Characterisation of dissimilar friction stir welds between 5754 Aluminium alloy and C11000 copper
- Authors: Akinlabi, Esther Titilayo
- Date: 2010
- Subjects: Friction stir welding , Aluminum alloys , Copper alloys
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9629 , http://hdl.handle.net/10948/1536 , Friction stir welding , Aluminum alloys , Copper alloys
- Description: Friction Stir Welding (FSW) is a solid state welding process invented and patented by The Welding Institute (TWI) in 1991, for joining ferrous and non-ferrous materials1. The FSW of Aluminium and its alloys has been commercialised; and recent interest is focused on joining dissimilar materials. However, in order to commercialise the process, research studies are required to characterise and establish process windows. This research work through material characterisation of the welded joints establishes a process window for the Friction Stir welding of 5754 Aluminium Alloy and C11000 Copper. Furthermore, preliminary studies83,85 on the FSW of aluminium and copper have revealed the presence of intermetallic compounds which are detrimental to the weld qualities. This research work is also aimed at establishing process parameters that will result in limited or no intermetallic formation in the weld. The joint integrity of the resulting welds will also be correlated with the input process parameters. Based on the preliminary investigations conducted, a final weld matrix consisting of twenty seven welds was produced by varying the rotational speed between 600 and 1200 rpm, and the feed rate between 50 and 300 mm/min using three different shoulder diameter tools – 15, 18 and 25 mm to compare the heat input into the welds and to achieve the best results. The welds were characterised through microstructural evaluation, tensile testing, microhardness profiling, X-Ray Diffraction analysis, electrical resistivity and statistical analysis – in order to establish the interrelationship between the process parameters and the weld qualities. viii Microstructural evaluation of the weld samples revealed that the interfacial regions are characterised by mixture layers of aluminium and copper; while 33 percent of the tensile samples are within the acceptable range (> 75 percent joint efficiency). High Vickers microhardness values were measured at the joint interfaces, which corresponded with the intermetallic compounds. The Energy Dispersive Spectroscopy analysis revealed the presence of thin layers of intermetallics in nanoscale at the interfacial regions. The diffractograms of the X-Ray Diffraction analysis showed small peaks for intermetallics in some of the welds. Low electrical resistivities were measured at the joint interfaces. The statistical analysis showed that the downward vertical force, (Fz) can significantly influence the resulting weld qualities. An overall summary of the analysis of the weld qualities - with respect to the shoulder diameter tools employed showed that the 18 mm shoulder diameter tool is most appropriate among the three shoulder diameters considered, and a process window of medium spindle speed of 950 rpm and low-to-medium feed rate between 50 and 150 mm/min is established for FSW of Aluminium and Copper. Welds produced at 1200 rpm and 300 mm/min with low heat input did not have intermetallics formed at the joint interface.
- Full Text:
- Date Issued: 2010
- Authors: Akinlabi, Esther Titilayo
- Date: 2010
- Subjects: Friction stir welding , Aluminum alloys , Copper alloys
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9629 , http://hdl.handle.net/10948/1536 , Friction stir welding , Aluminum alloys , Copper alloys
- Description: Friction Stir Welding (FSW) is a solid state welding process invented and patented by The Welding Institute (TWI) in 1991, for joining ferrous and non-ferrous materials1. The FSW of Aluminium and its alloys has been commercialised; and recent interest is focused on joining dissimilar materials. However, in order to commercialise the process, research studies are required to characterise and establish process windows. This research work through material characterisation of the welded joints establishes a process window for the Friction Stir welding of 5754 Aluminium Alloy and C11000 Copper. Furthermore, preliminary studies83,85 on the FSW of aluminium and copper have revealed the presence of intermetallic compounds which are detrimental to the weld qualities. This research work is also aimed at establishing process parameters that will result in limited or no intermetallic formation in the weld. The joint integrity of the resulting welds will also be correlated with the input process parameters. Based on the preliminary investigations conducted, a final weld matrix consisting of twenty seven welds was produced by varying the rotational speed between 600 and 1200 rpm, and the feed rate between 50 and 300 mm/min using three different shoulder diameter tools – 15, 18 and 25 mm to compare the heat input into the welds and to achieve the best results. The welds were characterised through microstructural evaluation, tensile testing, microhardness profiling, X-Ray Diffraction analysis, electrical resistivity and statistical analysis – in order to establish the interrelationship between the process parameters and the weld qualities. viii Microstructural evaluation of the weld samples revealed that the interfacial regions are characterised by mixture layers of aluminium and copper; while 33 percent of the tensile samples are within the acceptable range (> 75 percent joint efficiency). High Vickers microhardness values were measured at the joint interfaces, which corresponded with the intermetallic compounds. The Energy Dispersive Spectroscopy analysis revealed the presence of thin layers of intermetallics in nanoscale at the interfacial regions. The diffractograms of the X-Ray Diffraction analysis showed small peaks for intermetallics in some of the welds. Low electrical resistivities were measured at the joint interfaces. The statistical analysis showed that the downward vertical force, (Fz) can significantly influence the resulting weld qualities. An overall summary of the analysis of the weld qualities - with respect to the shoulder diameter tools employed showed that the 18 mm shoulder diameter tool is most appropriate among the three shoulder diameters considered, and a process window of medium spindle speed of 950 rpm and low-to-medium feed rate between 50 and 150 mm/min is established for FSW of Aluminium and Copper. Welds produced at 1200 rpm and 300 mm/min with low heat input did not have intermetallics formed at the joint interface.
- Full Text:
- Date Issued: 2010
Customer satisfaction with the guesthouse experience in Ghana
- Authors: Amoah, Felix
- Date: 2016
- Subjects: Consumer satisfaction -- Ghana , Hospitality industry -- Ghana -- Management , Tourism -- Ghana -- Marketing
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: http://hdl.handle.net/10948/6073 , vital:21036
- Description: Guesthouse accommodation plays an important role in Ghana’s hospitality industry and was therefore the focus of this study as little research dealing with guesthouses in Ghana could be found. The number of guesthouses in Ghana continues to grow and they thus represent an important alternative to hotels. However, these establishments seem to perform poorly and face several challenges such as lack of managerial knowledge, insufficiently skilled employees, poor interaction with customers, and criticisms of the provision of low quality service. The main reason for undertaking this research was to provide guesthouse managers in Ghana with information that might assist them in making decisions about the experience they offer. Such knowledge could make this type of accommodation more competitive and eventually help the hospitality sector in Ghana attract tourists and grow. It is imperative that guesthouses focus on the experience they offer, because contemporary tourism and hospitality literature suggest that successful businesses require a shift from functional and financial interests to a more profound focus on total experiences which embody emotional aspects. It is thus argued that, if guesthouse managers in Ghana do not know how their guests perceive their guesthouse experience, they might make costly mistakes and allocate resources to aspects that already provide quality and value in a functional sense, instead of those elements perceived as providing quality and value in the total experience. Two dominating concepts, namely experience quality and experience value, formed the basis of the examination of guests’ experience with the guesthouses in Ghana. In addition, the relationships between the experience and satisfaction were also investigated. Four experience quality dimensions, namely hedonics, peace of mind, involvement, and recognition, and seven value dimensions were examined. The experience value dimensions included atmospherics, enjoyment, entertainment, efficiency, excellence, escape, and economic value. A proportional stratified random sampling procedure was followed to select the guesthouses for the study. Thereafter, a structured questionnaire was distributed to the guesthouse guests selected by means of convenience sampling. Five hundred and forty one useable questionnaires were received. The guesthouse guests formed the primary sampling unit for this study. The results of the empirical study showed a strong positive correlation between all the dimensions of experience quality and experience value, while the factor analysis confirmed that all these dimensions loaded on a single factor. Therefore, experience quality and experience value cannot be separated, and the resulting single multi-dimensional factor was subsequently renamed, overall experience. The results also indicated a positive relationship between hedonics, peace of mind, involvement, recognition, atmospherics, enjoyment, entertainment, efficiency, excellence, escape, economic value, and overall satisfaction. The inferentially established rank-order of the dimensions contributing to satisfaction can guide managers when allocating resources. Overall, atmospherics was ranked first, followed by economic value. Escape was the lowest ranked dimension. In addition, it was found that, except for escape, all the experience dimensions were perceived as basic satisfiers. This implies that guests will be dissatisfied when provision of these dimensions is inadequate. With regard to escape, listed as a performance factor, guests will be satisfied when performance is improved and dissatisfied when performance is low. A positive relationship was also found between overall experience and overall satisfaction. The latter include the likelihood of return and recommending the guesthouse to others. Finally, structural equation modelling confirmed a model representing the 11 experience dimensions (hedonics, peace of mind, involvement, recognition, atmospherics, enjoyment, entertainment, escape, efficiency, excellence, and economic value) and the relationships between overall experience and overall satisfaction pertaining to guesthouses in Ghana.
- Full Text:
- Date Issued: 2016
- Authors: Amoah, Felix
- Date: 2016
- Subjects: Consumer satisfaction -- Ghana , Hospitality industry -- Ghana -- Management , Tourism -- Ghana -- Marketing
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: http://hdl.handle.net/10948/6073 , vital:21036
- Description: Guesthouse accommodation plays an important role in Ghana’s hospitality industry and was therefore the focus of this study as little research dealing with guesthouses in Ghana could be found. The number of guesthouses in Ghana continues to grow and they thus represent an important alternative to hotels. However, these establishments seem to perform poorly and face several challenges such as lack of managerial knowledge, insufficiently skilled employees, poor interaction with customers, and criticisms of the provision of low quality service. The main reason for undertaking this research was to provide guesthouse managers in Ghana with information that might assist them in making decisions about the experience they offer. Such knowledge could make this type of accommodation more competitive and eventually help the hospitality sector in Ghana attract tourists and grow. It is imperative that guesthouses focus on the experience they offer, because contemporary tourism and hospitality literature suggest that successful businesses require a shift from functional and financial interests to a more profound focus on total experiences which embody emotional aspects. It is thus argued that, if guesthouse managers in Ghana do not know how their guests perceive their guesthouse experience, they might make costly mistakes and allocate resources to aspects that already provide quality and value in a functional sense, instead of those elements perceived as providing quality and value in the total experience. Two dominating concepts, namely experience quality and experience value, formed the basis of the examination of guests’ experience with the guesthouses in Ghana. In addition, the relationships between the experience and satisfaction were also investigated. Four experience quality dimensions, namely hedonics, peace of mind, involvement, and recognition, and seven value dimensions were examined. The experience value dimensions included atmospherics, enjoyment, entertainment, efficiency, excellence, escape, and economic value. A proportional stratified random sampling procedure was followed to select the guesthouses for the study. Thereafter, a structured questionnaire was distributed to the guesthouse guests selected by means of convenience sampling. Five hundred and forty one useable questionnaires were received. The guesthouse guests formed the primary sampling unit for this study. The results of the empirical study showed a strong positive correlation between all the dimensions of experience quality and experience value, while the factor analysis confirmed that all these dimensions loaded on a single factor. Therefore, experience quality and experience value cannot be separated, and the resulting single multi-dimensional factor was subsequently renamed, overall experience. The results also indicated a positive relationship between hedonics, peace of mind, involvement, recognition, atmospherics, enjoyment, entertainment, efficiency, excellence, escape, economic value, and overall satisfaction. The inferentially established rank-order of the dimensions contributing to satisfaction can guide managers when allocating resources. Overall, atmospherics was ranked first, followed by economic value. Escape was the lowest ranked dimension. In addition, it was found that, except for escape, all the experience dimensions were perceived as basic satisfiers. This implies that guests will be dissatisfied when provision of these dimensions is inadequate. With regard to escape, listed as a performance factor, guests will be satisfied when performance is improved and dissatisfied when performance is low. A positive relationship was also found between overall experience and overall satisfaction. The latter include the likelihood of return and recommending the guesthouse to others. Finally, structural equation modelling confirmed a model representing the 11 experience dimensions (hedonics, peace of mind, involvement, recognition, atmospherics, enjoyment, entertainment, escape, efficiency, excellence, and economic value) and the relationships between overall experience and overall satisfaction pertaining to guesthouses in Ghana.
- Full Text:
- Date Issued: 2016
An evaluation of leadership characteristics required to meet the demands of a strategic change process in the automative cluster in the Eastern Cape region
- Authors: Angloher, Sanette
- Date: 2010
- Subjects: Leadership , Organizational change
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9341 , http://hdl.handle.net/10948/1261 , Leadership , Organizational change
- Description: Against a backdrop of increasing globalisation, deregulation, the rapid pace of technological innovation, a growing knowledge workforce, and shifting social and demographic trends, the primary task of management today is the leadership of organisational change (Graetz, 2000:550). In the words of Lussier and Achua Abstract v (2001:9): “The companies that will survive in the new global competitiveness environment are those that can attract and maintain leaders”. The above emphasises the important role of managers during times when change take place in the organisation. Yet employees are often managed inappropriately in a period of change. There are two reasons for this: (1) managers managing change are under pressure which undermines their own performance, (2) organisations often do not possess managers who are skilful at handling change. It is this second reason that will form the focus of this study. Carnall (1999:105) states that managing change effectively requires an understanding of both what is and seems likely to happen and of how people react to change, and a skilful management performance. Leaders must take on more facilitative roles, as competencies in change management become critical to creating and sustaining effective organisations. The major technological advances of today rely heavily on leaders to facilitate change. Leaders need to encourage people to “collaborate, take risks, take responsibility and be accountable for the change process the organisation must continually undergo to maintain a leadership position in its industry”, according to Moran and Brightman (2000:3). They furthermore argue that “change leaders recognise that they are always trying to balance stability and change. It is a delicate balance to accomplish since employees desire order and stability, while organisations must be ready to adapt to changing conditions quickly”. In this rapidly changing world, organisations must become more flexible, more responsive, and more willing to change and adapt. They must create and assimilate new knowledge at an increasing pace, encourage innovation, and learn to compete in new ways. Dess and Picken (2000:30) argue that the leaders of these organisations must be proactive in facilitating organisational learning and encouraging positive adaptation to external changes. The above shows what an important role leaders/managers have to play in the strategic change process. They need to possess the requisite skills in leadership, problem solving, continuous improvement, team effectiveness, and customer service in order to ensure the long-term growth and stability in the organisation which change can bring about. This research project will identify the various skills needed to successfully manage a change initiative.
