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리튬 2차 전지용 LiCo<sub>1-X</sub>Mg<sub>x</sub>O<sub>2</sub>(x=0.03)의 결정구조, 전기전도도 및 전기화학적 특성
김호진,정우창,정연욱,이준형,김정주,Kim, Ho-Jin,Chung, Uoo-Chang,Jeong, Yeon-Uk,Lee, Joon-Hyung,Kim, Jeong-Joo 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.9
[ $LiCoO_{2}$ ] is the most common cathode electrode materials in Lithium-ion batteries. $LiCo_{0.97}Mg_{0.03}O_2$ was synthesized by the solid-state reaction method. We investigated crystal structures, electrical conductivities and electrochemical properties. The crystal structure of $LiCo_{0.97}Mg_{0.03}O_2$ was analyzed by X-ray powder diffraction and Rietveld refinement. The material showed a single phase of a layered structure with the space group R-3m. The lattice parameter(a, c) of $LiCo_{0.97}Mg_{0.03}O_2$ was larger than that of $LiCoO_2$. The electrical conductivity of sintered samples was measured by the Van der Pauw method. The electrical conductivities of $LiCoO_2$ and $LiCo_{0.97}Mg_{0.03}O_2$ were $2.11{\times}10^{-4}\;S/cm$ and $2.41{\times}10^{-1}\;S/cm$ at room temperature, respectively. On the basis of the Hall effect analysis, the increase in electrical conductivities of $LiCo_{0.97}Mg_{0.03}O_2$ is believed due to the increased carrier concentrations, while the carrier mobility was almost invariant. The electrochemical performance was investigated by coin cell test. $LiCo_{0.97}Mg_{0.03}O_2$ showed improved cycling performance as compared with $LiCoO_2$.
다양한 디바이스를 고려한 직업훈련관리 시스템 설계 및 구현
김호진,김창수,Kim, Ho-Jin,Kim, Chang-Soo 한국정보통신학회 2014 한국정보통신학회논문지 Vol.18 No.4
최근 웹에 접근할 수 있는 다양한 기기들의 출현은 웹 개발 분야에 많은 기술적 변화를 가져왔다. 그러나 아직도 일부 웹 사이트들은 여전히 PC 중심으로 운영되고 있고, 특히 직업훈련관리 시스템은 폐쇄적이고 지원 부족으로 PC만을 타깃으로 한 사용자 웹 인터페이스를 제공하고 있다. 본 논문에서는 직업훈련관리 시스템을 대상으로 다양한 디바이스에서 적용할 수 있는 기술과 메뉴구성으로 훈련생들이 보다 쉽게 접근할 수 있는 적용 기술을 제시하고, 구현된 시스템을 실제 현장에서 적용하여 효율성을 검증하였다. Recently, the emergence of a variety of devices to be able to access web have brought many technological changes in the field of web development. However some web sites are still operating with a focus on computers, especially exclusive and slow developing job training related web sites which utilize a User Interface that targets only PCs. In this paper, we propose the job training management system which has a menu configuration and functions to be applied to a variety of devices, and also an applicable technologies for training students to access more easily. Finally, we evaluated its efficiency by applying the implemented system in the actual field.
Deposition of Epitaxial YBCO Films on $LaAlO_3$(100) Substrate by Spray Pyrolysis Method
김호진,주진호,홍석관,이선왕,임선원,이희균,홍계원,Kim Ho-Jin,Joo Jinho,Hong Suk-Kwan,Lee Sun-Wang,Lim Sun-Weon,Lee Hee-Gyoun,Hong Gye-Won The Korean Superconductivity Society 2005 Progress in superconductivity Vol.7 No.1
[ $YBa_{2}Cu_{3}O_y$ ] superconducting films were prepared on $LaAlO_3$(100) single crystal substrate by spray pyrolysis method. The precursor solution was prepared by dissolving nitrate powders in de-ionized water. Both of ultrasonic and concentric nebulizers were used in order to generate fine droplets of precursor solution. C-axis oriented films were obtained at deposition temperature of $750\~850^{\circ}C$ and working pressure of 100 Torr and 500 Torr. In case of ultrasonic nebulizer, films showed rough and porous surface morphology due to formation of enormous droplets, while smooth and dense films were obtained for concentric nebulizer. A transport $J_c$ value of $0.43\;MA/cm^2$ at 77 K and self field was achieved on $LaAlO_3$(100) single crystal substrate.
