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Jun Bai

Postdoctorate - McGill University
Supervisor
Yue Li
Research Topics
AI in Health
Computer Vision
Cybersecurity
Federated Learning

Publications

Source-free cross-modality medical image synthesis with diffusion priors
Jia Chen
Xin Wang
Jun Bai
Kai Yang
Xinrong Hu
Yue Li
2025-09-23
Journal of King Saud University Computer and Information Sciences (published)
doi.org
A Unified Solution to Diverse Heterogeneities in One-Shot Federated Learning
Jun Bai
Yiliao Song
Di Wu
Atul Sajjanhar
Yong Xiang
Wei Zhou
Xiaohui Tao
Yan Li
Yue Li
One-Shot Federated Learning (OSFL) restricts communication between the server and clients to a single round, significantly reducing communic… (see more)ation costs and minimizing privacy leakage risks compared to traditional Federated Learning (FL), which requires multiple rounds of communication. However, existing OSFL frameworks remain vulnerable to distributional heterogeneity, as they primarily focus on model heterogeneity while neglecting data heterogeneity. To bridge this gap, we propose FedHydra, a unified, data-free, OSFL framework designed to effectively address both model and data heterogeneity. Unlike existing OSFL approaches, FedHydra introduces a novel two-stage learning mechanism. Specifically, it incorporates model stratification and heterogeneity-aware stratified aggregation to mitigate the challenges posed by both model and data heterogeneity. By this design, the data and model heterogeneity issues are simultaneously monitored from different aspects during learning. Consequently, FedHydra can effectively mitigate both issues by minimizing their inherent conflicts. We compared FedHydra with five SOTA baselines on four benchmark datasets. Experimental results show that our method outperforms the previous OSFL methods in both homogeneous and heterogeneous settings. The code is available at https://github.com/Jun-B0518/FedHydra.
2025-08-02
Proceedings of the 31st ACM SIGKDD Conference on Knowledge Discovery and Data Mining V.2 (published)
doi.org
arxiv.org
FedWeight: mitigating covariate shift of federated learning on electronic health records data through patients re-weighting
He Zhu
Jun Bai
Na Li
Xiaoxiao Li
Dianbo Liu
David L. Buckeridge
Yue Li
Federated learning (FL) enables collaborative analysis of decentralized medical data while preserving patient privacy. However, the covariat… (see more)e shift from demographic and clinical differences can reduce model generalizability. We propose FedWeight, a novel FL framework that mitigates covariate shift by reweighting patient data from the source sites using density estimators, allowing the trained model to better align with the distribution of the target site. To support unsupervised applications, we introduce FedWeight ETM, a federated embedded topic model. We evaluated FedWeight in cross-site FL on the eICU dataset and cross-dataset FL between eICU and MIMIC III. FedWeight consistently outperforms standard FL baselines in predicting ICU mortality, ventilator use, sepsis diagnosis, and length of stay. SHAP-based interpretation and ETM-based topic modeling reveal improved identification of clinically relevant characteristics and disease topics associated with ICU readmission.
2024-12-31
npj Digital Medicine (published)
doi.org