Effects of natural antioxidants and thermal treatment on quality of meat from Bonsmara and non-descripts cattle
- Authors: Falowo, Andrew Bamidele
- Date: 2015
- Subjects: Meat -- Preservation Antioxidants Meat -- Microbiology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/2589 , vital:27906
- Description: The broad objective of this study was to determine the effects of natural antioxidants and thermal treatment on quality of meat from Bonsmara and non-descript cattle. A survey was conducted among 222 consumers in Alice (Fort Hare University community), Eastern Cape Province to determine the level of their awareness on application of antioxidants as preservatives in meat and meat products during storage. Representative samples of Muscularis longissimuss thoracis et lumborum and liver were collected from each carcass of Bonsmara (n=40) and non-descript (n=40) cattle reared on natural pasture to determine the effect of natural antioxidants and thermal treatment on their quality. The results from the survey revealed that 51.35 percent of the respondents had not heard about the use of antioxidant as preservatives in meat products. However, among the remaining respondents (48.65 percent) that were aware of antioxidant and its use as preservative, about 19 percent knew of natural antioxidants, 35 percent synthetic antioxidants while 46 percent had knowledge of both. The results further revealed that the majority of the respondents (82 percent) that had knowledge of natural antioxidants were concerned about the use of synthetic antioxidants in meat and meat products due to their health consequences. The in vitro antioxidant and antibacterial analyses of Bidens pilosa and Moringa oleifera leaf extracts revealed that they contain rich bioactive compounds. Furthermore, the addition of leaf extracts from Moringa oleifera (ML, 0.05 and 0.1 percent w/w) and Biden pilosa (BP, 0.05 and 0.1 percent w/w) to ground raw beef as a natural antioxidant were found to improve the physicochemical, oxidative stability and microbiological qualities of meat compared to the control (meat without extract) and BHT treatment (0.02 percent w/w) during 6 days storage at 40 C. Cattle breed did not have much effect on colour parameters. However, the overall pH of ground beef treated with extracts showed lower values than control and BHT treated beef. Also, ground beef samples containing extracts exhibited (P < 0.05) better colour stability, especially higher redness (a* values), than the control. The formation of TBARS in beef samples treated with extracts was significantly (P < 0.05) lower than the control and BHT treatment. The antibacterial assay of the extracts revealed an appreciable broad spectrum activity against the tested bacteria and microbial counts in ground beef samples compared to control and BHT group. Ground beef treated with plant extracts exhibited lower microbial and lactic acid bacterial counts (P < 0.05) at day 0 and 3 than control samples. Moreover, it was observed that application of sous vides thermal method did not significantly affect the fatty acids and mineral loss in beef and liver across the treatments. However, the total concentration of MUFA was lower in raw liver (20.11±2.38 - 21.08±1.23 percent) than in beef (40.22±1.90 - 42.53±1.29 percent), while total PUFA content were higher in liver (30.73±2.60 - 31.11±1.19 percent) than in beef samples (10.13±3.36 - 11.02±2.74 percent) (p < 0.05). The results also revealed that liver samples from Bonsmara and non-descript cattle had a higher percentage of intramuscular fat content of 4.67 ± 0.53 percent and 4.44 ± 0.53 percent respectively, and fat free dry matter of 27.51 ± 1.05 percent and 25.73 ± 1.05 percent, respectively, than the beef samples (p < 0.05). The concentrations of Mg (52.80±0.22 - 53.70±0.02mg/100g) and Zn (8.90±0.15 - 19.60±0.15mg/100g) were higher in beef than liver samples. The level of Ca (17.00±0.17 - 17.50 ± 0.17mg/100g) in liver was higher than that of beef samples. It was concluded that most consumers preferred the use of natural antioxidants in meat products than synthetic antioxidants due to their health risk. The effectiveness of M. oleifera and B. pilosa leaf extracts on meat quality also revealed that these plants are promising candidates as natural preservatives and their application should be considered in the meat industry. Lastly, findings from this study showed that application of the sous vide technique could protect meat products from nutritional loss during thermal treatment.
