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Öğe Bacterial Foraging Optimization Algorithm for assembly line balancing(SPRINGER, 2014) Atasagun, Yakup; Kara, YakupAssembly line balancing is the problem of assigning tasks to workstations by optimizing a performance measure while satisfying precedence relations between tasks and cycle time restrictions. Many exact, heuristic and metaheuristic approaches have been proposed for solving simple straight and U-shaped assembly line balancing problems. In this study, a relatively new optimization algorithm, Bacterial Foraging Optimization Algorithm (BFOA), based heuristic approach is proposed for solving simple straight and U-shaped assembly line balancing problems. The performance of the proposed algorithm is evaluated using a well-known data set taken from the literature in which the number of tasks varies between 7 and 111, and results are also compared with both an ant-colony-optimization-based heuristic approach and a genetic-algorithm-based heuristic approach. The proposed algorithm provided optimal solutions for 123 out of 128 (96.1 %) test problems in seconds and is proven to be promising.Öğe Balancing and sequencing mixed-model just-in-time U-lines with multiple objectives(ELSEVIER SCIENCE INC, 2007) Kara, Yakup; Ozcan, Ugur; Peker, AhmetThis study deals with the mixed-model U-lines utilized in just-in-time (JIT) production systems. Successful implementations of mixed-model U-lines requires solutions to two important problems called line balancing and model sequencing. In terms of some balance-dependent performance measures the effectiveness of a mixed-model U-line can be increased by solving line balancing and model sequencing problems simultaneously. However, this may lead to inefficient values of sequence-dependent performance measures. Hence, increasing the effectiveness of a mixed-model U-line requires balancing and sequencing problems that be dealt with multiple objectives. Balancing and sequencing mixed-model U-lines with multiple objectives has not been considered in the literature to date. In this study, a multi-objective approach for balancing and sequencing mixed-model U-lines to simultaneously minimize the absolute deviations of workloads across workstations, part usage rate, and cost of setups is presented. To increase the performance of the proposed algorithm, a newly developed neighbourhood generation method is also employed. Since the performance measures considered in the study are conflicting with each other, the proposed algorithm suggests much flexibility and more realistic results to decision makers. Solution methodology is illustrated using an example and a two-stage comprehensive experimental study is conducted to determine the effective values of algorithm parameters and investigate the relationships between performance measures. Results show that the proposed approach is more realistic than the limited number of existing methodologies. The proposed approach is also extended to consider the stochastic completion times of tasks. (C) 2006 Elsevier Inc. All rights reserved.Öğe Balancing Parallel Assembly Lines With Precise and Fuzzy Goals(Taylor & Francis Ltd, 2010) Kara, Yakup; Gökçen, Hadi; Atasagun, YakupBalancing parallel assembly lines provides flexibility to minimise the total idle times of assembly lines and the total number of workstations required in production facilities. This paper proposes two goal programming approaches to balance parallel assembly lines with precise and fuzzy goals. Three conflicting goals, namely number of workstations, cycle time, and number of tasks assigned to a workstation are optimised in crisp and fuzzy environments. The proposed approaches are also illustrated using numerical examples and sensitivity analyses. The proposed approaches provide flexibility for decision makers to balance parallel assembly lines based on their decision environments and preferred priorities.Öğe Balancing straight and U-shaped assembly lines with resource dependent task times(TAYLOR & FRANCIS LTD, 2011) Kara, Yakup; Ozguven, Cemal; Yalcin, Nese; Atasagun, YakupThe basic assumption of assembly line balancing is that every task's time is fixed. However, in practice, different processing alternatives may be available to process a task with different times. The problem in this case is to assign tasks and resources to work stations that minimise total cost and so-called resource dependent assembly line balancing (RDALB) in the literature. This study proposes a new integer programming formulation for RDALB. This formulation is then modified to develop a formulation for RDULB problem in U-shaped assembly lines. To the best knowledge of the authors, this study is the first RDULB study and the developed formulation is the first RDULB formulation. The proposed formulations are illustrated and validated using several examples. An experimental analysis is also conducted to examine the percent improvement in total cost when the line layout is switched into the U-shaped from the straight line shape. Experimental results show that an improvement in total operating cost is obtained when the straight line is switched into the U-shaped line configuration. Results also show that percentage improvement in total operating cost is significantly greater for problem instances having a large number of tasks and having greater values for the strength of the precedence relationships among tasks.