Water balance processes in indigenous and introduced spaces three production system in the Southern Cape region of South Africa
- Authors: Mapeto, Tatenda
- Date: 2020
- Subjects: Hydrology -- Research -- South Africa , Groundwater -- Research -- South Africa Trees -- Breeding Sustainable forestry
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49325 , vital:41621
- Description: Forests and trees are important modulators of water flow and their position in the landscape impacts the spatial and temporal availability of ground water and surface water resources. As such, the global extent of natural forests is linked to the availability of water. In the circumstances where tree production systems have been introduced and are managed in landscapes previously populated with other forms of vegetation, it is necessary to understand their hydrological impact so as to ensure that the benefits derived from these tree systems do not outweigh the costs of water availability for sustaining human and environmental water requirements.
- Full Text: false
- Date Issued: 2020
- Authors: Mapeto, Tatenda
- Date: 2020
- Subjects: Hydrology -- Research -- South Africa , Groundwater -- Research -- South Africa Trees -- Breeding Sustainable forestry
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49325 , vital:41621
- Description: Forests and trees are important modulators of water flow and their position in the landscape impacts the spatial and temporal availability of ground water and surface water resources. As such, the global extent of natural forests is linked to the availability of water. In the circumstances where tree production systems have been introduced and are managed in landscapes previously populated with other forms of vegetation, it is necessary to understand their hydrological impact so as to ensure that the benefits derived from these tree systems do not outweigh the costs of water availability for sustaining human and environmental water requirements.
- Full Text: false
- Date Issued: 2020
The potential of Raman spectroscopy in distinguishing between wool and mohair fibres
- Authors: Notayi, Mzwamadoda
- Date: 2020
- Subjects: Textile fabrics , Textile fibers -- Mechanical properties Wool -- Dissertations Mohair -- Dissertations
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49248 , vital:41614
- Description: The possible application of the FT Raman, Raman micro-spectroscopy and ATR-FTIR micro-spectroscopy, have been investigated for distinguishing between wool and mohair. Highly identical Raman and FTIR spectra were obtained from the two fibre types, indicating that indeed they share similar basic molecular structural chemistry. The analysis of the amide I through curve fitting of wool and mohair FT Raman spectra showed that the protein and polypeptide secondary structure exists mainly in the α-helical structural conformation with smaller proportions of β-pleated sheet and β-Turns. These proportions, however, could not be used to distinguish between wool and mohair, due to the significant overlap observed between the two fibres. This study also determined the disulphide contents for possibly distinguishing between wool and mohair fibres, with the average and standard deviation values of 0.20±0.04 and 0.17±0.03 for wool and mohair, respectively, being found. Despite the mean values being found to differ statistically significant (p<0.05), a considerable overlap was observed, posing a doubt in the possible application of the method for distinguishing between the two fibres and blend composition analysis of the two fibres. The application of ratiometric analysis, based on the relative peak heights of certain FT Raman bands, showed that a combination of ratios A (I2932/I1450) and D (I508/I1450) could hold great potential in distinguishing between wool and mohair fibre samples. The individual values of ratios A and D varied a great deal from one mohair sample to the other and even more from one wool sample to another, with the individual values for ratio A ranging from 2.71-3.68 and 2.35-3.08 for wool and mohair, respectively, while ratio D ranged from 0.18-0.32 and 0.17-0.22 for wool and mohair, respectively. An important observation from this study is that if, for an unknown sample, if individual values of ratios A and D exceed 3.1 and 0.22, respectively, are found then the sample is most likely to be either a pure wool or blend of wool and mohair, whereas if all the values fall below the two threshold values, then the unknown sample can be declared a pure mohair sample. A Raman spectral database or library of approximately 100 high quality Raman average spectra of wool and mohair fibres has been established for the Bruker 80V FTIR/Raman spectrophotometer at the Nelson Mandela University (NMU). Although this has not been fully validated due to the unforeseen frequent breakdown encountered with the FT Raman system, at this stage, it has been realized that verification of unknown materials is highly possible. A great need for the development of a classification model based on multivariate or chemometrics has been realized. An ATR-FTIR LUMOS micro-spectroscopic system was also investigated for the possible application in distinguishing between wool and mohair single fibres. The amide I/II band ratios were determined for both wool and mohair fibres to distinguish between the two fibre types. The mean and standard deviation values of 1.20±0.02 and 1.21±0.01 for mohair and wool, respectively, were found and were shown not to differ statistically significant (p˃0.05). The secondary structure analysis showed that the content of the α-helical secondary structure might be different between the two fibre types, with a great overlap of individual values, however, being observed between the two fibre types (wool and mohair), raising concerns in the possible application of the α-helical content for distinguishing the two fibres.
- Full Text:
- Date Issued: 2020
- Authors: Notayi, Mzwamadoda
- Date: 2020
- Subjects: Textile fabrics , Textile fibers -- Mechanical properties Wool -- Dissertations Mohair -- Dissertations
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49248 , vital:41614
- Description: The possible application of the FT Raman, Raman micro-spectroscopy and ATR-FTIR micro-spectroscopy, have been investigated for distinguishing between wool and mohair. Highly identical Raman and FTIR spectra were obtained from the two fibre types, indicating that indeed they share similar basic molecular structural chemistry. The analysis of the amide I through curve fitting of wool and mohair FT Raman spectra showed that the protein and polypeptide secondary structure exists mainly in the α-helical structural conformation with smaller proportions of β-pleated sheet and β-Turns. These proportions, however, could not be used to distinguish between wool and mohair, due to the significant overlap observed between the two fibres. This study also determined the disulphide contents for possibly distinguishing between wool and mohair fibres, with the average and standard deviation values of 0.20±0.04 and 0.17±0.03 for wool and mohair, respectively, being found. Despite the mean values being found to differ statistically significant (p<0.05), a considerable overlap was observed, posing a doubt in the possible application of the method for distinguishing between the two fibres and blend composition analysis of the two fibres. The application of ratiometric analysis, based on the relative peak heights of certain FT Raman bands, showed that a combination of ratios A (I2932/I1450) and D (I508/I1450) could hold great potential in distinguishing between wool and mohair fibre samples. The individual values of ratios A and D varied a great deal from one mohair sample to the other and even more from one wool sample to another, with the individual values for ratio A ranging from 2.71-3.68 and 2.35-3.08 for wool and mohair, respectively, while ratio D ranged from 0.18-0.32 and 0.17-0.22 for wool and mohair, respectively. An important observation from this study is that if, for an unknown sample, if individual values of ratios A and D exceed 3.1 and 0.22, respectively, are found then the sample is most likely to be either a pure wool or blend of wool and mohair, whereas if all the values fall below the two threshold values, then the unknown sample can be declared a pure mohair sample. A Raman spectral database or library of approximately 100 high quality Raman average spectra of wool and mohair fibres has been established for the Bruker 80V FTIR/Raman spectrophotometer at the Nelson Mandela University (NMU). Although this has not been fully validated due to the unforeseen frequent breakdown encountered with the FT Raman system, at this stage, it has been realized that verification of unknown materials is highly possible. A great need for the development of a classification model based on multivariate or chemometrics has been realized. An ATR-FTIR LUMOS micro-spectroscopic system was also investigated for the possible application in distinguishing between wool and mohair single fibres. The amide I/II band ratios were determined for both wool and mohair fibres to distinguish between the two fibre types. The mean and standard deviation values of 1.20±0.02 and 1.21±0.01 for mohair and wool, respectively, were found and were shown not to differ statistically significant (p˃0.05). The secondary structure analysis showed that the content of the α-helical secondary structure might be different between the two fibre types, with a great overlap of individual values, however, being observed between the two fibre types (wool and mohair), raising concerns in the possible application of the α-helical content for distinguishing the two fibres.
- Full Text:
- Date Issued: 2020
Radical transformation and sustainability for an advanced manufacturing industry: a progressive model
- Noor, Richard, Van der Merwe, Karl
- Authors: Noor, Richard , Van der Merwe, Karl
- Date: 2020
- Subjects: Manufacturing industries -- South Africa , Leadership Organisational learning
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/46849 , vital:39669
- Description: The manufacturing industry in one of the most significant contributors to a countries GDP across the world. South Africa is no different and yet it remains an interesting challenge for the country. Power and greed seem to have overtaken the moral fibre of our society and has inflicted pain and suffering to millions across the country. The manufacturing has not been immune to this challenge and appears to be in free fall on so many levels. The primary objective of this research was to develop a model for the manufacturing industry which would assist the role players to navigate the challenges and obstacle in this ever changing and demanding industry. An extensive review of literature was conducted which informed and guided the process of gathering information and data using a questionnaire and a survey conducted across the manufacturing industry. Structural Equation Modelling was used to test the relationships between the various factors identified during the literature review. Leadership Impact was confirmed as a significant contributor as well as the Economic Impact having a significant impact on both Radical Transformation and Sustainability. This study scientifically added to the body of knowledge having taken several factors within the manufacturing industry and analysed its impact on radical transformation and sustainability, the integration of these factors within one study has not been previously conducted and has contributed to the manufacturing industry, business leadership and management fields of study.
- Full Text:
- Date Issued: 2020
- Authors: Noor, Richard , Van der Merwe, Karl
- Date: 2020
- Subjects: Manufacturing industries -- South Africa , Leadership Organisational learning
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/46849 , vital:39669
- Description: The manufacturing industry in one of the most significant contributors to a countries GDP across the world. South Africa is no different and yet it remains an interesting challenge for the country. Power and greed seem to have overtaken the moral fibre of our society and has inflicted pain and suffering to millions across the country. The manufacturing has not been immune to this challenge and appears to be in free fall on so many levels. The primary objective of this research was to develop a model for the manufacturing industry which would assist the role players to navigate the challenges and obstacle in this ever changing and demanding industry. An extensive review of literature was conducted which informed and guided the process of gathering information and data using a questionnaire and a survey conducted across the manufacturing industry. Structural Equation Modelling was used to test the relationships between the various factors identified during the literature review. Leadership Impact was confirmed as a significant contributor as well as the Economic Impact having a significant impact on both Radical Transformation and Sustainability. This study scientifically added to the body of knowledge having taken several factors within the manufacturing industry and analysed its impact on radical transformation and sustainability, the integration of these factors within one study has not been previously conducted and has contributed to the manufacturing industry, business leadership and management fields of study.
- Full Text:
- Date Issued: 2020
Promoting leader integrity through the human resource management value chain
- Authors: De Villiers, Bridget
- Date: 2020
- Subjects: Leadership -- South Africa , Leadership -- South Africa -- Moral and ethical aspects Business ethics Professional ethics Personnel management
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/50469 , vital:42197
- Description: Ethical breaches in the public and private sector in South Africa are prevalent and the effects thereof pervasive on the economy and within broader society. These ethical breaches include corruption, bribery, and the mismanagement of resources and may be attributed to poor decision-making on the part of organisational leaders. The complexity of the circumstances in which organisations operate in the 21st century requires that leaders effectively navigate moral dilemmas while considering the broad range of interests represented by many organisational stakeholders. Leaders need to act in a manner that is ethically sound to avoid the negative consequences associated with unethical organisational conduct, including a loss of profit, credibility and reputation. Ethical leadership is central to moral organisational governance, as compliance with rules and regulations alone is ineffective in building and sustaining an ethical organisation. Literature points to the centrality of leader integrity to the notion of ethical leadership and that an ethical organisational culture is sustained by leaders who possess integrity. In promoting leader integrity studies highlight management interventions and organisational success factors that promote an ethical organisation. Within the context of this study these management interventions and success factors were identified as promoting leader integrity. Further, the literature identified the important role of leaders in supporting these interventions and creating the conditions necessary to foster the success factors. These management interventions are offered through and the success factors are linked to the human resource management value chain. The main aim of this study was to explore the promotion of leader integrity through the human resource management value chain in South African organisations. The main aim of the study led to the development of several theoretical and empirical sub-objectives that were addressed through the following actions: A literature study was conducted examining the nature of ethical leadership and leader integrity and included a consideration of the dark side of leadership. The literature was further examined in relation to the nature of an ethical organisation and organisational integrity, the role of the leader in promoting an ethical organisational culture, and regarding the management interventions and success factors that were seen to promote leader integrity. The insights gained from the literature review assisted in the compilation of a survey questionnaire, this being the Management Interventions and Success Factors Scale. This scale, together with an existing scale, The Perceived Leader Integrity Scale (version 1.2), were used in the empirical study to determine the perceptions of employees as to whether specific management interventions and success factors were seen to promote leader integrity, and the extent to which their managers were seen to act with integrity. These employees worked in the public and private sectors across South Africa, and a final sample size of 606 respondents was achieved. The empirical results of the study revealed that management interventions and success factors were seen to promote leader integrity. However, due to high levels of inconsistency in the responses received it was recommended that a clearer link needs to be created in terms of how the success factors and interventions promote leader integrity. The empirical study further revealed that South African leaders were seen to act with integrity, more especially not to engage in acts of extreme negative deviance such as theft or sabotage, but that there was room for improvement as there were employees who reported moderate and low levels of integrity among their managers. Together with the literature review the empirical study contributed towards the development of a model and a framework for the promotion of leader integrity across the HRM value chain. South African leaders have a crucial role to play in promoting not only the moral fibre of the organisations that they represent, but also in contributing positively to moral regeneration at both a national and a global level through effective and integrity-based organisational governance. This is achieved through adopting an integrated, strategic and holistic approach to the promotion of leader integrity as proposed in this study.
