Browsing by Author "Özfirat, PM"

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    A fuzzy analytic hierarchy process methodology for the supplier selection problem
    Özfirat, PM; Tasoglu, GT; Memis, GT
    Purpose - Purchasing activities of a company form a very important part in the operation of the company. The quality of production and services mainly rely on the performance of the suppliers. In addition, a large amount of the product's total cost belongs to the purchasing cost of its materials. Therefore, selecting the most suitable suppliers is very important for the firm. Unfortunately, most of the time, suppliers cannot provide the highest quality parts on-time at the lowest costs in the market. In other words, quality, delivery and cost objectives conflict with each other. The purpose of this paper is to determine the best supplier for the firm according to these conflicting objectives. Design/methodology/approach - In this study a fuzzy analytic hierarchy process (FAHP) approach is employed for the supplier selection problem of a textile company. First the selection criteria according to company's objectives are determined. Then the pair-wise comparisons are made on a fuzzy basis. Similarly, in the next step, the six alternative suppliers are compared by fuzzy means. Findings - Finally, the two suppliers which achieved the highest performance are advised to the company and this study is the first one which employs FAHP using fuzzy prioritization method in supplier selection problem. Originality/value - There are many different applications of FAHP in literature and some of these have found applications in supplier selection problem. However, to the best of the authors' knowledge this study is the first one which employs FAHP using fuzzy prioritization method in supplier selection problem.
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    The performance prediction of roadheaders with response surface analysis for underground metal mine
    Özfirat, KM; Malli, T; Özfirat, PM; Kahraman, B
    Roadheaders are being used in development roads in underground mines. Especially, as total reserve is enough for large investments and mine roads, roadheaders are important to increase production rate. Roadheaders are classified according to the weight head drive or total power. In this study, the effects of several factors on roadheader performance is examined. The factors examined are power of the machine, weight of the machine, ratio of power to weight, drilling rate index, uniaxial compressive strength and rock mass rating. Instantaneous cutting ratio is used to define the performance of the machine. Response surface methodology and linear regression are used to investigate the relations between these variables. In the results of the study, machine performance is found to be highly correlated with machine power (P), weight (W) and the P/W ratio of the machine.
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    SELECTION OF COAL TRANSPORTATION MODE FROM THE OPEN PIT MINE TO THE THERMIC POWER PLANT USING FUZZY ANALYTIC HIERARCHY PROCESS
    Özfirat, PM; Özfirat, MK; Malli, T
    Coal produced in open pit mines should be moved to thermic power plants for production of power. Thermic power plants require very large amounts of coal. In transportation process of this coal, both costs and technical parameters should be considered. Common alternative transportation modes in this process are belt conveyors, truck types, suspension rail conveying systems, pipelines and railways. Selection of one of these modes is influenced by transportation distance, inclination of the haulage road, amount of coal reserve, investment costs, production capacity and unit production cost of the open pit mine. In this study, advantages and disadvantages of alternative transportation modes are analysed using Fuzzy Analytic Hierarchy Process (F-AHP). The results revealed, belt conveyors and trucks transportation by are superior to others.