Browsing by Author "Alp, Osman"

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Open Access
Dahili imalat parça yöntemi: Evinde üret, sistemli yönet
(TMMOB Makina Mühendisleri Odası, 2005) Dalokay, Can; Ertürk, Gonca; Kaçar, İlkay Sarp; Ünlüönen, Onur; Yazıcı, Gizem; Alp, Osman
MAN Türkiye A.Ş. fabrikası bünyesindeki dahili imalat birimi, montaj hatlarında kullanılmak üzere birçok parça üretmektedir. Üretilen dahili imalat parçaları, montaj hattına girmeden önce ambarlarda stoklanmaktadır. Bu parçalara ihtiyaç duyulduğu anda, parçalar görevliler tarafından ambarlardan alınıp ilgili montaj hattına sunulmaktadır. Bu proje kapsamında, dahili imalat parçalarının yönetimine yönelik üç alt problem çözülmüştür: (i) envanter kontrol politikalarının belirlenmesi, (ii) depo yerleşim planlarının belirlenmesi, ve (iii) bazı parçaların hareketleri için Kanban stratejisinin uygulanması. Gerçekleşmiş kullanım verileri ile yapılan benzetim koşumları sonucunda, önerilen çözüm yöntemlerinin sistem performansına iyileştirdiği gösterilmiştir. Önerilen stok kontrol modelinin çözümü, belirli aralıklarda güncel veriler ile koşturulabilecek ve fabrikadaki mevcut ERP sistemi ile uyumlu olan bir yazılım ile sağlanmştır.
Open Access
Delegation of stocking decisions under asymmetric demand information
(Institute for Operations Research and the Management Sciences (INFORMS), 2021-01) Alp, Osman; Şen, Alper
Problem definition: We consider the incentive design problem of a retailer that delegates stocking decisions to its store managers who are privately informed about local demand. Academic/practical relevance: Shortages are highly costly in retail, but are less of a concern for store managers, as their exact amounts are usually not recorded. In order to align incentives and attain desired service levels, retailers need to design mechanisms in the absence of information on shortage quantities. Methodology: The headquarters knows that the underlying demand process at a store is one of J possible Wiener processes, whereas the store manager knows the specific process. The store manager creates a single order before each period. The headquarters uses an incentive scheme that is based on the end-of-period leftover inventory and on a stock-out occasion at a prespecified inspection time before the end of a period. The problem for the headquarters is to determine the inspection time and the significance of a stock-out relative to leftover inventory in eval uating the performance of the store manager. We formulate the problem as a constrained nonlinear optimization problem in the single period setting and a dynamic program in the multiperiod setting. Results: We show that the proposed “early inspection” scheme leads to perfect alignment when J equals two under mild conditions. In more general cases, we show that the scheme performs strictly better than inspecting stock-outs at the end and achieves near-perfect alignment. Our numerical experiments, using both synthetic and real data, reveal that this scheme can lead to considerable cost reductions. Managerial im plications: Stock-out-related measures are typically not included in store managers’ performance scorecards in retail. We propose a novel, easy, and practical performance measurement scheme that does not depend on the actual amount of shortages. This new scheme incentivizes the store managers to use their private information in the retailer’s best interest and clearly outperforms centralized ordering systems that are common practice.
Open Access
Tactical capacity management under capacity flexibility
(Institute of Industrial Engineers, 2008) Alp, Osman; Tan, T.
In many production systems a certain level of flexibility in the production capacity is either inherent or can be acquired. In that case, system costs may be decreased by managing the capacity and inventory in a joint fashion. In this paper we consider such a make-to-stock production environment with flexible capacity subject to periodic review under non-stationary stochastic demand, where we allow for positive fixed costs both for initiating production and for acquiring external capacity. Our focus is on tactical-level capacity management which refers to the determination of in-house production capacity while the operational-level integrated capacity and inventory management is executed in an optimal manner. We first develop a simple model to represent this relatively complicated problem. Then we elaborate on the characteristics of the general problem and provide the solution to some special cases. Finally, we develop several useful managerial insights as to the optimal capacity level, the effect of operating at a suboptimal capacity level and the value of utilizing flexible capacity.