基于重构信号模型的去噪技术     

刘春成  刘畅  王大利 《铀矿地质》2011,27(3):173-179

面波和多次波等噪音的产生是海上地震勘探的突出特点,如何高保真地对其进行压制一直是信号处理工作的难题。基于重构信号模型的去噪技术通过不同的方法,充分考虑不同入射角度和横波地震信息,重构信号模型,分离出剩余信号,然后针对剩余信号进行去噪处理,利用建立的信号模型和剩余有效信号结合,得到有效地震信号,达到突出有效信号衰减噪声的目的。  相似文献   

Influence of cavity shape on hydrodynamic noise by a hybrid LES-FW-H method     

王玉  王树新  刘玉红  陈超英 《中国海洋工程》2011,25(3):381-394

The flow past various mechanical cavity, which is a common structure on the surface of the underwater vehicle, and generating hydrodynamic noise has attracted considerable attention in recent years. In this paper, a hybrid method is presented to investigate the hydrodynamic noise induced by mechanical cavities with various shapes. With this method, the noise sources in the near wall turbulences or in the wake are computed by the large eddy simulation (LES) and the generation and propagation of the acoustic waves are solved by the Ffowcs Williams-Hawkings (FW-H) acoustic analogy method with acoustic source terms extracted from the time-dependent solutions of the unsteady flow. The feasibility and reliability of the current method was verified by comparing with experimental data (Wang, 2009). The 2D cavity models with different cross-section shapes and 3D cavity models with different cavity mouth shapes (rectangular and circular) are developed to study the influence of cavity shape on the hydrodynamic noise. By comparing the flow mechanisms, wall pressure fluctuations, near-field and far-field sound propagation distributions, it is found that the quadrangular cavity with equal depths of leading-edge and trailing-edge is preferred for its inducing lower hydrodynamic noise than the cylindrical cavity does.  相似文献   

Comparison of theoretical and experimental wall pressure wavenumber-frequency spectra for axisymmetric and flat-plate turbulent boundary layers     

A.W. Foley  K.M. Cipolla 《Ocean Engineering》2011,38(10):1123-1129

The measurement and analysis of turbulent boundary layer wall pressure fluctuations using a wavenumber filter of sensors provide quantitative knowledge of turbulence physics. In addition, the sources of flow-induced noise and vibration for towed SONAR arrays can be determined. An axisymmetric turbulent boundary layer can have significantly different features than those of a comparable flat-plate boundary layer. Here, a detailed comparison of the distribution of wall pressure energy in both wavenumber and frequency between flat-plate and thick axisymmetric boundary layers is presented. The background theory of wavenumber-frequency spectra and state-of-the-art models for flat-plate boundary layers are discussed. The widely used model of Chase (1987), valid for flat-plate boundary layers over a wide range of Reynolds numbers, is used and combined with a sensor response function to allow the effects of spatial averaging to be considered. It is demonstrated that when measured boundary layer parameters for the axisymmetric case are used in the Chase flat-plate model, the results accurately predict the axisymmetric boundary layer wall pressure measurements.  相似文献   

星间距离影响GRACE地球重力场精度研究     

郑伟  许厚泽  钟敏  员美娟  周旭华 《大地测量与地球动力学》2011,31(2):60-65

利用改进的能量守恒法,基于不同星间距离反演了120阶GRACE地球重力场.模拟结果表明:第一,基于相同的GRACE核心载荷精度指标反演长波(L≤20阶)地球重力场时,随着星间距离逐渐增大(110～330 km),累计大地水准面的精度依次提高.在20阶处,基于110 km星间距离反演精度为0.052 cm,基于220 k...  相似文献   

特征系统实现算法中的噪声问题研究     

李萍  王树青  李华军 《中国海洋大学学报(自然科学版)》2011,(Z2):176-182

研究特征系统实现算法在模态识别过程中的噪声处理问题。特征系统实现算法为目前土木工程领域应用较为广泛的一种模态识别法。在处理实测数据时,特征系统实现算法将实测数据分解为结构真实信号和噪声信号,从而将噪声消除。分块Hankel矩阵的维数对信噪分离过程影响很大。提出当分块Hankel矩阵的分块行与分块列数接近时,真实和噪声信号可以最好的分离。通过在实测信号里添加噪声(产生噪声-噪声信号),将实测信号和噪声-噪声信号识别的结果进行比较,提出了1种验证识别模态参数是否为结构真实模态的检验方法。本文应用导管架平台实例来验证提出方法的适用性。结果表明,当分块Hankel矩阵的分块行与分块列数接近时,真实和噪声信号能够有效地分离,此时添加的噪声主要影响噪声信号部分。由实测信号和噪声-噪声信号识别的模态参数非常吻合。  相似文献   

多维动态噪声信息的可视化研究     

黄宝香  韩勇  刘寿生  李文庆  陈戈 《中国海洋大学学报(自然科学版)》2011,(Z1):181-184,188

基于环境噪声声线追踪方法,提出基于不规则三角网格的噪声分析算法并通过噪声实测数据检验校正。基于自主知识产权的VRGIS平台,将区域范围内噪声源数据、地理数据、建筑的分布状况、道路状况等信息综合,分析和计算后生成反映区域噪声水平状况的多维噪声分布图,并以动态放映和趋势分析方式进行噪声时空演变分析。将抽象无形的噪声转化为可实时漫游的多维噪声场景,直观形象的表现区域的噪声分布,为声环境决策提供依据。  相似文献   

