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The rapid development of air filters is closely related to the development of military industry and electronic industry. In the first world war, the use of various chemical agents, asbestos fibre filter paper as the smoke filter layer of military gas masks came into being. The glass fiber filter medium is used in air filtration to obtain a patent in the United States in October 1940. In the 1950s, the United States studied the production process of glass fiber filter paper, and the air filter was improved and developed. In the 1960s, HEPA filters came out; In the 1970s, the filter paper of fine glass fiber was used as the HEPA filter of filter medium, and the filtration efficiency of particle size of 013 micron particle diameter was 99.9998%. Since the eighty s, with the emergence of new test method, use evaluation to improve and to improve the filtering performance requirements, found the HEPA filter there is a serious problem, and he had a higher ULPA filter performance. Countries are still working on it and expect more advanced air filters soon
A substantial reduction in the seamless rail joint, reducing the impact of rail wheels through joint, which saves line maintenance costs, prolong the service life of rail, abate the locomotive vehicle noise, etc., therefore, developed rapidly. In the 1930s, German and American railroads began to carry out small test lines, and by 1981, the world had laid a seamless line of about 300,000 kilometers, of which China lay about 8,000 kilometers
Principle: resulting in differential pressure. By differential pressure switch monitoring in and out of the nozzle pressure difference of change, when the differential pressure to set data, control device for hydraulic control valves, motor drive signal, caused by the following action: motor driving brush rotation, the filter cleaning, emission control valve to open at the same time, the whole cleaning process for dozens of seconds, at the end of the automatic brush filter when cleaning, close the valve, the motor stop running, system back to its initial state, began to filter into the next process
The four auto companies merged into the auto union ag in 1932. In terms of car production, the automobile alliance was the second largest automobile manufacturing company in Germany at the time, and the merchandise was marked by four connected rings, representing four automobile companies participating in the merger. For the first time in the world, there are four rings.
After the baby has been inoculated, the doctor will leave it for about 30 minutes. If there is any reaction, the doctor will deal with it in time. If there is no reaction, then leave. But this does not mean that the high pillow is carefree, the parents also need careful observation and meticulous care, in which the specific nursing has general nursing and symptomatic care.
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