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Characterization and some applications of ultrasonic

Ultrasound has two characteristics: one is energy, and the other is travelling in straight lines. Its application is carried out in accordance with the two characteristics.

Theoretical studies have shown that, with the same amplitude, the energy of vibration of an object is proportional to the square of the vibration frequency. When ultrasound spreads into the medium, the vibration frequency of medium point is high, so energy is big. In the dry winter of northern China, if passing ultrasound through the tank, the violent vibrations would break the water in the tank into many small droplets, and then a small fan blows these droplets into the room, which can increase the indoor air humidity. This is the principle of ultrasonic humidifiers. For laryngitis, bronchitis and other diseases, the drug is difficult to reach the diseased parts,so based on the principle of humidifiers, we can atomize liquid for patient to inhale, so as to promote healing . The great ultrasonic energy can also crush calculus in human body.

As the saying goes, "walls have ears," This shows that ultrasound can bypass the obstacles. However, the shorter the wavelength is, the less obvious diffraction phenomenon will be. Therefore, ultrasound is basically travel in straight lines and can make directional emission. If fishing boats are equipted with underwater ultrasonic generator, which rotates to emit ultrasound in all directions. And ultrasound will be reflected back by fish, so fishing boats can detect the location of the fish by the reflected wave. This instrument is called sonar, which can also be used to detect water reefs, enemy submarines, and measure water depth.

By the same reason, we can also use ultrasound to detect metal, ceramic concrete products, and even dams to check whether there are air bubbles ,holes or crack inside.

The reflectivity of every surface of the organs to the ultrasound is different, and also, the reflectivity of healthy organs and diseased organs are also not the same. B scan, as usually said, formes images of the ultrasound reflected by organs, so as to help doctors analyze the lesion of the body.

Interestingly, many animals have complete ultrasound transmitting and receiving organs. Insect-eating bats, whoes vision is poor, keep sending out ultrasonic pulses, and find food by the reflected waves of insects. Dolphins also have an excellent "sonar" system, which can accurately determine the location of small fishes in the far distant in turbit water . Radar - modern radio locator, is dozens, hundreds, or hundreds of kilograms weight, while the ultrasonic positioning system of bat is only a fraction of a gram, and it is far superior to the modern radio locator in a number of important performances, such as identifying the accurate target location, anti-jamming capacity, etc. Deeply studying functions and structure of various animal organs, we can gain the knowledge to improve existing facilities and develop new equipments. This is called bionics, a new discipline developed in recent decades.


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