Propõe-se o estudo do separador gravitacional de fundo de poço do tipo shroud invertido para poços direcionais e horizontais. A geometria inovadora é observada pela inclinação imposta, solução que transforma um escoamento vertical descendente, veloz e caótico, num escoamento inclinado e segregado em canal livre. Com a inclinação, minimizasse a incorporação de gás, no impacto do escoamento em superfície livre contra a interface de líquido formada pelo nível do anular interno (NAI), e a segregação é incrementada devido ao gradiente de velocidades e ao aparecimento da componente da gravidade na direção radial do poço de petróleo. O trabalho experimental tem como uma de suas metas o levantamento da eficiência de separação em função das vazões de líquido e gás, do ângulo de inclinação e o grau de interferência do escoamento no duto anular formado entre o separador e a parede do poço de petróleo, chamado neste trabalho de anular externo. Foi feito um trabalho de semelhança dimensional e foram detectados os números adimensionais pertinentes ao problema. Constatou-se que a vazão de gás e o escoamento no anular externo não interferem na eficiência de separação. Além disso, foi realizado um trabalho de caracterização dos padrões do escoamento gás-líquido em duto anular, através de visualização e análise no domínio do tempo e da frequência do sinal dinâmico da queda de pressão. Também são propostos dois modelos matemáticos, um modelo fenomenológico baseado em princípios físicos fundamentais, que foi capaz de prever com eficácia a região de máxima eficiência do separador shroud invertido, e um modelo numérico, que reproduziu a fenomenologia do processo de separação do gás. / This research project proposes the study of the inverted-shroud gravitational gas separator for directional and horizontal wells. The innovative geometry is observed by the inclination that transforms a vertical, fast and chaotic downward flow into an inclined and segregated free channel flow. Due to inclination, the incorporation of gas at the internal gasliquid interface (NAI) is minimized; the segregation is increased due to the velocity gradient and the gravitational term that arises in the radial direction of the oil well. One of the aims of the experimental work is the obtaining of new data of gas separation efficiency as a function of the flow of liquid and gas, inclination angle and the evaluation of the degree of interference of the external annular duct flow. A dimensional analysis was undertaken to identify the relevant dimensionless numbers. It was found that the gas flow and the flow pattern in the external annular duct do not interfere in the separation efficiency. A flow pattern characterization was carried out through visualization and time and frequency domain analysis of differential pressure signature signal. Two mathematical models are proposed, a phenomenological model based on fundamental physical principles, which was able to predict with good accuracy the region of maximum separation efficiency, and a numerical model, which reproduced the phenomenology of the gas separation process.

Propõe-se o estudo do separador gravitacional de fundo de poço do tipo shroud invertido para poços direcionais e horizontais. A geometria inovadora é observada pela inclinação imposta, solução que transforma um escoamento vertical descendente, veloz e caótico, num escoamento inclinado e segregado em canal livre. Com a inclinação, minimizasse a incorporação de gás, no impacto do escoamento em superfície livre contra a interface de líquido formada pelo nível do anular interno (NAI), e a segregação é incrementada devido ao gradiente de velocidades e ao aparecimento da componente da gravidade na direção radial do poço de petróleo. O trabalho experimental tem como uma de suas metas o levantamento da eficiência de separação em função das vazões de líquido e gás, do ângulo de inclinação e o grau de interferência do escoamento no duto anular formado entre o separador e a parede do poço de petróleo, chamado neste trabalho de anular externo. Foi feito um trabalho de semelhança dimensional e foram detectados os números adimensionais pertinentes ao problema. Constatou-se que a vazão de gás e o escoamento no anular externo não interferem na eficiência de separação. Além disso, foi realizado um trabalho de caracterização dos padrões do escoamento gás-líquido em duto anular, através de visualização e análise no domínio do tempo e da frequência do sinal dinâmico da queda de pressão. Também são propostos dois modelos matemáticos, um modelo fenomenológico baseado em princípios físicos fundamentais, que foi capaz de prever com eficácia a região de máxima eficiência do separador shroud invertido, e um modelo numérico, que reproduziu a fenomenologia do processo de separação do gás. / This research project proposes the study of the inverted-shroud gravitational gas separator for directional and horizontal wells. The innovative geometry is observed by the inclination that transforms a vertical, fast and chaotic downward flow into an inclined and segregated free channel flow. Due to inclination, the incorporation of gas at the internal gasliquid interface (NAI) is minimized; the segregation is increased due to the velocity gradient and the gravitational term that arises in the radial direction of the oil well. One of the aims of the experimental work is the obtaining of new data of gas separation efficiency as a function of the flow of liquid and gas, inclination angle and the evaluation of the degree of interference of the external annular duct flow. A dimensional analysis was undertaken to identify the relevant dimensionless numbers. It was found that the gas flow and the flow pattern in the external annular duct do not interfere in the separation efficiency. A flow pattern characterization was carried out through visualization and time and frequency domain analysis of differential pressure signature signal. Two mathematical models are proposed, a phenomenological model based on fundamental physical principles, which was able to predict with good accuracy the region of maximum separation efficiency, and a numerical model, which reproduced the phenomenology of the gas separation process.

