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11.
M. Kern T. Preimesberger M. Allesch R. Pail J. Bouman R. Koop 《Journal of Geodesy》2005,78(9):509-519
The satellite missions CHAMP, GRACE, and GOCE mark the beginning of a new era in gravity field determination and modeling. They provide unique models of the global stationary gravity field and its variation in time. Due to inevitable measurement errors, sophisticated pre-processing steps have to be applied before further use of the satellite measurements. In the framework of the GOCE mission, this includes outlier detection, absolute calibration and validation of the SGG (satellite gravity gradiometry) measurements, and removal of temporal effects. In general, outliers are defined as observations that appear to be inconsistent with the remainder of the data set. One goal is to evaluate the effect of additive, innovative and bulk outliers on the estimates of the spherical harmonic coefficients. It can be shown that even a small number of undetected outliers (<0.2 of all data points) can have an adverse effect on the coefficient estimates. Consequently, concepts for the identification and removal of outliers have to be developed. Novel outlier detection algorithms are derived and statistical methods are presented that may be used for this purpose. The methods aim at high outlier identification rates as well as small failure rates. A combined algorithm, based on wavelets and a statistical method, shows best performance with an identification rate of about 99%. To further reduce the influence of undetected outliers, an outlier detection algorithm is implemented inside the gravity field solver (the Quick-Look Gravity Field Analysis tool was used). This results in spherical harmonic coefficient estimates that are of similar quality to those obtained without outliers in the input data. 相似文献
12.
阿尔金地区构造应力场及其对金属矿产分布的控制作用 总被引:2,自引:0,他引:2
构造应力场研究可以为区域矿产预测提供依据。主要根据节理、擦痕的测试分析,结合区域构造解析,确定阿尔金山东西向拉配泉--红柳沟构造带经历了三期不同方向的应力作用:印支期以前的南北向挤压作用,印支-燕山期的北西-南东向的挤压和中生代晚期-新生代北东东-南南西向的挤压;并利用有限元数值模拟前两期构造应力场的演变过程,进而讨论了区域构造应力场对内生金属矿产分布规律的控制作用指出了区域寻找大型内生金属矿产的有利地段。 相似文献
13.
A major earthquake (M=6.6) occurred on 21 June 2000, in South Iceland. This paper presents an unusual example of left-lateral strike-slip displacement recorded in a newly asphalted car park surface through a mechanically consistent pattern of open fissures and pressure ridges resulting from simple shear and rotation. Measurement of these features allows accurate reconstruction of the local deformation. The behaviour of the asphalt layer resembles that of analogue physical models, especially in terms of rotations induced by shear deformation. It is finally shown that through a wide range of scales some basic patterns associating rotation and opposite senses of strike-slip exist in the South Iceland Seismic Zone. 相似文献
14.
Geographies of Displacement: The Karenni and The Shan Across The Myanmar-Thailand Border 总被引:1,自引:0,他引:1
First, central to our analysis is the argument that human movement within and across borders fundamentally challenges the view of geopolitics based upon fixed territorial states, inter-state relations, national identities and citizenship; indeed the whole idea of "national geographic". Using the examples of the Karen and Shan peoples, we explore the processes and patterns of forced relocation, displacement and migration in the border regions of Myanmar and Thailand. Our main concern is with forced displacement as a result of political and ethnic conflict; specifically, how the Burmese military regime's desire for "national unity" within Myanmar's "national space" has influenced the militarily inspired displacements of hundreds of thousands of villagers and civilians within the border zones inhabited mostly by so-called "national minorities". We examine the particular problems of the so-called "internally displaced persons" within "national" boundaries compared with the "refugees" and "undocumented migrants" who make it across "international" space into Thailand. We illustrate the ways displaced people are represented by state agencies and the media as "threats" and "transgressors". We consider some of the "long term" aspects of the displacement problem along the Myanmar-Thai border and the vital contribution geographers can make to the study of displacement. 相似文献
15.
Geoid determination using adapted reference field, seismic Moho depths and variable density contrast 总被引:4,自引:0,他引:4
The traditional remove-restore technique for geoid computation suffers from two main drawbacks. The first is the assumption
of an isostatic hypothesis to compute the compensation masses. The second is the double consideration of the effect of the
topographic–isostatic masses within the data window through removing the reference field and the terrain reduction process.
To overcome the first disadvantage, the seismic Moho depths, representing, more or less, the actual compensating masses, have
been used with variable density anomalies computed by employing the topographic–isostatic mass balance principle. In order
to avoid the double consideration of the effect of the topographic–isostatic masses within the data window, the effect of
these masses for the used fixed data window, in terms of potential coefficients, has been subtracted from the reference field,
yielding an adapted reference field. This adapted reference field has been used for the remove–restore technique. The necessary
harmonic analysis of the topographic–isostatic potential using seismic Moho depths with variable density anomalies is given.
A wide comparison among geoids computed by the adapted reference field with both the Airy–Heiskanen isostatic model and seismic
Moho depths with variable density anomaly and a geoid computed by the traditional remove–restore technique is made. The results
show that using seismic Moho depths with variable density anomaly along with the adapted reference field gives the best relative
geoid accuracy compared to the GPS/levelling geoid.
Received: 3 October 2001 / Accepted: 20 September 2002
Correspondence to: H.A. Abd-Elmotaal 相似文献
16.
利用常规天气图、物理量诊断分析、逐时红外云图、单站资料等,对2003年4月12日影响鹰潭市的强对流、暴雨天气过程进行分析,认为该过程是在一定的大尺度环流背景下,由不同层次的天气系统共同作用下产生的;其触发机制是冷空气从近地层楔入暖空气中,在高、低空急流、层结不稳定等诸多有利条件下,由几个小尺度对流云团合并发展成1个中尺度对流复合体(MCC). 相似文献
17.
18.
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
19.
921型超低频有源伺服式速度,位移计 总被引:1,自引:2,他引:1
本介绍一种在很小体积的往复式摆上采用有源伺服技术实现超低频大幅值测量用的速度计、位移计,它可在多个频带测量速度和位移。最低频率可达0.04Hz,最大可测位移为±15m。它可用于海浪浪高、抽油机行程、高柔结构的超低频大位移测量。该仪器于1992年获得国家专利,并获得中国专利博览会银奖。 相似文献
20.
科学计算可视化技术的研究与应用 总被引:7,自引:3,他引:7
本文介绍了科学计算可视化技术的发展和应用情况,论述了这一新技术的特点及其在油气藏描述,工程设计CAD等学科的应用和发展趋势。阐述了目前国际国内计算机图形学领域具体的研究方向和方法及图形软件、图形硬件的发展概况。 相似文献