水动力弥散与水化学前兆信息传递特征初步研究   总被引：1，自引：0，他引：1       下载免费PDF全文

刘春国 《地震地质》1997,19(4):71-362

在分析大量监测资料的基础上，将水化前兆异常变化归结为３种基本曲线类型，将这些基本曲线与水动力弥散曲线进行对比分析，进而提出了水化前兆信息传递机制实质是一种水动力弥散的新观点，并就水动力弥散理论在水化前兆信息机制研究中的应用进行了讨  相似文献   

区域地震通信网子台通信控制改造     

魏柳  刘友富 《东北地震研究》1995,(4)

为提高区域地震通信网数据通信的质量，解决子台通信控制（ＣＣＵ）的诸多不适应，决定对其改造，以目前在通信中广泛采用的个人计算机取代子台通信控制器（ＣＣＵ）。本文就个人计算机在通信中的接口安排、传输方式进行了研究，并通过区域地震通信网子台数据传输的实践证实了个人计算机在通信中的广泛用途和诸多优点。  相似文献   

白垩-第三纪界线样品异常铱的赋存状态及其地质意义   总被引：1，自引：0，他引：1       下载免费PDF全文

孔屏  柴之芳 《地质科学》1993,(1):87

 通过对地质样品中铱的赋存状态研究及对残渣相中微粒的透射电镜分析,得出:在K-T界线样品中铱主要存在于残渣相中,不利于地球化学过程富集铱;铱在残渣相的富集与有机不溶物的存在没有必然联系;白垩-第三纪的生物绝灭事件中有火山活动参与;K-T界线事件的触发物为地外物质撞击。最后提出了K-T界线样品异常铱来源于地外物质撞击和火山喷发的混合模型。  相似文献   

耗散作用对大气中声波传播影响的数值研究          下载免费PDF全文

宋杨  赵正予  张援农 《地球物理学报》2014,57(6):1746-1756

通过结合保色散关系空间差分格式和Runge-Kutta时间格式的数值方法,研究了耗散作用对声波传播的影响.结果表明,耗散的不均匀性会同时影响声波的传播轨迹和传输损耗.不均匀的耗散会使得波包上部和下部承受不同程度的衰减,造成波包能量中心向弱耗散方向移动,使波包能量中心的传播轨迹发生偏折.与此同时,声波的传输损耗也受到了改变：与无耗散情况相比,声波的几何扩散衰减受到抑制;与均一耗散情况相比,声波的大气声吸收明显减小.由于声波衰减系数与声波频率的平方成正比,耗散作用使声波传播具有色散性质.不均匀耗散对于声波波包能量中心传播轨迹的偏折作用随频率的增加而增强.  相似文献   

Wave damping by a vertical porous structure placed near and away from a rigid vertical wall     

Santu Das 《地球物理与天体物理流体动力学》2014,108(2):147-167

Damping of water waves by a vertical porous structure placed at some distance from a vertical wall is investigated within the framework of linear water wave theory. The rectangular porous structure is placed on a small rectangular elevation. An incident wave of small amplitude propagates through the structure – some portion gets reflected back while some portion gets transmitted to a third region bounded vertically by a rigid wall which is considered to be at a distance near the porous structure, and also away from the wall at a large distance as a separate case. Boundary value problems are set up in all three regions and, by using the matching conditions along the vertical boundaries, a system of linear equations is deduced. The roots of the relevant dispersion relation are used in setting up the system of equations. The overall scattering phenomenon is studied with respect to different relevant parameters. The dependence of the coefficients on the thickness (width) of the porous structure is investigated for different numbers of modes and porosity. It is observed that, except for the case when the porous structure is thin, the reflection and transmission coefficients give rise to values as expected. In the case, when the rigid wall is nearer to the structure, the reflection coefficient decreases rapidly for a thin structure and converges for all numbers of evanescent modes afterwards. The transmission coefficient also decreases as the width increases, ultimately converging and vanishing for a wide structure. When the wall is at a large distance away from the structure, the behavior of both the reflection and transmission coefficients remain the same. For both cases of the wall being nearer and away from the structure, higher porosity gives rise to lower reflection coefficients and higher transmission coefficients. However, the transmission coefficients converge and vanish when the porous structure is very wide. We also discuss the energy loss against the width of the porous structure for different values of number of modes and porosity. Irrespective of the positioning of the rigid wall, we observe that for higher values of porosity, energy loss is more pronounced when the structure is not thin, whereas energy loss is same for all numbers of modes. All our observations are supported by graphs. Good agreement of our result with earlier results justifies our model.  相似文献   

