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  • CR: 5.17  (143)
  • Springer  (143)
  • Blackwell Publishing Ltd
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  • Springer  (143)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Numerische Mathematik 41 (1983), S. 255-279 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L15 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Some methods for evaluating the characteristic exponents in connection with Newton's iteration are applied for solving the eigenvalue problem related to the finite Hill's differential equation or, in particular, Mathieu's equation. By using these methods a high accuracy is achieved, furthermore a complete error analysis, which yields rather realistic error bounds, is possible.
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Numerische Mathematik 41 (1983), S. 373-398 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary The paper introduces a new semi-implicit extrapolation method especially designed for the numerical solution of stiff systems of ordinary differential equations. The existence of a quadratic asymptotic expansion in terms of the stepsize is shown. Moreover, the new discretization is analyzed in the light of well-known stability models. The efficiency of the new integrator is clearly demonstrated by solving a series of challenging test problems including real life examples.
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Numerische Mathematik 41 (1983), S. 345-371 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Maximum-norm stability and error estimates of best approximation and nonsmooth data types are derived for the approximate solution of a parabolic equation in one space variable, using the continuous in time Galerkin method based on piecewise polynomial approximating functions on a quasi-uniform mesh.
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Numerische Mathematik 42 (1983), S. 119-123 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N10 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Many difference methods for the numerical solution of elliptic boundary value problems lead to systems of linear equations whose matrices areM-matrices and which therefore have nonnegative inverses. In this paper it is shown, that these difference methods are at most consistent of second order.
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Numerische Mathematik 42 (1983), S. 271-290 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65J10, 65L20, 65M10 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Consider a linear autonomous system of ordinary differential equations with the property that the norm |U(t)| of each solutionU(t) satisfies |U(t)|≦|U(0)| (t≧0). We call a numerical process for solving such a system contractive if a discrete version of this property holds for the numerical approximations. A givenk-step method is said to be unconditionally contractive if for each stepsizeh〉0 the numerical process is contractive. In this paper a general theory is given which yields necessary and sufficient conditions for unconditional contractivity. It turns out that unconditionally contractive methods are subject to an order barrierp≦1. Further the concept of a contractivity threshold is studied, which makes it possible to compare the contractivity behaviour of methods with an orderp〉1 as well. Most theoretical results in this paper are formulated for differential equations in arbitrary Banach spaces. Applications are given to numerical methods for solving ordinary as well as partial differential equations.
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Numerische Mathematik 42 (1983), S. 299-310 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary A new approach to the problem of numerically integrating stiff differential systems is described. In this approach a linear multistep method (the basic method) is split into a kind of predictor-corrector scheme, where the predictor is also implicit. If this splitting is done in an appropriate manner, the modified method has considerably better stability properties than the basic method. As a result, splitting methods are particularly useful for problems where conventional integration methods experience stability difficulties. In particular some highly stable split linear multistep methods based on backward differentiation formulae are derived and a highly stable variable step implementation is proposed.
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  • 7
    Digitale Medien
    Digitale Medien
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    Numerische Mathematik 42 (1983), S. 311-322 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65 N 30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary This paper presents Galerkin approximations for solutions of two dimensional interface problems by solving corresponding boundary integral equations. These are obtained by simple layer potential operators only. Due to the strong ellipticity of the integral equations the Galerkin procedure converges with optimal order. Smoothness of the given data implies high convergence rates for the layers.
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Numerische Mathematik 42 (1983), S. 349-357 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS) 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary In this paper theD-stability properties of some classes of perturbed collocation methods are investigated. Among others we show the implicit Runge-Kutta methods described by Ehle-Chipman to beD-stable. We also give implicit Runge-Kutta methods that are bothD-stable andA-stable but notB-stable. Finally we indicate in what senseB-stability is stronger thanA-stability together withD-stability. The results of this paper are based on recent results of Nørsett and Wanner on perturbed collocation methods.
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Numerische Mathematik 42 (1983), S. 359-377 
    ISSN: 0945-3245
    Schlagwort(e): AMS 65L05 ; 65L07 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary This paper is concerned with the stability of multistep methods for ordinary initial-value problems on grids with variable mesh-sizes. A necessary and sufficient condition for stability is given from which generalizations of recent results by Gear et al. and by Zlatev can be obtained as special cases. As an application the stability of the variable BDF-formulas is treated.
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  • 10
    Digitale Medien
    Digitale Medien
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    Numerische Mathematik 42 (1983), S. 379-389 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L20 ; 15A60 ; 65M20 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary If the field of values of a matrixA is contained in the left complex halfplaneH and a functionf mapsH into the unit disc then ∥f(A)∥2≦1 by a theorem of J.v. Neumann. We prove a theorem of this type, only the field of values ofA is used for functions which are absolutely bounded by one in only part ofH. An extension can be used to show norm-stability of single step methods for stiff differential equations. The results are applicable among others to several subdiagonal Padé approximations which are notA-stable.
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  • 11
    Digitale Medien
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    Numerische Mathematik 43 (1984), S. 105-119 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary A new formulation of the Dirichlet problem for the biharmonic operator is presented. This gives rise to a simple numerical method to solve the above problem. Convergence is proved in the unidimensional case. Numerical results in one and two dimensional test problems are presented.
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Numerische Mathematik 43 (1984), S. 175-198 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65 L 10 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary We present a difference scheme for solving a semilinear singular perturbation problem with any number of turning points of arbitrary orders. It is shown that a solution of the scheme converges, uniformly in a perturbation parameter, to that of the continuous problem.
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Numerische Mathematik 43 (1984), S. 199-224 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): 65 N 30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Beschreibung / Inhaltsverzeichnis: Summary This paper uses Augmented Lagrangian techniques for the numerical solution of equilibrium problems of compressible hyperelastic bodies subjected to large deformations. The resulting method is illustrated by several numerical examples.
    Notizen: Résumé Cet article applique les techniques de Lagrangien Augmenté à la résolution numérique des problèmes d'équilibre de corps hyperélastiques compressibles soumis à de grandes déformations. La méthode obtenue est illustrée par plusieurs exemples numériques.
