Endüstri Mühendisliği Bölümü

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Citation - WoS: 0
A Petri Net-based inference network for design automation under nondeterminism applied to mechatronic systems
(Pergamon Press Ltd, 1998) Erden, Z; Erkmen, AM; Erden, A
This paper introduces the completed part of an ongoing research, in which a Petri Net-based design inference network is developed for the representation and analysis of the functions and their interrelationships through information flow for the conceptual design stage of mechatronic systems in order to facilitate design automation. The theoretical framework behind the network is based on transition of Hybrid Automata into Petri Nets and application of this framework is introduced by a mechatronic design example.
Sansürlü veriler temelinde yeniden örnekleme tekniklerine dayalı tahmin edicilerin istatistiksel değerlendirilmesi
(2003) Yıldırım, Fetih; Yıldırım, Gonca; 4590; Ortak Dersler Bölümü; Endüstri Mühendisliği
TKİ-OAL çayırhan yeraltı işletmesinde hazırlık çalışmalarının değerlendirilmesi
(2004) Eyyuboğlu, E. Mustafa; Bölükbaşı, Naci
Orta Anadolu Linyitleri (OAL) ülkemizde tam mekanizasyonun uygulandığı ilk yeraltı işletmesidir. 1977 yılında ilk olarak Galeri Açma Makinaları'nm (GAM) kullanımı ile başlayan mekanizasyon çalışmaları 1985-1986 yıllarında yeraltı ocağında makinaların montajı ile devam etmiş ve 1987 yılında mekanize üretim başlamıştır. OAL'nin işletmecilik hakları 2000 yılından itibaren Park Termik A.Ş'ye devredilmiş olup kömür üretimi bu şirket tarafından yürütülmektedir. Bu çalışmada OAL'nin mekanize üretim için hazırlık çalışmalarını başlattığı 1977 yılından, işletme haklarını devrettiği 2000 yılına kadarki sürede yaptığı galeri açma çalışmalarının kapsamlı bir değerlendirilmesi sunulmuştur. Sonuçlar, işletmede özellikle son yıllarda yeterli performansa ulaşılamadığını göstermektedir.
Citation - WoS: 0
Differential Algebraic Equations in Primal Dual Interior Point Optimization Methods
(Amer inst Physics, 2004) Kasap, S; Kasap, Suat; Trafalis, TB; Endüstri Mühendisliği
Primal dual Interior Point Methods (IPMs) generate points that lie in the neighborhood of the central trajectory. The key ingredient of the primal dual IPMs is the parameterization of the central trajectory. A new approach to the parameterization of the central trajectory is presented. Instead of parameterizing the central trajectory by the barrier parameter, it is parameterized by the time by describing a continuous dynamical system. Specifically, a new update rule based on the solution of an ordinary differential equation for the barrier parameter of the primal dual IPMs is presented. The resulting ordinary differential equation combined with the first order Karush-Kuhn-Tucker (KKT) conditions, which are algebraic equations, are called differential algebraic equations (DAEs). By solving DAEs, we find an optimal solution to the given problem.
Citation - WoS: 201
Citation - Scopus: 228
Ammonia removal from anaerobically digested dairy manure by struvite precipitation
(Elsevier Sci Ltd, 2005) Uludag-Demirer, S; Demirer, GN; Chen, S
Ammonia is one of the most important contaminants impairing the quality of water resources. When this is considered along with the fact that the global demand for nitrogenous fertilizers is in constant rise, the need for recovery as well as removal of nitrogen is well justified. Crystallization of N and P in the form of struvite (MgNH4PO4 center dot 6H(2)O), which is a slow releasing and valuable fertilizer, is one possible technique for this purpose. This study investigated the removal of NR4+ through struvite precipitation from the effluents of one- (R1) and two-phase (R2) anaerobic reactors digesting dairy manure. To force the formation of struvite in the anaerobic reactor effluents, Ma(2+) ion was added by using both Mg(OH)(2) and MgCl2 center dot 6H(2)O. To prevent the effect of different total phosphorus (TP) concentration in the effluents of RI and R2, as well as to not limit the formation of struvite, an excess amount Of PO43- (0.14 M) was added in the form of NaHPO4. Different stoichiometric Mg2+:NH4+:PO43- ratios were tested to determine the required Mg2+ concentrations for maximum NH4+ removal by keeping NH4+:PO43- ratio constant for the effluents of reactors RI and R2. The results revealed that very high NH4+ removal efficiencies (above 95%) were possible by adding Mg 21 ions higher than 0.06 M concentration in the effluents from reactors RI and R2. It was also observed that the initial pH adjustment to 8.50 using NaOH did not result in any significant increase in the removal of NH4+ and the removal of NH4+ in the reactors treated with MgCl2 center dot 6H(2)O was higher than those treated with Mg(OH)(2) for the same Mg2+ concentration. (c) 2005 Published by Elsevier Ltd.
