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- research-articleDecember 1993
Convergence results for general linear methods on singular perturbation problems
AbstractMany numerical methods used to solve Ordinary Differential Equations, or Differential Algebraic Equations can be written as general linear methods. The B-convergence results for general linear methods are for algebraically stable methods, and ...
- research-articleSeptember 1993
Diagonally implicit general linear methods for ordinary differential equations
AbstractWe investigate some classes of general linear methods withs internal andr external approximations, with stage orderq and orderp, adjacent to the class withs=r=q=p considered by Butcher. We demonstrate that interesting methods exist also ifs+1=r=q, ...
- research-articleMarch 1993
Convergence of a class of runge-kutta methods for differential-algebraic systems of index 2
AbstractThis paper deals with convergence results for a special class of Runge-Kutta (RK) methods as applied to differential-algebraic equations (DAE's) of index 2 in Hessenberg form. The considered methods are stiffly accurate, with a singular RK matrix ...
- articleDecember 1990
A direct algorithm for optimal quadratic splines
Numerische Mathematik (NUMM), Volume 57, Issue 1Pages 313–332We develop an algorithm to find k , the minimal value of f (2) , where f C 1 is a quadratic spline with free knots, which interpolates the given p points { x i , y i } 1 p with increasing x i 's, has absolutely continuous f (1) ...
- articleDecember 1990
Power bounded prolongations and Picard-Lindelöf iteration
The possibility of balancing the iteration and discretization errors in iterative solution of large systems of initial value problems is discussed. The main result answers the question affirmatively by stating that in the convergence process, in a model ...
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- articleDecember 1990
The conditioning of the stiffness matrix for certain elements approximating the incompressibility condition in fluid dynamics
In order to solve the Stokes equations numerically, Crouzeix and Raviart introduced elements satisfying a discrete divergence condition. For the two dimensional case and uniform triangulations it is shown, that using the standard basis functions, the ...
- articleDecember 1990
Some upwinding techniques for finite element approximations of convection-diffusion equations
A uniform framework for the study of upwinding schemes is developed. The standard finite element Galerkin discretization is chosen as the reference discretization, and differences between other discretization schemes and the reference are written as ...
- articleDecember 1990
Two preconditioners based on the multi-level splitting of finite element spaces
The hierarchical basis preconditioner and the recent preconditioner of Bramble, Pasciak and Xu are derived and analyzed within a joint framework. This discussion elucidates the close relationship between both methods. Special care is devoted to highly ...
- articleDecember 1990
On block diagonal and Schur complement preconditioning
We study symmetric positive definite linear systems, with a 2-by-2 block matrix preconditioned by inverting directly one of the diagonal blocks and suitably preconditioning the other. Using an approximate version of Young's "Property A", we show that ...
- articleDecember 1990
The finite element method for nonlinear elliptic equations with discontinuous coefficients
The study of the finite element approximation to nonlinear second order elliptic boundary value problems with discontinuous coefficients is presented in the case of mixed Dirichlet-Neumann boundary conditions. The change in domain and numerical ...
- research-articleDecember 1989
Connections between the PCG method applied to systems with Red/Black form and its reduced system
AbstractThis paper is concerned with the (preconditioned) conjugate gradient method for solving systems of linear algebraic equationsAx=b withA having Red/Black form. The connections between the Conjugate Gradient (CG) scheme applied toAx=b and its two ...
- research-articleJune 1989
On the D-suitability of implicit Runge-Kutta methods
AbstractThe concept of suitability means that the nonlinear equations to be solved in an implicit Runga-Kutta method have a unique solution. In this paper, we introduce the concept of D-suitability and show that previous results become special cases of ...
- articleMay 1989
A posteriori error estimators for the Stokes equations
We present two a posteriori error estimators for the mini-element discretization of the Stokes equations. One is based on a suitable evaluation of the residual of the finite element solution. The other one is based on the solution of suitable local ...
- articleMay 1989
Homotopy algorithm for symmetric eigenvalue problems
The homotopy method can be used to solve eigenvalue-eigenvector problems. The purpose of this paper is to report the numerical experience of the homotopy method of computing eigenpairs for real symmetric tridiagonal matrices together with a couple of ...
- articleApril 1989
Cardinal Hermite-spline-interpolation on the equidistant lattice
The theory of Hermite-spline interpolation on the equidistant lattice Z is written in purly real terms and this for an arbitrary polynomial degree, Hermitian order and node-shift parameter. An explicit representation formula for the Hermitian ...
- research-articleJune 1988
A modification of the stiefel-bettis method for nonlinearly damped oscillators
AbstractWe report a modification of the Stiefel-Bettis method which is of trigonometric order one and of polynomial order two for the general second order initial value problems. We also discuss the modified Stiefel-Bettis method made explicit for the ...
- research-articleJune 1988
AnO(h 6) quintic spline collocation method for fourth order two-point boundary value problems
AbstractAnO(h 6) collocation method based on quintic splines is developed and analyzed for general fourth-order linear two-point boundary value problems. The method determines a quintic spline approximation to the solution by forcing it to satisfy a high ...
- research-articleDecember 1987
Closest normal matrix finally found!
AbstractA method of finding the closest normal matrix in the Frobenius matrix norm is developed. It is shown that if a matrix is represented in those coordinates where its closest normal matrix is diagonal, its restriction to any pair of coordinate ...
- research-articleJune 1987
Product integration rules for volterra integral equations of the first kind
AbstractThe numerical solution of Volterra integral equations of the first kind can be achieved via product integration. This paper establishes the asymptotic error expansions of certain product integration rules. The rectangular rules are found to ...
- research-articleMarch 1987
On some iteration functions for the simultaneous computation of multiple complex polynomial zeros
AbstractSecond order methods for simultaneous approximation of multiple complex zeros of a polynomial are presented. Convergence analysis of new iteration formulas and an efficient criterion for the choice of the appropriate value of a root are discussed. ...