• Transactions on Electrical and Electronic Materials
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• 제10권3호
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• pp.93-96
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• 2009

The Al-doped ZnO (AZO) films were deposited on a glass substrate by RF magnetron sputtering in pure Ar and $Ar+H_2$ gas ambient at temperature of $100^{\circ}C$ and annealed in hydrogen ambient at the temperature range from 100 to 300 $^{\circ}C$, respectively. It was found that either the addition of hydrogen to the sputtering gas or the annealing treatment effectively reduced the resistivity of the AZO films. When the AZO films were annealed at the temperature of 300 $^{\circ}C$ for lhr in a hydrogen atmosphere, the resistivity decreased from $2.60{\times}10^{-3}\;{\Omega}cm$ to $8.42{\times}l0^{-4}\;{\Omega}cm$ for the film deposited in pure Ar gas ambient. Under the same annealing conditions of temperature and hydrogen ambient, the resistivity of AZO films deposited in the $Ar+H_2$ gas mixture decreased from $8.22{\times}l0^{-4}\;{\Omega}cm$ to $4.25{\times}l0^{-4}\;{\Omega}cm$. The lowest resistivity of $4.25{\times}l0^{-4}\;{\Omega}cm$ was obtained by adding hydrogen gas to the deposition and annealing process. X-ray diffraction (XRD) pattern of all films showed preferable growth orientation of (002) plane. The average transmittance is above 85 % and in the range of 400-1000 nm for all films.

• 설비공학논문집
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• 제28권6호
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• pp.248-255
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• 2016

In this study, the degree of performance changes between the guaranteed performance and the performance after a certain operating start time is calculated by using the performance test of gas turbine CHP. The reason of the performance degradation will then be analysed. For some results of the CHP plant performance tests the comprehensive electric power output was 8,380 kW lower than the guaranteed performance, and the gas turbine's output was reduced to about 250 kW whenever ambient temperatures rose to $1^{\circ}C$. Also, causes of the performance degradation of gas turbines are ambient temperature rise, temperature aging and air compressor's efficiency drop.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.885-890
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• 2006

This study presents analysis results for the hybrid system combining solid oxide fuel cell and gas turbine. Two different system layouts(an ambient pressure system and pressurized system) are considered and their design performance are comparatively investigated taking into account critical design factor, the most critical parameter such as turbine inlet temperature, gas turbine pressure ratio, temperature difference at the fuel cell and fuel cell operating temperature are considered as design constraints. Performance variations according to system layout and design parameters are examined in energetic view point.

• 한국세라믹학회지
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• 제48권2호
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• pp.200-204
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• 2011

Increase of surface area and decrease of band gap in $TiO_2$ semiconductors are significant to improve the efficiency of water splitting by photoelectrolysis. In this study $TiO_2$ nanotube arrays with ~7 um length and ~100 nm diameter were fabricated by an anodizing technique of titanium foils using DMSO (dimethyl sulfoxide)-based electrolytes. Then to control the band gap of the $TiO_2$ arrays, they were annealed at $550^{\circ}C$ for up to 180 min in $NH_3$ gas ambient. The samples annealed in $NH_3$ gas for 30 min and 60 min showed superior photo-conversion efficiency for water splitting under white and visible light. A $TiO_2$ nanotube annealed in $NH_3$ gas ambient for a period longer than 120 min showed 1 order higher leakage current. It is believed that the decrease of band gap and increase of conductivity in $TiO_2$ nanotube arrays due to $NH_3$ gas treatments result in the superior water-splitting performance.

• 한국대기환경학회지
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• 제19권6호
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• pp.679-687
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• 2003

In this study, we investigated the analytical techniques to quantify the ambient concentration of hydrogen sulfide (H$_2$S) in air at ppt concentration level. For this purpose, an on-line GC analytical system equipped with both pulsed-flame photometric detector (PFPD) and thermal desorption unit (TDU) was investigated by collecting ambient air samples. The results of our study generally indicated that calibration conditions of GC system is highly sensitive to affect the accuracy of the analytical technique. Most importantly. we found that the use of different matrices in the the preparation stage of working standards was sensitive to control the overall performance of this technique. The calibration of our analytical system was tested by the two types of working standard (prepared by mixing either with high purity $N_2$ or with the ambient air). According to this test, the latter represented more efficiently the detecting conditions of actual air samples. The peak occurrence patterns of both air samples and standards (prepared by mixing with ambient air) were altered in a similar manner as the function of the loaded volume; however, it was not the case for the $N_2$-mixed standards. Results of our study suggest that detection of H$_2$S is highly different from other sulfides and that its quantification requires minimiaing interfering effects of non -pure substance (like water vapor) and (either sorptive or destructive) loss effects.

