Ultrasound velocity

Henderson RD, Steinman DA, Ehasziw M, Barnett HJ. Effect of contralateral carotid artery stenosis on carotid ultrasound velocity measurements. Stroke 2000 31(ll) 2636-2640. 

P. V. Nelson, M. J. W. Povey, Y. Wang 2001, (An ultrasound velocity and attenuation scanner for viewing the temporal evolution of a dispersed phase in fluids), Rev. Sci. Instrum. 72, 4234. 

V. J. Pinfield, M. J.W. Povey, E. Dickinson 1996, (Interpretation of ultrasound velocity creaming profiles), Ultrasonics 34, 695. 

Ultrasound is by far the most sensitive technique for detecting the initial stages of crystallization. Ultrasound velocity is very sensitive to the state of fat in a dairy emulsion (Figure 21.2) and can be used to follow changes in the amount of solid fat which occurs as the temperature changes. 

Figure 21.2. Characterization of margarine using ultrasound. (A) In-line ultrasound configuration using a single transducer to monitor the solid fat content of margarine. (B) and (C) Multiple transducer configuration for following the evolution of solid fat content and (D) Time evolution of solid fat content measured by NMR of ultrasound velocity.

Holmes, A.K., Challis, R.E., Wedlock, D.J. 1993. A wide bandwidth study of ultrasound velocity and attenuation in suspensions comparison of theory and experimental measurements. J. Coll. Interface Sci. 156, 261-268. 

The degree of emulsification in such materials can also be estimated by the measurement of ultrasound velocity in conjunction with attenuation [4]. It is possible to determine factors such as the degree of creaming (or settling ) of a sample, i.e. the movement of solid particles/fat droplets to the surface (or to the base) [5], Such information gives details, for example, of the long-term stability of fruit juices and the stability of emulsions such as mayonnaise. The combination of velocity and attenuation measurements shows promise as a method for the analysis of edible fats and oils [6], and for the determination of the extent of crystallization and melting in dispersed emulsion droplets [7]. 

Evstefeev, V. N., Skripov, V. P., Chukanov, V. N. (1979) Experimental Determination of Ultrasound Velocity in Superheated Ordinary and Heavy Water. Teplofizika vysokikh temperatur 17, 299-305... 

A related technique is the use of ultrasound velocity measurements [13,14]. The propagation of ultrasound is sensitive to both density and compressibility of the medium. The measuring devices are compact and not very sensitive to fouling. 

It turns out that the accuracy requirement from % is numerically minimal, because k TKj is small compared with the other terms contributing to the values. If the values of % are not known for the mixtures to be studied, they may be sufficiently well approximated by Kr XAKr,A + XBKr3. Otherwise, if the adiabatic compressibility, k, obtained from the ultrasound velocities and densities, is known as a function of the composition, the approximation Kj-= 1.1 x may be applied. 

In order to lay the foundations for a verifiable localization of AE sources, the ultrasound velocity of the compressional wave, which depends on the angle between the wave propagation direction and the fiber direction, has been measured (Fig. 6.7). 

Ultrasound velocity and attenuation All kinds of dispersions, to determine particle size distribution and zeta potential 449-453... 

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. 

Measurement of the 3-dimensional geometry is achieved by ultrasound velocity tomography (Mol, 1981 Mol et al, 1981), whereas measurement of intramural, endo- and epicardial deformations is performed by measuring distances between implanted radiopaque or natural (bifurcations of coronory arteries) markers with help of a biplane X-ray system (Elshuraydeh, 1981 Elshuraydeh et al., 1981). 

Interaction between ultrasound and tissue can be characterized by a number of parameters like speed of propagation, attenuation, absorption coefficients etc. As ultrasound velocity is characteristic for a particular tissue the possibility is opened for ultrasound velocity tomography. The principles hereof and implications for medicine have been described by Greenleaf et al. (1975). In ultrasound velocity tomography transmitters and receivers are positioned around the object under study. Times of flight of ultrasonic pulses from transmitter to receiver are measured accurately. By rotating the transmitters and receivers in a plane around... 

With ultrasound velocity tomography the local speed of ultrasound in a cross section of the subject under study is computed from a large set of ultrasound transmission times. These calculations (reconstructions) are based upon a model that describes the propagation of ultrasound in a medium. In its simplest form the ultrasonic pulses are supposed to travel along straight pathways from transmitter to receiver. The measured transmission times depends on the velocity distribution v(jc, y) in the plane of reconstruction ... 

In our model we aim to incorporate the interrelationship between cardiac muscle mechanics and coronary blood perfusion. In this model geometry of the heart plays an essential role. The method of ultrasound velocity tomography can be useful, as is demonstrated to measure the three-dimensional geometry of the heart in the laboratory with sufficient accuracy. The accuracy (the spatial resolution) of the tomogram depends on the total number of measurements. As the set of equations (lb) can be solved only if the number of variables does not exceed the... 

Afifi and El-Wakil measured the ultrasound velocity in NR/NBR (50/50) blends compatibilized with different weight percentages of NR-g-MA. It was found that at moderate concentrations of compatibilizer (2-6 phr) the ultrasonic velocity was increased. However, incorporating more NR-g-MA (up to 10 phr) decreased this property. This phenomenon was correlated with the degree of compatibility of the blend components. Increased ultrasound velocity relates to stronger interactions at the interfaces, thus better compatibility. The reason behind this is that the ultrasonic properties of the rubber blends are affected by the occurrence of phase inversion and variation of micro-voids within the blend. 

FIG. 11 Schematic presentation of changes in the ultrasound velocity V (arbitrary units) with temperature during the controlled cooling of n-hexadecane in water emulsions, emulsified with Tween-20. Parameters determined are the crystallization temperature and the magnitude of the change in V due to crystallization (AV). Curve 1, control curve 2, in the presence of an impurity (P-170). (Adapted from Ref. 78.)... 

Horvath-Szabo, G. and Hoeland, H., Compressibility determination of silica particles by ultrasound velocity and density measurements on their suspensions. Journal (f Colloid and Interface Science (1996), 177(2), 568-578. 

To obtain the elastic constants of IV SmS the ultrasound velocities of Y-substituted SmS have been measured in the three principal directions by Melcher et al. (1975) and Penney et al. (1975). Apparently similar measurements under pressure on undoped SmS are not possible because the crystals due to the first-order transition acquire micro-cracks which prevent any further ultrasonic measurements. Melcher et al. (1975) show that C44... 

Ott et al. (1977) have reported on a positive c 2 on an undefined TmSe, on the same sample on which also the unexpectedly low compressibility has been observed. It now becomes clear that this sample of TmSe must have had appreciable Tm deficiency because all values are close to the ones of Tmo.g7Se. In contrast, Barth and Giintherodt (1982) have measured the ultrasound velocities with Brillouin scattering in stoichiometric TmSe and computed the elastic moduli. They obtain with ci2 = —68GPa nearly the same value as Boppart et al. (1980a) with ci2 = -57 GPa at room temperature. The values for TmSe are of the same size as in IV SmS, where we computed a Ci2 of —51 GPa from the data of Melchcr et al. (1975). 

A last point shall be made in fig. 76. The temperature dependence of the ultrasound velocity is very different regarding the IV TmSe and the trivalent reference compound Tmo.87Se. Characteristic deviations are found near 60 K for the trivalent Tmo.gvSe which are typical for crystal-field excitations. In fact 60 K corresponds to about 5meV,... 

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