Authors:Kenan Çetin, Gülfem Tuzkaya, Ozalp Vayvay First page: 147 Abstract: Efficient planning and management of the workforce resources is one of the most essential requirements for the companies operating in the service sector. For banks, a large number of transactions coming to Central Operations Department from the branches or directly from the customers and their aim is to provide the best operational service with the highest efficiency with the limited workforce resources in the departments. In this study, a real assignment problem was discussed and the problem was considered as Generalized Assignment Problem. For the solution of the problem, related algorithms were listed and examined in the literature survey section. Then, a two-step method is proposed. First step prioritizes the task coming to the system by considering the customer types, service level agreement (SLA) times, cut-off times, task type. In the second step, a multi-objective mathematical model was developed to assign task to employee groups. A preference based optimization method called Linear Physical Programming (LPP) is used to solve the model. Afterward, proposed model was tested on real banking data. For all the tests, GAMS was used as a solver. Results show that proposed model gave better results compared with current situation. With the proposed solution method, the workloads of the profile groups working above their capacity were transferred to other profile groups with idle capacity. Thus, the capacity utilization rates of the profile groups were more balanced and the minimum capacity utilization rate was calculated as 41%. PubDate: 2020-04-07 DOI: 10.11121/ijocta.01.2020.00825 Issue No:Vol. 10, No. 2 (2020)

Authors:Hülya Gültekin Çitil Pages: 159 - 165 Abstract: In this work, we study the problem with fuzzy eigenvalue parameter in one of the boundary conditions. We find fuzzy eigenvalues of the problem using the Wronskian functions \underline{W}_{\alpha }\left( \lambda \right) and \overline{W} _{\alpha }\left( \lambda \right). Also, we find eigenfunctions associated with eigenvalues. We draw graphics of eigenfunctions. PubDate: 2020-05-31 DOI: 10.11121/ijocta.01.2020.00947 Issue No:Vol. 10, No. 2 (2020)

Authors:Nita H. Shah, Ankush H. Suthar, Ekta N. Jayswal Pages: 166 - 180 Abstract: The mosquito-borne infectious diseases like malaria and dengue are putative as important tropical infections and cause high morbidity and mortality around the world. In some cases, simultaneous coexistence of both the infections in one individual is seen which is very hard to distinguish as both diseases have almost similar symptoms. In this proposed article, dynamical system of non-linear differential equations is constructed with the help of mathematical modeling, which describe dynamics of the spread of these infectious diseases separately and concurrently. Basic reproduction number is evaluated to understand dynamical behaviour of the model. Local and global stability criteria have been deliberated rigorously. Control parameters are used to perceive effect of medication on these prevalent tropical diseases. Numerical simulations are used to observe effect of control parameters graphically. PubDate: 2020-06-04 DOI: 10.11121/ijocta.01.2020.00828 Issue No:Vol. 10, No. 2 (2020)

Authors:Hande Uslu, Murat Sari, Tahir Cosgun Pages: 181 - 187 Abstract: In the last few decades, stiff differential equations have attracted a great deal of interest from academic society, because much of the real life is covered by stiff behavior. In addition to importance of producing model equations, capturing an exact behavior of the problem by dealing with a solution method is also handling issue. Although there are many explicit and implicit numerical methods for solving them, those methods cannot be properly applied due to their computational time, computational error or effort spent for construction of a structure. Therefore, simulation techniques can be taken into account in capturing the stiff behavior. In this respect, this study aims at analyzing stiff processes through stochastic approaches. Thus, a Monte Carlo based algorithm has been presented for solving some stiff ordinary differential equations and system of stiff linear ordinary differential equations. The produced results have been qualitatively and quantitatively discussed. PubDate: 2020-06-04 DOI: 10.11121/ijocta.01.2020.00829 Issue No:Vol. 10, No. 2 (2020)

Authors:Emrullah Sonuç Pages: 188 - 197 Abstract: The Weapon-Target Assignment (WTA) problem is one of the most important optimization problems in military operation research. In the WTA problem, assets of defense aim the best assignment of each weapon to target for decreasing expected damage directed by the offense. In this paper, Modified Crow Search Algorithm (MCSA) is proposed to solve the WTA problem. In MCSA, a trial mechanism is used to improve the quality of solutions using parameter LIMIT. If the solution is not improved after a predetermined number of iterations, then MCSA starts with a new position in the search space. Experimental results on the different sizes of the WTA problem instances show that MCSA outperforms CSA in all problem instances. Also, MCSA achieved better results for 11 out of 12 problem instances compared with four state-of-the-art algorithms. The source codes of MCSA for the WTA are publicly available at http://www.3mrullah.com/MCSA.html. PubDate: 2020-06-04 DOI: 10.11121/ijocta.01.2020.00775 Issue No:Vol. 10, No. 2 (2020)

Authors:Sulaiman Mohammed Ibrahim, Usman Abbas Yakubu, Mustafa Mamat Pages: 198 - 205 Abstract: Conjugate gradient (CG) methods are among the most efficient numerical methods for solving unconstrained optimization problems. This is due to their simplicty and less computational cost in solving large-scale nonlinear problems. In this paper, we proposed some spectral CG methods using the classical CG search direction. The proposed methods are applied to real-life problems in regression analysis. Their convergence proof was establised under exact line search. Numerical results has shown that the proposed methods are efficient and promising. PubDate: 2020-06-04 DOI: 10.11121/ijocta.01.2020.00859 Issue No:Vol. 10, No. 2 (2020)

