Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 1999 / Since 1996, a team at the Centre for Research in Applied Technology (CRATECH) at Peninsula Technikon, under NRF sponsorship and with industrial co-operation, has been involved in the simulation of Non-Newtonian flow behaviour in industrial processes, in particular, injection moulding of polymers. This study is an attempt to deal with some current issues of Non-Newtonian flow, in small areas, from the viewpoint of computational mechanics. It is concerned with the numerical simulation of Non-Newtonian fluid flows in mould cavities with re-entrant corners. The major complication that exists in this numerical simulation is the singularity of the stresses at the entry of the corner, which is responsible for nonintegrable stresses and the propagation of solution errors. First, the study focuses on the derivation of the equations of motion of the flow which leads to Navier- Stokes equations. Thereafter, the occurrence of singularities in the numerical solution of these equations is investigated. Singularities require special attention no matter what numerical method is used. In finite element analysis, local refinement around the singular point is often employed in order to improve the accuracy. However, the accuracy and the rate of convergence are not, in general, satisfactory. Incorporating the nature of singularity, obtained by an asymptotic analysis in the numerical solution, has proven to be a very effective way to improve the accuracy in the neighborhood of the singularity and, to speed up the rate of convergence. This idea has been successfully adopted in solving mainly fracture mechanics problems by a variety of methods: finite difference, finite elements, boundary and global elements, and spectral methods. In this thesis, the singular finite elements method (SFEM), similar in principle to the crack tip element used in fracture mechanics, is proposed to improve the solution accuracy in the vicinity of the singular point and to speed up the rate of convergence. This method requires minor modifications to standard finite element schemes. Unfortunately, this method could not be implemented in this study due to the difficulty in generating the mesh for the singular element. Only the standard finite element method with mesh refinement has been used. The results obtained are in accordance with what was expected.

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2008. / Certain non-Newtonian fluids exhibit a yield stress which can be measured with a variety of instruments varying from very sophisticated rotary and tube viscometers to hand-held slump cones and cylinders of various sizes. Accurate yield stress measurement is significant for process design and disposal operations for thickenend tailings. The slump value was first related to the yield stress by Murata (1984). Later, that work was corrected by Christensen (1991) for an error in the mathematical analysis. Slump, based on a circular cylindrical geometry was first investigated by Chandler (1986). These concepts led to the study by Pashias et al., (1996) that formed the basis for the current research. The Flow Process Research Centre (FPRC) at the Cape Peninsula University of Technology developed a slump meter designed to lift the cone or cylinder vertically at controlled lifting speeds. In addition the simple hand-held cylinder which is an adaptation of slump cones which were originally developed by the concrete industry to determine the flowability of fresh concrete was also used. The vane technique was used as a control. Cones and cylinders made of stainless steel and PVC were fitted to the slump meter. The yield stresses of four non-Newtonian fluids at different concentrations were tested in four different configurations at different lift speeds to ascertain whether the measuring position, lift speed, slip, geometry, wall surface material, and stability has an effect on the value of yield stress measured. The effect of different predictive models was also ascertained.The cylinder, lump and cone models relating slump to yield stress was used in the dimensional analysis of the results. The objective of this work was to determine if the slump tests (cone, cylinder and the hand-held cylinder) would generate yield stress values comparable to those found using the vane technique. It was establised that there was no significant effect of lift speed, stability, geometry and wall surface material on the value of yield stress. The effect of measuring position on the value of yield stress calculated gave a difference of 25%. Using dimensional analysis, the lump model (Hallbom, 2005) more accurately predicts the material yield stress when using the hand-held cylinder as well as all the cone results (due to its specific geometry), and cylinder configurations, thus affirming the work of Clayton et al., 2003. It is concluded that, although the materials and concentrations tested induced errors within 40%, the hand-held cylinder shows promise as a reliable, quick and simple way of measuring the yield stress.

