• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 C
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• pp.1559-1561
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• 1994

At present, the principle of puffer action in high current interruption is adopted in almost of the EHV(Extra High Voltage) and UHV(Ultra High Voltage) GCB(Gas Circuit Breakers). The thermal interruption capability of these GCBs critically depends on the pressure rise in the puffer cylinder at current zero. The pressure rise in the puffer cylinder depends on the puffer cylinder volume, flow passage and leakage area in the interrupter, stroke curve etc. Recently commercial CFD(Computational Fluid Dynamics ) packages have been widely adopted to calculate the pressure distribution in the interrupter. However, there are still several problems with it, e.g. very expensive price, moving boundary problem, computation time, difficulty in using the package etc. Thus, the calculation of the puffer cylinder pressure in simple and relatively correct method is essential in early stage of GCB design. In these paper, the model ing technique and computed results for EHV class GCB (HICO, 145kV 40kA and 362kV 40kA GCB) are presented and compared with available measured results.

• 센서학회지
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• 제13권6호
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• pp.462-472
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• 2004

In this study, we measured the blood flow on arm by non-invasive method and implemented a system to measure variation of the blood flow by estimating bio-electrical impedance and arterial pressure according to cuff pressure. The implemented system measured impedance variation according to pressure variation applied by artificial cuff pressure on the measuring position. The system consisted of pressure measuring part and impedance measuring part using 4-electrode method. Pressure measuring part was composed of semiconductor pressure sensor and electronic circuit for signal processing of sensor output signal. In addition, impedance measuring part was composed of constant current source circuit and lock-in amplifier for detecting impedance signal. We conducted experiments of impedance measuring part using standard resistance for performance evaluation of the implemented system. In addition we experimented to estimate variation of the blood flow by measuring impedances of the experimental group. We estimated ratio of the blood flow resistance using mean arterial pressure and variation of the blood flow. As a result the ratio of the blood flow resistance and variation of blood flow were in an inverse relationship with each other and the correlation coefficient was -0.96776.

• 한국화재소방학회논문지
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• 제16권3호
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• pp.8-11
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• 2002

전기배선계통에 있어서 접속점의 접속 접촉불량과 순간단락 시 발생하는 스파크와 열축적은 절연물의 용착과 탄화현상을 발생하여 전기화재의 주요 원인이 되고 있다. 또한 접속점의 접속·접촉불량과 순간단락 시 발생하는 전류는 일종의 써지(Surge)전류가 되어 통신, 가전제품, 컴퓨터 그리고 각종 측정기기의 소손 및 고장을 일으키며, 특히 접속점의 접속·접촉불량과 순간단락은 다양한 현상을 나타내어 안전점검시 발견이 매우 어려운 실정이다. 따라서, 본 논문에서는 누전차단기(Earth Leakage Breaker)의 보조 제어장치, 즉 전기화재예방 제어장치(Electrical Fire Prevention Control Device)를 개발하여, 상기 접속점의 접속·접촉불량과 순간 단락 시 누전차단기의 동작신뢰성을 제고시켜, 스파크와 접속점의 과열에 의한 전기화재를 예방하고자 한다.

• Journal of Biosystems Engineering
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• 제27권1호
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• pp.11-18
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• 2002

One of the major obstructing factors against managing dairy farm in Korea has been a shortage of roughage supply, which resulted in excessive abuse of concentrate feed. In order to solve this problem, production of the wrap silage by the winter cereal forages raised in the fallow paddy field is strongly recommended in Korea. The main objective is to develop a tractor attached round bale wrapper which can process the silage by wrapping the round bales with thin plastic films. This is the first half of the study which is divided by two parts. In this first part, bale wrapping process was analyzed, and based on this results the followings were designed, developed and tested. 1. Bale wrapper which haying the maximum capacity of 1 ton bale with various functions such as loading, wrapping, discharging the round bales and supplying and cutting wrap films was designed. 2. An actuator and its hydraulic circuit of each process were developed and tested. 3. Also, the variations of hydraulic pressure and engine speed were investigated by operating bale wrapper developed. In this test, maximum pressure of the hydraulic circuit for the bale wrapping was 130 kg/㎠ when it raised the bale, which was quite below the relief pressure of 170 kg/㎠ of hydraulic circuit. In the engine speed test, speed drop was 20∼67 rpm, which meant that there was no over-load operation. Therefore, the experiment proved that developed hydraulic circuit and mechanism is stable in bale wrapping operation

