The role of ultrasound
Glass parts. Descaling of glass and ceramic products is a nuisance. If these items are put into the cleaning solution and then ultrasonic waves are applied, the violent vibration of the cleaning liquid will impact the dirt on the items and can be quickly cleaned.
Although humans cannot hear ultrasound, many animals have this ability. They can use ultrasound to "navigate", hunt down food, or avoid dangerous objects. You may have seen many bats flying back and forth in the courtyard during the summer night. Why do they fly without light and not lose their way? The reason is that the bat can emit ultrasonic waves of 20,000 to 100,000 Hz, which is like an active "radar station." The bat uses this "radar" to judge whether the front of the flight is an insect or an obstacle. The quality of the radar is tens, hundreds, thousands of kilograms, and in some important performance accuracy, anti-interference ability, etc., bat far superior and modern radio locator. In-depth study of the functions of various organs in animals and Construction, the knowledge gained is used to improve existing equipment, a new discipline developed in recent decades, called bionics.
We humans did not learn to use ultrasound until the First World War. This is to use the principle of "sound" to detect underwater targets and their status, such as the position of submarines. At this time, people emit a series of ultrasonic waves of different frequencies into the water, and then record and process the reflected echoes. From the characteristics of the echoes, we can estimate the distance, shape and dynamic changes of the probes. The earliest use of ultrasound in medicine was in 1942, when the Austrian doctor Dusik first scanned the brain structure with ultrasound technology; in the 1960s, doctors began to apply ultrasound to the detection of abdominal organs. Ultrasound scanning technology has become an indispensable tool for modern medical diagnosis.
The working principle of medical ultrasound examination has a certain similarity with sonar. The ultrasonic wave is emitted into the human body. When it encounters the interface in the body, it will reflect and refract, and it may be absorbed and attenuated in human tissue. Because the shape and structure of various tissues of the human body are different, the degree of reflection and refraction and the degree of absorption of ultrasound are different. Doctors distinguish the characteristics of the waveform, curve, or image reflected by the instrument. they. In addition, combined with anatomical knowledge, normal and pathological changes, it is possible to diagnose whether the organ being examined is ill.
At present, the ultrasonic diagnostic methods applied by doctors have different forms, which can be divided into four types: A type, B type, M type and D type.
Type A: A method of displaying tissue features in a waveform, which is mainly used to measure the diameter of an organ to determine its size. Can be used to identify some physical properties of the diseased tissue, such as substantial, liquid or gas presence.
Type B: Display the specific situation of the organization being explored in the form of a flat graphic. When inspecting, firstly, the reflected signal of the human body interface is converted into light spots with different strengths and weaknesses. These light spots can be visualized through the fluorescent screen. This method is intuitive and reproducible, and can be used for comparison before and after, so it is widely used in maternity products. Diagnosis of systemic diseases such as urology, urinary, digestive and cardiovascular diseases.
M type: is a method for observing the change of the time of the active interface. It is most suitable for checking the activity of the heart. The dynamic change of the curve is called echocardiography. It can be used to observe the position of the various layers of the heart, the state of activity, the condition of the structure, etc., and is used to assist the diagnosis of heart and large blood vessel diseases.
Type D: An ultrasound diagnostic method specifically designed to detect blood flow and organ activity, also known as Doppler ultrasound. It can be determined whether the blood vessels are unobstructed, whether the lumen is narrow, occlusion, and the lesion. A new generation of D-mode ultrasound also quantitatively measures the flow of blood in the lumen. In recent years, scientists have developed a color-coded Doppler system that displays the direction of blood flow in different colors under the direction of an echocardiographic anatomical landmark. The depth of the color represents the flow velocity of the bloodstream. Ultrasound techniques such as stereoscopic ultrasound imaging, ultrasound CT, and ultrasound endoscopy are emerging, and can be combined with other inspection instruments to greatly improve the diagnostic accuracy of diseases. Ultrasonic technology is playing a huge role in the medical world. As science advances, it will be more perfect and will benefit humanity better.
