• Journal of KIISE:Computer Systems and Theory
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• v.30 no.7_8
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• pp.387-396
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• 2003

This paper provides an approximation algorithm for STP-MSP(Steiner Tree Problem with minimum number of Steiner Points).Because it seems to be impossible to have a PTAS(Polynomial Time Approximation Schemes), which gives the near optimal solutions, for the problem, the algorithm of this paper is an alternative that has the approximation ratio 2 with $n^{O(1)}$ run time. The importance of this paper is the potential to solve other related unsolved problems. The idea of this paper is to distribute the error allowance over the problem instance so that we may reduce the run time to polynomial bound out of infinitely many cases. There are earlier works[1,2] that show the approximations that have practical run times with the ratio of bigger than 2, but this paper shows the existence of a poly time approximation algorithm with the ratio 2.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2002.06a
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• pp.53-53
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• 2002

• Proceedings of the Korea Multimedia Society Conference
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• 2012.05a
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• pp.417-418
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• 2012

최소 신장 트리를 이용하여 멀티미디어 통신을 위한 네트워크를 구축하는 것보다 효과적인 유클리드 스타이너 트리 생성과정에서 필연적으로 발생되는 막대한 계산 량과 실행시간 문제를 해결하기 위해 Delaunay 삼각망을 적용하는 방법을 제안한다.

• Journal of Information Technology Applications and Management
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• v.18 no.4
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• pp.81-93
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• 2011

By using GOSST theory, this paper models SSCFLP taking FLP, capacity of the facilities, single source capacitated limitation level and service enhancement issues into consideration. GOSST theory is strongly suggested as the solution procedure for these issues. We have used clustering of Center of Gravity method using the case study of the company S and then, took a heuristic GOSST measure in the alternative selection process. As a result, the research finds an alternative solution that both meets the satisfactory level of service and achieves consistent distribution capacity. When using this modeling, especially, to select the location of the logistics distribution center, the efficiency of current facilities is maximized while offering the minimum geometric distance for the alternative. Also, we can expect that the illustrated model and alternative solution can be applied to architecture of distribution system, to selection of telecommunication system locations for wireless network and to relocation of related facilities due to their sensitivities to location and weight.

• Journal of the Korea Society of Computer and Information
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• v.16 no.9
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• pp.107-114
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• 2011

Because of boost of communications devices furnishing diverse services and rapid expansion of mobile business, good use and management of the existing network system become very important. Also, offering service corresponding with user communication requirement grades which vary widely in each person, is vital for communication service provider. In this paper, SGOSST, a mechanism of efficient network construction with minimum cost for network QoS is proposed. In experiments, though spending 252.97% more execution times, our SGOSST QoS network consumed 5.11% less connecting costs than the network constructed by weighted minimum spanning tree method. Therefore our mechanism can work well for efficient operation and service providing in the network formed with users and communication devices of various service requirement grade as smart/mobile equipment.

• Journal of the Korea Society of Computer and Information
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• v.16 no.11
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• pp.153-161
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• 2011

As the problem of GOSST building belongs to NP compete domain, heuristics for the problem ask for immense amount execution time and computations in large scale inputs. In this paper, we propose an efficient mechanism for GOSST construction using space locality PTAS. For 40,000 input nodes with maximum weight 100, the proposed space locality PTAS GOSST with 16 unit areas can reduce about 4.00% of connection cost and 89.26% of execution time less than weighted minimum spanning tree method. Though the proposed method increases 0.03% of connection cost more, but cuts down 96.39% of execution time less than approximate GOSST method (SGOSST) without PTAS. Therefore the proposed space locality PTAS GOSST mechanism can work moderately well to many useful applications where a greate number of weighted inputs should be connected in short time with approximate minimum connection cost.

• 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.

• Journal of the Korean Operations Research and Management Science Society
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• v.25 no.3
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• pp.81-89
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• 2000

The real-time multicast problem is to construct a multicast tree starting from a source node and including multiple destination nodes and that has minimum network cost with delay constraints. It is known that to find a tree of the minimum network cost is the Steiner Tree problem which is NP-complete. In this paper, we propose a genetic algorithm to solve the multicast tree with minimum network cost and the delay constraints. The computational results obtained by comparing an existing algorithm. Kompella algorithm, and the proposed algorithm show that our algorithm tends to find lower network cost on the average than Kompella algorithm does.

• Journal of the Korean Operations Research and Management Science Society
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• v.15 no.1
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• pp.1-22
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• 1990

This susrvey is on modelling of various network design problems with tree configuration, which have a wide variety of practical applications, particularly in communication, which have a wide a variety of practical applications, particularly in communication and transportation network planning. Models which can be classified as either minimum spanning tree of Steiner tree, are investigated. Various important variants of each basic model are then classified according to model structurs. In addition to the calssification, the typical solution method for each problem is briefly sketched, along with some remarks on further research issues.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.9
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• pp.3138-3150
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• 2021

Multimedia services on the Internet are continuously increasing. Accordingly, the demand for a technology for efficiently delivering multimedia traffic is also constantly increasing. The multicast technique, that delivers the same content to several destinations, is constantly being developed. This technique delivers a content from a source to all destinations through the multicast tree. The multicast tree with low cost increases the utilization of network resources. However, the finding of the optimal multicast tree that has the minimum link costs is very difficult and its calculation complexity is the same as the complexity of the Steiner tree calculation which is NP-complete. Therefore, we need an effective way to obtain a multicast tree with low cost and less calculation time on SDN-based smart network platforms. In this paper, we propose a new multicast tree generation algorithm which produces a multicast tree using an agent trained by model-based meta reinforcement learning. Experiments verified that the proposed algorithm generated multicast trees in less time compared with existing approximation algorithms. It produced multicast trees with low cost in a dynamic network environment compared with the previous DQN-based algorithm.