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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
Signs of birth. Since the middle of the 20th century, technology has grown faster and faster. It was only six and a half years since the discovery of uranium fission in January 1939 to the first atomic bomb exploded in July 1945. The emergence of electronic computers has led to more profound changes in the fields of human social life. These technological breakthroughs can be called technological revolutions
The personnel of the duty station authorized to set up the checkpoints shall show the highway inspection certificate issued by the general office of the provincial people's government and wear industry inspection marks when performing the inspection tasks. Without the above certificates and marks the illegal inspection.
The Red Baron airplanes manufactured by Albatros evolved steadily throughout World War I. The first plane flown by Richthofen was an Albatross C.III, a two-seat general use biplane that has been eventually manufactured in larger numbers than any C series Albatros. It was employed for photo-reconnaissance, bomber escort, and light bombing, and is the plane that Richthofen trained as being a pilot in.
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