21,199 research outputs found
Brake wear warning device: A concept
Heat-insulated wire is introduced through brake shoe and partially into brake lining. Wire is connected to positive terminal and light bulb. When brakes wear to critical point, contact between wire and wheel drum grounds circuit and turns on warning light
A new look at microlensing limits on dark matter in the Galactic halo
The motivation for this paper is to review the limits set on the MACHO
content of the Galactic halo by microlensing experiments in the direction of
the Large Magellanic Cloud. This has been prompted by recent measurements of
the Galactic rotation curve, which suggest that the limits have been biassed by
the assumption of an over-massive halo. The paper first discusses the security
of the detection efficiency calculations which are central to deriving the
MACHO content of the Galactic halo. It then sets out to compare the rotation
curves from various halo models with recent observations, with a view to
establishing what limits can be put on an all-MACHO halo. The main thrust of
the paper is to investigate whether lighter halo models which are consistent
with microlensing by an all-MACHO halo are also consistent with recent measures
of the Galactic rotation curve. In this case the population of bodies
discovered by the MACHO collaboration would make up the entire dark matter
content of the Galactic halo. The main result of this paper is that it is easy
to find low mass halo models consistent with the observed Galactic rotation
curve, which also imply an optical depth to microlensing similar to that found
by the MACHO collaboration. This means that all-MACHO halos cannot be ruled out
on the basis of their observations. In conclusion, limits placed on the MACHO
content of the Galactic halo from microlensing surveys in the Magellanic Clouds
are inconsistent and model dependent, and do not provide a secure basis for
rejecting an all-MACHO halo.Comment: 8 pages, 4 figures, accepted for publication in A&
Time Dilation and Quasar Variability
The timescale of quasar variability is widely expected to show the effects of
time dilation. In this paper we analyse the Fourier power spectra of a large
sample of quasar light curves to look for such an effect. We find that the
timescale of quasar variation does not increase with redshift as required by
time dilation. Possible explanations of this result all conflict with widely
held consensus in the scientific community.Comment: 6 pages including 3 figures. Accepted for publication in ApJ Letter
Free radical propulsion concept
A free radical propulsion concept utilizing the recombination energy of dissociated low molecular weight gases to produce thrust was examined. The concept offered promise of a propulsion system operating at a theoretical impulse, with hydrogen, as high as 2200 seconds at high thrust to power ratio, thus filling the gas existing between chemical and electrostatic propulsion capabilities. Microwave energy used to dissociate a continuously flowing gas was transferred to the propellant via three body recombination for conversion to propellant kinetic energy. Power absorption by the microwave plasma discharge was in excess of 90 percent over a broad range of pressures. Gas temperatures inferred from gas dynamic equations showed much higher temperatures from microwave heating than from electrothermal heating. Spectroscopic analysis appeared to corroborate the inferred temperatures of one of the gases tested
Catalogue of lunar craters cross sections. I - Craters with peaks Research report no. 16
Lunar craters with centrally located peaks - tables and profile graph
Catalog of Lunar Craters I
This catalog gives the selenographic coordinates of all craters observable on a selected portion of the moon's surface. The diameter of the crater together with comments on shape are also given. Approximately 25 per cent of the craters have been measured previously by other observers. The catalog gives the position found in the present series of measurements and the name adopted by the International Astronomical Union
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