<p>Your chances look decent; scores are excellent across the board. Awards and ECs are well above avererage (especially Siemens and Intel). Obviously, having Cs and Ds on your transcript can be detrimental; also, 3.55 is low for Cornell (as is top 15%). </p>
<p>In my opinion, it will come down to your essays. If you are yourself and write them very well (with plenty of editing/revision), your chances will be a lot higher.</p>
<p>As for the topic of your personal essay, as long as you can reveal a lot about yourself personally and demonstrate your unique voice, it should be fine.</p>