Steel moment frames are often used in structures to provide lateral strength and stiffness to the structure. These frames are subject to failure modes including buckling in the out of plane direction in a lateral-torsional buckling mode. This failure mode is influenced by interactions of the members through their connections. While the flexural behaviour has been studied in depth and for some time, the effect of torsional warping interaction between members has not been studied extensively. This work presents an analysis of the effect of including the effects of warping interaction or neglecting them, as is done in the current design practice. The issues of inelastic behaviour are considered, as well as the case of torsionally sensitive members. A joint element model is created to treat the warping displacements and their continuity through the joint. The study finds that the current practice of neglecting the warping displacement continuity appears to be a conservative assumption. It is recommended that the present practice of neglecting the effects of warping in analysis of frames continues. / Structural Engineering

This study assessed the accuracy and reliability of tooth length measurements through axial, coronal and sagittal serial slices of CBCT volumes; conventional panoramic radiographs; and CBCT panoramic reconstructions to that of a digital caliper gold standard. Samples consisted of maxillary premolars collected from patients requiring extractions for routine orthodontic treatment. Extracted teeth were measured directly with digital calipers and images were digitally measured in Dolphin 3D software. Analysis of CBCT serial slices resulted in highly accurate and reliable tooth length measurements for all slice orientations compared to the gold standard. Conventional panoramic radiographs were relatively inaccurate, overestimating tooth lengths by 29%, while CBCT panoramic reconstructions underestimated lengths by 4%. CBCT serial slice volume analysis provides clinicians with greater measurement confidence, while panoramic radiographs, produced either by conventional means or reconstructed from 3-D volumes should be considered less accurate and reliable for the detection of mild root resorption. / Medical Sciences - Orthodontics

The procedure for milling micrometre scale cantilevers of lutetium iron garnet using a focused ion beam microscope was developed. The infrastructure to study these cantilevers using rotational hysteresis loops and ferromagnetic resonance experiments was set up. The cantilevers were shown to remain magnetic after milling, and the origin of their hysteresis loops investigated with a variant of the Stoner-Wohlfarth model. Ferromagnetic resonance in the cantilevers was demonstrated as the first step towards studying magnetomechanical coupling.

The purpose of this research was to compare skeletal and dental changes assessed by digital volumetric images produced during and after rapid maxillary expansion (RME) between a bone-borne anchored expansion appliance and a conventional tooth-borne RME. Initial steps included the development of a methodology to analyze CBCT images. Reliability of traditional two dimensional (2D) cephalometric landmarks identified in CBCT images was explored, and new landmarks identifiable on the CBCT images were also evaluated. This methodology was later tested through a clinical trial with 62 patients where skeletal and dental changes found after maxillary expansion using either a bone-borne or tooth-borne maxillary expander and compared to a non-treated control group. The conclusions that were obtained from this thesis were that the NewTom 9” and 12” three dimensional (3D) images present a 1-to-1 ratio with real coordinates, linear and angular distances obtained by a coordinate measurement machine (CMM). Landmark intra- and inter-reliability (ICC) was high for all CBCT landmarks and for most of the 2D lateral cephalometric landmarks. Foramen Spinosum, foramen Ovale, foramen Rotundum and the Hypoglossal canal all provided excellent intra-observer reliability and accuracy. Midpoint between both foramen Spinosums (ELSA) presented a high intra-reliability and is an adequate landmark to be used as a reference point in 3D cephalometric analysis. ELSA, both AEM and DFM points presented a high intra-reliability when located on 3D images. Minor variations in location of these landmarks produced unacceptable uncertainty in coordinate system alignment. The potential error associated with location of distant landmarks is unacceptable for analysis of growth and treatment changes. Thus, an alternative is the use of vectors. Selection of landmarks for use in 3D image analysis should follow certain characteristics and modifications in their definitions should be applied. When measuring 3D maxillary complex structural changes during maxillary expansion treatments using CBCT, both tooth-anchored and bone-anchored expanders presented similar results. The greatest changes occurred in the transverse dimension while changes in the vertical and antero-posterior dimension were negligible. Dental expansion was also greater than skeletal expansion. Bone-anchored maxillary expanders can be considered as an alternative choice for tooth-anchored maxillary expanders. / Medical Sciences in Orthodontics

No description available.

