• 한국항공우주학회지
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• 제47권2호
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• pp.90-97
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• 2019

스파크제트 액츄에이터는 플라즈마 합성 제트 액츄에이터(plasma synthetic jet actuator, PSJA)라고도 불리는 능동 유동 제어 장치로, 초음속 유동의 제어 가능성이 있어 많은 연구가 진행 중이다. 이 액츄에이터는 아크 플라즈마를 이용해 캐비티(cavity) 내부에 에너지를 주입하여 온도와 압력을 상승시킨다. 온도와 압력이 상승한 캐비티에서 오리피스(orifice)를 통해 압력파와 제트가 분출되어 외부 유동에 교란을 준다. 플라즈마의 영향으로 캐비티 유동은 고온, 고압의 평형 유동이 되기 때문에 스파크제트 액츄에이터의 유동 해석을 위해선 공기의 평형 상태를 고려해야 한다. 본 연구에서는 평형 유동의 특성을 고려하여 스파크제트 액츄에이터 유동 해석을 위한 수치해석 프로그램을 개발했다. 개발된 프로그램의 검증으로 문헌에서 얻을 수 있는 실험 결과와 시간에 따른 제트의 위치를 비교했다. 또한 상온, 상압의 무풍에서 액츄에이터의 추력 특성을 분석했다.

• 청정기술
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• 제19권2호
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• pp.113-120
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• 2013

화학적으로 안정한 과불화합물을 처리하기 위해서는 많은 양의 에너지를 필요로 한다. 이러한 단점을 극복하기 위해서 저전력 아크 플라즈마 시스템을 개발하였다. 분해대상은 $CF_4$, $SF_6$, $NF_3$가 플라즈마 토치로 직접 주입되었으며, 아크 플라즈마 토치의 열효율을 측정하여 실출력을 계산하였다. 실출력과 폐기체 유량 변화 그리고 추가적인 반응가스에 의한 분해효율을 확인하였다. 또한 열역학적 평형조성 분석을 수행하여 실험 결과와 비교하였다. 토치의 열효율은 60~66%의 결과를 보였으며 폐가스 유량이 증가함에 따라 분해효율이 감소하였고 입력전력이 늘어남에 따라 분해효율이 상승되었다. 추가적인 반응 가스가 없이 $CF_4$, $SF_6$, $NF_3$의 분해효율은 입력전력이 3 kW, 폐가스 유량이 70 L/min인 조건에서 각각 4, 15, 90%를 보였다. 반응가스로 산소와 수소를 이용하여 분해효율을 급격하게 증가시킬 수 있었으며, 실험 결과 산소보다 수소를 사용하였을 경우가 분해효율 상승효과와 부산물 제어에 효과적인 것을 알 수 있었다. 수소의 경우, 발생되는 부산물은 불화수소산이었으며 이는 일반적인 습식 스크러버를 이용하여 처리가 용이한 물질이다. 수소를 이용한 화학반응에서 입력전력이 3 kW, 폐가스유량이 100 L/min인 조건에서 $CF_4$가 25%, $SF_6$가 39%, $NF_3$가 99%의 분해효율을 각각 나타냈다.

• 한국연소학회지
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• 제13권4호
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• pp.47-53
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• 2008

The reaction mechanism of methane dry reforming has been investigated using an arc-jet reactor. The effects of input power, $CO_2/CH_4$ and added $O_2$ were investigated by product analysis, including CO, $H_2$, $C_{2}H_{Y}$ and $C_{3}H_{Y}$ as well as $CH_4$ and $CO_2$. In the process, input electrical power activated the reactions between $CH_4$ and $CO_2$ significantly. The increased feed ratio of the $CO_2$ to $CH_4$ in the dry reforming does not affect to the $CH_4$ conversion. but we could observe increase in CO selectivity together with decreasing $H_2$ generation. Added oxygen can also increase not only CO selectivity but also $CH_4$ conversion. However, hydrogen selectivity was decreased significantly due to a increased $H_{2}O$ formation.

• 천문학회보
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• 제36권1호
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• pp.87.2-87.2
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• 2011

We report our 110 ks Chandra observations of the supernova remnant (SNR) 0104-72.3 in the Small Magellanic Cloud (SMC). The X-ray morphology shows two prominent lobes along the northwest-southeast direction and a soft faint arc in the east. Previous low resolution X-ray images attributed the unresolved emission from the southeastern lobe to a Be/X-ray star. Our high resolution Chandra data clearly shows that this emission is diffuse, shock-heated plasma, with negligible X-ray emission from the Be star. The eastern arc is positionally coincident with a filament seen in optical and infrared observations. Its X-ray spectrum is well fit by plasma of normal SMC abundances, suggesting that it is from shocked ambient gas. The X-ray spectra of the lobes show overabundant Fe, which is interpreted as emission from the reverse-shocked Fe-rich ejecta. The overall spectral characteristics of the lobes and the arc are similar to those of Type Ia SNRs, and we propose that SNR 0104-72.3 is the first case for a robust candidate Type Ia SNR in the SMC. On the other hand, the remnant appears to be interacting with dense clouds toward the east and to be associated with a nearby star-forming region. These features are unusual for a standard Type Ia SNR. Our results suggest an intriguing possibility that the progenitor of SNR 0104-72.3 might have been a white dwarf of a relatively young population.

