The analysis of the Neumann and the oblique derivative problem: the theory of regularization and its stochastic version     

Y. Rozanov  F. Sansò 《Journal of Geodesy》2001,75(7-8):391-398

 Following a detailed analysis of the weak solution of Neumann and oblique derivative problems [Rozanov and Sansò (1999). The analysis of the Neumann and the oblique derivative problem. Weak theory], here the so-called regularization theory is presented. The result, which is already known in mathematical literature, is obtained via a so-called Ladyzenskaya identity, which is a very interesting tool in itself. The analysis of the stochastic versions of the same problems is tackled and solved. In so doing, the question of the equivalence between different definitions of generalized random fields is also analyzed. Received: 1 February 2000 / Accepted: 26 February 2001  相似文献   

Sulfur isotope systematics in icelandic geothermal systems and influence of seawater circulation at Reykjanes     

H. Sakai  E. Gunnlaugsson  J. Tòmasson  J.E. Rouse 《Geochimica et cosmochimica acta》1980,44(8):1223-1231

Pyrite from altered basalts from Nàmafjall and Krafla high-temperature fields and deep zones at Reykir, Leira and other low-temperature fields, and aqueous sulfides from Nàmafjall, have δ³⁴S values of 0 to 2.6%. These values are close to those for postglacial basaltic lavas from the Reykjanes Peninsula. The major source of sulfur in these meteoric hydrothermal systems is the upper-mantle or basalt. At the low-temperature fields, however, the δ³⁴S values of sulfide decrease with decreasing depth, suggesting the presence of a light sulfur source in the shallower aquifers.In contrast, in the Reykjanes and Svartsengi geothermal fields, where seawater contributes to the hydrothermal systems, sulfide sulfur is distinctly enriched in ³⁴S at all depths except for one Reykjanes pyrite from 84 m depth. The enrichment is about 8%. at the deepest core (1734 m) of Reykjanes and decreases with decreasing depth. These enrichments are most likely due to seawater sulfate being involved in the hydrothermal systems. However, in the Reykjanes fluid, dissolved heavy sulfates are not in isotopic equilibrium with sulfide. Disequilibrium between sulfate and sulfide is also demonstrated in all other Icelandic geothermal systems studied.  相似文献   

The geodetic boundary value problem and the coordinate choice problem     

Fernando Sansò 《Journal of Geodesy》1981,55(1):17-30

Summary The geodetic boundary value problem (g.b.v.p.) is a free boundary value problem for the Laplace operator: however, under suitable change of coordinates, it can be transformed into a fixed boundary one. Thus a general coordinate choice problem arises: two particular cases are more closely analyzed, namely the gravity space approach and the intrinsic coordinates (Marussi) approach.  相似文献   

On the influence of nonlinearities on the eigenfrequencies of five-minute oscillations of the Sun     

Gaetano Belvedere  Douglas Gough  Lucio Paternò 《Solar physics》1983,82(1-2):343-354

Fitting the results of linear normal-mode analysis of the solar five-minute oscillations to the observed k - ω diagram selects a class of models of the Sun's envelope. It is a property of all the models in this class that their convection zones are too deep to permit substantial transmission of internal g modes of degree 20 or more. This is in apparent conflict with Hill and Caudell's (1979) claim to have detected such modes in the photosphere. A proposal to resolve the conflict was made by Rosenwald and Hill (1980). They pointed out that despite the impressive agreement between linearized theory and observation, nonlinear phenomena in the solar atmosphere might influence the eigenfrequencies considerably. In particular, they suggested that a correct nonlinear analysis could predict a shallow convection zone. This paper is an enquiry into whether their hypothesis is plausible. We construct k - ω diagrams assuming that the modes suffer local nonlinear distortions in the atmosphere that are insensitive to the amplitude of oscillation over the range of amplitudes that are observed. The effect of the nonlinearities on the eigenfrequencies is parameterized in a simple way. Taking a class of simple analytical models of the Sun's envelope, we compute the linear eigenfrequencies of one model and show that no other model can be found whose nonlinear eigenfrequencies agree with them. We show also that the nonlinear eigenfrequencies of a particular solar model with a shallow convective zone, computed with more realistic physics, cannot be made to agree with observation. We conclude, therefore, that the hypothesis of Rosenwald and Hill is unlikely to be correct.  相似文献   

The influence of the angular velocity distribution on the energy transport in the Sun's convection zone     

