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RISS 인기검색어
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- 저자 : Hyeji Park (검색결과 117 건)
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Park, Hyeji,Um, Ji Hyun,Choi, Hyelim,Yoon, Won-Sub,Sung, Yung-Eun,Choe, Heeman Elsevier 2017 APPLIED SURFACE SCIENCE - Vol.399 No.-
<P><B>Abstract</B></P> <P>A Novel 3D porous Sn-Cu architecture is prepared as an anode material for use in an advanced lithium-ion battery. Micro-lamellar-structured 3D porous Cu foam, which is electroless-plated with Sn as an active material, is used as anode current collector. Compared to Sn-coated Cu foil, the 3D Sn-Cu foam exhibits superior Li-ion capacity and stable capacity retention, demonstrating the advantage of 3D porous architecture by preserving its structural integrity. In addition, the effect of heat-treatment after Sn plating is investigated. Sn/Sn<SUB>6</SUB>Cu<SUB>5</SUB> and SnO<SUB>2</SUB>/Cu<SUB>10</SUB>Sn<SUB>3</SUB> were formed on and in the 3D Sn-Cu foam under the heat-treatment at 150°C and 500°C, respectively. The development of Cu<SUB>10</SUB>Sn<SUB>3</SUB> in the 3D Sn-Cu foam heat-treated at 500°C can be a key factor for the enhanced cyclic stability because the Cu<SUB>10</SUB>Sn<SUB>3</SUB> inactively reacts with Li-ion and alleviates the volume expansion of SnO<SUB>2</SUB> as an inactive matrix.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Sn-Cu scaffold anode fabricated by freeze-casting and electroless plating. </LI> <LI> Sn-Cu scaffold architecture shows superior capacity and cyclic stability at high current density. </LI> <LI> Sn-Cu scaffold electrode is commercially promising. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Park, Hyeji,Cho, Hoon-Hwe,Kim, Kyungbae,Hong, Kicheol,Kim, Jae-Hun,Choe, Heeman,Dunand, David C. Elsevier 2018 ACTA MATERIALIA Vol.142 No.-
<P>Cobalt with anisotropic open porosity is fabricated by directional solidification of aqueous slurries of nanometric Co3O4 powder where ice dendrites push powders into aligned interdendritic spaces, followed by ice sublimation, reduction of the oxide to metallic Co powders, and sintering of these Co powders into parallel lamellae. As the Co3O4 powder slurry fraction decreases (from 10 to 4 vol%), Co lamellae width in the final foam also decreases (from 93 to 8 gm) while foam porosity increases (from 66 to 85%). A drop in solidification temperature (from -10 to -50 degrees C) decreases porosity (from 77 to 63%) and lamellae width (from 11 to 5 mu m) at a constant 8 vol% slurry fraction. Finally, with increasing sintering time (for -10 degrees C solidification temperature and 8% slurry fraction), Co foam porosity decreases (from 77 to 68%) and lamella width strongly increases (from 10 to 59 gm), consistent with sintering induced coalescence of lamellae. The Co foams exhibit high strength but relatively low stiffness as compared to simple theoretical models, consistent with internal Co lamella buckling. A uniform Co oxide layer is grown by oxidation to create an active coating on the Co lamellae useful for lithium-ion storage. A coin-cell test carried out on the oxidized Co foam demonstrates a capacity (1283 mAhg(-1)) almost twice that of a control oxidized Co foil anode, owing to its considerably larger surface area. Finite-element analysis is used to compute stresses and plastic strain evolutions during the lithiation process to understand the effect of oxide layer thickness and roughness, and micropores within the Co lamellae. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.</P>
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Park, Hyeji,Hong, Kicheol,Kang, Jin Soo,Um, Teakyung,Knapek, Michal,Miná,rik, Peter,Sung, Yung-Eun,Má,this, Kristiá,n,Yamamoto, Akiko,Kim, Hyun-Kyung,Choe, Heeman Elsevier 2019 Materials Science and Engineering C Vol.97 No.-
