中间极，二次发射电极一种用于一定电子管作第二次发射电极。
An electrode used in certain electron tubes to provide secondary emission.
其中，日渐增多的工作移动性——不论是通勤还是会见客户——都使得智能手机和平板电脑在这些上班族中间极受欢迎。
Among these is the increasing mobility of the workforce, whether commuting or visiting clients, which has made smartphones and tablets especially popular with corporate road-warriors.
为了测量两极之间的高程差，测量员在两极中间的一个水平基座上使用了光学水准望远镜。
To measure the difference in elevation between poles, surveyors used an optical level—a telescope on a level base—placed halfway between the poles.
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