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Kim, Shin Ae,Das, Sumit,Lee, Howon,Kim, Junghoon,Song, Yun Mi,Kim, In Sook,Byun, Kyung Min,Hwang, Soon Jung,Kim, Sung June Wiley Subscription Services, Inc., A Wiley Company 2011 Biotechnology and bioengineering Vol.108 No.6
<P><B>Abstract</B></P><P>Matrix mineralization is a terminal process in osteoblast differentiation, and several approaches have been introduced to characterize the process in tissues or cultured cells. However, an analytical technique that quantitates in vitro matrix mineralization of live cells without any labeling or complex treatments is still lacking. In this study, we investigate a simple and enhanced optical method based on surface plasmon resonance (SPR) detection that can monitor the surface‐limited refractive index change in real‐time. During monitoring MC3T3‐E1 cells in vitro culture every 2 days for over 4 weeks, the SPR angle is shifted with a greater resonance change in cells cultured with osteogenic reagents than those without the reagents. In addition, the SPR results obtained have a close relevance with the tendency of conventional mineralization staining and an inductively coupled plasma‐based calcium content measure. These results suggest a new approach of a real‐time SPR monitoring in vitro matrix mineralization of cultured cells. Biotechnol. Bioeng. 2011; 108:1473–1478. © 2010 Wiley Periodicals, Inc.</P>
실제 및 시뮬레이션 환경에서의 적대적 공격 기법 연구 동향
김용수(Yongsu Kim),윤영여(Youngyeo Yun),강효은(Hyoeun Kang),김명길(Myeongkil Kim),김호원(Howon Kim) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.2
딥러닝 기술은 지속적인 발전을 통해 실생활에 다양하게 적용되고 있지만, 악의적인 데이터를 주입하여 오작동하게 만드는 적대적 공격에 취약한 것으로 밝혀져 큰 위협이 되고 있다. 특히, 기존 연구에서 발전하여 실제 환경이나 이와 유사한 시뮬레이션 환경에서 딥러닝 모델을 공격할 수 있는 연구가 많이 제안되었다. 본 논문에서는 실제 및 시뮬레이션 환경에서의 적대적 공격 기법 연구 동향을 조사하여, 향후 실생활에 큰 위협이 되는 적대적 공격에 대한 효과적인 방어 연구를 진행하는 데 기여하고자 한다.
Kim, Howon,Mun, Bongjin Simon,Park, Changwoo,Ju, Honglyoul Elsevier 2017 Current Applied Physics Vol.17 No.2
<P>We have investigated the effect of over oxidized surface layer on the characteristics of metal-insulator transition (MIT) of vanadium dioxide (VO2) films grown by thermal oxidation method. During the oxidation, the over-oxidized V6O13 layer was formed, which increased contact resistance and thus reduced the resistivity ratio before and after MIT. The contact resistivity of the V02 film with over oxidized surface layer was in the range 4.2 x 10(-2) similar to 9.4 x 10(-4) Omega cm(2). Interestingly, the over-oxidized surface layer was removed by simply cooling the film under reduced oxygen pressure. Upon the removal of the over-oxidized layer, the resistivity ratio across MIT increased up to 1.2 x 10(4). The ratio of contact resistance to sample resistance was small (large) at low (high) temperature. (C) 2016 Elsevier B.V. All rights reserved.</P>
Kim, Howon,Chang, Yun Hee,Lee, Soon-Hyeong,Kim, Yong-Hyun,Kahng, Se-Jong American Chemical Society 2013 ACS NANO Vol.7 No.10
<P>Controlling and sensing spin states of magnetic molecules at the single-molecule level is essential for spintronic molecular device applications. Here, we demonstrate that spin states of Co–porphyrin on Au(111) can be reversibly switched over by binding and unbinding of the NO molecule and can be sensed using scanning tunneling microscopy and spectroscopy (STM and STS). Before NO exposure, Co–porphryin showed a clear zero-bias peak, a signature of Kondo effect in STS, whereas after NO exposures, it formed a molecular complex, NO–Co–porphyrin, that did not show any zero-bias feature, implying that the Kondo effect was switched off by binding of NO. The Kondo effect could be switched back on by unbinding of NO through single-molecule manipulation or thermal desorption. Our density functional theory calculation results explain the observations with pairing of unpaired spins in d<SUB><I>z</I><SUP>2</SUP></SUB> and ppπ* orbitals of Co–porphyrin and NO, respectively. Our study opens up ways to control molecular spin state and Kondo effect by means of enormous variety of bimolecular binding and unbinding reactions on metallic surfaces.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2013/ancac3.2013.7.issue-10/nn4039595/production/images/medium/nn-2013-039595_0007.gif'></P>
Probing Single-Molecule Dissociations from a Bimolecular Complex NO–Co-Porphyrin
Kim, Howon,Chang, Yun Hee,Jang, Won-Jun,Lee, Eui-Sup,Kim, Yong-Hyun,Kahng, Se-Jong American Chemical Society 2015 ACS NANO Vol.9 No.7
<P>Axial coordinations of diatomic NO molecules to metalloporphyrins play key roles in dynamic processes of biological functions such as blood pressure control and immune response. Probing such reactions at the single molecule level is essential to understand their physical mechanisms but has been rarely performed. Here we report on our single molecule dissociation experiments of diatomic NO from NO-Co-porphyrin complexes describing its dissociation mechanisms. Under tunneling junctions of scanning tunneling microscope, both positive and negative energy pulses gave rise to dissociations of NO with threshold voltages, +0.68 and -0.74 V at 0.1 nA tunneling current on Au(111). From the observed power law relations between dissociation rate and tunneling current, we argue that the dissociations were inelastically induced with molecular orbital resonances by stochastically tunneling electrons, which is supported with our density functional theory calculations. Our study shows that single molecule dissociation experiments can be used to probe reaction mechanisms in a variety of axial coordinations between small molecules and metalloporphyrins.</P>
Hyperelliptic Curve Crypto-Coprocessor over Affine and Projective Coordinates
Howon Kim,Thomas Wollinger,Doo-Ho Choi,Dong-Guk Han,이문규 한국전자통신연구원 2008 ETRI Journal Vol.30 No.3
This paper presents the design and implementation of a hyperelliptic curve cryptography (HECC) coprocessor over affine and projective coordinates, along with measurements of its performance, hardware complexity, and power consumption. We applied several design techniques, including parallelism, pipelining, and loop unrolling, in designing field arithmetic units, group operation units, and scalar multiplication units to improve the performance and power consumption. Our affine and projective coordinate-based HECC processors execute in 0.436 ms and 0.531 ms, respectively, based on the underlying field GF(289). These results are about five times faster than those for previous hardware implementations and at least 13 times better in terms of area-time products. Further results suggest that neither case is superior to the other when considering the hardware complexity and performance. The characteristics of our proposed HECC coprocessor show that it is applicable to high-speed network applications as well as resource-constrained environments, such as PDAs, smart cards, and so on.