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- Date Issued: 2015
Evaluating the effectiveness of public participation in the environmental impact assessment process in South Africa
- Authors: Uithaler, Eldrid Marlon
- Date: 2015
- Subjects: Environmental impact analysis -- South Africa , Environmental policy -- Citizen participation
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/5928 , vital:21015
- Description: This research is based on reflections of various practitioners and their views on how public participation processes may or may not contribute to effective EIA decisions. It is therefore grounded in what is described as practitioner-based research. To study comparative development activities effectively, one must draw on many disciplines and construct a balanced understanding of historical and contemporary development processes. No single conventional disciplinary area of research is able to integrate the issues of public participation, EIA and decision-making in the context of the current development debate. The emergence of Trans-disciplinary areas of research allows for such integration. The Africa Earth Observatory Network (AEON) institute creates the space for this study to achieve an integrated response to the question of the effectiveness of public participation in EIA and decision-making. This further creates the opportunity to contribute and expand the growing body of knowledge and literature of public participation in the earth stewardship science discipline. Making use of triangulation, this study fulfils four major tasks: firstly, an assessment is made on the historical and theoretical importance, process and outcome of both EIA and public participation internationally and in South Africa. Secondly, three prominent case studies (i) the Coega IDZ, (ii) the Pondoland N2 Toll Road, and (iii) the anticipated Hydraulic Fracturing in the Karoo each focusses on concerns of an environmental, socio-economic, and political nature to assess if the public participation process has had influence, if any, on the final decisions for these projects to go-ahead. Thirdly, a survey was conducted to establish the views and perceptions of practitioners in the EIA and public participation domain on the effectiveness of public participation in EIA processes. Lastly, face-to-face interviews were conducted with various ‘pracademics’, i.e. consultants, practitioners, government, and non-governmental officials to establish their views on how public participation may or may not influence EIA decisions. Utilising the International Association for Public Participation’s (IAP2) participation spectrum as an evaluation tool, this research explores thirteen key criteria normally attributed to effective public participation. This provides a scale (inform, involve, consult, collaborate) to assess whether public participation in EIA in South Africa is least effective (inform) or most effective (collaborate). My research confirms that in South Africa an enabling environment to address impacts on our environment is emerging. One of the main challenges remains putting in place robust, clear and effective regulations, models or approaches that provide for effective public participation and decision-making in EIAs. My research also suggests that the legislation on which EIA is based cannot by itself guarantee the effectiveness of public participation processes. In practice, EIA is an institutional process of power division between different actors, and the practitioner or ‘pracademic’ has to play a more fundamental role to ensure effectiveness and fairness in the public participation process. Academic commentators should therefore call for new approaches that emphasise collaborative interaction between decision-makers and the public as well as deliberation amongst participants.
