Service
· Department Chairperson from 1972 to 1978.
· Department Graduate Program Director from 1982 to 1986.
· Director of the Ph.D. Program in Applied Mathematical Sciences from 1992 to 1997.
· Member of the Scientific Committee for the International Conference EQUADIFF ’87,
August 24 - 28, Democritus University of Thrace, 67100 Xanthi, Greece.
· I chaired the International Workshop on Oscillation Theory which was held August 14 - 17, 1993, in Plovdiv, Bulgaria.
· Member of the Organizing Committee for the First International Conference on Difference Equations which was held May 24 - 27, 1994, at Trinity University in San Antonio, Texas.
· Member of the Scientific Committee for the Second International Conference on Difference Equations which was held August 7-11, 1995, in Veszpren, Hungary.
· Member of the Global Organizing Committee for the Second World Congress of Nonlinear Analysts which was held during July 10-17, 1996, in Athens, Greece. I also organized and chaired a Special Session on Differential and Difference Equations.
· Member of the Scientific Committee for the Third International Conference on Difference Equations which was held September 1-5, 1997, at the Institute of Mathematics, Academia Sinica, Nankang, Taipei, Taiwan.
· Member of the Scientific Committee for the Fourth International Conference on Difference Equations which was held August 27-31, 1998 in Poznan, Poland.
· I organized ( with E. Grove) a Special Session on Difference Equations and Applications at the Annual Meeting of the American Society in Baltimore, MD, January 9-10, 1998.
· I organized ( with S.Elaydi) a Special Session on Difference Equations at the Annual Meeting of the American Mathematical Society in San Antonio, Texas, January 13-14, 1999.
· I organized ( with J. Hoag) a Special Session on Difference Equations at the Providence Meeting of the American Mathematical Society in Providence, RI, October 2-3, 1999.
· I organized ( with S.Elaydi, H. Sedaghat, and A. Yakubu) a Special Session on Difference Equations with Application to Social Sciences at the Annual Meeting of the American Mathematical Society in Washington DC, January 21-22, 2000.
· Member of the Scientific Committee for the Fifth International Conference on Difference Equations and Applications which was held January 3-7, 2000 in Temuco, Chile.
· I organized (with S.Elaydi and B. Aulbach) a Special Session on Difference Equations at the Third World Congress of Nonlinear Analysts which was held July 19-26, 2000 in Catania, Sicily, Italy.
· I organized (with V.Kocic and A.Yakubu) a Special Session on the Asymptotic Behavior of Difference Equations with Applications at the Annual Meeting of the American Mathematical Society in New Orleans, LA, January 10-13, 2001.
· Member of the Scientific Committee of the Sixth International Conference on Difference Equations and Applications which was held in Augsburg, Germany, July 30-August 3, 2001.
· Member of the Scientific Committee of the Seventh International Conference on Difference Equations and Applications which was held in Changsha, China, August 12-17, 2002.
· Member of the Scientific Committee of the Eighth International Conference on Difference Equations and Applications which was held in Brno, Czech Republic, July 28-August 1, 2003.
· Member of the Scientific Committee of the Tenth International Conference on Difference Equations and Applications which was held in Munich, Germany, July 25-28, 2005.
· Member of the Scientific Committee of the Eleventh International Conference on Difference Equations and Applications which was held in Kyoto, Japan, July 24-28, 2006.
· Member of the Scientific Committee of the Twelfth International Conference on Difference Equations and Applications to be held in Lisbon, Portugal, July 2007.
· I organized (with S.Elaydi and D.A.Lutz) a Special Session on Chaos, Stability, and Asymptotics at the Annual Meeting of the American Mathematical Society in San Diego, CA, January 6-9, 2002.
· I organized (with S.Elaydi) a Special Session on Discrete Dynamics and Difference Equations at the Annual Meeting of the American Mathematical Society in Baltimore, MD, January 17-20, 2003.
· I organized (with S.Elaydi, J.M.Cushing, and J.A.Yorke) a Special Session on Discrete Dynamics and Difference Equations at the Annual Meeting of the American Mathematical Society in Phoenix, AZ, January 7-10, 2004.
· Member of the Organizing Committee of the 14th International Conference on Difference Equations and Applications in Istanbul, Turkey, July 21-25, 2008.
· Member of the Scientific Committee of the Conference "Progress on Difference Equation 2009", which will be held in the Mathematical Research and Conference Center in Bedlewo, Poland from May 25th to May 29th, 2009.
· Member of the Board of Directors of the International Society of Difference Equations.
· Treasurer of the International Society of Difference Equations.
· Member of the International Scientific Committee of the International Conference in Mathematics and Applications, which will be held in Bangkok, Thailand during 17-19 December, 2009
· I am co-Editor in Chief of the "Journal of Difference Equations and Applications" which is published by Taylor and Francis.
· I am a member of the editorial board of the following Journals:
1. Differential Equations and Dynamical Systems
2. Communications on Applied Nonlinear Analysis
3. Fasciculi Mathematici
4. Functional Differential Equations
5. Mathematical Sciences Research Journal
6. International Journal of Theoretical and Applied Mathematics
7. Cubo, Matematica Educacional
8. Journal of Concrete and Applicable Mathematics
9. International Journal of Difference Equations
10. Annals of Differential Equations
11. Journal of the Egyptian Mathematical Society
12. International Journal of Dynamical Systems and Differential Equations
13. Involve, A Journal of Mathematics
14. International Journal of Pure and Applied Mathematics
15. Journal of Numerical Mathematics and Stochastics
I have been the major professor of the following Ph.D. students:
1. Evangelos C. Partheniadis
2. Stephen W. Schultz
3. Kevin Farrell
4. Spiridon A. Kuruklis
5. Panagiotis N. Vlahos
6. Ieda W. Rodrigues
7. Elias Camouzis
8. Chuanxi Qian
9. John H. Jaroma
10. Richard DeVault
11. George K. Tzanetopoulos
12. Jeffrey J. Feuer
13. Amal Al-Amleh
14. Soudabeh Valicenti
15. Norman R. Prokup
16. William J. Briden
17. Chris T. Teixeira
18. Mihaela Predescu
19. Carol H. Gibbons
20. Esha Chatterjee
21. Eugene Quinn
22. Yevgeniy Kostrov