Microstructural based creep life assessment of 1CrMov Turbine rotor steels after long-term service
- Nyembe, Hlanganani Siphelele
- Authors: Nyembe, Hlanganani Siphelele
- Date: 2023-04
- Subjects: Materials – Creep –South Africa , Steel -- Creep
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61380 , vital:70622
- Description: Creep-resistant 1CrMoV steels are used for high-pressure turbine rotors in fossil fuel power stations operating at steam temperatures up to 565 °C in the creep regime. The upper bainitic microstructure of 1CrMoV rotors changes when exposed to high temperature service over long periods. The aim of this study was to relate these microstructural changes for service exposed 1CrMoV rotor steels to the remaining creep life as determined using existing methods. Analytical electron microscopy was used to quantitatively study the microstructural evolution of service-exposed 1CrMoV steel rotors. 1CrMoV rotor steel samples were characterised in the initial state, and three long-term (272 h to 300 kh) service exposed states. Detailed microstructural investigations were conducted to analyse the cavities; bainitic laths and packets; dislocations; carbide phases and their size, population, composition. The creep life fractions were estimated using conventional life assessment methods based on creep cavitation and hardness. The creep life fraction consumed of the rotors, estimated based on the creep cavities and hardness data, ranged from ~0.5 to 1. Electron backscattered diffraction (EBSD) was used to analyse the bainitic packets, laths, misorientations, and dislocations, which showed that the bainitic lath surface area to volume (SV) correlated with service time. The precipitates were extracted from the Fe-matrix using extraction replication and were further investigated using transmission Kikuchi diffraction (TKD), scanning transmission electron microscopy (STEM), selected area electron diffraction (SAED), and energy dispersive spectroscopy (EDS). STEM-EDS and TKD identified M3C, MC, M2C, M7C3, and M23C6 (M = Fe, Cr, Mo, V, Mn) in the 1CrMoV steels. STEM-EDS measurements revealed that Fe/Cr ratios in M3C decreased from 4.5 (initial state) to 2.5 (>272 kh). The Fe/Cr and Fe/Mo ratios in overall carbides decreased from 5 and 10 (initial state) to 1 and 2 (>272 kh), respectively. The TKD analysis indicated that the relative phase proportion of M2C and M7C3 carbides, relative to the total extracted carbides, is positively correlated with service exposure. These microstructural features correlate with the creep life fraction consumed and could potentially be used as another indicator of the remnant creep life. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics. 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Nyembe, Hlanganani Siphelele
- Date: 2023-04
- Subjects: Materials – Creep –South Africa , Steel -- Creep
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61380 , vital:70622
- Description: Creep-resistant 1CrMoV steels are used for high-pressure turbine rotors in fossil fuel power stations operating at steam temperatures up to 565 °C in the creep regime. The upper bainitic microstructure of 1CrMoV rotors changes when exposed to high temperature service over long periods. The aim of this study was to relate these microstructural changes for service exposed 1CrMoV rotor steels to the remaining creep life as determined using existing methods. Analytical electron microscopy was used to quantitatively study the microstructural evolution of service-exposed 1CrMoV steel rotors. 1CrMoV rotor steel samples were characterised in the initial state, and three long-term (272 h to 300 kh) service exposed states. Detailed microstructural investigations were conducted to analyse the cavities; bainitic laths and packets; dislocations; carbide phases and their size, population, composition. The creep life fractions were estimated using conventional life assessment methods based on creep cavitation and hardness. The creep life fraction consumed of the rotors, estimated based on the creep cavities and hardness data, ranged from ~0.5 to 1. Electron backscattered diffraction (EBSD) was used to analyse the bainitic packets, laths, misorientations, and dislocations, which showed that the bainitic lath surface area to volume (SV) correlated with service time. The precipitates were extracted from the Fe-matrix using extraction replication and were further investigated using transmission Kikuchi diffraction (TKD), scanning transmission electron microscopy (STEM), selected area electron diffraction (SAED), and energy dispersive spectroscopy (EDS). STEM-EDS and TKD identified M3C, MC, M2C, M7C3, and M23C6 (M = Fe, Cr, Mo, V, Mn) in the 1CrMoV steels. STEM-EDS measurements revealed that Fe/Cr ratios in M3C decreased from 4.5 (initial state) to 2.5 (>272 kh). The Fe/Cr and Fe/Mo ratios in overall carbides decreased from 5 and 10 (initial state) to 1 and 2 (>272 kh), respectively. The TKD analysis indicated that the relative phase proportion of M2C and M7C3 carbides, relative to the total extracted carbides, is positively correlated with service exposure. These microstructural features correlate with the creep life fraction consumed and could potentially be used as another indicator of the remnant creep life. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics. 2023
