Subordination des résolvantes

Résumé Soit (V ₎₀ une résolvante définie sur un espace mesurable telle que le noyau initial est borné; on trouve une condition nécéssaire et suffisante pour qu'un noyau borné U possède une résolvante (U ₎₀ telle que U V pour tout 0. On donne plusieurs applications de ce résultat.     

Convergence de mesures spectrales aléatoires et applications à des principes d'invariance

Nous présentons un cadre unificateur pour un certain nombre de résultats connus de convergence en loi pour des processus admettant une représentation linéaire par rapport à un bruit blanc faible pour lequel il existe un principe dinvariance faible. Nous montrons que ce principe dinvariance est équivalent à la convergence dune suite de mesures aléatoires spectrales. Ceci permet daffaiblir les hypothèses usuelles et donc dobtenir des résultats nouveaux de convergence en loi, notamment pour des processus à longue portée.     

On the fundamental sloshing frequency in the ice-fishing problemSur la fréquence de ballottement principale dans le problème de la glace avec trous pour pêcher

The sloshing problem is considered in a half-space covered by a rigid dock with apertures. The dependence of the fundamental sloshing frequency on the shape of the free surface region is studied. It is proved that the inequality holds between the fundamental eigenvalues corresponding to two different regions if some conditions are fulfilled. These conditions are verified for particular classes of regions of a fixed area in order to demonstrate that the disk yields the maximum of the fundamental eigenvalue for each of these classes. On the other hand, examples of regions are constructed for which the fundamental eigenfrequency is larger than that for the circular aperture of the same area and even as large as one wishes. To cite this article: V. Kozlov, N. Kuznetsov, C. R. Mecanique 330 (2002) 723–728.     

Volumic method for the variational sum of a 2D discrete model

The geometric complexity of some heterogeneous materials (for example, fibers distributed randomly or deterministically with high conductivity [5], [2]) can make it difficult to model their macroscopic behavior. In some cases, it is convenient to simplify the geometry by cutting it into “simple” elements, so that the first study is performed only on these items. The difficulties arise from the reconstruction of the material. In such study, we describe a method for reconstructing a material cut into thin plates having undergone a size reduction (see [6] and [5], for example). The method used is of variational summation limit.     

Gaussian Approximation to the Partial Sum Processes of Moving Averages

The authors study approximation to the partial sum processes which is based on the stationary sequences of random variables having the structure of the so-called moving averages of independent identically distributed observations. In particular, the rates of convergence both in Donsker's and Strassen's invariance principles are obtained in the case when the limit Gaussian process is a fractional Brownian motion with an arbitrary Hurst parameter.     

On two-dimensional water waves in a canalSur les ondes de surface bidimensionnelles dans un canal

This Note deals with an eigenvalue problem that contains a spectral parameter in a boundary condition. The problem for the two-dimensional Laplace equation describes free, time-harmonic water waves in a canal having uniform cross-section and bounded from above by a horizontal free surface. It is shown that there exists a domain for which at least one of eigenfunctions has a nodal line with both ends on the free surface. Since Kuttler essentially used the non-existence of such nodal lines in his proof of simplicity of the fundamental sloshing eigenvalue in the two-dimensional case, we propose a new variational principle for demonstrating this latter fact. To cite this article: V. Kozlov, N. Kuznetsov, C. R. Mecanique 331 (2003).     

Self adjoint extensions of differential operators in application to shape optimizationExtensions autoadjointes d'opérateurs différentiels et application à l'optimisation de forme

Two approaches are proposed for the modelling of problems with small geometrical defects. The first approach is based on the theory of self adjoint extensions of differential operators. In the second approach function spaces with separated asymptotics and point asymptotic conditions are introduced, and the variational formulation is established. For both approaches the accuracy estimates are derived. Finally, the spectral problems are considered and the error estimates for eigenvalues are given. To cite this article: S.A. Nazarov, J. Sokolowski, C. R. Mecanique 331 (2003).     

关于规范型拉丁方个数的上界

In this note,the author find an upper bound formula for the number of the p×p normalized Latin Square,the first row and column of which are both standard order 1,2,...,p.     

Évolution quasi-statique d'un fil souple inextensible sur un plan avec frottement sec : cas discretQuasi-static motion of a supple,homogenous and inextensible string on a horizontal plane with dry friction: discret case

The differential inclusion describing the quasi-static motion of a supple, homogeneous and inextensible string on a horizontal plane with dry friction (Coulomb's law) is a one dimensional evolution model of a continuous medium, with non-linear geometry, obeying a “plastic-rigid” law. With a view to numerical simulation, we treat the discrete case: the string is assimilated to a chain constituted by rigid rods perfectly articulated around ball-joints. We give variational formulation of the problem and prove existence and uniqueness of solutions. We construct an algorithm that describes the instantaneous solutions when the initial configuration of the string is given. Then, some examples are treated. To cite this article: H. Sayah, C. R. Mecanique 332 (2004).