Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

As ligas de alumínio são aplicadas em cerca de 70% dos componentes estruturais dos aviões e o processo de fadiga e o modo de falha predominante em estruturas aeronáuticas, para a maioria das quais a presença de concentradores de tensão e inevitável. O comportamento em fadiga e as propriedades mecânicas das ligas de alumínio endurecíveis por precipitação são fortemente influenciadas por parâmetros como tamanho, espaçamento e densidade dos precipitados endurecedores. Neste contexto, pesquisas anteriores tem mostrado que o envelhecimento interrompido (T6I4) pode proporcionar melhores combinações de propriedades mecânicas para estas ligas. O presente trabalho tem como objetivo o estudo das propriedades mecânicas e do comportamento em fadiga de alto ciclo das ligas de alumínio AA6351 e AA7050 nas condições de tratamento térmico convencionais (T6 e T7451, respectivamente) e na condição T6I4, bem como da influência das características microestruturais e do tratamento térmico sobre estas propriedades. Dentro deste contexto, analises de Microscopia Eletrônica de Transmissão (MET) da liga AA6351 mostraram que a condição T6I4 resultou em uma maior densidade de precipitados endurecedores com tamanho heterogêneo, quando comparada com a condição T6. Para esta liga, a condição T6I4 também resultou em menores valores de tensão limite de escoamento, resistência a tração, resistência a fadiga e sensibilidade ao entalhe, com maior ductilidade e tenacidade. Para a liga AA7050, as análises de MET mostraram que a condição T6I4 resulta em uma maior densidade de precipitados endurecedores com menor tamanho, promovendo um melhor impedimento ao movimento de discordâncias durante a deformação por fadiga, quando comparada com a condição T7451. Esta alteração microestrutural proporcionou a condição T6I4 valores de resistência ao escoamento e resistência a tração similares a condição T7451, com maior ductilidade e tenacidade. A resistência a fadiga da condição T6I4 foi similar a condição T7451, entretanto o envelhecimento interrompido resultou em um melhor comportamento em sensibilidade ao entalhe. / Aluminum alloys are applied in approximately 70% of the aircraft structural components and the fatigue process is the dominant failure mode in aeronautical structures, for the most of which, the presence of stress concentrators is unavoidable. The fatigue behavior and the mechanical properties of the age hardenable aluminum alloys are strongly influenced by parameters including the size, spacing and density of strengthening precipitates. Within this context, previous researches have shown that the interrupted ageing (T6I4) could provide an improved combination of mechanical properties for these alloys. This work aims to study the mechanical properties and the high cycle fatigue behavior of AA6351 and AA7050 aluminum alloys in the conventional heat treatment conditions (T6 and T7451, respectively) and in the T6I4 condition, as well as the influence of the microstructural characteristics and of the heat treatment on these properties. Within this context, Transmission Electron Microscopy (TEM) analyzes of the AA6351 alloy showed that T6I4 condition resulted in higher density of hardening precipitates with heterogeneous size compared to T6 condition. For this alloy, the T6I4 condition resulted in lower values of yield stress, ultimate tensile strength, fatigue strength and notch sensitivity, with higher ductility and toughness. For the AA7050 alloy, TEM analyses showed that T6I4 condition presented a higher density of strengthening precipitates with smaller size promoting an improved dislocation pinning effect during the fatigue deformation compared to T7451 condition. This microstructural change provided to T6I4 condition yield stress and ultimate tensile strength similar to T7451, with higher ductility and toughness. The fatigue strength of T6I4 condition was also similar to T7451, however the interrupted ageing provided a better notch sensitivity behavior.

