Spatial pattern analysis of thicket expansion in a semi-arid savanna
- Authors: Putzier, Rachel Rayne
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464484 , vital:76515
- Description: Woody thickening has negative economic and ecological impacts in savannas globally. While the increase of savanna trees as a form of bush encroachment has been well studied, less is known about the increase of thicket species in savannas, which is an important phenomenon resulting in the formation of closed-canopy clumps which may exclude the grass layer over time. The early stage of thicket expansion is often initiated by a nucleating savanna species which facilitates the establishment of woody thicket pioneer species, and as the thicket clump formation expands, bush clumps increase in dominance, thereby increasing the frequency of competitive interactions and leading to a possible switch from facilitative to competitive interactions. Spatial point pattern analysis provides a useful tool to elucidate these underlying patterns and ecological processes. I used high resolution LiDAR data combined with spatial point pattern analysis to understand tree-tree interactions in a semi-arid savanna in the Eastern Cape Province of South Africa. I conducted a cluster analysis based on vegetation structural variables to distinguish different stages of woody plant encroachment from open savanna to closed canopy thicket. Using the canopy height model, I quantified the change in the grass height from open savanna to closed canopy thicket clumps as an indicator of a possible biome shift. Additionally, I used spatial point pattern analyses to investigate the effect of thicket clump formation on the composition of savanna and thicket species, the overall patterns of trees, and the associations of small thicket species with large Vachellia karroo trees, which serve as clump initiators. Finally, I examined the mortality of savanna trees across increasing stages of thicket expansion using second order spatial statistics, namely the Mark- and Pair-Correlation Functions. Results confirmed that three vegetation states, influenced by elevation, are present at the study site, representing open canopy savanna (early-stage thicket encroachment), encroached savanna with low thicket dominance (intermediate-stage thicket encroachment), and highly encroached with dominant thicket clumps (late-stage thicket encroachment). These stages showed increasing tree height, canopy cover and canopy height density, as well as decreased (but not completely absent grass layer) as thicket encroachment progresses. Spatial point pattern analysis showed, as predicted, that there was an overall aggregation of trees at small-scales within early thicket clump formation, from which I inferred that facilitative relationships may exist between trees. Contrary to my predictions, at later stages of thicket clump formation I found dominant independent patterns between savanna adults and juvenile thicket species, which may result from a combination of facilitative and competitive effects. Lastly, as expected, I found that the density of V. karroo mortality increased as thicket encroachment increased, with an overall random spatial pattern of dead V. karroo across encroachment stages. As predicted, tree mortality was randomly distributed in space in the open savanna state, and as thicket clump formation increases, tree competitive mortality became more evident, as well as decreased tree performance. Overall, the study highlights the interplay between facilitation and competition in semiarid savanna where thicket clumps are expanding. Intervention strategies are suggested to target areas of intermediate thicket clump formation, as these areas provide an opportunity to remove V. karroo before the nucleation process has enabled the establishment and increase of thicket species and to ensure the grass layer is kept productive. I conclude that the use of remote sensing and LiDAR technology holds a wide range of possibilities for monitoring and managing woody encroachment in savanna systems, however these methods need to be further refined for effective use within African savanna and thicket context, which displays high spatial aggregation making typical segmentation methods difficult. , Thesis (MSc) -- Faculty of Science, Botany, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Putzier, Rachel Rayne
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464484 , vital:76515
