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    Modelling of WEEE recycling operation planning under uncertainty
    (Elsevier Sci Ltd, 2018) Polat, Olcay; Çapraz, Ozan; Güngör, Aşkıner
    Recycling is very important especially for hazardous materials considering their negative impacts on the environment. Waste electrical and electronic equipment (WEEE) is generally classified under hazardous waste. Determination of process methods and quantities of WEEE to be processed is significantly important since it enables the efficient operation and management of recycling systems. The presence of uncertainty in these systems requires to develop appropriate decision-making tools to deal with uncertain parameters in recycling-operation planning problems. In this study, we propose a linear programming (LP) model for multi-period operation planning for recycling of WEEE considering fuzzy parameters: demand, quantity of WEEE to be processed, operational capacity of resources, amount of output obtained from WEEE and processing times. The model aims to maximize the total profit by determining the best recycling strategies and types, quantity and stocks of WEEE to be recycled during the planning term. The solution method is based on ranking methods of fuzzy numbers through the comparison of their expected intervals. The proposed LP model is illustrated using a case study with experimental analysis. The findings indicated that the nature of fuzzy parameters have critical effect on the total cost and the total revenue at different levels. The results also show that the uncertainty in recycling of WEEE is a crucial factor in developing consistent plans to achieve the economic sustainability of recycling facilities. (C) 2018 Elsevier Ltd. All rights reserved.
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    Mühendislik Fakültesi Öğrencilerinin Bir Üniversite Kütüphanesi Hizmetlerine İlişkin Görüşlerinin İncelenmesi
    (2015) Çapraz, Ozan; Polat, Olcay
    Bu çalışmanın amacı, mühendislik fakültesi öğrencilerinin bir üniversite kütüphanesinin hizmetleri ile ilgili memnuniyet düzeylerinin ölçülmesi ve değerlendirilmesidir. Bu amaçla, çalışmada iki temel problem araştırılmıştır. Birinci problem, mühendislik fakültesi öğrencilerinin üniversite kütüphanesi hizmetleri ile ilgili düşüncelerinin saptanmasıdır. İkinci problem ise, mühendislik fakültesi öğrencilerinin kazandıkları mesleki eğitimin kütüphaneyi kullanma becerileri ve alışkanlıkları üzerindeki etkisinin tespit edilmesidir. Araştırmaya bölümlere göre tabakalı örneklem ile seçilmiş 160 kişilik mühendislik fakültesi son sınıf öğrencisi katılmıştır. Verilerin toplanmasında anket tekniği kullanılmış, analizinde ise frekans tabloları ve parametrik olmayan istatiksel analizler kullanılmıştır. Araştırmada, öğrencilerin aylık kütüphane kullanma sıklıkları, mühendislik eğitimlerinin kütüphaneyi kullanma beceri ve alışkanlıkları edindirmedeki yeterliliği ve kütüphane hizmetlerinin yeterliliği ölçülmüş ve değerlendirilmiştir. Çalışma sonuçlarına göre öğrencilerin coğrafi bölge ve yaş bağımsız değişkenlerine göre kütüphane hizmetleri ile ilgili düşüncelerde bir farklılık tespit edilmezken, bölümlere ve cinsiyete göre anlamlı bir farklılık tespit edilmiştir
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    Performance evaluation of waste electrical and electronic equipment disassembly layout configurations using simulation
    (Higher Education Press, 2017) Çapraz, Ozan; Polat, Olcay; Güngör, Aşkıner
    Recycling of waste electrical and electronic equipment (WEEE) is crucially important since it handles hazardous waste according to ever tightening laws and regulations and it adds benefits to economy and sustainable environment. Disassembly is one of the most important processes performed during the recovery of WEEE. The overall goal of disassembly is to maximize the retrieval of various metals and plastics contained in WEEE in order to reduce their negative effects on human health and environmental sustainability and to increase economic gains. This study aims to evaluate alternative layout configurations for WEEE disassembly systems (WDS). In this context, various configurations were compared in terms of pre-defined performance criteria, such as the total number of disassembled WEEE and the total revenue from sales, using simulation models. The results of this study show that the performance of a WDS was significantly affected by output transfer systems along with the specialization of operators on certain types of WEEE. (C) Higher Education Press and Springer-Verlag GmbH Germany 2017
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    Planning of waste electrical and electronic equipment (WEEE) recycling facilities: MILP modelling and case study investigation
    (Springer, 2015) Çapraz, Ozan; Polat, Olcay; Güngör, Aşkıner
    Waste electrical and electronic equipment (WEEE) consist of many different substances some of which contain hazardous components and valuable materials. The recovery of WEEE plays a key role on environmental sustainability because it minimizes the negative effects of hazardous materials and helps the efficient use of world's limited resources. Recovery strategies enable companies to collect reusable components and to recycle the material content of WEEE by using operations like sorting, disassembly and bulk recycling. Usually companies associated with municipals collect WEEE from end-users and/or collection points. Then they sell these items to WEEE recycling facilities through bidding. For recycling facilities, it is important to generate the best operational level decisions to receive and handle WEEE. This study contributes to the fulfillment of this need by presenting a mixed integer linear programming model to determine the maximum bid price offer while determining the best operation planning strategies. In order to demonstrate the potential of the proposed model, a real life case study along with several scenarios is studied. The findings of the case study indicate that the model has the potential to enable the decision maker to come with stronger decisions related to both bidding process and operational strategies of the facility.