• 대한전기학회논문지:전력기술부문A
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• 제50권8호
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• pp.388-394
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• 2001

This paper presents how to determine the optimal operating points of Unified Power Flow controllers (UPFC) the line flow control of which can enhance system security level. In order to analyze the effect of these devices on the power system, the decoupled model has been employed as a mathematical model of UPFC for power flow analysis. The security index that indicates the level of congestion of transmission line has been proposed and minimized by iterative method. The sensitivity of objective function for control variables of and UPFC has been derived, and it represents the change in the security index for a given set of changes in real power outputs of UPFC. The proposed algorithm with sensitivity analysis gives the optimal set of operating points of multiple UPECs that reduces the index or increases the security margin and Marquart method has been adopted as an optimization method because of stable convergence. The algorithm is verified by the 10-unit 39-bus New England system that includes multiple FACTS devices. The simulation results show that the power flow congestion can be relieved in normal state and the security margin can be guaranteed even in a fault condition by the cooperative operation of multiple UPECs.

• 인터넷정보학회논문지
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• 제11권4호
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• pp.41-49
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• 2010

Faloutsos et al.[1,2]은 파워-로(power-law)를 이용해 노드 차수와 같은 Autonomous System (AS) 레벨 인터넷 토폴로지 특성의 중꼬리(heavy-tailed) 분포를 성공적으로 나타내었다. 이러한 결과는 파워-로 지수(exponents)를 이용해 이들 인터넷 토폴로지 특성을 간단 명료하게 나타낼 수 있게 한다. 본 논문에서는 BGP 밸리-프리 라우팅 정책에 기반한 국내 AS 레벨 인터넷 토폴로지 속성 - 노드 차수, 홉 수에 따른 노드 쌍의 수, 그리고 그래프의 고유치 - 의 파워-로 지수를 조사하였다. UCLA IRL 연구실이 제공하는 실제 AS 레벨 데이터 셋을 이용하였으며 이들 파워-로 근사는 상관계수(correlation coefficient)가 각각 90.7%, 96.5%, 그리고 97%로 조사되었다. 특히, 실질적인 AS 레벨 토폴로지 직경이 3홉 이내에 존재하는 AS 노드 쌍이 전체 91% 이상이며, 따라서 국내 AS 레벨 토폴로지가 비교적 잘 정리된 것으로 판단된다.

• Asia pacific journal of information systems
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• 제11권3호
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• pp.105-126
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• 2001

The objective of research is to find out exogenous variables that influence the usage and performance EDI in the Korea firms. Specifically the goals of this research are; (1) to examine relationships between exogenous variables, such as management, technology, inter-firm relationship characteristics, and EDI performance, and (2) to measure EDI volume, EDI diversity, EDI depth among Korea firms. The questionnaire consists of two versions; One for the EDI system managers and the other for the EDI users. The analysis of this study is designed as cross level to examine the causal relationship among variables in different analysis level. The reliability and validity of data was tested by explanatory factor analysis, Cronbach's alpha coefficient, confirmatory factor analysis, and correlation analysis. Also, the structural equation model(SEM) analysis was performed to test the usefulness of the model. The analysis results revealed that education level, IS growth, trust, support, power are major influential variables on the usage level and performance of EDI. Especially, persuasive power turned out to be more important than coercive power, and technical financial support from organizations was also found to be a significant variables.

• 산업경영시스템학회지
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• 제32권2호
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• pp.158-170
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• 2009

This paper considers how the optimal export level is influenced by export risk, the degree of risk-averseness for exporting firms, and those firms' cost structure. In addition, export insurance is incorporated into some simple theoretical model to analyze the optimal export level. This paper applies genetic algorithm simulation to show that the exporting firms'risk-averseness do not affect the optimal export decision while export risk and cost function characteristic have relatively more significant effects on the optimal export level. Finally, our findings suggest that the most influential factor for the optimal export levels seems to be the monopoly power of exporting firms.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 전력전자학술대회 논문집
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• pp.83-84
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• 2014

