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基于局域波分解的地震信号时频属性提取 总被引：1，自引：0，他引：1
局域波分解可以得到有意义的频率并可以抑制时频分布交叉项,是1种新的自适应信号分解方法.在局域波分解基本原理的基础上,研究基于局域波分解的地震信号分频谱及频率属性的提取方法.将局域波分解与传统时频分析结合,进行有效数值实现与对比分析,通过模型地震数据与实际2D地震数据试算验证方法的正确性和有效性.研究表明:基于局域波分解的Wigner时频分布分频谱,具有较高的时频分辨率,交叉项得到简单有效的抑制;基于局域波分解的时频分析方法计算提取的频率属性,避免无意义的负频率,物理意义明确,为在地震储层研究和油气检测中的正确应用奠定基础. 相似文献
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《中国海洋大学学报(自然科学版)》2017,(2)
传统阵列信号的DOA估计可以同时对空间不同方向上的多个信号源实现方向估计,为了提高估计精度,可以进行时频变换,但小波及希尔伯特黄变换等,都存在交叉项问题,而S变换可以避免交叉项的影响。由于S变换中高斯窗宽度为频率的倒数,为提高信号的时频分辨率,本文在高斯窗中加入调节因子,可以灵活调节高斯窗函数随频率尺度的变化趋势。本文将改进S变换与阵列信号DOA估计结合,通过计算机仿真给出了该方法与传统方法的性能对比,并与高频地波雷达的实测数据结合,验证了此方法的有效性与可行性。 相似文献
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时频分析是对地震信号进行分解,可以在不同频带上显示不同级别的地质现象。采用连续小渡变换方法,对地震资料进行储层时频分析和分频属性提取,时频主极值频率曲线与伽马曲线有较好对应关系,尤其是其低频趋势线。对A区块周边的两口井井旁道进行了时频分析,揭示出该区15Hz低频数据体与储层及含油气相关性较好。针对这一特征,对该区三维地震体进行了运算及属性提取,描述其储层展布。 相似文献
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对水中弹性圆柱行声散射实验研究,结合弹性体的共振散射理论验证实验结果.在实验中得到较好的时域散射波形,与理论得出的时间间隔吻合,并利用准谐波法得到目标的形态函数,该结果与理论一致.文章使用维格纳威利(Wigner-Ville)分布来分析散射信号的时频关系,得到时频联合分布图,从中看出散射信号中存在频散现象和时间延迟现象. 相似文献
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《应用海洋学学报》2015,(2)
水下声探测是外国调查船和水下文物盗捞船进行非法调查和探测的主要技术手段,根据信号的主要声特征,对海洋水下声探测信号进行分类,分为宽带中、低频信号和窄带高频信号.在福建兴化湾海域采集了浅地层剖面仪信号、电火花声源信号、侧扫声纳信号和单频测深信号4种代表性的海洋水下声探测信号,根据声特征分析给出了对应的分类,其中:浅地层剖面仪信号为信号类型确定的中、低频信号;电火花声源信号为宽带脉冲中、低频信号;侧扫声纳信号和单频测深信号为窄带高频信号.通过对4种实测声探测数据的分析研究,给出了对应类型的海洋水下声探测信号的分析、提取方法,其中:信号类型确定的中低信号和窄带高频信号在初步的时、频分析基础上,可通过带通滤波提取;宽带脉冲中、低频信号在初步的时、频分析基础上,可尝试通过小波尺度相关滤波的方法提取.结合已知的水下声探测信号的主要声特征,实现对采集的海洋水下声探测信号的识别. 相似文献
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地震波穿过地层时会发生频散和衰减,岩层中含有油气等流体时,频散和衰减有其特殊性,双相介质理论能很好地刻画地下介质含有流体时的情况。本文基于双相介质理论公式,研究流体参数和频率对地震波衰减和频散的影响规律。结果表明:地震波低频成分衰减较弱,高频成分衰减较强;黏弹性强的流体频散强,粘弹性低的流体频散弱;衰减和频散可以作为油气存在的标志。文中通过广义S变换,对实际地震资料计算,较准确地提取地震波的低频、高频能量和频散特征曲线,并对实际资料进行了含油气性预测,取得了与钻井一致的结果。 相似文献
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提出1种将消频散变换应用到海底地声参数反演的方法。对单一水听器接收声压信号进行消频散处理后,根据群延时差建立代价函数,反演得到主要海底参数,最后根据贝叶斯统计理论给出了待反演地声参数的边缘后验概率密度。对单层波导进行仿真证明这种新方法的有效性。 相似文献
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针对海洋磁力测量数据中存在的高斯噪声,采用基于交叉证认的小波阈值去噪方法进行噪声去除。首先对磁力数据进行小波分解,利用交叉证认方法自动识别小波分解的信号层与噪声层,然后对噪声层小波系数进行阈值处理,进一步提取噪声层中的有用信息,最后进行小波重构得到去噪信号。同时提出了一种改进阈值处理函数,能够改善传统软、硬阈值函数存在的缺陷,提高重构信号的精度。实验分析表明,当噪声水平小于1.5nT时,相比于传统软、硬阈值函数的小波阈值去噪方法,该方法可更好地去除海洋磁力数据中的高斯噪声,并可较好地保留数据中的有用细节信息,使数据质量得到提高。 相似文献
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《Oceanic Engineering, IEEE Journal of》1996,21(4):537-544
The acoustic spectrum of a transiting aircraft, when received by a hydrophone located beneath the sea surface, changes with time due to the acoustical Doppler effect. The traditional method for analysing signals whose frequency content changes with time is the short-time Fourier transform that selects only a short segment of the signal (or window of data) for spectral analysis at any one time. The short-time Fourier transform requires the frequency content of the signal to be stationary during the analysis window, otherwise the frequency information will be smeared by the transformation. Recently, joint time-frequency distributions, which highlight the temporal localisation of a signal's spectral components, have been used to analyse nonstationary signals whose spectra are time dependent. In this paper, the short-time Fourier transform and the Wigner-Ville