BÜYÜKÖZKAN FEYZİOĞLU GÜLÇİN,GÜLERYÜZ SEZİN,KARPAK BİRSEN (2017).  A new combined IF-DEMATEL and IF-ANP approach for CRM partner evaluation.  International Journal of Production Economics, 191, 194-206.

ABSTRACT
Selection of the most suitable business partner is a strategic decision for outsourcing problems. This study aims to provide an effective evaluation approach for assessing alternative CRM partners. The choice of a suitable partner is a very complex decision, involving many conflicting objectives as well as complex considerations. Such decision processes involving several perspectives can be worked around by using Multi Criteria Decision Making (MCDM) techniques. MCDM can assist decision makers with reaching  consensus with collective participation and objective decisions based on value judgments. This paper proposes a combined approach for effectively evaluating CRM partners that integrates Intuitionistic Fuzzy Sets (IFS) with Group Decision Making (GDM). It consists of Intuitionistic Fuzzy Analytic Network Process (IF-ANP) for building and analyzing the criteria weights and Intuitionistic Fuzzy Decision Making Trial and Evaluation Laboratory (IF-DEMATEL), a useful technique for managing uncertainties to identify interrelations between criteria. As the IFS describe powerfully vagueness and uncertainty, IFS can depict decision makers’ evaluations with a structure which is more rich, allowing for a more accurate description of the decision making process. The scientific value of the paper stems from its ability to present a novel study that makes use of GDM based MCDM with combined IF-DEMATEL and IF-ANP approaches. This study contributes to the existing literature by providing a combined IFS based DEMATEL-ANP framework for the first time and developing a novel evaluation model for a real industrial problem to improve the CRM partner selection process.

Keywords: Intuitionistic fuzzy group decision making – MCDM – Intuitionistic Fuzzy ANP – Intuitionistic Fuzzy DEMATEL – CRM partner evaluation

BÜYÜKÖZKAN FEYZİOĞLU GÜLÇİN,GÜLERYÜZ SEZİN (2017).  Evaluation of Renewable Energy Resources in Turkey using an integrated MCDM approach with linguistic interval fuzzy preference relations.  Energy, 123, 149-163.

ABSTRACT
The use of Renewable Energy Resources (RER) is growing rapidly for energy generation and several studies indicate that these will have a huge contribution in the future. Selecting RER is a complex problem involving different criteria and alternatives. The first aim of the study is the development of an evaluation model to select the most appropriate RER in Turkey. Evaluation of RER alternatives can be seen as a multi criteria decision making (MCDM) problem that can be solved with flexible tools to handle complex situations and assist decision makers (DMs) in mapping out the situation. In this process, Group Decision Making (GDM) involves multiple DMs who have different goals or ways of thinking and can assess the decision process distinctively different from others. Linguistic interval fuzzy preferences with DEMATEL, ANP, TOPSIS integrated techniques are utilized to eliminate uncertainty and to better represent DMs’ preferences. The originality of the paper comes from its ability to propose effective and comprehensive evaluation model for both Turkey and literature and apply to a real industrial problem to improve the RER selection process. Another contribution is to adapt integrated techniques including linguistic interval fuzzy preferences with DEMATEL, ANP, TOPSIS for the first time.

Keywords: Renewable energy resources – Linguistic interval fuzzy preference relations – Group decision making – DEMATEL – ANP – TOPSIS

BÜYÜKÖZKAN FEYZİOĞLU GÜLÇİN,GÜLERYÜZ SEZİN (2016).  An integrated DEMATEL ANP approach for renewable energy resources selection in Turkey.  International Journal of Production Economics, 182, 435-448.

ABSTRACT
Renewable energy resources(RER) are globally emerging as an energy generation alternative and latest research points out that these resources will have vital importance in the future. Limited reserves and negative environmental impacts of fossil fuels make investors to consider RER for sustainable development. In this study, a multicriteria decision making (MCDM) approach is applied using the Decision Making Trial and Evaluation Laboratory Model (DEMATEL) technique, integrated with Analytic Network
Process (ANP) for selecting the most appropriate RER in Turkey from an investor-focused perspective. The originality of the work comes from its ability to combine technical, economic, political and social attributes with a developed RER  evaluation model and the effective and integrated framework it provides to select the most appropriate RER for Turkey for the first time using integrated DEMATEL and ANP approach.

Keywords: Renewable energy resources – MCDM – DEMATEL – ANP

BÜYÜKÖZKAN FEYZİOĞLU GÜLÇİN,GÜLERYÜZ SEZİN (2016).  Multi criteria group decision making approach for smart phone selection using intuitionistic fuzzy TOPSIS.  International Journal of Computational Intelligence Systems, 9(4), 709-725.

ABSTRACT

The objective of this study is to provide an effective multi criteria decision making (MCDM) approach with group decision making to evaluate different smart phone alternatives according to consumer preferences. The choice of the most appropriate phone is a very complex decision, involving several perspectives. In such complex situations intuitionistic fuzzy sets with TOPSIS (IF-TOPSIS) can be utilized to eliminate uncertainty and to better represent decision makers’ preferences. The originality of the paper comes from its ability to handle high uncertainty in a smart phone selection and provide a real case study with IFS for the first time.

