Ultrasonic waves propagate in the liquid, causing the liquid and the cleaning tank to vibrate together at the ultrasonic frequency. When the liquid and the cleaning tank vibrate, they have their own natural frequency. This vibration frequency is the sound wave frequency, so people hear the buzzing sound. With the continuous development of the cleaning industry, more and more industries and enterprises have used ultrasonic cleaning machines.
The advantages of the ultrasonic cleaning machine are: the ultrasonic cleaning effect is good, and the operation is simple. The sound that people hear is a sound wave signal with a frequency of 20-20000 Hz. The sound wave above 20000 Hz is called an ultrasonic wave. The transmission of the sound wave propagates longitudinally according to a sinusoidal curve, producing a large number of small bubbles. One reason is that partial tensile stress occurs in the liquid to form negative pressure. The decrease in pressure makes the gas originally dissolved in the liquid supersaturate and escape from the liquid and become small bubbles; the other reason is that the strong tensile stress tears the liquid apart. "A void is called cavitation.
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Autumn cabbage nursery, south and north are open field nursery. Selecting high-pitched terrain and well-drained land, there are no cruciferous vegetable plots within two years, and avoidance of pre-falls such as tomatoes, peppers, and zucchini with severe viral disease. The flat stilts are 1.2-1.5m wide, 8-10m long, and 12-15cm high. Approximately 100kg of organic fertilizer is applied in the pot, 0.5kg of compound fertilizer is mixed, and the pot is mixed with potash, soaked with water, and the dried seeds are sowed, sowing 4-5g per square meter. Each mu of nursery land can be planted about 15 acres of production fields. In the event of rain and no rain protection facilities, we can use the 8-10 cm row spacing in the seedbed to draw shallow trenches, cover them with fine sand, and then cover with fine soil about 1 cm thick after the rain.
Chinese cabbage seedlings are planted in autumn, and if it does not rain after sowing, it will be poured into a small water on the third day. After emergence, it is still necessary to pour water in order to cool down and humidify. When it rains, it must be drained in time. After the emergence of seedlings and weeding, weeding. Autumn seedlings, young seedlings are young, seedlings are short, and generally do not divide seedlings. When the basal leaves are unfolded, two or three true leaves are once seedlings, the seedling distance is 4-5cm and 6-8cm, and the seedlings are 3 or When 4 true leaves spread out, the seedlings colonize.
For the principle of ultrasonic cleaning machine, the high-frequency oscillation signal sent by the ultrasonic generator is converted into high-frequency mechanical oscillation by the transducer and propagated to the medium-the cleaning solvent. The ultrasonic wave radiates forward in the dense and dense phases in the cleaning liquid. The flow of liquid produces tens of thousands of tiny bubbles with a diameter of 50-500μm, and the tiny bubbles existing in the liquid vibrate under the action of the sound field. These bubbles form and grow in the negative pressure zone where the ultrasonic wave propagates longitudinally. In the positive pressure zone, when the sound pressure reaches a certain value, the bubbles increase rapidly and then suddenly close. And when the bubble is closed, a shock wave is generated, and thousands of atmospheres are generated around it, destroying insoluble dirt and dispersing them in the cleaning liquid. When the group particles are wrapped in oil and adhere to the surface of the cleaning part, the oil is emulsified and solid Particles and detachment, so as to achieve the purpose of cleaning parts purification. In this process known as the "cavitation" effect, the closed bubble can form a high temperature of several hundred degrees and an instantaneous high pressure of more than 1,000 atmospheres.
The sowing date of Chinese cabbage cultivation in the north is relatively strict. The seeding period of live broadcast in the Beijing-Tianjin region is in early August. The seedling cultivation is 3-5 days earlier than the live broadcast, and the seedling period is about 20 days. The middle and lower reaches of the Yangtze River are in mid-August, while southern China can be sown from September to October.