Dense medium cyclones are used extensively in the mineral processing industry to beneficiate various minerals including coal, diamonds and iron ore, amongst others. According to Reeves (2002), .the cyclone has been installed in over one-quarter of the coal preparation plants worldwide.. Dense medium cyclones have the ability to achieve high capacities, and simultaneously obtain sharp separations and high separation efficiencies. However, this piece of equipment does have a shortcoming in that its capacity is constrained by the solids carrying capacity of the spigot. This is termed the spigot capacity. There is uncertainty on whether the spigot capacities specified by DSM (Dutch State Mines), the original developers of the dense medium cyclone, can be increased or not, and how these capacities were determined. The purpose of this study is to establish a methodology to determine the spigot capacities of dense medium cyclones, and determine the parameters that influence these capacities. In order to illustrate the significance of increasing the capacity of dense medium cyclones, the following coal example is used: In 2005, South Africa produced about 245Mt of coal valued at R35.86 billion. A significant proportion of this coal is beneficiated through dense medium cyclones. Therefore, an increase in the cyclone capacity, even if relatively small, represents a large number in terms of tonnages of coal produced or monetary gains. It has been established clearly in this investigation that the maximum spigot capacity is reached at the onset of roping. A critical sinks ore concentration at which spigot overloading occurs has been observed. The simplest and best indicator of possible spigot overloading has been established to be the sinks ore concentration, measurement of this parameter could, however, prove challenging on most industrial cyclones. Further, spigot overloading of a dense medium cyclone can be detected visually by observing the discharge type at the sinks and monitoring particle misplacement to the floats stream. A regression model that quantifies the spigot capacity, in terms of ore and slurry, has been developed. Various parameters were considered in the model, these include: cyclone geometry, feed head, medium density, and medium grade. Parameters that influence the spigot capacity of dense medium cyclones have been established, and their effect on the spigot capacity has been quantified. The spigot capacity values obtained in this investigation were compared with those specified by DSM, and it was concluded that there is large potential to increase the .spigot capacities. specified by DSM. / Dissertation (MEng (Metallurgical))--University of Pretoria, 2008. / Materials Science and Metallurgical Engineering / unrestricted

Forskning visar att medier är en central del i samhället eftersom information och underhållning medieras. Barn möter ofta olika typer av texter genom olika medier på fritiden och i skolan. Om elever får koppla sina tidigare erfarenheter till ny information, befästs deras kunskaper på en djupare nivå. Eftersom läsförståelse är en central del i undervisningen bör därför medier integreras i undervisningen. Även Skolverket menar att elevers tidigare erfarenheter ska vara en del av undervisningen. Litteraturstudiens syfte är att utveckla kunskap om hur undervisning i grundskolans tidigare år kan stärka elevers utveckling i läsförståelse med hjälp av olika medier, vilket har lett fram till följande frågeställningar: Hur påverkar medier elevers utveckling av läsförståelse? Hur kan lärare använda medier för att bidra till en utvecklad läsförståelse? Undersökningsmaterialet består av nationellt och internationellt material bestående av sju artiklar, fyra doktorsavhandlingar, en licentiatavhandling samt en antologi. Materialet berör litteraturstudiens syfte och frågeställningar och är vetenskapligt granskade. Av den första frågeställningen har det framkommit att elevers läsförståelse påverkas i relation till medier och motivation. Resultatet visade att elever som hade medier integrerat i undervisning där de läste och tolkade multimodala texter fick en djupare förståelse av texters innehåll och budskap. Genom den andra frågeställningen har det framkommit att medier och elevers tidigare erfarenheter är något som sällan integreras i undervisningen, på grund av avsaknad erfarenhet hos lärare. Resultatet visade även att lärare som undervisar om läsförståelsestrategier explicit med hjälp av medier bidrar till att elever utvecklar sin läsförståelse. / Research shows that media is a central part of society because information and entertainment are mediated. Children often meet different types of texts through different media in their free time and at school. If students can connect their past experiences to new information, their skills are consolidated on a deeper level. Because reading comprehension is a central part of the teaching, media should therefore be integrated into the teaching. The Swedish National Agency of Education also believes that pupils' previous experiences should be part of the teaching. The purpose of the literature study is to develop knowledge about how teaching in primary school's previous years can strengthen students' development in reading comprehension using various media, which has led to the following issues: How does media influence pupils' development of reading comprehension? How can teachers use media to contribute to a developed reading comprehension? The study material consists of national and international material consisting of seven articles, four doctoral dissertations, a licentiate dissertation and anthology. The material concerns the purpose and the issues of the literature study and is scientifically reviewed. From the first question it has been found that pupils' reading comprehension is influenced in relation to media and motivation. The result showed that students who had media integrated in teaching where they read and interpreted multimodal texts gained a deeper understanding of texts content and messages. Through the second issue, it has been found that media and pupils' previous experiences are something that rarely integrates into teaching, due to lack of experience in teachers. The result also showed that teachers who teach explicitly through reading media strategies contribute to students developing their reading comprehension.

