Let's say that I gave you a sphere of radius a centered at the origin, or maybe just half of that sphere or some portion of it.
已知以原点为心，以a为半径的球面，也可以说是半球面或是球面的一部分。
This is significant because of the unique geometrical features of the Arecibo telescope: whereas most radio dishes are parabolic in shape, the Arecibo dish is a giant half-sphere dug into the ground.
这非常重要，由于阿雷西博望远镜的独特几何结构：尽管绝大多数的射电望远碟面都是抛物面型的，而阿雷西博的碟面是在地上挖出的一个巨大半球。
The principle and way of designing framework in processing a prominent half elliptical sphere die exactly with a vertical lathe have been described in this article.
介绍在立式车床上精确加工凸形半椭球形冲模的原理及其机构设计方法。
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