Papers by Ismail Karaoglan
Gazi Universitesi Muhendislik Mimarlık Fakultesi Dergisi, 2012
Bu çalışmada klasik Araç Rotalama Problemi"nin (ARP) genelleştirilmiş bir hali olan Çok Kullanıml... more Bu çalışmada klasik Araç Rotalama Problemi"nin (ARP) genelleştirilmiş bir hali olan Çok Kullanımlı ve Zaman Pencereli Araç Rotalama Problemi (ÇK_ZP_ARP) dikkate alınmıştır. ÇK_ZP_ARP"de klasik ARP"den farklı olarak araçların birden fazla rotada kullanılmasına izin verilmektedir. ÇK_ZP_ARP ile genellikle raf ömrünün kısa olduğu ürünlerin dağıtımının yapıldığı ya da dağıtım süresinin kısa olduğu sistemlerde karşılaşılmaktadır. Pratikte sıklıkla karşılaşılan bir problem olmasına rağmen, ÇK_ZP_ARP ile ilgili literatürde çok az sayıda çalışma bulunmaktadır. Bu çalışmada, ÇK_ZP_ARP için bir karma tamsayılı doğrusal programlama modeli önerilmiştir. Önerilen matematiksel model, literatürden türetilen değişik boyutlarda test problemleri üzerinde en iyi çözüme ulaşma zamanı açışından karşılaştırılmış ve sonuçları sunulmuştur.
Applied Soft Computing, 2015
Journal of the Faculty of Engineering and Architecture of Gazi University
In this study, the Time-Dependent Vehicle Routing Problem (TDVRP) is considered which is a genera... more In this study, the Time-Dependent Vehicle Routing Problem (TDVRP) is considered which is a generalized version of the classical Vehicle Routing Problem (VRP). Unlike the VRP, the TDVRP can be defined as the routing a fleet of vehicle in which vehicle speeds are variable between the nodes. For the first time in literature, a new mathematical model, based on linear function, is developed for the TDVRP which considers the time dependent speed function that satisfies the “first-in-first-out” (FIFO) property and differs from the existing models in literature. Computational results on a large set of instances, generated from literature, are presented and the performance of the model evaluated in terms of computation time and percentage deviations to optimal solution. Three scenario analyses are conducted to assess the effect of changing several parameters on the model performance.
Journal of the Faculty of Engineering and Architecture of Gazi University
In this paper, the vehicle routing problem with time windows and multiple use of vehicles (VRP_TW... more In this paper, the vehicle routing problem with time windows and multiple use of vehicles (VRP_TW_MUV) which is the generalized version of the classic vehicle routing problem, is considered. Unlike the classic Vehicle Routing Problem, vehicles are allowed to use more than one route in the VRP_TW_MUV. The VRP_TW_MUV is encountered usually in the distribution systems in which the product‟s shelf-life is short or duration of the distribution is short. Although, the VRP_TW_MUV is often encountered in practice, there are very few studies in literature. In this study, a mathematical model proposed for the VRP_TW_MUV. The proposed mathematical model is compared in terms of time to reach the best solution on the test problems of various sizes derived from the literature.
This paper addresses the vehicle routing problem with simultaneous pickup and delivery (VRPSPD) w... more This paper addresses the vehicle routing problem with simultaneous pickup and delivery (VRPSPD) which is the problem of optimally integrating goods deliver and pickup when there are no precedence restrictions on the order in which the operations must be performed. We review mixed integer programming formulations in the literature for VRPSPD and propose two new formulations, PM1 and PM2, for the problem. While PM1 is a two-index node-based formulation, PM2 is a two-index flow-based formulation and both formulations have O(n 2) binary variables and O(n 2) constraints. Additionally, we prove that PM2 produce better lower bounds than PM1. To identify the efficient formulation, we conduct an experimental study and compare existing and proposed formulations in terms of linear programming relaxations gap, optimality gap, the number of optimal solutions obtained within two hours of CPU and average CPU time on two sets of test problems adapted from the literature. The computational results i...