Orientador: Maria Cristina Pereira Lima / Resumo: Introdução: Os acidentes de trânsito (AT) fazem aumentar a população que possui alguma deficiência e os anos potenciais de vida perdidos; causam dor e sofrimento aos familiares das vítimas e geram gastos aos sistemas de saúde e previdenciário dos países. Objetivo: O objetivo deste trabalho foi avaliar os fatores associados aos óbitos causados por AT no Brasil à partir de uma série de quatro estudos produzidos com dados secundários. Método: O estudo 1 apresenta sínteses da prevalência do ato de beber e dirigir (%BD) no Brasil após a promulgação da Lei Seca de 2008 (LS08), obtidas por modelos de meta-análise de efeitos aleatórios, à partir de estudos selecionados nas bases Scielo, Medline, Embase e Web of Science. O estudo 2 é um “Interrupted Time Series” (ITS) que avalia o impacto da LS08 sobre o número mensal de óbitos por AT no Brasil entre 2002 a 2015 por meio de um modelo de séries temporais com resposta Binomial Negativa. O estudo 3 é um ITS que avalia o impacto da LS08 sobre a mortalidade por AT nos 27 estados brasileiros por meio de modelos de séries temporais da classe ARIMA, ajustados para cada um dos estados. O estudo 4 apresenta uma revisão sobre aspectos de planejamento e validade dos resultados de estudos conduzidos sob o delineamento ITS, à partir do referencial teórico de Campbell e Stanley (1963), com exemplos de estudos ITS aplicados no trânsito. Resultados: As sínteses obtidas no estudo 1 mostram que, em um período de 12 meses, 26,8% dos motoristas dirigem so... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Introduction: Traffic accidents (TA) increase the population with disabilities and the potential years of life lost, cause pain and suffering to the families of the victims, and generate expenses for the health and social security systems of the countries. Objective: The objective of this study was to evaluate the factors associated with deaths caused by TA in Brazil from a series of four studies produced with secondary data. Method: Study 1 presents a summary of the prevalence of drinking and driving (% BD) in Brazil after the enactment of the 2008 Dry Law (LS08), obtained by random effects meta-analysis models, based on studies selected at Scielo , Medline, Embase and Web the Science. Study 2 is an "Interrupted Time Series" (ITS) that assesses the impact of LS08 on the monthly number of TA deaths in Brazil between 2002 and 2015 through a time series model with Negative Binomial response. Study 3 is an ITS that assesses the impact of LS08 on TA mortality in the 27 Brazilian states through time series models of the ARIMA class, adjusted for each state. Study 4 presents a review on aspects of planning and validity of the results of studies conducted under the ITS design, based on the theoretical reference of Campbell and Stanley (1963), with examples of ITS studies applied in traffic. Results: The syntheses obtained in study 1 show that, in a 12-month period, 26.8% of the drivers drive under the influence of alcohol, 8.9% of the drivers are caught under the influence of alcoho... (Complete abstract click electronic access below) / Doutor

The purpose of this study was to examine temporal resolution in normal-hearing preschool children. Word recognition was evaluated in quiet and in spectrally identical continuous and interrupted noise at signal-to-noise ratios (S/Ns) of 10, 0, and −10dB−10dB−10dB. Sixteen children 4to5years4to5years4to5yearsof age and eight adults participated. Performance decreased with decreasing S/N. At poorer S/Ns, participants demonstrated superior performance or a release from masking in the interrupted noise. Adults performed better than children, yet the release from masking was equivalent. Collectively these findings are consistent with the notion that preschool children suffer from poorer processing efficiency rather than temporal resolution per se.

