• KIEE International Transactions on Power Engineering
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• 제5A권3호
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• pp.269-279
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• 2005

This paper presents an application of the parallel Adaptive Evolutionary Algorithm (AEA) to search an optimal solution of a reconfiguration in distribution systems. The aim of the reconfiguration is to determine the appropriate switch position to be opened for loss minimization in radial distribution systems, which is a discrete optimization problem. This problem has many constraints and it is very difficult to find the optimal switch position because of its numerous local minima. In this investigation, a parallel AEA was developed for the reconfiguration of the distribution system. In parallel AEA, a genetic algorithm (GA) and an evolution strategy (ES) in an adaptive manner are used in order to combine the merits of two different evolutionary algorithms: the global search capability of GA and the local search capability of ES. In the reproduction procedure, proportions of the population by GA and ES are adaptively modulated according to the fitness. After AEA operations, the best solutions of AEA processors are transferred to the neighboring processors. For parallel computing, a PC-cluster system consisting of 8 PCs·was developed. Each PC employs the 2 GHz Pentium IV CPU, and is connected with others through switch based fast Ethernet. The new developed algorithm has been tested and is compared to distribution systems in the reference paper to verify the usefulness of the proposed method. From the simulation results, it is found that the proposed algorithm is efficient and robust for distribution system reconfiguration in terms of the solution quality, speedup, efficiency, and computation time.

• 한국자동차공학회논문집
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• 제7권7호
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• pp.113-121
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• 1999

Diesel particulate matter is known to be one of the major harmful emissions produced by diesel engines. Diesel particulates are subject to diesel emission regulations and have lately become the focus in the diesel emission control technology. Thus, the aftertreatment system is adopted at the diesel engine exhaust to reduce the particulate emission. Although this benefit is recognized, it is not clear how the aftertreatment system influences quantitatively the particle size distribution distribution. In this study, the particle size distributions of diesel exhaust were measured using the scanning mobility particle sizer with and without the aftertreatment system. There results showed that the diesel particulate filter and plasm system reduced the number of emitted particles by more than 90% and about 80% respectivley in the particle size range of 20nm∼600nm. On the other hand no significant effect of the diesel oxidation catalyst on the particle number concentration was detected.

• 조명전기설비학회논문지
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• 제29권6호
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• pp.42-48
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• 2015

DC distribution system is difficult to compose the single-system because of the capacity restriction of power semiconductors. Therefore, DC Distribution system needs parallel operation of AC/DC converters for increase to system capacity. However, this system generates the circulating current. This paper is reducing the circulating current and safely sharing the load using the proposed DC current droop control method when each other 3-phase AC/DC converter connected. This system confirms through the simulation and experiment. Also, when each other converter of parallel operate. it is compared the response characteristics

• Journal of Electrical Engineering and Technology
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• 제3권4호
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• pp.484-490
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• 2008

In this paper, an integrated fault section detection and isolation strategy is proposed based on the application of the Distribution Automation System(DAS) utilizing advanced IT and communication technologies. The Feeder Remote Terminal Unit(FRTU) has been widely used to collect data in the Korean distribution system. The achieved data is adopted in this method for detecting multiple fault types. Especially in the case of single phase-to-ground fault, the fault section is detected by comparison of the zero-sequence current phase angle. The test results have verified the effectiveness of the proposed method in a radial distribution system through extensive simulations in Matlab/Simulink. Furthermore, a communication-based demo system identical to the simulation model has been developed, and it can be applied as an online monitoring and control program for fault section detection and isolation.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.49-52
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• 2003

As the power demand has increased, it is expected that the transmission system will have more complicated problems under the influence of investment reduction for overall power system. The route length per MW demand will be reduced gradually from 0.6［C-km/㎿］ to 0.53 ［C-km/㎿］ in 2010. This comes up to a real serious problem of system planning and operation viewpoints HTS power technologies have properties to solve these complex transmission and distribution constraints, especially for metropolitan area, in the future. As the HTS technology has developed, the HTS cable technology can be the most effective alternative to solve the future expected transmission constraints as compared with other countermeasures in terms of economics, environments and system operation. This paper describes the general application methodology of developing 22.9 ㎸ HTS cable by CAST for practical distribution system, particularly, step-by-step application methodology of 22.9 ㎸ HTS cable to substitute the existing and planning 154 ㎸ cable. In this scheme, almost of the downtown 154 ㎸ substation of metropolitan city such as Seoul will be changed into 22,9 ㎸ switching station.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제8권4호
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• pp.137-144
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• 2019

