Chabane Djeraba

136 papers A* 6A 4B 15C 12Misc 1Journal 24Unranked 55
YearRankTypeTitle / Venue / Authors
2022 J jnl
A comparative study on optical flow for facial expression analysis.
Neurocomputing
Benjamin Allaert, Isaac Ronald Ward, Ioan Marius Bilasco, Chabane Djeraba, Mohammed Bennamoun
2021 C conf
Human Action Recognition Based on Body Segmentation Models.
CBMI
Catherine Huyghe, Nacim Ihaddadene, Thomas Haessle, Chabane Djeraba
2018 J jnl
Impact of the face registration techniques on facial expressions recognition.
Signal Process. Image Commun.
Benjamin Allaert, José Mennesson, Ioan Marius Bilasco, Chabane Djeraba
2018 C conf
Mastering Occlusions by Using Intelligent Facial Frameworks Based on the Propagation of Movement.
CBMI
Delphine Poux, Benjamin Allaert, José Mennesson, Nacim Ihaddadene, Ioan Marius Bilasco, Chabane Djeraba
2018 — conf
Towards Spatio-temporal Face Alignment in Unconstrained Conditions.
VISIGRAPP (4: VISAPP)
Romain Belmonte, Nacim Ihaddadene, Pierre Tirilly, Chabane Djeraba, Ioan Marius Bilasco
2017 — conf
Consistent Optical Flow Maps for Full and Micro Facial Expression Recognition.
VISIGRAPP (5: VISAPP)
Benjamin Allaert, Ioan Marius Bilasco, Chabane Djeraba
2015 J jnl
Head pose estimation based on face symmetry analysis.
Signal Image Video Process.
Afifa Dahmane, Slimane Larabi, Ioan Marius Bilasco, Chabane Djeraba
2014 B conf
A Local Approach for Negative Emotion Detection.
ICPR
Adel Lablack, Taner Danisman, Ioan Marius Bilasco, Chabane Djeraba
2014 — conf
Affect Recognition Using Magnitude Models of Motion.
MMM (2)
Oussama Hadjerci, Adel Lablack, Ioan Marius Bilasco, Chabane Djeraba
2014 B conf
Cross-Database Evaluation of Normalized Raw Pixels for Gender Recognition under Unconstrained Settings.
ICPR
Taner Danisman, Ioan Marius Bilasco, Chabane Djeraba
2014 — book
Mathematical Tools for Data Mining - Set Theory, Partial Orders, Combinatorics. Second Edition.
Dan A. Simovici, Chabane Djeraba
2014 J jnl
Rapid and accurate face depth estimation in passive stereo systems.
Multim. Tools Appl.
Amel Aissaoui, Jean Martinet, Chabane Djeraba
2013 J jnl
Intelligent pixels of interest selection with application to facial expression recognition using multilayer perceptron.
Signal Process.
Taner Danisman, Ioan Marius Bilasco, Jean Martinet, Chabane Djeraba
2012 B conf
3D face reconstruction in a binocular passive stereoscopic system using face properties.
ICIP
Amel Aissaoui, Jean Martinet, Chabane Djeraba
2012 J jnl
An entropy approach for abnormal activities detection in video streams.
Pattern Recognit.
Md. Haidar Sharif, Chabane Djeraba
2012 — conf
Fast Stereo Matching Method based on Optimized Correlation Algorithm for Face Depth Estimation.
VISAPP (2)
Amel Aissaoui, Rémi Auguste, Tarek Yahiaoui, Jean Martinet, Chabane Djeraba
2012 B conf
Learning symmetrical model for head pose estimation.
ICPR
Afifa Dahmane, Slimane Larabi, Chabane Djeraba, Ioan Marius Bilasco
2012 — conf
Ré-identification de personnes dans les journaux télévisés basée sur les Histogrammes spatio-temporels.
EGC
Rémi Auguste, Amel Aissaoui, Jean Martinet, Chabane Djeraba
2012 J jnl
Toward a higher-level visual representation for content-based image retrieval.
Multim. Tools Appl.
Ismail Elsayad, Jean Martinet, Thierry Urruty, Chabane Djeraba
2011 — conf
A Semantic Higher-Level Visual Representation for Object Recognition.