- Full Text:
- Date Issued: 2020
- Authors: De Villiers, Bridget
- Date: 2020
- Subjects: Leadership -- South Africa , Leadership -- South Africa -- Moral and ethical aspects Business ethics Professional ethics Personnel management
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/50469 , vital:42197
- Description: Ethical breaches in the public and private sector in South Africa are prevalent and the effects thereof pervasive on the economy and within broader society. These ethical breaches include corruption, bribery, and the mismanagement of resources and may be attributed to poor decision-making on the part of organisational leaders. The complexity of the circumstances in which organisations operate in the 21st century requires that leaders effectively navigate moral dilemmas while considering the broad range of interests represented by many organisational stakeholders. Leaders need to act in a manner that is ethically sound to avoid the negative consequences associated with unethical organisational conduct, including a loss of profit, credibility and reputation. Ethical leadership is central to moral organisational governance, as compliance with rules and regulations alone is ineffective in building and sustaining an ethical organisation. Literature points to the centrality of leader integrity to the notion of ethical leadership and that an ethical organisational culture is sustained by leaders who possess integrity. In promoting leader integrity studies highlight management interventions and organisational success factors that promote an ethical organisation. Within the context of this study these management interventions and success factors were identified as promoting leader integrity. Further, the literature identified the important role of leaders in supporting these interventions and creating the conditions necessary to foster the success factors. These management interventions are offered through and the success factors are linked to the human resource management value chain. The main aim of this study was to explore the promotion of leader integrity through the human resource management value chain in South African organisations. The main aim of the study led to the development of several theoretical and empirical sub-objectives that were addressed through the following actions: A literature study was conducted examining the nature of ethical leadership and leader integrity and included a consideration of the dark side of leadership. The literature was further examined in relation to the nature of an ethical organisation and organisational integrity, the role of the leader in promoting an ethical organisational culture, and regarding the management interventions and success factors that were seen to promote leader integrity. The insights gained from the literature review assisted in the compilation of a survey questionnaire, this being the Management Interventions and Success Factors Scale. This scale, together with an existing scale, The Perceived Leader Integrity Scale (version 1.2), were used in the empirical study to determine the perceptions of employees as to whether specific management interventions and success factors were seen to promote leader integrity, and the extent to which their managers were seen to act with integrity. These employees worked in the public and private sectors across South Africa, and a final sample size of 606 respondents was achieved. The empirical results of the study revealed that management interventions and success factors were seen to promote leader integrity. However, due to high levels of inconsistency in the responses received it was recommended that a clearer link needs to be created in terms of how the success factors and interventions promote leader integrity. The empirical study further revealed that South African leaders were seen to act with integrity, more especially not to engage in acts of extreme negative deviance such as theft or sabotage, but that there was room for improvement as there were employees who reported moderate and low levels of integrity among their managers. Together with the literature review the empirical study contributed towards the development of a model and a framework for the promotion of leader integrity across the HRM value chain. South African leaders have a crucial role to play in promoting not only the moral fibre of the organisations that they represent, but also in contributing positively to moral regeneration at both a national and a global level through effective and integrity-based organisational governance. This is achieved through adopting an integrated, strategic and holistic approach to the promotion of leader integrity as proposed in this study.
- Full Text:
- Date Issued: 2020
Planning considerations for smart meter implementations in South Africa
- Authors: Muchenje, Tonderai
- Date: 2020
- Subjects: Application software -- Development , Smart power grids
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/46218 , vital:39515
- Description: Smart meter implementations are still in their infancy in many African countries. This is evident by the lack of research on the subject in the African context. Most of the research studies are either Eurocentric or US-centric. Although these studies are important and informative, they might not address the African challenges in context. Hence, South Africa was chosen as the testbed for an investigation that addresses the apparent knowledge gap. This study set out to formulate a framework for planning considerations in the implementation of smart meter technology within South Africa. Through extensive literature review and analysis, the technology acceptance model (TAM) was chosen as a foundational framework for this study. Although TAM is widely used for researching technology acceptance and use, its applicability was found to be inadequate in explaining customer centric factors in smart metering. Therefore, it was supplemented with factors from the theory of reasoned action (TRA), the theory of planned behavior (TPB), privacy calculus theory (PCT), as well as the unified theory of acceptance and use of technology (UTAUT). A total of 11 consumer-centric factors were identified, and these were statistically analysed using the structural equation modelling technique (SEM). Ten (10) consumer-centric factors was found to be significant. These were attitude, perceived value, monetary cost, privacy risk, perceived ease of use, perceived usefulness, facilitating conditions, social norms, trust in technology and behavioral intention. Hypothesis testing confirmed that, not one acceptance model could adequately be used to identify and explain the consumer-centric factors that can be incorporated for planning considerations for smart meter implementation in South Africa. It was further observed that the consumer-centric factors such as environmental issues, security, reliability and health issues that were important in developed countries were not deemed so in South Africa. From a methodological perspective, the study attests to contextual localised application as opposed to universal meaning and measurement invariance when incorporating planning consideration for smart meter implementation in South Africa as compared to European countries and the United States of America. Finally, the findings hold some practical implications, as they showed the practical utility of the model in predicting the consumer-centric factors that can be incorporated for planning considerations. In support, the Business Model Canvas (BMC) was found to be a useful tool in deriving and reporting on the formulation of planning consideration guidelines. Using the BMC, five planning consideration guidelines were derived: customer segmentation, partnerships, benefits communication, value identification and customer attitude. These planning considerations will allow smart meter providers to identify their customers, partners and value propositions they might need to offer consumers to facilitate a higher smart meter acceptance and use. The proposed planning consideration guidelines can practically be used by policymakers and regulators for several aspects for future pervasive technology acceptance studies. This research has, therefore, created a platform for further research in the smart technology domain while providing a usable predictive framework for the identification of consumer-centric factors and formulation of planning considerations guidelines for smart meter implementation within the South African context.
- Full Text:
- Date Issued: 2020
- Authors: Muchenje, Tonderai
- Date: 2020
- Subjects: Application software -- Development , Smart power grids
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/46218 , vital:39515
- Description: Smart meter implementations are still in their infancy in many African countries. This is evident by the lack of research on the subject in the African context. Most of the research studies are either Eurocentric or US-centric. Although these studies are important and informative, they might not address the African challenges in context. Hence, South Africa was chosen as the testbed for an investigation that addresses the apparent knowledge gap. This study set out to formulate a framework for planning considerations in the implementation of smart meter technology within South Africa. Through extensive literature review and analysis, the technology acceptance model (TAM) was chosen as a foundational framework for this study. Although TAM is widely used for researching technology acceptance and use, its applicability was found to be inadequate in explaining customer centric factors in smart metering. Therefore, it was supplemented with factors from the theory of reasoned action (TRA), the theory of planned behavior (TPB), privacy calculus theory (PCT), as well as the unified theory of acceptance and use of technology (UTAUT). A total of 11 consumer-centric factors were identified, and these were statistically analysed using the structural equation modelling technique (SEM). Ten (10) consumer-centric factors was found to be significant. These were attitude, perceived value, monetary cost, privacy risk, perceived ease of use, perceived usefulness, facilitating conditions, social norms, trust in technology and behavioral intention. Hypothesis testing confirmed that, not one acceptance model could adequately be used to identify and explain the consumer-centric factors that can be incorporated for planning considerations for smart meter implementation in South Africa. It was further observed that the consumer-centric factors such as environmental issues, security, reliability and health issues that were important in developed countries were not deemed so in South Africa. From a methodological perspective, the study attests to contextual localised application as opposed to universal meaning and measurement invariance when incorporating planning consideration for smart meter implementation in South Africa as compared to European countries and the United States of America. Finally, the findings hold some practical implications, as they showed the practical utility of the model in predicting the consumer-centric factors that can be incorporated for planning considerations. In support, the Business Model Canvas (BMC) was found to be a useful tool in deriving and reporting on the formulation of planning consideration guidelines. Using the BMC, five planning consideration guidelines were derived: customer segmentation, partnerships, benefits communication, value identification and customer attitude. These planning considerations will allow smart meter providers to identify their customers, partners and value propositions they might need to offer consumers to facilitate a higher smart meter acceptance and use. The proposed planning consideration guidelines can practically be used by policymakers and regulators for several aspects for future pervasive technology acceptance studies. This research has, therefore, created a platform for further research in the smart technology domain while providing a usable predictive framework for the identification of consumer-centric factors and formulation of planning considerations guidelines for smart meter implementation within the South African context.
- Full Text:
- Date Issued: 2020
Plankton dynamics in response to algal blooms in a highly eutrophic estuary in South Africa
- Authors: Smit, Taryn
- Date: 2020
- Subjects: Algal blooms -- South Africa , Estuaries -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49303 , vital:41619
- Description: The global rise in the incidence of harmful algal blooms in estuaries is a major concern given their importance as a nursery area for a variety of invertebrates and fishes. On the warm-temperate, south-east coast of South Africa, the Sundays Estuary experiences persistent, seasonal HABs due to stable eutrophic conditions. Spring blooms of the dinoflagellate, Heterosigma akashiwo, were recorded for several years in the estuary. This Raphidophyte is known for its consequences in fish and shellfish aquaculture and exhibits harmful properties such as mucilage and reactive oxygen species production. Subsequently, the dissertation investigated larval fish assemblage dynamics, larval prey and predator dynamics and body condition in association with H. akashiwo blooms. HABs mainly altered the water quality within the mesohaline zone in terms of microalgal biomass and dissolved oxygen. Hypereutrophic blooms of H. akashiwo reached 24 996 cells∙mL-1 during the study period. Supersaturated dissolved oxygen concentrations (up to ~13 mg∙L-1 at night and ~21 mg∙L-1 during the day) were recorded during hypereutrophic blooms (> 80 μg∙L-1, ≥ 2781 H. akashiwo cells∙mL-1). Dissolved oxygen differed significantly by bloom state, with the highest dissolved oxygen concentrations. Larval fish density, diversity and community structure variability were lower during hypereutrophic blooms compared to standard blooms and bloom absence, albeit statistically insignificant. Estuarine resident larval density was negatively correlated with dissolved oxygen concentration (P < 0.001). Dominant prey copepod of G. aestuaria larvae, P. hessei, was less abundant and variable during hypereutrophic blooms (mean: 664, range: 4-4301 individuals per m3) compared to standard blooms (mean: 950, range: 2-5237 individuals per m3) and bloom absence (mean: 1182, range: 23-7259 individuals per m3). Although HABs did not appear to drive a mismatch between prey and G. aestuaria larvae, early juvenile larvae made only a small contribution to the assemblage (0.2-1.8%). In terms of predator effects, yolk sac larvae were negatively related to R. terranatalis (P < 0.05). A significant positive relationship was found between prey, P. hessei and G. aestuaria preflexion (P < 0.001), flexion (P < 0.001) and postflexion (P < 0.05) larvae. In a world first, the effects of HABs were investigated on a larval fish species, Gilchristella aestuaria, using biochemical body condition analyses. During severe bloom conditions, G. aestuaria larvae were smaller and the assemblage consisted of mainly early developmental stages (stats). Body condition (RNA per dry weight) was poorest in the presence of hypereutrophic blooms (P < 0.001). A bell-curved relationship between RNA/DW and dissolved oxygen concentration was also produced in a 3-day time-lagged GAM (P < 0.001). In conclusion, hypereutrophic bloom conditions appeared to trigger adult G. aestuaria spawning in the upper mesohaline zone of the estuary in response to heightened primary productivity which occurs during the early bloom stage. However, reductions in copepod abundance (P. hessei) and unfavourable oxygen concentrations interfered with grow-out of G. aestuaria larvae. This research showed that HABs can alter nursery properties to the detriment of G. aestuaria larvae can have serious knock-on effects up the food chain. The loss in abundance of adult, juvenile and larval G. aestuaria, a key forage fish in South African estuaries, has major implications for estuarine food webs, especially in reduced prey availability to juvenile fishes and birds. There is still much to learn about the effects of HABs on the physiological and behavioural aspects on plankton communities worldwide.
