• The Korean Journal of Ceramics
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• v.5 no.3
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• pp.205-210
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• 1999

The thermodynamic properties and phase diagram of the$ PbO-ZrO_2$ system have been critically assessed using the Thermo-Calc program. Excess Gibbs energies were expressed by Redlich-Kister polynomials for the solid phases, by the two-sublattice ionic liquid model for the liquid phase and by the compound energy model for the solid solution phase. All solid phases were treated as stoichimetric compounds.

• Journal of the Korean Chemical Society
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• v.60 no.2
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• pp.111-117
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• 2016

In this article, new Gibbs free energy of mixing is derived when there are specific interactions between solvent-solute molecules and between solute-solute molecules in binary solutions. It is asssumed that a probability of specific interactions satisfies a binomial distribution. Using this Gibbs free energy of mixing, we investigate possible types of partial miscibilities and show that Ω-shaped temperature-composition phase diagrams can exist. We calculate Ω-shaped temperature-composition phase diagram of water-2-butanol system and compare that with result calculated by the method of Hino⁵ et al. and the experimental data.

• 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 $CO_2/CH_3COCH_3$.

• Resources Recycling
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• v.21 no.1
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• pp.66-74
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• 2012

In order to evaluate the feasibility of selective sulfidization of uranium and rare-earth(RE) oxides, an analysis on thermodynamic data, such as $M-O_2-S_2$ phase stability diagram and changes of Gibbs free energy for sulfidization of uranium and rare-earth oxides were carried out. Comparing $RE-O_2-S_2$ with $U-O_2-S_2$ phase stability diagram at wide range of sulfur potential, $UO_2$ remains unreacted, while RE oxides are sulfidized. The Gibbs free energy change(${\Delta}G^{\circ}$) of sulfidization of RE oxides is lower than that of uranium oxides. Thus, the selective formation of RE sulfides is possible during sulfidization of RE and uranium oxides at lower temperature. $CS_2$ was selected as a sulfidizing agent, because it is a stronger sulfidizing agent than other agents and reacts at lower temperature.

• Bulletin of the Korean Chemical Society
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• v.23 no.6
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• pp.811-817
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• 2002

Gibbs ensemble Monte Carlo simulations were performed to calculate the vapor-liquid coexistence properties for the binary mixtures $CO_2/CH_3OH$, $CO_2/C_2H_5OH$, and $CO_2/CH_3CH_2CH_2OH.$ The configurational bias Monte Carlo method was used in the simulation of alcohol. Density of the mixture, composition of the mixture, the pressure-composition diagram, and the radial distribution function were calculated at vapor-liquid equilibrium. The composition and the density of both vapor and liquid from simulation agree considerably well with the experimental values over a wide range of pressures. The radial distribution functions in the liquid mixtures show that $CO_2$ molecules interact more stogly with methyl group than methylene group of $C_2H_5OH$ and $CH_3CH_2CH_2OH$ due to the steric effects of the alcohol molecules.

• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.581-588
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• 2018

In this article, electrochemical investigation of the transfer reaction of ionizable cefotiam (CTM), an antibiotic molecule across a polarized water/1,2-dichloroethane (water/1,2-DCE) interface was studied. Ion partition diagram providing the preferred charged form of CTM in either water or 1,2-DCE phase was established via the voltammetric evaluation of the transfer process of differently charged CTM species depending upon the pH variation of aqueous solutions. Thermodynamic information including the formal transfer potential and formal Gibbs transfer energy values in addition to important pharmacokinetics including partition coefficients of ionizable CTM were also evaluated. In particular, the current associated with the transfer of CTM present at pH 3.0 aqueous solution proportionally increased with respect to the CTM concentration which was further used for developing CTM sensitive ion sensor. In order to improve the portability and convenient usage, a single microhole interface fabricated in a supportive polyethylene terephthalate film was used of which hole was filled with a polyvinylchloride-2-nitrophenyloctylether (PVC-NPOE) gel replacing 1,2-DCE, a toxic organic solvent. A dynamic range of $1-10{\mu}M$ CTM was obtained.

• Applied Chemistry for Engineering
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• v.28 no.5
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• pp.506-512
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• 2017

The transfer reaction characteristics of tetracycline (TC) across a polarized water/1,2-dichloroethane (1,2-DCE) interface was studied via controlling both pH and ionic strength of the aqueous phase in conjunction with cyclic and differential pulse voltammetries. Formal transfer potential values of differently charged TC ionic species at the water/1,2-DCE interface were measured as a function of pH values of the aqueous solution, which led to establishing an ionic partition diagram for TC. As a result, we could identify which TC ionic species are more dominant in the aqueous or organic phase. Thermodynamic properties including the formal transfer potential, partition coefficient and Gibbs transfer energy of TC ionic species at the water/1,2-DCE interface were also estimated. In order to construct an electrochemical sensor for TC, a single microhole supported water/polyvinylchloride-2-nitrophenyloctylether (PVC-NPOE) gel interface was fabricated. A well-defined voltammetric response associated with the TC ion transfer process was achieved at pH 4.0 similar to that of using the water/1,2-DCE interface. Also the measured current increased proportionally with respect to the TC concentration. A $5{\mu}M$ of TC in pH 4.0 buffer solution with a dynamic range from $5{\mu}M$ to $30{\mu}M$ TC concentration could be analyzed when using differential pulse stripping voltammetry.

• Korean Journal of Environmental Agriculture
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• v.39 no.1
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• pp.36-43
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• 2020

BACKGROUND: Wicheon watershed has the largest irrigation area among the mid-watershed of Nakdong river. However, no investigation of irrigation water quality has been conducted on the Wicheon watershed, which evaluates the effects on the soil quality and crop cultivation. Therefore, this study aims to provide various assessments of water quality of Wicheon watershed as the scientific basic data for efficient agricultural activities. METHODS AND RESULTS: Water sampling was performed in five locations of the first tributaries of Wicheon. Wicheon watershed showed clean water quality with very low organic matters and safe water quality from metals at all points of investigation. It was estimated that the natural chemical components of Wicheon watershed were originated from water-rock interaction in Gibbs diagram. All samples were concentrated in the type of Ca-HCO₃-Cl in the Piper diagram. The quality of irrigation water was evaluated with sodium adsorption ratio (SAR), residual sodium carbonate (RSC), permeability index (PI), and percent sodium (%Na). The values of these water quality indices were in the range of 0.37-0.67, -2.11--0.24, 41.13-84.52% and 11.28-21.84%, respectively, and were classified as good grades at all sites. CONCLUSION: The water quality of Wicheon watershed was very low in salt, indicating good irrigation water suitable for growing agricultural products. We hope that the results of this study will be used as the basic data for the cultivation of agricultural products and promotion of their excellence.