Thesis (Ph. D.)--University of Wisconsin--Madison, 1962. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: leaves 61-63.

Present day optical integrated circuits contain many continuously bending waveguides making it important to study EM field profiles of bending waveguides. The mostly widely used numerical method for analyzing bending waveguides is the beam propagation method (BPM). Although it can calculate very fast, BPM results are not accurate enough in many wide-angle applications due to BPM¡¦s intrinsic paraxial approximation. Recently, full-wave based finite-difference time-domain technique has become quite popular and has been used to study many optical devices. Unfortunately it can not be used to study smoothly bending waveguides due to huge computational resource requirements needed for these large optical devices. In the absence of reflection in a bending waveguide, other one way, wide-angle methods can be applied. In this thesis we propose two such methods to analyze different kinds of bending waveguides. We use full eigen-mode expansion technique (FEMET) when reflection is negligible. In cases where reflection is strong, we propose a cylindrical couple transverse-mode integral-equation (C-CTMIE) to do the job. Both FEMET and CTMIE methods are built on complete sets of circular layered modes of the underlying structure. These modes are not easy to solve because the standard cylindrical mode solver requires extensive references to Bessel functions of complex arguments and orders. Here in this thesis, we proposed to expand cylindrical layered modes from planar layered modes of an equivalent structure. In essence, we renormalize the existing planar layered waveguide modes and turn them into desired circular layered modes. We show that using a matrix eigenvector formulation, this relatively simple technique is not only quite fast but also produces very accurate results. Finally using these circular modes various S-bend waveguides are analyzed. We also present a design to minimize the radiation loss of a circular waveguide using whisper gallery modes.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1955. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Cylindrical shells are used for a variety of engineering applications such as undersea vehicles and aircraft. The models currently used to determine the vibration characteristics of these shells are often approximated by assuming the shell is infinitely long or has shear-diaphragm boundary conditions. These models also ignore complex loading conditions such as plane waves in favor of point forces or free vibration models. This work expands on the capabilities of these models by examining the acoustic response of a finite length cylinder with flat plate endcaps to multiple types of distributed loading conditions. Starting with the Donnell equations of motion for thin cylinders and the classical plate theory equations of motion for the endcaps, spacial domain displacement field solutions for the shell and plates take an assumed form that includes unknown wave propagation coefficients. These solutions are substituted into stress boundary conditions and continuity equations evaluated at the intersections between the shell and plates. An infinite summation is contained within the boundary conditions and continuity equations which is decoupled, truncated, and compiled in matrix form to allow for the propagation coefficients to be found via a convergent sum of vectors. System responses due to a ring loading and multiple cases of plane waves are studied and validated using a finite element analysis of the system. It is shown that the analytical model matches the finite element model well. / Master of Science

The thesis investigates the feasibility of utilising the tensile strength of glass-fibres in the reinforcement of concrete components. It tackles the initial problem of securing adequate bond and ensuring true composite action between the concrete and the glass fibres. Some of the fundamental characteristics of the reinforcement and of concrete members reinforced with it are established.

Cylindrical algebraic decomposition is a powerful algorithmic technique in semi-algebraic geometry. Nevertheless, there is a disparity between what algorithms output and what the abstract definition of a cylindrical algebraic decomposition allows. Some work has been done in trying to understand what the ideal class of cylindrical algebraic decom- positions should be — especially from a topological point of view. We prove a special case of a conjecture proposed by Lazard in [22]; the conjecture relates a special class of cylindrical algebraic decompositions to regular cell complexes. Moreover, we study the properties that define this special class of cell decompositions, as well as their implications for the actual topology of the cells that make up the cell decompositions.

Thermal contact conductance is highly important in a wide variety of applications, from the cooling of electronic chips to the thermal management of spacecraft. The demand for increased efficiency means that components need to withstand higher temperatures and heat transfer rates. Many situations call for contact heat transfer through nominally cylindrical interfaces, yet relatively few studies of contact conductance through cylindrical interfaces have been undertaken. This study presents a review of the experimental and theoretical investigations of the heat transfer characteristics of composite cylinders, presenting data available in open literature in comparison with relevant correlations. The present investigation presents a study of the thermal contact conductance of cylindrical interfaces. The experimental investigation of sixteen different material combinations offers an opportunity to develop predictive correlations of the contact conductance, in conjunction with an analysis of the interface pressure as a function of the thermal state of the individual cylindrical shells. Experimental results of the present study are compared with previously published conductance data and conductance models.

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In this work, nickel-gold multi-segmented magnetic nanowires were grown by electrodeposition in anodized alumina templates. The templates were fabricated by a two step anodization process of aluminum disks in an aqueous solution of oxalic acid. In this process, ordered pores grew in an alumina oxide layer at the exposed aluminum area. Each disk was electropolished before the anodization process and the features at its surface were characterized to assess the effect on the pore ordering. Nickel Watts and gold cyanide electrolyte baths were prepared to electrodeposit pure nickel and gold in the templates. Both solutions response to a range of externally applied voltages was characterized and a threshold voltage above which deposition occurs is reported. Single nanowires were isolated by chemically dissolving the template and dispersed in ethanol. Devices were fabricated with these isolated nanowires in which gold contacts were deposited to measure the resistance. A current pulse setup was implemented in a magnetoresistance system allowing to send current pulses with amplitude as low as 2nA and 50μs width. Magneto resistance measurement were carried out on the single nanowires devices and the effect of current pulses was studied. It was found that distinct resistance states can be achieved by applying a determined current pulse at a constant applied field and that the initial state can be recovered by removing excess charge from the nanowire. Finally, the effect of annealing the nanowires in an air atmosphere at 150°C for 24 hours is studied showing that the nickel sections oxidize and the gold sections remain unchanged.