• 한국생물물리학회:학술대회논문집
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• 한국생물물리학회 2003년도 정기총회 및 학술발표회
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• pp.75-75
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• 2003

We report here the results on N-acetyl-N'-dimethylamide of proline (Ac-Pro-NM $e_2$) calculated using the ab initio molecular orbital method with the self-consistent reaction field (SCRF) theory at the HF level with the 6-31+G(d) basis set to investigate the conformational preference of polyproline depending on the cis/trans peptide bonds and down/up puckerings along the backbone torsion angle $\square$ in the gas phase, chloroform, and water. In the gas phase, Ac-Pro-NM $e_2$ has seven local minima of tFd, tFu, cFd, cFu, cAu, tAu, and cAd conformations. In particular, polyproline conformations tFd, tFu, cFd, and cFu are found to be more stable than $\square$-helical conformations cAu, tAu, and cAd. In contrast, Ac-Pro-NHMe has seven local minima of tCd, tCu, cBd, cAu, tAu, cFd, and cFu conformations. Conformations tCd and tCu are found to be most stable, which is ascribed to the intramolecular hydrogen bond between C=O of acetyl group and $N^{~}$ H of N'-methyl amide group. The stability of the cFd conformation (i.e., the polyproline I structure) in chloroform is somewhat increased, relative to that in water, although tFd and tFu conformations (i.e., the polyproline II structure) are dominate both in chloroform and water. The population of backbone conformations feasible in chloroform and water is consistent with the experiments. This work is supported by a Korea Research Foundation Grant (KRF-2002-041-C00129).

• 대한금속재료학회지
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• 제46권5호
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• pp.296-303
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• 2008

Hydrogen permeation through dense palladium-based membranes has attracted the attention of many scientists largely due to their unmatched potential as hydrogen-selective membranes for membrane reactor applications. Although it is well known that the permeation mechanism of hydrogen through Pd involves various processes such as dissociative adsorption, transitions to and from the bulk Pd, diffusion within Pd, and recombinative desorption, it is still unclear which process mainly limits hydrogen permeation at a given temperature and hydrogen partial pressure. In this study, we report an all-electron density-functional theory study of hydrogen permeation through Pd membrane (using VASP code). Especially, we focus on the variation of the energy barrier of the penetration process from the surface to the bulk with hydrogen coverage, which means the large reduction of the fracture stress in the brittle crack propagation considering Griffith's criterion. It is also found that the penetration energy barrier from the surface to the bulk largely decreases so that it almost vanishes at the coverage 1.25, which means that the penetration process cannot be the rate determining process.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.108-111
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• 2009

We have determined the electronic energy level alignment at the interface between 4,4'-bis-N-phenyl-1-naphthylamino biphenyl (NPB) and 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile (HAT-CN) using ultraviolet photoelectron spectroscopy (UPS). The highest occupied molecular orbital (HOMO) of 20 nm thick HAT-CN film was located at 3.8 eV below the Fermi level. Thus the lowest unoccupied molecular orbital (LUMO) is very close to the Fermi level. The HOMO position of NPB was only about 0.3 eV below Fermi level at NPB/HAT-CN interface. This enables an easy excitation of electrons from the NPB HOMO to the HAT-CN LUMO, creating electron-hole pairs across this organic-organic interface. We also study the interaction of HAT-CN with a few metallic surfaces including Ca, Cu, and ITO using UPS and ab-inito electronic structure calculation techniques.

• EDISON SW 활용 경진대회 논문집
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• 제4회(2015년)
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• pp.292-295
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• 2015

The effect of Ligand Binding energy in quantum rod (CdS/ZnS) plays a critical role in anisotropic growth. As mimicking large chain of ligands and using the head of the chain, I plan to bind the quantum rod and ligands so that it can grow well consequently. So the ultimate goal of this study is on how ligand binding can affect the growth of this quantum rod. There are preferred surfaces between the quantum rod and ligands, and we empirically know that ligands which bind the quantum rod; Phosphoric oxide (PO), Phosphoric acid(PA), Carboxylic acid(CA), Trimethylamine(TMA), have strong tendency to be attached on the surfaces of CdS/ZnS; ($11{\bar{2}}0$), ($10{\bar{1}}0$), ($000{\bar{1}}$), (0001). I virtually bond the surface and the ligands, and calculated the ligand binding energy after optimizing their structure, utilizing EDISON simulator. After all, I figured out how they are linked each other and how the quantum rod grows.