Citation - WoS: 0
Citation - Scopus: 0
Control of trichloroethylene emissions from sparging systems by horizontal bio- and chemo-barriers
(Selper Ltd, Publications Div, 2005) Tezel, U; Demirer, GN; Uludag-Demirer, S
The scope of this study was to develop a continuous system to clean-up a trichloroethylene (TCE) contaminated gas stream, where biotic and abiotic removal mechanisms are undertaken sequentially simulating the horizontal bio- and chemo-barriers proposed for the in-situ remediation of the contaminated sites. The bio- and chemo-barriers were simulated by using glass columns packed with granular anaerobic mixed culture and Fe(0) filings, respectively. The effect of gas residence time, which is adjusted by the gas flowrate, on the TCE removal efficiency of the reactor system was investigated. TCE removal efficiency of over 90% was achieved at gas residence times above 1hr. Furthermore, the effluent of reactor system contained only ethane and ethylene, which are non-toxic by-products of TCE reduction reactions, along with trace amounts of TCE.
Control of trichloroethylene emissions from sparging systems by horizontal bio- and chemo- barriers
(2005) Tezel, U.; Demirer, G.N.; Uludag, Demirer S.
The scope of this study was to develop a continuous system to clean-up a trichloroethylene (TCE) contaminated gas stream, where biotic and abiotic removal mechanisms are undertaken sequentially simulating the horizontal bio- and chemo-barriers proposed for the in-situ remediation of the contaminated sites. The bio- and chemo-barriers were simulated by using glass columns packed with granular anaerobic mixed culture and Fe(0) filings, respectively. The effect of gas residence time, which is adjusted by the gas flowrate, on the TCE removal efficiency of the reactor system was investigated. TCE removal efficiency of over 90% was achieved at gas residence times above 1hr. Furthermore, the effluent of reactor system contained only ethane and ethylene, which are non-toxic by-products of TCE reduction reactions, along with trace amounts of TCE.
Citation - WoS: 37
Citation - Scopus: 54
Effects of circumferential pick spacing on boom type roadheader cutting head performance
(Pergamon-elsevier Science Ltd, 2005) Eyyuboglu, EM; Bolukbasi, N
Effects of equal and unequal circumferential pick spacing on the performance of boom type roadheaders having cylindrical cutting heads are investigated. For this purpose, two experimental cutting heads with equal and unequal circumferential spacing are designed and manufactured. The cutting head with unequal circumferential spacing is specifically designed to prevent tool-holder overlap at the nose section. Manufacturing difficulties associated with equal circumferential pick spacing due to tool-holder overlap are discussed with solid modeling and practical applications. The heads are tested at Park Cayirhan Coal Mine in Turkey and their cutting performances are analysed. Although better cutting performance for equal circumferential spacing are predicted by force-balance analysis, in situ measurements of instantaneous (net) traversing speed and cutting rate, pick consumption rate and machine vibration show that no significant difference exists between the performances of the two cutting heads. (C) 2005 Elsevier Ltd. All rights reserved.
Basit Doğrusal Otoregresif Modeller Sisteminde Parametre Tahmini ve Hipotez Testi: Simetrik İnovasyonlar
(2005) Türker, Özlem; Akkaya, Ayşen D.; 56416
Bu çalışmada, simetrik dağılıma sahip hata terimli basit otoregresif modeller sistemi incelenerek normal dağılım varsayımının geçersiz olduğu durumlardaki metodoloji birden fazla bağımsız bilgi kaynağı olduğu durumlara genellenmiş, uyarlanmış en çok olabilirlik yöntemi ile tahmin ediciler elde edilmiş ve parametre vektörünün tüm kaynaklar için değişip değişmediğini test edecek sağlam ve etkin test istatistikleri geliştirilmiştir. Elde edilen tahmin ediciler ve test istatistikleri bu alandaki uygulamalarda sıkça kullanılan en küçük kareler yöntemi ile elde edilen tahmin edici ve test istatistikleri ile karşılaştırılmış ve daha iyi sonuçlar verdiği görülmüştür.