Authors:Fuat Kilic, Serkan Sezen, Seyit Ahmet Sis Pages: 206 - 217 Abstract: One of the major challenges in inductive wireless power transfer (WPT) systems is that the optimal frequency of operation may shift predominantly due to coupling variation as a result of so-called frequency splitting phenomenon. When frequency splitting occurs, two additional resonance frequencies split from the coupler’s resonance frequency. Maximum power levels are observed at these split resonance frequencies; however, these frequencies are strongly-dependent on the coupling coefficient, hence the distance and alignment between the couplers. In addition to that, peak power values at these frequencies can be different from each other due to small impedance differences between the primary and secondary side resonant couplers, forming a local and a global maximum. Therefore, the WPT system should adaptively operate at the correct frequency for achieving maximum power transfer. In this paper, a metaheuristic Particle Swarm Optimization (PSO) based frequency tracking algorithm is proposed for use in WPT systems. The WPT system employs multi sub-coil flux pipe couplers, a full-bridge inverter which is driven by TMS320F28069 controller card and is suitable for high power charging applications. The control algorithm can accurately find the global maximum power point in case of frequency splitting with asymmetric peaks. The proposed frequency tracking algorithm operates only at the primary side based on measurement of the input power level. Therefore, no additional communication link is needed between the primary and the secondary side. Effectiveness of the proposed control method is validated by performing experiments under three different misalignment scenarios and compared to the traditional Perturb and Observe algorithm. PubDate: 2020-06-19 DOI: 10.11121/ijocta.01.2020.00926 Issue No:Vol. 10, No. 2 (2020)

Authors:Burcu Gürbüz, Mehmet Sezer Pages: 218 - 225 Abstract: In this study, by means of the matrix relations between the Laguerre polynomials, and their derivatives, a novel matrix method based on collocation points is modified and developed for solving a class of second-order nonlinear ordinary differential equations having quadratic and cubic terms, via mixed conditions. The method reduces the solution of the nonlinear equation to the solution of a matrix equation corresponding to system of nonlinear algebraic equations with the unknown Laguerre coefficients. Also, some illustrative examples along with an error analysis based on residual function are included to demonstrate the validity and applicability of the proposed method. PubDate: 2020-07-01 DOI: 10.11121/ijocta.01.2020.00827 Issue No:Vol. 10, No. 2 (2020)

Authors:Artion Kashuri, Rozana Liko Pages: 226 - 236 Abstract: Trapezoidal inequalities for functions of divers natures are useful in numerical computations. The authors have proved an identity for a generalized integral operator via twice differentiable preinvex function. By applying the established identity, the generalized trapezoidal type integral inequalities have been discovered. It is pointed out that the results of this research provide integral inequalities for almost all fractional integrals discovered in recent past decades. Various special cases have been identified. Some applications of presented results to special means have been analyzed. The ideas and techniques of this paper may stimulate further research. PubDate: 2020-07-01 DOI: 10.11121/ijocta.01.2020.00795 Issue No:Vol. 10, No. 2 (2020)

Authors:Mahmut Modanli, Bawar Mohammed Faraj, Faraedoon Waly Ahmed Pages: 237 - 243 Abstract: The variable telegraph partial differential equation depend on initial boundary value problem has been studied. The coefficient constant time-space telegraph partial differential equation is obtained from the variable telegraph partial differential equation throughout using Cauchy-Euler formula. The first and second order difference schemes were constructed for both of coefficient constant time-space and variable time-space telegraph partial differential equation. Matrix stability method is used to prove stability of difference schemes for the variable and coefficient telegraph partial differential equation. The variable telegraph partial differential equation and the constant coefficient time-space telegraph partial differential equation are compared with the exact solution. Finally, approximation solution has been found for both equations. The error analysis table presents the obtained numerical results. PubDate: 2020-07-01 DOI: 10.11121/ijocta.01.2020.00870 Issue No:Vol. 10, No. 2 (2020)

Authors:Ömer Oruç Pages: 244 - 258 Abstract: In this study we will investigate generalized regularized long wave (GRLW) equation numerically. The GRLW equation is a highly nonlinear partial differential equation. We use finite difference approach for time derivatives and linearize the nonlinear equation. Then for space discretization we use delta-shaped basis functions which are relatively few studied basis functions. By doing so we obtain a linear system of equations whose solution is used for constructing numerical solution of the GRLW equation. To see efficiency of the proposed method four classic test problems namely the motion of a single solitary wave, interaction of two solitary waves, interaction of three solitary waves and Maxwellian initial condition are solved. Further, invariants are calculated. The results of numerical simulations are compared with exact solutions if available and with finite difference, finite element and some collocation methods. The comparison indicates that the proposed method is favorable and gives accurate results. PubDate: 2020-07-01 DOI: 10.11121/ijocta.01.2020.00881 Issue No:Vol. 10, No. 2 (2020)

Authors:Saman Babaie-Kafaki, Saeed Rezaee Pages: 259 - 263 Abstract: Hybridizing the trust region, line search and simulated annealing methods, we develop a heuristic algorithm for solving unconstrained optimization problems. We make some numerical experiments on a set of CUTEr test problems to investigate efficiency of the suggested algorithm. The results show that the algorithm is practically promising. PubDate: 2020-07-27 DOI: 10.11121/ijocta.01.2020.00900 Issue No:Vol. 10, No. 2 (2020)