- Full Text:
- Date Issued: 2020
- Authors: Smit, Taryn
- Date: 2020
- Subjects: Algal blooms -- South Africa , Estuaries -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49303 , vital:41619
- Description: The global rise in the incidence of harmful algal blooms in estuaries is a major concern given their importance as a nursery area for a variety of invertebrates and fishes. On the warm-temperate, south-east coast of South Africa, the Sundays Estuary experiences persistent, seasonal HABs due to stable eutrophic conditions. Spring blooms of the dinoflagellate, Heterosigma akashiwo, were recorded for several years in the estuary. This Raphidophyte is known for its consequences in fish and shellfish aquaculture and exhibits harmful properties such as mucilage and reactive oxygen species production. Subsequently, the dissertation investigated larval fish assemblage dynamics, larval prey and predator dynamics and body condition in association with H. akashiwo blooms. HABs mainly altered the water quality within the mesohaline zone in terms of microalgal biomass and dissolved oxygen. Hypereutrophic blooms of H. akashiwo reached 24 996 cells∙mL-1 during the study period. Supersaturated dissolved oxygen concentrations (up to ~13 mg∙L-1 at night and ~21 mg∙L-1 during the day) were recorded during hypereutrophic blooms (> 80 μg∙L-1, ≥ 2781 H. akashiwo cells∙mL-1). Dissolved oxygen differed significantly by bloom state, with the highest dissolved oxygen concentrations. Larval fish density, diversity and community structure variability were lower during hypereutrophic blooms compared to standard blooms and bloom absence, albeit statistically insignificant. Estuarine resident larval density was negatively correlated with dissolved oxygen concentration (P < 0.001). Dominant prey copepod of G. aestuaria larvae, P. hessei, was less abundant and variable during hypereutrophic blooms (mean: 664, range: 4-4301 individuals per m3) compared to standard blooms (mean: 950, range: 2-5237 individuals per m3) and bloom absence (mean: 1182, range: 23-7259 individuals per m3). Although HABs did not appear to drive a mismatch between prey and G. aestuaria larvae, early juvenile larvae made only a small contribution to the assemblage (0.2-1.8%). In terms of predator effects, yolk sac larvae were negatively related to R. terranatalis (P < 0.05). A significant positive relationship was found between prey, P. hessei and G. aestuaria preflexion (P < 0.001), flexion (P < 0.001) and postflexion (P < 0.05) larvae. In a world first, the effects of HABs were investigated on a larval fish species, Gilchristella aestuaria, using biochemical body condition analyses. During severe bloom conditions, G. aestuaria larvae were smaller and the assemblage consisted of mainly early developmental stages (stats). Body condition (RNA per dry weight) was poorest in the presence of hypereutrophic blooms (P < 0.001). A bell-curved relationship between RNA/DW and dissolved oxygen concentration was also produced in a 3-day time-lagged GAM (P < 0.001). In conclusion, hypereutrophic bloom conditions appeared to trigger adult G. aestuaria spawning in the upper mesohaline zone of the estuary in response to heightened primary productivity which occurs during the early bloom stage. However, reductions in copepod abundance (P. hessei) and unfavourable oxygen concentrations interfered with grow-out of G. aestuaria larvae. This research showed that HABs can alter nursery properties to the detriment of G. aestuaria larvae can have serious knock-on effects up the food chain. The loss in abundance of adult, juvenile and larval G. aestuaria, a key forage fish in South African estuaries, has major implications for estuarine food webs, especially in reduced prey availability to juvenile fishes and birds. There is still much to learn about the effects of HABs on the physiological and behavioural aspects on plankton communities worldwide.
- Full Text:
- Date Issued: 2020
Ocean dynamics of the shelf and bays of the eastern Agulhas bank: a process-oriented numerical modelling study
- Authors: Bailey, Dylan Francis
- Date: 2020
- Subjects: Oceanography -- Research , Marine biology , Marine meteorology , Hydrography
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49038 , vital:41595
- Description: There is a general need for a broader base of information on the finer detail of ocean processes in the Eastern Agulhas Bank region. In this thesis, the Regional Ocean Modelling System (ROMS) was applied to resolve high resolution (~1km) bay and shelf scale ocean processes along the south eastern coastline of South Africa using an offline multi-nested approach. Experimental and reference ocean model runs were used with in situ instrument mooring data to investigate how currents and temperature in the bays and the adjacent shelf are affected by the bathymetry, Agulhas Current (AC), regional winds, and coastal trapped waves (CTW). Focus was given to temperature, circulation, and coastal trapped waves, given the abundance of hourly in situ mooring data for these variables, making them suitable for comparison with the ocean model. SST variability trends were seasonally and spatially predictable, being greatest in the summer months and smallest in the winter months. A region of high SST variability extended from Port Alfred toward the south-west, indicating entrainment of nearshore upwelled water and instabilities in the inshore front of the AC. Shelf bottom temperature variability had a more spatially diverse seasonal trend, with coastal variability the highest (lowest) and offshore variability the lowest (highest) during the summer (winter) months. A distinct asymmetry in mean seasonal shelf bottom temperatures evident to the south of Algoa Bay and St Francis Bay was shown to be dependent on the profile of the shelf margin in relation to the inshore front of the AC using an experimental model run. Bay-scale anti-cyclonic circulation patterns dominate the bays throughout the year, with regions of strong mean surface currents occurring south of Cape Recife and Cape St Francis. General circulation patterns over the shelf are strongly governed by regional wind regimes, with the strongest flows being south-westward occurring during north-easterly wind events. Shelf bottom flows typically follow the expected Ekman-veering response, apart from near coastal flows that are topographically steered. A region of consistently strong south-westward shelf bottom flow extends from the east of Port Alfred to the shelf margin south of Bird Island. This flow is predominantly driven by the AC, although its velocity is strongly governed by regional winds. Circulation patterns during powerful eastward moving wind systems are strongly governed by the passage of associated CTW. Comparisons with an experimental model run where surface winds were removed revealed that the shelf wave was responsible for 61% of water volume displacement during a CTW event, and that the coastal shear turbulence caused by this displacement has a direct effect on the mixed layer depth. The links made between the complex shelf and bay ocean processes indicate that subtle changes to the ocean state will have far reaching effects on the regional ocean environment and its biota. Given the challenges of climate change, this is of paramount importance if we are to quantify these effects and mitigate their impacts, particularly with respect to the socio-economic dependency of those who rely on the ocean for its living resources.
- Full Text:
- Date Issued: 2020
- Authors: Bailey, Dylan Francis
- Date: 2020
- Subjects: Oceanography -- Research , Marine biology , Marine meteorology , Hydrography
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49038 , vital:41595
- Description: There is a general need for a broader base of information on the finer detail of ocean processes in the Eastern Agulhas Bank region. In this thesis, the Regional Ocean Modelling System (ROMS) was applied to resolve high resolution (~1km) bay and shelf scale ocean processes along the south eastern coastline of South Africa using an offline multi-nested approach. Experimental and reference ocean model runs were used with in situ instrument mooring data to investigate how currents and temperature in the bays and the adjacent shelf are affected by the bathymetry, Agulhas Current (AC), regional winds, and coastal trapped waves (CTW). Focus was given to temperature, circulation, and coastal trapped waves, given the abundance of hourly in situ mooring data for these variables, making them suitable for comparison with the ocean model. SST variability trends were seasonally and spatially predictable, being greatest in the summer months and smallest in the winter months. A region of high SST variability extended from Port Alfred toward the south-west, indicating entrainment of nearshore upwelled water and instabilities in the inshore front of the AC. Shelf bottom temperature variability had a more spatially diverse seasonal trend, with coastal variability the highest (lowest) and offshore variability the lowest (highest) during the summer (winter) months. A distinct asymmetry in mean seasonal shelf bottom temperatures evident to the south of Algoa Bay and St Francis Bay was shown to be dependent on the profile of the shelf margin in relation to the inshore front of the AC using an experimental model run. Bay-scale anti-cyclonic circulation patterns dominate the bays throughout the year, with regions of strong mean surface currents occurring south of Cape Recife and Cape St Francis. General circulation patterns over the shelf are strongly governed by regional wind regimes, with the strongest flows being south-westward occurring during north-easterly wind events. Shelf bottom flows typically follow the expected Ekman-veering response, apart from near coastal flows that are topographically steered. A region of consistently strong south-westward shelf bottom flow extends from the east of Port Alfred to the shelf margin south of Bird Island. This flow is predominantly driven by the AC, although its velocity is strongly governed by regional winds. Circulation patterns during powerful eastward moving wind systems are strongly governed by the passage of associated CTW. Comparisons with an experimental model run where surface winds were removed revealed that the shelf wave was responsible for 61% of water volume displacement during a CTW event, and that the coastal shear turbulence caused by this displacement has a direct effect on the mixed layer depth. The links made between the complex shelf and bay ocean processes indicate that subtle changes to the ocean state will have far reaching effects on the regional ocean environment and its biota. Given the challenges of climate change, this is of paramount importance if we are to quantify these effects and mitigate their impacts, particularly with respect to the socio-economic dependency of those who rely on the ocean for its living resources.
- Full Text:
- Date Issued: 2020
Mechatronics based highspeed rotational piezo actuator
- Authors: Raffler, Oliver
- Date: 2020
- Subjects: Piezoelectric materials , Piezoelectric devices Mechatronics
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/${Handle} , vital:39811
- Description: The aim of this thesis is the development of a novel mechatronics-based high speed piezo actuator for rotational and linear motion. Mainly, the thesis deals with the development of a system for mechanical coupling of any number of piezostacks. This mechanical coupling allows the actuator to achieve a significantly increased deflection compared to current approaches. The developed concept offers the possibility of a linear or rotary motion. It is also possible to combine the two types of movement. In the first step, in order to gain a better understanding of the topic, the piezo technology and especially the existing piezo actuators and -motors are examined. Currently, the force generated by the piezo actuators is mainly transmitted by friction. The only exception is the PAD-Actuator, which transmits force by means of form locking. The concept developed here also transmits its force by means of form locking and, in addition to that, offers a novel and unique drive concept in the field of piezo actuators. In the course of this thesis a new concept for the mechanical coupling of piezo actuators was developed, simulated and subsequently manufactured. Thus the system could be examined under real conditions. The investigations carried out mainly dealt with quasi-static and dynamic investigations. In addition to that, the emission of the airborne and structure-borne noise of the system was analysed.
- Full Text:
- Date Issued: 2020
- Authors: Raffler, Oliver
- Date: 2020
- Subjects: Piezoelectric materials , Piezoelectric devices Mechatronics
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/${Handle} , vital:39811
- Description: The aim of this thesis is the development of a novel mechatronics-based high speed piezo actuator for rotational and linear motion. Mainly, the thesis deals with the development of a system for mechanical coupling of any number of piezostacks. This mechanical coupling allows the actuator to achieve a significantly increased deflection compared to current approaches. The developed concept offers the possibility of a linear or rotary motion. It is also possible to combine the two types of movement. In the first step, in order to gain a better understanding of the topic, the piezo technology and especially the existing piezo actuators and -motors are examined. Currently, the force generated by the piezo actuators is mainly transmitted by friction. The only exception is the PAD-Actuator, which transmits force by means of form locking. The concept developed here also transmits its force by means of form locking and, in addition to that, offers a novel and unique drive concept in the field of piezo actuators. In the course of this thesis a new concept for the mechanical coupling of piezo actuators was developed, simulated and subsequently manufactured. Thus the system could be examined under real conditions. The investigations carried out mainly dealt with quasi-static and dynamic investigations. In addition to that, the emission of the airborne and structure-borne noise of the system was analysed.
- Full Text:
- Date Issued: 2020
Managing the corporate reputation of a transforming organisation: a study of multimedia University of Kenya
- Authors: Mtange, Margaret Mulekani
- Date: 2020
- Subjects: Organizational change -- Management , Universities and colleges -- Kenya -- Sociological aspects -- Case studies , Universities and colleges -- Research -- Economic aspects -- Kenya -- Case studies
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/50837 , vital:42873
- Description: Universities, like other organisations, are challenged to manage corporate identity and reputation to maintain a competitive edge. Few studies in Africa focus on the impact of internal communication on corporate identity and reputation management during organisational transformation. Thus, this study interrogated how a transforming and complex university in Kenya managed the corporate identity, image and reputation for competitive advantage. The purpose of the study was to establish how Multimedia University of Kenya (MMU) management communicated with its employees to nurture the corporate identity, image and reputation during a ten-year period of transformation. The study draws insights from in-depth interviews with 23 university management members, 178 self-administered questionnaires through random stratification of MMU employees, and content review of two MMU strategic plans ranging from 2011 to 2021. The findings suggest that MMU management used formal and interactive channels to create awareness of organisational transformation. These channels included face-to-face engagements, formal meetings and mediated communication through telephone conversations and intranet that facilitated record keeping. The management engaged in top-down and bottom-up communication to build employee trust, while employees expressed reservations of bottom-up information accuracy, suggesting information exclusion. On the contrary, the employees preferred digital and interpersonal channels for internal communication, which included telephone conversations, social media, personal visits by MMU management, and university events. Publicity activities were to disseminate information to prospective students and sponsors through selected private television, vernacular radio, and MMU radio stations, traditional print media, and the MMU website to communicate the MMU brand and image. Employees acknowledged that MMU brands itself as a leader in telecommunication, technology, mechanical, manufacturing, and media training through state-of-the-art equipment, robust faculty, and problem-solving ventures through research. The current study proposes stronger employee involvement, executive packaging and positioning, coaching successful faculty members as brand ambassadors, retraining employees, and employee participation in policy formulation to enhance new culture. In addition, these opositions will enhance the corporate identity, brand, as well as university performance, product quality, policy and processes to enrich the corporate reputation during transformation. The findings challenge university management to actively engage the corporate communication function, emphasise employee participation, and focus on the continual improvement of corporate identity and reputation management practices for competitive advantage. The current study proposes a participative, multi-layered and multi-dimensional communication model for efficient and excellent internal communication. The current study recommends that corporate communication practitioner be strategically positioned to coordinate employee engagement, utilise appropriate communication channels and counsel university management on corporate identity, image and reputation management during organisational transformation.
