The further development, optimisation and application of a Yarn Dismantler
- Authors: Fassihi, Ali Akbar
- Date: 2012
- Subjects: Textile industry , Cotton yarn industry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10452 , http://hdl.handle.net/10948/d1016066
- Description: The fibre properties of cotton, which vary widely according to genetic and environmental conditions, determine its price and textile processing performance and product quality. It is therefore hardly surprising that cotton fibre properties are routinely measured for trading and quality control purposes, with a great deal of research having been, and still being, devoted towards developing instruments which enable the various fibre properties to be measured rapidly and accurately. In many cases, it is also necessary to be able to measure properties of cotton fibres when they have already been converted into yarn and fabric form. To do so, the yarn has to be dismantled into its component fibres, preferably without significantly changing the fibre properties. This could only be done by manually untwisting the yarn and carefully extracting the fibres from the untwisted yarn, care being taken not to break or lose any fibres in the process. This is a time consuming, laborious and labour intensive process. In view of this, a „yarn dismantler‟ which could automatically, cost effectively and within acceptable time frames, dismantle a cotton yarn into its constituent fibres, without undue damage or changes to the fibres, was developed and patented. This thesis reports the results of research undertaken to further develop, evaluate and optimize the yarn dismantler into the final prototype, as well as those relating to its practical applications, including tracking changes in fibre properties during miniature and pilot scale processing, up to, and including the yarn stage. Initial research undertaken on the original bench and first prototype models indicated that, although they produced very promising results, certain improvements and modifications were necessary, if the dismantler was to perform in an efficient and operator friendly manner at the required speeds. These included changes in the axial position of the untwisting spindle and the perforated screen of the suction drum, increasing the air suction at the perforated drum, installing a new motor for the untwisting spindle drive, separating the drives to the different parts of the unit in order to control them independently, integrating a more effective steaming unit into the unit etc. It was found that the dismantling rate had to be set to equal about 95 percent of the original twist in the yarn, and that steaming of the dismantled (untwisted) yarn on the perforated drum was necessary in order to eliminate any twist liveliness (residual torque) in the dismantled yarn, and enable it to be handled and tested on the AFIS instrument. When the final prototype Yarn Dismantler was produced, incorporating all the above mentioned improvements, it functioned very well at dismantling speeds of at least 2m/min, enabling the length of yarn required for subsequent AFIS testing to be dismantled within an acceptable time of less than 10 minutes, with excellent reproducibility and repeatability of results, also under commercial conditions. It was found that the AFIS measured length characteristics of fibres from the instrument dismantled yarns compared very well with those of fibres from manually dismantled yarns, differences in fibre length generally being less than 1mm, and it was concluded from these and other evaluation tests, that the yarn dismantler produced fibres without any significant fibre breakage. Some limited tests, carried out on commercially produced carded and combed yarns, indicated that short fibre content and dust and trash levels, as measured by the AFIS on fibres from dismantled yarn, together with the corresponding Uster Statistics, could enable a carded cotton yarn to be distinguished from a combed cotton yarn. Statistical analysis of fibre test results obtained at the different stages during miniature and pilot plant scale processing of various cottons, clearly showed that very significant changes in fibre properties could be caused by certain of the processes. For example, significant fibre breakage occurred during the drafting on the spinning frame, prior to twist insertion. The thesis provides detailed results of changes in various fibre properties, including length, short fibre content, maturity, immature fibre content, seed coat neps and fibrous neps, which occurred from the lint to the final yarn, as well as on the relationship between the properties of the fibres from the dismantled yarn and those from the lint. The results obtained have clearly demonstrated the practical value of the yarn dismantler in enabling yarns to be automatically dismantled into their constituent fibres, which can then be tested by an instrument, such as the AFIS, and the test results related to those of the original lint fibres, thereby opening up many fields of research and practical applications, some of which are captured under „Recommended Further Work‟.
- Full Text:
- Date Issued: 2012
- Authors: Fassihi, Ali Akbar
- Date: 2012
- Subjects: Textile industry , Cotton yarn industry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10452 , http://hdl.handle.net/10948/d1016066
- Description: The fibre properties of cotton, which vary widely according to genetic and environmental conditions, determine its price and textile processing performance and product quality. It is therefore hardly surprising that cotton fibre properties are routinely measured for trading and quality control purposes, with a great deal of research having been, and still being, devoted towards developing instruments which enable the various fibre properties to be measured rapidly and accurately. In many cases, it is also necessary to be able to measure properties of cotton fibres when they have already been converted into yarn and fabric form. To do so, the yarn has to be dismantled into its component fibres, preferably without significantly changing the fibre properties. This could only be done by manually untwisting the yarn and carefully extracting the fibres from the untwisted yarn, care being taken not to break or lose any fibres in the process. This is a time consuming, laborious and labour intensive process. In view of this, a „yarn dismantler‟ which could automatically, cost effectively and within acceptable time frames, dismantle a cotton yarn into its constituent fibres, without undue damage or changes to the fibres, was developed and patented. This thesis reports the results of research undertaken to further develop, evaluate and optimize the yarn dismantler into the final prototype, as well as those relating to its practical applications, including tracking changes in fibre properties during miniature and pilot scale processing, up to, and including the yarn stage. Initial research undertaken on the original bench and first prototype models indicated that, although they produced very promising results, certain improvements and modifications were necessary, if the dismantler was to perform in an efficient and operator friendly manner at the required speeds. These included changes in the axial position of the untwisting spindle and the perforated screen of the suction drum, increasing the air suction at the perforated drum, installing a new motor for the untwisting spindle drive, separating the drives to the different parts of the unit in order to control them independently, integrating a more effective steaming unit into the unit etc. It was found that the dismantling rate had to be set to equal about 95 percent of the original twist in the yarn, and that steaming of the dismantled (untwisted) yarn on the perforated drum was necessary in order to eliminate any twist liveliness (residual torque) in the dismantled yarn, and enable it to be handled and tested on the AFIS instrument. When the final prototype Yarn Dismantler was produced, incorporating all the above mentioned improvements, it functioned very well at dismantling speeds of at least 2m/min, enabling the length of yarn required for subsequent AFIS testing to be dismantled within an acceptable time of less than 10 minutes, with excellent reproducibility and repeatability of results, also under commercial conditions. It was found that the AFIS measured length characteristics of fibres from the instrument dismantled yarns compared very well with those of fibres from manually dismantled yarns, differences in fibre length generally being less than 1mm, and it was concluded from these and other evaluation tests, that the yarn dismantler produced fibres without any significant fibre breakage. Some limited tests, carried out on commercially produced carded and combed yarns, indicated that short fibre content and dust and trash levels, as measured by the AFIS on fibres from dismantled yarn, together with the corresponding Uster Statistics, could enable a carded cotton yarn to be distinguished from a combed cotton yarn. Statistical analysis of fibre test results obtained at the different stages during miniature and pilot plant scale processing of various cottons, clearly showed that very significant changes in fibre properties could be caused by certain of the processes. For example, significant fibre breakage occurred during the drafting on the spinning frame, prior to twist insertion. The thesis provides detailed results of changes in various fibre properties, including length, short fibre content, maturity, immature fibre content, seed coat neps and fibrous neps, which occurred from the lint to the final yarn, as well as on the relationship between the properties of the fibres from the dismantled yarn and those from the lint. The results obtained have clearly demonstrated the practical value of the yarn dismantler in enabling yarns to be automatically dismantled into their constituent fibres, which can then be tested by an instrument, such as the AFIS, and the test results related to those of the original lint fibres, thereby opening up many fields of research and practical applications, some of which are captured under „Recommended Further Work‟.
- Full Text:
- Date Issued: 2012
Growth and characterization of ZnO nanorods using chemical bath deposition
- Authors: Urgessa, Zelalem Nigussa
- Date: 2012
- Subjects: Zinc oxide , Photoluminescence , Semiconductor nanocrystals , Semiconductors -- Materials , Chemical reactions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10559 , http://hdl.handle.net/10948/d1021124 , http://hdl.handle.net/10948/d1021119
- Description: Semiconductor devices are commonplace in every household. One application of semiconductors in particular, namely solid state lighting technology, is destined for a bright future. To this end, ZnO nanostructures have gained substantial interest in the research community, in part because of its requisite large direct band gap. Furthermore, the stability of the exciton (binding energy 60 meV) in this material, can lead to lasing action based on exciton recombination and possibly exciton interaction, even above room temperature. Therefore, it is very important to realize controllable growth of ZnO nanostructures and investigate their properties. The main motivation for this thesis is not only to successfully realize the controllable growth of ZnO nanorods, but also to investigate the structure, optical and electrical properties in detail by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy (steady state and time resolved) and X-ray diffraction (XRD). Furthermore, strong rectification in the ZnO/p-Si heterojunction is demonstrated. Nanorods have been successfully synthesized on silicon by a two-step process, involving the pre-coating of the substrate by a seed layer, followed by the chemical bath deposition of the nanorods. ZnO seed layers with particle sizes of about 5 nm are achieved by the thermal decomposition of zinc acetate dihydrate dissolved in ethanol. The effects of the seed layer density on the distribution, alignment and uniformity of subsequently grown nanorods were studied. The aspect ratio, orientation and distribution of nanorods are shown to be well controlled through adjusting the density of the ZnO nanoparticles pre-coated onto the substrates. It is shown that the seed layer is a prerequisite for the growth of well aligned ZnO nanorods on lattice mismatched Si substrate. The influence of various nanorod growth parameters on the morphology, optical and electrical properties of the nanorods were also systematically studied. These include the oxygen to zinc molar ratio, the pH of the growth solution, the concentration of the reactants, the growth temperature and growth time, different hydroxide precursors and the addition of surface passivating agents to the growth solution. By controlling these xii parameters different architectures of nanostructures, like spherical particles, well aligned nanorods, nanoflowers and thin films of different thicknesses are demonstrated. A possible growth mechanism for ZnO nanostructures in solution is proposed. XRD indicated that all the as-grown nanostructures produced above 45 C crystallize in the wurtzite structure and post growth annealing does not significantly enhance the crystalline quality of the material. In material grown at lower temperature, traces of zinc hydroxide were observed. The optical quality of the nanostructures was investigated using both steady-state PL and time-resolved (TR) PL from 4 K to room temperature. In the case of as-grown samples, both UV and defect related emissions have been observed for all nanostructures. The effect of post-growth annealing on the optical quality of the nanostructures was carefully examined. The effect of annealing in different atmospheres was also investigated. Regardless of the annealing environment annealing at a temperature as low as 300 C enhances the UV emission and suppresses defect related deep level emission. However, annealing above 500 C is required to out-diffuse hydrogen, the presence of which is deduced from the I4 line in the low temperature PL spectra of ZnO. TRPL was utilized to investigate lifetime decay profiles of nanorods upon different post growth treatments. The bound exciton lifetime strongly depends on the post-growth annealing temperature: the PL decay time is much faster for as grown rods, confirming the domination of surface assisted recombination. In general, the PL analysis showed that the PL of nanorods have the same characteristics as that of bulk ZnO, except for the stronger contribution from surface related bound excitons in the former case. Surface adsorbed impurities causing depletion and band bending in the near surface region is implied from both time resolved and steady state PL. Finally, although strong rectification in the ZnO/p-Si heterojunction is illustrated, no electroluminescence has been achieved. This is explained in terms of the band offset between ZnO and Si and interfacial states. Different schemes are proposed to improve the performance of ZnO/Si heterojunction light emitting devices.
