Ayağ, Zeki

Ayağ, Zeki

Name Variants

Ayağ, Zeki
Z.,Ayağ
Z. Ayağ
Zeki, Ayağ
Ayag, Zeki
Z.,Ayag
Z. Ayag
Zeki, Ayag
Ayağ,Z.
Zeki Ayağ

Job Title

Prof. Dr.

Email Address

Zekıa@khas.edu.tr

Full item page

Scholarly Output

44

Articles

31

Citation Count

0

Supervised Theses

5 Scholarly Output Search Results

Now showing 1 - 10 of 44

Citation - Scopus: 87
An Analytic Network Process-Based Approach To Concept Evaluation in a New Product Development Environment
(Taylor & Francis, 2007) Ayağ, Zeki; Ayağ, Zeki; Özdemir, Rifat Gürcan
Selecting the best product concept is one of the most critical tasks in a new product development (NPD) environment. Making decisions at this stage becomes very difficult due to imprecise and uncertain product requirements. So the evaluation process of determining the most satisfying conceptual design has been a very vital issue for companies to survive in fast-growing markets for a long time. Therefore most companies have used various methods to successfully carry out this difficult and time-consuming process. Of these methods an analytic hierarchy process (AHP) has been widely used in multiple-criteria decision-making problems (i.e. concept selection equipment evaluation). In this study however we use an analytic network process (ANP) a more general form of AHP due to the fact that AHP cannot accommodate the variety of interactions dependencies and feedback between higher and lower level elements. Briefly in this paper an ANP-based approach is presented to evaluate a set of conceptual design alternatives in order to reach to the best concept satisfying the needs and expectations of both customers and company. In addition a numerical example is presented to illustrate the proposed approach.
Building a Framework for Adopting Lean Principles To Achieve Sustainability in Solar Energy Firms: Turkiye as a Case Study
(Kadir Has Üniversitesi, 2022) Aldewachi, Bilal; Ayağ, Zeki; Zeki Ayağ
The two terms lean, and sustainability have become one of the most important terms in the field of business because of their role in developing the work in line with increasing profits on the one hand and taking into account the future on the other. Solar energy firms are witnessing great competition to meet energy requirements and suffering from a huge amount of waste, which negatively affects in achieving sustainability. Hence, this study aims to build a framework for solar energy firms to achieve sustainability dimensions through adopting lean principles. The framework will help to solve problems that the solar energy sector is facing. The method in the study included reviewing the literature to examine the founding of the relation between lean and sustainability and using a questionnaire that was directed to the responsible people in Turkish solar energy companies. The results of the survey were analyzed to (1) Discover what the people in charge in solar energy firms think about lean and sustainability; (2) Measure the possible relationship between lean principles and sustainability dimensions by applying a linear regression and non-linear regression test; (3) Using the results of the second point to build the framework. The final results indicated a high level of the relative importance of the two terms from the perspective of the people in charge in the solar energy firms. Besides, the study found a relationship between adopting the two principles of lean, pull, and flow and achieving economic, social resources, and technology dimensions of sustainability; this finding is represented in a framework.
Citation - WoS: 17
Citation - Scopus: 20
An Intelligent Approach To Supplier Evaluation in Automotive Sector
(Springer, 2016) Ayağ, Zeki; Samanlıoğlu, Funda; Samanlıoğlu, Funda; Ayağ, Zeki
During the process of supplier evaluation selecting the best desirable supplier is one of the most critical problems of companies since improperly selected suppliers may cause losing time cost and market share of a company. For this multiple-criteria decision making selection problem in this paper a fuzzy extension of analytic network process (ANP) which uses uncertain human preferences as input information in the decision-making process is applied since conventional methods such as analytic hierarchy process cannot accommodate the variety of interactions dependencies and feedback between higher and lower level elements. The resulting fuzzy ANP enhances the potential of the conventional ANP for dealing with imprecise and uncertain human comparison judgments. In short in this paper an intelligent approach to supplier selection problem through fuzzy ANP is proposed by taking into consideration quantitative and qualitative elements to evaluate supplier alternatives and a case study in automotive sector is presented.
