• Journal of Soil and Groundwater Environment
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• v.10 no.4
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• pp.18-25
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• 2005

Characteristics of phenanthrene removal in an electrokinetic (EK)-Fenton process were investigated in a viewpoint of concentration and ionic strength of electrolytes. When three kinds of electrolytes (NaCl, $KH_2PO_4,\;and\;MgSO_4$) were used, the increase in electrolyte concentration caused the decrease of electrical potential gradient. The increase of electrical conductivity was due to the increase of ionic concentration in soil. The decrease of accumulated electroosmotic flow (EOF) with increase in electrolyte concentration was due to the decrease of zeta potential. The removal efficiency was in proportion to accumulated EOF which depended on ionic strength. Total energy expenditure without electrolyte was 10-30 times higher than its with 0.5 M electrolyte. The lower removal efficiency was caused by the lower energy expenditure with 0.5 M one. An effective EK-Fenton process was determined from considering the removal efficiency and the energy expenditure, simultaneously.

• New Physics: Sae Mulli
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• v.68 no.12
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• pp.1315-1323
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• 2018

We studied the carbonization due to the annealing condition of waste coffee powder for application as an active anode material for lithium-ion batteries (LIBs). The coffee powder used as an active anode material for LIBs was obtained from coffee beans, not from a coffee shells. The waste coffee powder was dried in air and heat-treated in an $Ar/H_2$ atmosphere to obtain a pore-forming activated carbon powder. The specific capacity of the sample annealed at $700^{\circ}C$ was still 303 mAh/g after 1000 cycles at a current density of 1000 mA/g and with a coulombic efficiency of over 99.5%. The number of pores and the pore size of the waste coffee powder were increased due to chemical treatment with KOH, which had the some effect as an increased specific surface area. The waste coffee powder is considered to be a very promising active anode material because of both its excellent electrochemical properties due to enhanced carrier conduction and its being a cost effective resource for use in LIBs.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.161-170
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• 2012

There are many factors to consider when attempting to improve the efficiency of fuel cell operation, such as the operation temperature, humidity, stoichiometry, operation pressure, geometric features, etc. In this paper, the effects of the operation pressure were investigated to find the current density and water saturation behavior on a cross section designated by the design geometry. A two-dimensional geometric model was established with a gas channel that can provide $H_2$ to the anode and $O_2$ and water vapor to the cathode gas diffusion layer (GDL). The results from this numerical modeling revealed that higher operation pressures would produce a higher current density than lower ones, and the water saturation behavior was different at operation pressures of 2 atm and 3 atm in the cathode GDL. In particular, the water saturation ratios are higher directly below the collector than in other areas. In addition, this paper presents the dependence of the velocity behavior in the cathode on pressure changes, and the velocity fluctuations through the GDL are higher in the output area than in inlet area. This conclusion will be utilized to design more efficient fuel cell modeling of real fuel cell operation.

• Journal of the Korean Chemical Society
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• v.37 no.1
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• pp.22-35
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• 1993

The transport phenomena of the free amino acids through poly(hydroxyethyl methacrylate)[P(HEMA)] have been investigated with and without various kinds of surfactants solution and in the mixed surfactants solution. Glutamine has the highest diffusivity among 4 amino acids at 1CMC of cetyldimethylethylammonium bromide(CTABr) surfactant. Glutamic acid is not affected by the concentration of CTABr. Methionine and Lysine shows slight decreased diffusivity at 0.5 CMC, but increase its diffusivity at 1CMC and 2CMC due to the structure change of membrane and the viscosity change of surfactant solution. Glutamic acid has the highest diffusivity among four amino acids at sodium dodecyl sulfate(SDS) and Triton X-100 surfactant. In mixed surfactant solution, each amino acids shows high diffusivity through 45% water content membrane at the 0.5 mole fraction of SDS in the SDS/TX-100 surfactant mixtures. It has been found that not only the property of membrane but also the effects of solute-solvent interactions and solvent effect are very important as the permeation of amino acids occurs through P(HEMA) membrane. The diffusivities of free amino acids through membrane depend upon their molecular shape, size and charge.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.679-684
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• 2002

