• 한국재료학회지
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• 제13권7호
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• pp.473-477
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• 2003

The hydrogen redistribution induced by thermotransport at temperatures likely to be encountered in nuclear power reactors (300-$340^{\circ}C$) was investigated in modified Zircaloy-4 alloys. Modified Zircaloy-4 alloys were prepared by altering the chemical composition of Zircaloy-4; the oxygen content of Zircaloy-4 (0.1 wt%) was increased to 0.2, 0.5 and 1.0 wt%. The heat of transport ($Q^{*}$ ) for hydrogen was measured by changing the initial hydrogen and oxygen concentrations. It was found that the heat of transport was not affected by increases in the initial hydrogen concentration from 63.3 to 91.7 ppm. However, the value of $Q^{Q}$ decreased from 6.8 to 4.5 ㎉/mol as the initial oxygen concentration was increased from 0.2 to 1.0 wt%.

• 한국기계기술학회지
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• 제13권2호
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• pp.115-121
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• 2011

The size of hydrogen molecule is not so small as to invade into the lattice of material, and therefore, hydrogen invades into the material as atom. Hydrogen movement is done by diffusion or dislocation movement in the near crack tip or plastic deformation. Hydrogen appeared to have many effects on the mechanical properties of the Cr-Mo steel alloys. The materials for this study are 1.25Cr-0.5Mo and 2.25Cr-1Mo steels used at high temperature and pressure. The hydrogen amount obtained by theoretical calculation was almost same with the result solved by finite element analysis. The distribution of hydrogen concentration and average concentration was calculated for a flat specimen. Also, finite element analysis was employed to simulate the redistribution of hydrogen due to stress gradient. The calculation of hydrogen concentration diffused into the material by finite element method will provide the basis for the prediction of delayed fracture of notched specimen. The distribution of hydrogen concentration invaded into the smooth and notched specimen was obtained by finite element analysis. The hydrogen amount is much in smooth specimen and tends to concentrate in the vicinity of surface. Hydrogen embrittlement susceptibility of notched specimen after hydrogen charging is more remarkable than that of smooth specimen.

• Bulletin of the Korean Chemical Society
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• 제14권4호
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• pp.491-496
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• 1993

A class A ${\beta}$-lactamase from Staphylococcus aureus PC1 complexed with 3R,5R-clavulanate is studied. The starting geometry for the computation is the crystal structure of the ${\beta}$-lactamase. Docking of the clavulanate to the enzyme is done exploiting the requirements of electrostatic and shape complementarity between the enzyme and clavulanate. This structure is then hydrated by water molecules and refined by energy minimization and short molecular dynamics simulation. In the energy refined structure of this complex, the carboxyl group of the clavulanate is hydrogen bonded to Lys-234, and the the carbonyl carbon atom of the clavulanate is adjacent to the $O_{\gamma}$ of Ser-70. It is found that a crystallographic water molecule initially located at the oxyanion hole, which is formed by the two -NH group of Ser-70 and Gln-237, is replaced by the carbonyl oxygen atom of the 3R,5R-clavulanate after docking and energy reginement. The crystallographic water molecules are proved to be important in ligand binding. Glu-166 residue is found to be repulsive to the binding of clavulanate, which is in agreement with experimental observation. Arg-244 residue is found to be important to the binding of clavulanate as well as to interaction with C2 side chain of the clavulanate. The electron density redistribution of the clavulanate on binding to the ${\beta}$-lactamase in studied by an ab initio quantum-mechanical calculation. A significant redistribution of electron density of the clavulanate is induced by the enzyme, toward the enzyme, toward the transition state of the enzymatic reaction.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.33-36
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• 2007

Currently, many structured catalysts using microchannel are researched to apply to fuel reforming. In this paper, ceramic monolith and metal mesh as structured catalysts are investigated for catalytic autothermal reforming. When GHSV increases, each structured catalyst has better performances(hydrogen production, fuel conversion) than packed bed catalyst for autothermal reforming. The major causes seem to be the elevated heat and mass transfer, gas phase reaction and redistribution of packed bed due to high pressure drop.