Marjinal Analiz Yoluyla Güvenilirlik Optimizasyonu
(2005) Yüceer, Ümit; Endüstri Mühendisliği
Marjinal analizin güvenilirlik redandansı optimizasyonuna bir uyarlaması anlatılmaktadır. Amaç fonksiyonu ayrışık hale dönüştürülüp, konkav olduğu gösterilecek ve marjinal analiz metodunun çok seri ve hızlı bir şekilde, optimal olmasa bile, optimala çok yakın çözümler ürettiği bir örnekle gösterilecektir.
Citation - WoS: 18
Citation - Scopus: 34
Comparison of globoid and cylindrical shearer drums' loading performance
(South African inst Mining Metallurgy, 2006) Ayhan, M; Eyyuboglu, EM; 5072
Drums of a modern longwall shearer are manufactured to include various constructional features conveying extracted material onto the face conveyor as efficiently as possible. Designing a drum with a conical shell or with reduced vane length, consequently with a stepper vane angle, is the most widely employed method in an attempt to increase loading efficiency. This study compares loading performances of two such drums, one having a conical shell with modified loading vanes, the other with a cylindrical shell with reduced vane length, Firstly, the loading performances of drums are predicted and the maximum haulage rate attainable with the drums are calculated. Then the performances of drum are compared by long-term comprehensive underground trials with coal shearers under similar conditions during the production operation of Park Termik Cayirhan coalmine in Turkey. Although higher loading performance is predicted for cylindrical drums, the in situ trials point out that Globoid drums have a slightly higher loading performance than cylindrical drums. Furthermore, the relationship between operational variables, i.e. extraction height, sumping depth, haulage rate and in situ loading performance, were investigated statistically on the basis of data gathered during the underground trials.
The equivalence of discrete convexity and the classical definition of convexity
(2006) Yüceer, Ümit; Endüstri Mühendisliği
This article presents a proof of the fact that the classical definition of convexity of nondecreasing (increasing) first forward differences for discrete univariate functions is actually a special case of the concept of discrete convexity for functions defined on a discrete space. Consequently proving the discrete convexity of separable functions is simplified and becomes simply showing each univariate function is convex in the classical sense. An illustrative example is provided.
An approach to discrete convexity and its use in an optimal fleet mix problem
(Springer-Verlag Berlin, 2006) Yüceer, Ümit; Riccardi, Rossana; Yüceer, Ümit; Endüstri Mühendisliği
A notion of convexity for discrete functions is first introduced, with the aim to guarantee both the increasing monotonicity of marginal increments and the convexity of the sum of convex functions. Global optimality of local minima is then studied both for single variable functions and for multi variables ones. Finally, a concrete optimal fleet mix problem is studied, pointing out its discrete convexity properties.
Citation - WoS: 2
Citation - Scopus: 3
Effects of privatization: A case study from Cayirhan coal district, Turkey
(Elsevier Sci Ltd, 2006) Eyyuboglu, E. Mustafa
Privatization of lignite coal-fired power plants in Turkey began in the middle of 1990 and is still an ongoing process. Among the 10 power plants offered to bidders in 1996, only Cayirhan power plant bundled with the coal mine was privatized. Considerable improvements have been obtained following the privatization of both the power plant and the coal mine. In view of its success, it is considered that Cayirhan experience could serve as a model for further privatization in energy sector, planned to be completed by the end of 2006 according to the agenda issued by government. This paper deals with the overall improvements following the privatization of both the power plant and the coal mine. In particular, mechanized roadway drivage performances before and after privatization are compared in order to highlight the specific effects of privatization in this area. It is found that competition, organizational and operational changes are the main causes of improvements attained in the post-privatization period. (c) 2005 Elsevier Ltd. All rights reserved.
Citation - Scopus: 1
Identification of eco-efficiency opportunities in a small enterprise producing vegetable oil in Eskisehir, Turkey
(Inderscience Publishers, 2007) Tepe, N.; Uludaǧ-Demirer, S.
In this study, the current processes and technologies in a small enterprise, Demircanlar Oil Industry1 (Eskisehir, Turkey), were audited and improved from the eco-efficiency point of view. The eco-efficient management of the vegetable oil production processes has been performed on the units of physical processes, extraction and purification. The results obtained indicated that the loss in raw material can be reduced simply by increasing me height of the sieves used to separate foreign materials (leaves, sand, stones, etc.) from sunflower seeds. Results also indicated that production costs and negative environmental impacts can be decreased by minimising the loss of hexane during the extraction process, and the product quality can be improved and product loss can be prevented by adjusting the amounts of bleaching clay and TriSyl® in me bleaching process. Although the reduction in environmental impacts of the factory could not be valuated, the study showed that the factory can be managed more eco-efficiently without undergoing major process changes with an immediate benefit of approximately 12,000 USD. Copyright © 2007 Inderscience Enterprises Ltd.
