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We report on the dynamics of interstellar dust grains above the plane of the Milky Way. Our Galactic model closely matches its large-scale observed properties, namely the luminosity output, the gas content and distribution, as well as the extinction of starlight by dust. The gravitational model is composed of a central bulge, a disk and a dark matter halo. In spite of the fact that the emphasis in the results is for our Galaxy, we also discuss the effects of varying key galactic parameters, such as the total luminosity output and gas distribution. The parameter space of the main dust grain properties is also explored; these include the grain type (graphite and silicate) and size (0.001 - 0.3 micron). The grains were launched at various positions in the Milky Way, but always in the disk-halo connection region; namely at three Galactocentric radii (5, 8 and 11 kpc) and three initial heights (150, 300 and 1000 pc). The grains were subject to radiation pressure, a gravitational force, as well as Coulomb and collisional drag with the gas. Due to the large size of the parameter space, there is a wide variety of possible grain dynamics. Indeed, depending on the physical conditions in which the grains were launched, the grains could either: (1) fall down towards the midplane, (2) stay at the same height, (3) rise at a more or less constant speed, (4) rise and then fall down, (5) rise and then stabilize at some height, and (6) be quickly expelled into the intergalactic medium. In general, graphite grains reach greater heights than silicate grains. The smaller grains (of radius a = 0.01 and 0.001 micron) tend to stay at the same height they started at. The classical grain (a = 0.1 micron) is the most sensitive to radiation pressure and usually reaches the highest heights, even if they are modest. The largest grain we have studied (a = 0.3 micron) also responds well to radiative forces, but its large mass prevents it from going as high as the classical grain, and it even falls down towards the midplane under some circumstances. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2007-09-20 12:47:04.861

Fibre reinforced polymers (FRPs) are currently being used in new bridge construction as a feasible alternative material for corroded bridge deck replacements, footbridges, and emergency vehicle bridges. For both military and civilian applications, there exists a need for bridges that are lightweight and inexpensive, that can be readily transported and easily erected. The 10 m glass FRP deployable box beam presented in this thesis was developed to aid cross-country mobility in areas where infrastructure has been damaged by conflict or natural disasters. The box beam represents one trackway of a dual trackway system. The quasi-static and dynamic behaviour of the box beam was investigated under laboratory and field conditions. Quasi-static tests were conducted to ensure the strength of the steel hinge, the hinge connection to the base plate of the box beam, and the overall box beam would support the vehicle loads in field testing. Data from these tests were used to validate the finite element model. Field testing was conducted to investigate the natural frequencies of the box beam, calculate the dynamic increment of the structure, and confirm the validity of the finite element model created in Matlab. Three vehicles were used to evaluate the response of the box beam to different types of suspension, loads, and number of wheels per trackway. A finite element model was developed to predict the displacement of the bridge under various vehicle loads. The analysis resulted in displacement contours within a reasonable amount of error when compared to those measured in field testing. Recommendations for future research and development of the structure are provided based on this research. / Thesis (Master, Civil Engineering) -- Queen's University, 2008-09-26 22:49:59.077

Semiconducting single-walled carbon nanotubes (S-SWCNTs) have direct band gaps with a range of 0.5 to 2 eV depending on the SWCNT chirality. The photoluminescence (PL) quantum efficiency and the carriers’ radiative lifetime have been previously studied but neither of them have been confirmed due to the large variation resulting from ensemble averaging, environmental effects, SWCNT defects, and SWCNT bundles. For example, quantum efficiency was estimated to be 0.01% to 7% and radiative lifetime was estimated or calculated to be 10 to 100 ns. In this thesis, we study absorption cross section, PL quantum efficiency and exciton relaxation dynamics from single air-suspended S-SWCNTs and extract “intrinsic” S-SWCNT properties. The photo-excited carriers are electron-hole pairs (called excitons) in a SWCNT due to the strong Coulomb interactions in the nm-scale system. We selected relatively bright and less defected S-SWCNTs on our samples for investigation. For each SSWCNT, the tube length, orientation, absorption and emission spectra were recorded. Experimentally, we observed that PL from a single S-SWCNT increases linearly at low excitation intensity (linear regime) and saturates at higher intensity (saturation regime). We also studied the exciton relaxation dynamics on each S-SWCNT by femtosecond excitation correlation (FEC) spectroscopy and resolved two relaxation time constants which were independent of the excitation intensity. We compare the simulation results based on a stochastic model to the experimental data and extract essential parameters including S-SWCNT unitless absorption coefficient (typically 0.02 to 0.06), PL quantum efficiency (typically 7 to 20 %) and exciton relaxation time constants. We observed very fast nonlinear exciton-exciton annihilation rate (>(2 ps)^−1) in a typical 5 μm-long S-SWCNTs. The exciton dynamics were consistent from 4 different S-SWCNTs in the saturation regime and the average total exciton number per pulse per tube in this saturation regime ranges from 2 to 12. Compared to past work, the results (PL saturation curves and FEC data) between S-SWCNTs are very consistent which supports our belief that we are studying “intrinsic properties”. We found a higher absorption coefficient, and higher PL quantum efficiency of S-SWCNTs compared to previous work. We also observe very fast nonlinear exciton-exciton annihilation in a relatively longer S-SWCNT and at lower exciton numbers. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2009-01-08 20:38:56.433

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