Browsing by Author "Toktas, Pelin"

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A Pilot Study on Comparison of Teaching Workloads of Academicians Based on Working Periods During and Before the COVID-19 Pandemic
(Başkent Üniversitesi Mühendislik Fakültesi, 2025-01-25) Yorulmaz, Muhammed; Can, Gulin Feryal; Toktas, Pelin
The COVID-19 pandemic has had a profound impact on society, greatly changing the structure of social and working lives. Educational institutions, especially in higher education, were forced to suspend face-to-face education and switch to distance education. This change inevitably affected the working styles and workloads of academics. This study aims to explore the effects of the COVID-19 pandemic on academic teaching workloads by examining transaction data for a one-year period before and during the pandemic. The data were obtained from the system logs of a learning management system platform, which was used extensively during the pre-pandemic and pandemic periods, and were analyzed in terms of transaction density, day, and time of transactions. The findings from the pre-pandemic period showed that the academic workload was higher on weekdays than on weekends. However, with the transition to distance education during the pandemic, the difference between weekday and weekend workloads diminished significantly. Additionally, the working hours shifted during the pandemic by approximately one hour to later hours in the day.
An Advanced Stochastic Risk Assessment Approach Proposal Based on KEMIRA-M, QFD and Fine-Kinney Hybridization
(2021) Can, Gulin Feryal; Toktas, Pelin
In this study, an advanced stochastic risk assessment approach based on integration of advanced version of quality function deployment (AV-QFD) and Modified Kemeny Median Indicator Rank Accordance (KEMIRA-M) is proposed. It is aimed to perform a new criterion weighting procedure based on four different distributions as uniform, symmetric triangular, left asymmetric triangular, right asymmetric triangular distributions. The AV-QFD includes correlations between criteria (top roof of QFD), risk degrees (RDs) of risk types (RTs) (customer needs part of QFD), correlations between RTs and criteria sets (CSs) (in the middle of QFD) to obtain the criteria priorities. Correlations on the top roof of QFD comprises three types: correlations between criteria in the first CS, correlations between criteria in the second CS and correlations between criteria in both CSs. Additionally, Fine-Kinney method is performed in AV-QFD to compute RDs of RTs in the customer needs part. Then for each expert, the correlation-based importance degree (CBID) of each criterion is obtained to rank criteria for each CS. MATLAB code was performed to see the effect of different trial numbers and replications on risk assessment. It was observed that although uniform distribution provides the best value, the same alternative ranking was obtained for all distributions. In addition, right asymmetric triangular distribution converged to the best value rapidly in practice made in this study.
Modeling The Dependency Structure Between Quality Characteristics İn Multi-Stage Manufacturing Processes With Copula Functions
(INTERNATIONAL JOURNAL OF OPTIMIZATION AND CONTROL-THEORIES & APPLICATIONS-IJOCTA, 2024-11-08) Gebizlioglu, Omer Lutf; Toktas, Pelin
This study is about multi-stage manufacturing processes and their control by statistical process control modeling. There are two kinds of dependence structures in a multi-stage manufacturing process: one is the dependence between the stages of the process, and the other is the dependence between the concerned quality characteristics. This study employs state-space models to demonstrate the dependency structure between the process stages and uses the Kalman filter method to estimate the states of the processes. In this setup, copula modeling is proposed to determine the dependence structure between the quality characteristics of interest. A simulation study is conducted to assess the model's accuracy. As a result, it was found that the model gives highly accurate predictions according to the mean absolute percentage error (MAPE) criteria (<10%).
