频率-波数域频散曲线提取方法及程序设计     

李杰  陈宣华  张交东  周琦  刘刚  刘志强  徐燕  李冰  杨婧 《物探与化探》2011,35(5):684-688

主要研究了地震瞬态瑞利波频率一波数域频散曲线的提取,以二维傅氏变换,半波长理论等作为理论基础.使用Delphi7.0将其程序化,通过工程应用验证了本方法及程序.结论证明f-k方法克服了-维数字处理技术存在的不足,充分利用了多道瑞利波数据记录信息.  相似文献   

A Certain Class of Laplace Transforms with Applications to Reaction and Reaction-Diffusion Equations     

A. M. Mathai  R. K. Saxena  H. J. Haubold 《Astrophysics and Space Science》2006,305(3):283-288

A class of Laplace transforms is examined to show that particular cases of this class are associated with production-destruction and reaction-diffusion problems in physics, study of differences of independently distributed random variables and the concept of Laplacianness in statistics, α-Laplace and Mittag-Leffler stochastic processes, the concepts of infinite divisibility and geometric infinite divisibility problems in probability theory and certain fractional integrals and fractional derivatives. A number of applications are pointed out with special reference to solutions of fractional reaction and reaction-diffusion equations and their generalizations.  相似文献   

Towards automation of palynology 3: pollen pattern recognition using Gabor transforms and digital moments     

Y. Zhang  D. W. Fountain  R. M. Hodgson  J. R. Flenley  S. Gunetileke 《第四纪科学杂志》2004,19(8):763-768

The classification of pollen grains using texture information in combination with shape features is presented in this paper. The surface texture of pollen is characterised by using Gabor transforms, the geometric shape is described by using moment invariants, and the pollen grains are classified by an artificial neural network. In an experiment with five types of pollen grains, more than 97% of samples are correctly classified. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

基于树型小波变换和尺度共生矩阵的居民地提取          下载免费PDF全文

金飞  张占睦  芮杰  夏朝贵 《海洋测绘》2009,29(6):48-51

利用基于树型框架小波变换和尺度共生矩阵的方法对遥感影像中居民地进行识别提取。通过非完全树型框架小波变换把图像变换到不同的尺度层上，然后在不同尺度层之间，提取相互依存的尺度共生矩阵信息，进而形成居民地的纹理特征。实验结果表明，用基于小波的尺度共生矩阵的方法对居民地有较好的提取结果。  相似文献   

Solution of Generalized Fractional Reaction-Diffusion Equations     

R. K. Saxena  A. M. Mathai  H. J. Haubold 《Astrophysics and Space Science》2006,305(3):305-313

This paper deals with the investigation of a closed form solution of a generalized fractional reaction-diffusion equation. The solution of the proposed problem is developed in a compact form in terms of the H-function by the application of direct and inverse Laplace and Fourier transforms. Fractional order moments and the asymptotic expansion of the solution are also obtained.  相似文献   

Estimating Net Radiation from Air Temperature for Diffusion Modelling Applications in a Tropical Area     

Oluwagbemiga O. Jegede 《Boundary-Layer Meteorology》1997,85(1):161-173

A simple and straightforward expression isproposed, which is based on the Fourier seriesdecomposition technique, for estimating hourly averagednet radiation from the corresponding values of airtemperature at a tropical location in West Africa. Thecomparisons made of the estimated net radiation withactual measurements (case studies) clearlydemonstrate that the scheme is efficient, both inclear and under cloudy weather conditions. Theestimates are also shown to be better than thosedetermined from an alternative relationship usingparametrizations for the shortwave and longwave components at the surface. The presentprocedure can easily be implemented in existingmeteorological preprocessors to calculate the sensibleheat flux for the Gaussian-based air pollutionmodels.  相似文献   

Isotropic and anisotropic correlations in turbulent wind speed data     

Katja Henjes 《Boundary-Layer Meteorology》1997,84(1):149-167

The correlations in turbulent wind speed data from the open ocean are studied. They are calculated as Fourier transforms of the spectraldensities, which are computed from Fourier transforms of the measured windspeed components. All correlations are found to decay within a few seconds.It is shown that the spectra are most efficiently calculated using data sections whose length does not exceed the observed correlation decay time.Longer runs include more random noise without containing more information.The ratio of the along-wind to transverse spectral levels is investigatedand found to be in excellent agreement with the assumption of isotropy inthe inertial wave number range.  相似文献   

Multivariate Spatial Modeling for Geostatistical Data Using Convolved Covariance Functions   总被引：1，自引：0，他引：1  

Anandamayee Majumdar  Alan E. Gelfand 《Mathematical Geology》2007,39(2):225-245

Soil pollution data collection typically studies multivariate measurements at sampling locations, e.g., lead, zinc, copper or cadmium levels. With increased collection of such multivariate geostatistical spatial data, there arises the need for flexible explanatory stochastic models. Here, we propose a general constructive approach for building suitable models based upon convolution of covariance functions. We begin with a general theorem which asserts that, under weak conditions, cross convolution of covariance functions provides a valid cross covariance function. We also obtain a result on dependence induced by such convolution. Since, in general, convolution does not provide closed-form integration, we discuss efficient computation. We then suggest introducing such specification through a Gaussian process to model multivariate spatial random effects within a hierarchical model. We note that modeling spatial random effects in this way is parsimonious relative to say, the linear model of coregionalization. Through a limited simulation, we informally demonstrate that performance for these two specifications appears to be indistinguishable, encouraging the parsimonious choice. Finally, we use the convolved covariance model to analyze a trivariate pollution dataset from California.  相似文献   

希尔伯特-黄变换地震信号时频分析与属性提取   总被引：13，自引：10，他引：13       下载免费PDF全文

杨培杰  印兴耀  张广智 《地球物理学进展》2007,22(5):1585-1590

地震信号属于非线性和非平稳信号,传统的分析方法主要包括短时傅立叶变换、小波变换和Cohen类时频分布等等;希尔伯特-黄变换是分析非平稳信号的新方法,该方法的关键部分是信号的经验模态分解,通过经验模态分解,复杂的信号可以分解为有限的数量很少的几个固有模态函数,从而可以得到信号的希尔伯特时频谱;将该方法应用于单个的地震道数据,可以对地震道进行经验模态分解并得到希尔伯特谱,应用于地震剖面,可以得到意义更加明确的瞬时频率和瞬时振幅等地震属性,模型试算和实际应用表明了该方法的有效性.  相似文献   

A novel analytical solution for a slug test conducted in a well with a finite-thickness skin     

Hund-Der Yeh  Shaw-Yang Yang 《Advances in water resources》2006

An aquifer containing a skin zone is considered as a two-zone system. A mathematical model describing the head distribution is presented for a slug test performed in a two-zone confined aquifer system. A closed-form solution for the model is derived by Laplace transforms and Bromwich integral. This new solution is used to investigate the effects of skin type, skin thickness, and the contrast of skin transmissivity to formation transmissivity on the distributions of dimensionless hydraulic head. The results indicate that the effect of skin type is marked if the slug-test data is obtained from a radial two-zone aquifer system. The dimensionless well water level increases with the dimensionless positive skin thickness and decreases as the dimensionless negative skin thickness increases. In addition, the distribution of dimensionless well water level due to the slug test depends on the hydraulic properties of both the wellbore skin and formation zones.  相似文献