Short Curriculum Vitae
Research Interests
Principal Publications

Constantin Popa



e-mail: cpopa@univ-ovidius.ro

Short Curriculum Vitae

 born October 10, 1956 in Bucharest, Romania; married, one child
1981 - Diploma in Mathematics at University of Bucharest, Romania
1995 - Doctorate (Numerical Analysis) at University of Bucharest, Romania
2000 - Full Professor on Applied Mathematics at Faculty of Mathematics and Computer Science, "OVIDIUS" University of Constanta, Romania; since 1998 - Head of Department of Computer Science and Numerical Methods

Memberships

since 1992 - GAMM, Germany
since 2008 - SIAM, USA
since 2003 - GAMM Group on Numerical Linear Algebra
since 1990 - Romanian Society of Mathematics (SSMR)
since 1991 - Romanian Society of Applied Mathematics (ROMAI)
since 2001 - Reviewer at Zentralblatt fuer Mathematik, Germany

Research visits (more than one month)

Dec. 1992- Jan. 1993 - DAAD grant at Institute for Informatics and Applied Mathematics, University of Kiel, Germany
1996-1997 - postdoc grant at Department of Applied Mathematics and Computer Science, Weizmann Institute of Science, Israel
April-June 1998 - postdoc DAAD grant at Institute of Mathematics, University of Augsburg, Germany
2002-2003 - visiting professor (DAAD Gastdozent) at IMMD 10 (Systemsimulation), University Erlangen-Nuernberg, Germany
Dec. 2005-Jan. 2006 - visiting professor (DAAD Research grant) at IMMD 10 (Systemsimulation), University Erlangen-Nuernberg, Germany

Research interests

 - image reconstruction from projections in computerized tomography
- iterative methods for least-squares formulation of linear systems of equalities and inequalities (projection and multigrid algorithms)
- inverse problems: regularization techniques and methods for numerical solution of first kind integral equations
- preconditioning techniques for finite element and finite differences discretizations

List of most important scientific publications

Books

  1. Popa C., Pelican E. Introduction to numerical analysis (in romanian), Editura MatrixRom, Bucharest 2005 (150 pages); ISBN 973-685-991-6
  2. Popa C., Iterative methods for linear least-squares problems, Series ''Monografii Matematice'', vol. 77, West University of Timisoara, Romania, 2003 (118 pages); ISSN 1453-7702
  3. Popa C., Preconditioning techniques for linear and nonlinear problems, PAMM Monographical Booklets, vol. MB 4, 1997 (80 pages); ISSN 1417 278x
  4. Juncu Gh., Popa C., Introduction to multigrid methods (in romanian); Editura Tehnica, Bucharest, 1991 (192 pages); ISBN 973-31-0309-8

