• 대한기계학회논문집B
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• 제26권2호
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• pp.177-183
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• 2002

The field tests on the waterhammer were carried out in the pump pipeline system with an air chamber. The effects of the input variables and the design parameters for the air chamber were investigated by both the numerical calculations and the experiments. Because the waterhammer problems as a result of the pump power failure were the most important, these situations were carefully studied. Among the input variables used in the waterhammer analysis, the polytropic exponent, the discharge coefficient and the wavespeed had influence on the simulated results in that order, and were calibrated in comparison with the experimental results. As the initial air volume in a vessel increased, the period of waterhammer increased and the pressure variation decreased, resulting from the reduction of the rate of pressure change in the air chamber. Using smaller orifice in the bypass pipe, the pressure rise was suppressed in some degree and the pressure surge was dissipated more rapidly as time passed. The simulations were in fairly good agreement with the measured values until 1∼2 periods of waterhammer. Not only the maximum and minimum pressures in the pipe1ine but also those occurring times were reasonably predicted. The computer program developed in this study will be useful in designing the optimum parameters of an air chamber for the real pump pipeline system.

• 조명전기설비학회논문지
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• 제13권4호
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• pp.82-86
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• 1999

본 연구에서는 푸로브법과 교류중첩법을 이용하여 고주파 유도결합 플라즈마에서 전자에너지 분포함수를 측정하였다. 실험조건은 압력 10∼40[mTorr], 입력파워는 100∼600[W]이고, 가스유량은 3∼12[sccm]이며, 전자에너지 분포함수의 공간분포 측정에 있어서 아스펙트비(R/L)는 2로 하였다. 전자에너지 분포함수는 압력 및 입력파워에 대하여 강한 의존성을 나타내었고, 가스유량이 증가할수록 증가 하였다. 전자에너지 분포함수의 반경방향 분포는 플라즈마 중심에서 최대가 되었다. 전자에너지 분포함수의 축방향 분포는 석영창과 기판 사이의 중심에서 최대가 되었다. 이러한 결과는 고주파 유도결합 플라즈마의 생성 메커니즘 이해와 간단한 ICP(Inductively Coupled Plasma) 모델링 응용에 기여할 수 있을 것이다.

• 공업화학
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• 제34권4호
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• pp.404-411
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• 2023

바이오가스 직접 개질을 위해 플라즈마 방전영역을 확장할 수 있는 3상 글라이딩 아크 플라즈마 수소 추출기를 설계하고 스팀과 메탄의 부피 비율, 가스 유량, 플라즈마 입력 전력에 대해 개질 특성을 평가하여 운전 조건을 최적화했다. 수소생산효율은 플라즈마 에너지 밀도가 작을수록 증가하는 것으로 확인되었지만 C_XH_Y 혹은 carbon soot와 같은 촉매 내구성에 영향을 줄 수 있는 부산물들이 발생했다. 부산물 생성을 억제하기 위해 스팀과 메탄의 비율 혹은 플라즈마 에너지 밀도를 높여야 했고 플라즈마 개질기 최적 조건으로 스팀과 메탄의 비율을 3, 플라즈마 에너지 밀도를 5.5 ~ 6.0 kJ/L로 선정했다. 또한 플라즈마 개질기에서 발생하는 열이 반응가스를 500 ℃ 이상까지 올려줄 수 있어 바이오가스 버너의 연료사용량을 줄여 수소생산효율을 높일 수 있을 것으로 기대할 수 있다.

• 한국식품영양학회지
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• 제30권2호
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• pp.290-296
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• 2017

In this study, using the surface dielectric barrier discharge (DBD) produced at atmospheric pressure to improve the physiological activities of quercetin was investigated. Quercetin (at 200 ppm) was treated using air DBD with an input power of 250 W. The tyrosinase inhibition effect and total phenolic content of quercetin increased from 38.96 to 91.58% and from 134.53 to 152.93 ppm, respectively, after 20 min of plasma treatment. The antioxidant activity of quercetin treated for 20 min in the lipid models was higher than that of quercetin treated for 0, 5, and 10 min. Furthermore, plasma-treated quercetin exhibited antimicrobial activity against Listeria monocytogenes, Salmonella Typhimurium, and Staphylococcus aureus, whereas activity was not shown in the control. Structural modifications of the quercetin molecule induced by plasma might be responsible for the improvements in its physiological activity. These results indicate that DBD plasma could be used to enhance the physiological activity of quercetin for various applications in food.