- Full Text:
- Date Issued: 2010
- Authors: Angloher, Sanette
- Date: 2010
- Subjects: Leadership , Organizational change
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9341 , http://hdl.handle.net/10948/1261 , Leadership , Organizational change
- Description: Against a backdrop of increasing globalisation, deregulation, the rapid pace of technological innovation, a growing knowledge workforce, and shifting social and demographic trends, the primary task of management today is the leadership of organisational change (Graetz, 2000:550). In the words of Lussier and Achua Abstract v (2001:9): “The companies that will survive in the new global competitiveness environment are those that can attract and maintain leaders”. The above emphasises the important role of managers during times when change take place in the organisation. Yet employees are often managed inappropriately in a period of change. There are two reasons for this: (1) managers managing change are under pressure which undermines their own performance, (2) organisations often do not possess managers who are skilful at handling change. It is this second reason that will form the focus of this study. Carnall (1999:105) states that managing change effectively requires an understanding of both what is and seems likely to happen and of how people react to change, and a skilful management performance. Leaders must take on more facilitative roles, as competencies in change management become critical to creating and sustaining effective organisations. The major technological advances of today rely heavily on leaders to facilitate change. Leaders need to encourage people to “collaborate, take risks, take responsibility and be accountable for the change process the organisation must continually undergo to maintain a leadership position in its industry”, according to Moran and Brightman (2000:3). They furthermore argue that “change leaders recognise that they are always trying to balance stability and change. It is a delicate balance to accomplish since employees desire order and stability, while organisations must be ready to adapt to changing conditions quickly”. In this rapidly changing world, organisations must become more flexible, more responsive, and more willing to change and adapt. They must create and assimilate new knowledge at an increasing pace, encourage innovation, and learn to compete in new ways. Dess and Picken (2000:30) argue that the leaders of these organisations must be proactive in facilitating organisational learning and encouraging positive adaptation to external changes. The above shows what an important role leaders/managers have to play in the strategic change process. They need to possess the requisite skills in leadership, problem solving, continuous improvement, team effectiveness, and customer service in order to ensure the long-term growth and stability in the organisation which change can bring about. This research project will identify the various skills needed to successfully manage a change initiative.
- Full Text:
- Date Issued: 2010
Development of a process for the preparation of linalool from CIS-2-pinanol
- Authors: Buddoo, Subash Ramnarain
- Date: 2009
- Subjects: Odors , Perfumes -- History , Perfumes -- Formulae , Fermentation
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10425 , http://hdl.handle.net/10948/d1016219
- Description: Linalool is a key intermediate for the production of important fragrance chemicals such as geraniol, nerol, geranial, and neral. Linalool can be produced via a two-step process from α-pinene which is a major component of crude sulphated turpentine (CST) a foul-smelling, volatile waste product of the pulp and paper industry. The key step in this process is the pyrolysis step which involves the isomerisation of cis-2-pinanol to linalool and requires high temperatures (600-650°C) and is not very selective due to the decomposition of the product itself under these conditions. A client of the CSIR, Teubes Pty. Ltd., is a manufacturer of flavour and fragrance compounds for the local and international fragrance market and expressed an interest in producing linalool since the company would then gain access to other valuable fragrance chemicals via relatively simple processes. Earlier work conducted by AECI, R & D did not meet with much success since the selectivity to linalool was very poor and the process could hardly be deemed as scalable. The main objective of this project was therefore to develop a process for the selective isomerisation of cis-2-pinanol to linalool with minimum by-product formation and using process equipment that could be scaled to full-scale production. Since cis-2- pinanol could not be purchased in sufficient quantities for process development, a process had to be developed for the bench-scale preparation of kilogram quantities of cis-2-pinanol from α-pinene obtained from the client. Although this synthesis formed a minor part of this investigation, several process improvements and innovations were introduced to produce high quality cis-2-pinanol, in very good yields at kilogram scale. A major part of this investigation was the design and set up of a pyrolyis rig capable of operating at elevated temperatures (400 - 750°C) for the evaluation of various process parameters. Various vaporizer, reactor, and condensation systems were evaluated for their ability to cope with the demanding conditions on a consistent basis. The initial part of the investigation was a screening exercise to evaluate various process parameters as well as solvents, materials of construction, catalysts, etc. A comprehensive statistical design was also conducted to determine the critical process parameters and the model obtained was used to predict the optimum conditions required for the preparation of in-specification product on a consistent basis. These conditions were used in the preparation of a 1kg sample which was required by theclient for market evaluation purposes. The use of a novel microreactor system was also evaluated for the pinanol pyrolysis reaction. To our knowledge, this is the first time that a microreactor has been successfully used for this type of reaction in the Fragrance industry and a patent application is being filed by the CSIR. The kinetics of the reaction in both the tubular reactor system and the microreactor system was investigated. Computer modelling studies on both the systems were also conducted. The raw material cost to produce a kilogram of linalool is $1.40. There is a significant margin of 60.8 percent between the raw material cost of linalool and the current selling price ($3.57/kg). This clearly indicates that the project is potentially feasible from an economic point of view and we can now proceed with confidence to the next stage which is the engineering design, building and commissioning of the large scale pyrolysis rig. The rest of the process steps will be conducted on existing equipment currently present at the CSIR’s large scale facility (Imbiza in Isando, Gauteng).
- Full Text:
- Date Issued: 2009
- Authors: Buddoo, Subash Ramnarain
- Date: 2009
- Subjects: Odors , Perfumes -- History , Perfumes -- Formulae , Fermentation
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10425 , http://hdl.handle.net/10948/d1016219
- Description: Linalool is a key intermediate for the production of important fragrance chemicals such as geraniol, nerol, geranial, and neral. Linalool can be produced via a two-step process from α-pinene which is a major component of crude sulphated turpentine (CST) a foul-smelling, volatile waste product of the pulp and paper industry. The key step in this process is the pyrolysis step which involves the isomerisation of cis-2-pinanol to linalool and requires high temperatures (600-650°C) and is not very selective due to the decomposition of the product itself under these conditions. A client of the CSIR, Teubes Pty. Ltd., is a manufacturer of flavour and fragrance compounds for the local and international fragrance market and expressed an interest in producing linalool since the company would then gain access to other valuable fragrance chemicals via relatively simple processes. Earlier work conducted by AECI, R & D did not meet with much success since the selectivity to linalool was very poor and the process could hardly be deemed as scalable. The main objective of this project was therefore to develop a process for the selective isomerisation of cis-2-pinanol to linalool with minimum by-product formation and using process equipment that could be scaled to full-scale production. Since cis-2- pinanol could not be purchased in sufficient quantities for process development, a process had to be developed for the bench-scale preparation of kilogram quantities of cis-2-pinanol from α-pinene obtained from the client. Although this synthesis formed a minor part of this investigation, several process improvements and innovations were introduced to produce high quality cis-2-pinanol, in very good yields at kilogram scale. A major part of this investigation was the design and set up of a pyrolyis rig capable of operating at elevated temperatures (400 - 750°C) for the evaluation of various process parameters. Various vaporizer, reactor, and condensation systems were evaluated for their ability to cope with the demanding conditions on a consistent basis. The initial part of the investigation was a screening exercise to evaluate various process parameters as well as solvents, materials of construction, catalysts, etc. A comprehensive statistical design was also conducted to determine the critical process parameters and the model obtained was used to predict the optimum conditions required for the preparation of in-specification product on a consistent basis. These conditions were used in the preparation of a 1kg sample which was required by theclient for market evaluation purposes. The use of a novel microreactor system was also evaluated for the pinanol pyrolysis reaction. To our knowledge, this is the first time that a microreactor has been successfully used for this type of reaction in the Fragrance industry and a patent application is being filed by the CSIR. The kinetics of the reaction in both the tubular reactor system and the microreactor system was investigated. Computer modelling studies on both the systems were also conducted. The raw material cost to produce a kilogram of linalool is $1.40. There is a significant margin of 60.8 percent between the raw material cost of linalool and the current selling price ($3.57/kg). This clearly indicates that the project is potentially feasible from an economic point of view and we can now proceed with confidence to the next stage which is the engineering design, building and commissioning of the large scale pyrolysis rig. The rest of the process steps will be conducted on existing equipment currently present at the CSIR’s large scale facility (Imbiza in Isando, Gauteng).
- Full Text:
- Date Issued: 2009
The development of motivational strategies for public sector workers in Kenya
- Authors: Chepkilot, Ronald Kiprop
- Date: 2005
- Subjects: Public administration -- Kenya , Employee motivation , Civil service -- Kenya -- Personnel management
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9380 , http://hdl.handle.net/10948/161 , Public administration -- Kenya , Employee motivation , Civil service -- Kenya -- Personnel management
- Description: The purpose of this study was to develop motivational strategies for motivating public sector workers in Kenya. To achieve this objective the following procedure was followed: • An examination of the public service was undertaken and the following factors were considered: The history of the public service; Past government reform programmes; The problem of corruption; Future government reform programmes; and The motivational climate in the service. iv • A literature survey was conducted on the approaches used by organisations in motivating employees. The findings were used to develop a motivational strategy model. On the basis of the strategies in the model, a questionnaire was developed for the empirical research study. • The empirical study was undertaken to examine the level of motivation in the public service and to identify the motivational strategies currently used in the public service in Kenya. The study also sought to determine the extent to which public sector managers agreed or disagreed that the motivational strategies developed by the study would be effective in motivating employees in their organisations. The results of the empirical study were incorporated into the integrated motivational strategy model presented in chapter six. The study established that the level of motivation among the public sector workers was extremely low. According to the research findings, 87 per cent of the respondents indicated that the level of motivation of employees in their organisation was low while 13 per cent indicated that it was high. It was also established that the climate in the public service was not conducive for motivating employees: the indicators were lack of job security; very low salaries; limited training and development opportunities; lack of career development programmes and lack of adequate working tools and equipment. It was further established that the government could no longer afford to make any substantial increases in salaries to the workers because the wage bill was extremely high at the level of 9.6 per cent of the GDP. It was observed that any further increases in salaries would v have a negative impact on the economy of the country. In view of the above, this study becomes extremely relevant as it suggests ways of enhancing the levels of motivation in the public service to improve service delivery in the public sector without allocation of vast financial resources. The study strongly recommends the application of the integrated motivational strategy model in its entirety; to enhance the level of employee’s motivation and work performance and achieve efficiency and effectiveness in service delivery. The study also recommends that further research be carried out to determine the effects of corruption on employee motivation and ways of eliminating the vice in the public service.
- Full Text:
- Date Issued: 2005
- Authors: Chepkilot, Ronald Kiprop
- Date: 2005
- Subjects: Public administration -- Kenya , Employee motivation , Civil service -- Kenya -- Personnel management
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9380 , http://hdl.handle.net/10948/161 , Public administration -- Kenya , Employee motivation , Civil service -- Kenya -- Personnel management
- Description: The purpose of this study was to develop motivational strategies for motivating public sector workers in Kenya. To achieve this objective the following procedure was followed: • An examination of the public service was undertaken and the following factors were considered: The history of the public service; Past government reform programmes; The problem of corruption; Future government reform programmes; and The motivational climate in the service. iv • A literature survey was conducted on the approaches used by organisations in motivating employees. The findings were used to develop a motivational strategy model. On the basis of the strategies in the model, a questionnaire was developed for the empirical research study. • The empirical study was undertaken to examine the level of motivation in the public service and to identify the motivational strategies currently used in the public service in Kenya. The study also sought to determine the extent to which public sector managers agreed or disagreed that the motivational strategies developed by the study would be effective in motivating employees in their organisations. The results of the empirical study were incorporated into the integrated motivational strategy model presented in chapter six. The study established that the level of motivation among the public sector workers was extremely low. According to the research findings, 87 per cent of the respondents indicated that the level of motivation of employees in their organisation was low while 13 per cent indicated that it was high. It was also established that the climate in the public service was not conducive for motivating employees: the indicators were lack of job security; very low salaries; limited training and development opportunities; lack of career development programmes and lack of adequate working tools and equipment. It was further established that the government could no longer afford to make any substantial increases in salaries to the workers because the wage bill was extremely high at the level of 9.6 per cent of the GDP. It was observed that any further increases in salaries would v have a negative impact on the economy of the country. In view of the above, this study becomes extremely relevant as it suggests ways of enhancing the levels of motivation in the public service to improve service delivery in the public sector without allocation of vast financial resources. The study strongly recommends the application of the integrated motivational strategy model in its entirety; to enhance the level of employee’s motivation and work performance and achieve efficiency and effectiveness in service delivery. The study also recommends that further research be carried out to determine the effects of corruption on employee motivation and ways of eliminating the vice in the public service.