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Numerische Mathematik 39 (1982), S. 449-463 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): 65L65 ; CR: 5.17 ; AMS (MOS): 65L65 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Beschreibung / Inhaltsverzeichnis: Summary In [10] a general procedureV is presented to obtain spline approximations by collocation for the solutions of initial value problems for first order ordinary differential equations. In this paper the attainable order of convergence with respect to the maximum norm is characterized in dependence of the parameters involved inV; in particular the appropriate choice of the collocation points is considered.
    Notizen: Zusammenfassung In [10] ist ein allgemeines VerfahrenV beschrieben, das die Lösungen von Anfangswertproblemen bei gewöhnlichen Differentialgleichungen erster Ordnung durch Splines approximiert. Die Konstruktion der Splines erfolgt hierbei mittels Kollokation. In dieser Arbeit wird die maximal erreichbare Konvergenzordnung vonV bezüglich der Maximumnorm in Abhängigkeit aller Parameter vonV charakterisiert, insbesondere wird auf die geeignete Wahl der Kollokationsknoten eingegangen.
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  • 15
    Digitale Medien
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    Numerische Mathematik 40 (1982), S. 169-177 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary The stability and accuracy of some explicit nonlinear methods for the numerical integration of stiff systems of ordinary differential equations are investigated. It is shown, that in the general case they can produce the essential error. The special class of stiff systems is singled out, for which these methods are highly efficient. Some numerical results are also presented.
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Numerische Mathematik 40 (1982), S. 179-199 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS) ; Primary 65N30 ; Secondary 35R35 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Two problems are considered in the paper: the first of them is connected with elliptic variational inequalities and consists in developing a moving obstacle algorithm for approximating the unknown free boundary; the other problem is linked with numerical solution of the Stefan problem, which is formulated in the similar way as in the elliptic case. Some computational aspects are also discussed in the paper.
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Numerische Mathematik 40 (1982), S. 207-227 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65M30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Several regularization methods for parabolic equations backwards in time together with the usual additional constraints for their solution are considered. The error of the regularization is estimated from above and below. For a “boundary value problem in time”-method, finite elements as well as a time discretization are introduced and the error with respect to the regularized solution is estimated, thus giving an overall error of the discrete regularized problem. The algorithm is tested in simple numerical examples.
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  • 18
    Digitale Medien
    Digitale Medien
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    Numerische Mathematik 40 (1982), S. 319-328 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): 65J05, 65L15 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Although multiparameter eigenvalue problems, as for example Mathieu's differential equation, have been known for a long time, so far no work has been done on the numerical treatment of these problems. So in this paper we extend the spectral theory for one parameter (cf. [7, II, VII]) to multiparameter eigenvalue problmes, formulate in the framework of discrete approximation a convergent numerical treatment, establish algebraic bifurcation equations for the intersection points of the eigenvalue curves and illustrate this with some numerical examples.
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  • 19
    Digitale Medien
    Digitale Medien
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    Numerische Mathematik 40 (1982), S. 373-406 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N30, 65M20 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary We extend in this paper the analysis of a posteriori estimates of the space discretization error presented in a previous paper [3] for time-independent space meshes. In the context of the model problem studied there, results are given relating the effectiveness of the error estimator to properties of the solution, space meshes, and manner in which the meshes change. A procedure based upon this theory is presented for the adaptive construction of time-dependent meshes. The results of some computational experiments show that this procedure is practically very effective and suggest that it can be used to control the space discretization error in more general problems.
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  • 20
    Digitale Medien
    Digitale Medien
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    Numerische Mathematik 40 (1982), S. 329-337 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary A widely used technique for improving the accuracy of solutions of initial value problems in ordinary differential equations is local extrapolation. It is well known, however, that when using methods appropriate for solving stiff systems of ODES, the stability of the method can be seriously degraded if local extrapolation is employed. This is due to the fact that performing local extrapolation on a low order method is equivalent to using a higher order formula and this high order formula may not be suitable for solving stiff systems. In the present paper a general approach is proposed whereby the correction term added on in the process of local extrapolation is in a sense a rational, rather than a polynomial, function. This approach allows high order formulae with bounded growth functions to be developed. As an example we derive anA-stable rational correction algorithm based on the trapezoidal rule. This new algorithm is found to be efficient when low accuracy is requested (say a relative accuracy of about 1%) and its performance is compared with that of the more familiar Richardson extrapolation method on a large set of stiff test problems.
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  • 21
    Digitale Medien
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    Numerische Mathematik 40 (1982), S. 339-371 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N30 ; 65M20 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary In this first of two papers, computable a posteriori estimates of the space discretization error in the finite element method of lines solution of parabolic equations are analyzed for time-independent space meshes. The effectiveness of the error estimator is related to conditions on the solution regularity, mesh family type, and asymptotic range for the mesh size. For clarity the results are limited to a model problem in which piecewise linear elements in one space dimension are used. The results extend straight-forwardly to systems of equations and higher order elements in one space dimension, while the higher dimensional case requires additional considerations. The theory presented here provides the basis for the analysis and adaptive construction of time-dependent space meshes, which is the subject of the second paper. Computational results show that the approach is practically very effective and suggest that it can be used for solving more general problems.
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  • 22
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    Numerische Mathematik 41 (1983), S. 55-62 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary The finite element method with Laplace transform of time variable is proposed for the solution of hyperbolic equations. Error estimates in Hardy spaces of functions with values in Sobolev spaces are derived. Due to the isometric isomorphism of Hardy spaces with weighted Hilbert spaces these estimates are valid also for original formulations of hyperbolic equations.
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  • 23
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    Numerische Mathematik 41 (1983), S. 165-175 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65LO5 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary The extrapolated midpoint rule is a popular way to solve the initial value problem for a system of ordinary differential equations. As originally formulated by Gragg, the results are smoothed to remove the weak instability of the midpoint rule. It is shown that this smoothing is not necessary. A cheaper smoothing scheme is proposed. A way to exploit smoothing to increase the robustness of extrapolation codes is formulated.
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  • 24
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary We study the difference equations obtained when a linear multistep method is applied to the scalar test equationdy/dt=λy and constant stepsizeh. LetS be the region of the absolute stability of the method, and letD be a closed subset ofS (on the Riemann sphere $$\mathbb{C}$$ ). It is shown that the solutions of these difference equations are bounded forn≧0, uniformly for λh∈D.S is itself closed in $$\mathbb{C}$$ iff ∂S is free of cusps. The question is studed by means of contractivity analysis and a matrix theorem, derived from the matrix theorem of Kreiss.