L’appropriation des biotechnologies par les artistes en vue de créer des œuvres de « bioart » a souvent été considérée comme une démarche transgressive par rapport à la frontière qui délimite l’art et la science. Ma recherche vise à analyser un corpus de productions bioartistiques (Que le cheval vive en moi du duo Art orienté objet, Natural History of the Enigma, d’E. Kac et Ear on Arm de Stelarc) afin de mettre en perspective les « paramètres » par lesquels ont juge qu’il y a, notamment, appropriation et transgression, c’est-à-dire qu’il y a « art ». À partir de l’idée que les œuvres de bioart sont celles qui mettent à contribution les biotechnologies pour leur spécificité, c’est-à-dire la capacité à transformer le vivant, une analyse sémiologique met en évidence l’« incarnation » comme principale stratégie plastique du faire art dans les œuvres du corpus. En expérimentant les œuvres, le spectateur expérimente leurs conditions biologiques d’existence, qui sont similaires aux siennes. Il prend alors acte de cette incarnation, ce qu’une analyse phénoménologique met à jour. En comparant les modes de médiation des œuvres du corpus à ceux des icônes byzantines, une analyse médiologique révèle enfin l’équivalence entre incarnation et médiation et la transparence des œuvres de bioart à la technique dont la cybernétique est facteur de totalisation. Il semble qu’en créant des sujets vivants technicisés, les œuvres de bioart posent un jalon à l’évolution des objets techniques, telle qu’elle a été conceptualisée par Simondon : c’est l’intuition sur laquelle se referme cette thèse. / The purpose of my research is to define the aesthetic aims of works of bioart. Its starting point is the need to make an aesthetic analysis of some productions of this movement in order to understand its strategies, for these are wrongly considered as coming from Duchamp’s readymade, since bioartists tend to use biotechnologies to create works of art. This research suggests “bioart” gathers various works which involve biotechnologies inasmuch as they manage to transform the living. In this thesis, three bioartworks are studied: Que le cheval vive en moi, by French artists Art Objet orienté, Natural History of the Enigma, by American artist E. Kac and Ear on Arm by the Australian Stelarc. In order to define the aesthetic aims of these three works of art, an analysis grid inspired by semiology highlights aesthetical mechanisms. This analysis shows that “embodiment” is the main plastic way to art. This embodiment provokes a “sense of presence” in the works of the corpus, which can be identified as their “aura”. The aura allows the viewer to become aware of the biological realm of existence he shares with the artworks themselves. Therefore the aura is the manifestation of the contact between the viewer and the biotechnological meaning of the work. This implies that the works of the corpus embody their messages. The corpus has been compared to the Byzantine icons, which also “embody” their messages, in order to understand to what extent the biotechnological production of the living in art represents such a shift in art theory. By using biotechnologies, the works of the corpus testify about cybernetics, which is one of the main organizing principles of globalization and of the increasing presence of technology in human ways of life. It even appears that with the creation of technical living subjects, they pave the way for the evolution of technical objects, as it was conceptualized by Simondon – this is how the thesis comes to its conclusion.

