• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.1
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• pp.19-33
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• 2002

A numerical method to efficiently secure necessary design informations of the hydraulic characteristics of rubble mound breakwater was attempted here. The method combines the exterior wave field with the interior wave field which is formulated incorporating porous media flow inside the breakwaters. An approximate method based on the long wave assumption was used for the exterior wave field while a boundary element method was used for the interior wave field. A hydraulic experiment was also performed to verify the validity of the numerical analysis. The numerical results were compared with experimental data and results from existing formulae. They generally agreed in both reflection and transmission coefficients. The calculated pore pressures also showed a similar pattern with experimental data, even if they gave some significant differences in their values fur some cases. The main cause of such differences can be attributed to the strongly nonlinear wave field occurring on the frontal slope of the breakwater. The direct input of dynamic pressures(measured from hydraulic experiment) into the numerical method was suggested as a promising method to enhance the predictability of pore pressures.

• Membrane Journal
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• v.7 no.3
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• pp.142-149
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• 1997

The extended analysis on the diverging flow through asymmetric membrane pores has been performed in this study. Afore rigorous equations of velocity profile relevant to the divergent slit and cone shaped channels, which are widely used as a general pore model, have been obtained by employing a creeping flow approach of Newtonian fluids. As a degree of asymmetry (i.e., diverging angle) is increased, the predicted flow function shifts Toward the center region due to the incorporated wall effect, so that the overall velocity profile becomes decreased. It is true, as expected, that when the divergent channel is in the low diverging angle limit, the channel flow results in the Poiseuillean fashion by utilizing a lubrication approximation. The flow rate equation of each type of channel has been developed from the combined solution of velocity profile and pressure fields. The effect of diverging flow on the flow rate enhancement has been remarkably predicted, in which the flow rate increases with the increase of pore asymmetry. The advantage of our theoretical results lies in the analytical expression for the diverging flow behavior through pore channels as well as its ability to play a fundamental role on the related membrane filtrations such as microfiltration and ultrafiltration.

• Journal of the Korean Geotechnical Society
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• v.34 no.11
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• pp.33-41
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• 2018

Soil internal erosion is a phenomenon in which fines attached to the solid skeleton are detached by fluid flow, and this continuous fine migration weakens the hydro-mechanical characteristics of the ground structure. This paper proposed governing equations for fine migration in pore spaces and its related scheme for the numerical analysis. Phase diagram for fine particles includes three different states: detached fines in the liquid phase ($c_e$), attached fines in the solid phase (${\sigma}_a$), and pore-clogged fines in the solid phase (${\sigma}_s$). Numerical formulations for finite element method are developed based on the hydraulic governing equations of pore fluid and fine migration. This study proposed a method of estimating model parameters for fine detachment, attachment, and clogging from 1D erosion experiments. And it proposed an analytical formula for hydraulic permeability function considering fine clogging. Numerical analysis of the previous erosion test developed the numerical scheme and verified the adequacy of fine migration models.

• Journal of the Korean Geotechnical Society
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• v.24 no.3
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• pp.35-51
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• 2008

In this paper, the application of the DSC model to the analysis of liquefaction potential is examined through experimental and analytical investigations. For more realistic description of dynamic responses of saturated sands, the DSC model was modified based on the dynamic effective stress path and excess pore pressure development. Both static and cyclic undrained triaxial tests were performed for sands with different relative densities and confining stresses. Based on test results, a classification of liquefaction phases in terms of the dynamic effective stress path and the excess pore pressure development was proposed and adopted into the modified DSC model. The proposed methods using the original and modified DSC models were compared with examples with different relative densities and confining stresses. Based on the comparisons between the predicted results using the original and modified DSC models and experimental data, the parameters required to define the model were simplified. It was also found that modified model more accurately simulate initial liquefaction and dynamic responses of soil under cyclic undrained triaxial tests.

• Journal of Hydrogen and New Energy
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• v.34 no.3
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• pp.283-291
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• 2023

The physical properties were analyzed for four gas diffusion layers, and gas diffusion electrodes (GDEs) for the cathode of high-temperature polymer electrolyte membrane fuel cell were fabricated through bar coating with three binder to carbon (B/C) ratios. Among them, The GDE from JNT30-A6P showed a significant change in secondary pore volume at a B/C ratio of 0.31, which had the largest pore volume among all GDEs. In the polarization curve, JNT30-A6P GDE showed the best membrane electrode assembly (MEA) performance with a peak power density of 384 mW/cm² at a a B/C ratio of 0.31. From the distribution of relaxation time analysis, the peak 1 corresponding to mass transfer resistance of oxygen reduction reaction (ORR) was significantly reduced in the JNT30-A6P GDE. This is the result that when the binder content decreased, the volume of the secondary pore increased, and the mass transfer resistance of ORR decreased, which played an essential role in the MEA performance.

