• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 춘계학술대회 논문집 에너지변화시스템부문
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• pp.29-31
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• 2009

Optimal efficiency control of synchronous reluctance motor(SynRM) is very important in the sense of energy saving and conservation of natural environment because the efficiency of the SynRM is generally lower than that of other types of AC motors. This paper is proposed an efficiency optimization control for the SynRM which minimizes the copper and iron losses. The design of the speed controller based on fuzzy-neural networks (FN)-PI controller that is implemented using fuzzy control and neural networks. There exists a variety of combinations of d and q-axis current which provide a specific motor torque. The objective of the efficiency optimization control is to seek a combination of d and q-axis current components, which provides minimum losses at a certain operating point in steady state. It is shown that the current components which directly govern the torque production have been very well regulated by the efficiency optimization control scheme. The proposed algorithm allows the electromagnetic losses In variable speed and torque drives to be reduced while keeping good torque control dynamics. The control performance of the proposed controller is evaluated by analysis for various operating conditions. Analysis results are presented to show the validity of the proposed algorithm.

• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.586-594
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• 2015

This paper proposes a maximum efficiency operation strategy for three-level T-type inverter in entire operation areas. The three-level T-type inverter has higher and lower efficiency areas compared with two-level inverter. The proposed strategy aims to operate in the maximum efficiency point for the low-voltage and low-power home appliances. The three-level T-type inverter is analyzed in detail, and the two operation mode selection strategy is developed. The proposed algorithm is verified by theoretical analysis and experimental results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권6호
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• pp.2946-2962
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• 2017

An improved energy-efficient compressed network coding method is proposed for the data communication in the wireless sensor networks (WSNs). In the method, the compressed sensing and network coding are jointly used to improve the energy efficiency, and the two-hop neighbor information is employed to choose the next hop to further reduce the number of the transmissions. Moreover, a new packet format is designed to facilitate the intermediate node selection. To theoretically verify the efficiency of the proposed method, the expressions for the number of the transmissions and receptions are derived. Simulation results show that, the proposed method has higher energy efficiency compared with the available schemes, and it only requires a few packets to reconstruct measurements with reasonable quality.

• 신재생에너지
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• 제17권1호
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• pp.1-6
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• 2021

Transparent conducting oxide (TCO) films have been widely used in optoelectronic devices, such as OLEDs, TFTs, and solar cells. However, thin films of indium tin oxide (ITO) have few disadvantages pertaining to process parameters such as substrate temperature and sputtering power. In this study, we investigated the requirements for using TCO films in silicon-based solar cells and the best alternative TCO materials to improve their efficiency. Moreover, we discussed the current status of high-efficiency solar cells using low-temperature TCO films such as indium zinc oxide and Zr-doped indium oxide.

• 동아시아식생활학회지
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• 제23권6호
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• pp.862-870
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• 2013

This study examines the effect of communication type of food service employees on the self-efficiency and organizational commitment. To accomplish the purpose of the study, a survey was conducted to employees of food service companies located in Seoul, from August 5, 2013 to August 25, 2013 as a method of empirical study. The results of this study was analyzed using the SPSS WIN 12.0 and statistical reliability analysis, factor analysis, frequency analysis, correlation analysis and multiple regression analysis were conducted for hypothesis verification. The analysis results of this study are as follows. First, the R-square of regression result for 'communication type will have a positive effect on self-efficiency' was .220. Also, it was found that factors of consideration (Beta=.286, t=5.622), instruction (Beta=.303, t=5.970) and business (Beta=.214, t=4.217) had positive effects on self-efficiency. Values for factors of consideration and instruction were higher than business. Second, the R-square of regression result for 'communication type will have a positive effect on organizational commitment' was .429. Also, it was found that factors of consideration (Beta=.453, t=10.428), instruction (Beta=.380, t=8.749) and business (Beta=.282, t=6.477) had positive effects on organizational commitment. Values for factors of instruction and business were high but value of consideration factor turned out the highest. Third, the R-square of regression result for 'self-efficiency will have a positive effect on organizational commitment' was .334. Also, it was found that out of the factors of positivity (Beta=.369, t=8.423), confidence (Beta=.415, t=8.833) and negativity (Beta=-.072, t=-1.536), positivity and confidence had positive effects on organization commitment, and only positivity and confidence showed high values in organization commitment. Upon analyzing the effect of factors of self-efficiency (positivity, confidence, negativity) on organizational commitment, it was found that positivity and confidence showed high relevance but the negativity factor did not have any correlation.

