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 Count: 15
A Combined Fuzzy Ahp-Simulation Approach To Cad Software Selection
(Taylor & Francis Ltd, 2010) 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.
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; 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 Count: 0
Evaluation of Gas-Fired Combi Boilers with HF-AHP-MULTIMOORA
(Hindawi Ltd, 2022) Samanlıoğlu, Funda; Ayag, Zeki; Kirkil, Goekhan; Yucal, Esra
There are many alternative gas-fired combi boilers that can be used to heat residential homes. Evaluation and selection of gas-fired combi boilers for buildings is an intricate multi-criteria decision-making (MCDM) problem involving perhaps contradictory quantifiable and qualitative criteria. In this research, as the MCDM approach, hesitant fuzzy linguistic analytic hierarchy process (HF-AHP) and hesitant fuzzy linguistic multiple objective optimization based on ratio analysis plus full multiplicative form (MULTIMOORA) (HF-MULTIMOORA) are integrated to assess and rank combi boiler alternatives for buildings. First, with HF-AHP, fuzzy criteria weights are determined and then with HF-MULTIMOORA, boiler alternatives are ranked from best to worst. In this integrated HF-AHP-MULTIMOORA method, evaluations of decision-makers are combined with fuzzy envelope approach and then triangular fuzzy numbers are utilized. For comparison analysis, HF-AHP-TOPSIS method is also applied to the same problem. A case study in Turkey is presented where ten combi boiler alternatives are assessed based on fifteen criteria by five decision-makers. We have used various selection criteria for boilers ranging from maximum temperature, heating capacity up to environmental effects and decided on the best combi boiler for heating residential buildings in Turkey.
Designing of an Enterprise Product Innovation System for Companies
(Kadir Has Üniversitesi, 2018) Demirhan, Mehmet Özhan; Ayağ, Zeki
Today, innovation is the most decisive factor for companies to grow and gain competitive edge in the market. In particular, firms support a product innovation policy in order to be permanent in the market. Product innovation refers to the emergence of new products and the development of existing products. By means of companies' product innovation reduces expenditure; new customers win and make high profits. AHP Method with a numerical example to evaluate the projects in this system. Organizational, technical, strategic and financial criteria have been examined. In the selection of the projects, companies have given much importance to the financial and organizational criteria. This research is expected to be very useful for evaluating and selecting projects for companies.
A Fuzzy Ahp Approach for Financial Performance Evaluation Airline Companies
(Kadir Has Üniversitesi, 2012) Gürel, Sinem; Ayağ, Zeki
Previous researches focused on operation performance. This thesis purposes for evaluating the financial performance of the airlines. In order to achieve financial objectives to be incorporated into the financial performance of their degree. It is a method to measure the results of a company?s operations in a monetary term. The problem is modeled by multi-criteria decision making (MCDM) one. Multi criteria decision making (MCDM) is a method of the most important fields of operations research and deals with the problems that include multiple and conflicting objectives. It is obvious that when more than objective exists in the problem, making a decision becomes more complex. To solve the problem, I used the fuzzy numbers to explain their values. After that, I used a method of fuzzy multi criteria group decision making (FMCGDM) as Fuzzy Analytic Hierarchy Process (FAHP) to solve the problem of the evaluation of airlines? financial performances. At first time the decision making process of the financial performance is investigated, when financial ratios are given by a fuzzy function, they are obtained through classical methods. After that, we will discuss the main advantages of the new approach. Finally, we illustrate an experimantal model of evaluation of the three domestic airlines? financial performance in Turkey.
Energy Trading in Turkish Power Market Through Options Bileteral Agreements and Spot Market
(Kadir Has Üniversitesi, 2013) Tasdemir, Ecem Ezgi; Ayağ, Zeki
in today’s world electricity energy which has a vital place in energy market is irreplaceable in any field because of being the basic entry in production factors and because of continuous increasing demand to electricity thanks to technological development. Especially in our country which has a rapid acceleration for the last decade by reorganizing Electricity Energy Market it is aimed to build a competitive structure in production and retail transactions. Also with the process of development in Turkey the structure of the market changed varied and created different alternatives for efficient buying-selling transactions. in this work we built a model on the purpose to find the solution of the most efficient scenarios and maximum efficiency by using electricity spot market which has transactions with a determined capacity limit derivatives market and bilateral agreements. The amount of efficiency is calculated by using the Model for each 100 different power scenarios’ in Excel and the results are got and interpreted. As a result of this the most efficient scenario determined. -- Abstract'tan
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
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%.
Citation Count: 44
A Hybrid Approach To Machine-Tool Selection Through Ahp and Simulation
(Taylor & Francis, 2007) Ayağ, Zeki
The selection process of a machine tool has been a critical issue for companies for years because the improper selection of a machine tool might cause many problems having a negative effect on productivity precision flexibility and a company's responsive manufacturing capabilities. Therefore in this paper to determine the best machine tool satisfying the needs and expectations of a manufacturing organization among a set of possible alternatives in the market a hybrid approach is proposed which integrates an analytic hierarchy process (AHP) with simulation techniques. The AHP as one of the most commonly used multiple criteria decision-making methods is used to narrow down all possible machine tool alternatives in the market by eliminating those whose scores (or weights) are smaller than a determined value obtained under certain circumstances. Then a simulation generator is used first to automatically model a manufacturing organization where the ultimate machine tool will be used and second to try each alternative remaining from the AHP as a scenario on the generated model. Finally the final alternative is selected by using the unit investment cost ratio which is calculated by dividing the investment cost per year of each alternative by the additional number of produced units obtained from the simulation experiment of the relevant alternative.
Citation Count: 224
A Fuzzy Ahp Approach To Evaluating Machine Tool Alternatives
(Springer, 2006) Ayağ, Zeki; Özdemir, Rifat Gürcan
Selecting process of a machine tool has been very important issue for companies for years because the improper selection of a machine tool might cause of many problems affecting negatively on productivity precision flexibility and company's responsive manufacturing capabilities. On the other hand selecting the best machine tool from its increasing number of existing alternatives in market are multiple-criteria decision making (MCDM) problem in the presence of many quantitative and qualitative attributes. Therefore in this paper an analytic hierarchy process (AHP) is used for machine tool selection problem due to the fact that it has been widely used in evaluating various kinds of MCDM problems in both academic researches and practices. However due to the vagueness and uncertainty on judgments of the decision-maker(s) the crisp pair wise comparison in the conventional AHP seems to insufficient and imprecise to capture the right judgments of decision-maker(s). That is why
Citation Count: 17
Fuzzy Anp-Based Promethee Ii Approach for Evaluation of Machine Tool Alternatives
(IOS Press, 2016) Ayağ, Zeki; Samanlıoğlu, Funda
Machine tool selection process has been a critical issue for companies for years since improper selection of a machine tool might cause many problems affecting negatively the productivity precision flexibility and company's responsive manufacturing capabilities. On the other hand selecting the best machine tool from its increasing number of existing alternatives in the market is a multiple-criteria decision making (MCDM) problem in the presence of many quantitative and qualitative attributes. Therefore most companies have utilized various methods to successfully carry out this difficult and time-consuming process. In this paper both of the most used MCDM methods