• Nuclear Engineering and Technology
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• v.53 no.3
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• pp.752-762
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• 2021

The Smoothed Particle Hydrodynamics is one of the most widely used mesh-free numerical method for thermo-fluid dynamics. Due to its Lagrangian nature and simplicity, it is recently gaining popularity in simulating complex physics with large deformations. In this study, the 3D single/two-phase numerical simulations are performed on the Liquid Metal Reactor (LMR) centralized sloshing benchmark experiment using the SPH parallelized using a GPU. In order to capture multi-phase flows with a large density ratio more effectively, the original SPH density and continuity equations are re-formulated in terms of the normalized-density. Based upon this approach, maximum sloshing height and arrival time in various experimental cases are calculated by using both single-phase and multi-phase SPH framework and the results are compared with the benchmark results. Overall, the results of SPH simulations show excellent agreement with all the benchmark experiments both in qualitative and quantitative manners. According to the sensitivity study of the particle-size, the prediction accuracy is gradually increasing with decreasing the particle-size leading to a higher resolution. In addition, it is found that the multi-phase SPH model considering both liquid and air provides a better prediction on the experimental results and the reality.

• Korean Journal of Soil Science and Fertilizer
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• v.35 no.6
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• pp.327-334
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• 2002

Method of besoil analysis were difficult to be applied universally since the use and the source material of bedsoils are diverse from country to country. Korean Standard Methods for Bedsoil Analysis was developed to measure the particle and bulk density. Fifty-three samples for horticultural bedsoil and nine samples for paddy rice bedsoil in the current market were collected. Particle density was measured by electrical pyconometer with He gas, and bulk density by the sandbox method, free fall method, plunger compaction method, free fall and plunger method, and sample weight compaction method. While the use of glass pycnometer which measures particle density to fill blank space with water was inappropriate due to floating organic and calcined inorganic materials in the water, the electrical pycnometer with gas type was suitable considering speed and accuracy. For bulk density, the sandbox method recommended as European Standard Method was more reasonable in principle than other methods. However, this method requires expensive apparatus and intricate process. Plunger compaction method was proposed as standard method, since it had higher consistence with the sandbox method than other methods, as well as an advantage of easy and prompt measurement. Particle density of bedsoil ranged $1.48{\sim}2.67Mg\;m^{-3}$(mean $1.93Mg\;m^{-3}$) for horticultural bedsoil and $2.33{\sim}2.67Mg\;m^{-3}$ (mean $2.43Mg\;m^{-3}$) for paddy rice bedsoil by the electrical pycnometer with He gas. Bulk density of bedsoil ranged $0.11{\sim}0.40Mg\;m^{-3}$ (mean $0.22Mg\;m^{-3}$) for horticultural bedsoil and $0.84{\sim}1.26Mg\;m^{-3}$(mean $1.01Mg\;m^{-3}$) for paddy rice bedsoil by plunger compaction method.

• Journal of the Korean Ceramic Society
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• v.29 no.9
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• pp.711-718
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• 1992

Pb(Fe1/2Nb1/2)O3 was prepared by the molten salt synthesis method using an equimolar mixture of NaCl-KCl. Initial particle size could be controlled by varying the weight ratio of the NaCl-KCl to raw materials from 0.1 to 1.0, and the initial particle size effects on the sintering and dielectric properties of Pb(Fe1/2Nb1/2)O3 were investigated at the sintering temperature range from 90$0^{\circ}C$ to 105$0^{\circ}C$. As the weight ratio of salt increased, the average particle size decreased and the particle size distributions tended to narrow. As the initial particle size decreased, the linear shrinkage and density increased due to the promotion of densification. Dielectric constant increased with decreasing the initial particle size resulting from the increase of density and grain size.

• The KSFM Journal of Fluid Machinery
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• v.15 no.1
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• pp.27-35
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• 2012

A numerical simulation for particle collection efficiency in a wire-plate electrostatic precipitator (ESP) has been performed. Method of characteristics and finite differencing method (MOC-FDM) were employed to obtain electric field and space charge density, and lattice boltzmann method (LBM) was used to predict the Electrohydrodynamic (EHD) flow according to the ion convection. Large eddy simulation (LES) was considered for turbulent flow and particle simulation was performed by discrete element method (DEM) which considered field charging, electric force, drag force and wall-collision. One way coupling from FDM to LBM was used with small and low density particle assumption. When the charged particle collided with the collecting plate, particle-wall collision was calculated for re-entertainment effect and the effect of gravity force was considered.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.6
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• pp.9-15
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• 2012

As a propellant of a high speed underwater vehicle, the hydro-reactive solid metal particles using seawater as a oxidizer maximizes its specific impulse when the solid metal particles and the seawater are uniformly mixed in the combustion chamber. The purpose of this study is to investigate the effects of injector geometry on the particle distribution of similarity point of view. For the purpose of this similarity of the mean velocity and particle number density along the radial direction was measured by Particle Image Velocimetry(PIV).

