Through transmission ultrasound

Ultrasound through-transmission ultrasound ( ITU) or pulse echo (PE) ultrasound is the primary method for the acceptance of composite laminate materials using an automated scanning system with water-coupled piezoelectric transducers and acceptance standards. Many variations are applicable depending on the material, configuration, thickness, and sensitivity requirements. 

In this paper we propose a multivariable regression approach for estimating ultrasound attenuation in composite materials by means of pulse-echo measurements, thus overcoming the problems with limited access that is the main drawback of through-transmission testing. 

The result from the work shows that we can obtain good approximations of the attenuation values using pulse echo ultrasound. This indicates that it will be possible to replace the through-transmission technique by a pulse echo technique. 

Nestleroth et al. [15], Segal et al. [16] considered some established novel signal processing schemes to assist in adhesive bond inspection. Sinclair et al. [17] and Filimonov [18] employed acoustic resonance methods for dynamic elastic modulus measurements in adhesively bonded structures. Yost and Cantrell [19], Achenbach and Parikh [20] and Nagy et al. [21] considered a nonlinear response of bonded structures to estimate material characteristics. In Achenbach and Parikh [20], failure was preceded by nonlinear behavior of thin boundary layers at the interfaces. Billson and Hutchins [22] considered lasers and EMATS in bond investigations. It was shown that this non-contact technique was reasonable when compared to that obtained by conventional piezoelectric transducers. Ince et al. [23] also characterized bonds with laser-generated ultrasound and through-transmission measurements. 

Ionizing radiation, microwaves, ultrasound, or hypothermia are the major physical agents that can affect the fetus via direct transmission through maternal tissues. In general, the dose required for a physical agent to cause detriment to the fetus surpasses that required to induce maternal toxicity. Mechanical impact or changes in temperature, unless extreme, are likely minimized by the hydrostatic pressure of the womb and maternal homeostatic capabilities. 

Ultrasound reflective spectroscopy application in the analysis of bubbly liquids has been known for many years. This technique is based on the transmission of ultrasound waves through a dispersion, and measuring the velocity and attenuation spectra. 

Novak, E.J. Experimental transmission of lidocaine through intact skin by ultrasound. Arch. Phys. Med. Rehab. 1964, May, 231-232. 

A very important point occurs in the transmission of acoustic power into a liquid which is termed the cavitation threshold. When very low power ultrasound is passed through a liquid and the power is gradually increased, a point is reached at which the intensity of sonication is sufficient to cause cavitation in the fluid. It is only at powers above the cavitation threshold that the majority of sonochemical effects occur because only then can the great energies associated with cavitational collapse be released into the fluid. In the medical profession, where the use of ultrasonic scanning techniques is widespread, keeping scanning intensities below the cavitation threshold is of vital importance. As soon as the irradiation power used in the medical scan rises above this critical value, cavitation is induced and, as a consequence, unwanted even possibly hazardous chemical reactions may occur in the body. Thus, for both chemical and medical reasons there is a considerable drive towards the determination of the exact point at which cavitation occurs in liquid media, particularly in aqueous systems. Historically, therefore, the determination of the cavitation threshold was one of the major drives in dosimetry. 

In principle, the ultrasonic techniques described for solid-liquid flow measurement can be applied to measure air flow rate and particle velocity. Direct measurement of air flow rate by measuring upstream and downstream transit times has been demonstrated. But, the Doppler and cross-correlation techniques have never been applied to solid/gas flow because the attenuation of ultrasound in the air is high. Recent developments have shown that high-frequency (0.5-MHz) air-coupled transducers can be built and 0.5-MI Iz ultrasound can be transmitted through air for a distance of at least 1 in. Thus, the cross-correlation technique should be applicable to monitoring of solid/gas flow. Here, we present a new cross-correlation technique that does not require transmission of ultrasonic waves through the solid/gas flow. The new technique detects chiefly the noise that interacts with the acoustic field established within the pipe wall. Because noise may be related to particle concentration, as we discussed earlier, the noise-modulated sound field in the pipe wall may contain flow information that is related to the variation in particle concentration. Therefore, crosscorrelation of the noise modulation may yield a velocity-dependent correlation function. 

There have been a number of previous attempts to relate the appearance of higher harmonics in the transmission of ultrasound through bonded structures to the quahty of the bonds [2-9]. Commonly used is the so-called nonhnearity parameter y 2, a measure of the generation of only the second harmonic [2], and the distortion factor K which describes the complete nonlinear content of the response [7]. In this paper cahbrated measurements on samples consisting of two aluminum plates joined together by a thin epoxy layer are presented and discussed. The amphtudes and phases of the ultrasonic waves transmitted through the bond are considered. The measurements are related to the results of destructive tensile tests of the adhesive layer. 

In this paper a method is described to measure accurately the three-dimensional geometry of the isolated, working canine heart during the cardiac cycle. Times of flight of ultrasonic pulses are measured with high accuracy for many directions through the object under study. These transmissions times are then used to reconstruct the ultrasound velocity distribution in the plane of measurement. 

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