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Hyunchul Kang,Youngjin Kim,Taeho Yoon,Junyoung Mun The Korean Electrochemical Society 2023 Journal of electrochemical science and technology Vol.14 No.4
In Li-ion batteries, a thick electrode is advantageous for lowering the inactive current collector portion and obtaining a high energy density. One of the critical failure mechanisms of thick electrodes is inhomogeneous lithiation and delithiation owing to the axial location of the electrode. In this study, it was confirmed that the top layer of the composite electrode contributes more to the charging step owing to the high ionic transport from the electrolyte. A high-loading multilayered electrode containing LiFePO<sub>4</sub> (LFP) and LiNi<sub>0.8</sub>Co<sub>0.1</sub>Mn<sub>0.1</sub>O<sub>2</sub> (NCM811) was developed to overcome the inhomogeneous electrochemical reactions in the electrode. The electrode laminated with LFP on the top and NCM811 on the bottom showed superior cyclability compared to the electrode having the reverse stacking order or thoroughly mixed. This improvement is attributed to the structural and interfacial stability of LFP on top of the thick electrode in an electrochemically harsh environment.
Hyunchul Kang(강현철),Kibum Hwang(황기범),Eunseon Shin(신은선),Jaekwang Kim(김재광),Sung Gyu Pyo(표성규),Songhun Yoon(윤성훈) 한국고분자학회 2021 폴리머 Vol.45 No.3
양이온계 계면활성제와 실리케이트 용액의 자기조립 반응을 이용하여 기공 형성의 주형으로 이용하고 여기에 레소시놀-포름알데하이드를 투여한 후 고분자화 반응을 통하여 계면활성제/실리케이트/고분자 나노 복합체를 제조하였다. 제조된 나노 복합체를 고온에서 탄화하고 이를 불산으로 에칭하여 메조다공성 나노막대형 탄소 재료를 성공적으로 제조하였다. 제조된 메조다공성 나노 막대 탄소 재료를 전기이중층 캐패시터 전극으로 적용하였으며, 다양한 전기화학 실험을 통하여 그 성능을 평가하였다. 이 결과 잘 발달된 메조 기공 내부의 원활한 이온 전달 특성 및 나노 막대에서의 최적화된 기공 길이로 인해, 기존의 활성탄 재료보다 매우 우수한 속도 특성(낮은 기공 저항) 및 높은 면적당 캐패시턴스(17.4 μF cm<SUP>-2</SUP>)를 갖는 전기이충층 캐패시터 전극 재료를 제조할 수 있었다. Using the self-assembly reaction between cationic surfactant and silicate solution, a direct templating method was investigated. After the addition of resorcinol and formaldehyde into the solution, the polymerization reaction was conducted and surfactant/silicate/polymer nanocomposite was prepared. After carbonization and following hydrofluoric acid etching, mesoporous carbon nanorod (MPCNR) particles were prepared. As-prepared material was applied into electrode in electric double-layer capacitors and various electrochemical analysis was carried out using the electrodes. Due to the well-developed mesoporosity and nanosized rod particles, a highly improved rate performance (low resistance in pores) and large double layer capacitance per area (17.4 μF cm<SUP>-2</SUP>) than the commercialized activated carbon electrode were observed, which was attributed to easy penetration through mesopores and optimized pore length for electrolyte transport.
Kang, SeHyun,Kim, Yu-Kang,Yeom, Mijung,Lee, Hyangsook,Jang, Hyunchul,Park, Hi-Joon,Kim, Kyuseok Elsevier 2018 Complementary Therapies in Medicine Vol.41 No.-
<P><B>Abstract</B></P> <P><B>Objectives</B></P> <P>To assess the feasibility of a definitive trial investigating the effects of acupuncture on atopic dermatitis symptoms including itching.</P> <P><B>Design</B></P> <P>A randomized, sham-controlled preliminary trial with three arms with a 4-week intervention period and a 4-week follow-up.</P> <P><B>Interventions</B></P> <P>Thirty participants were allocated to three arms (the verum acupuncture group 1 [VA1, 3 times weekly for 4 weeks], the verum acupuncture group 2 [VA2, twice weekly for 4 weeks], and the sham acupuncture group [SA, twice weekly for 4 weeks]) at a 1:1:1 ratio.</P> <P><B>Main outcome measures</B></P> <P>We determined the visual analogue scale (VAS) for itching and insomnia, SCORing Atopic Dermatitis (SCORAD), Eczema Area and Severity Index (EASI), Patient Oriented Eczema Measure (POEM), and Dermatology Life Quality Index (DLQI) scores over the course of the study. Baseline index score (BIS) comparison according to general symptom was performed.</P> <P><B>Results</B></P> <P>The SCORAD, VAS (Pruritus), VAS (Insomnia), POEM, DLQI, and EASI were significantly improved in the VA groups. Significant BIS mean differences were observed most predominantly in epigastric tenderness and dyspepsia. There was no significant difference between VA1 and VA2 groups in all the main evaluation indices.</P> <P><B>Conclusions</B></P> <P>For the following research, the authors suggest SCORAD (Total) as primary outcome and SCORAD (objective), VAS (Itch), VAS (insomnia), EASI, POEM, and DLQI as secondary outcomes. Thirty six participants should be conducted a 4-week acupuncture period (twice weekly) and a 4-week follow-up. It is necessary to compare the differences of general symptoms according to presence of epigastric tenderness or dyspepsia at the screening level.</P>
