Article
Business
Frank W. Geels, Martina Ayoub
Summary: This paper presents a socio-technical transitions perspective to study positive tipping points in climate mitigation. Through two case studies, it explores the co-evolutionary interactions between techno-economic improvements and actor reorientations, illustrating the importance of feedback loops in tipping point dynamics. The findings emphasize the role of policymakers and policy support in low-carbon tipping point dynamics.
TECHNOLOGICAL FORECASTING AND SOCIAL CHANGE
(2023)
Article
Mathematics, Interdisciplinary Applications
Haoming He, Min Xiao, Yunxiang Lu, Zhen Wang, Binbin Tao
Summary: A novel dynamic delayed feedback scheme is proposed and successfully applied to control the tipping phenomenon in small-world networks. The linear characteristic equation of the controlled system is analyzed, and the conditions for stability and bifurcation-induced tipping are given. The direction of Hopf bifurcation, revealing the further evolution mechanism of tipping, is analyzed using normal form theory and center manifold reduction. Numerical simulations are provided to support the theoretical analysis and verify the effectiveness of the proposed dynamic delayed feedback controller for small-world networks.
CHAOS SOLITONS & FRACTALS
(2023)
Article
Physics, Multidisciplinary
Franck Michael Tchakounte, Victor Bami Nana, Laurent Nana
Summary: The Lugiato-Lefever model utilizes global and local time-delay feedback to study wave dynamics in fiber cavities, impacting linear stability and spatiotemporal behavior. Delay feedback strongly influences modulational instability, leading to drifting cavity solitons and periodic waves.
EUROPEAN PHYSICAL JOURNAL PLUS
(2021)
Article
Optics
Jiaoyang Jin, Ning Jiang, Yiqun Zhang, Weizhou Feng, Anke Zhao, Shiqin Liu, Jiafa Peng, Kun Qiu, Qianwu Zhang
Summary: We propose an adaptive time-delayed photonic reservoir computing structure using the Kalman filter algorithm as a training approach. Simulation results on two benchmark tasks demonstrate that the proposed structure with adaptive KF training significantly enhances prediction and equalization performance compared to conventional reservoir computing with least-squares training. Furthermore, introducing a complex mask derived from a enhanced chaotic signal improves the performance further. The work presents a potential way to realize adaptive photonic computing.
Review
Green & Sustainable Science & Technology
Lukas P. Fesenfeld, Nicolas Schmid, Robert Finger, Alexander Mathys, Tobias S. Schmidt
Summary: This article emphasizes the importance of crossing positive tipping points to accelerate the transformation of complex energy, food, and transport systems. The authors argue that policy strategies enabling the creation and crossing of such points are needed, and propose a novel framework that links feedback research to core sustainability principles to inform these strategies.
Article
Multidisciplinary Sciences
Hassan Yahya Alfifi
Summary: This paper examines the stability and Hopf bifurcation of the Brusselator system under delayed feedback control, presenting equations and conditions determining the bifurcation point. Interaction of chemical species, feedback control, and diffusion parameters play significant roles. The results illustrate the effects of feedback and diffusion parameters on chemical control bifurcation points, supported by bifurcation diagrams and phase-plane maps. The study demonstrates strong agreement between analytical and numerical results.
Article
Multidisciplinary Sciences
Robbin Bastiaansen, Peter Ashwin, Anna S. von der Heydt
Summary: Climate response metrics, such as equilibrium climate sensitivity (ECS), assume linearity in climate response, but nonlinear responses can occur, especially for larger forcing levels. This paper discusses the problems and caveats in estimating ECS from transient simulations, highlighting the potential for poor estimation and late abrupt responses associated with nonlinearities. The implications for estimating ECS for global climate models are also discussed, emphasizing the difficulty in determining simulation times needed to reach equilibrium.
PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
(2023)
Article
Mathematics, Interdisciplinary Applications
Milena Cukic, Slobodanka Galovic
Summary: This paper introduces the central process of molecular transport through a composite multilayer membrane in transdermal drug delivery (TDD). Traditional Fickean approach treats skin as a pseudo-homogenous membrane, while skin is in reality a highly heterogeneous system. The anomalous diffusive behavior of particle transport across these systems is described by fractional models. These models do not consider the experimentally observed dependence of particle transport nature on time scale. This paper presents a possible way of including that observation in the model of transdermal transport.
CHAOS SOLITONS & FRACTALS
(2023)
Article
Mathematics, Interdisciplinary Applications
Lian Duan, Min Shi, Chuangxia Huang, Xianwen Fang
Summary: This paper investigates the finite-time synchronization problem between two delayed and diffusive complex-valued neural networks with discontinuous activations. By designing a negative exponent controller and an adaptive control scheme, novel and useful finite-time synchronization criteria are established with an explicit estimation of the upper-bound of the settling time. The effectiveness of the theoretical analysis is substantiated through numerical simulations.
