Classification and clustering based methods for outlier detection of solar resource data
- Authors: Abrahams, Waldo
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55423 , vital:51996
- Description: Almost 90% of the primary global energy demand is serviced from the burning of fossil fuels (Abas, Kalair & Khan, 2015). Owing to the detrimental environmental impact of this, a global energy transition to the use of renewable energy, including solar energy, is needed (Gielen et al., 2019). An important aspect that inhibits the growth of solar energy is accurate solar resource data. Such data is needed because knowledge of the future reliability and quality of energy production is required to analyse a system’s performance and determine financial implications (Sengupta et al., 2017). Existing methods used to detect outliers in solar resource data do not efficiently identify outliers and an accurate and robust approach is required (Eastwood, 2019). Using simulated and real-world data, this study investigates the use of several classification methods, along with a two-stage clustering-classification approach to accurately identify outliers in solar resource data. The Treebag method proves to be an adequate outlier detection method for solar resource data. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Abrahams, Waldo
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55423 , vital:51996
- Description: Almost 90% of the primary global energy demand is serviced from the burning of fossil fuels (Abas, Kalair & Khan, 2015). Owing to the detrimental environmental impact of this, a global energy transition to the use of renewable energy, including solar energy, is needed (Gielen et al., 2019). An important aspect that inhibits the growth of solar energy is accurate solar resource data. Such data is needed because knowledge of the future reliability and quality of energy production is required to analyse a system’s performance and determine financial implications (Sengupta et al., 2017). Existing methods used to detect outliers in solar resource data do not efficiently identify outliers and an accurate and robust approach is required (Eastwood, 2019). Using simulated and real-world data, this study investigates the use of several classification methods, along with a two-stage clustering-classification approach to accurately identify outliers in solar resource data. The Treebag method proves to be an adequate outlier detection method for solar resource data. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-04
The use of a rapid incineration field test for determining soil organic carbon in the Southern Cape Region
- Authors: Ackhurst, Albert Arthur
- Date: 2014-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53336 , vital:45135
- Description: Knowledge of soil organic carbon levels is important both for agricultural effectiveness and soil carbon sequestration accounting, especially against the backdrop of increased climate change impacts and pressure on food production landscapes. However, current methods for soil carbon determination are expensive, energy intensive, time consuming and potentially hazardous leading to a call for alternative methods, which should be cheap, fast, simple, accurate, safe and usable where resources and soil analysis laboratories are limited. To this end the student invented a novel rapid incineration field test (RIFT) for determining soil organic carbon and tested its validity in this study. This method incorporates principles found in dry combustion as well as loss-on-ignition and quantifying organic carbon through gravimetric analysis. In order to illustrate effectiveness and accuracy it was necessary to correlate RIFT with a reference method, in this instance dry combustion with a Leco device as well as another commonly used indirect method namely the Walkley-Black wet chemical oxidation method. Samples from eleven soil forms were collected from the Southern Cape region and they were subjected to the three testing methods. It was found that RIFT is indeed as effective and in 72% of the soil forms even more effective than Walkley-Black. Furthermore, it was ascertained whether the accuracy of RIFT can be improved by correcting for clay content. The correlation of RIFT with clay % was not very significant and clay % as a variable was therefore not used in this study to obtain further refinement of RIFT predictions. Another finding was also that RIFT illustrated less variability than both the Leco and Walkley-Black methods. Lastly it was ascertained that the RIFT device and methodology is indeed cost effective, energy efficient, fast and safe in terms of the need to use potentially hazardous chemicals. , Thesis (MA) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text:
- Date Issued: 2014-12
- Authors: Ackhurst, Albert Arthur
- Date: 2014-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53336 , vital:45135
- Description: Knowledge of soil organic carbon levels is important both for agricultural effectiveness and soil carbon sequestration accounting, especially against the backdrop of increased climate change impacts and pressure on food production landscapes. However, current methods for soil carbon determination are expensive, energy intensive, time consuming and potentially hazardous leading to a call for alternative methods, which should be cheap, fast, simple, accurate, safe and usable where resources and soil analysis laboratories are limited. To this end the student invented a novel rapid incineration field test (RIFT) for determining soil organic carbon and tested its validity in this study. This method incorporates principles found in dry combustion as well as loss-on-ignition and quantifying organic carbon through gravimetric analysis. In order to illustrate effectiveness and accuracy it was necessary to correlate RIFT with a reference method, in this instance dry combustion with a Leco device as well as another commonly used indirect method namely the Walkley-Black wet chemical oxidation method. Samples from eleven soil forms were collected from the Southern Cape region and they were subjected to the three testing methods. It was found that RIFT is indeed as effective and in 72% of the soil forms even more effective than Walkley-Black. Furthermore, it was ascertained whether the accuracy of RIFT can be improved by correcting for clay content. The correlation of RIFT with clay % was not very significant and clay % as a variable was therefore not used in this study to obtain further refinement of RIFT predictions. Another finding was also that RIFT illustrated less variability than both the Leco and Walkley-Black methods. Lastly it was ascertained that the RIFT device and methodology is indeed cost effective, energy efficient, fast and safe in terms of the need to use potentially hazardous chemicals. , Thesis (MA) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text:
- Date Issued: 2014-12
Refining predator-prey preference at the prey demographic level for cheetah and lion
- Authors: Annear, Eleesha
- Date: 2022-04
- Subjects: Social behavior in animals --South Africa , Predatory animals –Behavior
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55800 , vital:53880
- Description: Traditional prey preference models estimate prey preference using a coarse species-specific body mass of three-quarters of the mean adult female body mass. This is widely assumed to estimate the average mass across prey populations, accounting for neonates, juveniles, sub-adults, and adults. However, this approach negates the models’ ability to predict demography-specific prey preferences, thus reducing our ability to predict the impacts of predation on prey populations. The objectives of this study were to 1) refine the prey selection models, using lion Panthera leo and cheetah Acinonyx jubatus as model species, by incorporating prey demographic classes and season and, 2) determine the influence of seasonal variability in availability of these prey demographic classes on cheetah reproduction. Lions preferentially killed adults of larger species (e.g., wildebeest, waterbuck, and zebra) irrespective of the season, as predicted by optimal foraging theory. Sub-adult, juvenile, and neonate prey were killed by lions relative to their abundance. Cheetahs preferred juvenile prey of large species, namely kudu, zebra, and wildebeest. Season influenced cheetah preference with neonates and juveniles being preferred during the wet season and adults of smaller species, and juveniles of larger species being preferred during the dry season. Thus, results support the alternative demographic class hypothesis. Furthermore, the availability of neonate and juvenile prey drives cheetah reproduction patterns with conception and cub independence coinciding with the peak availability of easy-to-catch neonates. Lactation coincided with the high availability of relatively larger juveniles to ensure that females obtain enough resources to sustain the most energetically costly reproductive phase. In addition, I suggest cheetah may be particularly vulnerable to disturbances that impact on prey reproduction (e.g., drought, fire, and flood), given their reliance on neonate and juvenile prey. My findings highlight that estimating species-level prey preference using a coarse species-specific body mass masks the level of prey use and potential preferences for the different prey demographic classes. The use of some prey species may be largely confined to juveniles by smaller predators, meaning that prey availability would vary seasonally, may influence reproductive patterns, and carrying capacity models would need to be revised in terms of the available demographic-specific prey biomass. , Thesis (MSc) -- Faculty of Sciences, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Annear, Eleesha
- Date: 2022-04
- Subjects: Social behavior in animals --South Africa , Predatory animals –Behavior
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55800 , vital:53880
- Description: Traditional prey preference models estimate prey preference using a coarse species-specific body mass of three-quarters of the mean adult female body mass. This is widely assumed to estimate the average mass across prey populations, accounting for neonates, juveniles, sub-adults, and adults. However, this approach negates the models’ ability to predict demography-specific prey preferences, thus reducing our ability to predict the impacts of predation on prey populations. The objectives of this study were to 1) refine the prey selection models, using lion Panthera leo and cheetah Acinonyx jubatus as model species, by incorporating prey demographic classes and season and, 2) determine the influence of seasonal variability in availability of these prey demographic classes on cheetah reproduction. Lions preferentially killed adults of larger species (e.g., wildebeest, waterbuck, and zebra) irrespective of the season, as predicted by optimal foraging theory. Sub-adult, juvenile, and neonate prey were killed by lions relative to their abundance. Cheetahs preferred juvenile prey of large species, namely kudu, zebra, and wildebeest. Season influenced cheetah preference with neonates and juveniles being preferred during the wet season and adults of smaller species, and juveniles of larger species being preferred during the dry season. Thus, results support the alternative demographic class hypothesis. Furthermore, the availability of neonate and juvenile prey drives cheetah reproduction patterns with conception and cub independence coinciding with the peak availability of easy-to-catch neonates. Lactation coincided with the high availability of relatively larger juveniles to ensure that females obtain enough resources to sustain the most energetically costly reproductive phase. In addition, I suggest cheetah may be particularly vulnerable to disturbances that impact on prey reproduction (e.g., drought, fire, and flood), given their reliance on neonate and juvenile prey. My findings highlight that estimating species-level prey preference using a coarse species-specific body mass masks the level of prey use and potential preferences for the different prey demographic classes. The use of some prey species may be largely confined to juveniles by smaller predators, meaning that prey availability would vary seasonally, may influence reproductive patterns, and carrying capacity models would need to be revised in terms of the available demographic-specific prey biomass. , Thesis (MSc) -- Faculty of Sciences, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
Foraging behaviour of the Sooty Albatross in relation to climatic variability and fisheries
- Authors: Banda, Shamiso
- Date: 2022-04
- Subjects: Spatial behavior in animals , Conservation of natural resources --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55632 , vital:53383
- Description: As top predators, seabirds occupy the upper trophic level of marine ecosystems. They are consequently important for the maintenance of ecosystem structure and function, while also possessing characteristics which are useful for identifying climate-driven changes in oceanography at all trophic levels. This important faunal group is one of the most threatened, with climate change and fisheries bycatch mortality being the primary drivers of population declines. Understanding these threats is important for the management of threatened seabird populations. One impact of climate change and variability in climate occurs through changes in prey availability. As central place foragers, breeding seabirds have trip duration constraints due to the obligation of nest duties. This makes them particularly vulnerable to changes in prey availability within their foraging ranges. The ability to adjust foraging behaviour during environmental conditions which alter prey availability is an important attribute which can contribute to breeding success. Thus, investigating for this foraging behavioural plasticity during different breeding stages provides insights into how a species is likely to be impacted by climate change. The sooty albatross population on Marion Island was studied and displayed a degree of foraging behavioural plasticity during the five-year period of pronounced climatic variability studied. Incubating birds mainly foraged in the subtropical convergence zone (STCZ), the Sub Antarctic Front (SAF) and Subtropical Front (STF) which border it, and the region north of the STF. Brooding birds mainly used the SAF and Polar Frontal Zone (PFZ). Significantly different areas were used between years during both breeding stages. This population showed a lack of consistent habitat preferences which may offer resilience to progressive climatic variability and change. Interactions of sooty albatrosses, as well as white-chinned petrels for comparative purposes, with fisheries were also assessed. The two species were compared to shed light on possible explanations for differences in seabird-fishery interactions between the species. The impact of fisheries-related mortality (bycatch) is dependent on exposure to fishing activity and attraction to fishing boats encountered while foraging. Bycatch mortality has previously been proposed as the main cause of this sooty albatross population’s decline. Exposure and 6 attraction to fishing boats was found to be lower than that of white-chinned petrels which are bycatch prone. However, the current level of attraction exhibited by this sooty albatross population may expose a significant fraction of the population to bycatch risk due to its small population size. Additionally, all fishing boats were encountered north of the STF where non breeding individuals are now known to be distributed. Thus, the impact of fisheries on this population may mainly be mediated by more bycatch prone non-breeding individuals. Overall, the relative impact of fisheries bycatch mortality is suggested to be higher than that of climatic impacts on the sooty albatross population on Marion Island. However, this study did not incorporate dietary and demographic information which would reveal whether there are nutritional differences between years that may impact on breeding success. An integrated rather than independent assessment of foraging behavioural responses to climatic variability and fishing activity is recommended for improving our understanding of current and future conservation priorities. , Thesis (MSc) -- Faculty of Science, Zoology , 2021