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  • 25
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    Numerische Mathematik 41 (1983), S. 399-422 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary The paper presents a new theory for joint order and stepsize control in extrapolation methods. This theory defines a locally optimal order that can be determined along any trajectory to be computed. In addition, Shannon's information theory is applied to derive some ideal convergence model that is expected to describe the behavior of an extrapolation method over a large set of test problems. Extensive numerical comparisons document a drastic acceleration in stiff integration and a mild acceleration in non-stiff integration by the new device. Moreover, a significant increase in reliability, robustness, and portability of the extrapolation codes is achieved.
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  • 26
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    Numerische Mathematik 42 (1983), S. 15-30 
    ISSN: 0945-3245
    Schlagwort(e): AMS: 65L10 ; 34C25 ; 34K10 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary An iterative method is presented which starting from a lower or from an upper periodic solution, provides a monotone sequence converging to a periodic solution of (1). With some restrictions on the growth off, the method extends to functional differential equations of type (1′). Two numerical examples with an “a posteriori” error analysis are given.
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  • 27
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    Numerische Mathematik 42 (1983), S. 51-64 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): 65N99 ; 35L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Engquist and Majda [3] proposed a pseudodifferential operator as asymptotically valid absorbing boundary condition for hyperbolic equations. (In the case of the wave equation this boundary condition is valid at all frequencies.) Here, least-squares approximation of the symbol of the pseudodifferential operator is proposed to obtain differential operators as boundary conditions. It is shown that for the wave equation this approach leads to Kreiss well-posed initial boundary value problems and that the expectation of the reflected energy is lower than in the case of Taylor- and Padé-approximations [3, 4]. Numerical examples indicate that this method works even more effectively for hyperbolic systems. The least-squares approach may be used to generate the boundary conditions automatically.
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  • 28
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    Numerische Mathematik 42 (1983), S. 77-95 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N99 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Brakhage and Werner, Leis and Panich suggested to reduce the exterior Dirichlet boundary value problem for the Helmholtz equation to an integral equation of the second kind which is uniquely solvable for all frequencies by seeking the solution in the form of a combined double- and single-layer potential. We present an analysis of the appropriate choice of the parameter coupling the double- and single-layer potential in order to minimize the condition number of the integral operator.
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  • 29
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    Numerische Mathematik 42 (1983), S. 65-76 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65 N 20 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary We consider here a general class of algorithms for the numerical solution of variational inequalities. A convergence proof is given and in particular a multi-grid method is described. Numerical results are presented for the finite-difference discretization of an obstacle problem for minimal surfaces
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  • 30
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    Numerische Mathematik 42 (1983), S. 173-194 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary We consider the stationary Navier-Stokes equations, written in terms of the primitive variables, in the case where both the partial differential equations and boundary conditions are inhomogeneous. Under certain conditions on the data, the existence and uniqueness of the solution of a weak formulation of the equations can be guaranteed. A conforming finite element method is presented and optimal estimates for the error of the approximate solution are proved. In addition, the convergence properties of iterative methods for the solution of the discrete nonlinear algebraic systems resulting from the finite element algorithm are given. Numerical examples, using an efficient choice of finite element spaces, are also provided.
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  • 31
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    Numerische Mathematik 29 (1978), S. 381-396 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary In this paper, a general class ofk-step methods for the numerical solution of ordinary differential equations is discussed. It is shown that methods with order of consistencyq have order of convergence (q+1) if a very simple condition is satisfied. This result gives a new aspect to previous results of Spijker; it also serves as a starting point for a new theory of cyclick-step methods, completing an approach of Donelson and Hansen. It facilitates the practical determination of high-order cyclick-step methods, especially of stiffly stable,k-step methods.
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  • 32
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    Numerische Mathematik 29 (1978), S. 409-424 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): 65LO5 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary In a recent article [2] Frank and Überhuber define and motivate the method of iterated defect correction for Runge-Kutta methods. They prove a theorem on the order of that method using the theory of asymptotic expansions. In this paper we give similar results using the theory of Butcher series (see [4]). Our proofs are purely algebraic. We don't restrict our considerations to Runge-Kutta methods, but we admit arbitrary linear one-step methods. At the same time we consider more general defect functions as in [2].
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  • 33
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    Numerische Mathematik 29 (1978), S. 209-226 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L 10 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary In this paper we give a simple stability theory for finite difference approximations to linear ordinary boundary value problems. In particular we consider stability with respect to a maximum norm including all difference quotients up to the order of the differential equation. It is shown that stability in this sense holds if and only if the principal part of the differential equation is discretized in a “stable way”. This last property is characterized by root conditions which we prove to be satisfied for some classes of finite difference schemes. Our approach simplifies and generalizes some known results of the literature where Sobolev norms or merely the maximum norm are used.
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  • 34
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    Numerische Mathematik 29 (1978), S. 397-407 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): 31-04, 65N05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary A transformation method is developed which may be used to solve various types of boundary value problems on three-dimensional regions with an arbitrary boundary. The implementation of the method is illustrated in the solution of a potential flow problem. All computations are performed on a cubic mesh in a rectangular region.
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  • 35
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    Numerische Mathematik 29 (1978), S. 425-443 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65J05, 65L99 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Recently, a number of closely related techniques for error estimation and iterative improvement in discretization algorithms have been proposed. In this article, we expose the common structural principle of all these techniques and exhibit the principal modes of its implementation in a discretization context.
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  • 36
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    Numerische Mathematik 30 (1978), S. 385-409 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65 L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary High order implicit integration formulae with a large region of absolute stability are developed for the approximate numerical integration of both stiff and non-stiff systems of ordinary differential equations. The algorithms derived behave essentially like one step methods and are demonstrated by direct application to certain particular examples.
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  • 37
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    Numerische Mathematik 30 (1978), S. 93-101 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L10 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary We consider non-inverse positive differential operators of the second order and show that error estimates can be obtained through methods of inverse positivity alone. This means a significant simplification if the operator has only one negative eigenvalue. In addition we show how to obtain Range-Domain implications for operators with mixed boundary conditions.
