Search Results for author: Constantinos Siettos

Found 14 papers, 0 papers with code

A physics-informed neural network method for the approximation of slow invariant manifolds for the general class of stiff systems of ODEs

no code implementations18 Mar 2024 Dimitrios G. Patsatzis, Lucia Russo, Constantinos Siettos

We present a physics-informed neural network (PINN) approach for the discovery of slow invariant manifolds (SIMs), for the most general class of fast/slow dynamical systems of ODEs.

Tasks Makyth Models: Machine Learning Assisted Surrogates for Tipping Points

no code implementations25 Sep 2023 Gianluca Fabiani, Nikolaos Evangelou, Tianqi Cui, Juan M. Bello-Rivas, Cristina P. Martin-Linares, Constantinos Siettos, Ioannis G. Kevrekidis

We present a machine learning (ML)-assisted framework bridging manifold learning, neural networks, Gaussian processes, and Equation-Free multiscale modeling, for (a) detecting tipping points in the emergent behavior of complex systems, and (b) characterizing probabilities of rare events (here, catastrophic shifts) near them.

Gaussian Processes

Slow Invariant Manifolds of Singularly Perturbed Systems via Physics-Informed Machine Learning

no code implementations14 Sep 2023 Dimitrios G. Patsatzis, Gianluca Fabiani, Lucia Russo, Constantinos Siettos

A comparison of the computational costs between symbolic, automatic and numerical approximation of the required derivatives in the learning process is also provided.

Numerical Integration Physics-informed machine learning

Data-driven modelling of brain activity using neural networks, Diffusion Maps, and the Koopman operator

no code implementations24 Apr 2023 Ioannis K. Gallos, Daniel Lehmberg, Felix Dietrich, Constantinos Siettos

Importantly, we show that the proposed Koopman operator approach provides, for any practical purposes, equivalent results to the FNN-GH approach, thus bypassing the need to train a non-linear map and to use GH to extrapolate predictions in the ambient fMRI space; one can use instead the low-frequency truncation of the DMs function space of L^2-integrable functions, to predict the entire list of coordinate functions in the fMRI space and to solve the pre-image problem.

Time Series

Discrete-Time Nonlinear Feedback Linearization via Physics-Informed Machine Learning

no code implementations15 Mar 2023 Hector Vargas Alvarez, Gianluca Fabiani, Nikolaos Kazantzis, Constantinos Siettos, Ioannis G. Kevrekidis

We assess the performance of the proposed PIML approach via a benchmark nonlinear discrete map for which the feedback linearization transformation law can be derived analytically; the example is characterized by steep gradients, due to the presence of singularities, in the domain of interest.

Physics-informed machine learning

Data-driven Control of Agent-based Models: an Equation/Variable-free Machine Learning Approach

no code implementations12 Jul 2022 Dimitrios G. Patsatzis, Lucia Russo, Ioannis G. Kevrekidis, Constantinos Siettos

We present an Equation/Variable free machine learning (EVFML) framework for the control of the collective dynamics of complex/multiscale systems modelled via microscopic/agent-based simulators.

Parsimonious Physics-Informed Random Projection Neural Networks for Initial-Value Problems of ODEs and index-1 DAEs

no code implementations10 Mar 2022 Gianluca Fabiani, Evangelos Galaris, Lucia Russo, Constantinos Siettos

The unknown weights between the hidden and output layer are computed by Newton's iterations, using the Moore-Penrose pseudoinverse for low to medium, and sparse QR decomposition with regularization for medium to large scale systems.

Constructing coarse-scale bifurcation diagrams from spatio-temporal observations of microscopic simulations: A parsimonious machine learning approach

no code implementations31 Jan 2022 Evangelos Galaris, Gianluca Fabiani, Ioannis Gallos, Ioannis Kevrekidis, Constantinos Siettos

For our illustrations, we implemented the proposed method to construct the one-parameter bifurcation diagram of the 1D FitzHugh-Nagumo PDEs from data generated by $D1Q3$ Lattice Boltzmann simulations.

feature selection

Time Series Forecasting Using Manifold Learning

no code implementations7 Oct 2021 Panagiotis Papaioannou, Ronen Talmon, Ioannis Kevrekidis, Constantinos Siettos

We address a three-tier numerical framework based on manifold learning for the forecasting of high-dimensional time series.

EEG GPR +3

Numerical Solution of Stiff ODEs with Physics-Informed RPNNs

no code implementations3 Aug 2021 Evangelos Galaris, Gianluca Fabiani, Francesco Calabrò, Daniela di Serafino, Constantinos Siettos

We propose a numerical method based on physics-informed Random Projection Neural Networks for the solution of Initial Value Problems (IVPs) of Ordinary Differential Equations (ODEs) with a focus on stiff problems.

A biophysical network model reveals the link between deficient inhibitory cognitive control and major neurotransmitter and neural connectivity hypotheses in schizophrenia

no code implementations20 Jul 2021 Konstantinos Spiliotis, Giannis Kahramanoglou, Jens Starke, Nikolaos Smyrnis, Constantinos Siettos

We address a biophysical network dynamical model to study how the modulation of dopamine (DA) activity and related N-methyl-d-aspartate (NMDA) glutamate receptor activity as well as the emerging Pre-Frontal Cortex (PFC) functional connectivity network (FCN) affect inhibitory cognitive function in schizophrenia in an antisaccade task.

Extreme learning machine collocation for the numerical solution of elliptic PDEs with sharp gradients

no code implementations10 Dec 2020 Francesco Calabrò, Gianluca Fabiani, Constantinos Siettos

We show that a feedforward neural network with a single hidden layer with sigmoidal functions and fixed, random, internal weights and biases can be used to compute accurately a collocation solution.

Numerical Analysis Numerical Analysis

Construction of embedded fMRI resting state functional connectivity networks using manifold learning

no code implementations25 May 2020 Ioannis Gallos, Evangelos Galaris, Constantinos Siettos

We construct embedded functional connectivity networks (FCN) from benchmark resting-state functional magnetic resonance imaging (rsfMRI) data acquired from patients with schizophrenia and healthy controls based on linear and nonlinear manifold learning algorithms, namely, Multidimensional Scaling (MDS), Isometric Feature Mapping (ISOMAP) and Diffusion Maps.

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