Lithosphere mechanical behavior inferred from tidal gravity anomalies: a comparison of Africa and South America     

Marta S.M. Mantovani  Wladimir Shukowsky  Silvio R.C. de Freitas  Benjamim B. Brito Neves 《Earth and Planetary Science Letters》2005,230(3-4):397-412

  相似文献   

Energy–Momentum In The Viscous Kasner-Type Universe In Teleparallel Gravity     

Mustafa?SaltiEmail author 《Astrophysics and Space Science》2005,299(2):159-166

Using the teleparallel gravity versions of the Einstein and Landau–Lifshitz’s energy and/or momentum complexes, I obtain the energy and momentum of the universe in viscous Kasner-type cosmological models. The energy and momentum components (due to matter plus field) are found to be zero and this agree with a previous work of Rosen and Johri et al., who investigated the problem of the energy in Friedmann–Robertson–Walker (FRW) universe. The result that the total energy and momentum components of the universe in these models is zero same as Bergmann–Thomson’s energy–momentum and props the viewpoint of Tryon. Rosen found that the energy of the FRW space–time is zero, which agrees with the studies of Tryon. PACs Numbers: 04.20.-q; 04.50.+h An erratum to this article is available at .  相似文献   

Energy Of The Universe In Bianchi-Type I Models In MØLler’S Tetrad Theory Of Gravity     

Oktay?Aydo?duEmail author  Mustafa?Salti 《Astrophysics and Space Science》2005,299(3):227-232

In this paper, using the energy definition in MØller’s tetrad theory of gravity we calculate the total energy of the universe in Bianchi-type I cosmological models which includes both the matter and gravitational fields. The total energy is found to be zero and this result agrees with a previous works of Banerjee and Sen who investigated this problem using the general relativity version of the Einstein energy-momentum complex and Xulu who investigated same problem using the general relativity versions of the Landau and lifshitz, Papapetrou and Weinberg’s energy-momentum complexes. The result that total energy of the universe in Bianchi-type I universes is zero supports the viewpoint of Tryon.  相似文献   

用重复重力测量测定垂线偏差时变的精度   总被引：6，自引：0，他引：6  

李月锋  丁行斌 《天文学报》2005,46(4):460-473

列举两种垂线偏差时变测定的微分公式,从理论上对用重复重力测量的方法测定垂线偏差时变的精度进行了探讨．在目前情况下,垂线偏差时变测定精度可以达到0．005＂．远区域的点对它的影响可以忽略不计,通过对重力网的模拟计算,进一步得到验证．探讨了有效积分半径对垂线偏差时变测量精度的影响,并在此基础上讨论了重力网优化的问题．  相似文献   

Interannual variability of low-degree gravitational change, 1980–2002     

J.L. Chen  C.R. Wilson  B.D. Tapley 《Journal of Geodesy》2005,78(9):535-543

Time variations in the Earths gravity field at periods longer than 1 year, for degree-two spherical harmonics, C₂₁, S₂₁, and C₂₀, are estimated from accurately measured Earth rotational variations. These are compared with predictions of atmospheric, oceanic, and hydrologic models, and with independent satellite laser ranging (SLR) results. There is remarkably good agreement between Earth rotation and model predictions of C₂₁ and S₂₁ over a 22-year period. After decadal signals are removed, Earth-rotation-derived interannual C₂₀ variations are dominated by a strong oscillation of period about 5.6 years, probably due to uncertainties in wind and ocean current estimates. The model-predicted C₂₀ agrees reasonably well with SLR observations during the 22-year period, with the exception of the recent anomaly since 1997/1998.  相似文献   

多层界面快速反演在高精度石油重力勘探中的应用     

Li Qingchun  Pan Zuoshu 《地球科学与环境学报》1997,(1)

重力勘探作为一种快速普查方法，在深部地质构造研究、区域地质构造划分及找矿勘探中均已取得显著的地质效果。自８０年代后期，由于在重力测地工作中使用红外测距仪及高精度ＧＰＳ定位技术，确保了重力测点位置及高程有较高的精度；在重力观测中普遍采用目前世界上精度最高的Ｌａｃｏｓｔｅ型重力仪进行基点联测，采用对恒温系统改进后的Ｗｏｒｄｅｎ重力仪进行重力测点观测，使得重力测量的质量及精度都有了很大提高，为扩大重力法的应用提供了条件。本文给出的一例是；在我国某含油沉积盆地上，根据对实测１：２５０００高精度重力资料（布格重力异常总观测均方误差：６０×１０￣－８ｍ／ｓ￣２）的处理及约束信息下多层界面反演结果，确定有利油气聚集的圈闭范围，推断含油层的大致规模。  相似文献   

A Laser-induced Fluorescence Instrument for Detecting Tropospheric OH and HO2: Characteristics and Calibration   总被引：1，自引：0，他引：1  

