5 shows NOx emissions of various biodiesels. The literature also recorded increase in NOx emissions with the use of biodiesel [19-23]. 4. CONCLUSIONS Figure 5. NO X (ppm) emissions In this study, the effects of fuel properties as viscosity and density to exhaust emissions were investigated. Biodiesels were produced from sunflower, corn and canola oil via transesterification method. Biodiesels have higher density and viscosity values with respect to diesel fuel. According to engine tests, reduction in CO and increase in CO 2 and NOx emissions were observed when biodiesel was used. Biodiesel usage is important for our country which is dependent on other countries at the rate of 95% with regard to petroleum and petroleum-based fuels. Europa and developed countries encourage usage of biodiesel mixture at the rate of 20% with diesel fuel although pure biodiesel use both increase CO 2 and NO X emissions and decrease engine performance. Therefore, both exterior dependency of our country will decrease and transfer existing reserves to the next generations by using efficiently energy sources which are totally renewable will be possible. On the other hand, it was observed that reduction in CO release in these studies along project. 5. ACKNOWLEDGMENTS The authors are appreciated to Adana Science and Technology University for providing financial support. This work is supported financially by Adana Science and Technology University Scientific Research Office under contact no: MÜHDBF.MM REFERENCES [1] M. Akbalık, Ş. Kavcıoğlu, Energy Sector Outlook in Turkey, Dumlupınar Üniversitesi Sosyal Bilimler Dergisi, special issue, pp , [2] E. Buyukkaya, Effects of biodiesel on a DI diesel engine performance, emission and combustion characteristics, Fuel, vol. 89, pp , [3] G. Tüccar, T. Özgür, K. Aydın, Effect of diesel microalgae biodiesel butanol blends on performance and emissions of diesel engine, Fuel, vol. 132, pp ,

90 G TÜCCAR Academic Platform Journal of Engineering and Science 6-2, 81-85, 2018 [4] G. Tüccar, E. Tosun, T. Özgür, K. Aydın, Diesel engine emissions and performance from blends of citrus sinensis biodiesel and diesel fuel, Fuel, vol. 132, pp. 7-11, [5] K. Srithar, K. A. Balasubramanian, V. Pavendan, B. A. Kumar, Experimental investigations on mixing of two biodiesels blended with diesel as alternative fuel for diesel engines, Journal of King Saud University Engineering Sciences, vol. 29, pp , [6] P. K. Sahoo, L. M. Das, Combustion analysis of Jatropha, Karanja and Polanga based biodiesel as fuel in a diesel engine, Fuel, vol. 88, pp , [7] A. N. Özsezen M. Çanakçı, C. Sayın, Effects of Biodiesel from Used Frying Palm Oil on the Exhaust Emissions of an Indirect Injection (IDI) Diesel Engine, Energy & Fuels, vol. 22, pp , [8] C. Öner, Ş. Altun, Biodiesel production from inedible animal tallow and an experimental investigation of its use as alternative fuel in a direct injection diesel engine, Applied Energy, vol. 86, pp , [9] S. K. Hoekman, C. Robbins, Review of the effects of biodiesel on NOx emissions, Fuel Processing Technology, vol. 96, pp , [10]Yu Zhang, Jon H Van Gerpen. Combustion Analysis of Esters of Soybean Oil in a Diesel Engine. SAE paper [11]Dr Mohamed Y Selim, Radwan MS, Dandoush SK, Kader AMA. Ignition delay period of Jojoba diesel engine fuel. SAE paper No [12]Yu CW, Bari S, Ameen A. A comparison of combustion characteristics of waste cooling oil with diesel as fuel in a direct injection diesel engine. Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering, vol.216, pp , [13]Tashtoush Ghassan, Al-Widyan Mohamad I, Al- Shyoukh Ali O. Combustion performance and emissions of ethyl ester of a waste vegetable oil in a watercooled furnace. Applied Thermal Engineering vol.23, pp , [14] Y. Ulusoy, Y. Tekin, M. Çetinkaya, F. Kapaosmanoglu. The engine tests of biodiesel from used frying oil. Energ Source Part A, vol. 26, pp ,2004. [15] A.S. Ramadhas, C. Muraleedharan, S. Jayaraj, Performance and emission evaluation of a diesel engine fueled with methyl esters of rubber seed oil. Renew Energ vol.30, pp , [16]G. Fontaras, G., M. Karavalakis, Kousoulidou, T. Tzamkiozis, L. Ntziachristos, E. Bakeas, et al. Effects of biodiesel on passenger car fuel consumption, regulated and non-regulated pollutant emissions over legislated and realworld driving cycles, Fuel, pp , vol.88, [18]M. Canakci. Performance and emissions characteristics of biodiesel from soybean oil. P I Mech Eng D-J Aut,vol.219, pp ,2005. [18]B. Kegl, Numerical analysis of injection characteristics using biodiesel fuel, Fuel, vol. 85, pp , [19] M. Nabi, N. Hoque, Biodiesel production from linseed oil and performance study of a diesel engine with diesel biodiesel., JME, vol. 39(1), pp.40 44, [20] M. Nabi, M. Rahman, M. Akhter, Biodiesel from cotton seed oil and its effect on engine performance and exhaust emissions., Appl. Therm. Eng., vol. 29, pp , [21] S. Ghai, L. Das, G. Babu, Emissions and performance study with sunflower methyl ester as diesel engine fuel, J Eng. Appl. Sci., vol. 3(5), pp.75 80, [22] H. Serin, Ş. Yıldızhan, Influence of the compression ratio on the performance and emission characteristics of a VCR diesel engine fuelled with alcohol blended fuels. Eur. Mech. Sci., vol. 1(2), pp , [23] Ş. Yıldızhan, E. Uludamar, A. Çalık, G. Dede, M. Özcanlı Fuel properties, performance and emission characterization of waste cooking oil (WCO) in a variable compression ratio (VCR) diesel engine Eur. Mech. Sci., vol. 1(2), pp ,

91 Academic Platform Journal of Engineering and Science 6-2, 86-93, 2018 Academic Platform Journal of Engineering and Science journal homepage: Jeotermal Enerji Destekli Güç ve Temiz Su Üretim Sisteminin İncelenmesi ve Termodinamik Analizi * 1 Fatih YILMAZ( ) 1 Aksaray Üniversitesi Teknik Bilimler Meslek Yüksekokulu, Elektrik ve Enerji Bölümü, Geliş Tarihi: Kabul Tarihi: Öz Bu çalışmada, jeotermal enerji destekli güç ve deniz suyundan temiz su üretim çevrimi önerilmiş ve termodinamik analizi incelenmiştir. Çevrimin genel enerji ve ekserji verimleri araştırılmıştır. Bu bağlamda, çevrimdeki her bir elemana kütle, enerji, entropi ve ekserji denge bağıntı yöntemleri uygulanmıştır. Sistem organik Rankine çevrimi (ORC) ve tek kademeli distilasyon ünitesinden meydana gelmektedir. Aracı akışkan olarak ORC çevriminde çevre dostu CO 2 akışkanı tercih edilmiştir. Deniz suyundan temiz su üretimi için tek kademeli distilasyon ünitesi kullanılmıştır. Jeotermal enerji kullanılarak, çevrimden elde edilecek olan güç üretiminin aynı seviyede tutulması amaçlanmıştır. Yapılan bu çalışmada çevrimin genel enerji ve ekserji verimleri sırasıyla %10.18 ve %56.83 olarak hesaplanmıştır. Anahtar kelimler: Distilasyon, enerji, ekserji, jeotermal Investigation and thermodynamic Analysis of Geothermal Based Power and Fresh Water Production System Abstract * 1 Fatih YILMAZ ( ) 1Aksaray University of Technical Sciences Vocational School, Department of Electricity and Energy In this study, geothermal based power and fresh water production from sea water of the system proposed and thermodynamically analyzed. The overall energy and exergy efficiencies of cycle is investigated. In this regard, the mass, energy, entropy and exergy balances for the components of cycle are presented. This system consists of two subsystem such as organic Rankine cycle (ORC) and flash distillation unit. The environmentally friend CO 2 is used as working fluid in ORC. In order to keep the generated energy at the same level, geothermal energy is used. In the proposed study, the overall energy and exergy efficiencies are calculated as 10.18% and 56.83% respectively. Keywords: distillation, energy, exergy, geothermal Sorumlu Yazar: 1 Aksaray Üniversitesi Teknik Bilimler Meslek Yüksekokulu, Elektrik ve Enerji Bölümü, Doi: /apjes

92 F YILMAZ Academic Platform Journal of Engineering and Science 6-2, 86-93, GİRİŞ Fosil kökenli yakıtların kullanımı günümüzde birçok çevresel sorunlar oluşturmaktadır. Bu sorunlar içerisinde temel olarak bu yakıtların sürdürülebilirliği, onların çevreye ve sağlık üzerine etkileri daha öne çıkmaktadır. Bu yakıtların yanması sonucunda oluşan CO 2, NOx, SOx gibi gazlar özellikle çevre üzerine olan etkileri son yıllarda tartışılan konuların başında gelmektedir [1]. Çevresel sorunlarla beraber fosil kökenli yakıtların ilerleyen yıllarda rezervlerinin tükeneceği göz önüne alınırsa, dünyada ve ülkemizde bu yakıt türlerinden vazgeçilip yenilebilir enerji kaynaklarına olan yönelimin artması gerekmektedir. Yenilenebilir enerji kaynaklarının çevreye herhangi bir zararlı salınım meydana getirmemesi ve dışarıya bağımlı olmaması gibi birçok avantajları mevcuttur. Yenilenebilir enerji kaynakları içerisinde güneş, rüzgâr ve jeotermal enerji yaygın olarak kullanılmaya başlanmıştır. Dünya genelinde jeotermal enerjini kaynak sıcaklığı, jeotermal kaynağa bağlı olarak 50 o C den 350 o C ye kadar değişlik gösterebilmektedir [2]. Bu enerji kaynağı dünya üzerinde bol ve kararlı sıcaklık aralıklarında olduğu için güç üretim çevrimlerinde yaygın olarak kullanılmaktadır. Genellikle 220 o C den yüksek olan jeotermal su elektrik üretimi için daha uygundur. Düşük ve orta sıcaklık aralıklarındaki jeotermal su ise Organik Rankine çevrimlerinde (ORC) kullanılmaktadır [2, 3]. ORC çevrimleri 150 o C ve daha düşük sıcak kaynaklarda elektrik üretimi yapabilen bir teknolojidir. ORC çevrimleri buharlı güç çevrimlerinin aksine daha düşük maliyet gerektiren ve aracı akışkan olarak doğal soğutucu akışkanların kullanıldığı sistemlerdir. Bu çevrimlerde sıcak kaynak olarak genellikle güneş enerjisi, atık ısı, jeotermal enerji vb. kaynaklar kullanılabilir [4]. Ülkemiz açısından bakıldığında ise jeotermal enerji oldukça iyi bir noktadadır. Literatürde yapılan çalışmalar incelendiğinde jeotermal enerji destekli güç üretim çevrimleri ile ilgili birçok çalışma mevcuttur. Ezzat ve Dinçer [5], yeni güneş ve jeotermal enerji destekli sistemin enerji ve ekserji analizlerini incelemişlerdir. Yapılan bu çalışmada çoklu üretim yapan bir sistemin enerji ve ekserji verimleri incelenmiş ve tüm sistemin enerji ve ekserji verimleri sırasıyla %69.6 ve %42.8 olarak bulunmuştur. Esfahani ve Yoo[6] üç farklı kojenerasyon güç ve temiz su üretim sistemlerinin ekserji verimleri yönünden incelemişlerdir. Elde edilen sonuçlara göre, absorbsiyon soğutmalı kojenerasyon sisteminin en iyisi olduğu öne sürülmüştür. El Emam ve Dinçer [7], jeotermal enerji destekli rejeneratif ORC çevriminin termodinamik ve ekonomik analizini yapmışlardır. Çevrimin enerji ve ekserji verimleri sırasıyla %16.37 ve %48.8 olarak hesaplanmıştır. Yildirim ve Genç [8], jeotermal enerji temelli süt pastörizasyon prosesinin performansını termodinamik açısından incelemişlerdir. Tüm sistemin ekserji verimi ve ekserji yıkımı sırasıyla %56.81 ve kw olarak hesaplanmıştır. Jeotermal enerji destekli güç üretim sistemlerinin enerji, ekserji ve maliyet analizleri ile iliği literatürde bazı çalışmalar [9-12] mevcuttur. Burada jeotermal enerji sıcak kaynak girişi olarak kullanılmıştır. Bu çalışmalarda genellikle jeotermal enerji destekli güç ve hidrojen üretim potansiyelleri araştırılmıştır. Ele alınan bu çalışmada, jeotermal enerji destekli güç ve temiz su üretim prosesinin termodinamik analizi incelenmiştir. Güç çevrimi olarak ele alınan ORC çevriminde aracı akışkan olarak CO 2 kullanılmıştır. Aynı zamanda bu çalışmada, deniz suyunun distilasyonu sonucunda temiz su üretimi araştırılmıştır. Sistemin ihtiyaç duyduğu enerjinin doğalgazdan karşılanması durumunda ortaya çıkacak olan CO 2 emisyon değeri araştırılmıştır. Sistemin tüm termodinamik hesaplamalarında Engineering Equation Solver (EES) adlı paket program kullanılmıştır. 2. METOD 2.1. Jeotermal Destekli Güç Çevrimi Jeotermal enerjinin çıkış sıcaklıkları kurulu oldukları bölgelere göre değişiklik göstermektedir. Ülkemizde elektrik üretmek amacıyla kullanılan jeotermal santrallerin isimleri ve çıkış sıcaklıkları Tablo 1 de verilmiştir. Tablo 1. Türkiye de jeotermal santraller ve sıcaklıkları [13] İl İlçe Jeotermal sıcaklığı C Manisa Salihli 287 Denizli Kızıldere 242 Manisa Kavaklıdere 215 Aydın Ömerbeyli 232 Aydın Salavatlı 176 Çanakkale Tuzla 174 Kütahya Simav 184 İzmir Seferihisar 153 Manisa Caferbeyli 168 Aydın Yılmazköy 142 Aydın Umurlu 130 İzmir Dikili 120 İzmir Balçova 125 Jeotermal enerji destekli güç ve temiz su üretim prosesinin şematik gösterimi Şekil 1 de sunulmuştur. Ele alınan bu çevrimde, 1 noktasından gelen jeotermal enerji, ısı değiştiricisi-i e girerek ısısını 4 noktasından gelen ORC akışkanına aktarır. ORC çevriminde pompa çıkışında doymuş sıvı olan CO 2 akışkanı ısı değiştiricisi-i de jeotermal enerjiden aldığı ısı enerjisi ile birlikte 5 noktasında buhar fazına geçerek ORC türbinine gelir. Türbinde elektrik 87

93 F YILMAZ Academic Platform Journal of Engineering and Science 6-2, 86-93, 2018 üretimi meydana gelir. Sistem kapalı döngü olarak çalışmasına devam eder. Bu sistemin çalışma şekli buhar akışkanlı güç çevrimleri ile aynıdır. Çevrimdeki ısı değiştiricisi II ise yaklaşık çevre sıcaklığında distilasyon ünitesine giren deniz suyunun buharlaşmasını sağlayarak temiz su üretimini gerçekleştirir. Jeotermal enerji daha sonra 14 noktasından tekrar geri dönüşüm kuyusuna gider. Tek kademeli distilasyon ünitesi, tuzlu su ısıtıcısı ve dengeleme odasından oluşmaktadır. Denge odasında ise suyun yoğuşması ve bu yoğuşan sudan temiz su ayrıştırıcı olan zar bulunmaktadır. Denge odasının alt kısmında ise tuz havuzu bulunmaktadır. Tek kademeli distilasyon ünitesi ortalama 90 o C ve altı sıcaklık aralıklarında çalışmaktadır. Deniz suyu yaklaşık 22 o C de distilasyon ünitesine girer ve sonrasında ısı değiştiricisi II ye girerek burada jeotermal enerjiden gelen ısı ile yaklaşık 48 o C sıcaklığa ulaşır. Sıcaklığı artan deniz suyu devamında distilasyonu ünitesinde düşük basınçta yoğuşur ve temiz su üretimi gerçekleşir. Distilasyon ünitesi açık çevrim yöntemine göre çalışmaktadır. Bu çalışmada deniz suyundan temiz su üretimi için tek kademeli flaş distilasyon ünitesi ele alınmıştır. Distilasyon ünitesi hesaplamalarında yapılan bazı kabuller aşağıda verilmiştir[ 14,15]; Deniz suyunun özgül ısısı 4.18 kj/kg-k alınmıştır. Distilasyon ünitesinden elde edilen temiz su içerisinde tuz miktarı içermemektedir. Sistemden çevreye olan ısı kaybı ihmal edilmiştir. Deniz suyunun tuzluluk oranı ppm alınmıştır. Distilasyon ünitesinin tasarımında kaynak faydalanılmıştır. [14, 15] den Şekil 1. Jeotermal enerji destekli güç ve temiz su üretim çevrimi Şekil 2 de jeotermal destekli güç çevrimi olan CO 2 akışkanlı süperkritik ORC çevriminin P-h diyagramı verilmiştir. Şekil 2. CO 2 akışkanlı süperkritik ORC çevriminin p-h diyagramı 3. TERMODİNAMİK ANALİZ Çalışmanın bu bölümünde, enerji ve ekserji metotları kullanılarak termodinamik yönden sistemin değerlendirilmesi ele alınmıştır. Ele alınan bu sistemde termodinamik analizler dört temel yönteme göre gerçekleştirilmiştir. Bu yöntemler; a) kütle dengesi, b) enerji dengesi, c) entropi dengesi ve d) ekserji dengesidir [16-18]. Kütle Dengesi Düzgün akışlı kararlı sistemlerde kütle dengesi aşağıdaki şekilde yazılabilir; m g = m ç (1) Burada mm kütle akış debisini, g ve ç alt indisler ise sırasıyla giren ve çıkan kütleyi tanımlar. Enerji Dengesi... W =. H ç Hg Q (2) Eşitlik (2) de termodinamiğin birinci kanununda kinetik ve potansiyel enerjilerin ihmal edilmesi sonucunda ki durumu verilmiştir. Burada, Q, W ve H ifadeleri sırasıyla ısı transfer miktarını, iş ve entalpiyi tanımlar. Entropi Dengesi 88

94 F YILMAZ Academic Platform Journal of Engineering and Science 6-2, 86-93, 2018 m gs g + Q T g + S ür = m çs ç + Q T ç Burada s spesifik entropiyi, S ür entropi üretimini ve T Kelvin cinsinden sistem sıcaklığını tanımlar. Ekserji Dengesi m gex g + Eẋ g Q + Eẋ g W = m çex ç + Eẋ ç Q + Eẋ g W + Eẋ D (4) Burada, ex spesifik ekserjiyi, (3) Eẋ g Q ısı transferi ile gerçekleşen ısının ekserjisini, Eẋ g W üretilen işin ekserjisini ve Eẋ D ise ekserji yıkımını tanımlar. Spesifik ekserji ise aşağıdaki şekilde tanımlanabilir. ex = ex f + ex k + ex p + ex kn (5) Eşitlik (5) de ex f, ex k, ex p ve ex kn sırasıyla fiziksel, kimyasal, potansiyel ve kinetik ekserjileri tanımlar. Genel olarak bu çalışmada potansiyel, kinetik ve kimyasal ekserjiler ihmal edilmiştir. Fiziksel ekserji ise aşağıdaki şekilde detaylandırılır; ex f = h h 0 T 0 (s s 0 ) (6) Ekserji, kontrol hacimlerde sistemin çevresi ile olan ısı ve iş üretimleri ile orantılıdır. Eẋ Q = 1 T 0 T Q (7) Eẋ W = W (8) Distilasyon ünitesinin genel termodinamik dengesi aşağıdaki şekilde yazılabilir [15]; m ds = m ct + m ts (9) X ds m ds = X cs m ct (10) Burada ds, ct ve ts sırasıyla deniz suyu, konsantre su ve distilasyon sonunda oluşan temiz su kütlesini tanımlar. X ds ve X cs sırasıyla deniz suyunun ve konsantre suyun tuzluluk oranını ifade eder. Deniz suyunun tuzluluk oranı ppm olarak kabul edilmiştir. m 2h sb,su = m dscp(t 11 T 9 ) (11) m tsh b,su = (m ss + m ds)cp((t 11 T ss ) = m dscp(t 11 T ct ) (12) Burada T ct ve T ss konsantre tuz sıcaklığını ve soğuk su 10 noktasının sıcaklığını tanımlar. Önerilen bu çalışmadaki sistem alt bileşenlerinin genel termodinamik bağıntıları genel kütle, enerji, entropi ve ekserji dengeleri sürekli akışlı kararlı sistemler için aşağıdaki şekilde yazılabilir; Isı Değiştirici I; Kütle: m 1 = m 2; m 4 = m 5 (13) Enerji: Q ID_I = m 1(h 1 h 2 ) = m 4(h 4 m 5) (14) Entropi:m 1s 1 + m 4s 4 + Q ID_I T ID_I + S ür,id_i = m 2s 2 + m 5s 5 (15) Q Ekserji: m 1ex 1 + m 4ex 4 + Eẋ ID_I = m 2ex 2 + m 5ex 5 + Eẋ D,ID_I (16) Türbin; Kütle: m 5 = m 6 (17) Enerji: m 5h 5 = m 6h 6 + W T (18) Entropi:m 5s 5 + +S ür,t = m 6s 6 (19) Ekserji: m 5ex 5 = m 6ex 6 + W T + Eẋ D,T (20) Kondenser: Kütle: m 6 = m 3;m 15 = m 16 (21) Enerji: Q kon = m 6(h 6 h 3 ) = m 15(h 16 h 15 ) (22) Entropi:m 6s 6 + m 15s 15 + S ür,kon = m 3s 3 + m 16s 16 (23) Ekserji: m 6ex 6 + m 16ex 16 = m 3ex 3 + m 16ex 16 + E x D,kon (24) Pompa: Kütle: m 3 = m 4 (25) Enerji: m 3h 3 + W P = m 4h 4 (26) Entropi:m 3s 3 + S ür,p = m 4s 4 (27) Ekserji: m 3ex 3 + W P = m 4ex 4 + Eẋ D,P (28) Isı Değiştirici II; Kütle: m 2 = m 14; m 9 = m 11 (29) Enerji: Q ID_II = m 11(h 9 h 11 ) = m 2(h 2 h 14 ) (30) Entropi:m 2s 2 + m 9s 9 + Q ID_II T ID_II + S ür,id_ii = m 11s 11 + m 14s 14 (31) Q Ekserji: m 2ex 2 + m 9ex 9 + Eẋ ID_II = m 11ex 11 + m 14ex 14 + Eẋ D,ID_II (32) Distilasyon ünitesinin performans oranı (PO) aşağıdaki şekilde hesaplanır. PO = m 13 m 2 (33) Çevrimin genel enerji ve ekserji verimleri denklem (34) ve (35) de verilmiştir. η çevrim = W net+ m H2O(Δh) Q g (34) ψ çevrim = W net+ m H2O(Δh) Q Eẋ g (35) 89

95 F YILMAZ Academic Platform Journal of Engineering and Science 6-2, 86-93, SONUÇLAR VE TARTIŞMA Bu çalışmada jeotermal enerji destekli ORC çevriminden güç üretimi ve deniz suyundan temiz su üretimi incelenmiştir. Çevrimde aracı akışkan olarak çevre dostu olan CO 2 akışkanı kullanılmıştır. Aynı zamanda jeotermal enerjinin ısısından tekrar yararlanılarak tek kademeli distilasyon ünitesi ile deniz suyundan temiz su elde edilmesi araştırılmıştır. Yapılan çalışmada, tüm hesaplamalar için EES paket programı tercih edilmiştir [19]. Sistemin tasarım parametreleri Tablo 2 de sunulmuştur. Tablo 2 ye ek olarak termodinamik hesaplamalar için aşağıdaki kabuller yapılmıştır; Sistemde herhangi bir kimyasal reaksiyon gerçekleşmemektedir. Kinetik ve potansiyel enerji değişimleri ihmal edilmiştir. Çevreyle olan ısıl kayıpları ihmal edilmiştir. Tablo 2. Sistem tasarım parametreleri Parametreler Değer Jeotermal çıkış sıcaklığı o C Türbin izantropik verimi %80 Pompanın izantropik verimi %80 Soğutucu akışkan miktarı 10 kg/s Deniz suyunun tuzluluk miktarı ppm Referans çevre sıcaklığı 25 o C Referans çevre basıncı 100 kpa Tablo 2 deki değerlere göre yapılan termodinamik hesaplamalar sonucunda sistemin her bir noktasının değerleri Tablo 3 de sunulmuştur. 150 o C jeotermal çıkış sıcaklığında çevrimden 241 kw net güç elde edilmektedir. Sistemin genel enerji ve ekserji verimleri ise % ve % olarak hesaplanmıştır. Aynı şartlar altında entegre sistemde 7.23 kg/s temiz su elde edilmiştir. Tablo 3. Sistemin termodinamik analiz sonuçları Nokt a# P (kpa) T( o C) h (kj/ kg) s (kj/k g- o C) mm (kg/ s) , , , , , 9-207, 2 EEEE (k W) 1, , , , , , 6 258, 5 228, 7-0, , , , , , , , , , 5 11, ,5 127, 187, 39, ,5 127, 182, 38, ,5 127, 5,06 1, ,5 203, 182, 671, , 175, 14, , 0,505 7,23 4, , 0, , Sistem elemanlarının ekserji yıkımları, ekserji yıkım oranları ve ekserji verimleri 150 o C jeotermal çıkış sıcaklığında hesaplanmış ve Tablo 4 de sunulmuştur. Sistemin toplam ekserji yıkımı 3724 kw tır. Sistem elemanları içerisinde en yüksek ekserji yıkımı 1911 kw ile ısı değiştiricisi-i de görülmüştür. En küçük ekserji yıkımı ise ORC pompasında görülmektedir. Isı değiştiricileri ve kondenserdeki ekserji yıkımlarının yüksek olması, bu elemanlardaki ısı değişiminin fazla olmasından kaynaklanmaktadır. Tablo 4. Sistemin elemanlarının ekserji yıkım miktarları ve ekserji verimleri Sistem elemanları Ekserji yıkım miktarı (kw) Ekserji yıkım oranı (%) Ekserji verimi (%) Isı Değiştirici I Türbin Kondenser Pompa Isı Değiştirici II Distilasyon ünitesi Jeotermal enerji çıkış sıcaklığının değişiminin, sistemin enerji, ekserji verimlerine ve temiz su üretim miktarı üzerine etkisi incelenmiş ve Şekil 3 de sunulmuştur. Şekil 3 de görüldüğü gibi, jeotermal sıcaklığın 120 o C den 150 o C ye arttırılması sonucunda sistemin enerji veriminde artış 90

96 F YILMAZ Academic Platform Journal of Engineering and Science 6-2, 86-93, 2018 görülürken, ekserji veriminde ise düşüş görülmektedir. Ayrıca distilasyon sonucunda üretilen temiz su miktarının arttığı görülmektedir sistemin enerji verimi üzerine etkisinin olmadığı görülmüştür h çevrim y çevrim 0.7 Enerji ve ekserji verimleri Temiz su y çevrim h çevrim Temiz su kütlesi [kg/s] Enerji verimi Ekserji verimi Jeotermal çikis sicakligi ( o C) Şekil 3. Jeotermal çıkış sıcaklığının sistemin enerji ve ekserji verimleri üzerine etkisi Şekil 4 de ORC nin türbin giriş basıncının sistemden elde edilen net iş, çevrimin genel enerji ve ekserji verimlerine etkisi incelenmiştir. Türbin giriş basıncı 8000 kpa dan kpa a arttığında çevrimin genel enerji ve ekserji verimlerinin artığı görülmektedir. Türbin basıncın artması sonucunda elde edilen net iş miktarında artış görülmüştür. Jeotermal enerji çıkış sıcaklığı 150 o C de ve türbin giriş basıncı kpa da çevrimin genel enerji ve ekserji verimleri % ve % olarak hesaplanmıştır Referans çevre sicakligi ( o C) Şekil 5. Referans çevre sıcaklığının değişiminin çevrimin enerji ve ekserji verimlerine etkisi Şekil 6 de jeotermal kaynaktan çıkan akışkanın sıcaklık değişiminin distilasyon ünitesinin performansına ve elde edilen temiz su miktarı üzerine etkisi incelenmiştir. Jeotermal enerji kaynak sıcaklığının artması sonucunda elde edilen temiz su oranı da artmaktadır. Jeotermal enerji kaynak sıcaklığındaki artış, distilasyon ünitesinin performansı üzerine olumlu etkisi olduğundan elde edilen temiz su miktarı da artmaktadır Temiz su Performans orani Enerji ve ekserji verimleri h çevrim y çevrim W net W net (kw) Temiz su (kg/s) Performans orani Türbin giris basincini (kpa) Şekil 4. Türbin giriş basıncının sistemin enerji ve ekserji verimleri üzerine etkisi Referans çevre sıcaklığının değişiminin çevrimin genel enerji ve ekserji verimlerine etkisi incelenmiş ve Şekil 5 de verilmiştir. Referans çevre sıcaklığı 25 o C den 40 o C ye arttığında çevrimin ekserji verimi ise %56.83 den %73.88 e artmıştır. Referans çevre sıcaklığının beklenildiği gibi Jeotermal çikis sicakligi ( o C) Şekil 6. Jeotermal çıkış sıcaklığının distilasyon ünitesinin performansına ve temiz su üretimine etkisi. Bu çalışmada, eğer ısı kaynağı olarak jeotermal enerjinin yerine, doğalgaz tercih edilmesi durumunda CO 2 salınım miktarı incelenmiş ve Şekil 7 de sunulmuştur. Yapılan çalışmada ısı değiştiricisi-i den sisteme kw ısı 91

97 F YILMAZ Academic Platform Journal of Engineering and Science 6-2, 86-93, 2018 enerjisi girmektedir. Buna karşılık yakıt olarak doğalgaz kullanılmış olması durumunda atmosfere salınan CO 2 miktarı incelenmiştir. Doğalgazın yanma verimi bu çalışmada 0.85 olarak kabul edilmiş ve 0.49 kg/s doğalgaz miktarına karşılık atmosfere salınan CO 2 emisyon miktarı 1.3 kg/s olarak hesaplanmıştır. Bu sistemden 7.23 kg/s temiz su üretimi gerçekleşmektedir. Türbin giriş basıncı arttırıldığında çevrimden elde edilen net iş artmaktadır. Çevrimin ısı ihtiyacını karşılamak için, yakıt olarak doğalgaz kullanımı durumunda çevrimden 1.02 kg/s atmosfere salınan CO 2 miktarının önüne geçilmiştir. Bu çalışma vasıtasıyla, jeotermal enerji bakımından zengin, deniz ve okyanus kenarlarındaki ülkelerde ilerleyen yıllarda yapılacak olan deneysel çalışmalara yol gösterici nitelikte olması beklenmektedir. REFERANSLAR Şekil 7. Doğalgaz ve CO 2 emisyon miktarı 5.SONUÇLAR Ele alınan bu çalışmada, jeotermal enerji destekli güç ve temiz su üretim çevriminin termodinamik analizi, enerji ve ekserji yöntemleri kullanılarak incelenmiştir. Çevrimin her bir alt elemanlarına genel kütle, enerji, entropi ve ekserji bağıntı yöntemleri uygulanmıştır. Yapılan bu çalışmada ORC çevrimi ve deniz suyundan temiz su üretimi için tek kademeli distilasyon ünitesi incelenmiştir. ORC çevriminde aracı akışkan olarak çevre dostu CO 2 akışkanı seçilmiştir. Yapılan termodinamik hesaplamalar sonucunda elde edilen bazı önemli sonuçlar aşağıda kısaca sunulmuştur; Çevrimin genel enerji ve ekserji verimleri sırasıyla % ve % olarak hesaplanmıştır. Çevrimden 241 kw net iş üretimi gerçekleşmektedir. Çevrimin toplam ekserji yıkımı 3714 kw olarak hesaplanmıştır. Çevrimde en yüksek ekserji yıkım miktarı 1911 kw ile ısı değiştiricisi-i de görülürken, en düşük ekserji yıkım miktarı ise kw ile pompa da görülmüştür. Jeotermal enerji çıkış sıcaklığının artması sonucunda çevrimden elde edilen temiz su miktarı artmaktadır. [1] Ezzat, M.F., Dincer, I., Energy and exergy analyses of a new geothermal solar energy based system Solar Energy 134, (2016) [2] Hettiarachchi HDM, Golubovic M, Worek WM, et al. Optimum design criteria for an Organic Rankine Cycle using low- and mediumtemperature geothermal heat sources. Energy 2007; 32: [3] Tamamoto T, Furuhata T, Arai N, Mori K. Design and testing of the organic Rankine cycle. Energy 2001; 26: [4] Yilmaz, F. Güneş enerjisi destekli organik Rankine çevriminin Isparta şartlarında incelenmesi, S.D.Ü Üniversitesi Fen Bilimleri Ens. Yüksek Lisans Tezi, 2013 [5] Ezzat, M.F., Dincer, I., Energy and exergy analyses of a new geothermal solar energy based system, Solar Energy, 134 (2016) [6] Esfahani, I.J., Yoo, C.K., Exergy analysis and parametric optimization of three power and fresh water cogeneration systems using refrigeration chillers. Energy 59, [7] El Emam, R.S., Dincer, I., Exergy and exergoeconomic analyses and optimization of geothermal organic Rankine cycle. Appl. Therm. Eng. 59 (1 2), [8] Yildirim, N., Genc, S., Thermodynamic analysis of a milk pasteurization process assisted by geothermal energy, Energy 90 (2015) [9] Ratlamwala TAH, Dincer I, Gadalla MA. Performance analysis of a novel integrated geothermal-based system for multigeneration applications. Appl Therm Eng 2012;40:71-9. [10] Akrami E, Chitsaz A, Nami H, Mahmoudi SMS. Energetic and exergoeconomic assessment of a multigeneration energy system based on indirect use of geothermal energy. Energy 2017;124: [11] Coskun C, Oktay Z, Dincer I. Modified exergoeconomic modeling of geothermal power plants. Energy 2011;36: [12] Yuksel YE, Ozturk M. Thermodynamic and thermoeconomic analyses of a geothermal energy based 92

98 F YILMAZ Academic Platform Journal of Engineering and Science 6-2, 86-93, 2018 integrated system for hydrogen production. Int J Hydrogen Energy 2017;42(4): [13] Şahin A., Jeotermal Enerji Yatırımları Açısından Değerlendirme, Jeotermal Enerji ve Türkiye, Mayıs 2013, 1-40 [14] Demir, M.E., Dincer, İ., Development of an integrated hybrid solar thermal power system with thermoelectric generator for desalination and power production, Desalination 404 (2017) [15] H.T. El-Dessouky, H.M. Ettouney, Fundamentals of SaltWater Desalination, Elsevier, 2002, [16] Dincer, I., Rosen, M. A Exergy: energy, environment and sustainable development, Second Ed., Newness, [17] Moran, M., 1982 Availability Analysis: A Guide to Efficient Energy Usage, Englewood Cliffs, NJ: Prentice- Hall, [18] Bejan, A., Tsatsaronis, G., Moran, M Thermal Design and Optimization, New York: Wiley Inter-science. [19] Klein SA. Engineering equation solver. Academic professional, version

99 Academic Platform Journal of Engineering and Science 6-2, , 2018 Academic Platform Journal of Engineering and Science journal homepage: Hysteresis properties of a mixed ferromagnetic-ferrimagnetic ternary alloy Abstract: 1 Zeynep DEMİR VATANSEVER( ) * 1 Department of Physics, Faculty of Science, Dokuz Eylul University, İzmir, Turkey Arrival Date: Accepted Date: In this work, we have investigated the hysteresis properties of a mixed ferro-ferrimagnetic ternary alloy system by Monte Carlo simulation method. The ternary alloy system contains two interpenetrating sublattices. One of the sublattice consists of type-a magnetic components with spin-3/2 while the other one is randomly occupied type-b and type-c magnetic components with spin-1 and spin-5/2, respectively. We consider both ferromagnetic and antiferromagnetic exchange interactions between nearest-neighbor magnetic components. The influences of the exchange interaction ratio, R, and the concentration value of type-b magnetic ions, p, on the remanent magnetization, coercivity and hysteresis loops of the system have been investigated in detail. It has been demonstrated that it is possible to modify the remanent magnetization, coercivity and also the saturation magnetization of the system by changing the concentration value and exchange interaction ratio. Keywords: Hysteresis, ternary alloy, Monte Carlo simulation 1. INTRODUCTION Molecule-based magnets are center of interest during the last two decades thanks to their superior properties as compared to metal or metal-oxide magnets which make them attractive for technological applications [1]. Especially, a particular type of molecule based magnets, the multi-metal Prussian blue analogs, are in active investigations since the pioneering works of Okhoshi and his co-workers [2, 3, 4]. They have designed ternary metal Prussian blue compounds of the type (NNNN IIII IIII pp MMMM 11 pp ) CCCC IIIIII (CCCC) 66 which incorporate both ferromagnetic (JJ NNNN CCCC > 00) and antiferromagnetic (JJ MMMM CCCC < 00) superexchange interactions. The magnetic properties of these ternary metal Prussian blue compounds such as the saturation magnetization, Weiss temperature and coercive field can be well controlled by varying the active concentration of the magnetic ions in the compound [2]. The multi-metal Prussian blue analogs are also shown to display a photo induced magnetic pole inversion [5], two compensation temperatures [6, 7] and inverted magnetic hysteresis loop [8]. Moreover, nano-structured magnets comprised of Prussian blue analogs for instance, nanoparticles [9, 10, 11], nanowire arrays [12, 13] and nanotubes [14] have been synthesized in recent years. On the theoretical side, magnetic properties of ternary Prussian blue analogs of the type AABB pp CC 1 pp are investigated by several methods such as mean field theory (MFT) [15, 16, 17, 18, 19, 20, 21, 22], effective field theory (EFT) [23, 24, 25], Bethe lattice approximation [26, 27], Green s function technique [28], Monte Carlo (MC) simulation method [29, 30, 31, 32, 33, 34, 35, 36]. In these studies, in accordance with real mixed ferro-ferrimagnets which comprised of Prussian blue analogs [2], the ternary alloy is considered to be composed of two sublattices. One of the sublattice contains type-a magnetic components which interact ferromagnetically (JJ AAAA > 0) and antiferromagnetically (JJ AAAA < 0) with type-b and type-c magnetic components, respectively. Also, type-b and type-c magnetic components are distributed randomly throughout the other sublattice with probabilities p and 1 - p, respectively. One of the interesting feature that has been observed in some of these theoretical studies is the existence of a special interaction ratio RR CC = JJ AAAA /JJ AAAA where the critical temperature of the system becomes independent of the concentration ratio pp of the ternary alloy. For instance in Ref. [31], the authors have determined the critical interaction ratio, RR CC, for different lattice stoichiometries in the case of a three-dimensional Ising system with MC simulations. They have *Corresponding Author: Adana Science and Technology University, Faculty of Engineering, Mechanical Engineering Department, Adana, Doi: /apje

100 Z DEMİR VATANSEVER Academic Platform Journal of Engineering and Science 6-2, , 2018 showed that RR CC value changes very little with the lattice stoichiometry and lattice dimension. Also, many of the studies have focused on compensation temperatures of mixed ferro-ferrimagnetic ternary alloys which have been observed for certain values of the Hamiltonian parameters [30, 31, 35]. Despite the extensive theoretical studies about the magnetic properties of ternary alloys, to the best of our knowledge, a detailed study about hysteresis features of these systems has not been reported yet. Thus, our objective in this work is to present a detailed investigation of the hysteresis properties of the mixed ferro-ferrimagnetic ternary alloy of the type AABB pp CC 1 pp by means of Monte Carlo simulation based on Metropolis algorithm. The ternary alloy system includes three types of magnetic components A with spin-3/2, B with spin-1 and C with spin-5/2. We have examined the effects of the mixing ratio p and also the exchange interaction ratio R on the hysteresis loops, coercive field and remanent magnetization of the ternary alloy for a wide range of temperature values. We believe that this study will shed light on the future experimental and theoretical investigations of mixed ferroferrimagnetic compounds in the presence of an external magnetic field. The paper is organized as follows. In section 2, the details of the theoretical model and our MC simulations are given. Our numerical results are presented in section 3. Finally, our conclusions are summarized in section MODEL AND METHOD We consider a ternary alloy system of the type AABB pp CC 1 pp which contains two interpenetrating sublattices. One of the sublattice is occupied by type-a magnetic components while each site of the second sublattice is randomly occupied by type-b and type-c magnetic components with probabilities p and 1 p, respectively (see Figure 1). Thus, the Hamiltonian of ternary alloy system can be written as: H= JJ AAAA SS AA BB ii SS jj δδ jj JJ AAAA SS AA CC AA ii SS jj (1 δδ jj ) HH SS ii HH SS BB jj δδ jj + SS CC jj (1 δδ jj ) <iiii> <iiii> Here, δδ jj is a random variable which is unity (zero) if site- j is occupied by type-b (type-c) magnetic atoms. The first and second summations are over the pairs of the nearest-neighbor sites. SS AA, SS BB and SS CC are Ising spin variables which take the values of SS AA = ±1/2, ±3/2, SS BB = 0, ±1 and SS CC = ±1/2, ±3/2, ±5/2 for type-a, type-b and type-c magnetic components, respectively. The choice of the spin magnitudes correspond to the ternary metal Prussian blue compound, (NNNN IIII IIII pp MMMM 1 pp ) 1.5 CCCC IIIIII (CCCC) 6, where A=Cr with SS CCCC = 3/2, B=Ni with SS NNNN = 1 and C=Mn with SS MMMM = 5/2 [3]. Also, the exchange interaction between the components are reported as JJ NNNN CCCC > 0 and JJ MMMM CCCC < 0 [3]. Thus, we assume that there exists ferromagnetic interaction between type-a and type-b magnetic components (JJ AAAA > 0) whereas type-a and type-c components interact antiferromagnetically (JJ AAAA < 0). We have investigated the hysteresis features of the ternary alloy system by MC simulation method with single spin-flip Metropolis algorithm [37, 38]. As shown in Figure 1, ternary alloy system is located on a square lattice with L = 128 and we apply periodic boundary conditions in all directions. The simulations are started at high ii jj (1) temperature from kk BB TT/JJ AAAA =7.0 with randomly oriented spins and the system is gradually cooled with a temperature step of kk BB ΔΔΔΔ/JJ AAAA =0.1 where kk BB and TT are Boltzmann constant and absolute temperature, respectively MC steps per site (MCSS) are used for calculation of the thermal averages of interested physical quantities after discarding the first MCSS in order to obtain the equilibrium state. When the configuration for the interested temperature value is obtained, then magnetic field from HH/JJ AAAA to HH/JJ AAAA (decreasing field branch of the hysteresis) is applied. The configuration obtained for HH/JJ AAAA is taken as initial configuration for the increasing field branch and in a similar manner, by applying magnetic field from HH/JJ AAAA to HH/JJ AAAA, increasing field branch is completed. At each magnetic field step, the first MCSS are excluded for thermalization and the magnetizations are calculated over the next MCSS. We have performed 20 independent computer experiments which correspond to different initial states. We have calculated the thermal average and configurational average of sublattice magnetizations (mm AA, mm BB, mm cc ) per spin: NN AA MM AA = [ mm AA ] = 1 AA SS NN ii AA ii=1 NN BB MM BB = [ mm BB ] = 1 BB SS NN ii BB ii=1 95 2

