考虑动电效应的基坑渗漏电场三维正演及响应特征分析（英文）

针对传统的地面直流电法对基坑连续墙渗漏探测精度差、抗干扰能力低以及渗漏电场响应特征分布不清等问题,本文将渗漏通道内由于动电效应形成的电场和传导电流形成的稳定电场进行耦合建立了渗漏电场的响应机制及基本方程;构建了一种井-地联合观测的渗漏电场检测装置,该装置在辅助井和降水井内供电,基坑内地面快速测量电场分布特征,从而实现渗漏点的快速定位;然后利用有限元-无限元耦合法求解电场方程实现基坑渗漏模型三维正演模拟,并对检测装置的影响因素和不同渗漏通道的基坑模型进行数值模拟。结果表明：本文提出井-地联合观测装置可快速揭示渗漏引起的电位异常,动电效应产生的电场有效加强了渗漏处渗漏电场信号,从而提高了探测精度及探测效率。     

曲靖非相干散射雷达功率剖面的初步观测与分析

介绍了非相干散射雷达功率剖面与电离层电子密度剖面之间的关系,给出了曲靖非相干散射雷达功率剖面的一些观测结果,结合电离层垂直探测数据,初步介绍了曲靖非相干散射雷达在夜间电离层波状扰动、低纬电离层异常区北驼峰位置、电离层电子密度日落增强和暴时变化等观测研究中的应用.本文结果丰富了对我国曲靖地区电离层空间天气特性的认识,显示了该雷达在我国低纬电离层空间天气观测研究中的良好应用前景.     

广州地区一次严重灰霾过程的垂直探测

利用激光雷达和微波辐射计在广州地区一次严重灰霾过程进行探测,采用小波变换协方差方法反演边界层高度,从热力和动力的角度分析边界层气象因子和能见度之间的关系.结果表明,边界层高度有明显的日变化过程,和地面能见度变化有很好的一致性.在清洁过程,边界层高度超过1 km,发生严重灰霾时,最高仅为500 m.50-100 m的温度梯度滞后30 h和能见度相关性更加显著,相关系数达到0.77.高层能见度（255 m）和下层稳定度有显著的负相关,清洁日负相关系数最大达-0.76,灰霾日负相关系数最大达-0.49.在相关的边界层气象因子中,地表通风系数和地面能见度成线性关系,相关系数最高,达0.88.边界层高度、地面风速、相对湿度和地面能见度的相关系数分别为0.76,0.67和-0.77.各气象因子之间具有较高的相关性.此次灰霾过程的主控气象因子为地表通风系数,在没有边界层高度探测的地区可利用地面能见度和风速估算边界层高度.     

不同卫星载荷探测NDVI性能差异分析及变换参数确定

提出了一种多卫星载荷探测归一化差异植被指数(NDVI)的差异定量分析与改正新方法.该方法集成PROSPECT模型、SAIL模型和MODTRAN大气辐射传输模型来模拟不同卫星载荷的遥感信号,使用遥感模拟信号而非实际卫星图像进行NDVI差异分析和改正.信号模拟中考虑了传感器光谱响应和大气条件的影响,对国内外的30种卫星载荷探测NDVI的差异进行了定量分析.最后,针对不同卫星载荷探测NDVI之间存在的差异,利用模拟数据建立了地面能见度分别为10,23,50km大气条件时30种国内外主要卫星载荷NDVI值间的相互转换关系.本文方法对多载荷NDVI应用分析具有一定的理论及实用意义.     

基于CFAR的三亚非相干散射雷达数据预处理研究

三亚非相干散射雷达是一部位于低纬度地区的先进的相控阵雷达系统,其主要任务是对地球电离层进行观测研究.在其探测区域内有许多航天器及碎片飞越,这些硬目标的存在导致回波信号比电离层非相干散射信号强度高出几个量级,进而影响电离层参量反演.为了有效消除原始数据中的硬目标信号,本文采用CFAR (constant false alarm rate)的方法来检测和消除硬目标.由于电离层背景不稳定,我们提出了基于传统OS-CFAR的自适应VI-OS-CFAR算法.在本文中,我们将新算法与传统的四种算法进行比较并将其应用于三亚雷达观测的数据处理中,结果证明了我们方法的有效性,该方法有望应用于三亚非相干散射雷达实际信号处理中.     