The acoustic branch that studies the generation, propagation, and reception of ultrasound, as well as various ultrasound effects and applications, is called ultrasound. The ultrasonic generating device includes a mechanical ultrasonic generator (such as a whistle, a whistle, a whistle, etc.), an electric ultrasonic generator made by the principle of electromagnetic induction and electromagnetic action,
And an electroacoustic transducer made of an electrostrictive effect of a piezoelectric crystal and a magnetostrictive effect of a ferromagnetic substance.
Ultrasonic effect When ultrasonic waves propagate in a medium, physical and chemical changes occur in the medium due to the interaction of the ultrasonic waves with the medium.
A range of mechanical, thermal, electromagnetic, and chemical ultrasound effects, including the following four effects:
1 mechanical effect. The mechanical action of the ultrasonic waves contributes to the emulsification of the liquid, the liquefaction of the gel and the dispersion of the solid. When a standing wave is formed in the ultrasonic fluid medium, the fine particles suspended in the fluid are agglomerated at the nodes due to the mechanical force, forming a periodic accumulation in the space. When ultrasonic waves propagate in piezoelectric materials and magnetostrictive materials, induced polarization and induced magnetization due to the mechanical action of ultrasonic waves (see dielectric physics and magnetostriction).
2 cavitation. When ultrasonic waves act on a liquid, a large number of small bubbles can be generated. One reason is that a tensile stress is locally generated in the liquid to form a negative pressure, and the decrease in the pressure causes the gas originally dissolved in the liquid to be supersaturated, and escapes from the liquid to become a small bubble. Another reason is that the strong tensile stress “rips” the liquid into a void called cavitation. The cavity is a liquid vapor or another gas dissolved in a liquid, and may even be a vacuum. The small bubbles formed by the cavitation will continuously move, grow up or suddenly burst with the vibration of the surrounding medium. When it is shattered, the surrounding liquid suddenly rushes into the bubble to generate high temperature and high pressure, and at the same time, a shock wave is generated. The internal friction accompanying the cavitation can form a charge and cause a luminescence phenomenon in the bubble due to the discharge. The techniques for sonication in liquids are mostly related to cavitation.
3 thermal effects. Due to the high frequency of the ultrasonic wave and the high energy, it can produce significant thermal effects when absorbed by the medium.
4 chemical effects. The action of ultrasound can cause certain chemical reactions to occur or accelerate. For example, pure distilled water is subjected to ultrasonic treatment to produce hydrogen peroxide; water dissolved in nitrogen is subjected to ultrasonic treatment to produce nitrous acid; the aqueous solution of the dye may be discolored or discolored after sonication. The occurrence of these phenomena is always accompanied by cavitation. Ultrasound also accelerates the hydrolysis, decomposition, and polymerization of many chemicals. Ultrasound also has a significant impact on photochemical and electrochemical processes. After sonication of the aqueous solutions of various amino acids and other organic substances, the characteristic absorption band disappears and a uniform general absorption, indicating that the cavitation changes the molecular structure.
Ultrasound applications Ultrasound effects have been widely used in practice, mainly in the following areas:
1 ultrasonic test. Ultrasonic waves are shorter than normal sound waves, have good directivity, and can transmit opaque substances. This feature has been widely used in ultrasonic flaw detection, thickness measurement, ranging, remote control and ultrasonic imaging. Ultrasound imaging is a technique that uses ultrasound to present the internal image of an opaque object. The ultrasonic wave emitted from the transducer is focused on the opaque sample through the acoustic lens, and the ultrasonic wave emitted from the sample carries information of the illuminated portion (such as the ability to reflect, absorb and scatter sound waves), and is concentrated by the acoustic lens. On the piezoelectric receiver, the resulting electrical signal is input to an amplifier, and the image of the opaque sample is displayed on the phosphor screen using a scanning system. The above device is called an ultrasound microscope. Ultrasound imaging technology has been widely used in medical examinations, used in the microelectronics manufacturing industry to inspect large-scale integrated circuits, used in materials science to display regions and grain boundaries of different components in alloys. Acoustic holography is an acoustic imaging technique that uses the principle of ultrasonic interference to record and reproduce stereo images of opaque objects. The principle is basically the same as that of light holography, except that the recording methods are different (see holography). The same ultrasonic signal source is used to excite two transducers placed in the liquid, which respectively emit two coherent ultrasonic waves: one beam passes through the object under investigation and becomes a wave of matter, and the other beam acts as a reference wave. The object wave and the reference wave are coherently superimposed on the liquid surface to form an acoustic hologram, and the acoustic hologram is illuminated by the laser beam, and the image of the object is reproduced by the diffraction effect generated when the laser is reflected on the acoustic hologram, usually using a camera and a television. The machine is observed in real time.
