• Journal of Environmental Science International
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• v.21 no.2
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• pp.165-179
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• 2012

Indirect $CO_2$ effect due to non-methane volatile organic compound (NMVOC) emissions from solvent and product use and fugitive NMVOC emissions from fuels in the Republic of Korea and 13 Annex I countries under United Nations Framework on Climate Change were estimated and the proportions of them to total greenhouse gas (GHG) emissions ranged from 0.092% to 0.45% in 2006. Indirect greenhouse effect ($CO_2$, $CH_4$, and $O_3$) were estimated at 13 photochemical assessment monitoring sites in the Republic of Korea using concentrations of 8 NMVOCs of which indirect global warming potential (GWP) were available. The contribution of toluene to mixing ratio was highest at 11 sites and however, the contribution of toluene to indirect greenhouse effect was highest at nine sites. In contrast to toluene, the contributions of ethane, butane, and ethylene were enhanced. The indirect greenhouse effects of ethane and propane, of which ozone formation potentials are the lowest and the third lowest respectively among targeted 10 NMVOCs, ranked first and fourth highest respectively. Acetaldehyde has relatively higher maximum incremental reactivity and is classified as probable human carcinogen however, its indirect GWP ranked second lowest.

• Journal of the Korean Ceramic Society
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• v.36 no.9
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• pp.982-990
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• 1999

YSZ/LSM composite cathode was fabricated by dip-coating of YSZ sol on the internal pore surface of a LSM cathode followed by sintering at low temperature (800-100$0^{\circ}C$) The YSZ coating significantly increased the TPB(Triple Phase Boundary) where the gas the electrode and the electrolyte were in contact with each other. Sinter the formation of resistive materials such as La2Zr2O7 or SrZrO3 was prevented due to the low processing temperature and TPB was increased due to the YSZ film coating the electrode resistance (Rel) was reduced about 100 times compared to non-modified cathode. From the analysis of a.c impedance it was shown that microstructural change of the cathode caused by YSZ film coating affected the oxygen reduction reaction. In the case of non-modified cathode the RDS (rate determining step) was electrode reactions rather than mass transfer or the oxygen gas diffusion in the experimental conditions employed in this study ($600^{\circ}C$-100$0^{\circ}C$ and 0,01-1 atm of Po2) for the YSZ film coated cathode however the RDS involved the oxygen diffusion through micropores of YSZ film at high temperature of 950-100$0^{\circ}C$ and low oxygen partial pressure of 0.01-0.03 atm.

• Journal of electromagnetic engineering and science
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• v.15 no.3
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• pp.123-128
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• 2015

Previously, we investigated extremely low-frequency magnetic fields (ELF-MFs) on diverse DNA damage responses, such as phosphorylated H2AX (${\gamma}H2AX$), comet tail moments, and aneuploidy production in several non-tumorigenic epithelial or fibroblast cell lines. However, the effect of ELF-MF on DNA damage responses in neuronal cells may not be well evaluated. Here, we investigated the effects of ELF-MF on the DNA damage responses in HT22 non-tumorigenic mouse neuronal cells. Exposure to a 60-Hz, 2 mT ELF-MF did not produce any increased ${\gamma}H2AX$ expression, comet tail moments, or aneuploidy formation. However, 2 mT ELF-MF transiently increased the cell number. From the results, ELF-MF could affect the DNA damage responses differently, depending on the cell lines.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.231-232
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• 2008

The coupling between electric, magnetic, and structural order parameters results in the so-called multiferroics, which possess ferroelectricity, ferromagnetism, and/or ferroelasticity. The simultaneous ferroelectricity and ferromagnetism (magnetoelectricity) allow potential applications in information storage, spintronics, and in magnetic or electric field sensors. Perovskite compound $BiFeO_3$ (BFO) is antiferromagnetic below Neel temperature of 647K and ferroelectric with a high Curie temperature of 1043K. It exhibits weak magnetism at room temperature(RT) due to the residual moment from a canted spin structure. It is likely that non-stoichiometry and second-phase formation are the factors which cause leakage in BFO. It has been suggested that oxygen non-stoichiometry leads to valence fluctuations of Fe ions in BFO, resulting in high conductivity. To reduce the large leakage current of BFO, one attempt is fabricating donor doped BFO compounds and thin films. We report here the successful fabrication of the Nd, Ti co-doped $BiFeO_3$ ceramics and thin films by pulsed laser deposition technique.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.357-357
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• 2008

Spin injection experiment is conducted in epitaxially grown Fe/GaAs hybrid structure. For the formation of Schottky tunnel barrier between Fe and GaAs layers, highly n-doped GaAs layers are grown after n-doped channel layer. A non-local measurement, a voltage measurement probes do not contain a charge current path, is used for detecting only the chemical potential differences by the spin transport. As a result, the dips that are nicely matched with antiparallel region are obtained.

