Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/11727/4809
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Item Estimating the COVID-19 Death Counts Using a Hesitant Fuzzy Linear Regression Depend on Race, Age and Location(2022) Dengiz, Asiye Ozge; Atalay, Kumru DidemThe COVID-19 pandemic that has struck the world has caused social and economic problems in people's lives. Many countries are trying to reduce the impact of the pandemic by taking precautions to prevent the spread of the virus and reduce the number of deaths. Despite the precautions, many people have contracted the virus and a significant number have lost their lives. This suggests that some factors about the exact mechanism of how people contract the virus and get sick are still unclear. Therefore, many researchers wonder if there are other factors that make people more susceptible to the COVID-19 virus. In this study, hesitant fuzzy linear regression (HFLR) models are applied depending on variables such as age, race, and place of residence that are thought to influence COVID-19 deaths. HFLR provides an alternative approach to statistical regression for modeling situations with incomplete information. The models include input and output variables as hesitant fuzzy elements (HFEs). The relationship between the considered variables and the number of deaths is examined using data related to people living in different states of the United States. In addition, HFLR is used as an estimation model due to the uncertainty in the data obtained from the Centers for Disease Control and Prevention (CDC). The proposed HFLR models are used both to estimate COVID-19 deaths and to determine the effects of selected variables on COVID-19 deaths. In this way, countries can estimate the risk of death for individuals given these factors and determine what precautions to take for high-risk groups.Item Risk Analysis and Process Improvement for Medical Devices with Integrated Method DEA and FMEA(2022) Yamandir, Merve Nil; Dinler, Esra; Atalay, Kumru DidemRisk analysis is the identification of factors, conditions, activities, systems, components that are important concerning risk. Evaluating the systems in terms of risk plays a critical role in the production of products that are especially important for human health. The washing process of the medical devices at the production stage is important in terms of ensuring the acceptable sterility assurance level of the product before sterilization. In this process, the risk factors that may affect human health emerge. Risk Priority Number (RPN) which is used in the Failure Mode and Effect Analysis (FMEA) is calculated for each factor and it is considered to be equally important in general. Sometimes it can be difficult to clearly show the importance of these effects. These invisible effects cause great costs for companies, and they can also affect human health at risk. In this study, risk analysis of the washing process in a company producing medical devices is performed. Risk prioritization is made by scaling risk types and their effects by Data Envelopment Analysis (DEA) method to eliminate the disadvantages in question. As a result of the study, the prioritization of risk types with different methods is compared.Item A new hybrid method to determine the hazardous risk factors(2022) Dinler, Esra; Atalay, Kumru Didem; Guler, EzgiIn risk analysis, the quantification of risk, the modeling of identified risk, and how to make decisions are all topics considered. Risk analysis activity that companies must comply with and perform at a minimum level to produce medical devices. Manufacturers should consider all risks that the device may contain to indicate that the medical device is safe. Manufacturers must also justify that this device should be manufactured because the benefit of the device is greater than the risk. This study proposes a method to measure the risk factors of the medical devices on the patient. Accordingly, a mathematical model is developed, the model is applied to a device manufactured in a company, and the results are obtained. The aggregated method developed in this study, based on the Taguchi loss function and using the hesitant fuzzy the technique for order preference by similarity to ideal solution (HF-TOPSIS) method, ensures that the risks that may occur for the patient are minimized and the risk types to be taken into account are determined. In addition, the order of importance of the risk types obtained with the proposed method in the study is compared with the TOPSIS method.Item Focusing on the big picture while observing the concerns of both managers and passengers in the post-covid era(2021) Samanci, Simge; Atalay, Kumru Didem; Isin, Feride BaharThis study reveals how to improve and define the issues of service quality in the airline sector after the outbreak of COVID-19, to what extent customer needs (important issues) and expectations (expected performances) will differ, and the priorities of airline sector managers in terms of resource allocation, costs, planned strategies, and operational efficiency and effectiveness. It