- Full Text:
- Date Issued: 2005
Continuous flow synthesis of silicon compounds as feedstock for solar-grade silicon production
- Authors: Chigondo, Fidelis
- Date: 2016
- Subjects: Silicon -- Synthesis , Homogeneous catalysis
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: http://hdl.handle.net/10948/4529 , vital:20613
- Description: This thesis describes the key steps in the production of high purity (solar-grade) silicon from metallurgical-grade silicon for use in the production of photovoltaic cells as alternative renewable, environmentally benign and cheap energy source. The initial part of the project involves the development and optimization of a small chemical production platform system capable of producing alkoxysilanes from metallurgical-grade silicon as green precursors to solar-grade silicon production. Specifically, the main aim of the study was to synthesize trialkoxysilanes in continuous flow mode, although the synthesis on monosilane was also done in batch mode. The alkoxylation reaction was carried out in a traditional slurry phase batch reactor, packed bed flow tubular reactor and also attempted in a continuous flow falling film tubular reactor. The effect of key parameters which affect the silicon conversion and selectivity for the desired trialkoxysilane were investigated and optimized using ethanol as a reagent model. The synthesis was then extended to the other alcohols namely methanol, n-propanol and n-butanol. Copper catalysts which were tested in the alkoxylation reaction included: CuCl, Cu(OH)2, CuO and CuSO4. CuCl and Cu(OH)2 showed comparable activity in the batch mode but the former was more efficient in the packed bed flow tubular reactor. Cu(OH)2 could be used as a non-halide catalyst but its activity is limited to short reaction cycles (<10 h). The uncatalysed reaction resulted in negligible reaction rates in both types of reactors. High temperature catalyst pre-heating (>500 oC) resulted in a lower rate of reaction and selectivity than when slightly lower temperatures are used (<350 oC) in both reactors, although much difference was noticed in the packed bed flow tubular reactor. Synthesis in the batch reactor needed longer silicon-catalyst activation time, higher pre-heating temperature and higher catalyst amounts as compare to the packed bed flow tubular reactor. Reaction temperature and alcohol flow rate influenced the reaction in both methods. The optimum reaction temperature range and alcohol flow rate was comparable in both reactors (230 to 240 oC) and 0.1mL/min respectively. The effect of alcohol R-group (C1 to C4) on the reaction revealed that conversion and selectivity generally decrease with an increase in carbon chain length in both methods. Ethanol showed highest selectivity (>95% in batch and >97% in flow) and conversion (about 88% in batch and about 64% in flow) as compared to all other alcohols studied showing that it could be the most efficient alkoxylation alcohol for this reaction. Overally, the packed bed flow tubular reactor resulted in higher selectivity to trialkoxysilanes than the batch system. Performing the reaction under pressure resulted in increased conversion but selectivity to the desire trialkoxysilane diminished. Synthesis in a continuous flow falling film tubular reactor was not successful as it resulted in very poor conversion and selectivity. Monosilane was successfully synthesized from the disproportionation of triethoxysilane using homogeneous and heterogeneous catalysts in batch mode. The results obtained from homogeneous catalysis showed that the reaction can be conducted at room temperature. The heterogeneous catalysis method resulted in slow conversion at room temperature but mild heating up to 55 oC greatly improved the reaction. Conducting the reaction under neat conditions produced comparable results to reactions which were carried out using solvents. The disproportionation reaction was best described by the first order kinetic model. The results obtained in this research indicate that the packed bed flow tubular reactor can be utilized with future modifications for continuous flow synthesis of alkoxysilanes as feedstock for the solar-grade silicon production.
- Full Text:
- Date Issued: 2016
- Authors: Chigondo, Fidelis
- Date: 2016
- Subjects: Silicon -- Synthesis , Homogeneous catalysis
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: http://hdl.handle.net/10948/4529 , vital:20613
- Description: This thesis describes the key steps in the production of high purity (solar-grade) silicon from metallurgical-grade silicon for use in the production of photovoltaic cells as alternative renewable, environmentally benign and cheap energy source. The initial part of the project involves the development and optimization of a small chemical production platform system capable of producing alkoxysilanes from metallurgical-grade silicon as green precursors to solar-grade silicon production. Specifically, the main aim of the study was to synthesize trialkoxysilanes in continuous flow mode, although the synthesis on monosilane was also done in batch mode. The alkoxylation reaction was carried out in a traditional slurry phase batch reactor, packed bed flow tubular reactor and also attempted in a continuous flow falling film tubular reactor. The effect of key parameters which affect the silicon conversion and selectivity for the desired trialkoxysilane were investigated and optimized using ethanol as a reagent model. The synthesis was then extended to the other alcohols namely methanol, n-propanol and n-butanol. Copper catalysts which were tested in the alkoxylation reaction included: CuCl, Cu(OH)2, CuO and CuSO4. CuCl and Cu(OH)2 showed comparable activity in the batch mode but the former was more efficient in the packed bed flow tubular reactor. Cu(OH)2 could be used as a non-halide catalyst but its activity is limited to short reaction cycles (<10 h). The uncatalysed reaction resulted in negligible reaction rates in both types of reactors. High temperature catalyst pre-heating (>500 oC) resulted in a lower rate of reaction and selectivity than when slightly lower temperatures are used (<350 oC) in both reactors, although much difference was noticed in the packed bed flow tubular reactor. Synthesis in the batch reactor needed longer silicon-catalyst activation time, higher pre-heating temperature and higher catalyst amounts as compare to the packed bed flow tubular reactor. Reaction temperature and alcohol flow rate influenced the reaction in both methods. The optimum reaction temperature range and alcohol flow rate was comparable in both reactors (230 to 240 oC) and 0.1mL/min respectively. The effect of alcohol R-group (C1 to C4) on the reaction revealed that conversion and selectivity generally decrease with an increase in carbon chain length in both methods. Ethanol showed highest selectivity (>95% in batch and >97% in flow) and conversion (about 88% in batch and about 64% in flow) as compared to all other alcohols studied showing that it could be the most efficient alkoxylation alcohol for this reaction. Overally, the packed bed flow tubular reactor resulted in higher selectivity to trialkoxysilanes than the batch system. Performing the reaction under pressure resulted in increased conversion but selectivity to the desire trialkoxysilane diminished. Synthesis in a continuous flow falling film tubular reactor was not successful as it resulted in very poor conversion and selectivity. Monosilane was successfully synthesized from the disproportionation of triethoxysilane using homogeneous and heterogeneous catalysts in batch mode. The results obtained from homogeneous catalysis showed that the reaction can be conducted at room temperature. The heterogeneous catalysis method resulted in slow conversion at room temperature but mild heating up to 55 oC greatly improved the reaction. Conducting the reaction under neat conditions produced comparable results to reactions which were carried out using solvents. The disproportionation reaction was best described by the first order kinetic model. The results obtained in this research indicate that the packed bed flow tubular reactor can be utilized with future modifications for continuous flow synthesis of alkoxysilanes as feedstock for the solar-grade silicon production.
- Full Text:
- Date Issued: 2016
Factors influencing survivor qualities after downsizing
- Authors: Chipunza, Crispen
- Date: 2009
- Subjects: Downsizing of organizations -- South Africa , Organizational change -- South Africa , Cost control , Unemployment -- Psychological aspects
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9381 , http://hdl.handle.net/10948/1219 , Downsizing of organizations -- South Africa , Organizational change -- South Africa , Cost control , Unemployment -- Psychological aspects
- Description: Today organisations all over the world have to cope with the ever-increasing rate of local and global change. Those in developing countries have to cope with the inefficiencies engendered by state-led economic, developmental and political strategies, such as new government regulations. These have had an impact on the management of human resources and are exemplified by an increasing adoption of strategies meant to reduce pressure on costs and margins. An increasing popular management response to these challenges has been to engage in some form of organisational restructuring such as downsizing. Often employees who remain (survivors) after downsizing are not given much attention, yet the achievement of new strategic goals depends on the survivors having positive attitudes, relentless commitment and high motivation. Research indicates that employees who are motivated and committed contribute vastly to the financial-bottom-line of the organisation. Therefore, downsizing organisations should continuously search for ways to increase such qualities among their survivors. The objective of this study was to identify the factors that influence the attitudes, commitment and motivation of survivors in a developing economy with a volatile environment. To achieve this objective, a theoretical survivor quality model was presented. In order to present the model, firstly, a literature survey on the importance of survivor quality in terms of attitudes, commitment, and motivation among survivors was conducted. Secondly, literature survey pertaining to the drivers of survivor quality was done, and thirdly, literature dealing with strategies to deal with survivor quality was surveyed. The theoretical survivor quality model was used to compile the research instrument that determined the attitudinal, commitment and motivational levels of survivors, how the three constructs are related after downsizing, as well as the factors influencing the observed levels. The questionnaire was randomly distributed among survivors in the selected manufacturing organisations in Zimbabwe. The empirical results obtained from the study showed that survivors in a developing economy with a volatile environment had moderate levels of attitudes, commitment ad motivation. Two categories of factors were identified as important in influencing these levels. They were downsizing strategy and demographic factors. The downsizing strategy factors were communication and victim support, while education, age, and number of years employed emerged as the demographic factors. The study further highlighted that older survivors with less education contributed more to the moderate levels of attitude, commitment and motivation observed. The study highlights that these variables must be taken into consideration when implementing downsizing in an economically volatile environment in order to manage survivor quality. A further point emanating from the study is that prior to downsizing, organisations should adopt effective communication strategies throughout the process. The key factors identified as influencing survivor quality in this study were integrated into the survivor quality model which can be used by other organisations in a similar context to manage survivor quality in order to increase their efficiency, effectiveness, iv and competitive advantage after downsizing.
- Full Text:
- Date Issued: 2009
- Authors: Chipunza, Crispen
- Date: 2009
- Subjects: Downsizing of organizations -- South Africa , Organizational change -- South Africa , Cost control , Unemployment -- Psychological aspects
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9381 , http://hdl.handle.net/10948/1219 , Downsizing of organizations -- South Africa , Organizational change -- South Africa , Cost control , Unemployment -- Psychological aspects
- Description: Today organisations all over the world have to cope with the ever-increasing rate of local and global change. Those in developing countries have to cope with the inefficiencies engendered by state-led economic, developmental and political strategies, such as new government regulations. These have had an impact on the management of human resources and are exemplified by an increasing adoption of strategies meant to reduce pressure on costs and margins. An increasing popular management response to these challenges has been to engage in some form of organisational restructuring such as downsizing. Often employees who remain (survivors) after downsizing are not given much attention, yet the achievement of new strategic goals depends on the survivors having positive attitudes, relentless commitment and high motivation. Research indicates that employees who are motivated and committed contribute vastly to the financial-bottom-line of the organisation. Therefore, downsizing organisations should continuously search for ways to increase such qualities among their survivors. The objective of this study was to identify the factors that influence the attitudes, commitment and motivation of survivors in a developing economy with a volatile environment. To achieve this objective, a theoretical survivor quality model was presented. In order to present the model, firstly, a literature survey on the importance of survivor quality in terms of attitudes, commitment, and motivation among survivors was conducted. Secondly, literature survey pertaining to the drivers of survivor quality was done, and thirdly, literature dealing with strategies to deal with survivor quality was surveyed. The theoretical survivor quality model was used to compile the research instrument that determined the attitudinal, commitment and motivational levels of survivors, how the three constructs are related after downsizing, as well as the factors influencing the observed levels. The questionnaire was randomly distributed among survivors in the selected manufacturing organisations in Zimbabwe. The empirical results obtained from the study showed that survivors in a developing economy with a volatile environment had moderate levels of attitudes, commitment ad motivation. Two categories of factors were identified as important in influencing these levels. They were downsizing strategy and demographic factors. The downsizing strategy factors were communication and victim support, while education, age, and number of years employed emerged as the demographic factors. The study further highlighted that older survivors with less education contributed more to the moderate levels of attitude, commitment and motivation observed. The study highlights that these variables must be taken into consideration when implementing downsizing in an economically volatile environment in order to manage survivor quality. A further point emanating from the study is that prior to downsizing, organisations should adopt effective communication strategies throughout the process. The key factors identified as influencing survivor quality in this study were integrated into the survivor quality model which can be used by other organisations in a similar context to manage survivor quality in order to increase their efficiency, effectiveness, iv and competitive advantage after downsizing.