Öğe Binary fuzzy goal programming approach to single model straight and U-shaped assembly line balancing(ELSEVIER SCIENCE BV, 2009) Kara, Yakup; Paksoy, Turan; Chang, Ching-TerAssembly line balancing generally requires it set of acceptable solutions to the several conflicting objectives. In this study, a binary fuzzy goal programming approach is applied to assembly line balancing. Models for balancing straight and U-shaped assembly lines with fuzzy goals (the number of workstations and cycle time goals) are proposed. The binary fuzzy goal programming models are solved using the methodology introduced by Chang [Chang, C.T., 2007. Binary fuzzy goal programming. European Journal of Operational Research 180 (1), 29-37]. Ail illustrative example is presented to demonstrate the validity of the proposed models and to compare the performance of straight and U-shaped line configurations. (C) 2008 Elsevier B.V. All rights reserved.Öğe District design and route planning for customer-related field operations of natural gas distribution systems: a case study(Selçuk Üniversitesi Mühendislik Fakültesi, 2018) Atasagun, Gözde Can; Akhüseyin, Emine; Kara, Yakup; Karaoğlan, İsmailApproximately 24% of the world energy requirement is supplied by natural gas. A natural gas distribution system in a city consists of four main processes, i.e. construction, operating, internal installations, and customer services, which are connected to each other. In this study, customer services processes of the distribution system which are directly related to customers is considered. Mathematical formulations are presented for customer services processes such as district design, route planning and mobile team workload assignment, and applied on one of the authorized natural gas distribution company in Turkey. Performance of the proposed formulations is compared with the current system by means of the number of mobile teams and amount of workloads. The computational studies show that the number of mobile teams of the proposed system is 37% lower than the current system.Öğe Eşzamanlı dağıtımlı ve toplamalı araç rotalama problemlerinin çözümü için bakteriyel besin arama optimizasyonu tabanlı bir algoritma(2013) Hezer, Seda; Kara, YakupEşzamanlı Dağıtımlı ve Toplamalı Araç Rotalama Probleminde (EDT_ARP), her müşteri dağıtım talebi ile birlikte aynı zamanda toplama talebinde bulunmaktadır ve müşterilere eşzamanlı olarak hizmet verilmektedir. EDT_ARP çözümü oldukça zor kombinatoryal optimizasyon problemidir. Bu nedenle son yıllarda yapılan çalışmalarda metasezgisel metotlar üzerinde odaklanıldığı gözlemlenmiştir. Bu çalışmada oldukça yeni bir metasezgisel algoritma olan Bakteriyel Besin Arama Optimizasyonu Algoritması (BBAOA) tabanlı bir sezgisel çözüm yaklaşımı geliştirilmiş ve performansı değerlendirilmiştir. Çalışma kapsamında EDT_ARP katedilen toplam mesafe minimize edilerek çözülmüş ve sonuçlar literatürde bilinen ekleme tabanlı sezgisel bir algoritma ile karşılaştırılmıştır. Önerilen BBAOA ile göz önünde bulundurulan, toplam 40 test probleminden 24ünde karşılaştırma yapılan algoritmaya göre daha iyi sonuçlara ulaşılmıştır.Öğe Hücresel üretim sistemi tasarımında kullanılan yapay zeka teknikleri ile sezgisel yöntemlerin karşılaştırılması ve uygulamalı analizleri(Selçuk Üniversitesi Fen Bilimleri Enstitüsü, 2000) Kara, Yakup; Toklu, BilalÜretim kaynaklarının etkili kullanımını sağlamak amacıyla son yıllarda üreticilerin ilgi odağı haline gelen ve araştırmacılar tarafından üzerinde yoğun araştırmalar yapılan Hücresel Üretim, Sistemlerinin uygulamaya geçirilmesi için ilk adım olan tasarım aşaması bu çalışmanın kapsamını oluşturmaktadır. Bu çalışmada öncelikle, temelini Hücresel Üretim Sistemlerinin oluşturduğu bazı modern üretim sistemlerinden bahsedilmiş olup daha sonra H.Ü.S. tasarımında kullanılan 4 yapay zeka tekniği ve 3 sezgisel yöntem anlatılmıştır. Anlatılan yapay zeka tekniklerinden üçü ve sezgisel yöntemlerden ikisi olmak üzere toplam 5 tasarım yöntemi PASCAL programlama dilinde kodlanarak literatürden alınan toplam 10 adet test problemi üzerinde test edilmiş ve elde edilen sonuçlar 4 farklı değerlendirme kriterine göre yorumlanmıştır.