offers a systematic and interactive perspective by simultaneously providing the perspective of both airline managers and passengers by using a new hybrid method, namely Fuzzy Importance, Expected Performance, and Priority Analysis (FIEPA) with VIKOR. This method allows the use of different perspectives of different managers in the analysis, which can be prioritized with different weights. According to the results of the study, in which 449 passengers participated on Twitter, the attributes on which airline managers should focus were determined, having three distinctive characteristics of being important for customers, having high priority according managers, and having low expected performance according customers. Twenty-two attributes related to the service quality of airlines during outbreak periods were classified into three main dimensions as "social distance and hygiene during flight", "information awareness and concern", and "infection alert procedure".Item A goal programming approach for multi objective, multi-trips and time window routing problem in home health care service(2021) Dengiz, Asiye Ozge; Atalay, Kumru Didem; Altiparmak, FulyaThe structure of services in the health sector is changed by the epidemic diseases affecting the world, the population growth and developing technologies. Due to the advantages it provides, home health care (HHC) services are increasingly being demanded by patients. With the in-crease in demand for HHC, the interest of researchers in Home Health Care Routing Problem (HHCRP) is also increasing. In this study, HHCRP has been studied based on information gathered from a relevant unit of a State Hospital providing HHC services in Ankara. Due to the limited resources in the hospital under consideration, vehicles often need to be used for multiple rounds. Thus, the HHCRP is considered as a multi-tour routing problem. Besides, the problem has been created with time window constraints in order to ensure that the demands of the patients are met on time. Meantime, meeting all the patient demands and reducing the environmental impacts are two important goals in HHCRP. The reduction of the environmental impacts can be achieved by minimizing the carbon emission of the vehicles used in the HHC. Thus, the problem addressed in this study has been defined as a multi-objective, multi-trip and time-windows home healthcare routing problem (MTTW-HHCRP). Weighted goal programming (GP) method is used to solve the proposed problem. Test problems are randomly generated based on the data and the information obtained from the hospital in Ankara, and the solutions obtained through scenario analysis are evaluated to guide the decision-making process.Item The development of a reviewer selection method: a multi-level hesitant fuzzy VIKOR and TOPSIS approaches(2021) Kocak, Serdar; Ic, Yusuf Tansel; Atalay, Kumru Didem; Sert, Mustafa; Dengiz, Berna; 0000-0001-9274-7467; AGE-3003-2022This paper proposes a new approach for the selection of reviewers to evaluate research and development (R&D) projects using a new integrated hesitant fuzzy VIKOR and TOPSIS methodology. A reviewer selection model must have a multi-level framework in which reviewer selection strategies and related objectives guide the second level of the reviewer performance ranking process. The model must measure reviewer performance related to the activities that are necessary for the R&D project evaluation to be successful. A novel model is presented in this paper. In the proposed methodology, the aim is to select a reviewer in a hierarchical decision-making structure. The selection criteria values and their weights were obtained using the hesitant fuzzy VIKOR method. For the selection of a suitable reviewer, the conventional TOPSIS model was used. We developed a simpler procedure for effectively performing the reviewer selection process. The new approach was tested with a real case study and satisfactory results were obtained. A comparative analysis is also included in the article for illustrative purposes.Item Development of a new hesitant fuzzy ranking model for NTMP ranking problem(2021) Atalay, Kumru Didem; Ic, Yusuf Tansel; Kececi, Baris; 0000-0001-9274-7467; AGE-3003-2022Nontraditional manufacturing processes (NTMPs) bring the processing capabilities such as machining high strength and hard materials with desired accuracies and surface finish to the manufacturing companies. Therefore, there has been a significant increase in the use and number of NTMPs. Hence, choosing a particular NTMP for a specific application turns out to be a complex decision-making problem, which involves conflicting qualitative and quantitative ranking criteria. In recent NTMP ranking literature, it is noted that fuzzy approaches are better suited for handling uncertainties and incomplete information that exist within the NTMP ranking environment. This paper introduces such a fuzzy approach using the hesitant fuzzy preference selection index (PSI) method for the assessment of the criteria weights and the hesitant fuzzy correlation coefficient principle for ranking and recommending