Wavelength, ultrasonic system

It is also common to compare materials in terms of attenuation per wavelength (measured in dB) because the size of an experiment or ultrasonic system is usually an important underlying factor to consider and, generally, the size of the experiment in proportion to the wavelength. Table IV gives some typical attenuation values. 

Fig. 7. MR detection of ultrasonic waves oscillating at 515 kHz. (a) Phase image of a phantom without insonation. (b) Phase image with 40 W peak power insonation. In the NMR sequence 50,000 cycles of synchronized sine-shaped motion-sensitizing gradient were applied. Arrows indicate the null-gradient positions of the dedicated gradient coil system. Wavelength is around 2.9 mm and peak matter displacement is around 120 nm. From Ref. 30, reprinted by permission of Wiley-Liss, Inc., a subsidiary of John Wiley Sons, Inc.

Sensitivity is the ability of an ultrasonic test system to detect the presence of small defects. One of the factors affecting sensitivity is the wavelength of the signal in that the shorter the wavelength the higher the sensitivity... 

The transmitting frequency / of the UVP-DUO systems is 4 MHz in all tests. The ultrasound wavelength X is 370 pm and the sound velocity in water c is 1,480 m/s. 100 mm ion exchange (Diaion) particles are added to the flow as flow tracers their ability to follow the liquid flow has been assessed using Basset s analysis (Melling, 1997). Owing to theoretical considerations, the size of the flow tracers must be larger than one quarter of the emitted ultrasonic burst (Met-Flow, 2002). 

It is relatively easy to determine an empirical correlation line to measure the solids content of a mixture of soluble and insoluble fats (a good straight line was shown up to ( ) = 0.5), but these authors (14) were also able to show that the Wood equation (Eq. 2) may also be used to give some theoretical basis to the measurement. For a two-phase system with small density differences between the phases and particle sizes less than ultrasonic wavelength, the density (p) and adiabatic compressibility (K) in Equation 2 are given by volume fraction (< )) weighted averages K = (1 - ( ))Kj + ( )K2 and p = (1 - ( ))P[ + ( )P2 (subscripts 1 and 2 refer to the... 

Scattering of ultrasonic waves dominates over other types of losses in the intermediate wavelength regime (X rp), which represents the case of a system with rather coarse particles (>10 pm) subjected to rather high frequencies (>10 MHz). In the IWR the interaction of ultrasound with the disperse system results in the generation of many types of different waves, and thus many more scattering coefficients are required for the evaluation of the attenuation due to scattering. 

The variation in the orientation of the molecules in the ultrasonic field is observed as a system of alternating light and dark bands, the width and contrast of which depend on the ultrasound intensity. The distance between the centers of the light bands is of the order of the ultrasound wavelength [9, 12, 13, 21, 22, 27, 29, 35, 38-40]. The band configurations depend on the cell structure, the acoustic boundary conditions and the mutual orientation of the wavevector and director these clearing patterns may be distorted by nonuniformity of the wave field inside the ultrasonic beam. 

At least two nondestmctive evaluation methods have been suggested for the visualization of the internal structure of an opaque nanoscaled thin film system and to characterize the same by instruments utilizing basic features of ultrasoimd (e.g., reflection, transmission, refraction, and diffraction). One is a laser-based ultrasonic technique which is known as picosecond acoustics. Acoustic waves with frequencies ranging from approximately 10 GHz to 1.0 THz, corresponding to acoustic wavelengths in the range from approximately 5 to 500 nm may be generated and detected with a... 

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