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Application of the Fast Fourier Transform to linear systems in civil engineering (1973)

O'Brien, M. A. ; Fitzgerald, J. J. ; Dillon, E. C.

Chichester [u.a.] : Wiley-Blackwell

International Journal for Numerical Methods in Engineering 6 (1973), S. 381-394

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ISSN: 0029-5981

Keywords: Engineering ; Engineering General

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Mathematics , Technology

Notes: The Fast Fourier Transform is employed as a method of Laplace transform inversion to solve problems in the civil engineering fields of visco-elasticity and hydrology. When these problems are accurately represented by a linear time-invariant model, it is shown that the Fast Fourier Transform inversion procedure is often more accurate than standard convolution and inversion techniques. The speed and accuracy of solution resulting from this application of the Fast Fourier Transform is illustrated by referring to case studies solved on an IBM 1130 computer, model 3D processor with 32K memory.

Additional Material: 13 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/nme.1620060309

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Characteristics of Relativistic Microburst Intensity From SAMPEX Observations (2019)

E. Douma, C. J. Rodger, L. W. Blum, T. P. O'Brien, M. A. Clilverd, J. B. Blake

Wiley

In: Journal of Geophysical Research: Space Physics

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Publication Date: 2019

Description: Abstract Relativistic electron microbursts are an important electron loss process from the radiation belts into the atmosphere. These precipitation events have been shown to significantly impact the radiation belt fluxes and atmospheric chemistry. In this study we address a lack of knowledge about the relativistic microburst intensity using measurements of 21,746 microbursts from the Solar Anomalous Magnetospheric Particle Explorer (SAMPEX). We find that the relativistic microburst intensity increases as we move inward in L, with a higher proportion of low‐intensity microbursts (〈2,250 [MeV cm2 sr s]−1) in the 03–11 magnetic local time region. The mean microburst intensity increases by a factor of 1.7 as the geomagnetic activity level increases and the proportion of high‐intensity relativistic microbursts (〉2,250 [MeV cm2 sr s]−1) in the 03–11 magnetic local time region increases as geomagnetic activity increases, consistent with changes in the whistler mode chorus wave activity. Comparisons between relativistic microburst properties and trapped fluxes suggest that the microburst intensities are not limited by the trapped flux present alongside the scattering processes. However, microburst activity appears to correspond to the changing trapped flux; more microbursts occur when the trapped fluxes are enhancing, suggesting that microbursts are linked to processes causing the increased trapped fluxes. Finally, modeling of the impact of a published microburst spectra on a flux tube shows that microbursts are capable of depleting 〈500‐keV electrons within 1 hr and depleting higher‐energy electrons in 1–23 hr.

Print ISSN: 2169-9380

Electronic ISSN: 2169-9402

Topics: Geosciences , Physics