Keywords: Smart phone selection, Intuitionistic fuzzy sets, IF-TOPSIS, Group Decision Making, GDM

BÜYÜKÖZKAN FEYZİOĞLU GÜLÇİN,GÜLERYÜZ SEZİN (2016).  Lojistik Firma Web Sitelerinin Performanslarının Çok Kriterli Değerlendirilmesi.  Journal of the Faculty of Engineering and Architecture of Gazi University, 31(4), 889-902.

ÖZET

Web siteleri e-iş yapısının kullanıcı ile etkileşiminin gerçekleştiği ara yüzüdür. Bu nedenle web sitelerinin kalitesi müşteri memnuniyeti için esastır. Bu çalışmada lojistik firma web sitelerinin kalite performanslarının ölçümü problemine bir çözüm önerilmektedir. Web sitelerinin kalitesinin ve performansının analiz edilmesinde kullanılan ve herkes tarafından kabul edilen standart bir yapı yoktur. Oysa standart bir değerlendirme yapısı ile başarılı web sitelerinin belirlenmesi daha sağlıklı ve hızlı olacaktır. Bu doğrultuda bu çalışmada lojistik firma web sitelerinin kalitesini daha etkin bir şekilde değerlendirmek amacıyla bulanık mantık temelli bütünleşik çok kriterli karar verme (ÇKKV) yaklaşımı önerilmiştir. Çalışmanın ilk aşamasında detaylı yazın taraması ve uzman görüşleri ile web sitesi değerlendirme kriterleri ve kriter hiyerarşisi belirlenmiştir. Çalışmanın ikinci aşamasında değerlendirme kriter ağırlıkları ÇKKV yöntemlerinden Analitik Hiyerarşi Proses (AHP) tekniğinin bulanık uygulaması ile hesaplanmıştır. Son aşamada ise, Türk lojistik sektöründe öncü sayılan 15 firmanın web sitelerinin performansları bulanık TOPSIS tekniği uygulanarak iyiden kötüye doğru sıralanmıştır. Ayrıca kriter ağırlıklarındaki olası değişimlerin web sitesi sıralamasına etkilerini araştırmak amacıyla duyarlılık analizi yapılmıştır. Bu çalışma araştırmacıların web sitesi değerlendirme problemini teorik olarak daha iyi anlayabilmeleri, firmaların ise daha memnunluk verici web siteleri tasarlayabilmeleri için yazına katkı sağlamaktadır.

Anahtar Kelimeler: Web sitesi kalite performansı, çok kriterli karar verme, analitik Hiyerarşi Süreci, TOPSIS bulanık mantık

BÜYÜKÖZKAN FEYZİOĞLU GÜLÇİN,GÜLERYÜZ SEZİN (2016).  A  new integrated intuitionistic fuzzy group decision making approach for product development partner selection.  Computers & Industrial Engineering, 102, 383-395

ABSTRACT

Globally, customers are getting increasingly demanding in terms of quality, price and performance of products and are asking for shorter product development periods with more predictable cycles. These market pressures drive firms to collaborate with possible partners in product development (PD) processes. Nevertheless, choosing the suitable partner for an effective PD is a challenging, complex decision. This study proposes a combined Intuitionistic Fuzzy (IF) Group Decision Making (GDM) model that consists of the Intuitionistic Fuzzy Analytic Hierarchy Process (IF-AHP) and Intuitionistic Fuzzy Technique for Order Preference by Similarity to Ideal Solution (IF-TOPSIS) methods for effectively evaluating PD partners. In order to obtain a more complete evaluation and more precise results, IF-AHP is used for determining criteria weights, whereas IF-TOPSIS methodology is conducted for ranking partner alternatives. This study contributes to partner selection and IF set literature by providing a combined framework based on IF-AHP and IF-TOPSIS with GDM methodology for the first time. To assess the validity of the proposed integrated IF GDM approach, a case study is also provided. This study contributes to literature as it provides a better insight into the theoretical ground of the PD partner selection problem. It also supports organizations which aim to improve their PD evaluation systems.

Keywords: Intuitionistic fuzzy group decision making, Product development partner selection, Intuitionistic Fuzzy AHP, Intuitionistic Fuzzy TOPSIS

BÜYÜKÖZKAN FEYZİOĞLU GÜLÇİN,GÜLERYÜZ SEZİN (2016).  Fuzzy multi criteria decision making approach for evaluating sustainable energy technology alternatives.  International Journal of Renewable Energy Sources, 1, 1-6

ABSTRACT

Energy has been universally recognized as a key element for sustainable development. In developing countries, such as Turkey, energy demand increases thanks to a fast growing population and economy, posing threats of energy availability in the next decades. For this reason, Turkey has to evaluate and develop domestic, clean, and reliable energy sources from different alternative sources for sustainable development. In this process, as selecting the best energy alternatives requires both quantitative and qualitative evaluation criteria, two multi criteria decision making methods (MCDM) are employed for the analysis. More precisely, the fuzzy Analytic Hierarchy Process (AHP) is used to determine the evaluation criteria weights and fuzzy Technique for Order Performance by Similarity to Ideal Solution (TOPSIS) is applied to select the most suitable alternative. The originality of the paper comes from its ability to propose an effective framework for both Turkey and literature and apply it to a real industrial problem to improve the sustainable energy alternative technology selection process.

