• YAKHAK HOEJI
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• v.20 no.1
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• pp.76-82
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• 1976

The base-catalyzed hydrolysis of indomethacin over a range of pH 8,2 to 10.0 was investigated, according to the first order kinetic equation. The energy of activation for the reaction was calculated 20, 18 kcal/mole from the Arrhenius plot. And the optimal pH of indomethacin in aqueous solution was estimated as pH 4.93 by the extrapolation of the log k-pH profiles in strong acidic and alkaline regions. And the influences of alkaline earth metals, heavy metals and some other compounds on the degradation of indomethacin were observed with no effect.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.4
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• pp.397-400
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• 1995

Effects of rheological parameters, such as shear rate, temperature, concerntration, salts on the apparent viscosity of chitosan(deacetylation degree: $84\%$, Mw: 267,000) dissolved in acetate buffer(pH 4.5) were investigated. Rheologiral properties of chitosan solution from cuticle of red snow crab (Chinonecetes japonicus) are as follows. $0.5\%$ chitosan in 0.1M acetate buffer (pH 4.5) solution showed Bingham flow having hysteresis loop. It's flow equation was $\sigma=0.757+19.6_\gamma(r^2=0.99)$. The viscosity of chitosan solution is exponentially increased with its concentration, and showed Arrhenius dependence with respect to the temperature $(10^{\circ}C-40^{\circ}C).$ When various salts were added to chitosan solution, the viscosity decreased as the concentration of counterion increased. But the type ot counterions itself does not have any significant effects on the viscosity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.8
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• pp.501-507
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• 2015

In this paper, EPR (ethylene propylene rubber) insulation material was accelerated degradation test at $121^{\circ}C$, $136^{\circ}C$, $151^{\circ}C$, and experiment the typical EAB (elongation at break) at mechanical characteristics analysis. It is shown that the failure-time at the point of 50% of the initial value of Elongation rate to obtain the activation energy. The failure-time was shown each 5,219 hr, 3,165 hr, and 668 hr at three temperatures. In order to derive the activation energy, Arrhenius methodology was applied. Also, we got the Arrhenius plot from three accelerated temperatures. The activation energy values got 0.98 eV from EAB test. The experimental data were evaluated for estimating the probability density, and the suitable distribution by using statistical program MINITAB. It is shown that EAB data by the acceleration thermal degradation is most suitable for the Weibull distribution.

• Food Science and Biotechnology
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• v.15 no.1
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• pp.33-38
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• 2006

This study was performed to provide basic rheological data of dandelion root concentrates in order to predict their processing aptitude and usefulness as functional foods material. The hot water and 70% ethanol extracts of dandelion root were concentrated at 5, 20, and 50 Brix, and their static viscosity, dynamic viscosity, and Arrhenius plots were investigated. Almost all hot water concentrates showed the typical flow properties of a pseudoplastic fluid, but evaluation using the power law model indicated that the 70% ethanol concentrates showed a flow behavior close to a Newtonian fluid. The apparent viscosity of hot water and 70% ethanol concentrates decreased with increasing temperature. Yield stresses of hot water and 70% ethanol concentrates by Herschel-Bulkley model application were in the range of 0.026 - 1.368 Pa and 0.022 - 0.238 Pa, respectively. The effect of temperature and concentration on the apparent viscosity was examined by Arrhenius equation. The activation energies of hot water and 70% ethanol concentrates were in the range of $8.762-23.778{\times}10^3\;J/mol{\cdot}kg$ and $3.217-20.384{\times}10^3\;J/mol{\cdot}kg$ with increasing concentration, respectively. Storage (G') and loss (G") moduli were generally increased with increasing frequency. For the 70% ethanol concentrates, G" predominated over G' at all applied frequencies and so they showed the typical flow behavior of a low molecular solution. However, for the hot water concentrates, G' predominated over G" at more than 1.9 rad/sec (cross-over point) and so they showed the typical flow behavior of a macromolecular solution.

