• Journal of Power Electronics
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• 제15권1호
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• pp.235-245
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• 2015

This paper proposes a reactive current assignment and control strategy for a doubly-fed induction generator (DFIG) based wind-turbine generation system under generic grid voltage sag or swell conditions. The system's active and reactive power constrains during grid faults are investigated with both the grid- and rotor-side convertors (GSC and RSC) maximum ampere limits considered. To meet the latest grid codes, especially the low- and high-voltage ride-through (LVRT and HVRT) requirements, an adaptive reactive current control scheme is investigated. In addition, a torque-oscillation suppression technique is designed to reduce the mechanism stress on turbine systems caused by intensive voltage variations. Simulation and experiment studies demonstrate the feasibility and effectiveness of the proposed control scheme to enhance the fault ride-through (FRT) capability of DFIG-based wind turbines during violent changes in grid voltage.

• 비파괴검사학회지
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• 제12권2호
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• pp.14-20
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• 1992

Stress analysis has been performed using computer program ANSYS in the pressurizer surge line in accordance with ASME Sec. III in order to predict possibility of fatigue failure due to thermal stratification phenomena in pipes connected to reactor coolant system of nuclear power plants. Highly vulnerable area to crack generation has been chosen by the analysis of fatigue due to thermal stress in pressurizer surge line. This kind of result can be helpful to choose the location requiring intensive care during inservice inspection of nuclear power plants.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.497-501
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• 2001

Unbundled power quality service is paid much attention under the circumstances of deregulation and diversification of needs of customers for quality and price of electric power. Moreover, distributed generators (DGs) such as photovoltaic generations and wind turbines will be introduced to distribution system more and more, and reverse flow of active power has possibility to cause new problems in the distribution system such as voltage rise of distribution line and protection problem. Flexible, Reliable and Intelligent Electrical eNergy Delivery System, which is called FRIENDS, has been proposed as one of promising distribution system for such requirements, and intensive studies are under way. One of features of the system is introducing Quality Control Center (QCC) into the system for unbundled power quality service and easy installation of DGs. Two types of QCCs for such purposes are proposed, and simulation results are shown in this paper.

• Journal of the Korean Data and Information Science Society
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• 제28권3호
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• pp.669-684
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• 2017

Mediation models are widely used in many fields of research and have recently gained attention in epidemiology. The mediation proportion is a standard measure to evaluate what part of the total exposure effect on an outcome may be explained by a particular mediator and to examine how important that pathway is relative to the overall exposure effect. A common question is how large a sample size is needed to achieve high statistical power or, equivalently, what magnitude of effect can be detected. Current power and sample size calculations for mediation analysis are limited and additional research is needed. We therefore propose a computer-intensive power analysis using the mediation proportion. We conduct simulation studies to calculate statistical powers and sample sizes. And then, we illustrate our power analysis using an example from the Adult Health Study of atomic-bomb survivors and demonstrate that the method is relatively straightforward to understand and compute.

• Journal of Power Electronics
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• 제10권2호
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• pp.132-137
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• 2010

Interleaving techniques are widely used to reduce input/output ripples and to increase the power capacity of boost converters operating in critical conduction mode. Two types of phase-shift control schemes are studied in this paper, the turn-on time shifting method and the turn-off time shifting method. It is found that although the turn-off time shifting method exhibits better performance, it suffers from sub-harmonic oscillations at high input voltages. To solve this problem, an intensive quantitative analysis of the sub-harmonic oscillation phenomenon is made in this paper. Based upon that, a novel modified turn off time shifting control scheme for interleaved boost converters operating in critical conduction mode is proposed. An important advantage of this scheme is that both the master phase and the slave phase can operate stably in critical conduction mode without any oscillations in the full input voltage range. This method is implemented with a FPGA based digital PWM control platform, and tests were carried out on a two-phase interleaved boost PFC converter prototype. Experimental results demonstrated the feasibility and performance of the proposed phase-shift control scheme.

• 진공이야기
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• 제1권4호
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• pp.10-13
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• 2014

Since the development of 9.7% efficient long-term stable solid state perovskite solar cell in 2012, intensive study on perovskite solar cell has been performed. As a result, power conversion efficiency (PCE) has reached 20.1%. In-dept study on perovskite light absorber enabled understanding of origin of superb photovoltaic performance of perovskite solar cell. In this article, historical evolutions of perovskite solar cell along with key physical properties enabling high PCE are presented. Several important results for development of high efficiency perovskite solar cell are introduced. Finally, in-present research issues and future direction for solving these issues are discussed.