Citation - WoS: 15
Citation - Scopus: 12
Effects of adopting inflation targeting regimes on inflation variability
(Elsevier Science Bv, 2007) Berument, Hakan; Yuksel, Ebru; 160534; 18500
This paper investigates whether inflation-targeting programs have altered the pattern of inflation and its variability for five developed countries and four emerging economies implementing inflation-targeting programs. A GARCH specification is used to model inflation variability, which accounts for public perception of the future levels of inflation variability-conditional variance. We could not find lower conditional inflation expectations except for Australia, Chile and Sweden under various specifications. Moreover, the conditional variance decreases only for Chile and the UK. Therefore, the empirical support for the lower inflation and its variability for the inflation targeting regimes is limited. (c) 2006 Elsevier B.V. All rights reserved.
Citation - WoS: 27
Citation - Scopus: 30
Customer order scheduling problem: a comparative metaheuristics study
(Springer London Ltd, 2008) Hazir, Oncue; Gunalay, Yavuz; Erel, Erdal; 56488; 3019; 1986
The customer order scheduling problem (COSP) is defined as to determine the sequence of tasks to satisfy the demand of customers who order several types of products produced on a single machine. A setup is required whenever a product type is launched. The objective of the scheduling problem is to minimize the average customer order flow time. Since the customer order scheduling problem is known to be strongly NP-hard, we solve it using four major metaheuristics and compare the performance of these heuristics, namely, simulated annealing, genetic algorithms, tabu search, and ant colony optimization. These are selected to represent various characteristics of metaheuristics: nature-inspired vs. artificially created, population-based vs. local search, etc. A set of problems is generated to compare the solution quality and computational efforts of these heuristics. Results of the experimentation show that tabu search and ant colony perform better for large problems whereas simulated annealing performs best in small-size problems. Some conclusions are also drawn on the interactions between various problem parameters and the performance of the heuristics.
İmalat kafilesi bölme ve aktarma problemleri üzerine literatür taraması ve potansiyel araştırma konuları
(2008) Çetinkaya, Ferda Can; 50129; Endüstri Mühendisliği
Citation - Scopus: 12
On periodic solutions of linear impulsive delay differential systems
(2008) Akhmet, M.U.; Alzabut, J.O.; Zafer, A.; 351454
A necessary and sufficient condition is established for the existence of periodic solutions of linear impulsive delay differential systems. Copyright © 2008 Watam Press.
Citation - WoS: 17
Citation - Scopus: 17
A study on nutrient removal from municipal wastewater by struvite formation using Taguchi's design of experiments
(Mary Ann Liebert, inc, 2008) Uludag-Demirer, Sibel; 45685
The aim of this study is to investigate the removal of NH4+-N and PO43--P from the municipal wastewater by struvite (MgNH4PO4.6H(2)O) formation. The optimization of the NH4+-N and PO43--P removals is made by changing the total concentrations of struvite forming ions (Mg2+, NH4+, PO43-) and pH of the wastewater. The experimental design was made using Taguchi's L-9(3(4)) orthogonal array technique in the first stage of the study. The conditions yielding maximum removals of NH4+-N and PO43--P are found as molar concentration ratio of Mg:N:P of 2:2:2 and 3:3:2, respectively, using the signal-to-noise (S/N) ratio of experimental results. The removal of NH4+-N followed the stoichiometry of struvite formation, while PO43--P removal required the excess amount of Mg2+. The pH of wastewater in which the maximum NH4+-N and PO43--P removals are observed was 9.0. All of the factors tested influenced the removal of NH4+-N opposite to the removal Of PO43--P, in which the concentration of NH4+-N was found insignificant statistically. Therefore, the addition of NH4+ ion is eliminated and Taguchi's L-4(2(3)) orthogonal array was used in the second stage of experimental study. The molar concentration ratios of struvite forming ions (Mg:N:P) were found to be as 1:1:1 and 2:1:1 for maximum NH4+-N and PO43--P removals at the levels of 52.4 and 67.7%, respectively, at pH 9.0 using the S/N ratios of experimental results. The performance of proposed method in removing NH4+-N and PO43--P and foreseen problems related with effluent quality is discussed.

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