2. Ultrasonic therapy. Ultrasonic welding, drilling, solid crushing, emulsification, degassing, dust removal, cleaning, sterilization, promoting chemical reaction and biological research can be carried out by using the mechanical action, cavitation, thermal effect and chemical effect of ultrasound, which has been widely used in various departments such as industry, mining, agriculture and medical treatment.
3. Basic research. After the ultrasonic wave acts on the medium, the acoustic relaxation process occurs in the medium. The acoustic relaxation process is accompanied by the transport process of energy between molecular degrees, which is macroscopically manifested as the absorption of sound waves (see sound waves). The characteristics and structure of matter can be explored through the absorption law of ultrasonic waves, which constitutes a branch of molecular acoustics. The wavelength of ordinary sound waves is longer than the atomic spacing in solids. In this case, the solid can be regarded as a continuous medium. However, for ultrasonic waves with frequencies above 10 12 Hz, the wavelength can be comparable to the atomic spacing in solids. At this time, the solid must be regarded as a lattice structure with spatial periodicity. The energy of lattice vibration is quantized. It is called a phonon (see solid state physics). The effect of ultrasound on solids can be attributed to the interaction between ultrasound and thermal phonons, electrons, photons and various quasi-particles. It is a new field of modern acoustics to study the generation, detection and propagation of ultrasonic waves in solids and the sound phenomenon in quantum liquid-liquid helium.
2 the application of ultrasound in agriculture
2. 1 Basic principles of ultrasonic treatment and processing
Ultrasonic processing equipment is mainly composed of ultrasonic generator, transducer, ultrasonic concentrator and matching circuit between ultrasonic generator and transducer. As shown in figure 1, the ultrasonic generator generates certain high-frequency electric energy and provides it to the ultrasonic transducer, which converts the electric energy into mechanical energy, and then amplifies the mechanical energy through the ultrasonic concentrator. Acoustic energy is applied to the material to be treated. The biological effects of ultrasound are widely used, and the main biological effects are mechanical effects and thermal effects caused by cavitation. The basic principle of ultrasonic treatment and processing is mainly to use the cavitation phenomenon of fluid dynamics. Ultrasonic cavitation refers to various dynamic properties of ultrasonic activated bubbles. These manifestations can be regular mild steady-state cavitation or strong short-term transient cavitation. Transient cavitation bubbles contract adiabatically to the time of collapse, and the bubbles can present high temperature and high pressure of thousands of atmospheres, accompanied by powerful shock waves or jets. Ultrasonic irradiation can enhance the movement of particles in liquid medium, accelerate mass transfer, and also affect boundary layer, membrane, cell wall and vacuole. Ultrasonic cavitation can also destroy cells and denature enzymes. Quote as follows.
2.2 Ultrasonic determination of lead in soil. It can be seen that ultrasonic treatment with a certain frequency and intensity can strengthen some physiological and biochemical indexes of plants and promote their growth and development.
2.5 Effects of ultrasonic treatment on plant respiration
The study of plant respiration has always been a hot spot in plant physiology research, especially for crops, its respiration is directly related to yield, so its research has important theoretical and practical significance for the development of agriculture. In 1975, Albu E found that the respiratory intensity of annual plants (such as tomatoes and cucumbers) decreased after vegetables were treated with low-frequency ultrasound (25kHz). However, the respiration intensity of biennial plants (such as cabbage and onion) increased [7]. It can be speculated that ultrasonic treatment of related crops can improve crop yield.
2.6 ultrasonic ploughing
Traditional plows need heavy machine traction, which not only compacts the deep soil, but also makes it unable to maintain moisture and nutrients; Moreover, the turned topsoil will be eroded by wind and rain, which is a big worry for many farmers. In addition, due to repeated tillage, the roots of plants and rotting residual plants are turned out of the surface, and they will emit carbon dioxide gas. Nida Abuhard, an agricultural machinery engineer in Jordan, invented the use of ultrasonic waves to loosen soil. His experimental results show that the depth of scarification can reach 20cm, which fully meets the depth of scarification of general crops.
2.7 ultrasonic treatment of plant roots [8]
Sugar is one of the main components in plants, and soluble sugar mainly refers to monosaccharide and oligosaccharide. The content of phosphate monosaccharides in plant cells is not high, but they are the main intermediate products in photosynthesis and respiration, and they are extremely important in metabolism. After ultrasonic stimulation, the soluble sugar content in roots was 29.6% higher than that in control group. Rich protein is the material basis for cells to carry out a series of physiological activities. After ultrasonic stimulation, the soluble protein in roots increased by 35.3%, and the high level of soluble protein content ensured the vigorous division and growth ability of cells, which indicated that the root cells of plants had vigorous division and growth ability after ultrasonic stimulation.
2.8 ultrasonic pest control [9] and promote silkworm egg hatching
250 W-CFS ultrasonic generator (produced by Zhongyuan Electronic Instrument Factory) is used to match the independent cleaning tank. Chestnut with insects in the fruit was soaked in tap water in the cleaning tank, started at 19.5~20.5kHz 15min, then drained and stored for 2 weeks. The length of chestnut fruit was about 10 mm, but the larvae below 6mm died. With the extension of treatment time, the insect mortality rate was basically the same. In addition, some people use similar methods and equipment to treat silkworm eggs (about half a minute), and the direct result is that the incubation time of ant silkworms is basically the same. The results showed that the reeling rate was higher than that of adults growing under the same conditions. Some people try to deal with pests in fruits (apples, pears, etc.). ) passed the ultrasonic wave, but most of them failed.
2.9 Ultrasonic induced labor
3. The application of ultrasound in industry
ultrasonic level meter
supersonic flowmeter
ultrasonograph
Ultrasonic limit switch
Ultrasonic cleaning device
Application industry:
Industrial category electronics and electricity
Industrial machinery, optical machinery, treasures
Stone processing, watch industry, automobiles and motorcycles.
Chemical fiber textile food in motorcycle industry
Brewing the aviation and aircraft industries
4. The military application of ultrasound.
Acoustic weapon
Generally speaking, sound and hearing are interlinked, but as a kind of air waves, after focusing, it can become.
Attack weapons, for many people, are probably a new thing. Recently, it was located in San Diego, California.
The American technology company in the city has developed a gun with sound waves as bullets.
Active sonar: The basic principle is the same as that of bats.