Browsing by Subject "Lagrange interpolation"

Now showing 1 - 4 of 4

Open Access
Enhancing the accuracy of the interpolations and anterpolations in MLFMA
(Institute of Electrical and Electronics Engineers, 2006) Ergül, Özgür; Gürel, Levent
We present an efficient technique to reduce the interpolation and anterpolation (transpose interpolation) errors in the aggregation and disaggregation processes of the multilevel fast multipole algorithm (MLFMA), which is based on the sampling of the radiated and incoming fields over all possible solid angles, i.e., all directions on the sphere. The fields sampled on the sphere are subject to various operations, such as interpolation, aggregation, translation, disaggregation, anterpolation, and integration. We identify the areas on the sphere, where the highest levels of interpolation errors are encountered. The error is reduced by employing additional samples on such parts of the sphere. Since the interpolation error is propagated and amplified by every level of aggregation, this technique is particulary useful for large problems. The additional costs in the memory and processing time are negligible, and the technique can easily be adapted into the existing implementations of MLFMA.
Open Access
Lebesgue constants on cantor type sets
(2020-09) Paksoy, Yaman
The properties of compact subsets of the real line which are in the class of Bounded Lebesgue Constants (BLC) are investigated. Knowing that any such set must have 1-dimensional Lebesgue measure zero and nowhere density, and the fact that there are examples of countable sets both inside and outside of the class BLC, families of Cantor-type sets were focused on. Backed up by numerical experiments (up to degree 128) and analytical results, the conjecture “there exists no perfect set in BLC” was put forward.
Open Access
Optimal interpolation of translation operator in multilevel fast multipole algorithm
(Institute of Electrical and Electronics Engineers, 2006) Ergül, Özgür; Gürel, Levent
Lagrange interpolation of the translation operator in the three-dimensional multilevel fast multipole algorithm (MLFMA) is revisited. Parameters of the interpolation, namely, the number of interpolation points and the oversampling factor, are optimized for controllable error. Via optimization, it becomes possible to obtain the desired level of accuracy with the minimum processing time.
Open Access
Two-step lagrange interpolation method for the multilevel fast multipole algorithm
(Institute of Electrical and Electronics Engineers, 2009) Ergül, Z.; Bosch, I.; Gürel, Levent
We present a two-step Lagrange interpolation method for the efficient solution of large-scale electromagnetics problems with the multilevel fast multipole algorithm (MLFMA). Local interpolations are required during aggregation and disaggregation stages of MLFMA in order to match the different sampling rates for the radiated and incoming fields in consecutive levels. The conventional one-step method is decomposed into two one-dimensional interpolations, applied successively. As it provides a significant acceleration in processing time, the proposed two-step method is especially useful for problems involving large-scale objects discretized with millions of unknowns.