Authors:Bahriye Basturk Akay, Dervis Karaboga Pages: 98 - 111 Abstract: Optimization problems are generally classified into two main groups:unconstrained and constrained. In the case of constrainedoptimization, special techniques are required to handle withconstraints and produce solutions in the feasible space. Intelligentoptimization techniques that do not make assumptions on the problemcharacteristics are preferred to produce acceptable solutions to theconstrained optimization problems. In this study, the performance ofartificial bee colony algorithm (ABC), one of the intelligentoptimization techniques, is investigated on constrained problems andthe effect of some modifications on the performance of the algorithmis examined. Different variants of the algorithm have been proposedand compared in terms of efficiency and stability. Depending on theresults, when DE operators were integrated into ABC algorithm'sonlooker phase while the employed bee phase is retained as in ABCalgorithm, an improvement in the performance was gained in terms ofthe best solution in addition to preserving the stability of thebasic ABC. The ABC algorithm is a simple optimization algorithm thatcan be used for constrained optimization without requiring a prioriknowledge. PubDate: 2017-01-12 Issue No:Vol. 7, No. 1 (2017)

Authors:Ali Akgül, Mustafa Inc, Dumitru Baleanu Pages: 112 - 116 Abstract: Numerical calculation of the fractional integrals and derivatives is the code to search fractional calculus and solve fractional differential equations. The exact solutions to fractional differential equations are compelling to get in real applications, due to the nonlocality and complexity of the fractional differential operators, especially for variable-order fractional differential equations. Therefore, it is significant to enhanced numerical methods for fractional differential equations. In this work, we consider variable-order fractional differential equations by reproducing kernel method. There has been much attention in the use of reproducing kernels for the solutions to many problems in the recent years. We give two examples to demonstrate how efficiently our theory can be implemented in practice. PubDate: 2017-01-20 Issue No:Vol. 7, No. 1 (2017)

Authors:Eren Özceylan, Ayşenur Uslu, Mehmet Erbaş, Cihan Çetinkaya, Selçuk Kürşat İşleyen Pages: 117 - 129 Abstract: It is a known fact that basic health care services cannot reach the majority of the population due to poor geographical accessibility. Unless quantitative location-allocation models and geographic information systems (GIS) are used, the final decision may be made on pragmatic considerations which can result far from optimal. In this paper, current and possible (or potential) new locations of pharmacy warehouses in Gaziantep are investigated to provide optimal distribution of hospitals and pharmacies. To do so, first of all, geographic information of 10 current and 10 potential pharmacy warehouses, 231 pharmacies and 29 hospitals are gathered using GIS. Second, a set covering mathematical model is handled to determine coverage capability of current and potential pharmacy warehouses and minimize the number of warehouses to be opened. Finally, P-center and P-median mathematical models are applied to open potential warehouses and to assign pharmacies & hospitals to the opened warehouses so that the total distance and the demand’s longest distance to the source are minimized. Developed integer programming (IP) models and GIS software are compared with on a case study. Computational experiments prove that our approach can find new potential pharmacy warehouses which cover wider areas than current warehouses to service pharmacies and hospitals in the city. PubDate: 2017-01-20 Issue No:Vol. 7, No. 1 (2017)

Authors:Erkan Celik, Nezir Aydin, Alev Taskin Gumus Pages: 1 - 15 Abstract: This paper aims to decide on the number of facilities and their locations, procurement for pre and post-disaster, and allocation to mitigate the effects of large-scale emergencies. A two-stage stochastic mixed integer programming model is proposed that combines facility location- prepositioning, decisions on pre-stocking levels for emergency supplies, and allocation of located distribution centers (DCs) to affected locations and distribution of those supplies to several demand locations after large-scale emergencies with uncertainty in demand. Also, the use of the model is demonstrated through a case study for prepositioning of supplies in probable large-scale emergencies in the eastern and southeastern Anatolian sides of Turkey. The results provide a framework for relief organizations to determine the location and number of DCs in different settings, by using the proposed model considering the main parameters, as; capacity of facilities, probability of being affected for each demand points, severity of events, maximum distance between a demand point and distribution center. PubDate: 2016-10-11 Issue No:Vol. 7, No. 1 (2016)

