Electroacoustic technology has in many ways revolutionised the wireless telecommunication industry. The IC compatible fabrication technique of thin film electroacoustic devices has so far provided a considerable increase in device performance and reduction in size. At the moment, new areas where this technology can be of use is under investigation. In particular, thin film bulk acoustic wave resonators are promising candidates for biochemical and gravimetric sensor applications. For bulk acoustic waves, the thesis addresses a number of aspects in the design, fabrication, characterisation, and integration of thin film electroacoustic devices. The object of the studies conducted in the thesis has been to improve on design and thereby optimise the performance of the device to fit a particular application of interest. For high frequency and high power applications, a conceptually new design of the solidly mounted resonator has been investigated. A 1 GHz plate wave resonator with a much higher Q factor than its surface acoustic counterpart have also been fabricated. A multi-chip-module 2 GHz microwave oscillator featuring a monolithically integrated solidly mounted resonator and a flip chip transistor have been fabricated and characterised with a phase noise of -125 dBc/Hz at 100 kHz. For sensor applications, the fabrication of shear mode solidly mounted resonators featuring c-axis inclined AlN films has been studied. A process for the bonding of a microfluidic system on top of the resonator has been realised. Further, the effect of conductive liquids on the resonator performance has been investigated.For surface acoustic wave devices, acoustic manipulation of particles in microfluidic channels has been studied. Two functional devices have been fabricated by bonding piezoelectric substrates to glass or fused silica superstrates. By generating an interface acoustic wave, that propagates along the bonded interface, manipulation of sub-micrometer particles was realised. / wisenet

Thesis (M.S. in Mechanical Engineering and M.S. in Applied Physics)--Naval Postgraduate School, December 2009. / Thesis Advisor(s): Sinibaldi, Jose. O. ; Brophy, Christopher M. "December 2009." Description based on title screen as viewed on January 27, 2010. Author(s) subject terms: Pulse Detonation Engines, Shock Wave, Detonation Implosions, Induction Length, Detonation Cell Width, Deflagration-to-Detonation Transition, Specific Thrust. Includes bibliographical references (p. 93-94). Also available in print.

Thesis (M.S. in Engineering Acoustics and M.S. in Applied Physics)--Naval Postgraduate School, December 2009. / Thesis Advisor(s): Karunasiri, Gamani; Baker, Steven. "December 2009." Description based on title screen as viewed on January 26, 2010. Author(s) subject terms: MEMS, Model, Simulation, Pressure Gradient, Particle Velocity, Directional, Microphone, SOMSOL, Acoustic. Includes bibliographical references (p. 51-52). Also available in print.

This thesis presents the design of a high-frequency annular array ultrasound system suitable for medical imaging. To reduce the cost of the system, off-the-shelf parts were used whenever possible. The system consists of four main components; 1) a transmit beamformer, 2) a high voltage pulse generator, 3) an annular array transducer and 4) a receive beamformer. The transmit beamformer and pulser were designed for an 8-channel array but could be easily expanded for larger arrays. The pulser produces monocycle electrical pulses with centre frequencies that could be adjusted from 10-50 MHz and with amplitudes up to 90 Vpp. The annular array transducer has 12 equal area elements and a total active aperture of 6 mm. The transducer array produced pulses with a centre frequency of 20 MHz and 50% bandwidth. The resulting images had a lateral resolution of 172.5 μm at 10 mm and an axial resolution of 180 μm. A new fabrication method was developed that makes it easier to build the array. The receive beamformer was based on a commercial 8-channel analog-to-digital converter. The digital signals were transferred to a laptop where the beamforming was performed in software. This avoided the need to develop custom hardware and allowed it to be reconfigured for different transducers by simply modifying the software. The beamformer used a new interpolation method that reduced the required sampling frequency while maintaining a satisfactory radiation pattern. The system produces images at 10 frames/sec. / Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2011-05-06 13:15:34.495

Thesis (Ed.D.)--University of Tulsa, 1973. / Bibliography: leaves 34-35.

Thesis (PH.D.) -- Syracuse University, 2004. / "Publication number AAT 3132724."

