Current Issue : April - June Volume : 2012 Issue Number : 2 Articles : 4 Articles
Evaluated atomic data concerning the 4s and 4p configurations of Ar I are averaged in order to simplify their use in various cases of\nAr plasma modeling and diagnostics. These data are used here to model a low-power arcjet, running with Argon at low pressure.\nIn so doing, they are explicitly introduced in the chemical processes included in a fluid Navier-Stokes type code, allowing for\nevaluation of the spectroscopically measurable level populations and of the electronic temperatures. The characteristics of the\nmodel are described and the main processes are discussed in view of the results of the calculations....
Intergranular attack (IG) and exfoliation corrosion (EC) have a detrimental impact on the structural integrity of aircraft structures\nof all types. Understanding the mechanisms and methods for dealing with these processes and with corrosion in general has been\nand is critical to the safety of critical components of aircraft. Discussion of cases where IG attack and exfoliation caused issues in\nstructural integrity in aircraft in operational fleets is presented herein along with a much more detailed presentation of the issues\ninvolved in dealing with corrosion of aircraft. Issues of corrosion and fatigue related to the structural integrity of aging aircraft are\nintroduced herein.Mechanisms of pitting nucleation are discussed which include adsorption-induced, ion migration-penetration,\nand chemicomechanical film breakdown theories. In addition, pitting corrosion (PC) fatigue models are presented as well as a\ncritical assessment of their application to aircraft structures and materials. Finally environmental effects on short crack behavior\nof materials are discussed, and a compilation of definitions related to corrosion and fatigue are presented....
The differential geometric filter is implemented to estimate the absolute and relative positions of the spacecraft in a formation.\r\nThe extended Kalman Filter is also implemented as a benchmark for the differential geometric estimation. Only relative positions\r\nbetween the spacecraft are measured. Relative positions are measured using a wireless local positioning system (WLPS) installed in\r\nall spacecraft. Two different scenarios are studied: (1) the observations include WLPS measurements only and (2) the observations\r\ninclude WLPS measurements in addition to measurements for the absolute position of one spacecraft made by a radar that takes\r\nmeasurements from the earth�s surface. Results show that the differential geometric estimation has better stability performance\r\nand a faster convergence rate compared to the extended Kalman filter....
Numerical rebuilding of two trajectory points (t = 1634 s and t = 1643 s) of the Fire II mission has been carried out to predict the\nradiative heat flux for nonequilibrium and close-to-equilibrium conditions. The simulations have been performed with eilmer3 in\nan uncoupled way and using a tangent slab method for the radiation transport. Different population models (QSS and Boltzmann)\nhave been compared, and the influence of catalytic wall condition was taken into account. An analysis on the spectral range and\non the spectral resolution has also been carried out....
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