MMM (1)
Ismail Elsayad, Jean Martinet, Thierry Urruty, Chabane Djeraba
2011 A conf
A semantically significant visual representation for social image retrieval.
ICME
Ismail Elsayad, Jean Martinet, Thierry Urruty, Yassine Benabbas, Chabane Djeraba
2011 — conf
Analyse spatiotemporelle des vecteurs de mouvement : application au comptage des personnes.
EGC
Yassine Benabbas, Tarek Yahiaoui, Thierry Urruty, Chabane Djeraba
2011 — conf
Human Action Recognition using Direction and Magnitude Models of Motion.
VISAPP
Yassine Benabbas, Samir Amir, Adel Lablack, Chabane Djeraba
2011 J jnl
Motion Pattern Extraction and Event Detection for Automatic Visual Surveillance.
EURASIP J. Image Video Process.
Yassine Benabbas, Nacim Ihaddadene, Chabane Djeraba
2011 — conf
MuMIE : Une approche automatique pour l'interopérabilité des métadonnées.
EGC
Samir Amir, Ioan Marius Bilasco, Thierry Urruty, Chabane Djeraba
2011 J jnl
MuMIe: Multi-level Metadata Mapping System.
J. Multim.
Samir Amir, Ioan Marius Bilasco, Chabane Djeraba
2011 B conf
MuMIe: a new system for multimedia metadata interoperability.
ICMR
Samir Amir, Yassine Benabbas, Ioan Marius Bilasco, Chabane Djeraba
2011 — conf
Reconnaissance d'actions par modélisation du mouvement.
EGC
Yassine Benabbas, Adel Lablack, Thierry Urruty, Chabane Djeraba
2010 — conf
A framework for mining meaningful usage patterns within a semantically enhanced web portal.
C3S2E
Mehdi Adda, Petko Valtchev, Rokia Missaoui, Chabane Djeraba
2010 C conf
A new spatial weighting scheme for bag-of-visual-words.
CBMI
Ismail Elsayad, Jean Martinet, Thierry Urruty, Chabane Djeraba
2010 B conf
Action Recognition Using Direction Models of Motion.
ICPR
Yassine Benabbas, Adel Lablack, Nacim Ihaddadene, Chabane Djeraba
2010 B conf
An approach for synchronization and management of multimedia scenarios in an object-oriented database.
RCIS
Abdelghani Ghomari, Chabane Djeraba
2010 — conf
Analyse globale du flux optique pour la détection d'évènements dans une scène de foule.
EGC
Yassine Benabbas, Nacim Ihaddadene, Thierry Urruty, Chabane Djeraba
2010 — conf
Automatic Facial Feature Detection for Facial Expression Recognition.
VISAPP (2)
Taner Danisman, Ioan Marius Bilasco, Nacim Ihaddadene, Chabane Djeraba
2010 — conf
Crowd Behavior Surveillance Using Bhattacharyya Distance Metric.
CompIMAGE
Md. Haidar Sharif, Sahin Uyaver, Chabane Djeraba
2010 B conf
Detection and analysis of symmetrical parts on face for head pose estimation.
ICIP
Afifa Dahmane, Slimane Larabi, Chabane Djeraba
2010 — conf
Détection des mouvements anormaux dans des vidéos.
EGC
Md. Haidar Sharif, Husam Alustwani, Ioan Marius Bilasco, Chabane Djeraba
2010 — conf
Extraction de la région d'intérêt d'une personne sur un obstacle.
EGC
Adel Lablack, Thierry Urruty, Yassine Benabbas, Chabane Djeraba
2010 J jnl
Finding and Indexing of Eccentric Events in Video Emanates.
J. Multim.
Md. Haidar Sharif, Nacim Ihaddadene, Chabane Djeraba
2010 C conf
Multimedia metadata mapping: towards helping developers in their integration task.
MoMM
Samir Amir, Ioan Marius Bilasco, Taner Danisman, Ismail Elsayad, Chabane Djeraba
2010 — conf
Prédiction de séries temporelles et applications à l'analyse de séquences vidéos.
EGC
Rémi Auguste, Ahmed El Ghini, Ioan Marius Bilasco, Chabane Djeraba
2010 Misc conf
Semantics for intelligent delivery of multimedia content.