G. Belvedere  G. La Rosa  L. Paternò 《Solar physics》1981,74(1):107-110

This contribution is a purely exploratory search to investigate the way the distribution of angular velocity inside the Sun's convection zone affects the energy transport. This is related with problems concerning the magnetic activity, whose appearance at the Sun's surface depends on the shape of the isorotation surfaces, and the latitudinal variations in flux. The proposed model is non-linear and axisymmetric.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands.  相似文献   

Fast spherical collocation: theory and examples   总被引：2，自引：4，他引：2  

F. Sansò  C. C. Tscherning 《Journal of Geodesy》2003,77(1-2):101-112

 It has long been known that a spherical harmonic analysis of gridded (and noisy) data on a sphere (with uniform error for a fixed latitude) gives rise to simple systems of equations. This idea has been generalized for the method of least-squares collocation, when using an isotropic covariance function or reproducing kernel. The data only need to be at the same altitude and of the same kind for each latitude. This permits, for example, the combination of gravity data at the surface of the Earth and data at satellite altitude, when the orbit is circular. Suppose that data are associated with the points of a grid with N values in latitude and M values in longitude. The latitudes do not need to be spaced uniformly. Also suppose that it is required to determine the spherical harmonic coefficients to a maximal degree and order K. Then the method will require that we solve K systems of equations each having a symmetric positive definite matrix of only N × N. Results of simulation studies using the method are described. Received: 18 October 2001 / Accepted: 4 October 2002 Correspondence to: F. Sansò  相似文献   

The challenge of computing the geoid in the nineties     

F. Sansò  G. Sona 《Surveys in Geophysics》1993,14(4-5):339-371

This paper deals with the basic definitions and the numerical techniques used nowaday in the estimation of the gradiometric geoid. After a first introductory paragraph, the so-called 3-steps remove/restore method is presented. The computation and the use of global models is analysed in Section 2; the computation of topographic corrections, with particular care to the residual terrain correction, is presented in Section 3; the central solution or estimation of the anomalous potential either by solving a Molodensky's problem, or by applying the collocation theory, is examined in Section 4; the restore step is finally presented in Section 5.  相似文献   

IAG Newsletter     

Gyula Tòth 《Journal of Geodesy》2007,81(3):231-236

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Sulphuric acid geofluid contribution on thermal carbonate coastal springs (Italy)     

L. E. Zuffianò  M. Polemio  R. Laviano  G. De Giorgio  M. Pallara  P. P. Limoni  F. Santaloia 《Environmental Earth Sciences》2018,77(13):517

Hypogenic caves, developed by sulphuric acid speleogenesis, are known all over the world among which the Santa Cesarea Terme caves have been included. They are four submerged caves, located along a coastal carbonate sector in Southern Italy and hosting the outflow of coastal springs of thermal mixed waters (from 21 to 33 °C). These waters derive from the mixing of three water end members: the fresh pure groundwater of a wide karstic aquifer, the deep sulphur thermal water and the seawater. This cave system represents an almost unique case of hypogenic sea caves in carbonate environment. The thermal mixed waters have a different effect on the surrounding rocks of the caves, influencing the sulphuric acid speleogenetic process within the whole cave system. To understand the complex and overlapping natural processes acting on the development of these coastal caves, a multidisciplinary study has been carried out. This study has integrated all the data resulting from different methods and technologies, merging morphology, structural geology, hydrogeology, hydrogeochemistry and mineralogy. This multidisciplinary study has allowed to define the main geochemical processes acting within these caves, including the cave development and the formation of the mineral concretions. After the introduction of H₂S in the thermal waters, formed by the reduction of sulphates in the sedimentary deposits crossed at depth in the offshore, the oxidation occurs within the caves, producing sulphuric acid. Favoured by upwelling deep-seated thermal flows, this acid dissolves the limestone, with condensation corrosion process that involve replacement of limestone rock with gypsum. This process has resulted to be more active and remarkable within the Gattulla Cave, one of the Santa Cesarea Terme sea caves.  相似文献   

Environmental forcings and micro-seismic monitoring in a rock wall prone to fall during the 2018 Buran winter storm     

D’Angiò  D.  Fantini  A.  Fiorucci  M.  Iannucci  R.  Lenti  L.  Marmoni  G. M.  Martino  S. 《Natural Hazards》2021,106(3):2599-2617

Natural Hazards - This study reports a comparative analysis of the environmental conditions and micro-seismicity recorded on a rock wall resulting from an intense meteorological event. The...  相似文献