• Food Science and Preservation
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• v.30 no.4
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• pp.573-588
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• 2023

The purpose of this study was to monitor changes in the quality of ginseng and predict its shelf-life. As the storage period of ginseng increased, some quality indicators, such as water-soluble pectin (WSP), CDTA-soluble pectin (CSP), cellulose, weight loss, and microbial growth increased, while others (Na₂CO₃-soluble pectin/NSP, hemicellulose, starch, and firmness) decreased. Principal component analysis (PCA) was performed using the quality attribute data and the principal component 1 (PC1) scores extracted from the PCA results were applied to the multivariate analysis. The reaction rate at different temperatures and the temperature dependence of the reaction rate were determined using kinetic and Arrhenius models, respectively. Among the kinetic models, zeroth-order models with cellulose and a PC1 score provided an adequate fit for reaction rate estimation. Hence, the prediction model was constructed by applying the cellulose and PC1 scores to the zeroth-order kinetic and Arrhenius models. The prediction model with PC1 score showed higher R² values (0.877-0.919) than those of cellulose (0.797-0.863), indicating that multivariate analysis using PC1 score is more accurate for the shelf-life prediction of ginseng. The predicted shelf-life using the multivariate accelerated shelf-life test at 5, 20, and 35℃ was 40, 16, and 7 days, respectively.

• Computers and Concrete
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• v.19 no.6
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• pp.659-666
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• 2017

Based on the Arrhenius equations, several hydration exothermic models that precisely calculate the influence of concrete's self-temperature duration on its hydration exothermic rate have been presented. However, the models' convergence is difficult to achieve when applied to engineering projects, especially when the activation energy of the Arrhenius equation is precisely considered. Thus, the models' convergence performance should be improved. To solve this problem and apply the model to engineering projects, the relationship between fast iteration and proper expression forms of the adiabatic temperature rise, the coupling relationship between the pipe-cooling and hydration exothermic models, and the influence of concrete's self-temperature duration on its mechanical properties were studied. Based on these results, the rapid convergence of the hydration exothermic model and its coupling with pipe-cooling models were achieved. The calculation results for a particular engineering project show that the improved concrete hydration exothermic model and the corresponding mechanical model can be suitably applied to engineering projects.

• Conservation Science in Museum
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• v.10
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• pp.75-88
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• 2009

The purpose of this study is to determine the lifetime of acrylic resin Paraloid^TM B-72(EMA copolymer), which is widely used as a coating for metallic artifacts to prevent corrosion. Lifetime factor with temperature, selected chromaticity as the test parameter for lifetime prediction. The found result is that the temperature is the most crucial factor influencing the prediction of the lifetime of the EMA copolymer coated iron surface against corrosion. The simulation results, based on Arrhenius Equation, showed that the lifetime prediction of the EMA coated iron surface was 24.5 years at 16℃, 17.1 years at 20℃, and 12.0 years at 24℃, respectively.

• Korean Journal of Food Science and Technology
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• v.20 no.5
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• pp.711-717
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• 1988

The diffusivity of sodium chloride in Chinese cabbage was evaluated from its absorption data obtained by immersing the cabbage stalk in a salt solution. By using least squares method, the absorption and desorption diffusivity of NaCl in the cabbage stalk have been estimated to be $1.7{\times}10^{-11}$ and $11.6{\times}10^{-11}m^2/s$, respectively. The apparent diffusivity was not strongly dependent on the concentration of brine and the variety of Chinese cabbage. The influence of temperature on the apparent diffusivity could be expressed as the Arrhenius type equation, in which the activation energy was estimated to be 66 KJ/mol.

• Applied Biological Chemistry
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• v.31 no.1
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• pp.46-51
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• 1988

The effects of temperature on the water uptake rate of soybeans soaked in tap water and 0.5% $NaHCO_3$ solution were studied. The higher the soaking temperature, the faster the hydration rate, and among the three soybean varieties (Tanyob, Kwanggyo and Saeal), Tanyob(the smallest variety) showed faster rate than ocher varieties when soaking in tap water and 0.5% $NaHCO_3$ solution. Activation energy due to weight increase was calculated using Arrhenius equation. z-Values calculated from weight changes to reach different degrees of hydration during soaking showed the tendency to decrease with the increase of hydration degree when soaking in tap water and 0.5% $NaHCO_3$ solution.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.311-314
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• 2009

A two-dimensional thermal response and ablation simulation code for predicting charring material ablation and shape change on solid rocket nozzle is presented. For closing the problem of thermal analysis, Arrhenius' equation and Zvyagin's ablation model are used. The moving boundary problem and endothermic reaction in thermal decomposition are solved by rezoning and effective specific heat method. For simulation of complicated thermal protection systems, this method is integrated with a three-dimensional finite-element thermal and structure analysis code through continuity of temperature and heat flux.