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Cottbus, Germany

The Brandenburg University of Technology was founded in 1991 and is the top technical university in Brandenburg, Germany. Located in Cottbus, in English it is often called Technical University of Cottbus or TU Cottbus.In , the University had 112 professors, 594 academic staff and 6,972 students, of which 1,234 are of foreign origin from 89 nations. Wikipedia.

Kemm F.,TU Brandenburg
International Journal for Numerical Methods in Fluids | Year: 2011

This paper gives a comparative study of TVD-limiters for standard explicit Finite Volume schemes. In contrast to older studies, it includes also unsymmetrical limiter functions that depend on the local CFL-number. We classify the limiters and show how to extend these families of limiters. We introduce a new member of the Superbee family, which is adapted to Roe's linear third-order scheme. Based on an idea by Serna and Marquina, new smooth limiters are introduced, which turn the van Leer and van Albada limiters into complete classes of limiters. The comparison of the limiters is done with some standard test cases. The results clarify the influence of the chosen limiter on the quality of the numerical results. Compared with ENO or WENO schemes, they also show the high resolution, which can be obtained by a CFL-number-dependent limiter when the grid is not highly refined. © 2010 John Wiley & Sons, Ltd. Source

Bestehorn M.,TU Brandenburg
Physics of Fluids | Year: 2013

We consider thin liquid films on a horizontal, solid, and completely wetting substrate. The substrate is subjected to oscillatory accelerations in the normal direction and/or in the horizontal direction. A linear Floquet analysis shows that the planar film surface loses stability if amplitudes and frequencies of the harmonic oscillations meet certain criteria. Based on the long wave lubrication approximation, we present an integral boundary layer model where the z component is integrated out and the spatial dimension is reduced by one. The linear stability analysis of this model shows good agreement with the exact problem and with the linearized long wave equations. Pattern formation in the nonlinear regime is computed numerically from the long wave model in two and three spatial dimensions. Normal oscillations show the traditional Faraday patterns such as squares and hexagons. Lateral oscillations cause a pattern formation scenario similar to spinodal dewetting, namely coarsening and no rupture. For certain amplitude and frequency ranges, combined lateral and normal oscillations can give rise to one or more traveling drops. Finally, we discuss the control of a drop's motion in the horizontal plane. © 2013 AIP Publishing LLC. Source

Kleefeld A.,TU Brandenburg
Inverse Problems | Year: 2013

In this paper the numerical calculation of eigenvalues of the interior transmission problem arising in acoustic scattering for constant contrast in three dimensions is considered. From the computational point of view existing methods are very expensive, and are only able to show the existence of such transmission eigenvalues. Furthermore, they have trouble finding them if two or more eigenvalues are situated closely together. We present a new method based on complex-valued contour integrals and the boundary integral equation method which is able to calculate highly accurate transmission eigenvalues. So far, this is the first paper providing such accurate values for various surfaces different from a sphere in three dimensions. Additionally, the computational cost is even lower than those of existing methods. Furthermore, the algorithm is capable of finding complex-valued eigenvalues for which no numerical results have been reported yet. Until now, the proof of existence of such eigenvalues is still open. Finally, highly accurate eigenvalues of the interior Dirichlet problem are provided and might serve as test cases to check newly derived Faber-Krahn type inequalities for larger transmission eigenvalues that are not yet available. © 2013 IOP Publishing Ltd. Source

Testate amoebae play an important role in food and energy turnover of terrestrial ecosystems. These protists had been used to analyze possible immediate effects on soil functioning caused by prescribed burning deployed for habitat management. Soil samples from two test sites had been taken within 1. h before and after burning. Small, short and superficially burning fires did not severely affect soil testate amoebal communities, as shown by ANOVA, PCA, and cluster analysis. The results from this study corroborate a previously conducted study and highlight the fact that prescribed burning (transient fires) is a useful tool for habitat management without affecting soil testate amoebae communities (important for soil function), as shown for continental Calluna heathlands. © 2012 Elsevier B.V. Source

Phased microphone arrays are used in a variety of applications for the estimation of acoustic source location and spectra. The popular conventional delay-and-sum beamforming methods used with such arrays suffer from inaccurate estimations of absolute source levels and in some cases also from low resolution. Deconvolution approaches such as DAMAS have better performance, but require high computational effort. A fast beamforming method is proposed that can be used in conjunction with a phased microphone array in applications with focus on the correct quantitative estimation of acoustic source spectra. This method bases on an eigenvalue decomposition of the cross spectral matrix of microphone signals and uses the eigenvalues from the signal subspace to estimate absolute source levels. The theoretical basis of the method is discussed together with an assessment of the quality of the estimation. Experimental tests using a loudspeaker setup and an airfoil trailing edge noise setup in an aeroacoustic wind tunnel show that the proposed method is robust and leads to reliable quantitative results. © 2009 Elsevier Ltd. All rights reserved. Source

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