What is the principle of the ultrasonic power generator?
Sound waves are electromagnetic waves with frequencies ranging from 20 kHz to 50 MHz. It is a kind of mechanical wave that needs energy carrier medium to propagate. There is a period of alternation of positive and negative pressure in the propagation of ultrasound. In the normal phase, the medium molecules are squeezed to increase the initial density of the medium. In the negative phase, the medium molecules are sparse and discrete, and the medium density decreases. In other words, ultrasound can not polarize the molecules in the sample, but produce acoustic cavitation between the solvent and the sample, resulting in the formation, growth and explosive compression of bubbles in the solution, thus dispersing the solid sample, increasing the contact area between the sample and the extracting solvent, and increasing the mass transfer rate from solid to liquid.
Ultrasound is a member of the acoustic family.
Sound wave is the transmission form of mechanical vibration state (or energy) of an object. Vibration refers to the reciprocating motion of particles near their equilibrium position. For example, when the surface of the drum is impacted, it will vibrate up and down. This vibration state propagates in all directions through the air medium (sound wave). Ultrasound refers to the vibration frequency greater than 20 kHz, the vibration frequency per second (frequency) is very high, exceeding the upper limit of human ear hearing (20 000 Hz). People call this kind of inaudible sound wave ultrasound. Ultrasound and audible sound are basically the same, they have a common feature: mechanical vibration usually propagates through longitudinal wave in elastic medium, which is a form of energy transmission. The difference is that the ultrasonic frequency is high and the wavelength is short. It has good beam and directivity when propagating along a straight line in a certain distance. Currently, the frequency range for abdominal ultrasound imaging is 2 MHz. The frequency of sound waves ranges from 16 hertz to 2000 hertz.