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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Novel method of improving squirrel cage induction motor performance by using mixed conductivity fabricated rotors (MCFR) / Constantin Danut Pitis

Pitis, Constantin Danut January 2006 (has links)
The ideal squirrel cage motor should have a varying rotor resistance; large at standstill, and decreasing as the speed rises. Overseas - designed high impedance rotors try to fulfil these conditions - mostly used are double cage rotors and die cast aluminium rotors. However, in the South African coal-mining industry these rotors recorded high rate failures with heavy financial losses. As a result, the need for an alternative rotor type that was able to comply with basic conditions ignored before appeared on the market: • Higher reliability with extended life expectancy • Lower total ownership costs • Easy re-manufacturing with components available on the market • Specific performance stability at competitive price. Over the years, only two principles were tacitly accepted in designing squirrel cage rotors: 1. For a single cage rotor, in a circumferential direction around the rotor the squirrel cage bars are placed in the same cylindrical shell, with the same shape and same conductivity. 2. For a double cage rotor, the same rule as above applies; however, in the radial direction, the bars have different shapes and typically different conductivities. The Invention is based on a new principle, i.e. "in a circumferential direction around the squirrel cage rotor, squirrel cage bars may have different conductivities and same shapes, or different conductivities and different shapes”. Mixed Conductivity Fabricated Rotors (MCFR) are designed and manufactured based on this new principle, and are able to withstand the harsh South African mining conditions. Since patented, the invention has been materialised in a set of special rotors powering continuous miners of a reputable coal-mining house, which was spending about R5 million annually on replacing specific imported die cast aluminium rotors only. Fully complying with the above-mentioned basic conditions, the patent offers a large variety of technical and economical advantages, increasing mining processes efficiency beyond expectations. The thesis describes the MCFR's design adaptability by altering the rotor design to meet the demands of a specific engineering application as a base line of drives design. The patent is part of the new South African trend of increasing processes efficiency. It offers large possibilities of designing dedicated motors with a positive impact on the South African economy. Some socio-economical advantages are worthy of considerable study: • Being locally manufactured, the MCFR may reduce the country's economical dependence. • Requiring no special expertise, the MCFR can be produced in any quantity and size without excessive investment. • The MCFR offers an alternative option (product interchangeability) on the market as well as sound competition (with export potential). • The patent ensures business sustainability conditions which diffuse financial constraints on motor manufacturers and end-users during the re-capitalisation process (very loaded in South African economic and industrial environment). / Thesis (Ph.D. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2007.
32

Scarcity and wealth revisited : perspectives on commodity markets in the 21st century

McGill, Sarah Mary January 2014 (has links)
This thesis explores a selection of the ways in which an era of high mineral commodity prices - commonly dubbed the 'super-cycle' of the 2000s - is reshaping the map of global commodity markets. It pursues this agenda through three research aims: (1) to recast the relationship between geophysical resource supply, prices, and markets; (2) to examine some of the institutions that channel and benefit from resource wealth; and (3) to 'open the black box' of the commodity price formation process. The thesis pursues this agenda through four substantive papers, each with its own set of research objectives and findings, and primarily uses the example of phosphate as a vehicle for discussion. The first half of the thesis focuses on the production side of commodity markets. It begins by exploring the multidimensional nature of the concept of resource scarcity, both in its geophysical and socioeconomic aspects, by interrogating a prominent inherited conception of natural resource scarcity: 'peak' natural resources, specifically peak phosphorus discourses (chapter 3). The thesis then carries on the research agenda suggested by this initial study by conducting a field research-based case study of the little-known Moroccan state-owned phosphate mining and fertilizer company, OCP Group (chapter 4). It explores the particular type of principal-agent problem in generating and distributing national resource wealth that national extractive companies (NECs) such as OCP face. The second substantive half of the thesis is concerned with global commodity trading and price formation. It constructs an 'anatomy' of global phosphate markets in order to shed light on the phosphate price formation process (chapter 5). Based on this investigation, the thesis argues that despite the opacity of the processes by which phosphate is priced, an apparent lack of a 'benchmark' or reference price is not necessarily as problematic as market theorists might assume. Finally, the thesis takes a macro-level perspective of the relationship between finance and physical commodity trade by examining the role of financial trading in the governance of commodity markets (chapter 6). Overall the thesis distils the following findings. To begin with, a deeper and more nuanced understanding of the concept of resource scarcity puts short-term price movements as indicators of resource availability into perspective while revealing an unforeseen degree of complexity, as well as certain 'blind spots', in the geopolitical and institutional aspects of resource supply and trading. Second, the power of two particular, less-researched types of institutions that channel and benefit from resource wealth - names, national extractive companies and financial investors - is both less great and different in nature than is commonly assumed. Third, for institutional as well as geographic reasons that are specific to different types of commodities, the commodity price formation process is even further from the joint ideals of market transparency and liquidity than is commonly assumed. Finally, insofar as commodity production and trade can be conceived as part of the 'real economy', it cannot succumb to what is widely feared as the hegemony of 'financial logic'.
33

