Browsing by Subject "Expansion coefficients"

Now showing 1 - 3 of 3

Open Access
A modified equivalence principle for open surfaces
(IEEE, 2014) Takrimi, Manouchehr; Gürel, Levent
We introduce a new method for expanding equivalent surface current densities over open surfaces. The new method is based on the equivalence principle, which is theoretically used with closed surfaces. Utilizing low-order basis functions to compute the expansion coefficients of equivalent surface currents and then weighting these coefficients with an appropriate window function compensates for computational field errors originating from using truncated currents at the open boundaries. These modified coefficients can be used to reproduce the original electromagnetic fields inside a limited equivalent region. The simulations demonstrate that relative errors as low as 1-2.5% are achievable based on the specifics of the source and shape of the open surface. © 2014 IEEE.
Open Access
Subset selection with structured dictionaries in classification
(EURASIP, 2007) İnce, N. F.; Göksu, F.; Tewfik, A. H.; Onaran, İbrahim; Çetin, A. Enis
This paper describes a new approach for the selection of discriminant time-frequency features for classification. Unlike previous approaches that use the individual discrimination power of expansion coefficients, the proposed approach selects a subset of features by implementing a classifier directed pruning of an initial redundant set of candidate features. The candidate features are calculated from a structured redundant time-frequency analysis of the signal, such as an undecimated wavelet transform. We show that the proposed approach has a performance that is as good as or better than traditional classification approaches while using a much smaller number of features. In particular, we provide experimental results to demonstrate the superior performance of the algorithm in the area of impact acoustic classification for food kernel inspection. The proposed algorithm achieved 91.8% and 98.5% classification accuracies in separating open shell from closed shell pistachio nuts and discriminating between empty and full hazelnuts respectively. Traditional methods used in this area resulted in 82% and 97% classification accuracies respectively.
Open Access
Windowed equivalence principle for open surfaces
(IEEE, 2013) Takrimi, Manouchehr; Gürel, Levent
We introduce a modified current expansion scheme over open surfaces based on the equivalence theorem, which employs closed surfaces, in principle. Weighting the expansion coefficients with a suitable window function compensates for the computed field errors that occur because of the open surfaces. Numerical simulations demonstrate that the equivalent surface currents expanded with low-ordered basis functions on an open surface and weighted by suitable functions can be used to obtain the correct electromagnetic fields in a limited volume near the surface.