Variation principle
[计] 变分原理
🧩 词语组成解析
🗣️ 情景例句
Yes. And I'm not trying to take her place.
是的 ，我不想取代她。
I tried calling you several times yesterday but I couldn't get through.
我昨天给你打了几次电话，但都没有打通。
and we have to lower into the ground and haul out of the ground great lengths of drill pipe which are rotated by an engine at the top and are fitted with a cutting bit at the bottom.
我们必须把很长的钻杆一节节地钻入地下，然后再从地下拉出来。钻杆顶部安装的发动机带动钻杆旋转，它的底部装有钻头。