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Survey work has resolved certain reported anomalies in this system. In particular, TiNi was found to undergo two displacive phase transformations at temperatures near room temperature. Below 50°C the pseudo body-centered cubic compound undergoes a gradual distortion in an unusual second order phase transformation producing the "transition phase”, the existence of which is terminated by a typical martensitic burst transfor­mation at 20°C which produces the "martensitic phase". The crystal structures of the parent phase and transformation products, and the trans­formation characteristics have been studied with X-ray and electron diffrac­tion, electron microscopy, electrical resistance and density measurements. / Thesis / Master of Science (MS)

We examine discrete models with hexagonal symmetry to compare the sequence of transitions with the alpha-inc-beta phase transition of quartz. We examine a model by Parlinski which employs interactions of nearest and next-nearest neighbor atoms. We numerically determine the configurations which lead to minimum energy for a range of parameters. We then use Golubitsky's results on systems with hexagonal symmetry to derive the bifurcation diagram for Parlinski's model. Finally, we study a large class of modifications to Parlinski's model and show that all such modifications have the same bifurcation picture as the original model. / Ph. D.

Oscillator phase noise is an important factor in designing radio frequency (RF) communications hardware. Phase noise directly contributes to adjacent-channel interference and an increase in bit error rate (BER). Understanding the operation of an oscillator can help with the oscillator design process. Also, the understanding of the noise processes within an oscillator can add insight to the design process, allowing an intelligent low-noise design. It will be shown that although simulation software can be helpful, the understanding of the oscillator operation is a valuable tool in the design process. Oscillator design will be discussed, and then the noise processes of the oscillator will be investigated. A new method of decomposing shot noise into in-phase and quadrature components will be discussed. The noise processes discussed for a non-saturating bipolar junction transistor (BJT) Colpitts oscillator will be extended to the case of a saturating BJT Colpitts oscillator. This new method gives insight into the design of low-noise oscillators, and provides guidelines for design of low-noise oscillators. Example oscillators will support the theory and low-noise design guidelines. It will be seen that although designing an oscillator to saturate can provide a stable output level over a wide bandwidth, the added noise production may degrade the performance of the oscillator through both a lower effective Q and restricted signal level compared to the noise. / Master of Science

Buck converter is a power converter which drops high input voltage into a low output voltage in high efficiency. With this characteristic, it has been used in a great number of applications. Optimized the maximum load to increase the buck converter's efficiency at the cost of light load efficiency is a general way used in a traditional buck converter because it has a higher impact on power consumption. We propose a novel way of designing the two-phase buck converter with light load efficiency improvement in this thesis. The purposed two-phase buck converter uses RC delay to control switch frequency. Different frequency will affect the buck converter in output value and efficiency. RC delay includes two parts; part one connect with phase one, part two connect with phase two. After the test, when resister's value of part one is 100kΩ, and the capacitor's value is 50 pF, the resister's value of path two is 40kΩ, and the capacitors' value is 50 pF, the buck converter can reach maximum efficiency. The inspiration of the neural network is derived from the biological brain, neural is similar with the human neural, and the synaptic weights can treat as the connection between two nodes. Reservoir computing can be seen as an extension of the neural network since it is a framework for computation. Echo State Network(ESN) is one of the major types of reservoir computing, and it is a recurrent neural network. Compared with a neural network, it only trains output weights, which can save a lot of time but keep the accuracy of the training at the same time. The efficiency of the two-phase buck converter and power loss for each phase in the control scheme were measured. The input voltage set to be 30V, with the switch frequency change from 40's to 100's, the output voltages change from 9.2V to 6V, the output current range is 18 mA to 30 mA. The efficiency ranges are 94% to 98%. The teaching target set for the ESN is the output voltage of the two-phase buck converter. The ESN will read data from two-phase buck converter's simulation, including input voltage, the frequency of the switches and based on that to compute the output voltage. / Master of Science / Buck converter is a power converter which drops high input voltage into a low output voltage in high efficiency. With this characteristic, it has been used in a great number of applications. Most of the buck converter optimized the maximum load to increase the efficiency, however, it will also increase the power consumption of the buck converter. For this reason, we propose a novel way of designing the two-phase buck converter optimize with Echo State Network(ESN). The inspiration of neural network is derived from the biological brain, similar with a human brain, the neural network also have self-learning ability. Reservoir computing is one kind of neural network, it can save more time on computing data and increase the efficiency at the same time. Compare with normal two-phase buck converter, the purposed two-phase buck converter optimize with ESN can increase the efficiency and also decrease the running time.

