Person: AYHAN, MUSTAFA BATUHAN
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AYHAN
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MUSTAFA BATUHAN
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Publication Metadata only A two stage approach for supplier selection problem in multi-item/multi-supplier environment with quantity discounts(PERGAMON-ELSEVIER SCIENCE LTD, 2015) KILIÇ, HÜSEYİN SELÇUK; Ayhan, Mustafa Batuhan; Kilic, Huseyin SelcukSupplier selection, which is the basic process of finding the best supplier/suppliers to procure the items regarding various criteria, is an important decision problem to be studied. It becomes more complicated if there are various items and any supplier cannot provide all types of items individually. Such situations are called multi-item, multi-supplier environments and rarely studied in the literature. In addition, when quantity discounts are also considered, it gets more sophisticated. Although there are several studies dealing with these aspects separately, to the best knowledge of the authors, this study is the first candidate attempting to solve this type of problem with an integrated approach including Fuzzy Analytical Hierarchy Process (F-AHP) and Mixed Integer Linear Programming (MILP) model. This study mainly operates in two stages. In the first stage, the relative weights of each criterion for each type of item are determined via F-AHP technique. In the second stage, these outputs are used as inputs in the MILP model to determine the suppliers and the quantities to be provided. In order to validate the model, an application is performed in a gear motor company and numerical results of the problem are revealed to select the best suppliers among 6 alternatives, for the procurement of 5 items regarding 4 criteria, namely, price, quality, delivery time performance, and after sales performance, in case of quantity discounts. (C) 2015 Elsevier Ltd. All rights reserved.Publication Open Access A multi-agent based approach for change management in manufacturing enterprises(SPRINGER, 2015-10) ÖZTEMEL, ERCAN; Ayhan, Mustafa Batuhan; Aydin, Mehmet Emin; Oztemel, ErcanChange management becomes an unavoidable necessity for manufacturing enterprises. Since change in business processes carries significant impact on the performance of manufacturing companies, a change management model is definitely required to remain competitive. Moreover, utilizing agent based systems will provide computational provision and integrity to manage and measure the capabilities to follow the change in a progressive approach by employing the cooperation and collaboration properties of various agents helping for retrieval of the required information in a rapid way. Therefore, in this paper, a multi-agent based change management model is proposed to handle the changes in manufacturing enterprises. The model is validated through a case study done to measure the performance of change management capabilities in a manufacturing company. A sensitivity analysis on the results of this case study is also conducted to reveal the system reactivity to various parameters.Publication Metadata only Reverse logistics system design for the waste of electrical and electronic equipment (WEEE) in Turkey(ELSEVIER, 2015) KILIÇ, HÜSEYİN SELÇUK; Kilic, Huseyin Selcuk; Cebeci, Ufuk; Ayhan, Mustafa BatuhanDepending on the high consumption in the world, the amount of waste increases. One of the critical waste types to be handled is the electrical and electronic waste (WEEE). The recovery of WEEE is very important both from environmental and economic aspects and has become mandatory in most of the countries in the world. Reverse logistics which is mainly the backward flows of used products from consumers to producers is an important stage while constructing a recovery system. The network structure of reverse logistics system plays an important role in the total cost of the recovery system. These structures mainly include the locations of facilities and the flows between the related points. With this study, a reverse logistics system is designed for WEEE in Turkey which is one of the fast developing countries in the world. Ten scenarios are taken into account regarding different collection rates via a mixed integer linear programming model. Different types of storage sites and recycling facilities are considered within the model differing from the existing studies. The optimum locations of storage sites and recycling facilities are obtained for each scenario satisfying the minimum recycling rates stated by the European Union directive for each product category. (C) 2014 Elsevier B.V. All rights reserved.Publication Open Access An approach for the determination and correlation of diversity and efficiency of software development teams(ACAD SCIENCE SOUTH AFRICA A S S AF, 2018-03-27) AYHAN, MUSTAFA BATUHAN; Altiner, Seher; Ayhan, Mustafa B.We examined the impact of diversity on team efficiency. To do so, a model was developed to measure both the efficiency and diversity of the teams. Based on these measures, the correlation between efficiency and diversity was also analysed. In addition, to demonstrate the applicability of the model, it was applied to a real-life problem involving five teams dealing with different software development projects. Firstly, diversity indices were calculated based on age, experience, education and gender information on each member for each team by using Simpson's Diversity Index. Then, four key performance indicators (KPIs) were defined to measure the success rate of the teams. Depending on these KPIs, efficiencies of the teams were measured through data envelopment analysis (DEA). The correlation between team efficiency and each diversity factor was analysed and all four factors had positive correlation with efficiency. That is, in order to increase efficiency, teams should be composed of members with diverse characteristics. Education was the diversity factor that had the most positive correlation with team efficiency. This result highlights the importance of different educational backgrounds on team efficiency. Significance: This study represents the first attempt to measure team diversity using Simpson's Diversity Index. A new technique is proposed to measure team efficiency through DEA. Team efficiency is positively correlated with diversity, specifically educational level, which is important for many software development teams to consider.Publication Open Access A methodology to measure the degre of managerial innovation(2014-02-25) ÖZTEMEL, ERCAN; Ayhan, Mustafa Batuhan; Oztemel, ErcanPublication Metadata only A quantitative approach for measuring process innovation: a case study in a manufacturing company(TAYLOR & FRANCIS LTD, 2013) ÖZTEMEL, ERCAN; Ayhan, Mustafa Batuhan; Oztemel, Ercan; Aydin, Mehmet Emin; Yue, YongProcess management and innovation arguably remain among the concepts under focus of recent researches since there is no significantly outstanding method to measure and monitor the level of innovation in the manufacturing processes over a particular time period taking the fundamental activities of manufacturing processes into account. Although there are various studies relevant to process improvement, manufacturing processes are not focused on in the literature. This paper presents a novel performance indicator, called degree of process innovation, for monitoring and measuring innovation in manufacturing processes based on the four most important components among the fundamental activities of a manufacturing system. The components are namely Average Labour Utilisation, Cumulative Bottleneck Ratio, Unit Production Time and Unit Production Cost. The idea behind this approach has flourished on the basis of an indicator proposed in the literature to measure the general organisational improvements. The scope of that indicator has been narrowed down to manufacturing processes to accurately reflect the state of the manufacturing processes. The proposed approach has been verified with a case study in manufacturing industry, where each of the four sub-indicators was calculated based on the data provided and aggregated into the degree of process innovation. The innovation degree is successfully indicated.