뉴스 비디오에서의 효율적인 장면 전환과 앵커 화면 검출
강현철(Hyunchul Kang),이진성(Jin Sung Lee),이완주(Wanjoo Lee) 한국정보과학회 2005 정보과학회논문지 : 소프트웨어 및 응용 Vol.32 No.12
본 논문에서는 방대한 양의 방송 데이타를 처리하기 위하여 MPEG(Motion Picture Expert Group) 스트림 비디오에서 빠르고 효과적으로 비디오를 분할하는 기법을 제안한다. 이를 위해, MPEG 압축 도메인에서 최소 디코딩을 수행하여 I-프레임의 DC 이미지를 추출함으로써 통해 실행 시간을 단축하고, 밝기 정보와 색상 정보를 함께 고려한 변형된 히스토그램 비교법을 도입하여 장면전환을 빠르고 정확하게 검출하였다. 그리고 추출된 장면전환에 대해 앵커 프레임과 비앵커 프레임을 구별하기 위해 신경망 기법을 도입하였다. In this paper, an efficient and fast method to segment a video in the MPEG(motion picture expert group) video stream is proposed. For the real time processing of large amount of broadcasting data, we use DC images of I-frames in an MPEG compressed video with minimal decoding. Using the modified histogram comparison which counts on not only luminance but also chrominance information, the scene change detection was performed in the fast and accurate way. Also, to discriminate anchorperson frame from non-anchor frame, a neural network method was introduced.
강현철(Hyunchul Kang) 대한전자공학회 2016 전자공학회논문지 Vol.53 No.3
소나 영상에서 수중 물체의 검출과 분류는 도전적인 과제이다. 본 논문에서는 소나 영상과 영상처리기법을 이용하여 해저의 물체를 식별하는 시스템을 제안한다. 수중 물체의 식별 과정은 수중 물체 후보 영역 검출과 물체 식별의 두 단계로 구성된다. 영상 정합(image registration) 기법을 이용하여 수중 물체 후보 영역을 검출하고, 기존에 획득된 기준 배경 영상과 현재 스캔된 영상 사이의 공통된 특징점을 검출하여 정합한 후, 두 영상의 차 영상(difference image)을 구하여 검출한다. 검출된 물체는 고유벡터와 고유값을 특징으로 사용하여 데이터베이스내의 패턴과 가장 유사한 패턴으로 분류한다. 제안하는 수중 물체 식별시스템은 최단 소행 항로(Q route) 확보와 같은 응용에 효율적으로 사용될 수 있을 것으로 기대된다. Detection and classification of underwater objects in sonar imagery are challenging problems. This paper proposes a system that detects and identifies underwater objects at the sea floor level using a sonar image and image processing techniques. The identification process of underwater objects consists of two steps; detection of candidate regions and identification of underwater objects. The candidate regions of underwater objects are extracted by image registration through the detection of common feature points between the reference background image and the current scanning image. And then, underwater objects are identified as the closest pattern within the database using eigenvectors and eigenvalues as features. The proposed system is expected to be used in efficient securement of Q route in vessel navigation.
강현철(Hyunchul Kang),변유찬(Yu Chan Byun),박두환(Doo Hwan Park),백승민(Seung Min Paek) 한국정보과학회 1990 한국정보과학회 학술발표논문집 Vol.17 No.2
본 논문은 중앙대학교 전자계산학과 데이타베이스 연구실에서 IBM PC/AT에서 운용하도록 MS-DOS 상에 개발중인 RDBMS 프로토타입의 설계 및 구현 사항 중 사용자 명령어, 사용자 뷰 제공 기법, 시스템 하부 저장구조를 설명한다. 본 시스템의 가장 중요한 특징은 select 및 Join 뷰를 뷰 인덱스의 형태로 데이타베이스에 저장하고, 베이스릴레이션 변경의 뷰 인덱스로의 반영은 누증(incremental) 변경 기법을 이용하여 수행함으로써, 사용자에게 아주 빠른 응답 시간내에 뷰를 제공할 수 있다는 것이다.
직접분사식 소형 디젤엔진의 연소특성에 관한 3차원 시뮬레이션 연구
김현철(Hyunchul Kim),김병수(Byoungsoo Kim),강우(Woo Kang),정재우(Jaewoo Chung),강정호(Jeongho Kang),임규철(Kyuchul Lim) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In this paper, simulation of a light duty direct injection diesel engine using a three dimensional numerical method is presented in order to analyze flow characteristics, injection, and combustion phenomenon. A solid model is constructed after analyzing the specification of the subject engine, and moving meshes are generated for various crank angles. Flow fields of the combustion chamber generated at the intake stroke are analyzed, and the behavior of swirl and tumble is studied. Heat flow characteristics of the diesel engine is also studied through analyzing injection and combustion considering chemical reaction. The result is used to analyze temperature, velocity, pressure, and exhaust gas component of the combustion chamber.