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Wide provided suitable for busy trunk, also can be laid in tunnel and station floor maintenance difficulties, stone or soil subgrade are laid, but the mud pumping in the diseases of roadbed must be laid on the roadbed diseases after renovation. The main advantages of the wide sleeper circuit are: the suborbital sinking is small. The vibration acceleration is smaller than the concrete sleeper line, which gradually slows down and stops after laying. So the line maintenance work is greatly reduced, about a third of the general concrete sleeper line. The track is easy to keep clean. Dirt is not easy to break into the bed and prolong the repair cycle of the route. The line is smooth and stable, which is conducive to high-speed operation and the laying of seamless circuit. The disadvantage is that the cost is higher, and it is more difficult to change the shop on the busy trunk line
When using telephone scheduling command, must strictly abide by "a quasi, two sign (issue), director of the leadership, must be on duty according to regulations, issued three, four read-back check, five orders number and time," the release of the procedure. When issuing and receiving the dispatch order, please fill in the dispatch order register (appendix vii of the technical regulation), and record the name and time of the receiver.
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
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