A Comparative Study of Bootstrapping Techniques for Inventory Control
- Authors: Frederick, Lauren
- Date: 2020
- Subjects: Computer bootstrapping -- Inventory control
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48335 , vital:40849
- Description: Setting correct inventory levels is an important business consideration in order to minimise inventory investment while at the same time ensuring sufficient inventory levels to meet customer demand. Inventory management has a significant impact on both financial and customer service aspects of a business. Selecting appropriate inventory levels requires that products’ lead time demand be accurately estimated in order to calculate the reorder point. The purpose of this study was to empirically determine whether bootstrapping methods used to estimate the lead time demand distribution and reorder point calculation could match or even outperform a standard parametric approach. The two bootstrapping methods compared in this research included variations of those presented by Bookbinder and Lordahl [1989] and do Rego and de Mesquita [2015]. These were compared to the standard parametric approach common in practice which makes use of the Normal distribution for modelling lead time demand. The three reorder point calculation methods were each incorporated into the inventory policy simulations using data supplied by a South African automotive spare parts business. The simulations covered a period of twelve months and were repeated for multiple service levels ranging from 70 to 99 percent. Results of the simulations were compared at a high level as well as for groups of items identified using segmentation techniques which considered different item demand and lead time characteristics. Key findings were that the Normal approximation method was far superior in terms of the service level metric, while the variation of the Bookbinder and Lordahl [1989] method adopted in this study presented possible cost benefits at lower service levels.
- Full Text:
- Date Issued: 2020
- Authors: Frederick, Lauren
- Date: 2020
- Subjects: Computer bootstrapping -- Inventory control
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48335 , vital:40849
- Description: Setting correct inventory levels is an important business consideration in order to minimise inventory investment while at the same time ensuring sufficient inventory levels to meet customer demand. Inventory management has a significant impact on both financial and customer service aspects of a business. Selecting appropriate inventory levels requires that products’ lead time demand be accurately estimated in order to calculate the reorder point. The purpose of this study was to empirically determine whether bootstrapping methods used to estimate the lead time demand distribution and reorder point calculation could match or even outperform a standard parametric approach. The two bootstrapping methods compared in this research included variations of those presented by Bookbinder and Lordahl [1989] and do Rego and de Mesquita [2015]. These were compared to the standard parametric approach common in practice which makes use of the Normal distribution for modelling lead time demand. The three reorder point calculation methods were each incorporated into the inventory policy simulations using data supplied by a South African automotive spare parts business. The simulations covered a period of twelve months and were repeated for multiple service levels ranging from 70 to 99 percent. Results of the simulations were compared at a high level as well as for groups of items identified using segmentation techniques which considered different item demand and lead time characteristics. Key findings were that the Normal approximation method was far superior in terms of the service level metric, while the variation of the Bookbinder and Lordahl [1989] method adopted in this study presented possible cost benefits at lower service levels.
- Full Text:
- Date Issued: 2020
A Geochemical Comparison of Southern African Stromatolites and Stromatolite Pools
- Authors: Dodd, Carla
- Date: 2020
- Subjects: Stromatolites
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48235 , vital:40527
- Description: Microbialite accretion takes place via either mineral precipitation, the trapping and binding of mineral and sediment grains, or a combination of the two. Recently, the geochemistry of carbonate deposits, including microbialites, has been used to reconstruct palaeoenvironments and infer biogenicity. Numerous modern stromatolite (layered microbialites) systems are located on the southern African coastline and are formed predominantly by mineral precipitation with minor detrital input. In order to better understand the environmental and biological processes influencing the formation of microbialites, the geochemistry of southern African coastalstromatolites is examined. This is done by a spatial comparison of the hydrochemistry as well as the major and trace element geochemistry of various coastal stromatolite systems. The influence of the underlying geology on the composition of the stromatolites forms a particular focus of the study. In addition, the effect of metazoans on the micro-fabrics and sediment incorporation into the stromatolite matrix is assessed. Finally, the trace element geochemistry of active, inactive, and ancient stromatolites is compared with a speleothem sample in order to test the validity of using trace elements as a means to determine biogenicity of deposition. Results show that the bulk geochemistry of the South African stromatolites is not a simple function of the associated bedrock lithologies, although certain parallels do exist. It was found that metazoans indirectly influence sediment incorporation by increasing porosity and thereby accommodation space for detrital input. Furthermore, trace element signatures could not be directly attributed to microbial influence in the deposition of the carbonates. Ultimately, this study provides valuable insights into the formation processes of the active South African stromatolites and the use of trace elements as a geochemical tool to investigate the evolution of life and determine past environmental conditions.
- Full Text:
- Date Issued: 2020
- Authors: Dodd, Carla
- Date: 2020
- Subjects: Stromatolites
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48235 , vital:40527
- Description: Microbialite accretion takes place via either mineral precipitation, the trapping and binding of mineral and sediment grains, or a combination of the two. Recently, the geochemistry of carbonate deposits, including microbialites, has been used to reconstruct palaeoenvironments and infer biogenicity. Numerous modern stromatolite (layered microbialites) systems are located on the southern African coastline and are formed predominantly by mineral precipitation with minor detrital input. In order to better understand the environmental and biological processes influencing the formation of microbialites, the geochemistry of southern African coastalstromatolites is examined. This is done by a spatial comparison of the hydrochemistry as well as the major and trace element geochemistry of various coastal stromatolite systems. The influence of the underlying geology on the composition of the stromatolites forms a particular focus of the study. In addition, the effect of metazoans on the micro-fabrics and sediment incorporation into the stromatolite matrix is assessed. Finally, the trace element geochemistry of active, inactive, and ancient stromatolites is compared with a speleothem sample in order to test the validity of using trace elements as a means to determine biogenicity of deposition. Results show that the bulk geochemistry of the South African stromatolites is not a simple function of the associated bedrock lithologies, although certain parallels do exist. It was found that metazoans indirectly influence sediment incorporation by increasing porosity and thereby accommodation space for detrital input. Furthermore, trace element signatures could not be directly attributed to microbial influence in the deposition of the carbonates. Ultimately, this study provides valuable insights into the formation processes of the active South African stromatolites and the use of trace elements as a geochemical tool to investigate the evolution of life and determine past environmental conditions.
- Full Text:
- Date Issued: 2020
A smart home environment simulation tool to support the recognition of activities of daily living
- Authors: Ho, Brandon
- Date: 2020
- Subjects: Artificial intelligence , Internet of things Home automation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49334 , vital:41622
- Description: The prevalence of internet of things technologies and internet-connected devices enables the potential of introducing intelligence to a wide range of applications and fields. Smart homes are popular application of internet of things. Smart homes refer to domestic environments that can monitor their own state and the state of their inhabitants. Smart homes are identified as a promising solution for assisting inhabitants in completing daily activities and improving quality of life for inhabitants. This dissertation discusses the design and implementation of smart home simulation tool prototype, called smart environment stimulation (SESim). SESim is designed to conduct smart home simulation and generate synthetic sensor datasets which describe activity performances. This dissertation also discusses the evaluation of SESim, which focused on validating the utility of conducting smart home simulations and generating sensor datasets.
- Full Text: false
- Date Issued: 2020
- Authors: Ho, Brandon
- Date: 2020
- Subjects: Artificial intelligence , Internet of things Home automation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49334 , vital:41622
- Description: The prevalence of internet of things technologies and internet-connected devices enables the potential of introducing intelligence to a wide range of applications and fields. Smart homes are popular application of internet of things. Smart homes refer to domestic environments that can monitor their own state and the state of their inhabitants. Smart homes are identified as a promising solution for assisting inhabitants in completing daily activities and improving quality of life for inhabitants. This dissertation discusses the design and implementation of smart home simulation tool prototype, called smart environment stimulation (SESim). SESim is designed to conduct smart home simulation and generate synthetic sensor datasets which describe activity performances. This dissertation also discusses the evaluation of SESim, which focused on validating the utility of conducting smart home simulations and generating sensor datasets.
- Full Text: false
- Date Issued: 2020
A study of contaminants in fish in South Africa : linking science, management and society
- Authors: Ramparsad, Kerina
- Date: 2020
- Subjects: Estuarine fishes -- Contamination -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48609 , vital:40895
- Description: Contaminants in fish is a concern globally and locally. Fish have the propensity to accumulate contaminants to levels that may pose a threat to human health and disrupt ecosystem function. The purpose for investigating contaminants in this study for fish provides the public with information on the potential human health risks from the contaminated fish we consume. This study also investigated contaminants in estuarine fish and sediment, and is important to monitor as these components of ecosystems can indicate contamination in estuaries. Effective methods to determine contaminants in fish and sediment included the Direct Mercury Analyser 80 for mercury, Gas Chromatography for fatty acids and polychlorinated biphenyls and Inductively Coupled Plasma for aluminium, arsenic, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, nickel, vanadium and zinc. Basic statistical tools, geochemical techniques, a bioaccumulation model and human health risk assessment tools provided by the United States Environmental Protection Agency were used to interpret the data. Ultimately consumption advice was developed from the risk assessment results and showed predatory fish such as swordfish and bluenose species are recommended to be avoided while yellow tail, red roman, mackerel, fish fingers and canned tuna are some of the fish that can be eaten 10-14 times per month that would not cause potential health risks. It was found that estuarine ambassid fish investigated in this study were not suitable for contaminant monitoring. There were no clear spatial and seasonal trends observed in the estuaries suggesting that ambassid fish efficiently assimilate contaminants. There was little evidence that contaminants were transferred from sediment to ambassid fish in the eThekwini estuaries. Therefore, their use is limited as a cost-effective estuarine contaminant monitoring tool. Each estuary investigated is unique and requires its own management plan.
- Full Text:
- Date Issued: 2020
- Authors: Ramparsad, Kerina
- Date: 2020
- Subjects: Estuarine fishes -- Contamination -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48609 , vital:40895
- Description: Contaminants in fish is a concern globally and locally. Fish have the propensity to accumulate contaminants to levels that may pose a threat to human health and disrupt ecosystem function. The purpose for investigating contaminants in this study for fish provides the public with information on the potential human health risks from the contaminated fish we consume. This study also investigated contaminants in estuarine fish and sediment, and is important to monitor as these components of ecosystems can indicate contamination in estuaries. Effective methods to determine contaminants in fish and sediment included the Direct Mercury Analyser 80 for mercury, Gas Chromatography for fatty acids and polychlorinated biphenyls and Inductively Coupled Plasma for aluminium, arsenic, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, nickel, vanadium and zinc. Basic statistical tools, geochemical techniques, a bioaccumulation model and human health risk assessment tools provided by the United States Environmental Protection Agency were used to interpret the data. Ultimately consumption advice was developed from the risk assessment results and showed predatory fish such as swordfish and bluenose species are recommended to be avoided while yellow tail, red roman, mackerel, fish fingers and canned tuna are some of the fish that can be eaten 10-14 times per month that would not cause potential health risks. It was found that estuarine ambassid fish investigated in this study were not suitable for contaminant monitoring. There were no clear spatial and seasonal trends observed in the estuaries suggesting that ambassid fish efficiently assimilate contaminants. There was little evidence that contaminants were transferred from sediment to ambassid fish in the eThekwini estuaries. Therefore, their use is limited as a cost-effective estuarine contaminant monitoring tool. Each estuary investigated is unique and requires its own management plan.