- Full Text:
- Date Issued: 2009
Causal determinants of the public's attitudes towards hunting as a basis for strategies to improve the social legitimacy of hunting
- Coetzer, Wentzel Christoffel
- Authors: Coetzer, Wentzel Christoffel
- Date: 2014
- Subjects: Hunting -- South Africa , Wildlife management -- South Africa , Wildlife conservation -- South Africa
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10759 , http://hdl.handle.net/10948/d1021164
- Description: It is widely acknowledged that the organised wildlife and hunting industry in South Africa contributes significantly to the country’s economy, as well as to the effective management and conservation of wildlife on privately owned land. Despite this, hunting has come under increasing attack by anti-hunting proponents who wish to bring a ban on hunting. A number of broad shifts across society at large and lobbying against hunting by anti-hunting proponents have given rise to legitimate concerns regarding the social acceptability of hunting. To maintain the social legitimacy of hunting, it is imperative to put strategies in place to actively broaden the base of public acceptance of hunting. Towards this aim, this study is an empirical investigation of the causal determinants of the public’s attitudes towards hunting and of the implications it holds for improving the social legitimacy of hunting. The study commenced by building a sound theoretical foundation from the available literature on the measurement of attitudes, the structure and formation of attitudes, the instrumental and experiential aspects of attitudes, attitudinal ambivalence, the psychology of strong attitudes, as well as the phenomenon of cognitive dissonance. Thereafter, the study turned to identify an adequate and empirically valid research approach for investigating attitudes and its causal determinants. A popular attitude theory in social psychology, namely the theory of reasoned action, was identified as a suitable conceptual framework for conducting this study. According to the reasoned action model, the salient behavioural beliefs people associate with a particular behaviour form the informational foundation (or cognitive foundation) on which their attitudes towards the behaviour are based. More specifically, the model suggests that peoples’ overall attitude towards a behaviour is a function of their perceived probability that a behaviour will produce certain outcomes (belief strength), as well as the degree to which they judge the perceived outcomes of the behaviour as positive or negative (outcome evaluation). The methodological design of the study’s empirical component was strictly based on the standard procedures prescribed by the theory of reasoned action. Two consecutive and methodologically interrelated surveys were conducted amongst members of the public to collect the study’s primary data. The main salient behavioural beliefs on which different attitudes towards hunting are based were identified and further investigated. The results were analysed from the perspective of the theory of reasoned action and a clear understanding of the causal determinants of different attitudes towards hunting were attained. Based on the findings of the study, a number of conclusions and recommendations were made that may guide the development of future strategies to improve the social legitimacy of hunting. Amongst other things, it was suggested that public education programmes should be developed to address the public’s misconceptions of hunting; that public relation campaigns be undertaken to improve the public’s negative image of hunters; and that hunter education programmes be put in place to make hunters aware of the role they could play at community level to improve the social acceptability of hunting. Detailed guidelines regarding the contents of such education programmes and public relation campaigns were provided.
- Full Text:
- Date Issued: 2014
- Authors: Coetzer, Wentzel Christoffel
- Date: 2014
- Subjects: Hunting -- South Africa , Wildlife management -- South Africa , Wildlife conservation -- South Africa
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10759 , http://hdl.handle.net/10948/d1021164
- Description: It is widely acknowledged that the organised wildlife and hunting industry in South Africa contributes significantly to the country’s economy, as well as to the effective management and conservation of wildlife on privately owned land. Despite this, hunting has come under increasing attack by anti-hunting proponents who wish to bring a ban on hunting. A number of broad shifts across society at large and lobbying against hunting by anti-hunting proponents have given rise to legitimate concerns regarding the social acceptability of hunting. To maintain the social legitimacy of hunting, it is imperative to put strategies in place to actively broaden the base of public acceptance of hunting. Towards this aim, this study is an empirical investigation of the causal determinants of the public’s attitudes towards hunting and of the implications it holds for improving the social legitimacy of hunting. The study commenced by building a sound theoretical foundation from the available literature on the measurement of attitudes, the structure and formation of attitudes, the instrumental and experiential aspects of attitudes, attitudinal ambivalence, the psychology of strong attitudes, as well as the phenomenon of cognitive dissonance. Thereafter, the study turned to identify an adequate and empirically valid research approach for investigating attitudes and its causal determinants. A popular attitude theory in social psychology, namely the theory of reasoned action, was identified as a suitable conceptual framework for conducting this study. According to the reasoned action model, the salient behavioural beliefs people associate with a particular behaviour form the informational foundation (or cognitive foundation) on which their attitudes towards the behaviour are based. More specifically, the model suggests that peoples’ overall attitude towards a behaviour is a function of their perceived probability that a behaviour will produce certain outcomes (belief strength), as well as the degree to which they judge the perceived outcomes of the behaviour as positive or negative (outcome evaluation). The methodological design of the study’s empirical component was strictly based on the standard procedures prescribed by the theory of reasoned action. Two consecutive and methodologically interrelated surveys were conducted amongst members of the public to collect the study’s primary data. The main salient behavioural beliefs on which different attitudes towards hunting are based were identified and further investigated. The results were analysed from the perspective of the theory of reasoned action and a clear understanding of the causal determinants of different attitudes towards hunting were attained. Based on the findings of the study, a number of conclusions and recommendations were made that may guide the development of future strategies to improve the social legitimacy of hunting. Amongst other things, it was suggested that public education programmes should be developed to address the public’s misconceptions of hunting; that public relation campaigns be undertaken to improve the public’s negative image of hunters; and that hunter education programmes be put in place to make hunters aware of the role they could play at community level to improve the social acceptability of hunting. Detailed guidelines regarding the contents of such education programmes and public relation campaigns were provided.
- Full Text:
- Date Issued: 2014
The development of a framework to reduce water and energy consumption through the use of water and energy value stream mapping for the South African manufacturing industry
- Authors: Davies, Edward
- Date: 2015
- Subjects: Lean manufacturing -- South Africa , Stream mapping -- South Africa , Water consumption -- South Africa
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: http://hdl.handle.net/10948/4160 , vital:20564
- Description: The Republic of South Africa’s energy economy is under immense pressure and the main energy utility, Eskom, cannot reliably generate sufficient electrical energy to meet its customer demand. Water security in South Africa is also under threat as the country is currently amidst a water crisis. The South African manufacturing industry is the sector consuming the largest portion of the total energy consumption and second largest portion of the total water consumption (excluding urban use) nationally. Water and energy efficiency improvement is becoming imperative for organisational success as well as national economic sustainability. This is due to the significant increase in the cost of both electrical energy and water in recent years, and the drop in the reserve energy margin below the minimum level required for sustainable operation of energy utilities. The research objective therefore was to develop a Lean-based water and energy efficiency improvement framework for the manufacturing industry to encourage and realise a reduced demand for energy and water in it. A literature review was conducted on the water and energy landscape in South Africa, Lean manufacturing principles and their positive natural influence on water and energy efficiency, and the Value Stream Mapping tool. The survey of water and energy wastes in the manufacturing industry yielded the creation of standardised water and energy waste categories for use in conjunction with the conventional Lean wastes, tools and techniques. The literature survey indicated that the implementation of Lean manufacturing techniques naturally leads to the improvement of energy and water intensity. The researcher hypothesised that there is even greater potential for water and energy savings if a Lean-based tool is developed to specifically focus on the improvement of energy and water efficiency. A framework for this tool was developed through the literature survey. The tool is based on the Value Stream Mapping tool. A practical experiment was then conducted to establish the effectiveness of the tool in the South African manufacturing industry. The experiment design included an outline of the forecasting and statistical validation techniques to ensure the integrity of data utilised for approving or disproving the set hypotheses. The results of the practical experiment yielded positive results, confirming the hypothesis that the implementation of the developed framework will lead to improved energy and water efficiency in the manufacturing industry. After an explanation of the experimental results, the study concluded with recommendations and conclusions based on the findings.
- Full Text:
- Date Issued: 2015
- Authors: Davies, Edward
- Date: 2015
- Subjects: Lean manufacturing -- South Africa , Stream mapping -- South Africa , Water consumption -- South Africa
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: http://hdl.handle.net/10948/4160 , vital:20564
- Description: The Republic of South Africa’s energy economy is under immense pressure and the main energy utility, Eskom, cannot reliably generate sufficient electrical energy to meet its customer demand. Water security in South Africa is also under threat as the country is currently amidst a water crisis. The South African manufacturing industry is the sector consuming the largest portion of the total energy consumption and second largest portion of the total water consumption (excluding urban use) nationally. Water and energy efficiency improvement is becoming imperative for organisational success as well as national economic sustainability. This is due to the significant increase in the cost of both electrical energy and water in recent years, and the drop in the reserve energy margin below the minimum level required for sustainable operation of energy utilities. The research objective therefore was to develop a Lean-based water and energy efficiency improvement framework for the manufacturing industry to encourage and realise a reduced demand for energy and water in it. A literature review was conducted on the water and energy landscape in South Africa, Lean manufacturing principles and their positive natural influence on water and energy efficiency, and the Value Stream Mapping tool. The survey of water and energy wastes in the manufacturing industry yielded the creation of standardised water and energy waste categories for use in conjunction with the conventional Lean wastes, tools and techniques. The literature survey indicated that the implementation of Lean manufacturing techniques naturally leads to the improvement of energy and water intensity. The researcher hypothesised that there is even greater potential for water and energy savings if a Lean-based tool is developed to specifically focus on the improvement of energy and water efficiency. A framework for this tool was developed through the literature survey. The tool is based on the Value Stream Mapping tool. A practical experiment was then conducted to establish the effectiveness of the tool in the South African manufacturing industry. The experiment design included an outline of the forecasting and statistical validation techniques to ensure the integrity of data utilised for approving or disproving the set hypotheses. The results of the practical experiment yielded positive results, confirming the hypothesis that the implementation of the developed framework will lead to improved energy and water efficiency in the manufacturing industry. After an explanation of the experimental results, the study concluded with recommendations and conclusions based on the findings.
- Full Text:
- Date Issued: 2015
Material characterisation of laser formed dual phase steel components
- Authors: Els-Botes, Annelize
- Date: 2005
- Subjects: Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9609 , http://hdl.handle.net/10948/176 , Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Description: The nature and scope of this thesis can be divided into four categories: • FORMING PARAMETERS • Identification of various laser forming parameters in order to produce specimens of similar dimension (radius of curvature). • TEMPERATURE AND MICROSTRUCTURE • To study the effect of maximum temperature reached during the forming operation on the microstructure of the various specimens. • FATIGUE LIFE • Compare the fatigue life of the specimens produced by various laser parameters to that of the original material, and also the fatigue life of mechanical formed specimens. • RESIDUAL STRESS PROFILE Determine if the laser forming process induces detrimental residual stress magnitudes in the specimens. The main objective of this thesis was to gain an understanding of the way in which laser forming affects the fatigue performance and residual stress magnitude / distribution of dual phase steel. Although lasers have been used successfully in various manufacturing processes (welding, cutting, marking, etc.), little information is available on the influence of laser forming on many automotive alloys such as dual phase steel. The first part of the work involved a literature review of the process and factors affecting the laser forming process. It became clear from the literature overview that laser forming of sheet material thicker than 1mm is complex in nature. The variables that can influence the process are complicated and their interaction with each other is not easily controlled. The main parameters that were thus controlled in this study are as follows: • Laser power (P) • Laser head travel speed (v) • Laser beam size (mm) The chapters that follow the literature review, deals with the laser forming process of dual phase steel and the production of fatigue specimens using various laser parameters. It was found that the following laser parameters resulted in specimens with approximately the same radius of curvature: Laser power KW Beam diameter mm Interval spacing % Overlap Scanning velocity m/min Line Energy J/m 5 20 10 50 2,5 2000 3,1 14 10,5 25 2 1550 1,5 7,5 7,5 0 1,2 1250 From the results obtained from fatigue testing specimens produced with the above settings, it is clear that the laser forming process has the potential to be employed as a production stage in the manufacture of wheel centre discs while maintaining adequate fatigue strength. Large beam diameters which cause heat penetration through the thickness of the specimen and hence microstructure breakdown should be avoided, since it was shown that these specimens exhibited impaired mechanical properties than those produced with a smaller laser beam diameter. The microstructural changes observed during the forming process needs to be considered since the mechanical properties of the material changes with a change in microstructure. A dramatic change in microstructure was observed; therefore it is of crucial importance that microstructural evaluation plays an important part in deciding optimum laser parameters for the forming process of ferrous alloys. During residual stress analysis, trends were observed between measurements taken at the same location of the samples; regardless whether measurements were taken on the laser irradiated side or the reverse side of the specimen. The only difference was the magnitude of the relieved residual stress. In most cases the obtained relieved residual stress was much smaller in magnitude than that of the original plate (in the bulk of the material). The surface indicated a slight tensile residual stress for most samples evaluated. A good correlation in distribution profile was obtained between microhardness and relieved residual stress distribution at the ‘middle of sample’ location. This indicates that an increase in hardness indicates an increase in residual stress magnitude for the laser formed specimens. In conclusion, this research has proved that it is possible to deform metal plate of a 3,5mm thickness with a CO2 laser system. The research also established the effect of process parameters on the final product’s shape/bend angle and characterised the effect of the laser forming process on the material’s mechanical properties and structural integrity.