Bien que répandus dans l'environnement et dans l'industrie, les écoulements granulaires possèdent des caractéristiques particulières qui sont différentes de celles des écoulements de liquides ordinaires comme l'eau (fluides newtoniens). L'une de ces caractéristiques est de présenter un seuil d'écoulement, il est donc fréquent qu'une des frontières de l'écoulement soit constituée de grains au repos (frontière érodable). L'échange entre les deux états solide et liquide d'un écoulement granulaire est à l'origine du phénomène d'érosion et de déposition et constitue le cœur de cette thèse. Nous y effectuons à la fois des études expérimentales et des études théoriques en nous basant sur les modèles phénoménologiques concernant le taux d'échange proposés par Bouchaud, Cates, Ravi Prakash et Edwards et modifiés par Boutreux et de Gennes. A l'aide d'un dispositif expérimental permettant de lâcher sans vitesse initiale une colonne de grains sur une pente granulaire, nous avons quantifié l'importance relative des phénomènes d'érosion et de déposition notamment en déterminant l'angle neutre qui définit la pente critique pour laquelle ces deux processus s'équilibrent. Dans un deuxième temps nous avons appliqué le modèle proposé par Boutreux et de Gennes au cas de l'étalement d'une « marche » granulaire (marche du Sinaï). / Granular flows, which are common in nature and industry, have particular characteristics that are different from the ordinary flow of liquid (eg. water, oil, etc.) and are not yet well understood in the literature. This case underlines the lack of knowledge on the exchange rate between solid and liquid states of granular flows which is the origin of the erosion - deposition phenomenon and constitutes the core of this thesis. To address the issue of the exchange rate solid - liquid, this work is based mainly in two subjects. The first subject is to study the processes of erosion and deposition of a flow generated by the grains stocked in a reservoir. By releasing naturally with zero-velocity the grains to generate the granular flow, we quantified the relation between the erosion and deposition for determining the neutral angle which defines the slope where these two processes balance. The second subject is to analyze the fall of grains in Sinai step problem by studying the spread of the march. For both works, we conduct not only the experimental but also theoretical studies based on the phenomenological models of the exchange rate proposed by BCRE (Bouchaud, Cates, Ravi Prakash and Edwards) and BDG (Boutreux and de Gennes) with some modifications.

