• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.499-499
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• 2011

Silicon nanowires (Si NWs) have been extensively studied for nanoelectronics owing to their unique optical and electrical properties different from those of bulk silicon. For the development of Si NW devices, better understanding of oxidation behavior in Si NWs would be an important issue. For example, it is widely known that atomic scale roughness at the dielectric (SiOx)/channel (Si) interface can significantly affect the device performance in the nano-scale devices. However, the oxidation process at the atomic-scale is still unknown because of its complexity. In the present work, we investigated the oxidation behavior of Si NW in atomic scale by simulating the dry oxidation process using a reactive molecular dynamics simulation technique. We focused on the residual stress evolution during oxidation to understand the stress effect on oxidation behavior of Si NWs having two different diameters, 5 nm and 10 nm. We calculated the charge distribution according to the oxidation time for 5 and 10 nm Si NWs. Judging from this data, it was observed that the surface oxide layer started to form before it is fully oxidized, i.e., the active diffusion of oxygen in the surface oxide layer. However, it is well-known that the oxide layer formation on the Si NWs results in a compressive stress on the surface which may retard the oxygen diffusion. We focused on the stress evolution of Si NWs during the oxidation process. Since the surface oxidation results in the volume expansion of the outer shell, it shows a compressive stress along the oxide layer. Interestingly, the stress for the 10 nm Si NW exhibits larger compressive stress than that of 5 nm Si NW. The difference of stress level between 5 an 10 anm Si NWs is approximately 1 or 2 GPa. Consequently, the diameter of Si NWs could be a significant factor to determine the self-limiting oxidation behavior of Si NWs when the diameter was very small.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.173-182
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• 1997

The instantaneous flame temperature and soot formation and oxidation in a D. I. diesel engine are measured by using a two-color method. The proposed method based on the continuous spectral radiation from the soot particles in flames is applicable to industrial diesel engines without major modifications of their main characteristics. Measurements are performed at one location inside the combustion chamber of a D.I. diesel engine. Effects of different engine speeds and loads on flame temperature and KL factor which is an index of soot concentrations were examined. A little temperature change were observed with increasing engine speed, while increased with loads. The higher the flame temperature is, the lower the KL factor is.

• The Journal of Internal Korean Medicine
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• v.38 no.3
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• pp.367-375
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• 2017

Objective: To investigate the effect of Artemisiae Iwayomogii Herba, Curcumae Radix, and Aurantii Fructus Immaturus complex extract (ACA) on dyslipidemia-related factor expression and anti-oxidation in HepG2 cells. Method: After treatment with ACA in the HepG2 cells, DPPH, ABTS radical scavenging activity, ROS production, and glutathione (GSH) production were measured. The free fatty acid, lipid peroxidation (MDA), ACAT1, and HMG-CoA reductase mRNA expression were measured in the HepG2 cells after treatment with ACA. Results: 1. DPPH, ABTS radical scavenging activity increased in an ACA concentration-dependent manner. 2. ACA significantly decreased ROS production in comparison to the control group. 3. ACA significantly increased glutathione production. 4. ACA significantly decreased free fatty acid and lipid peroxidation (MDA) in the HepG2 cells. 5. ACA decreased the mRNA expression of ACAT1 and HMG-CoA reductase. Conclusion: These results suggest that Artemisiae Iwayomogii Herba, Curcumae Radix, and Aurantii Fructus Immaturus complex extract (ACA) inhibits dyslipidemia-related factor expression and that it is effective in anti-oxidation. A future in vivo experiment with ACA is needed to investigate the effect on anti-dyslipidemia. It is expected that ACA is effective in anti-dyslipidemia and applied to cardiovascular disease, ischemic heart disease, stroke, etc.

• Tribology and Lubricants
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• v.10 no.4
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• pp.13-26
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• 1994

Effects of resin contents, number of carbonization, graphitization, sliding speed, and oxidation on friction and wear behavior of carbon/carbon composite materials were investigated. Friction and wear tests were carried out under various sliding conditions. An experimental setup was designed and built in the laboratory. Stainless steel disks were used as the counterface material. Friction coefficient, emperature, and wear factor were measured with a data acquisition system. Wear surfaces were observed by the scanning electron microscope. It has been shown that the average friction coefficient was increased with the sliding speed in the range of 1.43~6.10 m/s, but it as decreased in the range of 6.10~17.35 m/s. Specimens prepared by different numbers of carbonization. showed variations in friction coefficient and friction coefficient of the graphitized specimen was the highest. Friction coefficients depended on contribution of the plowing and adhesive components. As the number of carbonization was increased, wear factor was reduced. Wear factor of the graphitized specimens dropped further. In the case of graphitized specimens, sliding speed had a large influence on wear behavior. When the tribological experiments were conducted in nitrogen atmosphere, the wear factor was decreased to two thirds of the wear factor obtained in air. It is obvious that the difference was affected by oxidation. Results of friction and wear tests were applied to a neural network system based on the backpropagation algorithm. A neural network may be a valuable tool for prediction of tribological behavior of the carbon/carbon composite material if ample data are present.