- Full Text:
- Date Issued: 2005
- Authors: Els-Botes, Annelize
- Date: 2005
- Subjects: Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9609 , http://hdl.handle.net/10948/176 , Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Description: The nature and scope of this thesis can be divided into four categories: • FORMING PARAMETERS • Identification of various laser forming parameters in order to produce specimens of similar dimension (radius of curvature). • TEMPERATURE AND MICROSTRUCTURE • To study the effect of maximum temperature reached during the forming operation on the microstructure of the various specimens. • FATIGUE LIFE • Compare the fatigue life of the specimens produced by various laser parameters to that of the original material, and also the fatigue life of mechanical formed specimens. • RESIDUAL STRESS PROFILE Determine if the laser forming process induces detrimental residual stress magnitudes in the specimens. The main objective of this thesis was to gain an understanding of the way in which laser forming affects the fatigue performance and residual stress magnitude / distribution of dual phase steel. Although lasers have been used successfully in various manufacturing processes (welding, cutting, marking, etc.), little information is available on the influence of laser forming on many automotive alloys such as dual phase steel. The first part of the work involved a literature review of the process and factors affecting the laser forming process. It became clear from the literature overview that laser forming of sheet material thicker than 1mm is complex in nature. The variables that can influence the process are complicated and their interaction with each other is not easily controlled. The main parameters that were thus controlled in this study are as follows: • Laser power (P) • Laser head travel speed (v) • Laser beam size (mm) The chapters that follow the literature review, deals with the laser forming process of dual phase steel and the production of fatigue specimens using various laser parameters. It was found that the following laser parameters resulted in specimens with approximately the same radius of curvature: Laser power KW Beam diameter mm Interval spacing % Overlap Scanning velocity m/min Line Energy J/m 5 20 10 50 2,5 2000 3,1 14 10,5 25 2 1550 1,5 7,5 7,5 0 1,2 1250 From the results obtained from fatigue testing specimens produced with the above settings, it is clear that the laser forming process has the potential to be employed as a production stage in the manufacture of wheel centre discs while maintaining adequate fatigue strength. Large beam diameters which cause heat penetration through the thickness of the specimen and hence microstructure breakdown should be avoided, since it was shown that these specimens exhibited impaired mechanical properties than those produced with a smaller laser beam diameter. The microstructural changes observed during the forming process needs to be considered since the mechanical properties of the material changes with a change in microstructure. A dramatic change in microstructure was observed; therefore it is of crucial importance that microstructural evaluation plays an important part in deciding optimum laser parameters for the forming process of ferrous alloys. During residual stress analysis, trends were observed between measurements taken at the same location of the samples; regardless whether measurements were taken on the laser irradiated side or the reverse side of the specimen. The only difference was the magnitude of the relieved residual stress. In most cases the obtained relieved residual stress was much smaller in magnitude than that of the original plate (in the bulk of the material). The surface indicated a slight tensile residual stress for most samples evaluated. A good correlation in distribution profile was obtained between microhardness and relieved residual stress distribution at the ‘middle of sample’ location. This indicates that an increase in hardness indicates an increase in residual stress magnitude for the laser formed specimens. In conclusion, this research has proved that it is possible to deform metal plate of a 3,5mm thickness with a CO2 laser system. The research also established the effect of process parameters on the final product’s shape/bend angle and characterised the effect of the laser forming process on the material’s mechanical properties and structural integrity.
- Full Text:
- Date Issued: 2005
Restoring trust by verifying information integrity through continuous auditing
- Authors: Flowerday, Stephen
- Date: 2006
- Subjects: Auditing, Internal , Corporate governance
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9796 , http://hdl.handle.net/10948/504 , http://hdl.handle.net/10948/d1011920 , Auditing, Internal , Corporate governance
- Description: Corporate scandals such as Enron, WorldCom and Parmalat, have focused recent governance efforts in the domain of financial reporting due to fraudulent and/or erroneous accounting practices. In addition, the ineffectiveness of the current system of controls has been highlighted, including that some directors have been weak and ineffective monitors of managers. This board of director ‘weakness’ has called for additional mechanisms for monitoring and controlling of management, focusing on financial reporting. This problem intensifies in that today companies function in real-time, and decisions are based on available realtime financial information. However, the assurances provided by traditional auditing take place months after the transactions have occurred and therefore, a trust problem arises because information is not verified in real-time. Consequently, the errors and fraud concealed within the financial information is not discovered until months later. To address this trust problem a conceptual causal model is proposed in this study based on the principles of systems theory. The emergent property of the causal model is increased trust and control. This study establishes that mutual assurances assist in building trust and that information security assists in safeguarding trust. Subsequently, in order to have a positive relationship between the company directors and various stakeholders, uncertainty needs to be contained, and the level of trust needs to surpass the perceived risks. The study concludes that assurances need to be provided in real-time to restore stakeholder confidence and trust in the domain of financial reporting. In order to provide assurances in real-time, continuous auditing is required to verify the integrity of financial information when it becomes available, and not months later. A continuous auditing process has its foundations grounded in information technology and attends to the challenges in real-time by addressing the standardisation of data to enable effective analysis, the validation of the accuracy of the data and the reliability of the system.
- Full Text:
- Date Issued: 2006
- Authors: Flowerday, Stephen
- Date: 2006
- Subjects: Auditing, Internal , Corporate governance
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9796 , http://hdl.handle.net/10948/504 , http://hdl.handle.net/10948/d1011920 , Auditing, Internal , Corporate governance
- Description: Corporate scandals such as Enron, WorldCom and Parmalat, have focused recent governance efforts in the domain of financial reporting due to fraudulent and/or erroneous accounting practices. In addition, the ineffectiveness of the current system of controls has been highlighted, including that some directors have been weak and ineffective monitors of managers. This board of director ‘weakness’ has called for additional mechanisms for monitoring and controlling of management, focusing on financial reporting. This problem intensifies in that today companies function in real-time, and decisions are based on available realtime financial information. However, the assurances provided by traditional auditing take place months after the transactions have occurred and therefore, a trust problem arises because information is not verified in real-time. Consequently, the errors and fraud concealed within the financial information is not discovered until months later. To address this trust problem a conceptual causal model is proposed in this study based on the principles of systems theory. The emergent property of the causal model is increased trust and control. This study establishes that mutual assurances assist in building trust and that information security assists in safeguarding trust. Subsequently, in order to have a positive relationship between the company directors and various stakeholders, uncertainty needs to be contained, and the level of trust needs to surpass the perceived risks. The study concludes that assurances need to be provided in real-time to restore stakeholder confidence and trust in the domain of financial reporting. In order to provide assurances in real-time, continuous auditing is required to verify the integrity of financial information when it becomes available, and not months later. A continuous auditing process has its foundations grounded in information technology and attends to the challenges in real-time by addressing the standardisation of data to enable effective analysis, the validation of the accuracy of the data and the reliability of the system.
- Full Text:
- Date Issued: 2006
A model to improve the effectiveness of the Occupational Health and Safety Inspectorate function relative to South African construction
- Authors: Geminiani, Franco Luciano
- Date: 2008
- Subjects: Construction industry -- Safety measures
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9695 , http://hdl.handle.net/10948/719 , Construction industry -- Safety measures
- Description: Irrespective of all the efforts made by the Department of Labour (DoL) and other relevant stakeholders to improve the performance of Occupational Health and Safety (OH&S) in construction. In the Construction Industry, there is still a very high level of accidents and fatalities in South Africa. Injuries and accidents to workers do not help a community in any nation. The construction industry in South Africa is generally known to be one of the most hazardous and has one of the most dismal OH&S records among all industrial segments with an unacceptably high level of injuries and fatalities resulting in considerable human suffering. A doctoral study was recently conducted with the aim of investigating the effectiveness and performance of the DoL OH&S Inspectorate in South Africa. The empirical study was conducted among a range of stakeholders: civil engineering and building contractors; OH&S consultants; project managers; DoL inspectors; and designers by means of a questionnaire survey. The methodology adopted in this study included the exploratory and descriptive methods, which entails the technique of observation including the use of questionnaires and data analysis. The salient findings of the study are presented and elucidate that the DoL OH&S Inspectorate is not effective in terms of OH&S relative to the construction industry in South Africa. Conclusions and recommendations included expound that the DoL OH&S Inspectorate is not effectively conducting their duties reinforcing the need for a reviewed OH&S Inspectorate model framework. The proposed structured normative model consists of fundamental elements which would improve the effectiveness of the DoL OH&S Inspectorate. The findings of the study with recommendations are included.
- Full Text:
- Date Issued: 2008
- Authors: Geminiani, Franco Luciano
- Date: 2008
- Subjects: Construction industry -- Safety measures
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9695 , http://hdl.handle.net/10948/719 , Construction industry -- Safety measures
- Description: Irrespective of all the efforts made by the Department of Labour (DoL) and other relevant stakeholders to improve the performance of Occupational Health and Safety (OH&S) in construction. In the Construction Industry, there is still a very high level of accidents and fatalities in South Africa. Injuries and accidents to workers do not help a community in any nation. The construction industry in South Africa is generally known to be one of the most hazardous and has one of the most dismal OH&S records among all industrial segments with an unacceptably high level of injuries and fatalities resulting in considerable human suffering. A doctoral study was recently conducted with the aim of investigating the effectiveness and performance of the DoL OH&S Inspectorate in South Africa. The empirical study was conducted among a range of stakeholders: civil engineering and building contractors; OH&S consultants; project managers; DoL inspectors; and designers by means of a questionnaire survey. The methodology adopted in this study included the exploratory and descriptive methods, which entails the technique of observation including the use of questionnaires and data analysis. The salient findings of the study are presented and elucidate that the DoL OH&S Inspectorate is not effective in terms of OH&S relative to the construction industry in South Africa. Conclusions and recommendations included expound that the DoL OH&S Inspectorate is not effectively conducting their duties reinforcing the need for a reviewed OH&S Inspectorate model framework. The proposed structured normative model consists of fundamental elements which would improve the effectiveness of the DoL OH&S Inspectorate. The findings of the study with recommendations are included.
- Full Text:
- Date Issued: 2008
A chemo-enzymatic process for the production of beta-thymidine, a key intermediate in antiretrovirol manufacture
- Gordon, Gregory Ernest Robert
- Authors: Gordon, Gregory Ernest Robert
- Date: 2010
- Subjects: HIV infections -- Treatment -- South Africa , HIV infections -- South Africa -- Prevention , Antiretroviral agents
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10423 , http://hdl.handle.net/10948/d1016217
- Description: The socio-economic impact of HIV/AIDS on South Africa has resulted in lower gross domestic product, loss of skills in key sectors such as education, and increased health-care costs in providing access to treatment. Currently active pharmaceutical ingredients (API’s) such as stavudine (d4T) and azidothymidine (AZT) are imported from India and China, while formulation is conducted locally. A strategy was initiated between CSIR Biosciences and LIFElab under the auspices of Arvir Technologies to investigate the feasibility of local antiretroviral manufacture (d4T and AZT) or the manufacture of a key intermediate such as β- thymidine (dT). Several advantages associated with successful implementation of this strategy include ensuring a local supply of API’s, thus reducing reliance on procurement from foreign sources and reducing the effect of foreign exchange rate fluctuations on providing cost effective access to treatment. A local supply source would also reduce the imports and thus aid the balance of payments deficit, and in addition to this, provide stimulus in the local pharmaceutical manufacturing industry (which has been in decline for several decades), resulting in increased skills and employment opportunities. This thesis describes the development of a superior chemo-enzymatic process for the production of β-thymidine (72 percent yield, prior to isolation), a key intermediate in the preparation of anti-retrovirals. Alternative processes based purely on chemical or bioprocess transformations to prepare either 5-methyluridine (5-MU) or dT suffer from several disadvantages: lengthy transformations due to protection/deprotection strategies, low selectivties and product yields (30 percent in the chemical process) and isolation of the product from dilute process streams requiring the use of large uneconomical reactors (bioprocesss). This contributes significantly to the cost of d4T and AZT manufacture. Our novel chemoenzymatic process comprises of a biocatalytic reaction for the production of 5-MU, with subsequent chemical transformation into dT (3 steps) negating and circumventing the limitations of the chemical or bioprocess routes. During the course of this project development, the β-thymidine selling price declined from 175 $/kg (2005) to 100 $/kg (2008). However, the process described in this work is still competitive based on the current β- thymidine selling price of 100 $/kg. The process economics show that with further optimization and increasing the isolated dT yield from 70 percent to 90 percent, the variable cost decreases from 136 $/kg to 110 $/kg. The increase in isolated yield is highly probable, based on solubility data of β-thymidine. The decrease in β-thymidine selling price and technological improvement in dT manufacture should translate into lower API manufacture costs and more cost effective access to treatment. Our novel biocatalytic process producing 5-MU uses a coupled enzyme system employing PNP, Purine Nucleoside Phosphorylase and PyNP, Pyrimidine Nucleoside Phosphorylase. The overall transglycosylation reaction may be decoupled into the phosphorolysis reaction (PNP) and synthesis reaction (PyNP). During the phosphorolysis reaction, guanosine is converted into guanine and ribose-1-phosphate (R-1-P) in the presence of PNP enzyme. The reaction intermediate R-1-P is then coupled to thymine in the presence of PyNP enzyme during the synthesis reaction, producing 5-MU. The process was scaled up from lab-scale to bench-scale (10 - 20 L) and demonstrated to be robust and reproducible. This is evident from the average guanosine conversion (94.7 percent ± 2.03) and 5-MU yield (88.2 percent ± 6.21) and mole balance (104 percent ± 7.61) which were obtained at bench-scale (3 replicates, 10 L). The reaction was carried out at reactor productivities of between 7 – 11 g.L-1.h-1. The integration of the biocatalytic process and chemical processes was successfully carried out, showing that 5-MU produced using our novel biocatalytic process behaved similarly to commercially available 5- MU (ex. Dayang Chemicals, China). A PCT patent application (Ref. No. P44422PC01) on this chemo-enzymatic process has been filed and currently public private partnerships are being explored through Arvir Technologies to evaluate and validate this technology at one ton scale.
