Statistical methods for the detection of non-technical losses: a case study for the Nelson Mandela Bay Municipality
- Authors: Pazi, Sisa
- Date: 2017
- Subjects: Nonparametric statistics Mathematical statistics , Statistics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/19706 , vital:28939
- Description: Electricity is one of the most stolen commodities in the world. Electricity theft can be defined as the criminal act of stealing electrical power. Several types of electricity theft exist, including illegal connections and bypassing and tampering with energy meters. The negative financial impacts, due to lost revenue, of electricity theft are far reaching and affect both developing and developed countries. . Here in South Africa, Eskom loses over R2 Billion annually due to electricity theft. Data mining and nonparametric statistical methods have been used to detect fraudulent usage of electricity by assessing abnormalities and abrupt changes in kilowatt hour (kWh) consumption patterns. Identifying effective measures to detect fraudulent electricity usage is an active area of research in the electrical domain. In this study, Support Vector Machines (SVM), Naïve Bayes (NB) and k-Nearest Neighbour (KNN) algorithms were used to design and propose an electricity fraud detection model. Using the Nelson Mandela Bay Municipality as a case study, three classifiers were built with SVM, NB and KNN algorithms. The performance of these classifiers were evaluated and compared.
- Full Text:
- Date Issued: 2017
- Authors: Pazi, Sisa
- Date: 2017
- Subjects: Nonparametric statistics Mathematical statistics , Statistics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/19706 , vital:28939
- Description: Electricity is one of the most stolen commodities in the world. Electricity theft can be defined as the criminal act of stealing electrical power. Several types of electricity theft exist, including illegal connections and bypassing and tampering with energy meters. The negative financial impacts, due to lost revenue, of electricity theft are far reaching and affect both developing and developed countries. . Here in South Africa, Eskom loses over R2 Billion annually due to electricity theft. Data mining and nonparametric statistical methods have been used to detect fraudulent usage of electricity by assessing abnormalities and abrupt changes in kilowatt hour (kWh) consumption patterns. Identifying effective measures to detect fraudulent electricity usage is an active area of research in the electrical domain. In this study, Support Vector Machines (SVM), Naïve Bayes (NB) and k-Nearest Neighbour (KNN) algorithms were used to design and propose an electricity fraud detection model. Using the Nelson Mandela Bay Municipality as a case study, three classifiers were built with SVM, NB and KNN algorithms. The performance of these classifiers were evaluated and compared.
- Full Text:
- Date Issued: 2017
Tree toppling by elephants and its consequences in thicket mosaic vegetation of Addo Elephant National Park
- Authors: Mgqatsa, Nokubonga
- Date: 2017
- Subjects: Elephants -- Behavior -- South Africa -- Addo Elephant National Park Woody plants -- South Africa -- Addo Elephant National Park
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/19365 , vital:28859
- Description: This study explored the extent of elephant tree toppling and possible cascading effects in Karoo Thicket Mosaic habitat in the Eastern Cape Province, South Africa. While the notion that elephants topple trees is well recognised, little is known about their indirect effects and the possible influence on several trophic levels. Changes brought about by elephants have the potential to influence microclimatic conditions, soil litter processes, plant community composition and other animals. Therefore, this study determined the impacts of elephants on tree toppling, and hence the production of coarse woody debris and the Coarse Woody Debris Profile. Additionally, I explored the consequences of elephant tree toppling on the plant community, small mammals and seed removal. Furthermore, I explored the potential factors facilitating the coexistence of woody plants and elephants. I compared coarse woody debris production and the Coarse Woody Debris Profile between sites with and without elephants. Further, I assessed the consequences of tree toppling in the elephant present site at a patch scale to explore the possible cascading effects of elephants. Firstly, I showed that elephants impacted woody plants through branch/stem breakages and toppling of trees, but that effects vary for different categories of the Coarse Woody Debris Profile. This result confirms the most recent findings that woody plants are at risk from elephant herbivory in Karoo Thicket Mosaic habitat. The elephant toppling effect on these landscapes is largely influenced by plant growth form, with woody trees suffering high levels of elephant toppling than shrubs of comparable size. However, toppled Pappea capensis is able to persist from being toppled by elephants, either through coppicing or resprouting. Additionally, I showed that toppled trees form discrete patches on the landscape, with altered microclimate and browsing pressures. While I detected no significant effect of these changes on plant composition and abundance within these patches, these findings indicate the possible influence of elephants on facilitating plant recruitment and altering plant communities of thicket through toppling of trees. Moreover, I showed that elephant toppling of trees provide habitat patches for small mammals, thus affecting seed removal by vertebrates within patches. These changes had no discernable effect on soil seed banks. However, they highlight the need to better understand the temporal dynamics of these patches and implications for seed dynamics and plant communities on the landscape. The results show the patterns of elephant impacts on woody plants and possible cascading effects in the presence of elephants. Therefore, the study advances our understanding of top-down effects of elephants and shows the relevance of understanding these effects in order to effectively manage elephant impacts in different systems.
- Full Text:
- Date Issued: 2017
- Authors: Mgqatsa, Nokubonga
- Date: 2017
- Subjects: Elephants -- Behavior -- South Africa -- Addo Elephant National Park Woody plants -- South Africa -- Addo Elephant National Park
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/19365 , vital:28859
- Description: This study explored the extent of elephant tree toppling and possible cascading effects in Karoo Thicket Mosaic habitat in the Eastern Cape Province, South Africa. While the notion that elephants topple trees is well recognised, little is known about their indirect effects and the possible influence on several trophic levels. Changes brought about by elephants have the potential to influence microclimatic conditions, soil litter processes, plant community composition and other animals. Therefore, this study determined the impacts of elephants on tree toppling, and hence the production of coarse woody debris and the Coarse Woody Debris Profile. Additionally, I explored the consequences of elephant tree toppling on the plant community, small mammals and seed removal. Furthermore, I explored the potential factors facilitating the coexistence of woody plants and elephants. I compared coarse woody debris production and the Coarse Woody Debris Profile between sites with and without elephants. Further, I assessed the consequences of tree toppling in the elephant present site at a patch scale to explore the possible cascading effects of elephants. Firstly, I showed that elephants impacted woody plants through branch/stem breakages and toppling of trees, but that effects vary for different categories of the Coarse Woody Debris Profile. This result confirms the most recent findings that woody plants are at risk from elephant herbivory in Karoo Thicket Mosaic habitat. The elephant toppling effect on these landscapes is largely influenced by plant growth form, with woody trees suffering high levels of elephant toppling than shrubs of comparable size. However, toppled Pappea capensis is able to persist from being toppled by elephants, either through coppicing or resprouting. Additionally, I showed that toppled trees form discrete patches on the landscape, with altered microclimate and browsing pressures. While I detected no significant effect of these changes on plant composition and abundance within these patches, these findings indicate the possible influence of elephants on facilitating plant recruitment and altering plant communities of thicket through toppling of trees. Moreover, I showed that elephant toppling of trees provide habitat patches for small mammals, thus affecting seed removal by vertebrates within patches. These changes had no discernable effect on soil seed banks. However, they highlight the need to better understand the temporal dynamics of these patches and implications for seed dynamics and plant communities on the landscape. The results show the patterns of elephant impacts on woody plants and possible cascading effects in the presence of elephants. Therefore, the study advances our understanding of top-down effects of elephants and shows the relevance of understanding these effects in order to effectively manage elephant impacts in different systems.
- Full Text:
- Date Issued: 2017
Resource partitioning in the world’s largest gannetry
- Authors: Botha, Jonathan Aubrey
- Date: 2017
- Subjects: Gannets -- South Africa Birds of prey -- Behavior -- South Africa , Birds -- Behavior
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/14707 , vital:27828
- Description: Understanding strategies of resource partitioning within populations is a fundamental aspect of the study of ecology, and one which has been well documented across various taxa. In seabirds, sex-specific differences in foraging behaviour are often thought to reflect strategies of resource partitioning to avoid intra-specific competition. At present Bird Island in Algoa Bay hosts the world’s largest breeding population of gannets, with recent population estimates numbering well over 90 000 breeding pairs. Given the large size of this colony, intense levels of intra-specific competition are expected during the breeding season, particularly in years of poor feeding conditions. In addition, continuous foraging around the breeding colony may lead to the local depletion of prey as the season progresses, calling for flexibility in the foraging behaviour and diet of breeding individuals. Therefore, the aim of this dissertation was to investigate resource partitioning in Cape gannets breeding at Bird Island through strategies of sex-specific foraging and intra-seasonal variability in foraging behaviour and diet. To achieve this, the spatial and temporal aspects of Cape gannet foraging behaviour were assessed during the early stages of chick rearing, over two consecutive breeding seasons (2011/12, 2012/13) using GPS tracking and VHF monitoring. In addition, intra-seasonal variability in foraging behaviour and diet were investigated, taking into account the influence of sex and chick age, to provide a comprehensive assessment of foraging behaviour throughout the chick rearing period. GPS tracking data for 79 birds revealed limited evidence for sex-specific differences over spatial dimensions. An extension in the foraging range of females during a year of lower prey availability (2012/13) was, however, evident. This suggests a possible sex-specific response to prey limitation, likely reflecting resource partitioning strategies or differences in nutritional requirements. VHF data for 95 additional birds revealed a clear pattern in temporal foraging behaviour. In general, females were more likely to be on a foraging trip during the early and mid-day hours, with the probability of males being on a foraging trip increasing towards the late afternoon. Continuous tracking of individuals throughout the 2015/16 breeding season further revealed little evidence for sex-specific differences in spatial distribution and forging effort during both the guard and post-guard stages of chick rearing. A clear increase in foraging range was evident during the early stages of chick rearing as the season progressed. However, birds attending chicks older than 50 days showed an unexpected contraction in foraging range, which appeared to coincide with a dietary shift. During the early stages of breeding the diet was comprised almost exclusively of anchovy, the proportion of which decreased progressively in the diet throughout the breeding season. This was mirrored by a substantial increase in the proportion of saury in the diet. These results suggest that Cape gannets increase their foraging range in response to local prey depletion as the breeding season progresses. However, when alternative prey becomes available they may shift their diet, allowing them to access prey closer to the breeding colony. Overall, this dissertation provides insight into sex-specific behaviour in a monomorphic seabird, suggesting a marginal degree of spatial segregation. The results provide the first support for sex-related temporal foraging segregation in gannets. Such separation could potentially be driven by resource partitioning, but could also relate to differential nutritional requirements. In addition, this study also provided the first comprehensive assessment of foraging behaviour throughout the guard and post guard stages of chick rearing in gannets. These results suggest that a combination of foraging and dietary flexibility may allow Cape gannets to buffer the effects of prey depletion during the breeding season. In conclusion, resource partitioning through sex-specific foraging appears to be limited in the Cape gannet population at Bird Island. Segregation via alternative pathways may however be possible and as such, future studies should consider the influence of individual level segregation and habitat specialization.
