Umut Rifat Tuzkaya

Integrating data envelopment analysis and analytic hierarchy for the facility layout design in manufacturing systems

Facility layout design (FLD) has a very important effect on the performance of a manufacturing system. The concept of FLD is usually considered as a multiobjective problem. For this reason, a layout generation and its evaluation are often challenging and time consuming due to their inherent multiple objectives in nature and their data collection process. In addition, an effective facility layout evaluation procedure necessitates the consideration of qualitative criteria, e.g., flexibility in volume and variety and quality related to the product and production, as well as quantitative criteria such as material handling cost, adjacency score, shape ratio, and material handling vehicle utilization in the decision process. This paper presents a decision-making methodology based on data envelopment analysis (DEA), which uses both quantitative and qualitative criteria, for evaluating FLD. The criteria that are to be minimized are viewed as inputs whereas the criteria to be maximized are considered as outputs. A computer-aided layout-planning tool, VisFactory, is adopted to facilitate the layout alternative design process as well as to collect quantitative data by using exact and vague data by means of fuzzy set theory. Analytic hierarchy process (AHP) is then applied to collect qualitative data related to quality and flexibility. The DEA methodology is used to solve the layout design problem by simultaneously considering both the quantitative and qualitative data. The purposed integrated procedure is applied to a real data set of a case study, which consists of 19 FLDs provided of the plastic profile production system.

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 fuzzy analytic network process based approach to transportation-mode selection between Turkey and Germany: A case study

A case study examining the different modes for transportation of freight by a Turkish logistics-service provider company is presented herein. A number of conflicting qualitative and quantitative criteria exist for evaluating alternative modes of transport. Qualitative criteria are often accompanied by ambiguity and vagueness. To cope with ambiguity and vagueness problem, the fuzzy analytic network process (ANP) method has been used. A large number of detailed criteria that interact with each other have been evaluated and synthesized to obtain the most suitable transportation mode. This evaluation has been carried out by a group of decision makers coming from different management levels and functional areas in the sector of logistics and from the service company with intent to provide a more accurate and mutually acceptable solution. Furthermore, the model used here has been validated by comparing the results obtained with the current preferences of the company.

A particle swarm optimization algorithm for the multiple-level warehouse layout design problem

Warehouse operation and management is one of the essential parts of manufacturing and service operations. The warehouse layout problem is a key to warehouse operations. Generally, warehouse layout design models attempt to optimize different objectives such as the orientation of storage racks, the allocation of space among competing uses, the number of cranes, the overall configuration of the facility, etc. The warehousing strategies can be classified as distribution-type, production-type and contract-type warehouse strategies. In this study, a distribution-type warehouse considered that various type products are collected from different suppliers for storing in the warehouse for a determined period and for delivery to different customers. The aim of the study is to design a multiple-level warehouse shelf configuration which minimizes the annual carrying costs. The turnover rates of the products are classified and they are considered while putting/picking them to/from shelves regarding the distances between the shelves and docks. Since proposed mathematical model was shown to be NP-hard, a particle swarm optimization algorithm (PSO) as a novel heuristic was developed for determining the optimal layout.

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 the environmental effects of transportation modes using an integrated methodology and an application

The increasing needs for transportation of freight and passengers causes environmental impacts. Preventing studies for these impacts should be considered by logistics firms and encouraged by the regulations of authorities. An important contribution can be provided by determining the environmental effects of the transportation modes in specific regions and using the most convenient ones. In this study, multiple criteria decision-making techniques, including human judgments, tangible and intangible criteria and priorities are used. Fuzzy analytic hierarchy process and preference ranking organization method for enrichment evaluation, as two of the multi criteria decision-making methodologies, are integrated for ranking the transportation modes in terms of the environmental effects of them. The proposed decision-making process is applied to chose the environmentally convenient transportation mode with respect to the determined evaluation criteria in Marmara Region of Turkey. The results indicate that, the main problem for the Marmara Region about transportation aspects is to pass from the intensive utilization of the road transportation mode to another one. In this study it is seen that the most convenient transformation mode in Marmara Region is the sea transportation mode.

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 holonic approach based integration methodology for transportation and warehousing functions of the supply network

The supply chain (SC) is often defined as a network that is composed of different functions, including suppliers, manufacturing plants, warehouses/distribution centers, retailers and customers. A supply network (SN) is a sequence of different and multiple numbers of functions and individual functional units that must satisfy all capacities and demand requirements imposed by customers with minimum cost to the network. The most important functions of a SN are warehousing and transportation functions. This paper addresses the warehousing and transportation network design problem that involves determining the best strategy for distributing the sub-products from the suppliers to the warehouse and from the warehouse to the manufacturers. Considering some similarities between holonic systems and SN systems, a holonic approach based modeling methodology is proposed in this study. A multiple supplier, single warehouse and multiple manufacturer system are considered to be an integrated warehousing and transportation network. Consequently, a linear programming model is presented to maximize the profit of both of the overall SN and the individual functional units of the SN functions.

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.

Supply Chain Performance Measurement: An Integrated DEMATEL and Fuzzy-ANP Approach

Supply chain performance measurement is vital for the continuous improvement of supply chain management. Effective supply chain performance measurement is one of the most important aspects for supply chain management in which decision makers can analyze the historical performance and current status, and set future performance targets. This chapter provides a conceptual point of view to supply chain performance measurement. Inevitably, quantification of the values with precision in a complex supply chain performance measurement system is difficult. The supply chain performance measurement under fuzziness can consider the uncertainty and ambiguity surrounding the supply chain performance measurement. The aim of this chapter is to present a fuzzy decision making approach to deal with the performance measurement in supply chain systems. In this chapter, DEMATEL method is adapted to model complex interdependent relationships and construct a relation structure using measurement criteria for evaluation. F-ANP is performed to overcome the problem of dependence and feedback among each measurement criteria. The integrated DEMATEL and F-ANP approach provides an effective decision tool for the supply chain performance measurement.