No description available.

<p> Sap flow measurements scaled to represent canopy transpiration (Ec) and eddy covariance measurements of total forest water vapour flux (E) were compared with soil water, meteorological measurements and modelled interception estimates to quantify the above canopy flux of water to the atmosphere from a temperate White pine ecosystem located on the Norfolk sand plain at Turkey Point, Ontario, for the growing season of 2006. Hydraulic redistribution (HR) was found to have occurred at the site on 26 days during the study (growing season of 2006). During a drought period in June, the nightly increases in stored water (up to 0.50 mm) provided by HR reduced drought intensity in the root zone by maintaining soil water contents ( 0) at levels above the water content associated with the approximate wilting point(() of 0.07). Daily forest water fluxes (E) averaged 2.4 mm d-1 and reached maximums of 4 mm d-1 regularly. Canopy transpiration (Ec) averaged 1.2 mm d-1• Modelled interception accounted for 18% of gross precipitation over the study period. Ec and interception loss (EI) contribute the majority (81%) of the water vapour exchanged between the forest and the atmosphere. E1 accounted for 34% of E and Ec accounted for 47%. Ec was controlled linearly by atmospheric demand (VPD) until a variable transition point was reached, after which mid-day Ec rates remained relatively constant. Ec rates were limited to approximately 0.10 mm hh-1 through the study period. This limitation was sensitive to early morning VPD and soil water deficit. Increases in early morning VPD caused maximum Ec rates to arrive earlier in the day and to be reduced in magnitude. This shift in the timing and magnitude of Ec rates masked a relationship between Ec and soil water content that caused Ec to be strictly limited once root zone soil water content (Bo-25cm) reduced to ~0.07. This study illustrates that the water storage capacities of different site characteristics (particularly the canopy and soil) are an important factor to consider when investigating how changing precipitation characteristics might affect the hydrology of an ecosystem, and discusses the interrelationship between transpiration, soil water supply and atmospheric demand. </p> / Thesis / Master of Science (MSc)

In an increasingly urgent climate crisis, the use of electric powertrains in smaller, purpose-built vehicles can expedite the global adoption of electrification. This thesis discusses the detailed design of an axial-flux switched reluctance motor for application in a light electric vehicle, such as an E-motorcycle. A vehicle application is studied based on typical driving conditions in an urban environment. The requirements of the propulsion motor are extracted, and a baseline machine topology is analyzed for its performance and manufacturability, towards the goal of a functional prototype. The prototype design includes a self-supporting foil winding, designed to maximize the use of axial space and allow for good conductive heat transfer to the machine casing. The rotor structure is found to be a limiting factor, where maximum speed is limited by the mechanical stresses. The performance of the motor is analyzed in detail, beginning with a numerical iron loss model that is implemented to provide faster simulation time of the machine efficiency than FEA. The efficiency is found to peak at 90%, comparable with other traction motors of similar size on the market. The switching angles are studied, and the trade-offs between torque quality and efficiency are quantified over the drive cycle. It was determined that the vehicle could save 19.6 Wh/km by accepting poor torque quality and operating with the most efficient control parameters. Thermal analysis is performed to determine the realistic performance limitations. The machine was found to have power ratings of 7.12 kW instantaneous and 4.76 kW continuous. The final temperature of the winding during the drive cycle was predicted not to exceed the temperature ratings of the insulation system. Finally, the prototype is assembled, and a test plan is outlined for qualification of the motor. / Thesis / Master of Applied Science (MASc) / This thesis documents the design of a new type of electric motor that is intended to be used in a small electric vehicle. The electric motor is different from the majority of motors used in this application for two reasons: firstly, the motor is a switched reluctance motor, which means that it does not contain any permanent magnets, offering cost savings and additional robustness. Secondly, the machine takes the form of a disk, where the magnetic interface between rotating and stationary components is on the face perpendicular to the axis of rotation. Normally, electric motors have the magnetic interface on the cylindrical surface which is parallel to the axis of rotation. The disk form factor presents multiple design challenges, which when coupled with the switched reluctance motor type, are addressed. A series of mathematical models are built to predict the performance of the motor in the vehicular application. Finally, a prototype of the motor is constructed.

No description available.