- Full Text:
- Date Issued: 2017
- Authors: Botha, Jonathan Aubrey
- Date: 2017
- Subjects: Gannets -- South Africa Birds of prey -- Behavior -- South Africa , Birds -- Behavior
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/14707 , vital:27828
- Description: Understanding strategies of resource partitioning within populations is a fundamental aspect of the study of ecology, and one which has been well documented across various taxa. In seabirds, sex-specific differences in foraging behaviour are often thought to reflect strategies of resource partitioning to avoid intra-specific competition. At present Bird Island in Algoa Bay hosts the world’s largest breeding population of gannets, with recent population estimates numbering well over 90 000 breeding pairs. Given the large size of this colony, intense levels of intra-specific competition are expected during the breeding season, particularly in years of poor feeding conditions. In addition, continuous foraging around the breeding colony may lead to the local depletion of prey as the season progresses, calling for flexibility in the foraging behaviour and diet of breeding individuals. Therefore, the aim of this dissertation was to investigate resource partitioning in Cape gannets breeding at Bird Island through strategies of sex-specific foraging and intra-seasonal variability in foraging behaviour and diet. To achieve this, the spatial and temporal aspects of Cape gannet foraging behaviour were assessed during the early stages of chick rearing, over two consecutive breeding seasons (2011/12, 2012/13) using GPS tracking and VHF monitoring. In addition, intra-seasonal variability in foraging behaviour and diet were investigated, taking into account the influence of sex and chick age, to provide a comprehensive assessment of foraging behaviour throughout the chick rearing period. GPS tracking data for 79 birds revealed limited evidence for sex-specific differences over spatial dimensions. An extension in the foraging range of females during a year of lower prey availability (2012/13) was, however, evident. This suggests a possible sex-specific response to prey limitation, likely reflecting resource partitioning strategies or differences in nutritional requirements. VHF data for 95 additional birds revealed a clear pattern in temporal foraging behaviour. In general, females were more likely to be on a foraging trip during the early and mid-day hours, with the probability of males being on a foraging trip increasing towards the late afternoon. Continuous tracking of individuals throughout the 2015/16 breeding season further revealed little evidence for sex-specific differences in spatial distribution and forging effort during both the guard and post-guard stages of chick rearing. A clear increase in foraging range was evident during the early stages of chick rearing as the season progressed. However, birds attending chicks older than 50 days showed an unexpected contraction in foraging range, which appeared to coincide with a dietary shift. During the early stages of breeding the diet was comprised almost exclusively of anchovy, the proportion of which decreased progressively in the diet throughout the breeding season. This was mirrored by a substantial increase in the proportion of saury in the diet. These results suggest that Cape gannets increase their foraging range in response to local prey depletion as the breeding season progresses. However, when alternative prey becomes available they may shift their diet, allowing them to access prey closer to the breeding colony. Overall, this dissertation provides insight into sex-specific behaviour in a monomorphic seabird, suggesting a marginal degree of spatial segregation. The results provide the first support for sex-related temporal foraging segregation in gannets. Such separation could potentially be driven by resource partitioning, but could also relate to differential nutritional requirements. In addition, this study also provided the first comprehensive assessment of foraging behaviour throughout the guard and post guard stages of chick rearing in gannets. These results suggest that a combination of foraging and dietary flexibility may allow Cape gannets to buffer the effects of prey depletion during the breeding season. In conclusion, resource partitioning through sex-specific foraging appears to be limited in the Cape gannet population at Bird Island. Segregation via alternative pathways may however be possible and as such, future studies should consider the influence of individual level segregation and habitat specialization.
- Full Text:
- Date Issued: 2017
A smart home environment to support safety and risk monitoring for the elderly living independently
- Authors: Chiridza, Tongai
- Date: 2017
- Subjects: Multisensor data fusion , Raspberry Pi (Computer) -- Programming Adaptive computing systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/14851 , vital:27880
- Description: The elderly prefer to live independently despite vulnerability to age-related challenges. Constant monitoring is required in cases where the elderly are living alone. The home environment can be a dangerous environment for the elderly living independently due to adverse events that can occur at any time. The potential risks for the elderly living independently can be categorised as injury in the home, home environmental risks and inactivity due to unconsciousness. The main research objective was to develop a Smart Home Environment (SHE) that can support risk and safety monitoring for the elderly living independently. An unobtrusive and low cost SHE solution that uses a Raspberry Pi 3 model B, a Microsoft Kinect Sensor and an Aeotec 4-in-1 Multisensor was implemented. The Aeotec Multisensor was used to measure temperature, motion, lighting, and humidity in the home. Data from the multisensor was collected using OpenHAB as the Smart Home Operating System. The information was processed using the Raspberry Pi 3 and push notifications were sent when risk situations were detected. An experimental evaluation was conducted to determine the accuracy with which the prototype SHE detected abnormal events. Evaluation scripts were each evaluated five times. The results show that the prototype has an average accuracy, sensitivity and specificity of 94%, 96.92% and 88.93% respectively. The sensitivity shows that the chance of the prototype missing a risk situation is 3.08%, and the specificity shows that the chance of incorrectly classifying a non-risk situation is 11.07%. The prototype does not require any interaction on the part of the elderly. Relatives and caregivers can remotely monitor the elderly person living independently via the mobile application or a web portal. The total cost of the equipment used was below R3000.
- Full Text:
- Date Issued: 2017
- Authors: Chiridza, Tongai
- Date: 2017
- Subjects: Multisensor data fusion , Raspberry Pi (Computer) -- Programming Adaptive computing systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/14851 , vital:27880
- Description: The elderly prefer to live independently despite vulnerability to age-related challenges. Constant monitoring is required in cases where the elderly are living alone. The home environment can be a dangerous environment for the elderly living independently due to adverse events that can occur at any time. The potential risks for the elderly living independently can be categorised as injury in the home, home environmental risks and inactivity due to unconsciousness. The main research objective was to develop a Smart Home Environment (SHE) that can support risk and safety monitoring for the elderly living independently. An unobtrusive and low cost SHE solution that uses a Raspberry Pi 3 model B, a Microsoft Kinect Sensor and an Aeotec 4-in-1 Multisensor was implemented. The Aeotec Multisensor was used to measure temperature, motion, lighting, and humidity in the home. Data from the multisensor was collected using OpenHAB as the Smart Home Operating System. The information was processed using the Raspberry Pi 3 and push notifications were sent when risk situations were detected. An experimental evaluation was conducted to determine the accuracy with which the prototype SHE detected abnormal events. Evaluation scripts were each evaluated five times. The results show that the prototype has an average accuracy, sensitivity and specificity of 94%, 96.92% and 88.93% respectively. The sensitivity shows that the chance of the prototype missing a risk situation is 3.08%, and the specificity shows that the chance of incorrectly classifying a non-risk situation is 11.07%. The prototype does not require any interaction on the part of the elderly. Relatives and caregivers can remotely monitor the elderly person living independently via the mobile application or a web portal. The total cost of the equipment used was below R3000.
- Full Text:
- Date Issued: 2017
Cape gannets in contrasting environments: ehaviour, demographics and indicators of environmental change
- Authors: Ryklief, Rabiah
- Date: 2017
- Subjects: Endemic birds -- South Africa Marine pollution -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/21167 , vital:29452
- Description: Marine communities represent biological networks, where physical and chemical changes in the marine environment can influence the physiology and behaviour of marine organisms. Stochastic marine conditions can alter key biological interactions and thus, influence the mechanisms that underpin population demography and phenotypic plasticity. Marine top predators, such as seabirds, are often controlled by bottom-up processes and their ability to cope with variable ocean conditions lies in their physiological and behavioural response to such perturbations. Seabirds are central-place foragers during the breeding season making them particularly vulnerable to environmental fluctuations as they face constrains associated with reproductive effort in addition to self-maintenance. The Cape gannet Morus capensis is a medium-sized pelagic seabird that is endemic to southern Africa. The Cape gannet has experienced considerable change in population distribution and abundance over the past 50 years. These changes have been linked to a combination of fishing pressure and climate-mediated regime shifts of their preferred prey, i.e. sardine Sardinops sagax and anchovy ngraulis encrasicolus. Historically, Malgas Island was the largest Cape gannet colony in South Africa. However, it is now in a state of population decline, despite its occurrence within one of the most productive upwelling systems in the world, the Benguela Current. At present, Bird Island is the largest Cape gannet colony and has recently stabilised, despite regular immigration of gannets from the west coast. Furthermore, Bird Island lies within the Agulhas bioregion and is subject to low levels of productivity from the nutrient-poor Agulhas current. Malgas and Bird islands are the two most populous of the six extant Cape gannet colonies. Birds at these colonies provided a natural experiment due to the contrasting population trajectories and environmental conditions at their colonies. The foraging ecology and behaviour of Cape gannets were studied during the breeding season to assess the mechanistic links connecting climate and fisheries to population demography. Cape gannets displayed considerable inter-annual variation in foraging effort and distribution across a five-year period. This highlights the importance of long-term datasets to contextualise the degree of natural variation within a species, as well as considerations for conservation management. For the first time, oceanographic variables such as sea surface temperature and chlorophyll-a, indices that reflect marine productivity, were used to predict Cape gannet foraging distribution. Furthermore, Cape gannets at Bird Island had an energy budget deficit in a year when foraging effort was much higher in comparison to what was observed at Malgas Island. This in turn was linked to the first identification of nutritional stress in a Sulid species. Reasons for this include a combination of higher intra-specific competition in conjunction with a lower energetic content of referential prey species at Bird Island. Foraging effort showed more variability at Malgas Island in comparison to Bird Island, likely due to Malgas Island gannets often taking two short foraging trips a day, whereas Bird Island gannets often spent the night at sea. Some degree of phenotypic plasticity was evidenced by substantial variations across breeding seasons and ocean basins in foraging effort and behaviour.
- Full Text:
- Date Issued: 2017
- Authors: Ryklief, Rabiah
- Date: 2017
- Subjects: Endemic birds -- South Africa Marine pollution -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/21167 , vital:29452
- Description: Marine communities represent biological networks, where physical and chemical changes in the marine environment can influence the physiology and behaviour of marine organisms. Stochastic marine conditions can alter key biological interactions and thus, influence the mechanisms that underpin population demography and phenotypic plasticity. Marine top predators, such as seabirds, are often controlled by bottom-up processes and their ability to cope with variable ocean conditions lies in their physiological and behavioural response to such perturbations. Seabirds are central-place foragers during the breeding season making them particularly vulnerable to environmental fluctuations as they face constrains associated with reproductive effort in addition to self-maintenance. The Cape gannet Morus capensis is a medium-sized pelagic seabird that is endemic to southern Africa. The Cape gannet has experienced considerable change in population distribution and abundance over the past 50 years. These changes have been linked to a combination of fishing pressure and climate-mediated regime shifts of their preferred prey, i.e. sardine Sardinops sagax and anchovy ngraulis encrasicolus. Historically, Malgas Island was the largest Cape gannet colony in South Africa. However, it is now in a state of population decline, despite its occurrence within one of the most productive upwelling systems in the world, the Benguela Current. At present, Bird Island is the largest Cape gannet colony and has recently stabilised, despite regular immigration of gannets from the west coast. Furthermore, Bird Island lies within the Agulhas bioregion and is subject to low levels of productivity from the nutrient-poor Agulhas current. Malgas and Bird islands are the two most populous of the six extant Cape gannet colonies. Birds at these colonies provided a natural experiment due to the contrasting population trajectories and environmental conditions at their colonies. The foraging ecology and behaviour of Cape gannets were studied during the breeding season to assess the mechanistic links connecting climate and fisheries to population demography. Cape gannets displayed considerable inter-annual variation in foraging effort and distribution across a five-year period. This highlights the importance of long-term datasets to contextualise the degree of natural variation within a species, as well as considerations for conservation management. For the first time, oceanographic variables such as sea surface temperature and chlorophyll-a, indices that reflect marine productivity, were used to predict Cape gannet foraging distribution. Furthermore, Cape gannets at Bird Island had an energy budget deficit in a year when foraging effort was much higher in comparison to what was observed at Malgas Island. This in turn was linked to the first identification of nutritional stress in a Sulid species. Reasons for this include a combination of higher intra-specific competition in conjunction with a lower energetic content of referential prey species at Bird Island. Foraging effort showed more variability at Malgas Island in comparison to Bird Island, likely due to Malgas Island gannets often taking two short foraging trips a day, whereas Bird Island gannets often spent the night at sea. Some degree of phenotypic plasticity was evidenced by substantial variations across breeding seasons and ocean basins in foraging effort and behaviour.
