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

Appearance-based tracking of 3D articulated structures

This article describes a method to track 3D articulated structures from a monocular perspective image sequence using a particle filter. This structure is composed of a set of linked degenerated quadrics (cones), which are truncated, by pairs of planes also modelled as degenerated quadrics. Joints containing one or more degrees of freedom connect this set of truncated cones. The method is based upon the estimation of the contours of the structures silhouette projected on the image plane, to validate each of the particles that correspond to proposed configurations. This validation is performed using a criterion that combines a measure based on the contours with a measure of similarity between the colour distribution around a point on the structure and a reference distribution. The results show the feasibility of the approach when applied to the problem of tracking a human arm using a 3D model containing three degrees of freedom. The extension of the approach for tracking 4 degrees of freedom structure is also discussed.

Combination of mid-infrared spectroscopy and curve resolution method to follow the antioxidant action of alkylated diphenylamines

The inhibition of the oxidation of lubricating base oils by dinonyldiphenylamine has been studied by combined Fourier transform infrared (FTIR) spectroscopy and multivariate curve resolution-alternating least squares (MCR-ALS) method. This allowed to extract chemical information during the induction period. The substituted diphenylamines are progressively converted to a degraded form which can be followed with the chemometric analysis. When concentration of dinonyldiphenylamine is too low, the induction period ends and the oxidation of the base oils begins