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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.
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.
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.
최혁(Hyuk Choi),황준성(Joon-Sung Hwang) 한국조세연구포럼 2017 조세연구 Vol.17 No.4
기업수명주기는 기업의 경제적 상황 변수로서 기업의 특성과 관련된 정보를 제공한다. 기업수명주기는 기업의 상황과 특성에 따라 성장기, 성숙기, 쇠퇴기 등으로 기업의 성장단계를 구분한 것이다. 기업은 수명주기 단계별로 경영환경, 재무구조 등이 다르기 때문에 기업수명주기에 적합한 경영전략을 수립할 것이므로 기업수명주기별로 조세회피 성향이 달라질 것이다. 본 연구는 기업수명주기에 따른 조세회피 성향을 분석하였다. 기업수명주기는 성장기, 성숙기, 쇠퇴기로 구분하였다. 연구결과를 요약하면 다음과 같다. 첫째, 성장기 기업은 조세회피 성향이 작게 나타났다. 성장기에는 시장점유율 확대를 위해 조세전략 보다는 기업성장을 위한 경영전략에 중점을 두게 된다. 또한 성장기에는 기업의 이미지나 명성을 중요시하여 경영진은 조세회피 적발로 인해 기업 투명성이 저하되는 것을 바람직하게 여기지 않을 것이다. 이와 같이 성장기에는 경영전략이나 기업 명성에 중점을 두기 때문에 조세회피 성향이 작게 나타난다고 볼 수 있다. 둘째, 쇠퇴기 기업은 조세회피 성향이 크게 나타났다. 쇠퇴기에는 이익 감소로 인해 영업현금흐름이 감소하여 현금흐름을 개선할 필요가 있다. 또한 쇠퇴기는 기존 사업에서 시장점유율이 낮아지는 상황이므로 신사업이나 성장 산업으로 진입이 필요한 시기이다. 이와 같이 쇠퇴기에는 영업현금흐름 감소와 신사업 투자로 인해 자금 소요가 발생하게 된다. 쇠퇴기에는 경영전략을 통해 이익을 증가시키기 어렵기 때문에 경영진은 조세회피를 통해 자금을 확보하려고 할 것이므로 조세회피 성향이 크게 나타난다고 볼 수 있다. 본 연구는 기업수명주기에 따라 조세회피 성향이 다르다는 사실에 근거하여 조세회피에 영향을 미치는 요인으로서 기업수명주기를 고려해야 한다는 점을 시사하고 있다. Firm life cycle provides information related to the characteristics of firm. The stage of firm is classified according to the situation and characteristics of firm. As the situation and characteristics of firms vary according to firm life cycle, firms should consider firm life cycle making strategies and decisions. As business strategy is likely to vary based on firm life cycle, firm’s propensity to engage in tax avoidance is likely to vary according to firm life cycle stage. This study examines the propensity to engage in tax avoidance according to firm life cycle. Firm life cycle consists of the growth stage, the maturity stage and the decline stage. It is found that firms in the growth stage have low propensity to engage in tax avoidance. In order to expand market share, firms in the growth stage focus on business strategy rather than tax strategy. Also, with emphasis on the image and reputation of firm, the management in the growth stage consider that it is not desirable to reduce financial transparency due to tax avoidance. Firms in the growth stage are likely to have low propensity to engage in tax avoidance focusing on business strategy and reputation. It is found that firms in the decline stage have high propensity to engage in tax avoidance. It is necessary to improve cash flow as operating cash flow decreases in the decline stage due to decrease in profit. Also, It is necessary to enter into new industry or growth industry as market share declines in the decline stage. It is difficult to increase profit through business strategy in the decline stage. Firms in the decline stage are likely to have high propensity to engage in tax avoidance increasing cash flow through tax avoidance. The results show that the propensity to engage in tax avoidance varies across firm life cycle stages. The results suggest that firm life cycle should be considered as factor influencing tax avoidance.