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- Date Issued: 2015
My living theory of the transformational potential of my educational leadership
- Authors: Johannes, Arnold Marius
- Date: 2015
- Subjects: Educational change -- South Africa , School management and organization , Leadership
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/4079 , vital:20510
- Description: In democratic South Africa, policies place much emphasis on the need for transformational leadership. This challenges school leaders to ensure that their practice is in line with the democratic and inclusive values espoused therein. This thesis is an account of my journey of learning about educational leadership and how I attempted to influence transformation at my own school. The development of my living theory of educational management is grounded in my desire to make a positive change to the quality of teaching and learning at my school, by embodying and exemplifying such values in my leadership. My learning as an educational leader comprises my living theory on improving my educational leadership within a socially challenged context. I explain the context and problems experienced at my school and provide evidence of the need to move from the hierarchic, autocratic form of leadership, still prevailing at many South African schools. I adopted the theoretical framework of servant leadership to enable me to develop a more contextually sensitive and visionary style of leadership through critical reflection on my own practice. My stimulus for this journey of learning stemmed from the perceived contradiction between my espoused beliefs about leadership and my actual practice. My own autocratic leadership style was one of the main barriers that prevented teachers from attaining autonomy and taking on leadership roles within the school. My leadership style was more in alignment with the values of accountability, discipline and efficiency than those of care, trust and the development of the potential of others. This interrogation of my ontological values informed my subsequent interventions to improve my practice. Following an action research design, I investigated the quality of my leadership to determine which areas I needed to improve, took action to improve these and evaluated the change against the values inherent in the notion of servant-leadership. I embarked on a journey that helped me to shift my practice from being based on previously held authoritarian professional values towards values that underpin a more transformational leadership, such as care and trust. My journey of learning was guided by the tenets of self-study action research, which required critical self-reflection and holding myself accountable for my own actions The practical knowledge I gained through this self-reflection on my practice enabled me to make professional judgements, which then became conceptual knowledge in the form of a living theory generated by my research. This was made possible through a continuous process of data generation to extract evidence to test the validity of the claims to knowledge I made. Multiple sources of data (written, graphic and multimedia) were used to better understand the scope of happenings throughout the research and to monitor my practice over time. I explain how I used my improved understanding of leadership to promote collegiality for building quality relationships to promote teacher leadership for school improvement and how I subjected these claims to social and personal validation procedures. The significance of this study is that it contributes to new forms of practice and theory in terms of showing how a values-based approach to school leadership can influence positive change in teacher practice. While this study is a narrative of my practice, it is also a narrative of theorising about how my colleagues and I have come to know and how our thinking has changed about our work and ourselves. Although I had to indicate a cut-off point in this action research enquiry, the knowledge gained will continue to develop and influence my practice in the future and hopefully will be judged as useful by others in positions of leadership. The thesis is thus an original contribution to educational knowledge in the field of self-study action research. It demonstrates how sociohistorical and sociocultural insights from Apartheid to Post-Apartheid South Africa can be integrated within a living theory of transformational leadership.
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- Date Issued: 2015
Nutritional value and cultivation requirements of Cleome Gynandra: a wild vegetable growing in the Eastern Cape Province, South Africa
- Authors: Sowunmi, Linda Ifeanyichukwu
- Date: 2015
- Subjects: Ethnobotany -- South Africa -- Eastern Cape Vegetables -- South Africa -- Eastern Cape Nutrition -- South Africa -- Evaluation
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/2600 , vital:27907
- Description: South Africa has wide ranges of plants among which are leafy vegetables growing in the wild. These wild vegetables have been reported to have high nutritive and medicinal potentials. Yet, there is still high prevalence of malnutrition and micronutrients deficiencies among the low income bracket of the population. Effective utilization of wild vegetables has been proposed as part of the solutions to address the problem of dietary deficiencies among the populace. Their importance is mainly as relish to accompany and complement starch based diets. They are also known to serve as supplements for food which have the potential to improve the health status of its consumers in many rural communities. Cleome gynandra L. (Capparaceae) is one of the underutilized species mentioned during asurvey conducted in Nkonkobe municipality of the Eastern Cape Province, South Africa. The plant is an erect annual herb with alternate, palmately compound leaves and its petals are white, pink or lilac. It grows as a weed in this part of the Province and is usually gathered from the wild for food and medicine. It is commonly