SAC
Ioan Marius Bilasco, Samir Amir, Patrick Blandin, Chabane Djeraba, Juhani Laitakari, Jean Martinet, Eduardo Martínez-Gracía, Daniel Pakkala, Mika Rautiainen, Mika Ylianttila, Jiehan Zhou
2010 — conf
Semi-automatic Multimedia Metadata Integration.
EKAW (Posters and Demos)
Samir Amir, Ioan Marius Bilasco, Taner Danisman, Thierry Urruty, Chabane Djeraba
2010 B conf
Spatio-Temporal Optical Flow Analysis for People Counting.
AVSS
Yassine Benabbas, Nacim Ihaddadene, Tarek Yahiaoui, Thierry Urruty, Chabane Djeraba
2010 C conf
Toward a higher-level visual representation for content-based image retrieval.
MoMM
Ismail Elsayad, Jean Martinet, Thierry Urruty, Samir Amir, Chabane Djeraba
2010 — conf
Using Association Rules and Spatial Weighting for an Effective Content Based-image Retrieval.
VISAPP (1)
Ismail Elsayad, Jean Martinet, Thierry Urruty, Taner Danisman, Md. Haidar Sharif, Chabane Djeraba
2010 B conf
Visual Gaze Estimation by Joint Head and Eye Information.
ICPR
Roberto Valenti, Adel Lablack, Nicu Sebe, Chabane Djeraba, Theo Gevers
2010 — conf
Visual sentence-phrase-based document representation for effective and efficient content-based image retrieval.
EGC
Ismail Elsayad, Jean Martinet, Thierry Urruty, Chabane Djeraba
2009 C conf
A Simple Method for Eccentric Event Espial Using Mahalanobis Metric.
CIARP
Md. Haidar Sharif, Chabane Djeraba
2009 — conf
Angles Estimation of Rotating Camera.
VISAPP (1)
Samira Ait Kaci Azzou, Slimane Larabi, Chabane Djeraba
2009 B conf
Exceptional motion frames detection by means of spatiotemporal region of interest features.
ICIP
Md. Haidar Sharif, Chabane Djeraba
2009 — conf
PedVed: Pseudo Euclidian Distances for Video Events Detection.
ISVC (2)
Md. Haidar Sharif, Chabane Djeraba
2009 A conf
Visual gaze projection in front of a target scene.
ICME
Adel Lablack, Frédéric Maquet, Nacim Ihaddadene, Chabane Djeraba
2008 — conf
An efficient indexing structure for multimedia data.
Multimedia Information Retrieval
Thierry Urruty, Chabane Djeraba, Joemon M. Jose
2008 B conf
Analysis of human behaviour in front of a target scene.
ICPR
Adel Lablack, Chabane Djeraba
2008 A* conf
Analyzing eye fixations and gaze orientations on films and pictures.
ACM Multimedia
Anthony Martinet, Jean Martinet, Nacim Ihaddadene, Stanislas Lew, Chabane Djeraba
2008 — conf
Covariance Matrices for Crowd Behaviour Monitoring on the Escalator Exits.
ISVC (2)
Md. Haidar Sharif, Nacim Ihaddadene, Chabane Djeraba
2008 A* conf
Crowd behaviour monitoring.
ACM Multimedia
Nacim Ihaddadene, Md. Haidar Sharif, Chabane Djeraba
2008 — conf
Determination of the Visual Field of Persons in a Scene.
VISAPP (2)
Adel Lablack, Frédéric Maquet, Chabane Djeraba
2008 — ch.
Gaze Tracking Applied to Image Indexing.
Encyclopedia of Multimedia
Jean Martinet, Adel Lablack, Nacim Ihaddadene, Chabane Djeraba
2008 — book
Mathematical Tools for Data Mining - Set Theory, Partial Orders, Combinatorics.
Dan A. Simovici, Chabane Djeraba
2008 — ch.
Motion Saliency.
Encyclopedia of Multimedia
Md. Haidar Sharif, Jean Martinet, Chabane Djeraba
2008 — ch.
Multimodal Analysis of Human Behavior.
Encyclopedia of Multimedia
Adel Lablack, Jean Martinet, Chabane Djeraba
2008 — ch.
Object Tracking in Video Using Covariance Matrices.
Encyclopedia of Multimedia
Md. Haidar Sharif, Jean Martinet, Chabane Djeraba
2008 — ch.
Optimization of Video Content Descriptions for Retrieval.
