Associate Professor
    Department of Computer Science
    University of Ioannina
    GR-45110 Ioannina, Greece
    Tel     : +30-26510-98810
    Fax     : +30-26510-98882

Research Interests

• Computational Intelligence: Neural Networks, Fuzzy Logic, Genetic Algorithms
• Machine Learning: Statistical Methods based on Mixture Models, Reinforcement Learning
• Pattern Recognition: Clustering, Classification
• Bioinformatics, Intelligent Medical Information Systems
• Machine Learning for Signal Processing
• Scientific Computing Using Neural Networks

Journal Publications

• Likas, A. and Stafylopatis, A., "Multiscaling in Binary Hopfield-type Neural Networks: Application to the Set Partitioning Problem", International Journal of Neural Networks , Vol. 3, No. 2, pp. 55-65, June 1992.

• Stafylopatis, A. and Likas, A., "Pictorial Information Retrieval Using the Random Neural Network", IEEE Transactions on Software Engineering , Vol. 18, No. 7, pp. 590-600, July 1992.

• Kontoravdis, D., Likas, A. and Stafylopatis, A., "A Path-Finding Technique Based on the Integration of Neural Network Models at Different Levels of Abstraction", Elektrik - Special Issue on Neural Networks , Vol. 2, No. 1, pp. 40-51, April 1994 (invited paper).

• Kontoravdis, D., Likas, A. and Stafylopatis, A., "Enhancing Stochasticity in Reinforcement Learning Schemes: Application to the Exploration of Binary Domains", Journal of Intelligent Systems , Vol. 5, No. 1, pp. 49-77, 1995.

• Likas, A. and Stafylopatis, A., "Differential Association and Operational Equivalence of Discrete Hopfield Networks", Neural Network World , Vol. 5, No. 1, pp. 81-89, 1995.

• Likas, A. and Stafylopatis, A., "A Parallel Algorithm for the Minimum Weighted Vertex Cover Problem", Information Processing Letters , Vol. 53, pp. 229-234, 1995.

• Likas, A., Kontoravdis, D. and Stafylopatis, A., "Discrete Optimization Based on the Combined Use of Reinforcement and Constraint Satisfaction Schemes", Neural Computing and Applications , Vol. 3, pp. 101- 112, 1995.

• Likas, A., Papageorgiou, G. and Stafylopatis, A., "A Parallelizable Operation Scheme of the Boltzmann Machine Optimizer Based on Group Updates", Neural, Parallel and Scientific Computations , Vol. 3, pp. 451-466, 1995.

• Afif, M., Likas, A. and Paschos, V., "A Natural Model and a Parallel Algorithm for Approximately Solving the Maximum Weighted Independent Set Problem", Chaos, Solitons & Fractals , Vol. 5, No. 5, pp. 739-746, 1995.

• Likas, A. and Stafylopatis, A., "Group Updates and Multiscaling: An Efficient Neural Network Approach to Combinatorial Optimization", IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics , Vol. 26, No. 2, pp. 222-232, April 1996.

• Likas, A., Blekas, K. and Stafylopatis, A., "Parallel Recombinative Reinforcement Learning: A Genetic Approach", Journal of Intelligent Systems , vol. 6, no. 2, pp. 145-177, 1996.

• Likas, A. and Blekas, K., "A Reinforcement Learning Approach Based on the Fuzzy Min-Max Neural Network ", Neural Processing Letters , vol. 4, no. 3, pp. 167-172, 1996.

• Likas, A. and Stafylopatis, A., "High Capacity Associative Memory Based on the Random Neural Network Model", International Journal of Pattern Recognition and Artificial Intelligence , vol. 10, no. 8, pp. 919-937, 1997.

• Likas, A., Papageorgiou, G. and Stafylopatis, A., "A Connectionist Approach for Solving Large Constraint Satisfaction Problems", Applied Intelligence , vol. 7, pp. 215-225, 1997.

• Lagaris, I.E., Likas, A. and Fotiadis, D.I., "Artificial Neural Network Methods in Quantum Mechanics", Computer Physics Communications , vol. 104, pp. 1-14, 1997.

• Likas, A., Karras, D. and Lagaris, I., "Neural Network Training and Simulation Using a Multidimensional Optimization System", International Journal of Computer Mathematics , vol. 67, pp. 33-46, 1998.

