The leach solution obtained by leaching of zinc containing ores typically has to be highly purified before it can be used as electrolyte for the electrowinning of zinc. Cobalt is a troublesome impurity in the sense that not only has it even at relatively low concentrations a very significant negative impact on the zinc electrowinning process, but that is also difficult to remove by the zinc cementation process typically used for this purpose. The aim with the present work was to better understand the arsenic activated cementation of cobalt using zinc powder to enable the optimization of an industrial purification plant. Thermodynamic based calculations confirmed that the role of arsenic in the process is to allow for the precipitation of the cobalt at more positive potentials as cobalt arsenide and that it should be possible to remove the cobalt to very low concentrations with zinc cementation. The kinetics of cobalt cementation was studied using batch cementation experiments using different sizes and quantities of zinc dust and by varying the temperature. The nature of the cementation products was characterized using scanning electron microscopy and energy dispersive spectroscopy. It was found that the cobalt cementation could be described by a first order rate equation but with a faster initial stage with an activation energy of 43 kJ/mol followed by a much slower temperature insensitive second stage. Activating species such as copper, cadmium and arsenic cemented faster than the cobalt on the zinc. The rate of cobalt cementation was increased by using the same mass of finer zinc, increasing the temperature and recirculation of some of the cemented cobalt. It was shown that the zinc dust consumption and/or the minimum temperature required to achieve the required cobalt removal could be reduced by recirculation of the cobalt cement from the early stages of a train of backmix reactors or by using zinc dust with a finer size distribution. / Dissertation (MSc)--University of Pretoria, 2014. / Materials Science and Metallurgical Engineering / unrestricted

Mobile devices have excelled in the 21st century due to the increasing popularity and continuous improvement of mobile technology. Today mobile devices have become all-in-one portable devices, providing inter-connectivity, device-to-device communication and the capability to compete with personal computers. The improved capabilities and popularity of mobile devices have, however, caught the attention of botnet developers, allowing the threat of botnets to move into the mobile environment. A mobile botnet is de fined as a collection of compromised mobile devices, controlled by a botmaster through a command and control (C&C) network to serve a malicious purpose. Previous studies of mobile botnet designs focused mostly on the C&C structure, investigating other mechanisms as potential C&C channels. None of these studies dealt with the use of a hybrid C&C structure within a mobile botnet design. This research consequently examines the problem of designing a new mobile botnet that uses a hybrid C&C structure. A model of this new hybrid design is proposed, describing the propagation vectors, C&C channels, and the topology. This hybrid design, called the Hybrid Mobile Botnet, explores the efficiency of multiple C&C channels against the following characteristics: no single point of failure must exist in the topology, low cost for command dissemination, limited network activities and low battery consumption per bot. The objectives were measured by using a prototype built according to the Hybrid Mobile Botnet model. The prototype was deployed on a small collection of mobile devices running the Android operating system. In addition, the prototype allowed for the design of a physical Bluetooth C&C channel, showing that such a channel is feasible, able to bypass security and capable of establishing a stealthy C&C channel. The successful execution of the prototype shows that a hybrid C&C structure is possible, allowing for a stealthy and cost-eff ective design. It also revels that current mobile technology is capable of supporting the development and execution of hybrid mobile botnets. Finally, this dissertation concludes with an exploration of the future of mobile botnets and the identifi cation of security steps users of mobile devices can follow to protect against their attacks. / Dissertation (MSc)--University of Pretoria, Pretoria 2014 / Computer Science / unrestricted

The reporting of the financial results of an organisation is the responsibility of the management of that organisation. However, value may be added to the financial statements by the auditing of such financial statements and by the opinion expressed by the external auditors. Furthermore, there is the expectation on the part of the users of the financial statements that the auditors are also responsible for detecting fraud and, more specifically, financial statement fraud. It was stated in the Association of Certified Fraud Examiners 2010 Report to the Nations that it is the high-level perpetrators who cause the greatest damage to their organisations. The costs arising from financial statement fraud were found to be more than three times higher than the costs arising from fraud committed by lower-level managers and nine times more than the costs involved in employee fraud. The question, thus, arises as to why the auditors would not detect financial statement fraud timeously. The external audit profession has formulated a specific standard which addresses the responsibility of the external auditor as regards the detection of fraud during the audit of financial statements. The aim of this research was to determine the adequacy of the internal auditor standards as regards providing guidance to the internal auditors in terms of detecting financial statement fraud. This research highlighted the lack of guidance in the internal audit standards regarding the responsibility of internal auditors relating to financial statement fraud. In the main, both the directives and the guidance refer to fraud in general but not specifically to financial statement fraud and, thus, the professional internal auditor is forced to seek guidance outside of the internal audit standards as regards the detection of financial statement fraud. / MPhil University of Pretoria, 2014 / Auditing / MPhil / Unrestricted

Despite effective antibiotics, Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis, still infects nearly one-third of the world's population. While key immune factors including CD4+ T cells and IFNg production have been identified, there are still many antimicrobial mechanisms yet to be explored. Here we characterized the role of invariant natural killer T (iNKT) cells and GM-CSF during Mtb infection.

