scholarly journals Theoretical study of the pulsed ultrasonic field radiated by a nonuniformly vibrating planar piston source

1981 ◽  
Vol 69 (S1) ◽  
pp. S60-S60
Author(s):  
Gerald R. Harris
Keyword(s):  
Theoretical Study ◽  
Ultrasonic Field ◽  
Pulsed Ultrasonic

Near-Field Uniform Beams for Pulsed Doppler Ultrasound

1980 ◽  
Vol 2 (4) ◽  
pp. 324-337 ◽  
Author(s):  
Chong-Cheng Fu ◽  
Sharbel E. Noujaim ◽  
Robert S. Jaffe ◽  
Levy Gerzberg ◽  
Roger D. Melen
Keyword(s):  
Flow Measurement ◽  
Pattern Analysis ◽  
Ultrasonic Transducer ◽  
Near Field ◽  
Ultrasonic Field ◽  
Beam Pattern ◽  
Field Approach ◽  
Pulsed Doppler Ultrasound ◽  
Pulsed Ultrasonic

A mathematical model for the beam pattern of a pulsed ultrasonic transducer is introduced. Beam-pattern analysis and simulation of a circular transducer based on this model agree well with the experimental results. It is demonstrated that, in its near field, the pulsed transducer is capable of generating a good approximation to a uniform ultrasonic field which cannot be achieved with a cw transducer. Preliminary error analysis indicates that the near-field beam pattern of the pulsed transducer is suitable for quantitative blood-flow measurement, and design criteria are developed for this application. A prototype has been fabricated and tested in in-vitro experiments, and the results verify the feasibility of the quantitative blood flowmeter principle and the pulsed-transducer near-field approach to the formation of uniform beams.

Time Reversal Focusing Applied to Lithotripsy

1996 ◽  
Vol 18 (2) ◽  
pp. 106-121 ◽  
Author(s):  
Jean-Louis Thomas ◽  
François Wu ◽  
Mathias Fink
Keyword(s):  
Time Reversal ◽  
Surrounding Medium ◽  
Ultrasonic Field ◽  
Ultrasonic Waves ◽  
Least Mean Square ◽  
Transducer Arrays ◽  
Sharp Focusing ◽  
Spatial Coordinates ◽  
Pulsed Ultrasonic ◽  
Focal Zone

Time reversal of ultrasonic field allows a very efficient approach to focusing pulsed ultrasonic waves through lossless inhomogeneous media. Time reversal mirrors (TRM) are made of large transducer arrays, allowing the incident acoustic field to be sampled, time reversed and re-emitted. Time reversal processing permits a choice of any temporal window to be time reversed, allowing operation in an iterative mode. In multitarget media, this process converges on the most reflective target, i.e., the dominant scatterer. In this paper, the time reversal process is applied to track, in real time, a moving gall bladder or kidney stone embedded in its surrounding medium. We investigate the feasibility of a piezoelectric shock wave generator in which the focal zone is moved electronically to track the stone during a lithotripsy treatment. We show that TRM allows us to obtain sharp focusing on one bright point of the stone. The time of flight profile is then determined and used in a least-mean-square method to calculate the spatial coordinates of the stone.

Adsorption of H2O and H2S on the (100) surface of silicon. A theoretical study

1987 ◽  
Vol 84 ◽  
pp. 799-803 ◽  
Author(s):  
Vincenzo Barone ◽  
Francesco Lelj ◽  
Nino Russo ◽  
Marirosa Toscano
Keyword(s):  
Theoretical Study
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