New Releases by Christopher Timothy

This note is part of Quality testing.

We use a four dimensional symplectic mapping, the coupled cubic-quadratic map, to provide evidence of Arnol’d Diffusion in phase space. We use the method of frequency analysis for dynamical systems to demonstrate the existence of regular orbits, and show that these orbits enclose weakly chaotic orbits which escape in finite time around the tori. A new collocation method for frequency analysis is employed by adapting it to allow for higher precision results. Arbitrary precision numerics are used to obtain highly accurate orbits for long timescales, and the adapted frequency method is used to obtain highly accurate frequencies of the mapping. We review the method of frequency analysis, demonstrate its effectiveness and accuracy in determining frequencies and finding tori in simple systems and low-dimensional mappings, and extend the results to higher dimensions. In the four dimensional mapping, we find several regular orbits with irrational frequency ratios, indicating the existence of tori in the phase space, as well as interior orbits that escape around these tori.

As the electric power grid incorporates an increasing number of renewable energy sources and large, variable loads, better electricity monitoring at increased resolution becomes essential. Simultaneously, the rise of wireless sensor nodes, a.k.a. "motes," has made larges-cale, low-power data collection increasingly-feasible. The existing technologies for AC current sensing, however, are less than optimally-suited for this sort of application; current transformers are large and bulky, and most proximity-based magnetic field sensors consume too much power for extended operation on batteries. In the work that follows, we will explore the modeling, design, prototyping, and testing of a new, novel type of proximity-based current sensor that is both small and ultra-low-power. By using a pair of interconnected piezoelectric cantilevers with permanent magnets mounted on their free ends, it is possible to sense AC current by proximity while simultaneously rejecting ambient mechanical vibrations. Starting from an analytic system-as-a-circuit model, a design strategy is implemented using dynamic range as a primary figure of merit to develop an aluminum nitride, MEMS-based candidate sensor. Primary production of this candidate design is completed by MEMSCAP Inc, and final assembly and integration of the designs is completed at UC Berkeley. Using the 11 mm-long MEMSCAP-produced aluminum nitride dies and two 750-micron magnets, a dual-cantilever current sensor with a sensitivity of 6.41 mV per gauss has been produced. Due to non-idealities in fabrication, this output voltage is less than originally modeled but still close to the design target of 7 mV per gauss . The vibration-cancellation technique functions as-intended for frequencies below 150 Hz or above 185 Hz. Proof of concept testing of this technique is demonstrated for 1-35 A of 60 Hz AC current with the sensor in proximity to a vibrating motor generating 50 mG of 120 Hz sinusoidal acceleration.

The narrative text was then analyzed from a critical perspective, considering it through the lens of culturally-relevant pedagogy (Ladson-Billings, 1995). The narrative shows how Project-Based Learning, when coupled with collective creation, can be used to enact a culturally-relevant pedagogy with at-risk youth.

There has been a precipitous growth in the number of black candidates nominated by major parties for Governor, US Senator, and the Presidency over the past twelve years. Unlike most of their predecessors who campaigned for elected offices at the local and congressional levels of government, this new group of high-level black candidates are campaigning in contexts where blacks make up a very small proportion of the electorate. Thus, this new cohort of high-level black candidates cannot only rely on black voters for success. To appeal to a broader array of voters, these high-level black candidates often minimize the role of race in their personal stories and primarily focus on issues that transcend racial stereotypes. This new style of campaigning may allow black candidates to appeal to white voters, but it may not empower blacks in the same way as the campaigns of black local and congressional elected officials who routinely made explicit racial appeals. As a result, this new cohort of black candidates may or may not advance black politics to the same degree as their predecessors. The growth in the number of African American US Senate and Gubernatorial candidates in recent years, Barack Obama''s success in the 2008 Presidential Election, and the deracialized campaign styles of these candidates raise several interesting questions that I address in this dissertation. First, what led to the dramatic increase in the number of African Americans campaigning for prominent statewide and national elected offices? Second, once nominated for these high level elected positions, what impact do these candidates have on the black and white electorate? Finally, what effect do these high profile black candidates have on black representation in lower levels of government? This work is significant because it expands our understanding of descriptive representation in several important ways. First, this research shows that black candidates who do not use racial appeals can still play an important role in black political empowerment. Second, this research demonstrates that prominent black politicians who do not hold elected office can also play a large role in altering black''s and white''s political attitudes and behaviors.

James Herriot illuminated the rich and rewarding day-to-day life of a small-town veterinarian, taking hundreds of thousands of listeners on a journey with him across the dales. He introduces a cast of truly unforgettable characters: humans, dogs, horses, lambs--even parakeets--all of them revealed with the same infinite fascination, affection and insight that made James Herriot one of the most beloved authors of our time. The stories are made all the more special by the world-renowned "voice" of Dr. Herriot-- Christopher Timothy, whose performance warmly and evocatively brings the stories to life. Now his first three classic works, digitally remastered on CD, are brought together in a beautiful gift set sharing with even more listeners the joy of James Herriot.

This dissertation introduces new technologies and techniques for low-cost phased arrays and scanning antennas. Special emphasis is placed on new approaches for low-cost millimeter-wave beam control. Several topics are covered. A novel reconfigurable grating antenna is presented for low-cost millimeter-wave beam steering. The versatility of the approach is proven by adapting the design to dual-beam and circular-polarized operation. In addition, a simple and accurate procedure is developed for analyzing these antennas. Designs are presented for low-cost microwave/millimeter-wave phased-array transceivers with extremely broad bandwidth. The target applications for these systems are mobile satellite communications and ultra-wideband radar. Monolithic PIN diodes are a useful technology, especially suited for building miniaturized control components in microwave and millimeter-wave phased arrays. This dissertation demonstrates a new strategy for extracting bias-dependent small-signal models for monolithic PIN diodes. The space solar-power satellite (SPS) is a visionary plan that involves beaming electrical power from outer space to the earth using a high-power microwave beam. Such a system must have retrodirective control so that the high-power beam always points on target. This dissertation presents a new phased-array architecture for the SPS system that could considerably reduce its overall cost and complexity. In short, this dissertation presents technologies and techniques that reduce the cost of beam steering at microwave and millimeter-wave frequencies. The results of this work should have a far-ranging impact on the future of wireless systems.

Thesis (M.Sc.)--University of Technology, Sydney, 2003.