• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 5952
  • 225
  • 8
  • 4
  • Tagged with
  • 14109
  • 1856
  • 1704
  • 873
  • 871
  • 738
  • 593
  • 588
  • 558
  • 544
  • 437
  • 421
  • 387
  • 358
  • 319
  • 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.

Plasma gasification of organic waste

Makaringe, Nkateko Petra 2017 (has links)
Four biomass materials, namely peach pips, pine wood, bamboo and Napier grass, and one example of chemical waste, lithium hexafluorophosphate (LiPF6), were studied. The biomass types were selected because they were easily accessible locally. The LiPF6 waste is solidified in poly(methyl methacrylate) (PMMA). Gasification of this solid is of interest to industry. Prior to the gasification studies, TGA-FTRI analyses were conducted on the biomass samples. This was done to study their thermal behaviour under nitrogen as well as under oxygen. The results indicated that, in general, pyrolysis of biomass takes place in three stages, namely hydration, active pyrolysis, and passive pyrolysis. These stages occur at different temperatures depending on the type of biomass as well as the heating rate used. The conversion efficiency of these materials is increased under oxygen, due to the fact that combustion takes place in the presence of oxygen, either partially or fully, depending on the amount made available. TGA results obtained under nitrogen were used to compute the kinetic parameters of each biomass material. Because their fluffy nature led to feed problems, bamboo and Napier grass were excluded from the plasma gasification experiments. Results obtained during the gasification of peach pips and pine wood indicated that conversion efficiency slightly increases with an increase in temperature. Feed rate seemed to have minimal effect on both conversion efficiency and gas concentration; the energy conversion efficiency did, however, improve. The conversion efficiencies obtained by TGA and by the plasma system, were roughly similar. Due to the higher temperatures, ~ 1000 °C, of the plasma reactor, the gaseous products obtained were predominantly carbon monoxide and hydrogen. On the other hand, carbon dioxide predominated in the TGA-FTIR experiments. Only a slight trace of monoxide was observed. Plasma treatment of PMMA encapsulated waste LiPF6 also yielded carbon monoxide and hydrogen as main products. The energy conversion efficiency observed for the plasma process was 30 40 %. This value is ratio of the combustion enthalpy of syngas yield and the electrical energy input into the plasma torch. The main heat loss was via the torch anode. This may be corrected by an improved thermo-mechanical design. Dissertation (MSc)--University of Pretoria, 2017. Chemical Engineering MSc Unrestricted

An insider-outsider's exploration of planning knowledges roles uses and construction in a post-1994 metropolitan setting : eThekwini Municipality

Moonsammy, Subhatri Tholsie 2017 (has links)
The 21st century calls for new approaches to urban planning theory and practice, in the context of failed but unchanging approaches to planning (UN-Habitat, 2009). What is increasingly clear is that there is an urgent need for the 'worlding' of planning epistemology, theory and practice to emerge from within a context, a place that considers the real, the practical, the basic and the strategic essentials beyond the generalisations of theory and practice that emerge from elsewhere (Roy, 2009; Parnell, 2016). This research draws from practice within the global south, from an important and ordinary city, Durban, South Africa. It delves into the everydayness of planning practice - it explores and uncovers the importance of land use planning knowledge as a point of focus, confrontation and an opportunity to (re)think practice. The research identifies planning knowledges as a deliberate 'space' and a future research agenda to theorise from and for planning practice. A multi-conceptual framework was used in this research, in a practical and advocacy manner to guide and make sense of the empirical findings. In particular, communicative planning theory, institutionalism, the culturisation of planning, power and rationality, and phronesis proved to be useful and relevant. The research uncovers the narrow and 'expert' defined approach to constructing land use planning knowledges, professionally and institutionally. It reveals the many roles of such knowledge, in particular the spatial development framework, lower levels of spatial plans and town planning schemes. The research also uncovers the philosophy, ideology, interests, agendas, relationships, power, conflicts and compromises embedded in the (re)development of land use planning knowledge for practice. It both confirms and 'maps' the social relations involved in the (re)development of planning knowledges for practice, including the making of national and local government planning legislation. Multiple qualitative research methods were used in this research, including institutional ethnography, focus groups, and the review of key documentation and interviews with a multiplicity of stakeholders. Beyond understanding the contemporary dynamics of land use planning knowledge in practice, the research explored what a multiplicity of stakeholder knowledges could mean for planning. What emerged are two very separate planning ideologies. The first is steeped in traditional planning concerns, informed by the planning profession both within and outside the municipality, where 'more of the same' is advocated - planning with more clout, more or better legislation and improved linkages to municipal budgets. Conversely, a new planning ideology arises from engaging with a multiplicity of stakeholders and their knowledges, where knowledge is practical and engages with realities of African urbanism, and continues to confront traditional planning approaches and waits to be recognised. In giving importance to this alternate ideology and belief system for planning, the society that lives, uses and negotiates the production of space as a daily occurrence is considered and in doing so, new planning opportunities and theorisation for practice emerge as possibilities. The study concludes with a contribution to local situated planning theory, recognising a local version of communicative planning theory. The study offers a theoretical framework that connects and integrates African urbanism, planning theory and planning practice. In theorising with and for planning practice, the study concludes with a theoretical framework for land use planning, as a dominant and everyday experience of municipal practice. In addition, the research nuances and enriches dominant themes in planning theory. Finally, the study demonstrates empirically the use of and exploration with social science research; and its possibilities to identify multiple actors and knowledges as an opportunity to create practice-informed relevance in planning. Thesis (PhD)--University of Pretoria, 2017. Town and Regional Planning PhD Unrestricted

