17,501 research outputs found
Some issues about neutrino processes in color superconducting quark matter
Several relevant issues in computing neutrino emissivity in Urca processes in
color superconducting quark matter are addressed. These include: (1) The
constraint on quark abundance is given from electric neutrality and the
triangle relation among Fermi momenta for participants. (2) The phase space
defined by Fermi momentum reduction of quarks is discussed in QCD and NJL
model. (3) Fermi effective model of weak interaction is reviewed with special
focus on its form in Nambu-Gorkov basis.Comment: Contribution to the proceedings of the Sixth China-Japan Joint
Nuclear Physics Symposium, May 16-20, Shanghai China. aipproc format, 8
pages, 5 figure
On the Regularity for 3D Navier-Stokes Equation
This paper deals with the influence of boundary values on the regularity of
3D incompressible Navier-Stokes equation, which is separated into two parts:
First part, we consider the potential theory of unsteady 3D Stokes flow. In
order to consider Dirichlet and Neumann boundary values, we establish the
Green's formula, and then give the double layer and single layer potentials.
Second part, based on problems separated and the potential theory we reach the
integral representations of the solutions with respect to Dirichlet and Neumann
boundary conditions. Consequently we change the integral representations of
solutions from velocity form into vorticity form so that we can construct
schemes in favor of numerical computation in this way. Finally we analyze the
regularity of the initial-boundary value problems for Navier-Stokes equation,
and obtain regular solutions by assuming the regularity on the boundary and
data.Comment: modificatio
Sidelobe Suppression for Capon Beamforming with Mainlobe to Sidelobe Power Ratio Maximization
High sidelobe level is a major disadvantage of the Capon beamforming. To
suppress the sidelobe, this paper introduces a mainlobe to sidelobe power ratio
constraint to the Capon beamforming. it minimizes the sidelobe power while
keeping the mainlobe power constant. Simulations show that the obtained
beamformer outperforms the Capon beamformer.Comment: 8 pages, 2 figure
Enhanced Compressive Wideband Frequency Spectrum Sensing for Dynamic Spectrum Access
Wideband spectrum sensing detects the unused spectrum holes for dynamic
spectrum access (DSA). Too high sampling rate is the main problem. Compressive
sensing (CS) can reconstruct sparse signal with much fewer randomized samples
than Nyquist sampling with high probability. Since survey shows that the
monitored signal is sparse in frequency domain, CS can deal with the sampling
burden. Random samples can be obtained by the analog-to-information converter.
Signal recovery can be formulated as an L0 norm minimization and a linear
measurement fitting constraint. In DSA, the static spectrum allocation of
primary radios means the bounds between different types of primary radios are
known in advance. To incorporate this a priori information, we divide the whole
spectrum into subsections according to the spectrum allocation policy. In the
new optimization model, the minimization of the L2 norm of each subsection is
used to encourage the cluster distribution locally, while the L0 norm of the L2
norms is minimized to give sparse distribution globally. Because the L0/L2
optimization is not convex, an iteratively re-weighted L1/L2 optimization is
proposed to approximate it. Simulations demonstrate the proposed method
outperforms others in accuracy, denoising ability, etc.Comment: 23 pages, 6 figures, 4 table. arXiv admin note: substantial text
overlap with arXiv:1005.180
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