I am a Science Manager at Amazon in the SF bay area in Alexa AI. I lead a team of scientists and language engineers that builds out Alexa's Natural Language Understanding (NLU) capabilities and Information Retrieval (IR) models to improve the user experience in the Local Information space. We apply machine learning and NLU techniques to develop comprehensive meaning representation frameworks, launch new customer facing features and improve the current user experience.

Before Amazon, I spent three years as a Senior Data Scientist at GE Digital in San Ramon, CA where I addressed statistical, machine learning, and data understanding problems for industrial clients in a commercial technology and consultancy development environment.

I received my PhD and MS in Electrical Engineering from the University  of Maryland, College Park (UMD) in December 2016 and December 2015, respectively, working under the supervision of Prof. Min Wu on research at the intersection of Signal Processing, Machine Learning, and Information Forensics & Security. 

During my graduate studies, my work experience included being a research and teaching assistant at UMD, interning at AT&T Research Labs in Middletown, New Jersey, and interning at Technicolor R&D France in Rennes, France. I was also part of the organizing team for the IEEE Signal Processing Cup 2016, overseen by the IEEE Signal Processing Society.

I received my Bachelor of Engineering in Electrical and Computer Engineering from the American University of Beirut in Lebanon in June 2011.



AWARDS & HONORS

Four internal GE awards ("impact" and "above and beyond") for performance in multiple projects (2017, 2018).

2016 Jimmy Lin Award for Innovation (UMD's ECE department). 

Northrop Grumman Graduate Fellowship in Engineering Education for the 2015-2016 academic year. 

Best Student Paper Award at ACM Workshop on Information Hiding and Multimedia Security 2015.

2015 Jimmy Lin Award for Invention (UMD's ECE department).

2014 Invention of the Year Award (UMD's Office of Technology Commercialization).

Co-authored paper ranked among Top 10% papers at the IEEE International Conference on Image Processing (ICIP) 2014.

Finalist in Qualcomm Innovation Fellowship (QInF) in 2013.

Distinguished Teaching Assistant Award (UMD) in 2013.

Distinguished Graduate Fellowship (UMD) for the 2011-2012 academic year.

PUBLICATIONS

Book Chapter

A. Hajj-Ahmad, C.-W. Wong, J. Choi, and M. Wu. Power Signature for Multimedia Forensics. In: H.-T. Sencar, L. Verdoliva, N. Memon (eds) Multimedia Forensics. Advances in Computer Vision and Pattern Recognition. Springer, Singapore, Apt. 2022. [Link to chapter]

Journals, Letters, and Magazines

1) J. Choi, C.-W. Wong, A. Hajj-Ahmad, M. Wu, and Y. Ren, “Invisible Geolocation Signature Extraction From a Single Image,” in IEEE Transactions of Information Forensics and Security (TIFS), vol. 17, pp. 2598-2613, Jun. 2022. [Link to paper]

2) A. Hajj-Ahmad, C.-W. Wong, S. Gambino, Q. Zhu, M. Yu, and M. Wu, "Factors Affecting ENF Capture in Audio," in IEEE Transactions of Information Forensics and Security (TIFS), vol. 14, no. 2, pp. 277-288, Feb. 2019.  [Link to paper]

3) A. Hajj-Ahmad, S. Baudry, B. Chupeau, G. Doërr, and M. Wu, “Flicker Forensics for Camcorder Piracy,” in IEEE Transactions on Information Forensics and Security (TIFS), vol. 12, no. 1, pp. 89-100, Jan. 2017. [Link to paper]

4) M. Wu, A. Hajj-Ahmad, M. Kirchner, Y. Ren, C. Zhang, and P. Campisi, “Location Signatures that You Don't See: Highlights from the IEEE Signal Processing Cup 2016 Student Competition [SP Education],” in IEEE Signal Processing Magazine, vol. 33, no. 5, pp. 149-156, Sept. 2016. [Link to paper]

5) A. Hajj-Ahmad, A. Berkovich, and M. Wu, “Exploiting Power Signatures for Camera Forensics,” IEEE Signal Processing Letters (SPL), vol. 23, no. 5, pp. 713-717, May 2016. [Link to paper]

