Investigating the experiences of grade 8 English first additional language learners within an English home language classroom: a case study
- Authors: Abader, Naadirah
- Date: 2018
- Subjects: Language and languages -- Study and teaching -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DEd
- Identifier: http://hdl.handle.net/10948/22662 , vital:30050
- Description: Teaching English home language (EHL) to a classroom of learners who are predominantly from another mother tongue context is a complex process because of the challenges faced by the learners. They struggle to cope with the demands of the EHL classroom, especially when their mother tongue is not recognized within the classroom context, as they move between different linguistic spaces. Despite their diverse identities, English language teachers continue to apply the linguistic approach of English only. This study was aimed at investigating the ways in which the experiences of non-mother tongue speakers in the EHL classroom affect the identities of these learners. Through a qualitative approach using photovoice with learners an attempt was made to probe their experiences of bringing other languages into an English home language classroom. Participants included 33 Grade 8 learners and their four English teachers from Taah High School in Nelson Mandela Bay. The findings have implications for the way in which diverse linguistic learners are taught in an EHL classroom, as the space that caged and rendered learner participants voiceless because they are not allowed to draw on their mother tongue linguistic repertoires, were changed. Learners mentioned that their teachers do not acknowledge the identity that each of them brings to the classroom.
- Full Text:
- Date Issued: 2018
- Authors: Abader, Naadirah
- Date: 2018
- Subjects: Language and languages -- Study and teaching -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DEd
- Identifier: http://hdl.handle.net/10948/22662 , vital:30050
- Description: Teaching English home language (EHL) to a classroom of learners who are predominantly from another mother tongue context is a complex process because of the challenges faced by the learners. They struggle to cope with the demands of the EHL classroom, especially when their mother tongue is not recognized within the classroom context, as they move between different linguistic spaces. Despite their diverse identities, English language teachers continue to apply the linguistic approach of English only. This study was aimed at investigating the ways in which the experiences of non-mother tongue speakers in the EHL classroom affect the identities of these learners. Through a qualitative approach using photovoice with learners an attempt was made to probe their experiences of bringing other languages into an English home language classroom. Participants included 33 Grade 8 learners and their four English teachers from Taah High School in Nelson Mandela Bay. The findings have implications for the way in which diverse linguistic learners are taught in an EHL classroom, as the space that caged and rendered learner participants voiceless because they are not allowed to draw on their mother tongue linguistic repertoires, were changed. Learners mentioned that their teachers do not acknowledge the identity that each of them brings to the classroom.
- Full Text:
- Date Issued: 2018
Machinability of rapidly solidified aluminium alloy for optical applications
- Authors: Abbas, Abdalla Abbas Said
- Date: 2020
- Subjects: Aluminum alloys , Mechatronics
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/45975 , vital:39402
- Description: The production of metal mirrors and critical components for optical devices and aerospace application requires extreme high accuracy and outstanding surface quality. Thus, to achieve such high dimensional accuracies, they are being mainly produced through ultra-high precision machining. Aluminium alloys have been used in the production of components for optics application as well as spaceborne for so many years but with the advancement in technology and demands for a superior material, a new modified grade of aluminium was developed by a rapid solidification process. These grades exhibit a much better mechanical and physical properties while having a finer microstructure. The only downside is the limited research in the correlation of surface roughness and reflectance when single point diamond turned. In this study, rapidly solidified aluminium RSA 905 were used to investigate the effect of varying the cutting parameters on the machined surface finish and its corresponding surface reflectance. The cutting parameters were cutting speed, feed rate and depth of cut. The surface roughness was measured using Taylor Hopson PGI Profilometer while the reflectance factor was measured by using VERTEX 80v Spectrometer. The results were used to develop two predictive models namely; response surface and artificial neural network which have indicated a very high accuracy to the experimental measurements. Finally, the results were very promising for the diamond turning of RSA 905 where it has achieved a very low values of surface roughness and high reflectance in the visual range without the need of any additional production/fabrication steps and to ensure that bi-metallic binding does not take place in extreme low temperatures. Therefore, RSA 905 is a very promising material for optical applications in the visual spectrum.
- Full Text:
- Date Issued: 2020
- Authors: Abbas, Abdalla Abbas Said
- Date: 2020
- Subjects: Aluminum alloys , Mechatronics
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/45975 , vital:39402
- Description: The production of metal mirrors and critical components for optical devices and aerospace application requires extreme high accuracy and outstanding surface quality. Thus, to achieve such high dimensional accuracies, they are being mainly produced through ultra-high precision machining. Aluminium alloys have been used in the production of components for optics application as well as spaceborne for so many years but with the advancement in technology and demands for a superior material, a new modified grade of aluminium was developed by a rapid solidification process. These grades exhibit a much better mechanical and physical properties while having a finer microstructure. The only downside is the limited research in the correlation of surface roughness and reflectance when single point diamond turned. In this study, rapidly solidified aluminium RSA 905 were used to investigate the effect of varying the cutting parameters on the machined surface finish and its corresponding surface reflectance. The cutting parameters were cutting speed, feed rate and depth of cut. The surface roughness was measured using Taylor Hopson PGI Profilometer while the reflectance factor was measured by using VERTEX 80v Spectrometer. The results were used to develop two predictive models namely; response surface and artificial neural network which have indicated a very high accuracy to the experimental measurements. Finally, the results were very promising for the diamond turning of RSA 905 where it has achieved a very low values of surface roughness and high reflectance in the visual range without the need of any additional production/fabrication steps and to ensure that bi-metallic binding does not take place in extreme low temperatures. Therefore, RSA 905 is a very promising material for optical applications in the visual spectrum.
- Full Text:
- Date Issued: 2020
The incorporation of smart production in future factories within the fourth industrial revolution towards 2030
- Authors: Abdoll, Delicia Megan
- Date: 2020
- Subjects: Manufacturing industry
- Language: English
- Type: Thesis , Masters , Degree
- Identifier: http://hdl.handle.net/10948/47521 , vital:40123
- Description: Industry 4.0 is impressively creating a lasting impact on the manufacturing industry and on the industry outlook on the benefits of the implementation of new technology. The concept currently trending entails merging cyber systems, the Internet of Things, and the Internet of Systems all together to construct the revolutionary ‘Smart Factories’. The use of advanced technologies brings about new methodologies to improve the results of manufacturing. Complex activities will be performed by machines equipped in using intelligent information systems and new technology to improve productivity, enhance quality, and reduce costs of manufacturing products. South Africa is at the height of the ‘Fourth Industrial Revolution’ (4IR) which will essentially change the way we work. This innovative rubric of high-tech modernisation is characterised by a merging of technologies from the physical, digital, biological, and neuro-technological spheres. The hesitation over jobs being substituted with co-bots, a robot envisioned to actually cooperate with humans in a communal workplace, is profound. Skills volatility is estimated to affect all industries. There are uncertainties that the underprivileged and non-skilled would be thrust into an even profounder deficiency with the upsurge of the digital age. Organisations regard robotics and modern technology as strategic corporate tools that are utilised to enhance short- and long-term profitability and achieve operating goals. In dissimilarity, the application of robotics and modern technology in the place of work increases labour stability concerns, anxiety of downsizings and terminations within the workforce. The purpose of this research was to heighten the comprehension of smart factories in the manufacturing industry by conclusively embracing a methodical examination of the factors which influence the outlook of those involved concerning smart factory implementation and also of assessing the readiness of the South African manufacturing industry for 4IR towards 2030. The ‘golden thread’ running through the study is the significance of the impact of the 4IR on the workforce and the creation of new jobs for the future, the reskilling of the workforce and the enhancement of capabilities of future factories in embracing the implementation and the incorporation of advanced manufacturing principles in production processes. This must form a substantial consideration in the preparation of the vision of the “Incorporation of smart production in future factories within the fourth industrial revolution towards 2030”. The results of the in-depth analysis of future studies practice and theory in this research study give credibility to the argument that the way in which planning for the future of the 4IR in the South African context is taking place requires insightful adaptation by all stakeholders. The development of new insights through the application of futures studies is vital to this planning process, as is progressively demonstrated in the propensity for present-day business to enable collaborative decisions and strategies that are established on, and informed by, futures studies. This research has attempted to gain insight into the possible future of the implementation of 4IR elements within the future manufacturing factories in South Africa through the creation of four scenarios towards 2030. These are defined as follows: The Fifth Element, which is the ‘best case’ scenario, and to which the country aspires; the ‘worst case’ scenario, in which everything goes badly; the outlier future founded on a surprising, disruptive, emerging matter; and ‘business as usual’ in which no change takes place. The research additionally made efforts to determine the preferred future for the 4IR from a South African perspective, as a base for the Future Vision of the 4IR in the South African manufacturing industry towards 2030. Throughout this study, Inayatullah’s (2008) pillars of futures studies were implemented as a guide in mapping the present and future, further deepening and widening the future through the development of scenarios and, lastly, by transforming the future by narrowing it down to the preferred future. The South African manufacturing sector must select which path to follow in the decisions surrounding the acceptance of the 4IR as the country progresses towards aligning itself with the global players in technology acceptance. Through a unique and innovative approach, the establishment of an atmosphere of trust and the sharing of purpose, values and benefits, a collective Future Vision of the implementing of 4IR elements such as smart production in future factories within South Africa towards 2030, is achievable. All stakeholders must be committed to operating in collaborative partnerships, with government, society, local communities and the workforce all treading boldly together into a sphere of technological, commercial, environmental and social innovation.
- Full Text:
- Date Issued: 2020
- Authors: Abdoll, Delicia Megan
- Date: 2020
- Subjects: Manufacturing industry
- Language: English
- Type: Thesis , Masters , Degree
- Identifier: http://hdl.handle.net/10948/47521 , vital:40123
- Description: Industry 4.0 is impressively creating a lasting impact on the manufacturing industry and on the industry outlook on the benefits of the implementation of new technology. The concept currently trending entails merging cyber systems, the Internet of Things, and the Internet of Systems all together to construct the revolutionary ‘Smart Factories’. The use of advanced technologies brings about new methodologies to improve the results of manufacturing. Complex activities will be performed by machines equipped in using intelligent information systems and new technology to improve productivity, enhance quality, and reduce costs of manufacturing products. South Africa is at the height of the ‘Fourth Industrial Revolution’ (4IR) which will essentially change the way we work. This innovative rubric of high-tech modernisation is characterised by a merging of technologies from the physical, digital, biological, and neuro-technological spheres. The hesitation over jobs being substituted with co-bots, a robot envisioned to actually cooperate with humans in a communal workplace, is profound. Skills volatility is estimated to affect all industries. There are uncertainties that the underprivileged and non-skilled would be thrust into an even profounder deficiency with the upsurge of the digital age. Organisations regard robotics and modern technology as strategic corporate tools that are utilised to enhance short- and long-term profitability and achieve operating goals. In dissimilarity, the application of robotics and modern technology in the place of work increases labour stability concerns, anxiety of downsizings and terminations within the workforce. The purpose of this research was to heighten the comprehension of smart factories in the manufacturing industry by conclusively embracing a methodical examination of the factors which influence the outlook of those involved concerning smart factory implementation and also of assessing the readiness of the South African manufacturing industry for 4IR towards 2030. The ‘golden thread’ running through the study is the significance of the impact of the 4IR on the workforce and the creation of new jobs for the future, the reskilling of the workforce and the enhancement of capabilities of future factories in embracing the implementation and the incorporation of advanced manufacturing principles in production processes. This must form a substantial consideration in the preparation of the vision of the “Incorporation of smart production in future factories within the fourth industrial revolution towards 2030”. The results of the in-depth analysis of future studies practice and theory in this research study give credibility to the argument that the way in which planning for the future of the 4IR in the South African context is taking place requires insightful adaptation by all stakeholders. The development of new insights through the application of futures studies is vital to this planning process, as is progressively demonstrated in the propensity for present-day business to enable collaborative decisions and strategies that are established on, and informed by, futures studies. This research has attempted to gain insight into the possible future of the implementation of 4IR elements within the future manufacturing factories in South Africa through the creation of four scenarios towards 2030. These are defined as follows: The Fifth Element, which is the ‘best case’ scenario, and to which the country aspires; the ‘worst case’ scenario, in which everything goes badly; the outlier future founded on a surprising, disruptive, emerging matter; and ‘business as usual’ in which no change takes place. The research additionally made efforts to determine the preferred future for the 4IR from a South African perspective, as a base for the Future Vision of the 4IR in the South African manufacturing industry towards 2030. Throughout this study, Inayatullah’s (2008) pillars of futures studies were implemented as a guide in mapping the present and future, further deepening and widening the future through the development of scenarios and, lastly, by transforming the future by narrowing it down to the preferred future. The South African manufacturing sector must select which path to follow in the decisions surrounding the acceptance of the 4IR as the country progresses towards aligning itself with the global players in technology acceptance. Through a unique and innovative approach, the establishment of an atmosphere of trust and the sharing of purpose, values and benefits, a collective Future Vision of the implementing of 4IR elements such as smart production in future factories within South Africa towards 2030, is achievable. All stakeholders must be committed to operating in collaborative partnerships, with government, society, local communities and the workforce all treading boldly together into a sphere of technological, commercial, environmental and social innovation.
