• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.127-132
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• 2003

A study of high-pressure n-heptane droplet vaporization is conducted with emphasis placed on equilibrium at vapor-liquid interface. General frame of previous rigorous model[1] is retained but tailored for flash equilibrium calculation of vapor-liquid interfacial thermodynamics. The model is based on complete time-dependent conservation equations with a full account of variable properties and vapor-liquid interfacial thermodynamics. The influences of high-pressure phenomena, including ambient gas solubility, thermodynamic non-ideality, and property variation on the droplet evaporation are investigated. The governing equations and associated moving interfacial boundary conditions are solved numerically using a implicit scheme with the preconditioning method and the dual time integration technique. And a parametric study of entire droplet vaporization history as a function of ambient pressure, temperature has been conducted. Some computational results are compared with Sato's experimental data for the validation of calculations. For low ambient temperatures, the droplet lifetime first increases with pressures, then decreases for high pressures. For higher ambient temperatures, the droplet lifetime increase with less amplitude than that of low ambient temperatures, which then decreases with more amplitude than that of low temperatures. The solubility of nitrogen can not be neglected in the high pressure and it becomes higher as the pressure goes up.

• Bulletin of the Korean Chemical Society
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• 제33권3호
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• pp.911-916
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• 2012

Ion selectivity in a simple cyclic peptide nanotube, composed of four cyclo[-(D-Ala-Glu-D-Ala-Gln)$_2-$] units, is investigated by calculating the PMF profiles of $Na^+$, $K^+$, and $Cl^-$ ions permeating through the peptide nanotube in water. The final PMF profiles of the ions obtained from the umbrella sampling (US) method show an excellent agreement with those from the thermodynamic integration (TI) method. The PMF profiles of $Na^+$ and $K^+$ display free energy wells while the PMF curve of $Cl^-$ features free energy barriers, indicating the selectivity of the cyclic peptide nanotube to cations. Decomposition of the total mean force into the contribution from each component in the system is also accomplished by using the TI method. The mean force decomposition profiles of $Na^+$ and $K^+$ demonstrate that the dehydration free energy barriers by water molecules near the channel entrance and inside the channel are completely compensated for by attractive electrostatic interactions between the cations and carbonyl oxygens in the nanotube. In the case of $Cl^-$, the dehydration free energy barriers are not eliminated by an interaction between the anion and the peptide nanotube, leading to the high free energy barriers in the PMF profile. Calculations of the coordination numbers of the ions with oxygen atoms pertaining to either water molecules or carbonyl groups in the peptide nanotube reveal that the stabilization of the cations in the midplane regions of the nanotube arises from the favorable interaction of the cations with the negatively charged carbonyl oxygens.

• 전산구조공학
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• 제10권3호
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• pp.241-250
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• 1997

콘크리트에 발생하는 변형률 국소화는 연화거동에 수반하여 변형이 국부적으로 집중되는 현상으로 이를 유한요소해석 할 수 있는 일관된 알고리즘을 개발하는 것이 본 연구의 목적이다. 변형률 국소화현상이 발생한 콘크리트는 변형률이 집중되는 국소화영역과 그외의 영역인 비국소화영역으로 크게 구분할 수 있으며 국소화영역에서는 연화현상을 포함하는 탄소성거동을 하게 되며 비국소화영역은 손상제하거동을 수반하게 된다. 변형률 국소화현상이 진행중인 콘크리트의 국소화영역을 모델링하기 위하여 열역학적으로 정식화된 전형적인 소성모델에 콘크리트의 극한응력 이후에 비선형 연화로 표현되는 소성거동을 고려할 수 있는 일반화된 Drucker-Prager모델을 도입하였으며 소성이론식의 적분을 위해 return-mapping 알고리즘을 사용하고 일관된 알고리즘을 전개하였다. 또한, 콘크리트의 비국소화영역의 모델링을 위하여 열역학적 자유에너지함수를 수정하여 비선형 탄성 및 손상의 일관된 알고리즘을 전개하였다. 개발된 알고리즘에 의한 유한요소해석을 통해 압축을 받는 콘크리트 부재의 변형률 국소화 현상을 해석하였다.

• 한국전기전자재료학회논문지
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• 제36권2호
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• pp.125-128
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• 2023

Recently, as the process of the MOS device becomes more detailed, and the degree of integration thereof increases, many problems such as leakage current due to an increase in electron tunneling due to the thickness of SiO₂ used as a gate oxide have occurred. In order to overcome the limitation of SiO₂, many studies have been conducted on HfO₂ that has a thermodynamic stability with silicon during processing, has a higher dielectric constant than SiO₂, and has an appropriate band gap. In this study, HfO₂, which is attracting attention in various fields, was doped with Al and the change in properties according to its concentration was studied. Al-doped HfO₂ thin film was deposited using Plasma Enhanced Atomic Layer Deposition (PEALD), and the structural and electrical characteristics of the fabricated MIM device were evaluated. The results of this study are expected to make an essential cornerstone in the future field of next-generation semiconductor device materials.