Nano-powders of BaTiO3, SrTiO3, Ba0.6Sr0.4TiO3, a mixture of the composition (BaTiO3)0.6(SrTiO3)0.4 with particle sizes in the range of 60 to 80 nm, and Bi4Ti3O12 with an average particle size of 100 nm were consolidated by spark plasma sintering (SPS). The kinetics of reaction, densification and grain growth were studied. An experimental procedure is outlined that allows the determination of a “kinetic window” within which dense nano-sized compacts can be prepared. It is shown that the sintering behaviour of the five powders varies somewhat, but is generally speaking fairly similar. However, the types of grain growth behaviour of these powders are quite different, exemplified by the observation that the kinetic window for the (BaTiO3)0.6(SrTiO3)0.4 mixture is 125 oC, ~75 oC for Bi4Ti3O12, ~25oC for BaTiO3 and SrTiO3, while it is hard to observe an apparent kinetic window for obtaining nano-sized compacts of Ba0.6Sr0.4TiO3. During the densification of the (BaTiO3)0.6(SrTiO3)0.4 mixture the reaction 0.6BaTiO3+0.4SrTiO3 → Ba0.6Sr0.4TiO3 takes place, and this reaction is suggested to have a self-pinning effect on the grain growth, which in turn explains why this powder has a large kinetic window. Notably, SPS offers a unique opportunity to more preciously investigate and monitor the sintering kinetics of nano-powders, and it allows preparation of ceramics with tailored microstructures. The dielectric properties of selected samples of (Ba, Sr)TiO3 ceramics have been studied. The results are correlated with the microstructural features of these samples, e.g. to the grain sizes present in the compacts. The ceramic with nano-sized microstructure exhibits a diffuse transition in permittivity and reduced dielectric losses in the vicinity of the Curie temperature, whereas the more coarse-grained compacts exhibit normal dielectric properties in the ferroelectric region. The morphology evolution, with increasing sintering temperature, of bismuth layer-structured ferroelectric ceramics such as Bi4Ti3O12 (BIT) and CaBi2Nb2O9 (CBNO) was investigated. The subsequent isothermal sintering experiments revealed that the nano-sized particles of the BIT precursor powder grew into elongated plate-like grains within a few minutes, via a dynamic ripening mechanism. A new processing strategy for obtaining highly textured ceramics is described. It is based on a directional dynamic ripening mechanism induced by superplastic deformation. The new strategy makes it possible to produce a textured microstructure within minutes, and it allows production of textured ferroelectric ceramics with tailored morphology and improved physical properties. The ferroelectric, dielectric, and piezoelectric properties of the textured bismuth layer-structured ferroelectric ceramics have been studied, and it was revealed that all textured samples exhibited anisotropic properties and improved performance. The highly textured Bi4Ti3O12 ceramic exhibited ferroelectric properties equal to or better than those of corresponding single crystals, and much better than those previously reported for grain-orientated Bi4Ti3O12 ceramics. Textured CaBi2Nb2O9 ceramics exhibited a very high Curie temperature, d33-values nearly three times larger than those of conventionally sintered materials, and a high thermal depoling temperature indicating that it is a very promising material for high-temperature piezoelectric applications.

The unique features of the Spark plasma sintering (SPS) were used to investigate the sintering and deformation behaviour of titanium and titanium–titanium diboride composites, and to control the sintering and grain growth of ferroelectric Na0.5K0.5NbO3 (NKN) and of hydroxyapatite (HAp). In the SPS the samples experience a temperature different from that recorded by the thermocouple (pyrometer) used and this temperature difference has been estimated for Ti and NKN.   Sintering and deformation of titanium was investigated. Increasing heating rate and/or pressure shifted the sintering to lower temperatures, and the sintering and deformation rates changed when the α→β phase transition temperature was passed. Fully dense Ti/TiB2 composites were prepared. The Ti/TiB2 composites could be deformed at high temperatures, but the hardness decreased due to the formation of TiB.    The kinetic windows within which it is possible to obtain fully dense NKN and HAp ceramics and simultaneously avoid grain growth are defined. Materials have a threshold temperature above which rapid and abnormal grain growth takes place. The abnormal grain growth of NKN is due to a small shift in the stoichiometry, which in turn impairs the ferroelectric properties. Fully transparent HAp nanoceramics was prepared, and between 900 and 1050 oC elongated grains are formed, while above 1050 oC abnormal grain growth takes place.NKN samples containing grains of the sizes 0.35–0.6 µm yielded optimum ferroelectric properties, i.e. a high remanent polarization (Pr = 30 µC/cm2) and high piezoelectric constant (d33= 160 pC/N). The ferroelectric domain structure was studied, and all grains exhibited a multi-domain type of structure. / At the time of doctoral defense the following articles were unpublished and had a status as follows: Article 4: Manuscript; Article 5 : Manuscript