Du fait de problèmes de santé publique, l’industrie agroalimentaire doit réduire la quantité de sel (chlorure de sodium) dans les aliments, et donc dans les charcuteries. Lors de la fabrication des jambons secs, une diminution du taux de sel pourrait se traduire par des problèmes de texture dus à une protéolyse excessive pouvant nuire à l’étape de tranchage industriel, et aussi par des problèmes de stabilité microbiologique. Dans ce contexte, les objectifs de cette thèse sont : (1) d’étudier le lien entre l’évolution de la protéolyse, de la texture et de la structure, tout au long des différentes étapes de fabrication de jambons secs et (2) de développer un modèle de « jambon numérique » afin de prédire spatialement les dynamiques d’évolution des teneurs en eau, en sel et celle de l’activité de l’eau (a w ), et de coupler ces évolutions à celle de la protéolyse. Ce travail combine études expérimentales et modélisation/simulation numérique. Tout d’abord, une méthode de quantification de la protéolyse utilisant la « Fluorescamine » a été développée et validée sur des échantillons de viande de porc et des échantillons extraits de jambons industriels ; un nouvel indice de protéolyse (IP) a été défini. Sur la base d’un plan d’expériences, l’évolution de la protéolyse au sein d’échantillons différemment salés et séchés et préparés à partir de 5 muscles différents d’un jambon de porc, a été quantifiée. Suite à l’application d’une régression linéaire multiple, des lois phénoménologiques ont été construites permettant de calculer la vitesse de protéolyse, pour un muscle donné, en fonction de la température et des teneurs en eau et en sel. Ensuite, au moyen du logiciel Comsol ® Multiphysics, ces lois ont été combinées avec des modèles de transferts de matière (eau, sel), de chaleur (température), et de calcul de l’a w , constituant ainsi un modèle de « jambon numérique ». Enfin, la dynamique d’évolution de l’IP, de 5 paramètres texturaux (dureté, fragilité, cohésion, élasticité et adhésion) et de 4 paramètres structuraux (nombre des fibres, espaces extracellulaires, taille des fibres et surface de tissu conjonctif) a été mesurée sur des échantillons prélevés dans deux muscles extraits de jambons industriels pris à cinq stades de fabrication différents. L’application d’une régression polynômiale multiple à ces données expérimentales a conduit à l’établissement de corrélations permettent de calculer certains paramètres texturaux et structuraux à partir de l’IP et des teneurs en eau et en sel. A court terme, ces lois seront incorporées dans le modèle numérique afin de constituer un vrai simulateur de procédé. A moyen terme, le modèle de « jambon numérique » devra être amélioré afin de tenir compte (1) de la diminution du volume du jambon, du fait du séchage et (2) de la diminution de la vitesse de protéolyse en fonction du temps, du fait de la réduction de la quantité de protéines hydrolysables dans le jambon. Une fois complété et amélioré, le simulateur de procédé pourra aider les professionnels à tester des scénarios visant à réduire la quantité de sodium dans les jambons secs, sans altérer leur qualité finale. / Because of public health problems, the food industry must lower sodium content in all food products, therefore in cured meat products. During the dry-cured ham elaboration process, decreasing salt content may induce microbial safety problems and texture defects due to an excessive proteolysis that could affect later the industrial stage of slicing. On account of that, this work of thesis aims at (1) studying the relationship between proteolysis, structure and texture during the various stages of dry-cured ham manufacture, and (2) building a “numerical ham” model to predict spatially the time course of water and salt content, and thus water activity (a w ), and to couple these variations with proteolysis. This work combines experimental studies and numerical modelling and simulation. Firstly, a new and powerful technique for quantifying proteolysis that uses “Fluorescamine” was developed and validated on pork meat samples and samples extracted from industrial dry-cured hams; a new proteolysis index (PI) was defined. Based on an experimental design, the time course of proteolysis was quantified in laboratory-salted and dried pork meat samples prepared from five different types of pork muscle. Applying multiple linear regression enabled us to build phenomenological models relating, for each pork muscle, PI velocity to temperature, and to water and salt content. Using Comsol ® Multiphysics software, these phenomenological models were then combined with heat and mass transfer models and associated with calculation of a w , thus constituting the “numerical ham” model. In addition, the time course of PI, five textural parameters (hardness, fragility, cohesiveness, springiness and adhesiveness), and four structural parameters (fiber number, extracellular spaces, cross section area, and connective tissue area) was quantified on samples extracted from two different muscles of industrial dry-cured hams removed from the process at five different processing times. Multiple polynomial regression was applied to build phenomenological models relating PI, salt and water content to some textural and structural parameters investigated. These last models could be rapidly incorporated in the “numerical ham” model to constitute a real process simulator. In the future, the “numerical ham” model should be improved in order to take into account (1) the strong decrease in ham volume due to drying and also (2) the decrease in proteolysis velocity with time as a result of the reduction in the amount of protein that can be hydrolysed in the ham. Once completed and improved, the process simulator will be available to professionals to test scenarios allowing sodium content to be reduced in dry-cured hams without altering their final quality.

