• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.300-303
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• 1991

Sulphur-hexafluoride has extensively been used as an insulating gas of electric power equipment in substation for its high dielectric strength, non-toixity and non-flammable properties. But it is very expensive and is liquidizable under the condition of low temperature and high pressure. And it is very sensible to the locally high electric field strength. To resolve these problems, we studied 50% FOV and V-t characteristics of $SF_6-N_2$ mixtures under positive and negative lightning impulses using a 25mm rod-plane gap. 50% FOV of $SF_6-N_2$ 50% mixture was about 85% of pure $SF_6$ and it was known that $SF_6-N_2$ mixtures can be used as an economic substitution insulating gas for $SF_6$.

• 한국재료학회지
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• 제15권8호
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• pp.496-502
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• 2005

Green-light emitting $BaMgAl_{10}O_{19}:Mn^{2+}$ (BAM:Mn) phosphor particles were prepared by spray Pyrolysis. The effect of reactor temperature and flow rate of carrier gas in the spray Pyrolysis on the morphology, crystallinity and photoluminescence characteristics under vacuum ultraviolet were investigated. The morphology of the as-Prepared Particles obtained by spray Pyrolysis had spherical shape and non-aggregation characteristics regardless of the reactor temperature. The spherical shape of the as-prepared Particles obtained by spray pyrolysis at low temperature disappeared after Post-treatment. On the other hand the as-Prepared Particles obtained by spray Pyrolysis at $1600^{\circ}C$ maintained spherical shape and non-aggregation characteristics after post-treatment at $1400^{\circ}C$ for 3 h under reducing atmosphere. The BAM:Mn Phosphor Particles Prepared by spray Pyrolysis at different reactor temperatures had pure crystal structure and high photoluminescence intensities under vacuum ultraviolet after post-treatment. BAM:Mn phosphor particles prepared by spray Pyrolysis at low How rate of carrier gas had complete spherical shape and filed morphology and high photoluminescence intensity after post-treatment under reducing atmosphere.

• 한국결정성장학회지
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• 제14권5호
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• pp.220-225
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• 2004

Four different Fluorine-based gases ($SF_6/,NF_3, PF_5,\; and \; BF_3$) were examined for high rate Inductively Coupled Plasma etching of Si. Etch rates up to ~8$\mu\textrm{m}$/min were achieved with pure $SF_6$ discharges at high source power (1500 W) and pressure (35 mTorr). A direct comparison of the four feedstock gases under the same plasma conditions showed the Si etch rate to increase in the order $BF_3$ < $NF_3$< $PF_5$ < $SF_6$. This is in good correlation with the average bond energies of the gases, except for $NF_3$, which is the least strongly bound. Optical emission spectroscopy showed that the ICP source efficiently dissociated $NF_3$, but the etched Si surface morphologies were significantly worse with this gas than with the other 3 gases.

• Journal of Mechanical Science and Technology
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• 제17권4호
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• pp.469-476
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• 2003

Despite of considerable research results or uniaxial tension creep available for superalloys, few studies have been made on high temperature creep using the Initial Stram Method (ISM) In this paper, the real-time prediction of high temperature creep strength and creep lift for the nickel-based superalloy Udimet 720 (high-temperature and high-pressure gas turbine engine materials) was performed on round-bar type specimens under pure static load at the temperatures of 538$^{\circ}C$. 649$^{\circ}C$, and 704$^{\circ}C$. The predictive equation derived from the ISM in creep tests showed better reliability than those from LMP (Larson-Miller Parameter) and LMP-lSM (Larson Miller Parameter-Initial Strain Method) specially for long time creep prediction (10$^3$∼10$\^$5/h).