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2009. / This study investigated water-in-oil (WIG) super-concentrated emulsions used as pumpable explosives. The aqueous phase of the emulsions is a supersaturated nitrate salt solution (at room temperature), with a volume fraction usually greater than 0.8. Aqueous phase droplets are deformed by packing and contact with neighbouring droplets. Compounds of this kind are thermodynamically unstable and their instability is related to the coarsening of emulsions (droplet coalescence) and phase transition (crystallisation) in the dispersed phase. However, it was demonstrated that the dominating mechanism is slow crystallisation inside the supercooled droplets. The main goal of this thesis therefore concerned a phenomenological study of the dependence of type and concentration of surfactant, as well as the ageing processes, on the rheological properties of these emulsions. The bulk rheological measurements were carried out using a rotational dynamic rheometer MCR 300 (Paar Physica). Samples of different types of surfactant (Pibsa-MEA, Pibsa-UREA, Pibsa-IMIDE, SMO and SMO/Pibsa-MEA) and different concentrations of surfactants were studied. The results of the measurements include the flow and viscoelastic properties of the materials. The rheological parameters have been correlated with the kinetics of structural changes during ageing as a function of emulsion formulation content. The emulsions under study were non-Newtonian liquids. It was demonstrated that different surfactant types yield different interfacial properties. In fact, both the interfacial tension and the interfacial elastic modulus were found to decrease according to the sequence MEA-UREAMEAlSMG- IMIDE-SMG. It was established that the surfactant type and surfactant concentration affected the bulk rheological properties of explosive emulsions. Indeed, both the elastic modulus and the yield stress as function of surfactant type decreased in the following order: MEA-IMIDE-UREA-MEAlSMG, whereas they also decreased as the surfactant concentration increased. However the sensitivity of the rheological parameters to the type or concentration of surfactant was found to decrease as the droplet size increased. Moreover, the changes in rheological parameters were more strongly expressed than any changes in interfacial tension. This last finding is considered as rather important. It seems reasonable to assume that it provides proof of an active role of a surfactant not only as a compound responsible for the interfacial tension, but also creating additional sources of elasticity.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2016. / This dissertation presents how material properties (solids densities, particle size distributions, particle shapes and concentration) of gold tailings slurries are related to their rheological parameters, which are yield stress and viscosity. In this particular case Bingham yield stresses and Bingham plastic viscosities. Predictive models were developed from analysing data in a slurry database to predict the Bingham yield stresses and Bingham plastic viscosities from their material properties. The overall goal of this study was to develop a validated set of mathematical models to predict Bingham yield stresses and Bingham plastic viscosities from their material properties. The interaction of the non-Newtonian material properties is very complex at varying mass solids concentrations. The evaluation of these interactions in terms of constitutive equations is almost impossible and the relationship between material properties, mass solids concentration and rheology can only be modelled in a statistical manner. The validity of each model is checked to ensure that predictions and interpretations are unbiased and efficient. This is done by comparing the resulting models to experimental data generated from test work. An in-depth analysis was conducted to see the interrelationship between the material properties and how they affect the yield stress and viscosity values.

