Sampling and series expansion theorems for fractional Fourier and other transforms

Cataloged from PDF version of article.We present muchbriefer and more direct and transparent derivations of some sampling and series expansion relations for fractional Fourier and other transforms. In addition to the fractional Fourier transform, the method can also be applied to the Fresnel, Hartley, and scale transform and other relatives of the Fourier transform. (C) 2003 Published by Elsevier B.

Modèles en iles pour le réglage automatique de paramètres : application au problème du bandit manchot

National audienc

Parameter Setting with Dynamic Island Models

In this paper we proposed the use of a dynamic island model which aim at adapting parameter settings dynamically. Since each island corresponds to a specific parameter setting, measuring the evolution of islands populations sheds light on the optimal parameter settings efficiency throughout the search. This model can be viewed as an alternative adaptive operator selection technique for classic steady state genetic algorithms. Empirical studies provide competitive results with respect to other methods like automatic tuning tools. Moreover, this model could ease the parallelization of evolutionary algorithms and can be used in a synchronous or asynchronous way

Non stationary operator selection with island models

The purpose of adaptive operator selection is to choose dynamically the most suitable variation operator of an evolutionary algorithm at each iteration of the search process. These variation operators are applied on individuals of a population which evolves, according to an evolutionary process, in order to find an optimal solution. Of course the efficiency of an operator may change during the search and therefore its application should be precisely controlled. In this paper, we use dynamic island models as operator selection mechanisms. A sub-population is associated to each operators and individuals are allowed to migrate from one sub-population to another one. In order to evaluate the performance of this adaptive selection mechanism, we propose an abstract operator representation using fitness improvement distributions that allow us to define non stationary operators with mutual interactions. Our purpose is to show that the adaptive selection is able to identify not only good operators but also suitable sequences of operators

Pourquoi rendre les modèles en iles autonomes ?

Date du colloque : 04/2012National audienc

Nanofiber-enhanced lightweight composite textiles for acoustic applications

This paper proposes lightweight textile acoustic structure, wherein electrospun polyacrylonitrile-based nanofibers enhance sound absorption properties with no weight and thickness penalty. Polyacrylonitrile nanofibers with diameter of 110 ± 7 nm were electrospun on spacer-knitted fabrics by varying deposition amount and surface coating arrangement. Proposed novel approach eliminated additional processing steps such as handling and post-lamination and provided easy scalability of nanofibers at macro-scale. The results showed that the sound absorption of nano-enhanced specimens was improved drastically when deposited amount of nanofibers or its effective surface area increased. Sound propagation paths in different configurations were interpreted from sound absorption and air permeability measurements. The sound absorption coefficient values up to 0.7 are achieved in the low and medium frequency ranges with no weight and thickness penalty by tuning deposition amount and surface coating arrangement

A dynamic island model for adaptive operator selection

In this paper we propose a generic framework for Dynamic Island Models, which can be used as an original approach for the adaptive selection of operators in evolutionary algorithms. Assigning a variation operator to each island, we show that the dynamic regulation of migrations, which takes into account the pertinence of recent migrations, distributes the individuals on the most promising islands, i.e., the most efficient operators, at each stage of the search. The efficiency of this approach is assessed on the One-Max problem by comparing theoretical expected results to those obtained by our dynamic island model. Experiments show that the model provides the expected behavior

Linear canonical transformations and quantum phase:a unified canonical and algebraic approach

The algebra of generalized linear quantum canonical transformations is examined in the prespective of Schwinger's unitary-canonical basis. Formulation of the quantum phase problem within the theory of quantum canonical transformations and in particular with the generalized quantum action-angle phase space formalism is established and it is shown that the conceptual foundation of the quantum phase problem lies within the algebraic properties of the quantum canonical transformations in the quantum phase space. The representations of the Wigner function in the generalized action-angle unitary operator pair for certain Hamiltonian systems with the dynamical symmetry are examined. This generalized canonical formalism is applied to the quantum harmonic oscillator to examine the properties of the unitary quantum phase operator as well as the action-angle Wigner function.Comment: 19 pages, no figure

The discrete harmonic oscillator, Harper's equation, and the discrete fractional Fourier transform

Certain solutions to Harper's equation are discrete analogues of (and approximations to) the Hermite-Gaussian functions. They are the energy eigenfunctions of a discrete algebraic analogue of the harmonic oscillator, and they lead to a definition of a discrete fractional Fourier transform (FT). The discrete fractional FT is essentially the time-evolution operator of the discrete harmonic oscillator