Hyungjun Yoon
Postdoctoral Researcher @ KAISTI am a postdoctoral researcher in the Mobile Intelligence & Interaction Lab at KAIST, working with Professor Sung-Ju Lee. I received my Ph.D. in Electrical Engineering from KAIST in 2026. Previously, I was a research intern at Nokia Bell Labs (mentored by Lorena Qendro and hosted by Fahim Kawsar) and Microsoft Research (mentored by Professor Lili Qiu), and a visiting researcher at NTU (advised by Professor Mo Li).
I develop Foundation Models and LLM Agents to understand people through mobile, wearable, and physiological data. I study how models can generalize across sensors and applications, adapt to individual users, and use tools and personal context to reason about health. I build systems end to end, from sensing hardware and data collection to on-device deployment and user studies. My current focus is personalized health agents and harness optimization: improving how agents select data, use tools, and verify their answers.
News
- Oct. 2026|🛫 Attending UbiComp/ISWC '26 in Shanghai, China (Oct. 11–15, including workshops)
- Oct. 2026|👔 Co-organized WellComp 2026, the Computing for Well-being Workshop @ UbiComp/ISWC '26
- Oct. 2026|🎉 Our SA4ME: Spatial Audio for Multisensory Experiences workshop proposal was accepted to IEEE VR '27; I will serve as an organizer
- Oct. 2026|📄 New preprint: Later Is Better, on token reduction for vision transformers under distribution shift
- Oct. 2026|📄 Introducing TimeNet, a unified data infrastructure for temporal foundation models, with an international team of collaborators
- Oct. 2026|🎤 Invited to the ML4H 2026 career panel (confirmed; upcoming)
- Oct. 2026|📝 Serving as a reviewer for ICLR 2027
- Sep. 2026|📄 New preprint: TISD: On-Policy Self-Distillation with Trajectory Intervention
- Aug. 2026|👨💻 Started as a Postdoctoral Researcher at KAIST
- Aug. 2026|💰 Selected as a BK21 FOUR Postdoctoral Researcher
- Aug. 2026|📰 Our Beyond Hearing research was featured in KAIST Breakthroughs
- Aug. 2026|🎓 Received my Ph.D. in Electrical Engineering from KAIST
- Jul. 2026|🛫 ICML '26 @ Seoul, Republic of Korea (Jul. 9 - Jul. 11)
- Jun. 2026|🛫 AHLI Health AI Summer Camp @ Seattle, USA (Jun. 22 - Jun. 28)
- Jun. 2026|🎉 Paper accepted to AI4Math Workshop @ ICML '26
- May. 2026|🎓 Passed my Ph.D. Dissertation Defense (committee: Prof. Sung-Ju Lee, Prof. Edward Choi, Prof. Kimin Lee, Prof. Mo Li, Prof. Lili Qiu)
- May. 2026|🎉 Accepted to AHLI Health AI Summer Camp with full scholarship
- May. 2026|🎤 Invited talk at KAIST AI (host: Prof. Seong Joon Oh)
- May. 2026|👔 Organizer at WellComp 2026 @ UbiComp/ISWC '26
- Apr. 2026|🛫 ICLR '26 @ Rio de Janeiro, Brazil (Apr. 23 - Apr. 27)
- Apr. 2026|🎉 Paper accepted to ACL '26 (findings)
- Jan. 2026|🎉 Paper accepted to IEEE PacificVis '26
- Jan. 2026|🎉 Paper accepted to ICLR '26
- Dec. 2025|🛫 NeurIPS '25 @ San Diego, USA (Dec. 2 - Dec. 7)
- Nov. 2025|🏆 Selected as Winner of the Qualcomm Innovation Fellowship
- Nov. 2025|🎤 Invited talk at KAIST Mobile Computing Course
