In this paper, we present a new method of performing extended dynamic mode decomposition (EDMD) on systems, which admit a symbolic representation. EDMD generates estimates of the Koopman operator, K, for a dynamical system by defining a dictionary of observables on the space and producing an estimate, Km, which is restricted to be invariant on the span of this dictionary. A central question for the EDMD is what should the dictionary be? We consider a class of chaotic dynamical systems with a known or estimable generating partition. For these systems, we construct an effective dictionary from indicators of the "cylinder sets," which arise in defining the "symbolic system" from the generating partition. We prove strong operator topology convergence for both the projection onto the span of our dictionary and for Km. We also prove practical finite-step estimation bounds for the projection and Km as well. Finally, we demonstrate some numerical results on eigenspectrum estimation and forecasting applied to the dyadic map and the logistic map.
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Sports Med Open
January 2025
Mechanical Engineering Department, Texas Tech University, Lubbock, TX, USA.
Background: Drafting for drag reduction is a tactic commonly employed by elite athletes of various sports. The strategy has been adopted by Kenyan runner Eliud Kipchoge on numerous marathon events in the past, including the 2018 and 2022 editions of the Berlin marathon (where Kipchoge set two official world records), as well as in two special attempts to break the 2 h mark for the distance, the Nike Breaking2 (2017) and the INEOS 1:59 Challenge (2019), where Kipchoge used an improved drafting formation to finish in 1:59:40, although that is not recognized as an official record.
Results: In this study, the drag of a realistic model of a male runner is calculated by computational fluid dynamics for a range of velocities.
Sci Rep
January 2025
Department of Physics, University of Oslo, P.O. Box 1048 Blindern, 0316, Oslo, Norway.
In the subauroral zone at the boundary of the auroral oval in the evening and night hours during geomagnetic disturbances, a narrow (about 1°-2°) and extended structure (several hours in longitude) is formed. It is known as a polarization jet (PJ) or the subauroral ion drift (SAID). The PJ/SAID is a fast westward ion drift and is one of the main signatures of a geomagnetic disturbance in the subauroral ionosphere at the altitudes of the F-layer, when the geomagnetic AE index reaches more than 500 nT.
View Article and Find Full Text PDFACS Appl Mater Interfaces
January 2025
School of Materials Science and Engineering, Shanghai JiaoTong University 800 Dongchuan Road, Shanghai 200240, P. R. China.
Solid polymer electrolytes (SPEs) with excellent ionic conductivity and a wide electrochemical stability window are critical for high-energy lithium metal batteries (LMBs). However, the widespread application of polymer electrolytes is severely limited by inadequate room-temperature ionic conductivity, sluggish interfacial charge transport, and uncontrolled reactions at the electrode/electrolyte interface. Herein, we present a uniform polymerized 1,3-dioxolane (PDOL) composite solid polymer electrolyte (PDOL-S/F-nano LiF CSE) that satisfies these requirements through the in situ catalytic polymerization effect of nano LiF on the polymerization of 1,3-dioxolane-based electrolytes.
View Article and Find Full Text PDFChaos
January 2025
School of Mathematics and Statistics, University College Dublin, Dublin 4 D04 V1W8, Ireland.
Synaptic plasticity plays a fundamental role in neuronal dynamics, governing how connections between neurons evolve in response to experience. In this study, we extend a network model of θ-neuron oscillators to include a realistic form of adaptive plasticity. In place of the less tractable spike-timing-dependent plasticity, we employ recently validated phase-difference-dependent plasticity rules, which adjust coupling strengths based on the relative phases of θ-neuron oscillators.
View Article and Find Full Text PDFChaos
January 2025
Agricultural and Ecological Research Unit, Indian Statistical Institute, 203 B. T. Road, Kolkata 700108, India.
Experimental observations and field data demonstrated that predators adapt their hunting strategies in response to prey abundance. While previous studies explored the impact of predation risk on predator-prey interactions, the impact of symbiotic relationships between fear-affected prey and non-prey species on system dynamics remains unexplored. This study uses a mathematical approach to investigate how different symbiotic relationships govern system dynamics when predators adapt to prey availability.
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