Depuis quelques années, les exigences des occupants de bâtiments ont sensiblement changé. On observe en effet une demande de confort de plus en plus rigoureux en particulier en période estivale. Cette augmentation des besoins de climatisation induit un accroissement important de la consommation d'énergie électrique dans les bâtiments, dû à une utilisation majoritaire de climatiseurs à compression mécanique de vapeur. Dans ce contexte énergétique difficile, les systèmes de rafraîchissement solaire font partie des alternatives intéressantes aux systèmes de climatisation classiques, dans la mesure où l'énergie primaire est principalement consommée sous forme de chaleur et provenant du soleil donc gratuite. L'autre grand intérêt de ces procédés est que le besoin en rafraîchissement coïncide la plupart du temps avec la disponibilité du rayonnement solaire. La compréhension et le développement de cette technologie passent par une étude expérimentale avec la réalisation d'installations pilotes à échelle réelle dans le but d'acquérir une expérience concrète. C'est dans ce sens que notre laboratoire s'est proposé de mettre en place une plateforme expérimentale d'une puissance frigorifique de 30 kWf chargée de rafraîchir des locaux d'enseignement de l'Institut Universitaire Technologique de Saint Pierre à La Réunion. La première partie de ce manuscrit présente une analyse expérimentale de cette installation. Une seconde approche purement fondamentale a été envisagée avec l'élaboration de modèles numériques permettant de prédire le comportement de l'installation dans son ensemble. Ces modèles numériques décrits sous plusieurs niveaux de finesse, sont validés par les données expérimentales avant d'être utilisés, soit comme outils de pré‐dimensionnement pour les modèles à descriptions simplifiés, soit comme outil d'optimisation et d'analyse pour les modèles détaillés. Le modèle détaillé représentant notre plateforme expérimentale a permis de réaliser une optimisation du fonctionnement de l'installation et de proposer des améliorations pour réduire la consommation d'électricité et augmenter le coefficient de performance électrique global.

The purpose of this study was to create a model for student learning in knowledge translation and transfer in Ontario. The study was informed by two focus groups, each associated with a student research communications skill development program at the University of Guelph, called Students Promoting Awareness of Research Knowledge (SPARK). One focus group (n=9) consisted of current and former SPARK participants. The second focus group (n=10) consisted of SPARK stakeholders who had variously supported SPARK through projects or benevolence, or had helped administer the program. Based on focus group feedback, a conceptual model was developed showing how SPARK participants translate knowledge from university researchers and transfer it to members of society, various communities (agriculture, health, environment, etc.) and stakeholders including the media, government and industry.