• ETRI Journal
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• 제27권5호
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• pp.628-634
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• 2005

From AC analysis results utilizing a 2-dimensional device simulator, we extracted an AC-equivalent circuit of a grounded-gate NMOS (ggNMOS) electrostatic discharge (ESD) protection device. The extracted equivalent circuit is utilized to analyze the effects of the parasitics in a ggNMOS protection device on the characteristics of a low noise amplifier (LNA). We have shown that the effects of the parasitics can appear exaggerated for an impedance matching aspect and that the noise contribution of the parasitic resistances cannot be counted if the ggNMOS protection device is modeled by a single capacitor, as in prior publications. We have confirmed that the major changes in the characteristics of an LNA when connecting an NMOS protection device at the input are reduction of the power gain and degradation of the noise performance. We have also shown that the performance degradation worsens as the substrate resistance is reduced, which could not be detected if a single capacitor model is used.

• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.189-197
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• 2017

This paper elaborates two novel proposed topologies (type-I and type-II) of the high step-up DC-DC converter using switched inductor and voltage multiplier cell. The advantages of these proposed topologies are the less voltage stress on semiconductor devices, low device count, high power conversion efficiency, high switch utilization factor and high diode utilization factor. We analyze the Type-II topologies operating principle and mathematical analysis in detail in continuous conduction mode. High-intensity discharge lamp for the automotive application can use the derived topologies. The proposed converters give better performance when compared to the existing types. Also, it is found that the proposed type-II converter has relatively higher voltage gain compared to the type-I converter. A 40 W, 12 V input voltage and 72 V output voltage has developed for the type-II converter and the performances are validated.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.360-363
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• 2000

A half bridge type double resonant high frequency resonant inverter using PFM is described. This proposed inverter can reduce distribution of the switching current because of using the current of the serial resonant circuit to the input current of the parallel one. In the case of variable capacitance of the DC voltage source separated capacitor the analysis of inverter circuit has generally described by using normalized parameter and operating characteristics has been evaluated in terms of switching frequency and parameters. Based on the characteristics value a method of the circuit design is proposed. The theoretical results are in good agreement with the experimental ones. In the future this proposed circuit is considerated to be useful for induction heating and discharge lamp.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 추계학술대회 논문집
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• pp.21-23
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• 2007

In this paper a high efficiency bi-directional DC-DC converter for hybrid vehicles is proposed. The proposed converter a three-phase half-bridge interleaved ZVS converter, is designed to have high efficiency in the main operation range. The component ratings are calculated, the actual devices are selected, and the efficiency analysis has been performed to determine optimal ZVS range. The input and output current ripples are significantly reduced due to the interleaved operation. The dual loop control for the interleaved three-phase converter is also presented. To confirm the proposed convert ter, The simulation and experimental results are presented.

• 대한전기학회논문지
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• 제36권9호
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• pp.651-654
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• 1987

There are a number of small scale application fields of ozone, such as food conservation and/or storage in refrigerators, containers and storage rooms, deodorization in the production and living areas, protection against biohazards, bleaching of fabrics, etc. For these applications, miniaturization, ozone controllability and costdown of the ozonizer are the most essential points, whereas power efficiency is the most imporant factor in the case of a large scale ozonizer used in various industrial applications. It has been developed a novel sawtooth-to-cylinder type micro-ozonizer meeting above the three points by using a negative pulse corona discharge. As a result of the observations of pulse coronas affecting ozone generation, it is found that the maximum ozone concentration is generated at the pulse streamer coronas in both positive and negative case. The ozone concentration (20ppm/2l/min) generated by the negative pulse corona is about 2 times higher than that of the positive pulse corona, and could be controllable linearly by adjusting the dc input voltage of the [supply-inth ] cinventional small scale ozonizers. As a result, the present ozonizer is also very good to be used as a micro-ozonizer.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 학술대회 논문집 전문대학교육위원
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• pp.157-161
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• 2000

The electronic ballasts for low pressure discharge lamps are produced and commercialized. However, the electronic ballasts for high pressure lamps are now in progress because of poor reliability and high cost. The major case of troubles with electronic ballasts are thermal destruction of semiconductor output switches due to non ideal i-v characteristics of switch. The loss converts to heat and rises the temperature of switch and it increases proportionally to switching frequency and value of current and voltage. This study shows the variable frequency ballasts which can suppress the heating of switches efficiently. It is used for the limitation the switch current and the rising temperature of switch by impedance variation of lamp inductor. As a result, initial warm-up time of the proposed ballasts was faster than that of magnetic ballasts about 90 msec. Power factor of tested ballasts follow as ; input and output average of magnetic ballasts are 93 [%] and 86 [%], respectively, And proposed ballasts are 97 [%] and 99 [%], respectively.