• 한국HCI학회논문지
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• 제9권2호
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• pp.13-21
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• 2014

줄넘기 운동은 간단하면서도 매우 효과적인 운동 효과를 갖고 있지만, 높은 강도의 단조로운 운동 패턴으로 인해 지속적으로 운동을 시행하기 어려운 단점이 있다. 한편 줄넘기를 할 때 수반되는 운동에너지로부터 전기에너지를 생성하는 자가발전이 가능하며, 이전 연구에서 자가발전이 가능한 에너지 자립형 줄넘기로써 그 가능성을 확인한 바 있다. 본 연구에서는 에너지 자립형 줄넘기의 내부에 자체 생산된 전력으로 구동되는 초소형 임베디드 시스템을 내장하여, 줄넘기 운동 중의 가속도를 측정하고 스마트폰으로 무선 전송하도록 하였다. 스마트폰에서는 전용 앱을 통해 전송받은 가속도 데이터로부터 사용자의 점프를 감지하여 음악 줄넘기를 접목한 게임 콘텐츠와 실시간 연동할 수 있도록 하였다. 개발된 스마트 줄넘기 프로토타입은 사용자 테스트를 통해 줄넘기 운동의 지속적인 동기부여 방법으로써 유용함을 확인 할 수 있었으며, 축적된 운동 데이터를 기반으로 사용자에게 체계적인 피드백을 제공함으로써 줄넘기 운동의 효과를 보다 높일 수 있을 것으로 기대한다. 아울러 건전지 교체가 불필요한 에너지 자립 특성은 비용 절감과 더불어 사용성과 지속가능성 향상에도 크게 기여할 수 있을 것이다.

• 임상간호연구
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• 제19권3호
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• pp.383-394
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• 2013

Purpose: This study was conducted to investigate the effects of preparatory nursing information and information offering by SMS on anxiety and nursing satisfaction among family members of ICU (Intensive Care Unit) inpatients. It utilized a quasi-experimental research design with a non-equivalent and non-synchronized control group. Methods: The experimental group and the control group were offered a booklet guiding ICU and were offered face-to-face information by nurses using Power Point. The experimental group was additionally offered SMS (short message service) message on patient's safety at night every morning during the hospital stay between 8 and 9 am. All participants in the experimental group and the control group were measured in reference to anxiety at the point of hospitalization and were surveyed anxiety and nursing satisfaction on the third day of hospital stay. Results: The anxiety demonstrated no significant difference between the groups, while the nursing satisfaction was significantly higher in the experimental group than that of the control group. Conclusion: Proving direct information and indirect information via SMS message were considered effective in improving the family member's satisfaction with nursing care. The frequencies of SMS message and the contents of the message and information need to be defined and specified in the given population.

• 중환자간호학회지
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• 제12권2호
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• pp.39-49
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• 2019

Purpose : The purpose of this study was to identify the extent to which intensive care unit (ICU) nurses' perceptions of life-sustaining treatment decisions and "a good death" affect attitudes toward terminal care. Method : Participants included 109 ICU nurses from three university hospitals. Data were collected using structured questionnaires, and collected data were analyzed using a t-test, ANOVA, the $Scheff{\acute{e}}$ test, Pearson correlation coefficients, and a multiple regression analysis (SPSS 24.0 program). Results : Perceptions of life-sustaining treatment decisions and a sense of closeness (a constituent for the awareness of "a good death") were positively correlated with terminal care attitudes. The factors affecting terminal care attitudes were a clinical career in ICU (${\beta}=.20$, p =.035), a sense of closeness(${\beta}=.19$, p =.041), and the perception of a life-sustaining treatment decision (${\beta}=.22$, p =.017). This finding indicates that more than 10 years of experience in ICU, a greater sense of closeness, and a higher view of life-sustaining treatment decisions results in more positive attitudes toward terminal care. The explanatory power of these variables on terminal care attitudes was 14% (F=6.84, p < .001, Adj $R^2=.140$). Conclusion : A sense of closeness and the perception of life-sustaining treatment decisions were identified as the factors affecting terminal care attitudes. Thus, various programs must be developed to raise awareness among ICU nurses of "a good death" and perceptions of life-sustaining treatment decisions.

• 복식문화연구
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• 제28권4호
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• pp.508-526
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• 2020

This study has established a fashion illustration education plan using the contour drawing that fosters observational ability and enables creative drawing. This study developed two illustration curriculum proposals consisting of 15 weeks, combining literature and case studies. The researchers organized a step-by-step teaching plan that utilizes contour drawing according to the three stages of fashion illustration classes: foundation courses, general courses, and intensive courses. When the contour drawing is used at the beginning stage of the foundation courses of fashion illustration, it can be used as a technique to reduce the fear of students about practical skills, induce interest in illustration, and cultivate observation ability about objects. In general process, it is combined with various tools and coloring materials to strengthen expression power, and it is possible to produce detailed expressions and illustrations about human body and clothing. In intensive courses, it is expanded to the production of creative works with new aesthetics through digital techniques and mixed materials. As such, the contour drawing is expanded in various ways according to the learning contents and goals of each step, and is flexibly adjusted according to the learning content. Contour drawing has the effect of acquiring observation and expression ability, and it is analyzed as a technique that enables the production of creative illustration of students.