• EDISON SW 활용 경진대회 논문집
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• 제2회(2013년)
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• pp.273-277
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• 2013

We apply a density functional theory (DFT) and DFT-based non-equilibrium Green's function approach to study the electronic and transport properties of graphene nanoribbons (GNRs) co-doped with boron-nitrogen, nitrogen-phosphorus and boron-phosphorus. We analyze the structures and charge transport properties of co-doped GNRs and particularly focus on the novel effects that are absent for the single N-, B-, or P-doped GNRs. It is found that co-doped GNRs tend to be doped at the edges and the electronic structures of co-doped GNRs are very sensitive to the doping sites. Also, in case of B-N and B-P co-doped GNRs, conductance dips of single-doped GNRs disappeared with the disappearance of localized states associated with doped atoms. This may lead to a possible method of band engineering of GNRs and benefit the design of graphene electronic devices.

• Bulletin of the Korean Chemical Society
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• 제31권3호
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• pp.595-598
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• 2010

Ab initio and DFT molecular orbital calculations predict that acetyl radical reacts with acetylene through interactions primarily involving the SOMO of the radical and the in-plane ${\pi}$-bond of acetylene. An energy barrier (${\Delta}E_1$) of 39.6 kJ $mol^{-1}$ is predicted for the preferred anti arrangement of reactants at the CCSD(T)/cc-pVDZ//BHandHLYP/cc-pVDZ level of theory. NBO analysis reveals additional interactions between the radical SOMO and the nearby C-H ${\sigma}$-bond in acetylene worth about 10% of the total transition state interaction energy. This type of orbital interaction has not previously been observed in radical addition reactions involving C-C ${\pi}$-bonds.

• 대한화학회지
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• 제56권6호
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• pp.669-672
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• 2012

Classical molecular dynamics (MD) simulations using a scaled OSS2 potential originally derived from ab initio calculations are used to study the radial distribution functions of water. The original OSS2 water potential is shown to represent a glassy or an ice at ambient temperature, but the diffusion coefficient increases on increasing the temperature of the system or decreasing the density. This suggests scaling the OSS2 potential. The O-O, O-H, and H-H radial distribution functions and the corresponding coordination numbers for the scaled OSS2 potential, obtained by MD simulation, are in good agreement with the experiment results and calculations for the SPC/E water potential over a range of temperatures.

• 한국항공운항학회지
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• 제3권1호
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• pp.7-19
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• 1995

현대 항공기의 특징인 자동화나 컴퓨터화는 조종석(Glass cockpit)에서의 조종사 임무를 변화시켜, 과거에는 항공기를 조종하기 위하여 속도, 고도, 항로를 유지하는 것이 주된 임무였으나, 현대 항공기의 경우에는 이러한 일은 거의 모두 자동화 되어 조종사는 일명 'Glass cockpit' 내에서 화면을 통하여 비행 진행 상태를 모니터하고 필요한 사항을 컴퓨터에 입력하여 지시하는 형태로 바뀌었다. 따라서 조종사 교육제도도 과거의 기술(Skill)이나 절차(Procedure)를 위주로 하던 형태에서, 이제는 조종사에게 관리자(Manager)로서의 능력을 부여할 수 있는 교육내용이 요구되고 있다. 본 연구에서는 항공기술 발전과 특히 미래 항행시스템의 개발에 관하여 살펴보고, 운항환경 변화에 따른 변화된 조종사의 역할과 이를 기준으로 우리나라의 대표적 민간 조종사 교육기관이라 할 수 있는 한국 항공대학교 항공운항학과와 대한항공의 기초비행 훈련원, 아시아나 항공의 초기조종사 훈련과정(Ab-initio)의 교육내용을 비교 분석하여 앞으로 조종사 교육에 있어서 추가되어야 하거나 개선되어야 할 내용에 관하여 연구하였다.

• Bulletin of the Korean Chemical Society
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• 제26권9호
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• pp.1421-1426
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• 2005

The stationary point structures and relative energies between them as well as binding energies of $(CO)_2$ have been investigated at the CCSD(T) level using the correlation-consistent basis sets aug-cc-pVXZ(X=T,Q,5). It is found that while the equilibrium structure corresponds to the C-bonded T-shaped configuration with intermolecular distance of 4.4 $\AA$, there exists another minimum, slightly higher in energy ($\sim$10 $cm^{-1}$) than the global minimum, corresponding to the O-bonded T-shaped configuration with the intermolecular distance of 3.9 $\AA$. The CCSD(T) basis set limit binding energy of $(CO)_2$ is estimated to be 132 $cm^{-1}$.

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2414-2418
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• 2007

N-Hydroxy diketopiperazine derivatives from L- and D-forms of Ser and Cys were synthesized for the first time and the ring conformation of both analogues in water was determined to be close to flat via NMR and ab initio calculations. However, the side chain of the Ser analogue was oriented toward a pseudo-equatorial position while that of the Cys analogue was slightly oriented toward a pseudo-axial direction, with a slightly distorted boat-shaped ring conformation. Among them, the D-Cys analogue was found to be a weak inhibitor of α- glucosidase.