- Full Text:
- Date Issued: 2012
- Authors: Urgessa, Zelalem Nigussa
- Date: 2012
- Subjects: Zinc oxide , Photoluminescence , Semiconductor nanocrystals , Semiconductors -- Materials , Chemical reactions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10559 , http://hdl.handle.net/10948/d1021124 , http://hdl.handle.net/10948/d1021119
- Description: Semiconductor devices are commonplace in every household. One application of semiconductors in particular, namely solid state lighting technology, is destined for a bright future. To this end, ZnO nanostructures have gained substantial interest in the research community, in part because of its requisite large direct band gap. Furthermore, the stability of the exciton (binding energy 60 meV) in this material, can lead to lasing action based on exciton recombination and possibly exciton interaction, even above room temperature. Therefore, it is very important to realize controllable growth of ZnO nanostructures and investigate their properties. The main motivation for this thesis is not only to successfully realize the controllable growth of ZnO nanorods, but also to investigate the structure, optical and electrical properties in detail by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy (steady state and time resolved) and X-ray diffraction (XRD). Furthermore, strong rectification in the ZnO/p-Si heterojunction is demonstrated. Nanorods have been successfully synthesized on silicon by a two-step process, involving the pre-coating of the substrate by a seed layer, followed by the chemical bath deposition of the nanorods. ZnO seed layers with particle sizes of about 5 nm are achieved by the thermal decomposition of zinc acetate dihydrate dissolved in ethanol. The effects of the seed layer density on the distribution, alignment and uniformity of subsequently grown nanorods were studied. The aspect ratio, orientation and distribution of nanorods are shown to be well controlled through adjusting the density of the ZnO nanoparticles pre-coated onto the substrates. It is shown that the seed layer is a prerequisite for the growth of well aligned ZnO nanorods on lattice mismatched Si substrate. The influence of various nanorod growth parameters on the morphology, optical and electrical properties of the nanorods were also systematically studied. These include the oxygen to zinc molar ratio, the pH of the growth solution, the concentration of the reactants, the growth temperature and growth time, different hydroxide precursors and the addition of surface passivating agents to the growth solution. By controlling these xii parameters different architectures of nanostructures, like spherical particles, well aligned nanorods, nanoflowers and thin films of different thicknesses are demonstrated. A possible growth mechanism for ZnO nanostructures in solution is proposed. XRD indicated that all the as-grown nanostructures produced above 45 C crystallize in the wurtzite structure and post growth annealing does not significantly enhance the crystalline quality of the material. In material grown at lower temperature, traces of zinc hydroxide were observed. The optical quality of the nanostructures was investigated using both steady-state PL and time-resolved (TR) PL from 4 K to room temperature. In the case of as-grown samples, both UV and defect related emissions have been observed for all nanostructures. The effect of post-growth annealing on the optical quality of the nanostructures was carefully examined. The effect of annealing in different atmospheres was also investigated. Regardless of the annealing environment annealing at a temperature as low as 300 C enhances the UV emission and suppresses defect related deep level emission. However, annealing above 500 C is required to out-diffuse hydrogen, the presence of which is deduced from the I4 line in the low temperature PL spectra of ZnO. TRPL was utilized to investigate lifetime decay profiles of nanorods upon different post growth treatments. The bound exciton lifetime strongly depends on the post-growth annealing temperature: the PL decay time is much faster for as grown rods, confirming the domination of surface assisted recombination. In general, the PL analysis showed that the PL of nanorods have the same characteristics as that of bulk ZnO, except for the stronger contribution from surface related bound excitons in the former case. Surface adsorbed impurities causing depletion and band bending in the near surface region is implied from both time resolved and steady state PL. Finally, although strong rectification in the ZnO/p-Si heterojunction is illustrated, no electroluminescence has been achieved. This is explained in terms of the band offset between ZnO and Si and interfacial states. Different schemes are proposed to improve the performance of ZnO/Si heterojunction light emitting devices.
- Full Text:
- Date Issued: 2012
An investigation into the impact of fairtrade in South Africa
- Authors: Jari, Bridget
- Date: 2012
- Subjects: Competition, Unfair -- Research -- South Africa Price maintenance -- Research -- South Africa Fair trade associations -- South Africa Sustainable development -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1006 , http://hdl.handle.net/10962/d1002741
- Description: World international trade is moving towards more free trade, through globalization and trade liberalization. These moves are guided by trade theories which state that on an aggregated level, nations involved in free trade should benefit, and further that free trade is fair. However, in practice, contradictory views have been raised, stating that free trade may not necessarily be benefiting all participants equally. Rather, other nations, especially developing nations, have become worse-off after opening up their markets for free trade. On the other hand, many developed nations have benefited substantially from free trade. Among other factors, the difference in benefits is believed to have been influenced by the types of commodities being traded (where developing nations mainly trade in primary goods and developed nations in anufactured goods) and unequal power relations (some nations for example, the EU and the US, still adopt protectionism in their agricultural sector). In order to address market imbalances resulting from free trade, Fairtrade has arisen. Fairtrade aims to improve international trading conditions in order to benefit small-scale farmers and farm workers in the developing nations. The Fairtrade organization further claims that its principles are in line with sustainable development. However, Fairtrade suffers a credibility gap because there is a lack of independent research to support their claims. To date in South Africa, there is little research examining the claims of the Fairtrade organization. In order to contribute to the Fairtrade discussion in South Africa, this study has investigated the validity of Fairtrade‘s claims that it contributes towards sustainable development. The study utilised primary data, which was collected from ten commercial farms and two small-scale farmer cooperatives located in the Eastern Cape and Western Cape provinces that are/were Fairtrade certified. The main reason for including commercial farmers and small-scale farmer cooperatives in the study was for comparing relative impacts in the two Fairtrade structures. The data was then analysed using a sustainable livelihoods framework, which was developed in the study. The study focussed on investigating the impact of Fairtrade tools, which are minimum prices, premiums, pre-financing and support for long-term relationships, on its intended beneficiaries. Minimum prices offered to producers cover production costs and are above market prices, and Fairtrade premiums are to be invested in developmental projects. Therefore, examining the influence of Fairtrade tools on individuals and communities provides an overview of how Fairtrade influences development. The results of the study show that sampled Fairtrade beneficiaries in South Africa have witnessed substantial positive changes as a result of Fairtrade. The Fairtrade initiative has managed to empower small-scale producers and farm workers, as well as leverage development opportunities for their wider communities. It has supported organizational development in the supply chain, facilitated investment in community development projects and in business-related training. Producers, both commercial and small-scale producers, managed to access a market that offers stable prices, and have gained from minimum prices. Furthermore, small-scale farmers have been allowed an opportunity to expand their business into export markets, and enjoyed an increase in incomes. Fairtrade benefits further trickle down to non-Fairtrade community members, in the form of employment creation and community development. Despite positive effects, Fairtrade producers faced challenges, including high Fairtrade administration costs and a small market for Fairtrade commodities. The study concludes that in the face of challenges, Fairtrade brings economic, social and environmental benefits, but as compared to economic and social development, the impact on environmental development is rather limited. Even though that is the case, Fairtrade offers valuable development opportunities to producers in South Africa.
