• Journal of the Korean Operations Research and Management Science Society
• /
• v.25 no.4
• /
• pp.15-25
• /
• 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
• /
• v.25 no.3
• /
• pp.81-89
• /
• 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.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2000.04a
• /
• pp.285-288
• /
• 2000

본 연구는 Heuristic 알고리즘 및 유전자알고리즘(GA)을 이용하여 수거(Pickup) 및 배달(Delivery)을 동시에 고려한 통합차량운송계획 모델의 개발이다. 본 연구는 기존의 TSP의 문제를 확장 응용하였으며, 이는 한 Route에서 수거지(Origin)와 운반지(Destination)를 포함하는 수요들을 만족하도록 운반되어야 하는 문제이다. 이러한 통합차량경로계획문제(VRP Vehicle Routing Problem)를 해결하기 위한 접근방법으로 Heuristic 방법을 사용하였으며, 기존의 Saving 알고리즘과 유전자알고리즘(Genetic Algorithm)의 각종 연산자(Operators)들을 계산하여 사용한 TSP문제의 해를 본 연구의 해의 초기해로 사용하였으며 수거 및 배달문제의 특성을 고려하여 해를 구하였다. 본 연구의 결과를 다양한 운송환경에서, 거리산정방법, 가용운송장비 대수, 운송시간의 제한, 물류센터 및 운송지점의 위치 및 수요량 등 다양한 인자들을 고려한 통합시스템으로 프로그램을 개발하고 Sample 문제를 통하여 응용결과를 보였다.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.13 no.4
• /
• pp.153-162
• /
• 2017

Advances in communication technologies and the decreasing cost of computers have made distributed computer systems an attractive alternative for satisfying the information needs of large organizations. This paper presents a distributed algorithm for performance improvement through load balancing and file migration in distributed systems. We employed a sender initiated strategy for task migration and used learning automata with several internal states for file migration. A task can be migrated according to the load information of a computer. A file is migrated to the destination processor when it is in the right boundary state. We also described an analytical model for load balancing with file migration to verify the proposed algorithm. Analytical and simulation results show that our algorithm is very well-suited for distributed system environments.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.26 no.4
• /
• pp.99-108
• /
• 2001

In the ring loading problem with demand splitting, traffic demands are given for each pall of nodes in an undirected ring network and a flow is routed in either of the two directions, clockwise and counter-clockwise. The load of a link is the sum of the flows routed through the link and the objective of the problem is to minimize the maximum load on the ring. The fastest a1gorithm to date is Myung, Kim and Tcha＇s a1gorithm that runs in Ο(n｜K｜) time where n is the number of nodes and K is the index set of the origin-destination pairs of nodes having flow traffic demands. Here we develop an a1gorithm for the ring loading problem with demand splitting that improves the rerouting step of Myung, Kim and Tcha＇s a1gorithm arid runs in Ο(min{n｜K｜, n$^2$}) time.

• Korean Management Science Review
• /
• v.14 no.2
• /
• pp.81-90
• /
• 1997

Network approach is used to find the shortest paths and transportation time between the subway stations in Seoul, Korea. Because of transfer stations, we reconstruct the subway network to compute the shortest routes and corresponding transportation times. The reconstructed network is useful to obtain desired information because it can handle the transfer time between tracks. Time and route information about the subway system is obtained and it will be displayed in the subway guide board at each station. Then, all passengers can have the information of shortest route to a destination and corresponding transportation time.

• Journal of Navigation and Port Research
• /
• v.28 no.9
• /
• pp.821-825
• /
• 2004

The purpose of this study is the assessment of changes in the leisure patterns of users of the Eulsook-do before and after the estuary dike construction. The following survey research method was conducted to implement the study, sampling by age was carried out selectively and randomly alike. A total of 319 persons were chosen for final analysis, excluding questionnaires answered found to be inappropriate. To measure the image of the lower Nakdong River around the Eulsook-do, with advice sought from experts, researchers, through several pilot tests, developed a 24-item semantic differential scale(SDS) that has two bi-polar adjectives at each end Study of the pre- and post- construction images of the Eulsook-do located on the coast of Busan suggests the dike construction has brought about negative changes in the Eulsook-do's overall image. There can be two alternatives for improving the negative image: restoration and development.

• Proceedings of the Korea Multimedia Society Conference
• /
• 2012.05a
• /
• pp.89-92
• /
• 2012

Wireless Mesh Network expanded the capability of the conventional wireless networking by allowing the nodes to operate in proactive mode, reactive mode or the combination of both, the hybrid mode in the multi-hopping nature. By doing so, the links between the nodes become much more robust and reliable because of the number of paths to reach a destination node from a source node can be more than 1 and do not need to rely on the access point (AP) alone to relay the messages. As there may be many possible ways to form an end-to-end link between 2 nodes, the routing security becomes another main concern of the 802.11s protocol. Besides its reliance on the 802.11i for the security measures, 802.11s also includes some new features such as the Mesh Temporal Key (MTK) and the Simultaneous Authentication of Equals (SAE). The authentication and key management (AKM) process of 802.11s were observed in this paper.

• Journal of Environmental Science International
• /
• v.14 no.10
• /
• pp.905-910
• /
• 2005

The purpose of this study is the comparative analysis of Susan citizens' images of Eulsook-do as a coastal tourism destination before and after the construction of a road bridge across the Nakdong estuary in order to analyze local people's changes in leisure patterns. Analysis of the images of a pre-construction Eulsook-do that people aged both 40 and less and 50 and more had on five dimensions showed values higher than zero(0) that suggests neutral image, while their images of a post-construction Eulsook-do showed the shrinking size of pentagon on all five dimensions: ET(Entertainment), CA(Culture & Art), EE(Environment & Ecology), RC(Recreation) and LP(Leports) dimensions. Its pre- and post- construction image analysis conducted 20 years after it came to be built finds that the road bridge construction has led to the ecological, environmental disruption of the coast and the lower Nakdong river, having negative influence on the images of Eulsook-so.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2006.05a
• /
• pp.1164-1169
• /
• 2006

본 논문은 차량운행경로문제(Vehicle Routing Problem)의 기본적인 정보가 되는 Origin-Destination (OD) Matrix 의 생성에 관한 문제를 다룬다. OD Matrix 를 만들기 위해서는 몇 개의 지점으로부터 몇 개의 지점(some-to-some)까지의 최단 거리를 계산해야 한다. 이를 위해 Dijkstra 알고리듬과 같은 one-to-all 알고리듬을 반복하여 사용할 수 있고 Floyd-Washall 알고리듬과 같은 all-to-all 알고리듬을 사용할 수 있으며 some-to-some 을 위해 고안된 알고리듬을 사용할 수 있다. 본 연구에서는 이러한 알고리듬들이 실제 도로 네트워크의 OD Matrix 를 생성할 때 어떤 성능을 보이는지 비교 분석한다.