Least-squares self-coherency analysis of superconducting gravimeter records in search for the Slichter triplet   总被引：3，自引：0，他引：3  

Spiros D. Pagiatakis  Hui Yin 《Physics of the Earth and Planetary Interiors》2007,160(2):108-123

We develop a new approach for the spectral analysis of the superconducting gravimeter data to search for the spheroidal oscillation ₁S₁ of the Earth solid inner core. The new method, which we call least-squares (LS) self-coherency analysis, is based on the product of the least-squares spectra of segments of the time series under consideration. The statistical foundation of this method is presented in the new least-squares product spectrum theorem that establishes rigorously confidence levels for detecting significant peaks. We apply this approach along with a number of other innovative ideas to a 6-year long gravity series collected at the Canadian Superconducting Gravimeter Installation (CSGI) in Cantley, Canada, by splitting it into 72 statistically independent monthly records. Each monthly record is analysed spectrally and all monthly LS spectra are multiplied to construct the self-coherency spectrum of the 6-year gravity series. The self-coherency spectrum is then used to detect significant peaks in the band 3-7 h at various significant levels with the aim to identify a triplet of periods associated with the rotational/ellipsoidal splitting of ₁S₁ (Slichter triplet). From all the Slichter periods predicted by various researchers so far, Smylie's triplet appears to be the most supported one, albeit very weakly, both, before and after the atmospheric pressure effect is removed from the series. Using the viscous splitting law [Smylie, D.E., 1992. The inner core translational triplet and the density near Earth's center. Science 255, 1678-1682] as guide, we can also see one interesting and statistically significant triplet with periods A = {4.261 h, 4.516 h, 4.872 h}, which changes slightly to A′ = {4.269 h, 4.516 h, 4.889 h} after the atmospheric pressure correction is applied to the gravity series.  相似文献   

Shape Similarity measures of Linear Entities     

ZhangQiaopin  LIDeren 《地球空间信息科学学报》2002,5(2):62-67

The essential of feature matching technology lies in how to measure the similarity of spatial entities.Among all the possible similarity measures,the shape similarity measure is one of the most important measures because it is easy to collect the necessary parameters and it is also well matched with the human intuition.In this paper a new shape similarity measure of linear entities based on the differences of direction change along each line is presented and its effectiveness is illustrated.  相似文献   

基于矩阵论的空间相似变换分析   总被引：1，自引：0，他引：1  

江刚武  姜挺等 《测绘学院学报》2002,19(3):191-194

根据空间相似变换的线性化公式，利用矩阵论分析误差方程的系数矩阵，给出求解空间相似变换参数所需控制点的具体要求。  相似文献   

Researches on Plants from the Lower Devonian Xujiachong Formation in the Qujing District, Eastern Yunnan   总被引：1，自引：0，他引：1  

WANG Deming  HAO Shougang  LIU Zhenfeng School of Earth  Space Sciences  Peking University  Beijing 《《地质学报》英文版》2002,76(4):393-407

Fossil plants Hedeia sinica Hao et Gensel 1998, Huia gracilis Wang et Hao 2001 and Guangnania cuneata Wang et Hao are described from the Lower Devonian Xujiachong Formation, the Qujing district, eastern Yunnan, China. They contribute to our knowledge of the flora in this district. Based on the occurrence of common plants (Hedeia, Huia, Guangnania and Zosterophyllum australianum) and their horizons, it is proved for the first time that the mid-lower assemblage of the Xujiachong flora is comparable with the Early Devonian ((late) Pragian) Posongchong flora of southeastern Yunnan and the upper Baragwanathia flora of Australia. In view of this fact and the stratigraphic sequence, the mid-lower part of the Xujiachong Formation is considered to be of (late) Pragian age. Through comprehensive analyses of plant, bivalve and fish assemblages and the lithology, the upper part of the Xujiachong Formation is dated to be of early Emsian age. The Xujiachong flora belonged to the northeastern Gondwana palaeophytogeogr  相似文献   

An Evaluation Of Local Similarity At The Top Of The Mixed Layer Based On Large-Eddy Simulations     