<P><B>Abstract</B></P> <P>We synthesized Fe foams using water suspensions of micrometric Fe<SUB>2</SUB>O<SUB>3</SUB> powder by reducing and sintering the sublimated Fe oxide green body to Fe under 5% H<SUB>2</SUB>/Ar gas. The resultant Fe foam showed aligned lamellar macropores replicating the ice dendrites. The compressive behavior and deformation mechanism of the synthesized Fe foam were studied using an acoustic emission (AE) method, with which we detected sudden localized structural changes in the Fe foam material. The evolution of the deformation mechanism was elucidated using the adaptive sequential <I>k</I>-means (ASK) algorithm; specifically, the plastic deformation of the cell struts was followed by localized cell collapse, which eventually led to fracturing of the cell walls. For potential biomedical applications, the corrosion and biocompatibility characteristics of the two synthesized Fe foams with different porosities (50% vs. 44%) were examined and compared. Despite its larger porosity, the superior corrosion behavior of the Fe foam with 50% porosity can be attributed to its larger pore size and smaller microscopic surface area. Based on the cytotoxicity tests for the extracts of the foams, the Fe foam with 44% porosity showed better cytocompatibility than that with 50% porosity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Iron foam synthesized from water suspension of Fe<SUB>2</SUB>O<SUB>3</SUB> powder under 5% H<SUB>2</SUB>/Ar gas. </LI> <LI> Compressive deformation mechanism of iron foam is analyzed using an acoustic emission. </LI> <LI> Not porosity but pore size is a dominant factor for corrosion behavior of iron foams. </LI> <LI> Concentration released Fe<SUP>n+</SUP> controls cytotoxicity of iron foam extracts. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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( Hyeji Yoon ),( Hyoung Su Park ),( Xiangxue An ),( Seok Jun Park ),( Gwang Woong Go ),( Hyunjung Kim ),( Hyesoon Lee ),( Mee Na Kim ),( Yoo Kyoung Park ) 한국임상영양학회 2022 Clinical Nutrition Research Vol.11 No.1
Through a survey on dietary intake of children and adolescents with brain lesions, the present study aimed to analyze the current status of nutrient intake and examine the effect of high-protein nutrient drink on their nutritional and muscle statuses. The study participants were 90 juvenile participants aged 8-19 years, with brain lesions. The participants were provided with a protein nutrient drink for 12 weeks and a questionnaire survey on dietary intake was performed to analyze the level of nutrient intake before and after ingestion. The physical measurements were taken to determine the improvements in nutrient and muscle statuses. The results showed that, before the intake of protein nutrient drink as a supplement, the participants exhibited lower height, weight, and body mass index than those of the standard levels of healthy individuals, and the level of nutrient intake through diet was lower than those of the required and recommended levels of nutrient intake for Koreans. Conversely, after the intake of protein nutrient drink for 12 weeks, the level of nutrient intake and physical statuses such as weight showed significant improvements. In addition, the muscle status had undergone approximately 10% of change during the intervention with no significant difference. Thus, to ensure an adequate level of nutrient supply to children and adolescents with brain lesions, there is an urgent need to develop a guideline of nutrient intake. The findings in this study are expected to serve as the basic data for such guidelines.
