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Tue, 15 Mar 2005 15:09:58 +0100Tue, 15 Mar 2005 15:09:58 +0100Frequency Filtering in Telecommunications
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1625
Piezoelectric filters are used in telecommunication to filter electrical signals. This report deals with the problem of calculating passing and damped frequency intervals for a filter with given geometrical configurations and materials. Only periodic filters, which are widely used in practice, were considered. These filters consist of periodically arranged cells. For a small amount of cells a numerical procedure to visualise the wave propagation in the filter was developed. For a big number of cells another model of the filter was obtained. In this model it is assumed that the filter occupies an infinite domain. This leads to a differential equation, with periodic coefficients, that describes propagation of the wave with a given frequency in the filter. To analyse this equation the Spectral Theory for Periodic Operators had to be employed. Different ways -- analytical and numerical -- to apply the theory were proposed and analysed.Ariadna Farres Basiana; Hanna Martinsson; Brage Ofstad Vik; Sergiy Pereverzyev; Martin Purrucker; Klaus Erich Schmitz Abe; David Stiel; Uldis Strautinsreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1625Tue, 15 Mar 2005 15:09:58 +0100Initial Temperature Reconstruction for a Nonlinear Heat Equation: Application to Radiative Heat Transfer
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1607
Consider a cooling process described by a nonlinear heat equation. We are interested to recover the initial temperature from temperature measurements which are available on a part of the boundary for some time. Up to now even for the linear heat equation such a problem has been usually studied as a nonlinear ill-posed operator equation, and regularization methods involving Frechet derivatives have been applied. We propose a fast derivative-free iterative method. Numerical results are presented for the glass cooling process, where nonlinearity appears due to radiation.Sergiy Pereverzyev; Rene Pinnau; Norbert Siedowpreprinthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1607Fri, 04 Feb 2005 10:33:11 +0100