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  • 38
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    Numerische Mathematik 30 (1978), S. 267-279 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L10 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary A finite element method using piecewise polynomials of degree ≦k is used to approximate the problem εu″+u′=f, ε〉0 a small parameter. A very irregular mesh is used. On this mesh error estimates of order0(h k+1) are obtained uniformly in ε,h the maximum stepsize, fork≧2. The condition number of the system of linear equations one has to solve in order to get the approximation is estimated. Extension of the results to more complicated problems is briefly indicated. Finally, a numerical example is given.
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  • 39
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    Numerische Mathematik 31 (1978), S. 1-16 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary We study the mixed finite element approximation of variational inequalities, taking as model problems the so called “obstacle problem” and “unilateral problem”. Optimal error bounds are obtained in both cases.
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  • 40
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    Numerische Mathematik 32 (1979), S. 247-270 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65D05, 65N30, 41A20 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Beschreibung / Inhaltsverzeichnis: Résumé Ce travail est consacré à l'étude d'éléments finis rationnels de Wachspress (cf. [15]) sur un quadrilatère. Après avoir étudié la construction et les propriétés de ces éléments finis, on obtient une évaluation de l'erreur d'interpolation correspondante.
    Notizen: Summary This paper is devoted to the study of Wachspress's rational finite elements (cf. [15]) over a quadrilateral. After studying construction and properties of these finite elements, we get an estimate of the corresponding interpolation error.
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  • 41
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    Numerische Mathematik 30 (1978), S. 411-414 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L99 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary It is shown that Liapunov functions may be used to obtain error bounds for approximate solutions of systems of ordinary differential equations. These error bounds may reflect the behaviour of the error more accurately than other bounds.
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  • 42
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    Numerische Mathematik 32 (1979), S. 343-358 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L65 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary In the first part [5] a general procedure is presented to obtain polynomial spline approximations of arbitrary defect for the solution of the initial value problem of ordinary differential equations. The essential result is a divergence theorem in dependence of the polynomial degree and the defect of the spline functions. In this second part the convergent procedures are investigated and two convergence theorems are proved. Furthermore the question is treated, whether the convergent procedures are appropriate for the numerical solution of stiff equations. The paper is finished by a convergence theorem for a procedure producing spline approximations in a natural way by the discrete approximations of an arbitrary difference method.
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  • 43
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    Numerische Mathematik 33 (1979), S. 291-301 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N25 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary A new method is proposed for the inclusion of the critical parameter λ* of some convex operator equationu=λTu (appearing e.g. in thermal explosion theory). It is based on the fact that for a fixed λ Newton's method starting with a suitable subsolution is not monotonically if and only if λ〉λ*. Several numerical examples arising from nonlinear boundary value problems illustrate the efficiency of the method.
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  • 44
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    Numerische Mathematik 33 (1979), S. 323-338 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Beschreibung / Inhaltsverzeichnis: Summary We consider the technique of using nonlinear splines to solve the initial value problem of ordinary differential equations. It is known, for example, that generalized rational splines with variable exponents yield good approximations to the exact solution in the neighborhood of a singularity. In the case of polynomial splines, convergence results may be derived by demonstrating the equivalence of the method to linear multistep methods. This sort of analysis has been done by many authors. In this paper we treat the nonlinear case and are able to prove convergence by directly estimating the local errors at interior knots. Some computational examples are given which illustrate the power of the method near a singularity.
    Notizen: Zusammenfassung In dieser Arbeit werden nichtlineare Splines zur Lösung von Anfangswertaufgaben bei gewöhnlichen Differentialgleichungen herangezogen. In der Nähe von Singularitäten besitzen z.B. verallgemeinerte rationale Splines mit variablen Exponenten gute Approximationseigenschaften. Bei Polynomsplines können Konvergenzaussagen hergeleitet werden, indem Äquivalenz dieser Verfahren mit gewissen linearen Mehrschrittverfahren gezeigt wird. In dieser Arbeit behandeln wir den nichtlinearen Fall, indem wir die lokalen Fehler in den Knoten direkt verfolgen. Einige numerische Beispiele zeigen die Güte dieser Verfahren insbesondere bei solchen Lösungen, die sehr steil anwachsen oder sogar im betrachteten Intervall singulär werden.
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  • 45
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    Numerische Mathematik 34 (1980), S. 1-13 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 34A45, 34A50, 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary In this paper Lie series are presented in Chebyshev form and applied to the iterative solution of initial value problems in differential equations. The resulting method, though algebraically complicated, is of theoretical interest as a generalisation of Taylor series methods and iterative Chebyshev methods. The theory of the method is discussed and the solutions of some simple scalar equations are analysed to illustrate the behaviour of the process.
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  • 46
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    Numerische Mathematik 33 (1979), S. 367-383 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary We consider a class of equilibrium finite element methods for elasticity problems. The approximate stresses satisfy the equilibrium equations but the symmetry of the stress tensor is relaxed. Optimal error bounds for the stresses and numerical examples are given.
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  • 47
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    Numerische Mathematik 34 (1980), S. 171-187 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Difference methods for the numerical solution of linear partial differential equations may often be improved by using a weighted right hand side instead of the original right hand side of the differential equation. Difference formulas, for which that is possible, are called “Mehrstellenformeln’ or Hermitian formulas. In this paper the Hermitian formulas for the approximation of Laplace's operator are characterized by a very simple condition. We prove, that in two-dimensional case for a Hermitian formula of ordern at leastn+3 discretization points are necessary. We give examples of such optimal formulas of arbitrary high-order.
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  • 48
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    Numerische Mathematik 34 (1980), S. 457-467 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L05, 65Q05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary By employing a numerical method which uses only rather classical tools of Numerical Analysis such as Newton's method and routines for ordinary differential equations, unstable periodic solutions of differential-difference equations can be computed. The method is applied to determine bifurcation diagrams with backward bifurcation.
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  • 49
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    Numerische Mathematik 35 (1980), S. 13-20 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): primary 65M05 ; 65M10 ; 65M15 ; secondary: 35M05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary We consider the numerical solution of the Tricomi problem. Using a weak formulation based on different spaces of test and trial functions, we construct a new Galerkin procedure for the Tricomi problem. Existence, uniqueness, and uniform stability of the approximate solution is proven, and a priori error bounds are given.