- Full Text:
- Date Issued: 2022-04
- Authors: Banda, Shamiso
- Date: 2022-04
- Subjects: Spatial behavior in animals , Conservation of natural resources --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55632 , vital:53383
- Description: As top predators, seabirds occupy the upper trophic level of marine ecosystems. They are consequently important for the maintenance of ecosystem structure and function, while also possessing characteristics which are useful for identifying climate-driven changes in oceanography at all trophic levels. This important faunal group is one of the most threatened, with climate change and fisheries bycatch mortality being the primary drivers of population declines. Understanding these threats is important for the management of threatened seabird populations. One impact of climate change and variability in climate occurs through changes in prey availability. As central place foragers, breeding seabirds have trip duration constraints due to the obligation of nest duties. This makes them particularly vulnerable to changes in prey availability within their foraging ranges. The ability to adjust foraging behaviour during environmental conditions which alter prey availability is an important attribute which can contribute to breeding success. Thus, investigating for this foraging behavioural plasticity during different breeding stages provides insights into how a species is likely to be impacted by climate change. The sooty albatross population on Marion Island was studied and displayed a degree of foraging behavioural plasticity during the five-year period of pronounced climatic variability studied. Incubating birds mainly foraged in the subtropical convergence zone (STCZ), the Sub Antarctic Front (SAF) and Subtropical Front (STF) which border it, and the region north of the STF. Brooding birds mainly used the SAF and Polar Frontal Zone (PFZ). Significantly different areas were used between years during both breeding stages. This population showed a lack of consistent habitat preferences which may offer resilience to progressive climatic variability and change. Interactions of sooty albatrosses, as well as white-chinned petrels for comparative purposes, with fisheries were also assessed. The two species were compared to shed light on possible explanations for differences in seabird-fishery interactions between the species. The impact of fisheries-related mortality (bycatch) is dependent on exposure to fishing activity and attraction to fishing boats encountered while foraging. Bycatch mortality has previously been proposed as the main cause of this sooty albatross population’s decline. Exposure and 6 attraction to fishing boats was found to be lower than that of white-chinned petrels which are bycatch prone. However, the current level of attraction exhibited by this sooty albatross population may expose a significant fraction of the population to bycatch risk due to its small population size. Additionally, all fishing boats were encountered north of the STF where non breeding individuals are now known to be distributed. Thus, the impact of fisheries on this population may mainly be mediated by more bycatch prone non-breeding individuals. Overall, the relative impact of fisheries bycatch mortality is suggested to be higher than that of climatic impacts on the sooty albatross population on Marion Island. However, this study did not incorporate dietary and demographic information which would reveal whether there are nutritional differences between years that may impact on breeding success. An integrated rather than independent assessment of foraging behavioural responses to climatic variability and fishing activity is recommended for improving our understanding of current and future conservation priorities. , Thesis (MSc) -- Faculty of Science, Zoology , 2021
- Full Text:
- Date Issued: 2022-04
An investigation of alternative separation strategies for common chemical mixtures by means of host-guest chemistry protocols with host compounds N,N′- bis(5-phenyl-5-dibenzo[a,d]cycloheptenyl)ethylenediamine and N,N’-bis(5-phenyl-10,11- dihydro-5-dibenzo[a,d]cycloheptenyl)ethylenediamine
- Authors: Barton, Danica Brione
- Date: 2023-04
- Subjects: Ethylenediaminetetraacetic acid -- South Africa , Enzymes –Analysis
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61176 , vital:69791
- Description: In this work, the selectivity behaviour of two host compounds, namely N,N’-bis(5-phenyl-5- ibenzo[a,d]cycloheptenyl)ethylenediamine (H1) and N,N’-bis(5-phenyl-10,11-dihydro-5- ibenzo[a,d]cycloheptenyl)ethylenediamine (H2), was assessed in mixtures of difficult-toseparate compounds, including the xylenes and ethylbenzene, pyridine and methylpyridines, and anisole and methylanisoles. These host compounds were synthesized using Grignard addition reactions with phenylmagnesium bromide on dibenzo[a,d]cyclohepten-5-one and 10,11- dihydrodibenzo[a,d]cyclohepten-5-one, respectively. The resultant alcohols were treated with perchloric acid to form the corresponding perchlorate salts, which were then reacted with ethylenediamine to afford the required H1 and H2 host compounds. Yields were 95 ad 52% for this final step in each case. An investigation of the conformations, both from experiment (using single crystal X-ray diffractometry (SCXRD) on the apohost compound) and computational calculations was undertaken. Unfortunately, H1 always crystallized out as a powder unless this host compound formed a complex with a guest species, and so could not be subjected to SCXRD analysis as apohost alone. However, a single crystal structure for apohost H2 was successfully obtained and compared with computational data from a previous investigation. It was observed that the conformation of apohost H2 compared favourably with that of the lowest energy conformer from that work. In single solvent recrystallization experiments with o-, m-, p-xylene (o-Xy, m-Xy, p-Xy) and ethylbenzene (EB), both H1 and H2 formed complexes with only one of the four guest species, namely p-Xy and o-Xy, respectively. The host:guest (H:G) ratios were 1:1 for both of these complexes. In the equimolar guest/guest competition experiments, inclusion complexes only formed when p-Xy or o-Xy, respectively, were present in the mixtures; if p-Xy (for experiments with H1) or o-Xy (H2) was absent from these mixtures, only apohost was recovered from the glass vessels. Three selectivity profiles were constructed for each of these host compounds, in which each one was recrystallized from binary mixed guests in various proportions. These demonstrated an overwhelming preference of H1 for p-Xy and H2 for o-Xy, which concurred with the results from the equimolar experiments. Thermal analysis using H1∙p-Xy revealed that this complex was unstable at ambient conditions, while SCXRD explained this observation: this complex may be defined as a true clathrate since no host‧‧‧guest interactions were identified at all, and the guest was retained in the complex by means of steric factors alone. Furthermore, the guest molecules resided in wide open channels that may have facilitated the guest release process. H2∙o-Xy, on the other hand, was stable at room temperature, and the guest release event only commenced at 69.7 °C (Ton). This too was explained by SCXRD analyses in that interactions between host and guest species were observed in this case. Additionally, the guest molecules were housed in discrete cages, which made their escape more challenging compared with p-Xy in H1∙p-Xy. It was concluded that, in this guest series, both of the host compounds would be effective as separatory tools employing host-guest chemistry protocols due to their remarkable selectivities for p-Xy (H1) and o-Xy (H2). , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Barton, Danica Brione
- Date: 2023-04
- Subjects: Ethylenediaminetetraacetic acid -- South Africa , Enzymes –Analysis
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61176 , vital:69791
- Description: In this work, the selectivity behaviour of two host compounds, namely N,N’-bis(5-phenyl-5- ibenzo[a,d]cycloheptenyl)ethylenediamine (H1) and N,N’-bis(5-phenyl-10,11-dihydro-5- ibenzo[a,d]cycloheptenyl)ethylenediamine (H2), was assessed in mixtures of difficult-toseparate compounds, including the xylenes and ethylbenzene, pyridine and methylpyridines, and anisole and methylanisoles. These host compounds were synthesized using Grignard addition reactions with phenylmagnesium bromide on dibenzo[a,d]cyclohepten-5-one and 10,11- dihydrodibenzo[a,d]cyclohepten-5-one, respectively. The resultant alcohols were treated with perchloric acid to form the corresponding perchlorate salts, which were then reacted with ethylenediamine to afford the required H1 and H2 host compounds. Yields were 95 ad 52% for this final step in each case. An investigation of the conformations, both from experiment (using single crystal X-ray diffractometry (SCXRD) on the apohost compound) and computational calculations was undertaken. Unfortunately, H1 always crystallized out as a powder unless this host compound formed a complex with a guest species, and so could not be subjected to SCXRD analysis as apohost alone. However, a single crystal structure for apohost H2 was successfully obtained and compared with computational data from a previous investigation. It was observed that the conformation of apohost H2 compared favourably with that of the lowest energy conformer from that work. In single solvent recrystallization experiments with o-, m-, p-xylene (o-Xy, m-Xy, p-Xy) and ethylbenzene (EB), both H1 and H2 formed complexes with only one of the four guest species, namely p-Xy and o-Xy, respectively. The host:guest (H:G) ratios were 1:1 for both of these complexes. In the equimolar guest/guest competition experiments, inclusion complexes only formed when p-Xy or o-Xy, respectively, were present in the mixtures; if p-Xy (for experiments with H1) or o-Xy (H2) was absent from these mixtures, only apohost was recovered from the glass vessels. Three selectivity profiles were constructed for each of these host compounds, in which each one was recrystallized from binary mixed guests in various proportions. These demonstrated an overwhelming preference of H1 for p-Xy and H2 for o-Xy, which concurred with the results from the equimolar experiments. Thermal analysis using H1∙p-Xy revealed that this complex was unstable at ambient conditions, while SCXRD explained this observation: this complex may be defined as a true clathrate since no host‧‧‧guest interactions were identified at all, and the guest was retained in the complex by means of steric factors alone. Furthermore, the guest molecules resided in wide open channels that may have facilitated the guest release process. H2∙o-Xy, on the other hand, was stable at room temperature, and the guest release event only commenced at 69.7 °C (Ton). This too was explained by SCXRD analyses in that interactions between host and guest species were observed in this case. Additionally, the guest molecules were housed in discrete cages, which made their escape more challenging compared with p-Xy in H1∙p-Xy. It was concluded that, in this guest series, both of the host compounds would be effective as separatory tools employing host-guest chemistry protocols due to their remarkable selectivities for p-Xy (H1) and o-Xy (H2). , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Estimating Bayesian tolerance intervals for a two - factor factorial model
- Authors: Besele, Kagiso Francis
- Date: 2021-04
- Subjects: Gqenerha (South Africa) , Eastern Cape (South Africa) , Mathematical statistics
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52302 , vital:43587
- Description: Quality improvement efforts have become the cornerstone of all manufacturing processes. Quality can be defined in terms of variability reduction, and since variability is a statistical concept, statistical techniques such as statistical quality control present techniques for assessing process variation. Methods such as experimental design provide a way to ascertain factor relationships and give a basis for computing variability that arises from each process variable, ultimately providing a way of calculating total process variability. This in turn results in variance components and eventually variance component estimation. As with any statistical model, estimates may be classified in any one of two ways, point estimates or interval estimates. Interval estimates that provide information about an entire population, and not only information on a few observations from a sample or knowledge about only a population parameter, are known as tolerance intervals. Wolfinger (1998) provided a Bayesian simulationbased approach for ascertaining three types of tolerance intervals using a balanced one-way random effects model. In this study, the method initially proposed by Wolfinger (1998), is extended in order to estimate tolerance intervals for the balanced two-way crossed classification random effects model with interaction. The suggested and derived techniques will be applied to the thermal impedance data initially collected by Houf and Berman (1988), and the method presented by Wolfinger (1998) will be expanded to also include the estimation of tolerance intervals for averages of observations from new or unknown measurements. This Bayesian approach provides a thorough but yet simplistic paradigm to using tolerance intervals in manufacturing settings. , Thesis (MSc) -- Faculty of Science, Statistics, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Besele, Kagiso Francis
- Date: 2021-04
- Subjects: Gqenerha (South Africa) , Eastern Cape (South Africa) , Mathematical statistics
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52302 , vital:43587
