Departments of Mathematical Science and Computer Science, Rensselaer Polytechnic Institute, Troy, New York, USA. aminim@cs.rpi.edu|Departments of Mathematical Science and Computer Science, Rensselaer Polytechnic Institute, Troy, New York, USA. aminim@cs.rpi.edu|Departments of Mathematical Science and Computer Science, Rensselaer Polytechnic Institute, Troy, New York, USA. aminim@cs.rpi.edu