[Can I withdraw my commitment?]

DO IT NOW (before April 15th for sure). like juilletmercredi said, they probably won't go after you, but it will certainly be frowned upon if you withdraw after April 15th.

[difference between Finite element analysis and computational mechanics]

I think FEA is more applicable to complex loading patters and BCs in which there are multiple expected failure mechanisms (buckling, fatigue, etc.). I know that the Aerospace industry uses a lot of FEA for aircraft/spacecraft structural analysis. On a slightly unrelated subject, FEA is becoming increasingly popular for solving flow problems (as opposed to Finite Difference). Other more popular and robust CFD methods are higher order methods like DG and SD.

[give me some help. I got 3 admissions.]

Like most people in this thread, I know nothing about Arts Studies, but here's how you can eliminate the schools:

Reputation: CMU=NYU>>UNC ~ Schools in general, don't know much about how they rate in your field

Location: NYU>>CMU>UNC ~ Mostly Contacts, opportunities

Funding: CMU>NYU>>UNC ~ I am not too sure about this one, but based on what juilletmercredi said, it looks like this unless you are instate at UNC

So, I would vote for NYU

[PhD EE@UT Austin VS UMD VS WSU]

I would say UT. Austin's an oasis in the middle of total sh** called texas. Austin is an awesome place. U Maryland is not really in Baltimore, and not as good as Texas when it comes to EE.

[Low GRE scores.]

I second stackoverflow. I wouldn't worry too much about the AW score. A 730 on Q could be a problem, since that places you into the 77th percentile. MOst graduate school place low weight in GRE score, and will overlook a poor GRE score if the applicant has strong GPA, ECs, etc.

[Mechanical Engineering Fall 2012 Results]

Hey did anyone here from Stanford or Berkeley's ME program? Or know when they will sent out their decisions, when their visiting days are, etc?

I have a friend who got admitted to the MS Mech program at Stanford in early February. She had a fellowship interview on February 16th. I am not sure about the Mech department at Stanford, but Aeronautics and Astronautics department already sent out all admits and rejections.

BTW, my friend who got the fellowship from Mech program did Aerospace Engr in her undergrad. It is much easier to get an admit and a subsequent funding offer from stanford if you apply to their Mech E program compared to their Aero-Astro since the former has undergraduate students that require TAs.

[Stanford MS vs. UCLA PhD - Need Advice!]

Okay, I have to disagree with most people in this thread. I am not a Chemistry or Environmental Engineering guy, but in my opinion your best bet is Stanford, PhD or Masters. If you are looking to do a PhD, given the current competition in PhD programs, a Stanford PhD will definitely give you a big advantage. Plus, Stanford is notorious for having very difficult PhD qualifying exams(procedures), especially in Engineering, which adds to their PhD prestige.

If you prefer the industry route after a quick Masters degree, Stanford is the obvious choice.