- Full Text:
- Date Issued: 2020
Molecularly imprinted polymeric materials for adsorptive removal of nitrogen compounds from fuel oils
- Abdul-Quadir, Muhammad Sabiu
- Authors: Abdul-Quadir, Muhammad Sabiu
- Date: 2018
- Subjects: Polymerization , Organonitrogen compounds Nitrogen compounds
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23426 , vital:30542
- Description: The deleterious effects of refractory polyaromatic hydrocarbons found in fuels such as organonitrogen compounds (quinoline, carbazole and its alkylated derivatives) are such that they emit NOx to the environment when combusted, thereby reducing air quality. These compounds also deactivate the catalyst used during fuel refinement and in catalytic converters of cars. Hydro-denitrogenation (HDN), a process currently being employed in petroleum refineries to eliminate organonitrogen compounds in fuels, is limited in treating these refractory compounds. Hence, this thesis describes the use of two separate complimentary approaches for the removal of organonitrogen compounds in fuel such as oxidative denitrogenation and adsorptive denitrogenation. The catalyzed oxidation of fuel oil model nitrogen containing compound, quinoline to quinoline N-oxide, was conducted under batch and continuous flow microreactor at 70°C by using tert-butylhydroperoxide (t-BuOOH) as oxidant and silica supported V2O5 as catalyst, followed by the selective adsorption of the quinoline N-oxide. An overall conversion of 62% quinoline N-oxide was observed. Quinoline-N-oxide in model fuel was absorbed by employing synthesized molecularly imprinted 2,6-pyridine-polybenzimidazole (2,6-PyPBI) nanofibers, 86% of quinoline-N-oxide was removed to give an adsorption capacity (qe) of 4.8 mg/g. DFT calculations to study the interactions of quinoline-N-oxide vs 2,6-PyPBI indicated that: (i) hydrogen bonding (through amino group of 2,6-PyPBI and oxygen atoms of the quinoline-N-oxide), (ii) pi-pi stacking and (iii) extensive number of van der Waals interactions took place. Several oxygenates from N-compounds were produced, thus, complicating the fuel matrix. Therefore, there is a need to move towards adsorptive denitrogenation. Poly-2-(1H-imidazol-2-yl)-4-phenol (PIMH) imprinted microspheres was prepared by suspension polymerization using 2-(2’-hydroxy-4-ethenylphenyl) imidazole as a functional monomer and ethylene glycol dimethacrylate as a crosslinker in the presence of various organonitrogen compounds (templates) to produce 2-(2’-hydroxy-4-ethenylphenyl) imidazole (PIMH). Imprinted microspheres show selectivity for various target model nitrogen-containing compounds with adsorption capacities of 6.8 ± 0.2 mg/g, 6.3 ± 0.3 mg/g and 5.8 ± 0.3 mg/g for quinoline, pyrimidine and carbazole, respectively. Adsorption selectivity increased in the order of quinoline (αi-r = 136.9) ˃ pyrimidine (αi-r = 126.2) ˃carbazole (αi-r = 86.3), when naphthalene was selected as a reference compound. Though, imprinted microspheres displayed excellent nitrogen compound removal both in model and real fuel, there was a need to improve the adsorbent adsorption capacity for N-compounds in fuel through the fabrication of imprinted nanofibers. Molecularly imprinted poly-2-(1H-imidazol-2-yl)-4-phenol nanofibers was prepared by electrospinning of 2-(2’-hydroxy-4-ethenylphenyl) imidazole (PIMH) in the presence of various organonitrogen compounds. These imprinted nanofibers show selectivity for various target model nitrogen-containing compounds with adsorption capacities of 11.7 ± 0.9 mg/g, 11.9 ± 0.8 mg/g and 11.3 ± 1.1 mg/g for quinoline, pyrimidine and carbazole, respectively. Adsorption selectivity increased in the order of pyrimidine (αi-r = 258.8) ˃ quinoline (αi-r = 235.5) ˃ carbazole (αi-r = 168.2). It further displayed excellent nitrogen removal in real fuel. The use of polybenzimidazole (PBI) nanofibers showed selective adsorption of organonitrogen compounds as imprinted sorbent also displayed high selectivity for their target model nitrogen-containing compounds with adsorption capacities of 11.4 ± 0.4 mg/g, 11.9 ± 0.2 mg/g and 10.9 ± 0.7 mg/g for quinoline, pyrimidine and carbazole respectively. Adsorption selectivity increased in the order of pyrimidine (αi-r = 241.5) ˃ quinoline (αi-r = 237.6) ˃ carbazole (αi-r = 170). Thermodynamic parameters obtained from isothermal titration calorimetry (ITC) revealed that quinoline-PIMH/PBI and pyrimidine-PIMH/PBI interactions are exothermic in nature, while carbazole-PIMH/PBI is endothermic in nature. DFT calculations indicated that π-π interactions/stacking and hydrogen bond interactions took place between N-compounds (carbazole, quinoline and pyrimidine) and adsorbent (PIMH and PBI). A significant reduction in the quantity of nitrogen containing compounds in hydrotreated fuel was observed (peak area reduction) when adsorbents (PIMH and PBI) was employed, however, the complex nature of organonitrogen compounds in fuel complicate the structure/function approach on MIPs for targeting these unwanted compounds.
- Full Text:
- Date Issued: 2018
- Authors: Abdul-Quadir, Muhammad Sabiu
- Date: 2018
- Subjects: Polymerization , Organonitrogen compounds Nitrogen compounds
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23426 , vital:30542
- Description: The deleterious effects of refractory polyaromatic hydrocarbons found in fuels such as organonitrogen compounds (quinoline, carbazole and its alkylated derivatives) are such that they emit NOx to the environment when combusted, thereby reducing air quality. These compounds also deactivate the catalyst used during fuel refinement and in catalytic converters of cars. Hydro-denitrogenation (HDN), a process currently being employed in petroleum refineries to eliminate organonitrogen compounds in fuels, is limited in treating these refractory compounds. Hence, this thesis describes the use of two separate complimentary approaches for the removal of organonitrogen compounds in fuel such as oxidative denitrogenation and adsorptive denitrogenation. The catalyzed oxidation of fuel oil model nitrogen containing compound, quinoline to quinoline N-oxide, was conducted under batch and continuous flow microreactor at 70°C by using tert-butylhydroperoxide (t-BuOOH) as oxidant and silica supported V2O5 as catalyst, followed by the selective adsorption of the quinoline N-oxide. An overall conversion of 62% quinoline N-oxide was observed. Quinoline-N-oxide in model fuel was absorbed by employing synthesized molecularly imprinted 2,6-pyridine-polybenzimidazole (2,6-PyPBI) nanofibers, 86% of quinoline-N-oxide was removed to give an adsorption capacity (qe) of 4.8 mg/g. DFT calculations to study the interactions of quinoline-N-oxide vs 2,6-PyPBI indicated that: (i) hydrogen bonding (through amino group of 2,6-PyPBI and oxygen atoms of the quinoline-N-oxide), (ii) pi-pi stacking and (iii) extensive number of van der Waals interactions took place. Several oxygenates from N-compounds were produced, thus, complicating the fuel matrix. Therefore, there is a need to move towards adsorptive denitrogenation. Poly-2-(1H-imidazol-2-yl)-4-phenol (PIMH) imprinted microspheres was prepared by suspension polymerization using 2-(2’-hydroxy-4-ethenylphenyl) imidazole as a functional monomer and ethylene glycol dimethacrylate as a crosslinker in the presence of various organonitrogen compounds (templates) to produce 2-(2’-hydroxy-4-ethenylphenyl) imidazole (PIMH). Imprinted microspheres show selectivity for various target model nitrogen-containing compounds with adsorption capacities of 6.8 ± 0.2 mg/g, 6.3 ± 0.3 mg/g and 5.8 ± 0.3 mg/g for quinoline, pyrimidine and carbazole, respectively. Adsorption selectivity increased in the order of quinoline (αi-r = 136.9) ˃ pyrimidine (αi-r = 126.2) ˃carbazole (αi-r = 86.3), when naphthalene was selected as a reference compound. Though, imprinted microspheres displayed excellent nitrogen compound removal both in model and real fuel, there was a need to improve the adsorbent adsorption capacity for N-compounds in fuel through the fabrication of imprinted nanofibers. Molecularly imprinted poly-2-(1H-imidazol-2-yl)-4-phenol nanofibers was prepared by electrospinning of 2-(2’-hydroxy-4-ethenylphenyl) imidazole (PIMH) in the presence of various organonitrogen compounds. These imprinted nanofibers show selectivity for various target model nitrogen-containing compounds with adsorption capacities of 11.7 ± 0.9 mg/g, 11.9 ± 0.8 mg/g and 11.3 ± 1.1 mg/g for quinoline, pyrimidine and carbazole, respectively. Adsorption selectivity increased in the order of pyrimidine (αi-r = 258.8) ˃ quinoline (αi-r = 235.5) ˃ carbazole (αi-r = 168.2). It further displayed excellent nitrogen removal in real fuel. The use of polybenzimidazole (PBI) nanofibers showed selective adsorption of organonitrogen compounds as imprinted sorbent also displayed high selectivity for their target model nitrogen-containing compounds with adsorption capacities of 11.4 ± 0.4 mg/g, 11.9 ± 0.2 mg/g and 10.9 ± 0.7 mg/g for quinoline, pyrimidine and carbazole respectively. Adsorption selectivity increased in the order of pyrimidine (αi-r = 241.5) ˃ quinoline (αi-r = 237.6) ˃ carbazole (αi-r = 170). Thermodynamic parameters obtained from isothermal titration calorimetry (ITC) revealed that quinoline-PIMH/PBI and pyrimidine-PIMH/PBI interactions are exothermic in nature, while carbazole-PIMH/PBI is endothermic in nature. DFT calculations indicated that π-π interactions/stacking and hydrogen bond interactions took place between N-compounds (carbazole, quinoline and pyrimidine) and adsorbent (PIMH and PBI). A significant reduction in the quantity of nitrogen containing compounds in hydrotreated fuel was observed (peak area reduction) when adsorbents (PIMH and PBI) was employed, however, the complex nature of organonitrogen compounds in fuel complicate the structure/function approach on MIPs for targeting these unwanted compounds.
