The piston problem is investigated in the case where the length of the cylinder is infinite (on both sides) and the ratio m/M is a very small parameter, where m is the mass of one particle of the gaz and M is the mass of the piston. Introducing initial conditions such that the stochastic motion of the piston remains in the average at the origin (no drift), it is shown that the time evolution of...

This article proposes a new modified anisotropic diffusion scheme for automatic defect detection in radiographic films. The new diffusion method allows to enhance, to sharpen anomalies, and to smooth the background of the image. This new technique is based on the modification of the classical diffusion rule by using a nonlinear sigmoidal function. Experimental results are carried out on multipl...

In this paper, motivated by the Galilean invariance of the solutions, we use the concept of orbital stability for the Vlasov–Poisson system. We prove that a family of stationary solutions, called polytropic gas spheres, are orbitally L1 stable in the gravitational case by considering direct variational arguments. Résumé. Dans cet article, motivés pour la propriété d’invariance Galiléenne des so...