Öğe Hücresel Üretim Sistemlerinde Hücrelerin Oluşturulması ve Hücre İçi Yerleşime Yönelik Melez Bir Sezgisel(2001) Kara, YakupBu çalışmada, hücresel üretim sistemlerinin tasarımı amacıyla geliştirilen ve birbirlerinin eksik kalan yönlerini tamamlayan melez bir sezgisel ele alınmıştır. Bu sezgisel yöntemlerden ilki olan çok boyutlu ölçeklendirme algoritması hücresel üretim sistemi tasarımında kullanılan ve 0 ve l değerlerinden meydana gelen makine-parça ilişki matrisi üzerinde satır ve sütunların yerlerini değiştirerek matrisi düzenlemekte, ikinci sezgisel yöntem elde edilen yeni matris üzerinde hücre sınırlarını belirlemekte ve üçüncü sezgisel ise oluşturulan üretim hücrelerindeki makine yerleşimini gerçekleştirmektedir.Öğe An Integrated Approach for Fuzzy Set Based Part-Machine Cell Formation(2008) Kara, Yakup; Paksoy, Turan; Chang, Ching-TerThe nature of cell formation is imprecise and uncertain which is fuzzy rather than crisp and/or random. The binary part–machine incidence matrix fails in reflecting the real world conditions such as design features, part demands, machine capacities and routing data. Using the non-binary part- machine incidence matrix, the relationships between parts and machines can be represented by fuzzy membership values based on the alternative process plans and machine capacity limitations. This paper presents an integrated approach for fuzzy set based part– machine cell formation. The proposed approach em ploys a fuzzy binary integer model and is capable of determining process plans of parts and fuzzy membership values in the non-binary incidence matrix considering part demands and machine capacities. The proposed approach is illustrated and tested on a numerical example. Results show that the proposed approach is valid and capable of reflecting real world conditions.Öğe Integrated Line Balancing to Attain Shojinka in a Multiple Straight Line Facility(Taylor & Francis Ltd, 2010) Gökçen, Hadi; Kara, Yakup; Atasagun, YakupTraditional straight assembly lines are still one of the most important elements and an important fact of today's production systems. If applicable, a company can combine its multiple straight assembly lines and obtain many advantages of Shojinka more or less. This paper analyses a new problem - integrated balancing of multiple straight assembly lines (MSLB) to attain Shojinka in a multiple straight assembly line facility. The MSLB problem is built on the concept that it could be possible for a company to obtain the advantages of Shojinka even if the company has not adopted the U-shaped line layout. Three connectivity types are suggested to integrate multiple assembly lines. A binary integer formulation for integrated balancing of multiple assembly lines is developed. The objective of the proposed formulation is to minimise the total number of workstations required in the assembly facility. The formulation is explained and validated using some illustrative examples. The proposed approach provides flexibility to minimise the total idle times of the lines and total number of workstations that are required in the assembly line facility.Öğe An integrated model to incorporate ergonomics and resource restrictions into assembly line balancing(TAYLOR & FRANCIS LTD, 2014) Kara, Yakup; Atasagun, Yakup; Gokcen, Hadi; Hezer, Seda; Demirel, NeslihanThis study incorporates ergonomics and resource restrictions into assembly line balancing (ALB). For this purpose, an integrated model is proposed. The proposed model is essentially a cost-oriented formulation for ALB under psychological strain, physical strain, worker skills, multiple workers, equipment, working postures and illumination level restrictions. The integrated nature of the proposed model is one of its distinctive features in ALB literature. In addition, the proposed model modifies the existing restrictions by means of real-life facts and introduces two new restrictions arisen from the industry that have not been addressed in the literature. The model minimises the overall cost associated with operating costs of workforce and resources utilised under the ergonomics and resource restrictions. The model is illustrated and validated using some examples.