- Full Text:
- Date Issued: 2023-04
Be more than a bystander, break the silence on violence: a discursive analysis of student responses to anti-rape poster campaigns
- Authors: Skae, Shannon Lalla Rookh
- Date: 2022-04
- Subjects: Women Violence against South Africa , Women college students Violence against South Africa , Women college students Abuse of South Africa , College students Attitudes , Sex crimes Prevention , Anti-rape movement South Africa , Bystander effect South Africa , Rape culture South Africa
- Language: English
- Type: Master's thesis , text
- Identifier: http://hdl.handle.net/10962/232866 , vital:50033
- Description: University students are a population vulnerable to sex and gender-based violence (SGBV). The use of alcohol is prominent in university life and is argued to contribute significantly to SGBV in South Africa and worldwide. Interventions to reduce SGBV at South African universities are thus a relevant social concern. One increasingly popular approach to addressing SGBV on university campuses is the bystander intervention. The bystander intervention goes to the cause of SGBV by targeting peer acceptance as the primary foundation supporting rape; arguing that witnesses to SGBV can be empowered to interrupt potential SGBV situations. The aim of this thesis was to investigate student responses to anti-rape intervention campaigns of various kinds. Different theories were examined, and this research then proceeded from a social constructionist theoretical perspective, which was relevant as it is about what individuals say, the societies formed, the rules made, the language used to pass on knowledge and the interactions experienced with others and how they all form the reality people inhabit. The study focused on the individual constructions and talk about the posters and the discursive positions he or she took up in relation to them, which is what social constructionism is interested in, as it is concerned with the language and talk people use and how these are molded by society. Forty five student volunteer participants were shown two examples of anti-rape poster campaigns (one using the bystander approach and the other not), and were asked to respond to a structured open-ended questionnaire. Responses to the questionnaire were subjected to Foucauldian Discourse Analysis (FDA). The analysis revealed the ways in which the constructions of sexual violence, perpetrators and victims in the poster campaigns shaped and limited participant responses and talk about SGBV in different ways, according to which of the two posters were being responded to. Key findings of this study showed that the bystander intervention poster produced more positive change in response to dominant discursive constructions in relation to the SGBV poster than did the non-bystander intervention poster. This means the establishment of the potential for success of the bystander intervention in helping to prevent SGBV in a South African context. , Thesis (MA) -- Humanities, Psychology, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Skae, Shannon Lalla Rookh
- Date: 2022-04
- Subjects: Women Violence against South Africa , Women college students Violence against South Africa , Women college students Abuse of South Africa , College students Attitudes , Sex crimes Prevention , Anti-rape movement South Africa , Bystander effect South Africa , Rape culture South Africa
- Language: English
- Type: Master's thesis , text
- Identifier: http://hdl.handle.net/10962/232866 , vital:50033
- Description: University students are a population vulnerable to sex and gender-based violence (SGBV). The use of alcohol is prominent in university life and is argued to contribute significantly to SGBV in South Africa and worldwide. Interventions to reduce SGBV at South African universities are thus a relevant social concern. One increasingly popular approach to addressing SGBV on university campuses is the bystander intervention. The bystander intervention goes to the cause of SGBV by targeting peer acceptance as the primary foundation supporting rape; arguing that witnesses to SGBV can be empowered to interrupt potential SGBV situations. The aim of this thesis was to investigate student responses to anti-rape intervention campaigns of various kinds. Different theories were examined, and this research then proceeded from a social constructionist theoretical perspective, which was relevant as it is about what individuals say, the societies formed, the rules made, the language used to pass on knowledge and the interactions experienced with others and how they all form the reality people inhabit. The study focused on the individual constructions and talk about the posters and the discursive positions he or she took up in relation to them, which is what social constructionism is interested in, as it is concerned with the language and talk people use and how these are molded by society. Forty five student volunteer participants were shown two examples of anti-rape poster campaigns (one using the bystander approach and the other not), and were asked to respond to a structured open-ended questionnaire. Responses to the questionnaire were subjected to Foucauldian Discourse Analysis (FDA). The analysis revealed the ways in which the constructions of sexual violence, perpetrators and victims in the poster campaigns shaped and limited participant responses and talk about SGBV in different ways, according to which of the two posters were being responded to. Key findings of this study showed that the bystander intervention poster produced more positive change in response to dominant discursive constructions in relation to the SGBV poster than did the non-bystander intervention poster. This means the establishment of the potential for success of the bystander intervention in helping to prevent SGBV in a South African context. , Thesis (MA) -- Humanities, Psychology, 2022
