• Proceedings of the Optical Society of Korea Conference
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• 2008.02a
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• pp.411-412
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• 2008

• Journal of KIISE
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• v.43 no.9
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• pp.1026-1033
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• 2016

Path-finding on a grid map is a problem generally addressed in the fields of robotics, intelligent agents, and computer games. As technology advances, virtual game worlds tend to be represented more accurately and more realistically, resulting in an excessive increase in the number of grid tiles and in path-search time. In this study, we propose a path-finding algorithm that allows a prompt response to real-time queries by constructing a reduced state space and by precomputing all possible paths in an offline preprocessing stage. In the preprocessing stage, we vertically decompose free space on the grid map, construct a connectivity graph where nodes are the decomposed regions, and store paths between all pairs of nodes in matrix form. In the real-time query stage, we first find the nodes containing the query points and then retrieve the corresponding stored path. The proposed method is simulated for a set of maps that has been used as a benchmark for grid-based path finding. The simulation results show that the state space and the search time decrease significantly.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.7
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• pp.943-948
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• 2018

In this paper, we propose a hybrid approach of combining $A^*$ and Genetic algorithm in the path search problem. In $A^*$, the cost from a start node to the intermediate node is optimized in principle but the path from that intermediate node to the goal node is generated and tested based on the cumulated cost and the next node in a priority queue is chosen to be tested. In that process, we adopt the genetic algorithm principle in that the group of nodes to generate the next node from an intermediate node is tested by its fitness function. Top two nodes are selected to use crossover or mutation operation to generate the next generation. If generated nodes are qualified, those nodes are inserted to the priority queue. The proposed method is compared with the original sequential selection and the random selection of the next searching path in $A^*$ algorithm and the result verifies the superiority of the proposed method.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.10a
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• pp.57-78
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• 2005

The vehicle routing problem (VRP) is to determine a set of feasible vehicle routes, one for each vehicle, such that each customer is visited exactly once and the total distance travelled by the vehicles is minimized. A feasible route is defined as a simple circuit including the depot such that the total demand of the customers in the route does not exceed the vehicle capacity. While there have been significant advances recently in exact solution methodology, the VRP is not a well solved problem. We find most approaches still relying on the branch and bound method. These approaches employ various methodologies to compute a lower bound on the optimal value. We introduce a new modelling approach, termed route-splitting, for the VRP that allows us to address problems whose size is beyond the current computational range of set-partitioning models. The route-splitting model splits each vehicle route into segments, and results in more tractable subproblems. Lifting much of the burden of solving combinatorially hard subproblems, the route-splitting approach puts more weight on the LP master problem, Recent breakthroughs in solving LP problems (Nemhauser, 1994) bode well for our approach. Lower bounds are computed on five symmetric VRPs with up to 199 customers, and eight asymmetric VRPs with up to 70 customers. while it is said that the exact methods developed for asymmetric instances have in general a poor performance when applied to symmetric ones (Toth and Vigo, 2002), the route splitting approach shows a competent performance of 93.5% on average in the symmetric VRPs. For the asymmetric ones, the approach comes up with lower bounds of 97.6% on average. The route-splitting model can deal with asymmetric cost matrices and non-identical vehicles. Given the ability of the route-splitting model to address a wider range of applications and its good performance on asymmetric instances, we find the model promising and valuable for further research.

• The KIPS Transactions:PartC
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• v.9C no.5
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• pp.699-708
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• 2002

Since various terminals and different networks get involved in playing of a multimedia presentation, the case that the presentation QoS at a destination should be different from the QoS of multimedia data at a source occurs frequently. For playing the multimedia presentation, the multimedia data at a source should be transcoded into the multimedia data satisfying the QoS required at the terminal. The problem of generating the transcoding path is that, for a given multimedia presentation, different transcoding paths depending the terminal and networks should be generated. That is, a fixed transcoding path cannot be applied to a multimedia presentation. Instead, whenever the terminal and network to play the presentation get determined, a proper transcoding path should be regenerated automatically. In this paper, the algorithm for generating the transcoding path and the method for checking the playability of the generated path are proposed. The generating algorithm adopted the technique of Context Free Grammar in describing the set of transcoding resources and a user's transcoding rules in order to utilize the well-known compiler techniques. For the playability check, a method of computing the transcoding time and the delay time between data units are proposed. Finally all the proposed methods were implemented in the stream engine, called Transcore and the presentation-authoring tool, called VIP, we had developed. And the test results with a sample scenario were presented at the last.

