Particle-in-cell and Monte Carlo Collision Simulation of Positive and Negative Corona Plasmas Pengxiang Wang and Junhong ChenTPF * FPT Department of Mechanical Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI 53211 Fa-Gung Fan and Joseph A. Swift Xerox Research Center Webster, Xerox Corporation, Webster, NY 14580 TP * PT To whom any correspondence should be addressed. E-mail: jhchen@uwm.edu. 1