Shape Identification in electrolocation and echolocation.

Cet exposé aura lieu au bâtiment E de l'UFR chimie (bâtiment André Rassat) dans le cadre du workshop Problèmes Inverses : http://www-ljk.imag.fr/membres/Faouzi.Triki/projetPbsInverses/workshopIV.html 

The aim of this talk is to exhibit possible mechanisms of shape identification observed in some biological phenomena. In electrolocation, the weakly electric fish orient themselves at night in complete darkness by employing their active electrosensing system. They generate a stable, high-frequency, weak electric field and perceive the transdermal potential modulations caused by a nearby target with different admittivity than the surrounding water. The electric fish would first locate the target using a specific location search algorithm. Then it could extract, from the perturbations of the electric field, features (generalized polarization tensors) of the target, and compute from the features shape descriptors invariant under rigid motions and scaling. When the data contain sufficient information, the fish could extract local features to perceive visually the geometric character of the target. This paradigm including feature extraction and construction of invariant shape descriptors can also be applied to other nonlinear inverse problems like the echolocation, a phenomenon that the bat use their bio sonar to identify targets.