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Lee, Kangsoo,Shin, Seoyoon,Degen, Thomas,Lee, Wooyoung,Yoon, Young Soo Elsevier 2017 Nano energy Vol.32 No.-
<P><B>Abstract</B></P> <P>Herein, we describe a microwave-assisted hydrothermal process to synthesize α-Fe<SUB>2</SUB>O<SUB>3</SUB> nanotubes/SnO<SUB>2</SUB> nanorods/reduced graphene oxide (FNT/S/RGO) for application as a high-performance anode in lithium-ion batteries (LIBs). The composite products exhibit anisotropic growth because of heteronucleation and the preferred orientation of SnO<SUB>2</SUB>. SnO<SUB>2</SUB> nanorods on the FNT surfaces are converted into Sn metal during the alloying/dealloying reaction, which offers improved electrical conductivity. The FNT/S/RGO show substantially enhanced electrochemical properties because of the reduced volume expansion effect, which improves the electrical and Li-ion conductivity and provides a large surface area. As a consequence, the FNT/S/RGO anode delivers a high reversible capacity of 883mAhg<SUP>−1</SUP> even at a current density of 200mAg<SUP>−1</SUP>, with a capacity retention of 90% between the 1st and 220th cycles, excellent high-rate capacity (382mAhg<SUP>−1</SUP> at 4320mAg<SUP>−1</SUP>), and long-term cycle durability (maintaining 629mAhg<SUP>−1</SUP> at 1000mAg<SUP>−1</SUP> for 1000 cycles<SUP>)</SUP>. The presented FNT/S/RGO electrodes are the most efficient SnO<SUB>2</SUB>- and Fe<SUB>2</SUB>O<SUB>3</SUB>-based anode electrodes reported thus far for LIBs. The origin of the synergistic effect and the reaction mechanism of the FNT/S/RGO was thoroughly investigated using various <I>in situ</I> transmission electron microscopy, electrochemical impedance spectroscopy, and X-ray diffraction analysis methods.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The template-free SnO<SUB>2</SUB> on Fe<SUB>2</SUB>O<SUB>3</SUB>/RGO shows superior rate capability and cyclability. </LI> <LI> The capacity drop was revealed by phase transformation and 3D strain distribution study. </LI> <LI> The mechanism and enhanced performances were examined by various <I>in situ</I> analyses. </LI> <LI> The excellent performances of FNT/S/RGO attributed to the short diffusion length and improved electrical conductivity. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
소용량 건물용 연료전지시스템 블로워의 가혹조건 평가에 관한 연구
김강수(Kangsoo Kim),이덕권(Deokkwon Lee),이정운(Jungwoon Lee),김은정(Eunjung Kim),김인찬(Inchan Kim),김영규(Younggyu Kim),신헌용(Hunyong Shin) 한국가스학회 2012 한국가스학회지 Vol.16 No.6
연료전지는 우수한 도시가스 인프라로 안정적인 에너지공급이 가능하고, 연료 다변화가 가능한 신에너지 기술이다. 연료전지 상용화를 위해 시스템의 성능 및 신뢰성뿐만 아니라, 가격의 저감이 필수적이다. 소용량 건물용 연료전지시스템에서 가격비중이 매우 높은 보조기기의 가격저감 연구의 일환으로, 국내 제작된 블로워의 안전 성능을 평가하고 개선방향을 모색하고자 하였다. 본 연구에서는 실제 연료전지시스템의 작동환경과 가장 유사한 환경에서 블로워의 성능 및 가혹조건 평가를 수행하였다. 블로워를 70℃ 온도조건에서 장기 가동 시 유량성능, 기밀성능 및 열적거동의 상관관계를 파악하여, 블로워의 성능 저하에 영향을 미치는 모터열화, 다이어프램 재질 및 토출구 구조 등의 주요인자를 도출하였다. The fuel cell is one of the renewable energy sources. And it is a new source of energy that can be applied to various fuels and continuously supported by the excellent city-gas infrastructure. It is important to improve performances and reliabilities, and reduce the cost of fuel cell systems for commercialization. And, some safety performances of blower domestically produced are evaluated and some improvements are researched to save the cost of fuel cell systems. In this paper, the performance and worst stress condition of blowers are evaluated in operating environment similar to the fuel cell systems. Actually, the correlation of flow, leakage and thermal behavior are evaluated in the worst stress condition at 70℃ and, some major factors of blower degradation such as a motor deterioration, material and structures of the outlet are examined.