Medium-manganese steels (5-12 wt%) are candidates for third-generation advanced high strength steel (AHSS). Potential applications for these steels are centered around the automotive industry due to their combination of high tensile strength, high tensile ductility, and low alloying cost. Previous studies at VT have been primarily focused on the effect of chemistry on mechanical properties with only a minor emphasis on microstructure. This led to a detailed investigation into the effect of carbon content on the microstructure of Fe8Mn2AlSiC alloys. Six different chemistries with carbon contents of 0.30, 0.34, 0.39, 0.44, 0.49 and 0.52 wt% were produced at the Kroehling Advanced Materials Foundry. After a variety of heat treatments, the samples were characterized using x-ray diffraction (XRD), electron backscatter diffraction (EBSD), electron probe microanalysis (EPMA), optical microscopy, and hardness testing. This thesis will discuss how the microstructure and hardness of these medium manganese steels is influenced by the carbon content. / Master of Science / This research will be used to help design steel alloys that might one day be used in automotive applications. These steels need to be tough and ductile so they can absorb impact without fracturing. This is especially important in the event of a car crash, in which the steel needs to deform without breaking and causing injury to the driver or passenger. In order to achieve such qualities today, expensive elements are often added to the steel which increases cost. Medium manganese steels hope to alleviate this issue by providing a less expensive alternative with similar deformation properties. The properties of steel can be correlated with its microstructure, and more specifically, the different phases that make up the microstructure. These phases give rise to the macroscopic properties that make steel so useful. Microstructure can be controlled through chemistry and through thermomechanical processes. This research focuses on the effects of carbon and on heat treatments. This research is unique in that it keeps the chemistry consistent between all of the samples, making the effect of carbon or of the heat treatment identifiable. A total of six different carbon contents were tested over eight different heat treatment conditions. After creating the samples, the hardness was measured. The samples were then characterized to understand the microstructure. The results of this research showed there is a direct connection between heat treatment and chemistry to the microstructure.

Phase noise from radio frequency (RF) oscillators is one of the major limiting factors affecting communication system performance. Phase noise directly effects short-term frequency stability, Bit-Error-Rate (BER), and phase-locked loop adjacent-channel interference. RF oscillator circuits contain at least one active device, usually a transistor. The active device has noise properties which generally dominate the noise characteristic limits of an oscillator. Since all noise sources, except thermal noise, are generally proportional to average current flow through the active device, it is logical that reducing the current flow through the device will lead to lower noise levels. A theory based on the time-varying properties of oscillators proposes that narrowing the current pulse width in the active device will decrease the time that noise is present in the circuit and therefore, decrease phase noise even further. The time-domain waveforms and phase noise of an active-biased 700MHz oscillator are analyzed, showing heavy saturation and high harmonic content. Redesigns of the example oscillator in active-bias and four-resistor-bias configurations show improved phase noise and lower harmonic levels at the output. Five oscillator designs of each bias configuration, each having a different pulse width, are simulated. As predicted by the theory, the narrowest current pulse corresponds to the lowest phase noise of the simulated oscillators. / Master of Science

No / The heat balance integral method is a familiar technique for treating transport problems, particularly phase-change scenarios. Here a number of differences arising in the method's implementation are investigated that result in quantitatively distinct solutions. As a consequence some guidance is provided for selecting the appropriate implementation of the method.

L’étude de la neurotransmission et de la plasticité synaptique à l’échelle biomoléculaire dans des cellules vivantes nécessite des outils qui permettent la visualisation et la localisation d’une grande variété de protéines synaptiques ainsi que d’autres composantes. La transparence des neurones, la taille nanométrique des structures d’intérêt et leur compacité motivent le choix des modalités d’imagerie pouvant servir à étudier ces phénomènes. La microscopie à super-résolution en fluorescence produit des images ayant une résolution de localisation de l’ordre du nanomètre d’échantillons marqués. Toutefois, cette technique ne permet d’observer que les structures ayant été marquées. C’est pourquoi nous voulons la combiner à une technique ne nécessitant aucun marquage afin d’obtenir le plus d’information possible au sujet de la structure des échantillons. L’imagerie de phase quantitative est une technique sans-marquage qui utilise l’indice de réfraction comme agent de contraste intrinsèque pour cartographier en 3D le contenu cellulaire. Le but principal de ce projet est de concevoir et construire un montage de microscopie de phase quantitative et de l’intégrer à un microscope STED existant de façon à créer un nouveau système d’imagerie multimodale. La performance de ce système sera ensuite caractérisée et sa capacité à produire des images multimodales de synapses de cellules vivantes sera évaluée. Ce projet est un premier pas vers la création d’un outil qui pourrait permettre de simultanément mesurer de façon très précise la position de structures marquées en 2D et 3D et cartographier l’indice de réfraction des cellules en 3D afin de situer les structures marquées dans leur environnement. / The study of neurotransmission at the biomolecular level in live cells requires tools that allow the simultaneous visualisation and localization of a variety of neuronal proteins at their scale: the nanometric scale. In order to do so, an imaging approach offering high spatial and temporal resolution combined to low invasiveness is required. STED microscopy is an optical super-resolution fluorescence microscopy technique that produces images of labelled samples with a spatial resolution below 50 nm in living cells. However, since it is based on the detection of fluorescent molecules, labeling of the structures of interestis necessary and non-labeled structures are invisible for this type of microscope. Therefore, we want to combine it to a label-free optical microscopy technique to maximize the information that can be obtained about the global structure of the samples of interest: optical diffraction tomography (ODT). This approach uses refractive index as an intrinsic contrast agent to produce 3D maps of the cell’s internal contents.The main goal of this project is to design and build a quantitative phase imaging system and to integrate it onto an existing STED microscope to create a novel multimodal super-resolution imaging system. The performance of the microscope will then be characterized. This project is a first step towards the creation of a tool that could eventually allow simultaneous precise2D and 3D mapping of labelled structures and label-free 3D mapping of the sample’s refractive index to situate marked structures in their surroundings.

