Abstract. A sharper L-error estimate is obtained for the non-Fickian flow of fluid in porous media by means of a mixed Ritz–Volterra projection instead of the mixed Ritz projection used in [R. E. Ewing, Y. Lin, and J. Wang, Acta Math. Univ. Comenian. (N.S.), 70 (2001), pp. 75–84]. Moreover, local L superconvergence for the velocity along the Gauss lines and for the pressure at the Gauss points ...

We are interested in (approximate) eigenvalue inclusion regions for matrix pencils (A,B), in particular of large dimension, based on certain fields of values. We show how the usual field of values may be efficiently approximated for large Hermitian positive definite B, but also point out limitations of this set. We introduce four field of values based inclusion regions, which may effectively be...

The procedure of level optimization for the (198)Hg I spectrum emitted by electrodeless discharge lamps is revisited. Wavelength-measurement uncertainties and systematic shifts caused by interactions with the buffer gas and by calibration procedures are carefully analyzed and accounted for. Based on this extended analysis of the original measurements, the energy levels are re-optimized, which r...

Quantitative bounds are presented for the superlinear convergence of the MINRES method of Paige and Saunders [SIAM J. Numer. Anal., 1975] for the solution of sparse linear systems Ax = b, with A symmetric and indefinite. It is shown that the superlinear convergence is observed as soon as the harmonic Ritz values approximate well the eigenvalues of A that are either closest to zero or farthest f...

We investigate the conditions under which an optimal continuous feedback control can be achieved. Chaotic oscillations in the single-well Duffing model, with either a positive or a negative nonlinear stiffness term, are tuned to their related Ritz approximation. The Floquet theory enables the stability analysis of the control. Critical values of the feedback control coefficient fulfilling the o...

This paper is concerned with bounds for the linear response eigenvalue problem for H = [ 0 K M 0 ] , where K and M admits a 2 × 2 block partitioning. Bounds on how the changes of its eigenvalues are obtained when K and M are perturbed. They are of linear order with respect to the diagonal block perturbations and of quadratic order with respect to the off-diagonal block perturbations in K and M ...

Using a function algebra characterization of exponential time due to Monien 5], in the style of Bellantoni-Cook 2], we characterize exponential time functions of linear growth via a safe course-of-values recursion scheme.

This article is a critical review of some of the methods that have been used for the sampling, analysis, and monitoring of vapor-phase toluene diisocyanate (TDI). Only some of the methods that have received relatively widespread application have been addressed in this article. This review includes a "tutorial style" discussion of basic definitions and basic principles and procedures of quality ...

Eigenvalue iterative methods, such as Arnoldi and Jacobi-Davidson, are typically used with restarting. This has signiicant performance shortcomings, since important components of the invariant subspace may be discarded. One way of saving more information at restart is the idea of \thick" restarting which keeps more Ritz vectors than needed. Our previously proposed dynamic thick restarting choos...