Mühendislik Fakültesi / Faculty of Engineering

Permanent URI for this collectionhttps://hdl.handle.net/11727/1401

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Author: search.filters.author.Atalay, Kumru Didem

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    A Plasma Arc-Based Electromechanical System Designed for Microchannel Processing
    (Başkent Üniversitesi Mühendislik Fakültesi, 2024-05-31) Akin, Fevzi; Ersoy, Ece; Idil, Deniz; Ozsimitci, Melih; Serdaroglu, Dilek Cokeliler; Ic, Yusuf Tansel; Atalay, Kumru Didem; Kocum, Cengiz; Okat, Kemal
    Plasma technology is based on a simple physical principle. When more energy enters the gas, it ionizes and becomes the fourth state of matter, the energy-dense plasma. The studies carried out within the scope of this study were designed to create microchannels on lamellar glass using an improved redesign of the current plasma arc device, which is the main subject of the paper. The created microchannel is examined at the microscale. Experimental analysis was conducted considering the effect of plasma on the effect of microchannel quality. We performed an experimental design study to determine the optimal parameter levels for improving microchannel quality. The predicted results have been validated with the experimental results. An experimental design study provides useful results, such as information about the distance between the probes, pulse duration, and material temperature, which enhances the channel dimensions. The improved device can be utilized effectively to establish microchannel processing in practice.
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    Improving The Quality Of Micro Holes Drilled With A Current Detection Plasma Arc Device
    (JOURNAL OF THE BRAZILIAN SOCIETY OF MECHANICAL SCIENCES AND ENGINEERING, 2024-10) Ic, Yusuf Tansel; Kocum, Cengiz; Atalay, Kumru Didem; Serdaroglu, Dilek Cokeliler; Akar, Gurel; Polat, Isil Yanki; Samsun, Berk; Caliskan, Sevde; Atmaca, Dicle Naz; Karayalcin, Serkan
    Today, microholes play a crucial role in many sectors. Microholes are used in fields such as aerospace, computer systems, and electronic and mechanical industries. In this paper, we improve the performance of the current sensing plasma arc device to create holes within the same diameter, appropriate delamination, and surface quality. In addition, we aim to improve the processing quality of the current sensing plasma arc device, which drills holes from the micron level to the millimeter level and creates microstructures on hard, durable, and inert materials such as glass and quartz. Additionally, we presented a multiobjective optimization model to reach the optimal factor levels to obtain the minimum hole diameter with minimum delamination. For this objective, we propose a design of an experiment-integrated goal programming model in this study. The optimal levels are 90 Watt, 18 Hz, 2.73 ms, and 11.6 cm for the parameter values Power, Frequency, Lead time, and Distance between the probes, respectively, to reach the optimal diameter (183 mu m) and delamination values (1.025).
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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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    Working Posture Analysis in Fuzzy Environment and Ergonomic Work Station Design Recommendations
    (2015) Can, Gulin Feryal; Atalay, Kumru Didem; Eraslan, Ergun; 0000-0002-5667-0391; AAE-7165-2019
    Realization of ergonomic design applications in working environments, makes it possible to preserve the health of employees, provide them working comfort and increase productivity. Therefore ergonomic work station design has an outstanding position in work places. In this study, an investigation was made on work stations in a metal accessor producer, which were found to be inappropriate from point of view of design considerations as a result of an ergonomic condition analysis. Inappropriate designs force workers to repetitively assume dangerous postures. As a result production process slows down and workers experience a feeling of increasing tiredness. Postures of workers were analyzed by The Fuzzy Rapid Entire Body Assessment (BREBA) developed by inserting triangular fuzzy scale to Rapid Entire Body Assessment (REBA). The BREBA method determines the level of risk in whole body caused by postures while prevents potential information loss and allows obtaining more accurate results in a fuzzy environment. In the said working place, 688 posture photographs belonging to four work stations (heat treatment, primary press, secondary press and transportation station) were examined. The consequent assessment suggested that; leg, upper arm and wrist in heat treatment, leg, wrist and torso in pres station, torso and arm were found to be the most enforced body sections. The results pointed out that 52,03% of postures displayed in production process introduced medium level risk and improvements were suggested.
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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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    Analysis of True Random Number Generation Method Utilizing FM Radio Signals
    (2015) Tanyer, Suleyman Gokhun; Inam, Sitki Cagdas; Atalay, Kumru Didem; 0000-0001-9506-2391; 0000-0003-0820-9186; I-5023-2013
    Random number generator (RNG)'s utilize some source of entropy. Various RNGs; pseudo, quasi and true RNGs provide observed samples for given distributions which are necessary in statistical signal processing and simulations applications. True random number generators generally utilize the last insignificant bit of observed samples obtained from a source of entropy. In this work, samples obtained from an FM broadcasting are examined. Least significant bit is used to generate 16 bits observed samples. Randomness and goodness-of-fit test results are compared with the raw samples. It is shown that it is possible to generate true random numbers of sufficient merits using FM signals even when the band is occupied with broadcasting signals.
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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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    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.