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  • 50
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    Numerische Mathematik 35 (1980), S. 21-33 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65B05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary The trapezoidal rule with deferred corrections using uncentered end formulas is shown to converge. While the proof technique is more specialized than the standard asymptotic expansion approach, it has some advantages. In addition to providing a more complete theoretical justification for current implementations of deferred corrections with the trapezoidal rule, the approach given here will hopefully apply for several other discretization methods.
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  • 51
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    Numerische Mathematik 35 (1980), S. 57-68 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L05 ; 65M20 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary This paper discussesrational Runge-Kutta methods for stiff differential equations of high dimensions. These methods are explicit and in addition do not require the computation or storage of the Jacobian. A stability analysis (based onn-dimensional linear equations) is given. A second orderA 0-stable method with embedded error control is constructed and numerical results of stiff problems originating from linear and nonlinear parabolic equations are presented.
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  • 52
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    Numerische Mathematik 35 (1980), S. 127-142 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): 34G05, 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary A class of approximation schemes of arbitrary accuracy, generated by a two-step recurrence relation, is devised for evolution equations of the second order. The schemes are effected via a specially constructed family of rational approximations to cos τ for τ≧0 and yield computationally efficient methods for systems of second-order ordinary differential equations and semidiscrete approximations for initial-boundary value problems for second-order hyperbolic equations.
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  • 53
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    Numerische Mathematik 35 (1980), S. 143-162 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65M15, 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary We study the error due to the discretization in time of a nonlinear parabolic problem by a multistep method. Error estimates are obtained if the method is of the orderp (p〉1) and stronglyA(Θ)-stable $$\left( {0〈 \Theta〈 \frac{\pi }{2}} \right)$$ . The method is also applied to the Navier-Stokes equations in two dimensions.
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  • 54
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    Numerische Mathematik 35 (1980), S. 231-240 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L10 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary The homotopy method is a frequently used technique in overcoming the local convergence nature of multiple shooting. In this paper sufficient conditions are given that guarantee the homotopy process to be feasible. The results are applicable to a class of two-point boundary value problems. Finally, the numerical solution of two practical problems arising in physiology is described.
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  • 55
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    Numerische Mathematik 35 (1980), S. 257-276 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS) ; 65M10 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Beschreibung / Inhaltsverzeichnis: Résumé Considérons une équation d'évolution parabolique linéaire associée à un opérateur linéaireA(t) dépendant du tempst. Nous développons dans cet article une méthode de discrétisation, basée sur les méthodes linéaires à pas multiples, traitant de manière implicite une partie de l'opérateurA(t) indépendante du temps, l'autre partie est traitée de manière explicite. Nous étudions la stabilité et la convergence de cette méthode.
    Notizen: Summary Let us consider a linear parabolic equation which is associated with a time dependent operatorA(t). In this paper, we present a method, which is founded on linear multistep methods, which discretize a time-independent part of the operatorA(t) in an implicit way, and the other part in an explicit way. We study stability and convergence for this method.
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  • 56
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    Numerische Mathematik 35 (1980), S. 315-341 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS) ; 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary We present here some new families of non conforming finite elements in ℝ3. These two families of finite elements, built on tetrahedrons or on cubes are respectively conforming in the spacesH(curl) andH(div). We give some applications of these elements for the approximation of Maxwell's equations and equations of elasticity.
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  • 57
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    Numerische Mathematik 35 (1980), S. 381-404 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary We study in this paper the convergence of a new mixed finite element approximation of the Navier-Stokes equations. This approximation uses low order Lagrange elements, leads to optimal order of convergence for the velocity and the pressure, and induces an efficient numerical algorithm for the solution of this problem.
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  • 58
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    Numerische Mathematik 36 (1980), S. 1-25 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65 N 30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary We begin in this paper the study of a general method of approximation of solutions of nonlinear equations in a Banach space. We prove here an abstract result concerning the approximation of branches of nonsingular solutions. The general theory is then applied to the study of the convergence of two mixed finite element methods for the Navier-Stokes and the von Kármán equations.
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  • 59
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    Numerische Mathematik 36 (1980), S. 33-52 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary A modified variational formulation, recently introduced by Taylor, Beresford and Wilson for solving second order problems, using the nonconforming Wilson element is here analysed. It is shown that the Patch Test is satisfied and that stresses and displacements are respectively first and second order accurate for arbitrary quadrilateral meshes.
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  • 60
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    Numerische Mathematik 36 (1980), S. 73-98 
    ISSN: 0945-3245
    Schlagwort(e): AMS: 35R35, 65P05, 76S05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary A new numerical method is used to solve stationary free boundary problems for fluid flow through porous media. The method also applies to inhomogeneous media, and to cases with a partial unsaturated flow.
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  • 61
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    Numerische Mathematik 36 (1980), S. 253-266 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65LO5 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Single step exponentially fitted integration formulae of orders 4 and 6 are derived. The final approximation to the required solution is obtained via a linear combination of asymptotically less accurate solutions obtained using conventional implicit integration formulae. This linear combination is performed in such a way that the final integration formula, as well as having an increased order of accuracy, integrates a certain pre-determined ordinary differential equation exactly. The algorithms developed are illustrated by means of some numerical examples.
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  • 62
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    Numerische Mathematik 36 (1980), S. 267-290 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary In this paper, we present a finite element lumped mass scheme for eigenvalue problems of circular arch structures, and give error estimates for the approximation. They assert that approximate eigenvalues and eigenfuctions converge to the exact ones. Some numerical examples are also given to illustrate our results.
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  • 63
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    Numerische Mathematik 36 (1980), S. 319-331 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS) ; 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Burrage and Butcher [1, 2] and Crouzeix [4] introduced for Runge-Kutta methods the concepts ofB-stability,BN-stability and algebraic stability. In this paper we prove that for any irreducible Runge-Kutta method these three stability concepts are equivalent.
