J. Granlund. / "January 20, 1949." / Bibliography: p. 79. / Army Signal Corps Contract No. W36-039-sc-32037 Project No. 102B. Dept. of the Army Project No. 3-99-10-022.

T.P. Cheatham, Jr. and W.G. Tuller. / "January 20, 1947." / Includes bibliographical references.

This Ph.D. thesis focuses on the high-frequency electrical capabilities of the carbon-nanotube, field-effect transistor (CNFET). The thesis can be categorized into three stages, leading up to an assessment of the RF capabilities of realistic array-based CNFETs. In the first stage, the high-frequency and time-dependent behavior of ballistic CNFETs is examined by numerically solving the time-dependent Boltzmann transport equation (BTE) self-consistently with the Poisson equation. The RF admittance matrix, which contains the transistor’s y-parameters, is extracted. At frequencies below the transistor’s unity-current-gain frequency fT, the y-parameters are shown to agree with those predicted from a quasi-static equivalent circuit, provided that the partitioning factor for the device charge is properly extracted. It is also shown that a resonance behavior exists in the transistor’s y-parameters. In the second stage, non-quasi-static effects in ballistic CNFETs are examined by analytically developing a transmission-line model from the BTE and Poisson equation. This model includes nonclassical transistor elements, such as the "quantum capacitance" and "kinetic inductance," and it is shown to represent the intrinsic (contact-independent) transistor’s behavior at high frequencies, including a correct prediction of the resonances in the y-parameters. Moreover, it is shown that the kinetic inductance can be represented using lumped elements in the transistor’s small-signal equivalent circuit, and it is demonstrated that the resulting circuit is capable of modeling intrinsic CNFET behavior to frequencies beyond fT. In the last stage, by building upon the first two stages, a comprehensive study is performed to assess the RF performance potential of array-based CNFETs. First, phonon scattering is incorporated into the time-dependent BTE to study the impacts of collisions on different aspects of intrinsic CNFET operation, including the intrinsic fT and the small-signal equivalent circuit. These results are then further extended by adding the effects of extrinsic (contact-dependent) parasitics and then examining the behavior of key RF figures of merit, such as the extrinsic fT, the attainable power gain, and the unity-power-gain frequency. The results are compared to those of state-of-the-art high-frequency transistors and to the next generation of RF CMOS, and they provide an indication of the potential advantages of array-based CNFETs for RF applications. / Micro-Electro-Mechanical Systems (MEMS) and Nanosystems

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 158-164).

Thesis (M.S.)--Brigham Young University. Dept. of Electrical and Computer Engineering, 2006. / Includes bibliographical references (p. 225-229).

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 134-141).

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Nearly one third of the 604,426 bridges in the United-States are either structurally deficient or functionally obsolete. Monitoring these bridges is essential to avoid catastrophic accidents. In steel bridges fatigue induced crack/rupture, which is one of the most common modes of failure, can be avoided if the crack is detected at the early stages of its formation. Cracks usually originate at stress concentration areas but their precise origin is random. Such strain concentration can be monitored with traditional strain gages, but their installation requires lengthy wires and equipment, which are expensive and labor intensive. Therefore wireless sensors are being developed to cope with these problems. In this work, a passive wireless strain sensor based on RFID technology is described. The sensor is a patch antenna that resonates at a certain frequency, which shifts in presence of strain. The relation between the resonance frequency and the strain is approximately linear. The slope of the relation is called sensitivity. The behavior of the sensor's sensitivity is studied using experimental work and simulations that couple electromagnetism and mechanics. The sensitivity measured in experiments and in simulations in presence of uniform strain is different. This difference is lower for the sensitivity in presence of a crack, probably due to a parameter variation that is currently not accurately modeled in the simulations.

Biological tissues are generally conductive and knowing the current distribution in these tissues is of great importance in many biomedical applications. Radio frequency current density imaging (RF-CDI) is a technology that measures current density distributions at the Larmor frequency utilizing magnetic resonance imaging (MRI). RF-CDI computes the applied current density, J, from the non-invasively measured magnetic field, H, produced by J. The previously implemented RF-CDI techniques could only image a single slice at a time. The previous method for RF current density reconstruction only computed one component of J. Moreover, this reconstruction required an assumption about H, which may be easily violated. These technical constraints have limited the potential biomedical applications of RF-CDI. In this thesis, we address the limitations of RF-CDI mentioned above. First, we implement a multi-slice RF-CDI sequence with a clinical MRI system and characterize its sensitivity to MRI random noise. Second, we present a novel method to fully reconstruct all three components of J without relying on any assumption of H. The central idea of our approach is to rotate the sample by 180 degrees in the horizontal plane to collect adequate MR data from two opposite sample orientations to compute one component of J. Furthermore, this approach can be extended to reconstruct the other two components of J by adding one additional sample orientation in the horizontal plane. This method has been verified by simulations and electrolytic phantom experiments. We have therefore demonstrated for the first time the feasibility of imaging the magnitude and phase of all components of the RF current density vector. The work presented in this thesis is expected to significantly enhance RF-CDI to image biological subjects. The current density vector J or any component of J can be measured over multiple slices without the compromise of motions of organs and tissues caused by gravitational force, thanks to the method of horizontal rotations. In addition, the reconstruction of the complex conductivity of biological tissues becomes possible due to the current advance in RF-CDI presented here.

Radio frequency identification (RFID) is a technology used in many applications for the identification of objects. This thesis presents a concept of how libraries could use RFID technology to locate physical items within the library. The ability to locate items within the library changes the way users interact with physical material, creates new ways of user collaboration, and influences the ability to browse the shelves for physical items. Several implementation scenarios are presented in detail and implications on collaboration and browsing are analyzed.