A large portion of the world’s population is multilingual. This trend is reflected in the population with communication disorders, and therefore in people with complex communication needs (CCN). People with CCN may need alternative and augmentative communication (AAC) systems to facilitate their participation in daily life. These systems are often related to the language of the person’s community. Yet, if this person lives in a multilingual community, little current research is available to guide the design of AAC systems that give access to expression in more than one language. This pilot study aimed to determine the ability of typically developing Afrikaans-English bilingual children, between the ages of 4;6 (years;months) and 6;11, to label Picture Communication Symbols (PCS) in both these languages when taught with mono medium (English) versus dual medium (Afrikaans and English) teaching. Four participants, who spoke Afrikaans and English, were included in the study. A withinsubjects crossover design was used. Each participant was taught two sets of symbols, one using mono medium and one dual medium teaching. Treatments were counterbalanced for order and set. Results tentatively showed that the teaching method was successful, with participants being able to label most symbols in English when taught in either mono (English) or dual medium. Participants were also able to label symbols in Afrikaans when taught the symbols by dual medium teaching. Some participants were spontaneously able to translate symbols taught by mono medium teaching (English) to Afrikaans. This pilot study tentatively suggests that this ability is dependent on the child’s receptive vocabulary ability in both languages, as well as their ability to express the concepts depicted by the symbols in both L1 and L2. Future research is needed with studies that include a larger sample size, to be able to draw more robust conclusions. / Mini Dissertation (M(AAC))--University of Pretoria, 2017. / National Research Foundation (NRF) / Centre for Augmentative and Alternative Communication (CAAC) / M(AAC) / Unrestricted

The South African Revenue Service (SARS) introduced tax incentives for the small, medium and micro enterprises (SMMEs) in 2001. These incentives were introduced to assist small business in stimulating economic activity, creating jobs and alleviating poverty. This policy decision is not unique to South Africa. Many other countries offer incentives to small businesses for a variety of reasons, which may differ from country to country. However, it is generally understood that small businesses often face challenges which require the State to intervene in the form of tax incentives. South Africa operates on a global economic platform. It is imperative that its efforts are comparable against those of its counterparts so that it can assess its situation and be able to channel resources in the right direction. This study uses a qualitative systematic literature review to compare the tax incentives offered to SMMEs in South Africa and Australia .Australia has been chosen because it is a developed country and also because it has a mature and simplified legislation. The findings of this study show that South Africa has provided good incentives, particularly in the area of attracting small businesses into the tax base but once these small businesses are in the base, there is nothing to ensure that they grow. On the other hand, Australia has not done much to bring small businesses into the tax base, but it provides good incentives, sufficient to enable business growth for those already in the system. One of the challenges faced by many small businesses is cash flow resources. This study has found that Australia’s tax incentives empower small businesses in the area of cash flow, as compared with the situation in South Africa. Future research studies should investigate the extent to which the respective small businesses are aware of the tax incentives available to them. That is, it must be established how far each country has gone in ensuring that small businesses are familiar with all the incentives at their disposal. / Die Suid-Afrikaanse Inkomstediens (SAID) het belastingaansporings skemas vir die klein, medium en makro-ondernemings (KMMOs) in 2001 ingestel. Hierdie aansporings is ingestel om die klein besighede te help om ekonomiese aktiwiteite te stimuleer, werk te skep, asook om armoede te verlig. Hierdie beleidsbesluit is nie uniek aan Suid-Afrika nie. Menige ander lande bied aansporings aan die klein ondernemings vir ‘n verskeidenheid van redes. Alhoewel hierdie redes kan verskil van land tot land, word dit algemeen verstaan dat klein ondernemings dikwels uitdagings ervaar wat vereis dat die staat ingryp in die vorm van belasting-aansporings. Suid-Afrika werk in ‘n wêreldwye ekonomiese platform. Dit is noodsaaklik dat Suid-Afrika se pogings met die van sy eweknieë vergelyk word om sodoende die huidige situasie te evalueer en in staat te wees om hulpbronne in die regte areas beskikbaar te stel. Hierdie studie maak gebruik van ‘n kwalitatiewe sistematiese literatuur oorsig om die belastingaansporings in beide Suid-Afrika en Australië vir KMMO’s te vergelyk. Australië is gekies weens die feit dat dit ‘n ontwikkelde land is en ook omdat dit oor goed ontwikkelde en eenvoudige wetgewing beskik. Die bevindinge van hierdie studie toon dat Suid-Afrika goeie belastingaansporings het, veral op die gebied om die klein ondernemings in die belastingbasis in te trek, maar wanneer hierdie klein ondernemings in die basis is, is daar niks in plek om te verseker dat hulle verder groei nie. Aan die ander kant, het Australië nie veel gedoen om klein besighede in die belastingbasis belastingbasis in te bring nie, maar Australië bied goeie voordele wat tot besigheidsgroei lei vir diegene wat reeds in die belastingsbasis ingeskakel is. Een van die uitdagings van baie klein besighede is kontantvloeibronne. Hierdie studie het bevind dat, Australië se belastingaansporings, die klein ondernemings se kontantvloei bevorder in teenstelling met die posisie in Suid-Afrika. Toekomstige Toekomstige navorsingstudies moet die mate waartoe die onderskeie klein ondernemings bewus is van die belastingaansporingsskemas wat beskikbaar is, ondersoek. Dit wil sê, daar moet vasgestel word hoe ver elke land gegaan het om te verseker dat kleinondernemings vertroud is met al die moontlikhede tot hulle beskikking. / Dissertation (MCom)--University of Pretoria, 2010. / Taxation / Unrestricted

