• Journal of Korean Society on Water Environment
• /
• v.27 no.2
• /
• pp.141-146
• /
• 2011

Loess, a natural clay, was evaluated as an adsorbent for the decolorization of Acid Orange II, an azo and reactive dye, from aqueous solution. Adsorption studies were performed at $30^{\circ}C$ and the effect of reaction time, loess dosage, initial concentration, loess particle size, pH, agitation rate were investigated to determine the optimum operation conditions. The removal efficiencies of color were measured to evaluate the effectiveness of loess. From this study, it was found that optimal reaction time was 10 min. Color removal efficiencies of Acid Orange II were increased as higher loess dosage, initial concentration and agitation rate. However, color removal efficiencies decreased when pH is high and loess particle becomes large. Adsorption of Acid Orange II fitted to the pseudo-second-order rate kinetics more than first-order rate kinetics. Langmuir and Freundlich adsorption isotherm constants and correlation coefficients were calculated and compared. It was concluded that the adsorption data of Acid Orange II onto loess fitted to the Freundlich model more than Langmuir model.

• Geomechanics and Engineering
• /
• v.32 no.1
• /
• pp.21-34
• /
• 2023

In order to analyze the effect of the cyclic lateral loading on the response of a pile-soil system, a full-scale single steel pile was subjected to one-way cyclic loading. The test pile was driven into a bi-layered soil consisting of a normally consolidated saturated clay overlying a silty sandy layer, the site being submerged by water up to one meter above the mudline in order to reproduce the conditions of an offshore pile foundation. The aim of this paper is to present the main results of interpretation of the cyclic lateral tests in terms of pile deflections, bending moment, and cyclic P-Y curves. From these latter an absolute secant reaction modulus E_AS,N was derived and a simple calculation model of the test single pile is proposed based on this modulus. Two applications of the proposed model are carried out, one with a 2D finite element modelling, and the second with a load transfer curves-based method.

• Journal of the Semiconductor & Display Technology
• /
• v.23 no.2
• /
• pp.60-64
• /
• 2024

The threshold voltage shift in thin-film transistors (TFTs) is modeled using stretched-exponential (SE) and stretched-hyperbola (SH) functions. These models are derived by introducing empirical parameters into reaction rate equations that describe defect generation or charge trapping caused by hydrogen diffusion in the dielectric or interface. Separately, the dielectric relaxation phenomena are also described by the same reaction rate equations based on defect diffusion. Dielectric relaxation was initially modeled using the SE model, and various models have been proposed using fractional calculus. In this study, the characteristics of the threshold voltage shift and the dielectric relaxation phenomena are compared and analyzed to explore the applicability of analytical models used in the field of dielectric relaxation, in addition to the conventional SE and SH models.

• Nuclear Engineering and Technology
• /
• v.55 no.11
• /
• pp.4026-4031
• /
• 2023

In this article, we report a new empirical formula for quick calculation of cross sections of (n, α) reactions with 14-15 MeV neutrons. Cross sections are analysed in terms of the compound nucleus model. A systematic trend for 14-15 MeV neutrons is found in the variation of (n, α) reaction cross sections with the parameters (N - Z + 1), (E_n + Q)^0.5 and N/Z. The empirical relation between the cross sections and these parameters has been obtained, which give fairly good fits with the experimental data. We have also investigated the odd-even effects on (n, α) cross sections considering binding energy systematic of the shell model. The present formula is very useful in predicting of the (n, α) cross sections, where the measurements are not available as well as in testing new experimental data.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.20 no.1
• /
• pp.95-105
• /
• 2012

The selective catalytic reduction (SCR) system is a highly-effective aftertreatment device for NOx reduction of diesel engines. Generally, the ammonia ($NH_3$) was generated from reaction mechanism of SCR in the SCR system using the liquid urea as the reluctant. Therefore, the precise urea dosing control is a very important key for NOx and $NH_3$ slip reduction in the SCR system. This paper investigated NOx and $NH_3$ emission characteristics of urea-SCR dosing system based on model-based control algorithm in order to reduce NOx. In the map-based control algorithm, target amount of urea solution was determined by mass flow rate of exhaust gas obtained from engine rpm, torque and $O_2$ for feed-back control NOx concentration should be measured by NOx sensor. Moreover, this algorithm can not estimate $NH_3$ absorbed on the catalyst. Hence, the urea injection can be too rich or too lean. In this study, the model-based control algorithm was developed and evaluated on the numerical model describing physical and chemical phenomena in SCR system. One channel thermo-fluid model coupled with finely tuned chemical reaction model was applied to this control algorithm. The vehicle test was carried out by using map-based and model-based control algorithms in the NEDC mode in order to evaluate the performance of the model based control algorithm.

• Proceedings of the Korean Nuclear Society Conference
• /
• 2005.05a
• /
• pp.1305-1306
• /
• 2005

• Bulletin of the Korean Chemical Society
• /
• v.29 no.12
• /
• pp.2365-2367
• /
• 2008

• Bulletin of the Korean Chemical Society
• /
• v.15 no.3
• /
• pp.179-181
• /
• 1994

• Korean Chemical Engineering Research
• /
• v.43 no.5
• /
• pp.621-626
• /
• 2005

The esterification reaction of free fatty acid with methanol was investigated in the presence of catalyst, Amberlyst-15, producing fatty acid methyl ester, namely, biodiesel. In this paper, the effects of the reaction parameters such as reaction temperature, mole ratio of alcohol to oleic acid and mass of catalyst on the catalytic activity have been examined. The results showed that the reaction rate increased about twice as the temperature increased every $20^{\circ}C$ in the reaction temperature range from 333 K to 373 K. The equilibrium conversion rate of oleic acid increased with the feed mole ratio of alcohol to acid ranging from 6:1 to 44:1. When the feed mole ratio was higher than 44:1, all the results were similar to that of 44:1. As for the influence of the mass of catalyst, the initial reaction rate increased from 1.2 to 1.3 times as the mass of catalyst doubles in the range of the catalyst weight from 5 to 20 wt%. The experiment data obtained were well described by the second reaction rate using a pseudo-homogeneous model.

• Korean Chemical Engineering Research
• /
• v.49 no.5
• /
• pp.628-632
• /
• 2011

L-ribose has recently attracted interest as a starting material for antiviral drug. It could be obtained from L-arabinose by epimerization reaction. Epimerization reaction was carried out with molybdenium oxide or molybdic acid catalyst and methanol/water solution. Reaction temperature, methanol percentage, and catalyst kind were selected to find an optimum reaction condition. Ion exhange chromatography was used for separating epimerization reaction mixture, and then HPLC chromatogram of L-ribose fraction obtained to calculate the yield of the reaction. Shodex ion exchange HPLC column(Model SC1011) and Phenomenex Luna $NH_2$ HPLC column were compared to employ a convenient HPLC analysis. It was found that the usage of 20% methanol, $60^{\circ}C$, and 40 g/L molybdic acid gives the best reaction condition with a yield of 21%.