13,525 research outputs found
Extragalactic radio source evolution under the dual-population unification scheme
We show that a dual-population unification scheme provides a successful
paradigm with which to describe the evolution and beaming of all bright
extragalactic radio sources. The paradigm consists of two intrinsic
radio-source populations, based on the two distinct radio-galaxy morphologies
of Fanaroff-Riley classes I and II. These represent the `unbeamed' or `side-on'
parent populations of steep radio spectra; the `beamed' source types including
flat-spectrum quasars and BL Lac objects, arise through the random alignment of
their radio-axis to our line-of-sight where Doppler-beaming of the relativistic
radio jets produces highly anisotropic radio emission.Comment: 18 pages & 18 postscript figures, accepted for publication in MNRA
Arc guidance development work for tack-welded joints
DOWNSTREAM HEAT TRANSFER OF UPSTREAM MASS INJECTION IN SUPERSONIC LAMINAR BOUNDARY LAYER FLO
The correlation function of radio sources
We investigate the large-scale clustering of radio sources in the Green Bank
and Parkes-MIT-NRAO 4.85 GHz surveys by measuring the angular two-point
correlation function w(\theta). Excluding contaminated areas, the two surveys
together cover 70 per cent of the whole sky. We find both surveys to be
reasonably complete above 50 mJy. On the basis of previous studies, the radio
sources are galaxies and radio-loud quasars lying at redshifts up to z \sim 4,
with a median redshift z \sim 1. This provides the opportunity to probe
large-scale structures in a volume far larger than that within the reach of
present optical and infrared surveys. We detect a clustering signal w(\theta)
\approx 0.01 for \theta = 1\degr. By assuming an evolving power-law spatial
correlation function in comoving coordinates \xi(r_c,z) = ( r_c / r_0
)^{-\gamma} (1+z)^{\gamma-(3+\epsilon)}, where \gamma = 1.8, and the redshift
distribution N(z) of the radio galaxies, we constrain the r_0--\epsilon
parameter space. For `stable clustering' (\epsilon = 0), we find the
correlation length r_0 \approx 18 Mpc/h, larger than the value for nearby
normal galaxies and comparable to the cluster-cluster correlation length.Comment: 8 pages, 7 ps figures included, LaTeX (mn,sty). Accepted by MNRA
Results of literature search on dielectric properties and electron interaction phenomena related to spacecraft charging
The objective of the literature search was to determine the required material properties and electron interaction parameters needed for modeling charge buildup and breakdown in insulators. A brief overview of the results of the literature search is given. A partial list of the references covered is included in a bibliography. Although inorganic insulators were also considered in the search, coverage is limited to the organics, primarily Kapton and Teflon
Walking a tightrope into 2008
Inflation (Finance) ; Housing ; Consumer behavior
Personal-bankruptcy cycles
This paper estimates the dynamics of the personal-bankruptcy rate over the business cycle by exploiting large cross-state variation in recessions and bankruptcies. We find that bankruptcy rates are significantly higher than normal during a recession and rise as a recession persists. After a recession ends, there is a hangover whereby bankruptcy rates begin to fall but remain above normal for several more quarters. Recovery periods see a strong bounce-back effect with bankruptcy rates significantly below normal for several quarters. Despite the significant increases in bankruptcies that occur during recessions, the largest contributor to rising bankruptcies during these periods has tended to be the longstanding upward trend.Bankruptcy ; Finance, Personal
Personal-bankruptcy cycles
This paper estimates the dynamics of the personal-bankruptcy rate over the business cycle by exploiting large cross-state variation. We find that bankruptcy rates are significantly higher than normal during a recession and rise as a recession persists. After a recession ends, there is a hangover whereby bankruptcy rates begin to fall but remain above normal for several more quarters. Recovery periods see a strong bounce-back effect with bankruptcy rates significantly below normal for several quarters. Despite the significant increases in bankruptcies during recessions, the largest contributor to rising bankruptcies during these periods has tended to be the longstanding upward trend.Personal Bankruptcy, Recessions
Structural characterization of YBa(2)Cu(3)O(7)/Y(2)O(3) composite films
Using 4-circle x-ray diffraction and transmission electron microscopy we have
studied the microstructure and in-plane orientation of the phases present in
thin film composite mixtures of YBa(2)Cu(3)O(7) and Y(2)O(3). We see a high
degree of in-plane orientation and have verified a previous prediction for the
in-plane order of Y(2)BaCuO(5) on (110) MgO. Transmission electron microscopy
shows the composite films to be a mixture of two phases, with YBCO grain sizes
of 1 micron. We have also compared our observations of the in-plane order to
the predictions of a modified near coincidence site lattice model.Comment: To be published in Journal of Materials Research, (4 pages, 4 jpeg
figures
- …