No description available.

Thesis (M.S.)--University of Wisconsin--Madison, 1960. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 30).

Thesis (M.S.)--University of Missouri-Columbia, 2005. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (month day, year) Includes bibliographical references.

The primary purpose of this thesis is to determine experimentally if the attenuation of small -amplitude elastic waves in metals is governed principally by a linear mechanism (i.e. one for which the principle of superposition is valid). The secondary purpose is to interpret the attenuation measurements in terms of existing theories on acoustic dissipation in solids. Attenuation measurements of the Fourier components of a Rayleigh pulse were compared with those of sinusoidal Rayleigh waves of the same frequency. One copper, one aluminum and two α-brass circular cylindrical shells were used, and Rayleigh waves propagating along the truncated edges of these tubes were studied. Rayleigh pulses were detected at strain levels of approximately four and forty microstrain in order to test for any amplitude-dependent effects accompanying the attenuation. The sinusoidal Rayleigh waves were detected at strain amplitudes between three and ten microstrain. For three out of the four tubes the results indicated that the dominant attenuation mechanism is a linear process in the frequency range from 100 to 500 kc/s and in the strain region from four to forty microstrain. For the copper tube, however, the scatter in the results is such that no definite conclusion could be drawn. For all four tubes the internal friction, 1/Q, increases with frequency. For some of them there is evidence of a relaxation peak, probably as a result of the Zener effect, superimposed on the general trend. Dislocation damping, as proposed by Koehler (1952) and later generalized by Granato and Lucke (1956), is suggested as a dissipative mechanism which could account for this general trend. Most of the internal friction values are found to be between 20 X 10¯⁵ and 100 X 10¯⁵. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The development of pulsed type radar signals is examined, with a brief review of matched filtering. Gated RF, linear and non-linear FM pulse-compression (chirp) and matched filtering of radar signals is reviewed in depth. Emphasis is given to identifying the desirable characteristics of each method. A new method of non-linear FM pulse-compression is introduced; it utilizes the Eigen Function (a form of the raised-cosine family) of functions) as its modulating term. Its properties are then compared to those of the linear and non-linear systems reviewed in the preceding sections. Design considerations for implementation on a surface acoustic wave device are presented.

Railguns have great potential in military roles; however, they currently lack a fieldable power supply. Recent advances in the state of low voltage power storage devices may enable practical Pulse Forming Inductive Network power supplies to be developed if a suitable current interruption device is developed. A solid-state device in a counterpulsed opening switch configuration is a possible solution. A demonstration counterpulsed solid-state opening switch was constructed and successfully tested. This circuit consisted of Silicon Controlled Rectifier components, which can nominally only turn on current. The counterpulsed configuration allowed them to function as opening switches and to do so at much higher current relative to their specifications. We demonstrated current interruption at up to 1 kA of peak current. This demonstration system validates the counterpulsing concept and prepares for the construction of a modular, 250 kJ system.

Thesis (M.S. in Physics)--Naval Postgraduate School, June 2005. / Thesis Advisor(s): William B. Maier II, Richard Harkins. Includes bibliographical references (p. 29). Also available online.

The use of quasi-optical techniques for signal processing at millimetre wave frequencies and their application to spread spectrum systems is presented in this thesis. Millimetre waves offer a number of advantages when compared to microwave and optical signals and as a result they are finding an increasing number of applications in the area of communications. Traditionally, millimetre wave research has been centred on scientific and experimental interests. In recent years, however, practical communications systems have been emerging at these frequencies. New technologies are being developed which aim to exploit the potential advantages of millimetric signals and the work undertaken here relates to one particular avenue - that of quasi-optics. This thesis introduces measurement methods for assessing millimetric components and quasi-optical systems, followed by an appraisal of Gunn oscillators and their associated power supplies as suitable signal sources for communications. A type of Gunn oscillator displaying semi-chaotic behaviour is described which may have potential as an inherently broadband source suitable for spread spectrum applications. The application of quasi-optical signal processing methods to a prototype spread spectrum millimetre wave system is presented. The system has been shown to operate satisfactorily in a number of demonstrations. Theoretical models of the quasi-optical circuit show good agreement with experiment and an analysis of the signal-to-noise behaviour predicts the potential receiver performance. Some ideas for future work, building on that presented here, are suggested.

This thesis is concerned with the development of Transmission Line Transfomer (TLT) pulsed power supplies and the generation of fast risetime (>50ns), good quality, high repetition-rate voltage pulses for flash x-ray preionisors and other applications. It explains the principle of the TLT and reports on two TLT pulsed power supplies that have been built. The first, or prototype, produced output voltage pulses with risetimes of 50ns and durations of 200ns and was used to power a flash x-ray preionisation source for a mercury bromide laser. The second, a 50kV, 100? device, was built as part of a wider research program concerned with the development of space based pulsed power supplies. The development of ceramic tile technology is also described and the relevant electrical, mechanical and thermal properties of some barium titanate tiles given; it is then shown how ceramic tiles can be used to construct compact pulse generators for TLT systems. Finally, the subject of nonlinear dielectric pulse sharpening is introduced and pulse sharpening in a delay line ladder network containing air-core inductors and non-linear capacitors is demonstrated. It is then explained how these lines can be used to improve the output risetime of a TLT.

No description available.