A Novel Multi-Criteria Decision-Making Approach Proposal Based on Kemira-M with Four Criteria Groups
(2022) Ay, Sefacan; Can, Gulin Feryal; Toktas, Pelin
This study aims to eliminate the subjectivity in the weight assignment process of Modified Kemeny Median Indicator Ranks Accordance (KEMIRA-M) and to remove the need for experts to reach a consensus on determining the criteria weights. Additionally, this study aims to apply KEMIRA-M for four different criteria groups and to prevent some criteria from taking a weight value of "0", as in other studies using KEMIRA-M. In this context, the weighting procedure of KEMIRA-M is advanced using three different ranking-based weighting methods such as Rank Sum (RS), Rank Exponent (RE) and Rank Reciprocal (RR) to operate Median Priority Components (MPCs) more effectively. Accordingly, to determine which weighting method for which criterion group is more suitable, the selection procedure of KEMIRA-M was applied and alternative rankings were obtained for 81 different weight set combinations. Additionally, MATLAB codes have been used to provide flexibility for the application of the proposed approach in a supplier selection problem selected for a case study.
Six Sigma Project Prioritization and Selection Using AHP-CODAS Integration: A Case Study in Healthcare Industry
(2023) Can, Gulin Feryal; Toktas, Pelin; Pakdil, Fatma; https://orcid.org/0000-0001-6622-4646; D-7271-2018
Given the complex nature of Six Sigma project (SSP) prioritization and selection processes, multicriteria decision-making (MCDM) methods may help organizations identify the most effective projects. Considering potential limitations of subjective methods and advantages of MCDM methods, this article proposes a model that integrates analytical hierarchy process (AHP) and combinative distance-based assessment (CODAS) in SSP prioritization and selection process. In the proposed approach, AHP is employed to assign criteria weights, and CODAS is performed to determine priorities of SSPs. CODAS was advanced in term of its threshold function. Differences between Euclidean distances of two alternatives were compared, based on the standard deviation of Euclidean distances of all alternatives to overcome the subjectivity. This is the first study that combines AHP and CODAS methods for SSP selection, and CODAS is used with objective threshold value computation, and developed for the healthcare industry. In this article, ten SSPs were evaluated for four key criteria groups as financial, operational, patient centric, and organizational main criteria groups. In total, 18 subcriteria were considered under these four main criteria groups. This article provides a support for executives who make implementation plans for the potential SSPs.
Six Sigma Project Prioritization and Selection Using AHP-CODAS Integration: A Case Study in Healthcare Industry
(2021) Can, Gulin Feryal; Toktas, Pelin
Given the complex nature of Six Sigma project (SSP) prioritization and selection processes, multicriteria decision-making (MCDM) methods may help organizations identify the most effective projects. Considering potential limitations of subjective methods and advantages of MCDM methods, this article proposes a model that integrates analytical hierarchy process (AHP) and combinative distance-based assessment (CODAS) in SSP prioritization and selection process. In the proposed approach, AHP is employed to assign criteria weights, and CODAS is performed to determine priorities of SSPs. CODAS was advanced in term of its threshold function. Differences between Euclidean distances of two alternatives were compared, based on the standard deviation of Euclidean distances of all alternatives to overcome the subjectivity. This is the first study that combines AHP and CODAS methods for SSP selection, and CODAS is used with objective threshold value computation, and developed for the healthcare industry. In this article, ten SSPs were evaluated for four key criteria groups as financial, operational, patient centric, and organizational main criteria groups. In total, 18 subcriteria were considered under these four main criteria groups. This article provides a support for executives who make implementation plans for the potential SSPs.