2 ultrasonic treatment. Ultrasonic welding, drilling, solid pulverization, emulsification, degassing, dust removal, descaling, cleaning, sterilization, chemical reaction and biological biology can be performed by ultrasonic mechanical action, cavitation, thermal and chemical effects. Research, etc., have been widely used in various sectors such as industry, mining, agriculture, and medical.
3 basic research. After the ultrasonic wave acts on the medium, an acoustic relaxation process is generated in the medium, and the acoustic relaxation process is accompanied by the transport process of energy between the respective electrical degrees of the molecules, and macroscopically exhibits absorption of sound waves (see sound waves). The properties and structure of matter can be explored by the law of absorption of ultrasound by matter. This aspect of research constitutes the acoustic branch of molecular acoustics. The wavelength of ordinary sound waves is much larger than the atomic spacing in solids, under which solids can be used as a continuous medium. However, for ultra-sonic waves with a frequency above 1012 Hz, the wavelength can be compared with 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, called phonons (see Solid State Physics). The effect of ultrasonography on solids can be attributed to the interaction of special ultrasound with thermal phonons, electrons, photons and various quasiparticles. The study of the generation, detection and propagation of ultra-sound ultrasound in solids, as well as the study of acoustic phenomena in quantum liquids - liquid helium constitute a new field of modern acoustics -
Sound wave is one of the categories belonging to sound, belonging to mechanical wave. Sound wave is a kind of longitudinal wave that can be felt by human ear, and its frequency range is 16Hz-20KHz. When the frequency of sound waves is lower than 16 Hz, it is called infrasound wave, and when it is higher than 20 kHz, it is called ultrasonic sound wave.
Ultrasound has the following characteristics:
1) Ultrasonic waves can be effectively transmitted in media such as gases, liquids, solids, and solid solutions.
2) Ultrasonic waves can transmit very strong energy.
3) Ultrasound produces reflection, interference, superposition and resonance.
4) When ultrasonic waves propagate in a liquid medium, strong impact and cavitation can occur at the interface.
Ultrasound is a member of the large family of sound waves.
Sound waves are the form of propagation of an object's mechanical vibration state (or energy). The so-called vibration refers to the round-trip motion of the mass point of the substance near its equilibrium position. For example, after the drum surface is knocked, it vibrates up and down. This vibration state is transmitted through the air medium in all directions, which is sound waves.
Ultrasonic waves are sound waves whose vibration frequency is greater than 20KHz and cannot be heard and felt by people in the natural environment.
The concept of ultrasound therapy:
Ultrasound therapy is an important part of ultrasound medicine. Ultrasound treatment applies ultrasonic energy to the human lesion site to achieve the purpose of treating the disease and promoting the body's recovery.
Ultrasound is widely used in the fields of diagnostics, therapeutics, engineering, and biology. Safrey's home ultrasound therapy machine belongs to the field of application of ultrasound therapy.
(1) Engineering applications: underwater positioning and communication, underground resource exploration, etc.
(2) Biological applications: cutting macromolecules, bioengineering, and processing seeds, etc.
(3) Diagnostic applications: Type A, Type B, Type M, Type D, Duplex and Color Doppler, etc.
(4) The application of therapeutics: physical therapy, cancer treatment, surgery, extracorporeal lithotripsy, dentistry, etc.