• Bulletin of the Korean Chemical Society
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• 제31권9호
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• pp.2531-2536
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• 2010

Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations have been employed to investigate the molecular structures and absorption spectra of two dyes containing diphenylaniline and 4-diphenylamino-diphenylaniline as donor moiety (TPA1 and TPA3). The geometries indicate that the strong conjugation is formed in the dyes. The electronic structures suggest that the intramolecular charge transfer from the donor to the acceptor occurs, and the electron-donating capability of 4-diphenylamino-diphenylaniline is stronger than that of diphenylaniline. The computed highest occupied molecular orbital (HOMO) energy levels are -5.31 and -4.90 eV, while the lowest unoccupied molecular orbital (LUMO) energies are -2.29 and -2.26 eV for TPA1 and TPA3, respectively, revealing that the interfacial charge transfer between the dyes and the semiconductor electrode are electron injection processes from the photon-excited dyes to the semiconductor conduction band. Furthermore, all the experimental absorption bands of TPA1 and TPA3 have been assigned according to the TDDFT calculations.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1951-1956
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• 2004

The transient nature and complex flow geometries of two-phase gas-liquid flows cause fundamental difficulties when measuring flow velocity using an electromagnetic flowmeter. Recently, a current-sensing flowmeter was introduced to obtain measurements with high temporal resolution (Ahn et $al.^{(1)}$). In this study, current-sensing flowmeter theory was applied to measure the fast velocity transients in slug flows. To do this, the velocity fields of axisymmetric gas-liquid slug flow in a vertical pipe were obtained using Volume-of-Fluid (VOF) method and the virtual potential distributions for the electrodes of finite size were also computed using the finite volume method for the simulated slug flow. The output signal prediction for slug flow was carried out from the velocity and virtual potential (or weight function) fields. The flowmeter was numerically calibrated to obtain the cross-sectional liquid mean velocity at an electrode plane from the predicted output signal. Two calibration parameters are required for this procedure: a flow pattern coefficient and a localization parameter. The flow pattern coefficient was defined by the ratio of the liquid resistance between the electrodes for two-phase flow with respect to that for single-phase flow, and the localization parameter was introduced to avoid errors in the flowmeter readings caused by liquid acceleration or deceleration around the electrodes. These parameters were also calculated from the computed velocity and virtual potential fields. The results can be used to obtain the liquid mean velocity from the slug flow signal measured by a current-sensing flowmeter.

• Nuclear Engineering and Technology
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• 제24권2호
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• pp.141-153
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• 1992

상온핵융합의 실험적 검증을 위하여 가공조건 및 기하학적조건이 다른 7종류의 팔라디움전극을 사용하여 24~28시간, 전류밀도 83~600 mA/$\textrm{cm}^2$의 조건하에 전기분해를 실시하였다. 상기조건 하에서 삼중수소의 농축에 기인한 분리팩타(separation factor)를 측정하였고 핵융합의 부산물일수도 있는 삼중수소 증가량을 측정하였다. 또한 초과열 계 산과 관련된 K(net Faradic efficiency)를 측정하여 산소/중수소 가스의 재결합정도를 조사하였다. 양전자소멸측정장치 및 일정체적 가스주입장치를 이용하여 팔라디움전극에서 격자결함과 수소의 반응 및 거동에 대하여 조사하였다. 전기분해하는 동안 삼중수소 농축현상이 관찰되었으나 핵융합의 증거가 될만한 삼중수소양은 검출되지 않았다. 한편 산소/수소 가스의 재결합 정도는 32%로 나타났다. 이는 재결합과정이 발열반응이므로 전기분해과정에서 핵반응과 관계없이 초과엔탈피가 발생할 수 있음을 의미한다. 양전자소멸측정장치를 이용하여 양전자수명, 양전자소멸밀도, P/W 및 R 파라메터의 측정을 통하여 전극의 격자결함(전위 및 공공)에 수소가 집적 (trap)되며 수소집적은 공공에서 보다 전위에 약간 더 선호하는 것으로 나타났다. 전극의 수소화물형성에 수반하여 대부분 전위가 발생한 것으로 나타났다. 또한 팔라디움수소화물의 등시소둔실험을 통하여 소량의 미소공동 형태의 결함이 존재하는 것으로 추정하였고 그 결함의 크기는 수 $\AA$정도인 것으로 생각된다.