154,158 research outputs found
Power Spectrum of Cosmic Momentum Field Measured from the SFI Galaxy Sample
We have measured the cosmic momentum power spectrum from the peculiar
velocities of galaxies in the SFI sample. The SFI catalog contains field spiral
galaxies with radial peculiar velocities derived from the I-band Tully-Fisher
relation. As a natural measure of the large-scale peculiar velocity field, we
use the cosmic momentum field that is defined as the peculiar velocity field
weighted by local number of galaxies. We have shown that the momentum power
spectrum can be derived from the density power spectrum for the constant linear
biasing of galaxy formation, which makes it possible to estimate \beta_S =
\Omega_m^{0.6} / b_S parameter precisely where \Omega_m is the matter density
parameter and b_S is the bias factor for optical spiral galaxies. At each
wavenumber k we estimate \beta_S(k) as the ratio of the measured to the derived
momentum power over a wide range of scales (0.026 h^{-1}Mpc <~ k <~ 0.157
h^{-1}Mpc) that spans the linear to the quasi-linear regimes. The estimated
\beta_S(k)'s have stable values around 0.5, which demonstrates the constancy of
\beta_S parameter at scales down to 40 h^{-1}Mpc. We have obtained
\beta_S=0.49_{-0.05}^{+0.08} or \Omega_m = 0.30_{-0.05}^{+0.09} b_S^{5/3}, and
the amplitude of mass fluctuation as
\sigma_8\Omega_m^{0.6}=0.56_{-0.21}^{+0.27}. The 68% confidence limits include
the cosmic variance. We have also estimated the mass density power spectrum.
For example, at k=0.1047 h Mpc^{-1} (\lambda=60 h^{-1}Mpc) we measure
\Omega_m^{1.2} P_{\delta}(k)=(2.51_{-0.94}^{+0.91})\times 10^3 (h^{-1}Mpc)^3,
which is lower compared to the high-amplitude power spectra found from the
previous maximum likelihood analyses of peculiar velocity samples like Mark
III, SFI, and ENEAR.Comment: 12 pages, 9 figures, accepted for publication in Ap
The Crime Bill of 1994 and the Law of Character Evidence: Congress Was Right About Consent Defense Cases
There is considerable debate as to whether to admit evidence of past sexual assaults in cases where the accused presents a defense of consent to a current sexual assault charge. The consent defense presents a unique situation where, due to the probative value of evidence that suggests propensity to rape, a strong justification can be made to admit this information as evidence. However, critics of this opinion have argued that admitting propensity evidence about the accused in a rape case is inconsistent with the rape shield rule which excludes propensity evidence about the victim. This argument is flawed in the sense that it does not properly take into account the full purpose of rape shield laws, nor does it acknowledge that evidence of a victim\u27s sexual history is less probative than evidence regarding the history of the accused
A concept for magazine Bimat processor
Concept utilizes existing film magazines to process photographic film as the film is exposed. A standard magazine can be converted to a Bimat processor by adding three stainless steel rollers. All chemicals required for processing and fixing the negative are contained in the Bimat film
A review of shock waves around aeroassisted orbital transfer vehicles
Aeroassisted orbital transfer vehicles (AOTVs) are a proposed type of reusable spacecraft that would be used to transport cargoes from one Earth-bound orbit to another. Such vehicles could be based on the proposed space station and used to transport commercial satellites from the space station to geostationary orbits or to polar orbits and return. During a mission, AOTVs would fly through Earth's atmosphere, thus generating aerodynamic forces that could be used for decelerating the vehicles or changing their direction. AOTV research findings were concerned with the shock-wave-induced, high-temperature airflows that would be produced around these vehicles during atmospheric flight. Special emphasis was placed on the problems of: (1) the chemical physics of multitemperature, ionizing, nonequilibrium air flows, and (2) the dynamics of the flows in the base region of a blunt body with complex afterbody geometry
Genus Topology of the Cosmic Microwave Background from the WMAP 3-Year Data
We have independently measured the genus topology of the temperature
fluctuations in the cosmic microwave background seen in the Wilkinson Microwave
Anisotropy Probe (WMAP) 3-year data. A genus analysis of the WMAP data
indicates consistency with Gaussian random-phase initial conditions, as
predicted by standard inflation. We set 95% confidence limits on
non-linearities of -101 < f_{nl} < 107. We also find that the observed low l (l
<= 8) modes show a slight anti-correlation with the Galactic foreground, but
not exceeding 95% confidence, and that the topology defined by these modes is
consistent with that of a Gaussian random-phase distribution (within 95%
confidence).Comment: MNRAS LaTeX style (mn2e.cls), EPS and JPEG figure
Shape change of Galileo probe models in free-flight tests
Scale models of the Galileo Probe made of polycarbonate, AXF5Q graphite, carbon-carbon composite, and carbon-phenolic were flown in a free flight range in an ambient gas of air, krypton, or xenon. Mach numbers varied between 14 and 24, Reynolds numbers between 300,000 and 1,000,000, stagnation pressures between 31 and 200 atm, and stagnation point heat transfer rates between 10 and 1,000 kW/sq cm. Shadowgraphs indicate gouging ablation of the aft portion of the frustum; the gouging was moderate in air and severe in the noble gases. The graphite models break in the same region. An explanation of the phenomena is offered in terms of the strong compression and shear caused by the reattachment of a turbulent separated flow. Conditions are calculated for similar tests appropriate for Von Karman Facility of the Arnold Engineering Development Center in which a larger model can be flown in argon
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