- Full Text:
- Date Issued: 2018
Optical surface quality and molecular dynamics modelling of ultra-high precision optical silicon machining
- Authors: Abdulkadir, Lukman Niyi
- Date: 2019-04
- Subjects: Engineering design -- Data processing , Manufacturing processes -- Data processing , Mechatronics
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/66552 , vital:75601
- Description: Hard and brittle materials, such as silicon, silicon carbide etc., are widely used in aerospace, integrated circuit, and other fields due to their excellent physical and chemical properties. However, these materials display poor machinability owing to hardness, brittleness, non-linearity in machining process and complexities in selecting suitable machining parameters and tool geometry. These leads to low quality lenses due to subsurface damage and surface micro-crack. Additionally, it is experimentally very difficult to observe all nanoscale physical phenomena due to in-process measurement problems, inaccessible contact area of tool and workpiece, and the difficulty of surface analysis. With the use of molecular dynamics (MD) which is a comprehensive nanoscale modelling technique, proper selection of process parameters, tool geometry and online monitoring techniques, production of freeform optics is possible through Ultra-high precision diamond turning (UHPDT). Though, depending on view point, machinability in UHPDT may be in terms of tool wear rate, hardness, chip morphology, surface roughness, and other benchmarks. These situations have called for more insights, which on the long run will help to achieve high precision manufacturing with predictability, repeatability, productivity and high infrared (IR) optical quality. In this thesis, UHPDT of monocrystalline silicon at atomistic scale was conducted to investigate combined effects of edge radius, feed rate, cutting speed, depth of cut, rake and clearance angles hitherto not done so far. Using appropriate potential functions with the MD algorithm, comprehensive analysis of thermal effects, diamond tool wear, phase change, cutting forces and machining stresses (normal, shear, hydrostatic and von Mises) were carried out. Dislocation extraction algorithm (DXA) and radial distribution function (RDF) were used to evaluate dislocation nucleation, variations in bond lengths, microstructural transformation and represents structural changes in histogram form. Selected parameters for optical quality surface roughness were afterwards compared and optimized through response surface methodology (RSM) based on Box Behnken (BBD) and Taguchi L9 methods. The results indicated that, silicon atoms in the chip formation zone undergo high pressure phase transformation (HPPT) at high hydrostatic pressure and temperature.Silicon microstructure transformed from four-coordinated diamond cubic structure (Si- I) to unstable six-coordinated body-centered tetragonal structure (β-silicon) which then transformed to amorphous silicon atoms (a-Si) through amorphization. These resulted in plastic deformation and defects in the machining zone causing subsurface damage. Stress analysis indicated that the compressive stress in the machining zone (i.e. amorphous region) suppressed crack formation contributing to continuous plastic flow which is responsible for silicon ductile-mode cutting. Furthermore, formation of silicon carbide which constituted diamond wear was observed to be by sp3 - sp2 diamond carbon atom disorder and tribochemistry. The tribochemistry occurred through both multiphase and solid-state single-phase reaction between diamond tool and silicon workpiece at cutting temperatures above and below 959 K. Both the experimental findings and the simulation results reveal that, at edge radius less than uncut chip thickness, tool wear was more of rake wear than flank wear. Tool wear and kinetic friction reduced as the edge radius approached the uncut chip thickness while forces, stresses and SCE increased. When machining silicon at differentratio, silicon stress state, SCE, SSD, forces (reduced with increase in clearance angle), shear plane, chip velocity and chip ratio increased as edge radius and rake angle increased, while, kinetic friction, chip length and thickness reduced. The crystal lattice of the machined surfaces and subsurface deformed layer depth increased with increase in edge radius, feed and rake angle. Amongst all tested and analysed parameters, feed rate had the highest influence on surface quality while depth of cut showed the least. Acoustic emission was also monitored during machining and its results statistically analysed. The trends of the monitored acoustic emissions showed its capability to adequately represent and predict surface roughness results. Based on the developed simulation model a novel method for quantitative assessment of tool wear was proposed. The proposed model can be used to compare tool wear using graphitization and tribochemistry to decide the path and mode of the diamond tool wear. Finally, based on the experiment results and predictive model, a novel combination and hierarchical arrangement of the considered factors capable of suppressing tool wear and improve attainable machined surface roughness when turning hard-to-machine materials was proposed. , Thesis (D.Phil) -- Faculty of Engineering, the Built Environment, and Technology, School of Engineering, 2019
- Full Text:
- Date Issued: 2019-04
- Authors: Abdulkadir, Lukman Niyi
- Date: 2019-04
- Subjects: Engineering design -- Data processing , Manufacturing processes -- Data processing , Mechatronics
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/66552 , vital:75601
- Description: Hard and brittle materials, such as silicon, silicon carbide etc., are widely used in aerospace, integrated circuit, and other fields due to their excellent physical and chemical properties. However, these materials display poor machinability owing to hardness, brittleness, non-linearity in machining process and complexities in selecting suitable machining parameters and tool geometry. These leads to low quality lenses due to subsurface damage and surface micro-crack. Additionally, it is experimentally very difficult to observe all nanoscale physical phenomena due to in-process measurement problems, inaccessible contact area of tool and workpiece, and the difficulty of surface analysis. With the use of molecular dynamics (MD) which is a comprehensive nanoscale modelling technique, proper selection of process parameters, tool geometry and online monitoring techniques, production of freeform optics is possible through Ultra-high precision diamond turning (UHPDT). Though, depending on view point, machinability in UHPDT may be in terms of tool wear rate, hardness, chip morphology, surface roughness, and other benchmarks. These situations have called for more insights, which on the long run will help to achieve high precision manufacturing with predictability, repeatability, productivity and high infrared (IR) optical quality. In this thesis, UHPDT of monocrystalline silicon at atomistic scale was conducted to investigate combined effects of edge radius, feed rate, cutting speed, depth of cut, rake and clearance angles hitherto not done so far. Using appropriate potential functions with the MD algorithm, comprehensive analysis of thermal effects, diamond tool wear, phase change, cutting forces and machining stresses (normal, shear, hydrostatic and von Mises) were carried out. Dislocation extraction algorithm (DXA) and radial distribution function (RDF) were used to evaluate dislocation nucleation, variations in bond lengths, microstructural transformation and represents structural changes in histogram form. Selected parameters for optical quality surface roughness were afterwards compared and optimized through response surface methodology (RSM) based on Box Behnken (BBD) and Taguchi L9 methods. The results indicated that, silicon atoms in the chip formation zone undergo high pressure phase transformation (HPPT) at high hydrostatic pressure and temperature.Silicon microstructure transformed from four-coordinated diamond cubic structure (Si- I) to unstable six-coordinated body-centered tetragonal structure (β-silicon) which then transformed to amorphous silicon atoms (a-Si) through amorphization. These resulted in plastic deformation and defects in the machining zone causing subsurface damage. Stress analysis indicated that the compressive stress in the machining zone (i.e. amorphous region) suppressed crack formation contributing to continuous plastic flow which is responsible for silicon ductile-mode cutting. Furthermore, formation of silicon carbide which constituted diamond wear was observed to be by sp3 - sp2 diamond carbon atom disorder and tribochemistry. The tribochemistry occurred through both multiphase and solid-state single-phase reaction between diamond tool and silicon workpiece at cutting temperatures above and below 959 K. Both the experimental findings and the simulation results reveal that, at edge radius less than uncut chip thickness, tool wear was more of rake wear than flank wear. Tool wear and kinetic friction reduced as the edge radius approached the uncut chip thickness while forces, stresses and SCE increased. When machining silicon at differentratio, silicon stress state, SCE, SSD, forces (reduced with increase in clearance angle), shear plane, chip velocity and chip ratio increased as edge radius and rake angle increased, while, kinetic friction, chip length and thickness reduced. The crystal lattice of the machined surfaces and subsurface deformed layer depth increased with increase in edge radius, feed and rake angle. Amongst all tested and analysed parameters, feed rate had the highest influence on surface quality while depth of cut showed the least. Acoustic emission was also monitored during machining and its results statistically analysed. The trends of the monitored acoustic emissions showed its capability to adequately represent and predict surface roughness results. Based on the developed simulation model a novel method for quantitative assessment of tool wear was proposed. The proposed model can be used to compare tool wear using graphitization and tribochemistry to decide the path and mode of the diamond tool wear. Finally, based on the experiment results and predictive model, a novel combination and hierarchical arrangement of the considered factors capable of suppressing tool wear and improve attainable machined surface roughness when turning hard-to-machine materials was proposed. , Thesis (D.Phil) -- Faculty of Engineering, the Built Environment, and Technology, School of Engineering, 2019
- Full Text:
- Date Issued: 2019-04
Optical surface quality and molecular dynamics modelling of ultra-high precision optical silicon machining
- Authors: Abdulkadir, Lukman Niyi
- Date: 2019-04
- Subjects: Lasers -- Industrial applications , Manufacturing processes , Materials science
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/66551 , vital:75600
- Description: Hard and brittle materials, such as silicon, silicon carbide etc., are widely used in aerospace, integrated circuit, and other fields due to their excellent physical and chemical properties. However, these materials display poor machinability owing to hardness, brittleness, non-linearity in machining process and complexities in selecting suitable machining parameters and tool geometry. These leads to low quality lenses due to subsurface damage and surface micro-crack. Additionally, it is experimentally very difficult to observe all nanoscale physical phenomena due to in-process measurement problems, inaccessible contact area of tool and workpiece, and the difficulty of surface analysis. With the use of molecular dynamics (MD) which is a comprehensive nanoscale modelling technique, proper selection of process parameters, tool geometry and online monitoring techniques, production of freeform optics is possible through Ultra-high precision diamond turning (UHPDT). Though, depending on view point, machinability in UHPDT may be in terms of tool wear rate, hardness, chip morphology, surface roughness, and other benchmarks. These situations have called for more insights, which on the long run will help to achieve high precision manufacturing with predictability, repeatability, productivity and high infrared (IR) optical quality. In this thesis, UHPDT of monocrystalline silicon at atomistic scale was conducted to investigate combined effects of edge radius, feed rate, cutting speed, depth of cut, rake and clearance angles hitherto not done so far. Using appropriate potential functions with the MD algorithm, comprehensive analysis of thermal effects, diamond tool wear, phase change, cutting forces and machining stresses (normal, shear, hydrostatic and von Mises) were carried out. Dislocation extraction algorithm (DXA) and radial distribution function (RDF) were used to evaluate dislocation nucleation, variations in bond lengths, microstructural transformation and represents structural changes in histogram form. Selected parameters for optical quality surface roughness were afterwards compared and optimized through response surface methodology (RSM) based on Box Behnken (BBD) and Taguchi L9 methods. The results indicated that, silicon atoms in the chip formation zone undergo high pressure phase transformation (HPPT) at high hydrostatic pressure and temperature Silicon microstructure transformed from four-coordinated diamond cubic structure (Si-I) to unstable six-coordinated body-centered tetragonal structure (β-silicon) which then transformed to amorphous silicon atoms (a-Si) through amorphization. These resulted in plastic deformation and defects in the machining zone causing subsurface damage. Stress analysis indicated that the compressive stress in the machining zone (i.e.amorphous region) suppressed crack formation contributing to continuous plastic flow which is responsible for silicon ductile-mode cutting. Furthermore, formation of silicon carbide which constituted diamond wear was observed to be by sp3 - sp2 diamond carbon atom disorder and tribochemistry. The tribochemistry occurred through both multiphase and solid-state single-phase reaction between diamond tool and silicon workpiece at cutting temperatures above and below 959 K. Both the experimental findings and the simulation results reveal that, at edge radius less than uncut chip thickness, tool wear was more of rake wear than flank wear. Tool wear and kinetic friction reduced as the edge radius approached the uncut chip thickness while forces, stresses and SCE increased. When machining silicon at different ratio, silicon stress state, SCE, SSD, forces (reduced with increase in clearance angle), shear plane, chip velocity and chip ratio increased as edge radius and rake angle increased, while, kinetic friction, chip length and thickness reduced. The crystal lattice of the machined surfaces and subsurface deformed layer depth increased with increase in edge radius, feed and rake angle. Amongst all tested and analysed parameters, feed rate had the highest influence on surface quality while depth of cut showed the least. Acoustic emission was also monitored during machining and its results statistically analysed. The trends of the monitored acoustic emissions showed its capability to adequately represent and predict surface roughness results. Based on the developed simulation model a novel method for quantitative assessment of tool wear was proposed. The proposed model can be used to compare tool wear using graphitization and tribochemistry to decide the path and mode of the diamond tool wear. Finally, based on the experiment results and predictive model, a novel combination and hierarchical arrangement of the considered factors capable of suppressing tool wear and improve attainable machined surface roughness when turning hard-to-machine materials was proposed. , Thesis (PhD) -- Faculty of Engineering, the Built Environment, and Technology, School of Engineering, 2019
- Full Text:
- Date Issued: 2019-04
- Authors: Abdulkadir, Lukman Niyi
- Date: 2019-04
- Subjects: Lasers -- Industrial applications , Manufacturing processes , Materials science
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/66551 , vital:75600
- Description: Hard and brittle materials, such as silicon, silicon carbide etc., are widely used in aerospace, integrated circuit, and other fields due to their excellent physical and chemical properties. However, these materials display poor machinability owing to hardness, brittleness, non-linearity in machining process and complexities in selecting suitable machining parameters and tool geometry. These leads to low quality lenses due to subsurface damage and surface micro-crack. Additionally, it is experimentally very difficult to observe all nanoscale physical phenomena due to in-process measurement problems, inaccessible contact area of tool and workpiece, and the difficulty of surface analysis. With the use of molecular dynamics (MD) which is a comprehensive nanoscale modelling technique, proper selection of process parameters, tool geometry and online monitoring techniques, production of freeform optics is possible through Ultra-high precision diamond turning (UHPDT). Though, depending on view point, machinability in UHPDT may be in terms of tool wear rate, hardness, chip morphology, surface roughness, and other benchmarks. These situations have called for more insights, which on the long run will help to achieve high precision manufacturing with predictability, repeatability, productivity and high infrared (IR) optical quality. In this thesis, UHPDT of monocrystalline silicon at atomistic scale was conducted to investigate combined effects of edge radius, feed rate, cutting speed, depth of cut, rake and clearance angles hitherto not done so far. Using appropriate potential functions with the MD algorithm, comprehensive analysis of thermal effects, diamond tool wear, phase change, cutting forces and machining stresses (normal, shear, hydrostatic and von Mises) were carried out. Dislocation extraction algorithm (DXA) and radial distribution function (RDF) were used to evaluate dislocation nucleation, variations in bond lengths, microstructural transformation and represents structural changes in histogram form. Selected parameters for optical quality surface roughness were afterwards compared and optimized through response surface methodology (RSM) based on Box Behnken (BBD) and Taguchi L9 methods. The results indicated that, silicon atoms in the chip formation zone undergo high pressure phase transformation (HPPT) at high hydrostatic pressure and temperature Silicon microstructure transformed from four-coordinated diamond cubic structure (Si-I) to unstable six-coordinated body-centered tetragonal structure (β-silicon) which then transformed to amorphous silicon atoms (a-Si) through amorphization. These resulted in plastic deformation and defects in the machining zone causing subsurface damage. Stress analysis indicated that the compressive stress in the machining zone (i.e.amorphous region) suppressed crack formation contributing to continuous plastic flow which is responsible for silicon ductile-mode cutting. Furthermore, formation of silicon carbide which constituted diamond wear was observed to be by sp3 - sp2 diamond carbon atom disorder and tribochemistry. The tribochemistry occurred through both multiphase and solid-state single-phase reaction between diamond tool and silicon workpiece at cutting temperatures above and below 959 K. Both the experimental findings and the simulation results reveal that, at edge radius less than uncut chip thickness, tool wear was more of rake wear than flank wear. Tool wear and kinetic friction reduced as the edge radius approached the uncut chip thickness while forces, stresses and SCE increased. When machining silicon at different ratio, silicon stress state, SCE, SSD, forces (reduced with increase in clearance angle), shear plane, chip velocity and chip ratio increased as edge radius and rake angle increased, while, kinetic friction, chip length and thickness reduced. The crystal lattice of the machined surfaces and subsurface deformed layer depth increased with increase in edge radius, feed and rake angle. Amongst all tested and analysed parameters, feed rate had the highest influence on surface quality while depth of cut showed the least. Acoustic emission was also monitored during machining and its results statistically analysed. The trends of the monitored acoustic emissions showed its capability to adequately represent and predict surface roughness results. Based on the developed simulation model a novel method for quantitative assessment of tool wear was proposed. The proposed model can be used to compare tool wear using graphitization and tribochemistry to decide the path and mode of the diamond tool wear. Finally, based on the experiment results and predictive model, a novel combination and hierarchical arrangement of the considered factors capable of suppressing tool wear and improve attainable machined surface roughness when turning hard-to-machine materials was proposed. , Thesis (PhD) -- Faculty of Engineering, the Built Environment, and Technology, School of Engineering, 2019
