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ELE Master of Science Thesis Defense by Ryan Ferreira

When: Tuesday, May 23, 2023
11:30 AM - 1:30 PM
Where: Science and Engineering Building 285 Old Westport Road, Dartmouth, MA
Cost: Free
Description: Topic: Performance Assessment of an Environmentally Aware Bayes Factor Monostatic Active Acoustic Detection System

Location: Science & Engineering Building (SENG), Room 212

Abstract:
The performance of a Bayes factor (BF) monostatic active acoustic detection scheme with small vertical aperture at relatively high frequencies under various refractive ocean conditions, and target body depth uncertainty scenarios for the noise limited regime is explored. The Bayes factor frames composite hypotheses via marginalization resulting in a time-varying quadratic form over the beam-delay space representation of the scattered acoustic field. The quadratic form rejects strong reverberation and noise subspaces, passing apriori highly probable target signatures at range while permitting target uncertainty in depth. The distribution of the BF under the composite null hypothesis is shown to be a superposition of weighted central chi-squared variates. The total degrees of freedom being the number of in-phase and quadrature components associated with the at-range target body subspace under depth uncertainty, a stark reduction relative to the observation space. The distribution under the composite alternative is likewise a weighted sum of non-central chi-squared variates with non-centrality parameters associated with the beam-delay target strength components at range. These distributions do not admit simple closed forms but can be well approximated in a number of ways and this thesis considers two such methods. The asymptotic method of Davies and a fast approximation based on the method of moments. The agreement of the two methods is demonstrated. From the distribution of the BF detector under null and alternative it is straightforward to summarize performance via the receiver operating characteristic (ROC) curve. The improved acoustic focusing that this environmentally aware BF provides is demonstrated. Understood features of the waveguide dispersion in beam and delay are identified and used to combine power and improve performance. A number of refractive and iso-velocity environments are considered in the noise limited regime and results demonstrate the improvement of the BF active sonar with uncertain depth with multipath combining over the case of a single fixed and known direct specular arrival.

Advisor(s): Dr. Paul J. Gendron, Associate Professor, Department of Electrical & Computer Engineering, UMASS Dartmouth

Committee Members: Dr. David A. Brown, Professor, Department of Electrical & Computer Engineering, UMASS Dartmouth; Dr. Dayalan P. Kasilingam, Professor, Department of Electrical & Computer Engineering, UMASS Dartmouth

NOTE: All ECE Graduate Students are ENCOURAGED to attend.
All interested parties are invited to attend. Open to the public.

*For further information, please contact Dr. Paul J. Gendron at 508.999.8510 or via email at pgendron@umassd.edu
Topical Areas: General Public, University Community, College of Engineering, Electrical and Computer Engineering