• Journal of the Korean Geotechnical Society
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• v.35 no.4
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• pp.37-42
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• 2019

Hydrate dissociation is required to produce methane, which generates both water and methane. Thus, multiphase fluid flow and desalination are expected during methane production, which causes the fine migration and clogging in pores. The goal of this study is to explore the effects of both multiphase fluid flow and desalination on the migration and clogging of kaolin particles as typical fines. The results are as follows : (1) the larger the pore size is, the more mounting the critical clogging concentration is, (2) kaolin particles are more easily clustering and clogging in deionized water than salty water, and (3) the critical clogging concentration of kaolin in multiphase fluid flow is lower than in singlephase fluid flow. Therefore, clustering and clogging of kaolin within pore occur easily due to desalination and multiphase fluid flow when methane is produced from hydrates, and the efficiency of methane production is expected to decrease due to the degradation of permeability coefficient.

• Nuclear Engineering and Technology
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• v.44 no.1
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• pp.79-88
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• 2012

Migration tests were performed with conservative tracers in a fractured zone that had a single fracture of about 2.5 m distance at the KURT. To interpret the migration of the tracers in the fractured rock, a solute transport model was developed. A two dimensional variable aperture channel model was adopted to describe the fractured path and hydrology, and a particle tracking method was used for solute transport. The simulation tried not only to develop a migration model of solutes for open flow environments but also to produce ideas for a better understanding of solute behaviours in indefinable fracture zones by comparing them to experimental results. The results of our simulations and experiments are described as elution and breakthrough curves, and are quantified by momentum analysis. The main retardation mechanism of nonsorbing tracers, including matrixdiffusion, was investigated.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1903-1908
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• 2003

The motion of a small, heavy rigid particle in the shear flow on a stationary wall is investigated in the context of Stokes flow. The lift force proposed by Saffman(1965) and later modified by Mclaughlin(1991) and Mei(1992) is considered in the prediction of the particle motion far away from the wall. Later, the expression of the lift force is modified to take into account the effect of wall(Cherukat and Mclaughlin, 1994). In the analysis the gravity and buoyancy effect are also taken into account. An analytical and numerical results for the terminal velocities and trajectories of the particle after the enough lapse of time are presented.

• Journal of the Korean Society of Visualization
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• v.18 no.2
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• pp.10-17
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• 2020

The curvature of wound boundaries has been identified as a key modulator that determines a type of force responsible for cell migration. While several studies report how certain curvatures of the boundary correlate with the rate at which the wound closes, it remains unclear how these curvatures are spatiotemporally formed to regulate the healing process. We investigated the dynamic changes in the boundary curvatures by visualizing cell migration patterns. Locally, cells at the convex boundary continuously move forward with transmitting kinetic responses behind to the cells away from the boundary, and cells at the concave boundary exhibit dramatic contracting motion, like a purse-string, when they accumulate enough negative curvatures to gain the thrust toward the void. Globally, the dynamics of boundary geometries are controlled by the diffusive flow of cells driven by the density gradient between the wound area and the cell layer.

• Geomechanics and Engineering
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• v.30 no.2
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• pp.201-210
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• 2022

This paper presents a study regarding the influence of various water levels on the characteristics of subgrade mud pumping through a self-developed test instrument. The characteristics of mud pumping are primarily reflected by axial strain, excess pore water pressure, and fine particle migration. The results show that the axial strain increases nonlinearly with an increase in cycles number; however, the increasing rate gradually decreases, thus, an empirical model for calculating the axial strain of the samples is presented. The excess pore water pressure increases rapidly first and then decreases slowly with an increase in cycles number. Furthermore, the dynamic stress within the soil first rapidly decreases and then eventually slows. The results indicate that the axial strain, excess pore water pressure, and the height and weight of the migrated fine particles decrease significantly with a low water level. In this study, when the water level is 50 mm lower than the subgrade soil surface, the issue of subgrade mud pumping no longer exist.

