The Antarctic Ice Sheets responded significantly to climatic conditions during the Last Glacial Maximum (LGM) and the subsequent warming that followed. Therefore, an understanding of how Antarctica reacted to past climates is necessary to predict the response of its ice sheets to current and future climate change. This thesis presents new evidence about the timing and magnitude of East and West Antarctic ice sheet (EAIS & WAIS) changes during the Quaternary Period, from the Darwin Hatherton glacial system (DHGS, 79.5S, 158E). The DHGS drains the EAIS through the Transantarctic Mountains into the Ross Ice Shelf and glacial deposits have been used to constrain ice sheet thicknesses in this sector of the Ross Sea Embayment. At four sites along the length of the system, glacial deposits were mapped and 73 erratic and bedrock samples collected for ¹⁰Be and ²⁶Al surface exposure dating (SED). The exposure ages range from 0.01 to 2.2 Ma and generally show a trend of oldest ages at the highest elevations, thus suggesting an overall decrease of ice volume within the DHGS over the Quaternary. The older ages suggest that during the Plio-Pleistocene, DHGS ice was at least 800-1000 metres thicker than present, while in the mid to late-Holocene thickening was less than 50-80 metres. Four glacial advance and retreat events were described and mapped previously from the DHGS by Bockheim et al (1989). The Isca and Danum drifts, are ~1-2 and 0.6 Ma respectively. The Britannia-II Drift, previously assumed to mark the maximum extent of the Last Glacial Maximum advance is more complex, with clusters of ages at ~6.5, ~36 and ~125 ka. The youngest drift, the Hatherton is mid to late-Holocene (<4.5 ka) and suggests that the DHGS has been near its equilibrium position during this period. Throughout the DHGS no unequivocal evidence of the LGM was observed and therefore poses questions about the past thickness of the Antarctic ice sheets during the LGM. Exposure ages from sites near the head of the Hatherton Glacier (Dubris Valley & Lake Wellman) suggest that at the LGM, the East Antarctic Ice Sheet may have been of similar size, or slightly smaller, than present. In stark contrast, at the confluence of the Darwin Glacier and the Ross Ice Shelf, a WAIS ~400-900 metres above the modern ice surface is tentatively suggested; A value in agreement with that proposed by modern glaciological models. Additionally, while the results from the Dubris and Bibra valleys show that the EAIS thins during glacial climates (i.e. the LGM), it also suggests thickening during interglacials. The Britannia-I and II drifts representing retreats at~6.5 and ~125 ka from glacial highstands. A number of key findings related to the application of SED in Antarctic settings are also presented. The use of dual-nuclides (¹⁰Be & ²⁶Al) show that within the DHGS, the proportion of samples displaying a prior burial history increases with distance from the catchment. The spread of exposure ages observed in the dataset also show the complexity of the depositional processes occurring at cold-based glacial margins and therefore judicious sample selection is required to obtain exposure ages that are representative of the true deglaciation age.

The continental margin in the area west of Shetland was subjected to repeated and extensive ice sheet advances during the Late Pleistocene. Seabed imagery, seismic survey and borehole core data show the Late Devensian ice sheets expanded across the continental shelf three times, two of these advances reaching the shelf edge. On the inner shelf, where present-day water depths are generally less than 100m, only thin sediments from the last retreat phase and exposed rock surfaces remain, all other deposits from earlier phases having been removed by the last advance. On the mid to outer shelf elements of all three phases are preserved, including lodgement and deformation tills, melt-out and water-lain till sheets, in-filled hollows left by stagnant ice decaying in situ and a series of large recessional and terminal moraines. In addition, there is evidence of shallow troughs and overdeepend basins which indicate preferential ice-drainage pathways across the shelf which were formerly occupied by ice streams. At the shelf edge, a thick wedge of glacigenic sediment forms a transition from the till sheets and moraines of the shelf to debris flows composed of glacigenic sediments on the upper slope. Shelf-edge moraines show an architecture indicating floating ice in modern water depths over approximately 180m, suggesting the West Shetland ice sheet was no more than about 250m thick. The upper and middle slope is dominated by glacigenic debris flows which are focused in the slope areas below the proposed ice stream discharges at the shelf edge. The mid-to-lower slope has been subjected to contour current activity which has re-worked much of the glacigenic sediment in this position. The lower slope and floor of the Faroe-Shetland Channel are marked by either large debris flow lobes of glacigenic sediment or thin glacimarine muds deposited from suspension. A conceptual model of the glacigenic development of a passive continental margin based upon the West Shetland example shows the deposited sequence for both advance and retreat phases of a glacial cycle, and the actual preserved sequence which might be expected in the rock record. The model also shows that ice sheet buoyancy, thickness, and to a lesser extent, basin subsidence, are the most important factors in the deposition and preservation of a glacially-influenced marine sequence.

