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    A Hierarchical Decision Model Proposal for Maintenance Strategy Selection in the Hydroelectric Power Plants
    (Gazi Univ, 2022) Yazici, Emre; Ozcan, Evrencan; Alakas, Haci Mehmet; Eren, Tamer
    Today, the energy demand is increasing day by day. Facilities that provide energy supply develop policies and practices that will continuously respond to this increasing demand. One of the factors that are effective in ensuring continuity in energy is to determine the maintenance strategies of the power plants where energy is produced in a way that does not interrupt the supply. In this study, it is aimed to find the most critical electrical equipment in a hydroelectric power plant and to choose the maintenance strategy for this equipment. This study consists of two stages. First, the most critical electrical equipment was identified. The Pythagorean Fuzzy Analytical Hierarchy Process (PFAHP) was used to determine the weights of the criteria used for ranking the equipment. For ranking the alternatives, the PBAHP method and the TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) method were integrated. The most appropriate maintenance strategy for generator equipment, which is determined as the most critical electrical equipment, has been determined as revision maintenance.
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    Analysis of operations research methods for decision problems in the industrial symbiosis: a literature review
    (Springer Heidelberg, 2022) Yazici, Emre; Alakas, Haci Mehmet; Eren, Tamer
    Industrial symbiosis (IS) is an approach that aims to use resources efficiently by cooperating between independent enterprises in raw materials, energy, and similar sectors. As a result of cooperation, businesses gain economic, environmental, and social benefits. Especially in recent years, IS applications have become widespread due to the problems experienced in the supply of resources. The presence of more than one enterprise in cooperation creates a complex network structure in IS applications. In this complex system, many decision problems are encountered in establishing and effectively maintaining the industrial symbiosis network. Operations research techniques are at the forefront of the methods used to solve decision problems. This study examined studies using operations research techniques in industrial symbiosis. Studies were divided into four classes according to the methods they used: exact methods, heuristic methods, multi-criteria decision-making, and simulation. In the literature review, the studies in the Web of Science (WOS) database are systematically presented by scanning with the determined keywords. As a result of the study, it was analyzed which method was preferred and where the methods could be applied in industrial symbiosis.
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    Determination of Bid Values for High Speed Train Superstructure Tenders by Game Theory
    (Turkish Chamber Civil Engineers, 2022) Alakas, Haci Mehmet; Kacar, Cem; Yazici, Emre
    The use of high-speed trains (YHT) is increasing for the world's speed and competitiveness in rail transport. In Turkey, new lines have been built for the development of the railway in recent years. This study, it is aimed to create a mathematical model to determine the final bid price in the superstructure and electromechanical construction works of the YHT lines built in Turkey. Game theory was used to analyze the conflict of interest between contractors or bidders in the mathematical model. In the model, the bid distributions were determined by using the bids given in the previous bids. To minimize the degree of the winner's curse in determining the final bid price, a mathematical model is proposed using an empirical approach, using past bids. The competitive final bid price of the superstructure and electromechanical works of the superstructure and electromechanical works of the new YHT railway lines can be calculated in the standards of the previous tenders examined with the mathematical model.
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    Evaluation of supply sustainability of vaccine alternatives with multi-criteria decision-making methods
    (Wiley, 2022) Yazici, Emre; Uner, Sabire Irem; Demir, Asli; Dinler, Sevda; Alakas, Haci Mehmet
    Background: The treatment of the COVID-19 epidemic, whose contagious features are changing day by day, is the most current problem today throughout of the world. In order to be protected from COVID-19 and reduce its spread, it is of great importance to follow the rules such as mask, distance and hygiene. In addition, one of the most important ways to prevent the epidemic is to develop population immunity. The most important tool in having population immunity is vaccination. Aims: During the COVID-19 pandemic, there have been problems in the supply process of many products in food and health sectors. Vaccine is also one of the most difficult tools to supply. In this context, the study focused on the selection of the vaccine provided by the countries within the scope of population vaccination studies. Materials & Methods: At the selection point, the criteria affecting the purchasing process were determined and the weights of these criteria were calculated using the AHP method. Then, the criteria weights obtained were used to rank the alternatives in an integrated manner in the Preference Ranking Organization Method for Enrichment of Evaluations (PROMETHEE) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) methods. The results of both methods were analyzed comparatively. Results: According to the TOPSIS Method, the first alternative is Oxford-AstraZeneca for all countries, and BioNTech for all countries in the PROMETHEE method. Discussion: The vaccine storage conditions criterion is the most important in vaccine supply. The criterion with the lowest importance is Supply Cost. It has been revealed that cost elements remain in the background under pandemic conditions. Conclusion: Vaccine evaluation studies and policy recommendations are presented by considering public health in the selection of vaccine alternatives.
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    Evaluation of the companies for applied education under fuzzy environment: a case in an industrial university
    (Springer London Ltd, 2023) Ciftci, Sema; Pinarbasi, Mehmet; Yazici, Emre; Alakas, Haci Mehmet
    Nowadays, the problem of university graduates being unemployed is gradually increasing. To keep down unemployment, universities are integrating the concept of applied education into their educational curricula. The concept of applied education brings with it the problem of the correct student-company matching. In this study, the company selection criteria were focused on to determine the companies that university students will be sent to within the scope of applied education. Company selection criteria are determined by experts in the field. However, the evaluation of experts with precise criteria values can be very challenging in the decision-making process. For this purpose, the criteria weights were calculated using the Pythagorean Fuzzy AHP method in this study. Evaluation of companies to which students will be matched for applied/workplace education is ranked with these fuzzy weights by using TOPSIS and PROMETHEE II methods. To evaluation the proposed decision process, a real case study is carried out in an industrial private university in Turkey. The case study results show that the proposed method can provide effective and consistent results in the evaluation of companies under fuzzy environment.