- Full Text:
- Date Issued: 2020
- Authors: Mtange, Margaret Mulekani
- Date: 2020
- Subjects: Organizational change -- Management , Universities and colleges -- Kenya -- Sociological aspects -- Case studies , Universities and colleges -- Research -- Economic aspects -- Kenya -- Case studies
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/50837 , vital:42873
- Description: Universities, like other organisations, are challenged to manage corporate identity and reputation to maintain a competitive edge. Few studies in Africa focus on the impact of internal communication on corporate identity and reputation management during organisational transformation. Thus, this study interrogated how a transforming and complex university in Kenya managed the corporate identity, image and reputation for competitive advantage. The purpose of the study was to establish how Multimedia University of Kenya (MMU) management communicated with its employees to nurture the corporate identity, image and reputation during a ten-year period of transformation. The study draws insights from in-depth interviews with 23 university management members, 178 self-administered questionnaires through random stratification of MMU employees, and content review of two MMU strategic plans ranging from 2011 to 2021. The findings suggest that MMU management used formal and interactive channels to create awareness of organisational transformation. These channels included face-to-face engagements, formal meetings and mediated communication through telephone conversations and intranet that facilitated record keeping. The management engaged in top-down and bottom-up communication to build employee trust, while employees expressed reservations of bottom-up information accuracy, suggesting information exclusion. On the contrary, the employees preferred digital and interpersonal channels for internal communication, which included telephone conversations, social media, personal visits by MMU management, and university events. Publicity activities were to disseminate information to prospective students and sponsors through selected private television, vernacular radio, and MMU radio stations, traditional print media, and the MMU website to communicate the MMU brand and image. Employees acknowledged that MMU brands itself as a leader in telecommunication, technology, mechanical, manufacturing, and media training through state-of-the-art equipment, robust faculty, and problem-solving ventures through research. The current study proposes stronger employee involvement, executive packaging and positioning, coaching successful faculty members as brand ambassadors, retraining employees, and employee participation in policy formulation to enhance new culture. In addition, these opositions will enhance the corporate identity, brand, as well as university performance, product quality, policy and processes to enrich the corporate reputation during transformation. The findings challenge university management to actively engage the corporate communication function, emphasise employee participation, and focus on the continual improvement of corporate identity and reputation management practices for competitive advantage. The current study proposes a participative, multi-layered and multi-dimensional communication model for efficient and excellent internal communication. The current study recommends that corporate communication practitioner be strategically positioned to coordinate employee engagement, utilise appropriate communication channels and counsel university management on corporate identity, image and reputation management during organisational transformation.
- Full Text:
- Date Issued: 2020
Integrating sustainability dimensions into construction labour productivity determinants in Zimbabwe
- Authors: Moyo, Tirivavi
- Date: 2020
- Subjects: Construction industry -- Labor productivity -- Zimbabwe , Construction workers -- Zimbabwe Construction industry -- Employees -- Zimbabwe Construction industry -- Management
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/46207 , vital:39514
- Description: Low construction labour productivity and inadequate welfare of construction workers is a compound challenge in Zimbabwe. This challenge is due to shortcomings situated in the Decent Work Agenda. Whilst a plethora of contributory factors exists, those that affect the Zimbabwean construction industry were identified for interrogation. Therefore, the study aimed to improve and sustain construction labour productivity in Zimbabwe through fulfilling significant decent work substantive elements, in consideration of demographic variables of stakeholders. A cross-sectional survey research strategy was utilised with quantitative data being collected from selected respondents through the use of questionnaires. The population for the study consisted of randomly selected construction companies registered with the Construction Industry Federation of Zimbabwe and based in Harare, Bulawayo and Shurugwi where site managers’/project managers’ participated. Construction skilled and semi-skilled workers on thirteen (13) construction sites, situated within the same study area, participated in the study. Educators from technical and vocational training institutions and respondents from relevant regulatory bodies were also selected to participate in the study. Quantitative data analysis methods which included Pearson chi-squared tests, Mann-Whitney U tests; Kruskal-Wallis tests, Pearson bivariate correlation method and Regression analysis were utilised. Demographic variables (age, gender, designation, educational levels and experience) were utilised to determine the existence of statistically significant differences in respondents’ perceptions. Construction companies are encouraged to implement corporate social responsibility strategies through equipping workers of different educational levels with knowledge and skills that can be transferred to and benefit themselves and their communities. Adequately trained construction workers best serve their communities through improving their livelihoods, improved safety and health consciousness and quality workmanship. People centred management aspects were found to be fundamental within construction sites as they promote the welfare of workers and should precede any productivity improvement drives. Technical and vocational training institutions need to inculcate sustainability learning objectives within their curricula if any meaning strides in enhancing welfare and productivity of workers is to be achieved. Also, establishing structured on-the-job training that incorporates sustainability learning objectives to achieve workers’ safety on sites is essential. There was a consensus that working conditions must ensure the welfare of workers first before any productivity gains can be realised. Provision of acceptable decent working conditions for different designations and educational levels was encouraged. A comprehensive model was developed for sustaining construction labour productivity that included statistically significant regression models and derived statistically significant demographics from construction labour productivity determinants under study. Validation of the regression models was undertaken through cross-validation and comparison with existing theory. Tenable labour productivity performance measurement and reporting must be inclusive of decent work accomplishments. Short-term interventions that include awareness campaigns and provision of adequate working conditions are required for project-based resolutions whilst, long-term interventions are required where structural reforms within the training of skilled, semi-skilled workers and managers are required, for continuous improvement.
- Full Text:
- Date Issued: 2020
Integrating sustainability dimensions into construction labour productivity determinants in Zimbabwe
- Authors: Moyo, Tirivavi
- Date: 2020
- Subjects: Construction industry -- Labor productivity -- Zimbabwe , Construction workers -- Zimbabwe Construction industry -- Employees -- Zimbabwe Construction industry -- Management
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/46207 , vital:39514
- Description: Low construction labour productivity and inadequate welfare of construction workers is a compound challenge in Zimbabwe. This challenge is due to shortcomings situated in the Decent Work Agenda. Whilst a plethora of contributory factors exists, those that affect the Zimbabwean construction industry were identified for interrogation. Therefore, the study aimed to improve and sustain construction labour productivity in Zimbabwe through fulfilling significant decent work substantive elements, in consideration of demographic variables of stakeholders. A cross-sectional survey research strategy was utilised with quantitative data being collected from selected respondents through the use of questionnaires. The population for the study consisted of randomly selected construction companies registered with the Construction Industry Federation of Zimbabwe and based in Harare, Bulawayo and Shurugwi where site managers’/project managers’ participated. Construction skilled and semi-skilled workers on thirteen (13) construction sites, situated within the same study area, participated in the study. Educators from technical and vocational training institutions and respondents from relevant regulatory bodies were also selected to participate in the study. Quantitative data analysis methods which included Pearson chi-squared tests, Mann-Whitney U tests; Kruskal-Wallis tests, Pearson bivariate correlation method and Regression analysis were utilised. Demographic variables (age, gender, designation, educational levels and experience) were utilised to determine the existence of statistically significant differences in respondents’ perceptions. Construction companies are encouraged to implement corporate social responsibility strategies through equipping workers of different educational levels with knowledge and skills that can be transferred to and benefit themselves and their communities. Adequately trained construction workers best serve their communities through improving their livelihoods, improved safety and health consciousness and quality workmanship. People centred management aspects were found to be fundamental within construction sites as they promote the welfare of workers and should precede any productivity improvement drives. Technical and vocational training institutions need to inculcate sustainability learning objectives within their curricula if any meaning strides in enhancing welfare and productivity of workers is to be achieved. Also, establishing structured on-the-job training that incorporates sustainability learning objectives to achieve workers’ safety on sites is essential. There was a consensus that working conditions must ensure the welfare of workers first before any productivity gains can be realised. Provision of acceptable decent working conditions for different designations and educational levels was encouraged. A comprehensive model was developed for sustaining construction labour productivity that included statistically significant regression models and derived statistically significant demographics from construction labour productivity determinants under study. Validation of the regression models was undertaken through cross-validation and comparison with existing theory. Tenable labour productivity performance measurement and reporting must be inclusive of decent work accomplishments. Short-term interventions that include awareness campaigns and provision of adequate working conditions are required for project-based resolutions whilst, long-term interventions are required where structural reforms within the training of skilled, semi-skilled workers and managers are required, for continuous improvement.
- Full Text:
- Date Issued: 2020
Influence of process energy on stress corrosion susceptibility of a friction hydro pillar repaired steam turbine rotor disc blade locating hole
- Authors: Pentz, Willem Gerhard
- Date: 2020
- Subjects: Friction welding , Mechanical engineering
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/47106 , vital:39810
- Description: Currently the power generation industry is struggling to keep older coal power plants running efficiently. One of the major hurdles is to keep repair and service cost low. Over time stress corrosion cracking (SCC) occurs in the locating pinholes of tier type rotors which locate the turbine blades. This is where this research aims to assist with an alternative repair technique, Friction Hydro Pillar Processing (FHPP) welding, to have longer service intervals thus saving cost and time. The same material can be used for welding and a new aligned hole can be drilled. FHPP welding is a solid state friction welding process. Four different FHPP axial forces were selected to compare their respective performance in subsequent tensile testing, impact testing and SCC testing. All the tensile samples extracted from preheated welds and post weld heat treated welds fracture in the parent material, which indicates good weld efficiency. The impact crack route from the weld nugget towards the parent material was identified in the energy and force graph. Axial force which promote impact toughness can be selected with this curve. SCC occurs when a tensile stress is applied to a susceptible material when in a conducive environment for cracking. A new SCC W-shape was designed and performed well during initial testing. With the SCC W-shape two specimens can be extracted opposite each other and tested. Both the preheated weld samples and the post weld heat treatment (PWHT) weld samples had improved SCC performance over their respective parent material samples. A high axial force, low process energy, and high process energy rate (low process energy and low weld time) produced a weld with improved SCC resistance. FHPP (with PWHT) is a promising repair technique as it improved on the SCC resistance and impact toughness as well as having 100% bond efficiency. More research is still required to identify the SCC mechanism of the FHPP weld.
- Full Text:
- Date Issued: 2020
- Authors: Pentz, Willem Gerhard
- Date: 2020
- Subjects: Friction welding , Mechanical engineering
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/47106 , vital:39810
- Description: Currently the power generation industry is struggling to keep older coal power plants running efficiently. One of the major hurdles is to keep repair and service cost low. Over time stress corrosion cracking (SCC) occurs in the locating pinholes of tier type rotors which locate the turbine blades. This is where this research aims to assist with an alternative repair technique, Friction Hydro Pillar Processing (FHPP) welding, to have longer service intervals thus saving cost and time. The same material can be used for welding and a new aligned hole can be drilled. FHPP welding is a solid state friction welding process. Four different FHPP axial forces were selected to compare their respective performance in subsequent tensile testing, impact testing and SCC testing. All the tensile samples extracted from preheated welds and post weld heat treated welds fracture in the parent material, which indicates good weld efficiency. The impact crack route from the weld nugget towards the parent material was identified in the energy and force graph. Axial force which promote impact toughness can be selected with this curve. SCC occurs when a tensile stress is applied to a susceptible material when in a conducive environment for cracking. A new SCC W-shape was designed and performed well during initial testing. With the SCC W-shape two specimens can be extracted opposite each other and tested. Both the preheated weld samples and the post weld heat treatment (PWHT) weld samples had improved SCC performance over their respective parent material samples. A high axial force, low process energy, and high process energy rate (low process energy and low weld time) produced a weld with improved SCC resistance. FHPP (with PWHT) is a promising repair technique as it improved on the SCC resistance and impact toughness as well as having 100% bond efficiency. More research is still required to identify the SCC mechanism of the FHPP weld.
