Sirisha Rambhatla | Publications

2025

FGVC @ CVPR 2025

Rethinking Semi-Supervised Domain Adaptation for Semantic Segmentation in the Era of Foundation Models

Kurien, J., Balaji, B., Lai, K.H., Vela, P. G., Thomas, C., Wong, A., and Rambhatla, S.

In Workshop on Fine-Grained Visual Categorization (FGVC) at IEEE/CVF Conference on Computer Vision and Pattern Recognition 2025

Bib

@inproceedings{Kurien2025, abbr = {FGVC @ CVPR 2025}, img = {ssda_fgvc.pdf}, title = {Rethinking Semi-Supervised Domain Adaptation for Semantic Segmentation in the Era of Foundation Models}, author = {Kurien, J. and Balaji, B. and Lai, K.H. and Vela, P. G. and Thomas, C. and Wong, A. and Rambhatla, S.}, booktitle = {Workshop on Fine-Grained Visual Categorization (FGVC) at IEEE/CVF Conference on Computer Vision and Pattern Recognition }, year = {2025} }
ICCV 2025

LOCATEdit: Graph Laplacian Optimized Cross Attention for Localized Text-Guided Image Editing

Soni, A., Soni, M., and Rambhatla, S.

IEEE International Conference on Computer Vision (ICCV) 2025

Bib PDF Code

@article{Soni2025, abbr = {ICCV 2025}, img = {locatedit_video_2.mp4}, title = {LOCATEdit: Graph Laplacian Optimized Cross Attention for Localized Text-Guided Image Editing}, author = {Soni, A. and Soni, M. and Rambhatla, S.}, journal = {IEEE International Conference on Computer Vision (ICCV)}, pdf = {https://arxiv.org/pdf/2503.21541}, url = {https://locatedit.github.io}, code = {https://github.com/criticalml-uw/LOCATEdit}, year = {2025}, selected = {true} }
Canadian AI 2025
🏆 Oral

Discrete-Survival Compatibility Score for Donor-Recipient Matching in Liver Transplantation

Wang, Y., Tan, E., Sun, Y., Bhat, M., He, X., and Rambhatla, S.

The 38th Canadian Conference on Artificial Intelligence (Canadian AI) 2025

Bib

@article{Wang2025, abbr = {Canadian AI 2025}, img = {DiscSurv.png}, title = {Discrete-Survival Compatibility Score for Donor-Recipient Matching in Liver Transplantation}, author = {Wang, Y. and Tan, E. and Sun, Y. and Bhat, M. and He, X. and Rambhatla, S.}, journal = {The 38th Canadian Conference on Artificial Intelligence (Canadian AI)}, url = {https://caiac.pubpub.org/pub/n651g7ur}, year = {2025}, award = {Oral} }
JMIR 2025

Forecasting Waitlist Trajectories for Patients with Metabolic Dysfunction-Associated Steatohepatitis Cirrhosis Using Neural Network Competing Risk Analysis

Punchhi, G., Sun, Y., Tan, E., Hlaing, N. K. T., Liu, C., Asrani, S., Rambhatla, S., and Bhat, M.

Journal of Medical Internet Research 2025

Bib

@article{Punchhi2025, abbr = {JMIR 2025}, img = {jmircirrhosis.pdf}, title = {Forecasting Waitlist Trajectories for Patients with Metabolic Dysfunction-Associated Steatohepatitis Cirrhosis Using Neural Network Competing Risk Analysis}, author = {Punchhi, G. and Sun, Y. and Tan, E. and Hlaing, N. K. T. and Liu, C. and Asrani, S. and Rambhatla, S. and Bhat, M.}, journal = {Journal of Medical Internet Research}, url = {https://github.com/criticalml-uw/DeepMASH/}, year = {2025} }
PLOS Digit. Health 2025

Leveraging Large Language Models for Automated Depression Screening

Tefera, B. G., Perivolaris, A., Hsiang, W. N., Sidharta, C. K., Rueda, A., Parkington, K., Wu, Y., Soni, A., Samavi, R., Jetly, R., Zhang, Y., Cao, B., Rambhatla, S., Krishnan, S., and Bhat, V.

PLOS Digital Health 2025

Bib

@article{Tefera2025, abbr = {PLOS Digit. Health 2025}, img = {llm_depression.pdf}, title = {Leveraging Large Language Models for Automated Depression Screening}, author = {Tefera, B. G. and Perivolaris, A. and Hsiang, W. N. and Sidharta, C. K. and Rueda, A. and Parkington, K. and Wu, Y. and Soni, A. and Samavi, R. and Jetly, R. and Zhang, Y. and Cao, B. and Rambhatla, S. and Krishnan, S. and Bhat, V.}, journal = {PLOS Digital Health}, url = {https://journals.plos.org/digitalhealth/article?id=10.1371/journal.pdig.0000943}, year = {2025} }
JMIR Form. Res. 2025
🏆 Extensive Media Coverage

Medical Misinformation in AI-Assisted Self-Diagnosis: The EvalPrompt Method for Analyzing Large Language Models

Zada, T., Tam, N., Barnard, F., Sittert, M. V., Bhat, V., and Rambhatla, S.

Journal of Medical Internet Research (JMIR) Formative Research 2025

Bib

@article{Zada2025, abbr = {JMIR Form. Res. 2025}, img = {evalprompt_misinformation.pdf}, title = {Medical Misinformation in AI-Assisted Self-Diagnosis: The EvalPrompt Method for Analyzing Large Language Models}, author = {Zada, T. and Tam, N. and Barnard, F. and Sittert, M. V. and Bhat, V. and Rambhatla, S.}, journal = {Journal of Medical Internet Research (JMIR) Formative Research}, volume = {9}, pages = {e66207}, year = {2025}, url = {https://pubmed.ncbi.nlm.nih.gov/40063849/}, award = {Extensive Media Coverage} }
Front. Psychiatry 2025

Opinion: Mental Health Research: To Augment or Not To Augment

Perivolaris, A., Rueda, A., Parkington, K., Soni, A., Rambhatla, S., Samavi, R., Jetly, R., Greenshaw, A., Zhang, Y., Cao, B., Krishnan, S., and Bhat, V.

Frontiers in Psychiatry 2025

Bib

@article{Perivolaris2025, abbr = {Front. Psychiatry 2025}, img = {augment_opinion.pdf}, title = {Opinion: Mental Health Research: To Augment or Not To Augment}, author = {Perivolaris, A. and Rueda, A. and Parkington, K. and Soni, A. and Rambhatla, S. and Samavi, R. and Jetly, R. and Greenshaw, A. and Zhang, Y. and Cao, B. and Krishnan, S. and Bhat, V.}, journal = {Frontiers in Psychiatry}, year = {2025}, url = {https://www.frontiersin.org/journals/psychiatry/articles/10.3389/fpsyt.2025.1539157/full} }
MMFM4 @ ICCV 2025

LOCATEdit: Graph Laplacian Optimized Cross Attention for Localized Text-Guided Image Editing

Soni, A., Soni, M., and Rambhatla, S.

In MMFM4: The 4th Workshop on What is Next in Multimodal Foundation Models? at IEEE International Conference on Computer Vision (ICCV) 2025

Bib

@inproceedings{Soni2026, abbr = {MMFM4 @ ICCV 2025}, img = {locatedit_video_2.mp4}, title = {LOCATEdit: Graph Laplacian Optimized Cross Attention for Localized Text-Guided Image Editing}, author = {Soni, A. and Soni, M. and Rambhatla, S.}, booktitle = {MMFM4: The 4th Workshop on What is Next in Multimodal Foundation Models? at IEEE International Conference on Computer Vision (ICCV)}, year = {2025} }
AIA @ IJCAI 2025

SafeTuneBed: A Safety Assessment Framework for Harmful Finetuning Defenses

Hossain, S., Vajpayee, S., and Rambhatla, S.