While modern epitaxial methods enable precise, monolayer (ML) control of the thin film deposition process, the complexity of certain device structures is ultimately limited by the capability and cost of the fabrication process. The objective of this work is to develop a pathway toward three-dimensional epitaxy (3DE) - the ability to intentionally and dynamically pattern regions of a film during the deposition process - in order to enable novel device concepts unbound by the traditional device fabrication paradigm. This work pioneers UV-assisted metal organic molecular beam epitaxy (MOMBE) as a particularly selective epitaxy technique to create a pathway toward 3DE of a crucial and topical material system - the III-Nitrides. A novel UV-assisted MOMBE system is developed enabling intense UV irradiation of films during growth. High quality, heavily (unintentionally) carbon-doped GaN is successfully grown by NH₃-based MOMBE and for the first time InGaN, AlGaN, and magnesium-doped GaN are demonstrated by NH₃-based MOMBE. Intense UV irradiation of films during NH₃-based MOMBE significantly enhances photo-desorption of species during the growth process, subsequently affecting the resultant InGaN alloy composition, carbon dopant concentration, or magnesium dopant concentration. A digital micromirror device is introduced to pattern incident UV radiation during InGaN growth, demonstrating that the effects of photoexcitation during MOMBE which have been proposed, discovered, and identified by this thesis indeed can be leveraged to deposit an InGaN film that is compositionally patterned within the growth plane. The results demonstrate that the new approach presented herein is possible for the 3DE of III-Nitrides if additional challenges in practical implementation can be overcome.

This thesis deals with developing a thermodynamically consistent model to simulate the electromechanical response of ionic polymer-metal composites based on Euler-Bernoulli beam theory. Constitutive assumptions are made for the Helmholtz free energy and the rate of dissipation. The governing equations involving small deformations are formulated using the conservation laws, the power theorem, and the maximum rate of dissipation hypothesis. The model is extended to solve large deformation cantilever beams involving pure bending which could be used in the characterization of the material parameters. A linear finite element solution along with a staggered time stepping algorithm is provided to numerically solve the governing equations of the small deformations problem under generalized electromechanical loading and boundary conditions. The results are in qualitative and quantitative agreement with the experiments performed on both Nafion and Flemion based Ionic Polymer-Metal Composite strips.

The deformation mechanisms operating in diamond-like carbon (DLC) coatings on (100) and (111) Si, has been investigated. The effect of coating thickness, indenter geometry, substrate orientation and deposition technique on the deformation of DLC coatings and the underlying substrate was studied by undertaking nanoindentation followed by subsurface microstructural characterization. Uncoated (111) Si was also investigated for comparison. The observed microstructural features were correlated to the indentation response of the coatings and compared with simulation studies, as well as observations on uncoated Si. In uncoated (111) Si, phase transformation was found to be responsible for the discontinuities in the load-displacement curves, similar to (100) Si. However, slip was activated on {311} planes instead of on {111} planes. Moreover, the density of defects was also significantly lower and their distribution asymmetric. The coatings were adherent, uniformly thick and completely amorphous. The load-displacement curves displayed several pop-ins and a pop-out, the indentation loads for the first pop-in and the pop-out depending primarily on the thickness of the coating. The coatings exhibited localized compressive deformation in the direction of loading without any through-thickness cracks. The extent of this localized deformation increased with indentation load. Hardness and thickness of the coatings and the geometry of the indenter influenced the magnitude of compressive strains. Harder and thinner coatings and a blunt indenter exhibited the minimum degree of deformation. Densification by rearrangement of molecules has been suggested as the mechanism responsible for plastic compression. At indentation loads corresponding to the first pop-in, (100) and (111) silicon substrates initially deformed by <111> and <311> slip respectively. Higher indentation loads caused phase transformation. Therefore, unlike in uncoated Si, dislocation nucleation in the Si substrate has been proposed as the mode responsible for the first pop-in. Subsequent pop-ins were attributed to further deformation by slip and twinning, phase transformation and extensive cracking (median and secondary cracks) of the substrate. The pop-out, however, was ascribed to phase transformation. Extensive deformation in the substrate, parallel to the interface, is attributed to the wider distribution of the stress brought about by the DLC coating. Good correlation was obtained between the nanoindentation response, microstructural features and simulation studies.

