Concept

Approximation diophantienne

Publications associées (136)

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A Fast Recursive Implementation of Gabor Filters

Michael Ansorge

This paper presents two methods, based on the rational approximation of functions, for designing Gabor like IIR filters with reduced computational complexity. The performance of the designed filters is discussed and comparisons with other approaches are ma ...

2005

Spectral methods based on prolate spheroidal wave functions for hyperbolic PDEs

Jan Sickmann Hesthaven

We examine the merits of using prolate spheroidal wave functions (PSWFs) as basis functions when solving hyperbolic PDEs using pseudospectral methods. The relevant approximation theory is reviewed and some new approximation results in Sobolev spaces are es ...

Society for Industrial and Applied Mathematics2005

Time-lag in Derivative Convergence for Fixed Point Iterations

Daniel Kressner

In an earlier study it was proven and experimentally confirmed on a 2D Euler code that fixed point iterations can be differentiated to yield first and second order derivatives of implicit functions that are defined by state equations. It was also asserted ...

2005

Hexagonal Versus Orthogonal Lattices: A New Comparison Using Approximation Theory

Dimitri Nestor Alice Van De Ville, Thierry Blu

We provide a new comparison between hexagonal and orthogonal lattices, based on approximation theory. For each of the lattices, we select the “natural” spline basis function as generator for a shift-invariant function space; i.e., the tensor-product B-spli ...

IEEE2005

New approaches for virtual private network design

Friedrich Eisenbrand

Virtual private network design is the following NP-hard problem. We are given a communication network, represented as a weighted graph with thresholds on the nodes which represent the amount of flow that a node can send to and receive from the network. The ...

2005

Lower bound to the AWGN remote rate-distortion function

Michael Christoph Gastpar

In the remote source coding problem, an underlying source is observed in noise. The noisy observations must be encoded into a bit stream in such a way as to enable the decoder to produce a good approximation to the original source sequence. The trade-off b ...

Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2005

Finite element approximation of multi-scale elliptic problems using patches of elements

Jacques Rappaz

In this paper we present a method for the numerical solution of elliptic problems with multi-scale data using multiple levels of not necessarily nested grids. The method consists in calculating successive corrections to the solution in patches whose discre ...

Springer-Verlag2005

Towards an optimal antenna for helicon waves excitation

Christoph Hollenstein

Helicon sources are known to produce high-density plasmas and have found many applications. Different types of antenna have been used for helicon excitation but none of them generate a radio-frequency (rf) field that matches the helicon wave field determin ...

2005

Pade-Jacobi Approximants

Jan Sickmann Hesthaven

We discuss projection based Pad ́e-Jacobi approximants in general and present in particular an exact rational approximation to the Sign function. This serves as vehicle to analyze the behavior of Pad ́e-Jacobi approximants for discontinuous functions. The ...

2004

Density-functional perturbational theory for dielectric tensors in the ultrasoft pseudopotential scheme

Alfredo Pasquarello

We introduce a density-functional perturbational scheme based on ultrasoft pseudopotentials for calculating dielectric tensors of periodic systems. We obtain a variational functional for the second-order derivative of the energy with respect to an electric ...

2004