CHAOS SOLITONS & FRACTALS
(2021)
Article
Computer Science, Theory & Methods
Lian Duan, Min Shi, Lihong Huang
Summary: This paper studies the finite-/fixed-time synchronization problem for delayed diffusive Hopfield neural networks and designs a novel state feedback controller using Filippov regularization approaches, inequality techniques, and a generalized stability theorem. The theoretical results obtained generalize and improve existing literature, and a numerical example is presented to demonstrate the effectiveness of the results.
FUZZY SETS AND SYSTEMS
(2021)
Article
Chemistry, Physical
Lionel Lacombe, Neepa T. Maitra
Summary: Simulating electron-ion dynamics using time-dependent density functional theory can be done through propagating time-dependent electronic Kohn-Sham equations or electronic coefficients on surfaces obtained from linear response. The use of an approximate functional leads to qualitatively different dynamics, with evaluations closer to the ground state leading to better performance in the approach involving electronic coefficients.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Automation & Control Systems
Bin Zhou, Wim Michiels, Jie Chen
Summary: This article studies the fixed-time stabilization of a general controllable linear system with an input delay, providing solutions based on linear periodic delayed feedback and linear predictor-based feedback. It also designs linear observers for cases where only an output signal is available for feedback, achieving system state convergence.
IEEE TRANSACTIONS ON AUTOMATIC CONTROL
(2022)
Article
Physics, Fluids & Plasmas
Jason Czak, Michel Pleimling
Summary: This study demonstrates that selectively perturbing part of a system can generate new space-time patterns that are not observed when controlling the entire system. These patterns may emerge either in the perturbed or unperturbed regions, showing stability and possibly perfect periodicity. The mechanism underlying the observed pattern generation is related to diffusion across the interfaces separating the perturbed and unperturbed regions.
Article
Automation & Control Systems
Zhe Zhang, Yunxia Song, Huaiyuan Jiang, Xuefei Yang
Summary: A family of observer-based periodic delayed feedback (PDF) controllers are proposed in this paper for the fixed-time stabilization of the linear input-delay system with immeasurable states. The relationship between the control gain and the system matrix is established by periodically switching the controller gain. Two different observer-predictor-based PDF controllers are proposed to address the open-loop problem faced by the standard PDF controller. Both controllers ensure that the closed-loop system converges asymptotically throughout the control period. Furthermore, a modified PDF is proposed for multi-input-multi-output systems utilizing the characteristic of controllability index set and observability index set.
INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL
(2023)
Article
Automation & Control Systems
Yunfei Dai, Yujuan Wang, Chao Wang
Summary: This article investigates the problem of finite-time tracking control for a class of nonlinear pure-feedback systems with both time-varying state delays and control input delays, proposing a new performance function and a novel construction of the Lyapunov-Krasovskii (LK) function. In addition, a continuous package function is introduced to handle the unknown nonlinear terms arising from uncertain perturbation and the derivation of the LK function. Simulation examples demonstrate the effectiveness of the proposed approach.
INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL
(2023)
Article
Green & Sustainable Science & Technology
K. C. Anup, Jonathan Whale, Joachim Peinke
Summary: This study analyzed wind conditions at two contrasting locations, finding that turbines in built environment sites have higher intermittency of turbulence and increased likelihood of extreme events. The turbines operating in sites with complex terrain need to be structurally robust and have better control systems.
Article
Engineering, Mechanical
Lars Neuhaus, Frederik Berger, Joachim Peinke, Michael Holling
Summary: This study focuses on a method of blockage induced flow design for generating special flow structures, where the excitation process is limited by the reduced frequency of the active grid motion. It is found that the imprinted flow structures are undamped for low reduced frequencies and damped for higher reduced frequencies, leading to the need for modifying the active grid motion to compensate for dynamic damping effects and increase inserted energy.
EXPERIMENTS IN FLUIDS
(2021)
Article
Green & Sustainable Science & Technology
P. Singh, L. Neuhaus, O. Huxdorf, J. Riemenschneider, J. Wild, J. Peinke, M. Hoelling
Summary: This study discusses the utilization of an active slat concept to reduce turbulence induced fluctuating loads on an airfoil, with wind tunnel tests confirming its effectiveness. By actively moving the trailing edge of the slat, the load fluctuations on the airfoil are successfully mitigated.
JOURNAL OF RENEWABLE AND SUSTAINABLE ENERGY
(2021)
Article
Physics, Multidisciplinary
A. Fuchs, M. Obligado, M. Bourgoin, M. Gibert, P. D. Mininni, J. Peinke
Summary: This study presents evidence for the existence of Markov property in Lagrangian turbulence based on direct numerical simulations with inertial particles, and introduces a method to describe multi-scale statistics of particle trajectories that relates to fluctuation theorems of non-equilibrium stochastic thermodynamics.
