"explosion" and "impact" are terms related to engineering and technology, not EI. Explosion usually refers to the explosive reaction of substances in the combustion process, which releases a lot of heat energy, gas and pressure, produces explosion waves and shock waves, and causes damage and influence to the surrounding objects and environment. Explosions are widely used in military, civil and industrial fields, such as explosives, rocket engines, car crash tests and so on. Impact refers to an instantaneous rapid movement and energy transfer process after an object is acted by an external force. Shock wave is a special kind of shock, which is a high-speed compressed wave of gas or liquid caused by explosion, impact and sound wave, and has strong destructive power. Impact is also widely used in engineering and technical fields, such as automobile crash test, earthquake engineering, military equipment and so on.