The ability to generate three dimensional (3D) microstructures in solids is of great importance in understanding their true nature, as it eliminates speculation about the spatial distribution of features associated with conventional two dimensional (2D) imaging techniques. There are several recently-developed 3D techniques for determining the spatial distribution of microstructural features, each with a given resolution. There is considerable interest in the development of a specific serial sectioning methodology, termed 3D electron backscatter diffraction (3D-EBSD), which combines a focused ion beam (FIB) with EBSD interfaced to a field emission gun scanning electron microscope. Here, FIB is used as a serial sectioning device for cutting parallel slices of single- and multi-phase materials with a site-specific accuracy of up to 50 nm. Each consecutive slice is mapped by EBSD and the complete dataset combined using advanced computer algorithms to generate a volume of a material whereby the true crystallographic features can be analyzed at submicron resolution. The aims of the thesis was to develop 3D-EBSD into a powerful materials analysis tool and use it to resolve several issues concerning the nature of the deformed state and the nucleation and the growth behaviour of recrystallizing grains. The study commenced with an investigation into the effect of material type (restricted to face centred cubic AI, Cu and Au metallic crystals), FIB milling conditions and EBSD software variables on the quality of EBSD patterns generated on ion-milled surfaces of these materials. The effect of material type on EBSD pattern quality following FIB milling was found to be significant with relatively poor quality EBSD patterns obtained for metals of low atomic number. It was demonstrated, particularly for the high atomic number metals, that moderate FIB milling currents (~1-5nA) generated good quality EBSD maps from a given ion-milled surface. This preliminary work was necessary for balancing the time required for serial sectioning during 3D-EBSD and the generation of sufficient quality EBSD maps from each ion-milled surface. The outcomes of this investigation were applied to two major 3D-EBSD investigations on the microstructural and crystallographic characteristics of: (i) deformation features generated in a cold rolled interstitial free (IF) steel, with particular emphasis on the formation of microbands; and (ii) recrystallization of a cold rolled nickel alloy containing coarse (>1 ??m) silica particles, with particular attention given to the generation of particle deformation zones and their influence on nucleation and growth of recrystallizing grains including particle stimulated nucleation (PSN), twin formation during PSN and the growth behaviour of various types of grain boundary into the deformation microstructure. The foregoing 3D-EBSD studies were significant as they revealed various microstructural and crystallographic features not usually clearly evident in conventional 2D micrographs obtained by either EBSD or optical metallography. For example, the technique demonstrated that microbands in cold rolled IF steel consist of irregular curved surfaces that reconcile findings that microbands straight and aligned parallel to slip planes when viewed in normal direction-rolling direction sections but are wavy in transverse direction-rolling direction sections. Three slip planes were found within the angular range of the curved surface of the microband, which indicates that multiple slip planes are operative during deformation. The work also showed the influence of particle diameter on the misorientations generated within particle deformation zones and clearly showed that particle stimulated nucleation (PSN) occurred at particles greater than 1.5-2 ??m. It was observed that PSN in the nickel sample also generates contiguous grains separated by both coherent and incoherent twin boundaries and, on further growth of these grains into the matrix, the coherent boundary dominates and remains parallel to the primary growth direction of the grains.

Composite materials are well-renown for their strength to weight ratios and are widely used in many industries where high strength and low weight is required. Although steel is the traditional material of choice in the mining industry, and particularly for conveyor support structures, the strength and weight advantages offered by composite materials has prompted this investigation into the feasibility of using composite materials in underground mining conveyor support structures. The first phase of the project centred on establishing and applying selection criteria for the materials and processes which could be used in such a structure. Key concerns include fire performance, electrical conductivity, cost, availability and manufacturability. Based on these considerations, the project identified a phenolic-glass laminate manufactured using the RTM method (for moulded components) or the pultrusion process (for tube sections) as a possible basis for a composite conveyor support structure. The second phase of the project developed a set of design criteria for the use of composite materials in conveyor support structures and a series of preliminary designs based on current conveyor configurations. After analysing each preliminary design against key design criteria, in particular cost, weight, assembly time, susceptibility to damage and torsional loading, the Linestand Suspended - Beam configuration was selected as the preferred option. The third phase of the project used the findings of the preliminary design analysis and the key design criteria to develop a prototype final design. The prototype design is based on a hybrid style of frame. The majority of the structure is constructed from a custom pultruded beam connected with a composite connection piece, while the interface between the rollers and the frame utilises a steel bracket to reduce the risk of damage to the composite frame. The final design is 12kg lighter than the current smaller steel design of similar function. The project has demonstrated the feasibility of using composite materials in conveyor support structures and the weight savings that may be achieved.