This study documents the integration and testing of a new variety of unsteady surface temperature gages designed to operate in high speed flow. Heat flux through the surface of the test article was determined from the unsteady temperature by applying a 3D reconstruction algorithm based on a Green's function approach. The surface temperature gages used in this work were 1.59 mm inserts designed to maximize material matching with the test article, in this case 316 stainless steel. A series of benchtop experiments were first performed to understand the individual properties of the gage and determine measurement uncertainty. Prior to testing, all temperature gages are calibrated using an environmental chamber. Gages were installed into slugs of several materials and subjected to a heated jet with a total temperature of 620 K to examine the effects of material mismatch. A shock tube with a notional operating Mach of 2.6 was used to determine the thermal response of the gages as a function of time. In both tests, reference Medtherm Schmidt-Boelter gages ensure consistent heat fluxes are applied across all runs. The time response of the entire electrical system was determined by subjecting the gage to a nanosecond scale laser pulse. Two experimental campaigns were conducted in Virginia Tech's Hypersonic Wind Tunnel. First, gages were integrated into a flat plate test article and subjected to a notionally 2D Mach 3 flow. Tunnel total pressures and temperatures ranged from 793-876 kPa and 493-594 K, respectively. A reference 3.18 mm Medtherm Schmidt-Boelter gage was also installed for comparison. All temperature data are reconstructed using the algorithm to determine heat flux. The second test campaign utilized a flat-faced cylindrical test article in a notionally axisymmetric Mach 6 flow environment. Flow total pressures and temperatures ranged from 8375-8928 kPa and 485.5-622 K. respectively. The Fay-Riddell analytical method was applied to the resulting temperature traces in order to infer the heat flux at the stagnation point for comparison with the reconstructed heat flux. This experiment was complimented with steady, 3D CFD in order to understand the temperature variation across the test article. Both campaigns demonstrate good agreement between the heat flux reconstructed from surface temperatures measured using the new gage, reference measurements, and simulations/analytical methods. The importance of material matching is highlighted during this study. The performance of this gage is shown to exceed the current state-of-the-art, opening the possibility for future analysis of phenomenon present in high-speed flow. / Doctor of Philosophy / At very fast speeds, it is important to understand how the temperatures of surfaces change with time. Traditional devices which can measure surface temperatures have a number of weaknesses, and to address these a new type of surface temperature device has been designed. By using computational methods, one can determine how much energy is being transferred through the surface by measuring how the surface temperature changes over time. A series of laboratory experiments were conducted to understand how this new instrument compares to the current state-of-the-art. Two experimental campaigns were then conducted to test the temperature gages. The first experiment used a simple flat plate geometry in a flow 3 times the speed of sound to serve as a benchmark test case, as the flow over a flat plate is well understood. The second test utilized a flat-faced cylindrical test article in a flow 6 times the speed of sound. The results of this test was compared to exact solutions and flow simulations. The result of this study is a well quantified tool to study how energy flows through a body subjected to very high speed flow, which will enable further study of the complicated thermal environments experienced at high speeds.

In order to create landscapes able to adapt to the constantly shifting demands placed upon it by human and ecological processes, there is a need to incorporate the flux of these human and ecological processes into a physical and dynamic share of the built environment. This will require a perceptual shift in understanding this human/ecological relationship (on the part of both the designer and the user) as well as a change in the design/implementation/management strategies currently employed by designers and planners. Instead of designing landscapes expected to be maintained to look and act in a static manner, the built environment needs to be designed with flux in mind. This thesis' methodology begins with a position paper narrating the current body of knowledge regarding human experience and treatment of dynamic systems within the built environment, focusing specifically on the Outer Banks, a series of barrier islands located off the northern coast of North Carolina. It looks at this relationship through three languages: scientific (or geomorphologic), legislative and design. Next is a sampling of case studies aimed at emphasizing this dynamic relationship between humans and their surroundings. Finally, the design project incorporates the viewpoint developed in the position paper and applies it to a hypothetical site design located in Kitty Hawk, North Carolina. The site is currently slated for a Hilton hotel that will be finished by Spring 2006; however, the spirit of the design has the potential to be incorporated into many sites along the coast. / Master of Landscape Architecture

Urban energy systems are often studied in a very similar way in the sense that the characteristics of the underlying physical infrastructure are weighted as the main determinants of energy use predictions, while the behavior of the human population in relation to this systemthe so-called ``energy consumers''in time and urban spaces is effectively neglected. The spatial and temporal variations in infrastructure-population interactivity greatly complicate urban energy systems; the unremitting growth in population and advances in technology mean that the dynamic interrelationship between the population and urban environment will continue to grow exponentially, resulting in increasing uncertainties, unreliable predictions and poor management decisions given the inadequacy of existing approaches. In this dissertation, I explore the interdependencies of spatiotemporal fluctuations of human mobility as an indicator for human activities and energy use in urban areas in three main studies. First, I show that the fluctuations of intra-urban human mobility and energy use have an underlying structure across both time and space, and that human mobility can indeed be used as a predictor for energy use in both dimensions. Second, I examine how one of the dominant drivers of this structure, namely individuals' location-based activities, influence patterns in energy supply and demand across building types (i.e. residential and commercial buildings) and show how variations in the human mobility networks of two distinct urban populations (the so-called returners and explorers) can explain fluctuations in energy use. Third, I introduce an integrated approach for predicting urban energy use across time and space by incorporating these interdependencies. Generating predictive models that capture the spatiotemporal variations in these determinants in urban settings, as suggested in this research, will contribute to our understanding of how variations in urban population activities for particular times and locations influence can be applied to estimate energy use patterns in surrounding areas. / PHD

