Browsing by Author "Dereli, Meryem Merve"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Placeholder
    Master ThesisPublicationMetadata only
    Economic lot sizing problem with tank scheduling
    (2021-08) Dereli, Meryem Merve; Önal, Mehmet; Önal, Mehmet; Yanıkoğlu, İhsan; Atan, S. T.; Department of Industrial Engineering; Dereli, Meryem Merve
    In this study, we consider an Economic Lot sizing Problem with Tank Scheduling (ELSTS). The problem is a real-world problem, which is generally found in fermented beverage and food facilities. A facility might produce an item or several different items which have various fermentation times. The facility might have a tank or several identical or non-identical tanks to produce items. If a tank starts the fermen tation process of an item, the tank will not be available to produce any item until its fermentation process is completed. Setup costs when tanks are filled, production costs when tanks are discharged, inventory costs after production is completed are incurred. The aim is to determine the lowest cost tank schedule and production plan which satisfies demands within a given finite planning horizon. Within the scope of the study, we analysed NP-hardness and solution methods of various variants of the ELSTS problem. In addition, for a variant of the ELSTS problem, which is classified as NP-Hard (multiple items that have different fermentation times and multiple iden tical parallel machines), a new heuristic method is proposed to find a near-optimal solution. The proposed heuristic method is compared with a mixed-integer program ming model, and that the heuristic method gives good solutions within seconds is observed.
  • Placeholder
    ArticlePublicationMetadata only
    Economic lot sizing problem with tank scheduling
    (Elsevier, 2023-07-01) Önal, Mehmet; van den Heuvel, W.; Dereli, Meryem Merve; Albey, Erinç; Industrial Engineering; ÖNAL, Mehmet; ALBEY, Erinç; Dereli, Meryem Merve
    We introduce a multiple-item economic lot sizing problem where items are produced through the fermentation of some raw materials. Fermentation takes place in specialized tanks that have finite capacities, and duration of the fermentation process is item dependent. When fermentation starts, the tanks are not available for the duration of the fermentation process. We analyze the complexity of this problem under various assumptions on the number of items and tanks. In particular, we show that several cases of the problem are (strongly) NP-hard, and we propose polynomial time algorithms to some single item cases. In addition, we propose a quick and simple heuristic approach for one of the multiple item cases.