• 한국표면공학회지
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• 제43권2호
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• pp.80-85
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• 2010

The surfaces of WC-Co and SCM415 were etched to form a micro size protrusion for oil based ultra low friction applications using an ion bombardment process in a filtered vacuum arc plasma. WC-Co species showed that a self-patterned surface was available by the ion bombarding process due to the difference of sputtering yield of WC and Co. And the increasing rate of roughness was 0.6 nm/min at -600 V substrate bias voltage. The increasing rate of roughness of SCM415 species was 1.5 nm/min at -800 V, but the selfpatterning effect as shown in WC-Co was not appeared. When the SCM415 species pretreated by electrical discharge machining is etched, the increasing rate of roughness increased from 1.5 nm/min to 40 nm/min at -800 V substrate bias voltage and the uniform surface treatment was available.

• Advances in materials Research
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• 제9권1호
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• pp.1-14
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• 2020

The hybrid method of three-dimensional ion implantation and electric arc is presented as a novel plasma-ion technique that allows by means of high voltage pulsed and electric arc discharges, the bombardment of non-metallic and metallic ions then implanting upon the surface of a solid surface, especially out of metallic nature. In this study AISI/SAE 4140 samples, a tool type steel broadly used in the industry due to its acceptable physicochemical properties, were metallographically prepared then surface modified by implanting titanium and simultaneously titanium and nitrogen particles during 5 min and 10 min. The effect of the ion implantation technique over the substrate surface was analysed by characterization and electrochemical techniques. From the results, the formation of Ti micro-droplets upon the surface after the implantation treatment were observed by micrographs obtained by scanning electron microscopy. The presence of doping particles on the implanted substrates were detected by elemental analysis. The linear polarization resistance, potentiodynamic polarization and total porosity analysis demonstrated that the samples whose implantation treatment with Ti ions for 10 min, offer a better protection against the corrosion compared with non-implanted substrates and implanted at the different conditions in this study.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권2호
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• pp.76-82
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• 2005

In this paper, a method for analyzing the thermal recovery characteristics of the nozzle of gas circuit breaker was described. In order to obtain thermal recovery characteristics, the transient simulation of SF6 arc plasma within the nozzle was carried out. In particular, the nozzle ablation was taken into account by simultaneously solving the PTFE concentration equation with the governing equations such as continuity, momentum and energy equation. After that, post arc current calculation was performed with the rate of rise of recovery voltage changed. From the calculated post arc current, it was possible to suggest the thermal recovery characteristics of the nozzle of gas circuit breaker.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.201-207
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• 2010

In this study, we calculated arc discharges happened in high-voltage circuit breakers for understanding the complex physics and the probability of thermal breakdown. The four main parts of arc model for this virtual-reality are radiation, PTFE abaltion, Cu evaporation and turbulence. Among these important parts the turbulence model can be critical to the reliability of computation results during high-current period because the plasma flow is affected by high eat energy and mass momentum. Two kinds of turbulence model, zero-equation model and two-equation model, are applied for these calculations and are compared with the measured pressure data inside a chamber.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권11호
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• pp.527-532
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• 2005

During the last ten years the new interruption techniques, which use the arc energy itself to increase the pressure inside a chamber by the PTFE nozzle ablation, have displaced the puffer circuit breakers due to reduced driving forces and better maintainability. In this paper, we have investigated the thermal flow characteristics inside a thermal puffer type gas circuit breaker by solving the Wavier-Stokes equations coupled with Maxwell's equations for considering all instabilities effects such as turbulence and Lorentz forces by transient arc plasmas. These relative inexpensive computer simulations might help the engineer research and design the new interrupter in order to downscale and uprating the GIS integral.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.498-498
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• 2012

직류 아크 토치를 이용하여 열플라즈마를 발생시키는 방법은 전극의 구성에 따라 크게 비이송식(non-transferred)과 이송식(transferred)의 2가지 형태로 나눌 수 있다. 1950년대 H. Maecker 등에 의해 이론적 기초가 형성되기 시작한 이송식 아크 플라즈마 발생장치는 처리 대상물질을 전극으로 사용하여 양극에서의 에너지 전달을 직접 이용할 수 있으므로 열효율이 매우 높기 때문에 이를 이용한 고출력 토치에 관한 활발한 연구가 지속되고 있다. 본 연구에서는 대기압 아르곤 자유연소아크 방전에 의해 발생되는 열플라즈마의 열유동 특성을 수치적으로 해석하기 위하여 아크 기둥의 온도, 압력 및 속도 특성을 Navier-Stokes 방정식과 Maxwell 방정식을 연계 계산하였다. 또한 아크-전극 상호작용(arc-electrode interaction) 모델링을 통한 양극(anode)인 처리 대상물질로의 에너지 플럭스 유입을 고려하여 전극 내부의 온도분포를 계산하였다. 해석결과를 검증하기 위하여 음극과 양극 사이 플라즈마 기둥(column)의 중심축 온도는 Haddad & Farmer(1984)의 실험데이터와 비교하였고, 양극으로의 에너지 플럭스 및 온도분포 데이터는 Bini 등(2006)의 실험 및 해석데이터와 비교하여 만족스런 일치를 확인하였다.