Technika a způsob těžby uhlí v Československu v letech 1918-1938 / The technology and method of coal mining in the Czechoslovakia in 1918-1938

Jureková, Dominika January 2012 (has links)
The content of this thesis is an analysis of coal mining in Czechoslovakia in 1918-1938. The accent is focused on technical and technological aspects of coal through to economic, political, mining law and other conditions that influence it. The technical part of mining has been for better visibility of work is divided into several stages. The thesis presents a summary of the regions of coal mining, the quantity of extracted coal and methods of coal mining. Keywords: The Czechoslovakia, coal mining, technology, methods of extraction, mining industry
34

A conceptual framework for supply : supply chain systems architecture and integration design based on practice and theory in the North Wales slate mining industry

Radanliev, Petar January 2014 (has links)
The aim of this thesis is to contribute to knowledge in the form of a new theory for supply chain strategy formulation. The objective is to design evaluation criteria, specific to the context of greenfield project architecture and integration design. This study addressed the aim and objective by synthesising existing methods and techniques which are outlined into a research framework of supply chain strategy problems. The study applied the case study and action research methods to pursue conceptual validity from the process of investigating the supply chain strategy formulation in a specific situation and presented the data collection and analysis process. The thesis derived a conceptual framework for investigating and identifying the relationship between multiple elements, dimensions, forces and factors that influence and affect supply chain strategy formulation in a greenfield project context, specific to the mining industry. The contribution to knowledge emerged from building upon the architecture of the conceptual framework, through synthesising existing techniques and adapting these techniques, to extend and redefine the existing knowledge on the practice of supply chain strategy formulation. Through critical analysis, a number of critical problems emerged and the process of addressing these problems, resulted with a new framework for evaluating the relationship between business and supply chain strategy, specific to greenfield project and integration context. The contribution to knowledge also derived from addressing the emerging obstacles in the process of identifying, defining and formulating, the visions and goals of individual supply chain participants from implicit into an explicit form. The process synthesised the knowledge for conceptualising the idea, through developing and evaluating information and issues, to derive insights into the complex and abstract concept, of greenfield project business and supply chain strategy formulation. The conceptual framework and evaluation framework advanced into designing greenfield project supply chain integration strategy. The process involved categorising individual supply chain strategic interests, decisions and problems into formulation areas, and was aimed at defining the process of greenfield project integration strategy as a system of concepts containing formulation areas, formulation principles, segregated into subcategories of formulation imperatives and formulation concepts. The thesis contributed to knowledge with advancement of the design engineering method, which enables visualisation of the supply chain strategy evaluation process. The design is not personalised for individual company business strategy or supply chain strategy formulation. The method was personalised to evaluate the integration of individual goals, and concepts in a supply chain strategy formulation. The novelty that emerged from the thesis was a conceptual framework for greenfield project architecture and integration design. The greenfield project architecture and design derived in the thesis a proposed conceptual system for applying the conceptual framework and the evaluation criteria.
35

Novel method of improving squirrel cage induction motor performance by using mixed conductivity fabricated rotors (MCFR) / Constantin Danut Pitis

Pitis, Constantin January 2006 (has links)
Thesis (Ph.D. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2007.
36

Psychological ability and the risk of human error in the mining industry / Dolly E. Mohlamme

Mohlamme, Eunice Dolly January 2014 (has links)
Local government, as government at grassroot, has, probably undergone transformation more than any institution in post-1994 South Africa. State-of the- art legislation have been passed that have restructured municipalities, and, especially, in the areas of performance and conduct of councillors and officials. Prominent in the areas of transformation are the roles of the Executive Mayor, which are no longer ceremonial as well as the radical changes which have been legislated in municipal financial management. This study was undertaken to determine the challenges that confront the Executive Mayor in financial management in selected local municipalities in the Free State. The hypothesis was formulated that “despite the state-of-the art legislation to regulate municipal finance, Executive Mayors in municipalities face the challenge of poor service delivery as a result of noncompliance to financial statutes due to human resource incapacity”. To test the hypothesis, use was made by empirical research that comprised questionnaires completed by sample of managers and officials in the selected local municipalities of Mafube, Metsimaholo, Moqhaka and Ngwathe.The findings, amongst others, were that: • Human capital in the 4 selected local municipalities are in their prime age. 69 present of managers are in the aged between 30 years to 50 years; • 57 present of the managers responded that they have adequate qualifications and training to pursue the challenges in municipal finance; • All 4 municipalities normally get their budgets approved as required by compliance. • The hypothesis was consequently, invalidated. The study ends with recommendations to help improve standards and quality of financial management practice in the 4 municipalities. / MA (Industrial Psychology), North-West University, Vaal Triangle Campus, 2014
37