• 공업화학
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• 제9권1호
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• pp.94-100
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• 1998

천연가스의 주성분인 메탄의 마이크로웨이브 플라즈마 촉매반응에 의한 C2+ 탄화수소로의 전환반응을 고찰하였다. 플라즈마 출력의 증가(40~120 watt)와 유량이 감소(40~5mL/min)함에 따라서 메탄의 C2+ 생성물로의 전환율을 29.2%에서 42.2%로 향상되었으며, 촉매를 플라즈마와 함계 사용하여 에틸렌과 아세틸렌의 선택도를 향상시키는 동시에 높은 전환율을 유지할 수 있다. 실험에 사용한 여러 촉매중에는 Fe계의 촉매가 가장 높은 에틸렌의 선택도(30%)를 나타내었다. 실제 천연가스의 전환실험에서는 C2+ 생성물의 수율이 33.3%에서 46%의 범위를 보였다. 순수한 메탄이 원료였을 때 보다 높은 C2+ 수율이 얻어진 것은 천연가스가 메탄 보다 반응성이 높은 성분인 에탄과 프로판등을 함유하고 있기 때문으로 생각된다.

• 멤브레인
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• 제21권2호
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• pp.177-192
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• 2011

바이오 가스의 분리와 정제를 위해 셀룰로오스 트리아세테이트(CTA) 고분자를 이용하여 중공사형 기체분리막을 상분리법에 의해 제조하고, 제조된 기체분리막을 사용하여 유효 막면적이 0.17 $m^2$인 중공사형 기체분리막 모듈을 제조하였다. 제조된 기체분리막 모듈의 순수 기체투과도틀 메탄, 산소, 이산화탄소에 대하여 측정하였다. 메탄의 투과도는 평균 0.46 GPU를 나타내었으며, 이산화탄소의 투과도는 평균 18.52 GPU였으며 이때 ${\alpha}CO_2$/$CH_4=40.4$를 나타내어 매우 높은 선택도를 나타내었다. 순수 가스 투과 테스트 후 혼합 가스에 대한 분리 정제 테스트를 4가지 모사가스에 대하여 진행하였으며 1 stage, 2 stage, 3 stage로 기체분리막 모듈을 구성하여 stage cut의 변화에 따른 각 부분에서 발생되는 기체의 농도 및 유량을 측정하였다. 1 stage에서는 stage cut이 상승함에 따라 메탄의 농도가 상승하는 것을 알 수 있었으며, 메탄 회수 효율은 떨어지는 것을 알 수 있었다. 2 stage 테스트에서는 1 stage와 유사한 거동을 보이는 것을 알 수 있었으며 메탄의 회수 효율은 1 stage보다 상승하는 것을 알 수 있었다. 바이오 가스 내에 존재하는 메탄의 손실을 줄이기 위해 3 stage 테스트를 진행하였으며, 그 결과 메탄가스의 손실율을 5% 이내로 줄일 수 있는 모듈의 배열을 찾아내었다.

• 한국물환경학회지
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• 제26권1호
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• pp.81-88
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• 2010

This study was conducted to find the capability of comparison of overall oxygen transfer coefficient in the membrane coupled high performance reactor (MPHCR) in treating high organic loading wastewater. Effluent quality had been analyzed while the influent organic loading rate was changed from 2 to $7kg\;COD/m^3{\cdot}day$. The oxygen transfer coefficients had been investigated using two-phase nozzle for operating variables which were internal circulation flowrate (5~8 L/min), air flow rate (0.0125~0.2 L/min), liquid temperature ($10{\sim}20^{\circ}C$), and pure-oxygen flow rate (0.0125~0.2 L/min). The overall oxygen transfer coefficient was increased with flowrate of internal circulation and air and high temperature. Especially, internal circulation flow rate showed distinct effect on overall oxygen transfer coefficient due to an increase of gas holdup and air-liquid contract area by two-phase nozzle. In the high range of organic loading rate from 4 to $7kg\;COD/m^3{\cdot}day$, the removable efficiency of COD was 91%. Conventional activated sludge process usually treat organic loading from 0.32 to $0.64kg\;COD/m^3{\cdot}day$ however, the MPHCR can treat 10 to 20 times higher if it would be compared to the conventional activated sludge process. Foaming problem often happened and caused biomass wash out of the reactor, therefore, the foaming should be controlled for the enhanced operation.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2006년도 전력전자학술대회 논문집
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• pp.413-416
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• 2006