- Description: Woody thickening has negative economic and ecological impacts in savannas globally. While the increase of savanna trees as a form of bush encroachment has been well studied, less is known about the increase of thicket species in savannas, which is an important phenomenon resulting in the formation of closed-canopy clumps which may exclude the grass layer over time. The early stage of thicket expansion is often initiated by a nucleating savanna species which facilitates the establishment of woody thicket pioneer species, and as the thicket clump formation expands, bush clumps increase in dominance, thereby increasing the frequency of competitive interactions and leading to a possible switch from facilitative to competitive interactions. Spatial point pattern analysis provides a useful tool to elucidate these underlying patterns and ecological processes. I used high resolution LiDAR data combined with spatial point pattern analysis to understand tree-tree interactions in a semi-arid savanna in the Eastern Cape Province of South Africa. I conducted a cluster analysis based on vegetation structural variables to distinguish different stages of woody plant encroachment from open savanna to closed canopy thicket. Using the canopy height model, I quantified the change in the grass height from open savanna to closed canopy thicket clumps as an indicator of a possible biome shift. Additionally, I used spatial point pattern analyses to investigate the effect of thicket clump formation on the composition of savanna and thicket species, the overall patterns of trees, and the associations of small thicket species with large Vachellia karroo trees, which serve as clump initiators. Finally, I examined the mortality of savanna trees across increasing stages of thicket expansion using second order spatial statistics, namely the Mark- and Pair-Correlation Functions. Results confirmed that three vegetation states, influenced by elevation, are present at the study site, representing open canopy savanna (early-stage thicket encroachment), encroached savanna with low thicket dominance (intermediate-stage thicket encroachment), and highly encroached with dominant thicket clumps (late-stage thicket encroachment). These stages showed increasing tree height, canopy cover and canopy height density, as well as decreased (but not completely absent grass layer) as thicket encroachment progresses. Spatial point pattern analysis showed, as predicted, that there was an overall aggregation of trees at small-scales within early thicket clump formation, from which I inferred that facilitative relationships may exist between trees. Contrary to my predictions, at later stages of thicket clump formation I found dominant independent patterns between savanna adults and juvenile thicket species, which may result from a combination of facilitative and competitive effects. Lastly, as expected, I found that the density of V. karroo mortality increased as thicket encroachment increased, with an overall random spatial pattern of dead V. karroo across encroachment stages. As predicted, tree mortality was randomly distributed in space in the open savanna state, and as thicket clump formation increases, tree competitive mortality became more evident, as well as decreased tree performance. Overall, the study highlights the interplay between facilitation and competition in semiarid savanna where thicket clumps are expanding. Intervention strategies are suggested to target areas of intermediate thicket clump formation, as these areas provide an opportunity to remove V. karroo before the nucleation process has enabled the establishment and increase of thicket species and to ensure the grass layer is kept productive. I conclude that the use of remote sensing and LiDAR technology holds a wide range of possibilities for monitoring and managing woody encroachment in savanna systems, however these methods need to be further refined for effective use within African savanna and thicket context, which displays high spatial aggregation making typical segmentation methods difficult. , Thesis (MSc) -- Faculty of Science, Botany, 2024
- Full Text:
- Date Issued: 2024-10-11
Photocatalytic reduction of CO2 into green fuels on microspherical nanocomposites comprising of CdS, TiO2, ZnFe2O4 semiconductors and heterojunctions
- Authors: Mudau, Rendani Julian
- Date: 2024-04
- Subjects: Heterojunctions , Chemistry, Inorganic , Nanochemistry
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64214 , vital:73665
