A Ranking Framework for Higher Education Institutions in South Africa
- Authors: Kanyutu, Teresia Watiri
- Date: 2020
- Subjects: Education, Higher -- South Africa
- Language: English
- Type: Thesis , Doctoral , DBA
- Identifier: http://hdl.handle.net/10948/48246 , vital:40746
- Description: In the past 16 years, the use of League Tables and Rankings (LTRs) as a tool to rank or measure the performance of Higher Education Institutions (HEIs) has grown in popularity. As a global practice, LTR outcomes are influencing how policies are developed and implemented within the Higher Education (HE) sector. Studies indicate that based on individual information requirements, HE stakeholders are using LTRs to compare HEIs with each other and make informed comparisons and decisions. University directors use LTRs as a basis for institutional strategic planning, reputation building and policy making, while students use LTRs to compare HEIs and make university of choice decisions. Further studies confirm that governments use LTRs for national higher education policy making, university funding, foreign partnerships and resource allocation. Globally and at a national level, the higher education sector has witnessed policy and structural changes, many of which are due to the increase in the use of international rankings and league tables. Despite the opportunities presented by participating in the production of and using LTRs, the ranking practice is contentious. Amongst the issues disputed by the HE stakeholders are the methodologies and criteria used in the production and publication of LTRs. Higher education experts argue that LTRs tend to favour institutional research output and ignore the teaching and learning function of HEIs. As a result, the ranking criteria differ across the higher education ranking institutions and their publication outcomes, which causes skepticism across the HE sector. Research indicates that these ranking criteria are often discussed from the standpoint of governments, the higher education management and the ranking institutions producing these LTR publications. The opinions of the students on the suitable ranking criteria used by ranking institutions lack. This study aims to address that gap. This study investigates the applicable criteria for ranking HEIs in South Africa, from the perspective of students. Building on the existing ranking criteria for three global and popular ranking institutions namely, Academic Ranking of World Universities (ARWU), Times Higher Education World University Ranking (THEWUR) and Quacquarelli Symonds World University Ranking (QSWUR), the study poses the question; “What framework can be used to rank HEIs in South Africa, from a student’s perspective?” The study argues that although some HEIs in South Africa have in the past and most recently appeared in the global LTRs, the current choice of ranking criteria fails to consider the perspectives of the students, who are major consumers of LTRs and important stakeholders in the HE sector. A positivistic research method was used, based on a review of literature on the current ranking criteria for the selected global ranking institutions. An empirical study was conducted amongst students in a South African Comprehensive University. An online survey was distributed through convenient and snowball sampling, where the students were requested to participate in the survey and share the questionnaire link with others. Eight hundred and eighty six (886) responses were received and used for the data analyses of this study.
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- Date Issued: 2020
Non-marital fertility in South Africa: trends, determinants and implications
- Authors: Kara, Reesha
- Date: 2020
- Subjects: Fertility, Human -- South Africa , Child rearing -- South Africa , Parenting -- South Africa , Motherhood -- South Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/165620 , vital:41264
- Description: Background: Non-martial fertility is traditionally associated with teenage pregnancy however international and South African literature has detailed increases in the number of adult women who are having children outside of a marriage. South African literature on non-marital fertility is sparse as it lacks a national overview of the trends and determinants of non-marital fertility among women aged 30 and older. The aim of this study was to present a national overview of non-marital fertility among women aged 30 and older. South African’s attitudes to and opinions of non-marital fertility were also investigated, and the lived realities of older mothers were explored. Methods: A mixed-methods research design was employed where the General Household Survey, National Income Dynamics Study and the South African Social Attitudes Survey were the main data sources. Using these data sets, descriptive and inferential statistics were computed using Stata. Using purposive and snowball sampling, four never-married older mothers (NMOMs) from KwaZulu-Natal (Durban) were identified as research participants. The in-depth life histories of these women were collected through face-to- face semi-structured interviews. Results: The results show an 18.43% increase in never-married mothers aged 15- 49 between 2002 and 2017 and interestingly, this increase is not necessarily driven by older mothers (30-49). NMOMs belonged to households with a lower average per capita total monthly household income (R1873.91) compared to all mothers aged 30-49 (R3428.76). NMOMs were also more likely to live in female-headed households (89.52%), to be household heads (64.22%) and to live in traditional areas (35.72%). Between 2002 and 2017, there was a 76.76% increase in mothers (aged 30-49) who were never married and a 7.74% decrease in those who were married, indicating a change in the marital profile of mothers. Despite this national increase in non-marital fertility, South African’s believe that premarital sexual activity is wrong, and that childbearing should take place within a marriage. Similar sentiments were echoed in the in-depth life histories as being the sole breadwinner and primary caregiver, the research participants experienced challenges as single mothers. Conclusion and recommendations: The study has found that there has been an increase in non-marital fertility in South Africa between 2002 and 2017 and that there is an economic element to non-marital fertility in the country. Additional research into non-marital fertility at a national level is recommended with a focus on all women aged 15-49.
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- Date Issued: 2020
The impact of the slum upgrading approach on the livelihoods of scheme participants in Uganda : using the sustainable livelihoods framework
- Authors: Karungi, Doreen
- Date: 2020
- Subjects: Slums -- Public welfare -- Uganda
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48412 , vital:40874
- Description: International and local agencies recommend implementing slum upgrading projects in slum areas for slum improvement. However, with no model or guiding principles provided to slum upgrading project implementers on how to upgrade a slum, slum clearance and redevelopment are implemented rather than slum upgrading consequently projects fail to benefit the target group, slum dwellers. Data collection, took place in five areas in Uganda that implemented slum upgrading. In depth interviews were held with project beneficiaries, local council officials and association executives, and government officials at the Ministry of Lands, Housing and Urban Development. Field observation, and document analysis was carried out. Data analysis involved the use of the sustainable livelihoods framework. This study demonstrates that the slum upgrading approach adopted in Uganda exhibited low sustainability and undercut the sustainability of livelihoods of scheme participants. Slum dwellers faced vulnerabilities from loss of land, characterized by rights based actions resulting in minimal to no compensation or eviction and loss of existing livelihoods. Slum upgrading projects introduced new livelihood opportunities that were too few for slum dwellers, were not sustainable and ended during or with project implementation, leaving beneficiaries without employment or income opportunities. Increased vulnerability was observed as slum dwellers that did not benefit from the project were displaced to worse conditions while slum dwellers that benefitted, project beneficiaries remained poor and in debt, with project loans to repay. Although project beneficiaries were provided with access to assets, they were unable to draw on these to build their livelihoods. Some beneficiaries sold plots and project houses allocated to them and moved to adjacent slums, where they lived in worse conditions. At the time of the current research, good quality houses in the slum upgrading areas did not belong to the original beneficiaries old dilapidated structures were occupied by project beneficiaries. This study shows that income earning activities carried out at the time of the study were similar to those carried out prior to the introduction of slum upgrading in project areas and were destroyed during project implementation or banned by implementers. These activities were however carried out in incomplete houses, vacant plots, temporary structures in project areas and in adjacent swamps and forest. Generally, after completion of slum upgrading projects, project areas, adjacent swamps and forest were characterized by haphazard developments including: rentals, informal businesses, farming, brewing and distilling local alcohol used by beneficiaries to derive livelihoods, in other words, slums were recreated, a problem slum upgrading project implementers set out to solve - except in one study area where the project was implemented differently as a result of persist rights based actions.