6) A. Hajj-Ahmad, R. Garg, and M. Wu, “ENF-Based Region-of-Recording Identification for Media Signals,” IEEE Transactions on Information Forensics and Security (TIFS), vol. 10, no. 6, pp. 1125-1136, June 2015. [Link to paper]

7) A. Hajj-Ahmad, R. Garg, and M. Wu, “Spectrum Combining for ENF Signal Estimation,” IEEE Signal Processing Letters (SPL), vol. 20, no. 9, pp. 885-888, Sept. 2013. [Link to paper]

8) R. Garg, A. L. Varna, A. Hajj-Ahmad, and M. Wu, “‘Seeing’ ENF: Power Signature Based Timestamp for Digital Multimedia via Optical Sensing and Signal Processing,” IEEE Transactions on Information Forensics and Security (TIFS), vol. 8, no. 9, pp. 1417-1432, Sept. 2013. [Link to paper]

Conferences and Workshops

1) C.-W. Wong, A. Hajj-Ahmad, and M. Wu, "Invisible Geo-Location Signature in A Single Image," Proceedings of IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP), Calgary, AB, Canada, April 2018, pp. 1987-1991.

2) A. Hajj-Ahmad, S. Baudry, B. Chupeau, and G. Doërr, “Flicker Forensics for Pirate Devices Identification,” Proceedings of the 3rd ACM Workshop on Information Hiding and Multimedia Security (IHMMSec), Portland, OR, USA, June 2015, pp. 75-84. [Won Best Student Paper Award]

3) H. Su, A. Hajj-Ahmad, C. W. Wong, R. Garg, and M. Wu, “ENF Signal Induced by Power Grid: A New Modality for Video Synchronization,” ACM Multimedia Workshop on Immersive Media Experiences, Orlando, FL, USA, Nov. 2014, pp.13-18. 

4) H. Su, A. Hajj-Ahmad, R. Garg, and M. Wu, “Exploiting Rolling Shutter for ENF Signal Extraction from Video,” Proceedings of International Conference on Image Processing (ICIP), Paris, France, Oct. 2014, pp. 5367-5371. [Among Top 10% papers in ICIP 2014, based on reviewers’ scores and recommendations] 

5) T. Clement, K. Kraus, …, M. Wu, D. W. Oard, A. Hajj-Ahmad, H. Su, et al, “Digital Humanities: The Intersections of Sound and Method,” Digital Humanities, July 2014. 

6) H. Su, A. Hajj-Ahmad, M. Wu, and D. W. Oard, “Exploring the Use of ENF for Multimedia Synchronization,” Proceedings of International Conference on Acoustics, Speech, and Signal Processing (ICASSP), Florence, Italy, May 2014, pp. 4613-4617. 

7) D. W. Oard, M. Wu, K. Kraus, A. Hajj-Ahmad, H. Su, and R. Garg, “It’s About Time: Projecting Temporal Metadata for Historically Significant Recordings,” iConference, Mar. 2014 

8) A. Hajj-Ahmad, R. Garg, and M. Wu, “ENF Based Location Classification of Sensor Recordings,” Workshop on Information Forensics and Security (WIFS), Guangzhou, China, Nov. 2013, pp.138-143. 

9) R. Garg, A. Hajj-Ahmad, and M. Wu, “Geo-Location Estimation from Electrical Network Frequency Signals,” Proceedings of International Conference on Acoustics, Speech, and Signal Processing (ICASSP), Vancouver, BC, Canada, May 2013, pp. 2862-2866. 

10) H. Su, R. Garg, A. Hajj-Ahmad, and M. Wu, “ENF Analysis on Recaptured Audio Recordings,” Proceedings of International Conference on Acoustics, Speech, and Signal Processing (ICASSP), Vancouver, BC, Canada, May 2013, pp. 3018-3022. 

11) A. Hajj-Ahmad, R. Garg, and M. Wu, “Instantaneous Frequency Estimation and Localization for ENF Signals,” Proceedings of Annual Summit and Conference of the Asia-Pacific Signal and Information Processing Association (APSIPA), Los Angeles, CA, USA, Dec. 2012, pp. 1-10.