In User-Aligned Assessment of Adaptive AI Systems (AIA) Workshop at International Joint Conferences on Artificial Intelligence (IJCAI) 2025

Bib

@inproceedings{Hossain2025, abbr = {AIA @ IJCAI 2025}, img = {stb_logo.png}, title = {SafeTuneBed: A Safety Assessment Framework for Harmful Finetuning Defenses}, author = {Hossain, S. and Vajpayee, S. and Rambhatla, S.}, booktitle = {User-Aligned Assessment of Adaptive AI Systems (AIA) Workshop at International Joint Conferences on Artificial Intelligence (IJCAI)}, year = {2025}, note = {Workshop paper}, url = {https://openreview.net/forum?id=yKetbTItcu} }
CVinW @ CVPR 2025

Gen4D: Synthesizing Humans and Scenes in the Wild

Bright, J., Wang, Z., Chen, Y., Rambhatla, S., Clausi, D. A., and Zelek, J. S.

In Workshop on Computer Vision in the Wild (CVinW) at IEEE/CVF Conference on Computer Vision and Pattern Recognition 2025

Bib

@inproceedings{Bright2025, abbr = {CVinW @ CVPR 2025}, img = {gen4d_synthesizing.pdf}, title = {Gen4D: Synthesizing Humans and Scenes in the Wild}, author = {Bright, J. and Wang, Z. and Chen, Y. and Rambhatla, S. and Clausi, D. A. and Zelek, J. S.}, booktitle = {Workshop on Computer Vision in the Wild (CVinW) at IEEE/CVF Conference on Computer Vision and Pattern Recognition}, year = {2025}, url = {https://arxiv.org/abs/2506.05397} }
T-PAMI 2025

Bringing Equity to Classification: Domain Generalization for Domain-Linked Classes

Kaai, K., Hossain, S., and Rambhatla, S.

IEEE Transactions on Pattern Analysis and Machine Intelligence (T-PAMI) 2025

Bib PDF

@article{Kaai2025, abbr = {T-PAMI 2025}, img = {fond.pdf}, title = {Bringing Equity to Classification: Domain Generalization for Domain-Linked Classes}, author = {Kaai, K. and Hossain, S. and Rambhatla, S.}, journal = {IEEE Transactions on Pattern Analysis and Machine Intelligence (T-PAMI)}, pdf = {https://arxiv.org/pdf/2306.00879}, url = {https://arxiv.org/abs/2306.00879}, year = {2025} }

2024

Acad. Psychiatry 2024

Opportunities and Barriers of Generative Artificial Intelligence in the Training of Psychiatrists: A Competencies-Based Perspective

Pang, H. Y. M., Meshkat, S., Teferra, B. G., Rueda, A., Samavi, R., Krishnan, S., Doyle, T., Rambhatla, S., DeJong, S., Sockalingam, S., Horsley, T., Hodges, B., and Bhat, V.

Academic Psychiatry 2024

Bib

@article{Pang2025, abbr = {Acad. Psychiatry 2024}, img = {genai_psychiatry_training.pdf}, title = {Opportunities and Barriers of Generative Artificial Intelligence in the Training of Psychiatrists: A Competencies-Based Perspective}, author = {Pang, H. Y. M. and Meshkat, S. and Teferra, B. G. and Rueda, A. and Samavi, R. and Krishnan, S. and Doyle, T. and Rambhatla, S. and DeJong, S. and Sockalingam, S. and Horsley, T. and Hodges, B. and Bhat, V.}, journal = {Academic Psychiatry}, publisher = {Springer}, year = {2024}, url = {https://pubmed.ncbi.nlm.nih.gov/39587003/} }
ICML 2024

Why do Variational Autoencoders Really Promote Disentanglement?

Bhowal, P., Soni, A., and Rambhatla, S.

International Conference on Machine Learning (ICML) 2024

Bib PDF

@article{Bhowal2024, abbr = {ICML 2024}, img = {VAE-ICML-2024.png}, title = {Why do Variational Autoencoders Really Promote Disentanglement?}, author = {Bhowal, P. and Soni, A. and Rambhatla, S.}, journal = {International Conference on Machine Learning (ICML)}, pdf = {https://openreview.net/pdf?id=Ao9UUaScAU}, url = {https://proceedings.mlr.press/v235/bhowal24a.html}, year = {2024}, selected = {true} }
M3L@NeurIPS

Optimizing Fine-Tuning Efficiency: Gradient Subspace Tracking on Grassmann Manifolds for Large Language Models

Rajabi, S., and Rambhatla, S.

Mathematics of Modern Machine Learning (M3L) Workshop at Neural Information Processing Systems (NeurIPS) 2024

Bib PDF

@article{Rajabi2024a, abbr = {M3L@NeurIPS}, img = {M3L-SubTrack.png}, title = {Optimizing Fine-Tuning Efficiency: Gradient Subspace Tracking on Grassmann Manifolds for Large Language Models}, author = {Rajabi, S. and Rambhatla, S.}, journal = {Mathematics of Modern Machine Learning (M3L) Workshop at Neural Information Processing Systems (NeurIPS)}, pdf = {https://openreview.net/pdf?id=ZP7VzpXmKR}, url = {https://openreview.net/forum?id=ZP7VzpXmKR}, year = {2024} }
AFM@NeurIPS

LangDA: Language-guided Domain Adaptive Semantic Segmentation

Liu, C., Hossain, S., Thomas, C, Lai, K.H., Vemulapalli, R., Rambhatla, S., and Wong, A.

Adaptive Foundation Models: Evolving AI for Personalized and Efficient Learning (AFM) Workshop at Neural Information Processing Systems (NeurIPS) 2024

Bib PDF

@article{Liu2024, abbr = {AFM@NeurIPS}, img = {LangDA.png}, title = {LangDA: Language-guided Domain Adaptive Semantic Segmentation}, author = {Liu, C. and Hossain, S. and Thomas, C and Lai, K.H. and Vemulapalli, R. and Rambhatla, S. and Wong, A.}, journal = {Adaptive Foundation Models: Evolving AI for Personalized and Efficient Learning (AFM) Workshop at Neural Information Processing Systems (NeurIPS)}, pdf = {https://openreview.net/pdf?id=iyULilaeYx}, url = {https://openreview.net/forum?id=iyULilaeYx}, year = {2024} }
AFM@NeurIPS

Enhancing Fine-Tuning Efficiency of LLMs Through Gradient Subspace Tracking

Rajabi, S., and Rambhatla, S.

Adaptive Foundation Models: Evolving AI for Personalized and Efficient Learning (AFM) Workshop at Neural Information Processing Systems (NeurIPS) 2024

Bib PDF

@article{Rajabi2024b, abbr = {AFM@NeurIPS}, img = {AFM-SubTrack.png}, title = {Enhancing Fine-Tuning Efficiency of LLMs Through Gradient Subspace Tracking}, author = {Rajabi, S. and Rambhatla, S.}, journal = {Adaptive Foundation Models: Evolving AI for Personalized and Efficient Learning (AFM) Workshop at Neural Information Processing Systems (NeurIPS)}, pdf = {https://openreview.net/pdf?id=lPIPYCqDGt}, url = {https://openreview.net/forum?id=lPIPYCqDGt}, year = {2024} }
CCAI@NeurIPS

Icy Waters: Developing a Test-Suite to Benchmark Sea Ice Concentration Forecasting

McGuigan, K., Rambhatla, S., and Scott, K. A.

Tackling Climate Change with Machine Learning Workshop (CCAI) at Neural Information Processing Systems (NeurIPS) 2024

Abs Bib PDF

Artificial intelligence (AI) for Climate Change efforts have made significant progress in forecasting atmospheric weather patterns and events. Despite this, translating these gains in the context of phenomenon on earth surface, e.g. sea-ice concentration, has been limited because of differences in how these physical processes evolve. Sea ice concentration is one of the key indicators of climate change and is also critical for a number of different applications and indigenous peoples. Consequently, there is an acute need to develop a baseline of a diverse set of modern machine learning techniques within the Arctic. Our work aims to fill this gap, with the goal of both informing current research, as well as pointing out limitations with certain architectures. We achieve this by providing baselines for a number of different convolutional LSTMs, transformer based, and neural operator based machine learning methods.