101 Z DEMİR VATANSEVER Academic Platform Journal of Engineering and Science 6-2, , 2018 and total magnetization, mm TT : NN CC MM CC = [ mm CC ] = 1 CC SS NN ii (2) CC ii=1 MM TT = [ mm TT ] = 1 NN TT mm AA + mm BB + mm CC (3) Here, denotes the thermal averages and [...] corresponds to the configurational averages. In order to determine the phase transition point separating the ordered and disordered phases from each other, we consider the thermal variation of the total susceptibility defined by: χχ TT = NN TT( MM 2 TT MM TT 2 ) (4). kk BB TT Figure 1: Schematic representation of the ternary alloy system. The red, black and blue circles correspond to type-a, type-b and type-c magnetic components, respectively. 3. RESULTS Figure 2: Magnetic phase diagrams of the ternary alloy system in a) (RR kk BB TT CC /JJ AAAA ), b)(pp kk BB TT CC /JJ AAAA ) plane. In this section, we will discuss the effects of an external cycling magnetic field on the magnetic properties of a ternary alloy of the type AABB pp CC 1 pp. Particularly, we pay attention to the effects of the exchange interaction ratio, RR = JJ AAAA /JJ AAAA, and mixing ratio, pp, on the magnetic properties of the system. Obviously, p = 0 case corresponds to a ferrimagnetic mixed spin-3/2 and spin-5/2 system while for p = 1, we have a mixed spin-3/2 and spin-1 ferromagnetic system. For the latter case, there are no JJ AAAA exchange interaction terms in the system which means that magnetic properties of the system does not alter with pp. Also, starting 3 96

102 Z DEMİR VATANSEVER Academic Platform Journal of Engineering and Science 6-2, , 2018 from small RR values, as RR takes larger values, the antiferromagnetic exchange interaction between type-a and type-c magnetic components becomes effective in the system. Firstly, in order to confirm the accuracy of our results and also to determine the temperature and concentration values to be studied, we show the phase diagram of the ternary alloy in (RR kk BB TT CC /JJ AAAA ) and (pp kk BB TT CC /JJ AAAA ) planes in Figure 2(a) and Figure 2(b), respectively. As one can readily see from Figure 2(a) that the phase separation curves belonging to different pp values intersect at a special interaction ratio, RR CC for which the transition temperature of the system does not vary with pp. We have also performed further simulations in a narrow range of RR in order to determine accurate value of RR CC as shown in Figure 2(b). According to our simulation results for the case of a two dimensional ternary alloy system, the special interaction ratio is RR CC = For R< RR CC (RR > RR CC ), the transition temperature of the system increases (decreases) as p takes larger (smaller) values. These results are in accordance with the previous investigations of ternary alloy systems reported in literature [29, 36]. Figure 3: Total susceptibility per spin as a function of temperature a) for R=1 with several values of concentration value of type-b atoms: p=0, 0.25, 0.5, 0.75 and 1 b) for p=0.5 with varying values of the interaction parameter: R=0.2,0.4,0.6,0.8 and 1. Total susceptibility curves of the system as a function of temperature are shown in Figure 3(a) for R=1 with several values of concentration of type-b atoms. In accordance with the expectations, the susceptibility curves exhibit a maximum at the transition temperature of the system and this maximum moves to higher temperature region with decreasing p. In order to see the effects of interaction parameter, R, on the transition temperature of the system, we also show the total susceptibility curves in the case of concentration of p=0.5 for varying values of R in Figure 3(b). As one can readily see, as the interaction parameter takes larger values, susceptibility exhibits a maximum at higher temperature region. These findings also support the phase diagram of the system (Fig 2(a)). In Figure 4(a)-(b), coercive field HH cc, and remanent magnetization, MM rr, of the ternary alloy as a function of RR for several values of concentration value, pp at a reduced temperature of kk BB TT CC /JJ AAAA = 1.0 have been displayed. The coercivity of the ternary alloy system shows an increment behavior as the exchange interaction ratio takes larger values for all pp values under consideration. Since the number of JJ AAAA spin-spin coupling terms increases with the number of type- C magnetic components in the system, the variation of HH cc with RR is more pronounced in the case of small pp values. It can be also seen from the figure that for a fixed value of RR, the coercivity and remanence strongly depend on the concentration value of type-b magnetic components in the system. Moreover, for all the p values except for pp = 0 and pp = 1 the remanent magnetization firstly decreases slightly with RR because of the enhanced antiferromagnetic exchange interaction in the system whereas an opposite is situation is true for pp =

103 Z DEMİR VATANSEVER Academic Platform Journal of Engineering and Science 6-2, , 2018 With a further increment in RR, remanent magnetization becomes very close to a value of MM TT = 1 2 [ MM AA(TT = 0) + pp MM BB (TT = 0) (1 pp) MM CC (TT = 0) ] for all the considered values of pp. Figure 4: a) Coercivity and b) remanence variations of the ternary alloy system as a function of RR at kk BB TT CC /JJ AAAA = 1.0 for several values of concentration value of type-b atoms: pp = 0, 0.25, 0.5, 0.75 and 1. Figure 5: Hysteresis curves of the ternary alloy with a) pp = 0, b) pp = 0.25, c) pp = 0.5, d) pp = 0.75 for several value of R. 5 The curves are shown for reduced temperature value of kk BB TT CC /JJ AAAA = 1. 98

104 Z DEMİR VATANSEVER Academic Platform Journal of Engineering and Science 6-2, , 2018 In order to investigate magnetic features of the ternary alloy, we have showed the hysteresis curves of the system in the case of varying values of R for a) pp = 00, b) pp = , c) pp = , d) pp = at a reduced temperature of kk BB TT CC /JJ AAAA = 1.0 in Figure 5. As one can also see from the phase plane of Figure 2(a), the system is in the ordered phase for all pp values at this temperature value. While the hysteresis curves display various shapes depending on the value of the concentration value of type-b magnetic components, they have some common features. For instance, if the magnetic field is large enough, it can overcome the antiferromagnetic exchange coupling. Therefore magnetization value saturates to a value MM TT = [ MM AA(TT = 00) + pp MM BB (TT = 00) + (11 pp) MM CC (TT = 00) ] corresponding to the case for which all the spins are aligned parallel to each other and to the external field. Also, starting from increasing or decreasing field branch, as the absolute value of the magnetic field decreases and reaches a particular value (depending on pp), the antiferromagnetic exchange coupling becomes effective and magnetization decreases to the value of MM TT = [ MM AA(TT = 00) + pp MM BB (TT = 00) (11 pp) MM CC (TT = 00) ]. We should also notice that as RR takes larger values, the hysteresis loops become wider in accordance with our observations of Figure 4. Another interesting point that should be underlined is the existence of triple hysteresis loops for pp = at particular values of exchange interaction ratio. This can explicitly be seen from the inset of Figure 5(c). A triple hysteresis loop is observed for RR = and RR = 11 and below a particular of RR single hysteresis loop is observed. In Figure 6(a) and 6(b), the variation of the hysteresis loops with p is illustrated at kk BB TT CC /JJ AAAA = 1.0 for RR = 0.2 and RR = 1 respectively. If one compares the width of the hysteresis loops, the hysteresis loops become narrower (wider) for RR = 1 (RR = 0.2) with increasing pp. The alteration of remanent magnetization with p is also in agreement with our discussions for Figure 4(b). Besides, the absolute value of the total magnetization at large fields increases with increasing number of type-c magnetic components in the system. Figure 6: Hysteresis curves of the ternary alloy with a) RR = 0.2, b) RR = 1 for several value of pp. The curves are shown for reduced temperature value of kk BB TT CC /JJ AAAA = 1.0. As a final investigation, we investigate the temperature dependence of coercivity and remanence of the ternary alloy system at an exchange coupling ratio of R = 1 for varying concentration value of type-b atoms in Figure 7(a) and 7(b), respectively. For all concentration values, HH cc and MM rr decrease with raising temperature due to the enhanced thermal agitation which destroys the magnetic order in the system and they become zero above the critical temperature of the system. As an example, we show the hysteresis curves of the system for pp = 0.5 and RR = 1 for varying temperature values in Figure 8. The hysteresis loop areas decrease with raising temperature and paramagnetic behavior is observed when the temperature is above the phase transition temperature of the system. 6 99

105 Z DEMİR VATANSEVER Academic Platform Journal of Engineering and Science 6-2, , 2018 Figure 7: Temperature dependence of the a) coercivity and b) remanence at a exchange coupling ratio of RR = 1 for varying concentration of type-b atoms:pp = 0, 0.25, 0.5, 0.75, 1. Figure 8: Hysteresis loop of the ternary alloy system for pp = 0.5 and RR = 1 for varying values of the temperature. As a final remark, we compare our numerical results about the hysteresis features of the ternary alloy system with the literature. From the experimental side, for a ternary metal Prussian blue compound of the type (NNNN IIII IIII pp MMMM 1 pp ) 1.5 CCCC IIIIII (CCNN) 6, it has been demonstrated that it is possible to modify saturation magnetization, coercivity and remanent magnetization by varying the mixing ratio of p of the system [3]. Therefore, our results are in a qualitative agreement with the available experimental result [3] in literature. On the theoretical side, as far as we know, there are not any works regarding the hysteresis features of ternary alloys. However, the limiting cases of the system (p=0 and p=1) correspond to mixed Ising spin systems which have been widely studied in literature. For instance, in reference [39], the authours have observed triple hysteresis behaviors similar to our results for a mixed spin-2 and spin- 5/2 ferrimagnetic Ising system. Also, triple hystresis loops are observed for the other type of mixed spin systems, such as nanowires [40,41], nanoparticles [42,43]

106 Z DEMİR VATANSEVER Academic Platform Journal of Engineering and Science 6-2, , CONCLUSIONS Hysteresis properties of a mixed ferro-ferrimagnetic ternary alloy of the type AABB pp CC 1 pp is studied by MC simulation method with Metropolis algorithm. Both ferromagnetic (JJ AAAA > 0) and antiferromagnetic (JJ AAAA < 0) spin-spin interactions between nearestneighbor magnetic components are considered. The dependence of the coercivity, remanence and also hysteresis loops of the ternary alloy system on the exchange interaction ratio and concentration value of type-b magnetic components are investigated in detail. Moreover, hysteresis properties of the system are analyzed in a wide temperature region. It has been shown that it is possible to tune the coercivity, remanence and saturation magnetization of the system by changing exchange interaction ratio and number of type-b components. As a further investigation, procedure followed in this work can be applied to nano-dimensional structures such as ternary alloy magnetic nanoparticles and nanowires. Such a study may reveal the effects of reduced dimensions on the magnetic features of ternary alloy systems. ACKNOWLEDGEMENTS The numerical calculations reported in this paper were performed at TÜBİTAK ULAKBİM (Turkish agency), High Performance and Grid Computing Center (TRUBA Resources). REFERENCES [1] J. S. Miller and M. Drillon, Magnetism: Molecules to Materials V, Weinheim: Wiley-VCH, [2] S. I. Ohkoshi, O. Sato, T. Iyoda, A. Fujishima, K. Hashimoto, Tuning of Superexchange Couplings in a Molecule-Based Ferroferrimagnet: (Ni II xmn II 1-x) 1.5[Cr III (CN) 6 ], Inorg. Chem., vol. 36, pp , [3] S. I. Ohkoshi, O. Sato, T. Iyoda, A. Fujishima, K. Hashimoto, Magnetic properties of mixed ferro-ferrimagnets composed of Prussian blue analogs, Phys. Rev. B, vol. 56, pp , [4] S. I. Ohkoshi and K. Hashimoto, Theoretical treatment of the mixed ferro-ferrimagnets composed of ternary-metal Prussian blue analogs in a paramagnetic region, Phys. Rev. B, vol. 60, no 18, pp , June [5] S. I. Ohkoshi, S. Yorozu, O. Sato, T. Iyoda and A. Fujishima, Photoinduced magnetic pole inversion in a ferro ferrimagnet: (Fe0.40IIMn0.60II)1.5CrIII(CN)6, Appl. Phys. Lett., vol. 70, pp. 1040, [6] S. I. Ohkoshi, Y. Abe, A. Fujishima and K. Hashimoto, Design and Preparation of a Novel Magnet Exhibiting Two Compensation Temperatures Based on Molecular Field Theory, Phys. Rev. Lett., vol. 82, pp. 1285, [7] S. I. Ohkoshi, T. Hozumi, M. Utsunomiya, M. Abe and K. Hashimoto, The observation of two compensation temperatures in a cobalt-manganese hexacyanochromate, Physica B, vol. 329, pp , [8] S. I. Ohkoshi, T. Hozumi and K. Hashimoto, Design and preparation of a bulk magnet exhibiting an inverted hysteresis loop, Phys. Rev. B, vol. 64, pp , [9] P. Bhatt, S. Banerjee, S. Anwar, M. D. Mukadam, S. S. Meena and S. M. Yusuf, Core Shell Prussian Blue Analogue Molecular Magnet Mn 1.5 [Cr(CN) 6 ] 1.5 [Cr(CN) 6 ] nh2o for Hydrogen Storage, Appl. Mater. Interfaces, vol. 6, pp , [10] C-H Lee, C-M Wu, E. Batsaikhan, H-C Li, C. H. Li, M. K. Peprah, D. R. Talham, M. W. Meisel and W-H Li, Complex Magnetic Phases in Nanosized Prussian Blue Analogue Cubes: Rb 0.48 Co[Fe(CN) 6 ] 0.75 [(H 2 O) 6 ] H Ni[Cr(CN) 6 ] 0.74 [(H 2 O) 6 ] H 2 O, J. Phys. Chem. C, vol. 119, pp , [11] P. Bhatt, A. Kumar, S.S. Meena, M.D. Mukadam and S.M. Yusuf, Magnetic proximity effect in ferrimagnetic ferromagnetic core shell Prussian blue analogues molecular magnet, Chem. Phys. Lett., vol. 651, pp , [12] P. Zhou, D. Xue, H. Luo and X. Chen, Fabrication, Structure, and Magnetic Properties of Highly Ordered Prussian Blue Nanowire Arrays, Nano Lett., vol. 2, pp , [13] P. H. Zhou and D. S. Xue, Finite-size effect on magnetic properties in Prussian blue nanowire arrays, J. Appl. Phys., vol. 96, pp , [14] A. Johansson, E. Widenkvist, J. Lu, M. Boman and U. Jansson, Fabrication of High-Aspect-Ratio Prussian Blue Nanotubes Using a Porous Alumina Template Nano Lett., vol. 5, no 8, pp , [15] A. Bobák, F. O. Abubrig and T. Balcerzak, Multicritical points in the mixed ferromagneticferrimagnetic ternary alloy with a single-ion anisotropy, Phys. Rev. B, vol. 68, pp , December [16] A. Bobák, J. Dely and T. Balcerzak, Compensation temperatures and susceptibility of ternary metal Prussian blue analogs, Czech. J. Phys, vol: 54, pp. D523-D-526, June [17] A. Bobák, F. O. Abubrig and T. Balcerzak, Phase diagrams of the mixed ferro-ferrimagnetic ternary alloy with a single-ion anisotropy, J. Magn. Magn. Mater., vol , pp , [18] A. Bobák and J. Dely, The effect of a singleion anisotropy on the phase diagram of a mixed

107 Z DEMİR VATANSEVER Academic Platform Journal of Engineering and Science 6-2, , 2018 ferro-ferrimagnetic ternary alloy, Physica A, vol. 341, pp , [19] J. Dely and A. Bobák, Magnetic properties of the ternary alloy with a structure of Prussian blue analogs Physica B, vol. 388, pp , [20] J. Dely and A. Bobák, Phase diagrams of the ternary alloy with a single-ion anisotropy in the mean-field approximation, J. Magn. Magn. Mater., vol. 305, pp , [21] J. Dely, A. Bobák and D. Horváth, Mean- Field and Monte Carlo Study of a Mixed Ferro- Ferrimagnetic Ternary Alloy, Acta Phys. Pol. A, vol. 113, no 1, pp , [22] J. Dely, A: Bobák and M. Žukovic, Critical temperature of a mixed ferro-ferrimagnetic ternary alloy, J. Phys. Conf. Ser., vol. 200, pp , [23] Bobák, A. O. F. Abubrig and D. Horváth, Magnetic properties of a mixed ferro ferrimagnetic ternary alloy, Physica A, vol. 312, pp , [24] H. Hu, Z. Xin and W. Liu, Magnetic properties of the mixed ferro-ferrimagnets composed of Prussian blue analogs with (A x B 1 x) y C, Phys. Lett. A, vol. 357, pp , [25]J. Wei, G. H. Yu and L. V. Cheong, Magnetization of mixed ferri-ferrimagnets composed of Prussian blue analogs A1 x A2 1 x B, Chin. Phys. B, vol. 20, no 5, pp , [26] E. Albayrak, J. Magn. Magn. Mater., The mixed-spin ternary-alloy in the form of AB p C 1-p on the Bethe lattice, vol. 323, pp , [27]B. Deviren, M. Keskin and Y. Aydin, Compensation Temperatures, Magnetic Susceptibilities and Phase Diagrams of a Mixed Ferrimagnetic Ternary System on the Bethe Lattice, JETP Letters, vol. 92, pp , [28]G. Mert, Green's function study of a threesublattice mixed-spin Heisenberg ferromagnetic and ferrimagnetic system, J. Magn. Magn. Mater., vol. 363, pp , [29] G. M. Buendía and J. E. Villarroel, Compensation temperatures of mixed ferroferrimagnetic ternary alloys, J. Magn. Magn. Mater., vol. 310, pp. e495-e497, [30]J. Dely, A. Bobák and M. Žukovic, Compensation temperatures and magnetic susceptibility of a mixed ferro-ferrimagnetic ternary alloy, Phys. Lett. A, vol. 373, pp , [31] M. Žukovic and A. Bobák, Critical and compensation phenomena in a mixed-spin ternary alloy: A Monte Carlo study, J. Magn. Magn. Mater., vol. 322, pp. 2868, [32] S. Tsuji, T. Kasama and T. Idogaki, Decoration iteration transformation and Monte Carlo simulation for mixed ferrimagnetic ternary alloy, J. Magn. Magn. Mater., vol. 310, pp. e471- e473, [33] E. K. Çam and E. Aydiner, J. Magn. Magn. Mater., Compensation temperature of 3d mixed ferro-ferrimagnetic ternary alloy, vol. 322, pp , [34] E. K. Çam and E. Aydiner, Magnetic Behavior of Ternary Prussian Blue Analog in Presence Single-Ion Anisotropy, E. IEEE Trans. Magn., vol. 49, no 9, pp , [35]Y. Yuksel, Monte Carlo simulation of Prussian blue analogs described by Heisenberg ternary alloy model J. Phys. Chem. Solids, vol. 86, pp , [36] E. Vatansever, and Y. Yuksel, Dynamic phenomena in magnetic ternary alloys, J. Alloys Compd., vol. 689, pp , [37] K. Binder, Monte Carlo Methods in Statistical Physics, Berlin: Springer, [38] M. E. J. Newman and G. T. Barkema, Monte Carlo Methods in Statistical Physics, Newyork: Oxford University Press, [39] W. Wang, D. Lv, F. Zhang, J-L Bi and J-N Chen, Monte Carlo simulation of magnetic properties of a mixed spin-2 and spin-5/2 ferrimagnetic Ising system in a longitudinal magnetic field, J. Magn. Magn. Mater., vol. 385, pp , [40] B. Boughazi, M. Boughrara and M. Kerouad, The hysteresis behavior of an Ising nanowire with core/shell morphology: Monte Carlo treatment, J. Magn. Magn. Mater., vol. 363, pp , [41] W. Jiang, X-X Li, L-M Liu, J-N Chen and F. Zhang, Hysteresis loop of a cubic nanowire in the presence of the crystal field and the transverse field, J. Magn. Magn. Mater., vol. 353, pp , [42] Y. Yuksel, E. Vatansever, and H. Polat, Dynamic phase transition properties and hysteretic behavior of a ferrimagnetic core shell nanoparticle in the presence of a time dependent magnetic field, J. Phys.: Condens. Matter, vol. 24, pp , [43] E. Kantar, B. Deviren and M. Keskin, Magnetic properties of mixed Ising nanoparticles with core-shell structure, Eur. Phys. J. B, vol. 86, pp. 253,

108 Academic Platform Journal of Engineering and Science 6-2, , 2018 Academic Platform Journal of Engineering and Science journal homepage: Kısa Analiz Verileri Kullanılarak Biyokütlenin Üst Isı Değerinin Hesaplanması *Neslihan DURANAY( ), Melek YILGIN( ) Fırat Üniversitesi, Mühendislik Fakültesi, Kimya Mühendisliği Bölümü, ELAZIĞ Geliş Tarihi: Kabul Tarihi: Öz Biyokütle küresel ısınmaya katkıda bulunmayan, alternatif enerji kaynaklarından biridir. Biyokütlenin yakıt olarak kullanımının, fosil yakıtlardan kaynaklanan sorunlara çözüm olacağı düşünülmektedir. Biyokütle ile çalışan bir tesis tasarlanacağı zaman ısıl değerinin belirlenmesi gerekmektedir. Çünkü ısıl değer tesisin kapasitesini belirlemede en önemli parametredir. Bu çalışmada bölgemizde fazla miktarda bulunan on farklı biyokütlenin kısa analiz verileri kullanılarak üst ısı değerleri (ÜID) hesaplandı. Hesaplamalarda dört farklı eşitlik kullanıldı. Eşitlik E1, E2, E3, E4 sırasıyla biyokütlenin kül, uçucu madde, kül ve uçucu madde, uçucu madde ve sabit karbon içeriklerini dikkate alarak ÜID ni tahmin etmek için kullanıldı. Ayrıca, adyabatik kalorimetre bombası kullanılarak numunelerin ÜID leri deneysel olarak belirlendi. Deneysel ve tahmin edilen ÜID leri her bir numune için karşılaştırıldı ve standart sapmanın 0.5 ila 1.87 kj/g aralığında değiştiği tespit edildi. Tahmin edilen değerler, deneysel değerlere karşı grafiğe geçirildiğinde R 2 değerlerinin yakın olduğu belirlendi. Ayrıca hesaplanan ve deneysel olarak belirlenen üst ısı değerlerinin biyokütlenin uçucu madde ve kül oranlarından etkilendiği tespit edildi. Anahtar Kelimeler: Biyokütle, üst ısı değeri, kısa analiz. Estimation of Higher Heating Value of Biomass Using Proximate Analysis Data Neslihan DURANAY*, Melek YILGIN Fırat Üniversitesi, Mühendislik Fakültesi, Kimya Mühendisliği Bölümü, ELAZIĞ Abstract Biomass is one of the alternative energy sources that do not contribute to global warming. The use of biomass as fuel is thought to be a solution to problems arising from fossil fuels. When designed a plant that works with biomass, the calorific value should be determined. Because the calorific value is the most important parameter in determining the capacity of the plant. In this study, higher heating value (HHV) were estimated using proximate analysis data of ten different biomass. Four different equations were used in estimations. The equations are used to estimate the HHV by considering the contents of the ash (E1), volatile matter (E2), ash and volatile matter (E3) and volatile matter and fixed carbon (E4) of the biomass. In addition, the HHV s of the samples were experimentally determined by using an adiabatic calorimeter bomb. The experimental and estimated HHV's were compared for each sample and the standard deviations were found to vary from 0.5 to 1.87 kj/g. When estimated values were plotted against experimental values, it was determined that R 2 values were close to each other. In addition, it was detected that estimated and experimentally determined HHV s were affected from the volatile matter and ash ratios of the biomass. Keywords: Biomass, higher heating value, proximate analysis *Sorumlu Yazar: Fırat Üniversitesi, Mühendislik Fakültesi, Kimya Mühendisliği Bölümü, ELAZIĞ Doi: /apjes

109 N DURANAY Academic Platform Journal of Engineering and Science 6-2, , GİRİŞ Enerji, sosyal ve ekonomik kalkınmanın ana kaynaklarından biridir. Son yüz yılda, dünyadaki enerji tüketimi yaklaşık 17 kat artmıştır [1,2]. Artan enerji ihtiyacı, toplumları ucuz, bol ve çevre üzerinde daha az etkiye sahip alternatif enerji kaynakları bulmaya yönlendirmiştir. Hızla tüketilen fosil yakıtlar, bu gereksinimleri karşılamaktan çok uzaktır. Bu yüzden, biyokütle bol miktarda, bulunması kolay, yenilenebilir ve sürdürülebilir bir enerji kaynağı olarak görülüyor [3]. Bu niteliklerin sonuncusu olan sürdürülebilirlik, uzun menzilli taşımalardan kaçınmak için yerel olarak tedarik edilen hammaddelerden yakıtların geliştirilmesi; gıda ve elyaf üretimi için kullanılan toprak ve su ile rekabet etmeyen; ve sera gazı emisyonlarını azaltması anlamına gelmektedir [4]. Bu yüzden biyolojik kütlenin sürdürülebilir bir enerji kaynağı olma potansiyeli, tüm dünyada önemli bir araştırma konusu olmuştur. Biyokütlenin enerjiye biyolojik veya termokimyasal dönüşümünün verimini belirlemek için, biyokütlenin potansiyel enerji içeriği bilinmelidir [4]. Bir yakıtın ısı değeri, alt ısı veya üst ısı değerinden biri kullanılarak verilir. Yakıtın üst ısı değeri, yakıtın birim kütlesi tamamen yakıldığında normal suyun yoğunlaşma derecesini standart koşullar altında yanma ürünü olarak hesaplayan ısı miktarına eşittir. Yüksek üst ısı değerine sahip yakıtlar yandığında yüksek enerji çıkışı elde edilir. Bu özellik biyokütle yakma sistemlerinin tasarımı ve işletilmesi açısından çok önemlidir. Yakıt olarak ele alınan biyokütlenin üst ısı değeri, bir reaktan ile ürünlerin entalpisi arasındaki değişikliklerin basit ve doğru bir ölçümü olan adyabatik bir oksijen bombası kalorimetresi kullanılarak deneysel olarak belirlenebilir. Basit olmasına rağmen, üst ısı değerini deneysel olarak analiz etmek her zaman mümkün olmayabilir [5,6]. Literatürde kömür ve biyokütle için üst ısı değerini yakıtın elementel bileşimine (C, H, N, O, S) dayandıran birçok model bulunmaktadır [5-9]. Yin [5] özellikle lignoselülozik bileşiklerden oluşan biyokütlelerin üst ısı değerlerinin kısa ve elementel analiz verileri kullanılarak hesaplanması için doğrusal regresyonla iki denklem geliştirmiş ve bu denklemlerin üst ısı değerinin hızlı hesaplanmasına katkıda bulunacağını belirtmiştir. Bununla birlikte, elementel analiz, masraflı ve zaman alıcı olabilir, bu nedenle araştırmacılar biyokütle gibi katı yakıtların üst ısı değerini tahmin etmek için deneysel yöntemlere yönelmiştir [1-4,7-11]. Garcia ve ark [1] hem elementel hem de kısa analiz verilerini kullanarak üst ısı değerlerini hesaplamışlar. Örneğin nem içeriğinin kullanılacak denklemin belirlenmesinde etkili olduğu ve kısa analiz verileri ile belirlenen üst ısı değerlerinin daha iyi sonuç verdiğini belirtmişlerdir. Biyokütlenin ısıl değerinin tahmininde kısa analiz verilerinin kullanılmasının en ucuz ve kolay yöntem olduğunu belirten Erol ve ark.[7] geliştirdikleri korelasyonların ısıl değerin tahmininde kullanılabileceğini göstermişlerdir. Uzun ve ark.[4] ise sadece kısa analiz verileri kullanılarak biyokütlenin üst ısı değerinin doğru olarak tahmin edilmesinin, yenilenebilir yakıt üretimi için biyokütle ve biyokütle karışımlarının belirlenmesine yardımcı olacağını vurgulamışlardır. Üst ısı değerini tahmin etmek için 131 biyokütle numunesi veri seti kullanarak bir yapay sinir ağı modeli oluşturmuşlardır. Bu tür matematiksel modeller, katı yakıtın nem, uçucu madde, sabit karbon ve külünün ağırlık yüzdelerine (ağırlıkça%) dayanmaktadır. Katı bir yakıtın nem, uçucu madde, kül ve sabit karbon içeriğinin belirlendiği kısa analizi basit bir şekilde [6] ve daha ayrıntılı analizlerden ucuz ve kısa sürede yapılabilir. Böylece kısa analiz gibi basit faktörlere dayanılarak üst ısı değeri hızlı bir şekilde hesaplanır ve ısı verimi yüksek karışımlar elde edilir. Bir yakıt veya yakıt karışımına ait üst ısı değerinin hızlı tahmin edebilme özelliği, biyokütlenin ön işlenmesi gerekliliğini belirler. Sunulan çalışmada, farklı kaynaklardan (tarım, orman ve gıda endüstrisi) elde edilen ve bölgemizde önemli potansiyele sahip lignoselülozik yapıdaki atık biyokütlelerin sadece kısa analiz verileri kullanılarak üst ısı değerlerinin belirlenmesi amaçlandı. Kısa analiz verileri ile yapılacak hesaplama için literatürde verilen dört farklı denklem kullanıldı. Denklemler, üst ısı değerinin hesaplamasında biyokütlenin içerdiği külün (E1), uçucu maddenin (E2), kül ile uçucu maddenin birlikte (E3) ve sabit karbon ile uçucu maddenin birlikte (E4) etkisini belirlemek üzere seçildi [2,5,12]. Hesaplanan üst ısı değerleri biyokütle numunelerinin literatürde verilen ve adyabatik oksijen kalorimetresi kullanılarak tespit edilen deneysel değerleri ile karşılaştırıldı. 2. MALZEME VE YÖNTEM 2.1. Örneklerin Hazırlanması Bu çalışmada on biyokütle örneği kullanıldı. Biyokütle örnekleri bölgemizde kolayca elde edilebilen tarımsal, orman ve gıda endüstrisi atıklarından seçildi. Bu çalışmada; ceviz kabuğu, fındık kabuğu, kayısı çekirdeği, pamuk kozası, ay çekirdeği kabuğu, şarap fabrikası atığı, mobilya fabrikası atık tozu, meşe talaşı, çam kozalağı ve çam talaşı kullanıldı. Nemli olan numuneler laboratuvar ortamında kurutuldu ve mobilya tozu dışındaki biyokütleler parçalayıcı kullanılarak öğütüldü ve elendi. Elenen numuneler kilitli poşetlerde nem almayacak şekilde muhafaza edildi. Elenen numunelerin 75 μm (100 mesh elek altı) parçacık boyutundaki taneler çalışmada kullanıldı. 2.2.Kısa (Proximate) Analiz Deneysel çalışmalarda kullanılan numunelerin öncelikle nem tayini yapıldı. Bu tayin 105 C de Mettler LJ16 nem tayin cihazında (±%0.01hassasiyet) gerçekleştirildi.numunenin uçucu madde (UM) ve kül oranı ASTM standardına [13,14] göre belirlendi. Sabit 104

110 N DURANAY Academic Platform Journal of Engineering and Science 6-2, , 2018 karbon (SK) miktarı aşağıda verilen Eşitlik (1) ile hesaplandı. % SK = (% UM+ % Nem + % Kül) (1) Deney verilerinin doğruluğunun kontrolü için, analizler birkaç kez tekrarlandı. ±%5 den daha düşük sapma görülen paralel çalışmaların sonuçlarının ortalaması alındı Üst Isı Değerinin (ÜID) Tayini Biyokütle örneklerinin deneysel olarak ÜID belirlemek için JULIUS PETERS IBERLİN adyabatik kalorimetresi kullanıldı. Analiz yapılırken kapsül, tel ve numunelerin tartımı yapıldı. Kapalı sistem içinde ağırlıkları bilinen örneklerin yanması sonucunda açığa çıkan ısı, ısı sensörleri yardımıyla tespit edildi. Üst ısı değerleri kalorimetrenin kullanım kılavuzunda belirtilen aşağıdaki eşitlik ile hesaplandı. ÜID = ( T 4713 m kap m tel ) m numune (2) Bu eşitlikte; m kap ;kapsül kütlesi (g), m tel ; yakma için kullanılan telin kütlesi (g) ve m numune ; numune kütlesi (g) olarak verilmektedir. ÜID nin belirlendiği deneyler de birçok defa tekrarlandı ve sapması ±%5 in altında olan değerlerin ortalaması alındı. Ayrıca Tablo 1 de verilen eşitlikler kullanılarak biyokütle numunelerinin ÜID leri hesaplandı. Tablo 1. Kısa analiz verilerinden ÜID (kj. g -1 ) Eşitlik hesaplamada kullanılan eşitlikler. E1 ÜID = Kül [2,12] E2 ÜID = UM [2,12] E3 ÜID = Kül UM[2,12] E4 ÜID = UM SK [2,5] 3. BULGULAR VE TARTIŞMA Tablo 2 de on biyokütlenin kısa analiz sonuçları verilmektedir. Genel olarak uçucu madde yüzdesinin yüksek olduğu görülmektedir. En yüksek uçucu madde oranı çam talaşında tespit edildi. Bu durumun çamın reçineli bir biyokütle olmasından kaynaklandığı düşünülmektedir. En düşük uçucu madde oranı ise nem ve kül içeriği yüksek olan pamuk kozasında tespit edildi. Şarap fabrikası atığı ve pamuk kozasının kül içeriği biyokütle olarak oldukça yüksek bulunurken diğer biyokütlelerin beklenen sınırlar içerisinde olduğu belirlendi. Biyokütle örneklerinin sabit karbon oranlarının ise %14 ile %20 arasında olduğu tespit edildi. Tablo 2 : Kısa analiz verileri. Numune % Nem %Uçucu Madde % Kül % Sabit Karbon* Ceviz kabuğu Şarap fabrikası atığı Mobilya atık tozu Meşe talaşı Fındık kabuğu Kayısı çekirdeği Pamuk kozası Çam kozalağı Çam talaşı Ay çekirdeği kabuğu *Farktan hesaplandı. Denklemlerden hesaplanan ÜID leri aynı tür biyokütleler için literatürde verilen ve deneysel olarak bulunan değerler ile Tablo 3 de karşılaştırılmaktadır. Hesaplanan ÜID nin literatürde verilen ve deneysel olarak tespit edilenler ile uygunluk içinde olduğu belirlendi. En yüksek ÜID çam talaşı için hesaplandı ve deneysel olarak bulunan değere oldukça yakın olduğu (ortalama % 2.25 hata) tespit edildi. Bu durum çam talaşının reçineli yapısı ve dolayısıyla uçucu madde miktarının fazla olmasından kaynaklanmaktadır. Diğer taraftan en düşük üst ısı değeri, nem ve kül içeriği yüksek, uçucu madde oranı düşük olan pamuk kozasında elde edildi ve bu numunenin deneysel ısıl değeri de düşük bulundu. Her bir numunenin kısa analiz verilerinden hesaplanan ve deneysel olarak bulunan ÜID nin standart sapması hesaplandı ve 0.5 ile 1.87 kj/g arasında değiştiği tespit edildi. Meşe, çam kozalağı ve şarap fabrikası atığı için deneysel olarak tespit edilen ÜID nin literatürde verilenlere [2] yakın olduğu görüldü. Diğer taraftan ceviz, fındık ve kayısı çekirdeği kabuğu ile şarap fabrikası atığının 105

111 Üst ısı değeri (hesaplanan) (kj/g) Üst ısı değeri (hesaplanan) (kj/g) Üst ısı değeri (hesaplanan) (kj/g) Üst ısı değeri (hesaplanan) (kj/g) N DURANAY Academic Platform Journal of Engineering and Science 6-2, , 2018 hesaplanan ÜID nin literatürle uygunluk gösterdiği tespit edildi. Şarap fabrikası atığının hesaplanan ÜID nin hem literatür hem de deneysel olarak belirlenen ÜID ile uygunluk içinde olması, bileşiminin üretildiği bölgeye göre değişmediğini göstermektedir. Tablo 3. Kısa analiz verilerinden hesaplanan üst ısı değerleri Eşitlik No: Numune E1 E2 E3 E4 Deneysel ÜID (kj/g) Standart Sapma (kj/g) Literatür [2] ÜID (kj/g) Ceviz kabuğu Şarap fabrikası atığı Mobilya fabrikası atık tozu Meşe talaşı Fındık kabuğu Kayısı çekirdeği Pamuk kozası Çam kozalağı Çam talaşı Ay çekirdeği kabuğu E1 25 E R² = 0, Üst ısı değeri (deneysel) (kj/g) R² = 0, Üst ısı değeri (deneysel) (kj/g) 25 E3 25 E R² = 0, Üst ısı değeri (deneysel) (kj/g) R² = 0, Üst ısı değeri (deneysel) (kj/g) Şekil 1. Deneysel ve hesaplanan üst ısı değerleri arasındaki ilişki. 106

112 Üst ısı değeri (kj/g) Üst ısı değeri (kj/g) N DURANAY Academic Platform Journal of Engineering and Science 6-2, , 2018 Denklemlerden elde edilen ÜID leri deneysel olarak belirlenenlere karşı grafiğe geçirildi ve R 2 değerleri hesaplandı (Şekil1) ve birbirine yakın olduğu tespit edildi. R 2 ve standart sapma değerleri birlikte ele alınırsa, bu çalışmada kullanılan denklemlerin, biyokütle örneklerinin kısa analiz verileri kullanılarak ÜID nin hesaplanabileceği söylenebilir. Uçucu madde termal bozunumu ve tesis tasarımını etkileyen önemli bir bileşendir. Yüksek uçucu içeriği düşük sıcaklıklarda ateşlemeyi kolaylaştırır, bu da yüksek reaktiviteye neden olur ve yanma sürecini zenginleştirir [2]. Şekil 2 de biyokütlelerin dört farklı denklemden hesaplanan ve deneysel olarak belirlenen ÜID nin uçucu madde konsantrasyonu ile değişimi verilmektedir. Biyokütlenin uçucu madde konsantrasyonu arttıkça üst ısı değerinin arttığı hem hesaplanan hem de deneysel değerlerde açıkça görülmektedir. Bu durumda bir biyokütlenin kısa analiz verilerinden ÜID tahmin 24 edilecekse uçucu madde oranın tek başına yeterli olabileceği söylenebilir. Sabit karbon yanmasından sonra kalan inorganik atıkları kül olarak tarif edebiliriz. Kül yanma teknolojisini belirlemede önemli parametrelerden biridir. Çünkü artan kül oranı biyokütleye oksijen difüzyonunu etkilediğinden oluşan yetersiz yanma ÜID ni ve yanma verimini düşürür [2]. Şekil 3 de deneysel ve hesaplanan ÜID nin biyokütlenin kül oranıyla değişimi verilmektedir. ÜID nin artan kül miktarı ile azaldığı tespit edildi. Bu durum hem deneysel hem de hesaplanan ısıl değerlerde görüldü. En yüksek oranda kül içeren pamuk kozası ve şarap fabrikası atığının ÜID nin diğer numunelerden düşük olduğu, diğer taraftan kül içeriği en düşük olan çam talaşının deneysel ve hesaplanan ÜID nin yüksek olduğu tespit edildi Deneysel E4 E3 E2 E % Uçucu Madde Şekil 2. Biyokütlenin uçucu madde içeriğinin üst ısı değerine etkisi Deneysel E4 E3 E2 E % Kül Şekil 3. Biyokütlenin kül içeriğinin üst ısı değerine etkisi. 107

113 N DURANAY Academic Platform Journal of Engineering and Science 6-2, , SONUÇLAR Bu çalışmada araştırılan denklemlerin, biyokütle örneklerinin kısa analiz verileri kullanılarak ÜID nin hesaplanabileceği tespit edildi. Her bir numunenin kısa analiz verilerinden belirlenen ÜID nin standart sapması hesaplandı ve 0.5 ile 1.87 kj/g arasında değiştiği ve R 2 değerlerinin birbirine yakın olduğu tespit edildi. Hesaplanan ÜID nin literatürden alınan ve deneysel olarak tespit edilenler ile uygunluk içinde olduğu belirlendi. Biyokütlenin uçucu madde içeriğinin yüksek olması ısı elde edilmesinde kullanımı için bir avantaj olacağı belirlendi. En yüksek ısıl değer çam talaşı için hesaplandı ve deneysel olarak bulunan ısı değeriyle oldukça yakın olduğu (ortalama % 2.25 hata) tespit edildi. Ayrıca kül oranının da biyokütlenin ısıl değeri üzerinde etkili olduğu açıkça görüldü. En düşük ÜID, kül içeriği yüksek olan pamuk kozasının deneysel ve hesaplanan ısıl değerinde elde edildi. Sonuç olarak enerji üretimi için biyokütlenin kullanılacağı sistemlerin tasarımı yapılırken, ÜID nin kısa analiz verilerinden hızlı ve orijinal değerine yakın olarak elde edilebileceği tespit edildi. KAYNAKLAR [1] R. García, C. Pizarro, A.G. Lavín and J.L.Bueno, Characterization of Spanish biomass wastes for energy use, Bioresource Technol, vol.103, pp , [2] R. García, C.. Pizarro, A.G. Lavín, J.L. Bueno, Spanish biofuels heating value estimation. Part II: Proximate analysis Data, Fuel, vol.117, pp , [3] E. Akkaya, ANFIS based prediction model for biomass heating value using proximate analysis components, Fuel, vol.180, pp , [4] H.Uzun, Z. Yıldız, J. L. Goldfarb, S. Ceylan, Improved prediction of higher heating value of biomass using an artificial neural network model based on proximate analysis, Bioresource Technology, vol.234, pp , [5] C.-Y. Yin, Prediction of higher heating values of biomass from proximate and ultimate analyses, Fuel, vol.90, pp , [6] A.J. Callejón-Ferre, J. Carreño-Sánchez, F.J. Suárez- Medina, J. Pérez-Alonso, B. Velázquez-Martí, Prediction models for higher heating value based on the structural analysis of the biomass of plant remains from the greenhouses of Almería (Spain), Fuel, vol.116, pp , [7] M. Erol, H. Haykiri-Acma, S.Küçükbayrak, Calorific value estimation of biomass from their proximate analyses data, Renew. Energy, vol.35, pp , [8] D.R. Nhuchhen, P.A. Salam, Estimation of higher heating value of biomass from proximate analysis: a new approach. Fuel, vol.99, pp.55 63, [9] J. Shen, S.Zhu, X. Liu, H. Zhang, J. Tan, The prediction of elemental composition of biomass based on proximate analysis. Energy Convers. Manag, vol.51, pp , [10] T. Cordero, F. Marquez, J. Rodriguez-Mirasol, J.J. Rodriguez, Predicting heating values of lignocellulosics and carbonaceous materials from proximate analysis, Fuel, vol. 80, pp , [11] J. Parikha, S.A. Channiwalab, G.K. Ghosalc, A correlation for calculating HHV from proximate analysis of solid fuels, Fuel, vol. 84, pp , [12] A.J. Callejón-Ferre, B. Velázquez-Martí, J.A. López- Martínez, F. Manzano-Agugliaro, Greenhouse crop residues: Energy potential and models for the prediction of their higher heating value, Renewable and Sustainable Energy Reviews, vol.15, pp , [13] ASTM-E 872. Volatile matter in the analysis of particulate wood fuels. Annual Book of ASTM Standards; [14] ASTM-E Ash in biomass. Annual Book of ASTM Standards;