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  • 64
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    Numerische Mathematik 36 (1981), S. 389-403 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N 30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary The paper deals with nonconforming finite element methods for the approximate solution of the interior boundary value problem for Maxwell equations in the time-harmonic case. The methods are based on penalization in the boundary conditions of total reflexion. Qualitative convergence results are obtained by a-priori estimates which are proven in the first part of this paper. The main object is to establish estimates for the global discretization error in various norms of the underlying spaces of approximating vector fields.
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  • 65
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    Numerische Mathematik 36 (1981), S. 455-465 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N25 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary In this paper we describe a nonconforming finite element method to compute the MHD spectrum of a plasma in a toroïdal configuration. We show that this method leads to a good approximation of the spectrum.
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  • 66
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    Numerische Mathematik 37 (1981), S. 1-28 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary We continue here the study of a general method of approximation of nonlinear equations in a Banach space yet considered in [2]. In this paper, we give fairly general approximation results for the solutions in a neighborhood of a simple limit point. We the apply the previous analysis to the study of Galerkin approximations for a class of variationally posed nonlinear problems and to a mixed finite element method for the NavierStokes equations.
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    Numerische Mathematik 37 (1981), S. 61-91 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Stability regions of explicit “linear” time discretization methods for solving initial value problems are treated. If an integration method needsm function evaluations per time step, then we scale the stability region by dividing bym. We show that the scaled stability region of a method, satisfying some reasonable conditions, cannot be properly contained in the scaled stability region of another method. Bounds for the size of the stability regions for three different purposes are then given: for “general” nonlinear ordinary differential systems, for systems obtained from parabolic problems and for systems obtained from hyperbolic problems. We also show how these bounds can be approached by high order methods.
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  • 68
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    Numerische Mathematik 37 (1981), S. 105-120 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary This study establishes an error estimate for a penalty-finite element approximation of the variational inequality obtained by a class of obstacle problems. By special identification of the penalty term, we first show that the penalty solution converges to the solution of a mixed formulation of the variational inequality. The rate of convergence of the penalization is ɛ where ɛ is the penalty parameter. To obtain the error of finite element approximation, we apply the results obtained by Brezzi, Hager and Raviart for the mixed finite element method to the variational inequality.
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  • 69
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    Numerische Mathematik 37 (1981), S. 157-166 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L07 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Consider the systemy′=f(x,y),y(a)=η,x∈[a,b],y∈R n wheref is continuous and Lipschitzian with respect to the second argument. Very often linear multistep variable stepsize variable formula methods (LM VSVFM's) are used to computey k≈y(xk) on the points of the grid:a=x 0〈x1〈x2〈...〈xN=b. The general LM VSVFM is based on formulae of the following type $$y_k = \sum\limits_{i = 1}^{s_k } {\alpha _i (\bar h_k ,sk)y_{k - i} } + \sum\limits_{i = 0}^{s_k } {h_{k - i} \beta _i (\bar h_k ,s_k )f(x_{k - i} ,y_{k - i} )} $$ whereh k=xk−xk−1, $$\bar h_k = (h_k ,h_{k - 1} , \ldots ,h_{k - s_k } )$$ ,s k≦k, k=1(1)N. The coefficients α i and β i depend on the lasts k+1 stepsizes and on the formula used at stepk. Only the zero-stability properties of some special classes of LM VSVFM's (as for example those based on Adams formulae) were investigated in the literature. A class of three-ordinate LM VSVFM's is defined in this paper. Some results concerning the zero-stability properties of these methods are proved. It is shown that some well-known results are simple corollaries of the results found for the three-ordinate LM VSVFM's. It is easily seen that similar results hold for the corresponding one-leg VSVFM's. Finally, the use of the theoretical results in the practical implementations is briefly discussed.
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  • 70
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    Numerische Mathematik 37 (1981), S. 235-255 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L05 ; 65Q05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary A class of numerical methods for the treatment of delay differential equations is developed. These methods are based on the wellknown Runge-Kutta-Fehlberg methods. The retarded argument is approximated by an appropriate multipoint Hermite Interpolation. The inherent jump discontinuities in the various derivatives of the solution are considered automatically. Problems with piecewise continuous right-hand side and initial function are treated too. Real-life problems are used for the numerical test and a comparison with other methods published in literature.
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  • 71
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    Numerische Mathematik 37 (1981), S. 257-277 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary In theh-version of the finite element method, convergence is achieved by refining the mesh while keeping the degree of the elements fixed. On the other hand, thep-version keeps the mesh fixed and increases the degree of the elements. In this paper, we prove estimates showing the simultaneous dependence of the order of approximation on both the element degrees and the mesh. In addition, it is shown that a proper design of the mesh and distribution of element degrees lead to a better than polynomial rate of convergence with respect to the number of degrees of freedom, even in the presence of corner singularities. Numerical results comparing theh-version,p-version, and combinedh-p-version for a one dimensional problem are presented.
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  • 72
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    Numerische Mathematik 37 (1981), S. 355-370 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Recently there has been considerable interest in the approximate numerical integration of the special initial value problemy″=f(x, y) for cases where it is known in advance that the required solution is periodic. The well known class of Störmer-Cowell methods with stepnumber greater than 2 exhibit orbital instability and so are often unsuitable for the integration of such problems. An appropriate stability requirement for the numerical integration of periodic problems is that ofP-stability. However Lambert and Watson have shown that aP-stable linear multistep method cannot have an order of accuracy greater than 2. In the present paper a class of 2-step methods of Runge-Kutta type is discussed for the numerical solution of periodic initial value problems.P-stable formulae with orders up to 6 are derived and these are shown to compare favourably with existing methods.
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  • 73
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    Numerische Mathematik 37 (1981), S. 405-421 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65 N 30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract The discretization by finite elements of a model variational problem for a clamped loaded beam is studied with emphasis on the effect of the beam thickness, which appears as a parameter in the problem, on the accuracy. It is shown that the approximation achieved by a standard finite element method degenerates for thin beams. In contrast a large family of mixed finite element methods are shown to yield quasioptimal approximation independent of the thickness parameter. The most useful of these methods may be realized by replacing the integrals appearing in the stiffness matrix of the standard method by Gauss quadratures.
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  • 74
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    Numerische Mathematik 37 (1981), S. 387-404 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N20 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary The treatment of a multigrid method in the framework of numerical analysis elucidates that regularity of the solution is not necessary for the convergence of the multigrid algorithm but only for fast convergence. For the linear equations which arise from the discretization of the Poisson equation, a convergence factor 0,5 is established independent of the shape of the domain and of the regularity of the solution.
