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Ahn, Juhyeon,Susanto, Dieky,Noh, Jae-Kyo,Ali, Ghulam,Cho, Byung Won,Chung, Kyung Yoon,Kim, Jong Hak,Oh, Si Hyoung Elsevier Sequoia 2017 Journal of Power Sources Vol. No.
<P><B>Abstract</B></P> <P>In this study, we target to find a new composition for a layered mixed metal oxide, which has a high structural stability and a good electrochemical performance. Our strategy is to alter the transition metal composition focusing on the relative amounts of redox active Ni and Co to the inactive Mn, based on highly-stabilized LiNi<SUB>1/3</SUB>Co<SUB>1/3</SUB>Mn<SUB>1/3</SUB>O<SUB>2</SUB>. X-ray absorption near-edge structure and X-ray diffraction analyses show that the degree of cation disorder decreases on increasing the ratio of Ni and Co to Mn, by the presence of Ni<SUP>3+</SUP>, suggesting that slightly higher Ni and Co contents lead to improved structural stability. Electrochemical studies demonstrate that LiNi<SUB>0.4</SUB>Co<SUB>0.4</SUB>Mn<SUB>0.2</SUB>O<SUB>2</SUB> cathodes exhibit considerable improvements in both the reversible capacity and the rate capabilities at a voltage range of 2.5–4.6 V. <I>In situ</I> XRD measurements reveal that LiNi<SUB>0.4</SUB>Co<SUB>0.4</SUB>Mn<SUB>0.2</SUB>O<SUB>2</SUB> maintains a single-phase and undergoes lesser structural variations compared to controlled compositions during a delithiation process up to 4.6 V, while achieving a high reversible capacity over 200 mAh g<SUP>−1</SUP>. As a result, LiNi<SUB>0.4</SUB>Co<SUB>0.4</SUB>Mn<SUB>0.2</SUB>O<SUB>2</SUB> experiences fewer structural degradations during electrochemical cycling, which explains the excellent long-term cycling performance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Composition of layered oxides are tuned for high capacity and rate capability. </LI> <LI> LiNi<SUB>0.4</SUB>Co<SUB>0.4</SUB>Mn<SUB>0.2</SUB>O<SUB>2</SUB> is proposed as one of the promising cathode materials. </LI> <LI> Lesser structural changes during charging lead to excellent cycling stability. </LI> <LI> LiNi<SUB>0.4</SUB>Co<SUB>0.4</SUB>Mn<SUB>0.2</SUB>O<SUB>2</SUB> delivers a capacity over 200 mAh g<SUP>−1</SUP> via single-phase reaction. </LI> </UL> </P>
Ahn, Juhyeon,Kim, Jong Hak,Cho, Byung Won,Chung, Kyung Yoon,Kim, Sangryun,Choi, Jang Wook,Oh, Si Hyoung American Chemical Society 2017 NANO LETTERS Vol.17 No.12
<P>Battery performance, such as the rate capability and cycle stability Of lithium transition metal oxides, is strongly correlated with the surface properties of active particles. For lithium-rich layered oxides, transition metal segregation in the initial state and migration upon cycling leads to a significant structural rearrangement, which eventually degrades the electrode performance. Here, we show that a fine-tuning of surface chemistry on the particular crystal facet can facilitate ionic diffusion and thus improve the rate capability dramatically, delivering a specific capacity of similar to 110 mAh g(-1) at 30C. This high rate performance is realized by creating a nanoscale zirconium-abundant rock-salt-like surface phase epitaxially grown on the layered bulk. This surface layer is spontaneously formed on the Li+ diffusive crystallographic facets during the synthesis and is also durable upon electrochemical cycling. As a result, Li-ions can move rapidly through this nanoscale surface layer over hundreds of cycles. This study provides a promising new strategy for designing and preparing a high-performance lithium-rich layered oxide cathode material.</P>
세대 간 커뮤니케이션을 위한 스마트 모듈형 텃밭 서비스
정주현(Juhyeon Jeong),이수빈(Subin Lee),안성희(Sunghee Ahn) 한국HCI학회 2020 한국HCI학회 학술대회 Vol.2020 No.2
국내에서 스마트시티(smart city) 관련 시장이 급격히 확산되고 이에 대한 연구도 늘고 있지만 스마트시티를 실감하는 연령층이 한정되어 있으며 향유 측면에서나 지역적인 특성을 고려하고 있는 부분에서는 아직 부족하다고 할 수 있다. 세대 간 디지털 정보의 격차가 심해지며 상대적으로 일상에서 스마트시티 서비스를 많이 향유하지 못하는 노년층들을 대상으로 문제 해결 중심 디자인을 진행하였다. 본 연구는 IoT 기능을 갖춘 모듈형 텃밭을 이용한 가드닝 클래스를 통해 다양한 세대 간 커뮤니케이션을 시도하였다. 또한 IoT 시스템 기반 앱(App)을 통해서 지역 주민이 같이 향유할 수 있는 시민 참여형 스마트 가든(on-line/off-line)을 통해 사용자가 중심이 되는 ‘스마트시티 플랫폼 서비스’를 구축하는 것이 본 연구의 최종 목표이다. 사용자는 앱을 통해 스마트 텃밭의 작물을 개인의 취향별로 선택하여 서로 매칭 후, 노년층 유저가 운영하는 텃밭 클래스(off-line)를 구성하고 텃밭을 함께 운영하는 자연스러운 세대 간 커뮤니케이션을 통해 작물을 재배하도록 유도하는 서비스이다. 수확철이 되면 앱을 통해 모여진 데이터(사진과 정보)로 ‘텃밭 일지’, 포토 북을 제작해 추억을 공유할 수 있도록 설계하였다.
Kim, Kyoung-Ran,Hwang, Dohyeon,Kim, Juhyeon,Lee, Chang-Yong,Lee, Wonseok,Yoon, Dae Sung,Shin, Dongyun,Min, Sun-Joon,Kwon, Ick Chan,Chung, Hak Suk,Ahn, Dae-Ro Elsevier 2018 Journal of controlled release Vol.280 No.-
<P><B>Abstract</B></P> <P>Despite the extremely high substrate specificity and catalytically amplified activity of enzymes, the lack of efficient cellular internalization limits their application as therapeutics. To overcome this limitation and to harness enzymes as practical biologics for targeting intracellular functions, we developed the streptavidin-mirror DNA tetrahedron hybrid as a platform for intracellular delivery of various enzymes. The hybrid consists of streptavidin, which provides a stoichiometrically controlled loading site for the enzyme cargo and an L-DNA (mirror DNA) tetrahedron, which provides the intracellular delivery potential. Due to the cell-penetrating ability of the mirror DNA tetrahedron of this hybrid, enzymes loaded on streptavidin can be efficiently delivered into the cells, intracellularly expressing their activity. In addition, we demonstrate tumor delivery of enzymes in an animal model by utilizing the potential of the hybrid to accumulate in tumors. Strikingly, the hybrid is able to transfer the apoptotic enzyme specifically into tumor cells, leading to strong suppression of tumor growth without causing significant damage to other tissues. These results suggest that the hybrid may allow anti-proliferative enzymes and proteins to be utilized as anticancer drugs.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>