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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
It is also known as welding long rail line, which is a kind of line that welded normal rails without rail seam. The welding rail is not less than 200 meters long, and the actual application is usually 800~1000 meters or more. The long track is laid in the specified temperature range and fixed on the pillow. The long rail ends with a rail joint, while the middle part cannot scale up and down with the temperature. Therefore, there will be a great temperature pressure in the middle of the rail during the summer, which will produce a great temperature tension in winter. The greatest pressure on the rail and tension according to the years of rail laying and the highest temperature and minimum temperature calculation, rail tracks the maximum pressure should not cause to drum up by maximum tension should not cause rail fracture
People worldwide love Afghan/Pashto music. It just isn't enough to allow them to simply pay attention to the music as watching a video is much more entertaining. If you are interested to find out more about the culture of Afghan Pashtoon, you have to definitely consider the opportunity and view these videos. You can do so from your comfort of your home of office. You do not need to venture to shops and get the CDs of Afghani music that you can save considerable time and energy whenever you view the songs videos online. The quality in the videos is fantastic and you'll be very happy with their services. You can save considerable time as buffering will not take much time. You can find the format of the video depending on your needs. The Gul Panra Video Songs make sure that the quality in the video isn't compromised with.
When using the computer to issue the dispatch order, it is necessary to strictly abide by the release procedures of "one, two, one, three, four, confirmed and signed". You must carefully check the contents of the order and sign in time.
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