- Description: Quality improvement efforts have become the cornerstone of all manufacturing processes. Quality can be defined in terms of variability reduction, and since variability is a statistical concept, statistical techniques such as statistical quality control present techniques for assessing process variation. Methods such as experimental design provide a way to ascertain factor relationships and give a basis for computing variability that arises from each process variable, ultimately providing a way of calculating total process variability. This in turn results in variance components and eventually variance component estimation. As with any statistical model, estimates may be classified in any one of two ways, point estimates or interval estimates. Interval estimates that provide information about an entire population, and not only information on a few observations from a sample or knowledge about only a population parameter, are known as tolerance intervals. Wolfinger (1998) provided a Bayesian simulationbased approach for ascertaining three types of tolerance intervals using a balanced one-way random effects model. In this study, the method initially proposed by Wolfinger (1998), is extended in order to estimate tolerance intervals for the balanced two-way crossed classification random effects model with interaction. The suggested and derived techniques will be applied to the thermal impedance data initially collected by Houf and Berman (1988), and the method presented by Wolfinger (1998) will be expanded to also include the estimation of tolerance intervals for averages of observations from new or unknown measurements. This Bayesian approach provides a thorough but yet simplistic paradigm to using tolerance intervals in manufacturing settings. , Thesis (MSc) -- Faculty of Science, Statistics, 2021
- Full Text: false
- Date Issued: 2021-04
Using spatial explicit capture-recapture model to investigate the demography and spatial dynamics of lion prides in Pilanesberg National Park
- Authors: Bettings, Isabella Aletta
- Date: 2022-12
- Subjects: Lions--Behavior--South Africa , Animals tracks -- Pilanesberg National Park -- North West
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59655 , vital:62318
- Description: Lions are apex predators that play a vital role in the ecosystem. They regulate prey species through predation and other non-consumptive means. Factors that have influenced the decline of lion populations across Africa in the last half century, are loss of habitat, human wildlife conflict and the depletion of prey species. Extensive reintroductions of lions have been conducted across South Africa in order to restore their numbers in protected areas. The Pilanesberg National Park (PNP) was one of many protected areas that reintroduced lions. Their numbers were well documented by management until 2005 where they lost track of the population numbers. During this unfortunate period, there was an observed decline in prey numbers. The aim of this dissertation was to estimate the abundance, movement, and sex ratio of lions, in PNP. Abundance, movement, and sex ratio were determined by a three-month intensive lion survey. The location of each lion encounter was recorded on a mobile device which had an application installed called Cybertracker (v3). Photographs were taken of each Lion to build identification kits. For the data analysis, I used the Bayesian spatial explicit capture-recapture (SECR) model. This model takes time, space, and the robustness of an individual lion into account. Robustness is the measure of how well a lion maintains their functionality, when various stressors are applied (Harmsen, Foster, & Quigley, 2020). The estimated lion population in PNP was 44 lions (>1 year) with a density of 8.8 lions per 100 km2 . The estimated mean home range size of male lions was 279 km2 with a highest probability density (HPD) range of 179 – 385 km2 . The estimated mean home range of female lions was 191 km2 with a HPD range of 135 – 262 km2 . The larger home range size for male lions and smaller home range size for females is found v throughout the African continent in protected areas. The estimated sex ratio was 0.9♀:1♂, which is unexpected as PNP sex ratios between male and female lions is usually 2♀:1♂. A future sampling design for PNP was produced from the completed lion survey dataset. I drove a total of 7350 km and evaluated the influence of varied sampling efforts (i.e., kms driven) on precision estimates and relative bias for abundance, movement, and sex ratio. I found that a minimum of 4 000 km was needed to adequately estimate the lion abundance, movement, and sex ratio in this small fenced protected area. These findings can be used to help guide management to the most cost-effective sampling method and still obtain accurate estimates for monitoring lions. By showing management what is required for appropriate lion surveys this might help improve future monitoring. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Bettings, Isabella Aletta
- Date: 2022-12
- Subjects: Lions--Behavior--South Africa , Animals tracks -- Pilanesberg National Park -- North West
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59655 , vital:62318
- Description: Lions are apex predators that play a vital role in the ecosystem. They regulate prey species through predation and other non-consumptive means. Factors that have influenced the decline of lion populations across Africa in the last half century, are loss of habitat, human wildlife conflict and the depletion of prey species. Extensive reintroductions of lions have been conducted across South Africa in order to restore their numbers in protected areas. The Pilanesberg National Park (PNP) was one of many protected areas that reintroduced lions. Their numbers were well documented by management until 2005 where they lost track of the population numbers. During this unfortunate period, there was an observed decline in prey numbers. The aim of this dissertation was to estimate the abundance, movement, and sex ratio of lions, in PNP. Abundance, movement, and sex ratio were determined by a three-month intensive lion survey. The location of each lion encounter was recorded on a mobile device which had an application installed called Cybertracker (v3). Photographs were taken of each Lion to build identification kits. For the data analysis, I used the Bayesian spatial explicit capture-recapture (SECR) model. This model takes time, space, and the robustness of an individual lion into account. Robustness is the measure of how well a lion maintains their functionality, when various stressors are applied (Harmsen, Foster, & Quigley, 2020). The estimated lion population in PNP was 44 lions (>1 year) with a density of 8.8 lions per 100 km2 . The estimated mean home range size of male lions was 279 km2 with a highest probability density (HPD) range of 179 – 385 km2 . The estimated mean home range of female lions was 191 km2 with a HPD range of 135 – 262 km2 . The larger home range size for male lions and smaller home range size for females is found v throughout the African continent in protected areas. The estimated sex ratio was 0.9♀:1♂, which is unexpected as PNP sex ratios between male and female lions is usually 2♀:1♂. A future sampling design for PNP was produced from the completed lion survey dataset. I drove a total of 7350 km and evaluated the influence of varied sampling efforts (i.e., kms driven) on precision estimates and relative bias for abundance, movement, and sex ratio. I found that a minimum of 4 000 km was needed to adequately estimate the lion abundance, movement, and sex ratio in this small fenced protected area. These findings can be used to help guide management to the most cost-effective sampling method and still obtain accurate estimates for monitoring lions. By showing management what is required for appropriate lion surveys this might help improve future monitoring. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2022
- Full Text:
- Date Issued: 2022-12
An investigation into the effects of nano-carbons on the negative electrode morphology of lead acid batteries under high rate partial state of capacity cycling
- Authors: Bolo, Lukanyo
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53324 , vital:45132
- Description: New technological developments in the field of Hybrid Electric Vehicles (HEV’s), vehicle stop-start applications and electrical power utility devices have brought about new demands on the use of energy storage devices such as the Pb-acid battery. These applications require a new understanding and research into the material chemistry of the battery where it has to functionin a Partial State of Capacity Cycling (PSoCC) or High Rate Partial State of Capacity Cycling (HRPSoCC)duty. The Pb-acid battery is well known for its use in the automotive industry where it had worked for decades as a typical Starter, Lighting and Ignition (SLI) power source. However, the conventional Pb-acid battery is not suitable for the new types of vehicle demands and applications. When the Pb-lead acid battery is subjected to PSoCC conditions, very quickly excessive amount of non-conducting PbSO4crystals are formed on the negative plates of the battery that then drastically reduce its useful life in application. Over the years, researchers have shown that the small addition of certain carbon types to the negative plate active material (NAM) during battery manufacturing can reduce the sulfation effect thereby increasing its use the modern vehicle applications. This study investigated industrial manufactured cells that contained up to 0.5 % by weight two types of carbons in the NAM. These were compared to standard built cells in terms of their standard achievable capacities at various rates, their Cold Cranking Ability (CCA), their Dynamic Charge Acceptance (DCA) and a simplified PSoCC test. The carbons were classified as an activated carbon and a carbon nano-fiber and were included as a dry weight additive during the standard paste manufacturing process of the negative plate. Cells were built with a 9-plate configuration using standard expanded grid positive plates with a nominal rated capacity of 36 Ah. The cells were formed and subjected to a number of electrochemical tests, of which selected negative plates were then studied using Scanning Electron Microscopy (SEM) and Electrochemical in-situ Atomic Force Microscopy (EC-AFM). The microscopic study was then used to try and relate the observed material characteristics of the NAM with the carbons to the electrochemical results observed when testing a built cell. , Thesis (MA) --Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Bolo, Lukanyo
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53324 , vital:45132
- Description: New technological developments in the field of Hybrid Electric Vehicles (HEV’s), vehicle stop-start applications and electrical power utility devices have brought about new demands on the use of energy storage devices such as the Pb-acid battery. These applications require a new understanding and research into the material chemistry of the battery where it has to functionin a Partial State of Capacity Cycling (PSoCC) or High Rate Partial State of Capacity Cycling (HRPSoCC)duty. The Pb-acid battery is well known for its use in the automotive industry where it had worked for decades as a typical Starter, Lighting and Ignition (SLI) power source. However, the conventional Pb-acid battery is not suitable for the new types of vehicle demands and applications. When the Pb-lead acid battery is subjected to PSoCC conditions, very quickly excessive amount of non-conducting PbSO4crystals are formed on the negative plates of the battery that then drastically reduce its useful life in application. Over the years, researchers have shown that the small addition of certain carbon types to the negative plate active material (NAM) during battery manufacturing can reduce the sulfation effect thereby increasing its use the modern vehicle applications. This study investigated industrial manufactured cells that contained up to 0.5 % by weight two types of carbons in the NAM. These were compared to standard built cells in terms of their standard achievable capacities at various rates, their Cold Cranking Ability (CCA), their Dynamic Charge Acceptance (DCA) and a simplified PSoCC test. The carbons were classified as an activated carbon and a carbon nano-fiber and were included as a dry weight additive during the standard paste manufacturing process of the negative plate. Cells were built with a 9-plate configuration using standard expanded grid positive plates with a nominal rated capacity of 36 Ah. The cells were formed and subjected to a number of electrochemical tests, of which selected negative plates were then studied using Scanning Electron Microscopy (SEM) and Electrochemical in-situ Atomic Force Microscopy (EC-AFM). The microscopic study was then used to try and relate the observed material characteristics of the NAM with the carbons to the electrochemical results observed when testing a built cell. , Thesis (MA) --Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-04
Cannabidiol: extraction and purification using flow Chemistry
- Authors: Bopape, Karabo
- Date: 2022-04
- Subjects: Supercritical fluid extraction -- South Africa , Cannabis -- Therapeutic use
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55723 , vital:53410
- Description: cannabinoids are of growing interest in research and pharmaceutical applications. Cannabidiol, which is a non-psychoactive cannabinoid, has many pharmaceutical applications. The current and main source of cannabidiol and other cannabinoids is from cannabis and hemp extractions. Current extraction methods involve the use of conventional solvent extraction, which employs the use of organic solvents, in some cases along with mechanical assistance from various equipment. Alternatively, another widely used extraction method is the use of supercritical extraction fluids (SC-CO2 being the most common). An alternative method, which uses chemical synthesis to derivatize cannabidiol to form an intermediate, which is crystalline and can easily be isolated from the extract; the crystalline intermediate can then be deprotected back to pure cannabidiol. In this research, we investigated and adapted the crystallisation method (originally employed by Adams) into continuous flow. In this research, hemp extracts and oilsrich in CBD were used as the source for cannabidiol. This synthesis was adapted into microreactors to synthesise the crystalline intermediate ester product (cannabidiol-3,5-bis-benzoate) which was subsequently reacted in a saponification ester hydrolysis to convert back and isolate pure CBD using continuous flow microreactor technology. Chapter one gives a comprehensive literature review and background on cannabidiol, along with its chemistry and pharmacological benefits in addition to a brief introduction to continuous flow technology with its advantages. Chapter two details the experimental procedures utilised for both batch and continuous flow syntheses. The continuous flow synthesis and subsequent hydrolysis of the ester intermediate, which shows the improvements in comparison to batch; giving higher product recovery (63% CBD), in shorter reaction times (2.5 min for CBD bis-benzoate; 30 min for CBD) is subsequently presented. This is expanded in chapter three with detailed discussions of the results attained during the continuous flow. The concluding remarks, the impact of this study and future work are elucidated in chapter four. , Thesis (MSc) -- Faculty of Science, Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Bopape, Karabo