the most appropriate NTMP for a specific application. The proposed methodology and its efficiency in dealing with incomplete information under the fuzzy decision-making environment are explored with a case study. As a result of the study, the proposed model preferred the electron beam machining (EBM) as the most suitable nontraditional manufacturing process. On the other hand, triangular fuzzy TOPSIS methods offered the electrochemical machining (ECM) as the best choice among the alternatives. The differences among the ranking decisions are also analyzed in the paper. It can be concluded from the authors' various applications of the proposed hesitant fuzzy PSI method that it is extremely effective in representing fuzzy decision-making environments in NTMP ranking decisions.Item A New Methodology for Solving Multiobjective Chance-Constrained Problems: An Application on IoT Systems(2021) Atalay, Kumru Didem; Pekin, Tacettin Sercan; Apaydin, Aysen; 0000-0002-9021-3565This study presents a newly developed methodology to transform the chance-constrained problem into a deterministic problem and then solving this multiobjective deterministic problem with the proposed method. Chance-constrained problem contains independent gamma random variables that are denoted as a(ij). Two methods are proposed to obtain the deterministic equivalent of chance-constrained problem. The first of the methods is directly based on using the distribution, and the second consists of normalizing probabilistic constraints using Lyapunov's central limit theorem. An algorithm which uses the Global Criterion Method is developed to solve the multiobjective deterministic equivalent of chance-constrained problem. The methodology is applied to a real-life engineering problem that consists of an IoT device and its data sending process. Using Lyapunov's central limit theorem for large numbers of random variables is found to be more appropriate.Item The effects of consumer confusion on hotel brand loyalty: an application of linguistic nonlinear regression model in the hospitality sector(2020) Kurtulmusoglu, Feride Bahar; Atalay, Kumru DidemThe aim of the study is to estimate the interaction and quadratic relationships between dimensions by estimating a model for the confusion dimensions that affect hotel brand loyalty, thus providing the interested parties with a perspective and direction regarding consumer confusion. This study also aimed to strengthen the use of FLS in the field of social sciences and will use this method to transform the discrete ordinal variable into a continuous variable while preserving the semantic meaning. Four hundred and six individuals participated in the study. Hypotheses demonstrating the interaction and quadratic effects between the continuous variables have been analysed using nonlinear multiple regression analysis. This study proposes a survey-based method to estimate a model for the confusion dimensions that affect hotel brand loyalty. The results demonstrated that ambiguity confusion, overload confusion, similarity confusion, quadratic effect of similarity confusion and interaction of ambiguity, overload and similarity confusion decrease the hotel brand loyalty. Also, quadratic effect of ambiguity confusion, interaction of ambiguity and overload confusion, interaction of overload and similarity confusion, interaction of ambiguity and similarity confusion increase the hotel brand loyalty. Despite its importance for marketing and consumer behaviour, the definition, measurement, dimensions and existing results of consumer confusion have begun to be discussed and examined recently in a limited scope. Studies have demonstrated that consumer confusion about tourism products is a non-functional and under-evaluated area but also is utmost prominent for tourism product. This study aimed to obtain a stronger model in which all the interactions between variables and their (quadratic) increasing effects are considered using a nonlinear regression model.Item Airfoil-slat arrangement model design for wind turbines in fuzzy environment(2020) Atalay, Kumru Didem; Dengiz, Berna; Yavuz, Tahir; Koc, Emre; Ic, Yusuf TanselIn this study, a multi-element wind turbine blade that consists of NACA 6411 and NACA 4412 leading-edge slat design is investigated computationally. Optimum design parameters of the slatted wind turbine blade leading to maximum value of C-L/C-D related to the turbine power are obtained. In the optimization process, a new fuzzy logic linear programming methodology integrating with fuzzy linear regression and 2D CFD analysis is proposed. The aerodynamic characteristics of the slatted blade are computed by using Incompressible Navier-Stokes equations and k-omega turbulence modeling. Results are compared with the results of linear programming method and direct search optimization method. The computational results reveal that the proposed methodology for performance optimization is more effective than other methods to obtain high-performance value of the C-L/C-D. The maximum value of the C-L/C-D is obtained as 25.1 leading the maximum efficiency of 0.52.