- Full Text:
- Date Issued: 2022-04
Hermēs Dolios: Performances of Hermes as trickster in the Homeric Hymn to Hermes
- Authors: Nel, Aiden Pieter
- Date: 2021-10-29
- Subjects: Hermes (Greek deity) , Hymn to Hermes , Tricksters in literature , Loki (Norse deity) , Hynes, William J , Doty, William G, 1939-J , Wakdjunkaga (Winnebago Trickster) , Ture (Zande Trickster)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190978 , vital:45046
- Description: This thesis explores the Greek god Hermes' representation in the Homeric Hymn to Hermes to establish the extent to which he partakes in Hynes' defined set of characteristics associated with mythological 'trickster' figures. Hermes is an unorthodox figure as although he embodies many aspects of the trickster, he willingly relinquishes some of these aspects within his hymn. I first outline and explore the trickster phenomenon and the complex methodological issue concerning global comparison. Hynes’ criteria are first applied to three other tricksters the Amerindian (Winnebago) trickster Wakdjunkaga, the central African (Azande) trickster Ture and the northern European (Norse) trickster Loki, which establishes a baseline that will help determine how Hermes conforms to this typology. All three figures’ cultural contexts are first addressed, as the cultural context is key in understanding a figure’s potential inclusion in the trickster category. I then explore Hermes’ performances within his hymn and other genres to formulate how his patron powers and actions relate to his designation as a trickster. I argue, in conclusion, that Hynes’ typology is a useful tool in determining any figure’s degree of ‘tricksterness’ and show that Hermes and the other three figures do embody Hynes’ characteristics. Each, however, embodies them differently and in a specific manner. I argue that the manner in which they relate to the criteria is dictated by their respective cultural contexts, and what their narrators intended to illustrate through the stories wherein tricksters reside. I further argue that narrative intent, genre and cultural context appear to be the main factors that mould each respective figure. , Thesis (MA) -- Faculty of Humanities, School of Languages and Literatures, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Nel, Aiden Pieter
- Date: 2021-10-29
- Subjects: Hermes (Greek deity) , Hymn to Hermes , Tricksters in literature , Loki (Norse deity) , Hynes, William J , Doty, William G, 1939-J , Wakdjunkaga (Winnebago Trickster) , Ture (Zande Trickster)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190978 , vital:45046
- Description: This thesis explores the Greek god Hermes' representation in the Homeric Hymn to Hermes to establish the extent to which he partakes in Hynes' defined set of characteristics associated with mythological 'trickster' figures. Hermes is an unorthodox figure as although he embodies many aspects of the trickster, he willingly relinquishes some of these aspects within his hymn. I first outline and explore the trickster phenomenon and the complex methodological issue concerning global comparison. Hynes’ criteria are first applied to three other tricksters the Amerindian (Winnebago) trickster Wakdjunkaga, the central African (Azande) trickster Ture and the northern European (Norse) trickster Loki, which establishes a baseline that will help determine how Hermes conforms to this typology. All three figures’ cultural contexts are first addressed, as the cultural context is key in understanding a figure’s potential inclusion in the trickster category. I then explore Hermes’ performances within his hymn and other genres to formulate how his patron powers and actions relate to his designation as a trickster. I argue, in conclusion, that Hynes’ typology is a useful tool in determining any figure’s degree of ‘tricksterness’ and show that Hermes and the other three figures do embody Hynes’ characteristics. Each, however, embodies them differently and in a specific manner. I argue that the manner in which they relate to the criteria is dictated by their respective cultural contexts, and what their narrators intended to illustrate through the stories wherein tricksters reside. I further argue that narrative intent, genre and cultural context appear to be the main factors that mould each respective figure. , Thesis (MA) -- Faculty of Humanities, School of Languages and Literatures, 2021
- Full Text:
- Date Issued: 2021-10-29
