| 2011- | Associate Professor (tenure track) | University of Central Florida |
| 2007-11 | Research Professor | University of Central Florida, Orlando, FL 32816-2385 |
| 2004-06 | Visiting Professor | Kansas State University, Manhattan, KS 66506 |
| 2003-04 | Visiting Professor | University of North Dakota, Grand Forks, ND 58202-7129 | >
| 2001-03 | Visiting Scientist | Max-Planck-Institut für Physik komplexer Systeme, Dresden 01187, Germany |
| 1992-00 | Techical Staff-Scientist | Argonne National Laboratory, Argonne, IL 60439 |
| 1990-92 | Technical Staff Member | Argonne National Laboratory, Argonne, IL 60439 |
| 1989-90 | Senior Staff Scientist | Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 |
| 1988-89 | Visiting Scientist | Ames Laboratory, Ames, IA 50011 |
| 1986-88 | Visiting Full Professor | University of California at San Diego, La Jolla, CA 92093 |
| 1984-86 | Senior Staff Physicist | Exxon Research & Engineering Co., Annandale, NJ 08801 |
| 1982-84 | Staff Physicist | Exxon Research & Engineering Co., Annandale, NJ 08801 |
| 1982 | Associate Professor (tenured) | Iowa State University, Ames, IA 50011 |
| 1976-81 | Assistant Professor | Iowa State University, Ames, IA 50011 |
| 1974-76 | Postdoctoral Fellow | Stanford University, Stanford, CA 94305 |
| 1969-70 | Research Technician | Synvar Research Institute, Palo Alto, CA 94305 |