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.

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

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

The effects of using an insert Heat Flux Microsensor (HFM) versus an HFM deposited directly on a turbine blade to measure heat flux in a transonic cascade are investigated. The HFM is a thin-film sensor, 6.35 mm (0.250") in diameter (for an insert gage, including the housing) which measures heat flux and surface temperature. The thermal time response of both gages was modeled using a 1-D, finite difference technique and a 2-D, finite element solver. The transient response of the directly deposited gage was also tested against insert gages using an unsteady shock wave in a bench test setup and using a laser of known output. The effects of physical gage offset from the blade surface were also investigated. The physical offset of an insert HFM near the stagnation point on the suction side of a turbine blade was intentionally varied and the average heat transfer coefficient measured. Turbulence grids were used to study how offset affects the heat transfer coefficient with freestream turbulence added to the flow. The time constant of the directly deposited gage was measured to be 856 ms compared to less than 30 ms for the insert gages. Model results predict less than 20 ms for both gages and rule out the anodization layer (used for electrical isolation of the directly deposited gage from the blade) as the cause for the directly deposited gage's much slower time response. Offsets of ± 0.254 mm (0.010") at the gage location with an estimated boundary layer thickness of 0.10 mm (0.004") produced a higher average heat transfer coefficient than the 0.000" offset case. Using an insert HFM resulted in a higher average heat transfer coefficient than using the directly deposited gage and reduced the effects of freestream turbulence. To accurately measure heat transfer coefficients and the effects of freestream turbulence, the disruption of the flow caused by a gage must be minimized. Depositing a gage directly on the blade minimizes the effects of offset, but the cause of the slow time response must first be resolved if high speed data is to be taken. / Master of Science

The effects of grid generated freestream turbulence on surface heat transfer to turbine blades were measured experimentally. Time-resolved and unsteady heat flux measurements were made with Heat Flux Microsensors at two positions on the suction side of turbine blades. The experiments were conducted on a stationary cascade of aluminum turbine blades for heated runs at transonic conditions. Non-dimensional flow parameters were matched to actual engine conditions including the design exit Mach number of 1.26 and the gas-to-wall temperature ratio of 1.4. Methods for determining the adiabatic wall temperature and heat transfer coefficient are presented and the results are compared to computer predictions for these blades. Heat transfer measurements were taken with a new, directly deposited HFM gage near the trailing edge shock on nitrogen cooled blades. The average heat transfer coefficient for Mach 1.26 was 765 W/(m² °C) and matched well with a predicted value of 738 W/(m² °C). Freestream turbulence effects were studied at a second gage location 1.0 cm from the stagnation point on uncooled blades. Results at this location show an increase in freestream turbulence from 1 % to 8% led to a 15% increase of the average heat transfer coefficient and also matched well with predictions. The fast response time of the HFM illustrated graphically the increase in energy spectra due to freestream turbulence at the 0 - 10kHz range. The heat flux turbulence intensity (Tu_q) was defined as another physical quantity important to turbine blade heat transfer. / Master of Science

Mono-energetic neutrons have been produced with the low-voltage Cockroft-Walton accelerator at North Texas State College using two different reactions. It is the purpose of this paper to report the angular distribution and total flux of the neutrons obtained from the T(D,n) reaction.