The power source of an AC-PDP fur sustainer circuit is operated in high-voltage and high frequency switching during the process required to achieve the gas discharge current to generate light in a PDP panel. Since PDP has the characteristics of a pure capacitive load, the displacement current that occurs during charge and discharge generates considerable reactive power. An auxiliary circuitry called Energy Recovery Circuit (ERC) reduces the capacitive displacement current. However, this auxiliary topology also bears high stress in its components. In this paper, a multilevel voltage wave shaping sustainer circuit with auxiliary ERC characteristics for an AC-PDP driver is proposed. A comparative analysis and experimental results are presented.

• 태양에너지
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• 제18권3호
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• pp.137-146
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• 1998

In this paper, the current status of manufacturing technologies for GaAs/Si solar cell were revived and provied new MOCVD. In the manufacturing process of GaAs/Si solar cells and an experiment to get the high efficiency GaAs solar cells, we must investigate the optimum growth conditions to get high quality GaAs films on Si substrates by MOCVD. The GaAs on Si substrates has been recognized as a lightweight alternative to pure substrate for space applicaton. Because its density is less the half of GaAs or Ge.So GaAs/Si has twofold weight advantage to GaAs monolithic cell. The theoretical conversion efficiecy limit of tandem GaAs/Si solar cell is 32% under AM 0 and $25^{\circ}C$ condition. It was concluded that the development of cost effective MOCVD technologies shoud be ahead GaAs solar cells for achived move high efficiency III-V solar cells involving tandem structure.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.45-45
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• 2017

The Indian meal moth, Plodia interpunctella, is one of the most important pests of stored food in the food processing industry worldwide. To control the Indian meal moth, methyl bromide, phosphine, high carbon dioxide, sulfuryl fluoride and plant essential oil fumigation have been considered. However, these treatments have disadvantages. For example, depleting the ozone layer, showing resistance in insect, low control efficacy or need high cost for treatment. Chlorine dioxide ($ClO_2$) is strong disinfectant and insecticide. The gas caused a malfunction in enzymes. The oxidative stress induced by $ClO_2$ gas treatment damaged to a physiological system and all life stages of P. interpunctella. The gaseous $ClO_2$ is a convincing alternative to methyl bromide for controlling P. interpunctella. The gaseous $ClO_2$ was generated by a chlorine dioxide generator (PurgoFarm Co., Ltd., Hwasung, Korea). It generated highly pure $ClO_2$ gas and the gas blown out through a vent into a test chamber. Gas entry to the chamber was automatically controlled and monitored by a PortaSene II gas leak detector (Analytical Technology, Collegeville, PA, USA). The properly prepared eggs, larvae, pupae, and adults of P. interpunctella were used in this experiment. Data were analyzed using SAS 9.4. Percentage data were statistically analyzed after arcsine-root transformation. Analysis of variance was performed using general linear model, and means were separated by the least significant difference test at P < 0.05. Fumigation is an effective management technique for controlling all stages of P. interpunctella. We found that $ClO_2$ gas treatment directly effects on egg, larvae, pupae and adults of P. interpunctella. The gas treatment with proper concentration for over a day achieved 100 % mortality in all stages of P. interpunctella and short time treatment or low concentration gas treatment results showed that the egg hatchability, pupation rate, and adult emergency rate were lowered compare with untreated control. Also, abnormal pupae or adult rate were increased. Gaseous $ClO_2$ treatment induced insecticidal reactive oxygen species (ROS), and it resulted in fatal oxidative stress in P. interpunctella. Taken together, these results showed that exposure proper concentration and time of the gas control all stages of P. interpunctella by inducing fatal oxidative stress. Further studies will be required to apply the gas treatment under real-world condition and to understanding physiological reaction in P. interpunctella caused by oxidative stress.