114 Academic Platform Journal of Engineering and Science 6-2, , 2018 Academic Platform Journal of Engineering and Science journal homepage: Meme Kanseri Tanısı İçin Özniteliklerin Öneminin Değerlendirilmesi Üzerine Bir Çalışma Kemal AKYOL( ) Kastamonu Üniversitesi Mühendislik ve Mimarlık Fakültesi Bilgisayar Mühendisliği Bölümü, Geliş Tarihi: Kabul Tarihi: Öz En yaygın kanser türlerinden biri olan meme kanseri kadınları etkileyen ölümcül bir hastalıktır. Önerilen çalışmada, Wisconsin meme kanseri veriseti üzerinde öznitelik seçimine dayalı Özyinelemeli Özellik Seçimi metodu kullanılarak özniteliklerin önemliliği araştırılmış ve sonrasında Rastele Orman ve Lojistik Regresyon sınıflandırıcı algoritmaları kullanılarak makine öğrenmeleri gerçekleştirilmiştir. Eğitim ve test aşamalarını içeren öğrenme süreci 5 katlı çapraz doğrulama tekniği kullanılarak gerçekleştirilmiştir. Deneysel çalışmalar, Rastgele Orman algoritması kullanılarak en iyi sınıflandırma başarısı ( %98 doğruluk) elde edildiğini göstermiştir. Anahtar Kelimeler: Meme kanseri risk tahmini, özniteliklerin önemliliği, Özyinelemeli Özellik Eleme, Rastgele Orman, Lojistik Regresyon. A Study on Assessing the Importance of Attributes for Breast Cancer Diagnosis Abstract *Sorumlu Yazar: Kastamonu Üniversitesi Mühendislik ve Mimarlık Fakültesi Bilgisayar Mühendisliği Bölümü, Doi: /apjes Kemal AKYOL Kastamonu University Faculty of Engineering and Architecture Computer Engineering Department Breast cancer, one of the most common types of cancer, is a deadly disease affecting women. The importance of attributes was investigated by using the Recursive Feature Selection based on feature selection on Wisconsin breast cancer dataset, and then the machine learnings were performed by utilizing Random Forest and Logistic Regression classifier algorithms in the proposed study. The learning process involving training and testing phases was performed by utilizing the 5-fold cross-validation technique. Experimental studies showed that the best classification performance (98% accuracy) was achieved by applying the Random Forest algorithm. Keywords: Logistic Regression, Breast cancer risk prediction, importance of attributes, Recursive Feature Elimination, Random Forest. 1. GİRİŞ Meme dokusundaki süt kanalları veya bezlerinde gelişen [1] ve kadın nüfusunu etkileyen yaygın kanser tiplerinden bir tanesi olarak bilinen ve dünya genelinde her yıl 1.38 milyon yeni vakanın tahmin edildiği bir hastalıktır [2]. Erken dönemde meme kanseri tespiti ve teşhisi, başarılı tedavinin ve hastanın iyileşmesinin başarı şansını arttırır. Pürüzsüz ve iyi tanımlanmış bir sınıra sahip kitle iyi huylu olabilir. Ancak, düzensiz bir sınıra sahip kütle kanserli olabilir [3]. Özyinelemeli Özellik Elemesi (ÖÖE, Recursive Feature Elimination [4]) ile özniteliklerin öneminin araştırıldığı ve sonrasında sırasıyla [5-6] da tanıtımları yapılan Lojistik Regresyon (LR) ve Rastgele Orman (RO) sınıflandırıcı algoritmaları ile eğitim ve test aşamaları yürütülerek sınıflandırma sürecinin tamamlandığı bu çalışmada meme kanseri hastalığı için önemli olan özniteliklerin araştırması yapılmıştır. Üzerinde çalışılan veriseti, Wisconsin Meme Kanseri Verisetidir (WMKV). Odaklanılan yöntemler çerçevesinde bu çalışmanın hibrid bir yaklaşım içerdiği ve %98 civarında doğru sınıflandırma oranı ile başarılı bir performans sergilediği ifade edilebilir. Çalışmanın ilerleyen bölümleri şu şekildedir: 2. bölümde önceki çalışmalara yer verilmiştir. 3. bölümde, üzerinde çalışılan veriseti hakkında detaylı bilgi verilmiştir. 4. bölümde deneysel sonuçlar ayrıntılı bir şekilde

115 K AKYOL Academic Platform Journal of Engineering and Science 6-2, , 2018 sunulmuştur. Son bölümde ise, çalışmanın sonuçlarına ve alan uzmanının faydalanabileceği bilgilere yer verilmiştir. 2. ÖNCEKİ ÇALIŞMALAR Meme kanseri her yıl milyonlarca hastada sıklıkla görülen bir hastalıktır [7]. Ve bu hastalığa dair yüksek risk içeren kadınların tespiti için öne sürülmüş birçok çalışma vardır. Powell ve ark [8], Kaliforniya eyaleti Marin ilçesindeki yüksek oranda meme kanseri, nulliparite ve gecikmiş doğum bilgisi içeren kadın topluluğu verilerini kullanarak Breast Cancer Risk Assessment Tool [9], BRCAPRO [10] ve International Breast Intervention Study [11] meme kanseri risk değerlendirme modellerini karşılaştırmışlardır. Al-Diab ve ark, sundukları çalışmada, Sudi Arabistandaki meme kanserinin tüm kanserli kadın hastaların içinde %19.8 bir orana sahip olduğunu ortaya koymuşlardır [12]. Alharbi ve Tchier, bulanık tabanlı sistemler ve evrimsel genetik algoritmalar kullanarak meme kanserinin erken tanısı için hekimlere yardımcı olacak otomatik bilgisayar tanı sistemi üzerine odaklanmışlardır. Hibrid bir çalışmayı içeren çalışmalarında %97 başarının elde edildiği optimize edilmiş yüksek performanslı bir tanı sistemi gerçekleştirmişlerdir [13]. Porto-Mascarenhas ve ark, tükürük biomarkerlarının meme kanserini karakterize etmekte yardımcı olabilecekleri düşüncesi doğrultusunda bu biomarkerların yeteneklerini değerlendirmek için gerçekleştirdikleri çalışmada, tükrük biomarkerlarının meme kanserinin erken evreden ziyade ileri aşamalarını tanımladıklarını görmüşlerdir [14]. Ramalho ve ark, meme kanseri hastalarındaki kanser tedavileri ile bilişsel olay bozuklukları arasındaki ilişkiyi, tedaviden önceki kaygı düzeylerini hesaba katarak değerlendirmeyi amaçlayan bir yaklaşım sunmuşlardır. Çalışmalarınd a, yalnızca başlangıçta kaygısı olmayan kadınlar üzerinde kimyasal tedavi ve bilişsel bozukluk arasındaki ilişikinin istatistiksel olarak önemli olduğunu ortaya koymuşlardır [15]. Peters ve ark, çalışmalarında özellikle erken evre yumurtalık kanseri teşhisi konan BRCA1/2 taşıyıcıları için düzenli meme kanseri verilerinin toplanmasını ve ilaç ve/veya profilaktik mastektomi yani iki memenin de ameliyatla alınması yöntemleri ile risk azaltmayı önermişlerdir [16]. Pudkasam ve ark, egzersiz programlarının meme kanserini iyileştiren yağ(adipozite) ve immünolojik belirteçler üzerindeki bilinen etkilerini araştırmışlardır [17]. Cimpean ve ark, çalışmalarında Mast hücrelerinin meme kanserinin adjuvan tedavisi için bir önemi olabileceği üzerine çalışmışlardır. Mast hücreleri, belirli tümörleri çevreleyen stromada birikirler ve tümörün çevresinde oluşan enflamasyon reaksiyonuna katılırlar. Meme kanseri de dâhil olmak üzere katı tümörlerle ilişkili anjiyojenezde bu hücrelerden artmış sayıda vardır [18]. Almutlaq ve ark, yaş, ilk doğum yaşı, erken menarş, cinsiyet, beslenme faktörleri, tütün içilmesi, alkol tüketimi, düşük doz radyasyon, obezite, fiziksel aktivite, emzirme, hormonal, hormon replasman tedavisi, steroid hormon reseptörleri, mamografik yoğunluk, iyi huylu meme hastalığı ve genetik faktörlerini inceleyerek Suudi Arabistan daki meme kanserine neden olan faktörleri araştırmışlardır [19]. Lukong, tüm dünyada ciddi bir sağlık sorunu olan bu hastalığın erken tanısı, tedavisi ve önlenmesi için daha fazla hedefin karakterize edildiği ve son derece yenilikçi yaklaşımların geliştirildiği daha özel tedavileri içeren çalışma üzerine yoğunlaşmışladır [20]. Coleman, yetkin klinik ve kendi kendine meme muayenesinin dikkatli bir kullanımı ile küçük tümörlerin tespitini ve morbiditenin azalmasını sağlayacağı yönünde bir çalışma sunmuştur [21]. 3. VERİSETİ Bu çalışmada kullanılan veriseti (1) Wisconsin Üniversitesi Hastanelerinden temin edilen halka açık bir verisetidir. Toplam 699 örnek veri içeren bu verisetindeki sonuç değişkeninde iyi huylu hastalık için 2, kötü huylu hastalık için 4 değeri vardır. Tablo 1 de sunulduğu üzere veri setinde örnek kayıt numarası haricinde toplam 10 öznitelik vardır. 110

116 K AKYOL Academic Platform Journal of Engineering and Science 6-2, , 2018 Tablo 1. Öznitelikler ve değer aralıkları Sıra No Öznitelik adı Kısaltması Değer aralığı 1 Clump Thickness (Kapanma Kalınlığı) KK Uniformity of Cell Size (Hücre Boyutunun HBE 1-10 Eşbiçimliliği) 3 Uniformity of Cell Shape (Hücre Şekil HŞE 1-10 Eşbiçimliliği) 4 Marginal Adhesion (Marjinal Yapışma) MY Single Epithelial Cell Size (Tek Epitelyal TEHB 1-10 Hücre Boyutu) 6 Bare Nuclei (Çıplak Çekirdekler) ÇÇ Bland Chromatin (Yumuşak Kromatin) YK Normal Nucleoli (Normal Nükleoli) NN Mitoses (Mitoz) M Class Class 2: iyi huylu, 4: kötü huylu 4. DENEYSEL SONUÇLAR Şekil 1. Önerilen yaklaşıma dair iş akışı. Önerilen yaklaşıma dair iş akışı Şekil 1 de sunulmuştur. Bu yaklaşım çerçevesinde ÖÖE + LR ve ÖÖE + RO olmak üzere iki ayrı melez kombinasyonu içeren deneysel çalışmalar scikit-learn makine öğrenmesi kütüphanesinin dâhil edildiği Python 2.7 platformunda gerçekleştirilmiştir. Bu yaklaşım sırasıyla şu adımları içermektedir: a) Boş değer içeren kayıtlar işleme alınacak olan verisetinden çıkartılmıştır. Böylece, verisetindeki veri sayısı 683 olmak üzere iyi huylu ve kötü huylu hastalık sayıları sırasıyla 458 ve 241 dir. Şekildeki iş akışından görüleceği üzere ilk olarak veriseti 0 ve 1 değerleri aralığında normalize edilmiştir. b) Dengesiz veriler ile çalışılması öğrenmeden ziyade sistemin ezberlemesine neden olmaktadır. Verisetindeki pozitif ve negatif hasta sayısı arasındaki büyük farklılıklardan ötürü dengesiz sınıf içeren çoğunluk verilerinin olduğu gruba Örneklem Altında Rastgele Seçim (ÖARS, Random Under Sampling) metodu uygulanmıştır. Böylece, iyi huylu ve kötü huylu hastalık sayıları sırasıyla 239 ve 239 olmak üzere her iki sınıf için dengelenmiş veriseti elde edilmiştir. Elde edilen sonuçlar Tablo 2 de sunulmuştur. 111

117 K AKYOL Academic Platform Journal of Engineering and Science 6-2, , 2018 Tablo 2. Dengesiz ve dengeli alt verisetlerine dair bilgiler. Dengesiz Verisetleri Dengeli Verisetleri Train Test Train True True 199 False False 183 Test WMKV True 239 False 444 True False True False WMKV True 239 False 239 True False True False True False True False True False True False c) Önerilen yaklaşım ile yüksek performans elde etmek için k katlı çapraz doğrulama kuralları çerçevesinde dengeli verisetinden alt verisetleri elde edilmiştir. Bu teknik sınıflandırma çalışmalarında kararlı ve doğru bir şekilde sınıflandırma yapmak için yayın bir şekilde kullanılır. Eğitim ve test verileri çapraz bir şekilde yer değiştirilerek rastgele örnekleme ile ilgili hatalar en aza indirilmiş olur [22]. Bu çalışmada 5 katlı çapraz doğrulama işlemi uygulanmış olup her bir sınıflandırma analizi için veriseti %80-20 oranında eğitim ve test kümeleri olarak bölünmüştür. Tablo 4 teki deneysel sonuçlar için sunulan karışıklık matrislerindeki veriler incelendiğinde görüleceği üzere eğitim ve test kümelerindeki veri dağlımı da dengeli bir yapıya sahiptir. d) Özniteliklerin değerlendirmesi sürecinde sonuç değişkeni ile ilişkili olan özniteliklerin tespiti yapılarak bilginin keşfi gerçekleştirilir. Ayrıca, bu teknik alakasız verilerden doğan hataların indirgenmesini sağlar. Bu düşünceyle, bu alt verisetlerindeki hedef değişkeni olan Class için önemli özniteliklerin tespiti için ÖÖE öznitelik seçim metodu kullanılmıştır. Her bir alt verisetindeki özniteliklerin önemliliği Şekil 2 de ve bu değerlerin ortalaması Tablo 3 te sunulmuştur. Tüm özniteliklerin önemli olduğunun görüldüğü bu tablodaki değerler 5 alt verisetinden elde edilen özniteliklerinin önemliliği değerlerinin ortalamasıdır. Tablo 3. Özniteliklerin ortalama önemlilik değerleri Test değişkeni Kısaltması Ortalama önemlilik değeri Kapanma Kalınlığı Hücre Boyutunun Eşbiçimliliği Hücre Şekil Eşbiçimliliği Normal Nükleoli Çıplak Çekirdekler Yumuşak Kromatin Mitoz Marjinal Yapışma Tek Epitelyal Hücre Boyutu KK HBE HŞE NN ÇÇ YK M MY TEHB e) Eğitim aşamasında verisetindeki eğitim verileri ile modelin inşa edildiği ve test aşaması olan ikinci aşamada test verilerinin değerlendirildiği veri sınıflandırması iki aşama içerir. Bu aşamaları içeren işlemler LR ve RO sınıflandırıcı algoritmaları ile her bir alt veriseti üzerinde yürütülmüştür. Yani, hastalığın tanısı için bu alt verisetleri bu sınıflandırıcı algoritamalarına girdi olarak verilmiş ve sistemin öğrenmesi gerçekleştirilmiştir. Sırasıyla Eşitlik 1 ve 2 de verilen Doğru Sınıflandırma Oranı (Dso) ve Duyarlılık (Duy) performans ölçüm metrikleri çerçevesinde elde edilen deneysel sonuçlar karışıklık matrisi yapısında Tablo 4 te sunulmuştur. Duy GP / (GP GN) (1) Dso= GP+GN / GP+YP+GN+YN (2) Eşitlik 1 deki Duy, gerçekte hasta olanlar arasından gerçek doğru bulunan hasta sayısının oranıdır. Model başarısının ölçülmesinde oldukça 112

118 K AKYOL Academic Platform Journal of Engineering and Science 6-2, , 2018 çok kullanılan belirleyici ölçüt olan Eşitlik 2 deki Dso değeri, doğru tanı konmuş örnek sayısının toplam örnek sayısına oranı şeklinde ifade edilebilir [23]. Örneğin, 1 nolu alt veriseti için LR ile yürütülen sınıflandırma sonuçlarına göre, gerçekte pozitif olan 40 verinin hepsi pozitif bulunmuştur. Dahası, negatif oaln 56 veriden 55 tanesi negatif olarak bulmuş, 1 tanesini yanlış tahmin yaparak pozitif bulunmuştur. Böylece, bu veriseti için Dso ve Duy metrikleri sırasıyla %98.96% ve %100 olarak elde edilmiştir. Bu doğrultuda, deneysel sonuçların ortalaması ilgili bölümün en altında verilmiştir. Yaklaşık olarak %98 civarında başarılı sınıflandırma oranı ile her iki sınıflandırıcı algoritmasının başarılı olduğunu ifade etmekle beraber, ÖÖE ve RO hibrit modelinin daha başarılı olduğu ifade edilebilir. Şekil 2. Özniteliklerin önemi: a) Veriseti no. 1, b) Veriseti no. 2, c) Veriseti no. 3, d) Veriseti no. 4, e) Veriseti no

119 K AKYOL Academic Platform Journal of Engineering and Science 6-2, , 2018 Dengeli alt verisetleri Tablo 4. Tüm alt veri setleri için sınıflandırma sonuçları. LR Sınıflandırma Algoritmaları TEN TEP 55 GN 1 (YP) (GN) Veriseti no. 1 GP 0 (YN) 40 (GP) Dso: %98.96 Duy: %100 TEN TEP GN 49 1 Veriseti no. 2 GP 2 44 Dso: %96.88 Duy: %95.65 TEN TEP GN 45 1 Veriseti no. 3 GP 3 47 Dso: %95.83 Duy: %94.0 TEN TEP GN 50 0 Veriseti no. 4 GP 3 43 Dso: %96.88 Duy: %93.48 TEN TEP GN 46 1 Veriseti no. 5 GP 3 46 Dso: 95.83% Duy: 93.88% Ortalama Dso %96.88 Ortalama Duy %95.4 * GN: Gerçek Negatif, GP: Gerçek Pozitif, TEN: Tahmin Edilen Negatif, TEP: Tahmin Edilen Pozitif, YN: Yanlış Negatif, YP: Yanlış Pozitif RF TEN TEP GN 55 1 GP 0 40 Dso: %98.96 Duy: %100 TEN TEP GN 49 1 GP 1 45 Dso: %97.92 Duy: %97.83 TEN TEP GN 45 1 GP 1 49 Dso: %97.92 Duy: %98.0 TEN TEP GN 50 0 GP 1 45 Dso: %98.96 Duy: %97.93 TEN TEP GN 46 1 GP 1 48 Dso: %97.92 Duy: %97.96 %98.34 % SONUÇ En yaygın kanser türlerinden biri olan meme kanseri kadınları etkileyen ölümcül bir hastalıktır. Kliniksel çalışmalara ve alan uzmanlarına faydalı olacağı düşüncesi çerçevesinde gerçekleştirilmiş olan bu çalışmada ÖÖE metodu ile Wisconsin meme kanseri verisetindeki özniteliklerin önemliliği araştırılmıştır. Böylelikle, ilgili verisetindeki sonuç değişkeni için önemli olan veya olmayan değişkenlerin tespiti yapılmıştır. Uygulanan özniteliklerin değerlendirilmesi yöntemine göre verisetindeki tüm öznitelikler oldukça anlamlı bulunmuştur. Bu bilgiler, alan uzmanının verisetindeki ilgili öznitelik bilgisinin önemi bilgisine ulaşmasını sağlayacaktır. Ardından, sonuç değişkeni için önemli olan öznitelikler kullanılarak LR ve RO sınıflandırma algoritmalarının her biri ile eğitim ve test aşamalarını içeren makine öğrenmesi gerçekleştirilmiştir. Bu süreçte öğrenmenin daha iyi olması için 5 katlı çapraz doğrulama tekniğinden faydalanılmıştır. Deneysel sonuçlara göre, LR ve RO algoritmalarının her ikisi ile başarılı sınıflandırmanın gerçekleştirilmiş olduğu, bunun yanında RO nun LR ye göre biraz daha iyi olduğu sonucuna varılabilir. Yazar, bu çalışmanın gerçek vaka kontrol verileri üzerinde yapılacak olan meme kanseri araştırmalarına ve onkolojistlere yardımcı olabileceğini düşünmekte ve ileride bu çerçevede bir çalışma planlamaktadır. Bu yönüyle çalışmanın literatüre katkı sağlayacağını düşünmektedir. Ayrıca yazar, bu yaklaşımın hastalık tanı işlemlerinde oldukça etkili olacağını düşünmekte ve alternatif öznitelik seçim yaklaşımlarını da araştırmaktadır. TEŞEKKÜR Yazar, çalışmada kullanılan verisetini araştırmacıların kullanımına sunan Breast Cancer Wisconsin Data Set geliştiricilerine teşekkür eder. KAYNAKÇA [1] Breast cancer basics, URL: (Erişim zamanı; Temmuz, 20, 2017). 114

120 K AKYOL Academic Platform Journal of Engineering and Science 6-2, , 2018 [2] A. Jemal, F. Bray, M.M. Center, J. Ferlay, E. Ward, D. Forman, Global cancer statistics, CA Cancer J. Clin. 61(2), 69 90, [3] E.I. Papageorgiou, J. Subramanian, A. Karmegam, N. Papandrianos, A risk management model for familial breastcancer: A new application using Fuzzy CognitiveMap method, Computer Methods and Programs in Biomedicine, 122(2), , [4] I. Guyon, J. Weston, S. Barnhill and V. Vapnik, Gene selection for cancer classification using support vector machines, Mach Learn 46(1-3), , [5] D.W. Hosmer, and S. Lemeshow, Applied logistic regression, 2nd ed., Wiley Series in Probability and Statistics, Canada, [6] L. Breiman, Random forests, Machine Learn, 45, 5-32, [7] Globocan 2012: Estimated Cancer Incidince, Mortaliyty and Prevalence Worldwide 2012, URL: (Erişim zamanı; 20 June 2017). [8] M. Powell, F. Jamshidian, K. Cheyne, J. Nititham, L.A. Prebil, R. Ereman, Assessing Breast Cancer Risk Models in Marin County, a Population With High Rates of Delayed Childbirth, Clinical Breast Cancer, 14(3), , [9] Breast Cancer Risk Assessment Tool for Health Care Providers. Office of Cancer Communication. Bethesda (MD): National Cancer Institute; [10] N. Elsayegh, A.M. Gutierrez Barrera, K.I. Muse, H. Lin, H.M. Kuerer, M. Helm, J.K. Litton, and B.K. Arun, Evaluation of BRCAPRO Risk Assessment Model in Patients with Ductal Carcinoma In situ Who Underwent Clinical BRCA Genetic Testing, Front Genet, 7, 1-7, [11] The International Breast Cancer Intervention Study, URL: (Erişim zamanı; Nisan, 8, 2018). [12] A. AlDiab, S. Qureshi, K. Al Saleh, F.H. AlQahtani, A. Aleem, A. AlSaif, V. Qureshi, M.R. Qureshi, Studies on the methods of diagnosis and biomarkers used in early detection of breast cancer in the Kingdom of Saudi Arabia, World Journal of Medical Sciences, 8(1), 36-47, [13] A. Alharbi, F. Tchier, Using a genetic-fuzzy algorithm as a computer aided diagnosis tool on Saudi Arabian breast cancer database, Mathematical Biosciences, 286, 39-48, [14] E.C. Porto-Mascarenhas, D.X. Assad, H. Chardin, D. Gozal, G.D. Luca Canto, A.C. Acevedo, E.N.S. Guerra, Salivary biomarkers in the diagnosis of breast cancer: A review, Critical Reviews in Oncology/Hematology 110, 62 73, [15] M. Ramalho, F. Fontes, L. Ruano, S. Pereira, N. Lunet, Cognitive impairment in the first year after breast cancer diagnosis: A prospective cohort study, Breast, 32, , [16] M.L. Peters, J.E. Garber, N. Tung, Managing hereditary breast cancer risk in women with and without ovarian cancer, Gynecologic Oncology, 146(1), , [17] S. Pudkasam, K. Tangalakis, N. Chinlumprasert, V. Apostolopoulos, L. Stojanovska, Breast cancer and exercise: The role of adiposity and immune markers, Maturitas, 105, 16-22, [18] A.M. Cimpean, R. Tamma, S. Ruggieri, B. Nico, A. Toma, D. Ribatti, Mast cells in breast cancer angiogenesis, Critical Reviews in Oncology/Hematology 115, 23 26, [19] B.A. Almutlaq, R.F. Almuazzi, A.A. Almuhayfir, A.M. Alfouzan, B.T. Alshammari, H.S. AlAnzi, H.G. Ahmed, Breast cancer in Saudi Arabia and its possible risk factors, Journal of Cancer Policy, 12, 83 89, [20] K.E. Lukong, Understanding breast cancer - The long and winding road, BBA Clinical, 7, 64 77, [21] C. Coleman, Early Detection and Screening for Breast Cancer, Seminars in Oncology Nursing, 33(2), , [22] R. Kohavi, A study of cross-validation and bootstrap for accuracy estimation and model selection, Proceedings of the 14th international joint conference on Artificial intelligence, 2, , [23] A. Baratloo, M. Hosseini, A. Negida and G.E. Ashal, Part 1: Simple Definition and Calculation of Accuracy, Sensitivity and Specificity, Emerg (Tehran), 3(2), 48-49,

121 Academic Platform Journal of Engineering and Science 6-2, , 2018 Academic Platform Journal of Engineering and Science journal homepage: Nano Al2O3 Oranının Ni-Co Matrisli Nano Kompozit Kaplamaların Tribolojik Özelliklerine Etkisi *Ramazan KARSLIOĞLU( ) Ankara Yıldırım Beyazit Üniversitesi, Mühendislik ve Doğa Bilimleri Fakültesi, Metalurji ve Malzeme Mühendisliği, 06010, Ankara, Turkey Öz Geliş Tarihi: Kabul Tarihi: Ni-Co esaslı nanokompozit kaplamaların Mikro Elektro Mekanik Sistemlerde (MEMS) ve Nano Elektro Manyetik Sistemlerde (NEMS) kullanım potansiyelinden dolayı teknolojik gelişmelere paralel olarak önemi gün geçtikçe artmaktadır. Ni-Co esaslı nanokompozit kaplamalar MEMS ve NEMS sistemlerinde karşılaşılan aşınma problemi için çözüm vadetmektedir. Bu bağlamda Ni-Co alaşımı ve Ni-Co/Al 2 O 3 kompozit kaplamalar Doğru Akım (DC) akım türünde, 7 A/dm 2 akım şiddetinde ve dört farklı oranda Al 2 O 3 banyo konsantrasyonuna ilave edilerek modifiye edilmiş Watt tipi kaplama banyosu ile bakır altlıklar üzerine kaplanmıştır. Banyo bileşimine Al 2 O 3 ilavesi ve oranın kaplama tabakasının fiziksel ve mekanik özelliklerine etkileri incelenmiştir. Üretilen kaplamaların yapısal özellikleri taramalı elektron mikroskobu (SEM) ve X-ışınları difraksiyonu (XRD) metodu kullanılarak karakterize edilmiştir. Kaplamaların mekanik özellikleri Vickers yöntemi ile ölçülmüştür. Sürtünme ve aşınma davranışları ise ball on disk metodu ve reciprocating yöntemi kullanılarak ortaya çıkarılmıştır. Yapılan inceleme ve karakterizasyonlar sonucunda Ni-Co kaplama banyo bileşimine 1 g/l Al 2 O 3 ilavesinin en iyi mekanik ve tribolojik özellikleri sağladığı tespit edilmiştir. Anahtar Kelimeler: Ni-Co, Al 2 O 3, Nanokompozit, elektrolitik kaplama Effect of Nanosize Al2O3 Concentration on Tribological Behavior of Ni-Co based Nanocomposite Coatings Ramazan KARSLIOĞLU Ankara Yildirim Beyazit University, Faculty of Engineering & Natural Sciences, Metallurgical and Materials Engineering Department, 06010, Ankara, Turkey Abstract Due to the micro-electrical mechanical system (MEMS) and Nano-electrical mechanical system (MEMS) usage potential, Ni- Co based nanocomposite coatings have been remarkable. Especially, they are promises to solve tribological problem of MEMS and NEMS system. Therefore, Ni-Co alloy and Ni-Co/ Al 2 O 3 composite coatings were prepared from a modified Watt's type electrolyte by Direct Current (DC) with 7A/dm 2 current density and four different amounts of Al 2 O 3 added to electrolyte concentration. Effect of amount of Al 2 O 3 in the Ni-Co matrix on mechanical and physical properties were investigated. Produced composite coating layers structure were characterized with scanning electron microscopy (SEM) and X-ray diffraction (XRD). Mechanical properties were determined with Vickers microhardness test method. Tribological properties was carried out with reciprocating pin on disk system. As a result of investigation and characterization best mechanical and tribological properties were achieved with 1 g/l Al 2 O 3 addition into electrolyte and at PRC current type. Keywords: Ni-Co, Al 2 O 3, Nanocomposite, electrodeposition Sorumlu Yazar: Ankara Yıldırım Beyazit Üniversitesi, Mühendislik ve Doğa Bilimleri Fakültesi Metalurji ve Malzeme Mühendisliği 06010, Ankara, TURKEY Tel: Doi: /apjes

122 R KARSLIOĞLU Academic Platform Journal of Engineering and Science 6-2, , GİRİŞ Nikel ve nikel esaslı alaşımlar günümüzde uzay, havacılık, enerji üretimi, korozyondan koruma, yüksek sıcaklık uygulamaları gibi birçok alanda kullanılmaktadır [1 3]. Özellikle iyi aşınma direnci ve yüksek sıcaklık oksidiyonu gereken uygulamalarda geniş bir kullanım alanı bulmaktadır. Ni alaşımları arasında, Ni-Co alaşımı mükemmel fonksiyonel özellikleri, korozyon direnci gibi özellikler sergilemelerinden dolayı öne çıkmaktadırlar [4 7]. Son yıllarda teknolojinin gelişmesi ile birlikte yeni uygulamalar ortaya çıkmıştır. Ortaya çıkan bu yeni uygumlalar yeni malzemeler ve özelliklere ihtiyaç duymaktadır. Günümüzdeki birçok yeni uygulama MEMS ve NEMS sistemlerine ihtiyaç duymaktadır [8 10]. Bu sistemlerde karşılaşılan en büyük problem; büyük sistemler ile karşılaştırıldığında, yüzey atomlarının içteki atomlara oranının yüksek olması nedeni ile yüzey karalılığının düşük olmasıdır. Bu durum MEMS ve NEMS sistemlerinde kullanılan malzemenin kolayca çevre ile reaksiyona girebilme eğilimini arttırmakla beraber hareketli sistemlerde aşınma direncinin ciddi oranda düşmesine neden olmaktadır [11 13]. Ni-Co alaşımları yukarıda belirtildiği gibi birçok üstün özelliklere sahiptir. Ancak yapı içerisine nano boyutta ikinci faz ilavesi ile oluşturulan nano kompozit kaplamaların mukavemet, aşınma direnci, korozyon direnci, biyolojik ve kimyasal uyumluluk gibi özellikleri daha da geliştirdiği çeşitli kaynaklarda belirtilmektedir [2], [14]. Nikel-kobalt alaşım kaplamaların üçüncü bir faz ilavesiyle özelliklerinin gelişmesine elverişli olduğu literatürde belirtilmiştir [15 17]. Parçacık takviyeli metal matrisli kompozitleri hazırlamak için birçok metot vardır. Ekonomik ve kolay uygulanabildiğinden dolayı en yaygın kullanılanı elektrodepozisyondur. Elektrodepozisyon ile kompozit kaplama işleminde takviye fazı ile matris malzemesi aynı anda altlık üzerinde biriktirilmektedir [18]. Elektrodepozisyon metodu kullanılarak yapı içerisine SiC, WC, Al 2 O 3, CNT, SiO 2, vb. gibi inert parçacıklar ilave edilebilmektedir. Parçacık ilave edilmiş yapı, saf metal yapı ile kıyaslandığında yüksek korozyon ve aşınma direnci gibi daha iyi fiziksel ve mekanik özellik göstermektedir. Bahsedilen özelliklerin sağlanabilmesi için ilave edilen parçacıkların metal matriks içerisine homojen dağılması gerekmektedir. Elektrodepozisyon tekniğinde yüksek sıcaklık ve yüksek basınca gerek duyulmadığından dolayı dağılım ve konsantrasyon kolayca kontrol edilebilmektedir [15]. Bu çalışmada temel amacı son yıllarda önemi artan mikro elektromekanik sistemler (MEMS) ve nano elektromekanik sistemler (NEMS) için yüksek aşınma direncine, üstün mekanik özelliklere ve iyi elektriksel özelliklere sahip Al 2 O 3 ile takviye edilmiş Ni-Co esaslı nano kompozit kaplamalar üretmektir. Üretilen kaplamaların kompozisyon-özellik ilişkisi incelenmiştir. 2. DENEYSEL ÇALIŞMALAR Nanokompozit kaplama prosesinde altlık olarak 20 x 30 x 2 mm boyutlarında yüksek saflıkta Cu levhalar kullanılmıştır. Kaplama öncesi Cu yüzeyler, homojen ve düşük yüzey pürüzlülüğüne sahip olması için sırası ile 120, 240, 400, 800 mesh lik zımpara kullanılarak mekanik olarak temizlenmiş ve yüzey pürüzlülüğü düşürülmüştür. Daha sonrasında Cu yüzeyleri %10 HCL çözeltisi ile kimyasal temizleme işlemine tabi tutulmuştur. Anot malzemesi olarak 25 x 40 x 2 mm boyutlarında yüksek saflıkta Ni kullanılmıştır. Kaplama banyosunda nikel kaynağı olarak 250 g/l NiSO 4.6H 2 O, kobalt kaynağı olarak 50 g/l CoSO 4.7H 2 O ve Ph dengeleyici olarak H 3 BO 3 kullanılmıştır. Nano kompozit yapıyı oluşturabilmek için kaplama banyosuna dört farklı oranda (0.5, 1.0, 2.0, 4.0 g/l) 80 nm parçacık boyutuna sahip α-al 2 O 3 ilave edilmiştir. Kaplama öncesi 30 dk boyunca ultrasonik homojenizetör kullanılarak Al 2 O 3 partiküllerinin elektrolit içerisine homojen dağılması sağlanmıştır. Kaplama akım şiddeti 7 A/dm 2 seçilmiştir. Banyo sıcaklığı hassas bir şekilde kontrol edilerek 55 o C (±0.5) ye ph ise e kaplama işlemi başlamadan önce sabitlenmiştir. Kaplama esnasında da ph ve sıcaklık kontrol altında tutulmuştur. Homojen bir kaplama tabakası elde edebilmek için elektrolit kaplama esnasında manyetik karıştırıcı ile 50 rpm hızla karıştırılmıştır. Farklı Al 2 O 3 banyo konsantrasyonları ile üretilen nano kompozit kaplamalar Taramalı Elektron Mikroskobu (Hitachi SU3500) kullanılarak kaplama tabakalarının yüzey ve tane yapıları, Enerji Dağılım Spekpektrometresi (EDS) kullanılarak kaplamaların elementel dağılımı incelenmiştir. X-ışınları difraktometresi (XRD) ile Å dalga boyunda CuK α ışını kullanılarak kristal yapı karakterize edilmiştir. Ni-Co ve Al 2 O 3 katkılı Ni-Co kaplama tabakasının kristal yapı karakterizasyonu için 2θ, 20º ile 100º arasındaki bölge taranmıştır. XRD analizi sonucunda elde edilen piklerin çözümü bilgisayar yazılım yardımı ile yapılmıştır. Çözümlemede kullanılan JPDS kart no: dir. Ayrıca Al 2 O 3 ilavesinin büyüme yönlerinde ve tane boyutuna etkileri XRD yardımı ile irdelenmiştir. Kaplama tabakasının mekanik özellikleri mikro sertlik cihazı (Shimadzu HMV-G) kullanılarak ölçülmüştür. Sertlik testi 50 g yük altında 10 sn süre ile tatbik edilmiştir. Her bir numune için en az 5 sertlik ölçümü yapılarak ortalamaları alınmıştır. Kaplamaların aşınma tesisleri 1 N yük altında aşınma testleri aşınma testleri için özel üretilmiş, düşük yüzey pürüzlülüğüne sahip 10 mm Al 2 O 3 bilye ile reciprocating yöntemi kullanılarak gerçekleştirilmiştir. Aşınma testi 250 metre mesafede ve 12 mm spam aralığında yapılmıştır. Aşınma izleri SEM ve optik mikroskop kullanılarak incelenmiştir. Optik mikroskop yardımı ile aşınma iz genişlikleri ölçülmüş ve matematiksel metot kullanılarak aşınma hacim kayıpları hesaplanmıştır. SEM ile aşınma mekanizmaları irdelenmiştir. 117

123 R KARSLIOĞLU Academic Platform Journal of Engineering and Science 6-2, , SONUÇLAR VE TARTIŞMA Watt tipi banyo kullanılarak 7.0 A/dm 2 akım şiddetinde farklı Al 2 O 3 konsantrasyonunda banyo bileşimine sahip nano kompozit kaplamaların SEM yüzey görüntüleri Şekil 1 de verilmiştir. Şekil 1 a banyo bileşimine Al 2 O 3 katılmaksızın, 1b de 0.5 g/l Al 2 O 3 katılarak üretilmiş, kaplamaların tane yapıları incelendiğinde banyo bileşimine Al 2 O 3 katkısının Ni-Co tanelerinin küçülmesine sebep olduğu görülmüştür. Kaplama esnasında yapı içerisine giren Al 2 O 3 heterojen çekirdeklenmeye sebep olmuş ve birim alandaki çekirdeklenme miktarını artırması sonucunda birim alandaki tane sayısını artırmış dolayısı ile yapının daha ince taneli olmasına neden olmuştur. Diğer bir neden ise taneler arasına yerleşen Al 2 O 3 parçacıkların tane büyümesini engellemesidir [19]. Şekiller 1b e incelendiğinde, kaplama banyosu içerisine ilave edilen Al 2 O 3 miktarının artmasıyla birlikte tane yapısının küçüldüğü görülmektedir. Bu durumun başlıca nedeni banyo içeriğindeki Al 2 O 3 miktarının artması ile birlikte kaplama tabakası içerisine gömülen Al 2 O 3 miktarının artmasıdır. Ayrıca banyo bileşimine ilave edilen dolayısı ile kaplama tabakası içerisine gömülen Al 2 O 3 miktarının artışı tane yapısını polihedrondan küresele kaymasına neden olmuştur. Yapı içerisindeki ikinci faz (Al 2 O 3 ) tanelerin farklı yönlerde dolayısı ile farklı morfolojilerde büyümesine neden olmuştur [1]. (a) (b) (c) (d) (e) Şekil 1. Banyo bileşimine a) 0.0, b) 0.5, c) 1.0, d) 2.0, ve 4.0 g/l oranında Al 2 O 3 katkısı ile üretilmiş nano kompozit yapıların SEM görüntüleri. 118

124 R KARSLIOĞLU Academic Platform Journal of Engineering and Science 6-2, , 2018 Şekil 2 de banyo bileşime Al 2 O 3 katkısız ve 1 g/l Al 2 O 3 katkılı kaplama tabakası EDS analizi verilmektedir. EDS analizi sonuçları karşılaştırıldığında katkılı kaplamanın EDS analizi Ni-Co piklerinin yanında fazladan Al 2 O 3 bileşiminde bulunan Al ve O pikleri verdiği görülmektedir. Dolayısı ile EDS sonuçları Al 2 O 3 ün yapı içerisine yerleştiği ve arzu edilen nanokompozit yapının üretildiğini kanıtlamaktadır. (a) (b) Şekil 2. Banyo bileşimine a) 0.0 ve b) 1 g/l Al 2 O 3 katkılı kaplama tabası EDS analizi sonuçları Farklı oranlarda banyo bileşimine Al 2 O 3 ilavesinin kristal yapı üzerindeki etkileri Şekil 3 teki XRD sonuçlarında görülmektedir. XRD sonuçlarından Al 2 O 3 ilavesinin pik şiddetinin düşmesine ve genişlemesine neden olduğu tespit edilmiştir. Pik şiddetinin düşmesi tane boyutunun küçülmesinden, genişlemesi de kristaloğrafik simetrinin değişmesinden kaynaklanmaktadır. Ni-Co içerisine ikinci faz ilavesi katot yüzeyine birikme esnasında yapı içerisine giren Al 2 O 3 tane büyümesini durdurarak yeni çekirdekleşme alanları oluşturduğu için proses esnasında daha fazla çekirdek oluşumu söz konusu olmuştur, bu durum da tane boyutunda küçülmeye neden olmuştur [17]. 7 A/dm 2 akım şiddetinde üretilen Ni-Co kaplama tabakasının ağırlıklı büyüme düzlemi (220) dır. Banyo içerinse 0.5 g/l Al 2 O 3 ilavesi (111) yönünde büyümeyi çekirdeklediği şekil 3 ten görülmektedir. Banyo içerisine katılan Al 2 O 3 miktarının artması ile birlikte ağırlıklı büyüme düzlemi (220) dan (111) düzlemine kaydığı ortaya çıkmıştır. Şekil 3. Ni-Co ve Ni-Co/Al 2 O 3 kaplama tabakalarının XRD analiz sonuçları 119

125 R KARSLIOĞLU Academic Platform Journal of Engineering and Science 6-2, , 2018 Üretilen kaplamaların mekanik özellikleri Vickers sertlik yöntemi kullanılarak ölçülmüştür. Elde edilen sertlik değerleri şekil 4 te grafik olarak verilmiştir. Setlik testi 50 g yük altında 10 sn süre ile yüzeye tatbik edilmiştir. Sertlik sonuçları incelendiğinde kaplama banyosuna Al 2 O 3 ilavesinin 1 g/l ye kadar sertliği artırdığı görülmüştür. Bunun nedeni olarak da ikinci faz parçacıklarının tane inceltici olarak davranması ve matris fazı üzerine gelen yükü, ikinci faza (Al 2 O 3 ) başarılı bir şekilde transferi şeklindedir [13]. hesaplanmıştır. Kaplama tabakalarında oluşan iz genişlikleri Şekil 6 da verilmiştir. Şekil 6 a- b incelendiğinde, banyo çözeltisine 0.5 g/l Al 2 O 3 ilavesi kaplama tabakası üzerinde oluşan aşınma iz genişliğini 647µm den 459 µm düşürmüştür. Aşınma hacim kaybında keskin bir düşüş olduğu şekil 6 f den görülmektedir. Banyo bileşimine 1g/l üzerindeki Al 2 O 3 ilavesinin ise sertlikte düşüşe neden olduğu gözlenmiştir. Banyo içerisine ilave edilen fazla miktardaki Al 2 O 3 yapı içerisinde ikinci fazın aglomerasyonuna neden olmaktadır. Aglomere olan parçacıklar arasında oluşan boşluklar nedeni ile mekanik özelliklerin zayıflamasına neden olabilmektedir. Aynı zamanda aglomere olan parçacıklar ile matris birleşme kabiliyetinin düşmesi de mekanik özellikleri kötü yönde etkilemektedir[1]. Şekil 4. Ni-Co ve Ni-Co/Al 2 O 3 kaplama tabakalarının sertlik değişimleri Ni-Co ve Ni-Co/Al 2 O 3 kaplamaların sürtünme ve aşınma testleri 1 N yük altında 25 mm/sn hızda reciprocating (gitmeli gelmeli) aşınma yöntemi kullanılarak yapılmıştır. Aşınma hareket mesafesi numune boyutları göz önünde bulundurularak + yönde 6 mm ve yönde 6 mm olmak üzere 12 mm seçilmiştir. Aşındırıcı olarak aşınma testlerinde kullanılmak üzere özel üretilmiş 10 mm çapa sahip Al 2 O 3 bilye kullanılmıştır. Aşınma cihazından elde edilen sürtünme katsayıları şekil 5 de verilmiştir. Aşınma testi sonrası numune üzerinde oluşan iz genişlikleri optik mikroskop yardımı ile ölçülmüştür. Ölçülen iz genişlik değerleri kullanılarak aşınma hacim kayıpları Şekil 5. Al 2 O 3 ilavesinin sürtünme katsayısına etkisi En düşük iz genişliği ve aşınma hacim kaybı banyo çözeltisine 1.0 g/l Al 2 O 3 ilave edilerek yapılmış kaplamadan elde edilmiştir. Banyo bileşimine 1 gr/l nin üzerinde Al 2 O 3 ilavesi aşınma iz genişliğini ve hacim kaybını artırmıştır. Aşınma direncini düşürdüğü şekil 6 d-f den görülmektedir. Aşınma testi sonrasında aşınma mekanizmasını daha iyi ortaya çıkarabilmek için aşınma izleri SEM ile yüksek çözünürlükte incelenmiştir. Aşınma izlerinin yüksek çözünürlüklü fotoğrafları Şekil 7 de verilmektedir. Katkısız kaplamanın yüksek çözünürlüklü SEM fotoğrafı incelendiğinde ağır abrasif ve kısmi ahdesif deformasyon izleri görülmektedir. Yapı içerisine nano Al 2 O 3 girmesi ile birlikte aşınma mekanizması abrasiften deleminasyon türüne geçmektedir. Delaminasyon aşınması yüzeye etkiyen kuvvetler neticesinde oluşan plastik deformasyon, bu plastik deformasyon sonucu yüzeyde oluşan mikro çatlaklar ve bu mikro çatlakların birleşmesi sonucunda yüzeyden kopması şeklinde meydana gelmektedir [1]. SEM fotoğrafı incelendiğinde deleminasyon bölgeleri ve deleminasyon öncesi oluşan çatlaklar açıkça görülmektedir. Banyo içerisine katılan Al 2 O 3 miktarının artması ile birlikte yüzeyde oluşan deleminasyon deformasyonunun azaldığı görülmektedir. Yüksek miktarlarda Al 2 O 3 ilavesinin (1.0 g/l nın üzerinde), oluşan deformasyonu artırdığı ve aşınma mekanizmasını deleminasyon artı adezyona dönüştürdüğü görülmektedir. 120