An occurrence which is sometimes observed in a model based on dichotomous dependent variables is separation in the data. Separation in the data is when one or more of the independent variables can perfectly predict some binary outcome and it primarily occurs in small samples. There are three different mutually exclusive and exhaustive classes into which the data from a logistic regression can be classified: complete separation, quasi-complete separation and overlap. Separation (either complete or quasi-complete) in the data gives rise to a number of problems since it implies in nite or zero maximum likelihood estimates which are idealistic and does not happen in practice. In this dissertation the theory behind a logistic regression model, the definition of separation and different methods to deal with separation are discussed in part I. The methods that will be focused on are exact logistic regression, Firth s method which penalises the likelihood function and hidden logistic regression. In part II of this dissertation the three fore mentioned methods will be compared to one another. This will be done by applying each method to data sets which exhibit either complete or quasi-complete separation for different sample sizes and different covariate types. / Dissertation (MSc)--University of Pretoria, 2013. / Statistics / Unrestricted

South Africa is blessed with a plethora of mineral resources, and as such several mineral beneficiation plants are in operation. In the mining value chain, a processing facility is seen as the bottleneck. The reason for this is quite simple. Large quantities of ore are removed in a highly industrialised process from mining activities. This large amount of ore needs to be beneficiated through capacity constrained processing facilities. In order to maintain an economically viable balance between life of mine, and maximum throughput, a large portion of ore extracted from South Africa is exported to foreign countries. The ore is then further beneficiated in plants that do not necessarily suffer from the same constraints as the South African plants. These constraints include labour costs, electricity availability and pricing, water usage etc. Even though the downstream beneficiation of minerals will have a profound effect on the South African economy, it is of utmost importance that the Mineral Beneficiation Plants (MBP’s) responsible for a large portion of the beneficiation strategy, be operated effectively to allow local end users of their products to remain internationally competitive. It is clear that MBP’s play an integral part in the value chain of the minerals industry, and effective operation of these plants are critical. It is of utmost importance to ensure that MBP’s are operating at full capacity, as effectively as possible, and within budget constraints. Development of a continuous improvement model for a South African Minerals Beneficiation Plant In order to achieve this objective, MBP’s need to implement a sustainable Continuous Improvement Programme. Several models are available and have been utilised with variable success rates in some MBP’s around the world, however none of these models specifically address CI from a minerals processing point of view. This study aims to develop a model which can be exclusively used for CI in South African MBP’s. A survey was conducted to understand the requirements that a CI model should fulfil. The survey was completed by respondents in both junior and senior roles within different resourcing and consulting organisations as well as academic institutions. It was found that most respondents prefer a model which involves an amalgamation of current CI models i.e. six sigma, theory of constraints and lean manufacturing. A new model was developed using the elements from these existing models that are applicable to MBP’s. The model also incorporates strategic direction required to implement it successfully. It focusses on the core elements that would result in process improvement. These are as follows: • Reduction in Waste • Improvement in Quality • Improvement in Efficiency • Decrease in cost A case study is shown which highlights the applicability and success of the model within a South African Ferro Alloy plant. / Dissertation (MSc)--University of Pretoria, 2014. / Graduate School of Technology Management (GSTM) / Unrestricted