- Full Text:
- Date Issued: 2010
- Authors: Gordon, Gregory Ernest Robert
- Date: 2010
- Subjects: HIV infections -- Treatment -- South Africa , HIV infections -- South Africa -- Prevention , Antiretroviral agents
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10423 , http://hdl.handle.net/10948/d1016217
- Description: The socio-economic impact of HIV/AIDS on South Africa has resulted in lower gross domestic product, loss of skills in key sectors such as education, and increased health-care costs in providing access to treatment. Currently active pharmaceutical ingredients (API’s) such as stavudine (d4T) and azidothymidine (AZT) are imported from India and China, while formulation is conducted locally. A strategy was initiated between CSIR Biosciences and LIFElab under the auspices of Arvir Technologies to investigate the feasibility of local antiretroviral manufacture (d4T and AZT) or the manufacture of a key intermediate such as β- thymidine (dT). Several advantages associated with successful implementation of this strategy include ensuring a local supply of API’s, thus reducing reliance on procurement from foreign sources and reducing the effect of foreign exchange rate fluctuations on providing cost effective access to treatment. A local supply source would also reduce the imports and thus aid the balance of payments deficit, and in addition to this, provide stimulus in the local pharmaceutical manufacturing industry (which has been in decline for several decades), resulting in increased skills and employment opportunities. This thesis describes the development of a superior chemo-enzymatic process for the production of β-thymidine (72 percent yield, prior to isolation), a key intermediate in the preparation of anti-retrovirals. Alternative processes based purely on chemical or bioprocess transformations to prepare either 5-methyluridine (5-MU) or dT suffer from several disadvantages: lengthy transformations due to protection/deprotection strategies, low selectivties and product yields (30 percent in the chemical process) and isolation of the product from dilute process streams requiring the use of large uneconomical reactors (bioprocesss). This contributes significantly to the cost of d4T and AZT manufacture. Our novel chemoenzymatic process comprises of a biocatalytic reaction for the production of 5-MU, with subsequent chemical transformation into dT (3 steps) negating and circumventing the limitations of the chemical or bioprocess routes. During the course of this project development, the β-thymidine selling price declined from 175 $/kg (2005) to 100 $/kg (2008). However, the process described in this work is still competitive based on the current β- thymidine selling price of 100 $/kg. The process economics show that with further optimization and increasing the isolated dT yield from 70 percent to 90 percent, the variable cost decreases from 136 $/kg to 110 $/kg. The increase in isolated yield is highly probable, based on solubility data of β-thymidine. The decrease in β-thymidine selling price and technological improvement in dT manufacture should translate into lower API manufacture costs and more cost effective access to treatment. Our novel biocatalytic process producing 5-MU uses a coupled enzyme system employing PNP, Purine Nucleoside Phosphorylase and PyNP, Pyrimidine Nucleoside Phosphorylase. The overall transglycosylation reaction may be decoupled into the phosphorolysis reaction (PNP) and synthesis reaction (PyNP). During the phosphorolysis reaction, guanosine is converted into guanine and ribose-1-phosphate (R-1-P) in the presence of PNP enzyme. The reaction intermediate R-1-P is then coupled to thymine in the presence of PyNP enzyme during the synthesis reaction, producing 5-MU. The process was scaled up from lab-scale to bench-scale (10 - 20 L) and demonstrated to be robust and reproducible. This is evident from the average guanosine conversion (94.7 percent ± 2.03) and 5-MU yield (88.2 percent ± 6.21) and mole balance (104 percent ± 7.61) which were obtained at bench-scale (3 replicates, 10 L). The reaction was carried out at reactor productivities of between 7 – 11 g.L-1.h-1. The integration of the biocatalytic process and chemical processes was successfully carried out, showing that 5-MU produced using our novel biocatalytic process behaved similarly to commercially available 5- MU (ex. Dayang Chemicals, China). A PCT patent application (Ref. No. P44422PC01) on this chemo-enzymatic process has been filed and currently public private partnerships are being explored through Arvir Technologies to evaluate and validate this technology at one ton scale.
- Full Text:
- Date Issued: 2010
Practical and scalable synthesis of N-Alkyl-N,N'Diacylhydrazines
- Authors: Gouws, Melissa Claire
- Date: 2008
- Subjects: Chemistry, Organic , Acylation , Insecticides
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10406 , http://hdl.handle.net/10948/696 , Chemistry, Organic , Acylation , Insecticides
- Description: The work presented in this thesis is concerned with the evaluation of potential synthetic routes for the diacylhydrazine group of compounds, and particularly, unsymmetrical diacylhydrazines. Diacylhydrazines form the basis for a relatively new group of insecticides that have molt accelerating properties, and which are considered to offer substantial advantages over other insecticides used for the control of certain insects. The overall objective for this study is to evaluate different potential synthetic routes for a model diacylhydrazine with the view to define potentially scaleable routes. The compound selected for this study was the unsymmetrical diacylhydrazine, N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)-carboxamide since it offers the same range of challenges that would be expected for the synthesis of other similar unsymmetrical diacylhydrazines. Thus, the synthesis of unsymmetrical diacylhydrazines require two reaction steps: The first step is the synthesis of the intermediate mono-acylhydrazine, while the second step is the synthesis of the desired diacylhydrazine from the intermediate mono-acylhydrazine. The most important factor in the two-step reaction sequence is to obtain a high degree of selectivity for the desired mono-acylhydrazine isomer. Acylation of t-butylhydrazine using 4-methylbenzoyl chloride can produce the desired product N-[(tert-butyl)amino](4-methylphenyl)carboxamide in yields above 90 percent, but this reaction produces a variety of by-products, including the “wrong” isomer (N-amino-N- (tert-butyl)(4-methylphenyl)carboximide). Unexpected byproducts for this particular acylation reaction, not previously reported in the literature have also been identified during this investigation. This includes a de-butylated diacylhydrazine, (4-methylphenyl)- N-[(4-methylphenyl)carbonylamino] carboxamide. Although the reaction between tert-butylhydrazine and 4-methylbenzaldehyde is very selective giving near quantitative yields of the desired hydrazone, the subsequent conversion of the hydrazone into the desired mono-acylhydrazine is problematic. The most promising route appears via bromination to form the hydrazidic bromide, followed by hydrolysis of the hydrazidic bromide. Yields for the bromination reaction during this investigation were somewhat higher than that reported previously in literature. Hydrolysis of the hydrazidic bromide, apparently also results in the hydrolysis of the reaction product to give an ester of the free acid (when an ester solvent is used). The synthesis of N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide was only briefly considered to evaluate essentially two approaches, namely: · The conversion of the monoacylhydrazine, N-[(tert-butyl)amino](4- methylphenyl)carboxamide, by acylating with either benzoyl chloride or methylbenzoate (gave 86 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide when benzoyl chloride was used as acylating agent); and · The one-pot conversion of the hydrazone, [(1E)-2-(4-methylphenyl)-1- azavinyl](tert-butyl)]amine, by bromination/hydrolysis and acylation. In this case, benzoyl chloride (2 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide), benzoic acid (80.67 percent N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)carboxamide) were evaluated as potential acylating agents.
- Full Text:
- Date Issued: 2008
- Authors: Gouws, Melissa Claire
- Date: 2008
- Subjects: Chemistry, Organic , Acylation , Insecticides
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10406 , http://hdl.handle.net/10948/696 , Chemistry, Organic , Acylation , Insecticides
- Description: The work presented in this thesis is concerned with the evaluation of potential synthetic routes for the diacylhydrazine group of compounds, and particularly, unsymmetrical diacylhydrazines. Diacylhydrazines form the basis for a relatively new group of insecticides that have molt accelerating properties, and which are considered to offer substantial advantages over other insecticides used for the control of certain insects. The overall objective for this study is to evaluate different potential synthetic routes for a model diacylhydrazine with the view to define potentially scaleable routes. The compound selected for this study was the unsymmetrical diacylhydrazine, N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)-carboxamide since it offers the same range of challenges that would be expected for the synthesis of other similar unsymmetrical diacylhydrazines. Thus, the synthesis of unsymmetrical diacylhydrazines require two reaction steps: The first step is the synthesis of the intermediate mono-acylhydrazine, while the second step is the synthesis of the desired diacylhydrazine from the intermediate mono-acylhydrazine. The most important factor in the two-step reaction sequence is to obtain a high degree of selectivity for the desired mono-acylhydrazine isomer. Acylation of t-butylhydrazine using 4-methylbenzoyl chloride can produce the desired product N-[(tert-butyl)amino](4-methylphenyl)carboxamide in yields above 90 percent, but this reaction produces a variety of by-products, including the “wrong” isomer (N-amino-N- (tert-butyl)(4-methylphenyl)carboximide). Unexpected byproducts for this particular acylation reaction, not previously reported in the literature have also been identified during this investigation. This includes a de-butylated diacylhydrazine, (4-methylphenyl)- N-[(4-methylphenyl)carbonylamino] carboxamide. Although the reaction between tert-butylhydrazine and 4-methylbenzaldehyde is very selective giving near quantitative yields of the desired hydrazone, the subsequent conversion of the hydrazone into the desired mono-acylhydrazine is problematic. The most promising route appears via bromination to form the hydrazidic bromide, followed by hydrolysis of the hydrazidic bromide. Yields for the bromination reaction during this investigation were somewhat higher than that reported previously in literature. Hydrolysis of the hydrazidic bromide, apparently also results in the hydrolysis of the reaction product to give an ester of the free acid (when an ester solvent is used). The synthesis of N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide was only briefly considered to evaluate essentially two approaches, namely: · The conversion of the monoacylhydrazine, N-[(tert-butyl)amino](4- methylphenyl)carboxamide, by acylating with either benzoyl chloride or methylbenzoate (gave 86 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide when benzoyl chloride was used as acylating agent); and · The one-pot conversion of the hydrazone, [(1E)-2-(4-methylphenyl)-1- azavinyl](tert-butyl)]amine, by bromination/hydrolysis and acylation. In this case, benzoyl chloride (2 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide), benzoic acid (80.67 percent N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)carboxamide) were evaluated as potential acylating agents.
- Full Text:
- Date Issued: 2008
The oxidative coupling of phenols using stoichiometric metal oxidants
- Authors: Hoffmann, Eric
- Date: 2005
- Subjects: Phenols , Oxidation , Stoichiometry
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10977 , http://hdl.handle.net/10948/180 , Phenols , Oxidation , Stoichiometry
- Description: The oxidative coupling of 2,6-di-t-butylphenol under mild reaction conditions is well documented and the subject of many patents. However, the coupling of other monoand di- substituted phenols is not as well documented and thus there is scope for further investigation for providing a convenient, environmentally friendly and economically viable method for the oxidative coupling of these phenols. In this study, the oxidative coupling of a variety of alkylated phenolic substrates, 2-tbutylphenol, 2,6-di-t-butylphenol, 2,4 -di-t-butylphenol and ,4-dimethylphenol, using a range of different oxidizing agents, were investigated by means of experimental and/or theoretical means. The dibutylated aromatics provided the highest selectivities to their respective coupled products, with results obtained with the dimethyl analogue being only satisfactory, and that for 2 -t-butylphenol being totally inefficient. PM3 Molecular orbital (MO) calculations were used to predict the possible modes of coupling for the substrates 2,6 -di-t-butylphenol and 2,4-di-t-butylphenol, and these results were then compared with those obtained experimentally in the laboratory. Preliminarily, the coupling of unsubstituted phenolics was also assessed by means of MO calculations. Much emphasis was placed on Ce(IV) as the oxidant, and the reaction conditions under which it was used and the results that were obtained have not been reported before and are therefore novel. The oxidation of 2,4-di-t-butylphenol using Ce(IV) in the presence of methanesulphonic acid was optimized to afford high yields and selectivities to the desired ortho C-ortho C coupled product under mild reaction conditions. Various reaction parameters were also investigated in this case, such as varying the MeSO3H concentration, the solvent, the reaction temperature, the reaction time, the substrate loading, the rate of oxidant addition and the substrate to oxidant ratio. Ce(IV) also gave a high selectivity to the para C-para C coupled product when IX using 2,6-di-t-butylphenol as the substrate. However, it was not as effective with 2,4- dimethylphenol, and even less so with 2-t-butylphenol. The oxidation reactions of 2-t-butylphenol and 2,4-dimethylphenol with various coupling agents were also investigated with the intention of obtaining high selectivities to the respective desired coupled products. In these studies, 2-t-butylphenol afforded a large number of products, irrespective of the oxidant used. The dimethyl analogue was more selective, but results were not optimal. It was clear that the number of substituents on the phenol ring, their nature and their position with regards to the hydroxyl moiety was of great importance and made a significant impact on the preferred coupling mode of the substrate. It was observed that steric effects also played a major role in the outcome of these reactions: 2,6-di-t-butylphenol never afforded any C-O coupled products whereas 2-t-butylphenol, 2,4-di-t-butylphenol and 2,4-dimethylphenol all appeared to undergo some C-O coupling. Finally, reaction mechanisms were provided for both the K3Fe(CN)6 and Ce(IV) work, these reacting in basic and acidic media, respectively. It was proposed that both of these mechanisms operate through the initial formation of the phenoxyl radical.
