7,602 research outputs found
Smaller SPS system sizing tradeoffs
The solar power satellite and associated microwave system was reoptimized with larger antennas (at 2.45 GHz), reduced output powers, and smaller rectennas. Four constraints were considered: (1) the 23 mw/sq cm ionospheric limit; (2) a higher (54 mW/sq cm) ionospheric limit; (3) the 23 KW/sq cm thermal limit in the antenna; and (4) an improved thermal design allowing 33% additional waste heat. The differential costs in electricity for seven antenna/rectenna configurations operating at 2.45 GHz and five satellite systems operating at 5.8 GHz were calculated. It is concluded that a larger antenna/smaller rectenna configurations are economically feasible under certain conditions; a transmit antenna diameters should be limited to 1 to 1.5 Km for 2.45 GHz operation and .75 to 1.0 Km for 5.8 GHz; the present ionospheric limit of 23 mw/sq cm is probably too low and should be raised after ionospheric heating tests and studies are completed; the 5.8 GHz configurations are constrainted by antenna thermal limitations, rather than ionospheric limits; and multiple (two to four) antennas on a single solar satellite are recommended regardless of the particular antenna/rectenna configuration chosen
Spontaneous Breaking of Translational Invariance in One-Dimensional Stationary States on a Ring
We consider a model in which positive and negative particles diffuse in an
asymmetric, CP-invariant way on a ring. The positive particles hop clockwise,
the negative counterclockwise and oppositely-charged adjacent particles may
swap positions. Monte-Carlo simulations and analytic calculations suggest that
the model has three phases; a "pure" phase in which one has three pinned blocks
of only positive, negative particles and vacancies, and in which translational
invariance is spontaneously broken, a "mixed" phase with a non-vanishing
current in which the three blocks are positive, negative and neutral, and a
disordered phase without blocks.Comment: 7 pages, LaTeX, needs epsf.st
Comment on `Measurement of the analyzing power at 68.3 MeV'
We comment on a recent paper by Weiser et al. [Phys. Rev. C {\bf 54}, 1930
(1996)]. The authors have performed a single-energy analysis of
scattering data at 68.3 MeV, finding a value for the phase shift about
1^o smaller than found in the Karlsruhe-Helsinki (KH) partial-wave analysis.
The authors use this result to argue for a dispersion relation analysis using
recently measured data, so that their effect on the coupling constant
(f^2) and amplitude can be determined. We note that these tasks were
accomplished prior to the submission of the above paper. We clarify the effect
of this new analyzing power data on f^2 and the amplitude.Comment: 5 pages of text. Revised according to Referee suggestion
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