Mühendislik Fakültesi / Faculty of Engineering

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

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End date: 2019Has files: Yes

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Now showing 1 - 10 of 72
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    Yöneylem araştırmasının yöntembilimi
    (1985) Kara, İmdat
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    An Exergetic Approach to The Age of Universe
    (2014) Kilkis, Birol I.; https://orcid.org/0000-0003-2580-3910; AAJ-2321-2020
    Recent finding by Bond et al. (2013) about the age of the star HD 140283 (14.46 +/- 0.8 Gyr) requires us to reconsider the estimates about the age of the universe, namely 13.817 +/- 0.048 Gyr. Their conflicting result is analytically supported by the paper in Int. J. Exergy by Kilkis (2004). This paper, which introduced the Radiating Universe Model (RUM) with exergy flow to an infinitely-sized thermal bath at 0 K, predicted that the age of the universe is 14.885 +/- 0.040 Gyr. It further calculated that Hubble constant is 65.7 km s(-1) Mpc(-1) and the expansion of the universe has been accelerating since the cosmic age of 4.4 Gyr due to a positive, time dependent cosmological number that is slightly decreasing and presently it is 8.8 x 10(-36) s(-2). The exergy flow rate, solved by the lumped-capacitance method, changes with the square of cosmic time and is currently 1.224 x 10(50) erg.s(-1).
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    Planning Decisions for Recycling Products Containing Hazardous and Explosive Substances: A Fuzzy Multi-Objective Model
    (2017) Dinler, Esra; Gungor, Zulal
    The rapid development of modern technology leads to the rapid consumption of natural resources, which in turn causes an increasing accumulation of waste materials. Manufacturers must now assume the responsibility for reclamation, recycling and disposal of their products that have reached the end of their life cycles. During the product recycling process, the detection and disposal of explosive substances must be performed with the utmost caution. This study proposes a fuzzy multi-objective linear programming model for use in planning of recycling processes for products that contain hazardous and explosive substances. Application of the proposed model has been carried out in a middle-sized factory, where various products that have completed their life cycles or has become inoperative are delivered to the factory at uncertain times from various warehouses. Results from the proposed model have been obtained using the system data to solve problems on various scales. A hybrid Monte Carlo simulation has been used to obtain Pareto-optimal solutions to solve the model. The planning model is shown to differ from the recycling production planning model in terms of its consideration of the explosion risk and the limitations and goals related to this risk; this model provides considerable flexibility for both the recycling process and the planning decisions taken for this process. (C) 2016 Elsevier B.V. All rights.reserved.
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    The Efficiency of Variance Reduction in Manufacturing and Service Systems: The Comparison of the Control Variates and Stratified Sampling
    (2009) Eraslan, Erguen; Dengiz, Berna; 0000-0002-5667-0391; AAE-7165-2019
    There has been a great interest in the use of variance reduction techniques (VRTs) in simulation output analysis for the purpose of improving accuracy when the performance measurements of complex production and service systems are estimated. Therefore, a simulation output analysis to improve the accuracy and reliability of the output is required. The performance measurements are required to have a narrow and strong confidence interval. For a given confidence level, a smaller confidence interval is supposed to be better than the larger one. The wide of confidence interval, determined by the half length, will depend on the variance. Generally, increased replication of the simulation model appears to have been the easiest way to reduce variance but this increases the simulation costs in complex-structured and large-sized manufacturing and service systems. Thus, VRTs are used in experiments to avoid computational cost of decision-making processes for more precise results. In this study, the effect of Control Variates (CVs) and Stratified Sampling (SS) techniques in reducing variance of the performance measurements of M/M/1 and GI/G/1 queue models is investigated considering four probability distributions utilizing randomly generated parameters for arrival and service processes. Copyright (C) 2009 E. Eraslan and B. Dengiz.
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    A Local Search Heuristic with Self-tuning Parameter for Permutation Flow-Shop Scheduling Problem
    (2009) Dengiz, Berna; Alabas-Uslu, Cigdem; Sabuncuoglu, Ihsan
    In this paper, a new local search metaheuristic is proposed for the permutation flow-shop scheduling problem. In general, metaheuristics are widely used to solve this problem due to its NP-completeness. Although these heuristics are quite effective to solve the problem, they suffer from the need to optimize parameters. The proposed heuristic, named STLS, has a single self-tuning parameter which is calculated and updated dynamically based on both the response surface information of the problem field and the performance measure of the method throughout the search process. Especially, application simplicity of the algorithm is attractive for the users. Results of the experimental study show that STLS generates high quality solutions and outperforms the basic tabu search, simulated annealing, and record-to-record travel algorithms which are well-known local search based metaheuristics.
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    Design of a portable and low-cost mass-sensitive sensor with the capability of measurements on various frequency quartz tuning forks
