http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Programmable Metallization Cell 응용을 위한 Ag-doped 칼코게나이드 박막의 전기적 저항 변화 특성
최혁,구상모,조원주,이영희,정홍배,Choi, Hyuk,Koo, Sang-Mo,Cho, Won-Ju,Lee, Young-Hie,Chung, Hong-Bay 한국전기전자재료학회 2007 전기전자재료학회논문지 Vol.20 No.12
We have demonstrated new functionalities of Ag doped chalcogenide glasses based on their capabilities as solid electrolytes. Formation of such amorphous systems by the introduction of silver via photo-induced diffusion in thin chalcogenide films is considered. The influence of silver on the properties of the newly formed materials is regarded in terms of diffusion kinetics and Ag saturation is related to the composition of the hosting material. Silver saturated chalcogenide glasses have been used in the formation of solid electrolyte which is the active medium in programmable metallization cell (PMC) devices. In this paper, we investigated electrical and optical properties of Ag-doped chalcogenide thin film on changed thickness of Ag and chalcogenide thin films, which is concerned at Ag-doping effect of PMC cell. As a result, when thickness of Ag and chalcogenide thin film was 30 nm and 50 nm respectively, device have excellent characteristics.
전자밀도함수이론을 이용한 세륨 산화물의 (111) 표면에서 일어나는 물 흡착 과정 분석
최혁,강은지,김현유,Choi, Hyuk,Kang, Eunji,Kim, Hyun You 한국재료학회 2020 한국재료학회지 Vol.30 No.5
Cerium oxide (ceria, CeO<sub>2</sub>) is one of the most wide-spread oxide supporting materials for the precious metal nanoparticle class of heterogeneous catalysts. Because ceria can store and release oxygen ions, it is an essential catalytic component for various oxidation reactions such as CO oxidation (2CO + O<sub>2</sub> 2CO<sub>2</sub>). Moreover, reduced ceria is known to be reactive for water activation, which is a critical step for activation of water-gas shift reaction (CO + H<sub>2</sub>O → H<sub>2</sub> + CO<sub>2</sub>). Here, we apply van der Waals-corrected density functional theory (DFT) calculations combined with U correction to study the mechanism of water chemisorption on CeO<sub>2</sub>(111) surfaces. A stoichiometric CeO<sub>2</sub>(111) and a defected CeO<sub>2</sub>(111) surface showed different water adsorption chemistry, suggesting that defected CeO<sub>2</sub> surfaces with oxygen vacancies are responsible for water binding and activation. An appropriate level of water-ceria chemisorption energy is deduced by vdW-corrected non-local correlation coupled with the optB86b exchange functional, whereas the conventional PBE functional describes weaker water-ceria interactions, which are insufficient to stabilize (chemisorb) water on the ceria surfaces.
모넬(Monel)-Clad 파이프의 오버레이 용접 적층수가 용접성에 미치는 영향에 관한 실험적 연구
최혁(Hyeok Choi),박준홍(Joon-Hong Park) 한국산학기술학회 2016 한국산학기술학회논문지 Vol.17 No.11
오버레이 용접은 희석율에 의해 적층 두께에 따라 화학성분 함량과 용접부의 경도에 영향을 미치며 이는 파이프 제품의 표면성질을 결정한다. 이로 인해 오버레이 용접은 적층의 수를 고려하여야 한다. 본 연구에서는 탄소강 모재에 내부식성 소재인 모넬 소재를 오버레이 용접하여 적층수에 따른 Fe함량, 모재와 모넬 소재와의 용접성, 부위별 경도와 표면 평탄도를 실험적으로 연구하였다. 각각의 평가는 평판의 모재와 파이프 모재에 3개의 층으로 오버레이 용접 후 실시하였다. Fe함량은 각 층별 시료를 채취하여 성분 분석을 통해 평가하였으며, 3Layer에서 만족하는 함량을 나타내었다. 또한 적층별 시편을 밴딩 시험하여 용접성을 평가하였다. 적층별 경도와 비드 평탄도는 Micro Vickers와 3차원 측정을 통해 평가하였다. 경도는 1Layer에서 발생하는 HAZ부에 의해 가장 높은 경도 값을 보였으며, 적층이 증가할수록 경도가 감소하였다. 비드 평탄도의 경우 적층수 증가에 따라 편차가 급격한 차이가 발생하였으며, 이는 경도와 함께 사용 목적의 측면에서 주의 깊게 고려해야 한다. 이러한 실험적 결과는 목적에 따른 용접 파이프 적층수의 결정 방법을 나타내었다. Overlay welding affects the chemical components and weld hardness by dilution of the lamination layer thickness, which determines the surface properties. This study experimentally investigates different numbers of layers for overlay welding monel materials, which are anti-corrosion materials. The Fe content, weldability of the base metal and monel materials, hardness, and surface flatness were examined. Each evaluation was carried out after overlay welding with three layers on the base material and pipe base material of the plate. The Fe content was evaluated by analyzing the constituents of each layer. The Fe content was satisfactory in the three layers. The weldability of the laminate specimens was evaluated by a bending test. The hardness and bead flatness of the laminate specimens were evaluated by micro Vickers and 3D measurements. The hardness was highest in the heat-affected zone with one layer, and it decreased with increasing lamination. In the case of bead flatness, there is a sharp difference in the deviation with increasing numbers of laminations, which should be considered carefully.
최혁(Hyock Choi),여태인(Taein Yeo) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The frictional heat generated at the interface of the rotor and pad of an automotive disk brake can result in thermal distortion of the frictional surface. Known as coning, this effect is found to be the main cause of RTV (rotor thickness variation) and judder. It is, therefore, important to predict the temperature rise and thermal deflection in the early design stage. For these purposes, a pie-shaped model is usually used for a ventilated disk that is evidently three dimensional in shape due to its vent holes. In this paper a new analysis technique is adopted for a ventilated disk in which the rotor is represented using an axisymmetric finite element model. To take into consideration the effects due to the cooling passages, a homogenization technique is used to give the equivalent diffusivity and elastic modulus for elements located at the vent holes. The convective heat transfer coefficients on the disk surface were obtained by CFD analysis and compared to the experimental results in terms of the outlet air speed at the vent holes. Temperature and the resulting runout of the disk were also determined by FEM analysis and compared to the ones from brake dynamometer tests. It is concluded that the assumption of a rotating disk in an infinite field in CFD analysis overestimate the cooling at the disk surface while predicting accurate values at the vent holes. The large undercut is proved to be effective in diminishing the amount of coning. The proposed axisymmetric FEM procedure can be successfully applied in practice, replacing 3-dimensional finite element analysis for optimal shape design to reduce judder in a ventilated disk.
서천터널 굴착 중 용출수 발생에 따른 터널 보수ㆍ보강 사례
최혁(Choi Hyuk),김선곤(Kim Sun-Kon),김흥국(Kim Heung Kuk),홍준표(Hong Jun Pyo) 한국철도학회 2006 한국철도학회 학술발표대회논문집 Vol.- No.-
During excavation in seocheon tunnel, sudden groundwater inundation occurred in complex hydro-geological environments prevailing in underground tunnel. Large volumes of groundwater flowed into tunnel at STA 54km600. The authors have provided a comprehensive background to hydro-mechanics of groundwater with a geological analysis, ground investigation, hydromechanical modelling etc. To reinforce tunnel, we have applied the TAS grouting and the steel multi-layer grouting, and comfirmed the effects of reinforcement.