- Full Text:
- Date Issued: 2017
Synthesis and investigation of the chemosensing properties of novel fluorescent triazolyl coumarin-based polymers
- Ngororabanga, Jean Marie Vianney
- Authors: Ngororabanga, Jean Marie Vianney
- Date: 2017
- Subjects: Fluorescent polymers Chemical detectors
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/20110 , vital:29120
- Description: Environmental pollution by ionic species has become one of the greatest challenges to the sustainable development of communities. Increasing amounts of these ionic species in the environment is associated with several detrimental effects to human health and ecological systems. Proper detection and monitoring of these ionic species is essential. Considering the diversity of the ions and the fact that the available sensors are limited, it is clear that there is need for a rapid and low-cost method for recognition and monitoring of these ions. Fluorescence based methods are ranked among the most powerful transduction systems to signal chemical recognition events. Fluorescent polymers containing triazolyl coumarin units in the polymer backbone or as pendant groups were therefore designed and investigated as potential sensors for these ions. Three methods were used to incorporate triazolyl coumarin units into the polymers. The first method involved polymerization of the vinyl monomer containing the triazolyl coumarin unit. The second method involved AA-BB step-grow click polymerization of diazide and dialkyne-functionalized monomers. The third method involved post-polymerization functionalization of an azide-functionalized polymer with an alkyne functionalized coumarin derivative. In each method, formation of the triazole ring was achieved using a Cu(I)-catalyzed 1,3-dipolar cycloaddition (CuAAC) reaction. The photophysical properties of the polymers and their starting monomers were investigated and compared. Polymers with triazolyl coumarin units in the backbone or as pendant groups were found to have higher absorption and emission intensities than their corresponding monomers while polymers resulting from functionalization of azide-functionalized polymer were found to exhibit improved photophysical properties compared to the starting azide-functionalized polymer. The chemosensing potential of the polymers was investigated through absorption and emission. The polymers were found to be selective towards different metal ions (Fe3+, Hg2+ and Al3+) and anions (-OH and F-). The mechanisms of interaction between the polymers and ions were investigated by comparing the absorption and emission spectra of the polymers to those of their monomers in the presence of an ion of interest. In some cases the mechanism of interaction was supported by 1H NMR and FT-IR.
- Full Text:
- Date Issued: 2017
- Authors: Ngororabanga, Jean Marie Vianney
- Date: 2017
- Subjects: Fluorescent polymers Chemical detectors
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/20110 , vital:29120
- Description: Environmental pollution by ionic species has become one of the greatest challenges to the sustainable development of communities. Increasing amounts of these ionic species in the environment is associated with several detrimental effects to human health and ecological systems. Proper detection and monitoring of these ionic species is essential. Considering the diversity of the ions and the fact that the available sensors are limited, it is clear that there is need for a rapid and low-cost method for recognition and monitoring of these ions. Fluorescence based methods are ranked among the most powerful transduction systems to signal chemical recognition events. Fluorescent polymers containing triazolyl coumarin units in the polymer backbone or as pendant groups were therefore designed and investigated as potential sensors for these ions. Three methods were used to incorporate triazolyl coumarin units into the polymers. The first method involved polymerization of the vinyl monomer containing the triazolyl coumarin unit. The second method involved AA-BB step-grow click polymerization of diazide and dialkyne-functionalized monomers. The third method involved post-polymerization functionalization of an azide-functionalized polymer with an alkyne functionalized coumarin derivative. In each method, formation of the triazole ring was achieved using a Cu(I)-catalyzed 1,3-dipolar cycloaddition (CuAAC) reaction. The photophysical properties of the polymers and their starting monomers were investigated and compared. Polymers with triazolyl coumarin units in the backbone or as pendant groups were found to have higher absorption and emission intensities than their corresponding monomers while polymers resulting from functionalization of azide-functionalized polymer were found to exhibit improved photophysical properties compared to the starting azide-functionalized polymer. The chemosensing potential of the polymers was investigated through absorption and emission. The polymers were found to be selective towards different metal ions (Fe3+, Hg2+ and Al3+) and anions (-OH and F-). The mechanisms of interaction between the polymers and ions were investigated by comparing the absorption and emission spectra of the polymers to those of their monomers in the presence of an ion of interest. In some cases the mechanism of interaction was supported by 1H NMR and FT-IR.
- Full Text:
- Date Issued: 2017
A best practice e-learning environment for software training
- Authors: Esterhuyse, Maxine Pier
- Date: 2017
- Subjects: Internet in education Computer-assisted instruction Web-based instruction -- Education
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/12165 , vital:27039
- Description: The incorporation of best practice in e-learning environments can increase the probability of success for companies and learners alike. By identifying and understanding the barriers that potential learners may face when interacting with e-learning products, the potential for e-learning failure may be alleviated. There are a variety of benefits that may be realised by companies incorporating e-learning opportunities into their management strategies. However, certain pedagogical principles, metrics and components need to be investigated and implemented in order for a corporate e-learning environment to be successful. The aim of this research is to prototype and evaluate a practical e-learning environment for software training (eLESTP) with e-learning components consisting of interactive learning objects that can guide the development and management of online training in the corporate context. The eLESTP is based on a theoretical contribution that is conceptualised in the form of an e-learning environment for software training (eLESTT). Hence, this study followed a research methodology that is appropriate for educational technologies, namely the Design-Based Research (DBR) methodology, which was applied in iterative cycles. Quantitative and qualitative data was collected by means of a case study, interviews, a focus group and survey. The proposed eLESTP underwent several iterations of feedback and improvement and the result is a real-world solution to the problem at hand. With the purpose of determining the success of corporate e-learning, the barriers and critical success factors for e-learning as well as evaluation criteria were explored. Interviews, a focus group and a survey were conducted in order to validate the investigated literature in a real-world context. Informal interviews enabled a better understanding of the organisational context of this study. The focus group was conducted with customers who were undergoing face-to-face training using conveyancing software developed by Korbitec. Many of the issues faced by learners identified in literature regarding e-learning in developing countries were identified by the participants from the case study. An e-learning survey was used to gather information regarding the intention of Korbitec’s customers to use e-learning as well as their satisfaction with using e-learning. From the survey, it was found that respondents were positive regarding intention to use and satisfaction toward e-learning usage. DBR Cycle 1: Problem Investigation and Proposal entailed the initial problem investigation by conducting a literature review, focus group and survey. DBR Cycle 2: Design Alternative 1 of this study involved a design alternative for eLESTP, namely Prototype 1. DBR Cycle 3: Design and Evaluate Alternative 2 involved the design and prototyping of Prototype 2 for eLESTP as well as the improvement of Prototype 2 through sub-cycles of testing and refinement. The suggestions for improvement were obtained from the relevant stakeholders at Korbitec who are content developers and subject-matter experts. The criteria used to evaluate the success of eLESTP, including its e-learning components, were synthesised and adapted from literature and a new set of evaluation criteria for e-learning environments in software training contexts was proposed. The evaluated eLESTP consists of the technology basis of the Modular Object Oriented Dynamic Learning Environment (Moodle), design guidelines for e-learning components, certification and competency-based training, pedagogical principles and best practice. Overall, eLESTP was positively received by various evaluator groups in formative and summative evaluations. The research results indicate that the use of an e-learning environment for software training purposes was useful and necessary. In support of this Masters dissertation, the following three conference papers have been published and presented at one local conference and two international conferences. In addition, an article has been published in an accredited journal: 1. IDIA 2015, Conference Paper – Zanzibar (Tanzania); 2. Conf-IRM 2016, Conference Paper – Cape Town (South Africa); 3. MCIS 2016, Conference Paper – Cyprus (Europe); and 4. IJIKM 2016, Journal Article.
- Full Text:
- Date Issued: 2017
- Authors: Esterhuyse, Maxine Pier
- Date: 2017
- Subjects: Internet in education Computer-assisted instruction Web-based instruction -- Education
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/12165 , vital:27039
- Description: The incorporation of best practice in e-learning environments can increase the probability of success for companies and learners alike. By identifying and understanding the barriers that potential learners may face when interacting with e-learning products, the potential for e-learning failure may be alleviated. There are a variety of benefits that may be realised by companies incorporating e-learning opportunities into their management strategies. However, certain pedagogical principles, metrics and components need to be investigated and implemented in order for a corporate e-learning environment to be successful. The aim of this research is to prototype and evaluate a practical e-learning environment for software training (eLESTP) with e-learning components consisting of interactive learning objects that can guide the development and management of online training in the corporate context. The eLESTP is based on a theoretical contribution that is conceptualised in the form of an e-learning environment for software training (eLESTT). Hence, this study followed a research methodology that is appropriate for educational technologies, namely the Design-Based Research (DBR) methodology, which was applied in iterative cycles. Quantitative and qualitative data was collected by means of a case study, interviews, a focus group and survey. The proposed eLESTP underwent several iterations of feedback and improvement and the result is a real-world solution to the problem at hand. With the purpose of determining the success of corporate e-learning, the barriers and critical success factors for e-learning as well as evaluation criteria were explored. Interviews, a focus group and a survey were conducted in order to validate the investigated literature in a real-world context. Informal interviews enabled a better understanding of the organisational context of this study. The focus group was conducted with customers who were undergoing face-to-face training using conveyancing software developed by Korbitec. Many of the issues faced by learners identified in literature regarding e-learning in developing countries were identified by the participants from the case study. An e-learning survey was used to gather information regarding the intention of Korbitec’s customers to use e-learning as well as their satisfaction with using e-learning. From the survey, it was found that respondents were positive regarding intention to use and satisfaction toward e-learning usage. DBR Cycle 1: Problem Investigation and Proposal entailed the initial problem investigation by conducting a literature review, focus group and survey. DBR Cycle 2: Design Alternative 1 of this study involved a design alternative for eLESTP, namely Prototype 1. DBR Cycle 3: Design and Evaluate Alternative 2 involved the design and prototyping of Prototype 2 for eLESTP as well as the improvement of Prototype 2 through sub-cycles of testing and refinement. The suggestions for improvement were obtained from the relevant stakeholders at Korbitec who are content developers and subject-matter experts. The criteria used to evaluate the success of eLESTP, including its e-learning components, were synthesised and adapted from literature and a new set of evaluation criteria for e-learning environments in software training contexts was proposed. The evaluated eLESTP consists of the technology basis of the Modular Object Oriented Dynamic Learning Environment (Moodle), design guidelines for e-learning components, certification and competency-based training, pedagogical principles and best practice. Overall, eLESTP was positively received by various evaluator groups in formative and summative evaluations. The research results indicate that the use of an e-learning environment for software training purposes was useful and necessary. In support of this Masters dissertation, the following three conference papers have been published and presented at one local conference and two international conferences. In addition, an article has been published in an accredited journal: 1. IDIA 2015, Conference Paper – Zanzibar (Tanzania); 2. Conf-IRM 2016, Conference Paper – Cape Town (South Africa); 3. MCIS 2016, Conference Paper – Cyprus (Europe); and 4. IJIKM 2016, Journal Article.
