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 search for daily meaning: A technique for career counselling
- Authors: Rainier, Markseller Garrett
- Date: 1994
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/193003 , vital:45289
- Description: Because work is such a tremendous potential source of meaning in an individual’s life, techniques which turn career choice into technical talent matching are inadequate. The individual’s search for authentic meaning needs to be the focus of career counselling, but few approaches have been able to addressed this relationship between working and living. Major developments in career theory are reviewed to highlight the distinction between the more technical logical positivist and the phenomenological approaches. Super’s Career- Development Assessment and Counselling (C-DAC) model is described in detail as it is the first significant attempt to move beyond the technical approaches by incorporating developmental theory into career counselling and by stressing the role of counsellee readiness to use the information provided. However, especially in South Africa, any test-based approach to career counselling runs the risk of shifting the locus of control from the counsellee to the counsellor, so an autobiographical non-test approach, the life-line, is introduced to assist counsellees in their search for personal meaning without running the risks associated with test-based assessments. The life-line helps to contextualise the choice of work within the counsellee’s subjective life experience and turns career counselling into a shared search for a range of personal meanings rather than the provision, by the counsellor, of a limiting interpretation. Three case studies are presented to demonstrate the use of the life-line, and the conclusions arrived at are shown to be essentially1 similar to conclusions obtained from using the C-DAC battery. The advantages and limitations of the life-line are discussed and its ability to combat problems associated with school based career counselling is outlined as well as its usefulness with mid-life career changers, in cross-cultural contexts, and in group counselling. , Thesis (MA) -- Faculty of Humanities, Psychology, 1990
- Full Text:
- Date Issued: 1994
- Authors: Rainier, Markseller Garrett
- Date: 1994
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/193003 , vital:45289
- Description: Because work is such a tremendous potential source of meaning in an individual’s life, techniques which turn career choice into technical talent matching are inadequate. The individual’s search for authentic meaning needs to be the focus of career counselling, but few approaches have been able to addressed this relationship between working and living. Major developments in career theory are reviewed to highlight the distinction between the more technical logical positivist and the phenomenological approaches. Super’s Career- Development Assessment and Counselling (C-DAC) model is described in detail as it is the first significant attempt to move beyond the technical approaches by incorporating developmental theory into career counselling and by stressing the role of counsellee readiness to use the information provided. However, especially in South Africa, any test-based approach to career counselling runs the risk of shifting the locus of control from the counsellee to the counsellor, so an autobiographical non-test approach, the life-line, is introduced to assist counsellees in their search for personal meaning without running the risks associated with test-based assessments. The life-line helps to contextualise the choice of work within the counsellee’s subjective life experience and turns career counselling into a shared search for a range of personal meanings rather than the provision, by the counsellor, of a limiting interpretation. Three case studies are presented to demonstrate the use of the life-line, and the conclusions arrived at are shown to be essentially1 similar to conclusions obtained from using the C-DAC battery. The advantages and limitations of the life-line are discussed and its ability to combat problems associated with school based career counselling is outlined as well as its usefulness with mid-life career changers, in cross-cultural contexts, and in group counselling. , Thesis (MA) -- Faculty of Humanities, Psychology, 1990
- Full Text:
- Date Issued: 1994
Bulimia Nervosa: a case study in cognitive psychotherapy
- Authors: Kanfer, Josephine
- Date: 1990
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/192988 , vital:45287
- Description: This project uses the case-study method to illustrate the application of integrating varied accepted modes of psychotherapeutic interventions. It concentrates on the first 22 out-patient sessions of therapy with a diagnosed bulimic, spanning a 6 month period. A brief summary of the subsequent 10 follow-up sessions is also given. The case presented is of a 22 year old female student diagnosed as bulimic (of 7 year duration), dysthymic and with a dependent personality disorder. She has symptoms of anxiety. She has a history of anorexia nervosa. Fairburn's (1985) cognitive-behavioural programme for bulimia was used initially. Its structured framework with the emphasis on the eating behaviour was an essential aspect in contributing to the success of the initial phase of the therapy. This patient had had previously experienced 8 sessions of non-directive depth psychotherapy which had confused and compounded her problems. The structure had provided her with a sense of control. In implementing the second stage of Fairburn's programme, where the focus is cognitive, the patient could no longer work in this this structured manner. The attempts to implement the standard cognitive techniques provided the catalyst for activating deeper underlying emotions and cognitions. Furthermore, this gave impetus to work actively with the interpersonal aspect of the therapeutic relationship. Young's (1989) model for identifying Early Maladaptive Schemas could be applied. The focus then moved from the behaviours and dealt with these schemas as activated in the therapeutic relationship. The patient was able to make links to her family and her past. The therapy proved successful, as not only were the behavioural symptoms alleviated, but also the patient's interpersonal problems which underlay her personality disorder were accessed. The patient had become more self-assertive, her mood had improved considerably, she was less concerned with body image and more accepting of herself. She had become more reality based and her interpersonal relational abi1ity had improved. , Thesis (MA) -- Faculty of Humanities, Psychology, 1990
