41,080 research outputs found
The branch processes of vortex filaments and Hopf Invariant Constraint on Scroll Wave
In this paper, by making use of Duan's topological current theory, the
evolution of the vortex filaments in excitable media is discussed in detail.
The vortex filaments are found generating or annihilating at the limit points
and encountering, splitting, or merging at the bifurcation points of a complex
function . It is also shown that the Hopf invariant of knotted
scroll wave filaments is preserved in the branch processes (splitting, merging,
or encountering) during the evolution of these knotted scroll wave filaments.
Furthermore, it also revealed that the "exclusion principle" in some chemical
media is just the special case of the Hopf invariant constraint, and during the
branch processes the "exclusion principle" is also protected by topology.Comment: 9 pages, 5 figure
Effect of deposition conditions and thermal annealing on the charge trapping properties of SiN[sub x] films
The density of charge trapping centers in SiNx:H films deposited by plasma enhanced chemical
vapor deposition is investigated as a function of film stoichiometry and postdeposition annealing
treatments. In the as-deposited films, the defect density is observed to increase with an increasing
N/Si ratio x in the range of 0.89–1.45, and to correlate with the N–H bond density. Following the
annealing in the temperature range of 500– 800 °C, the defect density increases for all N/Si ratios,
with the largest increase observed in the most Si rich samples. However, the defect density always
remains highest in the most N rich films. The better charge storage ability suggests the N rich films
are more suitable for the creation of negatively charged nitride films on solar cells.Financial support from
the Australian Research Council LP0883613 is gratefully
acknowledged
Superconductivity in heavily boron-doped silicon carbide
The discoveries of superconductivity in heavily boron-doped diamond (C:B) in
2004 and silicon (Si:B) in 2006 renew the interest in the superconducting state
of semiconductors. Charge-carrier doping of wide-gap semiconductors leads to a
metallic phase from which upon further doping superconductivity can emerge.
Recently, we discovered superconductivity in a closely related system:
heavily-boron doped silicon carbide (SiC:B). The sample used for that study
consists of cubic and hexagonal SiC phase fractions and hence this lead to the
question which of them participates in the superconductivity. Here we focus on
a sample which mainly consists of hexagonal SiC without any indication for the
cubic modification by means of x-ray diffraction, resistivity, and ac
susceptibility.Comment: 9 pages, 5 figure
High-Efficient Parallel CAVLC Encoders on Heterogeneous Multicore Architectures
This article presents two high-efficient parallel realizations of the context-based adaptive variable length coding (CAVLC) based on heterogeneous multicore processors. By optimizing the architecture of the CAVLC encoder, three kinds of dependences are eliminated or weaken, including the context-based data dependence, the memory accessing dependence and the control dependence. The CAVLC pipeline is divided into three stages: two scans, coding, and lag packing, and be implemented on two typical heterogeneous multicore architectures. One is a block-based SIMD parallel CAVLC encoder on multicore stream processor STORM. The other is a component-oriented SIMT parallel encoder on massively parallel architecture GPU. Both of them exploited rich data-level parallelism. Experiments results show that compared with the CPU version, more than 70 times of speedup can be obtained for STORM and over 50 times for GPU. The implementation of encoder on STORM can make a real-time processing for 1080p @30fps and GPU-based version can satisfy the requirements for 720p real-time encoding. The throughput of the presented CAVLC encoders is more than 10 times higher than that of published software encoders on DSP and multicore platforms
Recurrence interval analysis of high-frequency financial returns and its application to risk estimation
We investigate the probability distributions of the recurrence intervals
between consecutive 1-min returns above a positive threshold or
below a negative threshold of two indices and 20 individual stocks in
China's stock market. The distributions of recurrence intervals for positive
and negative thresholds are symmetric, and display power-law tails tested by
three goodness-of-fit measures including the Kolmogorov-Smirnov (KS) statistic,
the weighted KS statistic and the Cram\'er-von Mises criterion. Both long-term
and shot-term memory effects are observed in the recurrence intervals for
positive and negative thresholds . We further apply the recurrence interval
analysis to the risk estimation for the Chinese stock markets based on the
probability , Value-at-Risk (VaR) analysis and VaR analysis
conditioned on preceding recurrence intervals.Comment: 17 pages, 10 figures, 1 tabl
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