found on wastes land, road sides and on grass lands. Therefore, this research work was designed to contribute to the possible domestication of this wild vegetable in order to explore the nutritive and therapeutic potentials which would broaden the food base in the Eastern Cape Province. The ultra-micromorphological features of plants have become an essential tool in proper identification and authentication of several plant species. In the light of this, the micromorphology of Cleome gynandra was examined to reveal the micro-morphological characters of the plantand to determine if micro and macro mineral elements are present using energy dispersive x-rays. The present study revealed the epidermal cells of the leaves to be asymmetric in shape with undulating cell walls having four subsidiary cells around the stomata. The leaves have anomocyctic stomata which are more distributed in the abaxial surface than the adaxial surface. The mean length and width of the guard cells in the abaxial surface are 0.09 ± 0.01 mm and 0.08 ± 0.01 mm respectively while that of adaxial surface are 0.1± 0.01 mm and 0.07 ± 0.01 mm respectively. The energy dispersive x-rays (EDXS) micro-analysis of the leaf revealed the presence of phosphorus, manganese, iron, calcium, sodium, magnesium, potassium and zinc as the major constituents of the crystal deposits present in the stomata pores and the mesophyll. C. gynandra was collected from the wild and analysed for its mineral and proximatecomposition using standard analytical methods. The plant showed high levels of sodium, iron, zinc, calcium and potassium while many other macro and micro minerals were moderately present. Amongst the proximate factors investigated, moisture content was found to be 82.1% while crude fibre and protein contents were 39.9 percent and 31.03 percent respectively. Vitamin C was also high (345.3 mg/100g). The anti-nutrients compositions revealed low concentrations of oxalate (7.4 ± 0.4) and phytate (0.6 ± 0.0) mg/100g. The study revealed high nutritive value of the species growing naturally from the wild. Interest in the phenolic compounds has greatly increased recently because these compounds have been implicated in suppressing the risk of degenerative diseases in humans. The pharmacological properties of plants may be related to their antioxidant capacities and hence there was need to investigate the antioxidant potential using aqueous, ethanolic and acetone extracts of different parts of C. gynandra. The quantities of phenols, flavonoids and flavonols were significantly higher (p < 0.05) in both aqueous and ethanol extracts of the leaf while the concentration of proanthocyanidins was higher in the aqueous stem extract compared to other plant parts. The aqueous extract of the different parts exhibited better ABTS, reducing power and NO radical scavenging abilities than ethanol extract.
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- Date Issued: 2015
Relatedness, social behaviour, and population dynamics of the elephants (Loxodonta africana) of Addo Elephant National Park, South Africa
- Authors: Gough, Katie F
- Date: 2015
- Subjects: African elephant -- Behavior -- Addo Elephant National Park (South Africa) , African elephant populations -- Addo Elephant National Park (South Africa) , Animal population density -- Addo Elephant National Park (South Africa) , Addo Elephant National Park (South Africa)
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/3569 , vital:20443
- Description: This study presents an investigation into the population dynamics and social structure of a small, closed elephant population. Specifically, it examined population growth rates for evidence of density-dependent regulation. It also quantified the association patterns of female elephants groups, and male elephants groups. Social structure was examined using Hamilton’s kinship theories of inclusive fitness, and age. Male-female patterns of association were also examined for inbreeding avoidance behaviours. The study population was located in Addo Elephant National Park, South Africa. Density-dependence was assessed using a long-term data set. Densities were considerably higher than estimated carrying capacities. Population growth rate was positively correlated with increasing density. No relationship between birth rate, the age of first calving or calf sex ratio and elephant density was detected but there was a positive relationship between birth rate and rainfall during conception year. Mortality rates, particularly for juveniles, were low, and mean inter-calf interval was 3.3 years. There is no evidence of density dependent regulation in this population. These findings indicate that density dependence should not be considered as an option in the control of elephant numbers in this Park, or where elephant resources are not seasonally limited. Examination of association patterns of the adult female component revealed that associations were not random at the population, family or individual scale. This is the second study on African elephants to confirm previous behavioural studies that predicted that preferred associates were close maternal relatives. This supports many studies showing that social species preferentially associate with their kin. The adult males in this population were found to have a well differentiated society with non-random associations. Generally, males were found to have weak associations with most other males and strong associations with only a few males. This association pattern was found to be persistent over the time frame of the study, as indicated by the time lag analysis. Males returned to their natal family, even when maternally related females were in oestrus. Oestrous females directed positive behaviours towards musth males. It appears that behavioural inbreeding avoidance mechanisms in this small, closed population are inhibited: musth status seems to override inbreeding avoidance. General principles from this case study were interpreted in terms of their applicability to other small, closed populations.
