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The Effect of Oil Supply Conditions on the Dynamic Performance of a Hydrodynamic Journal Bearing
Son, Sang-Ik,Kim, Kyung-Woong Korean Tribology Society 2009 KSTLE International Journal Vol.10 No.1
In this study, the effect of oil supply conditions on the dynamic performance of a hydrodynamic journal bearing is analyzed numerically. Axial length, circumferential length and location of oil grooves are considered as oil supply conditions. The perturbation equations of the perturbed film contents are obtained by applying Elrod's universal equation implementing JFO film rupture / reformation boundary conditions to Lund's infinitesimal perturbation method. The dynamic coefficients of a hydrodynamic journal bearing are calculated by solving the perturbation equations, and the linear stability analysis is carried out by using those for a variety of oil supply conditions.
Son, Il-Hong,Park, Yong-Hoon,Yang, Hyun-Duk,Lee, Sung-Ik,Han, Sun-Jung,Lee, Jai-Kyoo,Ha, Dae-Ho,Kang, Hyung-Won,Park, Joo-Young,Lee, Sung-Soo The Korean Society of Toxicogenomics and Toxicopro 2008 Molecular & cellular toxicology Vol.4 No.2
Parkinson's disease (PD) progresses severely by a gradual loss of dopaminergic neurons in the substantia nigra (SN). Epidemiological studies showed that the incidences of PD were reduced by smoking of which the major component, nicotine might be neuroprotective. But the function of nicotine, which might suppress the incidences of PD, is still unknown. Fortunately, recently it was reported that a glial reaction and inflammatory processes might participate in a selective loss of dopaminergic neurons in the SN. The levels of tumour necrosis factor (TNF)-${\alpha}$ synthesised by astrocytes and microglia are elevated in striatum and cerebrospinal fluid (CSF) in PD. TNF-${\alpha}$ kills the cultured dopaminergic neurons through the apoptosis mechanism. TNF-${\alpha}$ release from glial cells may mediate progression of nigral degeneration in PD. Nicotine pretreatment considerably decreases microglial activation with significant reduction of TNF-${\alpha}$ mRNA expression and TNF-${\alpha}$ release induced by lipopholysaccharide (LPS) stimulation. Thus, this study was intended to explore the role of nicotine pretreatment to inhibit the expressions of TNF-${\alpha}$ mRNA in human fetal astrocytes (HFA) stimulated with IL-$1{\beta}$. The results are as follows: HFA were pretreated with 0.1, 1, and $10{\mu}g/mL$ of nicotine and then stimulated with IL-$1{\beta}$ (100 pg/mL) for 2h. The inhibitory effect of nicotine on expressions of TNF-${\alpha}$ mRNA in HFA with pretreated $0.1{\mu}g/mL$ of nicotine was first noted at 8hr, and the inhibitory effect was maximal at 12 h. The inhibitory effect at $1{\mu}g/mL$ of nicotine was inhibited maximal at 24 h. Cytotoxic effects of nicotine were noted above $10{\mu}g/mL$ of nicotine. Moreover, Nicotine at 0.1, 1 and $10{\mu}g/mL$concentrations significantly inhibited IL-$1{\beta}$-induced TF-${\kappa}B$ activation. Collectively, these results indicate that in activated HFA, nicotine may inhibit the expression of TNF-${\alpha}$ mRNA through the pathway which suppresses the NF-${\kappa}B$ activation. This study suggests that nicotine might be neuroprotective to dopaminergic neurons in the SN and reduce the incidences of PD.
Son, Mi-Young,Jun, Hyun-Ik,Lee, Kwang-Geun,Demple, Bruce,Sung, Jung-Suk Informa UK (TaylorFrancis) 2009 Journal of toxicology and environmental health. Pa Vol.72 No.21
<P>Numerous environmental carcinogens involve radical formation interacting with DNA to produce 2-deoxyribonolactone (dL), a major type of oxidized abasic site, implicated in DNA strand breaks, mutagenesis, and formation of covalent DNA-protein cross-links (DPC). Studies showed major dL-specific DPC occurred due to reactions with DNA polymerase beta (Polbeta) dependent on native conformation, while other DPC formed involved nonenzymatic reactions of DNA binding proteins with dL lesions. Polbeta appeared to play a major role in alleviating the cytotoxic effects of neocarzinostatin, which was used as a dL-producing agent. When a duplex DNA containing a dL at a site-specific position was incubated with purified histones, DPC were formed between dL and each histone protein, including H1, H2A, H2B, H3, and H4. Comparative kinetic analysis of DPC formation with histones and Polbeta revealed two distinct mechanisms of dL-mediated DPC formation. The rate of DPC formation with Polbeta was approximately two orders of magnitude higher than that with various histone proteins. These results indicate that catalytic activity of Polbeta mediates rapid DPC formation between dL and this DNA repair enzyme, whereas nonenzymatic reactions of dL with histones form DPC more slowly. The abundance of histones and their constant interaction with DNA may nevertheless yield significant levels of DPC with dL, as biomarkers of dL-induced cytotoxicity. Overall, data suggest that occurrence of dL-mediated DPC with histones may contribute to the genotoxic effects of dL in DNA.</P>
Frequency-domain equalization for distributed terrestrial DTV transmission environments
Son, Sang-Won,Kim, Ji-Hyun,Lee, You-Seok,Kim, Hyoung-Nam,Park, Sung Ik IEEE 2006 IEEE TRANSACTIONS ON CONSUMER ELECTRONICS - Vol.52 No.1
The 8-VSB modulation, the transmission standard for the terrestrial digital television (DTV) of the Advanced Television Systems Committee (ATSC), suffers from multipath fading because it conveys information on the amplitude. To solve this problem, decision feedback equalizers (DFEs) have been commonly used in the terrestrial DTV receivers. However, under severe channels, such as a 0-dB ghost channel or a distributed transmission environment, the DFEs have shown unstable convergence due to the error propagation caused by decision errors. Instead of unstable time-domain DFE schemes, by proposing a frequency-domain direct-inversion equalization method, we achieve stable equalization and low symbol error rates. To secure the existence of a channel inverse, channel-matched filtering and noncausal filtering are carried out before equalization. Simulation results show that the proposed method performs much better than the existing DFE schemes in terms of both the stability and the symbol error rates.
