Query Processing System for Efficient Range Query in Location Based Service

Segi Jeon,Chanil Woo 대한전자공학회 2005 ITC-CSCC :International Technical Conference on Ci Vol.2005 No.3

Genome editing of immune cells using CRISPR/Cas9

( Segi Kim ),( Cedric Hupperetz ),( Seongjoon Lim ),( Chan Hyuk Kim ) 생화학분자생물학회(구 한국생화학분자생물학회) 2021 BMB Reports Vol.54 No.1

The ability to read, write, and edit genomic information in living organisms can have a profound impact on research, health, economic, and environmental issues. The CRISPR/Cas system, recently discovered as an adaptive immune system in prokaryotes, has revolutionized the ease and throughput of genome editing in mammalian cells and has proved itself indispensable to the engineering of immune cells and identification of novel immune mechanisms. In this review, we summarize the CRISPR/Cas9 system and the history of its discovery and optimization. We then focus on engineering T cells and other types of immune cells, with emphasis on therapeutic applications. Last, we describe the different modifications of Cas9 and their recent applications in the genome-wide screening of immune cells. [BMB Reports 2021; 54(1): 59-69]

Single-Walled Carbon Nanotubes as a Chemical Sensor for <tex> $\hbox{SO}_{2}$</tex> Detection

SeGi Yu,Whikun Yi IEEE 2007 IEEE TRANSACTIONS ON NANOTECHNOLOGY Vol.6 No.5

<P>Single-walled carbon nanotubes (SWNTs) are Introduced as a chemical sensor for the detection of sulfur dioxide (SO<SUB>2</SUB>) molecules. For a single bundle of SWNTs, current-voltage (I-V) curves were measured for a series of different temperatures under adsorption of SO<SUB>2</SUB> molecules. The I-V characteristics for a 'MAT'-type thin film SWNTs, with respect to the amount of SO<SUB>2</SUB> adsorbed, were measured at room temperature and compared directly with O<SUB>2</SUB> adsorption. The change in current upon the adsorption of SO<SUB>2</SUB> is distinctly higher than that of O<SUB>2</SUB>, and is also reversible for adsorption and successive evacuation. Thus, the results strongly suggested that a thin film of SWNTs can be used as a chemical sensor in the nanometer scale devices.</P>

Emission Stability of Semiconductor Nanowires

SeGi Yu(유세기),Taewon Jeong(정태원),Sang Hyun Lee(이상현),Jungna Heo(허정나),Jeonghee Lee(이정희),Cheol Jin Lee(이철진),Jinyoung Kim(김진영),HyungSook Lee(이형숙),YoonPil Kuk(국윤필),J.M. Kim(김종민) 한국진공학회(ASCT) 2006 Applied Science and Convergence Technology Vol.15 No.5

열 화학기상법으로 만든 GaN와 GaP 나노와이어에서 전계 방출과, 산소와 아르곤 분위기에서 안정성에 대해 조사하였다. GaN 나노와이어의 경우 산소 분위기에서 전계 방출이 급격하게 줄었으나, GaP에서는 그렇지 않았다. 두 나노와이어 모두 아르곤 분위기에서는 큰 변화가 없었다. GaP 나노와이어의 외부에 존재하는 산화물 층이 전자 방출 안정성에 크게 기여한 것으로 생각된다. 나노와이어에서 방출된 전자의 에너지 분포를 통해 반도체 나노와이어는 탄소 나노튜브와 그 전계 방출 메카니즘이 다름을 유추할 수 있었다. Field emission of GaN and GaP nanowires, synthesized by thermal chemical vapor deposition, and their emission stabilities under oxygen and argon environments were investigated. The field emission current of GaN nanowires was seriously deteriorated under oxygen environment, while that of GaP was not. Both wires did not show any noticeable change under argon environment. The existence of oxide outer shell layers in the GaP nanowires was proposed to be a main reason for this emission stability behavior. Field emission energy distributions of electrons from these nanowires revealed that field emission mechanism of the semiconductor nanowires were different from that of carbon nanotubes.

