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991.
Wavetet transform was used to analyze the scaling law of temperature data (passive scalar) in Rayleigh-Bénard convection flow from two aspects. The first one was to utilize the method of extended self similarity, presented first by Benzi et al., to study the scaling exponent of temperature data. The obtained results show that the inertial range is much wider than that one determined directly from the conventional structure function, and find the obtained scaling exponent agrees well with the one obtained from the temperature data in an experiment of wind tunnel. The second one was that, by extending the formula which was proposed by A. Arneodo et al. for extracting the scaling exponent ζ(q) of velocity data to temperature data, a newly defined formula which is also based on wavelet transform, and can determine the scaling exponent ξ(q) of temperature data was proposed. The obtained results demonstrate that by using the method which is named as WTMM (wavelet transform maximum modulus) ξ(q) correctly can be extracted. 相似文献
992.
轴对称体声振耦合的边界子波谱与有限元耦合方法 总被引:3,自引:0,他引:3
探讨了子波在Helmholtz积分方程及声振耦合中的应用,在建立了求解轴对称Helmholtz积分方程的子波谱方法的基础上,构造了轴对称子波谱与轴对称有限元的耦合方法,该方法可以处理轴对称问题的任意边界条件.进行了声振耦合问题的模态分析. 相似文献
993.
二维小波变换及在青藏高原地形重构中的应用 总被引:1,自引:0,他引:1
计算和检验了4种不同小波基底和不同阶小波基底对单脉冲和尖峰两个信号的分解及重构的性质,结果表明双正交小波的精度最高,Coifman小波的精度最低.通过设阈值对小波和快速Fourier变换进行截断后再重构,说明小波具有重构精度高、所用非零系数少以及误差被局域化等优点,这就削弱了"Gibbs现象",限制了它的影响范围.在此基础上,用二维快速Fourier和二维离散小波变换对实际青藏高原及其附近地形做了分解、重构及截断后重构等,说明二维小波变换能以较之FFT更少的非零系数和误差局域化等重构大地形,表明了二维小波变换在未来大气环流数值模式中的应用潜力. 相似文献
994.
The prediction methods for nonlinear dynamic systems which are decided by chaotic time series are mainly studied as well as structures of nonlinear self-related chaotic models and their dimensions. By combining neural networks and wavelet theories, the structures of wavelet transform neural networks were studied and also a wavelet neural networks learning method was given. Based on wavelet networks, a new method for parameter identification was suggested, which can be used selectively to extract different scales of frequency and time in time series in order to realize prediction of tendencies or details of original time series. Through pre-treatment and comparison of results before and after the treatment, several useful conclusions are reached:High accurate identification can be guaranteed by applying wavelet networks to identify parameters of self-related chaotic models and more valid prediction of the chaotic time series including noise can be achieved accordingly. 相似文献
995.
Using the technique of integral within an ordered product (IWOP) of
operators we show that the wavelet transform can be recasted to a matrix
element of squeezing-displacing operator between the mother wavelet state vector and the state vector to be transformed in the context of quantum
mechanics. In this way many quantum optical states' wavelet transform can be
easily derived. 相似文献
996.
997.
Asymptotics for Wavelet Based Estimates of Piecewise Smooth Regression for Stationary Time Series 总被引:3,自引:1,他引:2
Young K. Truong Prakash N. Patil 《Annals of the Institute of Statistical Mathematics》2001,53(1):159-178
Wavelet methods are used to estimate density and (auto-) regression functions that are possibly discontinuous. For stationary time series that satisfy appropriate mixing conditions, we derive mean integrated squared errors (MISEs) of wavelet-based estimators. In contrast to the case for kernel methods, the MISEs of wavelet-based estimators are not affected by the presence of discontinuities in the curves. Applications of this approach to problems of identification of nonlinear time series models are discussed. 相似文献
998.
小波变换在区域波前重构算法中的应用 总被引:3,自引:0,他引:3
在自适应光学中使用区域法进行波前重构的一个主要困难是计算量非常大。通过对重构矩阵进行小波变换 ,并对生成的矩阵选取门限 ,获得稀疏矩阵 ,从而可在对重构精度仅有轻微影响的情况下 ,显著降低计算量 ,提高计算速度。文中根据 Bowman[1 ]的理论分析 ,证实了小波变换应用于 Kolmogorov大气扰动重构的适用性 ,提出了适合工程设计应用的门限选择方法和评价参数 ,针对 Kovlmogorov大气扰动进行了计算机仿真 ,给出了有实际应用价值的结果 相似文献
999.
YAN Jingwen SHEN Guiming HU Xiaoyi XU Fang 《Chinese Journal of Lasers》2001,10(4):263-270
1 IntroductionDigitizedimagesneedstoring ,transmittingandprocessing ,anddatacompressionisusuallyimplemented ,obtainingthebitrateandmaintaininganacceptablefidelityorimagequality .Compressioncanbeachievedbytransformingthedata,projectingitonabasisoffunctions… 相似文献
1000.