- Oct. 2025|🏆 Selected as Finalist of the Qualcomm Innovation Fellowship
- Sep. 2025|👔 I am serving as the lab leader of Mobile Intelligence & Interaction Lab
- Jun. 2025|👨💻 Research internship at Nokia Bell Labs (Mentor Lorena Qendro)
- May. 2025|🛫 SenSys '25 @ Irvine, USA (May. 5 - May. 9)
- May. 2025|🎉 Paper accepted to MobiSys Workshop (EnvSys) '25
- Apr. 2025|🎉 Paper accepted to IEEE TMC '25
- Mar. 2025|🎤 Invited talk at UNIST (host: Prof. Taesik Gong)
- Feb. 2025|🎉 Paper accepted to SenSys '25
- Feb. 2025|🎉 Paper accepted to ACM CHI '25 EA
- Nov. 2024|🛫 EMNLP '24 @ Miami, USA (Nov. 12 - Nov. 16)
- Nov. 2024|🎤 Invited talk at MSRA
- Sep. 2024|🎉 Paper accepted to UbiComp '25
- Sep. 2024|🎉 Paper accepted to EMNLP '24 (main)
- Sep. 2024|👨💻 Research internship at Microsoft Research (Mentor Prof. Lili Qiu)
- Oct. 2023|🎉 Paper accepted to EMNLP '23 (main)
- Sep. 2022|👔 Visiting researcher at NTU, Singapore (Advisor Prof. Mo Li) (by Dec. 2022)
- May. 2022|🛫 ACM CHI '22 @ New Orleans, USA (Apr. 30 - May. 5)
- Mar. 2022|🏆 Honorable Mention at ACM CHI '22
- Nov. 2021|🎉 Paper accepted to ACM CHI '22
- Mar. 2021|👔 Started my Ph.D. in Mobile Intelligence & Interaction Lab
- Mar. 2020|👔 Started my M.S. in Mobile Intelligence & Interaction Lab
- Feb. 2020|🎓 Graduated from KAIST as B.S. (Cum Laude)
Publications
Preprints
"Later Is Better: Token Reduction for ViTs Under Distribution Shift"
Hyeongheon Cha, Hyungjun Yoon, and Sung-Ju Lee
arXiv preprint, 2026 (in submission)
pdf arXiv code
Hyeongheon Cha, Hyungjun Yoon, and Sung-Ju Lee
arXiv preprint, 2026 (in submission)
pdf arXiv code
"TimeNet: An Extensible Unified Data Infrastructure for Next-Generation Temporal Foundation Models"
Martin Maritsch*, Timo Stoffregen*, Thomas Kaar, Behsad Riemer, Maxwell A. Xu, Max Rosenblattl, Juncheng Liu, Nicolas Zumarraga, Yu Yvonne Wu, Denys Herasymuk, Sparsh Rastogi, Hyungjun Yoon, et al. (* Equal contribution)
arXiv preprint, 2026 (in submission)
pdf arXiv
Martin Maritsch*, Timo Stoffregen*, Thomas Kaar, Behsad Riemer, Maxwell A. Xu, Max Rosenblattl, Juncheng Liu, Nicolas Zumarraga, Yu Yvonne Wu, Denys Herasymuk, Sparsh Rastogi, Hyungjun Yoon, et al. (* Equal contribution)
arXiv preprint, 2026 (in submission)
pdf arXiv
"TISD: On-Policy Self-Distillation with Trajectory Intervention"
Taeckyung Lee, Rinat Amankos, Jeonghye Kim, Hyungjun Yoon, Woogyeol Jin, and Sung-Ju Lee
arXiv preprint, 2026 (in submission)
pdf arXiv
Taeckyung Lee, Rinat Amankos, Jeonghye Kim, Hyungjun Yoon, Woogyeol Jin, and Sung-Ju Lee
arXiv preprint, 2026 (in submission)
pdf arXiv
"Wearable Foundation Models Should Go Beyond Static Encoders"Yu Yvonne Wu*, Yuwei Zhang*, Hyungjun Yoon*, Ting Dang, Dimitris Spathis, Tong Xia, Qiang Yang, Jing Han, Dong Ma, Sung-Ju Lee, and Cecilia Mascolo (* Equal contribution)arXiv preprint, 2026 (in submission) pdf
arXiv
Conferences and Journals
"ConSensus: Multi-Agent Collaboration for Multimodal Sensing"Hyungjun Yoon, Mohammad Malekzadeh, Sung-Ju Lee, Fahim Kawsar, and Lorena QendroACL 2026 Findings pdf