Novel method of improving squirrel cage induction motor performance by using mixed conductivity fabricated rotors (MCFR) / Constantin Danut Pitis

Pitis, Constantin Danut January 2006 (has links)
The ideal squirrel cage motor should have a varying rotor resistance; large at standstill, and decreasing as the speed rises. Overseas - designed high impedance rotors try to fulfil these conditions - mostly used are double cage rotors and die cast aluminium rotors. However, in the South African coal-mining industry these rotors recorded high rate failures with heavy financial losses. As a result, the need for an alternative rotor type that was able to comply with basic conditions ignored before appeared on the market: • Higher reliability with extended life expectancy • Lower total ownership costs • Easy re-manufacturing with components available on the market • Specific performance stability at competitive price. Over the years, only two principles were tacitly accepted in designing squirrel cage rotors: 1. For a single cage rotor, in a circumferential direction around the rotor the squirrel cage bars are placed in the same cylindrical shell, with the same shape and same conductivity. 2. For a double cage rotor, the same rule as above applies; however, in the radial direction, the bars have different shapes and typically different conductivities. The Invention is based on a new principle, i.e. "in a circumferential direction around the squirrel cage rotor, squirrel cage bars may have different conductivities and same shapes, or different conductivities and different shapes”. Mixed Conductivity Fabricated Rotors (MCFR) are designed and manufactured based on this new principle, and are able to withstand the harsh South African mining conditions. Since patented, the invention has been materialised in a set of special rotors powering continuous miners of a reputable coal-mining house, which was spending about R5 million annually on replacing specific imported die cast aluminium rotors only. Fully complying with the above-mentioned basic conditions, the patent offers a large variety of technical and economical advantages, increasing mining processes efficiency beyond expectations. The thesis describes the MCFR's design adaptability by altering the rotor design to meet the demands of a specific engineering application as a base line of drives design. The patent is part of the new South African trend of increasing processes efficiency. It offers large possibilities of designing dedicated motors with a positive impact on the South African economy. Some socio-economical advantages are worthy of considerable study: • Being locally manufactured, the MCFR may reduce the country's economical dependence. • Requiring no special expertise, the MCFR can be produced in any quantity and size without excessive investment. • The MCFR offers an alternative option (product interchangeability) on the market as well as sound competition (with export potential). • The patent ensures business sustainability conditions which diffuse financial constraints on motor manufacturers and end-users during the re-capitalisation process (very loaded in South African economic and industrial environment). / Thesis (Ph.D. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2007.
38

Job demands, job resources, burnout and engagement of employees in the mining industry in South Africa / Marthie van der Walt

Van der Walt, Martha Johanna Rieker January 2008 (has links)
The mining industry has been the bedrock of South African economy for more than a century, making an important contribution to employment opportunities, the gross domestic product and export earnings in the South African economy. Globally the mining industry is faced with a shortage of qualified talent to meet its production needs. Every year there are more people leaving than entering the mining industry to pursue job and career opportunities. The mining industry has to focus a lot on safety and health, training and development programmes, team building initiatives, and the recruitment and retention of affirmative action candidates in order to retain their valued staff. The mining industry also has to achieve production targets while at the same time assure that its employees are safe and happy workers. Therefore happy, productive and motivated employees are an important contributor to the stability and development within the mining industry. The objective of this study was to determine the relationship between job demands, job resources, burnout and engagement of employees in the mining industry. The research method consisted of a literature review and an empirical study. A cross-sectional survey design was used to collect the data. An availability sample (JV=199) from employees in the mining industry was taken. The Job Demands and Resources Scale (JDRS) (was used to measure job demands and job resources), the Utrecht Work Engagement Scale (was used to measure engagement) and the Oldenburg Burnout Inventory (was used to measure burnout). Descriptive statistics, product-moment correlation coefficients and multiple regression analyses were used to analyse the data. The statistical analysis was carried out with the help of the SPSS programme. The results of this study indicated that job resources, namely organisational support (including the relationship with superiors, role clarity, information, communication, and participation) are positively related to growth opportunities (including variety, opportunities to learn, and autonomy), advancement and social support. Multiple regression analysis showed that the best predictors of engagement were organisational support, growth opportunities and work-life balance. The best predictors of disengagement were lack of resources, including growth opportunities and social support, and demands of overload and a lack of work-life balance. The predictors of burnout were overload and a lack of advancement opportunities Recommendations for future research are made. / Thesis (M.A. (Industrial Psychology))--North-West University, Potchefstroom Campus, 2009.
39

A platinum life cycle assessment : potential benefits to Anglo Platinum / I. Caddy.