@article{McGuigan2024, abbr = {CCAI@NeurIPS}, img = {ICY_Waters.png}, title = {Icy Waters: Developing a Test-Suite to Benchmark Sea Ice Concentration Forecasting}, author = {McGuigan, K. and Rambhatla, S. and Scott, K. A.}, journal = {Tackling Climate Change with Machine Learning Workshop (CCAI) at Neural Information Processing Systems (NeurIPS)}, pdf = {papers/NeurIPS_2024_CLIM_KMCGUIGAN_CAMERA_READY_FINAL.pdf}, url = {https://www.climatechange.ai/events/neurips2024}, year = {2024} }
OPT@NeurIPS

Memory-Efficient Large Language Model (LLM) Training and Fine-Tuning via Gradient Subspace Tracking

Rajabi, S., and Rambhatla, S.

Optimization for Machine Learning (OPT) Workshop at Neural Information Processing Systems (NeurIPS) 2024

Bib PDF

@article{Rajabi2024c, abbr = {OPT@NeurIPS}, img = {OPT-SubTrack.png}, title = {Memory-Efficient Large Language Model (LLM) Training and Fine-Tuning via Gradient Subspace Tracking}, author = {Rajabi, S. and Rambhatla, S.}, journal = {Optimization for Machine Learning (OPT) Workshop at Neural Information Processing Systems (NeurIPS)}, pdf = {https://openreview.net/pdf?id=W61fzRYQdy}, url = {https://openreview.net/forum?id=W61fzRYQdy}, year = {2024} }
Compression@NeurIPS

Accelerating Memory-Efficient LLM Training and Fine-Tuning via Tracking the Gradient Subspace

Rajabi, S., and Rambhatla, S.

Machine Learning and Compression Workshop at Neural Information Processing Systems (NeurIPS) 2024

Bib PDF

@article{Rajabi2024d, abbr = {Compression@NeurIPS}, img = {Comp-SubTrack.png}, title = {Accelerating Memory-Efficient LLM Training and Fine-Tuning via Tracking the Gradient Subspace}, author = {Rajabi, S. and Rambhatla, S.}, journal = {Machine Learning and Compression Workshop at Neural Information Processing Systems (NeurIPS)}, pdf = {https://openreview.net/pdf?id=qgTvp6nzgW}, url = {https://openreview.net/forum?id=qgTvp6nzgW}, year = {2024} }
Acad. Psychiatry
🏆 Commentary

Opportunities and Barriers of Generative Artificial Intelligence in the Training of Psychiatrists: A Competencies-Based Perspective

Pang, H. Y. M., Meshkat, S., Teferra, B. G., Rueda, A., Samavi, R., Krishnan, S., Doyle, T., Rambhatla, S., DeJong, S., Sockalingam, S., Horsley, T., Hodges, B., and Bhat., V.

Academic Psychiatry (Springer Journal) 2024

Bib PDF

@article{Pang2024, abbr = {Acad. Psychiatry}, img = {Acad_Psy_2024.png}, title = {Opportunities and Barriers of Generative Artificial Intelligence in the Training of Psychiatrists: A Competencies-Based Perspective}, author = {Pang, H. Y. M. and Meshkat, S. and Teferra, B. G. and Rueda, A. and Samavi, R. and Krishnan, S. and Doyle, T. and Rambhatla, S. and DeJong, S. and Sockalingam, S. and Horsley, T. and Hodges, B. and Bhat., V.}, journal = {Academic Psychiatry (Springer Journal)}, pdf = {papers/Acad_Psychiatry_2024.pdf}, url = {https://link.springer.com/article/10.1007/s40596-024-02087-2}, year = {2024}, award = {Commentary} }
TRR

Embedding-Based Representation Learning for Forecasting Flight Characteristics

Biswal, A., Rambhatla, S., and Gzara, F.

Transportation Research Record (Sage Journal) 2024

Bib

@article{Biswal2024, abbr = {TRR}, img = {TRR-2024.png}, title = {Embedding-Based Representation Learning for Forecasting Flight Characteristics}, author = {Biswal, A. and Rambhatla, S. and Gzara, F.}, journal = {Transportation Research Record (Sage Journal)}, year = {2024} }
CORS
🏆 Abstract

Airline Crew Pairing Optimization with Learning

Biswal, A., Rambhatla, S., and Gzara, F.

65th Annual Canadian Operational Research Society (CORS) Conference 2024

Bib

@article{Biswal2025, abbr = {CORS}, img = {TRR-2024.png}, title = {Airline Crew Pairing Optimization with Learning}, author = {Biswal, A. and Rambhatla, S. and Gzara, F.}, journal = {65th Annual Canadian Operational Research Society (CORS) Conference}, year = {2024}, award = {Abstract} }
NeurIPS 2024

Seeing Beyond the Crop: Using Language Priors for Out-of-Bounding Box Keypoint Prediction

Balaji, B., Bright, J., Chen, Y., Rambhatla, S., Zelek, J. S., and Clausi, D. A.

Advances in Neural Information Processing Systems (NeurIPS) 2024

Bib PDF

@article{Balaji2024b, abbr = {NeurIPS 2024}, img = {NeurIPS-Token-Clip-Pose_2.png}, title = {Seeing Beyond the Crop: Using Language Priors for Out-of-Bounding Box Keypoint Prediction}, author = {Balaji, B. and Bright, J. and Chen, Y. and Rambhatla, S. and Zelek, J. S. and Clausi, D. A.}, journal = {Advances in Neural Information Processing Systems (NeurIPS)}, pdf = {https://openreview.net/pdf?id=LGus3wXPxc}, url = {https://openreview.net/forum?id=LGus3wXPxc}, year = {2024}, selected = {true} }
CRV 2024
🏆 Oral Presentation

Domain-Guided Masked Autoencoders for Unique Player Identification

Balaji, B., Bright, J., Rambhatla, S., Chen, Y., Wong, A., Zelek, J., and Clausi, D. A.

Conference on Robotics and Vision (CRV) 2024

Bib PDF

@article{Balaji2024a, abbr = {CRV 2024}, img = {CRV-2024-d-MAE.png}, title = {Domain-Guided Masked Autoencoders for Unique Player Identification}, author = {Balaji, B. and Bright, J. and Rambhatla, S. and Chen, Y. and Wong, A. and Zelek, J. and Clausi, D. A.}, journal = {Conference on Robotics and Vision (CRV)}, pdf = {https://openreview.net/pdf?id=LVLoMF1ZC9}, url = {https://openreview.net/forum?id=LVLoMF1ZC9}, year = {2024}, award = {Oral Presentation} }

2023

KDD
🏆 Oral and Poster Presentation

Domain-Guided Spatio-Temporal Self-Attention for Egocentric 3D Pose Estimation

Park, J., Kaai, K., Hossain, S., Sumi, N., Rambhatla, S., and Fieguth, P.

ACM SIGKDD International Conference on Knowledge Discovery & Data Mining (KDD) 2023

Bib PDF Code

@article{park2023a, abbr = {KDD}, title = {Domain-Guided Spatio-Temporal Self-Attention for Egocentric 3D Pose Estimation}, img = {egostan.gif}, author = {Park, J. and Kaai, K. and Hossain, S. and Sumi, N. and Rambhatla, S. and Fieguth, P.}, journal = {ACM SIGKDD International Conference on Knowledge Discovery \& Data Mining (KDD)}, url = {https://dl.acm.org/doi/10.1145/3580305.3599312}, month = aug, code = {https://github.com/jmpark0808/Ego-STAN}, pdf = {https://dl.acm.org/doi/10.1145/3580305.359931}, year = {2023}, award = {Oral and Poster Presentation} }
ICLR DistShift Workshop
🏆 Oral Presentation

Implicit Stylization for Domain Adaptation

Park, J., Barnard, F., Hossain, S., and Rambhatla, S.

