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This project investigated the viscosity of heavy medium suspensions. Heavy medium suspensions are used extensively in the minerals processing industry for separation of valuable materials from gangue on the basis of density. Rheological profiles for ferrosilicon and magnetite suspensions were determined using a laboratory-scale viscometer developed in the School of Chemical Engineering, University of KwaZulu-Natal, Howard College Campus, Durban. Ferrosilicon suspensions with specific gravities ranging from 2.0-3.2 were investigated in the presence of clay, to simulate higher density separations such as those used in the diamond industry, where slime build up can be a problem. Magnetite suspensions were prepared at specific gravities ranging from 1.6 - 2.6 to simulate separation densities used in the coal cleaning industry. Mixtures of suspensions of fine magnetite, and coarse magnetite, were also prepared to see what the effect of a coarser medium would have on the viscosity of the suspensions. The effect of viscosity on the separation efficiency of heavy medium separations was also investigated, using a laboratory-scale Dense Medium Separator designed and developed in the department. Suspensions with specific gravities between 1.6 and 1.8 were used to separate coal samples in the following size ranges: - 4mm + 1mm; -1mm + 500um; and -4mm + 500um. The rheograms for ferrosilicon suspensions showed that at low shear rates the suspensions behaved as pseudo-plastic liquids, while at high shear rates the behaviour resembled that of dilatant fluids. At low specific gravities the behaviour of magnetite suspensions was pseudo Newtonian. For specific gravities greater than 2.0, the suspensions became pseudo-plastic. The effect of a locally available dispersant (DP001), on the viscosity of the heavy medium suspensions, was also investigated. For ferrosilicon / clay mixtures, a reduction in viscosity of up to 20 percent was achievable for some specific gravities and slimes level. It was also observed that the dispersant had little effect or none at all, on the viscosity of uncontaminated ferrosilicon suspensions. Addition of the dispersant to fine magnetite suspensions achieved viscosity reductions between 8 and 10 percent. It was observed that the presence of coarse magnetite reduced the viscosity of fine magnetite suspensions by as much as 40 % at certain coarser solid ratios. Adsorption tests using a UV spectrometer showed that there was little or no DP001 adsorbed onto the surfaces of uncontaminated ferrosilicon particles. The results showed that DP001 was adsorbed onto the surfaces of magnetite #1 particles, with almost half the amount of 1 g DP001 / kg Mag #1 added to a test suspension of specific gravity 2.2 being adsorbed. This explained why magnetite #1suspensions were more susceptible to DP001 addition compared to ferrosilicon suspensions. For some of the coal size ranges separated, it was observed that there was a reduction of approximately 22% in the separation efficiency of the process as the specific gravity was increased. For some of the coal samples, an improvement in separation efficiency between 11% and 17% was achievable with DP001 additions of Ig DP001/kg solids, and 2g DP001/kg solids. The presence of coarse magnetite media initially improved the separation efficiency by up to 50% for some coal samples. However, as DP001 was added, there was a decline in the separation efficiency. In conclusion, the measured rheological profiles of the suspensions were comparable with those found in literature. It was shown that media particle size distribution affects the viscosity of heavy medium suspensions. It was also shown that surface active agents can be used to reduce the viscosity of heavy medium suspensions. / Thesis (M.Sc.Eng)-University of KwaZulu-Natal, 2005.

Class of 2009 Abstract / OBJECTIVES: The primary objective of this experiment was to characterize the pH stability range of 20% Pluronic lecithin organogel (PLO). We intended to determine the viscosity at varying pHs. We prepared six samples of 20% PLO. METHODS: An initial rheological reading of each sample was recorded by a dynamic stress rheometer. Each sample was titrated drop-wise with citric acid or KOH in 0.5 pH increments. When the desired pH was obtained, a 0.5 mL sample was analyzed with a dynamic stress rheometer, RS-200, using Rheos software. RESULTS: Since PLO is a non-Newtonian substance, viscosity changed relative to shear stress and we were not able to examine a correlation of pH with viscosity. Instead we inputted the data into Microsoft Excel® and plotted a shear stress versus viscosity curve for each sample to identify trends. CONCLUSIONS: We were unable to achieve our primary objective of determining the viscosity characterization of 20% PLO at varying pHs due to the non-Newtonian nature of the material. Subjectively, we determined the viscosity of 20% PLO is not substantially affected by pH. Other factors such as temperature, excess liquid, and surfactant ability may influence viscosity and need to be examined in the future.

