[susan53]

No. Notice that imperial has a lower case letter and is "just" an adjective preceding the proper noun. The name of the country is China. Compare this with eg the Ivory Coast where the capital letter shows that Ivory is part of the proper noun - the name of the country is Ivory Coast, not just Coast. This is the situation where the article is used.

As for your university examples - the same : Oxford and Cambridge are not adjectives so there's no need to use "the". But open is. Here it's part of the proper noun - again, notice the capital - and so the definite article is used.

This isn't a "rule" though, but a matter of convention. Notice I've said eg "there's no need to use the definite article" rather than "the definite article is not used". There are examples where The is used with a name + institution structure - eg The Chrysler Corporation Here the name is being used adjectivally whereas in eg Harvard University it isn't.