Numerous studies showed that cochlear implant (CI) users generally prefer individualized stimulation rates in order to maximize their speech understanding. The underlying reasons for the reported variation in speech perception performance as a function of CI stimulation rate is unknown. However, multiple interacting electrophysiological processes influence the auditory nerve (AN) in response to high-rate CI stimulation. Experiments studying electrical pulse train stimulation of cat AN fibers (ANFs) have demonstrated that spike rates slowly decrease over time relative to onset stimulation and is often attributed to spike rate (spike-triggered) adaptation in addition to refractoriness. Interestingly, this decay tends to adapt more rapidly to higher stimulation rates. This suggests that subthreshold adaptation (accommodation) plays a critical role in reducing neural excitability. Using biophysical computational models of cat ANF including ion channel types such as hyperpolarization-activated cyclic nucleotide-gated (HCN) and low threshold potassium (KLT) channels, we measured the strength of adaptation in response to pulse train stimulation for a range of current amplitudes and pulse rates. We also tested these stimuli using a phenomenological computational ANF model capable of applying any combination of refractoriness, facilitation, accommodation, and/or spike rate adaptation. The simulation results show that HCN and KLT channels contribute to reducing model ANF excitability on the order of 1 to 100 ms. These channels contribute to both spike rate adaptation and accommodation. Using our phenomenological model ANF we have also shown that accommodation alone can produce a slow decay in ANF spike rates responding to ongoing stimulation. The CI users that do not benefit from relatively high stimulation rates may be due to ANF accommodation effects. It may be possible to use electrically evoked compound action potentials (ECAP) recordings to identify CI users exhibiting strong effects of accommodation, i.e., the increasing strength of adaptation as a function of increasing stimulation rate. / Dissertation / Doctor of Philosophy (PhD) / Cochlear implants (CI) attempt to restore hearing to individuals with severe to profound hearing deficits by stimulating the auditory nerve with a series of electrical pulses. Recent CI stimulation strategies have attempted to improve speech perception by stimulating at high pulse rates. However, studies have shown that speech perception performance does not necessarily improve with pulse rate increases, leading to speculation of possible causes. Certain ion channels located in auditory nerve fibers may contribute to driving the nerve to reduce its excitability in response to CI stimulation. In some cases, those channels could force nerve fibers to cease responding to stimulation, causing a breakdown in communication from the CI to the auditory nervous system. Our simulation studies of the auditory nerve containing certain types of channels showed that the effective rate of communication to the brain is reduced when stimulated at high rates due to the presence of these channels.

Sound localization is a vital aspect of hearing for safe navigation of everyday environments. It is also an important factor in speech intelligibility. This ability is facilitated by the interaural level difference (ILD) cue, which arises from binaural hearing: a sound will be more intense at the nearer ear than the farther. In a hearing-impaired listener, this binaural cue may not be available for use and localization may be diminished. While conventional, bilateral, wide dynamic range compression (WDRC) hearing aids distort the interaural level difference by independently altering sound intensities in each ear, wirelessly-linked devices have been suggested to benefit this task by matching amplification in order to preserve ILD. However, this technology has been shown to have varying degrees of success in aiding speech intelligibility and sound localization. As hearing impairment has wide-ranging adverse impacts to physical and mental health, social activity, and cognition, the task of localization improvement must be urgently addressed. Toward this end, neural modelling techniques are used to determine neural representations of ILD cues for linked and unlinked bilateral WDRC hearing aids. Findings suggest that wirelessly-linked WDRC is preferable over unlinked hearing aids or unaided, hearing-impaired listening, although parameters for optimal benefit are dependent on sound level, frequency content, and preceding sounds. / Thesis / Master of Applied Science (MASc)