Galactic bulges of early-type spirals and elliptical galaxies comprise primarily old stars, which account for more than half of the total stellar mass in the local Universe. These stars collectively generate a long-lasting feedback via stellar mass loss and Type Ia supernovae. According to the empirical stellar mass loss and supernova rates, the stellar ejecta can be heated to more than 107 K, forming a very hot, diffuse, and ironrich interstellar medium. Conventionally a strong galactic wind is expected, especially in low- and intermediate-mass early-type galaxies which have a relatively shallow potential well. X-ray observations, however, have revealed that both the temperature and iron abundance of the interstellar medium in such galaxies are unexpectedly low, leading to the so-called “missing feedback” and “missing metal” problems. As an effort to address the above outstanding issues, we have carried out a series of hydrodynamic simulations of galactic bulge feedback on various scales. On galactic halo scales, we demonstrate that the feedback from galactic bulges can play an essential role in the halo gas dynamics and the evolution of their host galaxies. We approximately divide the bulge stellar feedback into two phases: 1) a starbusrtinduced blastwave from the formation of the bulge built up through frequent major mergers at high redshifts and 2) a gradual feedback from long-lived low mass stars. The combination of the two can heat the surrounding gas beyond the virial radius and stop further gas accretion, which naturally produces a baryon deficit around Milky Way-like galaxies and explains the lack of large-scale X-ray halos. On galactic bulge scales, we study the collective 3-dimensional effects of supernovae with their blastwaves resolved. We find that the sporadic explosions of supernovae can produce a wealth of substructures in the diffuse hot gas and significantly affect the spectroscopic properties of the X-ray-emitting gas. The differential emission measure in the temperature space has a broad lognormal-like distribution. Such distribution enhances the X-ray emission at both low and high energy bands. We further show that the SN Ia ejecta is not well-mixed with the ambient medium and the X-ray emission is primarily from the shocked stellar wind materials which in general have low metallicities. These 3-dimensional effects provide a promising explanation to the above “missing feedback” and “missing metal” problems. In addition, we demonstrate that the supernova iron ejecta forms a very hot bubbles, which have relatively larger radial velocities driven by buoyancy, resulting in a smaller iron mass fraction in the bulk outflow. These distinct properties give a natural explanation to the observed positive iron abundance gradient which has been a puzzle for decades.

