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Several cardiovascular diseases are caused from localised abnormal blood flow such as in the case of stenosis or aneurysms. Prevailing theories propose that the development is caused by abnormal wall-shear stress in focused areas.…

Optimization and Control · Mathematics 2016-07-12 S. W. Funke , M. Nordaas , Øyvind Evju , M. S. Alnæs , K. -A. Mardal

We have developed a variational data assimilation technique for the Sun using a toy {\alpha}{\Omega} dynamo model. The purpose of this work is to apply modern data assimilation techniques to solar data using a physically based model. This…

Solar and Stellar Astrophysics · Physics 2015-05-28 Laurene Jouve , Allan Sacha Brun , Olivier Talagrand

A thermal convection loop is a circular chamber filled with water, heated on the bottom half and cooled on the top half. With sufficiently large forcing of heat, the direction of fluid flow in the loop oscillates chaotically, forming an…

Dynamical Systems · Mathematics 2016-06-24 Andrew J. Reagan

Data assimilation of observational data into full atmospheric states is essential for weather forecast model initialization. Recently, methods for deep generative data assimilation have been proposed which allow for using new input data…

The performance of ensemble-based data assimilation techniques that estimate the state of a dynamical system from partial observations depends crucially on the prescribed uncertainty of the model dynamics and of the observations. These are…

Computation · Statistics 2021-02-24 Tadeo Javier Cocucci , Manuel Pulido , Magdalena Lucini , Pierre Tandeo

Machine Learning (ML) has shown great promise in revolutionizing weather forecasting, yet most ML systems still rely on initial conditions generated by Numerical Weather Prediction (NWP) systems. End-to-end ML models aim to eliminate this…

X-ray absorption spectroscopy (XAS) is a powerful technique to probe the electronic and structural properties of materials. With the rapid growth in both the volume and complexity of XAS datasets driven by advancements in synchrotron…

Computational Physics · Physics 2025-02-25 Xue Han , Haodong Yao , Fei Zhan , Xueqi Song , Junfang Zhao , Haifeng Zhao

Motivated by differential co-expression analysis in genomics, we consider in this paper estimation and testing of high-dimensional differential correlation matrices. An adaptive thresholding procedure is introduced and theoretical…

Methodology · Statistics 2015-10-22 T. Tony Cai , Anru Zhang

Data assimilation addresses the problem of identifying plausible state trajectories of dynamical systems given noisy or incomplete observations. In geosciences, it presents challenges due to the high-dimensionality of geophysical dynamical…

Machine Learning · Statistics 2023-11-03 François Rozet , Gilles Louppe

In this paper we consider estimation of sparse covariance matrices and propose a thresholding procedure which is adaptive to the variability of individual entries. The estimators are fully data driven and enjoy excellent performance both…

Methodology · Statistics 2011-02-14 Tony Cai , Weidong Liu

Variational methods are widely used for approximate posterior inference. However, their use is typically limited to families of distributions that enjoy particular conjugacy properties. To circumvent this limitation, we propose a family of…

Machine Learning · Computer Science 2012-06-22 Samuel Gershman , Matt Hoffman , David Blei

The specification of a covariance function is of paramount importance when employing Gaussian process models, but the requirement of positive definiteness severely limits those used in practice. Designing flexible stationary covariance…

Computation · Statistics 2024-05-01 Paul G. Beckman , Christopher J. Geoga

Data-driven machine learning (ML) models are reshaping weather forecasting and have shown the potential to accelerate and surpass traditional physics-based approaches, leading to a second revolution in the field after data assimilation.…

Machine Learning · Computer Science 2026-05-19 Hang Fan , Yi Xiao , Yongquan Qu , Juan Nathaniel , Fenghua Ling , Ben Fei , Lei Bai , Pierre Gentine

Data Assimilation (DA) is a computational tool that uses value from the model and the real measurement to arrive to an optimally acceptable value. Rather, this technique relies on the idea of Kalman gain. We point out that DA has two…

Optimization and Control · Mathematics 2020-12-15 Mohammad N. Murshed , Zarin Subah , M. Monir Uddin

Data assimilation provides a systematic framework for combining dynamical models with partial and noisy observations to infer the evolving state of a system. In this work, we undertake a comparative study of Data Assimilation with Transfer…

Computational Engineering, Finance, and Science · Computer Science 2026-05-07 Emanuele Donno , Giovanni Conti , Paolo Oddo , Silvio Gualdi , Luca Mainetti , Giovanni Aloisio

Accurate data assimilation (DA) for systems with piecewise-smooth or discontinuous state variables remains a significant challenge, as conventional covariance-based ensemble Kalman filter approaches often fail to effectively balance…

Numerical Analysis · Mathematics 2025-10-09 Tongtong Li , Anne Gelb , Yoonsang Lee

Data assimilation schemes are confronted with the presence of model errors arising from the imperfect description of atmospheric dynamics. These errors are usually modeled on the basis of simple assumptions such as bias, white noise, first…

Chaotic Dynamics · Physics 2009-11-13 A. Carrassi , S. Vannitsem , C. Nicolis

In using data assimilation to import information from observations to estimate parameters and state variables of a model, one must assume a distribution for the noise in the measurements and in the model errors. Using the path integral…

Chaotic Dynamics · Physics 2010-12-10 Henry D. I. Abarbanel

We present a supervised learning method to learn the propagator map of a dynamical system from partial and noisy observations. In our computationally cheap and easy-to-implement framework a neural network consisting of random feature maps…

Machine Learning · Computer Science 2021-10-27 Georg A. Gottwald , Sebastian Reich

The spatio-temporal interpolation of large geophysical datasets has historically been addressed by Optimal Interpolation (OI) and more sophisticated equation-based or data-driven Data Assimilation (DA) techniques. Recent advances in the…

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