过套管电阻率测井仪器的径向探测特性

为研究过套管电阻率测井仪器的径向探测特性,本文给出了反映地层径向介质变化的几何因子.利用过套管电阻率测井的传输线方程实现了电阻率测井几何因子的数值计算,针对Schlumberger公司的CHFR测井仪和俄罗斯的ЭКОС-31-7测井仪分别计算了几何因子响应曲线,通过曲线分析发现：两种测井仪对低侵剖面（有低阻流体侵入）均有较大的探测半径,但随侵入流体电阻的增大（高侵剖面）仪器的径向探测半径在减小,本文的研究为地层电阻率测井解释和仪器径向探测特性分析提供了理论依据.     

利用高频天波返回散射反演电离层水平不均匀结构

高频天波返回散射探测作为重要的电离层探测手段,能够实现遥远区域电离层空间上的连续监测,探测获取的返回散射扫频电离图显示了探测频率-群路径-回波能量三者之间的关系.由于电离图包含了探测路径上的电离层状态信息,通过对其反演可以实时获取大面积范围的电离层参数.本文提出了一种基于解空间约束的返回散射前沿反演算法,能够重构电离层水平不均匀结构.针对反演非线性问题,采用Newton-Kontorovich方法进行求解,同时又引入了求解不适定问题的Tikhonov正则化方法,有益于解的稳定性和唯一性.利用模拟数据和实测数据分别对本文建立的算法进行了验证,并与Fridman和Fridman于1994年提出的反演方法进行了对比.结果表明,本文算法反演结果稳定,对返回散射前沿判读误差不敏感,与Fridman和Fridman 1994年方法相比,本文方法对电离层局部精细结构反演更加准确,具有较高的反演精度.本文提出的算法不但能够反演白天和夜间这种电离层较平稳时期的电离层状态,而且对于日出/日落时段等电子浓度分布变化较快情形下的电离层,也有很好的反演效果,表明了该算法在处理复杂多变的实际探测的返回散射电离图中的应用价值.     

曲靖非相干散射雷达观测研究进展与展望

本文介绍了我国曲靖非相干散射雷达的主要技术方案，结合实测数据分析表明该雷达具备了电离层电子密度与等离子体温度观测、空间碎片凝视探测与月球二维成像探测等能力，可用于研究电离层F层气候学特征、电子密度暴时变化与异常增强等天气事件、E-F谷区结构与变化、约3 cm以上尺寸空间碎片的分布特征与模型、月球不同区域的散射回波特性等.下一步将重点开展低电离层与北驼峰结构及演化过程、电离层暴时与扰动特性观测.     

基于正则化方法的高频地波雷达海浪方向谱反演

提出了一种从高频地波雷达海面回波谱中提取海浪方向谱的新方法:基于高频电波海洋探测基本原理将线性化后的非线性积分方程离散为矩阵方程组,通过引入正则化数学模型将不适定方程转化为正规方程,然后采用奇异值分解法求解.对于正则化方法中正则化参数,采用L曲线法来确定.为了验证本文算法的有效性,分别在单部雷达和双部雷达探测下进行了不同噪声水平下的数值模拟,结果表明了该正则化反演方法的有效性.文中还给出了实测数据分析初步结果.该算法的工程性应用还需进一步研究.对于实际的地波雷达海浪反演具有良好的应用前景.     

基于实测PM_(2.5)、能见度和相对湿度分辨雾霾的新方法

霾是由于气溶胶增多或相对湿度增大引起气溶胶吸湿增长而导致的能见度降低的现象,而雾是气溶胶经过活化变成雾滴而造成的低能见度事件,在气象观测中如何对两者进行准确区分一直是一个存在争议的问题.本文以雾和霾在物理性质上的客观区别为基础,介绍了一种全新的基于实测PM2.5、能见度和相对湿度来分辨雾和霾的新方法.通过对当地历史观测的气溶胶谱分布数据进行拟合和统计,并结合气溶胶吸湿增长特性计算得到判别参考值.通过将实际测量的PM2.5、能见度和相对湿度与判别参考值相比对,来估计当前状况是雾或霾的概率.本方法可操作性强,基于常规观测仪器即可实现.     

On reconstruction of the Ito-like equation from persistent time series

The Langevin equation with finite-range persistence was introduced as a macroscopic model of various geophysical phenomena. The modified histogram procedure (MHP) of reconstruction of the equation from time series was proposed. An efficiency of MHP was tested on artificial persistent time series (with short and long-tail distributions) generated by different Ito-like equations. For an exemplary geophysical time series, the appropriate Ito-like equation was reconstructed.     

