• 대한기계학회논문집B
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• 제33권6호
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• pp.454-460
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• 2009

To analyze the mixture formation process of evaporating diesel spray is important for emissions reduction in actual engines. Then the effects of change in density of ambient gas on spray structure in high temperature and pressure field have been investigated in this study. The ambient gas density was changed from ${\rho}_a=5.0kg/m^3$ to ${\rho}_a=12.3kg/m^3$ with CVC(Constant Volume Chamber). Also, simulation study by modified KIVA-II code was conducted and compared with experimental results. The ambient temperature and injection pressure are kept as 700K and 72MPa, respectively. The images of liquid and vapor phase in the evaporating free spray were simultaneously taken by exciplex fluorescence method. As experimental results, with increasing ambient gas density, the tip penetration of the evaporating free spray decreases due to the increase in the drag force from ambient gas. The spatial structure of a diesel spray can be verified as 2-regions consisted of liquid with momentum decrease and vapor with large-scale vortex. The calculated results obtained by modified KIVA-II code show good agreements with experimental results.

• 한국세라믹학회지
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• 제50권6호
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• pp.533-538
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• 2013

Silicon carbide (SiC) materials are typical ceramic materials with a wide range of uses due to their high hardness and strength and oxidation resistance. In particular, due to the corrosion resistance of the material against acids and bases including the chemical resistance against ionic gases such as plasma, the application of SiC has been expanded to extreme environments. In the SiC deposition process, where chemical vapor deposition (CVD) technology is used, the reactions between the raw gases containing Si and C sources occur from gas phase to solid phases; thus, the merit of the CVD technology is that it can provide high purity SiC in relatively low temperatures in comparison with other fabrication methods. However, the product yield rarely reaches 50% due to the difficulty in performing uniform and dense deposition. In this study, using a computational fluid dynamics (CFD) simulation, the gas velocity inside the reactor and the concentration change in the gas phase during the SiC CVD manufacturing process are calculated with respect to the gas velocity and rotational speed of the stage where the deposition articles are located.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 지반공학 공동 학술발표회
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• pp.382-388
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• 2005

Soil vapor extraction(SVE) is an effective and cost efficient method of removing volatile organic compounds(VOCs) and petroleum hydrocarbons from unsaturated soils. However, soil vapor extraction becomes ineffective in soils with low gas permeability, for example soils with air permeabilities less than 1 Darcy. Prefabricated vertical drains(PVDs) have been used for dewatering fine-grained soils for more than 25 years. Incorporating PVDs in and SVE system can extend the effectiveness of SVE to lower permeability soils by shortening the air flow-paths and ultimately expediting contaminant removal. The objective of the work described herein was to effectively incorporate PVDs into a SVE remediation system and to demonstrate a PVDs enhanced SVE system at full scale. The finding from this research will facilitate the design of field PVD-SVE systems in terms by providing insight into the optimal spacing between PVDs, the radius of influence of the wells and the flow rates to be used to capture and extract gas phase contaminants.

• 한국막학회:학술대회논문집
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• 한국막학회 2001년도 춘계 총회 및 학술발표회(한국막학회)
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• pp.68-71
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• 2001

• 한국가스학회:학술대회논문집
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• 한국가스학회 2005년도 춘계학술대회 및 특별심포지움
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• pp.228-228
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• 2005

• 대한기계학회논문집B
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• 제21권5호
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• pp.589-601
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• 1997

A computer simulation program of a high efficiency condensing heat exchanger is developed. The flue gas flows outside bare tube bundles both in strong cross flow and in weak counter flow and the cooling water inside the tubes. Condensing heat exchangers achieve high efficiency by reducing flue-gas temperatures to a level at which most of the water vapor in the flue gas is condensed and the latent heat associated with phase change of the water is recovered. The computer model has been verified by comparison with measured data. To verify the model, heat transfer coefficient was adjusted, along with the mass transfer diffusion coefficient and pressure drop coefficient, to achieve agreement between predicted and measured data. The efficiencies of heat exchanger increase 2.3 ~ 8.1% by condensations of 6.3 ~ 62.6% of the water vapor in the flue gas.

• 반도체디스플레이기술학회지
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• 제21권2호
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• pp.45-50
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• 2022

The etching with high selectivity of silicon dioxide over silicon nitride is essential in semiconductor fabrication, and gas phase etch (GPE) can increase the competitiveness of the selective dielectric etch. In this work, GPE of plasma enhanced chemical vapor deposited SiO₂ was performed, and the effects of process parameters, such as temperature, partial pressure ratio, and gas supply cycle, are investigated in terms of etch rate and within wafer uniformity. Employing multiple regression analysis, the importance of each parameter elements is analyzed.

• 센서학회지
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• 제29권6호
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• pp.420-426
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• 2020

A metal oxide semiconductor gas sensor is operated by measuring the changes in resistance that occur on the surface of nanostructures for gas detection. ZnO, which is an n-type metal oxide semiconductor, is widely used as a gas sensor material owing to its high sensitivity. Various ZnO nanostructures in gas sensors have been studied with the aim of improving surface reactions. In the present study, the sol-gel and vapor phase growth techniques were used to fabricate nanostructures to improve the sensitivity, response, and recovery rate for gas sensing. The sol-gel method was used to synthesize SnO₂ nanoparticles, which were used as the seed layer. The nanoparticles size was controlled by regulating the process parameters of the solution, such as the pH of the solution, the type and amount of solvent. As a result, the SnO₂ seed layer suppressed the aggregation of the nanostructures, thereby interrupting gas diffusion. The ZnO nanostructures with a sol-gel processed SnO₂ seed layer had larger specific surface area and high sensitivity. The gas response and recovery rate were 1-7 min faster than the gas sensor without the sol-gel process. The gas response increased 4-24 times compared to that of the gas sensor without the sol-gel method.

• 한국분말재료학회지
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• 제11권6호
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• pp.515-521
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• 2004

Fe(C) nanocapsules were prepared by the chemical vapor condensation(CVC) process using the pyrolysis of iron pentacarbonyl $(Fe(CO)_5)$. Their characterizations were studied by means of X-ray diffraction, X-ray photoelectron spectrometer and transmission electron microscopy. The long-chained Fe(C) nanocapsules hav-ing the mean size of under 70 nm could be obtained below $1100^{\circ}C$ in different gas flow rates. The particle size of the powders was increased with increasing decomposition temperature, but it was decreased with increasing CO gas flow rate. The Fe powders produced at $500^{\circ}C$ consisted of three layers of ${\alpha}$-Fe/$Fe_3C$/amorphous phases, but it had two phase core-shell structure which consited of $Fe_3C$ phase of core and graphite of shell at $1100^{\circ}C$.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.581-584
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• 1998

TiN thin films were grown on (100) Si substrate by atomic layer epitaxy at 130 - $240^{\circ}C$ using TEMAT and NH3 as precursors. Reactants were injected into the reactor in sequence of TEMAT precursor vapor pulse, N2 purging gas pulse, NH3 gas pulse and N2 purging gas pulse so that gas-phase reactions could be removed. The films were characterized by means of x-ray diffraction(XRD), 4-point probe, atomic force microscopy(AFM) and auger electron spectroscopy(AES).