A proper understanding of the effects of turbulence on the diffusion and drift of cosmic-rays in the heliosphere is imperative for a better understanding of cosmic-ray modulation. This study presents an ab initio model for cosmic-ray modulation, incorporating for the first time the results yielded by a two-component turbulence transport model. The latter model is solved for solar minimum heliospheric conditions, utilizing boundary values chosen in such a way that the results of this model are in fair to good agreement with spacecraft observations of turbulence quantities, not only in the ecliptic plane, but also along the out-of-ecliptic trajectory of the Ulysses spacecraft. These results are employed as inputs for modelled slab and 2D turbulence energy spectra, which in turn are used as inputs for parallel mean free paths based on those derived from quasi-linear theory, and perpendicularmean free paths from extended nonlinear guiding center theory. The modelled 2D spectrum is chosen based on physical considerations, with a drop-off at the very lowest wavenumbers commencing at the 2D outerscale. There currently exist no models or observations for this quantity, and it is the only free parameter in this study. The use of such a spectrum yields a non-divergent 2D ultrascale, which is used as an input for the reduction terms proposed to model the effects of turbulence on cosmic-ray drifts. The resulting diffusion and drift coefficients are applied to the study of galactic cosmic-ray protons, electrons, antiprotons, and positrons using a three-dimensional, steady-state numerical cosmic-ray modulation code. The magnitude and spatial dependence of the 2D outerscale is demonstrated to have a significant effect on computed cosmic-ray intensities. A form for the 2D outerscale was found that resulted in computed cosmic-ray intensities, for all species considered, in reasonable agreement with multiple spacecraft observations. Computed galactic electron intensities are shown to be particularly sensitive to choices of parameters pertaining to the dissipation range of the slab turbulence spectrum, and certain models for the onset wavenumber of the dissipation range could be eliminated in this study. / Thesis (PhD (Physics))--North-West University, Potchefstroom Campus, 2013

A proper understanding of the effects of turbulence on the diffusion and drift of cosmic-rays in the heliosphere is imperative for a better understanding of cosmic-ray modulation. This study presents an ab initio model for cosmic-ray modulation, incorporating for the first time the results yielded by a two-component turbulence transport model. The latter model is solved for solar minimum heliospheric conditions, utilizing boundary values chosen in such a way that the results of this model are in fair to good agreement with spacecraft observations of turbulence quantities, not only in the ecliptic plane, but also along the out-of-ecliptic trajectory of the Ulysses spacecraft. These results are employed as inputs for modelled slab and 2D turbulence energy spectra, which in turn are used as inputs for parallel mean free paths based on those derived from quasi-linear theory, and perpendicularmean free paths from extended nonlinear guiding center theory. The modelled 2D spectrum is chosen based on physical considerations, with a drop-off at the very lowest wavenumbers commencing at the 2D outerscale. There currently exist no models or observations for this quantity, and it is the only free parameter in this study. The use of such a spectrum yields a non-divergent 2D ultrascale, which is used as an input for the reduction terms proposed to model the effects of turbulence on cosmic-ray drifts. The resulting diffusion and drift coefficients are applied to the study of galactic cosmic-ray protons, electrons, antiprotons, and positrons using a three-dimensional, steady-state numerical cosmic-ray modulation code. The magnitude and spatial dependence of the 2D outerscale is demonstrated to have a significant effect on computed cosmic-ray intensities. A form for the 2D outerscale was found that resulted in computed cosmic-ray intensities, for all species considered, in reasonable agreement with multiple spacecraft observations. Computed galactic electron intensities are shown to be particularly sensitive to choices of parameters pertaining to the dissipation range of the slab turbulence spectrum, and certain models for the onset wavenumber of the dissipation range could be eliminated in this study. / Thesis (PhD (Physics))--North-West University, Potchefstroom Campus, 2013

