基于单程波偏移算子的地表相关多次波成像

在常规地震资料处理中,多次反射波被视为噪声并从地震数据中去除,以免在之后的地震资料解释中造成误解.而事实上,多次波也是地震信号,是照明波场的一部分,能够对地下构造成像的精度做出贡献.本文分析了多次波在传统单程波叠前深度偏移中产生构造假象的机制和表现,为实现基于单程波偏移算子的多次波成像,修改了单程波叠前深度偏移的边界条件,即将输入的震源波场用包含多次波的记录来替代,输入的记录波场用预测出的表层相关多次波来替代,实现了基于单程波偏移算子的地表相关多次波成像,并从理论上给出了其成像依据.通过基于二范式最小能量差原则求取的匹配因子,将多次波成像结果与一次波成像结果进行匹配叠加,应用多次波成像来弥补一次波成像的不足.简单模型验证了基于单程波偏移算子的多次波成像方法的有效性,最后对Sigsbee2B模型进行了一次波与多次波联合成像试算,盐边界高陡构造成像质量得到了明显改善.     

Generalized diffraction‐stack migration and filtering of coherent noise

We reformulate the equation of reverse‐time migration so that it can be interpreted as summing data along a series of hyperbola‐like curves, each one representing a different type of event such as a reflection or multiple. This is a generalization of the familiar diffraction‐stack migration algorithm where the migration image at a point is computed by the sum of trace amplitudes along an appropriate hyperbola‐like curve. Instead of summing along the curve associated with the primary reflection, the sum is over all scattering events and so this method is named generalized diffraction‐stack migration. This formulation leads to filters that can be applied to the generalized diffraction‐stack migration operator to mitigate coherent migration artefacts due to, e.g., crosstalk and aliasing. Results with both synthetic and field data show that generalized diffraction‐stack migration images have fewer artefacts than those computed by the standard reverse‐time migration algorithm. The main drawback is that generalized diffraction‐stack migration is much more memory intensive and I/O limited than the standard reverse‐time migration method.     

Statistical models for shear strength of RC beam‐column joints using machine‐learning techniques

This paper proposes a new set of probabilistic joint shear strength models using the conventional multiple linear regression method, and advanced machine‐learning methods of multivariate adaptive regression splines (MARS) and symbolic regression (SR). In order to achieve high‐fidelity regression models with reduced model errors and bias, this study constructs extensive experimental databases for reinforced and unreinforced concrete joints by collecting existing beam‐column joint subassemblage tests from multiple sources. Various influential parameters that affect joint shear strength such as material properties, design parameters, and joint configuration are investigated through tests of statistical significance. After performing a set of regression analyses, the comparison of simulation results indicates that MARS approach is the best estimation method. Moreover, the accuracy of analytical predictions of the derived MARS model is compared with that of existing joint shear strength relationships. The comparison results show that the proposed model is more accurate compared to existing relationships. This joint shear strength prediction model can be readily implemented into joint response models for evaluation of earthquake performance and inelastic responses of building frames. Copyright © 2014 John Wiley & Sons, Ltd.     

傅里叶变换在深州井资料处理中的应用

深州井水位日常观测中,经常会因为仪器供电不稳、雷击等原因出现一些幅度很大的脉冲、突跳及数据缺测,严重影响了观测资料的内在质量。本文采用数字信号处理技术[1]对深州井水位资料进行分析处理,首先使用分段线性插值法对缺测数据进行插值处理,然后用快速傅里叶变换对水位数据进行频谱分析,绘制振幅谱,分析水位数据中的不同周期成分,选取恰当的截止频率进行滤波处理,去除了干扰,获得了井水位的变化动态,提高了资料质量。最后应用滤波后的水位数据做一些震例分析。     

用于变形监测的最小二乘滤波数据处理

随着全站仪在测量工作中的广泛使用,以坐标为观测值的数据处理成为内业工作的主要内容。根据最小二乘滤波原理,将工程岩土体变形监测中所获得的坐标观测值及其他常规观测值进行联合平差。结果表明,滤波后变形点的点位精度最大可提高1.35 mm,最弱点亦提高0.94 mm,均明显高于直接观测结果,而且各类观测值之间所形成的约束条件进一步增强了平差结果的可靠性。     

分布式虚拟地理环境中时空一致性研究

为了保证分布式虚拟地理环境的时空一致性和解决共享虚拟场景过程中的同步和一致,本文提出了在虚拟地理环境中通过统一的空间基准和环境描述来保证空间一致性,通过具体的减少数据传输延迟的技术方案来保证实时性.     

抗差卡尔曼滤波及其在动态水准网平差中的应用

介绍了标准卡尔曼滤波方程,总结了稳健M估计的基本方法,并根据等价权原理导出卡尔曼滤波的抗差估计方程,方程的形式与卡尔曼滤波方程相似,给出了卡尔曼滤波稳健估计的计算步骤.最后,以动态水准监测为例进行了模拟计算,证明了该方法的有效性.     

土木工程结构鲁棒控制的发展

评述了结构控制的发展,指出发展结构鲁棒控制策略的重要性。重点评述了结构双重调谐质量阻尼器(DTMD)和多重双重调谐质量阻尼器(MDTMD)的控制策略,提出了需进一步发展主动双重调谐质量阻尼器(ADTMD)和主动多重双重调谐质量阻尼器(AMDTMD)控制策略、此外,评述了结构鲁棒控制的设计准则与高层建筑和大跨桥梁在风与地震作用下的统一自适应主动鲁棒控制策略。     

2003—2019年邯郸市叶面积指数时空变化特征

研究和掌握叶面积指数(LAI)时空变化特征,对区域植被保护、植树造林和环境保护具有重要的参考意义.本文以邯郸市为例,基于MCD15A3H遥感影像数据、DEM数据和土地利用等多元数据,引入Sen趋势与Mann-Kendall趋势检验分析方法,系统分析了邯郸市像素尺度上的LAI数值的变化特征,并基于不同的土地利用类型、不同...     

Adaptive finite element modeling of marine controlled-source electromagnetic fields in two-dimensional general anisotropic media

In this paper, we extend the scope of numerical simulations of marine controlled-source electromagnetic (CSEM) fields in a particular case of anisotropy (dipping anisotropy) to the general case of anisotropy by using an adaptive finite element approach. In comparison to a dipping anisotropy case, the first order spatial derivatives of the strike-parallel components arise in the partial differential equations for generally anisotropic media, which cause a non-symmetric linear system of equations for finite element modeling. The adaptive finite element method is employed to obtain numerical solutions on a sequence of refined unstructured triangular meshes, which allows for arbitrary model geometries including bathymetry and dipping layers. Numerical results of a 2D anisotropic model show both anisotropy strike and dipping angles have great influence on the marine CSEM responses.