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  • 75
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    Numerische Mathematik 45 (1984), S. 201-206 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Bulirsch and Stoer have shown how to construct asymptotic upper and lower bounds on the true (global) errors resulting from the solution by extrapolation of the initial value problem for a system of ordinary differential equations. It is shown here how to do this for any one-step method endowed with an asymptotically correct local error estimator. The one-step method can be changed at every step.
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  • 76
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    Numerische Mathematik 38 (1982), S. 141-154 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 35 A 40 ; 35 K 05 ; 65 N 15 ; 65 K 05 ; 80 A 20 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary A nonlinear approximation technique for the numerical solution of certain free boundary problems is proposed. The method is shown for a degenerate one-dimensional Stefan problem. For this problem, an error estimate, which is independent of the used algorithm, is derived. Numerical examples are discussed.
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  • 77
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    Numerische Mathematik 39 (1982), S. 221-230 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary In this paper Adams type methods for the special case of neutral functional differential equations are examined. It is shown thatk-step methods maintain orderk+1 for sufficiently small step size in a sufficiently smooth situation. However, when these methods are applied to an equation with a “non-smooth” solution the order of convergence is only one. Some computational considerations are given and numerical experiments are presented.
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  • 78
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    Numerische Mathematik 39 (1982), S. 371-404 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): 65 N 30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary The purpose of this paper is to study the approximation of the Von Karman equations by the mixed finite element scheme of Miyoshi and to follow the solutions arcs at a neighbourhood of the first eigenvalue of the linearized problem. This last problem is solved by a continuation method.
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  • 79
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    Numerische Mathematik 29 (1978), S. 269-285 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): 65 M 99 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Several extrapolation procedures are presented for increasing the order of accuracy in time for evolutionary partial differential equations. These formulas are based on finite difference schemes in both the spatial and temporal directions. One of these schemes reduces to a Runge-Kutta type formula when the equations are linear. On practical grounds the methods are restricted to schemes that are fourth order in time and either second, fourth or sixth order in space. For hyperbolic problems the second order in space methods are not useful while the fourth order methods offer no advantage over the Kreiss-Oliger method unless very fine meshes are used. Advantages are first achieved using sixth order methods in space coupled with fourth order accuracy in time. The averaging procedure advocated by Gragg does not increase the efficiency of the scheme. For parabolic problems severe stability restrictions are encountered that limit the applicability to problems with large cell Reynolds number. Computational results are presented confirming the analytic discussions.
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  • 80
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    Numerische Mathematik 29 (1978), S. 329-344 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65M20 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary The method of lines is used to solve Poisson's equation on an irregular domain with nonlinear or free boundary conditions. The partial differential equation is approximated by a system of second order ordinary differential equations subject to multi-point boundary conditions. The system is solved with an SOR iteration which employs invariant imbedding for each one dimensional problem. An application of the method to a boundary control problem and to a free surface problem arising in electrochemical machining is described. Finally, some theoretical convergence results are presented for a model problem with radiative boundary conditions on fixed boundaries.
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  • 81
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    Numerische Mathematik 32 (1979), S. 271-279 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS) 49.04 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary This paper is concerned with the solution of the finite time Riccati equation. The solution to the Riccati equation is given in terms of the partition of the transition matrix. Matrix differential equations for the partition of the transition matrix are derived and are solved using computational methods. Examples illustrating the method are presented and the computational algorithms are given.
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  • 82
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    Numerische Mathematik 30 (1978), S. 25-38 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Brown introducedk-step methods usingl derivatives. We investigate for whichk andl the methods are stable or unstable. It is seen that to anyl the method becomes unstable fork large enough. All methods withk≦2(l+1) are stable. Fork=1,2,..., 18 there exists aλ k such that the methods are stable for anyl ≧λ k and unstable for anyl 〈λ k . Theλ k are given.
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  • 83
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    Numerische Mathematik 32 (1979), S. 307-332 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65Q05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary This paper deals with the convergence of nonstationary quasilinear multistep methods with varying step, used for the numerical integration of Volterra functional differential equations. A Perron type condition (appearing in the differential equations theory) is imposed on the increment function. This gives a generalization of some results of Tavernini ([19–21]).
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  • 84
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    Numerische Mathematik 30 (1978), S. 103-116 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary We consider some equilibrium finite element methods for two-dimensional elasticity problems. The stresses and the displacements are approximated by using piecewise linear functions. We establishL 2-estimates of orderO(h 2) for both stresses and displacements.
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  • 85
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    Numerische Mathematik 33 (1979), S. 303-313 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N20 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary In [9], Simpson proved some theorems concerning the approximation of mildly nonlinear Dirichlet problems −Δu=f (x, u) inD, u=0 on ∂D by finite differences. The assumptionsf(x, 0)≧0 andf u(x, u)〉0 in [9] have turned out to be unnecessarily restrictive and are eliminated in this paper. On the other hand, we considered it necessary to make the smoothness conditions forD slightly more stringent irrespective of the conditions imposed onf.
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  • 86
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    Numerische Mathematik 33 (1979), S. 43-53 
    ISSN: 0945-3245
    Schlagwort(e): AMS (Mos): 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Letu h be the finite element solution to−Δu=f with zero boundary conditions in a convex polyhedral domain Ω. Fromu h we calculate for eachz∈Ω and |α|≦1 an approximationu h −α (z) toD α u(z) with |D α u(z)−u h −α (z)|=O(h 2k−2) wherek is the order of the finite elements. The same superconvergence order estimates are obtained also for the boundary flux. We need not work on a regular mesh but we have to compute averages ofu h where the diameter of the domain of integration must not depend onh.
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  • 87
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    Numerische Mathematik 33 (1979), S. 69-75 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): 34B15 ; 65L10 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary In the first part of this paper we are dealing with theoretical statements and conditions which lead to existence and uniqueness of the solution of a nonlinear boundary value problem with delay. Next we apply this method successfully to a numerical example. The computations have been carried out at the computer Siemens 4004. The data obtained are presented in two tables.