- Full Text:
- Date Issued: 2017
Assessment of the host properties of selected optically pure, racemic and achiral compounds
- Authors: Jooste, Daniel Victor
- Date: 2017
- Subjects: Organic compounds -- Synthesis Cyclic compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/18826 , vital:28735
- Description: This study focussed on the synthesis and host properties of four different broad categories of potential host compounds, namely optically active and racemic TADDOL [(4R,5R)-α,α,α’,α’-tetraphenyl-1,3-dioxolane-4,5-dimethanol] and derivatives, TTFOL [(3R,4R)-2,2,5,5-tetraphenyltetrahydrofuran-3,4-diol], amino acid ester-derived compounds [(S)-4-(2-amino-3-hydroxy-3,3-diphenylpropyl)phenol], and compounds derived from xanthone [9-amino-9-phenylxanthene and 1,2-bis(9-phenyl-9H-xanthen-9-yl)hydrazine]. The potential hosts were recrystallized from a range of possible guest species and the resulting solids analysed by 1H-NMR spectroscopy. If inclusion was observed by this technique, the complexes were analysed further using single crystal X-ray techniques and thermal experiments where possible. Competition studies were carried out where these were deemed appropriate. Optically active and racemic TADDOLs were synthesized using L-(+) and DL-(±)-tartaric acid respectively. Two further derivatives were prepared whereby the hydroxyl groups were substituted for chlorine and azide in order to assess the effect of this change on the inclusion ability. Both the optically active and racemic TADDOLs displayed similar host abilities, complexing with guests with 1:1 host:guest ratios as determined through 1H-NMR spectroscopy. Competition experiments showed that both forms of TADDOL exhibited similar guest preferences for pyridine and the methylpyridine isomers. Pyridine however was preferred over 2-methylpyridine by optically active TADDOL while the racemic form preferred this methyl-substituted guest over pyridine. Thermal analysis studies showed, surprisingly, that the TADDOL complexes containing pyridine had higher relative thermal stabilities than those containing the methylpyridines, whether the host was optically active or not. The preference order of these hosts for these guests can, therefore, not be used as a predictor for the relative thermal stability of the complexes. TTFOL was found to include only ethanol, 2-methylpyridine and dioxane from the range of guest species used; the complex with dioxane did not produce X-ray quality crystals. The L-tyrosine derivative, (S)-4-(2-amino-3-hydroxy-3,3-diphenylpropyl)phenol, was an ineffective host incapable of including any of the guests used in these experiments. The two xanthone derivatives, 9-amino-9-phenylxanthene and 1,2-bis(9-phenyl-9H-xanthen-9-yl)hydrazine each formed complexes with one guest species (morpholine and DMF, respectively).
- Full Text:
- Date Issued: 2017
- Authors: Jooste, Daniel Victor
- Date: 2017
- Subjects: Organic compounds -- Synthesis Cyclic compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/18826 , vital:28735
- Description: This study focussed on the synthesis and host properties of four different broad categories of potential host compounds, namely optically active and racemic TADDOL [(4R,5R)-α,α,α’,α’-tetraphenyl-1,3-dioxolane-4,5-dimethanol] and derivatives, TTFOL [(3R,4R)-2,2,5,5-tetraphenyltetrahydrofuran-3,4-diol], amino acid ester-derived compounds [(S)-4-(2-amino-3-hydroxy-3,3-diphenylpropyl)phenol], and compounds derived from xanthone [9-amino-9-phenylxanthene and 1,2-bis(9-phenyl-9H-xanthen-9-yl)hydrazine]. The potential hosts were recrystallized from a range of possible guest species and the resulting solids analysed by 1H-NMR spectroscopy. If inclusion was observed by this technique, the complexes were analysed further using single crystal X-ray techniques and thermal experiments where possible. Competition studies were carried out where these were deemed appropriate. Optically active and racemic TADDOLs were synthesized using L-(+) and DL-(±)-tartaric acid respectively. Two further derivatives were prepared whereby the hydroxyl groups were substituted for chlorine and azide in order to assess the effect of this change on the inclusion ability. Both the optically active and racemic TADDOLs displayed similar host abilities, complexing with guests with 1:1 host:guest ratios as determined through 1H-NMR spectroscopy. Competition experiments showed that both forms of TADDOL exhibited similar guest preferences for pyridine and the methylpyridine isomers. Pyridine however was preferred over 2-methylpyridine by optically active TADDOL while the racemic form preferred this methyl-substituted guest over pyridine. Thermal analysis studies showed, surprisingly, that the TADDOL complexes containing pyridine had higher relative thermal stabilities than those containing the methylpyridines, whether the host was optically active or not. The preference order of these hosts for these guests can, therefore, not be used as a predictor for the relative thermal stability of the complexes. TTFOL was found to include only ethanol, 2-methylpyridine and dioxane from the range of guest species used; the complex with dioxane did not produce X-ray quality crystals. The L-tyrosine derivative, (S)-4-(2-amino-3-hydroxy-3,3-diphenylpropyl)phenol, was an ineffective host incapable of including any of the guests used in these experiments. The two xanthone derivatives, 9-amino-9-phenylxanthene and 1,2-bis(9-phenyl-9H-xanthen-9-yl)hydrazine each formed complexes with one guest species (morpholine and DMF, respectively).
- Full Text:
- Date Issued: 2017
Synthesis and characterisation of lanthanide complexes with O,O-donor ligands: towards a new generation of hydrophosphonylation catalysts
- Authors: Mkwakwi, Kwakhanya
- Date: 2017
- Subjects: Rare earth metals Catalysts
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/11986 , vital:27016
- Description: This study investigates the coordination behaviour of potentially bi- and tridentate O,O- and O,N,O-donor Schiff base ligands with trivalent lanthanide ions. The reactions of lanthanide nitrates with 2-((E)-(tert-butylimino)methyl)-6-methoxyphenol (HL1) have yielded five complexes that are described by the general formula [Ln(HL1)2(NO3)3] (Ln = Ce, Nd, Gd, Ho and Er) and were characterised using physico-chemical techniques including single-crystal X-ray diffraction spectroscopy. The cerium complex crystallised in a triclinic (P-1) space group, while the rest of the complexes crystallised in the monoclinic (P21/c) space group. All the complexes are ten-coordinate adopting a tetradecahedron geometry with two HL1 molecules coordinated through the phenolic and methoxy oxygen atoms. The coordination sphere is completed by six oxygen atoms from three bidentately coordinated nitrate ligands. Electronic data reveals that only the neodymium, holmium and erbium complexes exhibit weak f-f transitions in the visible region. The redox behaviour of the complexes was also investigated and reported. Five novel complexes were prepared by reacting 2-((E)-(tert-butylimino)methyl)phenol (HL2) with [Ln(NO3)3∙xH2O] (Ln = Gd and Dy ; x = 5 or 6) and [LnCl3∙6H2O] (Ln = Nd, Gd and Dy). The crystal structures of the former two complexes are isostructural and the coordination sphere is composed of three HL2 ligands bonded to the metal centre through the phenolic oxygen atom and three nitrate ions coordinated in a bidentate fashion. Both complexes are nine-coordinate and SHAPE analysis reveals that they adopted a muffin geometry. The average Ln-Onitrate and Ln-Ophenolate bond lengths are 2.5078 and 2.2814 Å, respectively. The complexes derived from the chloride salts exhibited an octahedral geometry with four monodentate ligands [Ln-Ophenolate distances range from 2.224(4) to 2.2797(17) Å] coordinating in the equatorial positions and two chloride ions [average Ln-Cl bond length is 2.6527 Å, and average Cl-Ln-Cl angles is 180o] in axial positions. The ligand coordinated through the phenolic oxygen with the phenolic proton migrating to the imino nitrogen to give a zwitterionic form of the ligand. There are weak C-H∙∙∙Cl interactions present and O-H∙∙∙N hydrogen bonds are also observed in the crystal packing. The synthesis of lanthanide complexes with methoxy-6-((E)-(phenylimino)methyl)phenol (HL3) was carried out in methanol to yield two mononuclear complexes with the formulae [Nd(HL3)2(NO3)3] and [Ho(HL3)(NO3)3(DMF)(H2O)]. Single-crystal crystallographic studies shows that the neodymium complex contains two HL3 ligands coordinated bidentately through its methoxide and phenolic oxygen atoms, with three nitrate ions also bonded to the metal in a bidentate manner. The coordination geometry in the holmium complex is composed of only oxygen atoms from the various ligands. Both complexes are ten-coordinate and exhibit a tetradecahedron geometry.
- Full Text:
- Date Issued: 2017
- Authors: Mkwakwi, Kwakhanya
- Date: 2017
- Subjects: Rare earth metals Catalysts
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/11986 , vital:27016
- Description: This study investigates the coordination behaviour of potentially bi- and tridentate O,O- and O,N,O-donor Schiff base ligands with trivalent lanthanide ions. The reactions of lanthanide nitrates with 2-((E)-(tert-butylimino)methyl)-6-methoxyphenol (HL1) have yielded five complexes that are described by the general formula [Ln(HL1)2(NO3)3] (Ln = Ce, Nd, Gd, Ho and Er) and were characterised using physico-chemical techniques including single-crystal X-ray diffraction spectroscopy. The cerium complex crystallised in a triclinic (P-1) space group, while the rest of the complexes crystallised in the monoclinic (P21/c) space group. All the complexes are ten-coordinate adopting a tetradecahedron geometry with two HL1 molecules coordinated through the phenolic and methoxy oxygen atoms. The coordination sphere is completed by six oxygen atoms from three bidentately coordinated nitrate ligands. Electronic data reveals that only the neodymium, holmium and erbium complexes exhibit weak f-f transitions in the visible region. The redox behaviour of the complexes was also investigated and reported. Five novel complexes were prepared by reacting 2-((E)-(tert-butylimino)methyl)phenol (HL2) with [Ln(NO3)3∙xH2O] (Ln = Gd and Dy ; x = 5 or 6) and [LnCl3∙6H2O] (Ln = Nd, Gd and Dy). The crystal structures of the former two complexes are isostructural and the coordination sphere is composed of three HL2 ligands bonded to the metal centre through the phenolic oxygen atom and three nitrate ions coordinated in a bidentate fashion. Both complexes are nine-coordinate and SHAPE analysis reveals that they adopted a muffin geometry. The average Ln-Onitrate and Ln-Ophenolate bond lengths are 2.5078 and 2.2814 Å, respectively. The complexes derived from the chloride salts exhibited an octahedral geometry with four monodentate ligands [Ln-Ophenolate distances range from 2.224(4) to 2.2797(17) Å] coordinating in the equatorial positions and two chloride ions [average Ln-Cl bond length is 2.6527 Å, and average Cl-Ln-Cl angles is 180o] in axial positions. The ligand coordinated through the phenolic oxygen with the phenolic proton migrating to the imino nitrogen to give a zwitterionic form of the ligand. There are weak C-H∙∙∙Cl interactions present and O-H∙∙∙N hydrogen bonds are also observed in the crystal packing. The synthesis of lanthanide complexes with methoxy-6-((E)-(phenylimino)methyl)phenol (HL3) was carried out in methanol to yield two mononuclear complexes with the formulae [Nd(HL3)2(NO3)3] and [Ho(HL3)(NO3)3(DMF)(H2O)]. Single-crystal crystallographic studies shows that the neodymium complex contains two HL3 ligands coordinated bidentately through its methoxide and phenolic oxygen atoms, with three nitrate ions also bonded to the metal in a bidentate manner. The coordination geometry in the holmium complex is composed of only oxygen atoms from the various ligands. Both complexes are ten-coordinate and exhibit a tetradecahedron geometry.
- Full Text:
- Date Issued: 2017
Electrostatic discharge and roughness modelling in diamond turning of contact lenses
- Authors: Kopi, Fundiswa
- Date: 2017
- Subjects: Diamond turning Contact lenses
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/18783 , vital:28723
- Description: With the increased application of ultra-high precision machining of polymers and the limited research in single point diamond turning (SPDT) of contact lens polymers, it became imperative to gather understanding on the production of contact lenses using the above-mentioned technology. A limiting factor in SPDT of polymers is wear of the diamond tool, resulting into poor surface finish due to unintended charges generated as a result of the contact/rubbing action between the cutting tool and the cut material. Central Composite Design (CCD) Face Centred experimental design was developed and applied to the SPDT of ONSI-56 and Polymethly methacrylate (PMMA) contact lens buttons. An electrostatic sensor coupled to a computer monitored the electrostatic discharge generated and a profilometer measured the surface roughness. The Response Surface Method (RSM) was utilised during the development of predictive models for both the surface roughness and the electrostatic discharge generated, to deduce the effects of cutting parameters during machining. The cutting speed and the feed rate deemed as the influential parameters on the surface roughness and electrostatic discharge, for both materials. The depth of cut induced more charge generation for PMMA. Predictive models were successfully developed and they were aimed at creating a database a guide to the SPDT of contact lens polymers.