Zbigniew Sorbjan 《Boundary-Layer Meteorology》2001,101(2):183-207

Local similarity, referred to as type II similarity,in the interfacial, stably-stratified layer at thetop of the atmospheric (or oceanic) mixed layer isdiscussed. Type II scales for scalars are based onthe local values of scalar gradients. Similaritypredictions are derived from the second-orderclosure model of Yamada and Mellor, and also fromsimilarity arguments. The obtainedformulation is verified for active and passive scalarsbased on the large-eddy simulation model.  相似文献   

VERTICAL STRUCTURE OF SECOND-MOMENT TURBULENT VARIABLES^*          下载免费PDF全文

AL-JIBOORI. M.H. XU Yumao  QIAN Yongfu 《Acta Meteorologica Sinica》2001,15(2):218-232

Two kinds of observational data,fluctuation and mean profile measurements,from a 325 m meteorological tower in Beijing,China,are used to evaluate local scales of velocity and temperature for higher heights by flux-gradient mean profiles and eddy-correlation techniques.A comparison of these methods each other was made in terms of vertical turbulence fluxes for momentum and beat at the same heigbt.The vertical profiles of non-dimensional second moments.such as vertical turbulent fluxes of momentum and heat.velocity and temperature standard deviations,were derived by local similarity theory.The local similarity relations expressed that the vertical distributions of non-dimensional second moment variables were found to be functions of z/Λ and z/h in the stable boundary layer and the function of z/Z_i for the convective boundary layer,where A the local Monin Obukhov(M-O) length. h the height of stable boundary layer and Z_i the height of mixed-layer.These relations are shown to agree well with the observational data.  相似文献   

基于螺旋线上谱因式分解的地震波场隐式辛算法   总被引：14，自引：8，他引：14       下载免费PDF全文

罗明秋  刘洪  李幼铭 《地球物理学报》2001,44(3):379-388

均匀介质、复杂各向同性介质和各向异性介质中的地震波传播过程,可用统一形式的标量声波方程描述.考虑到在无损耗条件下,地震波方程描述了地震波场这一个无穷维的哈密顿体系随时间的演化过程,该过程为一个单参数连续辛变换,因而可以在其哈密顿形式表述下导出其辛格式.与显式辛算法相比,隐式辛格式对应的隐式辛几何算法具有无条件稳定的特点,可以允许较大的计算步长.但是由于隐式算法不可避免地面临高阶矩阵的求逆,其每一步的计算速度较慢.为实现矩阵快速求逆,文中采用了螺旋边界条件下谱因式分解的方法.在螺旋边界条件下,需要求逆的矩阵化为带状矩阵,而且其各列非零元素的位置和大小具有非常好的相似性,因而可以采用谱因式分解的方法实现快速LU分解.文中采用二阶精度的隐式蛙跳辛格式和谱因式分解方法,计算了常速度、层状介质和Marmousi模型中的波场.计算表明,隐式辛算法不失为波场计算的一种好方法.  相似文献   

ALow-order　Model　of　Two-dimensional　Fluid　Dynamics　on　the　Surface　of　a　Sphere     

Mozheng Wei 《大气科学进展》1996,13(1):67-90

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论大气环流的季节划分和季节突变 Ⅰ:概念和方法   总被引：13，自引：4，他引：13  

曾庆存  张邦林 《大气科学》1992,(6)

本工作系列讨论大气环流的季节划分和季节突变问题.本文是第一篇,提出普适的概念、理论和方法,使大气环流和其他气候场的季节划分和季节突变定义建立在客观定量的基础之上.首先用两个场的相关系数R作为其相似性度量,也可以用归范化的两个场之差的根方值d作为差异性的度量.当存在着冬、夏季的典型场F_n和F_s时,取任何时刻t函数F与F~*≡(F_w+F_s)/2之差F~'作为变量场,则其与F~'_w≡F_w-F~*的相关系数R_w(t)及标准根方差d_w(t)可以作为F与其冬季典型的相似性或差异性度量.R_w与d_w~2之间有一定关系,一般只研究R_w即可.(1)可以定义冬季对应于1≥R_w(t)>0.5,夏季为-1≤R_w(t)<-0.5,过渡季节为-0.5相似文献   

重力波阻参数化方案及其预报试验   总被引：2，自引：0，他引：2  

江野 《高原气象》1992,11(2):152-160

  相似文献