Machinability of rapidly solidified aluminium alloy for optical applications
- Authors: Abbas, Abdalla Abbas Said
- Date: 2020
- Subjects: Aluminum alloys , Mechatronics
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/45975 , vital:39402
- Description: The production of metal mirrors and critical components for optical devices and aerospace application requires extreme high accuracy and outstanding surface quality. Thus, to achieve such high dimensional accuracies, they are being mainly produced through ultra-high precision machining. Aluminium alloys have been used in the production of components for optics application as well as spaceborne for so many years but with the advancement in technology and demands for a superior material, a new modified grade of aluminium was developed by a rapid solidification process. These grades exhibit a much better mechanical and physical properties while having a finer microstructure. The only downside is the limited research in the correlation of surface roughness and reflectance when single point diamond turned. In this study, rapidly solidified aluminium RSA 905 were used to investigate the effect of varying the cutting parameters on the machined surface finish and its corresponding surface reflectance. The cutting parameters were cutting speed, feed rate and depth of cut. The surface roughness was measured using Taylor Hopson PGI Profilometer while the reflectance factor was measured by using VERTEX 80v Spectrometer. The results were used to develop two predictive models namely; response surface and artificial neural network which have indicated a very high accuracy to the experimental measurements. Finally, the results were very promising for the diamond turning of RSA 905 where it has achieved a very low values of surface roughness and high reflectance in the visual range without the need of any additional production/fabrication steps and to ensure that bi-metallic binding does not take place in extreme low temperatures. Therefore, RSA 905 is a very promising material for optical applications in the visual spectrum.
- Full Text:
- Date Issued: 2020
- Authors: Abbas, Abdalla Abbas Said
- Date: 2020
- Subjects: Aluminum alloys , Mechatronics
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/45975 , vital:39402
- Description: The production of metal mirrors and critical components for optical devices and aerospace application requires extreme high accuracy and outstanding surface quality. Thus, to achieve such high dimensional accuracies, they are being mainly produced through ultra-high precision machining. Aluminium alloys have been used in the production of components for optics application as well as spaceborne for so many years but with the advancement in technology and demands for a superior material, a new modified grade of aluminium was developed by a rapid solidification process. These grades exhibit a much better mechanical and physical properties while having a finer microstructure. The only downside is the limited research in the correlation of surface roughness and reflectance when single point diamond turned. In this study, rapidly solidified aluminium RSA 905 were used to investigate the effect of varying the cutting parameters on the machined surface finish and its corresponding surface reflectance. The cutting parameters were cutting speed, feed rate and depth of cut. The surface roughness was measured using Taylor Hopson PGI Profilometer while the reflectance factor was measured by using VERTEX 80v Spectrometer. The results were used to develop two predictive models namely; response surface and artificial neural network which have indicated a very high accuracy to the experimental measurements. Finally, the results were very promising for the diamond turning of RSA 905 where it has achieved a very low values of surface roughness and high reflectance in the visual range without the need of any additional production/fabrication steps and to ensure that bi-metallic binding does not take place in extreme low temperatures. Therefore, RSA 905 is a very promising material for optical applications in the visual spectrum.
