• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.3
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• pp.179-187
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• 2008

A mathematical modeling of $NO_x$ reduction in $NH_3$-SCR process is conducted. The present deterministic model solves one-dimensional conservation equations of mass and species concentrations for channel flows and the catalytic reaction. NO and NO_2$ reactions by the vanadium catalyst in the presence of $NH_3$ are calculated with the rate expressions of Langmuir-Hinshelwood scheme. The modeling was validated with extensive empirical data regarding $NO_x$ reduction efficiency. Analysis of De-$NO_x$ sensitivity conducted with regard to oxygen and water yielded highly accurate prediction over a wide range of $NO_2/NO_x$ ratios from 0 to 1 in a temperature range of $200^{\circ}C{\sim}550^{\circ}C$. The $NO_x$ reduction largely depends on $NO_2/NO_x$ ratio at temperatures lower than $300^{\circ}C$. NO reduction efficiency is significantly augmented with increasing in $NH_3$/NO ratio at higher temperatures, whereas rather insensitive to the $NH_3$/NO ratio at lower temperatures.

• Journal of the Korean Society for Library and Information Science
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• v.25
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• pp.265-294
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• 1993

At the present. one of the very important functions of the information center or library is to provide information service on time and to the right person. But it is impossible if the shape of the material is not complete. So it is important to keep the material of information complete. This study is on deacidification of paper materials for enhancing useful life of information. This study can be summerized as follews; The material needs deacidification is all of machine-made paper except neutral paper, and hand made paper which are below pH 6.5. The best way for the deacidification for the small amount of materals is to use aqueous deacidifiers such as Calcium Carbonate, Magnesuim Carbonate and Borax. For mass deacidification process, Methoxy Magnesuim Methyle Carbonate and Magnesuim Oxide, called

• Toxicological Research
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• v.29 no.1
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• pp.69-79
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• 2013

The purpose of this study was to investigate the current status of metal pollution in the sediment from rivers, lakes, and streams in active gold mining districts in Ghana. Two hundred and fifty surface sediment samples from 99 locations were collected and analyzed for concentrations of As, Hg, Cr, Co, Cu, Fe, Zn, Pb, Cd, Ni, and Mn using inductively coupled plasma-mass spectroscopy (ICP-MS). Metal concentrations were then used to assess the human health risks to resident children and adults in central tendency exposure (CTE) and reasonable maximum exposure (RME) scenarios. The concentrations of Pb, Cd, and As were almost twice the threshold values established by the Hong Kong Interim Sediment Quality Guidelines (ISQG). Hg, Cu, and Cr concentrations in sediment were 14, 20, and 26 times higher than the Canadian Freshwater Sediment Guidelines for these elements. Also, the concentrations of Pb, Cu, Cr, and Hg were 3, 11, 12, and 16 times more than the Australian and New Zealand Environment and Conservation Council (ANZECC) sediment guideline values. The results of the human health risk assessment indicate that for ingestion of sediment under the central tendency exposure (CTE) scenario, the cancer risks for child and adult residents from exposure to As were $4.18{\times}10^{-6}$ and $1.84{\times}10^{-7}$, respectively. This suggests that up to 4 children out of one million equally exposed children would contract cancer if exposed continuously to As over 70 years (the assumed lifetime). The hazard index for child residents following exposure to Cr(VI) in the RME scenario was 4.2. This is greater than the United States Environmental Protection Agency (USEPA) threshold of 1, indicating that adverse health effects to children from exposure to Cr(VI) are possible. This study demonstrates the urgent need to control industrial emissions and the severe heavy metal pollution in gold mining environments.

• Journal of Plant Biotechnology
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• v.39 no.3
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• pp.182-188
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• 2012

Iris dichotoma Pall. is an important endangered plant belonging to the family Iridaceae. A method was developed for the rapid micropropagation of I. dichotoma through plant regeneration from leaf, rhizome, and root explant-derived calli. Leaf, rhizome, and root segments were cultured on Murashige and Skoog (MS) medium supplemented with 2,4-dichlorophenoxy acetic acid (2,4-D; $0-3.0mg{\cdot}L^{-1}$) for callus induction. Callus production was highest at $1.0mg{\cdot}L^{-1}$ 2,4-D, where 73.8% and 45.5% of cultured rhizome and root cuttings, respectively, produced calli. The viable calli were maintained at an induced concentration of 2,4-D ($3.0mg{\cdot}L^{-1}$). They were then transferred to MS medium supplemented with various concentrations of 2,4-D ($0-3.0mg{\cdot}L^{-1}$) in combination with 6-benzyladenine (BA: 0, 1.0 and $3.0mg{\cdot}L^{-1}$) for adventitious shoot regeneration. The addition of a low concentration of 2,4-D into BA-containing medium significantly increased the frequency of shoot regeneration in leaf, rhizome, and root-derived calli. The highest number of adventitious shoots (26.4 per callus) formed at $0.5mg{\cdot}L^{-1}$ 2,4-D and 1.0 mg/l BA. For rooting of the shoots, half- strength MS medium supplemented with different concentrations of indole 3-butyric acid (IBA) $0-3.0mg{\cdot}L^{-1}$ was tested. The optimal results were observed using half-strength MS medium supplemented with $1.0mg{\cdot}L^{-1}$ IBA, on which 98% of the regenerated shoots developed roots with an average of 3.5 roots per shoot within 45 days. The plantlets raised in vitro were acclimatized and transferred to soil with 95% success. This in vitro propagation protocol will be useful for conservation and mass propagation of this endangered plant.