This research project investigates a new technique to efficiently mix crystalline solid additives with polymers by gentle ball milling with steel balls in the presence of carbon dioxide (C02) at 17 to 30°C and 1300 to 2500 psig. As the ball milling system is agitated, the steel balls transfer mechanical energy to the fluoropolymer and additive thereby converting them to powders. C02 is added into the chamber to expand the polymer and make it amenable to impregnation by the additive. At the end of the mixing process, a free flowing powder is produced consisting of the additive coated with fluoropolymer. The additives were extracted from the powders and intrinsic viscosity measurements were done on the remnant fluoropolymer. Viscosity studies showed that the virgin and post-ball milled fluoropolymers had similar intrinsic viscosities, hence similar molecular weights within experimental error limits. This implies that most of the polymer chains were simply disentangled during the mixing process and not broken. Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA) were done on the virgin polymer, the additives and the fabricated powders to determine the loading levels and to ascertain if there were any changes to the physical properties of the polymer. Scanning electron micrographs showed that some of the powder particles had additive particles stuck on the surface, but when these additives were washed off the surface of the powders with a suitable solvent that did not dissolve the polymer, DSC analysis showed the presence of additive incorporated into the polymer matrix.

We study experimentally the gravity-driven bubbly flow inside a large Hele-Shaw cell. The bubbles and foam were created by a series of upside-down overturns of the half-filled cell about its horizontal axis. When the liquid flows down it entraps a large number of bubbles, which remain stable as the liquid contains surfactant molecules. The total number and sizes of these bubbles slowly asymptote to a steady state after dozens of overturns. It takes longer to reach this asymptote when the viscosity of the liquid is larger. The bubbles also become more monodisperse with more cell over-turns. The number and distribution of the bubbles in turn affects the average motion of the liquid phase, which is characterized by the downwards motion of the liquid center of mass. We use high-resolution 6k video-camera to track the trajectories of thousands of bubbles. This required the development of software codes to identify individual bubbles and follow them between video frames. Successful thresholding algorithm required a machine-learning component, which was integrated into the program. This program also needed to account for possible splitting or coalescence of adjacent bubbles. The program can also find the velocities along the trajectories. In this way we can find the vertical velocity of bubbles as a function of their sizes. The smaller bubbles are sometimes observed to move downwards against their buoyancy. This occurs when the viscous stress from the surrounding liquid phase overcomes the upwards buoyancy force. Bubbles with similar sizes were often found to be stacking together and having worm-like rising movement that is faster than their individual rising velocity. The occurrence of the bubble stacking was dependent on the distance between the bubbles, their sizes and their wakes. Clusters of tiny bubbles that are much smaller than the gap of the Hele-Shaw cell were observed to form layers which can severely hinder the overall liquid motion.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg / In this thesis we investigate the evolution of viscous FRW cosmological models for two different constitutive equations for the bulk viscous pressure a, namely (Abbreviation abstract) / Andrew Chakane 2018

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, / In this thesis we investigate the evolution of viscous FRW cosmological models for two different constitutive equations for the bulk viscous pressure a, namely: The truncated theory,,,,,,,,,,,,,,,, and the full (non-truncated] Israel-Stewart theory ...................We first review the relativistic theory of non-equilibrium thermodynamics developed by Eckart (1940) and the essentially equivalent formulation of the theory given by Landau and Lifshitz (1958). We give a, brief description of the relativistic second-order theories found by Israel and Stewart (1976) and subsequently developed by Pavon, Jou, and co-workers (1982, 1993). All this is done in order to develop the tools for the study of the evolution of FRW cosmological models in the context of causal thermodynamics. We find new exact and perturbative solutions of Einstein's field equations for the truncated Israel-Stewart theory of irreversible thermodynamics. We show that viscous effects speed up the expansion of the universe. We also consider a viscous fluid in the presence of a " non-interacting scalar field and show that inflationary solutions exist. The full theory of bulk viscosity is applied to dissipative FRW spacetimes. New causal viscous inflationary solutions are presented. These solutions extend the results obtained by Maartens (1995a) to cases where the coefficient of bulk viscosity e and the relaxation time r are independent. Power-law solutions for the scale factor are shown to exist. / Andrew Chakane 2018

