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Adhesion improvement of graphene/copper interface using UV/ozone treatments
Seo, Jeongmin,Chang, Won Seok,Kim, Taek-Soo Elsevier 2015 THIN SOLID FILMS - Vol.584 No.-
<P><B>Abstract</B></P> <P>The weak adhesion between graphene and its substrate is a potentially significant problem for graphene-based electronic devices. However, quantitative studies on adhesion improvement between graphene and its substrate using simple surface treatments have not yet been reported. In this study, we report the adhesion improvement of the graphene/copper interface using a UV/ozone treatment. The adhesion energy is measured directly using double cantilever beam fracture mechanics testing. A significantly improved adhesion energy of 2.10±0.27J/m<SUP>2</SUP> is achieved with 15min of UV/ozone treatment; the improved adhesion energy is approximately 200% of that without treatment. The chemical modification of the graphene/copper interface is also characterized using X-ray photoemission spectroscopy (XPS).</P> <P><B>Highlights</B></P> <P> <UL> <LI> The adhesion energy of the graphene/copper interface improve by UV/ozone treatment. </LI> <LI> A threshold amount of treatment time for adhesion improvement was found. </LI> <LI> Copper oxide pellets provide additional bonds that improve the adhesion energy. </LI> <LI> The binding between carbon and copper atoms is due to the bridges of oxygen atoms. </LI> </UL> </P>
Evaluation Study of T1 Relaxation Time via Contrast Agent Molarity and Magnet Field Strength in MR
Jeongmin Seo 한국자기학회 2020 Journal of Magnetics Vol.25 No.4
The purpose of this study was to evaluate the T1 relaxation times to distinguish between media with different contrast agent molarities (0.5 mmol/mL and 1.0 mmol/mL) for different magnetic field strengths (1.5 T and 3.0 T) in magnetic resonance imaging. Herein, we used the T1 mapping technique instead of signal intensities for evaluation. The T1 times were shorter for higher molarities at the same magnetic field strength (p = 0.043); however, there were no significant distinctions for the same molarity at different magnetic field strengths. The rate of change of the T1 duration for half the molarity of the phantom concentration was higher at low concentrations of the contrast agent. Therefore, the results indicate that higher concentrations of the contrast agent may not be necessary to obtain better imaging contrast.
Development and experimental investigation of a 500-W class ultra-micro gas turbine power generator
Seo, JeongMin,Lim, Hyung-Soo,Park, JunYoung,Park, Moo Ryong,Choi, Bum Seog Elsevier 2017 ENERGY Vol.124 No.-
<P><B>Abstract</B></P> <P>We experimentally investigate the feasibility of a 500-W class ultra-micro gas turbine power generator. System specifications include a design rotational speed of 400,000 rpm, a compressor ratio of 3:1, and a turbine inlet temperature of 1200 K. In a previous study, we used an integrated test rig to examine the feasibility of start-up and self-sustaining capabilities. Here, we describe our development and testing of a new integrated test rig to measure the performance of electric-power generation during self-sustaining and boosting operations. We controlled a motor-generator using an electric controller in fixed speed mode and guided the rotational speed according to the start-up sequence. We employed a radial-thrust integral metal-mesh bumper air foil bearing with which we obtained the design rotational speed of 400,000 rpm in a standalone motoring test. In the combustor, we used liquefied petroleum gas as the main fuel and kerosene as the ignition fuel and partially as the main fuel during the boost operation. The integrated test rig achieved electric power generation of 30 W at 200,000 rpm, 50% of the design rotational speed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We developed integrated test equipment for a 500-W ultra-micro gas turbine power generator. </LI> <LI> The tests were conducted in self-sustaining and boosting modes. </LI> <LI> In the self-sustaining operation, the test rig worked stably and produced 5 W of electric power. </LI> <LI> In the boost operation, the test rig produced 30 W of electric power. </LI> <LI> We verified the feasibility of a 500-W UMGT power generator for electric-power generation. </LI> </UL> </P>
Purification and Enzyme Activity Measurement of Rat Intestinal Mucosal α-Glucosidases
Jeongmin Seo,Soon Mi Kim,Byung-Hoo Lee 한국당과학회 2016 한국당과학회 학술대회 Vol.2016 No.01
Rat intestinal mucosal α-glucosidases could be a mammalian enzyme source to be used in in vitro carbohydrate digestion kinetic studies, and to further discern effects of substrate and inhibitor effects on the individual four enzymes – maltase, glucoamylase, sucrase, isomaltase. The commercialized rat intestinal powder enzyme comes with α-amylase contamination, and therefore needs to be purified for in vitro starch digestion. The objective of this study was to separate α-glucosidase from the crude rat intestinal powder by size-exclusion chromatography using a media with fractionation in the range of Mw 1 × 103 to Mw 1 × 105. Elution times of the α-glucosidases and α-amylase was found from 26.5 to 43.0 min ( expected molecular weight, 48-90 kDa, excepting a minor peak at 125 kDa) and from 43.0 to 63.0 min (expected molecular weight, 51–54 kDa), respectively. Good separation was achieved with specific enzyme activities of α-glucosidase (fraction range from 26.5 min to 43.0 min) of 44.7 (unit/mg protein) and negligible α-amylase activity (1.0 unit/mg protein). The results demonstrated that purified α-glucosidases from rat intestinal power with high α -glucosidase activity can be efficiently achieved for in vitro carbohydrate hydrolysis test.
서정민(JeongMin Seo),박준영(Jun Young Park),최범석(Bum Seok Choi),윤의수(Eui Soo Yoon) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.5
CFD flow analysis is applied to the labyrinth seal with and without dimples for steam turbine. Mass flow rate in pressure differences, pressure distributions and velocity distributions are obtained by 3D FVM.
서정민(Jeongmin Seo) 한국이슬람학회 2018 한국이슬람학회논총 Vol.28 No.1
Extremism is mostly used in a political or religious sense to refer to an ideology that is considered to be far outside the (acceptable) mainstream attitudes of society. Extremism is a complex phenomenon, although its complexity is often hard to see. Most simply, it can be defined as activities (beliefs, attitudes, feelings, actions, strategies) of a character far removed from the ordinary. In conflict settings it manifests as a severe form of conflict engagement. The threat of extremism is neither constrained by international borders nor limited to any single ideology. Increasingly sophisticated use of the Internet, social media, and information technology by extremists adds an additional layer of complexity. Extremism is very difficult to deal with as it emerges from diverse political, social, economic, and cultural reasons. This study hypothesizes that social identity crisis in South Korea may contribute to emergence of homegrown extremism. Thus, this research analyzed whether five main vulnerable social groups can be influenced by extremism. Categorizing such five groups in South Korea as extremist internet communities, multi-cultural families, ill-treated foreign workers, religious extremists, and school maladjusted students, this study conducted surveys with them. The interview results show that the vulnerable social groups with social identity problems are likely to support or sympathizes extremism.