Includes bibliographical references (p. 239-255).

Zugl.: Erlangen-Nürnberg, Universiẗat, Diss., 2008.

Macroscopic ductility is promoted in bulk metallic glasses by both composite reinforcements (at low temperatures) and by the activation of viscous flow mechanisms (at high temperatures). It is of fundamental interest to understand deformation physics when both of these strategies are employed at the same time. Despite the quickly growing literature around the room-temperature mechanical properties of metallic glass matrix composites (MGMCs), the deformation behavior of MGMCs over a wide range of temperatures and strain rates has yet to be systematically investigated, especially at high temperatures close to Tg. Here the high temperature compressive behavior of Zr-based MGMCs with in-situ reinforcements is explored systematically over a series of strain rates. Additionally, the volume fraction of second-phase reinforcements was tailored to explore its effect on both inhomogeneous and homogeneous deformation modes. / Singapore-MIT Alliance (SMA)

Master of Science / Department of Physics / Christopher M. Sorensen / An easier, cheaper and scalable method to obtain silver nanoparticles, AgNPs, directly from the bulk material has been obtained. Two different solvents were tried, water and ethylene glycol, the coating agent was polyvinylpyrrolidone, PVP, and two different silver sizes were used, micron size powder and silver shots, millimeter size. It was seen that changing the size of bulk silver, the temperature of reaction, the amount of oxygen, the concentration of PVP and its molecular weight all had an important influence in the synthesis of nanoparticles. Different morphologies could be obtained when these parameters were adjusted ranging from spheres to triangles and hexagons. A complex mechanism is proposed: during the first step, bulk silver is oxidized by oxygen in solution, forming a thin layer of oxidized silver on the surface. Then, PVP acts as a reducing agent at the oxidized surface, where silver becomes Ag⁰ again. At the same time that PVP reduces the oxidized silver back to metallic silver; it coordinates with the silver atoms acting as a protecting agent. That coordination between PVP and silver pulls out the atoms and produces a detachment of silver atoms from the bulk surface. These silver-PVP complexes in solution later combine to form silver nanospheres and evolve to rods first and then triangles and hexagon with longer reaction time.

Made available in DSpace on 2014-07-29T16:24:18Z (GMT). No. of bitstreams: 1 Dissertacao Glaucio F O e Silva.pdf: 407953 bytes, checksum: 6fc973eb2803412646e7b58019c28c3c (MD5) Previous issue date: 2007-07-05 / The common bean (Phaseolus vulgaris L.) is part of the daily diet of more than 300 million people worldwide, being an essential food for low income human populations, since it is a cheaper protein source. The beans protein content can be improved by breeding programs since the existence of genetic variability for this character can be explored. It is important to have the relative efficiency of the available methods evaluated. The objective of this research was to evaluate the genetic potential for protein content of segregant populations of common beans submitted to different breeding methods and evaluate the potential of the populations of the bulk method inside F2 families for the traits yield and flowering. The parental utilized in this study was from the bean group carioca , CNFC 7812 with 23% of total protein content and CNFC 8056 with 23% of total protein content. Starting with the F1 generation, was obtained the segregant population F2, witch were selected 150 plants wich families was utilized to produce the populations by three methods: Bulk, Bulk within of F2 and SSD method until the F5 generation. The average protein content of the families obtained by this cross was 16,58% for the method SSD, 20,37% for the method Bulk e 20,44% for the Bulk F2:5. Based on the results, it could be concluded that the best method for protein content was the Bulk method, on account of its easiness and its generation of a larger number of families superior than the best parental and the average of the genitors. Among the evaluated families there is enough genetic variability to be explored for the characters protein, grain yield and flowering. / O feijão (Phaseolus vulgaris L.) participa da dieta de mais de 300 milhões de pessoas no mundo, sendo alimento essencial para populações carentes, pois é fonte barata de proteína. O teor de proteína total de feijão pode ser melhorado com o auxílio de programas de melhoramento, já que existe variabilidade genética a ser explorada para esse caráter. É importante que seja avaliada a eficiência relativa dos métodos disponíveis de condução de populações segregantes. O objetivo desse trabalho foi avaliar o potencial genético de populações segregantes de feijoeiro comum para teor de proteína total, conduzidas por diferentes métodos de melhoramento e avaliar o potencial das populações do método de bulk dentro de F2 para os caracteres produtividade de grãos e florescimento. Os genitores utilizados para gerar estas populações foram do grupo de feijão carioca, CNFC 7812 com 16% de proteína total e CNFC 8056 com 23% de proteína total. A partir da geração F1 obteve-se a população segregante F2, da qual foram separadas 150 plantas cujas sementes foram utilizadas para conduzir as populações por três métodos: Bulk, Bulk dentro de F2 e método de uma única semente (SSD) até a geração F5. Foram realizadas avaliações de qualidade nutricional do grão para teor de proteína em todas as famílias provenientes dos três métodos de condução de populações na geração F5. O teor médio de proteína das famílias obtidas deste cruzamento ficou em 16,58% para o método SSD, 20,37% para o método Bulk e 20,44% para o Bulk F2:5. Dos resultados obtidos pode-se concluir que para o caráter proteína, o método mais indicado foi o método Bulk, pela sua praticidade e por ter gerado mais famílias superiores ao melhor genitor e à média dos genitores. Entre as famílias avaliadas observou-se que existe variabilidade genética suficiente para ser explorada para os caracteres teor de proteína total, produtividade de grãos e florescimento.

