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    Design of job assignment and routing policies in service logistics
    (2019) Düzgit, Zehra; Toy, Ayhan Özgür; Çoban, Simge; Alibaşoğlu, Zeynep; Özkeskin Tok, Özlem; Karakaya, Mert; Bayrak, Yücel
    In this study, we consider to improve efficiency of an after-sales technical service in home appliances industry. The efficiency measure is the total time spent in a day to serve customer requests. Hence, the objective is to minimize total working hours spent in a day in the aftersales services. We first analyze the system to identify causes of delays in job completion. Upon findings of our analysis we choose to focus on job assignment and job sequencing to improve efficiency. We propose a mixed integer programming model for the assignment of technicians to jobs and sequencing of jobs for each technician to minimize total time spent in a day. Through this model we solve the problem with expected job durations. We present a numerical study to illustrate the proposed solution procedure.
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    Dynamic lot sizing for a warm/cold process: Heuristics and insights
    (Elsevier Science BV, 2013-09) Toy, Ayhan Özgür; Berk, Emre
    We consider the dynamic lot sizing problem for a warm/cold process where the process can be kept warm at a unit variable cost for the next period if more than a prespecified quantity has been produced. Exploiting the optimal production plan structures, we develop nine rule-based forward solution heuristics. Proposed heuristics are modified counterparts of the heuristics developed previously for the classical dynamic lot sizing problem. In a numerical study, we investigate the performance of the proposed heuristics and identify operating environment characteristics where each particular heuristic is the best or among the best. Moreover, for a warm/cold process setting, our numerical studies indicate that, when used on a rolling horizon basis, a heuristic may also perform better costwise than a solution obtained using a dynamic programming approach. (C) 2012 Elsevier B.V. All rights reserved.