<p> X-ray computed tomography (CT)&mdash;more commonly known as CAT scan&mdash;has recently evolved from the world of medical imaging and nondestructive evaluation to the field of dimensional metrology; the CT technique can now be used to measure a specimen&rsquo;s geometrical dimensions (of both internal and external features). As a result, CT presently contributes to the areas of dimensional inspection and geometric analysis for technology companies that produce manufactured parts for a variety of industries such as automotive, aerospace, medical devices, electronics, metalworking, injection molding plastics, composite materials, ceramics, and 3D printing or additive manufacturing. While dimensional accuracy is not crucial for medical diagnoses or other qualitative analyses, accurate dimensional quantification is the essence of X-ray CT metrology. Despite increasing advances in this technology, the current state of the art of CT metrology still confronts challenges when trying to estimate measurement uncertainties, mainly due to the plethora of influencing factors contributing to the CT measurement process. Gradual progress has occurred over the last decade toward a better understanding of some of these influencing factors that were illuminated by a series of collaborative research initiatives between a collective of several universities and institutions (predominantly located in the European Union) committed to the advancement and development of industrial CT scanning as a measuring technology. In an effort to further understand phenomenologically the role of variables affecting the precision and accuracy of CT dimensional measurements, this dissertation presents a series of experimental studies that evaluate the performance of cone-beam CT measurements, and their uncertainty estimates, in comparison with reference measurements generally obtained from tactile coordinate measurement machines (CMMs). In some cases, the results are contrasted against simulations performed in Matlab software (to compute fan-beam projection data) and an additional simulation tool called &ldquo;Dreamcaster&rdquo; (for ray casting and Radon-space analysis). The main CT variables investigated were: temperature in the X-ray CT enclosure, number of projections for a CT scan, workpiece tilt orientation, sample magnification, material thickness influences, software post-filtration, threshold determination, and measurement strategies. For dimensions of geometric features ranging from 0.5 mm to 65 mm, a comparison between dimensional CT and CMM measurements, performed at optimized conditions, typically resulted in differences of approximately 5 &micro;m or less for data associated with dimensional lengths (length, width, height, and diameters) and around 5 to 50 &micro;m for data associated with measurements of form, while expanded uncertainties computed for the CT measurements ranged from 1 to over 50 &micro;m. Methods for estimating measurement uncertainty of CT scanning are also assessed in this work. Special attention is paid to the current state of measurement comparisons (in the field of dimensional X-ray CT) by presenting a comprehensive study of metrics used for proficiency testing, including rigorous tests of statistical consistency (null-hypothesis testing) performed with Monte Carlo simulation, and particularly applied to results from two recent CT interlaboratory comparisons. This latter study contributes to the knowledge of methods for performance assessment in measurement comparisons. In particular, it is shown that the use of the En-metric in the current state of CT interlaboratory comparisons could be difficult to interpret when used to evaluate performance and/or statistical consistency of CT measurement sets.</p><p>

<p> From investigating movement in an insect to deciphering cognition in a human brain to treating Parkinson's disease, hearing loss, or even blindness, electronic implants are an essential tool for understanding the brain and treating neural diseases. Currently, the stimulating and recording resolution of these implants remains low. For instance, they can record all the neuron activity associated with movement in an insect, but are quite far from recording, at an individual neuron resolution, the large volumes of brain tissue associated with cognition. Likewise, there is remarkable success in the cochlear implant restoring hearing due to the relatively simple anatomy of the auditory nerves, but are failing to restore vision to the blind due to poor signal fidelity and transmission in stimulating the more complex anatomy of the visual nerves. The critically important research needed to improve the resolution of these implants is to optimize the neuron-electrode interface. This thesis explores geometrical and material modifications to both stimulating and recording electrodes which can improve the neuron-electrode interface. First, we introduce a fractal electrode geometry which radically improves the restored visual acuity achieved by retinal implants and leads to safe, long-term operation of the implant. Next, we demonstrate excellent neuron survival and neurite outgrowth on carbon nanotube electrodes, thus providing a safe biomaterial which forms a strong connection between the electrode and neurons. Additional preliminary evidence suggests carbon nanotubes patterned into a fractal geometry will provide further benefits in improving the electrode-neuron interface. Finally, we propose a novel implant based off field effect transistor technology which utilizes an interconnecting fractal network of semiconducting carbon nanotubes to record from thousands of neurons simutaneously at an individual neuron resolution. Taken together, these improvements have the potential to radically improve our understanding of the brain and our ability to restore function to patients of neural diseases.</p><p>