김호진 ( Kim Ho-jin ),김창현 ( Kim Chang-hyun ),최정욱 ( Choi Jung-wook ),박선규 ( Park Sun-gyu ) 한국건축시공학회 2023 한국건축시공학회지 Vol.23 No.6
In concrete, the interface between the aggregate and cement paste is often the most critical factor in determining strength, representing the weakest zone. Lightweight aggregate, produced through expansion and firing of raw materials, features numerous surface pores and benefits from low density; however, its overall aggregate strength is compromised. Within concrete, diminished aggregate strength can lead to aggregate fracture. When applying lightweight aggregate to concrete, the interface strength becomes critical due to the potential for aggregate fracture. This study involved coating the surface of the aggregate with blast furnace slag fine powder to enhance the interfacial strength of lightweight aggregate. The impedance of test specimens was measured to analyze interface changes resulting from this surface modification. Experimental results revealed a 4% increase in compressive strength following the coating of the lightweight aggregate surface, accompanied by an increase in resistance values within the impedance measurements corresponding with strength enhancement.
EIS를 활용한 경량골재 종류별 시멘트 경화체의 계면특성 분석
김호진(Ho-Jin Kim),정용훈(Yoong-Hoon Jung),배제현(Je-Hyun Bae),박선규(Sun-Gyu Park) 한국건설순환자원학회 2020 한국건설순환자원학회 논문집 Vol.8 No.4
골재는 콘크리트 체적의 약 70∼85%를 차지하며, 콘크리트의 건조수축을 저감시켜주는 필수요소이다. 하지만 고층건축물 건설시 천연골재의 높은 하중으로 인해 문제점으로 작용한다. 고층 건물 건설시 하중이 커지게 되면 크리프가 발생하고 지반이 침식될 우려가 있으므로 기초를 크게 설계하고 암반층까지 깊게 내린 지정이나 파일등을 설치해야 하므로 공사비 및 재료비가 늘어 경제적 문제점이 있다. 콘크리트의 하중을 줄이기 위해 골재의 경량화를 진행하고 있다. 하지만 인공경량골재는 천연골재에 비해 높은 흡수율과 낮은 부착강도로 인해 골재와 페이스트 사이의 계면에 영향을 주고 콘크리트 전체 강도에 영향을 미친다. 따라서 본 연구에서는 천연골재와 경량골재 종류별 계면을 파악하기 위해 비파괴 실험인 EIS측정 장비를 활용하여 전기저항을 측정하는 방식을 채택하였고, 경량골재 겉면을 고로슬래그 코팅을 통해 계면상태의 변화를 실험하였다. 실험결과, 골재 종류별 및 코팅유무에 따른 압축강도의 차이를 보였고, 경량골재 종류별 임피던스 값과 위상각의 차이를 보였다. Aggregate occupies about 70-85% of the concrete volume and is an important factor in reducing the drying shrinkage of concrete. However, when constructing high-rise buildings, it acts as a problem due to the high load of natural aggregates. If the load becomes large during the construction of a high-rise building, creep may occur and the ground may be eroded. Material costs increase and there are financial problems. In order to reduce the load on concrete, we are working to reduce the weight of aggregates. However, artificial lightweight aggregates affect the interface between the aggregate and the paste due to its higher absorption rate and lower adhesion strength than natural aggregates, affecting the overall strength of concrete. Therefore, in this study, in order to grasp the interface between natural aggregate and lightweight aggregate by type, we adopted a method of measuring electrical resistance using an EIS measuring device, which is a non-destructive test, and lightweight bone. The change in the state of the interface was tested on the outside of the material through a blast furnace slag coating. As a result of the experiment, it was confirmed that the electric resistance was about 90% lower than that in the air-dried state through the electrolyte immersion, and the electric resistance differs depending on the type of aggregate and the presence or absence of coating. As a result of the experiment, the difference in compressive strength depending on the type of aggregate and the presence or absence of coating was shown, and the difference in impedance value and phase angle for each type of lightweight aggregate was shown.