- Full Text:
- Date Issued: 2020
Foraging in a dynamic environment: movement and stable isotope ecology of marine top predators breeding at the Prince Edward Archipelago
- Authors: Carpenter-Kling, Tegan
- Date: 2020
- Subjects: Marine ecology , Stable isotope tracers , Estuarine ecology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49049 , vital:41596
- Description: Marine ecosystems are experiencing rapid changes due to climate change. The associated temporal and spatial changes in resource distribution impacts on the foraging behaviour of marine top predators. If these changes negatively affect the ability of marine predators to forage efficiently, there may be dire consequences for their populations. However, evidence of foraging plasticity during adverse conditions, or generalist foraging behaviour, can allow inference about the resilience of species to environmental change and provide essential knowledge towards effective and proactive conservation measures. I examined plasticity in the trophic ecology of 12 marine predator species breeding on Marion Island, southern Indian Ocean, over three years (2015 – 2018), a period characterized by pronounced environmental variability. Firstly, I correlated behavioural states inferred along the GPS tracks of incubating wandering, grey-headed, sooty and light-mantled albatrosses to environmental variables that are indicative of biologically productive oceanographic features. Secondly, I analysed δ13C and δ15N blood values in 12 marine predator species (the afore-mentioned albatrosses as well as king, gentoo, macaroni and eastern rockhopper penguins, northern and southern giant petrels and Antarctic and sub-Antarctic fur seals) over two seasons: summer and autumn. My results revealed that the foraging behaviour of all the species is, to some degree, either plastic (temporally variable isotopic niche) or general (large isotopic niche which remained similar over time), except for the king penguin (small isotopic niche which remained similar over time), a known foraging specialist. Furthermore, despite their dynamic foraging behaviour, resource partitioning among the predators was maintained over time. Due to the ease and relatively low cost of collecting tissues for stable isotope analysis it has the potential to be a powerful tool to monitor the trophic ecology of marine predators. I thus used my simultaneously collected dataset of GPS tracks with the stable isotope blood compositions to investigate some of the assumptions underlying the inferences made from marine predator δ13C and δ15N blood values. I reconstructed species- and guild- specific δ13C and δ15N isoscapes for eight seabird species. Following this, I coupled individual-based movement models of northern giant petrels with global marine isotope models to explore the sensitivity of tissue δ13C values to a range of extrinsic (environmental) and intrinsic (behavioural, physiological) drivers. My results demonstrate the strong influence of reference isoscapes on the inference of stable isotope compositions of marine predators. Furthermore, I show that caution should be used when using non-species-specific or temporally inaccurate isoscapes. I furthermore demonstrate that biological interactions, such as competition for food resources, either past or present, as well as spatio-temporal distribution of food patches strongly influence the foraging behaviour of marine predators. These findings highlight the importance of integrating biological interactions in species distribution models which are used to predict possible distributional shifts of marine predators in the context of global changes. My thesis further developed previously available methods and presents a novel approach to investigate sources of variance in the stable isotopic composition of animals’ tissues.
- Full Text:
- Date Issued: 2020
- Authors: Carpenter-Kling, Tegan
- Date: 2020
- Subjects: Marine ecology , Stable isotope tracers , Estuarine ecology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49049 , vital:41596
- Description: Marine ecosystems are experiencing rapid changes due to climate change. The associated temporal and spatial changes in resource distribution impacts on the foraging behaviour of marine top predators. If these changes negatively affect the ability of marine predators to forage efficiently, there may be dire consequences for their populations. However, evidence of foraging plasticity during adverse conditions, or generalist foraging behaviour, can allow inference about the resilience of species to environmental change and provide essential knowledge towards effective and proactive conservation measures. I examined plasticity in the trophic ecology of 12 marine predator species breeding on Marion Island, southern Indian Ocean, over three years (2015 – 2018), a period characterized by pronounced environmental variability. Firstly, I correlated behavioural states inferred along the GPS tracks of incubating wandering, grey-headed, sooty and light-mantled albatrosses to environmental variables that are indicative of biologically productive oceanographic features. Secondly, I analysed δ13C and δ15N blood values in 12 marine predator species (the afore-mentioned albatrosses as well as king, gentoo, macaroni and eastern rockhopper penguins, northern and southern giant petrels and Antarctic and sub-Antarctic fur seals) over two seasons: summer and autumn. My results revealed that the foraging behaviour of all the species is, to some degree, either plastic (temporally variable isotopic niche) or general (large isotopic niche which remained similar over time), except for the king penguin (small isotopic niche which remained similar over time), a known foraging specialist. Furthermore, despite their dynamic foraging behaviour, resource partitioning among the predators was maintained over time. Due to the ease and relatively low cost of collecting tissues for stable isotope analysis it has the potential to be a powerful tool to monitor the trophic ecology of marine predators. I thus used my simultaneously collected dataset of GPS tracks with the stable isotope blood compositions to investigate some of the assumptions underlying the inferences made from marine predator δ13C and δ15N blood values. I reconstructed species- and guild- specific δ13C and δ15N isoscapes for eight seabird species. Following this, I coupled individual-based movement models of northern giant petrels with global marine isotope models to explore the sensitivity of tissue δ13C values to a range of extrinsic (environmental) and intrinsic (behavioural, physiological) drivers. My results demonstrate the strong influence of reference isoscapes on the inference of stable isotope compositions of marine predators. Furthermore, I show that caution should be used when using non-species-specific or temporally inaccurate isoscapes. I furthermore demonstrate that biological interactions, such as competition for food resources, either past or present, as well as spatio-temporal distribution of food patches strongly influence the foraging behaviour of marine predators. These findings highlight the importance of integrating biological interactions in species distribution models which are used to predict possible distributional shifts of marine predators in the context of global changes. My thesis further developed previously available methods and presents a novel approach to investigate sources of variance in the stable isotopic composition of animals’ tissues.
- Full Text:
- Date Issued: 2020
Food and Nihilism :a Nietzschean and Deleuzian exploration of contemporary dominant food discourses
- Authors: Du Plessis, Karen
- Date: 2020
- Subjects: Nihilism (Philosophy) -- History , Food culture -- Religious Aspects
- Language: English
- Type: Thesis , Masters , DPhil
- Identifier: http://hdl.handle.net/10948/46870 , vital:39718
- Description: This study is based on the proposition that the respective philosophies of Nietzsche and Deleuze, including his collaborative work with Guattari, provide a way to rethink the underlying structures that inform ways of thinking about food and eating. In Nietzschean and Deleuzian terms, many of the dominant ways that humans currently think about food and eating are fraught with multiple anxieties that lead to passivity and despair, as well as obsessive concerns and feelings of guilt. This can be understood as various ways to say No to life and to difference‘. For the sake of overcoming (or at least addressing) such forms of eating-related nihilism, or life-denying attitudes, I argue that there is an urgent need for philosophical research that deals critically with the underlying food values‘ that lead to contemporary nihilistic ways of thinking about food. Further, I argue that critiquing contemporary dominant nihilistic food discourses and values from a Deleuzian and Nietzschean perspective, as well as exploring what produces nihilism, opens up Avenues/possibilities for shifts in approaching the problem of food and eating in a more life-affirming way. Specifically, Nietzsche‘s work on active and reactive forces, coupled with Deleuze and Guattari‘s account of concepts, allows for an exploration of what a starting point for overcoming nihilism might look like. In this case I argue that in order to think in a new way about the different aspects of eating, a more life-affirming and active concept of a body‘ should be produced.
- Full Text:
- Date Issued: 2020
- Authors: Du Plessis, Karen
- Date: 2020
- Subjects: Nihilism (Philosophy) -- History , Food culture -- Religious Aspects
- Language: English
- Type: Thesis , Masters , DPhil
- Identifier: http://hdl.handle.net/10948/46870 , vital:39718
- Description: This study is based on the proposition that the respective philosophies of Nietzsche and Deleuze, including his collaborative work with Guattari, provide a way to rethink the underlying structures that inform ways of thinking about food and eating. In Nietzschean and Deleuzian terms, many of the dominant ways that humans currently think about food and eating are fraught with multiple anxieties that lead to passivity and despair, as well as obsessive concerns and feelings of guilt. This can be understood as various ways to say No to life and to difference‘. For the sake of overcoming (or at least addressing) such forms of eating-related nihilism, or life-denying attitudes, I argue that there is an urgent need for philosophical research that deals critically with the underlying food values‘ that lead to contemporary nihilistic ways of thinking about food. Further, I argue that critiquing contemporary dominant nihilistic food discourses and values from a Deleuzian and Nietzschean perspective, as well as exploring what produces nihilism, opens up Avenues/possibilities for shifts in approaching the problem of food and eating in a more life-affirming way. Specifically, Nietzsche‘s work on active and reactive forces, coupled with Deleuze and Guattari‘s account of concepts, allows for an exploration of what a starting point for overcoming nihilism might look like. In this case I argue that in order to think in a new way about the different aspects of eating, a more life-affirming and active concept of a body‘ should be produced.
- Full Text:
- Date Issued: 2020
Development of Tio 2 nanostructure arrays for photonic extraction of hydrogen gas
- Authors: Suliali, Nyasha Joseph
- Date: 2020
- Subjects: Nanostructures , Nanostructured materials Hydrogen
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49314 , vital:41620
- Description: Amid the energy crisis of the 21st century, renewable energy is a thriving field of study, light harvesting materials being a central theme due to the abundance of solar energy. Nanostructured TiO2 is the most studied photocatalysis material, since the discovery of its energy harvesting properties by Fujishima and Honda in 1972. Environmentally friendly products such as hydrogen fuel, can be produced using TiO2 due to its non-toxicity, chemical stability and photocatalytic activity. The surprising aspect of this important material is that it can be prepared using cost-effective methods such as hydrothermal synthesis, solution gelation and anodic oxidation. This research focused on the three key elements required to develop TiO2 photoelectrodes i.e. the deposition of Ti films on transparent substrates, a thorough analysis of the chemistry of the anodic oxidation process and the development of the TiO2 thin films. Glass substrates that have Ti films are the base component for TiO2 photoelectrode production. Ti films with thicknesses up to 4 μm, were developed on commercial F-doped SnO2 (FTO) glass substrates using high-power impulse magnetron sputtering (HiPIMS). The sputter deposition experiments were performed in the 1 to 8 kW range at a substrate temperature of 500 °C and Ar pressure of 400 mPa. At higher powers, thicker films were deposited, resulting in increased intensity of Xray-diffraction peaks. However, on comparing the XRD patterns, the (001) peak outgrew the rest regardless of thickness of the film. The deposition process therefore favoured orientation of most of the α-Ti phase crystallites with the [001] axis perpendicular to the substrate surface. Surface roughness results were interesting, showing a non-linear dependence of the surface roughness on HiPIMS pulse energy in the 1 to 8 kW range. The surface roughness is highest at the starting deposition power of 1450 W and reduces to a minimum at 4500 W. From this minimum, it increases to its second highest value at 7900 W. From this data, the parameters required to produce Ti films of lowest surface roughness, for deposition on commercial Technistro® FTO glass, were deduced at the inflection point, where the deposition power was 4500 W. The surface roughness obtained is a critical result for the anodic production of quality TiO2 photoelectrodes, which if high, leads to uneven etching, thus irregular and inefficient photoelectrodes. Direct current magnetron sputtering was also carried out in the 1 to 5 kW range to obtain ratios of power-normalised growth rates of the Ti films. This investigation provided the Ti films on FTO glass, the transparent, conductive substrates which were used to develop TiO2 photoelectrodes. To elucidate the chemistry of anodic oxidation of Ti, a mathematical model of the anodic current density, which had not been reported at the time of its publication, was developed. The technique, a highlight of this research, is a predictive numerical computation of the instantaneous quantities of species that participate in the anodization process. From eleven chemical reactions, 14 first order ordinary differential equations were compiled using the principles of chemical reaction kinetics. The pattern, transient behaviour and response to anodization parameters of the current density signal, were successfully predicted. Strong agreement between the model and measurements was demonstrated in seven experiments. The results confirm that the current density signal is a numerical integral of the kinetics of redox reactions of water. The bulk of this research was on the development of TiO2 nanotubular arrays on Ti foil substrates and Ti films on FTO glass. TiO2 films with well-defined tubular structures were synthesised. The films were developed in anhydrous, polar organic hosts with water and etching agents in the range of 10 V to 70 V. The control of geometrical properties of the tubes such as the length, pore diameter, wall thickness, tube separation and number of nanotubes per unit area was demonstrated. Anatase only and mixed anatase-rutile phase compositions were obtained at different annealing temperatures. Nanotubes with diameters as small as 20 nm and thickness as high as 29 μm were produced. Apart from an increase in nanotube thickness, a decrease in distance between nanotubes grown in diethylene glycol was observed at longer anodization times. Studies of the effects of anodization parameters on the current density measured, morphological and crystallographic properties of the nanotube films were conducted in three main investigations. The first was the study of the effect of anodization parameters on current density. Besides the obvious increase of current density with anodic voltage, the first steady state of the growth process was found to depend on the NH4F concentration. The second investigation focused on the effect of accelerated growth of TiO2 nanotubular films. In the study, 9 μm-thick nanotube films were synthesised at twice the growth rate of a 9 μm-thick control sample. The array obtained by accelerated growth had distinguishable nanotubes, however, the morphological quality was reduced. The third investigation demonstrates the control of the number of nanotubes per unit area. By varying the etchant content, the anodic voltage and the viscosity of the electrolyte host, various distributions were obtained. The research ends with a photoelectrochemical application: measurement on photocurrents generated in a two-electrode setup. The photocurrent densities measured in the off and on conditions were 30 nA/cm2 and 2.57 μA/cm2, respectively, demonstrating photoactivity of the developed films.