• Blekas, K., Stafylopatis, A., Kontoravdis, D., Likas, A. and Karakitsos, P., "Cytological Diagnosis Based on Fuzzy Neural Networks", Journal of Intelligent Systems , vol. 8, pp. 55-79, 1998.

• Papageorgiou, G., Likas, A. and Stafylopatis, A., "A Hybrid Neural Optimization Scheme Based on Parallel Updates", International Journal of Computer Mathematics , vol. 67, pp. 223-237, 1998.

• Papageorgiou, G., Likas, A. and Stafylopatis, A., "Improved exploration in Hopfield Network State-Space through Parameter Perturbation Driven by Simulated Annealing ", European Journal of Operations Research , vol. 108, no. 2, pp. 283-292, 1998.

• Lagaris, I.E., Likas, A. and Fotiadis, D.I., "Artificial Neural Networks for Solving Ordinary and Partial Differential Equations", IEEE Trans. on Neural Networks , vol. 9, no. 5, pp. 987-1000, 1998.

• Likas, A. and Lagaris, I.E., "Training Reinforcement Neurocontrollers Using the Polytope Algorithm ", Neural Processing Letters , vol. 9, no. 2, pp. 119-127, 1999.

• Likas, A., "A Reinforcement Learning Approach to On-Line Clustering ", Neural Computation, vol. 11, no. 8, pp. 1915-1932, 1999.

• Vlassis, N. and Likas, A., "A Kurtosis-Based Dynamic Approach to Gaussian Mixture Modeling ", IEEE Trans. on Systems, Man and Cybernetics: Part A , vol. 29, no. 4, pp. 393-399, July 1999.

• Likas, A. and Stafylopatis, A., "Training the Random Neural Network Using Quasi-Newton Methods ", European Journal of Operations Research , vol. 126, no. 2, pp. 331-339, 2000.

• Lagaris, I.E., Likas, A. and Papageorgiou, D.G., "Neural Networks Methods for Boundary Value Problems with Irregular Boundaries", IEEE Trans. on Neural Networks , vol. 11, no. 5, pp. 1041-1049, Sept. 2000.

• Likas, A., "Reinforcement Learning Using the Stochastic Fuzzy Min-Max Neural Network", Neural Processing Letters, vol. 13, pp. 213-220, 2001.

• Likas, A., "Probability Density Estimation Using Artificial Neural Networks", Computer Physics Communications , vol. 135, no. 2, pp. 167-175, 2001.

• Papaloukas, C., Fotiadis, D.I., Liavas, A.P, Likas, A., Michalis, L.K., "A Knowledge-based Technique for Automated Detection of Ischemic Episodes in Long Duration ECGs", Medical and Biological Engineering and Computing , vol. 39, pp. 105-112, 2001.

• Titsias M. and Likas, A., "Shared Kernel Models for Class Conditional Density Estimation", IEEE Trans. on Neural Networks , vol. 12, no. 5, pp. 987-997, September 2001.

• Likas, A. and Paschos, V.T., "A note on a new greedy solution representation and a new greedy parallelizable heuristic for the traveling salesman problem", Chaos, Solitons & Fractals , vol. 13, pp. 71-78, 2001.

• Vlassis, N. and Likas, A., "A greedy EM algorithm for Gaussian mixture learning" , Neural Processing Letters , vol. 15, pp. 77-87, 2002.

• Papaloukas, C., Fotiadis, D.I., Likas, A. and Michalis, L.K., "An Ischemia Detection Method based on Artificial Neural Networks", Artificial Intelligence in Medicine , vol. 24, no. 2, pp. 167-178, February 2002.

• Papaloukas, C., Fotiadis, D.I., Likas, A., Michalis, L.K., "Use of a Novel Rule-Based Expert System in the Detection of Changes in the ST Segment and T Wave in Long Duration ECGs", Journal of Electrocardiology , vol. 35, no. 1, pp. 27-34, 2002.

• Papadopoulos, A., Fotiadis, D.I. and Likas, A., "An Automatic Microcalcification System based on a Hybrid Neural Network Classifier", Artificial Intelligence in Medicine , vol. 25, no. 2, pp. 149-167, 2002.

• Likas, A., Vlassis, N. and Verbeek, J., "The Global K-Means Clustering Algorithm" , Pattern Recognition , vol. 36, pp. 451-461, 2003.

• Titsias, M. and Likas, A., "Mixture of Experts Classification Using a Hierarchical Mixture Model" , Neural Computation , vol. 14, no. 9, pp. 2221-2244, 2002.

