共查询到17条相似文献，搜索用时 156 毫秒
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海底沉积物声速是海洋物理学和水声学研究的一个重要物理量。声速测量的准确性取决于如何准确计量超声波在沉积物介质中的传播时间。针对传统的观察波形突变法存在不足,文中基于小波变换独特的时-频局部化特征,阐明了小波变换信号奇异性检测原理,分析讨论如何利用该原理来检测海底沉积物声速测量中的超声回波信号起跳点。用Matlab数值计算软件,把记录的波形数据文件导入工作空间,选用Db3小波进行5层小波分解,观测其模极大值点的位置;用Gauss小波进行连续小波变换,观测其模极大值线的位置。并用两个实例验证了小波变换检测超声回波起跳点可行性及优越性,可提高海底沉积物声速测量的准确性,为海底智能化检测仪器的研发提供技术基础。 相似文献
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Hartley变换是一种基于谐函数的实变换,具有Fourier变换的特性,在海洋工程中使用Fourier变换的大部分应用都可以通过Hartley变换实现,并且快速Hartley变换的计算效率是快速Fourier变换的2倍,并易于实现,所以Hartley变换可以在许多应用中代替Fourier变换。详细介绍了Hartley变换在海洋工程领域的应用,包括:波谱分析、波浪分离、PIV(粒子图像测速法)技术和微分方程的Hartley域变换,举例说明了Hartley变换在节约计算空间和提高计算效率上具备的优越性。 相似文献
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研究短期海况中海洋结构物在宽带波浪载荷作用下交变应力过程中的应力范围的概率分布及结构疲劳损伤问题.首先从应力的功率谱密度出发,利用小波变换作为工具,对应力过程进行模拟.然后用雨流计数法识别出应力过程中对结构造成疲劳损伤的应力范围,并用Weibull分布对应力范围的分布进行了拟合;最后给出了应力范围服从Weibull分布时结构疲劳损伤的计算方法. 相似文献
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根据波浪图像的纹理特征,提出了一种基于数学形态学图像分割的波向检测方法,该方法首先利用顶帽变换和底帽变换,得到增强的波浪纹理图像,然后对图像波谷进行应用标记的分水岭分割,最后利用波谷形态方向提取出波浪方向,实验结果证明该算法能够有效地实现波向检测。 相似文献
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首先介绍了小波阈值消噪的基本原理,认为小波阈值消噪的性能受三方面因素的影响:(1)小波母函数的选择;(2)阈值方法的选择;(3)阈值函数的选择.为了寻找小波母函数、阈值估计和阈值函数的最优组合,文中以实测海洋磁力测量数据为背景,采用小波阈值法进行消噪,把得到的磁异常值作为"真值".仿真了波浪噪声和随机噪声并加入到"真值"磁异常中,作为噪声磁异常.在此基础上采用两种小波族系(Symlets,Daubechies)、四种阈值选取方法和软、硬阈值函数对噪声磁异常进行了基于小波变换的消噪计算,客观分析了不同组合方法的消噪精度和可靠性.实际计算结果表明:对磁异常突变点较多且分布杂乱的测线进行消噪,Sym6、软阈值函数、混合阈值或基于Stein无偏似然估计消噪效果最好;对磁异常突变点少且大部分光滑的测线进行消噪,db7、基于Stein无偏似然估计和软阈值函数的消噪效果最好. 相似文献
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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
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山东海洋资源丰富,海洋科技力量集中,海洋技术成果的应用推广具有巨大经济意义。目前已经采用的措施不足以解决科技成果的大量转化问题,中介功能不全是最大的瓶颈。需要发育结构完整、功能连续、分层覆盖的推广体系。山东在技术发展方面做了许多工作,但这种体系尚未形成。必须加强薄弱环节,寻找适当的组织形式,完善各项政策,实现从技术到经济的全程统一管理。 相似文献
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The application of Hartley transform to ocean engineering 总被引：1，自引：0，他引：1
The Hartley transform is a real integral transform based on harmonic functions and hassome characteristics similar to the Fourier transform. Most applications in ocean engineering requiring the Fourier transform can also be performed by the Hartley transform. The fast Hartley transform is twice faster and more convenient to handle than the corresponding fast Fourier transform, so it is a real valued alternative to the complex Fourier transform in many applications. The use of the Hartley transform in ocean engineering is presented in detail in this paper, including wave spectral analysis, separation of waves, cross-correlation in PIV technique and expression of equation in the Hartley domain. The examples in the paper show deeply the advantage and efficiency of the Hartley transform over the Fourier transform. 相似文献
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Wavelet analysis for processing of ocean surface wave records 总被引：2，自引：0，他引：2
Stanis
aw R. Massel 《Ocean Engineering》2001,28(8):165
Wavelet analysis is a relatively new technique and in the recent years enormous interest in application of wavelets has been observed. This modern technique is particularly suitable for non-stationary processes as in contrast to the Fourier transform, (FT), the wavelet transform (WT) allows exceptional localization, both in time and frequency domains. The wavelet transform has been successfully implemented in signal and image processing, ordinary and partial differential equation theory, numerical analysis, communication theory and other fields. On the other hand, the application of the WT to ocean engineering and oceanography is rare. In this paper the WTs capability to give a full time–frequency representation of the wave signals is demonstrated. The processing of the time series of the non-stationary deep water waves, waves breaking at the tropical coral reefs and mechanically generated waves in the wave flume demonstrates the ability of the wavelet transform technique to detect a complex variability of these signals in the time–frequency domain. Various spectral representations resulting from the wavelet transform are discussed and their application for wave signals is shown. 相似文献
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The present paper presents the results of a wavelet transform-based coherence analysis of freak wave and its impact. Wavelet transform has been used as a tool in analyzing signals in the time domain as well as in the frequency domain. The analysis was applied to laboratory-generated freak waves. The wavelet transform of the time history of the freak wave and its impact force revealed that a wide range of frequency components were contained in them. The coherence analysis was conducted on the wave and its impact force time histories. The coherence analysis revealed that some high-frequency components were highly correlated with the impact forces. The present study demonstrates that the wavelet transform can be an alternative tool in the analysis of strongly nonlinear freak wave and its impact. 相似文献
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Wave grouping characteristics in nearshore Great Lakes 总被引：2，自引：0，他引：2
The recently advanced approach of wavelet transform is applied to the analysis of wave data measured in the nearshore areas of the Great Lakes. The conventional spectrum analysis of wave time series in the frequency domain can be readily generalized to the frequency and time domain using the wavelet transform. The traditional Fourier transform approach has not been able to directly assess the time localized nature of wave groups. With the application of wavelet transformation, the relatively unexplored wave grouping characteristics come to light as the predominant feature of wave processes. 相似文献
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Fourier transform (FT) is a commonly used method in spectral analysis of ocean wave and offshore structure responses,but it is not suitable for records of short length.In this paper another method,wavelet transform (WT),is applied to analyze the data of short length.The Morlet wavelet is employed to calculate the spectral density functions for wave records and simulated Floating Production Storage and Offloading (FPSO) vessels' responses.Computed wave data include simulated wave data based on JONSWAP spectr... 相似文献