- Full Text:
- Date Issued: 2020
A stunting profile of children under the age of five visiting Bhisho hospital clinic, part of the umbrella project: a profile of stunting in children under the age of five in food insecure villages in Mqanduli, Ngqushwa and Bhisho hospital, Eastern Cape, South Africa
- Authors: Beyleveld, Janine
- Date: 2020
- Subjects: Children -- growth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/50201 , vital:42066
- Description: Introduction and Background: Stunting is the most prevalent form of childhood malnutrition where about 149 million children under the age of five can be classified as stunted globally. South Africa has one of the highest stunting rates in the world at 27%, causing devastating effects on economic productivity as well as on an individual’s nutritional status. The presence of stunted growth in children is a strong indicator of chronic undernutrition and highlights injustices experienced within communities. Aims and Objectives: The aim of this study is to develop a stunning profile of children under the age of five, visiting BhishoHospital’s gateway clinic in the Eastern Cape, South Africa. The objectives were to determine the prevalence of stunting of the children visiting Bhisho Hospital’s clinic and to identify the drivers of stunting in the area. Methodology: A quantitative study with a descriptive, cross-sectional design was used. The study population included all children under the age of five visiting Bhisho Hospital’s clinic. Data was collected by means of an interview-administered questionnaire. Results: The prevalence of stunting in the area was 47.5%. A significant association was found between the participants' main form of sanitation and stunting category in the group of infants younger than six months (p = 0.007) and the group older than six months(p = 0.040). Discussion: The prevalence of stunting in the area was far higher than the national average of 27%, although the majority of the sample had a normal weight. The use of non-flush toilets was found to be a risk factor for childhood stunting. Recommendation: Financial and political investment in child health needs to be placed as a top priority in South Africa to reduce stunting rates.
- Full Text:
- Date Issued: 2020
- Authors: Beyleveld, Janine
- Date: 2020
- Subjects: Children -- growth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/50201 , vital:42066
- Description: Introduction and Background: Stunting is the most prevalent form of childhood malnutrition where about 149 million children under the age of five can be classified as stunted globally. South Africa has one of the highest stunting rates in the world at 27%, causing devastating effects on economic productivity as well as on an individual’s nutritional status. The presence of stunted growth in children is a strong indicator of chronic undernutrition and highlights injustices experienced within communities. Aims and Objectives: The aim of this study is to develop a stunning profile of children under the age of five, visiting BhishoHospital’s gateway clinic in the Eastern Cape, South Africa. The objectives were to determine the prevalence of stunting of the children visiting Bhisho Hospital’s clinic and to identify the drivers of stunting in the area. Methodology: A quantitative study with a descriptive, cross-sectional design was used. The study population included all children under the age of five visiting Bhisho Hospital’s clinic. Data was collected by means of an interview-administered questionnaire. Results: The prevalence of stunting in the area was 47.5%. A significant association was found between the participants' main form of sanitation and stunting category in the group of infants younger than six months (p = 0.007) and the group older than six months(p = 0.040). Discussion: The prevalence of stunting in the area was far higher than the national average of 27%, although the majority of the sample had a normal weight. The use of non-flush toilets was found to be a risk factor for childhood stunting. Recommendation: Financial and political investment in child health needs to be placed as a top priority in South Africa to reduce stunting rates.
- Full Text:
- Date Issued: 2020
Alternative pine species/hybrids for the Cape timber growing regions of South Africa
- Authors: Van der Hoef, André
- Date: 2020
- Subjects: Species -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47613 , vital:40258
- Description: Pinus radiata has been the preferred commercial sawtimber species for the Cape forestry region for many years. Since the introduction of Fusarium circinatum, and the susceptibility of P. radiata to this disease, the sustainable production of this pine species for the Cape has been negatively impacted due to poor survival in the nursery and in field plantings. For this reason, a number of additional pine species and hybrids have been established in the Cape region of South Africa since 2006 to identify taxa that would perform as well as or better than P. radiata. Three research trials were implemented on contrasting sites that contained eight common species/hybrids treatments that included P. elliottii, P. elliottii x P. caribaea, P. radiata, P. patula x P. greggii var. australis, P. patula x P. oocarpa, P. patula x P. tecunumanii (HE), P. patula x P. tecunumanii (LE) and P. tecunumanii (HE) x P. oocarpa were established at Witelsbos, Kruisfontein and Garcia across diverse soil types, drainage and climate conditions in the Cape. Survival, growth data and tree morphology (forking, foxtails, broken tops and stem form) were assessed at five years of age and individual tree volume was calculated. Five year results indicate that on the waterlogged site at Witelsbos P. elliottii and its hybrid with P. caribaea was best in terms of productivity, at the dry site of Garcia, P. taeda and P. elliottii demonstrated promise, and at Kruisfontein, the most fertile site, P. elliottii x P. caribaea, P. patula x P. tecunumanii (LE) and P. maximinoi were found to be promising alternatives to P. radiata. Wood properties were assessed at Kruisfontein at six-years of age. Basic density and Modulus of Elasticity (MOE) were found to be significantly different for the various species/hybrids. Pinus patula x P. tecunumanii (LE), P. patula x P. greggii (S), P. maximinoi and P. patula x P. tecunumanii (HE) were all significantly better than P. radiata, which would suggest that these taxa would have similar or superior wood strength over P. radiata, the preferred sawtimber species for the Cape region. Only P. tecunumanii (HE) x P. oocarpa had a higher basic density than P. radiata, but not significantly different. Species that had similar basic density were P. patula x P. greggii (S), P. taeda and P. tecunumanii (LE) x P. caribaea. Although P. elliottii x P. caribaea had the highest volume at Witelsbos and Kruisfontein, the timber qualities were the worst, suggesting that some breeding is needed to improve this hybrid to be an acceptable sawtimber species. From this study, several potential alternative species/hybrids have been identified that are tolerant to the F. circinatum pathogen and have acceptable growth and wood properties, compared to P. radiata.
- Full Text:
- Date Issued: 2020
- Authors: Van der Hoef, André
- Date: 2020
- Subjects: Species -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47613 , vital:40258
- Description: Pinus radiata has been the preferred commercial sawtimber species for the Cape forestry region for many years. Since the introduction of Fusarium circinatum, and the susceptibility of P. radiata to this disease, the sustainable production of this pine species for the Cape has been negatively impacted due to poor survival in the nursery and in field plantings. For this reason, a number of additional pine species and hybrids have been established in the Cape region of South Africa since 2006 to identify taxa that would perform as well as or better than P. radiata. Three research trials were implemented on contrasting sites that contained eight common species/hybrids treatments that included P. elliottii, P. elliottii x P. caribaea, P. radiata, P. patula x P. greggii var. australis, P. patula x P. oocarpa, P. patula x P. tecunumanii (HE), P. patula x P. tecunumanii (LE) and P. tecunumanii (HE) x P. oocarpa were established at Witelsbos, Kruisfontein and Garcia across diverse soil types, drainage and climate conditions in the Cape. Survival, growth data and tree morphology (forking, foxtails, broken tops and stem form) were assessed at five years of age and individual tree volume was calculated. Five year results indicate that on the waterlogged site at Witelsbos P. elliottii and its hybrid with P. caribaea was best in terms of productivity, at the dry site of Garcia, P. taeda and P. elliottii demonstrated promise, and at Kruisfontein, the most fertile site, P. elliottii x P. caribaea, P. patula x P. tecunumanii (LE) and P. maximinoi were found to be promising alternatives to P. radiata. Wood properties were assessed at Kruisfontein at six-years of age. Basic density and Modulus of Elasticity (MOE) were found to be significantly different for the various species/hybrids. Pinus patula x P. tecunumanii (LE), P. patula x P. greggii (S), P. maximinoi and P. patula x P. tecunumanii (HE) were all significantly better than P. radiata, which would suggest that these taxa would have similar or superior wood strength over P. radiata, the preferred sawtimber species for the Cape region. Only P. tecunumanii (HE) x P. oocarpa had a higher basic density than P. radiata, but not significantly different. Species that had similar basic density were P. patula x P. greggii (S), P. taeda and P. tecunumanii (LE) x P. caribaea. Although P. elliottii x P. caribaea had the highest volume at Witelsbos and Kruisfontein, the timber qualities were the worst, suggesting that some breeding is needed to improve this hybrid to be an acceptable sawtimber species. From this study, several potential alternative species/hybrids have been identified that are tolerant to the F. circinatum pathogen and have acceptable growth and wood properties, compared to P. radiata.
- Full Text:
- Date Issued: 2020
An investigation of the morphological and electrochemical properties of anode titanate materials used in li-ion batteries
- Authors: Gelant, Charmaine
- Date: 2020
- Subjects: Electrodes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48346 , vital:40851
- Description: The chemistry involved in the synthesis of lithium titanium oxide (Li4Ti5O12) for lithium ion battery applications is critical for understanding and optimizing the most cost-efficient manufacturing route. This study investigates the sol-gel synthesis technique of Li4Ti5O12 using triethanolamine (TEOA) as complexing agent by means of in-situ Powder X-ray Diffraction (PXRD). The influence of doping with various metals such as Al3+, Mg2+ , Co3+ and Ni2+ that were made as precursors was considered for comparison purposes due to literature showing improved electrochemical performance using the molecular formula of Li4Ti4.95M0.05O12. The in-situ PXRD technique was used to identify the phase changes that occurred in the thermal synthesis process from the sol-gel precursors to the final crystalline oxides. The materials’ decomposition mechanisms were characterized by thermal gravimetric analysis (TGA) as the precursors were gradually heated to obtain the final oxides. BET surface area analysis and scanning electron microscopy (SEM) were used in order to obtain a morphological understanding of the materials during the synthetic route at specific temperature regions. The in-situ studies have shown that the precursor materials are amorphous at room temperature to about 550 °C, after which the spinel and anatase formed, with relatively small crystallites and a large surface area. The study also showed that a crystalline intermediate phase formed at around 150-200 °C, which then disappeared above 250 °C and was speculated to be a titanium acid (H2Ti2O5.H2O). Upon further heating above 250 °C, the anatase phase converted to the high temperature stable TiO2 phase, rutile, also with an increased formation of the expected LTO spinel phase around 850 °C. Keeping the material at 850 °C, isothermally, did show further conversion of the rutile into the desired spinel phase Li4Ti5O12 (LTO) with an increase in the crystallite size and a decrease in surface area. SEM analysis of the material at 850 °C did show some extensive sintering of the particles with some samples indicating the presence of an additional β-Li2TiO3 phase that formed at the high temperatures. Upon cooling, the βLi2TiO3 phase showed a distinctive powder diffraction pattern besides the typical spinel II LTO phase. The study showed that in comparison to the oxide formed at 850 °C, a mixed phase material of the spinel LTO, anatase and rutile could be achieved at temperatures close to 650 °C with very small crystallites and a relatively large surface area that showed desirable electrochemical properties. Suitable Li-ion coin cells were built with the undoped spinel and doped materials that were isothermally made at 650 °C and 850 °C, whereby their electrochemical properties were tested in the form of cell capacity, electrochemical impedance spectroscopy (EIS) and differential capacity (dQ/dV) studies. The cells made with the materials at 850 °C provided reasonable capacity where the dQ/dV plots did show a single step redox reaction at around 1.5V vs Li/Li+ . These were compared to cells made with commercially available LTO and highlighted the importance of high surface area and small particle size of the active material in order to achieve acceptable electrochemical performances. The cells with the materials made at 650 °C showed to have good capacity upon the first discharge with a number of irreversible phase transitions that were subsequently not observed upon recharging. The dQ/dV graphs showed that the phase transitions were unique to the mixed phase composition of the material made at low temperatures and the cells made with the doped spinel materials were on average better performing than the undoped LTO material. Subsequent grinding steps of the active material made at 850 °C improved the capacity performance of the cells but were still lower when compared to the commercially available material. Hence, significantly longer grinding and processing time would be required to achieve battery active materials that are acceptable for commercial use. This study highlights the importance of understanding the phase transitions that occur during the synthesis route of making battery active material, where doping with different elements and using lower temperatures during synthesis could lead to electroactive materials that do not require additional excessive processing steps such as grinding.
