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1.
Modal analysis of structural acoustic radiation from a vibrating structure is discussed using structural vibration modes and acoustic radiation modes based on the quadratic form of acoustic power. The finite element method is employed for discretisizing the structure. The boundary element method and Rayleigh integral are used for modeling the acoustic fluid. It is shown that the power radiated by a single vibration mode is to increase the radiated power and the effect of modal interaction can lead to an increase or a decrease or no change in the radiated power, moreover, control of vibration modes is a good way to reduce both vibration and radiated sound as long as the influence of interaction of vibration modes on sound radiation is insignificant. Stiffeners may change mode shapes of a plate and thus change radiation efficiency of the plate‘s modes. The CHIEF method is adopted to obtain an acoustic radiation mode formulation without the nonuniqueness difficulty at critical frequencies for three-dimensional structures by using Moore-Penrose inverse. A pulsating cube is involved to verify the formulation. Good agreement is obtained between the numerical and analytical solutions. The shapes and radiation efficiencies of acoustic radiation modes of the cube are discussed. The structural acoustic control using structural vibration modes and acoustic radiation modes are compared and studied.  相似文献   

2.
A Lower Bound on the Entanglement in the Jaynes-Cummings Model   总被引:1,自引:0,他引:1       下载免费PDF全文
蔡金芳  邹健 《中国物理快报》2005,22(7):1584-1587
The entanglement between an atom and field is investigated by using the 3aynes-Cummings model. The initial atomic state is supposed in a mixed state and the field is in a squeezed state. The lower bound on the entanglement quantified by concurrence is calculated. It is found that the entanglement with the atom being initially in a mixed state can be larger than that with the atom being initially in a pure state. The entanglement is not a monotone function of the squeezing parameter r of the field and it achieves the maximum for certain r and then decreases with further increase of r.  相似文献   

3.
In a three-dimensional off-lattice model,the method of Shakhnovich and Gutin for minimizing the Hamiltonian is applied to the design of a protein-model chain.The effect of the number of hydrophobic and hydrophilic monomer types on the designability of a protein-model chain is investigated.The simulation results reveal that the number of hydrophobic monomer types is a much more important factor than that of the polar monomer types in the design of a protein-model chain.  相似文献   

4.
王行翔 《中国物理快报》2006,23(7):1702-1704
The Bianchi type-Ⅲ cosmological model for a cloud string in the presence of bulk viscosity and magnetic field are presented. To obtain the determinate model it is assumed that there is an equation of state ρ = kA and the scalar of expansion is proportional to the shear scalar θ ∝ σ, which leads to a relation between metric potentials B = mC^n. The physical and geometric aspects of the model are also discussed. The model describes a shearing non-rotating continuously expanding universe with a big-bang start. In the absence of magnetic field, it reduces to the string model with bulk viscosity that was previously given in the literature.  相似文献   

5.
A nonlinear money exchange model is revised and a correct master equation is derived. The evolution of the distribution is studied from direct numerical and analytical calculations. The stability of the final steady state of the system is investigated. It is argued that the final distribution is valid for a group of conservative money exchange models.  相似文献   

6.
A fuzzy Wiener model is proposed to identify chaotic systems. The proposed fuzzy Wiener model consists of two parts, one is a linear dynamic subsystem and the other is a static nonlinear part, which is represented by the Takagi-Sugeno fuzzy model. Identification of chaotic systems is converted to find optimal parameters of the fuzzy Wiener model by minimizing the state error between the original chaotic system and the fuzzy Wiener model. Particle swarm optimization algorithm, a global optimizer, is used to search the optimal parameter of the fuzzy Wiener model. The proposed method can identify the parameters of the linear part and nonlinear part simultaneously. Numerical simulations for Henon and Lozi chaotic system identification show the effectiveness of the proposed method.  相似文献   

7.
The phenomenon of stochastic resonance (SR) in the tumour cell growth model subjected cross-correlated noises is investigated. When a weakly periodic signal is added to the system, the signal-to-noise ratio RSNR is derived by the quasi-steady-state probability distribution function and the adiabatic elimination method. Based on the derived RSNR, the effects of these parameters (the cross-correlated strength λ and the cross-correlated time τ) are analysed by numerical calculation. It is found that the existence of a maximum in RSNR is the identifying characteristic of the SR phenomenon. The maximum of RsNR decreases with the increase of λ and increases with the increase of τ.  相似文献   

8.
We propose a method to test the correctness of the coupling model of a qubit interacting with environment and to determine the type of dissipation.The environment is modelled by a bath of oscillators with infinite degrees of freedom and the qubit-bath coupling is chosen to be a general dissipation-decoherence form.The proposed method can be realized in current experiments.  相似文献   

9.
Sum-frequency generation (SFG) is investigated using the two-coupled-oscillator molecular model.The influence of the polarization states and angles of two incident beams on reflected and transmitted sum-frequency lights is discussed by considering the circular birefringence in a chiral medium.The different response of media with two kinds of enantiomers to polarization states of incident beams is also discussed.Furthermore,the relations between the SFG spectrum and the polarization states are studied.The theoretical result is consistent with a known experimental fact.  相似文献   

10.
A Geometry Model for Tortuosity of Flow Path in Porous Media   总被引:2,自引:0,他引:2       下载免费PDF全文
A simple geometry model for tortuosity of flow path in porous media is proposed based on the assumption that some particles in a porous medium are unrestrictedly overlapped and the others are not. The proposed model is expressed as a function of porosity and there is no empirical constant in this model. The model predictions are compared with those from available correlations obtained numerically and experimentally, both of which are in agreement with each other. The present model can also give the tortuosity with a good approximation near the percolation threshold. The validity of the present tortuosity model is thus verified.  相似文献   

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