Performance evaluation of baseline-dependent window functions with several weighing functions
- Authors: Vanqa, Kamvulethu
- Date: 2024-04-04
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/435850 , vital:73206
- Description: Radio interferometric data volume is exponentially increasing with the potential to cause slow processing and data storage issues for radio observations recorded at high time and frequency resolutions. This necessitates that a sort of data compression is imposed. The conventional method to compress the data is averaging across time and frequency. However, this results in amplitude loss and source distortion at the edges of the field of view. To reduce amplitude loss and source distortion, baseline-dependent window functions (BDWFs) are proposed in theliterature. BDWFs are visibility data compression methods using window functions to retainthe signals within a field of interest (FoI) and to suppress signals outside this FoI. However,BDWFs are used with window functions as discussed in the signal processing field without any optimisation. This thesis evaluates the performance of BDWFs and then proposes to use machine learning with gradient descent to optimize the window functions employed in BDWFs. Results show that the convergence of the objective function is limited due to the band-limited nature of the window functions in the Fourier space. BDWFs performance is also investigated and discussed using several weighting schemes. Results show that there exists an optimal parameter tuning (not necessarily unique) that suggests an optimal combination of BDWFs and density sampling. With this, ∼ 4 % smearing is observed within the FoI, and ∼ 80 % source suppression is achieved outside the FoI using the MeerKAT telescope at 1.4 GHz, sampled at 1 s and 184.3 kHz then averaged with BDWFs to achieve a compression factor of 4 in time and 3 in frequency. , Thesis (MA) -- Faculty of Science, Mathematics, 2024
- Full Text:
- Date Issued: 2024-04-04
- Authors: Vanqa, Kamvulethu
- Date: 2024-04-04
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/435850 , vital:73206
- Description: Radio interferometric data volume is exponentially increasing with the potential to cause slow processing and data storage issues for radio observations recorded at high time and frequency resolutions. This necessitates that a sort of data compression is imposed. The conventional method to compress the data is averaging across time and frequency. However, this results in amplitude loss and source distortion at the edges of the field of view. To reduce amplitude loss and source distortion, baseline-dependent window functions (BDWFs) are proposed in theliterature. BDWFs are visibility data compression methods using window functions to retainthe signals within a field of interest (FoI) and to suppress signals outside this FoI. However,BDWFs are used with window functions as discussed in the signal processing field without any optimisation. This thesis evaluates the performance of BDWFs and then proposes to use machine learning with gradient descent to optimize the window functions employed in BDWFs. Results show that the convergence of the objective function is limited due to the band-limited nature of the window functions in the Fourier space. BDWFs performance is also investigated and discussed using several weighting schemes. Results show that there exists an optimal parameter tuning (not necessarily unique) that suggests an optimal combination of BDWFs and density sampling. With this, ∼ 4 % smearing is observed within the FoI, and ∼ 80 % source suppression is achieved outside the FoI using the MeerKAT telescope at 1.4 GHz, sampled at 1 s and 184.3 kHz then averaged with BDWFs to achieve a compression factor of 4 in time and 3 in frequency. , Thesis (MA) -- Faculty of Science, Mathematics, 2024
- Full Text:
- Date Issued: 2024-04-04
Arbuscular mycorrhizal fungi associated with maize in South Africa, under conventional and conservation agricultural cultivation
- Maússe Sitoe, Sílvia Natal David
- Authors: Maússe Sitoe, Sílvia Natal David
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431846 , vital:72808
- Description: Access restricted. Expected release date in 2025. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Maússe Sitoe, Sílvia Natal David
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431846 , vital:72808
- Description: Access restricted. Expected release date in 2025. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2023
- Full Text:
- Date Issued: 2023-10-13
The challenges and opportunities in ESG integration in investment activities for private equity firms/funds in South Africa
- Authors: Dube, Cuma Velile
- Date: 2022-04-06
- Subjects: Social responsibility of business South Africa , Investments Moral and ethical aspects South Africa , Private equity South Africa , Investments Environmental aspects South Africa , Investments Social aspects South Africa , Investments Law and legislation South Africa , United Nations Principles of Responsible Investing (UNPRI)
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/284493 , vital:56068
- Description: Responsible Investing (RI) is an investment strategy that considers not only the economic but also the environmental, social and governance (ESG) issues in the investment analysis and post-investment activities. The consideration of ESG issues is aimed at generating long-term risk-adjusted financial returns and a positive social and environmental impact. This research seeks to contribute to the study of responsible investment (RI), as it relates to private equity investments, an area not well researched. This research also seeks to contribute to the academic literature on responsible institutional investment in South Africa; the opportunities it presents to optimise portfolios, as well as the means with which the challenges faced in integrating ESG factors in investment activities may be overcome. More specifically, the challenges and opportunities for the integration of ESG factors in the investment process were investigated through the experiences of a small sample of South African private equity firms. The sample of private equity firms that participated in this research are signatories of the United Nations Principles of Responsible Investing (UNPRI). Representatives of the participating firms were interviewed in line with the qualitative research design and the post-positivist paradigm of this research. The research design and paradigm are chosen to explore the experiences of practitioners in their integration of ESG issues in the investment process. This research shows that the challenges to ESG integration for the private equity firms considered have remained largely consistent over the last ten years. The challenges include industry skills and knowledge gap and the lack of reliable and comparable ESG data at the portfolio company level. The Opportunities presented, by adopting responsible investing as an investment strategy, are rooted in protecting the downside (risk management) and in finding new value creation opportunities. In summary, it was found that the participating firms continue to face significant capacity challenges in overcoming the challenges to mainstreaming ESG in investment processes. Further research may explore whether the challenges and opportunities that persist from the findings of this research are pervasive throughout the entire sector and whether innovative ways have been found to overcome the challenges have been found by private equity firms that are not signatories of the UNPRI. , Thesis (MBA) -- Faculty of Commerce, Rhodes Business School, 2022
