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Theoretical and Applied Mechanics Letters

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Theoretical & Applied Mechanics Letters 2021年第2期11卷 63-69页

作者： Xuan Zhao Lin Du Xuhao Peng Zichen Deng Weiwei Zhang College of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China National Key Laboratory Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical UniversityXi’an 710072China School of Mathematics and Statistics Northwestern Polytechnical UniversityXi’an 710129China MIITKey Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversityXi’an 710072China School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an 710129China

The placement of pressure taps on the surface of the wind tunnel test model is an important means toobtain the surface pressure ***,limited by space location and experimental cost,it isdifficult to arrange enough pressure measuring taps on the surface of complex models to obtain completepressure distribution information,thus it is impossible to obtain accurate lift and moment characteristicsthrough *** paper proposes a refined reconstruction method of airfoil surface pressure basedon compressed sensing,which can reconstruct the pressure distribution with high precision with lesspressure measurement *** on typical airfoil subsonic flow around flow show that the accuracyof lift and moment after the pressure integration reconstructed by 4-8 measuring points can meet therequirements of the national military *** algorithm is robust to noise,and provides a new ideafor obtaining accurate force data from sparse surface pressure tests in engineering.

关键词： Pressure test Compressed sensing Proper orthogonal decomposition Pressure field reconstruction

Convergence of martingale solutions to the hybrid slow-fast system

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arXiv

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

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

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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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基于子区域的结构拓扑优化并行策略

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

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

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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

Could Feedback-Based Self-Learning Help Solve Networked Prisoner's Dilemma?

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Could Feedback-Based Self-Learning Help Solve Networked Pris...

Joint 48th IEEE Conference on Decision and control and 28th Chinese control Conference

作者： Xiaojie Chen Feng Fu Long Wang State Key Laboratory for Turbulence and Complex Systems Center for Systems and ControlCollege of EngineeringPeking University Department of Zoology University of British Columbia Program for Evolutionary Dynamics Harvard University

We present a self-learning evolutionary Prisoner's Dilemma game model to study the evolution of cooperation in network-structured *** the evolutionary process,each agent updates its current strategy with a probability depending on the difference feedback between its actual score and score *** agent's score is a weighed mean of its payoff coming from its neighbors(social partners) and the payoff of its social partners obtaining from *** results show that the cooperation level in the structured populations increases with increasing the weight of partners' obtaining payoff in the *** interestingly,we find that very similar evolution of cooperation can respectively emerge in lattice,small-world and scale-free networks under the learningfeedback updating ***,we provide theoretical analysis and qualitative explanations for these numerical *** work may provide an effective way to solve the dilemma of cooperation for structured populations.

关键词： Could Feedback-Based Self-Learning Help Solve Networked Prisoner's Dilemma

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

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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

Thermoelastic Modeling and Transient Responses with Piezoelectric and Size Effects

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SSRN 2024年

作者： Li, Si-Yang Wu, Hua Yu, Ya-Jun 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 School of Aeronautics Northwestern Polytechnical University Xi’an710072 China National Key Laboratory of Strength and Structural Integrity Xi’an710072 China

Generalized piezoelectric thermoelastic models play significantly important role in multi-field coupling analysis, especially in extreme environments, of nanosensors, nanogenerators and superconductivity. In this work, generalized thermoelastic theory is firstly proposed by considering higher-order thermal lagging and size effect. Then, unified generalized piezoelectric thermoelastic coupling model is obtained by further combining piezoelectric effect. Transient piezoelectric thermoelastic responses of piezoelectric materials under thermal shock are investigated. Numerical results are obtained from analytical solution in Laplace domain by adopting numerical inverse Laplace transform. The obtained results are graphically illustrated, from which the effects of lagging effect and size effect are clarified. This work provides theoretical model and numerical method to predict transient thermoelastic behaviors of piezoelectric materials across different time and space scales. © 2024, The Authors. All rights reserved.

关键词： Transient analysis

Reservoir computing with higher-order interactive coupled pendulums

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Physical Review E 2023年第6期108卷 064304-064304页

作者： Xueqi Li Michael Small Youming Lei School of Mathematics and Statistics Northwestern Polytechnical University Xi'an 710072 China Complex Systems Group Department of Mathematics and Statistics The University of Western Australia Crawley WA 6009 Australia Mineral Resources CSIRO Kensington WA 6151 Australia Ministry of Industry and Information Technology Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Xi'an 710072 China

The reservoir computing approach utilizes a time series of measurements as input to a high-dimensional dynamical system known as a reservoir. However, the approach relies on sampling a random matrix to define its underlying reservoir layer, which leads to numerous hyperparameters that need to be optimized. Here, we propose a nonlocally coupled pendulum model with higher-order interactions as a novel reservoir, which requires no random underlying matrices and fewer hyperparameters. We use Bayesian optimization to explore the hyperparameter space within a minimal number of iterations and train the coupled pendulums model to reproduce the chaotic attractors, which simplifies complicated hyperparameter optimization. We illustrate the effectiveness of our technique with the Lorenz system and the Hindmarsh-Rose neuronal model, and we calculate the Pearson correlation coefficients between time series and the Hausdorff metrics in the phase space. We demonstrate the contribution of higher-order interactions by analyzing the interaction between different reservoir configurations and prediction performance, as well as computations of the largest Lyapunov exponents. The chimera state is found as the most effective dynamical regime for prediction. The findings, where we present a new reservoir structure, offer potential applications in the design of high-performance modeling of dynamics in physical systems.

关键词： Chaos Collective behavior in networks dynamics of networks