Characterization of segregation in bidispersed granular media by linear and nonlinear acoustic methods

AbstractThe segregation of size is studied by linear and nonlinear acoustic methods for an unconsolidated granular medium. By applying vertical vibrations we study the variation of the average compacity and the acoustic transfer function in order to follow the segregation process with an acoustic probing

Inhomogeneous losses and complexness of wave functions in chaotic cavities

In a two-dimensional microwave chaotic cavity Ohmic losses located at the contour of the cavity result in different broadenings of different modes. We provide an analytic description and establish the link between such an inhomogeneous damping and the complex (non-real) character of biorthogonal wave functions. This substantiates the corresponding recent experimental findings of Barthélemy et al. (Europhys. Lett., 70 (2005) 162)

Statistics of eigenfunctions in open chaotic systems: a perturbative approach

We investigate the statistical properties of the complexness parameter which characterizes uniquely complexness (biorthogonality) of resonance eigenstates of open chaotic systems. Specifying to the regime of isolated resonances, we apply the random matrix theory to the effective Hamiltonian formalism and derive analytically the probability distribution of the complexness parameter for two statistical ensembles describing the systems invariant under time reversal. For those with rigid spectra, we consider a Hamiltonian characterized by a picket-fence spectrum without spectral fluctuations. Then, in the more realistic case of a Hamiltonian described by the Gaussian Orthogonal Ensemble, we reveal and discuss the r\^ole of spectral fluctuations

Optical second harmonic generation probe of two-dimensional ferroelectricity

Optical second harmonic generation (SHG) is used as a noninvasive probe of two-dimensional (2D) ferroelectricity in Langmuir-Blodgett (LB) films of copolymer vinylidene fluoride with trifluorethylene. The surface 2D ferroelectric-paraelectric phase transition in the topmost layer of LB films and a thickness independent (almost 2D) transition in the bulk of these films are observed in temperature studies of SHG.Comment: 9 pages, 2 figures, Optics Letters, in prin

Some results on approximating the minimax solution in approval voting

Voting has been a very popular method for preference aggregation in multiagent environments. It is often the case that a set of agents with different preferences need to make a choice among a set of alternatives, where the alternatives could be various entities such as potential committee members, or joint plans of action. A standard methodology for this scenario is to have each agent express his preferences and then select an alternative according to some voting protocol. Several decision making applications in AI have followed this approach including problems in collaborative filtering [10] and planning [3, 4]

Gain-controlled wave chaos in a chaotic optical fibre

International audienceIn this paper, we present a non-standard fibre amplifier specially designed to amplify scar modes of a multimode chaotic optical fibre. More precisely, we introduce Ytterbium in the optical fibre as a gain medium localised on the maximum of intensity of the scar modes. After briefly recalling the relevance of a chaotic optical fibre as a device to visualise quantum chaos, we describe the amplification process of scars. We present some numerical results that demonstrate the selective amplification of scar modes, with an amplification rate proportional to the overlap between these modes and the gain area

Les différentes politiques forestières des Conseils généraux et régionaux méditerranéens.

Si la politique forestière reste de la compétence de l'Etat, partagée entre les ministères de l'Agriculture et de la Pêche, de l'Environnement et de l'Intérieur, les collectivités comme les Départements se sont investis d'un rôle plus ou moins important en fonction du contexte forestier départemental. Dans cette étude, Véronique Legrand nous fait part des résultats d'une enquête menée auprès des départements méditerranéens pour connaître la place qui est réservée à la forêt dans leurs politiques départementales et quelle en est la teneur