- Description: Human anthropogenic activities have led to an increase in CO2 levels resulting in global warming. There is a need to reduce CO2 levels in the atmosphere by capturing the gas and converting the captured CO2 into fuels. Photocatalytic conversion of CO2 into valuable products via photoreduction is a promising technique to reduce carbon dioxide using sunlight and water. Redox reactions between CO2 and water using photocatalysts offer an effective method of lowering CO2, which has detrimental effects on the environment. This dissertation reports the synthesis and characterization of five photochemical catalysts comprising of CdS, TiO2, ZnFe2O4 semiconductors and heterojunctions and their use as photocatalysts for the photocatalytic reduction of CO2 into green fuels. Mott−Schottky plot of TiO2, CdS and CdS/TiO2 confirmed the formation of n-type, n-type, and n-n type material respectively. The band gap of TiO2, CdS, and CdS/TiO2 obtained were 3.21,2.24, 2.04 eV, respectively, the combination of TiO2 and CdS resulted in the lowering of band gap energy which is favourable for photocatalytic reduction studies. XRD of TiO2, CdS and CdS/TiO2 provided relevant information about the various phase reflections of the photocatalysts, it also supported reports confirming the increase in crystallite size of TiO2 anatase phase upon calcination. Chemical environment of the various photocatalysts, such as Ti2p1/2, Ti2p3/2, O1s, Cd3d3/2, Cd3d5/2, S2p1/2 and S2p3/2 were observed in TiO2, CdS and CdS/TiO2. BET surface area of TiO2, CdS and CdS/TiO2 was also observed to be 2.9243, 4.0605, and 9.8450 m2g, respectively. Photocatalytic reduction of CO2 resulted in formic acid, formaldehyde, acetic acid, carbon monoxide, ethanol, and methanol after 12 h. Modification of CdS with TiO2 to form CdS/TiO2 produced high yield of formic acid (217.7 μmol/g) compared to CdS (8.7 μmol/g) and TiO2 (122.5 μmol/g). CdS had high yield of formaldehyde (20.4 μmol/g) and ethanol (57.8 μmol/g) compared to TiO2 (12.9, 3.6 μmol/g of formaldehyde and ethanol, respectively) and CdS/TiO2 (19.7 μmol/g and there was no detection of ethanol). TiO2 shows high yield of methanol (145.2 μmol/g) and is the only catalysts that produced carbon monoxide (52.2 μmol/g) compared to CdS (87.8 μmol/g of methanol) and CdS/TiO2 (50.2 μmol/g of methanol). A detailed elucidation of the various products was reported by means of nuclear magnetic resonance (NMR) spectrometer. ZnFe2O4 and CdS/TiO2/ZnFe2O4 were characterized and employed for photocatalytic reduction of CO2 in water. XRD and XPS confirmed the presence Fe (2+) and Fe (3+) in tetrahedral/octahedral and Zn (2+) in tetrahedral on ZnFe2O4 and CdS/TiO2. CdS/TiO2/ZnFe2O4 presented a lowered band gap of 1.98 eV due to the presence of ZnFe2O4 while the band gap of ZnFe2O4 obtained is 1.95 eV. The Mott-Schottky plots confirmed the conduction (2.81 and 2.59 eV) and valence band (–0.86 and –6.1 eV) of ZnFe2O4 and CdS/TiO2/ZnFe2O4 together with their junctions, respectively. ZnFe2O4 and CdS/TiO2/ZnFe2O4 are p-type and p-n type junctions, respectively. Photocatalytic reduction of CO2 under visible light for 12 h using CdS/TiO2/ZnFe2O4 hollow microspheres nanocomposites produced methanol (182.1 μmol/g), formic acid (1.9 μmol/g), formaldehyde (9.5 μmol/g), ethanol (67.1 μmol/g), and oxalic acid (38.9 μmol/g). Amongst the synthesized catalysts, CdS/TiO2/ZnFe2O4 produced high yield of methanol, ethanol, and oxalic acid. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Mudau, Rendani Julian
- Date: 2024-04
- Subjects: Heterojunctions , Chemistry, Inorganic , Nanochemistry
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64214 , vital:73665
- Description: Human anthropogenic activities have led to an increase in CO2 levels resulting in global warming. There is a need to reduce CO2 levels in the atmosphere by capturing the gas and converting the captured CO2 into fuels. Photocatalytic conversion of CO2 into valuable products via photoreduction is a promising technique to reduce carbon dioxide using sunlight and water. Redox reactions between CO2 and water using photocatalysts offer an effective method of lowering CO2, which has detrimental effects on the environment. This dissertation reports the synthesis and characterization of five photochemical catalysts comprising of CdS, TiO2, ZnFe2O4 semiconductors and heterojunctions and their use as photocatalysts for the photocatalytic reduction of CO2 into green fuels. Mott−Schottky plot of TiO2, CdS and CdS/TiO2 confirmed the formation of n-type, n-type, and n-n type material respectively. The band gap of TiO2, CdS, and CdS/TiO2 obtained were 3.21,2.24, 2.04 eV, respectively, the combination of TiO2 and CdS resulted in the lowering of band gap energy which is favourable for photocatalytic reduction studies. XRD of TiO2, CdS and CdS/TiO2 provided relevant information about the various phase reflections of the photocatalysts, it also supported reports confirming the increase in crystallite size of TiO2 anatase phase upon calcination. Chemical environment of the various photocatalysts, such as Ti2p1/2, Ti2p3/2, O1s, Cd3d3/2, Cd3d5/2, S2p1/2 and S2p3/2 were observed in TiO2, CdS and CdS/TiO2. BET surface area of TiO2, CdS and CdS/TiO2 was also observed to be 2.9243, 4.0605, and 9.8450 