• Korean Chemical Engineering Research
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• v.54 no.5
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• pp.659-664
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• 2016

In order to resolve the AAEM species migration routes and the interaction relationship between biochar structure and AAEM species during biomass pyrolysis, experiments were performed in an entrained flow reactor with $N_2$ at $500{\sim}900^{\circ}C$. ICP-AES, XPS and SEM-EDX were used to examine content and distribution of AAEM species and the physicochemical structures of biochar. The results show that at $500{\sim}700^{\circ}C$, the precipitation rate of AAEM species is relatively high. At high temperature (>$700^{\circ}C$), the AAEM species continue to migrate from interior to exterior, but little precipitation from biochar surface. And the migration of AAEM species is mainly realized by the C-O bond as the carrier medium. The AAEM species on biochar surface are mainly Na, Mg and Ca (<$700^{\circ}C$), while changing to K, Mg and Ca (${\geq}700^{\circ}C$). From $500^{\circ}C$ to $900^{\circ}C$, the biochar particle morphology gradually changes from fibers to porous structures, finally to molten particles. At $700{\sim}900^{\circ}C$, Ca element is obviously enriched on the molten edge of the biochar porous structures.

• Fashion & Textile Research Journal
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• v.6 no.5
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• pp.667-672
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• 2004

Poly(ethylene terephthalate) (PET) fabrics were treated with a silica particle and phosphate flame retardant to determine the optimum process condition of the digital textile printing(DTP) media. The treating conditions for the study were 6 conditions, from F1 to F6, in which F3, F4 and F5 were treated with mixture of both silica particle and phosphate compound in process of pad, dry and cure fixation. F6 was treated with phosphate compound only and silica particle coating successively. Xanthan gum was used to control the migration of liquid phosphate compound onto PET fabrics. The change in surface morphology of fabrics treated with silica particle and phosphate compound was observed by SEM and flame retardance was evaluated by limiting oxygen index(LOI). It was observed that F6 was the excellent flame retardance and low bleeding in printing, Collectively, the printing characteristics of silica to cyan, magenta, yellow and black ink and flame retardance of fabrics finished with phosphate compound were identified in this study.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.10
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• pp.1284-1293
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• 1997

The electrostatic effect on particle deposition onto a heated, Horizontal free-standing wafer surface was investigated numerically. The deposition mechanisms considered were convection, Brownian and turbulent diffusion, sedimentation, thermophoresis and electrostatic force. The electric charge on particle needed to calculate the electrostatic migration velocity induced by the local electric field was assumed to be the Boltzmann equilibrium charge. The electrostatic forces acted upon the particle included the Coulombic, image, dielectrophoretic and dipole-dipole forces based on the assumption that the particle and wafer surface are conducting. The electric potential distribution needed to calculate the local electric field around the wafer was calculated from the Laplace equation. The averaged and local deposition velocities were obtained for a temperature difference of 0-10 K and an applied voltage of 0-1000 v.The numerical results were then compared with those of the present suggested approximate model and the available experimental data. The comparison showed relatively good agreement between them.

• Nuclear Engineering and Technology
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• v.30 no.6
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• pp.485-495
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• 1998

Migration characteristics of tracers in a rock fracture in a case of line-source and line-collection was studied. The fracture plane was discretized into a square mesh to which variable apertures were assigned. The spatially varying apertures of a fracture were generated using a geostatistical method, based on a given aperture probability density distribution and a specified spatial correlation length. The flow potential and pressure at each node were computed. Calculations showed that fluid flow occurs predominantly through a few preferred paths. Hence, the large range of apertures in the fracture gives rise to flow channeling. The solute transport was calculated using a particle tracking method. The migration plumes of tracer between injection line and withdrawal line are displayed in contour plots. The elution curves are shown to be controlled by the aperture density distribution and to be insensitive to statistical realization and spatial correlation length.

• The Korean Journal of Ceramics
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• v.5 no.3
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• pp.260-264
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• 1999

Effect of the particle size of $MgTiO_3$ and $CaTiO_3$ on the microstructural evolution during sintering of $0.93MgTiO_3-0.07CaTiO_3$ system was investigated. Microwave dielectric characteristics of the sintered ceramics were also measured. The microstructural evolutions were explained with an emphasis on the entrapping behavior of $CaTiO_3$ grain into the $MgTiO_3$ grain and were correlated with microwave dielectric characteristics. With an increasing particle size ratio between $CaTiO_3$and $MgTiO_3$, the fraction of entraped $CaTiO_3$ grains increased, which grain growth of $MgTiO_3$were concurrently accelerated due to decreasing drag force of its boundary migration. Besides, $CaTiO_3$-grain entrapment into the $MgTiO_3$grain interior led to decreaseing quality factor values.