time-frequency distribution are applied to time-series data from a hydrophone so that the instantaneous frequency of the propeller blade rate of a turbo-prop aircraft can be estimated at short time intervals during the aircraft's transit over the hydrophone. The variation with time of the estimates of the Doppler-shifted blade rate is then compared with the corresponding temporal variation predicted using a model that assumes the sound propagates from the airborne acoustic source to the subsurface receiver through two distinct isospeed media (air and water) separated by a plane boundary (the air-sea interface). The results for five transits are presented in which the altitude of the aircraft ranged from 350 to 6050 ft with the speed of the aircraft varying from 232 to 245 kn 相似文献
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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
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A methodology is proposed for efficient processing of sea wave field data via compressive sensing (CS), and joint time-frequency analysis via harmonic wavelets (HWs) based evolutionary power spectrum (EPS) estimation. In this regard, it is possible to record and store relatively long wave data sequences, whereas the commonly adopted in-practice assumption of stationary data is abandoned. Currently, most wave records are measured by buoys, which acquire data for a time interval representative of stationary time series. Next, following a Fourier transform processing, only few spectral parameters are stored. Thus, detailed information about localized-in-time phenomena are completely lost. Herein, it is shown that CS can be adopted for efficiently compressing and reconstructing wave data, while retaining localized information. For this purpose, CS is used in conjunction with a HW basis for processing long time series. In particular, storage capacity demands are drastically decreased as only the HW coefficients need to be saved. These are determined from a randomly-sampled record by invoking a L1/2 norm minimization procedure. The resulting reconstructed record, being longer than conventional wave time series, can no longer be regarded as stationary; thus, a HW based EPS estimate is employed for describing the joint time-frequency features of the record. Finally, the reliability of the methodology is assessed by analyzing wave field data measured at the Natural Ocean Engineering Laboratory (NOEL) of Reggio Calabria. Specifically, comparisons between original and reconstructed records demonstrate a satisfactory agreement regarding the time-histories, and the estimated EPS and relevant statistical quantities, even for up to 60% missing/removed data. 相似文献
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In this paper, we define a time-domain pressure transfer function calculated from SIWEH (smoothed instantaneous wave energy history) transforms, and a time-frequency domain pressure transfer function calculated from wavelet transforms, of synchronized wave and pressure data. It is our objective to study whether the time-domain pressure transfer function and the time-frequency domain pressure transfer function can provide new interpretation of wind wave behaviors. The detail structure of local time-frequency pressure transfer function in three-dimensional plot from wavelet transform is not employed due to its