Geological variation in S-wave velocity structures in Northern Taiwan and implications for seismic hazards based on ambient noise analysis     

《Journal of Asian Earth Sciences》2014

Ambient noise analysis in Northern Taiwan revealed obvious lateral variations related to major geological units. The empirical Green’s functions extracted from interstation ambient noise were regarded as Rayleigh waves, from which we analyzed the group velocities for period from 3 to 6 s. According to geological features, we divided Northern Taiwan into seven subregions, for which regionalized group velocities were derived by using the pure-path method. On average, the group velocities in mountain areas were higher than those in the plain areas. We subsequently inverted the S-wave velocity structure for each subregion down to 6 km in depth. Following the analysis, we proposed the first models of geology-dependent shallow S-wave structures in Northern Taiwan. Overall, the velocity increased substantially from west to east; specifically, the mountain areas, composed of metamorphic rocks, exhibited higher velocities than did the coastal plain and basin, which consist of soft sediment. At a shallow depth, the Western Coastal Plain, Taipei Basin, and Ilan Plain displayed a larger velocity gradient than did other regions. At the top 3 km of the model, the average velocity gradient was 0.39 km/s per km for the Western Coastal Plain and 0.15 km/s per km for the Central Range. These S-wave velocity models with large velocity gradients caused the seismic waves to become trapped easily in strata and, thus, the ground motion was amplified. The regionalized S-wave velocity models derived from ambient noises can provide useful information regarding seismic wave propagation and for assessing seismic hazards in Northern Taiwan.  相似文献   

Crustal and upper mantle S-wave velocity structures across the Taiwan Strait from ambient seismic noise and teleseismic Rayleigh wave analyses     

《Journal of Asian Earth Sciences》2014

Although orogeny tapers off in western Taiwan large and small earthquakes do occur in the Taiwan Strait, a region largely untouched in previous studies owing mostly to logistical reasons. But the overall crustal structure of this region is of particular interest as it may provide a hint of the proto-Taiwan before the orogeny.By combining time domain empirical Green’s function (TDEGF) from ambient seismic noise using station-pairs and traditional surface wave two-station method (TS) we are able to construct Rayleigh wave phase velocity dispersion curves between 5 and 120 s. Using Broadband Array in Taiwan for Seismology (BATS) stations in Taiwan and in and across the Strait we are able to derive average 1-D Vs structures in different parts of this region. The results show significant shear velocity differences in the upper 15 km crust as expected. In general, the highest Vs in the upper crust observed in the coastal area of Mainland China and the lowest Vs appears along the southwest offshore of the Taiwan Island; they differ by about 0.6–1.1 km/s. For different parts of the Strait, the upper crust Vs structures are lower in the middle by about 0.1–0.2 km/s relative to those in the northern and southern parts. The upper mantle Vs structure (Moho – 150 km) beneath the Taiwan Strait is about 0.1–0.3 km/s lower than the AK135 model. The overall crustal thickness is approximately 30 km, much thinner and less variable than under the Taiwan Island. The inversion of seismic velocity structures using shorter period band dispersion data in the sea areas with water depth deeper than 1000 m should take water layer into consideration except for the continental shelves.  相似文献   

溶洞型储层成像分辨率分析     

徐颖 《物探化探计算技术》2014,(2):194-199

结合塔河油田溶洞型储层的特点,通过大量的数值模拟,分析了溶洞绕射波的波场特征,深入探讨了溶洞成像纵向、横向分辨率的本质,定量分析了信噪比对溶洞成像分辨率的影响,并给出了图像分辨率的概念及意义。研究表明:①溶洞的绕射波尾巴长,要选取较大的偏移孔径才能使绕射波能量得到较好的收敛;②溶洞较小时串珠远大于溶洞真实大小,随溶洞尺度增大串珠逐渐接近于溶洞真实大小;③纵向上不同高度的溶洞,如果连续地排在一起,实际上类似于一楔形体,其振幅变化呈调谐曲线;④传统的菲涅耳带半径不宜作为成像横向分辨率的评价参数,溶洞横向、纵向分辨率以λ大小为宜;⑤成像信噪比的改善趋势与炮集信噪比成反比,低信噪比资料成像处理后,溶洞的可识别度能得到明显提高;⑥要重视计算机图像分辨率的概念,注意高密度勘探最佳道距的合理选取。  相似文献   

安徽省CORS坐标时间序列噪声和速度场分析     

何蓉  陶庭叶  丁鑫  陶征广 《大地测量与地球动力学》2021,41(4):368-373

利用GAMIT/GLOBK软件解算安徽省卫星定位综合服务系统（AHCORS）2013-01～2018-06数据,得到参考站坐标时间序列,并对其进行噪声分析。结果表明,安徽省境内参考站的最佳噪声模型为白噪声+闪烁噪声（WN+FN）模型。在顾及有色噪声影响时,AHCORS在ITRF2008框架下的平均运动速度为31.72 mm/a,方向为E22.76°S;以欧亚板块为参考的平均运动速度为6.28 mm/a,方向为E2.65°N。垂直方向上整体平均运动速率为-0.71 mm/a,以淮河为界呈现出南方隆升、北方沉降的趋势。其中,大别山地区的隆起速率大于江淮丘陵区和黄山地区,江淮丘陵区抬升速率相对平缓,淮河以南一带平均抬升速率为2.94 mm/a。淮北地区沉降明显,平均沉降速率为10.92 mm/a,最大沉降速率为32.82 mm/a,发生在宿州砀山（SZDS）站,可能是近年来开采矿产资源所致。  相似文献