- Full Text:
- Date Issued: 2022-04-06
- Authors: Dube, Cuma Velile
- Date: 2022-04-06
- Subjects: Social responsibility of business South Africa , Investments Moral and ethical aspects South Africa , Private equity South Africa , Investments Environmental aspects South Africa , Investments Social aspects South Africa , Investments Law and legislation South Africa , United Nations Principles of Responsible Investing (UNPRI)
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/284493 , vital:56068
- Description: Responsible Investing (RI) is an investment strategy that considers not only the economic but also the environmental, social and governance (ESG) issues in the investment analysis and post-investment activities. The consideration of ESG issues is aimed at generating long-term risk-adjusted financial returns and a positive social and environmental impact. This research seeks to contribute to the study of responsible investment (RI), as it relates to private equity investments, an area not well researched. This research also seeks to contribute to the academic literature on responsible institutional investment in South Africa; the opportunities it presents to optimise portfolios, as well as the means with which the challenges faced in integrating ESG factors in investment activities may be overcome. More specifically, the challenges and opportunities for the integration of ESG factors in the investment process were investigated through the experiences of a small sample of South African private equity firms. The sample of private equity firms that participated in this research are signatories of the United Nations Principles of Responsible Investing (UNPRI). Representatives of the participating firms were interviewed in line with the qualitative research design and the post-positivist paradigm of this research. The research design and paradigm are chosen to explore the experiences of practitioners in their integration of ESG issues in the investment process. This research shows that the challenges to ESG integration for the private equity firms considered have remained largely consistent over the last ten years. The challenges include industry skills and knowledge gap and the lack of reliable and comparable ESG data at the portfolio company level. The Opportunities presented, by adopting responsible investing as an investment strategy, are rooted in protecting the downside (risk management) and in finding new value creation opportunities. In summary, it was found that the participating firms continue to face significant capacity challenges in overcoming the challenges to mainstreaming ESG in investment processes. Further research may explore whether the challenges and opportunities that persist from the findings of this research are pervasive throughout the entire sector and whether innovative ways have been found to overcome the challenges have been found by private equity firms that are not signatories of the UNPRI. , Thesis (MBA) -- Faculty of Commerce, Rhodes Business School, 2022
- Full Text:
- Date Issued: 2022-04-06
Who are you? Online practices of self-representation of black gay men at Rhodes University on the geosocial networking application Grindr
- Authors: Olivier, Jason Eben
- Date: 2021-10-29
- Subjects: Grindr (Computer program) , Gay men, Black South Africa Makhanda , Gay men Identity , Internet and gay men South Africa Makhanda , Social media and college students South Africa Makhanda , Masculinity South Africa Makhanda , Racism in the sexual minority community South Africa Makhanda , Sexism South Africa Makhanda , Rhodes University
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/294851 , vital:57262
- Description: The study investigates how young black gay men at Rhodes University use technology to explore their sexual identity and focuses specifically on their self-representation choices. Incorporating qualitative semi-structured interviews and a walkthrough of Grindr, the research asked participants to share their experiences of using Grindr, a geo-social networking application, and how their self-representation practices on the site contributed to their conception of what it means to be a young black gay man online. Using a thematic analysis of the data collected from five self-identified black gay Rhodes University students, findings indicate that self-representation choices of black gay men on Grindr become a complex experience influenced by overt sexist and racist micro-aggressions in an environment where masculinities operate in a hierarchy of desire, preference, and attractiveness with race operating as an important signifier of these even in a post-Apartheid South Africa that is celebrated for its world-class Constitution. , Thesis (MA) -- Faculty of Humanities, School of Journalism and Media Studies, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Olivier, Jason Eben
- Date: 2021-10-29
- Subjects: Grindr (Computer program) , Gay men, Black South Africa Makhanda , Gay men Identity , Internet and gay men South Africa Makhanda , Social media and college students South Africa Makhanda , Masculinity South Africa Makhanda , Racism in the sexual minority community South Africa Makhanda , Sexism South Africa Makhanda , Rhodes University
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/294851 , vital:57262
- Description: The study investigates how young black gay men at Rhodes University use technology to explore their sexual identity and focuses specifically on their self-representation choices. Incorporating qualitative semi-structured interviews and a walkthrough of Grindr, the research asked participants to share their experiences of using Grindr, a geo-social networking application, and how their self-representation practices on the site contributed to their conception of what it means to be a young black gay man online. Using a thematic analysis of the data collected from five self-identified black gay Rhodes University students, findings indicate that self-representation choices of black gay men on Grindr become a complex experience influenced by overt sexist and racist micro-aggressions in an environment where masculinities operate in a hierarchy of desire, preference, and attractiveness with race operating as an important signifier of these even in a post-Apartheid South Africa that is celebrated for its world-class Constitution. , Thesis (MA) -- Faculty of Humanities, School of Journalism and Media Studies, 2021
- Full Text:
- Date Issued: 2021-10-29
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