Some time ago, a woman in Chengdu refused security after taking the subway and pushed security checkers down the stairs to cause fainting. He was detained for 10 days. In fact, there are many people who reject security screening, including the author, but very few people respond as strongly as this woman does.
One of the reasons why everyone rejects security screening is because they do not understand the principles of security inspection equipment . Therefore, it is necessary to fully understand the security inspection equipment and security inspection operations.
Security X-ray machines, also known as security checkers or baggage screening machines, are the main baggage screening devices for subways and airports. The principle is very simple, that is, the ability to use X-rays to penetrate substances. Different density, different thickness, composition, X-ray penetration ability is also different. X-ray machines identify objects in baggage based on their different penetrating powers.
The X-ray machine can not only recognize the shape of objects, but also show colors. The colors of various substances are not the same. Organic materials such as paper, clothes, and various foods are usually displayed in orange. Mixed materials and light metals, such as those containing sodium, silicon, and aluminum, are usually displayed in green. ; And iron, copper, silver, etc. are shown in black and blue. The degree of lightness and darkness of each of the above colors depends on the density and thickness of the material.
Many people who reject security are worried that the food in their packs will be contaminated when they are swept away by the X-rays. In fact, there is no need to worry about this. The X-ray power emitted by baggage screening machines is very small. Once detected, the radiation dose received is less than 5 microsieverts, far lower than those used to sterilize food. The dose. The food we usually eat is irradiated by X-rays for preservation and sterilization, such as packaged frozen or frozen red meat, poultry meat, fresh fruits and vegetables, and grains.
Security doors, also known as metal detection doors , mainly detect metallic weapons carried by passengers, using the principle of electromagnetic induction. Rapidly changing magnetic fields are generated on both sides of the security door. These magnetic fields do not affect the human body, but the exception is metal. Metals generate eddy currents in a rapidly changing magnetic field, and eddy currents generate a magnetic field, which is detected when the security gate detects this. When a new magnetic field is applied, a beep or flash will be automatically generated.
Many people also often resist emotions when they pass security checks. They think that it will be harmful to the body, especially if pregnant women worry that the fetus in the body will be affected. Specifically, safety gates do not produce ionizing radiation, and only electromagnetic fields are generated. This kind of electromagnetic field is very weak, only about 1 micro-Tesla, this data is worse than 30 micro Tesla specified in the “General Specifications for Pass Through Metal Detection Doors†and it will not harm the human body. Having said that, if there is damage, then no one is willing to over many years waited at the security gate did the screeners.
Many people have this kind of experience. Every time they fly over a security gate, they must be touched up and down by security personnel. This feeling is very unpleasant. In fact, such security personnel are not happy, if not for work, if it is not for safety, who is willing to idle and do nothing to do the search game?
In fact, no matter how publicity is conducted in routine security inspections, there will still be concerns about radiation. Moreover, conventional security devices are slow and waste a lot of manpower and material resources. So, can you use a security inspection device that does not need to be searched and does not emit X-rays or electromagnetic waves? Of course, this is the terahertz human security instrument.
“Tai†is an order of magnitude unit, which is the same as the “Thousands,†“Summer,†“Kyrgyzstan,†etc. that we often hear. For example, your mobile phone has 16G space, where G is "Kyrgyzstan", and your network hard disk has 5T, where T is "too." "Hertz" is a unit of frequency, so "terahertz" means a frequency range with a frequency between 0.3 and 3 THz. The corresponding wavelength is between 1 mm and 0.1 mm. Therefore, in the field of electronics, electromagnetic waves in the terahertz band are also called millimeter waves or submillimeter waves; in the optical field, they are called far-infrared rays. Electromagnetic waves in the terahertz band have a frequency smaller than that of infrared rays, and at the same time have a larger frequency than microwaves in microwave ovens. However, with the use of a terahertz human body security device, the cost will increase a lot and it will not be easy to popularize at one and the same time.
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