Estimation of peak flows from small watersheds on the Loess Plateau of China

Peak flow rate from watersheds is an important criterion used to develop soil conservation plans and to design engineering projects. A peak flow rate equation used in the CREAMS model, with four parameters, can be employed to predict peak flow rate. The purpose of this study was to test and improve this equation of peak flow rate in CREAMS for use on the Loess Plateau of China. Data from 331 storms in 20 small watersheds were used to verify the the peak flow rate equation in CREAMS. The calculated flow rates using the CREAMS equation greatly underestimated the measured peak flows. The model efficiency was only 0·15. Nonlinear regression analysis was then performed to develop a new equation: which gave a model efficiency of 0·94. A second set of data, including 68 storms from four completely different watersheds, was used to test the new equation, with a resultant model efficiency of 0·90. The result has significant implications for improving the design of soil and water supporting practices, for assessing the soil and water resources, and for implementing conservation programmes. Copyright © 2008 John Wiley & Sons, Ltd.     

A quasi three-dimensional model for flow and transport in unsaturated and saturated zones: 1. Implementation of the quasi two-dimensional case

A quasi three-dimensional (QUASI 3-D) model is presented for simulating the subsurface water flow and solute transport in the unsaturated and in the saturated zones of soil. The model is based on the assumptions of vertical flow in the unsaturated zone and essentially horizontal groundwater flow. The 1-D Richards equation for the unsaturated zone is coupled at the phreatic surface with the 2-D flow equation for the saturated zone. The latter was obtained by averaging 3-D flow equation in the saturated zone over the aquifer thickness. Unlike the Boussinesq equation for a leaky-phreatic aquifer, the developed model does not contain a storage term with specific yield and a source term for natural replenishment. Instead it includes a water flux term at the phreatic surface through which the Richards equation is linked with the groundwater flow equation. The vertical water flux in the saturated zone is evaluated on the basis of the fluid mass balance equation while the horizontal fluxes, in that equation, are prescribed by Darcy law. A 3-D transport equation is used to simulate the solute migration. A numerical algorithm to solve the problem for the general quasi 3-D case was developed. The developed methodology was exemplified for the quasi 2-D cross-sectional case (QUASI2D). Simulations for three synthetic problems demonstrate good agreement between the results obtained by QUASI2D and two fully 2-D flow and transport codes (SUTRA and 2DSOIL). Yet, simulations with the QUASI2D code were several times faster than those by the SUTRA and the 2DSOIL codes.     

AN INTEGRATED APPROACH FOR SIMULATING AND PREDICTING SCOUR AROUND ABUTMENTS

1 INTRODUCTION The local scour around bridge piers and abutments has always had heightened interest to hydraulic engineers. An accurate and efficient method to estimate the local scour is greatly desired. However, the behavior of flows passing through bri…     

Testing a conceptual hillslope recession model based on the storage–discharge relationship with the Richards equation

The conceptual recession model based on the storage–discharge relationship was proposed to account for the unsaturated–saturated water storage interaction. The recession model was formulated by combining the constitutive storage–discharge relationship with the integral balance equation for unsaturated and saturated water storage. The functional form of the constitutive storage–discharge relationship was determined from the spatial integration of the Richards equation. The performance of the recession model was tested by comparing with the solution of the Richards equation for different simulation geometric shapes and soil types. The conceptual recession model incorporating the unsaturated–saturated water storage interaction was in good agreement with the recession response of the Richards equation. However, the recession model that neglected the unsaturated–saturated water storage interaction was comparable to the Richards equation only for soils with the weak interaction between unsaturated water storage and saturated water storage. This result suggests the important role of the unsaturated–saturated water storage interaction in the formulation of the recession process when the derivative of the functional relationship between the unsaturated water storage and saturated water storage becomes significant. Copyright © 2007 John Wiley & Sons, Ltd.     

融合GOCE和GRACE卫星数据的无约束重力场模型Tongji-GOGR2019S

本文在法方程层面融合GOCE卫星的V_xx、V_yy、V_zz和V_xz重力梯度分量观测数据和GRACE卫星观测数据,采用直接法解算了220阶次的重力场模型Tongji-GOGR2019S.首先利用ⅡR带通滤波器在5~41 mHz的重力梯度带宽范围内对约24个月的GOCE重力梯度观测方程进行无相移滤波处理,并组成解算220阶次重力场模型的法方程,各梯度分量根据相对于参考模型统计精度进行定权;然后与13.5 a GRACE数据建立的180阶次Tongji-Grace02s重力场模型的法方程进行叠加,解算了220阶次的无约束纯卫星重力场模型Tongji-GOGR2019S.利用EIGEN-6C4重力场模型、GNSS/水准数据、DTU15重力异常数据以及欧洲区域似大地水准面模型EGG2015等数据对Tongji-GOGR2019S模型精度进行全面的检核评定,结果表明：引入GOCE卫星梯度数据后,高于72阶的位系数精度优于Tongji-Grace02s模型,Tongji-GOGR2019S模型的整体精度接近同阶次的DIR-R6等GOCE卫星第6代模型.     

