1. Department of Biomedical Engineering, Virginia Commonwealth University, 401 West Main Street, P.O. Box 843067, Richmond, VA 23284-3067, USA
2. Department of Electrical Engineering, Virginia Commonwealth University, 601 West Main Street, P.O. Box 843072, Richmond, VA 23284-3072, USA
3. Department of Mathematics & Applied Mathematics, Virginia Commonwealth University, 1015 Floyd Avenue, P.O. Box 842014, Richmond, VA 23284-2014, USA