Öğe Konya' da Çalışan Endüstri ve Makina Mühendislerinin İş Hayatı Profilinin Belirlenmesine Yönelik Bir Araştırma(2004) Kara, Yakup; Kalyoncu, MeteBu çalışmada, Konya'da çalışan Endüstri ve Makina Mühendislerinin iş hayatı profili incelenmiştir. Araştırmaya, Konya'da değişik sektörlerde ve endüstri kollarında olmak üzere toplam 151 mühendis gönüllü olarak katılmıştır. Araştırma kapsamında, mühendislerin maaş durumları, mesleklerinden memnuniyetleri, hedeflerine ulaşabilme durumları,,almış oldukları mühendislik öğreniminin yeterliliği hakkındaki görüşleri ve TMMOB Makina Mühendisleri Odası'ndan beklentileri olmak üzere beş temel konu, bazı değişkenler açısından ele alınmıştırÖğe Line balancing and model sequencing to reduce work overload in mixed-model U-line production environments(TAYLOR & FRANCIS LTD, 2008) Kara, YakupMixed-model U-lines (MMULs) are important elements of just-in-time production systems. For successful implementation of MMULs, a smoothed workload distribution among workstations is important. This requires that line balancing and model sequencing problems are solved simultaneously. This article presents a mixed, zero-one, nonlinear mathematical programming formulation for balancing and sequencing MMULs simultaneously with the objective of reducing work overload. Since the problem is NP-hard, an effective simulated annealing approach is also presented and its performance compared with existing approaches. The results show that the proposed simulated annealing algorithm outperforms existing approaches.Öğe A mixed integer linear programming formulation for optimal balancing of mixed-model U-lines(TAYLOR & FRANCIS LTD, 2009) Kara, Yakup; Tekin, MahmutThe mixed-model U-line balancing problem was first studied by Sparling and Miltenburg (Sparling, D. and Miltenburg, J., 1998. The mixed-model U-line balancing problem. International Journal of Production Research, 36(2), 485-501) but has not been mathematically formulated to date. This paper presents a mixed integer programming formulation for optimal balancing of mixed-model U-lines. The proposed approach minimises the number of workstations required on the line for a given model sequence. The proposed formulation is illustrated and tested on an example problem and compared with an existing approach. This paper also proposes a new heuristic solution procedure to handle large scale mixed-model U-line balancing problems. A comprehensive experimental analysis is also conducted to evaluate the performance of the proposed heuristic. The results show the validity and usefulness of the proposed integer formulation and effectiveness of the proposed heuristic procedure.Öğe Multi-objective approaches to balance mixed-model assembly lines for model mixes having precedence conflicts and duplicable common tasks(SPRINGER LONDON LTD, 2011) Kara, Yakup; Ozguven, Cemal; Secme, Nese Yalcin; Chang, Ching-TerThe existence of common tasks for model mixes is the main characteristic of the mixed-model assembly lines. The decision problem considered in this study is how some common tasks can be duplicated to improve the efficiency of a mixed-model assembly line under the assumption that some of the precedence relationships among common tasks for different products are conflicting. This decision problem is called by the authors as "mixed-model assembly line balancing with precedence conflicts and duplicable common tasks (MALB-CD)." Although precedence conflicts have been mentioned in some of the earlier studies, to the best knowledge of the authors, this is the first study that deals with precedence conflicts by mathematical modeling. In the first step of this study, a new binary mathematical model with single objective for MALB-CD is developed where the single-objective is to minimize the number of workstations. Three goals relevant to MALB-CD are then incorporated into this single-objective model to give rise to two pre-emptive goal programming models, one with precise and the other with fuzzy goals. Minimizing the number of workstations, the cycle time and the total cost required to duplicate common tasks are the goals in question. The proposed mathematical models are illustrated and validated by means of a number of numerical illustrations.Öğe A network-based shortest route model for parallel disassembly line balancing problem(TAYLOR & FRANCIS LTD, 2015) Hezer, Seda; Kara, YakupDisassembly lines should be balanced efficiently to increase productivity of the line and to reduce disassembly costs. This problem is called disassembly line balancing problem (DLBP). The objective of the DLBP is usually to find the minimum number of disassembly workstations required. This study introduces parallel DLBP (PDLBP) with single-product and proposes a network model based on the shortest route model (SRM) for solving PDLBP. The proposed model is illustrated via numerical examples. A comprehensive experiment is also conducted to evaluate problem-specific features of disassembly lines. To the best of our knowledge, this is the first study dealing with PDLBP. This paper will present a different point of view regarding DLBP.