• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.379-384
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• 2012

It is investigated that that the physical properties of Glutathione layer formed on gold surfaces may make an effect on the distribution of either gold particle adsorbed to the $TiO_2$ surface or vice versa with the adjustment of the electrostatic interactions. For the investigation, the atomic force microscope (AFM) was used to measure the surface forces between the surfaces as a function of the salt concentration and pH value. With the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the forces were quantitatively analyzed to acquire the surface potential and charge density of the surfaces for each salt concentration and each pH value. The surface potential and charge density dependence on the salt concentration was described with the law of mass action, and the pH dependence was explained with the ionizable groups on the surface. The salt concentration dependence of the surface properties, found from the measurement at pH 8 and 11, was consistent with the prediction from the law. It was found that the Glutathione layer had higher values for the surface charge densities and potentials than the titanium dioxide surfaces at pH 8 and 11, which may be attributed to the ionized-functional-groups of the Glutathione layer.

• Journal of the Korean Chemical Society
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• v.39 no.12
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• pp.946-954
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• 1995

The physico-chemical nature of the rare earth oxide which was produced by the caustic fritting of monazite was studied to furnish fundamental data that are required for its efficient use and processing. It was found that the material which was mainly constituted of light rare earths and thorium was a solid solution phase of oxide whose structure was fluorite-type face centered cubic. Its density was 6.75 g/$cm^3$ and it had a uniform particle size distribution at around 1 ${\mu}m.$ The crystallinity improved by heating to elevated temperatures, whereas the solubility in HCl decreased as the crystallinity improved. Complete dissolution in conc. HCl solution in short time (30 min.) was attained by heating to 70$^{\circ}C$. The measurement of zeta potential showed its I.E.P. to be at pH 8.6 of the suspension.

• Clean Technology
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• v.20 no.2
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• pp.130-135
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• 2014

It is investigated that the surface properties of mercaptopyruvic-acid layer formed on gold surfaces may make an effect on the distribution of either gold particle adsorbed to the zirconia surface or vice versa. For the investigation, the atomic force microscope was used to measure the surface forces between the surfaces as a function of the salt concentration and pH value. The forces were quantitatively analyzed with the derjaguin-landau-verwey-overbeek (DLVO) theory to estimate the electrostatic properties, potential and charge density, of the surfaces for each condition of salt concentration and pH value. The estimatedvalue dependence on the salt concentration was explained with the law of mass action, and the pH dependence was interpreted with the ionizable groups on the surface. The salt concentration dependence of the surface properties, found from the measurement at pH 4 and 8, was predictable from the law. It was found that the mercaptopyruvic-acid layer had higher values for the surface charge densities and potentials than the zirconia surfaces at pH 4 and 8, which may be attributed to the ionizedfunctional-groups of the mercaptopyruvic-acid layer.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.604-605
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• 2017

The present work aims at visualization of the supersonic air jet flows discharged from C-D nozzles. In the present experiments, Prticle Image Velocimetry (PIV) was employed to specify the jet flow field quantitatively, and a color Schlieren optical method was applied to observe the same jets qualitatively. The $0.5{\mu}s$ duration of spark light source was used for Schlieren and it can be controled as $0.5{\mu}s$, $1{\mu}s$, $2{\mu}s$ and focusing mode. The convergent-divergent nozzles were used to generate the jet flow with the design Mach number of 2.0, 2.2. Nozzle pressure ratios (NPRs) were varied from 5 to 8. A good comparison of the jet size and shock location from the Schlieren images with the PIV quantitative values is obtained. The obtained images clearly showed the major features of the under-expanded jet, over-expanded jet, sound wave, turbulent eddies and so on.

• Polymer(Korea)
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• v.27 no.1
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• pp.46-51
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• 2003

In this work, the electrode far fuel cell was fabricated by mixing carbon blacks with activated carbon fibers (ACFs) in order to form the proper three phase distribution, and then the change of electrode in three phase distribution was investigated. Pt loading yield with ACF content and Pt particle size were determined by AAS and XRD measurements, respectively. And the pore structures, including specific surface area ($S_{BET}$), microporosity, and pore size distribution (PSD) for each electrode were systematically investigated by BET volumetric measurement. The morphology of electrode in three phase distribution was determined by SEM. As an experimental result, it was observed that Pt loading yield was not influenced on the content of ACF. While, the electrode in three phase distribution was largely improved in the case of 30% ACF addition on carbon blacks. These results were probably explained by the increase of the portion of micropores, resulting in increasing the active sites of catalyst.

