on

Upon her head she wore a black velvet hat. 她头戴一顶黑色天鹅绒帽子。

You can never place enough emphasis upon the importance of safety. 无论怎样强调安全的重要性都不过分。

Upon your arrival (= as soon as you arrive), please report to the reception desk. 到达后请即刻到接待处报到。

to be something that someone will experience or have to deal with soon

Another few weeks and spring will be upon us. 再过几个星期，春天就要来了。