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281.
282.
C. C. Tscherning 《Journal of Geodesy》1999,73(6):332-336
A reproducing-kernel Hilbert space (RKHS) of functions harmonic in the set outside a sphere with radius R
0, having a reproducing kernel K
0(P,Q) is considered (P, Q, and later P
n
being points in the set of harmonicity). The degree variances of this kernel will be denoted σ0
n
.
The set of Riesz representers associated with the evaluation functionals (or gravity functionals) related to distinct points
P
n
,n = 1,…,N, on a two-dimensional surface surrounding the bounding sphere, will be linearly independent. These functions are used to
define a new N-dimensional RKHS with kernel (a
n
>0)
If the points all are located on a concentric sphere with radius R
1>R
0, and form an ε-net covering the sphere, and a
n
are suitable area elements (depending on N), then this kernel will converge towards an isotropic kernel with degree variances
Consequently, if K
N
(P,Q) is required to represent an isotropic covariance function of the Earth's gravity potential, COV(P,Q), σ0
n
can be selected so that σ
n
becomes equal to the empirical degree variances.
If the points are chosen at varying radial distances R
n
>R
0, then an anisotropic kernel, or equivalent covariance function representation, can be constructed. If the points are located
in a bounded region, the kernel may be used to modify the original kernel
Values of anisotropic covariance functions constructed based on these ideas are calculated, and some initial ideas are presented
on how to select the points P
n
.
Received: 24 September 1998 / Accepted: 10 March 1999 相似文献
283.
空间测边交会的优化解法及精度分析 总被引:2,自引:1,他引:1
给出了形式简单,规律,无需初值,迭代和过渡点的优化解法公式,适合于手工计算和计算机编辑,推出了空间测边交会点位精度的通用精度估算公式,并据此找到了各精度指标与各边倾角的内在关系。对应用条件提出了具体建议。 相似文献
284.
We describe our ongoing program of HST observations of Sakurai's Object(V4334 Sgr). Direct WFPC2 imaging from August 1996 through August 2000 revealsno transient features (such as light echoes), and documents the decline of thestar to below 24th visual magnitude in 2000. The surrounding planetary nebulahas shown no changes from 1996 through 2000. There are no obvious peculiarfeatures (such as blobs or knots) in the immediate vicinity of the star. Wealso have in place a target-of-opportunity program to obtain UV spectra withHST in the event that the star begins to retrace its evolution back to highsurface temperature. We also present older HST FOC imaging of V605 Aql. The central object is aresolved nebula that emits in [O III] (but not in hydrogen), whose 0.6diameter is consistent with a dust cloud ejected during the 1919 outburst. Thecentral star itself is not seen due to its being embedded in the nebula.Several other central stars (including H 3-75, IC 2120, and Abell 14) havelate-type nuclei and no evidence for hot companions. They may be furthercandidates for born-again red-giant nuclei. 相似文献
285.
H.-L. Lam 《Journal of Atmospheric and Solar》2004,66(18):2162
A study has been carried out to determine the relationship between high energy relativistic (>2 MeV) electron fluence and auroral zone geomagnetic activity for a solar cycle. Data for 1987–1997, spanning Solar Cycle 22, were used in the study. The relativistic electron fluence data were based on fluxes observed by the GOES geosynchronous satellites. The geomagnetic data were the DRX indices derived from a Canadian magnetic observatory located in the auroral zone at Fort Churchill, near the footprint of field lines passing through geostationary satellites. This work, based on data from a solar cycle, confirms earlier findings using limited data from segments of a solar cycle of enhancement in fluence 2–3 days after increases in geomagnetic activity, and shows the cycle dependence of fluence with respect to geomagnetic activity. This study underlines the influence of recurrent coronal holes on fluence level as well as the possible role of Pc5 magnetic pulsations as an electron acceleration mechanism, and highlights the predictability of fluence from ground geomagnetic data. A fluence prediction algorithm can now solely be based on derived expressions relating fluence and DRX. Thus, a simple fluence prediction scheme can easily be implemented to provide a 2–3 day advance warning of space weather conditions hazardous to geosynchronous satellites, since during days of high fluence, the likelihood of internal charging in a satellite is high, with possible discharges that could result in satellite operational anomalies. For verification purpose, daily values of fluence for 1997–2000 and for January 1994 were postcast using the derived expressions. The postcast values were validated, and the results give credence to the fluence prediction scheme. 相似文献
286.
287.
288.
河西地区几次强震前的垂直地形变分维特征研究 总被引:1,自引:0,他引:1
采用关联维的计算方法,对河西地区门源6.4级和天祝一景泰6.2级地震过程中的垂直地形变序列的时、空分维数分别进行了计算,得到:本文研究区内远场(远离震中区)的地形变序列分维数在0.63~0.80之间,而近场(震中地区)的序列分维数在0.17~0.44之间,近场出现明显的降维现象;地震的孕、发过程中地形变观测序列分维数在0.22~0.37之间,而无震期间则在0.57~0.77之间,地震孕、发过程中地形变观测时间序列亦存在明显的降维现象。 相似文献
289.
290.
In this paper, we examine the development and implementation of new technical systems designed to more effectively manage and produce driving, drivers and driving spaces. These new systems change the governmentality of automobilities by altering the relationship between driver, vehicle and transport infrastructure and produce new subjects and spaces. They do this principally through the process of automation, creating a system of regulation that we term ‘automated management’. Automated management consists of two interlocking sets of regulatory technologies: automated surveillance that seeks to enforce more effective (self)disciplining and capture systems that actively reshape activity. We argue that these work together to alter the automobilities landscape creating new socio-spatial arrangements with respect to access, movement, flow, and behaviour. Some of these arrangements are benign and empowering to individuals, others enhance the power of state and corporations. We illustrate our argument with examples predominately drawn from the UK, though the technologies we discuss are increasingly being developed and implemented throughout Western countries and beyond. 相似文献