Weight reduction in automobiles is amongst the most economical ways of reducing greenhouse gas emissions and increasing fuel efficiency. The recently invented ablation casting process is a novel technique of producing high performance light weight parts which meet this objective. In this technique a water jet demolds the water soluble sand mold and subsequently impinges upon the solidifying metal, thereby producing high cooling rates in the casting which in turn leads to microstructural refinement and higher mechanical properties. The objective of this study was to develop a comprehensive understanding of the effect of various parameters involved in the casting of a thin walled part using the HiPerMag casting process for the wrought aluminum alloy AA 7050. The study is divided into three major parts that deal with the composition of the sand binder system, optimization of the sand mold thickness, various aspects of the water jet parameters and the desired microstructural parameters which will result in a defect free part. In first phase of the study, sand mold properties such as the green and dry strengths of the water soluble sand binder system used in the study were tested to ensure that they meet the molding requirements. An average green strength of 160 kPa and an average dry strength of 3825 kPa were found for the water soluble sand binder system. These values were similar to those reported in the literature for clay bonded sands and were sufficient to make molds for casting in the current study. Secondly, a heat transfer model was developed to find a minimum mold thickness required to design a mold for the HiPerMag casting process such that the liquid metal remained sufficiently insulated before being quenched. Based on the model, for a mold with a cope thickness of 12.9 cm, the heat flux losses to the surroundings were reduced by up to 90 % versus a case where a thinner mold was used. In addition, an analytical solution was derived for the mold thickness problem from which it was found that at a distance of 10 cm from the mold cavity there was a negligible increase in temperature of the sand at that location at large times. Further, the minimum mold thickness was determined based on the temperature profile in the sand mold during the HiPerMag casting process. This study showed that a thin mold of about 2 cm thickness was sufficient to provide insulation to the hot metal during the HiPerMag casting process. Thirdly, it was found that, based on cooling curve data and microstructural analysis, that a jet spacing of 15.3 cm and a time delay of 7.4 s between successive jet activations starting from the farthest jet (located near the edge of the casting), was necessary to obtain a single solidification front throughout the casting. This also ensured that grain size variation in the casting was less than 10 μm for having uniform mechanical properties. Also, it was found for a thin walled casting, the amount of solid present in the solidifying casting at the time of water jet impingement had a negligible effect on the movement of the solidification interface. Finally, the effect of jet momentum on surface defects was examined. It was determined that the maximum jet momentum resulting in no surface defects at temperatures close to the liquidus for Al AA 6061 alloy was approximately 2 kg.m/s. / Thesis / Master of Applied Science (MASc)

To investigate the generation of mesoscale gravity waves from upper-tropospheric jet-front systems, five different life cycles of baroclinic waves are simulated with a high-resolution mesoscale model (MM5 with 10-km grid spacing). The baroclinicity (and the growth rates) of the baroclinic waves differs significantly among these five experiments as a result of using different tropospheric static stability and tropopause geometry for the initial two-dimensional baroclinic jet. After a short initial adjustment, the baroclinic waves in each experiment grow nearly linearly for as long as five days before the final nonlinear growth stage. Vertically propagating mesoscale gravity waves are generated universally in the exit region of the upper-tropospheric jet streaks near the tropopause level at the later stage of quasi-linear growth and the early stage of nonlinear growth of baroclinic waves. The synoptic environments of gravity waves are consistent with previous studies of typical mesoscale gravity waves. The low-stratospheric gravity waves generated from the upper-level jet streak in these experiments have a horizontal wavelength of 75-175 km and an intrinsic frequency 3-10 times of the Coriolis parameter. The intrinsic frequency of these gravity waves appears to be directly correlated with the growth rate and the strength of the baroclinic waves. In general, the faster the growth rate of the baroclinic waves, the higher the intrinsic frequency of the gravity waves. Similar frequencies of the gravity waves are found in experiments with smaller quasi-linear growth rates of baroclinic waves but with significantly different initial tropospheric static stability and tropopause geometry. The residuals of the nonlinear balance equation are used to assess the flow imbalance. It is also suggested that growth of imbalance is directly related to the growth rate of baroclinic waves and thus the frequency of primary gravity waves of interest. Diagnosis of flow imbalance suggests that balance adjustment, as a generalization of geostrophic adjustment, may be responsible for the generation of the gravity waves in the upper-tropospheric jet-front systems.

