Electron Kinetics in a Positive Column of AC Discharges in a Dynamic Regime

We have performed hybrid kinetic-fluid simulations of a positive column in AC Argon discharges over a range of driving frequencies f and gas pressure p for the conditions when the spatial nonlocality of the Electron Energy Distribution Function (EEDF) is substantial. Our simulations confirmed that the most efficient conditions of plasma maintenance are observed in the dynamic regime when time modulations of mean electron energy (temperature) are substantial. The minimal values of the root mean square (rms) electric field and the electron temperature have been observed at f/p values of about 3 kHz/Torr in a tube of radius R = 1 cm. The ionization rate and plasma density reached maximal values under these conditions. The numerical solution of a kinetic equation allowed accounting for the kinetic effects associated with spatial and temporal nonlocality of the EEDF. Using the kinetic energy of electrons as an independent variable, we solved an anisotropic tensor diffusion equation in phase space. We clarified the role of different flux components during electron diffusion in phase space over surfaces of constant total energy. We have shown that the kinetic theory uncovers a more exciting and rich physics than the classical ambipolar diffusion (Schottky) model. Non-monotonic radial distributions of excitation rates, metastable densities, and plasma density have been observed in our simulations at pR > 6 Torr cm. The predicted off-axis plasma density peak in the dynamic regime has never been observed in experiments so far. We hope our results stimulate further experimental studies of the AC positive column. The kinetic analysis could help uncover new physics even for such a well-known plasma object as a positive column in noble gases

Hydrogen-silicon carbide interactions

A study of the thermochemistry and kinetics of hydrogen environmental attack of silicon carbide was conducted for temperatures in the range from 1100 C to 1400 C. Thermodynamic maps based on the parameters of pressure and oxygen/moisture content were constructed. With increasing moisture levels, four distinct regions of attack were identified. Each region is defined by the thermodynamically stable solid phases. The theoretically stable solid phases of Region 1 are silicon carbide and silicon. Experimental evidence is provided to support this thermodynamic prediction. Silicon carbide is the single stable solid phase in Region 2. Active attack of the silicon carbide in this region occurs by the formation of gases of SiO, CO, CH4, SiH4, and SiH. Analysis of the kinetics of reaction for Region 2 at 1300 C show the attack of the silicon carbide to be controlled by gas phase diffusion of H2O to the sample. Silicon carbide and silica are the stable phases common to Regions 3 and 4. These two regions are characterized by the passive oxidation of silicon carbide and formation of a protective silica layer

The Oxidation of AlN in Dry and Wet Oxygen

The oxidation kinetics of AlN containing 3.5 wt% Y2O3 were studied by thermogravimetric analysis in dry oxygen and 10% H2O/balance oxygen at temperatures between 1000 and 1200 C for times between 48 and 100 h. The oxidation kinetics for AlN in dry oxygen were parabolic and of approximately the same magnitude and temperature dependence as other alumina forming materials. In this case, diffusion of oxygen and/or aluminum through the alumina scale is the rate limiting mechanism. The oxidation kinetics for AlN in wet oxygen were nearly linear and much more rapid than rates observed in dry oxygen. Numerous micropores were observed in the alumina formed on AIN in wet oxygen. These pores provide a fast path for oxygen transport. The linear kinetics observed in this case suggest that the interface reaction rate of AlN with wet oxygen is the oxidation rate limiting step

Virtual Reality Therapy for Fall Prevention in Older Adults A Comparative Study to Conventional Exercise

Purpose The purpose of this critically appraised topic is to investigate if VR-HMD interventions have a superseding impact on older adults in preventing falls in comparison to conventional physical therapy balance exercises. Introduction Increases in technology, one of the newest being virtual reality, has positively impacted the world of rehabilitation. There are many different types of virtual reality systems that are used, but the most common is the Virtual Reality Head Mounted Display (VR-HMD). In the United States, 28% of adults aged 65 and older report falling each year. This is significant because falls are the leading cause of injury-related death among this population, and the age-adjusted fall death rate is increasing

The Grizzly, March 5, 2009

Memorable Performance Depicts Life of Anne Frank • Batter Up! Baseball Hopes for Home Run Season • Cheapest Trip to Italy • Young Invincibles Shun Medical Care • Black in History: Tribute to Debbie Allen • Money, Sex, Faith, Health and a True Happiness Formula? • Finding Inspiration on the Back of Your Dove Chocolate Wrapper • Opinions: Updike\u27s Death Calls for a Greater Appreciation for His Life • Senior Leatherman Hurdles Into Eighth and Final Season at UChttps://digitalcommons.ursinus.edu/grizzlynews/1782/thumbnail.jp

The Grizzly, January 29, 2009

UC Students Attend Inauguration • Wrestling Wants Results On and Off the Mat • Caffeine Correlation to Hallucinations? • Inauguration 2009 • Winter in Senegal: How Four Students Spent Their Holiday • Author Sheree R. Thomas Visits UC • B-Nats to Sing National Anthem for 76ers • Cruxshadows: A Live Experience not to be Missed • Opinions: In Response to Letter to the Editor by Julie Tran; Obama in Office: Observations from the Bomb Shelter • Gymnasts Tumble with Temple and Towson in Tri-meethttps://digitalcommons.ursinus.edu/grizzlynews/1777/thumbnail.jp

The Grizzly, September 11, 2008

Republican National Convention Rallies Supporters • Studies Show Half of College Students Contemplate Suicide • Start of New Now on View Art Film Festival • Science, Strife and Speculation of Hurricane Season \u2708 • UC Senior Implements First Ever Bike Share Program • Cinematic Guild Brings Creative Filmography to Campus • Introducing Cassandra Aguilar • The Grizzly Catches Up with Dean Nolan • Celebrating Herencia Latina Fall Events • Molly Maguire\u27s: A Bit O\u27 Irish Spirit • UC Women\u27s Soccer Fights for Another Strong Season • Football\u27s New Motto: No Interceptions, No Exceptionshttps://digitalcommons.ursinus.edu/grizzlynews/1767/thumbnail.jp