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Full-Text Articles in Physical Sciences and Mathematics
Fragmentation And Wake Formation In Faint Meteors: Implications For The Structure And Ablation Of Small Meteoroids, Edward Stokan
Fragmentation And Wake Formation In Faint Meteors: Implications For The Structure And Ablation Of Small Meteoroids, Edward Stokan
Electronic Thesis and Dissertation Repository
Meteors with peak magnitudes fainter than +2 are typically called faint meteors, resulting from the atmospheric entry and ablation of meteoroids less massive than 10-4 kg. The processes of luminous wake formation and fragmentation, which occur during ablation, are poorly understood for faint meteors, and are important constraints for models of meteoroid structure. The goal of this work is to improve understanding of these processes through analysis of high-resolution intensified video observations, and creation of a detailed meteoroid ablation model.
In the first part of this work, thirty faint meteors observed with the Canadian Automated Meteor Observatory (CAMO) are …
Gravity Wave Spectra Morphology In The Arctic And Non-Arctic Lower Atmosphere, Melanie C. Wright
Gravity Wave Spectra Morphology In The Arctic And Non-Arctic Lower Atmosphere, Melanie C. Wright
Electronic Thesis and Dissertation Repository
The spectral analysis of data from three VHF radars (one high-Arctic and two mid-latitudes) show support for the universal spectrum theory for gravity waves in the lower atmosphere (altitudes of 2.0-11.0 km), provided that the impact of the off-vertical beam and noise are taken into consideration. This analysis also reveals that local gravity wave generation is of secondary importance, but still significant for determining the spectra.
A total of eight spectral methods were considered and scrutinized for the purposes of determining gravity wave spectra from VHF radar data. A definition for the “best” method was given and examined. The method …
Advances In Image Acquisition And Filtering For Mri Neuroimaging At 7 Tesla, Andrew T. Curtis
Advances In Image Acquisition And Filtering For Mri Neuroimaging At 7 Tesla, Andrew T. Curtis
Electronic Thesis and Dissertation Repository
Performing magnetic resonance imaging at high magnetic field strength promises many improvements over low fields that are of direct benefit in functional neuroimaging. This includes the possibility of improved signal-to-noise levels, and increased BOLD functional contrast and spatial specificity. However, human MRI at 7T and above suffers from unique engineering challenges that limit the achievable gains. In this thesis, three technological developments are introduced, all of which address separate issues associated with functional magnetic resonance neuroimaging at very high magnetic field strengths.
First, the image homogeneity problem is addressed by investigating methods of RF shimming — modifying the excitation portion …