- Full Text:
- Date Issued: 2017
- Authors: Kopi, Fundiswa
- Date: 2017
- Subjects: Diamond turning Contact lenses
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/18783 , vital:28723
- Description: With the increased application of ultra-high precision machining of polymers and the limited research in single point diamond turning (SPDT) of contact lens polymers, it became imperative to gather understanding on the production of contact lenses using the above-mentioned technology. A limiting factor in SPDT of polymers is wear of the diamond tool, resulting into poor surface finish due to unintended charges generated as a result of the contact/rubbing action between the cutting tool and the cut material. Central Composite Design (CCD) Face Centred experimental design was developed and applied to the SPDT of ONSI-56 and Polymethly methacrylate (PMMA) contact lens buttons. An electrostatic sensor coupled to a computer monitored the electrostatic discharge generated and a profilometer measured the surface roughness. The Response Surface Method (RSM) was utilised during the development of predictive models for both the surface roughness and the electrostatic discharge generated, to deduce the effects of cutting parameters during machining. The cutting speed and the feed rate deemed as the influential parameters on the surface roughness and electrostatic discharge, for both materials. The depth of cut induced more charge generation for PMMA. Predictive models were successfully developed and they were aimed at creating a database a guide to the SPDT of contact lens polymers.
- Full Text:
- Date Issued: 2017
Statistical modelling applied to perceptions of fraud
- Authors: Mnci, Mihlali
- Date: 2017
- Subjects: Mathematical statistics Statistics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/41064 , vital:36288
- Description: This study aims to investigate and identify attitudes, behaviours and perceptions harboured by bank cardholders and merchants, which are associated with a higher susceptibility towards experiencing bank card fraud. Primary data was obtained from bank cardholders and merchants, from various business categories, in both the Nelson Mandela Bay Metropolitan Municipality and the City of Johannesburg Metropolitan Municipality. Following the use of parametric Multinomial Logistic Regression (MLR) and nonparametric conditional density estimation to analyse the data, the results are compared and relevant covariates/perceptions are determined from the more accurate of the two techniques. The results of the analysed survey data serve as a tool, highlighting areas which require further education and awareness on the part of merchants and bank clients.
- Full Text:
- Date Issued: 2017
- Authors: Mnci, Mihlali
- Date: 2017
- Subjects: Mathematical statistics Statistics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/41064 , vital:36288
- Description: This study aims to investigate and identify attitudes, behaviours and perceptions harboured by bank cardholders and merchants, which are associated with a higher susceptibility towards experiencing bank card fraud. Primary data was obtained from bank cardholders and merchants, from various business categories, in both the Nelson Mandela Bay Metropolitan Municipality and the City of Johannesburg Metropolitan Municipality. Following the use of parametric Multinomial Logistic Regression (MLR) and nonparametric conditional density estimation to analyse the data, the results are compared and relevant covariates/perceptions are determined from the more accurate of the two techniques. The results of the analysed survey data serve as a tool, highlighting areas which require further education and awareness on the part of merchants and bank clients.
- Full Text:
- Date Issued: 2017
Optical fibre measurement for clock tones in telescope networks
- Authors: Dlamini, Phumla Patience
- Date: 2017
- Subjects: Fiber optics Very large array telescopes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/22200 , vital:29872
- Description: Astronomy dates back to the early man’s impression of the heavens with little information recorded including some drawings of comets, eclipse and supernovas[1]. Major progress has been made in the field of Astronomy since then. Scientific curiosity to probe the universe in attempt to answer questions such as the origin of the universe, the matter it is made of, the formation of stars, planets and galaxies, and tracking life in other solar systems has brought about the need for more advanced tools capable of detailed observations. In 1608 H. Lippershey developed the first refracting telescope[2], [3]. A year later Galileo used a similar telescope pointing skywards discovering mountains and craters on the earth’s moon, the moons of Jupiter and the phases of Venus. Over the years telescopes have been developed with advancements from the optical telescope towards much larger and more sensitive radio telescopes. The first radio signal from space was detected by Karl Jansky and ever since then astronomers have been using radio telescopes to explore the universe by detecting radio waves emitted by cosmic objects[4]. The ability of radio telescopes to detect weak signals is related to the signal capture surface. As the demand for sensitivity, transmission bandwidth and data rate increases, so does the need for telescopes with a large field of view and capability to observe different parts of the sky at once[5]. This is possible with radio telescope array, with the data from the antennas combined electronically to produce a high resolution image of the sky. The South African MeerKAT radio telescope is an array of 64 interlinked antennas each transmitting up to 160 Gbps of data to the central processing site over optical fibre which is ideal for carrying large volumes of data at high speeds. The MeerKAT telescope is a precursor to the Square kilometer Array which will have up to 50 times the sensitivity and 10000 times the survey speed than the best telescope[6].
- Full Text:
- Date Issued: 2017
- Authors: Dlamini, Phumla Patience
- Date: 2017
- Subjects: Fiber optics Very large array telescopes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/22200 , vital:29872
- Description: Astronomy dates back to the early man’s impression of the heavens with little information recorded including some drawings of comets, eclipse and supernovas[1]. Major progress has been made in the field of Astronomy since then. Scientific curiosity to probe the universe in attempt to answer questions such as the origin of the universe, the matter it is made of, the formation of stars, planets and galaxies, and tracking life in other solar systems has brought about the need for more advanced tools capable of detailed observations. In 1608 H. Lippershey developed the first refracting telescope[2], [3]. A year later Galileo used a similar telescope pointing skywards discovering mountains and craters on the earth’s moon, the moons of Jupiter and the phases of Venus. Over the years telescopes have been developed with advancements from the optical telescope towards much larger and more sensitive radio telescopes. The first radio signal from space was detected by Karl Jansky and ever since then astronomers have been using radio telescopes to explore the universe by detecting radio waves emitted by cosmic objects[4]. The ability of radio telescopes to detect weak signals is related to the signal capture surface. As the demand for sensitivity, transmission bandwidth and data rate increases, so does the need for telescopes with a large field of view and capability to observe different parts of the sky at once[5]. This is possible with radio telescope array, with the data from the antennas combined electronically to produce a high resolution image of the sky. The South African MeerKAT radio telescope is an array of 64 interlinked antennas each transmitting up to 160 Gbps of data to the central processing site over optical fibre which is ideal for carrying large volumes of data at high speeds. The MeerKAT telescope is a precursor to the Square kilometer Array which will have up to 50 times the sensitivity and 10000 times the survey speed than the best telescope[6].
- Full Text:
- Date Issued: 2017
The effect of synthetically-derived xanthone compounds on the suppression of the progression of breast cancer and the associated complications
- Authors: Davison, Candace
- Date: 2017
- Subjects: Breast -- Cancer -- Chemotherapy Breast -- Cancer -- Prevention , Antibacterial agents -- Therapeutic use
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/13889 , vital:27354
- Description: Breast cancer is the most frequently diagnosed cancer in women worldwide.A treatment regime, both effective and safe and can only be achieved once more effective chemotherapeutic agents are discovered or identified. These “drugs” must selectively induce cell death such as apoptosis or necroptosis in the cancer cells. Apoptotic cell death allows a cell to “commit suicide” in genetically- controlled or programmed mechanism(s). The microenvironment of the tumour is important since a nurturing malignant environment is required for tumour maintenance, progression and ultimately the development of metastasis. Due to the correlation of the tumour microenvironment to aggressive tumour progression, emphasis should be placed on the constituents of the tumour’s microenvironment. In recent years, the understanding of intracellular pathways in cancer cells has increased rapidly, contributing to the development of drugs with more specific targets such as growth factors, signalling molecules, cell adhesion proteins, proteases, cell-cycle proteins, modulators of apoptosis and molecules that promote angiogenesis and metastasis. The main aim of this study was thus to identify a few potential or active compounds from a library of synthetically-derived compounds as possible alternative breast cancer treatment candidates.
- Full Text:
- Date Issued: 2017
- Authors: Davison, Candace
- Date: 2017
- Subjects: Breast -- Cancer -- Chemotherapy Breast -- Cancer -- Prevention , Antibacterial agents -- Therapeutic use
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/13889 , vital:27354
- Description: Breast cancer is the most frequently diagnosed cancer in women worldwide.A treatment regime, both effective and safe and can only be achieved once more effective chemotherapeutic agents are discovered or identified. These “drugs” must selectively induce cell death such as apoptosis or necroptosis in the cancer cells. Apoptotic cell death allows a cell to “commit suicide” in genetically- controlled or programmed mechanism(s). The microenvironment of the tumour is important since a nurturing malignant environment is required for tumour maintenance, progression and ultimately the development of metastasis. Due to the correlation of the tumour microenvironment to aggressive tumour progression, emphasis should be placed on the constituents of the tumour’s microenvironment. In recent years, the understanding of intracellular pathways in cancer cells has increased rapidly, contributing to the development of drugs with more specific targets such as growth factors, signalling molecules, cell adhesion proteins, proteases, cell-cycle proteins, modulators of apoptosis and molecules that promote angiogenesis and metastasis. The main aim of this study was thus to identify a few potential or active compounds from a library of synthetically-derived compounds as possible alternative breast cancer treatment candidates.
- Full Text:
- Date Issued: 2017
A new synthetic approach for preparation of Efavirenz
- Authors: Chada, Sravanthi
- Date: 2017
- Subjects: Antiretroviral agents , Asymmetric synthesis , Enzyme inhibitors , HIV (Viruses) -- Enzymes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/15512 , vital:28265
- Description: Efavirenz, a drug that is still inaccessible to millions of people worldwide, is potent non nucleoside reverse transcriptase inhibitor (NNRTI), is one of the preferred agents used in combination therapy for first-line treatment of the human immunodeficiency virus (HIV). NNRTIs attach to and block an HIV enzyme called reverse transcriptase, by blocking reverse transcriptase; NNRTIs prevent HIV from multiplying and can reduce the amount of HIV in the body. Efavirenz can't cure HIV/AIDS, but taken in combination with other HIV medicines (called an HIV regimen) every day helps people with HIV live longer healthier lives. Efavirenz also reduces the risk of HIV transmission and can be used by children who are suffering from HIV/AIDS. All the above therapeutic uses of efavirenz prompted us to identify the novel and hopefully cost efficient synthetic methodology for the preparation of efavirenz. In this thesis a new synthetic method for asymmetric synthesis of efavirenz is described. This route started from commercially available starting materials and it is first established in traditional batch chemistry and further the parameters transferred to a semi continuous flow protocol for optimization.
- Full Text:
- Date Issued: 2017
- Authors: Chada, Sravanthi
- Date: 2017
- Subjects: Antiretroviral agents , Asymmetric synthesis , Enzyme inhibitors , HIV (Viruses) -- Enzymes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/15512 , vital:28265
- Description: Efavirenz, a drug that is still inaccessible to millions of people worldwide, is potent non nucleoside reverse transcriptase inhibitor (NNRTI), is one of the preferred agents used in combination therapy for first-line treatment of the human immunodeficiency virus (HIV). NNRTIs attach to and block an HIV enzyme called reverse transcriptase, by blocking reverse transcriptase; NNRTIs prevent HIV from multiplying and can reduce the amount of HIV in the body. Efavirenz can't cure HIV/AIDS, but taken in combination with other HIV medicines (called an HIV regimen) every day helps people with HIV live longer healthier lives. Efavirenz also reduces the risk of HIV transmission and can be used by children who are suffering from HIV/AIDS. All the above therapeutic uses of efavirenz prompted us to identify the novel and hopefully cost efficient synthetic methodology for the preparation of efavirenz. In this thesis a new synthetic method for asymmetric synthesis of efavirenz is described. This route started from commercially available starting materials and it is first established in traditional batch chemistry and further the parameters transferred to a semi continuous flow protocol for optimization.
