• Nuclear Engineering and Technology
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• v.37 no.5
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• pp.469-478
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• 2005

The subchannel analysis capability of MARS, a multi-dimensional thermal-hydraulic system code, has been enhanced. In particular, the turbulent mixing and void drift models for the flow-mixing phenomena in rod bundles were improved. Then, the subchannel analysis feature was combined with the existing coupled system thermal-hydraulics (T/H) and 3D reactor kinetics calculation capability of MARS. These features allow for more realistic simulations of both the hot channel behavior and the global system T/H behavior. Using the coupled features of MARS, a coupled analysis of a main steam line break (MSLB) is carried out for demonstration purposes. The results of the calculations are very reasonable and promising.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.186-191
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• 2004

Sorption kinetics of 2-chlorophenol(2-ChP), 2,4-dichlorophenol(2,4-DChP) and 2,4,5-trichlorophenol (2,4,5-TChP), onto montmorillonite modified with hexadecyltrimethyl ammonium cations(HDTMA-mont) were investigated. One-site mass transfer model(OSMTM) and two compartment first-order kinetic model(TCFOKM) were used to analyze kinetics. As expected from the number of model parameters involved, the three-parameter TCFOKM was better than the two-parameter OSMTM in describing sorption and desorption kinetics of chlorophenols in HDTMA-mont. For all chlorophenols, the results of OSMTM analysis indicate that the predominant deprotonated speciation(at pH 9.15) exhibited higher mass transfer coefficient( $k_{s}$ ) than the protonated speciation(at pH 4.85). This is because the deprotonated speciation has stronger hydrophobic interaction than protonated speciation. Most sorption completes in three hours. The fraction of the fast sorption and the first-order sorption rate constants for the fast and slow compartments in TCFOKM were determined by fitting experimental data to the TCFOKM. The results of kinetics reveal that the fraction of the fast sorption( $f_1$) and the sorption rate constants in the fast compartments( $k_1$) were in the order 2,4,5-TChP > 2,4-DChP > 2-ChP, which agrees with the magnitude of the $K_{ow}$ . The first-order sorption rate constants in the fast compartment(10$^{0.8}$ - 10$^{1.22}$ h $r^{-1}$ ) were much larger than those in the slow compartment(10$^{-1}$.74/ - 10$^{-2}$.622/ h $r^{-1}$ ).> ).).

• The Journal of Korean Institute for Practical Engineering Education
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• v.2 no.1
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• pp.35-41
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• 2010

An enzyme-catalized reaction is usually characterized by a very large increase in the rate and high specificity. Kinetics of simple enzyme-catalized reactions are often referred to as Michelis-Menten kinetics. A chemical that interferes with an enzyme's activity is called inhibitor. There are two types of enzyme inhibitions (viz. reversible and irreversible). If an inhibitor attaches to the enzyme with weak bonds, such as hydrogen bonds, the inhibition is usually reversible. Many enzyme reactions are also inhibited reversibly by their corresponding products. The rate of substrate disappearance together with the rate of product formation may be written by nonlinear differential equations. In the present study, numerical analyses of simple enzyme kinetics and inhibited enzyme kinetics are reported for the purpose of undergraduate education in engineering.

• Journal of the Korean Ceramic Society
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• v.29 no.1
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• pp.9-14
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• 1992

Some of non-isothermal analysis methods are applied to CaO-MgO-Al2O3-SiO2 glass system to find the kinetics parameters of crystallisation, activation energy, Avrami component and frequency factor. The results using the non-isothermal analysis were compared to that of microstructure experiment. Analysis of the result has enabled to some methods to be to recommend as being the most appropriate equation to use in a glass system. It was shown that in the thermal analysis using the non-isothermal method of Kissinger, Augis-Bennett, Bansal, and Marotta, the calculation of activation energy is not much different, while Avrami component and frequency factor are different from applied each methods.

• Transactions on Electrical and Electronic Materials
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• v.16 no.2
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• pp.74-77
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• 2015

The cure kinetics of a neat epoxy system and epoxy/silica composite were investigated by DSC analysis. A cycloaliphatic type epoxy resin was diglycidyl 1,2-cyclohexanedicarboxylate and curing agent was anhydride type. To estimate kinetic parameters, the Kissinger equation was used. The activation energy of the neat epoxy system was 88.9 kJ/mol and pre-exponential factor was 2.64×10¹² min⁻¹, while the activation energy and pre-exponential factor for epoxy/silica composite were 97.4 kJ/mol and 9.21×10¹² min⁻¹, respectively. These values showed that the silica particles have effects on the cure kinetics of the neat epoxy matrix.

