Linear models with nearly frequency independent complex stiffness leading to causal behaviour in time domain     

G. B. Muravskii 《地震工程与结构动力学》2007,36(1):13-33

In the paper, several causal linear models leading to nearly frequency independent complex stiffness are studied in time and frequency domains. Along with Biot model other three hereditary models are introduced into analysis. They all ensure practical constancy for damping properties but have limitations concerned with an increase in the real part of complex stiffness of corresponding material elements, as frequency grows. A new suggested method deals with given mechanical system as a whole: the imaginary part of the system compliance is constructed assuming that all elements have constant stiffness (with a modification for imaginary parts near zero frequency) and further the imaginary part of the system is used directly for studying transient vibrations supposing causality of the given mechanical system. The corresponding real part (not needed in the transient response analysis) is determined by Hilbert transformation. Examples relating to systems with one, two and infinite (shear beam) degrees of freedom are carried out for five compared models, allowing to reveal advantages and shortcomings of the models. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Hilbert Transform Applied to Separation of Waves   总被引：1，自引：0，他引：1  

SUN  Hequan 《中国海洋工程》2002,16(2):239-248

The analytical method (AM) for separation of composite waves is presented based on the Hilbert transform. It is ap-plicable to both regular and irregular trains of waves. The wave data series measured with two wave gauges in the experi-ments are separated into two series of incident and reflected waves. Then, the reflection coefficient can be easily ob-tained. The arrival of reflected waves can also be detected for improvement of the accuracy of the reflection coefficient.The reflection performance of the physical model can be estimated exactly without calculation of wave height and phasedifference. Numerical samples developed to test the method are proved to be accurate. Physical experiments are conduct-ed and compared with Goda‘s method and satisfactory results are obtained.  相似文献   

Local properties of sea waves derived from a wave record     

Elzbieta M. Bitner-Gregersen  Sverre Gran 《Applied Ocean Research》1983,5(4):210-214

It is demonstrated that for linear deep sea waves with small directional scattering the particle motion at the sea surface and energy transmission may be retrieved from a wave record by means of the Hilbert transform. A physical interpretation of the envelope of the two-dimensional deep sea waves as well as a new method for wave group analysis is presented.  相似文献   

浅谈数学变换在海洋技术中的应用     

孙鹤泉 《海洋技术学报》2006,25(1):58-66,93

根据以往的工作积累,作者在文中介绍了在海洋技术中得到应用的几种数学变换,包括基于Fourier变换的频谱分析、波浪分离、相关分析及定义的H artley实现,连续M orlet小波变换在波浪信号分析中的应用,以及离散正交小波变换的降噪作用与悬沙图像的特征提取。文中通过公式推导和数据比较,展示了数学变换在海洋技术应用中的科学魅力。  相似文献   

Analysis and simulation of wave records through fast Hartley transform   总被引：1，自引：0，他引：1  

Germn Rodríguez 《Ocean Engineering》2003,30(17):2255-2273

The Hartley transform, a real-valued alternative to the complex Fourier transform, is presented as an efficient tool for the analysis and synthesis of ocean surface wave records. Basic theoretical properties of this real-valued transform are briefly reviewed. Similarities and differences between Fourier and Hartley integral transforms, as well as computational benefits and disadvantages between numerical algorithms used to evaluate their discrete versions, are presented. The fast Hartley transform algorithm is used to simulate stationary Gaussian time series of the sea surface elevation and to estimate the spectral density function, the Hilbert transform and the envelope function of wave records.  相似文献   

地震信号的复地震道分析及应用   总被引：8，自引：3，他引：5       下载免费PDF全文

石颖  刘洪 《地球物理学进展》2008,23(5):1538-1543

复地震道分析又称三瞬分析,该分析方法可将反映地震信号局部变化情况的地震波的瞬时振幅、瞬时相位和瞬时频率等信息分离开.本文应用Hilbert变换求解虚地震记录,用复地震道分析方法求取"三瞬"信息,并用该方法计算了理论合成地震记录的瞬时振幅、瞬时相位和瞬时频率,获得了较好的效果.同时,本文也利用该方法对某区块实际地震资料进行了处理,结果表明,复地震道分析方法获得的"三瞬"信息可反映地震信号的局部变化,有助于进行地震薄互层分析,并能提高数据的解释精度.  相似文献   

