Imperial College London

STEFANOS ZAFEIRIOU, PhD

Faculty of EngineeringDepartment of Computing

Reader in Machine Learning and Computer Vision
 
 
 
//

Contact

 

+44 (0)20 7594 8461s.zafeiriou Website CV

 
 
//

Location

 

375Huxley BuildingSouth Kensington Campus

//

Summary

 

Publications

Publication Type
Year
to

220 results found

Eyben F, Petridis S, Schuller B, Tzimiropoulos G, Zafeiriou S, Pantic Met al., 2011, Audiovisual Classification of Vocal Outbursts in Human Conversation Using Long-Short-Term Memory Networks, Publisher: IEEE, Pages: 5844-5847

Conference paper

Tzimiropoulos G, Zafeiriou S, Pantic M, 2011, Robust and efficient parametric face alignment, ICCV 2011, Publisher: IEEE, Pages: 1847-1854, ISSN: 1550-5499

Conference paper

Zafeiriou S, Petrou M, 2010, Sparse representations for facial expressions recognition via l<inf>1</inf> optimization, Pages: 32-39

In this paper, the principles of sparse signal representation theory are explored in order to perform facial expressions recognition from frontal views. Motivated by the success such methods have demonstrated in the face recognition problem, we formulate the feature extraction procedure in order to achieve facial expression recognition as an l1 optimization problem. We show that the straightforward application of these methods to expressive images imposes certain difficulties. The use of difference images (i.e., the images that are derived from the subtraction of the neutral image from the expressive one) for sparse facial expression representations is justified. The use of expressive facial grids for similar tasks is also studied. Finally, the robustness of the proposed representations under facial image occlusion is shown and the efficacy of the proposed method in a series of experiments is demonstrated © 2010 IEEE.

Conference paper

Zafeiriou S, Laskaris N, 2010, Nonnegative Embeddings and Projections for Dimensionality Reduction and Information Visualization, 2010 20th International Conference on Pattern Recognition (ICPR), Publisher: IEEE

Conference paper

Argyriou V, Sevaslidou M, Zafeiriou S, 2010, Virtual university as a role playing game, Pages: 743-747

Research and development in design of games for education focus on understanding better what features of games can be inherited to further motivate students and simultaneously improve learning outcomes. Since, a common design standard is not available for educational games solutions are usually carried out by an ad hoc process. In this paper, a novel approach to design this kind of games is presented taking into consideration key features of the most successful massively multiplayer online role-playing games (MMORPG). The proposed design incorporates fun and learning through the key ingredients of MMORPGs that make them 'addictive' keeping the players constantly motivated. Our main contribution is to suggest design issues that should be taken into consideration when designing educational games. © 2010 IEEE.

Conference paper

Tzimiropoulos G, Argyriou V, Zafeiriou S, Stathaki Tet al., 2010, Robust FFT-Based Scale-Invariant Image Registration with Image Gradients, IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol: 32, Pages: 1899-1906, ISSN: 0162-8828

Journal article

Nikolopoulos S, Zafeiriou S, Nikolaidis N, Pitas Iet al., 2010, Image replica detection system utilizing R-trees and linear discriminant analysis, Pattern Recognition, Vol: 43, Pages: 636-649, ISSN: 0031-3203

Journal article

Toderici G, Passalis G, Zafeiriou S, Tzimiropoulos G, Petrou M, Theoharis T, Kakadiaris IAet al., 2010, Bidirectional relighting for 3D-aided 2D Face Recognition, 23rd IEEE Conference on Computer Vision and Pattern Recognition (CVPR), Publisher: IEEE COMPUTER SOC, Pages: 2721-2728, ISSN: 1063-6919

Conference paper

Zafeiriou S, Hansen MF, Atkinson GA, Petrou M, Smith MLet al., 2010, Baseline face recognition using photometric stereo data, International Conference and Exhibition on Biometrics Technology, Publisher: ELSEVIER SCIENCE BV, Pages: 20-25, ISSN: 1877-0509

Conference paper

Zafeiriou S, Petrou M, 2010, Nonlinear non-negative component analysis algorithms, Image Processing, IEEE Transactions on, Vol: 19, Pages: 1050-1066

Journal article

Tzimiropoulos G, Zafeiriou S, 2010, On the Subspace of Image Gradient Orientations, CoRR, Vol: abs/1005.2715

Journal article

Zafeiriou S, Petrou M, Argyriou V, 2009, 2.5D elastic graph matching algorithms, Pages: 703-710

In this paper, a series of advances in Elastic Graph Matching (EGM) for face recognition assisted by the availability of 3D facial geometry is proposed. More specifically, we conceptually extend the EGM algorithm in order to exploit the 3D nature of human facial geometry for face recognition/verification. In order to achieve that, first we extend the matching module of the EGM algorithm in order to capitalize on the 2.5D facial data. Moreover, we incorporate the 3D geometry into the multiscale analysis used and build a novel geodesic multiscale morphological pyramid of dilations/erosions in order to fill the graph jets. We demonstrate the effficiency of the proposed advances in the face recognition/verification problem. ©2009 IEEE.