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- Date Issued: 2020
The effects of economic and political instability on decentralised secondary schools in Mashonaland Central Province, Zimbabwe: a case study
- Authors: Katsinde, Tapfuiwa James
- Date: 2020
- Subjects: Education, Secondary -- Political aspects -- Zimbabwe , Political violence -- Zimbabwe , Zimbabwe -- Economic conitions -- 1980- , Zimbabwe -- Politics and government -- 1980-
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/165610 , vital:41263
- Description: The purpose of the study was to analyse the effects of economic and political instability on decentralised secondary schools in Mashonaland Central Province, Zimbabwe between 2000 and 2017. Previous studies in Zimbabwe and elsewhere have shown that schools were negatively affected by economic and political instability. This study adds to this literature by using habitus as a conceptual framework. This was a qualitative study which made use of a multi-case research design. Data was collected using focus group discussions, interviews and document analysis. Eight research sites in the form of secondary schools in four districts were used. Data analysis was done using theoretical prepositions guided by research objectives and research questions. Data presentations was characterised by quotes of participants. Trustworthiness based on dependability, credibility, transferability and conformability formed the basis of quality assurance measures. The study revealed that economic and political instability had similar negative results in the field of secondary schools in the province. Economic instability negatively affected school activities which included teaching and learning, administration and development work. In addition economic instability affected individual secondary school actors psychologically. Economic instability affected relations among the secondary school actors by aggravating already existing contestations amongst actors. Similarly, political instability affected secondary school activities such as teaching and learning, school administration, development, donations and social benefits. Secondary school actors were individually affected psychologically and through physical abuse and the way they responded to political instability. The study has shown that decentralised secondary schools found it difficult to solve the problems introduced by economic and political instability especially when the instabilities occurred within the difficulties of the broader Zimbabwean context. It is therefore recommended that decentralised secondary schools should be assisted financially and with resources to withstand economic challenges. There is a need to protect secondary schools from political activities and activists as these have devastating effects on education if allowed to have a free reign. Further similar research is recommended for other provinces in the country.
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- Date Issued: 2020
Invasion status and impact potential of Florida bass Micropterus floridanus in South Africa
- Authors: Khosa, Dumisani
- Date: 2020
- Subjects: Micropterus floridanus , Florida largemouth bass -- South Africa , Black bass -- South Africa , Micropterus floridanus -- South Africa -- Habitat , Florida largemouth bass -- South Africa -- Habitat , Black bass -- South Africa -- Habitat , Introduced fishes -- Environmental aspects -- South Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/165733 , vital:41276
- Description: In South Africa, the introduction of alien fishes was largely driven by the development of recreational fishing opportunities. Government-backed programmes resulted in the introduction of four Black Bass species: Micropterus salmoides, Micropterus dolomieu, Micropterus punctulatus and Micropterus floridanus. These species are regarded as the primary threat to native biota and there is an urgent need to assess their spread and impacts. This thesis focuses on: assessing the current distribution of all four Black Basses; using genetic techniques to establish the extent of hybridisation between M. salmoides and M. floridanus, and using functional responses to assess the impact potential of M. salmoides and M. floridanus under the context dependence of temperatures and habitat complexity. Maximum entropy modelling of habitat suitability for Black Bass highlighted that M. salmoides had broad climatic suitability across South Africa, while suitability for M. dolomieu and M. punctulatus was restricted to the Cape Fold Ecoregion. An extensive area-based invasion debt was observed for all Micropterus spp. To better understand the dynamics of hybridisation between M. salmoides and M. floridanus, 38 species-diagnostic single nucleotide polymorphism was used to screen Black Bass populations from the Breede River and Kowie River catchments. Micropterus salmoides alleles were more prevalent than M. floridanus in both the Breede River catchments (69.1% and 30.9%, respectively) and Kowie River catchments (63.3% and 36.7%, respectively). However, isolated populations found in dams (reservoirs) remained free from hybridisation. To compare resource utilisation (i.e. per capita effects) between M. salmoides and M. floridanus, two experimental chapters were designed. Chapter 4 focuses on how temperature mitigates per capita effects between the two Black Basses. There was a significant decrease in per capita effects for M. salmoides with increasing temperatures, while the converse was true for M. floridanus. Chapter 5 gives an account of the influence of habitat complexity on per capita effects. The results showed that habitat complexity did mitigate per capita effects, specifically on M. floridanus, which showed a significant drop in per capita effects; however, no significant difference was recorded for M. salmoides. In the two experimental chapters, M. floridanus exhibited a superior per capita effect compared to M. salmoides, implying higher predation impact on native biota.
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- Date Issued: 2020
Contesting boundaries: a case of municipal demarcation disputes in Vuwani Vhembe District
- Authors: Khowa, Thandeka Promise
- Date: 2020
- Subjects: Geographical boundaries
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/50767 , vital:42670
- Description: The research study in Vuwani Vhembe district sought to investigate demarcation disputes, the relationship between service delivery and demarcation disputes. The study further investigates the role of municipal demarcation board and local government adherence to sound governance principles and the causes of the demarcation dispute in Vuwani. The study additionally examines the conceptions and misconceptions, their impact on the current demarcation disputes in Vuwani. It further intended to establish the role and involvement of Vuwani stakeholders such as traditional structures/ leaders, civil unions, community members etc. in the processes of demarcating Vuwani. “What is the cause of Vuwani community member’s rejection of the re-demarcation, which is said to correct the past spatial injustices and promote municipal sizing, thus enabling better performance in service provision by municipalities?” The study employed a mixed-method involving the use of both quantitative (mini-survey) and qualitative (use of in-depth, semi structures interviews and focus group discussions). Research findings suggest that re-demarcation is a sensitive aspect/process in South Africa, mainly due to the past Apartheid era. There was forceful removal of people from their land supported by Apartheid legislation such as the Native Land Act 1913, Group Act 1950, Native Resettlement Act 1954 etc. Thus, fears of the past Apartheid system cloud any attempt to correct spatial injustices of the country. The new democratic South African government, therefore, needs to be cautious in its acts to correct the spatial injustices, thus adhering to sound governance principles. Findings reveal that several misconceptions and lack of adherence of good governance principles by the Municipal Demarcation Board and Local government have, to some extent, fueled the demarcation disputes in Vuwani. Municipal performance in the rendering of service delivery has a major impact and contributes to the community’s acceptance or rejection of demarcation/ amalgamations. The study further reveals that in Vuwani municipal performance with the establishment of the new Collins Chabane municipality has been clouded by fear of the unknown as this form of “demarcation of establishing a new municipality” altogether is relatively new. Rural land authority, the role of traditional leaders, ethnicity ties have all been found to have contributed to the disputes in Vuwani. Limpopo Province is home to three ethnic groups, namely, vaVhenda, baPedi and xiTsonga. The study findings have presented traits of tribalism as contributing to on-going demarcation disputes in Vuwani.
