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1994

Faculty Publications from the Department of Engineering Mechanics

Articles 1 - 3 of 3

Full-Text Articles in Mechanical Engineering

Radiative Transfer Of Ultrasound, Joseph A. Turner, Richard L. Weaver Dec 1994

Radiative Transfer Of Ultrasound, Joseph A. Turner, Richard L. Weaver

Faculty Publications from the Department of Engineering Mechanics

A radiative transfer equation is used to model the diffuse multiple scattering of ultrasound in a medium containing discrete random scatterers. An assumption of uncorrelated phases allows one to write an equation of energy balance for the diffuse intensity. This ultrasonic radiative transfer equation contains single-scattering and propagation parameters that are calculated using the elastic wave equation. Polarization effects are included through the introduction of an elastodynamic Stokes vector which contains a longitudinal Stokes parameter and four shear Stokes parameters similar to the four Stokes parameters used in optical radiative transfer theory. The theory is applied to a statistically homogeneous ...


Radiative Transfer And Multiple Scattering Of Diffuse Ultrasound, Joseph A. Turner, Richard L. Weaver Dec 1994

Radiative Transfer And Multiple Scattering Of Diffuse Ultrasound, Joseph A. Turner, Richard L. Weaver

Faculty Publications from the Department of Engineering Mechanics

A model is presented fro the multiply scattered incoherent field in a continuous polycrystalline elastic medium. Unlike a previous development based upon energy conservation considerations [J. A. Turner and R.L. Weaver, J. Acoust. Soc. Am. 93, 2312 (A) (1993)] for a medium containing discrete random scatterers, the present model has been developed from the wave equation and first principles. Appropriate ensemble averaging of the wave equation leads to Dyson and Bethe-Salpeter equations which govern the mean Green’s function and the covariance of the Green’s function, respectively. These equations are expanded for weak heterogeneity and equations of radiative ...


Inhomogeneous Anisotropic Percolation: Two-Dimensional Numerical Threshold Analysis, Yuris A. Dzenis, S. P. Joshi Feb 1994

Inhomogeneous Anisotropic Percolation: Two-Dimensional Numerical Threshold Analysis, Yuris A. Dzenis, S. P. Joshi

Faculty Publications from the Department of Engineering Mechanics

Monte Carlo simulations of percolation on a square lattice with anisotropic inhomogeneous probability distribution are reported. Finite-size scaling is used for data analysis. As inhomogeneity increases, the critical probability decreases; whereas the correlation-length exponent remains, within computation errors, the same as in classical two-dimensional percolation.