scholarly journals Parallel projection methods and the resolution of ill-posed problems

1994 ◽  
Vol 27 (1) ◽  
pp. 11-24 ◽  
Author(s):  
M.A. Diniz-Ehrhardt ◽  
J.M. Martínez ◽  
S.A. Santos
2006 ◽  
Vol 6 (1) ◽  
pp. 87-93 ◽  
Author(s):  
Sergei G. Solodky ◽  
Evgeniya V. Lebedeva

AbstractAn approach to constructing regularized projection methods to solve illposed problems is proposed. This approach is based on a modification of the Galerkin discretization scheme. It has been established that such a modification leads to a significant reduction of information expenses compared to other known methods.


2016 ◽  
Vol 16 (2) ◽  
pp. 257-276 ◽  
Author(s):  
Stefan Kindermann

AbstractWe consider the discretization of least-squares problems for linear ill-posed operator equations in Hilbert spaces. The main subject of this article concerns conditions for convergence of the associated discretized minimum-norm least-squares solution to the exact solution using exact attainable data. The two cases of global convergence (convergence for all exact solutions) or local convergence (convergence for a specific exact solution) are investigated. We review the existing results and prove new equivalent conditions when the discretized solution always converges to the exact solution. An important tool is to recognize the discrete solution operator as an oblique projection. Hence, global convergence can be characterized by certain subspaces having uniformly bounded angles. We furthermore derive practically useful conditions when this holds and put them into the context of known results. For local convergence, we generalize results on the characterization of weak or strong convergence and state some new sufficient conditions. We furthermore provide an example of a bounded sequence of discretized solutions which does not converge at all, not even weakly.


Computing ◽  
1995 ◽  
Vol 55 (2) ◽  
pp. 113-124 ◽  
Author(s):  
S. V. Pereverzev
Keyword(s):  

Author(s):  
E. P. Serrano ◽  
M. I. Troparevsky ◽  
M. A. Fabio

We consider the Inverse Problem (IP) associated to an equation of the form Af = g, where A is a pseudodifferential operator with symbol[Formula: see text]. It consists in finding a solution f for given data g. When the operator A is not strongly invertible and the data is perturbed with noise, the IP may be ill-posed and the solution must be approximate carefully. For the present application we regard a particular orthonormal wavelet basis and perform a wavelet projection method to construct a solution to the Forward Problem (FP). The approximate solution to the IP is achieved based on the decomposition of the perturbed data calculating the elementary solutions that are nearly the preimages of the wavelets. Based on properties of both, the basis and the operator, and taking into account the energy of the data, we can handle the error that arises from the partial knowledge of the data and from the non-exact inversion of each element of the wavelet basis. We estimate the error of the approximation and discuss the advantages of the proposed scheme.


1995 ◽  
Vol 34 (20) ◽  
pp. 3883 ◽  
Author(s):  
Tuvia Kotzer ◽  
Joseph Rosen ◽  
Joseph Shamir

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