IV: GEODESY: Remarks on the Role of Height Datum in Altimetry-Gravimetry Boundary-Value Problems

2003 ◽  
Vol 108 (1/2) ◽  
pp. 253-260 ◽  
Author(s):  
Fausto Sacerdote ◽  
Fernando Sansò
Author(s):  
PAOLO FERNANDES ◽  
MIRCO RAFFETTO

The aim of this work is to analyze the role of the impressed sources in determining the well or ill-posedness of time harmonic electromagnetic boundary value problems involving isotropic effective media. It is shown, in particular, that, even if all interfaces are regular, the class of ill-posed problems can be very large in the presence of general square-integrable impressed sources. However, when a simple and realistic constraint is enforced on these sources, requiring that the support of the sources does not include any interface between a traditional medium and a metamaterial, among the problems here considered just those involving an interface between complementary materials remain ill-posed. These considerations have a very significant impact also on the approximability of the solution of well-posed problems since the numerical noise can introduce small fictitious sources even where the sources to be simulated are not present. These effects on finite element simulators are fully analyzed. Finally, we propose an algorithm that allows to obtain much better approximations of the solutions of the most critical well-posed problems.


Author(s):  
А. Kalybay ◽  
◽  
Zh. Keulimzhaeva ◽  

When solving differential equations with variable coefficients, especially when the coefficients degenerate at the boundary of a given domain, problems arise in the formulation of boundary value problems. Usually, differential equations with variable coefficients are investigated in a suitable weight functional space. Often in the role of such spaces the weight Sobolev space or various generalizations are considered, which are currently sufficiently studied. However, in some cases, when the coefficients of the considered differential equation are strongly degenerate, the formulation of boundary value problems becomes problematic. In this work, we consider the so-called space with multiweighted derivatives, where after each derivative, the function is multiplied by the weight function and then the next derivative is taken. By controlling the behavior of the weight functions on the boundary, strongly degenerate equations can be investigated. Here we investigate the existence of traces on the boundary of a function from such spaces.


2007 ◽  
Vol 60 (3) ◽  
pp. 87-106 ◽  
Author(s):  
A. P. S. Selvadurai

This article presents an overview of the application of analytical methods in the theories of elasticity, poroelasticity, flow, and transport in porous media and plasticity to the solution of boundary value problems and initial boundary value problems of interest to geomechanics. The paper demonstrates the role of the analytical method in geomechanics in providing useful results that have practical importance, pedagogic value, and serve as benchmarking tools for calibrating computational methodologies that are ultimately used for solving more complex practical problems in geomechanics. There are 315 references cited in this article.


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