Fe<sub>3</sub>O<sub>4</sub> Nanoparticles on MWCNTs Backbone for Lithium Ion Batteries
Lee, Kangsoo,Shin, Seo Yoon,Yoon, Young Soo The Korean Ceramic Society 2016 한국세라믹학회지 Vol.53 No.3
A composite electrode made of iron oxide nanoparticles/multi-wall carbon nanotube (iNPs/M) delivers high specific capacity and cycle durability. At a rate of $200mAg^{-1}$, the electrode shows a high discharge capacity of ${\sim}664mAhg^{-1}$ after 100 cycles, which is ~ 70% of the theoretical capacity of $Fe_3O_4$. Carbon black, carbon nanotube, and graphene as anode materials have been explored to improve the electrical conductivity and cycle stability in Li ion batteries. Herein, iron oxide nanoparticles on acid treated MWCNTs as a conductive platform are combined to enhance the drawbacks of $Fe_3O_4$ such as low electrical conductivity and volume expansion during the alloying/dealloying process. Enhanced performance was achieved due to a synergistic effect between electrically 3D networks of conductive MWCNTs and the high Li ion storage ability of $Fe_3O_4$ nanoparticles (iNPs).
신광성(Kwangsung Shin),서덕원(Duckwon Seo),유기형(Gihyoung Yoo),김대중(Daejung Kim),김미화(Mihwa Kim),유강수(Kangsoo Yoo),곽훈성(Kwak Hoonsung) 한국정보과학회 2004 한국정보과학회 학술발표논문집 Vol.31 No.1B
MPEG-7은 형태나 질감, 컬러 등의 속성 및 분포 등을 나타내기 위한 여러 가지 기술자(descriptor)들을 제공함으로써 검색의 효율을 높일 수 있는 방법을 포함한 표준화를 제시하고 있다. 본 논문에서는 영상의 특징을 MPEG-7의 여러 기술자중 에지 히스토그램 기술자(Edge Histogram Descriptor)를 통해 얻는다. 추출된 에지 특징을 이용하여 영상의 정해진 각 영역의 전체 후보영상과의 상대적 유사도를 비교하여 검색에 반영함으로써 검색의 효율을 향상시키는 방법을 제안한다.
원심형 압축기 파생 설계 인자에 따른 성능 특성에 관한 수치적 연구
신봉근(Bong Gun Shin),이승훈(Seounhoon Lee),조종재(Jongjae Cho),임강수(Kangsoo Lim),김길영(Kilyoung Kim) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
In this study, the numerical analysis on performance characteristics of a centrifugal compressor in accordance with different derived design parameters, such as flow cut, impeller scaling, and machined Mach number, were performed. Before numerical analysis on the effect of a centrifugal compressor for these parameters, the numerical results were compared with experimental results performed at aero-component test rig at Hanwha Techwin. It is found that the simulated performance results are good agreement with the measured test results. In this study, it is found that derived designed parameters affects centrifugal compressor’s performance caused by the change of Reynolds effect and the friction loss generated within impeller, diffuser and scroll. This study indicates that performance characteristics for each derived design parameter shows different pattern and that it is difficult to predict performance map for various design parameter combination. However, the relative change in performance with relative change in volume flow rate is not depended upon design parameters to reference design performance value. The result shows a new approach idea to predict performance map for design parameters.