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1.
    
Random dynamical models obtained as a perturbation of the GOY (Gledzer-Ohkitani-Yamada) shell model for three-dimensional turbulence are defined. Both static (time-independent) and dynamical scaling properties of the randomly perturbed model are studied. The random static-inviscid manifold, in contrast to the dynamical evolution, does not show intermittent scaling laws. This behavior is linked to the absence of large deviation in the random-map connecting fluctuations of velocities at different scales. The importance of inviscid conserved quantities on the intermittent statistics is discussed. Different random dynamical perturbations such that only energy is conserved in the inviscid and unforced limit are investigated. Intermittency is weakly affected by random perturbations.  相似文献   

2.
Turbulent wind data measured in the atmospheric surface layer and wind tunnels are used to estimate the Kolmogorov constant Ck. The analysis discusses distinct procedures to obtain the mean energy dissipation rate and Ck. We find that for our datasets the most reliable method is the third-order structure function one. The value found for the skewness of longitudinal velocity differences is in accordance with a multifractal approach recently proposed. Despite the limitations of the data discussed in the paper, the results point to a value of Ck independent of the Reynolds number.  相似文献   

3.
Large-deviations estimates for the autocorrelations of order kof the random process Z n=(X n)+ n, n0, are obtained. The processes (X n) n0and ( n) n0are independent, n, n0, are i.i.d. bounded random variables, X n=T n(X 0), n , T: MMis expanding leaving invariant a Gibbs measure on a compact set M, and : M is a continuous function. A possible application of this result is the case where Mis the unit circle and the Gibbs measure is the one absolutely continuous with respect to the Lebesgue measure on the circle. The case when Tis a uniquely ergodic map was studied in Carmona et al.(1998). In the present paper Tis an expanding map. However, it is possible to derive large-deviations properties for the autocorrelations samples (1/n) n–1 j=0 Z j Z j+k . But the deviation function is quite different from the uniquely ergodic case because it is necessary to take into account the entropy of invariant measures for Tas an important information. The method employed here is a combination of the variational principle of the thermodynamic formalism with Donsker and Varadhan's large-deviations approach.  相似文献   

4.
Chun-Kai Cheng 《Physica A》2008,387(13):3093-3102
The aim of this paper is to propose an output coupling and feedback scheme, which is not only to guarantee the asymptotic synchronization between the master and the slave chaotic systems with multiple time-delays but also to attenuate the effects of noise perturbation on the overall error system to a prescribed level in terms of the performance index H-norm. The output coupling and feedback gain is derived on the basis of the Lyapunov theory and the linear matrix inequality (LMI) technique. Some numerical examples are given to demonstrate the effectiveness of the main results.  相似文献   

5.
杨颖  顾铮天 《光学学报》2012,32(10):1006006-79
基于光纤光栅的模式耦合理论,采用传输矩阵法对啁啾长周期光纤光栅(LPFG)的超宽带滤波特性进行了分析。研究表明当啁啾LPFG的纤芯模同时与同向传输的多个阶次的包层模发生耦合,且与多个不同阶次包层模对应的谐振峰交叠时,其传输谱带宽可扩展到500nm以上,可用做超宽带带阻滤波器。传输谱带宽随模式序数、啁啾系数、光栅长度、周期和折射率调制量的增加单调递增,但随光纤包层半径的增大单调递减。采用高斯折射率切趾技术抑制了传输谱旁瓣,为设计超宽带滤波器提供了新的方法。  相似文献   

6.
A chirped fiber grating with cladding made of uniaxial crystal material whose optical axis is parallel to the axis of grating, i.e., z-axis is proposed. Electro-optic effect and elasto-optic effect in this kind of fiber gratings are theoretically analyzed for the first time. The influences of the electric field and the strain applied to the fiber grating cladding along z-axis on Bragg wavelength λ B and the reflectivity spectra of this kind of chirped grating are theoretically examined using coupled-mode theory and transfer matrix method. The curves of Bragg wavelength λ B as a function of an external electric field or the strain are theoretically obtained respectively for three kinds of uniaxial crystal materials as the grating claddings. The calculated results indicate that when the axial electric field applied to the grating cladding varies from 1 × 107 to 8 × 107 V/m, λ B has the decreases of 0.12 nm, and when the applied strain varies from 0 to 0.04, λ B has the decreases of 0.45 nm.  相似文献   

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