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Auditory nerve fiber models provide further insight into the inner workings of the ear and brain. These models have helped us to develop physiologically based speech intelligibility metrics, to assess the difficulty of understanding speech objectively. Several metrics have been developed, but they have been developed using a range of auditory nerve (AN) fiber models. A full comparison of different metrics on even footing should be performed to evaluate the accuracy of their predictions. Speech intelligibility is understood to be dependant on both temporal fine structure and envelope cues in the acoustic speech signal, which are however linked in a way where they are very difficult to split. This makes the evaluation of speech intelligibility metrics tricky, as metrics often aim to analyze mean rate and fine timing information in the auditory nerve representation of the acoustic cues. In this study, a method of phase distortion was developed, with the goal of degrading the fine timing information of a speech signal to the point where only the mean rate representation in the AN is contributing to the speech intelligibility. Also, the neural cross correlation coefficients developed in Heinz & Swaminathan (2009) were adapted from the Zilany & Bruce (2007) auditory nerve model to the Bruce, Erfani & Zilany (2018) AN model. / Thesis / Master of Applied Science (MASc)

The perovskite solar cells have attracted much attention recently due to their low fabrication cost and high power conversion efficiency. However, the instability of such devices remained a serious challenge, which is yet to be resolved despite many attempts. In this thesis, the moisture degradation mechanism has been uncovered. It was found that the perovskite structure can be reconstructed when annealed at around 90℃, which leads to a reversible device of a much higher device lifetime. Following the experimental explorations, modelling work has also been conducted to simulate the water diffusion during the degradation and recovery. It was found that the moisture diffusion was initiated at the surface imperfection, where the activation energy for diffusion can be reduced. Based on these discoveries, a fresh structural negotiation method has been proposed to obtain a stable FAPbI3 phase of a suitable bandgap for photovoltaics, which showed a reduced Gibbs free energy of 0.12eV compared with the δ phase. In addition, the activation energy for such phase transition was calculated to be 0.45eV, meaning that the discovered phase is protected by both thermodynamics and kinetics. All this opens an unprecedented avenue in perovskite research, which will hopefully be of intrinsic interest to the broad materials research community as well. / Thesis / Doctor of Philosophy (PhD)

This research studies the effects of a postulated Main Steam Line Break accident in a nuclear plant on the transient loading of steam generator tubes. The problem involves complex transient two-phase flow dynamics and fluid-structural loading processes. A better understanding of this phenomenon will permit the development of improved design tools to ensure steam generator safety. This Thesis presents the results of an experimental laboratory study of the transient loading of a sectional model of steam generator tubes during a simulated two-phase blowdown. The research was carried out in a purpose designed and built experimental facility. The thermodynamic phenomena were investigated through dynamic pressures and temperatures. The transient tube loads were directly measured using dynamic load cells. The working fluid was R-134a and the tube bundle was a normal triangular array with a pitch ratio of 1.36. Preliminary testing indicated parasitic loading on the instruments and remedial actions were taken to ensure measurement accuracy. The success of the instrumentation development methodologies was validated in a series of single- phase blowdowns. Two-phase blowdown experiments were then conducted with various levels of liquid and numbers of tube rows. The results provided hitherto unknown information relating the nature of the fluid-structure interaction and flow development during a two-phase transient blowdown across a tube bundle. The pressure drop across the tube bundle established the thermal hydraulic fluid behaviour in the pressure vessel and controlled the upstream fluid discharge from the system. The flow through the bundle was choked for the majority of the transient. The transient tube loading was explained in terms of the associated fluid mechanics and the maximum load was compared with existing models obtained under steady flow conditions. An empirical model was developed that enables the prediction of the maximum tube loads once the pressure drop is known. / Thesis / Doctor of Philosophy (PhD) / The design of nuclear plant systems requires that public safety be ensured for the worst-case imaginable accident scenarios. This means that radioactive materials produced by nuclear fission must be safely contained. If the main steam pipe from a nuclear steam generator were to break, the water in the steam generator would rapidly boil off in what is called a blowdown. Such an event could produce significant loading on the heat exchanger tubes. Should the tubes rupture, radioactive materials may breach reactor containment. Thus, knowing the tube loading during this hypothetical scenario is an important input for safe design. The goal of this research is to improve our understanding of the effects of this postulated accident on the transient loading of the tubes. A laboratory study was carried out to simulate the blowdown. The experimental results provided valuable insights and guidance for the development of improved design tools.

Biodiesel is a renewable, biodegradable, clean burning fuel, produced from vegetable oils and animal fat. It is a mixture of fatty acid alkyl esters, products that result from the catalytic transesterification of lipids. The first part of this research describes the development of a new and direct method used to rapidly and quantitatively determine the amount of free methanol in biodiesel samples. The analytical method developed is different from the current standards for methanol determination, and it is the first headspace-SPME method used to extract methanol from biodiesel as matrix. The second part of this research describes the direct analysis of acetic acid and 2uraldehyde in an aqueous mixture using headspace SPME. The direct and accurate determination and quantitation of these two analytes is very important, as they can be inhibitors or food sources for microorganisms capable of producing lipids or ethanol.

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