- Full Text:
- Date Issued: 2017
Agribusiness challenges to effectiveness of contract farming in commercialisation of small-scale vegetable farmers
- Authors: Khapayi, Musa
- Date: 2017
- Subjects: Farms, Small -- South Africa -- Eastern Cape , Agriculture -- Economic aspects -- South Africa -- Eastern Cape , Agricultural industries -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: http://hdl.handle.net/10948/13981 , vital:27363
- Description: The spread of contract farming in South Africa in recent years has provoked an ideological debate in literature. Linking small-scale vegetable farmers with lucrative agricultural markets through agribusiness value chains is seen as one of the foremost emerging agricultural practices to develop the subsistence farming sector into a mainstream economic sector – thereby revitalising the rural economy and alleviating poverty levels in the developing rural areas of South Africa. However, the challenges agribusiness and small-scale farmers experience in contract farming engagement and the prospects for enhancing the inclusion of small-scale farmers into modern value chains remain open to debate – two decades after transition to democracy. Yet the factors and mechanisms influencing the effective application of contract farming in the transition to commercial farming by small-scale farmers have not been thoroughly explored in South African research. Despite the efforts and the substantial investments made and the various policies and initiatives instigated to fast-track the linkages of small-scale farmers into high-value markets, the success stories of previously disadvantaged farmers operating in commercial agri-food chains are rare. Given the millions of small-scale farmers in former homelands alone, the negligible number of small-scale farmers successfully operating in commercial agri-food chains shows that the objectives to enable small-scale farmers to improve their livelihoods through participation in commercial agri-food chains have not yet been met. The broad objectives of the study were therefore to investigate the agribusiness challenges inherent in contract farming and the conditions and incentives required by agribusiness firms to engage small-scale vegetable farmers in contract farming programmes. Furthermore, the study examined the role played by the South African government to reduce the high transaction costs incurred by agribusinesses when engaging small-scale farmers in contractual arrangements. The Amathole and Sarah Baartman (formerly Cacadu) district municipalities in the Eastern Cape Province of South Africa were chosen as the composite survey area for this study. A predominantly qualitative research approach was applied to gather data on the phenomena under study. The following methodologies and research instruments and tools were selected. Firstly – as the secondary component of the research – a systematic review of literature to date was conducted to guide the empirical research and primary methodology. Secondly, the empirical component of the study comprised a questionnaire survey, unstructured interviews and focus group discussions. The questionnaire survey was used to collect data from the agribusiness firms in the area surveyed concerning the following aspects: the significant determinants of contract farming, the incentives required by the agribusiness firms to engage small-scale vegetable farmers in their contract farming programmes and the challenges faced by agribusiness firms in their interaction with small-scale farmers in contractual arrangements. Unstructured interviews were used to gather data from officials at each of the three levels of government – the Department of Rural Development and Land Reform nationally, Department of Agriculture and Land Reform provincially and (at local government level) two district municipalities – on the role played by government to reduce the high transaction costs incurred by agri-firms when procuring agricultural raw materials from small-scale vegetable farmers. Focus group discussions were conducted with small-scale farmers regarding their perspective on working with agribusiness firms and to establish the distinguishing characteristics of small-scale farmers in the area surveyed. Relevant policy documents collected from two of the three representative groups of the study population, i.e. agribusiness personnel and government officials, provided the essential context. The study revealed a limited number of contract farming business linkages between small-scale vegetable farmers and agribusiness firms in the survey area. Those that do exist are problematic to both the agribusiness firms and the small-scale farmers. It emerged that the contract farming environment in the area surveyed is highly polarised and characterised by a fundamental conflict of interest between agribusiness and farmer. Among the divergent key factors inhibiting contract farming engagement were a lack in terms of quality seeds, trust, entrepreneurial skills and formal contract agreements. Asset endowment (both land and non-land assets) was found to be significant pre-selection determinants in the farmer’s capacity to be contracted. Access to innovative technology, as well as government incentives such as production inputs, were found to be critical to agribusiness firms to engage smallscale farmers in their contract farming programmes. Government assistance in terms of high transaction costs to agribusiness firms working with large groups of small-scale farmers was found to be essential but inadequate under current policy. This impacts directly on the effectiveness and promotion of contract farming. Furthermore, the current results corroborate the findings of numerous South African studies in the vast body of worldwide research. Firstly, lack of land and non-land assets continue to be major impediments to the direct participa-tion of small-scale farmers in contract farming programmes and, secondly, the transaction and market information costs incurred by agribusiness prevent the participation of less endowed farmers in contract farming programmes. Conducted within the interpretivist paradigm, the explorative research identified wide-ranging challenges in the relationship between agri-business and small-scale farmers which directly impact the effective-ness of contract farming as a development and agrarian reform strategy. Despite their problematic relationship, however, agribusiness and small-scale contract farmers were in agreement that the government needs to expand its support for agri-firms to incentivise greater numbers of small-scale farmers having the opportunity to achieve commercial status through contract farming. The study therefore recommends a collaborative partnership between private firms and government, with state support through revised policies and development programmes. These amendments are crucial to enhancing the engagement of small-scale vegetable farmers in lucrative agri-food chains.
- Full Text:
- Date Issued: 2017
- Authors: Khapayi, Musa
- Date: 2017
- Subjects: Farms, Small -- South Africa -- Eastern Cape , Agriculture -- Economic aspects -- South Africa -- Eastern Cape , Agricultural industries -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: http://hdl.handle.net/10948/13981 , vital:27363
- Description: The spread of contract farming in South Africa in recent years has provoked an ideological debate in literature. Linking small-scale vegetable farmers with lucrative agricultural markets through agribusiness value chains is seen as one of the foremost emerging agricultural practices to develop the subsistence farming sector into a mainstream economic sector – thereby revitalising the rural economy and alleviating poverty levels in the developing rural areas of South Africa. However, the challenges agribusiness and small-scale farmers experience in contract farming engagement and the prospects for enhancing the inclusion of small-scale farmers into modern value chains remain open to debate – two decades after transition to democracy. Yet the factors and mechanisms influencing the effective application of contract farming in the transition to commercial farming by small-scale farmers have not been thoroughly explored in South African research. Despite the efforts and the substantial investments made and the various policies and initiatives instigated to fast-track the linkages of small-scale farmers into high-value markets, the success stories of previously disadvantaged farmers operating in commercial agri-food chains are rare. Given the millions of small-scale farmers in former homelands alone, the negligible number of small-scale farmers successfully operating in commercial agri-food chains shows that the objectives to enable small-scale farmers to improve their livelihoods through participation in commercial agri-food chains have not yet been met. The broad objectives of the study were therefore to investigate the agribusiness challenges inherent in contract farming and the conditions and incentives required by agribusiness firms to engage small-scale vegetable farmers in contract farming programmes. Furthermore, the study examined the role played by the South African government to reduce the high transaction costs incurred by agribusinesses when engaging small-scale farmers in contractual arrangements. The Amathole and Sarah Baartman (formerly Cacadu) district municipalities in the Eastern Cape Province of South Africa were chosen as the composite survey area for this study. A predominantly qualitative research approach was applied to gather data on the phenomena under study. The following methodologies and research instruments and tools were selected. Firstly – as the secondary component of the research – a systematic review of literature to date was conducted to guide the empirical research and primary methodology. Secondly, the empirical component of the study comprised a questionnaire survey, unstructured interviews and focus group discussions. The questionnaire survey was used to collect data from the agribusiness firms in the area surveyed concerning the following aspects: the significant determinants of contract farming, the incentives required by the agribusiness firms to engage small-scale vegetable farmers in their contract farming programmes and the challenges faced by agribusiness firms in their interaction with small-scale farmers in contractual arrangements. Unstructured interviews were used to gather data from officials at each of the three levels of government – the Department of Rural Development and Land Reform nationally, Department of Agriculture and Land Reform provincially and (at local government level) two district municipalities – on the role played by government to reduce the high transaction costs incurred by agri-firms when procuring agricultural raw materials from small-scale vegetable farmers. Focus group discussions were conducted with small-scale farmers regarding their perspective on working with agribusiness firms and to establish the distinguishing characteristics of small-scale farmers in the area surveyed. Relevant policy documents collected from two of the three representative groups of the study population, i.e. agribusiness personnel and government officials, provided the essential context. The study revealed a limited number of contract farming business linkages between small-scale vegetable farmers and agribusiness firms in the survey area. Those that do exist are problematic to both the agribusiness firms and the small-scale farmers. It emerged that the contract farming environment in the area surveyed is highly polarised and characterised by a fundamental conflict of interest between agribusiness and farmer. Among the divergent key factors inhibiting contract farming engagement were a lack in terms of quality seeds, trust, entrepreneurial skills and formal contract agreements. Asset endowment (both land and non-land assets) was found to be significant pre-selection determinants in the farmer’s capacity to be contracted. Access to innovative technology, as well as government incentives such as production inputs, were found to be critical to agribusiness firms to engage smallscale farmers in their contract farming programmes. Government assistance in terms of high transaction costs to agribusiness firms working with large groups of small-scale farmers was found to be essential but inadequate under current policy. This impacts directly on the effectiveness and promotion of contract farming. Furthermore, the current results corroborate the findings of numerous South African studies in the vast body of worldwide research. Firstly, lack of land and non-land assets continue to be major impediments to the direct participa-tion of small-scale farmers in contract farming programmes and, secondly, the transaction and market information costs incurred by agribusiness prevent the participation of less endowed farmers in contract farming programmes. Conducted within the interpretivist paradigm, the explorative research identified wide-ranging challenges in the relationship between agri-business and small-scale farmers which directly impact the effective-ness of contract farming as a development and agrarian reform strategy. Despite their problematic relationship, however, agribusiness and small-scale contract farmers were in agreement that the government needs to expand its support for agri-firms to incentivise greater numbers of small-scale farmers having the opportunity to achieve commercial status through contract farming. The study therefore recommends a collaborative partnership between private firms and government, with state support through revised policies and development programmes. These amendments are crucial to enhancing the engagement of small-scale vegetable farmers in lucrative agri-food chains.
