Continuous window functions for NFFT

NFFT: Algorithm for irregular sampling

The nonuniform discrete Fourier transform (NDFT), used in many processing schemes, can be computed using a fast algorithm known as the non uniform fast Fourier transform (NFFT). The NFFT is not a new algorithm, but it is an approximation scheme that can be use to calculate an approximate spectrum. In one dimension, computational complexity of the NFFT is O(NlogN) which is a dramatic improvement...

Window Functions for CMB Experiments

We discuss the applicability and derivation of window functions for cosmic microwave background experiments on large and intermediate angular scales. These window functions describe the response of the experiment to power in a particular mode of the fluctuation spectrum. We give general formulae, illustrated with specific examples, for the most common observing strategies. Subject headings: cos...

NFFT 3.0 - Tutorial

Contra $beta^{*}$-continuous and almost contra $beta^{*}$-continuous functions

The notion of contra continuous functions was introduced and investigated by Dontchev. In this paper, we apply the notion of $beta^{*}$-closed sets in topological space to present and study a new class of functions called contra $beta^{*}$-continuous and almost contra $beta^{*}$-continuous functions as a new generalization of contra continuity.

Vorwissensbasierte NFFT zur CT-Metallartefaktreduktion

Kurzfassung. Metallobjekte können bei einer CT-Aufnahme zu Artefakten im rekonstruierten Bild führen. Um diesen Einfluss zu reduzieren und die resultierende Bildqualität zu erhöhen, ist eine Artefaktreduktion möglich. In dieser Arbeit wird ein Verfahren basierend auf nichtäquidistanten Fouriertransformationen (NFFT) als Reduktionsmöglichkeit betrachtet. Durch geeignete Dämpfung dieser Transform...