In the low temperature, corrosive medium or vacuum conditions, with special performance should be considered the gasket.
在低温，腐蚀性介质或真空条件下，应考虑具有特殊性能的密封垫。
If the electron flow takes place in a vacuum, as in the case of electronic valve, the electrons will travel at considerable speed, since little resistance is offered the medium.
如果电子在真空里流动，比如电子真空管，那么电子的运行速度非常快，因为介质对电子几乎不产生什么阻力。
As the Roots pump is a non-vacuum inside the compression, the compression ratio is usually very low, so high, medium and vacuum pumps need to pump before.
由于罗茨泵是一种无内压缩的真空泵，通常压缩比很低，故高、中真空泵需要前级泵。
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