• Bulletin of the Korean Chemical Society
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• v.26 no.7
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• pp.1083-1089
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• 2005

Most experimental studies available in the literature on filtration are based on observed average zeta potential of particles (usually 10 measurements). However, analyses of data using the average zeta potential alone can lead to misleading and erroneous conclusions about the attachment behavior because of the variation of particle zeta potentials and the heterogeneous distribution of the collector surface charge. To study characteristics of zeta potential, zeta potential distributions (ZPDs) of silica particles under 9 different chemical conditions were investigated. Contrary to many researchers’ assumptions, most of the ZPDs of silica particles were broad. The solids concentration removal was better near the isoelectric point (IEP) as many researchers have noticed, thus proper destabilization of particles is very important to achieve better particle removal in particle separation processes. While, the mean zeta potential of silica particles at a given coagulant dose was a function of particle concentration; the amount of needed coagulant for particle destabilization was proportional to the total surface charge area of particles in the suspension.

• Journal of the Korean Chemical Society
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• v.56 no.6
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• pp.669-672
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• 2012

Classical molecular dynamics (MD) simulations using a scaled OSS2 potential originally derived from ab initio calculations are used to study the radial distribution functions of water. The original OSS2 water potential is shown to represent a glassy or an ice at ambient temperature, but the diffusion coefficient increases on increasing the temperature of the system or decreasing the density. This suggests scaling the OSS2 potential. The O-O, O-H, and H-H radial distribution functions and the corresponding coordination numbers for the scaled OSS2 potential, obtained by MD simulation, are in good agreement with the experiment results and calculations for the SPC/E water potential over a range of temperatures.

• Journal of the Korean Ceramic Society
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• v.47 no.1
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• pp.8-18
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• 2010

When metal oxides are exposed to chemical potential gradients, ions are driven to diffusive mass transport. During this transport process, the divergence of ionic fluxes offers the formation/annihilation of oxides. Therefore, the divergence of ionic flux may play an important role in the void formation in oxides. Kinetic equations were derived for describing chemical potential distribution, ionic fluxes and their divergence in oxides. The divergence was found to be the measure of void formation. Defect chemistry in scales is directly related to the sign of divergence and gives an indication of the void formation behavior. The quantitative estimation on the void formation was successfully applied to a growing magnetite scale in high temperature oxidation of iron at 823 K.

• Clean Technology
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• v.12 no.4
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• pp.211-216
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• 2006

In this study, we investigated the potential changes in the cross sectional area of the rectangular microchannel with various zeta potentials and hydraulic diameters. We changed height/width ratio as 1, 1/2, and 1/3 and investigated its effect on the potential change. For this research, FEMLAB(Comsol, verson 3.0) was used to investigate the theoretical potential distribution. The potential changes in the cross section shows that right and left surfaces affect to some ranges. For the same area and shape, the potential value is directly proportional to the zeta potential change. With the decrease in the H/W ratio, the electrical double layer is condensed to the side surfaces.

• Macromolecular Research
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• v.17 no.7
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• pp.483-490
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• 2009

Stable poly(styrene-co-divinylbenzene) [P(St-co-DVB)] micro spheres with narrow size distribution were synthesized in the presence of 2,2'-azobis(2,4-dimethyl valeronitrile) (V-65) and co-initiator in an acetone/water mixture in the precipitation polymerization at $53^{\circ}C$ for 24 h. Potassium peroxodisulfate (KPS), ammonium peroxodisulfate (APS) and sodium peroxodisulfate (NaPS) were used as co-initiators. The optimum ratio of acetone to water for the formation of a narrow distribution of P(St-co-DVB) particles was 49:11 (g/g). The optimum co-initiator compositions for narrow distribution were 9:1 (g/g) for V-65 to KPS, 11:1 for V-65 to APS and 6:1 for V-65 to NaPS. The yield for these compositions was $54{\sim}57%$ and the largest particle size was obtained with the lowest zeta-potential and CV values. From the XPS measurements, the charge density was increased but the zeta potential decreased with increasing sulfur content, implying that the sulfate group provides the electrostatic stabilization on the particle surface. This suggested that the self-crosslinking between styrene and DVB, the electrostatic stabilization of initiators, and the balanced hydrophobic and hydrophilic properties of the solvents are responsible for the formation of stable P(St-co-DVB) spherical particles with narrow size distribution.