• 한국자기공명학회논문지
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• 제14권2호
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• pp.134-143
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• 2010

We studied the hydrogen-bonded $TlH_2PO_4$ (TDP) ferroelectrics treated with the proton-beam bombardment. The TDP material was irradiated with 1-MeV proton beam at a dose of $10^{15}/cm^2$. In order to analyze the hydrogen environment in TDP, we carried out the $^1H$ high resolution nuclear magnetic resonance (NMR) - i.e., Combined Rotation And Multiple Pulse Spectroscopy (CRAMPS) measurement. The isotropic chemical shift of hydrogen indicates its displacive property is related to the $PO_4$ lattice deformation which occurs throughout the antiferroelectric-, the ferroelastic- and the paraelastic-phase transitions. The temperature dependence of $\sigma_{iso}$ reveals the electronic charge redistribution is induced by the proton-beam irradiation and the elastic property.

• Nuclear Engineering and Technology
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• 제40권1호
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• pp.1-8
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• 2008

One of the major current challenges to nuclear energy lies in its competitiveness. To stay competitive the industry needs to reduce maintenance and fuel cycle costs, while enhancing safety features. Extended burnup is one of the methods applied to meet these objectives However, there are a number of potential fuel failure causes related to increased burnup, as follows: l) Corrosion of zirconium alloy cladding and the water chemistry parameters that enhance corrosion; 2) Dimensional changes of zirconium alloy components, 3) Stresses that challenge zirconium alloy ductility and the effect of hydrogen (H) pickup and redistribution as it affects ductility, 4) Fuel rod internal pressure, 5) Pellet-cladding interactions (PCI) and 6) pellet-cladding mechanical interactions (PCMI). This paper discusses current and potential failure mechanisms of these failure mechanisms.

• 한국컴퓨터정보학회논문지
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• 제17권8호
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• pp.41-50
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• 2012

우리나라를 비롯한 선진국 국가의 대부분은 기존의 탄소 자동차 대용으로 전기 자동차, 메탄올 자동차, 수소 자동차 등 저탄소 자동차 개발에 막대한 투자를 계속하고 있다. 그러나, 궁극적이고 현실적인 무공해 교통수단은 자전거가 유일하기 때문에 각국의 중앙 정부 및 지방 정부들은 자전거 전용 도로를 개설하고 공공 임대 서비스 시스템 구축을 서두르고 있다. 현재 운영되고 있는 거의 모든 자전거 관제 시스템들은 자전거 보관소에서의 대여 및 반납과정의 자동화를 이루고 있으나, 보관소를 떠난 자전거의 이동 경로 및 소재를 모니터링하지는 않는다. 이 연구에서는 자전거 공공 임대 서비스를 위해 CDMA 모뎀과 결합된 GPS 단말기 및 이를 사용하는 위치기반 자전거 관제 시스템을 개발한다. 이 관제 시스템은 이동통신을 통하여 자전거에 부착된 GPS 관제 단말기로부터 위치 정보를 수신하고, 그 이동 경로를 GIS 연동 맵에 표시함으로써 자전거의 회수 및 재분배를 용이하게 하고, 도난 및 고의 파손을 최소화 시키며, 이용자들에게는 가까운 곳에 위치한 자전거 보관소를 추천해 줄 수 있다.

• 한국진공학회지
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• 제15권2호
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• pp.223-230
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• 2006

