• Korean Management Science Review
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• v.21 no.1
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• pp.77-86
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• 2004

In this paper, we present a methodology for solving the multicommodity network flow problems using interior point methods. In our method, the minimum cost network flow problem extracted from the given multicommodity network flow problem is solved by primal-dual barrier method in which normal equations are solved partially using preconditioned conjugate gradient method. Based on the solution of the minimum cost network flow problem, a warm-start point is obtained from which Castro's specialized interior point method for multicommodity network flow problem starts. In the computational experiments, the effectiveness of our methodology is shown.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.507-513
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• 2004

In the railway system, transportation plan corresponds to a m aster plan for transport services. This service plan must be constructed to minimize operational cost or maximize revenue considering transportation demands and resource capacities in the railway operation company, and it includes several sub-planning activities such as train operation frequency plan, train (schedule) plan, train capacity assignment plan, and rolling stock requirement plan. In these sub- planning processes, train can be con side red as a product for providing customer services, and customer demands and operational advantages must be considered. In this paper, we present an effect estimation system for the train capacity pattern in a train schedule, and the effect of capacity pattern can be expressed as minimum spilled demand, minimum train service cost, and maximum train revenue or profit.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.05a
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• pp.25-32
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• 2006

Given a schedule of train to be routed by a Railway Stock, Railway Stock Routing Problem determine a sequence of train while satisfying turnaround time and maintenance restrictions. The objective is to minimize the Railway Stock during a week and each day simultaneously. And we prove that Railway Stock Routing Problem with maintenance restrictions is NP-hard. In this paper, we present two stage approaches that solve the Railway Stock Routing Problem in a reasonable time. In first stage we relax maintenance restrictions and formulate as a Min-cost-flow problem. Then, in the second stage, we attempt to satisfy maintenance restrictions using ours heuristic algorithm. We show the computational result of applying to an actual train schedule data.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.1
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• pp.52-57
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• 2007

In this paper we proposed multi-directional matching windows combined by multi-dimensional feature vector matching, which uses not only intensity values but also multiple feature values, such as variance, first and second derivative of pixels. Multi-dimensional feature vector matching has the advantage of compensating the drawbacks of area-based stereo matching using one feature value, such as intensity. We define matching cost of a pixel by the minimum value among eight multi-dimensional feature vector distances of the pixels expanded in eight directions having the interval of 45 degrees. As best stereo matches, we determine the two points with the minimum matching cost within the disparity range. In the experiment we used aerial imagery and IKONOS satellite imagery and obtained more accurate matching results than that of conventional matching method.

• Journal of Communications and Networks
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• v.12 no.1
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• pp.86-94
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• 2010

In this paper, we present a decentralized algorithm to find minimum cost quality of service (QoS) flow subgraphs in network coded multicast schemes. The main objective is to find minimum cost subgraphs that also satisfy user-specified QoS constraints, specifically with respect to rate and delay demands. We consider networks with multiple multicast sessions. Although earlier network coding algorithms in this area have demonstrated performance improvements in terms of QoS parameters, the proposed QoS network coding approach provides a framework that guarantees QoS constraints are actually met over the network.

• Journal of the Korea Society of Computer and Information
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• v.20 no.12
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• pp.75-82
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• 2015

Generally, the optimal solution of assignment problem can be obtained by Hungarian algorithm of two-sided optimization with time complexity $O(n^4)$. This paper suggests one-sided optimal assignment and swap optimization algorithm with time complexity $O(n^2)$ can be achieve the goal of two-sided optimization. This algorithm selects the minimum cost for each row, and reassigns over-assigned to under-assigned cell. Next, that verifies the existence of swap optimization candidates, and swap optimizes with ${\kappa}-opt({\kappa}=2,3)$. For 27 experimental data, the swap-optimization performs only 22% of data, and 78% of data can be get the two-sided optimal result through one-sided optimal result. Also, that can be improves on the solution of best known solution for partial problems.

• Journal of Korea Society of Digital Industry and Information Management
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• v.5 no.4
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• pp.117-126
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• 2009

The recent interest in sensor networks has led to a number of routing schemes that use the limited resources available at sensor nodes more efficiently. These schemes typically try to find the minimum energy path to optimize energy usage at a node. Some schemes, however, are prone to unbalance of the traffic and energy. To solve this problem, we propose a novel solution: a gradient-field approach which takes account of the minimum cost data delivery, energy consumption balancing, and traffic equalization. We also modify the backoff-based cost field setup algorithm to establish our gradient-field based sensor network and give the algorithm. Simulation results show that the overhead of routing establishment obtained by our algorithm is much less than the one obtained by Flooding. What's more, our approach guarantees the basic Quality of Service (QoS) without extra spending.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.493-496
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• 2000

We study the problem of designing at minimum cost a two-connected network topology such that the shortest cycle to which each edge belongs does not exceed a given maximum number of hops. This problem is considered as part of network planning and arises in the design of backbone networks. We propose a genetic algorithm approach that uses a solution representation, in which the connectivity and ring constraints can be easily encoded. We also propose a crossover operator that ensures a generated solution is feasible. By doing so, the checking of constraints is avoided and no repair mechanism is required. We carry out experimental evaluations to investigate the solution representation issues and GA operators for the network design problem.

• Journal of Families and Better Life
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• v.22 no.1
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• pp.169-179
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• 2004

This study investigated female-head's employment and household economic status of the single-mother households compared to those in the two-parent households using the data from the Korean Labor and Income Panel Study. Major findings are: first, female-heads showed lower educational attainment, lower labor force participation rate, lower occupational status, and lower wage rates than male-heads; second, the level of household income was as 1.3 times as the Minimum Living Cost and the level of household expenditure was close to the Minimum Living Cost; third, one-thirds of single-mother households were in poverty. Based on the results, the implications to public policy were suggested.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.1
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• pp.105-108
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• 2013

To resolve global environmental problems, many automobile companies are making a great deal of effort to develop so-called green-cars. One of the solutions is an electric vehicle equipped with the PEMFC (Proton Exchange Membrane Fuel Cell) stack. However, the cost of the stack, at the moment, is still too high. This obstacle must be resolved for commercialized fuel cell cars. One of the reasons for high cost is a relatively large amount of Pt (platinum) in the membrane. In this paper, a method for reducing the Pt-loading is introduced. Furthermore, the durability of the stack will be important for a company to stay competitive in world markets (in the future). For this, the diagnosis of the stack must be conducted on-line. Some diagnosis methods as key technology are also introduced in this paper.