M.Ing. (Engineering Management) / In a tender bid to energy and chemical company Sasol, a request to offer a technical solution for a two-flight overland conveyor system whose function is to transport coal from a 15 000 tonne bunker into an external stockpile storage facility in the plant was made. This conveyor consisted of two conveyor flight sections of lengths 18 423m and 8 537m each. The prospect of combining the two flights of conveyors to form one, super-efficient conveyor structure with additional cost saving benefits was identified. It was found that this occurrence was not unique to the individual project as other researching engineers have been faced with similar problems before [18]. This then lead the researcher into believing that there could be some advantage in investigating the possible benefits to the overall cost, maintainability and scheduling of the fabrication and erection activities for the entire project of combining the multiple flight conveyors into a single-flight conveyor. It is also the conviction of the researcher that the achieved outcomes will prove beneficial to the bulk materials handling industry as a whole. The problem is traditionally short, multiple flight conveyors have always been used for performing the function of transporting bulk material from one location in a mining plant to another hence; long, single-flight overland conveyors of lengths exceeding 26 km have not been commonly installed. In this dissertation the possibility of employing a single-flight overland as opposed to a two-flight conveyor in the Sasol Impumelelo coal plant is investigated. This is done against the work of other researchers who have conducted similar studies in the field as well as by utilizing project-specific data using applicable industry standards as well as Engineering Management course theory. By employing actual project procurement and engineering design data; the investigation is done by calculating and comparing the individual capital and operational costs that encompass the total cost of ownership (TCO) for both conveyor systems as well as the two systems’ reliability, availability and maintainability to establish each system’s complete life cycle costs. It is the opinion of the researcher that the investigation method is valid as it is in line with the guidelines given by The Miami University of Ohio [24] as well as J Hanek [25] and thus provides the researcher with a plausible technique for establishing which between the single-flight overland conveyor and two-flight overland conveyor configurations is overall the more superior system to install. It was found that even though its initial capital and operational costs are higher; the single-flight conveyor system is more reliable, readily available and cheaper to run and sustain over the 30 year expected life-span of the plant. It also is less labour intensive to perform maintenance on, yields less material degradation and results in less material spillage because of the elimination of additional transfer points and transfer towers. These results can be taken as valid on a global scale, for any mining plant, not restricted to any specific material as they are not subject to South African temperature, altitude or seismic conditions nor are they constrained to the type of bulk material being mined.

Large populations of controlled hybrids are essential to the most rapid progress in many phases of plant breeding programs. Plant species vary in the ease with which they may be hybridized. Hand hybridization of forage grasses is usually slow and laborious, and the minuteness of the floral parts of most of the species which have perfect flowers renders their hybridization by hand especially difficult and tedious. This difficulty limits the use that forage grass breeders are making of the significant principles of hybridization and thereby retards progress in this phase of plant breeding. Any dependable, rapid technique of hybridization which would eliminate many of the present hand operations, that is "bulk" hybridization, would make possible more rapid progress in the breeding of forage grasses. The study herein reported was designed to estimate the feasibility of applying various methods of bulk emasculation and bulk pollination to forage grasses. In limiting the scope of the study, smooth bromegrass (Bromus inermis) was selected to receive the greatest attention because of its importance among forage grasses and the wide range of self-fertility among individual plants of the species, a characteristic which proved very helpful in the study.

This paper investigates the Baltic Dry Index; an often misunderstood index, which tracks the cost of shipping dry bulk cargo globally. The research is based on the hypothesis that movements in the Baltic Dry Index price are driven largely by changes in the underlying demand for goods which are consumed globally. Accordingly, this paper aims to investigate whether changes in the Baltic Dry Index price may be used to predict future economic movements in a South African context. In this regard, the paper first conducts a thorough synthesis of the available literature, in order to formulate the conclusion that the Baltic Dry Index price is driven by a multitude of variables, including the global demand for goods, the global supply of ships, the laycan period, bunker prices, global piracy, global winter severity, as well as the inclusion of a cyclical component. The global demand for goods is concluded to be chief among these. Based on these findings, the paper then conducts empirical testing on the usefulness of the BDI in a South African context, and concludes that the Baltic Dry Index is useful when used as a leading economic indicator in South African, especially when used in order to predict long-term economic movements, across a period of 3 – 4.5 years. Finally, strong evidence is found to support the existence of a relationship between the BDI and the Johannesburg Stock Exchange Mining Index, although further investigation is required in order to form a definitive conclusion in this regard.

