21,742 research outputs found
Statistical Properties of Multiple Optical Emission Components in Gamma-Ray Bursts and Implications
Well-sampled optical lightcurves of 146 gamma-ray bursts (GRBs) are complied
from the literature. Multiple optical emission components are extracted with
power-law function fits to these lightcurves. We present a systematical
analysis for statistical properties and their relations to prompt gamma-ray
emission and X-ray afterglow for each component. We show that peak luminosity
in the prompt and late flares are correlated and the evolution of the peak
luminosity may signal the evolution of the accretion rate. No tight correlation
between the shallow decay phase/plateau and prompt gamma-ray emission is found.
Assuming that they are due to a long-lasting wind injected by a compact object,
we show that the injected behavior favors the scenarios of a long-lasting wind
after the main burst episode. The peak luminosity of the afterglow onset is
tightly correlated with Eiso, and it is dimmer as peaking later. Assuming that
the onset bump is due to the fireball deceleration by the external medium, we
examine the Gamma_0-Eiso relation and find that it is confirmed with the
current sample. Optical re-brightening is observed in 30 GRBs in our sample. It
shares the same relation between the width and the peak time as found in the
onset bump, but no clear correlation between the peak luminosity and Eiso as
observed in the onset bumps is found. Although its peak luminosity also decays
with time, the slope is much shallower than that of the onset peak. We get L
t^{-1}_{p}$, being consistent with off-axis observations to an expanding
external fireball in a wind-like circum medium. The late re-brightening may
signal another jet component. Mixing of different emission components may be
the reason for the observed chromatic breaks in different energy bands.Comment: 10 pages, 5 figures, to be published by IJMPD (Proceedings of "The
Third Galileo - Xu Guangqi meeting", Beijing, October 11-15, 2011
Computational Simulation of Comb-plate Expansion Joints
A finite element model of the expansion Joints’ common damages of a novel comb-plate by using the finite element software ABAQUS is presented in this paper. The mechanical behavior of expansion Joints is analyzed to verify the weak parts of it. The research results provide a reference for the design of the comb-plate expansion Joints
Approximation Algorithm for Unrooted Prize-Collecting Forest with Multiple Components and Its Application on Prize-Collecting Sweep Coverage
In this paper, we introduce a polynomial-time 2-approximation algorithm for
the Unrooted Prize-Collecting Forest with Components (URPCF) problem.
URPCF aims to find a forest with exactly connected components while
minimizing both the forest's weight and the penalties incurred by unspanned
vertices. Unlike the rooted version RPCF, where a 2-approximation algorithm
exists, solving the unrooted version by guessing roots leads to exponential
time complexity for non-constant . To address this challenge, we propose a
rootless growing and rootless pruning algorithm. We also apply this algorithm
to improve the approximation ratio for the Prize-Collecting Min-Sensor Sweep
Cover problem (PCMinSSC) from 8 to 5.
Keywords: approximation algorithm, prize-collecting Steiner forest, sweep
cover
Analysis in-Depth of the Factors that Impact the Development of E-Commerce in Underdeveloped Areas from the Perspective of Operating Process
The booming e-commerce has played an important role in the growth of regional economy and the e-commerce of underdeveloped regions has been developing rapidly as well. However, there is a large gap between underdeveloped and developed regions due to the limitation of economic foundation, geographical condition and other factors. The research of effects on the e-commerce development of underdeveloped regions played an important role in the promotion of e-commerce. Based on the perspective of operating process, starting from the indicator of information flow, capital flow and logistics, this article established the indicator system of effects on e-commerce in underdeveloped region. After collecting data by questionnaire survey, getting the right of each index by AHP and comparing the differences of important indicators between the en-commerce developments in the eastern and western important indicators, summarize the factors which affect the e-commerce development of underdeveloped regions, proposes to suggestions such as strengthen the guide of government functions and so on
Magnon dark modes and gradient memory
Extensive efforts have been expended in developing hybrid quantum systems to
overcome the short coherence time of superconducting circuits by introducing
the naturally long-lived spin degree of freedom. Among all the possible
materials, single-crystal yttrium iron garnet has shown up very recently as a
promising candidate for hybrid systems, and various highly coherent
interactions, including strong and even ultra-strong coupling, have been
demonstrated. One distinct advantage of these systems is that the spins are in
the form of well-defined magnon modes, which allows flexible and precise
tuning. Here we demonstrate that by dissipation engineering, a non-Markovian
interaction dynamics between the magnon and the microwave cavity photon can be
achieved. Such a process enables us to build a magnon gradient memory to store
information in the magnon dark modes, which decouple from the microwave cavity
and thus preserve a long life-time. Our findings provide a promising approach
for developing long-lifetime, multimode quantum memories.Comment: 18 pages, 12 figure
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