Transportation accidents and the resulting fires are an important field of study. At the University of Waterloo Live Fire Research Facility (UWLFRF), an experiment was conducted in partnership with Sandia National Laboratories in Albuquerque, New Mexico. This experiment was designed to simulate an aircraft accident where fuel is spilled on the runway and is subsequently ignited. A crosswind pushes the 2.0 m diameter pool fire towards the aircraft fuselage and the conditions around the fire are monitored. Literature on the subject is examined first, examining the relationship between the fire, the crosswind, and the 2.7 m diameter blocking object (aircraft fuselage). A full wind characterization is then presented of the UWLFRF both with and without the blocking object in place, using five distinct wind speeds ranging from 3 m/s to 13.5 m/s. Turbulence intensity measurements are made on the centerline of the facility when possible. Details about the two sets of live fire tests are presented, a control experiment without the blocking object in place and then fire tests with the blocking object in place. Additionally, the control experiment has two different setups, one involving a floor surround in order to diminish the effect of the forward facing step on the front of the fuel pan. The fuel regression rate, the wind speed, the ambient conditions and the heat flux near the fuel pan are monitored during each live fire test. The fuel regression rate, defined as the rate at which the height of the liquid fuel level decreases as the fire burns, is then analyzed versus all other monitored variables. During no blocking object tests, trends of increasing wind speed and increasing heat flux on some gauges and decreasing flux on others was observed with increasing fuel regression rate when the floor surround was in place. During no blocking object tests without the floor surround and tests with the blocking object in place, no strong trends were observed when comparing the monitored variables. The ambient conditions were not observed to have an effect on any test. The average fuel regression for tests without the blocking object in place is 4.0 mm/min without the floor surround, and 4.4 mm/min with it in place. With the blocking object in place the average fuel regression rate was measured to be 4.8 mm/min using load cells and 4.1 mm/min using the sight glass.

In an effort to improve the fuel efficiency of automobiles, car designers are investigating new materials to reduce the overall vehicle weight. Magnesium alloys are good candidates to achieve that weight reduction due in part to their low density and high specific strength. To support their introduction into vehicle body structures, the dynamic behavior of magnesium alloys must be determined to assess their performance during a crash event. In this work, the tensile high strain rate behavior of AZ31B magnesium alloy sheets was characterized. Two different temper conditions were considered: AZ31B-O (fully annealed) and AZ31B-H24 (partially hardened). Three different sheet thicknesses were considered for the O temper condition, 1.0, 1.6 and 2.5 mm, while the H24 temper was 1.6 mm in thickness. The sheet condition of the magnesium alloys implies an in-plane anisotropy induced by the rolling process. Therefore, both the rolling and transverse directions were investigated in the current research. In order to characterize the constitutive behaviour of AZ31B-O and AZ31B-H24 magnesium alloy sheets, tensile tests were performed over a large range of strain rates. Quasi-static experiments were performed at nominal strain rates of 0.003s-1, 0.1s-1 and 1s-1 using a servohydraulic tensile machine. Intermediate strain rate experiments were performed at 30s-1 and 100s-1 using an instrumented falling weight impact (IFWI) apparatus, and high strain rate experimental data at 500s-1, 1000s-1 and 1500s-1 was collected using a tensile split Hopkinson bar (TSHB) apparatus. Elevated temperature experiments (up to 300°C) were also performed at high strain rates using a radiative furnace mounted on the TSHB apparatus. The tensile experiments show a significant strain rate sensitivity of the constitutive behavior of both the O and H24 temper conditions. The two tempers exhibit an average increase of stress level of 60-65 MPa over the range of strain rates considered. As the strain rate increases, the strain rate sensitivity of both tempers also increases. The strain rate has a different effect on the ductility of the two material conditions. The ductility of AZ31B-O is significantly improved under high strain rate deformations, whereas the AZ31B-H24 exhibits similar ductility at low and high strain rates. Both material conditions presented a strong in-plane anisotropy, with an average stress level in the transverse direction higher than in the rolling direction by 15 MPa and 35 MPa for the O and H24 tempers, respectively. The thermal sensitivity for both tempers at high strain rates was obtained. The two material conditions exhibit a clear thermal softening. From room temperature to 250°C, the loss in strength at 5% plastic strain was found to be 55 MPa and 125 MPa for the AZ31B-O and AZ31B-H24 materials, respectively. The thickness of the AZ31B-O sheets has a mild effect on the measured constitutive behavior. The flow stress increases with increasing thickness. An average difference of 10-15 MPa was seen between the flow stress of the 1.0mm and 2.5mm sheets. However, similar strain rate sensitivity was seen for the three thicknesses. The experimental data was fit to three constitutive models: the Johnson-Cook model, its modified version with a Cowper-Symonds strain rate sensitivity formulation, and the Zerilli-Armstrong model. The three models were evaluated by numerical simulation of the TSHB experiment under various testing conditions. It was found that the Zerilli-Armstrong model was the most accurate in predicting the flow stress of the different material conditions. However, finite element models incorporating the three constitutive fits failed to predict necking in the specimen.