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- Date Issued: 2015
Strategies to facilitate community-based health care for severely and persistently mentally ill persons
- Authors: Shasha, Nontembeko Grycelda
- Date: 2015
- Subjects: Mentally ill -- Rehabilitation , Community mental health services , Community mental health services -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/3755 , vital:20461
- Description: The goal of mental health delivery system is to allow the individual with severe and persistent mental illness to live and function effectively in the community and to ensure that the consumers and their families have access to accurate information that promotes learning, self-monitoring and accountability (Stuart & Laraia, 2005:710). In community-based health care, the persons living with severe and persistent mental illness (SPMI) are in their natural environment in the context of the family and the community. The goals of care are focused around maximizing the person living with SPMI’s quality of life (Hunt, 2001:15-16). In South Africa, an integrated package of essential Primary Health Care (PHC) services has been made available to the entire population in order to provide the solid foundation of a single unified health care service (Department of Health, 2000:4). The assessment of health care needs of persons living with SPMI is a dynamic on-going process that is used to collect information, recognise changes, analyse needs and plan health care to provide baseline information to help evaluate the physiological and psychological normality and functional capacity of persons with SPMI (Hunt, 2001:100). There is insufficient information from the Department of Health to either satisfy the enquiry of whether the health care needs of persons living with SPMI are being met comprehensively or whether the practitioners rendering community-based health care are knowledgeable and comply with PHC norms and standards developed by this Department. The researcher is interested in understanding how the persons living with SPMI and their families experience the community-based health care provided by PHC nurses. The purpose of this research study is to develop strategies that would assist the PHC nurses in the selected rural areas of the Eastern Cape to facilitate community-based health care and to render a health care service relevant to the health care needs of the persons living with SPMI and their families. To achieve the objective of the study, the research design was based on a qualitative, exploratory, descriptive, contextual research approach. Phase one includes describing and selecting the research population and the sampling process prior to conducting the field work which comprises individual interviews with persons living with SPMI and their families as well as PHC nurses. According to Dickoff, James and Weidenbach (1968:422) and Chinn and Kramer (1995:78), this strategy involves identifying concepts from fieldwork and creating conceptual meaning to provide a foundation for developing strategies to facilitate community-based care for persons living with mental illness. Phase two of the research design will focus on development of conceptual framework in order to allow better understanding of the phenomenon of interest, as the major concepts will be simplified by connecting all related concepts together by means of statements. This was done by making use of the themes identified during data analysis and the literature sources used throughout this research process. The evaluation criteria of Chinn and Kramer (2008:237-248) were used to evaluate the strategies. It is therefore concluded that the researcher succeeded in achieving the purpose of this study because strategies which were understandable, clear, applicable and relevant to the nursing practice have been developed for use by Department of Health and Primary Health Care to facilitate the multifaceted role of the PHC nurses.
