• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.127_128
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• 2009

A new technique using a search method which is based on fuzzy multi-criteria function is proposed for GMS(generator maintenance scheduling) in order to consider multi-objective function. Not only minimization of probabilistic production cost but also maximization of system reliability level are considered for fuzzy multi-criteria function. To obtain an optimal solution for generator maintenance scheduling under fuzzy environment, fuzzy multi-criteria relaxation method(fuzzy search method) is used. The practicality and effectiveness of the proposed approach are demonstrated by simulation studies for a real size power system model in Korea in 2010.

• Korean Management Science Review
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• v.12 no.2
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• pp.89-103
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• 1995

Traditionally, the scarce and expensive resources in communication networks has been the bandwidth of transmission facilities; accordingly, the techniques used for networking and switching have been chosen so as to optimize the efficient use of that resource. One of them is the packet switching for data communications, which is much different from the circuit switching. It allows multiple users to share the data network facilities and bandwidth, rather than providing specific amounts of dedicated bandwidth to each users. One main challenge therefore has been to design and build cost-effective packet switching networks. In this paper, we develop a mathematical programming medel and heuristic algorithm for designing the packet switching networks with hop-count constraints. To develop an efficient heuristic, we apply the Lagrangian relaxation method. Some valid inequalities, which have been known as the tight constraints, are considered to improve the bound for Lagrangian sub-problem. The computational experiments show that the performance of the proposed heuristic is very satisfactory in both the speed and the quality of design solutions generated.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1998.10a
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• pp.397-400
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• 1998

This paper has a dual purpose. First, we consider a relaxation algorithm which seems to be particularly suitable for multicasting routing problems. We show that the algorithm has polynomial complexity. Second, to measure the quality of solutions in comparison to the optimal solutions over a wide range of network sizes for which the computation of the optimal costs is too excessive, we also propose a random graph generation scheme in which an asymptotic lower bound on the expected optimal cost can be computed as a function of network node size.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2008.10a
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• pp.131-135
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• 2008

In this paper, we deal with a hierarchical location-allocation problem in designing the broadband convergence networks (BcN). The objective is to minimize the total cost of switch and cable while satisfying the quality of service (QoS). We formulate the problem as an integer programming model and develop the Tabu Search (TS) heuristic algorithm to find a good feasible solution within a reasonable time limit. Initial solution is obtained by using the tree structure. Three neighborhood generation mechanisms are used by local search heuristic: insertion, switch up, and switch down. In order to demonstrate the effectiveness of the proposed algorithm, we generate lower bounds from nonlinear QoS relaxation problem. We present promising computational results of the proposed solution procedures.

• Sleep Medicine and Psychophysiology
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• v.7 no.1
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• pp.5-9
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• 2000

Several nonpharmacological treatment methods of insomnia and their effects were reviewed. A long-term use of most hypnotics may produce tolerance, dependence, cognitive and psychomotor impairments at daytime, shallow sleep, and rebound insomnia on drug withdrawal. To reduce hypnotic abuse, nonpharmacological strategies have been developed to correct disordered behavioral and cognitive factors. These treatments aim at modifying maladaptive sleep habits, lowering physiological and cognitive arousal levels, and correcting dysfuctional beliefs and attitudes about sleep. These non-pharmacological or cognitive behavior treatments include stimulus control, sleep restriction, relaxation training, sleep hygiene education, cognitive therapy, and light therapy. Among them the stimulus control therapy has been demonstrated most effective as a single treatment or in combination with other treatments. Through nonpharmacological treatments, sleep latency was most significantly reduced and wake time after sleep onset was also reduced. About 50% of insomniacs reported clinical improvements in terms of nearly normalized sleep latency, awakening time, sleep efficiency, and reduction of hypnotic use. Compared to the hypnotic therapy, nonpharmacological treatments are more cost-effective and more readily accepted by patients, and their effects last longer.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1104-1107
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• 1999

A new technique using search method based on fuzzy multi-criteria function is proposed fur flexible generator maintenance scheduling. Minimization of probabilistic production cost, maximization of system reliability level and air pollution are considered fur fuzzy multi-criteria function. To obtain an optimal solution for generator maintenance scheduling under fuzzy environment fuzzy multi-criteria relaxation method(fuzzy search method) is used. The practicality and effectiveness of the proposed approach are demonstrated by the simulation results of the real size model system of KEPCO-1997 SYSTEM.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.825-828
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• 1997

The market share of plastic fuel tube in automobile part is now growing rapidly. Especially fuel tube makers have had their efforts to develop tube module not only with dimensional accuracy, spring back and cost competitiveness. In this study, we used steam bending process for heat relaxation on PA12 plastic fuel tube's 128 types experimental bending conditions. we present the results of this process system in term of dimensional accuracy, and spring back.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.6
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• pp.1074-1079
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• 1987

We present a fast, constructive algorithm for the automatic placement of standard cells, which consists of two steps. The first step is responsible for cell-row assignment of each cell, and converts the circuit connectivity into a multi-stage graph under to constraint that sum of the cell-widths in each stage of the multi-state graph does not exceed maximum cell-row width. Generatin of feed-through cells in the final layout was shown to be drastically reduced by this step. In the second step, the position of each cell within the row is determined one by one from left to right so that the cost function such as the local channel density is minimized. Our experimental result shows that this algorithm yields near optimal results in terms of the number of feed-through cells and the horizontal tracks, while running about 100 times faster than other iterative procedures such as pairwise interchange and generalized force directed relaxation method.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2002.05a
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• pp.426-433
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• 2002

This paper deals with an offline routing problem, which can be used as an explicit routing procedure in MPLS(Multiprotocol Label Switching) network, for traffic engineering. This problem is formulated as an MIP(Mixed Integer Programming) with the objective function which is to minimize the sum of the maximum link utilization for load balancing (link utilization) and the routing cost. Constraints arc composed of link capacity restriction and demand requirement that has origin-destination pair, bandwidth requirement and hop restriction. The problem is proved to be NP-hard so that the Lagrangean relaxation method is applied to propose a Lagrangean heuristic. To test the effectiveness & efficiency of the proposed algorithm, computational experiments are performed with numerical instances. The experiment results show that the proposed algorithm solves the problem within a reasonable time.

• Korean Management Science Review
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• v.30 no.2
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• pp.133-141
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• 2013

In this paper, we considers the outsourcing decision problem in a single machine scheduling problem. The decision problem is to determine for each job whether to be processed on an in-house manufacturing or external facilities(outsourcing). Moreover, this paper considers a situation where each job has a due date. The objective of the problem is to minimize the outsourcing cost, subject to the due date constraints. The considered problem is proved to be NP-hard. Some solution properties and valid inequalities are derived, and an effective lower bound is derived based on the LP-relaxation. The results of experimental tests are presented to evaluate the performance of the suggested lower bound.