126 R KARSLIOĞLU Academic Platform Journal of Engineering and Science 6-2, , 2018 (a) (b) (c) (d) (e) (f) Şekil 6. Banyo çözeltisine a) 0.0, b) 0.5, c) 1.0, d) 2.0, e) 4.0 gr/l Al 2 O 3 ilave edilmiş numunelerde aşınma testi sonrası oluşan iz genişlikleri ve f) hesaplanmış aşınma kayıpları Sürtünme katsayıları, aşınma miktar ve mekanizmaları birlikte incelendiğinde mikro sertlik sonuçlarında olduğu gibi banyo bileşimine 1.0 g/l ye kadar Al 2 O 3 ilavesi aşınma direncini artırmakta sürtünme özelliklerini iyileştirmektedir. Kompozit yapıdan beklenen mukavemet artış mekanizmalarının etkileri görülmektedir. Ancak, banyo 1.0 g/l nin üzerinde Al 2 O 3 ilavesi setlik ölçüm sonuçlarından da anlaşılacağı üzere mekanik özellikleri düşürdüğü tespit edilmiştir. Dolayısı ile aşınma esnasında kaplama tabakası yüzeyinden ayrılan malzeme miktarı artmıştır. Ayrılan bu parçacıklar aşındırıcı ile kaplama tabakası arasına girerek sürtünme katsayısının, aşınma hacim kaybının ve oluşan deformasyonun artmasına neden olmuştur. 121

127 R KARSLIOĞLU Academic Platform Journal of Engineering and Science 6-2, , 2018 (a) (b) (c) (d) (e) Şekil 7. Banyo çözeltisine a) 0.0, b) 0.5, c) 1.0, d) 2.0 ve e) 4.0 gr/l Al 2 O 3 ilave edilmiş numune aşınma izleri yüksek çözünürlüklü SEM fotoğrafları 4. GENEL SONUÇLAR Bakır altlıklar üzerine Ni-Co alaşım ve Ni-Co/Al 2 O 3 nano kompozit kaplamalar elektrodepozisyon yöntemi kullanılarak başarılı bir şekilde üretilmiştir. Banyo bileşimindeki Al 2 O 3 miktarı arttıkça kaplama tane boyutu küçülmüştür. Banyo bileşimine Al 2 O 3 ilavesi ağırlıklı büyüme yönünü (220) dan (111) yönüne kaydırmıştır. En yüksek mekanik özellikler ve aşınma direnci kaplama banyosuna 1.0 g/l Al 2 O 3 eklenmesi ile elde edilmiştir. 1.0 g/l üzerinde Al 2 O 3 ilavesi, mekanik özellikleri ve aşınma direncinin düşmesine neden olmuştur. Banyo bileşimine Al 2 O 3 ilavesi aşınma mekanizmasının ağır abrazif ten deleminasyon türü aşınma mekenizmasına geçmesine neden olmuştur. KAYNAKLAR [1] R. Karslioglu and H. Akbulut, Comparison microstructure and sliding wear properties of nickel cobalt/cnt composite coatings by DC, PC and PRC current electrodeposition, Appl. Surf. Sci., vol. 353, pp , Oct [2] D. P. Weston, P. H. Shipway, S. J. Harris, and M. K. Cheng, Friction and sliding wear behaviour of 122

128 R KARSLIOĞLU Academic Platform Journal of Engineering and Science 6-2, , 2018 electrodeposited cobalt and cobalt tungsten alloy coatings for replacement of electrodeposited chromium, Wear, vol. 267, no. 5, pp , Jun [3] M. Surender, B. Basu, and R. Balasubramaniam, Wear characterization of electrodeposited Ni WC composite coatings, Tribol. Int., vol. 37, no. 9, pp , Sep [4] Y. Shacham-Diamand and Y. Sverdlov, Electrochemically deposited thin film alloys for ULSI and MEMS applications, Microelectron. Eng., vol. 50, no. 1 4, pp , Jan [5] C. Lupi and D. Pilone, Electrodeposition of energy consumption, Miner. Eng., vol. 14, no. 11, pp , Nov [6] N. E. Fenineche, R. Hamzaoui, and O. El Kedim, Structure and magnetic properties of nanocrystalline Co Ni and Co Fe mechanically alloyed, Mater. Lett., vol. 57, no , pp , Sep [7] W. E. G. Hansal, B. Tury, M. Halmdienst, M. L. Varsányi, and W. Kautek, Pulse reverse plating of Ni Co alloys: Deposition kinetics of Watts, sulfamate and chloride electrolytes, Electrochimica Acta, vol. 52, no. 3, pp , Nov [8] N. V. Myung, D.-Y. Park, B.-Y. Yoo, and P. T. A. Sumodjo, Development of electroplated magnetic materials for MEMS, J. Magn. Magn. Mater., vol. 265, no. 2, pp , Sep [9] S. E. Lyshevski, MEMS and NEMS: Systems, Devices, and Structures. CRC Press, [10] M. P. Q. Argañaraz et al., The chemistry and structure of nickel tungsten coatings obtained by pulse galvanostatic electrodeposition, Electrochimica Acta, vol. 72, pp , Jun [11] B. Bhushan, Nanotribology and nanomechanics of MEMS/NEMS and BioMEMS/BioNEMS materials and devices, Microelectron. Eng., vol. 84, no. 3, pp , Mar [12] N. S. Tambe and B. Bhushan, Scale dependence of micro/nano-friction and adhesion of MEMS/NEMS materials, coatings and lubricants, Nanotechnology, vol. 15, no. 11, p. 1561, [13] L. Shi, C. Sun, P. Gao, F. Zhou, and W. Liu, Mechanical properties and wear and corrosion resistance of electrodeposited Ni Co/SiC nanocomposite coating, Appl. Surf. Sci., vol. 252, no. 10, pp , Mar [14] L. Shi, C. F. Sun, F. Zhou, and W. M. Liu, Electrodeposited nickel cobalt composite coating containing nano-sized Si3N4, Mater. Sci. Eng. A, vol. 397, no. 1, pp , Apr [15] G. Wu, N. Li, D. Zhou, and K. Mitsuo, Electrodeposited Co Ni Al2O3 composite coatings, Surf. Coat. Technol., vol. 176, no. 2, pp , Jan [16] X. Li, T. Ono, R. Lin, and M. Esashi, Resonance enhancement of micromachined resonators with strong mechanical-coupling between two degrees of freedom, Microelectron. Eng., vol. 65, no. 1 2, pp. 1 12, Jan [17] L. Shi, C. F. Sun, P. Gao, F. Zhou, and W. M. Liu, Electrodeposition and characterization of Ni Co carbon nanotubes composite coatings, Surf. Coat. Technol., vol. 200, no , pp , Apr [18] D EMİRKESEN, E., Kompozit Malzemeler, İTÜ Kimya Fakültesi, 1. Baskı s.1-5, [19] L. M. Chang, M. Z. An, and S. Y. Shi, Microstructure and characterization of Ni-Co/Al2O3 composite coatings by pulse reversal electrodeposit, Mater. Chem. Phys., vol. 100, no. 2 3, pp , Dec

129 Academic Platform Journal of Engineering and Science 6-1, , 2018 Academic Platform Journal of Engineering and Science journal homepage: Designing an Object Tracker Self-Balancing Robot 1 Yunus Çelik( ), * 2 Mahit Güneş( ) 1 Karamanoğlu Mehmetbey University, Faculty of Engineering, Department of Electrical and Electronics Karaman, Turkey 2 Kahramanmaraş Sütçü İmam University, Faculty of Engineering, Department of Electrical and Electronics Kahramanmaraş, Turkey Geliş Tarihi: Kabul Tarihi: Abstract Real-time robots are quite common in our daily life. These robots are working as a part of the process in industry or a medical assistance in hospitals to serve humanity. Designing the robots according to the desired referent and making the given tasks with high accuracy makes them more and more popular in these days. In this work, the designed two-wheeled balancing robots with integrated camera track object autonomously. This work has two important stages. The first stage is about balancing the robot with the angle information taken from IMU sensor and implementation of PID control. IMU sensors create lots of noisy signals because of its natural structures. Kalman filter was used to denoise these noisy signals to have a smooth signal for a better balance control. The second stage is about image processing and objects recognition. This section was completed by using Matlab Image Processing Toolbox which can be used Arduino microcontroller board synchronously. In this section, algorithm infers motion information of objects. Motors were controlled according to motion information of moving objects. In the end, an object tracker self-balance robot was constructed. Balance control of the robot was managed by PID controller and accelerometer signals were denoised by a Kalman Filter. It was clarified that using PID controller and Kalman Filter together have a positive effect to balance the robot on the desired angle. Keywords: Balance robot, Kalman filter, Object recognition 1. INTRODUCTION Thanks to the latest technological developments, image processing and control methods can be applied successfully in a very short time. Advanced computers play an important role in shortening the process and getting successful results. Camera-assisted robots are starting to take their place in daily life. These robots are helping us in almost every step of our daily works so image processing techniques and control methods are an indispensable part of fulfilling given tasks for the robots. Most of unmanned aerial vehicles and vehicles that draw a specific route without the need for a driver were designed by using image processing techniques and control techniques. Some of these vehicles have the ability to destroy the target in case of needed and they are commonly used in military defence systems. It is possible to say that countries having such technologies are more powerful in terms of military and economy. Moreover, they are in a better position than other countries in terms of prestige. That s why, countries invest more money for the defence industry day by day. Another usage area of real time robotic application is related to human transportation vehicles. Segway can be an example of a two-wheeled human transportation vehicle. It was invented by Kamen Segway in The working principle of Segway robot is quite similar to two-wheeled hoverboards and two-wheeled scooters. By means of the angle information obtained from the acceleration sensor, the robot tries to keep the mass in upright position. When the robot is tilted by a user, it autonomously tries to reach upright position [1-4].During this process, the wheels turn into the side where the robot was tilted to keep the body upright. In this way robot moves to the side of tilt. Since the balance robots have a non-linear structure, the study of modelling and evaluating the success of control methods are quite useful to understand control theory. The robot was successfully designed by combining Kalman filter and PID control method. Several difficulties were encountered during the designing phase of the robot. The first one was about adjusting sensitively the centre of gravity in the middle of mass by taking into account the hardware weights. The mass of the robot was printed by a 3-D printer and hardware were attached carefully. The second difficulty was derived from noisy sensor signals. The difficulty was solved by using Kalman filter. Another problem was about tuning PID parameters. It was difficult to tune PID Corresponding Author: *Kahramanmaraş Sütçü İmam University, Faculty of Engineering, Department of Electrical and Electronics Engineering, Kahramanmaraş, Turkey. Tel: (344) Doi: /apjes

130 M GÜNEŞ Academic Platform Journal of Engineering and Science 6-2, , 2018 parameter automatically when the exact mathematical model of the system was unknown. This tuning has been done by trial and error method. The last difficulty was about detection of RGB objects in the environments having unstable amount of lights [5-7]. W is the width of body, D is thickness of body, H is the length of body and R is the radius of the wheels. Figure 2 shows the top and side view of the body on coordinate the system. In this paper, it was aimed to point out the positive effect of usage of Kalman filter and PID control on balance robot. It was clarified that using these methods balance can be more stable and robust. The results and measurements of balance robot were presented in the result section [5-7]. 2. RELATED RESEARCHES In the literature, there are several balancing robot designs. These designs use different control methods and different mechanical models. Nonlinearity of these robots attract the researchers for designing and controlling. Karla and friends were heavily interested in the reducing of noise amount of IMU sensors [4, 8, 9]. In another work, Kao and friends designed a robot quite similar to this project. Raspberry Pi microcontroller process the PID phase and image processing phase together. David P. who is the inventor of N BOT combined accelerometer and gyroscope sensors to have more accurate signals. In another paper, Grasser and friends evaluated the performance of balance control by putting some weight on the robot [6-10]. In another work, Segway which is a human transporter vehicle have 5 IMU sensors inside. Three of the sensors are working actively and other two are backup sensors. This design can reach 20 km/h speed. In another work, Linear Quadratic Regulator control was used to balance the robot named Gyro boy.[10-14]. While designing the robot, literature works helped a lot to get to know the working principle of balance robots. The necessary hardware was chosen carefully by looking at the previous studies. 3. SYSTEM MODEL AND ARDWARE 3.1. System Model and Parameters Balance robot can be referred as two wheeled inverted pendulums in the literature. Operation logic of balance robot is so similar to the inverted pendulum. Figure 1 shows the physical model of two wheeled inverted pendulum and its parameters. Figure 2. Top and Side View of Body Ψ is the balance angle of the body. θ l,r is the wheels angle. φ is turning angles. Below table shows some parameters of robot. Table 1. Physical Parameters of Robot Parameter s g=9,81m/sn 2 Explanation Gravitational acceleration m=3 grams Weight of wheels R=4 cm Radius of wheels Jw=mR2/2 M=1.5 kg Moment of inertia for wheels Weight of robot W=19 cm Width of body D=9 cm Thickness of body H= 1 cm Length of body L=H/2 m Centre height of body Motion equations of robot was derived from the above parameters [4, 9, 10, 12, 13]. ( θ, f ) = [ 1/2 ( θ l + θr ) R / W ( θ r - θ l )] (1) Xm, Ym = ( Xmdt &, Ymdt & ) = ( Rθ& cos φ, Rθ& sinφ) (2) Figure 1. Physical Model of Balance Robot 1252

131 M GÜNEŞ Academic Platform Journal of Engineering and Science 6-2, , 2018 ( X, Y, Z ) = left left left ( X, Y, Z ) = right right right W Xm sin f, Ym 2 W + cos f, Zm 2 W Xm + sin φ, Ym 2 W cos φ, Zm 2 (3) (4) Motor speed is adjusted according to body angle, that s why the speed always prone to changes. Pulse with modulation (PWM) signals are used to drive motor in certain speed [9, 10, 12, 15]. Figure 4. Shows a picture of motor driver. ( Xb, Yb, Zb) = 3.2. System Hardware Xm + L sinψ cos φ, Ym + L cosψ sin φ, Zm + L cosψ (5) The robot consists of a body, 2 motors, a motor driver, an IMU sensor and a camera. Component selection was carefully managed according to related work and simulation results Motors Direct Current motors are both cheap and highperformance motors. Balance robot motors are 24 V, 500 rpm DC motors with reductor. The reason why it was chosen a motor with reductor is that it helps to have a big momentum with low power. Voltage range and RPM (Revolutions per Minute) range is enough to have a balance control of the robot [9, 10, 12-15]. Figure 3. Shows a picture of DC motor Sensor Figure 4. Motor Driver Picture Acceleration and gyroscope sensors give the main and most important parameters of robot. In this robot, IMU 6 axis sensor was used to get the mass angle. The disadvantage of the sensor is the amount of noise it creates. It is important to attach the sensor to a place away from the motors because of motor vibrations. The sensor can read accelerometer and gyroscope values for x, y and z axis. It uses I2C protocol to communicate with microcontroller board up to 400 khz. Figure 5. Gyro Sensor Picture To overcome the noise ratio, Kalman filter was used. Sensor gives better and smoother results after filtering Microcontroller Motor Driver Figure 3. DC Motor Picture L298N is a motor driver which can drive two motors at the same time. It can perform in the temperature range from - 20 to The input voltage of motor driver is 5-35 V and it can give max 2 A to drive a motor. It is important to connect the ground of motor driver and microcontroller ground at the same point because of I 2 C communication platform. Arduino microcontroller board uses ATmega328 processor attached over the card. Arduino is one of the most common microcontrollers for educational purposes. It is an open source platform which is easy to be programmed. In recent years, this microcontroller can operate with Matlab simultaneously. This feature is the key for the second part of our system. 6 digital pins of Arduino were used in this project. 4 pins were used to drive motor with HIGH, LOW to determine the rotation. Other 2 pins were PWM pins for analogue inputs. IMU sensor is also used 2 analogue pins [9, 10, 12-15]

132 M GÜNEŞ Academic Platform Journal of Engineering and Science 6-2, , 2018 Z represents the sensor measurements. A, B and H state matrix Camera Figure 6. Microcontroller Picture The camera used in the robot has 0.3 Megapixel and takes 640x480 pixel photos. The quality of the camera resolution is low because low-quality images are faster to process than high quality images. 4. METHODS In this section, the methodology of control theory and image processing were presented. Below equation is the project error covariance; P ˆ = k AP k 1 AT + Q K k is the Kalman gain. (8) K = P HT( HP HT + R) 1 (9) k k k Below equation updates the estimate with Z k measurement. xˆ = xˆ + K ( z Hxˆ ) (10) k k k k k Noise covariance Q and the measurement noise covariance R are assumed as constant values. When these values update themselves, filter turns into an adaptive filter Kalman Filter Kalman Filter is an algorithm which recursively computes estimates of observed states over time [1]. It is also a mathematical equation which is used as a predictor[2]. As it is stated above, IMU sensor has lots of noise because of its sensitive structure. It can be affected by the magnetic field and vibration negatively. That s why it is crucial to implement a Kalman filter. Kalman filter is a quite applicable method for the noisy sensors. This digital filter can be applied to control systems because it also minimizes square error [16]. Noisy signals make difficult to have a balance control. Balance control is more sensitive than other types of controls because when it failed, the body falls down and camera misses the target. The mathematical equations are based on the mathematical model of the system. In conventional Kalman filtering, it is necessary to know the dynamic model of the current system. ˆx k and Z represent state vector and measurement vector k respectively and [2]. Kalman filter consist of two phases, including predict and update phases. Equation 6,7 are belonging to predict steps and equation 8, 9, 10 belonging to update steps. Update steps use predict step parameters as inputs. xˆ = Axˆ + Bu + w k k k 1 1 k 1 (6) Z = Hx + v (7) k k k u represents the control signal and random variables k w and v k represent the process and measurements noises. k Figure 7. Kalman Filter Block Diagram Knowledge about systems dynamic model is quite necessary for Kalman filter [3]. As it can be seen clearly from Figure 7. block diagram, Kalman filter uses IMU sensor data as an input. The filter predicts and updates angle. After this stage, Kalman output was sent to the system directly [3]. The filter updates and minimize error by feedbacks. Thanks to this infinite loop, Kalman parameters updates itself. These updates keep the mass in upright position against distortion. Angle (degree) Time (ms) Accelerometer Figure 8. Kalman & Accelerometer Outputs Kalman X-axis 127 4

133 M GÜNEŞ Academic Platform Journal of Engineering and Science 6-2, , PID Controller PID controller which is known as the combination of proportional (P), integral (I) and derivative (D) controllers. PID control is one of the most common control methods in the industry because of its easy applicable structure. It doesn t require the mathematical model of the system unlike some modern control system like a Linear Quadratic Regulator (LQR). PID controllers are first used in mechanical systems. After its high performance in mechanic systems, it was started to use it in electrical systems [5]. As industry improved, the necessity of control was increased. The easy implementation of software made PID controller more interesting for the engineering. One of the important feature of PID controllers is that it manipulates the process inputs according to the change of the signal, in another word it evaluates the error which is the difference between the setpoint and current angle. In the control of balance robot, PID control method was used to maintain the balance [14,16]. The mathematical equation of the PID controller can be seen in the equation (15) [29]. Figure 10. helps to understand rise time, settling time and overshoot parameters visually. A represents the rise time. C represents the overshoot and B represents the settling time. Having small values of rising time, overshoot and settling time increase the quality of the balance. The control signal must catch the reference signal. Most of the times, it is expected to have a zero steady state error [30-33]. Figure 10. Physical Effects of Control Parameters The system aims to make the error zero. Table 2. shows the physical effect of K P, K I and K D terms. Table 2. PID Effects on Control Parameters Increasing Parameters K P K I K D Rise Time Decrease Decrease Small effect Figure 9. PID Block Diagram As shown in the above figure, e represents the error of the system which is the difference between reference and output, u represent the output signal. Closed loop control systems have a feedback block. Feedback block helps to update the error and this is quite useful to have a better control. In this figure, error fed into the PID controller. Below Equations show the mathematical representation of PID terms. Pterm = K pe() t (11) t Iterm = K e() t dt (12) i 0 de() t Dterm = K (13) D dt error = ref u() t (14) t de() t ut () = K et () + K et () dt + K (15) p i 0 D dt Over shoot Increase Increase Decrease Settling Time Small effect Increase Steady-State Decrease Big effect Decrease Small effect Those effects are gained by experimental results of PID controllers. This table is quite useful while tuning the PID manually. Increasing K P and K I terms improves the rise time which is quite important for balance robots. But it has negative effects on overshoot and settling time. Increased overshoot prevents the robot to stay stable and increased settling time means robot can reach the balance position after a while. Increasing K I will have a positive effect on steady-state error. This is also an important parameter to fix. Increasing K D decreases the overshoot and settling time and has small effects on rising time and steady state errors. When all these parameter and conditions considered and PID parameter were chosen [33-36]

134 M GÜNEŞ Academic Platform Journal of Engineering and Science 6-2, , Color Detection Color detection is one of the ways of object recognition. Objects can be recognized because of their color [30]. Color detection is the visual part of our system. The importance of this part is quite high. In this stage, direction control of the robot was determined and processed. Thanks to the MATLAB & Arduino interface, it is possible to process an image and control motors. RGB color detection is a quite easy task to process via image acquisition and image processing toolbox[17-19]. b ( R, G, B) B = R+ G+ B (19) I represents the intensity, r, g, and b represent the color amount over 255. H (hue) can be calculated with following equation; 3( G B) H( RGB,, ) = arctan( (20) ( R G ) + ( R B ) Saturation (S) measures the relative white content of a color and it can be calculated in the following equations [25-27]; min( RGB,, ) SRGB (,, ) = 1 R+ G+ B (21) Figure 12. A Blue Object in Visual Field of Camera Figure 11. Block Diagram of Object Detection Algorithm Figure 11 shows the steps for color detection algorithm. It starts with the introducing the camera to the computer as a video object. The camera takes snap-shot of real-time video. The algorithm converts the snapshot image to grayscale image to start the process. The software determined the RGB object and eliminate the noise by using a median filter. After all, it computes the place of the object on the screen in x and y axis. This is where we read the motion information of the object [19-21]. If the object moves to the left on the screen, it means object moves to the right in real time. This situation can be explained by the mirror effect [21-24]. Below equations belonging to color detection in an image. I ( R, G, B) = R+ G+ B (16) Figure 12 shows a blue object in the visual field of the camera. In this stage, it is aimed to point out blue objects in the image. By using above algorithm in Figure 11, the system eliminates the non-blue parts of the image. This can be seen in Figure 13. Figure 13. Detected Color in the Image After the elimination of non-blue parts, we compute the coordinates of blue objects in the image. This can be seen in Figure 14. r ( R, G, B) R = R + G+ B (17) g ( R, G, B) G = R + G+ B (18) Figure 14. Coordinates of the Object 129 6

135 M GÜNEŞ Academic Platform Journal of Engineering and Science 6-2, , 2018 Now we have the central coordinates of a bounding box of blue objects in the image. This information update itself when the object moves and this inform us about the motion information of objects. This information was used in the direction control of robot mass[27, 28]. 5. RESULTS This paper presents the design of an autonomous robot which can track colorful objects while balancing itself on two wheels at the same time. Figure 15 shows the top and side view of the robot. Table 3 shows the commands and object positions together. Computer perceives the object position from its central coordinates. 4 Go Forward Figure 16 shows a graph belonging to the robot s IMU sensor for experiment 1.a. Accelerometer signal which is represented with the blue signal has plenty of noise and vibration. After implementation of Kalman filtering, it is more stable and less noisy and represented with the orange signal. 1.5 second after the robot starts to stay in balance, the body was disturbed. Between seconds robot achieved to get back balance position. After 2 seconds, the body is in balance position again. In this experiment, PID parameter was adjusted like following K P =300, K I =1, K D =70. It is quite clear that the degree signal of the robot has lots of overshoot because of the high value of K P. As it was stated above, having a high value of K P and K I increase the overshoot Degree with Noise Degree with Kalman 30 Figure 15. Robot Body Degree Number 1 situation illustrates where the robot goes back. In this illustration, 2 motors turn to go back without losing balance control. Similarly, in the second illustration, the right motor goes forward while the left motor is stable. This action turns the mass to the left. In the third illustration, the left motor goes forward while the right motor is stable and this action turns the mass to the right. In the last illustration, motors go forward without losing balance control. Table 3. Direction Control According to Motion Information Time(ms) Figure 16. Experiment 1.a IMU Signal The control signal of experiment 1.a can be seen in Figure 17. Between 1.5 and 2 seconds, motors were driven with max PWM value (255) to get back balance position as it should be. PWM Signal Object Positions Track Command PWM Go back 2 Turn Left 3 Turn Right Time(ms) Figure 17. Experiment 1.a Control Signal In the experiment 2.a PID parameters were adjusted with following values K P =30, K I =10, K D =70. IMU signal of the robot has lots of noise and vibration like the previous experiment. K P was decreased but K I was increased so increasing K I also effects overshoot. When it compared with the previous experiment, total overshoot is less. This situation also affects the control signal in Figure

136 M GÜNEŞ Academic Platform Journal of Engineering and Science 6-2, , Degree 30 Degree with Noise Degree with Kalman Time(ms) Figure 18. Experiment 2.a IMU Signal PWM Signal simultaneously. A physical model of the robot and necessary hardware were presented. Balance control was managed by using PID control. The effect of PID values over PID parameters were discussed. Optimal PID values were determined by trial and error method. The output of IMU sensor was also presented. The problems of IMU sensors were solved by using a Kalman Filter. Moreover, a color detection algorithm was presented and explained with block diagrams and process steps. A blue object was chosen as an object to track. According to motion information of the object, motors were driven to keep the object in the visual field of the camera. During the construction of this autonomous robot, many methods were learned and practiced. 200 ACKNOWLEDGEMENT PWM Time(ms) The author wishes to thank The Dean of Architecture and Engineering Faculty of Kahramanmaras Sutcu Imam University Mahit Gunes because of his technical supports. REFERENCES Figure 19. Experiment 2.a Control Signal In the last experiment, PID parameters were adjusted with following values K P =90, K I =0.5, K D =0. Increasing K I affects overshoot parameters positively. In balance position, control signal value is less than 255. The control signal is more stable for these parameters. Degree PWM Time(ms) Figure 20. Experiment 3.a IMU Signal Degree with Noise Degree with Kalman Time(ms) Figure 21. Experiment 3.a Control Signal 6. CONCLUSIONS This paper presents a real-time robot which can track a colourful object and stand in upright position PWM Signal [1] Y. Ding, J. Gafford, and M. Kunio, "Modeling, Simulation and Fabrication of a Balancing Robot", Advanced Dynamics and Control, vol. 151, p. 22, [2] A. Fakharian, T. Gustafsson, and M. Mehrfam, "Adaptive Kalman filtering based navigation: An IMU/GPS integration approach", IEEE International Conference on Networking, Sensing and Control, April, Delft, Netherlands, pp , (2011). [3] R. C. Ooi, "Balancing a two-wheeled autonomous robot", Final Year Thesis, School of Mechanical Engineering, University of Western Australia, vol. 3, [4] A. Castro, "Modeling and dynamic analysis of a twowheeled inverted-pendulum", Master Thesis, Mechanical Engineering, Georgia Institute of Technology, Georgia, [5] A. Gani, E. Kılıç, Ö. F. Keçecioğlu, H. Açıkgöz, And M. Şekkeli, "PID And Fuzzy Logic Controller Design For The Level And Temperature Control Of Mixing Tank Used In Industrial Applications", Engineer & the Machinery Magazine, vol.57, no. 675, pp , [6] H. Açıkgöz, Ö. F. Keçecioğlu, M. Güneş, and M. Şekkeli," Simulation Study of Hydraulic Turbine by Using Self-Tuning Fuzzy PID Controller", Academic Platform- Journal of Engineering and Science, vol. 3, no. 1, pp. 7-15, [7] A. Gani, O. F. Kececioglu, H. Acikgoz, and M. Sekkeli,"Fuzzy Logic Controller Design Based On Sugeno Inference Method For Nonlinear Inverted Pendulum Dynamical System", Sigma Journal Of Engineering And Natural Sciences-Sigma, Vol. 8, No. 1, Pp , [8] C. Sundin and F. Thorstenson, "Autonomous balancing robot: Design and construction of a balancing robot", Master Thesis, Mechanical Engineering Chalmers University Of Technology, Goteborg, Sweden, [9] S. A. Junoh, "Two-wheeled balancing robot controller designed using PID", Master Thesis, Faculty of Electrical 131 8

137 M GÜNEŞ Academic Platform Journal of Engineering and Science 6-2, , 2018 and Electronic Engineering, Universiti Tun Hussein Onn Malaysia, [10] M. A. Şen, "Design And Optimisation Of A Fuzzy Logic Based Controller For A Two-Wheeled Robot By Using The Bees Algorithm", Master Thesis, Institution of Science and Technology, Selcuk University, Konya, [11] A. Ünlütürk, U. Güner, And Ö. Aydoğdu," A New PI- V Type Controller Design and Its Application on Balance Robot",TOK Conference, (September 11-13, Kocaeli, Turkey) pp , (2014). [12] H.-C. Sung, "Balancing Robot Control and Implementation", Master Thesis, Department of Mechanical Engineering Texas A&M University, [13] H. Guducu, "Building Detection from Satellite Images Using Shadow and Color Information", Master Thesis, Electrical And Electronics Engineering Natural And Applied Sciences Of Middle East Technical University, Texas, [14] S. Balasubramanian and M. N. Lathiff, "Self balancing robot", Undergraduate Thesis, Engineering Physics Project Laboratory, The University Of British Columbia, Vancouver, [15] O. Enginoğlu, "Design and control of balancing robot", Master Thesis, DEÜ Institue of Scince and Engineering, [16] J. L. C. Miranda, "Application of Kalman Filtering and PID Control for Direct Inverted Pendelum Control", Master Thesis, Electrical and Computer Engineering, California State University, California, [17] M. S. Uzuner, N. Yilmaz, And M. Bayrak, "A Real- Time Tracking Application Of Different Coloured Objects with A Vision Based Mobile Robot", Journal of Engineering and Architecture of Gazi University, Vol. 25, No. 4, [18] S. Dutta and B. B. Chaudhuri, "A color edge detection algorithm in RGB color space", International Conference on, IEEE Advances in Recent Technologies in Communication and Computing, October, Kottayam-India, pp , (2009). [19] V. Kravtchenko, "Tracking color objects in real time", Master of Science, Computer Science, University of British Columbia, Vancouver, [20] T. Şentürk, "Real Time Object Tracking with Moving Camera", Master of Science, Computer Science, Institue of Scince and Engineering YTU, Istanbul, [21] H. Takemura, K. Ito, and H. Mizoguchi, "Person following mobile robot under varying illumination based on distance and color information", IEEE International Conference on Robotics and Biomimetics, December, Sanya-China, pp , (2007). [22] M. S. Uzer, " A Tracking Application of Different Coloured Targets With A Vision Based Mobile Robot", Master Thesis, Institue of Scince and Engineering Selcuk University, Konya, [23] B. Karasulu, "Review and evaluation of well-known methods for moving object detection and tracking in videos", Journal of aeronautics and space technologies, vol. 4, no. 4, pp , [24] T. Gevers and A. W. Smeulders, "Color-based object recognition", Pattern recognition, vol. 32, no. 3, pp , [25] Y. Çelik, M. Altun, and M. Güneş, "Color based moving object tracking with an active camera using motion information", Artificial Intelligence and Data Processing Symposium (IDAP), September, Malatya-Turkey, pp. 1-4, (2017). [26] M. F. Aslan, A. Durdu, and K. Sabanci, "Shopping Robot That Make Real Time Color Tracking Using Image Processing Techniques", International Journal of Applied Mathematics, Electronics and Computers, vol. 5, no. 3, pp , [27] W. ladys law Skarbek and A. Koschan, "Colour image segmentation a survey", IEEE Transactions on circuits and systems for Video Technology, vol. 14, [28] M. M. Kelek, M. F. Aslan, and A. Durdu, "Real-Time Target Tracking Using Fast Object Detection", International Congress on Engineering and Natural Science, May, Sarajevo-Bosnia, pp , (2016). [29] A. Kayabası, B. Yıldız, K. Sabancı, E. Yigit, A. Toktas and M. Tekbas," Colour Feature-Based Classification of Wheat Grain Using ANN with Bayesian Regularization Learning Algorithm",3rd International Conference on Science, Ecology and Technology (ICONSETE), August, Rome-Italy, pp , (2016). [30] K. Sabanci, A. Kayabasi, and A. Toktas, "Computer vision based method for classification of wheat grains using artificial neural network", Journal of the Science of Food and Agriculture, vol. 97, no. 8, pp , [31] T. Selcuk and A. Alkan," Pv Modul Simulation And Pv System Toolbox Implementation In Simulink", Academic Knowledge Conference, 5-7 February, Mersin- Turkey, pp , (2014). [32] M. Altun, Y. Celik, M. Gunes, Investigation of The Success of Particle Swarm Optimization Based PID Classic PID and Fuzzy Type Inspection Methods in Speed Control of DC Motor, Journal of Engineering Science Kahramanmaras Sutcu Imam University, vol. 20, no. 4, pp , Dec [33] M. Altun, Y. Celik, M. Gunes," Investigation of The Success Of Pid And Fuzzy Type Inspection Methods In Speed Control Of Shunt Excited Dc Motor", 2nd International Energy and Engineering Conference October Gaziantep- Turkey, pp , (2017). [34] O. Doğmuş, E. Kiliç, S. Şit, And M. Güneş,"Adaptation of Optimized PID Controller with PSO Algorithm to Photovoltaic MPPT System", Journal of Engineering Science Kahramanmaraş Sutcu Imam University, vol. 20, no. 4, pp. 1 8, Dec [35] S. Şit, H. R. Özçalik, E. Kiliç, And M. Altun, Comparative Study of the Success of PI and PI Fuzzy Controller for Induction Motor Drive using SVPWM Method, International Journal of Engineering Science Invention (IJESI), vol. 5, no. 11, pp , Nov [36] A. Gani, E. Kiliç, Ö. F. Keçecioğlu, H. Açikgöz, M. Tekin, And M. Şekkeli, A Simulation Study on 132 9

138 M GÜNEŞ Academic Platform Journal of Engineering and Science 6-2, , 2018 Controlling Excitation Current of Synchronous Motor and Reactive Power Compensation via PSO Based PID and PID Controllers, Conference on Innovations and Applications in Intelligent Systems, 5-7 October, Alanya- Turkey, (2017)

139 Academic Platform Journal of Engineering and Science 6-2, , 2018 Academic Platform Journal of Engineering and Science journal homepage: Parçacık Sürüsü Eniyilemesine Dayalı Yığılmış Genelleme Yöntemi ve Metin Sınıflandırma Üzerinde Uygulanması * 1 Aytuğ Onan( ) 1 Manisa Celal Bayar Üniversitesi, Teknoloji Fakültesi, Yazılım Mühendisliği Bölümü, Manisa Öz Arrival Date: Accepted Date: Topluluk öğrenmesi, birden fazla öğrenme algoritmasının çıktılarının birleştirilmesi ile daha yüksek başarımlı ve güvenilir sınıflandırma modelleri oluşturulmasını amaçlar. Topluluk öğrenmesi yöntemleri, aralarında metin madenciliğinin de yer aldığı birçok alanda başarı ile uygulanmaktadır. Yığılmış genelleme algoritması, heterojen sınıflandırma algoritmaları ile sınıflandırıcı topluluğu oluşturulmasına yönelik bir yöntemdir. Yığılmış genelleme algoritmasında, temel öğrenme algoritmalarının çıktıları, üst seviyeli bir öğrenme algoritması aracılığıyla birleştirilir. Yığılmış genelleme algoritmasının etkin bir biçimde işleyebilmesi için, temel öğrenme algoritması olarak görev alacak yöntemlerin seçilmesi gerekmektedir. Bunun yanı sıra, üst seviye öğrenme algoritması olarak hangi yöntemin kullanılacağının belirlenmesi gereklidir. Bu nedenle, yığılmış genelleme algoritması için uygun bir konfigürasyon belirlenmesi, zor bir problemdir. Bu çalışmada, yığılmış genelleme algoritması için uygun bir konfigürasyon belirlenmesi işlemi bir eniyileme problemi olarak ele alınmış ve parçacık sürüsü eniyilemesine dayalı bir yöntem önerisinde bulunulmuştur. Metin sınıflandırma alanında gerçekleştirilen deneysel analizlerde, parçacık sürüsü eniyilemesine dayalı yöntem, genetik algoritma, karınca kolonisi eniyilemesi ve yapay arı kolonisine dayalı yığılmış genelleme yöntemleri ile karşılaştırılmıştır. Anahtar Kelimeler: Sınıflandırıcı topluluğu, yığılmış genelleme yöntemi, parçacık sürüsü eniyilemesi, metin sınıflandırma. Particle Swarm Optimization Based Stacking Method with an Application to Text Classification * 1 Aytuğ Onan Abstract 1 Manisa Celal Bayar University, Faculty of Technology, Department of Software Engineering, Manisa Multiple classifier aims to integrate the predictions of several learners so that classification models can be constructed with high performance of classification. Multiple classifiers can be employed in several application fields, including text categorization. Stacking is an ensemble algorithm to construct ensembles with heterogeneous classifiers. In Stacking, the predictions of baselevel classifiers are integrated by a meta-learner. To configure Stacking, appropriate set of learning algorithms should be selected as base-level classifiers. Besides, the learning algorithm that will perform the meta-learning task should be identified. Hence, the identification of an appropriate configuration for Stacking can be a challenging problem. In this paper, we introduce an efficient method for stacking ensemble based text categorization which utilizes particle swarm optimization to upgrade arrangement of the ensemble. In the empirical analysis on text categorization domain, particle swarm optimization based Stacking method has been compared to genetic algorithm, ant colony optimization and artificial bee colony algorithm. Keywords: Classifier ensembles, stacking method, particle swarm optimization, text classification. 1. INTRODUCTION principle thought behind multiple classifier is to obtain a combined prediction model with higher predictive Multiple classifier system (also known as ensemble performance based on multiple classifiers. Multiple learning) is a promising field in pattern recognition. The classifier can result in reduction of the variance of learners. *Corresponding Author: Manisa Celal Bayar Üniversitesi, Teknoloji Fakültesi, Yazılım Mühendisliği Bölümü, Doi: /apjes

140 A ONAN Academic Platform Journal of Engineering and Science 6-2, , 2018 In addition, more expressive classification models can be generated [1]. Multiple classifier systems yield better classification accuracy than a single learning algorithm, due to representational, statistical and computational factors [2]. Statistically, with the existence of sufficient data, different classifier can be generated by sampling distributions. Computationally, the parameter dependency of learning algorithms and the risk of generating a local optimum result can be reduced. Besides, obtaining different representational configurations may be beneficial in some applications. Multiple classifiers can be assigned into four groups based on the ways of building ensembles as data-level, featurelevel, classifier-level and combination-level ensembles [1]. In data-level ensembles, different datasets obtained by bootstrapping of training dataset are trained on different classifiers. In feature-level, different feature subsets are utilized, whereas classifier-level ensembles use different base learning algorithms. In combination-level ensembles, different combiners are designed. Another taxonomy for classification of multiple classifiers is the structure of ensemble construction [3]. Based on the structure employed in ensemble generation from base learning algorithms, there are two main groups of ensemble algorithms, namely dependent algorithms and independent algorithms. In dependent algorithms, prediction of a classifier is employed to obtain the output of the subsequent classifier, whereas the output of classifiers are obtained separately and their results are integrated in independent methods [3]. There are several dependent learning methods, such as incremental batch learning (IBL) and model-guided instance selection (MGIS) [4]. In IBL, predictions obtained in a particular cycle is provided for the learner of ensuing cycle as a prior knowledge. Likewise, in model-guided instance selection, the learners of the earlier cycles are employed to manipulate the training set of ensuing cycles. Dependent algorithms include AdaBoost. In independent methods, several datasets are generated from the original dataset and these datasets are employed to train the classifiers. Then, the output for final classification is obtained by a combination method. There are several independent ensemble algorithms, such as Bagging and Random Forest method. Combining base learning algorithms is another important issue in multiple classifier. The outputs of learners can be integrated by weighting methods and meta-learning algorithms [5]. The conventional weighting methods include majority voting, performance weighting, distribution summation, Bayesian combination and the conventional meta-learning algorithms include Stacking, arbiter trees, combiner trees and Grading [3]. Stacking (Stacked generalization) is a meta-learning based ensemble algorithm to combine multiple classification models [6]. Compared to the other multiple classifiers, such as Bagging and Boosting, Stacking has been less widely utilized in the literature [7]. Yet, the classification accuracy of learning algorithms can be substantially enhanced with the use of stacking algorithm [8]. In Stacking, the training set is divided into two disjoint set (namely, one training set and one test set).based on the predictions of base learning algorithms and the correct responses, a meta-learner is trained [8]. To use stacking, there are a number of issues to be considered. The algorithms that will be employed as base-level classifiers and their parameters should be identified, the number of base learners should be determined, the algorithm that will be employed as a metalearner and its parameters should be determined and types of features that will be employed to generate meta-data should be decided [9]. Hence, the identification of an appropriate/optimal configuration for Stacking is a challenging task. Metaheuristic algorithms are widely recognized as established and efficient methods in optimization problems. Metaheuristic methods can be classified as single-solution metaheuristics and population-based metaheuristics [10]. Tabu search, simulated annealing and local search are some representatives of single-solution based metaheuristics and genetic algorithms, particle swarm optimization, ant colony optimization, artificial bee colony are population based metaheuristics. Metaheuristic algorithms have been successfully applied in a wide range of optimization problems, such as job shop scheduling, vehicle routing, resource allocation, pattern recognition, data mining, clustering and engineering design optimization [11, 12]. Some researchers introduced various metaheuristics to identify the optimal scheme for Stacking algorithm. In [13], a good configuration for Stacking algorithm is obtained by a genetic search algorithm. In [14], ant colony optimization is utilized to identify an optimized configurations for Stacking algorithm. In [15], artificial bee colony algorithm based method is proposed to configure Stacking algorithm. In this paper, we present a Stacking based scheme which employs particle swarm optimization algorithm to find an optimal configuration for base-level and meta-level classification algorithms. 2. THEORETICAL FOUNDATIONS In this section, classification algorithms and multiple classification algorithms are introduced Classification Algorithms In the experiments, eight machine learning algorithms (namely, logistic regression, Naïve Bayes algorithm, C4.5, K-nearest neighbour algorithm, K-star algorithm, ZeroR algorithm, Decision Stump algorithm and PART algorithm) have been considered. Logistic regression (LR) is a linear learner, which employs a linear function to estimate the class labels for each instance [16]. Linear regression algorithm can be utilized for classification and regression problems. LR algorithm can be employed for classification problems with nominal features. 135

