• Analytical Science and Technology
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• v.20 no.4
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• pp.296-301
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• 2007

Carbon nanofibers (CNFs) are non-microporous materials with a high surface area ($100{\sim}200m^2/g$) and high purity. Therefore, the material has a high potential for use as catalyst support. Activated carbon fibers (ACFs) are of increasing concern with regard to the levels of toxic air pollutants emitted from high-technology industry. Rayon-based CNFs and ACFs was subjected to thermal oxidation under a wide variety of temperature and air conditions to modify the surface properties. Rayon-based CNFs and ACFs were prepared by using thermal chemistry. CNFs were synthesized at temperatures above $600^{\circ}C$ in an air atmosphere and grew with increased temperature and air conditions. After heating at $800^{\circ}C$ for 72 hr, carbonized rayon with ACFs had $2,662m^2/g$ (BET) of surface area and $1.41cm^3/g$ of pore volume. The resulting ACFs had a 99% surface area in which pore size was 10 nm or less, and a 60 % surface area in which pore size was 2 nm or less.

• Clean Technology
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• v.9 no.1
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• pp.37-42
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• 2003

Biofiltration was successfully applied to treat a mixture of volatile organic compounds(benzene, xylene) from contaminated air stream. Immobilized Ps. oleovorans biofilter was evaluated for its value in simultaneous removal of benzene and xylene from waste air stream. The variety of operating conditions were tested to evaluate important factors such as space velocity, pH, water content, etc.

• Proceedings of the SAREK Conference
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• 2004.06a
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• pp.55-55
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• 2004

• Analytical Science and Technology
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• v.23 no.1
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• pp.45-53
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• 2010

For the determination of chlorine in uranium compound, analytical methods by using a steam distillation and a pyrohydrolysis have been developed. The steam distillation apparatus was composed of steam generator, distilling flask and condenser etc. The samples were prepared with an aliquot of LiCl standard solution and a simulated spent nuclear fuel. A sample aliquot was mixed with a solution containing 0.2 M ferrous ammonium sulfate-0.5 M sulfamic acid 3 mL, phosphoric acid 6 mL and sulfuric acid 15 mL. The chloride was then distilled by steam at the temperature of $140^{\circ}C$ until a volume of $90{\pm}5\;mL$ is collected. The pyrohydrolysis equipment was composed of air introduction system, water supply, quartz reaction tube, combustion tube furnace, combustion boat and absorption vessel. The chloride was separated from powdered sample which is added with $U_3O_8$ accelerator, by pyrohydrolysis at the temperature of $950^{\circ}C$ for 1 hour in a quartz tube with a stream of air of 1 mL/min supplied from the water reservoir at $80^{\circ}C$. The chlorides collected in each absorption solution by two methods was diluted to 100 mL and measured with ion chromatography to determine the recovery yield. For the ion chromatographic determination of chlorine in molten salt retained in a metal ingot, the chlorine was separated by means of pyrohydrolysis after air and dry oxidation, and grinding for the sample.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.4
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• pp.487-498
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• 2006

Total 438 precipitation samples were collected in Jeju City between 1997 and 2005, and their major ionic components were analyzed. The comparison tests using ion balance, electric conductivity and acid fraction were performed. It was found their correlation coefficients were in the range of 0.977$\sim$0.994, indicating the good quality of collected dam. The volume-weighted mean pH and electric conductivity were 4.8 and 23.0 $\mu$S/cm, respectively. with the ionic strength of 0.23$\pm$0.20 mM. The marine ($Na^+$, $Mg^{2+}$, and $CI^-$), anthropogenic (nss$SO_4{2-}$, $NO_3^-$, and $NH_4^+$) and soil (nss-$Ca^{2+}$) species have contributed to the ionic components of precipitation samples with 43$\sim$74%, 16$\sim$37% and $\sim$5%, respectively. The seasonal variations of $NO_3^-$ and nss-$SO_4^{2-}$ showed a distinct seasonality with higher concentrations in winter than summer, indicating an increase of fossil fuel consumption and a possibility of long-range transport of those pollutants from continental area along the dominant winter westerly. The levels of nss-$Ca^{2+}$ also were appeared the highest in winter and increased comparatively in spring season. possibly due to the soil influences including the Asian Dust. The acidification contribution of nss-$SO_4^{2-}$ and $NO_3^-$ showed 88$\sim$96%, and the free acidity was in the range of 6.0$\sim$40.1%. Interestingly, the backward trajectories for the case of upper 10% nss-$SO_4^{2-}$ and $NO_3^-$ levels have passed through the China continent before their arrival to Jeju. The precipitation of pH below 4.5 has been occurred frequently when the trajectory's path lied over the China continents. On the other hand, the air masses from the North Pacific area were characterized by lower 10% of nss-$SO_4^{2-}$- and $NO_3^-$ concentration, which demonstrated that air mass from the North Pacific was the cleanest among air masses moved to Jeju.