m2g, respectively. Photocatalytic reduction of CO2 resulted in formic acid, formaldehyde, acetic acid, carbon monoxide, ethanol, and methanol after 12 h. Modification of CdS with TiO2 to form CdS/TiO2 produced high yield of formic acid (217.7 μmol/g) compared to CdS (8.7 μmol/g) and TiO2 (122.5 μmol/g). CdS had high yield of formaldehyde (20.4 μmol/g) and ethanol (57.8 μmol/g) compared to TiO2 (12.9, 3.6 μmol/g of formaldehyde and ethanol, respectively) and CdS/TiO2 (19.7 μmol/g and there was no detection of ethanol). TiO2 shows high yield of methanol (145.2 μmol/g) and is the only catalysts that produced carbon monoxide (52.2 μmol/g) compared to CdS (87.8 μmol/g of methanol) and CdS/TiO2 (50.2 μmol/g of methanol). A detailed elucidation of the various products was reported by means of nuclear magnetic resonance (NMR) spectrometer. ZnFe2O4 and CdS/TiO2/ZnFe2O4 were characterized and employed for photocatalytic reduction of CO2 in water. XRD and XPS confirmed the presence Fe (2+) and Fe (3+) in tetrahedral/octahedral and Zn (2+) in tetrahedral on ZnFe2O4 and CdS/TiO2. CdS/TiO2/ZnFe2O4 presented a lowered band gap of 1.98 eV due to the presence of ZnFe2O4 while the band gap of ZnFe2O4 obtained is 1.95 eV. The Mott-Schottky plots confirmed the conduction (2.81 and 2.59 eV) and valence band (–0.86 and –6.1 eV) of ZnFe2O4 and CdS/TiO2/ZnFe2O4 together with their junctions, respectively. ZnFe2O4 and CdS/TiO2/ZnFe2O4 are p-type and p-n type junctions, respectively. Photocatalytic reduction of CO2 under visible light for 12 h using CdS/TiO2/ZnFe2O4 hollow microspheres nanocomposites produced methanol (182.1 μmol/g), formic acid (1.9 μmol/g), formaldehyde (9.5 μmol/g), ethanol (67.1 μmol/g), and oxalic acid (38.9 μmol/g). Amongst the synthesized catalysts, CdS/TiO2/ZnFe2O4 produced high yield of methanol, ethanol, and oxalic acid. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2024
- Full Text:
- Date Issued: 2024-04
Factors affecting pinniped skull morphology
- Authors: Penaluna, Julia Elizabeth
- Date: 2023-04
- Subjects: hybridisation -- South Africa , Sexual dimorphism (Animals) , Craniology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61306 , vital:70077
- Description: Morphologies have evolved due to trade-offs between competing selective pressures. This is especially true for the skull. Not only does it contain the brain and the organs that are responsible for sensory function, but it is also contains components that play important roles in feeding, breathing, balance, defence, aggression and communication. The pinnipeds, a group of species that has evolved from terrestrial origins and became adapted to the marine environment, are under numerous selective pressures within the marine environment. These species have had to evolve in order to capture and process food underwater, and to dive. In addition, they are also characterised by substantial sexual size dimorphism in some species. Pinnipeds also make use of numerous marine and haul-out habitats with varying characteristics and complexity. Hybridisation has been recorded among pinnipeds, resulting in the production of hybrid offspring with characteristics that are different to their parent species. The aim of the study was to investigate the effect of these life history characteristics on skull and mandible morphology of pinniped species using three dimensional geometric morphometrics. To achieve this, 43 skull and 15 mandible 3D landmarks were collected using a Microscribe G2X digitizer with 0.2mm accuracy, on the skull and mandibles of 17 species of pinnipeds across three families, and one hybrid species. In total, 96 specimens across these species were examined. Data on the different life history characteristics of each species were collected from the literature. These data were plotted onto the PCA results in order to create and visually compare minimum convex polygons for each life history category. The results found that phylogeny, feeding strategy and sexual dimorphism were the most important factors in explaining differences in pinniped skull and mandible shape and size. may have resulted in these changes. Similarly, the inclusion of more species, covering a broader range of life histories may be beneficial. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Penaluna, Julia Elizabeth
- Date: 2023-04
- Subjects: hybridisation -- South Africa , Sexual dimorphism (Animals) , Craniology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61306 , vital:70077
