When you walk into a subway station with a bag on your back and take the subway, you will be asked by the staff to put the bag on a conveyor belt of a detector. Then you go through a "door" and the security guard holds a black "longboard" waved on you while taking your water bottle to a machine for testing. After completing these operations, even if you pass the security check, you can take the subway normally.
In the eyes of many people, these security check procedures have become normal things in life. Whether it is taking airplanes, trains, high-speed rails, cars, subways, visiting museums, entering convention centers, performance venues, etc., they all need to go through “security checks”. "This pass. So, do you know what happens every time you go through the security check?
As the name implies, "security inspection" is an inspection method to reduce security risks. By checking your luggage, cargo, personal belongings, etc., to prevent guns, explosives, controlled knives, flammable and explosive materials, poisons, and other items that endanger safety. Brought into public places, causing explosions or other terrorist threats.
To complete this series of inspections, you need the help of safety inspection equipment. The security inspection equipment mainly includes X-ray security inspection machines, security doors, hand-held metal detectors, dangerous liquid detectors, drug, and explosive detectors, etc. These instruments pass various This principle to check whether you are carrying illegal items has been widely used in public security counter-terrorism, transportation, performance activities, and other fields. Let's look at the specific process below:
First, you put your backpacks, suitcases, etc. on the X-ray security inspection machine, and the conveyor belt transfers your items to the inside of the machine for X-ray scanning and outputs images for the inspector to judge whether contraband is contained. With a clear imaging effect, with the help of multiple image processing functions, it can easily and quickly assist the inspector in distinguishing different substances.
Generally speaking, organic materials such as plastics, food, clothing, etc. are displayed in orange or yellow, and metal inorganic materials such as iron, copper, steel, and silver are displayed in blue. The overlapping areas of organic and inorganic materials are displayed in green, and some are too thick or too dense. Because the object cannot be penetrated by X-rays, it is displayed in red (such as lead plate, gold, etc.).
Then, you will walk through a security gate, which includes a metal detection gate and a temperature detection metal detection integrated security gate. The door panels on both sides are equipped with sensors that can transmit and receive alternating electromagnetic fields. When the metal conductor is affected by the alternating electromagnetic field, an eddy current will be generated inside, and the current will emit a magnetic field with the same frequency as the original magnetic field and the opposite direction. The metal detector captures the signal. When the metal carried by the person exceeds the parameter value preset according to the weight, quantity, or shape, the security gate will immediately alarm and display the location of the metal that caused the alarm, so that the security inspector can find the person carried by the person in time. Metal items.
The temperature detection and metal detection integrated security gate is equipped with a high-precision temperature detection probe at the door head. The detection angle can be moved up and down, which can measure the surface temperature of the human forehead, and then obtain the actual body temperature of the human body according to the relationship between the temperature of the human forehead and the body temperature. . The optical component of the detector collects the energy emitted and reflected by the body onto the sensor. The electronic component converts this information into a temperature reading and displays it on the display panel. When the temperature reading exceeds the high-temperature alarm value, the instrument will sound an alarm.
Then, maybe the metal parts on your clothing trigger the security gate alarm. The security inspector is holding a hand-held metal detector and scanning the surface of your body. Similar to a metal detection gate, it detects you on your body through the principle of electromagnetic induction. When the hand-held metal detector sweeps the human body, if it makes a low sound and the sound will gradually disappear after the probe stays above the sounding place, it can be determined that it is a very small piece of metal, such as a belt buckle, a zipper, etc. . If the sound is very sharp, even if the probe is stopped, the sound is still continuous, it is likely to be a large piece of metal, such as a dagger, a pistol, etc.
Finally, after you have passed the above inspections, the security inspector instructs you to take out the water bottle in your backpack and put it on the desktop dangerous liquid detector or hand-held dangerous liquid detector for inspection. The detector uses the microwave reflection method, heat conduction method, or quasi-static computer tomography technology to determine the type of liquid by measuring the dielectric constant and conductivity of the liquid to be measured. This detector can distinguish liquid explosives, gasoline, acetone, ethanol, banana water, and other flammable and explosive liquids from safe liquids such as water, cola, milk, and juice without direct contact with liquids. Sometimes security inspectors will also You are required to drink the liquid in the bottle to prove that it is safe drinking water.
The above is the security check methods that we often encounter in daily life. Of course, if you are going to the airport, there will be processes such as drug and explosive testing. When entering the airport, the staff will take a small "test paper" on your clothes, suitcase, and even your hands to wipe, and then send the paper to the drug/explosive detector for inspection.
According to Rocca's law (where two objects touch, there must be a transfer phenomenon), if someone has held or used explosives before boarding, some particles in the explosives will remain on their skin and luggage Even after washing hands repeatedly, a small amount of explosive residue will be captured by the adhesive on the test paper. This type of detector mainly uses ion mobility technology. As long as the explosive powder component is greater than 0.0000000001 grams, it can be successfully identified. In addition, there will be special police dogs in airports, customs, and other places to search for drugs and explosions to ensure that there are no drugs and explosives in the luggage.
The implementation of the security check policy is not only to protect the lives and property of the general public but also to combat smuggling crimes and terrorist attacks. As a qualified citizen, consciously accepting security checks is not only responsible to others, but also to oneself. Security check takes only a few seconds, but it guarantees a better tomorrow for the country and society.
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