12,897 research outputs found
Asymptotic behavior of global entropy solutions for nonstrictly hyperbolic systems with linear damping
In this paper we investigate the large time behavior of the global weak
entropy solutions to the symmetric Keyftiz-Kranzer system with linear damping.
It is proved that as t tends to infinite the entropy solutions tend to zero in
the L p nor
Fast Adaptive S-ALOHA Scheme for Event-driven Machine-to-Machine Communications
Machine-to-Machine (M2M) communication is now playing a market-changing role
in a wide range of business world. However, in event-driven M2M communications,
a large number of devices activate within a short period of time, which in turn
causes high radio congestions and severe access delay. To address this issue,
we propose a Fast Adaptive S-ALOHA (FASA) scheme for M2M communication systems
with bursty traffic. The statistics of consecutive idle and collision slots,
rather than the observation in a single slot, are used in FASA to accelerate
the tracking process of network status. Furthermore, the fast convergence
property of FASA is guaranteed by using drift analysis. Simulation results
demonstrate that the proposed FASA scheme achieves near-optimal performance in
reducing access delay, which outperforms that of traditional additive schemes
such as PB-ALOHA. Moreover, compared to multiplicative schemes, FASA shows its
robustness even under heavy traffic load in addition to better delay
performance.Comment: 5 pages, 3 figures, accepted to IEEE VTC2012-Fal
The Effect of Agenda for Change on the Career Progression of the Radiographic Workforce 2009
Report compiled by the University of Hertfordshire in collaboration with the Inst for Employment Studies and Oxford Radcliffe Hospitals NHS Trust for the Society and College of RadiographersFinal Published versio
Optimization of thin n-in-p planar pixel modules for the ATLAS upgrade at HL-LHC
The ATLAS experiment will undergo around the year 2025 a replacement of the
tracker system in view of the high luminosity phase of the LHC (HL-LHC) with a
new 5-layer pixel system. Thin planar pixel sensors are promising candidates to
instrument the innermost region of the new pixel system, thanks to the reduced
contribution to the material budget and their high charge collection efficiency
after irradiation. The sensors of 50-150 m thickness, interconnected to
FE-I4 read-out chips, have been characterized with radioactive sources and beam
tests. In particular active edge sensors have been investigated. The
performance of two different versions of edge designs are compared: the first
with a bias ring, and the second one where only a floating guard ring has been
implemented. The hit efficiency at the edge has also been studied after
irradiation at a fluence of \neqcm. Highly segmented sensors will
represent a challenge for the tracking in the forward region of the pixel
system at HL-LHC. In order to reproduce the performance of 50x50 m
pixels at high pseudo-rapidity values, FE-I4 compatible planar pixel sensors
have been studied before and after irradiation in beam tests at high incidence
angles with respect to the short pixel direction. Results on the hit efficiency
in this configuration are discussed for different sensor thicknesses
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