直立堤前海床的局部冲刷   总被引：2，自引：0，他引：2  

赵子丹  薛晓春 《海洋学报》1998,20(5):136-141

对不规则波作用下直立堤前海床的局部冲刷进行了研究。研究了由于波浪作用导致床面的底沙运动,从而造成提前海床的局部冲刷,即所谓的“相对粒沙”的情况。报导了;(1)堤前海床面为水平、堤下无基床情况下的堤前局部冲刷,以及堤下有明基床时基床尺度对堤前局部冲刷的影响;(2)堤前海床面为斜坡面时堤前的局部冲刷,以及当堤下有明基床时基床尺度对堤前局部冲刷的影响;(3)从波浪作用下床面边界层的理论分析出发,对于在不规则波作用下,离堤面愈远处的冲刷坑深度愈小的事实给出了解释。  相似文献   

An analysis of horizontal dispersion due to the drift current with an Ekman layer     

Hidekazu Yasuda 《Journal of Oceanography》1998,54(2):151-164

An analytical method for describing horizontal matter dispersion in shear currents is presented using a tensor expression from the point of view that matter dispersion due to the shear effect should be one of the principal mixing dilution processes. Although the behavior of horizontal dispersion is considerably more complicated than common longitudinal dispersion, the present study elucidates the vertical structure of dispersion and the dispersing process from the initial to the stationary stage, besides the usual depth-averaged dispersion coefficient at the stationary stage. As one of the typical applications of horizontal dispersion, dispersion due to the pure drift current with an Ekman layer is examined theoretically using the present method. This examination reveals that the displacement of the centroid and the major axis of dispersion are twisted in the vertical direction more than the direction of the current vector forming the Ekman spiral; that the variance increases in proportion to the third power of the elapsed time; and that the dispersion coefficient at the stationary stage remains constant, independent of the depth normalized by an Ekman layer thickness. Such dependence of the dispersion coefficient in the steady current is shown to be different from that in the oscillatory current, which is inversely proportional to the depth normalized by a Stokes layer thickness. This is considered to be induced by the difference of the vertical profiles of the first order moment in both currents, that is, the shear region of the first order moment is restricted around the floor by the alternation of the current shear in the oscillatory current while it is diffused in the whole depth in the steady current.  相似文献   

瑞雷波多阶模式频散曲线稀疏正则化反演方法研究     

崔岩  王彦飞 《地球物理学报》2022,65(3):1086-1095

目前瑞雷波多阶模式频散曲线反演中仅考虑数据的拟合,缺乏对模型的约束,不能很好地刻画地层间断面的问题,针对此问题,研究了瑞雷波多阶模式频散曲线稀疏正则化反演方法.正演模拟基于广义反射-透射系数法,数值计算上采用一种快速求根方法,与二等分方法相比,能够在很短的时间内达到最优的收敛效果;反演建模时采用L1范数正则化方法对模型...  相似文献   

地震层析成像反演中3种广义解的误差分析与评价   总被引：8，自引：3，他引：5       下载免费PDF全文

常旭  卢孟夏  刘伊克 《地球物理学报》1999,(5):1

在地震波速度和地震波　值层析成像中,对于非线性反演问题解的可靠性研究非常重要．为了讨论ＡＲＴ（ＡｌｇｅｂｒａｉｃＲｅｃｏｎｓｔｒｕｃｔｉｏｎ　Ｔｅｃｈｎｉｑｕｅ）、ＳＶＤ（Ｓｉｎｇｕｌａｒ　ＶａｌｕｅＤｅｃｏｍｐｏｓｉｔｉｏｎ）、ＬＳＱＷ（ＬｅａｓｔＳｕａｒｅ）３种方法的算法稳定性以及反演效果,本研究将这３种算法用于求解非常病态问题和一般稳定问题,根据数值计算结果,分别给出了在非常病态问题和一般稳定问题中３种算法的相对误差及其算法稳定性评价．进而针对３种算法在同一地质模型上的速度成像结果进行了比较,为地震层析成像反演效果分析提供了定量参数．  相似文献   

小波变换多尺度地震波形反演   总被引：29，自引：5，他引：24       下载免费PDF全文

孟鸿鹰  刘贵忠 《地球物理学报》1999,42(2):241-248

完全非线性地震波形反演问题是石油地球物理勘探领域中一个非常重要而又难度很大的问题。本文提出了多尺度地震波形反演的小波变换方法,对于一维非线性地震波形反演问题,将该方法和已有的简单迭代法及多重网格法作了比较,数值实验结果表明,本方法效果较好。  相似文献   

