Physics Commons^™

Measurements Of Methyl Radicals And Temperatures By Using Coherent Microwave Rayleigh Scattering From Resonance Enhanced Multiphoton Ionization, Yue Wu

Doctoral Dissertations

This thesis includes two main parts: (I) The CH₃[methyl radical] detection in methane/air flames and (II) the rotational temperature measurement of O₂[molecular oxygen] in a variety of environments by using coherent microwave Rayleigh scattering from resonance enhanced multiphoton ionization (Radar REMPI).

In first the part, from Chapter I to Chapter III, the methyl radical detection and quantitative measurements have been conducted in hydrocarbon flame with one-dimensional and two-dimensional spatial-resolved concentration distribution. Due to the proximity of the argon resonance state (4+1 REMPI by 332.5 nm) with the CH₃ state (2+1 REMPI by 333.6 nm), in …

Mathematical Model: Comparative Study Of Thermal Effects Of Laser In Corneal Refractive Surgeries, Gokul Kc, Dil B. Gurung, Pushpa R. Adhikary

Applications and Applied Mathematics: An International Journal (AAM)

Lasers have been widely used in ophthalmology. Refractive errors are some of the most common ophthalmic abnormalities worldwide. Laser refractive surgery was developed to correct refractive errors myopia, hyperopia and astigmatism. Two types of laser surgical techniques: lamellar and thermal are available to reshape the corneal curvature. Ultraviolet (UV) emitting argon fluoride (ArF) excimer laser is used to sculpt cornea in lamellar procedures, whereas, infrared (IR) emitting holmium yttrium aluminum garnet (Ho: YAG) laser is used to shrink cornea in thermal procedure. Tissue heating is common in all types of laser surgical techniques. Hence, in this paper, a finite element …

“Ultra Cold” Room Temperature Plasma, Stephen Rupper, Dr. Scott Bergeson

Journal of Undergraduate Research

Many scientists throughout the world are currently doing research on ultra cold neutral plasmas (UCNP). These plasmas are difficult to make and require quite a sophisticated setup. A method that we employ in our lab requires multiple laser pulses to be timed perfectly and aligned precisely in order to ionize the atoms. It also requires the use of a magneto optical trap, which traps the atoms before they are ionized. This setup is very time consuming to build and maintain but we have a mathematical model for it. Since the current methods of creating ultra cold plasmas are hard to …

Long-Term Midlatitude Mesopause Region Temperature Trend Deduced From Quarter Century (1990-2014) Na Lidar Observations, Chiao Y. She, D. A. Krueger, Tao Yuan

All Physics Faculty Publications

The long-term midlatitude temperature trend between 85 and 105 km is deduced from 25 years (March 1990-December 2014) of Na Lidar observations. With a strong warming episode in the 1990s, the time series was least-square fitted to an 11-parameter nonlinear function. This yields a cooling trend starting from an insignificant value of 0.64 ± 0.99 K decade^-1 at 85 km, increasing to a maximum of 2.8 ± 0.58K decade^-1 between 91 and 93 km, and then decreasing to a warming trend above 103 km. The geographic altitude dependence of the trend is in general agreement with model predictions. …

Simulation Study Of Hemt Structures With Hfo2 Cap Layer For Mitigating Inverse Piezoelectric Effect Related Device Failures, Deepthi Nagulapally, Ravi P. Joshi, Aswini Pradhan

Electrical & Computer Engineering Faculty Publications

The Inverse Piezoelectric Effect (IPE) is thought to contribute to possible device failure of GaN High Electron Mobility Transistors (HEMTs). Here we focus on a simulation study to probe the possible mitigation of the IPE by reducing the internal electric fields and related elastic energy through the use of high-k materials. Inclusion of a HfO₂ "cap layer" above the AlGaN barrier particularly with a partial mesa structure is shown to have potential advantages. Simulations reveal even greater reductions in the internal electric fields by using "field plates" in concert with high-k oxides