• Frossyniotis, D., Stafylopatis, A. and Likas, A., "A Divide-and-Conquer Method for Multi-net Classifiers", Pattern Analysis and Applications Journal, vol. 6, no. 1, pp. 32-40, 2003.

• Blekas, K., Fotiadis, D. and Likas, A., "Greedy Mixture Learning for Multiple Motif Discovery in Biological Sequences", Bioinformatics , vol. 19, no. 5, pp. 609-617, 2003.

• Titsias, M. and Likas, A., "Class Conditional Density Estimation Using Mixtures with Constrained Component Sharing" , IEEE Trans. on Pattern Analysis and Machine Intelligence , vol. 25, no.7, pp. 924-928, 2003.

• Blekas, K., Fotiadis, D. and Likas, A., "A Sequential Method for Discovering Probabilistic Motifs in Proteins", Methods of Information in Medicine ,vol. 43, pp. 9-12, 2004.

• Frossyniotis, D., Likas, A. and Stafylopatis, A., "A Clustering Method Based on Boosting", Pattern Recognition Letters , vol. 25, pp. 641-654, 2004.

• Likas, A. and Galatsanos, N., "A Variational Approach for Bayesian Blind Image Deconvolution", , IEEE Trans. on Signal Processing, Special Issue on Machine Learning Methods in Signal Processing , vol. 52, no. 8, pp. 2222-2233, August 2004.

• Goletsis, Y., Papaloukas, C., Fotiadis, D.I., Likas, A., Michalis, L.K., "Automated Ischemic Beat Classification Using Genetic Algorithms and Multicriteria Decision Analysis", IEEE Trans. on Biomedical Engineering, vol. 51, no. 10, pp. 1717-1725, October, 2004.

• Blekas, K., Fotiadis, D.I. and Likas, A., "Motif-Based Protein Sequence Classification Using Neural Networks", Journal of Computational Biology, vol. 12, no. 1, pp. 64-82, 2005.

• Tsoulos I.G., Lagaris, I.E. and Likas, A., "Exploiting Parallelism for Function Approximation Using Modular Neural Networks", Neural, Parallel and Scientific Computations, vol. 13, pp. 161-178, 2005.

• Blekas, K., Likas, A., Galatsanos, N. and Lagaris I.E., "A Spatially-Constrained Mixture Model for Image Segmentation", IEEE Trans. on Neural Networks, vol. 16, no.2, March 2005.

• Papadopoulos, A., Fotiadis, D.I. and Likas, A., "Characterization of Clustered Microcalcifications in Digitized Mammograms Using Neural Networks and Support Vector Machines", Artificial Intelligence in Medicine,vol. 34, pp. 141-150, 2005.

• Blekas, K., Galatsanos, N. Likas, A. and Lagaris I.E., "Mixture Model Analysis for DNA Microarray Images", IEEE Trans. on Medical Imaging, vol 24, no. 7, pp. 901-909, July 2005.

• Protopappas, V., Baga, D.,Fotiadis, D.I., Likas, A., Papachristos, C. and Malizos, K, "An Ultrasound Wearable System for the Monitoring and Acceleration of Fracture Healing in Long Bones", IEEE Trans. on Biomedical Engineering,vol. 52, no. 9, pp. 1597-1608, September 2005.

• Constantinopoulos C., Titsias M.K. and Likas, A., "Bayesian Feature and Model Selection for Gaussian Mixture Models", IEEE Trans. on Pattern Analysis and Machine Intelligence, vol. 28, no. 6, pp. 1013-1018, June 2006.

• Constantinopoulos C. and Likas, A., "An Incremental Training Method for the Probabilistic RBF Network", IEEE Trans. on Neural Networks, vol. 17, no.4, pp. 966-974, July 2006.

• Chantas G, Galatsanos N and Likas, A., "Bayesian Image Restoration Using a New Nonstationary Edge-Preserving Image Prior", IEEE Trans. on Image Processing, vol. 15, no. 10, pp. 2987-2997, October 2006.

• Nikou C., Galatsanos N. and Likas A., "A Class-Adaptive Spatially Variant Mixture Model for Image Segmentation", IEEE Trans. on Image Processing, vol. 16, no. 4, pp. 1121-1130, April 2007.

• Constantinopoulos C. and Likas, A., "Unsupervised Learning of Gaussian Mixtures Based on Variational Component Splitting", IEEE Trans. on Neural Networks, vol. 18, no. 3, pp. 745-755, 2007.

