Nihan Çetin Demirel

Multi-criteria warehouse location selection using Choquet integral

The location of a warehouse is generally one of the most important and strategic decision in the optimization of logistic systems. Warehouse location is a long-term decision and is influenced by many quantitative and qualitative factors. Among the main criteria taken into account in this paper, some are costs, labor characteristics, infrastructure, and markets. This paper also includes some sub-criteria because of the hierarchical structure of the problem, like tax incentives and tax structures, availability of labor force, quality and reliability of modes of transportation, and proximity to customers. The conventional approaches to warehouse location selection problem tend to be less effective in dealing with the imprecise or vague nature of the linguistic assessment. Under many situations, the values of the qualitative criteria are often imprecisely defined for the decision-makers. Choquet integral is a suitable multi-criteria method to capture this imprecise or vague nature. This paper shows a successful application of multi-criteria Choquet integral to a real warehouse location selection problem of a big Turkish logistic firm.

Prioritization of e-Government strategies using a SWOT-AHP analysis: the case of Turkey

The e-Government agenda is being pursued throughout the world to one degree or another, but it has added significance in Central Europe. The region is just beginning to emerge from a period of far-reaching political and economic transformation following the collapse of repressive communist systems. For these countries, e-Government is more than simply a new channel of delivering services; it offers an opportunity to achieve a quantum leap in transparency and efficiency of administration, which the regions leaders have promised their citizens since the early 1990s. Turkey is currently working hard to catch this opportunity. Turkish Government has initiated the Urgent Action Plan in December 2002 to remedy long-lasting economic problems and to improve social and well-being of the country. One of the basic components of this plan is ‘e-Transformation Turkey Project’ which aims to carry Turkey into Information society. One of the two purposes of this study is to define and to prioritize the strengths, weaknesses, opportunities, and threats (SWOT) groups and their subfactors for e-Government in Turkey. The other purpose is to determine and to evaluate the alternative strategies for e-Government applications at the national level in Turkey. We use the SWOT approach in combination with analytic hierarchy process (AHP) to achieve this task. The strategies have been prioritized and sensitivity analyses of the obtained results have been made using a software.

Group decision making process for insurance company selection problem with extended VIKOR method under fuzzy environment

In recent years, because of the high potential for insurability in Turkey and the rapid improvement of insurance sector, foreign investors are interested in Turkish insurance market. Since insurability rate has reached saturation point in their countries, foreign investors tended to make investments in Turkey and start to purchase local insurance companies in Turkey. In this paper we analyze five Turkish insurance companies for a foreign investor who wants to purchase a local insurance company. For selecting the most appropriate alternative we used the extended VIKOR method which applied to determine the best feasible solution according to the selected criteria. This method was developed to solve multiple criteria decision making problems with conflicting and non-commensurable criteria, assuming that compromising is acceptable for conflict resolution. In this paper, the alternatives are evaluated according to all established criteria with the VIKOR method completely under fuzzy environment with fuzzy sets.

A new geometric shape-based genetic clustering algorithm for the multi-depot vehicle routing problem

In this paper, a new type of geometric shape based genetic clustering algorithm is proposed. A genetic algorithm based on this clustering technique is developed for the solution process of the multi-depot vehicle routing problem. A set of problems obtained from the literature is used to compare the efficiency of the proposed algorithm with the nearest neighbor algorithm so as to solve the multi-depot vehicle routing problem. The experimental results show that the proposed algorithm provides a better clustering performance in terms of the distance of each customer to each depot in clusters. This result in a considerably less computation time required, when compared with the nearest neighbor algorithm.

A SWOT-AHP Application Using Fuzzy Concept: E-Government in Turkey

E-government refers to the delivery of information and services online via the Internet. Many governmental units across the world have embraced the digital revolution and placed a wide range of materials on the web, from publications to databases. The purpose of this study is to evaluate and to determine the alternative strategies for e-government applications in Turkey. We use the strengths, weaknesses, opportunities, and threats (SWOT) approach in combination with the crisp and fuzzy analytic hierarchy process (AHP) to achieve this task. The strategies have been prioritized by using both methods comparatively and sensitivity analyses of the obtained results have been presented.

Fuzzy Analytic Hierarchy Process and its Application

The analytic hierarchy process (AHP) is one of the most widely-used multiattribute decision-making methods. In this section we overview the fuzzy AHP methods existing in the literature. We present the four different approaches of fuzzy AHP methods by giving numerical examples.

Multi-Criteria Evaluation of Land Cover Policies Using Fuzzy AHP and Fuzzy ANP: The Case of Turkey

ABSTRACT Land cover and use strategies have gained importance with decreases in per capita availability of land worldwide. The food deficit is increasing as a result of increases in the population, more so in developing and under-developed countries. A multi-criteria decision-making method using fuzzy Analytic Hierarchy Process (AHP) and fuzzy Analytic Network Process (ANP) for the evaluation of alternate land cover policies under various confidence levels of the decision-makers has been proposed. Computations have been done by using fuzzy AHP in terms of reflection ambiguity and uncertainty of the real world. Comparisons were made with the results obtained by using fuzzy ANP.

Risk-Based Evaluation of Turkish Agricultural Strategies using Fuzzy AHP and Fuzzy ANP

ABSTRACT In this article, we propose a model for selection of an agricultural strategy for Turkey by using fuzzy analytical hierarchy process (AHP) and analytical network process (ANP) based on linguistic terms. Fuzzy AHP-based methodology will be discussed to tackle the different decision criteria such as risk factors, ecological structure, socioeconomic structure, and technological structure involved in the selection of an agricultural strategy for Turkey and ANP will represent an effective tool for providing a suitable solution for managers and government administrators of this case. The linguistic levels of comparisons produced by the experts for each comparison are tapped in the form of triangular fuzzy numbers in order to construct fuzzy pairwise comparison matrices. The implementation of the system is demonstrated by a problem having four stages of hierarchy that contains 4 criteria and 15 sub-criteria.

Evolutionary algorithms for solving the airline crew pairing problem

Abstract Solving the airline crew pairing problem (CPP) requires a search to generate a set of minimum-cost crew pairings covering all flight legs, subject to a set of constraints. We propose a solution comprising two consecutive stages: crew pairing generation, followed by an optimisation stage. First, all legal crew pairings are generated with the given flights, and then the best subset of those pairings with minimal cost are chosen via an optimisation, process based on an evolutionary algorithm. This paper investigates the performance of two previously proposed genetic algorithm (GA) variants, and a memetic algorithm (MA) hybridising GA with hill climbing, for solving the CPP. The empirical results across a set of benchmark real-world instances illustrate that the proposed MA is the best performing approach overall.

Novel search space updating heuristics-based genetic algorithm for optimizing medium-scale airline crew pairing problems

This study examines the crew pairing problem, which is one of the most comprehensive problems encountered in airline planning, to generate a set of crew pairings that has minimal cost, covers all flight legs and fulfils legal criteria. In addition, this study examines current research related to crew pairing optimization. The contribution of this study is developing heuristics based on an improved dynamic-based genetic algorithm, a deadhead-minimizing pairing search and a partial solution approach (less-costly alternative pairing search). This study proposes genetic algorithm variants and a memetic algorithm approach. In addition, computational results based on real-world data from a local airline company in Turkey are presented. The results demonstrate that the proposed approach can successfully handle medium sets of crew pairings and generate higher-quality solutions than previous methods.