Citation - WoS: 1
Citation - Scopus: 1
Achieving Sustainability in Solar Energy Firms in Turkey Through Adopting Lean Principles
(Mdpi, 2022) Aldewachi, Bilal; Ayağ, Zeki; Ayag, Zeki
Lean principles and sustainability are considered important terms in business. Solar firms are witnessing great competition to fulfill energy requirements, suffering from a huge amount of waste, negatively affecting the sustainability dimensions. Thus, the aim of the study is to build a framework for solar energy firms to achieve sustainability through adopting lean principles, which will help to fix many problems as waste and costs. The method included reviewing the literature to explore the founding of the relation between the two terms, and using a questionnaire that was directed to the responsible people in Turkish solar energy firms. The results of the survey were analyzed to: (1) Find out what the responsible people think about the two terms lean and sustainability; (2) Measure the probable relationship between lean principles and sustainability dimensions by applying a linear regression test; (3) Use the results of point number two to build the framework. The result showed there was a high level of relative importance about the two terms from the point of view of managers and experts in solar firms. In addition, the study found a relationship between adopting pull and flow principles of lean, and achieving economic and social dimensions of sustainability, this finding is represented in a framework.
Citation - Scopus: 3
Determining Master Schedule of Surgical Operations by Integer Programming: a Case Study
(Institute of Industrial Engineers, 2010) Samanlıoğlu, Funda; Samanlıoğlu, Funda; Ayağ, Zeki; Ayağ, Zeki; Batili, Burcin; Evcimen, Esra; Yılmaz, Gulsah; Atalay, Ozlem
Fixed amounts of available Operating Room (OR) time compatibility of ORs and restrictions related to surgery equipment and surgeon availabilities complicate the process of preparing the master surgical schedule at hospitals. In this research an integer programming model and its application at Etiler World Eye Hospital (in Turkey) are presented in order to create a master surgical schedule that includes the most common surgery types on weekly basis and resolves surgeon equipment and operating room restriction and availability issues. The integer programming model utilizes the available OR time at the hospital by minimizing the total underallocation of OR time with respect to targeted OR time of surgeons taking into consideration surgeon equipment and OR restrictions and availabilities. The mathematical model is then solved using a commercial solver to obtain a weekly master surgical schedule for the hospital.
Citation - Scopus: 0
A Network Model for the Location-Routing Decisions of a Logistics Company
(Institute of Industrial Engineers, 2012) Sama, Funda; Samanlıoğlu, Funda; Yücekaya, Ahmet; Ayağ, Zeki; Ayağ, Zeki; Yücekaya, Ahmet Deniz
In this paper, part of the logistics network of one of the leading logistics companies in Turkey is analyzed. Data related to the candidate warehouse locations, supplies and demands of customers are collected. A network model is developed in order to reconfigure the logistics network. The aim of the mathematical model is to help decision makers decide on the locations of warehouses, as well as routing products from suppliers to the distribution center; from distribution center to warehouses; and finally from warehouses to customers. The mathematical model is solved optimally with LINGO solver, and the comparison of the current network with the optimal solution revealed that the overall operating costs can be reduced by approximately 7%.
Citation - WoS: 6
Citation - Scopus: 10
An Intelligent Approach for the Evaluation of Transformers in a Power Distribution Project
(IOS Press BV, 2020) Samanlıoğlu, Funda; Samanlıoğlu, Funda; Ayağ, Zeki; Ayağ, Zeki
