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Öğe A Novel Decision-Making Framework Based on Interval-Valued Pythagorean Fuzzy AHP and CODAS: An Application to Healthcare Supplier Selection(Springer Science and Business Media Deutschland GmbH, 2023) Otay, I.; Bulut, B.; Barutbaş, K.; Arat, A.E.; Tekin, E.; Gürz, Z.Ş.Especially after the COVID-19 pandemics where market dynamics have changed dramatically, supplier selection has been one of the crucial subjects for almost every industry. After the pandemics, the healthcare industry has played a major role and gained even more importance in all over the world; therefore, selecting the best appropriate supplier has become more critical than ever. In this paper, supplier selection and evaluation problem is analyzed for a specific area of the healthcare industry, i.e. laboratory (lab.) equipments including test tubes and sample containers. Considering the vagueness and imprecise information in the decision-making environment, the problem is handled by considering five main criteria and 20 sub-criteria under fuzzy environment. In the study, a relatively recent extension of the fuzzy sets called as Pythagorean Fuzzy Sets (PFS), which provides more flexibility to the decision makers with membership and non-membership degrees, are utilized. This paper aims to contribute to the literature by proposing a novel fuzzy methodology integrating Analytic Hierarchy Process (AHP) and Combinative Distance-based Assessment (CODAS) method based on interval-valued PFS. Finally, sensitivity analysis is constructed in the paper. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.Öğe An integrated fuzzy multi-criteria approach for e-waste collection center location problem(IGI Global, 2021) Bolat, H.B.; Otay, I.; Temur, G.T.; Imre, Ş.Selection of locations for collecting end of life goods is a multi-dimensional problem. In this study, the objective is to propose a hybrid multi-criteria decision model for e-waste collection center location selection problem employing an integrated Pythagorean fuzzy AHP (analytical hierarchy process)-VIKOR (multi-criteria optimization and compromise solution) methodology. A case study from Turkish e-waste recycling industry is conducted in order to verify the success of the proposed methodology. Thirty-nine alternative collection center districts are evaluated and ranked by employing Pythagorean fuzzy VIKOR based on "cost, logistics, environment, socio-culture, and population" and 11 sub-criteria. The study involves 39 e-waste collection location centers, and the model was solved for 50 times for 10 scenarios for each criterion. The results of sensitivity analysis indicate that the evaluation of criteria and determination of their weights have critical effects on the results. © 2021 IGI Global. All rights reserved.Öğe Evaluating Sustainable Vehicle Technologies for Freight Transportation Using Spherical Fuzzy AHP and TOPSIS(Springer, 2021) Jaller, M.; Otay, I.Freight transportation is vital for the economy and everyday life. It brings the goods and services needed for industrial and manufacturing processes, as well as those to be consumed by the population. However, the vehicles (mostly diesel trucks) used are responsible for a disproportionate amount of environmental externalities. Therefore, it is imperative to manage transport demand, and foster the use of cleaner vehicles, fuels and technologies. The most common alternatives include compressed (renewable) natural gas (CNG/RNG), hybrid electric (HE), battery electric (BE) and fuel-cell hydrogen (H2) vehicles. However, the technical and operational characteristics, market readiness, and other factors related to these technologies can be very different. Therefore, the most appropriate option for different uses (e.g., last mile, long-haul distribution) and users’ preferences is not necessarily clear. Consequently, this paper proposes Analytic Hierarchy Process (AHP) and The Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) based on Spherical fuzzy sets to evaluate the sustainable vehicle technology alternatives over multiple criteria for freight transportation. Spherical fuzzy sets have been receiving increasing attention because of their ability to better consider uncertainty by defining membership functions on a Spherical surface and covering a larger domain. Specifically, the authors evaluate the alternatives using five criteria: Financial; Business & market-related; Environmental & legal; Maintenance & repair availability; and Safety & vehicle performance factors, and 21 sub-criteria. Moreover, the authors also performed sensitivity analysis. © 2021, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG.Öğe Extension of VIKOR Method Using Circular Intuitionistic Fuzzy Sets(Springer Science and Business Media Deutschland GmbH, 2022) Kahraman, C.; Otay, I.VIKOR method is used to solve a variety of MCDM problems including a variety of criteria that can be conflicting and noncommensurable. This method is based on the distances of alternatives to positive and negative ideal solutions, and provides compromising solutions. Decision makers generally prefer to evaluate the alternatives with respect to the criteria by using linguistic terms rather than assigning exact numerical values. The fuzzy set theory captures the uncertainty and subjectivity in these linguistic terms successfully. Many classical MCDM methods have been extended to their fuzzy versions by using the fuzzy set theory for handling this uncertainty. VIKOR method has been extended by using several fuzzy set extensions such as intuitionistic fuzzy VIKOR, hesitant fuzzy VIKOR, Pythagorean fuzzy VIKOR, picture fuzzy VIKOR, and spherical fuzzy VIKOR methods. Circular intuitionistic fuzzy sets (C-IFS) introduced as an extension of intuitionistic fuzzy sets, enables decision makers to define membership and the non-membership degrees as circular membership functions. In this paper, we develop C-IFS VIKOR method and apply it to a waste disposal location selection problem. