• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.753-755
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• 1993

Full Bridge Diode Rectification and Phase Controlled SCR Rectification are the most widely used methods of power conversion($AC{\rightarrow}DC$) in Power Electronic products such as UPS systems. But using these types of converters can lead to the following problems. First, they generate harmonics on the AC input side, which can cause interference in other equipment connected to the same commercial power line. Second, they deteriorate the power factor so that the input power capacity or the equipment becomes larger than the actual rated output capacity. As a means to overcome these problems an IGBT type PWM Converter, which applies a current control algorithm, is proposed. In this paper the enhancement of the converter performance is shown through simulation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.326-328
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• 2005

In order to reduce the capital and overall operating cost of a fuel-cell system, a high-efficiency fuel-cell power inverter with a simple framework is required. The high-order two-inductance two-capacitance (LLCC) resonant technique is adopted in this study to implement a low-frequency 60-Hz sine wave voltage inverter utilized in the proton exchange membrane fuel-cell (PEMFC) system. The methodology for inverting dc voltage into low-frequency ac boltage is usually generated by the pulse-width-modulation (PWM) technique. However, the PWM-type inverter output has high-frequency harmonic components. Although an adequately designed filter could be utilized to overcome this problem, there are still some undesirable effects introduced by the high-frequency switching loss, electromagnetic-interference, harmonic current, and load variation. A novel power inverter via the LLCC resonant technique is designed for inverting dc voltage into 60-Hz ac sine wave voltage in the PEMFC system. This circuit scheme has the merits of low harmonic components, soft switching, high efficiency, and simplified implementation. The effectiveness of the proposed resonant inverter used for the PEMFC system is verified by numerical simulations and experimental results.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 추계학술대회 논문집
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• pp.318-325
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• 1999

Modern AC electric car has PWM(Pulse Width Modulation)-controlled converters, which give rise to higher harmonics. The current harmonics injected from AC electric car is propagated through power feeding circuit, As the feeding circuit is a distributed constant circuit composed of RLC, the capacitance of the feeding circuit and the inductance on the side of power system cause a parallel resonance and a magnification of current harmonics at a specific frequency. The magnified current harmonics usually brings about various problems. That is, the current harmonics makes interference in the adjacent lines of communications and the railway signalling system. Furthermore, in case it flows on the side of power system, not only overheating and vibration at the power capacitors but also wrong operation at the protective devices can occur. Therefore, the exact assessment of the harmonic current flow must be undertaken at design and planning stage for the electric traction systems. From these point of view, this study presents an approach to model and to analyse traction power feeding system focused on the amplification of harmonic current The proposed algorithm is applied to a standard AT(Auto-transformer)-fed test system in which electric car with PWM-controlled converters is running.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2011년도 추계학술대회
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• pp.255-258
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• 2011

무선 LAN(Wi-Fi: Wireless Fidelity)은 스마트폰 대중화와 더불어 급속히 확대되는 통신망으로 컴퓨터, 노트북, 태블릿 PC 그리고 스마트폰 등 다양한 기기가 접속되어 유비쿼터스 기반의 핵심 네트워크로 자리 잡아 가고 있다. 현재 많은 무선 LAN 통신 기술이 개발되어 다양한 데이터 전송이 가능해졌으며, 표준인 IEEE 802.11n은 2.4GHz 대역과 5GHz 주파수 대역을 사용하고 있다. 2.4GHz 대역은 파장이 길고 회절 및 수신 거리가 좋아서 802.11b/g 방식으로 널리 보급되었다. 5GHz 주파수 대역은 2.4GHz보다 활용할 수 있는 더 많은 채널을 가지고 있어 블루투스, RFID 등 다른 무선 장치의 주파수 대역과 간섭이 없으며 주파수 사용자가 적어 채널 간섭이 적은 특징을 가지고 있다. 본 논문에서는 초기부터 사용된 802.11b/a/g과 현재 사용되고 있는 802.11n 기술 분석 및 동향 그리고 최근 차세대 무선 LAN 통신망으로 대두되고 있는 802.11ac와 802.11ad의 개발 현황 및 표준화 방향에 대하여 살펴본다. 또한, 무선 LAN 보안 취약점 및 이용 현황과 추가적인 대책 방안에 대하여 논하고자 한다.