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- Date Issued: 2020
Towards a community-based model for Agricultural development in Uganda : a case study of Kumi and Gomba districts
- Authors: Kiggundu, Joseph
- Date: 2020
- Subjects: Agricultural development projects -- Uganda
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48654 , vital:41056
- Description: This study intended to design a community-based model for agricultural development in Uganda, using Kumi and Gomba districts as case studies. The surge in attention towards community-based development is attributed to the growing challenges posed by the traditional approaches to community development, dominated by top-down mechanisms during the planning, implementation, management, monitoring, and evaluation phases of community development programmes. Driven by Robert Chambers and Conway’s theoretical perspectives, this study discusses that a community-based model is capable of filling knowledge gaps, not only in scientific research, but also in the community development process of many developing nations, such as Uganda. In this study particularly, a community-based approach has been identified as the better option in aiding and facilitating the current government efforts to transform the agricultural sector from its predominantly subsistence nature to commercial orientation. It has been acknowledged that the Ugandan government and its development partners do realise the significant role agriculture plays in directly or indirectly impacting the social welfare of Ugandans. The agricultural sector has been identified as a major source of livelihood for most rural Ugandans (over 95% depend on it for food, employment and income). Unfortunately, even with such recognition, coupled with many reforms initiated by government and supported by various development partners who have invested huge sums of money into the sector, agricultural productivity and profitability has remained extremely low. Most rural Ugandans still languish in abject poverty, hunger, malnutrition, vulnerability and powerlessness. This study has established that, while the agricultural sector in Uganda suffers from enormous institutional, technological, market, research and land-oriented challenges, if all these factors are kept constant, an effective community-based approach is capable of facilitating effective planning, implementation, management, monitoring, and evaluation of agricultural reforms, for increased agricultural productivity and profitability hence the improved quality of life of Ugandans. A qualitative elicitation interviewing technique involving in-depth discussions with agricultural extension workers, community development officers, representatives from NGOs, local farmers, farmers’ associations, local and religious leaders as well as key persons from the Ministry of Agriculture and other line ministries was conducted. The participants were selected through chain referrals until the level of theoretical saturation. In addition, directed field observations, document analysis and key informant interviews with other respondents selected through theoretical sampling enhanced the robustness of data acquisition methods. Group-based participatory data analysis and reflexive pragmatism also enhanced the rigour and quality of research findings intended to balance the knowledge generated from the recognised scientific audience and the views of the important but unknown “knowledge generators” (the local experts).The key findings indicate that, historically and currently, agriculture has been and is the predominant community development activity at household, community and national levels in Uganda. It is also anticipated that agriculture will remain a major contributor to the national economic development of Uganda even over the next hundred years. The efforts by government and its development partners to transform the sector are therefore justified by the sector’s strategic importance. It has been found out that although the sector faces huge challenges, there are numerous opportunities for the sector to become a driver of Uganda’s socio-economic development. A community-based model has been proposed as a viable option for facilitating faster agricultural development in Uganda, where technocratic developers tend to impose development reforms on local people. With the traditional approaches to planning and implementation, it was thought that local people do not know what they want, they are illiterate and ignorant and therefore incapable of driving government crafted programmes for effective change. From the proposed model, government technocratic development agents should engage local farmers who practically experience poverty, powerlessness, hunger, malnutrition and vulnerability, to jointly craft effective agricultural reforms that are not only life-changing, but also relevant and sustainable within the confines of community needs. Under this approach, the designers, planners, implementers, monitors, and evaluators, whether of government-initiated reforms, or initiatives from other development agencies, should learn to treat local people as subjects of the community development processes, as opposed to the traditional top-down mechanisms which view them as objects to be used and abused. The involvement of local experts during the planning, implementation, and management of development reforms, should cease to be applied as merely routine fulfilment of donor conditionality and requirements. Rather, the participation of local farmers during all phases of community programming should become intentional and consciously aimed at empowering local people to actively participate in the making of decisions critical to their own development.