Conferences (not updated recently)

• Gelenbe, E., Stafylopatis, A. and Likas, A., "Associative Memory Operation of the Random Network Model", Proc. International Conference on Artificial Neural Networks (ICANN 91) , Vol. 1, pp. 307-312, Espoo, Finland, June 1991, (North-Holland, 1991).

• Likas, A. and Stafylopatis, A., "An Investigation of the Analogy between the Random Network and the Hopfield Network", Proc. 6th International Symposium on Computer and Information Sciences , pp. 849-857, Antalya, Turkey, Nov. 1991, (North-Holland, 1991).

• Kontoravdis, D., Likas, A. and Stafylopatis, A., "Collision-Free Movement of an Autonomous Vehicle Using Reinforcement Learning", Proc. European Conference on Artificial Intelligence (ECAI 92) , pp. 666-670, Vienna, August 1992, (John Wiley and Sons, 1992).

• Kontoravdis, D., Likas, A. and Stafylopatis, A., "A Reinforcement Learning Algorithm for Networks of Units with Two Stochastic Levels", Proc. International Conference on Artificial Neural Networks (ICANN 92) , pp. 143-146, Brighton, UK, Sep. 1992, (North-Holland, 1992).

• Kontoravdis, D., Likas, A. and Stafylopatis, A., "Embedding Knowledge into Stochastic Learning Automata for Fast Solution of Binary Constraint Satisfaction Problems", Proc. European Symposium on Artificial Neural Networks (ESANN'93) , pp. 21-26, Brussels, April 1993.

• Likas, A. and Stafylopatis, A., "A Neural Network Technique for Associative Retrieval of Symbolic Pictures", Proc. IEEE Int. Conf. on Neural Network Applications to Signal Processing (NNASP'93) , pp. 204-209, Singapore, August 1993.

• Kontoravdis, D., Likas, A. and Stafylopatis, A., "Efficient Reinforcement Learning Stategies for the Pole Balancing Problem", Proc. International Conference on Artificial Neural Networks (ICANN 94) , Vol. 1, pp. 659-662, Sorento, Italy, May 1994.

• Kontoravdis, D., Likas, A., Blekas, K. and Stafylopatis, A., "A Fuzzy Neural Network Approach to Autonomous Vehicle Navigation", Proc. European Robotics and Intelligent Systems Conference (EURISCON'94) , pp. 243-252, Malaga, Spain, August 1994.

• Likas, A., Blekas, K. and Stafylopatis, A., "Application of Fuzzy Min-Max Neural Network Classifier to Problems with Continuous and Discrete Attributes", Proc. IEEE Int. Workshop on Neural Networks for Signal Processing (NNSP'94) , pp. 163-170, Ermioni, Greece, September 1994.

• Likas, A., Blekas, K. and Stafylopatis, A., "Parallel Recombinative Reinforcement Learning", Proc. 8th European Conference on Machine Learning (ECML-95) , Heraklion, Greece, April 1995, (Lecture Notes in Artificial Intelligence, Vol. 912, pp. 311-314, Springer Verlag, 1995).

• Bouju, A., Boyce, J.F., Dimitropoulos, C.H.D., vom Scheidt, G., Taylor, J.G., Likas, A., Papageorgiou, G. and Stafylopatis, A., "Intelligent Search for the Radio Links Frequency Assignment Problem", Proc. Int. Conference on Digital Signal Processing (DSP95) , pp. 408-414, Limassol, Cyprus, June 1995.

• Blekas, K., Likas, A. and Stafylopatis, A., "A Fuzzy Neural Network Approach Based on Dirichlet Tesselations for Nearest Neighbor Classification of Patterns", Proc. IEEE Int. Workshop on Neural Networks for Signal Processing (NNSP'95) , pp. 153-161, Boston, MA, Aug.-Sep. 1995.

• Lagaris, I.E, Likas, A., Fotiadis, D.I. and Massalas, C.V., "A Hardware Implementable Non-linear Method for the Solution of Ordinary, Partial and Integrodifferential Equations", Workshop on Applied Mathematics in Science and Modern Technology , Metsovo, Greece, July 1997.

• Blekas, K., Likas, A. and Stafylopatis, A., "A Fuzzy Neural Network Approach to Classification Based on Proximity Characteristics of Patterns", Proc. 9th IEEE Int. Conference on Tools with Artificial Intelligence (ICTAI'97) , Newport Beach, CA, November, 1997.

