Ultrasonic propagation

Vanhille C, Campos-Pozuelo C (2008) Nonlinear ultrasonic propagation in bubbly liquids A numerical model. Ultrasound Med Biol 34 792-808... 

After understanding the generation of various free radicals as a result of ultrasonic propagation and cavitation in pure water as well as in the presence of different gases, we can perhaps understand the aqueous chemical reactions better. However, for the sake of simplicity, all reactions involving inorganic species, have been broadly classified into following sections and would be taken up one by one... 

The objectives of this chapter are to introduce the basic concepts of ultrasonic propagation in materials, to describe some of the most important methods for measuring and interpreting ultrasonic measurements, and to outline existing and possible applications of the technique in the food industry. 

Relationships can either be established in an empirical fashion, or by using theories which describe ultrasonic propagation in materials (see section 4). To utilize the full potential of ultrasound for characterizing food materials it is important to choose the most suitable method of carrying out the measurements and to carefully analyze the data. Many applications have failed in the past because workers have used poorly designed experiments or have interpreted measurements in an inappropriate manner. 

In non-ideal mixtures, or systems where scattering of ultrasound is significant, the above equations are no longer applicable. In these systems the ultrasonic properties depend on the microstructure of the system, and the interactions between the various components, as well as the concentration. Mathematical descriptions of ultrasonic propagation in emulsions and suspensions have been derived which take into account the scattering of ultrasound by particles [20-21]. These theories relate the velocity and attenuation to the size (r), shape (x) and concentration (0) of the particles, as well as the ultrasonic frequency (co) and thermophysical properties of the component phases (TP). 

Measurements of the velocity and attenuation, usually as a function of frequency, can be used to provide valuable information about a system, e.g. microstructure. Theories are available which describe ultrasonic propagation in emulsions, suspensions, bubbly liquids, laminated solids, porous solids, fibrous materials and a number of other materials [20-29],... 

Table 11.2 Crosslink density, glass transition temperature, and Young s modulus (Et from tensile test at 10 3, s 1 strain rate, Eu from ultrasonic propagation at 5 MHz frequency) for triglycidyl aminophenol-diaminodyphenylmethane-aniline (TGAP-DDM-AN) networks. (After Morel et a ., 1989.)... 

Since the unrelaxed bulk modulus, Ku e.g., determined by ultrasonic propagation velocity measurements, is a good measure of the cohesive energy density, CED (Ku 11 CED Chapter 10), and CED gives a good indication of the overall material s polarity, one can expect a correlation between Ku and W. This is shown in Fig. 14.3 for the amine-epoxy and styrene-vinyl ester networks. The following relationship is found ... 

A variety of experimental techniques are available for the investigation of the electron-lattice interaction. For static phenomena such as thermal expansion and magnetostriction one can use dilatometric and X-ray techniques. For dynamic effects such as elastic constant measurements, ultrasonic propagation and phonon dispersion the methods of sound velocity and attenuation measurements, and inelastic neutron or light scattering are available. In addition high-pressure work can give valuable information for some quantities. 

Golding, B. Barmatz, M. (1969). Ultrasonic propagation near the magnetic critical point of Nickel, Physical Review Letters, 23 (5), p>p. 223. 

Characteristics Figures 33.2 and 33.3 show the appearance and the scanning electron microscope (SEM) image of an aerogel synthesized by the above process, respectively. Density was calculated from the volume and weight. The acoustic velocity was calculated from thicknesses and ultrasonic propagation time (about 500 kHz). 

J. Pellam, J.R. Galt, Ultrasonic Propagation in Liquids I. Application of pulse technique to velocity and absorption measurements at 15 megacycles. J. Chem. Phys. 14(10), 608-614 (1946). doi 10.1063/1.1724072... 

The response time of the nematic to an absorbed energy pulse is determined by the order parameter response. Here a connection can be made to experiments on ultrasonic propagation. The order parameter cannot change faster than a molecular vibration period. Since S is determined by the interactions of many molecules, the characteristic time is much longer than the molecular time scale. Moreover, as the phase transition point is approached, there is a slowing of order parameter response typical of critical phenomena. This has been verified by ultrasonic experiments. Therefore, the thermal grating response time should be comparable with the ultrasonic data. ... 

Figure 26 Effects of scattering from microcrystallites on the ultrasonic propagation...

---