Orientador: Nereu Carlos Prestes / Banca: Maria Denise Lopes / Banca: Fabiana Ferreira de Souza / Banca: Luiz Henrique de Araújo Machado / Banca: Maria Isabel de Mello Martins / Resumo: O feto prematuro não sobrevive à vida extra-uterina devido a imaturidade de órgãos vitais como os pulmões e rins. O objetivo desse trabalho foi avaliar a maturidade renal através da identificação de proteínas de baixa massa molecular; pulmonar através da citologia com azul de Nilo (0,1%), teste de Clements modificado e densidade óptica dos fluidos; alfa-fetoproteína através da eletroforese em SDS-PAGE (12%) e concentração de cortisol nos líquidos fetais por radioimunoensaio. Foram obtidas 40 amostras de líquido amniótico e alantoideano de 16 cadelas gestantes pela cesariana. Ajustes no teste de Clements favorecem a análise de fluidos caninos promovendo resultados confiáveis (p<0,05) para as diluições. Células morfologicamente diferentes e com porcentagem de células orangeofílicas e cianofílicas refletem a maturidade pulmonar sugerindo feto em estágio de pós-maturidade. Na densidade óptica (DO) dos líquidos fetais encontramos 220l0,190 para os líquidos amniótico e 0,250l0,02 para o alantoideano sendo indicativo de maturidade (= 0,150). A concentração proteica nos fluidos estudados reflete a fisiologia fetal (p<0,05). A dosagem de cortisol indica a exposição do feto no ambiente uterino (p<0,05). A IOD da banda protéica de 66kDa foi de 15,94 para o líquido amniótico e 13,3 para o alantoideano. Cinco bandas proteicas presentes nos dois fluidos podem espelhar a maturidade renal (32; 30; 28; 20 e 12). Com base nestes dados conclui-se que a obtenção de informações básicas sobre a maturidade e viabilidade do feto canino podem ser avaliada com os testes propostos. / Abstract: The premature fetus is unable to survive in extra-uterine environment due to immaturity of its vital organs as the lungs and kidneys. The objective of this work was to evaluate the renal maturity through the identification of low molecular mass proteins; pulmonary maturity through the cytology with Nile blue (0,1%), modified Clements test and optic density of fluids; moreover, the alpha-fetoprotein was evaluated through electrophoresis using SDS-PAGE (12%); and the cortisol concentration from fetal liquids was determinated by radioimunoassay. Forty amniotic and allantoic liquid samples from 16 pregnant bitches were colleted by punction during cesarean section. The Clements test was adapted to canine fluid analysis to promote true results (p<0,05) for the diluitions. Cells morphologically and with percentage of different orangeo and cyanophilia cells reflect the maturity. The optic density (DO) of the fetal fluids liquids were 220l0,190 and 0,250l0,02 to the amniotic and allantoic liquid, respectively, indicating maturity (= 0,150). The protein concentractions reflect the fetal physiology (p<0,05) in evaluated fluids. The cortisol concentration indicates the fetal exposition in the uterine environment (p<0,05). The IOD of 66 kDa protein band was 15,94 to amniotic and 13,30 to allantoic liquid. Five protein band in two fluids can reflect the renal maturity (32; 30; 28; 20 e 12). Based in these results we conclude that the tests considered in the study can evaluate the maturity and viability of canine fetus. / Doutor

This thesis investigates two methods of optical analysis of multiphase fluids. These two methods are nephelometry and the statistical analysis of scattered light intensity fluctuations. Nephelometry is an established technique for investigating particulate suspensions. In this work the basic technique is combined with neural network processing to develop a system capable of automatically distinguishing and quantifYing different suspensions, in particular suspensions of oil. Evidence obtained in this study suggests that neural networks can distinguish the light scattering from suspensions of different size distributions and produce a more accurate estimate of volume fraction than commonly used turbidity measurements. Non-Gaussian, fluctuating light intensities arise from the scattering of light from a varying population of suspended particles. Successful measurement of these intensity fluctuations makes feasible new instrumentation based on the statistical behaviour of the detected signal. Analyses that could prove possible include particle number, size, type and flow characteristics. Photon counting methods have traditionally been used to measure fluctuations from random media but the lower cost of analogue pin diodes makes them the preferred choice of detector if they can be applied usefully. A method of quantifYing the effect of noise from the diode detectors and removing it from the statistics of the fluctuations is developed from a model of the pin diode detectors. Experimental results show that detector noise can be compensated for in the analysis of scattered light fluctuations. Results also indicate that the model used to describe the scattering process is valid and that further work can lead to a practical instrument for the study of suspensions.

Research on dolomitic limestones and dolomites from selected localities of the Barrandian, stratigraphically related to the Scyphocrinites Horizon near the Silurian-Devonian boundary, showed the occurrence of two distinct types of dolomite - diagenetic and epigenetic - differing in petrography and genesis. The diagenetic dolomite is quantitatively predominant. It is finely to moderately coarsely grained with crystal size from 20 μm to 450 μm. Crystals of this dolomite form mostly xenotopic and hypidiotopic textures (occasionally even idiotopic). This type of dolomite formed at low temperature and depth by recrystallization of a carbonate mud during early diagenesis, or during subsequent deeper burial. It is also possible that it originated from recrystallization of previously formed syngenetic dolomite. Fine texture of the diagenetic dolomite is a proof of fast dolomitization and of formation of numerous crystallization centers. Very fine-grained variant of dolomite was also detected (forming aphanotopic texture, size of crystals below 0,002 mm). The epigenetic dolomite, also known as baroque or saddle dolomite, is less common than the former one. It forms white, milky-turbid or clear crystals of large dimensions (0.8 - 3.1 mm). The shapes of these crystals are conspicuous, variously twisted,...

