Thank you very much for your reply. It was much helpful. However, when I was reading the income tax treaty between India and US on the IRS website - Article number 22, (please see the link below, page 49 for payments to research scholars)
http://www.irs.gov/pub/irs-trty/inditech.pdf
It is mentioned here that the tax is exempted for researcher if he is going to stay here for not more than 2 years. Tax will be exempted for the first two years and after that if oneself is still working, then he is liable to pay tax for the entire stay of his period. While I am here for a 3 year Project. Am I exempted for the first two years. Will I be required to pay the tax after 2 years for all the three years?? Or only from the third year? I am very confused about this. I would much appreciate your reply in this regard. Thank you.