连续小波变换识别位场场源法的噪声影响分析与尺度因子的选择

为提高连续小波变换识别位场场源准确度,研究噪声对场源识别结果的影响和尺度因子优选方法问题。根据连续小波变换识别位场场源的基本原理,用该方法对不同噪声水平的合成数据进行场源识别,分析噪声对于场源识别结果的影响,研究小波变换的尺度因子对噪声压制的效果,讨论连续小波变换进行场源识别时尺度因子的选取方法。理论模型和实测资料场源识别结果表明,噪声会降低连续小波变换场源识别结果的准确度,笔者提出的尺度因子优选方法能有效压制噪声干扰,提高场源识别结果的准确度。     

基于f-x域时频非凸正则化低秩矩阵近似的共偏移距道集去噪方法

随机噪声压制是地震数据处理的关键环节,而时频稀疏低秩近似算法逐道处理地震数据过程中无法利用信号的道间相干性。为此,将时频稀疏低秩近似与f-x域去噪结合,提出一种f-x域时频非凸正则化低秩矩阵近似算法。该算法对f-x域中每一单频分量作时频分解后,再对时频系数矩阵作低秩矩阵近似计算,能够利用信号和噪声的时频谱差异实现非平稳信号去噪处理。与共炮点道集和共中心点道集相比,共偏移距道集具有平缓甚至接近水平的同相轴结构,基本满足f-x域去噪的线性同相轴假设前提,建议将所提算法应用于共偏移距道集去噪处理。通过数值模拟和实际地震数据试算,证明本文方法能够有效压制随机噪声,同时保持有效信号不被损害。     

Three dimensional shear wave velocity structure of the crust and upper mantle beneath China from ambient noise surface wave tomography

We determine the three-dimensional shear wave velocity structure of the crust and upper mantle in China using Green's functions obtained from seismic ambient noise cross-correlation.The data we use are from the China National Seismic Network,global and regional networks and PASSCAL stations in the region.We first acquire cross-correlation seismograms between all possible station pairs.We then measure the Rayleigh wave group and phase dispersion curves using a frequency-time analysis method from 8 s to 60 s.After that,Rayleigh wave group and phase velocity dispersion maps on 1° by 1° spatial grids are obtained at different periods.Finally,we invert these maps for the 3-D shear wave velocity structure of the crust and upper mantle beneath China at each grid node.The inversion results show large-scale structures that correlate well with surface geology.Near the surface,velocities in major basins are anomalously slow,consistent with the thick sediments.East-west contrasts are striking in Moho depth.There is also a fast mid-to-lower crust and mantle lithosphere beneath the major basins surrounding the Tibetan plateau (TP) and Tianshan (Junggar,Tarim,Ordos,and Sichuan).These strong blocks,therefore,appear to play an important role in confining the deformation of the TP and constraining its geometry to form its current triangular shape.In northwest TP in Qiangtang,slow anomalies extend from the crust to the mantle lithosphere.Meanwhile,widespread,a prominent low-velocity zone is observed in the middle crust beneath most of the central,eastern and southeastern Tibetan plateau,consistent with a weak (and perhaps mobile) middle crust.     

响应矩阵技术在唐马试验场地下水管理中的应用

响应矩阵技术是解决地下水管理问题的方法之一,它是通过表征系统结构特征的单位脉冲响应函数来求得由抽水产生的水位分布,并以此作为线性规划的约束条件建立地下水系统的水动力管理模型。本文造过对唐马试验场水文地质条件的分析,建立数学模型并将其分解和离散,对渗流区内各井点作用一单位脉冲来形成响应矩阵,建立水动力管理模型和水位预报方程,对本区未来地下水开采进行优化决策。     

地震随机噪声压缩感知迭代压制方法

复杂地表和复杂介质条件下,随机噪声往往严重影响着复杂地震信号的信噪比,同时深层地球物理目标探查中弱地震信号总是被随机噪声所掩盖,如何有效地压制随机噪声干扰、恢复有效地震信号仍然是高精度地震勘探中的关键问题.压缩感知理论突破了奈奎斯特采样定理的限制,利用有效地震信号的可压缩性和稀疏性,提供了从不可压缩随机噪声中进行有效信号分离的数据原理.本文系统分析压缩感知框架下地震随机噪声压制的稀疏优化反问题,提出了基于迭代软阈值算法的"采集-重建-修复"方案对该问题进行求解.在实现高度稀疏表征的基础上进行地震数据的压缩感知随机观测,通过迭代反演对有效地震信号进行重构,有效提高复杂地震数据的信噪比,同时,当求解稀疏优化问题时,如果出现正则化项引起重构信号衰减现象,可以匹配除偏对衰减的有效信号进行修复.通过与工业标准f-x预测滤波方法进行比较,理论模型和实际数据处理的结果表明,压缩感知迭代噪声压制方法对复杂地震数据中的随机噪声有较好的压制效果,可以有效恢复出被较强非平稳随机噪声干扰的时空变同相轴信息.     

Spatial Scale and Population Assignment Choices in Environmental Justice Analyses 1

Abstract

Environmental justice laws protect certain populations against discriminatory actions that may result from a myriad of enterprises, including transportation activities. Previous environmental equity studies examining the effects of transportation-engendered externalities have been criticized on several points, including (1) that the choice of a reference population for comparison to the criterion variable may influence the outcome of research results and (2) that the selection and use of inappropriate methodologies intended to identify and characterize populations may foreordain research outcomes. This article examines the potentially confounding effects of selected spatial scale and population assignment strategies as applied to a study of excessive noise levels at a large Midwestern airport, finding that reported outcomes can vary significantly as a function of methodological choices.     

平面监测网的动态滤波

在假定形变区域为分块连续弹性体的基础上,本文提出一个所谓虚拟形变速率参数形变模型,由它的特例可推出常见的单点位移形变模型。之后又讨论和研究了平面监测网的观测数据滤波问题,设计出一个虚拟形变速率参数卡尔曼滤波器,具体做了这几项工作:(1)在所提出的形变模型下,推导出平面监测网的状态方程;(2)解决了初始状态及其方差阵的估计问题;(3)在极大似然的原则下,得到了动态噪声方差阵的逐次修正公式。在对两个模拟网的几种不同方案进行试算之后,本文提出了几点结论和建议。     

图像平滑算法比较研究及改进策略

图像平滑作为去除图像中含有噪声的图像增强处理技术，是各种与图像有关软件中必不可少的功能模块。文中在分析噪声模型的基础上，对均值平滑、中值平滑、边缘保持平滑等技术从图像处理空间域中的算法原理、实现方法及效率等方面进行了详细比较。针对图像中含有的不同噪声模型，通过多次试验，得出了值得从事图像处理研究者参考的结论。这将有助于提高图像处理软件开发的效率。     

Single epoch GPS deformation signals extraction and gross error detection technique based on wavelet transform

IntroductionGPS technique is widely used for deformationmonitoring thanks for the high precision. Usual-ly , there are three working modes associatedwith GPS deformation observation: periodicalGPS deformation monitoring net , GPS monito-ring array and rea…     

基于可分解马尔科夫网的极端椒盐噪声图像滤波

提出了一种基于可分解马尔科夫网(decomposableMarkovnetworks,DMN)的极端椒盐噪声的均值滤波方法,指出其网络节点的阈值衰减特性和网络节点的连接特性具有很好的对椒盐噪声污染图像的噪声定位的作用,并提出一种在该网络控制下,只对与噪声相关的像素进行均值计算以替代噪声像素的亚均值滤波算法,实现了图像的较强自适应滤波。实验表明,本文方法具有良好的滤波性能。