Browsing by Author "Meincken, Martina"

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    Characteristics of selected non-woody invasive alien plants in South Africa and an evaluation of their potential for electricity generation
    (University of Cape Town, Energy Research Centre, 2017) Melane, Mandlakazi; Ham, Cori; Meincken, Martina
    ENGLISH ABSTRACT: Alien invasive plants (AIPs) pose a threat to the existence of plant and animal biodiversity in the ecosystems they invade. They need to be cleared, monitored and eventually eradicated from the landscape. The potential and the economic viability to supply non-woody AIP biomass for electricity generation were assessed in this study, which was conducted on samples from 13 common non-woody AIPs in South Africa, namely: Arundo donax (giant reed), Lantana camara (lantana), Pontederia cordata (pickerel weed), Ricinus communis (castor-oil plant), Opuntia ficus-indica (sweet prickly pear), Solanum mauritianum (bugweed), Atriplex nummularia (saltbush), Cestrum laevigatum (inkberry), Senna didymobotrya (peanut butter cassia), Chromoleana odorata (chromoleana), Eichhornia crassipes (water hyacinth), Cerus jamacaru (queen of the night) and Agave sisilana (sisal plant). Proximate and ultimate analysis was made in order to assess the suitability of the biomass for different thermo-chemical conversion techniques for electricity generation. A financial evaluation of the costs to supply biomass to the plant gate was performed by combining the harvesting, chipping and transport costs. The results showed that the biomass of giant reed, lantana, bugweed, saltbush, inkberry, cassia and Chromoleana may be used to generate electricity through combustion, although the total average cost was approximately 50% higher than that of woody biomass feedstock, requiring a ‘fuel cost subsidy’ to justify their utilisation for energy production.
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    Film formation and thermal transitions of polymers studied by atomic force microscopy
    (Stellenbosch : Stellenbosch University, 2002-03) Meincken, Martina; Sanderson, R. D.; Stellenbosch University. Faculty of Science. Dept. of Chemistry & Polymer Science.
    ENGLISH ABSTRACT: The kinetics of drying and film formation of different polymeric latices were studied. Various theoretical models predict a strong dependency of the film formation characteristics on the particle size and morphology. This could be confirmed by experimental studies. The influence of particle size and morphology of differently structured latices on the film formation process was investigated by Atomic Force Microscopy (AFM) and Ultrasonic shear wave reflection. These two methods allow a comprehensive characterization of the drying and film formation process of emulsions. The studies confirmed the theoretical model, that the film formation behavior is influenced by the particle size and particle morphology. Furthermore the influence of different additives, such as coalescent solvents and rheology modifiers on the film formation behavior was investigated. As a second part of the studies, a novel technique was developed to measure thermal transitions of polymers with the AFM in the non-contact mode, using it as a Dynamic Mechanical Analyzer (DMA) on a local scale. The resonance frequency of the AFM cantilever was measured as a function of the temperature and thermal transitions of a polymer were clearly visible as changes in the resonance frequency / temperature response curve. Using the AFM in this mode allows the determination of the thermal properties of a material at a specific position on a sample, thereof on a macromolecular scale. A simple model was developed to explain the response of the cantilever caused by the transitions in the polymer and the related form of the frequency/temperature curves. This new technique adds a new dimension to standard thermal analysis techniques. It is now possible to resolve the individual thermal transitions of different polymer phases, for example in structured multiphase polymers.
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    Powering Africa
    (Academy of Science of South Africa, 2012-01-26) Meincken, Martina
    ENGLISH ABSTRACT: Africa, as a developing continent, is in a position to learn from the mistakes of the developed world. In terms of energy production, instead of trying to meet its requirements with fossil fuels alone, it should aim to implement renewable energy strategies wherever possible in the course of extending supply to its people. In terms of connectivity, the situation differs from the developed world in that a large proportion of the population (typically outside urban centres) is not connected to the electricity grid. This proportion varies from about 10% connectivity in Uganda to nearly 100% in Mauritius. In South Africa, about 35% of the population are not connected to the main grid, and these are mostly people living in remote rural areas.