• Journal of Radiation Protection and Research
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• v.48 no.1
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• pp.28-43
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• 2023

Background: High-fidelity meteorological data is a prerequisite for the realistic simulation of atmospheric dispersion of radioactive materials near nuclear power plants (NPPs). However, many meteorological models frequently overestimate near-surface wind speeds, failing to represent local meteorological conditions near NPPs. This study presents a new high-resolution (approximately 1 km) meteorological downscaling method for modeling short-range (< 100 km) atmospheric dispersion of accidental NPP plumes. Materials and Methods: Six considerations from literature reviews have been suggested for a new dynamic downscaling method. The dynamic downscaling method is developed based on the Weather Research and Forecasting (WRF) model version 3.6.1, applying high-resolution land-use and topography data. In addition, a new subgrid-scale topographic drag parameterization has been implemented for a realistic representation of the atmospheric surface-layer momentum transfer. Finally, a year-long simulation for the Kori and Wolsong NPPs, located in southeastern coastal areas, has been made for 2016 and evaluated against operational surface meteorological measurements and the NPPs' on-site weather stations. Results and Discussion: The new dynamic downscaling method can represent multiscale atmospheric motions from the synoptic to the boundary-layer scales and produce three-dimensional local meteorological fields near the NPPs with a 1.2 km grid resolution. Comparing the year-long simulation against the measurements showed a salient improvement in simulating near-surface wind fields by reducing the root mean square error of approximately 1 m/s. Furthermore, the improved wind field simulation led to a better agreement in the Eulerian estimate of the local atmospheric dispersion. The new subgrid-scale topographic drag parameterization was essential for improved performance, suggesting the importance of the subgrid-scale momentum interactions in the atmospheric surface layer. Conclusion: A new dynamic downscaling method has been developed to produce high-resolution local meteorological fields around the Kori and Wolsong NPPs, which can be used in short-range atmospheric dispersion modeling near the NPPs.

• Biotechnology and Bioprocess Engineering:BBE
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• v.1 no.1
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• pp.46-50
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• 1996

In order to design industrial scale reactors and proceises for multi-phase biocatalytic reactions, it is essential to understand the mechanisms by which such systems operate. To il-lustrate how such mechanisms can be modeled, the hydrolysis of the primary ester groups of triglycerides to produce fatty acids and monoglycerides by lipased (glycerol-ester hydrolase) catalysis has been selected as an example of multiphase biocatalysis. Lipase is specific in its behavior such that it can act only on the hydrolyzed (or emulsified) part of the substrate. This follows because the active center of the enzyme is catalytically active only when the substrate contacts it in its hydrolyzed form. In other words, lipase acts only when it can shuttleback and forth between the emulsion phase and the water phase, presumably within an interphase or boundary layer between these two phases. In industrial applications lipase is employed as a fat splitting enzyme to remove fat stains from fabrics, in making cheese, to flavor milk products, and to degrade fats in waste products. Effective use of lipase in these processes requires a fundamental understanding of its kinetic behavior and interactions with substrates under various environmental conditions. Therefore, this study focuses on modeling and simulating the enzymatic activity of the lipase as a step towards the basic understanding of multi-phase biocatalysis processes.

• The KSFM Journal of Fluid Machinery
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• v.12 no.1
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• pp.22-27
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• 2009

The important problems that arise in the design and performance of the axial flow turbine are the prediction and control of secondary flows. Some progresses have been made on understanding flow conditions that occur when the inlet endwall boundary layer separates at the point in the endwall and rolls up into the horseshoe vortex. And the flows though an axial turbine tend to be extremely complex due to its inherent unsteady and viscous phenomena. The passing wakes generated from the trailing edge of the stator make an interaction with the rotor. Unsteady flow should be considered rotor/stator interactions. The main purpose of this research is control of secondary flow and improvement efficiency in turbine by leading edge modification in unsteady state. When the wake from the stator ran into the modified leading edge of the rotor, the leading edge generated the weak pressure fluctuation by complex passage flows. In conclusion, leading edge modification(bulb2) results in the reduced total pressure loss in the flow field.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1494-1498
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• 2007

