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As most mathematically justifiable Lagrangian coherent structure detection methods rely on spatial derivatives, their applicability to sparse trajectory data has been limited. For experimental fluid dynamicists and natural scientists…

Fluid Dynamics · Physics 2024-11-20 Nikolas O. Aksamit , Alex P. Encinas-Bartos , George Haller , David E. Rival

We review and test twelve different approaches to the detection of finite-time coherent material structures in two-dimensional, temporally aperiodic flows. We consider both mathematical methods and diagnostic scalar fields, comparing their…

Many complex flows such as those arising from ocean plastics in geophysics or moving cells in biology are characterized by sparse and noisy trajectory datasets. We introduce techniques for identifying Lagrangian Coherent Structures (LCSs)…

Fluid Dynamics · Physics 2022-09-21 Saviz Mowlavi , Mattia Serra , Enrico Maiorino , L Mahadevan

The quasi-coherent effects in two-dimensional incompressible turbulence are analyzed starting from the test particle trajectories. They can acquire coherent aspects when the stochastic potential has slow time variation and the motion is not…

Plasma Physics · Physics 2017-04-05 M. Vlad , F. Spineanu

Hyperbolic Lagrangian Coherent Structures (LCSs) are locally most repelling or most attracting material surfaces in a finite-time dynamical system. To identify both types of hyperbolic LCSs at the same time instance, the standard practice…

Dynamical Systems · Mathematics 2015-06-12 Mohammad Farazmand , George Haller

We present a frame-invariant method for detecting coherent structures from Lagrangian flow trajectories that can be sparse in number, as is the case in many fluid mechanics applications of practical interest. The method, based on principles…

Fluid Dynamics · Physics 2017-03-08 Kristy L. Schlueter-Kuck , John O. Dabiri

One way to analyze complicated non-autonomous flows is through trying to understand their transport behavior. In a quantitative, set-oriented approach to transport and mixing, finite time coherent sets play an important role. These are…

Dynamical Systems · Mathematics 2019-07-10 Péter Koltai , D. R. Michiel Renger

Quasiperiodic arrangements of the constitutive materials in composites result in effective properties with very unusual electromagnetic and elastic properties. The paper discusses the cut-and-projection method that is used to characterize…

Analysis of PDEs · Mathematics 2019-11-12 Niklas Wellander , Sébastien Guenneau , Elena Cherkaev

Recent advances enable the simultaneous computation of both attracting and repelling families of Lagrangian Coherent Structures (LCS) at the same initial or final time of interest. Obtaining LCS positions at intermediate times, however, has…

Dynamical Systems · Mathematics 2019-01-29 Daniel Karrasch , Mohammad Farazmand , George Haller

We derive a set of criteria to decide whether a given projection measurement can be, in principle, exactly implemented solely by means of linear optics. The derivation can be adapted to various detection methods, including photon counting…

Quantum Physics · Physics 2016-08-16 Peter van Loock , Norbert Lütkenhaus

Partial coherence is an important quantity derived from spectral or precision matrices and is used in seismology, meteorology, oceanography, neuroscience and elsewhere. If the number of complex degrees of freedom only slightly exceeds the…

Statistics Theory · Mathematics 2016-11-03 D. Schneider-Luftman , A. T. Walden

Similarity learning has been recognized as a crucial step for object tracking. However, existing multiple object tracking methods only use sparse ground truth matching as the training objective, while ignoring the majority of the…

Computer Vision and Pattern Recognition · Computer Science 2023-09-29 Tobias Fischer , Thomas E. Huang , Jiangmiao Pang , Linlu Qiu , Haofeng Chen , Trevor Darrell , Fisher Yu

Lagrangian coherent structures (LCSs) are material surfaces that shape finite-time tracer patterns in flows with arbitrary time dependence. Depending on their deformation properties, elliptic and hyperbolic LCSs have been identified from…

Dynamical Systems · Mathematics 2016-11-23 David Oettinger , George Haller

This paper presents a formulation of Lagrangian dynamics of constrained mechanical systems in terms of reduced quasi-velocities and quasi-forces that can be used for simulation, analysis, and control purposes. In this formulation, Cholesky…

Computational Physics · Physics 2021-08-17 Farhad Aghili

A reliable and accurate 3D tracking framework is essential for predicting future locations of surrounding objects and planning the observer's actions in numerous applications such as autonomous driving. We propose a framework that can…

Computer Vision and Pattern Recognition · Computer Science 2021-03-15 Hou-Ning Hu , Yung-Hsu Yang , Tobias Fischer , Trevor Darrell , Fisher Yu , Min Sun

The optical conductivity contains relevant information on the properties of correlated electron systems. In infinite dimensions, where dynamical mean field theory becomes exact, vertex corrections can be neglected and the conductivity…

Strongly Correlated Electrons · Physics 2021-03-17 Olivier Simard , Shintaro Takayoshi , Philipp Werner

We study transient patterns appearing in a class of SPDE using the framework of quasi-stationary and quasi-ergodic measures. In particular, we prove the existence and uniqueness of quasi-stationary and quasi-ergodic measures for a class of…

Probability · Mathematics 2024-06-19 Zachary P. Adams

We introduce a new Lagrangian particle tracking algorithm that tracks particles in three dimensions to separations between trajectories approaching contact. The algorithm also detects low Weber number binary collisions that result in…

Fluid Dynamics · Physics 2020-07-15 Reece Vincent Kearney , Gregory Paul Bewley

We present a number of measures and techniques to characterise and effectively construct quasi-isodynamic stellarators within the near-axis framework, without the need to resort to the computation of global equilibria. These include…

Plasma Physics · Physics 2025-05-06 Eduardo Rodriguez , Gabriel G Plunk

In absence of a lens to form an image, incoherent or partially coherent light scattering off an obstructive or reflective object forms a broad intensity distribution in the far field with only feeble spatial features. We show here that…

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