- Full Text:
- Date Issued: 2020
- Authors: Suliali, Nyasha Joseph
- Date: 2020
- Subjects: Nanostructures , Nanostructured materials Hydrogen
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49314 , vital:41620
- Description: Amid the energy crisis of the 21st century, renewable energy is a thriving field of study, light harvesting materials being a central theme due to the abundance of solar energy. Nanostructured TiO2 is the most studied photocatalysis material, since the discovery of its energy harvesting properties by Fujishima and Honda in 1972. Environmentally friendly products such as hydrogen fuel, can be produced using TiO2 due to its non-toxicity, chemical stability and photocatalytic activity. The surprising aspect of this important material is that it can be prepared using cost-effective methods such as hydrothermal synthesis, solution gelation and anodic oxidation. This research focused on the three key elements required to develop TiO2 photoelectrodes i.e. the deposition of Ti films on transparent substrates, a thorough analysis of the chemistry of the anodic oxidation process and the development of the TiO2 thin films. Glass substrates that have Ti films are the base component for TiO2 photoelectrode production. Ti films with thicknesses up to 4 μm, were developed on commercial F-doped SnO2 (FTO) glass substrates using high-power impulse magnetron sputtering (HiPIMS). The sputter deposition experiments were performed in the 1 to 8 kW range at a substrate temperature of 500 °C and Ar pressure of 400 mPa. At higher powers, thicker films were deposited, resulting in increased intensity of Xray-diffraction peaks. However, on comparing the XRD patterns, the (001) peak outgrew the rest regardless of thickness of the film. The deposition process therefore favoured orientation of most of the α-Ti phase crystallites with the [001] axis perpendicular to the substrate surface. Surface roughness results were interesting, showing a non-linear dependence of the surface roughness on HiPIMS pulse energy in the 1 to 8 kW range. The surface roughness is highest at the starting deposition power of 1450 W and reduces to a minimum at 4500 W. From this minimum, it increases to its second highest value at 7900 W. From this data, the parameters required to produce Ti films of lowest surface roughness, for deposition on commercial Technistro® FTO glass, were deduced at the inflection point, where the deposition power was 4500 W. The surface roughness obtained is a critical result for the anodic production of quality TiO2 photoelectrodes, which if high, leads to uneven etching, thus irregular and inefficient photoelectrodes. Direct current magnetron sputtering was also carried out in the 1 to 5 kW range to obtain ratios of power-normalised growth rates of the Ti films. This investigation provided the Ti films on FTO glass, the transparent, conductive substrates which were used to develop TiO2 photoelectrodes. To elucidate the chemistry of anodic oxidation of Ti, a mathematical model of the anodic current density, which had not been reported at the time of its publication, was developed. The technique, a highlight of this research, is a predictive numerical computation of the instantaneous quantities of species that participate in the anodization process. From eleven chemical reactions, 14 first order ordinary differential equations were compiled using the principles of chemical reaction kinetics. The pattern, transient behaviour and response to anodization parameters of the current density signal, were successfully predicted. Strong agreement between the model and measurements was demonstrated in seven experiments. The results confirm that the current density signal is a numerical integral of the kinetics of redox reactions of water. The bulk of this research was on the development of TiO2 nanotubular arrays on Ti foil substrates and Ti films on FTO glass. TiO2 films with well-defined tubular structures were synthesised. The films were developed in anhydrous, polar organic hosts with water and etching agents in the range of 10 V to 70 V. The control of geometrical properties of the tubes such as the length, pore diameter, wall thickness, tube separation and number of nanotubes per unit area was demonstrated. Anatase only and mixed anatase-rutile phase compositions were obtained at different annealing temperatures. Nanotubes with diameters as small as 20 nm and thickness as high as 29 μm were produced. Apart from an increase in nanotube thickness, a decrease in distance between nanotubes grown in diethylene glycol was observed at longer anodization times. Studies of the effects of anodization parameters on the current density measured, morphological and crystallographic properties of the nanotube films were conducted in three main investigations. The first was the study of the effect of anodization parameters on current density. Besides the obvious increase of current density with anodic voltage, the first steady state of the growth process was found to depend on the NH4F concentration. The second investigation focused on the effect of accelerated growth of TiO2 nanotubular films. In the study, 9 μm-thick nanotube films were synthesised at twice the growth rate of a 9 μm-thick control sample. The array obtained by accelerated growth had distinguishable nanotubes, however, the morphological quality was reduced. The third investigation demonstrates the control of the number of nanotubes per unit area. By varying the etchant content, the anodic voltage and the viscosity of the electrolyte host, various distributions were obtained. The research ends with a photoelectrochemical application: measurement on photocurrents generated in a two-electrode setup. The photocurrent densities measured in the off and on conditions were 30 nA/cm2 and 2.57 μA/cm2, respectively, demonstrating photoactivity of the developed films.
- Full Text:
- Date Issued: 2020
Development of MOVPE-grown InAsSb for barrier diode applications
- Authors: Dobson, Stephen R
- Date: 2020
- Subjects: Gallium arsenide semiconductors , Electronics
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49071 , vital:41598
- Description: In this study, layers of GaSb, InAs and InAsSb are grown by metalorganic vapour phase epitaxy and characterised. Growth is conducted using the precursors of trimethylgallium, trimethylindium, trimethylantimony and tertiarybutylarsine. Focus is then placed on the characterisation of the materials, carried out by the techniques of X-ray diffraction, photoluminescence spectroscopy, Hall measurements and photocurrent spectroscopy. It is observed that V/III ratio plays a vital role in the growth of the GaSb and InAsSb layers. Epilayers of GaSb showed best crystalline quality when a V/III ratio of 1.2 was used at a growth temperature of 600 °C and a cell pressure of 600 Torr. Resultant Hall measurements indicated p-type GaSb. The Hall carrier concentrations of the p-type GaSb samples were analyzed considering electrical neutrality conditions and found to be highly compensated with evidence of band impurity conduction at low measurement temperatures. Both the donor and acceptor concentrations were determined to be of the order of 1016 cm−3 for all samples. For low temperature (< 150 K) a monovalent acceptor concentration is calculated to have an activation energy at approximately 20 meV. At high temperature (> 150 K) a divalent acceptor is extracted with an activation energy varying between samples based on compensation in a range of 90 meV to 70 meV. Photoluminescence measurements show four peaks with recombination mechanisms linked to the native acceptor identified in literature as either the gallium antisite and/or vacant gallium site. A fifth peak observed is attributed to the longitudinal phonon of the native acceptor. InAs and InAsSb epilayer are all grown at a temperature of 600 °C and cell pressure of 600 Torr. InAs is grown at a V/III ratio of 9.5 on GaAs substrate. Photoluminescence of the InAs layer shows two distinct peaks, one of which is an extrinsic band to band recombination. The other is attributed to free electron to acceptor or a donor-acceptor pair transition. An additional weak peak is also observed which is assigned to the longitudinal phonon of the band to band. InAsSb growth was conducted under a range of V/III ratios of 4.8 to 5, with a vapour phase composition of 0.4 to 0.435. Structural analysis via X-ray diffraction showed a 6 % to 12 % solid antimony content. Photoluminescence exhibited a single broad peak for all samples, with extended band tails. Temperature and power dependant analysis of luminescence indicated a convolution of extrinsic band to tail and band to band recombinations. Hall measurements indicated the InAsSb was n-type material with an apparent measured maximum mobility at 120 K of 9.5 × 103 cm2/V.s. and a room temperature apparent mobility of 7.5 × 103 cm2/V.s. Analysis of hall results using a two-layer model calculated a true bulk mobility of the epilayer at room temperature with an increased value of 15.4 × 103 cm2/V.s. The two-layer model details the effects of the surface conduction. From photoconductivity measurements and further analysis a resultant effective lifetime, at room temperature, was found to be on same order of magnitude as that of InAs materials. Application of a single Einstein oscillator extrapolated 0 K energy gaps for two samples of solid Sb contents of 6 % and 12 %, of 354 meV and 332 meV, respectively. Finally consideration was given to the growth of aluminium containing compounds, particularly AlGaSb. Multiple phases were observed under scanning electron microscope showing growth of GaSb regions surrounded by amorphous solid aluminium and/or aluminium oxide phases. The failure of the aluminium to incorporate into the desired crystal structure is speculated to be due to impure precursor introducing oxygen into the films. Additionally, the effectiveness of the gallium precursor compared to the aluminium precursor in helping the removal of the methyl groups at the growth surface, could also promote a preference for GaSb growth.
- Full Text:
- Date Issued: 2020
- Authors: Dobson, Stephen R
- Date: 2020
- Subjects: Gallium arsenide semiconductors , Electronics
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49071 , vital:41598
- Description: In this study, layers of GaSb, InAs and InAsSb are grown by metalorganic vapour phase epitaxy and characterised. Growth is conducted using the precursors of trimethylgallium, trimethylindium, trimethylantimony and tertiarybutylarsine. Focus is then placed on the characterisation of the materials, carried out by the techniques of X-ray diffraction, photoluminescence spectroscopy, Hall measurements and photocurrent spectroscopy. It is observed that V/III ratio plays a vital role in the growth of the GaSb and InAsSb layers. Epilayers of GaSb showed best crystalline quality when a V/III ratio of 1.2 was used at a growth temperature of 600 °C and a cell pressure of 600 Torr. Resultant Hall measurements indicated p-type GaSb. The Hall carrier concentrations of the p-type GaSb samples were analyzed considering electrical neutrality conditions and found to be highly compensated with evidence of band impurity conduction at low measurement temperatures. Both the donor and acceptor concentrations were determined to be of the order of 1016 cm−3 for all samples. For low temperature (< 150 K) a monovalent acceptor concentration is calculated to have an activation energy at approximately 20 meV. At high temperature (> 150 K) a divalent acceptor is extracted with an activation energy varying between samples based on compensation in a range of 90 meV to 70 meV. Photoluminescence measurements show four peaks with recombination mechanisms linked to the native acceptor identified in literature as either the gallium antisite and/or vacant gallium site. A fifth peak observed is attributed to the longitudinal phonon of the native acceptor. InAs and InAsSb epilayer are all grown at a temperature of 600 °C and cell pressure of 600 Torr. InAs is grown at a V/III ratio of 9.5 on GaAs substrate. Photoluminescence of the InAs layer shows two distinct peaks, one of which is an extrinsic band to band recombination. The other is attributed to free electron to acceptor or a donor-acceptor pair transition. An additional weak peak is also observed which is assigned to the longitudinal phonon of the band to band. InAsSb growth was conducted under a range of V/III ratios of 4.8 to 5, with a vapour phase composition of 0.4 to 0.435. Structural analysis via X-ray diffraction showed a 6 % to 12 % solid antimony content. Photoluminescence exhibited a single broad peak for all samples, with extended band tails. Temperature and power dependant analysis of luminescence indicated a convolution of extrinsic band to tail and band to band recombinations. Hall measurements indicated the InAsSb was n-type material with an apparent measured maximum mobility at 120 K of 9.5 × 103 cm2/V.s. and a room temperature apparent mobility of 7.5 × 103 cm2/V.s. Analysis of hall results using a two-layer model calculated a true bulk mobility of the epilayer at room temperature with an increased value of 15.4 × 103 cm2/V.s. The two-layer model details the effects of the surface conduction. From photoconductivity measurements and further analysis a resultant effective lifetime, at room temperature, was found to be on same order of magnitude as that of InAs materials. Application of a single Einstein oscillator extrapolated 0 K energy gaps for two samples of solid Sb contents of 6 % and 12 %, of 354 meV and 332 meV, respectively. Finally consideration was given to the growth of aluminium containing compounds, particularly AlGaSb. Multiple phases were observed under scanning electron microscope showing growth of GaSb regions surrounded by amorphous solid aluminium and/or aluminium oxide phases. The failure of the aluminium to incorporate into the desired crystal structure is speculated to be due to impure precursor introducing oxygen into the films. Additionally, the effectiveness of the gallium precursor compared to the aluminium precursor in helping the removal of the methyl groups at the growth surface, could also promote a preference for GaSb growth.
- Full Text:
- Date Issued: 2020
Decision analysis to inform invasive alien plant management in the Garden Route Biosphere Reserve
- Authors: Masunungure, Current
- Date: 2020
- Subjects: Invasive plants -- South Africa , Alien plants -- South Africa , Biodiversity -- South Africa -- Management , Ecosystem management -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49159 , vital:41606
- Description: Invasive alien plants (IAP) pose significant threats to global economies and biodiversity and are often considered as wicked problems. With an increasing number of IAP and limited resources, their management and decision-making processes are becoming difficult because of uncertainty, multiple and conflicting objectives, and diverse stakeholder views, facts and values. This is particularly challenging given the complex interactions between economic, ecological, and social elements that exist in invaded areas. Consequently, it is important to incorporate new ways of thinking and novel methodologies to improve our understanding of IAP management and the decision-making processes around them, which are currently inadequate. Decision analysis can help with dealing with these challenges and support decision-making under uncertainty. Drawing on the systems thinking approach and the concepts of leverage points, transition management and transformational change, the aim of this thesis was to explore the effectiveness of IAP management and the decision-making process in the Garden Route Biosphere Reserve (GRBR). This was achieved using a mixed methods approach involving: social-ecological inventory (identifying relevant stakeholders); review of literature on the available decision support tools; key informant interviews (stakeholder perspectives on the current decision-making process); and stakeholder workshop and expert consultation (casual loop modelling). The results of this thesis provide evidence that application of the proposed principles of robust decision-making has the potential to overcome the weaknesses of the current decision-making process and as such, enables decision-makers to efficiently allocate resources towards IAS management. A novel causal loop diagram (CLD) was developed to highlight the interconnections between key variables in IAP management and decision-making. This revealed that to transcend ‘policy resistance’ and ‘quickfixes that fail’ archetypes, and improve IAP management, the stakeholders need to consider deep leverage points, for example, fostering trust and shared understanding among different stakeholder groups. These can be realistically maintained over the long-term and can cause a fundamental change in IAP management, rather than focusing on shallow leverage points that are relatively easy to implement but do not result in significant systemic change. The findings of this thesis are flexible and could guide various stakeholder groups at local, national, and international scales in improving the effectiveness of IAP management and decision-making.