- Full Text:
- Date Issued: 2012
- Authors: Jari, Bridget
- Date: 2012
- Subjects: Competition, Unfair -- Research -- South Africa Price maintenance -- Research -- South Africa Fair trade associations -- South Africa Sustainable development -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1006 , http://hdl.handle.net/10962/d1002741
- Description: World international trade is moving towards more free trade, through globalization and trade liberalization. These moves are guided by trade theories which state that on an aggregated level, nations involved in free trade should benefit, and further that free trade is fair. However, in practice, contradictory views have been raised, stating that free trade may not necessarily be benefiting all participants equally. Rather, other nations, especially developing nations, have become worse-off after opening up their markets for free trade. On the other hand, many developed nations have benefited substantially from free trade. Among other factors, the difference in benefits is believed to have been influenced by the types of commodities being traded (where developing nations mainly trade in primary goods and developed nations in anufactured goods) and unequal power relations (some nations for example, the EU and the US, still adopt protectionism in their agricultural sector). In order to address market imbalances resulting from free trade, Fairtrade has arisen. Fairtrade aims to improve international trading conditions in order to benefit small-scale farmers and farm workers in the developing nations. The Fairtrade organization further claims that its principles are in line with sustainable development. However, Fairtrade suffers a credibility gap because there is a lack of independent research to support their claims. To date in South Africa, there is little research examining the claims of the Fairtrade organization. In order to contribute to the Fairtrade discussion in South Africa, this study has investigated the validity of Fairtrade‘s claims that it contributes towards sustainable development. The study utilised primary data, which was collected from ten commercial farms and two small-scale farmer cooperatives located in the Eastern Cape and Western Cape provinces that are/were Fairtrade certified. The main reason for including commercial farmers and small-scale farmer cooperatives in the study was for comparing relative impacts in the two Fairtrade structures. The data was then analysed using a sustainable livelihoods framework, which was developed in the study. The study focussed on investigating the impact of Fairtrade tools, which are minimum prices, premiums, pre-financing and support for long-term relationships, on its intended beneficiaries. Minimum prices offered to producers cover production costs and are above market prices, and Fairtrade premiums are to be invested in developmental projects. Therefore, examining the influence of Fairtrade tools on individuals and communities provides an overview of how Fairtrade influences development. The results of the study show that sampled Fairtrade beneficiaries in South Africa have witnessed substantial positive changes as a result of Fairtrade. The Fairtrade initiative has managed to empower small-scale producers and farm workers, as well as leverage development opportunities for their wider communities. It has supported organizational development in the supply chain, facilitated investment in community development projects and in business-related training. Producers, both commercial and small-scale producers, managed to access a market that offers stable prices, and have gained from minimum prices. Furthermore, small-scale farmers have been allowed an opportunity to expand their business into export markets, and enjoyed an increase in incomes. Fairtrade benefits further trickle down to non-Fairtrade community members, in the form of employment creation and community development. Despite positive effects, Fairtrade producers faced challenges, including high Fairtrade administration costs and a small market for Fairtrade commodities. The study concludes that in the face of challenges, Fairtrade brings economic, social and environmental benefits, but as compared to economic and social development, the impact on environmental development is rather limited. Even though that is the case, Fairtrade offers valuable development opportunities to producers in South Africa.
- Full Text:
- Date Issued: 2012
Curriculum reform in Lesotho: exploring the interface between environmental education and geography in selected schools
- Authors: Raselimo, Mohaeka Gabriel
- Date: 2012
- Subjects: Curriculum planning -- Lesotho Curriculum change -- Lesotho Educational evaluation -- Lesotho Environmental education -- Study and teaching (Secondary) -- Lesotho Geography -- Study and teaching (Secondary) -- Lesotho Agenda 21 (Program)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1488 , http://hdl.handle.net/10962/d1003369
- Description: This study sought to explore the interface between environmental education (EE) and school geography with a view to understanding a process of curriculum reform in the context of Lesotho. The research was based on the curriculum reform process that was initiated by a Danish donor-funded project, known as the Lesotho Environmental Education Support Project (LEESP), which operated from 2001 to 2004. Driven by a sustainable development imperative, the project was intended to assist Lesotho in the implementation of local action for Agenda 21 by introducing environmental education into the formal education system. Deviating slightly from much published research on geographical and environmental education, which focuses on how geography contributes to environmental education, this study explored how the latter has shaped the former in terms of content and pedagogy. Using the lens of critical curriculum theory, I sought to understand the political nature of the curriculum and of curriculum change, focusing on the LEESP curriculum policy development, dissemination and implementation at classroom level. The study employed Bernstein's concepts of classification and framing to illuminate issues of power and control between discourses, and between teachers and learners. Operating within an interpretive qualitative research orientation, the study used a case study method focusing on five secondary/high schools in Lesotho. The data was generated through document analysis, interviews and classroom observations. The study examined the assumptions, values and ideologies underpinning environmental education curriculum intentions as reflected in LEESP documents. It also investigated the social process of conceptualising and disseminating environmental education to understand the challenges faced as education practitioners made sense of environmental education innovations in the specific contexts of Lesotho, and how these could possibly influence what happens at the classroom level. The analysis of the LEESP documents revealed that while there are many areas of synergy between the LEESP environmental education policy guidelines and the national education ideals in Lesotho, achievement of the transformational visions of action competence, which was the overarching concept in the reform process, would require major structural changes. The study also highlights issues of participation, contestations, tensions and contradictions associated with the conceptualisation and dissemination of environmental education. At implementation level, there is a disjuncture between environmental education policy intentions and practice. Geography teachers in the research schools generally understood the existence of environmental education in their schools in terms of environmental management. The findings also revealed that while there is generally a strong environmental dimension in geography content, as reflected in both curriculum materials and classroom practice, the subject still retains its disciplinary boundaries and makes little use of knowledge from other subjects or the everyday knowledge of the learners. Finally, it emerged that while the geography teachers in their rhetoric espoused learner-centred methods, in practice they generally employed traditional teacher-centred and book-centred methods. The study concludes that a lack of change in school geography in Lesotho, of the sort envisaged in LEESP, may be attributed to contextual and structural factors such as an overemphasis on examinations, and certain perceptions on the part of teachers and learners embedded in the history and culture of their society. A model of teacher professional development capable of supporting curriculum change is therefore proposed.
- Full Text:
- Date Issued: 2012
- Authors: Raselimo, Mohaeka Gabriel
- Date: 2012
- Subjects: Curriculum planning -- Lesotho Curriculum change -- Lesotho Educational evaluation -- Lesotho Environmental education -- Study and teaching (Secondary) -- Lesotho Geography -- Study and teaching (Secondary) -- Lesotho Agenda 21 (Program)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1488 , http://hdl.handle.net/10962/d1003369
- Description: This study sought to explore the interface between environmental education (EE) and school geography with a view to understanding a process of curriculum reform in the context of Lesotho. The research was based on the curriculum reform process that was initiated by a Danish donor-funded project, known as the Lesotho Environmental Education Support Project (LEESP), which operated from 2001 to 2004. Driven by a sustainable development imperative, the project was intended to assist Lesotho in the implementation of local action for Agenda 21 by introducing environmental education into the formal education system. Deviating slightly from much published research on geographical and environmental education, which focuses on how geography contributes to environmental education, this study explored how the latter has shaped the former in terms of content and pedagogy. Using the lens of critical curriculum theory, I sought to understand the political nature of the curriculum and of curriculum change, focusing on the LEESP curriculum policy development, dissemination and implementation at classroom level. The study employed Bernstein's concepts of classification and framing to illuminate issues of power and control between discourses, and between teachers and learners. Operating within an interpretive qualitative research orientation, the study used a case study method focusing on five secondary/high schools in Lesotho. The data was generated through document analysis, interviews and classroom observations. The study examined the assumptions, values and ideologies underpinning environmental education curriculum intentions as reflected in LEESP documents. It also investigated the social process of conceptualising and disseminating environmental education to understand the challenges faced as education practitioners made sense of environmental education innovations in the specific contexts of Lesotho, and how these could possibly influence what happens at the classroom level. The analysis of the LEESP documents revealed that while there are many areas of synergy between the LEESP environmental education policy guidelines and the national education ideals in Lesotho, achievement of the transformational visions of action competence, which was the overarching concept in the reform process, would require major structural changes. The study also highlights issues of participation, contestations, tensions and contradictions associated with the conceptualisation and dissemination of environmental education. At implementation level, there is a disjuncture between environmental education policy intentions and practice. Geography teachers in the research schools generally understood the existence of environmental education in their schools in terms of environmental management. The findings also revealed that while there is generally a strong environmental dimension in geography content, as reflected in both curriculum materials and classroom practice, the subject still retains its disciplinary boundaries and makes little use of knowledge from other subjects or the everyday knowledge of the learners. Finally, it emerged that while the geography teachers in their rhetoric espoused learner-centred methods, in practice they generally employed traditional teacher-centred and book-centred methods. The study concludes that a lack of change in school geography in Lesotho, of the sort envisaged in LEESP, may be attributed to contextual and structural factors such as an overemphasis on examinations, and certain perceptions on the part of teachers and learners embedded in the history and culture of their society. A model of teacher professional development capable of supporting curriculum change is therefore proposed.
- Full Text:
- Date Issued: 2012
Bayliss-Hillman adducts as scaffolds for the construction of novel compounds with medicinal potential
- Authors: Idahosa, Kenudi Christiana
- Date: 2012
- Subjects: Antimalarials -- Research Malaria -- Chemotherapy -- Research AIDS (Disease) -- Treatment -- Research AIDS (Disease) -- Chemotherapy -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4410 , http://hdl.handle.net/10962/d1006763
- Description: This project has focused on exploring the application of Baylis-Hillman (BH) {a.k.a. Morita-Baylis-Hillman (MBH)} scaffolds in the construction of various compounds with medicinal potential. A series of 2-nitrobenzaldehydes has been treated under BH conditions, with two different activated alkenes, viz., (MVK) and methyl acrylate, using (DABCO) or (3-HQ) as catalyst. While most of the BH reactions were carried out at room temperature, some reactions were conducted using microwave irradiation. The resulting BH adducts have been subjected to dehydration, conjugate addition and allylic substitution to obtain appropriate intermediates, which have been used in turn, to synthesize possible lead compounds, viz., cinnamate esters as HIV-1 integrase inhibitors, 3-(aminomethyl)quinolines and quinolones as anti-malarials and cinnamate ester-AZT conjugates as dual-action HIV-1 integrase-reverse transcriptase (IN-RT) inhibitors. Conjugate addition reactions of methyl acrylate-derived BH β-hydroxy esters with the amines, piperidine, propargylamine and 2-amino-5-(diethylamino)pentane, has afforded a range of products as diastereomeric mixtures in moderate to excellent yields. Catalytic hydrogenation of the aminomethy β-hydroxy esters derivatives, using a palladium-oncarbon (Pd-C) catalyst, has afforded the corresponding, novel 3-aminomethyl-2- quinolone derivatives in moderate yields. Effective allylic substitution reactions of the MVK-derived BH β-hydroxy ketones (via a conjugate addition-elimination pathway) using in situ-generated HCl has afforded the corresponding α-chloromethyl derivatives, which have been reacted with various amines, including piperidine, piperazine, propargylamine and 2-amino-5-(diethylamino)pentane, to yield α-aminomethyl derivatives. Catalytic hydrogenation of selected α-aminomethyl derivatives, using a Pd-C catalyst, has afforded the corresponding, novel 3- (aminomethyl)-2-methylquinoline derivatives in low to moderate yields. A bioassay, conducted on a 6-hydroxy-2-methyl-3-[(piperidin-1-yl)methyl]quinoline isolated early in the study indicated anti-malarial activity and prompted further efforts in the synthesis of analogous compounds. Reaction of the methyl acrylate-derived BH adducts with POCl3 has provided access to α-(chloromethyl)cinnamate ester derivatives, which have been aminated to afford α- (aminomethyl)cinnamate ester derivatives as potential HIV-1 integrase inhibitors. The α- (propargylaminomethyl)cinnamates were used, in turn, as substrates for the “click chemistry” reaction with 3'-azido-3'-deoxythymidine (AZT– an azide and an established reverse transcriptase HIV-1 inhibitor) to afford cinnamate ester-AZT conjugates as potential dual-action HIV-1 integrase-reverse transcriptase (IN-RT) inhibitors. Computer modelling and docking studies of a cinnamate ester-AZT conjugate into the HIV-1 integrase and reverse transcriptase active-sites revealed potential hydrogen-bonding interactions with amino acid residues within the receptor cavities. The isolated products have been appropriately characterized using IR, 1- and 2-D NMR and HRMS techniques, while elucidation of the stereochemistry of the double bond in the BH-derived halomethyl derivatives has been assigned on the basis of NOE, computer modelling and X-ray crystallographic data.
