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arXiv 2023年

作者： An, Xiao-Kai Du, Lin Deng, Zi-Chen Zhang, Yu-Jia Miit Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Xi'An710072 China School of Mathematics and Statistics Northwestern Polytechnical University Xi'An710072 China School of Aeronautics Northwestern Polytechnical University Xi'An710072 China

Stochastic differential equations can describe a wide range of dynamical systems, and obtaining the governing equations of these systems is the premise of studying the nonlinear dynamic behavior of the system. Neural networks are currently the most popular approach in the inverse problem of dynamical systems. In order to obtain accurate dynamical equations, neural networks need a large amount of trajectory data as a training set. To address this shortcoming, we propose a residual-based multi-peaks sampling algorithm. Evaluate the training results of each epoch of neural network, calculate the probability density function P(x) of the residual, perform sampling where the P(x) is large, and add samples to the training set to retrain the neural network. In order to prevent the neural network from falling into the trap of overfitting, we discretize the sampling points. We conduct case studies using two classical nonlinear dynamical systems and perform bifurcation and first escape probability analyzes of the fitted equations. Results show that our proposed sampling strategy requires only 20∼30% of the sample points of the original method to reconstruct the stochastic dynamical behavior of the system. Finally, the algorithm is tested by adding interference noise to the data, and the results show that the sampling strategy has better numerical robustness and stability. Copyright © 2023, The Authors. All rights reserved.

关键词： Dynamical systems

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Rate-dependent tipping-delay phenomenon in a thermoacoustic system with colored noise

arXiv

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arXiv 2020年

作者： Zhang, Xiaoyu Xu, Yong Liu, Qi Kurths, Jürgen Department of Applied Mathematics Northwestern Polytechnical University Xi’an710072 China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Xian710072 China Potsdam Institute for Climate Impact Research Potsdam14412 Germany

Tipping is a phenomenon in multistable systems where small changes in inputs cause huge changes in outputs. When the parameter varies within a certain time scale, the rate will affect the tipping behaviors. These behaviors are undesirable in thermoacoustic systems, which are widely used in aviation, power generation and other industries. Thus, this paper aims at considering the tipping behaviors of the thermoacoustic system with the time-varying parameters and the combined excitations of additive and multiplicative colored noises. Transient dynamical behaviors for the proposed thermoacoustic model are implemented through the reduced Fokker-Planck-Kolmogorov equation derived by a standard stochastic averaging method. Then, the tipping problems of the rate-dependent thermoacoustic systems with random fluctuations are studied by virtue of the obtained probability density functions. Our results show that the rate delays the value of the tipping parameter compared to the one with the quasi-steady assumption, which is called as a rate-dependent tipping-delay phenomenon. Besides, the influences of the initial values, the rate, the changing time of the parameters, and the correlation time of the noises on the rate-dependent tipping-delay phenomenon are analyzed in detail. These results are of great significance for research in related fields such as aviation and land gas turbines. Copyright © 2020, The Authors. All rights reserved.

关键词： White noise

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Convergence of martingale solutions to the hybrid slow-fast system

arXiv

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arXiv 2018年

作者： Xu, Yong Yang, Xiaoyu Pei, Bin Bai, Yuzhen School of Mathematics and Statistics Northwestern Polytechnical University Xi’an710072 China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Xi’an710072 China School of Mathematical Sciences Qufu Normal University Qufu273165 China

This paper is devoted to studying the weak convergence for a slow-fast system with jumps modulated by Markovian switching regimes with the martingale method. However, due to the coexistence of fast component and Markovian switching regimes, the martingale method and perturbed test functions can not be applied directly. In this situation, a combination of perturbed test functions and the time discretization is applied efficiently. And the choice of appropriate perturbed test functions, which are related to the averaged coefficients, plays a decisive role. Our results also cover the case of slow-fast system without Markovian switching regimes. Finally, some examples are presented, and numerical simulations are carried out to observe a good *** Codes 70K70, 60J25, 60G51 Copyright © 2018, The Authors. All rights reserved.

关键词： Markov processes

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Aluminum Nitride Ring Resonator-Coupled Spin Defects in Hexagonal Boron Nitride for Integrated Quantum Photonics

Aluminum Nitride Ring Resonator-Coupled Spin Defects in Hexa...

