• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1975-1977
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• 2000

In this study, a relationship between AC discharge progress and the radiated electromagnetic waves were investigated by measuring electromagnetic waves using a biconical antenna and a spectrum analyzer. The characteristics of frequency spectrum of the radiated electromagnetic waves was measured at the atmospheric pressure in liquid nitrogen($LN_2$) during partial discharges progress in nonuniform electric field depend on AC power supply. From this results, it was confirmed that when partial discharge was produced in liquid nitrogen, the signal of partial discharge was detected by frequency spectrum of the radiated electromagnetic waves. It is considered that these results obtained from this investigation may be used as fundamental data for diagnosis and prediction of insulation on superconducting and cryogenic power equipments.

• 조명전기설비학회논문지
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• 제17권3호
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• pp.49-55
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• 2003

본 논문에서는 고온 초전도체의 냉매로서 주목받고 있는 액체질소 중에서 고체절연물 표면의 연면 방전과 트래킹 현상에 관하여 연구하였다 액체질소중 연면 방전에 많은 영향을 주는 기포 효과를 연구하기 위해 Knife형태의 전극과 평판형태의 전극을 사용하여 A-mod, B-mode, C-mode의 전극배치형태를 각각 구성하였다. 본 실험의 결과는 향후 연구되고 개발될 초전도·극저온 전력설비의 절연설계의 기초 데이터를 제공할수 있다고 판단된다.

• 한국환경과학회지
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• 제23권3호
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• pp.369-378
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• 2014

Effect of improvement of the dielectric barrier discharge (DBD) plasma system on the inactivation performance of bacteria were investigated. The improvement of plasma reactor was performed by combination with the basic plasma reactor and UV process or combination with the basic plasma reactor and circulation system which was equipped with gas-liquid mixer. Experimental results showed that tailing effect was appeared after the exponential decrease in basic plasma reactor. There was no enhancement effect on the Ralstonia Solanacearum inactivation with combination of basic plasma process and UV process. The application of gas-liquid mixing device on the basic plasma reactor reduced inactivation time and led to complete sterilization. The effect existence of gas-liquid mixing device, voltage, air flow rate (1 ~ 5 L/min), water circulation rate (2.8 ~ 9.4 L/min) in gas-liquid mixing plasma, plasma voltage and UV power of gas-liquid mixing plasma+UV process were evaluated. The optimum air flow rate, water circulation rate, voltage of gas-liquid mixing system were 3 L/min, 3.5 L/min and 60 V, respectively. There was no enhancement effect on the Ralstonia Solanacearum inactivation with combination of gas-liquid mixing plasma and UV process.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.114-118
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• 2002

This paper were investigated discharge characteristics in the Liquid Nitrogen($LN_{2}$) noticed as a cooling medium of high temperature superconductor, and the characteristics of surface discharge and tracking phenomena on the solid insulators of cryocable. In order to investigate the bubbles which have much influence on electric surface discharge in Liquid Nitrogen, knife type electrode and plane electrode was formed oppositely with mode A and B, C configuration. It is considered that these result are fundamental data for electric insulation design of superconductivity and cryogenic application machinery which will be studied and developed in the future.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 춘계학술대회 논문집
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• pp.178-184
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• 1996

Electrical properties such as surface flashover discharge and discharge degradations of insulating materials for superconducting cable have been investigated. It is found that the surface voltage is proportional to /$\^$0.7/(/: discharge length) in LHe(Liquid Helium). V-t characteristic LHe were a n=5.5 that was less than liquid N$_2$. After applied AC voltage, the surface condition of polymer films were observed non-eroded area and eroded area. The eroded area is depending on the applied voltage. In case of LHe, the crack was observed.

• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.647-652
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• 2015

A fully coupled finite element analysis (FEA) technique was developed for analyzing the discharge phenomena and dielectric liquid flow while considering surface charge density effects in dielectric flow guidance. In addition, the simulated speed of surface charge propagation was compared and verified with the experimental results shown in the literature. Recently, electrohydrodynamics (EHD) techniques have been widely applied to enhance the cooling performance of electromagnetic systems by utilizing gaseous or liquid media. The main advantage of EHD techniques is the non-contact and low-noise nature of smart control using an electric field. In some cases, flow can be achieved using only a main electric field source. The driving sources in EHD flow are ionization in the breakdown region and ionic dissociation in the sub-breakdown region. Dielectric guidance can be used to enhance the speed of discharge propagation and fluidic flow along the direction of the electric field. To analyze this EHD phenomenon, in this study, the fully coupled FEA was composed of Poisson's equation for an electric field, charge continuity equations in the form of the Nernst-Planck equation for ions, and the Navier-Stokes equation for an incompressible fluidic flow. To develop a generalized numerical technique for various EHD phenomena that considers fluidic flow effects including dielectric flow guidance, we examined the surface charge accumulation on a dielectric surface and ionization, dissociation, and recombination effects.

• International Journal of Precision Engineering and Manufacturing
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• 제9권3호
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• pp.18-21
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• 2008

The study deals with the effects of parameters in the synthesis of carbon nanotubes in liquid nitrogen to find the most appropriate conditions such as electrical voltage and time that give carbon nanotubes with large volume and less proportion of impurity, which is a non-nanotubed carbon. The experiment employed the method of arc-discharge between graphite cathode and anode which are immersed in liquid nitrogen. The electrical DC current of 60A and 70A were applied with the time period ranging from 10 seconds to 25 seconds. It was found that the electrical current of 60A and 13 seconds arc-discharge time allowed the largest volume of carbon nanotubes generation. The longer time leads to more impurities around the carbon nanotubes. By the filtration of CNTs-suspended solution using 0.2 micrometers porous paper filter and the characterization using TEM, the carbon nanotubes synthesized in the study were approximately 25 layers multi-walled nanotubes with the average diameter of 18.2 nanometers.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 E
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• pp.1669-1671
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• 1997

Liquid nitrogen has many adventages. It is cheaper than other cooling medium. It is easy to obtain high purity. It's utilized with easy. In future, liquid nitrogen is able to be accepted cooling medium for the superconducting and cryogenic applicated equipments. Cryogenic liquid may be atmospheric pressure state because thermoinsulation is ineffective, airtight decreasing by long time using and bubble occured by flowing current. If it is to be atmospheric pressure state, the electrical insulation strength is dropped and processed partial discharge, finally breakdown. Processing of breakdown has anticipated by measuring radiated-electromagnetic wave which is happened in time of breakdown. There is a measurement of radiated electromagnetic wave as a method that proceeding breakdown is anticipated. In this paper, radiated electromagnetic wave was measured in arc discharge by above conditions as a basic experiment.

• 한국인터넷방송통신학회논문지
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• 제24권4호
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• pp.129-134
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• 2024

본 논문에서는 적외선 센서, 레이저 센서, 초음파 센서, 정전용량 센서로 실험을 통해 수위의 변화를 선형적으로 감지할 수 있는 수위센서를 이용한 액적 토출 시스템을 연구하였다. 전원 공급으로 SMPS, 레귤레이터 5V, LDO 3.3V를 설계하였으며 수위 센서 입력부 ADC 회로와 마이크로프로세서를 이용하였다. 또한 솔레노이트 밸브 제어, 양압/음압 발생을 위한 펌프 출력 제어부와 산업용 통신을 위한 CAN 통신, 이터넷 통신, UART 통신, USB를 사용하였다. 수위의 변화를 통해 압력의 변화를 확인하였으며, 압력의 변화를 최소화하여 액적 토출을 위한 시스템을 구현하였다.

• 한국분무공학회지
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• 제25권3호
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• pp.95-102
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• 2020

Six shear coaxial injectors for a 3 tonf-class liquid rocket engine using oxygen and methane as propellants were designed and manufactured by considering geometric design parameters such as a recess length and a taper angle. Cold-flow tests on the injectors were performed using water and air as simulants. By changing the water mass flow rate and air mass flow rate, the injection pressure drop under single-injection and bi-injection was measured. The discharge coefficients through the injector oxidizer-side and fuel-side were calculated and the discharge coefficient ratio between bi-injection and single-injection was obtained. Under single-injection, the recess served to reduce the injection pressure drop on the injector fuel-side. For the injectors without recess, the discharge coefficients under bi-injection were almost the same as those under single-injection. However, for the injectors with recess, the taper angle and bi-injection had a significant effect on the discharge coefficient.