T. C. Yang
Naval Res. Lab., Washington, DC 20375
Vector Res. Co., 2101 E. Jefferson St., Rockville, MD 20852
Low-frequency reverberation data received on a large aperture planar array of hydrophones are used to estimate the under-ice scattering strength over a basin wide area. The result is interpreted as a large scale under-ice keel distribution which, unlike the ice surface ridge distribution, has not been measured over a wide area. The reverberation data were collected during the CEAREX 89 experiment using explosive sources. Scatterer localization was performed for each time segment. The range-bearing ambiguity distributions at depth near the surface was range gated according to estimated two-way travel times, and combined to form the ambiguity surface for a large area. Ice keel distribution is obtained by removing the two-way transmission loss to and from the surface scatterers. This image is compared with that obtained using conventional beamforming techniques.
Standards Committee S2 on Mechanical Shock and Vibration. Working group chairs will present reports of their recent progress on writing and processing various shock and vibration standards. There will be a report on the interface of S2 activities with those of ISO/TC 108 (the Technical Advisory Group for ISO/TC 108 consists of members of S2, S3, and other persons not necessarily members of those committees) including a report on the current activities of ISO/TC 108, and its most recent meeting, which took place in London, United Kingdom, from 22 March to 2 April 1993.