• Journal of applied mathematics & informatics
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• v.15 no.1_2
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• pp.53-75
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• 2004

First, we present two classes of sequential algorithms for minimum flow problem: decreasing path algorithms and preflow algorithms. Then we describe another approach of the minimum flow problem, that consists of applying any maximum flow algorithm in a modified network. In section 5 we present several parallel preflow algorithms that solve the minimum flow problem. Finally, we present an application of the minimum flow problem.

• Journal of applied mathematics & informatics
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• v.23 no.1_2
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• pp.193-203
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• 2007

In this paper we consider the inverse minimum flow (ImF) problem, where lower and upper bounds for the flow must be changed as little as possible so that a given feasible flow becomes a minimum flow. A linear time and space method to decide if the problem has solution is presented. Strongly and weakly polynomial algorithms for solving the ImF problem are proposed. Some particular cases are studied and a numerical example is given.

• Journal of the military operations research society of Korea
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• v.25 no.2
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• pp.84-96
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• 1999

The purpose of this paper is to find the most vital arc in the minimum cost flow problem. The most vital arc is the arc whose removal results in the greatest influence in the costs or the amount of demands in a given minimum cost flow network. This problem can be well applied to the conflict situations such as military logistics network or communications network. In this situation, network user wants to know which arcs are the most vital to him so that he can reinforce these arcs against attack, while interdictor wants to destroy these arcs which increase the distance of the shortest path most through the network. When one of arcs is removed from the network of the minimum cost flow problem, two kinds of situations can be occurred ; breaking feasibility and increasing cost. In case of breaking feasibility, the rank of arcs are determined using the amount of modified flow in a related network which is made of modifying the optimal alternative of the minimum cost flow problem. The rank of arcs with the increased costs are determined by using a method which finds the directed cycle with the minimum cost in a related network.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.213-216
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• 2000

Minimum-cost linear network flow problems could be transformed with equal to assignment problems. Traditional method to solve the linear network flow problems are improved source-cost by transform the simple cycle flow. Auction algorithm could be applied to same element using the initial target price and dispersion calculation. Also, each elements are obtained by $\varepsilon$-relaxation methods. In this paper we proposed; 1)minimum-cost flow problem, 2)minimum-cost flow problem by the mathematical equivalent and 3) extraction $\varepsilon$-relaxation & expand transfer problem with minimum-cost flow. It can be applicant to PCB design by above mentioned.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2003.09a
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• pp.195-204
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• 2003

Network optimization is being increasingly important and fundamental issue in the fields such as engineering, computer science, operations research, transportation, telecommunication, decision support systems, manufacturing, and airline scheduling. Networks provide a useful way to modeling real world problems and are extensively used in practice. Many real world applications impose on more complex issues, such as, complex structure, complex constraints, and multiple objects to be handled simultaneously and make the problem intractable to the traditional approaches. Recent advances in evolutionary computation have made it possible to solve such practical network optimization problems. The invited talk introduces a thorough treatment of evolutionary approaches, i.e., hybrid genetic algorithms approach to network optimization problems, such as, fixed charge transportation problem, minimum cost and maximum flow problem, minimum spanning tree problem, multiple project scheduling problems, scheduling problem in FMS.

• 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.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.20 no.43
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• pp.67-79
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• 1997

In this paper we develop the integrated software that can compare algorithms of the minimum cost flow problem using PC. The chosen algorithms are the network simplex method, dual network simplex method, and out-of-kilter method, which methods correspond to primal, dual, and primal-dual approach respectively. We also present the improved methods obtaining the initial solution to increase the efficiency of algorithms, and experiment results shown the difference between the entering(dropping) selection rules.

• Journal of the Korean Operations Research and Management Science Society
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• v.25 no.4
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• pp.15-25
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• 2000

In this paper, we introduce a point-to-multipoint minimum cost flow problem with convex and demand splitting. A source node transmits the traffic along the tree that includes members of the point-to-multipoint connection. The traffic is replicated by the nodes only at branch points of the tree. In order to minimize the sum of arc costs, we assume that the traffic demand can be splitted and transmitted to destination nodes along different trees. If arc cost is linear, the problem would be a Steiner tree problem in networks eve though demand splitting is permitted. The problem would be applied in transmitting large volume of traffic from a serve to clients in Internet environments. Optimality conditions of the problem are presented in terms of fair tree routing. The proposed algorithm is a finite terminating algorithm for $\varepsilon$-optimal solution. convergence of the algorithm is obtained under monotonic condition and strict convexity of the cost function. Computational experiences are included.

• 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 the Korean Institute of Landscape Architecture
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• v.30 no.6
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• pp.17-25
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• 2003

The physical components of a river, such as water surface width/river width ratio, water level, and flow velocity vary according to different flowrates. Moreover, the riverside landscapes are greatly affected by the change of physical components of the stream or river. This paper provides an analysis of the influence of changing physical components of a river on the riverside landscape using a survey-based quantification method. The questionnaire was developed based on current literature, and was submitted to 326 people who each visited a representative station along the riverside.This survey was implemented three times at each representative station during periods of different flowrates. The results of this analysis and survey have Produced an understanding of the relationship between the variation of physical components and riverside landscapes. Survey results about the flow comparison are summarized as follows. Viewing riverside landscapes, most respondents are sensitive to the change of the flow velocity and prefer high water levels to low water levels. As a whole, respondents prefer abundant stream flows and moderate flow velocity in which they can perceive the flow of water. The minimum instream flows for riverside landscapes is estimated at each representative station by using a survey-based quantification method, and the estimated results of some representative stations were greater than the mean monthly flow at each station. The result of this analysis shows that establishing minimum instream flows for riverside landscapes is not only a technical problem, but also a legal problem. Therefore, in the to establish the instream flows in a river, the estimated results have to be considered as a relative standard. Regarding the survey results, respondents' satisfaction level didn't show any clear inclination according to the variation of various hydraulic properties. In determining the minimum instream flow using such an inquiry method, the structure of riverside scenery may vary according to the change of seasons or months. Therefore, to determine a consistent general inclination about the flow rate, it is necessary to have more detailed flow rates for each season or month combined with more inquiries.