Optical reflectance of the quasi two dimensional compound Hg₂.₈₆AsF₆ has been investigated in the optical range, 0.5 to 4 eV. The spectra clearly show a plasma edge at 3 eV. They are fitted to a Drude model and two Lorentz oscillators. From the plasma frequency and the model parameters values for the dc conductivity and the effective mass and an estimate of the crytsal anisotropy have been obtained. The results compare well with earlier electrical measurements on this compound. / Thesis / Master of Science (MSc)

A more robust method for solving the governing equations of a one-dimensional stage-by-stage dynamic compression system model was developed and validated. The improved method was then applied to two-dimensional post-stall models. The improvement in robustness was achieved by modeling the governing equations with upwind differencing and use of implicit time integration. A special form of upwind flux, flux difference splitting with source term treatment, FDSS, was developed for the model. A two-dimensional axisymmetric model was developed to allow post-stall modeling of split flowpath systems such as turbofans. This model was an entirely new concept. Additionally, a two-dimensional axial-circumferential model of rotating stall cell development and propagation was developed based on previous work. All of the models developed applied upwind differencing techniques to improve upon central-difference methods. / Ph. D.

<p> The behavior of concrete block walls subjected to vertical compressive loads with out-of-plane eccentricities was investigated both experimentally and analytically. Particular attention was devoted to the effect of wall slenderness on capacity.</p> <p> In the experimental study, 14 full scale walls and numerous small specimens were tested to provide complete and reliable data concerning the behavior of concrete block walls and its components. Plain walls and partially grouted reinforced walls were tested in symmetric single curvature under compressive loads with out-of-plane eccentricities. Reinforced walls were tested in pure bending, as well.</p> <p> Prisms were tested to analyze the behavior of concrete masonry in compression with no slenderness or eccentricity effects. Bond tests were carried out to determine the behavior at interfaces of grout and steel reinforcing bars as well as between mortar and concrete blocks. Material tests were conducted to determine the mechanical properties of the blocks, mortar, grout and steel reinforcement used.</p> <p> A two-dimensional finite element model for the vertical cross section of block masonry walls was developed. It is capable of modeling local failure modes such as cracking, crushing and debonding. Material properties of the concrete blocks, mortar, grout, and steel bars were treated individually. The large deformation analysis allowed for consideration of the slenderness effect. The model was verified through comparison with experimental results. Fairly good agreement was obtained.</p> <p> The material properties of specimens tested during the experimental investigation were the basis of a parametric study. Results of this study were used to investigate the effect of the wall slenderness and the eccentricity of applied loads on the capacity of concrete block walls. They were used to evaluate the current provisions in the Canadian Masonry Code, CAN3-S304-M84. An attempt was made to develop original design equations based on the reduction coefficient approach. The proposed equations for plain and reinforced blockwork were shown to provide more consistent predictions of capacity than current design methods.</p> / Thesis / Master of Engineering (MEngr)

In the search for nano-scale, highly customizable materials for next-generation electronic devices, two-dimensional (2D) materials have generated much interest. 2D materials have complex, layer-dependent optical and electronic properties of which many aspects remain yet to be explored and fully understood. The aim of this thesis was to investigate and explain optoelectronic properties of several 2D materials systems towards device design. This was accomplished using predictive physical modelling at the density functional theory level (DFT) as well as many-body theory (GW+BSE). The optical transitions of bulk ReS2 and ReSe2 were studied using DFT in comparison with experiment. We found that the orbital composition of the band edges determined the sign of the pressure coefficient of the optical gap. Our results provide a step towards understanding the perceived layer-independence of the optical properties of ReS2 and ReSe2. The exciton landscape of MoS2 monolayer was explored in detail using many-body theory (GW+BSE). We found dark excitons very close to bright excitons and even lower in energy. Our results help reverse the common assumption that the lowest-energy exciton in MoS2 is bright. The ideal band offset between recently predicted monolayers of the CaP3 family was predicted using GW theory. We observed chemical trends in the band offsets and explained their origin. Our results serve as indicators for heterojunction design with these novel materials. The effective mass of a test set of eighteen semiconductors including several 2D materials was calculated using DFT with semi-local and non-local hybrid exchange-functionals and compared for accuracy with respect to experimental data. Our analysis details the effect of the nonlocal exchange potential on the accuracy of the effective mass. Our results give guidelines for high-throughput calculations of the effective mass for different material classes, including 2D materials. / Thesis / Doctor of Philosophy (PhD)