Encyclopedia of Multimedia
Thierry Urruty, Fatima Belkouch, Chabane Djeraba, Edouard Gérard, Jean de Bissy, Olivier Lombard, Patrick Alleaume
2008 B conf
Real-time crowd motion analysis.
ICPR
Nacim Ihaddadene, Chabane Djeraba
2008 C conf
Supervised Learning for Head Pose Estimation Using SVD and Gabor Wavelets.
ISM
Adel Lablack, Zhongfei (Mark) Zhang, Chabane Djeraba
2008 — ch.
Video Usage Mining.
Encyclopedia of Multimedia
Sylvain Mongy, Fatma Bouali, Chabane Djeraba
2007 A* conf
Clustering by Random Projections.
ICDM
Thierry Urruty, Chabane Djeraba, Dan A. Simovici
2007 J jnl
Data mining from multimedia.
Int. J. Parallel Emergent Distributed Syst.
Chabane Djeraba
2007 J jnl
Introduction to special issue on eye-tracking applications in multimedia systems.
ACM Trans. Multim. Comput. Commun. Appl.
Gheorghita Ghinea, Chabane Djeraba, Stephen R. Gulliver, Kara Pernice Coyne
2007 — conf
On Clustering Users' Behaviors in Video Sessions.
DMIN
Sylvain Mongy, Chabane Djeraba, Dan A. Simovici
2007 — conf
RPyR: Nouvelle Structure d'Indexation avec Classification par Projections Aléatoires.
INFORSID
Thierry Urruty, Fatima Belkouch, Chabane Djeraba, Dan A. Simovici
2007 J jnl
Toward Recommendation Based on Ontology-Powered Web-Usage Mining.
IEEE Internet Comput.
Rokia Missaoui, Petko Valtchev, Chabane Djeraba, Mehdi Adda
2006 J jnl
Content-based multimedia information retrieval: State of the art and challenges.
ACM Trans. Multim. Comput. Commun. Appl.
Michael S. Lew, Nicu Sebe, Chabane Djeraba, Ramesh C. Jain
2006 — ed.
Extraction et gestion des connaissances (EGC'2006), Actes des sixièmes journées Extraction et Gestion des Connaissances, Lille, France, 17-20 janvier 2006, 2 Volumes
EGC
Gilbert Ritschard, Chabane Djeraba
2006 A* conf
Eye/gaze tracking in web, image and video documents.
ACM Multimedia
Chabane Djeraba, Stanislas Lew, Dan A. Simovici, Sylvain Mongy, Nacim Ihaddadene
2006 — conf
Indexation Multidimensionnelle : KpyrRec, une amélioration de Kpyr.
INFORSID
Thierry Urruty, Fatima Belkouch, Chabane Djeraba
2006 A* conf
Is there a grand challenge or X-prize for data mining?
KDD
Gregory Piatetsky-Shapiro, Robert Grossman, Chabane Djeraba, Ronen Feldman, Lise Getoor, Mohammed Javeed Zaki
2006 J jnl
Multimedia indexing and retrieval: ever great challenges.
Multim. Tools Appl.
Chabane Djeraba, Moncef Gabbouj, Patrick Bouthemy
2006 — ch.
Optimization of Video Content Descriptions for Retrieval.
Encyclopedia of Multimedia
Thierry Urruty, Fatima Belkouch, Chabane Djeraba, Bruno Bachimont, Edouard Gérard, Jean de Bissy, Olivier Lombard, Patrick Alleaume
2006 — ch.
Video Usage Mining.
Encyclopedia of Multimedia
Sylvain Mongy, Fatma Bouali, Chabane Djeraba
2006 J jnl
What are the grand challenges for data mining?: KDD-2006 panel report.
SIGKDD Explor.
Gregory Piatetsky-Shapiro, Chabane Djeraba, Lise Getoor, Robert Grossman, Ronen Feldman, Mohammed Javeed Zaki
2005 — conf
Analyzing user's behavior on a video database.
MDM/KDD
Sylvain Mongy, Fatma Bouali, Chabane Djeraba
2005 A conf
KPYR: An Efficient Indexing Method.
ICME
Thierry Urruty, Fatima Belkouch, Chabane Djeraba
2005 — conf
Kpyr, une structure efficace d'indexation de documents vidéo.