• Korean Journal of Food Science and Technology
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• v.31 no.1
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• pp.224-230
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• 1999

The ddh gene encoding meso-DAP-dehydrogenase (DDH) involved in the dehydrogenase pathway is essential for high-level lysine production in Brevibacterium lactofermentum. To investigate its influence on lysine production by overexpression of the ddh gene in a lysine-producing B. lactofermentum, recombinant plasmid pRK1 and pRK31 containing the ddh gene of B. lactofermentum were constructed and they were introduced into B. lactofermentum by electroporation. Multiple copies of pRK1 and pRK31 caused 7-fold and 14-fold increase of DDH activity in B. lactofermentum cell extracts, respectively. As determined in shake flask fermentation, lysine production of B. lactofermentum harboring pRK1 or pRK31 was 22% or 19% higher than that of the control, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.8
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• pp.1503-1517
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• 1994

Intelligent Motion Planning System(IMPS) is presented for a robot to achieve an efficient path toward the given target point in two dimensional unknown environment is constructed with unrestricted obstacle shapes. IMPS consists of three components for making intelligent motion. These components are real-time motion planning algorithm based on a discontinous boundary method, fuzzy neural network decision system for heuristic knowledge representation, and world modeling with forgetting and reinforcing memory cells. First of all, in real-time motion planning algorithm, the behavior-based architectural method is used to generate subgoal. A behavior generates a subgoal independently by using the method of discontinuous boundary in sensed area. The discontinuous boundary method is a new proposed fast obstacle avoidance algorithm. The second component is fuzzy neural network decision system for accomplishing the subgoal. The heuristic rules are imbedded on the fuzzy neural network to make an intelligent decision. The last one is a forgetting, reinforcing memory technique for the construction of external world map. The activation values of all activated memory cells in grid space are decreased monotonically and after all they are burned out. Therefore, after sufficient journey, robot can have a stationary world map even if the dynaic obstacles exist. Using the IMPS, several simulations show the efficient achievement of target point in unknown enviroment with obstcles of various shapes.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2008.04a
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• pp.60-63
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• 2008

본 논문에서는 신경망 모델(neural network model)과 유전자 알고리즘(genetic algorithm)을 이용한 실시간 경로 계획(real-time path-planning)과 퍼지 룰(fuzzy rule)을 이용한 효율적인 다중경로계획(multiple path-planning)을 제안한다. 실시간 경로 계획은 빠른 시간 내에 최적 경로의 생성이 반드시 수행되어야 하므로, 본 논문에서는 경로 계획 중 장애물 지역과 비장애물 지역을 빠르게 확인하기 위해 신경망 모델을 이용하여, 이동 방향 및 최적경로 탐색을 위하여 유전자 알고리즘을 이용하였다. 또한 충돌 구역에서의 효율적인 다중 경로 계획을 위해, 퍼지를 이용하여 경로를 재계획 하였다. 퍼지의 경우, 현재 위치에서 목표 지점으로의 방향을 계산하기 위한 퍼지 소속 함수와 현재 위치와 충돌 구역까지의 거리 값을 가중치로 세우고 퍼지 룰을 결정하여 경로계획을 수행하였다. 시뮬레이션을 통해 실험해본 결과, 퍼지 룰을 사용했을 때 사용하지 않았을 때 보다 좋은 성능을 나타남을 확인할 수 있었다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11b
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• pp.745-747
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• 2005

수많은 웹페이지들이 하이퍼링크를 통해 복잡하게 연결된 그래프 구조를 가지고 있는 웹사이트를 계층적으로 구조화하는 것은 해당 사이트를 검색하고자 할 때, 정보를 재조직화하고 고려해야 할 대안들의 개수를 감소시킨다는 점에서 매우 유용하다. 본 논문은 웹사이트의 의미론적인 계층화를 최적화하기 위하여 사용자의 순회 경로, 즉 웹아크의 중요도 합을 최대화할 수 있는 트리 구조를 생성하였다. 구체적으로 첫째 PageRank에 기반한 웹아크 중요도를 생성하였고, 둘째 Minimum-Cost Arborescence 문제를 이용하여 최적 트리 구조를 생성하였다. 사용자의 질의에 독립적으로 생성된 트리 구조는 웹사이트의 의미 있는 계층 구조로서 사용자로 하여금 해당 사이트를 보다 효과적으로 검색할 수 있도록 도와줄 것이다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1996.10a
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• pp.106-110
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• 1996

고밀도 집적회로(VLSI)의 설계 과정에 있어 테스트(test)는 매우 중요한 과정으로서, 회로내의 결함(fault)을 찾기 위해 일련의 입력값을 넣어 그 출력값으로 고장 여부를 판단한다. 회로의 테스트를 위하여 사용되는 일련의 입력값을 테스트패턴(test pattern)이라 하며 최고 2n개의 테스트패턴이 생성될 수 있다. 그러므로 얼마나 작은 테스트패턴을 사용하여 회로의 결함 여부를 판단하느냐가 주된 관점이 된다. 기존의 테스트 패턴 생성 알고리즘인 휴리스틱(heuristic)조건에서 가장 큰 문제점은 빈번히 발생하는 백트랙(backtrack)과 이로 인한 시간과 기억장소의 낭비이다. 본 논문에서는 이러한 문제점을 보완하기 위해 퍼지 기법을 이용한 새로운 알고리즘을 제안한다. 제안된 기법에서는 고장신호 전파과정에서 여러개의 전파경로가 존재할 때, 가장 효율적인 경로를 선택하는 단계에서 퍼지 관계곱(Fuzzy Relational Product)을 이용한다. 이 퍼지 기법은 백트랙 수를 줄이고 기억장소와 시간의 낭비를 줄여 테스트 패턴 생성의 효율을 증가시킨다.