Six sigma project prioritization and selection: a multi-criteria decision making approach in healthcare industry
(2020) Pakdil, Fatma; Toktas, Pelin; Can, Gulin Feryal
Purpose The purpose of this study is to develop a methodology in which alternate Six Sigma projects are prioritized and selected using appropriate multi-criteria decision-making (MCDM) methods in healthcare organizations. This study addresses a particular gap in implementing a systematic methodology for Six Sigma project prioritization and selection in the healthcare industry. Design/methodology/approach This study develops a methodology in which alternate Six Sigma projects are prioritized and selected using a modified Kemeny median indicator rank accordance (KEMIRA-M), an MCDM method based on a case study in healthcare organizations. The case study was hypothetically developed in the healthcare industry and presented to demonstrate the proposed framework's applicability and validity for future decision-makers who will take place in Six Sigma project selection processes. Findings The study reveals that the Six Sigma project prioritized by KEMIRA-M assign the highest ranks to patient satisfaction, revenue enhancement and sigma level benefit criteria, while resource utilization and process cycle time receive the lowest rank. Practical implications The methodology developed in this paper proposes an MCDM-based approach for practitioners to prioritize and select Six Sigma projects in the healthcare industry. The findings regarding patient satisfaction and revenue enhancement mesh with the current trends that dominate and regulate the industry. KEMIRA-M provides flexibility for Six Sigma project selection and uses multiple criteria in two-criteria groups, simultaneously. In this study, a more objective KEMIRA-M method was suggested by implementing two different ranking-based weighting approaches. Originality/value This is the first study that implements KEMIRA-M in Six Sigma project prioritization and selection process in the healthcare industry. To overcome previous KEMIRA-M shortcomings, two ranking based weighting approaches were proposed to form a weighting procedure of KEMIRA-M. As the first implementation of the KEMIRA-M weighting procedure, the criteria weighting procedure of the KEMIRA-M method was developed using two different weighting methods based on ranking. The study provides decision-makers with a methodology that considers both benefit and cost type criteria for alternates and gives importance to experts' rankings related to criteria and the performance values of alternates for criteria.
Stochastic KEMIRA-M Approach with Consistent Weightings
(2019) Toktas, Pelin; Can, Gulin Feryal
This study proposes an advanced Modified KEmeny Median Indicator Rank Accordance (KEMIRA-M) approach based on stochastic evaluation process considering consistent weights to improve effective usage of KEMIRA-M. In the proposed approach, tasks related to the decision issue are performed by decision makers to ensure the understanding sufficiency of alternatives in terms of criteria more clearly. The weighting procedure of Analytic Hierarchy Process (AHP) is implemented in a stochastic manner benefited from discrete uniform distribution to provide obtaining consistent criteria weights considering median priority components. Therefore, different trials including different number of replications that shows the number of decision makers are performed and the most consistent weightings are determined for each trial in the stochastic process. In this way, the dependency to the limited numbers of decision makers and to determine criteria weights in a heuristic manner in KEMIRA-M is prevented. Additionally, the effect of the number of decision makers on criteria weightings and alternatives' ranking process is shown. To obtain the most consistent weighting results, this stochastic process is utilized until acquiring approximate consistency ratios. The proposed stochastic KEMIRA-M approach is utilized to rank nine shopping malls (SMs) in Ankara in terms of technical criteria (TC) and universal design criteria (UDC). It was seen from the ranking results that the first SM (SM1) is the best one.
A Three-Stage Holistic Risk Assessment Approach Proposal Based on KEMIRA-M And DEMATEL Integration
(2023) Toktas, Pelin; https://orcid.org/0000-0001-6622-4646; D-7271-2018
This study proposes a three-stage Modified Kemeny Median Indicator Rank Accordance (KEMIRA-M) and Decision-Making Trial and Evaluation Laboratory (DEMATEL) integration for RA. At the first stage, risk criteria rankings are obtained for each expert separately by implementing DEMATEL. At the second stage, criteria weights obtained from DEMATEL are used to determine Median Priority Components which is an aggregated criterion ranking for all experts as in traditional KEMIRA-M. In this stage, initial decision matrix including danger sources' performance values for risk criteria is formed and rankings of danger sources are obtained via KEMIRA-M selection procedure considering criteria weights obtained from DEMATEL. At the third stage, direct relationship matrix of DEMATEL is used again to determine affect level of measures on danger sources. Then, by using the danger sources' weights obtained from the second stage, the measures were prioritized according to the weighted means. This study is the first one that advance KEMIRA-M's weighting procedure by implementing DEMATEL. In this way, a systematic weighting procedure has been gained for KEMIRA-M and a rule-based weight assignment can be performed for risk criteria in KEMIRA-M. Additionally, a three-step KEMIRA-M and DEMATEL is first proposed in this study as a holistic RA to prioritize measures. There is no study that considers risk criteria, danger sources and measures at the same time to prioritize measures. This study provides a new comprehensive approach for experts and executives to make a work plan for measure applications considering risk criteria and danger sources.