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- Date Issued: 2015
The contribution of guest houses to economic growth and employment as key components of local economic development in the Eden District Area
- Authors: Ramukumba, Takalani
- Date: 2015
- Subjects: Economic development -- South Africa -- Western Cape , Sustainable tourism -- South Africa -- Western Cape
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/5214 , vital:20821
- Description: Tourism has come to be seen as a key driver for local economic development in South Africa, as it provides opportunities for pro-poor and community-based initiatives. On a global scale, the challenges of confronting poverty and unemployment continue to dominate the development agenda. The ability of Local Economic Development (LED) to empower local people has earned favour with national governments and development theorists. The imperative facing South Africa to achieve a more equitable and sustainable economy is essentially the challenge to adopt and implement a development approach that will reduce poverty and unemployment (which are the two key objectives of LED) to the greatest extent. It is within this context that the South African government has sought to incorporate LED into their economic development framework, predominantly through the decentralisation of development control and planning to the local government level. This study examined the contribution of guest houses to economic growth and employment as key components of LED in a sustainable manner. The study revealed that guest houses are playing a key role in the development of the local economy in the Eden district region. Guest houses are providing employment opportunities to the local residents both on a full-time and part-time basis. Further to this, guest houses are buying many locally-produced products and services from local suppliers and this contributes to economic growth of the local economy. However, this study also found that many of the guest houses in the area are not aware of government incentives available to support them and very few of them have made use of these services. This is something that needs to be addressed if these guest houses are to continue to strengthen the local economy and provide employment opportunities in a sustainable manner. The study revealed that many of the guest houses are operating in an environmentally friendly manner and this will ensure their future sustainability. The broader situation and the contribution of the accommodation sector as critical assets in local and national tourism economies has been thoroughly researched in tourism research around the world. Existing work on the accommodation sector in the South African tourism economy is mainly urban-focused and indicates that its local development impacts can be positive albeit not always maximised through local linkages, however, only a limited amount of academic investigations examines the contribution of tourism sub-sectors to economic growth and employment. The authenticity of this study is based on Its contribution which must be viewed in relation to the relatively limited body of literature in the contribution of tourism sub-sectors to economic growth and employment and in this case guest houses as one type of accommodation sub-sector.
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- Date Issued: 2015
The effects of outsourcing practices conducted by organisations in Nairobi
- Authors: Wachira, Wanjungu
- Date: 2015
- Subjects: Contracting out , Industrial management
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/4988 , vital:20775
- Description: The purpose of this study is to investigate the relationship between outsourcing and development in Nairobi. The key research question for this study is what are the impacts of outsourcing practices conducted by organisations in Nairobi? Data were obtained from questionnaires distributed in December 2010. A total of 85 profit-making firms in Nairobi with a sample of 165 management employees were selected for this study. The empirical findings obtained relate to four outsourcing theories. Transaction Cost Analysis (TCA) Theory focuses on the cost savings that result from outsourcing. Agency Outsourcing Theory centres on outsourcing firms hiring agents to achieve productivity. Hiring agents may result in permanent staff being retrenched and additional outsourcing personnel being contracted and job creation and/or job loss results. Expectation Confirmation Theory (ECT) emphasises the importance of an outsourcing provider conforming to quality management principles. Resource Based Theory (RBT) proposes that organisations need a collection of resources and capabilities to execute outsourcing successfully. Findings further suggested that outsourcing can yield positive and/or negative outcomes depending on risks encountered, the business environment, company policies, function/s to be outsourced, and the competence and commitment of an outsourcing vendor. To further enhance the positive impact of outsourcing three improvements need to be executed: formulation of standard policies, price regulations, and commitment of outsourcing firms in adhering to set contract deadlines. It is suggested that the following would allow organisations to gain more from outsourcing in the future: the adoption of international/offshore outsourcing practices, more commitment by outsourcing consultants, the standardisation of charges for outsourcing contracts, and the use of new technology that would improve how outsourcing is conducted. It is concluded that the positive impacts of outsourcing would foster development to some extent while the possible negative impact of outsourcing would impede development.
