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Estimation of the initial state of turbulent channel flow from limited data is investigated using an adjoint-variational approach. The data are generated from a reference direct numerical simulation (DNS) which is sub-sampled at different…

Fluid Dynamics · Physics 2021-07-01 Mengze Wang , Tamer A. Zaki

The probabilistic-stream model was introduced by Jayram et al. \cite{JKV07}. It is a generalization of the data stream model that is suited to handling ``probabilistic'' data where each item of the stream represents a probability…

Data Structures and Algorithms · Computer Science 2007-05-23 Andrew McGregor , S. Muthukrishnan

Variational data assimilation and machine-learning based super-resolution are two alternative approaches to state estimation in turbulent flows. The former is an optimisation problem featuring a time series of coarse observations, the…

Fluid Dynamics · Physics 2025-10-21 Markus Weyrauch , Moritz Linkmann , Jacob Page

In an environment of increasingly volatile financial markets, the accurate estimation of risk remains a major challenge. Traditional econometric models, such as GARCH and its variants, are based on assumptions that are often too rigid to…

Artificial Intelligence · Computer Science 2025-08-19 Fredy Pokou , Jules Sadefo Kamdem , François Benhmad

In this paper, our proposal consists of incorporating frailty into a statistical methodology for modeling time-to-event data, based on non-proportional hazards regression model. Specifically, we use the generalized time-dependent logistic…

The immense computational cost of traditional numerical weather and climate models has sparked the development of machine learning (ML) based emulators. Because ML methods benefit from long records of training data, it is common to use…

Machine Learning · Computer Science 2023-09-25 Timothy A. Smith , Stephen G. Penny , Jason A. Platt , Tse-Chun Chen

Considering non-stationary environments in online optimization enables decision-maker to effectively adapt to changes and improve its performance over time. In such cases, it is favorable to adopt a strategy that minimizes the negative…

Systems and Control · Electrical Eng. & Systems 2024-04-05 Siyi Wang , Zifan Wang , Xinlei Yi , Michael M. Zavlanos , Karl H. Johansson , Sandra Hirche

The paper proposes a time-varying parameter global vector autoregressive (TVP-GVAR) framework for predicting and analysing developed region economic variables. We want to provide an easily accessible approach for the economy application…

Econometrics · Economics 2022-09-14 Yukang Jiang , Xueqin Wang , Zhixi Xiong , Haisheng Yang , Ting Tian

Prior work on safe Reinforcement Learning (RL) has studied risk-aversion to randomness in dynamics (aleatory) and to model uncertainty (epistemic) in isolation. We propose and analyze a new framework to jointly model the risk associated…

Machine Learning · Computer Science 2024-05-15 Jia Lin Hau , Marek Petrik , Mohammad Ghavamzadeh , Reazul Russel

Sampling a target probability distribution with an unknown normalization constant is a fundamental challenge in computational science and engineering. Recent work shows that algorithms derived by considering gradient flows in the space of…

Machine Learning · Statistics 2024-03-12 Yifan Chen , Daniel Zhengyu Huang , Jiaoyang Huang , Sebastian Reich , Andrew M Stuart

Rare transitions in stochastic processes can often be rigorously described via an underlying large deviation principle. Recent breakthroughs in the classification of reversible stochastic processes as gradient flows have led to a connection…

Statistical Mechanics · Physics 2019-05-22 Tobias Grafke

Estimating the parameters of mathematical models is a common problem in almost all branches of science. However, this problem can prove notably difficult when processes and model descriptions become increasingly complex and an explicit…

Machine Learning · Statistics 2024-02-09 Stefan T. Radev , Ulf K. Mertens , Andreas Voss , Lynton Ardizzone , Ullrich Köthe

Hourly predictions are critical for issuing flood warnings as the flood peaks on the hourly scale can be distinctly higher than the corresponding daily ones. Currently a popular hourly data-driven prediction scheme is multi-time-scale long…

Geophysics · Physics 2025-10-10 Wencong Yang , Haoyu Ji , Leo Lonzarich , Yalan Song , Chaopeng Shen

The contour maps of the error of historical resp. parametric estimates for large random portfolios optimized under the risk measure Expected Shortfall (ES) are constructed. Similar maps for the sensitivity of the portfolio weights to small…

Risk Management · Quantitative Finance 2015-10-19 Fabio Caccioli , Imre Kondor , Gábor Papp

Reinforcement Learning with Verifiable Rewards (RLVR) has established itself as the dominant paradigm for instilling rigorous reasoning capabilities in Large Language Models. While effective at amplifying dominant behaviors, we identify a…

Machine Learning · Computer Science 2026-02-16 Zesheng Hong , Jiadong Yu , Hui Pan

In the hydrology field, time series forecasting is crucial for efficient water resource management, improving flood and drought control and increasing the safety and quality of life for the general population. However, predicting long-term…

Machine Learning · Computer Science 2023-12-19 Yanhong Li , Jack Xu , David C. Anastasiu

We study a first-order primal-dual subgradient method to optimize risk-constrained risk-penalized optimization problems, where risk is modeled via the popular conditional value at risk (CVaR) measure. The algorithm processes independent and…

Optimization and Control · Mathematics 2021-09-03 Avinash N. Madavan , Subhonmesh Bose

Simulating turbulent fluid flows is a computationally prohibitive task, as it requires the resolution of fine-scale structures and the capture of complex nonlinear interactions across multiple scales. This is particularly the case in direct…

Fluid Dynamics · Physics 2026-04-22 Ismaël Zighed , Nicolas Thome , Patrick Gallinari , Taraneh Sayadi

These notes are based on lectures delivered by G. Schehr at the XVIth School on Fundamental Problems in Statistical Physics (FPSP), held in Oropa (Italy) from 30 June to 11 July 2025. After a brief introduction to extreme value statistics…

Statistical Mechanics · Physics 2026-03-20 Marcin Piotr Pruszczyk , Gregory Schehr

We study risk-sensitive planning under partial observability using the dynamic risk measure Iterated Conditional Value-at-Risk (ICVaR). A policy evaluation algorithm for ICVaR is developed with finite-time performance guarantees that do not…

Artificial Intelligence · Computer Science 2026-01-29 Yaacov Pariente , Vadim Indelman