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Spectroscopic study of ⁸⁰SrDavie, Raoul Francis January 1986 (has links)
High spin states in <sup>80</sup>Sr have been studied using the techniques of in-beam γ-ray spectroscopy. The reaction used was <sup>54</sup>Fe(<sup>29</sup>Si, 2pn)<sup>80</sup>Sr at beam energies between 85 and 110 MeV. γ-γ coincidence measurements were performed with a thin target to investigate the level structure. Both neutron gated and singles angular distribution measurements were carried out to aid in the assignment of level spins. The directional correlation ratios extracted from the γ-γ coincidence data provided a consistency check for the spin assignments. Level lifetimes were measured by the Doppler shift attenuation method in a thick target γ-γ coincidence measurement. The ground state band has been identified up to (26<sup>+</sup>) and three previously unobserved sidebands have been discovered. The deduced level scheme is compared with cranking model calculations; the predicted transformation to mostly non-collective excitations of an oblate shape is not observed experimentally. The behaviour of the J<sup>(1)</sup> and J<sup>(2)</sup> moments of inertia is discussed and presented as evidence for either static or dynamic γ-deformation in the light Sr isotopes. In addition, the level structure is compared with IBM-2 calculations. These calculations indicate the importance of proton excitations across the Z=40 subshell gap, into the g<sub>9/2</sub> orbital, and suggest that the lowest lying <sup>80</sup>Sr sideband can be identified with the collective IBM-2 quasi-γ band. NUCLEAR REACTIONS <sup>54</sup>Fe(<sup>29</sup>Si, 2pn), ,em>E = 85 - 110 MeV; measured Eγ, Iγ(θ), γ-γ, n-γ coincidences, DCO ratios, Doppler shifted γ-ray lineshapes. <sup>80</sup>Sr deduced levels, J, π, τ. Enriched target, Ge(Li), Ge, NE213 detectors.
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Experimental and theoretical analysis of boltless semi-rigid connectorsDavaee-Markazi, Farid January 1999 (has links)
No description available.
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A finite element study of the elastic-plastic indentation and the response of composite structural components to impact and impulse loadingOguibe, Chukwuma Nnamdi January 1996 (has links)
No description available.
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Deposition and characterization of thin alumina films grown by electron beam evaporationMuhammed, Harun 06 1900 (has links)
In thin film fabrication, growth of high quality thin films with reproducibile properties is one of the main challenges. In order to achieve this goal, the influnce of the deposition system control parameters on film properties must be studied. This can be a complex process since many parameters may need to be considered. In this thesis, the electron beam evaporation of thin aluminum oxide films was investigated. Films were deposited with and without oxygen supply in the chamber, and at various ebeam source settings. A Varialble Angle Spectroscopic Ellipsometry system was used to characterize the films. Refractive index, which depends on material density and stoichiometry, was used as the figure of merit. It was observed that refractive index increases with deposition rate. Refractive index also changes with oxygen pressure and upon exposure to air. Various models to explain this behaviour are proposed and discussed. / Materials Engineering
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Simultaneous optimization of beam positions for treatment planning and for image reconstruction in radiotherapyWidita, Rena, Physics, Faculty of Science, UNSW January 2006 (has links)
From one treatment to the next, considerable effort is made to accurately position radiotherapy patients according to their treatment plans. However, some variation is unavoidable. The target volume and the organs at risk may also move within the patient and/or change shape during the treatment. Thus, it is important to be able to verify the success of the treatment by determining the position of patient and the dose deposited in the patient at each fraction. One possibility to achieve this, particularly when equipment, time and budgets are limited, would be to collect limited information while the patient is on the treatment couch. This research was aimed to develop a method for optimum beam position determination, for each patient-specific case. The optimized beam positions would balance the both treatment planning and image reconstruction, so that the patient???s image can be obtained during the treatment delivery using the information collected from the same angles as used for treatment. This will allow verification of the dose deposited in the patient for every fraction. Using a limited number of angles for image reconstruction, the dose to the patient can be minimized. This work has two major parts, beam position optimization for image reconstruction and beam position optimization for treatment planning. These two optimizations are then combined to obtain the optimum beam position for both image reconstruction and treatment planning. An objective function, projection correlation, was developed to investigate the image reconstruction method using limited information. Another objective function, the average optimization quality factor, was also introduced to optimize beam positions for treatment planning. Two optimization methods, the gradient descent method and the simulated annealing based on these objective functions were used to determine the beam angles. The results show that the projection correlation presents several advantages. It can be applied without any iterations, and it produces a fast algorithm. The present research will allow selection of the optimum beam positions without excessive computational cost for treatment planning and imaging. By combining the projection correlation and the average optimization quality factor together with more advanced image reconstruction software this could potentially be used in a clinical environment.
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A study of power transmission in actively controlled simple structures / Xia Pan.Pan, Xia, 1959- January 1996 (has links)
Bibliography: leaves 189-195. / xii, 197 leaves ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This study investigates feedforward active control of harmonic vibratory power transmission in simple structures, theoretically and experimentally. The structures investigated are a beam, a plate and a cylinder. / Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 1997?
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New fibre-reinforced polymer box beam: investigation of static behaviourSpringolo, Mario January 2005 (has links)
This thesis discusses the development of a new type of fibre-reinforced polymer (FRP) beam for use in civil engineering systems. After a detailed evaluation of the advantages and disadvantages of current FRP beam technology, a different approach is proposed which combines traditional laminates with a novel casting technique. To pre-dimension the beam, the classical beam theory is adapted to allow for FRP materials. The resulting formulae were used to determine critical parameters, such as laminate thickness and location in the cross-section, and core dimensions, and to identify failure modes. Based on the results of this analytical study, a detailed testing program was developed. In addition to classical tests, such as bending, shear, and lateral torsion, the performance of the beam was also examined under particular loading regimes specifically designed to induce local failure modes, such as buckling of the web and bearing failure of the section under concentrated loads. The experimental results revealed very good agreement with the analytical predictions. These results were corroborated by a detailed non-linear finite-element analysis, including core cracking and laminate damage. This analysis, in particular, highlighted the synergy between bending and shear behaviour of the beam. This study has revealed that this new type of FRP beam behaves in a predictable manner. Furthermore, the experimental results verified that the cross-section, which combines traditional laminates with cast polymer concrete, did not suffer from many of the disadvantages identified in current FRP beams. The cracking of the polymer concrete under shear, however, does cause the beam to fail prior to the laminates reaching their ultimate shear stress.
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Photonic studies of defects and amorphization in ion beam damaged GaAs surfaces /Vaseashta, Ashok K. January 1990 (has links)
Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 198-208). Also available via the Internet.
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GSMBE growth on V-groove patterned substrates for InP-based quantum wires /Wang, Jun. January 1997 (has links)
Thesis (Ph.D) -- McMaster University, 1997. / Includes bibliographical references (leaves 130-139). Also available via World Wide Web.
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Molecular-beam epitaxial growth of low-dark-current avalanche photodiodesHurst, Jeffrey Byron, January 1900 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.
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