- Full Text:
- Date Issued: 2020
- Authors: Masunungure, Current
- Date: 2020
- Subjects: Invasive plants -- South Africa , Alien plants -- South Africa , Biodiversity -- South Africa -- Management , Ecosystem management -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49159 , vital:41606
- Description: Invasive alien plants (IAP) pose significant threats to global economies and biodiversity and are often considered as wicked problems. With an increasing number of IAP and limited resources, their management and decision-making processes are becoming difficult because of uncertainty, multiple and conflicting objectives, and diverse stakeholder views, facts and values. This is particularly challenging given the complex interactions between economic, ecological, and social elements that exist in invaded areas. Consequently, it is important to incorporate new ways of thinking and novel methodologies to improve our understanding of IAP management and the decision-making processes around them, which are currently inadequate. Decision analysis can help with dealing with these challenges and support decision-making under uncertainty. Drawing on the systems thinking approach and the concepts of leverage points, transition management and transformational change, the aim of this thesis was to explore the effectiveness of IAP management and the decision-making process in the Garden Route Biosphere Reserve (GRBR). This was achieved using a mixed methods approach involving: social-ecological inventory (identifying relevant stakeholders); review of literature on the available decision support tools; key informant interviews (stakeholder perspectives on the current decision-making process); and stakeholder workshop and expert consultation (casual loop modelling). The results of this thesis provide evidence that application of the proposed principles of robust decision-making has the potential to overcome the weaknesses of the current decision-making process and as such, enables decision-makers to efficiently allocate resources towards IAS management. A novel causal loop diagram (CLD) was developed to highlight the interconnections between key variables in IAP management and decision-making. This revealed that to transcend ‘policy resistance’ and ‘quickfixes that fail’ archetypes, and improve IAP management, the stakeholders need to consider deep leverage points, for example, fostering trust and shared understanding among different stakeholder groups. These can be realistically maintained over the long-term and can cause a fundamental change in IAP management, rather than focusing on shallow leverage points that are relatively easy to implement but do not result in significant systemic change. The findings of this thesis are flexible and could guide various stakeholder groups at local, national, and international scales in improving the effectiveness of IAP management and decision-making.
- Full Text:
- Date Issued: 2020
Database and guide for Lesotho wool and mohair production and quality
- Authors: Maqalika, Papali Elizabeth
- Date: 2020
- Subjects: Mohair -- Dissertations -- Lesotho , Wool -- Dissertations -- Lesotho Textile fabrics -- Lesotho Textile industry -- Lesotho
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49148 , vital:41605
- Description: Lesotho produces significant quantities of Merino apparel wool and mohair, both of a quality that allows them to compete on the global market and to make a significant contribution to the economy of the country. Nevertheless, very little production and quality data and trends of these fibres have been documented. This is a serious disadvantage in terms of international trading and benchmarking as well as attempts to improve the production and quality of Lesotho wool and mohair. In the light of the aforementioned, the available production and quality data of the past 10 years have been captured and analysed for trends and also benchmarking, where considered applicable. The main focus is on fibre diameter (fineness), staple length, and yield since they largely determine fibre quality, application and price. Some quality related tests were undertaken to fill certain important gaps in the available data. In addition, prickle and medullation were evaluated on representative wool and mohair samples, respectively, because they represent important quality measures for apparel wool and mohair, respectively. It was found that Lesotho wool and mohair are of a fairly good and internationally competitive quality, with the wool having an average fibre diameter (MFD) of ≈20μm, an average staple length of about 64mm, an average VM level of about 4%, an average yield of about 57%, and the annual production being about 4 million kilograms greasy. The average staple length of the mohair was about 140mm, average MFD about 29μm and the average medullation, which unless otherwise specified, refers to the objectionable medullated fibres (kemp type) including the flat medullated fibre, relatively high at about 5.7%. The latter is certainly an area of concern which needs attention and improvement. It was found that the prickle level (Comfort Factor), of some of the wools tested was of such a level as to make the wool suitable for wearing against the skin. With respect to mohair, there is considerable scope to substantially reduce the level of objectionable medullated (kemp style) fibre level through the appropriate breeding interventions. Production of both wool and mohair has increased slightly over the ten years covered by this study. It also became apparent that Lesotho wool and mohair quality and production are greatly influenced by the farming practices and climatic conditions. Greater adoption of the merino sheep breed, sheds/barns and sheep coats are suggested as ways to reduce mortality rate (due to extremely cold temperatures), improve quality and increase yield and production. Some farming practices such as the lack of barns, supplementary feeding and veterinary care present constraints in terms of production of both wool and mohair. The districts in the Highlands region had the highest production of mostly wool, this being ascribed to better pastures, climatic and other conditions conducive to wool and mohair production. Both wool and mohair are considered to have potential for improved quality and production, which could be affected by appropriate interventions by the Small Agricultural and Development Project (SADP) and others through National Wool and Mohair Growers Association (NWMGA). Nevertheless, since the wool and mohair growers (farmers) do not form part of these and other interventions, they do not readily adopt the various strategies and decisions and do not receive the associated benefits immediately. It is therefore advised that local farmers, relevant educators and researchers be represented in policy and other decision making forums. In this way, educational campaigns will be demand driven with greater chance of adoption and success.
- Full Text:
- Date Issued: 2020
- Authors: Maqalika, Papali Elizabeth
- Date: 2020
- Subjects: Mohair -- Dissertations -- Lesotho , Wool -- Dissertations -- Lesotho Textile fabrics -- Lesotho Textile industry -- Lesotho
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49148 , vital:41605
- Description: Lesotho produces significant quantities of Merino apparel wool and mohair, both of a quality that allows them to compete on the global market and to make a significant contribution to the economy of the country. Nevertheless, very little production and quality data and trends of these fibres have been documented. This is a serious disadvantage in terms of international trading and benchmarking as well as attempts to improve the production and quality of Lesotho wool and mohair. In the light of the aforementioned, the available production and quality data of the past 10 years have been captured and analysed for trends and also benchmarking, where considered applicable. The main focus is on fibre diameter (fineness), staple length, and yield since they largely determine fibre quality, application and price. Some quality related tests were undertaken to fill certain important gaps in the available data. In addition, prickle and medullation were evaluated on representative wool and mohair samples, respectively, because they represent important quality measures for apparel wool and mohair, respectively. It was found that Lesotho wool and mohair are of a fairly good and internationally competitive quality, with the wool having an average fibre diameter (MFD) of ≈20μm, an average staple length of about 64mm, an average VM level of about 4%, an average yield of about 57%, and the annual production being about 4 million kilograms greasy. The average staple length of the mohair was about 140mm, average MFD about 29μm and the average medullation, which unless otherwise specified, refers to the objectionable medullated fibres (kemp type) including the flat medullated fibre, relatively high at about 5.7%. The latter is certainly an area of concern which needs attention and improvement. It was found that the prickle level (Comfort Factor), of some of the wools tested was of such a level as to make the wool suitable for wearing against the skin. With respect to mohair, there is considerable scope to substantially reduce the level of objectionable medullated (kemp style) fibre level through the appropriate breeding interventions. Production of both wool and mohair has increased slightly over the ten years covered by this study. It also became apparent that Lesotho wool and mohair quality and production are greatly influenced by the farming practices and climatic conditions. Greater adoption of the merino sheep breed, sheds/barns and sheep coats are suggested as ways to reduce mortality rate (due to extremely cold temperatures), improve quality and increase yield and production. Some farming practices such as the lack of barns, supplementary feeding and veterinary care present constraints in terms of production of both wool and mohair. The districts in the Highlands region had the highest production of mostly wool, this being ascribed to better pastures, climatic and other conditions conducive to wool and mohair production. Both wool and mohair are considered to have potential for improved quality and production, which could be affected by appropriate interventions by the Small Agricultural and Development Project (SADP) and others through National Wool and Mohair Growers Association (NWMGA). Nevertheless, since the wool and mohair growers (farmers) do not form part of these and other interventions, they do not readily adopt the various strategies and decisions and do not receive the associated benefits immediately. It is therefore advised that local farmers, relevant educators and researchers be represented in policy and other decision making forums. In this way, educational campaigns will be demand driven with greater chance of adoption and success.
- Full Text:
- Date Issued: 2020
Data transport over optical fibre for ska using advanced modulation flexible spectrum technology
- Authors: Dlamini, Phumla Patience
- Date: 2020
- Subjects: Fiber optics
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/50666 , vital:42329
- Description: Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA.We optimise the flexible spectrum for real-time dynamic channel wavelength assignment, to ensure optimum network performance. We needed to identify and develop novel hardware and dynamic algorithms for these networks to function optimally to perform critical tasks. Such tasks include wavelength assignment, signal routing, network restoration and network protection. The antennas of the Square Kilometre Array (SKA) network connect to the correlator and data processor in a simple point-to-point fixed configuration. The connection of the astronomer users to the data processor, however, requires a more complex network architecture. This is because the network has users scattered around South Africa, Africa and the whole world. This calls for upgrade of the classical fixed wavelength spectrum grids, to flexible spectrum grid that has improved capacity, reliable, simple and cost-effectiveness through sharing of network infrastructure. The exponential growth of data traffic in current optical communication networks requires higher capacity for the bandwidth demands at a reduced cost per bit. All-optical signal processing is a promising technique to improve network resource utilisation and resolve wavelength contention associated with the flexible spectrum. Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA. Each DWDM channel is capable of 10 Gbps transmission rate, which is sliceable into finer flexible grid 12.5 GHz granularity to offer the network elastic spectrum and channel spacing capable of signal routing and wavelength switching for the scalability of aggregate bandwidth. The variable-sized portions of the flexible spectrum assignment to end users at different speeds depend on bandwidth demand, allowing efficient utilisation of the spectrum resources. The entire bandwidth of dynamic optical connections must be contiguously allocated. However, there is an introduction of spectrum fragmentation due to spectrum contiguity related to the optical channels having different width. Thus large traffic demands are likely to experience blocking regardless of available bandwidth. To minimise the congestion and cost-effectively obtain high performance, the optical network must be reconfigurable, achievable by adding wavelength as an extra degree of freedom for effectiveness. This can introduce colourless, directionless and contentionless reconfigurability to route individual wavelengths from fibre to fibre across multiple nodes to avoid wavelength blocking/collisions, increasing the flexibility and capacity of a network. For these networks to function optimally, novel hardware and dynamic algorithms identification and development is a critical task. Such tasks include wavelength assignment, signal routing, network restoration and network protection. In this work, we for the first time to our knowledge proposed a spectrum defragmentation technique through reallocation of the central frequency of the optical transmitter, to increase the probability of finding a sufficient continuous spectrum. This is to improve network resource utilisation, capacity and resolve wavelength contention associated with a flexible spectrum in optical communication networks. The following chapter provides details on a flexible spectrum in optical fibre networks utilising DWDM, optimising transmitter-receivers, advanced modulation formats, coherent detection, reconfigurable optical add and drop multiplexer (ROADM) technology to implement hardware and middleware platforms which address growing bandwidth demands for scalability, flexibility and cost-efficiency. A major attribute is tunable lasers, an essential component for future flexible spectrum with application to wavelength switching, routing, wavelength conversion and ROADM for the multi-node optical network through spectrum flexibility and cost-effective sharing of fibre links, transmitters and receivers. Spectrum slicing into fine granular sub-carriers and assigning several frequency slots to accommodate diverse traffic demands is a viable approach. This work experimentally presents a spectral efficient technique for bandwidth variability, wavelength allocation, routing, defragmentation and wavelength selective switches in the nodes of a network, capable of removing the fixed grid spacing using low cost, high bandwidth, power-efficient and wavelength-tunable vertical-cavity surface-emitting laser (VCSEL) transmitter directly modulated with 10 Gbps data. This to ensure that majority of the spectrum utilisation at finer channel spacing, wastage of the spectrum resource as caused by the wavelength continuity constraint reduction and it improves bandwidth utilisation. The technique is flexible in terms of modulation formats and accommodates various formats with spectrally continuous channels, fulfilling the future bandwidth demands with transmissions beyond 100 Gbps per channel while maintaining spectral efficiency.
