Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 119-124).

Thesis (Ph. D.) in Physics--University of Maine, 2000. / Includes vita. Includes bibliographical references (leaves 149-153).

No description available.

The phenomenon of spiral wave propagation in Belousov-Zhabotinsky media is a remarkable example of self-organisation. This distinctive waveform arises in a variety of excitable systems. The primary objective of the work described in this thesis is the construction and analysis of deterministic reaction-diffusion models in terms of partial differential equations, to explain the local and global geometry of the spiral pattern. The secondary objective is to design experiments that enable observation and recording of evolving chemical waves in three dimensional Belousov-Zhabotinsky media. A mathematical formulation of the one dimensional A-w system based on a hierarchy of trial phase functions is introduced. A Schr8dinger type boundary value problem in an eigen sub-domain is established; an algebraic formula for the wave number spectrum and an analytical representation for the concentration amplitude are derived. This formulation suggests a piece-wise linear approach to X-w systems in higher dimensions. The concentrations are expressible in terms of real combinations of solutions to the Helmholtz equation with complex wave number and the solutions are matched by using continuity, differentiability and threshold conditions. A detailed analysis of the existence of solutions to piece-wise linear A-w systems in two dimensions is presented; existence is demonstrated by solving the matching equations. A stability analysis completes the discussion. Plots of the concentration contours characterised by the matching parameters are included. These contours simulate the cross-section of the scroll wave observed in experiments carried out in three dimensional media. The experimental design allows direct observation of undistorted three dimensional chemical waves in situ. The kinematics, dynamics and transformations of a variety of three dimensional scroll-based structures are recorded. The dominant waveforms are simple scroll waves. In addition, transient but significant events such as fission of a complex structure are recorded.

Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / The present stuqy is an investigation of the effects of two parameters of the spiral aftereffect. Clinical psychologists have been interested in aftereffect research because of the possibility of utilizing the phenomenon as a diagnostic tool for brain damage. The parameters which were studied are frequoocy of stmulation (FS) and boundary velocity (BV). Frequency of stimulation is the frequency with which a given retinal element is stimulated by a contour (boundary) of the moving stimulus. The frequency of stimulation for the spiral is defined as the product of number of spiral arms and rotational velocity. In this study, variations in frequenqy of stimulation were effected by varying the number of spiral arms. Boundary velocity is the velocity with which a given contour (boundary) passes across a retinal element. In the spiral, boundary velocity corresponds to the rate of expansion or contraction, and it is proportional to: [(Rotational Velocity) x (Visual Angle Subtended by Spiral)]/(Number of Spiral Turns) Variations in boundary velocity were effected by simultaneously varying number of spiral arms and rotational velocity in such a way that frequency of stimulation remained constant and boundary velocity varied. In this study, a population of responses was sampled from two male subjects, each of Whom viewed five Archimedes spirals rotated at four rotational velocities. The spirals were drawn with one, two, four, eight, and sixteen arms, and were rotated at 40 rpm, 80 rpm, 160 rpn, and (all except the sixteen arm spiral) at 320 rpm. Each spiral-speed combination was repeated three times each day for eight days, resulting in a total of 24 replications for each spiral-speed combination. The dependent variable was the aftereffect, as measured by extent and duration. [TRUNCATED] / 2031-01-01

Presented in this work is a novel design technique for a low-phase-noise high-frequency CMOS voltage-controlled oscillator. Phase noise is generated from electrical noise near DC, the oscillation frequency, and its harmonics. In CMOS technology, low-frequency flicker noise dominates the close-in phase noise of the VCO. The proposed technique minimizes the VCO phase noise by seeking to eliminate the effect of flicker noise on the phase noise. This is accomplished by canceling out the DC component of the impulse sensitivity function (ISF) corresponding to each flicker-noise source, thus preventing the up-conversion of low-frequency noise into phase noise. The proposed circuit topology is a modified version of the complementary cross-coupled transconductance VCO, where additional feedback paths are introduced such that a designer can choose the feedback ratios, transistor sizes, and bias voltages to achieve the previously mentioned design objectives. A step-by-step design algorithm is presented along with a MATLAB script to aid in the computation of the ISFs and the phase noise of the VCO. Using this algorithm, a 5-GHz VCO was designed and fabricated in a 0.18μm CMOS process, and then tested for comparison with simulated results.

Erlangen, Nürnberg, Universiẗat, Diss., 2006. / Enth. 1 Sonderabdr. aus: European radiology ; 14. 2004. - Beitr. teilw. dt., teilw. engl.

Ulm, Univ., Diss., 2007.

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Scott, Waymond; Committee Member: Eslinger, Owen; Committee Member: Ingram, Mary; Committee Member: Peterson, Andrew; Committee Member: Smith, Glenn. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2002. / Includes bibliographical references. Also available on microfiche.