新一代天气雷达产品共享平台的设计与实现   总被引：1，自引：0，他引：1       下载免费PDF全文

郜凌云  曲晓波  陈传雷 《气象与环境学报》2006,22(2):67-68

为将新一代天气雷达产品自动、实时传输到各级气象部门,根据辽宁已有的雷达产品显示终端和通信条件,依托省—市—县的2 M数字电路,采用FTP协议,建立新一代天气雷达资料全省共享平台,实现了雷达产品信息资料的共享。  相似文献   

Comparative review of marine mammal guidance implemented during naval exercises     

Sarah J. Dolman  Caroline R. Weir  Michael Jasny 《Marine pollution bulletin》2009,58(4):465-477

This article reviews the types and effectiveness of marine mammal mitigation measures used during some naval activities worldwide. The three main standard methods used to mitigate the potential impacts of naval sonar sound on marine mammals are (1) time/area planning (of exercises/active sonar use) to avoid marine mammals; (2) implementation of operational procedures (e.g. ‘soft start’ - where sound levels are gradually increased over time); and (3) monitoring of animals for the purpose of maintaining an ‘exclusion zone’ around the sound source. Suggestions towards a minimum worldwide mitigation standard are made.  相似文献   

Anisotropic Mean Traveltime Curves: A Method to Estimate Anisotropic Parameters from 2D Transmission Tomographic Data     

Juan L. Fernández Martínez  Luis M. Pedruelo González 《Mathematical Geosciences》2009,41(2):163-192

We present the mathematical deduction and properties of the mean traveltime curves for homogeneous elliptical anisotropic media. These curves generalize their isotropic counterparts which have been introduced in the past as a simple data quality analysis technique at the pre-inversion stage for 2D transmission experiments, allowing the inference of prior velocity models to gain stability at the tomographic inversion. Also, the anisotropy parameters (maximum velocity, anisotropic direction and ratio) are shown to affect the shape of these curves. The degree of asymmetry of the anisotropic mean traveltime curves (displacement of the mean time and standard deviation minima from the middle of the gathering line) is related to the direction of anisotropy which can then be visually estimated. Least squares’ fitting of the anisotropic theoretical models to their experimental counterparts is an effective method to estimate at the pre-inversion stage a macroscopic elliptical anisotropic velocity model, valid at the scale of the experiment, and able to match the experimental mean traveltime distribution. Sensitivity analysis has shown that the mean curve is less prone to errors than the standard deviation curve. Parameter identification from the standard deviation curve becomes unstable for noise levels higher than 5%; data errors produce smearing of the value of the estimated anisotropy ratio and wrong directions of anisotropy biased towards zero degrees. Also, identification from the mean traveltime curve becomes stable when the maximum velocity is well constrained. Finally, this methodology is illustrated with the application to the Grimsel data set. Performing MTC analysis is always recommended since it does not need high numerical requirements, and as shown in the sensibility analysis section, errors in data can be misinterpreted as geological anisotropies. J.L. Fernández Martínez is a visiting professor at UC Berkeley, Department of Civil and Environmental Eng., CA 94720-1710.  相似文献   

基于T-matrix的非线性参数估计方法          下载免费PDF全文

王本锋  吴如山  陈小宏  陆文凯 《地球物理学报》2016,59(6):2257-2265

全波形反演可提供高精度的地下介质参数空间分布,但传统的全波形反演方法建立在Born近似的基础上,对初始模型具有一定的依赖性.为了摆脱Born近似的束缚,本文基于二维常密度声波方程,在De Wolf近似的前提下,借助传输矩阵(T-matrix)方法,深入研究了逆薄板传播算子(Inverse Thin-Slab Propagator,ITSP),实现了速度扰动的非线性估计.ITSP方法避免了Born级数方法在扰动较强、扰动区域较大时的发散性问题,且只经过一次扫描校正,计算效率较高.二维模拟数据分析验证了本文方法的可行性以及有效性.  相似文献   

过套管电阻率测井的地层电阻率快速反演算法          下载免费PDF全文

刘福平  王安玲  刘华群  杨长春 《地球物理学报》2016,59(6):2326-2332

过套管电阻率测井是通过测量套管壁电势实现测量地层的视电阻率,基于传输线方程理论,针对层状地层,给出了套管壁电势、电流对地层横向电阻导数的微分方程(称Jacobi矩阵微分方程)及边界条件;利用Jacobi矩阵微分方程边值问题导出了过套管电阻率测井反演地层参数的Jacobi矩阵系数的解析表示,利用Marquardt方法实现了过套管测井的地层电阻率反演;通过计算对Jacobi矩阵的特性进行了探讨,并获得了较快的计算速度(因为Jacobi矩阵是用解析解表示的),反演结果与地层模型取得了较好的逼近.本文实现了过套管电阻率测井地层参数的Jacobi系数矩阵的快速计算及地层电阻率反演,为进一步开展电阻率测井数据处理提供了理论依据和快速反演算法.  相似文献