于其赴京之时

when he arrives in Beijing

于其赴京之前

before he arrives in Beijing

于十个月以内

in less than ten months

于今年二月间

during this February

苏州位于沪宁之间。

Suzhou is located between Shanghai and Nanjing.

会议定于明天举行。

The meeting is scheduled for tomorrow.

求救于人

ask someone for help

问计于我

ask me for advice

出于不得已

because there is no alternative

出于自愿

of one's own free will

拯民于水火

rescue the people from extreme misery

忠于人民

be loyal to the people

于人有益

be good for people

于事无补。

It doesn't help the situation.

于心不忍

not have the heart to

于我何干?

what does it have to do with me?

世界形势于我们有利

the world situation is in our favour

大于

be bigger than

小于

be smaller than