• Proceedings of the Korean Information Science Society Conference
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• 2012.06c
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• pp.169-171
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• 2012

일반적인 경로 생성 기법에서는 거리가 가장 짧은 최단경로 및 시간이 적게 소요되는 빠른 경로와 같이 사용자의 이동 성향을 고려하지 않고 경로를 생성하였다. 하지만 사용자들은 시간, 거리, 도로 혼잡도와 같은 속성들에 의해 선호하는 경로가 있기 때문에 사용자의 이동 성향에 맞는 경로를 생성하는 기법들이 필요하다. 기존의 기법들은 이동 성향을 고려하여 경로를 생성하기 위해서는 사용자의 이동 성향 정보를 추가적으로 입력하여야 한다. 하지만 네비게이션 및 모바일 장치의 불편한 인터페이스 특성상 이러한 정보 입력은 거의 하지 않고 출발지와 목적지만을 입력하여 경로를 추천 받는 경향이 있다. 따라서 본 논문에서는 추가적인 이동 성향에 대한 정보 입력 없이 과거 궤적 데이터를 통해 사용자의 이동 성향을 암시적으로 추출하고 이동 성향에 맞는 경로를 생성하는 기법을 제안한다. 성능평가를 통해 최소 시간 경로나 최단 거리 경로와 비교하여 제안하는 기법이 사용자의 이동 성향을 고려한 경로가 생성됨을 입증한다.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.11
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• pp.1373-1381
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• 1999

이 논문에서는 통신망 설계 응용분야의 문제를 그래프 이론 문제로써 고려해 보았다. 개별 기업체가 서로 떨어진 두 곳을 연결하고자 할 때 공용통신망의 회선을 빌려 통신망을 구축하게 되는데 많은 경우 여러 종류의 회선들이 공급됨으로 어떤 회선을 선택하느냐의 문제가 생긴다. 일반적으로 빠른 회선(low delay)은 느린 회선(high delay)에 비해 비싸다. 그러나 서비스의 질(Quality of Service)이라는 요구사항이 종종 종단지연(end-to-end delay)시간에 의해 결정되므로, 무조건 낮은 가격의 회선만을 사용할 수는 없다. 결국 개별 기업체의 통신망을 위한 통로를 공용 통신망 위에 덮어씌워(overlaying) 구축하는 것의 여부는 두 개의 상반된 인자인 가격과 속도의 조절에 달려 있다. 따라서 일반적인 최소경로 찾기의 변형이라 할 수 있는 다음의 문제가 본 논문의 관심사이다. 두 개의 지점을 연결하는데 종단지연시간의 한계를 만족하면서 최소경비를 갖는 경로에 대한 해결을 위하여, 그래프 채색(coloring) 문제와 최단경로문제를 함께 포함하는 그래프 이론의 문제로 정형화시켜 살펴본다. 배낭문제로의 변환을 통해 이 문제는 {{{{NP-complete임을 증명하였고 {{{{O($\mid$E$\mid$D_0 )시간에 최적값을 주는 의사선형 알고리즘과O($\mid$E$\mid$)시간의 근사 알고리즘을 보였다. 특별한 경우에 대한 {{{{O($\mid$V$\mid$ + $\mid$E$\mid$)시간과 {{{{O($\mid$E$\mid$^2 + $\mid$E$\mid$$\mid$V$\mid$log$\mid$V$\mid$)시간 알고리즘을 보였으며 배낭 문제의 해결책과 유사한 그리디 휴리스틱(greedy heuristic) 알고리즘이 그물 구조(mesh) 그래프 상에서 좋은 결과를 보여주고 있음을 실험을 통해 확인해 보았다.Abstract This paper considers a graph-theoretic problem motivated by a telecommunication network optimization. When a private organization wishes to connect two sites by leasing physical lines from a public telecommunications network, it is often the cases that several categories of lines are available, at different costs. Typically a faster (low delay) lines costs more than a slower (high delay) line. However, low cost lines cannot be used exclusively because the Quality of Service (QoS) requirements often impose a bound on the end-to-end delay. Therefore, overlaying a path on the public network involves two diametrically opposing factors: cost and delay. The following variation of the standard shortest path problem is thus of interest: the shortest route between the two sites that meets a given bound on the end-to-end delay. For this problem we formulate a graph-theoretical problem that has both a shortest path component as well as coloring component. Interestingly, the problem could be formulated as a knapsack problem. We have shown that the general problem is NP-complete. The optimal polynomial-time algorithms for some special cases and one heuristic algorithm for the general problem are described.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.6
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• pp.711-718
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• 2019

BDD is a well-known alternative to the conventional Boolean logic method in fault tree analysis. As the size of fault tree increases, the calculation time and computer resources for BDD dramatically increase. A new failure path search and path restructure method is proposed for efficient calculation of CS and MCS from BDD. Failure path grouping and bottom-up path search is proved to be efficient in failure path search in BDD and path restructure is also proved to be used in order to reduce the number of CS comparisons for MCS extraction. With these newly proposed methods, the top event probability can be calculated using the probability by ASDMP(Approximate Sum of Disjoint MCS Products), which is shown to be equivalent to the result by the conventional MCUB(Minimal Cut Upper Bound) probability.