    (2019) Unal, Mehmet Altay; Kocum, Ismail Cengiz; Cokeliler Serdaroglu, Dilek; 0000-0001-8645-9047
    Recently, sensor and biosensor applications have become widespread and are now significant tools in the biomedical field and other areas. Since quartz tuning fork (QTF) resonance frequency depends on the mass adsorbed to its prongs, it is generally used to measure minor mass change and detect target analyte in picogram levels. This study is undertaken to design and fabricate a sensor device for the measurement of QTF transducers. When QTF sensor studies were investigated, it was found that explanations on the details of instrumentation part were limited, and in addition, there was no compact commercial products. In this study, a novel, low-cost, portable quartz tuning fork sensor device with ability to work with any kind of display is presented in detail. Moreover, the effect of the ambient temperature during the measurements was checked. Six other QTF transducer types, 32, 32.768, 40, 65.536, 75, and 100 kHz, have been studied as the other novel part of the research. As a result, a QTF sensor device was fabricated that has further advanced features when compared with its alternatives and works with a more accurate measurement method. Owing to this advancement, using biosensor/chemical sensor which consists of QTF transducers with features that can take sensitive analyte measurement in picogram level will be able to spread.
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    An optimization for milling operation of Kevlar fiber-epoxy composite material using factorial design and goal programming methods
    (2019) Ic, Yusuf Tansel; Elaldi, Faruk; Kececi, Baris; Uzun, Gozde Onder; Limoncuoglu, Nur; Aksoy, Irem; 0000-0003-0592-6868; 0000-0002-2730-5993; AAI-1081-2020; AAG-5060-2019; F-1639-2011; AAC-4793-2019
    Kevlar fiber-epoxy composite material is extensively used in manufacturing areas because of the advantages of composite material's characteristics. It is usually processed by traditional machining methods but the drawbacks for determination of optimum cutting parameters might cause some material deformations during machining process. In this study, the cutting parameters are concurrently optimized by using the integrated 2k factorial design and goal programming methods for minimum delamination and minimum surface roughness of Kevlar fiber-epoxy composite and the best machining parameters have been obtained for the material. The results were compared with the results of the multi-criteria decision-based Taguchi methods.
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    A portable microfluidic platform for rapid determination of microbial load and somatic cell count in milk
    (2019) Duven, Gamze; Cetin, Barbaros; Kurtuldu, Huseyin; Gunduz, Guelten Tiryaki; Tavman, Sebnem; Kisla, Duygu; 0000-0003-0876-4999; 31201569
    Microfluidics systems that have been emerged in the last 20years and used for processing the fluid in a microchannel structure at microliter levels are alternative to the conventional methods. The objective of the study is to develop a microfluidic platform for determination of the microbial load and the number of somatic cells in milk. For this purpose, a polydimethylsiloxane (PDMS) chip with a channel size of 300mx60m was produced. Cells/bacteria labeled with fluorescent stain in milk were counted with the proposed microfluidic platform and the results were compared with the reference cell concentration/the bacterial counts by conventional method. It was found that our platform could count somatic and bacterial cells with an accuracy above 80% in 20min run for each analysis. The portable overall platform has an overall dimension of 25x25x25 cm and weighs approximately 9kg.
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    Investigating the Effect of Auto-Focus and Auto-Threshold Algorithms in Advanced Nodularity Analysis of Austempered Ductile Iron Castings
    (2019) Cetin, B.; Kurtuldu, H.; Durkaya, G.; Davut, K.; 0000-0003-0876-4999
    Austempered ductile iron castings have a wide range of application fields including defense and heavy-duty industries due to their promising mechanical properties. Austempered ductile iron castings could provide excellent combination of high strength, toughness, and wear resistance at the same time. Unlike other spheroidal ductile cast irons, austempered ductile iron castings need to be processed by a special austempering heat treatment which enables the verification of the conformity of the nodularity level after the casting operations. Previous studies have shown that wide area mappings for determining nodularity are crucial to eliminate the representativeness problems. In this sense, some precautions should be taken for the accuracy of results in large scale nodularity examination. In this study, the effect of auto-thresholding and auto-focusing algorithms on the advanced nodularity analysis is investigated. The results suggest that auto-thresholding and auto-focusing methods have significant contributions for determining average nodularity levels and average graphite sizes.
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    Non-Invasive 3D Optical Measurement of Round Surfaces
    (2019) Kurtuldu, H.; Durkaya, G.; Cetin, B.; 0000-0003-0876-4999
    Precise measurement of wear profiles in large areas of round surfaces such as shafts, suspension bars and high-deviation geometry surfaces is a challenge in manufacturing engineering. An optical measurement method is developed to overcome this challenge. This method, relying on angular reconstruction of scattered light profiles, is used for the measurement of irregular wear in quality testing of round surfaces which provides information on estimating the surface lifetime after prolonged use. This approach achieves a 3D depth accuracy better than 50 mu m in suspension bars with diameters up to 50 mm from an imaging distance of 250 mm.