Athens Tech College

• Machine Learning
• Image Processing, Computer Vision
• Algorithms and Programming (Web, E-Media, Mobile, Object Oriented, Procedural, Parallel)
• High Performance Computing
• VLSI systolic/wavefront systems
• Performance evaluation of high performance systems.

• 2003 – 2013, Athens University of Economics and Business,
  Department of Business Administration – Ast. Professor (Lecturer form 2006 and back) (P.D. 407/80),
•  2003-2012, Hellenic Open University, Department of informatics – Instructor – Advisor
•  2001 – 2002, Democritus University of Thrace, Faculty of Engineering, Department of Electrical and Computer Engineering – Ast. Professor (P.D. 407/80),
•  1999 – 2001, Athens University of Economics and Business, Department of Informatics – Lecturer (P.D. 407/80),
•  1999 – 2000, University of Patras, School of Engineering, Department of Electrical and Computer Engineering – Ast. Professor (P.D. 407/80),
•  1999 – 2013, University of Hertfordshire, UK, IST College, Greece (franchise), Dept. of Computer Science – Lecturer
• 1993 – 1999, Athens University of Economics and Business, Department of Informatics – Instructor BSc, MSc (Tutorials, Labs) 
• 2000-2003, National and Capodistrian University of Athens, Aristotle University of Thessaloniki, University of Ioannina, University of Piraeus – Inter-University Cooperation MSc Program, Health Services Management & Administration – Health Informatics, Visitor Lecturer,
•  1999-2002, National and Capodistrian University of Athens, Athens University of Economics and Business. Inter-University Cooperation MSc Program, Basic and Applied Knowledge Science, Visitor Lecturer

Papers in International Journals

• B. Efremides, Detection of Seam Carving in Uncompressed Images using eXtreme Gradient Boosting, International Journal of Computer Science and Information Security, vol. 16, no. 5, pp. 1–5, 2018.
• O.B. Efremides, From Emotion Recognition to Website Customizations, International Journal of Advanced Computer Science and Applications, Vol. 7, No. 7, pp. 521-525, 2016.
• D.P. Iracleous, K. Moutsakis, O.B. Efremides, Performance of Web Services Security Mechanisms: Analysis and Evaluation, Journal of Applied Mathematics & Bioinformatics, Sciencepress Ltd, Vol. 3, No. 4, pp. 107-123, 2013
• Dervisi, O.B. Efremides, D.P. Iracleous, Terrain Coverage Ant Algorithms: The Random Kick Effect, International Journal of Advanced Computer Science and Applications, Vol. 4, No. 10, 2013.
• O.B. Efremides and A.P. Goudas, Extending ADO.NET using a Decorator-Pattern Based Framework, International Journal of Software Engineering and Computing, Serials Pubs. Vol. 1, pp. 37-46, 2009
• O.B. Efremides and G. L. Ivanov, A Study for Data Pool Dynamic Workload Approaches of a String Matching Algorithm over a Heterogeneous Cluster, World Scientific and Engineering Academy and Society,  Transactions on Computers, pp. 1466-1473, 2006
• O.B. Efremides and G. L. Ivanov, High-Level Checkpoint Thread Based Mechanism for Fault Tolerant Parallel Text Matching, Transactions on Information Science and Applications, World Scientific and Engineering Academy and Society, pp. 1316-1323, 2006
• G.A. Gravvanis, K.M. Giannoutakis, M.P. Bekakos and O.B. Efremides, Parallel and Systolic Solution of Normalized Explicit Approximate Inverse Preconditioning, The Journal of Supercomputing, Vol, 30, pp.77-96, 2004
• O.B. Efremides, M.P. Bekakos and D.J. Evans, Integrated Classifier Simulator and Neurochip VHDL Implementation, International Journal of Computer Mathematics, Vol, 80, No. 11,  pp. 1343-1350, 2003.
• O.B. Efremides, M.P. Bekakos, A Multicomputer System Performance Predictor based on an ALN Neurochip, Journal of Mathematical Modelling and Algorithms, Vol 1, pp. 215–223, 2002.
• O.B. Efremides, M.P. Bekakos and D.J. Evans, Performance Evaluation Model for Multicomputer Systems, Journal of Neural Parallel & Scientific Computations, Vol. 10, pp. 15-24, 2002
• O.B. Efremides and M.P. Bekakos and D.J. Evans, Implementation of the Generalized WZ Factorization on a Wavefront Array Processor, International Journal of Computer Mathematics, Vol. 79, No. 7, pp. 807-815, 2002
• A.N. Kastania M.P. Bekakos and O.B. Efremides, Neurochip Logic Design and Simulation of an Integrated Classifier, Nonlinear Analysis, Vol. 47, No. 4, pp. 2301-2308, 2001
• M.P. Bekakos, O.B. Efremides and A.N. Kastania Concurrent Exploitation of Multiple Pipes Arrangements on 3D Mesh(d) Architectures, Journal of Neural Parallel & Scientific Computations, Vol. 9, No. 1, pp. 1-18, 2001
• O.B. Efremides, Distributed-Memory Systems Performance Evaluation using Synthetic Parametric Workloads, Journal of Neural Parallel and Scientific Computations, Vol. 8, No. 3-4, pp. 299-316, 2000
• M.P. Bekakos and O.B. Efremides, An Efficient Approach to Mapping Large ANNs onto Fixed Systolic Architectures, International Journal of Computer Mathematics, Vol. 67, pp. 127-137, 1998
• M.P. Bekakos and O.B. Efremides, A New Efficient Pipelined-Systolic Matrix-Vector Multiplication Algorithm for a Tree-Structured Machine, Nonlinear Analysis, Theory, Methods & Applications: An International Multidisciplinary Journal, Vol. 30, No. 8, pp. 5015-5019, 1997
• M.P. Bekakos and O.B. Efremides, An Alternative Faster Systolic Tridiagonal Linear Solver, Journal of Neural Parallel and Scientific Computations, Vol. 4, No. 1, pp. 13-24, 1996
• M.P. Bekakos and O.B. Efremides, A Class of Systolic Tridiagonal Linear Solvers, Journal of Parallel Processing Letters, Vol. 6, No. 3, pp. 355-364, 1996