- Full Text:
- Date Issued: 2019-04
A co-constructed practice model for supporting parents of children in conflict with the law
- Authors: Abdulla, Zurina
- Date: 2019
- Subjects: Children's rights -- South Africa , Children -- Legal status, laws, etc --South Africa , Parent and child -- Research -- South Africa , Social work with youth -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/30474 , vital:30949
- Description: The unique historical stressors linked to South Africa’s apartheid legacy, continues to manifest in the form of economic exclusion, social exclusion, inequality and poverty, with parents being subjugated to service users and extenders rather than included as service advocates, particularly in the child justice system. Furthermore, policies and practices do not include, engage and support parents on an intra and interpersonal level. Parents of children in conflict with the law, experience their children’s charge or arrest as well as their subsequent journey through the child justice system as a crisis resulting in their need for emotional, informational, practical and professional support during the child justice process. The similarities and differences between the contexts of child protection and child justice in supporting parents illuminates the existing gaps in child justice legislation, policy and practice resulting in a lack of support for parents during the child justice process. In the Children’s Act 38 of 2005, it is recognised that parents have a legal responsibility towards their children and that in fulfilling this responsibility parents can access support services to assist them when they face challenges in fulfilling this responsibility. In contrast, despite 80 percent of children in conflict with the law being released into parental care and parents expressing the need for support in fulfilling their parental responsibility, in this regard the Child Justice Act 75 of 2008 fails to make provision for parents to access support services. The child justice system’s narrow focus on parents as service extenders contributes to parents’ being excluded from targeted support services resulting in parents’ support needs not being addressed. The lack of programmes and services aimed at supporting parents highlight the need for coordinated services that address the multiple stressors parents are exposed to. To this end, this study was aimed at coconstructing a practice model for supporting parents of children in conflict with the law. The theoretical lenses employed in the current study namely; the Ecological systems model and the Buffering effect model describes the various systems parents need support from and the type of support they need from their family, community and professionals. Guided by a qualitative approach, the present study integrated applied research, in particular intervention design and development with participatory action research as it allowed systematic collaboration during the research process to ensure rigour. This study involved participants from two research sites namely, the Nerina One- Stop Child Justice Centre in Port Elizabeth and the Reception, Assessment and Referral office at the Uitenhage magistrates’ court. Employing a non-probability purposive sampling method, this study facilitated the participation of parents of children in conflict with the law and child justice officials who met the inclusion criteria, in the co-design and development of a practice model for supporting parents of children in conflict with the law. Participants assumed an expert and collaborative role, which enabled the co-construction of knowledge, meaning and innovation of the practice model. Qualitative data collection methods namely, twelve focus groups and thirty two participant observations, were used to explore, co-construct, describe and design a practice model for supporting parents of children in conflict with the law during the child justice process. Thematic analyses was employed to condense the data, search for codes, categories, themes, relationships and patterns in the data. Due to the research approach and design, data analysis was ongoing and informed design and development of the practice model. Based on the thematic analysis and synthesis both descriptive and analytic themes emerged. To ensure trustworthiness, this study employed various strategies to strengthen commitment, rigour, transparency and coherence. In addition, the participative research process, the inclusion of multiple forms of qualitative inquiry and the significance of the study contributed to the validity and quality of the study. Ethical considerations applicable to the study included participants’ voluntary participation, their informed consent and ensuring participants’ privacy or maintaining confidentially. Various strategies were employed to prevent or minimise risk to participants. The findings showed that formal sources of support, in particular, offer opportunities for parents to access individual and family counselling, parenting advice, and peer support. The study also highlighted the importance of recognising parents as a subsystem in the child justice system offers potential opportunities for inclusion of parents as co-facilitators of parenting programmes or support groups, as peer supporters during the child justice process. Parents’ inclusion as a partner in the child justice system is highlighted as an opportunity for parents to be able to vi participate in child justice fora, oversight committees and accreditation committees to influence policy, services and budget allocations for services to support parents of children in conflict with the law. This study’s contribution to the existing body of knowledge is an integrated, multidisciplinary, multi-phase co-constructed practice model that would enable inclusion of, and support for, parents of children in conflict with the law prior to, during and after the child justice. The co-constructed practice model (a) involves a continuum of parent-centred support for and inclusion of parents prior to, during and after the child justice process; (b) advances an inclusive and collaborative child justice system that views parents as important stakeholders in determining the type of services they need and being involved in developing practice; and (c) promotes parents as equal partners in decision making and policy making to influence legislation, policy and practice in the child justice system.
- Full Text:
- Date Issued: 2019
- Authors: Abdulla, Zurina
- Date: 2019
- Subjects: Children's rights -- South Africa , Children -- Legal status, laws, etc --South Africa , Parent and child -- Research -- South Africa , Social work with youth -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/30474 , vital:30949
- Description: The unique historical stressors linked to South Africa’s apartheid legacy, continues to manifest in the form of economic exclusion, social exclusion, inequality and poverty, with parents being subjugated to service users and extenders rather than included as service advocates, particularly in the child justice system. Furthermore, policies and practices do not include, engage and support parents on an intra and interpersonal level. Parents of children in conflict with the law, experience their children’s charge or arrest as well as their subsequent journey through the child justice system as a crisis resulting in their need for emotional, informational, practical and professional support during the child justice process. The similarities and differences between the contexts of child protection and child justice in supporting parents illuminates the existing gaps in child justice legislation, policy and practice resulting in a lack of support for parents during the child justice process. In the Children’s Act 38 of 2005, it is recognised that parents have a legal responsibility towards their children and that in fulfilling this responsibility parents can access support services to assist them when they face challenges in fulfilling this responsibility. In contrast, despite 80 percent of children in conflict with the law being released into parental care and parents expressing the need for support in fulfilling their parental responsibility, in this regard the Child Justice Act 75 of 2008 fails to make provision for parents to access support services. The child justice system’s narrow focus on parents as service extenders contributes to parents’ being excluded from targeted support services resulting in parents’ support needs not being addressed. The lack of programmes and services aimed at supporting parents highlight the need for coordinated services that address the multiple stressors parents are exposed to. To this end, this study was aimed at coconstructing a practice model for supporting parents of children in conflict with the law. The theoretical lenses employed in the current study namely; the Ecological systems model and the Buffering effect model describes the various systems parents need support from and the type of support they need from their family, community and professionals. Guided by a qualitative approach, the present study integrated applied research, in particular intervention design and development with participatory action research as it allowed systematic collaboration during the research process to ensure rigour. This study involved participants from two research sites namely, the Nerina One- Stop Child Justice Centre in Port Elizabeth and the Reception, Assessment and Referral office at the Uitenhage magistrates’ court. Employing a non-probability purposive sampling method, this study facilitated the participation of parents of children in conflict with the law and child justice officials who met the inclusion criteria, in the co-design and development of a practice model for supporting parents of children in conflict with the law. Participants assumed an expert and collaborative role, which enabled the co-construction of knowledge, meaning and innovation of the practice model. Qualitative data collection methods namely, twelve focus groups and thirty two participant observations, were used to explore, co-construct, describe and design a practice model for supporting parents of children in conflict with the law during the child justice process. Thematic analyses was employed to condense the data, search for codes, categories, themes, relationships and patterns in the data. Due to the research approach and design, data analysis was ongoing and informed design and development of the practice model. Based on the thematic analysis and synthesis both descriptive and analytic themes emerged. To ensure trustworthiness, this study employed various strategies to strengthen commitment, rigour, transparency and coherence. In addition, the participative research process, the inclusion of multiple forms of qualitative inquiry and the significance of the study contributed to the validity and quality of the study. Ethical considerations applicable to the study included participants’ voluntary participation, their informed consent and ensuring participants’ privacy or maintaining confidentially. Various strategies were employed to prevent or minimise risk to participants. The findings showed that formal sources of support, in particular, offer opportunities for parents to access individual and family counselling, parenting advice, and peer support. The study also highlighted the importance of recognising parents as a subsystem in the child justice system offers potential opportunities for inclusion of parents as co-facilitators of parenting programmes or support groups, as peer supporters during the child justice process. Parents’ inclusion as a partner in the child justice system is highlighted as an opportunity for parents to be able to vi participate in child justice fora, oversight committees and accreditation committees to influence policy, services and budget allocations for services to support parents of children in conflict with the law. This study’s contribution to the existing body of knowledge is an integrated, multidisciplinary, multi-phase co-constructed practice model that would enable inclusion of, and support for, parents of children in conflict with the law prior to, during and after the child justice. The co-constructed practice model (a) involves a continuum of parent-centred support for and inclusion of parents prior to, during and after the child justice process; (b) advances an inclusive and collaborative child justice system that views parents as important stakeholders in determining the type of services they need and being involved in developing practice; and (c) promotes parents as equal partners in decision making and policy making to influence legislation, policy and practice in the child justice system.
- Full Text:
- Date Issued: 2019
Executing a process enhancement intervention on the processing lines at Seavuna Fishing Company
- Authors: Abdullah, Philip Rodger
- Date: 2017
- Subjects: Organizational effectiveness -- South Africa , Small business -- South Africa Workflow -- South Africa -- Management Business planning
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/13592 , vital:27255
- Description: The fresh hake processing lines at Seavuna fishing company in Mossel Bay are not consistently achieving their volume output standards and this is resulting in higher processing costs and loss of processing opportunities. The company’s senior management are concerned about this trend and require a complete review of the effectiveness of the resources deployed on the lines. This with the view of establishing the causes of poor process volume output. In order to resolve the process inefficiency challenges mentioned, this study used both empirical and time studies to investigate the effectiveness of the company’s resources directly deployed in the processing unit. The study focused on investigating the human factor, machinery and equipment, the environment and the current efficiency standards. Relevant literature in the field of process efficiency improvement was consulted to assist in identifying factors that are known to cause process inefficiencies, and also to establish which improvement techniques would be relevant in correcting the situation. From the Literature reviewed, it was evident that a ‘one size fits all’ solution to resolving inefficiencies is almost non-existent and that a solution that is relevant to the problem is more effective. In addition, a benchmarking exercise was also done to establish how Seavuna’s current volume output standards fair against its major rivals. Once data from both studies were collected, the results were analysed using the some of the basic quality tools. Thereafter, lean manufacturing principles were used to attempt to resolve the current efficiency challenges. The study recommended that the company construct a business strategy and a corresponding organisational culture to direct its continuous improvement interventions. The use of strategic quality planning would go a long way in assisting the company to execute some of the interventions recommended.
- Full Text:
- Date Issued: 2017
- Authors: Abdullah, Philip Rodger
- Date: 2017
- Subjects: Organizational effectiveness -- South Africa , Small business -- South Africa Workflow -- South Africa -- Management Business planning
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/13592 , vital:27255
- Description: The fresh hake processing lines at Seavuna fishing company in Mossel Bay are not consistently achieving their volume output standards and this is resulting in higher processing costs and loss of processing opportunities. The company’s senior management are concerned about this trend and require a complete review of the effectiveness of the resources deployed on the lines. This with the view of establishing the causes of poor process volume output. In order to resolve the process inefficiency challenges mentioned, this study used both empirical and time studies to investigate the effectiveness of the company’s resources directly deployed in the processing unit. The study focused on investigating the human factor, machinery and equipment, the environment and the current efficiency standards. Relevant literature in the field of process efficiency improvement was consulted to assist in identifying factors that are known to cause process inefficiencies, and also to establish which improvement techniques would be relevant in correcting the situation. From the Literature reviewed, it was evident that a ‘one size fits all’ solution to resolving inefficiencies is almost non-existent and that a solution that is relevant to the problem is more effective. In addition, a benchmarking exercise was also done to establish how Seavuna’s current volume output standards fair against its major rivals. Once data from both studies were collected, the results were analysed using the some of the basic quality tools. Thereafter, lean manufacturing principles were used to attempt to resolve the current efficiency challenges. The study recommended that the company construct a business strategy and a corresponding organisational culture to direct its continuous improvement interventions. The use of strategic quality planning would go a long way in assisting the company to execute some of the interventions recommended.
