• Journal of Welding and Joining
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• 제30권2호
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• pp.70-75
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• 2012

In this study, effect of nitrogen volume in the shielding gas of Ar-$N_2$ mixing gas on the bead shape, hardness and microstructure of GTA welds of 3mm thick Commercial Pure Ti was investigated. As the nitrogen volume increased, the welding current for full penetration was reduced and hardness in the fusion zone significantly increased compared with that of the base metal, but there is no difference in the hardness of HAZ. Microstructure in the fusion zone with pure Ar gas changed from equiaxed alpha of the base metal to serrated alpha. On the other hand, microstructure using Ar-$N_2$ mixing gas changed to acicular alpha. With the increasing of nitrogen content, the amount of acicular alpha increased and the size of that was fine.

• 전기학회논문지
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• 제59권10호
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• pp.1850-1855
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• 2010

The application field of the pulse power is very wide. Recently, Pulse power technologies take a large place in several applications. Then, many civil and military applications proceed. Marx generator is widely used in high voltage applications. Marx generator is widely used in high voltage applications, such as eletromagnetic wave and power lasers. This paper, we described about the high voltage pulse generator. A compact size high voltage pulse generator with nanosecnd rise time has been fabricated and investigated experimentally. The marx generator has 2 stages. Each stage was constructed one charging capacitor, two electrodes and one charging resistor. A inductance structure is used in order to improve the switching performances fo the whole generator. The experiments of rise time in pure gas and mixtures of gases were described. We tested the Marx generator at different insulation gas. the results show that the dielectric strength of the $N_2-SF_6$ mixture was significantly increased compared with pure nitrogen gas. The experimental results show that the rise time characteristics of the Marx generator can be controlled through varying insulation gas.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.549-552
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• 2009

Methane hydrate is crystalline ice-like compounds which formed methane gas enters within water molecules composed cavity at specially temperature and pressure condition, and water molecule and each other from physically-bond. $1m^3$ hydrate of pure methane can be decomposed to the maximum of $172m^3$ at standard condition. If these characteristics of hydrate are reversely utilized, natural gas is fixed into water in the form of hydrate solid. Therefore the hydrate is considered to be a great way to transport and store natural gas in large quantity. Especially the transportation cost is known to be 18~24% less than the liquefied transportation. However, when methane hydrate is formed artificially, the amount of consumed gas is relatively low due to a slow reaction rate between water and methane gas. In this study, for the better hydrate reaction rate, there is make nano fluid using ultrasonic dispersion of carbon nano tube. and then, Experiment with hydrate formation by nano fluid and methane gas reaction. The results show that when the carbon nano tubes of 0.004 wt% was added to pure water, the amount of consumed gas was about 300% higher than that in pure water and the hydrate formation time decreased.

• 한국초전도ㆍ저온공학회논문지
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• 제11권2호
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• pp.1-6
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• 2009

We report a successful fabrication of $high-J_c\;NdBa_2Cu_3O_{7-{\delta}}$ (NdBCO) films on $SrTiO_3$(STO) (100) substrates by pulsed laser deposition (PLD) in a relatively wide processing window. Under various oxygen pressures controlled by either 1%$O_2$/Ar mixture gas or pure $O_2$ gas, strongly c-axis oriented NdBCO films were grown at the substrate temperature $(T_s)\;of\;800^{\circ}C$ in 800 mTorr with 1%$O_2$/Ar gas and also in 400 and 800 mTorr with pure $O_2$ gas. These samples exhibited $T_c$ values over 90K and $J_c$ values of $2.8-3.5MA/cm^2$ at 77K in self-field (77K, sf). On the other hand, $J_c$ values over $1A/cm^2$ were obtained at the temperature regions of $700-830^{\circ}C$ in 800 mTorr with 1%$O_2$/Ar gas at those of $750-830^{\circ}C$ in 800 mTorr with pure $O_2$ gas. Unlike previous reports, resent results support that the PLD processing window for high-Jc NdBCO films is not narrow.

• 한국가스학회지
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• 제8권3호
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• pp.24-30
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• 2004

본 연구에서는 개선된 view cell 실험 장치를 통하여 가스 하이드레이트 생성 과정을 관찰하고 이의 동특성을 고찰하였다. 순수한 물과 촉진제로 음이온계 계면활성제를 미량 첨가한 물에 천연가스를 넣어 가스 하이드레이트를 생성 과정을 관찰하였다. 본 실험에서 사용한 276.65 K, 6 MPa 조건 상태에서는 충분한 지체 지연 시간이후 물에 순간 교반을 줌으로써 형성자 생성을 쉽게 유도할 수 있었다. 가스 하이드레이트 필름의 생성은 정적상태에서 가스와 접촉된 물의 표면에 생성되었다. 이는 육안으로 구분하기 어려운 매우 얇은 막이 수초 안에 물의 표면 전체를 덮는 선행과정과 이후 다시 육안관찰이 쉬운 필름층이 재생성되었다. 순수한 물에는 짧고 굵은 섬유 다발의 형태로 끝 부분이 둥글게 말려서 결정이 형성된 모습인 반면 촉진제를 넣은 경우 작은 섬유 다발 형태로 길게 생성되었고 다른 다발과 접촉되어 엉킨 결정 상상을 보였다.