Historians have established the framework of Canada’s general political, economic, and military participation in the Second World War, but there has been little research into the ways that the national war effort affected individuals or local communities. This dissertation explores the wartime experience of ordinary Winnipeggers through their responses to recruiting, the treatment of minorities, war finance publicity, participation in voluntary community service, and the adjustments made necessary by family separation. It questions the prevailing narrative of the war as a unifying national experience, focusing on issues like civilian morale and the relationship between citizens and the state. In some ways, the depth of the patriotic consensus was remarkable in a city that was far removed from any real enemy threat. The population was highly polyethnic, with strong class divisions and a vibrant tradition of political protest. Both factors meant a greater number of potential fault lines. But the large number of ethnic groups in Winnipeg and the Left’s relative lack of political power also meant that there was no dominant minority to seriously challenge the interpretation of the war expressed by the city’s charter group. Social cohesion was enhanced in Winnipeg despite the absence of real danger for a number of reasons: the connection of ethnic communities to occupied or threatened homelands, like Poland or the United Kingdom; the effectiveness of both official and unofficial information management, such as Victory Loan publicity; and the strong identification people maintained with family and friends in the armed forces, war industries, or state institutions. The war effort affected people as individuals and as members of families and the wider community. Its impact was at times unjust and destructive yet most hardships were ultimately accepted as necessary for the war’s successful prosecution. / February 2009

The increasing demands for improving magnetic resonance imaging (MRI) quality, especially reducing the imaging time have been driving the channel number of parallel magnetic resonance imaging (Parallel MRI) to increase. When the channel number increases to 64 or even 128, the traditional method of stacking the same number of radio-frequency (RF) receivers with very low level of integration becomes expensive and cumbersome. However, the cost, size, power consumption of the Parallel MRI receivers can be dramatically reduced by designing a whole receiver front-end even multiple receiver front-ends on a single chip using CMOS technology, and multiplexing the output signal of each receiver front-end into one channel so that as much hardware resource can be shared by as many channels as possible, especially the digitizer. The main object of this research is focused on the analysis and design of fully integrated multi-channel RF receiver and multiplexing technology. First, different architectures of RF receiver and different multiplexing method are analyzed. After comparing the advantages and the disadvantages of these architectures, an architecture of receiver front-end which is most suitable for fully on-chip multi-channel design is proposed and a multiplexing method is selected. According to this proposed architecture, a four-channel receiver front-end was designed and fabricated using TSMC 0.18μm technology on a single chip and methods of testing in the MRI system using parallel planar coil array and phase coil array respectively as target coils were presented. Each channel of the receiver front-end includes an ultra low noise amplifier (LNA), a quadrature image rejection down-converter, a buffer, and a low-pass filter (LPF) which also acts as a variable gain amplifier (VGA). The quadrature image rejection downconverter consists of a quadrature generator, a passive mixer with a transimpedance amplifier which converts the output current signal of the passive mixer into voltage signal while acts as a LPF, and a polyphase filter after the TIA. The receiver has an over NF of 0.935dB, variable gain from about 80dB to 90dB, power consumption of 30.8mW, and chip area of 6mm2. Next, a prototype of 4-channel RF receiver with Time Domain Multiplexing (TDM) on a single printed circuit board (PCB) was designed and bench-tested. Then Parallel MRI experiment was carried out and images were acquired using this prototype. The testing results verify the proposed concepts.

