• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.5
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• pp.379-389
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• 1988

In this paper, an algorithm for obtaining 2-state switching failure function and a terminal pair reliability evaluation method in a communication network are proposed. The communication network is modeled by a graph. By using the sequence of matrix transformations for the graph, minimal cut-set matrix representing all minimal cut-sets which completely interrupt the communication path is determined and 2-state switching failure function is then obtained from the minimal cut-set matrix. The terminal pari reliability of the communication network is evaluated by corresponding the random variables to 2-state switching failure function. Illustrative examples are provided to demonstrate the algorithm. A computer program evaluating the terminal pair reliability in a complex and large network has also been developed.

• Journal of the Korean Society of Safety
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• v.30 no.3
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• pp.100-106
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• 2015

A module or independent subtree is a part of a fault tree whose child gates or basic events are not repeated in the remaining part of the fault tree. Modules are necessarily employed in order to reduce the computational costs of fault tree quantification. This quantification generates fault tree solutions such as minimal cut sets, minimal path sets, or binary decision diagrams (BDDs), and then, calculates top event probability and importance measures. This paper presents a new linear time algorithm to detect modules of large fault trees. It is shown through benchmark tests that the new method proposed in this study can very quickly detect the modules of a huge fault tree. It is recommended that this method be implemented into fault tree solvers for efficient probabilistic safety assessment (PSA) of nuclear power plants.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.9
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• pp.767-773
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• 2014

An economic ship routing means to sail a ship with a goal of minimizing the fuel consumption by utilizing weather forecast information, and there have been various systems which have been recently studied. For a successful economic ship routing system, it is needed to properly control an engine power or change a geographical path considering weather forecast. An optimal geographical path is difficult to be determined, though, because it is a minimal dynamic-cost path search problem where the actual fuel consumption is dynamically variable by the weather condition when the ship will pass the area. In this paper, we propose an geographical path-search algorithm based on evolutionary strategy to efficiently search a good quality solution out of tremendous candidate solutions. We tested our approach with the shortest path-based sailing method over seven testing routes and observed that the former reduced the estimated fuel consumption than the latter by 1.82% on average and the maximum 2.49% with little difference of estimated time of arrival. In particular, we observed that our method can find a path to avoid bad weather through a case analysis.

• Bulletin of the Korean Mathematical Society
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• v.37 no.4
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• pp.649-657
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• 2000

The 2-step competition graph of D has the same vertex set as D and an edge between vertices x and y if and only if there exist (x, z)-walk of length 2 and (y, z)-walk of length 2 for some vertex z in D. The 2-step competition number of a graph G is the smallest number k such that G together with k isolated vertices is the 2-step competition graph of an acyclic digraph. Cho, et al. showed that the 2-step competition number of a path of length at least two is two. In this paper, we characterize all the minimal acyclic digraphs whose 2-step competition graphs are paths of length n with two isolated vertices and construct all such digraphs.

• Proceedings of the Korean Reliability Society Conference
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• 2001.06a
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• pp.455-462
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• 2001

We propose a new method to evaluate the network reliability which greatly reduces the intermediate steps toward calculations of maximum capacity flow by excluding unnecessary simple paths contained in the set of failure simple paths. By using signed simple paths and signed flow, we show that our method is more efficient than that of Lee and Park (2001a) in the number of generated composite paths and in the procedure for obtaining minimal success composite paths. Numerical examples are given to illustrate the use and the efficiency of the method.

• Communications for Statistical Applications and Methods
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• v.13 no.3
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• pp.577-585
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• 2006

This paper presents a method for reliability evaluation of a telecommunication network with variable link-capacities when the simple paths of the network are known. The LP-EM, suggested by Lee and Park (2001), identifies a composite path as a subnetwork and adds only a minimal set of links at each step which gives maximal increase on the maximum capacity flow of the subnetwork. Thereby the LP-EM reduces the possible occurrence of redundant composite paths significantly over other existing methods. Based on the LP-EM, our method further reduces the possible redundancy by identifying such simple paths that could give no increase of maximum capacity flow on the current subnetwork and excluding those simple paths from consideration in the process of constructing composite paths.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1320-1323
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• 1996

This paper describes an interpolation method for a parametric surface. A parametric surface is approximated to triangular mesh surfaces and then the basic paths are achieved. As the generated path is a series of linear segments, this algorithm can be easily adapted to general NC controllers. The generated paths have minimal transfer length and are gouge-free within the approximation tolerance. The problems, induced when the paths are represented by linear segments, are overcome without making any path deviation by this algorithm. This algorithm saves machining time by eliminating overdetermined tool paths and keeping the desired average feedrate, which improve productivity and lead to lower production costs.

• Journal of IKEEE
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• v.23 no.4
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• pp.1150-1156
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• 2019

This paper explores a model-free value-based approach for solving survival gridworld problem. Survival gridworld problem opens up a challenge involving taking risks to gain better rewards. Classic value-based approach in model-free reinforcement learning assumes minimal risk decisions. The proposed method involves a hybrid on-policy and off-policy updates to experience roll-outs using a modified Q-based update equation that introduces a parametric linear rectifier and motivational discount. The significance of this approach is it allows model-free training of agents that take into account risk factors and motivated exploration to gain better path decisions. Experimentations suggest that the proposed method achieved better exploration and path selection resulting to higher episode scores than classic off-policy and on-policy Q-based updates.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.2
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• pp.146-153
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• 1998

NC machines with 4 or 5 axes are capable of various tool approach motions, which makes interference-free and high machinablity machining possible. This paper deals with how to integrate these two advantages (interference-free and high machinability machining) in multi-axes NC machining with a ball-end mill. Feasible tool approach region at a point on a surface is first computed, then among which an approach direction is determined so as to minimize the cutting force required. Tool and spindle volumes are considered in computing the feasible tool approach region, and the computing time is improved by trans-forming surface patches into minimal enclosing spheres. A cutting force prediction model is used for estimating the cutting force. The algorithm is developed so as to be applied to 4- or 5-axes NC machining in common.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1991.10a
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• pp.145-149
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• 1991

In this paper, an algorithm is proposed to analyze the approximating reliability of the capacity considered communication networks. In the case ofthe former methods to evaluate the source-to-termianl node reliability, it is very difficult to contract and delete the jointed terms in the simple path group. Therefore, the reliability bounds are used and compared to the exact reliability by TURBO PROLOG, the natural lanquage of artficial intelligence. In the reliability bounds, the upper bound used the valid cutset that isthe group of simple path and the lower bound used the minimal cutset by complement operation and the esact reiability is compared to this reliability bounds.