- Full Text:
- Date Issued: 2020
The determinants of waste separation behaviour in Uitenhage, South Africa
- Authors: Basson, Anna-Marie
- Date: 2018
- Subjects: Recycling industry -- South Africa , Sustainable development -- South Africa Economic development -- South Africa -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/23658 , vital:30593
- Description: The value of waste as a resource, diverting waste from landfills and the need for a circular economy, was emphasised at the South African and European Colloquium on recycling hosted by PETCO, the polyethylene terephthalate company (Godfrey, 2013, p. 17). In South Africa, the recycling industry is seen as a means to provide income and skills development, and to create sustainable livelihoods. Yet, the country remains deeply entrenched in landfilling (Godfrey, 2013, p. 19). According to Zhang, Huang, Yin and Gong (2015, p. 9475) “understanding the factors that affect residents’ waste separation behaviours helps in constructing effective environmental campaigns for the community”. The focus of a waste management system should be to motivate and convince the consumer to dispose of their waste in a sustainable manner. The waste separation decision is complex and can be explained by the theory of planned behaviour and theory of reasoned action (Nguyen, Nguyen, Lobo & Dao, 2017, p. 2). The aim of this study is to identify and evaluate the factors that influence the waste separation behaviour of households in the Uitenhage area. In order to achieve this aim, secondary research (literature review) and primary research (empirical study) were conducted. The study has shown that if the residents are presented with free containers and have access to a collection service which facilitates the flow of the recyclables from the point of consumption to the point of sustainable disposal and conversion, it could motivate them to separate the waste. The only variable that was found significant in relation to household waste separation behaviour was motivation. The respondents are motivated to separate their household waste; yet, they do not separate it. The frequency distribution analysis reported that the sample was not experienced waste separators, where less than half of the sample was engaged in some waste separation activities. Yet, the respondents had a positive attitude towards the importance of waste separation and disagreed that waste separation is inconvenient. The majority of the respondents agreed that they have control over their behaviour and that the decision to separate their waste is within their control, but yet they do not separate their waste. The respondents agreed that they have the knowledge of what and how to separate waste, however, disagreed that they know where to take their separated waste. Interestingly, the respondents agreed that waste separation is The determinants of waste separation behaviour in Uitenhage, South Africa part of their moral norms; yet, they do not consider family and friends, including the municipality, to exert social pressure on them to separate their household waste. It is recommended that the municipality investigates the requirements for implementing a waste management scheme which provides containers for free and collects separated waste from households. Entrepreneurs can also play a pivotal role in bridging the gap in the waste management supply chain by establishing buy-back centres and sustainable recycling depots to facilitate the collection of separated waste for recycling. These collection services, buy-back centres and recycling depots present business opportunities and job creation potential, which will drive the economic growth in the Nelson Mandela Bay area.
- Full Text:
- Date Issued: 2018
- Authors: Basson, Anna-Marie
- Date: 2018
- Subjects: Recycling industry -- South Africa , Sustainable development -- South Africa Economic development -- South Africa -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/23658 , vital:30593
- Description: The value of waste as a resource, diverting waste from landfills and the need for a circular economy, was emphasised at the South African and European Colloquium on recycling hosted by PETCO, the polyethylene terephthalate company (Godfrey, 2013, p. 17). In South Africa, the recycling industry is seen as a means to provide income and skills development, and to create sustainable livelihoods. Yet, the country remains deeply entrenched in landfilling (Godfrey, 2013, p. 19). According to Zhang, Huang, Yin and Gong (2015, p. 9475) “understanding the factors that affect residents’ waste separation behaviours helps in constructing effective environmental campaigns for the community”. The focus of a waste management system should be to motivate and convince the consumer to dispose of their waste in a sustainable manner. The waste separation decision is complex and can be explained by the theory of planned behaviour and theory of reasoned action (Nguyen, Nguyen, Lobo & Dao, 2017, p. 2). The aim of this study is to identify and evaluate the factors that influence the waste separation behaviour of households in the Uitenhage area. In order to achieve this aim, secondary research (literature review) and primary research (empirical study) were conducted. The study has shown that if the residents are presented with free containers and have access to a collection service which facilitates the flow of the recyclables from the point of consumption to the point of sustainable disposal and conversion, it could motivate them to separate the waste. The only variable that was found significant in relation to household waste separation behaviour was motivation. The respondents are motivated to separate their household waste; yet, they do not separate it. The frequency distribution analysis reported that the sample was not experienced waste separators, where less than half of the sample was engaged in some waste separation activities. Yet, the respondents had a positive attitude towards the importance of waste separation and disagreed that waste separation is inconvenient. The majority of the respondents agreed that they have control over their behaviour and that the decision to separate their waste is within their control, but yet they do not separate their waste. The respondents agreed that they have the knowledge of what and how to separate waste, however, disagreed that they know where to take their separated waste. Interestingly, the respondents agreed that waste separation is The determinants of waste separation behaviour in Uitenhage, South Africa part of their moral norms; yet, they do not consider family and friends, including the municipality, to exert social pressure on them to separate their household waste. It is recommended that the municipality investigates the requirements for implementing a waste management scheme which provides containers for free and collects separated waste from households. Entrepreneurs can also play a pivotal role in bridging the gap in the waste management supply chain by establishing buy-back centres and sustainable recycling depots to facilitate the collection of separated waste for recycling. These collection services, buy-back centres and recycling depots present business opportunities and job creation potential, which will drive the economic growth in the Nelson Mandela Bay area.