- Full Text:
- Date Issued: 2020
- Authors: Gelant, Charmaine
- Date: 2020
- Subjects: Electrodes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48346 , vital:40851
- Description: The chemistry involved in the synthesis of lithium titanium oxide (Li4Ti5O12) for lithium ion battery applications is critical for understanding and optimizing the most cost-efficient manufacturing route. This study investigates the sol-gel synthesis technique of Li4Ti5O12 using triethanolamine (TEOA) as complexing agent by means of in-situ Powder X-ray Diffraction (PXRD). The influence of doping with various metals such as Al3+, Mg2+ , Co3+ and Ni2+ that were made as precursors was considered for comparison purposes due to literature showing improved electrochemical performance using the molecular formula of Li4Ti4.95M0.05O12. The in-situ PXRD technique was used to identify the phase changes that occurred in the thermal synthesis process from the sol-gel precursors to the final crystalline oxides. The materials’ decomposition mechanisms were characterized by thermal gravimetric analysis (TGA) as the precursors were gradually heated to obtain the final oxides. BET surface area analysis and scanning electron microscopy (SEM) were used in order to obtain a morphological understanding of the materials during the synthetic route at specific temperature regions. The in-situ studies have shown that the precursor materials are amorphous at room temperature to about 550 °C, after which the spinel and anatase formed, with relatively small crystallites and a large surface area. The study also showed that a crystalline intermediate phase formed at around 150-200 °C, which then disappeared above 250 °C and was speculated to be a titanium acid (H2Ti2O5.H2O). Upon further heating above 250 °C, the anatase phase converted to the high temperature stable TiO2 phase, rutile, also with an increased formation of the expected LTO spinel phase around 850 °C. Keeping the material at 850 °C, isothermally, did show further conversion of the rutile into the desired spinel phase Li4Ti5O12 (LTO) with an increase in the crystallite size and a decrease in surface area. SEM analysis of the material at 850 °C did show some extensive sintering of the particles with some samples indicating the presence of an additional β-Li2TiO3 phase that formed at the high temperatures. Upon cooling, the βLi2TiO3 phase showed a distinctive powder diffraction pattern besides the typical spinel II LTO phase. The study showed that in comparison to the oxide formed at 850 °C, a mixed phase material of the spinel LTO, anatase and rutile could be achieved at temperatures close to 650 °C with very small crystallites and a relatively large surface area that showed desirable electrochemical properties. Suitable Li-ion coin cells were built with the undoped spinel and doped materials that were isothermally made at 650 °C and 850 °C, whereby their electrochemical properties were tested in the form of cell capacity, electrochemical impedance spectroscopy (EIS) and differential capacity (dQ/dV) studies. The cells made with the materials at 850 °C provided reasonable capacity where the dQ/dV plots did show a single step redox reaction at around 1.5V vs Li/Li+ . These were compared to cells made with commercially available LTO and highlighted the importance of high surface area and small particle size of the active material in order to achieve acceptable electrochemical performances. The cells with the materials made at 650 °C showed to have good capacity upon the first discharge with a number of irreversible phase transitions that were subsequently not observed upon recharging. The dQ/dV graphs showed that the phase transitions were unique to the mixed phase composition of the material made at low temperatures and the cells made with the doped spinel materials were on average better performing than the undoped LTO material. Subsequent grinding steps of the active material made at 850 °C improved the capacity performance of the cells but were still lower when compared to the commercially available material. Hence, significantly longer grinding and processing time would be required to achieve battery active materials that are acceptable for commercial use. This study highlights the importance of understanding the phase transitions that occur during the synthesis route of making battery active material, where doping with different elements and using lower temperatures during synthesis could lead to electroactive materials that do not require additional excessive processing steps such as grinding.
- Full Text:
- Date Issued: 2020
Analysis of the effectiveness of Tulbaghia Violacea extracts as devulcanizing agents for synthetic CIS-1,4-polyisoprene vulcanizates
- Authors: Gxakuma, Lutho
- Date: 2020
- Subjects: Plant extracts , Plant products -- South Africa Medicinal plants -- South Africa Plants -- Analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49093 , vital:41600
- Description: Tulbaghia violacea is an indigenous plant commonly known as wild garlic, wilde knoffel in Afrikaans, isihaqa in Zulu or itswele lomlambo in Xhosa. Its leaves and bulbs are widely used as herbal remedies for various ailments and its medicinal uses include fever and colds, asthma, tuberculosis and stomach problems. Like all other members of the Alliacea family, Tulbaghia violacea produces a distinctive garlic-like odour when its leaves or rhizomes are damaged, resulting in the release of cysteine-derived sulphur compounds which include the oil-soluble organo-sulphur compounds and water-soluble cysteine derivatives. Chemically synthesized sulphur containing compounds have been reported to be effective devulcanizing agents and many industries prefer to perform devulcanization using them. Most commonly applied devulcanizing agents include disulphides, thiophenols and their zinc salts, and mercaptans which are mixed with the rubber scrap powder under specific reaction conditions. In this study, instead of performing devulcanization by using industrial synthesized sulphur containing compounds, the effectiveness of the extracts of organo-sulphur containing compounds from Tulbaghia violacea are evaluated as potential devulcanizing agents for synthetic cis-1,4-polyisoprene vulcanizates. This is a new, cheap and greener practice of rubber devulcanization. Diallyl disulphide, which is one of the organo-sulphur containing compounds present in Tulbaghia violacea, is the devulcanizing agent of interest to this study. The organo-sulphur containing compounds were extracted from the bulbs, roots and leaves of the plant using the soxhlet and ultrasonic bath extraction method. The solvent system used in the soxhlet extraction method was 2% of 2-propanol in n-hexane whereas in ultrasonic bath extraction method the solvent system used was 100% ethanol. An essential oil extract was obtained from the plant organs. The yield of the essential oil extracts obtained using the soxhlet extraction method was higher compared to the yield of the essential oil extracts obtained using the ultrasonic bath extraction method. According to the Fourier-Transform Infrared spectroscopy, the organo-sulphur containing compounds were present in the essential oil extracts of the plant. The essential oil extracts that were extracted using the soxhlet extraction method were chosen for further analysis. It was found out that the allyl sulphide and diallyl disulphide have the same retention time from the High Performance Liquid Chromatography (using a normal phase column). The Differential Scanning Calorimeter indicated that the allyl sulphide was not present in the essential oil extracts whereas the diallyl disulphide was present in the essential oil extract of the roots and leaves. The High Performance Liquid Chromatography was used to quantify the presence of the diallyl disulphide in the essential oil extract of roots and leaves. The quantity of diallyl disulphide was 23% in the dry mass of the essential oil extract of roots. In the essential oil extract of leaves the diallyl disulphide was very low concentrated and the High Performance Liquid Chromatography was less sensitive to detect it. According to the Thermogravimetric Analyser, it was found that the essential oil extracts begin to degrade at 120 °C and experience a multistage degradation. The softening temperature of the essential oil extracts was 60 °C from the Simultaneous Differential Scanning Calorimeter-Thermogravimetric Analyser. Conventional vulcanization of synthetic cis-1,4-polyisoprene was prepared with the vulcanization ingredients of zinc oxide, sulphur, stearic acid and N-tert-butyl-2-benzothiazole sulphenamide. The vulcanized synthetic cis-1,4-polyisoprene produced, under the heating temperature of 160 °C, was mixed with the essential oil extracts using the internal mixer at 60 °C and the two-roll mill. The overall torque, tan delta and the total crosslink density were the properties of interest of synthetic cis-1,4-polyisoprene vulcanizate in this study. The devulcanization temperature for the treated synthetic cis-1,4-polyisoprene vulcanizate with the essential oil extracts was optimized using the Dynamic Moving Die Rheometer and Dynamic Rubber Process Analyser. The amount of essential oil extracts at which they are effective devulcanizing agents for synthetic cis-1,4-polyisoprene vulcanizate was also optimized. During optimization a change on the latter mentioned properties of synthetic cis-1,4-polyisoprene vulcanizate was observed, indicating that the essential oil extracts have an effect as potential devulcanizing agents. The essential oil extracts increased the tan delta and reduced the overall torque, and total crosslink density of synthetic cis-1,4-polyisoprene vulcanizate as expected from devulcanizing agents. 200 °C was a preferable devulcanization temperature whereas essential oil extracts were effective as devulcanizing agent at 1.4%. However, the essential oil extracts influenced the overall torque and tan delta of synthetic cis-1,4-polyisoprene vulcanizate during the mixing process in the internal mixer at 60 °C, which was before heating at 200 °C. The essential oil extracts had a higher influence on the overall torque of synthetic cis-1,4-polyisoprene vulcanizate under heating at 200 °C whereas at 60 °C, during the mixing process, they had a higher influence on the tan delta of synthetic cis-1,4-polyisoprene vulcanizate. The essential oil extract of leaves had a higher influence on the overall torque whereas the essential oil extract of bulbs had a higher influence on the tan delta of synthetic cis-1,4-polyisoprene vulcanizate at 200 °C. The essential oil extract of roots shown a greater influence on the overall torque and tan delta of synthetic cis-1,4-polyisoprene vulcanizate at 60 °C during the mixing process. The effect of the essential oil extracts on the reversing heat capacity of synthetic cis-1,4-polyisoprene vulcanizate was also investigated using the Modulated Differential Scanning Calorimetry method. The essential oil extract of bulbs and roots influenced the reversing heat capacity of synthetic cis-1,4-polyisoprene vulcanizate by reducing it whereas the essential oil extract of leaves caused a temperature shift of the reversing heat capacity curve from the Modulated Differential Scanning Calorimeter thermogram of synthetic cis-1,4-polyisoprene vulcanizate. Therefore, the results indicated that the essential oil extracts of Tulbaghia violacea have an effect as an alternative potential devulcanizing agents for conventional vulcanized synthetic cis-1,4-polyisoprene whether the diallyl disulphide compound is present or not in them.