Papers in International Conferences Proceedings (refereed)

• P. Iracleous, O. B. Efremides, V. Karelia, I. Baziotis, Sequential and Threaded Internal Sorting of Large XML Files, International Conference on Software Engineering, Parallel and Distributed Systems, Cambridge, UK, 2013
• D.P. Iracleous, T. Dovras, I. Neokosmidis, O.B. Efremides, Fuzzy Consensus Algorithms for Mobile Ad Hoc Networks Flocking, Mathematical Methods for Information Science and Economics,  Montreux, Switzerland 2012
• K.D. Papadimakis and O.B. Efremides, A Lightweight Protocol for Multi-Channel Audio Transfer over Ethernet, 2nd International Conference on Information and Multimedia Technology IACSIT-IEEE, Hong Kong, pp. V-2.1-2.5, 2010
• P.S. Stergiopoulos and O.B. Efremides, Optimizing ANN’s Architecture for Audio Music Genre Classification, International Conference on Machine Learning and Computing, Perth, Australia, Vol.20, pp. 230-233, 2009. Also appeared: Journal of International Proceedings of Computer Science and Information Technology,  Vol. 3, IACSIT Press, Singapore, 2011
• O.B. Efremides and G. L. Ivanov, A Dynamic Workload Balancing Technique of a Text Matching Algorithm on a Cluster, The 5th International Conference on Telecommunication and Informatics, Istanbul, Turkey, pp. 287-292, 2006
• O.B. Efremides and G. L. Ivanov, A Fault-Tolerant Parallel Text Searching Technique on a Cluster of Workstations, The 5th International Conference on Applied Computer Science, Hangzhou, China, pp. 368-373, 2006
• Gravvanis, M. Bekakos and O. Efremides, Parallel Implicit Preconditioned Conjugate Gradient Methods For Solving Biharmovic Equations, 6th Hellenic-European Conference on Computer Mathematics and its Applications, Athens, Greece, 2003
• O.B. Efremides, M.P. Bekakos and K.D. Antonakopoulos, Systolic Systems Description Using State Equations, 6th Hellenic-European Conference on Computer Mathematics and its Applications, 2003
• Ο.Β. Efremides and M.P. Bekakos, A Study of a B&F Linear Solver, 5th Hellenic-European Conference on Computer Mathematics and its Applications, pp. 294-297 Athens, Greece, 2001
• Ο.Β. Efremides and M.P. Bekakos, Design of a Neurochip Performance Predictor for a Multicomputer System, International Conference on Parallel and Distributed Processing Techniques and Applications 2001, pp. 1769-1772, Las Vegas, USA, 2001
• Ο.Β. Efremides and M.P. Bekakos, Processor-Time Optimal Systolic Matrix Multiplication, International Conference on High Performance Computing, Applications of High Performance Computers in Engineering VI, pp. 223-232, Hawaii, USA, 2000
• M.P. Bekakos and O.B. Efremides, An Area Efficient MDR Systolic Procedure for Solving Linear Systems, 4th Hellenic-European Conference on Computer Mathematics and its Applications, pp. 337-345, Athens, Greece, 1998
• O.B. Efremides and M.P. Bekakos, A Nonlinear Approach to Design Processor-Time Optimal Systolic Arrays For Matrix-Vector Multiplication, 4th Hellenic-European Conference on Computer Mathematics and its Applications, pp. 327-336, Athens, Greece,1998
• M.P. Bekakos, O.B. Efremides, and E.A. Lipitakis, Parallel Simulators of Artificial Neural Networks, 4th Hellenic-European Conference on Computer Mathematics and its Applications, pp. 318-326, Athens, Greece, 1998
• M.P. Bekakos and O.B. Efremides, A New Efficient Pipelined-Systolic Matrix Multiplication Algorithm for a Tree-Structured Machine, 3rd Hellenic-European Conference on Mathematics and Informatics, pp. 282-288, Athens, Greece, 1996
• M.P. Bekakos and O.B. Efremides, An Efficient Parallel Approach to Reduce Sparse Matrices with Invariant Entries, 4th International Conference on Applications of High-Performance Computing in Engineering, pp. 11-18, Milan, Italy, 1995
• O.B. Efremides and M.P. Bekakos, A Parallel Approach to the Bandwidth Minimization (BM) Problem, 3rd Balkan Conference on Operational Research, pp. 450-457, Thessaloniki, Greece, 1995
• M.P. Bekakos, E.A. Lipitakis and O.B. Efremides, Parallel Exploitation of Multiple Pipes Arrangements on Mesh Architectures, 2nd Hellenic-European Conference on Mathematics and Informatics, pp. 855-868, Athens, Greece, 1994
• M.P. Bekakos and O.B. Efremides, Implementation of a Modified Systolic Solver on Mesh Architectures, 27th International Symposium on Advanced Transportation Applications, International Dedicated Conference on Supercomputer Applications in the Transportation Industries, pp. 899-906, Aachen, Germany, 1994
• M.P. Bekakos and O.B. Efremides, Program Representation of a R&F Systolic Algorithm, 26th International Symposium on Automotive Technology and Automation, Conference on Supercomputer Applications in the Automotive Industries, pp. 199-205, Aachen, Germany, 1993

