5,466 research outputs found

    Stand-alone flat-plate photovoltaic power systems: System sizing and life-cycle costing methodology for Federal agencies

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    A simple methodology to estimate photovoltaic system size and life-cycle costs in stand-alone applications is presented. It is designed to assist engineers at Government agencies in determining the feasibility of using small stand-alone photovoltaic systems to supply ac or dc power to the load. Photovoltaic system design considerations are presented as well as the equations for sizing the flat-plate array and the battery storage to meet the required load. Cost effectiveness of a candidate photovoltaic system is based on comparison with the life-cycle cost of alternative systems. Examples of alternative systems addressed are batteries, diesel generators, the utility grid, and other renewable energy systems

    Tailoring teleportation to the quantum alphabet

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    We introduce a refinement of the standard continuous variable teleportation measurement and displacement strategies. This refinement makes use of prior knowledge about the target state and the partial information carried by the classical channel when entanglement is non-maximal. This gives an improvement in the output quality of the protocol. The strategies we introduce could be used in current continuous variable teleportation experiments.Comment: 16 pages, 6 figures, RevTeX, made changes as recommended by referee, other minor textual corrections, resubmitted to Phys. Rev.

    Teleportation-based number state manipulation with number sum measurement

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    We examine various manipulations of photon number states which can be implemented by teleportation technique with number sum measurement. The preparations of the Einstein-Podolsky-Rosen resources as well as the number sum measurement resulting in projection to certain Bell state may be done conditionally with linear optical elements, i.e., beam splitters, phase shifters and zero-one-photon detectors. Squeezed vacuum states are used as primary entanglement resource, while single-photon sources are not required.Comment: 9 pages, 4 figures, Misprints are corrected. 3 figures for number sum measurement are added. Discussion on manipulations are expanded. Calculations for success probabilities are added. Fig.4 is adde

    The Performance of Private Equity Funds: Does Diversification Matter?

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    This paper is the first systematic analysis of the impact of diversification on the performance of private equity funds. A unique data set allows the exact evaluation of diversification across the dimensions financing stages, industries, and countries. Very different levels of diversification can be observed across sample funds. While some funds are highly specialized others are highly diversified. The empirical results show that the rate of return of private equity funds declines with diversification across financing stages, but increases with diversification across industries. Accordingly, the fraction of portfolio companies which have a negative return or return nothing at all, increase with diversification across financing stages. Diversification across countries has no systematic effect on the performance of private equity funds

    Efficient Quantum Computation using Coherent States

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    Universal quantum computation using optical coherent states is studied. A teleportation scheme for a coherent-state qubit is developed and applied to gate operations. This scheme is shown to be robust to detection inefficiency.Comment: 6 pages, 5 figures, extended and modified (in print, PRA

    The art of being human : a project for general philosophy of science

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    Throughout the medieval and modern periods, in various sacred and secular guises, the unification of all forms of knowledge under the rubric of ‘science’ has been taken as the prerogative of humanity as a species. However, as our sense of species privilege has been called increasingly into question, so too has the very salience of ‘humanity’ and ‘science’ as general categories, let alone ones that might bear some essential relationship to each other. After showing how the ascendant Stanford School in the philosophy of science has contributed to this joint demystification of ‘humanity’ and ‘science’, I proceed on a more positive note to a conceptual framework for making sense of science as the art of being human. My understanding of ‘science’ is indebted to the red thread that runs from Christian theology through the Scientific Revolution and Enlightenment to the Humboldtian revival of the university as the site for the synthesis of knowledge as the culmination of self-development. Especially salient to this idea is science‘s epistemic capacity to manage modality (i.e. to determine the conditions under which possibilities can be actualised) and its political capacity to organize humanity into projects of universal concern. However, the challenge facing such an ideal in the twentyfirst century is that the predicate ‘human’ may be projected in three quite distinct ways, governed by what I call ‘ecological’, ‘biomedical’ and ‘cybernetic’ interests. Which one of these future humanities would claim today’s humans as proper ancestors and could these futures co-habit the same world thus become two important questions that general philosophy of science will need to address in the coming years

    Continuous pumping and control of mesoscopic superposition state in a lossy QED cavity

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    Here we consider the continuous pumping of a dissipative QED cavity and derive the time-dependent density operator of the cavity field prepared initially as a superposition of mesoscopic coherent states. The control of the coherence of this superposition is analyzed considering the injection of a beam of two-level Rydberg atoms through the cavity. Our treatment is compared to other approaches.Comment: 15 pages, 6 PostScript figures, To appear in Phys. Rev.

    Synthesis and characterization of entangled mesoscopic superpositions for a trapped electron

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    We propose a scheme for the generation and reconstruction of entangled states between the internal and external (motional) degrees of freedom of a trapped electron. Such states also exhibit quantum coherence at a mesoscopic level.Comment: 4 pages, 1 figure, RevTeX (twocolumn

    High speed imaging and Fourier analysis of the melt plume during close coupled gas atomisation

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    A high speed digital analysis technique has been used to study the atomisation plume of a superheated sample of Ni–Al in a close coupled gas atomiser. The atomisation, incorporating a generic melt nozzle and die design was captured using a Kodak high speed digital analyser at a frame rate of 18 k frames per second. The resulting 65 536 frames were then analysed using a specially designed routine, which calculates values of optical brightness and position of the intensity maximum for all frames and performs Fourier analysis on the sequence. The data produced from this analysis show that the plume, pulses at low frequencies (<25 Hz) and precesses at higher frequencies (∌360 Hz) around the atomiser's centreline. To aid investigation into the origins of this precession and other phenomena it was decided to conduct further experiments using an analogue system. The analogue atomiser reproduces the important features of the full atomiser but instead of atomising molten metal, the analogue system atomises water, providing a quick and easy way of testing the effects of changing parameters. Using this system it was found that the precession of the melt plume is independent of the atomiser's gas inlet pressure but strongly dependent on both the die and melt nozzle's geometry
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