22,366 research outputs found

    A unified approach to blending of constant and varying parametric surfaces with curvature continuity

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    In this paper, we develop a new approach to blending of constant and varying parametric surfaces with curvature continuity. We propose a new mathematical model consisting of a vector-valued sixth-order partial differential equation (PDE) and time-dependent blending boundary constraints, and develop an approximate analytical solution of the mathematical model. The good accuracy and high computational efficiency are demonstrated by comparing the new approximate analytical solution with the corresponding accurate closed form solution. We also investigate the influence of the second partial derivatives on the continuity at trimlines, and apply the new approximate analytical solution in blending of constant and varying parametric surfaces with curvature continuit

    Superconducting properties of nanocrystalline MgB2_2 thin films made by an in situ annealing process

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    We have studied the structural and superconducting properties of MgB2_2 thin films made by pulsed laser deposition followed by in situ annealing. The cross-sectional transmission electron microscopy reveals a nanocrystalline mixture of textured MgO and MgB2_2 with very small grain sizes. A zero-resistance transition temperature (Tc0T_{c0}) of 34 K and a zero-field critical current density (JcJ_c) of 1.3×1061.3 \times 10^6 A/cm2^2 were obtained. The irreversibility field was \sim 8 T at low temperatures, although severe pinning instability was observed. These bulk-like superconducting properties show that the in situ deposition process can be a viable candidate for MgB2_2 Josephson junction technologies

    How do foreign institutional investors enhance firm innovation?

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    We examine the effect of foreign institutional investors on firm innovation. Using firm-level data across 26 non-U.S. economies between 2000 and 2010, we show that foreign institutional ownership has a positive, causal effect on firm innovation. We further explore three possible underlying mechanisms through which foreign institutions affect firm innovation: Foreign institutions act as active monitors, provide insurance for firm managers against innovation failures, and promote knowledge spillovers from high-innovation economies. Our article sheds new light on the real effects of foreign institutions on firm innovation

    Quantum Phase Diffusion in a Small Underdamped Josephson Junction

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    Quantum phase diffusion in a small underdamped Nb/AlOx_x/Nb junction (\sim 0.4 μ\mum2^2) is demonstrated in a wide temperature range of 25-140 mK where macroscopic quantum tunneling (MQT) is the dominant escape mechanism. We propose a two-step transition model to describe the switching process in which the escape rate out of the potential well and the transition rate from phase diffusion to the running state are considered. The transition rate extracted from the experimental switching current distribution follows the predicted Arrhenius law in the thermal regime but is greatly enhanced when MQT becomes dominant.Comment: 4 pages, 4 figures, 1 tabl
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