Authors:Vildan Cetinsaya Özkır Pages: 16 - 27 Abstract: The technological advances decrease electrical/electronic product lifecycles and boost consumption of high-tech products. The rapid growth in the electronic market produces electronic waste streams and potential threats arise on sustainability in terms of depleting natural resources and improper disposal. End-of-life electrical/electronic equipment (EEEs) involves complex mixture of materials, has hazardous content, and if not properly disposed, they can cause major environmental and health problems. To prevent the consequences of improper disposal, authorities and researchers conduct large-scale projects aligned with European union legislations. However, these efforts are still not sufficient to establish effective and organized systems due to the problem complexity and the need for specialized arrangements. This study proposes conceptual decision support framework and a bi-objective mathematical model to construct an effective collection network for end-of-life mobile phones. A real case study is presented for constructing an effective collection system in Istanbul. The main reason that we select Istanbul, is the requirement of urgency to deal with the large quantities of e-wastes. The result of this study will encourage academicians to conduct further research studies and strongly assist the authorities to configure well-structured e-waste collection system. PubDate: 2016-10-12 Issue No:Vol. 7, No. 1 (2016)

Authors:Olcay Alpay, Elvan Aktürk Hayat Pages: 28 - 34 Abstract: Determination of the input/output variables is an important issue in Data Envelopment Analysis (DEA). Researchers often refer to expert opinions in defining these variables. The purpose of this paper is to propose a new approach to determine the input/output variables, it is important to keep in mind that especially when there is no any priori information about variable selection. This new proposed technique is based on a theoretical method which is called “Copula”. Copula functions are used for modeling the dependency structure of the variables with each other. Also we use the local dependence function which analyzes the point dependency of variables of copulas to define the input/output variables. To illustrate the usefulness of the proposed approach, we conduct two applications using simulated and real data and compare the efficiencies in DEA. Our results show that new approach gives values close to perfection. PubDate: 2016-10-25 Issue No:Vol. 7, No. 1 (2016)

Authors:Görkem Sarıyer Pages: 35 - 41 Abstract: Service providers can adjust the entrance price to the state of the demand in real life service systems where the customers' decision to receive the service, is based on this price, state of demand and other system parameters. We analyzed service provider's short and long term pricing problems in unobservable M/M/1 queues having the rational customers, where, for customers, the unit cost of waiting in the queue is higher than unit cost of waiting in the service. We showed that waiting in the queue has a clear negative effect on customers’ utilities, hence the service provider's price values. We also showed that, in the short term, monopolistic pricing is optimal for congested systems with high server utilization levels, whereas in the long term, market capturing pricing is more profitable. PubDate: 2016-11-01 Issue No:Vol. 7, No. 1 (2016)

Authors:Seyma Tuluce Demiray, Hasan Bulut Pages: 42 - 49 Abstract: This study is based on new soliton solutions of the system of equations for the ion sound wave under the action of the ponderomotive force due to high-frequency field and for the Langmuir wave. The generalized Kudryashov method (GKM), which is one of the analytical methods, has been tackled for finding exact solutions of the system of equations for the ion sound wave and the Langmuir wave. By using this method, dark soliton solutions of this system of equations have been obtained. Also, by using Mathematica Release 9, some graphical simulations were designed to see the behavior of these solutions. PubDate: 2016-11-29 Issue No:Vol. 7, No. 1 (2016)

Authors:Zeydin Pala Pages: 50 - 58 Abstract: Wireless sensor networks (WSNs) still attract the attention of researchers, users and the private sector despite their low power and low range tendency for malfunction. This attraction towards WSNs results from their low cost structure and the solutions they offer for many prevalent problems. Many conditions, which remain unforeseen or unexpected during the design of the system, may arise after the initialization of the system. Similarly, many situations where security vulnerabilities take place may emerge in time in WSNs operating normally. In this study, we called nodes which enter sleeping mode without any further waking up and causing a sparser number of nodes in the network without any function in data transmission as Long-Term Sleep Nodes (LT-SN); and considered energy spaces caused by such nodes as a problem; and established two Linear Programming (LP) models based on the efficiency of the present nodes. We offered two different models which present the effect of sensor nodes, which were initially operating in wireless sensor network environment and did not wake up following sleep mode, on network lifetime. The results of the present study report that as the number of LT-SN increases, the lifetime of the network decreases. PubDate: 2016-11-29 Issue No:Vol. 7, No. 1 (2016)

