82,880 research outputs found
The timing behavior of magnetar Swift J1822.3-1606: timing noise or a decreasing period derivative?
The different timing results of the magnetar Swift J1822.3-1606 is analyzed
and understood theoretically. It is pointed that different timing solutions are
caused not only by timing noise, but also that the period derivative is
decreasing after outburst. Both the decreasing period derivative and the large
timing noise may be originated from wind braking of the magnetar. Future timing
of Swift J1822.3-1606 will help us make clear whether its period derivative is
decreasing with time or not.Comment: 5 pages, 1 figure. Accepted by Research in Astronomy and Astrophysic
Mixed Power Control Strategies for Cognitive Radio Networks under SINR and Interference Temperature Constraints
Without consideration of the minimum signal-to-interference-plus-noise ratio (SINR) and frequent information exchange, traditional power control algorithms can not always satisfy SINR requirements of secondary users (SUs) and primary users (PUs) in cognitive radio networks. In this paper, a distributed power control problem for maximizing total throughput of SUs is studied subject to the SINR constraints of SUs and the interference constraints of PUs. To reduce message exchange among SUs, two improved methods are obtained by dual decomposition approaches. For a large-scale network, an average interference constraint is presented at the cost of performance degradation. For a small-scale network, a weighted interference constraint with fairness consideration is proposed to obtain good performance. Simulation results demonstrate that the proposed algorithm is superior to ADCPC and TPCG algorithms
Control of fast electron propagation in foam target by high-Z doping
The influence of high-Z dopant (Bromine) in low-Z foam (polystyrene) target
on laser-driven fast electron propagation is studied by the 3D hybrid
particle-in-cell (PIC)/fluid code HEETS.It is found that the fast electrons are
better confined in doped targets due to the increasing resistivity of the
target, which induces a stronger resistive magnetic field which acts to
collimate the fast electron propagation.The energy deposition of fast electrons
into the background target is increased slightly in the doped target, which is
beneficial for applications requiring long distance propagation of fast
electrons, such as fast ignition
The optical/UV excess of isolated neutron stars in the RCS model
The X-ray dim isolated neutron stars (XDINSs) are peculiar pulsar-like
objects, characterized by their very well Planck-like spectrum. In studying
their spectral energy distributions, the optical/UV excess is a long standing
problem. Recently, Kaplan et al. (2011) have measured the optical/UV excess for
all seven sources, which is understandable in the resonant cyclotron scattering
(RCS) model previously addressed. The RCS model calculations show that the RCS
process can account for the observed optical/UV excess for most sources . The
flat spectrum of RX J2143.0+0654 may due to contribution from bremsstrahlung
emission of the electron system in addition to the RCS process.Comment: 6 pages, 2 figures, 1 table, accepted for publication in Research in
Astronomy and Astrophysic
Reconstruction of Cosmological Models From Equation of State of Dark Energy
We consider a class of five-dimensional cosmological solutions which contains
two arbitrary function and . We found that the arbitrary
function contained in the solutions can be rewritten in terms of the
redshift as a new arbitrary function . We further showed that this
new arbitrary function could be solved out for four known parameterized
equations of state of dark energy. Then the models can be reconstructed
and the evolution of the density and deceleration parameters of the universe
can be determined.Comment: 10 pages, 4 eps figures, ws-ijmpd.cls styl
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