54,965 research outputs found

    A Comparison Between the Variational Solution and the Experimental Data

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    Current distribution on dipole antenna with nonreflecting resistive loading, expressed using variation metho

    An experimental study of imperfectly conducting dipoles

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    Input admittances of imperfectly conducting dipole antennas measured in ultrahigh frequency rang

    The Cylindrical Antenna with Tapered Resistive Loading Scientific Report No. 5

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    Current, input impedance, and far field pattern of cylindrical antenna with tapered resistive loadin

    Absence of magnetic long range order in Y2_{2}CrSbO7_{7}: bond-disorder induced magnetic frustration in a ferromagnetic pyrochlore

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    The consequences of nonmagnetic-ion dilution for the pyrochlore family Y2_{2}(M1xNxM_{1-x}N_{x})2_{2}O7_{7} (MM = magnetic ion, NN = nonmagnetic ion) have been investigated. As a first step, we experimentally examine the magnetic properties of Y2_{2}CrSbO7_{7} (xx = 0.5), in which the magnetic sites (Cr3+^{3+}) are percolative. Although the effective Cr-Cr spin exchange is ferromagnetic, as evidenced by a positive Curie-Weiss temperature, ΘCW\Theta_\mathrm{{CW}} = 20.1(6) K, our high-resolution neutron powder diffraction measurements detect no sign of magnetic long range order down to 2 K. In order to understand our observations, we performed numerical simulations to study the bond-disorder introduced by the ionic size mismatch between MM and NN. Based on these simulations, bond-disorder (xbx_{b} \simeq 0.23) percolates well ahead of site-disorder (xsx_{s} \simeq 0.61). This model successfully reproduces the critical region (0.2 < xx < 0.25) for the N\'eel to spin glass phase transition in Zn(Cr1x_{1-x}Gax_{x})2_{2}O4_{4}, where the Cr/Ga-sublattice forms the same corner-sharing tetrahedral network as the M/NM/N-sublattice in Y2_{2}(M1xNxM_{1-x}N_{x})2_{2}O7_{7}, and the rapid drop in magnetically ordered moment in the N\'eel phase [Lee etet alal, Phys. Rev. B 77, 014405 (2008)]. Our study stresses the nonnegligible role of bond-disorder on magnetic frustration, even in ferromagnets

    Anomalous high energy dispersion in photoemission spectra from insulating cuprates

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    Angle resolved photoelectron spectroscopic measurements have been performed on an insulating cuprate Ca_2CuO_2Cl_2. High resolution data taken along the \Gamma to (pi,pi) cut show an additional dispersive feature that merges with the known dispersion of the lowest binding energy feature, which follows the usual strongly renormalized dispersion of ~0.35 eV. This higher energy part reveals a dispersion that is very close to the unrenormalized band predicted by band theory. A transfer of spectral weight from the low energy feature to the high energy feature is observed as the \Gamma point is approached. By comparing with theoretical calculations the high energy feature observed here demonstrates that the incoherent portion of the spectral function has significant structure in momentum space due to the presence of various energy scales.Comment: 5 pages, 3 figure

    NIMBUS-5 sounder data processing system. Part 2: Results

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    The Nimbus-5 spacecraft carries infrared and microwave radiometers for sensing the temperature distribution of the atmosphere. Methods developed for obtaining temperature profiles from the combined set of infrared and microwave radiation measurements are described. Algorithms used to determine (a) vertical temperature and water vapor profiles, (b) cloud height, fractional coverage, and liquid water content, (c) surface temperature, and (d) total outgoing longwave radiation flux are described. Various meteorological results obtained from the application of the Nimbus-5 sounding data processing system during 1973 and 1974 are presented

    A simple theory of dipole antennas

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    Simple and quantitatively accurate representation of current distribution in dipole antenna

    Dynamics of quantum-classical hybrid system: effect of matter-wave pressure

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    Radiation pressure affects the kinetics of a system exposed to the radiation and it constitutes the basis of laser cooling. In this paper, we study {\it matter-wave pressure} through examining the dynamics of a quantum-classical hybrid system. The quantum and classical subsystem have no explicit coupling to each other, but affect mutually via a changing boundary condition. Two systems, i.e., an atom and a Bose-Einstein condensate(BEC), are considered as the quantum subsystems, while an oscillating wall is taken as the classical subsystem. We show that the classical subsystem would experience a force proportional to Q3Q^{-3} from the quantum atom, whereas it acquires an additional force proportional to Q2Q^{-2} from the BEC due to the atom-atom interaction in the BEC. These forces can be understood as the {\it matter-wave pressure}.Comment: 7 pages, 6 figue

    An experimental study of the dipole antenna with nonreflecting resistive loading

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    Current distribution, input admittance, and radiation field pattern of dipole antenna with nonreflecting resistive loadin
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