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Author: search.filters.author.Atalay, Kumru Didemsearch.filters.applied.f.language: search.filters.language.eng

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    Goodness-of-fit and Randomness Tests for the Sun's Emissions True Random Number Generator
    (2014) Tanyer, Suleyman Gokhun; Atalay, Kumru Didem; Inam, Sitki Cagdas; 0000-0003-0820-9186; I-5023-2013; JHU-3888-2023
    Random number generators ( RNGs) are one of the key tools necessary for statistical analysis and optimization methods such as Monte Carlo, particle swarm optimization ( PSO) and the genetic algorithm. Various pseudo and true RNGs are available today, and they provide sufficient randomness. Unfortunately, they generate data that do not always represent the required distribution accurately, especially when the data length is small. This could possibly threaten the 'repeatability' of an academic study. A novel true RNG ( TRNG) using the method of uniform sampling ( MUS) is recently proposed. In this work, the Sun's RF emissions MUS-TRNG is comparatively tested with well known pseudo and true RNGs. It is observed that both randomness and very high goodness-of-fit qualities are possible.
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    Multi-Criteria Usability Evaluation of Electronic Devices in a Fuzzy Environment
    (2014) Atalay, Kumru Didem; Eraslan, Ergun; https://orcid.org/0000-0002-9021-3565; https://orcid.org/0000-0002-5667-0391; AAE-7165-2019
    The user-oriented design is the most important competition issue in today's market. In recent years, user-oriented design (i.e., usability) has become expected, particularly in electronic devices. Usability considers high user satisfaction in conjunction with user performance. Usability of electronic products is essential for high customer satisfaction as well as product life cycles in companies. Therefore, MP3 players were selected among the electronic products. Designing usable MP3 players is extremely important for users who have close interaction with them. In this study, MP3 players of different types and sizes were selected and their usability evaluated. The usability criteria used in the MP3 players' evaluation were divided into two major categories: performance and emotional expectations. The alternatives were ranked with fuzzy multi-criteria decision-making methods, namely, Fuzzy TOPSIS (FTOPSIS), Fuzzy Analytic Hierarchy Process (FAHP), and Fuzzy Axiomatic Design Theory (FADT), and the results were compared. Although the same decision matrices and data obtained from semantic differential experiment were used for all fuzzy multi-criteria decision-making methods, it is shown that different rankings were obtained. (c) 2012 Wiley Periodicals, Inc.
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    A Hybrid Algorithm Based on Fuzzy Linear Regression Analysis by Quadratic Programming for Time Estimation: An Experimental Study in Manufacturing Industry
    (2015) Atalay, Kumru Didem; Eraslan, Ergun; Cinar, M. Oya; 0000-0002-5667-0391; AAE-7165-2019
    In time studies, estimation of the standard times with direct or indirect measurement methods is particularly difficult in companies having complex production schedules or ones employing an inexperienced workforce. Such companies require new and specific time measurement procedures. In this study, a new time estimation algorithm based on fuzzy linear regression analysis (FLRA) by quadratic programming (QP) is proposed for specific manufacturing systems. In our study, data is provided by one of the biggest casting and machining companies in Europe. The database includes items that have similar production processes. A fuzzy linear regression model is built by using the previously measured standard times of a product family. The model developed is used for estimating the standard times of the remaining products. FLRA based on QP approach facilitates integration of the central tendency of least squares and possible properties of fuzzy regression. The main factors that directly impact standard times are determined and used for the estimation of the fuzzy standard times. Through utilization of sum of squares error (SSE) and index of confidence (IC), the important factors in the model are identified. The use of QP makes it possible to reconcile the minimization of the deviation of central tendency and the spreads of membership functions in a simultaneous manner. In this study, the efficiency of the proposed algorithms in casting companies is authenticated. Besides, it is seen that this estimation procedure could be implemented easily for various sectors using the relevant algorithms. (C) 2014 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.
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    Randomness Tests For The Method Of Unıform Sampling Quasi-Random Number Generator (MUS-QRNG)
    (2014) Atalay, Kumru Didem; Tanyer, Suleyman Gokhun; https://orcid.org/0000-0001-9506-2391; I-5023-2013
    Random number generation is still an important research field in many scientific applications today. Cryptography, Monte Carlo simulations and commertial applications all rely on reference random data. Randomness tests and basic statistics share the same history. Randomness can be summarized as the unpredictability of future samples of a random number generator even in the presence of known all past values. Various randomness tests are developed and due to their individual contributions, usually a battery of tests are applied to verify a random number generator. In signal processing however, the error of a specific observed sample set to a given distribution could be much more important when it is used as the input for a system model. Recently, this distance of finite samples set to a given distribution is studied and a quantitative measure for quality is proposed Multi run computations like Monte Carlo simulations, often rely on accurate statistical data for high repetibility. Otherwise when the data is not accurate, the results could often rely on the source of random data generator. Many runs are often required to gain a confidence in the presence of those variances. In this work, recently proposed quasi-random number generator utilizing method of uniform sampling NUS) is tested using standard goodness-of-fitness tests. MUS-QRNG numbers are shown to have exact statistics and also their randomness test results are observed to be similar to well known reference generator of Matlab. MUS-QRNG is proposed for high quality random data generation.
