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991.
992.
993.
Hard photon emitted from energetic heavy ion collisions is of very interesting since it does not experience the late-stage nuclear interaction, therefore it is useful to explore the early-stage information of matter phase. In this work, we have calculated the impact parameter and beam energy dependence for azimuthal asymmetry, characterized by directed transverse flow parameter F and elliptic asymmetry coefficient v2, of direct photons and the corresponding free protons in intermediate energy heavy-ion collisions. It is further shown the anti-correlated azimuthal asymmetry between direct photons and free protons. 相似文献
994.
If the incident angle of a light beam on the boundary surface between the thin metal film of a surface plasmon resonance (SPR) apparatus and a test medium is equal to or very near the resonant angle, then the phase difference between the p- and s-polarizations of the reflected light is related to the associated physical parameter. The phase difference can be measured accurately with heterodyne interferometry. If the relationship between the phase difference and the associated physical parameter is specified, then the associated physical parameter can be estimated from the phase difference data. This method has the benefits of both common-path interferometry and heterodyne interferometry, such as simple structure, high stability, high resolution, easy operation, and rapid real-time measurement. 相似文献
995.
We investigate Bianchi type V cosmological models with bulk viscous fluid source. Exact solutions of the Einstein field equations
are presented via a suitable power law assumption for the Hubble parameter. We show that the corresponding solutions retain
the well established features of the standard cosmology and in addition, are in accordance with recent type Ia supernovae
observations. Some observational parameters for the models have also been discussed. 相似文献
996.
David K. Anthony 《Applied Acoustics》2009,70(9):1219-1225
For a single degree of freedom system, especially with non-light damping, the use of the real spectral part of either the displacement or velocity responses (or the transfer functions based on them) has the advantages of determining the natural frequency (fn) directly, independent of the response parameter, and providing an accurate measurement for damping (ζ). However, this method is sensitive to spectral phase errors due to temporal misalignment of the signal or due to net inter-channel delay differences caused by signal filtering. Two techniques are presented to correct for these errors; one based on the correct temporal alignment of the impulsive part, and the other on the infimum of the imaginary spectral part. These are first demonstrated using a numerical model, and are shown to facilitate the correct measurement of fn and bring ζ within the expected error limits due to quantisation. Secondly, they are applied to an experimental system and are seen to greatly improve the consistency between measurements using different methods. 相似文献
997.
In three-dimensional (3D) freehand ultrasound (US), reconstructing a set of B-scans into a regular voxel array is the key procedure for consequent visualization and analysis. This paper presents a new adaptive interpolation algorithm for computing the voxel array to suppress speckle noises and enhance contrast. The local statistics of homogeneous regions including mean and variance were measured and the ratio of variance to mean was used as homogeneity criteria. For the computation of each voxel, the interpolation method was adaptively determined with respect to its local statistics. If the neighbouring pixels of a voxel satisfied the homogeneity criterion, its value was computed with an arithmetic mean filter. Otherwise, the voxel was probably locating in an inhomogeneous region and an adaptive distance-weighted (ADW) interpolation method was employed to compute its value. A resolution phantom and a subject’s forearm were reconstructed using the proposed algorithm and two other well-known methods - conventional distance-weighted (DW) and voxel nearest neighbourhood (VNN) interpolations. The comparison results demonstrated that the adaptive interpolation algorithm was able to suppress speckles, preserve edges and enhance contrast effectively for the volume reconstruction. 相似文献
998.
Saibal Ray P. C. Ray M. Khlopov P. P. Ghosh U. Mukhopadhyay P. Chowdhury 《International Journal of Theoretical Physics》2009,48(9):2499-2510
Choosing the three phenomenological models of the dynamical cosmological term Λ, viz.,
,
and Λ∼ρ where a is the cosmic scale factor, it has been shown by the method of numerical analysis for the considered non-linear differential
equations that the three models are equivalent for the flat Universe k=0 and for arbitrary non-linear equation of state. The evolution plots for dynamical cosmological term Λ vs. time t and also the cosmic scale factor a vs. t are drawn here for k=0,+1. A qualitative analysis has been made from the plots which supports the idea of inflation and hence expanding Universe. 相似文献
999.
R. Chaubey 《International Journal of Theoretical Physics》2009,48(4):952-960
We have studied the evolution of a homogeneous, anisotropic universe given by a Bianchi type-I cosmological model with modified
Chaplygin gas. We have assumed that the equation of state of this modified model is valid from the radiation era to the ΛCMD
model. We have used state-finder parameters in characterizing different phase of the model. 相似文献
1000.
The paper presents a spatially homogeneous and anisotropic Bianchi type-I cosmological model consisting of a dissipative fluid.
The field equations are solved explicitly by using a law of variation for mean Hubble parameter, which is related to average
scale factor and yields a constant value for deceleration parameter. We find that the constant value of deceleration parameter
describes the different phases of the evolution of universe. A barotropic equation of state (p=γ
ρ) together with a linear relation between shear viscosity and expansion scalar, is assumed. It is found that the viscosity
plays a key role in the process of the isotropization of the universe. The presence of viscous term does not change the fundamental
nature of initial singularity. The thermodynamical properties of the solutions are studied and the entropy distribution is
also given explicitly. 相似文献