무기체계 기술의 국산화 과정에서 경험과 기술이 부족한 상태로 개발 중인 체계에 대한 테스트 기술의 성숙도는 매우 중요하다. 테스트에서 발견하지 못한 결함은 시스템 운용 중 막대한 영향을 미친다. 잠수함에서 실시간 정보공유 체계는 신속한 지휘결심과 임무능력으로 이어진다. 데이터 분산 시스템은 매우 중요한 정보 공유체계이며 제조사나 데이터 형태가 다른 체계들 간에 이루어진다. 본 논문에서는 데이터 분산 시스템의 데이터 분산 특성을 분석하여 데이터별 체계를 그룹핑하고, 경로 테스트 기법에 트리순회 방법인 후위트리순회, 전위트리순회를 이용하여 테스트케이스 생성기법을 제시한다. 제시한 기법은 기존기법들에 비해 73.7% 테스팅 리소스를 감소시킬 수 있다.

• 유통과학연구
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• 제10권10호
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• pp.25-33
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• 2012

Purpose - The Garak agricultural wholesale market ('Garak Market') plays a central role in the distribution of agricultural products in Korea and is important in connecting consumers with producers. However, problems regarding inefficiencies and the high-cost structure of the wholesale market's distribution/logistical system are being raised in relation to severe competition among retailers. Furthermore, the service needs of retailers and market users are not being fulfilled due to the inconsistency of the wholesale market's functions and facilities, thus reducing the competitiveness of the market. In this regard, innovative changes are being requested of the agricultural wholesale market according to changes in the agricultural product distribution environment. In particular, the lack of unloading facilities and the outdated unloading system of the wholesale market must be improved to enhance system efficiency. Research design, data, and methodology - This study observed the problems of the unloading system of the agricultural wholesale market in order to present relevant measures for improvement. The need for unloading auctions was also researched in this study. The survey of 70 forwarders belonging to the producing district distributor association of the Garak market was conducted by post. Additionally, 20 auction dealers and 59 shippers and transporters were individually interviewed. The survey on the need for unloading auctions used five-point Likert Scales. The statistical analysis was conducted with SPSS WIN 12.0 software. Results - First, the wholesale market must employ members of the unloading labor union to allow these employees to directly manage the unloading process. Second, it is crucial to revise regulations to ensure that the principal agent pays the unloading cost according to the standard unloading cost system. Third, the vehicle auction carried out for certain vegetable products must be converted to the unloaded auction system. According to the related interviews with the wholesale market's distribution agents, whereas shippers and transporters recognized the need for unloaded auctions, auction dealers tend to have a negative view of this system. Furthermore, the stated reasons in favor of unloaded cabbage, radish, and other vegetable auctions were prevention of constraint, creation of transparent trade conditions, and reduction of corrected seller tickets. Many of the respondents answered that the transport cost reduction rate in unloaded auctions must be below 20%. Fourth, the unloading system must be mechanized and a detailed, reasonable plan must be provided to settle the existing conflict with the unloading labor union. Conclusions - The proposals in this study are expected to play an important role in improving the cargo handling system of the wholesale agricultural product market in the future. Improving the system is expected to help shore up the competitiveness of the industry. If all the related bodies closely cooperate with each other and work harder, taking advantage of the synergies created by the facility modernization project, the Garak market will play a pivotal role in the distribution of agricultural products.

• 유통과학연구
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• 제14권4호
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• pp.103-110
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• 2016