- Full Text:
- Date Issued: 2018
Crop yields from organic and conventional farming systems in South Africa's Southern Cape
- Authors: Mashele, N'wa-Jama
- Date: 2016
- Subjects: Organic farming -- South Africa Sustainable agriculture -- South Africa Agricultural systems -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11637 , vital:26946
- Description: South Africa (SA) is food secure on a national level, however citizens in rural and marginalised areas face household food insecurity due to lack of access to this food. South Africa has low fertility soils and scarce water resources. Climate change reports of unpredictable weather conditions will further exacerbate these challenges. The majority of the agricultural production methods in SA are industrialised and rely heavily on external inputs. Alternative agricultural production methods which are environmentally less taxing, are affordable and yield nutritious food, need to be investigated and adopted. A long-term trial investigating the differences in yields between conventional and organic farming systems was established at the NMMU George Saasveld campus. A baseline study preceded the cropping seasons to establish pre-treatment soil conditions before the two farming systems were be implemented. The trial was a randomized complete block design split into organic, conventional and control plots. In the first cropping season (summer) three crops cabbage (Brassica oleracea var. capitata), sweet potato (Ipomea batatas) and cowpea (vigna ungucuilata) were planted under the different treatments. Soil fertility changes after application of chemical and organic fertilizer were measured. Soil pH and phosphorus increased whilst potassium and soil carbon decreased from baseline levels. The organic plots were found to have higher soil pH, potassium and carbon, whilst P was higher in the conventional plots. The organic cabbages had a yield 12% lower than conventional cabbages, organic cowpeas were 51% lower than conventional cowpeas. Baboons damaged sweet potato plots before maturity. Broccoli (Brassica oleracea var. italica), radish (Raphanus sativa) and green pea (Pisum sativum) were planted in the second cropping season (winter). Organic broccoli yields were 51% lower than conventional broccoli, organic green peas were 18 % lower than conventional green peas. The organic radish yields were 36% lower than conventional yields and this was statically significant. The yield differences were statically significant between control and conventional cabbages (25%) and broccolis (68%). The results indicate that there is on average an initial 25% yield difference between organic and conventional farming systems. Similar studies have shown that the yield gap can be reduced within three to four years. This study presents preliminary results of trials that are to continue for ten years, during which time the yield differences may vary.
- Full Text:
- Date Issued: 2016
- Authors: Mashele, N'wa-Jama
- Date: 2016
- Subjects: Organic farming -- South Africa Sustainable agriculture -- South Africa Agricultural systems -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11637 , vital:26946
- Description: South Africa (SA) is food secure on a national level, however citizens in rural and marginalised areas face household food insecurity due to lack of access to this food. South Africa has low fertility soils and scarce water resources. Climate change reports of unpredictable weather conditions will further exacerbate these challenges. The majority of the agricultural production methods in SA are industrialised and rely heavily on external inputs. Alternative agricultural production methods which are environmentally less taxing, are affordable and yield nutritious food, need to be investigated and adopted. A long-term trial investigating the differences in yields between conventional and organic farming systems was established at the NMMU George Saasveld campus. A baseline study preceded the cropping seasons to establish pre-treatment soil conditions before the two farming systems were be implemented. The trial was a randomized complete block design split into organic, conventional and control plots. In the first cropping season (summer) three crops cabbage (Brassica oleracea var. capitata), sweet potato (Ipomea batatas) and cowpea (vigna ungucuilata) were planted under the different treatments. Soil fertility changes after application of chemical and organic fertilizer were measured. Soil pH and phosphorus increased whilst potassium and soil carbon decreased from baseline levels. The organic plots were found to have higher soil pH, potassium and carbon, whilst P was higher in the conventional plots. The organic cabbages had a yield 12% lower than conventional cabbages, organic cowpeas were 51% lower than conventional cowpeas. Baboons damaged sweet potato plots before maturity. Broccoli (Brassica oleracea var. italica), radish (Raphanus sativa) and green pea (Pisum sativum) were planted in the second cropping season (winter). Organic broccoli yields were 51% lower than conventional broccoli, organic green peas were 18 % lower than conventional green peas. The organic radish yields were 36% lower than conventional yields and this was statically significant. The yield differences were statically significant between control and conventional cabbages (25%) and broccolis (68%). The results indicate that there is on average an initial 25% yield difference between organic and conventional farming systems. Similar studies have shown that the yield gap can be reduced within three to four years. This study presents preliminary results of trials that are to continue for ten years, during which time the yield differences may vary.
- Full Text:
- Date Issued: 2016
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