INFORSID
Thierry Urruty, Fatima Belkouch, Chabane Djeraba
2005 C conf
On the discovery of semantically enhanced sequential patterns.
ICMLA
Mehdi Adda, Petko Valtchev, Rokia Missaoui, Chabane Djeraba
2005 J jnl
Systems and architectures for multimedia information retrieval.
Multim. Syst.
Chabane Djeraba, Nicu Sebe, Michael S. Lew
2004 — conf
High performance crawling system.
Multimedia Information Retrieval
Younes Hafri, Chabane Djeraba
2004 — ed.
Proceedings of the 6th ACM SIGMM International Workshop on Multimedia Information Retrieval, MIR 2004, October 15-16, 2004, New York, NY, USA
Multimedia Information Retrieval
Michael S. Lew, Nicu Sebe, Chabane Djeraba
2003 B conf
A Markovian Approach for Web User Profiling and Clustering.
PAKDD
Younes Hafri, Chabane Djeraba, Peter L. Stanchev, Bruno Bachimont
2003 C conf
A Web User Profiling Approach.
APWeb
Younes Hafri, Chabane Djeraba, Peter L. Stanchev, Bruno Bachimont
2003 J jnl
Association and Content-Based Retrieval.
IEEE Trans. Knowl. Data Eng.
Chabane Djeraba
2003 — ed.
Mining Multimedia and Complex Data, KDD Workshop MDM/KDD 2002, PAKDD Workshop KDMCD 2002, Revised Papers
MDM/KDD-PAKDD/KDMCD (Revised Papers)
Osmar R. Zaïane, Simeon J. Simoff, Chabane Djeraba
2003 — ed.
Proceedings of the 5th ACM SIGMM International Workshop on Multimedia Information Retrieval, MIR 2003, November 7, 2003, Berkeley, CA, USA
Multimedia Information Retrieval
Nicu Sebe, Michael S. Lew, Chabane Djeraba
2003 — conf
Towards a Timed-Petri Net Based Approach for Multimedia Scenario Synchronization.
ICEIS (1)
Abdelghani Ghomari, Chabane Djeraba
2002 — conf
Cluster Analysis in Image Repositories.
KDMCD
Gregory Fernandez, Chabane Djeraba
2002 J jnl
Guest Editor's Introduction: Content-Based Multimedia Indexing and Retrieval.
IEEE Multim.
Chabane Djeraba
2002 — conf
Intelligent Image Clustering.
EDBT Workshops
Gregory Fernandez, Abdelouahab Mekaouche, Philippe Peter, Chabane Djeraba
2002 — ed.
International Workshop on Knowledge Discovery in Multimedia and Complex Data (KDMCD 2002), in conjunction with the Sixth Pacific-Asia Conference on Knowledge Discovery and Data Mining (PAKDD-02), Taipei, Taiwan, May 6-8
KDMCD
Chabane Djeraba, Osmar R. Zaïane
2002 — conf
K-automatic discovery in large image databases.
INFORSID
Gregory Fernandez, Philippe Peter, Abdelouahab Mekaouche, Chabane Djeraba
2002 J jnl
MDM/KDD 2002: Multimedia Data Mining between Promises and Problems.
SIGKDD Explor.
Simeon J. Simoff, Chabane Djeraba, Osmar R. Zaïane
2002 — book
Multimedia Mining: A Highway to Intelligent Multimedia Documents
Chabane Djeraba
2002 — conf
Partition Cardinality Estimation in Image Repositories.
MDM/KDD-PAKDD/KDMCD (Revised Papers)
Gregory Fernandez, Chabane Djeraba
2002 — ed.
Proceedings of the Third International Workshop on Multimedia Data Mining, MDM/KDD'2002, July 23rd, 2002, Edmonton, Alberta, Canada
MDM/KDD
Simeon J. Simoff, Chabane Djeraba, Osmar R. Zaïane
2002 — ed.
XML-Based Data Management and Multimedia Engineering - EDBT 2002 Workshops, EDBT 2002 Workshops XMLDM, MDDE, and YRWS, Prague, Czech Republic, March 24-28, 2002, Revised Papers
EDBT Workshops
Akmal B. Chaudhri, Rainer Unland, Chabane Djeraba, Wolfgang Lindner
2001 — conf
Automatic Discrimination in Audio Documents.
