155,411 research outputs found
A VLSI architecture of JPEG2000 encoder
Copyright @ 2004 IEEEThis paper proposes a VLSI architecture of JPEG2000 encoder, which functionally consists of two parts: discrete wavelet transform (DWT) and embedded block coding with optimized truncation (EBCOT). For DWT, a spatial combinative lifting algorithm (SCLA)-based scheme with both 5/3 reversible and 9/7 irreversible filters is adopted to reduce 50% and 42% multiplication computations, respectively, compared with the conventional lifting-based implementation (LBI). For EBCOT, a dynamic memory control (DMC) strategy of Tier-1 encoding is adopted to reduce 60% scale of the on-chip wavelet coefficient storage and a subband parallel-processing method is employed to speed up the EBCOT context formation (CF) process; an architecture of Tier-2 encoding is presented to reduce the scale of on-chip bitstream buffering from full-tile size down to three-code-block size and considerably eliminate the iterations of the rate-distortion (RD) truncation.This work was supported in part by the China National High Technologies Research Program (863) under Grant 2002AA1Z142
The Numerical Solution of Scalar Field for Nariai Case in 5D Ricci-flat SdS Black String Space with Polynomial Approximation
As one exact candidate of the higher dimensional black hole, the 5D
Ricci-flat Schwarzschild-de Sitter black string space presents something
interesting. In this paper, we give a numerical solution to the real scalar
field around the Nariai black hole by the polynomial approximation. Unlike the
previous tangent approximation, this fitting function makes a perfect match in
the leading intermediate region and gives a good description near both the
event and the cosmological horizons. We can read from our results that the wave
is close to a harmonic one with the tortoise coordinate. Furthermore, with the
actual radial coordinate the waves pile up almost equally near the both
horizons.Comment: 8 pages, 4 figure
A study of the parity-odd nucleon-nucleon potential
We investigate the parity-violating nucleon-nucleon potential as obtained in
chiral effective field theory. By using resonance saturation we compare the
chiral potential to the more traditional one-meson exchange potential. In
particular, we show how parameters appearing in the different approaches can be
compared with each other and demonstrate that analyses of parity violation in
proton-proton scattering within the different approaches are in good agreement.
In the second part of this work, we extend the parity-violating potential to
next-to-next-to-leading order. We show that generally it includes both
one-pion- and two-pion-exchange corrections, but the former play no significant
role. The two-pion-exchange corrections depend on five new low-energy constants
which only become important if the leading-order weak pion-nucleon constant
turns out to be very small.Comment: Published versio
Intra-day variability observations and the VLBI structure analysis of quasar S4 0917+624
The IDV observations of S4 0917+624 were carried out monthly, from August
2005 to January 2010, with the Urumqi 25m radio telescope at 4.8 GHz. The
quasar S4 0917+624 exhibits only very weak or no IDV during our 4.5 year
observing interval. Prior to the year 2000, the source S4 0917+624 was one of
the most prominent IDV sources. Our new data indicate that the previous strong
IDV has ceased. We analyzed the long-term VLBI structural variability using
Gaussian model-fitting. From this we obtained the flux densities and the
deconvolved sizes of core and inner-jet components of the source. We studied
the properties such as core fraction, angular size, spectral index, and
brightness temperature of VLBI core for S4 0917+624, as well as the time delay
between 5 and 15 GHz variations, and compared them with the IDV properties of
S4 0917+624. The source shows ejection of several jet components that are
suspected to have partially reduced the IDV amplitude of S4 0917+624. However,
during 2005-2006, the VLBI core size was comparable to the size before the year
2000, but no strong IDV was detected in the period, suggesting that the
quenching effect due to source size changes may not be responsible for the lack
of strong IDV after the year 2000. The refractive scattering properties for the
strong IDV phase of S4 0917+624 before the year 2000 are discussed. The
disappearance of strong IDV in S4 0917+624 after the year 2000 is a mystery and
cannot be explained via the quenching effect by changes in the observable VLBI
structure. However, it may be caused by changes in the interstellar medium,
i.e. by interstellar weather, which induces changes in the scintillation
pattern on timescales of several years. Further coordinated multi-frequency
observations will be required to distinguish between the effect of
source-intrinsic variability and changing properties of the interstellar
medium.Comment: 8 pages, 6 figures, accepted for publication in A&
Integer quantum Hall effect and topological phase transitions in silicene
We numerically investigate the effects of disorder on the quantum Hall effect
(QHE) and the quantum phase transitions in silicene based on a lattice model.
It is shown that for a clean sample, silicene exhibits an unconventional QHE
near the band center, with plateaus developing at and
a conventional QHE near the band edges. In the presence of disorder, the Hall
plateaus can be destroyed through the float-up of extended levels toward the
band center, in which higher plateaus disappear first. However, the center
Hall plateau is more sensitive to disorder and disappears at a
relatively weak disorder strength. Moreover, the combination of an electric
field and the intrinsic spin-orbit interaction (SOI) can lead to quantum phase
transitions from a topological insulator to a band insulator at the charge
neutrality point (CNP), accompanied by additional quantum Hall conductivity
plateaus.Comment: 7 pages, 4 figure
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