• Journal of the Korean Electrochemical Society
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• v.6 no.4
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• pp.255-260
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• 2003

The complex capacitance analysis was performed in order to examine the potential-dependent EDLC characteristics of porous carbon electrodes. The imaginary capacitance profiles $(C_{im}\;vs.\;log\lf)$ were theoretically derived for a cylindrical pore and further extended to multiple pore systems. Two important electrochemical parameters in EDLC can be estimated from the peak-shaped imaginary capacitance plots: total capacitance from the peak area and $\alpha_0$ from the peak position. Using this method, the variation of capacitance and ion conductivity in pores can be traced as a function of electric potential. The electrochemical impedance spectroscopy was recorded on the mesoporous carbon electrode as a function of electric potential and analyzed by complex capacitance method. The capacitance values obtained from the peak area showed a maximum at 0.3V (vs. SCE), which was in accordance with cyclic voltammetry result. The ionic conductivity in pores calculated from the peak position showed a maximum at 0.2 V (vs. SCE), then decreased with an increase in potential. This behavior seems due to the enhanced electrostatic interaction between ion and surface charge that becomes enriched at more positive potentials.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.02a
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• pp.32-41
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• 2000

Sand drain as a vertical drainage is widely used in soft ground improvement Recently, sand, the principal source of sand drain, is running out. The laboratory model tests were carried out to utilize gravel as a substitute for sand. Though which the characteristics of gravel are compared to those of sand for engineering purpose. Two cylindrical containers for the model test were filled with marine clayey soil from the west coast of Korea with a column in the center, one with sand, the other with gravel. Vibrating wire type piezometers were installed at the distance of 1.0D, 1.5D and 2.0D from the center of the column. The characteristics of consolidation were studied with data obtained from the measuring instrument place on the surface of the container. The parameter study was performed on the marine clayey soil before and after the test in order to verify the effectiveness of the improvement. The clogging effect was checked at various depth in gravel column after the test. In-situ tests area was divided into two areas by material used. One is Sand Drain(SD) and Sand Compaction Pile(SCP) area, the other is Gravel Drain(GD) and Gravel Compaction Pile(GCP) area. Both areas were monitored to obtain the information on settlement, pore water pressure and bearing capacity by measuring instruments for stage loading caused by embankment. The results of measurements were analyzed. According to the test results, the settlement was found to be smaller in gravel drain than in sand drain. The increase in bearing capacity by gravel pile explains the result. The clogging effect was not found in gravel column. It is assumed that gravel is relatively acceptable as a drainage material. Gravel is considered to be a better material than sand for bearing capacity, and it is found that bearing capacity is larger when gravel is used as a gravel compaction pile than as a gravel drain.

• Journal of the Korean Ceramic Society
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• v.41 no.6
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• pp.485-492
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• 2004

We prepared cylindrical y-alumina pellets using amorphous alumina and pore generating agent. The pellets were immersed in an aqueous solution of the mixture of Fe(NO$_3$)$_3$ㆍ9$H_{2}O$ and $CH_3$COOH. They were then hydrothermally treated at 20$0^{\circ}C$ for 3 h in autoclave, dried and calcined. For the application of environmental catalyst for its, we investigated the decomposition characteristics of 4-chlorophenol and the initiation characteristics of OH' conversion action in $O_3$ environment with or without the Fe$_2$O$_3$ supported ${\gamma}$-alumina catalyst and $O_3$ molecule.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.271-278
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• 1999

Soil filters are commonly used to protect the soil structures from eroding and piping. When filters are clogged by fine particles which are progressively accumulated, these may lead to buildup of excessive pore pressures also leading to instability in subsurface infrastructure. A filter in the backfill of a retaining wall, a filter adjacent to the lining of a tunnel, or a filter in the bottom of an earth dam can be clogged by transported fine particles. This causes reduction in the permeability, which in turn may lead to intolerable decreases in their drainage capacity. In this thesis, the extent of this reduction is addressed using results from both experimental and theoretical investigations. In the experimental phase, the permeability reduction of a filter is monitored when an influent of constant concentration flows into the filter (uncoupled test), and when the water flow through the soil-filter system to simulate an in-situ condition (coupled test), respectively. The results of coupled and uncoupled test are compared with among others. In the theoretical phase of the investigation, a representative elemental volume of the soil filter was modeled as an ensemble of capillary tubes and the permeability reduction due to physical clogging was simulated using basic principles of flow in cylindrical tubes. In general, it was found that the permeability was reduced by at least one order of magnitude, and that the results from the uncoupled test and theoretical investigations were in good agreement. It is observed that the amount of deposited particles of the coupled test matches fairly well with that of the uncoupled test, which indicates that the prediction of permeability reduction is possible by preforming the uncoupled test instead of the coupled test, and/or by utilizing the theoretical model.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.7
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• pp.589-594
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• 2014

Recently, higher capacity and energy density of lithium ion batteries are increasingly demanded for enhancing their performance in view of the rise in the commercial distribution of electric and hybrid vehicles. Computational analysis of a porous structure of vanadium pentoxide cathode was performed, employing a phase field model. The incipient model was designed as a spherical structure with cylindrical-shaped pores. Modifying the diameters and lengths of the pore cylinder and the number of pores, we considered different conditions for the porous vanadium pentoxide cathodes for analyzing their effect on the amount of lithium ion intercalated to them. Subsequently, we optimized the porous structure to contain the largest amount of intercalated lithium ion during discharge.

