The paper is copyright of SAE, so unfortunately I can't post it up for public consumption. But your team can get it from SAE using this info:
http://www.sae.org/technical/papers/2005-01-3803
05FFL-188
Development and Validation of an Impedance Transfer Model for High Speed Engines
Sam Zimmerman, Dan Cordon, Michael Anderson, and Steven Beyerlein
Mechanical Engineering, University of Idaho
Copyright © 2005 SAE International