Life Detector in Earthquake Relief

　　On September 5, an earthquake of magnitude 6.8 occurred in Luding County, Garze Tibetan Autonomous Prefecture, Sichuan, and another earthquake of magnitude 3.2 occurred on September 6. Luding and Ya’an were severely affected, and dozens of people were killed.
　　In the past, natural disasters such as floods and earthquakes were considered to be punishments from gods. Although this statement is completely wrong from the perspective of current science, it undoubtedly proves the terrifying power of natural disasters and the insignificance of people in them. Today, we still cannot completely avoid the huge losses caused by natural disasters. However, with the advancement of science and technology, continuously reducing losses is the goal we have been striving for.
　　Taking earthquakes as an example, one of the important ways to reduce casualties is to carry out emergency rescue as soon as possible after the earthquake, which also best demonstrates the status of the mainstay of technological power. So, do the students know what is the most common scientific equipment in earthquake relief? Next, we will introduce to you one of the most important scientific equipment in earthquake relief – life detector.
　　Sensitive “wind ear”
　　- audio life detector The
　　audio life detector applies the principle of sound waves, which can detect various sound waves with air as the carrier and vibration with other media as the carrier, and then quickly determine the position of the trapped person.
　　A sound wave is actually a wave produced by vibrating matter, such as a guitar string, a person’s vocal cords, or a speaker cone. These vibrations have an effect on nearby microscopic particles. For example, when we speak, the vibration of the vocal cords has an effect on the air molecules in the throat, which slightly increases the air pressure. At this pressure, the air molecules then push on the surrounding air molecules, which in turn push on the next set of air molecules, and so on. When a high-pressure area passes through the air, it leaves a low-pressure area behind, and such pressure fluctuations are a type of sound wave. When these sound waves reach the human ear, they vibrate the nerve endings in the ear, and our brain then converts these vibrations into sound, so we hear the voice of speech.
　　In earthquake relief, such sound waves can play a huge role. The besieged in the earthquake generally all is trapped under the rubble, because heavy obstacle, its calling for help under the rubble is difficult to be discerned by human ear. However, through the audio life detector, search and rescue personnel can sensitively detect the sound wave signal emitted from the ground. Audio sound waves and vibration waves such as the groaning, shouting, crawling, and knocking of the trapped people can be obtained by search and rescue personnel through audio life detectors, and then judge the existence of life under the ruins and carry out rescue.
　　However, since the audio life detector is an instrument that passively receives audio signals and vibration signals, it is necessary to find a gap in the ruins to insert the probe during rescue, which is easily affected by on-site noise, and the detection speed is relatively slow. Therefore, such life detectors are gradually being replaced by other detectors.
　　The “see- through eye” that passes through the barrier
　　-infrared life detector
　　Due to defects of the audio life detector, scientists invented the infrared life detector. You should know that any object will produce infrared radiation as long as the temperature is above absolute zero, and the human body is also a natural source of infrared radiation. However, due to differences in the core temperature of the human body and the temperature of various parts of the body surface, the infrared radiation characteristics of the human body and the infrared radiation characteristics of the surrounding environment will be different. The infrared life detector uses this principle to separate the trapped people in the earthquake ruins from the background environment by means of imaging, so that search and rescue personnel can find the trapped people.
　　The infrared life detector can withstand the harsh conditions of the rescue site, and can search for life in the thick smoke, fire and dark environment after the earthquake, just like a pair of see-through eyes through the barrier. After the infrared life detector detects the infrared radiation characteristics of the victim’s body, the optical system equipped on the detector can further focus the received human body thermal radiation energy on the infrared sensor, and then convert it into an electrical signal, and finally pass through Processing, get infrared thermal image, so as to help rescuers determine the position of the trapped person.
　　However, since infrared radiation is a long-wave radiation with low energy and strong penetrating power, it is easily absorbed by ordinary substances, which limits the detection range of infrared life detectors. If the trapped person is buried by an object with strong infrared absorption ability or buried deeply, it may not be detected. For this reason, scientists continued to tackle key problems and invented the “clairvoyance” in earthquake relief – the radar life detector.
　　The “clairvoyance” for discerning the details
　　- radar life detector
　　Radar life detector is a life detection device integrating radar technology and biomedical engineering technology. It is mainly made by using the principle of electromagnetic wave reflection. From these micro-movements, information about breathing and heartbeat can be obtained, so as to identify whether there is life or not. Just like a bat in the dark, through the reflection of ultrasonic waves, it can judge its surrounding environment, where there are rocks and where there are caves. The radar life detector uses electromagnetic waves instead of ultrasonic waves. If bats use this kind of detection, it can not only judge the orientation of rocks, but also receive more comprehensive and detailed information such as rock materials, temperature, and humidity.
　　Therefore, the use of radar life detectors can detect the post-earthquake ruins in all directions, just like a pair of omniscient clairvoyance, once “looking” away, the trapped place of the trapped person can be clearly known by the searcher and rescuer , so as to rescue. The active detection method of the radar life detector makes it less susceptible to factors such as temperature, humidity, noise, and site terrain, and the nature of electromagnetic waves also increases the detection range. It can be said that this is the most advanced life detector in the world.
　　Of course, life detectors are not the only scientific equipment used in earthquake relief. Others, such as hydraulic clamps, air cushions, and snake eye detectors, also play a role that cannot be ignored. With the advancement of science and technology, more and more new scientific equipment will be developed to benefit the public.
　　In the face of natural disasters, under the shaking of the sky and the earth, only the giant dragon of science and technology stands upright, propping up a “blue sky” of hope for the people in the disaster.