Impulsive shooting noise is basically complex phenomenon which contains the linear and non-linear characteristics. For those reasons, numerical analysis of impulsive shooting noise has the difficulties in control of the numerical stability and accuracy on the simulation. In this research, Wave-number Extended Finite Volume Scheme (WEFVS) is applied to the numerical analysis of impulsive shooting noise. In the muzzle blast flow simulation, the generation of the precursor wave and the induced vortex ring are observed. Consequently, blast wave. vortex ring interaction and vortex ring. bow shock wave interaction are evaluated on the shooting process using the accurate and stable scheme. The sound generation in the interactions can be explained by the vorticity transport theorem. The shear layer is evolved behind the projectiles due to the jet flow. In these computations, the impulsive shooting noise is generated by the complex interaction with shooting process and is propagated to the far-field boundary. The impulsive shooting noise generation can be observed by the applications of WEFVS and analyzed by the physical phenomena.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.2
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• pp.136-142
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• 2007

A small supersonic wind tunnel was designed and built to study the flow characteristics of a supersonic impulse turbine cascade. The supersonic cascade with a 2-dimensional supersonic nozzle was tested for the axial gap ratio (${\delta}$) of the supersonic turbine that is the one of the turbine design parameter. Firstly, the flow was visualized by a single pass Schlieren system. Next, total and static pressure of the cascade were measured by a pressure scanning system. Highly complicated flow patterns including shocks, nozzle-cascade interaction and shock boundary layer interactions, flow characteristics of the supersonic turbine were observed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.361-366
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• 2006

A small supersonic wind tunnel was designed and built to study the flow characteristics of a supersonic impulse turbine cascade. The supersonic cascade with a 2-dimensional supersonic nozzle was tested for the leading edge chamfer angle $(\gamma)$ of the supersonic turbine that is the one of the turbine design parameter. Firstly, the flow was visualized by a single pass Schlieren system. Next, total and static pressure of the cascade were measured by a pressure scanning system. Finally, highly complicated flow patterns including shocks, nozzle-cascade interaction and shock boundary layer interactions, flow characteristics of the supersonic turbine were observed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.100-105
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• 2005

In this paper, a small supersonic wind tunnel is designed and built to study the flow characteristics of a supersonic impulse turbine cascade. The flow is visualized by means of a single pass Schlieren system. The supersonic cascade with 2-dimensional supersonic nozzle is tested for various gaps between the nozzle and cascade. By the experiment, the flow is visualized and static pressure of the cascade was measured. And highly complicated flow patterns including shocks, nozzle-cascade interaction and shock boundary layer interactions, flow characteristics of the supersonic turbine are observed.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.4
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• pp.66-72
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• 2005

In this paper, a small supersonic wind tunnel is designed and built to study the flow characteristics of a supersonic impulse turbine cascade. The flow is visualized by means of a single pass Schlieren system. The supersonic cascade with 2-dimensional supersonic nozzle was tested for various blade leading edge shapes and gaps between the nozzle and cascade. Highly complicated flow patterns including shocks, nozzle-cascade interaction and shock boundary layer interactions are observed.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.3
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• pp.30-38
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• 2010

Experiments were performed to investigate the flow characteristics of a partial admission supersonic turbine depending on the relative positions of nozzle and cascade. The flow was visualized by a Schlieren system. The static pressures at the turbine cascade inlet, passage and outlet were measured by pressure transducers. Highly complicated flow patterns including shocks, nozzle-cascade interaction and shock boundary layer interactions of the supersonic turbine were observed by the experiments. And the flow characteristics in the supersonic turbine as the relative positions were observed.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.6
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• pp.713-725
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• 1999

Air pollutants($SO_2$, NOx, $O_3$ and aerosol number) were measured using an aircraft to investigate the characteristical features of long-range transport of sulfur compounds over the Yellow Sea for the periods of 26~27 April and 7~10 November in 1998. The mean $SO_2$ concentrations of April 26th~27th and November 7th~10th flight were 0.6~1.8 ppb and 0.5~8.3 ppb, respectively, and the sulfur transport was largely limited to the atmospheric boundary layer. Especially, $SO_2$ increased up to 8.3 ppb altogether with the increase of particle number concentraton especially on November 8, 1998. In addition, $O_3$ was remarkably decreased against the increase of $SO_2$and particle number concentrations. This enhanced $SO_2$ concentration occurred in the low level westerlies in association with the anticyclonic flow over Southern China and the cyclonic circulation over Manchuria. Aerosol analyses at Taean site also showed that sulfate concentration increased 2~3 times higher than those of another sampling days, which could suggest possible interactions between aerosol particels and tropospheric ozone. A rigorous evaluation will be possible after the more intensive measurements and quantitative analyses with detailed chemistry model including the postulated heterogeneous mechanism.