Yazar "Kurt, Atil" seçeneğine göre listele

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    An integrated inventory and distribution planning problem for the blood products: An application for the Turkish Red Crescent
    (Growing Science, 2023) Kurt, Atil; Azizoglu, Meral; Cetinkaya, Ferda Can
    This study considers an integrated inventory planning and distribution problem based on an applied case at the Turkish Red Crescent's Central Anatolian Regional Blood Center. We define two echelons, the first echelon being the regional blood center and the second echelon being the districts. The blood products are perishable so that the outdated products are disposed of at the end of their lives. We aim to minimize the cost of inventory keeping at both echelons, the shortage, and disposal amounts at the second echelon. We consider two distribution strategies: all deliveries are realized by the regional blood center (current implementation), and the deliveries are directly from the regional blood center or the other districts. We develop a mixed -integer linear programming model for each strategy. Our experimental results show that the decentralized strategy brings significant cost reductions over the centralized strategy. The mathematical model for the centralized distribution strategy can handle large-sized instances. On the other hand, the model for the decentralized distribution strategy is more complex and could not handle large-sized instances in our pre-specified termination limit of two hours. For large -sized instances of the decentralized distribution strategy, we design a decomposition-based heuristic algorithm that benefits from the optimal solutions of the original model and finds near -optimal solutions very quickly. (c) 2023 by the authors; licensee Growing Science, Canada.
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    Analysis of national strategic innovation objectives using adapted Porter's diamond model: a comparison of Romania and Türkiye
    (Emerald Group Publishing Ltd, 2025) Militaru, Andreea Maria Gabriela; Kurt, Atil; Gumus, Mehmet
    PurposeNowadays, nations are rapidly changing and evolving, both because of global competitiveness and technological development. The fast change of the economies and the interconnected world has brought a more globalized world than ever. The purpose of this paper is to assess Romania (RO) and T & uuml;rkiye (TR) by using a customized version of Porter's diamond model (PDM), with an emphasis on identifying the key components of their innovation systems.Design/methodology/approachThe paper uses a recognized model to unfold its structure. Based on the PDM, this paper tackles the topic of innovation systems both of RO and TR. Applying the model, a mapping of indicators representing components of the national innovation system is made possible. Besides the traditional four determinants (dimensions) of the model, the authors adapted it and added the technology conditions. Using the five dimensions, a comparison of strategical objectives is made between RO and TR.FindingsThe results show the potential for both countries to develop and embrace the innovation capacity, while there is still room for improvement in this regard. Another point is the map of innovation system components that were used for the comparison. The implications of innovation are analyzed at a strategical level, comparing the mapping with the national strategical objectives.Originality/valueThere are many studies using this model, however a few bring into the light the impact of innovation systems at national level. Hence, a new framework is provided to evaluate innovative systems using a selection of modern indicators. This study uses an existing model in literature, Porter's model mapping indicators, which highlight the innovation capacity.
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    Dynamic Freight Planning with Hybrid Cross-Docking under Carbon Tax and Bounded Storage Age
    (Sage Publications Inc, 2025) Kurt, Atil; Gumus, Mehmet
    This paper discusses the dynamics of supply chain network optimization, specifically focusing on the role of cross-docking. As experienced by the disruptions of the COVID-19 era, external events can trigger supply chain interruptions, necessitating temporary storage solutions. The study examines a network with diverse suppliers, retailers, products, and hybrid cross-docking (HCD) facilities, wherein both transshipment and short-term inventory with restricted storage-age are permitted. Routing of goods from suppliers to retailers encompasses both direct paths and intermediate HCD points, involving multiple truck types. Importantly, all shipments are subject to a carbon tax, factoring in the imperative of mitigating carbon emissions. A dynamic mixed-integer linear programming model is formulated, alongside a greedy-type heuristic algorithm, to optimize the system's total cost. Various computational experiments are used to evaluate the efficacy and solution quality of these methods. Extensive sensitivity analysis, complemented by statistical tests, dissects the impact of various model parameters within the computational experiments. Findings show that allowing storage at HCD facilities, with limited holding time, does not increase system-wide costs but instead bolsters supply chain flexibility. Moreover, carbon tax requires a shift in truck-type selection and plays an important role in reducing the total load-distance traveled, and, therefore, the total carbon emissions.
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    Integrating sequence-dependent setup times and blocking in hybrid flow shop scheduling to minimize total tardiness
    (Growing Science, 2025) Kurt, Atil
    This study addresses the minimization of total tardiness in a hybrid flow shop scheduling problem with sequence-dependent setup times and blocking constraints. Each production stage includes multiple machines, and there are no buffers between the stages. The setup time required to process a job depends on the previously processed job. Two mixed-integer linear programming models are developed to formulate the problem. Moreover, an iterative local search algorithm and hybrid genetic algorithms are proposed to have quality solutions with minimal computational efforts. Several computational tests are conducted to tune the heuristic parameters for better performance. Computational experiments are carried out to evaluate the performance of solution methodologies in terms of quality and time. The results indicate that while mixed-integer programming models can solve small-size problem instances, they are not capable of solving large-sized instances. However, the proposed heuristic algorithms find quality solutions for all instances in a very short time.
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    Sustainable planning of penal facilities through multi-objective location-allocation modelling and data envelopment analysis
    (Elsevier Science Inc, 2025) Kurt, Atil; Gumus, Mehmet
    The escalating population of inmates necessitates a substantial increase in penal facilities. Consequently, there arises a pressing need for strategic planning to identify the location and capacities of new penal facilities, along with the appropriate allocation of prisoners therein. This study proposes a solution methodology to address this imperative by considering multiple future periods and objectives. Specifically, the study examines three objective functions simultaneously based on the three dimensions of sustainability, delineated along economy, society, and environment. To operationalize this framework, a multi-objective mixed integer linear programming model is developed, and an iterative solution methodology is proposed to generate alternative solutions. The alternative solutions are created for two scenarios: exact and fractional assignment of prisons in cities. Subsequently, the efficacy of these alternatives is assessed through the application of super-efficiency and cross-efficiency data envelopment analysis techniques. In each of these scenarios, the most efficient solution among alternatives is identified as the final solution. The empirical data utilized in the study is sourced from real-world cases in Turkey. Comparative analyses of the solutions under each scenario offer valuable insights into their respective advantages and disadvantages, thereby contributing to a comprehensive understanding of the problem.