To eb1doc and ixora78
I would like share with you my experiences. Hope it is useful for others who is still doing it.
My research is in the field of computational engineering and sciences, and I have worked on Navy projects for about 6 years. My research is not confidential, so it does not directly related to military industries. But since the project was founded by Navy, I tried to argue how my research benifits the military interests. I think this is the key point in my case.
I do not have many publications and the citation of my papers is also very low. The major part of my application is the commendation letters.
I initially got 11 letters, but my lawyer only used 7 letters ( 1 national lab, 1 NSF, 1 Goodyear, 1 military industry, 3 university) in the first submission. My lawyer had several reasons to do it in this way, one of which is to prepare for the RFE. But later when I received RFE notice, I found it's hard to use the un-used letters because the dates on the letters were too old and I had to contact the references to re-sign the letters. It's difficult for me to explain to them why their letters were not used in the initial submission. So I gave up, and started to contact other peoples.
For RFE, I got 7 letters (1 current employer, 1 national lab, 1 military industry, 3 university, and 1 non-professional letter from AirForce). I think that, for NIW case, non-professional letter is also useful, as loong as the letter can self-prove the writer qualifies to support you.
I would like to thank everybody here who contribute a lot to this forum.