large variations, instead the time-integral wavelet spectral pressure transfer function and frequency-integral wavelet SIWEH pressure transfer function are used. These two averaged pressure transfer functions are smooth approximations of frequency-domain Fourier and time-domain SIWEH pressure transfer functions, respectively.Application to real ocean waves reveals that in frequency-domain the measured Fourier and wavelet spectral pressure transfer functions can be approximated by the linear pressure transfer function in the dominant wave range. In time-domain, the wavelet SIWEH pressure transfer function is a better indicator of wind wave behaviors than the SIWEH pressure transfer function. A value higher than 0.5 for the wavelet SIWEH pressure transfer function is a good discriminator of relative shallow-water long waves and wave groups are mostly composed of relative low frequency long waves. 相似文献
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本文针对温度差异对沉积物的声学特性的影响，研究不同温度下沉积物的频谱特征规律。把南海深海沉积物的人工样品置于温控环境中，采集经历沉积物的超声信号，对其进行快速傅里叶变换获得频谱特征，分别从主频漂移、主频幅值、主频频宽、接收能量等方面归纳出温度影响下的海底沉积物超声信号的频谱特征规律：如温度变化影响频谱特征，但可重复性低；温度增加使沉积物对声信号的衰减增大；频宽与频率幅值呈负相关，但温度-幅值的关系明显于温度-频宽的关系。因此，温度改变导致沉积物超声信号频谱的规律性变化。 相似文献
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南海北部陆坡海域是孤立内波的活跃区,孤立内波在该海域能够引起水体环境较强烈的水平不均匀性,从而影响声场干涉结构。将描述宽带声信号强度干涉条纹斜率的波导不变量视为一种分布,能更准确地分析声场的距离*频率干涉结构。本文研究了孤立内波环境下过渡海域声场的距离*频率干涉结构,依据实测孤立内波海洋环境,得到孤立内波环境下随距离变化的声速剖面,利用抛物方程方法仿真过渡海域声场干涉结构。在此基础上,利用拉东变换和傅里叶变换结合的谱值分离方法在低信噪比环境下提取波导不变量分布。分析表明孤立内波环境下过渡海域的声场类影区、类会聚区的波导不变量取值更丰富。 相似文献
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系泊方柱在畸形波与波群伴生波浪作用下运动响应试验研究 总被引：1，自引：1，他引：0
畸形波与波群伴生波浪作用于系泊浮体,和常规随机波浪作用比较,运动响应时频域特征均将发生显著变化。基于物理模型试验,采用小波方法计算伴生波浪和常规随机波浪作用下系泊浮体运动响应的时频域特征变化及波群因子与浮体运动响应时频域特征的定量关系。结果表明:伴生波浪作用下浮体运动响应显著大于常规随机波浪的作用结果,且波群因子G A对浮体运动响应时频域特征有显著影响;伴生波浪作用下浮体纵荡运动的广义能量谱E(t)统计特征值E max(t)、E 1/10(t)、E 1/3(t)、E average(t)均明显大于相同波谱下常规随机波浪的结果,且随着波群因子G A增大显著增大;伴生波浪作用下各运动响应能量集中度δE显著大于常规随机波浪作用结果,且能量集中时域分布范围参数ΔT E以纵荡运动分量最为显著。 相似文献
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The Wigner-Ville distribution (WVD) function was originally proposed by Wigner in quantum mechanics and Ville applied it for signal analysis. This method has made it possible to represent a signal's power density spectrum in the time-frequency domain as a natural extension of the Fourier transform method (FTM). Recently, it has attracted great interest for its validity to analyze time-varying signals accomplished by the development of high-speed digital signal processing, and it is used for analyzing nonstationary signals. Conventionally, a sonar beamformer is constructed using delay lines, but the development of the high-speed processor has made it possible to apply the FTM for sonar beamforming. However, the bearing resolution of the beamformer is not enough for discriminating small underwater objects on the sea bottom by this method. To solve this problem, we aim to apply the WVD method, which can represent finer structure of signals as a natural extension of the FTM, for sonar beamforming to obtain sharper beam patterns than those of the beamforming method by FTM. Simulation results by computational calculations to clarify the resolution by the WVD method, which is presented in this paper, becomes approximately twice as high as by conventional FTM. The results of an experiment at sea also show the performance of this method 相似文献