Papers in ISI journals

  1. Popa C., Constrained Kaczmarz extended algorithm for image reconstruction, Linear Algebra and its Applications, 429(2008), 2247 - 2267
  2. Popa C., Algebraic Multigrid Smoothing Property of Kaczmarz's Relaxation for General Rectangular Linear Systems, Electronic Transactions in Numerical Analysis (ETNA), 29(2008), 150 - 162
  3. Mohr M., Popa C., Numerical solution of symmetric least-squares problems with an inversion-free Kovarik type-algorithm, Intern. Journal of Computer Math., 85(2)(2008), 271-286
  4. Popa C., On numerical solution of arbitrary symmetric linear systems by approximate orthogonalization, Mathematics and Computers in Simulation 79(4)(2008) 1033 - 1038
  5. Juncu Gh., Mosekilde E., Popa C., Numerical experiments with MG continuation algorithms, Applied Numerical Mathematics, 56(2006), 844-861
  6. Petcu D., Popa C., A new version of Kovarik's approximate orthogonalization algorithm without matrix inversion, Intern. J. Computer Math., 82(10)(2005), 1235-1246
  7. Popa C., Zdunek R., Kaczmarz extended algorithm for tomographic image reconstruction from limited-data, Math. and Computers in Simulation, 65(6)(2004), 579-598
  8. Mohr M, Popa C., Ruede C., An iterative algorithm for approximate orthogonalization of symmetric matrices, Intern. J. Computer Math., 81(2)(2004), 215-226
  9. Popa C., Modified Kovarik algorithm for approximate orthogonalization of arbitrary matrices, Intern. J. Computer Math., 80(4)(2003), 519-525
  10. Juncu Gh., Popa C., Preconditioning by Gramm matrix approximation for diffusion-convection-reaction equations with discontinuous coefficients, Math. and Computers in Simulations., 60(2002), 487-506
  11. Evans D.J., Popa C., Projections and preconditioning for inconsistent least-squares problems, Intern. J. Computer Math., 78(4)(2001), 599-616
  12. Popa C., Extension of an approximate orthogonalization algorithm to arbitrary rectangular matrices, Linear Alg. Appl., 331(2001), 181-192
  13. Popa C., A method for improving orthogonality of rows and columns of matrices, Intern. J. Computer Math., 77(3)(2001), 469-480
  14. Popa C., An approximate orthogonalization technique for arbitray rectangular matrices, ZAMM 81(2001), suppl. 4, S1019-S1020
  15. Juncu Gh., Popa C., Numerical experiments with preconditioning by Gram matrix approximations for non-linear elliptic equations, Math. and Computers in Simulation, 52(1)(2000), 53-71
  16. Popa C., A fast Kaczmarz-like solver for linear least squares problems, ZAMM 80(Supplement 3)(2000), S811-S812
  17. Popa C., Block-projections algorithms with blocks containing mutually orthogonal rows and columns, B I T , 39(2)(1999), 323-338
  18. Popa C., Extensions of block-projections methods with relaxation parameters to inconsistent and rank-defficient least-squares problems, B I T, 38(1)(1998), 151-176
  19. Popa C., Mesh independence principle for non-linear equations in Hilbert spaces by preconditioning, Intern. J. Comp. Math., 69(1998), 295-318
  20. Juncu Gh., Popa C., Preconditioning by approximations of the Gram matrix for convection-diffusion equations, Math. and Computers in Simulation, 48(2)(1998), 225-233
  21. Popa C., Least-squares solution of overdetermined inconsistent linear systems using Kaczmarz's relaxation, Intern. J. Comp. Math., 55(1995), 79-89
  22. Popa C., Preconditioning conjugate gradient method for non- symmetric systems, Intern. J. Comp. Math., 58(1995), 117-133
  23. Popa C., Mesh independence of the condition number of discrete Galerkin systems by preconditioning, Intern. J. Comp. Math., 51(1994), 127-132
  24. Popa C., An iterative method for CVBEM systems. Part II: The unigrid method, Advances in Engineering Software, 16(1993), 64-69
  25. Popa C., An iterative method for CVBEM systems. Part I: The Kaczmarz algorithm, Advances in Engineering Software, 16(1993), 61-63