In Mpumalanga, only about 25 per cent of households have car access, which makes Mpumalanga one of the provinces with the highest use of public transport by means of bus or taxi in South Africa. Even though the road network in Mpumalanga is extensive, the maintenance and upgrade of this network is a concern, especially for municipal and provincial roads. Deteriorating roads have a direct (such as vehicle operating costs, VOCs) and indirect impact (such as high bus fares) on the road user. This study focuses on the interaction between one bus from Buscor and the pavement surface of one specific bus route, including the associated VOCs generated. The ride comfortability of the bus route was evaluated by interpreting International Roughness Index (IRI), Power Spectral Density (PSD), and vertical accelerations (awz) data, after which the associated vehicle operating costs (VOCs) for the bus were projected. The judgement of ride comfortability in a vehicle is an area of controversy, and studies on this topic dates back from the 1920sThe threshold values from ISO (1997), Cantisani, and Loprencipe (2010) were used for the purposes of this study. The vertical accelerations generated from the surface of the bus route, for a bi-articulated bus were measured with accelerometers. The accelerometers were placed on the bus where the vertical accelerations were expected to be the highest. The identified bus route included different roads with different responsible authorities and roughness levels. A profiler conducted a survey on the route and five different sections were identified. The collected data were analysed with various programs. From the data collected from the accelerometers the PSD, awz, and the speed that the bus travelled on each section could be determined. The IRI data for each section was categorised in three categories, very good to good, fair to mediocre and poor. Anomalies in each section were identified, and the cause of these anomalies determined. The anomalies were analysed with the data, as these values formed part of the route. The impact of road roughness on fuel consumption, tyre wear and repair and maintenance costs were analysed. The calibrated Highway Development and Management System (HDM 4) model was used to predict the fuel consumption, tyre wear and repair and maintenance cost per km of each section of the bus route under consideration. In this analysis, the impact of the vehicle speed proved to be significant, as it affected the PSD values, the awz values and the VOC. The scenario was analysed to improve the riding quality of the two worst sections of the bus route, and by improving the road surface of these two sections, travel time could be reduced and costs could be saved. The scenario of an increase in road roughness was also analysed, to indicate the percentage of increase in costs, if these roads kept deteriorating. The analysis showed a significant increase in repair and maintenance cost, fuel consumption, and tyre wear. The limitations of this study included some correlation issues with the profiler data and the accelerometer data, unidentified bus stops on gravel shoulders, and the suspension system and interior of the bus that were deemed constants and not variables within the scope of this study. Despite these limitations, there are still a number of possibilities with the data collected. Apart for the analyses conducted for the study, recommendations for further refinement include the impact of bus mass on the data (full bus versus empty bus), the suspension type and condition, the interior of the bus, trip duration and congestion, evaluation of driver fatigue, tyre pressure and dynamic wheel loads, and safety. Furthermore, the construction cost of upgrading the two worst sections of the route versus the increase in VOCs because of the deteriorating state of the route could be investigated. In conclusion, the speed played a determining role in the generation of vertical accelerations, therefore user comfort or discomfort, and VOCs. An increase in IRI indicates deteriorating riding quality that affects the comfortability of a ride and the VOCs negatively. IRI can be used to determine the state of the road and qwz gives an indication of the comfortability of a ride. / Dissertation MEng--University of Pretoria 2014 / ay2014 / Civil Engineering / unrestricted

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No description available.

A biotecnologia tem como uma de suas principais aplicações a área agrícola, especialmente no contexto da geração de sementes geneticamente modificadas (GM). Apesar da importância econômica dos produtos dessa natureza, poucas fontes trazem informações a fundo sobre a gestão de projetos, desenvolvimento de produtos, e geração de inovações a partir de cooperação tecnológica entre empresas. Esse estudo visa mitigar esta lacuna apresentando, informações relativas aos temas citados, com um mapeamento dos stakeholders de empresas de sementes GM pela ótica das mesmas, além de estudar a cooperação tecnológica dessas empresas com base em dados de patentes. Entre as ferramentas metodológicas utilizadas nesse estudo, se optou por entrevistas semi-estruturadas para a parte de projetos e stakeholders, e análise de redes sociais na parte de stakeholders e de cooperação tecnológica. Os resultados obtidos, além de enriquecer o arcabouço teórico do tema ligado a essa indústria, indicam que, em relação ao gerenciamento dos projetos, a definição de objetivos em um projeto é tanto um recurso crítico como um dos principais problemas encontrados pelos entrevistados, sendo que má comunicação e falta de recursos também entraram na lista de problemas encontrados neste tipo de projeto. A análise de stakeholders mapeou os relacionamentos quanto aos critérios de urgência, legitimidade, poder, e as demandas dos stakeholders entre os critérios de simplicidade e compatibilidade, sendo que ao final em um modelo de redes indicou que possíveis alterações nos relacionamentos poderiam ser positivas para o relacionamento das empresas com os clientes. Por fim, a análise de inovações e cooperações indicou que a rede de cooperações tem ficado progressivamente mais centralizada, com novas iniciativas partindo de empresas menores, institutos e universidades, de países de origem asiática / Genetically modified (GM) seeds are among of the main applications related to agricultural biotechnology. Despite the economic importance of products of this nature, few sources provide in-depth information on project management, product development, and the generation of innovations through technological cooperation between companies. This study aims to mitigate this gap by presenting, in addition to information related to the themes mentioned, a multi-approach mapping of the stakeholders of GM seed companies. Among the tools used in this study, for the projects and stakeholders were chosen semi-structured interviews, and also for the stakeholders analysis and for study of innovation in the form of joint patenting network analysis were chosen. The results obtained, besides enriching the theoretical framework of this industry, indicate that the definition of objectives is both a critical resource and one of the main problems encountered by the interviewees, as well as poor communication and lack of resources, which also entered the list of problems encountered in this type of project. Stakeholder analysis mapped relationships relating to the criteria of urgency, legitimacy, power, to the stakeholder demands which were classified through their simplicity and compatibility to the company´s. Then, a stakeholder network indicated which possible change in the relationships could be positive for the relationship with customers. Finally, through the analysis of innovations and cooperation, it was indicated that the cooperation network became progressively more centralized, with new initiatives from smaller companies, institutes and universities, from countries of Asian origin