- Academic Affilate and Distinguished Professor Emeritus, University of South Carolina, 2021-present
- Professor, University of South Carolina, 1990-2020
- Chair, University of South Carolina, 2012-2018
- Assistant Chair, University of South Carolina, 2005-2012
- Graduate Director, University of South Carolina, 1989-1994, 1995-2004
- Associate Professor, University of South Carolina, 1984-1990
- Assistant Professor, University of South Carolina, 1981-1984
- Research instructor, California Institute Of Technology, 1977-1981
Fellowships and honors
- Visiting Research Fellow, Department of Mathematics and Statistics,
Flinders University, Bedford Park, South Australia,
- Visiting Research fellow, Department of Mathematics and Statistics, Flinders University, Bedford Park, South Australia, June-
- Alexander von Humboldt Research Fellow, Arbeitsgemeinschaft Funktionalanalysis ,
University of Tübingen, Federal Republic of Germany, October 1987 - May 1988
- Visiting Professor, Delft University of Technology, Functional Analysis group, Delft, The Netherlands,
September - November 1994
- Corresponding Member of the Royal Dutch Academy of Sciences (KNAW), 1995-present
- Positivity, An international Mathematics Journal devoted to Theory and Applications of Positivity. Birkhäuser-Springer Verlag.
- Indagationes Mathematicae, Editor Special Issue, 2020.
- Yong S. Shim, ``Summability of eigenvalues of Hille-Tamarkin
- Gary C. de la Pena, ``Rearrangement of series in normed spaces'',1990
- J.P. Deshabandu, ``Zero-Two law in Banach lattice algebras'',1990
- Colin Day, ``Spectral Mapping Theorems of integrated
- James Sweeney, ``States and the Numerical Range in the Regular Algebra'', 2018.