• The KIPS Transactions:PartA
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• v.18A no.5
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• pp.215-224
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• 2011

In this paper, a mechanism connecting all weighted migration routes with minimum cost with EGOSST is proposed. Weighted migration routes may be converted to weighted input edges considered as not only traces but also traffics or trip frequencies of moving object on communication lines, roads or railroads. Proposed mechanism can be used in more wide and practical area than mechanisms considering only moving object traces. In our experiments, edge number, maximum weight for input edges, and detail level for grid are used as input parameters. The mechanism made connection cost decrease average 1.07% and 0.43% comparing with the method using weight minimum spanning tree and weight steiner minimum tree respectively. When grid detail level is 0.1 and 0.001, while each execution time for a connecting solution increases average 97.02% and 2843.87% comparing with the method using weight minimum spanning tree, connecting cost decreases 0.86% and 1.13% respectively. This shows that by adjusting grid detail level, proposed mechanism might be well applied to the applications where designer must grant priority to reducing connecting cost or shortening execution time as well as that it can provide good solutions of connecting migration routes with weights.

• Journal of the Korea Society of Computer and Information
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• v.19 no.5
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• pp.89-98
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• 2014

This paper suggests heuristic algorithm for single-model simple assembly line balancing problem that is a kind of NP-hard problem. This problem primarily can be solved metaheuristic method. This heuristic algorithm set the main-path that has a most number of operations from start to end-product. Then the clustering algorithm can be assigns operations to each workstation within cycle time follow main-path. This algorithm decides minimum number of workstations and can be reduces the cycle time. This algorithm can be better performance then metaheuristic methods.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.3
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• pp.654-662
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• 2016

As the number of gates and basic events in fault trees increases, it becomes difficult to calculate the exact probability of the top event. In order to overcome this difficulty the BDD methodology can be used to calculate the exact top event probability for small and medium size fault trees in short time. Fault trees are converted to BDD by using CUDD library functions and a failure path search algorithm is proposed to calculate the exact top event probability. The backward search algorithm is more efficient than the forward one in finding failure paths and in the calculation of the top event probability. This backward search algorithm can reduce searching time in the identification of disjoint failure paths from BDD and can be considered as an effective tool to find the cut sets and the minimal cut sets for the given fault trees.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.5_6
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• pp.319-323
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• 2003

Let P be a set of n points in the plane. A minimum spanning tree(MST) is a spanning tree connecting n points of P such that the sum of lengths of edges of the tree is minimized. A diameter of a tree is the maximum length of paths connecting two points of a spanning tree of P. The problem considered in this paper is to compute the spanning tree whose diameter is minimized over all spanning trees of P. We call such tree a minimum-diameter spanning tree(MDST). The best known previous algorithm[3] finds MDST in $O(n^2)$ time. In this paper, we suggest an approximation algorithm to compute a spanning tree whose diameter is no more than 5/4 times that of MDST, running in O(n$^2$log$^2$n) time. This is the first approximation algorithm on the MDST problem.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.2
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• pp.227-233
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• 2000

In this paper, we present a new high-level data path synthesis algorithm which solves the two design problems, namely, scheduling and allocation, with power minimization as a key design parameter. From the observations in previous works on data path synthesis for low power, we derive an integer programming (IP) formulation for the problem, from which we then develop an efficient heuristic to carry out the scheduling and allocation simultaneously. Our experimental results demonstrate that the proposed algorithm is very effective in saving power consumption of circuits significantly.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.565-569
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• 2007

To find optimal path is killer application in the telematics system. The shortest path of conventional system, however, isn't always optimal path. That is, the path with minimum travelling time could be defined as optimal path in the road networks. There are techniques and algorithms for finding optimal path. Hierarchical path algorithm categorizes road networks into major layer and minor layer so that the performance of operational time increases. The path searched is accurate as much as optimal path. At above 2 system, a method to allocate minor roads to major road region influences the performance extremely. This paper proposes methods to determine search space for selecting major roads in the hierarchical path algorithm. In addition, methods which apply the proposed methods to hierarchical route algorithm is presented.

• Proceedings of the Acoustical Society of Korea Conference
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• 1993.06a
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• pp.195-198
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• 1993

해수의 물리적 성질 변화에 의한 수중음속 변화는 수중음파 전파에 커다란 영향을 미친다. 매질변동에 의한 음파 전파경로 변동특성, 즉 음파 도달시간 변동에 의한 매질변위량 추정으로 해양을 탐사하는“해양음향 토모그라피”를 운용하기 위하여 비균질 매질에서의 음파 전파경로 파악이 우선이다. 수심이 일정한 비균질한 매질에서의 음파 전파경로를 파악하기 위해 파동방정식의 해를 Ray theory에 의거 ray path를 구하고 송,수신기 사이를 연결하는 eigenray 정보를 얻었다. 음원의 주파수가 400Hz($\pm$25Hz), pulse length가 20ms인 LFM pulse를 사용하였다. 이 음원을 동해의 최소음속층에서 송,수신하였을 경우 음원에서 150Km 떨어진 수신기에 도달한 신호는 평균음속분포 일 때 보다 약 66ms 정도 빨리 도착한다. 또한 Eigenray 정보에 의거 모의된 수신신호는 토모그라피 운용을 위한 필수 조건인 ray path의 식별, 안정성, 그리고 분해능을 만족한다. 또한 모의 수신신호 음파 도달시간 변동 분석으로 송,수신기 사이의 매질 변동을 파악 할 수 있다.