基于LS-RSGFD方法优化的横向各向同性(TI)介质一阶qP波高精度数值模拟

为克服各向异性介质弹性波数值模拟中存在着计算量大和波场分离困难等局限,研究了声学近似的VTI介质和TTI介质一阶qP波数值模拟方法.首先对VTI介质弹性波方程进行声学近似,推导了VTI介质一阶qP波方程;然后基于精确的TTI介质频散关系,引入一个包含各向异性控制参数σ的新辅助波场,推导了稳定的TTI介质二阶耦合qP波波动方程,并通过引入波场的伪速度分量,推导了等价的一阶应力-速度形式.结合旋转交错网格有限差分(RSGFD)和基于最小二乘优化的有限差分(LS-FD)两种各具优势的方法,研究了最小二乘旋转交错网格有限差分(LS-RSGFD)方法,并用其数值求解VTI和TTI介质一阶qP波方程,然后通过构造其LS-RSGFD格式,实现了高精度的各向异性介质qP波波场数值模拟.数值模拟结果表明:TI介质一阶qP波方程能够准确地模拟各向异性介质中qP波的运动学特征,引入控制参数σ能够有效地减弱不稳定性问题,保证非均匀TTI介质中qP波场的稳定传播;利用优化的LS-RSGFD方法可以得到高精度的合成地震记录,同时还可以相对地提高计算效率.     

P-SV反射转换波的倾角时差校正（DMO）方法研究

倾角时差校正（ＤＭＯ）方法对于复杂地质构造条件下的纵波反射波（Ｐ－Ｐ）的多次覆盖地震数据的叠加具有显著的提高信噪比的效果．对于转换反射波（Ｐ－ＳＶ）来说，进行倾角时差校正（ＤＭＯ）处理就更需要．本文首先对Ｐ－ＳＶ波的倾角时差校正（ＤＭＯ）的几何原理进行了分析，然后重点研究用波动方程进行ＤＭＯ的方法，即Ｐ－ＳＶ转换反射波的叠前部分偏移的波动方程法．这种方法也适用于Ｐ－Ｐ反射波的叠前部分偏移处理．研究结果表明，波动方程ＤＭＯ方法在振幅保真方面比几何原理的ＤＭＯ方法有显著改善．     

Forward plane-wave electromagnetic model in three dimensions using hybrid finite volume–integral equation scheme

We present a concept of the hybrid finite volume–integral equation technique for solving Maxwell's equation in a quasi-static form. The divergence correction was incorporated to improve the convergence and stability of the governing linear system equations which pose a challenge on the discretization of the curl–curl Helmholtz equation. A staggered finite volume approach is applied for discretizing the system of equations on a structured mesh and solved in a secondary field technique. The bi-conjugate gradient stabilizer was utilized with block incomplete lower-upper factorization preconditioner to solve the system of equation. To obtain the electric and magnetic fields at the receivers, we use the integral Green tensor scheme. We verify the strength of our hybrid technique with benchmark models relative to other numerical algorithms. Importantly, from the tested models, our scheme was in close agreement with the semi-analytical solution. It also revealed that the use of a quasi-analytical boundary condition helps to minimize the runtime for the linear system equation. Furthermore, the integral Green tensor approach to compute at the receivers demonstrates better accuracy compared with the conventional interpolation method. This adopted technique can be applied efficiently to the inversion procedure.     

两相饱和介质中的集中力点源位移场解与应用

通过两相饱和介质Ｂｉｏｔ方程变换,利用势场分解较好地解决了饱和两相介质中Ｐ１和Ｐ２波的耦合问题．再由Ｐｏｉｓｓｏｎ方程和Ｈｅｌｍｈｏｔｚ方程的特性,求解得到两相饱和介质在集中力点源作用下的位移场Ｇｒｅｅｎ函数,进而通过阶跃函数和Ｆｏｕｒｉｅｒ逆变换,求得两相介质在集中力．作用下的波场．由上述结果,根据扩容进水模型,合理地解释了孕震前各主要阶段在地震记录中垂直向振幅与振幅比统计值的变化．最后结合工作实例,利用两相介质波场理论求得由一般弹性介质理论不易求得的骨架固体力学参数．