7,114 research outputs found
Dependence of Temporal Properties on Energy in Long-Lag, Wide-Pulse Gamma-Ray Bursts
We employed a sample compiled by Norris et al. (2005, ApJ, 625, 324) to study
the dependence of the pulse temporal properties on energy in long-lag,
wide-pulse gamma-ray bursts. Our analysis shows that the pulse peak time, rise
time scale and decay time scale are power law functions of energy, which is a
preliminary report on the relationships between the three quantities and
energy. The power law indexes associated with the pulse width, rise time scale
and decay time scale are correlated and the correlation between the indexes
associated with the pulse width and the decay time scale is more obvious. In
addition, we have found that the pulse peak lag is strongly correlated with the
CCF lag, but the centroid lag is less correlated with the peak lag and CCF lag.
Based on these results and some previous investigations, we tend to believe
that all energy-dependent pulse temporal properties may come from the joint
contribution of both the hydrodynamic processes of the outflows and the
curvature effect, where the energy-dependent spectral lag may be mainly
dominated by the dynamic process and the energy-dependent pulse width may be
mainly determined by the curvature effect.Comment: 20 pages, 7 figures, added references, matched to published version,
accepted for publication in PAS
Method of determining cosmological parameter ranges with samples of candles with an intrinsic distribution
In this paper, the effect of the intrinsic distribution of cosmological
candles is investigated. We find that, in the case of a narrow distribution,
the deviation of the observed modulus of sources from the expected central
value could be estimated within a ceratin range. We thus introduce a lower and
upper limits of , and , to
estimate cosmological parameters by applying the conventional minimizing method. We apply this method to a gamma-ray burst (GRB) sample as well as
to a combined sample including this GRB sample and an SN Ia sample. Our
analysis shows that: a) in the case of assuming an intrinsic distribution of
candles of the GRB sample, the effect of the distribution is obvious and should
not be neglected; b) taking into account this effect would lead to a poorer
constraint of the cosmological parameter ranges. The analysis suggests that in
the attempt of constraining the cosmological model with current GRB samples,
the results tend to be worse than what previously thought if the mentioned
intrinsic distribution does exist.Comment: 6 pages,4 figures,1 tables.Data updated. Main conclusion unchange
Characteristics of profiles of gamma-ray burst pulses associated with the Doppler effect of fireballs
In this paper, we derive in a much detail the formula of count rates, in
terms of the integral of time, of gamma-ray bursts in the framework of
fireballs, where the Doppler effect of the expanding fireball surface is the
key factor to be concerned. Effects arising from the limit of the time delay
due to the limited regions of the emitting areas in the fireball surface and
other factors are investigated. Our analysis shows that the formula of the
count rate of fireballs can be expressed as a function of which is the
observation time scale relative to the dynamical time scale of the fireball.
The profile of light curves of fireballs depends only on the relative time
scale, entirely independent of the real time scale and the real size of the
objects. It displays in detail how a cutoff tail, or a turn over, feature
(called a cutoff tail problem) in the decay phase of a light curve can be
formed. This feature is a consequence of a hot spot in the fireball surface,
moving towards the observer, and was observed in a few cases previously. By
performing fits to the count rate light curves of six sample sources, we show
how to obtain some physical parameters from the observed profile of the count
rate of GRBs. In addition, the analysis reveals that the Doppler effect of
fireballs could lead to a power law relationship between the of pulses
and energy, which were observed previously by many authors.Comment: 38 pages, 10 figures; accepted for publication in ApJ (10 December
2004, v617
Quantum Robot: Structure, Algorithms and Applications
A kind of brand-new robot, quantum robot, is proposed through fusing quantum
theory with robot technology. Quantum robot is essentially a complex quantum
system and it is generally composed of three fundamental parts: MQCU (multi
quantum computing units), quantum controller/actuator, and information
acquisition units. Corresponding to the system structure, several learning
control algorithms including quantum searching algorithm and quantum
reinforcement learning are presented for quantum robot. The theoretic results
show that quantum robot can reduce the complexity of O(N^2) in traditional
robot to O(N^(3/2)) using quantum searching algorithm, and the simulation
results demonstrate that quantum robot is also superior to traditional robot in
efficient learning by novel quantum reinforcement learning algorithm.
Considering the advantages of quantum robot, its some potential important
applications are also analyzed and prospected.Comment: 19 pages, 4 figures, 2 table
Theoretical Study for Detection of Defects in Weakly Absorbing Samples by Crossed-Beam Photothermal Technique
The photothermal techniques have been successfully applied as tools for nondestructive evaluation (NDE) of inhomogeneous materials. For optically opaque samples, photothermal techniques are widely used for detection and characterization of subsurface defects and interfaces within the samples [1,2]. For optically transparent samples, photothermal techniques are used for absorption mapping of thin films deposited on optical substrates [3], biological and medical samples [4 ]. Due to nondestructive micro-analyses is very important for studies of thin films and interfaces, as well as biological, and medical samples. Photothermal techniques with two crossed-beams are developed for highly spatially resolved detection, in which the excitation and probe beams interact only in the intersection volume, therefore very high spatial resolution in three dimensions can be achieved by tightly focusing both beams. Highly resolved depth profiling of weakly absorbing samples can be achieved with the photothermal crossed-beam techniques by scanning either the samples or the intersection point of both beams along the depth direction. The optical absorbency or thermal conductivity inhomogeneities of small, localized regions within larger samples can be detected by the technique. In this paper the theoretical investigation on the depthprofiling capability of the crossed-beam photothermal deflection (PTD) is described in detail. The theoretical results provide quantitative evaluation for depth-profiling capability of weakly absorbing samples with crossed-beam photothermal techniques
RIS-Assisted Self-Interference Mitigation for In-Band Full-Duplex Transceivers
The wireless in-band full-duplex (IBFD) technology can in theory double the
system capacity over the conventional frequency division duplex (FDD) or
time-division duplex (TDD) alternatives. But the strong self-interference of
the IBFD can cause excessive quantization noise in the analog-to-digital
converters (ADC), which represents the hurdle for its real implementation. In
this paper, we consider employing a reconfigurable intelligent surface (RIS)
for IBFD communications. While the BS transmits and receives the signals to and
from the users simultaneously on the same frequency band, it can adjust the
reflection coefficients of the RIS to configure the wireless channel so that
the self-interference of the BS is sufficiently mitigated in the propagation
domain. Taking the impact of the quantization noise into account, we propose to
jointly design the downlink (DL) precoding matrix and the RIS coefficients to
maximize the sum of uplink (UL) and DL rates. The effectiveness of the proposed
RIS-assisted in-band full-duplex (RAIBFD) system is verified by simulation
studies, even taking into considerations that the phases of the RIS have only
finite resolution.Comment: 11 page
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