Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Citation - WoS: 5Citation - Scopus: 5Taking Advantage of a Diverse Set of Efficient Production Schedules: A Two-Step Approach for Scheduling With Side Concerns(Pergamon-Elsevier Science Ltd, 2013-08) Goren, Selcuk; Pierreval, HenriIn many practical scheduling problems, the concerns of the decision-maker may not be all known in advance and therefore may not be included in the initial problem definition as an objective function and/or as constraints. In such a case, the usual techniques of multi-objective optimization become inapplicable. To cope with this problem and to facilitate handling the concerns of the decision-maker, which can be implicit or qualitative, a dedicated methodological framework is needed. In this paper we propose a new two-step framework. First, we aim at obtaining a set of schedules that can be considered efficient with respect to a performance measure and at the same time different enough from one another to enable flexibility in the final choice. We formalize this new problem and suggest to address it with a multimodal optimization approach. Niching considerations are discussed for common scheduling problems. Through the flexibility induced with this approach, the additional considerations can be taken into account in a second step, which allows decision-makers to select an appropriate schedule among a set of sound schedules (in contrast to common optimization approaches, where usually a single solution is obtained and it is final). The proposed two-step approach can be used to handle a wide range of underlying scheduling problems. To show its potential and benefits we illustrate the framework on a set of hybrid flow shop instances that have been previously studied in the literature. We develop a multimodal genetic algorithm that employs an adapted version of the restricted tournament selection for niching purposes in the first step. The second step takes into account additional concerns of the decision-maker related to the ability of the schedules to absorb the negative effects due to random machine breakdowns. Our computational experiments indicate that the proposed framework is capable of generating numerous high-performance (mostly optimal) schedules. Additionally, our computational results demonstrate that the proposed framework provides the decision-maker a high flexibility in dealing with subsequent side concerns, since there are drastic differences in the capabilities of the efficient solutions found in Step 1 to absorb the negative impacts of machine breakdowns. (C) 2013 Elsevier Ltd. All rights reserved.Conference Object Citation - Scopus: 2Parallel Machine Scheduling With Re-Entrant Jobs With Consideration of Set Up Times(ISRES Publishing, 2024-12-30) Kayisoglu, Betul; Bekli, Seyma; Sahin, Ayse Sena; Akyurek, Gamze Gul; Aydinli, Ruveyda; Copur, Sevda Nur; Ekinci, TugbaWe study the identical parallel machine problem with re-entrant jobs. Re-entrant jobs require to pass through the processing line multiple times. In many real-life manufacturing systems with parallel machine environments, one of the scheduling problems that needs to be addressed is the order of jobs on each machine with re-entrant jobs. In addition, manufacturing systems may require periodic maintenance, systematic manufacturing equipment cleaning, or predetermined upper limits on the overtime. Therefore, machine availability may vary during the scheduling horizon. We propose an integer programming model to find the optimal sequence of the re-entrant jobs at parallel machines with consideration of machine availability. The model aims to reduce setup times and maximize capacity utilization by scheduling tasks with similar set up requirements consecutively. We tested the proposed model at a panel line manufacturing company located in Turkey. The order of the panels is scheduled optimally by the proposed model for 3 different instances on the identical parallel machines for the coating process. We also provided relevant information on the user interface we developed to make the proposed scheduling model usable to by the company. The proposed model and interphase offer a systematic approach to panel line planning and can also be implemented in other industries. © 2025 Elsevier B.V., All rights reserved.Conference Object Citation - Scopus: 1Incorporating Worker Heterogeneity in Flexible Flow Shop Environment(ISRES Publishing, 2025-08-15) Ozpacaci, Kubra; Bekli, Seyma; Kayisoglu, BetulWe study the flexible flow shop scheduling problem with the heterogeneous worker assignment. In many real-life manufacturing systems with flow shop environments, one of the fundamental scheduling challenges that needs to be addressed is job sequences across multiple workers. In addition, the manufacturing system may require workers to have different skills at various stages during their assignment. Therefore, worker availability at each stage may vary during the scheduling horizon. Unlike traditional flexible flow shop scheduling problem, where homogeneous workers are assumed, we consider workers with different skill levels, capabilities, and capacities. We present a mixed integer linear programming model to find the optimal sequence of job assignments, guaranteeing that jobs follow their predefined operation sequence while assigning workers with various skill sets in a flexible flow shop environment. The proposed model is tested at a battery manufacturing company. By analyzing the solution, we confirm its capability to represent the problem accurately. The proposed model offers a systematic scheduling approach for a flexible flow shop environment with a heterogeneous workforce and can be implemented in other industries. © 2025 Elsevier B.V., All rights reserved.