Authors:Nesir Huseyin Pages: 59 - 65 Abstract: The control system with integralconstraint on the controls is studied, where the behavior of the system by a Urysohn type integral equation is described. It is assumed thatthe system is nonlinear with respect to the state vector, affine with respect to the control vector. The closed ball ofthe space $L_p(E;\mathbb{R}^m)$ $(p>1)$ with radius $r$ and centered at theorigin, is chosen as the set of admissible control functions, where $E\subset \mathbb{R}^k$ is a compact set. Itis proved that the set of trajectories generated by all admissible control functions is a compact subset of the space of continuous functions. PubDate: 2016-12-12 Issue No:Vol. 7, No. 1 (2016)

Authors:Yalçın Öztürk, Mustafa Gülsu Pages: 66 - 74 Abstract: In this paper, we present efficient direct solver for solving the generalized pantographequations with variable coefficients. The approach is based on the second kind Chebyshev polynomialstogether with operational method. The main characteristic behind this approach is that it reducessuch problem to ones of solving systems of algebraic equations. Only a small number of Chebyshevpolynomials are needed to obtain a satisfactory result. Numerical results with comparisons are givento confirm the reliability of the proposed method for solving generalized pantograph equations with variable coefficients. PubDate: 2016-12-12 Issue No:Vol. 7, No. 1 (2016)

Authors:Aytekin CIBIK, Fikriye YILMAZ Pages: 75 - 82 Abstract: In this study, we consider a Brezzi-Pitkaranta stabilization scheme for the optimal control problem governed by stationary Stokes equation, using a P1-P1 interpolation for velocity and pressure. We express the stabilization as extra terms added to the discrete variational form of the problem. We first prove the stability of the finite element discretization of the problem. Then, we derive a priori error bounds for each variable and present a numerical example to show the effectiveness of the stabilization clearly. PubDate: 2016-12-12 Issue No:Vol. 7, No. 1 (2016)

Authors:Betül BULCA, Kadri ARSLAN, Bengü BAYRAM, Günay ÖZTÜRK Pages: 83 - 89 Abstract: In the present study, we consider canal surfaces imbedded in an Euclidean space of four dimensions. The curvature properties of these surface are investigated with respect to the variation of the normal vectors and curvature ellipse. We also give some special examples of canal surfaces in E^4. Further, we give necessary and sufficient condition for canal surfaces in E^4 to become superconformal. Finally, the visualization of the projections of canal surfaces in E^3 are presented. PubDate: 2016-12-13 Issue No:Vol. 7, No. 1 (2016)

Authors:Barış Şimşek, Emir Hüseyin Şimşek Pages: 90 - 97 Abstract: This paper proposes a Response Surface Methodology (RSM) based Genetic Algorithm (GA) using MATLAB® to assess and optimize the thermal and fluidity of high strength concrete (HSC). The overall heat transfer coefficient, slump-spread flow and T50 time was defined as thermal and fluidity properties of high strength concrete. In addition to above mentioned properties, a 28-day compressive strength of HSC was also determined. Water to binder ratio, fine aggregate to total aggregate ratio and the percentage of super-plasticizer content was determined as effective factors on thermal and fluidity properties of HSC. GA based multi-objective optimization method was carried out by obtaining quadratic models using RSM. Having excessive or low ratio of water to binder provides lower overall heat transfer coefficient. Moreover, T50 time of high strength concrete decreased with the increasing of water to binder ratio and the percentage of superplasticizer content. Results show that RSM based GA is effective in determining optimal mixture ratios of HSC. PubDate: 2016-12-22 Issue No:Vol. 7, No. 1 (2016)