• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 A
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• pp.172-175
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• 1992

This paper proposes the methods to construct the tree-structured database and analyze the distribution system network. In order to cope with an extensive amount of data and the frequent breaker switching operations in distribution systems, the database for system configuration is constructed using binary trees. Once the tree-structured database has been built, the system tracing of distribution network can be rapidly performed. This remarkably enhances the efficiency of data search and easily adapts to system changes due to switching operations. The computation method of fast power flow using tree search strategies is presented. The methods in the paper may be available in the field of distribution system operation.

• 대한전기학회논문지
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• 제43권3호
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• pp.363-371
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• 1994

This thesis investigates an expert system(ES) to propose fault restoration plan by utilizing tree search strategies. In order to cope with an extensive amount of data and frequent breaker switching operations in distribution systems, the database of system configuration is constructed by using binary trees. This remarkably enhances the efficiency of search algorithm and makes the proposed ES easily adaptable to system changes due to switching operations. The rule-base is established to fully utilize the meris of tree-structured database. The inferring strategy is developed mainly based on the best-first search algorithm to increase computation efficiency. The proposed ES has been implemented to efficiently deal with large distribution systems by reducing computational burden remarkably compared with the conventional ES's.

• 대한전기학회논문지:전력기술부문A
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• 제50권5호
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• pp.241-247
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• 2001

Network reconfiguration in distribution systems is realized by changing the status of sectionalizing switches, and is usually done for loss reduction of load balancing in the system. This paper presents an effective heuristic based switching scheme to solve the distribution feeder loss reduction problem. The proposed algorithm consists of two parts. One is to set up a decision tree to represent the various switching operations available. Another is to apply a proposed technique called cyclic best first search. the proposed algorithm identify the most effective the set of switch status configuration of distribution system for loss reduction. To demonstrate the validity of the proposed algorithm, numerical calculations are carried out the 32, 69 bus system models.

• 경영과학
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• 제22권2호
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• pp.99-107
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• 2005

Recently, Tang and Chanson proposed a minimum cost distribution model for replicated Web contents subject to an expiration-based consistency management. Their model is a progress in that it can consider multiple replicas via the network of servers located on the Web. The proposed greedy heuristic, however, has an undesirable feature that the solution tends to converge a local optimum at an early stage of the algorithm. in this paper, we propose an algorithm based on a simple idea of preventing the early local convergence. The new algorithm provides solutions whose cost are, on the average, 27$\%$ lower than in the previous algorithm.

• 전기학회논문지
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• 제59권5호
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• pp.854-859
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• 2010

Distribution Automation System(DAS) is designed to improve operational efficiency by acquisition and control of remote data using its components such as central computation units, communication network and feeder remote terminal units. A conventional human machine interface of the DAS adopts a schematic diagram which is made by drawing power equipments on the geographic information system map. The single line diagram is more useful than the schematic diagram for the main tasks of distribution system operation such as protective relay coordination, service restoration and loss minimization. Since the configuration of the distribution line is changed according to the relocation of the open tie switches, the auto-drawing algorithm based on the connection between the sections and the switches is an essential technique. This paper proposes a new auto-drawing algorithm for a single line diagram of distribution systems based on tertiary tree and collision avoidance method. The feasibility of the proposed algorithm has been testified for various cases using practical distribution system with 12 feeders.

• 대기
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• 제25권4호
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• pp.685-692
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• 2015

In this study, the effects of trees on flow and scalar dispersion in an urban street canyon were investigated using a computational fluid dynamics (CFD) model. For this, we implemented the drag terms of trees to the CFD model, and compared the CFD-simulated results to the wind-tunnel results. For comparison, we considered the same building configuration as the wind-tunnel experiment. The trees were located at the center of street canyon with the aspect ratio (defined as the ratio of the street width to the building height) of 1. First, the flow characteristics were analyzed in the tree-free and high-density tree cases and the results showed that the CFD model reproduced well the flow pattern of the wind-tunnel experiment and reflected the drag effect of trees in the street canyon. Then, the dispersion characteristics of scalar pollutants were investigated for the tree-free, low-density tree and medium-density tree cases. In the tree-free case, the nondimensionalized concentration distribution simulated by the CFD model was quite similar to that in the wind-tunnel experiment in magnitude and pattern. The correlation coefficients between the measured and simulated concentrations are more than 0.9 in all the cases. As the tree density increased, nondimensionalized concentration increased (decreased) near the wall of the upwind (downwind) building, which resulted from the decrease in wind speed case by the drag effect of trees. However, the CFD model underestimated (overestimated) the concentration near the wall of upwind (downwind) building.

• 한국약용작물학회지
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• 제4권1호
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• pp.1-6
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• 1996

황칠나무 재배의 기초 자료를 얻고자 우리나라 남부해안 지대인 완도 지역의 황칠나무 자생지 환경조사와 재배지의 수령별 생육특성을 조사한 결과는 다음과 같다. 1. 황칠나무는 완도 지역에 광범위 하게 자생하고 있었으며, 대부분 해발 $30{\sim}280m$의 산에 분포하고 있었고, 특히 해발 $50{\sim}150m$ 부근에서 빈도(頻度)가 가장 높게 나타났으며, 자생지의 방향은 주로 동남향에 분포되었고, 지형은 사면에 자생하고 있었다. 2. 자생지의 토양은 $PH\;5.2{\sim}5.4$로 약산성이며, 유기물 함량도 $8.4{\sim}9.8%$로 일반재배 토양보다 높은 경향이었고, 토양수분은 $18.2{\sim}21.3%$로 비교적 습기가 많은 지역에 자생하고 있었다. 3. 황칠나무의 개화는 6년생묘에서 최초로 시작되었고 개화시기는 7월 중순경이었다. 6년생묘의 생육상은 수고 129.8cm, 경직경 34.1mm 잎수는 15.4매, 엽병장은 12.9cm가 생장하였다.