The viscoelastic and creep properties of salt create challenges in the design of salt mines. Salt undergoes steady state creep for a long period of time, and the time of failure is not easily predicted. Developing functions for creep behavior is important in predicting the deformation of salt pillars. Through literature reviews, it was found that there are many relationships to determine the deformation rate of salt specimens through constitutive models. Mine panels have also been modeled to understand the stress and deformational behavior of the pillars. The purpose of this was project was to develop a relationship that determines the convergence rate from knowing the pillar width to pillar height ratio and thickness of the salt strata immediately above and below the mine. The third power law was adopted in the modeling of salt pillars, which is applicable to low stresses of less than 10 MPa that is typical of salt mine conditions. The finite difference software, FLAC3D was used for the simulations of salt pillar models. A square pillar was modeled using four pillar width to pillar height ratios from 1.5 to 4.6. In mining practices, the pillar width to pillar height ratios are designed to be 1.0 to 5.0. Three sets of pillar dimensions were used for each pillar width to pillar height ratio, this was done to determine whether different room and pillar dimensions for each pillar width to pillar height ratio resulted in different convergence rates. Eight salt thicknesses of 0 m to 26 m were modeled for each set of pillar dimensions, which was sufficient to determine the effect of salt thickness on convergence rate. From the modeled results, general trends among the various pillar width to pillar height ratios were observed. The convergence rate increased as the pillar width to pillar height ratio decreased. In addition, an exponential relationship was found between the convergence rate and the pillar width to pillar height ratio. There was a strong correlation between convergence values calculated from the developed function and the modeled values for the power law exponent of three. The developed expression can be used to estimate the convergence rate due to pillar compression and room convergence.

In resource polymorphism, ecological opportunity and selective predatory pressure can be considered key factors in phenotypic divergence. In post-glacial lakes of Scandinavia, the European whitefish (Coregonus lavaretus L.) is a common species and has repeatedly diverged along the benthic - pelagic resource axis. Recent studies suggest that predation by northern pike (Esox lucius L.) induces rapid divergence in whitefish, leading to two reproductively isolated ecotypes: a dwarf planktivore and a giant benthivore. In lakes where pike is absent, whitefish are only found as monomorphic populations. In this study I estimated growth rates in two monomorphic and two polymorphic populations having giant and dwarf ecotypes. The aim was to use growth rates as a tool to distinguish between juvenile giants and dwarfs, but also to find out if a population's resource use was reflected in the growth rate. Scales were used to calculate growth rate, where like trees, variations in seasonal growth could be observed in a ring-like structure. Growth rates differed between the morphs, and mirrored their use of resources. The two monomorphic populations had the highest average growth rate the first six years (40.1 and 35.5 mm/year), and quickly reached maximum size. Dwarfs and giants in the dimorphic systems had equal growth the first two years, after which giants grew at a substantially higher rate. Categorization between juvenile giants and dwarfs could be done if an individual had passed its third growth season.

Foreign aid has shaped the economies of Sub-Saharan Africa since independence. There has been passionate debate as to whether this has helped or hurt Africa’s poor economies. One of the downsides to foreign aid is the effect it can have on appreciating the real exchange rate and on harming the competitiveness of export-oriented sectors in favour of producers of non-traded goods. I find that the influence of aid flows on the real exchange rate varies greatly across countries, and that movements in the real exchange rate driven by foreign aid have been overshadowed by policy changes and structural adjustment.

