An Efficient Algebraic Algorithm for the Geometric Completion to Involution

 We describe an adaption of a differential algebraic completion algorithm for linear systems of partial differential equations that allows us to deduce intrinsic differential geometric information like the number of prolongations and projections needed for the completion. This new hybrid algorithm represents a much more efficient realisation of the classical Cartan–Kuranishi completion than previous purely geometric ones. A classical problem in geometric completion theory is the existence of δ-singular coordinate systems in which the algorithms do not terminate. We develop a new and a very simple criterion for δ-singularity based on a comparison of the Janet and the Pommaret division. This criterion can also be used for the direct construction of δ-regular coordinates. Received: July 28, 2000; revised version: October 16, 2001     

Sauerstoffbeweglichkeit und photooxidativer zerfall von 1-(4′-N,N-diethylaminophenyl)-azo-2-naphthol in polymerfilmen

The relative oxygen permeabilities of layer-forming polymeric compounds are determined by means of extinguishing the delayed fluorescence of Pyronin B by oxygen. In comparison with the fading rates of the photooxidative initiated decomposition of an azo dye into the corresponding polymer one can argue, that the temporally and spatially limited diffusion of the singlet oxygen from the position of its formation on the dye is the rate determining step of this reaction.     

A self-similar fractal radiation pattern synthesis technique for reconfigurable multiband arrays

A novel method for designing reconfigurable multiband linear and planar antenna arrays is presented. The technique is based on a generalized Fourier series synthesis approach that exploits the self-similarity of a specified fractal radiation pattern in order to achieve the desired multiband performance. The fractal radiation patterns are composed of scaled and shifted copies of an appropriately chosen generating window function that exhibits low sidelobe levels and rapid spectral rolloffs in the transform domain. A newly developed thinning algorithm is presented which may be employed to reduce considerably both the overall physical size and the total number of elements in a synthesized multiband array. Finally, a band-switching scheme is introduced that is well-suited for implementation in the form of a reconfigurable common aperture array.     

Interactional features of a paper-based monitoring system

Traditional desktop computers have a tendency to drag users towards the desk and away from the object of their work. Researchers working within fields covered by the term ‘tangible computing’ are trying to find ways to integrate computer technology in a more radical way and minimise the gravitation to a desk. In this paper, we argue for different interactional features that are connected to a design idea for monitoring treatment sessions of remote haemodialysis. We discuss interactional features with a non-traditional computer interface in a highly mobile work environment.