Caddy, Irene January 2011 (has links)
There has been an increased awareness of the inter-dependence between man and the environment since the 1960’s. Environmental awareness has evolved from representing fairly radical views opposing all development, to a current emphasis on sustainable development between development and the environment. Life Cycle Assessment (LCA) is defined as the identification and quantification of the environmental impacts of a product, process or service during the entire life cycle being studied. The life cycle starts at the extraction of raw materials and the production of energy used to create the product through the use and final disposal of the product. LCA therefore considers the production, use and disposal of a product, which constitutes the life cycle of the product. LCA can be combined with methodologies that study other parameters such as costs in order to optimise the benefits from LCA. It is suggested that cost implications of processes to reduce environmental impacts should be included in a methodology used for a Platinum LCA. A comment that is consistently raised in the case studies is that the minerals industry regards LCA as an effective tool to determine the impacts of the industry, however extraction & beneficiation of minerals are often grouped together, with accurate data not being available, and databases either not available or not updated. The case studies indicated several benefits from the various LCA’s conducted. A Platinum LCA should clearly define and group the environmental impacts being studied into categories such as greenhouse gas emissions, global warming, acidification, and resource consumption. A Platinum LCA will be resource- and time intensive due to the large scale of the processes involved. It is suggested that a Platinum LCA firstly focuses on the production phase, i.e. cradle-to-gate, with potential future work done on the use and end-of-life stages. It is suggested that individual facility-based LCA’s for AMPLATS and other platinum producers are conducted in order to get a true reflection of the environmental burden of each company, and then selectively share technological improvements to reduce the environmental burden without disclosing sensitive information. The benefit of LCA in the case of platinum will be optimised if it can be used to make business decisions, together with consideration of financial and production benefits in addition to anticipated environmental benefits of alterations to processes. It is essential that LCA is seen as a business tool that will assist the company to make informed business decisions about process improvements, as well as new projects and design of new facilities. LCA on its own will not determine which product or process is the most cost effective or works best. The information developed in a LCA study should be used as one component of a more comprehensive decision making process assessing the trade-offs with cost and performance. The results from a LCA could be used to make informed decisions about optimisation between costs and reduced environmental impacts. / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2011.
40

Job demands, job resources, burnout and engagement of employees in the mining industry in South Africa / Marthie van der Walt

Van der Walt, Martha Johanna Rieker January 2008 (has links)
The mining industry has been the bedrock of South African economy for more than a century, making an important contribution to employment opportunities, the gross domestic product and export earnings in the South African economy. Globally the mining industry is faced with a shortage of qualified talent to meet its production needs. Every year there are more people leaving than entering the mining industry to pursue job and career opportunities. The mining industry has to focus a lot on safety and health, training and development programmes, team building initiatives, and the recruitment and retention of affirmative action candidates in order to retain their valued staff. The mining industry also has to achieve production targets while at the same time assure that its employees are safe and happy workers. Therefore happy, productive and motivated employees are an important contributor to the stability and development within the mining industry. The objective of this study was to determine the relationship between job demands, job resources, burnout and engagement of employees in the mining industry. The research method consisted of a literature review and an empirical study. A cross-sectional survey design was used to collect the data. An availability sample (JV=199) from employees in the mining industry was taken. The Job Demands and Resources Scale (JDRS) (was used to measure job demands and job resources), the Utrecht Work Engagement Scale (was used to measure engagement) and the Oldenburg Burnout Inventory (was used to measure burnout). Descriptive statistics, product-moment correlation coefficients and multiple regression analyses were used to analyse the data. The statistical analysis was carried out with the help of the SPSS programme. The results of this study indicated that job resources, namely organisational support (including the relationship with superiors, role clarity, information, communication, and participation) are positively related to growth opportunities (including variety, opportunities to learn, and autonomy), advancement and social support. Multiple regression analysis showed that the best predictors of engagement were organisational support, growth opportunities and work-life balance. The best predictors of disengagement were lack of resources, including growth opportunities and social support, and demands of overload and a lack of work-life balance. The predictors of burnout were overload and a lack of advancement opportunities Recommendations for future research are made. / Thesis (M.A. (Industrial Psychology))--North-West University, Potchefstroom Campus, 2009.

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