• Environmental Analysis Health and Toxicology
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• v.18 no.1
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• pp.63-67
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• 2003

Benzoic acid is produced about 700 tons/year in Korea as of 1998 survey. Most is used as a stabilizer in the processes of synthesis of pharmaceuticals and dyes. It is also used for ingradient of paint, disinfections, and antifungals. Due to the antioxidant activity of benzoic acid, the chemical is also used as food preservatives. Although the chemical is widely used in Korea, exposure levels in air, water, soil or sediment have not been monitored or estimated so that risk evaluation of benzoic acid was not possible. In this study, distribution of the chemical among environmental media was estimated using EQC model based on the chemical-physical properties. In Level I and II of which the chemical are hypothesized in equilibrium and no transfer through the media, more than 93％ of benzoic acid are estimated to be distributed in water. However, in Level III of which non-equilibrium and intermedia transfer could be occurred, the chemical is estimated to distributed to soil, 64％ and water,35% as of total amount.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.1
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• pp.61-66
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• 2006

The simple Langmuir isotherm is frequently employed to describe the equilibrium behavior of protein adsorption on a wide variety of adsorbents. The two adjustable parameters of the Langmuir isotherm - the saturation capacity, or $q_m$, and the dissociation constant, $K_d$ - are usually estimated by fitting the isotherm equation to the equilibrium data acquired from batch equilibration experiments. In this study, we have evaluated the possibility of estimating $q_m$ and $K_d$ for the adsorption of bovine serum albumin to a cation exchanger using batch kinetic data. A rate model predicated on the kinetic form of the Langmuir isotherm, with three adjustable parameters ($q_m,\;K_d$, and a rate constant), was fitted to a single kinetic profile. The value of $q_m$ determined as the result of this approach was quantitatively consistent with the $q_m$ value derived from the traditional batch equilibrium data. However, the $K_d$ value could not be retrieved from the kinetic profile, as the model fit proved insensitive to this parameter. Sensitivity analysis provided significant insight into the identifiability of the three model parameters.

• Journal of Institute of Convergence Technology
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• v.2 no.2
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• pp.30-34
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• 2012

The SI thermochemical cycle process accomplishes water splitting through distinctive three chemical reactions. We focused on thermodynamic models applicable to the process. Recently, remarkable models based on the assumed ionic species have been developed to describe highly nonideal behavior on the liquid phase reactions. ElecNRTL models with ionic reactions were proposed in order to provide reliable process simulation results for phase equilibrium calculations in Section II and III. In this study, the current thermodynamic models of SI thermochemical cycle process were briefly described and the calculation results of the applied ElecNRTL models for phase equilibrium calculations were illustrated for binary systems.

• Bulletin of the Korean Chemical Society
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• v.3 no.1
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• pp.5-9
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• 1982

Reactions of cobalt(II) chloride with 2,2'-dipyridylamine (dpa) in alcoholic solutions afford the complex of octahedral $Co(dpa)_2Cl_2{\cdot}CH_3OH$. The octahedral complex is converted to tetrahedral $Co(dpa)Cl_2$ in certain solvents or at the elevated temperature, and the tetrahedral complex is changed to the octahedral one with added dpa. The electronic spectra of the complexes in DMF, measured with various concentrations of 2,2'-dipyridylamine, establish the equilibrium; $td-Co(dpa)Cl_2+dpa_\rightleftarrows^Koh-Co(dpa)_2Cl_2$. The equilibrium constants determined by the analysis of the visible spectra are 6.4, 3.6 and 2.0 $M^{-1}$, respectively, at 25.5, 38.0 and $49.0^{\circ}C,\;with\;{\Delta}H^{\circ}\;and\;{\Delta}S^{\circ}$being -9.5 kcal/mole and -28 eu.

• Korean Chemical Engineering Research
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• v.45 no.3
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• pp.219-225
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• 2007

The equilibrium solubilization capacity of pure hydrocarbon oils by 2.5 wt% $C_{12}E_8$ nonionic surfactant solution was measured at $30^{\circ}C$ by gas chromatography (GC) analysis. Experimental results indicated that the molar solubilization ratio (MSR) for pure alkanes was found to decrease almost linearly with the alkane carbon number (ACN) of the hydrocarbon oil. For the binary mixture systems of the hydrocarbon oils both selective and nonselective solubilization behaviors were observed depending on the difference in carbon number of the two hydrocarbon oils. Equilibrium solubilization tests for the two n-octane/n-nonane and n-nonane/n-decane mixture systems in $C_{12}E_8$ surfactant solutions suggest slightly selective solubilization in favor of n-octane, but the small difference in solubilization rates between two hydrocarbon oils does not allow ruling out non-selective solubilization for these particular systems. This is certainly not the case for the n-octane/n-decane mixture, for which selective solubilization was conclusively demonstrated by GC analysis data.