• 마이크로전자및패키징학회지
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• 제5권1호
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• pp.1-6
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• 1998

Two kinds of the ac-plasma display panel (PDP) with the comb type and the matrix type electrodes were fabricated. The discharge properties were studied as a function of as species (Ne and Ne+He+Xe) and its pressure. The firing voltages (Vf) of the PDP with comb type electrodes were 159 V and 195 V under pure Ne and ne+He+Xe(68:30:2) gas mixture respectively. In case of PDP cell with the matrix type electrodes the Vf was increased to 200 V for pure Ne and 240 V for Ne+He+Xe gas mixture under the same gas pressure(300 mbar).

• 센서학회지
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• 제19권1호
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• pp.58-61
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• 2010

This paper describes the fabrication and characteristics of NO sensor using ZnO thin film by RF magnetron sputter system. The sensitivity, working temperature, and response time of sputtered pure ZnO thin film and added catalysts such as Pt, Pd, Al, Ti on those films were measured and analyzed. The sensitivity of pure ZnO thin film at working temperature of $300^{\circ}C$ is 0.875 in NO gas concentration of 0.046 ppm. At same volume of the gas in chamber, measuring sensitivity of 1.87 at $250^{\circ}C$ was the case of Pt/ZnO thin film. The ZnO thin films added with catalyst materials were showed higher sensitivity, lower working temperature and faster adsorption characteristics to NO gas than pure ZnO thin film.

• 한국가스학회지
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• 제19권2호
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• pp.37-44
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• 2015

본 연구에서는 CBM의 1차 생산뿐 아니라 $CO_2$나 $N_2$ 주입을 통한 ECBM, 혹은 지중저장을 목적으로 석탄층에 $CO_2$를 주입할 때 발생할 수 있는 암체의 부피변화 영향을 고려하여 기존의 Langmuir 흡착 관계식을 개선하였다. 본 모델의 검증을 위해 $CO_2$나 $CH_4$, $N_2$의 단일성분 흡착실험 데이터에 기존 Langmuir 모델값과 본 모델의 결과값을 비교하였다. 그 결과, 기존 모델에서는 흡착용량이 큰 석탄일수록, 흡착친화도가 큰 가스일수록 실험값과 모델값 사이의 오차가 커지는 경향이 나타났지만 본 모델에서는 모든 조건에서 실험결과를 잘 묘사하였고 본 모델을 통해 예측한 부피변형률 역시 실험값과 유사함을 확인하였다. 이렇게 개선된 단일성분 흡착모델을 혼합가스의 흡착모델인 IAS 모델에 적용하여 부피변화가 고려된 IAS모델로 개선하였다. 그 결과 혼합가스에 대한 흡착거동 역시 기존 모델에 비해 정확도를 높였고 이는 Hall 등(1994)이 수행한 혼합가스의 흡착실험결과와의 매칭을 통해 확인하였다.

• The Korean Journal of Ceramics
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• 제4권2호
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• pp.103-113
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• 1998

By using a gas-tight electrochemical cell, we can perform high-temperature coulometric titration and measure electronic transport properties to determine the elecronic defect structure of metal oxides. This technique reduces the time and expense required for conventional thermogravimetric measurements. The components of the gas-tight coulometric titration cell are an oxygen sensor, Pt/yttria stabilitized zirconia(YSZ)/Pt, and an encapsulated metal oxide sample. Based on cell design, both transport and thermodynamic measurements can be performed over a wide range of oxygen partial pressure ($pO_2=10^{-35}$ to 1 atm). This paper describes the high-temperature gas-tight electrochemical cells used to determine electronic defect structures and transport properties for pure and doped-oxide systems, such as YSZ, doped and pure ceria $(Ca-CeO_2 \;and\; CeO_2)$, copper oxides and copper-oxide-based ceramic superconductors, transition metal oxides, $SrFeCo_{0.5}O_x,\; and \;BaTiO_2$.

• 열처리공학회지
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• 제22권2호
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• pp.88-94
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• 2009

The effect of high temperature gas nitrding (HTGN) on the surface microstructure in pure Ti was investigated. Two phases of TiN and $Ti_2N$ appeared at the outmost surface, and the wide ${\alpha}$-Ti layer was formed at the next layer. On the other hand, the interior region, where the nitrogen was not permeated, exhibited ${\alpha}$'phase. The outmost surface of TiN and $Ti_2N$ showed the maximum hardness of 1000Hv, while the interior ${\alpha}$'phase was ${\sim}350$ Hv. The permeation depth of nitrogen increased with increasing the gas nitriding temperature and time. The nitrogen concentration of the surface layer seems to be over 12.7% at $1100^{\circ}C$.