http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Highly Enhanced Gas Adsorption Properties in Vertically Aligned MoS<sub>2</sub> Layers
Cho, Soo-Yeon,Kim, Seon Joon,Lee, Youhan,Kim, Jong-Seon,Jung, Woo-Bin,Yoo, Hae-Wook,Kim, Jihan,Jung, Hee-Tae American Chemical Society 2015 ACS NANO Vol.9 No.9
<P>In this work, we demonstrate that gas adsorption is significantly higher in edge sites of vertically aligned MoS<SUB>2</SUB> compared to that of the conventional basal plane exposed MoS<SUB>2</SUB> films. To compare the effect of the alignment of MoS<SUB>2</SUB> on the gas adsorption properties, we synthesized three distinct MoS<SUB>2</SUB> films with different alignment directions ((1) horizontally aligned MoS<SUB>2</SUB> (basal plane exposed), (2) mixture of horizontally aligned MoS<SUB>2</SUB> and vertically aligned layers (basal and edge exposed), and (3) vertically aligned MoS<SUB>2</SUB> (edge exposed)) by using rapid sulfurization method of CVD process. Vertically aligned MoS<SUB>2</SUB> film shows about 5-fold enhanced sensitivity to NO<SUB>2</SUB> gas molecules compared to horizontally aligned MoS<SUB>2</SUB> film. Vertically aligned MoS<SUB>2</SUB> has superior resistance variation compared to horizontally aligned MoS<SUB>2</SUB> even with same surface area exposed to identical concentration of gas molecules. We found that electrical response to target gas molecules correlates directly with the density of the exposed edge sites of MoS<SUB>2</SUB> due to high adsorption of gas molecules onto edge sites of vertically aligned MoS<SUB>2</SUB>. Density functional theory (DFT) calculations corroborate the experimental results as stronger NO<SUB>2</SUB> binding energies are computed for multiple configurations near the edge sites of MoS<SUB>2</SUB>, which verifies that electrical response to target gas molecules (NO<SUB>2</SUB>) correlates directly with the density of the exposed edge sites of MoS<SUB>2</SUB> due to high adsorption of gas molecules onto edge sites of vertically aligned MoS<SUB>2</SUB>. We believe that this observation extends to other 2D TMD materials as well as MoS<SUB>2</SUB> and can be applied to significantly enhance the gas sensor performance in these materials.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2015/ancac3.2015.9.issue-9/acsnano.5b04504/production/images/medium/nn-2015-04504g_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn5b04504'>ACS Electronic Supporting Info</A></P>
Reduction of magnetic resonance image artifacts of NiTi implant by carbon coating
Han, Taeyang,Sohn, Youhan,Park, Sang Jin,Kim, Yu-Chan,Lee, Kang Sik,Kim, Hye Sung,Yoon, Soon-Gil,Kim, Dojin,Han, Jun Hyun Elsevier 2019 Materials science & engineering. C, Materials for Vol.98 No.-
<P><B>Abstract</B></P> <P>A paramagnetic NiTi substrate was coated with diamagnetic carbon materials, i.e., graphene, graphene oxide (GO), and carbon nanotubes (CNTs), in order to reduce magnetic resonance (MR) image artifacts of NiTi implants. The present study focused on the effect of magnetic susceptibility variations in NiTi caused by the carbon coating on MR image artifacts. In the case of the graphene and GO coatings, the reduction of the magnetic susceptibility was greater along the perpendicular direction than the parallel direction. In contrast, the CNT coating exhibited a larger reduction along the parallel direction. The reduction of magnetic susceptibility measured in CNT-coated NiTi (CNT/NiTi) was smaller than the theoretical prediction especially when measured along the parallel direction, because CNTs on the NiTi surface were randomly arranged, rather than in a single direction. MR image artifacts were substantially reduced in all carbon-coated NiTi specimens, which is due to the reduction of magnetic susceptibility in NiTi by the carbon coating. This method can also be applied to other paramagnetic bio-metallic materials such as Co-Cr.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Graphene and GO coating caused a larger susceptibility reduction in the perpendicular direction. </LI> <LI> CNT coating exhibited a larger reduction in susceptibility along the parallel direction. </LI> <LI> Graphene/NiTi, GO/NiTi, and CNT/NiTi resulted in a significant reduction of MR image artifacts. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Noncoherent Unitary Space-Time Modulated DSSS Systems in Multipath Channels
전경훈,김정창,Youhan Kim,Soongyoon Choi 한국통신학회 2012 Journal of communications and networks Vol.14 No.2
In this paper, in order to effectively apply unitary spacetime modulation to the direct-sequence spread-spectrum multipleaccess (DSSS-MA) networks, we propose a low-rate, noncoherent,unitary, and space-time modulated DSSS system supporting any number of transmit antennas based on Walsh matrices. The proposed scheme simultaneously performs bandwidth spreading and space-time coding and outperforms those using high-rate, conventional unitary space-time constellations. Furthermore, the proposed scheme allows for a simple detector structure based on fast Walsh transforms.
직조된 SiC 섬유에 무전해 구리도금 시 도금 조건의 영향
이기환(Kee Hwan Lee),손유한(Youhan Sohn),한태양(Taeyang Han),이경진(Kyung Jin Lee),김혜성(Hye Hung Kim),한준현(Jun Hyun Han) 한국표면공학회 2017 한국표면공학회지 Vol.50 No.4
Effects of plating conditions (dispersant concentration, plating time, and ultrasonication) on electroless Cu plating on SiC fabric woven by crossing of SiC continuous fibers vertically were studied. The ultrasonic dispersion treatment not only did not improve the dispersion of the SiC fibers, but also did not change the plating thickness. The ultrasonication in the pretreatment step of electroless plating did not improve the dispersion of the fibers, while the ultrasonication in the plating step enhanced the dispersion of the fibers and decreased the thickness of the Cu films. It was possible to control the thickness of the Cu coating layer as well as the dispersion of the fibers in the fabric by changing the plating conditions such as dispersant concentration, plating time, and ultrasonication, but it was very difficult to coat copper on the intersection of vertical fibers in the fabric.
한태양,손유한,김상열,정현철,김현유,이상로,한준현,Han, Taeyang,Sohn, Youhan,Kim, Sangyeol,Jung, Hyun-Chul,Kim, Hyun You,Lee, San-ro,Han, Jun Hyun 한국재료학회 2018 한국재료학회지 Vol.28 No.12
We investigate the reduction of $SnO_2$ and the generation of syngas($H_2$, CO) using methane($CH_4$) and hydrogen($H_2$) or a mixed gas of methane and hydrogen as a reducing gas. When methane is used as a reducing gas, carbon is formed by the decomposition of methane on the reduced Sn surface, and the amount of generated carbon increases as the amount and time of the supply of methane increases. However, when hydrogen is used as a reducing gas, carbon is not generated. High purity Sn of 99.8 % and a high recovery rate of Sn of 93 % are obtained under all conditions. The effects of reducing gas species and the gas mixing ratio on the purity and recovery of Sn are not significantly different, but hydrogen is somewhat more effective in increasing the purity and recovery rate of Sn than methane. When 1 mole of methane and 1 mole of hydrogen are mixed, a product gas with an $H_2/CO$ value of 2, which is known to be most useful as syngas, is obtained.