141 A ONAN Academic Platform Journal of Engineering and Science 6-2, , 2018 Naïve Bayes algorithm (NB) is a probabilistic learner, which employs Bayes theorem with independence assumptions between attributes [17]. Though the algorithm is based on the independence assumption, the algorithm is scalable with comparable predictive performance to other conventional learning algorithms, such as k-nearest neighbor algorithm and support vector machines. NB algorithm is regarded as a standard technique for many pattern recognition tasks, including text categorization. C4.5 algorithm is a decision tree based learner, which is a successor of ID3 [18]. In the algorithm, the selection of test feature is determined based on the information gain metric. For a particular set, the algorithm identifies a feature with the highest information gain as the attribute. The algorithm has a pruning mechanism. Hence, the algorithm can eliminate overfitting and can deal with noisy instances [19]. K-nearest neighbour algorithm (KNN) is a nonparametric lazy learner, which can be employed for classification and regression problems [20]. Regarding classification problem, the class label for a new instance is determined by majority voting of class labels for k-closest instances. K-star algorithm is another instance based learner, which employs entropy-based evaluation function to estimate the class label of each instance. The algorithm can be employed for problems with symbolic and real-valued feature sets. ZeroR algorithm is a simple classifier that relies on the target value and ignores all the predictors [15]. The algorithm simply predicts the majority category (class). Decision Stump (DS) is a decision tree based learner [22]. In this scheme, one-level decision tree is constructed, such that there is one root and its leaves. The class label for a particular instance is determined based on the value of a single attribute. PART algorithm is a rule based learner, which builds partial decision trees to obtain classification rules [23]. In this scheme, decision trees are constructed with the use of C4.5 algorithm. In each iteration of algorithm, decision tree returns the best leaf as a classification rule Multiple Classifier Methods In the empirical analysis, four multiple classifier methods (namely, Bagging, AdaBoost, Random Forest and Stacking) have been considered. Bagging (Bootstrap aggregating) algorithm [24] is a multiple classifier algorithm, which reduces the variance and avoids overfitting. Diversity among the base learners is achieved by bootstrap sampling from the original dataset to obtain training set. In bagging algorithm, replicated datasets are utilized to train base classification algorithms. The predictions of classification algorithms are combined by majority voting scheme. Bagging yields promising results when the base learners are unstable. Boosting is a multiple classifier method, which aims to construct strong learners from weak learners (such as decision trees) by adjusting iteratively the weight of instances and the weights of classification methods. AdaBoost algorithm [25] is one of the most popular Boosting algorithm, with high predictive performance on several different application fields. AdaBoost algorithm is an adaptive algorithm, which aims to obtain a robust classification scheme by dedicating more iterations to harder instances [25]. Random Forests algorithm (RF) is an ensemble classification scheme, which combines tree predictors such that each tree grows in randomly selected subspaces of data [24]. In this scheme, a random feature selection is employed to split each node. In Random Forests, each tree in the ensemble is grown based on a random parameter and the final prediction of ensemble is obtained by aggregation. The predictive performance has been enhanced by growing an ensemble of trees and aggregating the trees by voting for the most popular class. Random Forests achieves high diversity by employing bootstrap aggregation (i.e. simple random sampling with replacement) and node splitting from a subset of total feature set. Stacking (namely, stacked generalization) is another multiple classifier algorithm [26]. The other multiple classifier algorithms (such as Bagging and AdaBoost) are based on the combination of the same type weak learning algorithms. In contrast, Stacking algorithm obtains multiple classifier system by following a two-staged procedure. In the first level, the base learning algorithms are trained on the instances to estimate the class labels. In the second level, a combiner algorithm is trained on meta-instances. The meta-instances consists of the predictions of all algorithms. 3. PARTICLE SWARM OPTIMIZATION BASED STACKING Particle swarm optimization (PSO) algorithm is a stochastic population-based algorithm, which simulates the social behaviour of organisms, such as bird flocking and fish schooling [27]. In PSO algorithm, each single candidate solution is denoted as a particle in the search space. Each particle has its own position (which corresponds to its direction) and its own velocity (which corresponds to its current direction). In this way, search space of possible solutions is explored by the particles. In PSO algorithm, search characteristics of particles are influenced by the cooperation among the particles of swarm. The algorithm has a simple structure and involves a small number of parameters [30]. There are many optimization problems with discrete-valued search spaces. To operate on binary search spaces, a discrete variant of PSO was developed [27]. In the binary PSO, particles correspond to the positions in the binary search space. The position vector of a particle can take the values of zero or one and the change of the position of a particle 136

142 A ONAN Academic Platform Journal of Engineering and Science 6-2, , 2018 indicates flipping number of bits from one value to another. In this way, a particle can move on a hypercube by flipping the number of bits. In binary PSO, velocity values are limited to a range of [0, 1]. Hence, velocities and particle directions are regarded as the probability of finding the particle in one state or the other. To limit the range of velocity to [0, 1], a normalization method, such as sigmoid function can be utilized [28]. v new pd wv old pd old c1rand1 ( pbest pd x pd ) c2rand2 ( gbest As emphasized by the earlier works mentioned in advance, an optimal configuration for Stacking algorithm can be modelled as an optimization problem [13-15]. In this work, binary particle swarm optimization algorithm is utilized in the construction of an appropriate configuration for Stacking ensemble [30]. Particle swarm optimization based optimization is conducted at two different levels: optimization at the base-level classifier selection and optimization at the base-level and meta-level classifier selection. These methods are referred as PSO-Stacking1 and PSO-Stacking2, respectively. The general framework for particle swarm optimization based Stacking is adapted from [14]. In this framework, particle swarm optimization algorithm is applied to search Stacking configurations, Stacking is trained and validation with training sets and validation sets, respectively and the best particle is obtained as a final configuration of Stacking. Then, this final configuration is evaluated by the testing set. In PSO- Stacking1, there is a pool of classifiers consisting of ten classification algorithms from which the optimal subset of classifiers will be selected. These classifiers include logistic regression, Naïve Bayes, C4.5, K-nearest neighbour, K-star, ZeroR, Decision Stump and PART algorithms. In this scheme, the meta-level classification algorithm is kept fixed and logistic regression method is utilized as the meta-level classifier. In contrast, PSO-Stacking2 has the same set of classifiers for base-level classification, whereas the metalevel classification algorithm is not kept fixed. Instead, ten classification algorithms examined for base-level classification are possible candidates of meta-level classification. The only difference between PSO-Stacking1 and PSO-Stacking2 is in the selection of meta-level classifier. Hence, we denote the general principles of particle swarm optimization based Stacking by PSO- Stacking. In PSO-Stacking, a binary string is employed to represent the position of each particle. The value of zero implies that the corresponding classifier is not selected, whereas the value of one implies that the corresponding classifier is selected. To evaluate the particles, F-measure is utilized as the fitness function. F-measure is the harmonic mean of precision and recall. Precision (PRE) is computed as given by Equation 1. Recall (REC) is computed as given by Equation 2. Based on the precision and recall values, F- measure is computed as given by Equation 3. TP PRE (1) TP FP TP REC (2) TP FN 2 * PRE * REC F measure PRE REC Each particle is updated based on the equations as given by Equations 4-7, where pbest p denotes the best fitness value for each particle, gbest denotes the best fitness value within a group of pbest p, w denotes the inertia weight, c 1 and c 2 denote acceleration parameters, rand, rand 1 and rand 2 are random numbers, v pd old and v pd new are velocities of old and new particles, respectively [30]: (4) new new pd ( V min, Vmax then v max(min( Vmax, v pd ), V ) v new If ) new If ( S( )) v pd d min x old pd pd (5) new 1 S( v pd ) new (6) v 1 e pd new new rand then x 1 else 0 pd x (7) Randomly initialize particle swarm While maximum number of iterations have not been reached Evaluate fitness value of particle swarm by the ensemble classification scheme. For p=1 to number of particles If fitness of X p is greated than the fitness of pbest p then Pbest p =X p endif If fitness of gbest is the same Max times then reset gbest Endif For d=1 to number of dimensions of particle pd ) (3) v new pd wv old pd old c1rand1 ( pbest pd x pd ) c2rand2 ( gbestd x old pd ) 137

143 A ONAN Academic Platform Journal of Engineering and Science 6-2, , 2018 If v new pd ( V min, Vmax) then new new v max(min( V, v ), V ) S( v new pd 1 ) 1 e new v pd new If ( rand S( )) then v pd pd new x pd 1 Next d Next p Next generation until stopping criterion is met Figure 1. The general structure for PSO-Stacking1 else max new x pd pd 0 min The general structure of PSO-Stacking1 is outlined in Figure 1, where the maximum number of iterations is set to 100, rand, rand 1 and rand 2 are random numbers in the range of [0, 1], c 1 and c 2 acceleration parameters are set to 2 based on the earlier empirical results [27, 30]. As emphasized in advance in PSO-Stacking1, meta-level classification algorithm remains fixed during the evaluation of the ensemble configuration. In PSO-Stacking2, on the other hand, any classification algorithm can perform the metalearning task. Hence, the framework of PSO-Stacking1 is modified as follows: For each base-level classification algorithm configuration, fitness values with different metalearners (logistic regression, Naïve Bayes, C4.5, K-nearest neighbour, K-star, ZeroR, Decision Stump and PART algorithms) are examined and the configuration with the highest F-measure value is selected. 4. RESULTS AND DISCUSSIONS In this section, datasets, evaluation measure, empirical settings and experimental results are given Text Collections To empirically analyze the classification accuracy of PSO- Stacking approaches, we have employed four text categorization datasets from web pages domain. The descriptive information regarding the datasets is summarized in Table 1, where text collections are represented via unigram data representation scheme. In the experimental evaluations, we have utilized latent Dirichlet allocation (LDA) based representation with Gibbs sampling for text documents [31-32]. Table 1. Descriptive information for text collections [12] Text Collection Number of documents Number of features Number of classes DMOZ-Business DMOZ-Computers DMOZ-Science DMOZ-Sports Evaluation Metric In the empirical evaluation, classification accuracy (ACC) is employed as the evaluation criteria. Classification accuracy is computed as given by Equation 8: ACC TN TP TP FP FN TN (8) where TN, TP, FP and FN represents true negatives, true positives, false positives and false negatives, respectively Empirical Settings In the empirical analysis, k-fold cross validation method (k=10) is utilized. The result reports the average performance across all ten trials. The experiments are done on WEKA The metaheuristic based ensemble configuration schemes are also implemented in Java. For each algorithm, the default set of parameters of WEKA are considered. To obtain an optimal configuration for Stacking ensemble, ten classification algorithms in WEKA are taken into account. In PSO-Stacking1, these classifiers are candidates for base-level classification. In PSO-Stacking2, these classifiers are candidates for base-level and meta-level classification. In order to be consistent with the earlier work on the use of metaheuristics to determine the optimal configuration for Stacking, ten classifiers are the same with these references. Hence, logistic regression, Naïve Bayes, C4.5, K-nearest neighbour, K-star, ZeroR, Decision Stump and PART algorithms are selected [14, 15]. In this classifier pool, there are classification algorithms from various classification approaches. Hence, the diversity involved in the classifier ensemble construction is achieved. In the empirical analysis, the stacking configuration found by PSO-stacking is examined with several base learners and ensemble approaches. First, it is compared to baseclassifiers, such as logistic regression, Naïve Bayes, C4.5, K-nearest neighbour, K-star, ZeroR, Decision Stump and PART algorithms. Secondly, it is compared to conventional ensemble approaches, such as Bagging, AdaBosot, Random 138

144 A ONAN Academic Platform Journal of Engineering and Science 6-2, , 2018 Forest, Stacking and StackingC. Bagging with RepTree decision tree as its base-level learning algorithm, Bagging with C4.5 decision tree as its first-level learning algorithm, AdaBoost with Decision Stump as its base-level learning algorithm, AdaBoost with C4.5 decision tree as its firstlevel learning algorithm are examined. Naïve Bayes, C4.5 and K-nearest neighbour algorithms are utilized in Stacking and StackingC based ensemble construction. Logistic regression is employed as a metalearner in Stacking and linear regression is employed as a meta-learner in StackingC. For PSO-Stacking1, logistic regression method is utilized as the meta-level classifier. Besides, PSO-Stacking approaches are compared to the other metaheuristic based configuration optimization approaches, such as GA-Stacking, ACO-Stacking and ABC-Stacking. For these algorithms, the parameters assigned the values mentioned in the corresponding references [14, 15] Experimental Results In Table 2, the average classification accuracy of classification algorithms and multiple classifier methods have been presented, where the best results for a particular configuration are denoted by using boldface. First, we examined the classification accuracy enhancement of PSOstacking over individual base learning algorithms. The particle swarm optimization based configurations of Stacking yield better classification accuracy than individual learning algorithms. Regarding results of learning algorithms, the highest results are achieved by logistic regression and Naïve Bayes classifiers. Secondly, we examined the classification accuracy of PSO- Stacking and the other well-known multiple classifiers, such as Bagging, AdaBoost, Random Forest, Stacking and StackingC. Particle swarm optimization based Stacking ensemble configuration generally yields better classification accuracy than the other well-known multiple classifier methods. Besides, Stacking and StackingC multiple classifiers generally obtain better classification accuracies than multiple classifier methods, such as Bagging, AdaBoost and Random Forest. Regarding the classification accuracys of PSO-stacking and other metaheuristic multiple classifiers, the highest classification accuracies among the metaheuristic based ensemble configurations for Stacking is obtained by PSO- Stacking2. The second highest classification accuracies for metaheuristic based ensemble configurations for Stacking are obtained by PSO-Stacking1, ACO-Stacking2, ABC- Stacking2 depending on the different datasets. Table 2. Classification accuracies of compared algorithms on text categorization benchmarks Algorithm DMOZ-Business-500 DMOZ-Computers-500 DMOZ-Science-500 DMOZ-Sports-500 LR NB C KNN (k=1) KNN (k=2) K-star OneR PART ZeroR Decision Stump Bagging (REP Tree) Bagging (C4.5) AdaBoost (Decision Stump) AdaBoost (C4.5) Random Forest Stacking StackingC GA-Stacking GA-Stacking ACO-Stacking ACO-Stacking ABC-Stacking ABC-Stacking PSO-Stacking

145 A ONAN Academic Platform Journal of Engineering and Science 6-2, , 2018 PSO-Stacking CONCLUSION Multiple classifier system is a research field of pattern recognition, aiming to integrate individual classifiers to obtain a scheme with better classification performance. This study introduces a multiple classifier approach to text categorization. In this scheme, Stacking method is utilized to construct ensembles. The two configuration issues of Stacking, i.e. base-level classifier selection and meta-level classifier selection are addressed by the use of binary particle swarm optimization. The proposed approach is empirically evaluated with base learners, well-known techniques (such as Bagging, AdaBoost, Random Forest, Stacking and StackingC) and other metaheuristic based Stacking methods (such as ACO- Stacking and ABC-Stacking) in terms of classification accuracies. The experimental results indicate that PSO- Stacking can outperform conventional classification methods for text categorization. REFERENCES [1] L.I. Kuncheva, Combining pattern classifiers, methods and algorithms, New York: Wiley InterScience, [2] J.Kittler and F. Roli, Multiple classifier systems, Berlin: Springer, [3] L.Rokach, Ensemble-based classifiers, Artificial Intelligence Review, vol.33, pp.1-39, [4] F.J.Provost and V.Kolluri, A survey of methods for scaling up inductive learning algorithms, Data Mining and Knowledge Discovery, vol. 3, pp , [5] A.Onan, S.Korukoğlu and H.Bulut, A multiobjective weighted voting ensemble classifier based on differential evolution algorithm for text sentiment classification, Expert Systems with Applications, vol. 62, pp. 1-16, [6] D.H.Wolpert, Stacked generalization, Neural Networks, vol. 5, no 2, pp , [7] M.Sewell, Multiple classifier UCL, Department of Computer Science Technical Report RN-11-02, (2011). [8] R.Polikar, Ensemble based systems in decision making, IEEE Circuits and Systems Magazine, vol. 6, no 3, pp , [9] M.P.Sesmero, A.I.Ledezma and A.Sanchis, Generating ensembles of heterogeneous classifier using stacked generalization, Wiley Interdisciplinary Reviews: Data Mining and Knowledge Discovery, vol. 5, no 1, pp , [10] E.G.Talbi, Metaheuristics from design to implementation, New York: Wiley, [11] A. Gogna and A.Tayal, Metaheuristics: review and application, Journal of Experimental & Theoretical Artificial Intelligence, vol. 25, no 4, pp , [12] A.Onan, H.Bulut and S.Korukoğlu, An improved ant algorithm with LDA-based representation for text document clustering, Journal of Information Science, vol.43, no 2, pp , [13] H.A.Abbas, C.S.Newton and R.Sarkar, Heuristic search-based stacking of classifiers, Berlin: Springer, [14] Y.Chen and M.L.Wong, An ant colony optimization approach for stacking ensemble, in Proceedings of the Second World Congress on Nature and Biologically Inspired Computing, (December 15-17, Kitakyushu, Japan, 2010), , (2010). [15] P.Shunmugapriya and S.Kanmani, Optimization of stacking ensemble configurations through artificial bee colony algorithm, Swarm and Evolutionary Computation, vol.12, pp.24-32, [16] M.Kantardzic, Data mining: concepts, models, methods and algorithms, New York: Wiley-IEEE Press, [17] G.Shmueli, N.R.Patel and P.C.Bruce, Data mining for business intelligence: concepts, techniques, and applications in Microsoft Office Excel with XLMiner, New Jersey: John Wiley & Sons, [18] R.Quinlan, C4.5: programs for machine learning, San Mateo: Morgan Kaufmann, [19] X.Niuniu and L.Yuxun, Review of decision trees, in Proceedings of the third IEEE International Conference on Computer Science and Information Technology, (July, Chengdu, China, 2010), , (2010). [20] D.W.Aha, D.Kibler and M.K.Albert, Instance based learning algorithm, Machine Learning, vol.6, pp.37-66, [21] J.G.Clearly and L.E.Trigg, K*: an instance-based learner using an entropic distance measure, in Proceedings of the twelfth international conference on machine learning, (July 9-12, Tahoe City, California, 1995), , (1995). [22] W.Iba and P.Langley, Induction of one-level decision trees, in Proceedings of the 9th International Workshop on Machine Learning, (Aberdeen, UK, 1992), , (1992). [23] E.Frank and I.H.Witten, Generating accurate rule sets without global optimization, in Proceedings of the 15th International Conference on Machine Learning, (July 24-27, 1998), , (1998). [24] L.Breiman, Bagging predictors, Machine Learning, vol. 4, no 2, pp , [25] Y.Freund and R.E.Schapire, Experiments with a new boosting algorithm, in Proceedings of the Thriteenth International Conference on Machine Learning, (July 3-6, 1996), 1-9, (1996). [26] D.H. Wolpert, Stacked generalization, Neural Networks, vol.5, no 2, pp , [27] J.Kennedy and R.C.Eberhart, Particle swarm optimization, in Proceedings of the International Conference on Neural Networks, , (1995). [28] A.P. Engelbrecht, Computational intelligence: an introduction, New York: Wiley, [29] M.N.A.Wahab, S.Nefti-Meziani and A.Atyabi, A comprehensive review of swarm optimization algorithms, Plos One, doi: /journal.pone [30] L.Y.Chuang, H.W.Chang, C.J.Tu and C.H.Yang, Improved binary PSO for feature selection using gene 140

146 A ONAN Academic Platform Journal of Engineering and Science 6-2, , 2018 expression data, Computational Biology and Chemistry, vol. 32, pp.29-38, [31] A.Onan, S.Korukoğlu and H.Bulut, LDA-based topic modelling in text sentiment classification: an empirical analysis, International Journal of Computational Linguistics and Applications, vol.7,no 1, pp , [32] A.Onan, Hybrid supervised clustering based ensemble scheme for text categorization, Kybernetes, vol. 46, no 2, pp ,

147 Academic Platform Journal of Engineering and Science 6-2, , 2018 Academic Platform Journal of Engineering and Science journal homepage: An ABC Algorithm Inspired by Boolean Operators for Knapsack and Lot Sizing Problems * 1 Emrah Hancer( ) 1 Mehmet Akif Ersoy University, Department of Computer Technology and Information Systems, Burdur, Turkey Abstract. Received Date: Accepted Date: This paper proposes a logically inspired artificial bee colony algorithm (ABCLO) to deal with the knapsack and lot sizing problems shown in many forms such as in economics, engineering and business. The proposed ABC-LO algorithm aims to find fitter solutions using the search mechanism designed through the basic Boolean operators. To verify the effectiveness of the ABC-LO algorithm, it is analyzed and compared with the recent variants of particle swarm optimization, artificial bee colony and genetic algorithms. The results indicate that the proposed ABC-LO algorithm performs well in knapsack and lot sizing problem sets compared to the others. Keywords: artificial bee colony, Boolean logic, knapsack, lot sizing. 1 INTRODUCTION In recent years, swarm intelligence based algorithms have attracted attention due to the ability of producing promising solutions in a reasonable time. Among swarm intelligence based algorithms, artificial bee colony (ABC) [1] is one of the most robust, recent and popular algorithms proposed to solve real-parameter, non-convex and non-smooth problems. The standard ABC algorithm synergizes minimalistic foraging procedure with waggle dance mechanism and is enacted through a bee colony equally partitioned among employed and onlooker bees [2]. The neighborhood search is carried out through positional perturbation of the foragers in search for fitter food sources followed by the greedy selection in order to keep the positions of the fitter source. The waggle dance mechanism is performed by employed bees to share information with onlooker bees through a kind of fitness and roulette-wheel based selection mechanism. Using this information, onlooker bees tend to search in the neighborhood of fitter solutions. In addition to onlooker and employed bees in the hive, scout bees derived from employed bees are responsible of finding new sources instead of poor ones. Since the standard ABC algorithm was first proposed to solve numeric problems, it needs to be redesigned to deal with discrete or binary problems. To apply ABC to binary problems, a number of ABC variants were developed by researchers. Kashan et al. [3] introduced a discrete ABC (DisABC) variant for uncapacited facility location problem (UFLP). In DisABC, the neighborhood search is performed by measuring the dissimilarity/similarity between binary vectors. Although DisABC performs better than binary particle swarm optimization (BPSO), it does not perform well in high dimensional problems. Kiran and Gunduz [4] embedded XOR logical operator into the basic ABC search mechanism (XORABC) to address UFLP. The experimental results showed that it performed better than BPSO and DisABC. However, XOR-ABC may converge to local minima due to the search scheme. Pampara and Engelbrecht [5] proposed an angle modulation based ABC algorithm. Despite its simplicity, transformation mechanism between the continuous and binary spaces may lead to local convergence problems. Ozturk et al. [6] proposed an improved version of DisABC (IDisABC) to automatically determine the number of clusters in the data. In contrast to DisABC, IDisABC considers all similarity cases to produce effective solutions. In another study, Ozturk et al. [7] proposed a genetically inspired ABC algorithm (GBABC) to automatically evolve clusters in the data. It was also tested on numeric and knapsack problems. It is simple implement and can search the possible solution space thoroughly but may be computationally intensive for high dimensional problems. Hancer et al. [8] proposed an advanced similarity based ABC (MDisABC) algorithm for feature selection. The *Corresponding Author: Mehmet Akif Ersoy University, Department of Computer Technology and Information Systems, Burdur, Turkey, Doi: /apjes

148 E HANÇER Academic Platform Journal of Engineering and Science 6-2, , 2018 results showed that MDisABC selected a smaller number of features and obtained higher classification accuracy than the existing approaches. It can be inferred from the above discussed studies that the potential of ABC for discrete and binary problems has not been fully investigated and the need for the studies concerning discrete ABC variants has not come to end. The main goal of this study is to develop an ABC variant for the knapsack and lot sizing problems with the expectation of loading the knapsack with valuable items and minimizing the order cost for a company. In order to achieve this goal, the idea of using logic operations is integrated to the ABC search mechanism, referred as ABC-LO. The effectiveness of the proposed ABC-LO algorithm is verified and examined by comparing it with recent discrete evolutionary algorithms. Specifically, we will investigate: the performance of ABC-LO versus the existing approaches on knapsack problem sets, the performance of ABC-LO versus the existing approaches on uncapacited lot sizing problem sets, and the performance of ABC-LO versus the existing approaches on capacited lot sizing problem sets. The rest of the paper is organized as follows. Section 2 defines the considered problems and provides a general knowledge concerning Boolean operators. Section 3 presents the proposed ABC algorithm with its implementations. Section 4 introduces the experimental design and Section 5 presents the experimental results. Finally, Section 6 concludes the study through providing an insight into the future trends. 2 BACKGROUND 2.1 Knapsack Problem Suppose that a friend living abroad wants from you to bring some devices or items. It is known that one can only have the luggage not exceeding kilograms in the planes. Therefore, both valuable and lightweight items should be chosen to pick a luggage. Well then, how to pick a luggage in an optimal way? That question can be enhanced to the many real world problems such as in economics, industry, transportation, logistic, computer science and etc. All these problems are considered in the same structure, referred as the knapsack problem. The mathematical description of the knapsack problem can be presented by: n f ( x ) = j= 1 c j x j max (1) where w j represents weight of the jth item; c j represents cost of the jth item; x j denotes the status of the jth item, whether it is loaded into knapsack or not (1 or 0); and W is the capacity of knapsack. In order to solve the knapsack problem, a large number of methods such as branch-bound [10], dynamic programming [9] or hybridization of both approaches [11, 12] have been proposed. In fact, evolutionary computation techniques such as genetic algorithm [13, 14], particle swarm optimization [15, 16], differential evolution [17, 18] and artificial bee colony [19, 20] have also been applied to address the knapsack problem. More information concerning the approaches proposed to cope with the knapsack problem can be found in [10]. 2.2 Lot Sizing Problem Assume that a company orders quantities in order to provide the net requirements of customer demand. The order decision needs to be partitioned into the periods in order to minimize the total cost. But, which periods are the most optimal ones to order? Several factors such as ordering cost, holding cost, capacity, minimum-maximum order quantity, shortage cost and etc. should be considered before making decisions, i.e., it may be single or multi item, capacited or uncapacited, shortage allowed or not, and single or multilevel. In this paper, single item, single level and no shortages allowed model is considered with both capacited and uncapacited versions. The basic notations for lot sizing are defined as follows: K: setup cost h: holding cost O i : Order quantity for period i R i : Net requirements for period i I i : Ending inventory for period i x i : An order decision is made or not for period i Cap : Capacity of the order quantity 143 2

149 E HANÇER Academic Platform Journal of Engineering and Science 6-2, , 2018 In terms of the notations, the lot sizing problem can be defined as follows: n ( Kx i + hi i ) min (2) i = 1 subject to: I 0 = 0 (3) I + x O I = R i 1 i i i i (4) I 0, i { 1,2,..., n} (5) i O (6) i 0 x {0,1}, i { 1,2,..., n} (7) i O i < Cap (8) where Eq. (4) means no initial inventory is available before starting trade; Eq. (5) keeps the inventory balance between requirements and orders; Eq. (6) reveals no shortage is allowed; and Eq. (8) is for the capacited form of lot sizing. Many approaches have been proposed to deal with the lot sizing problem. Wagner and Whitin [21] introduced a method based on dynamic programming, which guarantees optimal solutions. Tasgetiren and Liang [22] proposed a modified version of PSO to solve single item, single level and uncapacited lot sizing problem. The results indicated that the modified PSO algorithm performed better than GA. Deroussi and Lemoine [23] hybridized BPSO with the Wagner-Whitin algorithm to cope with multi-level lot sizing problems. The detailed information concerning lot sizing problem solvers can be found in [24, 25]. 2.3 Boolean Algebra In Boolean algebra, there are two truth variables, known as true (1) and false (0), respectively. In contrast to elementary algebra using addition and multiplication, the main operators of Boolean algebra are as follows: AND (conjuction), denoted by x Λ y, satisfies 1 if x = y =1; otherwise 0. OR (disjunction), detoned by x y, satisfies 0 if x = y = 0; otherwise 1. NOT (negation), denoted by x, satisfies 1 if x = 0, and 0 if x = 1. These Boolean operators can be combined or compounded to build other Boolean operators. The main derived operators of Boolean algebra are as follows: Material implication, denoted by x y, satisfies y if x is 1. Exclusive or XOR, denoted by x y, satisfies 0 if x = y = 1 or x = y = 0; otherwise 0. Complement of exclusive, denoted by x y, satisfies 1 if x y = 0; otherwise 1. 3 PROPOSED ABC-LO ALGORITHM In this section, the overall algorithm is first introduced. Then, its implementations to the knapsack and lot sizing problems are described. 3.1 Overall algorithm Swarm intelligence (SI), which is an artificial intelligence discipline, concerns with the behaviors of natural and artificial systems composed of many individuals, including schools of fish, colonies of ants, termites flocks of birds and herds of land animals. SI based behaviours resulting from the local interactions of the individuals with each other and with their environment comprise two main characteristics: self-paced labour and self-organization. The well-accepted examples of the SI discipline are ant colony optimization (ACO) [26], particle swarm optimization (PSO) [27], bacterial foraging optimization (BFO) [28] and artificial bee colony (ABC) [1] algorithms. This paper concentrates on the ABC algorithm since it is simple, easy to implement, has fewer parameters and performs successful performance in a variety of fields such as numerical problems [29], clustering [30], image analysis [31], etc. Although ABC has been successfully applied to several problems, the structure of ABC is not suitable to binary and discrete problems. In other words, the solution initialization and neighborhood search mechanisms of ABC need to be redesigned for binary space. In this study, binary solutions are initialized using Eq. (9) which is the most-widely preferred binary solution initialization way among binary evolutionary algorithms. 0 if U ij (0,1) < 0.5 x ij = (9) 1 if U ij (0,1) > 0.5 where U ij (0,1) is a uniformly generated number within the range of 0 and 1. To adapt neighborhood search mechanism for the binary solution space, the idea of using Boolean operators to design search mechanism is a novel and recent way used also in XOR-ABC and XOR-PSO. Although XOR-ABC and XORPSO are the first examples of adapting search mechanism through logical operators, they suffer from the local stagnation problems arising from their design. The detailed information concerning XOR-ABC and XOR-PSO can be found in Section 4.1. Motivated from the previously 144 3

150 E HANÇER Academic Platform Journal of Engineering and Science 6-2, , 2018 described issue, we introduce a new logically inspired ABC (ABC-LO) algorithm, in which the neighborhood search mechanism has effectively redesigned through the XOR and AND logical operators by Eq. (10). V i = X β ( X X )) (10) i ( i k where denotes XOR operator; denotes AND operator; X i ={x i1,x i2,,x id } and X j ={x j1,x j2,,x jd } are the current and neighbor binary solutions, respectively; and β is a randomly D-dimensional binary vector initialized by Eq. (9). The fundamental steps of the ABC-LO algorithm are as follows: 1. Initialize the population by Eq. (9). 2. Search in the neighborhood of each solution X i by Eq. (10). 3. Apply greedy selection between X i and V i. 4. Produce probabilistic value p i for each solution X i using roulette-wheel mechanism by Eq. (11). 5.Select SN number of solutions in a probabilistic manner, where rand(0,1) > p i. 6. Search in the neighborhood of each selected solution by Eq. (10). 7. Apply greedy selection between the selected solution and its neighborhood. 8.If there exists any abandoned solution which cannot be improved for a predefined number of trials, referred as limit, a new solution is initialized by Eq. (9) instead of the abandoned one. 9.Repeat Steps 2 to 8 until the maximum number of cycles is met. p i = SN i = 1 fitness i fitness i (11) where SN is the population size and fitness i is the fitness value of X i. 3.2 Implementations of ABC-LO The implementations of ABC-LO are presented as follows. 1. Knapsack: Considering the implementation of the ABC- LO algorithm to the knapsack problem, each solution X i ={x i1,x i2,,x id } represents the probable items for the knapsack. If any position of X i is equal to 1, the corresponding item is loaded into the knapsack. The objective function of knapsack can be defined through Eq. (1) as follows: D D f ( x j ) = ci x ji + Q min 0, W w jx ji (12) i = 1 i = 1 where Q is a penalty factor kg 5 kg 4 kg 2 kg 6 kg 1kg 3 kg 2 kg 6 kg Fig. 1 An illustrative example of how items are selected We provide the following example to show how the fitness value of a solution is evaluated in the knapsack problem. Assume that X i = {1, 0, 0, 1, 1, 0}, w i = {3kg, 5kg, 4kg, 2kg, 6kg, 1kg}, c i = {2, 1, 4, 2, 5, 6 } and W = 15kg. The items whose corresponding positions are equal to 1 are selected to load the knapsack, shown in Fig. 1. Accordingly, the total weight of items is 11 kg that does not exceed the capacity, and the total cost of items is 9. If the total weight of items in a solution exceeds the knapsack capacity, a new solution is generated by Eq. (9) instead of that solution. 2. Lot sizing: In terms of the lot sizing problem, each solution X i ={x i1,x i2,,x id } represents the time periods for order decisions. If any position of X i is equal to 1, the order is given for the corresponding period. The objective function of lot sizing is defined by Eq. (3). We provide the following example to show how the fitness value of a solution is evaluated in the uncapacited lot sizing problem. Assume that X i = {1,0,0,1,1,0,0}, R = {100,40,50,60,70,30,50}, setup cost (K) is set to 100 and hosting cost is set to 1. For the first period, the order quantity (O i1 ) is set to 190 which is equal to the sum of net requirements (R i1, R i2, R i3 ), since no order decision is made for the second and third periods. Then, the setup cost (Kx i1 ) is 100 and the remaining number of orders is 100. For the second period, the remaining number of orders is 40 and the holding cost for the requirements is 60. For the third period, there is no remaining order, and the holding cost for the requirements is 100 (50 x 2) since two periods were passed. For the fourth period, the order quantity (O i4 ) is set to 60, and so the setup cost is 100. For the fifth period, the order quantity (O i5 ) is set to 150, and so the setup cost (Kx i5 ) is 100, and the number of remaining orders are 80. For the sixth period, the remaining number of orders is 50 and the holding cost for the requirements is 30. For the final period, the holding cost for the requirements is (50x2) 100. Then, the fitness value of X i is calculated as 570. To clearly illustrate the example, please see Fig Total R id x id

151 E HANÇER Academic Platform Journal of Engineering and Science 6-2, , 2018 O id I id Kx i I id h Sum (Kx i + I id h) Fig. 2 An illustrative example for uncapacited lot sizing. 4 EXPERIMENTAL DESIGN 4.1 Algorithms Used For Comparisons In this section, the binary evolutionary algorithms used for comparisons are presented as follows: 1. Binary particle swarm optimization (BPSO) [32]: In BPSO, each velocity is first updated by Eq. (13) as in standard PSO. For each position of velocities, a value in the range of [0,1] is generated using a sigmoid function by Eq. (14). Then, new positions of particles are determined by Eq. (15). Although it is simple to implement, it has local stagnation problems. t+ 1 t t t t t V = wv + c r pbest x ) + c r ( gbest x ) (13) ij ij 1 1( ij ij sig( v) = (14) 1 v + e 0 rand(0,1) sig( vi, j ( t + 1)) xi, j ( t + 1) = (15) 1 rand(0,1) < sig( vi, j ( t + 1)) where w is a inertia weight; c 1 and c 2 are balance factors between global best and local best positions; pbest is the jth position of the ith local best particle at iteration t; gbest is the jth position of global best particle at iteration t j t; r 1 and r 2 are random numbers in the range of [0,1]; x ij is the jth position of the ith particle; and rand(0,1) is a uniformly generated number between [0,1]. 2. XOR based particle swarm optimization (XOR-PSO) [33]: In XOR-PSO, the positions of velocities and particles are updated using logic operators by Eqs. (16) and (17): t 1 t t t t V + = w pbest x ) + w ( gbest x ) (16) ij X t +1 ij 1 = X ( j ij 2 t ij V t ij j j ij ij (17) where + denotes OR operator; denotes AND operator; denotes XOR operator; and r 1 and r 2 are uniformly generated numbers between 0 and XOR based Artificial Bee Colony (XOR-ABC) [4]: Inspired by XOR-PSO, the neighbor search mechanism of standard ABC is modified using XOR logical operator by Eq. (18): t ij v i, j i, j [ i, j k, j = x γ ( x x )], i k (18) where j is the randomly selected position; represents XOR operator; and γ is a uniformly generated number between 0 and 1, which behaves like a probabilistic logic gate. If γ is smaller than 0.5, the logic gate is invoked, i.e., the value of x ij x kj will be inverted. Otherwise, the result will not be inverted. 4. Discrete Artificial Bee Colony (DisABC) [3]: DisABC uses Jaccard Coefficient to measure the similarity between binary vectors. Let, X i ={x i1,x i2,,x id } and X k ={x k1,x k2,,x kd } are two binary vectors. The similarity between them is evaluated by Eq. (19), and the dissimilarity between them is then evaluated by Eq. (20). After the evaluation of dissimilarities, new solution generator mechanism is applied to find a better solution. (19) where M 11 is the number of bits where both vector positions are equal to 1; M 10 is the number of bits where the positions of X i and X k are equal to 1 and 0, respectively; M 01 is the number of bits where the positions of X i and X k are equal to 0 and 1, respectively. (20) 5. Angle Modulated Artificial Bee Colony (AMABC) [5]: In contrast to typical binary evolutionary algorithms, AMABC searches in the four-dimensional continuous solution space, where each solution X i is represented by (a i, b i, c i, d i ), a, b, c, d ϵ [-1,1]. To evolve solutions, the standard ABC framework is carried out. To evaluate the fitness value of a solution, that solution is mapped from the four-dimensional continuous space to the D-dimensional binary space through function g(x), defined by Eq. (21): (21) where a determines the amplitude of function g; b determines the frequency or period of sinus function in g; c controls the frequency or period of cosin function in g; and d controls the vertical shift. How the mapping process is carried out is described as follows. First, the values of (a i, b i, c i, d i ) are substituted into g(x). Then, a D-dimensional continuous vector is generated by sampling g(x) for the predefined range of x (e.g. x = {0, 0.1, 0.2,, D 0.1}). Using this continuous vector, the D- dimensional binary solution (bitstring) is then determined by Eq. (22): 146 5

152 E HANÇER Academic Platform Journal of Engineering and Science 6-2, , 2018 bitstring ij 1 = 0 vector ij 0 otherwise (22) where vector i is a continuous vector generated by sampling g(x) for the ith solution. 6. Genetic Algorithm (GA) [34]: GA belongs to the subclass of evolutionary algorithms of evolutionary computation techniques. GA has three fundamental operators: 1) selection: a number of solutions from the population are selected during each generation. Fitter solutions tend to be selected since fitness-based selection strategy is applied; 2) crossover: a number of new solutions to form new generation are produced using the selected individuals; and 3) mutation is applied to the new generation obtained by selection and mutation to ensure diversity within the population. We should notify that the dissimilarity between any pairs of solutions in DisABC cannot be properly measured in a lot sizing problem set, since the first position of a solution should be assigned as 1 to evaluate the fitness. Thus, DisABC is not used in the experiments of the lot sizing problem. 4.2 Problem used for comparisons To investigate the performance of the evolutionary algorithms on the knapsack problem, six benchmark problem sets (referred as K-Set ) [35] comprising of a wide range of items from 40 to 750 and capacities from 400 to are selected, the details of which can be found in Table 1. Table 1 Knapsack problem sets used in experiments. Set 1 Set 2 Set 3 Set 4 Set 5 Set 6 # Orders Capacity To investigate the performance of the evolutionary algorithms on the lot sizing problem, five problem sets are uniformly generated, where the values of requirements are in the range of 50 and 500, and the total number of periods are 250. For the capacited form of lot sizing, the capacity (Cap) is set to 1300 in all problems. 4.3 Parameter Settings In the experiments of knapsack, the following parameter values are used: the population size is chosen as 30 and the maximum number of cycles is set to 100 for all algorithms; the limit value of all ABC variants is chosen as 50; ϕ max and ϕ min values of DisABC are selected 0.9 and 0.5 as in [3]; the parameters of BPSO are selected as in [36]: c 1 = 2, c 2 = 2, w start = 0.9, w end = 0.4, V max = 6; the crossover rate and mutation rate of GA are set to 0.8 and 0.2. In the experiments of lot sizing, the following parameter values are used: the population size is chosen as 50 and the maximum number of cycles is set to 1500 for all algorithms; the limit value of all ABC variants is chosen as 50 as in the experiments of knapsack; and the parameter values of BPSO and GA are selected as in the experiments of knapsack. 5 EXPERIMENTAL RESULTS The results are presented in Table 2, 3 and 4 over the 30 independent runs in terms of best, worst, mean and standard deviation ( std ). In Tables, T shows the results of the Wilcoxon Rank Sum Test at 95% of confidence, where + or - denotes that ABC-LO performs significantly better or worse than the corresponding algorithm, and = denotes that the results of ABC-LO and the corresponding algorithm is similar to each other, i.e., there exists no such a significant difference between them. The experimental study is considered in three subsections: 1) comparisons on knapsack problem sets, 2) comparisons on uncapacited lot sizing problem sets and 3) comparisons on capacited lot sizing problem sets. 5.1 Results of Knapsack Presenting the results of binary variants on knapsack problem sets, Table 2 shows that ABC-LO performs significantly better than other algorithms in terms of best, mean and worst values in all cases. It can be also observed from Table 2 that the performance of XOR-ABC and XOR- PSO mimicking logical operations is low compared to ABC- LO in terms of loading the knapsack with valuable items. For instance, the item subsets for knapsacks selected by ABC-LO from all available items are at least 11% more valuable than XOR-ABC, and in some problem sets, that rate is increased from 11% to 20%. It can therefore be inferred that ABC-LO is the most well-designed algorithm using the principles of Boolean logic for knapsack problem sets.considering the binary ABC variants except for ABC- LO, DisABC and XOR-ABC generally obtain similar item subsets in terms of the total value. On the other hand, AMABC performs better than DisABC and XOR-ABC almost in all cases. However, the performance of AMABC cannot be treated as successful in terms of loading the knapsack with fitter items, when compared to the proposed ABC-LO algorithm. Considering the performance of binary PSO variants, XOR-PSO performs better than BPSO in all problem sets except for the first one. Compared to the others except for ABC-LO, GA achieves successful results, thereby getting the second position after ABC-LO among all binary variants. It can therefore be concluded that ABC-LO achieves significantly better results not only than the logically inspired binary variants, but also the other binary variants based on a variety of principles

153 E HANÇER Academic Platform Journal of Engineering and Science 6-2, , Results of Uncapacited Lot Sizing Presenting the results of binary variants on uncapacited lot sizing problem sets, Table 3 shows that ABC-LO reduces the order cost significantly better than others almost in all cases. Considering other algorithms, binary PSO variants, especially BPSO, cannot successfully minimize the order cost, i.e., the order cost obtained by PSO variants are very intensive compared to the others. For instance, BPSO and XOR-PSO subsequently obtain and in terms of the average total cost for the first problem, while the others obtain between and Such gap between binary PSO variants and the others can be also illustrated in other problem sets. Accordingly, it can be indicated that binary PSO variants are not suitable for uncapacited lot sizing problem sets. Furthermore, XOR- ABC and GA generally achieve similar order costs, but performs better than AMABC in all cases. Accordingly, XOR-ABC and GA gets the second position after ABC-LO in terms of minimizing the order cost. It can therefore be stated that ABC-LO is also the most well-designed algorithm mimicking the principles of Boolean algebra for uncapacited lot sizing problem sets. BPSO XOR-PSO GA DisABC AMABC XOR- ABC ABC-LO Table 2 Results of knapsack problem sets. Set 1 Set 2 Set 3 Set 4 Set 5 Set 6 Best Mean Std Worst T Best Mean Std Worst T Best Mean Std Worst T = = + Best Mean Std Worst T Best Mean Std Worst T Best Mean Std Worst T Best Mean Std Worst

154 E HANÇER Academic Platform Journal of Engineering and Science 6-2, , 2018 BPSO XOR-PSO GA AMABC XOR- ABC ABC-LO Table 3 Results of uncapacited lot sizing problem sets. L-Set 1 L-Set 2 L-Set 3 L-Set 4 L-Set 5 Best Mean Std Worst T Best Mean Std Worst T Best Mean Std Worst T + + = + + Best Mean Std Worst T Best Mean Std Worst T + + = + + Best Mean Std Worst Results of Capacited Lot Sizing Presenting the results of binary variants on lot sizing problem sets in terms of the capacited form, Table 4 shows that ABC-LO also performs significantly better than other binary variants in all cases. Further, the cost difference between ABC-LO and others in the capacited form becomes wider than the uncapacited form (see Table 3). For instance, the gap between ABC-LO and XOR-ABC, both of which are based on logic operators, is increased nearly from 121 to 170 for the first problem set. Such a gap can be also illustrated on different problem sets. Considering other algorithms, binary PSO variants cannot also perform well in reducing the order cost in all cases as in the uncapacited form. Furthermore, XOR-ABC and GA reduces the order cost better than AMABC, but XOR-ABC performs better than GA. Therefore, it can be concluded without no doubt that ABC- LO can better search the possible solution space yielding lower order cost not only in uncapacited form, but also in capacited form

155 E HANÇER Academic Platform Journal of Engineering and Science 6-2, , 2018 BPSO XOR-PSO GA AMABC XOR- ABC ABC-LO Table 4 Results of capacited lot sizing problem sets. L-Set 1 L-Set 2 L-Set 3 L-Set 4 L-Set 5 Best Mean Std Worst T Best Mean Std Worst T Best Mean Std Worst T Best Mean Std Worst T Best Mean Std Worst T Best Mean Std Worst CONCLUSIONS The overall goal of this paper is to develop an ABC variant mimicking the principles of Boolean logic for the knapsack and lot sizing problems. This goal has been achieved by embedding a new locally inspired search mechanism into ABC. To verify the effectiveness of the proposed algorithm, it was compared and examined on knapsack and lot sizing problem sets with a number of recent binary variants which are XOR- ABC, AMABC, DisABC, XOR-PSO, BPSO and GA. The results showed that ABC-LO outperformed the others in terms of all the considered problems. Accordingly, it can be inferred that ABC-LO is much better designed algorithm using the principles of Boolean logic than XOR-ABC and XOR-PSO. To our knowledge, it is the first time in the literature an evolutionary algorithm has been applied to different types of industrial problems in a study. In the future, it will be interesting if the proposed algorithm is hybridized using the principles of quantum computing, which has been recently applied to develop new evolutionary algorithms. REFERENCES [1] Karaboga, D., Basturk, B A powerful and efficient algorithm for numerical function optimization: artificial bee colony (ABC) algorithm. Journal of Global Optimization, 39 (3), [2] Das, S., Biswas, S., Kundu S Synergizing fitness learning with proximity-based food source selection in artificial bee colony algorithm for numerical optimization. Applied Soft Computing, 13 (12), [3] Kashan, M. H., Nahavandi, N., Kashan, A. H DisABC: A new artificial bee colony algorithm for binary optimization. Applied Soft Computing, 12 (1), [4] Kiran M. S., Gunduz M XOR-based artificial bee colony algorithm for binary optimization. Turkish Journal of 150