Double - to one - humped secondary electron emission curve change for thermal silicon oxide layers

SeGi Yu,TaeWon Jeong,Whikun Yi,Jeonghee Lee,S.H. Jin,J.M. Kim,D. Jeon 한국진공학회 2000 한국진공학회 학술발표회초록집 Vol.- No.-

Ordered, Scalable Heterostructure Comprising Boron Nitride and Graphene for High-Performance Flexible Supercapacitors

Byun, Segi,Kim, Joon Hui,Song, Sung Ho,Lee, Minku,Park, Jin-Ju,Lee, Gyoungja,Hong, Soon Hyung,Lee, Dongju American Chemical Society 2016 Chemistry of materials Vol.28 No.21

<P>Heterostructures based on combining two-dimensional (2D) crystals in one stack have unusual physical properties and allow the creation of novel devices. Although this method of mechanically transferring individual 2D crystals is required for precise control, it is not scalable. Large-scale fabrication of heterostructures remains a key challenge for practical applications. Here, we provide a simple solution-based method using electrostatic interaction assembly of boron nitride (h-BN) and graphene to produce hybrid films with van der Waals heterostructures. The hybrid films prepared by this fabrication method tend to be alternately stacked and provide compact structured films. For a potential application, the h-BN/graphene hybrid films are fabricated supercapacitor's electrodes revealing high volumetric capacitance, superior rate capability, a permanent life cycle, and high flexibility due to their synergistic effects. We anticipate that the hybrid films are useful as scalable flexible electrodes in supercapacitors, and our solution-based method has great potential for application in energy storage and electronics.</P>

Metal sputtered graphene based hybrid films comprising tin oxide/reduced graphene oxide/Ni as electrodes for high-voltage electrochemical capacitors

Byun, Segi,Shin, Byungha,Yu, Jin Elsevier 2018 Carbon Vol.129 No.-

<P><B>Abstract</B></P> <P>The high voltage aqueous electrochemical capacitor (EC) is a promising energy storage device because of eco-friendliness and high electrochemical performance with a wide operational voltage and high energy density. However, it typically experiences a stability problem that includes cell aging and capacitance loss. Here, to overcome the stability issue, a thin metal layer of Ni is created on one side of a SnO<SUB>2</SUB>/reduced graphene oxide (rGO) hybrid film to produce a binder-free film of SnO<SUB>2</SUB>/rGO/Ni. Due to the formation of the highly conductive metal layer of Ni, the fabricated film can be well interconnected with the current collector and have lower contact resistance and open-circuit potential compared with untreated SnO<SUB>2</SUB>/rGO film, which results in a remarkable enhancement of electrochemical performance, including a wide operational voltage (1.8 V), semi-permanent cycle-life (95% retention after 10k cycles), and ultrahigh volumetric energy density with a high power density, all of which are superior values compared to bare SnO<SUB>2</SUB>/rGO film based devices. We anticipate that the fabricated SnO<SUB>2</SUB>/rGO/Ni film could be utilized as a promising electrode for high voltage ECs, and our simple surface engineering technique will provide an effective electrode design for the fabrication of high performance thin-film ECs.</P> <P><B>Graphical abstract</B></P> <P>Forming a highly conductive metal layer of Ni on the SnO<SUB>2</SUB>/rGO based electrode can be dramatically enhanced the electrochemical performance.</P> <P>[DISPLAY OMISSION]</P>

Compositional engineering of solution-processed BiVO₄ photoanodes toward highly efficient photoelectrochemical water oxidation

Byun, Segi,Jung, Gihun,Moon, Song-Yi,Kim, Bumsoo,Park, Jeong Young,Jeon, Seokwoo,Nam, Sung-Wook,Shin, Byungha Elsevier 2018 Nano energy Vol.43 No.-