Validation of Qualitative Aspects Oof The Lean Assessment Tool (LAT)
(2018) Pakdil, Fatma; Toktas, Pelin; Leonard, Karen Moustafa
Purpose - The purpose of this paper is to test the reliability and validity of the qualitative section of Lean Assessment Tool (LAT) starting from the point where a reliable and valid tool is needed to measure increasing leanness level of business organizations. Design/methodology/approach - The questionnaire used in this study included the qualitative component of LAT developed by Pakdil and Leonard (2014). The unit of the study was individual employees who work in manufacturing firms participating in this study. This study focused on the data collected from three firms that operate in Turkey and two firms that operate in the USA. The total respondents from Turkish firms were 263 employees, while the 205 employees responded from US firms. Findings - Exploratory factor analysis and confirmatory factor analysis were completed to determine valid and reliable factors that compose LAT's qualitative component. The statistical analysis showed five distinct factors, namely process, delivery, quality, customer satisfaction and human resource. In addition, the fuzzy logic showed appropriate loadings to make the argument for its use in analysis of the LAT. Research limitations/implications - This study moves the debate about the success or failure of lean efforts forward. With the debates about lean and its potential, it is necessary to have a scientific determination of success and the areas where further work in the firm is needed. Such measurement is the backbone of management progress, and the authors believe that this paper is useful. Second, the necessity of reliable and valid tools of lean assessment is obvious in the literature and practice. The findings of this study help academicians find reliable and valid tools to measure lean success both in the literature and practice. Practical implications - Managerial implications include the development of a way to assess the areas of success and areas requiring further work. Failure to measure success and needs for further work has been the reason for the questionable results found in investigating lean implementation efforts. If there is no way to determine what is needed to improve lean efforts, they will be seen as failure, even if part of the implementation has been successful. This tool has been found to be potentially useful for evaluation of these crucial and time-consuming efforts. Originality/value - In this study, the qualitative section of LAT has been validated. The results demonstrated that, based on two countries' data sets, the scale was found to be reliable and valid within itself and across sociocultural boundaries.
Warehouse Location selection for an electricity distribution company by KEMIRA-M method
(2020) Kis, Oznil; Can, Gulin Feryal; Toktas, Pelin
In this study, by using Modified Kemeny Median Indicator Ranks Accordance (KEMIRA-M) approach which begins to become popular in recent times for solution of Multi criteria Decision Making (MCDM) problems, warehouse location selection for an electricity distribution company is performed. KEMIRA-M logically distinguishes criteria into two groups and it computes criteria importance weights by including interactions between both groups. KEMIRA-M considers both decision makers' preferences related to the priorities of criteria and quantitative or qualitative values of these criteria in decision making process. Decision makers can change importance weights of criteria based on median priority component representing expected rankings of criteria importance weights and they can see the effect of this variability on rankings of alternatives. In warehouse location selection problem investigated in this study, it is aimed to choose the favorable location considering different criteria and these criteria were grouped firm related and environmental criteria to evaluate 20 alternative warehouse locations. In this context, as firm related criteria; Operation Center-Meeting Point (OC-MP) transportation cost per month, main warehouses' transportation costs per month, number of connected OC-MP, consumption amounts of OC-MP were considered. Population, distance to the closest main road, average distance to main supplier, mobility, investment amounts in 2018, average delivery time and land cost were taken into account as environmental criteria group.