101,480 research outputs found
X-Ray Flares from Postmerger Millisecond Pulsars
Recent observations support the suggestion that short-duration gamma-ray
bursts are produced by compact star mergers. The X-ray flares discovered in two
short gamma-ray bursts last much longer than the previously proposed postmerger
energy release time scales. Here we show that they can be produced by
differentially rotating, millisecond pulsars after the mergers of binary
neutron stars. The differential rotation leads to windup of interior poloidal
magnetic fields and the resulting toroidal fields are strong enough to float up
and break through the stellar surface. Magnetic reconnection--driven explosive
events then occur, leading to multiple X-ray flares minutes after the original
gamma-ray burst.Comment: 10 pages, published in Scienc
Punch-through jets in collisions at RHIC/LHC
High single and dihadron production is studied within a NLO pQCD parton
model with jet quenching in high energy collisions at the RHIC/LHC
energy. A simultaneous -fit to both single and dihadron spectra can be
achieved within a narrow range of energy loss parameter. Punch-through jets are
found to result in the dihadron suppression factor slightly more sensitive to
medium than the single hadron suppression factor at RHIC. Such jets at LHC are
found to dominate high dihadron production and the resulting dihadron
spectra are more sensitive to the initial parton distribution functions than
the single hadron spectra.Comment: 4 pages, 4 figures, proceedings for the 20th international conference
on ultra-relativistic nucleus-nucleus collisions (QM2008), Jaipur, India,
February 4-10, 200
Superconductivity and Phase Diagram in (LiFe)OHFeSeS
A series of (LiFe)OHFeSeS (0 x 1)
samples were successfully synthesized via hydrothermal reaction method and the
phase diagram is established. Magnetic susceptibility suggests that an
antiferromagnetism arising from (LiFe)OH layers coexists with
superconductivity, and the antiferromagnetic transition temperature nearly
remains constant for various S doping levels. In addition, the lattice
parameters of the both a and c axes decrease and the superconducting transition
temperature T is gradually suppressed with the substitution of S for Se,
and eventually superconductivity vanishes at = 0.90. The decrease of T
could be attributed to the effect of chemical pressure induced by the smaller
ionic size of S relative to that of Se, being consistent with the effect of
hydrostatic pressure on (LiFe)OHFeSe. But the detailed
investigation on the relationships between and the crystallographic
facts suggests a very different dependence of on anion height from
the Fe2 layer or -Fe2- angle from those in FeAs-based superconductors.Comment: 6 pages, 6 figure
A NLO analysis on fragility of dihadron tomography in high energy collisions
The dihadron spectra in high energy collisions are studied within the
NLO pQCD parton model with jet quenching taken into account. The high
dihadron spectra are found to be contributed not only by jet pairs close and
tangential to the surface of the dense matter but also by punching-through jets
survived at the center while the single hadron high spectra are only
dominated by surface emission. Consequently, the suppression factor of such
high- hadron pairs is found to be more sensitive to the initial gluon
density than the single hadron suppression factor.Comment: 4 pages, 4 figures, proceedings for the 19th international Conference
on ultra-relativistic nucleus-nucleus collisions (QM2006), Shanghai, China,
November 14-20, 200
Compact Circularly Polarized Patch Antenna Using a Composite Right/Left-Handed Transmission Line Unit-Cell
A compact circularly polarized (CP) patch antenna using a composite right/left-handed (CRLH) transmission line (TL) unit-cell is proposed. The CRLH TL unit-cell includes a complementary split ring resonator (CSRR) for shunt inductance and a gap loaded with a circular-shaped slot for series capacitance. The CSRR can decrease the TM10 mode resonance frequency, thus reducing the electrical size of the proposed antenna. In addition, the asymmetry of the CSRR brings about the TM01 mode, which can be combined with the TM10 mode by changing the slot radius. The combination of these two orthogonal modes with 90° phase shift makes the proposed antenna provide a CP property. The experimental results show that the proposed antenna has a wider axial ratio bandwidth and a smaller electrical size than the reported CP antennas. Moreover, the proposed antenna is designed without impedance transformer, 90° phase shift, dual feed and ground via
Numerical Simulation of Quartz Tube Solid Particle Air Receiver
AbstractThe quartz tube solid particle air receiver is a new type of solar receiver in which fluidized particles absorb the solar radiation directly and heat the air effectively, improving the efficiency of solar thermal power generation and reducing costs. In this article, transient numerical simulation was conducted to simulate the heat transfer and flow processes in single quartz tube under concentrated solar radiation. The results showed that the distribution of solid particles temperature was uniform in the fluidized region, which could overcome the problem of overheating in the volumetric solar receiver. The temperature difference between solid particles and air was no more than 25K, indicating that heat transfer between particles and air was very effective. Further, as the direct solar radiation increased, the average air temperature in the outlet increased while the thermal efficiency decreased. The high tube wall temperature caused heat loss to the environment by radiative and convective heat transfer. With the air inlet velocity increasing, the averaging air temperature in the outlet decreased while the efficiency of the receiver increased. The simulation results provided important reference for improving the performance of the quartz tube solid particle air receiver
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