• 한국정보전자통신기술학회논문지
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• 제6권1호
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• pp.51-56
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• 2013

본 논문에서는 LED 조명을 기반으로 미디어 전송기법 가시광통신 시스템 모듈 설계 및 효율 연구와 성능분석을 하였다. 고휘도 Withe LED조명을 이용한 가시광통신(Visible Light Communication) 송 수신기 모듈을 통해 미디어 전송 시스템을 구현하기 위해 송신부에는 1~12개의 LED 발광 소자와 수신부에는 PD(Photo Diode)센서를 구성하여 전송속도에 따른 최대 송 수신의 통신 거리를 실험해 보고자 가시광통신 시스템을 제안하였다. 또한 미디어 전송 시스템의 효율을 증대시키기 위해 LED모듈에 렌즈 착용시와 미착용시 각각의 성능을 측정하여 약 20%의 효율이 증가하였음을 확인 할 수 있었다.

• 한국항행학회논문지
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• 제14권3호
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• pp.351-357
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• 2010

이 논문은 RFID와 같은 무선통신 시스템에 적용할 수 있는 고 효율을 유지하는 적응형 E급 증폭기를 제안하였다. 스위치 모드의 이 증폭기는 출력의 공진기를 제어하기 위하여 MCU를 사용하였고, 이에 따라서 입력 주파수 변화에 공진기 주파수를 적용하여 고 효율을 유지하도록 하였다. 이러한 적응형 E급 증폭기의 동작을 보이기 위해서 중심 주파수 450 MHz. 대역폭은 100 MHz인 증폭기를 제작하여 이 주파수 구간에서는 60% 이상의 효율을 유지하였고, 최대 효율은 74.8%를 얻었다.

• 한국음향학회지
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• 제33권6호
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• pp.413-419
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• 2014

수중음향 채널은 시변적인 특징을 가진다. 채널의 시변동성은 지속적인 정보 데이터 전송을 방해하여 수중음향통신의 신뢰도를 감소시키는 요인이 된다. 본 논문에서는 채널의 시변동성을 시간영역 상관도로 기술하고, 정보 데이터의 실질 전송시간을 스루풋 효율로 표현하였다. 그리고 수중음향 채널의 시변동성이 통신 스루풋 효율에 미치는 영향을 분석하였다. 실제 수중음향통신 실험을 통하여 수중채널의 시변동성이 클수록 통신의 스루풋 효율도 감소한다는 것을 확인하였다.

• 통상정보연구
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• 제16권4호
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• pp.55-75
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• 2014

본 연구는 국내 ICT 제조업과 서비스업의 경쟁력 강화를 위한 기초 연구로서 효율성과 생산성 추이 및 생산성의 결정요인을 분석하는 것을 목적으로 하였다. 구체적으로 본 연구는 ICT산업의 효율성 분석을 위해 ICT 제조업 23개 업종과 ICT 서비스업 18개 업종에 대하여 2007년부터 2011년까지 5년간 규모의 수익불변을 가정한 DEA(Data Envelopment Analysis)의 CCR모형과 규모의 수익가변을 가정한 BCC모형을 통해 기술효율성과 순수기술효율성의 정태적 효율성을 살펴보고, 기술효율성에 대한 DEA/Window 분석과 Malmquist 생산성 지수를 이용하여 동태적 효율성을 분석하였다.

• 한국전자파학회논문지
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• 제14권6호
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• pp.543-549
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• 2003

OFDM 시스템뿐만 아니라 통신 시스템에서는 HPA(High Power Amplifier)의 비선형 특성을 고려하는 것이 중요하다. 본 논문에서는 OFDM통신 시스템에서 전력 효율과 대역효율을 동시에 고려한 새로운 성능 평가지수(D)를 분석한다. IBO(Input Backoff)의 크기와 부반송파 수에 따라 다른 값을 갖는 비선형 왜곡 잡음 성분(Nd)을 고려하며, 대역폭의 변화에 따른 대역 효율을 사용하여 성능 지수를 구함으로써 IBO에 대해 서로 상반관계 (tradeoff)에 있는 전력 효율과 대역 효율의 특성을 분석하였다.