- Date: 2022-04
- Subjects: Supercritical fluid extraction -- South Africa , Cannabis -- Therapeutic use
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55723 , vital:53410
- Description: cannabinoids are of growing interest in research and pharmaceutical applications. Cannabidiol, which is a non-psychoactive cannabinoid, has many pharmaceutical applications. The current and main source of cannabidiol and other cannabinoids is from cannabis and hemp extractions. Current extraction methods involve the use of conventional solvent extraction, which employs the use of organic solvents, in some cases along with mechanical assistance from various equipment. Alternatively, another widely used extraction method is the use of supercritical extraction fluids (SC-CO2 being the most common). An alternative method, which uses chemical synthesis to derivatize cannabidiol to form an intermediate, which is crystalline and can easily be isolated from the extract; the crystalline intermediate can then be deprotected back to pure cannabidiol. In this research, we investigated and adapted the crystallisation method (originally employed by Adams) into continuous flow. In this research, hemp extracts and oilsrich in CBD were used as the source for cannabidiol. This synthesis was adapted into microreactors to synthesise the crystalline intermediate ester product (cannabidiol-3,5-bis-benzoate) which was subsequently reacted in a saponification ester hydrolysis to convert back and isolate pure CBD using continuous flow microreactor technology. Chapter one gives a comprehensive literature review and background on cannabidiol, along with its chemistry and pharmacological benefits in addition to a brief introduction to continuous flow technology with its advantages. Chapter two details the experimental procedures utilised for both batch and continuous flow syntheses. The continuous flow synthesis and subsequent hydrolysis of the ester intermediate, which shows the improvements in comparison to batch; giving higher product recovery (63% CBD), in shorter reaction times (2.5 min for CBD bis-benzoate; 30 min for CBD) is subsequently presented. This is expanded in chapter three with detailed discussions of the results attained during the continuous flow. The concluding remarks, the impact of this study and future work are elucidated in chapter four. , Thesis (MSc) -- Faculty of Science, Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-04
Effect of livestock management and services to ecosystems on rangeland health and resilience in the NamaKaroo
- Authors: Boshoff, Mishak
- Date: 2023-04
- Subjects: Livestock – Management --South Africa—Karoo , Range ecology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/60611 , vital:66017
- Description: Rangelands offer great opportunities for mutualisms between nature conservation and economic productivity if positive feedback loops can be identified and described. The effects of different livestock management practices are controversial. This research examined the effect of different grazing intensities on soil health using springtails (Collembola) and ants (Formicidae) as bioindicators, combined with soil and vegetation variables. The relationship between rangeland managers and rangeland ecosystems, particularly with regard to feedback loops between land care and economic production, was also investigated. Bioindicator samples were collected at different treatments of livestock grazing intensity and a questionnaire was submitted to 65 rangeland managers in the semi-arid Nama-Karoo biome of South Africa. In most cases we found no significant relationship between grazing intensity and Collembola and ant community composition, vegetation variables, and soil variables. The few significant relationships we found were contradictory in their implications for the effect of high intensity grazing on soil health. The results suggested that differences in livestock management are relatively unimportant for soil health, at least in semi-arid systems under conditions immediately following a drought. The questionnaire yielded results on outline of management practices, basis of management decisions, consequences of monitoring veld to inform management decisions, and indicators of successful management. Respondents characterized by higher ecological fluency focused on livestock production when making management decisions, stocked at higher densities, and monitored the rangeland ecosystem to inform their decisions. For monitoring the ecosystem, they used bioindicators such as diversity of biota, successional stage, and ecologically important functional groups. We concluded that the development of ecological knowledge in rangeland managers enables the establishment of feedback loops between ecosystem services and services to ecosystems, which are desirable for economic productivity and nature conservation. Development of relevant ecological knowledge and management techniques should be based on forums and dialogue among rangeland managers, developing distributed cognition and resilience in the community of rangeland managers. , Thesis (MSc) -- Faculty of Science, School Natural Resource Science and Management, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Boshoff, Mishak
- Date: 2023-04
- Subjects: Livestock – Management --South Africa—Karoo , Range ecology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/60611 , vital:66017
- Description: Rangelands offer great opportunities for mutualisms between nature conservation and economic productivity if positive feedback loops can be identified and described. The effects of different livestock management practices are controversial. This research examined the effect of different grazing intensities on soil health using springtails (Collembola) and ants (Formicidae) as bioindicators, combined with soil and vegetation variables. The relationship between rangeland managers and rangeland ecosystems, particularly with regard to feedback loops between land care and economic production, was also investigated. Bioindicator samples were collected at different treatments of livestock grazing intensity and a questionnaire was submitted to 65 rangeland managers in the semi-arid Nama-Karoo biome of South Africa. In most cases we found no significant relationship between grazing intensity and Collembola and ant community composition, vegetation variables, and soil variables. The few significant relationships we found were contradictory in their implications for the effect of high intensity grazing on soil health. The results suggested that differences in livestock management are relatively unimportant for soil health, at least in semi-arid systems under conditions immediately following a drought. The questionnaire yielded results on outline of management practices, basis of management decisions, consequences of monitoring veld to inform management decisions, and indicators of successful management. Respondents characterized by higher ecological fluency focused on livestock production when making management decisions, stocked at higher densities, and monitored the rangeland ecosystem to inform their decisions. For monitoring the ecosystem, they used bioindicators such as diversity of biota, successional stage, and ecologically important functional groups. We concluded that the development of ecological knowledge in rangeland managers enables the establishment of feedback loops between ecosystem services and services to ecosystems, which are desirable for economic productivity and nature conservation. Development of relevant ecological knowledge and management techniques should be based on forums and dialogue among rangeland managers, developing distributed cognition and resilience in the community of rangeland managers. , Thesis (MSc) -- Faculty of Science, School Natural Resource Science and Management, 2023
- Full Text:
- Date Issued: 2023-04
Linking agrochemical pollution with the aquatic ecological integrity of the Twee River Catchment, Western Cape
- Authors: Brink, Zanné
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Ecological integrity
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52326 , vital:43588
- Description: This study was initiated in the Twee River system due to the threat posed by agrochemicals on the occurrence of the endemic and endangered fish species found within the catchment. Poor knowledge and understanding of the environmental effects of fertilizers, pesticides and other agrochemicals among small and large commercial farmers within the study area, in combination with their intensive use may have resulted in chemical contamination above environmentally safe concentrations. Numerous studies have highlighted the fact that more research needs to be conducted to identify the key threats to the continued existence of specifically the Critically Endangered Sedercypris erubescens. The overall aim of this study was to determine the spatial and temporal patterns in aquatic ecosystem diversity in the Twee River catchment as indicated by macroinvertebrate and native fish distribution and abundance. It was further investigated if there was a link between agrochemical pollution and the aquatic ecological integrity of the Twee River catchment. Selected sampling sites were identified and sampled to determine the presence and concentration of pesticides entering the water of the Twee River system during run-off and event-based spraying. Furthermore, the effect of these pesticides on the distribution and abundance of the aquatic biota were determined using SASS5 for the macroinvertebrate populations and visually sampling the distribution of the native and non-native fish in the Twee River catchment. This study supports suggestions made by previous studies, that sub-lethal to lethal concentrations of insecticides could be a threat to the long-term survival of benthic macroinvertebrates and potentially the more sensitive endemic fish species within the Twee River system. More focussed research is needed to address impacts of pesticides within this catchment. Agricultural and conservation efforts should be aimed at developing of a shared vision amongst stakeholders, to allow for the longterm conservation of the endemic fish of the Twee River. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Brink, Zanné
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Ecological integrity
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52326 , vital:43588
- Description: This study was initiated in the Twee River system due to the threat posed by agrochemicals on the occurrence of the endemic and endangered fish species found within the catchment. Poor knowledge and understanding of the environmental effects of fertilizers, pesticides and other agrochemicals among small and large commercial farmers within the study area, in combination with their intensive use may have resulted in chemical contamination above environmentally safe concentrations. Numerous studies have highlighted the fact that more research needs to be conducted to identify the key threats to the continued existence of specifically the Critically Endangered Sedercypris erubescens. The overall aim of this study was to determine the spatial and temporal patterns in aquatic ecosystem diversity in the Twee River catchment as indicated by macroinvertebrate and native fish distribution and abundance. It was further investigated if there was a link between agrochemical pollution and the aquatic ecological integrity of the Twee River catchment. Selected sampling sites were identified and sampled to determine the presence and concentration of pesticides entering the water of the Twee River system during run-off and event-based spraying. Furthermore, the effect of these pesticides on the distribution and abundance of the aquatic biota were determined using SASS5 for the macroinvertebrate populations and visually sampling the distribution of the native and non-native fish in the Twee River catchment. This study supports suggestions made by previous studies, that sub-lethal to lethal concentrations of insecticides could be a threat to the long-term survival of benthic macroinvertebrates and potentially the more sensitive endemic fish species within the Twee River system. More focussed research is needed to address impacts of pesticides within this catchment. Agricultural and conservation efforts should be aimed at developing of a shared vision amongst stakeholders, to allow for the longterm conservation of the endemic fish of the Twee River. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-04
A study of the airflow on the windward slope of a transverse dune in the Alexandria coastal dunefield
- Authors: Burkinshaw, Jennifer Ruth
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52734 , vital:43883