Workshop on What do we need for successful domain generalization? International Conference on Learning Representations (ICLR) 2023

Bib PDF

@article{park2023b, abbr = {ICLR DistShift Workshop}, img = {imsty.jpeg}, title = {Implicit Stylization for Domain Adaptation}, author = {Park, J. and Barnard, F. and Hossain, S. and Rambhatla, S.}, journal = {Workshop on What do we need for successful domain generalization? International Conference on Learning Representations (ICLR)}, pdf = {https://openreview.net/forum?id=fkFFh4fAbH}, url = {https://openreview.net/forum?id=fkFFh4fAbH}, month = feb, year = {2023}, award = {Oral Presentation} }
NeurIPS DistShift Workshop

Are all classes created equal? Domain Generalization for Domain-Linked Classes

Kaai, K., Hossain, S., and Rambhatla, S.

Workshop on Distribution Shifts (DistShift) at Neural Information Processing Systems 2023

Bib PDF

@article{kaai2023, abbr = {NeurIPS DistShift Workshop}, img = {average_dl_ds_plot_workshop.pdf}, title = {Are all classes created equal? Domain Generalization for Domain-Linked Classes}, author = {Kaai, K. and Hossain, S. and Rambhatla, S.}, journal = {Workshop on Distribution Shifts (DistShift) at Neural Information Processing Systems}, pdf = {https://openreview.net/forum?id=Zz7eZoR1VN}, url = {https://openreview.net/forum?id=Zz7eZoR1VN}, month = dec, year = {2023} }

2022

AAAI

I-SEA: Importance Sampling and Expected Alignment-based Deep Distance Metric Learning for Time Series Analysis and Embedding

Rambhatla, S., Che, Z., and Liu, Y.

36th Association for the Advancement of Artificial Intelligence (AAAI) conference on Artificial Intelligence 2022

Abs Bib PDF Code

Learning effective embeddings for potentially irregularly sampled time-series, evolving at different times scales, is fundamental for machine learning tasks such as classification and clustering. Task-dependent embeddings rely on similarities between data samples to learn effective geometries. However, many popular time-series similarity measures are not valid distance metrics, and as a result they do not reliably capture the intricate relationships between the multi-variate time-series data samples for learning effective embeddings. One of the primary ways to formulate an accurate distance metric is by forming distance estimates via Monte-Carlo-based expectation evaluations. However, the high-dimensionality of the underlying distribution, and the inability to sample from it, pose significant challenges. To this end, we develop an Importance Sampling based distance metric – ISEA – which enjoys the properties of a metric while consistently achieving superior performance for machine learning tasks such as classification and representation learning. ISEA leverages Importance Sampling and Non-parametric Density Estimation to adaptively estimate distances, enabling implicit estimation from the underlying high-dimensional distribution, resulting in improved accuracy and reduced variance. We theoretically establish the properties of ISEA and demonstrate its capabilities via experimental evaluations on real-world healthcare datasets.

@article{Rambhatla2022isea, abbr = {AAAI}, title = {I-SEA: Importance Sampling and Expected Alignment-based Deep Distance Metric Learning for Time Series Analysis and Embedding}, author = {Rambhatla, S. and Che, Z. and Liu, Y.}, journal = {36th Association for the Advancement of Artificial Intelligence (AAAI) conference on Artificial Intelligence}, img = {IS_visualization.png}, pdf = {papers/ISEA_AAAI2022.pdf}, code = {https://github.com/srambhatla/ISEA}, month = feb, year = {2022} }
UCNA

Artificial Intelligence Applications in Urology: Reporting Standards to Achieve Fluency for Urologists

Chen, A. B., Haque, T., Roberts, S., Rambhatla, S., Cacciamani, G., Dasgupta, P., and Hung, A. J.

Urology Clinics North America 2022

Bib

@article{Chen2022a, abbr = {UCNA}, title = {Artificial Intelligence Applications in Urology: Reporting Standards to Achieve Fluency for Urologists}, author = {Chen, A. B. and Haque, T. and Roberts, S. and Rambhatla, S. and Cacciamani, G. and Dasgupta, P. and Hung, A. J.}, img = {RAS.gif}, journal = {Urology Clinics North America}, month = feb, url = {https://pubmed.ncbi.nlm.nih.gov/34776055/}, year = {2022} }
TSAS

Towards Accurate Spatiotemporal COVID-19 Risk Scores using High Resolution Real-World Mobility Data.

Rambhatla*, S., Zeighami*, S., Shahabi, K., Shahabi, C., and Liu., Y.

ACM Transactions on Spatial Algorithms and Systems (TSAS) 2022

Abs Bib arXiv PDF

As countries look towards re-opening of economic activities amidst the ongoing COVID-19 pandemic, ensuring public health has been challenging. While contact tracing only aims to track past activities of infected users, one path to safe reopening is to develop reliable spatiotemporal risk scores to indicate the propensity of the disease. Existing works which aim to develop risk scores either rely on compartmental model-based reproduction numbers (which assume uniform population mixing) or develop coarse-grain spatial scores based on reproduction number (R0) and macro-level density-based mobility statistics. Instead, in this paper, we develop a Hawkes process-based technique to assign relatively fine-grain spatial and temporal risk scores by leveraging high-resolution mobility data based on cell-phone originated location signals. While COVID-19 risk scores also depend on a number of factors specific to an individual, including demography and existing medical conditions, the primary mode of disease transmission is via physical proximity and contact. Therefore, we focus on developing risk scores based on location density and mobility behaviour. We demonstrate the efficacy of the developed risk scores via simulation based on real-world mobility data. Our results show that fine-grain spatiotemporal risk scores based on high-resolution mobility data can provide useful insights and facilitate safe re-opening.

@article{Rambhatla2022highres, abbr = {TSAS}, title = {Towards Accurate Spatiotemporal COVID-19 Risk Scores using High Resolution Real-World Mobility Data.}, author = {Rambhatla*, S. and Zeighami*, S. and Shahabi, K. and Shahabi, C. and Liu., Y.}, arxiv = {2012.07283v1}, img = {spread_sim.gif}, url = {https://arxiv.org/abs/2012.07283v1}, pdf = {https://arxiv.org/pdf/2012.07283v1.pdf}, journal = {ACM Transactions on Spatial Algorithms and Systems (TSAS)}, month = feb, year = {2022} }
ILTS
🏆 Oral Presentation

Predicting Future Trajectories of the Waitlisted NASH patients using Deep Learning

Punchhi, G., Sun, Y., Rambhatla, S., and Bhat, M.

Abstract at International Liver Transplantation Society 2022

Bib

@article{Punchhi2022a, abbr = {ILTS}, title = {Predicting Future Trajectories of the Waitlisted NASH patients using Deep Learning}, author = {Punchhi, G. and Sun, Y. and Rambhatla, S. and Bhat, M.}, img = {liver.png}, journal = {Abstract at International Liver Transplantation Society}, url = {}, month = mar, year = {2022}, award = {Oral Presentation} }
EPIC and Ego4D @ CVPR
🏆 Oral Presentation

Building Spatio-temporal Transformers for Egocentric 3D Pose Estimation

Park, J., Kaai, K., Hossain, S., Sumi, N., Rambhatla, S., and Fieguth, P.

Joint International Workshop on Egocentric Perception, Interaction and Computing (EPIC) and Ego4D, IEEE/CVF Computer Vision and Pattern Recognition Conference (CVPR) 2022

Bib

@article{Park2022a, abbr = {EPIC and Ego4D @ CVPR}, title = {Building Spatio-temporal Transformers for Egocentric 3D Pose Estimation}, author = {Park, J. and Kaai, K. and Hossain, S. and Sumi, N. and Rambhatla, S. and Fieguth, P.}, img = {egostan.gif}, journal = {Joint International Workshop on Egocentric Perception, Interaction and Computing (EPIC) and Ego4D, IEEE/CVF Computer Vision and Pattern Recognition Conference (CVPR)}, url = {http://arxiv.org/abs/2206.04785}, month = jun, year = {2022}, award = {Oral Presentation} }

2021

Surgery

Road to Automating Robotic Suturing Skills Assessment: Battling Mislabeling of the Ground Truth

Hung, A. J., Rambhatla, S., Sanford, D. I., Pachauri, N., Vanstrum, E., Nguyen, J. H., and Liu, Y.