- Full Text:
- Date Issued: 2017
Ant colony optimisation-based algorithms for optical burst switching networks
- Gravett, Andrew Scott, Gibbon, Timothy B
- Authors: Gravett, Andrew Scott , Gibbon, Timothy B
- Date: 2017
- Subjects: Distributed algorithms , Ants -- Behavior -- Mathematical models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/18939 , vital:28757
- Description: This research developed two novel distributed algorithms inspired by Ant Colony Optimisation (ACO) for a solution to the problem of dynamic Routing and Wavelength Assignment (RWA) with wavelength continuity constraint in Optical Burst Switching (OBS) networks utilising both the traditional International Telecommunication Union (ITU) Fixed Grid Wavelength Division Multiplexing (WDM) and Flexible Spectrum scenarios. The growing demand for more bandwidth in optical networks require more efficient utilisation of available optical resources. OBS is a promising optical switching technique for the improved utilisation of optical network resources over the current optical circuit switching technique. The development of newer technologies has introduced higher rate transmissions and various modulation formats, however, introducing these technologies into the traditional ITU Fixed Grid does not efficiently utilise the available bandwidth. Flexible Spectrum is a promising approach offering a solution to the problem of improving bandwidth utilisation, which comes with a potential cost. Transmissions have the potential for impairment with respect to the increased traffic and lack of large channel spacing. Proposed routing algorithms should be aware of the linear and non-linear Physical Layer Impairments (PLIs) in order to operate closer to optimum performance. The OBS resource reservation protocol does not cater for the loss of transmissions, Burst Control Packets (BCPs) included, due to physical layer impairments. The protocol was adapted for use in Flexible Spectrum. Investigation of the use of a route and wavelength combination, from source to destination node pair, for the RWA process was proposed for ACO-based approaches to enforce the establishment and use of complete paths for greedy exploitation in Flexible Spectrum was conducted. The routing tuple for the RWA process is the tight coupling of a route and wavelength in combination intended to promote the greedy exploitation of successful paths for transmission requests. The application of the routing tuples differs from traditional ACO-based approaches and prompted the investigation of new pheromone calculation equations. The two novel proposed approaches were tested and experiments conducted comparing with and against existing algorithms (a simple greedy and an ACO-based algorithm) in a traditional ITU Fixed Grid and Flexible Spectrum scenario on three different network topologies. The proposed Flexible Spectrum Ant Colony (FSAC) approach had a markably improved performance over the existing algorithms in the ITU Fixed Grid WDM and Flexible Spectrum scenarios, while Upper Confidence Bound Routing and Wavelength Assignment (UCBRWA) algorithm was able to perform well in the traditional ITU Fixed Grid WDM scenario, but underperformed in the Flexible Spectrum scenario. The results show that the distributed ACO-based FSAC algorithm significantly improved the burst transmission success probability, providing a good solution in the Flexible Spectrum network environment undergoing transmission impairments.
- Full Text:
- Date Issued: 2017
- Authors: Gravett, Andrew Scott , Gibbon, Timothy B
- Date: 2017
- Subjects: Distributed algorithms , Ants -- Behavior -- Mathematical models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/18939 , vital:28757
- Description: This research developed two novel distributed algorithms inspired by Ant Colony Optimisation (ACO) for a solution to the problem of dynamic Routing and Wavelength Assignment (RWA) with wavelength continuity constraint in Optical Burst Switching (OBS) networks utilising both the traditional International Telecommunication Union (ITU) Fixed Grid Wavelength Division Multiplexing (WDM) and Flexible Spectrum scenarios. The growing demand for more bandwidth in optical networks require more efficient utilisation of available optical resources. OBS is a promising optical switching technique for the improved utilisation of optical network resources over the current optical circuit switching technique. The development of newer technologies has introduced higher rate transmissions and various modulation formats, however, introducing these technologies into the traditional ITU Fixed Grid does not efficiently utilise the available bandwidth. Flexible Spectrum is a promising approach offering a solution to the problem of improving bandwidth utilisation, which comes with a potential cost. Transmissions have the potential for impairment with respect to the increased traffic and lack of large channel spacing. Proposed routing algorithms should be aware of the linear and non-linear Physical Layer Impairments (PLIs) in order to operate closer to optimum performance. The OBS resource reservation protocol does not cater for the loss of transmissions, Burst Control Packets (BCPs) included, due to physical layer impairments. The protocol was adapted for use in Flexible Spectrum. Investigation of the use of a route and wavelength combination, from source to destination node pair, for the RWA process was proposed for ACO-based approaches to enforce the establishment and use of complete paths for greedy exploitation in Flexible Spectrum was conducted. The routing tuple for the RWA process is the tight coupling of a route and wavelength in combination intended to promote the greedy exploitation of successful paths for transmission requests. The application of the routing tuples differs from traditional ACO-based approaches and prompted the investigation of new pheromone calculation equations. The two novel proposed approaches were tested and experiments conducted comparing with and against existing algorithms (a simple greedy and an ACO-based algorithm) in a traditional ITU Fixed Grid and Flexible Spectrum scenario on three different network topologies. The proposed Flexible Spectrum Ant Colony (FSAC) approach had a markably improved performance over the existing algorithms in the ITU Fixed Grid WDM and Flexible Spectrum scenarios, while Upper Confidence Bound Routing and Wavelength Assignment (UCBRWA) algorithm was able to perform well in the traditional ITU Fixed Grid WDM scenario, but underperformed in the Flexible Spectrum scenario. The results show that the distributed ACO-based FSAC algorithm significantly improved the burst transmission success probability, providing a good solution in the Flexible Spectrum network environment undergoing transmission impairments.
- Full Text:
- Date Issued: 2017
Evaluation of near infrared reflectance (NIR) spectroscopy to determine the nutrient composition of raw materials and compound ostrich feeds
- Swart, Etheresia, Lehmann-Maritz, Maryna
- Authors: Swart, Etheresia , Lehmann-Maritz, Maryna
- Date: 2017
- Subjects: Near infrared spectroscopy , Animal nutrition , Animal feeding
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/13779 , vital:27307
- Description: The chemical analysis of feed samples can be time consuming and expensive. The use of near infrared reflectance (NIR) spectroscopy was evaluated in a range of studies as a rapid technique to predict the chemical constituents in feedstuffs and compound ostrich feeds. The prediction of accurate results by NIR spectroscopy relies heavily upon obtaining a calibration set which represents the variation in the main population, accurate laboratory analyses and the application of the best mathematical procedures. This research project was designed to meet five objectives: The first objective was to determine the feasibility of using near infrared reflectance (NIR) spectroscopy to predict dry matter, ash, crude protein, crude fibre, oil content, and fatty acids such as palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1) and linoleic acid (C18:2) in sunflower seed meal. The second objective was to develop calibration models to predict the dry matter, crude protein and oil content in milled canola seed, compared to whole canola seeds. The third objective was to investigate the feasibility of using NIR spectroscopy to predict the dry matter, ash, crude protein, crude fibre and oil content in milled lupin seeds, compared to whole lupin seeds. The fourth objective was to describe the development of near infrared reflectance (NIR) spectroscopy calibration equations for the prediction of chemical composition and amino acid content from different populations of alfalfa hay (Medicago sativa L.). The last objective was to determine the potential of NIR spectroscopy to predict the dry matter, ash, crude protein, crude fibre, ether extract, acid detergent fibre (ADF), neutral detergent fibre (NDF), calcium, phosphorus, in vitro organic matter digestibility (IVOMD) and amino acids such as lysine, methionine, threonine and arginine in compound ostrich feed samples. The results of this study indicate that NIR spectroscopy calibrations in sunflower seed meal are only applicable in sunflower breeding programmes for a fast screening as it was not suitable for prediction purposes. Screening of sunflower seeds by NIR spectroscopy represents a rapid, simple and cost effective alternative that is a great utility for users who need to analyse a large number of samples. Calibrations developed for crude protein and oil content in milled canola seeds proved to be better than calibrations for whole canola seeds. Although the results indicated that calibrations were better for milled canola seeds, it indicated values that were typical of equations suitable for screening purposes to select samples for more detailed chemical analysis. According to calibration statistics obtained for crude protein, crude fibre and oil content in whole lupin seeds, there is no need to grind the seeds to scan the meal as similarly accurate results were obtained by analysing whole seeds. Screening of whole lupin seeds by NIR spectroscopy represents a rapid, simple and cost effective alternative that may be of great utility for users who need to analyse a large number of samples with no sample preparation. The calibration and validation statistics obtained in the study to test the potential of NIR spectroscopy to predict the chemical composition and amino acid contents in alfalfa hay, showed the accuracy was too low for routine analysis, although NIR spectroscopy could be used as a screening tool. Further research needs to be done to improve the accuracy of the NIR spectroscopy analysis, including more samples from different cultivars and years. In the study to examine the possibility of using NIR spectroscopy to predict the chemical composition of compound ostrich feeds, the results indicated that NIR spectroscopy is a suitable tool for a rapid and reliable prediction of the crude protein, crude fibre, ether extract, IVOMD, ADF and NDF in compound ostrich feeds. Calibrations can be improved for amino acids if a larger sample pool is used to develop the calibrations. These studies indicated that NIR spectroscopy can be a rapid and successful tool for the prediction of the nutritive value up to certain amino acid contents of feedstuffs and compound ostrich feeds.
- Full Text:
- Date Issued: 2017
- Authors: Swart, Etheresia , Lehmann-Maritz, Maryna
- Date: 2017
- Subjects: Near infrared spectroscopy , Animal nutrition , Animal feeding
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/13779 , vital:27307
- Description: The chemical analysis of feed samples can be time consuming and expensive. The use of near infrared reflectance (NIR) spectroscopy was evaluated in a range of studies as a rapid technique to predict the chemical constituents in feedstuffs and compound ostrich feeds. The prediction of accurate results by NIR spectroscopy relies heavily upon obtaining a calibration set which represents the variation in the main population, accurate laboratory analyses and the application of the best mathematical procedures. This research project was designed to meet five objectives: The first objective was to determine the feasibility of using near infrared reflectance (NIR) spectroscopy to predict dry matter, ash, crude protein, crude fibre, oil content, and fatty acids such as palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1) and linoleic acid (C18:2) in sunflower seed meal. The second objective was to develop calibration models to predict the dry matter, crude protein and oil content in milled canola seed, compared to whole canola seeds. The third objective was to investigate the feasibility of using NIR spectroscopy to predict the dry matter, ash, crude protein, crude fibre and oil content in milled lupin seeds, compared to whole lupin seeds. The fourth objective was to describe the development of near infrared reflectance (NIR) spectroscopy calibration equations for the prediction of chemical composition and amino acid content from different populations of alfalfa hay (Medicago sativa L.). The last objective was to determine the potential of NIR spectroscopy to predict the dry matter, ash, crude protein, crude fibre, ether extract, acid detergent fibre (ADF), neutral detergent fibre (NDF), calcium, phosphorus, in vitro organic matter digestibility (IVOMD) and amino acids such as lysine, methionine, threonine and arginine in compound ostrich feed samples. The results of this study indicate that NIR spectroscopy calibrations in sunflower seed meal are only applicable in sunflower breeding programmes for a fast screening as it was not suitable for prediction purposes. Screening of sunflower seeds by NIR spectroscopy represents a rapid, simple and cost effective alternative that is a great utility for users who need to analyse a large number of samples. Calibrations developed for crude protein and oil content in milled canola seeds proved to be better than calibrations for whole canola seeds. Although the results indicated that calibrations were better for milled canola seeds, it indicated values that were typical of equations suitable for screening purposes to select samples for more detailed chemical analysis. According to calibration statistics obtained for crude protein, crude fibre and oil content in whole lupin seeds, there is no need to grind the seeds to scan the meal as similarly accurate results were obtained by analysing whole seeds. Screening of whole lupin seeds by NIR spectroscopy represents a rapid, simple and cost effective alternative that may be of great utility for users who need to analyse a large number of samples with no sample preparation. The calibration and validation statistics obtained in the study to test the potential of NIR spectroscopy to predict the chemical composition and amino acid contents in alfalfa hay, showed the accuracy was too low for routine analysis, although NIR spectroscopy could be used as a screening tool. Further research needs to be done to improve the accuracy of the NIR spectroscopy analysis, including more samples from different cultivars and years. In the study to examine the possibility of using NIR spectroscopy to predict the chemical composition of compound ostrich feeds, the results indicated that NIR spectroscopy is a suitable tool for a rapid and reliable prediction of the crude protein, crude fibre, ether extract, IVOMD, ADF and NDF in compound ostrich feeds. Calibrations can be improved for amino acids if a larger sample pool is used to develop the calibrations. These studies indicated that NIR spectroscopy can be a rapid and successful tool for the prediction of the nutritive value up to certain amino acid contents of feedstuffs and compound ostrich feeds.