• Preventive Nutrition and Food Science
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• v.2 no.1
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• pp.6-10
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• 1997

The reaction mechanisms and kinetics of tertiary butylhydroquinone(TBHQ) as an antioxidant in soybean oil oxidation were studied. The oxidation reaction of soybean oil at 55, 60 and $65^{\circ}C$ was a first order. The activation energies of soybean oil containing 0, 25, 50, and 75ppm TBHQ were 12.15, 6.05, 6.15 and 6.17kcal/mole. respectively. The addition of THQ to soybean oil containing 0, 25, 50, and 75ppm TBHQ were 1.88$\times${TEX}$10^{7}${/TEX}, 4.10$\times${TEX}$10^{2}${/TEX}, 4.32 $\times${TEX}$10^{2}$p/TEX} and 3.97$\times${TEX}$10^{2}${/TEX}, respectively. The decrease of frequency factor rather than the activation energy. The effects of antioxidants on the temperature dependecy of lipid oxidation could be effectively evaluated by measuring their effects on the activation energy of lipid oxidation.

• Bulletin of the Korean Chemical Society
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• v.20 no.12
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• pp.1457-1463
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• 1999

Structure and their redox property of the vanadium oxides prepared by decomposing NH₄VO₃ at various temperatures were studied by XRD, SEM, XPS, and temperature programmed reduction/temperature programmed oxidation (TPR/TPO) experiment. All TPR profiles have two sharp peaks in the temperature range 650-750℃, and the area ratio of the two sharp peaks changed from sample to sample. There were three redox steps in TPR/TPO profiles. The oxidation proceeded in the reverse order of the reduction process, and both the reactions proceeded via quite a stable intermediates. The changes of the morphological factor $(I_{(101)}/I_{(010)})$, the ratio of $O_{1S}$ peak area (O$_{1S}$( α)/O$_{1S}$( β)) in the XPS results, and the ratio of hydrogen consumption in TPR profiles with various vanadium oxides showed the distinct relationship between the structural property and their redox property of vanadium oxides. The change of the specific yield of phthalic anhydride with various vanadium oxides showed a very similar trend to those of the peak area ratio in TPR profiles, which meant that the first reduction step related to the partial oxidation of o-xylene on the vanadium oxide catalyst.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1573-1576
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• 2010

Bacillus subtilis PerR is a metal-dependent peroxide-sensing transcription factor which uses metal-catalyzed histidine oxidation for peroxide-sensing. PerR contains two metal binding sites, one for structural $Zn^{2+}$ and the other for the regulatory/peroxide-sensing metal. Here we investigated the effect of mutations at both the structural and regulatory metal binding sites on the oxidation of either H37 or H91, two of the peroxide-sensing ligands. All four serine substitution mutants at the structural $Zn^{2+}$ site (C96S, C99S, C136S and C139S) exhibited no detectable oxidation at histidine residues. Two of the alanine substitution mutants at regulatory metal site (H37A and D85A) exhibited selective oxidation preferentially at the H91-containing tryptic peptide, whereas no oxidation was detected in the other mutants (H91A, H93A and D104A). Our results suggest that the cysteine residues coordinating structural $Zn^{2+}$ are essential for peroxide sensing by PerR, and that the C-terminal regulatory metal binding site composed of H91, H93 and D104 can bind $Fe^{2+}$, providing a possible explanation for the peroxide sensing mechanisms by PerR.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.8
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• pp.1370-1376
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• 2003

We investigated the effect of seatangle drink and seatangle extract on lipid oxidation, blood coagulation and intestinal movement in rats fed a hyperlipidemic diet. In the dietary hyperlipidemic induced group, the serum superoxide dismutase activity decreased and formation of hydroxy radical increased when compared to normal group, but these were controlled by seatangle drink treatment. The decreased of bleeding time and increased of tissue factor in the dietary hyperlipidemic rats were regulated by seatangle drink and seatangle extract, and especially the activity of tissue factor was remarkably decreased. Seatangle drink and seatangle extract were increased contraction on intestinal movement. Therefore, it can be concluded that seatangle drink or seatangle extract treatment depresses changing in absorption of gastrointestinal track in rats fed a hyperlipidemic diet.

• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.54-63
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• 1996

We establish an expert system for the xylene oxidation reaction process of chemical plants using HAZOP(Hazard and Operability Studies). Our research focus Is only reduced to the cooling system of the total chemical plant due to lack of information. This expert system shows the priority of reasons for the system failure using confidence factor.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3331-3337
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• 2012

Ru-modified Pt nanoparticles of various sizes on platelet carbon nanofiber toward methanol oxidation were investigated in terms of particle size effect. The sizes of Pt nanoparticles, prepared by polyol method, were in the range of 1.5-7.5 nm and Ru was spontaneously deposited by contacting Pt nanoparticles with the Ru precursor solutions of 2 and 5 mM. The Ru-modified Pt nanoparticles were characterized using transmission electron microscopy, X-ray photoelectron spectroscopy and cyclic voltammetry. The methanol oxidation activities of Ru-modified Pt nanoparticles, measured using cyclic voltammetry and chronoamperometry, revealed that when the Pt particle size was less than 4.3 nm, the mass specific activity was fairly constant with an enhancement factor of more than 2 at 0.4 V. However, the surface area specific activity was maximized on Pt nanoparticles of 4.3 nm modified with 5 mM Ru precursor solution. The observations were discussed in terms of the enhancement of poison oxidation by Ru and the population variation of Pt atoms at vertices and edges of Pt nanoparticles due to selective deposition of Ru on the facets of (111) and (100).