MDDE
Chabane Djeraba, Hakim Saadane
2001 J jnl
Guest Editorial: Content-Based Multimedia Indexing and Retrieval.
Multim. Tools Appl.
Chabane Djeraba
2001 — conf
Knowledge-Based Access to Categorized Image Documents.
MDDE
Chabane Djeraba
2001 — conf
Rule and Visual Content-Based Indexing.
MDM/KDD
Chabane Djeraba
2000 — conf
Image Access and Data Mining: An Approach.
PKDD
Chabane Djeraba
2000 B conf
Intelligent content-based retrieval.
ICTAI
Chabane Djeraba, Cherif El Asri Mohamed
2000 J jnl
Shape Processing and Image retrieval.
Obj. Logiciel Base données Réseaux
Marinette Bouet, Chabane Djeraba, Ali Khenchaf, Henri Briand
2000 J jnl
Visual and Textual Content Based Indexing and Retrieval.
Int. J. Digit. Libr.
Chabane Djeraba, Marinette Bouet, Henri Briand, Ali Khenchaf
2000 — conf
When image indexing meets knowledge discovery.
MDM/KDD
Chabane Djeraba
1998 — conf
Concept-Based Query in Visual Information Systems.
ADL
Chabane Djeraba, Marinette Bouet, Henri Briand
1998 — ch.
Content Based Image Retrieval Model in an Object Oriented Database.
Image Databases and Multi-Media Search
Chabane Djeraba, Ian Savory, Max Barere, Stève Marchand
1998 — conf
Introduction of high level descriptions in a visual information system.
BDA
Chabane Djeraba, Marinette Bouet
1998 A* conf
Powerful Image Organization in Visual Retrieval Systems.
ACM Multimedia
Marinette Bouet, Chabane Djeraba
1998 — conf
Visual Content Based Retrieval in an Image Database with Relevant Feedback.
IW-MMDBMS
Marinette Bouet, Chabane Djeraba
1997 — conf
A Search System based on Image Features.
DEXA Workshop
Chabane Djeraba, Patrick Fargeaud, Henri Briand
1997 A conf
Digital Information Retrieval.
CIKM
Chabane Djeraba, Marinette Bouet
1997 J jnl
Management of Multimedia Scenarios in an Object-Oriented Database System.
Multim. Tools Appl.
Chabane Djeraba, Karima Hadouda, Henri Briand
1997 — conf
Objects and Interactive Application in Term of Scenario in a Multimedia Database.
DEXA Workshop
Karima Hadouda, Chabane Djeraba, Henri Briand
1997 — conf
Retrieval and extraction by content of images in an object oriented database.
INFORSID
Chabane Djeraba, Patrick Fargeaud, Henri Briand
1997 — conf
Scènes multimédias dans une base de données à objets.
BDA
Chabane Djeraba, Karima Hadouda, Henri Briand
1997 — conf
Temporal and Interactive Relations in a Multimedia Database System.
ECMAST
Chabane Djeraba, Henri Briand
1996 — conf
Gestion des scénarios multi-média.
INFORSID
Chabane Djeraba, Karima Hadouda
1996 — conf
Management Of Multimedia Scenarios In An Object-Oriented Database System.
IW-MMDBMS
Chabane Djeraba, Karima Hadouda, Henri Briand
1996 C conf
Multimedia Scenes in a Database System.
DEXA
Chabane Djeraba, Karima Hadouda
1996 — conf
Temporal and interactive relations in a multimedia database system.
ICECS
Chabane Djeraba, Fouad Maaref, Henri Briand
1995 C conf
Rule Evaluations in a KDD System
DEXA
Laurent Fleury, Chabane Djeraba, Henri Briand, Jacques Philippe
1995 — conf
Some Aspect of Rule Discovery in Data Bases.
CISMOD
Laurent Fleury, Chabane Djeraba, Henri Briand, Jacques Philippe
1994 — conf
Objets composites dans un modele a objets.
BDA
Chabane Djeraba
1993 C conf
Composition and Dependency Relationships in Production Information System Design.
DEXA
Chabane Djeraba, A. Ait Hssain, B. Descotes-Genon
1991 — conf
Instanciation multiple et classification d'objets.
BDA
Dominique Rieu, Gia Toan Nguyen, Annie Culet, José Escamilla, Chabane Djeraba