24,168 research outputs found

    Satellite altimeters after Skylab and GEOS-C - should they utilize a single transmitter or an array of pulsed amplifiers?

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    An attempt was made to determine if future satellite altimeters, operating at K-band, should use a single transmitter or an array of pulsed amplifiers. The two systems were compared as a function of reliability, power, service life, system requirements, and weight. Preliminary results indicate the modular system to be superior in service life and reliability although it requires more power and is substantially heavier than the single system. No concrete conclusions were reached as to which system should be used

    Smooth Approximation of Lipschitz functions on Riemannian manifolds

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    We show that for every Lipschitz function ff defined on a separable Riemannian manifold MM (possibly of infinite dimension), for every continuous ϵ:M→(0,+∞)\epsilon:M\to (0,+\infty), and for every positive number r>0r>0, there exists a C∞C^\infty smooth Lipschitz function g:M→Rg:M\to\mathbb{R} such that ∣f(p)−g(p)∣≤ϵ(p)|f(p)-g(p)|\leq\epsilon(p) for every p∈Mp\in M and Lip(g)≤Lip(f)+r\textrm{Lip}(g)\leq\textrm{Lip}(f)+r. Consequently, every separable Riemannian manifold is uniformly bumpable. We also present some applications of this result, such as a general version for separable Riemannian manifolds of Deville-Godefroy-Zizler's smooth variational principle.Comment: 10 page

    Design and fabrication of Rene 41 advanced structural panels

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    The efficiency was investigated of curved elements in the design of lightweight structural panels under combined loads of axial compression, inplane shear, and bending. The application is described of technology generated in the initial aluminum program to the design and fabrication of Rene 41 panels for subsequent performance tests at elevated temperature. Optimum designs for two panel configurations are presented. The designs are applicable to hypersonic airplane wing structure, and are designed specifically for testing at elevated temperature in the hypersonic wing test structure located at the NASA Flight Research Center. Fabrication methods developed to produce the Rene panels are described, and test results of smaller structural element specimens are presented to verify the design and fabrication methods used. Predicted strengths of the panels under several proposed elevated temperature test load conditions are presented

    An investigation of the use of Faraday rotation for the measurement of magnetic fields

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    Potential use of Faraday rotation and Kerr magnetooptical effect for magnetic field measurement

    High-field Hall resistivity and magnetoresistance in electron-doped Pr_2-xCe_xCuO_{4-\delta}

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    We report resistivity and Hall effect measurements in electron-doped Pr2−x_{2-x}Cex_{x}CuO4−δ_{4-\delta} films in magnetic field up to 58 T. In contrast to hole-doped cuprates, we find a surprising non-linear magnetic field dependence of Hall resistivity at high field in the optimally doped and overdoped films. We also observe a crossover from quadratic to linear field dependence of the positive magnetoresistance in the overdoped films. A spin density wave induced Fermi surface reconstruction model can be used to qualitatively explain both the Hall effect and magnetoresistance.Comment: PRL in pres
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