Chapters in Edited Books (International Editions)

• M.P. Bekakos, O.B. Efremides and D.J. Evans, Quadrant Interlocking Factorization on Systolic and Wavefront Array Processors, Neural Networks and Systolic Array Design, Series in Machine Perception and Artificial Intelligence, Vol. 49, World Scientific Publications, ISBN 981-02-4840-7, 2002
• Ο.Β. Efremides and M.P. Bekakos, Designing Processor-Time Optimal Systolic Configurations, Highly Parallel Computations: Algorithms and Applications, Series in High Performance Computing, Vol. 5, Computational Mechanics Publications, ISBN 1-85312-748-5, 2001

Text Books

• Introduction to Programming with Pascal & Turbo Pascal, M.P. Bekakos, Ο.Β. Εfremides and Α.Ν. Κastania, Stamoulis Pub., Athens-Peiraias, 1994 (in greek)

Technical Reports

• M.P. Bekakos and O.B. Efremides, An Area Efficient MDR Systolic Procedure for Solving Linear Systems, AUEB INFO TR: 14, Athens University of Economics and Business, Athens, February 1998
• O.B. Efremides and M.P. Bekakos, Implementation of the Generalized WZ Factorization on a Wavefront Array Processor, AUEB INFO TR: 13, Athens University of Economics and Business, Athens, February 1998
• M.P. Bekakos and O.B. Efremides, An Efficient Approach to Mapping Large ANNs onto Fixed Systolic Architectures, AUEB INFO TR: 9, Athens University of Economics and Business, Athens, December 1996
• M.P. Bekakos and O.B. Efremides, A New Efficient Pipelined-Systolic Matrix Multiplication Algorithm for a Tree-Structured Machine, AUEB INFO TR: 5, Athens University of Economics and Business, Athens, July 1996
• M.P. Bekakos and O.B. Efremides, A New Efficient Pipelined-Systolic Matrix-Vector Multiplication Algorithm for a Tree-Structured Machine, AUEB INFO TR: 1, Athens University of Economics and Business, Athens, July 1996