- Description: Our understanding of the evolution of dune morphology has been hampered by a lack of empirical observations of airflow behaviour over dune forms. Sand dunes intrude into the atmospheric boundary layer and convergence of streamlines results in an acceleration of airflow up the windward slopes of dunes. This study examines the airflow structure and corresponding bedform development on the windward slope of a 7 m high transverse dune on the edge of the Alexandria coastal dunefield, Algoa Bay, South Africa. The Alexandria dunefield is subjected to a trimodal wind regime, consisting of the dominant south-westerly which blows all year round, summer easterlies and winter northwesterlies. The morphology of the study dune, Dune13, is controlled by the easterlies and north-westerlies, and reverses seasonally with respect to these two winds. Seven section lines 30 m apart and normal to the dune crest were surveyed regularly over the period of a year to monitor the reversal process. Three detailed topographic surveys were also done during this period. Airflow behaviour was monitored during the year. Wind speed profiles on the windward slope of the dune were measured using 4 to 5 vertical arrays of anemometers positioned from the base of the dune to the crest on a 1 selected section line. Usually 4 to 5 anemometers were deployed in each vertical array, from a height of 6 to 10 cm above the surface, up to a height of 150 cm above the surface. Initially 8 microanemometers were available; ultimately 28 anemometers were run simultaneously. An independent weather station at an elevation of 6 m recorded the unaccelerated flow. Local gradient measurements and erosion and deposition rates were recorded along selected section lines. Strong summer easterly winds (14 m/sec at 1.4 m above the dune crest) were measured on a dune slope in the process of being transformed from a slipface to a stoss slope. The following winter, light north-westerly winds (typically B m/sec at 1.6 m above the dune crest) were measured on the new windward slope already reversed by the prevailing winter wind. Airflow data confirm the compression of airflow against the windward slope resulting in a non-logarithmic wind speed profile. Compression results in an increased shear velocity within 30 cm of the dune surface, and the dune slope is eroded. Higher up in the wind speed profile, shear velocity decreases to 0.1 m/sec. It is not known at what height the wind speed profile recovers from the intrusion of the dune into the boundary layer. High values of shear velocity (1.6 m/sec) above the rounded crestal area of the dune record the recovery of the wind speed profile from flow divergence, which is a response to the rapid reduction of dune gradient and is accompanied by deposition of sand in this region. 2 The erosion pin data act as a simple and sensitive test for changes in gradient, reflecting the dune's response to changes in the airflow regime. The shape of the dune plays a major role in determining the extent of the compression and the distribution of shear velocity up the slope. Increased shear velocity is experienced on that part of the slope which is nonaerodynamic with respect to the prevailing wind. Under unidirectional conditions, feedback between flow and form results ultimately in a slope with a curvature such that shear velocity increases systematically upslope. The survey data and erosion pin data record the reversal process as the dune achieves a new steady state during each wind season. The existence of a non-logarithmic wind speed profile makes it difficult to know what relevant measure of shear velocity is to be used in sand transport equations. Future work should include wind speed measurements within 10 cm of the surface. An ideal study modelling aeolian bedform development would utilise wind tunnel measurements, combined with field measurements such as obtained in this study, for comparison with numerical modelling. The study needs to be extended to 3-dimensional airflow measurements. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Burkinshaw, Jennifer Ruth
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52734 , vital:43883
- Description: Our understanding of the evolution of dune morphology has been hampered by a lack of empirical observations of airflow behaviour over dune forms. Sand dunes intrude into the atmospheric boundary layer and convergence of streamlines results in an acceleration of airflow up the windward slopes of dunes. This study examines the airflow structure and corresponding bedform development on the windward slope of a 7 m high transverse dune on the edge of the Alexandria coastal dunefield, Algoa Bay, South Africa. The Alexandria dunefield is subjected to a trimodal wind regime, consisting of the dominant south-westerly which blows all year round, summer easterlies and winter northwesterlies. The morphology of the study dune, Dune13, is controlled by the easterlies and north-westerlies, and reverses seasonally with respect to these two winds. Seven section lines 30 m apart and normal to the dune crest were surveyed regularly over the period of a year to monitor the reversal process. Three detailed topographic surveys were also done during this period. Airflow behaviour was monitored during the year. Wind speed profiles on the windward slope of the dune were measured using 4 to 5 vertical arrays of anemometers positioned from the base of the dune to the crest on a 1 selected section line. Usually 4 to 5 anemometers were deployed in each vertical array, from a height of 6 to 10 cm above the surface, up to a height of 150 cm above the surface. Initially 8 microanemometers were available; ultimately 28 anemometers were run simultaneously. An independent weather station at an elevation of 6 m recorded the unaccelerated flow. Local gradient measurements and erosion and deposition rates were recorded along selected section lines. Strong summer easterly winds (14 m/sec at 1.4 m above the dune crest) were measured on a dune slope in the process of being transformed from a slipface to a stoss slope. The following winter, light north-westerly winds (typically B m/sec at 1.6 m above the dune crest) were measured on the new windward slope already reversed by the prevailing winter wind. Airflow data confirm the compression of airflow against the windward slope resulting in a non-logarithmic wind speed profile. Compression results in an increased shear velocity within 30 cm of the dune surface, and the dune slope is eroded. Higher up in the wind speed profile, shear velocity decreases to 0.1 m/sec. It is not known at what height the wind speed profile recovers from the intrusion of the dune into the boundary layer. High values of shear velocity (1.6 m/sec) above the rounded crestal area of the dune record the recovery of the wind speed profile from flow divergence, which is a response to the rapid reduction of dune gradient and is accompanied by deposition of sand in this region. 2 The erosion pin data act as a simple and sensitive test for changes in gradient, reflecting the dune's response to changes in the airflow regime. The shape of the dune plays a major role in determining the extent of the compression and the distribution of shear velocity up the slope. Increased shear velocity is experienced on that part of the slope which is nonaerodynamic with respect to the prevailing wind. Under unidirectional conditions, feedback between flow and form results ultimately in a slope with a curvature such that shear velocity increases systematically upslope. The survey data and erosion pin data record the reversal process as the dune achieves a new steady state during each wind season. The existence of a non-logarithmic wind speed profile makes it difficult to know what relevant measure of shear velocity is to be used in sand transport equations. Future work should include wind speed measurements within 10 cm of the surface. An ideal study modelling aeolian bedform development would utilise wind tunnel measurements, combined with field measurements such as obtained in this study, for comparison with numerical modelling. The study needs to be extended to 3-dimensional airflow measurements. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text:
- Date Issued: 2021-04
An assessment of different methods for measuring mammal diversity in two Southern African arid ecosystems.
- Authors: Burt, Chloe
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Biodiversity -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52338 , vital:43591
- Description: A current critical environmental problem is the loss of biodiversity. To allow for adaptive management and effective conservation interventions, reliable data needs to be readily available and effectively collected. To gather reliable data, the most appropriate method must be used. The aim of this thesis was to compare the effectiveness and efficiency of different mammal diversity sampling techniques, including discussing specificities and complementarity of each. I also assessed the limitation of methods in terms of the influence of species traits on detectability. I used standard mammal field methods such as block transects, camera traps, track plates, spotlight surveys, mist nets, acoustic surveys, and live traps for a wide range of mammal taxa, and also included the use of local knowledge in the comparison. I assessed the cost-efficiency of each method by determining the cost per species. The efficiency of each method was assessed by observing when the species accumulation curve reached an asymptote. The effectiveness was determined by the species richness and the taxonomic groups the method detected. My results indicated that block transects were the most efficient and effective method to assess species richness. However, a combination of methods allowed for a more comprehensive survey and my results indicate that block transects and live traps were the best combination. It is important to note, not only the effectiveness and efficiency of methods be assessed, but also their limitations. I therefore also assessed the influence of species traits on the detectability of five methods. The species traits that I tested were body size, diet, activity, and if they lived in groups. On both study areas, body size was the main trait that influenced detectability with most field methods. Diet and activity had varying influence on detectability depending on the method. Group living did not significantly influence detectability. Based on my results, I provide guidelines for choosing the most appropriate survey method for targeted studies on mammals in arid ecosystems as well as guidelines for choosing the most appropriate methods for a terrestrial mammal inventory. Survey methods selection and guidelines provided here can allow for effective monitoring and therefore effective and adaptive management and having reliable and repeatable outcomes from surveys. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Burt, Chloe
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Biodiversity -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52338 , vital:43591
- Description: A current critical environmental problem is the loss of biodiversity. To allow for adaptive management and effective conservation interventions, reliable data needs to be readily available and effectively collected. To gather reliable data, the most appropriate method must be used. The aim of this thesis was to compare the effectiveness and efficiency of different mammal diversity sampling techniques, including discussing specificities and complementarity of each. I also assessed the limitation of methods in terms of the influence of species traits on detectability. I used standard mammal field methods such as block transects, camera traps, track plates, spotlight surveys, mist nets, acoustic surveys, and live traps for a wide range of mammal taxa, and also included the use of local knowledge in the comparison. I assessed the cost-efficiency of each method by determining the cost per species. The efficiency of each method was assessed by observing when the species accumulation curve reached an asymptote. The effectiveness was determined by the species richness and the taxonomic groups the method detected. My results indicated that block transects were the most efficient and effective method to assess species richness. However, a combination of methods allowed for a more comprehensive survey and my results indicate that block transects and live traps were the best combination. It is important to note, not only the effectiveness and efficiency of methods be assessed, but also their limitations. I therefore also assessed the influence of species traits on the detectability of five methods. The species traits that I tested were body size, diet, activity, and if they lived in groups. On both study areas, body size was the main trait that influenced detectability with most field methods. Diet and activity had varying influence on detectability depending on the method. Group living did not significantly influence detectability. Based on my results, I provide guidelines for choosing the most appropriate survey method for targeted studies on mammals in arid ecosystems as well as guidelines for choosing the most appropriate methods for a terrestrial mammal inventory. Survey methods selection and guidelines provided here can allow for effective monitoring and therefore effective and adaptive management and having reliable and repeatable outcomes from surveys. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-04
Hydraulic vulnerability of Subtropical Thicket to drought : a remote sensing and physiological perspective
- Authors: Buttner, Daniel Harry
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55455 , vital:52017
- Description: Water availability is one of largest constraints on plant survival, growth, and species distribution globally. The recent escalation in tree mortality coupled with declining precipitation and amplified temperatures has implicated drought as a major cause behind many large-scale dieback events observed across the world. Raising the question, what makes some species more resistant and persist while others dwindle and vanish from the landscape? The observed variability in species drought susceptibility demonstrates the complexity of physiological responses of plants to changes in water availability. Hydraulic dysfunction in plants has been purported to be the key mechanism behind drought-induced mortality provoking interest in hydraulic traits and critical thresholds of xylem physiological function. The capability of species to maintain hydraulic functionality under drought strongly influences the survival and general productivity towards water deficits. Hence, two core objectives, and subsequently aims, of this thesis are firstly to investigate the effect of drought on Subtropical Thicket vegetation health and productivity, and secondly to examine the underpinning physiological mechanisms and functional thresholds relaying speciesspecific drought vulnerability within this semi-arid biome. In first data chapter, this thesis offers an assessment of vegetation change under drought and its influence on plant physiological function and productivity across a subsection of Subtropical Thicket distribution. Additionally, this chapter provides a regional scale perspective of drought on Subtropical Thicket flora in the Eastern Cape of South Africa. A severe anomalous dieback event, which coincided with extreme, accumulative drought conditions was observed in 2020. Employing a combination of field-based approaches and remote sensing, this chapter aimed to provide a comprehensive report of the extent and severity of crown defoliation and canopy dieback following this event, additionally describing predisposing and compounding factors. Based on Standardized Precipitation Evapotranspiration and Standardized Precipitation Indices this event began in 2015 and coincided with amplified temperatures, exacerbating evaporative demand. Aerial UAV surveys and field-based investigations were undertaken. Remotely sensed (RS) indices provided an avenue for extensive spatiotemporal investigations to uncover the extent of drought-related impact on vegetation productivity and discuss potential underpinning mechanisms behind drought-induced mortality in Subtropical Thicket. Leveraging long-term time series RS data, Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI), from Moderate Resolution Imaging Spectroradiometer (MODIS) satellites as a proxy vegetation physiological status in combination with SPI and SPEI describing drought condition and groundbased surveying defining canopy vitality condition this study incidentally addressed the aim of endeavoring to link drought-induced