No, it is not necessary to contact a professor in advance as it will not affect your admission result or scholarship decision. However, if you are applying for the Ph.D. program and feel the need to discuss your research interests and study plans, you may proceed to contact professors after doing some research about the expertise of the faculty members. It's important to note that the admissions office cannot advise on which faculty member to contact, so you should make your own decision in this regard.