- Full Text:
- Date Issued: 2015
The impact of domain knowledge-driven variable derivation on classifier performance for corporate data mining
- Authors: Welcker, Laura Joana Maria
- Date: 2015
- Subjects: Data mining , Business -- Data processing , Database management
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/5009 , vital:20778
- Description: The technological progress in terms of increasing computational power and growing virtual space to collect data offers great potential for businesses to benefit from data mining applications. Data mining can create a competitive advantage for corporations by discovering business relevant information, such as patterns, relationships, and rules. The role of the human user within the data mining process is crucial, which is why the research area of domain knowledge becomes increasingly important. This thesis investigates the impact of domain knowledge-driven variable derivation on classifier performance for corporate data mining. Domain knowledge is defined as methodological, data and business know-how. The thesis investigates the topic from a new perspective by shifting the focus from a one-sided approach, namely a purely analytic or purely theoretical approach towards a target group-oriented (researcher and practitioner) approach which puts the methodological aspect by means of a scientific guideline in the centre of the research. In order to ensure feasibility and practical relevance of the guideline, it is adapted and applied to the requirements of a practical business case. Thus, the thesis examines the topic from both perspectives, a theoretical and practical perspective. Therewith, it overcomes the limitation of a one-sided approach which mostly lacks practical relevance or generalisability of the results. The primary objective of this thesis is to provide a scientific guideline which should enable both practitioners and researchers to move forward the domain knowledge-driven research for variable derivation on a corporate basis. In the theoretical part, a broad overview of the main aspects which are necessary to undertake the research are given, such as the concept of domain knowledge, the data mining task of classification, variable derivation as a subtask of data preparation, and evaluation techniques. This part of the thesis refers to the methodological aspect of domain knowledge. In the practical part, a research design is developed for testing six hypotheses related to domain knowledge-driven variable derivation. The major contribution of the empirical study is concerned with testing the impact of domain knowledge on a real business data set compared to the impact of a standard and randomly derived data set. The business application of the research is a binary classification problem in the domain of an insurance business, which deals with the prediction of damages in legal expenses insurances. Domain knowledge is expressed through deriving the corporate variables by means of the business and data-driven constructive induction strategy. Six variable derivation steps are investigated: normalisation, instance relation, discretisation, categorical encoding, ratio, and multivariate mathematical function. The impact of the domain knowledge is examined by pairwise (with and without derived variables) performance comparisons for five classification techniques (decision trees, naive Bayes, logistic regression, artificial neural networks, k-nearest neighbours). The impact is measured by two classifier performance criteria: sensitivity and area under the ROC-curve (AUC). The McNemar significance test is used to verify the results. Based on the results, two hypotheses are clearly verified and accepted, three hypotheses are partly verified, and one hypothesis had to be rejected on the basis of the case study results. The thesis reveals a significant positive impact of domain knowledge-driven variable derivation on classifier performance for options of all six tested steps. Furthermore, the findings indicate that the classification technique influences the impact of the variable derivation steps, and the bundling of steps has a significant higher performance impact if the variables are derived by using domain knowledge (compared to a non-knowledge application). Finally, the research turns out that an empirical examination of the domain knowledge impact is very complex due to a high level of interaction between the selected research parameters (variable derivation step, classification technique, and performance criteria).
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- Date Issued: 2015
Ultra-high precision machining of contact lens polymers
- Authors: Olufayo, Oluwole Ayodeji
- Date: 2015
- Subjects: Contact lenses , Polymers
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/3001 , vital:20385
- Description: Contact lens manufacture requires a high level of accuracy and surface integrity in the range of a few nanometres. Amidst numerous optical manufacturing techniques, single-point diamond turning is widely employed in the making of contact lenses due to its capability of producing optical surfaces of complex shapes and nanometric accuracy. For process optimisation, it is ideal to assess the effects of various conditions and also establish their relationships with the surface finish. Presently, there is little information available on the performance of single point diamond turning when machining contact lens polymers. Therefore, the research work undertaken herewith is aimed at testing known facts in contact lens diamond turning and investigating the performance of ultra-high precision manufacturing of contact lens polymers. Experimental tests were conducted on Roflufocon E, which is a commercially available contact lens polymer and on Precitech Nanoform Ultra-grind 250 precision machining. Tests were performed at varying