2,527 research outputs found

    Enhancing the Quality of Data on Income: Recent Developments in Survey Methodology

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    In this paper, we evaluate two survey innovations aimed at improving income measurement. These innovations are (1) integrating the question sequences for income and wealth which may elicit more accurate estimates of income from capital than has been true in the past, and (2) changes in the periodicity over which income flows are measured, which may provide a closer match between what the survey respondent knows best and the periodicity contained in survey measurement. These innovations have been introduced into both the Health and Retirement Study (HRS) and the study of Asset and Health Dynamics Among the Oldest Old (AHEAD). Based on the results reported in this paper, the potential return in quality of income measurement from these innovations is substantial.

    Tunneling spectra for (dx2y2+isd_{x^2-y^2}+is)-wave superconductors versus tunneling spectra for (dx2y2+idxyd_{x^2-y^2}+id_{xy})-wave superconductors

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    The tunneling conductance spectra of a normal metal / insulator / singlet superconductor is calculated from the reflection amplitudes using the Blonder-Tinkham-Klapwijk (BTK) formulation. The pairing symmetry of the superconductor is assumed to be dx2y2+isd_{x^2-y^2}+is, or dx2y2+idxyd_{x^2-y^2}+id_{xy}. It is found that in the (dx2y2+isd_{x^2-y^2}+is)-wave case there is a well defined conductance peak in the conductance spectra, in the amplitude of the secondary s-wave component. In the (dx2y2+idxyd_{x^2-y^2}+id_{xy})-wave case the tunneling conductance has residual values within the gap, due to the formation of bound states. The bound state energies depend on the angle of the incident quasiparticles, and also on the boundary orientation. On the basis of this observation an electron focusing experiment is proposed to probe the (dx2y2+idxyd_{x^2-y^2}+id_{xy})-wave state.Comment: 17 pages with 9 figure

    Intercontinental antenna arraying by symbol stream combining at ICE Giacobini-Zinner encounter

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    Deep space tracking stations on different continents were arrayed during the encounter of the International Cometary Explorer (ICE) spacecraft with the comet Giacobini-Zinner during September 9 through 12, 1985. This is the first time that telemetry signals received on different continents have been combined to enhance signal to noise ratio. The arraying was done in non-real time using the method of symbol stream combining. The improvement in signal to noise ratio was typically 2 dB over the stronger of the two stations in each array

    Attractions between charged colloids at water interfaces

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    The effective potential between charged colloids trapped at water interfaces is analyzed. It consists of a repulsive electrostatic and an attractive capillary part which asymptotically both show dipole--like behavior. For sufficiently large colloid charges, the capillary attraction dominates at large separations. The total effective potential exhibits a minimum at intermediate separations if the Debye screening length of water and the colloid radius are of comparable size.Comment: 8 pages, 1 figure, revised version (one paragraph added) accepted in JPC

    Analytical and experimental study of stratification and liquid-ullage coupling, 1 June 1964 - 31 May 1965

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    Closed-form solution for stratification of subcooled fluids in containers subjected to heating, and for liquid-ullage vapor couplin

    High-purity silicon crystal growth investigations

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    The study of silicon sheet material requirements for high efficiency solar cells is reported. Research continued on obtaining long lifetime single crystal float zone silicon and on understanding and reducing the mechanisms that limit the achievement of long lifetimes. The mechanisms studied are impurities, thermal history, point defects, and surface effect. The lifetime related crystallographic defects are characterized by X-ray topography and electron beam induced current

    A precursor state to unconventional superconductivity in CeIrIn5{_5}

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    We present sensitive measurements of the Hall effect and magnetoresistance in CeIrIn5{_5} down to temperatures of 50 mK and magnetic fields up to 15 T. The presence of a low temperature coherent Kondo state is established. Deviations from Kohler's rule and a quadratic temperature dependence of the cotangent of the Hall angle are reminiscent of properties observed in the high temperature superconducting cuprates. The most striking observation pertains to the presence of a \textit{precursor} state--characterized by a change in the Hall mobility--that appears to precede the superconductivity in this material, in similarity to the pseudogap in the cuprate high TcT_c superconductors.Comment: 4 figure

    Hamiltonian approach to the ac Josephson effect in superconducting-normal hybrid systems

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    The ac Josephson effect in hybrid systems of a normal mesoscopic conductor coupled to two superconducting (S) leads is investigated theoretically. A general formula of the ac components of time-dependent current is derived which is valid for arbitrary interactions in the normal region. We apply this formula to analyze a S-normal-S system where the normal region is a noninteracting single level quantum dot. We report the physical behavior of time-averaged nonequilibrium distribution of electrons in the quantum dot, the formation of Andreev bound states, and ac components of the time-dependent current. The distribution is found to exhibit a population inversion; and all Andreev bound states between the superconducting gap Δ\Delta carry the same amount of current and in the same flow direction. The ac components of time-dependent current show strong oscillatory behavior in marked contrast to the subharmonic gap structure of the average current.Comment: 23 pages, 10 figures, LaTe

    Matching concepts across HOL libraries

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    Many proof assistant libraries contain formalizations of the same mathematical concepts. The concepts are often introduced (defined) in different ways, but the properties that they have, and are in turn formalized, are the same. For the basic concepts, like natural numbers, matching them between libraries is often straightforward, because of mathematical naming conventions. However, for more advanced concepts, finding similar formalizations in different libraries is a non-trivial task even for an expert. In this paper we investigate automatic discovery of similar concepts across libraries of proof assistants. We propose an approach for normalizing properties of concepts in formal libraries and a number of similarity measures. We evaluate the approach on HOL based proof assistants HOL4, HOL Light and Isabelle/HOL, discovering 398 pairs of isomorphic constants and types
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