• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.215-220
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• 2008

A numerical method for gas-liquid two-phase flow is applied to solve shock-bubble interaction problems. The present method employs a finite-difference Runge-Kutta method and Roe's flux difference splitting approximation with the MUSCL-TVD scheme. A homogeneous equilibrium cavitation model is used. By this method, a Riemann problem for shock tube was computed for validation. Then, shock-bubble interaction problems between cylindrical bubbles located in the liquid and incident liquid shock wave are computed.

• Journal of the Korean Chemical Society
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• v.53 no.2
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• pp.99-110
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• 2009

Characteristics of supercooled liquid and glass, which are the states involved in glass transition, are reviewed. These states are non-equilibrium states, therefore, the glass transition is different from the usual phase transitions. Theories of glass transition and related experimental methods are briefly summarized.

• Journal of computational fluids engineering
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• v.13 no.4
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• pp.50-57
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• 2008

The prediction of hydrate pellet decomposition characteristics is required to design the regasification process of GTS (gas to solid) technology, which is considered as an economic alternative for LNG technology to transport natural gas produced from small and stranded gas wells. Mathematical model based on the conservation principles, the phase equilibrium relation, equation of gas state and phase change kinetics was set up and numerical solution procedure employing volume averaged fixed grid formulation and extended enthalpy method are implemented. Initially, porous methane hydrate pellet is at uniform temperature and pressure within hydrate stable region. The pressure starts to decrease with a fixed rate down to the final pressure and is kept constant afterwards while the bounding surface of pellet is heated by convection. The predicted convective heat and mass transfer accompanied by the decomposed gas flow through hydrate/ice solid matrix is reported focused on the comparison of spherical and cylindrical pellets having the same effective radius.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.135-137
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• 2014

Excess enthalpy flame propagating an porous inert medium, which recirculate exhaust heat to the upstream cold mixture, is theoretically analyzed. Using the activation-energy asymptotics, the flame structure is divided into the thin reaction and the gas-phase preheat zone, as is traditionally done. Ahead and behind of the two, there exist an outer preheat zone, where heat is convectively transferred from solid to gas, and a downstream re-equilibrium zone, where thermal equilibrium between phases is established. Asymptotic solutions of species and energy equations in each zone are obtained and then matched to each other, and finally the mass burning rate is obtained as a function of the flame propagation velocity with respect to the solid phase and physical properties of gas and solid.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.268-275
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• 2008

The prediction of hydrate pellet decomposition characteristics is required to design the regasification process of GTS (gas to solid) technology, which is considered as an economic alternative for LNG technology to transport natural gas produced from small and stranded gas wells. Mathematical model based on the conservation principles, the phase equilibrium relation, equation of gas state and phase change kinetics was set up and numerical solution procedure employing volume averaged fixed grid formulation and extended enthalpy method are implemented. Initially, porous methane hydrate pellet is at uniform temperature and pressure within hydrate stable region. The pressure starts to decrease with a fixed rate down to the final pressure and is kept constant afterwards while the bounding surface of pellet is heated by convection. The predicted convective heat and mass transfer accompanied by the decomposed gas flow through hydrate/ice solid matrix is reported focused on the comparison of spherical and cylindrical pellets having the same effective radius.

• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.268-275
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• 2008

The prediction of hydrate pellet decomposition characteristics is required to design the regasification process of GTS (gas to solid) technology, which is considered as an economic alternative for LNG technology to transport natural gas produced from small and stranded gas wells. Mathematical model based on the conservation principles, the phase equilibrium relation, equation of gas state and phase change kinetics was set up and numerical solution procedure employing volume averaged fixed grid formulation and extended enthalpy method are implemented. Initially, porous methane hydrate pellet is at uniform temperature and pressure within hydrate stable region. The pressure starts to decrease with a fixed rate down to the final pressure and is kept constant afterwards while the bounding surface of pellet is heated by convection. The predicted convective heat and mass transfer accompanied by the decomposed gas flow through hydrate/ice solid matrix is reported focused on the comparison of spherical and cylindrical pellets having the same effective radius.

• Corrosion Science and Technology
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• v.5 no.6
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• pp.206-212
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• 2006

The effects of sub-ppm levels of $H_2S$ and the adsorbed water on the atmospheric corrosion of silver were studied with In situ weight balance to study the effect of the adsorbed water on the kinetic behavior and to determine the rate-controlling step, with XPS to analyze the tarnish film, and with calculation of phase equilibrium to predict the stable solid phase, the concentrations of dissolved species ($Ag^-$, $H^+$, $S^{2-}$, $HS^-$) and the equilibrium potentials ($E_{Ag^+/Ag}$, $E_{H^+/H_2}$, $E_{O_2/O^{2-}$). The results of weight measurements showed that oxygen was required for the sulfidation of silver in 100 ppb $H_2S$ and humidified environments enhanced the tarnished rate and oxidizing power. In addition, the rate determining step for tarnishing silver was shown to be changed to transport though the tarnish film.

• Journal of Biomedical Engineering Research
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• v.13 no.3
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• pp.235-244
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• 1992

In this paper, fluttering behavior of mechanical monoleaflet tilting disc heart valve prostheses during the opening phase was analyzed taking into consideration the impact between the occluder and the guiding strut at the fully open position. The motion of the valve occluder was modeled as a rotating system, and equations were derived by employing the moment equilibrium principle. Forces due to lift, drag, gravity and buoyancy were considered as external forces acting on the occluder. The 4th order Runge-Kutta method was used to solve the governing equations. The results iimonstrated that the occludes reaches steady equilibrium position only after damped vibration. Fluttering frequency varies as a function of time after opening and is in the range of 8-84 Hz. Valve opening appears to be affected by the orientation of the valve relative to gravitational force. The opening velocities are in the range of 0.65-1.42m/sec and the dynamic loads by impact of the occludes and the strut are in the range of 90-190 N.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.4
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• pp.307-314
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• 2005

In this work, a static volumetric method was experimentally implemented to measure the adsorption isotherm of hydrogen and methane by the activated carbon. The equilibrium data of stationary phase and mobile phase were correlated into the Langmuir, Freundlich, Langmuir-Freundlich, and Toth isotherms, respectively. In addition, the comparison between prediction and experimental data was made. By a nonlinear regression analysis, the experimental parameters in the equilibrium isotherms were estimated and compared. Then, the linear and quadratic equations for pressure and temperature to adsorption amounts were expressed. The adsorption amounts were increased with the pressure increase and the temperature decrease.

• Particle and aerosol research
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• v.11 no.3
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• pp.77-85
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• 2015

A Belousov-Zhabotinsky reaction in a liquid-liquid system under microwave radiation was observed under non-stirring conditions. To control this non-equilibrium reaction, nano-particle, which is active under microwave irradiation, was added to the solution. Color changes of the solution during the oscillatory reaction were found to be influenced by the irradiation power although the droplet temperature was equal to the temperature of surrounding oil. During the irradiation, the period of oscillation became shorter because the reaction rate was faster. It could also be observed that there is possibility to eliminate oscillatory behaviors of the reaction using higher power of microwave. The possibility of controlling non-linear reaction using microwave was shown since microwave can easily travel through oil phase and reach water phase.