Article
Green & Sustainable Science & Technology
Ingrid Neunaber, Michael Hoelling, Jonathan Whale, Joachim Peinke
Summary: An experimental wind tunnel study compared the turbulence in the wakes of a static actuator disc and a model wind turbine, finding that both models have similar properties in the far wake, with turbulence in the central wake being independent of the inflow conditions. Both models filter larger scale intermittency in the far wake, and the turbine generates its own turbulence with strong features of homogeneous, isotropic turbulence.
Article
Physics, Multidisciplinary
A. Fuchs, C. Herbert, J. Rolland, M. Wachter, F. Bouchet, J. Peinke
Summary: This study examines the intermittency phenomenon and cascade trajectories in turbulent flows. The concept of an instanton, representing the optimal path among selected trajectories, is introduced to explain the emergence of non-Gaussian statistics at small scales.
PHYSICAL REVIEW LETTERS
(2022)
Article
Energy & Fuels
Khaled Yassin, Hassan Kassem, Bernhard Stoevesandt, Thomas Klemme, Joachim Peinke
Summary: One of the emerging problems in modern computational fluid dynamics is the simulation of flow over rough surfaces. This study compares different models and finds that using Colebrook RWF can provide the most accurate results with the lowest computational cost.
Article
Mechanics
Andre Fuchs, Swapnil Kharche, Aakash Patil, Jan Friedrich, Matthias Waechter, Joachim Peinke
Summary: We present an open-source package that facilitates basic statistical analysis of turbulence datasets, including estimation of various statistical quantities and advanced analysis using scale-dependent statistical description and non-equilibrium stochastic thermodynamics. The package can also be applied to analyze data with turbulence-like complexity.
Article
Green & Sustainable Science & Technology
Ingrid Neunaber, Joachim Peinke, Martin Obligado
Summary: The evolution of wind turbine wakes within the atmospheric boundary layer has been studied, but an analytical description is still missing. This paper introduces the analytical model of classical wake theory and verifies its applicability through wind tunnel experiments. The study finds that wind turbine wakes consist of both equilibrium and non-equilibrium turbulence, and the classical wake models perform better than the wind turbine wake models. The findings suggest the possibility of improving wind turbine wake models by implementing parameters from classical bluff body wake models.
WIND ENERGY SCIENCE
(2022)
Proceedings Paper
Energy & Fuels
Ingrid Neunaber, Martin Obligado, Joachim Peinke, Sandrine Aubrun
Summary: Importance: Understanding the evolution of wind turbine wakes is crucial for improving the performance of wind turbines.
Research Status: Existing wake models lack construction based on basic and robust assumptions.
Research Approach: Researchers analyzed the wakes of two wind turbines in a wind farm using data obtained with a scanning LiDAR.
WAKE CONFERENCE 2021
(2021)
Proceedings Paper
Energy & Fuels
G. Centurelli, L. Vollmer, J. Schmidt, M. Doerenkaemper, M. Schroeder, L. J. Lukassen, J. Peinke
Summary: This study compares the cumulative induction effects of wind turbines in a wind farm using analytical models and Large-Eddy-Simulations, and finds notable differences between the two. The linear superposition of induction consistently underestimates the upstream velocity deficit, revealing that interactions with the atmospheric boundary layer may outweigh the turbine induction in determining the global blockage effect.
WAKE CONFERENCE 2021
(2021)
Article
Mathematics, Interdisciplinary Applications
J. Friedrich, J. Peinke, A. Pumir, R. Grauer
Summary: Complex systems involve random fluctuations with self-similar properties and fractional Brownian motions. In certain strongly interacting systems, multiscale interactions may deviate from self-similarity and require more complex descriptions. The Kolmogorov-Oboukhov model describes anomalous scaling in turbulence.
JOURNAL OF PHYSICS-COMPLEXITY
(2021)
Article
Green & Sustainable Science & Technology
Sirko Bartholomay, Tom T. B. Wester, Sebastian Perez-Becker, Simon Konze, Christian Menzel, Michael Hoelling, Axel Spickenheuer, Joachim Peinke, Christian N. Nayeri, Christian Oliver Paschereit, Kilian Oberleithner
Summary: This experimental study compares pressure-based lift estimation methods for active trailing-edge flap feedforward control of wind turbine applications. Surface-pressure-based method generally provides more accurate results compared to three-hole probe estimates. Using the latter as input to the feedforward controller shows promise due to introducing a beneficial phase lead.
WIND ENERGY SCIENCE
(2021)