Surgery 2021

Bib

@article{Hung2021b, abbr = {Surgery}, title = {Road to Automating Robotic Suturing Skills Assessment: Battling Mislabeling of the Ground Truth}, author = {Hung, A. J. and Rambhatla, S. and Sanford, D. I. and Pachauri, N. and Vanstrum, E. and Nguyen, J. H. and Liu, Y.}, journal = {Surgery}, img = {NoiseRank.png}, url = {https://authors.elsevier.com/c/1dlnr90L~q2da}, year = {2021} }
Plastic Surgery

Predicting burn surgical candidacy using deep learning on photographic images.

Huang*, S., Rambhatla*, S., Trinh, L., Zhang, M., Dong, M., Unadkat, V., Lin, J., Sheth, M. K., Dang, J., Yenikomshian, H. A., Liu, Y., and Gillenwater, J.

Plastic Surgery: The Meeting 2021

Bib

@article{Huang2021a, abbr = {Plastic Surgery}, title = {Predicting burn surgical candidacy using deep learning on photographic images.}, author = {Huang*, S. and Rambhatla*, S. and Trinh, L. and Zhang, M. and Dong, M. and Unadkat, V. and Lin, J. and Sheth, M. K. and Dang, J. and Yenikomshian, H. A. and Liu, Y. and Gillenwater, J.}, img = {burn_cnn.png}, journal = {Plastic Surgery: The Meeting}, month = jan, year = {2021} }
KDD

Cross-Node Federated Graph Neural Network for Spatio-Temporal Data Modeling

Meng, C., Rambhatla, S., and Liu, Y.

ACM SIGKDD International Conference on Knowledge Discovery & Data Mining 2021

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Vast amount of data generated from networks of sensors, wearables, and the Internet of Things (IoT) devices underscores the need for advanced modeling techniques that leverage the spatio-temporal structure of decentralized data due to the need for edge computation and licensing (data access) issues. While federated learning (FL) has emerged as a framework for model training without requiring direct data sharing and exchange, effectively modeling the complex spatio-temporal dependencies to improve forecasting capabilities still remains an open problem. On the other hand, state-of-the-art spatio-temporal forecasting models assume unfettered access to the data, neglecting constraints on data sharing. To bridge this gap, we propose a federated spatio-temporal model – Cross-Node Federated Graph Neural Network (CNFGNN) – which explicitly encodes the underlying graph structure using graph neural network (GNN)-based architecture under the constraint of cross-node federated learning, which requires that data in a network of nodes is generated locally on each node and remains decentralized. CN-FGNN operates by disentangling the temporal dynamics modeling on devices and spatial dynamics on the server, utilizing alternating optimization to reduce the communication cost, facilitating computations on the edge devices. Experiments on the traffic flow forecasting task show that CNFGNN achieves the best forecasting performance in both transductive and inductive learning settings with no extra computation cost on edge devices, while incurring modest communication cost.

@article{Meng2021a, abbr = {KDD}, title = {Cross-Node Federated Graph Neural Network for Spatio-Temporal Data Modeling}, author = {Meng, C. and Rambhatla, S. and Liu, Y.}, img = {cross-node.png}, journal = {ACM SIGKDD International Conference on Knowledge Discovery \& Data Mining}, month = jan, year = {2021} }
AUA
🏆 Podium Talk

Automating suturing skills assessment with a limited surgeon dataset: Meta learning

Hung, A. J., Rambhatla, S., Sanford, D. I., Pachauri, N., Nguyen, J. H., and Liu, Y.

American Urology Association 2021

Bib

@article{Hung2021a, abbr = {AUA}, title = {Automating suturing skills assessment with a limited surgeon dataset: Meta learning}, author = {Hung, A. J. and Rambhatla, S. and Sanford, D. I. and Pachauri, N. and Nguyen, J. H. and Liu, Y.}, img = {RAS.gif}, journal = {American Urology Association}, award = {Podium Talk}, month = jan, year = {2021} }
IJCAI

Physics-aware Spatiotemporal Modules with Auxiliary Tasks for Meta-Learning

Seo, S., Meng, C., Rambhatla, S., and Liu, Y.

International Joint Conferences on Artificial Intelligence (IJCAI) 2021

Abs Bib arXiv PDF

Modeling the dynamics of real-world physical systems is critical for spatiotemporal prediction tasks, but challenging when data is limited. The scarcity of real-world data and the difficulty in reproducing the data distribution hinder directly applying meta-learning techniques. Although the knowledge of governing partial differential equations (PDEs) of the data can be helpful for the fast adaptation to few observations, it is difficult to generalize to different or unknown dynamics. In this paper, we propose a framework, physics-aware modular meta-learning with auxiliary tasks (PiMetaL) whose spatial modules incorporate PDE-independent knowledge and temporal modules are rapidly adaptable to the limited data, respectively. The framework does not require the exact form of governing equations to model the observed spatiotemporal data. Furthermore, it mitigates the need for a large number of real-world tasks for meta-learning by leveraging simulated data. We apply the proposed framework to both synthetic and real-world spatiotemporal prediction tasks and demonstrate its superior performance with limited observations.

@article{seo2021physics, abbr = {IJCAI}, title = {Physics-aware Spatiotemporal Modules with Auxiliary Tasks for Meta-Learning}, author = {Seo, S. and Meng, C. and Rambhatla, S. and Liu, Y.}, journal = {International Joint Conferences on Artificial Intelligence (IJCAI)}, url = {https://arxiv.org/abs/2006.08831}, pdf = {https://arxiv.org/pdf/2006.08831.pdf}, arxiv = {2006.08831}, img = {PiMetal_zoom.png}, month = jan, year = {2021} }
ICLR Workshop

Simulating continuous-time human mobility trajectories.

Xu*, N., Trinh*, L., Rambhatla, S., Assefa, S., Chen, J., Zeng, Z., and Liu, Y.

Deep Learning for Simulation Workshop, International Conference on Learning Representations (ICLR) 2021

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Recent pandemic events have greatly emphasized the need to understand how hu-mans navigate in modern day cities for both urban planning and recommendingeffective public health policy. In this paper, we propose a two-stage generativemodel,DeltaGAN, to simulate realistic human mobility trajectories. Comparedwith existing work where time was discretized,DeltaGANgenerates continuousvisitation time which better captures temporal irregularity in human mobility be-haviors. Conditioned on the generated time,DeltaGANproduces accurate loca-tions via limiting the range of realizable candidates. Experimental results demon-strate our model achieves competitive distributional similarity to real-world GPStrajectories across 6 individual trajectory and geographical metrics. We furthervalidateDeltaGAN’s utility on COVID-19 spread simulation and observe the dif-fusion process under generated trajectories is consistent with that under real data.

@article{Xu2021a, abbr = {ICLR Workshop}, title = {Simulating continuous-time human mobility trajectories.}, img = {DeltaGAN.png}, author = {Xu*, N. and Trinh*, L. and Rambhatla, S. and Assefa, S. and Chen, J. and Zeng, Z. and Liu, Y.}, journal = {Deep Learning for Simulation Workshop, International Conference on Learning Representations (ICLR)}, month = jan, year = {2021} }
JHIR

PolSIRD: Modeling Epidemic Spread under Intervention Policies and an Application to the Spread of COVID-19

Kamra, N., Zhang, Y., Rambhatla, S., Meng, C., and Liu, Y.

Journal of Healthcare Informatics Research 2021

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Epidemic spread in a population is traditionally modeled via compartmentalized models which represent the free evolution of disease in absence of any intervention policies. In addition, these models assume full observability and do not account for under-reporting of cases. We present a mathematical model, namely PolSIRD, which accounts for the under-reporting by introducing an observation mechanism. It also captures the effects of intervention policies on the disease spread parameters by leveraging intervention policy data along with the reported disease cases. Furthermore, we allow our recurrent model to learn the initial hidden state of all compartments end-to-end along with other parameters via gradient-based training. We apply our model to spread of the recent global outbreak of COVID-19 where our model outperforms the current methods employed by the CDC in most of the metrics. We also provide actionable guidance on the lifting of intervention policies via counterfactual simulations from our model.