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    Personnel scheduling problem in law systems: The example of expropriation cases
    (Gazi Univ, Fac Engineering Architecture, 2023) Yazici, Emre; Eren, Tamer; Alakas, Haci Mehmet
    Public institutions make expropriation to provide service access to individuals in the fulfillment of public services. Due to the wide range of service areas and needs, an average of 50000 cases is filed annually in our country regarding expropriation. The appointment of lawyers assigned to represent public institutions in lawsuits without calculating the files' workload causes an unbalanced workload distribution among lawyers. Although the activities that constitute the workload of lawyers seem to be participating in hearings and discoveries, preparation of the case file, preparation for hearings and discovery findings to courthouses on the relevant days, preparation of petitions during the trial examination of the files are also among the workloads. These workloads are not taken into account in file assignments and cause an unbalanced distribution of lawyers' workloads. In this study, the problem of assigning the case files related to expropriation procedures in a public institution to lawyers is addressed. In the institution, 724 case files of three different types are opened in 15 different regions within one month, and six lawyers work in the institution. A goal programming model has been proposed to balance lawyers' workloads by calculating the cases' workloads. Preparation, trial, discovery, file review, and travel times were taken into account to estimate the files' workload. The proposed model can also be used in other public institutions and for assigning different case files.
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    Prioritizing Individuals Who Will Have Covid-19 Vaccine with Multi-Criteria Decision Making Methods
    (Gazi Univ, 2023) Yazici, Emre; Uner, Sabire Irem; Demir, Asli; Dinler, Sevda; Alakas, Haci Mehmet
    This study aims to prioritize individuals in vaccination for the effective use of the COVID-19 vaccine, which has limited supply and does not seem possible to be supplied by all countries at the same time. In the study, multi-criteria decision-making methods (MCDM), which offer practical solutions to decision problems, were used considering the structure of the problem. First, the analytic hierarchy process (AHP) method was used to calculate the weights of the criteria. Then, the ranking of the priorities of the individuals was carried out with the PROMETHEE method. Here, the AHP and PROMETHEE methods are used in an integrated manner. It has been determined that the highest priority individual in vaccination is a healthcare worker with a high potential for transmission. In order of priority, the second individual was identified as workers. In this study, a hierarchical structure was created to prioritize individuals who will be vaccinated against COVID-19 and the problem was solved in two stages. A health policy proposal was made to health managers to use limited vaccine resources by prioritizing individuals effectively. In terms of efficient and effective use of resources during possible pandemic periods, the application process of the study provides an exemplary solution for decision-makers and contributes to the solution of similar decision problems encountered both in the literature and in real life. At the same time, offers solution for disasters that require effective use of limited resources, etc. The implementation process of the study may also be taken into account in exceptional circumstances.
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    Prioritizing of sectors for establishing a sustainable industrial symbiosis network with Pythagorean fuzzy AHP- Pythagorean fuzzy TOPSIS method: a case of industrial park in Ankara
    (Springer Heidelberg, 2023) Yazici, Emre; Alakas, Haci Mehmet; Eren, Tamer
    Difficulty in accessing resources and increasing environmental concerns encourage industrial manufacturing enterprises to establish a symbiosis network. The identification of symbiotic relationships contributes to the more sustainable development of industrial activities. However, businesses operating in industrial parks are diversified by sector. In order to establish a sustainable symbiosis network in industrial parks, the symbiotic relations of each sector in industrial parks should be evaluated separately. Thus, the installation process of the symbiosis network will be easier and more sustainable. In this context, this study aims to prioritize the sector in which a symbiosis network will be established by presenting an innovative approach for the evaluation of symbiosis potentials. For this purpose, criteria for the implementation process affecting the establishment of the symbiosis network were determined. Multi-criteria decision-making methods were used to solve the problem. Considering the uncertainties in the process, fuzzy multi-criteria decision-making methods were used. As a result, a decision-making model has been proposed to determine the priority sector in order to establish a symbiosis network in industrial parks. According to the results obtained with the multi-criteria decision-making methods, the number of enterprises that will evaluate the waste, that is, the number of customers with waste, has been determined as the criterion with the highest level of importance. While evaluating the alternatives, the casting sector was chosen as a priority. This sector is followed by the petro and chemical sector as the second alternative.
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    Selection of 3D printing technologies for prosthesis production with multi-criteria decision making methods
    (Springer Heidelberg, 2024) Alakas, Haci Mehmet; Yazici, Emre; Ebiri, Ufukcan; Kizilay, Berat Alperen; Oruc, Onur
    Today, innovations are emerging in every field that comes with the constantly developing technology. 3D printers, among the developing technologies and making essential contributions, are significant in fields such as industry and health. 3D printers are used in many areas and provide various benefits, especially flexibility in production. 3D printers provide flexibility in producing products using multiple technologies according to the effect produced. However, differentiating the methods and alternatives creates an alternative selection problem for decision-makers. In this study, which is examined in this context, 3D printer technologies used in prosthesis production will be discussed. The study aims to find the most suitable prosthetic construction technology by comparing the 3D printer technologies used in prosthesis production to minimize the machine cost for prosthesis, eliminate mold production for personal prosthesis production, reduce production time, and customize. Five criteria were determined in selecting the 3D printer technology used in prosthesis production, and ten alternative technologies were listed according to the criteria. The criterion weights are calculated using the Analytical Hierarchy Process, a Multi-Criteria Decision-Making method-alternatives ranked by TOPSIS and PROMETHEE. The most suitable alternative was selected for prosthesis production. A decision-making procedure is proposed for decision-makers. The study demonstrates its originality by presenting analysis with multi-criteria decision-making methods to evaluate alternative 3D printers for prosthesis production.