We introduce a new across-peer rate allocation algorithm with successive refinement to improve the video transmission performance in P2P networks, based on the combination of multiple description coding and network coding. Successive refinement is implemented through layered multiple description codes. The algorithm is developed to maximize the expected video quality at the receivers by partitioning video bitstream into different descriptions depending on different bandwidth conditions of each peer. Adaptive rate partition adjustment is applied to ensure the real reflection of the packet drop rate in the network. Also the granularity is changed to the scale of atomic blocks instead of stream rates in prior works. Through simulation results we show that the algorithm outperforms prior algorithms in terms of video playback quality at the peer ends, and helps the system adjust better to the peer dynamics.

Microgyroscopes find popular applications in modern life, such as, vehicle navigation, inertial positioning, human body motion monitoring, etc. In this study, three unique MEMS gyroscopic sensors were investigated using experimental methods and finite element analysis (FEA) modelling, particularly their modal behaviour. The analytical, simulated and experimental results were compared and the discrepancy between resonant frequencies of the significant mode shapes was discussed. Three microfabricated gyroscopes were investigated: a thermally-actuated in-plane gyroscope, an electrostatically-actuated in-plane gyroscope and an electrostatically-actuated out-of-plane gyroscope. Numerical finite element modal analysis for these three gyroscopes was conducted using COMSOL Multiphysics. The experimental testing was conducted using a microsystem analyzer (MSA-400 PolyTec) with an integrated laser vibrometer. The simulation models predicted that the frequencies for driving and sensing modes were 4.948kHz and 5.459kHz for a thermally-actuated gyroscope, which agreed well with experimentally determined results of 5.98kHz and 6.0kHz respectively. The power requirements of a thermally-actuated gyroscope were 363.39mW to elicit a maximum peak-to-peak displacement of 4.2μm during dynamic operation. Similarly, the simulated frequencies for the driving and sensing modes were 1.170kHz and 1.644kHz for an electrostatically-actuated in-plane gyroscope, which corresponded to experimentally determined resonant frequencies 1.6kHz and 1.9kHz. Simulation for the electrostatically-actuated out-of-plane gyroscope was conducted and the frequencies for the driving and sensing modes were found to be 2.159kHz and 3.298kHz. Due to some fabrication defects, the experimental testing for this microgyroscope was not successful. Some recommendations to improve the design were provided for the future work. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2010-06-02 22:00:52.994

In patients with normal hearts, increased vagal tone is associated with the onset of paroxysmal atrial fibrillation (AF). Vagal denervation of the atria renders AF less inducible. Circumferential pulmonary vein ablation (CPVA), with or without isolation (CPVI), is effective for treating paroxysmal AF, and has been shown to impact HRV indices, in turn reflecting vagal denervation. We examined the impact of CPVI on HRV indices over time, and evaluated the relationship between vagal modification and rate of recurrence of AF. High resolution ECG recordings were collected from 64 patients (49 male, 15 female, mean age 57.1±9.7) undergoing CPVI for paroxysmal (n=46) or persistent (n=18) AF. Recordings were made pre-procedure, and at intervals up to 12 months. Success was defined as no recurrence. After CPVI, 27 patients presented recurrence. Pre-procedure HRV variables did not differ from controls in patients with a subsequent successful procedure. However, patients with recurrence demonstrated significantly-reduced pre-procedure HRV compared both with controls, and with patients having successful procedures (39.6±23.4 & 33.7±19.2 vs 21.8±11.8, P =0.01 & P=0.04). Following the procedure, HRV was reduced vs pre-procedure in patients with successful procedures (33.7±19.2 vs 18.6±15.8, P=0.01), and did not differ from unsuccessful procedures over a 12 month FU. Both groups were reduced compared with a control value. There was no significant difference in HRV between patients who experienced recurring AF (n=9), and those who experienced AT or flutter (n=18). Our data suggests that patients experiencing recurrence after one procedure have reduced HRV that is not changed by CPVI; whereas patients with a successful single procedure experience a change in HRV variables that is sustained over a long period, but is no different post-procedure from patients experiencing recurrence. These data suggest that denervation associated with CPVI may benefit patients with normal vagal tone prior to the procedure, but that sustained denervation is not a critical factor in successful outcome after CPVI. / Thesis (Master, Computing) -- Queen's University, 2010-12-07 08:32:15.066

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