We extend an efficient cone beam transform inversion formula, proposed earlier for helices, to a general class of curves. The conditions that describe the class are very natural. Curves C are smooth, without self-intersections, have positive curvature and torsion, do not bend too much in a certain sense, and do not admit lines which are tangent to C at one point and intersect C at another point. A domain U is found where reconstruction is possible with a filtered backprojection type algorithm. Results of numerical experiments demonstrate very good image quality. The algorithm developed is useful for image reconstruction in computerized tomography.

In this work, we have utilized an ion beam process known as gettering to migrate implanted Ni ions much deeper into the bulk substrate than their initial projected end of the range. The projected mean depth is known as Rp. The gettering effect is the most crucial part of the fabrication and we have found that for an H fluence of 3x 1016 cm-2 there is a threshold fluence of approximately 7.5 x 1015 cm-2 that cannot be surpassed if the gettering process is to be completed along with the substrate recovered to the high crystalline quality. This hard threshold is due to the gettering process relaxation induced mechanism that is responsible for migrating the Ni to the Rp/2 location while the H is vacating during the thermal annealing process. If the total number of vacancies produced by the H dissociation is not substantially larger than the total number of implanted Ni atoms the Ni will migrate to the Rp location of the Ni implantation at the amorphous and crystalline interface and toward the surface. When the gettering condition is not met the resulting magnetic responses vary from an exceptionally weak ferromagnetic response to not exhibiting a magnetic response. Additionally, conducting the ion implantation at an elevated substrate temperature does not increase the threshold Ni fluence above our established limit. During the elevated substrate temperature implantation, the hydrogen ions diffuse out to the surface resulting in less migration of the Ni to the initial Rp location within the Ni implantation region. The elevated temperature implantation condition appears to not create a sharp amorphous crystalline interface at the end of the range for the Ni implantation.

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<p> The major purpose of the work described in this thesis has been the development of an analytical model for the electron-beam pumped semiconductor laser system consistent with the main dynamic effects observed experimentally in the stimulated emission. The lasing mat4:!rials used in this study were single crystals of CdS, CdS1e and GaAs. The choice was made on the basis of the availability of high purity single crystals and for representation of both II-VI and III-V materials in the study. </p> <p> Generally, the light output from a pulse-excited semiconductor laser changes in both wavelength and far-field pattern as a function of time during the excitation pulse. The effects investigated divide naturally into two parts. The first part deals with the tuning of the peak output of the stimulated emission toward lower energies during the excitation pulse. The second part deals with a deviation of the far-field radiation pattern of the spatial laser mode with respect to the cavity axis and the changes of this angle with time during the pump pulse. </p> <p> In parallel with these investigations, a theoretical model of the semiconductor laser was developed. This model takes into account spatial variations in the gain and refractive index in the semiconductor material and changes in these profiles with time. The analysis, in terms of the experimental parameters, leads to a prediction of angular tuning of the far-field mode and can account for certain features of faster-than-bandgap wavelength tuning in a number of disparate laser materials. A particularly significant consequence of the model is the prediction of dramatic variations in cavity loss as a function of time. The major consequences of this effect for laser dynamics are discussed. </p> / Thesis / Doctor of Philosophy (PhD)

<p> Turbidity over Hamilton is determined using direct beam radiation in two manners for the summer period of 1975. These turbidities are then studies with respect to local regional and continental synoptic air masses.</p> <p> The results of the study show a high correlation between the actinometric and residual methods of determining direct beam radiation. This allows turbidity to be easily evaluated at radiation measurement sites.</p> <p> The most significant influence on the amount of particulate matter over Hamilton is the continental scale synoptic patterns.</p. / Thesis / Bachelor of Science (BSc)

<p> Using atomic beam magnetic resonance techniques the hyperfine structure (hfs) constants for the magnetic dipole and electric quadrupole interaction, AJ and BJ, have been measured for the following isotopes: 40-hour 140La, 1.8-hour 149Nd and 11-day 147Nd.</p> <p> For 140La the hfs constants are (relative to the J = 5/2 state of 2D) |A5/2| = 55.9(4) MHz, |B5/2| = 38(4) MHz, B5/2/A5/2 > 0. Application of the Fermi-Segre relations in comparison with 139La yields the nuclear moments; μI = (+)0.73(3) n.m., and Q =(+)0.11(4) b. The adopted signs are based on Blok's measured sign of Q for 140La.</p> <p> For 149Nd the hfs constants are: |A4| = 91.0(19) MHz, |B4| = 266(53) MHz, and B4/A4 > 0. Comparison with 145Nd yields μI = (-)0.350(10) nm., and Q = +1.3(3)b. The signs of these moments are based on Q>0 as indicated by nuclear systematics in this region.</p> <p> For 147Nd the hfs constants are |A4| = 143(4) MHz, |B4| = 181(64) MHz, and B4/A4 > 0. Comparison with 145Nd yields |μI| = 0.553(15) n.m., |Q| = 0.9(3) b and μI/Q <0.</p> <p> The error in the 140La magnetic moment allows for a possible 2% hfs anomaly. The quadrupole moments allow for a possible 25% error in the core polarization correction (Sternheimer).</p> <p> These results are discussed in terms of the shell model, the quasi-particle model, and the Nilsson model.</p> / Thesis / Doctor of Philosophy (PhD)

<p> Transverse vibrations of a beam with one end fixed and the other supported on nonlinear spring have been studied. Theoretical analysis has been carried out for two different cases of springs, viz.; cubic nonlinear and bilinear types. </p> <p> Theoretical results for bilinear case have been compared with those obtained experimentally. The effect of end mass has also been considered in theoretical analysis. </p> / Thesis / Master of Engineering (MEngr)

This thesis documents the design and development of a robust backpackable proof-of-concept unmanned aerial vehicle. The unmanned aerial vehicle?s design departs from existing configurations in utilizing a keel beam fuselage which replaces the enclosed fuselage by a flat keel beam on which the sensors, the autopilot, their related power sources, and flight control systems are mounted. The keel beam fuselage is provides enhanced mounting capability for multiple sensors and quick reconfiguration in the field. The keel beam fuselage can also be manufactured quicker than a traditional enclosed fuselage. The objective of this study is to demonstrate that the keel beam configuration is a viable design for an unmanned aerial vehicle and the challenges of modular, plug-n-play hardware. The design, fabrication, and flight testing of the air vehicle are addressed.

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