<P><B>Abstract</B></P> <P>While BiVO<SUB>4</SUB> is a promising photoanode for solar-driven photoelectrochemical (PEC) water splitting, fine control of its chemical composition (Bi/V ratio) and modification of its electrical properties via extrinsic doping are necessary to improve its PEC performance. Here, we performed compositional engineering of BVO—varying Bi/V ratio and inclusion of different concentrations of Mo dopants. Through physical and chemical analyses, we found that the materials properties of BiVO<SUB>4</SUB> and its PEC performance were highly sensitive to the chemical composition. Our optimized BiVO<SUB>4</SUB>-based photoanode exhibited the highest photocurrent density among the state-of-the-art SnO<SUB>2</SUB>/BiVO<SUB>4</SUB> heterojunction photoanodes reported in the literature: 2.62 and 4.20mAcm<SUP>−2</SUP> measured at 1.23V vs. a reversible hydrogen electrode for the oxygen evolution reaction and sulfite oxidation reaction, respectively. A complete picture explaining various PEC performances with different chemical compositions via the band structure of BiVO<SUB>4</SUB> has emerged. This work points to the importance of specific control of the chemical composition in achieving highly efficient BiVO<SUB>4</SUB>-based photoanodes, which will guide future research directions in the fabrication of other high performance photoelectrodes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Highly efficient SnO<SUB>2</SUB>/BiVO<SUB>4</SUB> photoanodes are achieved by engineering its composition. </LI> <LI> The material and PEC properties of BiVO<SUB>4</SUB> are affected by its chemical composition. </LI> <LI> The improved PEC performance is correlated with band alignments of SnO<SUB>2</SUB>/BiVO<SUB>4</SUB>. </LI> <LI> Our optimized sample exhibits superior performance in PEC water oxidation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Secondary electron emission characteristics of microchannel plates

Yu, SeGi 한국외국어대학교 외국학종합연구센터 부설 기초과학연구소 2003 기초과학연구 Vol.16 No.-

The electron apmplification of microchannel plates (MCPs) through secondary electron emission were evaluated for three different shapes of MCPs. An MCP was made of an alumina green-sheet by punching, laminating, and firing, sequentially. The channel walls of pore arrays of an MCP was coated with an electron emissive layer by electroless copper plating, and a resistive layer was formed upon the emissive layer by sol-gel process, subsequently. The slant and chevron-shaped MCPs were fabricated by aligning the channel holes in the alumina green sheet during laminating process. The maximum secondary electron emission efficiencies of slant and chevron-shaped MCPs were found to be around 300 at the applied bias voltage of 3000 V on the MCP. The amplification gain of the straight MCP was increased from 90 to 860, when the primary electron beam current was decreased from 0.75 A to 0.05 ㎂.

경성 실시간 커널 RT-eCos 3.0 기반 고정익 UAV 제어 HILS 시스템의 설계 및 구현

김세기(Kim SeGi),서한석(Seo HanSeok),김정국(Kim JungKuk) 한국정보과학회 2009 한국정보과학회 학술발표논문집 Vol.36 No.2B

본 논문은 분산 실시간 객체 TMO 기반의 고정익 무인 비행체의 정밀제어 시스템의 설계 및 구현을 기술한다. TMO로 설계되어 비행체의 FCC (Flight Control Computer)에 탑재되는 시스템의 기반 운영체제로는 공개 소스 eCos 3.0 기반으로 TMO(Time-triggered Message-triggered Object)의 지원을 위해 수정개발된 RT-eCos3.0이 사용되었다. FCC 내의 OFP (Operational Flight Program)의 각 주기적 또는 이벤트 처리 모듈들을 설계하는 데에는 TMO 객체 내의 시간 구동 스레드 (time-triggered thread)와 메시지 구동 스레드 (message-triggered thread)가 기본 모델로 사용되었다. 이렇게 설계 개발된 시스템의 제어의 정확성을 입증하기 위한 실험 환경으로 공개 소스 비행체 시뮬레이터인 FlightGear와 FCC 타겟 보드를 연계한 HILS (Hardware in-the-loop Simulation) 시스템이 구축되어, 각 고정익 비행체의 제어 포인트의 목적 지표와 실제 지표가 비교되었다. 즉, 비행 시뮬레이터를 이용하여 환경적인 변화(바람, 중력, 고도, 방위 등)의 조건하에서 무인 고정익 비행체를 이륙시키고 특정 고도를 유지 및 자세 제어하는 것과 특정 목적지로 이동 및 착륙하는 것에 대하여 실험하였다. 이러한 실험으로 RT-eCos 3.0의 실시간성과 TMO에 의한 실시간 프로그램 설계의 편리성을 입증하는 결과를 획득하였다.