• Journal of the Korean Ceramic Society
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• v.42 no.4
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• pp.237-244
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• 2005

We prepared the cylindrical $\gamma-alumina$ pellets of 5 mm in diameter and 10 mm in average length using amorphous alumina and pore generating agent. The pellets were immersed in an aqueous solution of the mixture of $Fe(NO_{3})_{3}{\cdot}9H_{2}O$ and $CH_{3}COOH$. They were then hydrothermally treated at $200^{\circ}C$ for 3 h in autoclave, dried and calcined. For the application as an environmental catalyst, we investigated the decomposition characteristics of aniline and the initiation characteristics of $OH^{\cdot}$ conversion action in $O_{3}$ environment with or without the $Fe_{2}O_{3}$ supported y-alumina catalyst and $O_{3}$ molecule.

• Geomechanics and Engineering
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• v.15 no.2
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• pp.793-803
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• 2018

Based on the theory of porous media, an interaction system of a floating pile and a saturated soil in cylindrical coordinates subjected to vertical harmonic load is presented in this paper. The surrounding soil is separated into two distinct layers. The upper soil layer above the level of pile base is described as a saturated viscoelastic medium and the lower soil layer is idealized as equivalent spring-dashpot elements with complex stiffness. Considering the cylindrically symmetry and the pile-soil compatibility condition of the interaction system, a frequency-domain analytical solution for dynamic impedance of the floating pile embedded in saturated viscoelastic soil is also derived, and reduced to verify it with existing solutions. An extensive parametric analysis has been conducted to reveal the effects of the impedance of the lower soil base, the interaction coefficient and the damping coefficient of the saturated viscoelastic soil layer on the vertical vibration of the pile-soil interaction system. It is shown that the vertical dynamic impedance of the floating pile significantly depends on the real stiffness of the impedance of the lower soil base, but is less sensitive to its dynamic damping variation; the behavior of the pile in poro-visco-elastic soils is totally different with that in single-phase elastic soils due to the existence of pore liquid; the effect of the interaction coefficient of solid and liquid on the pile-soil system is limited.

• Journal of Korean Society on Water Environment
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• v.21 no.1
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• pp.29-33
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• 2005

In order to recycle the waste material and to develop the thickening unit of waste activated sludge from wastewater treatment facilities, the filtration bio-reactor equipped with a shadow mask filter module was employed for this work from which the operating properties and parameters were drawn. The sludge thickening and filtration unit is made of cylindrical acryl tank(12cm i.d. ${\times}$ 58cm height: working volume of 6L), where the flat-sheet type of shadow mask filter module(pore size: 220~250um, opening area: 34.8~39.6%) was installed and the effluent was withdrawn from the effluent port at the lowest point of the reactor, and the filtration was performed only by the hydraulic pressure. For evaluating the operating performance of this reactor, some parameters such as the solid-liquid separation of different biomass concentrations, the water quality of filtrate, the aeration cleaning time and the cleaning effect were investigated. Depending on the MLSS concentrations, the different time to withdraw 3L of filtrate was required in which the longer filtration time was necessary for the higher MLSS concentrations caused by the thicker formation of cake layer: 40 minutes for 5,000 mg/L, 70 minutes for 10,000 mg/L and 100 minutes for 15,000 mg/L, where the concentrations of SS were 8.9, 6.7 and 6.5 mg/L, respectively. Under the same operating conditions (the intensity of aeration cleaning: 80 L/min, MLSS: 10,000 mg/L), the proper aeration cleaning time was revealed 30 seconds, and the stable formation of cake layer was in the range of 10 to 15 minutes. Therefore, the shadow mask considered as a waste material can be of use as a filter material for the sludge thickening system.

• Journal of the Korean Geosynthetics Society
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• v.11 no.1
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• pp.47-56
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• 2012

Discharge capacity of PBD is sensitive in proportion to thickness and ground condition, and drainage of PBD declines due to disturbance effect in surrounding ground by mandrel used for vertical drainage setting and setting machines and type. Also, deviation of discharge capacity gets larger according to ground condition, construction condition and soil properties. But cause and analysis of those problems like reduced discharge of capacity and delayed dissipation of pore water pressure for discharge capacity is lack. Thus, in this text, ground improvement and discharge capacity is investigated by implementing composite discharge capacity test for analysis of an effect factor of PBD discharge capacity with in-situ ground condition. After fixing the vertical drain on a cylindrical cylinder, put churned sample into the cylinder. After in-situ ground and reclamation of ground are dredged, load following the loading step of 30, 70 and 120kPa using a pressure device. Result of the test, The discharge capacity was SM>ML>CL>CL(dredged soil) in situ condition and more fine-grained content, the amount of discharge was greater.

• Membrane Journal
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• v.21 no.3
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• pp.236-246
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• 2011

In this study, we used prepared a cylindrical module consisting 100 hollow fibers of commercialized (hydrophobic) polyethylene membrane of $0.4{\mu}m$ pore size and systematically studied performance of direct contact membrane distillation (DCMD) and sweep gas membrane distillation (SGMD) in terms of variation of permeate flux and salt rejection with respect to temperature drop across the membrane, salt concentrations in feed, and flow rates of cooling water and sweep gas. SGMD was regarded as DCMD with a sweep gas layer between permeate-side membrane surface and cooling water. Sweep gas flow decreases the permeate flux from that of DCMD by providing an additional gas-layer resistance. We compared DCMD and SGMD performance by using mass balance with a fitting parameter (${\omega}$), indicating fraction of permeate flow rate.