To investigate the generation of mesoscale gravity waves from upper-tropospheric jet-front systems, five different life cycles of baroclinic waves are simulated with a high-resolution mesoscale model (MM5 with 10-km grid spacing). The baroclinicity (and the growth rates) of the baroclinic waves differs significantly among these five experiments as a result of using different tropospheric static stability and tropopause geometry for the initial two-dimensional baroclinic jet. After a short initial adjustment, the baroclinic waves in each experiment grow nearly linearly for as long as five days before the final nonlinear growth stage. Vertically propagating mesoscale gravity waves are generated universally in the exit region of the upper-tropospheric jet streaks near the tropopause level at the later stage of quasi-linear growth and the early stage of nonlinear growth of baroclinic waves. The synoptic environments of gravity waves are consistent with previous studies of typical mesoscale gravity waves. The low-stratospheric gravity waves generated from the upper-level jet streak in these experiments have a horizontal wavelength of 75-175 km and an intrinsic frequency 3-10 times of the Coriolis parameter. The intrinsic frequency of these gravity waves appears to be directly correlated with the growth rate and the strength of the baroclinic waves. In general, the faster the growth rate of the baroclinic waves, the higher the intrinsic frequency of the gravity waves. Similar frequencies of the gravity waves are found in experiments with smaller quasi-linear growth rates of baroclinic waves but with significantly different initial tropospheric static stability and tropopause geometry. The residuals of the nonlinear balance equation are used to assess the flow imbalance. It is also suggested that growth of imbalance is directly related to the growth rate of baroclinic waves and thus the frequency of primary gravity waves of interest. Diagnosis of flow imbalance suggests that balance adjustment, as a generalization of geostrophic adjustment, may be responsible for the generation of the gravity waves in the upper-tropospheric jet-front systems.

The early Laramide tectonic history and Proterozoic metamorphic history of the northeastern Colorado Front Range were examined using kinematic data from minor faults at 25 locations, and U-Th/He dating of apatite from 2 samples (3 unsuccessful) supported by optical petrography, X-ray maps and geothermometry. The role of strike-slip faulting in Laramide uplift of the eastern flank of the northern Front Range was analyzed through kinematic analysis of 97 minor (<100 m trace) faults. The dominant fault population was oriented approximately perpendicular to bedding, with lineations sub-parallel to bedding. Rotating bedding to horizontal showed these faults to have the pattern of a strike-slip conjugate set. Unfolded left-lateral faults have an average orientation of (287, 87N) with lineations to (287, 01); right-lateral faults have an orientation of (065, 88S) with lineations to (245, 00). The timing of motion on these faults postdates 98 Ma deposition of Dakota group sandstones, and predates the folds that rotated them (68 Ma from the age of synorogenic conglomerates). The conclusion is that strike-slip motion was active during the earliest Laramide. The principal strain axes from these faults, after rotation, give an average shortening axis orientation of (276, 03) and an average extension direction of (006, 02). The calculated shortening axis orientation is consistent with that of later Laramide deformation, supporting the hypothesis that strike-slip deformation occurred in the northeast Front Range during the earliest Laramide. Analysis of minor faults on part of the eastern flank of the northern Front Range shows that strike-slip faulting was a locally important deformation mechanism at the onset of the Laramide orogeny. Principal strain axis analysis suggests that the regional tectonic regime was one of east-west shortening and north-south extension prior to the onset of the main phase of Laramide deformation, at which time the regional strain field rotated to one of east-west shortening and vertical extension. Twenty-seven thin-sections of Big Thompson Canyon metapelites were petrologically characterized prior to selection for mineral separation and U-Th/He analysis of apatite. All samples show late high-temperature static recrystallization that has partially recovered prior fabrics. At high grades, sillimanite porphyroblasts overgrow all fabrics. X-ray maps and geothermometry were also conducted to enhance the characterization of the sample suite. Garnet-biotite phase equilibria indicate that initial prograde metamorphism took place at approximately 550 °C. Apatites separated from five of the twenty-seven samples analyzed in thin section were analyzed for U-Th/He thermochronometry. Three samples returned no plausible results; one sample returned one plausible age; and one sample returned three similar and plausible ages. Basement rocks cooled through the closure temperatures for helium and fission-tracks in apatite nearly simultaneously, at about 55 Ma. These temperatures, 40 and 60 °C respectively, correspond to depths of ~ 1.5 and 2.5 km. Laramide exhumation of the Northern Front Range was very rapid. Estimates of minimum magnitude of exhumation during Laramide time may need to be increased from ~2 km to ~3 km. / text

