• 한국대기환경학회지
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• 제26권1호
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• pp.85-93
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• 2010

$CF_4$ removal characteristics were investigated using an elongated arc reactor. The advantage of the elongated arc reactor includes direct use of treated gas as plasma operating gas and the enhancement of the removal reaction by using a thermo-chemistry and a plasma induced chemistry at the same time. Geometrical configurations, such as the length of the reactor and the shape of a throat, were tested to get an optimized removal efficiency with low power consumption. As results, over 95% of $CF_4$ removal was obtained with 300 lpm of total flowrate for various $CF_4$ concentration (0.1~1%). Corresponding specific energy density (SED), which means required electrical energy to treat the unit volume of treated gas, is about 3.5 kJ/L, The present technique can be applied to real applications by satisfying three major concerns, those are the high flowrate of treated gas, high removal efficiency (> 95%), and low power consumption (< 10 kJ/L).

• 한국연소학회:학술대회논문집
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• 한국연소학회 2006년도 제32회 KOSCO SYMPOSIUM 논문집
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• pp.144-148
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• 2006

Characteristics of a plasma reactor for partial oxidation of methane, especially focused on the role and effectiveness of plasma chemistry, is investigated. Partial oxidation of methane is investigated using a rotating arc which is a three dimensional version of a typical glidingarc. The rotating arc has both the characteristics of equilibrium and non-equilibrium plasma. Non-equilibrium characteristics of the rotating gliding arc can be increased by rotating an elongated arc string attached at both the tip of inner electrode and the edge of outer electrode. In this way, plasma chemistry can be enhanced and hydrogen selectivity can reach almost 100% that is much higher than thermal equilibrium condition. As a result, the present study enables the strategic approach of the plasma reforming process by means of appropriate reactor design to maximize plasma effect and resulting in maximized reaction efficiency.

• 한국대기환경학회지
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• 제26권6호
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• pp.683-689
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• 2010

Reforming of methane with carbon dioxide has been carried out using a bipolar pulse driven elongated arc reactor operating at atmospheric pressure and non-equilibrium regime. This plasma reactor is driven by two kinds of power supply, characterized by different voltage-current characteristics under the same operating power and frequency. Varying the $CO_2/CH_4$ ratio and the discharge power, the conversion rate, yield, and reforming efficiency for the two power supplies are investigated in conjunction with the static and dynamic behaviors of voltage and current. It is found that not only the values of voltage and current but also their shapes give an influence on the reforming performances. Finally, a better electrical operation regime for the efficient plasma reforming is proposed based on the relationship between the voltage-current characteristics and the reforming performance.

• 대한환경공학회지
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• 제35권5호
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• pp.356-362
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• 2013

암모니아 처리용 플라즈마 스크러버 공정 최적화 연구를 수행하였다. 여러 반도체공정 중 확산과 이온주입공정에서는 불가피하게 부산물로서 암모니아가 배출되며, 따라서 효율적인 건식처리공정기술이 필요하다. 플라즈마 처리공정은 연소공정에서 배출되는 NOx가 발생하지 않으며, 촉매공정에서 나타나는 비활성문제가 없다. 그러나 전기에너지를 사용하기 때문에 실제 적용을 위한 최적화 연구가 필요하며, 본 연구에서는 공정 최적화를 위한 해결책으로 회전아크 반응기의 모드제어에 대한 연구를 수행하였다. 기존 회전아크 반응기에 대한 스케일 업 및 그에 대한 모드 매핑을 수행하였다. 설계 반응기를 이용하여 암모니아 분해특성을 평가하였고, 최적화 설계가 가능한 것으로 나타났다. 또한 열교환기를 포함한 전체 스케일의 스크러버 실험에서 암모니아 분해공정이 보다 안정적이고, 효율적인 것으로 나타났다.

• Journal of Welding and Joining
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• 제31권6호
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• pp.71-76
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• 2013

Gas nitriding is a surface hardening process where nitrogen is introduced into the surface of a ferrous alloy. During fusion welding of nitrided carbon steel, the nitride inside weld metal is dissolved and generates nitrogen gas, which causes porosities - blow holes and pits. In this study, several laser welding processes such as weaving welding, two-pass welding, dual beam welding and laser-arc hybrid welding were investigated to elongate the weld pool to enhance nitrogen gas evacuation. The surface pits were successfully eliminated with elongated weld pool. However blowholes inside the weld metal were effective reduced but not fully disappeared.

• 한국대기환경학회지
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• 제29권1호
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• pp.27-37
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• 2013

CFCs (Chlorofluorocarbons) and HCFCs (Hydrochlorofluorocarbons) that are chemically stable were proven to be a greenhouse gases that can destroy ozone layer. On the other hand, HFCs (Hydrofluorocarbons) was developed as an alternative refrigerant for them, but HFCs still have a relatively higher radiative forcing, resulting in a large Global Warming Potential (GWP) of 1,300. Current regulations prohibit production and use of these chemicals. In addition, obligatory removal of existing material is in progress. Methods for the decomposition of these material can be listed as thermal cracking, catalytic decomposition and plasma process. This study reports the development of low cost and high efficiency plasma scrubber. Stability of steam plasma generation and effect of plasma parameters such as frequency of power supply and reactor geometry have been investigated in the course of the development. Method for effective removal of by-product also has been investigated. In this study, elongated rotating arc was proven to be efficient in decomposition of HFCs above 99% and to be able to generate stable steam plasma with steam contents of about 20%.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.1832-1834
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• 2005

In the electrical equipments, there are lots of phenomena such as loosening of connectin parts, So, heat generation and oxidation growth is considered to have a possibility to cause fire. In this Paper, we were carried out to study the oxidation growth and voltage waveform of connecting parts. In case of copper and copper connection, the growing of Cu2O elongated more than the other copper alloys. According to oxidation growth, the voltage waveform is distorted. And the contact voltage and the power dissipation increased rapidly.