- Full Text:
- Date Issued: 2020
- Authors: Gxakuma, Lutho
- Date: 2020
- Subjects: Plant extracts , Plant products -- South Africa Medicinal plants -- South Africa Plants -- Analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49093 , vital:41600
- Description: Tulbaghia violacea is an indigenous plant commonly known as wild garlic, wilde knoffel in Afrikaans, isihaqa in Zulu or itswele lomlambo in Xhosa. Its leaves and bulbs are widely used as herbal remedies for various ailments and its medicinal uses include fever and colds, asthma, tuberculosis and stomach problems. Like all other members of the Alliacea family, Tulbaghia violacea produces a distinctive garlic-like odour when its leaves or rhizomes are damaged, resulting in the release of cysteine-derived sulphur compounds which include the oil-soluble organo-sulphur compounds and water-soluble cysteine derivatives. Chemically synthesized sulphur containing compounds have been reported to be effective devulcanizing agents and many industries prefer to perform devulcanization using them. Most commonly applied devulcanizing agents include disulphides, thiophenols and their zinc salts, and mercaptans which are mixed with the rubber scrap powder under specific reaction conditions. In this study, instead of performing devulcanization by using industrial synthesized sulphur containing compounds, the effectiveness of the extracts of organo-sulphur containing compounds from Tulbaghia violacea are evaluated as potential devulcanizing agents for synthetic cis-1,4-polyisoprene vulcanizates. This is a new, cheap and greener practice of rubber devulcanization. Diallyl disulphide, which is one of the organo-sulphur containing compounds present in Tulbaghia violacea, is the devulcanizing agent of interest to this study. The organo-sulphur containing compounds were extracted from the bulbs, roots and leaves of the plant using the soxhlet and ultrasonic bath extraction method. The solvent system used in the soxhlet extraction method was 2% of 2-propanol in n-hexane whereas in ultrasonic bath extraction method the solvent system used was 100% ethanol. An essential oil extract was obtained from the plant organs. The yield of the essential oil extracts obtained using the soxhlet extraction method was higher compared to the yield of the essential oil extracts obtained using the ultrasonic bath extraction method. According to the Fourier-Transform Infrared spectroscopy, the organo-sulphur containing compounds were present in the essential oil extracts of the plant. The essential oil extracts that were extracted using the soxhlet extraction method were chosen for further analysis. It was found out that the allyl sulphide and diallyl disulphide have the same retention time from the High Performance Liquid Chromatography (using a normal phase column). The Differential Scanning Calorimeter indicated that the allyl sulphide was not present in the essential oil extracts whereas the diallyl disulphide was present in the essential oil extract of the roots and leaves. The High Performance Liquid Chromatography was used to quantify the presence of the diallyl disulphide in the essential oil extract of roots and leaves. The quantity of diallyl disulphide was 23% in the dry mass of the essential oil extract of roots. In the essential oil extract of leaves the diallyl disulphide was very low concentrated and the High Performance Liquid Chromatography was less sensitive to detect it. According to the Thermogravimetric Analyser, it was found that the essential oil extracts begin to degrade at 120 °C and experience a multistage degradation. The softening temperature of the essential oil extracts was 60 °C from the Simultaneous Differential Scanning Calorimeter-Thermogravimetric Analyser. Conventional vulcanization of synthetic cis-1,4-polyisoprene was prepared with the vulcanization ingredients of zinc oxide, sulphur, stearic acid and N-tert-butyl-2-benzothiazole sulphenamide. The vulcanized synthetic cis-1,4-polyisoprene produced, under the heating temperature of 160 °C, was mixed with the essential oil extracts using the internal mixer at 60 °C and the two-roll mill. The overall torque, tan delta and the total crosslink density were the properties of interest of synthetic cis-1,4-polyisoprene vulcanizate in this study. The devulcanization temperature for the treated synthetic cis-1,4-polyisoprene vulcanizate with the essential oil extracts was optimized using the Dynamic Moving Die Rheometer and Dynamic Rubber Process Analyser. The amount of essential oil extracts at which they are effective devulcanizing agents for synthetic cis-1,4-polyisoprene vulcanizate was also optimized. During optimization a change on the latter mentioned properties of synthetic cis-1,4-polyisoprene vulcanizate was observed, indicating that the essential oil extracts have an effect as potential devulcanizing agents. The essential oil extracts increased the tan delta and reduced the overall torque, and total crosslink density of synthetic cis-1,4-polyisoprene vulcanizate as expected from devulcanizing agents. 200 °C was a preferable devulcanization temperature whereas essential oil extracts were effective as devulcanizing agent at 1.4%. However, the essential oil extracts influenced the overall torque and tan delta of synthetic cis-1,4-polyisoprene vulcanizate during the mixing process in the internal mixer at 60 °C, which was before heating at 200 °C. The essential oil extracts had a higher influence on the overall torque of synthetic cis-1,4-polyisoprene vulcanizate under heating at 200 °C whereas at 60 °C, during the mixing process, they had a higher influence on the tan delta of synthetic cis-1,4-polyisoprene vulcanizate. The essential oil extract of leaves had a higher influence on the overall torque whereas the essential oil extract of bulbs had a higher influence on the tan delta of synthetic cis-1,4-polyisoprene vulcanizate at 200 °C. The essential oil extract of roots shown a greater influence on the overall torque and tan delta of synthetic cis-1,4-polyisoprene vulcanizate at 60 °C during the mixing process. The effect of the essential oil extracts on the reversing heat capacity of synthetic cis-1,4-polyisoprene vulcanizate was also investigated using the Modulated Differential Scanning Calorimetry method. The essential oil extract of bulbs and roots influenced the reversing heat capacity of synthetic cis-1,4-polyisoprene vulcanizate by reducing it whereas the essential oil extract of leaves caused a temperature shift of the reversing heat capacity curve from the Modulated Differential Scanning Calorimeter thermogram of synthetic cis-1,4-polyisoprene vulcanizate. Therefore, the results indicated that the essential oil extracts of Tulbaghia violacea have an effect as an alternative potential devulcanizing agents for conventional vulcanized synthetic cis-1,4-polyisoprene whether the diallyl disulphide compound is present or not in them.
- Full Text:
- Date Issued: 2020
Applying high-resolution remote sensing to quantify baboon damage at a sub-compartment level in pine stands in the Mpumalanga escarpment region of South Africa
- Authors: Ferreira, Regardt
- Date: 2020
- Subjects: Environmental sciences -- Remote sensing , Geographic information systems Remote sensing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49082 , vital:41599
- Description: Managing risk in intensively managed monoculture plantation forests is an essential task to ensure sustainable yield and a continuous flow of forest products. However, since risks can be either biotic or abiotic, not all of them have a predictable pattern of spread, which can cause severe losses if management does not have the chance to implement mitigation action. Monitoring the change in forest health is vital as this provides the opportunity for preventative management and quantifies the amount of damage that management has to deal with. To provide this window of opportunity for appropriate action, constant monitoring is required. Until recently, forest health was measured through field surveys which provided adequate data. This procedure, however, is time consuming. Remote sensing has become very popular as a monitoring tool, due to its ability to provide assessment data in a fraction of the time. In this study, baboon damage in plantations along the Mpumalanga escarpment area of South Africa was monitored using remote sensing methods. While there are many methods of forest health monitoring using remote sensing, some approaches are less suitable as they either monitor damage caused at a plantation level, use lower spatial resolution (>10m) datasets or map damage using one available time period. The purpose of this study was first to establish the impact of baboon damage through time, using Sentinel-2 satellite imagery with all vegetation indices available, and the Extreme Gradient Boosting (XGboost) algorithm. The second part focused on analysing the damage at a tree level using PlanetScope imagery using a deep Learning approach. Overall, the study found that the use of Sentinel-2 data and PlanetScope data could accurately distinguish between the varying severity of baboon damage, achieving an accuracy of 95% and 82%. The processing time of the deep learning Artificial Neural Network (ANN) was greatly affected by the number of hidden layers and neurons used. Implementation of techniques used in this study has the potential to improve the accuracy of forest health monitoring in compartment forestry in South Africa.
- Full Text:
- Date Issued: 2020
- Authors: Ferreira, Regardt
- Date: 2020
- Subjects: Environmental sciences -- Remote sensing , Geographic information systems Remote sensing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49082 , vital:41599
- Description: Managing risk in intensively managed monoculture plantation forests is an essential task to ensure sustainable yield and a continuous flow of forest products. However, since risks can be either biotic or abiotic, not all of them have a predictable pattern of spread, which can cause severe losses if management does not have the chance to implement mitigation action. Monitoring the change in forest health is vital as this provides the opportunity for preventative management and quantifies the amount of damage that management has to deal with. To provide this window of opportunity for appropriate action, constant monitoring is required. Until recently, forest health was measured through field surveys which provided adequate data. This procedure, however, is time consuming. Remote sensing has become very popular as a monitoring tool, due to its ability to provide assessment data in a fraction of the time. In this study, baboon damage in plantations along the Mpumalanga escarpment area of South Africa was monitored using remote sensing methods. While there are many methods of forest health monitoring using remote sensing, some approaches are less suitable as they either monitor damage caused at a plantation level, use lower spatial resolution (>10m) datasets or map damage using one available time period. The purpose of this study was first to establish the impact of baboon damage through time, using Sentinel-2 satellite imagery with all vegetation indices available, and the Extreme Gradient Boosting (XGboost) algorithm. The second part focused on analysing the damage at a tree level using PlanetScope imagery using a deep Learning approach. Overall, the study found that the use of Sentinel-2 data and PlanetScope data could accurately distinguish between the varying severity of baboon damage, achieving an accuracy of 95% and 82%. The processing time of the deep learning Artificial Neural Network (ANN) was greatly affected by the number of hidden layers and neurons used. Implementation of techniques used in this study has the potential to improve the accuracy of forest health monitoring in compartment forestry in South Africa.
- Full Text:
- Date Issued: 2020
Assessing the Social Sustainability of Wind Energy in the Karoo
- Authors: Hechter, J P
- Date: 2020
- Subjects: Wind power -- South Africa -- Karoo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48378 , vital:40854
- Description: Background: In an ecologically conscious world, the need for sustainable development and the need to produce alternative energy is at the forefront of discussions. South Africa has been witnessing to a surge in wind energy developments in recent years. Although, environmental impacts often enjoy more emphasis, social impacts are equally important. Recently social sustainability was seen as an integral part of sustainable development for the future and can no longer be ignored. Wind energy is pathway towards sustainable development but can have detrimental impacts on social sustainability. On the one hand wind energy is said to impact culture, sense of places and cause unrest in a community, however, on the other hand it is said to be socially sustainable to the point where wind energy is incorporated into local culture and not to mention the employment opportunities it can create. This is particularly important for vulnerable communities found in the Karoo, where unemployment is very high. Purpose/ Aim: The aim of this study was to assess the social sustainability of a wind energy project in the Karoo by constructing a theoretical assessment model designed to produce appropriate and specific social indicators. Methodology: A literature review was undertaken to gain insights into the social sustainability of wind energy which also served as the theoretical backbone for the model and assessment parameters. The assessment model produced 10 indicators which was used as interview schedule with key stakeholders in the study area. A total of 31 qualitative interviews were conducted and produced a good data set. Findings: The results from this study show that here was no significant negative impact reported with regards to social sustainability. The wind developer is committed to the community based on the various social initiative funded by it. Although a definite positive impact and improvement in terms of social sustainability is evident in the area, there is still a long way to go as many outcomes set by the wind developer is yet to achieved.
- Full Text:
- Date Issued: 2020
- Authors: Hechter, J P
- Date: 2020
- Subjects: Wind power -- South Africa -- Karoo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48378 , vital:40854
- Description: Background: In an ecologically conscious world, the need for sustainable development and the need to produce alternative energy is at the forefront of discussions. South Africa has been witnessing to a surge in wind energy developments in recent years. Although, environmental impacts often enjoy more emphasis, social impacts are equally important. Recently social sustainability was seen as an integral part of sustainable development for the future and can no longer be ignored. Wind energy is pathway towards sustainable development but can have detrimental impacts on social sustainability. On the one hand wind energy is said to impact culture, sense of places and cause unrest in a community, however, on the other hand it is said to be socially sustainable to the point where wind energy is incorporated into local culture and not to mention the employment opportunities it can create. This is particularly important for vulnerable communities found in the Karoo, where unemployment is very high. Purpose/ Aim: The aim of this study was to assess the social sustainability of a wind energy project in the Karoo by constructing a theoretical assessment model designed to produce appropriate and specific social indicators. Methodology: A literature review was undertaken to gain insights into the social sustainability of wind energy which also served as the theoretical backbone for the model and assessment parameters. The assessment model produced 10 indicators which was used as interview schedule with key stakeholders in the study area. A total of 31 qualitative interviews were conducted and produced a good data set. Findings: The results from this study show that here was no significant negative impact reported with regards to social sustainability. The wind developer is committed to the community based on the various social initiative funded by it. Although a definite positive impact and improvement in terms of social sustainability is evident in the area, there is still a long way to go as many outcomes set by the wind developer is yet to achieved.
