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No description available.

Thesis (Ph.D.)--Old Dominion University, 2004.

Thesis (M.S.)--Marquette University, 2009. / Richie James, Juan Luglio, Advisors.

Thesis (Ph.D. in mechanical engineering)--Washington State University, August 2005. / Includes bibliographical references.

Graduate

Note:

Tuned vibration absorbers (TVA) have been discussed in literature since the early twentieth century. These devices are implemented to suppress the system's vibration by transferring energy to the absorber mass. This research examines an electromagnetic tuned vibration absorber that can have its tuned frequency altered by gap and current variation. The advantage of an adjustable TVA is that the system can be tuned to various excitation frequencies to cancel vibration. This research examines a unique embodiment using permanent magnets and an electromagnetic absorber to alter the system dynamics. The focus is to allow changes in tuned frequency to cancel system vibrations. This research develops the electromagnetic theory, presents absorber system simulations, and tests the dynamic absorber's response. The electromagnetic field is investigated to determine the field between a stationary magnet and the absorber electromagnet. This field can be numerically calculated as the superposition of four constituent fields. With the electromagnetic field determined, the force to displacement relation between the stationary magnet and the absorber electromagnet is calculated. The best fit is determined to be an inverse square relationship. Once the spring force relation is determined, the damping mechanisms are discussed and experiments proposed to isolate the different damping mechanisms. In the simulations, it is found that by having an adjustable electromagnetic TVA the natural frequency can be adjusted 2-3% with a +10 amp input and over 50% for a variable gap. The advantage of the variable gap is that it may be adjusted once and then no additional energy is needed, while the advantage of the variable current is that the system may be rapidly altered. The experiments are undertaken to test the constructed absorber for the spring and damping force. The tests confirm the spring force relation and quantify the high damping present in the tested configuration. Then the absorber system transfer functions are recorded. The absorber is then applied to a single degree of freedom system to verify its cancellation results by a gap variation. / Ph. D.

published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

This dissertation examines aspects of the interaction of multiple coherent light fields for the two-photon two-level model. In this model the interacting energy levels are not connected by an atomic dipole and a two-photon transition between them is necessary. We employ the density matrix formalism allowing easy comparison between the one- and two-photon two-level models. Significant differences are found due to dynamic Stark shifts and conjugate scattering off the pump-induced two-photon coherence. Averages over Doppler broadening are performed and the new upper-level relaxation mechanisms of decay to an intermediate nonresonant level and ionization from the upper state are included. The new relaxation mechanisms, introduced to the theory to better model experiments, are similar except that ionization is intensity dependent. They cause the resulting probe absorption spectra to become more complex and in general asymmetric. Doppler broadening is also important in experiments using gases. We analytically average over a Lorentzian velocity distribution for both co- and counterpropagating pump and probe beams. For copropagating fields the results are similar to those for the one-photon case averaged over inhomogeneous broadening, whereas counterpropagating pump and probe fields yield the so-called Doppler-free configuration that is normally only modelled to third order in the pump amplitude. We consider the pump field amplitude to all orders and find that as long as the width of the Doppler velocity distribution is significantly larger than the two-photon Rabi frequency the results are Doppler-free. The final part of the dissertation treats the question of two-photon squeezed states. This requires quantized sidemodes. Squeezed states are minimum uncertainty states with unequal variances in the two quadratures of the electromagnetic field amplitude. One way to generate these states is via multiwave mixing and we present here the first calculation for nondegenerate two-photon multiwave mixing as it applies to squeezed states. We find that in general two-photon squeezed states require lower intensities and detuning than those predicted by the one-photon model.