- Full Text:
- Date Issued: 2017
Statistical viability assessment of a photovoltaic system in the presence of data uncertainty
- Authors: Clohessy, Chantelle May
- Date: 2017
- Subjects: Bayesian field theory , Photovoltaic power systems
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/15655 , vital:28280
- Description: This thesis investigates statistical techniques that can be used to improve estimates and methods in feasibility assessments of photovoltaic (PV) systems. The use of these techniques are illustrated for a case study of a 1MW PV system proposed for the Nelson Mandela Metropolitan University South Campus in Port Elizabeth, South Africa. The results from the study provide strong support for the use of multivariate profile analysis and interval estimate plots for the assessment of solar resource data. A unique view to manufacturing process control in the generation of energy from a PV system is identified. This link between PV energy generation and process control is lacking in the literature and exploited in this study. Variance component models are used to model power output and energy yield estimates of the proposed PV system. The variance components are simulated using Bayesian simulation techniques. Bayesian tolerance intervals are derived from the variance components and are used to determine what percentage of future power output and energy yield values fall within an interval with a certain probability. The results from the estimated tolerance intervals were informative and provided expected power outputs and energy yields for a given month and specific season. The methods improve on current techniques used to assess the energy output of a system.
- Full Text:
- Date Issued: 2017
- Authors: Clohessy, Chantelle May
- Date: 2017
- Subjects: Bayesian field theory , Photovoltaic power systems
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/15655 , vital:28280
- Description: This thesis investigates statistical techniques that can be used to improve estimates and methods in feasibility assessments of photovoltaic (PV) systems. The use of these techniques are illustrated for a case study of a 1MW PV system proposed for the Nelson Mandela Metropolitan University South Campus in Port Elizabeth, South Africa. The results from the study provide strong support for the use of multivariate profile analysis and interval estimate plots for the assessment of solar resource data. A unique view to manufacturing process control in the generation of energy from a PV system is identified. This link between PV energy generation and process control is lacking in the literature and exploited in this study. Variance component models are used to model power output and energy yield estimates of the proposed PV system. The variance components are simulated using Bayesian simulation techniques. Bayesian tolerance intervals are derived from the variance components and are used to determine what percentage of future power output and energy yield values fall within an interval with a certain probability. The results from the estimated tolerance intervals were informative and provided expected power outputs and energy yields for a given month and specific season. The methods improve on current techniques used to assess the energy output of a system.
- Full Text:
- Date Issued: 2017
Assessing the outcomes and consequences of large carnivore reintroductions to the Eastern Cape, South Africa
- Banasiak, Natalia Matgorzata
- Authors: Banasiak, Natalia Matgorzata
- Date: 2017
- Subjects: Carnivores -- Reintroduction , Wildlife reintroduction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11963 , vital:27011
- Description: Reintroduction is a potentially powerful tool available to conservationists to cope with species population declines. Nonetheless, it is poorly understood and past reviews tend to indicate poor results. Reintroduction, under the sensu stricto IUCN definition, must have a primary objective of conservation; however species can be released to sites in their indigenous range (reintroduction sensu lato) to meet other objectives. The outcomes of these reintroductions s.l need to be assessed to determine how effectively they achieve their varied objectives. A Web of Science review revealed that only 32.1% of 131 publications on reintroduction provided clearly defined success criteria. Using economic, ecological, conservation and problem animal management objectives as reintroduction s.l. drivers, I developed context-dependent success definitions for each objective to use in reintroduction outcome assessments. These success criteria were then used to assess the reintroductions s.l. of large carnivores, namely lion, leopard, cheetah, African wild dog, spotted hyaena, and brown hyaena, to 16 private- and state-owned reserves in the Eastern Cape Province, South Africa. Ecotourism and ecological restoration were the most common objectives for the reintroduction of top predators to these reserves. Overall the reintroductions of large carnivores have been successful in meeting their objectives. Only African wild dogs have failed to establish in the province. Causes of objective-specific failures for the other species in some reserves included introductions of same-sex populations, lack of breeding events and changes in reserve management objectives. Assessments for leopard and brown hyaena were inconclusive due to lack of monitoring data. The reintroduction of large carnivores to the Eastern Cape Province has also resulted in the emergence of human-carnivore conflict on neighbouring properties. Carnivores have reportedly escaped from 8 reserves (61.5% of reserves) in the Eastern Cape. A total of 75 conflict events on 68 neighbouring properties (36.7% of neighbouring properties) have been reported. There is a major gap in research around conflict resulting from carnivore reintroductions and future research is required to fully understand the situation in the province in order to develop effective mitigation methods. An adaptive management approach to reintroductions is encouraged to improve monitoring and ensure reintroductions continue to meet their objectives. Furthermore, emerging consequences, such as human-wildlife conflict, and related mitigation strategies should be incorporated into management of reintroduced populations. Communities surrounding reintroduction sites should be educated on lifting baselines where conflict-causing species are recovering to ensure continued success of reintroduction undertakings. National management plans should be developed for all large carnivore species to improve the conservation value of small, fenced reserves that are typical of South African conservation, through a managed metapopulation approach. Management plans should include social, political, and economic factors that can influence the success of reintroductions and ultimate conservation outcomes.
- Full Text:
- Date Issued: 2017
- Authors: Banasiak, Natalia Matgorzata
- Date: 2017
- Subjects: Carnivores -- Reintroduction , Wildlife reintroduction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11963 , vital:27011
- Description: Reintroduction is a potentially powerful tool available to conservationists to cope with species population declines. Nonetheless, it is poorly understood and past reviews tend to indicate poor results. Reintroduction, under the sensu stricto IUCN definition, must have a primary objective of conservation; however species can be released to sites in their indigenous range (reintroduction sensu lato) to meet other objectives. The outcomes of these reintroductions s.l need to be assessed to determine how effectively they achieve their varied objectives. A Web of Science review revealed that only 32.1% of 131 publications on reintroduction provided clearly defined success criteria. Using economic, ecological, conservation and problem animal management objectives as reintroduction s.l. drivers, I developed context-dependent success definitions for each objective to use in reintroduction outcome assessments. These success criteria were then used to assess the reintroductions s.l. of large carnivores, namely lion, leopard, cheetah, African wild dog, spotted hyaena, and brown hyaena, to 16 private- and state-owned reserves in the Eastern Cape Province, South Africa. Ecotourism and ecological restoration were the most common objectives for the reintroduction of top predators to these reserves. Overall the reintroductions of large carnivores have been successful in meeting their objectives. Only African wild dogs have failed to establish in the province. Causes of objective-specific failures for the other species in some reserves included introductions of same-sex populations, lack of breeding events and changes in reserve management objectives. Assessments for leopard and brown hyaena were inconclusive due to lack of monitoring data. The reintroduction of large carnivores to the Eastern Cape Province has also resulted in the emergence of human-carnivore conflict on neighbouring properties. Carnivores have reportedly escaped from 8 reserves (61.5% of reserves) in the Eastern Cape. A total of 75 conflict events on 68 neighbouring properties (36.7% of neighbouring properties) have been reported. There is a major gap in research around conflict resulting from carnivore reintroductions and future research is required to fully understand the situation in the province in order to develop effective mitigation methods. An adaptive management approach to reintroductions is encouraged to improve monitoring and ensure reintroductions continue to meet their objectives. Furthermore, emerging consequences, such as human-wildlife conflict, and related mitigation strategies should be incorporated into management of reintroduced populations. Communities surrounding reintroduction sites should be educated on lifting baselines where conflict-causing species are recovering to ensure continued success of reintroduction undertakings. National management plans should be developed for all large carnivore species to improve the conservation value of small, fenced reserves that are typical of South African conservation, through a managed metapopulation approach. Management plans should include social, political, and economic factors that can influence the success of reintroductions and ultimate conservation outcomes.
- Full Text:
- Date Issued: 2017
Synthesis of L-menthyl glyoxylate, an important intermediate in the manufacture of ARVS, using flow chemistry technology
- Authors: Moyo, McQuillan
- Date: 2017
- Subjects: Chemistry , Pharmaceutical chemistry , Organic compounds -- Synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/12019 , vital:27018
- Description: Herein an alternative approach to the conventional batch synthesis of L-menthyl glyoxylate hydrate (MGH), an important intermediate in the synthesis of drugs of importance is reported, through flow chemistry technology. MGH was initially synthesized in batch and various reaction parameters optimized. It was found to proceed to completion after 6 hours of esterifying glyoxylic acid with excess alcohol (L-menthol) in the presence of a catalyst, ideally amberlyst-15 (an ion exchange resin) at 105 °C giving a yield of 72 %. The batch reaction conditions were adopted in a continuous flow synthesis setup, using the Labtrix Start system, in which reaction conditions were optimized. The optimization of glyoxylic acid conversion (92 %) in the Labtrix Start system gave reaction conditions that resulted in low MGH selectivity (25 %) whereas the optimization for MGH selectivity (100 %) gave a conversion a poor glyoxylic acid conversion (15 %). The FlowSyn system fitted with a column reactor gave the best results, in which the optimum conditions were an excess of L-menthol (1.5 M, 6.0 equiv.), temperature (80 °C) and a residence time of 2.5 minutes with a high selectivity (77 %) and average conversion (50 %). The optimized reaction conditions for conversion and selectivity on the different flow systems did not vary significantly and similar trends were observed for the systems. It was shown that an increase in temperature, mole equivalents and residence time led to an increase in MGH conversion in all flow systems. The scale up of the esterification reaction from the Labtrix Start system (19 μL microreactor) to the FlowSyn system fitted with a 2 mL reactor chip, showed that the reaction proceeds with a slight drop in selectivity from 100 % to 92 % while conversion dropped from 15 to 12 %. On the contrary, a significant drop in conversion and selectivity were observed when the FlowSyn column reactor was up-scaled to the Elite-tubular furnace, owing to the poor mixing in the larger channel size reactor.
- Full Text:
- Date Issued: 2017
- Authors: Moyo, McQuillan
- Date: 2017
- Subjects: Chemistry , Pharmaceutical chemistry , Organic compounds -- Synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/12019 , vital:27018
- Description: Herein an alternative approach to the conventional batch synthesis of L-menthyl glyoxylate hydrate (MGH), an important intermediate in the synthesis of drugs of importance is reported, through flow chemistry technology. MGH was initially synthesized in batch and various reaction parameters optimized. It was found to proceed to completion after 6 hours of esterifying glyoxylic acid with excess alcohol (L-menthol) in the presence of a catalyst, ideally amberlyst-15 (an ion exchange resin) at 105 °C giving a yield of 72 %. The batch reaction conditions were adopted in a continuous flow synthesis setup, using the Labtrix Start system, in which reaction conditions were optimized. The optimization of glyoxylic acid conversion (92 %) in the Labtrix Start system gave reaction conditions that resulted in low MGH selectivity (25 %) whereas the optimization for MGH selectivity (100 %) gave a conversion a poor glyoxylic acid conversion (15 %). The FlowSyn system fitted with a column reactor gave the best results, in which the optimum conditions were an excess of L-menthol (1.5 M, 6.0 equiv.), temperature (80 °C) and a residence time of 2.5 minutes with a high selectivity (77 %) and average conversion (50 %). The optimized reaction conditions for conversion and selectivity on the different flow systems did not vary significantly and similar trends were observed for the systems. It was shown that an increase in temperature, mole equivalents and residence time led to an increase in MGH conversion in all flow systems. The scale up of the esterification reaction from the Labtrix Start system (19 μL microreactor) to the FlowSyn system fitted with a 2 mL reactor chip, showed that the reaction proceeds with a slight drop in selectivity from 100 % to 92 % while conversion dropped from 15 to 12 %. On the contrary, a significant drop in conversion and selectivity were observed when the FlowSyn column reactor was up-scaled to the Elite-tubular furnace, owing to the poor mixing in the larger channel size reactor.
- Full Text:
- Date Issued: 2017