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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.
331

An Ocean Surface Wind Vector Model Function For A Spaceborne Microwave Radiometer And Its Application

Soisuvarn, Seubson 01 January 2006 (has links)
Ocean surface wind vectors over the ocean present vital information for scientists and forecasters in their attempt to understand the Earth's global weather and climate. As the demand for global wind velocity information has increased, the number of satellite missions that carry wind-measuring sensors has also increased; however, there are still not sufficient numbers of instruments in orbit today to fulfill the need for operational meteorological and scientific wind vector data. Over the last three decades operational measurements of global ocean wind speeds have been obtained from passive microwave radiometers. Also, vector ocean surface wind data were primarily obtained from several scatterometry missions that have flown since the early 1990's. However, other than SeaSat-A in 1978, there has not been combined active and passive wind measurements on the same satellite until the launch of the second Advanced Earth Observing Satellite (ADEOS-II) in 2002. This mission has provided a unique data set of coincident measurements between the SeaWinds scatterometer and the Advanced Microwave Scanning Radiometer (AMSR). AMSR observes the vertical and horizontal brightness temperature (TB) at six frequency bands between 6.9 GHz and 89.0 GHz. Although these measurements contain some wind direction information, the overlying atmospheric influence can easily obscure this signal and make wind direction retrieval from passive microwave measurements very difficult. However, at radiometer frequencies between 10 and 37 GHz, a certain linear combination of vertical and horizontal brightness temperatures causes the atmospheric dependence to be nearly cancelled and surface parameters such as wind speed, wind direction and sea surface temperature to dominate the resulting signal. This brightness temperature combination may be expressed as ATBV-TBH, where A is a constant to be determined and the TBV and TBH are the brightness temperatures for the vertical and horizontal polarization respectively. In this dissertation, an empirical relationship between the AMSR's ATBV-TBH and SeaWinds' surface wind vector retrievals was established for three microwave frequencies: 10, 18 and 37 GHz. This newly developed model function for a passive microwave radiometer could provide the basis for wind vector retrievals either separately or in combination with scatterometer measurements.
332

Walking through time: a window onto the prehistory of the Yorkshire Dales through multi-method, non-standard survey approaches

Saunders, Mary K. January 2017 (has links)
Walking through time: a window onto the prehistory of the Yorkshire Dales through multi-method, non-standard survey approaches Keywords: Yorkshire Dales, prehistory, veneration, natural places, geophysical survey, walkover survey, field-system, clearance, land tenure The large-scale field-systems, ubiquitous across upland and marginal parts of the Yorkshire Dales, are insecurely dated and poorly understood. Apart from some sporadic academic interest, the archaeology of this region has yet to receive the level of scholarly attention it deserves. The research presented here involved an intensive investigation of an area near Grassington, Upper Wharfedale, UK. Detailed field analysis revealed a section of one of these field-systems to be only a single element in a complex, multi-layered prehistoric landscape, which it is proposed may have roots as far back as the early Neolithic. Contextualisation of the survey area against palynological data, radiocarbon dates and comparative material moves the date of inception of the field-systems back to the middle Bronze Age, some 1000 years earlier than is currently assumed. The combination of empirical data and theoretical ideas has allowed a relative chronology to be determined in the survey area, together with the creation of a testable hypothesis surrounding the development of Upper Wharfedale and the wider Yorkshire Dales through prehistory. A sense of place and the veneration of natural places are key themes within this landscape and it was possible through these to draw out elements of prehistoric society and to show the evolution of ideas such as land tenure and monument significance. This dual empirical-theoretical approach is novel in upland landscape archaeology in the UK and is shown here to have significant merit. / Arts and Humanities Research Council (AHRC) collaborative doctoral award / The data and photo files are not available online.
333

Cation Diffusion in Periclase

Crispin, Katherine L. 30 June 2011 (has links)
No description available.
334

Analysis of Upper Mantle Reflections Beneath the Trans-Uralian and East-Uralian Zones of the Ural Mountains, Russia

Anderson, Michael D. January 2014 (has links)
No description available.
335

Exploration of the potential for hydrologic monitoring via passive microwave remote sensing with a new footprint-based algorithm

Li, Dongyue 22 July 2011 (has links)
No description available.
336

New constraints on timing and kinematics of rifting at Cape Roberts Basin and Roberts Ridge from integrated seismic and core analysis of fault arrays

Trunkely, Zachary J. 06 January 2012 (has links)
No description available.
337

High-resolution lake-based magnetic mapping and modelling of basement structures, with examples from Küçükçekmece Lagoon, Turkey and Charity Shoal, Lake Ontario

Suttak, Philip A. 10 1900 (has links)
<p>Magnetic surveys are one of the principal geophysical methods employed to map the structure of basement rocks deeply buried below cover strata. In resource studies, aeromagnetic surveys are commonly acquired at regional scales (100-1000’s km2) while very few studies have attempted to resolve basement structures at site-scale (<10 >km2). In this study, high-resolution lake-based magnetic survey methods were evaluated for mapping of deeply-buried basement faults (Küçükçekmece Lagoon, Turkey; 6 km2) and a suspected meteorite impact crater (Charity Shoal, Lake Ontario; 9 km2). Total magnetic intensity (TMI) surveys were acquired using a single Overhauser magnetometer with 50-150 m line spacing. Interpretation of the magnetic data was aided by forward modelling of TMI data and depth to basement estimates using Euler and analytic signal methods. Total magnetic intensity (TMI) maps of Küçükçekmece Lagoon identify several north-northwest trending (340-350°) magnetic lineaments that are aligned with strike-slip faults mapped from offshore seismic data. The pattern of magnetic anomalies in the lagoon is consistent with extensional normal faulting of bedrock and lake sediments. Magnetic results from Charity Shoal reveal a large (>1400 nT) parabolic-shaped magnetic anomaly centered over the crater basin and an annular magnetic high (40-50 nT) corresponding with the basin rim. Modelling results exclude the origin of the CSS as a shallow glacial erosional or karst sinkhole feature and are most consistent with a pre-Paleozoic meteorite impact in the Precambrian basement.</p> / Master of Science (MSc)
338

