6,415 research outputs found
Outflow and hot dust emission in high redshift quasars
Correlations of hot dust emission with outflow properties are investigated,
based on a large z~2 non-broad absorption lines quasar sample built from the
Wide-field Infrared Survey and the Sloan Digital Sky Survey data releases. We
use the near infrared slope and the infrared to UV luminosity ratio to indicate
the hot dust emission relative to the emission from the accretion disk. In our
luminous quasars, these hot dust emission indicators are almost independent of
the fundamental parameters, such as luminosity, Eddington ratio and black hole
mass, but moderately dependent on the blueshift and asymmetry index (BAI) and
full width at half-maximum (FWHM) of CIV lines. Interestingly, the latter two
correlations dramatically strengthen with increasing Eddington ratio. We
suggest that, in high Eddington ratio quasars, CIV regions are dominated by
outflows so the BAI and FWHM(CIV) can reliably reflect the general properties
and velocity of outflows, respectively. While in low Eddington ratio quasars,
CIV lines are primarily emitted by virialized gas so the BAI and FWHM(CIV)
become less sensitive to outflows. Therefore, the correlations for the highest
Eddington ratio quasars are more likely to represent the true dependence of hot
dust emission on outflows and the correlations for the entire sample are
significantly diluted by the low Eddington ratio quasars. Our results show that
an outflow with a large BAI or velocity can double the hot dust emission on
average. We suggest that outflows either contain hot dust in themselves or
interact with the dusty interstellar medium or torus.Comment: 14 page, 4 figures, accepted for publication in ApJ
The verification of the Taylor-expansion moment method in solving aerosol breakage
The combination of the method of moment, characterizing the particle population balance, and the computational fluid dynamics has been an emerging research issue in the studies on the aerosol science and on the multiphase flow science. The difficulty of solving the moment equation arises mainly from the closure of some fractal moment variables which appears in the transform from the non-linear integral-differential population balance equation to the moment equations. Within the Taylor-expansion moment method, the breakage-dominated Taylor-expansion moment equation is first derived here when the symmetric fragmentation mechanism is involved. Due to the high efficiency and the high precision, this proposed moment model is expected to become an important tool for solving population balance equations
Outflow and hot dust emission in broad absorption line quasars
We have investigated a sample of 2099 broad absorption line (BAL) quasars
with z=1.7-2.2 built from the Sloan Digital Sky Survey Data Release Seven and
the Wide-field Infrared Survey. This sample is collected from two BAL quasar
samples in the literature, and refined by our new algorithm. Correlations of
outflow velocity and strength with hot dust indicator (beta_NIR) and other
quasar physical parameters, such as Eddington ratio, luminosity and UV
continuum slope, are explored in order to figure out which parameters drive
outflows. Here beta_NIR is the near-infrared continuum slope, a good indicator
of the amount of hot dust emission relative to accretion disk emission. We
confirm previous findings that outflow properties moderately or weakly depends
on Eddington ratio, UV slope and luminosity. For the first time, we report
moderate and significant correlations of outflow strength and velocity with
beta_NIR in BAL quasars. It is consistent with the behavior of blueshifted
broad emission lines in non-BAL quasars. The statistical analysis and composite
spectra study both reveal that outflow strength and velocity are more strongly
correlated with beta_NIR than Eddington ratio, luminosity and UV slope. In
particular, the composites show that the entire C IV absorption profile shifts
blueward and broadens as beta_NIR increases, while Eddington ratio and UV slope
only affect the high and low velocity part of outflows, respectively. We
discuss several potential processes and suggest that dusty outflow scenario,
i.e. dust is intrinsic to outflows and may contribute to the outflow
acceleration, is most likely. The BAL quasar catalog is available from the
authors upon request.Comment: 16 pages, 10 figures, 2 tables; Accepted for publication in The
Astrophysical Journa
Accurately recover global quasiperiodic systems by finite points
Quasiperiodic systems, related to irrational numbers, are space-filling
structures without decay nor translation invariance. How to accurately recover
these systems, especially for non-smooth cases, presents a big challenge in
numerical computation. In this paper, we propose a new algorithm, finite points
recovery (FPR) method, which is available for both smooth and non-smooth cases,
to address this challenge. The FPR method first establishes a homomorphism
between the lower-dimensional definition domain of the quasiperiodic function
and the higher-dimensional torus, then recovers the global quasiperiodic system
by employing interpolation technique with finite points in the definition
domain without dimensional lifting. Furthermore, we develop accurate and
efficient strategies of selecting finite points according to the arithmetic
properties of irrational numbers. The corresponding mathematical theory,
convergence analysis, and computational complexity analysis on choosing finite
points are presented. Numerical experiments demonstrate the effectiveness and
superiority of FPR approach in recovering both smooth quasiperiodic functions
and piecewise constant Fibonacci quasicrystals. While existing spectral methods
encounter difficulties in accurately recovering non-smooth quasiperiodic
functions
Energy Risks Zoning and Demand Forecasting in Jiangsu rovince
AbstractThis paper takes Jiangsu province as an example, divides the zone of energy risks and uses GM (1, 1) and the combination of BP network model to forecast energy demand in this region.Finally, we adopt ARCEngine secondary development achieving the system simulation, and putting forward a strategic suggestion on energy problem of Jiangsu province. The study provides the scientific data support for making energy policy rationally, reducing the increasingly prominent phenomenon of energy demand and offer support for different levels in different departments.It can provide the scientific basis for risk prevention and comprehensive risk management plan.© 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of RIUD
BEAUTY Powered BEAST
We study inference about the uniform distribution with the proposed binary
expansion approximation of uniformity (BEAUTY) approach. Through an extension
of the celebrated Euler's formula, we approximate the characteristic function
of any copula distribution with a linear combination of means of binary
interactions from marginal binary expansions. This novel characterization
enables a unification of many important existing tests through an approximation
from some quadratic form of symmetry statistics, where the deterministic weight
matrix characterizes the power properties of each test. To achieve a uniformly
high power, we study test statistics with data-adaptive weights through an
oracle approach, referred to as the binary expansion adaptive symmetry test
(BEAST). By utilizing the properties of the binary expansion filtration, we
show that the Neyman-Pearson test of uniformity can be approximated by an
oracle weighted sum of symmetry statistics. The BEAST with this oracle leads
all existing tests we considered in empirical power against all complex forms
of alternatives. This oracle therefore sheds light on the potential of
substantial improvements in power and on the form of optimal weights under each
alternative. By approximating this oracle with data-adaptive weights, we
develop the BEAST that improves the empirical power of many existing tests
against a wide spectrum of common alternatives while providing clear
interpretation of the form of non-uniformity upon rejection. We illustrate the
BEAST with a study of the relationship between the location and brightness of
stars
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