Horn vibration

Ultrasonic insertion an ultrasonic transducer (horn) vibrates the insert, which heats by vibrating against the plastic. The advantages and drawbacks of this process are ... 

Reding, F. P., and D. F. Horning Vibrational Spectra of Molecules and Complex Ions in Crystals (V). Ammonia and Deutero-Ammonia. J. chem. Physics 19, 594, 601 (1951). 

Small droplets of a uniform size may be formed by feeding the fluid at a controlled rate through a small orifice in the tip of a horn vibrating ultrasonically in a longitudinal mode. The process parameters influencing ultrasonic liquid processing are energy and intensity, pressure, temperature, and viscosity. 

Recently, dry wire-pipe ESPs are being cleaned acoustically with sonic horns (Flynn, 1999). The horns, typically cast metal horn bells, are usually powered by compressed air, and acoustic vibration is introduced by a vibrating metal plate that periodically interrupts the airflow (AWMA, 1992). As with a rapping system, the collected particulate slides downward into the hopper. The hopper is evacuated periodically, as it becomes full. Dust is removed through a valve into a dust-handling system, such as a pneumatic conveyor, and is then disposed of in an appropriate marmer. 

Ultrasonic head forming and welding is a fast assembly technique. It is a very rapid operation of about 2 seconds or less and lends itself to full automation. In this process high-frequency vibrations and pressure are applied to the products to be joined, heat is generated at the plastic causing it to flow, and, when the vibrations cease, the melt solidifies. The heart of the ultrasonic system is the horn, which is made of a metal that can be carefully tuned to the frequency of the system. The manufacture of the horn and its shape is normally developed by the manufacturer of the equipment. The results from this operation are not only economical, but also most satisfactory from a quality control standpoint. 

This technique is used mainly for nonpolar compounds. Typically a small aliquot of soil (10-30 g) is dried by mixing with sodium sulfate prior to extraction. Next, the sample is extracted with a solvent for 10-20 min using a sonicator probe. The choice of solvent depends on the polarity of the parent compound. The ultrasonic power supply converts a 50/60-Hz voltage to high-frequency 20-kHz electric energy that is ultimately converted into mechanical vibrations. The vibrations are intensified by a sonic horn (probe) and thereby disrupt the soil matrix. The residues are released from soil and dissolved in the solvent. 

Coordinates such as these, which have the symmetry properties of the point group are known as symmetry coordinates. As they transform in the same manner as the IRs when used as basis coordinates, they factor the secular determinant into block-diagonal form. Thus, while normal coordinates most be found to diagonalize the secular determinant, the factorization resulting horn the use of symmetry coordinates often provides considerable simplification of the vibrational problem. Furthermore, symmetry coordinates can be chosen a priori by a simple analysis of the molecular structure. 

Dahlem O, Reisse J, Halloin V (1999) The radially vibrating horn A scaling up possibility for sonochemical reactions. Chem Eng Sci 54 2829-2838... 

Tool attached to horn which conducts ultrasonic vibrations to workpiece... 

Let us now turn our attention to the application of the sound wave to a liquid since this is the medium of importance to the practising chemist. The sound wave is usually introduced to the medium by either an ultrasonic bath or an ultrasonic horn (see Chapter 7). In either case, an alternating electrical field (generally in the range 20-50 kHz) produces a mechanical vibration in a transducer, which in turn causes vibration of the probe (or bottom of the bath) at the applied electric field frequency. The horn (or bath bottom) then acts in a similar manner to one prong of a tuning fork. As in the case of air, the molecules of the liquid, under the action of the applied acoustic field, will vibrate about their mean position and an acoustic pressure (P = P sin 2k ft) will be superimposed upon the already ambient pressure (usually hydrostatic, Pjj) present in the liquid. The total pressure, P, in the liquid at any time, t, is given by Eq. 2.4. 

Horn design is a very important aspect of ultrasonic engineering. The vibrational amplitude of the piezoelectric crystal itself is normally so small that the intensity of sonication attainable by direct coupling of the transducer to the chemical system is not large enough to cause cavitation. The horn acts as an amplifier for the vibration of the transducer and the precise shape of the horn will determine the gain or mechanical amplification of the vibration. It is for this reason that it is sometimes referred to as a... 

The significance of the position at which the step is placed should be appreciated. It is always at the nodal point of the horn because at this point there is zero vibration (i. e. no stress). If the size reduction is not precisely at this null point stress will develop at this point. Fortunately however titanium has high tensile strength and so small errors in the position of constriction can be accommodated. 

Horn, K., in Proceedings of Vibrations in Adsorbed Layers Conference (H. Ibach, ed.) p. 140. Kernforschungsanlage, Jiilich GmbH, Germany, 1978. 

A sonicator (Model W-370) was purchased from Heat Systems-Ultrasonic with a cup horn attachment. The horn was the resonant body, which vibrated at 20 kHz (20,000 cycles per second) and served as a second stage of acoustic amplification. The standard tapped titanium disrupter horn was immersed in circulating water at 50°C during sonication. 

Eng J, Raghavachari K, Struck LM, Chabal YJ, Bent BE, Flynn GW, Christman SB, Chaban EE, Williams GP, Radermacher K, Mantl S (1997) A vibrational study of ethanol adsorption on Si(100), J Chem Phys 106 9889—9898 Casaletto MP, Zanoni R, Carbone M, Piancastelli MN, Aballe L, Weiss K, Horn K (2000) High-resolution photoemission study of ethanol on Si( 100)2 x 1, Surf. Sci. 447 237-244... 

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