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<p> The objective of this thesis was to undertake an uncertainty analysis on the outputs from a two-dimensional hydrodynamic model. The analysis utilized an application of the Resource Management Associates' RMA2 model for the Upper St. Lawrence River in Ontario, Canada. Two uncertainty analysis methods, First-Order Second Moment (FOSM) and Monte Carlo analysis, are applied to calculate the uncertainty in water levels and velocities computed by the model.</p> <p> Both uncertainty analysis methods can be applied together with two-dimensional hydrodynamic modelling, but based on the findings of this work, the FOSM method is preferred. First, FOSM estimates of uncertainty are slightly larger than those obtained using Monte Carlo analysis. Thus, FOSM provides a conservative estimate of the uncertainty, a positive characteristic. Second, the FOSM method is simpler to apply than Monte Carlo analysis, requiring less information to describe the model inputs, fewer model executions and computations to calculate the uncertainty. Third, FOSM provides an immediate indication of the primary contributors to the uncertainty in the output, where Monte Carlo analysis requires additional effort to do the same.</p> <p> The model input that contributed the most to the uncertainty in the model outputs is the bottom resistance represented in RMA2 using Manning's n. The uncertainty in Manning's n is large and the model is sensitive to the parameter. As a result, a significant amount of uncertainty in the model outputs is contributed by this parameter.</p> <p> Uncertainty analysis is a practical addition to the two-dimensional hydrodynamic modelling process. The effort required to complete an uncertainty analysis using the FOSM method is minimal and the resulting insight is meaningful. It provides information to the model developer, quantifying how good the model actually is. It also provides a measure of the accuracy of the model for future model users or clients using hydrodynamic modelling outputs.</p> / Thesis / Master of Applied Science (MASc)

<p> The progress of technology in the electronic components industry has been rapidly growing. The evolution of various techniques has made it possible for this industry to grow and diversify with the market demand. Thus, the development of electronic component products over a short span of time requires having highly efficient tools for design and manufacturing. Advances in commercial Computational Fluid Dynamics (CFD) softwares and computational power have enabled modeling to a high level of architectural details. Nowadays, computer aided design becomes an essential design tool in the engineering environment. Computer analysis reduces both the time development cycle and the prototyping costs in the early to intermediate design phases. The accuracy of the computational prediction of heat transfer rates depends mostly on the correct choice of turbulent model. Although many turbulent models, rather than a universal turbulent model, have been developed during the last two decades, there is usually one model that performs better than others for certain flow conditions. </p> <p> In the present research, a turbulence model is selected from amongst a few candidates, namely standard k- 8, RNG k- 8, shear stress transport (SST), and Reynolds Stress Model (RSM), based on comparisons with experimental data and direct numerical simulation (DNS) results from previous work. The SST turbulence model shows excellent agreement with the DNS results and, hence, is considered an appropriate turbulence model for thermal analysis of electronic packages with elements that have almost the same heights. Moreover, the average Nusselt number of array of obstacles is obtained numerically using commercial code ANSYS-CFX 1 0.0. The effects upon the mean Nusselt number arising from parameteric changes in Reynolds number, element height, element width, and element-to-element distance are compared and discussed. Finally, the parametric study has offered a set of correlations for the mean Nusselt number of arrays of mounted obstacles in the channel flow. </p> / Thesis / Master of Applied Science (MASc)