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Bibliography: leaves 178-188. / An outline of the main features of the West Coast environment establishes that it has potential value for recreation, tourism and nature conservation,in addition to that of diamond mining, and that it is sensitive to disturbance. The diamond mining process is analysed and mining actions that cause environmental impact are identified. A matrix approach is employed to relate particular mining actions to specific environmental elements. It is found that there is major impact on scenic and vegetation elements and that primary impact is magnified significantly through the process of wind erosion. It is argued that much environmental impact can be prevented if the objective of environmental protection was incorporated into the management of mine sites and that unavoidable impact can be mitigated by rehabilitation,which is a reasonable requirement.

A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 1993. / Since the discovery of diamonds in South Africa, Government has played an active role in the establishment of a local processing industry, aimed at the adding of value to locally mined rough diamonds. This study evaluates the influence of Government support and regulation in the performance of South Africa's diamond industry. Statistics were supplied mainly by the South African Diamond Board, the Minerals Bureau and the departments of Finance, and Trade and Industry. Discussions with prominent diamantaires were also undertaken to contrast statutory reporting with informally sourced facis. South Africa's diamond industry undetperforms, particularly the processing industry which benefits from State support at the expense of the other diamond sectors. Government's indirect support of the processing sector cannot be justified in view of its dismal performance. The entire diamond industry should be deregulaled, and State involvement in the processing sector (with special emphasis on the taxation structure) re-evaluated. / GR 2016

With sub-micrometric form accuracy and nanometer scale surface roughness, the diamond turning process provides a great solution of fast prototyping optical systems with aspheric or freeform surfaces. On the other hand, with relatively lower cost and lighter weight, optical plastics are now widely used in consumer products. To study and optimize the cutting parameters of the diamond turning process on optical plastics, a series of tests with different cutting parameters settings are conducted on seven different optical plastic materials: E48R, OKP1, OKP4, OKP4HT, PC, PMMA, and Rexolite 1422. The relationship between the surface roughness and optical plastic materials is found, and the optimized cutting parameters are recommended.

A thesis submitted to the Faculty of Commerce, Law and Management, University of the Witwatersrand in fulfilment of the requirements for the degree of Doctor of Philosophy / Lack of common understanding of corporate reputation in the diamond industry in South Africa has attracted a lot of interest in this aspect of the mining industry. The recent Marikana Massacre in the platinum belt in the Rustenburg area at Lonmin Mine in 2012, together with on-going debates on resource nationalisation and negative relations between mine communities and diamond mining companies have prompted the call for more research in reputation management in the mining industry in South Africa. The purpose of this research is to define the meaning of corporate reputation in the diamond industry, to understand key perceptions of the diamond industry, to identify key effects of corporate reputation in the diamond industry and to evaluate key management approaches to corporate reputation in the diamond industry from multi-stakeholder perspectives. Mixed methods research methodology was used in this study, comprising quantitative and qualitative data collection and data analysis. Key findings include that there is no one single definition of corporate reputation. Each stakeholder has his/her unique definition which is based on his/her own assessments of the organisation, the past and future actions of the corporation, and their experience and perception of the organisation. Poor relations between mine communities and diamond companies; prospects for the collapse of the Kimberley Process (KP); violent strikes; environmental issues, including rehabilitation of old mines; poverty and high unemployment in the mining communities; failure of BEE transactions in delivering real value to the mine employees and local communities; illegal mining; the rise of synthetic un-natural diamonds and negative perceptions of the diamond industry in South Africa are the current major challenges and risks affecting the diamond industry in South Africa. This study concludes that positive corporate reputation would result in improved investor confidence, higher levels of attracting and retaining top level talent in the organisation, improved attraction of customers, better relations with communities and improved stakeholder relations. The study did not find evidence proving that a positive reputation will result in higher prices for diamond products. It found that corporate reputation management initiatives in the diamond industry are not well understood and, as a result, they are not delivering the full results as expected. ii | P a g e Effective stakeholder relations management with a special focus on community engagement including youth groups’ involvement in the mining towns; targeted social investment programmes with special focus on enterprise development and effective management of industry perceptions are identified as the most critical steps to be adopted in the diamond industry in order to improve its reputation. / GR2018

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Micro cutting is becoming increasingly important since miniature and micro components/products have become more and more demanded in precision engineering applications and consumer goods in a daily life. Meanwhile, it has not been thoroughly investigated yet. Scientific understanding of the fundamentals in micro cutting mechanics and physics is vital for micro manufacturing of micro or miniature components and products. Consequently, the scientific investigation on micro cutting mechanics is critically needed, particularly on its key fundamental aspects on which a systematic approach and key enabling technologies are developed for micro manufacturing. Therefore, three key fundamental aspects of micro cutting mechanics have been identified for this PhD project and a comprehensive systematic research has been performed through both theoretical and experiment-based investigations. The three aspects of micro cutting mechanics mainly include dynamic stiffness investigation, innovative micro cutting force modelling, and the study on micro cutting heat, temperature and their partitioned distribution. All experiment-based investigations are undertaken on a diamond turning machine test rig supported with a fast tool servo (FTS) using different reconfigured experimental setups. The finite element (FE)-based analysis is conducted to further support the in-depth analysis on the micro cutting phenomena especially the modelling and simulation of micro cutting force and temperature. Accordingly, both micro cutting force modelling and micro cutting temperature are investigated using modelling and simulation supported by well-designed experimental cutting trials and validations. The investigation on dynamic stiffness in the micro cutting system is focused on its effects on the micro cutting process and its control strategies. The burrs formation and machining accuracy are explored in relation with control of the dynamic stiffness. Furthermore, the control algorithm for dynamic stiffness is developed accordingly in order to minimise burrs formation and stabilize the micro cutting accuracy. The micro cutting force modelling is performed based on specific cutting force, i.e. modelling the cutting force at the unit cutting length or area as coined as the amplitude aspect of the proposed cutting force modelling. The cutting force against a dynamically varied cutting time interval is proposed as the spatial aspect of the cutting force formulation. The amplitude aspect can provide the insight into the micro cutting phenomena particularly in relation with the chip formation and size-effects. The spatial aspect, using a on the wavelet transform (WT) technique and standard deviation analysis can render the dynamic behaviour of the micro cutting force, particularly representing the dynamic effects of the cutting process and its correlation with tool wear. The micro cutting temperature is investigated to formulate the scientific understanding of cutting temperature, heat and their partitioned distribution particularly at the tool-workpiece-chip interface zone in ultraprecision and micro cutting using a diamond cutting tool. The contribution to knowledge at this aspect is to represent the partitioned cutting heat in the micro cutting process and their different behaviours compared to the conventional metal cutting. The scientific approach to modelling micro cutting application (MMCA), i.e. based on modelling-simulation combined with experimental validation, is further evaluated and validated to illustrate the overall benefits of this research investigation through micro cutting of single crystal silicon (for ultraprecision machining of large-sized infrared devices). This approach is established in light of combining all the three aspects of the above investigation on micro cutting mechanics. The research results show the approach can lead to industrial scale advantages for ultraprecision and micro cutting but driven by the scientific understanding of micro manufacturing technology. The systematic investigation on dynamic stiffness control, micro cutting force modelling, micro cutting heat and temperature and their integrated approach can contribute well to the future micro cutting applications.

published_or_final_version / Business Administration / Master / Master of Business Administration

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