• Journal of the Korean Society of Combustion
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• v.4 no.2
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• pp.1-10
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• 1999

Pulverized coal is widely used as the source of electrical power generation and industrial processes. Numerical analysis on the transient ignition process of the cloud of pulverized coal particles in various cases is carried out. Particle radius, initial particle temperature, number density are chosen as major parameters that influence the characteristics of ignition and combustion. The result can be summarized as follow. The ignition occurs at the position that is closed to the surface of the cloud. Maximum temperature and velocity appear at ignition point, and the concentrations of gaseous fuel and oxidizer decrease rapidly near the ignition point. The chemical reaction takes place in wider zone as number density and particle radius decrease. The ignition delay is shortest when particle radius is about $50\;{\mu}m$, and tends to be shorter as number density and initial ambient temperature increase.

• The Journal of Korea Robotics Society
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• v.12 no.3
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• pp.332-338
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• 2017

As an interpretation of existing jamming effects, the main variables affecting the increase in stiffness due to jamming are known as system density, jamming density, pressure, and particulate temperature. The main variable, jamming density, is closely related to the distribution of particle size and contact properties such as particle shape and friction. However, the complexity of these variables makes it difficult to fully understand the mechanism of the jamming effect. In this paper, we focus on the jamming effects of particles that have more elastic properties than particles such as sand and coffee powder, which are commonly used as constituent particles of existing jamming, in order to reduce complicated factors such as temperature and concentrate on jamming effects based on elastic characteristics of particles. It was experimentally explored the possibility of increasing stiffness by mixing particles of different sizes rather than simply increasing the bending stiffness by controlling the particle size. Through simulations and experiments, we found a case where the stiffness of each particle size distribution is larger than the stiffness of each particle size.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.5
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• pp.632-638
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• 2005

Membrane fouling index such as Silt Density Index (SDI) and Modified Fouling Index (MFI) is an important parameter in design of the integrated RO/NF membrane processes for drinking water treatment. In this study, the effect of particle, membrane and feed water characteristics on membrane fouling index were investigated systematically. Higher fouling index values were observed when filtering suspensions with smaller particle size and higher feed particle concentration. Larger membrane resistance due to smaller pore size resulted in an increased membrane fouling index. The variations of feed water hardness and TDS concentrations did not show any impact on fouling index, suggesting that there were no significant colloidal interactions among particles and thus the porosity of particle cake layer accumulated on the membrane surface could be assumed to be 0.36 according to random packing density. Based on the experimental observations, fundamental membrane fouling index model was developed using Happel Cell. The effect of primary model parameters including particle size ($a_p$), particle concentration ($C_o$), membrane resistance ($R_m$), were accurately assessed without any fitting parameters, and the prediction of membrane fouling index such as MFI exhibited very good agreement with the experimental results.

• Journal of the Korean Applied Science and Technology
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• v.28 no.4
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• pp.386-392
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• 2011

We are crystallized to the linear low density polyethylene(LLDPE) particles by a thermally induced phase separation(TIPS). TIPS process based on the phase separation mechanism was performed for the LLDPE system which undergoes liquid-solid phase separation. The linear low density polyethylene particle formation occurred by the nucleation and growth mechanism in the metastable region. Although the growth rates depended on the experimental conditions such as the polymer concentration and temperature, the particles were larger when the polymer concentration was higher or temperature was higher. The particles were observed by SEM. The LLDPE particle size distribution became broader when the polymer concentration was higher.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.9
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• pp.2342-2352
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• 1995

Deposition of flame-synthesized silica particles onto a target is utilized in optical fiber preform fabrication processes. The particles are convected and deposited onto the target. Falkner-Skan wedge flow was chosen as the particle laden flow. Typically the particles are polydisperse in size and follow a lognormal size distribution. Brownian diffusion, thermophoresis, and coagulation of the particles were considered and effects of these phenomena on particle deposition were studied. A moment model was developed in order to predict the particle number density and the particle size distribution simultaneously. Particle deposition with various wedge configurations was examined for conditions selected for a typical VAD process. When coagulation was considered, mean particle size and its standard deviation increased and particle number density decreased, compared to the case without coagulation. These results proved the fact that coagulation effect expands particle size distribution. The results were discussed with characteristics of thermal and diffusion boundary layers. As the boundary layers grow in thickness, overall temperature and concentration gradients decrease, resulting in decrease of deposition rate and increase of particle residence time in the flow and thus coagulation effect.