18,112 research outputs found

    Method of fabricating a photovoltaic module of a substantially transparent construction

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    A method characterized by the steps of positioning a plurality of uniformly dimensioned photovoltaic cells in registered relation with a plurality of openings formed in a planar tool is disclosed. The method allows acess to the P contact surface of each of the cells. The steps of the method are: (1) connecting the N contact surface of alternate cells to the P contact surface of the cells interposed therebetween, (2) removing therefrom residue of solder flux, (3) applying to the N contact surfaces of the cells a transparent adhesive, (4) placing a common transparent cover plate in engaged relation with the adhesive, (5) placing a film over the circular openings for hermetically sealing the openings, and (6) establishing a vacuum between the film and the cover plate

    Optimization of Al/AlOx/AlAl/AlO_x/Al-Layer Systems for Josephson Junctions from a Microstructure Point of View

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    Al/AlOx/AlAl/AlO_x/Al-layer systems are frequently used for Josephson junction-based superconducting devices. Although much work has been devoted to the optimization of the superconducting properties of these devices, systematic studies on influence of deposition conditions combined with structural analyses on the nanoscale are rare up to now. We have focused on the optimization of the structural properties of Al/AlOx/AlAl/AlO_x/Al-layer systems deposited on Si(111) substrates with a particular focus on the thickness homogeneity of the AlOxAlO_x-tunnel barrier. A standard high-vacuum electron-beam deposition system was used and the effect of substrate pretreatment, different Al-deposition temperatures and Al-deposition rates was studied. Transmission electron microscopy was applied to analyze the structural properties of the Al/AlOx/AlAl/AlO_x/Al-layer systems to determine the thickness homogeneity of the AlOxAlO_x layer, grain size distribution in the Al layers, Al-grain boundary types and the morphology of the Al/AlOxAl/AlO_x interface. We show that the structural properties of the lower Al layer are decisive for the structural quality of the whole Al/AlOx/AlAl/AlO_x/Al-layer system. Optimum conditions yield an epitaxial Al(111) layer on a Si(111) substrate with an Al-layer thickness variation of only 1.6 nm over more than 10 μm\mu m and large lateral grain sizes up to 1 μm\mu m. Thickness fluctuations of the AlOxAlO_x-tunnel barrier are minimized on such an Al layer which is essential for the homogeneity of the tunnel current. Systematic variation of the Al-deposition rate and deposition temperature allows to develop an understanding of the growth mechanisms

    Geophysical characteristics of the Atlantic Ocean

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    A Technique to Derive Improved Proper Motions for Kepler Objects of Interest

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    We outline an approach yielding proper motions with higher precision than exists in present catalogs for a sample of stars in the Kepler field. To increase proper motion precision we combine first moment centroids of Kepler pixel data from a single Season with existing catalog positions and proper motions. We use this astrometry to produce improved reduced proper motion diagrams, analogous to a Hertzsprung-Russell diagram, for stars identified as Kepler Objects of Interest. The more precise the relative proper motions, the better the discrimination between stellar luminosity classes. With UCAC4 and PPMXL epoch 2000 positions (and proper motions from those catalogs as quasi-bayesian priors) astrometry for a single test Channel (21) and Season (0) spanning two years yields proper motions with an average per-coordinate proper motion error of 1.0 millisecond of arc per year, over a factor of three better than existing catalogs. We apply a mapping between a reduced proper motion diagram and an HR diagram, both constructed using HST parallaxes and proper motions, to estimate Kepler Object of Interest K-band absolute magnitudes. The techniques discussed apply to any future small-field astrometry as well as the rest of the Kepler field.Comment: Accepted to The Astronomical Journal 15 August 201

    Capital Structure with Risky Foreign Investment

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    American multinational firms respond to politically risky environments by adjusting their capital structures abroad and at home. Foreign subsidiaries located in politically risky countries have significantly more debt than do other foreign affiliates of the same parent companies. American firms further limit their equity exposures in politically risky countries by sharing ownership with local partners and by serving foreign markets with exports rather than local production. The residual political risk borne by parent companies leads them to use less domestic leverage, resulting in lower firm-wide leverage. Multinational firms with above-average exposures to politically risky countries have 8.4 percent less domestic leverage than do other firms. These findings illustrate the impact of risk exposures on capital structure.
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