• Bulletin of the Korean Chemical Society
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• 제23권3호
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• pp.488-496
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• 2002

SPME techniques have proven to be very useful tools in the analysis of wide VOCs in the air. In this study, we estimated VOCs in ambient and workplace air using a Tedlar ba /SPME/GC/MS system. The calibration curve was set to be linear over the range of 1-30 ppbv. The detection limits ranged from 10 pptv to 0.93 ppbv for all VOCs. Reproducibility of TO-14 target gas mixtures by SPME/GC/MS averaged at 8.8 R.S.D (%). Air toxic VOCs (hazardous air pollutants, HAPs) containing a total of forty halohydrocarbons, aromatics, and haloaro-matic carbons could be analyzed with significant accuracy, detection limit and linearity at low ppbv level. Only reactive VOCs with low molecular weight, such as chloromethane, vinylchloride, ethylchloride and 1,2-dichloro-ethane, yielded relatively poor results using this technique. In ambient air samples, ten VOCs were identified and quantified after external calibration. VOC concentration in ambient and workplace air ranged from 0.04 to 1.85 ppbv. The overall process was successfully applied to identify and quantify VOCs in ambient/workplace air.

• 한국산업융합학회 논문집
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• 제13권1호
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• pp.31-39
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• 2010

An exergy analysis is carried out for the regenerative gas turbine cycle which has a potential of enhanced thermal efficiency and specific power owing to the more possible water injection than that of inlet fogging under the ambient conditions. Using the analysis model in the view of the second law of thermodynamics, the effects of pressure ratio, water injection ratio and ambient temperature are investigated on the performance of the system such as exergetic efficiency, heat recovery ratio of recuperator, exergy destruction or loss ratios, and on the optimal conditions for maximum exergy efficiency. The results of computation for the typical cases show that the regenerative gas turbine system with afterfogging can make a notable enhancement of exergy efficiency.

• 한국세라믹학회지
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• 제27권8호
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• pp.1004-1010
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• 1990

SnO2-ThO2-PdCl2-In2O3 gas sensing ceramic systems were studied in order to lowr the operating temperatures and reduce the dependence of ambient temperatures and humidities. Sensing materials were coated by brush on the alumina tube followed by the impregnation of solidfier(ethylsilicate). Coated species were dried and sintered at 75$0^{\circ}C$ for 30min. carbon monoxide gas detecting sensitiviteis were measured in various ambinet temperatures and humidities. In the composition of 94SnO2-5ThO2-PdCl2 system carbon monoxide gas detecting sensors showed the highest detecting sensitivities and the lowest operating temperature(15$0^{\circ}C$). As the ambient temperatures and humidities were increased, sensitivities were decreased. Because the oscillation effects were observed at high humidities, it was suggested that the sensitivities of sensors depend greatly on the humidities.

• 대한기계학회논문집B
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• 제27권11호
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• pp.1595-1603
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• 2003

Droplet combustion at high ambient pressures is studied numerically by formulating one dimensional combustion model in the mixture of n-heptane fuel and air. The ambient pressure is supercritical conditions. The modified Soave-Redlich-Kwong state equation is used in the evaluation of thermophysical properties to account for the real gas effect on fluid p-v-T properties in high pressure conditions. Non-ideal thermodynamic and transport property at near critical and supercritical conditions are also considered. Several parametric studies are performed by changing ambient pressure and initial droplet diameter. Droplet lifetime decreased with increasing pressure. Surface temperature increased with increasing pressure. Ignition time increased with increasing initial droplet diameter. Temporal or spatial distribution of mass fraction, mass diffusivity, Lewis number, thermal conductivity, and specific heat were presented.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.113-114
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• 2008

Conventional furnace annealing (CFA) for activating Mg-doped p-type GaN films had been performed in pure $N_2$ ambient. All sample activated the same gas ambient. The annealing process change temperature: the first process is performed at $550^{\circ}C$ for 10 min. but, the first process is the same bulk. From second to five process increase activation temperature to change $50^{\circ}C$ and annealing time keeping for 10 min. It is found that the samples characteristic measure hall measurement. Similar results were also evidenced by photoluminescence (PL) measurement.