Papers in other refereed journals and proceedings

  1. Popa C., On Cimmino's reflection algorithm}, Proceedings of the Romanian Academy, Series A, vol. 9, No. 1, January-April 2008.
  2. Popa C., Zdunek R., On some constraining strategies in image reconstruction from projections, in Proceedings of the 5th Workshop on Mathematical Modelling on Environmental and Life Sciences Problems, September 10-13, 2006 Constanta, Romania; Editura Academiei Romane, Bucuresti 2008, 173-180.
  3. Koestler H., Popa C., Pruemmer M., Ruede U., Algebraic full multigrid in image reconstruction, in Proceedings of the 5th Workshop on Mathematical Modelling on Environmental and Life Sciences Problems, September 10-13, 2006 Constanta, Romania; Editura Academiei Romane, Bucuresti 2008, 123-130
  4. Duluman T., Popa C., Algebraic reconstruction technique versus conjugate gradient in image reconstruction from projections, in Proceedings of the 5th Workshop on Mathematical Modelling on Environmental and Life Sciences Problems, September 10-13, 2006 Constanta, Romania; Editura Academiei Romane, Bucuresti 2008, 67-78
  5. Bautu A., Bautu E., Popa C., A weighted Kaczmarz algorithm in image reconstruction, in Proceedings of the 5th Workshop on Mathematical Modelling on Environmental and Life Sciences Problems, September 10-13, 2006 Constanta, Romania; Editura Academiei Romane, Bucuresti 2008, 43-50
  6. Popa C., Kovarik's function orthogonalization algorithm with approximate inversion, Revue d'Analyse Numerique et Theorie de l'Approximation, Tome 36, No. 1(2007), 79 - 87
  7. Pelican E., Popa C., Least squares data shape preserving, Carpathian J. Math., 23(1-2)(2007), 165-171
  8. Popa C., Udrescu T., A fast solver for magnetostatic field problems , Romanian Journal of Physics, 52(3-4)(2007), 237-249
  9. Bautu A., Bautu E., Popa C., Hybrid Algorithms in Image Reconstruction, Proc. in Appl. Math. and Mech. (PAMM), 6(1)(2006), 707-708
  10. Koestler H., Popa C., Pruemmer M., Rueude U., Towards an algebraic multigrid method for tomographic image reconstruction - improving convergence of ART, paper 476 in Electronic Proceedings of European Conference on Computational Fluid Dynamics ECCOMAS CFD 2006, The Netherlands, 2006
  11. Mohr M., Popa C., Rueude U., Analysis of a preconditioned CG method for an inverse bioelectric field problem, in Proceedings of the 4th Workshop on Mathematical Modelling on Environmental and Life Sciences Problems, September 7-10, 2005 Constanta, Romania; Editura Academiei Romane, Bucuresti 2006, 135-146
  12. Popa C., Zdunek R., Gibbs regularized tomographic image reconstruction with DW algorithm based on generalized oblique projections, in Proceedings of the 4th Workshop on Mathematical Modelling on Environmental and Life Sciences Problems, September 7-10, 2005 Constanta, Romania; Editura Academiei Romane, Bucuresti 2006, 191-200
  13. Popa C. , Udrescu T., A fast approximation for discrete Laplacian, in Proceedings of the 4th Workshop on Mathematical Modelling on Environmental and Life Sciences Problems, September 7-10, 2005 Constanta, Romania; Editura Academiei Romane, Bucuresti 2006, 181-190
  14. Bautu A., Bautu E., Popa C., Evolutionary algorithms in image reconstruction from limited data, in Proceedings of the 4th Workshop on Mathematical Modelling on Environmental and Life Sciences Problems, September 7-10, 2005 Constanta, Romania; Editura Academiei Romane, Bucuresti 2006, 15-26
  15. Bautu A., Bautu E., Popa C., Tikhonov regularization in image reconstruction with Kaczmarz Extended algorithm, in Proceedings of ASIM Conference, September 12-15 2005, Erlangen, Germany, SCS Publishing House e.V., 650-655
  16. Popa C., Zdunek R., Regularized ART with Gibbs priors for tomographic image reconstruction, in Proceedings of ASIM Conference, September 12-15 2005, Erlangen, Germany, SCS Publishing House e.V., 656-661
  17. Popa C., Zdunek R., Penalized least-squares image reconstruction for borehole tomography, in Proceedings of Algoritmy 2005 Conference on Scientific Computing, Vysoke Tatry - Podbanske, March 13-18, 2005; Slovak Univ. of Tech., Bratislava, 260-269
  18. Nicolescu B., Popa C., Ruede U., An extended-matrix preconditioner for nonself-adjoint nonseparable elliptic equations, in Proceedings of Algoritmy 2005 Conference on Scientific Computing, Vysoke Tatry - Podbanske, March 13-18, 2005; Slovak Univ. of Tech., Bratislava, 230-239
  19. Popa C., Zdunek R., New generalized oblique projections in DW algorithm with applications to borehole tomography, in Proceedings of The Third Workshop on Mathematical Modeling of Environmental and Life Sciences Problems, May 27-30, 2004, Constanta, Romania; Editura Academiei Romane, Bucuresti, 2004, 189-204
