Gülfem Tuzkaya

Environmental performance evaluation of suppliers: A hybrid fuzzy multi-criteria decision approach

Increasing environmental problems enforce companies to be more environmental responsible. A company’s environmental performance is not only related to the company’s inner environmental efforts, but also it is affected by the suppliers’ environmental performance and image. As a stakeholder of the company, a supplier with bad environmental image affects badly the company’s environmental image. Also, raw materials and semi-finished products supplied from out of the company recourses- suppliers- affects the products environmental features such as life cycle, re-usability, re-manufacturability, hazardous substances, etc. Considering these direct and indirect effects, managers should also consider environmental performances of their suppliers in their supplier evaluation process. In this paper, a methodology for the evaluation of suppliers’ environmental performances is proposed. In this methodology, a hybrid Fuzzy-Analytic Network Process and Fuzzy-Preference Ranking Organization METHod for Enrichment Evaluations approach is utilized. Additionally, a numerical example is given to foster the better understanding of the methodology and the obtained results are analyzed with sensitivity analyses.

A two-phase possibilistic linear programming methodology for multi-objective supplier evaluation and order allocation problems

In this study, an integration of the analytic hierarchy process (AHP) and a multi-objective possibilistic linear programming (MOPLP) technique is developed to account for all tangible, intangible, quantitative, and qualitative factors which are used to evaluate and select suppliers and to define the optimum order quantities assigned to each. A multi-objective linear programming technique is first employed to solve the problem. To model the uncertainties encountered in the integrated supplier evaluation and order allocation methodology, fuzzy theory is adopted. Hence, possibilistic linear programming (PLP) is proposed for solving the problem, as it is believed to be the best approach for absorbing the imprecise nature of the real world. In the supplier evaluation phase, environmental criteria are also considered.

Evaluating centralized return centers in a reverse logistics network: An integrated fuzzy multi-criteria decision approach

In this paper, the centralized return centers location evaluation problem in a reverse logistics network is investigated. This problem is solved via an integrated analytic network process-fuzzy technique for order preference by similarity to ideal solution approach. Analytic network process allows us to evaluate criteria preferences while considering interdependence between them. On the other hand, technique for order preference by similarity to ideal solution decreases the number of computational steps compared to simple analytic network process evaluation. An important characteristic of the centralized return centers location evaluation problem, vagueness, is adapted to the methodology via the usage of fuzzy numbers in the technique for order preference by similarity to ideal solution approach. Finally, a numerical example is given to demonstrate the usefulness of the methodology. The results indicate that, this integrated multi-criteria decision making methodology is suitable for the decision making problems that needs considering multiple criteria conflicting each other. Also, by using this methodology, the interdependences between the criteria may be considered for these kinds of problems in a flexible and systematic manner.

Supply chain partners and configuration selection

The concept of a supply chain exists for over twenty years but partners and configuration selection process still is rather unstructured. In order to increase value in any supply chain, a more comprehensive and integrative approach is required to select the right partners and establish the right configuration along the chain. Under economic growth, wrong decisions does not jeopardize profitability dramatically. However, recent economy downtrends has made the choice of suitable partners in the dynamic supply chain a key strategic concern. The nature of these decisions usually is complex and unstructured. This paper aims to present an intuitionistic fuzzy Choquet integral operator based approach to partners and configuration selection. In order to bring structure in the evaluation process, the supply chain operations reference (SCOR) model developed by Supply Research Council is employed. The paper discusses the development of the value chain concept from partners selection perspective, outlines general similarities and differences of the value chain and the SCOR, and uses a simple V-form supply chain example to establish the proposed approach. Finally, results of the application and sensitivity of the results to the change in the selection criteria weights are discussed.

A methodology for the strategic design of reverse logistics networks and its application in the Turkish white goods industry

In this study, a multi-objective model for the reverse logistics network design (RLND) problem and a novel methodology are proposed. The proposed methodology is comprised of two stages: the centralised return centre (CRC) evaluation stage and the reverse logistics network design (RLND) stage. In the first stage an integrated ANP and fuzzy-TOPSIS methodology is utilised. In the second stage, using the CRC weights obtained in the first stage, the RLND model is solved via genetic algorithms (GAs). The proposed methodology is applied to a case from the Turkish white goods industry. The results are discussed and analysed.

