Purnima Ratilal

Assistant Professor
Department of Electrical and Computer Engineering
Northeastern University

Address:
302 Stearns Center, Rm 311,
360 Huntington Ave,
Boston, MA 02115, USA

Phone:        1-617-373-8458
Fax:            1-617-373-8627
E-Mail:       purnima@ece.neu.edu

Research Interests:

Underwater Acoustics, Acoustical Oceanograpy, Bioacoustics, Ultrasound Imaging, Seismics, Nonlinear Scattering, Wave Propagation in Random Media, Signal, Image and Array Processing, Statistical Inference Theory

Current Research and Development:

• A remote acoustic sensing system for rapidly imaging and localizing schools of fish and other biology over wide areas, spanning thousands of square kilometers, in near real time, including rapid-at-sea navigation, charting and registration.
  

• An Extinction Theorem for object scattering in a dispersive waveguide. This theorem will be used to design an acoustic ''burglar alarm'' or ''trip-wire'' system for detecting submerged objects.
  

• Physics-based model for the statistics (mean and spatial covariance) of the forward propagated acoustic field in a dispersive ocean waveguide containing random inhomogeneities. Model applied to analyze long range acoustic propagation through internal waves, oceanic bubble clouds, fish schools and seabottom surface and volume inhomogeneities.
  

• Unified full-field computational model for 3-D acoustic target scattering and reverberation in a range-varying ocean waveguide. The model has been applied to show that densely concentrated fish schools can be imaged remotely from tens of kilometers range in continental shelf environments.
  

• Long-range Synthetic Aperture Sonar (SAS) system for localizing objects with acoustics in highly dispersive shallow water waveguides.
  

• Fully coherent nonlinear wave and object scattering model. Applied to analyze mechanisms for nonlinear wave generation in medical ultrasonic imaging.
  

• Full-field model to simulate the performance of a scanning ultrasound vibrometer. Applied in landmine confirmation research to investigate ultrasound measurement of ground displacement and velocity.

• Low frequency instantaneous wide-area active seismic imaging of shallow buried tunnels.

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Postdoctoral Associate:

• Elizabeth Kusel

Current Graduate Students:

• Mark Andrews and Roger Gong

Undergraduate Students:

• Daniel Cocuzzo and Saumitro Dasgupta

Former Students:

• Ninos Donabed (M.Sc., 2006)

• Ameya Galinde (M.Sc., 2007)

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• ONR Young Investigator Award (2007)
• R. Bruce Lindsay Award (2006)
• MIT T. Francis Ogilvie Young Investigator Lectureship in Ocean Engineering (2006)
• ONR Postdoctoral Award in Ocean Acoustics (2002-2004)
• Young Investigator Keynote Address, Acoustical Society of America (ASA) 75th Anniversary Celebration, New York (May, 2004)
• Best Student Paper Awards, Acoustical Society of America Meetings:
• DSO National Laboratories Graduate Scholarship, Singapore (1998)

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Education:

• Ph.D. in Ocean Engineering, Massachusetts Institute of Technology, 2002
• B.Sc.(Hons.) in Physics, National University of Singapore, 1994

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Teaching:

• ECE G398 - Wave Based Remote Sensing and Imaging/Acoustic Sensing and Imaging (Graduate)
  
• ECE G203 - Complex Variables and Differential Equations
  Graduate level calculus course on integration of complex functions and solution methods for partial differential equations.
• ECE U468 - Probability, Noise and Stochastic Processes (Undergraduate)
  
• GE U111 - High Tech Tools and Toys Lab
  Undergraduate level course offered through the Department of Electrical and Computer Engineering at Northeastern University (2004).
  The course is an introduction to computing in Matlab and C++ that also introduces students to the basics of remote sensing with experiments conducted using ultrasound.
  

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Previous Work Experience:

• Postdoctoral Associate at MIT Department of Ocean Engineering (2002-2004)
  Conducted 2 major experiments and research under the ONR-sponsored Acoustic Clutter (Geoclutter) Program to examine the dominant source of long range sonar clutter in continental shelf environments.
• Research Engineer at DSO National Laboratories, Singapore (1994-1998)
  Examined the characteristics of sound propagation in shallow waters. Conducted experiments and modelling to study the impact of the environment on sound propagation. Also investigated various inverse methods to recover properties of the environment through match field processing and travel time inversions.

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Selected Journal Publications:

• A. Galinde, N. Donabed, S. Lee, N. C. Makris and P. Ratilal, "Range-dependent waveguide scattering model calibrated for bottom reverberation in continental shelf environments," submitted to J. Acoust. Soc. Am.
• P. Ratilal, M. Andrews, N. Donabed, A. Galinde, C. Rappaport and D. Fenneman, "Model for continuously scanning ultrasound vibrometer sensing displacements of randomly rough vibrating surfaces," J. Acoust. Soc. Am. 121, 863-878 (2007).
• N.C. Makris, P. Ratilal, D.T. Symonds, S. Jagannathan, S. Lee, and R. Nero, ''Fish Population and Behavior Revealed by Instantaneous Continental-Shelf-Scale Imaging,'' Science, Volume 311, 660-663 February 3, (2006).
• P. Ratilal and N.C. Makris, " Mean and covariance of the forward field propagated through a stratified ocean waveguide with three-dimensional random inhomogeneities," J. Acoust. Soc. Am. 118, 3532-3559 (2005).
• T. Chen, P. Ratilal and N.C. Makris, ''Mean and variance of the forward field propagated through three-dimensional random internal waves in a continental-shelf waveguide,'' J. Acoust. Soc. Am. 118, 3560-3574 (2005).
• P. Ratilal, Y. Lai, D.T. Symonds, L.A. Ruhlmann, J. Goff, C.W. Holland, J.R. Preston, E.K. Scheer, M.T. Garr and N.C. Makris, "Long range acoustic imaging of the Continental Shelf Environment: The Acoustic Clutter Reconnaisance Experiment 2001," J. Acoust. Soc. Am. 117, 1977-1998 (2005).
• P. Ratilal, Y. Lai and N.C. Makris, "Validity of the Sonar Equation and Babinet's Principle in a Stratified Medium," Journal of the Acoustical Society of America, Vol. 112, 1797-1816 (2002).
• P. Ratilal and N.C. Makris, "Extinction theorem for object scattering in a stratified medium," Journal of the Acoustical Society of America, Vol. 110, 2924-2945 (2001).
• N.C. Makris and P. Ratilal, "A unified model for reverberation and submerged object scattering in a stratified ocean waveguide," Journal of the Acoustical Society of America, Vol. 108, 909-941 (2001).
• P. Ratilal, P. Gerstoft and J. T. Goh, "Subspace approach to inversion by genetic algorithms involving multiple frequencies," Journal of Computational Acoustics, Vol. 6, 99-115 (1998).
• P. Ratilal, P. Gerstoft, J.T. Goh and K.P. Yeo, "Inversion of pressure data on a vertical array to determine the seafloor geoacoustic properties," Journal of Computational Acoustics, Vol. 6, 269-289 (1998).

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