Browsing by Author "Topan, Engin"

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Citation Count: Topan, E., Avşar, Z.M. (2011). An approximation for kanban controlled assembly systems. Annals of Operations Research, 182(1), 133-162. http://dx.doi.org/10.1007/s10479-009-0560-1
An approximation for kanban controlled assembly systems
(Springer, 2011) Topan, Engin; Avşar, Zeynep Müge; 164129
An approximation is proposed to evaluate the steady-state performance of kanban controlled two-stage assembly systems. The development of the approximation is as follows. The considered continuous-time Markov chain is aggregated keeping the model exact, and this aggregate model is approximated replacing some state-dependent transition rates with constant rates. The approximate aggregate model is, then, decomposed into submodels and a product-form steady-state distribution is obtained for each submodel. Finally, the submodels are combined in such a way that the size of the problem becomes independent of the number of kanbans. This leads to the computational advantage in solving the combined model using numerical matrix-geometric solution algorithms. Numerical comparisons of the combined model with simulation, exact model, approximate aggregate model and an approximation in the literature show that the proposed approximation performs well in terms of accuracy and computational burden
Citation Count: Topan,E., Bayındır, Z.P., Tan,T. (2010). An exact solution procedure for multi-item two-echelon spare parts inventory control problem with batch ordering in the central warehouse. Operations Research Letters, 38(5), 454-461. http://dx.doi.org/10.1016/j.orl.2010.05.006
An exact solution procedure for multi-item two-echelon spare parts inventory control problem with batch ordering in the central warehouse
(Elsevier Science BV, 2010) Topan, Engin; Bayındır, Z. Pelin; Tan, Tarkan
We consider a multi-item two-echelon inventory system in which the central warehouse operates under a (Q, R) policy, and the local warehouses implement basestock policy. An exact solution procedure is proposed to find the inventory control policy parameters that minimize the system-wide inventory holding and fixed ordering cost subject to an aggregate mean response time constraint at each facility
Citation Count: Topan, E., Bayındır, Z.P. (2012). Multi-item two-echelon spare parts inventory control problem with batch ordering in the central warehouse under compound Poisson demand. Journal Of The Operational Research Society, 63(8), 1143-1152. http://dx.doi.org/10.1057/jors.2011.125
Multi-item two-echelon spare parts inventory control problem with batch ordering in the central warehouse under compound Poisson demand
(Palgrave Macmillan Ltd., 2012) Topan, Engin; Bayındır, Z. P.; 17941
We consider a multi-item two-echelon spare part inventory system in which the central warehouse operates under an (nQ, R) policy and the local warehouses implement order-up-to S policy, each facing a compound Poisson demand. The objective is to find the policy parameters minimizing expected system-wide inventory holding and fixed ordering costs subject to an aggregate mean response time constraint at each warehouse. In this paper, we propose four alternative approximations for the steady state performance of the system; and extend a heuristic and a lower bound proposed under Poisson demand assumption to the compound Poisson setting. In a computational study, we show that the performances of the approximations, the heuristic, and the lower bound are quite satisfactory; and the relative cost saving of setting an aggregate service level rather than individually for each part is quite high