- Full Text:
- Date Issued: 2017
Ultra-high precision manufacturing
- Authors: Abou-El-Hossein, Khaled
- Subjects: Machining , Diamond turning , f-sa
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/10948/20878 , vital:29410
- Description: One of the engineering areas focusing on the research and development of highvalue components and manufacturing technologies is precision engineering. Precision engineering represents a variety of engineering and science disciplines ranging from areas such as mechanical, electronics and industrial engineering to chemistry, physics, optics and materials science. This paper aims at familiarising the reader with the recent advances in ultra-high precision manufacturing technologies and their applications for the production of various critical components employed in different sectors of the industry. In this paper, the principles of ultra-high precision manufacturing will be discussed followed by examples of its use in various industrial applications. The status of ultra-high precision manufacturing in terms of current research issues and future trends will be discussed. In addition, research activities and projects in the area of precision manufacturing that are currently conducted at the NMMU will be also highlighted. Finally, the author looks forward to presenting herewith comprehensive information that could be useful to the reader and easy to understand by the bigger NMMU’s community.
- Full Text:
- Authors: Abou-El-Hossein, Khaled
- Subjects: Machining , Diamond turning , f-sa
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/10948/20878 , vital:29410
- Description: One of the engineering areas focusing on the research and development of highvalue components and manufacturing technologies is precision engineering. Precision engineering represents a variety of engineering and science disciplines ranging from areas such as mechanical, electronics and industrial engineering to chemistry, physics, optics and materials science. This paper aims at familiarising the reader with the recent advances in ultra-high precision manufacturing technologies and their applications for the production of various critical components employed in different sectors of the industry. In this paper, the principles of ultra-high precision manufacturing will be discussed followed by examples of its use in various industrial applications. The status of ultra-high precision manufacturing in terms of current research issues and future trends will be discussed. In addition, research activities and projects in the area of precision manufacturing that are currently conducted at the NMMU will be also highlighted. Finally, the author looks forward to presenting herewith comprehensive information that could be useful to the reader and easy to understand by the bigger NMMU’s community.
- Full Text:
Family interaction patterns in maternal alcohol abuse: an application of Murray Bowen's family system theory
- Authors: Abraham, Hanlie
- Date: 2017
- Subjects: Family psychotherapy , Social psychology Bowen, Murray, -- 1913-1990 Women -- Alcohol use Alcoholism -- Psychological aspects
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/13669 , vital:27293
- Description: The aim of this study was to explore and describe the intergenerational interactional patterns in a Coloured family where the mother has abused alcohol. Researchers have found that drinking behaviours of parents can have major effects on the children’s lives throughout generations. Substance abuse of a parent has major influences on the family, their interactions, and relationships, mostly between the parent and the child. There is a major gap in the study of the Coloured families and how substance abuse affects their families and children. The study employed Bowen’s constructs of differentiation of self, multigenerational transmission process, triangulation, emotional cut-off, nuclear family emotional system, sibling position, family projection process, and societal regression and utilized analytical generalization of the concepts to achieve its aim. The mother, an older sibling and maternal mother were the main sources of data although the perspective of the mother herself was privileged in the study. Semi-structured interviews were utilized to gather the data. This allowed participants to freely narrate their personal perceptions and experiences of interaction in both the family of origin and the current nuclear family. The research used a single case study of a purposively sampled family. The researcher is a Coloured female who had specific interest in this specific cultural group and their interactional patterns, which optimised cultural familiarity during the research process and reduced the likelihood of potential discriminatory racial bias of the participants. The findings demonstrate that perceptions of interactional patterns in the nuclear family and family of origin coincided with certain of Bowen’s Family Systems concepts, particularly, triangulation and differentiation. However, the need for further exploration of concepts such as the nuclear family emotional system and the family projection process in Coloured families are still needed in future studies. The findings provided insight into the functioning of the relationships and FAMILY INTERACTION IN MATERNAL ALCOHOL ABUSE interactions in both the nuclear family and the family of origin. Limitations of the current study are identified and recommendations for future studies in this field are also offered.
- Full Text:
- Date Issued: 2017
- Authors: Abraham, Hanlie
- Date: 2017
- Subjects: Family psychotherapy , Social psychology Bowen, Murray, -- 1913-1990 Women -- Alcohol use Alcoholism -- Psychological aspects
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/13669 , vital:27293
- Description: The aim of this study was to explore and describe the intergenerational interactional patterns in a Coloured family where the mother has abused alcohol. Researchers have found that drinking behaviours of parents can have major effects on the children’s lives throughout generations. Substance abuse of a parent has major influences on the family, their interactions, and relationships, mostly between the parent and the child. There is a major gap in the study of the Coloured families and how substance abuse affects their families and children. The study employed Bowen’s constructs of differentiation of self, multigenerational transmission process, triangulation, emotional cut-off, nuclear family emotional system, sibling position, family projection process, and societal regression and utilized analytical generalization of the concepts to achieve its aim. The mother, an older sibling and maternal mother were the main sources of data although the perspective of the mother herself was privileged in the study. Semi-structured interviews were utilized to gather the data. This allowed participants to freely narrate their personal perceptions and experiences of interaction in both the family of origin and the current nuclear family. The research used a single case study of a purposively sampled family. The researcher is a Coloured female who had specific interest in this specific cultural group and their interactional patterns, which optimised cultural familiarity during the research process and reduced the likelihood of potential discriminatory racial bias of the participants. The findings demonstrate that perceptions of interactional patterns in the nuclear family and family of origin coincided with certain of Bowen’s Family Systems concepts, particularly, triangulation and differentiation. However, the need for further exploration of concepts such as the nuclear family emotional system and the family projection process in Coloured families are still needed in future studies. The findings provided insight into the functioning of the relationships and FAMILY INTERACTION IN MATERNAL ALCOHOL ABUSE interactions in both the nuclear family and the family of origin. Limitations of the current study are identified and recommendations for future studies in this field are also offered.
- Full Text:
- Date Issued: 2017
An exploration into an ESD-based teaching strategy to improve the critical thinking and problem-solving skills amongst development studies students at Nelson Mandela University
- Authors: Abrahams, Andre John
- Date: 2021-04
- Subjects: Sustainable development -- Study and teaching , Universities and colleges -- South Africa , Critical thinking
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/50906 , vital:43149
- Description: In recent years, Education for Sustainable Development (ESD) has been a significant focus for research pertaining to teacher education and transformative approaches to teaching and learning. However, there has been less specific focus on the implementation of ESD in the context of higher education. This study, therefore, explored the use of an ESD-based teaching and learning approach in an undergraduate Development Studies programme. The focus was on developing a teaching approach that was informed by the principles of ESD and which could assist Development Studies lecturers in creating a more transformative, student-centred environment. This study was a qualitative undertaking, conducted at the Nelson Mandela University’s (NMU) Development Studies undergraduate programme. The ESD-based approach was implemented by two participating lecturers who utilised the approach across four undergraduate classes. Qualitative data were generated through a systematic literature analysis (SLA), exploratory interviews, student exercises and assessments, focus group discussions, and reflective journal entries. The gathered data were then analysed using a framework analysis rubric adapted from the theoretical framework utilised in the study. In addition, the data were coded using the six coding techniques promoted by Saldaña (2013). The findings suggest that the ESD-based approach developed in the study could effectively contribute towards promoting ESD in the Development Studies programme. The findings also suggest that, when properly implemented, the ESD-based approach could assist lecturers in creating a more transformative learning environment where students have greater control over their learning experience. In addition, this study found that students in the selected Development Studies undergraduate programme could benefit from continued exposure to the teaching methods and techniques adopted in the approach. The implementation of the approach also uncovered some of the inhibiting factors that may prevent an ESD-based approach being mainstreamed into the context of higher education. , Thesis (DPhil) -- Faculty of Business and Economic Sciences, Development Studies, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Abrahams, Andre John
- Date: 2021-04
- Subjects: Sustainable development -- Study and teaching , Universities and colleges -- South Africa , Critical thinking
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/50906 , vital:43149
- Description: In recent years, Education for Sustainable Development (ESD) has been a significant focus for research pertaining to teacher education and transformative approaches to teaching and learning. However, there has been less specific focus on the implementation of ESD in the context of higher education. This study, therefore, explored the use of an ESD-based teaching and learning approach in an undergraduate Development Studies programme. The focus was on developing a teaching approach that was informed by the principles of ESD and which could assist Development Studies lecturers in creating a more transformative, student-centred environment. This study was a qualitative undertaking, conducted at the Nelson Mandela University’s (NMU) Development Studies undergraduate programme. The ESD-based approach was implemented by two participating lecturers who utilised the approach across four undergraduate classes. Qualitative data were generated through a systematic literature analysis (SLA), exploratory interviews, student exercises and assessments, focus group discussions, and reflective journal entries. The gathered data were then analysed using a framework analysis rubric adapted from the theoretical framework utilised in the study. In addition, the data were coded using the six coding techniques promoted by Saldaña (2013). The findings suggest that the ESD-based approach developed in the study could effectively contribute towards promoting ESD in the Development Studies programme. The findings also suggest that, when properly implemented, the ESD-based approach could assist lecturers in creating a more transformative learning environment where students have greater control over their learning experience. In addition, this study found that students in the selected Development Studies undergraduate programme could benefit from continued exposure to the teaching methods and techniques adopted in the approach. The implementation of the approach also uncovered some of the inhibiting factors that may prevent an ESD-based approach being mainstreamed into the context of higher education. , Thesis (DPhil) -- Faculty of Business and Economic Sciences, Development Studies, 2021
- Full Text:
- Date Issued: 2021-04
An exploration into an ESD-based teaching strategy to improve the critical thinking and problem-solving skills amongst development studies students at Nelson Mandela University
- Authors: Abrahams, André John
- Date: 2021-04
- Subjects: Problem solving -- Study and teaching , Divergent thinking -- Study and teaching , Sustainable development -- Study and teaching , Environmental education
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/50907 , vital:43148
- Description: In recent years, Education for Sustainable Development (ESD) has been a significant focus for research pertaining to teacher education and transformative approaches to teaching and learning. However, there has been less specific focus on the implementation of ESD in the context of higher education. This study, therefore, explored the use of an ESD-based teaching and learning approach in an undergraduate Development Studies programme. The focus was on developing a teaching approach that was informed by the principles of ESD and which could assist Development Studies lecturers in creating a more transformative, student-centred environment. This study was a qualitative undertaking, conducted at the Nelson Mandela University’s (NMU) Development Studies undergraduate programme. The ESD-based approach was implemented by two participating lecturers who utilised the approach across four undergraduate classes. Qualitative data were generated through a systematic literature analysis (SLA), exploratory interviews, student exercises and assessments, focus group discussions, and reflective journal entries. The gathered data were then analysed using a framework analysis rubric adapted from the theoretical framework utilised in the study. In addition, the data were coded using the six coding techniques promoted by Saldaña (2013). The findings suggest that the ESD-based approach developed in the study could effectively contribute towards promoting ESD in the Development Studies programme. The findings also suggest that, when properly implemented, the ESD-based approach could assist lecturers in creating a more transformative learning environment where students have greater control over their learning experience. In addition, this study found that students in the selected Development Studies undergraduate programme could benefit from continued exposure to the teaching methods and techniques adopted in the approach. The implementation of the approach also uncovered some of the inhibiting factors that may prevent an ESD-based approach being mainstreamed into the context of higher education. , Thesis (DPhil) -- Faculty of Business and Economic Sciences, Development Studies, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Abrahams, André John
- Date: 2021-04
- Subjects: Problem solving -- Study and teaching , Divergent thinking -- Study and teaching , Sustainable development -- Study and teaching , Environmental education
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/50907 , vital:43148
- Description: In recent years, Education for Sustainable Development (ESD) has been a significant focus for research pertaining to teacher education and transformative approaches to teaching and learning. However, there has been less specific focus on the implementation of ESD in the context of higher education. This study, therefore, explored the use of an ESD-based teaching and learning approach in an undergraduate Development Studies programme. The focus was on developing a teaching approach that was informed by the principles of ESD and which could assist Development Studies lecturers in creating a more transformative, student-centred environment. This study was a qualitative undertaking, conducted at the Nelson Mandela University’s (NMU) Development Studies undergraduate programme. The ESD-based approach was implemented by two participating lecturers who utilised the approach across four undergraduate classes. Qualitative data were generated through a systematic literature analysis (SLA), exploratory interviews, student exercises and assessments, focus group discussions, and reflective journal entries. The gathered data were then analysed using a framework analysis rubric adapted from the theoretical framework utilised in the study. In addition, the data were coded using the six coding techniques promoted by Saldaña (2013). The findings suggest that the ESD-based approach developed in the study could effectively contribute towards promoting ESD in the Development Studies programme. The findings also suggest that, when properly implemented, the ESD-based approach could assist lecturers in creating a more transformative learning environment where students have greater control over their learning experience. In addition, this study found that students in the selected Development Studies undergraduate programme could benefit from continued exposure to the teaching methods and techniques adopted in the approach. The implementation of the approach also uncovered some of the inhibiting factors that may prevent an ESD-based approach being mainstreamed into the context of higher education. , Thesis (DPhil) -- Faculty of Business and Economic Sciences, Development Studies, 2021
- Full Text:
- Date Issued: 2021-04
The protection against child labour in South Africa
- Authors: Abrahams, Collis
- Date: 2019
- Subjects: Child labor
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10948/40204 , vital:35986
- Description: This treatise seeks to describe the legal protection of children against child labour in South Africa. It does so within the context of international-law-protection in the form of Conventions of the International Labour Organisation. The treatise distinguishes between the concepts of child labour and child work and traces the history of international law prohibiting and regulating child labour. The two most important ILO Conventions, Convention 138 of 1973 and 182 of 1998 are considered in some detail before the national legislature is explained and analysed. From the discussion it is apparent that South Africa is giving effect to the applicable ILO Conventions. Not only does national legislation prohibit child labour, the state also adopted nation-wide programmes to eradicate child labour. Despite the efforts there is still room for improvement. The fight to eradicate child labour must continue!
