Énergie orbitale spécifique

Résumé

En mécanique spatiale, l'énergie orbitale spécifique \epsilon de deux corps orbitants est la somme constante de leur énergie potentielle mutuelle (\epsilon_p,!) et de l'énergie cinétique totale (\epsilon_k,!), divisé par leur masse réduite m = {1 \over {{1 \over m_1} + {1 \over m_2}}} = {{m_1 m_2} \over {m_1 + m_2}}\ , sachant que \frac{1}{m} = \frac{1}{m_1}+\frac{1}{m_2} . Selon l'équation de la force vive, selon la Loi universelle de la gravitation, cela donne l'équation qui ne varie pas avec le temps : : \epsilon = \epsilon_k+\epsilon_p ! Considérant le mouvement d'un satellite ou une sonde autour d'un attracteur, en l'absence de perturbations orbitales spécifique de l'énergie totale, \epsilon est conservée. L'équation est : Pour chaque point de la trajectoire la loi de la conservation de l'énergie orbitale spécifique : :\epsilon=\epsilon_k+\epsilon_p={v^2\over{2}}-{\mu\ov

Source officielle

https://fr.wikipedia.org/wiki/%C3%89nergie_orbitale_sp%C3%A9cifique

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Intramolecular Charge-Transfer Tuning of Perylenes: Spectroscopic Features and Performance in Dye-Sensitized Solar Cells

Felix Thomas Eickemeyer, Ulf Anders Hagfeldt, Chen Li

Five novel perylene mols. with different intramol. charge-transfer (ICT) characters have been synthesized. The relation between the ICT character for different donating groups and the results for their electro- and photochem. properties as well as their performance in nanostructured dye-sensitized solar cells (nDSC) are reported. With the stronger donors, we obtain a shift of the LUMO to more neg. potential vs. normal hydrogen electrode (NHE) as well as an increased charge sepn. in the dye upon excitation. Ab initio calcns. were used to analyze the effects on orbital energies and electron distribution with the different donors. Incorporating the dyes in nDSCs, we see a drastic improvement in the performance for the more polar dyes. In particular, we find a much improved photovoltage because of higher LUMO levels, allowing conduction band tuning in the TiO2 as well as a contribution from the permanent dipoles in the dyes. The photocurrent improves remarkably with increasing ICT character of the dyes. The external quantum efficiency reached over 70%, and the overall solar-to-elec. energy conversion efficiency was improved to almost 4% for the dye with highest ICT character, which can be compared with devices with the std. N719 dye (Ru(dcbpy)2(NCS)2) showing 6% under similar conditions. The performance is a significant improvement compared to previous reports for perylenes and lifts the performance from modest to promising. Initial stability tests show that the dye with the highest performance was spectrally stable after more than 2000 h of irradn. in a solar-cell device.

2007

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A chemo-dynamical analysis of 115 metal-poor candidate stars selected from the narrow band Pristine photometric survey is presented based on CFHT high-resolution ESPaDOnS spectroscopy, We have discovered 28 new bright (V < 15) stars with I Fe/H]

OXFORD UNIV PRESS2020

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Microfabrication of free-standing micro-solid oxide fuel cells on Foturan® and silicon substrates

Danick Briand, Jérôme Courbat, Nico de Rooij, Paul Muralt, Yan Yan

Due to their high specific energy and energy density, micro-solid oxide fuel cells1,2 (µ-SOFCs) are seen as one of the technologies that could help satisfying the continuously increasing demand for electric energy in portable electronic devices. The µ-SOFC is a less than 1 µm thin free-standing membrane. The membrane consists of ceramic and metallic thin film layers integrated on a micro-structurable substrate based on MEMS technologies. In this study, Foturan® glass ceramic and silicon µ-SOFCs substrates are compared in terms of etching behavior, mechanical and thermomechanical properties

2011

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