Incremental sheet forming process is a relatively new method of forming which is increasingly being used in the industry. Complex shapes can be manufactured using this method and the forming operation doesn't require any dies. High strains of over 300 % can also be achieved. Incremental sheet forming method is used to manufacture many different components presently. Prototype examples include car headlights, tubs, train body panels and medical products. The work done in the thesis deals with the prediction of the steady state forces acting on the tool during forming. Prediction of forces generated would help to design the machine against excessive vibrations. It would help the user to protect the tool and the material blank from failure. An efficient design ensures that the tool would not get deflected out of its path while forming, improving the accuracy of the finished part. To study the forces, experiments were conducted by forming pyramid and cone shapes. An experimental arrangement was set up and experimental data was collected using a data acquisition system. The effect that the various process parameters, like the thickness of the sheet, wall angle of the part and tool diameter had on the steady state force were studied. A three dimensional model was developed using commercial finite element software ABAQUS using a new modeling technique to simulate the deformation of the sheet metal blank during incremental sheet forming. The steady state forces generated for any shape, with any set of parameters used, could be predicted using the numerical model. The advantage of having a numerical model is that the forces can be predicted without doing experiments. The model was used to predict the steady state forces developed during forming of pyramid and cone shapes. The results were compared and were seen to be reasonably close to the experimental results. Later, the numerical model was validated by forming arbitrary shapes and comparing the value obtained from simulations to the value of the measured steady state forces. The results obtained from the numerical model were seen to match very well with the experimental forces for the new shapes. The numerical model developed using the new technique was seen to predict forces to a reasonable extent with less computational time as compared to the models currently available.

The general trend in the car body manufacturing industry is towards low-series production and reduction of press lubricants and car weight. The limited use of lubricants, in combination with the introduction of high and ultrahigh-strength sheet materials, continuously increases the demands on the forming tools. The major cause for tool failure during the forming process is transfer and accumulation of sheet material on the tool surfaces, generally referred to as galling. The adhered material creates unstable frictional conditions and scratching of the tool/sheet interface. To provide the means of forming new generations of sheet materials, development of new tool materialswith improved galling resistance is required, which may include tailored microstructures introducing specific carbides and nitrides, coatings and improved surface finish. In the present work, the galling wear mechanisms in real forming operations have been studied and emulated at a laboratory scale by developing a test equipment. The wear mechanisms, identified in the real forming process, were distinguished into a sequence of events. At the initial stage, local adhesive wear of the sheets led to transfer of sheet material to the tool surfaces. Successive forming operations resulted in growth of the transfer layer with initiation of scratching of the sheets. Finally, scratching changed into severe adhesive wear, associated withgross macroscopic damage. The wear process was successfully repeated in the laboratory test equipment in sliding between several tool materials, ranging from cast iron and conventional ingot cast tool steels, to advanced powder metallurgy tool steel, sliding against medium and high-strength steel sheets. By use of the test equipment, selected tool materials were ranked regarding galling resistance. The controlling mechanism for galling in sheet metal forming is adhesion. The initial sheet material transfer was found to occur, preferably, to the metallic matrix of the tool steels. Hence, the carbides in the particular steels appeared less prone to adhesion as compared to the metallic matrix. Therefore, an improved galling resistance was observed for a tool steel comprising a high amount of small homogeneously distributed carbides offering a low-strength interface to the transferred sheet material.Further, atomic force microscopy showed that nanoscale adhesion was influenced by temperature, with increasing adhesion as temperature increases. A similar dependence was observed at the macroscale where increasing surface temperature led to initiation of severe adhesive wear. The results were in good agreement to the nano scale observations and temperature-induced high adhesion was suggested as a possible mechanism.