156 E HANÇER Academic Platform Journal of Engineering and Science 6-2, , 2018 Electrical Engineering & Computer Sciences, 21 (Sup.2), [5] Pampara, G., Engelbrecht, A. P Binary artificial bee colony optimization IEEE Symposium on Swarm Intelligence (SIS), April, Paris, 1-8 [6] Ozturk, C., Hancer, E., Karaboga, D Dynamic Clustering with Improved Binary Artificial Bee Colony Algorithm, Applied Soft Computing, 28, [7] Ozturk, C., Hancer, E., Karaboga, D A Novel Binary Artificial Bee Colony Algorithm Based on Genetic Operators, 297, [8] Hancer, E., Xue B., Karaboga, D., Zhang, M A binary ABC algorithm based on advanced similarity scheme for feature selection, Applied Soft Computing, 36, [9] Andonov, R., Poirriez, V., Rajopadhye, S Unbounded knapsack problem: Dynamic programming revisited. European Journal of Operational Research, 123 (2), [10] Martello, S., Toth, P Knapsack problems: algorithms and computer implementations. John Wiley & Sons, Inc. New York, NY, USA. [11] Martello, S., Toth, P Dynamic programming and strong bounds for the 0-1 knapsack problem. Management Science, 45 (3), [12] Martello, S., Toth, P A mixture of dynamic programming and branch-and-bound for the subset-sum problem. Management Science, 30 (6), [13] Singh, R. P Solving 0-1 Knapsack problem using Genetic Algorithms, 3rd IEEE International Conference on Communication Software and Networks (ICCSN), May, Xi an, [14] Chu, P. C., Beasley, J. E A Genetic Algorithm for the Multidimensional Knapsack Problem. Journal of Heuristics, 4 (1), [15] AbdulHalim, M.F., Attea, B.A., Hameed, S.M A binary Particle Swarm Optimization for attacking knapsacks Cipher Algorithm. International Conference on Computer and Communication Engineering (ICCCE), May, Kuala Lumpur, [16] Fangguo, H An Improved Particle Swarm Optimization for Knapsack Problem. International Conference on Computational Intelligence and Software Engineering (CISE), December, Wuhan, 1-4. [17] Changshou, D., Bingyan, Z., Yanling, Y., Anyuan, D Modified Dynamic Differential Evolution for 0-1 Knapsack Problems. International Conference on Computational Intelligence and Software Engineering (CISE), December, Wuhan, 1-4. [18] Jun, S., Jian, L Solving 0-1 Knapsack Problems via a Hybrid Differential Evolution. Third International Symposium on Intelligent Information Technology Application (IITA), November, Nanchang, [19] Pulikanti, S., Singh, A An Artificial Bee Colony Algorithm for the Quadratic Knapsack Problem. 16th International Conference on Neural Information Processing (ICONIP), December 1-5, Bangkok, [20] Sabet, S., Farokhi, F., Shokouhifar, M A novel artificial bee colony algorithm for the knapsack problem. International Symposium on Innovations in Intelligent Systems and Applications (INISTA), 2-4 July, Trabzon, 1-5. [21] Wagner, H. M., Whitin, T. M Dynamic Version of the Economic Lot Size Model, Management Science, 50 (12), [22] Tasgetiren, M. F., Liang, Y-C A Binary Particle Swarm Optimization Algorithm for Lot Sizing Problem. Journal of Economic and Social Research, 5 (2), [23] Deorussi, L., Lemoine, D Discrete Particle Swarm Optimization for the Multi-Level Lot-Sizing Problem. Trends in Developing Metaheuristics, Algorithms, and Optimization Approaches, IGI Publishing Hershey, PA, USA. [24] Brahimi, N., Dauzere-Peres, S., Najid, N. M., Nordli, A Single item lot sizing problems. European Journal of Operational Research, 168 (1), [25] Van den Heuvel, W The Economic Lot-Sizing Problem: New Results and Extensions. Erasmus School of Economics (ESE), Erasmus University of Rotterdam, PhD Thesis. [26] Dorigo, M., Stutzle T Ant Colony Optimization. Bradford Company Scituate, MA, USA. [27] Kennedy, J., Eberhart, R Particle swarm optimization, IEEE International Conference on Neural Networks, [28] Das, S., Biswas, A., Dasgupta, S., Abraham, A Bacterial Foraging Optimization Algorithm: Theoretical Foundations, Analysis, and Applications pp Abraham, A., Hassanien, A.-E., Siarry, P., Engelbrecht, A., ed Foundations of Computational Intelligence, Springer Berlin Heidelberg. [29] Akay, B., Karaboga, D A modified Artificial Bee Colony algorithm for real-parameter optimization. Information Sciences, 192, [30] Hancer, E., Karaboga, D A comprehensive survey of traditional, merge-split and evolutionary approaches proposed for determination of cluster number. Swarm and Evolutionary Computation, 32, [31] Hancer, E., Ozturk, C., Karaboga, D Artificial Bee Colony Based Image Clustering Method. IEEE Congress on Evolutionary Computation (CEC), June, Brisbane, 1-5. [32] Kennedy, J., Eberhart, R. C A discrete binary version of the particle swarm algorithm. IEEE International Conference on Computational Cybernetics and Simulation, October, Orlando, [33] Yuan, X., Nie, H., Su, A., Wang, L., Yuan, Y An improved binary particle swarm optimization for unit commitment problem. Expert Systems with Applications, 36 (4),

157 E HANÇER Academic Platform Journal of Engineering and Science 6-2, , 2018 [34] Holland, J Genetic algorithms. Scholarpedia, 7, [35] Zitzler, E., Laumans, M Test Problems and Test Data for Multiobjective Optimizers. (Access Date: 05/05/2016). [36] Mirjalili S., Lewis, A S-shaped versus V-shaped transfer functions for binary Particle Swarm Optimization. Swarm and Evolutionary Computation, 9,

158 Academic Platform Journal of Engineering and Science 6-2, , 2018 Academic Platform Journal of Engineering and Science journal homepage: Uleksitin Amonyum Sülfat Çözeltilerindeki Çözünürlüğüne Dehidrasyon İşleminin Etkisi * 1 Nizamettin DEMİRKIRAN( ), 2 Mehmet Kayra TANAYDIN( ), 1 G.Deniz TURHAN ÖZDEMİR( ) 1 İnönü Üniversitesi Mühendislik Fakültesi Kimya Mühendisliği Bölümü, 44280, Malatya 2 Munzur Üniversitesi Mühendislik Fakültesi Kimya Mühendisliği Bölümü, 62000, Tunceli Geliş Tarihi: Kabul Tarihi: Öz Uleksit ticari olarak önemli bor minerallerinden birisi olup Türkiye de bol miktarda bulunmaktadır. Uleksit genellikle diğer boratlarla birlikte bulunur ve bor bileşikleri üretiminde ham madde olarak kullanılabilir. Önemli miktarda hidratasyon suyu içeren uleksit, dehidrasyon işlemine maruz bırakıldığı zaman uygulanan sıcaklığa bağlı olarak bu suyun bir kısmını kaybeder. Dehidrasyon işlemi sonucunda kimyasal olarak daha aktif olan gözenekli bir katı elde edilir. Oluşan gözenekli yapı katı ile akışkan arasındaki reaksiyonun daha kolaylıkla meydana gelmesine olanak sağlar ve çözünme hızı artar. Bu çalışmada, kalsine edilmiş uleksitin amonyum sülfat çözeltilerindeki çözünme kinetiği incelenmiştir. Deneylerde uleksitin çözünmesi üzerine dehidrasyon sıcaklığı, çözelti derişimi, reaksiyon sıcaklığı, katı/sıvı oranı ve karıştırma hızının etkileri araştırılmıştır. Çözelti derişimi ve sıcaklığın artması, katı/sıvı oranının ise azalmasıyla reaksiyon hızının arttığı gözlenmiştir. En yüksek çözünme hızı 150 C de kalsine edilmiş örneklerden elde edilmiştir. Çözünme kinetiğinin yalancı birinci mertebe kinetik modele uyduğu belirlenmiştir. Çözünme prosesi için aktivasyon enerjisinin değeri 42 kj/mol olarak hesaplanmıştır. Anahtar Kelimeler: Uleksit, Kalsinasyon, Çözünme kinetiği. Effect of Dehydration Treatment on Dissolution of Ulexite in Ammonium Sulfate Solutions * 1 Nizamettin DEMİRKIRAN, 2 Mehmet Kayra TANAYDIN, 1 G.Deniz TURHAN ÖZDEMİR 1 İnönü University, Faculty of Engineering, Department of Chemical Engineering, 44280, Malatya 2 Munzur University, Faculty of Engineering, Department of Chemical Engineering, 62000, Tunceli Abstract Ulexite is commercially one of important boron minerals, and it is found abundantly in Turkey. Ulexite is generally available together with other borates, and it can be used as a raw material in the production of boron compounds. It includes a significant amount of hydration water. When ulexite is subjected a dehydration process, it loses some part of hydrate water depending upon applied temperature. A porous solid is obtained in consequence of dehydration treatment, and the solid material becomes more chemically active. The resulting porous structure allows occurring more readily the reaction between solid and fluid, and the dissolution rate increases. In this study, the dissolution kinetics of calcined ulexite in ammonium sulfate solutions was examined. In the experiments, the effects of the dehydration temperature, solution concentration, reaction temperature, solid-to-liquid ratio, and stirring speed on *Sorumlu Yazar: 1 İnönü Üniversitesi Mühendislik Fakültesi Kimya Mühendisliği Bölümü, 44280, Malatya,. Tel: Doi: /apjes

159 N DEMİRKIRAN Academic Platform Journal of Engineering and Science 6-2, , 2018 dissolution of ulexite were investigated. It was observed that the reaction rate increased with increasing solution concentration and reaction temperature, and with decreasing solid-to-liquid ratio. The highest dissolution rate was obtained with the sample calcined at 150 C. It was determined that the dissolution kinetics fit to the first order pseudo-homogeneous kinetic model. The activation energy of the dissolution process was calculated to be 42 kj/mol. Keywords: Ulexite, Calcination, Dissolution kinetics 1. GİRİŞ Teknolojinin hızlı gelişmesine bağlı olarak başta borik asit olmak üzere çeşitli bileşikleri halinde geniş bir kullanım alanına sahip olan bor, doğada genellikle alkali ve toprak alkali metal boratları halinde bulunur. Bor mineralleri içerdikleri B 2 O 3 yüzdesine göre değer kazanırlar ve yapılarında genellikle kristal suyu barındırırlar. Endüstriyel ve ekonomik sebeplerden dolayı yapılarında kristal suyu bulunduran bor minerallerine bir ısıl işlem uygulandığı zaman sıcaklığa ve zamana bağlı olarak bu suyun bir kısmını veya tamamını verirler. Bu işlem dehidrasyon veya kalsinasyon olarak bilinir. Kalsinasyon işleminin uygulanmasıyla mineralin içermiş olduğu su miktarı azaltılabilir veya tamamen uzaklaştırılabilir. Bunun sonucunda konsantre cevher elde edilerek B 2 O 3 tenörü yükseltilmiş ve cevherin fiyatının artması sağlanmış olur. Dehidrasyon prosesinin uygulanması sırasında oluşan su buharının yapıyı terk etmesiyle çok sayıda mikro çatlaklar meydana gelir ve gözenekli bir katı elde edilmiş olur. Gözenekli bir yapının oluşması neticesinde mineral kimyasal olarak daha aktif hale gelir. Kalsine edilmiş mineral liç işlemine tabi tutulduğu zaman çözücü ile gözenekli katı arasındaki reaksiyon kolaylaşır ve borik asidin katı fazdan çözelti ortamına ekstraksiyon hızı arttırılmış olur [1-4]. sonucunda daha gözenekli bir katı elde edilirken bu sıcaklıktan sonra amorflaşmanın hızlanmasıyla sert ve tamamen amorf yapıda bir katı oluşmaktadır [4-8]. Dehidrasyon işlemine tabi tutulmuş veya kalsine edilmiş uleksitin sülfürik asit [9], amonyum klorür [10], etilen diamin tetra asetik asit [11], okzalik asit [12], amonyum karbonat [13], amonyum nitrat [14] ve amonyum asetatın [15] sulu çözeltilerinde çözünme kinetiği incelenmiştir. Bu çalışmalarda, farklı sıcaklıklarda kalsine edilmiş uleksitin çözünürlükleri belirlenmiş ve genellikle C arasındaki sıcaklıklarda kalsine edilmiş katılardan en yüksek çözünürlük değerlerinin elde edildiği tespit edilmiştir. Daha yüksek kalsinasyon sıcaklıklarında hazırlanan uleksit örnekleri ile yapılan deneylerde ise çözünürlüğün azaldığı belirlenmiş ve bu azalma sinterlenme olayına bağlanmıştır. Önceki çalışmada kalsinasyon işlemine tabi tutulmamış uleksit örneklerinin amonyum sülfat çözeltilerindeki çözünme kinetiği incelenmiştir [16]. Bu çalışmada, farklı sıcaklıklarda kalsine edilmiş uleksit örneklerinin amonyum sülfat çözeltilerindeki çözünme kinetiği araştırılmıştır. Kalsinasyon sıcaklığı, çözelti derişimi, reaksiyon sıcaklığı, katı/sıvı oranı ve karıştırma hızının kalsine uleksitin çözünmesi üzerine olan etkileri belirlenmiştir. Kimyasal formülü Na 2 O.2CaO.5B 2 O 3.16H 2 O olan uleksit ekonomik değere sahip önemli bor minerallerinden birisi olup genellikle diğer boratlarla birlikte bulunur ve borik asit üretiminde kullanılabilir. Uleksitin dehidrasyonu farklı araştırmacılar tarafından incelenmiştir. Deney şartlarına bağlı olarak uleksitin dehidrasyonunun C arasındaki sıcaklıklarda başladığı ve C sıcaklıklara kadar dehidrasyonun oldukça hızlı olduğu, bu sıcaklıklardan daha yüksek sıcaklıklarda C ye kadar reaksiyonun yavaş bir şekilde ilerlediği ve daha yüksek sıcaklıklarda ise hemen hemen hiç ağırlık kaybının olmadığı araştırmacılar tarafından ifade edilmiştir. Termal dekompozisyon sırasında dehidrasyon ve dehidroksilasyon olmak üzere iki tür reaksiyonun gerçekleştiği, uygulanan sıcaklığa ve zamana bağlı olarak cevherin yapısında bazı değişikliklerin de meydana geldiği belirtilmiştir. Dehidrasyonla yapıya bağlı bulunan kristalizasyon suyu uzaklaşırken dehidroksilasyonla hidroksil birleşmesi sonucunda oluşan su molekülleri uzaklaşmaktadır. 240 C nin altındaki sıcaklıklarda yapılan dehidrasyon işlemi 2. MATERYAL VE METOT Çalışmada kullanılan uleksit minerali Eskişehir, Kırka dan temin edilmiştir. Mineral kırılıp öğütüldükten sonra farklı parçacık boyutlarına sahip örnekler elde etmek için elenmiştir. Mineralin kimyasal analizi sonucunda % B 2 O 3, % CaO, % 7.95 Na 2 O, % H 2 O ve % 0.17 çözünmeyen kısımdan ibaret olduğu tespit edilmiştir. Uleksit mineralinin XRD analiz sonucu Şekil 1 de ve SEM görüntüsü ise Şekil 2 de gösterilmiştir. Uleksitin izotermal dehidrasyonu mm ortalama parçacık boyutuna sahip örnekler kullanılarak C sıcaklık aralığında bir etüvde yapılmıştır. Mineralden 1 g alınarak porselen krozelere konulmuş ve 180 dk süresince farklı sıcaklıklarda kalsinasyon işlemi gerçekleştirilmiştir. Dehidrasyon işleminden sonra krozeler etüvden çıkarılıp bir desikatöre konulmuş ve sabit tartıma getirilmiştir. Kalsine edilmiş örneğin kütlesinden başlangıçtaki kütle çıkarılarak mineralden uzaklaşan su miktarı Eşitlik 1 deki denklemle hesaplanmıştır. % KKütttttt kkkkkkkkkk = mm 0 mm mm (1) Bu bağıntıdaki m o dehidrasyon işleminden önce uleksitin kütlesini (g), m ise dehidrasyon işleminden sonra kalsine uleksitin kütlesini (g) göstermektedir. Kalsine edilmiş örneklerin B 2 O 3 içerikleri uzaklaşan su kütlesi dikkate alınarak teorik olarak hesaplanmıştır. 154

160 N DEMİRKIRAN Academic Platform Journal of Engineering and Science 6-2, , 2018 Şekil 1. Kalsine edilmemiş uleksit örneğine ait XRD difraktogramı. Kalsine uleksitin çözünürlüğünün incelendiği deneyler 500 ml hacimli ceketli bir cam reaksiyon kabında yapılmıştır. Çözünme reaksiyonları sırasında sıcaklığı sabit tutmak için sirkülatörlü su banyosundan yararlanılmış ve reaktör içeriği bir mekanik karıştırıcı ile karıştırılmıştır. Derişimi bilinen 200 ml amonyum sülfat çözeltisi cam reaktöre konulduktan sonra bu çözelti reaksiyon sıcaklığına ulaşıncaya kadar ısıtılmıştır. Çalışılacak sıcaklığa ulaşıldıktan sonra belirli miktarda kalsine uleksit örneği reaktöre ilave edilmiş ve reaktör içeriği karıştırılmıştır. Farklı zamanlarda reaktörden çözelti örnekleri alınmak suretiyle kalsine uleksitten çözünerek çözelti ortamına geçmiş olan B 2 O 3 miktarı belirlenmiştir. B 2 O 3 tayini analizi yapılacak çözeltiye mannitol ilave edildikten sonra sodyum hidroksit çözeltisi kullanılarak titrimetrik yöntemle yapılmıştır [17]. Kalsine uleksitin çözünme kesri Eşitlik 2 kullanılarak hesaplanmıştır. XX BB2 OO 3 = Çözzzzzzzzzzzzzzzzzz BB 2 OO 3 mmmmmmmmmmmmmm KKKKKKKKKKKKKK eeeeeeeeeeeeş uuuuuuuuuuuuuuuuuuuuuu BB 2 OO 3 mmmmmmmmmmmmmm (2) Şekil 2. Kalsine edilmemiş uleksit örneğine ait SEM görüntüsü. 155

161 N DEMİRKIRAN Academic Platform Journal of Engineering and Science 6-2, , BULGULAR ve TARTIŞMA Uleksitin dehidrasyon reaksiyonu Eşitlik 3 teki gibi yazılabilir. Na 2 O.2CaO.5B 2 O 3.16H 2 O(k) Na 2 O.2CaO.5B 2 O 3.nH 2 O(k) + (16-n)H 2 O(g) (3) Burada n dehidrasyon işleminden sonra katıda kalan suyun mol sayısıdır. Dehidrasyon sıcaklığındaki artışla birlikte mineralden uzaklaşan su miktarında da bir artma meydan gelir. Katıdaki su miktarı azaldıkça kalsine edilmiş olan mineral örneğinin birim kütlesindeki B 2 O 3 miktarında ise bir artma söz konusu olur. 180 dk kalsinasyon süresinden sonra 100 ve 250 C lerde kalsine edilmiş uleksitin su içeriğinin sırasıyla %7.52 ve %30.42 azaldığı belirlenmiştir. Bu kütle kaybı sebebiyle 100 ve 250 C lerde kalsine edilmiş örneklerin birim kütlesinde B 2 O 3 içeriği ise sırasıyla %46.46 ve %61.75 olarak hesaplanmıştır. Amonyum sülfat çözeltisine kalsine uleksit ilave edildiği zaman meydana gelebilecek toplam çözünme reaksiyonu Eşitlik (4) deki gibi yazılabilir. Na 2 O.2CaO.5B 2 O 3.nH 2 O(k) + 3(NH 4 ) 2 SO 4 (aq) + (12-n)H 2 O(s) Na 2 SO 4 (aq) + 2CaSO 4 (k) + 6NH 3 (aq) + 10H 3 BO 3 (aq) (4) 3.1. Çözünme Üzerine Kalsinasyon Sıcaklığının Etkisi Uleksit mineralinin amonyum sülfat çözeltilerinde çözünmesi üzerine dehidrasyon işleminin etkisini görmek için 100, 120, 140, 150, 160, 180, 200 ve 250 C sıcaklıklarda kalsine edilmiş uleksit örnekleri kullanılarak deneyler yapılmıştır. Bu deneylerde çözelti derişimi, karıştırma hızı, katı/sıvı oranı ve reaksiyon sıcaklığı sırasıyla 1 mol/l, 400 rpm, 2/200 g/ml ve 30 C değerlerinde alınmıştır. Şekil 3 te 20 dk deney süresi sonunda elde edilen çözünme değerleri verilmiştir. 150 C ye kadar olan sıcaklıklarda kalsine edilmiş örneklerle yapılan deneylerde uleksitin çözünme kesrinin arttığı, en yüksek çözünme değerlerine 150 C de kalsine edilmiş örneklerde ulaşıldığı ve bu sıcaklıktan daha yüksek sıcaklıklarda kalsine edilmiş örneklerin ise çözünürlüğünün azaldığı gözlenmiştir. 150 C de kalsine edilmiş uleksitteki B 2 O 3 ün %99 unun çözünerek çözeltiye geçtiği tespit edilmiştir. Aynı deney şartları ve deney süresi için kalsine edilmemiş örnekle yapılan deneyde ise %35 lik bir çözünme değeri elde edilmiştir. Şekil 3. Kalsine edilmiş uleksitin çözünmesine kalsinasyon sıcaklığının etkisi. Yukarıda da ifade edildiği gibi dehidrasyon işlemi ile uygulanan sıcaklığa bağlı olarak katıdaki kristal suyunun bir kısmı uzaklaşır ve gözenekli bir yapı oluşur. Şekil 4 te 150 C de kalsine edilmiş uleksite ait SEM görüntüsü verilmiştir. Şekil 2 de verilmiş olan kalsine edilmemiş uleksit örneğine ait SEM görüntüsü ile Şekil 4 te verilmiş olan kalsine edilmiş örneğe ait SEM görüntüsü mukayese edildiği zaman, dehidrasyon işlemine tabi tutulan örnekte çatlaklar gözlenmektedir. Kalsine edilmiş katı çözünme işlemine tabi tutulduğu zaman çözücü reaktif bu çatlak veya boşluklardan katı iç kısımlarına doğru daha kolay bir şekilde nüfuz edebilir ve çözünme hızında bir artış söz konusu olabilir. 156

162 N DEMİRKIRAN Academic Platform Journal of Engineering and Science 6-2, , 2018 Şekil C de kalsine edilmiş uleksit örneğine ait SEM görüntüsü. Dehidrasyon sıcaklığının daha fazla arttırılması sinterlenmeye sebep olabilir ve bunun sonucunda oluşan çatlak veya boşluklar kısmen tıkanabilir. Bu durum katıda gözeneklerin azalmasına sebep olacağından akışkan çözücünün katı içine doğru difüzlenmesi zorlaşabilir ve neticede kalsine edilmiş katının çözünme hızı azalabilir. 200 C de kalsine edilmiş örneğe ait SEM görüntüsü Şekil 5 te gösterilmiştir. Şekil 5 te sinterleşmeden dolayı gözeneklerin kısmen tıkanmış olduğu gözlenmektedir. Şekil C de kalsine edilmiş uleksit örneğine ait SEM görüntüsü. Elde edilen bulgulara göre dehidrasyon işleminin uleksit mineralinin çözünmesi üzerinde önemli bir etkisinin olduğu söylenebilir. Daha yüksek çözünme değerleri 150 C de kalsine edilmiş örnekten elde edildiğinden diğer parametrelerin çözünme hızı üzerindeki etkisi incelenirken bu sıcaklıkta kalsine edilmiş uleksit örnekleri kullanılmıştır Çözünme Üzerine Çözelti Derişiminin Etkisi Kalsine uleksitin amonyum sülfat çözeltilerinde çözünme hızı üzerine çözelti derişiminin etkisi 0.10, 0.25, 0.50 ve 1.00 mol/l derişim değerlerinde incelenmiştir. Deneylerde katı/sıvı oranı 2/200 g/ml, karıştırma hızı 400 rpm ve reaksiyon sıcaklığı 30 C olarak alınmıştır. Şekil 6 bu deneylere ait sonuçları göstermektedir. Bu şekilden 157

163 N DEMİRKIRAN Academic Platform Journal of Engineering and Science 6-2, , 2018 görüleceği gibi çözelti derişimi arttıkça kalsine edilmiş uleksitin çözünme kesri de artmaktadır. Amonyum sülfat sulu ortamda iyonlaştığı zaman açığa çıkan amonyum iyonları (NH 4 + ) hidroliz reaksiyonuyla hidronyum (H 3 O + ) iyonlarını oluşturur. Bazik karaktere sahip olan uleksit mineralinin çözünmesinde esas olarak hidronyum iyonları rol alır. Amonyum sülfat derişimi arttıkça oluşan hidronyum derişimi de artacağından kalsine uleksitin çözünme hızı artmış olur. Şekil 6. Kalsine edilmiş uleksitin çözünmesine çözelti derişiminin etkisi Çözünme Üzerine Karıştırma Hızının Etkisi Karıştırma hızının kalsine uleksitin çözünmesi üzerine olan etkisi rpm aralığında farklı karıştırma hızlarında araştırılmıştır. Bu deneyler yapılırken diğer deneysel parametreler olan çözelti derişimi, katı/sıvı oranı ve reaksiyon sıcaklığı sırasıyla 1 mol/l, 2/200 g/ml ve 30 C değerlerinde alınmıştır. Karıştırma hızının etkisinin incelendiği deneylerden elde edilen veriler Şekil 7 de grafiksel olarak gösterilmiştir. Şekil 7 den görüldüğü gibi karıştırma hızının artması ile çözünme hızında bir miktar artış olmuştur. Karıştırma hızının artmasıyla katı etrafındaki durgun sıvı film tabakasının kalınlığı azaltılmış olur. Böylece katı yüzeyine doğru dış difüzyon direnci azalacağından çözünme hızında bir artış söz konusu olacaktır. Şekil 7. Kalsine edilmiş uleksitin çözünmesine karıştırma hızının etkisi. 158

164 N DEMİRKIRAN Academic Platform Journal of Engineering and Science 6-2, , Çözünme Üzerine Katı/Sıvı Oranının Etkisi Katı/sıvı oranının çözünme hızı üzerine olan etkisini incelemek için 1/200, 2/200 ve 4/200 g/ml katı/sıvı oranlarında deneyler yapılmıştır. Çözelti derişimi 1 mol/l, karıştırma hızı 400 rpm ve reaksiyon sıcaklığı 30 C değerlerinde alınmıştır. Bu deneylere ait sonuçların verildiği Şekil 8 e göre katı/sıvı oranının azalmasıyla çözünme hızında artış olmaktadır. Katı/sıvı oranının azalmasıyla çözücünün birim hacmi başına düşen katı miktarında azalma olacağından çözünme hızında artış olmaktadır. Şekil 8. Kalsine edilmiş uleksitin çözünmesine katı/sıvı oranının etkisi Çözünme Üzerine Sıcaklığın Etkisi Reaksiyon sıcaklığının kalsine uleksitin çözünmesi üzerine olan etkisi C aralığında farklı sıcaklıklarda incelenmiştir. Bu deneyler yapılırken çözelti derişimi 1 mol/l, karıştırma hızı 400 rpm ve katı/sıvı oranı 2/200 g/ml değerlerinde alınmıştır. Şekil 9 da verilen deney sonuçlarına göre sıcaklığın artmasıyla kalsine uleksitin çözünme kesri değerinde artış olmaktadır. Reaksiyon sıcaklığının artmasıyla moleküller daha hızlı hareket ederek birbirleriyle daha sık çarpışırlar. Bunun sonucunda moleküllerin reaksiyona girme olasılıkları artmış olur. Ayrıca reaksiyon hız sabitinin sıcaklığa üstel olarak bağlı olması sebebiyle sıcaklıktaki küçük artışlar dahi reaksiyon hızında önemli bir artmaya sebep olabilir. Şekil 9. Kalsine edilmiş uleksitin çözünmesine reaksiyon sıcaklığının etkisi. Amonyum sülfat çözeltilerinde uleksitin çözünmesi üzerine dehidrasyon işleminin etkisini daha iyi görebilmek için Çizelge 1 de hem kalsine edilmemiş [16] hem de kalsine edilmiş uleksit örnekleri ile yapılmış olan 159

165 N DEMİRKIRAN Academic Platform Journal of Engineering and Science 6-2, , 2018 deneylerin sonuçları topluca verilmiştir. Çizelge 1 den açıkça görüleceği gibi her bir deneysel parametrenin aynı değeri için kalsine uleksit örnekleri kullanılarak yapılan deneylerde daha kısa sürelerde yüksek dönüşüm değerlerine ulaşılmaktadır. Tablo 1. Kalsine edilmemiş ve kalsine edilmiş uleksit ile yapılan deneylerden elde edilen sonuçlar. Kalsine edilmemiş uleksit Kalsine edilmiş uleksit Parametre ve değerler Reaksiyon süresi, dk. % Çözünme Reaksiyon süresi, dk. % Çözünme Derişim, mol/l / Katı/sıvı oranı, 2/ g/ml 4/ Karıştırma hızı, rpm Sıcaklık, C Çözünme Kinetiği Kalsine uleksit ile amonyum sülfat çözeltisi arasındaki reaksiyon katı sıvı heterojen bir reaksiyondur. Bu tip reaksiyonların kinetik analizi genellikle katalitik olmayan katı akışkan heterojen reaksiyon modelleri kullanılarak yapılmaktadır. Bu modeller arasında büzülen çekirdek modeli liç veya çözünme reaksiyonlarının kinetik analizi için sıklıkla kullanılmaktadır. Söz konusu modele göre bir liç reaksiyonun hızı akışkan filminden difüzyon, kimyasal reaksiyon veya ürün tabakasından difüzyon basamaklarından biri veya birkaçı tarafından kontrol edilebilir. Bu modeller için integre edilmiş hız ifadeleri Eşitlik 5-7 deki gibi yazılabilir [18, 19]. xx = kk ll. tt (aaaaaaşkkkkkk ffffffffffffffffff ddddddüzzzzzzzz) (5) 1 (1 xx) 1 3 = kk rr. tt (kkkkkkkkkkkkkkkk rrrrrrrrrrrrrrrrrr) (6) 1 3(1 xx) (1 xx) = kk dd. tt (ürrünn vvvvvvvv kküll tttttttttttttttttttttttt ddddddüzzzzzzzz) (7) Yukarıdaki eşitliklerde, x dönüşüm kesrini, k l akışkan filminden difüzyon için görünür hız sabitini, k r yüzey kimyasal reaksiyonu için görünür hız sabitini, k d ürün veya kül tabakasından difüzyon için görünür hız sabitini ve t reaksiyon süresini temsil etmektedir. Deneysel olarak bulunan dönüşüm kesri değerleri kullanılarak Eşitlik 5-7 nin sol taraflarının t zamanına karşı grafikleri çizildiğinde orijinden geçen düz doğrular hangi model için elde ediliyorsa reaksiyon hızını o basamak kontrol eder. Elde edilen deneysel verilere yukarıda sözü edilen modeller uygulandığı zaman orijinden geçen düz doğruların oluşmadığı gözlenmiştir. Katı akışkan reaksiyonların kinetiğini izah etmek için yukarıda verilmiş olan heterojen reaksiyon modellerinden başka homojen reaksiyon modelleri de kullanılarak deneysel veriler analiz edilebilmektedir. Elde edilen dönüşüm kesri verilerine homojen modeller uygulandığı zaman kalsine uleksitin amonyum sülfat çözeltilerinde çözünme kinetiğini ifade etmek için en uygun modelin, integre edilmiş hali Eşitlik 8 de verilen yalancı birinci mertebe kinetik model olduğu gözlenmiştir. ln(1 xx) = kk. tt (8) Eşitlik 8 de x dönüşüm kesrini, k reaksiyonun görünür hız sabitini ve t reaksiyon süresini temsil etmektedir. Çözelti derişimi, katı/sıvı oranı, karıştırma hızı ve reaksiyon sıcaklıkları için Eşitlik 8 in sol tarafının t ye karşı çizilen grafikleri Şekil de gösterilmiştir. Bu şekillerden görüleceği gibi orijinden geçen düz doğrular elde edilmiştir. 160

166 N DEMİRKIRAN Academic Platform Journal of Engineering and Science 6-2, , 2018 Şekil 10. Farklı derişimler için reaksiyon süresine karşı ln(1-xb 2 O 3 ) grafiği. Şekil 11. Farklı katı/sıvı oranları için reaksiyon süresine karşı ln(1-xb 2 O 3 ) grafiği. 161

167 N DEMİRKIRAN Academic Platform Journal of Engineering and Science 6-2, , 2018 Şekil 12. Farklı karıştırma hızları için reaksiyon süresine karşı ln(1-xb 2 O 3 ) grafiği. Şekil 13. Farklı sıcaklıklar için reaksiyon süresine karşı ln(1-xb 2 O 3 ) grafiği. Reaksiyon hız sabitinin (k) deney parametrelerine bağlılığı Eşitlik 9 daki gibi yazılabilir. kk = kk 0. (CC) aa. (KK/SS) bb. (KKKK) cc. exp EE aa. tt (9) RRRR Bu eşitlikte k 0, Arrhenius sabitini (1/s); C, çözelti derişimini (mol/l); K/S, katı/sıvı oranını (g/ml); KH, karıştırma hızını (rpm); E a, aktivasyon enerjisini (J/mol); R, ideal gaz sabitini (J/mol.K); T, sıcaklığı (K) temsil etmektedir. a, b ve c sabitleri reaksiyon hızının ilgili parametreye olan bağlılığını ifade etmektedir. Şekil 10, 11 ve 12 deki doğruların eğimleri sırasıyla çözelti derişimi, katı/sıvı oranı ve karıştırma hızı için görünür hız sabiti değerlerini verir ve a, b ve c üslerinin hesaplanmasında kullanılır. Yapılan hesaplamalar sonucunda a, b ve c üslerinin değerleri sırasıyla 0.55, ve 0.50 olarak belirlenmiştir. Çözünme prosesinin aktivasyon enerjisini hesaplamak için Şekil 13 teki düz doğruların eğimlerinden görünür hız sabitleri belirlenmiş ve Şekil 14 de verilmiş olan Arrhenius grafiği oluşturulmuştur. Şekil 14 deki doğrunun eğiminden de mevcut çözünme prosesi için aktivasyon enerjisi 42 kj/mol olarak hesaplanmıştır. Doğrunun kaymasından Arrhenius sabiti 4.16x10 4 (1/s) olarak belirlenmiştir. Şekil 14. Çözünme prosesi için Arrhenius grafiği. 162

168 N DEMİRKIRAN Academic Platform Journal of Engineering and Science 6-2, , 2018 Sonuç olarak, kalsine uleksitin amonyum sülfat çözeltilerindeki çözünme kinetiğini temsil etmek üzere Eşitlik 10 da verilmiş olan ifade yazılabilir.. ln 1 XX BB2 OO 3 = 4.16xx10 4 (CC) 0,55 (KK/SS) 0,89 (KKKK) 0.50 exp 5045 tt (10) TT 4. SONUÇLAR Bu çalışmada uleksit mineralinin amonyum sülfat çözeltilerinde çözünmesi üzerine kalsinasyon işleminin etkisi araştırılmıştır. Farklı sıcaklıklarda kalsine edilmiş uleksit minerali kullanılarak yapılan deneyler sonucunda, kalsinasyon prosesinin uleksitin çözünme hızı üzerinde önemli bir etkisinin olduğu belirlenmiştir. 150 C ye kadar kalsine edilmiş uleksit örneklerinin çözünme hızında artış olduğu görülmüştür. Bu sıcaklıktan daha yüksek sıcaklıklarda kalsine edilmiş örneklerle yapılan deneylerde ise çözünme hızında bir azalma olduğu tespit edilmiştir. En yüksek çözünme değerlerinin elde edildiği kalsine örnekler kullanılarak çözelti derişimi, katı/sıvı oranı, karıştırma hızı ve reaksiyon sıcaklığının çözünme hızı üzerindeki etkileri incelenmiştir. Çözelti derişimi ve reaksiyon sıcaklığın artması, katı/sıvı oranının ise azalmasıyla çözünme hızının arttığı bulunmuştur. Çözünme kinetiğinin yalancı birinci mertebe kinetiğe uyduğu belirlenmiş ve çözünme prosesi için aktivasyon enerjisi 42 kj/mol olarak hesaplanmıştır. KAYNAKLAR [1] Ü. İpekoğlu, and M. Polat, Bor endüstrisine genel bakış, Madencilik, vol. 26, pp. 5-16, [2] M. S. Celik, H. A. Uzunoglu, and F. Arslan, Decrepitation properties of some boron minerals, Powder Technology, vol. 79, pp , [3] M. Tunç, H. Erşahan, S. Yapici, and S. Çolak, Dehydration kinetics of ulexite from thermogravimetric data, Journal of Thermal Analysis and Calorimetry, vol. 48, pp , [4] S. Şener, G. Özbayoğlu, and Ş. Demirci, Changes in the structure of ulexite on heating, Thermochimica Acta, vol. 362, pp , [5] L. Stoch, On a model of thermal internal decomposition of solids, Thermochimica Acta, vol. 203, pp , [6] H. Erşahan, M. Tunç, A. Ekmekyapar, and S. Yapıcı, Flash dehydration of ulexite and investigation of dehydration kinetics from thermogravimetric data, Thermochimica Acta, vol. 250, pp , [7] Y. Erdoğan, A. Zeybek, A. Şahin, and A. Demirbaş, Dehydration kinetics of howlite, ulexite, and tunellite using thermogravimetric data, Thermochimica Acta, vol. 326, pp , [8] S. Şener, and G. Özbayoğlu, Investigation of structural chemistry of thermal processes applied for improvement of grindability of ulexite, Physicochemical Problems of Mineral Processing, vol. 34, pp , [9] A. Künkül, S. Yapıcı, M. M. Kocakerim, and M. Çopur, Dissolution of thermally dehydrated ulexite in sulfuric acid solution, Industrial and Engineering Chemistry Research, vol. 36, pp , [10] G. Tekin, Y. Onganer, and M. Alkan, Dissolution kinetics of ulexite in ammonium chloride solution, Canadian Metallurgical Quarterly, vol. 37, pp , [11] M. Alkan, C. Çifçi, F. Ayaz, and M. Doğan, Dissolution kinetics of ulexite in aqueous EDTA solutions, Canadian Metallurgical Quarterly, vol. 39, pp , [12] M. Alkan, M. Doğan, and H. Namlı, Dissolution kinetics and mechanism of ulexite in oxalic acid solutions, Industrial and Engineering Chemistry Research, vol. 43, pp , [13] A. Künkül, and N. Demirkıran, Dissolution kinetics of calcined ulexite in ammonium carbonate solutions, Korean Journal of Chemical Engineering, vol. 24, pp , [14] N. Demirkıran, Leaching kinetics of calcined ulexite in ammonium nitrate solutions, Journal of Chemical Engineering of Japan, vol. 40, pp , [15] N. Demirkiran, N. Bayrakçı, and C. Asin, Dissolution of thermally dehydrated ulexite in ammonium acetate solutions, Transactions of Nonferrous Metals Society of China, vol. 23, pp , [16] A. Künkül, N. Demirkıran, and A. Baysar, Dissolution kinetics of ulexite in ammonium sulfate solutions, Industrial and Engineering Chemistry Research, vol. 42, pp , [17] H. Gülensoy, Kompleksometrinin Esasları ve Kompleksometrik Titrasyonlar, İstanbul: Fatih Yayınevi Matbaası, [18] C. Y. Wen, Noncatalytic heterogeneous solidfluid reaction models, Industrial and Engineering Chemistry, vol. 60, pp , [19] O. Levenspiel, Chemical Reaction Engineering, New York: John Wiley,

169 Academic Platform Journal of Engineering and Science 6-2, , 2018 Academic Platform Journal of Engineering and Science journal homepage: Analytical Solutions for Buckling Behavior of Two Directional Functionally Graded Beams Using a Third Order Shear Deformable Beam Theory *Armağan Karamanlı( ) Department of Mechatronics Engineering, Faculty of Engineering and Architecture, Assistant Professor, Istanbul Gelişim University, Istanbul, Turkey. Received Date: Accepted Date: Abstract This paper is dedicated to present a Ritz-type analytical solution for buckling behavior of two directional functionally graded beams (2D-FGBs) subjected to various sets of boundary conditions by employing a third order shear deformation theory. The material properties of the beam vary in both axial and thickness directions according to the power-law distribution. The axial, transverse deflections and rotation of the cross sections are expressed in polynomial forms to obtain the buckling load. The auixiliary functions are added to displacement functions to satisfy the boundary conditions. Simply supported Simply supported (SS), Clamped-Simply supported (CS), Clamped clamped (CC) and Clamped-free (CF) boundary conditions are considered. Computed results are compared with earlier works for the verification and convergence studies. The effects of the different gradient indexes, various aspect ratios and boundary conditions on the buckling responses of the two directional functionally graded beams are investigated. Keywords: Two Directional Functionally Graded Beam, Buckling Behavior, Third Order Shear Deformation Theory, Ritz Method 1. INTRODUCTION With the advance of the production technology, the functionally graded materials (FGMs) which can be classified as advanced materials formed of two or more different materials whose volume fractions vary continuously in a required direction have been developed to satisfy the new demands of military, aerospace, nuclear energy, biomedical, automotive, marine and civil engineering applications. It has received great attention from researchers due to its lower transverse shear stresses, high resistance to temperature shocks and no interface problems through the layer interfaces [1-22]. In some engineering applications, the FGMs with material properties only varying in one direction are not efficient to fulfill the technical requirements such as the temperature and stress distributions in two or three directions for aerospace craft and shuttles [23]. To obtain more effective high-temperature resistant materials, a new type FGM with material properties varying in two or three directions is needed. However, the number of the studies related to the mechanical and thermal behavior of two-directional FG structures is still very limited. Based on the the Element Free Galerkin Method, 2D steady-state free and forced vibrations of two-directional functionally graded beams (FGBs) are investigated in [24]. Bending and thermal deformations of FGBs with various end conditions are obtained by employing the state-space based differential quadrature method [25]. The static and free vibration analysis of two-directional FGBs is investigated in [26] by obtaining a symplectic elasticity solution. The fully coupled thermomechanical behavior of bi-directional FGM beam structures is studied using an isogeometric finite element model in [27]. Free and forced vibration of Timoshenko two directional functionally graded beams under a moving load is investigated in [28] for the case that the material properties of the 2D- FGB vary exponentially through the length and height directions. Based on the power-law distribution of the material properties, the buckling of Timoshenko beams composed of two directional FGM is studied in [29]. The static behavior of the two directional FGBs by using various beam theories is presented in [30]. An analytical solution for the static deformations of the bi-directional *Corresponding Author: Armağan Karamanlı, Istanbul Gelişim University, 34215, Istanbul, Turkey, Tel: , Doi: /apjes