Ian C. Faloona  David Tan  Robert L. Lesher  Nathan L. Hazen  Christopher L. Frame  James B. Simpas  Hartwig Harder  Monica Martinez  Piero Di Carlo  Xinrong Ren  William H. Brune 《Journal of Atmospheric Chemistry》2004,47(2):139-167

  相似文献   

Comparison of the dynamic response of a saturated soil between two models     

LIN Mian Institute of Mechanics  Chinese Academy of Sciences  Beijing  China 《中国科学D辑(英文版)》2004,47(6):551-558

The dynamic response of marine sediment to ocean surface waves is treated extremely by marine geotechnical and coastal engineers. In the area of conventional hydrodynamics, the assumption of im-permeable rigid seabed has been used as the boundary of water waves theories and the waves parameters de-duced from the theory have not referred to the interac-tion of water waves and seabed. In the area of soil mechanics, many engineers regard the response as slow loading according to the Zienkewiczs[1…  相似文献   

Ellipsoidal geoid computation   总被引：1，自引：1，他引：0  

R. G.?HipkinEmail author 《Journal of Geodesy》2004,78(3):167-179

Modern geoid computation uses a global gravity model, such as EGM96, as a third component in a remove–restore process. The classical approach uses only two: the reference ellipsoid and a geometrical model representing the topography. The rationale for all three components is reviewed, drawing attention to the much smaller precision now needed when transforming residual gravity anomalies. It is shown that all ellipsoidal effects needed for geoid computation with millimetric accuracy are automatically included provided that the free air anomaly and geoid are calculated correctly from the global model. Both must be consistent with an ellipsoidal Earth and with the treatment of observed gravity data. Further ellipsoidal corrections are then negligible. Precise formulae are developed for the geoid height and the free air anomaly using a global gravity model, given as spherical harmonic coefficients. Although only linear in the anomalous potential, these formulae are otherwise exact for an ellipsoidal reference Earth—they involve closed analytical functions of the eccentricity (and the Earths spin rate), rather than a truncated power series in e². They are evaluated using EGM96 and give ellipsoidal corrections to the conventional free air anomaly ranging from –0.84 to +1.14 mGal, both extremes occurring in Tibet. The geoid error corresponding to these differences is dominated by longer wavelengths, so extrema occur elsewhere, rising to +766 mm south of India and falling to –594 mm over New Guinea. At short wavelengths, the difference between ellipsoidal corrections based only on EGM96 and those derived from detailed local gravity data for the North Sea geoid GEONZ97 has a standard deviation of only 3.3 mm. However, the long-wavelength components missed by the local computation reach 300 mm and have a significant slope. In Australia, for example, such a slope would amount to a 600-mm rise from Perth to Cairns.  相似文献   

A technique for modeling the Earth’s gravity field on the basis of satellite accelerations   总被引：3，自引：2，他引：1  

P. Ditmar  A. A. van Eck van der Sluijs 《Journal of Geodesy》2004,78(1-2):12-33

A technique is proposed for Earths gravity field modeling on the basis of satellite accelerations that are derived from precise orbit data. The functional model rests on Newtons second law. The computational procedure is based on the pre-conditioned conjugate-gradient (PCCG) method. The data are treated as weighted average accelerations rather than as point-wise ones. As a result, a simple three-point numerical differentiation scheme can be used to derive them. Noise in the orbit-derived accelerations is strongly dependent on frequency. Therefore, the key element of the proposed technique is frequency-dependent data weighting. Fast convergence of the PCCG procedure is ensured by a block-diagonal pre-conditioner (approximation of the normal matrix), which is derived under the so-called Colombo assumptions. Both uninterrupted data sets and data with gaps can be handled. The developed technique is compared with other approaches: (1) the energy balance approach (based on the energy conservation law) and (2) the traditional approach (based on the integration of variational equations). Theoretical considerations, supported by a numerical study, show that the proposed technique is more accurate than the energy balance approach and leads to approximately the same results as the traditional one. The former finding is explained by the fact that the energy balance approach is only sensitive to the along-track force component. Information about the cross-track and the radial component of the gravitational potential gradient is lost because the corresponding force components do no work and do not contribute to the energy balance. Furthermore, it is shown that the proposed technique is much (possibly, orders of magnitude) faster than the traditional one because it does not require the computation of the normal matrix. Hints are given on how the proposed technique can be adapted to the explicit assembling of the normal matrix if the latter is needed for the computation of the model covariance matrix.Acknowledgments. Professor R. Klees is thanked for support of the project and for numerous fruitful discussions. The authors are also thankful to Dr. J. Kusche for useful remarks and to Dr. E. Schrama, his solid background in satellite geodesy proved to be very helpful. A large number of valuable comments were made by Dr. S.-C. Han, Dr. P. Schwintzer, and an anonymous reviewer; their contribution is greatly acknowledged. The satellite orbits used in the numerical study were kindly provided by Dr. P. Visser (Aerospace Department, Delft University of Technology). Access to the SGI Origin 3800 computer was provided by Stichting Nationale Computerfaciliteiten (NCF), grant SG-027.  相似文献