中国东部含金矽卡岩矿床分布规律 与深部地球物理背景研究   总被引：2，自引：0，他引：2  

① 《物探与化探》1999,23(6):415-420

在收集整理中国大陆上十几条地学断面、数十条地震剖面、大地电磁剖面、地壳上地幔剪切波资料的基础上,对含金矽卡岩矿床的深部地球物理背景进行了深入的研究,作者认为岩石圈剪切带是控制含金矽卡岩矿床的最主要的深部地球物理背景条件。壳内低速高导层因与地幔流体分布有关,同样对含金矽卡岩矿床有控制作用、大（ 深） 断裂带的交汇部位控制着与矿有关的中酸性侵入岩浆,可以利用这些因素的共同制约作用进一步圈定含金矽卡岩矿床和铜伴生金矽卡岩矿床分布的远景预测区。  相似文献   

二维视电阻率断面的快速最小二乘反演   总被引：12，自引：0，他引：12  

张大海  王兴泰 《物探化探计算技术》1999,21(1):2-13

快速最小二乘反演是以平滑限定的最小二乘方法为基础,是对二维视电阻率断面进行反演的一种方法。反演过程不需要提供初始模型,在首次迭代时使用一均匀介质地下模型作为初始模型,该模型的视电阻率偏导数值可以用解析法得到。在后面的迭代中,使用了拟牛顿法去修改每一次迭代的偏导数矩阵,避免了偏导数矩阵的直接计算,从而减少了计算时间和存储空间。同时运用牛顿矩阵校正技术解最小二乘方程组也减少了大量的计算时间。总之,该方  相似文献   

Remarks on the Definition and Estimation of Friction Velocity   总被引：3，自引：1，他引：2  

Rudolf O. Weber 《Boundary-Layer Meteorology》1999,93(2):197-209

One of the mainscaling parameters in similarity theory of the atmospheric boundary layer is friction velocity. Unfortunately, several definitions of friction velocity exist in the literature. Some authors use the component of the horizontal Reynolds stress vector in the direction of the mean wind vector to define friction velocity. Others define the friction velocity by means of the absolute value of the horizontal Reynolds stress vector. The two definitions coincide only if the direction of the mean wind vector is parallel to the horizontal Reynolds stress vector. In general, the second definition gives larger values for the friction velocity. Over complex terrain the situation is further complicated by the fact that the terrain following flow is not necessarily horizontal. Thus, several authors have proposed to use terrain following coordinate systems for the definition of friction velocity. By means of a large dataset of fast-response wind measurements with an ultrasonic anemometer the friction velocities resulting from the different definitions are compared. Furthermore, it is shown that friction velocity can be well estimated from horizontal wind speed, and even better from simple horizontal or vertical turbulence parameters.  相似文献   

A Note on the Flux-Variance Similarity Relationships for Heat and Water Vapour in the Unstable Atmospheric Surface Layer   总被引：12，自引：11，他引：1  

Gabriel G. Katul  Cheng-I Hsieh 《Boundary-Layer Meteorology》1999,90(2):327-338

Atmospheric surface layer (ASL) experiments over the past 10 years demonstrate that the flux-variance similarity functions for water vapour are consistently larger in magnitude than their temperature counterpart. In addition, latent heat flux calculations using the flux-variance method do not compare as favorably to eddy- correlation measurements when compared to their sensible heat counterpart. These two findings, in concert with measured heat to water vapour transport efficiencies in excess of unity, are commonly used as evidence of dissimilarity between heat and water vapour transport in the unstable atmospheric surface layer. In this note, it is demonstrated that even if near equality in flux-profile similarity functions for heat and water vapour is satisfied, the flux-variance similarity functions for water vapour are larger in magnitude than temperature for a planar, homogeneous, unstably-stratified turbulent boundary-layer flow.  相似文献   

Constraint inversion Algorithm of Lidar Equationfor Deriving Aerosol Optical Property     

邱金桓 《大气科学进展》1999,(2)

1.IntroductionLidarisincreasinglyusedinmeasuringtheopticalpropertiesofaerosolsandcloudssincethe1960's.Ithasbeenshownthatthedeterminationoftheextinctioncoefficientasafunctionofheightisfeasible(Klett,1980;Fernald,1984;LuDarenetal.,1977;Spinhirneetal.,...  相似文献