Tout comme la dépression, le suicide revêt plusieurs figures. Et au-delà de tout cadre nosographique ou structurel, ce qui les détermine tous-deux réside dans la confrontation à l’épreuve de la perte, du deuil. La mort elle-même prend-t-elle figure dans le vécu de perte de l’objet aimé ? La clinique des sujets survivants au suicide révèle en effet cet étrange paradoxe : Se tuer physiquement pour survivre psychiquement à la souffrance engendrée dans l’actuel par le vécu de perte de l’objet aimé. Inquiétante étrangeté de la mort qui, non seulement se mêle ici intimement à la vie, mais semble aussi détenir en elle une figure autoconservatrice pour la psyché menacée par l’anéantissement : c’est bien lorsqu’il est confronté à la menace d’effondrement que le sujet décide de se tuer, le suicide apparaissant telle une défense contre l’angoisse. Pour appréhender ce paradoxe, il s’agit donc en premier lieu d’interroger le suicide dans son rapport aux problématiques dépressives, et de lier l’expérience primitive de la perte aux fondements de la réalité psychique du sujet. Emergent alors certaines équivalences entre l’expérience de séparation et l’anéantissement psychique, qui permettent elles-mêmes d’envisager l’existence d’une correspondance entre l’éprouvé archaïque de mort psychique et la mort de soi. Cette correspondance entre mort psychique et mort physique, opérant sous l’œuvre du clivage de la personnalité, pourrait bien être active dans la formation du suicide interrompu. / As for depression, suicide reveals different features. And beyond nosographical or structural framework, what determines them both lies in the confrontation of the ordeal of loss, mourning. Is death itself taking in the lived experience of the loss of the loved objet? The clinical study of suicide survivors shows indeed a strange paradox: physically killing oneself in order to survive psychically the suffering generated in the present by the experience of the loss of the loved object. Disturbing oddness of death, which not only mingles here intimately with life, but also seems to hold in itself a self-preserving feature for the psyche threatened by annihilation: it is indeed when confronted with the threat of collapse that the subject decides to kill himself, suicide appearing as a defense against anxiety. In order to understand this paradox, we need first and foremost to question suicide in its relation to depressive problems and to link the initial experience of loss with the foundations of the psychic reality of the subject. Then certain equivalences are emerging between the experience of separation and psychic annihilation, which allow us to envisage the existence of a connection between the archaic proved of psychic death and the death of oneself. This connection between psychic death and physical death, acting under the personality cleavage, may well be active in the development of interrupted suicide.

This thesis systematically investigates the effects of a recently developed modified ageing procedure of aluminium alloys, termed the T6I6 temper, on the microstructural development and mechanical properties of the Al ??? Mg ??? Si - Cu alloy 6061. For the T6I6 temper, a conventional single stage T6 temper is interrupted by an ageing period at a reduced temperature (65??C) to facilitate secondary precipitation, before resuming the final ageing at the temperature of the initial T6 treatment. The T6I6 temper was found to cause simultaneous increases in tensile properties, hardness, and toughness as compared with 6061 T6. Al ??? Mg ??? Si ??? Cu alloys are medium strength alloys widely used in the automotive industry and their further improvement is underpinned by stringent demands for weight reduction placed on the transportation industry in recent years. The potential for further improvement of the mechanical properties was found in the control of secondary precipitation that may take place even in some fully aged alloys when exposed to reduced temperatures. The overall improvement in the mechanical properties of 6061 T6I6 was attributed to the formation of finer and more densely dispersed precipitates in the final microstructure. The refinement of precipitates was facilitated by control of the precipitation processes and gradual evolution of the microstructure throughout each stage of the T6I6 treatment. The results indicated that the concentration and the chemical environment of the vacancies controlled the precipitation processes in this alloy. Findings also show that the proportion of the different precipitate phases present in the final microstructure, as well as the amount of the solute in these precipitates, can be controlled and modified utilizing secondary precipitation. A number of analytical techniques were used in this study. The evolution of the microstructure was studied using Transmission Electron Microscopy (TEM), High Resolution TEM (HRTEM) and Three Dimensional Atom Probe (3DAP). Vacancy-solute interactions were studied using Positron Annihilation Lifetime Spectroscopy (PALS) and 3DAP. The distribution of the solute was studied using 3DAP and Nuclear Magnetic Resonance (NMR). Differential Scanning Calorimetry (DSC) was used to identify precipitation reactions and to determine the stability of vacancy-associated aggregates.

