Ant colony optimization for the single model U-type assembly line balancing problem

Cataloged from PDF version of article.An assembly line is a production line in which units move continuously through a sequence of stations. The assembly line balancing problem is defined as the allocation of tasks to an ordered sequence of stations subject to precedence constraints with the objective of optimizing a performance measure. In this paper, we propose ant colony algorithms to solve the single-model U-type assembly line balancing problem. We conduct an extensive experimental study in which the performance of the proposed algorithm is compared against best known algorithms reported in the literature. The results indicate that the proposed algorithms display very competitive performance against them. & 2009 Elsevier B.V. All rights reserved

Backtracking and exchange of information: Methods to enhance a beam search algorithm for assembly line scheduling

Cataloged from PDF version of article.Beam search (BS) is used as a heuristic to solve various combinatorial optimization problems, ranging from scheduling to assembly line balancing. In this paper, we develop a backtracking and an exchange-of-information (EOI) procedure to enhance the traditional beam search method. The backtracking enables us to return to previous solution states in the search process with the expectation of obtaining better solutions. The EOI is used to transfer information accumulated in a beam to other beams to yield improved solutions. We developed six different versions of enhanced beam algorithms to solve the mixed-model assembly line scheduling problem. The results of computational experiments indicate that the backtracking and EOI procedures that utilize problem specific information generally improve the solution quality of BS. 2007 Elsevier B.V. All rights reserved

Turkish version of impact on family scale: a study of reliability and validity

<p>Abstract</p> <p>Background</p> <p>Although there is a considerably high prevalence of developmental disorders in Turkey there are not many assessment tools related to evaluating the impact of these children on their family. The aim of this study was to determine the validity and reliability of the Turkish version of the Impact on Family Scale (IPFAM), a health related quality of life measurement to be utilized in clinical trials, health care services, research and evaluation.</p> <p>Methods</p> <p>Caregivers of 85 children with developmental disabilities answered the questionnaire and 65 of them answered it twice with a one week interval. The reliability of the measurement was assessed by Cronbach's alpha coefficient, and with intraclass correlation coefficient (ICC) for test-retest reliability. Construct validity was assessed by calculating the correlation between total impact score of IPFAM, WeeFIM and the physiotherapists' evaluation via Visual Analogue Scale (VAS) to determine the child's disability.</p> <p>Results</p> <p>Test-retest reliability was found to be ICC = 0.953 for total impact, 0.843 for financial support, 0.940 for general impact, 0.871 for disruption of social relations and 0.787 for coping. Internal consistency was tested using Cronbach's alpha and was found to be 0.902 for total impact of IPFAM. For construct validity the correlation between total impact score of IPFAM and WeeFIM was r = -0,532 (p < 0.001) and the correlation between total impact score of IPFAM and the physiotherapist's evaluation was r = 0.519 (p < 0.001).</p> <p>Conclusion</p> <p>The Turkish version of IPFAM was found to be a reliable and valid instrument for assessing the impact of developmental disorders of the child on the family.</p

Stochastic assembly line balancing using beam search

This paper presents a beam search-based method for the stochastic assembly line balancing problem in U-lines. The proposed method minimizes total expected cost comprised of total labour cost and total expected incompletion cost. A beam search is an approximate branch and bound method that operates on a search tree. Even though beam search has been used in various problem domains, this is the first application to the assembly line balancing problem. The performance of the proposed method is measured on various test problems. The results of the computational experiments indicate that the average performance of the proposed method is better than the best-known heuristic in the literature for the traditional straight-line problem. Since the proposed method is the first heuristic for the stochastic U-type problem with the total expected cost criterion, we only report its results on the benchmark problems. Future research directions and the related bibliography are also provided in the paper. © 2005 Taylor & Francis Ltd

Balancing of U-type assembly systems using simulated annealing

The paper presents a new simulated annealing (SA)-based algorithm for the assembly line-balancing problem with a U-type configuration. The proposed algorithm employs an intelligent mechanism to search a large solution space. U-type assembly systems are becoming increasingly popular in today's modern production environments since they are more general than the traditional assembly systems. In these systems, tasks are to be allocated into stations by moving forward and backward through the precedence diagram in contrast to a typical forward move in the traditional assembly systems. The performance of the algorithm is measured by solving a large number of benchmark problems available in the literature. The results of the computational experiments indicate that the proposed SA-based algorithm performs quite effectively. It also yields the optimal solution for most problem instances. Future research directions and a comprehensive bibliography are also provided here

Mixed-model assembly line sequencing using beam search

In today's manufacturing environments, companies have to produce a large variety of products in small quantities on a single assembly line. In this paper, we use a beam search (BS) approach to solve the model-sequencing problem of mixed-model assembly lines (MMALs). Specifically, we develop six BS algorithms for part-usage variation and load-leveling performance measures. The results of computational experiments indicate that the proposed BS methods are competitive with the well-known heuristics in the literature. A comprehensive bibliography is also provided

Two exact formulations for disassembly line balancing problems with task precedence diagram construction using an AND/OR graph

In this paper, the disassembly line balancing problem, which involves determining a line design in which used products are completely disassembled to obtain useable components in a cost-effective manner, is studied. Because of the growing demand for a cleaner environment, this problem has become an important issue in reverse manufacturing. In this study, two exact formulations are developed that utilize an AND/OR Graph (AOG) as the main input to ensure the feasibility of the precedence relations among the tasks. It is also shown that traditional task precedence diagrams can be derived from the AOG of a given product structure. This procedure leads to considerably better solutions of the traditional assembly line balancing problems; it may alter the approach taken by previous researchers in this area

Analysis of serial production lines: Characterisation study and a new heuristic procedure for optimal buffer allocation

Buffer allocation in serial production lines is one of the important design issues, and hence it has been studied extensively in the literature. In this paper, we analyse the problem to characterise the optimal buffer allocation; specifically, we study the cases with single and multiple bottleneck stations under various experimental conditions. In addition, we develop an efficient heuristic procedure to allocate buffers in serial production lines to maximise throughput. The results of the computational experiments indicate that the proposed algorithm is very efficient in terms of both solution quality and CPU time requirements. Moreover, the characterisation study yields interesting findings that may lead to important practical implications. A comprehensive bibliography is also provided in the paper

Analysis of assembly systems for interdeparture time variability and throughput

This paper studies the effect of the number of component stations (parallelism), work transfer, processing time distributions, buffers and buffer allocation schemes on throughput and interdeparture time variability of assembly systems. As an alternative to work transfer, variability transfer is introduced and its effectiveness is assessed. Previous research has indicated that the optimal throughput displays an anomaly at certain processing time distributions and, this phenomenon is now thoroughly analyzed and the underlying details are uncovered. This study also yields several new findings that convey important practical implications

Analyses of serial production line systems for interdeparture time variability and WIP inventory systems

This paper investigates the well-known and extensively studied unpaced production line problem for the interdeparture time variability and work-in-process (WIP) inventory. The primary objective is to examine the relationships between the interdeparture time variability and some system design factors such as the number of stations, buffer capacity, and location of a bottleneck station. The performance of the system is also evaluated for average and variance of WIP inventory. Simulation is used as a modeling and analysis tool with the results being tested by appropriate statistical procedures. The analysis of the results reveals several important findings on the interdeparture time variability and WIP inventory. We confirm and strengthen some of the previous findings on throughput. In this paper, we also discuss managerial implications and suggest further research areas