The first chapter of this dissertation examines welfare impacts of a combination of subsidies to alternative fuels (AFs) and alternative fuel vehicles (AFVs), and how they compare to gasoline taxes. The particular AF examined here is ethanol that is produced from agricultural products in a small open economy. The model in this paper characterizes a country or state where gasoline is the major source of fuel for automobiles, but that also produces and consumes ethanol as an AF. Gasoline combustion is polluting and its use equals the total amount of emissions produced. Thus, a gasoline tax here is the same as an emissions tax and is the most direct environmental instrument. However, increasing gasoline taxes for pollution purposes is often politically not feasible. Thus, this paper studies how closely subsidies to alternative fuels (AFs) and alternative fuel vehicles (AFVs) emulate abatement behavior from a unit gasoline tax in a simple three sector general equilibrium model, and in the presence of pre-existing labor taxes. The model can also be used to track the effects of each policy on outputs, exports, and fuel use. The analytical results of the model are then calibrated to data from the largest ethanol producing state in the U.S., namely Illinois. The paper finds that subsidies can achieve up to 64 percent of the welfare gains from the gasoline tax, if the uncompensated wage elasticity is low enough or the elasticities of substitution between the transportation goods is high enough. The second chapter estimates behavior of households who jointly make discrete decisions about vehicle ownership and continuous decisions about miles driven. The paper uses seven years of data from 1995-2001 for the 35 states and union territories of India. The estimated parameters will be used to calculate elasticities of each different type of vehicle for percentage changes in petrol price per unit distance travelled and in vehicle taxes. The paper also computes income and price elasticities for petrol consumption. Two types of vehicles predominant in India are cars and two-wheelers such as motorcycles, mopeds, and scooters. The latter type of vehicle is more fuel efficient than the former. However, patterns of vehicle ownership across the country reflect a growing number of cars relative to motorcycles. This paper investigates the impact alternative policies such as taxes on petrol or on cars have on efficient methods of vehicle emission abatement in India. In particular, the chapter estimates the effect of each such policy on vehicle choice and driving behavior, and how they in turn affect emissions. The main results are summarized as follows: First, continuous choice own-price elasticities are higher for 4w relative to 2w, given age, and for older vehicles relative to newer ones, within each category. Second, discrete choice own-price elasticities with respect to capital cost are higher for 2w relative to 4w. Moreover, older vehicles of each type are more sensitive to higher vehicle prices relative to their newer counterparts. Third, income elasticities for discrete vehicle choices are all positive and greater than unity. Thus, higher income encourages purchase of newer vehicles of each type. Moreover, usage of vehicles rises with income, conditional on the particular vehicle choice. Finally, the paper conducts simulations that alter the price per kilometer by adding either an additional gas tax, a distance tax or an emissions tax. Results show that a distance tax reduces vehicle kilometers traveled the most, followed by an emissions tax and lastly by the gas tax. However, local emissions are reduced the most by an emissions tax, followed by a distance tax and then by a gasoline tax. Even though it would be ideal to compare the results obtained in this paper to results generated using a micro-level data set, the estimates presented here are indicative of whether a distance tax or a gasoline tax is more effective for emissions abatement in India. The third chapter of this dissertation evaluates how information asymmetry in private automobile markets affects programs to accelerate vehicle retirement, also known as scrappage programs. We use a dynamic framework where agents have heterogenous preference for car quality. Cars can either be new, or used. While all new cars have the same quality, used cars can be of high- or low-quality. The quality of a car is perfectly correlated with emissions. The goal of a scrappage program is to induce car owners to voluntarily scrap low-quality used cars. One key result is that in the presence of adverse selection a subsidy that maintains an active resale market unambiguously makes all types of consumers better off. However, if this option of implementing the subsidy does not exist, then the only other way to induce effective scrappage in our framework is to shut down the used car market. Welfare implications suggest that it might be better not to do anything rather than have a scrappage program such as the latter. / text

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Fusion neutrons from high energy density plasmas generated by pulsed laser irradiation of nanoscale atomic clusters have been explored in recent experiments at the University of Texas at Austin. A sufficiently strong (~200 T) magnetic field is expected to produce a magnetized, high temperature (10 keV) plasma with beta [approximately equal to] 1. Such a field along the laser axis may confine the plasma’s radial expansion, thus increasing fusion yield. As part of a multi-stage project to implement this experiment, a scaled (~40 T, ~500 KA) version of the final 200 T, 2.2 MA pulsed power device has been designed and built by Sandia National Laboratories and is now at UT-Austin. This apparatus, named MegaGauss, is meant to serve as a preparation tool for the 200 T system; as such, its current pulse was recorded for analysis, and is compared to a theoretical model to verify its response parameters (e.g. peak current, time to peak). Techniques and results of this comparison are discussed, followed by explanations of basic construction of the 40 T device and current sensing instrumentation. Discussion of MegaGauss is completed with a survey of notable failure modes, and a description of the often severe effects the miniature field-generating Helmholtz coil experiences due to the current pulse and magnetic field. Finally, a novel data archive scheme, structured around the familiar MDSplus archive system, is implemented in Labview and integrated into the main pulsed power control program. Specifically, methods for linking MDSplus’s robust functionality with Labview’s intuitive development environment are realized by means of a specialized software bridge between the two. These methods are used in software that allows MDSplus archives to be written and read exclusively through Labview. / text

Currently, there is a high demand for lightweight aerospace materials, driven by the desire to provide enhanced fuel efficiency by reducing vehicular weight. Aluminum alloys are attractive due to their excellent mechanical properties and high strength to weight ratios. Powder metallurgy (PM), which converts metal powder into a high performance product, presents an alternative to traditional forming techniques, which are often unable to provide adequate dimensional tolerances. The challenge is to determine if aluminum PM alloys and technologies can be successfully employed within aerospace applications. This research focuses on the PM processing technologies (die compaction, cold isostatic pressing (CIP), and spark plasma sintering (SPS)) of two alloys, PM2024 and PM7075. Processing parameters were assessed using attributes such as density, hardness, and tensile properties. Both powders showed comparable densities and tensile properties to their wrought equivalents. Ultimately, the groundwork was laid for future research into these alloys and their processing methods.

No description available.

No description available.