Objectifs. L’objectif de ce mémoire est de parfaire nos connaissances quant à l’effet des actions policières sur les collisions routières au Québec. Ultimement, ce mémoire permettra d’identifier les conditions nécessaires pour que l’action policière influe sur les comportements des automobilistes. Pour se faire, deux études de cas sont employées. Dans un premier temps, nous évaluons l’effet d’un relâchement d’environ 60 % dans l’émission de constats d’infraction par les policiers de la ville de Québec sur les collisions avec blessures. Dans cet article, nous distinguons également les effets respectifs des constats d’infraction, des interceptions policières sans constat et des médias. Dans un second temps, nous évaluons l’impact d’une stratégie de sécurité routière mise en place conjointement par l’Association des directeurs de police du Québec (ADPQ) et la Société de l’assurance automobile du Québec (SAAQ). Dans les deux cas, un changement important est survenu dans l’émission de constats d’infraction émis en vertu du Code de la sécurité routière (CSR). Méthodologie. Afin d’évaluer l’effet de ces deux stratégies, nous avons agrégé les données sur les collisions et infractions au CSR sur une base mensuelle. Ces données proviennent principalement des rapports de collisions et des constats d’infraction remplis par les policiers et transmis à la SAAQ. Dans l’ensemble, nous avons utilisé un devis quasi-expérimental, soit celui des séries chronologiques interrompues. Résultats. Les résultats des deux articles démontrent que les policiers sont des acteurs clés en matière de sécurité routière. Les collisions avec blessures sont affectées par les fluctuations de leurs activités. La première série d’analyses établit qu’un relâchement d’environ 60 % dans le nombre de constats émis par les policiers se traduit par une hausse d’environ 10 % des collisions avec blessures, ce qui correspond à 15 collisions avec blessures supplémentaires par mois sur le territoire du Service de police de la ville de Québec. De plus, nos résultats montrent qu’une interception policière suivie d’un avertissement verbal n’est pas suffisante pour prévenir les collisions. De même, l’effet observé n’est pas attribuable aux médias. La deuxième série d’analyse montre que la stratégie conjointe de l’ADPQ et de la SAAQ, caractérisée par une hausse des constats émis et des campagnes médiatiques, fut suivie de baisses variant entre 14 et 36 % des collisions avec blessures graves. Interprétation. Les résultats démontrent que les actions policières ont une influence sur le bilan routier. Par contre, avant d’influer sur le comportement des automobilistes, certaines conditions doivent être respectées. Premièrement, l’intensité des contrôles policiers doit être suffisamment modifiée par rapport à son niveau initial. Deuxièmement, que ce soit une hausse ou une baisse, ce niveau doit être maintenu sur une période relativement longue (entre 12 et 24 mois environ) pour que les automobilistes soient exposés au message pénal et qu’ils considèrent ce changement dans le niveau de répression comme étant crédible. Troisièmement, l’émission de constats est un élément clé; la simple présence policière n’est pas suffisante pour prévenir les collisions. Enfin, les campagnes de sensibilisation semblent importantes, mais d’autres études sont nécessaires pour mieux apprécier leur rôle. / Objectives. The goal of this thesis is to further our understanding about the effect of police activities on traffic collisions in the Province of Quebec. The study also aims to pinpoint conditions that must be met to insure the effectiveness of such police interventions. To do so, we use two case studies. In the first place, we assess the impact of a 60% reduction in traffic citations issued by police officers on collisions with injuries. In this article, we are also able to estimate the respective effects of traffic citations, police interceptions not leading to the issuance of a citation and media coverage. In the second place, we evaluate a road safety program implemented by the Quebec Association of Chiefs of Police (ADPQ) and the Societé de l’assurance automobile du Québec (SAAQ). In both cases, there was a substantial change in the level of traffic citations handed down by police officers. Method. In order to assess the impact of both strategies, data on collisions and citations were aggregated on a monthly basis. These data come from police reports on traffic citations and collisions that are transmitted and managed by the SAAQ. In all cases, we used a quasi experimental design: interrupted time series. Results. Results from both articles show that police officers are key players in a road safety policy. Collisions with injuries vary according to the intensity of police enforcement activities. The first set of analyses establishes that a 60% reduction in the issuance of traffic citations is associated with a 10% increase in collisions with injuries (about 15 additional collisions per month on the Quebec City Police jurisdiction). Furthermore, simple interceptions (not leading to the issuance of a citation) as well as media coverage were not statistically linked to this increase. The second series of analyses demonstrate that the joint strategy of the ADPQ and SAAQ, characterized by an increase in police arrests and media campaigns, was associated with decreases varying between 14 and 36% in collisions with serious injuries in the Province of Quebec. Conclusion. Results from our analyses show that police activities have an important impact on the road toll. However, some conditions must be met in order to stimulate changes in driver behaviors. First, the intensity of police controls must be substantially leveled up relatively to the previous level. Second, this new level must be maintained for a long lasting period (between 12 and 24 months). By doing so, automobilists will have the opportunity to be exposed the legal threat and consider this threat as credible. Third, the issuance of traffic citations is a key component; the simple presence of police officers is not sufficient to produce a preventive effect on collisions. At last, media campaigns appear to be a central component of police enforcement programs but further studies are need to precisely estimate their role and contribution to collision prevention.

