1. Department of Applied Mathematics, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
2. Department of Electrical and Computer Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
3. Department of Automatic Control and Systems Engineering, University of Sheffield, Mappin Street, Sheffield, Yorkshire S1 3JD, UK