Historians have established the framework of Canada’s general political, economic, and military participation in the Second World War, but there has been little research into the ways that the national war effort affected individuals or local communities. This dissertation explores the wartime experience of ordinary Winnipeggers through their responses to recruiting, the treatment of minorities, war finance publicity, participation in voluntary community service, and the adjustments made necessary by family separation. It questions the prevailing narrative of the war as a unifying national experience, focusing on issues like civilian morale and the relationship between citizens and the state. In some ways, the depth of the patriotic consensus was remarkable in a city that was far removed from any real enemy threat. The population was highly polyethnic, with strong class divisions and a vibrant tradition of political protest. Both factors meant a greater number of potential fault lines. But the large number of ethnic groups in Winnipeg and the Left’s relative lack of political power also meant that there was no dominant minority to seriously challenge the interpretation of the war expressed by the city’s charter group. Social cohesion was enhanced in Winnipeg despite the absence of real danger for a number of reasons: the connection of ethnic communities to occupied or threatened homelands, like Poland or the United Kingdom; the effectiveness of both official and unofficial information management, such as Victory Loan publicity; and the strong identification people maintained with family and friends in the armed forces, war industries, or state institutions. The war effort affected people as individuals and as members of families and the wider community. Its impact was at times unjust and destructive yet most hardships were ultimately accepted as necessary for the war’s successful prosecution.

Historians have established the framework of Canada’s general political, economic, and military participation in the Second World War, but there has been little research into the ways that the national war effort affected individuals or local communities. This dissertation explores the wartime experience of ordinary Winnipeggers through their responses to recruiting, the treatment of minorities, war finance publicity, participation in voluntary community service, and the adjustments made necessary by family separation. It questions the prevailing narrative of the war as a unifying national experience, focusing on issues like civilian morale and the relationship between citizens and the state. In some ways, the depth of the patriotic consensus was remarkable in a city that was far removed from any real enemy threat. The population was highly polyethnic, with strong class divisions and a vibrant tradition of political protest. Both factors meant a greater number of potential fault lines. But the large number of ethnic groups in Winnipeg and the Left’s relative lack of political power also meant that there was no dominant minority to seriously challenge the interpretation of the war expressed by the city’s charter group. Social cohesion was enhanced in Winnipeg despite the absence of real danger for a number of reasons: the connection of ethnic communities to occupied or threatened homelands, like Poland or the United Kingdom; the effectiveness of both official and unofficial information management, such as Victory Loan publicity; and the strong identification people maintained with family and friends in the armed forces, war industries, or state institutions. The war effort affected people as individuals and as members of families and the wider community. Its impact was at times unjust and destructive yet most hardships were ultimately accepted as necessary for the war’s successful prosecution.

