Virtual Element Method for fourth order problems: L2−L^2-estimates

We analyse the family of $C^1$-Virtual Elements introduced in \cite{Brezzi:Marini:plates} for fourth-order problems and prove optimal estimates in $L^2$ and in $H^1$ via classical duality arguments

Rotating Electromagnetic Waves in Toroid-Shaped Regions

Electromagnetic waves, solving the full set of Maxwell equations in vacuum, are numerically computed. These waves occupy a fixed bounded region of the three dimensional space, topologically equivalent to a toroid. Thus, their fluid dynamics analogs are vortex rings. An analysis of the shape of the sections of the rings, depending on the angular speed of rotation and the major diameter, is carried out. Successively, spherical electromagnetic vortex rings of Hill's type are taken into consideration. For some interesting peculiar configurations, explicit numerical solutions are exhibited.Comment: 27 pages, 40 figure

Remarks on some mixed finite element schemes for Reissner--Mindlin plate model

Two different stabilization procedures for mixed finite element schemes for Reissner--Mindlin plate problems are introduced. They are based on a suitable modification of the discrete shear energy like that introduced when a partial selective reduced integration technique is used. Some numerical results will be presented in order to show the performance of these schemes with respect to the locking phenomenon. The dependence of the approximate solution on the stabilising parameter is also analized

Approximation of functionally graded plates with non-conforming finite elements

In this paper rectangular plates made of functionally graded materials (FGMs) are studied. A two-constituent material distribution through the thickness is considered, varying with a simple power rule of mixture. The equations governing the FGM plates are determined using a variational formulation arising from the Reissner-Mindlin theory. To approximate the problem a simple locking-free Discontinuous Galerkin finite element of non-conforming type is used, choosing a piecewise linear non-conforming approximation for both rotations and transversal displacement. Several numerical simulations are carried out in order to show the capability of the proposed element to capture the properties of plates of various gradings, subjected to thermo-mechanical loads. (C) 2006 Elsevier B.V. All rights reserved

Penalized approximation of the vibration frequencies of a fluid in a cavity

Here we point out some difficulties arising in the approximation of the vibration frequencies of a fluid in a cavity in the case of non convex polygonal domains. Since the eigensolutions must satisfy an irrotationality condition, a classical way to face the problem is to consider a penalized formulation. Unfortunately standard conforming finite elements fail to give good results. We intend to justify this failure and to suggest a finite element method based on a reduced integration strategy able to give reasonable results