- Full Text:
- Date Issued: 2019
- Authors: Abrahams, Collis
- Date: 2019
- Subjects: Child labor
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10948/40204 , vital:35986
- Description: This treatise seeks to describe the legal protection of children against child labour in South Africa. It does so within the context of international-law-protection in the form of Conventions of the International Labour Organisation. The treatise distinguishes between the concepts of child labour and child work and traces the history of international law prohibiting and regulating child labour. The two most important ILO Conventions, Convention 138 of 1973 and 182 of 1998 are considered in some detail before the national legislature is explained and analysed. From the discussion it is apparent that South Africa is giving effect to the applicable ILO Conventions. Not only does national legislation prohibit child labour, the state also adopted nation-wide programmes to eradicate child labour. Despite the efforts there is still room for improvement. The fight to eradicate child labour must continue!
- Full Text:
- Date Issued: 2019
Financial inclusion in South Africa
- Authors: Abrahams, Rayghana
- Date: 2017
- Subjects: Financial services industry -- South Africa , Financial institutions -- South Africa Finance -- South Africa South Africa -- Economic conditions
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/13579 , vital:27240
- Description: The research for this study was guided by the question on whether the financial inclusion improvement strategies of the South African government adequately address the financial inclusion targets, as set out in the National Development Plan. This descriptive non-empirical study was conducted by means of a literature review. The secondary data used for the study were collected from a number of sources, namely: (i) the 2015 Brookings Financial and Digital Inclusion Project report; (ii) the 2014 Global Findex survey; (iii) the InterMedia surveys; (iv) Financial Access surveys; (v) various national FinScope surveys; and (iv) a number of working papers of the World Bank related to financial inclusion. The data revealed that South Africa, with its sophisticated financial sector, was early to adopt policies and initiatives to advance financial inclusion and the country has experienced a noticeable increase in financial inclusion from 61% in 2004 to 87% in 2015. South Africa is 3% away from its National Development Plan goal of 90% financial inclusion by 2030. This indicates that overall, the financial inclusion initiatives adopted by the South African government were successful.
- Full Text:
- Date Issued: 2017
- Authors: Abrahams, Rayghana
- Date: 2017
- Subjects: Financial services industry -- South Africa , Financial institutions -- South Africa Finance -- South Africa South Africa -- Economic conditions
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/13579 , vital:27240
- Description: The research for this study was guided by the question on whether the financial inclusion improvement strategies of the South African government adequately address the financial inclusion targets, as set out in the National Development Plan. This descriptive non-empirical study was conducted by means of a literature review. The secondary data used for the study were collected from a number of sources, namely: (i) the 2015 Brookings Financial and Digital Inclusion Project report; (ii) the 2014 Global Findex survey; (iii) the InterMedia surveys; (iv) Financial Access surveys; (v) various national FinScope surveys; and (iv) a number of working papers of the World Bank related to financial inclusion. The data revealed that South Africa, with its sophisticated financial sector, was early to adopt policies and initiatives to advance financial inclusion and the country has experienced a noticeable increase in financial inclusion from 61% in 2004 to 87% in 2015. South Africa is 3% away from its National Development Plan goal of 90% financial inclusion by 2030. This indicates that overall, the financial inclusion initiatives adopted by the South African government were successful.
- Full Text:
- Date Issued: 2017
Classification and clustering based methods for outlier detection of solar resource data
- Authors: Abrahams, Waldo
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55423 , vital:51996
- Description: Almost 90% of the primary global energy demand is serviced from the burning of fossil fuels (Abas, Kalair & Khan, 2015). Owing to the detrimental environmental impact of this, a global energy transition to the use of renewable energy, including solar energy, is needed (Gielen et al., 2019). An important aspect that inhibits the growth of solar energy is accurate solar resource data. Such data is needed because knowledge of the future reliability and quality of energy production is required to analyse a system’s performance and determine financial implications (Sengupta et al., 2017). Existing methods used to detect outliers in solar resource data do not efficiently identify outliers and an accurate and robust approach is required (Eastwood, 2019). Using simulated and real-world data, this study investigates the use of several classification methods, along with a two-stage clustering-classification approach to accurately identify outliers in solar resource data. The Treebag method proves to be an adequate outlier detection method for solar resource data. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Abrahams, Waldo
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55423 , vital:51996
- Description: Almost 90% of the primary global energy demand is serviced from the burning of fossil fuels (Abas, Kalair & Khan, 2015). Owing to the detrimental environmental impact of this, a global energy transition to the use of renewable energy, including solar energy, is needed (Gielen et al., 2019). An important aspect that inhibits the growth of solar energy is accurate solar resource data. Such data is needed because knowledge of the future reliability and quality of energy production is required to analyse a system’s performance and determine financial implications (Sengupta et al., 2017). Existing methods used to detect outliers in solar resource data do not efficiently identify outliers and an accurate and robust approach is required (Eastwood, 2019). Using simulated and real-world data, this study investigates the use of several classification methods, along with a two-stage clustering-classification approach to accurately identify outliers in solar resource data. The Treebag method proves to be an adequate outlier detection method for solar resource data. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-04
The role of climate change on food security in Northern Uganda a case study of Lira district
- Authors: Aciro, Prudence Estel
- Date: 2022-04
- Subjects: Food security -- Uganda , Food security -- Climatic factors , Climatic changes
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/57513 , vital:58054
- Description: The study examines the effects of climate change in Northern Uganda to create food security solutions through the improvement of local resilience mechanisms and adaptation devices. The study adopted the interpretive paradigm within the qualitative research methodology as it investigated the subjective opinions of the respondents about the role of climate change on food security in the Lira district. The researcher used non-probability purposive sampling to identify nine officials that possessed knowledge on resilience mechanisms and also interacted directly with individual farmers. The researcher used semi-structured interviews as a tool to collect data and thematic analysis to make conclusions on findings based on the emerging themes. The findings from the study revealed that the four determinants of food security are greatly affected by climate events and these are: food utilisation, food production, food availability and access to food as well as the stability of food supply. Food storage is a problem facing the community of Lira due to extreme climate events. Climate change was found to affect food prices in such a way that when agricultural inputs are bought expensively, it leads the cost of producing crops to increase, which in turn makes food more expensive at the market. The findings also displayed that Lira’s local communities are trying to apply adaptive farming practices to ensure there is an adequate food supply, such as planting a local variety of seeds that withstand the effect of climate change, such as sorghum millet and cassava. Based on the findings, valuable recommendations are offered. These include the government rolling out a national irrigation scheme to ease the use of the drip irrigation mechanism. Also, there is a need for more interventions that support local resilience mechanisms such as the use of agricultural inputs, as these require subsidisation. It emerged from the findings of this study that there is a need for better interventions to deal with flooding. For future researchers, it was found that there is a need to explore the best post-harvest handling methods as well as food storage. , Thesis (MA) -- Faculty of Business and Economic Sciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Aciro, Prudence Estel
- Date: 2022-04
- Subjects: Food security -- Uganda , Food security -- Climatic factors , Climatic changes
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/57513 , vital:58054
- Description: The study examines the effects of climate change in Northern Uganda to create food security solutions through the improvement of local resilience mechanisms and adaptation devices. The study adopted the interpretive paradigm within the qualitative research methodology as it investigated the subjective opinions of the respondents about the role of climate change on food security in the Lira district. The researcher used non-probability purposive sampling to identify nine officials that possessed knowledge on resilience mechanisms and also interacted directly with individual farmers. The researcher used semi-structured interviews as a tool to collect data and thematic analysis to make conclusions on findings based on the emerging themes. The findings from the study revealed that the four determinants of food security are greatly affected by climate events and these are: food utilisation, food production, food availability and access to food as well as the stability of food supply. Food storage is a problem facing the community of Lira due to extreme climate events. Climate change was found to affect food prices in such a way that when agricultural inputs are bought expensively, it leads the cost of producing crops to increase, which in turn makes food more expensive at the market. The findings also displayed that Lira’s local communities are trying to apply adaptive farming practices to ensure there is an adequate food supply, such as planting a local variety of seeds that withstand the effect of climate change, such as sorghum millet and cassava. Based on the findings, valuable recommendations are offered. These include the government rolling out a national irrigation scheme to ease the use of the drip irrigation mechanism. Also, there is a need for more interventions that support local resilience mechanisms such as the use of agricultural inputs, as these require subsidisation. It emerged from the findings of this study that there is a need for better interventions to deal with flooding. For future researchers, it was found that there is a need to explore the best post-harvest handling methods as well as food storage. , Thesis (MA) -- Faculty of Business and Economic Sciences, 2022
- Full Text:
- Date Issued: 2022-04
Student discourses: influences on identity and agency
- Authors: Ackerdien, Raeesah
- Date: 2017
- Subjects: English language -- Rhetoric -- Study and teaching (Higher) -- Psychological aspects , Psychoanalysis and education Identity (Psychology) in youth Educational sociology
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/13625 , vital:27258
- Description: South Africa‟s racialised history dates back to a colonial period where South Africans were separated by race, language and laws which prevented people of colour from mixing with those who were termed White. 22 years after the end of apartheid, race and language remain a painful part of history and a topic which is always visible in our private and public discourses. Students, as of recent, have pointed to the challenges and legacies of apartheid they face in higher education and broader society. The lack of broader transformation and racial prejudice leave a great divide amongst different groups of students. Given this background, this study sought to examine how students were making sense of themselves and others. The participants of this study included 50 second year students from the Department of Language Studies at the Nelson Mandela Metropolitan University in Port Elizabeth. This research study focused on the identity development of students and how these factors impacted their identities taking into account aspects of race, language, sense of agency and those impacting their sense of agency and sense of self. This study used a qualitative research method which involves an interpretive approach to research as this method was best suited for this study‟s analysis of student narratives. This study is a case study of the single case of second year students. The research, furthermore, used a Poststructuralist approach as theoretical underpinning and Critical Discourse Analysis for analysis of the data. Relevant literature were read and reviewed to determine what studies were saying about factors impacting on youth identity. Student narratives were analysed in order to determine which factors impacted on their identity formation, as well as the perceptions of their own identities and those of others. The results of the findings showed that students‟ identity development was affected by factors such as cultural background, parents, death of loved ones, aesthetic interest, race and language. Socio-economic inequalities in South Africa, race and language strongly defined student identities. Identities were found to be multiple and dynamic. The impact on student agency was as a result of the influences of their parents but also because of the inequalities in society. The only commonality students identified as having with other students was study. Students revealed that they did not cross racial or language boundaries to socialise with other students. There were students who indicated that they resisted racial categorisations and spoke of the celebration of diversity in South Africa but these were in the minority. Unlike previous studies that showed students wanting to move on to a new unified South Africa while simultaneously using old apartheid discourses, this study showed that students remained rooted in these discourses but reverted to these discourses because of societal inequalities. They did not foresee any moves to a new unified South Africa if inequalities not addressed. They were more radical about what a new future looks like with the battle against privilege won. Language was identified as a barrier and the fallacies of English being linked to superior intelligence was pointed out. The divides between White and Black students were apparent in the data. The study therefore recommended that curriculation of modules be undertaken with teaching of fluidity of identities and providing of critical tools for students to deconstruct race and language. The South African context should be foregrounded in all faculty study areas so that students work to a public good that seeks to eradicate inequalities. Safe spaces need to be provided for debating of these issues as well as social spaces for interaction across racial divides.