Information monitoring and current awareness services supporting the information behaviour of pregnant women

Akanbi, Olubukola Mercy 2017 (has links)
The future of any society lies with the unborn and young children of that generation: pregnant women are an important part of any society because the outcome of any pregnancy directly affects the hope and future of any society. Provision of reliable pregnancy-related information to pregnant women is especially important if the outcomes of these pregnancies are to be healthy. Africa, particularly Southern African nations, has in the past years recorded a high number of maternal and infant mortality rates, prevalence of HIV/AIDS, diverse forms of abuse, poverty and the increased incidence of communicable and non-communicable diseases. These problems also affect pregnancies. Information monitoring and current awareness services could assist with the promotion of patient-centered healthcare systems, provision of reliable and new information and a decrease in the maternal and infant mortality rate through the provision of relevant pregnancy-related information to pregnant women. The data for this study was collected over a period of three months (between August and October 2015). The study involved pregnant women visiting two private medical practices of gynaecologists in Pretoria, South Africa. An explanatory sequential design mixed methods research was adopted for the study (involving both quantitative and qualitative approaches in data collection and analysis). Thirty-seven pregnant women were given copies of the questionnaire to complete and eleven of the thirty-seven were interviewed for the purpose of providing in-depth understanding and explanation of the participants' experiences. The McKenzie two-dimensional model of information practices in everyday life information seeking (ELIS) guided this study. Findings from the study show that pregnant women have some unique information needs regarding specific uncertainties about their pregnancies, among others on how age can affect their pregnancy because of the possibility of Down syndrome, high-risk pregnancy and the well-being of the fetus. There are also many overlaps in information needs, such as needs for information on breastfeeding, safety and well-being of the fetus, medication, diet and supplements, to mention a few. The study confirmed that pregnant women need information throughout and after the pregnancy, hence they desire information on an on-going bases. Problems pregnant women encounter when seeking for information include contradictory and/or unclear advice and information from their information sources, feelings of embarrassment to ask questions on pregnancy, insufficient discussion time with their healthcare providers and lack of access to information sources other than the internet. The study found that current awareness services and information monitoring could benefit pregnant women, because they showed interest in receiving new pregnancy-related information on safety during pregnancy, new trends regarding pregnancy, experiences and advices from other mothers. They also desired to be updated about free access to pregnancy-related information in order to meet their pregnancy-related information needs on among others medication, diet and supplements, disease and treatment, labour and method of delivery. This study adapted the McKenzie two-dimensional model of information practices in ELIS adding two other modes of information seeking (namely directed monitoring, passive and accidental encountering). In addition, two new models were developed in the course of the study to deal with key activities of information behaviour that stood out from the findings of this study and pregnant women's pre and postnatal information needs and potential of information monitoring. This study recommends that information monitoring and current awareness services should promote monitoring of new information and generate more reliable health information for pregnant women at little or no cost for the purpose of staying abreast with new information, which could assist in reducing their uncertainties about pregnancy. More consideration should be given to mobile devices as a channel of communication with pregnant women and for information monitoring. This study also recommends more investigation into both expressed and unexpressed information needs of pregnant women in a social context, taking positioning theory into consideration. Social context could further reveal the ELIS of pregnant women. Social context tends to shed light on the area of needs of pregnant women especially through their discussions with other people (chatting). In addition, their discursive interactions with other people especially their healthcare providers and family members can reveal the relevant health topics or pregnancy-information needed. Dissertation (MIS)--University of Pretoria, 2017. Information Science MIS Unrestricted

