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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
611

Optical studies of the mesospheric region

Woithe, Jonathan Mark January 2000 (has links)
A three-field photometer has been employed at the University of Adelaide's Buckland Park field site to collect optical observations of the 557.7nm OI and 730nm OH airglow emissions. Data have been collected on an almost continuous basis since May 1995 through to May 2000, with observations made whenever the moon was not up. Techniques and analysis procedures have been developed which allow routine extraction of the parameters of gravity waves observed each night. A cross-spectral analysis was performed on processed data from the photometer to identify short period (less than 3 hours) wave activity on nights where the impact of clouds on the data was minimal. The resulting wave parameters are analysed for seasonal variability and used to build up a climatology of wave parameters over the 5 years of observation. No consistent seasonal variation was observed, although there was a strong eastward perference to the wave's propagation direction. Implications of this finding are discussed. A co-located MF radar has been operating in spaced antenna mode providing wind data concurrent with the optical observations for most of the acquisition period. When available the wind data allowed calculation of the intrinsic parameters for waves identified in the optical data. The seasonal variablility of these parameters was investigated. An evaluation of energy and momentum fluxes estimated using the method of Swenson et al (1998b) was carried out. Approximations made in this method were found to be inappropriate for the waves detected by the photometer, and a refined procedure was therefore developed. This gave more realistic results, although large number of physically unreasonable momentum flux measurements were reported. Possible reasons for these were explored, and the need for further investigations emphasised. The five year dataset also allowed investigation of the long-term behaviour of the airglow. Both the intensity and variance were analysed using the Lomb-Scargle method across the complete dataset to identify the dominant periods present. Following similar treatment, the MF spaced antenna winds were compared with the optical results; this utilised a complex spectrum extension to the basic Lomb algorithm. Seasonally related periodicities of two years, one year, one half of a year and one third of a year were observed in the optical data, along with a possible signature of a five and a half year period potentially linked to the eleven year solar cycle. The radar data did not have stong signatures of the one third of a year periodicity although the presence of an five and a half year periodicity could not be ruled out. Gravity wave activity, as measured by the optical intensity variance, reached a maximum during autumn with a secondary maximum occurring in spring. The annual variability of the wave spectrum detected by the photometer was also studied which showed a falloff in the wave energy at short periods (less than thirty minutes) during autumn and spring. This suggested that the enhanced wave activity at these times consisted mainly of waves with periods greater than thirty minutes. / Thesis (Ph.D.)--Department of Physics and Mathematical Physics, 2000.
612

Radar and optical studies of the atmosphere.

Reid, Iain M. January 2008 (has links)
The research described in this thesis can be categorized into three main areas. The first area concerns the interpretation of observations of various atmospheric processes and phenomena. The focus here has been on internal atmospheric gravity waves and their manifestation in radar winds and in airglow intensities, but also includes investigation of atmospheric tides and planetary scale waves, D-region electron densities and collision frequencies, the aspect sensitivity of backscattering and partially reflecting regions of the atmosphere, Polar Mesosphere Summer Echoes and Mesosphere Summer Echoes, meteor trails, mesospheric temperatures, long period variations in airglow intensities, and Kelvin Helmholtz Instabilities. The second major area has been in the development of new experimental techniques and the validation of existing techniques for investigating the atmosphere. New techniques have included the dual–beam radar technique for measuring momentum fluxes, and radar Time Domain Interferometry and Hybrid Doppler Interferometry for use with multi-receiver channel Doppler radars. The Doppler Beam Steering technique in the presence of non-uniform and periodically varying wind fields has been investigated analytically, and various spaced sensor techniques have been investigated using a numerical model of atmospheric radar backscattering and by direct comparison with other techniques. The Sodium Lidar technique has been investigated through numerical model calculations and a solid state system is currently being developed. Finally, a major activity has been the development of new radars and radar subsystems. This has included the development of a modular Medium Frequency Doppler radar and a Medium Frequency Spaced Antenna radar, a variety of Stratosphere Troposphere / Mesosphere Stratosphere Troposphere radars, an Ionospheric radar, a Boundary Layer Tropospheric radar and an All-Sky meteor radar. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1347218 / Thesis (D.Sc.) - University of Adelaide, School of Chemistry and Physics, 2008
613

Liquid Jet Breakup in Reduced Gravity

Mr Barnaby Osborne Unknown Date (has links)
No description available.
614

Fluctuations of the expansion : the Langevin-Raychaudhuri equation /

Borgman, Jacob. January 2004 (has links)
Thesis (Ph.D.)--Tufts University, 2004. / Adviser: Larry H. Ford. Submitted to the Dept. of Physics. Includes bibliographical references (leaves 117-120). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
615

Finite element modelling of cracking in concrete gravity dams

Cai, Qingbo. January 2007 (has links)
Thesis (PhD(Engineering)(Civil Engineering)) --University of Pretoria, 2007. / Includes bibliographical references.
616

Gravity and aeromagnetic modelling of the Longmenshan Fold-and-Thrust Belt, SW China

Chan, Mei-ki, January 2008 (has links)
Thesis (M. Phil.)--University of Hong Kong, 2008. / Includes bibliographical references (leaf 141-151) Also available in print.
617

High performance vibration isolation techniques for the AIGO gravitational wave detector /

Chin, Eu-Jeen. January 2007 (has links)
Thesis (Ph. D.)--University of Western Australia, 2007.
618

A method for field calibration of a gyroscope in an airborne gravimetry inertial stable platform /

Daoudi, Amina, January 1900 (has links)
Thesis (M. Eng.)--Carleton University, 2001. / Includes bibliographical references p. (115-117). Also available in electronic format on the Internet.
619

The development of a deep-towed gravity meter, and its use in marine geophysical surveys of offshore Southern California and an airborn laser altimeter survey of Long Valley, California /

Ridgway, Jeffrey R., January 1997 (has links)
Thesis (Ph. D.)--University of California, San Diego, 1997. / Vita. Includes bibliographical references.
620

An analytical and numerical study of internal gravity waves forced by isolated topography /

Nikitina, Lidia, January 1900 (has links)
Thesis (M.Sc.) - Carleton University, 2008. / Includes bibliographical references (p. 127-129). Also available in electronic format on the Internet.

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