The difference between microwave and ultrasonic wave
Characteristics of microwave heating
1, rapid heating conventional heating such as flame, hot air, electric heating, steam, etc. Both use the principle of heat conduction to transfer heat from the outside to the inside of the heated object, so that the central temperature of the object gradually rises, which is called external heating. It takes some time for the central part to reach the required temperature, especially for objects with poor thermal conductivity. Microwave heating is to make the heated object itself become a heating body, which is called internal heating. It does not need the process of heat conduction, and can be heated both inside and outside, so it can achieve the heating effect in a short time.
2, uniform heating conventional heating, in order to improve the heating speed, it is necessary to increase the heating temperature, which is easy to produce endogenous coke. When heated by microwave, electromagnetic waves can usually penetrate into all parts of the object evenly, generating heat, so the uniformity is greatly improved.
3. Energy saving and high efficiency In microwave heating, microwave energy can only be absorbed by the heated object to generate heat, and the air in the heating chamber and the corresponding container will not generate heat, so the thermal efficiency is extremely high and the production environment is obviously improved.
4. The thermal inertia of microwave heating is easy to control. If it is controlled by microcomputer, it is especially suitable for automatic control of heating process.
5, low-temperature sterilization, pollution-free microwave energy itself will not pollute food, and the dual sterilization effect of microwave thermal effect can kill bacteria at a lower temperature, which provides a heating sterilization method that can retain more nutrients in food.
6. Selective heating microwave has different effects on materials with different properties, which is beneficial to drying operation. Because water molecules absorb microwave best, the part with high water content absorbs more microwave power than the part with low water content, which is the characteristic of selective heating. When drying wood, paper and other products, this characteristic can be used to realize uniform heating and uniform drying.
It is worth noting that the higher the temperature, the better the absorbability of some substances, which will lead to a vicious circle, and the local temperature will rise sharply, leading to drying and even carbonization. When microwave heating this kind of substance, we should pay attention to making a reasonable heating process.
7. Microwave heating and drying is safe and harmless, with no waste water, waste gas and waste, and no radiation residue. Microwave leakage is also guaranteed to be far below the national safety standards, which is a very safe and harmless high-tech.
What is ultrasound?
Ultrasonic waves are sound waves: sound waves with frequencies higher than the upper limit of human hearing (about 20000 Hz) are called ultrasonic waves, or ultrasonic waves.
There is no essential difference between the propagation law of reflection, refraction, diffraction and scattering of ultrasonic waves in media and audible sound waves. But the wavelength of ultrasonic wave is very short, only a few centimeters, even a few thousandths of a millimeter. Compared with audible sound waves, ultrasonic waves have many strange characteristics: propagation characteristics: the wavelength of ultrasonic waves is very short, and the size of obstacles is usually many times larger than ultrasonic waves, so the diffraction ability of ultrasonic waves is very poor, and they can travel in a straight line in a uniform medium. The shorter the wavelength of ultrasonic wave, the more remarkable this characteristic is. Power characteristics When sound propagates in the air, it pushes particles in the air to vibrate back and forth and do work on them. Sound wave power is a physical quantity, indicating the speed at which sound waves do work. At the same intensity, the higher the frequency of sound wave, the greater its power. Because the frequency of ultrasonic wave is very high, its power is very large compared with ordinary sound wave. Cavitation phenomenon When ultrasonic waves propagate in liquid, tiny holes will be generated in the liquid due to the violent vibration of liquid particles. The rapid expansion and closure of these small cavities will cause violent collisions between liquid particles, thus generating pressures of thousands to tens of thousands of atmospheres. This strong interaction between particles will make the temperature of the liquid suddenly rise and play a good role in stirring, thus emulsifying two immiscible liquids (such as water and oil), accelerating the dissolution of solute and accelerating the chemical reaction. This effect produced by the action of ultrasound in liquid is called ultrasonic cavitation.
What's the difference between laser, radio frequency and ultrasonic scalpel?
The development of medical beauty technology provides us with more and more choices. The same disease can be solved by different means, but because of this, people have no choice.
For example, laser, radio frequency (RF) and ultrasonic technology are unknown to many people. Today I will give you an academic article that you can understand.
Laser, radio frequency and ultrasound have certain similarities, for example, they all have the functions of wrinkle removal and skin rejuvenation, and they all cause certain damage to the skin in the mechanism of action, thus causing healing reaction, stimulating collagen formation and cell regeneration, and achieving therapeutic effects.
Since there are similarities, what are their differences?
Different principles
The principle is different:
Laser: Laser belongs to the principle of blasting. The energy gathered by high-energy radio frequency instantly breaks the pigment group in the diseased tissue, and the pigment part will be blown out of the body.
Radio frequency: It is a very important part of the electromagnetic spectrum. The energy of radio and microwave belongs to the category of electromagnetic radiation energy, commonly known as radio frequency. Radio frequency is based on frequency, and the range can be extended from several hundred KHZ to several hundred MHZ.
Ultrasonic scalpel: Ultrasonic scalpel uses the principle of high-energy focusing of sound waves! (Ultrasonic principle) Concentrate energy on one point, quickly penetrate epidermis, fat layer and fascia layer, form a network freezing point in fascia layer, stimulate muscle tissue to contract and tighten, and regenerate collagen elastic fiber, thus achieving layer-by-layer tightening.
laser
heat effect
When the radio frequency starts to work, it can change the polarity of the electrode of the electric field in biological tissue for millions of times within 1 second, and the charged tissue particles in the electric field change polarity at the frame frequency, so that the natural impedance of the skin tissue generates heat for the electron movement, and the friction generated by the electron movement causes the thermal effect of the deep columnar distribution of the skin.
This thermal effect will first change collagen, leading to collagen contraction, and then regenerate new collagen, leading to dermal reconstruction and thickening.
Ultrasonic thermal effect
In the process of ultrasonic propagation, skin and subcutaneous tissue absorb ultrasonic energy and convert it into heat energy, which can increase the kinetic energy of carbohydrate, lipid and protein in skin cell membrane, increase skin temperature, enlarge skin pores and sweat gland ducts, thus facilitating transdermal diffusion and absorption of drugs. The generated warm effect can activate deep tissue cells and strengthen local metabolism.
mechanical effect
Ultrasound can temporarily change the lipid structure of skin keratinocyte matrix, increase the effective penetration area, increase the permeability of cell membrane and increase the micropores between epidermal cells. It causes high-speed vibration of intracellular particles, reduces cell membrane potential and increases cell membrane permeability.
Convection transportation
Under the action of ultrasonic wave, the continuous vibration of bubbles in diffusion system causes particle rotation and liquid circulation around bubbles. In addition, high-frequency physical vibration can produce fine massage and promote blood and lymphatic circulation.
Invalid effect
Under the action of ultrasonic waves, gas molecules and bubbles in media and cells vibrate, and then bubbles burst to form gaps or empty sacs, which is called cavitation effect. This effect can change the lipid structure of the skin, cause cavitation of the medium outside the skin, and a large number of water molecules enter the lipid structure to form water-soluble channels.
Classification and indications are different
The practical application of laser in skin is classified according to its medium, wavelength, target pigment basis and purpose. In recent years, a new technology has emerged, which releases laser in the form of microbeam, so it can be divided into traditional and microbeam.
Grinding laser
The target pigment is based on water, which has a low degree of penetration. Because water is ubiquitous in the skin, it actually selectively evaporates and removes skin layers. Such as carbon dioxide lasers and erbium lasers.
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