• Journal of the Korean Operations Research and Management Science Society
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• v.25 no.2
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• pp.1-10
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• 2000

With every passing month a number of new virtual enterprises emerge on the internet. Many companies have responded to the idea of distributed manufacturing in which the value adding activities comprising a finished product are dispersed geographically in a remote place. This study suggests an idea for selecting suppliers in a distributed manufacturing environment which enables machining companies to share their capacities. A mathematical model is constructed to show how to minimize the sum of the operation and transportation costs based on alternative process plans considering several kinds of operation characteristics in the real world. Four heuristic algorithms are developed to get an optimal or near-optimal solution using tabu search since the model is proven NP-hard. Example problems are tested to illustrate their procedure and performance.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.37 no.4
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• pp.116-125
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• 2014

In this paper, we investigate an inventory and production system in a three-layer supply chain system involving a single supplier, single manufacturer and multiple retailers. Earlier study in this type of supply chain only consider a single raw material in order to produce single item, but we consider raw materials in order to produce multiple items. It is assumed that the cycle time at each stage is an integer multiple of the adjacent downstream stage. We develop an iterative solution procedure to find the order quantity for the multiple items and raw materials that minimizes the supply chain-wide total cost per unit time of the supplier and manufacturer's raw materials ordering and holding, setup and finished items holding, the retailer's ordering and inventory holding. Numerical examples are presented to show that the proposed heuristic gives good performance.

• Journal of the Korea Safety Management & Science
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• v.4 no.1
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• pp.37-47
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• 2002

Risk analysis is a formal deductive procedure for determining combinations of component failures and human errors that could result in the occurrence of specified undesired events at the system level. This method can be used to analyze the vast majority of industrial system reliability problems. This study deals with the application of knowledge-engineering and a methodology for the assessment ＆ measurement of reliability, availability, maintainability, and safety of industrial systems using FTA(fault tree analysis), A fuzzy methodology for fault-tree evaluation seems to be an alternative solution to overcome the drawbacks of the conventional approach (insufficient Information concerning the relative frequencies of hazard events). To improve the quality of results, the membership functions must be approximated based on heuristic considerations, The purpose of this study is to describe the knowledge engineering approach, directed to integrate the various sources of knowledge involved in a FTA.

• Earthquakes and Structures
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• v.8 no.3
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• pp.639-663
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• 2015

Time history dynamic structural analysis is a time consuming procedure when used for large-scale structures or iterative analysis in structural optimization. This article proposes a new methodology for approximate prediction of extremum point of the response history via wavelets. The method changes original record into a reduced record, decreasing the computational time of the analysis. This reduced record can be utilized in iterative structural dynamic analysis of optimization and hence significantly reduces the overall computational effort. Design examples are included to demonstrate the capability and efficiency of the Reduced Record Method (RRM) when utilized in optimal design of frame structures using meta-heuristic algorithms.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.10a
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• pp.553-559
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• 1998

Simple Genetic Algorithm(SGA) proposed by J. H. Holland is a population-based optimization method based on the principle of the Darwinian natural selection. The theoretical foundations of GA are the Schema Theorem and the Building Block Hypothesis. Although GA goes well in many applications as an optimization method, still it does not guarantee the convergence to a global optimum in some problems. In designing intelligent systems, specially, since there is no deterministic solution, a heuristic trial-and error procedure is usually used to determine the systems' parameters. As an alternative scheme, therefore, there is a growing interest in a co-evolutionary system, where two populations constantly interact and co-evolve. In this paper we review the existing co-evolutionary algorithms and propose co-evolutionary schemes designing intelligent systems according to the relation between the system's components.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1993.06a
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• pp.1033-1036
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• 1993

Most of the today realized fuzzy logic control applications has been designed using different heuristic approaches for synthesis and implemented with conventional programming languages on general purpose microcontrollers. This paper aims to present a new methodology to design a fuzzy controller. The methodology is based on the Cell-to-Cell approach to extract the control law. A set of fuzzy rules is then found by using a FAM (Fuzzy associative memories) approach. The proposed procedure was implemented to control the rotor position of a DC motor.

• IE interfaces
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• v.12 no.2
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• pp.210-221
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• 1999

Several researchers have previously studied the problem of allocating buffer storage to maximize the throughput rate and/or minimize the mean buffer average of a transfer line for a given total amount of buffer space. But there seems to be very little difference in performance between intuitively reasonable and optimal allocations. This paper proposes and illustrates a methodology, based on the robust design concept of Taguchi, to allocate buffer storage of long transfer lines with a given total amount of buffer capacity when up and down times follow exponential distributions, respectively. We show how this procedure using simple heuristic rule can be used for design of long transfer lines.

• IE interfaces
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• v.12 no.2
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• pp.166-173
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• 1999

In this paper, a load balancing problem among operators is considered, when one or more identical machines can be assigned to an operator. The operations of a job are separated into three categories : machine-controlled elements, operator-controlled elements and machine/operator-controlled elements. Machining or forming operations are included into the first category. The second category includes inspection and moving to another machine, and the last category includes setup and loading/unloading operation. The objective is to balance the workloads among operators under the constraints of available machine-time and operator-time. A hierarchical heuristic solution procedure is suggested for allocating jobs to each machine and allocating machines to each operator. The performance of the algorithm is evaluated with various data set.

• Journal of Korean Institute of Industrial Engineers
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• v.24 no.4
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• pp.571-578
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• 1998

In this paper, we deal with a node weighted Steiner Ring Problem (SRP) arising from the deployment of Synchronous Optical Networks (SONET), a standard of transmission using optical fiber technology. The problem is to find a minimum weight cycle (ring) covering a subset of nodes in the network considering node and link weights. We have developed two mathematical models, one of which is stronger than the other in terms of LP bounds, whereas the number of constraints of the weaker one is polynomially bounded. In order to solve the problem optimally, we have developed some preprocessing rules and valid inequalities. We have also prescribed an effective heuristic procedure for providing tight upper bounds. Computational results show that the stronger model is better in terms of computation time, and valid inequalities and preprocessing rules are effective for solving the problem optimally.

• IE interfaces
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• v.13 no.4
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• pp.694-702
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• 2000

For the graceful transition from the analog to digital TV systems, a systematic frequency assignment scheme must be incorporated into the transition planning procedure. In this study, we have studied the frequency assignment methodology for the efficient management of the limited spectrum resources. By applying the graph-theoretic approach, this study developed a new solution method for additional frequency assignment problem whose objective is to assign available frequencies for newly generated requirements (digital TV stations) with minimum reassignment of the preassigned frequencies to LPTV stations while meeting the interference-related constraints. The proposed algorithm can be effectively applied not only to the current digital TV introduction phase but also to the development phase with some further development. This study can be utilized as the basis for the future study on frequency assignments that aims at graceful transition from analog TV to digital TV.