mortality and early warning symptoms observed in the field with RS time series data to describe drought impacts across Subtropical Thicket. Furthermore, the findings of this chapter demonstrate the spatial and temporal heterogeneity in drought impacts on Subtropical Thicket. The recent drought of 2015 till 2021 is the longest documented period for the past 50 years in which there has been no accumulated net positive water availability, this apparently perpetual state of water deficiency has enacted a high cost for vegetation productivity and growth for the study area, exhibited well by average NDVI values of less than -0.5 for over 70% of the research site. The findings of this chapter report, to the contrary of anecdotal suggestions in the literature, on the intrinsic tolerance of Subtropical Thicket and that ii drought has a far more significant role on overall vegetation productivity, growth, and mortality in this region. The second data chapter assess whole-plant physiological functionality during a drought event in the Eastern Cape, South Africa. This is the first study in Subtropical Thicket to quantify in situ hydraulic functional integrity under a natural drought event testing the leading hypothesis describing tree mortality – hydraulic dysfunction. This chapter firstly, investigates hydraulic traits (e.g., turgor loss point) and describe key physiological thresholds (e.g., P50) for maintaining function during drought. Secondly, levels of native embolism were determined under drought conditions and combined with measurements of xylem vulnerability to embolism providing an estimation of degree of hydraulic dysfunction experienced by six dominant woody canopy species in Subtropical Thicket – to quantify interspecific drought tolerance and susceptibility. Subtropical Thicket species exhibited remarkable tolerance towards desiccation (TLP from as low as -3MPa) and hydraulic functional resistance to embolism (P50 value as low as -7.89MPa). The observed unexpected drought resilience of subtropical derived lineages highlights the intrinsic evolutionary role aridification had, selecting for greater embolism resistance and community-level conservatism in drought resistance of Subtropical Thicket. The level of native embolism and hydraulic safety margins identified two species (Schotia latifolia and Polyagla myrtifolia) that were the most vulnerable, and a third (Pappea capensis) moderately vulnerable, then the remaining studied species – this could result in community-level adjustments in species composition and structure under future projected climate change scenarios where, increased frequencies of drought events are anticipated. This retrospective assessment of canopy vigor with physiological functional thresholds evokes hydraulic dysfunction as the principal mechanism of observed Subtropical Thicket dieback to drought. This chapter provides crucial in situ data for predictive assertions around drought-induced mortality risk in a phylogenetically diverse and climatically unique biome of southern Africa; and is the first to identify critical hydraulic thresholds for tree species within this region. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Buttner, Daniel Harry
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55455 , vital:52017
- Description: Water availability is one of largest constraints on plant survival, growth, and species distribution globally. The recent escalation in tree mortality coupled with declining precipitation and amplified temperatures has implicated drought as a major cause behind many large-scale dieback events observed across the world. Raising the question, what makes some species more resistant and persist while others dwindle and vanish from the landscape? The observed variability in species drought susceptibility demonstrates the complexity of physiological responses of plants to changes in water availability. Hydraulic dysfunction in plants has been purported to be the key mechanism behind drought-induced mortality provoking interest in hydraulic traits and critical thresholds of xylem physiological function. The capability of species to maintain hydraulic functionality under drought strongly influences the survival and general productivity towards water deficits. Hence, two core objectives, and subsequently aims, of this thesis are firstly to investigate the effect of drought on Subtropical Thicket vegetation health and productivity, and secondly to examine the underpinning physiological mechanisms and functional thresholds relaying speciesspecific drought vulnerability within this semi-arid biome. In first data chapter, this thesis offers an assessment of vegetation change under drought and its influence on plant physiological function and productivity across a subsection of Subtropical Thicket distribution. Additionally, this chapter provides a regional scale perspective of drought on Subtropical Thicket flora in the Eastern Cape of South Africa. A severe anomalous dieback event, which coincided with extreme, accumulative drought conditions was observed in 2020. Employing a combination of field-based approaches and remote sensing, this chapter aimed to provide a comprehensive report of the extent and severity of crown defoliation and canopy dieback following this event, additionally describing predisposing and compounding factors. Based on Standardized Precipitation Evapotranspiration and Standardized Precipitation Indices this event began in 2015 and coincided with amplified temperatures, exacerbating evaporative demand. Aerial UAV surveys and field-based investigations were undertaken. Remotely sensed (RS) indices provided an avenue for extensive spatiotemporal investigations to uncover the extent of drought-related impact on vegetation productivity and discuss potential underpinning mechanisms behind drought-induced mortality in Subtropical Thicket. Leveraging long-term time series RS data, Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI), from Moderate Resolution Imaging Spectroradiometer (MODIS) satellites as a proxy vegetation physiological status in combination with SPI and SPEI describing drought condition and groundbased surveying defining canopy vitality condition this study incidentally addressed the aim of endeavoring to link drought-induced mortality and early warning symptoms observed in the field with RS time series data to describe drought impacts across Subtropical Thicket. Furthermore, the findings of this chapter demonstrate the spatial and temporal heterogeneity in drought impacts on Subtropical Thicket. The recent drought of 2015 till 2021 is the longest documented period for the past 50 years in which there has been no accumulated net positive water availability, this apparently perpetual state of water deficiency has enacted a high cost for vegetation productivity and growth for the study area, exhibited well by average NDVI values of less than -0.5 for over 70% of the research site. The findings of this chapter report, to the contrary of anecdotal suggestions in the literature, on the intrinsic tolerance of Subtropical Thicket and that ii drought has a far more significant role on overall vegetation productivity, growth, and mortality in this region. The second data chapter assess whole-plant physiological functionality during a drought event in the Eastern Cape, South Africa. This is the first study in Subtropical Thicket to quantify in situ hydraulic functional integrity under a natural drought event testing the leading hypothesis describing tree mortality – hydraulic dysfunction. This chapter firstly, investigates hydraulic traits (e.g., turgor loss point) and describe key physiological thresholds (e.g., P50) for maintaining function during drought. Secondly, levels of native embolism were determined under drought conditions and combined with measurements of xylem vulnerability to embolism providing an estimation of degree of hydraulic dysfunction experienced by six dominant woody canopy species in Subtropical Thicket – to quantify interspecific drought tolerance and susceptibility. Subtropical Thicket species exhibited remarkable tolerance towards desiccation (TLP from as low as -3MPa) and hydraulic functional resistance to embolism (P50 value as low as -7.89MPa). The observed unexpected drought resilience of subtropical derived lineages highlights the intrinsic evolutionary role aridification had, selecting for greater embolism resistance and community-level conservatism in drought resistance of Subtropical Thicket. The level of native embolism and hydraulic safety margins identified two species (Schotia latifolia and Polyagla myrtifolia) that were the most vulnerable, and a third (Pappea capensis) moderately vulnerable, then the remaining studied species – this could result in community-level adjustments in species composition and structure under future projected climate change scenarios where, increased frequencies of drought events are anticipated. This retrospective assessment of canopy vigor with physiological functional thresholds evokes hydraulic dysfunction as the principal mechanism of observed Subtropical Thicket dieback to drought. This chapter provides crucial in situ data for predictive assertions around drought-induced mortality risk in a phylogenetically diverse and climatically unique biome of southern Africa; and is the first to identify critical hydraulic thresholds for tree species within this region. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
The aesthetics of hegemony: a speculative design proposal exploring the convergence of surveillance capitalism and brain-computer interface technologies in the future
- Authors: Davies, James Tibbott
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54417 , vital:46517
- Description: This study examines the power dynamics of surveillance capitalism, and its role in shaping cultural hegemony. The research was expressed using graphic design to illustrate a (potential) future where Brain-Computer Interfaces (BCIs) and surveillance capitalism converge. The critique focused on Google and Facebook’s hegemony in the data-surveillance marketplace and what role this has in shaping global discourse. Both companies are funding the development of BCIs, with the aim of using brain signals as a means of interacting with the digital world, which would give the two biggest advertising companies in the world access to new sources of data. A speculative design framework was utilized to visually question the societal implications of this emerging technology and the funding behind its development. A theoretical investigation of the concepts underpinning critical theory and critical design was conducted to help clarify and critically inform this methodological approach, promoting the use of practice-based design as a critically reflective investigative tool. The resulting artefacts designed using this process were showcased in the form of a website and video that act as a visual embodiment the research, demonstrating the efficacy of this approach and the value of using communication design as a mechanism to question the status quo. , Thesis (MA) -- Faculty of Humanities, School of Visual and Performing Arts, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Davies, James Tibbott
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54417 , vital:46517
- Description: This study examines the power dynamics of surveillance capitalism, and its role in shaping cultural hegemony. The research was expressed using graphic design to illustrate a (potential) future where Brain-Computer Interfaces (BCIs) and surveillance capitalism converge. The critique focused on Google and Facebook’s hegemony in the data-surveillance marketplace and what role this has in shaping global discourse. Both companies are funding the development of BCIs, with the aim of using brain signals as a means of interacting with the digital world, which would give the two biggest advertising companies in the world access to new sources of data. A speculative design framework was utilized to visually question the societal implications of this emerging technology and the funding behind its development. A theoretical investigation of the concepts underpinning critical theory and critical design was conducted to help clarify and critically inform this methodological approach, promoting the use of practice-based design as a critically reflective investigative tool. The resulting artefacts designed using this process were showcased in the form of a website and video that act as a visual embodiment the research, demonstrating the efficacy of this approach and the value of using communication design as a mechanism to question the status quo. , Thesis (MA) -- Faculty of Humanities, School of Visual and Performing Arts, 2021
- Full Text:
- Date Issued: 2021-12
Perceptions of small-scale vegetable farmers on drought mitigation strategies in the Amathole District Municipality of the Eastern Cape Province
- Authors: Dingiswayo, Xolisile
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53676 , vital:45686
- Description: The present study aimed to investigate perceptions of small-scale vegetable farmers on drought mitigation strategies in the Amathole District Municipality of the Eastern Cape Province. The research objective was to investigate what small-scale vegetable farmers’ perceptions and readiness are in terms of strategies to cope with drought conditions. The study was conducted within the Mbashe, Mnquma, Amahlathi and Great Kei local municipalities of the Eastern Cape. Primary data collection was conducted among 44 small-scale vegetable farmers of the Amathole municipal district. These are farmers who receive social support from the government, are registered with the Department of Rural Development and Agrarian Reform and contribute to the fight against food insecurity in the Amathole district. The primary data was also collected from 13 agricultural extension officers with high experience in advising small-scale farmers residing in the Amathole district. Data collection took place in various local municipalities under Amathole District Municipality, namely: Mbashe, Mnquma, Amahlathi and Great Kei. A multi-method approach was adopted in this study as an appropriate technique to create an improved quality of research which eliminates the deep-rooted bias to either qualitative or quantitative methods alone. A self-administered questionnaires with both closed and open-ended questions – one for the small-scale farmer survey and the second for the extension officer survey – was employed as data collection instrument. The demographic characteristics of small-scale vegetable farmers in the survey area indicated that the present majority of farmers are married male Xhosa farmers between the ages of 56 and 65 years old, with a secondary level of education. The majority of the farmers are typically resource-poor − which implies that the added menace of drought poses the risk that small-scale vegetable farming could decline to mere subsistence level or worse. Drought was found to be a major problem in Mbashe, Mnquma, Amahlathi and Great Kei local municipalities within the Amathole municipal district, with an acute impact on farmers’ production and generation of income. From the data, it emerged that farmers are not sufficiently informed about and do not receive specific training in drought mitigation strategies. Farmers rely on drought alleviation methods but there is a lack of adaptive strategies and timely, long-term ii state intervention. Being resource-poor, these small-scale producers are reliant on natural resources – notably water for irrigating crops. The study established further that there is neither the resources nor sufficient training by and involvement of the extension service. Farmers therefore rely on the use of drought coping mechanisms and drought mitigation techniques and on adapting their production systems. The information-sharing sessions recommended can assist in improving rural livelihoods and the productivity of small-scale vegetable farmers. The absence of engagement of youth in farming means that modern conservation and innovative farming techniques and systems are not implemented towards reducing the impacts of climate change − as well as revitalizing rural areas such Amathole. Access to education about drought, improved drought coping mechanisms and adaptive strategies should be created to facilitate an exchange of traditional and modern agricultural information. The development of infrastructure in rural communities and farming areas is another factor crucial to improving farming systems and operations in the Amathole municipal district. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-12
