Advanced Hybrid Modeling of Hall Thruster Plumes

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83623/1/AIAA-2010-6525-581.pd

Simulation of Hall Thruster Plumes in a Vacuum Chamber Using a Hybrid Method

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77275/1/AIAA-2008-5103-811.pd

The influence of alcohol content variation in UK packaged beers on the uncertainty of calculations using the Widmark equation

It is common for forensic practitioners to calculate an individual's likely blood alcohol concentration following the consumption of alcoholic beverage(s) for legal purposes, such as in driving under the influence (DUI) cases. It is important in these cases to be able to give the uncertainty of measurement on any calculated result, for this reason uncertainty data for the variables used for any calculation are required. In order to determine the uncertainty associated with the alcohol concentration of beer in the UK the alcohol concentration (%v/v) of 218 packaged beers (112 with an alcohol concentration of ≤5.5%v/v and 106 with an alcohol concentration of >5.5%v/v) were tested using an industry standard near infra-red (NIR) analyser. The range of labelled beer alcohol by volume (ABV's) tested was 3.4%v/v – 14%v/v. The beers were obtained from a range of outlets throughout the UK over a period of 12 months. The root mean square error (RMSE) was found to be ±0.43%v/v (beers with declared %ABV of ≤5.5%v/v) and ±0.53%v/v (beers with declared %ABV of >5.5%v/v) the RMSE for all beers was ±0.48%v/v. The standard deviation from the declared %ABV is larger than those previously utilised for uncertainty calculations and illustrates the importance of appropriate experimental data for use in the determination of uncertainty in forensic calculations

A New Puzzle About Aristotelian Accidents

Aristotle gives a surprisingly broad menu of examples of something being accidental to something else. But the breadth of these examples seems to threaten a basic feature of accidentality, namely its asymmetry. ‘Accident’ has different senses, and one might think that that fact offers a way out, but some examples resist such an understanding. The best way forward, I argue, is to take accidentality to be contextual: relative to some context or condition, something might be accidental to something else; relative to another context or condition, the latter might be accidental to the former

Improving Hall Thruster Plume Simulation through Refined Characterization of Near-field Plasma Properties.

Due to the rapidly expanding role of electric propulsion (EP) devices, it is important to evaluate their integration with other spacecraft systems. Specifically, EP device plumes can play a major role in spacecraft integration, and as such, accurate characterization of plume structure bears on mission success. This dissertation addresses issues related to accurate prediction of plume structure in a particular type of EP device, a Hall thruster. This is done in two ways: first, by coupling current plume simulation models with current models that simulate a Hall thruster's internal plasma behavior; second, by improving plume simulation models and thereby increasing physical fidelity. These methods are assessed by comparing simulated results to experimental measurements. Assessment indicates the two methods improve plume modeling capabilities significantly: using far-field ion current density as a metric, these approaches used in conjunction improve agreement with measurements by a factor of 2.5, as compared to previous methods. Based on comparison to experimental measurements, recent computational work on discharge chamber modeling has been largely successful in predicting properties of internal thruster plasmas. This model can provide detailed information on plasma properties at a variety of locations. Frequently, experimental data is not available at many locations that are of interest regarding computational models. Excepting the presence of experimental data, there are limited alternatives for scientifically determining plasma properties that are necessary as inputs into plume simulations. Therefore, this dissertation focuses on coupling current models that simulate internal thruster plasma behavior with plume simulation models. Further, recent experimental work on atom-ion interactions has provided a better understanding of particle collisions within plasmas. This experimental work is used to update collision models in a current plume simulation code. Previous versions of the code assume an unknown dependence between particles' pre-collision velocities and post-collision scattering angles. This dissertation focuses on updating several of these types of collisions by assuming a curve fit based on the measurements of atom-ion interactions, such that previously unknown angular dependences are well-characterized.Ph.D.Aerospace ScienceUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/89770/1/huismann_1.pd