• Titsias M. and Likas, A., "A Probabilistic RBF Network for Classification", Proc. of the Int. Joint Conference on Neural Networks (IJCNN'2000) , Como, Italy, July 2000.

• Titsias, M., Fotiadis, D.I. and Likas, A., "Estimation of Concrete Characteristics Using Pattern Recognition Methods", 6th National Congress on Mechanics , Thessaloniki, Greece, 2001.

• Papaloukas, C., Fotiadis, D.I., Likas, A. and Michalis, L.K., "A Neural Network Methodology for Ischaemia Detection in Long Duration Elec trocardiograms", Neural Networks and Expert Systems in Medicine and Healthcare, NNESMED 2001 , Milos, Greece, June 2001.

• Papadopoulos, A., Fotiadis, D.I. and Likas, A., "A Hybrid Neural Network Method for Microcalcification Cluster Detection in Mammography", Neural Networks and Expert Systems in Medicine and Healthcare, NNESMED 2001 , Milos, Greece, June 2001.

• Frossyniotis, D., Vrettos, S., Stafylopatis, A., Fotiadis, D.I., Likas, A. and Potamias, G., "An Intelligent System for the Early Diagnos is of Coronary Artery Disease", Neural Networks and Expert Systems in Medicine and Healthcare, NNESMED 2001 Milos, Greece, June 2001.

• Blekas, K, Fotiadis, D.I. and Likas, A., "A Sequential Method for Discovering Probabilistic Motifs in Proteins", 4th International Workshop on Biosignal Interpretation , June 2002, Villa Olmo, Como, Italy.

• Valasoulis, K, Fotiadis, D.I., Lagaris I.E. and Likas, A., "Solving Differential Equations with Neural Networks: Implementation on a DSP Platform", 14th International Conference on Digital Signal Processing , Santorini, Greece, July 2002.

• Constantinopoulos, C., Titsias, M. and Likas, A., "A Bayesian Regularization Method for the Probabilistic RBF Network", Proc. 2nd Hellenic Conference on AI, SETN 2002 , pp. 337-345, Springer, 2002.

• Tsoulos I.G., Lagaris, I.E. and Likas, A., "Piecewise Neural Networks for Function Approximation Cast in a Form Suitable for Parallel Implementation", Proc. 2nd Hellenic Conference on AI, SETN 2002 , pp. 314-324, Springer, 2002.

• Blekas, K., Fotiadis, D.I. and Likas, A., "Protein Sequence Classification using Probabilistic Motifs and Neural Networks ", Proc. Intern. Conference on Artificial Neural Networks (ICANN/ICONIP 2003) , Istanbul, Turkey, Lecture Notes in Computer Science, vol. 2714, Springer -Verlag, pp. 702-709, 2003.

• Blekas, K. and Likas, A., "Incremental Mixture Learning for Clustering Discrete Data", Proc. 3rd Hellenic Conference on AI, SETN 2004 , pp. 210-219, Springer, 2004.

• Constantinopoulos, C. and Likas, A., "Efficient Training Algorithms for the Probabilistic RBF Network", Proc. 3rd Hellenic Conference on AI, SETN 2004 , pp. 183-190, Springer, 2004.

• Likas, A. and Galatsanos, N., "A Variational Method for Bayesian Blind Image Deconvolution", Proceedings of the IEEE International Conference on Image Processing (ICIP'03), Barcelona, Spain, September 2003.

• Valasoulis, K. and Likas, A., "Probabilistic Shape-Based Image Indexing and Retrieval", Proceedings of the IEEE International Conference on Pattern Recognition (ICPR'04) , Cambridge, UK, August 2004.

• Chantas, G., Galatsanos, N. and Likas, A., "Non Stationary Bayesian Image Restoration", Proceedings of the IEEE International Conference on Pattern Recognition (ICPR'04), Cambridge, UK, August 2004.

• Tzikas, D., Likas, A., Galatsanos, N., Lukic, A. and Wernick, M., "Bayesian Regression of Functional Neuroimages", Proc. EUSIPCO-2004 , Vienna, August 2004.

• Blekas, K., Likas, A., Galatsanos, N. and Lagaris, I.E., "Mixture Model Based Image Segmentation with Spatial Constraints", Proc. EUSIPCO-2004 , Vienna, August 2004.