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31.
The decomposition of a monochromatic wave over a submerged plate is investigated experimentally in a wave flume. Bound and free higher harmonic modes propagating upstream and downstream the structure are discriminated by means of moving resistive probes. The first-order analysis shows a resonant behaviour linked to the ratio of the plate's width and the fundamental mode wavelength over the plate. The second-order analysis shows an energy transfer from the fundamental mode towards free harmonics propagating downstream the structure. This transfer is linked to the ratio of the width of the plate and the bound harmonic wavelength over the plate. We also performed experiments with a submerged step to compare the efficiency of both structures. The submerged plate is shown to be a more efficient breakwater than the step, at the first as well as the second-order. 相似文献
32.
扼要地介绍了非球形粒子光散射的散射矩阵元素按广义球函数展开的基本理论,以及球形粒子散射矩阵元素间的关系。在此基础上较详细地阐述了计算展开系数的方法以及在程序研制中所遇到的一些问题。最后,对非球形的Chebyshev粒子光散射的散射矩阵元素的展开系数进行了计算,结果表明数值技术和计算的正确性。 相似文献
33.
基于ECMWF全球大气模型和中国地面气候资料日值数据集中新疆及周边的气象站气压数据,根据弹性地壳形变理论,采用移去-恢复法,利用负荷格林函数法和球谐函数法,计算新疆及周边区域2011~2015年大气负荷变化对地壳垂直、水平形变的影响,同时采用大气导纳方法计算大气变化对地面重力的影响。结果表明,大气负荷对新疆地区垂直形变的影响达到cm级,对地面重力的影响可达10μGal;大气负荷影响具有明显的季节性。 相似文献
34.
利用青藏高原东南缘1999~2007年与2011~2017年高精度GNSS监测资料,充分顾及GNSS测站非均匀分布的特性,构建青藏高原东南缘地壳形变多尺度球面小波模型,定量分析汶川强震前后该区域地壳形变与不同空间尺度下地壳应变率场变化特征。研究结果表明,汶川强震前后研究区整体地壳运动具有一定继承性发展特征,均在龙门山、安宁河、则木河与小江断裂处形成明显的速度差异梯度带,且高应变率值也主要聚集在上述主干断裂及附近区域;汶川强震后,研究区域整体地壳运动速率量值,特别是龙门山断裂带西北侧地壳运动速度量值显著增大,羌塘、巴颜喀拉与川滇地块也呈现出加速向南东运移并推动华南块体的趋势。不同尺度下的应变率场反映出不同空间范围下区域应变积累特征,青藏高原东南缘区域在尺度因子q=7时的计算结果是合理的(合理的最大尺度因子);当尺度因子q=6时,能较好地揭示出区域整体构造活动特性,即清晰地揭示出汶川强震后龙门山断裂处呈现出的显著主压应变、面压缩与最大剪应变率高值特征;当尺度因子q=3~7时(最佳组合尺度因子),可较好地综合揭示出区域地壳大尺度(整体)形变与局部形变特征。汶川强震后,研究区域主干断裂带,特别是震中及其附近区域地震活动性显著增强。 相似文献
35.
Christopher Kotsakis 《Journal of Geodesy》2009,83(1):31-50
All gravity field functionals obtained from an Earth gravitational model (EGM) depend on the underlying terrestrial reference
frame (TRF), with respect to which the EGM’s spherical harmonic coefficients refer to. In order to maintain a coherent framework
for the comparison of current and future EGMs, it is thus important to investigate the consistency of their inherent TRFs,
especially when their use is intended for high precision studies. Following the methodology described in an earlier paper
by Kleusberg (1980), the similarity transformation parameters between the associated reference frames for several EGMs (including
the most recent CHAMP/GRACE models at the time of writing this paper) are estimated in the present study. Specifically, the
differences between the spherical harmonic coefficients for various pairs of EGMs are parameterized through a 3D-similarity
spatial transformation model that relates their underlying TRFs. From the least-squares adjustment of such a parametric model,
the origin, orientation and scale stability between the EGMs’ reference frames can be identified by estimating their corresponding
translation, rotation and scale factor parameters. Various aspects of the estimation procedure and its results are highlighted
in the paper, including data weighting schemes, the sensitivity of the results with respect to the selected harmonic spectral
band, the correlation structure and precision level of the estimated transformation parameters, the effect of the estimated
differences of the EGMs’ reference frames on their height anomaly signal, and the overall feasibility of Kleusberg’s formulae
for the assessment of TRF inconsistencies among global geopotential models. 相似文献
36.
37.
E. Knobloch 《地球物理与天体物理流体动力学》2013,107(1-4):105-116
Abstract Unbounded stratified plane Couette flow is shown to be stable against small amplitude disturbances. The Brunt-Väisälä frequency is assumed to be constant. Both viscosity and thermal diffusion are included, and shown to be stabilizing. 相似文献
38.
Robert A. Langel 《Journal of Earth System Science》1990,99(4):581-618
Among the first measurements made from near-Earth orbiting satellites were measurements of the magnetic field. The sources
of that field lie both within the Earth, in its core and crust, and in the surrounding ionosphere and magnetosphere. This
article summarizes some of the methodology and results for studies of the Earth’s mantle and crust. Mantle conductivity studies
can be made either by studying signals impressed on the Earth from outside, e.g., the ionosphere or magnetosphere, or by studying
signals originating in the core and transmitted through the mantle. Crustal field studies begin with a careful selection of
the data and subsequent removal of core and external fields by some sort of filtering. Average maps from different local times
sometimes differ, presumably due to the remaining presence of fields of external origin. Several techniques for further filtering
are discussed. Where large-area aeromagnetic maps are available, crustal maps derived from satellite data can be compared
with upward continued data. In general, the comparisons show agreement, with some differences, particularly in and near the
auroral belts. The satellite data are further reduced by various methods of inverse and forward modelling, sometimes including
reduction to the pole (RTP). These techniques are generally unstable at the equator. Common methods of stabilizing the inversions
include principle components analysis and ridge regression. Because of the presence of the core field, the entire crustal
contribution from the field is not known. Also, there is a basic nonuniqueness to the inverse solutions. Nevertheless, magnetizations
that are interpretable can be derived. 相似文献
39.
Clifford R. Stanley 《Mathematical Geology》1990,22(8):933-956
Recent publications have demonstrated that the composition of a system can be described by the angles which define the vector resulting from the projection of the composition onto the unit hypersphere. Although published trigonometric relationships allow determination of the angles in any number of dimensions, no general hyperdimensional recursive formulae exist for the calculation of these quantities and their variances and covariances. A general methodology for calculating the angles which describe the compositions of systems in any number of dimensions is presented. These angles can be used to calculate statistics (central moments and resultant vectors) describing the central tendency and dispersion among rock compositions, as well as to quantify the angular differences between compositions. Equations that relate the variances and covariances of these angular variables to the variances and covariances of the actual component proportion variables are presented, allowing projection of these measurements from one reference frame to another (cartesian to spherical and vice versa). 相似文献
40.
申宁华 《吉林大学学报(地球科学版)》1990,(4)
本文从球谐函数理论的物理含义、中国地磁数据的分布情况及实际计算结果的分析,提出对当前用球谐函数拟合法提取中国大陆区域地磁异常的几点认识。 相似文献