Browsing by Author "Erdem, Mehmet"

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Citation Count: 46
Analysis of electric vehicles in home health care routing problem
(Elsevier Sci Ltd, 2019) Erdem, Mehmet; Koc, Cagri; Industrial Engineering
The road transportation is one of the largest contributors to greenhouse gas emissions globally, and rapid urbanisation increases the environmental and economic challenges. Electric vehicles support green supply chain and clean routing operations when compared with the traditional fossil fuel-powered vehicles. This paper analyses a variant of the home health care routing problem in which a group of health care workers performs a requested number of jobs by using electric vehicles. The problem considers multi-depot, heterogeneous fleet, time windows, preferences, competencies, connected activities, the range of electric vehicles, charging status, and charge strategies. We develop a hybrid metaheuristic which successfully combines genetic algorithm and a variable neighbourhood descent, and offer several algorithmic procedures tailored to handle the rich constraints of the problem. Extensive computational experiments on small, medium and large-scale instances have shown that the hybrid metaheuristic is effective on the problem. (C) 2019 Elsevier Ltd. All rights reserved.
Citation Count: 47
Optimization of electric vehicle recharge schedule and routing problem with time windows and partial recharge: A comparative study for an urban logistics fleet
(Elsevier, 2021) Bac, Ugur; Erdem, Mehmet; Industrial Engineering
The use of electric vehicles (EVs) is becoming more and more widespread and the interest in these vehicles is increasing each day. EVs promise to emit less air pollution and greenhouse gas (GHG) emissions with lower operational costs when compared to fossil fuel-powered vehicles. However, many factors such as the limited mileage of these vehicles, long recharging times, and the sparseness of available recharging stations adversely affect the preferability of EVs in industrial and commercial logistics. Effective planning of EV routes and recharge schedules is vital for the future of the logistics sector. This paper proposes an electric vehicle routing problem with the time windows (EVRPTW) framework, which is an extension of the well-known vehicle routing problem (VRP). In the proposed model, partial recharging is considered for the EVRPTW with the multiple depots and heterogeneous EV fleet and multiple visits to customers. While routing a set of heterogeneous EVs, their limited ranges, interdependent on the battery capacity, should be taken into consideration and all the customers' deliveries should be completed within the predetermined time windows. To deal with this problem, a series of neighbourhood operators are developed for the local search process in the variable neighbourhood search (VNS) and variable neighbourhood descent (VND) heuristics. The proposed solution algorithms are tested in large-scale instances. Results indicate that the proposed heuristics perform well as to this problem in terms of optimizing recharging times, idle waiting times, overtime of operators, compliance with time windows, number of vehicles, depots, and charging stations used.
Citation Count: 0
TEDARİK ZİNCİRİ PERFORMANSININ ENTEGRE İKİ AŞAMALI KÜMELEME VE ARALIK TİP-2 BULANIK TOPSİS YÖNTEMİ KULLANARAK DEĞERLENDİRİLMESİ: BİR VAKA ÇALIŞMASI
(2019) Erdem, Mehmet; Erkan, Turan Erman; Industrial Engineering
Tedarik zinciri (TZ) yönetiminde birçok araştırmacı ve kuruluş sistemin performansını iyileştirmek için farklı perspektiflerde çaba sarfetmektedir. Farklı sektörlerde TZ performansını değerlendirmek için çeşitli metrikler ve karar verme metodolojileri önerilmiştir. Bu çalışmada, TZ performans değerlendirme süreçleri için bütünleşik iki aşamalı kümeleme ve aralık tip-2 bulanık TOPSIS yöntemi önerilmektedir. Önerilen bu yaklaşımın ilk adımında, iki aşamalı kümeleme analizi ile sektörlerin homojen olarak bölümlendirilmesi ve aynı zamanda problemin boyutunun azaltılması sağlanmaktadır. İkinci adımda, bulanık TOPSIS ile oluşturulan kümeler değerlendirilmektedir. Yaklaşımın sonuçları, örgütsel etkinlik ve şirket performansı gibi konularda makro bakış açısı sağlamaktadır. Ayrıca sonuçlar, her şirketin bulunduğu kümelerdeki rakipleri arasında ve diğer sektörlerdeki rakiplere karşı kendini değerlendirme fırsatı sağlamaktadır.
Citation Count: 15
A TWO-STAGE SOLUTION APPROACH FOR THE LARGE-SCALE HOME HEALTHCARE ROUTEING AND SCHEDULING PROBLEM
(Southern African inst industrial Engineering, 2017) Erdem, M.; Bulkan, S.; Industrial Engineering
The purpose of this study is to introduce a two-stage solution approach for a large-scale home healthcare routeing and scheduling problem (HHCRSP). In the first part of the two-stage solution approach, a cluster-assign algorithm is employed, based on the home location and the time to obtain feasible clusters. In the second stage, using these clusters, route construction heuristics start to create schedules and routes, taking the side constraints of the model into consideration. Using the novelty of this two-stage solution approach, higher diversification is achieved with a series of newly-developed cross movement strategies. The computational results show that our solution approach offers certain advantages, such as an increase in the efficient use of human resources, and a decrease in the working time of nurses.