Materials outgassing rate decay in vacuum at isothermal conditions
As a laboratory for scientific research, the International Space Station has been in Low Earth Orbit for over 17 years and is planned to be on-orbit for another 10 years. The ISS has been maintaining a relatively pristine contamination environment for science payloads. Materials outgassing induced contamination is currently the dominant source for sensitive surfaces on ISS and modelling the outgassing rate decay over a 20 to 30 year period is challenging. Using ASTM E 1559 rate data, materials outgassing is described herein as a diffusion-reaction process with the interface playing a key role. The observation of -1/2 (diffusion) or non-integers (reaction limited) as rate decay exponents for common ISS materials indicate classical reaction kinetics is unsatisfactory in modelling materials outgassing. Nonrandomness of reactant concentrations at the interface is the source of this deviation from classical reaction kinetics. A t-1/2 decay is adopted as the result of the correlation of the contaminant layer thicknesses and composition on returned ISS hardware, the existence of high outgassing silicone exhibiting near diffusion limited decay, the confirmation of nondepleted material after ten years in Low Earth Orbit, and a potential slowdown of long term materials outgassing kinetics due to silicone contaminants at the interface.
Molecular flow venting of a volume with an outgassing or desorbing source
A venting equation commonly used to describe the transient evolution of pressure within a volume containing an outgassing or offgassing source and a restrictive vent conductance under conditions of molecular flow has been solved analytically. Solutions are found for sources of finite thickness characterized by classical diffusion-limited behavior (proportional to inverse square root of time), as well as responses for thick material sources often observed in testing that are characterized by a more general form of power-law decay, up to inverse time behavior associated with surface desorption. Solutions involve evaluating integrals where both numerators and denominators of the integrands diverge with time, making wide-ranging transient solutions difficult to directly compute numerically. Usually, one can avoid evaluating these integrals by assuming quasistatic conditions at long time scales. A novel approach is used in this work to analytically produce solutions by generating bespoke mathematical functions, some of which solve integrals that have apparently had no previous analytical solution.
Byron: Augustan and Romantic
The impact of Byron's writings - an evaluative approach, William St Clair "My brain is feminine" - Byron and the poetry of deception, Jerome J. McGann Byron and the romantic heroine, Malcolm Kelsall Byron and the Empire in the East, Marilyn Butler Byron Augustan - mutations of mock-heroic in "Don Juan" and Shelley's "Peter Bell the Third", Claude Rawson continuities and discontinuities of language and voice in Dryden, Pope, and Byron, Bernard Beatty Augustan satires and Panegyrics on London and Byron's image of the city, Michael Gassermeier Byron, Pope, and the Grand Tour, Michael G. Cooke Byron in Italy - the return of Augustus, Donald H. Reiman "Don Juan" transformed, Anne Barton Byron's "Wrong Revolutionary System" and romanticism, Hermann Fischer the quintessential Byron, Leslie A. Marchand.