Keywords: Sustainable energy selection, Multi-criteria decision-making, Fuzzy AHP, Fuzzy TOPSIS

BÜYÜKÖZKAN FEYZİOĞLU GÜLÇİN,GÜLERYÜZ SEZİN (2015).  Extending Fuzzy QFD Methodology with GDM Approaches  An Application for IT Planning in Collaborative Product Development.  International Journal of Fuzzy Systems, 17(4), 544-558.

ABSTRACT

Collaborative product development (CPD) is a technology intensive process and effective planning in information technologies (IT) can improve the performance of CPD activities. Considering that quality function deployment (QFD) can be utilized as a planning tool for products and systems, the use of the QFD can enable IT systems to align their structure for CPD. In the QFD approach, the house of quality matrix is used for converting customer requirements into engineering characteristics. The challenge in this process is the profile of the inputs that are collected from the participants who provide feedback on customer requirements. Individual judgments of these participants can be in various formats, or can indicate preferences that are incomplete. This study aims to tackle with this issue by making use of an extended QFD methodology in CPD for IT planning. For this purpose, two group decision making (GDM) approaches are used to address both challenges of multiple preference formats and incomplete information. The validity of the developed IT planning model for CPD is tested with a case study at a Turkish software company using the two GDM approaches, and the obtained results are discussed. As customer requirements are important at every phase of CPD, the proposed model can help implementers to improve their decision processes.

Keywords: Collaborative product development – Information technology planning – Quality function deployment – Fuzzy group decision making – Incomplete preference relations – Multi-preference relations

BÜYÜKÖZKAN FEYZİOĞLU GÜLÇİN,GÜLERYÜZ SEZİN (2014).  A new GDM based AHP framework with linguistic interval fuzzy preference relations for renewable energy planning.  JOURNAL OF INTELLIGENT & FUZZY SYSTEMS, 27(6), 3181-3195.

ABSTRACT

Renewable energy resources (RER) are one of the most growing energy sources in theworld and various researches point out that these resources will have vital importance in the future. On the other hand, limited reserves and negative environmental impacts of fossil fuels make investors to consider RER for their needs in a sustainable way. To select most appropriate RER alternatives, it is essential to prioritize alternatives which provide minimum negative environmental impact caused by RER operations and maximum financial benefits to the investor. This study aims to develop a novel RER evaluation model that can help investors with their critical selection process and identify the priority of RER alternatives. High complexity of socioeconomic environments often makes it difficult for a single decision maker (DM), investor in our case, to consider all important aspects of selection problems. Therefore, group decision making (GDM) is often preferred to avoid the bias and minimize the partiality in this kind of decision process. In some critical situations DMs’ judgments can be under uncertainty where it is difficult for them to provide exact numerical values. In these cases, linguistic interval fuzzy preference relations are utilized to better represent DMs’ preferences. This paper develops a new GDM approach based on fuzzy analytic hierarchy process (AHP) with linguistic interval fuzzy preference relations for obtaining weights of selected evaluation criteria. Then, the fuzzy technique for order performance by similarity to ideal solution (TOPSIS) approach is applied for ranking suitable RER alternatives. The originality of the paper comes from the application of these combined methodologies in literature for the first time and no previous work has investigated this RER subject using this kind of an integrated method. For demonstrating the potential of the proposed approach, a motivated example is given to select the most suitable RER for Turkey.

Keywords: Renewable energy resources, MCDM, group decision making, AHP, Linguistic interval fuzzy references, fuzzyTOPSIS

BÜYÜKÖZKAN FEYZİOĞLU GÜLÇİN,ÇİFÇİ GİZEM,GÜLERYÜZ SEZİN (2011).  Strategic analysis of healthcare service quality using fuzzy AHP methodology.  Expert Systems with Applications, 38(8), 9407-9424.

ABSTRACT

Managers in the service sector are under pressure to demonstrate that their services are customer focused and that continuous performance improvement is being delivered. It is essential that customer expectations are properly understood and measured under the constraints that organizations must manage. The majority of the work to date has attempted to use the SERVQUAL (service quality) methodology in an effort to measure service quality. In this study, firstly the concept and factors of service quality are examined. Then a fuzzy AHP (analytic hierarchy process) is structured to evaluate the proposed service quality framework. A case study in healthcare sector in Turkey is presented to clarify the methodology.

Keywords: Service quality – SERVQUAL – Healthcare quality – Fuzzy AHP