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- Date Issued: 2020
Computer aided approaches against Human African Trypanosomiasis
- Authors: Kimuda, Magambo Phillip
- Date: 2020
- Subjects: African trypanosomiasis , African trypanosomiasis -- Chemotherapy , Genomics , Macrophage migration inhibitory factor , Trypanosoma brucei , Pteridines , Tetrahydrofolate dehydrogenase , Adenylic acid , Molecular dynamics , Principal components analysis , Bioinformatics , Single nucleotide polymorphisms , Single Nucleotide Variants , Candidate Gene Association Study (CGAS)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/142542 , vital:38089
- Description: The thesis presented here is divided into two parts under a common theme that is the use of computer based tools, genomics, and in vitro experiments to develop innovative ways of tackling Human African Trypanosomiasis (HAT). Part I of this thesis focused on the human host genetic determinants while Part II focused on the discovery of novel chemotherapeutics against the parasite. Part I is further sub-divided into two parts: The first involves a Candidate Gene Association Study (CGAS) on an African population to identify genetic determinants associated with disease and/or susceptibility to HAT. The second involves studying the effects of missense Single Nucleotide Variants (SNVs) on protein structure, dynamics, and function using Macrophage Migration Inhibitory Factor (MIF) as a case study. Part II is also sub-divided into two parts: The first involves a computer based rational drug discovery of potential inhibitors against the Trypanosoma the folate pathway; particularly by targeting Trypanosoma brucei Pteridine Reductase (TbPTR1) which is an enzyme used by trypanosomes to overcome T. brucei Dihydrofolate Reductase (TbDHFR) inhibition. Lastly the derivation of CHARMM force-field parameters that can be used to accurately model the geometry and dynamics of the T. brucei Phosphodiesterase B1 enzyme (TbrPDEB1) bimetallic active site center. The derived parameters were then used in MD simulations to characterise protein-ligand residue interactions that are important in TbrPDEB1 inhibition with the goal of targeting the cyclic Adenosine Monophosphate (cAMP) signalling pathway. In the CGAS we were unable to detect any genetic associations in the Ugandan cohort analysed that passed correction for multiple testing in spite of the study being sufficiently powered. Additionally, our study found no association of the Apo lipoprotein 1 (APOL1) G2 allele association with protection against acute HAT that has been previously reported. Future investigations for example, Genome Wide Association Studies using larger samples sizes (>3000 cases and controls) are required. Macrophage migration inhibitory factor (MIF) is a cytokine that is important in both innate and adaptive immunity that has been shown to play a role in T. brucei pathogenicity using murine models. A total of 27 missense SNVs were modelled using homology modelling to create MIF protein mutants that were investigated using in silico effect prediction tools, molecular dynamics (MD), Principal Component Analysis (PCA), and Dynamic Residue Network (DRN) analysis. Our results demonstrate that mutations P2Q, I5M, P16Q, L23F, T24S, T31I, Y37H, H41P, M48V, P44L, G52C, S54R, I65M, I68T, S75F, N106S, and T113S caused significant conformational changes. Further, DRN analysis showed that residues P2, T31, Y37, G52, I65, I68, S75, N106, and T113S are part of a similar local residue interaction network with functional significance. These results show how polymorphisms such as missense SNVs can affect protein conformation, dynamics, and function. Trypanosomes are auxotrophic for folates and pterins but require them for survival. They scavenge them from their hosts. PTR1 is a multifunctional enzyme that is unique to trypanosomatids that reduces both pterins and folates. In the presence of DHFR inhibitors, PTR1 is over-expressed thus providing an escape from the effects of DHFR inhibition. Both TbPTR1 and TbDHFR are pharmacologically and genetically validated drug targets. In this study 5742 compounds were screened using molecular docking, and 13 promising binding modes were further analysed using MD simulations. The trajectories were analysed using RMSD, Rg, RMSF, PCA, Essential Dynamics Analysis (EDA), Molecular Mechanics Poisson–Boltzmann surface area (MM-PBSA) binding free energy calculations, and DRN analysis. The computational screening approach allowed us to identify five of the compounds, named RUBi004, RUBi007, RUBi014, RUBi016 and RUBi018 that exhibited antitrypanosomal growth activities against trypanosomes in culture with IC50 values of 12.5 ± 4.8 μM, 32.4 ± 4.2 μM, 5.9 ± 1.4 μM, 28.2 ± 3.3 μM, and 9.7 ± 2.1 μM, respectively. Further when used in combination with WR99210 a known TbDHFR inhibitor RUBi004, RUBi007, RUBi014 and RUBi018 showed antagonism while RUBi016 showed an additive effect. These results indicate that the four compounds might be competing with TbDHFR while RUBi016 might be more specific for TbPTR1. These compounds provide scaffolds that can be further optimised to improve their potency and specificity. Lastly, using a systematic approach we derived CHARMM force-field parameters to accurately describe the TbrPDEB1 bi-metal catalytic center. For dynamics, we employed mixed bonded and non-bonded approach. We optimised the structure using a two-layer QM/MM ONIOM (B3LYP/6-31(g): UFF). The TbrPDEB1 bi-metallic center bonds, angles, and dihedrals were parameterized by fitting the energy profiles from Potential Energy Surface (PES) scans to the CHARMM potential energy function. The parameters were validated by means of MD simulations and analysed using RMSD, Rg, RMSF, hydrogen bonding, bond/angle/dihedral evaluations, EDA, PCA, and DRN analysis. The force-field parameters were able to accurately reproduce the geometry and dynamics of the TbrPDEB1 bi-metal catalytic center during MD simulations. Molecular docking was used to identify 6 potential hits, that inhibited trypanosome growth in vitro. The derived force-field parameters were used to simulate the 6 protein-ligand complexes with the aim of elucidating crucial protein-ligand residue interactions. Using the most potent ligand RUBi022 that had an IC50 of 14.96 μM we were able to identify key residue interactions that can be of use in in silico prediction of potential TbrPDEB1 inhibitors. Overall we demonstrate how bioinformatics tools can complement current disease eradication strategies. Future work will focus on identifying variants identified in Genome Wide Association Studies and partnering with wet labs to carry out further enzyme-ligand activity relationship studies, structure determination or characterisation of appropriate protein-ligand complexes by crystallography, and site specific mutation studies
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- Date Issued: 2020
The precarious ‘good mother’ position: a psychosocial reading of maternal subjectivity of working mothers in scarcely-resourced South African communities
- Authors: Kinahan-Sweeney, Siobhan
- Date: 2020
- Subjects: Motherhood -- Psychological aspects -- South Africa , Working mothers -- South Africa -- Attitudes , Working mothers -- South Africa -- Psychology
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/142464 , vital:38082
- Description: This psychosocial study investigates the maternal subjectivities of mothers returning to work after maternity leave, who are living in scarcely-resourced Cape Town communities in South Africa. Engaging with interview texts and listening to mothers’ talk, I explore how and why maternal subjectivity is constructed discursively and defensively in our talk. This thesis claims that these particular mothers predominately employ instrumental mothering discourse. The traditional subject position of the intensive mother – which is typically assumed to be the ‘good mother’ – is not a position available to these mothers due to their social circumstances and working role. Subsequently, material provision, the baby’s thriving and surviving body, finding substitute carers and maternal preoccupation are constructed as qualities of ‘good mothering’ in their talk. This ‘good mother’ position, however, is a precarious position that both these mothers and I invest in to defend against feelings towards their babies and themselves as well as to deny (maternal) ambivalence in a problematic social system. In a combined analysis drawing on discursive theory and psychoanalysis, more specifically contemporary attachment theory and intersubjectivity theory, I illustrate how both these mothers and I – as emotional, social and political subjects – co-construct maternal subjectivity. Based on the findings, recommendations for parent-infant interventions are discussed. Arguing that a purely psychoanalytic reading of investment perpetuates notions of individual blame and pathology, I advocate for a psychosocial reading that does not neglect failing social systems but rather pursues an open and reflective, yet critical, mindfulness when listening to talk.