Titre de l'écran-titre (visionné le 26 avril 2023) / L'approche intégrée de soins palliatifs et de fin de vie (SPFV) est préconisée pour les personnes atteintes de démence sévère, considérant l'évolution rapide et dégénérative de leur diagnostic. But et objectifs : Cette étude avait pour but de cibler et rendre disponible un instrument de mesure qui permettrait d'évaluer la qualité des SPFV des personnes âgées atteintes de démence sévère au Québec. Plus spécifiquement, elle avait pour objectifs de : 1) Identifier le meilleur instrument de mesure pour évaluer la qualité des SPFV pour une clientèle âgée atteinte de démence sévère et 2) Traduire et adapter culturellement le meilleur instrument de mesure pour évaluer la qualité des SPFV pour une clientèle âgée atteinte de démence sévère. Méthode : Dans un premier temps, une recension des écrits visant à analyser de manière critique des instruments de mesure a été menée afin de cibler le meilleur instrument selon un cadre d'analyse prédéfini. Dans un deuxième temps, l'instrument identifié a été traduit et adapté par un processus standardisé et selon les meilleures pratiques. Résultats: L'analyse critique des qualités psychométriques des instruments recensés dans la littérature a montré que l'End-of-life care in dementia (EOLD) constitue le meilleur instrument de mesure pour évaluer la qualité des SPFV pour une clientèle âgée atteinte de démence sévère. Lors du processus de traduction et d'adaptation de l'EOLD, plusieurs questionnements d'ordre sémantique, idiomatique et conceptuel ont été soulevés à différentes étapes du processus. La mise à l'essai a permis de confirmer que d'éventuels répondants auraient une bonne compréhension des items. Discussion: La recension des écrits a permis de clarifier un domaine d'études peu documenté à ce jour et d'identifier l'EOLD comme étant la mesure la plus adéquate. L'utilisation de sa version française pourra soutenir l'évaluation de la qualité des SPFV offerts dans différents milieux de soins. Conclusion: Au final, l'EOLD a été traduit et adapté culturellement au contexte franco-québécois et il est maintenant disponible dans une version expérimentale prête à être validée. / The integrated approach to palliative and end-of-life care is recommended for people with severe dementia, considering the rapid and degenerative evolution of their diagnosis. Goal and objectives: The goal of this study was to identify and make a measurement tool available that would allow the assessment of quality of the palliative and end-of-life care of elderly people with severe dementia in Quebec. More specifically, its objectives were to: 1) Identify the best measurement instrument to assess the quality of the palliative and end-of-life care for an elderly clientele with severe dementia and 2) Translate and culturally adapt the best measurement instrument to assess the quality of the palliative and end-of-life care for an elderly clientele suffering from severe dementia. Methods: First, a literature review aimed at critically analyzing tools was conducted to target the best tool according to a predefined analysis framework. Secondly, the identified tool was translated and adapted through a standardized process according to best practices. Results: The critical analysis of the psychometric qualities of the tools surveyed in the literature showed that the End-of-life care in dementia (EOLD) constitutes the best measurement instrument to evaluate the quality of the the palliative and end-of-life care for an elderly clientele suffering from severe dementia. During the process of translating and adapting the EOLD, several semantic, idiomatic and conceptual questions were raised at different stages of the process. The piloting confirmed that potential respondents would have a good understanding of the items. Discussion: The literature review has clarified a field of study that is poorly documented to date and identified EOLD as the most appropriate measure. The use of its French version can support the evaluation of the quality of the palliative and end-of-life care offered in different care settings. Conclusion: There for, the EOLD has been translated and culturally adapted to fit French Quebec's context and it is now available in an experimental version ready to be validated.