3 resultados para elliptical core non-hexagonal symmetry

em QSpace: Queen's University - Canada


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This study was performed to characterize evidence of potential unconformity-type U mineralizing fluids in drill core fractures from the Stewardson Lake prospect, in the Athabasca Basin, located in Northern Saskatchewan and Alberta, Canada. Fractures were visually classified into eight varieties. This classification scheme was improved with the use of mineralogical characterization through SEM (Scanning Electron Microscope) and XRD analyses of the fracture fills and resulted in the identification of various oxides, hydroxides, sulfides, and clays or clay-sized minerals. Fractures were tallied to a total of ten categories with some commonalities in color. The oxidative, reductive or mixed nature of the fluids interacting with each fracture was determined based on its fill mineralogy. The measured Pb isotopic signature of samples was used to distinguish fractures affected solely by fluids emanating from a U mineralization source, from those affected by mixed fluids. Anomalies in U and U-pathfinder elements detected in fractures assisted with attributing them to the secondary dispersion halo of potential mineralization. Three types of fracture functions (chimney, composite and drain) were defined based on their interpreted flow vector and history. A secondary dispersion halo boundary with a zone of dominance of infiltrating fluids was suggested for two boreholes. The control of fill mineralogy on fracture color was investigated and the indicative and non-indicative colors and minerals, with respect to a secondary dispersion halo, were formally described. The fracture colors and fills indicative of proximity to the basement host of the potential mineralization were also identified. In addition, three zones of interest were delineated in the boreholes with respect to their geochemical dynamics and their relationship to the potential mineralization: a shallow barren overburden zone, a dispersion and alteration zone at intermediate depth, and a second deeper zone of dispersion and alteration.

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This study investigates the effect of foam core density and skin type on the behaviour of sandwich panels as structural beams tested in four-point bending and axially compressed columns of varying slenderness and skin thickness. Bio-composite unidirectional flax fibre-reinforced polymer (FFRP) is compared to conventional glass-FRP (GFRP) as the skin material used in conjunction with three polyisocyanurate (PIR) foam cores with densities of 32, 64 and 96 kg/m3. Eighteen 1000 mm long flexural specimens were fabricated and tested to failure comparing the effects of foam core density between three-layer FFRP skinned and single-layer GFRP skinned panels. A total of 132 columns with slenderness ratios (kLe/r) ranging from 22 to 62 were fabricated with single-layer GFRP skins, and one-, three-, and five-layer FFRP skins for each of the three foam core densities. The columns were tested to failure in concentric axial compression using pinned-end conditions to compare the effects of each material type and panel height. All specimens had a foam core cross-section of 100x50 mm with 100 mm wide skins of equal thickness. In both flexural and axial loading, panels with skins comprised of three FFRP layers showed equivalent strength to those with a single GFRP layer for all slenderness ratios and core densities examined. Doubling the core density from 32 to 64 kg/m3 and tripling the density to 96 kg/m3 led to flexural strength increases of 82 and 213%, respectively. Both FFRP and GFRP columns showed a similar variety of failure modes related to slenderness. Low slenderness of 22-25 failed largely due to localized single skin buckling, while those with high slenderness of 51-61 failed primarily by global buckling followed by secondary skin buckling. Columns with intermediate slenderness experienced both localized and global failure modes. High density foam cores more commonly exhibited core shear failure. Doubling the core density of the columns resulted in peak axial load increases, across all slenderness ratios, of 73, 56, 72 and 71% for skins with one, three and five FFRP layers, and one GFRP layer, respectively. Tripling the core density resulted in respective peak load increases of 116, 130, 176 and 170%.

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In this work I study the optical properties of helical particles and chiral sculptured thin films, using computational modeling (discrete dipole approximation, Berreman calculus), and experimental techniques (glancing angle deposition, ellipsometry, scatterometry, and non-linear optical measurements). The first part of this work focuses on linear optics, namely light scattering from helical microparticles. I study the influence of structural parameters and orientation on the optical properties of particles: circular dichroism (CD) and optical rotation (OR), and show that as a consequence of random orientation, CD and OR can have the opposite sign, compared to that of the oriented particle, potentially resulting in ambiguity of measurement interpretation. Additionally, particles in random orientation scatter light with circular and elliptical polarization states, which implies that in order to study multiple scattering from randomly oriented chiral particles, the polarization state of light cannot be disregarded. To perform experiments and attempt to produce particles, a newly constructed multi stage thin film coating chamber is calibrated. It enables the simultaneous fabrication of multiple sculptured thin film coatings, each with different structure. With it I successfully produce helical thin film coatings with Ti and TiO_{2}. The second part of this work focuses on non-linear optics, with special emphasis on second-harmonic generation. The scientific literature shows extensive experimental and theoretical work on second harmonic generation from chiral thin films. Such films are expected to always show this non-linear effect, due to their lack of inversion symmetry. However no experimental studies report non-linear response of chiral sculptured thin films. In this work I grow films suitable for a second harmonic generation experiment, and report the first measurements of non-linear response.