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- Date Issued: 2020
A strategy towards implementing standardised data structures in municipal information systems
- Authors: Koekemoer, Silma Marguerite
- Date: 2020
- Subjects: Data structures (Computer science) , Municipal government -- Data processing Public administration -- Data processing Management information systems
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/46064 , vital:39482
- Description: The regulation pertaining to a Standard Chart of Accounts (SCOA) for Municipalities was published in 2014 and is applicable to all 257 municipalities and municipal entities in South Africa. The regulation represents a data classification framework or structure and affects all financial management and internal control systems (FMICS) used by municipalities and municipal entities, and affects key business processes within these organisations. Compliance with the SCOA regulation means that the full municipal accountability cycle should accommodate all seven of the SCOA segments, from the budget through transacting and reporting at the transaction level, with all seven of the segments being embedded in the master data table of the municipal FMICS. While the change to technology and systems may be self-evident, the related business change should not be underestimated. This information technology (IT) driven organisational change across the whole municipal environment represents the research topic and key objective of this research study, namely, a strategy towards implementing standard data structures in municipal IT systems. The study followed a pragmatic philosophy using diagnostic reasoning based on an inductive approach, multiple action research methods and a descriptive case study to derive the proposed implementation strategy. The research subjects, which included 25 pilot municipalities, were studied for the duration of the pilot implementation of the strategy with the objective of identifying and utilising the lessons learnt from their experience to fast track the rollout of the strategy to non-pilot municipalities. The study was limited to the local government environment and to South Africa as a geographic area and involved an accidental sample aligned to the implementation project under investigation. The proposed implementation strategy was, however, of a generic nature and is therefore applicable to any other institution or environment engaged in a similar implementation project. The main contribution of the study is an implementation strategy for standard data structures in municipal financial information systems and which consists of seven diagnostics, 17 guiding policies and 48 coherent actions. The strategy was developed and refined during six cycles of data collection, which were conducted at 25 municipalities actively involved in implementing of the standard data structures. The secondary contributions of the research study include three conference papers and one submission to an academic journal.
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- Date Issued: 2020
Conceptualising community radio: from global histories to the Kenyan example
- Authors: Korir, Geoffrey Kiplimo
- Date: 2020
- Subjects: Community radio , Community radio -- Kenya , Community development -- Kenya , Social change -- Kenya , Radio broadcasting -- Kenya
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/165766 , vital:41279
- Description: This study sets out to gain insight into the way that the establishment of community radio in Kenya is located within the global history of ideas about such radio. The first four chapters in this study provide terms of reference for this examination through a series of literature reviews. It sets out, firstly, to locate the internationally shared conceptualisaiton of community radio within an existing spectrum of approaches to social analysis. It proposes that community radio can be located at the critical, emancipatory end of this spectrum. It then maps out the global circulation of ideas about community radio and proposes that such circulation was informed by the broader history of critical, emancipatory social analysis. The final literature review then deals with community radio in Kenya and examines the way in which the establishment of this sector was shaped by the social and political history of this country. It is argued that the establishment of a community radio sector became possible only when support for emancipatory approaches to media became acceptable in Kenya, in context of the establishment of multiparty democracy. It is proposed, further, that the articulation of a vision for community radio in Kenya depended in part on the existence of international support for such radio and in part on the efforts of local actors in civil society. The empirical component then focuses on the way global ideas about community radio have become realised in Kenya. The study achieves this purpose by drawing on qualitative interviews with individuals from within civil society who have participated in the history of the establishment and growth of community radio in Kenya. These individuals demonstrate consciousness of the internationally shared set of principles that can facilitate a successful establishment of community radio. However, they are also sceptical of the assumption that guidelines for community radio are universally applicable. They point, in particular, to the challenges involved in the realisation of these guidelines in an environment in which economic resources are limited, and which is characterised by extreme social inequality and conflict. The study concludes that it is individuals such as these participants, who are embedded within the local context, who are best placed to articulate locally appropriate alternatives to these guidelines.
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- Date Issued: 2020
Indigenous Knowledge on Birthing Practices and the Use of Uterotonic Medicinal Plants to Prevent and Treat Postpartum Haemorrhage: A Mixed Methods Approach
- Authors: Kovane, Gaotswake Patience
- Date: 2020
- Subjects: Medicinal plants Uterine hemorrhage
- Language: English
- Type: Thesis , Doctoral , PhD (Nursing)
- Identifier: http://hdl.handle.net/10353/11385 , vital:39067
- Description: There is a dearth of publications on women’s use of TMPs during the perinatal period. (Nergard et al., 2015). It is recommended that “plants used by pregnant women need to be better known in order to ensure that pregnant women receive effective treatment, to identify potentially unsafe use, and also to preserve valuable information about medicinal plants for women’s reproductive health for the future” (Nergard et al., 2015). Tripathi, Stanton and Anderson (2013:16) conclude that “[f]urther research is needed on the uterotonic efficacy of traditional preparations and on interventions to address the use [of TMPs] during labour”. Gruber and O’Brien (2011:218) support the statement and argue that the search for a “novel cyclotide-producing plant…may eventually lead to the development of novel uterotonic …drugs”. Pharmacological evidence of TMPs may promote the safe use of TMPs by IKHs during birth and the postpartum period. Kaingu, Oduma and Kanui (2011:495) emphasized that TBAs still have a crucial role to play in society, by assisting labouring women in rural communities and their “knowledge on medicinal plants is equally important and should be preserved for posterity”.
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- Date Issued: 2020
BODIPY dyes for use in nonlinear optics and optical sensing
- Authors: Kubheka, Gugu Patience
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/163352 , vital:41032 , doi:10.21504/10962/163352
- Description: Thesis (PhD)--Rhodes University, Faculty of Science, Department of Chemistry, 2020.