- Full Text:
- Date Issued: 2012
- Authors: Idahosa, Kenudi Christiana
- Date: 2012
- Subjects: Antimalarials -- Research Malaria -- Chemotherapy -- Research AIDS (Disease) -- Treatment -- Research AIDS (Disease) -- Chemotherapy -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4410 , http://hdl.handle.net/10962/d1006763
- Description: This project has focused on exploring the application of Baylis-Hillman (BH) {a.k.a. Morita-Baylis-Hillman (MBH)} scaffolds in the construction of various compounds with medicinal potential. A series of 2-nitrobenzaldehydes has been treated under BH conditions, with two different activated alkenes, viz., (MVK) and methyl acrylate, using (DABCO) or (3-HQ) as catalyst. While most of the BH reactions were carried out at room temperature, some reactions were conducted using microwave irradiation. The resulting BH adducts have been subjected to dehydration, conjugate addition and allylic substitution to obtain appropriate intermediates, which have been used in turn, to synthesize possible lead compounds, viz., cinnamate esters as HIV-1 integrase inhibitors, 3-(aminomethyl)quinolines and quinolones as anti-malarials and cinnamate ester-AZT conjugates as dual-action HIV-1 integrase-reverse transcriptase (IN-RT) inhibitors. Conjugate addition reactions of methyl acrylate-derived BH β-hydroxy esters with the amines, piperidine, propargylamine and 2-amino-5-(diethylamino)pentane, has afforded a range of products as diastereomeric mixtures in moderate to excellent yields. Catalytic hydrogenation of the aminomethy β-hydroxy esters derivatives, using a palladium-oncarbon (Pd-C) catalyst, has afforded the corresponding, novel 3-aminomethyl-2- quinolone derivatives in moderate yields. Effective allylic substitution reactions of the MVK-derived BH β-hydroxy ketones (via a conjugate addition-elimination pathway) using in situ-generated HCl has afforded the corresponding α-chloromethyl derivatives, which have been reacted with various amines, including piperidine, piperazine, propargylamine and 2-amino-5-(diethylamino)pentane, to yield α-aminomethyl derivatives. Catalytic hydrogenation of selected α-aminomethyl derivatives, using a Pd-C catalyst, has afforded the corresponding, novel 3- (aminomethyl)-2-methylquinoline derivatives in low to moderate yields. A bioassay, conducted on a 6-hydroxy-2-methyl-3-[(piperidin-1-yl)methyl]quinoline isolated early in the study indicated anti-malarial activity and prompted further efforts in the synthesis of analogous compounds. Reaction of the methyl acrylate-derived BH adducts with POCl3 has provided access to α-(chloromethyl)cinnamate ester derivatives, which have been aminated to afford α- (aminomethyl)cinnamate ester derivatives as potential HIV-1 integrase inhibitors. The α- (propargylaminomethyl)cinnamates were used, in turn, as substrates for the “click chemistry” reaction with 3'-azido-3'-deoxythymidine (AZT– an azide and an established reverse transcriptase HIV-1 inhibitor) to afford cinnamate ester-AZT conjugates as potential dual-action HIV-1 integrase-reverse transcriptase (IN-RT) inhibitors. Computer modelling and docking studies of a cinnamate ester-AZT conjugate into the HIV-1 integrase and reverse transcriptase active-sites revealed potential hydrogen-bonding interactions with amino acid residues within the receptor cavities. The isolated products have been appropriately characterized using IR, 1- and 2-D NMR and HRMS techniques, while elucidation of the stereochemistry of the double bond in the BH-derived halomethyl derivatives has been assigned on the basis of NOE, computer modelling and X-ray crystallographic data.
- Full Text:
- Date Issued: 2012
Nation branding: case study of Zimbabwe
- Authors: Sena, Steven
- Date: 2012
- Subjects: Branding (Marketing) -- Zimbabwe , Nation-building -- Zimbabwe , Sports and tourism -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9303 , http://hdl.handle.net/10948/d1015616
- Description: Every nation exists as a brand with either positive or negative attributes and any other nation and individual that interact with it either will positively or negatively contribute to its nation image. A nation’s brand image may have evolved over many years, shaped by wars, religion, diplomacy or the lack of it, international sporting triumph or disasters, and by the brand itself. Zimbabwe as a nation is suffering from a negative image gained during 2000-2008 that has been characterised by inter alia the fast track land reform programme, political instability, corruption, hyperinflation, and so forth. The country has experienced a major transformation in its political environment that has had a positive effect on all sectors of national development. The new inclusive government, thriving on national unity has seen the people of Zimbabwe combining effort to work together to sustain the development of the country. The aim of this study was to investigate how nation branding for Zimbabwe can help the country to brand itself as a safe destination for tourists, investors, and visitors. The major question therefore, pertains to how all sectors in the economy of Zimbabwe can combine their efforts to brand Zimbabwe and make it compete more efficiently at all levels. Empirical findings revealed that tourist attractions have a positive relationship with nation branding. The empirical results also indicated that entertainment events have a positive relationship with nation branding. It can be recommended that Zimbabwe needs to identify tourist attractions and entertainment events to increase its nation branding. The empirical results of the study also indicated that nation branding has a positive relationship with nation building in Zimbabwe. It was also shown that nation branding has a positive relationship with good governance in Zimbabwe. These results indicate that it would be easier to build the Zimbabwean nation when its brand is strong. Good governance, on the other hand, will increase if the nation’s branding improves.
- Full Text:
- Date Issued: 2012
- Authors: Sena, Steven
- Date: 2012
- Subjects: Branding (Marketing) -- Zimbabwe , Nation-building -- Zimbabwe , Sports and tourism -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9303 , http://hdl.handle.net/10948/d1015616
- Description: Every nation exists as a brand with either positive or negative attributes and any other nation and individual that interact with it either will positively or negatively contribute to its nation image. A nation’s brand image may have evolved over many years, shaped by wars, religion, diplomacy or the lack of it, international sporting triumph or disasters, and by the brand itself. Zimbabwe as a nation is suffering from a negative image gained during 2000-2008 that has been characterised by inter alia the fast track land reform programme, political instability, corruption, hyperinflation, and so forth. The country has experienced a major transformation in its political environment that has had a positive effect on all sectors of national development. The new inclusive government, thriving on national unity has seen the people of Zimbabwe combining effort to work together to sustain the development of the country. The aim of this study was to investigate how nation branding for Zimbabwe can help the country to brand itself as a safe destination for tourists, investors, and visitors. The major question therefore, pertains to how all sectors in the economy of Zimbabwe can combine their efforts to brand Zimbabwe and make it compete more efficiently at all levels. Empirical findings revealed that tourist attractions have a positive relationship with nation branding. The empirical results also indicated that entertainment events have a positive relationship with nation branding. It can be recommended that Zimbabwe needs to identify tourist attractions and entertainment events to increase its nation branding. The empirical results of the study also indicated that nation branding has a positive relationship with nation building in Zimbabwe. It was also shown that nation branding has a positive relationship with good governance in Zimbabwe. These results indicate that it would be easier to build the Zimbabwean nation when its brand is strong. Good governance, on the other hand, will increase if the nation’s branding improves.