Submitted by Juliana Aparecida Marques Eburneo null (julianaeburneo@gmail.com) on 2017-03-27T19:09:19Z No. of bitstreams: 1 Dissertação Final Versão Impressão.pdf: 1337107 bytes, checksum: a68b8582ead29404b314742e523864b0 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-03-29T19:40:50Z (GMT) No. of bitstreams: 1 eburneo_jam_me_bot.pdf: 1337107 bytes, checksum: a68b8582ead29404b314742e523864b0 (MD5) / Made available in DSpace on 2017-03-29T19:40:50Z (GMT). No. of bitstreams: 1 eburneo_jam_me_bot.pdf: 1337107 bytes, checksum: a68b8582ead29404b314742e523864b0 (MD5) Previous issue date: 2017-01-30 / A batata é a hortaliça com maior área cultivada no Brasil, sendo que sua produção se concentra nos estados da região sul e sudeste. Na cultura da batata o manejo inadequado da adubação nitrogenada pode causar crescimento exagerado da parte aérea, reduzir a qualidade de tubérculos e aumentar o custo de produção. Além disso, as condições de cultivo também podem influenciar as características do amido, principal carboidrato de reserva da batata, o que pode levar a interferências na aplicabilidade deste pelas indústrias alimentícias. Frente ao exposto, este trabalho teve por objetivo caracterizar amidos extraídos de batata cv Ágata cultivada sob diferentes doses de adubação nitrogenada e avaliar a possível interferência desta prática sobre a morfologia e distribuição de tamanho dos grânulos de amido, teor de amilose, teores de fósforo, cálcio, potássio e magnésio, composição físico-química, propriedades de pasta e térmicas; parâmetros estes determinantes para o estabelecimento das potencialidades de aplicabilidades do amido pelas indústrias. Para o alcance deste objetivo foram utilizados tubérculos de batata resultantes da colheita de ensaio experimental com adubação nitrogenada instalado em propriedade rural na região da cidade de Avaré, estado de São Paulo. Após o cultivo de 117 dias, as batatas foram colhidas, lavadas e processadas para a extração e análise do amido. Os resultados obtidos mostram que o amido de batata extraído de plantas cultivadas sem a aplicação de adubo nitrogenado apresentou grânulos redondos e ovalados, com predomínio de diâmetro maior na faixa de 26 a 50μm, padrão de difração de raio X do tipo B, 22,16% de cristalinidade relativa, elevada pureza, presença de 1090 ppm de fósforo, 893 ppm de potássio, 200 ppm de cálcio e 88 ppm de magnésio. Temperatura de pasta de 67,94°C, pico de viscosidade de 796,88 RVU, quebra de viscosidade de 622,03 RVU, viscosidade final de 236,28 RVU e tendência a retrogradação de 65,76 RVU. A gelatinização iniciou em 65,85°C, com pico em 68,03°C e final em 70,79°C, com variação de entalpia de 9,92 J g-1. A análise dos dados mostrou interferência da adubação nitrogenada sobre as características do amido de batata cv Ágata, sendo que o incremento nas doses de nitrogênio levou a obtenção de amidos com menor cristalinidade relativa, menores teores de fósforo, cálcio e magnésio, menor resistência à temperatura e agitação e menores temperaturas de gelatinização. Estes resultados indicam que o manejo cultural pode afetar importantes propriedades determinantes de aplicabilidade do amido de batata. / Potato is a vegetable with the largest cultivated area in Brazil and its production is concentrated in the states of the southeast region. In potato cultivation nitrogen fertilization management can cause overgrown growth, reduce the quality of tubers and increase the cost of production. In addition, the cultivation conditions may also influence the characteristics of the starch, main reserve carbohydrate of the potato, which can lead to interference in applicability of starch by industries. In view of the above, the objective of this work was to characterize starches extracted from Ágata cultivar cultivated under different rates of nitrogen fertilization, and to evaluate possible interference on morphology and size distribution of starch granules, amylose content, phosphorus, calcium, potassium and magnesium, physical-chemical composition, pasting and thermal properties, important characteristics for establishing the potential of starch application by industries. In order to reach this objective was analyzed tubers obtained from experimental area in the region of the Avaré city, state of São Paulo. After cultivation of 117 days potatoes were harvested, washed and processed for extraction and analysis of the starches. The results obtained show that potato starch extracted from plants cultivated without a nitrogen fertilizer application showed round and oval granules, with a larger diameter in the range of 26 to 50μm, pattern type B of X-ray diffraction, 22,16% of relative crystalline, high purity, presence of 1090 ppm of phosphorus, 893 ppm of potassium, 200 ppm of calcium and 88 ppm of magnesium. The pasting temperature was 67.94°C, viscosity peak was 796.88 RVU, viscosity breakdown was 622.03 RVU, final viscosity was 236.28 RVU and seatback was 65.76 RVU. The gelatinization of starch granules started at 65.85°C, with peak at 68.03°C, and final at 70.79°C, with enthalpy variation of 9.92 J g-1. The analysis of the data showed the interference of nitrogen fertilization on the characteristics of Ágata potato starch. The increase in nitrogen rates led to the obtaining of starches with lower relative crystalline, lower phosphorus, calcium and magnesium contents, lower resistance to temperature and agitation and lower gelatinization temperatures. These results indicate that cultural management can affect important determining properties of potato starch application, which is of great interest to the food industry.