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    Bacterial Foraging Optimization Algorithm for assembly line balancing
    (SPRINGER, 2014) Atasagun, Yakup; Kara, Yakup
    Assembly 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.
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    Bakteriyel besin arama optimizasyonu algoritması ile montaj hattı dengeleme
    (Selçuk Üniversitesi Fen Bilimleri Enstitüsü, 2010-08-16) Atasagun, Yakup; Kara, Yakup
    Montaj hattı dengeleme problemi, montaj hattında yerine getirilecek görevlerin, aralarındaki öncelik ilişkileri ihlal edilmeden, belirlenen bir çevrim zamanını aşmayacak ve belirli bir performans ölçütünü en iyileyecek şekilde istasyonlara atanması problemidir. Basit düz ve U-Tipi montaj hattı dengeleme problemlerinin çözümü için çok sayıda kesin, sezgisel ve metasezgisel yaklaşımlar geliştirilmiştir. Bu çalışmada basit düz ve U-Tipi montaj hattı dengeleme problemlerinin çözümü için son yıllarda araştırmacıların ilgisini çekmiş bir optimizasyon algoritması olan Bakteriyel Besin Arama Optimizasyonu Algoritması tabanlı bir metasezgisel çözüm yaklaşımı geliştirilmiş ve performansı değerlendirilmiştir. Çalışma kapsamında, tek modelli ve deterministik görev zamanlı, görev sayıları 7 ile 111 arasında değişen düz ve U-Tipi montaj hattı dengeleme problemleri istasyon sayısı minimize edilmeye çalışılarak çözülmüştür. Elde edilen sonuçlar, optimal istasyon sayıları, karınca kolonisi optimizasyonu algoritması sonuçları ve genetik algoritma sonuçları ile karşılaştırılmıştır. Önerilen algoritma ile düz ve U-tipi dengeleme göz önünde bulundurulan, toplam 128 test probleminden 123'ünde, saniyelerle ifade edilebilecek sürelerde optimal sonuçlara ulaşılmıştır.
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    Balancing Parallel Assembly Lines With Precise and Fuzzy Goals
    (Taylor & Francis Ltd, 2010) Kara, Yakup; Gökçen, Hadi; Atasagun, Yakup
    Balancing 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.
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    Balancing straight and U-shaped assembly lines with resource dependent task times
    (TAYLOR & FRANCIS LTD, 2011) Kara, Yakup; Ozguven, Cemal; Yalcin, Nese; Atasagun, Yakup
    The 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.
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    Integrated Line Balancing to Attain Shojinka in a Multiple Straight Line Facility
    (Taylor & Francis Ltd, 2010) Gökçen, Hadi; Kara, Yakup; Atasagun, Yakup
    Traditional 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.
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    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, Neslihan
    This 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.
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    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, Yakup
    In 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.