Strategy for South African public libraries to bridge the digital divide

Mphidi, Hamilton Hamilton 2017 (has links)
This thesis reports on a study that investigated the role of public libraries in addressing the digital divide in South Africa. The study started in 2006. This study addressed the main research question: "How should a theoretical model look for South African public libraries to contribute to bridging the digital divide?" The central research problem was further addressed by asking the following questions: • What are the scope and implications of the digital divide? (These include the meaning of the concept, the dimensions and the factors leading to the digital divide.) • What has been reported on the role of libraries (including information services) in bridging the digital divide? • What have libraries in South Africa done to address the digital divide, and which possibilities are foreseen? • How can South African libraries be positioned to contribute to bridging the digital divide? The study followed a survey method using interviews with directors of Provincial Library Services (or their representatives), which are the controlling bodies of public libraries in South Africa, questionnaires distributed to representative staff members of participating public libraries in Gauteng, Limpopo and KwaZulu-Natal and individual interviews with selected heads/representatives of public libraries in Gauteng, Limpopo and KwaZulu-Natal. Data collected through the questionnaires were both quantitative and qualitative. Data was collected between 2011 and 2012. Quantitative data were analysed using Statistical Package for Social Sciences (SPSS), while qualitative data from interviews were analysed by content analysis and thematic categorising of information. In October 2015 a follow-up study of limited scope was conducted with three representatives from the three provincial library services to establish developments since the first round of data collections. Seven out of nine directors of Provincial Library Services in South Africa participated in the study. Furthermore, 247 public libraries from Gauteng, Limpopo and KwaZulu-Natal out of 463 public libraries and 18 heads/representatives of public libraries participated in this study. Findings on the opinions expressed on the role of public libraries in bridging the digital divide include the following: providing access to information and communication technologies (ICTs), offering information literacy and ICT literacy training, providing information to reduce the gap between "haves" and "have-nots", providing communities with equal, free access, reaching out and spreading ICTs to those who may not have online access and support and facilitating and promoting information exchange and communication between citizens and the government. The overall findings from the study were that although provincial library services have documents containing information on their mission and vision, their mission and vision statements do not address the digital divide or shed any light in this regard. The study found that provincial library services aimed to support public libraries to provide information resources, services to communities and access to information through ICT via targeted fund transfers to municipalities. None of the provincial library services included in the study had an explicit policy and strategies aligned to its vision and mission to guide and enable it in addressing the digital divide. Although all provincial library services included in the study had access to computer facilities in their headquarters, there were still disparities in the number of computer facilities available. It was also found that none of the provincial library services had its own website at the time of the study. They depended on the websites of their parent organisations. The study found that very few provincial library services had information technology (IT) units/departments charged with the responsibility of taking care of ICT facilities. They depended on external ICT service providers or the IT departments of their parent organisations to maintain the library's ICT infrastructure. Thesis (PhD)--University of Pretoria, 2017. Information Science PhD Unrestricted

