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We propose a general strategy for reduced order modeling of systems that display highly nonlinear oscillations. By considering a continuous family of forced periodic orbits defined in relation to a stable fixed point and subsequently…

Dynamical Systems · Mathematics 2023-02-07 Dan Wilson , Kai Sun

We propose a general algorithm for non-conforming adaptive mesh refinement (AMR) of unstructured meshes in high-order finite element codes. Our focus is on h-refinement with a fixed polynomial order. The algorithm handles triangular,…

Numerical Analysis · Computer Science 2019-05-13 Jakub Červený , Veselin Dobrev , Tzanio Kolev

We consider a time series model involving a fractional stochastic component, whose integration order can lie in the stationary/invertible or nonstationary regions and be unknown, and an additive deterministic component consisting of a…

Statistics Theory · Mathematics 2007-06-13 P. M. Robinson

For time series data observed at non-random and possibly non-equidistant time points, we estimate the trend function nonparametrically. Under the assumption of a bounded total variation of the function and low-order moment conditions on the…

Statistics Theory · Mathematics 2025-02-13 Michael H. Neumann , Anne Leucht

Classical high-order weighted essentially non-oscillatory (WENO) schemes are designed to achieve optimal convergence order for smooth solutions and to maintain non-oscillatory behaviors for discontinuities. However, their spectral…

Numerical Analysis · Mathematics 2025-08-20 Jinrui Zhou , Yiqi Gu , Song Jiang , Hua Shen , Liwei Xu , Guanyu Zhou

The unique functionalities of antiferromagnets offer promising routes to advance information technology. Their compensated magnetic order leads to spin resonances in the THz-regime, which suggest the possibility to coherently control…

Mesoscale and Nanoscale Physics · Physics 2019-09-06 Christian Tzschaschel , Takuya Satoh , Manfred Fiebig

Robust online estimation of oscillation frequency belongs to classical problems of system identification and adaptive control. The given harmonic signal can be noisy and with varying amplitude at the same time, as in the case of damped…

Systems and Control · Electrical Eng. & Systems 2022-01-26 Michael Ruderman

This paper considers nonparametric estimation and inference in first-order autoregressive (AR(1)) models with deterministically time-varying parameters. A key feature of the proposed approach is to allow for time-varying stationarity in…

Econometrics · Economics 2024-11-04 Donald W. K. Andrews , Ming Li

We develop new adaptive alternative weighted essentially non-oscillatory (A-WENO) schemes for hyperbolic systems of conservation laws. The new schemes employ the recently proposed local characteristic decomposition based central-upwind…

Numerical Analysis · Mathematics 2022-11-15 Alina Chertock , Shaoshuai Chu , Alexander Kurganov

A biomechanical model often requires parameter estimation and selection in a known but complicated nonlinear function. Motivated by observing that data from a head-neck position tracking system, one of biomechanical models, show…

Methodology · Statistics 2024-02-13 Hojun You , Kyubaek Yoon , Wei-Ying Wu , Jongeun Choi , Chae Young Lim

The synchrosqueezing transform (SST) was developed recently to separate the components of non-stationary multicomponent signals. The continuous wavelet transform-based SST (WSST) reassigns the scale variable of the continuous wavelet…

Signal Processing · Electrical Eng. & Systems 2020-08-26 Jian Lu , Qingtang Jiang , Lin Li

This paper deals with the estimation of hidden periodicities in a non-linear regression model with stationary noise displaying cyclical dependence. Consistency and asymptotic normality are established for the least-squares estimates.

Statistics Theory · Mathematics 2013-06-25 A. V. Ivanov , N. N. Leonenko , M. D. Ruiz-Medina , B. M. Zhurakovsky

The article considers the problem of identifying the variable frequency of a sinusoidal signal. To obtain a regression model of the signal, an iterative differentiation of the original analytical expression is performed, and the swapping…

Systems and Control · Electrical Eng. & Systems 2021-09-21 S. I. Nizovtsev , S. V. Shavetov , A. A. Pyrkin

Hyperspectral unmixing (HU) is a critical yet challenging task in remote sensing. However, existing nonnegative matrix factorization (NMF) methods with graph learning mostly focus on first-order or second-order nearest neighbor…

Computer Vision and Pattern Recognition · Computer Science 2025-09-26 Hui Chen , Liangyu Liu , Xianchao Xiu , Wanquan Liu

This paper considers the problem of frequency estimation for a multi-sinusoidal signal consisting of n sinuses in finite-time. The parameterization approach based on applying delay operators to a measurable signal is used. The result is the…

Systems and Control · Electrical Eng. & Systems 2020-09-15 Anastasiia Vediakova , Alexey Vedyakov , Anton Pyrkin , Alexey Bobtsov , Vladislav Gromov

Latency in the control loop of adaptive optics (AO) systems can severely limit performance. Under the frozen flow hypothesis linear predictive control techniques can overcome this, however identification and tracking of relevant turbulent…

Instrumentation and Methods for Astrophysics · Physics 2020-06-10 Xuewen Liu , Tim Morris , Chris Saunter , Francisco Javier de Cos Juez , Carlos González-Gutiérrez , Lisa Bardou

We propose a new algorithm for time stretching music signals based on the theory of nonstationary Gabor frames (NSGFs). The algorithm extends the techniques of the classical phase vocoder (PV) by incorporating adaptive time-frequency (TF)…

Sound · Computer Science 2017-09-14 Emil Solsbæk Ottosen , Monika Dörfler

Most adaptive optics (AO) systems using pyramid wavefront sensors (PyWFS) to estimate the phase of the pupil field use mechanical modulation of the beam in order to increase the dynamic range in low-order modes so the PyWFS can usefully…

Instrumentation and Methods for Astrophysics · Physics 2017-08-31 Richard Frazin

This paper introduces an effcient class of adaptive stencil extension reconstruction methods based on a discontinuity feedback factor, addressing the challenges of weak robustness and high computational cost in high-order schemes,…

Numerical Analysis · Mathematics 2024-10-10 Hong Zhang , Yue Zhao , Xing Ji , Kun Xu

We apply the recently developed adaptive non-harmonic model based on the wave-shape function, as well as the time-frequency analysis tool called synchrosqueezing transform (SST) to model and analyze oscillatory physiological signals. To…