@article{kamra2020pred, abbr = {JHIR}, title = {{PolSIRD}: Modeling Epidemic Spread under Intervention Policies and an Application to the Spread of COVID-19}, author = {Kamra, N. and Zhang, Y. and Rambhatla, S. and Meng, C. and Liu, Y.}, img = {polsird.png}, arxiv = {2009.01894}, url = {https://arxiv.org/abs/2009.01894}, pdf = {https://arxiv.org/pdf/2009.01894.pdf}, journal = {Journal of Healthcare Informatics Research}, month = jan, year = {2021} }
WACV

Interpretable and Trustworthy Deepfake Detection via Dynamic Prototypes

Trinh, L., Tsang, M., Rambhatla, S., and Liu, Y.

IEEE Winter Conference on Applications of Computer Vision (WACV) 2021

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In this paper we propose a novel human-centered ap- proach for detecting forgery in face images, using dynamic prototypes as a form of visual explanations. Currently, most state-of-the-art deepfake detections are based on black-box models that process videos frame-by-frame for inference, and few closely examine their temporal inconsistencies. However, the existence of such temporal artifacts within deepfake videos is key in detecting and explaining deep- fakes to a supervising human. To this end, we propose Dynamic Prototype Network (DPNet) – an interpretable and effective solution that utilizes dynamic representations (i.e., prototypes) to explain deepfake temporal artifacts. Extensive experimental results show that DPNet achieves competitive predictive performance, even on unseen test- ing datasets such as Google’s DeepFakeDetection, Deep- erForensics, and Celeb-DF, while providing easy referential explanations of deepfake dynamics. On top of DPNet’s pro- totypical framework, we further formulate temporal logic specifications based on these dynamics to check our model’s compliance to desired temporal behaviors, hence providing trustworthiness for such critical detection systems.

@article{trinh2020interpretable, abbr = {WACV}, title = {Interpretable and Trustworthy Deepfake Detection via Dynamic Prototypes}, author = {Trinh, L. and Tsang, M. and Rambhatla, S. and Liu, Y.}, journal = {IEEE Winter Conference on Applications of Computer Vision (WACV)}, pdf = {https://openaccess.thecvf.com/content/WACV2021/papers/Trinh_Interpretable_and_Trustworthy_Deepfake_Detection_via_Dynamic_Prototypes_WACV_2021_paper.pdf}, arxiv = {2006.15473}, url = {https://arxiv.org/abs/2006.15473}, img = {DPNet_resized.gif}, month = jan, year = {2021} }
AMIA
🏆 Oral Presentation

DL4Burn: Burn surgical candidacy using multimodal deep learning.

Huang*, S., Rambhatla*, S., Trinh, L., Zhang, M., Dong, M., Unadkat, V., Yenikomshian, H. A., Gillenwater, J., and Liu, Y.

American Medical Informatics Association (AMIA) Annual Symposium 2021

Bib

@article{Huang2021b, abbr = {AMIA}, award = {Oral Presentation}, title = {DL4Burn: Burn surgical candidacy using multimodal deep learning.}, author = {Huang*, S. and Rambhatla*, S. and Trinh, L. and Zhang, M. and Dong, M. and Unadkat, V. and Yenikomshian, H. A. and Gillenwater, J. and Liu, Y.}, img = {DL4Burn.png}, journal = {American Medical Informatics Association (AMIA) Annual Symposium}, month = jan, year = {2021} }

2020

NeurIPS

Provable Online CP/PARAFAC Decomposition of a Structured Tensor via Dictionary Learning

Rambhatla, S., Li, X., and Haupt, J.

Advances in Neural Information Processing Systems (NeurIPS) 2020

Abs Bib arXiv PDF Code Slides

We consider the problem of factorizing a structured 3-way tensor into itsconstituent Canonical Polyadic (CP) factors. This decomposition, whichcan be viewed as a generalization of singular value decomposition (SVD)for tensors, reveals how the tensor dimensions (features) interact with eachother. However, since the factors area prioriunknown, the correspondingoptimization problems are inherently non-convex. The existing guaranteedalgorithms which handle this non-convexity incur an irreducible error (bias),and only apply to cases where all factors have the same structure. To thisend, we develop a provable algorithm for online structured tensor factor-ization, wherein one of the factors obeys some incoherence conditions, andthe others are sparse. Specifically we show that, under some relatively mildconditions on initialization, rank, and sparsity, our algorithm recovers thefactorsexactly(up to scaling and permutation) at a linear rate. Comple-mentary to our theoretical results, our synthetic and real-world data eval-uations showcase superior performance compared to related techniques.

@article{Rambhatla19Tensor, abbr = {NeurIPS}, title = {Provable Online {CP/PARAFAC} Decomposition of a Structured Tensor via Dictionary Learning }, author = {Rambhatla, S. and Li, X. and Haupt, J.}, journal = {Advances in Neural Information Processing Systems (NeurIPS)}, slides = {/posters/Poster_TensorNOODL.pdf}, img = {TensorNOODL.png}, url = {https://papers.nips.cc/paper/2020/hash/85b42dd8aae56e01379be5736db5b496-Abstract.html}, pdf = {https://papers.nips.cc/paper/2020/file/85b42dd8aae56e01379be5736db5b496-Paper.pdf}, arxiv = {2006.16442}, code = {https://github.com/srambhatla/TensorNOODL}, selected = {true}, year = {2020} }
NeurIPS

How does this interaction affect me? Interpretable attribution for feature interactions

Tsang, M., Rambhatla, S., and Liu, Y.

Advances in Neural Information Processing Systems (NeurIPS) 2020

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Machine learning transparency calls for interpretable explanations of how inputs relate to predictions. Feature attribution is a way to analyze the impact of features on predictions. Feature interactions are the contextual dependence between features that jointly impact predictions. There are a number of methods that extract feature interactions in prediction models; however, the methods that assign attributions to interactions are either uninterpretable, model-specific, or non-axiomatic. We propose an interaction attribution and detection framework called Archipelago which addresses these problems and is also scalable in real-world settings. Our experiments on standard annotation labels indicate our approach provides significantly more interpretable explanations than comparable methods, which is important for analyzing the impact of interactions on predictions. We also provide accompanying visualizations of our approach that give new insights into deep neural networks.

@article{tsang2020does, abbr = {NeurIPS}, title = {How does this interaction affect me? Interpretable attribution for feature interactions}, author = {Tsang, M. and Rambhatla, S. and Liu, Y.}, journal = {Advances in Neural Information Processing Systems (NeurIPS)}, arxiv = {2006.10965}, pdf = {https://proceedings.neurips.cc/paper/2020/file/443dec3062d0286986e21dc0631734c9-Paper.pdf}, url = {https://proceedings.neurips.cc/paper/2020/hash/443dec3062d0286986e21dc0631734c9-Abstract.html}, code = {https://github.com/mtsang/archipelago}, img = {archipelago.png}, selected = {true}, year = {2020} }
NeurIPS Workshop

Physics-aware Spatiotemporal Modules with Auxiliary Tasks for Meta-Learning

Seo, S., Meng, C., Rambhatla, S., and Liu, Y.

Workshop on Machine Learning and the Physical Sciences, NeurIPS 2020

Abs Bib arXiv PDF

Modeling the dynamics of real-world physical systems is critical for spatiotemporal prediction tasks, but challenging when data is limited. The scarcity of real-world data and the difficulty in reproducing the data distribution hinder directly applying meta-learning techniques. Although the knowledge of governing partial differential equations (PDEs) of the data can be helpful for the fast adaptation to few observations, it is difficult to generalize to different or unknown dynamics. In this paper, we propose a framework, physics-aware modular meta-learning with auxiliary tasks (PiMetaL) whose spatial modules incorporate PDE-independent knowledge and temporal modules are rapidly adaptable to the limited data, respectively. The framework does not require the exact form of governing equations to model the observed spatiotemporal data. Furthermore, it mitigates the need for a large number of real-world tasks for meta-learning by leveraging simulated data. We apply the proposed framework to both synthetic and real-world spatiotemporal prediction tasks and demonstrate its superior performance with limited observations.

