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191.
M. C. Kim 《Journal of Geodesy》1997,71(12):749-767
The fundamental geometry of satellite ground tracks and their crossover problem are investigated. For idealized nominal ground
tracks, the geometry is governed by a few constant parameters whose variations lead to qualitative changes in the crossover
solutions. On the basis that the theory to locate crossovers has not been studied in sufficient detail, such changes are described
in regard to the number of crossover solutions in conjunction with their bifurcations. Employing the spinor algebra as a tool
for establishing the ground-track crossing condition, numerical methodologies to locate crossovers appearing in general dual-satellite
ground-track configurations are also presented. The methodologies are applied to precisely determined orbital ephemerides
of the GEOSAT, ERS-1, and TOPEX/POSEIDON altimeter satellites.
Received: 19 November 1996 / Accepted: 12 May 1997 相似文献
192.
Least-squares prediction using an empirically deduced local covariance function was performed to investigate the temporal
change in the rates of vertical crustal movements in the Tohoku district, Japan. Levelling data covering an area of approximately
450 × 275 km2 observed between 1966 and 1995 were used and the results shown in the form of contour maps. Firstly we derived a covariance
function of the rates of vertical crustal movement with a Gaussian form function. We used this function to estimate the spatial
distribution of the rates of vertical crustal movements. By the present method, a steady tilt of the Tohoku district to the
east, toward the Japan Trench and an areal uplift in the southwestern part were well reproduced. Moreover, a significant temporal
change in vertical movement rates is clearly seen.
Received: 15 July 1996 相似文献
193.
Construction of Green's function to the external Dirichlet boundary-value problem for the Laplace equation on an ellipsoid of revolution 总被引:1,自引:0,他引:1
Green's function to the external Dirichlet boundary-value problem for the Laplace equation with data distributed on an ellipsoid
of revolution has been constructed in a closed form. The ellipsoidal Poisson kernel describing the effect of the ellipticity
of the boundary on the solution of the investigated boundary-value problem has been expressed as a finite sum of elementary
functions which describe analytically the behaviour of the ellipsoidal Poisson kernel at the singular point ψ = 0. We have
shown that the degree of singularity of the ellipsoidal Poisson kernel in the vicinity of its singular point is of the same
degree as that of the original spherical Poisson kernel.
Received: 4 June 1996 / Accepted: 7 April 1997 相似文献
194.
R. Lehmann 《Journal of Geodesy》1997,71(9):533-540
Geodetic surface integrals play an important role in the numerical solution of geodetic boundary-value problems. In many
cases they can be evaluated using fast methods in the frequency domain (FFT). However, this is not possible in general, because
the domain of integration may be non-trivial (as is the surface of the Earth), the kernel function may not be of convolution
type, or the data distribution may be heterogeneous. Therefore, fast evaluation strategies are also required in the space
domain. They are more difficult to design because only one property is left where a more or less fast evaluation strategy
can be built upon: the potential type of the kernel function. Consequently, the idea is not to replace well-established frequency
domain techniques, but to supplement them. Our approach to this problem goes in two directions: (1) we use advanced cubature
methods where the integration nodes automatically densify in the vicinity of the evaluation points; (2) we use powerful computer
hardware, namely MIMD computers with distributed memory. This enables us to evaluate geodetic surface integrals of any practical
complexity in reasonable time and accuracy. This is shown in a numerical example.
Received: 7 May 1996 / Accepted:17 March 1997 相似文献
195.
The spacetime gravitational field of a deformable body 总被引:3,自引:0,他引:3
The high-resolution analysis of orbit perturbations of terrestrial artificial satellites has documented that the eigengravitation
of a massive body like the Earth changes in time, namely with periodic and aperiodic constituents. For the space-time variation
of the gravitational field the action of internal and external volume as well as surface forces on a deformable massive body
are responsible. Free of any assumption on the symmetry of the constitution of the deformable body we review the incremental
spatial (“Eulerian”) and material (“Lagrangean”) gravitational field equations, in particular the source terms (two constituents:
the divergence of the displacement field as well as the projection of the displacement field onto the gradient of the reference
mass density function) and the `jump conditions' at the boundary surface of the body as well as at internal interfaces both
in linear approximation. A spherical harmonic expansion in terms of multipoles of the incremental Eulerian gravitational potential
is presented. Three types of spherical multipoles are identified, namely the dilatation multipoles, the transport displacement
multipoles and those multipoles which are generated by mass condensation onto the boundary reference surface or internal interfaces.
The degree-one term has been identified as non-zero, thus as a “dipole moment” being responsible for the varying position
of the deformable body's mass centre. Finally, for those deformable bodies which enjoy a spherically symmetric constitution,
emphasis is on the functional relation between Green functions, namely between Fourier-/ Laplace-transformed volume versus
surface Love-Shida functions (h(r),l(r) versus h
′(r),l
′(r)) and Love functions k(r) versus k
′(r). The functional relation is numerically tested for an active tidal force/potential and an active loading force/potential,
proving an excellent agreement with experimental results.
Received: December 1995 / Accepted: 1 February 1997 相似文献
196.
Vertical Ozone Profile over Tibet Using Sage I and II Data 总被引:8,自引:0,他引:8
VerticalOzoneProfileoverTibetUsingSageIandIData①ZouHan(邹捍)andGaoYongqi(郜永祺)InstituteofAtmosphericPhysics,ChineseAcademyofScie... 相似文献
197.
丽江地震序列的震源机制,发震应力场和破裂特征 总被引:17,自引:5,他引:17
丽江7.0级地震震区位于我国西南地区现代构造应力场空间分布的复杂地区,区域应力场主压应力优势方位为南南东。震区位于可能受到多种构造动力源作用的特定构造运动环境中。获得了主震和22个ML≥4.0级余震的震源机制P波初动解,分析表明,主震发震应力场为北3°东,与震区区域应力场主压应力优势方位有一个小角度的偏差。主震的发震应力不仅有水平应力的作用,同时还有显的垂直应力的作用。在余震序列发展中震区呈现出 相似文献
198.
云南地壳形变与丽江7.0级地震 总被引:9,自引:5,他引:9
本利用滇西、滇中地区大地垂直形变和跨断层短水准、短基线的监测资料进行综合分析论证,其结果表明:1996年2月滇西丽江7.0级地震前,该区应力场方向自1990年以来产生了由北东-北西的转变,震源区出现高达109mm的垂直差异运动1993-1996年有75%的断层形变测点相继出现不同程度的中期、短期和临震异常。大地垂直形变与断层形变的共性演变特性,为强震的预测提供了一个较好的震例。 相似文献
199.
研究讨论了云南强震活动的时空特征,指出区内M≥68级地震呈现活跃与平静;主体活动区东西交替及时空轮回迁移等特征。据此指出1988年云南地区进入了M≥68级地震强震活跃期,主体地区在云南西部,1995—1997年存在发生6—7甚至7级以上地震的危险。同时讨论了孟连73级地震前相关区地震活动,滇西北、滇西南有关b值、小震频度、调制比异常等8种地震学异常的空间分布、时间进程等特征。特别指出了1994年9月至1995年5月滇西南地区M≥47级地震形成的时空密集现象,及其在短临阶段对震级及地点方面判断的重要作用。 相似文献
200.
应用神经网络建立加速度峰值衰减规律 总被引:2,自引:0,他引:2
在假定了加速度峰值衰减规律的形式后,本采用人工神经网络拟合实际加速度峰值观测资料来求取方程中的待定系数。为加速神经网络的训练,本设计了基于BP学习算法的目标分段网络训练法。 相似文献