日长亚季节变化的振幅调制与厄尔尼诺现象   总被引：7，自引：0，他引：7  

钟敏  朱耀仲  高布锡 《天文学报》1999,40(1):101-106

利用Ｈｉｌｂｅｒｔ变换解算了１９６２年至１９９６年日长亚季节振荡的包络变化．结果显示,日长亚季节变化的振幅调制不仅具有一线性增长趋势,而且包含一个超前厄尔尼诺变化历程的年际变化．分别研究日长亚季节准５０天包络变化以及准１２０天包络变化后发现,这种超前性来自日长亚季节准５０天的振幅变化,这一结论与大气的研究结果一致．日长亚季节准１２０天的振幅变化在１９７２年附近发生了位相１８０°反转,因此日长亚季节准１２０天的振幅变化自１９７６年以来与厄尔尼诺的历程正好同步,１９７２年以前则截然相反．众所周知,日长变化在亚季尺度上具有显著的易变性,然而上述的非线性调制现象不仅表明了日长亚季节变化的内在规律性,而且证实了地球自转运动在不同时间尺度上存在极明显的非线性相互作用．同时也表明,日长变化作为全球风系变化的一个有价值的信息指标,将逐渐成为研究气候系统全球状态的有效手段之一．  相似文献   

在频率域基于小波变换和Hilbert解析包络的CSEM噪声评价   总被引：1，自引：0，他引：1       下载免费PDF全文

杨洋  何继善  李帝铨 《地球物理学报》2018,61(1):344-357

传统CSEM一般只提取主频信号,或以谐波与主频的振幅比为依据提取部分低阶谐波信号,但缺乏判断标准,实际操作中存在很大的不确定性.本文基于小波变换和希尔伯特解析包络提出一种新的CSEM信号噪声评价方法,首先在时间域中基于混合基快速傅里叶变换获得原始信号准确功率谱;其次在频率域中根据CSEM频率位置相邻频率幅值进行频谱预处理,基于离散小波变换将预处理后的频谱分成低频部分和高频部分,基于希尔伯特变换识别高频部分的上包络线,并与低频部分重构得到频谱的整体上包络线;最后根据包络线与对应CSEM频率振幅的比值估计噪声的影响幅度,根据阈值筛选出高信噪比的主频和谐波信号.本方法不需增加野外工作量即可提取大量的频率信号,特别是高阶谐波信号,实现频率加密,提高CSEM的纵向分辨能力和能源利用率.  相似文献   

自然资源大数据快速服务平台关键技术的研究与实现     

郭双仁  唐芝青  唐先龙 《测绘通报》2020,(8):131

目前行业内普遍存在难以实现海量空间数据快速服务（包括快速存取、显示、检索、分发和在线服务）的难题，制约了自然资源数据的共享应用。针对上述问题，本文提出了一套"基于分布式列式数据库和Hilbert空间编码规则优化海量空间数据的存取、检索、显示效率"的解决方案，对其具体技术路线进行了详细阐述，并进一步介绍了大数据快速服务平台研发和推广情况。本文旨为满足新时代经济社会发展对海量空间信息快速服务的迫切需求。  相似文献   

利用Hilbert变换计算重力归一化总梯度   总被引：12，自引：3，他引：9       下载免费PDF全文

张凤旭  孟令顺  张凤琴  刘财  王世煜 《地球物理学报》2005,48(3):704-709

针对提高重力勘探正反演解释的分辨率问题,提出利用Hilbert变换计算和研究重力归一化总梯度.文中从理论上详细地证明了方法的可行性,给出了适合计算机实现的计算方法.为探讨该方法对油气藏的分辨能力,在模型计算中,分别利用Fourier级数法、Fourier变换法和本文提出的Hilbert变换法计算模型的GH场值,发现当三度体储油球冠模型（模拟似三度贮油气藏背斜模型）油气藏部分（低密度体）厚度减小到低于球冠厚度的十分之一时,Fourier级数及变换法不能分辨出低密度体所产生的异常,而Hilbert变换法仍然可以清晰地识别,这说明用Hilbert变换法计算的GH场对异常识别的分辨率优于其他两种方法.  相似文献