This research entails the synthesis and characterization of a novel class of materials which incorporate both magnetic and piezoelectric characteristics. The composite is made up of the piezoelectric polymer PVDF and magnetic nanoparticles. The testing samples are produced using a spin casting process. The characterizations of the samples were performed using X-ray diffraction, Atomic force microscopy, linear staging, Dynamic mechanical analysis, Differential scanning calorimetry, and Fourier transform Infra-Red. X-ray diffraction and Atomic force microscopy showed that the presence of the Fe3O4 particles have no effect on the crystallinity of the polymer matrix, therefore allowing for the incorporation of inclusions without directly affecting the piezoelectric property. Changes in the thermal characteristics of the polymer matrix, observed using Differential scanning calorimetry, indicated increases in the thermal conductivity of the composite. Decreases in the heat of melting and crystallization were also observed and further solidified the conclusion that the presence of the Fe3O4 nanoparticles changes the thermal behavior of the polymer. It was observed from the DMA results caused an increase in the storage modulus of the polymer matrix which is related to an increase in the material's ability to store energy. Linear staging results showed that the presence of the nanoparticles had an effect on the mechanical properties of the composites and altered the time dependent voltage output readings. These results were used to calculate the energy capabilities of the composite material and it was found that the composites showed greater energy outputs with increasing amounts of nanoparticles. Interaction was observed between the embedded particles and an external magnetic field, which was found to decrease the energy outputs of the composites. This research showed enhancements in the composite material's energy outputs in comparison to the pure PVDF samples. This research also showed that the embedded nanoparticles interacted with an exteriorly applied magnetic field. This observation introduces a new dimension of possible activation processes for piezoelectric devices which have been largely based on physical forms of activation. PVDF which is widely used in research and applications for its superior output capabilities has been enhanced in this research and shown to have capabilities to exhibit higher energy outputs.

In Magnetic Resonance Imaging, the time required to generate an image is proportional to the number of steps used to encode the spatial information. In rapid imaging, an array of coil elements and receivers are used to reduce the number of encoding steps required to generate an image. This is done using knowledge of the spatial sensitivity of the array and receiver channels. Recently, these arrays have begun to include a large number of coil elements. Ideally, each coil element would have its own receiver channel to acquire the image data. In practice, this is not always possible due to economic or other constraints. In this dissertation, methods are explored to combine a large array to a limited number of receivers so as to optimize the performance for parallel imaging; this dissertation focuses on SENSE in particular. Simple combinations that represent larger coils that might be constructed are discussed. More complex solutions form current sheets. One solution uses Roemer'€™s method to optimize image SNR at a set of points. In this dissertation, Roemer's solution is generalized to give the weighting coefficients that optimize SNR over regions. Also, solutions fitted to ideal profiles that minimize noise amplification are shown. These fitted profiles can allow the SENSE algorithm to function at optimal reduction factors. Finally, a description of how to build the combiner in hardware is discussed.

The mechanism for the room temperature magnetic coupling and electric conduction in oxide diluted magnetic semiconductors (DMS) has been studied simultaneously on the Co:ZnO thin film by utilization of the electric field effect. We find that the carriers are bound on a defect in a radius much larger than the bounded magnetic polaron (BMP) radius, and can move by the variable range hopping (VRH) over a relative small distance. Therefore, a concentric bounded model consisting of a concentric localization configuration with a limited carrier VRH capability was proposed. In this model, the carriers localized around defects couples strongly with the doped magnetic ions forming a BMP in the inner sphere and can only itinerate with no spin coherence in the outer shell. Carriers can hop either by spin-polarized or by spin-independent VRH directly between or not directly between adjacent inner spheres, respectively. This model can explain both the electric and magnetic properties of the oxide DMS, and depicts an evolution of electric and magnetic properties associated with defect concentration.

Thesis (M.S.)--University of Arizona, 2001. / Added thesis t.p. Title from HTML title screen (viewed Apr. 25, 2002). Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 89-90).

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

Thesis (M.S.) in Mechanical Engineering--University of Maine, 2009. / Includes vita. Includes bibliographical references (leaves 214-219).

Thesis (Masters)--California Institute of Technology, 1959. / Advisor names found in the Acknowledgments pages of the thesis. Title from home page. Viewed 02/09/10. Includes bibliographical references.

Thesis (Ph. D.)--University of Queensland, 2001. / Includes bibliographical references.

Proefschrift--Leiden. / eContent provider-neutral record in process. Description based on print version record. Bibliography: p. 91.