This paper proposes the development of double conversion Uninterruptible Power Supply using 3-Level Converter/TNPC Inverter. The Rectifier of proposed system is operating not only 3-Level boost PFC but also battery discharger. The Inverter is converting DC voltage to AC voltage. And in terms of the efficiency, 3-Level TNPC inverter is improved compared to the origin 2-Level type. To verify the validity of proposed system, experiments were carried out.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 추계학술대회 논문집
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• pp.75-76
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• 2012

This paper presents an analysis of power losses in three-level T-Type Inverters. The switching loss in different switching frequencies and the conduction loss at different modulation indices and power factors are investigated. Finally, it is shown that the results of analysis coincide with those which resulted from CASPOC software simulation.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(2)
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• pp.329-332
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• 2000

This paper proposed resource allocation algorithm for the minimum power consumption of functional unit in high level synthesis process as like DSP which is circuit to give many functional unit. In this paper, the proposed method though high level simulation find switching activity in circuit each functional unit exchange for binary sequence length and value bit are logic one value. To used the switching activity find the allocation with minimal power consumption, the proposed method visits all control steps one by one and determines the allocation with minimal power consumption at each control step.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(2)
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• pp.188-191
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• 2000

This paper presents a register scheduling and allocation algorithm for high level synthesis. The proposed algorithm executes the low power scheduling to reduce the switching activity using shut down technique which was not unnecessary the calculation through the extraction DFG from VHDL description. Also, the register allocation algorithm determines the minimum register after the life time analysis of all variable. It is minimum the switching activity using graph coloring technique for low power consumption. The proposed algorithm proves the effect through various filter benchmark to adopt a new scheduling and allocation algorithm considering the low power.

• 한국산학기술학회논문지
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• 제20권9호
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• pp.240-246
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• 2019

공사장에서 운용하는 건설기계에서 발생하는 소음은 인근 주민들과 환경 분쟁의 주요 원인이 된다. 공사장 소음저감을 위해 저소음 건설기계의 사용과 저소음 공법을 우선적으로 사용하도록 하고 있다. 아울러 발생 가능한 소음을 예측하고 소음원에 맞는 예방책을 세우도록 하고 있다. 공사 전 과정에서 다양하게 사용되는 건설기계의 소음도 수준을 정확하게 파악하는 것은 소음 예측 및 저감 대책을 세우는데 가장 먼저 선행되어야할 과제이다. 이에 본 연구에서는 공사장에서 사용빈도가 가장 높은 굴삭기 소음도 현황을 분석하였다. 그 방법으로 2008년 이후 국내 판매되는 굴삭기 297기의 소음도 현황 분석하였고, 측정 자료를 기초로 굴삭기 엔진의 형식과 출력(kW) 그리고 생산지에 따라 소음도 수준을 구분해 보았다. 그 결과 엔진의 형식 변화에 따라 소음도는 1 dB(A) 씩 감소하였고, 엔진의 출력이 2배 증가하면 소음도는 약 3 dB(A) 정도 증가하는 것을 확인하였다. 또한 엔진 출력에 따라 국외 제품은 55 kW 미만의 소형급, 국내 제품은 55 이상 ~ 104 미만 kW 중 소형급 제품에서 소음도 수준이 낮은 것으로 나타났다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.7-11
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• 2017

This paper describes a design concept of NPC1 power stack for 1500VDC megawatt level solar inverter. This stack uses three latest half-bridge IGBT modules with highest power density and operation junction temperature, which enable realization of power level beyond 1MW without paralleling. Critical design concept on loop inductance is explained. Dynamic characteristics are verified by double-pulse test. Thermal characteristics and output power limits are verified by thermal test. Temperature-sensitive component on PCB as output power constraint is identified. Different PCB repositioning solutions are tested to give the overall output power thermal derating curves, which enable output power of 1.15MW at $T_A=55^{\circ}C$ with $15^{\circ}C$ thermal margin. The power stack characteristic and performance change under different thermal environment is further analyzed.