- Full Text:
- Date Issued: 2012
Peri-urban agriculture and population growth : the case of Asmara, Eritrea
- Authors: Fessahaie, Tesfamichael
- Date: 2012
- Subjects: Urban agriculture -- Eritrea -- Asmara , Cities and towns -- Eritrea -- Asmara -- Growth
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10668 , http://hdl.handle.net/10948/d109790
- Description: The aim of this thesis is to provide a differentiated view of peri-urban agriculture in the context of urban population growth in Asmara, Eritrea. Peri-urban agriculture is viewed as a distinct type of broader urban agriculture, and in this case is not as subsistence-orientated as other branches of it. Urban population growth is comprised of three elements, namely, natural population increase, rural-urban migration and outward movement of people to the urban periphery linked to urban expansion. Each receives extensive treatment. Asmara is the capital city of Eritrea and using Weeks (2004:473) phrase can be termed as a “primate city”. As such, it exerts a major influence on the political, economic and cultural life of the country, but has never been subjected to this type of research. The analytical framework that is adopted is that of urban population growth. In order to operationalize it, theoretical insights into each of its three branches were applied. For example, the informalisation of the economy in developing cities was used to explain the operation of peri-urban agriculture in the context of natural population growth. An adaption of the original Harris-Todaro Model by Fields (2004) was used for the migrants, and the Mosaic Model by Bryant and Johnson (1992) for those facing urban encroachment. Primary data were collected in the field by the author with the help of research assistants. This was supplemented by secondary data which involved reports commissioned by the Ministry of Agriculture and the Ministry of Public Works. Focus Group discussions were also held to supplement the data with information, views and insights that do not emerge in one-to-one interviews. This thesis demonstrates that those respondents operating within the context of natural population growth make a viable living from peri-urban agriculture, but that they also recognise that there are considerable challenges to be faced. Three sub-groups of farmers are identified. Of these, poultry farmers are the most vulnerable because of the high costs of the inputs, the uncertainty associated with avian „flu and an undeveloped distribution network. The vegetable producers, on the other hand, have a sophisticated marketing network, but low levels of education, high household numbers and an impending shortage of land and water. The agriculturalists that have migrated to Asmara seem to have created sustainable occupations for themselves over a number of years. However, 75 percent of them felt that migration to Asmara was not worthwhile. This negative view is explained in terms of the struggle it has taken to maintain such a living and the growing shortage of land. This set of farmers achieves lower production levels than its city-reared counterparts, carries considerable expenses and has to hire its land. The farmers who have had to cope with urban encroachment fall into two classes. The first has chosen to remain in peri-urban agriculture despite feeling the pressure to scale down activities and thus have a lower income. The majority of this group are dairy farmers who have to trade off increasing costs of cattle feed against shrinking grazing land. They are unwilling to take the initiative to solve their land problems, but look to the authorities to do so. The second class of respondents in this category have abandoned their agricultural holdings. The majority of these agriculturalists are poultry farmers living in the Eastern side of the city. A shortage of agricultural land, high population densities and high costs of inputs make poultry farming difficult. This thesis, therefore, presents a multifaceted view of peri-urban agriculture. While each set of farmers has to cope with its own particular circumstances, there is a common factor. This is the tension between preserving agricultural land on the urban fringe and the need to expand the city to accommodate its inhabitants.
- Full Text:
- Date Issued: 2012
- Authors: Fessahaie, Tesfamichael
- Date: 2012
- Subjects: Urban agriculture -- Eritrea -- Asmara , Cities and towns -- Eritrea -- Asmara -- Growth
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10668 , http://hdl.handle.net/10948/d109790
- Description: The aim of this thesis is to provide a differentiated view of peri-urban agriculture in the context of urban population growth in Asmara, Eritrea. Peri-urban agriculture is viewed as a distinct type of broader urban agriculture, and in this case is not as subsistence-orientated as other branches of it. Urban population growth is comprised of three elements, namely, natural population increase, rural-urban migration and outward movement of people to the urban periphery linked to urban expansion. Each receives extensive treatment. Asmara is the capital city of Eritrea and using Weeks (2004:473) phrase can be termed as a “primate city”. As such, it exerts a major influence on the political, economic and cultural life of the country, but has never been subjected to this type of research. The analytical framework that is adopted is that of urban population growth. In order to operationalize it, theoretical insights into each of its three branches were applied. For example, the informalisation of the economy in developing cities was used to explain the operation of peri-urban agriculture in the context of natural population growth. An adaption of the original Harris-Todaro Model by Fields (2004) was used for the migrants, and the Mosaic Model by Bryant and Johnson (1992) for those facing urban encroachment. Primary data were collected in the field by the author with the help of research assistants. This was supplemented by secondary data which involved reports commissioned by the Ministry of Agriculture and the Ministry of Public Works. Focus Group discussions were also held to supplement the data with information, views and insights that do not emerge in one-to-one interviews. This thesis demonstrates that those respondents operating within the context of natural population growth make a viable living from peri-urban agriculture, but that they also recognise that there are considerable challenges to be faced. Three sub-groups of farmers are identified. Of these, poultry farmers are the most vulnerable because of the high costs of the inputs, the uncertainty associated with avian „flu and an undeveloped distribution network. The vegetable producers, on the other hand, have a sophisticated marketing network, but low levels of education, high household numbers and an impending shortage of land and water. The agriculturalists that have migrated to Asmara seem to have created sustainable occupations for themselves over a number of years. However, 75 percent of them felt that migration to Asmara was not worthwhile. This negative view is explained in terms of the struggle it has taken to maintain such a living and the growing shortage of land. This set of farmers achieves lower production levels than its city-reared counterparts, carries considerable expenses and has to hire its land. The farmers who have had to cope with urban encroachment fall into two classes. The first has chosen to remain in peri-urban agriculture despite feeling the pressure to scale down activities and thus have a lower income. The majority of this group are dairy farmers who have to trade off increasing costs of cattle feed against shrinking grazing land. They are unwilling to take the initiative to solve their land problems, but look to the authorities to do so. The second class of respondents in this category have abandoned their agricultural holdings. The majority of these agriculturalists are poultry farmers living in the Eastern side of the city. A shortage of agricultural land, high population densities and high costs of inputs make poultry farming difficult. This thesis, therefore, presents a multifaceted view of peri-urban agriculture. While each set of farmers has to cope with its own particular circumstances, there is a common factor. This is the tension between preserving agricultural land on the urban fringe and the need to expand the city to accommodate its inhabitants.
- Full Text:
- Date Issued: 2012
Electrochemistry and photophysicochemical studies of titanium, tantalum and vanadium phthalocyanines in the presence of nanomaterials
- Authors: Chauke, Vongani Portia
- Date: 2012
- Subjects: Phthalocyanines -- Synthesis Electrochemistry Titanium Tantalum Vanadium
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4313 , http://hdl.handle.net/10962/d1004971
- Description: The syntheses of tetra- and octa-substituted phthalocyanine complexes of titanium (IV) oxide vanadium (IV) oxide and tantalum (V) hydroxide and their electrochemical characterisation are presented in this work. The structures and purity of these complexes were confirmed by NMR, infrared and mass spectroscopies and elemental analysis. They show good solubility in most common solvents especially non-viscous solvents such as dichloromethane and chloroform. The cyclic voltammograms (CV) showed reversible to quasi reversible behavior for all the reduction couples and the oxidation peaks were irreversible. Spectroelectrochemistry of the complexes confirmed metal and ring redox processes for TaPc and TiPc derivatives and ring based processes only for VPc complexes. The synthesis of gold nanoparticles and their conjugation with the new phthalocyanines was carried out. Similarly, single walled carbon nanotubes were conjugated to selected tantalum complexes and the characterization of all the nanomaterials and their conjugates using different techniques that include TEM, XRD and AFM is also presented in this work. The photophysical and photochemical properties and photocatalytic oxidation of cyclohexene properties of the newly synthesised in the presence of gold nanoparticles were investigated. The compounds were stable, well within the stability range for phthalocyanines. The singlet oxygen quantum yield values increased drastically in the presence of gold nanoparticles. The photocatalytic products obtained from the reaction were cyclohexene oxide, 2-cyclohexen-1-ol, 2-cyclohexene-1-one and 1,4-cyclohexanediol. The percentage conversion values, yields and selectivity values improved significantly in the presence of AuNPs. Singlet oxygen was determined to be the main agent involved in the photocatalytic oxidation of cyclohexene. The electrocatalytic oxidation of bisphenol A and p-nitrophenol was carried out using nickel tetraamino phthalocyanine and all the newly synthesised metallophthalocyanine in the presence of gold nanoparticles and single walled carbon nanotubes. The charge transfer behaviour of AuNPs was enhanced in the presence of TaPc, TiPc and VPc complexes. The presence of single walled carbon nanotubes further improved electron transfer and minimised electrode passivation.
- Full Text:
- Date Issued: 2012
- Authors: Chauke, Vongani Portia
- Date: 2012
- Subjects: Phthalocyanines -- Synthesis Electrochemistry Titanium Tantalum Vanadium
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4313 , http://hdl.handle.net/10962/d1004971
- Description: The syntheses of tetra- and octa-substituted phthalocyanine complexes of titanium (IV) oxide vanadium (IV) oxide and tantalum (V) hydroxide and their electrochemical characterisation are presented in this work. The structures and purity of these complexes were confirmed by NMR, infrared and mass spectroscopies and elemental analysis. They show good solubility in most common solvents especially non-viscous solvents such as dichloromethane and chloroform. The cyclic voltammograms (CV) showed reversible to quasi reversible behavior for all the reduction couples and the oxidation peaks were irreversible. Spectroelectrochemistry of the complexes confirmed metal and ring redox processes for TaPc and TiPc derivatives and ring based processes only for VPc complexes. The synthesis of gold nanoparticles and their conjugation with the new phthalocyanines was carried out. Similarly, single walled carbon nanotubes were conjugated to selected tantalum complexes and the characterization of all the nanomaterials and their conjugates using different techniques that include TEM, XRD and AFM is also presented in this work. The photophysical and photochemical properties and photocatalytic oxidation of cyclohexene properties of the newly synthesised in the presence of gold nanoparticles were investigated. The compounds were stable, well within the stability range for phthalocyanines. The singlet oxygen quantum yield values increased drastically in the presence of gold nanoparticles. The photocatalytic products obtained from the reaction were cyclohexene oxide, 2-cyclohexen-1-ol, 2-cyclohexene-1-one and 1,4-cyclohexanediol. The percentage conversion values, yields and selectivity values improved significantly in the presence of AuNPs. Singlet oxygen was determined to be the main agent involved in the photocatalytic oxidation of cyclohexene. The electrocatalytic oxidation of bisphenol A and p-nitrophenol was carried out using nickel tetraamino phthalocyanine and all the newly synthesised metallophthalocyanine in the presence of gold nanoparticles and single walled carbon nanotubes. The charge transfer behaviour of AuNPs was enhanced in the presence of TaPc, TiPc and VPc complexes. The presence of single walled carbon nanotubes further improved electron transfer and minimised electrode passivation.