170 A KARAMANLI Academic Platform Journal of Engineering and Science 6-2, , 2018 functionally graded thick circular beams is developed based on a new shear deformation theory with a logarithmic function in the postulated expression for the circumferential displacement in [31]. The flexure behavior of the two directional FG sandwich beams by using a quasi-3d theory and a meshless method is studied in [32]. The bending and buckling analysis of two-directional functionally graded plates are investigated by employing a new third order shear deformation theory via finite element method [33]. By employing a third order shear deformation theory and exponential material distribution, the free vibration behavior of the 2D-FGBs is investigated in [34]. As it is seen from above discussions, one may easily notice that the most of the studies are related to the static, dynamic and buckling analysis of conventional functionally graded (1D-FG) beams and the number of studies regarding to 2D-FGBs is very limited. According to the best of author s knowledge, there is no reported work on the buckling analysis of the two directional FGBs based on a third order shear deformable beam theory. Shear deformation may have a significant effect on the buckling loads of the thick two directional FGBs, so that a third order shear deformation theory should be considered for this problem. This paper focuses on the bifurcation buckling of 2D-FGBs based on the power-law variation of material properties with various end conditions, aspect ratios and gradient indexes. 2. THEORY AND FORMULATION 2.1 Homogenization of Material Properties Consider a two-directional functionally graded beam as shown in Fig. 1 with length L, width b and thickness h. The beam is made of two different constituents. The material properties vary both in the x (along the length of the beam) and z (thickness direction) directions. The origin of the coordinate system is at the midpoint of the beam. In this study, the rule of mixture is used to find the effective material properties at a point. The effective material properties of the beam, Young s modulus E and shear modulus G can be given by EE(xx, zz) = EE 1 VV 1 (xx, zz) + EE 2 VV 2 (xx, zz) GG(xx, zz) = GG 1 VV 1 (xx, zz) + GG 2 VV 2 (xx, zz) (1) where EE 1, EE 2, GG 1 and GG 2 are the material properties of two constituents, VV 1 and VV 2 are volume fractions of the constituents. The relation of the volume fractions can be expressed as follows; z EE 22 EE( LL 22, hh 22 ) b x h EE 22 L EE 22 Figure 1. Geometry and coordinate of a two-directional FGB VV 1 (xx, zz) + VV 2 (xx, zz) = 1 (2) According to the power law variation, the volume fraction of the constitute 1 can be given by VV 1 (xx, zz) = xx LL pp xx zz h pp zz (3) where pp xx and pp zz are the gradient indexes which determine the material properties through the thickness (h) and length of the beam (L), respectively. When the pp xx and pp zz are set to zero then the beam becomes homogeneous. The effective material properties can be found by using the Eqs. (1), (2) and (3) as follows [29], GG(xx, zz) = (GG 1 GG 2 ) xx LL pp xx zz h pp zz + GG 2 (4) 2.2 Third Order Shear Deformable Beam Theory The following displacement field is given for the third order shear deformation theory (Reddy Beam Theory (RBT)) [5] UU(xx, zz) = uu(xx) + zzzz(xx) ααzz 3 φφ(xx) + dddd(xx) dddd WW(xx, zz) = ww(xx) (5) Here uu and ww are the axial and transverse displacements of any point on the neutral axis, φφ the rotation of the cross sections, αα = 4/(3h 2 ). By EE(xx, zz) = (EE 1 EE 2 ) xx LL pp xx zz h pp zz + EE

171 A KARAMANLI Academic Platform Journal of Engineering and Science 6-2, , 2018 using the Eq. (5), the strain-displacement relations εε xxxx = = dddd dddd + zz dddd dddd ααzz3 dddd dddd + dd2 ww ddxx 2 γγ xxxx = UU + dddd = φφ + dddd ββzz2 φφ + dddd (6) dddd where ββ = 3αα = 4/(h 2 ). The stress-strain relationship of a two directional functionally graded beam in the material coordinate axes is given by σσ xxxx σσ xxxx = EE(xx, zz) 0 0 GG(xx, zz) εε xxxx γγ (7) xxxx where (σσ xxxx, σσ xxxx ) are the stresses and (εε xxxx, γγ xxxx ) are the strains with respect to the axes. of the RBT are given by 2.3 Variational Formulation of Buckling of Two- Directional Functionally Graded Beam The strain energy of the beam including the energy associated with the shearing strain can be written as UU = 1 2 (σσ xxxxεε xxxx + σσ xxxx γγ xxxx )dddd (8) VV where VV is the volume of the beam. By substituting Eqs. (6) and (7) into Eq. (8), the strain energy can be obtained as the form of UU = 1 2 [ VV EE(xx, zz){ dddd 2 dddd + (zz 2 +αα 2 zz 6 2ααzz 4 ) dddd 2 dddd + αα 2 zz 6 dd2 2 ww ddxx 2 + 2(zz ααzz 3 ) dddd dddd dddd dddd dd 2 ww 2ααzz3 ddxx 2 + 2(αα2 zz 6 ααzz 4 ) dddd dd 2 ww dddd ddxx 2 } + GG(xx, zz){(1 + ββ 2 zz 4 2ββzz 2 )φφ 2 + (1 + ββ 2 zz 4 2ββzz 2 ) dddd dddd 2 + 2(1 + ββ 2 zz 4 2ββzz 2 )φφ dddd }]dddd (9) dddd The stiffness coefficients can be introduced as follows (AA, BB, DD, CC, FF, HH) = bb (AA ss, DD ss, FF ss ) = bb +h/2 h/2 +h/2 h/2 (EE 1 EE 2 ) zz h pp zz (1, zz, zz 2, zz 3, zz 4, zz 6 )dddd (GG 1 GG 2 ) zz h pp zz (1, zz 2, zz 4 )dddd +h/2 (10) (11) (AA 1, DD 1, FF 1, HH 1 ) = bb EE 2 (1, zz 2, zz 4, zz 6 )dddd (12) h/2 +h/2 (AA ss1, DD ss1, FF ss1 ) = bb GG 2 (1, zz 2, zz 4 )dddd h/2 Using Eqs. (4), (10), (11), (12) and (13), the strain energy can be rewritten as UU = 1 2 LL/2 AA xx pp xx LL + AA 1 dddd 2 dddd dddd LL/2 + DD xx pp xx LL + DD 1 + αα 2 HH xx pp xx LL + HH 1 2αα FF xx pp xx LL + FF 1 dddd 2 dddd +αα 2 HH xx pp xx LL + HH 1 dd2 2 ww ddxx 2 dddd dddd 2αααα xx ppxx LL dddd +2 αα 2 HH xx pp xx LL + HH 1 αα FF xx pp xx LL + FF 1 dddd dd 2 ww dddd ddxx 2 +2 BB xx LL pp xx αααα xx LL pp xx dddd dddd dd 2 ww dddd ddxx 2 +( AA ss xx pp xx LL + AA ss1 + ββ 2 FF ss xx pp xx LL + FF ss1 2ββ DD ss xx pp xx LL + DD ss1 )(φφ 2 + dddd 2 dddd + 2φφ dddd ) dddd (14) dddd The total potential energy of the external axial load (NN 0 ) can be given by VV = 1 LL/2 2 NN 0 dddd 2 dddd dddd (15) LL/2 (13) 166 3

172 A KARAMANLI Academic Platform Journal of Engineering and Science 6-2, , 2018 Using Eqs. 14 and 15, the total potential energy (Π) can be obtained by: Π = UU + VV (16) Therefore, the displacement functions uu(xx), ww(xx) and the rotation function φφ(xx) are presented by the following polynomial series which are satisfy the kinematic boundary conditions given in Table 1. mm uu(xx) = AA jj θθ jj (xx), jj=1 mm ww(xx) = BB jj φφ jj (xx), jj=1 mm φφ(xx) = CC jj ψψ jj (xx), jj=1 where AA jj, BB jj and CC jj are unknown coefficients to be determined, θθ jj (xx), φφ jj (xx) and ψψ jj (xx) are the shape functions which are proposed for the boundary conditions (BC) to be studied within this paper and θθ jj (xx) = xx + LL 2 pp uu xx LL 2 qq uu xx mm 1 φφ jj (xx) = xx + LL 2 pp ww xx LL 2 qq ww xx mm 1 ψψ jj (xx) = xx + LL 2 pp φφ xx LL 2 qq φφ xx mm 1 (17aa) (17bb) (17cc) pp ξξ and qq ξξ (ξξ = uu, ww, φφ) are the boundary exponents of auxiliary functions related with the boundary conditions given in Table 2. Table 1. Kinematic boundary conditions used for the numerical computations. BC xx = LL/2 xx = LL/2 SS uu = 0, ww = 0 ww = 0 CS uu = 0, ww = 0, φφ = 0, ww = 0 ww = 0 CC uu = 0, ww = 0, φφ = 0, ww = 0 uu = 0, ww = 0, φφ = 0, ww = 0 CF uu = 0, ww = 0, φφ = 0, ww = 0 Table 2. Boundary exponents for various boundary conditions. BC Left end Right end pp uu pp ww pp φφ qq uu qq ww qq φφ SS CS CC CF Substituting Eq. (17) into Eq. (16) and then using principle of minimum potential energy given by Eq. (18), the system of equations given in Eq. (19) is obtained to calculate the critical buckling loads of two directional FGBs: Π AA jj = 0, Π BB jj = 0, Π CC jj = 0 jj = 1,2,3,, mm (18) [KK 11 ] [KK 12 ] [KK 13 ] [KK 12 ] TT [KK 22 ] [KK 23 ] NN cccc [KK 13 ] TT [KK 23 ] TT [KK 33 ] where [KK kkkk ] are the stiffness matrices and [KK NN0 ] is the geometic stiffness matrix. All the matrices are KK 13 (ii, jj) = KK 11 (ii, jj) = [0] [0] [0] {AA} {0} [0] KK NN0 [0] {BB} = {0} (19) [0] [0] [0] {CC} {0} LL/2 symmetric in size mxm. The components of the stiffness matrices are given by: AA xx pp xx LL + AA 1 θθ ii,xx θθ jj,xx dddd, LL/2 KK 12 (ii, jj) = αα LL/2 LL/2 CC xx pp xx LL θθ ii,xx φφ jj,xxxx dddd LL/2 BB xx pp xx LL αααα xx pp xx LL θθ ii,xx ψψ jj,xx dddd LL/

173 A KARAMANLI Academic Platform Journal of Engineering and Science 6-2, , 2018 KK 33 (ii, jj) = KK 22 (ii, jj) = αα 2 KK 23 (ii, jj) = LL/2 LL/2 LL/2 HH xx pp xx LL + HH 1 φφ ii,xxxx φφ jj,xxxx dddd LL/2 LL/2 + AA ss xx LL pp xx + AA ss1 + ββ 2 FF ss xx LL pp xx + FF ss1 LL/2 2ββ DD ss xx LL pp xx + DD ss1 φφ ii,xx φφ jj,xx dddd αα 2 HH xx pp xx LL + HH 1 αα FF xx pp xx LL + FF 1 φφ ii,xxxx ψψ jj,xx dddd LL/2 LL/2 + AA ss xx LL pp xx + AA ss1 + ββ 2 FF ss xx LL pp xx + FF ss1 LL/2 2ββ DD ss xx LL pp xx + DD ss1 φφ ii,xx ψψ jj dddd DD xx pp xx LL + DD 1 + αα 2 HH xx pp xx LL + HH 1 2αα FF xx pp xx LL + FF 1 ψψ ii,xx ψψ jj,xx dddd LL/2 LL/2 + AA ss xx LL pp xx + AA ss1 + ββ 2 FF ss xx LL pp xx + FF ss1 LL/2 3. NUMERICAL RESULTS 2ββ DD ss xx LL pp xx + DD ss1 ψψ ii ψψ jj dddd KK NN0 (ii, jj) = LL/2 φφ ii,xx φφ jj,xx dddd LL/2 In this section, a number of numerical examples are studied to verify the accuracy of the present method and understand the effects of gradient indexes (or material composition), aspect ratios (L/h) and boundary conditions on the buckling behavior of the two directional FGBs. The material properties of the two constitutes are given as follows CCCCCCCCCCCCCC (AAAA 2 OO 3 ) EE 1 = 380GGGGGG aaaaaa νν 1 = 0.3 MMMMMMMMMM (AAAAAAAAAAAAAAAAAA) EE 2 = 70GGGGGG aaaaaa νν 2 = 0.3 The height of the beam is varied to examine the effect of the shear deformation. Four different boundary conditions, namely simply supportedsimply supported (SS), clamped-simply supported (CS), clamped-clamped (CC) and clamped-free (CF) are considered. The following dimensionless buckling load (NN cccc ) parameter is used for the representation of the results; NN cccc = 12NN ccccll 2 EE 2 bbh 3 (16) To perform the convergence and verification studies, a homogeneous beam is considered and the displacement functions with different number of terms (m=2, 4, 6, 8, 10 and 12) are employed. The computed results are presented in terms of dimensionless critical buckling load (NN cccc ) considering various gradient indexes in both ii, jj = 1,2,3,., mm (20) directions, aspect ratios and boundary conditions, namely SS, CC and CF. The results from the previous studies [22-23] in terms of dimensionless critical buckling load (NN cccc ) are used for comparison purposes in Table 3. It can be seen that the solutions converge quickly for the buckling behavior of SS and CF beams, when the number of terms in the displacement function is set to 6. However, the agreed results are obtained for CC boundary condition by employing 8 terms in the displacement function as given in Table 3. For the sake of accuracy, 8 terms in the polynomial expansion is employed for the extensive buckling analysis of two directional FGBs. In Tables 4-7, the first three dimensionless critical buckling loads of the 2D-FGBs with SS, CS, CC and CF boundary condtions are presented for two different aspect ratios (L/h=5 and L/h=20) and various gradient indexes in both directions (p z and p x ). It is seen that that the first three critical buckling loads decrease for all type of end conditions while the gradient indexes increase. It is found that the shear deformation effect becomes very important when the buckling mode number increases. For CC beams, the relative difference between critical buckling loads with respect to variation of the aspect ratio increases as the order of buckling mode becomes higher

174 A KARAMANLI Academic Platform Journal of Engineering and Science 6-2, , 2018 Table 3. Verification and convergence studies, dimensionless critical buckling load (NN cccc ) of homogeneous beams with respect to various boundary conditions and aspect ratio change. L/h 5 20 Theory Boundary Condition SS CC CF HBT [23] HBT [22] terms terms Present 6 terms terms terms terms HBT [23] HBT [22] terms terms Present 6 terms terms terms terms Table 4. The first three dimensionless critical buckling load (NN cccc ) of SS two directional FGBs with respect to gradient index and aspect ratio change. NN cccc p x p z p z L/h=5 L/h= NN cccc1 NN cccc2 NN cccc For instance, the first dimensionless critical buckling loads of a CC beam with p z =1 and p x =1 are NN cccc1 = and NN cccc1 = for L/h=5 and L/h=20, respectively. On the other hand, the third dimensionless critical buckling loads are NN cccc3 = and NN cccc1 = for L/h=5 and L/h=20, respectively. The relative difference can be obtained by taking the value of the aspect ratio L/h=5 as a reference. The relative difference is % 37 and % 152 for the beams whose aspect ratios are L/h=5 and L/h=20, respectively. These results can be compared with ones given in [29]. It is clear that the relative difference is the least for CF beam while it is the most for CC beam. And finally, the reduction in the dimensionless critical buckling load because of the gradient index variation in the x direction is more than the gradient index variation in the z direction

175 A KARAMANLI Academic Platform Journal of Engineering and Science 6-2, , 2018 Table 5. The first three dimensionless critical buckling load (NN cccc ) of CS two directional FGBs with respect to gradient index and aspect ratio change. NN cccc p x p z p z L/h=5 L/h= NN cccc1 NN cccc2 NN cccc Table 6. The first three dimensionless critical buckling load (NN cccc ) of CC two directional FGBs with respect to gradient index and aspect ratio change. NN cccc p x p z p z L/h=5 L/h= NN cccc1 NN cccc2 NN cccc

176 A KARAMANLI Academic Platform Journal of Engineering and Science 6-2, , 2018 Table 7. The first three dimensionless critical buckling load (NN cccc ) of CF two directional FGBs with respect to gradient index and aspect ratio change. NN cccc p x p z p z L/h=5 L/h= NN cccc1 NN cccc2 NN cccc To illustrate the effect of gradient indexes (p x and the x direction on the dimensionless critical p z ) and aspect ratios on the dimensionless buckling buckling load is more significant than the gradient loads of the 2D-FGBs for all type of boundary index in the z direction for all type of boundary conditions, Figs 2 to 5 are plotted. It is observed conditions. that the dimensionless critical buckling load The first four normalized buckling mode shapes of decreases with the increase of the gradient indexes. the two directional FGBs for all type of boundary This is because the rigitdity of the beam decreases. conditions are presented in Fig. 6 (L/h=5, p Moreover, with the increase of the aspect ratio, the z =1 and p critical buckling loads become very close to each x =1). One may expect that for a homogeneous CC beam the mode shapes are symmetric about the other after in the region of, LL/h 25 for SS and midpoint of the beam. However, because of the CS, LL/h 15 for CF and LL/h 35 for CC. On the material variation along the length of the beam the other hand, for CC beams, the effect of the shear mode shapes become anti-symmetric about the deformation is significant in the region of LL/h midpoint of the 2D-FGB. 15. It reveals that the effect of the gradient index in 171 8

177 A KARAMANLI Academic Platform Journal of Engineering and Science 6-2, , 2018 Dimensionless First Critical Buckling Load - N cr p z =0 p z =0.5 p z =1 p z =2 p z =5 p z = Aspect Ratio - L/h a) p x =1 Dimensionless First Critical Buckling Load - N cr p x =0 p x =0.5 p x =1 p x =2 p x =5 p x = Aspect Ratio - L/h b) p z =1 Figure 2. Variation of the dimensionless first critical buckling loads of two directional FG SS beams with respect to gradient index a) p x =1 and b) p z =1 and various aspect ratios 172 9

178 A KARAMANLI Academic Platform Journal of Engineering and Science 6-2, , 2018 Dimensionless First Critical Buckling Load - N cr p z =0 p z =0.5 p z =1 p z =2 p z =5 p z = Aspect Ratio - L/h a) p x =1 Dimensionless First Critical Buckling Load - N cr p x =0 p x =0.5 p x =1 p x =2 p x =5 p x = Aspect Ratio - L/h b) p z =1 Figure 3. Variation of the dimensionless first critical buckling loads of two directional FG CS beams with respect to gradient index a) p x =1 and b) p z =1 and various aspect ratios

179 A KARAMANLI Academic Platform Journal of Engineering and Science 6-2, , 2018 Dimensionless First Critical Buckling Load - N cr p z =0 p z =0.5 p z =1 p z =2 p z =5 p z = Aspect Ratio - L/h a) p x =1 Dimensionless First Critical Buckling Load - N cr p x =0 p x =0.5 p x =1 p x =2 p x =5 p x = Aspect Ratio - L/h b) p z =1 Figure 4. Variation of the dimensionless first critical buckling loads of two directional FG CC beams with respect to gradient index a) p x =1 and b) p z =1 and various aspect ratios

180 A KARAMANLI Academic Platform Journal of Engineering and Science 6-2, , 2018 Dimensionless First Critical Buckling Load - N cr p z =0 p z =0.5 p z =1 p z =2 p z =5 p z = Aspect Ratio - L/h a) p x =1 Dimensionless First Critical Buckling Load - N cr p x =0 p x =0.5 p x =1 p x =2 p x =5 p x = Aspect Ratio - L/h b) p z =1 Figure 5. Variation of the dimensionless first critical buckling loads of two directional FG CF beams with respect to gradient index a) p x =1 and b) p z =1 and various aspect ratios

181 A KARAMANLI Academic Platform Journal of Engineering and Science 6-2, , Normalized Buckling Mode Shapes First Mode Second Mode Third Mode Fourth Mode Dimensionless Lenght - x/l Normalized Buckling Mode Shapes First Mode Second Mode -0.8 Third Mode Fourth Mode Dimensionless Lenght - x/l a) SS b) CS 1 1 Normalized Buckling Mode Shapes First Mode Second Mode Third Mode Fourth Mode Normalized Buckling Mode Shapes First Mode Second Mode Third Mode Fourth Mode Dimensionless Lenght - x/l Dimensionless Lenght - x/l c) CC d) CF Figure 6. First four normalized buckling mode shapes of the two directional FGBs for various boundary conditions (L/h=5, p x =1 and p z =1) 4. CONCLUSION In this study, the buckling behavior of the two directional functionally graded beams having different boundary conditions is presented. Analytical polynomial series solutions are derived for Simply supported Simply supported (SS), Clamped-Simply supported (CS), Clamped clamped (CC) and Clamped-free (CF) boundary conditions by employing various gradient indexes in both axial and thickness directions. The effects of the boundary conditions, gradient indexes and aspect ratios on the cirtical buckling load of the 2D- FGBs are discussed. By using auxiliary functions the boundary conditions are satisfied. Based on the results obtained by extensive analysis, it is clear that the dimensionless buckling load of the 2D- FGBs is greatly affected by the gradient indexes. However, the effect of the gradient index in the z direction is more significant than the the gradient index in the x direction. To meet the design requirements, the buckling behavior of the 2D- FGBs can be controlled by selecting suitable gradient indexes. As the aspect ratio increases, the shear deformation effect on the critical buckling loads of the 2D-FGBs decreases. It is observed that CC 2D-FGB is much more sensitive to shear deformation effect than the other 2D-FGB models. The third order shear deformable beam theory which is employed within this paper for the solution of the buckling behavior of the two directional FGBs satisfies the zero traction boundary conditions on the top and bottom surfaces of the beam, thus a shear correction factor is not required. It allows having a better prediction of buckling response for the 2D-FGBs. Especially for thick beams, the shear deformation effect is very important and higher order shear deformation beam theories are necessary. And finally, the proposed theory provides accurate results and is efficient in solving the buckling behavior of the 2D-FGBs

182 A KARAMANLI Academic Platform Journal of Engineering and Science 6-2, , 2018 REFERENCES [1] R. Kadoli, K. Akhtar, N. Ganesan, Static analysis of functionally graded beams using higher order shear deformation theory, Appl. Math. Model., vol. 32, pp , [2] X.F. Li, A unified approach for analyzing static and dynamic behaviors of functionally graded Timoshenko and Euler Bernoulli beams, Journal of Sound and Vibration, vol. 318, pp , [3] S.R. Li, D.F. Cao, Z.Q. Wan, Bending solutions of FGM Timoshenko beams from those of the homogenous Euler Bernoulli beams, Appl. Math. Model., vol. 37, pp , [4] M. Aydogdu, V. Taskin, Free vibration analysis of functionally graded beams with simply supported edges, Materials&Design., vol. 28, pp , [5] M. Simsek, Fundamental frequency analysis of functionally graded beams by using different higher-order beam theories, Nuc. Eng. and Des., vol. 240, pp , [6] M. Simsek, Vibration analysis of a functionally graded beam under a moving mass by using different beam theories, Compos. Struct., vol. 92, pp , [7] K.K. Pradhan, S. Chakraverty, Free vibration of Euler and Timoshenko functionally graded beams by Rayleigh-Ritz method, Compos. Part B., vol. 51, pp , [8] H. Su, J.R. Banerjee, C.W. Cheung, Dynamic stiffness formulation and free vibration analysis of functionally graded beams, Compos. Struct., vol. 106, pp , [9] S.R. Li, Z.G. Wan, J.H. Zhang, Free vibration of functionally graded beams based on both classical and first-order shear deformation beam theories, Applied Mathematics and Mechanics, vol. 35, pp , [10] M. Aydogdu, Semi-inverse method for vibration and buckling of axially functionally graded beams, Journal of Reinforced Plastics&Composites, vol. 27, pp , [11] Y. Huang, X.F. Li, Buckling analysis of nonuniform and axially graded columns with varying flexural rigidity, Journal of Engineering Mechanics, vol. 137, no.1, pp , [12] X.F. Li, B.L. Wang, J.C. Han, A higher-order theory for static and dynamic analyses of functionally graded beams, Archive of Applied Mechanics, vol. 80, pp , [13] T.P. Vo, H.T. Thai, T.K. Nguyen, F. Inam, J. Lee, Static behaviour of functionally graded sandwich beams using a quasi-3d theory, Compos. Part B, vol. 68, pp , [14] M. Filippi, E. Carrera, A.M. Zenkour, Static analyses of FGM beams by various theories and finite elements, Compos. Part B, vol. 72, pp. 1-9, [15] D.S. Mashat, E. Carrera, A.M. Zenkour, S.A.A. Khateeb, M. Filippi, Free vibration of FGM layered beams by various theories and finite elements, Compos. Part B, vol. 59, pp , [16] T.P. Vo, H.T. Thai, T.K. Nguyen, F. Inam, J. Lee, A quasi-3d theory for vibration and buckling of functionally graded sandwich beams, Compos. Struct., vol. 119, pp. 1 12,2015. [17] J.L. Mantari, J. Yarasca, A simple and accurate generalized shear deformation theory for beams, Compos. Struct., vol. 134, pp , [18] J.L. Mantari, A refined theory with stretching effect for the dynamics analysis of advanced composites on elastic foundation, Mech. Mater., vol. 86, pp , [19] J.L. Mantari, Refined and generalized hybrid type quasi-3d shear deformation theory for the bending analysis of functionally graded shells, Compos. Part B, vol. 83, pp , [20] T.K. Nguyen, T.P. Vo, B.D. Nguyen, J. Lee, An analytical solution for buckling and vibration analysis of functionally graded sandwich beams using a quasi-3d shear deformation theory, Compos. Struct., vol. 156, pp , [21] T.P. Vo, H.T. Thai, T.K. Nguyen, A. Maheri, J. Lee, Finite element model for vibration and buckling of functionally graded sandwich beams based on a refined shear deformation theory, Eng. Struct., vol. 64, pp , [22] T.K. Nguyen, T.T.P. Nguyen, T.P. Vo, H.T. Thai, Vibration and buckling analysis of functionally graded sandwich beams by a new higher-order shear deformation theory, Compos. Part B, vol. 76, pp , [23] M. Nemat-Alla, Reduction of thermal stresses by developing two-dimensional functionally graded materials, Int. Journal of Solids and Structures, vol. 40, pp , [24] A.J. Goupee, S.S. Vel, Optimization of natural frequencies of bidirectional functionally graded beams, Struct. Multidisc. Optim., vol. 32, pp , [25] C.F. Lü, W.Q. Chen, R.Q. Xu, C.W. Lim, Semi-analytical elasticity solutions for bidirectional functionally graded beams, Int. Journal of Solids and Structures, vol. 45, pp , [26] L. Zhao, W.Q. Chen, C.F. Lü, Symplectic elasticity for two-directional functionally graded materials, Mech. Mater., vol. 54, pp , [27] M. Nazargah, Fully coupled thermomechanical analysis of bi-directional FGM beams using NURBS isogeometric finite element approach, Aerospace Science and Technology, vol. 45, pp , [28] M. Simsek, Bi-Directional functionally graded materials (BDFGMs) for free and forced vibration of Timoshenko beams with various 177

183 A KARAMANLI Academic Platform Journal of Engineering and Science 6-2, , 2018 boundary conditions, Compos. Struct., vol. 141, pp , [29] M. Simsek, Buckling of Timoshenko beams composed of two-dimensional functionally graded material (2D-FGM) having different boundary conditions, Compos. Struct., vol. 149 pp , [30] A. Karamanli, Elastostatic analysis of twodirectional functionally graded beams using various beam theories and Symmetric Smoothed Particle Hydrodynamics method, Compos. Struct., vol. 160, pp , [31] A. Pydah, R.C. Batra, Shear deformation theory using logarithmic function for thick circular beams and analytical solution for bi-directional functionally graded circular beams, Compos. Struct., vol. 172, pp , [32] A. Karamanli, Bending behaviour of two directional functionally graded sandwich beams by using a quasi-3d shear deformation theory, Compos. Struct., vol. 174, pp , [33] T.V. Do, D.K. Nguyen, D.D. Nguyen, D.H. Doan, T.Q. Bui, Analysis of bi-directional functionally graded plates by FEM and a new thirdorder shear deformation plate theory, Thin-Walled Struct., vol. 119, pp , [34] A. Karamanli, Free vibration analysis of two directional functionally graded beams using a third order shear deformation theory, Compos. Struct., vol. 189, pp ,

184 Academic Platform Journal of Engineering and Science 6-2, , 2018 Academic Platform Journal of Engineering and Science journal homepage: Synthesis of Novel Thio-Substituted Aminonaphthoquinones * 1 Mahmut Yıldız( ), 2 Amaç Fatih Tuyun( ) 1 Gebze Technical University, Department of Chemistry, Faculty of Science, Gebze, Kocaeli, Turkey 2 Istanbul University-Cerrahpaşa, Engineering Faculty, Engineering Sciences Department, Avcılar, Istanbul, Turkey Received Date: Accepted Date: Abstract Novel thio-substituted aminonaphthoquinones were synthesized by the reactions of 2-(4-(trifluoromethyl)phenylamino)-3- chloronaphthalene-1,4-dione (3a) and 2-(3-(trifluoromethyl)phenylamino)-3-chloronaphthalene-1,4-dione (3b) with various thiol compounds such as ethanethiol (4a), methyl 2-mercaptoacetate (4b), ethyl 2-mercaptoacetate (4c). 2,3-dichloro-1,4- naphthoquinone (1) was reacted with aryl amines (2a, 2b) containing trifluoromethyl group to give compounds 3a and 3b by applying a method published in literature. Finally, obtained novel compounds (5a-5f) were characterized via IR, 1 H NMR, 13 C NMR, and MS techniques. Based on previous studies in the literature, it is expected that some potential biological activities of new compounds could find application in medicinal chemistry. Keywords: Aminonaphthoquinone, 1,4-naphthoquinone, thiol, aryl amine, trifluoromethyl group, CF 3, electron withdrawing group, nucleophilic substitution. 1. INTRODUCTION Among the quinoid structures, naphthoquinones appear as a remarkable subclass owing to their diverse biological responses which exhibit a wide range of biological activities such as antimalarial, anticancer, antibacterial, antifungal, antiparasitic, antithrombotic, antiviral, antiallergic, anti-inflammatory, antiplatelet, anti-ringworm, radical scavenging, apoptosis and lipoxygenase type of activity [1-25]. Naphthalene-like naphthoquinone structures, which bear a benzene ring and a cyclic diketone, are redox-active compounds generating oxygen species. Therefore, above-mentioned structures have attracted great attention in the field of drug discovery and new medicine development in medicinal chemistry [26-29]. On the other hand, the isolation, synthesis and reactions of some bioactive naphthoquinone compounds have been reported and also the biosynthesis of a naphthoquinone derivative, vitamin K, was discussed briefly and given references therein [30-37]. The insertion of strong electron-withdrawing perfluoroalkyl moieties into organic compounds changes their physiochemical and chemical properties, especially a distortion in the molecule occurs because of their bulky structure with steric hindrance [31, 38-41]. Recently, *Corresponding Author: 1 Gebze Technical University, Department of Chemistry, Faculty of Science, Gebze, Kocaeli, Turkey, Doi: /apjes various synthetic methods have attracted a considerable attention to introduce perfluoroalkyl functional groups to the organic fragments [42-44]. Since trifluoromethyl groups and amino naphthoquinones are known as desirable structures in medicinal chemistry due to their interesting properties which contribute to the biological activity and drug development, Li et al. have recently carried a synthesis out to add directly a trifluoromethyl moiety into 2-amino-1,4-naphthoquinone at room temperature in air [45]. The developed new method has been successful and a number of synthesized compounds have exhibited antiproliferative activity. Therefore, the introduction of a trifluoromethyl group to amino naphthoquinones has been suggested as a promising approach for pharmacological applications against cancer [45]. Recently, sulfanyl and trifluoromethyl containing aryl amine substituted 1,4-naphthoquinones have been synthesized and characterized successfully [46-48]. The different influences of the -CF 3 group position in aryl amine ring of the newly prepared compounds were clearly elucidated and the molecular docking studies have also supported the experimental results. Some of these compounds were reported as promising antibacterial and

185 M YILDIZ Academic Platform Journal of Engineering and Science 6-2, , 2018 antimicrobial agents [46]. In this respect, herein, novel trifluoromethyl bearing nitrogen- and sulfur-substituted 1,4- naphthoquinone compounds have been prepared and characterized, expecting that the new structures contribute to researches in the literature on biological activity desired investigations and applications. 2. MATERIALS AND METHODS Commercial materials obtained from different suppliers were used directly in all experiments. Thin-layer chromatography (TLC) technique was adopted to follow the progress of reactions by using analytical TLC plates (aluminium based DC-plates) which were supplied from Merck KGaA (silica gel 60 F254). TLC plates were checked under 254 nm-uv light. To separate and/or purify the compound(s), column chromatography technique was implemented by means of silica gel 60 (Merck, μμm particle size, mesh). A Varian UNITY INOVA instrument ( 1 H NMR frequency: 500 MHz and 13 C NMR frequency: 125 MHz) was used to obtain NMR spectra recorded in CDCl 3 as solvent and its signals appeared at δδ 7.19 ppm ( 1 H NMR) and δδ 76.0 ppm ( 13 C NMR). For the identification and splitting of NMR peaks, s, br s, d, t, q, dd, td and m stand for singlet, broad singlet, doublet, triplet, quartet, doublet of doublets, triplet of doublets and multiplet, respectively. In ppm (δ) relative to TMS were shown the chemical shifts and in hertz (Hz) were given the coupling constants (J). Infrared spectrums were recorded as ATR on a Perkin Elmer Spectrum 100 Optical FT-IR Spectrometer. The mass spectra were obtained on a BRUKER Microflex LT by MALDI (Matrix Assisted Laser Desorption Ionization)-TOF technique via addition of 1,8,9- anthracenetriol (DIT, dithranol) as matrix. A Stuart SMP-10 melting point apparatus was used to determine the melting points (mp) that were uncorrected. Standard Method for Preparation of the Chlorosubstituted Aminonaphthoquinone Compounds (3a-3b) 2,3-Dichloro-1,4-naphthoquinone (1) reacted with trifluoromethyl substituted aryl amines (2a-2b) to form 2- arylamino-3-chloro-1,4-naphthoquinone compounds (3a- 3b, Scheme 1) by applying a method from the previously reported publications and cited references therein [49-51]. Standard Method for Preparation of the Thiosubstituted Aminonaphthoquinone Compounds (5a-5f) The standard method was adapted from the literature [52]. The chloro-substituted aminonaphthoquinone compounds (3a-3b) and various thiol compounds (4a, 4b, 4c) in CH 2 Cl 2 were stirred at room temperature by addition of Et 3 N. The extraction of the reaction product was performed with CHCl 3. After that, it was washed with distilled H 2 O and dried over CaCl 2. The solvent was evaporated under vacuum. Column chromatography on silica gel using CHCl 3 for 5a, 5b, 5d, 5f and CH 2 Cl 2 for 5c, 5e was conducted for the crude product to give the separated and purified products (5a-5f, scheme 1). 2-(Ethylthio)-3-((4- (trifluoromethyl)phenylamino)naphthalene-1,4-dione (5a): 2-Chloro-3-((4-(trifluoromethyl)phenylamino)naphthalene- 1,4-dione (3a) and ethanethiol (4a) were reacted to yield the 5a as red powder by applying the standard method. Yield: g, 44%; mp C. FTIR (ATR) ν(cm -1 ): 3340 (-NH), 3067 (CH arom ), 2928, 2872 (CH aliphatic ), 1658, 1644 (C=O), 1615, 1586 (C=C). 1 H NMR (500 MHz, CDCl 3 ) δ (ppm): 8.17 dd, J:7.81, 0.97 Hz, 1H (-CH arom ); 8.11 dd, J:7.32, 0.98 Hz, 1H (-CH arom ); 7.82 br s, 1H (-NH); 7.77 td, J:7.81, 1.46 Hz, 1H (-CH arom ); 7.71 td, J: 7.32, 1.46 Hz, 1H (-CH arom ); 7.59 d, J: 8.30 Hz, 2H (-CH arom ); 7.06 d, J: 8.30 Hz, 2H (-CH arom ); 2.67 q, J:7.32 Hz, 2H (S-CH 2 -); 1.08 t, J:7.32 Hz, 3H (-CH 3 ). 13 C NMR (125 MHz, CDCl 3 ) δ(ppm): 181.2, 180.1, 143.6, 141.5, 134.6, 133.3, 133.2, 130.6, 127.0, 126.8, 125.8, 125.7, 125.6, 125.2, 121.6, 121.1, 27.9, MS MALDI TOF (m/z): Calc.: , Found: 377 [M] +. Methyl 2-((1,4-dioxo-3-((4-(trifluoromethyl)phenylamino)- 1,4-dihydronaphthalen-2-yl)thio)acetate (5b): 2-Chloro-3- ((4-(trifluoromethyl)phenylamino)naphthalene-1,4-dione (3a) and methyl 2-mercaptoacetate (4b) were reacted to yield the 5b as dark red oil by applying the standard method. Yield: g, 82%. FTIR (ATR) ν(cm -1 ): 3459 (- NH), 3296 (CH arom ), 3000, 2954, 2848 (CH aliphatic ), 1730 (C=O), 1592, 1557 (C=C). 1 H NMR (500 MHz, CDCl 3 ) δ (ppm): 8.15 dd, J: 7.32, 0.98 Hz, 1H (-CH arom ); 8.08 dd, J: 7.81, 0.98 Hz, 1H (-CH arom ); 8.00 br s, 1H (-NH); 7.75 td, J: 7.81, 1.47 Hz, 1H (-CH arom ); 7.70 td, J: 7.32, 0.98 Hz, 1H (- CH arom ); 7.58 d, J: 8.79 Hz, 2H (-CH arom ); 7.10 d, J: 8.30 Hz, 2H (-CH arom ); 3.76 s, 3H (O-CH 3 ); 3.59 s, 2H (S-CH 2 -). 13 C NMR (125 MHz, CDCl 3 ) δ(ppm): 180.6, 179.9, 169.8, 169.7, 145.6, 142.2, 134.8, 133.3, 133.1, 130.6, 130.1, 130.0, 126.0, 125.9, 121.9, 117.9, 52.6, 35.1, MS MALDI TOF (m/z): Calc.: , Found: 421 [M] +. Ethyl 2-((1,4-dioxo-3-((4-(trifluoromethyl)phenylamino)- 1,4-dihydronaphthalen-2-yl)thio)acetate (5c): 2-Chloro-3- ((4-(trifluoromethyl)phenylamino)naphthalene-1,4-dione (3a) and ethyl 2-mercaptoacetate (4c) were reacted to yield the 5c as a red powder by applying the standard method. Yield: g, 6%; mp C. FTIR (ATR) ν(cm -1 ): 3276 (-NH), 3071 (CH arom ), 2955, 2916, 2848 (CH aliphatic ), 1718, 1671, 1632 (C=O), 1590, 1545 (C=C). 1 H NMR (500 MHz, CDCl 3 ) δ (ppm): 8.18 dd, J: 7.81, 0.97 Hz, 1H (- CH arom ); 8.10 dd, J: 7.81, 0.97 Hz, 1H (-CH arom ); 7.99 br s, 1H (-NH); 7.78 td, J: 7.81, 1.47 Hz, 1H (-CH arom ); 7.71 td, J: 7.81, 1.46 Hz, 1H (-CH arom ); 7.60 d, J: 8.79 Hz, 2H (- CH arom ); 7.11 d, J: 8.29 Hz, 2H (-CH arom ); 4.03 q, J: 7.32 Hz, 2H (O-CH 2 -); 3.55 s, 2H (S-CH 2 -); 1.15 t, J: 6.83 Hz, 3H (-CH 3 ). 13 C NMR (125 MHz, CDCl 3 ) δ(ppm): 180.6, 179.9, 169.2, 145.6, 142.2, 134.8, 134.6, 134.2, 133.3, 133.2, 130.6, 128.2, 127.0, 126.9, 126.1, 126.0, 121.8, 118.2, 61.5, 29.7, MS MALDI TOF (m/z): Calc.: , Found: 435 [M]

186 M YILDIZ Academic Platform Journal of Engineering and Science 6-2, , (Ethylthio)-3-((3- (trifluoromethyl)phenylamino)naphthalene-1,4-dione (5d): 2-Chloro-3-((3-(trifluoromethyl)phenylamino)naphthalene- 1,4-dione (3b) and ethanethiol (4a) were reacted to yield the 5d as red powder by applying the standard method. Yield: g, 51%; mp C. FTIR (ATR) ν(cm -1 ): 3282 (-NH), 3076 (CH arom ), 2962, 2929 (CH aliphatic ), 1664, 1635 (C=O), 1591, 1522 (C=C). 1 H NMR (500 MHz, CDCl 3 ) δ (ppm): 8.16 dd, J: 7.81, 1.46 Hz, 1H (-CH arom ); 8.10 dd, J: 7.81, 1.46 Hz, 1H (-CH arom ); 7.85 br s, 1H (-NH); 7.76 td, J: 7.32, 1.46 Hz, 1H (-CH arom ); 7.70 td, J: 7.32, 1.46 Hz, 1H (-CH arom ); 7.46 t, J: 7.81 Hz, 1H (-CH arom ); 7.40 d, J: 7.81 Hz, 1H (-CH arom ); 7.28 s, 1H (-CH arom ); 7.18 d, J: 8.30 Hz, 1H (-CH arom ); 2.66 q, J: 7.81 Hz, 2H (S-CH 2 -); 1.06 t, J: 7.32 Hz, 3H (-CH 3 ). 13 C NMR (125 MHz, CDCl 3 ) δ(ppm): 181.1, 180.2, 144.1, 138.9, 134.6, 133.4, 133.0, 130.5, 131.0, 128.9, 127.0, 126.7, 125.1, 120.9, 120.8, 119.9, 118.8, 28.0, MS MALDI TOF (m/z): Calc.: , Found: 377 [M] +. Methyl 2-((1,4-dioxo-3-((3-(trifluoromethyl)phenylamino)- 1,4-dihydronaphthalen-2-yl)thio)acetate (5e): 2-Chloro-3- ((3-(trifluoromethyl)phenylamino)naphthalene-1,4-dione (3b) and methyl 2-mercaptoacetate (4b) were reacted to yield the 5e as a dark red powder by applying the standard method. Yield: g, 47%; mp C. FTIR (ATR) ν(cm -1 ): 3275 (-NH), 3111 (CH arom ), 2959, 2924, 2852 (CH aliphatic ), 1735, 1682 (C=O), 1623, 1592 (C=C). 1 H NMR (500 MHz, CDCl 3 ) δ (ppm): 8.17 dd, J: 7.81, 0.98 Hz, 1H (-CH arom ); 8.10 dd, J: 7.81, 0.98 Hz, 1H (-CH arom ); 8.01 br s, 1H (-NH); 7.78 td, J: 7.32, 0.98 Hz, 1H (-CH arom ); 7.70 td, J: 7.32, 0.98 Hz, 1H (-CH arom ); m, 2H (-CH arom ); 7.33 s, 1H (-CH arom ); 7.23 d, J: 7.80 Hz, 1H (-CH arom ); 3.63 s, 3H (O-CH 3 ); 3.54 s, 2H (S-CH 2 -). 13 C NMR (125 MHz, CDCl 3 ) δ(ppm): 180.6, 179.9, 169.7, 146.1, 139.6, 134.8, 133.3, 133.0, 131.1, 130.6, 129.3, 127.0, 126.9, 125.9, 121.6, 119.6, 116.4, 52.5, 35.2, MS MALDI TOF (m/z): Calc.: , Found: 421 [M] +. Ethyl 2-((1,4-dioxo-3-((3-(trifluoromethyl)phenylamino)- 1,4-dihydronaphthalen-2-yl)thio)acetate (5f): 2-Chloro-3- ((3-(trifluoromethyl)phenylamino)naphthalene-1,4-dione (3b) and ethyl 2-mercaptoacetate (4c) were reacted to yield the 5f as dark red oil by applying the standard method. Yield: g, 9%. FTIR (ATR) ν(cm -1 ): 3295 (-NH), 3074 (CH arom ), 2985, 2925, 2851 (CH aliphatic ), 1730, 1667 (C=O), 1591,1556 (C=C). 1 H NMR (500 MHz, CDCl 3 ) δ (ppm): 8.18 dd, J: 7.81, 1.47 Hz, 1H (-CH arom ); 8.10 dd, J: 7.81, 0.97 Hz, 1H (-CH arom ); 8.00 br s, 1H (-NH); 7.78 td, J: 7.81, 1.47 Hz, 1H (-CH arom ); 7.70 td, J: 7.81, 1.46 Hz, 1H (- CH arom ); m, 2H (-CH arom ); 7.32 s, 1 H (-CH arom ); 7.22 d, J: 7.32 Hz, 1H (-CH arom ); 4.07 q, J: 7.32 Hz, 2H (O- CH 2 -); 3.52 s, 2H (S-CH 2 -); 1.15 t, J: 6.83 Hz, 3H (-CH 3 ). 13 C NMR (125 MHz, CDCl 3 ) δ(ppm): 180.6, 179.9, 169.2, 146.0, 139.6, 134.8, 133.4, 133.0, 131.4, 131.1, 130.6, 129.3, 127.0, 126.9, 125.7, 121.5, 119.5, 116.8, 61.5, 29.7, MS MALDI TOF (m/z): Calc.: , Found: 435 [M] RESULTS AND DISCUSSION Precursors of novel thio-substituted aminonaphthoquinone compounds were prepared by performing nucleophilic substitution reactions of 2,3-dichloro-1,4-naphthoquinone (1) with trifluoromethyl group substituted aryl amines (2a, 2b) applying preparation method previously explained in the literature [50-51] and shown in Scheme 1. In these reactions, one chlorine atom of 2,3-dichloro-1,4- naphthoquinone (1) was substituted with primary aryl amines (2a, 2b) in ethanolic medium yielding 2-arylamino- 3-chloro-1,4-naphthoquinone compounds (3a-3b). Since compounds 3a and 3b still contain one chlorine atom, they can easily give different nucleophilic substitution products with various functional group, e.g. thiols. The reactions with thiols resulted in nitrogen, sulfur, and trifluoromethyl group containing 1,4-naphthoquinone structures. Various thiol compounds, such as ethanethiol (4a), methyl 2- mercaptoacetate (4b), ethyl 2-mercaptoacetate (4c) reacted with 3a and 3b to yield novel sulfanyl substituted aminonaphthoquinone derivatives, 2-(ethylthio)-3-((4- (trifluoromethyl)phenyl)amino)naphthalene-1,4-dione (5a), methyl 2-((1,4-dioxo-3-((4-(trifluoromethyl)phenyl)amino)- 1,4-dihydronaphthalen-2-yl)thio)acetate (5b), ethyl 2-((1,4- dioxo-3-((4-(trifluoromethyl)phenyl)amino)-1,4- dihydronaphthalen-2-yl)thio)acetate (5c), 2-(ethylthio)-3- ((3-(trifluoromethyl)phenyl)amino)naphthalene-1,4-dione (5d), methyl 2-((1,4-dioxo-3-((3- (trifluoromethyl)phenyl)amino)-1,4-dihydronaphthalen-2- yl)thio)acetate (5e), ethyl 2-((1,4-dioxo-3-((3- (trifluoromethyl)phenyl)amino)-1,4-dihydronaphthalen-2- yl)thio)acetate (5f) in reasonable yields. The experiments were carried out at room temperature by addition a base (triethylamine, (C 2 H 5 ) 3 N) as performed in previous studies (52). Chloroform and dichloromethane were used during column chromatography technique for separation and purification of crude products after reactions. A number of spectroscopic methods were utilized to characterize novel compounds of 5a-5f (Scheme 1). In the 1 H NMR spectra, doublets, doublet of doublets, triplets and triplet of doublets at ppm for the aromatic protons of 5a-5f and a singlet at around ppm for the amine hydrogen, quartets at ppm for the CH 2 protons of 5c and 5f which are adjacent to oxygen atom, singlets at ppm for the SCH 2 protons of 5b, 5c, 5e, 5f and quartets at ppm for the -SCH 2 protons of 5a and 5d, triplets at ppm for the methyl protons of 5a, 5c, 5d, 5f and singlets at 3.63 and 3.76 ppm for the methyl protons of 5b and 5e which are adjacent to oxygen atom were assigned. The 13 C NMR spectrum exhibited the peaks of methyl carbons around ppm, methylene carbons around ppm, carbonyl carbons around ppm, carbon-carbon double bond and aromatic carbons around ppm. The structure of novel compounds were also supported by MS results of 5a-5d (377 [M] + ), 5b-5e (421 [M] + ) and 5c-5f (435 [M] + ). The IR spectra of (5a-5f) showed characteristic carbonyl (C=O) signals between 1735 and 1632 cm -1 and (C=C) signals between 1623 and 1522 cm