In this study, a hybrid approach is presented for the evaluation and selection of transformers in a power distribution project. Ranking transformers and selecting the best among alternatives is a complex multiple criteria decision making (MCDM) problem with various possibly conflicting quantitative and qualitative criteria. In this research, two hesitant fuzzy MCDM methods; hesitant fuzzy Analytic Hierarchy Process (hesitant F-AHP) and hesitant fuzzy Preference Ranking Organization Method for Enriching Evaluations II (hesitant F-PROMETHEE II) are combined to evaluate and rank transformers. In the hesitant fuzzy AHP-PROMETHEE II, hesitant F-AHP is implemented to determine criteria weights and hesitant F-PROMETHEE II is applied to rank transformer alternatives, utilizing obtained criteria weights. An illustrative example is presented to demonstrate the effectiveness and applicability of the proposed approach. In the example, five transformers are evaluated based on twelve criteria by three decision makers (DMs) and best alternative is selected. For comparison analysis, integration of hesitant F-AHP and hesitant fuzzy Technique for Order Preference by Similarity to Ideal Solution (hesitant F-TOPSIS) is used and results are compared.
Citation - WoS: 15
Citation - Scopus: 19
A Combined Fuzzy Ahp-Simulation Approach To Cad Software Selection
(Taylor & Francis Ltd, 2010) Ayağ, Zeki; Ayağ, Zeki
In this paper a combined approach where the fuzzy analytic hierarchy process (AHP) and simulation come together is presented to select the best computer-aided design (CAD) software out of the available options in the market. The fuzzy AHP is used due to the vagueness and uncertainty of the judgements of a decision maker(s) because the crisp pair-wise comparison in the conventional AHP seems to be insufficient and imprecise to capture the right judgements of the decision maker(s). In this study first the fuzzy AHP is used to reduce a possible number of alternatives for the CAD system to an acceptable level for further study simulation analysis. Secondly a simulation generator as an integrated part of the fuzzy AHP is used to try the remaining alternatives on the generated model of a real-life product organisation in which the final alternative will be used. The results of simulation experiments are obtained and then evaluated to reach to the ultimate CAD alternative.
Citation - WoS: 0
Citation - Scopus: 1
An Intelligent Approach To Cam Software Selection
(IEEE, 2012) Ayağ, Zeki; Ayağ, Zeki
In this paper an intelligent approach is presented to help the companies select most suitable CAM software for their current and future needs. For this purpose fuzzy AHP method is used to carry out CAM selection process more effectively easily and applicable for a company. Shortly the objectives of the research are
Minimizing the Defect Rate Using Six Sigma Dmaic Method; a Case Study in Supsan A.ş.
(Kadir Has Üniversitesi, 2016) Aslan, Nazmiye Yağmur; Ayağ, Zeki; Ayağ, Zeki
Today manufacturing industries are highly impacted by the fast changing economic conditions. In this scenario, manufacturing industries become face to face with global competition due to globalization. The major problems of these industries are declining profit margin, customer demand for high quality product and product variety. Therefore so many organizations, especially in manufacturing sector, understand the importance of quality. Companies try to implement various strategies and innovations for enhancing their producing process. A very powerful philosophy in this area is Six Sigma. The aim of Six Sigma is to reduce cost, waste and increase productivity to produce high-quality products. So this study is applied to improve the quality of the manufactured valves, reduce the manufacturing waste and increase the yield of the manufacturing process by applying the Six Sigma methodology. Also comparison analysis is made between approaches as DMAIC, Jidoka, Value Stream Tranformation, Kaizen. In result of the analysis DMAIC is chosen for this project. DMAIC approach is a business strategy help to improve business profitability and efficiency of operations to meet customer needs and expectations. In this search discusses the quality and productivity improvement in an manufacturing enterprise which is called SUPSAN. And this search deals with an application of Six Sigma DMAIC methodology in SUPSAN to improve quality performance, to identify root causes of failure in Stellite Coating Process which is found with help of DMAIC tools. Several tools are used to identify root causes and situation analysed with help of Pareto Charts, FMEA, SIPOC, C&E Diagram. In improve phase Process Capability Analysis and Implementation Plan are made. Also improvement solutions are applied. Then with the help of tools as Control Charts, SPC Analysis results tracked, documented and controlled.In SUPSAN, the appliation of Six Sigma DMAIC methodology resulted in a reduction in the defect rate from 4.34% to 2%.