• Journal of Applied Biological Chemistry
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• v.60 no.4
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• pp.351-355
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• 2017

Tolaasin, peptide toxin produced by Pseudomonas tolaasii, causes a brown blotch disease on the cultivated mushrooms. Tolaasin peptides form membrane pores and disrupt cellular membrane structure. Molecular actions of tolaasin consist of the aggregation of peptide molecules, binding to the cell membrane, and formation of membrane pores. Therefore, the inhibitions of any of these actions are able to suppress the blotch disease. We have isolated and identified several tolaasin inhibitors (named tolaasin inhibitory factors, TIF) from food additives. TIFs were able to suppress the blotch-formation by the pathogen inoculated to the mushrooms. In this study, TIFs were incubated under various conditions and their activities for the inhibition of tolaasin-induced hemolytic activity were investigated. Since TIFs are unsaturated carbon compounds, they were sensitive to the air exposure and light irradiation. In the anaerobic conditions, TIFs were stable and their activities were decreased by 10% for three months. However, near 90% of TIF activity was suppressed by two weeks in the presence of air and sun light. Temperature did not show any significant effects on the activity of TIF, since storages at 5, 25, $45^{\circ}C$ did not show any difference. Therefore, for the stable storage of TIF compounds, container should be designed to be dark and air-tight.

• Asian Journal of Atmospheric Environment
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• v.11 no.4
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• pp.217-234
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• 2017

Indoor air pollutants can cause severe health problems, specifically in terms of toxicological impacts on human. Every day, a complex mixture of many air pollutants is emitted from various sources and subject to atmospheric processes that can create varied classes of pollutants such as carboxylic acids, aldehydes, ketones, peroxyacetyl nitrate, and hydrocarbons. To adhere to indoor air quality standards, a number of techniques such as photocatalytic oxidation of various volatile organic compounds (VOCs) have been employed. Among these techniques, titania ($TiO_2$) based photocatalytic reactions have proven to be the best benchmark standard approach in the field of environmental applications. Over the last 45 years, $TiO_2$-based photocatalytic reactions have been explored for the degradation of various pollutants. This review discusses the indoor air quality profile, types of indoor pollutants, available indoor air cleaning approaches, and performance of $TiO_2$-based catalysts. Finally, we have presented the perspectives on the progress of $TiO_2$ induced photocatalysis for the purification of indoor air.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.8
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• pp.1158-1164
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• 2003

Steady-state structure and acoustic-pressure responses of $H_2$/Air counterflow diffusion flames are studied numerically with a detailed chemistry in view of acoustic instability. The Rayleigh criterion is adopted to judge acoustic amplification or attenuation from flame responses. Steady-state flame structures are first investigated and flame responses to various acoustic-pressure oscillations are numerically calculated in near-equilibrium and near-extinction regimes. The acoustic responses of $H_2$/Air flame show that the responses in near-extinction regime always contribute to acoustic amplification regardless of acoustic-oscillation frequency Flames near extinction condition are sensitive to pressure perturbation and thereby peculiar nonlinear responses occur, which could be a possible mechanism in generating the threshold phenomena observed in combustion chamber of propulsion systems.

• 한국연소학회:학술대회논문집
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• 1999.10a
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• pp.241-249
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• 1999

Soot particle temperatures in co-flow diffusion flames have been measured using a two-color pyrometry at the pressure of 0.2 MPa(2 atm). The measured soot particle temperatures along with the integrated soot volume fractions are analyzed to understand soot formation characteristics. At 0.2 MPa, the addition of small amount of air into ethylene do not change the soot particle temperature in soot formation regions. This result showed that the increase of soot formation with addition of air is mostly due to the chemical effect of the added air, such as the increased role of C3 chemistry during the early stage of soot inception process. The addition of sufficient air into ethylene, however, changes soot particle temperatures and the understanding of soot formation characteristics becomes complicated. Measured soot particle temperatures also showed that there is no significant temperature effect for the synergistic effect of ethylene/propane mixture on soot formation.

• Korean Journal of Crystallography
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• v.16 no.2
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• pp.128-137
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• 2005

We report on the phase transitions of the perovskite nanostructures made by sol-gel template synthesis. The lead titanate ($PbTiO_{3}$) nanostructures were prepared with a chelate sol-gel of titanium tetrabutoxide ($Ti(O^{i}Pr){4}$) and lead acetate ($Pb(OAc)_{2}-3H_{2}O$). $Whatman^{\circledr}$ anodisc membranes (with about 200 nm pore size) served as the template. The template was dipped into the sol, allowed to air dry, and then calcined at $650^{\circ}C$. We have characterized the temperatures of the phase transitions in the $PbTiO_{3}$ nano-structures using DSC, DTA, and second harmonic generation (SHG).