Novel Application of Nondestructive Testing to Evaluate Anomalous Conditions in Drilled Shafts and the Geologic Materials Underlying Their Excavations

Kordjazi, Alireza January 2019 (has links)
Drilled shafts are deep foundation elements created by excavating cylindrical shafts into the ground and filling them with concrete. Given the types of structures they support, failure to meet their performance criteria can jeopardize public safety and cause severe financial losses. Consequently, quality control measures are warranted to ensure these foundations meet design specifications, particularly with respect to their structural integrity and geotechnical capacity. Due to their inaccessibility, non-destructive testing (NDT) techniques have received much attention for drilled shaft quality control. However, there are limitations in the NDT tools currently used for structural integrity testing. Moreover, there is no current NDT tool to evaluate conditions underlying drilled shaft excavations and aid in verifying geotechnical capacity. The main objective of this research is to examine the development of new NDT methodologies to address some of the limitations in the inspection of drilled shaft structural integrity and geotechnical conditions underlying their excavations. The use of stress waves in large laboratory models is first examined to evaluate the performance of ray-based techniques for detecting anomalies. The study then continues to investigate the improvements offered by using a full waveform inversion (FWI) approach to analyze the stress wave data. A hybrid, multi-scale FWI workflow is recommended to increase the chance of the convergence of the inversion algorithms. Additionally, the benefits of a multi-parameter FWI are discussed. Since FWI is computationally expensive, a sequential optimal experimental design (SOED) analysis is proposed to determine the optimal hardware configurations for each application. The resulting benefit-cost curves from this analysis allow for designing an NDT survey that matches the available resources for the project. / Civil Engineering
339

Assessment of the CMD Mini-Explorer, a New Low-frequency Multi-coil Electromagnetic Device, for Archaeological Investigations

Bonsall, James P.T., Fry, Robert J., Gaffney, Christopher F., Armit, Ian, Beck, A., Gaffney, Vincent January 2013 (has links)
No / In this article we assess the abilities of a new electromagnetic (EM) system, the CMD Mini-Explorer, for prospecting of archaeological features in Ireland and the UK. The Mini-Explorer is an EM probe which is primarily aimed at the environmental/geological prospecting market for the detection of pipes and geology. It has long been evident from the use of other EM devices that such an instrument might be suitable for shallow soil studies and applicable for archaeological prospecting. Of particular interest for the archaeological surveyor is the fact that the Mini-Explorer simultaneously obtains both quadrature (conductivity') and in-phase (relative to magnetic susceptibility') data from three depth levels. As the maximum depth range is probably about 1.5m, a comprehensive analysis of the subsoil within that range is possible. As with all EM devices the measurements require no contact with the ground, thereby negating the problem of high contact resistance that often besets earth resistance data during dry spells. The use of the CMD Mini-Explorer at a number of sites has demonstrated that it has the potential to detect a range of archaeological features and produces high-quality data that are comparable in quality to those obtained from standard earth resistance and magnetometer techniques. In theory the ability to measure two phenomena at three depths suggests that this type of instrument could reduce the number of poor outcomes that are the result of single measurement surveys. The high success rate reported here in the identification of buried archaeology using a multi-depth device that responds to the two most commonly mapped geophysical phenomena has implications for evaluation style surveys. Copyright (c) 2013 John Wiley & Sons, Ltd.
340

The thermal shallow water equations, their quasi-geostrophic limit, and equatorial super-rotation in Jovian atmospheres

Warneford, Emma S. January 2014 (has links)
Observations of Jupiter show a super-rotating (prograde) equatorial jet that has persisted for decades. Shallow water simulations run in the Jovian parameter regime reproduce the mixture of robust vortices and alternating zonal jets observed on Jupiter, but the equatorial jet is invariably sub-rotating (retrograde). Recent work has obtained super-rotating equatorial jets by extending the standard shallow water equations to relax the height field towards its mean value. This Newtonian cooling-like term is intended to model radiative cooling to space, but its addition breaks key conservation properties for mass and momentum. In this thesis the radiatively damped thermal shallow water equations are proposed as an alternative model for Jovian atmospheres. They extend standard shallow water theory by permitting horizontal variations of the thermodynamic properties of the fluid. The additional temperature equation allows a Newtonian cooling term to be included while conserving mass and momentum. Simulations reproduce equatorial jets in the correct directions for both Jupiter and Neptune (which sub-rotates). Quasi-geostrophic theory filters out rapidly moving inertia-gravity waves. A local quasi-geostrophic theory of the radiatively damped thermal shallow water equations is derived, and then extended to cover whole planets. Simulations of this global thermal quasi-geostrophic theory show the same transition, from sub- to super-rotating equatorial jets, seen in simulations of the original thermal shallow water model as the radiative time scale is decreased. Thus the mechanism responsible for setting the direction of the equatorial jet must exist within quasi-geostrophic theory. Such a mechanism is developed by calculating the competing effects of Newtonian cooling and Rayleigh friction upon the zonal mean zonal acceleration induced by equatorially trapped Rossby waves. These waves transport no momentum in the absence of dissipation. Dissipation by Newtonian cooling creates an eastward zonal mean zonal acceleration, consistent with the formation of super-rotating equatorial jets in simulations, while the corresponding acceleration is westward for dissipation by Rayleigh friction.

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