- Full Text:
- Date Issued: 2020
Associations between family history of diseases of lifestyle, lifestyle behaviour and anthropometric nutritional status of pre-school children in ECD centres in the Nelson Mandela Bay Municipality
- Authors: Wilson, Teresa Margaret
- Date: 2020
- Subjects: Nutrition--Evaluation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46344 , vital:39602
- Description: Introduction: Childhood overweight and obesity is an escalating global health issue. In Africa, overweight and obesity prevalence in children has nearly doubled since 2000(World Health Organisation, 2018).TheSANHANES-1 study (2013) identified that overweight and obesity in were most prevalent in urban informal areas of South Africa, with approximately a quarter of the children classified as overweight or obese (Shisana et al., 2013).In the Nelson Mandela Bay Municipality(NMBM), a double burden of disease was identified in the lower socio-economic population (Phekana et al., 2016). This study and others recommended further study into the contributing factors and behaviours which play a role in the development of overweight and obesity in children. These include household dietary intake, family history of lifestyle diseases, as well as the children’s and parental physical activity and sedentary time (Zhang et al.,2016).Aim: The aim of the study was to determine the associations between family history of diseases of lifestyle, lifestyle behaviour and anthropometric nutritional status of pre-school children in NMBM to describe underlying causes of childhood overweight and obesity.Methods: A cross-sectional design, using a quantitative approach, was used for this study(Ethics approval: H18-HEA-DIET-004). The study population included adult parents and/or caregivers of children from urban areas of Nelson Mandela Bay Municipality attending crèches and schools in these areas, in the age group from birth to 96 months (8 years). Randomised cluster sampling of crèches and schools from an existing database of anthropometrical data of children attending these crèches and schools in the area was done and a final sample of n=155obtained. With the assistance of a trained fieldworker, respondents completed a questionnaire detailing the family history of lifestyle diseases, physical activity levels and sedentary screen time behaviours, and a graphical adjusted version of a household dietary diversity questionnaire. Data about children’s activity levels in the preschool/creche environment was collected by the fieldworker by assessing the ECD centres’daily activity schedules. The anthropometric data of the children of the respondents was accessed from an existing database of these measurements. The data was described using means and standard deviations. Inferential statistics determined any existing associations between these underlying influences of childhood obesity.Results: Only 2% (n=3) of the children were underweight and 12% (n=9) were at risk of becoming underweight as classified by WAZ. HAZ scores identified26% (n=40) of the children at risk of becoming stunted, and 6% (n=9) of the children were already stunted. WHZ classified5% (n=8)of the children as overweight and 5% (n=8)as obese. A further 22% (n=34) of the children were at risk of becoming overweight.BMI/age classificationidentified25% (n=38) of the children as overweight and a further 12% (n=19) as obese. Out of the sample, 12%(n=17) of mothers and 8% (n=7) of fathers were categorised as overweight-to-obese according to the SA specific waist circumference(WC)cut-offs. Out of the children, 15% (n=22) have at least one parent who was overweight-to-obese. Traditional WC categories were classified48% (n=67) of the mothers as overweight-to-obese and at high risk for metabolic syndrome. Of all the lifestyle diseases, hypertension was the most prevalent with 29% (n=41) of households having at least one parent with hypertension. Parental physical activity was grossly overestimated, and the results found to be invalid. The Diet Variety and Frequency score resulted in a mean of 65.00 (n=154, SD=27.37) out of a possible 100 for the households in this sample, and junk food was consumed on three to four occasions per day in 32% (n=49) of households. There were no significant associations found between the parents’ variables and underweight children. Statistically small to medium effect associations were found between parental weight (both SA specific and traditional categories) and overweight children (classified by WHZ and BMI/age). Conclusions and recommendations: The prevalence of overweight and obesity among children in the NMBM was high. The only possible underlying cause of childhood overweight and obesity in pre-school children in the NMBM that could be determined by this study was parents’ weight classified by WC. However, it must be reiterated that due to the cross-sectional nature of the study, an association does not immediately mean causation, and the results are not adequate to rule out other underlying factors influencing childhood obesity. It is recommended that the results of the study are used to incentivise the final implementation of all the intervention targets laid out in the Strategic Plan for the Prevention and Control of Obesity in South Africa 2015-2020 in NMB, and for the development of the future obesity strategy after 2020. The results have shown the necessity for future health interventions to be targeted at the family as a unit.
- Full Text:
- Date Issued: 2020
- Authors: Wilson, Teresa Margaret
- Date: 2020
- Subjects: Nutrition--Evaluation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46344 , vital:39602
- Description: Introduction: Childhood overweight and obesity is an escalating global health issue. In Africa, overweight and obesity prevalence in children has nearly doubled since 2000(World Health Organisation, 2018).TheSANHANES-1 study (2013) identified that overweight and obesity in were most prevalent in urban informal areas of South Africa, with approximately a quarter of the children classified as overweight or obese (Shisana et al., 2013).In the Nelson Mandela Bay Municipality(NMBM), a double burden of disease was identified in the lower socio-economic population (Phekana et al., 2016). This study and others recommended further study into the contributing factors and behaviours which play a role in the development of overweight and obesity in children. These include household dietary intake, family history of lifestyle diseases, as well as the children’s and parental physical activity and sedentary time (Zhang et al.,2016).Aim: The aim of the study was to determine the associations between family history of diseases of lifestyle, lifestyle behaviour and anthropometric nutritional status of pre-school children in NMBM to describe underlying causes of childhood overweight and obesity.Methods: A cross-sectional design, using a quantitative approach, was used for this study(Ethics approval: H18-HEA-DIET-004). The study population included adult parents and/or caregivers of children from urban areas of Nelson Mandela Bay Municipality attending crèches and schools in these areas, in the age group from birth to 96 months (8 years). Randomised cluster sampling of crèches and schools from an existing database of anthropometrical data of children attending these crèches and schools in the area was done and a final sample of n=155obtained. With the assistance of a trained fieldworker, respondents completed a questionnaire detailing the family history of lifestyle diseases, physical activity levels and sedentary screen time behaviours, and a graphical adjusted version of a household dietary diversity questionnaire. Data about children’s activity levels in the preschool/creche environment was collected by the fieldworker by assessing the ECD centres’daily activity schedules. The anthropometric data of the children of the respondents was accessed from an existing database of these measurements. The data was described using means and standard deviations. Inferential statistics determined any existing associations between these underlying influences of childhood obesity.Results: Only 2% (n=3) of the children were underweight and 12% (n=9) were at risk of becoming underweight as classified by WAZ. HAZ scores identified26% (n=40) of the children at risk of becoming stunted, and 6% (n=9) of the children were already stunted. WHZ classified5% (n=8)of the children as overweight and 5% (n=8)as obese. A further 22% (n=34) of the children were at risk of becoming overweight.BMI/age classificationidentified25% (n=38) of the children as overweight and a further 12% (n=19) as obese. Out of the sample, 12%(n=17) of mothers and 8% (n=7) of fathers were categorised as overweight-to-obese according to the SA specific waist circumference(WC)cut-offs. Out of the children, 15% (n=22) have at least one parent who was overweight-to-obese. Traditional WC categories were classified48% (n=67) of the mothers as overweight-to-obese and at high risk for metabolic syndrome. Of all the lifestyle diseases, hypertension was the most prevalent with 29% (n=41) of households having at least one parent with hypertension. Parental physical activity was grossly overestimated, and the results found to be invalid. The Diet Variety and Frequency score resulted in a mean of 65.00 (n=154, SD=27.37) out of a possible 100 for the households in this sample, and junk food was consumed on three to four occasions per day in 32% (n=49) of households. There were no significant associations found between the parents’ variables and underweight children. Statistically small to medium effect associations were found between parental weight (both SA specific and traditional categories) and overweight children (classified by WHZ and BMI/age). Conclusions and recommendations: The prevalence of overweight and obesity among children in the NMBM was high. The only possible underlying cause of childhood overweight and obesity in pre-school children in the NMBM that could be determined by this study was parents’ weight classified by WC. However, it must be reiterated that due to the cross-sectional nature of the study, an association does not immediately mean causation, and the results are not adequate to rule out other underlying factors influencing childhood obesity. It is recommended that the results of the study are used to incentivise the final implementation of all the intervention targets laid out in the Strategic Plan for the Prevention and Control of Obesity in South Africa 2015-2020 in NMB, and for the development of the future obesity strategy after 2020. The results have shown the necessity for future health interventions to be targeted at the family as a unit.
- Full Text:
- Date Issued: 2020
Biology, stock assessment and angler attitudes towards the introduction of slot size limits for a recreationally important species Sparodon durbanensis (Sparidae) in South Africa
- Authors: Hewett, Kyle
- Date: 2020
- Subjects: Sparidae -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48389 , vital:40855
- Description: Sparodon durbanensis (white musselcracker) is an endemic fish species in the Family Sparidae found in shallow (< 20 m) coastal waters from the Western Cape to KwaZulu-Natal. It is large-growing, late-maturing, long-lived and is a popular target species in the South African marine shore-based line and spear fisheries. Management regulations for the species have remained the same for over two decades despite anecdotal information of population declines. However, since the last life history-information for S. durbanensis was collected in the late 1980s, there is a paucity of contemporary information needed to inform wise management. The aim of this study was to collect contemporary socio-ecological information on the species and its fishery in order to better inform the management of the species. In order to do this, the growth-rate of historical and contemporary samples of Sparodon durbanensis was compared, a length-based stock assessment was performed and the knowledge and attitudes of anglers towards the introduction of improved regulations were investigated. The growth-rate was compared using otolith width as a proxy for fish growth. It was found that the growth-rate had remained relatively stable between 1963 and 2010, suggesting that S. durbanensis may be resilient to the increasing levels of environmental variability observed throughout its range and that the historical growth parameters determined for this species may remain applicable for contemporary stock assessment. The batch fecundity was determined for 50 mm size classes and used to estimate the percentage cumulative population batch fecundity using historical 803 mm FL (904 mm TL) and contemporary 776 mm FL (874 mm TL) length structure, respectively. Based on these observations a suitable harvest slot limit of 600-850 mm TL was suggested. A Length-Based Spawning Potential Ratio (SPR) model was used to provide the first formal stock assessment for S. durbanensis. The input parameters of M/k=1.44, L∞=1021 mm FL, L50=350 mm FL and L95=800 mm FL and length composition data comprising of 134 lengths obtained from a collection of competitive angling catches, estimated a SPR of 41%, which is above the 40% target reference point. A total of 126 online and face– to-face, replica questionnaires were completed by spearfishermen and recreational shore anglers. Responses indicated that anglers that target S. durbanensis are generally a specialized group who are knowledgeable about the biology and ecology of the species and are passionate about the conservation of the species. Participants indicated that Marine Protected Areas are likely the most effective regulation in the current suite of regulations used to manage the fishery and suggested that poor law enforcement was the major factor inhibiting the efficacy of fishery regulations. New proposed regulations, such as a harvest slot limit (and particularly the one between 600-850 mm TL) for S. durbanensis, was well supported, however participants suggested that non-compliance was a concern. Although, the SPR remained above the 40% target reference point, further declines in the stock status should be prevented through the implementation of a 600-850 mm TL harvest slot limit. Based on the findings of this study, this limit should provide protection against both growth and recruitment overfishing by providing protection to sexually immature, fast growing fish and to large adults that contribute the greatest proportion to population replenishment.
- Full Text:
- Date Issued: 2020
- Authors: Hewett, Kyle
- Date: 2020
- Subjects: Sparidae -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48389 , vital:40855
- Description: Sparodon durbanensis (white musselcracker) is an endemic fish species in the Family Sparidae found in shallow (< 20 m) coastal waters from the Western Cape to KwaZulu-Natal. It is large-growing, late-maturing, long-lived and is a popular target species in the South African marine shore-based line and spear fisheries. Management regulations for the species have remained the same for over two decades despite anecdotal information of population declines. However, since the last life history-information for S. durbanensis was collected in the late 1980s, there is a paucity of contemporary information needed to inform wise management. The aim of this study was to collect contemporary socio-ecological information on the species and its fishery in order to better inform the management of the species. In order to do this, the growth-rate of historical and contemporary samples of Sparodon durbanensis was compared, a length-based stock assessment was performed and the knowledge and attitudes of anglers towards the introduction of improved regulations were investigated. The growth-rate was compared using otolith width as a proxy for fish growth. It was found that the growth-rate had remained relatively stable between 1963 and 2010, suggesting that S. durbanensis may be resilient to the increasing levels of environmental variability observed throughout its range and that the historical growth parameters determined for this species may remain applicable for contemporary stock assessment. The batch fecundity was determined for 50 mm size classes and used to estimate the percentage cumulative population batch fecundity using historical 803 mm FL (904 mm TL) and contemporary 776 mm FL (874 mm TL) length structure, respectively. Based on these observations a suitable harvest slot limit of 600-850 mm TL was suggested. A Length-Based Spawning Potential Ratio (SPR) model was used to provide the first formal stock assessment for S. durbanensis. The input parameters of M/k=1.44, L∞=1021 mm FL, L50=350 mm FL and L95=800 mm FL and length composition data comprising of 134 lengths obtained from a collection of competitive angling catches, estimated a SPR of 41%, which is above the 40% target reference point. A total of 126 online and face– to-face, replica questionnaires were completed by spearfishermen and recreational shore anglers. Responses indicated that anglers that target S. durbanensis are generally a specialized group who are knowledgeable about the biology and ecology of the species and are passionate about the conservation of the species. Participants indicated that Marine Protected Areas are likely the most effective regulation in the current suite of regulations used to manage the fishery and suggested that poor law enforcement was the major factor inhibiting the efficacy of fishery regulations. New proposed regulations, such as a harvest slot limit (and particularly the one between 600-850 mm TL) for S. durbanensis, was well supported, however participants suggested that non-compliance was a concern. Although, the SPR remained above the 40% target reference point, further declines in the stock status should be prevented through the implementation of a 600-850 mm TL harvest slot limit. Based on the findings of this study, this limit should provide protection against both growth and recruitment overfishing by providing protection to sexually immature, fast growing fish and to large adults that contribute the greatest proportion to population replenishment.
