A supersonic crowdion in mica: Ultradiscrete kinks with energy between 40^{40}K recoil and transmission sputtering

In this chapter we analyze in detail the behaviour and properties of the kinks found in an one dimensional model for the close packed rows of potassium ions in mica muscovite. The model includes realistic potentials obtained from the physics of the problem, ion bombardment experiments and molecular dynamics fitted to experiments. These kinks are supersonic and have an unique velocity and energy. They are ultradiscrete involving the translation of an interstitial ion, which is the reason they are called 'crowdions'. Their energy is below the most probable source of energy, the decay of the $^{40}$K isotope and above the energy needed to eject an atom from the mineral, a phenomenon that has been observed experimentallyComment: 28 pages, 15 figure

Discovery of Isotopes of the Transuranium Elements with 93 <= Z <= 98

One hundred and five isotopes of the transuranium elements neptunium, plutonium, americium, curium, berkelium and californium have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.Comment: To be published in Atomic Data and Nuclear Data Table

A novel approach to soft-switching power converters

Modern power converters operate using PWM (Pulse Width Modulation) and switching their semiconductor switches on and off at a very high rate to achieve a high efficiency. While the losses of the switches are very low in either the on or the off state, the transition times give rise to switching losses, which increase with increasing switching frequency. Soft-switching techniques aim to eliminate this by forcing a zero-voltage or a zero-current condition on the switch during a switching cycle such that the switching losses are eliminated. This is very important to improve the efficiency of power electronics in light of ever-increasing demands to conserve energy and to also allow the power electronics to be made smaller and more compact. While soft-switching has been successfully applied for simpler applications such as DC-DC converters, it has been difficult to apply to general-purpose inverters (such as to drive AC motors). The ARCP (Auxiliary Resonant Commutated Pole) is a topology that is one of the most promising approaches to soft-switching an inverter; however, it has some drawbacks. During the course of my research, I have devised two alternative topologies which aim to address the ARCP's limitations. In addition, I have developed several novel control schemes to more efficiently and reliably gate these ARCP inverters with a minimum of sensor feedback. I have developed my ARCP technology on Simulink models and on a 20kW experimental prototype. I have also implemented and tested some of the control scheme improvements on a 2MW ARCP machine at CEM (UT Center for Electromechanics), which is still the largest ARCP converter ever built. In the process I have also developed techniques to accurately measure the efficiency of high efficiency power converters.Electrical and Computer Engineerin

Development of an advanced electrical system for a solar powered racing vehicle with an emphasis on the battery protection and management system

textThis thesis describes the development of an electrical system for a solar powered racing vehicle with en emphasis on the Battery Protection System (BPS). This battery protection system was designed for the UTSVT’s (University of Texas Solar Vehicles Team) solar powered vehicle, the Samsung Solorean. The system is required due to the dangers of the lithium-ion cobalt battery chemistry. The system monitors the voltage, temperature, and current of each battery module in the 22 module battery pack and will physically isolate the pack from the rest of the vehicle with a high-current electromechanical contactor if any parameter is outside of the safe range. The system can be expanded to monitor any number of series battery cells. The system uses a master-slave microcontroller architecture with a single master microcontroller that interrogates several slave microcontroller boards for readings over a common serial bus. The system uses a new voltage sensing ASIC to monitor cell voltages, along with an analog current output device to measure temperature and a hall-effect device to measure current. The system was a complete success and has allowed the UT solar car to finish the American Solar Challenge cross-country “Rayce.”Electrical and Computer Engineerin

Iu Mien Tone Change in Real Time: A Restudy Of L-Thongkum (1988)

This study investigates tone changes in Iu Mien, a Hmong-Mien language with two complex contour tones: high rising-falling (T3) and low rising-falling (T4). L-Thongkum (1988) observed younger speakers producing rising variants of T3 and T4, which she attributed to Thai contact. This study replicates L-Thongkum’s study 34 years later to observe tone changes in real time and examine the potential role of peak delay, a phonetic bias resulting in a later f0 peak. 40 speakers (ages 12-84) produced T3 and T4 monosyllables in isolation and in a carrier phrase. f0 was modeled using Generalized Additive Mixed Modeling (GAMM). Results confirm incremental change toward rising variants of T3 and T4. Older speakers showed peak delay (with more of a rising contour) under conditions of shorter duration and preceding low tone. Critically, younger speakers produced peak-delayed, rising variants in all conditions, indicating generalization of the rising contour. While language contact may have initiated the changes, a phonetic bias toward peak delay generated the seeds of potential change. The change from rising-falling > rising aligns with apparent-time studies in other Asian languages, suggesting this may be a crosslinguistically unidirectional pathway

High Power Density and High Efficiency Converter Topologies for Electric Ships

Power electronic converters are expected to be significant contributors to system mass, system loss, and system cost in the all-electric ship, and are therefore a significant area of interest. This paper investigates the reduction of switching losses in high power (MW level) converters. These losses remain a major obstacle to the development of converters capable of operating at higher frequencies and higher power densities. The Auxiliary Resonant Commutated Pole (ARCP) soft-switching converter topology offers the potential for minimization of switching losses but has some inherent limitations. This paper examines two new converter designs based on the ARCP soft-switching topology that allow for more compact units by reducing the semiconductor switching losses generated within them. These concepts have been proven in principle by preliminary laboratory testing of a scaled 20 kW converter prototype. The new proposed topologies are described and simulation results and experimental waveforms obtained on the prototype unit are also reported.Center for Electromechanic