L'agriculture biologique se développe rapidement au Québec comme partout dans le monde. Si les motivations des agriculteurs et l'évolution des marchés biologiques sont assez bien identifiés, le processus de formation des prix des produits biologiques reste peu traité dans la littérature. Afin, entre autres, d'améliorer la compréhension globale du secteur et de mieux informer les acteurs, notre mémoire analyse le processus de formation des prix de quatre filières de produits (pommes, carottes, œufs de consommation et poulet entier). Cette décomposition du prix a pour objectif de déterminer comment les marges brutes se répartissent entre les acteurs des filières de produits biologiques du Québec comparativement aux produits non certifiés. Dans une logique exploratoire sans prétention à l'exhaustivité, une reconstitution des prix à chaque passage entre les maillons, de la production à la consommation, est effectuée pour les produits biologiques sélectionnés et comparée aux produits conventionnels. Environ 60 entretiens ont permis de compléter les données de prix recueillies en magasin et sur le web. Au final, l'analyse des données montre que la répartition des marges brutes varie selon le circuit de commercialisation emprunté (circuits courts de vente directe ou de vente indirecte et circuit long). La répartition entre les acteurs semble plus « équitable » lorsque le produit est biologique et vendu en circuits courts. Selon les données récoltées en circuit long, les marges brutes absolues sont similaires ou supérieures pour les intermédiaires commercialisant les produits biologiques. Si l'on connaît la nature des coûts plus élevés liés à la production, peu d'informations ont permis d'expliquer la nature de ces écarts pour la transformation ou la distribution. Il est donc possible de conclure que la répartition des marges entre les acteurs dans les diverses filières biologiques du Québec varie selon le produit et le circuit de commercialisation emprunté par ce dernier. / Organic farming is developing rapidly in Quebec as well as throughout the world. If the motivations of farmers and the evolution of organic markets are well identified, the process of price formation of organic products remains rarely addressed in literature. In order, among other things, to improve the overall understanding of the sector and to better inform stakeholders, our research analyzes the price formation process of four food product sectors (apples, carrots, table eggs and whole chicken). The purpose of this price breakdown is to determine how gross margins are distributed among players in Quebec's organic food product sectors compared to non-certified food products. In an exploratory logic without pretension to completeness, a reconstruction of prices at each passage between the links, from production to consumption, is carried out for the selected organic food products and compared to conventional food products. About 60 interviews were used to complete the price data collected in store and on the web. In the end, the analysis of the data shows that the distribution of gross margins varies according to the marketing circuit used (short direct or indirect sales circuits and long circuit). The distribution between the players seems more « equitable » when the product is organic and sold in short circuits. According to the data collected in long circuit, the absolute gross margins are similar or higher for the intermediaries marketing organic food products. While the nature of the higher costs associated with production is known, little information has been provided to explain the nature of these differences for processing or distribution. It is therefore possible to conclude that the distribution of margins among the players in the various organic sectors of Quebec varies according to the product and the marketing circuit used by the latter.