- Full Text:
- Date Issued: 2012
Fire regimes in eastern coastal fynbos: drivers, ecology and management
- Authors: Kraaij, Tineke
- Date: 2012
- Subjects: Forest fires -- South Africa , Climatic changes , Prescribed burning , Fire ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10607 , http://hdl.handle.net/10948/d1008047 , Forest fires -- South Africa , Climatic changes , Prescribed burning , Fire ecology -- South Africa
- Description: Conventional knowledge of fynbos fire ecology is based on the summer-autumn fire regimes of the western Cape Floral Kingdom (CFK) where the climate is Mediterranean. However, the climate in the eastern coastal-CFK is milder and rainfall occurs year-round, with presumed effects on fire regimes. The Garden Route National Park (GRNP) has recently been established in the region, in a landscape where indigenous forests, fire-prone fynbos shrublands and fire-sensitive plantations of invasive alien trees are interspersed. The park faces considerable challenges related to the management of fire, including significant pressure from the adjacent plantation industry to reduce wildfire hazard by burning fynbos at short intervals, and high levels of invasion by alien trees (largely Pinus species originating from plantations). This study sought to improve understanding of fire regimes in eastern coastal fynbos shrublands, and to provide guidelines for ecologically sound management of fire in the area. My approach entailed (i) an assessment of the context within which fire management was practiced during the past century; (ii) characterisation of the recent fire history and fire regime (1900–2010); (iii) characterisation of the seasonality of fire weather and lightning; (iv) estimation of minimum fire return intervals (FRIs) from juvenile periods and post-fire recruitment success of overstorey proteoids (non-sprouting, slow-maturing, serotinous Proteaceae); and (v) determination of the ecologically appropriate fire season from post-fire recruitment seasonality of proteoids. I established that historically, plantation protection enjoyed priority over fynbos conservation in the area that is now the GRNP. Fynbos close to plantations has most likely been compromised by frequent and low-intensity burning in the past, as well as by invasion by alien trees. In terms of area burnt (1900–2010), natural (lightning-ignited) fires dominated the fire regime, particularly in the east, whereas prescribed burning was relatively unimportant. Typical fire return intervals (FRIs; 8–26 years; 1980–2010) were comparable to those in other fynbos protected areas and appeared to be shorter in the eastern Tsitsikamma than in the western Outeniqua halves of the study area. Proteaceae juvenile periods (4–9 years) and post-fire recruitment success (following fires in ≥7 year-old vegetation) suggested that for biodiversity conservation purposes, FRIs should be no less than nine years in moist, productive fynbos. Increases in the total area burnt annually (since 1980) were correlated with long-term increases in average fire danger weather, suggesting that fire regime changes may be related to global change. Collectively, findings on the seasonality of actual fires and the seasonality of fire danger weather, lightning, and post-fire proteoid recruitment suggested that fires in eastern coastal fynbos are not limited to any particular season, and for this reason managers do not need to be concerned if fires occur in any season. The ecological requirements for higher fire intensity may nonetheless be constrained by a need for safety. I articulated these findings into ecological thresholds pertaining to the different elements of the fire regime in eastern coastal fynbos, to guide adaptive management of fire in the Garden Route National Park. I also recommended a fire management strategy for the park to address the aforementioned operational considerations within the constraints posed by ecological thresholds. Finally, I highlighted further research and monitoring needs.
- Full Text:
- Date Issued: 2012
- Authors: Kraaij, Tineke
- Date: 2012
- Subjects: Forest fires -- South Africa , Climatic changes , Prescribed burning , Fire ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10607 , http://hdl.handle.net/10948/d1008047 , Forest fires -- South Africa , Climatic changes , Prescribed burning , Fire ecology -- South Africa
- Description: Conventional knowledge of fynbos fire ecology is based on the summer-autumn fire regimes of the western Cape Floral Kingdom (CFK) where the climate is Mediterranean. However, the climate in the eastern coastal-CFK is milder and rainfall occurs year-round, with presumed effects on fire regimes. The Garden Route National Park (GRNP) has recently been established in the region, in a landscape where indigenous forests, fire-prone fynbos shrublands and fire-sensitive plantations of invasive alien trees are interspersed. The park faces considerable challenges related to the management of fire, including significant pressure from the adjacent plantation industry to reduce wildfire hazard by burning fynbos at short intervals, and high levels of invasion by alien trees (largely Pinus species originating from plantations). This study sought to improve understanding of fire regimes in eastern coastal fynbos shrublands, and to provide guidelines for ecologically sound management of fire in the area. My approach entailed (i) an assessment of the context within which fire management was practiced during the past century; (ii) characterisation of the recent fire history and fire regime (1900–2010); (iii) characterisation of the seasonality of fire weather and lightning; (iv) estimation of minimum fire return intervals (FRIs) from juvenile periods and post-fire recruitment success of overstorey proteoids (non-sprouting, slow-maturing, serotinous Proteaceae); and (v) determination of the ecologically appropriate fire season from post-fire recruitment seasonality of proteoids. I established that historically, plantation protection enjoyed priority over fynbos conservation in the area that is now the GRNP. Fynbos close to plantations has most likely been compromised by frequent and low-intensity burning in the past, as well as by invasion by alien trees. In terms of area burnt (1900–2010), natural (lightning-ignited) fires dominated the fire regime, particularly in the east, whereas prescribed burning was relatively unimportant. Typical fire return intervals (FRIs; 8–26 years; 1980–2010) were comparable to those in other fynbos protected areas and appeared to be shorter in the eastern Tsitsikamma than in the western Outeniqua halves of the study area. Proteaceae juvenile periods (4–9 years) and post-fire recruitment success (following fires in ≥7 year-old vegetation) suggested that for biodiversity conservation purposes, FRIs should be no less than nine years in moist, productive fynbos. Increases in the total area burnt annually (since 1980) were correlated with long-term increases in average fire danger weather, suggesting that fire regime changes may be related to global change. Collectively, findings on the seasonality of actual fires and the seasonality of fire danger weather, lightning, and post-fire proteoid recruitment suggested that fires in eastern coastal fynbos are not limited to any particular season, and for this reason managers do not need to be concerned if fires occur in any season. The ecological requirements for higher fire intensity may nonetheless be constrained by a need for safety. I articulated these findings into ecological thresholds pertaining to the different elements of the fire regime in eastern coastal fynbos, to guide adaptive management of fire in the Garden Route National Park. I also recommended a fire management strategy for the park to address the aforementioned operational considerations within the constraints posed by ecological thresholds. Finally, I highlighted further research and monitoring needs.
- Full Text:
- Date Issued: 2012
A methodology to institutionalise user experience in a South African provincial government
- Authors: Pretorius, Marco Cobus
- Date: 2012
- Subjects: Human-computer interaction , User interfaces (Computer systems) , Government Web sites -- South Africa , Web site development , Electronic government information
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10489 , http://hdl.handle.net/10948/d1019961
- Description: The number of citizens, who access e-Government websites, is growing significantly and their expectations for additional services are increasing. The Internet has become an essential instrument to distribute information to citizens. Poorly designed websites, however, can divide governments and its citizens. Consensus amongst researchers is that user experience (UX) is an important factor in designing websites specifically e-Government websites. Problems, experienced with website usability, prevent people from accessing and eventually adopting technology, such as e-Government. Countries, such as the United States, United Kingdom and Canada, have shown increased support for UX in e-Government websites. At present, a number of guidelines and design principles exists for e-Government website UX design; however, the effectiveness of the implementation of these guidelines and principles depends on the profiles of the individuals on a website development team and on an organisation’s understanding of UX. Despite the highlighted importance of UX, guidelines and principles are rarely adopted in South African e-Government websites. Usability and UX guidelines cannot be implemented; if there is no executive support; an inadequately trained staff; no routine UX practice; insufficient budget; inefficient use of usability methodologies and user-centred design (UCD) processes. The challenge at present in the UX design field is the institutionalisation of UX, specifically at government level. The goal of this research was to propose and evaluate a methodology to institutionalise UX in South African Provincial Governments (PGs), named the “Institutionalise UX in Government (IUXG) methodology”. The research used the Western Cape Government (WCG) in South Africa as a case study to evaluate the proposed methodology to institutionalise UX in a South African PG. The IUXG methodology (1.0) was proposed from five UX methodologies, as well as from best practices found in literature. The IUXG methodology (1.1) was updated, based on results of a survey to South African PGs, a survey to WCG employees, as well as literature from the WCG. The IUXG methodology (2.0) was updated a final time, based on the case study results and on a confirmation survey with WCG employees after the implementation of the case study. The research study made use of three surveys during this research. The first survey, incorporating UX maturity models, confirmed that understanding and buy-in of UX are limited and that UX maturity levels are low at South African PG level. The second and third surveys were administered to WCG e-Government website officials before and after the implementation of the IUXG methodology. The surveys measured the UX maturity level of the WCG in the component, e-Government for Citizens (e-G4C), responsible for the WCG e-Government website. The final survey results demonstrated that, after the implementation of the IUXG methodology, the WCG improved its level of UX maturity on the identified UX maturity models. Implementation of the IUXG methodology institutionalised UX in the WCG. UX activities became standard practice in the e-Government website environment after the systems development lifecycle (SDLC) incorporated UCD. UX policy, strategy and guidelines were documented for the WCG e-Government website. The WCG constructed the first usability testing facility for a South African PG and improvements to the WCG e-Government website were implemented. The proposed IUXG methodology institutionalised UX in the WCG e-Government website environment. This research is a major contribution, to addressing the current lack of UX practices in South African PGs. South African PGs can use the proposed IUXG methodology to institutionalise UX and it will assist PG officials to develop increased UX maturity levels. The advantage of the IUXG methodology is that it provides PG officials with a step-by-step method how to institutionalise UX in a PG by following the six phases of the IUXG methodology: startup, setup, organisation, method, standards and long-term. The IUXG methodology will assist South African PGs to establish UX practice as a norm. The IUXG methodology will assist PGs with the resources, methods and tools to enable them to implement UX guidelines, which will result in an improved, more usable and more user-centric PG e-Government website.