Lorsque la Grande Guerre éclate en 1914, le champ mondial de la géographie universitaire est structuré en écoles locales et nationales, liées par des publications, des débats scientifiques et des rassemblements au niveau international. Cette étude d’histoire comparée montre que les trois principales communautés de la discipline (Allemagne, France, Etats-Unis) sont ébranlées par la violence du conflit et participent aux multiples cultures de guerre des pays belligérants. Entre combats pour les plus jeunes, travail pour les armées, notamment dans la géologie de guerre allemande et états-unienne, engagement (autour des atrocités allemandes et russes, des buts de guerre, de la géographie militaire et politique) et diplomatie culturelle chez les géographes des fronts domestiques, les spécialistes des sciences de la terre se mobilisent de façons diverses et occupent un rôle inédit d’experts, en particulier dans les discussions autour des négociations de paix, entre 1917 et 1919. Enseignants, savants, intellectuels et citoyens, ils connaissent donc une phase brutale mais intense de leur identité professionnelle, devant concilier la « géographie moderne » avec une nouvelle géographie appliquée. Le résultat est décevant, tant dans la mobilisation politique et militaire, vécue avec enthousiasme, puis avec malaise, que dans l’expertise, insatisfaisante et peu efficace auprès des autorités chargées de redessiner la carte de l’Europe et du monde. Malgré ces limites, la Première Guerre mondiale constitue un moment fort dans l’identité collective de la géographie universitaire, lente à se démobiliser et marquée par la persistance des alliances et de la violence de guerre. / When the Great War broke out in 1914, the field of academia in geography was divided into local and national schools, connected together through publications, scientific debates and international meetings. My work in comparative history aims at showing that the three main “communities” in the field (namely Germany, France and the United States of America) were affected by the war violence, and that they took an active part in many aspects of “war cultures” in the fighting countries. Indeed, the youngest ones fought, some others did some research for the army (above all in German and American war geology), some others wrote committed books (about German and Russian atrocities, war goals, political and military geography) and geographers of the Home fronts played an important role in cultural diplomacy – every specialist in Earth Sciences mobilized in various ways. They were even to be used as experts, specially during the 1919 peace negotiations. As teachers, scholars, intellectuals and citizens, these men and women went through a very brutal and intense period as far as the shaping of their professional identity is concerned, for they had to reconcile “modern geography” with applied geography. The results proved to be quite disappointing for them: political mobilization, at first enthusiastic, soon turned sour; and their expertise could appear useless as it failed to help political leaders to frame a new map of the world based on scientific grounds. Despite these frustrations and limits, the First World War seems to be a turning point in the shaping of the collective identity of academic geography: its demobilization took a long time, and remained unfinished as long as violence and alliances persisted. / Als der Erste Weltkrieg 1914 ausbrach, war die Hochschulgeographie in lokalen und nationalen Schulen organisiert, die durch Fachzeitschriften und Publikationen, wissenschaftlichen Debaten und internationalen Zusammentreffen in Verbindung waren. Diese Arbeit zeigt in einer vergleichenden Perspektive, dass die drei wichtigsten Fachgemeinschaften (Deutschland, Frankreich, Vereinigten Staaten) von der Gewalt des Konflikts erschüttert wurden und an der vielseitigen Kultur des Krieges in den Krieg führenden Mächten teilgenommen haben. Zwischen Kämpfen für die Jüngeren, wissenschaftlichen Werken für die Truppen, insbesondere im Rahmen der deutschen und amerikanischen Kriegsgeologie, politischem Engagement (über die deutschen und russischen Gräueltaten, die Kriegszielen und die Kriegs- und politische Geographie) und kulturelle Diplomatie für die Hochschulgeographen des Home fronts, mobilisieren sich die Spezialisten der Erdwissenschaften und spielen eine sehr neue Rolle von Experten, insbesondere in den Debaten über die Friedensverhandlungen, zwischen 1917 und 1919. Als Lehrer, Wissenschaftler, Intellektuellen und Bürger, erleben sie also eine brutale und intensive Etappe ihrer Berufsidentität, in der sie die „moderne Geographie“ mit einer neuen angewandten Geographie vereinbaren sollen. Die Ergebnisse sind aber enttäuschend, sowohl bei der politischen und militärischen Mobilisierung, die zuerst mit Begeisterung, dann mit Unzufriedenheit empfunden wurde, als auch bei der unbefriedigenden und unwirksamen Expertentätigkeit, insbesondere über die Neugestaltung der politischen Karte Europas und der Welt. Trotz dieser Schwierigkeiten hat der Erste Weltkrieg eine grosse Bedeutung in der kollektiven Identität der Hochschulgeographie, deren Entmobilisierung sehr langsam ist und die von dem Andauern der Kriegsbündnisse und Gewalt geprägt wird.

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