• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1885-1887
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• 1996

Power transformers are the most important facilities in the substation of electrical power, yet they do not have the efficient operating life characteristics which are the important elements of repairing and maintenance in regional conditions. This paper describes the statistical analysis of operating conditions and troubles on transformers for the operating life assessment using Statistical Analysis System programs, Hazard method and Weibull distributions. We analyze transformers in several methods, and compares correlation relationship of operating life and troubles. Therefore, this study will be the useful basic operating life prediction technique of power transformers in the future.

• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.80-89
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• 2014

A stochastic optimal power flow (S-OPF) model considering uncertainties of load and wind power is developed based on chance constrained programming (CCP). The difficulties in solving the model are the nonlinearity and probabilistic constraints. In this paper, a limit relaxation approach and an iterative learning control (ILC) method are implemented to solve the S-OPF model indirectly. The limit relaxation approach narrows the solution space by introducing regulatory factors, according to the relationship between the constraint equations and the optimization variables. The regulatory factors are designed by ILC method to ensure the optimality of final solution under a predefined confidence level. The optimization algorithm for S-OPF is completed based on the combination of limit relaxation and ILC and tested on the IEEE 14-bus system.

• 한국경영과학회지
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• 제41권1호
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• pp.113-126
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• 2016

This study investigates the effect of power dynamics on R&D and market performances. Various types of relationships in a supply chain are considered. An R&D company offering new technology for product quality and a manufacturer responsible for both production and sales are utilized as subjects. The company with bargaining power differs with respect to the supply chain situation in practice, and no fixed single relationship and supply chain structure exist. However, only a few studies have considered the various relationships among players in a supply chain and their effects on performance. Therefore, we propose three models with different supply chain structures and power dynamics among players. This study contributes to the academia and supply chain practice by revealing the different characteristics of supply chain models.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 A
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• pp.322-325
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• 1997

Concerns for wind energy as alternative energy have been highly increased. In this paper, the mechanism between mechanical wind turbine and power generating system is presented to specify the relationship of the energy transfer. Grid-connected DFIG could achieve unity leading power factor, in addition to variable speed operation at the wide sub-synchronous and super-synchronous shaft speed range and also its independent control of torque and reactive power is possible.

• 한국전기전자재료학회논문지
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• 제28권4호
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• pp.222-228
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• 2015

Power MOSFETs (metal oxide semiconductor field effect transistor) operate as energy control semiconductor switches. In order to reduce energy loss of the device, it is essential to increase its conductance. However, a trade-off relationship between the breakdown voltage and conductance of the device have been the critical difficulty to improve. In this paper, theoretical analysis of electrical benefits on single floating island power MOSFET is proposed. By the method, the optimization point has set defining the doping limit under single floating island structure. The numerical multiple 2.22 was obtained which indicates the doping limit of the original device, improving its ON state voltage drop by 45%.

• Nuclear Engineering and Technology
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• 제36권1호
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• pp.64-72
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• 2004

The purpose of this study is to develop a system dynamics model for the assessment of the organizational and human factors in a nuclear power plant which contribute to nuclear safety. Previous studies can be classified into two major approaches. One is the engineering approach using tools such as ergonomics and Probability Safety Assessment (PSA). The other is the socio-psychology approach. Both have contributed to find organizational and human factors and to present guidelines to lessen human error in plants. However, since these approaches assume that the relationship among factors is independent they do not explain the interactions among the factors or variables in Nuclear Power Plants. To overcome these restrictions, a system dynamics model, which can show cause and effect relationships among factors and quantify the organizational and human factors, has been developed. Handling variables such as the degree of leadership, the number of employees, and workload in each department, users can simulate various situations in nuclear power plant organization. Through simulation, users can get insights to improve safety in plants and to find managerial tools in both organizational and human factors.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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• pp.1987-1989
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• 2001