No description available.

Regulation of chloride, sodium, potassium, calcium, and magnesium ions was determined for hypo- and hypersaline conditions in the crab, Cancer magister, from an estuarine environment. Animals from both summer and winter were examined. Chloride regulation in the blood was hypertonic in dilute salinities and hypotonic in concentrated salinities, with summer animals maintaining a greater gradient in the former and winter animals a greater gradient in the latter. Sodium in the blood is regulated hypertonically in all experimental salinities, with summer animals maintaining a greater gradient. Blood potassium is regulated hypertonically in dilute salinities, approaching isotonicity in hypersaline media. Summer animals maintain a greater gradient of potassium concentration. Blood calcium is regulated hypertonically in all experimental salinities, with summer animals maintaining a greater gradient in dilute salinities and winter animals a greater gradient in concentrated salinities. Magnesium is regulated at a pronounced hypotonic level in the blood over the entire experimental salinity range, with winter animals maintaining the greater gradient. Major changes in the adaptation of blood ionic concentrations occur within a few hours of exposure to the experimental salinities, with half of the final equilibrated concentration values attained by twelve hours. Animal weight was found to bear no significant relationship to the ionic regulatory activity observed. Renal involvement in regulation has been shown for all the ions, with the production of a urine hypertonic to the blood for chloride and magnesium, and a urine hypotonic to the blood for sodium, potassium, and calcium. Renal regulation was greater in winter animals for chloride, and greater in summer animals for sodium and potassium. Ionic regulation by the gills of summer and winter animals was investigated by potential difference measurements, and was suggested to occur for all ions. Chloride may have been regulated by the absorption from dilute media and excretion into concentrated media. Sodium may have been regulated by secretion into dilute media. The involvement of the gill in potassium, calcium, and magnesium regulation was implicated. / Science, Faculty of / Zoology, Department of / Graduate

Clinical Issue Health Canada recommends exclusive breastfeeding for the first 6 months post birth and then the addition of complementary foods with breastfeeding extending to a minimum of two years. Breastfeeding initiation rates in Canada are currently at around 87% but, by one month, about 21% of women have stopped breastfeeding. Engorgement and edema in breast tissue can lead to breastfeeding challenges which may contribute to early weaning. Purpose The purpose of this pilot research study was to explore the relationship between intravenous (IV) fluids given to mothers during the peripartum period and postpartum breast or nipple swelling in the first ten days postpartum and determine if a larger study was warranted and feasible. The research question for this pilot study was, "What is the relationship between the amount of IV fluids given to labouring women and edema of the breast and areola complex experienced by breastfeeding women in the first 10 days postpartum?" Methods It is a prospective, longitudinal, observational cohort pilot study with repeated measures and a within-subjects design. Participants are first time mothers who planned to exclusively breastfeed and gave birth to a single, healthy newborn by means of a spontaneous vaginal birth, Mother and baby were discharged home together with no contraindications to exclusive unrestricted breastfeeding. Descriptive statistics are reported and linear regression analysis is used to model the relationship between IV therapy and postpartum breast edema. Results Women who received IV fluids during labour had higher levels of edema postpartum and rated their breasts as firmer as and more tender than women who did not receive IV fluids. Participants who had IV fluids appeared to be less aware of the fullness associated with lactogenesis II, and the pattern of fullness they described appeared to be related to edema noted. Participants who did not have IV fluids appeared to have unrelated patterns of fullness and edema, and therefore appeared more aware of the onset of lactogenesis II. The results support a larger study about the relationships between maternal perinatal IV fluids and breast or nipple changes.