Room temperature elastic properties of thin supported TiC films, deposited on silicon and silicon carbide substrates and of single Rh-based alloy crystals, Rh3Nb and Rh3Zr, are investigated by the Surface Brillouin Scattering (SBS) technique. Velocity dispersion curves of surface acoustic waves in TiC films of various thicknesses, deposited on each substrate (Si and SiC) were obtained from SBS spectra. Simulations of SBS spectra of TiC thin hard films on germanium, silicon, diamond and silicon substrates have been carried out over a range of film thickness from 5 nm to 700 nm. The simulations are based on the elastodynamic Green's functions method that predicts the surface displacement amplitudes of acoustic phonons. These simulations provide information essential for analysis of experimental data emerging from SBS experiments. There are striking differences in both the simulated and experimental SBS spectra depending on the respective elastic properties of the film and the substrate. In fast on slow systems (e.g. TiC on silicon), the Rayleigh mode is accompanied by both broad and sharp resonances; in slow on fast systems (e.g TiC on SiC), several orders of Sezawa modes are observed together with the Rayleigh mode. The velocity dispersion of the modes has been obtained experimentally for both situations, allowing the elastic constants of the films to be determined. Effects of two deposition conditions, RF power and substrate bias, on the properties of the films are also considered. Platinum metal group alloys are promising candidates for future ultra high temperatures gas turbines materials due to their excellent high-temperature properties. In the present work, room temperature elastic properties of single crystals of Rh3Nb and Rh3Zr are investigated. SBS spectra for a range of wave vector directions from the (001) surface have been acquired in order to determine the angular variation of the surface acoustic wave velocities and the longitudinal wave threshold within the Lamb shoulder. The elastic stiffnesses of the specimens were determined using two approaches; one approach involves a least-square fit of the experimental data to calculated results and the other is an analytical approach which involves the 2 c minimization of secular equations for the Rayleigh surface acoustic wave and the longitudinal wave threshold velocities in the [100] and [110] directions on the (001) surface of a cubic crystal. Results from the two methods were in good agreement.

Peat is an accumulation of soil formed from partially decomposed organic matter. Peat can burn, especially in hot, dry weather which is happening more often due to climate change; smouldering releases stored carbon to the atmosphere. Peat that has higher organic bulk density and lower moisture content is more vulnerable to fire: it will burn more severely (more deeply) if ignited. Shallower peat is less able to retain moisture during droughts and is therefore likely more vulnerable to fire; however, mapping peat depths at high spatial resolution is expensive or requires extensive fieldwork. This project uses remote sensing in combination with machine learning to estimate peat depth across a peatland and rock barren landscape. A Random Forest model was used to map peat depths across the landscape at a 1 m spatial resolution using LiDAR data and orthophotography. The resulting map was able to predict peat depths (R2 = 0.73, MAE = 28 cm) and showed that the peat depths which are especially vulnerable to high severity fire are distributed in numerous small patches across the landscape. This project also examined peat bulk density and found that the Von Post scale for peat decomposition can be used as a field method for estimating bulk density (R2 = 0.71). In addition, in this landscape, peat bulk densities at the same depth (within the top 45 cm) are higher in shallower peat because in shallower peat, more decomposed peat was found closer to the surface, and because peat with high mineral content was found close to the bedrock or mineral soil. The findings of this project will be valuable for wildfire managers to determine which areas on the landscape are most vulnerable to fire, allowing them to mobilize resources more rapidly for wildfire suppression. / Thesis / Master of Science (MSc) / Peat is organic soil made from decomposing plant material. Peat can burn, especially in the hot, dry weather which is happening more often due to climate change. Dense, dry peat is more vulnerable to fire: it will burn more deeply. Because it is known that areas with deeper peat can retain moisture better, peat depth can be used as a proxy for vulnerability to fire. Since peat depth is expensive and time consuming to map directly, remotely sensed data such as aerial imagery was used in a model to predict peat depths. The model was able to predict peat depths and displayed that the most vulnerable areas are scattered across the landscape in small patches. This project also found that denser peat is found farther from the surface in deeper peat areas, further supporting the use of peat depth as a proxy for vulnerability to smouldering.