Center Participants

Assad Oberai
Assistant Professor Mechanical, Aerospace and Nuclear Engineering
Rensselaer Polytechnic Institute

Education:
Ph.D., Stanford University Mechanical Engineering
M.S., University of Colorado at Boulder Mechanical Engineering
B.S., Osmania University Mechanical Engineering

Career Highlights:
Assad Oberai received his PhD. in Mechanical Engineering from Stanford University in 1998. His doctoral work involved developing accurate and efficient finite element methods for solving time-harmonic, wave propagation problems in unbounded domains. As a post-doctoral researcher at Stanford University he developed multiscale formulations of large eddy simulation for modeling turbulent flows and numerical methods for predicting noise generated by such flows. In 2001, Assad joined Boston University as an Assistant Professor and in 2006 he moved to the Mechanical, Aerospace and Nuclear Engineering Department at RPI. Here, he continues to work on numerical methods for inverse problems and problems with multiple scales.

In 2004, Assad was awarded the DOD Breast Cancer Research Program Concept Award for work on quantifying the nonlinear, elastic properties of tissue. In 2004, he was also awarded the DOE Early Career PI award in applied mathematics for developing algorithms for solving multiscale problems. In 2005 he received the NSF CAREER award for work on Large Eddy Simulation of turbulent flows.

Research Areas:
Assad's research involves developing numerical methods for solving inverse problems and problems with multiple spatial and temporal scales. His work on multiscale problems includes modeling turbulent flows, problems with shocks and coupling molecular and continuum descriptions in fluids.

In the field of inverse problems Assad is working on the promising new area of biomechanical imaging. Here the goal is to develop algorithms that quantify the spatial distribution of mechanical properties of tissue. This is accomplished by first deforming the tissue by some means (a gentle compression for example) and observing its deformation using ultrasound (or sometimes MRI). Once the displacement is known an inverse problem is solved wherein the given an appropriate mechanical model for the tissue (linear elastic, or hyperelastic or poroelastic) and the deformation, the spatial distribution of the mechanical properties is sought. Assad's work is focused on developing algorithms for solving these types of inverse problems. This approach can be used to measure the mechanical properties of tissue in-vivo and has found applications in the detection and diagnosis of different types of cancers and in the development of patient specific mechanical models for surgical planning.

Gokhale, N.H. P.E. Barbone and A.A. Oberai, Solution of the nonlinear elasticity imaging inverse problem: the compressible case. Inverse Problems, 24(4), 2008.

Adjoint-weighted variational formulation for direct solution of inverse heat conduction problem. PE Barbone, AA Oberai and I Harari, Inverse Problems, Vol. 23, pp. 2325-2342, 2007. (text of paper)

The adjoint weighted equation for steady advection in a compressible fluid. A.A. Oberai, P.E. Barbone & I. Herari, International Journal for Numerical Methods in Fluids, Vol. 54(6-8), pp. 683-693, 2007. (text of paper)

Elastic modulus imaging: some exact Solutions of the compressible elastography inverse problem. P.E. Barbone & A.A. Oberai. Physics in Medicine and Biology, Vol. 52(6), pp. 1577-1593, 2007. (text of paper)

A Dynamic Multiscale Viscosity Method for the Spectral Approximation of Conservation Laws. A.A. Oberai & J. Wanderer, Computer Methods in Applied Mechanics and Engineering, Vol. 195(13-16), pp. 1778-1792, 2006. (text of paper)

Acoustic eigenvalues of rectangular rooms with arbitrary wall impedances using the interval Newton/generalized bisection method. Y. Naka, A.A. Oberai & B. Shinn-Cunningham, Journal of Acoustical Society of America, Vol. 118(6), pp. 3662-3671, 2005. (text of paper)

Variational Formulation of the Germano Identity for the Navier-Stokes Equations. A.A. Oberai & J. Wanderer, Journal of Turbulence, Vol. 6, 2005.

A Dynamic Approach for Evaluating Parameters in a Numerical Method. A.A. Oberai & J. Wanderer, International Journal for Numerical Methods in Engineering, Vol. 62, pp. 50-71, 2005. (text of paper)

Simultaneous Elastic Image Registration and Elastic Modulus Reconstruction. N. Gokhale, M. Richards, A. Oberai, P. Barbone, M. Doyley, Proceedings of the IEEE International Symposium on Biomedical Imaging, April 15-18, 2004, Arlington, VA, USA.

Evaluation of the Adjoint Equation Based Algorithm for Elasticity Imaging. A.A. Oberai, N.H. Gokhale, M.M. Doyley, J.C.Bamber, Physics in Medicine and Biology, Vol. 49, pp. 2955-2974, 2004. (text of paper)

Sensitivity of the Scale Partition for Variational Multiscale LES of Channel Flow. J. Holmen, T.J.R. Hughes, A.A. Oberai and G.N. Wells, Physics of Fluids, Vol. 16(3), pp. 824-827, 2004.

An Application of Shape Optimization in the Solution of Inverse Acoustic Scattering Problems. G.R. Feijoo, A.A. Oberai and P.M. Pinsky, Inverse Problems, Vol. 20, pp. 199-228, 2004. (text of paper)

A Krylov subspace projection method for simultaneous solution of Helmholtz problems at multiple frequencies. M.M. Wagner, P.M.Pinsky, A.A. Oberai and M. Malhotra, Computer Methods in Applied Mechanics and Engineering, Vol. 192(41-42), pp. 4609-4640, 2003. (text of paper)

Solution of Inverse Problems in Elasticity Imaging Using the Adjoint Method. A.A. Oberai, N.H. Gokhale and G.R. Feijoo, Inverse Problems, Vol. 19, pp. 297-313, 2003.. (text of paper)

Calculation of Shear Stresses in Fourier-Galerkin Formulation of Turbulent Channel Flows: Projection, the Dirichlet Filter and Conservation. T.J.R. Hughes and A.A. Oberai, Journal of Computational Physics, Vol. 188(1), pp. 281--295, 2003. (text of paper)

Shape sensitivity calculations for exterior acoustics problems. G.R. Feijoo, M. Malhotra, A.A. Oberai, and P.M. Pinsky, Engineering Computations, Vol.18(3/4), pp. 376--391.

Trailing-edge noise from a finite chord airfoil. A.A. Oberai, F. Roknaldin and T.J.R. Hughes,AIAA Journal, Vol 40(11), pp. 2206-2216, 2002.

Important Talks:

Oberai, A., Inverse Problems in Mechanics, Unified Framework Workshop , CenSSIS, Boston, MA, Nov. 2008.

Oberai, A., Inverse Problems in Mechanics, Department of Theoretical and Applied Mechanics, Cornell University, Sept., 2008.

Oberai, A., Studies of Inverse Problems in Biomechanics, Mechanics and Materials Colloquium, University of Colorado, May,2008.

Contact Information:
Assad Oberai
Department of Mechanical, Aerospace and Nuclear Engineering
Jonsson Engineering Center rm: 5048
Rensselaer Polytechnic Institute
110 Eighth Street
Troy, N.Y. 12180
U.S.A.
(518) 276-3386
http://www.rpi.edu/~oberai

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Inverse Problems Center at Rensselaer
Rensselaer Polytechnic Institute, 110 8th St., Troy, NY 12180-3590.
(518) 276-2145• E-mail: mclauj3@rpi.edu