• 한국주조공학회지
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• 제23권2호
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• pp.77-85
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• 2003

Some alloying elements such as Cr, B, Ti and Si were added individually or as a mixture to Fe-30 at.%Al alloys. The alloys were melted using an arc furnace and then heat-treated for homogenization at 1000$^{\circ}C$ for 7 days and followed by rolling at 1000$^{\circ}C$. The alloying elements on rolling characteristics were investigated by the microstructures and fracture mode before and after rolling. The microstructures before rolling showed that all of the alloys had equiaxed grains. On the other hand, the microstructures of rolling plane as well as its perpendicular plane became elongated after rolling. The alloys such as Fe-30Al, Fe-30Al-3Ti, Fe-30Al-0.5B, Fe-30Al-5Cr and Fe-30Al-3Ti-0.5B revealed better rolling behaviour from the point that intergranular and cleavage fractures were not fundamentally occurred. But the addition of 5Ti or 3Si to Fe-Al alloys had detrimental effects. The Ti-added alloy system such as Fe-30Al-5Ti, Fe-30Al-5Ti-5Cr, Fe-30Al-3Ti-5Cr and Fe-30Al-5Ti-0.5B were cracked through grain and showed cleavage fracture. The Si-added alloy system such as Fe-30Al-5Si, Fe-27Al-3Si and Fe-27Al-5Cr-3Si were cracked along the grain boundary and showed intergranular fracture. $DO_3{\leftrightarrow}B_2$ transition temperature of Fe-30at.%Al alloy was 520$^{\circ}C$, whereas the addition of 3Ti and 3Ti+0.5B comparably increased the temperature to 797 and 773$^{\circ}C$, respectively.

• Radiation Oncology Journal
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• 제9권2호
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• pp.351-359
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• 1991

LINAC 뇌정위적 방사선 수술은 주로 multiple noncoplanar arc를 이용한 single isocenter를 이용하고 있다. 이러한 방법에 의하면 구형선량 분포를 얻게 되는데, 뇌동정맥 기형이나 뇌종양의 경우 구형이 아닌 임의의 형태를 가진 경우도 많다. 본 논문에서는 임의의 병소형태에 대하여 multiple isocenters를 이용하여 병소모양과 같은 형태의 선량분포를 얻는 방법에 대하여 논하고져 한다. 적당한 조사변수들을 처음에 잘 선정하는 것은, 빠른 시간내에 최적선량 계획을 수행하는데 중요하다. 긴 병소모양에 대하여 같은 형태의 선량분포를 얻기 위한 isocenter 간격 및 조사면에 대한 guideline이 만들어졌다. 특히, 3차원 선량분포를 이용한 multiple isocenters의 응용에 대하여 논하여진다.

• 자원환경지질
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• 제39권3호
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• pp.235-253
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• 2006

해양탄성파 프로파일을 정밀수심 및 자력자료와 함께 해석하여, 일본열도가 분리되어 동해가 형성된 한반도의 대륙 주변부에서 진행된 리프팅과 지각의 분리 과정을 연구하였다. 한반도의 주변부는 바다쪽으로 리프트분지와 융기된 리프트 측면부, 그리고 경사가 급한 대륙사면이 연속된, 비활성 대륙주변부에서 전형적으로 볼 수 있는 기본적인 리프트구조로 이루어져 있다. 북쪽지역에서는 한반도로부터 연장되고 부분적으로 분절된 대륙지각인 한국대지에서 리프팅이 발생하였다. 한국대지는 상대적으로 넓은 신장지역을 제공하여 많은 수의 리프트를 형성하였다. 한국대지 내에서 두 개의 눈에 띄는 리프트 분지(온누리와 반달 분지)는 주된 synthetic 단층과 더 작은 규모의 antithetic 단층에 의해 형성되어 넓고 대칭적인 구조를 갖는다. 이들 분지에서 변위가 큰 경계단층지역은 볼록한 경사면을 가지며 주향방향으로 지그재그 모양을 보인다. 대조적으로, 남쪽 주변부에는 비대칭적인 반지구로서 하나의 좁은 리프트분지(후포 분지)가 길게 형성되어 있다. 한반도 주변부의 리프팅은 주향이동 운동에 의한 변위가 아니라 대륙사면의 기저부를 따라 발생하였다고 유추되는 지각의 분리에 수직하는 서쪽 및 남동방향의 신장의 결과인 정단층작용에 의해 주로 유도되었다고 해석된다. 리프팅 동안에는 화산작용이 거의 없었으나 해저면 확장의 초기단계에서는 상당한 화산작용이 수반되었으며 이것은 특히 남쪽지역에서 리프트에 의해 유도되는 맨틀대류뿐만 아니라 슬랩에 의해 유도되는 약권의 상승을 반영한다고 보여 진다. 동해의 생성과 관련된 한반도 주변부의 구조 및 화산운동은 후열도 환경에서의 약권 상승에 의해 영향을 받는 화산작용을 수반한 비활성 대륙주변부에서 일어나는 과정으로 설명할 수 있다고 해석된다.