Human body tracking by monocular vision

This article describes a tracking method of 3D articulated complex objects (for example, the human body), from a monocular sequence of perspective images . These objects and their associated articulations must be modelled . The principle of the method is based on the interpretation of image features as the 3D perspective projections points of the object model and an iterativ e Levenberg-Marquardt process to compute the model pose in accordance with the analysed image . This attitude is filtered (Kalman filter) to predict the model pose relative to the following image of the sequence . The image features are extracted locally according to the computed prediction . Tracking experiments, illustrated in this article by a cycling sequence, have been conducted to prove the validity of the approach.Cet article décrit une méthode de suivi d'objets 3D articulés, de forme complexe telle que les membres du corps humain, à partir d'une séquence monoculaire d'images perspectives. Ces objets devront être préalablement modélisés ainsi que les articulations associées. Le principe de la méthode est basé sur l'interprétation de points caractéristiques dans l'image comme étant les projections perspectives de points 3D liés au modèle de l'objet et d'un processus itératif fondé sur la méthode de Levenberg-Marquardt pour calculer l'attitude de ce modèle conforme à l'image analysée. Cette attitude et la covariance associée sont fournies à un filtre de Kalman de haut niveau pour prédire l'attitude du modèle relative à l'image suivante de la séquence. L'extraction de primitives s'effectue localement par prise en compte de la prédiction obtenue. Des expérimentations de suivi, illustrées dans cet article par une séquence de pédalage, ont été effectuées, prouvant ainsi la validité de l'approche

Adaptive density estimation for stationary processes

We propose an algorithm to estimate the common density $s$ of a stationary process $X_1,...,X_n$. We suppose that the process is either $\beta$ or $\tau$-mixing. We provide a model selection procedure based on a generalization of Mallows' $C_p$ and we prove oracle inequalities for the selected estimator under a few prior assumptions on the collection of models and on the mixing coefficients. We prove that our estimator is adaptive over a class of Besov spaces, namely, we prove that it achieves the same rates of convergence as in the i.i.d framework

Estimator selection

The paper presents recent developments of the theory of estimator selection. We introduce, in the density estimation framework, the main methods used by the participants of the session ”Variable and estimator selection” in the Journées MAS 2014. The purpose of the selection is always to prove oracle inequalities, that is, to compare the selected estimator with the best estimator in the original collection via some risk function. The first part of the paper deals with the selection by minimization of a penalized empirical loss and the second presents the methods based on robust tests

Corrosion behaviour of galvanized steel and electroplating steel in aqueous solution: AC impedance study and XPS

International audienceThe efficiency of a new triazole deriv., namely, 2-{(2-hydroxyethyl)[(4-methyl-1H-1,2,3-benzotriazol-1-yl)methyl]amino}ethanol (TTA) has been studied for corrosion inhibition of galvanized steel and electroplating steel in aq. soln. Corrosion inhibition was studied using electrochem. impedance spectroscopy (EIS). These studies have shown that TTA was a very good inhibitor. Data obtained from EIS show a frequency distribution and therefore a modeling element with frequency dispersion behavior, a const. phase element (CPE) has been used. The corrosion behavior of galvanized steel and electroplating steel in aq. soln. was also investigated in the presence of 4-methyl-1H-benzotriazole (TTA unsubstituted) by EIS. These studies have shown that the ability of the mol. to adsorb on the steel surface was dependent on the group in triazole ring substituent. XPS surface anal. with TTA shows that it chemisorbed on surface of galvanized steel and electroplating steel