This research takes a multidisciplinary approach to comprehensively investigate the material and mechanical properties as well as pore water chemistry of the Bearpaw shale. This made it possible to characterize how these properties relate to the mechanical strength of this material. The results of this research challenge our ideas of the hydrogeology and of the geological history of the region. Core samples of the Bearpaw Formation and the overlying glacial till were collected from a field site in southern Saskatchewan, Canada. A combination of laboratory tests including multi-staged oedometer tests, constant rate of strain oedometer tests, specialized triaxial swell tests, along with pore water chemistry and finite element modelling were used to meet the following objectives: (1) To investigate the material properties and compression behaviour of the Bearpaw in addition to assessing disturbance due to specimen size; (2) Examine the time dependent behaviour of the Bearpaw and the transferability of time rate models developed for soft soils to stiff soils; (3) Examine the swelling potential and behaviour of the Bearpaw Formation and the influence of boundary conditions on this behaviour, while assessing the applicability of the swell concepts developed for compacted materials to a naturally swelling clay material; and (4) Constrain the depositional age of the till overlying the Bearpaw Shale. Contrary to what is seen in soft soils, smaller sized specimens were found to reduce disturbance, and produce more accurate and consistent results. Creep was found to follow the same laws as it does in soft soils, calling into question whether the use of preconsolidation pressure to predict geological history in stiff clays is appropriate. There was significant variation in the observed swell pressures of samples of the same size and depth. Finally, the glacial till at site was found to belong uniquely to the Battleford Formation and ranges in age from 22,500 to 27,500 years which is much younger (over 100,000 years younger) than previously believed. / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2010-01-29 01:34:14.071

The effect of calcium uptake by hydration and diffusion from an adjacent calcium-rich soil on the performance of a geosynthetic clay liner (GCL) is examined for three cases. In Case 1 the GCL rested directly on a soil with a high calcium (1800 mg/l) concentration in the pore water (called “calcium rich soil” herein). Case 2 involved a GCL resting on 300 mm of soil with a low (200 - 300 mg/l) calcium concentration in the pore water (“foundation soil”) overlying the calcium rich soil. In the third (“control case”), the GCL only rested on the foundation soil. The overburden pressure was 15 kPa. The moisture content of GCL increased to 96%, 86% and 108% in the first 279 days for Cases 1, 2 and 3 respectively. Under isothermal conditions, the GCL moisture content decreased to 80% and 67% for Cases 1 and 2 respectively and increased to 113% for Case 3. After 1100 days, the hydraulic conductivity (k) of the GCL was 4×10-11 m/s for Case 3 but had increased up to about 7×10-11 m/s and 2×10-10 m/s for cases with and without the foundation layer respectively. The results are used to calibrate finite element models. A good correlation was found between k the bulk void ratio (eB) of GCL. Leakage and contaminant transport through 10 mm diameter hole in a geomembrane in a composite liner involving a GCL is examined at a stress of 100 kPa for hydraulic heads of 0.3 or 1 m. When permeated with distilled water, the interface transmissivity (θ) was about 2.3 × 10 11 m2/s. After 800 days of permeation with 0.14M NaCl there was only about 3% increase in the flow despite an order of magnitude increase in GCL permeability near the hole because θ decreased from 2.3×10-11 m2/s to 1.1×10-11 m2/s and controlled the leakage despite the increase in GCL permeability. Numerical modeling demonstrated reasonable agreement with the observed transport. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2010-09-09 12:20:42.298

No description available.

<p><font face="Tahoma"> <p align="left">The purpose of this study is to evaluate the need for prophylactic antibiotic treatment in third molar surgery and to establish specific guidelines for antibiotic prophylaxis in the department of Maxillo-Facial and Oral Surgery (MFOS) at Tygerberg Academic, Groote Schuur and Mitchells Plain Hospitals.</p> </font></p>

