18,489 research outputs found
Broad-line and Multi-wave Band Emission from Blazars
We study the correlations of the flux of the broad-line emission ()
with the X-ray emission flux, optical emission flux at 5500 \AA and radio
emission flux at 5 GHz, respectively, for a large sample of 50 Blazars (39
flat-spectrum radio quasars (FSRQs) and 11 BL Lac objects). Our main results
are as follows. There are very strong correlations between and
and between and in both states for 39 FSRQs and the
slopes of the linear regression equations are almost equal to 1. There are weak
correlations between and and between and
for 11 BL Lac objects in both states, and the slopes of the linear regression
equations are close to 1. There are significant correlations between
and and between and for 50 blazars in both states,
the slopes of both the linear regression equations are also close to 1. These
results support a close link between relativistic jets and accretion on to the
central Kerr black hole. On the other hand, we find that BL Lac objects have
low accretion efficiency , whereas FSRQs have high accretion efficiency
. The unified model of FSRQs and BL Lac objects is also discussed.Comment: 15 pages, 8 figure
Morphology, structure, optical, and electrical properties of AgSbO₃
The morphology of defect pyrochlore-type, AgSbO₃ microparticle/nanoparticles obtained via solid state reaction evolve from irregular to Fullerene-like polyhedra before finally decomposing into metal-organic framework-5 like particles with increase in sintering temperature. The defect pyrochlore-type AgSbO₃ particles are slightly Ag deficient while the valence of the antimony ion is shown to be +5 giving rise to a probable stoichiometry of Ag₁ˍₓ SbVO₃ˍₓ/₂, with x∼0.01–0.04. A highly structured diffuse intensity distribution observed via electron diffraction is interpreted in terms of correlated displacements of one-dimensional (1D) silver ion chains along ⟨110⟩ directions. A redshifting in the absorption edges in UV-visible absorption spectra is observed for samples prepared at sintering temperatures higher than 1000 °C and attributed to the surface plasma resonance effect associated with small amounts of excess metallic Ag on the Ag₁ˍₓ SbVO₃ˍₓ/₂ particles. An electrical properties investigation of the silver antimonate samples via dielectric, conductivity, and electric modulus spectroscopy shows a prominent dielectric relaxation associated with grain boundaries. The silver ion conductivity is associated with correlated displacements of 1D silver ion chains along ⟨110⟩ directions.Z.G.Y., Y.L., and R.L.W. acknowledge financial support
from the Australian Research Council ARC in the form of
ARC Discovery Grants
Distinguishing RBL-like objects and XBL-like objects with the peak emission frequency of the overall energy spectrum
We investigate quantitatively how the peak emission frequency of the overall
energy spectrum is at work in distinguishing RBL-like and XBL-like objects. We
employ the sample of Giommi et al. (1995) to study the distribution of BL
Lacertae objects with various locations of the cutoff of the overall energy
spectrum. We find that the sources with the cutoff located at lower frequency
are indeed sited in the RBL region of the plane,
while those with the cutoff located at higher frequency are distributed in the
XBL region. For a more quantitative study, we employ the BL Lacertae samples
presented by Sambruna et al. (1996), where, the peak emission frequency, , of each source is estimated by fitting the data with a parabolic function.
In the plot of we find that, in the four different
regions divided by the line and the line,
all the RBL-like objects are inside the upper left region, while most XBL-like
objects are within the lower right region. A few sources are located in the
lower left region. No sources are in the upper right region. This result is
rather quantitative. It provides an evidence supporting what Giommi et al.
(1995) suggested: RBL-like and XBL-like objects can be distinguished by the
difference of the peak emission frequency of the overall energy spectrum.Comment: 7 pages, 2 figure
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Nonlinear response history analysis and collapse mode study of a wind turbine tower subjected to tropical cyclonic winds
The use of wind energy resources is developing rapidly in recent decades. There is an increasing number of wind farms in high wind-velocity areas such as the Pacific Rim regions. Wind turbine towers are vulnerable to tropical cyclones and tower failures have been reported in an increasing number in these regions. Existing post-disaster failure case studies were mostly performed through forensic investigations and there are few numerical studies that address the collapse mode simulation of wind turbine towers under strong wind loads. In this paper, the wind-induced failure analysis of a conventional 65m hub high 1.5-MW wind turbine was carried out by means of nonlinear response time-history analyses in a detailed finite element model of the structure. The wind loading was generated based on the wind field parameters adapted from the cyclone boundary layer flow. The analysis results indicate that this particular tower fails due to the formation of a full-section plastic hinge at locations that are consistent with those reported from field investigations, which suggests the validity of the proposed numerical analysis in the assessment of the performance of wind-farms under cyclonic winds. Furthermore, the numerical simulation allows to distinguish different failure stages before the dynamic collapse occurs in the proposed wind turbine tower, opening the door to future research on the control of these intermediate collapse phases
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