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CLEO: Science and Innovations in CLEO 2024, CLEO: S and I 2024 - Part of Conference on Lasers and Electro-Optics

作者： Roberts, Henry C. Waseem, Aadil Wicker, Scott A. Abudayyeh, Hamza Kim, Dong Seob Liu, Zhida Randolph, Steven Li, Xiaoqin Li, Xiuling Department of Electrical and Computer Engineering Microelectronics Research Center The University of Texas at Austin 10100 Harry Ransom Trail AustinTX78758 United States Department of Physics Center for Complex Quantum Systems Center for Dynamics Control of Materials Texas Materials Institute The University of Texas at Austin 2515 Speedway AustinTX78712 United States Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak RidgeTN37830 United States

We report a new approach to generate waveguide-coupled emission from deterministically implanted boron vacancy spin defects in hBN using single-crystal AlN-on-sapphire ring resonators. This facilitates the eventual development of hBN-based integrated quantum technologies. © Optica Publishing Group 2024

关键词： Single crystals

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Aluminum Nitride Ring Resonator-Coupled Spin Defects in Hexagonal Boron Nitride for Integrated Quantum Photonics

Aluminum Nitride Ring Resonator-Coupled Spin Defects in Hexa...

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2024 Conference on Lasers and Electro-Optics, CLEO 2024

作者： Roberts, Henry C. Waseem, Aadil Wicker, Scott A. Abudayyeh, Hamza Kim, Dong Seob Liu, Zhida Randolph, Steven Li, Xiaoqin Li, Xiuling Department of Electrical and Computer Engineering Microelectronics Research Center The University of Texas at Austin 10100 Harry Ransom Trail AustinTX78758 United States Department of Physics Center for Complex Quantum Systems Center for Dynamics and Control of Materials Texas Materials Institute The University of Texas at Austin 2515 Speedway AustinTX78712 United States Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak RidgeTN37830 United States

ISBN: (纸本)9781957171395

关键词： Aluminum nitride

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基于子区域的结构拓扑优化并行策略

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Acta Mechanica Sinica 2023年第9期39卷 114-125页

作者：赵子龙荣毅燕翌冯西桥谢亿民 Institute of Solid Mechanics School of Aeronautic Science and EngineeringBeihang UniversityBeijing 100191China Centre for Innovative Structures and Materials School of EngineeringRMIT UniversityMelbourne 300lAustralia Department of Engineering Mechanics MIIT Key Laboratory of Dynamics and Control of Complex SystemsNorthwestern Polytechnical UniversityXi'an710072China Institute of Biomechanics and Medical Engineering Department of Engineering MechanicsTsinghua UniversityBejing 100084China

结构拓扑优化在过去的三十年里经历了巨大的发展,充分利用高性能计算资源有助于拓宽拓扑优化在大规模设计问题中的应用。本文提出了一种针对一般三维拓扑优化的基于子区域的并行策略。通过子区域划分、矩阵运算、引入单元硬杀算法,优化... 详细信息

结构拓扑优化在过去的三十年里经历了巨大的发展,充分利用高性能计算资源有助于拓宽拓扑优化在大规模设计问题中的应用。本文提出了一种针对一般三维拓扑优化的基于子区域的并行策略。通过子区域划分、矩阵运算、引入单元硬杀算法,优化过程得以显著提速.将该策略整合进高效、简洁的Python代码;该代码可适用于任意形状的设计域.附录一中给出的完整代码,易于扩展,扩展后可解决多类优化问题.通过求解四个柔度最小化问题展示了该策略的高效性.本研究在机械工程、先进制造,以及建筑设计等领域有潜在的应用价值.

关键词：并行策略高性能计算子区域划分最小化问题结构拓扑优化 Python 设计域建筑设计

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Symplectic Stiffness Method for the Buckling Analysis of Hierarchical and Chiral Cellular Honeycomb Structures

SSRN

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SSRN 2023年

作者： Jin, Mingzhu Hou, Xiuhui Zhao, Wenhao Deng, Zichen School of Aeronautics Northwestern Polytechnical University Xi’an710072 China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Xi’an710072 China School of Mechanics Civil Engineering and Architecture Northwestern Polytechnical University Xi’an710072 China

Structure-function-material integration design based on the buckling instability of flexible cellular structures has attracted much attention. According to the reversible and repeatable characteristics of buckling deformation, phonon bandgap switches, the autonomous drive of soft robots, programmable logic controllers, and reusable spacecraft landing buffer devices can be designed. Based on the Hamiltonian variational principle and symplectic eigen expansion, a theoretical analysis model of the symplectic stiffness method is established, and analytical expressions for the stiffness of several typical buckling modes of elastically supported beams are obtained. The analytical closed-form expressions for the macroscopic buckling strength of honeycombs are obtained according to the bending moment equilibrium equation. The buckling modes of regular hexagonal, hierarchical hexagonal, and tri-chiral honeycombs are obtained by numerical simulation and experimental verification, and some novel higher-order modes are observed. Uniaxial compression experiments reveal that these higher-order buckling modes can be triggered by adjusting the geometric parameters of the unit cells. The high agreement between experimental, numerical, and existing literature results for the failure surfaces of cellular structures verifies the effectiveness of the proposed symplectic stiffness method. In a word, the buckling modes can be designed to meet different functional requirements by changing the initial configuration of flexible cellular structures. This provides a new idea and theoretical guidance for the development of metamaterials and structures with tailored properties. © 2023, The Authors. All rights reserved.