<p> The work of this thesis is devoted to examining the impact of silicon dioxide (silica or SiO₂) planarization on the optical properties and laser damage resistance of thin-film coatings. SiO₂ planarization is a process to smooth out fluence limiting nodular defects within multilayer coatings for high-energy laser applications. Mitigating these defects will improve the power handling abilities and improve the lifetime of laser coatings. </p><p> Presented here is a combination of work with the aim of evaluating the optical and laser damage properties of SiO₂ planarization within single layers, bilayers, and multilayers. As compared to control (non-planarized) samples, a 2&ndash;3x increase in the thin-film absorption, which decreases with post-process annealing, was discovered for SiO₂ planarized samples. This suggests that planarization creates oxygen-related defects which can be annealed out and little impurity implantation. Investigations of laser damage resistance were carried out at &lambda; = 1030nm and pulse durations of &tau; = 220ps and 9ps. The laser damage of single and bilayer coatings is known to be dependent on the substrate-coating interface and this is further evidenced within this thesis. This is because the effects of planarization are masked by the extrinsic laser damage processes within the single and bilayers. Slight change (&lt; 15%) in the laser induced damage threshold (LIDT) at 220ps and 9ps was observed for planarized single and bilayers. Depending on coating design, post-process annealing was shown to increase the LIDT by ~10% to ~75% at 220ps and ~10% to ~45% at 9ps. Although the fused silica substrate surface LIDT was shown to follow the &radic;&tau; pulse scaling law for pulses above ~10ps, the single and bilayer coatings do not follow this pulse scaling. The divergence from the &radic;&tau; pulse scaling on the coatings suggests a variation in the laser damage initiation mechanisms between 220ps and 9ps. </p><p> Multilayer high-reflecting (HR) mirrors with varying planarization design were also damage tested. A 6&ndash;7 J/cm² LIDT, with 220ps, was observed for HR coatings with SiO₂ planarization layers within high electric-field areas within the coating. However, SiO₂ planarization at the substrate-coating interface, where the electric-field is minimal, and control (non-planarized) was shown to have a LIDT of 63 &plusmn; 1.2 J/cm² and 21.5 &plusmn; 0.5 J/cm² for 220ps, respectively. At 9ps, the LIDT varied less than 90% difference between the various planarization designs. The substrate-coating planarization multilayer and control coating had an equal LIDT of 9.6 &plusmn; .3 J/cm² at 9ps.</p><p>

<p> Efficient thermal management is becoming a critical issue for development of the next generation of electronics. As the size of electronic devices shrinks, the dissipated power density increases, demanding a better heat removal. The discovery of graphene&rsquo;s unique electrical and thermal properties stimulated interest of electronic industry to development of graphene based technologies. In this dissertation, I report the results of my investigation of thermal properties of graphene derivatives and their applications in thermal management. The dissertation consists of three parts. In the first part, I investigated thermal conductivity of graphene laminate films deposited on thermally insulating polyethylene terephthalate substrates. Graphene laminate is made of chemically derived graphene and few layer graphene flakes packed in overlapping structure. Two types of graphene laminate were studied: as deposited and compressed. The thermal conductivity of the laminate was found to be in the range from 40 <i>W/mK</i> to 90 <i>W/mK</i> at room temperature. It was established that the average size and the alignment of graphene flakes are parameters dominating the heat conduction. In the second part of this dissertation, I investigated thermal conductivity of chemically reduced freestanding graphene oxide films. It was found that the in-plane thermal conductivity of graphene oxide can be increased significantly using chemical reduction and temperature treatment. Finally, I studied the effect of defects on thermal conductivity of suspended graphene. The knowledge of the thermal conductivity dependence on the concentration of defects can shed light on the strength of the phonon - point defect scattering in two-dimensional materials. The defects were introduced to graphene in a controllable way using the low-energy electron beam irradiation. It was determined that as the defect density increases the thermal conductivity decreases down to about 400 <i> W/mK</i>, and then reveal saturation type behavior. The thermal conductivity dependence on the defect density was analyzed using the Boltzmann transport equation and molecular dynamics simulations. The obtained results are important for understanding phonon transport in two-dimensional systems and for practical applications of graphene in thermal management.</p><p>