Passive plant actuators have fascinated many researchers in the field of botany and structural biology since at least one century. Up to date, the most investigated tissue types in plant and artificial passive actuators are fibre-reinforced composites (and multilayered assemblies thereof) where stiff, almost inextensible cellulose microfibrils direct the otherwise isotropic swelling of a matrix. In addition, Nature provides examples of actuating systems based on lignified, low-swelling, cellular solids enclosing a high-swelling cellulosic phase. This is the case of the Delosperma nakurense seed capsule, in which a specialized tissue promotes the reversible opening of the capsule upon wetting. This tissue has a diamond-shaped honeycomb microstructure characterized by high geometrical anisotropy: when the cellulosic phase swells inside this constraining structure, the tissue deforms up to four times in one principal direction while maintaining its original dimension in the other. Inspired by the example of the Delosoperma nakurense, in this thesis we analyze the role of architecture of 2D cellular solids as models for natural hygromorphs. To start off, we consider a simple fluid pressure acting in the cells and try to assess the influence of several architectural parameters onto their mechanical actuation. Since internal pressurization is a configurational type of load (that is the load direction is not fixed but it “follows” the structure as it deforms) it will result in the cellular structure acquiring a “spontaneous” shape. This shape is independent of the load but just depends on the architectural characteristics of the cells making up the structure itself. Whereas regular convex tiled cellular solids (such as hexagonal, triangular or square lattices) deform isotropically upon pressurization, we show through finite element simulations that by introducing anisotropic and non-convex, reentrant tiling large expansions can be achieved in each individual cell. The influence of geometrical anisotropy onto the expansion behaviour of a diamond shaped honeycomb is assessed by FEM calculations and a Born lattice approximation. We found that anisotropic expansions (eigenstrains) comparable to those observed in the keels tissue of the Delosoperma nakurense are possible. In particular these depend on the relative contributions of bending and stretching of the beams building up the honeycomb. Moreover, by varying the walls’ Young modulus E and internal pressure p we found that both the eigenstrains and 2D elastic moduli scale with the ratio p/E. Therefore the potential of these pressurized structures as soft actuators is outlined. This approach was extended by considering several 2D cellular solids based on two types of non-convex cells. Each honeycomb is build as a lattice made of only one non-convex cell. Compared to usual honeycombs, these lattices have kinked walls between neighbouring cells which offers a hidden length scale allowing large directed deformations. By comparing the area expansion in all lattices, we were able to show that less convex cells are prone to achieve larger area expansions, but the direction in which the material expands is variable and depends on the local cell’s connectivity. This has repercussions both at the macroscopic (lattice level) and microscopic (cells level) scales. At the macroscopic scale, these non-convex lattices can experience large anisotropic (similarly to the diamond shaped honeycomb) or perfectly isotropic principal expansions, large shearing deformations or a mixed behaviour. Moreover, lattices that at the macroscopic scale expand similarly can show quite different microscopic deformation patterns that include zig-zag motions and radical changes of the initial cell shape. Depending on the lattice architecture, the microscopic deformations of the individual cells can be equal or not, so that they can build up or mutually compensate and hence give rise to the aforementioned