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- Date Issued: 2020
Not Yet Uhuru! Attuning to, re-imagining and regenerating transgressive decolonial pedagogical praxis across times Khapa(ring) the rising cultures of change drivers in contemporary South Africa
- Authors: Kulundu-Bolus, Injairu
- Date: 2020
- Subjects: Not Yet Uhuru (Arts Project) , Anti-imperialist movements -- South Africa , Education -- Social aspects -- South Africa , Social change -- South Africa , Education -- Philosophy -- South Africa , Arts and society -- South Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/166081 , vital:41327 , 10.21504/10962/166081
- Description: The “Not yet Uhuru!” project positions itself as emancipatory African research in motion. It is a regenerative project that responds to the concern that whilst dominant discourses can articulate what African states, societies and economies are not, we still know very little about what they actually are. This is a particularly important gap in how research on Africa is conceptualised, especially as it pertains to apprehending the futures that the majority of young people on the continent are instinctively leading themselves to (Mbembe, 2001, p.9). The project seeks to forgo youth development strategies that act as a form of containment by prescribing normative aspects of citizenship on young leaders in ways that stifle the transgressive impulses they have reason to value (Kelley in Tuck and Yang, 2014, p.89). The study traces rising cultures in transgressive decolonial pedagogical praxis across times, as a way of “khapa(ring)” or accompanying the contemporary questions that Change Drivers in South Africa hold at the edge of their praxis. The study co-conspired with 21 Change Drivers in South Africa who were interested in regenerating and re-imagining what transgressive decolonial praxis could be in these times based on their experiences and learnings. Residential art-based workshops that explored each co-conspirator’s offerings on the subject were distilled through the medium of film. These in turn were analysed using an “ethics of attunement” that produced songs as a reflexive pedagogical tool (Lispari, 2014, p.176). Sharing the resonate echoes of their praxis through song created another iterative reflection on their praxis two years after their initial offerings. As a way of weaving together the findings with a historical perspective, the resonant praxis of Change Drivers was put into conversation with three unconventional reviews that trace impulses around transgressive decolonial pedagogical praxis through fictional texts, political theory, poetry and intergenerational analysis, in order to surface resonant themes in praxis that echo across different times in history. This methodology sought to engage the question of the archive in pluriversal ways that appealed to different sensibilities, including the imaginative and hermeneutical, the traditionally analytical as well as the gifts of the lyrical and the erotic as different conceptual threads needed to resource the study. The reviews additionally spanned periods in the history of the continent that hold questions around precolonial and nascent colonial encounters, efforts to transgress within the liberatory movements and the intergenerational transmissions embedded in women and queer people’s struggles. The themes that coalesced across times were leveraged into capsules of rising cultures that form an experimental nexus for the practice of transgressive decolonial pedagogical praxis that is already underway. These rising cultures were conceptualised as meditations on what it means to live into a vision of home built on the explorations of a paradigm of peace, humanness, pluriversality and decolonial love for those like and unlike us that strive for freedom on this continent (Dlala, 2017, p.52; Ndlovu- Gatsheni, 2013, p.142; Gqola, 2017, pp.197, 199). The rising ultures were reconciled through the creation of a litany that chronicles different refrains in transgressive decolonial pedagogical praxis in contemporary times. The litany is a tool that charts particular experiences that are surfacing as symptomatic. It seeks to generously surface the contradictions that we are collectively starting to see past, whilst acknowledging the tensions that we need to straddle, integrate and navigate towards greater synthesis. The litany is an honest way of acknowledging the glimpses gained of who we are in this present moment, while we continually challenge ourselves to open up to questions about what it means to grapple towards decolonial futures. This stance has influenced my role as an educator to unconditionally embrace movements that already underway, and reflect these back to those that I am conspiring with in ways that promote an ethic of care, solidarity and critical engagement. The study celebrates what is possible when we do not theorise ourselves away from the questions embedded in our current praxis. This is an ethic that chooses to stay close to the phenomena arriving at present, whilst acknowledging the historical experiences that echo it as a collective pulse for meaningful experimentation and praxis. The study believes by being faithful to ways of amplifying, integrating and reflecting what has been emerging for us over time, we build our capacity to better respond with an ethic centred on transgressive decolonial pedagogical praxis. This is the kind of accompaniment and care that Change Drivers across the continent deserve as they make the way towards a future worthy of their longing (Rushdie, 1999).
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- Date Issued: 2020
Investigation of potential induced degradation as a performance limiting defect in photovoltaic modules
- Authors: Kwembur, Isaac Morko
- Date: 2020
- Subjects: Photovoltaic cells
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48423 , vital:40875
- Description: Potential Induced Degradation (PID) impacts negatively on photovoltaic (PV) module durability because it significantly affects the output of PV modules and systems. Unless detected at infancy, PID progression can be catastrophic. This study involved systematic PID stressing of PV modules using a custom-built environmental chamber that can achieve suitable environmental conditions, viz., of the 35 °C ± 1 °C and relative humidity of 75 % ± 5 %. The first part of this work was to induce PID using three approaches: climate chamber testing, inducing PID using a conductive aluminium plate on the surface of the module without touching the frame and a localised PID induction on one cell in a module. The second part is to detect induced PID using Electroluminescence (EL) images taken at current corresponding to 10% Isc, EL histograms analysis and Voc ratio taken at 1000 W/m2 to 200 W/m2 . The third part is to study module regeneration after PID shunting degradation in two ways, viz., forced reverse polarization and natural recovery. The PID detection tools used in this work are well known module characterization techniques such as EL imaging, Infrared imaging, and light and dark current-voltage measurements. These characterisation tools are used in combination to detect defects such as optical losses, cracks, breakage, electric circuit degradation and PID. Under normal testing PID was detected and in some cases, modules were able to recover, while for advanced stage PID regeneration or PID reversal was difficult. This thesis focuses on PID detection at infancy using three approaches; EL imaging at current corresponding to 10% of Isc. Light and dark current – voltage measurements (L-IV & D-IV) and open circuit voltage (Voc) ratios at low irradiance. The early detection procedures are essential in reversing the degradation caused by PID which is reversible. The time taken to reverse the PID degradation will depend on the extent of the degradation. If detected early, it will take a short period of time to completely reverse lost power. Infrared thermography is a non-contact characteristic tool that can be deployed in large scale plants using drones to detect the presence of PID in PV plants. Module performance and device parameters extracted from the L-IV curves on a module before and after PID stress, such as Pmpp, Voc, Isc Fill Factor (FF), shunt resistance (Rsh) and series resistance (Rs) and ideality (n) are sensitive to PID shunting. Voc and Rsh drop significantly with the onset of PID, while Rs increases. The decrease in Voc and Rsh is due to heavy shunting on the module resulting in increased carrier recombination, while the increase in Rs is due to increased shunting paths leading to decreased photocurrent. When substantial degradation on a module occurs Pmpp, FF and n will drop and at very advanced stage of PID degradation Isc may drop excessively.
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- Date Issued: 2020
A novel, improved throughput bioassay for determining the delative speed of antimalarial drug action using fluorescent vitality probes
- Authors: Laming, Dustin
- Date: 2020
- Subjects: Plasmodium falciparum , Malaria -- Treatment -- Africa , Antimalarials , Malaria vaccine
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/139902 , vital:37810
- Description: Malaria is one of the most prevalent diseases in Africa and Plasmodium falciparum is widely accepted as the most virulent of the malaria parasite species, with a fatality rate of 15 – 20 % of reported cases of infection. While various treatments have been accepted into early stage clinical trials, there has been little progress towards a proven vaccine. Pending a long-term solution, endemic countries rely heavily on the development of innovative drugs that are not only efficacious but are also quick acting. Traditional methods of evaluating antimalarial killing speeds via morphological assessments are inherently flawed by tedious, subjective interpretations of the heterogenous parasite morphology encountered in routine parasite culture conditions. This has led to the introduction of alternative assay formats to determine how rapidly compounds act on parasites in vitro: a parasite reduction ratio (PRR) assay that measures the recovery of parasite cultures from drug exposure; determining the shift in IC50 values of compounds when dose-response assays are carried out for different time periods; a bioluminescence relative rate of kill (BRRoK) assay that compares the extent to which compounds reduce firefly luciferase activity in transgenic parasites. Recent whole cell in vitro screening efforts have resulted in the generation of chemically diverse compound libraries such as the Medicines for Malaria Venture’s Pathogen Box, which houses 125 novel compounds with in vitro antiplasmodial activity. Assessing the relative killing speeds of these compounds would aid prioritizing fast-acting compounds that can be exploited as starting points for further development. This study aimed to develop a bioassay using the calcein-acetoxymethyl and propidium iodide fluorescent vitality probes, which would allow the relative speed of drug action on Plasmodium falciparum malaria parasites to be assessed and ranked in relation to each other using a quantitative, improved throughput approach. Initially applied to human (HeLa) cells, the assay was used to compare the relative speeds of action of 3 potential anti-cancer compounds by fluorescence microscopy. Subsequently adapted to P. falciparum, the assay was able to rank the relative speeds of action of standard antimalarials by fluorescence microscopy and two flow cytometry formats. Application of a multiwell flow cytometer increased throughput and enabled the assessment of experimental compounds, which included a set of artemisinin analogs and 125 antimalarial compounds in the MMV Pathogen Box. The latter culminated in the identification of five rapidly parasiticidal compounds in relation to the other compounds in the library, which may act as benchmark references for future studies and form the basis of the next generation of fast acting antimalarials that could be used to combat modern, resistant malaria.
