• Transactions of the Korean hydrogen and new energy society
• /
• v.30 no.1
• /
• pp.8-13
• /
• 2019

In order to apply the Sievert's type automatic apparatus to thermal analysis of hydrogen absorbing materials, the Sievert's type automatic apparatus was modified in my laboratory. In this study, an experiment was conducted to see if hydrogen absorption and desorption reactions are possible under near constant pressure (${\pm}0.05atm$) using this device. The hydrogenation and dehydrogenation of the Mg-H system was investigated. And the program was also modified for the kinetics. It was found that it is possible to measure the hydrogen absorption rate under near constant pressure of Mg by using the modified Sievert's type automatic apparatus at 573 K and 598 K. And using this system, the hydrogen desorption rate of Mg hydride under near constant pressure at 623 K was also measurable. However, since the hydrogen desorption rate of Mg hydride is fast at 648 K, the hydrogen desorption reaction did not proceed within a constant pressure range of $0.15{\pm}0.05atm$.

• The KIPS Transactions:PartC
• /
• v.9C no.3
• /
• pp.399-406
• /
• 2002

We consider design of multiservice network link, in which connections of constant- and adaptive-rate services arrive and leave dynamically. We propose performance analysis and design methods of these dynamic multiservice networks. A multiservice network link is modeled by a Markov chain, and data rates for adaptive-rate connections are derived using QBD (Quasi-Birth-Death) processes and matrix-geometric equations. We estimate average number of adaptive-rate connections, average data rate and average connection delay. The performance of constant-rate connections is determined from the blocking probability of the connections. Based on the performance of constant-and adaptive- rate connections, we propose a design methods of a network link to satisfy performance requirements of constant- and adaptive-rate connections (data rates, delay, blocking probability). Our methods can be used for the analysis and design of network switch supporting dynamic data and voice (video) traffic simultaneously.

• Journal of Mechanical Science and Technology
• /
• v.20 no.5
• /
• pp.692-709
• /
• 2006

Nucleate pool boiling experiments with constant wall temperature were performed using pure R1l3 for subcooled, saturated, and superheated pool conditions. A microscale heater array and Wheatstone bridge circuits were used to maintain the constant wall temperature and to measure the instantaneous heat flow rate accurately with high temporal and spatial resolutions. Images of bubble growth were taken at 5,000 frames per second using a high-speed CCD camera synchronized with the heat flow rate measurements. The bubble geometry was obtained from the captured bubble images. The effect of the pool conditions on the bubble growth behavior was analyzed using dimensionless parameters for the initial and thermal growth regions. The effect of the pool conditions on the heat flow rate behavior was also examined. This study will provide good experimental data with precise constant wall temperature boundary condition for such works.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2015.10a
• /
• pp.1045-1046
• /
• 2015

When using the Support Vector Machine in the online signature verification, SVM kernel function should be chosen to use non-linear SVM and the constant parameters in the kernel functions should be adjusted to appropriate values to reduce the error rate of signature verification. Non-linear SVM which is built on a strong mathematical basis shows better performance of classification with the higher discrimination power. However, choosing the kernel function and adjusting constant parameter values depend on the heuristics of the problem domain. In the signature verification, this paper deals with the problems of selecting the correct kernel function and constant parameters' values, and shows the kernel function and coefficient parameter's values with the minimum error rate. As a result of this research, we expect the average error rate to be less than 1%.

• Bulletin of the Korean Chemical Society
• /
• v.25 no.7
• /
• pp.1081-1084
• /
• 2004

• Journal of the Korean Chemical Society
• /
• v.42 no.1
• /
• pp.22-27
• /
• 1998

Fluorescence quenching of coumarin 153 and coumarin 481 with N,N-dimethylaniline in various solvents was investigated. Quenching rate constants are related to diffusion-limited rate constants to some extent. It is noted that smaller discrepancy was observed between the diffusion-limited rate constant and the experimental quenching rate constant when the stick boundary condition rather than the slip boundary condition was applied for estimating the diffusion coefficients. In nonpolar solvent like cyclohexane fluorescence quenching is adequately explained by the diffusion controlled process within the experimental error, but in acetonitrile the quenching rate constant was estimated to be consistently smaller than the diffusion limited rate constant. This may suggest that fluorescence quenching of coumarin dyes be affected not only by the molecular diffusion but also by the intramoleccular process such as charge separation.