proceedings
arXiv
code
"Evaluating Visual Prompts with Eye-Tracking Data for MLLM–Based Human Activity Recognition"Jae Young Choi, Seon Gyeom Kim, Hyungjun Yoon, Taeckyung Lee, Donggun Lee, Jaeryung Chung, Jihyung Kil, Ryan Rossi, Sung-Ju Lee, and Tak Yeon LeeIEEE PacificVis 2026 pdf
arXiv
"Beyond Hearing: Learning Task-agnostic ExG Representations from Earphones via Physiology-informed Tokenization"Hyungjun Yoon*, Seungjoo Lee*, Yu Wu*, Xiaomeng Chen*, Taiting Lu, Freddy Yifei Liu, Taeckyung Lee, Hyeongheon Cha, Haochen Zhao, Gaoteng Zhao, Dongyao Chen, Cecilia Mascolo, Sung-Ju Lee, and Lili Qiu (* Equal contribution)ICLR 2026 pdf
website
Featured in KAIST Breakthroughs
"From Vision to Motion: Translating Large-Scale Knowledge for Data-Scarce IMU Applications"Hyungjun Yoon, Hyeongheon Cha, Hoang C. Nguyen, Taesik Gong, and Sung-Ju LeeIEEE TMC 2025 (JCR '23 IF < 5%) pdf
website
"SelfReplay: Adapting Self-Supervised Sensory Models via Adaptive Meta-Task Replay"Hyungjun Yoon, Jaehyun Kwak, Biniyam Aschalew Tolera, Gaole Dai, Mo Li, Taesik Gong, Kimin Lee, and Sung-Ju LeeSenSys 2025 pdf
website
"ContrastSense: Domain-invariant Contrastive Learning for In-the-wild Wearable Sensing"Gaole Dai, Huatao Xu, Hyungjun Yoon, Mo Li, Rui Tan, and Sung-Ju LeeACM IMWUT 2024 (presented at UbiComp 2025) pdf
website
"By My Eyes: Grounding Multimodal Large Language Models with Sensor Data via Visual Prompting"Hyungjun Yoon, Biniyam Aschalew Tolera, Taesik Gong, Kimin Lee, Sung-Ju LeeEMNLP 2024 Main pdf
website
Qualcomm Innovation Fellowship Winner
"FedTherapist: Mental Health Monitoring with User-Generated Linguistic Expressions on Smartphones via Federated Learning"Jaemin Shin, Hyungjun Yoon, Seungjoo Lee, Sungjoon Park, Yunxin Liu, Jinho D. Choi, and Sung-Ju LeeEMNLP 2023 Main pdf
website
"MyDJ: Sensing Food Intakes with an Attachable on Your Eyeglass Frame"Jaemin Shin, Seungjoo Lee, Taesik Gong, Hyungjun Yoon, Hyunchul Roh, Andrea Bianchi, and Sung-Ju LeeACM CHI 2022 pdf
website
video
Honorable Mention Award
Workshop Publications
"Dense Supervision but Sparse Guidance: A Token-Level Analysis of On-Policy Self-Distillation"Taeckyung Lee, Jeonghye Kim, Hyungjun Yoon, and Sung-Ju LeeAI4Math 2026 (ICML Workshop) (non-archival) pdf
OpenReview
"CrashSniffer: UWB-Based Anchor-Free Pedestrian Collision Prediction for Personal Mobility Vehicles"Taeckyung Lee, Juseung Lee, Ryuhaerang Choi, Seungjoo Lee, Hyeongheon Cha, Hyungjun Yoon, Song Min Kim, Sangwook Bak, and Sung-Ju LeeEnvSys 2025 (MobiSys Workshop) (Oral presentation, peer-reviewed, archived) pdf
website
“I know my data doesn't leave my phone, but still feel like being wiretapped”: Understanding (Mis)Perceptions of On-Device AI Vishing Detection AppsSubin Park, Hyungjun Yoon, Janu Kim, Hyoungshick Kim, and Sung-Ju LeeACM CHI 2025 EA pdf
website
Archived Manuscripts