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Park, Sangmin,Shin, Hyeji,Park, Yeeun,Choi, Ilgyu,Park, Byoungduck,Lee, Ki Yong Elsevier 2018 Bioorganic chemistry Vol.80 No.-
<P><B>Abstract</B></P> <P>An effective screening method for inhibitors of NO production in natural products using LC-QTOF MS/MS coupled with a cell-based assay was proposed. The ethyl acetate fraction of <I>Catalpa ovata</I> exhibited a strong inhibitory effect on NO production in lipopolysaccharide-induced BV2 microglia cells. We attempted to identify the active constituents of <I>C. ovata</I> by using LC-QTOF MS/MS coupled with a cell-based assay. Peaks at approximately 14–15 min on the MS chromatogram were estimated to be the bioactive constituents. A new iridoid compound, 6-<I>O-trans</I>-feruloyl-3β-hydroxy-7-deoxyrehamaglutin A (<B>4</B>), and nine known compounds (<B>1</B>–<B>3, 5</B>–<B>10</B>) were isolated from the ethyl acetate fraction of <I>C. ovata</I> by repeated column chromatography. Compounds <B>3</B>, <B>4</B>, <B>5</B>, <B>7</B>, and <B>8</B> significantly attenuated lipopolysaccharide-stimulated NO production in BV2 cells. Our results indicate that LC-QTOF MS/MS coupled with a cell-based NO production inhibitory assay successfully predicted active compounds without a time-consuming isolation process.</P> <P><B>Highlights</B></P> <P> <UL> <LI> LC-QTOF MS/MS coupled with a cell-based NO production inhibitory assay was developed. </LI> <LI> EtOAc fraction of <I>Catalpa ovata</I> showed inhibitory effect on NO production. </LI> <LI> Compounds between 14 and 15 min on Mass chromatogram inhibited NO production. </LI> <LI> Anti-inflammatory activity was tested on isolated compounds including a new compound. </LI> <LI> Predicted active compounds from developed method matched with the experimental data. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Dependence of Alternating Magnetic Field Intensity on Proliferation Rate of Human Breast Cancer Cell
Hyeji Park,Hyun Sook Lee,Do Guwn Hwang 한국자기학회 2015 Journal of Magnetics Vol.20 No.3
To investigate the effects of alternating magnetic field intensity and stimulation time on the proliferation of human breast cancer cells (BT-20), we cultured the cells under a magnetic field with a saw tooth waveform of 2 kHz. The field intensities varied from 3 to 7 mT, and the stimulation time varied from 24 to 72 hours. Cell proliferation decreased dramatically to 40% during magnetic stimulation for 72 hours at 5 mT. However, the cells were not affected by a strong magnetic field of 7 mT. The p-values obtained using statistical package for social science software were below 0.05 for 5-7 mT. This means that the results have statistical significance. However, it is difficult to explain our results based on the physiology of cell membranes, which have various ionic flows at ion channels.
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Park, Hyeji,Choi, Myounggeun,Choe, Heeman,Dunand, David C. Elsevier Sequoia 2017 Materials science & engineering Structural materia Vol.679 No.-
<P><B>Abstract</B></P> <P>Copper foams are fabricated by directional freezing of aqueous suspensions of nanometric CuO powders followed by ice sublimation, reduction to Cu in Ar–5% H<SUB>2</SUB> gas and sintering. During slurry solidification, parallel, lamellar, centimeter-long ice dendrites grow, pushing the CuO powders into lamellar interdendritic spaces. Upon subsequent ice sublimation, the ice dendrites create lamellar pores surrounded by CuO walls that are subsequently reduced to copper and sintered; these ice-templated walls display surface micropores and, depending on the reduction/sintering parameters, internal micropores. Varying the main processing parameters – powder fraction in the slurry (from 13 to 19vol%) and casting temperature (from −10 to −30°C) – has a strong effect on the foam microstructure: (i) porosity (varying from 45% to 73%) is inversely related to slurry powder fraction, (ii) oriented lamellar macropores width increases from 15 to 64µm with decreasing slurry fraction and increasing freezing temperature and (iii) oriented lamellar Cu wall width increases from 19 to 63µm with increasing slurry fraction and freezing temperature. The resulting Cu foams show oriented, lamellar macropores (beneficial to permeability) and walls micropores (which increase the surface area) and are promising for use in electrochemical cells given the simplicity, scalability, low cost, and microstructure tunability associated with the ice-templating process. The ice-templated Cu foams, with pore directions parallel and perpendicular to the direction of compressive loading, show ductile compressive behavior with high yield stress, ductility and energy absorption; they are compared to model predictions and literature data of Cu lotus foams with elongated, cylindrical pores.</P>
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