- Authors: Dingiswayo, Xolisile
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53676 , vital:45686
- Description: The present study aimed to investigate perceptions of small-scale vegetable farmers on drought mitigation strategies in the Amathole District Municipality of the Eastern Cape Province. The research objective was to investigate what small-scale vegetable farmers’ perceptions and readiness are in terms of strategies to cope with drought conditions. The study was conducted within the Mbashe, Mnquma, Amahlathi and Great Kei local municipalities of the Eastern Cape. Primary data collection was conducted among 44 small-scale vegetable farmers of the Amathole municipal district. These are farmers who receive social support from the government, are registered with the Department of Rural Development and Agrarian Reform and contribute to the fight against food insecurity in the Amathole district. The primary data was also collected from 13 agricultural extension officers with high experience in advising small-scale farmers residing in the Amathole district. Data collection took place in various local municipalities under Amathole District Municipality, namely: Mbashe, Mnquma, Amahlathi and Great Kei. A multi-method approach was adopted in this study as an appropriate technique to create an improved quality of research which eliminates the deep-rooted bias to either qualitative or quantitative methods alone. A self-administered questionnaires with both closed and open-ended questions – one for the small-scale farmer survey and the second for the extension officer survey – was employed as data collection instrument. The demographic characteristics of small-scale vegetable farmers in the survey area indicated that the present majority of farmers are married male Xhosa farmers between the ages of 56 and 65 years old, with a secondary level of education. The majority of the farmers are typically resource-poor − which implies that the added menace of drought poses the risk that small-scale vegetable farming could decline to mere subsistence level or worse. Drought was found to be a major problem in Mbashe, Mnquma, Amahlathi and Great Kei local municipalities within the Amathole municipal district, with an acute impact on farmers’ production and generation of income. From the data, it emerged that farmers are not sufficiently informed about and do not receive specific training in drought mitigation strategies. Farmers rely on drought alleviation methods but there is a lack of adaptive strategies and timely, long-term ii state intervention. Being resource-poor, these small-scale producers are reliant on natural resources – notably water for irrigating crops. The study established further that there is neither the resources nor sufficient training by and involvement of the extension service. Farmers therefore rely on the use of drought coping mechanisms and drought mitigation techniques and on adapting their production systems. The information-sharing sessions recommended can assist in improving rural livelihoods and the productivity of small-scale vegetable farmers. The absence of engagement of youth in farming means that modern conservation and innovative farming techniques and systems are not implemented towards reducing the impacts of climate change − as well as revitalizing rural areas such Amathole. Access to education about drought, improved drought coping mechanisms and adaptive strategies should be created to facilitate an exchange of traditional and modern agricultural information. The development of infrastructure in rural communities and farming areas is another factor crucial to improving farming systems and operations in the Amathole municipal district. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-12
Incidence of parasitic trematodes effects on the energetics and behaviour of Coryogalops sordidus (Family: Gobiidae) resident in microbialite pools, warm temperate South Africa
- Authors: Du Toit, Hendrik Daniël
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Gobiidae -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52458 , vital:43666
- Description: Coryogalops sordidus(Epaulette goby), is a cryptobenthic species of the Family Gobiidae that iscommonly foundoccupying turbulent surf zones, calm rock pools, and sand and mud flats, where they are generally carnivorous predators. The distribution of C. sordidushas been recorded for Kenya, Tanzania, Mozambique, and South Africa. The species is also resident in the microbialite pools on the temperate south east coast of South Africa. Recent reports indicated these gobies to be covered in numerous dark lesions, possibly suggesting that the microbialite pools are a sub-optimal habitat. Preliminary analyses have indicated that the dark lesions are a result of encysted metacercaria of a digenetic trematode (fluke). There werehowever,no current recorded parasiticspecies occurring within microbialite pool nor any records of any parasitic species utilizingC. sordidus as a host in South Africa. Therefore, the aim of this study was to investigate parasite-host interactions and parasite presence in and around themicrobialite pool systems of Algoa Bay using C. sordidusas a study species. Coryogalops sordiduswas identified to be parasitised by digenetic trematode metacercaria of the Family Diplostomidae Poirier, 1886, localised primarily to the host musculature, fins, eyes, and integument with no settlement on any of the visceral organs. Furthermore, C. sordidus was found additionally parasitised by a green leech (Class: Hirundinea) of the Family Piscicolidae Johnston, 1865, localised exclusively to the ventral body surface, underneath the pelvic fin of the host. Further investigation into the life cycle of the trematode, suggested that the most probable final hosts wereherons,namely Ardea cinereaand Egretta garzetta garzetta, and intermediate host likely being the freshwater gastropod Assimineacf.capensis, present inthe upper microbialite pools. In both the microbialite and neighbouring rock pools trematode prevalence was found to oscillate in response to seasonal chemical and climatic conditions, whereas the secondary piscicolid leech parasite was influencedmoreby host presence than environmental conditions. Greater prevalence and intensity were measured in the microbialite pools suggesting that these systems likely contained a suit of favourable conditions that allowed for greater trematode loads to be maintained as compared to neighbouring rock pools. As parasites often have deleterious effects on their hosts, the response can manifest as an altered host behaviour or an increased energetic debt due to elevated immune response activity and the associated cost of tissue repair at sites of parasite aggregation.This study further investigatedifgobies (C. sordidus) infected with metacercarial cysts display higher metabolic ratesordifferent swimming behaviour compared to non-infected individuals. The results indicated that the metacercarial load carried by infected hosts had on average no significant impact on energetics, swimming ability, or swimming behaviour, concluding that the average metacercarial intensity present on the gobies is therefore below the threshold of an altered host response. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Du Toit, Hendrik Daniël
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Gobiidae -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52458 , vital:43666
- Description: Coryogalops sordidus(Epaulette goby), is a cryptobenthic species of the Family Gobiidae that iscommonly foundoccupying turbulent surf zones, calm rock pools, and sand and mud flats, where they are generally carnivorous predators. The distribution of C. sordidushas been recorded for Kenya, Tanzania, Mozambique, and South Africa. The species is also resident in the microbialite pools on the temperate south east coast of South Africa. Recent reports indicated these gobies to be covered in numerous dark lesions, possibly suggesting that the microbialite pools are a sub-optimal habitat. Preliminary analyses have indicated that the dark lesions are a result of encysted metacercaria of a digenetic trematode (fluke). There werehowever,no current recorded parasiticspecies occurring within microbialite pool nor any records of any parasitic species utilizingC. sordidus as a host in South Africa. Therefore, the aim of this study was to investigate parasite-host interactions and parasite presence in and around themicrobialite pool systems of Algoa Bay using C. sordidusas a study species. Coryogalops sordiduswas identified to be parasitised by digenetic trematode metacercaria of the Family Diplostomidae Poirier, 1886, localised primarily to the host musculature, fins, eyes, and integument with no settlement on any of the visceral organs. Furthermore, C. sordidus was found additionally parasitised by a green leech (Class: Hirundinea) of the Family Piscicolidae Johnston, 1865, localised exclusively to the ventral body surface, underneath the pelvic fin of the host. Further investigation into the life cycle of the trematode, suggested that the most probable final hosts wereherons,namely Ardea cinereaand Egretta garzetta garzetta, and intermediate host likely being the freshwater gastropod Assimineacf.capensis, present inthe upper microbialite pools. In both the microbialite and neighbouring rock pools trematode prevalence was found to oscillate in response to seasonal chemical and climatic conditions, whereas the secondary piscicolid leech parasite was influencedmoreby host presence than environmental conditions. Greater prevalence and intensity were measured in the microbialite pools suggesting that these systems likely contained a suit of favourable conditions that allowed for greater trematode loads to be maintained as compared to neighbouring rock pools. As parasites often have deleterious effects on their hosts, the response can manifest as an altered host behaviour or an increased energetic debt due to elevated immune response activity and the associated cost of tissue repair at sites of parasite aggregation.This study further investigatedifgobies (C. sordidus) infected with metacercarial cysts display higher metabolic ratesordifferent swimming behaviour compared to non-infected individuals. The results indicated that the metacercarial load carried by infected hosts had on average no significant impact on energetics, swimming ability, or swimming behaviour, concluding that the average metacercarial intensity present on the gobies is therefore below the threshold of an altered host response. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text:
- Date Issued: 2021-04
Beneficiation of pyrolysis-derived waste tyre char by blending with torrefied wood and microalgae to produce solid fuel
- Authors: Dube, Cleopatra Thulani
- Date: 2021-12
- Subjects: Pyrolysis , Solid fuel reactors
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/58439 , vital:59241
- Description: he thermal decomposition of waste tyres via pyrolysis is considered to be amongst the most promising methods of recycling tyres due to its minimal environmental impact (in terms of reduction in pollution). During pyrolysis, tyres are thermally degraded in an inert environment to produce gas, oil and char. The gas and oil have promising commercialization prospects while the char remains a pollutant despite the strides made in a lot of research to upgrade the char to carbon black, activated carbon and even for reuse as a filler in tyre manufacture. For pyrolysis to be profitable, or worthy of investments, all three of its products (oil, char and gas) need to be valorised. Pyrolysis-derived tyre chars (PT-char) have an energy value equivalent to high rank coals, however, the use of PT char as a solid fuel is uncommon due to the high contents of sulphur and mineral matter as well as low volatile matter content of the PT-char. As such, the combustion of PT-char is characterised by high ignition temperature, low thermal reactivity, and no flame formation due to the low amounts of volatile matter. On the other hand, biomass are clean, renewable feedstock, having low sulphur and mineral matter contents, as well as high thermal reactivity. The blending of PT-char with biomass could potentially improve the combustion properties of PT-char and minimise the release of toxic emissions from the char, and thus, could make PT-char suitable for use as a fuel source. In this study, PT-char was blended with torrefied wood and microalgae biomass to demonstrate the suitability of using PT-char-biomass-fuel blend as an energy feedstock. To this effect, a mixture design of experiments was used to formulate the PT-char biomass blends and regression analysis was employed to select an optimum blend formulation for the combustion and mechanical properties of the blends. Proximate analysis results showed a non-linear increase in the volatile matter and a non-linear decrease in the fixed carbon and ash yield as the biomass ratio increased. The calorific value also increased on an additive basis with increasing biomass proportion. The elemental analysis results showed a decrease in the calcium, zinc and bromine contents and an increase in the potassium and iron contents increased with increasing biomass proportion. Likewise, the sulphur content decreased while the oxygen, hydrogen and nitrogen contents increased with increasing biomass ratio. vi Thus, the fuel properties of the blends improved with increasing biomass ratio and without compromising the calorific value of the PT-char. Moreover, the TG-MS analysis showed that the PT-char and the respective blends did not show any release SO2 up to 650°C. Thus, making the fuel suitable for use in low temperature applications such as household and certain boilers. The results of the regression analysis showed that the blend formulation with the highest proportions of biomass, thus C55-T30-M15, is the optimum blend to produce a solid fuel with a low initial decomposition (214°C) and char ignition temperatures (532°C) as well as maximum burn-out temperature (640°C). In essence, the high thermal reactivity of PT-char is improved when both biomasses are loaded at maximum ratios as per the experimental design. The results of the MS showed a decrease in CO2 and NO2 emissions with increasing biomass proportion. The optimum blend (C55-T30-M15) was found to have a comparably higher gross calorific value (26 MJ/kg), lower sulphur content (1.1 wt.%), low ash yield (11wt.%) and lower concentration of minerals (i.e. zinc) than raw PT-char. In addition, the volatile matter content of the blend (20 wt.%) was found to be higher than that of PT-char and the ignition temperature of the optimum fuel blend was relatively lower and its burnout temperature higher than that of PT char. The MS results revealed that the CO2 and NO2 emissions were higher in the optimum blend than the PT-char. The mechanical properties of the pellets; impact resistance and compressive strength increased with increasing biomass blending ratio and even more so with increasing microalgae ratio. The C55-T30-M15 and C75-T10-M15 were selected as optimum blends using regression analysis and both blends exceeded the benchmark for mechanical properties except for water resistance. The blending did not improve the water resistance and all the blends did not meet the minimum threshold for water resistance. Overall, the blending of PT-char with torrefied wood and microalgae biomass has shown to improve the fuel properties PT-char, and therefore, making it a suitable potential fuel source. , Thesis (MSc) -- Faculty of Science, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Dube, Cleopatra Thulani