"Recover as It is Designed to Be: Recovering from Compatibility Mobile App Crashes by Reusing User Flows"Donghwi Kim, Hyungjun Yoon, Chang Min Park, Sujin Han, Youngjin Kwon, Steve Ko, and Sung-Ju LeearXiv preprint pdf
arXiv
Honors
🎓 Full Scholarship, AHLI Health AI Summer Camp
Selected for the Advanced Health and Life Intelligence summer program, 2026For qualified papers in the field of AI/ML (Top 15), 2025
For qualified papers in the field of AI/ML (Top 30), 2025
🏆 Best Paper Honorable Mention
ACM CHI 2022; Awarded for the top 5% of all submissions🏆 Dean's List
KAIST, Spring 2019; Awarded to the top 3% students in College of EngineeringExperience
2026.08 – Present
Postdoctoral Researcher, Mobile Intelligence & Interaction Lab, KAIST, Republic of Korea
2024.09 – 2025.03
Research Intern, Microsoft Research, Shanghai, China
Academic Service
Organizer
SA4ME: Spatial Audio for Multisensory Experiences @ IEEE VR '27 (accepted workshop; upcoming)
2027
WellComp 2026 @ UbiComp/ISWC '26
2026
Invited Panelist
ML4H Career Panel (confirmed; upcoming)
2026
Reviewer
ICLR
2027
NeurIPS
2026
ACM CHI Posters
2026
ACL ARR
2026
ACM MobiCom
2020 – 2026
ACM MobiSys
2021, 2023 – 2025
ACM UbiComp
2022, 2025
ACM UIST
2025
ICML
2025
IEEE IoT-J
2025
IEEE TCCN
2025
ACM SIGCOMM
2023
IEEE INFOCOM
2021 – 2022
Patents
"UWB-Based Pedestrian Collision Avoidance System for Personal Mobility Devices"
Sung-Ju Lee, Hyeongheon Cha, Taeckyung Lee, Seungjoo Lee, Hyungjun YoonKorea Patent; Filing date: 2025.11.06, No. 10-2025-0166592"Adaptive State-Space Model-Based Deep Learning System for Real-Time Data Inference on Mobile Devices"
Sung-Ju Lee, Seungjoo Lee, Hyungjun YoonKorea Patent; Filing date: 2025.03.31, No.10-2025-0040898"Inference Method Using Dynamic Resource-Based Adaptive Deep Learning Model and Deep Learning Model Inference Device Performing Method"
Sung-Ju Lee, Donghwi Kim, Hyungjun Yoon, Yewon Kim, Sujin HanUS Patent; Filing date: 2023.12.20, No.18/389,848; Korea patent; Filing date: 2023.05.10, No.10-2023-0060780"A System of Mental Health Monitoring with User-Generated Linguistic Expressions on Smartphones via Federated Learning"
Sung-Ju Lee, Hyungjun Yoon, Seungjoo Lee, Jaemin ShinKorea Patent; Filing date: 2023.11.23, No.10-2023-0164077"Artificial Intelligence Model Training Method and Apparatus for Voice Phishing Detection"
Sung-Ju Lee, Seungjoo Lee, Hyungjun YoonKorea Patent; Filing date: 2023.10.04, No.10-2023-0131748"Dynamic Resource-Based Adaptive Smartphone On-Device Inference Method"
Sung-Ju Lee, Hyungjun Yoon, Donghwi Kim, Sujin Han, Yewon KimKorea Patent; Filing date: 2022.12.21, No.10-2022-0180842"Time-Aware Reinforcement-Learning Method for Geographic Ad Hoc Routing with Pre-defined Mobility and Computer Device for the Same"
Jaeha Ahn, Sung-Ju Lee, Taesik Gong, Hyungjun Yoon, Taeckyung LeeKorea Patent; Filing date: 2022.11.11, No.10-2022-0150662"Reinforcement Learning for Ad-hoc Routing Using Pre-defined Mobility"
Sung-Ju Lee, Taesik Gong, Hyungjun Yoon, Taeckyung Lee, Jaeha AhnKorea Patent; Filing date: 2022.03.21, No.10-2022-0034824