- Full Text:
- Date Issued: 2020
- Authors: Dlamini, Phumla Patience
- Date: 2020
- Subjects: Fiber optics
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/50666 , vital:42329
- Description: Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA.We optimise the flexible spectrum for real-time dynamic channel wavelength assignment, to ensure optimum network performance. We needed to identify and develop novel hardware and dynamic algorithms for these networks to function optimally to perform critical tasks. Such tasks include wavelength assignment, signal routing, network restoration and network protection. The antennas of the Square Kilometre Array (SKA) network connect to the correlator and data processor in a simple point-to-point fixed configuration. The connection of the astronomer users to the data processor, however, requires a more complex network architecture. This is because the network has users scattered around South Africa, Africa and the whole world. This calls for upgrade of the classical fixed wavelength spectrum grids, to flexible spectrum grid that has improved capacity, reliable, simple and cost-effectiveness through sharing of network infrastructure. The exponential growth of data traffic in current optical communication networks requires higher capacity for the bandwidth demands at a reduced cost per bit. All-optical signal processing is a promising technique to improve network resource utilisation and resolve wavelength contention associated with the flexible spectrum. Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA. Each DWDM channel is capable of 10 Gbps transmission rate, which is sliceable into finer flexible grid 12.5 GHz granularity to offer the network elastic spectrum and channel spacing capable of signal routing and wavelength switching for the scalability of aggregate bandwidth. The variable-sized portions of the flexible spectrum assignment to end users at different speeds depend on bandwidth demand, allowing efficient utilisation of the spectrum resources. The entire bandwidth of dynamic optical connections must be contiguously allocated. However, there is an introduction of spectrum fragmentation due to spectrum contiguity related to the optical channels having different width. Thus large traffic demands are likely to experience blocking regardless of available bandwidth. To minimise the congestion and cost-effectively obtain high performance, the optical network must be reconfigurable, achievable by adding wavelength as an extra degree of freedom for effectiveness. This can introduce colourless, directionless and contentionless reconfigurability to route individual wavelengths from fibre to fibre across multiple nodes to avoid wavelength blocking/collisions, increasing the flexibility and capacity of a network. For these networks to function optimally, novel hardware and dynamic algorithms identification and development is a critical task. Such tasks include wavelength assignment, signal routing, network restoration and network protection. In this work, we for the first time to our knowledge proposed a spectrum defragmentation technique through reallocation of the central frequency of the optical transmitter, to increase the probability of finding a sufficient continuous spectrum. This is to improve network resource utilisation, capacity and resolve wavelength contention associated with a flexible spectrum in optical communication networks. The following chapter provides details on a flexible spectrum in optical fibre networks utilising DWDM, optimising transmitter-receivers, advanced modulation formats, coherent detection, reconfigurable optical add and drop multiplexer (ROADM) technology to implement hardware and middleware platforms which address growing bandwidth demands for scalability, flexibility and cost-efficiency. A major attribute is tunable lasers, an essential component for future flexible spectrum with application to wavelength switching, routing, wavelength conversion and ROADM for the multi-node optical network through spectrum flexibility and cost-effective sharing of fibre links, transmitters and receivers. Spectrum slicing into fine granular sub-carriers and assigning several frequency slots to accommodate diverse traffic demands is a viable approach. This work experimentally presents a spectral efficient technique for bandwidth variability, wavelength allocation, routing, defragmentation and wavelength selective switches in the nodes of a network, capable of removing the fixed grid spacing using low cost, high bandwidth, power-efficient and wavelength-tunable vertical-cavity surface-emitting laser (VCSEL) transmitter directly modulated with 10 Gbps data. This to ensure that majority of the spectrum utilisation at finer channel spacing, wastage of the spectrum resource as caused by the wavelength continuity constraint reduction and it improves bandwidth utilisation. The technique is flexible in terms of modulation formats and accommodates various formats with spectrally continuous channels, fulfilling the future bandwidth demands with transmissions beyond 100 Gbps per channel while maintaining spectral efficiency.
- Full Text:
- Date Issued: 2020
Commercial maritime higher education needs in South Africa
- Authors: Allison, Lee-Anne
- Date: 2020
- Subjects: Education, Higher -- Curricula , Education, Higher -- Research Merchant marine Shipping -- Economic aspects
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/50350 , vital:42111
- Description: Seaborne cargo trade accounts for over 80% of the physical volume of global trade. Maritime transport thus fulfils an integral function in the economy of the world. South Africa generates approximately 3.5% of the world’s seaborne trade by value and 1.61% by tonnage; but the business of shipping all that cargo is undertaken by foreign firms. Operation Phakisa, the Comprehensive Maritime Transport Policy and the South African Maritime Road Map, in pursuance of the National Development Plan, aim to revive the commercial maritime sector. In order to meet the demand for the skills and innovative abilities sought at executive and managerial levels in the commercial maritime sector, higher education in the knowledge of maritime business is increasingly becoming a prerequisite. Investment in higher education of quality and relevance in the maritime field would contribute to achieving the goals of the government for harnessing the potential of South Africa’s blue economy. The literature is researched in order to establish an authoritative view that the knowledge and the inspiration for entrepreneurial activity in the maritime sector can be imparted through higher education; and for example, that a viable shipping sector can contribute to the growth of a country’s economy. The South African maritime sector is then described. The commercial maritime higher education available at universities and other institutions of higher learning in South Africa, as well as in other African countries and elsewhere in the world, is examined, in order to be able to identify the degree and diploma courses available. Maritime courses imply not only the content of the educational material, but also the method whereby the knowledge is instilled in learners, and which extends well beyond the classroom. A survey, by way of the personal interviews of leaders in maritime business, maritime government affairs, and academics teaching maritime topics, is then undertaken to ascertain their views on the education required to promote the maritime sector in South Africa, using the list of subjects available for study worldwide, to assist their choice. The literature research and the interview survey by design also enable the secondary aims of the study to be achieved. Those aims include determining how awareness of the maritime domain could be raised and how co-operation between academia, business and government, known as the triple helix could be organised, to promote the growth of the maritime sector. The results of the survey are analysed and tabulated, in order to illustrate the extent of the agreement between those interviewed and the conclusions reached. These conclusions establish: that the commercial maritime education currently available in South Africa, is inadequate to meet the aim of the government to the sector; that a post-graduate degree in the specified maritime studies incorporating a period of internship, and following on a first degree in business subjects, is required; that a triple helix of co-operation between academia, business and the government is essential to grow the commercial maritime sector in which South African entrepreneurs educated in such business will have the advantage; that greater awareness of the maritime domain is essential in South Africa if entrepreneurship in maritime business is to be cultivated; and that such awareness can be cultivated in various ways; but it should start by including more maritime topics in the current school curricula.
- Full Text:
- Date Issued: 2020
- Authors: Allison, Lee-Anne
- Date: 2020
- Subjects: Education, Higher -- Curricula , Education, Higher -- Research Merchant marine Shipping -- Economic aspects
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/50350 , vital:42111
- Description: Seaborne cargo trade accounts for over 80% of the physical volume of global trade. Maritime transport thus fulfils an integral function in the economy of the world. South Africa generates approximately 3.5% of the world’s seaborne trade by value and 1.61% by tonnage; but the business of shipping all that cargo is undertaken by foreign firms. Operation Phakisa, the Comprehensive Maritime Transport Policy and the South African Maritime Road Map, in pursuance of the National Development Plan, aim to revive the commercial maritime sector. In order to meet the demand for the skills and innovative abilities sought at executive and managerial levels in the commercial maritime sector, higher education in the knowledge of maritime business is increasingly becoming a prerequisite. Investment in higher education of quality and relevance in the maritime field would contribute to achieving the goals of the government for harnessing the potential of South Africa’s blue economy. The literature is researched in order to establish an authoritative view that the knowledge and the inspiration for entrepreneurial activity in the maritime sector can be imparted through higher education; and for example, that a viable shipping sector can contribute to the growth of a country’s economy. The South African maritime sector is then described. The commercial maritime higher education available at universities and other institutions of higher learning in South Africa, as well as in other African countries and elsewhere in the world, is examined, in order to be able to identify the degree and diploma courses available. Maritime courses imply not only the content of the educational material, but also the method whereby the knowledge is instilled in learners, and which extends well beyond the classroom. A survey, by way of the personal interviews of leaders in maritime business, maritime government affairs, and academics teaching maritime topics, is then undertaken to ascertain their views on the education required to promote the maritime sector in South Africa, using the list of subjects available for study worldwide, to assist their choice. The literature research and the interview survey by design also enable the secondary aims of the study to be achieved. Those aims include determining how awareness of the maritime domain could be raised and how co-operation between academia, business and government, known as the triple helix could be organised, to promote the growth of the maritime sector. The results of the survey are analysed and tabulated, in order to illustrate the extent of the agreement between those interviewed and the conclusions reached. These conclusions establish: that the commercial maritime education currently available in South Africa, is inadequate to meet the aim of the government to the sector; that a post-graduate degree in the specified maritime studies incorporating a period of internship, and following on a first degree in business subjects, is required; that a triple helix of co-operation between academia, business and the government is essential to grow the commercial maritime sector in which South African entrepreneurs educated in such business will have the advantage; that greater awareness of the maritime domain is essential in South Africa if entrepreneurship in maritime business is to be cultivated; and that such awareness can be cultivated in various ways; but it should start by including more maritime topics in the current school curricula.
- Full Text:
- Date Issued: 2020
A transportation management framework for the Polokwane local municipality during Zion Christian Church (ZCC) Easter weekend pilgrimage
- Authors: Mathebula, Andrew Mabila
- Date: 2020
- Subjects: Transportation -- Management , Urban transportation -- Planning Urban transportation -- Management Christian pilgrims and pilgrimages
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/46152 , vital:39509
- Description: The study investigated the impact of the high volume of vehicular traffic on pilgrims and the community during the Zion Christian Church (ZCC) Easter weekend pilgrimage. The researcher adopted an interpretivist research philosophy, and thus attempted to understand policy, planning, and management of the ZCC Easter pilgrimage through meanings that municipal officials assign to them. The study employed the action research approach by collaborating with the Polokwane Local Municipality (PLM) with a view to evolving lasting solutions to traffic congestion during the Easter weekend. The researchers used the seven-step model proposed by Van Tonder and Dietrichsen (Van Tonder and Dietrichsen, 2008). The justification of the model is that it is aligned with the action research model of Organisational Development (OD). It requires that a diagnosis process should be collaborative and participative towards offering solutions to organisational challenges as opposed to imposing a unilateral theoretical generated solution. This model also fits the ontological stance of the researchers which assumes that reality is co-constructed through engagement with other stakeholders. The researcher conducted semi-structured individual and focus groups discussion (FGD) using openended guides. The data from the informants were collected until a point of saturation. In addition to facilitation FGD discussion, the researcher made his own personal reflection of the participatory action research (PAR). A content analysis method was used to synthesise the qualitative data. The contents were extracted from transcribed interviews. The researcher carefully reviewed the notes several times and coded the notes independently. After that, the researcher coded the codes with each other for any potential contradiction. These codes were converted into themes and sub-themes. The qualitative content analysis process, led by the researcher, was both inductive and deductive. Prior to the inductive process, the researcher listened carefully to the audio recordings transcriptions to get a general understanding of participants’ experiences. The findings indicate that the South African transportation planning approach is ossified and divorced from reality. There is a lacuna to address peak traffic challenges during the Easter weekend and the festive season. It is notable that the government-led seasonal road safety campaigns such as ‘Arrive Alive’ are curiously inadequate to address peak traffic and road accidents challenges in South Africa during the ZCC Easter pilgrimage. The transportation management framework for the PLM as well as a peak traffic standard were developed as part of the study recommendations. These recommendations augur a shift to transport planning in South Africa.
- Full Text:
- Date Issued: 2020
- Authors: Mathebula, Andrew Mabila
- Date: 2020
- Subjects: Transportation -- Management , Urban transportation -- Planning Urban transportation -- Management Christian pilgrims and pilgrimages
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/46152 , vital:39509
- Description: The study investigated the impact of the high volume of vehicular traffic on pilgrims and the community during the Zion Christian Church (ZCC) Easter weekend pilgrimage. The researcher adopted an interpretivist research philosophy, and thus attempted to understand policy, planning, and management of the ZCC Easter pilgrimage through meanings that municipal officials assign to them. The study employed the action research approach by collaborating with the Polokwane Local Municipality (PLM) with a view to evolving lasting solutions to traffic congestion during the Easter weekend. The researchers used the seven-step model proposed by Van Tonder and Dietrichsen (Van Tonder and Dietrichsen, 2008). The justification of the model is that it is aligned with the action research model of Organisational Development (OD). It requires that a diagnosis process should be collaborative and participative towards offering solutions to organisational challenges as opposed to imposing a unilateral theoretical generated solution. This model also fits the ontological stance of the researchers which assumes that reality is co-constructed through engagement with other stakeholders. The researcher conducted semi-structured individual and focus groups discussion (FGD) using openended guides. The data from the informants were collected until a point of saturation. In addition to facilitation FGD discussion, the researcher made his own personal reflection of the participatory action research (PAR). A content analysis method was used to synthesise the qualitative data. The contents were extracted from transcribed interviews. The researcher carefully reviewed the notes several times and coded the notes independently. After that, the researcher coded the codes with each other for any potential contradiction. These codes were converted into themes and sub-themes. The qualitative content analysis process, led by the researcher, was both inductive and deductive. Prior to the inductive process, the researcher listened carefully to the audio recordings transcriptions to get a general understanding of participants’ experiences. The findings indicate that the South African transportation planning approach is ossified and divorced from reality. There is a lacuna to address peak traffic challenges during the Easter weekend and the festive season. It is notable that the government-led seasonal road safety campaigns such as ‘Arrive Alive’ are curiously inadequate to address peak traffic and road accidents challenges in South Africa during the ZCC Easter pilgrimage. The transportation management framework for the PLM as well as a peak traffic standard were developed as part of the study recommendations. These recommendations augur a shift to transport planning in South Africa.
- Full Text:
- Date Issued: 2020