just my 2 cents.

do not think it is necessary to mention about that. But you can make a phone call to the Chinese professors who you know and ask if they can help. Donot mention anything in the email. You may just email him/her, and briefly remind them who you are and ask what is a good time to call them. In the phone, you may ask their help. Mentioning them in your application materials will not help you too much. again, just my 2 cents.