Presumably you have a reason why you didn't just post your draft for us to review so just call the prof you want to study under at that school and ask him/her what you should put in it. If they don't give good advice then you wouldn't want to be apprenticed to them anyway. They're only vaguely interested in your specific smartness which nothing you write is going to affect evaluation of, they really want to know what you want to study specifically and if it matches a prof who needs or will soon need a new apprentice, or is a question/problem one of them would really like to shepherd. Unless you just want a grammar check there's nothing any of us can suggest adding, especially since you're in a tech field and a native English Speaker they aren't going to care about your diction and vocabulary beyond that.

Edit: If you've done much teaching and/or tutoring or public speaking make sure to highlight those, especially if you're aiming for a Teaching Assistantship.