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Lee, Dae-Won,Ryu, Jae-Hong,Jeong, Dong-Hoon,Lee, Hyeong-Sang,Chun, KwangMin,Lee, Kwan-Young 한국공업화학회 2003 Journal of Industrial and Engineering Chemistry Vol.9 No.1
Nano-sized gold catalysts supported on alumina were prepared and applied to the lean DeNOx reaction by plasma-enhanced catalysis. The average size of metallic gold particles estimated by dark field TEM analysis was 4.5 nm. The plasma-Au/A1₂O₃system showed an improved DeNOx activity at low temperatures below 250℃. In case of plasma-2.0 wt%Au/ A1₂O₃, NOx conversion was about 40% and N₂yield was 10~30% at 100~250℃. The NOx reduction activity to N₂using hydrocarbon reductant at this temperature range has not been reported yet. This low-temperature DeNOx activity seems to be caused by the increase of Au - alumina interface due to the formation of nano-sited Au particles, which facilitated plasma-activated NO₂and hydrocarbon being adsorbed on the metallic Au and alumina, respectively, migrated and then reacted with each other.
Scratch-tip-size effect and change of friction coefficient in nano / micro scratch tests using XFEM
Lee, Kwangmin,Marimuthu, Karuppasamy Pandian,Kim, Chang-Lae,Lee, Hyungyil Elsevier 2018 Tribology international Vol.120 No.-
<P><B>Abstract</B></P> <P>Compared to the experimental studies, numerical studies on scratch test have been limited due to the difficulty of numerical modeling. Here, we experimentally investigate the scratch-tip-size effect (STSE) based on coefficient of friction (COF) change to make extended finite element (XFE) models considering STSE, COF change, failure modes, yielding strength, shear strength, elastic recovery and pile-up. XFE models are then validated through nano/micro scratch tests on soda-lime glass. Finally, components of COF are extracted and then effects of tensile cracks and parameters of Drucker-Prager model on COF are investigated. We expect that proposed XFE models contribute to the understanding of damage characteristics during the scratch test.</P> <P><B>Highlights</B></P> <P> <UL> <LI> FE models for nano/micro scratch test on soda-lime glass are proposed. </LI> <LI> Scratch-tips of different size cause various failure modes. </LI> <LI> Scratch-tip size effect significantly influences friction coefficient change. </LI> <LI> Drucker-Prager model of material is calibrated considering indentation size effect. </LI> <LI> Components of coefficient of friction are extracted from experiment by using FEM. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Seroprevalence of SARS-CoV-2 antibodies in South Korea
Lee Kwangmin,조성일,이재용 한국통계학회 2021 Journal of the Korean Statistical Society Vol.50 No.3
In 2020, Korea Disease Control and Prevention Agency reported three rounds of surveys on seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARSCoV- 2) antibodies in South Korea. SARS-CoV-2 is the virus which inflicts the coronavirus disease 2019 (COVID-19). We analyze the seroprevalence surveys using a Bayesian method with an informative prior distribution on the seroprevalence parameter, and the sensitivity and specificity of the diagnostic test. We construct the informative prior of the sensitivity and specificity of the diagnostic test using the posterior distribution obtained from the clinical evaluation data. The constraint of the seroprevalence parameter induced from the known confirmed coronavirus 2019 cases can be imposed naturally in the proposed Bayesian model. We also prove that the confidence interval of the seroprevalence parameter based on the Rao’s test can be the empty set, while the Bayesian method renders interval estimators with coverage probability close to the nominal level. As of the 30th of October 2020, the 95% credible interval of the estimated SARS-CoV-2 positive population does not exceed 318, 685, approximately 0.62% of the Korean population.
