4,726 research outputs found
Wavelet-based video codec using human visual system coefficients for 3G mobiles
A new wavelet based video codec that uses human visual system coefficients is presented. In INTRA mode of operation, wavelet transform is used to split the input frame into a number of subbands. Human Visual system coefficients are designed for handheld videophone devices and used to regulate the quantization stepsize in the pixel quantization of the high frequency subbands’ coefficients. The quantized coefficients are coded using quadtreecoding scheme. In the INTER mode of operation, the displaced frame difference is generated and a wavelet transform decorrelates it into a number of subbands. These subbands are coded using adaptive vector quantization scheme. Results indicate a significant improvement in frame quality compared to motion JPEG200
Some Quantitative Characterizations of Certain Symplectic Groups
Given a finite group , denote by the degree pattern of
and by the set of all order components of . Denote by (resp. ) the number of isomorphism classes of finite
groups satisfying conditions and (resp.
). A finite group is called OD-characterizable
(resp. OC-characterizable) if (resp. ). Let
be a symplectic group over binary field, for which is a
Mersenne prime. The aim of this article is to prove that
Spin Exciton Formation inside the Hidden Order Phase of CeB6
The heavy fermion metal CeB6 exhibits hidden order of antiferroquadrupolar
(AFQ) type below T_Q=3.2K and subsequent antiferromagnetic (AFM) order at
T_N=2.3K. It was interpreted as ordering of the quadrupole and dipole moments
of a quartet of localised Ce electrons. This established
picture has been profoundly shaken by recent inelastic neutron scattering (G.
Friemel et al., arXiv:1111.4151) that found the evolution of a feedback spin
exciton resonance within the hidden order phase at the AFQ wave vector which is
stabilized by the AFM order. We develop an alternative theory based on a
fourfold degenerate Anderson lattice model, including both order parameters as
particle-hole condensates of itinerant heavy quasiparticles. This explains in a
natural way the appearance of the spin exciton resonance and the momentum
dependence of its spectral weight, in particular around the AFQ vector and its
rapid disappearance in the disordered phase. Analogies to the feedback effect
in unconventional heavy fermion superconductors are pointed out.Comment: 5 pages, 3 figure
A Classical String in Lifshitz-Vaidya Geometry
We study the time evolution of the expectation value of a rectangular Wilson
loop in strongly anisotropic time-dependent plasma using gauge-gravity duality.
The corresponding gravity theory is given by describing time evolution of a
classical string in the Lifshitz-Vaidya background. We show that the
expectation value of the Wilson loop oscillates about the value of the static
potential with the same parameters after the energy injection is over. We
discuss how the amplitude and frequency of the oscillation depend on the
parameters of the theory. In particular, by raising the anisotropy parameter,
we observe that the amplitude and frequency of the oscillation increase.Comment: 19 pages, 5 figure
Quasiparticle interference in iron-based superconductors
We systematically calculate quasiparticle interference (QPI) signatures for
the whole phase diagram of iron-based superconductors. Impurities inherent in
the sample together with ordered phases lead to distinct features in the QPI
images that are believed to be measured in spectroscopic imaging-scanning
tunneling microscopy (SI-STM). In the spin-density wave phase the rotational
symmetry of the electronic structure is broken, signatures of which are also
seen in the coexistence regime with both superconducting and magnetic order. In
the superconducting regime we show how the different scattering behavior for
magnetic and non-magnetic impurities allows to verify the symmetry of
the order parameter. The effect of possible gap minima or nodes is discussed.Comment: 19 pages, 7 figure
Average energy efficiency contours with multiple decoding policies
This letter addresses energy-efficient design in multi-user, single-carrier uplink channels by employing multiple decoding policies. The comparison metric used in this study is based on average energy efficiency contours, where an optimal rate vector is obtained based on four system targets: Maximum energy efficiency, a trade-off between maximum energy efficiency and rate fairness, achieving energy efficiency target with maximum sum-rate and achieving energy efficiency target with fairness. The transmit power function is approximated using Taylor series expansion, with simulation results demonstrating the achievability of the optimal rate vector, and negligible performance difference in employing this approximation
Incorporating family function into chronic pain disability: the role of catastrophizing
Background. Observers' responses to pain are recently investigated to more comprehensively explain chronic pain (CP) and disability. However, the role of family context, defined as interference in roles, communication, and problem-solving, and how (i.e., through which mechanisms) these variables contribute to CP related disability have yet to be examined. Objectives. The aim of the present study is to examine family context in relationship to pain catastrophizing, fear of movement, and depression and its role in understanding CP disability. Three different models were examined. Methods. A total sample of 142 patients with musculoskeletal chronic pain was recruited to examine the role of fear of movement, pain intensity, pain catastrophizing, and depression in relationship to family functioning as predictors of disability. Results. Findings indicated that two models showed acceptable fit, but one of them revealed superior fit indices. Results of the model with superior fit indices indicated that family dysfunction may contribute to catastrophic thinking, which, in turn, contributes to patients' disability through increasing fear of movement and depression. Discussion. The current study provides further support for the notion that the impact of emotional and cognitive variables upon CP-related disability can be better understood when we consider the social context of pain patients and family function in particular
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