The development of a thermoplastic road marking material standard

Naidoo, Soma 2017 (has links)
Public roads without road markings, especially roads carrying high traffic volumes, would lead to chaos and accidents resulting in injuries and loss of life. The road authorities need to ensure that all signage is well maintained and conforms to the Southern African Development Community Road Traffic Signs Manuals (SADC RTSM) (1999) and the South African Road Traffic Signs Manuals (SARTSM) (1999). The most important aspect of road markings is that they must be retroreflective. The minimum RL for white and yellow road markings is 100 mcd/m2/lx and 70 mcd/m2/lx respectively (SADC RTSM, 1999). There are other important parameters to which road markings should conform, such as the Qd, colour and skid resistance. There are various types of road marking paints and road marking materials, namely solvent-borne, water-borne, cold plastic, thermoplastic and preformed tape applied universally. In SA, solvent-borne paints, water-borne paints and thermoplastic materials are widely used, with cold plastic materials being increasingly used of late. There are SABS standards on solvent-borne and water-borne road marking paints covering a wide range of aspects. However, there are insufficient standards on plastic road marking materials and therefore some road marking applicators could be applying inferior quality plastic road marking materials. The only specification related to thermoplastic road marking materials published by the SABS is the SABS EN 1424:1997 (1997) (Road marking materials - premix glass beads). This specification was adopted by the SABS exactly as per the European Standard EN 1424:1997 (1997) and it specifies the requirements for laboratory tests on aspects of premix glass beads such as the granulometry, refractive index, chemical resistance, quality and surface treatment. Since the European specifications are widely adopted by many countries, the BS EN 1436:2007 (2007) specification was used in conjunction with the available SA standards in this study to develop the thermoplastic road marking standard. It is more advantageous for the road authority to stipulate the specifications with which road marking products must comply than to give the detailed specification of each constituent. It would be time consuming and costly to test each constituent, besides which the equipment to test the constituents is not readily available in SA. The onus should be on the manufacturer to ensure that the formulation of the road marking material is such that the product meets the required specifications. The service life of road markings is affected by volume and type of vehicles passing over them, the type of road surface, sand and dirt, climatic conditions and application of the road markings. On clean roads, both asphalt and chip seal surfaces, thermoplastic road marking materials have longer RL and Qd service lives than water-borne road marking paints. The white road marking paints and materials generally complied with the colour specification. However, the yellow road markings complied minimally with the colour specification on both clean and dirty roads. Although thermoplastic road marking materials have a longer RL service life on clean roads, it might not be economical to use them on dirty roads since the RL service life was similar for water-borne road marking paints and cold plastic road marking materials. The initial skid resistance of white and yellow 1.2 mm thermoplastic complied with the specification. Dissertation (MSc)--University of Pretoria, 2017. Civil Engineering MSc Unrestricted

Analysis of conflict in managing sectional title properties

Ndala-ka Dlamini, Nathaniel 2017 (has links)
The aim of this study was to establish whether or not conflict existed in residential sectional title schemes and if so the causes thereof. Residential sectional title properties, unlike conventional residential freehold properties, imposed co-ownership, co-management and expense sharing amongst owners in this type of development. This means that owners in this development are not just owners of sections that they purchased and exclusively occupied, but they were also jointly responsible for the administering, controlling and managing of the common property in the scheme in which they had become owners. This dissertation revealed that, despite their popularity, sectional title properties might be marked by conflict which can affect the smooth and efficient operation of this type of property ownership. Causes of conflict include violation of the scheme rules by owners or residents, trustees' failure and/or refusal to adhere to their bodies' corporate rules, conditions or restrictions, financial mismanagement or misappropriation by the trustees and managing agents, power struggle amongst individuals over the control of the body' corporate resources, lack or poor understanding, amongst owners and their trustees, of how this type of development works, and disrespect of the bodies corporate and its members by their managing agents. This study suggests compulsory information disclosure to prospective and current owners regarding the requirements and obligations of owners in this type of development. Further, that there should be regular and compulsory trainings for the trustees. Accordingly, the study suggests how conflict in multi-owned properties can be mitigated and ensured that the ownership of this type of property can be protected. Dissertation (MSc (Real Estate))--University of Pretoria, 2017. Town and Regional Planning MSc (Real Estate) Unrestricted

A system dynamics approach to managing project risks in the electricity industry in sub Saharan Africa

