Aerospace Engineering Commons^™

Determination Of Plate Source, Detector Separation From One Signal, Stephen D. Holland, Tadej Kosel, Richard Weaver, Wolfgang Sachse

Stephen D. Holland

We address the problem of locating a transient source, such as an acoustic emission source, in a plate. We apply time-frequency analysis to the signals detected at a receiver. These highly dispersive and complex waveforms are measured for source-receiver separations ranging from 40 to 180 plate thicknesses and at frequencies such that ten to twenty Rayleigh-Lamb branches are included. Re-assigned, smoothed, pseudo-Wigner-Ville distributions are generated that exhibit the expected sharp ridges in the time-frequency plane, lying along the predicted frequency-time-of-arrival relations. The source-receiver separation can be determined from such plots.

Portfolio Assessment In Aerodynamics, Nikos J. Mourtos

Nikos J. Mourtos

A new way of assessing student learning in an aerodynamics course through the use of portfolios is presented. The approach is portable to any engineering course, with a few modifications depending on content.

The main idea is to allow students more responsibility for their own learning. Instead of having everyone in the class perform identical activities (homework, experiments, projects, tests, etc.), a cadre of assignments is made available to them. Students choose and perform (within reason) the ones that suit them better in terms of their own strengths and learning styles. The ultimate goal is for each student to demonstrate …

Minimum Error Fickian Diffusion Coefficients For Mass Diffusion In Multicomponent Gas Mixtures, Shankar Subramaniam

Shankar Subramaniam

Mass diffusion in multicomponent gas mixtures is governed by a coupled system of linear equations for the diffusive mass fluxes in terms of thermodynamic driving forces, known as the generalized Stefan–Maxwell equation. In computations of mass diffusion in multicomponent gas mixtures, this coupling between the different components results in considerable computational overhead. Consequently, simplified diffusion models for the diffusive mass fluxes as explicit functions of the driving forces are an attractive alternative. These models can be interpreted as an approximate solution to the Stefan–Maxwell equation. Simplified diffusion models require the specification of “effective” diffusion coefficients which are usually expressed as …