• Applied Chemistry for Engineering
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• v.17 no.1
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• pp.111-117
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• 2006

The improvement of energy conservation mandates decrease consumption of fossil fuels and minimize negative impacts on the environment, which originates from large cooling and heating demand. The absorption heat pump technology has a large potential for energy saving in this respect. Adsorption heat pump is a means to upgrade waste heat without addition of extra thermal energy. The increase of absorbed amount is of great importance for absorption heat pump cycle. In this study, in order to improve the performance of absorber, the absorbers of two different types have been investigated using methanol-glycerine as a working fluid. The former was tangential feed of liquid phase without spiral tube in the absorber and the latter was with spiral tube in the absorber. The latter was found to be more effective in enhancing the mass and heat transfer to increase the absorption performance.

• Fire Science and Engineering
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• v.14 no.3
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• pp.6-12
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• 2000

This paper describes the smoke movement of a fire field model based on a self-developed SMEP(Smoke Movement Estimating Program) code to the simulation of fire induced flows in the two types of compartment space containing the radiation effect under smoke movement in room fire. The SMEP using PISO algorithm solves conservation equations for mass, momentum, energy and species, together with those for the modified k-$\varepsilon $ turbulence model with buoyancy term. Also it solves the radiation equation using the discrete ordinates method. The result of the calculated smoke temperature containing radiation effect has shown reasonable agreement compared with the experimental data. On the other hand, a difference of a lot was found between the temperature predicted by the SMEP with only convection effect and obtained by the experimental result. This seems to come from the radiation effect of $H_2$O and $CO_2$ gas under smoke productions. Thus, the consideration of the radiation effect under smoke in fire may be necessary in order to produce more realistic result.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.4
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• pp.18-25
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• 2011

Solid propulsion systems have simple structures compared to other propulsion systems and are suitable for long-term storage. However the systems generally have limits on control of thrust levels. In this paper we suggest control algorithms for combustion chamber pressure of variable thrust solid propulsion systems using special nozzles such as pintle valve. For the pressure control within the chamber, we use a simple pressure change model by considering only mass conservation within the combustion chamber, design a classical algorithm and also a nonlinear controller using the feedback linearization technique. Also we derive the equation of the thrust for an under-expanded one-dimensional nozzle and then design a proportional-intergral controller after linearizing the thrust model for an operating point. Finally, we demonstrate the performance of the controller through a numerical simulation.

• 보존과학연구
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• s.17
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• pp.65-99
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• 1996

We exanmined the each effect of $NO_2$ and $SO_2$gas, the maincomponets of air pollutants, on the deterioration of 6 organic materials with Gasexposure cabinet. The organic materials were used 2 kind of papers(Korean paper, Oldbook paper) and 4 kind of textiles (Cotton, Silk, Hemp, ramie) in gas exposure experiments. In order to know how to change of physical conditions, the materials were exposed to 2000, 1000 ppm. h of $SO_2$dose, to 100 ppm. h of $NO_2$ dose at 65% RH. The color difference, tensile strength, elongation coeffient, mass reduction and fabric status of each materials were discussed the following below.1. The color difference of cotton and hemp was larger than that of silk and ramie in the presence of $SO_2$ gas. and the color difference of korean paper was less than that of the textile materials in the presence of $SO_2$ gas.2. The tensile strength of cotton fell suddenly at 100ppm.h of $SO_2$ dose and even became 56% of the unexposed cotton.3. The weight of 6 materials began to decrease in the presence of $SO_2$ gas.4. The tensile strength and elongation of the materials tended to decrease at 12.5ppm.h of $NO_2$ especially silk was the strongest tendency to decrease.5. Cotton, hemp and ramie were influenced by $SO_2$ gas more than by $NO_2$, but silk were influenced by $NO_2$ more thang by $SO_2$ at 10ppm.h of each noxious gas.

• Journal of Microbiology and Biotechnology
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• v.24 no.11
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• pp.1551-1558
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• 2014

The esterase gene Est8 from the thermophilic bacterium Bacillus sp. K91 was cloned and expressed in Escherichia coli. The monomeric enzyme exhibited a theoretical molecular mass of 24.5 kDa and an optimal activity around $50^{\circ}C$ at pH 9.0. A model of Est8 was constructed using a hypothetical YxiM precursor structure (2O14_A) from Bacillus subtilis as template. The structure showed an ${\alpha}/{\beta}$-hydrolase fold and indicated the presence of a typical catalytic triad consisting of Ser-11, Asp-182, and His-185, which were investigated by site-directed replacements coupled with kinetic characterization. Asp-182 and His-185 residues were more critical than the Ser-11 residue in the catalytic activity of Est8. A comparison of the amino acid sequence showed that Est8 could be grouped into the GDSL family and further classified as an SGNH hydrolase. Est8 is a new member of the SGNH hydrolase subfamily and may employ a different catalytic mechanism.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.1
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• pp.33-42
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• 2003

This paper deals with the FEM analysis of nonlinear sloshing of incompressible, invicid and irrotational flow in two dimensional rectangular tank. We use laplace equation based on potential theory as governing equation. For large amplitude sloshing motion, kinematic and dynamic free surface conditions derived from Bernoulli equation are applied. This problem is solved by FEM using 9-node elements. For the time integration and accurate velocity calculation, we introduce predictor-corrector time marching scheme and least square method. Also, numerical stability in tracking of free surface is obtained by direct calculation of free surface location to time variation. Numerical results of sloshing induced by harmonic excitations, while comparing with those of linear theory and references, prove the accuracy and stability. After verification of our program, we analyze sloshing response characteristics to the fluid height and the excitation amplitude.