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  • 88
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    Numerische Mathematik 32 (1979), S. 17-29 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L10 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary We present a new method for the numerical solution of bifurcation problems for ordinary differential equations. It is based on a modification of the classical Ljapunov-Schmidt-theory. We transform the problem of determining the nontrivial branch bifurcating from the trivial solution into the problem of solving regular nonlinear boundary value problems, which can be treated numerically by standard methods (multiple shooting, difference methods).
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  • 89
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    Numerische Mathematik 32 (1979), S. 51-68 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): 65L10 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary This paper deals with the computation of branch points in ordinary differential equations. A direct numerical method is presented which requires the solution of only one boundary value problem. The method handles the general case of branching from a nontrivial solution which is a-prioriunknown. A testfunction is proposed which may indicate branching if used in continuation methods. Several real-life problems demonstrate the procedure.
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  • 90
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    Numerische Mathematik 32 (1979), S. 69-74 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N25, 35J60, 49D20 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary In recent years, a group of inverse iteration type algorithms have been developed for solving nonlinear elliptic eigenvalue problems in plasma physics [4]. Although these algorithms have been very successful in practice, no satisfactory theoretical justification of convergence has been available. The present paper fills this gap and proves for a large class of such problems and a simple version of such algorithms that linear convergence to a local maximum of a certain potential is obtained.
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  • 91
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    Numerische Mathematik 32 (1979), S. 167-181 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS) ; 65L05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary Brown [1] introducedk-step methods usingl derivatives. Necessary and sufficient conditions forA 0-stability and stiff stability of these methods are given. These conditions are used to investigate for whichk andl the methods areA 0-stable. It is seen that for allk andl withk≦1.5 (l+1) the methods areA 0-stable and stiffly stable. This result is conservative and can be improved forl sufficiently large. For smallk andl A 0-stability has been determined numerically by implementing the necessary and sufficient condition.
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  • 92
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    Numerische Mathematik 32 (1979), S. 209-232 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS) ; 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Beschreibung / Inhaltsverzeichnis: Resumé Le but de cet article est l'étude de l'approximation numérique des solutions non-triviales des équations de Von Karman pour le flambage d'une plaque mince encastrée. S'inspirant de la méthode de Kikuchi pour des problèmes quasi-linéaires du second ordre, on propose une méthode itérative d'éléments finis qui donne des approximations des solutions de norme «petite» qui bifurquent de la solution triviale au voisinage d'une valeur propre simple du problème linéarisé. On démontre la convergence et on obtient des estimations de l'erreur.
    Notizen: Summary The aim of this article is to study the numerical approximation of non-trivial solutions of the Von Karman equations for the buckling of a thin elastic clamped plate. Following Kikuchi's method for second order quasilinear problems, we propose an iterative finite element method which produces approximations of non-trivial solutions of “small” norm which bifurcate from the trivial solution near simple eigenvalues of the linearised problem. The convergence is proved and error estimates are obtained.
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  • 93
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65M25, 35L20 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary The ALGOL-procedure1 char2 presented in this paper can be applied to the initial or initial-boundary value problem of a quasilinear hyperbolic differential equation of second order. A method of characteristics is combined with extrapolation to the limit. Thus, the results are very accurate. The same accuracy can also be obtained if the initial values are only piecewise smooth.
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  • 94
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    Numerische Mathematik 44 (1984), S. 75-102 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65L10 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary This paper examines the concepts of feedback and adaptivity for the Finite Element Method. The model problem concernsC 0 elements of arbitrary, fixed degree for a one-dimensional two-point boundary value problem. Three different feedback methods are introduced and a detailed analysis of their adaptivity is given.
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  • 95
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    Numerische Mathematik 37 (1981), S. 333-337 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary A nonconforming mixed finite element method is presented for approximation of ∇w with Δw=f,w| r =0. Convergence of the order $$\left\| {\nabla w - u_h } \right\|_{0,\Omega } = \mathcal{O}(h^2 )$$ is proved, when linear finite elements are used. Only the standard regularity assumption on triangulations is needed.
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  • 96
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    Numerische Mathematik 38 (1982), S. 1-30 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary In the first two papers of this series [4, 5], we have studied a general method of approximation of nonsingular solutions and simple limit points of nonlinear equations in a Banach space. We derive here general approximation results of the branches of solutions in the neighborhood of a simple bifurcation point. The abstract theory is applied to the Galerkin approximation of nonlinear variational problems and to a mixed finite element approximation of the von Kármán equations.
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  • 97
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    Numerische Mathematik 38 (1982), S. 39-52 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): Primary 65L10 ; Secondary 35R35 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary An approximate method for nonlinear problems with functional constraints is considered, in which the constraint in the whole domain is replaced by the constraint on a manifold of lower dimension. The stability criterion is introduced, and convergence theorems are proved for the onedimensional problem. Numerical results for the elastic-plastic torsion problem are given.
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  • 98
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    Numerische Mathematik 28 (1977), S. 121-142 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): primary: 65M99 ; 65M25 ; secondary: 65B05 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary The procedurediwiex presented in this paper provides an approximate solution to Cauchy's initial value problem for general hyperbolic systems of first order. The procedurecharex can be applied to the initial value problem for a hyperbolic system of quasi-linear differential equations. This second method is a kind of method of characteristics. It produces a solution for the whole domain of determinancy. Both procedures use extrapolation to the limit.
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    Springer
    Numerische Mathematik 39 (1982), S. 97-112 
    ISSN: 0945-3245
    Schlagwort(e): AMS (MOS): 65N30 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary We introduce some new families of finite element approximation for the stationary Stokes and Navier Stokes equations in a bounded domain in ℝ3. These elements can used tetahedrons or cubes. The approximation satisfie exactly the incompressibility condition.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    Digitale Medien
    Digitale Medien
    Springer
    Numerische Mathematik 29 (1977), S. 65-82 
    ISSN: 0945-3245
    Schlagwort(e): AMS(MOS): 65M20 ; CR: 5.17
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Summary The line method discussed in [19] is improved by considering several time slices. It is applied to parabolic initial-value problems, and with techniques similar to [16] it is proved that the root conditions of Dahlquist [5] and Widlund [17] are sufficient for stability. Stable methods up to order 6 are given and illustrated by numerical calculations.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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