I was submitted visa applications to US Embassy in Beijing on Aug. 9, and interviewed by one of their visa officers on Aug. 28, between which were wasted time for mistakes and purposed delays of US Embassy in Beijing, despite their approval to me for expediting.
That visa officer thought I need an SAO from Department of States, but I actually had one clearance last year and it's still valid since it's valid for F-1 visas for 4 years. However I am still waiting for the issuance of my visa, while my program at Columbia University has been undergoing for 3 weeks. Any further delay is likely to cause serious financial problems.
I know a bunch of fellows are experiencing similar situations as I am, most of whom are or will be important technical assets to the US. Please issue visas to us.