- Full Text:
- Date Issued: 2020
Change of perspectives and behaviour regarding lifestyle, with emphasis on dietary habits, in a rural community
- Authors: Barnard, Mariska
- Date: 2020
- Subjects: Food habits
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46384 , vital:39565
- Description: Background: The steady increase in deaths due to non-communicable diseases (NCDs) in South Africa is raising concern, as 63% of all deaths worldwide are attributed to NCDs and these diseases cause 36 million deaths each year, with 80 % of incidences occurring in low-and middle-income countries. In rural communities where income is increasing, the prevalence of NCDs are increasing as well. Due to the lack of NCD prevention and treatment in rural communities, it is expected that, if health promotion strategies are not implemented and socio-economic development in South Africa continues, there will soon be an uncontrollable NCD epidemic. It has been found that dietary risks affected people’s healthirrespective of their age, gender or residential sociodemographic development and that dietary improvement might prevent one in every five deaths worldwide.Aim:The aim of this study was to determine the factors that influence the perceptions and behaviour in a rural community with a low socio-economic status regarding dietary habits and to use the knowledge to formulate an effective dietary modification strategy.Designand methodology:For this study,action research with a quantitative and qualitative component was followed.The quantitative component focuses on measureable aspects, and the qualitative component focuses on meaning. Data was collected following the standard operating procedure for anthropometry, blood pressure and blood glucose. Further methods used were questionnaires, 24-hour dietary recalls and focus group discussions. Data were analysed using Microsoft Excel, FoodFinder3 and other calculations.Sample and setting:A convenience sample (n = 16) wasused and this study was undertaken on request of the non-governmental organization, Karoo Angels and included all participants who earn an income and who do not work for themselves, that were willing to participate and living in Rietbron and Vondeling, in the Sarah BaartmanDistrict in the Eastern Cape. Results:Weight changes took place, both the crafters in the mild thinness category gained weight, one gained 3.9 kg and the other 0.5 kg. The three crafters in the normal category did not have to gain or lose weight, but all three ofthem gained an average of 3.6 kg. For the group who had to lose weight, no statistically significant weight change took place from before the intervention (76.08 ±17.67 kg) to after the intervention (75.81 ± 17.81 kg, t(10) = 0.692, p = 0.505). The maximum weight lost ivwas 3.1 kg and the maximum weight gained was 3.2 kg. Changes took place regarding BMI, waist circumference, waist-to-hip ratio and neck circumference. Some positively changed their BMI status.After the implementation of the intervention, there was a slight decrease in frequency of alcohol consumption, but smoking and physical activity remained mostly the same. Hypertension was the most prevalent NCD and is linked to smoking and alcohol consumption which is prevalent in this study. Fruit and vegetable consumption is low, and a slight increase in consumption was evident. A maximum dietary diversityscore of seven and minimum of two, where the mean was 3.81was found. The crafters’ diet did not meet the DASH diet recommendation,the mean energy distribution is of all macronutrients differ with ±4% and none of the participants’ mean micronutrients intake met the recommendations of the DASH diet or RDA. Factors that prevent them from reaching their goals included low income, low availability of fruit, vegetables and transport and no storage for food.Conclusion:It is important to consider the individuals’ living conditions, resources, knowledge, motivation and social group. The environment and resources available have a significant impact on the lifestyle of the individuals. Directing efforts of behaviour change to increase dietary diversity as the main objective, might be a more efficient way to change behaviour.Recommendations:Future studies should consider doing this study over a longer time period. The involvement of a psychologist would also be beneficial to assist the process of behaviour change.
- Full Text:
- Date Issued: 2020
- Authors: Barnard, Mariska
- Date: 2020
- Subjects: Food habits
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46384 , vital:39565
- Description: Background: The steady increase in deaths due to non-communicable diseases (NCDs) in South Africa is raising concern, as 63% of all deaths worldwide are attributed to NCDs and these diseases cause 36 million deaths each year, with 80 % of incidences occurring in low-and middle-income countries. In rural communities where income is increasing, the prevalence of NCDs are increasing as well. Due to the lack of NCD prevention and treatment in rural communities, it is expected that, if health promotion strategies are not implemented and socio-economic development in South Africa continues, there will soon be an uncontrollable NCD epidemic. It has been found that dietary risks affected people’s healthirrespective of their age, gender or residential sociodemographic development and that dietary improvement might prevent one in every five deaths worldwide.Aim:The aim of this study was to determine the factors that influence the perceptions and behaviour in a rural community with a low socio-economic status regarding dietary habits and to use the knowledge to formulate an effective dietary modification strategy.Designand methodology:For this study,action research with a quantitative and qualitative component was followed.The quantitative component focuses on measureable aspects, and the qualitative component focuses on meaning. Data was collected following the standard operating procedure for anthropometry, blood pressure and blood glucose. Further methods used were questionnaires, 24-hour dietary recalls and focus group discussions. Data were analysed using Microsoft Excel, FoodFinder3 and other calculations.Sample and setting:A convenience sample (n = 16) wasused and this study was undertaken on request of the non-governmental organization, Karoo Angels and included all participants who earn an income and who do not work for themselves, that were willing to participate and living in Rietbron and Vondeling, in the Sarah BaartmanDistrict in the Eastern Cape. Results:Weight changes took place, both the crafters in the mild thinness category gained weight, one gained 3.9 kg and the other 0.5 kg. The three crafters in the normal category did not have to gain or lose weight, but all three ofthem gained an average of 3.6 kg. For the group who had to lose weight, no statistically significant weight change took place from before the intervention (76.08 ±17.67 kg) to after the intervention (75.81 ± 17.81 kg, t(10) = 0.692, p = 0.505). The maximum weight lost ivwas 3.1 kg and the maximum weight gained was 3.2 kg. Changes took place regarding BMI, waist circumference, waist-to-hip ratio and neck circumference. Some positively changed their BMI status.After the implementation of the intervention, there was a slight decrease in frequency of alcohol consumption, but smoking and physical activity remained mostly the same. Hypertension was the most prevalent NCD and is linked to smoking and alcohol consumption which is prevalent in this study. Fruit and vegetable consumption is low, and a slight increase in consumption was evident. A maximum dietary diversityscore of seven and minimum of two, where the mean was 3.81was found. The crafters’ diet did not meet the DASH diet recommendation,the mean energy distribution is of all macronutrients differ with ±4% and none of the participants’ mean micronutrients intake met the recommendations of the DASH diet or RDA. Factors that prevent them from reaching their goals included low income, low availability of fruit, vegetables and transport and no storage for food.Conclusion:It is important to consider the individuals’ living conditions, resources, knowledge, motivation and social group. The environment and resources available have a significant impact on the lifestyle of the individuals. Directing efforts of behaviour change to increase dietary diversity as the main objective, might be a more efficient way to change behaviour.Recommendations:Future studies should consider doing this study over a longer time period. The involvement of a psychologist would also be beneficial to assist the process of behaviour change.
- Full Text:
- Date Issued: 2020
Coherent detection of data and timing signals over optical fiber for telescope networks
- Authors: Nfanyana, Ketshabile
- Date: 2020
- Subjects: Fiber optics , Very large array telescopes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49226 , vital:41612
- Description: Telescope networks are increasingly being developed with networks such as the SKA telescope demanding the use of high-end technology to be incorporated. These networks require accurate clock signals to be transported to antennas as well as massive data to be transported from individual parabolic array antennas to a central computer for data analysis. To achieve this, optical fiber technology forms the backbone of these networks, proving high speed transmission and required bandwidth. For a distributed telescope network, coherent detection technology serves as the ideal optical fiber technology candidate for transport of information to a correlator. Use of this technology constitutes too many benefits. Sensitivity of the system is improved, and advanced modulation formats can be employed thereby improving spectral efficiency. Furthermore, coherent detection allows for digital signal processing algorithms to be employed for equalization of transmission impairments such as chromatic dispersion (CD), polarization mode dispersion (PMD), phase noise and nonlinear effects in the electrical domain. CD equalization is performed in the time or frequency domain using digital filters which suppress the fibers dispersion effectively. PMD equalization is usually performed in the time domain through the use of adaptive filters which employ algorithms such as least mean squares (LMS) and constant modulus algorithm (CMA). These algorithms further equalize residual CD. In mitigation of phase noise (carrier phase recovery), feed-forward and feedback carrier phase algorithms are used. Fiber nonlinearities and other impairments are compensated using the digital backpropagation algorithm which solves for the Manakov equation and nonlinear Schrödinger equation (NLSE). Distribution of stable clock signals to individual antennas is an important aspect of telescope networks. Clock signals are used to drive the digitizers and time stamping of received antenna information. These clock signals can be distributed using coherent detection technology by phase modulating the clock so as to provide inherent phase modulation robustness to noise through the fiber. In this thesis, we present coherent detection of non-return-to-zero pseudorandom binary sequence (PRBS-7) using binary phase shift keying (BPSK) through 26.6 km non-zero dispersion shifted fiber (NZDSF) at 10 Gbps. Digital signal processing for equalization of CD and PMD was performed offline using MATLAB software. For residual CD and PMD equalization, the LMS algorithm was used. The performance of the system, bit error rate (BER), was compared with that of an intensity modulated on-off keying (OOK) signal at the same bit rate. Basing on receiver sensitivity performance of OOK at 10-9 bit error rate, BPSK achieved superior performance with receiver sensitivity improvements of 18.37 dB and 13.89 dB attained for back-to-back and transmission over fiber, respectively. Phase modulation transmission of a 4 GHz clock signal was also conducted. Frequency instability, Allan variance and phase noise, of phase modulated clock was compared with that of intensity modulated clock. Moreover, we present an all optical clock generation scheme using frequency heterodyning technique. Allan variance values in the range of 10-10 were attained. The frequency instability of this clock generation scheme was quantified using the spectrum analyzer method. Furthermore, an all-photonic technique for data latency tracking of 5G networks over optical fiber is presented. The technique is spectrally efficient and is able to track latency down to the nano second timescale.
- Full Text:
- Date Issued: 2020
- Authors: Nfanyana, Ketshabile
- Date: 2020
- Subjects: Fiber optics , Very large array telescopes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49226 , vital:41612
- Description: Telescope networks are increasingly being developed with networks such as the SKA telescope demanding the use of high-end technology to be incorporated. These networks require accurate clock signals to be transported to antennas as well as massive data to be transported from individual parabolic array antennas to a central computer for data analysis. To achieve this, optical fiber technology forms the backbone of these networks, proving high speed transmission and required bandwidth. For a distributed telescope network, coherent detection technology serves as the ideal optical fiber technology candidate for transport of information to a correlator. Use of this technology constitutes too many benefits. Sensitivity of the system is improved, and advanced modulation formats can be employed thereby improving spectral efficiency. Furthermore, coherent detection allows for digital signal processing algorithms to be employed for equalization of transmission impairments such as chromatic dispersion (CD), polarization mode dispersion (PMD), phase noise and nonlinear effects in the electrical domain. CD equalization is performed in the time or frequency domain using digital filters which suppress the fibers dispersion effectively. PMD equalization is usually performed in the time domain through the use of adaptive filters which employ algorithms such as least mean squares (LMS) and constant modulus algorithm (CMA). These algorithms further equalize residual CD. In mitigation of phase noise (carrier phase recovery), feed-forward and feedback carrier phase algorithms are used. Fiber nonlinearities and other impairments are compensated using the digital backpropagation algorithm which solves for the Manakov equation and nonlinear Schrödinger equation (NLSE). Distribution of stable clock signals to individual antennas is an important aspect of telescope networks. Clock signals are used to drive the digitizers and time stamping of received antenna information. These clock signals can be distributed using coherent detection technology by phase modulating the clock so as to provide inherent phase modulation robustness to noise through the fiber. In this thesis, we present coherent detection of non-return-to-zero pseudorandom binary sequence (PRBS-7) using binary phase shift keying (BPSK) through 26.6 km non-zero dispersion shifted fiber (NZDSF) at 10 Gbps. Digital signal processing for equalization of CD and PMD was performed offline using MATLAB software. For residual CD and PMD equalization, the LMS algorithm was used. The performance of the system, bit error rate (BER), was compared with that of an intensity modulated on-off keying (OOK) signal at the same bit rate. Basing on receiver sensitivity performance of OOK at 10-9 bit error rate, BPSK achieved superior performance with receiver sensitivity improvements of 18.37 dB and 13.89 dB attained for back-to-back and transmission over fiber, respectively. Phase modulation transmission of a 4 GHz clock signal was also conducted. Frequency instability, Allan variance and phase noise, of phase modulated clock was compared with that of intensity modulated clock. Moreover, we present an all optical clock generation scheme using frequency heterodyning technique. Allan variance values in the range of 10-10 were attained. The frequency instability of this clock generation scheme was quantified using the spectrum analyzer method. Furthermore, an all-photonic technique for data latency tracking of 5G networks over optical fiber is presented. The technique is spectrally efficient and is able to track latency down to the nano second timescale.