Computers & Operations Research, 2015
ABSTRACT The design of distribution networks is one of the most important problems in supply chai... more ABSTRACT The design of distribution networks is one of the most important problems in supply chain and logistics management. The main elements in designing a distribution network are location and routing decisions. As these elements are interdependent in many distribution networks, the overall system cost can decrease if location and routing decisions are simultaneously tackled. In this paper, we consider a Capacitated Location-Routing Problem with Mixed Backhauls (CLRPMB) which is a general case of the capacitated location-routing problem. CLRPMB is defined as finding locations of the depots and designing vehicle routes in such a way that pickup and delivery demands of each customer must be performed with the same vehicle and the overall cost is minimized. Since CLRPMB is an NP-hard problem, we propose a memetic algorithm to solve the problem. To evaluate the performance of the proposed approach, we conduct an experimental study and compare its results with the lower bounds obtained by the branch-and-cut algorithm on a set of instances derived from the literature. Computational results indicate that the proposed approach is able to find optimal or very good quality solutions in a reasonable computation time.
2007 IEEE Congress on Evolutionary Computation, 2007
Journal of the Operational Research Society, 2008
ABSTRACT The transportation problem (TP) is one of the most popular network problems because of i... more ABSTRACT The transportation problem (TP) is one of the most popular network problems because of its theoretical and practical importance. If the transportation cost linearly depends on the transported amount of the product, then TP is solvable in polynomial time with linear programming methods. However, in the real world, the transportation costs are generally nonlinear, frequently concave where the unit cost for transporting products decreases as the amount of products increases. Since concave cost transportation problems (ccTPs) are NP-hard, solving large-scale problems is time consuming. In this study, we propose a hybrid algorithm based on the concepts borrowed from tabu search (TS) and simulated annealing (SA) to solve the ccTP. This algorithm, called ATSA (adaptive tabu-simulated annealing), is an SA approach supplemented with a tabu list and adaptive cooling strategy. The effectiveness of ATSA has been investigated in two stages using a set of TPs with different sizes. The first stage includes performance analysis of ATSA using SA, ASA (adaptive simulated anealing) and TS, which are basic forms of ATSA. In the second stage, ATSA has been compared with the heuristic approaches given in the literature for ccTP. Statistical analysis shows that ATSA exhibits better performance than its basic forms and heuristic approaches.Journal of the Operational Research Society (2008) 59, 331-341. doi:10.1057/palgrave.jors.2602301 Published online 18 October 2006
European Journal of Operational Research, 2013
ABSTRACT In this paper, we introduce a new variant of the Vehicle Routing Problem (VRP), namely t... more ABSTRACT In this paper, we introduce a new variant of the Vehicle Routing Problem (VRP), namely the Two-Stage Vehicle Routing Problem with Arc Time Windows (TS_VRP_ATWs) which generally emerges from both military and civilian transportation. The TS_VRP_ATW is defined as finding the vehicle routes in such a way that each arc of the routes is available only during a predefined time interval with the objective of overall cost minimization. We propose a Mixed Integer Programming (MIP) formulation and a heuristic approach based on Memetic Algorithm (MA) to solve the TS_VRP_ATW. The qualities of both solution approaches are measured by using the test problems in the literature. Experimental results show that the proposed MIP formulation provides the optimal solutions for the test problems with 25 and 50 nodes, and some test problems with 100 nodes. Results also show that the proposed MA is promising quality solutions in a short computation time.
Computers & Industrial Engineering, 2013
ABSTRACT Vehicle routing problem (VRP) is an important and well-known combinatorial optimization ... more ABSTRACT Vehicle routing problem (VRP) is an important and well-known combinatorial optimization problem encountered in many transport logistics and distribution systems. The VRP has several variants depending on tasks performed and on some restrictions, such as time windows, multiple vehicles, backhauls, simultaneous delivery and pick-up, etc. In this paper, we consider vehicle routing problem with simultaneous pickup and delivery (VRPSPD). The VRPSPD deals with optimally integrating goods distribution and collection when there are no precedence restrictions on the order in which the operations must be performed. Since the VRPSPD is an NP-hard problem, we present a heuristic solution approach based on particle swarm optimization (PSO) in which a local search is performed by variable neighborhood descent algorithm (VND). Moreover, it implements an annealing-like strategy to preserve the swarm diversity. The effectiveness of the proposed PSO is investigated by an experiment conducted on benchmark problem instances available in the literature. The computational results indicate that the proposed algorithm competes with the heuristic approaches in the literature and improves several best known solutions.