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- Date Issued: 2020
Investigating the fitness of sea turtles nesting in South Africa
- Authors: Le Gouvello du Timat, Diane Z M
- Date: 2020
- Subjects: Sea turtles -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48445 , vital:40877
- Description: The South African rookeries of the South Western Indian Ocean (SWIO) loggerhead and leatherback regional management units have been continuously monitored for more than 5 decades, representing one of the longest-running sea turtle beach protection and monitoring programmes in the world. Although such conservation has been successful in protecting adults on land when they come to nest, it might not be enough to ensure population recovery if survival is not ensured across all life stages. Sea turtles are particularly vulnerable to direct threats and changing environmental conditions because they are long-lived, slow maturing, and have low survival rates at early life stages, making them conservation-dependent. These characteristics also render them difficult to conserve as a consequence of their wide geographic distributions, spanning multiple jurisdictions and legislative systems with different conservation targets, and a complex life cycle with changes in habitats and diets at different life stages. Sea turtle populations have been severely depleted as a result of historical over-exploitation and current threats including fisheries bycatch, direct harvest, habitat loss, pollution and pathogens, and climate change. In many cases however, population declines have been reversed by a variety of effective conservation measures such as beach protection programs, and marine protected areas, enabling successful population recovery around the world. Despite protection and apparent increase in abundance, indirect pressures can still affect turtle populations. Therefore, it is fundamental to evaluate the effectiveness of conservation measures (using fitness traits such as female and hatchling sizes) and examine underlying trends. The aim of this thesis was thus to evaluate the fitness of loggerhead and leatherback sea turtles nesting in South Africa. Long-term female size trends over time were evaluated and the populations were split between first-time nesters and experienced nesters. As sea turtle reproductive output (clutch size only) is correlated with female size and evidence is showing that in some populations individual female size is decreasing, the effects of maternal body size on reproductive output and hatchling fitness were investigated for both species. Crawling and swimming speeds were used as proxies of hatchling fitness, because these two traits positively influence their survival. An oceanic model was further used in combination with a particle tracking framework to estimate, for the first time, post-hatchling dispersal of loggerhead and leatherback turtles in the SWIO. I investigated whether the trend in female size for loggerhead turtles nesting in South Africa is a result of their foraging strategy to determine if there is a foraging dichotomy (neritic and oceanic). Despite an apparent increasing population, a significant 3.7 and 3.6 cm decrease in the size of both recruit and remingrant female loggerhead turtles, but a stable mean size of leatherbacks for both age groups was observed. I hypothesise that these contradictory effects are attributable to the very distinct foraging ecologies of the two turtle species and speculate that these variations in carapace length may be driven by environmental change. The reproductive strategy of both loggerhead and leatherback turtles nesting in South Africa supports the optimal egg size theory with larger turtles producing larger clutches but not larger eggs. Egg size was thus constant irrespective of maternal length. Hatchlings with longer carapaces and flippers had higher swimming speed, suggesting that larger hatchlings are fitter (potentially higher survival) than smaller ones by spending less time in high predation risk areas (i.e. beach and nearshore). The model revealed that dispersal trajectories of both loggerhead and leatherback sea turtle hatchlings were very similar and simulations indicated that initial active swimming (frenzy) as well as variability in oceanic conditions strongly influenced dispersal of virtual hatchlings. The trends observed in this study emphasize the importance of long-term monitoring, examining not only abundance but also individual size, to understand population dynamics, support recovery planning and prioritize future conservation practices. Furthermore, the findings of this study have important implications for overall population growth if smaller hatchlings of lower fitness are produced as a result of climate change and thus have decreased dispersal abilities and lower likelihood of survival.