- Full Text:
- Date Issued: 2020
Constraints in attainment of sustainable human settlements at Kwamaphumulo Local Municipality
- Authors: Sikhosana, Phindokuhle
- Date: 2020
- Subjects: Human settlements , Sustainable development
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47181 , vital:39829
- Description: This study sought to investigate the constraints in the attainment of sustainable human settlement in KwaMaphumulo Local Municipality at iLembe District in KwaZulu-Natal, South Africa. The aim of this study was to investigate the constraints that limit the achievement of the ideal of sustainable human settlement development in the KwaMaphumulo Local Municipality. Furthermore, the study sought to determine the impact of these constraints on sustainable development and to proffer measures that can be taken to combat stagnant or underdevelopment in the area. A mixed-method approach is followed in this study, which considers a triangulation of quantitative and qualitative data collection, analysis and interpretation techniques. It is important to note that in the past years since South Africa became a democratic country, there have been countless efforts with regard to overcoming the problems created during the apartheid era. These problems stemmed from a distorted spatial, social, economic and political background that was advocated by both segregationist public policies and the planning systems of the Apartheid Regime. In recent years, South African cities have also been faced with environmental issues, which are imperative to the future development of the country. With all these issues in mind, we see that the many efforts that are put in place by government always fall short of solving the problems. This research report looked at the constraints that affect the KwaMaphumulo Local Municipality in attaining sustainable human settlements and whether the efforts of redistribution and equality have been enough to overcome the problems. The key findings of the study were that constraints in attaining sustainable human settlements in the KwaMaphumulo Local Municipality negatively impacts on the development in the area. The level of services being provided is poor. There is an apparent disconnect between traditional leaders and the municipality councillor as development management and vision are concerned. Furthermore, the development programmes and projects do not seem to address the critical needs of the community. Housing development is narrow minded with a focus on the top structure and a failure to include basic services and infrastructure. Houses built that are financed by subsidies are of poor quality. The latter situation results in more able‐ bodied, skilled and capable people emigrating to developed areas.
- Full Text:
- Date Issued: 2020
- Authors: Sikhosana, Phindokuhle
- Date: 2020
- Subjects: Human settlements , Sustainable development
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47181 , vital:39829
- Description: This study sought to investigate the constraints in the attainment of sustainable human settlement in KwaMaphumulo Local Municipality at iLembe District in KwaZulu-Natal, South Africa. The aim of this study was to investigate the constraints that limit the achievement of the ideal of sustainable human settlement development in the KwaMaphumulo Local Municipality. Furthermore, the study sought to determine the impact of these constraints on sustainable development and to proffer measures that can be taken to combat stagnant or underdevelopment in the area. A mixed-method approach is followed in this study, which considers a triangulation of quantitative and qualitative data collection, analysis and interpretation techniques. It is important to note that in the past years since South Africa became a democratic country, there have been countless efforts with regard to overcoming the problems created during the apartheid era. These problems stemmed from a distorted spatial, social, economic and political background that was advocated by both segregationist public policies and the planning systems of the Apartheid Regime. In recent years, South African cities have also been faced with environmental issues, which are imperative to the future development of the country. With all these issues in mind, we see that the many efforts that are put in place by government always fall short of solving the problems. This research report looked at the constraints that affect the KwaMaphumulo Local Municipality in attaining sustainable human settlements and whether the efforts of redistribution and equality have been enough to overcome the problems. The key findings of the study were that constraints in attaining sustainable human settlements in the KwaMaphumulo Local Municipality negatively impacts on the development in the area. The level of services being provided is poor. There is an apparent disconnect between traditional leaders and the municipality councillor as development management and vision are concerned. Furthermore, the development programmes and projects do not seem to address the critical needs of the community. Housing development is narrow minded with a focus on the top structure and a failure to include basic services and infrastructure. Houses built that are financed by subsidies are of poor quality. The latter situation results in more able‐ bodied, skilled and capable people emigrating to developed areas.
- Full Text:
- Date Issued: 2020
Constraints in attainment of sustainable human settlements at Kwamaphumulo Local Municipality
- Authors: Sikhosana, Phindokuhle
- Date: 2020
- Subjects: Human settlements -- South Africa -- Kwamaphumulo Local Municipality , Land settlement -- South Africa -- Kwamaphumulo Local Municipality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48808 , vital:41141
- Description: This study sought to investigate the constraints in the attainment of sustainable human settlement in KwaMaphumulo Local Municipality at iLembe District in KwaZulu-Natal, South Africa. The aim of this study was to investigate the constraints that limit the achievement of the ideal of sustainable human settlement development in the KwaMaphumulo Local Municipality. Furthermore, the study sought to determine the impact of these constraints on sustainable development and to proffer measures that can be taken to combat stagnant or underdevelopment in the area. A mixed-method approach is followed in this study, which considers a triangulation of quantitative and qualitative data collection, analysis and interpretation techniques. It is important to note that in the past years since South Africa became a democratic country, there have been countless efforts with regard to overcoming the problems created during the apartheid era. These problems stemmed from a distorted spatial, social, economic and political background that was advocated by both segregationist public policies and the planning systems of the Apartheid Regime. In recent years, South African cities have also been faced with environmental issues, which are imperative to the future development of the country. With all these issues in mind, we see that the many efforts that are put in place by government always fall short of solving the problems. This research report looked at the constraints that affect the KwaMaphumulo Local Municipality in attaining sustainable human settlements and whether the efforts of redistribution and equality have been enough to overcome the problems. The key findings of the study were that constraints in attaining sustainable human settlements in the KwaMaphumulo Local Municipality negatively impacts on the development in the area. The level of services being provided is poor. There is an apparent disconnect between traditional leaders and the municipality councillor as development management and vision are concerned. Furthermore, the development programmes and projects do not seem to address the critical needs of the community. Housing development is narrow minded with a focus on the top structure and a failure to include basic services and infrastructure. Houses built that are 6 financed by subsidies are of poor quality. The latter situation results in more able‐ bodied, skilled and capable people emigrating to developed areas.
- Full Text:
- Date Issued: 2020
- Authors: Sikhosana, Phindokuhle
- Date: 2020
- Subjects: Human settlements -- South Africa -- Kwamaphumulo Local Municipality , Land settlement -- South Africa -- Kwamaphumulo Local Municipality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48808 , vital:41141
- Description: This study sought to investigate the constraints in the attainment of sustainable human settlement in KwaMaphumulo Local Municipality at iLembe District in KwaZulu-Natal, South Africa. The aim of this study was to investigate the constraints that limit the achievement of the ideal of sustainable human settlement development in the KwaMaphumulo Local Municipality. Furthermore, the study sought to determine the impact of these constraints on sustainable development and to proffer measures that can be taken to combat stagnant or underdevelopment in the area. A mixed-method approach is followed in this study, which considers a triangulation of quantitative and qualitative data collection, analysis and interpretation techniques. It is important to note that in the past years since South Africa became a democratic country, there have been countless efforts with regard to overcoming the problems created during the apartheid era. These problems stemmed from a distorted spatial, social, economic and political background that was advocated by both segregationist public policies and the planning systems of the Apartheid Regime. In recent years, South African cities have also been faced with environmental issues, which are imperative to the future development of the country. With all these issues in mind, we see that the many efforts that are put in place by government always fall short of solving the problems. This research report looked at the constraints that affect the KwaMaphumulo Local Municipality in attaining sustainable human settlements and whether the efforts of redistribution and equality have been enough to overcome the problems. The key findings of the study were that constraints in attaining sustainable human settlements in the KwaMaphumulo Local Municipality negatively impacts on the development in the area. The level of services being provided is poor. There is an apparent disconnect between traditional leaders and the municipality councillor as development management and vision are concerned. Furthermore, the development programmes and projects do not seem to address the critical needs of the community. Housing development is narrow minded with a focus on the top structure and a failure to include basic services and infrastructure. Houses built that are 6 financed by subsidies are of poor quality. The latter situation results in more able‐ bodied, skilled and capable people emigrating to developed areas.
- Full Text:
- Date Issued: 2020
Constraints in attainment of sustainable human settlements at Kwamaphumulo Local Municipality
- Authors: Sikhosana, Phindokuhle
- Date: 2020
- Subjects: Human settlements -- South Africa -- KwaZulu-Natal , Low-income housing -- South Africa -- KwaZulu-Natal City planning Land use, Urban
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47198 , vital:39826
- Description: This study sought to investigate the constraints in the attainment of sustainable human settlement in KwaMaphumulo Local Municipality at iLembe District in KwaZulu-Natal, South Africa. The aim of this study was to investigate the constraints that limit the achievement of the ideal of sustainable human settlement development in the KwaMaphumulo Local Municipality. Furthermore, the study sought to determine the impact of these constraints on sustainable development and to proffer measures that can be taken to combat stagnant or underdevelopment in the area. A mixed-method approach is followed in this study, which considers a triangulation of quantitative and qualitative data collection, analysis and interpretation techniques. It is important to note that in the past years since South Africa became a democratic country, there have been countless efforts with regard to overcoming the problems created during the apartheid era. These problems stemmed from a distorted spatial, social, economic and political background that was advocated by both segregationist public policies and the planning systems of the Apartheid Regime. In recent years, South African cities have also been faced with environmental issues, which are imperative to the future development of the country. With all these issues in mind, we see that the many efforts that are put in place by government always fall short of solving the problems. This research report looked at the constraints that affect the KwaMaphumulo Local Municipality in attaining sustainable human settlements and whether the efforts of redistribution and equality have been enough to overcome the problems. The key findings of the study were that constraints in attaining sustainable human settlements in the KwaMaphumulo Local Municipality negatively impacts on the development in the area. The level of services being provided is poor. There is an apparent disconnect between traditional leaders and the municipality councillor as development management and vision are concerned. Furthermore, the development programmes and projects do not seem to address the critical needs of the community. Housing development is narrow minded with a focus on the top structure and a failure to include basic services and infrastructure. Houses built that are 6 financed by subsidies are of poor quality. The latter situation results in more able‐ bodied, skilled and capable people emigrating to developed areas.
