On Křížek’s decomposition of a polyhedron into convex components and its applications in the proof of a general Ostrogradskij’s theorem
The finite element method is a generalized Ritz method using special admissible functions. In the paper, triangular elements and functions are considered which are linear or quadratic polynomials on each triangle. The convergence is proved for variational problems arising from second order boundary value problems. The order of accuracy of the procedure is in case of inhomogeneous Dirichlet conditions and in other cases ( is the degree of the polynomial used).
Approximation of nonhomogeneous boundary conditions of Dirichlet and Neumann types is suggested in solving boundary value problems of elliptic equations by the finite element method. Curved triangular elements are considered. In the first part of the paper the convergence of the finite element method is analyzed in the case of nonhomogeneous Dirichlet problem for elliptic equations of order , in the second part of the paper in the case of nonhomogeneous mixed boundary value problem for second order...
Existence and uniqueness theorem is established for a variational problem including Biot's model of consolidation of clay. The proof of existence is constructive and uses the compactness method. Error estimates for the approximate solution obtained by a method combining finite elements and Euler's backward method are given.
The paper deals with an initial problem of a parabolic variational inequality whichcontains a nonlinear elliptic form having a potential , which is twice -differentiable at arbitrary . This property of makes it possible to prove convergence of an approximate solution defined by a linearized scheme which is fully discretized - in space by the finite elements method and in time by a one-step finite-difference method. Strong convergence of the approximate solution is proved without any regularity...
Curved triangular -elements which can be pieced together with the generalized Bell’s -elements are constructed. They are applied to solving the Dirichlet problem of an elliptic equation of the order in a domain with a smooth boundary by the finite element method. The effect of numerical integration is studied, sufficient conditions for the existence and uniqueness of the approximate solution are presented and the rate of convergence is estimated. The rate of convergence is the same as in the...
The finite element analysis of linear elliptic problems in two-dimensional domains with cusp points (turning points) is presented. This analysis needs on one side a generalization of results concerning the existence and uniqueness of the solution of a constinuous elliptic variational problem in a domain the boundary of which is Lipschitz continuous and on the other side a presentation of a new finite element interpolation theorem and other new devices.
Making use of a line integral defined without use of the partition of unity, Green’s theorem is proved in the case of two-dimensional domains with a Lipschitz-continuous boundary for functions belonging to the Sobolev spaces .
A modification of the Nikolskij extension theorem for functions from Sobolev spaces is presented. This modification requires the boundary to be only Lipschitz continuous for an arbitrary ; however, it is restricted to the case of two-dimensional bounded domains.
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