- Description: Morphologies have evolved due to trade-offs between competing selective pressures. This is especially true for the skull. Not only does it contain the brain and the organs that are responsible for sensory function, but it is also contains components that play important roles in feeding, breathing, balance, defence, aggression and communication. The pinnipeds, a group of species that has evolved from terrestrial origins and became adapted to the marine environment, are under numerous selective pressures within the marine environment. These species have had to evolve in order to capture and process food underwater, and to dive. In addition, they are also characterised by substantial sexual size dimorphism in some species. Pinnipeds also make use of numerous marine and haul-out habitats with varying characteristics and complexity. Hybridisation has been recorded among pinnipeds, resulting in the production of hybrid offspring with characteristics that are different to their parent species. The aim of the study was to investigate the effect of these life history characteristics on skull and mandible morphology of pinniped species using three dimensional geometric morphometrics. To achieve this, 43 skull and 15 mandible 3D landmarks were collected using a Microscribe G2X digitizer with 0.2mm accuracy, on the skull and mandibles of 17 species of pinnipeds across three families, and one hybrid species. In total, 96 specimens across these species were examined. Data on the different life history characteristics of each species were collected from the literature. These data were plotted onto the PCA results in order to create and visually compare minimum convex polygons for each life history category. The results found that phylogeny, feeding strategy and sexual dimorphism were the most important factors in explaining differences in pinniped skull and mandible shape and size. may have resulted in these changes. Similarly, the inclusion of more species, covering a broader range of life histories may be beneficial. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Enhancing the use of large-scale assessment data in South Africa: Multidimensional Item Response Theory
- Authors: Lahoud, Tamlyn Ann
- Date: 2023-03-29
- Subjects: Differential item functioning , Item response theory , Mathematical ability Testing , Educational tests and measurements , Multidimensional scaling
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/422389 , vital:71938
- Description: This research aims to enhance the use of large-scale assessment data in South Africa by evaluating assessment validity by means of multidimensional item response theory and its associated statistical techniques, which have been severely underutilised. Data from the 2014 administration of the grade 6 Mathematics annual national assessment was used in this study and all analyses were conducted using the mirt package in R. A two parameter logistic item response theory model was developed which indicated a clear alignment between the model parameters and difficulty specifications of the test. The test was found to favour learners within the central band on the ability scale. An exploratory five dimensional item response theory model was then developed to investigate the alignment with the test specifications as evidence for construct validity. Significant discrepancies between the factor structure and the specifications of the test were identified. Notably, the results suggest that some items measured an ability that was not purely mathematical, such as reading ability, which would distort the test’s representation of Mathematics ability, disadvantage learners with lower English literacy, and reduce the construct validity of the test. Further validity evidence was obtained by differential item functioning analyses which revealed that fourteen items function differently for learners from different provinces. Although possible reasons for the presence of differential item functioning among provinces were not discussed, its presence provided sufficient evidence against the validity of the test. In conclusion, multidimensional item response theory provided an effective and rigorous approach to establishing the validity of a large-scale assessment. To avoid the pitfalls of the annual national assessments, it is recommended that this multidimensional item and differential item functioning techniques are utilised for the development and evaluation of future national assessment instruments in South Africa. , Thesis (MSc) -- Faculty of Science, Statistics, 2023
- Full Text:
- Date Issued: 2023-03-29
- Authors: Lahoud, Tamlyn Ann
- Date: 2023-03-29
- Subjects: Differential item functioning , Item response theory , Mathematical ability Testing , Educational tests and measurements , Multidimensional scaling
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/422389 , vital:71938