- Full Text:
- Date Issued: 2020
- Authors: Sikhosana, Phindokuhle
- Date: 2020
- Subjects: Human settlements -- South Africa -- KwaZulu-Natal , Low-income housing -- South Africa -- KwaZulu-Natal City planning Land use, Urban
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47198 , vital:39826
- Description: This study sought to investigate the constraints in the attainment of sustainable human settlement in KwaMaphumulo Local Municipality at iLembe District in KwaZulu-Natal, South Africa. The aim of this study was to investigate the constraints that limit the achievement of the ideal of sustainable human settlement development in the KwaMaphumulo Local Municipality. Furthermore, the study sought to determine the impact of these constraints on sustainable development and to proffer measures that can be taken to combat stagnant or underdevelopment in the area. A mixed-method approach is followed in this study, which considers a triangulation of quantitative and qualitative data collection, analysis and interpretation techniques. It is important to note that in the past years since South Africa became a democratic country, there have been countless efforts with regard to overcoming the problems created during the apartheid era. These problems stemmed from a distorted spatial, social, economic and political background that was advocated by both segregationist public policies and the planning systems of the Apartheid Regime. In recent years, South African cities have also been faced with environmental issues, which are imperative to the future development of the country. With all these issues in mind, we see that the many efforts that are put in place by government always fall short of solving the problems. This research report looked at the constraints that affect the KwaMaphumulo Local Municipality in attaining sustainable human settlements and whether the efforts of redistribution and equality have been enough to overcome the problems. The key findings of the study were that constraints in attaining sustainable human settlements in the KwaMaphumulo Local Municipality negatively impacts on the development in the area. The level of services being provided is poor. There is an apparent disconnect between traditional leaders and the municipality councillor as development management and vision are concerned. Furthermore, the development programmes and projects do not seem to address the critical needs of the community. Housing development is narrow minded with a focus on the top structure and a failure to include basic services and infrastructure. Houses built that are 6 financed by subsidies are of poor quality. The latter situation results in more able‐ bodied, skilled and capable people emigrating to developed areas.
- Full Text:
- Date Issued: 2020
Continuous flow synthesis of 5-formyl-2,4- dimethyl-1h-pyrrole-3-carboxylic acid, a key intermediate towards the synthesis of sunitinib anti-cancer drug
- Authors: Gqokoma, Zizo
- Date: 2020
- Subjects: Flow chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48356 , vital:40852
- Description: The present trend in the pharmaceutical industry is towards adapting continuous flow processing with the main driving force behind this being the need to reduce environmental and economic costs. Continuous flow systems have proven to produce better quality products at lower costs, time and energy. As a result, this technique has diversified and expanded to provide novel, and practical solutions to not only organic synthesis but also renewable fuels and material science. The focus of this research work was to exploit continuous flow systems, to develop a continuous flow process that is energy and time effective, using commercial micro reactors to synthesize 5-formyl-2,4-dimethyl-1H-pyrrole-3-carboxylic acid, a key intermediate towards the synthesis of sunitinib, an anti-cancer drug. In this thesis, a successful study on the individual translation of a 5 step batch synthesis of 5- formyl-2,4-dimethyl-1H-pyrrole-3-carboxylic acid into optimised continuous flow syntheses is demonstrated. A comprehensive literature review and background on cancer, and an introduction to pyrrole rings, their role in disease treatments in addition to a brief introduction to continuous flow technology with its advantages, and comparison to classical batch methods are provided in the first chapter. Chapter two is detailing the experimental procedures utilised for both batch and continuous flow syntheses. The continuous flow synthesis of the four intermediates towards the target compound in this work proved to be far superior compared to their batch syntheses; excellent improvements in reaction yields and selectivity in addition to tremendously shorter reaction times were observed. This is expounded in chapter three with detailed discussions of the results attained during the continuous flow optimisation of each step within the scope of this research, are provided. The concluding remarks, the impact of this study and future work are elucidated in chapter four.
- Full Text:
- Date Issued: 2020
- Authors: Gqokoma, Zizo
- Date: 2020
- Subjects: Flow chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48356 , vital:40852
- Description: The present trend in the pharmaceutical industry is towards adapting continuous flow processing with the main driving force behind this being the need to reduce environmental and economic costs. Continuous flow systems have proven to produce better quality products at lower costs, time and energy. As a result, this technique has diversified and expanded to provide novel, and practical solutions to not only organic synthesis but also renewable fuels and material science. The focus of this research work was to exploit continuous flow systems, to develop a continuous flow process that is energy and time effective, using commercial micro reactors to synthesize 5-formyl-2,4-dimethyl-1H-pyrrole-3-carboxylic acid, a key intermediate towards the synthesis of sunitinib, an anti-cancer drug. In this thesis, a successful study on the individual translation of a 5 step batch synthesis of 5- formyl-2,4-dimethyl-1H-pyrrole-3-carboxylic acid into optimised continuous flow syntheses is demonstrated. A comprehensive literature review and background on cancer, and an introduction to pyrrole rings, their role in disease treatments in addition to a brief introduction to continuous flow technology with its advantages, and comparison to classical batch methods are provided in the first chapter. Chapter two is detailing the experimental procedures utilised for both batch and continuous flow syntheses. The continuous flow synthesis of the four intermediates towards the target compound in this work proved to be far superior compared to their batch syntheses; excellent improvements in reaction yields and selectivity in addition to tremendously shorter reaction times were observed. This is expounded in chapter three with detailed discussions of the results attained during the continuous flow optimisation of each step within the scope of this research, are provided. The concluding remarks, the impact of this study and future work are elucidated in chapter four.
- Full Text:
- Date Issued: 2020
Continuous flow synthesis of imatinib intermediates
- Authors: Rupapa, Harold Takunda
- Date: 2020
- Subjects: Flow chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47464 , vital:39993
- Description: In this thesis, an alternative approach using continuous flow chemistry towards imatinib intermediates is described; an important drug in the treatment of acute myeloid leukemia. Various protocols that describe the multistep batch organic synthesis of imatinib are outlined. Many of the batch synthetic protocols require long reaction times in the multistep synthesis towards the various imatinib intermediates. A broad description into the cancer epidemic such as myeloid leukemia, the cost of drug manufacture and the effect that the high cost of manufacture has on the accessibility to such treatment in Africa is outlined. Use of continuous flow reactors, the exploitation of various technologies and their advantages on organic synthesis compared to batch synthesis are also described. The batch reaction conditions needed for the multistep transformation towards imatinib were adapted to a continuous flow set up. The optimization investigation shows an improvement in the conversion in the various steps. The flow synthesis of the enaminone provided a conversion of 99% when in o-xylene and the ability to use backpressure regulators assisted the investigation at high temperatures. Solution-phase flow synthesis of the guanidinium nitrate, which gave low yields in batch, also showed an improvement in conversion, where in 30 minutes a conversion of 99% was confirmed by altering the co-solvent mixture. The cycloaddition reaction of the enaminone and the guanidinium nitrate salt, achieved 90% conversion to the 2-aminopyridine core at 180 oC. The nitro group reduction was achieved in the presence of a greener catalyst, namely iron pentanedionate, in the presence of hydrazine hydrate. The effect of temperature, molar equivalence and solvent on reaction conversions could be observed in these steps. The thesis is concluded in chapter 4, with the conclusion and recommendations for future work towards a scalable continuous flow synthesis of the imatinib intermediates.
- Full Text:
- Date Issued: 2020
- Authors: Rupapa, Harold Takunda
- Date: 2020
- Subjects: Flow chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47464 , vital:39993
- Description: In this thesis, an alternative approach using continuous flow chemistry towards imatinib intermediates is described; an important drug in the treatment of acute myeloid leukemia. Various protocols that describe the multistep batch organic synthesis of imatinib are outlined. Many of the batch synthetic protocols require long reaction times in the multistep synthesis towards the various imatinib intermediates. A broad description into the cancer epidemic such as myeloid leukemia, the cost of drug manufacture and the effect that the high cost of manufacture has on the accessibility to such treatment in Africa is outlined. Use of continuous flow reactors, the exploitation of various technologies and their advantages on organic synthesis compared to batch synthesis are also described. The batch reaction conditions needed for the multistep transformation towards imatinib were adapted to a continuous flow set up. The optimization investigation shows an improvement in the conversion in the various steps. The flow synthesis of the enaminone provided a conversion of 99% when in o-xylene and the ability to use backpressure regulators assisted the investigation at high temperatures. Solution-phase flow synthesis of the guanidinium nitrate, which gave low yields in batch, also showed an improvement in conversion, where in 30 minutes a conversion of 99% was confirmed by altering the co-solvent mixture. The cycloaddition reaction of the enaminone and the guanidinium nitrate salt, achieved 90% conversion to the 2-aminopyridine core at 180 oC. The nitro group reduction was achieved in the presence of a greener catalyst, namely iron pentanedionate, in the presence of hydrazine hydrate. The effect of temperature, molar equivalence and solvent on reaction conversions could be observed in these steps. The thesis is concluded in chapter 4, with the conclusion and recommendations for future work towards a scalable continuous flow synthesis of the imatinib intermediates.
- Full Text:
- Date Issued: 2020
Contributions to the systematics and ecology of Tulista Raf(Asphodelaceae subfam. Alooideae)
- Authors: Molteno, Steven Martin
- Date: 2020
- Subjects: Plant ecology -- South Africa , Plant ecology -- Comparative method Biodiversity , Species diversity
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49182 , vital:41608
- Description: The subject of this study is the taxonomy, morphology, distribution and ecology of Tulista Raf. (Asphodelaceae subfam. Alooideae), a genus of succulent plants that are endemic to South Africa. A lack of clarity on the taxonomy of this genus, coupled with an incomplete understanding of the distribution, ecology and habitat preferences of the constituent species, risks hampering the conservation of Tulista species, two of which are endangered species. The purpose of this study is therefore to address the need for a more detailed and consistent treatment of Tulista taxonomy and morphology, complemented by a study of the plants’ distribution and ecology. The work first provides a review of the relevant taxonomy and nomenclature, concluding with the presentation of the validly published names referring to Tulista. A detailed morphometric study resulted in strong support for one species, Tulista marginata (Lam.) G.D.Rowley, as well as for a grouping comprising Tulista pumila (L.) G.D.Rowley and Tulista minor (Aiton) Gideon F.Sm. & Molteno, with further moderate support for the distinction between the latter two species. The fourth out of the currently recognised species, Tulista kingiana (Poelln.) Gideon F.Sm. & Molteno, was only weakly characterised by the morphometric results, which suggested that its closest morphological affinity may be with hybrid plants that are sometimes found near T. marginata populations. The characterisation of some more controversial taxa was not supported in the results. Some changes to the circumscription of currently recognised Tulista species are also suggested by the results. In addition, field work conducted during the course of the study resulted in an expanded set of distribution data for the genus, together with certain habitat variables identified as potentially significant for the distribution and ecology of Tulista species.
- Full Text:
- Date Issued: 2020
- Authors: Molteno, Steven Martin
- Date: 2020
- Subjects: Plant ecology -- South Africa , Plant ecology -- Comparative method Biodiversity , Species diversity
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49182 , vital:41608
- Description: The subject of this study is the taxonomy, morphology, distribution and ecology of Tulista Raf. (Asphodelaceae subfam. Alooideae), a genus of succulent plants that are endemic to South Africa. A lack of clarity on the taxonomy of this genus, coupled with an incomplete understanding of the distribution, ecology and habitat preferences of the constituent species, risks hampering the conservation of Tulista species, two of which are endangered species. The purpose of this study is therefore to address the need for a more detailed and consistent treatment of Tulista taxonomy and morphology, complemented by a study of the plants’ distribution and ecology. The work first provides a review of the relevant taxonomy and nomenclature, concluding with the presentation of the validly published names referring to Tulista. A detailed morphometric study resulted in strong support for one species, Tulista marginata (Lam.) G.D.Rowley, as well as for a grouping comprising Tulista pumila (L.) G.D.Rowley and Tulista minor (Aiton) Gideon F.Sm. & Molteno, with further moderate support for the distinction between the latter two species. The fourth out of the currently recognised species, Tulista kingiana (Poelln.) Gideon F.Sm. & Molteno, was only weakly characterised by the morphometric results, which suggested that its closest morphological affinity may be with hybrid plants that are sometimes found near T. marginata populations. The characterisation of some more controversial taxa was not supported in the results. Some changes to the circumscription of currently recognised Tulista species are also suggested by the results. In addition, field work conducted during the course of the study resulted in an expanded set of distribution data for the genus, together with certain habitat variables identified as potentially significant for the distribution and ecology of Tulista species.
- Full Text:
- Date Issued: 2020