The association of statistical models and multiresolution data analysis in a consistent and tractable mathematical framework remains and intricate theoretical and practical issue. Several consistent approaches have been proposed recently to combine Markov Random Field (MRF) models and multiresolution algorithms in image analysis: renormalization group, subsampling of stochastic processes, MRFs ...

Precision orbit ephemerides (POE) are used to estimate atmospheric density along the orbits of CHAMP (Challenging Minisatellite Payload) and GRACE (Gravity Recovery and Climate Experiment). The densities are calibrated against accelerometer derived densities and considering ballistic coefficient estimation results. The 14-hour density solutions are stitched together using a linear weighted blen...

Given a planar vector field U which generates the Lie symmetry of some other vector field X , we prove a new criterion to control the stability of the periodic orbits of U . The problem is linked to a classical problem proposed by A.T. Winfree in the seventies about the existence of isochrons of limit cycles (the question suggested by the study of biological clocks), already answered by Guckenh...

[1] The atmospheric limb sounding technique making use of radio signals transmitted by the Global Positioning System (GPS) has already proven to be a promising approach for global atmospheric measurements. In this study, we assess for the first time the potential of GPS radio occultation soundings for detecting the migrating diurnal tide. Retrieved temperatures between 10 and 30 km in the tropi...

Using groupoid S-central extensions, we present, for a compact simple Lie group G, an infinite dimensional model of S-gerbe over the differential stack G/G whose Dixmier-Douady class corresponds to the canonical generator of the equivariant cohomology H G(G). c © 2001 Académie des sciences/Éditions scientifiques et médicales Elsevier SAS Gerbes Equivariantes sur les groupes de Lie simples compa...