As we traverse the tree, changes are local to the current focal node, meaning all constant-time operations except for up.
遍历树时，更改是在当前关注节点的本地做出的，也就是说除了向上移动之外，所有操作都是常量时间的。
2
At the same time, a level of global standardization is required for the network of national IHR focal points to operate effectively.
同时，为了能有效地运转，国际卫生条例国家归口单位网络需要建立一定的全球规范。
3
This can be a tedious process because the first time you create the plane, you have to rotate the camera and change the focal length at the same time to get a good match.