In this study we performed test to compare and analyze the chloride diffusion properties in concrete according to organic coating materials used at concrete structures widely and inorganic coating materials as eco-materials in recently. The results of study were shown as follow ; 1) Chloride diffusion coefficient was low as low as and that of organic and inorganic painted was lower than non-painting 2) In case of inorganic coating material applied in this study, it should be possible to evaluate the chloride diffusion properties by CTH method. Because presumption value by CTH method is similar with real estimate value by digestion experiment.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.673-678
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• 2002

There are various methods for the electrochemical techniques to estimate diffusion coefficient of chloride ions in concrete, such as ASTM C 1202 test method, Andrade's method, Dhir's method, Tang's method, and etc. In the case of estimating diffusion coefficient of chloride ions in concrete by using these methods, applied voltage and resistivity nay exercise some influence on the characteristics of chloride ions diffusion. Thus. in this study, effect of applied voltage and resistivity on the characteristics of chloride ions diffusion in concrete were researched by applying voltage in 12V, 30V, and 60V, and by using resistivity in 0.2Ω and 1.0Ω, respectively. It can be concluded that diffusion coefficient of chloride ions are found to be increasing as the individual applied voltage and resistivity decrease, when water-cement ratio is constant.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.365-368
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• 2002

This paper considers transference number in calculating diffusion coefficient of chloride ions of concrete and mercury intrusion porosimetry to investigate the volume and distribution of pore size, respectively, analyzing and discussing the property of resistance to chloride ion of concrete with granulated blast furnace slag. The experimental results show that the diffusion coefficient of chloride ion decreases with the rise of quantity of granulated blast furnace slag and pore structure of concrete with granulated blast furnace slag is different from that of OPC concrete. And from the results of regression analysis, the result showed that the diffusion coefficient of chloride ions is affected by capillary pore above 50nm.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.299-304
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• 2002

This research was to investigate the invasion and diffusion properties of chloride ion on the concrete containing mineral admixtures by the electrically accelerated test. Mineral admixtures selected in mixes were fly-ash, ground granulated blast-furnace slag, silica fume, and meta-kaolin with 3 degrees of replacement ratios. Tang and Nilsson's test method was used to estimate chloride diffusion coefficients of that mixes. As a result, the total current passing charge and the diffusion coefficient of chloride ion were reduced with the use of mineral admixtures and the increase of replacement ratios. In addition, compressive strength was related with diffusion coefficient of chloride ion. Diffusion coefficients of concrete mixed with ground granulated blast-furnace slag showed relatively low value under the range of compressive strength of 400㎏f/㎠.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.787-790
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• 1999

To estimate durability of reinforced concrete structures located in or nearby seawater, many different kinds of accelerated tests for evaluation of chloride ion permeation in concrete were proposed. At present the only standardized test is the ASTM C 1202(RCP test). This test method is used to estimate the concrete's resistivity of the chloride penetration in concrete by using the total charges passed and sometimes used to calculate the chloride diffusion coefficients. However, this test may lead to an erroneous chloride diffusion coefficient. So this test method was compared with the modified Dhir's test and the traditional concentration diffusion test. Experimental results showed that the diffusion coefficients determined the RCP test and the PD Index gave wrongous values, but the diffusion coefficient acquired by considering a migration term was nearly the same to the CD Test.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.677-682
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• 2001

In this study, a method to evaluate diffusion coefficient of chloride ion in cracked concrete is proposed. For cracked concrete having either anisotropic or isotropic crack network, each crack of saturated concrete is considered as a V shape crack, and an effective diffusion coefficient is expressed with diffusion coefficients of cracked part and noncracked part and a so-called crack spacing factor. A comparison with experimental results shows that the diffusion coefficient for cracked concrete is accurately predicted by the effective diffusion coefficient. Prediction results also show that the cracks in concrete markedly change the diffusion properties and accelerate penetration of drifting species. The method in this paper can be effectively used to consider the effect of cracks on concrete diffusion coefficient of cracked concrete.