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이성광(Sung-Gwang Lee),박한준(Han June Park),이인재(Injae Lee),남예빈(Yebin Nam),황원태(Wontae Hwang) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
As the critical dimension of semiconductors is miniaturized, the semiconductor fabrication process requires extreme purity and cleanliness, and many semiconductor facilities perform the process after creating a vacuum environment. Precursor gases used during the process make patterns by repeating deposition and etching through wafer surface reaction. In order to increase the production yield of circular wafers, it is essential to predict the behavior of process gases in a vacuum environment. Although computational fluid dynamics (CFD) is being performed to predict the airflow, there are very few studies that visualize and analyze the airflow through an experiment in a vacuum environment due to the difficulty of measuring the airflow. Therefore, there is a limit to verifying the CFD results. This study visualizes a supersonic round jet airflow in a vacuum environment in a 2D plane where the absolute pressure is lowered to 1 Torr. Using PIV, the structure of the jet, turbulent kinetic energy (TKE), and vorticity are analyzed by measuring the flow velocity of the jet. In addition, the location, size, and structure of the shockwave were analyzed using shadowgraphy. Through this study, we intend to provide an experimental basis for visualization of airflow in a vacuum environment.
박한준(Han June Park),이성광(Sung-Gwang Lee),오정석(Jeong Suk Oh),Steven Barrett,황원태(Wontae Hwang) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
After the World Health Organization (WHO) proclamation of the Severe Acute Respiratory Syndrome-2 (SARS-Cov-2) as a pandemic in 2020, there have been various efforts on establishing the correlation between temperature and humidity on the spread of COVID-19. However, worldwide consensus has not yet been established. The cause of this is that the indoor environment in which virus transmission occurs is not considered, and there is also a lack of physical understanding of droplet evaporation with temperature and humidity. Therefore, in this study, we examine actual droplet dynamics by first measuring droplet evaporation within a constant temperature and humidity environmental chamber. Based on this experiment, simulations were conducted to estimate the effects of temperature and humidity on droplet dispersion. Our results showed that there was no significant correlation between temperature, but that high humidity greatly helps in suppressing virus transmission via respiratory droplets.
고리 원자력 발전 단지 사고 발생에 따른 방사능 물질 확산 가능성의 계절적 특성 연구
김지선 ( Ji-seon Kim ),이순환 ( Soon-hwan Lee ),박강원 ( Kang-won Park ),이성광 ( Sung-gwang Lee ),최세용 ( Se-young Choi ),조규찬 ( Kyu-chan Cho ),이혁우 ( Hyeuk-woo Lee ) 한국환경과학회 2018 한국환경과학회지 Vol.27 No.6
To establish initial response scenarios for nuclear accidents around the Kori nuclear power plants, the potential for radionuclide diffusion was estimated using numerical experiments and statistical techniques. This study used the numerical model WRF (Weather Research and Forecasting) and FLEXPART (Flexible Particle dispersion model) to calculate the three-dimensional wind field and radionuclide dispersion, respectively. The wind patterns observed at Gijang, near the plants, and at meteorological sites in Busan, were reproduced and applied to estimates of seasonally averaged wind fields. The distribution of emitted radionuclides are strongly associated with characteristics of topography and synoptic wind patterns over nuclear power plants. Since the terrain around the power plants is complex, estimates of radionuclide distribution often produce unexpected results when wind data from different sites are used in statistical calculations. It is highly probable that in the summer and autumn, radionuclides move south-west, towards the downtown metropolitan area. This study has clear limitations in that it uses the seasonal wind field rather than the daily wind field.