Glaciers and ice sheets covered extensive areas in the Northern Hemisphere during the last glacial period. Subsequently to the Last Glacial Maximum (LGM), they retreated rapidly and, except for Greenland and some other ice caps and glaciers, they vanished after the last glacial termination. This thesis examines the dynamics of deglacial environments by analysing the glacial geomorphological record with focus on the landforms created by glacial meltwater. The aims are (i) to evaluate the data available for mapping glacial meltwater features at the regional scale, and (ii) to demonstrate the potential of such features for regional ice retreat reconstructions in high-relief landscapes. Meltwater landforms such as ice-marginal meltwater channels, eskers, deltas and fossil glacial lake shorelines are used to infer former ice surface slope directions and successive positions of retreating ice margins. Evaluated high-resolution satellite imagery and digital elevation models reveal their potential to replace aerial photographs as the primary data for mapping glacial meltwater landforms. Following a methods study, reconstructions of the deglacial dynamics are carried out for central Transbaikalia, Siberia, Russia, and for the Cordilleran Ice Sheet (CIS) in central British Columbia, Canada, using regional geomorphological mapping surveys. Mapped glacial landforms in central Transbaikalia show evidence of a significant glaciation that possibly extended beyond the high mountain areas. Large glacial lakes were formed as advancing glaciers blocked rivers, and of these, Glacial Lake Vitim was the most prominent. Deglacial dynamics of the CIS reveals that the ice divide shifted to the Coast Mountains in north-central British Columbia and the eastern ice margin retreated towards the ice divide in late glacial time. This thesis demonstrates the potential to reconstruct ice retreat patterns and deglacial dynamics at regional scales by interpretation of the meltwater landform record. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Submitted. Paper 6: Manuscript.

The deformed Permian Dun Mountain Ophiolite Belt (DMOB) forms the basement of the Dun Mountain-Maitai terrane and is traceable through the entire length of New Zealand. The DMOB contains a variably serpentinised mantle portion and a crustal portion containing gabbros, dolerites, cross cutting dikes and extrusives, together they are similar to oceanic crust. The initial crustal portion, however, is atypical when compared to other ophiolites, being thin and lacking a sheeted dike complex, but has well spaced inclined intrusive sheets and sills. At least four post-Permian deformation periods affect the DMOB; collision and rotation during emplacement of the DMOB on the Gondwana margin, compression during Mesozoic orogenies, extensional deformation during the Gondwana break-up and transpressive deformation related to the modern plate boundary through New Zealand. Structural work in the Northern Bryneira Range focused on well preserved outcrops to investigate crustal growth and contemporaneous deformation during the Permian. Structural evidence of Permian deformation was determined by examination of pseudostratigraphy, structures constrainable to the Permian, and the geometric relationships with the overlying Maitai sedimentary sequence. Crosscutting by intrusive phases was used to determine a chronological order of crustal growth and deformation episodes. It was concluded that all deformation was extensional and that two major phases of magmatism were separated by a period of deformation and were followed by ongoing syn-sedimentary deformation during the deposition of the Maitai Group. After removal of Mesozoic rotation, the resulting orientations of paleo-horizontal markers and diverse orientations of intrusive sheets were analysed. Two hypothesises were tested to assess the origin of inclined intrusive sheets: a) that the diverse orientations were the result of tectonic rotation coeval with the intrusion of dikes. b) that primary orientations of the sheets had been diverse. Results show that the sheets were intruded with diverse orientations, probably related to variation in the principle horizontal stress over time. Further rotation of the assemblage of sheets occurred during the last stages of magmatism and during the subsequent period of sedimentation. The last stage probably relates to large scale normal faulting during the development of the sedimentary basin. iii

Thesis (PhD) - Swinburne University of Technology, Faculty of Engineering and Industrial Sciences, 2005. / Thesis submitted to Swinburne University of Technology, for the degree of Doctor of Philosophy, 2005. Typescript. Bibliography p. 144-149.

Thesis (M.S.)--Ohio University, June, 2004. / Title from PDF t.p. Includes bibliographical references (leaves 78-80).