21,448 research outputs found
An investigation into a wavelet accelerated gauge fixing algorithm
We introduce an acceleration algorithm for coulomb gauge fixing, using the
compactly supported wavelets introduced by Daubechies. The algorithm is similar
to Fourier acceleration. Our provisional numerical results for on
lattices show that the acceleration based on the DAUB6 transform can
reduce the number of iterations by a factor up to 3 over the unaccelerated
algorithm. The reduction in iterations for Fourier acceleration is
approximately a factor of 7.Comment: Resubmitted as a uuencode-compressed-tar postscript file. A
Daubechies wavelet transform will transform a vector of length in
operations, and not in O(N log N) operations as we incorrectly stated in the
first version of this pape
Map online system using internet-based image catalogue
Digital maps carry along its geodata information such as coordinate that is important in one particular topographic and thematic map. These geodatas are meaningful especially in military field. Since the maps carry along this information, its makes the size of the images is too big. The bigger size, the bigger storage is required to allocate the image file. It also can cause longer loading time. These conditions make it did not suitable to be applied in image catalogue approach via internet environment. With compression techniques, the image size can be reduced and the quality of the image is still guaranteed without much changes. This report is paying attention to one of the image compression technique using wavelet technology. Wavelet technology is much batter than any other image compression technique nowadays. As a result, the compressed images applied to a system called Map Online that used Internet-based Image Catalogue approach. This system allowed user to buy map online. User also can download the maps that had been bought besides using the searching the map. Map searching is based on several meaningful keywords. As a result, this system is expected to be used by Jabatan Ukur dan Pemetaan Malaysia (JUPEM) in order to make the organization vision is implemented
TRUFAS, a wavelet based algorithm for the rapid detection of planetary transits
Aims: We describe a fast, robust and automatic detection algorithm, TRUFAS,
and apply it to data that are being expected from the CoRoT mission. Methods:
The procedure proposed for the detection of planetary transits in light curves
works in two steps: 1) a continuous wavelet transformation of the detrended
light curve with posterior selection of the optimum scale for transit
detection, and 2) a period search in that selected wavelet transformation. The
detrending of the light curves are based on Fourier filtering or a discrete
wavelet transformation. TRUFAS requires the presence of at least 3 transit
events in the data. Results: The proposed algorithm is shown to identify
reliably and quickly the transits that had been included in a standard set of
999 light curves that simulate CoRoT data. Variations in the pre-processing of
the light curves and in the selection of the scale of the wavelet transform
have only little effect on TRUFAS' results. Conclusions: TRUFAS is a robust and
quick transit detection algorithm, especially well suited for the analysis of
very large volumes of data from space or ground-based experiments, with long
enough durations for the target-planets to produce multiple transit events.Comment: 9 pages, 10 figures, accepted by A&
Determination of the Hurst Exponent by Use of Wavelet Transforms
We propose a new method for (global) Hurst exponent determination based on
wavelets. Using this method, we analyze synthetic data with predefined Hurst
exponents, fracture surfaces and data from economy. The results are compared
with those obtained from Fourier spectral analysis. When many samples are
available, the wavelet and Fourier methods are comparable in accuracy. However,
when one or only a few samples are available, the wavelet method outperforms
the Fourier method by a large margin.Comment: 10 pages RevTeX, 13 Postscript figures. Some additional material
compared to previous versio
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