Thursday, March 7, 1996 4:00 p.m. Dr. Mark F. Hamilton Mechanical Engineering Department The University of Texas at Austin Nonlinear effects in surface waves, like those in bulk elastic waves, are enhanced dramatically by microinhomogeneous features such as cracks and grains that are common in rocks. Since surface waves experience less geometrical spreading loss than…
Friday, March 1, 1996 4:00 p.m. Dr. David T. Blackstock Mechanical Engineering Department The University of Texas at Austin and Applied Research Laboratories The history of developments in nonlinear acoustics, from Euler (1755) to Lord Rayleigh (1910) is described. Results that are taken for granted today, such as the propagation speed for a finite-amplitude wave…
Friday, February 23, 1996 4:00 p.m. Dr. Martin Frenz Biomedical Engineering The University of Texas at Austin Conversion of energy from a laser generated heat pulse to acoustic stress in an absorbing liquid is studied in detail. Pulses with a duration of 6ns created by an optical parametric oscillator (OPO) were used. The laser radiation…
Friday, February 16, 1996 4:00 p.m. Dr. Stephan J. Bless Institute for Advanced Technology The University of Texas at Austin This lecture will start with a review of some basic principles of dynamic compression by shock waves, and then consider results for glass, which is a material of particular current interest, and which exhibits interesting…
Friday, February 9, 1996 4:00 p.m. Dr. Claes Hedberg Department of Mechanics Royal Institute of Technology Stockholm, Sweden This seminar is dedicated to modulated, plane, weak shock waves where the nonlinear and dissipative effects are of the same order. Such waves are well described by the Burgers equation. In the first part of the seminar,…
Friday, January 26, 1996 4:00 p.m. Paul B. Umbanhowar Department of Physics The University of Texas at Austin Pattern formation in thin layers of vertically vibrated granular material has been investigated as a function of oscillation frequency, acceleration amplitude, and layer thickness. Above a critical acceleration of approximately 2.5g (where g is the acceleration due…
Friday, January 19, 1996 4:00 p.m. Dr. Nicholas P. Chotiros Applied Research Laboratories The University of Texas at Austin Wave propagation in water-saturated sand is modeled using Biot’s theory. A unique feature of Biot’s theory is the prediction of two compressional waves, in addition to the shear wave. The experimental data are reviewed. Measurements of the speeds…
Friday, December 8, 1995 4:00 p.m. Philippe Blanc-Benon Centre Acoustique, Ecole Centrale de Lyon Lyon, France One of the most interesting features of sound is that its propagation characteristics are greatly influenced by the medium through which it travels. Through the processes of convection, refraction and scattering, acoustic waves may be bent, attenuated, or amplified.…
Monday, December 4, 1995 3:00 p.m. Monica Obermier Electrical Engineering Department The University of Texas at Austin Accurate acoustical measurements in a reverberant enclosure are very important for applications which range from determining the sound power output of noisy machinery to measurement of the sound transmission loss of partitions. The sound power can be determined…
Friday, November 17, 1995 4:00 p.m. William A. Engblom Aerospace Engineering and Engineering Mechanics Department University of Texas at Austin There is substantial interest in increasing the flight speed of kinetic energy anti-armor penetrators. Unfortunately, in the range of interest (Mach 6 to 12), it is expected that the aerodynamic heating of nose regions of…
Friday, November 10, 1995 4:30 p.m. Michael Bailey Mechanical Engineering Department and Applied Research Laboratories The University of Texas at Austin An underwater bubble grows in response to a strong negative acoustic pulse and then collapses because of inertial forces. An auxiliary positive pulse, delayed to arrive after collapse begins, is shown numerically and experimentally…
Friday, November 10, 1995 4:00 p.m. Penelope Menounou Mechanical Engineering Department The University of Texas at Austin The Helmholtz-Kirchhoff integral is used to predict the edge wave on axis behind a disk (or an aperture) that has a ragged edge. The ragged edge is modeled as being made up of N arcs of equal angle…
Friday, November 3, 1995 4:00 p.m. Won-Suk Ohm Mechanical Engineering Department The University of Texas at Austin The performance of an irregularly-edged barrier is investigated numerically. The main motivation of this work is Steve Ho’s model experiment on an irregularly-edged barrier (reported in a recent acoustics seminar). The simplest case of a plane N wave…
Thursday, November 2, 1995 3:00 p.m. Dr. Won-Kyu Moon Mechanical Engineering Department The University of Texas at Austin The thermal variable is successfully included into a model for the piezoelectric thickness vibrator by use of the bond graph approach. In the process of developing this model, a proper thermodynamic material property model of piezoelectric ceramics…
Friday, October 27, 1995 4:00 p.m. Steven Younghouse Mechanical Engineering Department The University of Texas at Austin Although recorded music has become an integral part of our culture, most people do not know about the methods and equipment used to make a professional recording. The layman might say that some sort of “studio magic” is…
Friday, October 20, 1995 4:00 p.m. Tom Kite Electrical Engineering Department The University of Texas at Austin The last fifteen years have seen an enormous improvement in the quality of sound recorded on film, with Dolby Stereo becoming the standard distribution format. Magnetic audio, with four and even six tracks, was the system of choice…
Friday, October 13, 1995 4:00 p.m. Kenneth Gallia Physics Department The University of Texas at Austin A method for acoustically tracking airborne supersonic projectiles is discussed. An array of transducers is used to detect the shock wave generated by the passage of a supersonic projectile. The time of arrival of the shockwave at each sensor…
Friday, October 6, 1995 4:00 p.m. Steve Ho Mechanical Engineering Department The University of Texas at Austin A preliminary model experiment showed that a random-edged barrier provided a higher insertion loss than a straight-edged barrier of the same average height. Based on this promising result, we have conducted a 3-level full factorial model experiment on…
Friday, September 22, 1995 4:00 p.m. Dr. David P. Knobles The Applied Research Laboratories The University of Texas at Austin Modeling acoustic propagation in shallow water and/or littoral ocean environments is a difficult problem in present day computational ocean acoustics. Unlike deep water propagation, the propagation of sound in shallow water waveguides is usually characterized…
Detection Using Biocorrelations Friday, September 15, 1995 4:00 p.m. Dr. Melvin J. Hinich Mike Hogg Professor of Local Government Consider the problem of detecting an unknown waveform in additive noise. The waveform may be unknown due to changes in a known waveform used in active radar or sonar, or it may be a waveform used…