A Multi-Criteria Decision Making Approach for Machine Tool Selection Problem in a Fuzzy Environment

Tools and machines have an important effect on the manufacturing operations’ effectiveness and the selection process of appropriate tools and machines is a complex issue with the consideration of multiple criteria. Considering the complexity of the problem area and the difficulties in machine tools evaluation processes, the main purpose of this study is to present a novel and effective methodology for machine tool selection problem. The proposed methodology constituted for this aim combines the modified DELPHI method, AHP (Analytical Hierarchy Process) and PROMETHEE (Preference Ranking Organization METHod for Enrichment Evaluations) approaches with fuzzy sets theory to be able to reflect the vagueness related to judgment of the decision-maker(s). A real life application is realized for pressing machine selection problem of a fixing products manufacturer from Turkey, Istanbul. The results of the proposed approach are compared with the results of fuzzy AHP-fuzzy TOPSIS approach. Additionally, sensitivity analyses are realized to show the changes in the results with the change in the criteria weights.

A comparative analysis of meta-heuristic approaches for facility layout design problem: a case study for an elevator manufacturer

In this study, a facility layout problem having NP-hard problem characteristic is attempted to be solved by using two different meta-heuristic approaches—Genetic Algorithm (GA) and Simulated Annealing (SA)—and a hybrid approach—Genetic Algorithm/Simulated Annealing (HGASA). The case study is completed for a company which can be seen as a small or a medium size enterprise. First, parameter values of GA and SA are determined by testing for various combinations of them. Then, the algorithms are run for one hundred times. The results of the algorithms are compared based on their fitness values and calculation time requirements using the paired-t test, mean and standard values. The results show that SA performs better than the others in terms of the fitness values and the time requirements. In this study, we also test the performance of our GA, SA and HGASA methodologies using some of the well-known test problems from the literature. We obtain very close results to those in literature.

Design of demand driven return supply chain for high-tech products

Many high-tech supply chain operate in a context of high process and market uncertainties due to shorter product life cycles. When introducing a new product, a company must manage the cost of supply, including the cost of returns over its short life cycle. The returns distribution looks like a negative exponential curve, starting with a high flow in returns for a period followed by a sudden drop and low from then on until the peak of life cycle. An important operations decision when launching a new product is the sizing of the capacity and location of return and repair centers in order to stay responsive and serve the market downstream after such a surge in early returns. It is the intention of this paper to extend the classical location models to include the demand return uncertainties and demand driven characteristics of high-tech return centers. We discuss first the operating environment, then brief the existing literature, finally present our fuzzy multi-objective location model, showing its complexities and propose an integrated AHP-weighted max-min solution approach. We show that our model can assist managing the dynamics of early or late return surge and supply of return centers, while target service time is maintained, returned centers’ capacities are balanced, and the total costs are minimized.

An Integrated Methodology for the Emergency Logistics Centers Location Selection Problem and its Application for the Turkey Case

Abstract Urgent response is vitally important after unpredictable disasters and it is highly dependent to the location of the emergency centers. Considering this importance degree, in this study, a location selection methodology for emergency logistics centers (ELCs) is proposed. There are various influencing factors or criteria to choose the most convenient locations for ELCs. However, we focused on some of the most important and prior criteria to obtain a more feasible approach and less calculation intensity. The main point is ranking and weighting the convenient locations or cities for constructing an ELC in a region or country. The alternative locations are chosen through the mostly natural disaster-prone cities. Decision criteria are determined according to the expert opinions. Decision Making Trial and Evaluation Laboratory (DEMATEL) and Analytic Network Process (ANP) methods are integrated to determine the convenient locations considering the relations between criteria and alternative locations. Afterwards, a real life application of the proposed methodology is realized for the Turkey case. Finally, results are examined and analyzed in terms of their sensitivity on the criteria weight changes.

A Strategic Planning Methodology for the Multimodal Transportation Systems: A Case Study from Turkey

Transportation costs have an important effect on companies’ competition capability in various sectors. To realize a positive effect, transportation industry should provide some specific performance criteria related with the economical efficiency and service quality. Also an increase in this performance degree depends on the obtaining optimum results of using the logistical resources in a convenient manner by the specialized logistics service providers. In this study, considering the effects of transportation modes on constituting a methodology that is interested in a strategic subject like constructing a transportation network is emphasized. In the process of selecting the most convenient transportation modes, all the required criteria are determined considering the related literature and the opinions of the experts. Then the analytical network process methodology is used to solve this selection problem. The close relationship between the transportation modes that will be used among the points in the network and the points that will be used for short storages and transshipment activities is considered. And the analytical network process is again used to select the most convenient ones among the alternative port locations. After decision making on these two important points, optimizing the freight flow among the supply chain by choosing the right transportation modes at each stage is aimed. To realize that optimization, the aims of decision makers from different levels or from different functional areas are satisfied by using the multilevel programming technique. Finally, the proposed methodology is applied on a transportation project of a logistic service provider, which gives service in a multimodal, multicommodity, multilevel and multiechelon transportation network.