- Full Text:
- Date Issued: 2005
- Authors: Hoffmann, Eric
- Date: 2005
- Subjects: Phenols , Oxidation , Stoichiometry
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10977 , http://hdl.handle.net/10948/180 , Phenols , Oxidation , Stoichiometry
- Description: The oxidative coupling of 2,6-di-t-butylphenol under mild reaction conditions is well documented and the subject of many patents. However, the coupling of other monoand di- substituted phenols is not as well documented and thus there is scope for further investigation for providing a convenient, environmentally friendly and economically viable method for the oxidative coupling of these phenols. In this study, the oxidative coupling of a variety of alkylated phenolic substrates, 2-tbutylphenol, 2,6-di-t-butylphenol, 2,4 -di-t-butylphenol and ,4-dimethylphenol, using a range of different oxidizing agents, were investigated by means of experimental and/or theoretical means. The dibutylated aromatics provided the highest selectivities to their respective coupled products, with results obtained with the dimethyl analogue being only satisfactory, and that for 2 -t-butylphenol being totally inefficient. PM3 Molecular orbital (MO) calculations were used to predict the possible modes of coupling for the substrates 2,6 -di-t-butylphenol and 2,4-di-t-butylphenol, and these results were then compared with those obtained experimentally in the laboratory. Preliminarily, the coupling of unsubstituted phenolics was also assessed by means of MO calculations. Much emphasis was placed on Ce(IV) as the oxidant, and the reaction conditions under which it was used and the results that were obtained have not been reported before and are therefore novel. The oxidation of 2,4-di-t-butylphenol using Ce(IV) in the presence of methanesulphonic acid was optimized to afford high yields and selectivities to the desired ortho C-ortho C coupled product under mild reaction conditions. Various reaction parameters were also investigated in this case, such as varying the MeSO3H concentration, the solvent, the reaction temperature, the reaction time, the substrate loading, the rate of oxidant addition and the substrate to oxidant ratio. Ce(IV) also gave a high selectivity to the para C-para C coupled product when IX using 2,6-di-t-butylphenol as the substrate. However, it was not as effective with 2,4- dimethylphenol, and even less so with 2-t-butylphenol. The oxidation reactions of 2-t-butylphenol and 2,4-dimethylphenol with various coupling agents were also investigated with the intention of obtaining high selectivities to the respective desired coupled products. In these studies, 2-t-butylphenol afforded a large number of products, irrespective of the oxidant used. The dimethyl analogue was more selective, but results were not optimal. It was clear that the number of substituents on the phenol ring, their nature and their position with regards to the hydroxyl moiety was of great importance and made a significant impact on the preferred coupling mode of the substrate. It was observed that steric effects also played a major role in the outcome of these reactions: 2,6-di-t-butylphenol never afforded any C-O coupled products whereas 2-t-butylphenol, 2,4-di-t-butylphenol and 2,4-dimethylphenol all appeared to undergo some C-O coupling. Finally, reaction mechanisms were provided for both the K3Fe(CN)6 and Ce(IV) work, these reacting in basic and acidic media, respectively. It was proposed that both of these mechanisms operate through the initial formation of the phenoxyl radical.
- Full Text:
- Date Issued: 2005
Monitoring and intelligent control for complex curvature friction stir welding
- Hua, Tao
- Authors: Hua, Tao
- Date: 2006
- Subjects: Friction welding , Fuzzy systems
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9612 , http://hdl.handle.net/10948/420 , Friction welding , Fuzzy systems
- Description: A multi-input multi-output system to implement on-line process monitoring and intelligent control of complex curvature friction stir welding was proposed. An extra rotation axis was added to the existing three translation axes to perform friction stir welding of complex curvature other than straight welding line. A clamping system was designed for locating and holding the workpieces to bear the large force involved in the process between the welding tool and workpieces. Process parameters (feed rate, spindle speed, tilt angle and plunge depth), and process conditions (parent material and curvature), were used as factors for the orthogonal array experiments to collect sensor data of force, torque and tool temperature using multiple sensors and telemetry system. Using statistic analysis of the experimental data, sensitive signal features were selected to train the feed-forward neural networks, which were used for mapping the relationships between process parameters, process conditions and sensor data. A fuzzy controller with initial input/output membership functions and fuzzy rules generated on-line from the trained neural network was applied to perceive process condition changes and make adjustment of process parameters to maintain tool/workpiece contact and energy input. Input/output scaling factors of the fuzzy controller were tuned on-line to improve output response to the amount and trend of control variable deviation from the reference value. Simulation results showed that the presented neuro-fuzzy control scheme has adaptability to process conditions such as parent material and curvature changes, and that the control variables were well regulated. The presented neuro-fuzzy control scheme can be also expected to be applied in other multi-input multi-output machining processes.
- Full Text:
- Date Issued: 2006
- Authors: Hua, Tao
- Date: 2006
- Subjects: Friction welding , Fuzzy systems
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9612 , http://hdl.handle.net/10948/420 , Friction welding , Fuzzy systems
- Description: A multi-input multi-output system to implement on-line process monitoring and intelligent control of complex curvature friction stir welding was proposed. An extra rotation axis was added to the existing three translation axes to perform friction stir welding of complex curvature other than straight welding line. A clamping system was designed for locating and holding the workpieces to bear the large force involved in the process between the welding tool and workpieces. Process parameters (feed rate, spindle speed, tilt angle and plunge depth), and process conditions (parent material and curvature), were used as factors for the orthogonal array experiments to collect sensor data of force, torque and tool temperature using multiple sensors and telemetry system. Using statistic analysis of the experimental data, sensitive signal features were selected to train the feed-forward neural networks, which were used for mapping the relationships between process parameters, process conditions and sensor data. A fuzzy controller with initial input/output membership functions and fuzzy rules generated on-line from the trained neural network was applied to perceive process condition changes and make adjustment of process parameters to maintain tool/workpiece contact and energy input. Input/output scaling factors of the fuzzy controller were tuned on-line to improve output response to the amount and trend of control variable deviation from the reference value. Simulation results showed that the presented neuro-fuzzy control scheme has adaptability to process conditions such as parent material and curvature changes, and that the control variables were well regulated. The presented neuro-fuzzy control scheme can be also expected to be applied in other multi-input multi-output machining processes.
- Full Text:
- Date Issued: 2006
Selective para-funtionalization of phenol
- Authors: Indurkar, Jayant R
- Date: 2008
- Subjects: Phenol
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10402 , http://hdl.handle.net/10948/710 , Phenol
- Description: In previous work done in our laboratories, a method was discovered to produce phenolic mono-ethers from 4-hydroxyacetophenone and other 4-hydroxyketones by treating with ammonium peroxy-disulfate in an alcohol as a reaction solvent and in the presence of concentrated sulphuric acid or other strong protonic acids. Since this method of producing 4-alkoxyphenol ethers provides a very convenient way to modify hydroquinone and substituted hydroquinones to produce a variety of phenol mono-ethers, it was of interest to study the general scope of this reaction, including a more detailed investigation of the reaction mechanism. In previous studies, it was suggested that interaction between the aromatic pi-system of hydroquinone and the cyclohexa-2,5-diene structure of benzoquinone plays a significant role during the reaction. It was therefore of interest to investigate whether other compounds that are also capable of forming the cyclohexa-2,5-diene structure, will interact in a manner analogous to the hydroquinone/benzoquinone couple. Two specific compounds were selected for this purpose, namely 4-nitrosophenol and 4- (diphenylmethylene)cyclohexa-2,5-dien-1-one . The scope of etherification reactions of hydroquinone-benzoquinone or hydroquinone/benzoquinone like substrates such as 4-nitrosophenol and 4- (diphenylmethylene)cyclohexa-2,5-dien-1-one in the presence of acid catalyst and alcohols was investigated. These studies showed that hydroquinone, 4- nitrosophenol and 4-(diphenylmethylene)cyclohexa-2,5-dien-1-one successfully affords the phenolic ethers in good to excellent yield. For example, quantitative yield of 4-methoxyphenol could be obtained from a 1:1 mixture of hydroquinone and benzoquinone at the reflux temperature of methanol. In order to study the reaction mechanism, the cross-over reaction between tertbutylhydroquinone and benzoquinone (or hydroquinone and tertbutylbenzoquinone) was studied in detail. The results of these cross-over reactions were used to propose a mechanistic pathway that could explain the requirement for pi-interaction between the hydroquinone and benzoquinone molecules, the role of the acid catalyst, as well as the relative rates of hydroquinone and benzoquinone consumption during these reactions. The mechanism was also capable of explaining all the reaction products observed during these reactions. The work was then extended to reactions of 4-nitrosophenol and 4- (diphenylmethylene)cyclohexa-2,5-dien-1-one with methanol in the presence of either hydroquinone or benzoquinone. The results of these investigations strongly suggest the presence of similar interactions between these molecules that also influence the outcome of the reactions. The exploitation of pi-interactions between two molecules of these types investigated during this work opens an interesting field of chemistry. Clearly, the level of understanding developed during this work is only beginning to address this interesting field of chemistry and much work will need to be done to gain a fuller understanding of the chemistry involved as well as the potential synthetic value of these interactions.
- Full Text:
- Date Issued: 2008
- Authors: Indurkar, Jayant R
- Date: 2008
- Subjects: Phenol
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10402 , http://hdl.handle.net/10948/710 , Phenol
- Description: In previous work done in our laboratories, a method was discovered to produce phenolic mono-ethers from 4-hydroxyacetophenone and other 4-hydroxyketones by treating with ammonium peroxy-disulfate in an alcohol as a reaction solvent and in the presence of concentrated sulphuric acid or other strong protonic acids. Since this method of producing 4-alkoxyphenol ethers provides a very convenient way to modify hydroquinone and substituted hydroquinones to produce a variety of phenol mono-ethers, it was of interest to study the general scope of this reaction, including a more detailed investigation of the reaction mechanism. In previous studies, it was suggested that interaction between the aromatic pi-system of hydroquinone and the cyclohexa-2,5-diene structure of benzoquinone plays a significant role during the reaction. It was therefore of interest to investigate whether other compounds that are also capable of forming the cyclohexa-2,5-diene structure, will interact in a manner analogous to the hydroquinone/benzoquinone couple. Two specific compounds were selected for this purpose, namely 4-nitrosophenol and 4- (diphenylmethylene)cyclohexa-2,5-dien-1-one . The scope of etherification reactions of hydroquinone-benzoquinone or hydroquinone/benzoquinone like substrates such as 4-nitrosophenol and 4- (diphenylmethylene)cyclohexa-2,5-dien-1-one in the presence of acid catalyst and alcohols was investigated. These studies showed that hydroquinone, 4- nitrosophenol and 4-(diphenylmethylene)cyclohexa-2,5-dien-1-one successfully affords the phenolic ethers in good to excellent yield. For example, quantitative yield of 4-methoxyphenol could be obtained from a 1:1 mixture of hydroquinone and benzoquinone at the reflux temperature of methanol. In order to study the reaction mechanism, the cross-over reaction between tertbutylhydroquinone and benzoquinone (or hydroquinone and tertbutylbenzoquinone) was studied in detail. The results of these cross-over reactions were used to propose a mechanistic pathway that could explain the requirement for pi-interaction between the hydroquinone and benzoquinone molecules, the role of the acid catalyst, as well as the relative rates of hydroquinone and benzoquinone consumption during these reactions. The mechanism was also capable of explaining all the reaction products observed during these reactions. The work was then extended to reactions of 4-nitrosophenol and 4- (diphenylmethylene)cyclohexa-2,5-dien-1-one with methanol in the presence of either hydroquinone or benzoquinone. The results of these investigations strongly suggest the presence of similar interactions between these molecules that also influence the outcome of the reactions. The exploitation of pi-interactions between two molecules of these types investigated during this work opens an interesting field of chemistry. Clearly, the level of understanding developed during this work is only beginning to address this interesting field of chemistry and much work will need to be done to gain a fuller understanding of the chemistry involved as well as the potential synthetic value of these interactions.