- Full Text:
- Date Issued: 2012
- Authors: Pretorius, Marco Cobus
- Date: 2012
- Subjects: Human-computer interaction , User interfaces (Computer systems) , Government Web sites -- South Africa , Web site development , Electronic government information
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10489 , http://hdl.handle.net/10948/d1019961
- Description: The number of citizens, who access e-Government websites, is growing significantly and their expectations for additional services are increasing. The Internet has become an essential instrument to distribute information to citizens. Poorly designed websites, however, can divide governments and its citizens. Consensus amongst researchers is that user experience (UX) is an important factor in designing websites specifically e-Government websites. Problems, experienced with website usability, prevent people from accessing and eventually adopting technology, such as e-Government. Countries, such as the United States, United Kingdom and Canada, have shown increased support for UX in e-Government websites. At present, a number of guidelines and design principles exists for e-Government website UX design; however, the effectiveness of the implementation of these guidelines and principles depends on the profiles of the individuals on a website development team and on an organisation’s understanding of UX. Despite the highlighted importance of UX, guidelines and principles are rarely adopted in South African e-Government websites. Usability and UX guidelines cannot be implemented; if there is no executive support; an inadequately trained staff; no routine UX practice; insufficient budget; inefficient use of usability methodologies and user-centred design (UCD) processes. The challenge at present in the UX design field is the institutionalisation of UX, specifically at government level. The goal of this research was to propose and evaluate a methodology to institutionalise UX in South African Provincial Governments (PGs), named the “Institutionalise UX in Government (IUXG) methodology”. The research used the Western Cape Government (WCG) in South Africa as a case study to evaluate the proposed methodology to institutionalise UX in a South African PG. The IUXG methodology (1.0) was proposed from five UX methodologies, as well as from best practices found in literature. The IUXG methodology (1.1) was updated, based on results of a survey to South African PGs, a survey to WCG employees, as well as literature from the WCG. The IUXG methodology (2.0) was updated a final time, based on the case study results and on a confirmation survey with WCG employees after the implementation of the case study. The research study made use of three surveys during this research. The first survey, incorporating UX maturity models, confirmed that understanding and buy-in of UX are limited and that UX maturity levels are low at South African PG level. The second and third surveys were administered to WCG e-Government website officials before and after the implementation of the IUXG methodology. The surveys measured the UX maturity level of the WCG in the component, e-Government for Citizens (e-G4C), responsible for the WCG e-Government website. The final survey results demonstrated that, after the implementation of the IUXG methodology, the WCG improved its level of UX maturity on the identified UX maturity models. Implementation of the IUXG methodology institutionalised UX in the WCG. UX activities became standard practice in the e-Government website environment after the systems development lifecycle (SDLC) incorporated UCD. UX policy, strategy and guidelines were documented for the WCG e-Government website. The WCG constructed the first usability testing facility for a South African PG and improvements to the WCG e-Government website were implemented. The proposed IUXG methodology institutionalised UX in the WCG e-Government website environment. This research is a major contribution, to addressing the current lack of UX practices in South African PGs. South African PGs can use the proposed IUXG methodology to institutionalise UX and it will assist PG officials to develop increased UX maturity levels. The advantage of the IUXG methodology is that it provides PG officials with a step-by-step method how to institutionalise UX in a PG by following the six phases of the IUXG methodology: startup, setup, organisation, method, standards and long-term. The IUXG methodology will assist South African PGs to establish UX practice as a norm. The IUXG methodology will assist PGs with the resources, methods and tools to enable them to implement UX guidelines, which will result in an improved, more usable and more user-centric PG e-Government website.
- Full Text:
- Date Issued: 2012
An ecosystem-based spatial conservation plan for the South African sandy beaches
- Authors: Harris, Linda Rozanne
- Date: 2012
- Subjects: Seashore -- South Africa , Bathing beaches -- South Africa , Shorelines -- South Africa , Conservation biology , PhD Thesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10688 , http://hdl.handle.net/10948/d1007920 , Seashore -- South Africa , Bathing beaches -- South Africa , Shorelines -- South Africa , Conservation biology
- Description: An ecosytem-based spatial conservation plan for the South African sandy beaches. Sandy beaches are valuable ecosystems. They support a collection of species that is unique, comprising many endemic species, and provide a number of key ecosystem goods and services, including scenic vistas for human recreation, nesting sites for turtles and birds, and important areas for biogeochemical recycling, water filtration and purification. However, sandy beaches have not been well understood or appreciated as ecosystems, and consequently have a legacy of poor coastal management. In many instances this has lead to a "tyranny of small decisions", where multiple, seemingly insignificant management decisions and actions have resulted in complete transformation and degradation of the shoreline in several places. In addition to inappropriate management strategies, beaches are also poorly represented in conservation areas. Further, where they are recognised as being "conserved" in marine protected areas, this often is a false sense of protection because the far more sensitive dune portion of the littoral active zone is invariably not included in the reserve. In short, there is a need for a new way to approach sandy beach conservation and management that includes the system (dunes, intertidal beaches and surf zones) as a whole. On one hand, the approach should make provision for use of the abundant natural resources and opportunities associated with sandy shores in ways that are sustainable and contribute to biodiversity stewardship - through ecosystem-based management and marine spatial planning. But, on the other hand, it must simultaneously contribute to securing a sufficient amount of the key ecological attributes of beaches (habitats, biodiversity and processes) in a network of reserves, to ensure that the ecosystem, natural resources, and services all persist in perpetuity - through systematic conservation planning. The aim of this Thesis is to integrate these into a single approach, which I call ecosystem-based spatial conservation planning for sandy beaches, using the South African sandy shores as a case study. To achieve this broad aim, the Thesis is divided into three parts. Part 1 deals with establishing baseline information by quantifying spatial patterns in sandy beach habitats (Chapter 1), biodiversity, key assemblages and processes, and outstanding physical features (Chapter 2). First, mapping sandy beach habitats is a challenge given the vast, linear extent of shorelines and significant resources required to complete the project. Therefore, a novel approach was derived using statistical techniques (conditional inference trees) to identify physical features of beaches that can be observed on Google Earth (or similar) imagery, and that can provide good predictions of beach morphodynamic (habitat) types. Based on the results of this analysis, sandy beaches (and all other coastal habitat types) were mapped digitally in ArcGIS. Second, spatial patterns in sandy beach biodiversity (vertebrates, macrofauna, microflora and foredune plants) were mapped by compiling existing data on the distributions of key species that have been well studied or mapped previously (vertebrates and foredune plants), and by niche modelling (macrofauna and microflora). For the latter, data from all previous sandy-beach sampling events in South Africa were compiled from published and unpublished sources, and supplemented with additional sampling of 23 beaches along the national shoreline, targeting macrofauna and phytoplankton. Altogether, the macrofauna database comprised data from 135 sites and 186 sampling events, and the microflora (phytoplankton and microphytobenthos) database comprised data from 73 sites and 510 samples. The probabilistic distribution of each "resident" species (present at 10 or more sites) was modelled in MaxEnt version 3.3.3k, probability thresholds were determined statistically (to convert the data into predicted presence-absence), and displayed as a digital map. A composite biodiversity map was compiled, and key trends in species richness and endemism along the national shoreline were quantified. To supplement biodiversity proper, additional valued-features of sandy beaches were mapped, including: important assemblages; unique habitat features; and sites associated with key ecological processes. Part 2 considers threats to sandy beaches in the context of deriving an appropriate management strategy that seeks to provide for use of the coast, but in a way that has least overall impact to the ecosystem. A method for assessing cumulative threats to sandy beaches is adapted from an existing framework (Chapter 4). This entailed compiling a list of threats to beaches, and scoring these (out of 10) in terms of the severity of their respective impacts to beaches, and how long it would take the ecosystem to recover should the threat be removed. The scoring was based on the collective expert opinion of the scientific community working on sandy beaches, at a workshop during the VIth International Sandy Beach Symposium 2012. To standardize the scores and ensure broad applicability, a base case scenario of a pristine beach was established, and maximum theoretical scores were provided for this context. The method for integrating these scores into a spatial, cumulative threat assessment was then determined. In Chapter 5, the maximum theoretical scores (from Chapter 4) were down-scaled to suit the current threat regime to the South African sandy beaches, and the cumulative threat assessment methodology was applied. From this analysis, the most threatened beaches in South Africa, and the most important threats were highlighted. A decision-support tool for managers was derived from the site-specific cumulative threat-impact scores, based first on the degree of permanent habitat transformation, and second on the cumulative impact of other stressors where the impacts these stressors have could potentially be mitigated or ameliorated. Part 3 concerns conservation of beaches explicitly. It addresses how much of which valued features of beaches is required to ensure their long-term persistence, and the design of a network of beaches in South Africa that are of ecological importance and should be set aside as reserves. Conservation targets are set in Chapter 6, using species-area curves to determine a baseline percentage-area required to protect sandy beach habitats, which is modified using heuristic principles based on habitat rarity and threat status (from a recent national assessment). A fixed target was applied to all species, also modified by heuristic principles, and another fixed target was applied to key assemblages and processes.