전력선 통신은 디지털 변복조 통신 기술의 발달에 힘입어 높은 신뢰성과 고속의 데이터 전송 속도를 제공하게 됨에 따라 차세대 통신 기술로 기대되고 있다. 아울러 배전 계통에서의 원격 검침은 단순히 검침 비용의 절감 차원이 아닌 수용가 정보 취득 및 수요관리 등의 기능을 함께 수용할 수 있어 보다 효율적인 에너지 사용관리 및 감시가 가능한 배전 계통 구축이 가능하다. 아울러 구성된 통신망을 이용하여 제공되는 다양한 부가서비스를 통하여 CRM(Customer Relationship Management)의 차원을 한 단계 높일 수 있는 방안의 하나로서 인식되어 선진국 전력회사들간에 지대한 관심의 대상이 되고 있다. 본 논문에서는 전력선 통신을 이용하여 저압 수용가의 원격 검침 시스템의 구축 방안을 소개하며, 시스템 구축 상에 관련된 기술적 사항과 효과적인 네트웍 구축을 위한 프로토콜 등을 다루었다.

• Journal of Power Electronics
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• 제17권6호
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• pp.1480-1489
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• 2017

In this study, a carrier-based pulse-width modulation (PWM) method for two-level voltage source inverters in the over-modulation region is proposed. Based on the superposition principle, the reference voltage vectors outside the linear modulation boundary are adjusted to relocate to the vector hexagon, while their fundamental magnitudes are retained. In accordance with the adjusted reference vector, the corresponding modulated waves are respectively deduced in over-modulation mode I and II to generate the gate signals of the power switches, guaranteeing the linearity of the fundamental output phase voltage in the over-modulation region. Moreover, due to the linear relationship between the voltage vector and the duty ratios, the complicated sector identification and holding angle calculation found in previous methods are avoided in the modulated wave synthesis, which provides great simplicity for the proposed carrier-based over-modulation strategy. Experimental results demonstrate the effectiveness and validity of the proposed method.

• 한국생활과학회지
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• 제18권1호
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• pp.65-74
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• 2009

The study was conducted by regression analysis based on a survey with the subjects of 107 daycare teachers working at 120 daycare facilities located in Gyeonggi-do, so as to investigate the influence of daycare teachers' 'job stress' and 'job satisfaction' on their 'psychological happiness'. The results are: first, there was significant difference in job stress(F(3,103)=2.85, p<.05), job satisfaction(F(3,103)=5.88, p<.05) and psychological happiness(F(3,103)=3.52, p<.05) accordant to the kind of work facilities among social demographic variables. In the correlation between 'job stress' and 'job satisfaction', there was negative correlation(r= .-56, p<.(01). Second, in the correlation between 'job stress' and 'psychological happiness', there was negative correlation(r= .-41, p<.001). Third, in the correlation between 'job satisfaction' and 'psychological happiness', there was positive correlation(r= .54, p<.001). In the relationship between 'job satisfaction' and 'job stress', job stress had influence on job satisfaction($R^2$= .43, F=79.42, p<.001). The explanatory power of it was 43%. In the relationship between 'job stress' and 'psychological happiness', 'job stress' had influence on 'psychological happiness'($R^2$= .41, F=21.46, p<.001). The explanatory power of it was 17%. In the relationship between 'job satisfaction' and 'psychological happiness', 'job satisfaction' had influence on 'psychological happiness'($R^2$= 59, F=5457, p<.001). The explanatory power of it was 34%.

• 한국항해항만학회지
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• 제46권3호
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• pp.259-268
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• 2022

일반적인 구매자와 공급자 간의 관계와 달리, 구매자보다 공급자의 교섭력이 높은 경우가 있다. 이러한 관계는 특히 조선 산업에서 자주 찾아볼 수 있다. 본 연구는 Kraljic의 연구에서 제시된 전략품목(strategic items) 개념을 중심으로 연구하고자 한다. 본 연구는 공급자의 교섭력이 우위인 시장에서 구매자의 전략품목 구매에 영향을 미치는 요인을 살펴보는 것에 그 목적이 있다. 분석을 실시한 결과 환경요인과 신뢰요인 간의 경로계수가 가장 높은 것으로 나타났다. 또한 환경요인과 만족요인간의 경로계수도 차순위로 높은 것으로 나타났다. 또한 구매자가 지각하는 교섭력의 우열에 따른 인식차이가 존재하는지를 분석한 결과 일부 경로계수에서 유의한 결과를 발견하였다.