Oxygen Transfer in a Three-Phase Circulating Fluidized Bed with Viscous Liquid Medium
Son, Sung Mo,Kang, Suk Hwan,Kim, Uk Yeong,Shin, Ik Sang,Kang, Yong,Kim, Sang Done The Society of Chemical Engineers, Japan 2008 Journal of chemical engineering of Japan Vol.41 No.7
<P>Characteristics of oxygen transfer were investigated in the riser of a viscous three-phase circulating fluidized bed, with a diameter of 0.102 m (ID) and a height of 3.5 m. Effects of gas (0.01–0.09 m/s) and liquid (0.12–0.43 m/s) velocities, fluidized solid particle size (1.0, 1.7, 2.1, 3.0 mm), solid circulation rate (2–8 kg/(m<SUP>2</SUP>·s)) and liquid viscosity (0.96–38 mPa·s) on the volumetric oxygen transfer coefficient in the riser were examined. The oxygen transfer coefficient was found to increase with increasing gas velocity, particle size and solid circulation rate, while it decreased with increasing viscosity of the continuous liquid medium, and changed very little with the variation of liquid velocity. The oxygen transfer coefficients were well correlated in terms of dimensionless groups as well as operation variables.</P>
Perfluorooctanoic acid-induced hepatic toxicity following 21-day oral exposure in mice.
Son, Hee-Young,Kim, Sang-Hyun,Shin, Hong-In,Bae, Han Ik,Yang, Jae-Ho Springer-Verlag 2008 Archives of toxicology Vol.82 No.4
<P>Perfluorooctanoic acid (PFOA) is a member of the perfluoroalkyl acids that have wide commercial applications and is a widespread pollutant of toxicological importance that has been detected in environmental matrices. The NOAEL and LOAEL of PFOA in rodent were reported 1 and 10 ppm, respectively. The current study characterizes the hepatic toxicities of PFOA in mice. Male ICR mice were exposed continuously to 0, 2, 10, 50 and 250 ppm of PFOA in drinking water for 21 days. Food and water consumption decreased in mice exposed to 250 ppm of PFOA. Mean body weight gain was reduced in mice exposed to 50 and 250 ppm of PFOA. The size and relative weight of the liver increased dose-dependently in PFOA-treated mice. Serum enzyme activities, alanine aminotransferase and aspartate aminotransferase, increased in mice exposed to PFOA in a dose-dependent manner. In the histopathological evaluation, the liver of PFOA-treated mice showed remarkable hepatocytomegaly and acidophilic cytoplasm. At the high doses of PFOA, diffuse hepatic damage by multifocal coagualation and liquefaction necrosis were noted. In contrast to the remarkable change of liver, the kidney had little change. The size and relative weights of the kidney, biomarkers of kidney damage (blood urea nitrogen, creatinine), and histopathological changes had no differences between PFOA-untreated and PFOA-treated mice. In conclusion, our results demonstrate that PFOA causes a toxic effect on the liver but not to the kidney.</P>
Prediction of Defects in Nano-Imprint Lithography Using FEM Simulation
Son, Ji Won,Song, Nam Ho,Rhim, Sung Han,Oh, Soo Ik Trans Tech Publications, Ltd. 2007 Key Engineering Materials Vol.345 No.-
<P>In nano-imprint lithography (NIL) process, which has shown to be a good method to fabricate polymeric patterns, several kinds of pattern defects due to thermal effects during polymer flow and mold release operation have been reported. A typical defect in NIL process with high aspect ratio and low resist thickness pattern is a resist fracture during the mold release operation. It seems due to interfacial adhesion between polymer and mold. In the present investigation, FEM simulation of NIL process was carried out to predict the defects of the polymer pattern and to optimize the process by FEA. To achieve the above mentioned purpose, FEM simulation technique based on constitutive modeling of polymer with experiments was firstly investigated [1]. Secondly, the embossing operation in NIL process was investigated in detail by FEM. From the analytical results, it was found that the non-uniform flow-pattern of polymer and the applied pressure in the embossing operation induce the cavity and the drastic lateral-strain at the edge of pattern. It was also shown that the low polymer-thickness result in the delamination of polymer from the substrate. It seems that the above phenomena cause the defects of the final polymer pattern.</P>