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.Öğe Extensions of Ordinary Fuzzy Sets: A Comparative Literature Review(Springer, 2021) Kahraman, C.; Oztaysi, B.; Otay, I.; Onar, S.C.Fuzzy sets extensions have been often used in the modeling of problems including vagueness and impreciseness in order to better define the membership functions together with the hesitancy of decision makers. More than 20 different extensions of ordinary fuzzy sets have appeared in the literature after the introductions of ordinary fuzzy sets by Zadeh (1965). These sets involve interval-type fuzzy sets, type-2 fuzzy sets, hesitant fuzzy sets, intuitionistic fuzzy sets, Pythagorean fuzzy sets, q-rung orthopair fuzzy sets, spherical fuzzy sets, picture fuzzy sets, fermatean fuzzy sets, etc. Mainly, these extensions can be divided into two classes: extensions with two independent membership parameters and extensions with three independent membership parameters. In this paper, we briefly classify these extensions and present some comparative graphical illustrations. © 2021, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG.Öğe Modeling Humanoid Robots Mimics Using Intuitionistic Fuzzy Sets(Springer, 2021) Kahraman, C.; Onar, S.C.; Oztaysi, B.; Otay, I.Intuitionistic fuzzy sets (IFS) have been often used in modeling the problems under vagueness and impreciseness in order to better define the problems together with the hesitancy of decision makers. IFS have been often employed in modeling decision making problems in the literature. Human decision making process can be used in humanoid robots by imitating the human decisions and behaviors. © 2021, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG.Öğe Multi-criteria Cloud Computing Service Provider Selection Employing Pythagorean Fuzzy AHP and VIKOR(Springer, 2021) Otay, I.; Yıldız, T.With the wide usage of Cloud Computing Services (CCS), finding the most suitable cloud service by matching criteria provided by different CCS providers have gained considerable importance in various commercial and scientific tasks. In this paper, we analyze cloud service provider evaluation and selection problem under fuzzy environment. To solve the problem, a novel fuzzy integrated multicriteria decision making method is proposed. In the proposed model, a hierarchical structure with six criteria which are financial, performance, security and privacy, assurance, agility and usability, and four alternatives, is designed based on comphrehensive literature review and consulting to the experts. The evaluations regarding to the cloud alternatives are expressed using Pythagorean fuzzy sets being an extension of intuitionistic fuzzy sets where the square sum of membership and non-membership degrees is at most “1”. In the analysis, the weights of the criteria are obtained using fuzzy Analytical Hierarchy Process (AHP) based on single-valued Pythagorean fuzzy sets. Then, to rank the alternatives, the calculated weights from the previous analysis are used as inputs in single-valued Pythagorean fuzzy VlseKriterijumska Optimizacija I Kompromisno Resenje, meaning of multi-criteria optimization and compromise solution (VIKOR) method. Finally, sensitivity analysis is performed to check the robustness and the applicability of the proposed model. © 2021, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG.Öğe Multi-criteria Oil Station Location Evaluation Using Spherical AHP&WASPAS: A Real-Life Case Study(Springer, 2021) Otay, I.; Atik, S.The world’s dependence on oil and gas has been increasing as global economies and infrastructure continue to rely heavily on petroleum-based products. Thus, there is a significant increase in the number of stations to meet the growing needs of the world. In this study, we concentrate on the location evaluation and selection problem of an oil station. Location selection of an oil & gas station is a Multiple Criteria Decision Making (MCDM) problem comprising several quantitative & qualitative criteria such as environmental, economic, and traffic related factors. In the literature, there are a number of studies focusing on oil-gas station location selection problem using different MCDM methods. The literature review has pointed out that traditional methods for location selection are insufficient for dealing with the indefinite or uncertain nature of linguistic assessment. Thus, considering uncertainties and subjectivity in human judgments, many researchers have been solving the multicriteria decision making problems employing MCDM methods based on the fuzzy sets. There are many extensions of the fuzzy sets such as Type-2, Hesitant, Pythagorean, and Neutrosophic fuzzy sets. In this study, a recently popular extension namely Spherical fuzzy set is used for solving a real-life oil station location evaluation and selection problem. In the study, Spherical fuzzy Analytical Hierarchy Process (SF-AHP) and Spherical fuzzy Weighted Aggregated Sum Product ASsessment (SF-WASPAS) methods are proposed for the solution of the problem. Then, sensitivity analysis is performed. © 2021, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG.