The development of the interrupted Nazarov cyclization of allenyl vinyl ketones is presented. The intermediate oxyallyl cation, derived from an allenyl vinyl ketone, may be trapped efficiently by a divergent array of nucleophilic species generating functionalized cyclopent-2-enone products. Allenyl vinyl ketones are also a versatile source of cyclic molecules via a tandem reaction sequence terminated via reaction with acyclic dienes, cyclic dienes, aza-heterocycles, electron-rich alkenes, or styrenes by the formation of an additional ring by a [4 + 3] and/or [3 + 2] cyclization or by the formation of one additional carbon-carbon bond. The bicyclic compounds generated by these processes are densely substituted, and would be difficult to access as succinctly in other ways. The products of these interrupted Nazarov reactions generally reflect excellent regio- and stereoselectivity in the trapping reaction. In some instances, equilibrating conditions were shown to enhance the proportion of one product at the expense of another or to provide a different carbon skeleton. This process appears fairly general, and can be conducted with unsubstituted or alkyl, aromatic, or heteroaromatic allenyl vinyl ketones. The exceptional affinity of allenyl vinyl ketones to undergo interrupted Nazarov reactions is likely a result of the increased longevity of the intermediate oxyallyl cation, due in part to the increased resonance stabilization provided by the allene unit. The high regioselectivity noted in the trapping process was computationally and experimentally confirmed to be a result of a localization of the positive charge in the intermediate oxyallyl cation. The application of this recently developed methodology towards the synthesis of the natural product (+)-roseadione is also described. The tandem Nazarov/[4 + 3] cascade of allenyl vinyl ketones provides a unique manner in which to access the tricyclic core of this cyclooctanoid natural product, a molecule which, to date, has never been synthesized.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

This thesis systematically investigates the effects of a recently developed modified ageing procedure of aluminium alloys, termed the T6I6 temper, on the microstructural development and mechanical properties of the Al ??? Mg ??? Si - Cu alloy 6061. For the T6I6 temper, a conventional single stage T6 temper is interrupted by an ageing period at a reduced temperature (65??C) to facilitate secondary precipitation, before resuming the final ageing at the temperature of the initial T6 treatment. The T6I6 temper was found to cause simultaneous increases in tensile properties, hardness, and toughness as compared with 6061 T6. Al ??? Mg ??? Si ??? Cu alloys are medium strength alloys widely used in the automotive industry and their further improvement is underpinned by stringent demands for weight reduction placed on the transportation industry in recent years. The potential for further improvement of the mechanical properties was found in the control of secondary precipitation that may take place even in some fully aged alloys when exposed to reduced temperatures. The overall improvement in the mechanical properties of 6061 T6I6 was attributed to the formation of finer and more densely dispersed precipitates in the final microstructure. The refinement of precipitates was facilitated by control of the precipitation processes and gradual evolution of the microstructure throughout each stage of the T6I6 treatment. The results indicated that the concentration and the chemical environment of the vacancies controlled the precipitation processes in this alloy. Findings also show that the proportion of the different precipitate phases present in the final microstructure, as well as the amount of the solute in these precipitates, can be controlled and modified utilizing secondary precipitation. A number of analytical techniques were used in this study. The evolution of the microstructure was studied using Transmission Electron Microscopy (TEM), High Resolution TEM (HRTEM) and Three Dimensional Atom Probe (3DAP). Vacancy-solute interactions were studied using Positron Annihilation Lifetime Spectroscopy (PALS) and 3DAP. The distribution of the solute was studied using 3DAP and Nuclear Magnetic Resonance (NMR). Differential Scanning Calorimetry (DSC) was used to identify precipitation reactions and to determine the stability of vacancy-associated aggregates.