• 한국가스학회지
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• 제5권4호
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• pp.21-26
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• 2001

최근 국내에서는 효율적인 공간활용을 위해 해저터널을 이용하여 전력을 공급하는 것이 시도되고 있으며, 해저터널 내에 에너지 공급 기간시설물(진력케이블, 가스배관, 송유관, 지역난방배관 등)들이 같이 포설될 수 있으면 공사비 절감의 효과는 엄청날 것이므로 관심도가 높아지고 있다. 최근, 국내에서도 해저터널 내에 가스배관과 전력선이 병행 시공되는 경우가 발생하여 가스배관에 대한 안전성에 대한 평가가 요구되고 있다. 따라서 본 논문에서는 해해저터널 내 고전압 전력케이블에 의한 가스배관의 교류부식, 가스배관의 코팅과 용융. 절연 플랜지, 전기방식용 정류기 등의 전기방식설비의 안정성에 대하여 검토함으로써, 최종적으로 가스배관의 안전성을 평가$\cdot$연구하였다.

• 말소리와 음성과학
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• 제4권2호
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• pp.21-31
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• 2012

The purpose of this study is to find the influence of Chinese falling-rising tone on the pitch pattern of corresponding partly-different-form-same-meaning Sino-Korean words delivered by Chinese learners of Korean and to examine how the falling-rising tone of corresponding Chinese words affects the pitch patterns of Sino-Korean words. The scope of this research is limited to Chinese learners of Korean, especially on two groups of Sino-Korean words - AB:CB type and AB:AC type that the are second-most frequently occuring different-form-same-meaning Sino-Korean words. In this study, Chinese learners pronounced both Chinese words and corresponding Sino-Korean words. Learners' pitch patterns were recorded and analyzed using software and compared with the tone of corresponding Chinese words. Experimental results showed that AB:CB type Sino-Korean words were not affected by Chinese 'falling-rising tone - high and level tone'. As well as AB:CB type, experimental results showed there were no significant influence on the pitch pattern of AB:AC type Sino-Korean words by Chinese falling-rising tone. But it was clear that Chinese learners' made pitch errors on both AB:CB type and AB:AC type Sino-Korean words. In conclusion, the Chinese learners' pitch patterns of partly-different-form-same-meaning Sino-Korean words are different from Korean native speakers', but their pitch errors cannot be attributed to Chinese falling-rising tone.

• 전기학회논문지
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• 제65권12호
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• pp.1958-1964
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• 2016

AC railway feeding system use single phase to supply power to the railway vehicles. And the system use the rail track as a return current path, so that current flows in the rail. In this situation inductive interference on communication system and unsafe environment can appear on railway system. Therefore knowing the current distribution of catenary system and analysing the return current is required. In this study detail return current distribution was analyzed by modeling the catenary system as 4-conductors group. The distribution characteristics and trends of return current were studied by using the PSCAD/EMTDC and FDTD method that based on Maxwell equation was used to calculate the induced voltage. Simulation code was made by MATLAB. Using this study result data, we can suggest the proper installation location of digital device and these data can be used for additional studies related to return current or induced voltage as a base data.

• 대한기계학회논문집
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• 제16권10호
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• pp.1816-1823
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• 1992

본 연구에서는 CMAC의 훈련에 관련된 문제점 뿐만 아니라 효율적인 CMAC 훈련 방법의 개발에 관한 문제를 연구하였으며, 학습간섭의 영향을 전혀 받지 않으면서 CM- AC의 학습일반화(learning generalization) 특성을 살린, 일반적으로 응용될 수 있는 이웃간훈련방법을 제안하였다. 이 훈련 방법을 2변수 연속함수를 위한 2차원 CMAC의 훈련모사에 적용하여 전체 입력점 수의 1.3% 정도의 훈련 회수로 그 연속함수의 최대 함수값 1.0에 대해 0.0025의 제곱 평균 제곱근 오차(root mean square error, 이하 RMS error라 함)를 갖는 수준의 훈련성과를 거둘 수 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.605-610
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• 1991

In inverter system for driving induction motor, the output harmonics are hamrful in induction motor drive because it leads to ripple torque and induction interference. For electrical drives using PWM(Pulsewidth Modulation) inverters and ac motors, the methods for efficiency optimal control have been developed. In this paper, two different PWM methods for inverter and voltage control technique are described. In order to reduce or minimize losses, various forms of PWM strategy such as, PM (Positive Modulation) and NM (Negative Modulation) are discussed. The results show the feasibility of obtaining practically sinusoidal output waveforms which are highly desirable in most inverter application.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2005년도 춘계학술대회논문집
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• pp.174-177
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• 2005

Offline switching power supplies have high voltage and high current switching waveforms that generate Electromagnetic Interference(EMI) in the form of both conducted and radiated emissions. Consequently, all off-line power supplies must be designed to attenuate or suppress EMI emissions below commonly acceptable limits. Electrodeless fluorescent lamp's ballasts have AC/DC flyback converter, so we must control the EMI emissions.