1,329,211 research outputs found
Characterization of reflected light from the space power system
Sunlight reflected off large space structures is examined. To assure that this illumination does not exceed the irradiance tolerances of the eye, reflections from these satellites must be controlled by vehicle orientation and surface specifications. The components of various space power system vehicles to determine the reflectances which will significantly contribute to the ground illumination are evaluated. Calculations of reflected solar intensity from various satellite system elements requires description of the elements and of the geometry potential reflectance paths. Surface intensity and the conditions under which it will illuminate a portion of the Earth are also determined
The Exact Ground State of the Frenkel-Kontorova Model with Repeated Parabolic Potential: II. Numerical Treatment
A procedure is described for efficiently finding the ground state energy and
configuration for a Frenkel-Kontorova model in a periodic potential, consisting
of N parabolic segments of identical curvature in each period, through a
numerical solution of the convex minimization problem described in the
preceding paper. The key elements are the use of subdifferentials to describe
the structure of the minimization problem; an intuitive picture of how to solve
it, based on motion of quasiparticles; and a fast linear optimization method
with a reduced memory requirement. The procedure has been tested for N up to
200.Comment: 9 RevTeX pages, using AMS-Fonts (amssym.tex,amssym.def), 3 Postscript
figures, accepted by Phys.Rev.B to be published together with
cond-mat/970722
The General Electric MOD-1 wind turbine generator program
The design, fabrication, installation and checkout of MOD-1, a megawatt class wind turbine generator which generates utility grade electrical power, is described. A MOD-1/MOD-1A tradeoff study is discussed
Semi-realistic nucleon-nucleon interactions with improved neutron-matter properties
New parameter-sets of the semi-realistic nucleon-nucleon interaction are
developed, by modifying the M3Y interaction but maintaining the tensor channels
and the longest-range central channels. The modification is made so as to
reproduce microscopic results of neutron-matter energies, in addition to the
measured binding energies of doubly magic nuclei including Sn and the
even-odd mass differences of the Z=50 and N=82 nuclei in the self-consistent
mean-field calculations. Separation energies of the proton- or neutron-magic
nuclei are shown to be in fair agreement with the experimental data. With the
new parameter-sets M3Y-P6 and P7, the isotropic spin-saturated symmetric
nuclear matter remains stable in the density range as wide as , while keeping desirable results of the previous parameter-set on
finite nuclei. Isotope shifts of the Pb nuclei and tensor-force effects on
shell structure are discussed.Comment: 18 pages including 7 figure
Measurements of antenna polar diagrams and efficiencies using a phase-switched interferometer
It is desirable to know antenna polar patterns and efficiencies accurately. In the past, calibration measurements have been made using balloons and aircraft and more recently satellites. These techniques are usually very expensive. It is shown that under certain circumstances it is possible to use a simpler and inexpensive technique by connecting together the antenna under test with another antenna to form a phase switched interferometer as first described by Ryle (1952). The technique does require a suitable radio source which gives measurable powers when using small antennas and since dipoles have broad patterns, radio sources with similar right ascensions but different declinations to the primary source can be a problem. These problems can partly be overcome by filtering the interference pattern
Reversal of particle-hole scattering-rate asymmetry in Anderson impurity model
We study the particle-hole asymmetry of the scattering rate in strongly
correlated electron systems by examining the cubic and
terms in the imaginary part of the self-energy of the Anderson impurity model.
We show that the sign is opposite in the weak-coupling and strong-coupling
limits, explaining the differences found in theoretical approaches taking the
respective limits as the starting points. The sign change in fact precisely
delineates the cross-over between the weak and strong correlation regimes of
the model. For weak interaction the sign reversal occurs for small values
of the doping , while for interaction of order , being the hybridization strength, the cross-over curve
rapidly shifts to the large-doping range. This curve based on the impurity
dynamics is genuinely different from other cross-over curves defined through
impurity thermodynamic and static properties.Comment: 4 pages, 5 figure
Collective Fields for QCD
A gauge-symmetric approach to effective Lagrangians is described with special
emphasis on derivations of effective low-energy Lagrangians from QCD. The
examples we discuss are based on exact rewritings of cut-off QCD in terms of
new collective degrees of freedom. These cut-off Lagrangians are thus
``effective'' in the sense that they explicitly contain some of the physical
long-distance degrees of freedom from the outset.(Talk presented by P.H.
Damgaard at the workshop on ``Quantum Field Theoretical Methods in High Energy
Physics'', Kyffhauser, Germany, Sept. 1993. To appear in those proceedings).Comment: LaTeX, 12 pages, CERN--TH-7035/9
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