- Full Text:
- Date Issued: 2017
- Authors: Ackerdien, Raeesah
- Date: 2017
- Subjects: English language -- Rhetoric -- Study and teaching (Higher) -- Psychological aspects , Psychoanalysis and education Identity (Psychology) in youth Educational sociology
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/13625 , vital:27258
- Description: South Africa‟s racialised history dates back to a colonial period where South Africans were separated by race, language and laws which prevented people of colour from mixing with those who were termed White. 22 years after the end of apartheid, race and language remain a painful part of history and a topic which is always visible in our private and public discourses. Students, as of recent, have pointed to the challenges and legacies of apartheid they face in higher education and broader society. The lack of broader transformation and racial prejudice leave a great divide amongst different groups of students. Given this background, this study sought to examine how students were making sense of themselves and others. The participants of this study included 50 second year students from the Department of Language Studies at the Nelson Mandela Metropolitan University in Port Elizabeth. This research study focused on the identity development of students and how these factors impacted their identities taking into account aspects of race, language, sense of agency and those impacting their sense of agency and sense of self. This study used a qualitative research method which involves an interpretive approach to research as this method was best suited for this study‟s analysis of student narratives. This study is a case study of the single case of second year students. The research, furthermore, used a Poststructuralist approach as theoretical underpinning and Critical Discourse Analysis for analysis of the data. Relevant literature were read and reviewed to determine what studies were saying about factors impacting on youth identity. Student narratives were analysed in order to determine which factors impacted on their identity formation, as well as the perceptions of their own identities and those of others. The results of the findings showed that students‟ identity development was affected by factors such as cultural background, parents, death of loved ones, aesthetic interest, race and language. Socio-economic inequalities in South Africa, race and language strongly defined student identities. Identities were found to be multiple and dynamic. The impact on student agency was as a result of the influences of their parents but also because of the inequalities in society. The only commonality students identified as having with other students was study. Students revealed that they did not cross racial or language boundaries to socialise with other students. There were students who indicated that they resisted racial categorisations and spoke of the celebration of diversity in South Africa but these were in the minority. Unlike previous studies that showed students wanting to move on to a new unified South Africa while simultaneously using old apartheid discourses, this study showed that students remained rooted in these discourses but reverted to these discourses because of societal inequalities. They did not foresee any moves to a new unified South Africa if inequalities not addressed. They were more radical about what a new future looks like with the battle against privilege won. Language was identified as a barrier and the fallacies of English being linked to superior intelligence was pointed out. The divides between White and Black students were apparent in the data. The study therefore recommended that curriculation of modules be undertaken with teaching of fluidity of identities and providing of critical tools for students to deconstruct race and language. The South African context should be foregrounded in all faculty study areas so that students work to a public good that seeks to eradicate inequalities. Safe spaces need to be provided for debating of these issues as well as social spaces for interaction across racial divides.
- Full Text:
- Date Issued: 2017
IL-4/ IL-13 directed microglial activation and differentiation in response to LPS-induced neuroinflammation
- Authors: Ackerdien, Shiraz
- Date: 2024-04
- Subjects: Inflammation , Inflammation -- Treatment , Anti-inflammatory agents
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63606 , vital:73554
- Description: Microglia activation is a common hallmark of neuroinflammation that occurs during pathogen invasion or lipopolysaccharide (LPS)-induced inflammation. A neuroinflammatory response is elicited by the release of proinflammatory cytokines which stimulates microglia in an autocrine manner to be polarized into classically activated, pro-inflammatory M1 cells. Prolonged exposure to the inflammatory response can have disastrous effects on the central nervous system (CNS). However, microglia can alternatively be polarized into the activated M2 anti-inflammatory phenotype, but the exact molecular mechanism mediating this phenotypic switch remains poorly understood. Studies have shown that interleukin (IL)-4 can induce the M2 phenotype and activate the signal transducer and activator of the transcription 6 (STAT6) signalling pathway that in turn provokes a beneficial Th2 immune response. Since IL-4 and IL-13 share a common IL-4 receptor alpha (IL-4Rα) chain, it is possible that alternative microglia differentiation and its anti-inflammatory action also involve IL-13. This study aimed to investigate how IL-13 and STAT6 signalling orchestrates the microglial response and differentiation associated with LPS-induced inflammation. Furthermore, the molecular mechanisms that relieve LPS-induced neuroinflammation and neural protection through IL-13-enhanced BDNF signalling were also investigated. C8-B4 microglial cells were induced with LPS to exhibit an M1 pro-inflammatory phenotype or stimulated with IL-4 and/or IL-13 to exhibit an M2 anti-inflammatory microglial phenotype. The cell viability following LPS, IL-4, and/ or IL-13 exposure was determined. The LPS-induced neuroinflammatory response and the anti-inflammatory response induced by IL-4 and IL-13 which promotes STAT-6 signalling were determined by measuring TNFα, IL-1β, and BDNF protein concentrations using ELISA assays. The polarising effects of LPS and IL-4/IL-13 cytokines were also examined via changes in the expression of Iba-1, CD206, CD86, and STAT-6 determined by immunofluorescence analysis. These changes were further investigated by quantifying the mRNA transcripts of TNFα, IL-1 β, Arg-1, CD206, IL-4R, and STAT-6 and BDNF using qRT-PCR. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Ackerdien, Shiraz
- Date: 2024-04
- Subjects: Inflammation , Inflammation -- Treatment , Anti-inflammatory agents
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63606 , vital:73554
- Description: Microglia activation is a common hallmark of neuroinflammation that occurs during pathogen invasion or lipopolysaccharide (LPS)-induced inflammation. A neuroinflammatory response is elicited by the release of proinflammatory cytokines which stimulates microglia in an autocrine manner to be polarized into classically activated, pro-inflammatory M1 cells. Prolonged exposure to the inflammatory response can have disastrous effects on the central nervous system (CNS). However, microglia can alternatively be polarized into the activated M2 anti-inflammatory phenotype, but the exact molecular mechanism mediating this phenotypic switch remains poorly understood. Studies have shown that interleukin (IL)-4 can induce the M2 phenotype and activate the signal transducer and activator of the transcription 6 (STAT6) signalling pathway that in turn provokes a beneficial Th2 immune response. Since IL-4 and IL-13 share a common IL-4 receptor alpha (IL-4Rα) chain, it is possible that alternative microglia differentiation and its anti-inflammatory action also involve IL-13. This study aimed to investigate how IL-13 and STAT6 signalling orchestrates the microglial response and differentiation associated with LPS-induced inflammation. Furthermore, the molecular mechanisms that relieve LPS-induced neuroinflammation and neural protection through IL-13-enhanced BDNF signalling were also investigated. C8-B4 microglial cells were induced with LPS to exhibit an M1 pro-inflammatory phenotype or stimulated with IL-4 and/or IL-13 to exhibit an M2 anti-inflammatory microglial phenotype. The cell viability following LPS, IL-4, and/ or IL-13 exposure was determined. The LPS-induced neuroinflammatory response and the anti-inflammatory response induced by IL-4 and IL-13 which promotes STAT-6 signalling were determined by measuring TNFα, IL-1β, and BDNF protein concentrations using ELISA assays. The polarising effects of LPS and IL-4/IL-13 cytokines were also examined via changes in the expression of Iba-1, CD206, CD86, and STAT-6 determined by immunofluorescence analysis. These changes were further investigated by quantifying the mRNA transcripts of TNFα, IL-1 β, Arg-1, CD206, IL-4R, and STAT-6 and BDNF using qRT-PCR. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
A framework for managing the impact of information communication technology on employee well-being
- Authors: Ackerman, Richard
- Date: 2018
- Subjects: Work environment -- Psychological aspects , Work -- Technological innovations Employees -- Mental health Job stress Flextime
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/21449 , vital:29523
- Description: Employees who work with Information Communication Technology (hereafter referred to as ICT) face a risk in a rise of portable work. This in turn provides a means for employees to be connected to work, even when at home. Flexible work solutions and ability to work any hour of the week creates non-standard work schedules, which in turn can lead to a condition of work-a-holism. In most cases, this phenomena is driven by the belief that being constantly available to work demonstrates a devotion to one’s career and employer. The higher demands placed on employees, are in most cases at the expense of employees’ health, work-life balance and overall well-being. The primary objective of this study is therefore to establish whether the use of ICT outside of normal working hours affects employee well-being, as measured in terms of work-life balance. The second objective of this study is to provide the Target Company within the automotive component supply industry located in Port Elizabeth, in the Republic of South Africa, with a framework for managing the impact of ICT on employee well-being. The research paper has been prompted by the Target Company having recently introduced flexible working solutions for its employees. Research on the topic of alternative forms of work schedules, has shown flexible working arrangements gives employees more choice and control over where, when and by how much they work. Flexibility allows employees to actively shape their working conditions which helps them solve the demands of integrating personal life and work commitments. Whether management should encourage or permit the use of ICT amongst its employees to extend beyond normal working hours however remains unclear. In order to answer the research questions, this study has applied a quantitative, positivistic and deductive research based methodology. The approach applied within this study included conducting an extensive literature review on the effects of ICT use after hours on employee well-being. Thereafter using literature as a foundation, a measuring instrument was constructed in the form of an online questionnaire. The questionnaire was emailed to respondents to collect primary data, in order to measure the dependent and independent variables in terms of the hypothesised relationships. Testing of the variables followed, in order to establish whether the use of ICT use after hours negatively impacts employee well-being as measured in terms of work-life balance and stress. Secondly, the study set out to establish whether flexible working conditions linked to ICT use after hours negatively impacts on employee work-life balance. Thirdly, the relationship between physiological aspects such as age, gender and ethnicity were interrogated to establish an employees’ ability to adapt to changing work conditions, brought about as a direct result of ICT. Lastly, this study set out to establish which ICT tool (email, cellular phone, smartphone or other) has the highest impact on employee wellness. The data collection process yielded a sample of 103 respondents in middle and senior management levels of the Target Company, with 97% being recipients of employer provided ICT tools. These respondents represented the employees who are most likely to be affected by the phenomena under investigation. The survey data was captured and analysed using descriptive statistical techniques. The interpretation revealed aspects which formed the basis for managerial recommendations in the form of a proposed framework to manage the impact of ICT on employee well-being. The findings of the study found that the use of ICT outside of normal working hours has a negative influence on employee well-being as measured in terms of work-life balance and stress. The literature review findings were confirmed as supporting the statement that flexible working conditions linked to ICT use after hours having a positive influence on employee work-life balance. A further finding of the study was the confirmation of physiological aspects affects an employees’ ability to adapt to changing working conditions, thereby having a negative influence on employee work-life balance. Lastly, to the question of which ICT tool has the biggest impact on well-being, it was found that differing ICT tools (email, cellular, smartphone, or other) do not have a negative influence on employee wellness. These findings formed the basis for the recommendations in the form of a framework which has been proposed to manage the impact of ICT on employee well-being. The most pertinent aspect of the framework includes the employer communicating a well-defined ICT usage policy, which clearly outlines a standard operating procedure in relation to ICT use to all its employees. The findings furthermore propose that the employer should take the time to explain and train its employees as to what is considered acceptable and non-acceptable use of ICT devices, especially in relation to after hour use and leave absences from work. To ensure employee well-being, employees should be encouraged to implement defined time blocks for when they are available for work and when they are not. This can be applied through the act of switching off their ICT devices, which constitutes a boundary work tactic as an action in order to prevent work-related interruptions in the private sphere. While the employer can take described measures, it should also be noted that there is responsibility on the part of the employee to ensure personal wellness, including regular exercise, relaxation, and taking appropriate breaks when necessary. Moreover, employees can apply work and life boundary management techniques through the selective use of devices. By not applying automatic work email updates on ICT devices such as smart phones is yet another boundary management technique which can be utilised by employees. There are a range of practical suggestions which are proposed as a method to minimize the risk of ICT use on employee well-being within this research document. The above proposals have only served to highlight a select few aspects. While it is acknowledged that there are important advantages associated with the development and use of ICT, it is equally important to allow employees to recharge their batteries in the form of appropriate downtime to regain perspective, thus allowing the organisation to maintain its competitive advantage, with the well-being of its employees taken to heart.