- Description: This research aims to enhance the use of large-scale assessment data in South Africa by evaluating assessment validity by means of multidimensional item response theory and its associated statistical techniques, which have been severely underutilised. Data from the 2014 administration of the grade 6 Mathematics annual national assessment was used in this study and all analyses were conducted using the mirt package in R. A two parameter logistic item response theory model was developed which indicated a clear alignment between the model parameters and difficulty specifications of the test. The test was found to favour learners within the central band on the ability scale. An exploratory five dimensional item response theory model was then developed to investigate the alignment with the test specifications as evidence for construct validity. Significant discrepancies between the factor structure and the specifications of the test were identified. Notably, the results suggest that some items measured an ability that was not purely mathematical, such as reading ability, which would distort the test’s representation of Mathematics ability, disadvantage learners with lower English literacy, and reduce the construct validity of the test. Further validity evidence was obtained by differential item functioning analyses which revealed that fourteen items function differently for learners from different provinces. Although possible reasons for the presence of differential item functioning among provinces were not discussed, its presence provided sufficient evidence against the validity of the test. In conclusion, multidimensional item response theory provided an effective and rigorous approach to establishing the validity of a large-scale assessment. To avoid the pitfalls of the annual national assessments, it is recommended that this multidimensional item and differential item functioning techniques are utilised for the development and evaluation of future national assessment instruments in South Africa. , Thesis (MSc) -- Faculty of Science, Statistics, 2023
- Full Text:
- Date Issued: 2023-03-29
A decision-making model to guide securing blockchain deployments
- Authors: Cronje, Gerhard Roets
- Date: 2021-10-29
- Subjects: Blockchains (Databases) , Bitcoin , Cryptocurrencies , Distributed databases , Computer networks Security measures , Computer networks Security measures Decision making , Ethereum
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188865 , vital:44793
- Description: Satoshi Nakamoto, the pseudo-identity accredit with the paper that sparked the implementation of Bitcoin, is famously quoted as remarking, electronically of course, that “If you don’t believe it or don’t get it, I don’t have time to try and convince you, sorry” (Tsapis, 2019, p. 1). What is noticeable, 12 years after the famed Satoshi paper that initiated Bitcoin (Nakamoto, 2008), is that blockchain at the very least has staying power and potentially wide application. A lesser known figure Marc Kenisberg, founder of Bitcoin Chaser which is one of the many companies formed around the Bitcoin ecosystem, summarised it well saying “…Blockchain is the tech - Bitcoin is merely the first mainstream manifestation of its potential” (Tsapis, 2019, p. 1). With blockchain still trying to reach its potential and still maturing on its way towards a mainstream technology the main question that arises for security professionals is how do I ensure we do it securely? This research seeks to address that question by proposing a decision-making model that can be used by a security professional to guide them through ensuring appropriate security for blockchain deployments. This research is certainly not the first attempt at discussing the security of the blockchain and will not be the last, as the technology around blockchain and distributed ledger technology is still rapidly evolving. What this research does try to achieve is not to delve into extremely specific areas of blockchain security, or get bogged down in technical details, but to provide a reference framework that aims to cover all the major areas to be considered. The approach followed was to review the literature regarding blockchain and to identify the main security areas to be addressed. It then proposes a decision-making model and tests the model against a fictitious but relevant real-world example. It concludes with learnings from this research. The reader can be the judge, but the model aims to be a practical valuable resource to be used by any security professional, to navigate the security aspects logically and understandably when being involved in a blockchain deployment. In contrast to the Satoshi quote, this research tries to convince the reader and assist him/her in understanding the security choices related to every blockchain deployment. , Thesis (MSc) -- Faculty of Science, Computer Science, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Cronje, Gerhard Roets