• Bulletin of the Korean Chemical Society
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• v.11 no.6
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• pp.487-493
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• 1990

A complete potential profile of an electrical double layer is calculated from a distribution function of charged particles based upon a model where the effect of a charged electrode and the finite size of ion are explicitly included. Electrons which are distributed on the electrode surface are assumed not to penetrate the electrode/electrolyte boundary. Formation of the constant density regions and their effects on potential and the electrical double layer capacitances are studied in great detail. The distribution of surface electrons as well as the constant density regions are found to be essential in characterizing the electrical double layer. The introduction of the ion size into the prior electrical double layer model of an ideally polarizable electrode/point charged electrolyte system, shows a great improvement in its characteristics mostly at negative potential region.

• Bulletin of the Korean Chemical Society
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• v.21 no.11
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• pp.1133-1137
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• 2000

Gibbs ensemble Monte Carlo simulations were performed to calculate the vapor- liquid coexistence properties for the binary mixtures $CO_2/C_3H8$, $CO_2/CH_3OCH_3$, and $CO_2/CH_3COCH_3.$ For all the molecules the potential between sites in different molecules was simply calculated by the Lennard-Jones potential. Density of the mixture, composition of the mixture, the pressure-composition diagram, the chemical potential of component, and the radial distribution function were calculated at vapor- liquid equilibrium. The composition and the density of both vapor and liquid from simulation agreed considerably well with the experimental values over a wide range of pressures. The radial distribution functions in the liquid mixtures showed that $CO_2$ molecules tended to form cluster with each other and $C_3H8$ molecules also aggregated each other due to the weak interaction between $CO_3$ and $C_3H8$ molecule. However the interaction potentials between the same components were similar to those between the different components in the liquid mixtures $CO_2/CH_3OCH_3$ and $CO_2/CH_3COCH_3$.

• Bulletin of the Korean Chemical Society
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• v.18 no.3
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• pp.291-295
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• 1997

The adsorption of methane in K+ ion exchanged zeolite L has been studied using grand canonical ensemble Monte Carlo simulation. Average number of molecules per unit cell, number density of molecules in zeolite, distribution of molecules per unit cell, average potential per sorbate molecule, and isosteric heats of adsorption were calculated, and these results were compared with experimental results. The simulation results agreed fairly well with experimental ones. All methane molecules were located in the main channel, and the average potential of sorbate molecule was almost constant regardless of average number of molecules per unit cell and the amounts sorbed in zeolite.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.4
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• pp.447-461
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• 2016

Recently, the Renewable Fuel Standard(RFS) has been commenced from July 31, 2015 in the New and Renewable Energy Act for expanding the supply of renewable energy and reduction of national GHG target in Korea. The biodiesel is only a means of implementation for the RFS, therefore the biodiesel supply expansion is important for fulfilling the RFS obligation policy. The major key points of the biodiesl supply are expanding domestic feedstocks due to the over 60% dependence on foreign feedstock and reducing the price of feedstock because of the over 70% occupation of feed stock price in the biodiesl production cost. Therefore, we estimated actual amount of potential feedstocks which are possible to use for biodiesl production in Korea and investigated technical and political improvements for expanding biodiesl. For estimating a potential feedstocks, first selected the potential biodiesl feedstocks by investigating the status of global biodiesl feedstocks and then analyzed the possible potential amount of each feedstock by surveying the generation situations, the distribution structures and the technical level.

• Korean Journal of Microbiology
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• v.24 no.3
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• pp.308-316
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• 1986

Vertical distribution of heterotrophic bacteria and physico-chemical characteristics were measuted in Kum River estuarine sediments. And interrelationship between heterotrophic bacterka and environmental factors was also studied. The type of sediment of Site 1 was silty clay, and sand at Site 2. Annual pH ranges were between 7.1 and 7.7 in the clay type sediment (Site 1) and 6.9-7.2 in the sand type sediment (Site 2). It was shown that organic matter contents were higher in the clay type sediment than those of sand type sediment. Redox potential values of sediments were decreased rapidly with depth at Site 1, but those of Sete 2 showed vertical fluctuation. Nitrogens(ammonia+amino acid-N, nitrate-N, nitrite-N) and phosphate in the clay type sediment showed higher values than those of sand type sediment. Annual distribution of heterotrophic bacteria were ranged $6.71{\times}10^4$ cells/g dry wt. $-2.50{\times}10^6$ cells/g dry wt. In the clay type sediment and $2.67{\times}10^3$ cells/g dry wt. $-1.94{\times}10^6$ cells/g dry wt. in the sand type sediment. Distribution of proteolytic, lipolytic, and amylolytic bacteria were decreased with the depth and the highest density was found in April and the lowest in January. Bacterial populations in sediments were closely correlated with such environmental factors as pH, redox potential, moisture content, organic matter contents, and inorganic nutrients such as nitrite-N and phosphate-P.