关键词： Stiffness

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Origami-Inspired Metamaterial with Cpmpression-Twist Coupling Effect For Low-Frequency Vibration Isolation

SSRN

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SSRN 2023年

作者： Liu, Xiangbing Zhang, Kai Shi, Haizhou Hong, Fang Liu, Hong Deng, Zichen School of Mechanics Civil Engineering and Architecture Northwestern Polytechnical University Xi’an710072 China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Xi’an710072 China State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian116024 China

Through unique folding methods and material selection, origami structures enable optimum structural design within a restricted space and provide strong force support. In aerospace engineering, origami-inspired structures are used in designing satellites, probes and other space devices for lightweight, compact and adjustable design requirements. A compression-twist coupled metamaterial inspired by Kresling origami structure consisting of beams and plates is presented in this study, and the vibration response of the structure is investigated. The bandgaps of the structure along longitudinal and transverse directions are studied separately due to the application of the polarization factor. The vibrational modes of the structure are further investigated to elucidate the mechanism of bandgap generation. Parametric studies make the optimal design of bandgap in graded structures possible. Finally, experiments are carried out to verify the correctness of the structural dynamic response. This research provides a new perspective on the design of origami-inspired metamaterial structures in terms of dynamics control and bandgap tuning. © 2023, The Authors. All rights reserved.

关键词： Energy gap

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Explosive synchronization in multiplex neuron-glial networks

arXiv

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arXiv 2023年

作者： Laptyeva, Tetyana Jalan, Sarika Ivanchenko, Mikhail Department of Control Theory and Systems Dynamics Lobachevsky State University of Nizhny Novgorod Nizhny Novgorod Russia Complex Systems Lab Department of Physics Indian Institute of Technology Indore Indore Simrol452020 India Department of Applied Mathematics Laboratory of Systems Medicine of Healthy Aging Lobachevsky State University of Nizhny Novgorod Nizhny Novgorod Russia

Explosive synchronization refers to an abrupt (first order) transition to non-zero phase order parameter in oscillatory networks, underpinned by the bistability of synchronous and asynchronous states. Growing evidence suggests that this phenomenon might be no less general then the celebrated Kuramoto scenario that belongs to the second order universality class. Importantly, the recent examples demonstrate that explosive synchronization can occur for certain network topologies and coupling types, like the global higher-order coupling, without specific requirements on the individial oscillator dynamics or dynamics-network correlations. Here we demonstrate a rich picture of explosive synchronization and desynchronization transitions in multiplex networks, where it is sufficient to have a single random sparsly connected layer with higher-order coupling terms (and not necessarily in the synchronization regime on its own), the other layer being a regular lattice without own phase transitions at all. Moreover, explosive synchronization emerges even when the random layer has only low-order pairwise coupling, althoug the hysteresis interval becomes narrow and explosive desynchronization is no longer observed. The relevance to the normal and pathological dynamics of neural-glial networks is pointed out. © 2023, CC BY.

关键词： Synchronization

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A Meta-Design of Hollow-Square-Frustum-Core Sandwich Structures for Improved Compression and Vibration Isolation Properties

SSRN

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SSRN 2024年

作者： Zhang, Kai Ding, Bin Shi, Haizhou Hong, Fang Gu, Xudong Deng, Zichen School of Mechanics Civil Engineering and Architecture Northwestern Polytechnical University Xi’an710072 China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Xi’an710072 China State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian116024 China

Metamaterials can satisfy the demand for lightweight and multifunctional structures. In this study, we propose a double hollow-square-frustum-core sandwich meta-structure (meta-DHSFCSS) for vibration isolation. The out-of-plane compressive performance of the sandwich meta-structure specimen is experimentally and numerically studied. The bandgap in the band structure for out-of-plane vibration of the meta-DHSFCSS is numerically computed and verified by the frequency-domain and time-domain responses and vibration test. Parameter study is performed on the meta-DHSFCSS to investigate the effects on the structural compressive performance and vibration isolation property. The maximum load-mass ratio exceeds 283 N/g and the maximum SEA reaches 2000 kJ/kg. These two indexes are dramatically better than those of certain previous studies. The meta-DHSFCSS has a wide bandgap for vibration isolation. Gradient design and waveguide design are introduced to the meta-DHSFCSS supercell. Its vibration isolation property is improved. The locational and directional transmission of the elastic wave can be achieved by the rainbow trapping effect of gradient meta-DHSFCSS and the waveguides with different transmission routes. These demonstrate the great application of the meta-DHSFCSS in elastic wave manipulation. © 2024, The Authors. All rights reserved.

关键词： Metamaterials

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