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  • Shape detection in multispectral imagery
    (1989) Ryan, Michael
    Thesis
    An investigation of shape analysis methods is presented for application to remotely sensed images. The Method of Moments, in conjunction with linear pattern classification techniques, is shown to be suitable for the recognition of simple polygonal shapes in the absence of noise and in the presence of additive Gaussian noise with positive signal-to- noise ratios. The appropriate weight vectors for linear separation are presented and a suitable decision process is described for the recognition of desired shapes. The Method of Moments is successfully applied to a region which has been extracted from a real remotely sensed image using various segmentation thresholds. Finally, some recommendations are made for further work.
  • Gas exchange in air-breathing crabs
    (1989) Farrelly, Caroline
    Thesis
  • The use of 238U and 232Th decay series radionuclides in sediment tracing
    (1994) Olley, Jonathan Martin
    Thesis
    A variety of geochemical tracers, including natural radioactivity, can be used to trace the source of sediment. If the source of sediment is to be correctly determined, we need to understand the nature of the material being traced and why the parameter being used to 'fingerprint' the sediment varies. Previous studies using correlations between 238U and 232Th decay series nuclides to trace sediment have been empirically based. This thesis examines the mechanisms which cause variations in the concentrations and ratios of the decay series nuclides in modern sediments, and develops a mechanistic framework for the application of decay series nuclides to tracing sediment. Radionuclide concentrations and ratios have been examined in rocks, and soils from nine sites, the effects of grain abrasion and of sorting soil material by both density and particle-size have been investigated. It is shown that sediments derived from a uniform lithology will have a constant 230Th/232Th ratio, the· same ratio as that in the rock from which they are ultimately derived. The 230Th/232Th ratio can therefore be used to distinguish between sediments derived from different lithologies within a catchment, providing that the lithologies have distinctive 230Th/232Th ratios. In contrast the 226Ra/232Th ratio has been found to be more variable and in many cases significantly different to the U/Th ratio in the rock. This variability was due largely to the presence of a 226Ra excess over 230Th. In certain circumstances it was found that the 226Ra/232Th could be used to distinguish sediments derived from different points in the catchment even if it had a uniform lithology, and hence a uniform 230Th/232Th ratio. In addition concentrations of 228Ra (half-life 5.75years) in excess of 232Th concentration are reported in both soils and sediments and it is suggested that this excess should provide a useful new tool for examining the transport rates and residence times of bedload and suspended load sediments in streams and lakes on time scale of up to30 years. Examples are given of the application of both 226Ra/232Th and 230Th/232Th ratios to sediment sourcing problems, and of the application of the 228Ra/232Th ratio to determining sediment transport rates and residence times.