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DJ Tang

Senior Principal Oceanographer

Email

djtang@apl.washington.edu

Phone

206-543-1290

Biosketch

Dr. Tang research encompasses ocean bottom interacting acoustics, especially problems involving horizontal, as well as vertical, environmental variabilities; acoustic tomography of sediments; sediment conductivity; wave propagation in range-dependent waveguides; array processing; acoustic scattering by gas bubbles and man-made objects in sediments.

Department Affiliation

Acoustics

Education

B.S. Physics, University of Science and Technology, Hefei, China, 1981

M.S. Physics/Acoustics, Institute of Acoustics, Beijing, China, 1985

Ph.D. Oceanographic Engineering, MIT/WHOI, 1991

Publications

2000-present and while at APL-UW

Six decades of evolution in underwater acoustics at the Applied Physics Laboratory, University of Washington

Williams, K.L. D. Tang, P.H. Dahl, E.I. Thorns, D.R. Jackson, and T.E. Ewart, "Six decades of evolution in underwater acoustics at the Applied Physics Laboratory, University of Washington," J. Acoust. Soc. Am., 137, 2331, doi:10.1121/1.4920514, 2015

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1 Apr 2015

Professor Joe Henderson of the University of Washington physics department formed the Applied Physics Laboratory during WWII. The lab’s initial efforts were to redesign the magnetic influence exploders used in US torpedoes. One of the lab’s first Underwater Acoustics (UA) successes was development of transducers used in the Bikini Atoll Able test (1946). Those transducers, used to trigger other instrumentation, proved critical. Combining UA and torpedo expertise brought APL-UW to the forefront of tracking range design, construction and deployment in Dabob Bay, Nanoose, and St. Croix in the 1950s and 1960. Understanding the torpedo behavior seen in tracking ranges required measuring both the ocean environment and the acoustics within that environment. Making those measurements, as well as development and testing of models based on those measurements, also became standard operating procedure at APL, led in the 50’s by Murphy and Potter. This blueprint of applied research motivating basic research, and the pursuit of basic research via ocean experiments and high fidelity modeling, continues to this day. The presentation will follow this evolution. APL-UW ocean experiments carried out during that time, as well as notable APL-UW research papers, technical reports, computer codes and textbooks, will be used as guideposts.

Overview of the reverberation component of TREX13

Hefner, B.T., and D. Tang, "Overview of the reverberation component of TREX13," Proc., 2nd International Conference and Exhibition on Underwater Acoustics, 22-27 June, Rhodes, Greece, 144, 2014.

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22 Jun 2014

In the spring of 2013, a shallow water reverberation experiment was conducted to measure contemporaneous acoustic and sufficient environmental data so detailed model/data comparisons could be achieved and important environmental factors could be identified for different applications. The Target and Reverberation Experiment (TREX13) was sponsored by the US Office of Naval Research and the Strategic Environmental Research and Development Program. It was conducted from April to June of 2013 off the coast of Panama City Beach, Florida, in collaboration with multiple institutions and involving three research vessels: The R/V Sharp, R/V Walton Smith, and the Canadian Force Auxiliary Vessel Quest. From a SONAR viewpoint, reverberation consists of two-way propagation and a single backscatter. Therefore, reverberation, transmission loss, and bottom backscatter were repeatedly measured over a time period of several weeks in the frequency band of 2-10 kHz, along with extensive environmental measurements. To reduce the area over which environmental measurements were needed, the reverberation was measured using a horizontal line array mounted 1 m above the seafloor in 19 m of water. The reverberation, transmission loss, and bottom backscatter were measured along a single beam of the array out to a distance of 7 km. Discussed will be planning and execution of the field experiments, strategies and steps for data analysis, and modeling efforts.

Reverberation clutter induced by nonlinear internal waves in shallow water

Henyey, F.S., and D. Tang, "Reverberation clutter induced by nonlinear internal waves in shallow water," J. Acoust. Soc. Am., 134, EL289, doi:10.1121/1.4818937, 2013.

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1 Oct 2013

Clutter is related to false alarms for active sonar. It is demonstrated that, in shallow water, target-like clutter in reverberation signals can be caused by nonlinear internal waves. A nonlinear internal wave is modeled using measured stratification on the New Jersey shelf. Reverberation in the presence of the internal wave is modeled numerically. Calculations show that acoustic energy propagating near a sound speed minimum is deflected as a high intensity, higher angle beam into the bottom, where it is backscattered along the reciprocal path. The interaction of sound with the internal wave is isolated in space, hence resulting in a target-like clutter, which is found to be greater than 10 dB above the mean reverberation level.

More Publications

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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