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- Date Issued: 2020
The Integration of Personally-owned Information and Communication Technologies (PICTs) for Teaching and Learning in Resource-Constrained Higher Education Environments – The Case of a Nigerian University
- Authors: Lewis, Oláñrewájú Olúrotimi
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/163582 , vital:41050 , doi:10.21504/10962/163582
- Description: Thesis (PhD)--Rhodes University, Faculty of Commerce, Information Systems, 2020
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- Date Issued: 2020
A classification of large wetlands in Africa’s elevated drylands based on their formation, structure, and hydrological functioning using Earth Observation (EO) data and Geographic Information System (GIS)
- Authors: Lidzhegu, Zwidofhelangani
- Date: 2020
- Subjects: Wetlands -- Africa -- Classification , Wetlands -- Africa -- Research , Wetlands -- Africa -- Monitoring , Topographical surveying -- Africa , Hydrological surveys == Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/142668 , vital:38100
- Description: Due to wetland inaccessibility and limited wetland geomorphological studies, there is limited information on the geomorphological origin and hydrological functioning of different types of wetlands in Africa’s elevated drylands. As a result, there is limited information for the development of a comprehensive wetland classification system that classifies wetlands based on long-term geomorphic processes that determine their formation and shape, their structure and hydrological functioning. Therefore, the current study was designed to classify large wetlands in Africa’s elevated drylands based on processes that determine their formation, and shape their structure and hydrological functioning using remote sensing and Geographic Information System (GIS) techniques. Although wetlands perform a number of hydrological functions including groundwater recharge and water purification, the current study focuses mainly on their flood attenuation function. Detailed analysis of topographic information was undertaken using Shuttle Radar Topographic Mission (SRTM) elevations measured at the scale of 30 m x 30 m. LandsatLook and Google Earth images, tectonic as well as geological data were used as supplementary data for developing an understanding of the origin, structure and hydrological characteristics of wetlands. The Principal Component Analysis (PCA) of wetland environmental variables was used to identify and explain wetland heterogeneity. The results of the study showed that fluvial processes, tectonic history and the evolution of Africa’s landscape played a fundamental role in the formation and evolution of wetlands. This study demonstrates a wide range of processes that contribute to wetland formation, structure and functioning. At one extreme it is clear that tectonic processes may be primarily responsible for the creation of basins that host wetlands. At another extreme, wetlands may be structured primarily by fluvial processes. At a third extreme are wetlands that superficially appear to be structured by fluvial processes, but which have their structures modified by gradual rising of the base level at their distal ends, either through marginal uplift adjacent to rift valleys, or through aggradation of a floodplain that blocks a tributary valley. Overall, the classification of wetlands considered in this study can be summarised into four distinct groupings, with two of these divided further into two groupings each: (1) Tectonic basins with little or no indication of fluvial development (Bahi and Wembere wetlands), (2) Tectonic basins evolving towards a wetland with a structure increasingly shaped by fluvial characteristics (Usangu wetland), (3) Fluvially modified valleys with a local base level at the toe of the wetland such as a resistant lithology or a tectonic control that limits the rate of incision of easily weathered and eroded lithologies, leading to valley widening and longitudinal slope reduction, which are of two distinct types: (a) With a catchment on Kalahari Group sediment that is transported fluvially as bedload, and therefore with no prominent alluvial ridge or backwater depressions (Upper Zambezi and Barotse wetlands), (b) With a catchment that produces abundant fine sediment that is deposited as overbank sediments, leading to channel migration via meandering and to the construction of an elevated alluvial ridge (Lufira wetland), (4) Fluvially modified basins with evidence of gradual elevation of the base level at the toe of the wetland, which are of two types: (a) Tectonic marginal rift valley uplift such that they behave more as depression wetlands rather than as wetlands shaped by fluvial processes (Kafue and Luapula wetlands), (b) Tributary valley wetlands blocked by aggradation of the trunk valley (Lukanga wetland). In conclusion, although few geomorphological studies have been conducted on southern African wetlands because of their inaccessibility, Africa’s surface topography and its historical evolution, as well as aridity, provide an opportunity for illustrating the important role that the long-term tectonic, geological and geomorphological processes play in determining wetland origin, structure and dynamics. GIS methodology and Earth Observation (EO) data on the other hand, provide a practical means for acquiring information on inaccessible and hard to traverse wetland systems. A novel cut-and-fill approach for delineating wetlands from a Digital Elevation Model (DEM) was presented as another way in which GIS methodology and Earth Observation (EO) data can provide practical means for assessing inaccessible and hard to traverse wetland systems.
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- Date Issued: 2020
Ultra-high precision diamond turning of advanced contact lens polymers
- Authors: Liman, Muhammad Mukhtar
- Date: 2020
- Subjects: Contact lenses , Electrostatic lenses Lenses -- Design and construction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/46108 , vital:39496
- Description: Contact lens polymer-based materials are extensively used in the optical industry owing to their excellent corrosion resistance, the possibility of mass production and their ability to be processed without external lubrication. Owing to the fast growth in optical industries, contact lens (CL) requires high accuracy and a high surface quality. The demand for high-accuracy and minimal surface roughness drives the development of ultra-high precision machining technology with regard to single point diamond turning (SPDT). Ultra-high precision diamond turning is an advanced manufacturing technique employed in the machining of CLs owing to its capability of producing high optical surfaces with complex shapes and nanometric accuracy. Yet, even with the advances in ultra-high precision machining (UHPM), it is not continuously easy to achieve a highquality surface finish during polymers machining as the adhesion of the tool chip around the tool dictates the presence of electrostatic charges. The electrostatic charges encountered by a cutting tool when turning advanced CLs are important as they reflect the quality and condition of the tool, machine, fixture, and sometimes even the finished surface, which is responsible for tool wear and poor surface quality. This study investigates the role of cutting parameters, namely cutting speed, feed rate and depth of cut on surface roughness (Ra), electrostatic charge (ESC) and material removal rate (MRR), which determines machine economics and the quality of machining contact lens polymers. The experiments were mainly conducted on two different advanced polymeric materials: polymethyl methacrylate (PMMA) and Optimum Extreme (Roflufocon E) CLs. Experimentation was carried out on the Nanoform 250 ultra-grind turning machine with a monocrystalline diamond-cutting tool for machining the PMMA and Roflufocon E CL polymers, covering a wide range of machining parameters. Before conducting the experiments, a design of experiment was conducted according to the response surface methodology (RSM) that is based on the Box-Behnken Design (BBD). In addition, the research study focused on the determination of the optimum cutting conditions leading to minimum Ra and ESC as well as maximum productivity in the SPDT of the PMMA and Roflufocon E CL polymers, using a monocrystalline diamondcutting tool. The optimization was based on RSM together with the desirability function approach. In addition, a mathematical model was developed for Ra, ESC and MRR using a RSM regression analysis for PMMA and Roflufocon E CL polymers by means of Design Expert software. RSM allowed for the optimization of the cutting conditions for minimal Ra and ESC as well as maximal MRR, which provides an effective knowledge base for process parameters to enhance process performance in the SPDT of CL polymers. Furthermore, this study also deals with the development of Ra, ESC and MRR prediction models for the diamond turning of PMMA and Roflufocon E CL polymers, using the fuzzy logic based artificial intelligence (AI) method. The fuzzy logic model has been developed in terms of machining parameters for the prediction of Ra, ESC and MRR. To judge the accuracy and ability of the fuzzy logic model, an average percentage error was used. The comparative evaluation of experiments and the fuzzy logic approach suggested that the obtained average errors of Ra, ESC and MRR using the fuzzy logic system were in agreement with the experimental results. Hence, the developed fuzzy logic rules can be effectively utilized to predict the ESC, Ra and MRR of PMMA and Roflufocon E CL polymers in automated optical manufacturing environments for high accuracy and a reduction of computational cost. Moreover, owing to the brittle nature of optical polymers, the Roflufocon E CL polymer requires ductile-mode machining for improved surface quality. Molecular Dynamics (MD) simulation methods are thus applied to investigate the atomistic reaction at the tool/workpiece surface to clearly study and observe conditions occurring at nanometric scale in polymer machining. This research study is particularly concerned with the comparative analysis of experiments and a MD study of the Roflufocon E optical polymer nano cutting approach to the atomistic visualization of the plastic material flow at the tool/workpiece interface during cutting. The simulated MD acting force, machine stresses, and the temperature at the cutting region were evaluated to access the accuracy of the model. Hence, the nanomachining simulations were found to have a correlation to the experimental machining results.
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- Date Issued: 2020