• Journal of the Optical Society of Korea
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• v.14 no.3
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• pp.221-227
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• 2010

Aerosol size distribution provides good information for predicting weather changes and understanding cloud formation. Aerosol extinction coefficient and backscattering coefficient are measured by many scientists, but these parameters depend not only on aerosol size but on aerosol concentrations. An algorithm has been developed to measure aerosol parameters such as ${\AA}$ngstr$\ddot{o}$m exponent, color ratio, and LIDAR ratio without any assumptions by using two wavelength rotational Raman LIDAR signals. These parameters are good indicators for the aerosol size. And we can find ${\AA}$ngstr$\ddot{o}$m exponent, color ratio, and LIDAR ratio under various weather conditions. Finally, it can be seen that the ${\AA}$ngstr$\ddot{o}$m exponent has an inverse relationship to the particle size of the aerosol and the color ratio is linearly dependent on the aerosol size. An ${\AA}$ngstr$\ddot{o}$m exponent from 1.2 to 3.1, a color ratio from 0.28 to 1.04, and a LIDAR ratio 66.9 sr at 355 nm and 32.6 sr at 532 nm near the cloud were obtained.

• Journal of the Korean Society for Railway
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• v.11 no.4
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• pp.378-383
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• 2008

In December 2006, the Ministry of Environment Republic of Korea established the guideline which is "Indoor Air Quality Management Guidelines in Public Transportation." as control items, $CO_2$ (carbon dioxide) and PM10 (particle matter) are classified two categories, that is, Level 1 (non-rush hour), Level 2 (rush hour). Therefore, the quality of air in train and subway should be controlled in accordance with the guideline. We took a measure the air freshness inside train twice at Line 4 (Tangogae-Oido), in Sep. 2007 and at Line 1 (Dongincheon-Yongsan) in Nov. 2007, respectively and, also expected the emitted $CO_2$ concentration by using a property of matter such as EMU (Electric Multiple Unit) design reviewing specification and air. According to the measured values, the concentration of PM10 was 44, 57, 45% and the concentration of $CO_2$ was 39, 36, 44% respectively, all measured values are within the guideline and also, as a result we found the expected value and measured value are similar.

• Journal of Environmental Science International
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• v.4 no.1
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• pp.53-62
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• 1995

To collect and evaluate an aerosol acidity ($H^+$) in ambient air, the cyclone/annular denuder/filter pack sampling system (ADS) was used. Aerosol acidity was collected in Chicago using the ADS for 81 12-hr samples divided in spring/summer/fall 1990 and winter 1991. This study illustrated that the ADS was suitable for measuring aerosol acidity. The $10^{-5}N$ $HCIO_4$ extraction solution for pH determination provided more reliable scale than $10^{-4}N$ HClO4. NH3 should be removed prior to particle collection to accurately measure $H^+$ concentration on the filter. There was seasonal variation in aerosol acidity concertrations. Aerosols were more acidic in the summer. High correlations between $SO_4^{2+} and$NH_4^+$, and between TEX>$SO_4^{2+}$H^+$ were observed during the entire sampling period.

• Journal of the Korea Institute of Building Construction
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• v.18 no.1
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• pp.59-65
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• 2018

Radon gas is a colorless, odorless, tasteless gas that occurs when uranium, a natural radioactive material in rocks and soils, collapses. 85% of the annual radiation exposure of the human body is due to natural radiation, of which 50% is radon. According to the US Environmental Protection Agency (EPA) survey, 62 out of 1,000 smokers and 7 out of 1,000 nonsmokers are exposed to lung cancer when exposed to radon gas for a long time. In order to reduce the risk of radon gas, activate carbon was used to fabricate matrix, and the pore properties and radon reduction properties were investigated. When the activate carbon was used, the radon gas concentration was drastically reduced and the graph was changed as the measurement period became longer. The pore distribution and microporous properties, which are one of the material properties of activate carbon, can be grasped.

• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.42-48
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• 2018

Silicon has attracted extensive attention due to its high theoretical capacity, low discharge potential and non-toxicity as anode material for lithium ion batteries. In this study, Si-CNT-C composites were fabricated for use as a high-efficiency anode material in a lithium ion battery. Aerosol self-assembly and post-heat treatment processes were employed to fabricate the composites. The morphology of the Si-CNT-C composites was spherical and an average particle size was $2.72{\mu}m$. The size of the composite increased as concentration of Si and CNT increased in the precursor solution. In the Si-CNT-C composites, CNT and C carbonized from glucose were attached to the surface of Si particles. Electrochemical measurement showed that the cycle performance of Si-CNT-C composites was better than that of silicon particles.