@article{seo2020physics, abbr = {NeurIPS Workshop}, title = {Physics-aware Spatiotemporal Modules with Auxiliary Tasks for Meta-Learning}, author = {Seo, S. and Meng, C. and Rambhatla, S. and Liu, Y.}, journal = {Workshop on Machine Learning and the Physical Sciences, NeurIPS}, url = {https://arxiv.org/abs/2006.08831}, pdf = {https://arxiv.org/pdf/2006.08831.pdf}, arxiv = {2006.08831}, img = {PiMetal_zoom.png}, year = {2020} }
Under Review

Coronavirus on social media: Analyzing misinformation in Twitter conversations

Sharma, K., Seo, S., Meng, C., Rambhatla, S., and Liu, Y.

arXiv preprint arXiv:2003.12309 2020

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The ongoing Coronavirus (COVID-19) pandemic highlights the inter-connectedness of our present- day globalized world. With social distancing policies in place, virtual communication has become an important source of (mis)information. As increasing number of people rely on social media platforms for news, identifying misinformation and uncovering the nature of online discourse around COVID-19 has emerged as a critical task. To this end, we collected streaming data related to COVID-19 using the Twitter API, starting March 1, 2020. We identified unreliable and misleading contents based on fact-checking sources, and examined the narratives promoted in misinformation tweets, along with the distribution of engagements with these tweets. In addition, we provide examples of the spreading patterns of prominent misinformation tweets. The analysis is presented and updated on a publically accessible dashboard1 to track the nature of online discourse and misinformation about COVID-19 on Twitter from March 1 - June 5, 2020. The dashboard provides a daily list of identified misinformation tweets, along with topics, sentiments, and emerging trends in the COVID-19 Twitter discourse. The dashboard is provided to improve visibility into the nature and quality of information shared online, and provide real-time access to insights and information extracted from the dataset.

@article{sharma2020coronavirus, abbr = {Under Review}, title = {Coronavirus on social media: Analyzing misinformation in Twitter conversations}, author = {Sharma, K. and Seo, S. and Meng, C. and Rambhatla, S. and Liu, Y.}, url = {https://arxiv.org/abs/2003.12309}, pdf = {https://arxiv.org/pdf/2003.12309.pdf}, arxiv = {2003.12309}, img = {spread_misinfo.gif}, journal = {arXiv preprint arXiv:2003.12309}, year = {2020} }
TSP

A Dictionary-Based Generalization of Robust PCA With Applications to Target Localization in Hyperspectral Imaging

Rambhatla, S., Li, X., Ren, J., and Haupt, J.

IEEE Tran. on Signal Processing 2020

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We consider the decomposition of a data matrix assumed to be a superposition of a low-rank matrix and a component which is sparse in a known dictionary, using a convex demixing method. We consider two sparsity structures for the sparse factor of the dictionary sparse component, namely entry-wise and column-wise sparsity, and provide a unified analysis, encompassing both undercomplete and the overcomplete dictionary cases, to show that the constituent matrices can be successfully recovered under some relatively mild conditions on incoherence, sparsity, and rank. We leverage these results to localize targets of interest in a hyperspectral (HS) image based on their spectral signature(s) using the a priori known characteristic spectral responses of the target. We corroborate our theoretical results and analyze target localization performance of our approach via experimental evaluations and comparisons to related techniques.

@article{Rambhatla20LrTheoApp, abbr = {TSP}, author = {{Rambhatla}, S. and {Li}, X. and {Ren}, J. and {Haupt}, J.}, journal = {IEEE Tran. on Signal Processing}, title = {A Dictionary-Based Generalization of Robust PCA With Applications to Target Localization in Hyperspectral Imaging}, year = {2020}, volume = {68}, code = {https://github.com/srambhatla/Dictionary-based-Robust-PCA}, number = {}, pdf = {https://arxiv.org/pdf/1902.08304v3.pdf}, arxiv = {1902.08304v3}, img = {LplusDA_hyper_spectral.gif}, url = {https://arxiv.org/abs/1902.08304}, pages = {1760-75}, selected = {false}, blog = {2017/HyperSpectral/} }

2019

ICLR
🏆 Travel Award

NOODL: Provable Online Dictionary Learning and Sparse Coding

Rambhatla, S., Li, X., and Haupt, J.

International Conference on Learning Representations (ICLR) 2019

Abs Bib arXiv PDF Code Slides

We consider the dictionary learning problem, where the aim is to model the givendata as a linear combination of a few columns of a matrix known as adictionary,where the sparse weights forming the linear combination are known ascoeffi-cients. Since the dictionary and coefficients, parameterizing the linear model areunknown, the corresponding optimization is inherently non-convex. This was amajor challenge until recently, when provable algorithms for dictionary learningwere proposed. Yet, these provide guarantees only on the recovery of the dic-tionary, without explicit recovery guarantees on the coefficients. Moreover, anyestimation error in the dictionary adversely impacts the ability to successfully lo-calize and estimate the coefficients. This potentially limits the utility of existingprovable dictionary learning methods in applications where coefficient recoveryis of interest. To this end, we develop NOODL: a simple Neurally plausible alter-nating Optimization-based Online Dictionary Learning algorithm, which recoversboththe dictionary and coefficientsexactlyat a geometric rate, when initializedappropriately. Our algorithm, NOODL, is also scalable and amenable for largescale distributed implementations in neural architectures, by which we mean thatit only involves simple linear and non-linear operations. Finally, we corroboratethese theoretical results via experimental evaluation of the proposed algorithmwith the current state-of-the-art techniques.

@article{Rambhatla2019, abbr = {ICLR}, title = {{NOODL}: Provable Online Dictionary Learning and Sparse Coding}, author = {Rambhatla, S. and Li, X. and Haupt, J.}, journal = {International Conference on Learning Representations (ICLR)}, year = {2019}, url = {https://openreview.net/forum?id=HJeu43ActQ}, selected = {true}, arxiv = {1902.11261}, slides = {/posters/NOODL_poster_ICLR.pdf}, pdf = {https://openreview.net/pdf?id=HJeu43ActQ}, code = {https://github.com/srambhatla/NOODL}, img = {NOODL.png}, award = {Travel Award} }
Doctoral Thesis

Provably Learning from Data: New Algorithms and Models for Matrix and Tensor Decompositions

Rambhatla, S.

University of Minnesota – Twin Cities, Minneapolis, MN 2019

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Learning and leveraging patterns in data has fueled the recent advances in data driven services. As these solutions become more ubiquitous, and get incorporated into critical applications in healthcare and transportation, there is an increasing need to understand the limits of these learning algorithms and to develop algorithms with guar- antees. Moreover, with data being generated at unprecedented rates, these algorithms need to be fast, learn on-the-fly (online), handle large volumes of data (scalable), and be computationally efficient, while possessing guarantees on their behavior. Further- more, to make the learning-based products widely applicable there is also a need to make their reasoning and decision making process transparent (interpretable). These challenges inspire and motivate this dissertation. Specifically, we focus on analyzing various matrix/tensor demixing and factorization tasks, where we leverage the inherent interpretability endowed by the structure of problem (such as sparsity and low-rankness) to characterize the (theoretical) conditions for successful recovery, and analyze their performance in real-world settings.sTo this end, we make contributions on three fronts. First, we develop algorithm- aware theoretical guarantees for sparse matrix and tensor factorization tasks. Second, we establish algorithm-agnostic theoretical results for matrix demixing models and demonstrate their applications on real-world datasets. Lastly, we develop application-specific techniques for navigation and source separation. Bringing together Algorithms, Theory, and Applications, the techniques and theoretical results developed as part of this dissertation facilitate and motivate future explorations into the inner workings of learning algorithms for their safe use in critical applications.

@article{Rambhatla2019thesis, abbr = {Doctoral Thesis}, author = {Rambhatla, S.}, title = {Provably Learning from Data: New Algorithms and Models for Matrix and Tensor Decompositions}, journal = {{U}niversity of {M}innesota -- {T}win {C}ities, {M}inneapolis, {MN}}, year = {2019}, img = {phd_thesis.png}, pdf = {PhD_thesis_Sirisha_Rambhatla.pdf} }

2018

ICASSP

Robust PCA via Dictionary Based Outlier Pursuit

Li, X., Ren, J., Rambhatla, S., Xu, Y., and Haupt, J.