Interstellar plasma — interstellar clouds in particular — play an important role in determining the structure and evolution of galaxies. Understanding the time evolution of such plasmas requires knowledge of the chemical processes that drive their dynamics. Two processes are studied in this dissertation: radiative electron attachment (REA) via dipole-bound states (DBSs) and dissociative recombination (DR). Of the several hundred molecules detected in the interstellar medium, only eight anions have been detected: CN-, C3N-, C5N-, C7N-, C4H-, C6H-, C8H-, and C10H-. Their production mechanism is not well known; REA was suggested as a possible formation pathway, but previous theoretical studies have found that REA rate coefficients were too low to explain the formation of CN-, C3N-, and C5N-. It was later suggested that including DBSs — an electron weakly bound at a large distance to the large dipole moment of a neutral molecule — could appreciably enhance the REA rate coefficients. The first portion of this study is dedicated to investigating the role of the large dipole moment of rotating C3N using an accurate \it ab initio approach with electronic and rotational resolution. DBS wavefunctions of C3N- are calculated and used to obtain REA cross sections that produce even smaller rate coefficients, suggesting that C3N- is efficiently formed by a different process. The second part of this study investigates DR in the difficult case of molecules with low-lying eletronic resonances, although these are not necessary for the approach. An approach to treat both direct and indirect mechanisms of DR in a diatomic ion with electronic, vibrational, and rotational resolution using R-matrix scattering calculations, frame transformation theory, and multichannel quantum defect theory is presented and applied to the CH+ and CF+ molecular ions at low collision energies. The calculated CH+ cross sections agree well with recent rotationally state-resolved experimental results and overall better than previous theoretical results. The calculated CF+ cross sections agree well with experimental results, although these do not have rotational resolution, and overall better than previous theoretical results at low energies. Additionally, the method can study rovibronic (de-)excitation — a process in competition with DR. These are calculated and compared to previous theoretical calculations for CH+, which which our results agree well with the exception of dipole-driven rotational excitation cross sections. This discrepancy is tentatively attibuted to negelcting the contribution of higher partial waves in the description of the incident electron, which will be incorporated in future studies.

<p>The gravitational collapse of a giant molecular cloud produces localized dense regions, called clumps, within which low-mass star formation is believed to occur. Recent studies have shown that limitations of current observing techniques make it difficult to correctly identify and measure properties of these clumps that reflect the true nature of the star-forming regions. In order to make a direct comparison with observations, we produced synthetic column density maps and a spectral-line cube from the simulated collapse of a large 5000 solar mass molecular cloud. The synthetic observations provide us with the means to study the formation of star-forming clumps and cores in our simulation using methods typically used by observers. Since we also have the full 3D simulation, we are able to provide a direct comparison of `observed' and `real' star-forming objects, highlighting any discrepancies in their physical properties, including the fraction of cores which are gravitationally bound. We have accomplished this by studying the global properties of the star-forming objects, in addition to performing a direct correlation of individual objects to determine the error in the observed mass estimates. By correlating the clumps found in the simulation to those found in the synthetic observations, we find that the properties of objects derived from the spectral-line data cube were more representative of the true physical properties of the clumps, due to effects of projection greatly impacting the estimates of clump properties derived from two-dimensional column density maps.</p> / Master of Science (MSc)

<p>A deep, wide-field survey was conducted to hunt for the light echo systems associated with SN 1054 (Crab) and SN 1181 as an initial step to acquiring spectra and the prospect of extracting lightcurves of these historical, core-collapse supernovae. Images were acquired by the Canada-France-Hawaii Telescope’s MegaCam during the 2011A and 2011B semesters for fields adjacent to SN 1054 and SN 1181, respectively. A total of 367 Sloan g’ fields for the Crab and 195 Sloan r’ fields for SN 1181 were imaged twice, with a minimum of one month separation.</p> <p>Examination of 13,880 and 11,052 difference images for the Crab and SN 1181, respectively, revealed no light echoes with surface brightnesses brighter than 24.0 mag/arcsec² (the threshold for being able to acquire useful spectra). Based on our non-detections and assuming similar dust properties to nearby (detected) supernova light echo systems (Tycho and Cas A), we conclude it is unlikely that either SN was a Type II-L outburst but cannot provide constraints on other sub-types.</p> <p>We further examined the known light echo locations for Tycho and Cas A and found a statistically-significant correlation between CO brightness temperature and the presence of scattering dust. However, the spacing of grid points in existing CO surveys is too sparse to be useful even a few degrees away from the galactic plane. We have yet to identify a search strategy based on survey data which is superior than random field placement.</p> / Master of Science (MSc)

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