variety of macroscopic behaviours. Interestingly, simple geometrical arguments involving the undeformed cell shape and its local connectivity enable to predict the results of the FE simulations. Motivated by the results of the simulations, we also created experimental 3D printed models of such actuating structures. When swollen, the models undergo substantial deformation with deformation patterns qualitatively following those predicted by the simulations. This work highlights how the internal architecture of a swellable cellular solid can lead to complex shape changes which may be useful in the fields of soft robotics or morphing structures. / Passive pflanzliche Aktuatoren sind bewegliche Strukturen, die eine komplexe Bewegung ohne jegliche metabolische Energiequelle erzeugen können. Diese Fähigkeit entstammt dabei der Materialverteilung mit unterschiedlicher Quellbarkeit innerhalb der Gewebsstruktur.Die bis heute am besten untersuchten Gewebearten pflanzlicher und künstlicher Passivaktuatoren sind Faserverbundwerkstoffe, in denen steife, fast undehnbare Zellulosemikrofibrillen die ansonsten isotrope Schwellung einer Matrix leiten. Darüber hinaus gibt es in der Natur Beispiele für Aktuationssysteme, wie z.B. die Delosoperma nakurense Samenkapsel, in der das Aktuatorgewebe eine Wabenstruktur aufweist, deren Zellen mit einem hochquellenden Material gefüllt sind. Dabei hat die Wabenstruktur des Gewebes eine hohe geometrische Anisotropie, so dass sich das Gewebe bei Wasseraufnahme bis zur vierfachen Länge entlang einer Hauptrichtung ausdehnt und somit die reversible Öffnung der Kapsel angetrieben wird. Inspiriert durch das Vorbild der Delosoperma nakurense, wird in der vorliegenden Arbeit die Rolle der Architektur von 2D-Zellulärmaterialien als Modell für natürliche passive Aktuatoren analysiert. Zunächst wird anhand eines einfachen Flüssigkeitsdrucks in den Zellen der Einfluss verschiedener architektonischer Parameter auf deren mechanische Betätigung untersucht. Wohingegen regelmäßige konvexe Wabenstrukturen (wie z. B. sechseckige, dreieckige oder quadratische Gitter) sich unter Druck isotropisch verformen, wird durch Finite-Elemente-Simulationen gezeigt, dass es bei anisotropen und nicht-konvexen Zellen zu großen Ausdehnungen jeder einzelnen Zelle kommt. Auch wenn nur eine einzelne Zellgeometrie betrachtet wird, können hierbei viele verschiedene Gitter entstehen. Die Ausdehnungsrichtung des Gitters ist variabel und hängt von der lokalen Konnektivität der Zellen ab. Dies hat Auswirkungen sowohl auf makroskopischer (Gitter-) als auch auf mikroskopischer (Zell-) Ebene. Auf makroskopischer Ebene erfahren diese nicht-konvexen Gitter entweder große anisotrope (ähnlich der Delosperma nakurense Samenkapsel) oder vollkommen isotrope Eigendehnungen, große Scherverformungen oder jeweilige Mischformen. Überdies können Gitter mit ähnlichem makroskopischem Verhalten gänzlich unterschiedliche mikroskopische Verformungsmuster zeigen, wie z.B. Zick-Zack-Bewegungen oder radikale Änderungen der ursprünglichen Zellform. Dies verursacht auch eine entsprechende Änderung der elastischen Eigenschaften. In Abhängigkeit der Gitterarchitektur kann es zu gleichen oder unterschiedlichen mikroskopischen Zelldeformationen kommen, die sich in Summe entweder verstärken oder ausgleichen, und somit die Vielzahl an makroskopischen Verhalten erklären. Interessanterweise lassen sich mit Hilfe einfacher geometrischer Argumente aus der nichtdeformierten Zellform und Zellkonnektivität die Ergebnisse der FE-Simulationen vorhersagen. Die Ergebnisse der Finite-Elemente-Simulationen wurden durch Laborversuche bestätigt, in denen (mit 3D-Drucktechnik gefertigte) Modellgitter ähnliches Ausdehnungsverhalten beim Quellen zeigen. Diese Arbeit zeigt auf, wie die Innenarchitektur eines quellfähigen zellulären Feststoffs zu komplexen Formänderungen führen kann, die in den Bereichen der Soft-Robotik oder bei Morphing-Strukturen angewandt werden können.