• 대한기계학회논문집B
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• 제21권11호
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• pp.1458-1465
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• 1997

This study investigated the effects of pressure on the growth of an impinging spray. We obtained the frozen images which were scattered by Nd ; YAG laser light (pulse width : 7 ns) using synchronization circuit made in the laboratory. For an impinging spray a growth of the penetration length was progressed with increase of the injection pressure but an ambient pressure restrained its growth. The effect of an ambient pressure on penetration was larger than that of an injection pressure. The pressure ratio had an effect on the penetration growth rate. The thickness growth rate depended on both the injection pressure and the ambient pressure compositively. A lower injection pressure or a higher ambient pressure was required for spatial distribution of impinging spray.

• 한국소음진동공학회논문집
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• 제17권8호
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• pp.757-765
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• 2007

Enhanced PSPICE circuit model for vented-box loudspeaker system with lumped parameters was proposed to more accurately simulate real vented-box loudspeaker system. Frequency dependent parameters were used to model voice coil inductor. Acoustic pressure response curves and electrical impedance curves were simulated and investigated by PSPICE circuit model according to circuit parameters' variations. Finally, it was used to identify faults detection in woofers manufactured by unskilled persons.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.695-698
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• 2008

Self-blast circuit breakers utilize the energy dissipated by the arc itself to create the required conditions for arc quenching during the current zero. During the arcing period, high pressure, temperature and radiation of the arc could burn in pure SF6 gas and PTFE nozzle. Ablated nozzle shape and $SF_6$-PTFE mixture vapor affect the performance of an self-blast circuit breaker. After a number of tests, nozzle in circuit breaker is disassembled, a section of ablated nozzle is investigated precisely. Using computational fluid dynamics, the conservation equation for the gas and temperature, velocity and electric fields within breaker is solved. Before applying a section model, developed program is verified with experimental data. Performance of ablated nozzle shape is compared with original model through analysis program.

• 한국표면공학회지
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• 제34권5호
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• pp.378-383
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• 2001

An out line of the material process with using the atmospheric pressure glow plasma is described as follows : (1) TiO powder coating with SiO$_2$ (2) Surface treatment of Fluorinated polymers and (3) Surface cleaning of electronic circuit board with using splay type.

• 대한기계학회논문집
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• 제15권6호
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• pp.1872-1885
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• 1991

본 연구에서는 자기장의 상호작용을 고려해야 하며 본 연구에서는 유한요소법 을 이용하여 전자기장 해석을 함으로써 이 문제를 해결하였다. 또한 여기서 계산된 자기압력을 이용하여 피가공재의 동적변형 거동을 유한요소법으로 해석하였다.

• KIEE International Transactions on Electrophysics and Applications
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• 제2C권5호
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• pp.246-252
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• 2002

Two-dimensional steady state simulations of planar type radio frequency inductively coupled plasma (RFICP) have been performed. The characteristics of RFICP were investigated in terms of power transfer efficiency, equivalent circuit analysis, spatial distribution of plasma density and electron temperature. Plasma density and electron temperature were determined from the equations of ambipolar diffusion and energy conservation. Joule heating, ionization, excitation and elastic collision loss were included as the source terms of the electron energy equation. The electromagnetic field was calculated from the vector potential formulation of ampere's law. The peak electron temperature decreases from about 4eV to 2eV as pressure increases from 5 mTorr to 100 mTorr. The peak density increases with increasing pressure. Electron temperatures at the center of the chamber are almost independent of input power and electron densities linearly increase with power level. The results agree well with theoretical analysis and experimental results. A single turn, edge feeding antenna configuration shows better density uniformity than a four-turn antenna system at relatively low pressure conditions. The thickness of the dielectric window should be minimized to reduce power loss. The equivalent resistance of the system increases with both power and pressure, which reflects the improvement of power transfer efficiency.