187 M YILDIZ Academic Platform Journal of Engineering and Science 6-2, , 2018 SH 4a O H N H 2 N 2a CF 3 O H N CH 2 Cl 2 Et 3 N O O 4b SH O 5a O S CF 3 CH 3 H N CH 2 Cl 2 Et 3 N O 3a Cl CF 3 CH 2 Cl 2 Et 3 N O 5b S O CF 3 O O 4c SH O H N OCH 3 O Cl Cl CH 2 Cl 2 Et 3 N O 5c S O O CF 3 O 1 SH 4a O CH 3 H N CF 3 H 2 N 2b CF 3 O H N CH 2 Cl 2 Et 3 N CF 3 O O 4b SH O 5d O S H N CH 3 CF 3 CH 2 Cl 2 Et 3 N O 3b Cl CH 2 Cl 2 Et 3 N O 5e S O O O 4c SH O H N OCH 3 CF 3 CH 2 Cl 2 Et 3 N O S O 5f O CH 3 Scheme 1. Preparation of various thio-substituted amino 1,4-naphthoquinone compounds containing highly electron withdrawing group. 4. CONCLUSION To sum up, novel thio-substituted amino 1,4- naphthoquinone compounds (5a-5f) were synthesized and characterized by IR, 1 H NMR, 13 C NMR, and MS in the present work. Compounds 3a and 3b were also used as precursors in the preparation. Standard conditions were applied during experiments and reasonable yields were obtained. Since the new structures contain electron withdrawing trifluoromethyl group, highly electronegative nitrogen, oxygen and sulfur atoms and well-known role of 1,4-naphthoquinone moiety in pharmaceutical chemistry, it can be expected that novel compounds could potentially exhibit anticancer and antimicrobial biological type of activity. Considering the importance of these type of quinone compounds, future studies are being continued in our laboratory

188 M YILDIZ Academic Platform Journal of Engineering and Science 6-2, , 2018 ACKNOWLEDGMENTS The authors thank to the Scientific Research Projects Coordination Unit of Istanbul University. REFERENCES [1]. G.J. Kapadia, M.A. Azuine, V. Balasubramanian and R. Sridhar, Aminonaphthoquinones-A Novel Class Of Compounds With Potent Antimalarial Activity Against Plasmodium Falciparum Pharmacol. Res., Vol. 43, No. 4, pp , [2]. P.J. O Brien, Molecular mechanisms of quinone cytotoxicity Chem. Biol. Interact., Vol. 80, pp. 1-41, [3]. D.W. Lamson and S.M. Plaza, The anticancer effects of vitamin K Altern. Med. Rev., Vol. 8, pp , [4]. S.T. Huang, H.S. Kuo, C.L. Hsiao and Y.L. Lin, Efficient Synthesis of Redox-Switched Naphthoquinone Thiol-Crown Ethers and Their Biological Activity Evaluation Bioorg. Med. Chem., Vol. 10, pp , [5]. V.K. Tandon, R.B. Chhor, R.V. Singh, S. Rai and D.B. Yadav, Design, synthesis and evaluation of novel 1,4-naphthoquinone derivatives as antifungal and anticancer agents Bioorg. Med. Chem. Lett., Vol. 14, pp , [6]. A.G. Ravelo, A. Estevez-Braun, H. Chavez- Orellana, E. Perez-Sacau and D. Mesa-Siverio, Recent Studies on Natural Products as Anticancer Agents Curr. Top. Med. Chem., Vol. 4, pp , [7]. L.F.C. Medina, V. Stefani and A. Brandell, Use of 1,4-naphthoquinones for control of Erwinia carotovora Can. J. Microbiol., Vol. 50, pp , [8]. T.B. Machado, A.V. Pinto, M.C.F.R. Pinto, I.C.R. Leal, M.G. Silva, A.C.F. Amaral, R.M. Kuster and K.R. Netto-dosSantos, In vitro activity of Brazilian medicinal plants, naturally occurring naphthoquinones and their analogues, against methicillin-resistant Staphylococcus aureus Int. J. Antimicrob. Agents., Vol. 21, pp , [9]. J.J. Inbaraj and C.F. Chignell, Cytotoxic Action of Juglone and Plumbagin: A Mechanistic Study Using HaCaT Keratinocytes Chem. Res. Toxicol., Vol. 17, pp , [10]. G. Meazza, F.E. Dayan and D.E. Wedge, Activity of quinones on Colletotrichum species J. Agric. Food Chem., Vol. 51, , [11]. O. Kayser, A.F. Kiderlen, S.L. Croft, Natural products as antiparasitic drugs Parasitol. Res., Vol.90, pp. S55-62, [12]. Y.R. Jin, C.K. Ryu, C.K. Moon, M.R. Cho and Y.P. Yun, Inhibitory effects of J78, a newly synthesized 1,4-naphthoquinone derivative, on experimental thrombosis and platelet aggregation Pharmacology, Vol. 70, pp , [13]. V.K. Tandon, R.V. Singh, S. Rai, R.B. Chhor and Z.K. Khan, Synthesis and Pharmacological Studies of Some 2-T-Amino and 2,3-Di-T-Amino Substituted 1,4- Naphthoquinones and Related Compounds Boll. Chim. Farm., Vol. 141, pp , [14]. T.V. Ilina, E.A. Semenova, T.R. Pronyaeva, A.G. Pokrovskii, I.V. Nechepurenko, E.E. Shults, O.I. Andreeva, S.N. Kochetkov and G.A. Tolstikov, Inhibition of HIV-1 Reverse Transcriptase by Aryl-Substituted Naphto- and Anthraquinones Dokl. Biochem. Biophys., Vol. 382, pp , [15]. L.J. Huang, F.C. Chang, K.H. Lee, J.P. Wang, C.M. Teng and S.C. Kuo, Synthesis and antiplatelet, antiinflammatory, and antiallergic activities of substituted 3-chloro-5,8-dimethoxy-1,4-naphthoquinone and related compounds Bioorg. Med. Chem., Vol. 6, pp , [16]. J.C. Lien, L.J. Huang, J.P. Wang, C.M. Teng, K.H. Lee and S.C. Kuo, Synthesis and Antiplatelet, Antiinflammatory and Antiallergic Activities of 2, 3- Disubstituted 1, 4-Naphthoquinones Chem. Pharm. Bull., Vol. 44, pp , [17]. J.C. Lien, L.J. Huang, C.M. Teng, J.P. Wang and S.C. Kuo, Synthesis of 2-Alkoxy 1,4-Naphthoquinone Derivatives as Antiplatelet, Antiinflammatory, and Antiallergic Agents Chem. Pharm. Bull., Vol. 50, pp , [18]. K. Sasaki, H. Abe and F. Yoshizaki, In vitro antifungal activity of naphthoquinone derivatives Biol. Pharm. Bull., Vol. 25, pp , [19]. C.Y. Ting, C.T. Hsu, H.T. Hsu, J.S. Su, T.Y. Chen, W.Y. Tarn, Y.H. Kuo, J. Whang-Peng, F. Liu and J. Hwang, Isodiospyrin as a novel human DNA topoisomerase I inhibitor Biochem. Pharmacol., Vol. 66, pp , [20]. Y.H. Zhang, K.H. Chung, C.K. Ryu, M.H. Ko, M.K. Lee and Y.P. Yun, Antiplatelet effect of 2-chloro-3- (4-acetophenyl)-amino-1,4-naphthoquinone (NQ301): a possible mechanism through inhibition of intracellular Ca 2+ mobilization Biol. Pharm. Bull., Vol. 24, pp , [21]. G.Y. Song, Y. Kim, Y.J. You, H. Cho, S.H. Kim, D.E. Sok and B.Z. Ahn, Naphthazarin Derivatives (VI): Synthesis, Inhibitory Effect on DNA Topoisomerase-I and Antiproliferative Activity of 2- or 6-(1-Oxyiminoalkyl)-5,8- dimethoxy-1,4-naphthoquinones Arch. Pharm., Vol. 333, pp , [22]. H.J. Kim, J.Y. Mun, Y.J. Chun, K.H. Choi, S.W. Ham and M.Y. Kim, Effects of a naphthoquinone analog on tumor growth and apoptosis induction Arch. Pharmacal. Res., Vol. 26, pp , [23]. D. Gao, M. Hiromura, H. Yasui and H. Sakurai, Direct reaction between shikonin and thiols induces apoptosis in HL60 cells Biol. Pharm. Bull., Vol. 25, pp , [24]. A. Richwien and G. Wurm, Influence of 2-aryl-3- halogen/3-hydroxy-1,4-naphthoquinones with salicylic and cinnamic acid partial structures on the arachidonic acid cascade Pharmazie, Vol. 59, pp , [25]. G. Wurm and S. Schwandt, Methylated 2-aryl- 1,4-naphtoquinone derivatives with diminished antioxidative activity Pharmazie, Vol. 58, pp , [26]. J.R. Widhalm and D. Rhodes, Biosynthesis and molecular actions of specialized 1,4-naphthoquinone natural products produced by horticultural plants Hortic. Res., Vol. 3, No , pp. 1-17,

189 M YILDIZ Academic Platform Journal of Engineering and Science 6-2, , 2018 [27]. K.W. Wellington, Understanding cancer and the anticancer activities of naphthoquinones - a review RSC Adv., Vol. 5, pp , [28]. R. Munday, B.L. Smith and C.M. Munday, Structure-activity relationships in the haemolytic activity and nephrotoxicity of derivatives of 1,2- and 1,4- naphthoquinone J. Appl. Toxicol., Vol. 27, pp , [29]. L.O. Klotz, X. Hou and C. Jacob, 1,4- Naphthoquinones: From Oxidative Damage to Cellular and Inter-Cellular Signaling Molecules, Vol.19, pp , [30]. V.J. Bulbule, P.S. Koranne, Y.S. Munot, H.B. Borate and V.H. Deshpande, Simple Synthesis of Two Naphthoquinone Antibiotics Psychorubrin and Pentalongin Synth. Commun., Vol.33, No. 4, pp , [31]. S. Claessens, G. Verniest, J. Jacobs, E.V. Hende, P. Habonimana, T.V. Van, L.V. Puyvelde and N. De Kimpe, A Survey of Synthetic Routes towards the Pyranonaphthoquinone Antibiotic Pentalongin and Syntheses of the Corresponding Nitrogen Derivatives Synlett, Vol. 6, pp , [32]. S.P. Devi, S. Kumaria, S.R. Rao and P. Tandon, Carnivorous Plants as a Source of Potent Bioactive Compound: Naphthoquinones Tropical Plant Biol., Vol. 9, pp , [33]. A. Geronikaki, M. Fesatidou, V. Kartsev and F. Macaev, Synthesis and Biological Evaluation of Potent Antifungal Agents Curr. Top. Med. Chem., Vol. 13, pp , [34]. A.K. Jordão, M.D. Vargas, A.C. Pinto, F.C.D. Silva and V.F. Ferreira, Lawsone in organic synthesis RSC Adv., Vol. 5, pp , [35]. A.T. Mbaveng, V. Kuete and T. Efferth, Potential of Central, Eastern and Western Africa Medicinal Plants for Cancer Therapy: Spotlight on Resistant Cells and Molecular Targets Front. Pharmacol., Vol. 8, No. 343, pp. 1-31, [36]. C. Müller, A. Bauer and T. Bach, Chirogenic [3 + 2]-photocycloaddition reactions of 2-substituted naphthoquinones with cyclic alkenes Photochem. Photobiol. Sci., Vol.10, pp , [37]. K. Nakagawa, New Developments in Research on Vitamin K Biosynthesis J. Health Sci., Vol. 56, No. 6, pp , [38]. M. Suzuki, S. Neya and Y. Nishigaichi, Synthesis of 5,10-bis(Trifluoromethyl) Substituted β- Octamethylporphyrins and Central-Metal-Dependent Solvolysis of Their meso-trifluoromethyl Groups Molecules, Vol. 21, No. 2529, pp. 1-8, [39]. J. Zhu, M. Pérez, C.B. Caputo and D.W. Stephan, Use of Trifluoromethyl Groups for Catalytic Benzylation and Alkylation with Subsequent Hydrodefluorination Angew. Chem. Int. Ed., Vol. 55, pp , [40]. G. O Mahony and A.K. Pitts, Synthesis of Tertiary Amides from Anionically Activated Aromatic Trifluoromethyl Groups Org. Lett., Vol. 12, No. 9, pp , [41]. Y. Kobayashi and I. Kumadaki, Reactions of Aromatic Trifluoromethyl Compounds with Nucleophilic Reagents Acc. Chem. Res., Vol. 11, pp , [42]. X. Yang, T. Wu, R.J. Phipps and F.D. Toste, Advances in Catalytic Enantioselective Fluorination, Mono-, Di-, and Trifluoromethylation, and Trifluoromethylthiolation Reactions Chem. Rev., Vol. 115, pp , [43]. M.G. Campbell and T. Ritter, Modern Carbon Fluorine Bond Forming Reactions for Aryl Fluoride Synthesis Chem. Rev., Vol. 115, pp , [44]. C.N. Neumann and T. Ritter, Late-stage fluorination: fancy novelty or useful tool? Angew. Chem. Int. Ed., Vol. 54, pp , [45]. J. Li, X. Zhang, H. Xiang, L. Tong, F. Feng, H. Xie, J. Ding and C. Yang, C-H Trifluoromethylation of 2 Substituted/Unsubstituted Aminonaphthoquinones at Room Temperature with Bench-Stable (CF 3 SO 2 ) 2 Zn: Synthesis and Antiproliferative Evaluation J. Org. Chem., Vol. 82, pp , [46]. H. Yildirim, N. Bayrak, A.F. Tuyun, E.M. Kara, B.O. Celik and G.K. Gupta, 2,3-Disubstituted-1,4- naphthoquinones Containing an Arylamine with Trifluoromethyl Group: Synthesis, Biological Evaluation, and Computational Study RSC Advances, Vol. 7, No. 378, pp , [47]. N. Bayrak, Novel Straight-chained Sulfanyl Members of Arylamino-1,4-naphthoquinones: Synthesis and Characterization JOTCSA, Vol. 4, No. 2, pp , [48]. H. Yildirim, Synthesis and Structural Analysis of Some New Sulfanyl Amino 1,4-Naphthoquinone Derivatives JOTCSA, Vol. 5, No. 1, pp , [49]. A.F. Tuyun, N. Bayrak, H. Yildirim, N. Onul, E.M. Kara and B.O. Celik, Synthesis and In Vitro Biological Evaluation of Aminonaphthoquinones and Benzo[b]phenazine-6,11-dione Derivatives as Potential Antibacterial and Antifungal Compounds J. Chem., pp , [50]. R. Buu-Hoi NPR and M. Hubert-Habart, Empêchement stérique dans la réaction des amines sur les quinones halogénées Recl. Trav. Chim. Pay. B., Vol. 73, pp , [51]. M. Mital AS, S. Bindal, S. Mahlavat and V. Negi, Substituted 1,4-naphthoquinones as a new class of antimycobacterial agents Der Pharma Chem, Vol. 2, pp , [52]. V.K. Tandon, H.K. Maurya, N.N. Mishra and P.K. Shukla, Design, synthesis and biological evaluation of novel nitrogen and sulfur containing hetero-1,4- naphthoquinones as potent antifungal and antibacterial agents Eur. J. Med. Chem., Vol. 44, pp ,

190 Academic Platform Journal of Engineering and Science 6-2, , 2018 Academic Platform Journal of Engineering and Science journal homepage: Optimization of Solid Particle Erosion by ZrN Coating Applied Fiber Reinforced Composites by Taguchi Method Abstract Mehmet Bağcı( X) Selcuk University, Engineering Faculty, Mechanical Engineering Department, Konya, Turkey / Received Date: Accepted Date: In this study, ZrN coatings are applied on glass and carbon fiber reinforced epoxy composite materials by magnetron sputtering method to gain an improved understanding of the solid particle erosion (SPE) wear resistance. The tests were carried out by selecting two different impact velocities (34, 53 m/s), four different impingement angles (30, 45, 60, 90 ) and two different abrasive (SiO 2 ) particle sizes (approximate 250, 500 m). The thickness of ZrN coating material was 0.15 m. Protective coatings produced by using Physical Vapor Deposition (PVD) method can increase the life time of the components. All test specimens regardless of their various parameter properties exhibit maximum erosion rates at 45 impingement angle and thus exhibiting similar behavior as that observed for semi ductile materials. Optic microscopic views were performed on the surfaces in order to characterize the erosion mechanism. The erodent particles of the both coating layer and composite matrix were found of main role in governing the wear progression. The measured erosion rates were sensitively correlated with the material removal process in order to explain the changes within the coated interfaces. Moreover, an erosion test facility at room temperature and Taguchi s orthogonal arrays were used for experimentation. The expression derived from the results of Taguchi experimental design is proposed as a predictive equation for estimation of erosion rate of these composites. It is demonstrated that the predicted results from this equation are consistent with the experimental observations. Finally, an optimal parameter combination was determined, which led to minimization of erosion rate (ER). Keywords: ZrN, Magnetron Sputtering, SPE, PVD, Taguchi. 1. INTRODUCTION The advanced science and technology world needed materials with superior features for better operational performance. In parallel with such needs, the precious and industrial use of composite materials has greatly increased. The main reason for this is that the glass and carbon fiber reinforced composite materials have high strength, better coating properties and are economical at the same time. In the meantime, advanced scientific research on these materials is being carried out gradually. Erosion wear occurs when solid particles moving at a certain speed strike a surface and some materials are removed from the top surface. The characteristics of the target material as well as the impact angle, velocity, size and shape of the particles impacting the surface are important variables affecting solid particle erosion wear. The rough and sensitive areas such as the spacecraft industry, energy conversion systems, jet engines, helicopter rotor blades, and the effects of erosion wear on coal mine sites have prompted researchers to further investigate this type of wear. In terms of lightness and strength with the increasing use of coated polymer *Corresponding Author: Selcuk University, Engineering Faculty, Mechanical Engineering Department, Konya, Turkey, / / Doi: /apjes composites in erosive working environments, it has become extremely important to investigate erosion properties intensively. Because of many variables are not able to process a single variant, alternative additives and coating materials have been derived in research aimed at actual erosion mechanism models. Many researchers have been interested in the solid particle erosion behavior of metal, polymer and their composite materials worn by erodent. While fiber reinforced polymers take place in most of the studies conducted on erosion of composites, studies involving erosion on composites with coating materials can hardly be encountered. The poor erosion wear resistance of thermoplastic composites causes severe problems if the material is subjected to solid particle erosion. To overcome this problem, erosion wear resistant magnetron sputtered PVD coatings were deposited on glass and carbon fiber reinforced epoxy substrates. This is due to the fact that it is not easy to clearly understand wear mechanisms of these types of composites, properties of their components and their interface interactions.

191 M BAĞCI Academic Platform Journal of Engineering and Science 6-2, , 2018 In this area of research, additive materials were generally developed for ductile and brittle materials and in case single abrasive particle or multiple abrasive particles track the surface. Bagci [1] described the development of unidirectional and multidirectional laminated composites consisting of thermoplastic epoxy resin reinforced with glass/carbon fiber, and studies their solid particle erosion behavior under different operating conditions. The erosion rates of the unidirectional carbon fiber/epoxy composites [0, 30, 45, 60, 90 ] and multidirectional glass fiber/epoxy composites ([0 /-90 /0 ], [30 /-60 /30 ], [45 /- 45 /45 ], [60 /-30 /60 ], [90 /0 /90 ]) were especially scrutinized based on their respective fiber orientations. An optimal fiber orientation combination was determined, which led to minimization of the erosion rate. Kumar et al. [2] investigated the application of Taguchi s experimental design methodology to determine the erosion wear behavior of in situ -formed A356-5TiB 2 composite subjected to thixo-forming. The results indicated that impact velocity is the most significant factor and accounts for 42.31% of the total effect on the erosion rate of the thixo-formed A356-5TiB2 composite. It is found that material loss during erosive wear is primarily due to micro ploughing (i.e., abrasive type) and micro fracture (i.e., impact type). Biswas and Satapathy [3] scrutinized a mathematical model for estimating erosion damage caused by solid particle impact on red mud filled glass fiber reinforced epoxy matrix composites and also found a correlation derived from the results of Taguchi experimental design. The filler content in the composites, erodent temperature, the impact angle and velocity are found to have substantial influence in determining the rate of material loss from the composite surface due to erosion. Jena et al. [4] investigated SPE wear behavior of bamboo fiber-reinforced epoxy composite with cenosphere filler. The present composites consisting of varying weight percentage of fibers and cenosphere fillers were prepared by hand lay-up technique. The study reveals that addition of cenosphere filler to the bamboo epoxy composite reduces its erosion wear rate. Deshpande and Rangaswamy [5] developed E-glass/jute fiber reinforced epoxy composites with an addition of Al 2 O 3 and bone powder by using hand-lay-up technique and to compare tribological properties of these composites under similar test conditions. The wear experiments were designed according to Taguchi s (L 27 ) orthogonal array. The results indicated that the normal load for Al 2 O 3 and filler content for bone powder emerged as the significant factors affecting specific wear rate of hybrid composites. Studies continued with Bagci s [6] development of a multicomponent composite system consisting of thermoplastic epoxy resin reinforced with E glass fiber and (Al 2 O 3 +SiO 2 ) particles, and studies its erosion behavior under different operating conditions. With this target in mind, this empirical study investigates the solid particle erosion wear behavior of a new composite material made of glass fiber and epoxy as the main materials and (Al 2 O 3 +SiO 2 ) particles added into the structure at the amount of 30% [15% (Al 2 O 3 ) + 15% (SiO 2 )] of the resin used for the composite. Andreska and et al. [7] investigated the erosion resistance of the galvanic coating the polymer composites examined at two different impact angles and particle impinging velocity. The coatings showed a ductile erosion mechanism under all testing conditions. A higher particle velocity did not change this mechanism, but reduced the time to coating failure. At perpendicular impact angle, the coatings failed through delamination, while this effect was not observed at 20º where failure occurred by local complete removal from the substrate. In the present study, two different ZrN coating thickness are applied on GF/EP and CF/EP by magnetron sputtering to gain an improved understanding of the erosion resistance. All test specimens regardless of their various properties exhibit maximum erosion rates at 45 impingement angle and thus exhibiting similar behavior as that observed for semi ductile materials. Firstly, pure chrome coating is applied on the GF/EP and CF/EP composites to increase the adhesion of the zirconium nitride to the surface. An erosion test facility at room temperature and Taguchi s orthogonal arrays were used for experimentation. Moreover, the surface topography of the eroded composites was investigated by an optical microscope and a non-contact 3D digital mapping method. 2. DESCRIPTION OF THE TAGUCHI METHOD Genichi Taguchi has developed a methodology for the application of designed experiments. This methodology has taken the design of experiments from the exclusive world of the statistician and brought it more fully into the world of manufacturing. His contributions have also made the practitioner work simpler by advocating the use of fewer experimental designs, and providing a clearer understanding of the variation nature and the economic consequences of quality engineering in the world of manufacturing [8]. Taguchi introduces his approach, using experimental design in order to obtain products or processes that are robust with respect to environmental conditions. The approach also helps to cope with component variations during development of the products/processes. In addition; the Taguchi method plays an important role in minimizing variation around a targeted value of a product/process [9]. The philosophy of Taguchi is broadly applicable. He proposed that engineering optimization of a process or product should be carried out in a three-step approach, i.e., system design, parameter design, and tolerance design. In system design, the engineer applies scientific and engineering knowledge to produce a basic functional prototype design; this design includes the product design 186

192 M BAĞCI Academic Platform Journal of Engineering and Science 6-2, , 2018 stage and the process design stage. In the product design stage, the selection of materials, components, tentative product parameter values, etc., are involved. As to the process design stage, the analysis of processing sequences, the selections of production equipment, tentative process parameter values, etc., are involved. Since system design is an initial functional design, it may be far from optimum in terms of quality and cost. The objective of the parameter design [10] is to optimize the settings of the process parameter values for improving performance characteristics and to identify the product parameter values under the optimal process parameter values. In addition, it is expected that the optimal process parameter values obtained from the parameter design are insensitive to the variation of environmental conditions and other noise factors. Therefore, the parameter design is the key step in the Taguchi method to achieving high quality without increasing cost. Basically, classical parameter design, developed by Fisher [11], is complex and not easy to use. Especially, a large number of experiments have to be carried out when the number of the process parameters increases. To solve this task, the Taguchi method uses a special design of orthogonal arrays to study the entire parameter space with a small number of experiments only. A loss function is then defined to calculate the deviation between the experimental value and the desired value. Taguchi recommends the use of the loss function to measure the performance characteristic deviating from the desired value. The value of the loss function is further transformed into a Signal-to-Noise (S/N) ratio η. There are three categories of the performance characteristic in the analysis of the S/N ratio, that is, the lower-the-better, the higher-the-better, and the nominal-the-better. The S/N ratio for each level of process parameters is computed based on the S/N analysis. Regardless of the category of the performance characteristic, the larger S/N ratio corresponds to the better performance characteristic. Therefore, the optimal level of the process parameters is the level with the highest S/N ratio η. Furthermore, a statistical analysis of variance (ANOVA) is performed to see which process parameters are statistically significant. With the S/N and ANOVA analyses, the optimal combination of the process parameters can be predicted. Finally, a confirmation experiment is conducted to verify the optimal process parameters obtained from the parameter design. In this paper, the erosion parameter design by the Taguchi method is adopted to obtain optimal erosion performance in wear. Lower-the-better; S / N L 10 * log 1 n * 2 y (1) Nominal-the-better; S / N N 10 * log Higher-the-better: S / N H where n is the number of observations; y is the observed data; y A is the average of observed data; and S y 2 is the variance of y. Notice that these S/N ratios are expressed on a decibel scale. We would use S/N N if the objective is to reduce variability around a specific target, S/N H if the system is optimized when the response is as high as possible, and S/N L if the system is optimized when the response is as low as possible. Factor levels that maximize the appropriate S/N ratio are optimal. The goal of this research is to produce minimum erosion rate (ER) in a wear operation. Lower ER values represent better or improved erosion rate. Therefore, a lower-the-better quality characteristic was implemented and introduced in this study. The use of the parameter design of the Taguchi method to optimize a process with multiple performance characteristics includes several steps [12], like identifying performance characteristics together by selecting process parameters to be evaluated, determining the number of levels for the process parameters and possible interactions between the process parameters. Another step is to select an appropriate orthogonal array and assignment of process parameters to the array. This also involves conducting the experiments based on the arrangement of the orthogonal array. On top of that, it is important that the total loss function and S/N ratio are calculated. The calculated S/N ratio together with ANOVA can be used for analysis of the experimental results. Another important step is to select optimal levels of process parameters and finally; the selected optimal process parameters should be verified through a confirmation experiment. 3. EXPERIMENTAL PROCEDURE 3.1 Test Materials 10 * log y A S 2 y 1 n 1 * 2 y In this experimental study, the unidirectional CF/EP and multidirectional GF/EP composites were used as substrate (2) (3) 187

193 M BAĞCI Academic Platform Journal of Engineering and Science 6-2, , 2018 materials and industrially produced at Izoreel Composite Insulating Materials, a Turkish Materials Company where hand lay-up technique is used to fabricate the composites. Fibers with diameter of 17 μm, thickness of 0.20 mm and mass per unit area of 200 g/m 2 arranged in a uni/multi directional location provide homogeneously distributed fibers in the matrix form. All test specimens were produced as plates by hand layup technique (110 Bar pressure, 120 C temperature and a time of 3 top of the hour) with a thickness of 3 mm and dimensions of (1x1m 2 ). Then, to enable the attachment of specimens to the holder, a diamond-impregnated slitting saw was used to cut notches on the samples with size of mm 3 from the manufactured composite plate for the erosion tests. Mechanical properties were evaluated as per the ASTM standards and given in Table 1 and abbreviations are used. In Figure 1 and Table 2, respectively, optic microscope views of SiO 2 erodent and chemical compositions of these particles are shown. As the test specimens are deformed due to particle bombardments, the abrasive particles also undergo some deformations and fractures. To prevent this condition from affecting the tests conducted, fresh particles were used in each test. Table 1. Mechanical properties of the test specimens. Material GF/EP (uncoated) GF/EP (ZrN coated) CF/EP (uncoated) CF/EP (ZrN coated) g/cm 3 t MPa H HB E MPa (b) Figure 1. Optic microscopic views of SiO 2 abrasive particles; (a) 250 m and (b) 500 m. Table 2. Chemical compositions of SiO 2 abrasive particles (% weight). Content Minimum Maximum % Humidity 3 8 % Clay % SiO % Fe 2 O % Al 2 O In addition to all these details which define the test specimens, as shown in Figure 2, the X-ray diffraction patterns were obtained in order to prove the presence of the glass/carbon fibre and epoxy. A sharp peak at 2θ=17.6 for glass fibre and at 2θ=26.9 for carbon fibre can be distinguished. However; a different diffraction pattern is observed for epoxy resin in which a broad peak appears around 2θ=21.5. The observed peaks for GF, CF and EP indicate that all the layers have been sufficiently disordered. (a) Figure 2. XRD patterns of test specimens. 188

194 M BAĞCI Academic Platform Journal of Engineering and Science 6-2, , ZrN Coating Process Physical Vapor Deposition (PVD) is a collective set of processes used to deposit thin layers of material, typically in the range of few nanometers to several micrometers [13]. PVD processes are environmentally friendly vacuum deposition techniques consisting of three fundamental steps; Vaporization of the material from a solid source assisted by high temperature vacuum or gaseous plasma. Transportation of the vapor in vacuum or partial vacuum to the substrate surface. Condensation onto the substrate to generate thin films. Different PVD technologies utilize the same three fundamental steps but differ in the methods used to generate and deposit material (for example TiN, ZrN, CrN, CrCN, TiAlN). The two most common PVD processes are thermal evaporation and magnetron sputtering. Thermal evaporation is a deposition technique that relies on vaporization of source material by heating the material using appropriate methods in vacuum. Magnetron sputtering is a plasma-assisted technique (Figure 3) that creates a vapor from the source target through bombardment with accelerated gaseous ions (typically Argon). transportation stage by introducing a reactive gas (nitrogen, oxygen or simple hydrocarbon containing the desired reactant), and post-deposition modification through thermal or mechanical processing [15]. PVD is used in a variety of applications, including fabrication of microelectronic devices, interconnects, battery and fuel cell electrodes, diffusion barriers, optical and conductive coatings, and surface modifications [16-18]. Zirconium nitride (ZrN) is an inorganic compound used in a variety of ways due to its properties. ZrN grown by PVD is a light gold color similar to elemental gold. The hardness of single-crystal ZrN is 22.7±1.7 GPa, elastic modulus is 450 GPa and density is 7.09 g/cm3. Zirconium nitride is a hard ceramic material similar to titanium nitride and is a cement-like refractory material. Thus it is used in refractories, cermets and laboratory crucibles. When applied using the physical vapor deposition coating process it is commonly used for coating medical devices, industrial parts, automotive and aerospace components and other parts subject to high wear and corrosive environments. on glass and carbon fiber reinforced epoxy (CF/EP) composites by magnetron sputtering were produced at Ionbond Turkey where PVD, CVD and PACVD techniques are used to fabricate the coating materials. In both evaporation and sputtering, the resulting vapor phase is subsequently deposited onto the desired substrate through a condensation mechanism [14]. Deposited films can span a range of chemical compositions based on the source material(s). Figure 3. Schematic view of the magnetron sputtering system. Further compositions are accessible through reactive deposition processes. Relevant examples include codeposition from multiple sources, reaction during the 189

195 M BAĞCI Academic Platform Journal of Engineering and Science 6-2, , SPE Test Equipment composite plate for the erosion tests. All edges cut were finished using a fine SiC paper. The distance from specimen surface to nozzle end was 10 1 mm as described in ASTM G76-95 standards [20]. The standard test process was performed in accordance with ASTM G76-95 for each erosion test. Erosion wear losses in the test specimen with an electronic balance on accuracy of 0.1 mg was measured. Then 25 kg of erodent particles were spurted on the specimen and then, the latter was weighed again to determine its weight loss. At the same time, these measurements as well as volumetric losses occurring in the test sample for detecting the digital map method of the surfaces is simulated using the point cloud and the mesh modeling. In addition, volumetric losses occurring in the test sample was determined. Surface mapping of the numerical method for three-dimensional (3D) scanning has been used on the Figure 5. Weight loss and volumetric loss changes of a similar trend has emerged in terms of the comparison of results. Figure 4. Test device for solid particle erosion wear. The erosion test equipment used in this scientific study (Figure 4) which was specifically designed for the tests consists of upper and lower particle tanks, universal valves, manometers, flow and pressure regulators, nozzle, specimen holder, particle collecting basin and a compressor. The impact velocity of the particles can be varied by varying the pressure of the compressed air. In order to determine the velocity of the eroding particles, the most common method [19] was used previously. The particles impact velocities used in the tests (34 and 53 m/s) were adjusted by using the double disc method. Dry compressed air is mixed with the particles, which are fed at a constant rate from the sand hopper into the pressurized particle tank and then accelerated by a compressor thereby forcing the mixture through a WC converging nozzle of 8 mm diameter. These accelerated particles impact the specimen, which can be held at various angles with respect to the impacting particles using an adjustable sample holder. A diamond-impregnated slitting saw was used to cut test specimens with size of mm 3 from the manufactured (a) (b) 190

196 M BAĞCI Academic Platform Journal of Engineering and Science 6-2, , 2018 Figure 6 shows the effects of all four control factors with their corresponding levels. This figure clearly indicates how coating material, impingement angle, impact velocity and erodent size change. This experimental study has shown that the most effective influence on erosion rate appears due to variations on the impingement angle used for the specimens. The variation of coating materials follows suit after this parameter. It was found that any changes in these angles caused significant variations on erosion rates. These first two parameters were followed by erodent size and impact velocity which played a determining role in increasing erosion rates. (c) Figure 5. The digital map method of the surfaces; (a) Point cloud with OPTOCAT, (b) Mesh modeling with Rapidform XOR/ Redesign, (c) Volumetric loss with CatalystEX. 3.4 Taguchi Method The design parameters of the system to be studied are known as the control factors or design variables, which mainly affect the output of the objective function [21 22]. In this study, four parameters, namely coating material, impact velocity, impingement angle and erodent size are determined as the control factors which significantly affect the performance of ER. Moreover, an L 16 ( ) orthogonal array was used in this study and the results of the experiments are reported in the completed design layout as seen in Table 3.Analysis of the influence of each solid particle erosion parameter was performed by using MINITAB 17. Based on Eq.(1), having obtained the S/N L ratios, the effect of each factor level on the quality characteristic is studied. Table 3. Experimental layout and results using an L 16 ( ) orthogonal array. Figure 6. Main effects of control factors on ER. The best erosion rate value is at the higher S/N L ratios on the response graph. Optimal testing conditions of these control factors can be very easily determined from the S/N L response table. The table of the erosion rate for test specimens is presented in Table 4. Level Table 4. Response table for S/N L ratios. Coat. Mat. Imp. Ang Imp. Vel. Erod. Size 1-20,72-27,54-21,90-20, ,23-28,37-21,77-22, ,83-17, ,55-13,71 Delta 2,83 14,67 0,12 1,71 Rank The final step was to verify the improvement of the quality characteristic using the optimal levels of the design parameters (A1B4C2D1). 191

197 M BAĞCI Academic Platform Journal of Engineering and Science 6-2, , 2018 Using the optimal level of the erosion parameters, the estimated S/N L ratio, η can be calculated as; q η = η m + i=1 (η i η m ) (4) where η m is the total mean of the S/N L ratio, η i is the mean S/N L ratio at the optimal level and q is the number of the main design parameters that significantly affect the performance characteristic. Table 5 shows a comparison of the predicted erosion rate with the experimental ER using the optimal wear values. The increase in the S/N L ratio from initial wear values to optimal wear values was about db, which meant that the erosion rate was increased by about 4.38 times. Therefore, based on the S/N L ratio analysis, the optimal wear values for the erosion rate with ZrN coating materials added GF/EP composites were in this order, the coating material (A) at level 1, the impingement angle (B) at level 4, the impact velocity (C) at level 2 and the fiber direction (D) at level 1. Table 5. Results of the confirmation experiment When deposited on GF/CF, electro plated coatings require extensive pre-treatment processes to create conductivity and to ensure adhesion. Coatings produced by thermal spraying can increase the surface roughness and an additional post-treatment may be needed to guarantee adequate flow conditions at the surface. In contrast, simple processing can be realized by PVD methods. When the tests are analyzed it is seen that regardless of the fact the results is at different materials, the specimens in both sets of results seem to undergo much erosion rates at impingement angle of 45. Together with this, it has also been observed that, parallel to the increase of the impingement angles (60 90 ), the erosion rates tend to reduce abruptly. This situation shows that, a similar erosion trend is observed as that seen in literature for semi ductile materials [23-24]. It was determined that beside the remarkable effects of ZrN coating material also have considerable effects on solid particle erosion wear. From the experimental result data, it is seen that the effects of the GF/EP composites with ZrN coated on SPE wear are more evident than those of the CF/EP composites with ZrN coated Initial Wear values Optimal wear values Experiment Prediction When the results and optical microscope views based on the tests done are studied, it is seen that GF/EP and CF/EP of the ZrN coating material have had positive and negative effects respectively on erosion. Level A1B1C1D1 A1B4C2D1 A1B4C2D1 ER 17,424 3,978 3,83 S/N L -24,82-11,99-11,67 *Improvement of S/N L ratio = db 4. RESULTS AND DISCUSSION To ensure a sufficient lifetime of glass/ carbon fiber reinforced epoxy components which are exposed to solid particle erosion, protective coatings are needed. Metallic coatings on composites are mainly produced by electro plating, thermal spraying, or PVD. This condition though can be perfectly recognized from the results, the microscope views also indicate extensive surface resistivity for the specimens with GF/EP. ZrN coating material adhered to the GF/EP substrate surface and reacted to the attack of abrasive particles. But CF/EP composites could not match with ZrN coating materials and the surface resistance is weakened. The optical microscope views in Figure 7 show variations of erosion rates with test specimens (uncoated and ZrN coated composites) at impingement angles of 45 with an impact velocity of 53 m/s where the slightly rounded SiO 2 abrasive particles used had average diameters of 400 µm. 192

198 M BAĞCI Academic Platform Journal of Engineering and Science 6-2, , 2018 (a) (c) (b) (d) Figure 7. Optical microscope view of test specimens; (a) GF/EP (uncoated), (b) GF/EP (ZrN coated), (c) CF/EP (uncoated), (d) CF/EP (coated). 5. CONCLUSIONS This paper has presented the parameter design of the Taguchi method provides a simple, systematic and efficient methodology for the optimization of the erosion wear parameters. Taguchi s robust orthogonal array design method is suitable for analyzing the erosion rate as described in this paper. It was found that material removal from the surfaces of the test specimens as a result of solid particle erosion wear took place at several different stages. First of all, micro cracking appeared on the surfaces as the particles stroked the surface and as the particle bombardments continued material delamination took place over the affected areas. The structural bonds got damaged as the particles kept striking the surfaces. Due to this damage, the rate of material delamination off the surfaces increased. Consequently; the cracks and grooves on the surfaces became more vivid. It has been observed that the application of coating to the materials caused the differentiation of these processes. According to the experimental results, The L 16 ( ) orthogonal arrays were adopted to investigate the effects of impingement angle, impact velocity and erodent size on the solid particle erosion wear of four different fiber reinforced epoxy composites. According to S/N L response table, the most significant factor in affecting the erosion rate is the impingement angle, followed by the coating materials, erodent size and impact velocity. ZrN coated and uncoated composites exhibit maximum erosion rates at 45⁰ impingement angle and thus exhibiting similar behavior as that observed for semi ductile materials. Parallel to the increase of a impinging angle, the values of erosive wear rates dropped. Inclusion of ZrN coating material in GF/EP composites considerably increases the value of hardness, tensile strength, modulus of elasticity and density. The erosion rate of ZrN coated GF/EP gives the lower value as it restricts surface delamination. GF/EP composites without any coated show the upper erosion rate due to weak bonding strength. In CF/EP composites, it decreased the erosion resistance due to the thermal and physical effects applied to the surface. The difference in erosion of GF/EP and CF/EP materials should be even higher. The difference in fiber orientations has been influential in this case. Experience 193