- Full Text:
- Date Issued: 2012
- Authors: Harris, Linda Rozanne
- Date: 2012
- Subjects: Seashore -- South Africa , Bathing beaches -- South Africa , Shorelines -- South Africa , Conservation biology , PhD Thesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10688 , http://hdl.handle.net/10948/d1007920 , Seashore -- South Africa , Bathing beaches -- South Africa , Shorelines -- South Africa , Conservation biology
- Description: An ecosytem-based spatial conservation plan for the South African sandy beaches. Sandy beaches are valuable ecosystems. They support a collection of species that is unique, comprising many endemic species, and provide a number of key ecosystem goods and services, including scenic vistas for human recreation, nesting sites for turtles and birds, and important areas for biogeochemical recycling, water filtration and purification. However, sandy beaches have not been well understood or appreciated as ecosystems, and consequently have a legacy of poor coastal management. In many instances this has lead to a "tyranny of small decisions", where multiple, seemingly insignificant management decisions and actions have resulted in complete transformation and degradation of the shoreline in several places. In addition to inappropriate management strategies, beaches are also poorly represented in conservation areas. Further, where they are recognised as being "conserved" in marine protected areas, this often is a false sense of protection because the far more sensitive dune portion of the littoral active zone is invariably not included in the reserve. In short, there is a need for a new way to approach sandy beach conservation and management that includes the system (dunes, intertidal beaches and surf zones) as a whole. On one hand, the approach should make provision for use of the abundant natural resources and opportunities associated with sandy shores in ways that are sustainable and contribute to biodiversity stewardship - through ecosystem-based management and marine spatial planning. But, on the other hand, it must simultaneously contribute to securing a sufficient amount of the key ecological attributes of beaches (habitats, biodiversity and processes) in a network of reserves, to ensure that the ecosystem, natural resources, and services all persist in perpetuity - through systematic conservation planning. The aim of this Thesis is to integrate these into a single approach, which I call ecosystem-based spatial conservation planning for sandy beaches, using the South African sandy shores as a case study. To achieve this broad aim, the Thesis is divided into three parts. Part 1 deals with establishing baseline information by quantifying spatial patterns in sandy beach habitats (Chapter 1), biodiversity, key assemblages and processes, and outstanding physical features (Chapter 2). First, mapping sandy beach habitats is a challenge given the vast, linear extent of shorelines and significant resources required to complete the project. Therefore, a novel approach was derived using statistical techniques (conditional inference trees) to identify physical features of beaches that can be observed on Google Earth (or similar) imagery, and that can provide good predictions of beach morphodynamic (habitat) types. Based on the results of this analysis, sandy beaches (and all other coastal habitat types) were mapped digitally in ArcGIS. Second, spatial patterns in sandy beach biodiversity (vertebrates, macrofauna, microflora and foredune plants) were mapped by compiling existing data on the distributions of key species that have been well studied or mapped previously (vertebrates and foredune plants), and by niche modelling (macrofauna and microflora). For the latter, data from all previous sandy-beach sampling events in South Africa were compiled from published and unpublished sources, and supplemented with additional sampling of 23 beaches along the national shoreline, targeting macrofauna and phytoplankton. Altogether, the macrofauna database comprised data from 135 sites and 186 sampling events, and the microflora (phytoplankton and microphytobenthos) database comprised data from 73 sites and 510 samples. The probabilistic distribution of each "resident" species (present at 10 or more sites) was modelled in MaxEnt version 3.3.3k, probability thresholds were determined statistically (to convert the data into predicted presence-absence), and displayed as a digital map. A composite biodiversity map was compiled, and key trends in species richness and endemism along the national shoreline were quantified. To supplement biodiversity proper, additional valued-features of sandy beaches were mapped, including: important assemblages; unique habitat features; and sites associated with key ecological processes. Part 2 considers threats to sandy beaches in the context of deriving an appropriate management strategy that seeks to provide for use of the coast, but in a way that has least overall impact to the ecosystem. A method for assessing cumulative threats to sandy beaches is adapted from an existing framework (Chapter 4). This entailed compiling a list of threats to beaches, and scoring these (out of 10) in terms of the severity of their respective impacts to beaches, and how long it would take the ecosystem to recover should the threat be removed. The scoring was based on the collective expert opinion of the scientific community working on sandy beaches, at a workshop during the VIth International Sandy Beach Symposium 2012. To standardize the scores and ensure broad applicability, a base case scenario of a pristine beach was established, and maximum theoretical scores were provided for this context. The method for integrating these scores into a spatial, cumulative threat assessment was then determined. In Chapter 5, the maximum theoretical scores (from Chapter 4) were down-scaled to suit the current threat regime to the South African sandy beaches, and the cumulative threat assessment methodology was applied. From this analysis, the most threatened beaches in South Africa, and the most important threats were highlighted. A decision-support tool for managers was derived from the site-specific cumulative threat-impact scores, based first on the degree of permanent habitat transformation, and second on the cumulative impact of other stressors where the impacts these stressors have could potentially be mitigated or ameliorated. Part 3 concerns conservation of beaches explicitly. It addresses how much of which valued features of beaches is required to ensure their long-term persistence, and the design of a network of beaches in South Africa that are of ecological importance and should be set aside as reserves. Conservation targets are set in Chapter 6, using species-area curves to determine a baseline percentage-area required to protect sandy beach habitats, which is modified using heuristic principles based on habitat rarity and threat status (from a recent national assessment). A fixed target was applied to all species, also modified by heuristic principles, and another fixed target was applied to key assemblages and processes.
- Full Text:
- Date Issued: 2012
A structural and functional specification of a SCIM for service interaction management and personalisation in the IMS
- Authors: Tsietsi, Mosiuoa Jeremia
- Date: 2012
- Subjects: Internet Protocol multimedia subsystem , Internet Protocol multimedia subsystem -- Specifications , Long-Term Evolution (Telecommunications) , European Telecommunications Standards Institute , Wireless communication systems , Multimedia communications
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4606 , http://hdl.handle.net/10962/d1004864 , Internet Protocol multimedia subsystem , Internet Protocol multimedia subsystem -- Specifications , Long-Term Evolution (Telecommunications) , European Telecommunications Standards Institute , Wireless communication systems , Multimedia communications
- Description: The Internet Protocol Multimedia Subsystem (IMS) is a component of the 3G mobile network that has been specified by standards development organisations such as the 3GPP (3rd Generation Partnership Project) and ETSI (European Telecommunication Standards Institute). IMS seeks to guarantee that the telecommunication network of the future provides subscribers with seamless access to services across disparate networks. In order to achieve this, it defines a service architecture that hosts application servers that provide subscribers with value added services. Typically, an application server bundles all the functionality it needs to execute the services it delivers, however this view is currently being challenged. It is now thought that services should be synthesised from simple building blocks called service capabilities. This decomposition would facilitate the re-use of service capabilities across multiple services and would support the creation of new services that could not have originally been conceived. The shift from monolithic services to those built from service capabilities poses a challenge to the current service model in IMS. To accommodate this, the 3GPP has defined an entity known as a service capability interaction manager (SCIM) that would be responsible for managing the interactions between service capabilities in order to realise complex services. Some of these interactions could potentially lead to undesirable results, which the SCIM must work to avoid. As an added requirement, it is believed that the network should allow policies to be applied to network services which the SCIM should be responsible for enforcing. At the time of writing, the functional and structural architecture of the SCIM has not yet been standardised. This thesis explores the current serv ice architecture of the IMS in detail. Proposals that address the structure and functions of the SCIM are carefully compared and contrasted. This investigation leads to the presentation of key aspects of the SCIM, and provides solutions that explain how it should interact with service capabilities, manage undesirable interactions and factor user and network operator policies into its execution model. A modified design of the IMS service layer that embeds the SCIM is subsequently presented and described. The design uses existing IMS protocols and requires no change in the behaviour of the standard IMS entities. In order to develop a testbed for experimental verification of the design, the identification of suitable software platforms was required. This thesis presents some of the most popular platforms currently used by developers such as the Open IMS Core and OpenSER, as well as an open source, Java-based, multimedia communication platform called Mobicents. As a precursor to the development of the SCIM, a converged multimedia service is presented that describes how a video streaming application that is leveraged by a web portal was implemented for an IMS testbed using Mobicents components. The Mobicents SIP Servlets container was subsequently used to model an initial prototype of the SCIM, using a mUlti-component telephony service to illustrate the proposed service execution model. The design focuses on SIP-based services only, but should also work for other types of IMS application servers as well.
- Full Text:
- Date Issued: 2012
- Authors: Tsietsi, Mosiuoa Jeremia
- Date: 2012
- Subjects: Internet Protocol multimedia subsystem , Internet Protocol multimedia subsystem -- Specifications , Long-Term Evolution (Telecommunications) , European Telecommunications Standards Institute , Wireless communication systems , Multimedia communications
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4606 , http://hdl.handle.net/10962/d1004864 , Internet Protocol multimedia subsystem , Internet Protocol multimedia subsystem -- Specifications , Long-Term Evolution (Telecommunications) , European Telecommunications Standards Institute , Wireless communication systems , Multimedia communications
- Description: The Internet Protocol Multimedia Subsystem (IMS) is a component of the 3G mobile network that has been specified by standards development organisations such as the 3GPP (3rd Generation Partnership Project) and ETSI (European Telecommunication Standards Institute). IMS seeks to guarantee that the telecommunication network of the future provides subscribers with seamless access to services across disparate networks. In order to achieve this, it defines a service architecture that hosts application servers that provide subscribers with value added services. Typically, an application server bundles all the functionality it needs to execute the services it delivers, however this view is currently being challenged. It is now thought that services should be synthesised from simple building blocks called service capabilities. This decomposition would facilitate the re-use of service capabilities across multiple services and would support the creation of new services that could not have originally been conceived. The shift from monolithic services to those built from service capabilities poses a challenge to the current service model in IMS. To accommodate this, the 3GPP has defined an entity known as a service capability interaction manager (SCIM) that would be responsible for managing the interactions between service capabilities in order to realise complex services. Some of these interactions could potentially lead to undesirable results, which the SCIM must work to avoid. As an added requirement, it is believed that the network should allow policies to be applied to network services which the SCIM should be responsible for enforcing. At the time of writing, the functional and structural architecture of the SCIM has not yet been standardised. This thesis explores the current serv ice architecture of the IMS in detail. Proposals that address the structure and functions of the SCIM are carefully compared and contrasted. This investigation leads to the presentation of key aspects of the SCIM, and provides solutions that explain how it should interact with service capabilities, manage undesirable interactions and factor user and network operator policies into its execution model. A modified design of the IMS service layer that embeds the SCIM is subsequently presented and described. The design uses existing IMS protocols and requires no change in the behaviour of the standard IMS entities. In order to develop a testbed for experimental verification of the design, the identification of suitable software platforms was required. This thesis presents some of the most popular platforms currently used by developers such as the Open IMS Core and OpenSER, as well as an open source, Java-based, multimedia communication platform called Mobicents. As a precursor to the development of the SCIM, a converged multimedia service is presented that describes how a video streaming application that is leveraged by a web portal was implemented for an IMS testbed using Mobicents components. The Mobicents SIP Servlets container was subsequently used to model an initial prototype of the SCIM, using a mUlti-component telephony service to illustrate the proposed service execution model. The design focuses on SIP-based services only, but should also work for other types of IMS application servers as well.
- Full Text:
- Date Issued: 2012