Ultrasonic wave length

Further evidence in favour of the amorpho-crystalline texture was recently provided by Ranby [46]. In a series of his papers several questions connected with the microstructure of cellulose are made clear. Cellulose to be examined in an electron microscope was initially dispersed by means of ultrasonic waves. In this way Ranby has isolated elementary thread-like micelles of about 70 A dia. Any dimension characterizing the length of the micelle is however missing. 

Observations of the liver reveal an anatomically unique and complicated structure, over a range of length scales, dominating the space where metabolism takes place. Consequently, the liver was considered as a fractal object by several authors [4,248] because of its self-similar structure. In fact, Javanaud [275], using ultrasonic wave scattering, has measured the fractal dimension of the liver as approximately df 2 over a wavelength domain of 0.15-1.5mm. 

The study of molecular interactions in liquid mixtures is of considerable importance in the elucidation of the structural properties of molecules. Interactions between molecules influence the structural arrangement and shape of molecules. Dielectric relaxation of polar molecules in non-polar solvents using microwave absorption has been widely employed to study molecular structures and molecular interactions in liquid mixtures [81]. Ever since Lagemann and Dunbar developed a US velocity approach for the qualitative determination of the degree of association in liquids [82], a number of scientists have used ultrasonic waves of low amplitude to investigate the nature of molecular interactions and the physico-chemical behaviour of pure liquids and binary, ternary and quaternary liquid mixtures, and found complex formation to occur if the observed values of excess parameters (e.g. excess adiabatic compressibility, intermolecular free length or volume) are negative. These parameters can be calculated from those for ultrasonic velocity (c) and density (p). Thus,... 

Figure 2 Ultrasonic absorption per wave length a function of frcquenq.- for aqueous solution of Ci. TAB added by C TAB. Concentration of CmTAB added are open circles 1.86 10 M Closed circles 4 09 10" M. Open mangle 1 49 10 - M...

X = wave length of ultrasound, A = crystal size) perpendicular to the beam axis and a quarter of the pulse length along the beam axis. Taking typical values of A 10mm for conventional probes, A = 6mm for a SAFT probe, R = 100 mm and X 1 mm the lateral resolutions of the conventional pulse echo technique and SAFT are 10 mm and 1.5 mm respectively. Thus SAFT substantially Improves the lateral resolution of ultrasonics. SAFT therefore finds applications In... 

The depolymerising action of ultrasonic waves, which has already been mentioned in Section 5 seems to be restricted to intermediate concentrations According to Schmid it is essential that the macromolecules should form a coherent structure, since presumably the isolated molecule is too small compared with the wave-length to be aiEfected to any appreciable extent. On the other hand, at very high concentrations the structure becomes so strong that it is able to withstand the action of ultrasonics. This explains why the optimum effect is observed at intermediate con-... 

In this paper, we have exposed a solution to improve the resolution in Low Frequency Ultrasonic Tomography. Since the basic principle of ultrasonic reflection tomography prohibits the inspection of objects with strong contrast and large extension, we turn down the frequency of the transducer, in order to increase the penetration length of the wave and the validity of the method. But this is done at the expense of resolution. 

Erequendy, a single ultrasonic transducer serves both as the sender of the ultrasonic pulse and as a receiver for the sound waves reflected from surfaces and interior discontinuities. The receiver transforms the stress pulse back into electrical oscillations. AH of the signals are displayed on an oscilloscope screen for interpretation. Eor a material of length E having a wave speed C, the anomaly shown in Eigure 4 would reflect a signal back to the... 

An ultrasonic horn transducer consists of a transducer unit attached to a horn (rod) usually made from titanium alloy and which has a length a multiple of half-wavelengths of the sound wave. For the commonly encountered 20-kHz horn this corresponds to 12.5 cm. The horn is then partially inserted into the fluid medium of interest and intense ultrasound is generated at its tip so that, for adequately large intensities, a cloud of cavitation bubbles is visible. This arrangement permits significantly higher ultrasonic intensities (10-1000 W cm ) to be applied than are achievable with a bath. 

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