Purpose - This study investigates the improvement of rationalization of distribution structure in Korean diamond market. It also explores the international distribution of diamond and how the distribution of Korean diamond market system was improved. This study also for providing the evaluation method in case of purchasing diamond on the consumers. Research Design, Data, and Methodology - The research investigates how international diamond distribution market has been changed since 1933 by De Beers. The international Diamond rough stone has been deregulated in supply and demand by Debeers since July, 2000, therefore, the price maintenance policy of diamond market also has been changed. In the short term, the diamond price in market has been down, whereas, in the long term, the market share of Debeers has affected the high quality of diamond price in world market. Before 1985, both G color and VVS1 clarity were used as the level of percentages in the diamond certificate of authenticity in Korea. But, after 1985, the diamond certificate of authenticity uses Diamond Grading Report. Results - Between the 1970's and 1980's, Debeers had controlled about 80 percentages of international diamond supply market. But, Debeers share in diamond market fell by 60 percentages in 2000's. Debeers supplied 31%(4390 carets) of international diamond supply and 41%(39 billion dollars) in 2003. However, Debeers shares 50% of market shares in the diamond supply market by Alosa in Russia. In Korea, the diamond grading report system has been used since 1985. But, the diamond grading report system has price bubbles and much irrational parts in grading system methods. Conclusions - 4C, the grading system of diamond, is a method for comparing and evaluating diamond objectively. Diamond is graded according to its color, cut, clarity, and carat. The price of diamond is determined based on its each item. Consumers purchase diamond for the purpose of investment and wearing. In terms of investment, it is recommended to purchase diamond with color of D grade, cut with Excellent or Very Good Cut grade, Clarity of FL or IF, and more than 3 carat. As for wearing purpose, it is highly recommended for diamond to have color of F or G grade, cut of Excellent or Very Good Cut, clarity of VS2 or SI1, and more than 1 carat Before 2000, Central Selling Organization(CSO) distributed about 80 percentages rough diamond to world market exclusively by purchase, classification, assessment, and sales. After 2000, Dbeers diamond company looses slowly market shares, while Almosa diamond company etc. in Russia are taking over world market shares more and more. Debeers market shares have been falling over the years, and the international diamond markets are gradually growing by other international diamond companies. But, there is no change in Korean diamond market after 1980's. Korean diamond distribution needs to follow international level of Diamond Grading System. By using different grading systems with different panel members, Korean diamond grading system needs to follow international perfect grading systems to grow diamond markets and maintain within top 10 diamond markets countries.

• 유통과학연구
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• 제7권1호
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• pp.5-34
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• 2009

인터넷 환경은 화훼 유통 서비스를 급격히 변화 시켰을 뿐만 아니라, 화원의 경쟁 방식 자체를 변화시켰다. 이러한 변화의 중심에는 ROSEWeb 솔루션이 있었다. 사용자 환경이 모바일 인터넷으로 전환되고 있고, 온라인 서비스 업체들은 비즈니스 컨버전스를 통해 새로운 서비스를 제공하고 상황이다. 이에 본 사례연구는 (주)뉴런의 ROSEWeb 사례를 통해 유통과 정보기술이 결합한 비즈니스 모델을 이해하고 이와 관련된 주요 이슈를 파악하여 기업들이 새로운 비즈니스 가치를 창출하기 위한 비즈니스 모델과 화훼 유통 서비스 전략을 수립하는데 있어서 좋은 가이드라인을 제시하고자 한다. 본 사례연구는 인터넷 화훼 유통 서비스뿐만 아니라 인터넷 비즈니스의 다양한 서비스 영역에서 창업이후 단계별 사업 전략수립을 위한 기본 모델로 폭 넓게 적용 할 수 있을 것이다. 사례 내용은 외부환경 측면(화훼 유통서비스 시장, 협회-화원간 전략적 파트너십 관계)과 내부환경 측면(ROSEWeb 솔루션, 비즈니스 모델, 수익원)으로 나누어 구성되어 있다. 각 장의 내용들을 이 두 관점에서 살펴본다면 모바일 인터넷 환경에서 새로운 서비스를 준비하는 기업들에게 많은 시사점을 제공할 수 있을 것으로 기대된다. 마지막으로 이 사례를 읽고 두 가지 의문을 가지고 토의를 했으면 한다. "인터넷 포탈업체들이 화훼 유통서비스에 진입했을 때 ROSEWeb은 지속적으로 경쟁우위를 확보할 수 있는가?"와 "(주)뉴런의 다음 비즈니스 모델은 무엇인가?"

• Journal of the Korean Statistical Society
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• 제25권1호
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• pp.111-122
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• 1996

A model for a system whose state changes continuously with time is introduced. It is assumed that the system is modeled by a Brownian motion with negative drift and an absorbing barrier at the origin. A repairman arrives according to a Poisson process and repairs the system according to an (s,S) policy, i.e., he increases the state of the system up to S if and only if the state is below s. A partial differential equation is derived for the distribution function of X(t), the state of the system at time t, and the Laplace-Stieltjes transform of the distribution function is obtained by solving the partial differential equation. For the stationary case the explicit expression is deduced for the distribution function of the stationary state of the system.