The economic valuation of ecosystem services using deliberation as a tool for value elicitation
- Authors: Marriner, James Derek
- Date: 2021-10-29
- Subjects: Seagrasses Economic aspects South Africa , Ecosystem services South Africa , Focus groups , Deliberative democracy South Africa , Nature Effect of human beings on South Africa , Environmental economics , Contingent valuation
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/294712 , vital:57247
- Description: Marine seagrass, Zostera capensis, is a highly productive flowering marine seagrass found on the eastern and southern coasts of South Africa and provides a variety of ecosystem services, which include reducing the effects of erosion, trapping nutrients, creating a nursery habitat for fish species and reducing sedimentation. Despite their formal protection status, Z. capensis meadows are regressing, often due to anthropogenic influences. Globally, multiple studies have documented the ecological importance of seagrass services, to both humans and nature, but economic evaluations of these services have not been as extensive. Numerous valuation methods have been used in literature and in practice to value non-market environmental resources and ecosystem services, where results vary. The most widely used non-market environmental valuation method is the contingent valuation (CV) method, which allows for the valuation of environmental resources that are not sold in the market through a stated willingness to pay (WTP) amount, contingent upon a particular scenario. However, the CV method is susceptible to various limitations and forms of bias. As a result, alternative environmental valuation techniques have been reviewed in literature. Deliberation has been suggested as an improved valuation approach to overcome the criticisms of the CV technique, as it increases respondents’ understanding and knowledge of the environmental resource under discussion, through the incorporation of debate, discussion, participation and social learning, thereby producing more reliable valuations of non-market environmental resources. The deliberative monetary valuation (DMV) method has been advocated as an important valuation method to achieve more comprehensive and reliable valuations of complex and unfamiliar public goods, such as ecosystem services. This thesis explored the determinants of WTP for the protection of seagrass, and whether deliberation can be used to supplement findings and values obtained from the individually sourced WTP values. As a result, the study used a dual-method approach to obtain both individual and deliberated WTP values from a range of stakeholders with varied socio-demographic characteristics by using both the CV method and a deliberative focus group, for the ecosystem services that seagrass Z. capensis provides to the Knysna community, South Africa. The results showed that age, education, use frequency and mistrust in local government were determinants in WTP, while deliberative elements uncovered that respondents’ knowledge of an environmental resource and a consideration of the valuation scenario were important factors in determining WTP. It was found that 55% of the respondents were willing to pay to conserve the ecosystem services of seagrass in the Knysna estuary through a monitoring programme. Among those that were willing, the mean WTP amount was approximately R132 per month per household. Although the circumstances in which the deliberative focus group discussion were run were not ideal because of the COVID-19 lockdown, the results showed some interesting potential benefits of using deliberation in complex public good valuation studies. , Thesis (MEcon) -- Faculty of Commerce, Economics and Economic History, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Marriner, James Derek
- Date: 2021-10-29
- Subjects: Seagrasses Economic aspects South Africa , Ecosystem services South Africa , Focus groups , Deliberative democracy South Africa , Nature Effect of human beings on South Africa , Environmental economics , Contingent valuation
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/294712 , vital:57247
- Description: Marine seagrass, Zostera capensis, is a highly productive flowering marine seagrass found on the eastern and southern coasts of South Africa and provides a variety of ecosystem services, which include reducing the effects of erosion, trapping nutrients, creating a nursery habitat for fish species and reducing sedimentation. Despite their formal protection status, Z. capensis meadows are regressing, often due to anthropogenic influences. Globally, multiple studies have documented the ecological importance of seagrass services, to both humans and nature, but economic evaluations of these services have not been as extensive. Numerous valuation methods have been used in literature and in practice to value non-market environmental resources and ecosystem services, where results vary. The most widely used non-market environmental valuation method is the contingent valuation (CV) method, which allows for the valuation of environmental resources that are not sold in the market through a stated willingness to pay (WTP) amount, contingent upon a particular scenario. However, the CV method is susceptible to various