• Textile Coloration and Finishing
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• v.13 no.5
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• pp.24-24
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• 2001

Kinetics and mechanism for alkaline hydrolysis of C. I. Disperse Blue 79(B-79) which is 4-N, N-diacetoxyethyl-2-acylamino-5-ethoxy -2′-bromo-4′,6′-dinitroazobenzene were investigated. The color strength of B-79 in acetone/water solutions of various NaOH concentrations decreased continuously. The hydrolysis rate of B-79 increased with increasing alkali concentration and appeared following first order reaction. The observed rate constants for various concentrations of B-79 showed similar values, and B-79 was hydrolyzed by first order reaction for dye concentration. Therefore, it was confirmed that the overall reaction follow second order kinetics and proceed via S/sub n/2 reaction. From the study on kinetics and spectrometric analysis, it was proposed that the rate determining step of the hydrolysis reaction of B-79 is the nucleophilic substitution reaction - that is the reaction of the rapid attack of $OH^{-}$ on the carbon atom, which is in acceptor ring, adjacent to azo group to break the C-N bond. And it was also found that the final hydrolysis products of B-79 include both the acceptor ring in the form of sodium salt and the donor ring possessing 4-N,N-dihydroxyethyl group converted from 4-N,N-diacetoxyethyl group.

• Textile Coloration and Finishing
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• v.13 no.5
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• pp.312-319
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• 2001

Kinetics and mechanism for alkaline hydrolysis of C. I. Disperse Blue 79(B-79) which is 4-N, N- diacetoxyethyl -2- acylamino-5-ethos y -2'-bromo-4',6'-dinitroazobenzene were investigated. The color strength of B-79 in acetone/water solutions of various NaOH concentrations decreased continuously. The hydrolysis rate of B-79 increased with increasing alkali concentration and appeared following first order reaction. The observed rate constants for various concentrations of B-79 showed similar values, and B-79 was hydrolyzed by first order reaction for dye concentration. Therefore, it was confirmed that the overall reaction follow second order kinetics and proceed via $S_N2$ reaction. From the study on kinetics and spectrometric analysis, it was proposed that the rate determining step of the hydrolysis reaction of B-79 is the nucleophilic substitution reaction - that is the reaction of the rapid attack of OH- on the carbon atom, which is in acceptor ring, adjacent to auto group to break the C-N bond. And it was also found that the final hydrolysis products of B-79 include both the acceptor ring in the form of sodium salt and the donor ring possessing 4-N,N-dihydroxyethyl group converted from 4-N, N-diacetoxyethyl group.

• Nuclear Engineering and Technology
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• v.43 no.6
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• pp.531-546
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• 2011

The backward differentiation formula (BDF) method is applied to a three-dimensional reactor kinetics calculation for efficient yet accurate transient analysis with adaptive time step control. The coarse mesh finite difference (CMFD) formulation is used for an efficient implementation of the BDF method that does not require excessive memory to store old information from previous time steps. An iterative scheme to update the nodal coupling coefficients through higher order local nodal solutions is established in order to make it possible to store only node average fluxes of the previous five time points. An adaptive time step control method is derived using two order solutions, the fifth and the fourth order BDF solutions, which provide an estimate of the solution error at the current time point. The performance of the BDF- and CMFD-based spatial kinetics calculation and the adaptive time step control scheme is examined with the NEACRP control rod ejection and rod withdrawal benchmark problems. The accuracy is first assessed by comparing the BDF-based results with those of the Crank-Nicholson method with an exponential transform. The effectiveness of the adaptive time step control is then assessed in terms of the possible computing time reduction in producing sufficiently accurate solutions that meet the desired solution fidelity.

• Journal of Environmental Science International
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• v.21 no.7
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• pp.805-813
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• 2012

The removal property of Cu and Zn ions by chemical precipitation and adsorption using zeolite(Z-C1) prepared from coal fly ash(CFA) were evaluated in this study. Adsorption kinetic and equilibrium mechanisms described to analyze parameters and correlation factors with Lagergen $1^{st}$ and $2^{nd}$ order model and Langmuir and Freundlich model. Analysis of adsorption kinetics data revealed that the pseudo $2^{nd}$ order kinetics mechanism was predominant. The equilibrium data in pH 3 - 5 were able to be fitted well to a Langmuir model, by which the maximum adsorption capacities($q_{max}$) were determined at 124.9 - 140.1 mg $Cu^{2+}/g$ and 153.2 - 166.9 mg $Zn^{2+}/g$, respectively. We found that Z-C1 has a potential application as absorbents in metal ion recovery with low pH.

• Journal of Microbiology and Biotechnology
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• v.13 no.3
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• pp.332-337
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• 2003

Enzyme kinetics data play a vital role in the design of reactors and control of processes. In the present study, kinetic studies on pectinases were carried out. Partially purified polymethylgalacturonase (PMG) and polygalacturonase (PG) were the two pectinases studied. The plot of initial rate vs. initial substrate concentration did not follow the conventional Michaelis-Menten kinetics, but substrate inhibition was observed. For PMG, maximum rate was attained at an initial pectin concentration of 3 g/l, whereas maximum rate was attained when the initial substrate concentration of 2.5 g/l of polygalacturonic acid for PG I and PG II. The kinetic data were fitted to five different kinetic models to explain the substrate inhibition effect. Among the five models tested, the combined mechanism of protective diffusion limitation of both high and inhibitory substrate concentrations (semi-empirical model) explained the inhibition data with 96-99% confidence interval.