- Date: 2021-10-29
- Subjects: Blockchains (Databases) , Bitcoin , Cryptocurrencies , Distributed databases , Computer networks Security measures , Computer networks Security measures Decision making , Ethereum
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188865 , vital:44793
- Description: Satoshi Nakamoto, the pseudo-identity accredit with the paper that sparked the implementation of Bitcoin, is famously quoted as remarking, electronically of course, that “If you don’t believe it or don’t get it, I don’t have time to try and convince you, sorry” (Tsapis, 2019, p. 1). What is noticeable, 12 years after the famed Satoshi paper that initiated Bitcoin (Nakamoto, 2008), is that blockchain at the very least has staying power and potentially wide application. A lesser known figure Marc Kenisberg, founder of Bitcoin Chaser which is one of the many companies formed around the Bitcoin ecosystem, summarised it well saying “…Blockchain is the tech - Bitcoin is merely the first mainstream manifestation of its potential” (Tsapis, 2019, p. 1). With blockchain still trying to reach its potential and still maturing on its way towards a mainstream technology the main question that arises for security professionals is how do I ensure we do it securely? This research seeks to address that question by proposing a decision-making model that can be used by a security professional to guide them through ensuring appropriate security for blockchain deployments. This research is certainly not the first attempt at discussing the security of the blockchain and will not be the last, as the technology around blockchain and distributed ledger technology is still rapidly evolving. What this research does try to achieve is not to delve into extremely specific areas of blockchain security, or get bogged down in technical details, but to provide a reference framework that aims to cover all the major areas to be considered. The approach followed was to review the literature regarding blockchain and to identify the main security areas to be addressed. It then proposes a decision-making model and tests the model against a fictitious but relevant real-world example. It concludes with learnings from this research. The reader can be the judge, but the model aims to be a practical valuable resource to be used by any security professional, to navigate the security aspects logically and understandably when being involved in a blockchain deployment. In contrast to the Satoshi quote, this research tries to convince the reader and assist him/her in understanding the security choices related to every blockchain deployment. , Thesis (MSc) -- Faculty of Science, Computer Science, 2021
- Full Text:
- Date Issued: 2021-10-29
Investigation of microbial fuel cell technologies for flexible, small-scale domestic and educational use
- Authors: Mpofu, Trisha Lerato
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/192539 , vital:45235
- Description: Thesis (MSc) -- Faculty of Science, Biotechnology Innovation Centre, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Mpofu, Trisha Lerato
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/192539 , vital:45235
- Description: Thesis (MSc) -- Faculty of Science, Biotechnology Innovation Centre, 2021
- Full Text:
- Date Issued: 2021-10-29
Reactor development and process optimisation for the bioremediation of phenolic wastewaters by trametes species
- Authors: Ryan, Daniel Reginald
- Date: 2004-04
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191487 , vital:45103
- Description: In many service industries, the source of a company’s value has shifted from capital to knowledge and ideas, the quality of which is dependent on its employees (Wooldridge, 2006). In fact, human resources can be considered part of factor conditions which can positively impact on a firm’s competitive context. This impact can ultimately translate into improved financial results (Porter and Kramer, 2002). There is therefore a growing interest in ways to attract and retain talent. According to the managers of many big companies, well communicated corporate responsibility practices can improve staff attraction as well as retention rates by improving morale (CSRwire, 2002). To explore this, a small, creative company in Johannesburg which engages in charity work was selected as a case study, with the goal being to understand whether their culture of good deeds has a positive impact on staff wellbeing. While the owner of the company actively attempts to make the company an enjoyable place to work at, he appears to have initiated the philanthropic activities in a true spirit of giving, rather than with the motive of engaging staff