Richard L Weaver
- Ph.D. Astrophysics Cornell University 1977
Professor Richard Weaver received an A.B. degree in physics from Washington University in St Louis in 1971 and a Ph.D in astrophysics from Cornell University in 1977. He came to Illinois in 1981 after a research associateship in theoretical elastic wave propagation and ultrasonics at Cornell. He was elected a fellow of the Acoustical Society of America in 1996 and received the Hetenyi Award from the Society for Experimental Mechanics in 2004. He is associate editor of the Journal of the Acoustical Society of America. Formerly a professor in the Department of Theoretical and Applied Mechanics at Illinois, he joined the Department of Physics in 2006.
Ultrasonic Analog for a Random Laser (with colleagues Oleg Lobkis, UIUC, and Alexey Yamilov, U Missouri) — We report measurements on ultrasonic systems analogous to random lasers. An auto-oscillating, and spontaneously emitting, piezoelectric device is found to emit more energetically when stimulated by an incident wave field. The emission is at the same frequency as the stimulating field, and with a phase relation corresponding to super radiance. Over a wide range of parameters we observe narrow single emission lines, sensitivity to linear cavity properties, complex multi-mode emissions, and line narrowing. Line widths are more narrow than we can measure. Theory suggests they have Schawlow–Townes widths as low as 10-9 Hz. Systems of several such oscillators are observed to self-organize into a coherent state with power emission that rises faster than the first power of the number of oscillators.
Statistical Elastodynamics of Large Structures and Quantum Chaos (with Oleg Lobkis, UIUC, and Thomas Seligman, Centro de Ciencias Fisicas, UNAM) — Numerical simulations, analytic theory and laboratory measurements are used to study the statistics of linear waves in complex systems. Particular attention is paid to wave energy density (or probability for quantum waves), and its mean flow and fluctuations. We seek methods to predict mean flow and fluctuations over long times, based on information in ray optics or direct numerical simulations over short times.
Seismic Noise Correlations (with M Campillo, B van Tiggelen and E Larose, U Joseph Fourier, and O Lobkis UIUC and X Song UIUC Geology) — Recent attention to diffuse fields in seismology, inspired in part by laboratory experiments done at UIUC, is leading to new methods for probing the interior of the earth. We observe and exploit mesoscopic residual correlations in nominally incoherent multiply scattered elastic wave fields, on the moon, in the seismic coda, in local geophone noise, and in long period world-wide background seismicity.
Determination of Thin-Film Interfacial Properties by Laser Generated Stress Waves (with N Sottos UIUC MatSE) — We investigate, both theoretically and experimentally, the generation of high-amplitude compression waves due to the sudden deposition of heat from a YAG laser pulse in a thin metallic film between two solids. The resulting pulse, with a duration of 10 nsec and a strain amplitude of the order of 1%, is measured using laser interferometry. Particular issues of concern include the effects of nonlinearity in the wave propagation and the corresponding development of shocks, and mode conversion at oblique interfaces with consequent generation of high-amplitude shear waves. Each of these effects is critical in ultimate application to the testing, by high-speed stress loading, of thin-film coatings.
Graduate Research Opportunities
Theory and large scale numerical simulations of stochastic wave propagation with a view towards applications in seismology, in particular the retrieval of information on the earth's structure and its changes from analysis of seismic noise correlations.
Undergraduate Research Opportunities
Design and analysis and numerical simulations of self-synchronizing sets of mechanical auto-oscillators, eccentric DC motors on plates, with a view towards emulation of lasing.
Large scale numerical simulations of stochastic seismic wave propagation.
Selected Articles in Journals
- R. Weaver. On the retrieval of attenuation and site amplifications from ambient noise on linear arrays: further numerical simulations. Geophys. J. Int. 193:3, 1644-1657 (2013).
- R. Weaver. Retrieval of Green's function in the radiative transfer regime. J. Acoust. Soc. Am. 133:2, 792-798 (2013).
- P. Zhao, J. Zhao, R. Weaver. Dynamic surface acoustic response to a thermal expansion source on an anisotropic half space. J. Acoust. Soc. Am. 133,2634 (2013).
- S. Scharfenberg, N. Mansukhani, C. Chialvo, R. Weaver, N. Mason. Observation of a Snap-Through Instability in Graphene. Appl. Phys. Lett. 100, 021910 (2012).
- Mertens, David; Weaver, Richard. Individual and Collective Behavior of Vibrating Motors Interacting Through a Resonant Plate. Complexity 16 (5): 45-53 MAY-JUN 2011
- R. Weaver, C. Hadziioannou, E. Larose, M. Campillo. On the precision of noise-correlation Interferometry. Geophys. J. Int. 185:3, 1384-1392 (2011).
- R.Weaver. Equipartition and Retrieval of the Green's function. J. Acoust. Soc. Am. 128, 2300 (2010).
- B. Froment, M.Campillo, P. Roux, P. Gouédard, A. Verdel, R. Weaver. Estimation of the effect of nonisotropically distributed energy on the apparent arrival time in correlations. Geophysics. 75:5, SA85-SA93 (2010).
- R. Weaver, O. Lobkis, A. Yamilov. Entrainment and stimulated emission of ultrasonic piezoelectric auto-oscillators. J. Acoust. Soc. Am. 122, 3409-18 (2007).
- R. Weaver. Wave Diffusion and Mesoscopic Dynamics, towards a universal time dependent scattering matrix. New J. Phys. 9:8 (2007).
- E. Larose, O. Lobkis, R. Weaver. Passive correlation imaging of a buried scatterer. J. Acoust. Soc. Am. 119, 3549 (2006).
- R. Weaver, O. Lobkis. On the linewidth of the ultrasonic Larsen effect in a reverberant body. J. Acoust. Soc. Am. 120:1, 102-109 (2006).
- Gorin, T., Seligman, T. H. and Weaver, Richard L. Scattering fidelity in elastodynamics. Phys Rev E 73 015202 (2006)
- Weaver, Richard L. Transport and localization amongst coupled substructures. Phys Rev E 73 036610-1-8 (2006)
- R. Weaver, O. Lobkis. Diffuse fields in ultrasonics and seismology. Geophysics 71:4, SI5-SI9 (2006).
- U. Kuhl, H. Stockmann, R. Weaver. Classical wave experiments on chaotic scattering. J. Phys. A: Math. Gen. 38, 10433-10463 (2005).
- N. Wolff, R. Weaver. Towards a theory of wave energy transport in large irregular structures. J. Acoust. Soc. Am. 118:1, 222-231 (2005).
- R. Weaver. Information from Seismic Noise. Science. 11:307, 5715 (2005).
- Eotvos Award of the European Association of Geoscientists and Engineers (2009)
- Society of Experimental Mechanics, Hetenyi Award (2004)
- Fellow, Acoustical Society of America (1996)