Ogano, Noah Omondi 2017 (has links)
In Africa, major projects are presently in progress to upgrade and expand energy sector infrastructure. Many such projects have run into delays, quality problems and cost overruns. To overcome these challenges, Governments in the region have devoted effort and resources in seeking to improve the management of energy sector projects in many countries in the continent. The objective of this research was to develop a means and method by which risk can be better managed in projects in the electricity energy sector in Kenya and the Sub Saharan Africa region. The research focused on risks prevalent in the electricity sector projects in the region from which a System Dynamics model that mirrors the prevailing dynamics in the sector was developed. Views from key stakeholders in the industry in Kenya such as contractors, utility companies and the Ministry of Energy officials were solicited through an exploratory study that gave rise to the conceptual System Dynamics model developed in this research. The primary motivation of the research was to expand the understanding of the dynamic interaction of risks in the electricity energy sub-sector by focusing on the dynamics of projects in the electricity power industry in Sub Saharan Africa. System Dynamics was chosen as the modeling and simulation tool based on insights from literature that revealed that projects in the electricity industry can be framed as complex dynamic systems since they comprise multiple interdependent and dynamic components, and include multiple feedback processes and non-linear relationships. A qualitative research approach was used in the research study, designed as a guided participative cooperative enquiry based on active interviewing as well as use of archival data from previous projects. The new basic model developed in this research was presented to a workshop comprising experts in the power industry in Kenya, where the model structure and the simulation results were shared with the participants in a discussion forum. The results from the workshop indicated that the simulation results from the model mirrored the reality of project dynamics in the industry in Kenya, and by extension, the wider Sub Saharan Africa region. The results indicated that the forces that cause project delays and quality challenges in the electricity sector in Kenya include a shortage of testing / commissioning engineers that lead to multitasking and late discovery of tasks that require rework. Political risk, unforeseen technical difficulties as well as below average project management skills also featured prominently during the workshop discussions. Various policy scenarios arising from experimentation on the new model were explored and analyzed in the research. The results of the policy scenario analysis show that by employing more competent project managers and engaging of skilled testing and commissioning engineers in adequate numbers, projects in the sector will likely finish on time and with improved quality. The study also reveals that inclusion of an insurance component in the procurement process for the project contractors can be used to mitigate the effects of political risk, and that spreading the workforce, rather than having a skeleton workforce at the beginning of the project, would be more desirable as it would help eliminate effects associated with multitasking that contribute to project delays. This research contributes to new knowledge by expanding and extending the previous model by Richardson (2013) through the inclusion of political risk, project management competence, unforeseen technical difficulties and an insurance index to derive scenarios that can be used to reduce project delays and improve on quality of the completed project. Thesis (PhD)--University of Pretoria, 2017. Graduate School of Technology Management (GSTM) PhD Unrestricted

High pressure feedwater heaters replacement optimisation

Pieterse, Casper 2017 (has links)
Widespread uncertainty exists regarding the ideal replacement time of installed feedwater heaters in coal fired power plants. Eskom consequently identified the need for this research project to find the optimal age at which to replace high pressure (HP) feedwater heaters. Previous work has failed to quantify the unique financial risk of tube failures, which varies for individual heaters. Using life cycle cost (LCC) methodology, a framework is developed for the optimisation of the HP feedwater heater replacement age in Eskom coal fired power plants and integrated into existing software used in the organization. This entails identifying the most significant cost factors involved in the lifecycle of HP heaters and determining how they evolve over time by conducting a case study. Minimum life cycle cost for an actual HP heater is calculated in the case study based on failure data and cost information supplied by the power plant. This optimisation of replacement time can realise significant savings in annualised LCC compared to current practice. Dissertation (MEng)--University of Pretoria, 2017. Mechanical and Aeronautical Engineering MEng Unrestricted

Investigating the stage-gate model as a research and development implementation process in modernising the mining industry