Enhanced mass transfer rate of methane in aqueous phase via methyl-functionalized SBA-15
Lee, Jaewon,Kim, Kwangmin,Chang, In Seop,Kim, Myung-Gil,Ha, Kyoung-Su,Lee, Eun Yeol,Lee, Jinwon,Kim, Choongik Elsevier 2016 Journal of molecular liquids Vol.215 No.-
<P><B>Abstract</B></P> <P>Methyl-functionalized mesoporous silica SBA-15, synthesized from tetraethyl-orthosilicate (TEOS) and methyltriethoxysilane (MTES), were employed as additives for the enhancement of volumetric mass transfer coefficient (<I>k</I> <SUB>L</SUB> <I>a</I>) of methane in aqueous solution. The surface functional group, highly ordered structure, and exceptionally high surface area exerted great influence on mass transfer rate of methane in aqueous solution. Especially, the fraction of surface functional groups controlled by adjusting the ratio of TEOS to MTES was found to be a crucial factor. Mesoporous characteristics of synthesized materials were investigated via BET surface area analysis, small angle X-ray diffraction, and FT-IR spectroscopy. At an optimal molar ratio (20:1) of TEOS and MTES, an 88% enhancement of <I>k</I> <SUB>L</SUB> <I>a</I> for methane in water was observed at 30°C.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Methyl-functionalized silica SBA-15 were synthesized and characterized. </LI> <LI> Synthesized materials were employed as additives in aqueous solution. </LI> <LI> Enhanced methane–water volumetric mass transfer coefficient was observed. </LI> <LI> 88% enhancement of <I>k</I> <SUB>L</SUB> <I>a</I> for methane in water was observed. </LI> </UL> </P>
Enhancement of Drucker-Prager yield model by adding corner points for pressure-dependent materials
Kwangmin Lee,Karuppasamy Pandian Marimuthu,한정무,이형일 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.3
To flexibly describe the pressure-dependent behaviors of materials, DruckerPrager yield model is enhanced by introducing corner points. We call it piecewise DruckerPrager (pDP) yield model. Constitutive model is derived by considering strain hardening with non-associative yield flows. Integration algorithm includes the return mapping to corner point. Consistent tangent operator is also formulated, and user material subroutine is written. It is demonstrated that the pDP model is effective in describing the pressure-dependent yield behavior of polymers.
Cho, Kwangmin,Jang, You-Jin,Lee, Se-Jong,Jeon, Yu-Na,Shim, Young-Lim,Lee, Ji-Yong,Lim, Da-Som,Kim, Dong-Hou,Yoon, Seung-Yong Elsevier 2020 Biochemical and biophysical research communication Vol.524 No.3
<P><B>Abstract</B></P> <P>β-Amyloid (Aβ) plaque in the brains of patients with Alzheimer’s disease (AD) is mainly caused by impaired clearance of Aβ by glial cells, including microglia and astrocytes. Because microglia play an important protective role in the central nervous system, many efforts have been made to identify agents that effectively improve microglial Aβ phagocytosis. This study found that TLQP-21, which is cleaved from VGF (VGF nerve growth factor inducible) precursor protein, enhanced Aβ phagocytosis and degradation by microglial BV2 cells. TLQP-21 also improved microglial phagocytic activity and promoted fibrillar amyloid-β (fAβ) uptake by microglial BV2 cells via a C3AR1-dependent mechanism. Moreover, TLQP-21 stimulated Aβ degradation by enhancing lysosome activity, thereby enhancing fAβ clearance. These results suggest that treatment with TLQP-21 may be a novel therapeutic strategy to efficiently enhance microglial Aβ clearance in AD.</P> <P><B>Highlights</B></P> <P> <UL> <LI> TLQP-21 increases extracellular fAβ uptake by microglial BV2 cells. </LI> <LI> TLQP-21 enhances phagocytic activity of microglial BV2 cells. </LI> <LI> TLQP-21 increases fAβ uptake by microglial BV2 cells via C3AR1-dependent mechanisms. </LI> <LI> TLQP-21 enhances the degradation of engulfed Aβ by stimulating a lysosomal degradation pathway. </LI> </UL> </P>