분자선 에피택시 (MBE)법으로 성장된 양자점 원적외선 수광소자(Quantum Dot Infrared Photodetector: QDIP)구조의 $In_{0.5}Ga_{0.5}As/GaAs$ 자발형성 양자점에 대하여, 수소화 처리(Hydrogen Plasma treatment) 전후의 각각의 특성을 광학적인 방법으로 분석하였다. 광학적 특성은 광루미네센스(photoluminescence: PL) 그리고 광전류(Photocurrent: PC)방법으로 각각 15K 300K 10K 130k 범위에서 측정되었으며, 수소화 처리 전후의 $In_{0.5}Ga_{0.5}As$ 자발형성 양자점의 광학적 특성을 비교 분석해보면, 원시료(as-grown)의 하나의 봉우리가 수소화 처리를 통하여 두개의 봉우리로 나뉘지만 PL의 전체 세기(intensity)에는 큰 변화가 없었으며, 광전류는 수소화 처리 후에 감소함을 알 수 있다. 수소화 처리 전후의 샘플에 대해 PL의 결과로부터 활성화 에너지를 계산하여 비교해보면, 수소화 처리 전후의 활성화 에너지가 다름을 알 수 있고, 이 변화된 활성화 에너지 값은 측정된 광전류의 봉우리에 해당하는 에너지 값과 거의 일치함을 알 수 있다. 수소화 처리된 샘플은 역 수소화 처리를 통하여 PL 그래프의 모양이 원시료의 모양으로 되돌아가야 함에도 불구하고, 수소화 처리된 시료의 PL의 그래프와 동일한 모습을 보였다. 이러한 현상은 자발형성 양자점의 수소화 처리에 따른 양자점 내부의 양자점 조성의 변동에 그 원인이 있는 것으로 보인다.

• 한국독성학회:학술대회논문집
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• 한국독성학회 2002년도 국제심포지움
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• pp.59-72
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• 2002

The anticarcinogenic effects of epicatechin(EC) and ginsenoside Rb2(Rb2), which are major components of green tea and Korea ginsen, respectively, were investigated using a model system of gap junctional intercellular communication (GJIC) in WB-F344 rat liver epithelial cells. 12-O-Tetradecanoylphorbol-13-accetate (TPA) and hydrogen preoxide, known as cancer promoters, inhibited GJIC in the epithelial cells as determined by the scrape loading/dye transfer assay, fluorescence redistribution assay after photobleaching, and immunofluorescent staining of connexin 43 using a laser confocal microscope. The inhibition of GJIC by TPA and H2O2 was prevented with treatment of Rb2 or Ec. The effect of EC on GJIC was stronger in TPA-treated cells than in H2O2-treated cells, while the effect of Rb2 was opoosite to that of EC. EC, at the concentration of 27.8$\mu$g/ml, prevented the TPA-induced GJIC inhibition by about 60%. Rb2, at the concentration of 277$\mu$g/ml, recovered the H2O2-induced GJIC inhibition by about 60%. These results suggest that Rb2 and EC may prevent human cancers by preventing the down-regulation of GJIC during the cancer promotion phase and that the anticancer effect of green tea and Korea ginseng may come from the major respective conponents, EC and Rb2.

• 한국결정성장학회지
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• 제11권5호
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• pp.224-230
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• 2001

초박막 게이트 유전막 및 비휘발성 기억소자의 게이트 유전막으로 연구되고 있는 $NO/N_2O$ 열처리된 재산화 질화산 화막의 특성을 D-SIMS(Dynamic Secondary Ion Mass Spectrometry), ToF-SIMS(Time-of-Flight Secondary Ion Mass Spectrometry), AES(Auger Electron Spectroscopy)으로 조사하였다. 시료는 초기산화막 공정후에 NO 및 $N_2O$ 열처리를 수행하였으며, 다시 재산화공정을 통하여 질화산화막내 질소의 재분포를 형성토록하였다. 재산화에 있어서 습식산화시 공정에 사용된 수소에 의한 영향으로 계면 근처에 축적된 질소가 Si≡N 결합을 쉽게 이탈함에 따라 방출이 촉진되어 건식산화에 비하여 질소의 감소가 더욱 두드러지게 나타났다. 재산화에 따른 질화산화막내 질소의 거동은 외부로의 방출과 기판으로의 확산이 동시에 나타난다. 재산화후 질화산화막내 축적된 질소의 결합종을 분석한 결과, 초기산화막 계면근처의 질소는 SiON의 결합종이 주도적으로 나타나는 반면 재산화 후 새롭게 형성된 $Si-SiO_2$ 계면근처로 확산한 질소는 $Si_2NO$ 결합종이 주로 검출된다. SiON에 의한 질소의 미결합손과 $Si_2$NO에 의한 실리콘의 미겨랍손은 기억특성에 기여하는 결함을 포함하기 때문에 재산화 질화산화막내 존재하는 SiON과 $Si_2$NO 결합종은 모두 전하트랩의 기원과 관련된 결합상태로 예상된다.