• Proceedings of the Korean Environmental Health Society Conference
• /
• 2004.12a
• /
• pp.45-50
• /
• 2004

Indoor air quality can be affected by indoor sources, ventilation, decay and outdoor levels. Alt hough technologies exist to measure these factors, direct measurements are often difficult. The purpose of this study was to develop an alternative method to characterize indoor environmental factors by multiple indoor and outdoor measurements. Daily indoor and outdoor NO2 concentrations were measured for 30 consecutive days in 28 houses in Brisbane, Australia, and for 21 consecutive days in 37 houses in Seoul, Korea. Using a mass balance model and regression analysis, penetration factor (ventilation rate divided by the sum of ventilation rate and deposition constant) and source strength factor (source strength divided by the sum of ventilation rate and deposition constant) were calculated using multiple indoor and outdoor measurements. Subsequently, the ventilation rate and NO2 source strength were estimated. Geometric means of ventilation rate were 1.44 ACH in Brisbane, assuming a residential NO2 deposition constant of 1.05 hr-1, and 1.36 ACH in Seoul, with the measured residential NO2 deposition constant of 0.94 hr-1. Source strengths of N02 were 15.8 ${\pm}$ 18.2 ${\mu}$g/m3${\cdot}$hr and 44.7 ${\pm}$ 38.1 ${\mu}$g/m3${\cdot}$hr in Brisbane and Seoul, respectively. In conclusion, indoor environmental factors were effectively characterized by this method using multiple indoor and outdoor measurements.

• Journal of Pharmaceutical Investigation
• /
• v.19 no.3
• /
• pp.131-136
• /
• 1989

This study was attempted to investigate the dissolution rate and the bioavailability after oral administration of commercially available aspirin tablets in normal volunteers. The dissolution test was conducted in artificial gastric juice using basket method with three aspirin preparations (A, B and C) which were chemically equivalent. The results were as follows; The dissolution rate was higher in the order of three different brand B>A >C. Area under the blood concentration and peak blood concentration were larger in the order of brand A>B>C. Absorption rate constant and peak time were larger in the order of brand B>A>C, and there was a little difference in elimination rate constant and biological half-life. The correlation of the dissolution rate and absorption rate constant, as well as correlation of the dissolution rate and peak time showed significant linear relationship respectively. From the results of this experiment, it can be concluded that the bioavailability of aspirin tablets showed much difference according to commercial preparations, and that the bioavailability of aspirin tablets in human may be predicted from the results of dissolution rate studies.

• Journal of Environmental Science International
• /
• v.17 no.10
• /
• pp.1069-1073
• /
• 2008

Indoor air quality can be affected by indoor sources, ventilation, decay and outdoor levels. Although technologies exist to measure these factors, direct measurements are often difficult. The purpose of this study was to develop an alternative method to characterize indoor environmental factors by multiple indoor and outdoor measurements. Using a mass balance model and regression analysis, penetration factor (ventilation rate divided by the sum of ventilation rate and deposition constant) and source strength factor (source strength divided by the sum of ventilation rate and deposition constant) were calculated using multiple indoor and outdoor measurements. Subsequently, the ventilation rate and $NO_2$ generation rate were estimated. Mean of ventilation rate was 1.41 ACH in houses, assuming a residential N02 deposition constant of 0.94 $hr^{-1}$. Mean generation rate of $NO_2$ was 16.5 ppbv/hr. According to house characterization, inside smoking and family number were higher $NO_2$ generation rates, and apartment was higher than single-family house. In conclusion, indoor environmental factors were effectively characterized by this method using multiple indoor and outdoor measurements.

• Journal of Environmental Science International
• /
• v.13 no.1
• /
• pp.37-40
• /
• 2004

In this study, the decomposition of gas-phase TCE, Benzene and Toluene, in air streams by direct UV Photolysis and UV/TiO$_2$ process was studied. For direct UV Photolysis, by regressing with computer calculation to the experimental results the value of reaction rate constant k of TCE, Toluene and Benzene in this work were determined to be 0.00392s$\^$-l/, 0.00230s$\^$-1/ and 0.00126s$\^$-1/, respectively. And the adsorption constant K of TCE, Toluene and Benzene in this work were determined to be 0.0519 mol$\^$-l/ ,0.0313mo1$\^$-1/ and 0.0084mo1$\^$-1/, respectively. For UV/TiO$_2$ system by regressing with computer calculation to the experimental results the value of reaction rate constant k of TCE, Toluene, and Benzene in this work were determined to be 5.74g/$\ell$$.$min, 3.85g/$\ell$$.$min, and 1.18g/$\ell$$.$min, respectively. And the catalyst adsorption constant K of TCE, Toluene, and Benzene in this work were determined to be 0.0005㎥/mg, 0.0043㎥/mg and 0.0048㎥/mg, respectively.