Chitosan membrane has found applications in biomedical, wastewater treatment, and petrochemical fields that involve the use of silver ions (Ag+). However, mobility of Ag+ in chitosan membranes has seldom been studied. In this study, transport properties of Ag+ in chitosan membranes are studied in-depth, to determine diffusivity coefficient, permeability coefficient, and sorption uptake of Ag+ in chitosan. All parameters are evaluated based on the influence of feed concentration, membrane thickness and operating temperature. The diffusivity is determined from the time lag obtained from transient diffusion experiments. The permeability is determined from the steady state of permeation experimentally. The diffusivity and corresponding permeability coefficients of Ag+ in chitosan range from to 2.0 10-7 (cm2/s) and from 6.6 10-8 to 2.0 10-7 {mol m/[m2 s (mol/L)]}, respectively, over the conditions tested. Temperature dependencies of these two parameters are found to follow the Arrhenius relationship. Sorption uptake of the silver salt in chitosan correlates well with the Langmuir isotherm. Also determined from the sorption tests are degree of membrane swelling at different concentrations. This information allows diffusivity coefficients to be determined from the steady state permeation rate. These values of diffusivity are compared with that obtained using the time lag method.

Homogenization of alloying elements is desired during sintering of powder metallurgy components. The redistribution processes such as penetration of liquid phase into the interparticle/grain boundaries of solid particles and subsequent solid-state  diffusion of alloy element(s) in the base powder, are important for the effective homogenization of alloy element(s) during liquid phase sintering of the mixed powders. The aim of this study is to increase the understanding of alloy element redistribution processes and their effect on the dimensional properties of the compact by means of numerical and experimental techniques. The phase field model coupled with Navier-Stokes equations is used for the simulations of dynamic wetting of millimeter- and micrometer-sized metal drops and liquid phase penetration into interparticle boundaries. The simulations of solid particle rearrangement under the action of capillary forces exerted by the liquid phase are carried out by using the equilibrium equation for a linear elastic material. Thermodynamic and kinetic calculations are performed to predict the phase diagram and the diffusion distances respectively. The test materials used for the experimental studies are three different powder mixes; Fe-2%Cu, Fe-2%Cu-0.5%C, and Fe-2%(Cu-2%Ni-1.5%Si)-0.5%C. Light optical microscopy, energy dispersive X-ray spectroscopy and dilatometry are used to study the microstructure, kinetics of the liquid phase penetration, solid-state diffusion of the Cu, and the dimensional changes during sintering. The wetting simulations are verified by matching the spreading experiments of millimeter-sized metal drops and it is observed that wetting kinetics is much faster for a micrometer-sized drop compared to the millimeter-sized drop. The simulations predicted the liquid phase penetration kinetics and the motion of solid particles during the primary rearrangement stage of liquid phase sintering in agreement with the analytical model. Microscopy revealed that the C addition delayed the penetration of the Cu rich liquid phase into interparticle/grain boundaries of Fe particles, especially into the grain boundaries of large Fe particles, and consequently the Cu diffusion in Fe is also delayed. We propose that the relatively lower magnitude of the sudden volumetric expansion in the master alloy system could be due to the continuous melting of liquid forming master alloy particles. / <p>QC 20140515</p>

Global concern about the environmental impacts of waste disposal and stringent implementation of environmental laws lead to numerous research on recycled materials. Increased awareness about the inherent engineering values of waste materials, lack of landfill sites and strong demand for construction materials have encouraged research on composite materials, which are either fully or partly made of recycled materials. This trend is particularly strong in transportation and geotechnical projects, where huge quantities of raw materials are normally consumed. Owing to the low mass-to-volume ratio, disposal of Expanded Polystyrene (EPS) is a major problem. In addition, EPS recycling methods are expensive, labour intensive and energy demanding. Hence, this thesis is focused on the development of a new soil composite made by mixing recycled EPS with expansive clays. Given the high cost of damage to various buildings, structures and pavements caused by the unpredictable ground movements associated with expansive soils, it has been considered prudent to try and develop a new method of soil modification using recycled EPS beads as a swell-shrink modifier and desiccation crack controller. The innovative application of recycled EPS as a soil modifier will minimise the quantity of waste EPS destined to the landfill considerably. An extensive experimental investigation has been carried out using laboratory reconstituted expansive soils - to represent varied plasticity indices - consisting of fine sand and sodium bentonite. Three soils notated as SB16, SB24 and SB32 representing 16%, 24% and 32% of bentonite contents respectively were tested with four EPS contents of 0.0%, 0.3%, 0.6% and 0.9%. The tests performed include compaction, free swell, swell pressure, shrinkage, desiccation, shear strength and hydraulic conductivity. All the tests have been performed at the respective maximum dry unit weight and optimum moisture content of the mixes. It has been observed that by mixing of recycled EPS beads with the reconstituted soil, a lightweight geomaterial is produced with improved engineering properties in terms of dry unit weight, swelling, shrinkage and desiccation. The EPS addition depends on the moulding moisture content of the soil. With increasing moisture content, additional EPS can be added. Also, there is a reduction in dry unit weight with the addition of EPS. Furthermore, the reduction of swell-shrink potential and desiccation cracking in soils, for example, is related to the partial replacement of soil particles as well as the elasticity of the EPS beads. There is a reduction in shear strength with the addition of EPS to soils. However, mixing of chemical stabilisers along with EPS can enhance the strength in addition to improved overall properties.

Thesis (Ph. D.)--University of Adelaide, Dept. of Soil Science. / Copies of author's previously published articles inserted. Includes bibliographical references (leaves 173-196).

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2006. / Härtill 5 uppsatser.