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1920-1926
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• 2010

Yoon et $al.^1$ presented an approximate mathmatical model to describe ammonia removal from an experimental batch reactor system with gaseous headspace. The development of the model was initially based on assuming instantaneous equilibrium between ammonia in the aqueous and gas phases. In the model, a "saturation factor, $\beta$" was defined as a constant and used to check whether the equilibrium assumption was appropriate. The authors used the trends established by the estimated $\beta$ values to conclude that the equilibrium assumption was not valid. The authors presented valuable experimental results obtained using a carefully designed system and the model used to analyze the results accounted for the following effects: speciation of ammonia between $NH_3$ and $NH^+_4$ as a function of pH; temperature dependence of the reactions constants; and air flow rate. In this article, an alternative model based on the exact solution of the governing mass-balance differential equations was developed and used to describe ammonia removal without relying on the use of the saturation factor. The modified model was also extended to mathematically describe the pH dependence of the ammonia removal rate, in addition to accounting for the speciation of ammonia, temperature dependence of reactions constants, and air flow rate. The modified model was used to extend the analysis of the original experimental data presented by Yoon et $al.^1$ and the results matched the theory in an excellent manner.

• Environmental Analysis Health and Toxicology
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• v.16 no.3
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• pp.133-137
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• 2001

Acetanilide is a High Production Volume Chemical, which is produced about 2,300 tons/year in Korea as of 1998 survey. Most is used as an intermediate for synthesis of pharmaceuticals and dyes and the chemical is one of seven chemicals of which human and environmental risks are being assessed by National Institute of Environmental Research under the frame of OECD SIDS program. The chemical is water soluble (4 g/1 at 20$\^{C}$) and readily biodegradable (68.7％). Partition coefficiency (Log Pow) is 1.16 at 23$\^{C}$ so that the chemical has a low potential for bioaccumulation. The acute toxicities of algae, daphnia and fish are not high. The 72 hr-EｂC50 of algae is 13.5 mg/1,48 hr-EC50 of daphnia is over 100 mg/1 and 96 hr-LC50 of Oryzias latipes is over 100mg/1. Regarding the exposure, levels in air, water, soil or sediment have not been monitored or estimated so that risk evaluation of acetanilide was not possible. In this study, distribution of the chemical among environmental media was estimated using EQC model based on the chemical-physical properties. In Level I and IIof which the chemical are hypothesized in equilibrium and no transfer through the media, more than 98％ of acetanilide are estimated to be distributed in water. However, in Level Ⅲ of which non-equilibrium and intermedia transfer could be occurred, the chemical is estimated to distributed to soil as 51.8％ and water as 47.8％ as of total amount.

• Carbon letters
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• v.3 no.4
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• pp.219-225
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• 2002

The two-step surface modifications of activated carbon was carried out to improve the adsorption capacity of toxic heavy metal ions in liquid phase. Physical and chemical properties of the as-received activated carbon (AC) and two kinds of surface-modified activated carbons ($1^{st}AC$ and $2^{nd}AC$) were evaluated through the BET analysis, surface acidity, and oxides measurements. Specific surface area and pore volume did not significantly change, but surface oxide-group remarkably increased by the surface modification. Equilibrium and batch adsorptions of the various metals, such as Pb, Cd, and Cr, using AC, $1^{st}AC$, and $2^{nd}AC$ were performed at initial pH 5. The adsorption capacity and rate of $2^{nd}AC$ were higher than those of AC and $1^{st}AC$. The carboxylic/sodium carboxylate complex groups were developed from the two-step surface modification of activated carbon, which strongly affected the adsorption of metal ions.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.1
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• pp.1-8
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• 2005

An axisymmetric compressible flow solver accounting for chemical equilibrium has been developed as an analysis tool exclusively suitable for performance prediction and optimum contour design of LRE thrust chamber. By virtue of several features focusing on user-friendliness and effectiveness including automatical grid generation and iterative calculations with changes in design parameters prescribed through only one keyword-type input file, a design engineer can evaluate very fast and easily the influences of various design inputs such as geometrical parameters and operating conditions on propulsive performance. Validations have been carried out for various aspects by detailed comparisons with the result of CEA code, experimental data of JPL nozzle, actual data for two historical engines, and ReTF data for KSR-III.

• Aerospace Engineering and Technology
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• v.7 no.2
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• pp.157-161
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• 2008

This study introduce a newly developed program to calculate the combustion process of combustion chamber and gas generator of liquid rocket engine by use of Gibbs free energy minimization method based on chemical equilibrium. The simulation results of the new program and CEA code of NASA were compared and showed good agreement, thus proving the validity of the newly developed in-house program for combustion analysis.