• 전기의세계
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• 제23권4호
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• pp.46-52
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• 1974

Generally, it has been regarded that there are two kinds of the effect of the electrodes, especially of the cathode in the gas discharge, (a) the effect caused by the difference of the cathode meterial and (b) the effect by the change of the cathode surface state even in the same meterials. Thus the two effects must be investigated independently to study the roles of the cathode in gas discharges. This paper measured sparking voltage in Rare gas (Ar, He) for the change of sparking voltage in repeating sparks and for the effect of (a) and (b) mentioned above, under the condition that the desorption of impurities from the cathod can be nigligible, and it is obtained that the correlative relations of the work function, sparking voltage and secondary coefficient are comparatively simple. In addition, the interesting character of the minimum point of the paschen's curves is found. The results were as follows; 1) The value of (pd)min with minimum pint of sparking voltage, (Vs)min, is 0.7-0.9 Torr. cm in Argon, but is 5.6-7.1 Torr. cm in Helium, and Paschen's curve in Helium shows slow curve than in Argon. 2) The minimum point of the Paschen's curve is satisfied actually Townsend's self sustaining criterion in Argon, but non-satisfaction in Helium, and the Townsend's secondary coefficient .gamma. action have compound property (.gamma.$_{i}$, .gamma.$_{p}$, .gamma.$_{m}$) in Helium. 3) The dependenting character of work function in Helium is less than in Argon. 4) The minimum point of sparking voltage increase under oxidized electrode than clear electrode in Au and Ag, but minimum point decrease in Ni and Cu.

• 전기학회논문지
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• 제60권9호
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• pp.1651-1655
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• 2011

The reference impedances which is about 95% supply impedance value of residential consumers' supply impedances was published by IEC in 1980. The reference impedances are the standard values for use in determining the voltage disturbance characteristics of electrical equipment like the flicker. In IEC 60725, the reference impedances for premises having service current capacities less than 100A per phase and for service current capacities more than 100A per phase are recommended. And these reference impedances are targeted for the countries using 50Hz power frequency. Because of the frequency difference, the reactance values of the reference impedances will be increased in 60Hz power system like Korea, And also the reference impedances are different significantly each other according to declared voltage variation, power consumption and service wire length etc. Therefore It is needed to calculate the reference impedances suitable for domestic low-voltage power system. In this paper, the reference impedances for service current capacities less than 100A in 220/380V, 60Hz single-phase two wire and three-phase four wire low-voltage system are calculated, And the equations for service current capacities more than 100A to calculate the modulus value of maximum supply impedances are suggested base on IEC 60725 and the reference impedances for those are calculated on service current of 100A per phase.

• 한국안전학회지
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• 제29권2호
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• pp.12-17
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• 2014

This paper is aimed to analyze the characteristics of simultaneous voltage, current and temperature signals for poor connection on electrical connector. In order to attain this purpose, detected were the current and voltage signals on electric wire with series arc, named arc signals, and also monitored were the changes of RMS, instantaneous value of waveform in time domain and temperature value with video. Two states are made normal state over $5kgf{\cdot}cm$ and poor connections state below $0.5kgf{\cdot}cm$ by screw gage. In the voltage signal case, the voltage drop was increased with which the current was increased. In the current signal case, poor connections at the time interval 1~4A all showed "shoulder", as distinct difference from the normal state shown waveform pattern. In the temperature signal case, poor connections are twice at 1A and five times at 4A in the normal state. The temperature continues insulation of electrical wiring and connector can be carbonized. The results of this study will be effectively used in developing the preventive devices and system for electric fire by poor connections.

• 전력전자학회논문지
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• 제24권2호
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• pp.71-77
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• 2019

This study proposes a circulating current reduction method that uses high-frequency voltage compensation when carrier phase difference occurs between two inverters in MSIS. In MSIS, inverters are configured in parallel to increase power capacity and to increase efficiency by using inverters only as needed. However, in the parallel inverter structure, circulating current is inevitably generated. Circulating current increases the stress on the switch, adversely affects the current control performance, and renders load sharing difficult. The proposed method compensates for the output voltage reference of the slave module by using the high-frequency voltage so that the switching pattern of each module is matched even in asynchronous carriers. The validity of the proposed method is verified by simulations and experiments with 600 W IPMSM.

• 한국전문물리치료학회지
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• 제6권3호
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• pp.1-10
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• 1999

The purpose of this study was to determine whether high voltage pulsed current stimulation (HVPCS) would enhance wound healing in neuropathic rabbits. Ten rabbits were assigned to either an experimental or a control group. The wounded part around the peripheral neuropathy of the experimental rabbits was stimulated for two hours twice a day for six days under the following conditions: pulse frequency 80 pps, pulse duration $100{\mu}s$, and stimulation intensity 30~40 V. The results indicated that there was no difference in the wound closure between the experimental and control groups. The two groups showed similar aspects in collagen and reticulum, which were observed by colored Masson's trichome. While the rabbits in the control group had more or less thick fibers, the rabbits in the experimental group had thin and branched-shape fibers. The rabbits in the experimental group showed both strong responses in the shaping of elastic fibers and the increased aspects in fibroblast when compared with the control group.