in order to make more money. Nevertheless, the researcher’s investigative stance is that of an enlightened egoist, and the study focuses on the business case of giving being beneficial to the giver (ultimately the company) in the long term, as well as to the recipient. While the danger of suggesting that philanthropy could be instrumentalised is acknowledged (Morton, 2004), the investigation explores the possibility because such evidence could persuade other companies to become more socially concerned. Through a qualitative approach involving interviews, observation and analysis of video footage, it becomes apparent that there is clearly value for the staff in the charity work they do. Unfortunately the multiple initiatives undertaken to keep staff morale high at the company make it impossible to establish a clear link between the philanthropy and overall wellbeing, but as the study was conducted in the phenomenological paradigm the main concern was with understanding the experience of participants. However, an unexpected finding was that the employees derive great satisfaction from using their professional skills for charity work rather than just donating money to the charity. They feel that their skills uniquely position them to make significant changes to the lives of others, which gives them a sense of pride and achievement that they don’t necessarily experience in their ordinary activities at work. On the basis of this, it is recommended that companies look to involve staff with projects that require their specific expertise when evaluating philanthropic initiatives. , Thesis (PhD) -- Faculty of Science, Biochemistry, Microbiology and Biotechnology, 2004
- Full Text:
- Date Issued: 2004-04
- Authors: Ryan, Daniel Reginald
- Date: 2004-04
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191487 , vital:45103
- Description: In many service industries, the source of a company’s value has shifted from capital to knowledge and ideas, the quality of which is dependent on its employees (Wooldridge, 2006). In fact, human resources can be considered part of factor conditions which can positively impact on a firm’s competitive context. This impact can ultimately translate into improved financial results (Porter and Kramer, 2002). There is therefore a growing interest in ways to attract and retain talent. According to the managers of many big companies, well communicated corporate responsibility practices can improve staff attraction as well as retention rates by improving morale (CSRwire, 2002). To explore this, a small, creative company in Johannesburg which engages in charity work was selected as a case study, with the goal being to understand whether their culture of good deeds has a positive impact on staff wellbeing. While the owner of the company actively attempts to make the company an enjoyable place to work at, he appears to have initiated the philanthropic activities in a true spirit of giving, rather than with the motive of engaging staff in order to make more money. Nevertheless, the researcher’s investigative stance is that of an enlightened egoist, and the study focuses on the business case of giving being beneficial to the giver (ultimately the company) in the long term, as well as to the recipient. While the danger of suggesting that philanthropy could be instrumentalised is acknowledged (Morton, 2004), the investigation explores the possibility because such evidence could persuade other companies to become more socially concerned. Through a qualitative approach involving interviews, observation and analysis of video footage, it becomes apparent that there is clearly value for the staff in the charity work they do. Unfortunately the multiple initiatives undertaken to keep staff morale high at the company make it impossible to establish a clear link between the philanthropy and overall wellbeing, but as the study was conducted in the phenomenological paradigm the main concern was with understanding the experience of participants. However, an unexpected finding was that the employees derive great satisfaction from using their professional skills for charity work rather than just donating money to the charity. They feel that their skills uniquely position them to make significant changes to the lives of others, which gives them a sense of pride and achievement that they don’t necessarily experience in their ordinary activities at work. On the basis of this, it is recommended that companies look to involve staff with projects that require their specific expertise when evaluating philanthropic initiatives. , Thesis (PhD) -- Faculty of Science, Biochemistry, Microbiology and Biotechnology, 2004
- Full Text:
- Date Issued: 2004-04
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