A proper methodological approach of investigating Holocene sea level changes is a prerequisite in order that the sea-level index points can be useful and significant. This requires the correct identification of the indicative meaning. The indicative meaning of the sea level indicator is defined as the altitudinal relationship of the local environment in which it accumulated to the contemporaneous reference tide level. This study identifies the index points using the litho-, bio-, and chrono-stratigraphic approach. The sea level indicator is derived from the regressive contact of the intercalated peat and marine clastic sequence, while the indicative meaning is estimated based upon the relationship with the contemporary samples. The study was carried out at two contrasting coastal locations, the fossil sites from Meru and Mardi in Kelang in the west and Penur (north and south transects) in Kuantan in the east, while the contemporary sites are from various ecological environments from both areas. Microfossil analysis of pollen and diatoms indicates that the former are more applicable, and defined the changing microfossil assemblages within the regressive contact of the sea level indicator samples. Seven sea level index points are identified. The finding agrees to the general assumptions of high mid-Holocene sea level history in peninsular Malaysia. A relative sea level difference between the west and east coast is indicated, but the significance, if any, is dealt with caution. The explanations of presumed differential crustal movement or sheer age/altitude variability of the index points are suggested.

Thesis (Ph. D.)--University of Canterbury, 2007. / Typescript (photocopy). Includes bibliographical references (p. 185-196). Also available via the World Wide Web.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 172-182). Available also in a digital version from Dissertation Abstracts.

In Iceland, glaciers cover approximately 11% of the land surface and comprise the country's largest reservoir of freshwater. Increases in summer temperatures since the mid-1980s have led to rapid mass loss from the Icelandic ice caps of 9.5-11.4 Gt/yr, and continuously operating GPS stations nationwide have recorded rapid and accelerating surface uplift. Understanding the behavior of Icelandic ice caps-and their relationship to surface uplift, which is modulated by the rheological structure of the crust and upper mantle-has important implications for water resource management and geohazards analysis. The goals of this study are twofold. First, we aim improve the current estimates of glacial isostatic adjustment (GIA)-related uplift in Iceland and to examine if and how uplift rates have changed over the last several decades. Secondly, we explore the utility of motion recorded by continuously operating Global Positioning System stations (cGPS) as an independent measure of ice cap mass variation over both decadal and annual time scales. We take advantage of the now longstanding cGPS network in Iceland and consider position time series from 62 stations across the entire island. Observations made by cGPS stations from 1995-2014.7 show a broad region of rapid uplift in central Iceland with near zero uplift observed along the coastal regions to the north and west. The most rapid uplift and uplift accelerations occur near the center of the island, between the Vatnajökull and Hofsjökull ice caps, with rates exceeding 30 mm/yr and accelerations of 1-2 mm/yr². Statistically significant uplift and uplift accelerations are recorded at 27 of the 62 cGPS stations, and estimates for the timing of uplift initiation correlate with Arctic warming trends and observations of increasing summer temperatures since the mid-1980s. These results represent a significant improvement over previous uplift estimates and indicate a likely relationship between accelerated ice cap melting and contemporaneous changes in uplift rates. Incorporating cGPS-recorded information about modern-day uplift rates affects estimates of mantle viscosity. Ice cap thinning rates are computed by a weighted least squares estimation scheme utilizing cGPS-derived secular uplift rates and accelerations and Green's functions for an elastic layer over a Maxwell viscoelastic half-space. We test a range of viscosities from 8 x 10¹⁷ and 1 x 10²⁰ Pa·s and find that thinning rates computed with low viscosities between 2 x 10¹⁸ and 1 x 10¹⁹ Pa·s match independently derived ice cap thinning rates best, in accordance with previous upper mantle viscosity estimates. Similar estimation techniques demonstrate the utility of cGPS to provide a seasonal mass variation time series as a potential low-cost compliment to traditional field-based mass balance measurements. We use estimates of secular site velocity and acceleration to reduce the time series and focus only on the annual periodic motion. The increased temporal resolution afforded by the daily cGPS position estimates recovers the interannual variability in the timing and magnitude of accumulation and melt seasons with a small RMS reduction relative to a sinusoidal model. We also find we are able to identify of the effects of both ice cap insulation as well as reduced surface albedo following volcanic eruptions.

A dissertation submitted to the faculty of Engineering, University of the Witwatersrand, Johanuesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. / Ferritic stainless steels possess a number of properties which render them superior to austenitic stainless steels in certain applications. The ferritic stainless steels are highly resistant to stress-corrosion cracking and are generally of lower cost. Previous work had shown that the corrosion properties of the ferritic steels were optimised at a chromium content of forty percent. Extensive research had already characterised the mechanical and corrosion behaviour of the Fe"40Cr alloy in the cast and wrought form. This investigation involves the development of the material by powder metallurgy processing. Particular emphasis is placed on a proprietary powder production technique as well as on powder consolidation by Hot Isostatic Pressing. The effect of Ni, Mo, Ru, Nb, Al and Fe additions and well as various techniques of introducing these additions are examined. The unique effect of powder metallurgy manufacture on microstructure and the kinetics of sigma phase formation is highlighted. Corrosion tests in various concentrations of sulphuric acid and an industrial field trial were performed. It was found that combined Ni and Mo contents exceeding four percent resulted in severe embrittlement due to widespread formation of sigma phase during the HIP process. The use of powder metallurgy techniques was also found to enhance the kinetics of sigma phase formation in a particular alley when compared to the as-cast state. Direct additions of Fe powder were successful in inhibiting embrittlement, possibly due to a mechanism of Fe diffusion into Cr-rich regions. This lowered of the Cr content in these regions, thereby reducing the tendency for sigma precipitation. Corrosion tests indicate satisfactory resistance for the Fc-40Cr-2Ni-2Mo alloys in 70 weight percent sulphuric acid at 50°C. Alloys with 0.2 percent Ru additions were found to be especially resistant, due to the role of Ru as a cathodic modifier. The method of mixing and diffusion bonding metallic powders of varying composition was found to be feasible and certain novel combinations of Ni and Fe-rich alloys exhibited satisfactory corrosion resistance. A mathematical diffusion model was found to provide an order of magnitude approximation of the time required for hornogentsation in a certain mixture of powders. / Andrew Chakane 2018