- Full Text:
- Date Issued: 1990
- Authors: Kanfer, Josephine
- Date: 1990
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/192988 , vital:45287
- Description: This project uses the case-study method to illustrate the application of integrating varied accepted modes of psychotherapeutic interventions. It concentrates on the first 22 out-patient sessions of therapy with a diagnosed bulimic, spanning a 6 month period. A brief summary of the subsequent 10 follow-up sessions is also given. The case presented is of a 22 year old female student diagnosed as bulimic (of 7 year duration), dysthymic and with a dependent personality disorder. She has symptoms of anxiety. She has a history of anorexia nervosa. Fairburn's (1985) cognitive-behavioural programme for bulimia was used initially. Its structured framework with the emphasis on the eating behaviour was an essential aspect in contributing to the success of the initial phase of the therapy. This patient had had previously experienced 8 sessions of non-directive depth psychotherapy which had confused and compounded her problems. The structure had provided her with a sense of control. In implementing the second stage of Fairburn's programme, where the focus is cognitive, the patient could no longer work in this this structured manner. The attempts to implement the standard cognitive techniques provided the catalyst for activating deeper underlying emotions and cognitions. Furthermore, this gave impetus to work actively with the interpersonal aspect of the therapeutic relationship. Young's (1989) model for identifying Early Maladaptive Schemas could be applied. The focus then moved from the behaviours and dealt with these schemas as activated in the therapeutic relationship. The patient was able to make links to her family and her past. The therapy proved successful, as not only were the behavioural symptoms alleviated, but also the patient's interpersonal problems which underlay her personality disorder were accessed. The patient had become more self-assertive, her mood had improved considerably, she was less concerned with body image and more accepting of herself. She had become more reality based and her interpersonal relational abi1ity had improved. , Thesis (MA) -- Faculty of Humanities, Psychology, 1990
- Full Text:
- Date Issued: 1990
A comparison of the self-esteem of black and white high school pupils
- Authors: Morrow, Brian Robert
- Date: 1988
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/193033 , vital:45292
- Description: This study investigated the level of self-esteem of black and white high-school students using the Rosenberg self-esteem scale. One hundred and eighty six subjects were used, 63 of them being white while 118 were black. A validation of the Rosenberg scale for the black sample was attempted using a correlation between the scale score and a rating of the subjects by teachers. The results of the study showed no significant difference between the self-esteem levels, while the validation study failed to confirm the validity of the test for black subjects in South Africa. However, the validation study v/as rejected as inconclusive and the results of the comparison accepted as confirmatory of previous research. An incidental positive finding revealed that white males have higher self-esteem than white females,. The theory and past research of self-esteem comparisons between racial groups is reviewed. The conclusion is reached in this study that the concept of self-esteem has outlasted its usefulness in the field of comparisons between racial groups and research of a qualitative nature .can provide further data for the understanding of differences between racial groups. , Thesis (MA) -- Faculty of Humanities, Psychology, 1988
- Full Text:
- Date Issued: 1988
- Authors: Morrow, Brian Robert
- Date: 1988
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/193033 , vital:45292
- Description: This study investigated the level of self-esteem of black and white high-school students using the Rosenberg self-esteem scale. One hundred and eighty six subjects were used, 63 of them being white while 118 were black. A validation of the Rosenberg scale for the black sample was attempted using a correlation between the scale score and a rating of the subjects by teachers. The results of the study showed no significant difference between the self-esteem levels, while the validation study failed to confirm the validity of the test for black subjects in South Africa. However, the validation study v/as rejected as inconclusive and the results of the comparison accepted as confirmatory of previous research. An incidental positive finding revealed that white males have higher self-esteem than white females,. The theory and past research of self-esteem comparisons between racial groups is reviewed. The conclusion is reached in this study that the concept of self-esteem has outlasted its usefulness in the field of comparisons between racial groups and research of a qualitative nature .can provide further data for the understanding of differences between racial groups. , Thesis (MA) -- Faculty of Humanities, Psychology, 1988
- Full Text:
- Date Issued: 1988
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