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#Biography

#News
- Our paper has been accepted to KDD 2026.
- Our paper has been accepted to ICML 2026.
- Our paper has been accepted to IPSJ Transactions on Databases (TOD).
- I have been granted a full exemption from repayment of the JASSO scholarship.
- I have received the DEIM 2025 Best Paper Award Runner-up.
- I have completed my M.Sc. degree at Osaka University.
- I have received the Osaka University Graduate School of Information Science and Technology Award.
- I have received the DEIM 2025 Student Presentation Award.
- I have been selected for the JST BOOST Program.
- Our paper has been accepted to KDD 2025.
- I have been preliminarily selected for the JSPS DC1 Research Fellowship.
- I have received the IPSJ Yamashita SIG Research Award.
- Our paper has been accepted to the PhD Consortium at KDD 2024.
- I have received the DEIM 2024 Best Paper Award Runner-up.
- Our paper has been accepted to IPSJ Transactions on Databases (TOD).
- Our paper has been accepted to Astronomy and Computing.
- I have completed my B.Sc. degree at Osaka University.
- I have passed the selection exam for the Humanware Innovation Program.
#Research Overview
In fields ranging from industry to the life sciences and medicine, the causal mechanisms underlying a system often shift as the environment changes (e.g., across time, locations, or experimental conditions). These shifts also determine whether estimates obtained in the past can be reused in a new environment. It is therefore essential to understand what drives these changes and, building on that understanding, to develop update algorithms that adapt to new environments, along with methods for treatment effect estimation and decision-making that account for heterogeneity. Specifically, our research is organized around the following three directions.
- Identifying Causal Mechanism ShiftsBuilding on mathematical models of causal mechanisms, I aim to identify the causes of distribution shifts and estimate how the underlying changes propagate along causal pathways to affect the distributions of other variables.
- Stream Processing for Non-Stationary Time Series DataI develop scalable algorithms for sequentially processing observations that arrive successively in order to adapt to time-evolving patterns under limited computational and memory resources.
- Heterogeneous Treatment Effect Estimation and Decision-MakingI present an estimation procedure to capture heterogeneity in effects across multiple environments and changes in effects over time, and construct a decision-making approach to select what treatment to apply and when, while accounting for uncertainty.
Research KeywordsStatistical causal inference / Data mining / Machine learning / Stream processing / Non-stationarity / Dynamical systems
#Selected Publications
- Naoki Chihara et al., AdaKoop: Efficient Modeling of Nonlinear Dynamics from Nonstationary Data Streams with Koopman Operator Regression, KDD 2026.
- Naoki Chihara et al., Modeling Covariate Transition for Efficient Estimation of Longitudinal Treatment Effects in Randomized Experiments, ICML 2026.
- Naoki Chihara et al., Modeling Time-evolving Causality over Data Streams, KDD 2025.