NOTES

1.. The ultrasonic measurement system contained: an IF oscillator and quadrature phase-sensitive detectors; a direct digital synthesizer; a high-power gated RF amplifier; a broadband RF receiver; a mixer and IF amplifier; gated analog integrators; a coherent timer; and a 12-bit analog-to-digital converter (A/D converter).

REFERENCES

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SUPPLIERS

Ritec, Inc., 60 Alhambra Rd., Ste. 5, Warwick, R.I. 02886

SONIX, Inc., 8700 Morrissette Dr. Springfield, Va. 22152

Staveley Sensors, Inc., 91 Prestige Park Circle, East Hartford, Conn. 06108-1918

Inframetrics, Inc., 16 Esquire Rd., North Billerica, Mass. 01862

AUTHOR INFORMATION

ALISON MURRAY is an assistant professor in the art conservation program at Queen's University, Kingston, Ontario. She received her honors B.Sc. in chemistry from McGill University and her M.Sc. and Ph.D. degrees in materials science and engineering with a specialization in conservation science from the Johns Hopkins University. Her graduate work was funded by a predoctoral conservation science fellowship from the Conservation Analytical Laboratory at the Smithsonian Institution. She held a fellowship in the Analytical Research Services Division at the Canadian Conservation Institute and was funded by the Samuel H. Kress Foundation for a work term in the Scientific Department at the National Gallery in London. Her research interests include nondestructive testing and digital imaging systems. Address: Art Conservation Program, Art Centre Extension, Queen's University, Kingston, Ont., Canada K7L 3N6.

MARION F. MECKLENBURG is a senior research engineer at the Conservation Analytical Laboratory, Smithsonian Institution. He has worked for 20 years as a paintings conservator in the United States. He holds B.Sc., M.Sc., and Ph.D. degrees in structural engineering from the University of Maryland. His research areas are in the mechanics of materials and the effects of the environment on the mechanical properties of materials. Address: Conservation Analytical Laboratory, Smithsonian Institution, Washington, D.C. 20560.

C. M. FORTUNKO heads the composite material characterization group, part of the Material Reliability Division of the Materials Science and Engineering Laboratory at the National Institute of Standards and Technology. He holds a B.Sc. degree from Tufts University and a Ph.D. degree from Stanford University, both in applied physics. He has also consulted for a number of industrial and educational institutions. Address: Materials Reliability Division, National Institute of Standards and Technology, Boulder, Colo. 80303.

ROBERT E. GREEN is director of the Center for Nondestructive Evaluation, professor and former chairman of the Department of Materials Science and Engineering, and a staff member of the Applied Physics Laboratory of the Johns Hopkins University. He received his Ph.D. in physics from Brown University. He has served as a technical editor for the ultrasonics volume of the American Society for Nondestructive Testing Nondestructive Testing Handbook, is on the advisory board of the newsletter Materials and Processing Report, and is on the editorial board of the journal Research in Nondestructive Evaluation. Address: Materials Science and Engineering Department, Johns Hopkins University, Baltimore, Md. 21218.