- Full Text:
- Date Issued: 2018
- Authors: Ackerman, Richard
- Date: 2018
- Subjects: Work environment -- Psychological aspects , Work -- Technological innovations Employees -- Mental health Job stress Flextime
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/21449 , vital:29523
- Description: Employees who work with Information Communication Technology (hereafter referred to as ICT) face a risk in a rise of portable work. This in turn provides a means for employees to be connected to work, even when at home. Flexible work solutions and ability to work any hour of the week creates non-standard work schedules, which in turn can lead to a condition of work-a-holism. In most cases, this phenomena is driven by the belief that being constantly available to work demonstrates a devotion to one’s career and employer. The higher demands placed on employees, are in most cases at the expense of employees’ health, work-life balance and overall well-being. The primary objective of this study is therefore to establish whether the use of ICT outside of normal working hours affects employee well-being, as measured in terms of work-life balance. The second objective of this study is to provide the Target Company within the automotive component supply industry located in Port Elizabeth, in the Republic of South Africa, with a framework for managing the impact of ICT on employee well-being. The research paper has been prompted by the Target Company having recently introduced flexible working solutions for its employees. Research on the topic of alternative forms of work schedules, has shown flexible working arrangements gives employees more choice and control over where, when and by how much they work. Flexibility allows employees to actively shape their working conditions which helps them solve the demands of integrating personal life and work commitments. Whether management should encourage or permit the use of ICT amongst its employees to extend beyond normal working hours however remains unclear. In order to answer the research questions, this study has applied a quantitative, positivistic and deductive research based methodology. The approach applied within this study included conducting an extensive literature review on the effects of ICT use after hours on employee well-being. Thereafter using literature as a foundation, a measuring instrument was constructed in the form of an online questionnaire. The questionnaire was emailed to respondents to collect primary data, in order to measure the dependent and independent variables in terms of the hypothesised relationships. Testing of the variables followed, in order to establish whether the use of ICT use after hours negatively impacts employee well-being as measured in terms of work-life balance and stress. Secondly, the study set out to establish whether flexible working conditions linked to ICT use after hours negatively impacts on employee work-life balance. Thirdly, the relationship between physiological aspects such as age, gender and ethnicity were interrogated to establish an employees’ ability to adapt to changing work conditions, brought about as a direct result of ICT. Lastly, this study set out to establish which ICT tool (email, cellular phone, smartphone or other) has the highest impact on employee wellness. The data collection process yielded a sample of 103 respondents in middle and senior management levels of the Target Company, with 97% being recipients of employer provided ICT tools. These respondents represented the employees who are most likely to be affected by the phenomena under investigation. The survey data was captured and analysed using descriptive statistical techniques. The interpretation revealed aspects which formed the basis for managerial recommendations in the form of a proposed framework to manage the impact of ICT on employee well-being. The findings of the study found that the use of ICT outside of normal working hours has a negative influence on employee well-being as measured in terms of work-life balance and stress. The literature review findings were confirmed as supporting the statement that flexible working conditions linked to ICT use after hours having a positive influence on employee work-life balance. A further finding of the study was the confirmation of physiological aspects affects an employees’ ability to adapt to changing working conditions, thereby having a negative influence on employee work-life balance. Lastly, to the question of which ICT tool has the biggest impact on well-being, it was found that differing ICT tools (email, cellular, smartphone, or other) do not have a negative influence on employee wellness. These findings formed the basis for the recommendations in the form of a framework which has been proposed to manage the impact of ICT on employee well-being. The most pertinent aspect of the framework includes the employer communicating a well-defined ICT usage policy, which clearly outlines a standard operating procedure in relation to ICT use to all its employees. The findings furthermore propose that the employer should take the time to explain and train its employees as to what is considered acceptable and non-acceptable use of ICT devices, especially in relation to after hour use and leave absences from work. To ensure employee well-being, employees should be encouraged to implement defined time blocks for when they are available for work and when they are not. This can be applied through the act of switching off their ICT devices, which constitutes a boundary work tactic as an action in order to prevent work-related interruptions in the private sphere. While the employer can take described measures, it should also be noted that there is responsibility on the part of the employee to ensure personal wellness, including regular exercise, relaxation, and taking appropriate breaks when necessary. Moreover, employees can apply work and life boundary management techniques through the selective use of devices. By not applying automatic work email updates on ICT devices such as smart phones is yet another boundary management technique which can be utilised by employees. There are a range of practical suggestions which are proposed as a method to minimize the risk of ICT use on employee well-being within this research document. The above proposals have only served to highlight a select few aspects. While it is acknowledged that there are important advantages associated with the development and use of ICT, it is equally important to allow employees to recharge their batteries in the form of appropriate downtime to regain perspective, thus allowing the organisation to maintain its competitive advantage, with the well-being of its employees taken to heart.
- Full Text:
- Date Issued: 2018
Investigation of the host potential of compounds derived from tartaric acid, succinic acid and 1,4-cyclohexanedioic acid
- Authors: Adam, Muhammad Ameen
- Date: 2024-04
- Subjects: Chemical reactions , Chemistry, Organic , Bacteriology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63617 , vital:73562
- Description: The present investigation considered the host behaviour of three compounds, namely (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (H1), 1,1,4,4-tetraphenyl-1,4-butanediol (H2) and cyclohexane-1,4-diylbis(diphenylmethanol) (H3) in various guest mixtures. These host compounds were readily synthesized by means of Grignard addition reactions on the diesters of tartaric acid, succinic acid and 1,4-cyclohexanedioic acid. The guest mixtures included cyclopentanone, cyclohexanone, cycloheptanone and cyclooctanone, γ-butyrolactone, 2-pyrrolidone, N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone, and pyridine, 2-methylpyridine, 3-methylpyridine and 4-methylpyridine. Crystals of (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (H1) were grown from cyclopentanone (5-ONE), cyclohexanone (6-ONE), cycloheptanone (7-ONE) and cyclooctanone (8-ONE,) producing 1:1 host:guest complexes in each instance. Thermal analysis showed the thermal stabilities of these complexes to be in the order 6-ONE > 7-ONE > 8-ONE > 5-ONE which correlated exactly with results from binary guest/guest competition experiments, where 6-ONE was always preferred by H1, while 5-ONE was consistently disfavoured. Single crystal X-ray diffraction (SCXRD) analyses demonstrated that each guest compound was retained in the crystals by means of a hydrogen bond with an alcohol moiety of the host compound. Furthermore, preferred guests 6- and 7-ONE produced crystals with greater densities than guests less favoured (5- and 8-ONE). A conformational analysis of the guest geometries in the four complexes with H1 revealed that the low energy guest conformers were present. The host selectivity for 6- and 7-ONE was proposed to be due to the improved molecular packing in the crystals of the complexes containing these two guest compounds, observed from their higher crystal densities. Hirshfeld surface analyses were not useful in explaining the preference of H1 for 6-ONE relative to 7-ONE (these types of analyses were not possible for the 5-ONE and 8-ONE-containing inclusion compounds due to the nature and degree of disorder present in the guest molecules). H1 was also crystallized from γ-butyrolactone (GBL), 2-pyrrolidone (NP), N-methyl-2-pyrrolidone (NMP) and N-ethyl-2-pyrrolidone (NEP), and 1H-NMR spectroscopy revealed that all but GBL were included. The host compound was also presented with these guest solvents in various mixtures, and it was observed that NMP was an extremely favoured guest solvent, followed by NEP and NP, with GBL being consistently disfavoured in every experiment. It was therefore shown that in certain instances, H1 may serve as an alternative tool for separating some of these mixtures through host-guest chemistry strategies. The hydrogen bonding motifs present in each of the successfully formed complexes were extensively investigated through SCXRD analysis, as was the thermal behaviour of these complexes. In the latter instance, the peak temperature of the endotherm (from the DSC trace) representing the guest release was greater for the inclusion compound with favoured NMP (145.5 °C) relative to the complexes with NP (139.8 °C) and NEP (120.5 °C). Host compounds H2 and H3 were revealed to have the ability to include each of pyridine (PYR), 2-methylpyridine (2MP), 3-methylpyridine (3MP) and 4-methylpyridine (4MP). H2 displayed selective behaviour for 3MP and 4MP when presented with mixtures of these guest compounds, whilst H3 preferred PYR. In the latter case, this PYR-containing inclusion compound was also the more stable one (the guest release onset temperature was highest, Ton 66.0 °C). It was demonstrated that H2 has the ability to separate very many binary mixtures of these pyridines on a practical platform, since K (the selectivity coefficient) values were 10 or greater in many instances. However, unfortunately, the more difficult-to-separate mixtures containing 3MP and 4MP cannot be purified or separated by employing H2 and supramolecular chemistry strategies. H3 was also shown to be a likely candidate for binary guest separations in very many of the guest solutions considered here, where K was also 10 or greater, and even infinity in many cases. SCXRD demonstrated that 2MP, 3MP and 4MP were retained in the crystals of their complexes by means of classical hydrogen bonds with the host compound. Satisfyingly, this hydrogen bond between 2MP and H2 (3.0213(18) Å) was significantly longer than that between this host compound and both disorder components of 3MP (2.875(2) and 2.825(9) Å) and that between H2 and 4MP (2.8458(13) Å). This observation explains the affinity of H2 for both 3MP and 4MP, and why 2MP was disfavoured. The results of thermal experiments did not wholly concur with observations from the guest/guest competition experiments. Hirshfeld surface analyses were also conducted but were not entirely conclusive with respect to explaining the host selectivity behaviour. In the case of H3, SCXRD analyses revealed that favoured PYR experienced a classical hydrogen bond with the host compound that was statistically significantly shorter (2.795(2) Å, 165°) than those between the other guest compounds and H3. Additionally, this guest compound was the only one to be involved in a (host)C−H···π(guest) interaction (2.91 Å, 139°) and also a non-classical hydrogen bond with the host compound ((host)C−H···N−C(guest), 2.77 Å (144°)). Finally, Hirshfeld surface analyses showed also that preferred PYR experienced a greater percentage of C···H/H···C (33.1%) and H···N/N···H (11.1%) interactions compared with the complexes with 2MP, 3MP and 4MP. However, it is not clear whether these Hirshfeld observations explain the affinity of H3 for PYR. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Adam, Muhammad Ameen
- Date: 2024-04
- Subjects: Chemical reactions , Chemistry, Organic , Bacteriology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63617 , vital:73562
- Description: The present investigation considered the host behaviour of three compounds, namely (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (H1), 1,1,4,4-tetraphenyl-1,4-butanediol (H2) and cyclohexane-1,4-diylbis(diphenylmethanol) (H3) in various guest mixtures. These host compounds were readily synthesized by means of Grignard addition reactions on the diesters of tartaric acid, succinic acid and 1,4-cyclohexanedioic acid. The guest mixtures included cyclopentanone, cyclohexanone, cycloheptanone and cyclooctanone, γ-butyrolactone, 2-pyrrolidone, N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone, and pyridine, 2-methylpyridine, 3-methylpyridine and 4-methylpyridine. Crystals of (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (H1) were grown from cyclopentanone (5-ONE), cyclohexanone (6-ONE), cycloheptanone (7-ONE) and cyclooctanone (8-ONE,) producing 1:1 host:guest complexes in each instance. Thermal analysis showed the thermal stabilities of these complexes to be in the order 6-ONE > 7-ONE > 8-ONE > 5-ONE which correlated exactly with results from binary guest/guest competition experiments, where 6-ONE was always preferred by H1, while 5-ONE was consistently disfavoured. Single crystal X-ray diffraction (SCXRD) analyses demonstrated that each guest compound was retained in the crystals by means of a hydrogen bond with an alcohol moiety of the host compound. Furthermore, preferred guests 6- and 7-ONE produced crystals with greater densities than guests less favoured (5- and 8-ONE). A conformational analysis of the guest geometries in the four complexes with H1 revealed that the low energy guest conformers were present. The host selectivity for 6- and 7-ONE was proposed to be due to the improved molecular packing in the crystals of the complexes containing these two guest compounds, observed from their higher crystal densities. Hirshfeld surface analyses were not useful in explaining the preference of H1 for 6-ONE relative to 7-ONE (these types of analyses were not possible for the 5-ONE and 8-ONE-containing inclusion compounds due to the nature and degree of disorder present in the guest molecules). H1 was also crystallized from γ-butyrolactone (GBL), 2-pyrrolidone (NP), N-methyl-2-pyrrolidone (NMP) and N-ethyl-2-pyrrolidone (NEP), and 1H-NMR spectroscopy revealed that all but GBL were included. The host compound was also presented with these guest solvents in various mixtures, and it was observed that NMP was an extremely favoured guest solvent, followed by NEP and NP, with GBL being consistently disfavoured in every experiment. It was therefore shown that in certain instances, H1 may serve as an alternative tool for separating some of these mixtures through host-guest chemistry strategies. The hydrogen bonding motifs present in each of the successfully formed complexes were extensively investigated through SCXRD analysis, as was the thermal behaviour of these complexes. In the latter instance, the peak temperature of the endotherm (from the DSC trace) representing the guest release was greater for the inclusion compound with favoured NMP (145.5 °C) relative to the complexes with NP (139.8 °C) and NEP (120.5 °C). Host compounds H2 and H3 were revealed to have the ability to include each of pyridine (PYR), 2-methylpyridine (2MP), 3-methylpyridine (3MP) and 4-methylpyridine (4MP). H2 displayed selective behaviour for 3MP and 4MP when presented with mixtures of these guest compounds, whilst H3 preferred PYR. In the latter case, this PYR-containing inclusion compound was also the more stable one (the guest release onset temperature was highest, Ton 66.0 °C). It was demonstrated that H2 has the ability to separate very many binary mixtures of these pyridines on a practical platform, since K (the selectivity coefficient) values were 10 or greater in many instances. However, unfortunately, the more difficult-to-separate mixtures containing 3MP and 4MP cannot be purified or separated by employing H2 and supramolecular chemistry strategies. H3 was also shown to be a likely candidate for binary guest separations in very many of the guest solutions considered here, where K was also 10 or greater, and even infinity in many cases. SCXRD demonstrated that 2MP, 3MP and 4MP were retained in the crystals of their complexes by means of classical hydrogen bonds with the host compound. Satisfyingly, this hydrogen bond between 2MP and H2 (3.0213(18) Å) was significantly longer than that between this host compound and both disorder components of 3MP (2.875(2) and 2.825(9) Å) and that between H2 and 4MP (2.8458(13) Å). This observation explains the affinity of H2 for both 3MP and 4MP, and why 2MP was disfavoured. The results of thermal experiments did not wholly concur with observations from the guest/guest competition experiments. Hirshfeld surface analyses were also conducted but were not entirely conclusive with respect to explaining the host selectivity behaviour. In the case of H3, SCXRD analyses revealed that favoured PYR experienced a classical hydrogen bond with the host compound that was statistically significantly shorter (2.795(2) Å, 165°) than those between the other guest compounds and H3. Additionally, this guest compound was the only one to be involved in a (host)C−H···π(guest) interaction (2.91 Å, 139°) and also a non-classical hydrogen bond with the host compound ((host)C−H···N−C(guest), 2.77 Å (144°)). Finally, Hirshfeld surface analyses showed also that preferred PYR experienced a greater percentage of C···H/H···C (33.1%) and H···N/N···H (11.1%) interactions compared with the complexes with 2MP, 3MP and 4MP. However, it is not clear whether these Hirshfeld observations explain the affinity of H3 for PYR. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04