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    A New Hybrid Intuitionistic Approach for New Product Selection
    (2018) Atalay, Kumru Didem; Can, Gulin Feryal
    This paper proposes a new hybrid approach for multi-criteria decision-making problems combining intuitionistic fuzzy analytic hierarchy process and intuitionistic fuzzy multi-objective optimization by ratio analysis. Analytic hierarchy process has an inherent ability for handling intangible problems and implements a simple scale to represent evaluations in the structure of pairwise comparisons. Multi-objective optimization by ratio analysis optimizes the solution of a problem having two or more conflicting objectives, taking into account certain constraints. In real-life decision problems, evaluations of decision makers related to performance of alternatives and criteria weights can be expressed by linguistic terms comprising vagueness and uncertainty. These uncertain, vague and hesitant judgments of decision makers can be described more comprehensively by using intuitionistic fuzzy set theory. The proposed approach is a powerful tool for dealing with information which consists of hesitancy and vagueness. An illustrative example related to new product selection for a company is also presented to demonstrate the implementation of the approach.
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    Assessment of Mental Workload and Academic Motivation in Medical Students
    (2016) Atalay, Kumru Didem; Can, Gulin Feryal; Erdem, Saban Remzi; Muderrisoglu, Ibrahim Haldun; https://orcid.org/0000-0002-7537-2170; 27183939; AAJ-2370-2021
    Objectives: To investigate the level of correlation and direction of linearity between academic motivation and subjective workload. Method: The study was conducted at Baskent University School of Medicine, Ankara, Turkey, from December 2013 to February 2014, and comprised Phase 5 Phase 6 medical students. Subjective workload level was determined by using National Aeronautics and Space Administration Task Load Index scale that was adapted to Turkish. Academic motivation values were obtained with the help of Academic Motivation Scale university form. SPSS 17 was used for statistical analysis. Results: Of the total 105 subjects, 65(62%) students were in Phase 5 and 40(38%) were in Phase 6. Of the Phase 5 students, 18(27.7%) were boys and 47(72.3%) were girls, while of the Phase 6 students, 16(40%) were boys and 24(60%) were girls. There were significant differences in Phase 5 and Phase 6 students for mental effort (p= 0.00) and physical effort (p= 0.00). The highest correlation in Phase 5 was between mental effort and intrinsic motivation (r= 0.343). For Phase 6, highest correlation was between effort and amotivation (r= -0.375). Conclusion: Subjective workload affected academic motivation in medical students.
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    Quality Improvement Strategies of Highway Bus Service Based On A Fuzzy Quality Function Deployment Approach
    (2016) Kurtulmusoglu, Feride Bahar; Pakdil, Fatma; Atalay, Kumru Didem; A-7058-2017
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    A Case Study on Shopping Malls Attributes for Young Consumers
    (2016) Can, Gulin Feryal; Kurtulmusoglu, Feride Bahar; Atalay, Kumru Didem
    Purpose - This study aims to determine the mall criteria that are the most crucial for the youth market by determining the winning brand in comparison to other offerings to understand what is required to gain a competitive advantage and to differentiate a mall from its rivals. Design/methodology/approach - This study chose the Stochastic Multicriteria Acceptability Analysis-2 method to evaluate the mall preferences of young people. By using this method, the various criteria were evaluated for more than one alternative to find the best solution. JSMA program was used to analyze the data. The survey was administered using the mall intercept method to reduce sample bias. Findings - The study identifies that the criteria that have the highest impact on the mall preferences of young people are the mall campaigns for loyal customers; the traffic in the mall locality and the mall's parking facilities; the mall's facilities for disabled people; the quality of the mall locality; and the quality of the people visiting the mall. The study reveals that a mall's physical features, its facilities and the criteria related to employees have a very low impact on the mall choices of young people. The study further finds that the youth market has very low satisfaction levels for all of the identified criteria. This study reveals that this macro accessibility criterion is less relevant for the youth market than for the general population. Originality/value - Despite the importance of this market, there is insufficient research on the shopping behavior of young people. They have a considerable impact on the purchasing decisions of their families, significant disposable income and constitute the future market for the sector. This study uniquely enables the sequential ordering of customers' decision-making criteria and determines the effectiveness or impact of these criteria in the mall sector.
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    Evaluation of Effect of Different Membership Functions on Risk Assessment
    (2018) Atalay, Kumru Didem; Can, Guelin Feryal; Eraslan, Ergun; 28330411
    This study aims to define the relationship between risk degrees and risk indexes on different functional structures with the assumption that risk degrees may not always present a linear relationship with the risk indexes. In this way, risk indexes suitable for expert evaluation of working conditions and computed using three different membership functions are determined. Among the membership functions used, one is preferred as linear and the others are preferred as non-linear. Additionally, a new fuzzy risk assessment (RA) algorithm is developed using these three membership functions. With this new fuzzy RA algorithm, a more flexible and precise process becomes available, while information loss during the determination of the risk index of danger sources is prevented. As a result, non-linear increasing membership function is selected as most suitable for the expression of the relationship between risk degrees and risk indexes.
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    A New Stochastic MCDM Approach Based on COPRAS
    (2018) Ayrim, Yelda; Atalay, Kumru Didem; Can, Gulin Feryal
    This study proposes a novel integrated Complex Proportional Assessment (COPRAS) approach by using stochastic decision process named as Stochastic COPRAS (COPRAS-S) to increase the evaluation performance of COPRAS. In COPRAS-S, criteria importance weights and the performance values of alternatives are determined by generating random numbers from uniform distribution in a range of minimum and maximum values of a limited number of decision-maker evaluations. Thus, the numbers of experts are increased and decision-making process is performed in an effective way because different opinions are incorporated. In addition, randomness feature brought with vagueness in decision is modeled in this process. A special normalization approach based on standard deviation is also implemented in COPRAS-S. In this way, cost and benefit type criteria are evaluated in a different way. This proposed stochastic structure for COPRAS is a practical and powerful tool that strengthens the decision.