Preis, Eugene Pieter 2017 (has links)
In recent years, innovation in the mining industry has shifted from being a non-essential business activity to a necessity. Key challenges in the last decade (such as declining ore grades and increased mining costs) have forced companies to focus on innovative business initiatives in order to gain incremental cost and productivity improvements. These key challenges have placed the mining industry in a difficult position they are substantial and in many cases, complex in nature. In order to ultimately solve (and not merely mitigate) these challenges, fundamental innovation step-changes are required. The success of the potential implementation of these changes is to rethink the "starting point" of innovation, namely the research and development (R&D) strategy and process. Contrary to popular belief, innovation does not occur spontaneously. It is, in the majority of cases, a product of meticulous planning, thinking, testing, iteration, and implementation. This study investigated the Stage-Gate model as a potential R&D implementation process in solving the aforementioned challenges, and ultimately modernising the South African mining industry. The study focused on firstly deriving a skeleton Stage-Gate model, in order to conduct further research into the associated key gate criteria, stage activities and critical success factors. The research findings were used to develop a proposed Stage-Gate model, which was then assessed at the hand of a South African mining case study (Missing Person Locator System). From the research findings, proposed Stage-Gate model and the case study evaluation, it was generally concluded that the Stage-Gate model has the potential to assist in the successful modernisation of the South African mining industry (SAMI), through focused R&D efforts into the industry's key problem areas and challenges. The study further recommended that in general, the outcomes of the study should be used to conduct R&D in the SAMI, in order to more effectively and efficiently conduct R&D in the SAMI (and ultimately modernise the SAMI). Lastly it was suggested that the outcomes of the study (and in particular, the proposed Stage-Gate model) be tested through conducting an actual R&D effort into a new value proposition. The actual application of the proposed model will reveal the degree of value that the Stage-Gate approach could deliver, and could serve as proof that the Stage-Gate model and approach can work as a tool in modernising the SAMI. Dissertation (MEng)--University of Pretoria, 2017. Mining Engineering MEng Unrestricted

Investigation of turbulent heat transfer and pressure drop characteristics in the annuli of tube-in-tube heat exchangers (horizontal lay-out)

Prinsloo, Francois P.A. 2017 (has links)
Tube-in-tube heat exchangers are commonly used in many applications and are generally operated in a counterflow configuration. Unfortunately, existing correlations developed for heat transfer and pressure drop predictions for the outer annular flow passage have been found to sometimes produce large discrepancies between them. In this experimental study research was performed to obtain experimental data with the lowest possible uncertainties associated with it in order to validate existing correlations and to identify the core aspects that influence the heat transfer and pressure drop characteristics in annular flow passages that have neither uniform wall temperatures nor uniform wall heat fluxes. Focus was placed on the turbulent flow regime and temperature and pressure drop measurements were taken at different fluid velocities, annular diameter ratios, and inlet temperature of water. Four horizontal test sections with annular diameter ratios of 0.327, 0.386, 0.409 and 0.483 and hydraulic diameter of 17.00, 22.98, 20.20 and 26.18 respectively were constructed from hard drawn copper tubes. The test sections were equipped with industry standard inlet and outlet configurations and had pressure drop lengths of between 5.02 m and 5.03 m and heat transfer lengths of between 5.06 m and 5.10 m. This resulted in length to hydraulic diameter ratios of between 194 and 300. A wide range of annular flow rates were considered and Reynolds numbers ranges from 15 000 to 45 000 were covered for both heated and cooled annulus operating conditions. Specific attention was given to the influence of the inlet fluid temperature. For heated annulus cases an inlet temperature range of 10°C to 30°C was covered, while for cooled annulus cases an inlet temperature range of 30°C to 50°C was covered. Since one of the main focuses of the study was to provide accurate temperature measurement, especially local wall temperature measurements of the inner tube, an in-situ calibration technique of the wall thermocouples were used. This enabled continuous verification of the measurement accuracy and allowed re-evaluation of readings. Based on the processed experimental results, it was found that the direction of heat transfer did not affect the average heat transfer coefficient across the inner tube wall. Longitudinal local heat transfer coefficients were found to not be constant along the test section length, but continually decreased towards the annulus outlet, indicating undeveloped thermal flow. Heated annuli had a larger average heat transfer coefficients compared to cooled annuli at similar Reynolds numbers. This can be attributed to a dependency on fluid properties, which were less at higher bulk temperatures. Analysis showed although both had about the same local Nusselt numbers at the exit region, the heated annuli had much larger Nusselt numbers at the entrance region of the test section. The friction factor was mostly affected by the fluid velocity, but at low velocities higher friction factors were detected when inlet temperatures were lower. For the data sets considered in this study, the average Nusselt number and the Colburn j-factor decreased somewhat with increase in annular diameter ratio. It seemed that the friction factor was also not influenced by the annular diameter ratio. Dissertation (MEng)--University of Pretoria, 2017. Mechanical and Aeronautical Engineering MEng Unrestricted

Page generated in 0.0371 seconds