The solution of partial differential equations on adaptively generated grids play an important role in scienti£c computation. In this paper we compare two Poisson solvers for data on nonequispaced mesh points. A new meshless Fourier method based on NFFT is constructed in R3. This algorithm is compared to the well-established multigrid method working on nonequidistant meshes. Our investigations are motivated especially by simulations of the behaviour of charged particles in accelerators.
Spherical filters have recently been introduced in order to avoid the
spherical harmonic transform. Spherical filtering can be used in a variety of applications, such as climate modelling, electromagnetic and acoustic scattering, and several other areas. However, up to now these methods have been restricted to special grids on the sphere. The main reason for this was to enable the use of FFT techniques. In this paper we extend the spherical filter to arbitrary grids by using the the Nonequispaced Fast Fourier Transform (NFFT). The new algorithm can be applied to a variety of different distributions on
the sphere, equidistributions on the sphere being an important example. The algorithm's performance is illustrated with several
numerical examples.
In this paper we propose two new algorithms for high quality Fourier reconstructions of digital N by N images from their Radon transform. Both algorithms are based on fast Fourier transforms for nonequispaced data (NFFT) and require only O(N2 log N) arithmetic operations. While the first algorithm includes a bivariate NFFT on the polar grid, the second algorithm consists of several univariate NFFTs on the so-called linogram.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.