• Journal of computational fluids engineering
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• v.12 no.2
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• pp.21-25
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• 2007

A general purpose program NUFLEX has been extended for two-phase flows with topologically complex interface and cavitation flows with liquid-vapor phase change caused by large pressure drop. In analysis of two-phase flow, the phase interfaces are tracked by employing a LS(Level Set) method. Compared with the VOF(Volume-of-Fluid) method based on a non-smooth volume-fraction function, the LS method can calculate an interfacial curvature more accurately by using a smooth distance function. Also, it is quite straightforward to implement for 3-D irregular meshes compared with the VOF method requiring much more complicated geometric calculations. Also, the cavitation process is computed by including the effects of evaporation and condensation for bubble formation and collapse as well as turbulence in flows. The volume-faction and continuity equations are adapted for cavitation models with phase change. The LS and cavitation formulation are implemented into a general purpose program for 3-D flows and verified through several test problems.

• Economic and Environmental Geology
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• v.30 no.2
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• pp.105-116
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• 1997

This study is for extent of polluted area by acid mine drainage from the Daeseong coal mine, Keumsan. Black shales of the Changri Formation containing the Daeseong coal mine are geochemically similar to those from the North America as well as Europe. Comparing with geochemical compositions and relative ratios, coal bearing and non-coal bearing soils are similar to the stream sediments influenced and not influnced by the acid mine drainage, respectively. These characteristics suggest that acidification of the soils and of the stream sediments are related to the the coal bearing black shale. Soil waters beneath the coal bearing soil have low pH and high cation contents than those beneath non-coal bearing soil, suggestive of extractions of cations with increasing oxidizations within the soils. Surface waters show that those influenced by the acid mine drainage are low pH, and have high $SO_4{^{2-}}$, $Mg^{2+}$, $Fe^{2+}$, Mn and slightly lower DO, suggesting that heavy pollutions have been progressed in these area. Geochemical comparisons between the polluted surface water and adjacent black shales suggest that pollutions of the surface water are related to the black shales.

• Proceedings of the Korean Society of Applied Pharmacology
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• 2000.04a
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• pp.6-7
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• 2000

Recently, free radicals such as active oxygen species, nitric oxide, etc are believed to be one of the key substances in physiological and pathological, toxicological phenomena, and oxidative damages, and all organism have defencing system against such as free radicals. Formation and extinction of free radicals may be regulated through bio-redox system, in which various enzymes and compounds should be involved in very complicated manner. Thus, direct and non-invasive measurement of in vivo free radical reactions with living animals must be essential to understand the role of free radicals in pathophysiological phenomena. Electron spin resonance spectroscopy (ESR) is very selective and sensitive technique to detect free radicals, but a conventional ESR spectrometer has large detect in application to living animals, since high frequent microwave is absorbed with water, resulting in generation of high fever in living body. In order to estimate in vivo free radical reactions in living whole animals, we develop in vivo ESR-CT technique using nitroxide radicals as spin probes. Nitroxide radicals and their reduced forms, hydroxylamines, are known to interact with various redox systems. We found that! ! the signal decay due to reduction of nitroxyl radicals is influenced by aging, inspired oxygen concentration, ischemia-referfusion injury, radiation, etc. In the present paper, I will introduce in vivo ESR technique and my laboratory recent results concerning non-invasive evaluation of free radical reactions in living mice.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.27.1-27.1
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• 2010

Globular cluster (GC) systems in most galaxies, particularly in ellipticals, show bimodal color distributions. Because broadband colors trace metallicity at old ages, this phenomenon has been commonly interpreted as bimodal metallicity distributions, implying the presence of two sub-populations in the globular cluster system within a galaxy. However, a new explanation has recently been proposed, in which the non-linear nature of color-metallicity relations induced by horizontal-branch stars can produce bimodal color distributions even from unimodal metallicity distributions. In this study, we put these two explanations to the test on the origin of color bimodality, using multi-band (U,B,V and I) photometry of globular clusters in NGC 1399, the central giant elliptical galaxy in Fornax galaxy cluster. We find significant changes in the morphology of color distributions when using different colors. The observation is also well reproduced by the Monte Carlo realization of GC color when a unimodal metallicity distribution and the theoretical non-linear color-metallicity relations are assumed. We discuss the implications regarding theories on galaxy formation and evolution.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.6
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• pp.84-91
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• 1999

The goal of this study is to analyse the stress and the strain occurring within the work piece at the fine-blanking process and hence to assume the size direction and a distribution chart of the shearing stress as the penetration of the punch is being increased trough the application of the FEM. For this analysis we introduced the piece-wise linear method in the non linear structural analysis program for large deformation sheet metal forming and we defined it as the problem of the non linear contact. Therefore we modeled the above problems as quadratic-nodded axi-symmetrical elements for the character-istics of the work piece. From the result of this analysis it was found that the shearing stress is a great deal occurred on the surface of the work piece during the beginning process of the punch penetration and it's effect is expected to influence importantly for the formation of burnish because the deeper is the penetration of the punch in the narrow clearance zone. the greater is the degree of the strain stress.