Browsing by Author "Yozgat, Simge"

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Mathematical Modelling Approach to Increase Cell Efficiency in a Furniture Firm
(2018) Yozgat, Simge; Atmaca, H.E.; 01. Çankaya Üniversitesi
Bir Mobilya Fabrikasında Hücre Tasarımı ve Hücre Etkinliğinin Belirlenmesi
(2018) Yozgat, Simge; Atmaca, Ediz; 218939; 01. Çankaya Üniversitesi
Günümüzde, işletmeler artan rekabete uyum sağlayabilmek ve müşterilere daha hızlı cevap verebilmek için geleneksel üretim yöntemlerinin dışına çıkmak zorunda kalmaktadır. Üretkenliği arttırmak için benzer parça ve makinelerin bir araya getirilmesi felsefesine dayanan grup teknolojisi birçok işletme tarafından yaygın bir şekilde kullanılmaktadır. Hücresel imalat yaklaşımında, parçalar, tasarım ve imalat açısından benzerliklerine göre gruplandırılıp parça aileleri haline getirilirken, makineler ise iş akışına göre hücrelerde gruplandırılmaktadır. Böylece, hazırlık zamanları ve ara stoklardaki yığılmalar azalarak, üretim planlama ve çizelgelemede etkinlik artışı gözlenmektedir. Bu da üretimde verimliliği sağlar. Yapılan çalışmada, hat akışı üretim sistemine sahip olan bir mobilya fabrikasının taşımalardan kaynaklanan kayıplarını önlemek ve üretimde verimliliği artırmak amacıyla hücresel imalata geçiş için bir ön hazırlık yapılmıştır. Fabrikada makine grupları, parça aileleri ve hücre oluşum problemi üzerinde durulmuştur. Grup etkinliğini sağlamayı hedefleyen bir matematiksel model yardımıyla problem çözümlenmeye çalışılmıştır. Matematiksel model sonuçlarının mevcut durum ile karşılaştırılması yapılarak, firmaya önerilerde bulunulmuştur.
Pricing and remanufacturing decisions with speculators and strategic consumers
(Çankaya Üniversitesi, 2017) Yozgat, Simge; 01. Çankaya Üniversitesi
We investigate pricing and remanufacturing decisions with speculators and strategic consumers for a single type of a product over a two-period sales horizon. A monopolist manufacturer produces a fixed quantity in the first period. Some of the sold products are returned at the end of the first period, which are collected by the manufacturer and/or speculators. Returned products are remanufactured, and then sold in the second period, along with any new products remaining from the first period. Mathematical models take into account the behavioral patterns of different types of customers to maximize the manufacturer's expected total profit. Solution to the mathematical models show that one particular customer behavior is optimal. Specifically, the manufacturer should use a fixed-pricing policy for all products –new and remanufactured alike– and set the price at the maximum level that strategic customers are willing to buy. This will force customers to wait for the second period to buy any products, and hence, will yield the maximum profit for the manufacturer. Additionally, the manufacturer is better off remanufacturing. The sensitivity analysis has shown that the profit is most sensitive to the number of strategic customers.
Citation - WoS: 2
Citation - Scopus: 2
Sustainable Closed-Loop Supply Chain Network Design and Optimization
(Springer Nature Switzerland Ag, 2022) Yozgat, Simge; Erol, Serpil; 01. Çankaya Üniversitesi
The sustainability conception encompasses a wide range from economy to environment and society. Sustainable supply chains, when managed with the right strategies, will ensure several advantages for all collaborators in the chain. With the increasing consumer awareness, the studies conducted in recent years focus on the environmental and social dimensions as well as the economic factor of sustainability. Sustainability factors; "environmental, economic and social" also known as three pillars of sustainability are considered together in order to increase the benefits offered by the sustainable supply chain. In this study, closed-loop supply chain themed studies that deal with three pillars of sustainability in the literature were examined based on sub-factors. Studies have shown that, Life Cycle Analysis (LCA) methods such as ReCipe, Eco-Indicator 99 and CO2 emission are the approaches used to determine the environmental factors of sustainability. Cost, profit and Net Present Value (NPV) methods are used to measure the economic dimension of sustainability. Job opportunities, losses and Customer Service Level (CSL) are most commonly used as sub-criteria to determine social factors. Accordingly, a sustainable closed-loop supply chain model consisting of seven echelons has been examined. A deterministic mixed integer linear programming model (MILP), which includes the economic dimension of sustainability, has been developed and enclosed with sample solutions. Suggestions for sustainability criteria and improving the proposed model have been made for future studies.
Citation - WoS: 6
Citation - Scopus: 7
Sustainable Factors for Supply Chain Network Design Under Uncertainty: a Literature Review
(Springer-verlag Singapore Pte Ltd, 2022) Yozgat, Simge; Erol, Serpil; 218939; 01. Çankaya Üniversitesi
The concept of sustainability, which is considered three pillars covering the concept of economic, environmental, and social factors, has become an effectual attempt to increase competitiveness for institutions. Being sustainable in the supply chain enables enterprises to respond to increasing customer needs in the most appropriate way. Today, traditional supply chains are replaced by sustainable logistics network designs due to environmental and social requirements. In this study, considering the uncertainty situation, the studies carried out on closed loop supply chains that are formed as a result of integration of forward and reverse logistics aswell as forward and reverse logistics by itself are examined on the basis of sustainability factors. Sustainability sub-factors are also included in this study. As a result of the research, brief explanations can be seen about sustainable supply chain network under the uncertainty covering all three sustainability factors and gaps in the literature are clarified for future research opportunities.