cutting feeds, speed and depth of cut. Initial experimental tests investigated the influence of process factors affecting surface finish in the UHPM of lenses. The acquired data were statistically analysed using Response Surface Method (RSM) to create a model of the process. Subsequently, a model which uses Runge-Kutta’s fourth order non-linear finite series scheme was developed and adapted to deduce the force occurring at the tool tip. These forces were also statistically analysed and modelled to also predict the effects process factors have on cutting force. Further experimental tests were aimed at establishing the presence of the triboelectric wear phenomena occurring during polymer machining and identifying the most influential process factors. Results indicate that feed rate is a significant factor in the generation of high optical surface quality. In addition, the depth of cut was identified as a significant factor in the generation of low surface roughness in lenses. The influence some of these process factors had was notably linked to triboelectric effects. This tribological effect was generated from the continuous rubbing action of magnetised chips on the cutting tool. This further stresses the presence of high static charging during cutting. Moderately humid cutting conditions presented an adequate means for static charge control and displayed improved surface finishes. In all experimental tests, the feed rate was identified as the most significant factor within the range of cutting parameters employed. Hence, the results validated the fact that feed rate had a high influence in polymer machining. The work also established the relationship on how surface roughness of an optical lens responded to monitoring signals and parameters such as force, feed, speed and depth of cut during machining and it generated models for prediction of surface finishes and appropriate selection of parameters. Furthermore, the study provides a molecular simulation analysis for validating observed conditions occurring at the nanometric scale in polymer machining. This is novel in molecular polymer modelling. The outcome of this research has contributed significantly to the body of knowledge and has provided basic information in the area of precision manufacturing of optical components of high surface integrity such as contact lenses. The application of the research findings presented here cuts across various fields such as medicine, semi-conductors, aerospace, defence, telecom, lasers, instrumentation and life sciences.
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- Date Issued: 2015
Whither South Africa – neoliberalism or an embodied communitarian indigenous ethic?
- Authors: Konik, Inga
- Date: 2015
- Subjects: Neoliberalism -- South Africa Communitarianism , Literature and society South Africa -- Politics and government -- 21st century
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/21656 , vital:29729
- Description: This thesis offers a critique of neoliberal transformation in South Africa, which process results in growing social inequality and political apathy among citizens. Many scholars have made political-economic and historical analyses of the neoliberal transition, emphasizing structural changes at work at a ‘macro’ level. However, little attention has been paid to changes that have taken place in South Africa at the ‘micro’ level – changes to individual subjectivity and gender codes. That said, the thesis opens by summarizing the above mentioned political-economic accounts of neoliberalism in South Africa, because such works are indispensable to understanding how the regime is embedded within and buttressed by major global institutions. Yet, to achieve a holistic grasp of ‘neoliberal South Africa,’ more is needed. A sociological investigation into the impact of neoliberalism on ordinary people’s self-identification uncovers deep cultural reasons for the continued perpetuation of this unjust political-economic system. Only if it can be understood why people comply with the system in the face of suffering, can effective counter-measures be proposed and implemented over time. This thesis is inherently transdisciplinary. The approach rejects the privileging of one discipline over others, and likewise cautions against collapsing or dissolving disciplines into one another. Instead, recognizing the valuable contribution that each discipline can make to critical scrutiny of a particular issue, a form of methodological transversalism is used to bring different disciplines into dialogue with one another. Following this interplay of structural and subjective analysis, the thesis uncovers the role that consumerism plays in the political neutralization of South Africans. Consumer culture, tied as it is to profitable accumulation, instigates the neoliberal ‘values’ of economistic calculation, competition, and social atomization. This ethos is inculcated in individuals, both at work and during leisure hours. Moreover, consumerism derives much of its power from its ‘sexual sell,’ the creation of fashionable and ‘exemplary’ models of masculinity and femininity. In South Africa, these hegemonic gender models serve to instill competitive individualism while derogating indigenous values. The thesis proposes that in order to counter neoliberal hegemony in South Africa, and begin reclaiming the cultural autonomy of its peoples, it is important to invigorate indigenous communitarian practices and norms. The original contribution of this thesis consists in placing the African ethos of ubuntu in transversal dialogue with global ecological feminist voices. Both political perspectives reinforce a liberatory alternative vision for a future based on principles of embodied relationality, care giving and protection of community.
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- Date Issued: 2015