Computers & Industrial Engineering, 2009
Supply chain network (SCN) design is to provide an optimal platform for efficient and effective s... more Supply chain network (SCN) design is to provide an optimal platform for efficient and effective supply chain management (SCM). The problem is often an important and strategic operations management problem in SCM. The design task involves the choice of facilities (plants and distribution centers (DCs)) to be opened and the distribution network design to satisfy the customer demand with minimum cost. This paper presents a solution procedure based on steady-state genetic algorithms (ssGA) with a new encoding structure for the design of a single-source, multi-product, multi-stage SCN. The effectiveness of the ssGA has been investigated by comparing its results with those obtained by CPLEX, Lagrangean heuristic, hyrid GA and simulated annealing on a set of SCN design problems with different sizes.
mmfdergi.gazi.edu.tr
Tam Zamanında Üretim (TZÜ) sisteminde ara stok seviyesi düşük olduğu için makine arızaları sistem... more Tam Zamanında Üretim (TZÜ) sisteminde ara stok seviyesi düşük olduğu için makine arızaları sistemin verimliliği üzerinde büyük bir etkiye sahiptir. Bu nedenle bu çalışmada, tek ürünlü, çok hatlı ve çok aşamalı bir TZÜ sisteminde düzeltici ve koruyucu bakım politikalarının, kanban sayısının ve makinelerin arızalar arası ortalama sürelerinin etkisi benzetim tekniği kullanılarak incelenmiştir. Sistemde izin verilen kanban sayısı, arızalar arası ortalama süre ve koruyucu bakım politikaları dikkate alınarak yapılan bu deney tasarımı uyarınca, hangi koşullarda hangi bakım politikalarının performans ölçütleri üzerinde etkisi olduğu ayrıca incelenmiştir.
Applied Soft Computing, 2012
The aim of this work is to propose a hybrid heuristic approach (called hGA) based on genetic algo... more The aim of this work is to propose a hybrid heuristic approach (called hGA) based on genetic algorithm (GA) and integer-programming formulation (IPF) to solve high dimensional classification problems in linguistic fuzzy rule-based classification systems. In this algorithm, each chromosome represents a rule for specified class, GA is used for producing several rules for each class, and finally IPF is used for selection of rules from a pool of rules, which are obtained by GA. The proposed algorithm is experimentally evaluated by the use of non-parametric statistical tests on seventeen classification benchmark data sets. Results of the comparative study show that hGA is able to discover accurate and concise classification rules.
arastirmax.com
... Toplam talep toplam kapasiteden büyük ise aylak tedarikçi, tam tersi durumda iseaylak müşteri... more ... Toplam talep toplam kapasiteden büyük ise aylak tedarikçi, tam tersi durumda iseaylak müşteri eklenmek sureti ile problemde denge şartı sağlanır. Aylak tedarikçinin kapasitesi artık talebe (= toplam taleptoplam kapasite), aylak ...
European Journal of Operational Research, Jun 1, 2011
This paper addresses a location-routing problem with simultaneous pickup and delivery (LRPSPD) wh... more This paper addresses a location-routing problem with simultaneous pickup and delivery (LRPSPD) which is a general case of the location-routing problem. The LRPSPD is defined as finding locations of the depots and designing vehicle routes in such a way that pickup and delivery demands of each customer must be performed with same vehicle and the overall cost is minimized. We propose an effective branch-and-cut algorithm for solving the LRPSPD. The proposed algorithm implements several valid inequalities adapted from the literature for the problem and a local search based on simulated annealing algorithm to obtain upper bounds. Computational results, for a large number of instances derived from the literature, show that some instances with up to 88 customers and 8 potential depots can be solved in a reasonable computation time.
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Papers by Ismail Karaoglan