- Date: 2021-12
- Subjects: Pyrolysis , Solid fuel reactors
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/58439 , vital:59241
- Description: he thermal decomposition of waste tyres via pyrolysis is considered to be amongst the most promising methods of recycling tyres due to its minimal environmental impact (in terms of reduction in pollution). During pyrolysis, tyres are thermally degraded in an inert environment to produce gas, oil and char. The gas and oil have promising commercialization prospects while the char remains a pollutant despite the strides made in a lot of research to upgrade the char to carbon black, activated carbon and even for reuse as a filler in tyre manufacture. For pyrolysis to be profitable, or worthy of investments, all three of its products (oil, char and gas) need to be valorised. Pyrolysis-derived tyre chars (PT-char) have an energy value equivalent to high rank coals, however, the use of PT char as a solid fuel is uncommon due to the high contents of sulphur and mineral matter as well as low volatile matter content of the PT-char. As such, the combustion of PT-char is characterised by high ignition temperature, low thermal reactivity, and no flame formation due to the low amounts of volatile matter. On the other hand, biomass are clean, renewable feedstock, having low sulphur and mineral matter contents, as well as high thermal reactivity. The blending of PT-char with biomass could potentially improve the combustion properties of PT-char and minimise the release of toxic emissions from the char, and thus, could make PT-char suitable for use as a fuel source. In this study, PT-char was blended with torrefied wood and microalgae biomass to demonstrate the suitability of using PT-char-biomass-fuel blend as an energy feedstock. To this effect, a mixture design of experiments was used to formulate the PT-char biomass blends and regression analysis was employed to select an optimum blend formulation for the combustion and mechanical properties of the blends. Proximate analysis results showed a non-linear increase in the volatile matter and a non-linear decrease in the fixed carbon and ash yield as the biomass ratio increased. The calorific value also increased on an additive basis with increasing biomass proportion. The elemental analysis results showed a decrease in the calcium, zinc and bromine contents and an increase in the potassium and iron contents increased with increasing biomass proportion. Likewise, the sulphur content decreased while the oxygen, hydrogen and nitrogen contents increased with increasing biomass ratio. vi Thus, the fuel properties of the blends improved with increasing biomass ratio and without compromising the calorific value of the PT-char. Moreover, the TG-MS analysis showed that the PT-char and the respective blends did not show any release SO2 up to 650°C. Thus, making the fuel suitable for use in low temperature applications such as household and certain boilers. The results of the regression analysis showed that the blend formulation with the highest proportions of biomass, thus C55-T30-M15, is the optimum blend to produce a solid fuel with a low initial decomposition (214°C) and char ignition temperatures (532°C) as well as maximum burn-out temperature (640°C). In essence, the high thermal reactivity of PT-char is improved when both biomasses are loaded at maximum ratios as per the experimental design. The results of the MS showed a decrease in CO2 and NO2 emissions with increasing biomass proportion. The optimum blend (C55-T30-M15) was found to have a comparably higher gross calorific value (26 MJ/kg), lower sulphur content (1.1 wt.%), low ash yield (11wt.%) and lower concentration of minerals (i.e. zinc) than raw PT-char. In addition, the volatile matter content of the blend (20 wt.%) was found to be higher than that of PT-char and the ignition temperature of the optimum fuel blend was relatively lower and its burnout temperature higher than that of PT char. The MS results revealed that the CO2 and NO2 emissions were higher in the optimum blend than the PT-char. The mechanical properties of the pellets; impact resistance and compressive strength increased with increasing biomass blending ratio and even more so with increasing microalgae ratio. The C55-T30-M15 and C75-T10-M15 were selected as optimum blends using regression analysis and both blends exceeded the benchmark for mechanical properties except for water resistance. The blending did not improve the water resistance and all the blends did not meet the minimum threshold for water resistance. Overall, the blending of PT-char with torrefied wood and microalgae biomass has shown to improve the fuel properties PT-char, and therefore, making it a suitable potential fuel source. , Thesis (MSc) -- Faculty of Science, 2021
- Full Text:
- Date Issued: 2021-12
Mesozooplankton and particle dynamics in Algoa Bay, South Africa
- Engelbrecht, Melindi Frances
- Authors: Engelbrecht, Melindi Frances
- Date: 2022-12
- Subjects: Marine zooplankton – Algoa bay -- South Africa , Estuarine ecology , Zooplankton –Ecology --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59544 , vital:62157
- Description: Coastal ecosystems provide society with important ecosystem services: climate regulation, biogeochemical nutrient and waste cycling, food security, shoreline protection, tourism, and recreational support. Increased anthropogenic pressure on coastal ecosystems and changing environmental variables ultimately affect the provision of ecosystem services. Mesozooplankton are key trophic species and biological indicators of change within the marine environment and provide sound predictions of ecosystem responses to a changing climate due to their short life cycles and physiology linked to temperature. Algoa Bay has been the subject of extensive research and monitoring and encompasses a marine protected area (Addo Elephant National Park MPA). The Underwater Vision Profiler 5 (UVP5) was utilised with conventional sampling techniques of the PELTER monitoring program (i.e., Bongo nets) to investigate mesozooplankton (200 – 2000 µm) and particle (> 100 µm) dynamics within the dynamic coastal ecosystem of Algoa Bay, located within warmtemperate South Africa, in spring 2020 and summer 2021. This study revealed seasonal shifts in mesozooplankton taxa succession from spring herbivorous/omnivorous, dominated by copepods, to summer omnivorous/carnivorous mesozooplankton, dominated by copepods, Noctiluca sp., Cladocera, doliolids, salps and siphonophores. The mesozooplankton integrated abundance (mean ± standard error) increased from spring to summer, with 101 ± 26 (min. – max.: 18 – 200) x 103 ind m¯ 2 and 422 ± 80 (min. – max.: 37 – 1056) x 103 ind m¯ 2 , respectively. In summer, mesozooplankton composition was affected by the passage of a Natal Pulse, identified from satellite-derived sea level anomaly data. This study also provided the first vertical profiles of copepod distributions and suspended particles in Algoa Bay, with a peak of small particle (< 1 mm ESD) biomass close to the bottom and often, but not systematically, higher copepod abundances above the thermocline. The results presented herein are expected to contribute to the understanding of the coastal pelagic ecosystem in Algoa Bay in response to environmental perturbations , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Engelbrecht, Melindi Frances
- Date: 2022-12
- Subjects: Marine zooplankton – Algoa bay -- South Africa , Estuarine ecology , Zooplankton –Ecology --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59544 , vital:62157
- Description: Coastal ecosystems provide society with important ecosystem services: climate regulation, biogeochemical nutrient and waste cycling, food security, shoreline protection, tourism, and recreational support. Increased anthropogenic pressure on coastal ecosystems and changing environmental variables ultimately affect the provision of ecosystem services. Mesozooplankton are key trophic species and biological indicators of change within the marine environment and provide sound predictions of ecosystem responses to a changing climate due to their short life cycles and physiology linked to temperature. Algoa Bay has been the subject of extensive research and monitoring and encompasses a marine protected area (Addo Elephant National Park MPA). The Underwater Vision Profiler 5 (UVP5) was utilised with conventional sampling techniques of the PELTER monitoring program (i.e., Bongo nets) to investigate mesozooplankton (200 – 2000 µm) and particle (> 100 µm) dynamics within the dynamic coastal ecosystem of Algoa Bay, located within warmtemperate South Africa, in spring 2020 and summer 2021. This study revealed seasonal shifts in mesozooplankton taxa succession from spring herbivorous/omnivorous, dominated by copepods, to summer omnivorous/carnivorous mesozooplankton, dominated by copepods, Noctiluca sp., Cladocera, doliolids, salps and siphonophores. The mesozooplankton integrated abundance (mean ± standard error) increased from spring to summer, with 101 ± 26 (min. – max.: 18 – 200) x 103 ind m¯ 2 and 422 ± 80 (min. – max.: 37 – 1056) x 103 ind m¯ 2 , respectively. In summer, mesozooplankton composition was affected by the passage of a Natal Pulse, identified from satellite-derived sea level anomaly data. This study also provided the first vertical profiles of copepod distributions and suspended particles in Algoa Bay, with a peak of small particle (< 1 mm ESD) biomass close to the bottom and often, but not systematically, higher copepod abundances above the thermocline. The results presented herein are expected to contribute to the understanding of the coastal pelagic ecosystem in Algoa Bay in response to environmental perturbations , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Bootstrap-based tolerance intervals for nested two-way random effects models
- Authors: Erasmus, Christopher Daniel
- Date: 2022-04
- Subjects: Mathematical statistics-South Africa , Multilevel models
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55573 , vital:53331
- Description: Variance component, or random effects, models are frequently used by manufacturers to model the variance present in a manufacturing process. By applying tolerance intervals to variance component models, manufacturers are able to set upper and lower limits to monitor the variance within a process. Existing methods for constructing tolerance intervals are constrained by the necessity for data to be normally distributed. Recently, non-parametric bootstrap-based methods were developed by Deyzel (2018) to obtain α-expectation and (α, β) two-sided tolerance intervals for the two-way nested random effects model. Classical and non-parametric methods for obtaining tolerance intervals for the one way random effects model have been assessed in accordance with Rebafka et al. (2007). The present study assesses and compares classical, Bayesian and non-parametric methods for obtaining tolerance intervals for the two-way nested random effects model under different assumptions of the underlying distribution. Results show that the non-parametric methods provided relatively narrow intervals, and generally retain the nominal content and guarantee levels, regardless of the underlying distribution , Thesis (MSc) -- Faculty of Science, Mathematical Statistics , 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Erasmus, Christopher Daniel
- Date: 2022-04
- Subjects: Mathematical statistics-South Africa , Multilevel models
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55573 , vital:53331
- Description: Variance component, or random effects, models are frequently used by manufacturers to model the variance present in a manufacturing process. By applying tolerance intervals to variance component models, manufacturers are able to set upper and lower limits to monitor the variance within a process. Existing methods for constructing tolerance intervals are constrained by the necessity for data to be normally distributed. Recently, non-parametric bootstrap-based methods were developed by Deyzel (2018) to obtain α-expectation and (α, β) two-sided tolerance intervals for the two-way nested random effects model. Classical and non-parametric methods for obtaining tolerance intervals for the one way random effects model have been assessed in accordance with Rebafka et al. (2007). The present study assesses and compares classical, Bayesian and non-parametric methods for obtaining tolerance intervals for the two-way nested random effects model under different assumptions of the underlying distribution. Results show that the non-parametric methods provided relatively narrow intervals, and generally retain the nominal content and guarantee levels, regardless of the underlying distribution , Thesis (MSc) -- Faculty of Science, Mathematical Statistics , 2022
- Full Text:
- Date Issued: 2022-04