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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
As the capital of the city of romance, its auto show is like fashion, which always gives people a sense of struggle. The exhibition originated from the international car salon in 1898 until the year 1976, and then every two years. From the end of September to the beginning of October. In October 1998, the Paris motor show at centennial, European fans looking forward to for a long time of Paris "in one hundred s show" to "century car parade", let the paint in the street for people to watch. French car design always with new and unique known in the world, full of romantic and full of imagination of the French, always in pursuit of the most unique models, wind speed and enjoy the most comfortable car, the French hobby, are revealed in the Paris motor show, make the Paris motor show is always around the word for "new" article. At the same time, the Paris motor show is a sea of concept cars, with quirky concept cars that often make the audience shine. A total of 140,000 people attended the first Paris motor show. In 2000, the number of exhibitors increased tenfold to 1.4 million, including 8,500 journalists from 81 countries. In 2002, the Paris international auto show in Paris lasted 16 days and welcomed more than 5,000 journalists and 1.25 million spectators. According to statistics, the Paris motor show directly earns about 8.5 billion francs, with a turnover of 150 billion francs.
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