• Geophysics and Geophysical Exploration
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• v.9 no.1
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• pp.50-59
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• 2006

The risk of fault reactivation in the Gippsland Basin was calculated using the FAST (Fault Analysis Seal Technology) technique, which determines fault reactivation risk by estimating the increase in pore pressure required to cause reactivation within the present-day stress field. The stress regime in the Gippsland Basin is on the boundary between strike-slip and reverse faulting: maximum horizontal stress $({\sim}\;40.5\;Mpa/km)$ > vertical stress (21 Mpa/km) ${\sim}$ minimum horizontal stress (20 MPa/km). Pore pressure is hydrostatic above the Campanian Volcanics of the Golden Beach Subgroup. The NW-SE maximum horizontal stress orientation $(139^{\circ}N)$ determined herein is broadly consistent with previous estimates, and verifies a NW-SE maximum horizontal stress orientation in the Gippsland Basin. Fault reactivation risk in the Gippsland Basin was calculated using two fault strength scenarios; cohesionless faults $(C=0;{\mu}=0.65)$ and healed faults $(C=5.4;\;{\mu}=0.78)$. The orientations of faults with relatively high and relatively low reactivation potential are almost identical for healed and cohesionless fault strength scenarios. High-angle faults striking NE-SW are unlikely to reactivate in the current stress regime. High-angle faults oriented SSE-NNW and ENE-WSW have the highest fault reactivation risk. Additionally, low-angle faults (thrust faults) striking NE-SW have a relatively high risk of reactivation. The highest reactivation risk for optimally oriented faults corresponds to an estimated pore pressure increase (Delta-P) of 3.8 MPa $({\sim}548\;psi)$ for cohesionless faults and 15.6 MPa $({\sim}2262\;psi)$ for healed faults. The absolute values of pore pressure increase obtained from fault reactivation analysis presented in this paper are subject to large errors because of uncertainties in the geomechanical model (in situ stress and rock strength data). In particular, the maximum horizontal stress magnitude and fault strength data are poorly constrained. Therefore, fault reactivation analysis cannot be used to directly measure the maximum allowable pore pressure increase within a reservoir. We argue that fault reactivation analysis of this type can only be used for assessing the relative risk of fault reactivation and not to determine the maximum allowable pore pressure increase a fault can withstand prior to reactivation.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1699-1702
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• 2012

$TiO_2$ nanostructures with various morphologies like cubes, spheres, hexahedral pillars and spherical tubes were synthesized by microwave-assisted hydrothermal process. Each structure was obtained by changing the relative concentrations of titanium tetraisoproxide (TTIP), tetrabutylammonium hydroxide (TBAH) and ethanol. Scanning electron microscopy (SEM), transmission electoron microscopy (TEM), X-ray diffraction and Brunauer-Emmett-Teller (BET) surface area analysis were used to characterize the synthesized $TiO_2$ nanostructures. From these results, it has been proved that $TiO_2$ structure could be controlled to have specific morphology, size, surface area, pore volume and pore size distribution.

• Bulletin of the Korean Chemical Society
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• v.27 no.3
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• pp.399-402
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• 2006

Porous organic-inorganic hybrids have been prepared from tetraethylorthosilicate (TEOS) and organosilane precursors by sol-gel method. Two organosilanes, 3-(2,4-dinitrophenylamino)propyltriethoxysilane (DNPTES) and N-[[(2-nitrophenyl)methoxy]carbonyl]-3-triethoxysilylpropylamine (NPTES) were used to incorporate electron-accepting (di)nitrophenyl groups into the hybrids. The hybrids were characterized by FT-IR spectroscopy and elemental analysis, and their pore characteristics were studied by nitrogen sorption porosimetry. Surface area of the hybrids ranged from 563 to 770 $m^2$/g, pore volume, 0.23-0.30 $cm^3$/g, and porosity, 35-41%. It was demonstrated by UV-vis spectroscopy that aniline, ethylenediamine, and 1-aminonaphthalene could be removed from their hexane solutions in the presence of the hybrid powders. The removal of amines is attributable to donor-acceptor interaction between the electron-donating amines and electron-accepting (di)nitrophenyl moiety.

• Steel and Composite Structures
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• v.36 no.6
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• pp.631-642
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• 2020

This paper studies nonlinear stability behavior of a nanocrystalline silicon curved nanoshell considering strain gradient size-dependency. Nanocrystallines are composite materials with an interface phase and randomly distributed nano-size grains and pores. Imperfectness of the curved nanoshell has been defined based on an initial deflection. The formulation of nanocrystalline nanoshell has been established by thin shell theory and an analytical approach has been used in order to solve the buckling problem. For accurately describing the size effects related to nano-grains or nano-pores, their surface energies have been included. Nonlinear stability curves of the nanoshell are affected by the size of nano-grain, curvature radius and nano-pore volume fraction. It is found that increasing the nano-pore volume fraction results in lower buckling loads.

• Journal of the Korean Ceramic Society
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• v.35 no.9
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• pp.958-968
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• 1998

Porous silica ceramics were prepared using DCCA(Drying Control Chemical Additives) Such as uncharged polymer(Polyethylene glycol) and protein (Lipase) under H2O/Low-grade TEOS=10 C2H5OH/Low-grade TEOS=1 HC1/Low=grade TEOS=0.01 After Plain which doesn't added DCCA and samples of 11 sorts which varied molecular weight of PEG(Mw=600, 1000, 2000) quantity of Lipase and concentration of wat-er were synthesized gellation time and thermal analysis were investigated. After heat-treated at 600, cry-stal structures analyses of SiO2 polymer and characteristics of pores were investigated. Gellation time was retarded about 2-6 times as compared with plain resulting in addition of DCCA and crystal structures ex-hibited amorphous state. Moreover as increase of water a short gellation time was obtained. The samples added PEG showed increase of specific surface areas up to 20-40% and had micropores while those of Lipase were decreased about 90% and showed broad pore size distribution.