• Journal of Power Electronics
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• 제13권1호
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• pp.70-76
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• 2013

For high power high step-down dc-dc conversion applications, conventional three-level dc-dc converters are subject to extreme duty cycles or increased volume and cost due to the use of transformers. In this paper, a transformerless three-level dc-dc buck converter with a high step-down conversion ratio is proposed. The converter comprises two asymmetrical half bridges, which are of the neutral point clamped structures. Therefore, the output pulse voltage of the converter can be obtained in terms of the voltage difference between the two half bridges. In order to realize harmonious switching of the converter, a modulation strategy with capacitor voltages self balance is presented. According to the deduced output dc voltage function, transformerless operation without extreme duty cycles can be implemented. Experimental results from a 1kW prototype verify the validity of the proposed converter. It is suitable for ship electric power distribution systems.

• 전기학회논문지
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• 제64권5호
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• pp.708-717
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• 2015

This paper proposes a new reduction scheme of circulating current when two units of BESS (Battery Energy Storage System) are operated in parallel with conventional droop control. In case of using conventional droop, the terminal voltage of each BESS are not equal due to the unequal line impedance, which causes the circulating current. The operation performance of BESS is critically dependant on the circulating current because it increases system losses which causes the increasement of required system rating. This paper introduces a new reduction scheme of circulating current in which the terminal voltage difference of each BESS is compensated by adding feed-forward path of line voltage drop to the droop control. The feasibility of proposed scheme was first verified by computer simulations with PSCAD/EMTDC software. After then a hardware prototype with 5kW rating was built in the lab and many experiments were carried out. The experimental results were compared with the simulation results to confirm the feasibility of proposed scheme. Two parallel operating BESS with proposed scheme shows more accurate performance to suppress the circulating current than those with the conventional droop control.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2017년도 추계학술대회
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• pp.243-244
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• 2017

이 논문은 터널링 전계효과 트랜지스터의 밴드 간 터널링 전류 계산에 대하여 1차원과 2차원 방향의 터널링이 어떤 차이를 나타내는지 알아보았다. 2차원 방향의 터널링은 1차원 방향의 터널링에서 계산 되지 않는 대각선 방향의 터널링이 나타나기 때문에 더 정확한 터널링 전류를 계산할 수 있다. 시뮬레이션 결과는 문턱전압 이상의 전압에서는 2차원 방향으로 일어나는 터널링이 큰 영향을 미치지 않지만, 문턱전압 이하에서는 문턱전압 이하 기울기에 많은 영향을 미친다.

• Journal of Electrochemical Science and Technology
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• 제9권2호
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• pp.99-108
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• 2018

Proton exchange membrane (PEM) water electrolysis systems offer several advantages over traditional technologies including higher energy efficiency, higher production rates, and more compact design. In this study, all the experiments were performed with a self-designed PEM electrolyser operated at 1 atm and $25^{\circ}C$. Two types of electrolyte were used: (i) potassium hydroxide (KOH), and (ii) sulfuric acid ($H_2SO_4$). In the experiments, the voltage, current, and time were measured. The concentration of the electrolyte significantly affected the electrolyser performance. Overall the best case was with 15 wt% $H_2SO_4$ at the anode channel and 20 wt% at the cathode channel with. In addition, increasing the difference in concentration of the sulfuric acid had an effect on the diffusion. The diffusion flux became larger when the difference in concentration became larger, increasing electrolyser efficiency without the addition of extra energy.

• 한국산학기술학회논문지
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• 제10권11호
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• pp.3104-3109
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• 2009

정보수집용 ELINT 장비에서 전파의 방위를 정확하게 찾는 기술은 매우 중요하다. 신호도착 시간차(TDOA)를 이용하는 방위탐지 장치는 수신용 배열 안테나와 시간차 측정장치로 구성된다. TDOA 기술은 에미터 신호가 수신용 배열 안테나 시스템의 각각의 안테나에 도달하는 시간차를 계산하여 에미터의 방위를 산출하는 방법이다. TDOA 방식은 광대역 주파수에서 사용 가능하며 위상변별기나 주파수 측정기와 같은 복잡한 장치가 필요하지 않기 때문에 구성이 간단하다. 그러나 방위 탐지정확도를 높이기 위해서는 시간 측정 분해능이 좋아야하고 수신 안테나 배열간격이 길어야 한다. 본 논문에서는 실제 환경과 유사한 잡음을 고려한 환경에서 방위탐지 정확도를 모사하고 그 결과를 분석하였다.