limitations and forms of bias. As a result, alternative environmental valuation techniques have been reviewed in literature. Deliberation has been suggested as an improved valuation approach to overcome the criticisms of the CV technique, as it increases respondents’ understanding and knowledge of the environmental resource under discussion, through the incorporation of debate, discussion, participation and social learning, thereby producing more reliable valuations of non-market environmental resources. The deliberative monetary valuation (DMV) method has been advocated as an important valuation method to achieve more comprehensive and reliable valuations of complex and unfamiliar public goods, such as ecosystem services. This thesis explored the determinants of WTP for the protection of seagrass, and whether deliberation can be used to supplement findings and values obtained from the individually sourced WTP values. As a result, the study used a dual-method approach to obtain both individual and deliberated WTP values from a range of stakeholders with varied socio-demographic characteristics by using both the CV method and a deliberative focus group, for the ecosystem services that seagrass Z. capensis provides to the Knysna community, South Africa. The results showed that age, education, use frequency and mistrust in local government were determinants in WTP, while deliberative elements uncovered that respondents’ knowledge of an environmental resource and a consideration of the valuation scenario were important factors in determining WTP. It was found that 55% of the respondents were willing to pay to conserve the ecosystem services of seagrass in the Knysna estuary through a monitoring programme. Among those that were willing, the mean WTP amount was approximately R132 per month per household. Although the circumstances in which the deliberative focus group discussion were run were not ideal because of the COVID-19 lockdown, the results showed some interesting potential benefits of using deliberation in complex public good valuation studies. , Thesis (MEcon) -- Faculty of Commerce, Economics and Economic History, 2021
- Full Text:
- Date Issued: 2021-10-29
Argyroploce Leucotreta: “The false Codlin moth”
- Authors: Horne, H M R
- Date: 1939
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/193375 , vital:45326
- Description: This introduction and ensuing essay are something in the nature of a personal confession. Deemed as such what I have written concerning Samuel Palmer has not, in any way, been written as an exercise, but rather for the purpose of self-edification. This I will elaborate upon while disclosing my motive for writing on Palmer. Palmer's works - when I first saw them - were something of a revelation. They seemed the alpha and omega of my own artistic endeavour. Perhaps the term which best describes the euphoria I felt is 1deja vu1, because although it describes a connectedness of sorts, the words have in their sound an exotic ring. There is in it an implied equivocation - and equivocality best describes my understanding of Samuel Palmer at that juncture. This euphoria I felt dimmed with the realisation that by purportedly claiming, as I was, Samuel Palmer's visionary landscapes as my goal I was treading on sacred ground; I'd arrived, as it were, in another's Paradise. The effects of this upon my own creativity were completely negative. Worse still, I lacked the necessary means to extricate myself from Palmer's paradisiacal visions. His influence was incapacitating and convoluting my own growth. It was obvious then that I had to be rid of Samuel Palmer. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 1939
- Full Text:
- Date Issued: 1939
- Authors: Horne, H M R
- Date: 1939
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/193375 , vital:45326
- Description: This introduction and ensuing essay are something in the nature of a personal confession. Deemed as such what I have written concerning Samuel Palmer has not, in any way, been written as an exercise, but rather for the purpose of self-edification. This I will elaborate upon while disclosing my motive for writing on Palmer. Palmer's works - when I first saw them - were something of a revelation. They seemed the alpha and omega of my own artistic endeavour. Perhaps the term which best describes the euphoria I felt is 1deja vu1, because although it describes a connectedness of sorts, the words have in their sound an exotic ring. There is in it an implied equivocation - and equivocality best describes my understanding of Samuel Palmer at that juncture. This euphoria I felt dimmed with the realisation that by purportedly claiming, as I was, Samuel Palmer's visionary landscapes as my goal I was treading on sacred ground; I'd arrived, as it were, in another's Paradise. The effects of this upon my own creativity were completely negative. Worse still, I lacked the necessary means to extricate myself from Palmer's paradisiacal visions. His influence was incapacitating and convoluting my own growth. It was obvious then that I had to be rid of Samuel Palmer. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 1939
- Full Text:
- Date Issued: 1939
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