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Electrical and Computer Engineering
Electrical and Computer Engineering Faculty Publications and Presentations
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Full-Text Articles in Engineering
Dynamic Phase-Control Of A Rising Sun Magnetron Using Modulated And Continuous Current, Sulmer Fernandez-Gutierrez, Jim Browning, Ming-Chieh Lin, David N. Smithe, Jack Watrous
Dynamic Phase-Control Of A Rising Sun Magnetron Using Modulated And Continuous Current, Sulmer Fernandez-Gutierrez, Jim Browning, Ming-Chieh Lin, David N. Smithe, Jack Watrous
Electrical and Computer Engineering Faculty Publications and Presentations
Phase-control of a magnetron is studied via simulation using a combination of a continuous current source and a modulated current source. The addressable, modulated current source is turned ON and OFF at the magnetron operating frequency in order to control the electron injection and the spoke phase. Prior simulation work using a 2D model of a Rising Sun magnetron showed that the use of 100% modulated current controlled the magnetron phase and allowed for dynamic phase control. In this work, the minimum fraction of modulated current source needed to achieve a phase control is studied. The current fractions (modulated versus …
Simulation Of A Rising Sun Magnetron Employing A Faceted Cathode With A Continuous Current Source, Sulmer Fernandez-Gutierrez, Jim Browning, Ming-Chieh Lin, David N. Smithe, Jack Watrous
Simulation Of A Rising Sun Magnetron Employing A Faceted Cathode With A Continuous Current Source, Sulmer Fernandez-Gutierrez, Jim Browning, Ming-Chieh Lin, David N. Smithe, Jack Watrous
Electrical and Computer Engineering Faculty Publications and Presentations
It has been proposed that gated field emitters could be used in place of conventional thermionic cathodes to control the current injection in a magnetron, both temporally and spatially. Since gated field emitters have to be fabricated on flat surfaces, a faceted cathode would be used to implement this approach. A 2D ten cavity, rising sun magnetron has been modeled using the particle-in-cell code VORPAL. Cylindrical, five-sided, and ten-sided faceted cathodes were modeled to study the variation of magnetron operation due to the cathode shape. This work shows the results of the device performance employing three different cathode geometries with …
Photographic Studies Of Laser-Induced Bubble Formation In Absorbing Liquids And On Submerged Targets: Implications For Drug Delivery With Microsecond Laser Pulses, Hanqun Shangguan, Lee W. Casperson, Dennis L. Paisley, Scott A. Prahl
Photographic Studies Of Laser-Induced Bubble Formation In Absorbing Liquids And On Submerged Targets: Implications For Drug Delivery With Microsecond Laser Pulses, Hanqun Shangguan, Lee W. Casperson, Dennis L. Paisley, Scott A. Prahl
Electrical and Computer Engineering Faculty Publications and Presentations
Pulsed laser ablation of blood clots in a fluid-filled blood vessel is accompanied by an explosive evaporation process. The resulting vapor bubble rapidly expands and collapses to disrupt the thrombus (blood clot). The hydrodynamic pressures following the bubble expansion and collapse can also be used as a driving force to deliver clot-dissolving agents into thrombus for enhancement of laser thrombolysis. Thus, the laser-induced bubble formation plays an important role in the thrombus removal process. We investigate the effects of boundary configurations and materials on bubble formation with time-resolved flash photography and high-speed photography. Potential applications in drug delivery using microsecond …
Pressure Impulses During Microsecond Laser Ablation, Hanqun Shangguan, Lee W. Casperson, Scott A. Prahl
Pressure Impulses During Microsecond Laser Ablation, Hanqun Shangguan, Lee W. Casperson, Scott A. Prahl
Electrical and Computer Engineering Faculty Publications and Presentations
The collapse of laser-induced cavitation bubbles creates acoustic transients within the surrounding medium and also pressure impulses to the ablation target and light-delivery fiber during microsecond laser ablation. The impulses are investigated here with time-resolved flash photography, and they are found to occur whether or not the light-delivery fiber is in contact with the target. We demonstrate that the impulses depend primarily on the energy stored in the cavitation bubble. They are not directly dependent on the mode of light delivery (contact versus noncontact), and they are also not directly correlated to the other acoustic transients. The pressure impulses do …
Drug Delivery With Microsecond Laser Pulses Into Gelatin, Hanqun Shangguan, Lee W. Casperson, Alan Shearin, Kenton W. Gregory, Scott A. Prahl
Drug Delivery With Microsecond Laser Pulses Into Gelatin, Hanqun Shangguan, Lee W. Casperson, Alan Shearin, Kenton W. Gregory, Scott A. Prahl
Electrical and Computer Engineering Faculty Publications and Presentations
Photo acoustic drug delivery is a technique for localized drug delivery by laser-induced hydrodynamic pressure following cavitation bubble expansion and collapse. Photoacoustic drug delivery was investigated on gelatin-based thrombus models with planar and cylindrical geometries by use of one microsecond laser pulses. Solutions of a hydrophobic dye in mineral oil permitted monitoring of delivered colored oil into clear gelatin-based thrombus models. Cavitation bubble development and photoacoustic drug delivery were visualized with flash photography. This study demonstrated that cavitation is the governing mechanism for photoacoustic drug delivery, and the deepest penetration of colored oil in gels followed the bubble collapse. Spatial …