  20. Mohr M., Popa C., Ruede U., A differential inverse problem for cardiac imaging, in Proceedings of The Third Workshop on Mathematical Modeling of Environmental and Life Sciences Problems, May 27-30, 2004, Constanta, Romania; Editura Academiei Romane, Bucuresti, 2004, 231-242
  21. 26. Popa C. , Petcu D., Petcu M., On Kovarik's orthogonalization algorithm without matrix inversion, Sci. Bull. of ''Politehnica'' Univ. of Timisoara, Trans. on Automatic Control and Comp. Sci., 49(63), no. 2(2004), 223-226
  22. Popa C., A Kaczmarz-Kovarik algorithm for symmetric ill-conditioned matrices, Annals of ''Ovidius'' Univ. Constanta, Series Mathematics, vol. XII(2) (2004), 137-148
  23. Popa C., Extended Kaczmarz-like methods with oblique projections, Proc. Appl. Math. Mech. (PAMM) 2(2003), 491-492
  24. Popa C., On a modified Kovarik algorithm for symmetric matrices, Annals of ''Ovidius'' Univ. Constanta, Series Mathematics, vol. XI(1)(2003), 147-156
  25. Popa C., Supplementary directional relaxations for the acceleration of Kaczmarz's projections method, Revue d'Analyse Numerique et Optimization, Tome XXXII(1)(2003), 99-108
  26. Popa C., Some properties and applications of a modified Kovarik algorithm, Bulet. St. Tehnic, Univ. ''Politehnica'' Timisoara, Tom 48(63), nr. 2(2003), 49-56
  27. Petcu D., Popa C., On the parallel implementation of Kovarik's approximate orthogonalization algorithm, Proceedings of the 4th International Workshop SYNASC02, October 9-12, 2002 Timisoara, Romania, Editura Mirton Timisoara, 263-274
  28. Popa C., Direct and iterative Kaczmarz-like solvers, Annals of the West University of Timisoara, Romania, Series Mathematics, XL(2)(2002), 107-125
  29. Popa C., A fast Kaczmarz-Kovarik algorithm for consistent least-squares problems, Korean J. Comp. Appl. Math., 8(1) (2001), 9-26
  30. Pelican E., Popa C., Approximate orthogonalization of linearly independent functions with applications to Galerkin-like discretization techniques, Annals of Bucharest University, Mathematics, Anul L(2001), 179-184
  31. Popa C., On numerical solution of first kind Fredholm integral equations, Revue Roumaine Math. Pure et Appl., XLV(2) (2000), 305-311
  32. Popa C., Preconditioned Kaczmarz-extended algorithm with relaxation parameters, Korean Journal on Comp. and Appl. Math., 6(3) (1999), 523-535
  33. Popa C., Characterization of the solutions set of inconsistent least-squares problems by an extended Kaczmarz algorithm, Korean Journal on Comp. and Appl. Math., 6(1)(1999), 51-64
  34. Popa C., On some extensions of Kaczmarz's projections method, in ''Applied and Computing Mathematics II'' - T. U. Kosice, Slovak Republik, 1998, 113-120
  35. Popa C., Preconditioning for the fulfilment of the approximation assumption in the algebraic multigrid method, Studia Univ. ''Babes-Bolyai'' Cluj-Napoca, 40(1995), 77-102
  36. Golubovici G., Popa C., Supplementary relaxations for the acceleration of a class of iterative mathods, Annals of ''Ovidius'' Univ. Constanta, Series Mathematics, vol. 3(1995), 52-62
  37. Juncu Gh., Popa C., Preconditioning by approximations of the discrete Laplacian for non-selfadjoint elliptic equations, Annals of ''Ovidius'' Univ. Constanta, Series Mathematics, vol. 3(1995), 93-105
  38. Popa C., A coarsening algorithm for the algebraic multigrid method, Studii si Cerc. Matem., 46(1994), 613-624
  39. Golubovici G., Popa C., Interpolation and related coarsening techniques for the algebraic multigrid method, Intern. Series of Numer. Math., Birkhauser-Verlag, Berlin, 116(1994), 201-213
  40. Popa C., The construction of the interpolation operator with ILU decomposition for algebraic positive definite systems, Notes on Numerical Fluid Mech., 41(1993), 122-129
  41. Golubovici G., Popa C., Convergence study of a two grid algebraic multigrid algorithm for symmetric systems (in romanian), Studii si Cerc. Matem., 45 (1993), 139-149
  42. Popa C., A note on factorization of symmetric matrices with applications to least-squares problems, Annals of ''Ovidius'' Univ. Constanta, Series Mathematics, 1(1993), 59-64
  43. Popa C., ILU decomposition for coarse grid correction step on algebraic multigrid, ''Multigrid Methods: Special Topics and Appl. II, GMD - Studien 189(1991), 263-272
  44. Popa C., On the invertibility of a class of irreducible matrices, Studii si Cerc. Matem., 43(1991), 47-51
  45. Paraschiv I., Popa C., Numerical solutions of heat convective transfer equations, Rev. Roum. Mec. Appl., 34(1989), 527-530
  46. Popa C., On smoothing properties of SOR relaxation for algebraic multigrid method, Studii si Cerc. Matem., 41(1989), 399-406
  47. C. Popa, Rounding errors analysis for Jacobi and Gauss - Seidel iterative methods (in romanian), Studii si Cerc. Matem., 39(1987), 252-260