2018 IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP) 2018

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In this paper, we examine the problem of locating vector out- liers from a large number of inliers, with a particular focus on the case where the outliers are represented in a known basis or dictionary. Using a convex demixing formulation, we provide provable guarantees for exact recovery of the space spanned by the inliers and the supports of the outlier columns, even when the rank of inliers is high and the number of outliers is a constant proportion of total observations. Comprehensive numerical experiments on both synthetic and hyper-spectral imaging real datasets demonstrate the efficiency of our pro- posed method.

@article{Li2018icassp, abbr = {ICASSP}, title = {Robust PCA via Dictionary Based Outlier Pursuit}, author = {Li, X. and Ren, J. and Rambhatla, S. and Xu, Y. and Haupt, J.}, journal = {2018 IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP)}, year = {2018}, code = {https://github.com/srambhatla/Dictionary-based-Robust-PCA}, pdf = {Robust_PCA_via_Dictionary_Based_Outlier_Pursuit.pdf}, img = {DRPCA.png}, organization = {IEEE} }
GlobalSIP

TensorMap: Lidar-based Topological Mapping and Localization via Tensor Decompositions

Rambhatla, S., Sidiropoulos, N., and Haupt, J.

IEEE Global Conference on Signal and Information Processing (GlobalSIP) 2018

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We propose a technique to develop (and localize in) topological maps from light detection and ranging (Lidar) data. Localizing an autonomous vehicle with respect to a reference map in real-time is crucial for its safe operation. Owing to the rich information provided by Lidar sensors, these are emerging as a promising choice for this task. However, since a Lidar outputs a large amount of data every fraction of a second, it is progressively harder to process the information in real-time. Consequently, current systems have migrated towards faster alternatives at the expense of accuracy. To overcome this inherent trade-off between latency and accuracy, we propose a technique to develop topological maps from Lidar data using the orthogonal Tucker3 tensor decomposition. Our experimental evaluations demonstrate that in addition to achieving a high compression ratio as compared to full data, the proposed technique, TensorMap, also accurately detects the position of the vehicle in a graph-based representation of a map. We also analyze the robustness of the proposed technique to Gaussian and translational noise, thus initiating explorations into potential applications of tensor decompositions in Lidar data analysis.

@article{Rambhatla18TensorMap, abbr = {GlobalSIP}, author = {Rambhatla, S. and Sidiropoulos, N. and Haupt, J.}, title = {TensorMap: Lidar-based Topological Mapping and Localization via Tensor Decompositions}, journal = {IEEE Global Conference on Signal and Information Processing (GlobalSIP)}, year = {2018}, organization = {IEEE}, arxiv = {1902.10226}, img = {TensorMap.png}, code = {https://github.com/srambhatla/TensorMap}, url = {https://arxiv.org/abs/1902.10226}, pdf = {https://arxiv.org/pdf/1902.10226.pdf} }

2017

Asilomar
🏆 Best Paper Finalist

Target-based hyperspectral demixing via generalized robust PCA

Rambhatla, S., Li, X., and Haupt, J.

51st Asilomar Conference on Signals, Systems, and Computers, 2017 2017

Bib arXiv PDF Blog Code

@article{Rambhatla17DRPCAApp, abbr = {Asilomar}, author = {Rambhatla, S. and Li, X. and Haupt, J.}, title = {Target-based hyperspectral demixing via generalized robust {PCA}}, journal = {51st Asilomar Conference on Signals, Systems, and Computers, 2017}, img = {LplusDA_hyper_spectral.gif}, pages = {420--424}, year = {2017}, crossref = {DBLP:conf/acssc/2017}, doi = {10.1109/ACSSC.2017.8335372}, timestamp = {Fri, 20 Apr 2018 22:49:39 +0200}, biburl = {https://dblp.org/rec/bib/conf/acssc/RambhatlaLH17}, bibsource = {dblp computer science bibliography, https://dblp.org}, arxiv = {1902.11111}, code = {https://github.com/srambhatla/Dictionary-based-Robust-PCA}, pdf = {https://arxiv.org/pdf/1902.11111.pdf}, url = {https://arxiv.org/abs/1902.11111}, award = {Best Paper Finalist}, blog = {2017/HyperSpectral/} }

2016

GlobalSIP
🏆 NSF Travel Award

A Dictionary Based Generalization of Robust PCA

Rambhatla, S., Li, X., and Haupt, J.

IEEE Global Conference on Signal and Information Processing (GlobalSIP) 2016

Bib arXiv PDF Blog Code Slides

@article{Rambhatla2016DRPCA, abbr = {GlobalSIP}, title = {A Dictionary Based Generalization of Robust {PCA}}, author = {Rambhatla, S. and Li, X. and Haupt, J.}, journal = {IEEE Global Conference on Signal and Information Processing (GlobalSIP)}, year = {2016}, slides = {/slides/Dictionary_based_generalization_of_robust_PCA_Sirisha_R.pdf}, organization = {IEEE}, arxiv = {1902.08171}, img = {DRPCA.png}, code = {https://github.com/srambhatla/Dictionary-based-Robust-PCA}, pdf = {https://arxiv.org/pdf/1902.08171.pdf}, url = {https://arxiv.org/abs/1902.08171}, award = {NSF Travel Award}, blog = {2017/HyperSpectral/} }

2013

Asilomar

Semi-blind source separation via sparse representations and online dictionary learning

Rambhatla, S., and Haupt, J.

Asilomar Conference on Signals, Systems and Computers 2013

Abs Bib arXiv PDF Blog Slides

This work examines a semi-blind single-channel source separation problem. Our specific aim is to separate one source whose local structure is approximately known, from another a priori unspecified background source, given only a single linear combination of the two sources. We propose a separation technique based on local sparse approximations along the lines of recent efforts in sparse representations and dictionary learning. A key feature of our procedure is the online learning of dictionaries (using only the data itself) to sparsely model the background source, which facilitates its separation from the partially-known source. Our approach is applicable to source separation problems in various application domains; here, we demonstrate the performance of our proposed approach via simulation on a stylized audio source separation task.

@article{Rambhatla2013sbmca, abbr = {Asilomar}, title = {Semi-blind source separation via sparse representations and online dictionary learning}, author = {Rambhatla, S. and Haupt, J.}, journal = {Asilomar Conference on Signals, Systems and Computers}, pages = {1687--1691}, year = {2013}, organization = {IEEE}, arxiv = {1212.0451}, pdf = {https://arxiv.org/pdf/1212.0451.pdf}, img = {SBMCA.png}, blog = {2016/SBMCA/}, slides = {PresentationThesisPDF.pdf} }

2012

Masters Thesis

Semi-blind source separation via sparse representations and online dictionary learning

Rambhatla, S.

University of Minnesota – Twin Cities, Minneapolis, MN 2012

Abs Bib PDF Blog

This work examines a semi-blind source separation problem having applications in audio, image, and video processing. The essential aim is to separate one source whose local structure is partially or approximately known from another a priori unspecified but structured source, given only a single linear combination of the two sources. We propose a novel separation technique based on local sparse approximations. A key feature of our procedure is the online learning of dictionaries (using only the data itself) to sparsely model the unknown structured background source. The performance of the proposed approach is demonstrated via simulation in a stylized application of audio source separation.

@article{Rambhatla2012mthesis, abbr = {Masters Thesis}, author = {Rambhatla, S.}, title = {Semi-blind source separation via sparse representations and online dictionary learning}, journal = {{U}niversity of {M}innesota -- {T}win {C}ities, {M}inneapolis, {MN}}, year = {2012}, img = {SBMCA_thesis.png}, blog = {2016/SBMCA/}, pdf = {Sirisha_Rambhatla_Masters_Thesis.pdf}, organization = {{U}niversity of {M}innesota -- {T}win {C}ities, {M}inneapolis, {MN}} }