The Doppler technique has traditionally been the method used to extract motion information from ultrasonic echoes reflected by moving tissues. The Doppler technique has been around for a long time, and has been extensively reviewed and analyzed in the literature. Recently, time-domain methodologies for estimating tissue motion have gained in popularity. Time-domain methods have advantages over Doppler methods in many applications, and as of yet have not been comprehensively reviewed. An overview of time-domain techniques that have appeared in the literature over the past few years is presented. Their potential advantages over Doppler are examined, and the individual techniques are compared. >

Current time-domain methods for assessing tissue motion by analysis from reflected ultrasound echoes-a review

We demonstrate that a simple acoustic time-of-flight experiment can measure the state of charge and state of health of almost any closed battery. An acoustic conservation law model describing the state of charge of a standard battery is proposed, and experimental acoustic results verify the simulated trends; furthermore, a framework relating changes in sound speed, via density and modulus changes, to state of charge and state of health within a battery is discussed. Regardless of the chemistry, the distribution of density within a battery must change as a function of state of charge and, along with density, the bulk moduli of the anode and cathode changes as well. The shifts in density and modulus also change the acoustic attenuation in a battery. Experimental results indicating both state-of-charge determination and irreversible physical changes are presented for two of the most ubiquitous batteries in the world, the lithium-ion 18650 and the alkaline LR6 (AA). Overall, a one- or two-point acoustic measurement can be related to the interaction of a pressure wave at multiple discrete interfaces within a battery, which in turn provides insights into state of charge, state of health, and mechanical evolution/degradation.

Electrochemical-acoustic time of flight: in operando correlation of physical dynamics with battery charge and health

Ultrasonic Transducers for Materials Testing and Their Characterization

A random signal flaw detection system has been devel- oped with a signal-to-noise ratio enhancement approximately10 000 times greater than conventional ultrasonic pulse-echo systems.Ex- perimental results are presented which demonstrate thatthe system can penetrate highly absorbent materials suchas plexiglass,high- density siliconnitride and alumina at greater distances than is possible with conventional pulse-echo systems. The systemis shown to detect echoes fromgrain boundarieswhich indicate that the system could have applications in microstructure evaluationof materials. Finally, the possible applicationof this systemto accurate sound velocity mea- surement in strongly absorbing materialsis discussed.

Evaluation of a Random Signal Correlation System for Ultrasonic Flaw Detection

When ultrasonically imaging sharp-edged targets en- closed by a strongly scattering medium, such as flaws in grainy metal or organ outlines in tissue, the target signal is frequently obscured by time-invariant "clutter" echoes generated by the microstructure of the environment. The target visibility with respect to the clutter can be improved by compounding statistically independent echoes of each re- gion of the medium. Algorithms for accomplishing this are analyzed and compared, in which the independent signals are obtained by split- ting each ,4-line echo into nonoverlapping frequency bands. One of these algorithms, in which compounding is performed by choosing the min- imum squared signal at each range, is found to provide considerable improvement in signal to clutter ratio and mixed results in receiver operating characteristic at the expense of resolution.

Analysis and Comparison of Some Frequency Compounding Algorithms for the Reduction of Ultrasonic Clutter

Application of random signal correlation techniques to ultrasonic flaw detection

: This report describes four areas of work In the first area random signal beam forming techniques are developed which make it possible to transmit several independent beams from a phased array using the same number of incoherent noise sources Following this ultrasound beam scanning techniques are demonstrated in which random signal correlation systems and RF correlation systems using quadrature phase techniques are used in methods for scanning the intensity profile of ultrasound transducer beams using respectively broadband signals and narrow band signals In addition two types of deconvolution procedure are described and demonstrated which have been successful in improving the effective resolution of ultrasound correlation systems when viewing surface features Finally the design and construction of a random signal correlation system is described which uses an electronic delay line (Author)

http://ieeexplore.ieee.org/iel5/10274/32707/01533371.pdf

G.R. Cooper

Papers

Application of random signal correlation techniques to ultrasonic flaw detection

Random Signal Flaw Detection