abstract: The rigidity of a material is the property that enables it to preserve its structure when deformed. In a rigid body, no internal motion is possible since the degrees of freedom of the system are limited to translations and rotations only. In the macroscopic scale, the rigidity and response of a material to external load can be studied using continuum elasticity theory. But when it comes to the microscopic scale, a simple yet powerful approach is to model the structure of the material and its interparticle interactions as a ball$-$and$-$spring network. This model allows a full description of rigidity in terms of the vibrational modes and the balance between degrees of freedom and constraints in the system. In the present work, we aim to establish a microscopic description of rigidity in \emph{disordered} networks. The studied networks can be designed to have a specific number of degrees of freedom and/or elastic properties. We first look into the rigidity transition in three types of networks including randomly diluted triangular networks, stress diluted triangular networks and jammed networks. It appears that the rigidity and linear response of these three types of systems are significantly different. In particular, jammed networks display higher levels of self-organization and a non-zero bulk modulus near the transition point. This is a unique set of properties that have not been observed in any other types of disordered networks. We incorporate these properties into a new definition of jamming that requires a network to hold one extra constraint in excess of isostaticity and have a finite non-zero bulk modulus. We then follow this definition by using a tuning by pruning algorithm to build spring networks that have both these properties and show that they behave exactly like jammed networks. We finally step into designing new disordered materials with desired elastic properties and show how disordered auxetic materials with a fully convex geometry can be produced. / Dissertation/Thesis / Doctoral Dissertation Physics 2018

No description available.

Graduation date: 1999

No description available.

In northern Canada, the glacial isostatic adjustment (GIA) response of the Earth to the former Pleistocene Laurentide and Innuitian ice sheets contributes significantly to the Earth's past and ongoing sea-level change and land deformation. In this dissertation, measurements of Holocene sea-level change and observations of GPS-measured vertical crustal uplift rates are employed as constraints in numerical GIA models that examine the thickness and volume history of the former ice sheets in northern North America. The study is divided into two main sections; the first provides new measurements of Holocene sea-level change collected west of Hudson Bay, while the second presents a GIA modelling analysis for the entire study area of northern Canada. Radiocarbon dating of post-glacial deposits collected in an area just west of central Hudson Bay provides several new constraints on regional Holocene sea-level change. The field collection area is near a former load centre of the Laurentide Ice Sheet (LIS), and the sea-level measurements suggest that following deglaciation, regional sea level fell rapidly from a high-stand of nearly 170 m elevation just after 8000 cal yr BP to 60 m elevation by 5200 cal yr BP. Sea level subsequently fell at a decreased rate (approximately 30 m since 3000 cal yr BP). The fit of GIA model predictions to relative sea-level (RSL) data and present-day GPS-measured vertical land motion rates from throughout the study area constrains the peak thickness of the LIS to be 3.4-3.6 km west of Hudson Bay, and up to 4 km east of Hudson Bay. The ice model thicknesses inferred for these two regions represent, respectively, a 30% decrease and an average 20-25% increase to the load thickness relative to the ICE-5G reconstruction (Peltier 2004), generally consistent with other studies focussing on space geodetic measurements of vertical crustal motion. Around Baffin Island, the fit of GIA model predictions to RSL data indicate peak regional ice thicknesses of 1.2-1.3 km, a modest reduction compared to ICE-5G. A new reconstruction of the Innuitian Ice Sheet (IIS), which covered the Queen Elizabeth Islands at LGM, incorporates the current glacial-geological constraints on its spatial extent and timing history. The new IIS reconstruction provides RSL predictions that are more consistent with regional observations of post-glacial sea-level change than ICE-5G. The results suggest that the peak thickness of the IIS was 1600 m, approximately 400 m thicker than the minimum peak thickness indicated by glacial geology studies, but between 1000-1500 m thinner than the peak thicknesses used in previous regional ice sheet reconstructions. On Baffin Island and in the Queen Elizabeth Islands, however, the modelled elastic crustal response of the Earth to present-day ice mass changes is large. Accounting for this effect improves the agreement between GPS measurements of vertical crustal motion and the GIA model predictions. However, improvements such as the inclusion of spatially non-uniform mass loss and a sensitivity analysis that examines uncertainties of this effect should be incorporated into the modelling of present-day changes to glaciers and ice caps. / Graduate