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951.
952.
Schuhmacher A Hald J Rasmussen KB Hansen PC 《The Journal of the Acoustical Society of America》2003,113(1):114-127
Whereas standard boundary element calculations focus on the forward problem of computing the radiated acoustic field from a vibrating structure, the aim in this work is to reverse the process, i.e., to determine vibration from acoustic field data. This inverse problem is brought on a form suited for solution by means of an inverse boundary element method. Since the numerical treatment of the inverse source reconstruction results in a discrete ill-posed problem, regularization is imposed to avoid unstable solutions dominated by errors. In the present work the emphasis is on Tikhonov regularization and parameter-choice methods not requiring an error-norm estimate for choosing the right amount of regularization. Several parameter-choice strategies have been presented lately, but it still remains to be seen how well these can handle industrial applications with real measurement data. In the present work it is demonstrated that the L-curve criterion is robust with respect to the errors in a real measurement situation. In particular, it is shown that the L-curve criterion is superior to the more conventional generalized cross-validation (GCV) approach for the present tire noise studies. 相似文献
953.
In this article we describe a non-equispaced fast Fourier transform. It is similar
to the algorithms of Dutt and Rokhlin and Beylkin but is based on an exact Fourier series
representation. This results in a greatly simplified analysis and increased flexibility. The latter
can be used to achieve more efficiency. Accuracy and efficiency of the resulting algorithm are
illustrated by numerical examples.
In the second part of the article the non-equispaced FFT is applied to the reconstruction
problem in Computerized Tomography. This results in a different view of the gridding method of
OSullivan and in a new ultra fast reconstruction algorithm. The new reconstruction algorithm
outperforms the filtered backprojection by a speedup factor of up to 100 on standard hardware
while still producing excellent reconstruction quality. 相似文献
954.
955.
Karsten Keller 《International Journal of Theoretical Physics》1992,31(5):835-842
We investigate the right annihilator lattice of a*-ring and ask whether it is orthomodular with respect to a naturally given involution. In particular, we introduce a new class of*-rings with orthomodular right annihilator lattice. 相似文献
956.
957.
Archiv der Mathematik - 相似文献
958.
Karsten Krogh-Jespersen Claire M. Young Robert A. Moss Marek Wiostowski 《Tetrahedron letters》1982,23(23):2339-2342
Both ab initio calculations and experimental observations support the intermediacy of diazirinyl or azirinyl cation-chloride anion pairs in transformations (1), (2), and (4). 相似文献
959.
960.
Theoretical Chemistry Accounts - An INDO model Hamiltonian, incorporating screening within the π-system and parametrized particularly to describe dynamical properties (photoemission and... 相似文献