Conference paper

Laskaris NA, Zafeiriou SP, Garefa L, 2009, Use of random time-intervals (RTIs) generation for biometric verification, Pattern Recognition, Vol: 42, Pages: 2787-2796, ISSN: 0031-3203

Journal article

Zafeiriou S, 2009, Discriminant Nonnegative Tensor Factorization Algorithms, IEEE TRANSACTIONS ON NEURAL NETWORKS, Vol: 20, Pages: 217-235, ISSN: 1045-9227

Journal article

Kotsia I, Zafeiriou S, Pitas I, 2009, Novel Multiclass Classifiers Based on the Minimization of the Within-Class Variance, IEEE TRANSACTIONS ON NEURAL NETWORKS, Vol: 20, Pages: 14-34, ISSN: 1045-9227

Journal article

Zafeiriou S, Petrou M, 2009, Nonlinear nonnegative component analysis, Pages: 2860-2865

In this paper general solutions for Nonlinear Nonnega- tive Component Analysis for data representation and recog- nition are proposed. That is, motivated by a combination of the Nonnegative Matrix Factorization (NMF) algorithm and kernel theory, which has lead to an NMF algorithm in a polynomial feature space [1], we propose a general frame- work where one can build a nonlinear nonnegative compo- nent analysis using kernels, the so-called Projected Gradi- ent Kernel Nonnegative Matrix Factorization (PGKNMF). In the proposed approach, arbitrary positive kernels can be adopted while at the same time it is ensured that the limit point of the procedure is a stationary point of the optimiza- tion problem. Moreover, we propose fixed point algorithms for the special case of Radial Basis Function (RBF) kernels. We demonstrate the power of the proposed methods in face and facial expression recognition applications. © 2009 IEEE.

Conference paper

Zafeiriou S, Petrou M, 2009, Nonlinear Nonnegative Component Analysis, IEEE-Computer-Society Conference on Computer Vision and Pattern Recognition Workshops, Publisher: IEEE, Pages: 2852-2857, ISSN: 1063-6919

Conference paper

Zafeiriou S, Pitas I, 2008, Discriminant Graph Structures for Facial Expression Recognition, IEEE TRANSACTIONS ON MULTIMEDIA, Vol: 10, Pages: 1528-1540, ISSN: 1520-9210

Journal article

Nikitidis S, Zafeiriou S, Pitas I, 2008, Camera Motion Estimation Using a Novel Online Vector Field Model in Particle Filters, IEEE Transactions on Circuits and Systems for Video Technology, Vol: 18, Pages: 1028-1039, ISSN: 1051-8215

Journal article

Laskaris NA, Zafeiriou SP, 2008, Beyond FCM: Graph-theoretic post-processing algorithms for learning and representing the data structure, Pattern Recognition, Vol: 41, Pages: 2630-2644, ISSN: 0031-3203

Journal article

Kotsia I, Zafeiriou S, Pitas I, 2008, Texture and shape information fusion for facial expression and facial action unit recognition, Pattern Recognition, Vol: 41, Pages: 833-851, ISSN: 0031-3203

Journal article

Kotsia I, Zafeiriou S, Nikolaidis N, Pitas Iet al., 2008, Texture and Shape Information Fusion for Facial Action Unit Recognition, First International Conference on Advances in Computer-Human Interaction, Publisher: IEEE

Conference paper

Goudelis G, Zafeiriou S, Tefas A, Nikolaidis N, Pitas Iet al., 2008, Motivating class-specific nonlinear projections for single and multiple view face verification., Publisher: IEEE, Pages: 2752-2755

Conference paper

Nikitidis S, Zafeiriou S, Pitas I, 2008, Camera Motion Estimation Using Particle Filters., Publisher: INSTICC - Institute for Systems and Technologies of Information, Control and Communication, Pages: 670-673

Conference paper

Kotsia I, Zafeiriou S, Pitas I, 2008, Discriminant Non-negative Matrix Factorization and Projected Gradients for Frontal Face Verification., Publisher: Springer, Pages: 82-90

Conference paper

Zafeiriou S, Tefas A, Pitas I, 2007, Minimum Class Variance Support Vector Machines, IEEE Transactions on Image Processing, Vol: 16, Pages: 2551-2564, ISSN: 1057-7149

Journal article

Zafeiriou S, Tefas A, Pitas I, 2007, The discriminant elastic graph matching algorithm applied to frontal face verification, Pattern Recognition, Vol: 40, Pages: 2798-2810, ISSN: 0031-3203

Journal article

Goudelis G, Zafeiriou S, Tefas A, Pitas Iet al., 2007, Class-Specific Kernel-Discriminant Analysis for Face Verification, IEEE Transactions on Information Forensics and Security, Vol: 2, Pages: 570-587, ISSN: 1556-6013

Journal article

Kotsia I, Zafeiriou S, Pitas I, 2007, A Novel Discriminant Non-Negative Matrix Factorization Algorithm With Applications to Facial Image Characterization Problems, IEEE Transactions on Information Forensics and Security, Vol: 2, Pages: 588-595, ISSN: 1556-6013

Journal article

Zafeiriou S, Tefas A, Pitas I, 2007, Learning Discriminant Person-Specific Facial Models Using Expandable Graphs, IEEE Transactions on Information Forensics and Security, Vol: 2, Pages: 55-68, ISSN: 1556-6013

Journal article

This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.

Request URL: http://wlsprd.imperial.ac.uk:80/respub/WEB-INF/jsp/search-html.jsp Request URI: /respub/WEB-INF/jsp/search-html.jsp Query String: id=00581716&limit=30&person=true&page=7&respub-action=search.html