Öğe A new approach for rebalancing of U-lines with stochastic task times using ant colony optimisation algorithm(TAYLOR & FRANCIS LTD, 2014) Celik, Erkan; Kara, Yakup; Atasagun, YakupIn real world, line balancing involves existing lines in existing factories and the line typically needs to be rebalanced rather than balanced. Rebalancing of a U-line can be defined as a changeover process from its initial configuration to a new configuration for a while due to the reasons such as demand variations, changes in product design and changes in task times, etc. This study defines U-line rebalancing problem with stochastic task times and proposes a solution procedure based on ant colony optimisation. The objective of the proposed algorithm is to minimise total cost of rebalancing which is the sum of task transposition costs, workstation opening/closing costs and operating costs of workstations for a particular planning horizon. A comprehensive experiment is conducted to generate problem instances and to compare rebalancing costs of U-lines by means of several factors. A total of 6600 rebalancing solutions are obtained and several comparisons are performed.Öğe Predicting 10-day Mortality in Patients with Strokes Using Neural Networks and Multivariate Statistical Methods(ELSEVIER, 2014) Celik, Guner; Baykan, Omer K.; Kara, Yakup; Tireli, HulyaBackground: The aim of the present study was to evaluate the performance of 2 different multivariate statistical methods and artificial neural networks (ANNs) in predicting the mortality of hemorrhagic and ischemic patients within the first 10 days after stroke. Methods: The multilayer perceptron (MLP) ANN model and multivariate statistical methods (multivariate discriminant analysis [MDA] and logistic regression analysis [LRA]) have been used to predict acute stroke mortality. The data of total 570 patients (230 hemorrhagic and 340 ischemic stroke), who were admitted to the hospital within the first 24 hours after stroke onset, have been used to develop prediction models. The factors affecting the prognosis were used as inputs for prediction models. Survival or death status of the patients was taken as output of the models. Results: For the MLP method, the accuracies were 99.9% in a training data set and 80.9% in a testing data set for the hemorrhagic group, whereas 97.8% and 75.9% for the ischemic group, respectively. For the MDA method, the training and testing performances were 89.8%, 87.8% and 80.6%, 79.7% for hemorrhagic and ischemic groups, respectively. For the LRA method, the training and testing performances for the hemorrhagic group were 89.7% and 86.1%, and for the ischemic group were 81.7% and 80.9%, respectively. Conclusions: Training and test performances yielded different results for ischemic and hemorrhagic groups. MLP method was most successful for the training phase, whereas LRA and MDA methods were successful for the test phase. In the hemorrhagic group, higher prediction performances were achieved for both training and testing phases. (C) 2014 by National Stroke AssociationÖğe Predicting bank financial failures using neural networks, support vector machines and multivariate statistical methods: A comparative analysis in the sample of savings deposit insurance fund (SDIF) transferred banks in Turkey(PERGAMON-ELSEVIER SCIENCE LTD, 2009) Boyacioglu, Melek Acar; Kara, Yakup; Baykan, Oemer KaanBank failures threaten the economic system as a whole. Therefore, predicting bank financial failures is crucial to prevent and/or lessen the incoming negative effects oil the economic system. This is originally a classification problem to categorize banks as healthy or non-healthy ones. This study aims to apply various neural network techniques, support vector machines and multivariate statistical methods to the bank failure prediction problem in a Turkish case, and to present a comprehensive computational comparison of the classification performances of the techniques tested. Twenty financial ratios with six feature groups including capital adequacy, asset quality, management quality, earnings, liquidity and sensitivity to market risk (CAMELS) are selected as predictor variables in the study. Four different data sets with different characteristics are developed using official financial data to improve the prediction performance. Each data set is also divided into training and validation sets. In the category of neural networks, four different architectures namely multi-layer perceptron, competitive learning, self-organizing map and learning vector quantization are employed. The multivariate statistical methods; multivariate discriminant analysis, k-means cluster analysis and logistic regression analysis are tested. Experimental results are evaluated with respect to the correct accuracy performance of techniques. Results show that multi-layer perceptron and learning vector quatization can be considered as the most successful models in predicting the financial failure of banks. (C) 2008 Elsevier Ltd. All rights reserved.
