Bulletin of the American Physical Society
2008 Joint Fall Meeting of the Texas and Four Corners Sections of APS, AAPT, and Zones 13 and 16 of SPS, and the Societies of Hispanic & Black Physicists
Volume 53, Number 11
Friday–Saturday, October 17–18, 2008; El Paso, Texas
Session C2: Applied and Industrial Physics |
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Chair: Heather Galloway, Texas State University - San Marcos Room: Union East, 3rd Floor Ray |
Friday, October 17, 2008 1:30PM - 1:42PM |
C2.00001: Use of Exotic Coordinate Systems in the Design of RF Resonators for High-Field MRI Edward Butterworth High field human MRI (11.7 Tesla is FDC approved for human research) renders standard RF coil design inadequate because the resonant wavelength in human soft tissue (about 8 cm at 500 MHz) is significantly smaller than the physical size of the human body. I propose optimizing the design of such RF coils using coordinate systems appropriate to human body parts, as has been done with elliptical\footnote{Crozier et al, \textit{Concepts Magn Reson} 1997; \textbf{9}:195-210.} and Cassinian oval\footnote{De Zanche et al, \textit{Magn Reson Med} 2005; \textbf{53}:201-211.} cross sections. I have computed analytically the magnetic fields produced by a device of toroidal cross section using a cascade of conformal transformations.\footnote{Butterworth {\&} Gore, J Magn Reson 2005; 175:114-123.} Building upon these efforts, I will use the eleven coordinate systems of Moon {\&} Spencer,\footnote{Moon {\&} Spencer, Field\textit{ Theory Handbook,} Berlin: Springer-Verlag; 1971.} along with other possible coordinate systems and conformal transformations, to identify a small number of configurations that have the highest probability of being useful as RF coil designs for ultrahigh-field MRI. [Preview Abstract] |
Friday, October 17, 2008 1:42PM - 1:54PM |
C2.00002: Process Developments for the Improvement of Critical Current Density in Bi 2212 Multifilament Round Wire Kyle Damborsky, Nathaniel Pogue, Chris English, Al McInturff, Peter McIntyre Fabricating high critical current density Bi 2212 multifilament round wire is a primary concern for high field magnet technology. Bi 2212 round wire is of particular interest in the development of future accelerator magnet technology and NMR devices. Currently, wire performance is hindered by filament porosity and a lack of texturing within the superconducting cores. The development of precursor powder refinement techniques, metallurgical processes, and novel filament construction show promise in reducing filament porosity and improving texturing of superconducting cores resulting in higher critical currents. [Preview Abstract] |
Friday, October 17, 2008 1:54PM - 2:06PM |
C2.00003: Investigation of LaOx Removal for Application in CMOS Devices Kelly Rader Following Moore's Law, transistor devices continue to scale down and the use of silicon dioxide as the insulating oxide layer is no longer feasible due to gate leakage. Investigation into new ``high-k materials'' has become necessary. Research on LaOx will be presented with potential application in CMOS technology. Specifically, experimental results about LaOx wet etch development, a key step in CMOS processing, will be presented. [Preview Abstract] |
Friday, October 17, 2008 2:06PM - 2:18PM |
C2.00004: Microwave-assisted Magnetization Reversal Dynamics Zihui Wang, Mingzhong Wu Microwave-assisted magnetization reversal (MAMR) was proposed as one promising approach for the realization of fast low-field switching in high-anisotropy perpendicular media. Previous work on MAMR was done with static or quasi-static reversal fields and, therefore, provided no direct information on the magnetization reversal dynamics. This simulation work utilized the standard Gilbert equation to explore the actual MAMR dynamics in perpendicular-anisotropy magnetic thin film elements. The reversal time and reversal field threshold were calculated, and various approaches to reduce them were also examined. It is found that both the reversal time and field can be significantly reduced with increasing the amplitude of microwave fields and/or reducing the damping constant of the film materials. It is also found that one can significantly reduce the reversal field by the use of frequency-chirped microwaves. [Preview Abstract] |
Friday, October 17, 2008 2:18PM - 2:30PM |
C2.00005: Effects of non-uniformities on thin-film solar module performance Galymzhan Koishiyev A mathematically rigorous circuit model to numerically simulate a thin-film solar module has been developed. General results were obtained for a uniform baseline module. In particular analytic relations between physical and model parameters were obtained. The model was then used to study effects of non-uniformities such as shunts, weak diodes and shading. It was also used to predict and fit experimental data for shading non-uniformities, and qualitative results were obtained for selected types of shading. [Preview Abstract] |
Friday, October 17, 2008 2:30PM - 2:42PM |
C2.00006: Characterization and Design of Two-Axis Bi-Directional Microstages James Matthews, Tim Dallas, Ganapathy Sivakumar Micro Electro Mechanical Systems (MEMS) are critical components of many cutting edge technologies. We are developing novel microstages for positioning and scanning applications. The microdevices are fabricated using Sandia National Laboratory's SUMMiT V MEMS foundry process. We present the tested performance of a two-axis, bi-directional stage system that is actuated using electrostatic forces. The stage has a maximum travel of $\sim$40 microns in both axes and is capable of simultaneous actuation in both X and Y directions. Other characterizations focus on stiction and friction forces within the device and operating the device at high frequencies. Based on the results of these tests, we have made some major design changes to increase the maximum travel of the stages. A new design for a long distance travel stage is also presented. This design provides two-axis, bi-directional motion with a maximum displacement of $\sim$1000 microns in both axes. Other design changes are also presented which will improve the overall functionality of the device. [Preview Abstract] |
Friday, October 17, 2008 2:42PM - 2:54PM |
C2.00007: Design and Simulation of an Electrothermal Actuator Based Rotational Drive Sterling Beeson, Tim Dallas As a participant in the Micro and Nano Device Engineering (MANDE) Research Experience for Undergraduates program at Texas Tech University, I learned how MEMS devices operate and the limits of their operation. Using specialized AutoCAD-based design software and the ANSYS simulation program, I learned the MEMS fabrication process used at Sandia National Labs, the design limitations of this process, the abilities and drawbacks of micro devices, and finally, I redesigned a MEMS device called the Chevron Torsional Ratcheting Actuator (CTRA). Motion is achieved through electrothermal actuation. The chevron (bent-beam) actuators cause a ratcheting motion on top of a hub-less gear so that as voltage is applied the CTRA spins. The voltage applied needs to be pulsed and the frequency of the pulses determine the angular frequency of the device. The main objective was to design electromechanical structures capable of transforming the electrical signals into mechanical motion without overheating. The design was optimized using finite element analysis in ANSYS allowing multi-physics simulations of our model system. [Preview Abstract] |
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