The typical trench system in World War I consisted of a series of two, three, four, or more trench lines running parallel to each other and being at least 1 mile (1.6 km) in depth.
第一次世界大战时典型的堑壕体系由2至4条以至更多的一系列壕沟组成，壕沟之间彼此平行，而且纵深可以达到1英里（合1.6公里）。
Three approaches to the graphic representation for lines of intersection are introduced in this article, namely, central projection, parallel skew projection and arc line projection.
本文介绍了图解截交线的三种方法，中心投射法、平行斜投射法、弧线投射法。
The design principle is analysed for band-pass filters using three parallel coupled-lines and the related design curves are given.
本文分析了三线平行耦合线带通滤波器的设计原理，给出了有关设计曲线。
The design principle is analysed for band-pass filters using three parallel coupled-lines and the related design curves are given.
本文分析了三线平行耦合线带通滤波器的设计原理，给出了有关设计曲线。
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