The development of an organ preservation system (primarily kidneys and livers, but could be adapted to fit hearts, lungs, and even limbs in the future) that can provide surgeons and doctors with real-time quantitative feedback on the health of the organ would be a significant improvement on current transplant practices. This organ transport system will provide surgeons and doctors the opportunity to make more educated decisions towards whether or not to proceed with organ transplantation. Here, we discuss the use Smart Perfusion's organ preservation system as a platform for determining the optimal perfusion temperature of an organ. Porcine kidneys were procured and perfused with a modified PBS solution on the Vasowave™. While on this organ preservation system, a heart emulating pressure waveform (90/50 mmHg) was generated and sent to the specimen. The pressure response, flow rate, temperature, pH, dissolved oxygen content, and conductivity of the fluid stream were all monitored throughout the duration of experimentation. In addition to inline sensors, IR imaging captured the surface temperature of the organ while on the system. Lastly, the use of a combined heat flux-temperature (CHFT) sensor, previously developed at Virginia Tech, was applied for the first time to monitor and measure local tissue perfusion of an explanted organ. A total of 12 experiments were performed (6 at a set fluid temperature of 15°C, and 6 at 20°C). All system data was collected, statistically evaluated and finally compared against blind histological readings (taken at the termination of each experiment at the hilum and pole) to investigate the effects of temperature on organ vasculature. The results of this experiment indicated that the effects of temperature on explanted kidneys can be affectively measured using a non-invasive bioheat perfusion sensor. Specifically, the lower temperature group of kidneys was measured to have lower perfusion. Furthermore, an enhancement to the CHFT sensor technology (CHFT+) was developed and tested for compliance. A controllable thin filmed heat resistor was added to the CHFT assembly to replace the current convective thermal event. This enhancement improved the measured heat flux and temperature signals and enables autonomy. Also, the thin and semi-flexible nature of the new CHFT+ sensor allows for perfusion measurements to be taken from the underside of the organ, permitting a quantitative measure of pressure ischemia. Results from a live tissue test illustrated, for the first time, the effects of pressure ischemia on an explanted porcine kidney. / Master of Science

In 1990, creosote contamination was discovered at a railroad tie yard in Oneida, Tennessee. A phytoremediation system that included over 1,200 hybrid poplar trees was installed between 1997 and 1998 for hydraulic control of the groundwater and enhancement of the natural biodegradation processes in the subsurface. Since then, Virginia Polytechnic Institute and State University has monitored eight polycyclic aromatic hydrocarbons (PAHs) in the soil and groundwater. They have found that concentrations of smaller and more volatile PAHs have decreased over the years as the DNAPL contamination has become more enriched with the larger PAHs. This thesis focuses on the movement of naphthalene through the subsurface because it comprises the majority of the creosote and evidence for its remediation exists. Of the many mechanisms within the phytoremediation system that serve to remediate contaminated groundwater and soil, the most important are rhizosphere bioremediation and plant uptake. However, another mechanism, direct volatilization through the soil, was thought to have significant remediation capabilities at this site. Because naphthalene is a highly volatile PAH, it was hypothesized that naphthalene is volatilizing directly through the soil to the atmosphere and that the rate of volatilization may be enhanced by the presence of the phytoremediation system. The goals of this research are to measure the amount of naphthalene that volatilizes from the subsurface and determine the factors that significantly influence this direct volatilization. A flux chamber was designed and constructed to measure naphthalene fluxes from the soil. Factors that influence direct volatilization include the groundwater level, soil moisture, precipitation, pressure changes, temperature and humidity, the most important of which we found to be the groundwater level through its influence on naphthalene concentrations in the groundwater. We found that the presence of the trees significantly affects groundwater levels. As trees transpire and lower the groundwater table, concentrations in the uppermost portion of the groundwater increase, and under dry conditions, naphthalene fluxes from the soil are maximized. To complement the field measurements of direct volatilization, we also investigated rates of volatilization and biodegradation in the laboratory. Column experiments were conducted to determine the importance of direct volatilization on biodegradation in the vadose zone. We hypothesize that the combined mechanisms of contaminant transfer to the vadose zone, followed by rapid biodegradation, speeds up remediation in contrast to biodegradation that occurs only in the saturated zone under high groundwater conditions. Several columns using contaminated and uncontaminated soil from the site were constructed with a naphthalene source. Vertical naphthalene vapor concentration profiles were measured, and first-order biodegradation rates were determined. We found that biodegradation rates in the bacterially active columns were small initially, but that the biodegradation rates of the contaminated soil dramatically increased at day 60, while the biodegradation rates of the uncontaminated soil did not begin to increase until day 150. By the end of the experiment, both soil types had approximately the same biodegradation rate, signifying that soil that had previously been exposed to naphthalene degrades naphthalene more efficiently in the early stages than soil that has not been exposed, but that over time the non-exposed soil degrades naphthalene as efficiently as the pre-exposed soil. We determined that the combined mechanisms of diffusion and biodegradation in the unsaturated zone have significant remediation capabilities. Because long-term exposure risks are associated with inhaling indoor contaminant vapors, the Johnson and Ettinger vapor intrusion model was applied to the creosote-contaminated site, as outlined in Appendix C. This model takes into account soil, chemical, and building foundation characteristics to determine a dimensionless attenuation ratio, which is the ratio of contaminant vapor concentration in an enclosed space (i.e. basement) to the vapor concentration directly above the source. For a conservative case, the Johnson and Ettinger model without biodegradation was used. We found that if the land were developed, naphthalene vapor intrusion would not pose any health risks based on regulatory standards and levels at which health effects have been recorded. / Master of Science