- Full Text:
- Date Issued: 2008
The development of a self-disintegrating core-body for use in an art bronze-casting foundry which employs the ceramic-shell investment technique
- Authors: Lomax, Lawrence Talbot
- Date: 2004
- Subjects: Sculpture -- Technique , Bronze founding , Precision casting , Shell molding (Founding)
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:8499 , http://hdl.handle.net/10948/219 , Sculpture -- Technique , Bronze founding , Precision casting , Shell molding (Founding)
- Description: The development of a disintegrating core-body for use in an art bronze foundry, which employs the ceramic shell investment process, begins with an investigation of four principal materials that will constitute the core formula. The specifications for the disintegration of the designed core-body formula fall within the parameters that are normally set and used in the ceramic shell art bronze casting process. The raison d’ être for the disintegrating formula is based on the premise that cement breaks down (spalling) after being subjected to heat above a certain temperature. It was shown that pure cement in the form of naked test bars 100 mm x 20 mm x 20 mm does indeed break down into separate pieces when fired to and above 9000C; where 9000C is the lowest recommended temperature required for sintering the ceramic shell investment mould. The addition of calcium carbonate to pure cement in the form of naked test bars, produced a more unified formula that did not break into separate pieces when fired to 9450C. However this combination of cement and calcium carbonate had a slow setting time of 12 hours and a shrinkage value of 2,3%, which were both above the parameters being sought for a quick-setting formula with a shrinkage value of below 1%. The combination of cement, plaster of paris and silica produced formulae that set within six hours and had shrinkage values of less than 1% but did not disintegrate within 72 hours. It was only after the addition of calcium carbonate to the these mixes that formulae resulted that set within six hours, had relatively low shrinkage values and showed signs of breaking up after 60 hours. It was further shown that by altering the ratios of cement, plaster of paris, calcium carbonate and silica, that the parameters for quick-setting formulae with shrinkage values of 1% and below, that also disintegrated within 55 hours, could be achieved. xvi It was also proved by subjecting these formulae to higher relative humidity conditions that the disintegrating times could be reduced and brought to below 48 hours. Selected formulae were then subjected to temperatures of between 9000C and 10000C. It was found that as the temperatures were increased so the disintegration times were reduced and were even further reduced under higher relative humidity conditions. It was found from the above experiments that the selected formula determined to be suitable in all respects as a disintegrating core-body was too difficult to remove from the hollow bronze cast when subjected to an actual bronze pour. Further experimentation using increased proportions of silica in the formula resulted in a final core-body that could be quickly and easily removed from its bronze cast as soon as the core-body had cooled to room temperature. The selected core-body formula (F21D) that was used in the final set of bronze casting procedures was found to function optimally when fired to a temperature of 9000C and could be quickly and easily removed from the bronze casts leaving a clean inner bronze surface, free from any remnants of the fired core. The document concludes by recording the delimitations and advantages of the final core-body formula F21D, as well as making recommendations based on these parameters for further study relating to disintegrating core-body formulations.
- Full Text:
- Date Issued: 2004
- Authors: Lomax, Lawrence Talbot
- Date: 2004
- Subjects: Sculpture -- Technique , Bronze founding , Precision casting , Shell molding (Founding)
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:8499 , http://hdl.handle.net/10948/219 , Sculpture -- Technique , Bronze founding , Precision casting , Shell molding (Founding)
- Description: The development of a disintegrating core-body for use in an art bronze foundry, which employs the ceramic shell investment process, begins with an investigation of four principal materials that will constitute the core formula. The specifications for the disintegration of the designed core-body formula fall within the parameters that are normally set and used in the ceramic shell art bronze casting process. The raison d’ être for the disintegrating formula is based on the premise that cement breaks down (spalling) after being subjected to heat above a certain temperature. It was shown that pure cement in the form of naked test bars 100 mm x 20 mm x 20 mm does indeed break down into separate pieces when fired to and above 9000C; where 9000C is the lowest recommended temperature required for sintering the ceramic shell investment mould. The addition of calcium carbonate to pure cement in the form of naked test bars, produced a more unified formula that did not break into separate pieces when fired to 9450C. However this combination of cement and calcium carbonate had a slow setting time of 12 hours and a shrinkage value of 2,3%, which were both above the parameters being sought for a quick-setting formula with a shrinkage value of below 1%. The combination of cement, plaster of paris and silica produced formulae that set within six hours and had shrinkage values of less than 1% but did not disintegrate within 72 hours. It was only after the addition of calcium carbonate to the these mixes that formulae resulted that set within six hours, had relatively low shrinkage values and showed signs of breaking up after 60 hours. It was further shown that by altering the ratios of cement, plaster of paris, calcium carbonate and silica, that the parameters for quick-setting formulae with shrinkage values of 1% and below, that also disintegrated within 55 hours, could be achieved. xvi It was also proved by subjecting these formulae to higher relative humidity conditions that the disintegrating times could be reduced and brought to below 48 hours. Selected formulae were then subjected to temperatures of between 9000C and 10000C. It was found that as the temperatures were increased so the disintegration times were reduced and were even further reduced under higher relative humidity conditions. It was found from the above experiments that the selected formula determined to be suitable in all respects as a disintegrating core-body was too difficult to remove from the hollow bronze cast when subjected to an actual bronze pour. Further experimentation using increased proportions of silica in the formula resulted in a final core-body that could be quickly and easily removed from its bronze cast as soon as the core-body had cooled to room temperature. The selected core-body formula (F21D) that was used in the final set of bronze casting procedures was found to function optimally when fired to a temperature of 9000C and could be quickly and easily removed from the bronze casts leaving a clean inner bronze surface, free from any remnants of the fired core. The document concludes by recording the delimitations and advantages of the final core-body formula F21D, as well as making recommendations based on these parameters for further study relating to disintegrating core-body formulations.
- Full Text:
- Date Issued: 2004
A strategy for the development of team leaders in the East Cape motor industry cluster : a competency based approach
- Authors: Melamed, Graham Morrison
- Date: 2006
- Subjects: Leadership , Teams in the workplace , Automobile industry and trade -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:8568 , http://hdl.handle.net/10948/419 , Leadership , Teams in the workplace , Automobile industry and trade -- South Africa -- Eastern Cape
- Description: The research undertaken in this study was to identify the strategy needed to be adopted by the East Cape Motor Industry Cluster (ECMIC) in order to develop the competencies of its Team Leaders. v Hamel and Prahalad (1994: 28) are of the opinion that the focus of a company must move from current market share, to the share of tomorrow’s opportunities that the company can reasonably expect to gain. The company must therefore consider what it can achieve with its existing set of competencies, and what new competencies need to be acquired in order to prosper in the future. The development of competencies is thus deemed to be critical to the South African economy as the various local automotive manufacturers enter the export field. The ECMIC has traditionally been considered the heart of the automotive industry in South Africa with three of the major manufacturers located in the Nelson Mandela and Buffalo City Metropoles. In order to support these manufacturers, a vast number of component manufacturers and service providers have been established to support the automotive manufacturers both in the ECMIC and in other areas of the country. Since the establishment of a democratic South Africa and the removal of sanctions, the automotive industry has started to establish itself globally. This study will undertake a literature study of the application of competencies in the workplace, teams and team leaders and how competencies are applied in the ECMIC. The results of an empirical study into core competencies in the ECMIC will be used to elucidate a set of competencies which will be used to develop a strategy utilising the competency approach in team leaders in the ECMIC.
- Full Text:
- Date Issued: 2006
- Authors: Melamed, Graham Morrison
- Date: 2006
- Subjects: Leadership , Teams in the workplace , Automobile industry and trade -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:8568 , http://hdl.handle.net/10948/419 , Leadership , Teams in the workplace , Automobile industry and trade -- South Africa -- Eastern Cape
- Description: The research undertaken in this study was to identify the strategy needed to be adopted by the East Cape Motor Industry Cluster (ECMIC) in order to develop the competencies of its Team Leaders. v Hamel and Prahalad (1994: 28) are of the opinion that the focus of a company must move from current market share, to the share of tomorrow’s opportunities that the company can reasonably expect to gain. The company must therefore consider what it can achieve with its existing set of competencies, and what new competencies need to be acquired in order to prosper in the future. The development of competencies is thus deemed to be critical to the South African economy as the various local automotive manufacturers enter the export field. The ECMIC has traditionally been considered the heart of the automotive industry in South Africa with three of the major manufacturers located in the Nelson Mandela and Buffalo City Metropoles. In order to support these manufacturers, a vast number of component manufacturers and service providers have been established to support the automotive manufacturers both in the ECMIC and in other areas of the country. Since the establishment of a democratic South Africa and the removal of sanctions, the automotive industry has started to establish itself globally. This study will undertake a literature study of the application of competencies in the workplace, teams and team leaders and how competencies are applied in the ECMIC. The results of an empirical study into core competencies in the ECMIC will be used to elucidate a set of competencies which will be used to develop a strategy utilising the competency approach in team leaders in the ECMIC.
- Full Text:
- Date Issued: 2006
The development and evaluation of a new manufacturing process for β-sitosterol-D glucoside
- Mtyopo, Mthetheleli Bethwell
- Authors: Mtyopo, Mthetheleli Bethwell
- Date: 2016
- Subjects: Pharmaceutical chemistry Chemistry, Organic
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: http://hdl.handle.net/10948/45920 , vital:39320
- Description: The existing production sequence of β-sitosterol-D-glucoside, a glucoside used in an “over-the-counter” (OTC) preparation under the brand name of Moducare® comprises of three process steps with an overall yield of less than 20%. The low yield is partly due to the instability of intermediates at reaction temperatures > 0oC, and partly due to the thermodynamic equilibrium between two stereoisomers. An economically alternative process was developed, evaluated and scaled-up in a 2l reactor. The project was initiated with a specific limitation in terms of the starting material that comprised a mixture of plant sterols, which necessitated a study of the isolation and purification of the desired product from a rather complex reaction mixture. The use of silver as halide acceptor for the Koenigs-Knorr synthesis did not give statistically significant different results from the same approach but using cadmium as halide acceptor instead. However, using the direct O-glucosylation approach not only gave statistically significant higher results, but also resulted in a much more convenient procedure. Under optimum conditions, a yield of approximately 83% (isolated) of 2,3,4,6- tetra-О-acetyl-β-sitosterol-D-glucoside could be achieved, which was substantially higher than that achieved with the traditional Koenigs-Knorr methodology and above reported yields in the literature (60-80%) for direct glycosylation. Separation of 2,3,4,6-tetra-О-acetyl-β-sitosterol-D-glucoside (BSSGT) from a reaction mixture that contains 2,3,4,6-tetra-О-acetyl-campesterol-D-glucoside (CSGT), 2,3,4,6-tetra-О-acetyl campestanol-glucoside (CSSGT), and 2,3,4,6-tetra-О-acetyl-sitostanol-Dglucoside (SSGT) was investigated using column chromatography. When using silica gel particles, very good separation efficiency and product recovery could be achieved using hexane/ethyl hexane as eluent. The isolated 2,3,4,6-tetra-О-acetyl-β-sitosterol-Dglucoside was easily hydrolysed to β-sitosterol-D-glucoside in high yields (79%) using methanolic KOH. The process for the production of β-sitosterol-D-glucoside was scaled-up from the laboratory bench scale (250 cm3) to a laboratory scale of 2 l using the direct Oglycosylation method. The overall yields of the scaled reaction for β-sitosterol-D-glucoside was slightly above the literature reported values (59%, 8/92) for the KnoenigsKnorr synthesis and compares well above (62%, 0/100) the current production process (less than 20% yields). When using catalogue prices, the material costs (without recycling) for the direct Oglucosylation route is approximately 57% less for the synthesis of 1kg of β-sitosterol-Dglucoside compared to the Koenigs-Knorr route. Given further savings for recycling, the direct O-glucosylation route provides an attractive alternative route for the synthesis ofthe target compound.
- Full Text:
- Date Issued: 2016
- Authors: Mtyopo, Mthetheleli Bethwell
- Date: 2016
- Subjects: Pharmaceutical chemistry Chemistry, Organic
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: http://hdl.handle.net/10948/45920 , vital:39320
- Description: The existing production sequence of β-sitosterol-D-glucoside, a glucoside used in an “over-the-counter” (OTC) preparation under the brand name of Moducare® comprises of three process steps with an overall yield of less than 20%. The low yield is partly due to the instability of intermediates at reaction temperatures > 0oC, and partly due to the thermodynamic equilibrium between two stereoisomers. An economically alternative process was developed, evaluated and scaled-up in a 2l reactor. The project was initiated with a specific limitation in terms of the starting material that comprised a mixture of plant sterols, which necessitated a study of the isolation and purification of the desired product from a rather complex reaction mixture. The use of silver as halide acceptor for the Koenigs-Knorr synthesis did not give statistically significant different results from the same approach but using cadmium as halide acceptor instead. However, using the direct O-glucosylation approach not only gave statistically significant higher results, but also resulted in a much more convenient procedure. Under optimum conditions, a yield of approximately 83% (isolated) of 2,3,4,6- tetra-О-acetyl-β-sitosterol-D-glucoside could be achieved, which was substantially higher than that achieved with the traditional Koenigs-Knorr methodology and above reported yields in the literature (60-80%) for direct glycosylation. Separation of 2,3,4,6-tetra-О-acetyl-β-sitosterol-D-glucoside (BSSGT) from a reaction mixture that contains 2,3,4,6-tetra-О-acetyl-campesterol-D-glucoside (CSGT), 2,3,4,6-tetra-О-acetyl campestanol-glucoside (CSSGT), and 2,3,4,6-tetra-О-acetyl-sitostanol-Dglucoside (SSGT) was investigated using column chromatography. When using silica gel particles, very good separation efficiency and product recovery could be achieved using hexane/ethyl hexane as eluent. The isolated 2,3,4,6-tetra-О-acetyl-β-sitosterol-Dglucoside was easily hydrolysed to β-sitosterol-D-glucoside in high yields (79%) using methanolic KOH. The process for the production of β-sitosterol-D-glucoside was scaled-up from the laboratory bench scale (250 cm3) to a laboratory scale of 2 l using the direct Oglycosylation method. The overall yields of the scaled reaction for β-sitosterol-D-glucoside was slightly above the literature reported values (59%, 8/92) for the KnoenigsKnorr synthesis and compares well above (62%, 0/100) the current production process (less than 20% yields). When using catalogue prices, the material costs (without recycling) for the direct Oglucosylation route is approximately 57% less for the synthesis of 1kg of β-sitosterol-Dglucoside compared to the Koenigs-Knorr route. Given further savings for recycling, the direct O-glucosylation route provides an attractive alternative route for the synthesis ofthe target compound.
- Full Text:
- Date Issued: 2016