检索结果-内蒙古大学图书馆

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

来源：评论

学校读者我要写书评

暂无评论

Data-Driven Learning and control with Event-Triggered Measurements

引用

IEEE Transactions on Automatic control 2025年

作者： Feng, Shilun Shi, Dawei Chen, Tongwen Shi, Ling Beijing Institute of Technology State Key Laboratory of Intelligent Control and Decision of Complex Systems MIIT Key Laboratory of Servo Motion System Drive and Control School of Automation Beijing100081 China University of Alberta Department of Electrical and Computer Engineering EdmontonABT6G 1H9 Canada Hong Kong University of Science and Technology Department of Electronic and Computer Engineering Clear Water Bay Kowloon Hong Kong

Event-triggered control has attracted considerable attention for its effectiveness in resource-restricted applications. To make event-triggered control as an end-to-end solution, a key issue is how to effectively learn unknown system dynamics from event-triggered measurements and consequently, develop a learning-based event-triggered controller. Existing works learn system dynamics based on periodic time-triggered measurements, and it is yet to know how to learn a controller with performance guarantee based on event-triggered measurements. To address this issue, we consider the problem of learning an event-triggered state feedback controller for an unknown linear system based on event-triggered state measurements in this work. In particular, we first analyze the event-triggered measurements within a set-membership framework. We prove that the estimation error belongs to a bounded ellipsoid determined by the historical measurements and the event-triggering condition. Subsequently, we demonstrate that all admissible systems compatible with the collected data samples can be explicitly represented in the form of quadratic matrix inequalities using the state estimates. With the acquired set of admissible systems, a co-design problem for the data-driven controller and event-triggering condition is solved using the linear matrix inequality technique, with guaranteed closed-loop stability and L2-gain performance. Finally, numerical examples and comparisons are provided to illustrate the effectiveness of the proposed event-triggered learning and control approach. © 1963-2012 IEEE.

关键词： Networked control systems

来源：评论

学校读者我要写书评

暂无评论

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

引用

Science China(Technological Sciences) 2020年第11期63卷 2315-2327页

作者： ZHANG XiaoYu XU Yong LIU Qi KURTHS Jurgen Department of Applied Mathematics Northwestern Polytechnical UniversityXi’an 710072China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversityXi’an 710072China Potsdam Institute for Climate Impact Research Potsdam 14412Germany

Tipping is a phenomenon in multistable systems where small changes in inputs cause huge changes in *** the parameter varies within a certain time scale,the rate will affect the tipping *** behaviors are undesirable in thermoacoustic systems,which are widely used in aviation,power generation and other ***,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 *** dynamical behaviors for the proposed thermoacoustic model are implemented through the reduced Fokker-Planck-Kolmogorov equation derived by a standard stochastic averaging ***,the tipping problems of the rate-dependent thermoacoustic systems with random fluctuations are studied by virtue of the obtained probability density *** 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 ***,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 *** results are of great significance for research in related fields such as aviation and land gas turbines.

关键词： thermoacoustic system colored noise rate-dependent tipping-delay phenomenon stochastic averaging method

来源：评论

学校读者我要写书评

暂无评论

Stability for acoustic wave motion with random force on the locally reacting boundary

arXiv

引用

arXiv 2022年

作者： Jiao, Zhe Xu, Yong School of Mathematics and Statistics Northwestern Polytechnical University Xi'An710129 China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Xi'An710072 China

This paper concerns about the stability for the acoustic wave motion with boundary frictions and random forces. We will show there exists a unique invariant measure for the stochastic evolution equation associated with this acoustic wave motion, and the invariant measure possesses the property of strong mixing. This result is new with respect to the literature on two accounts: (i) stochasticity is accounted for in the acoustic wave model;(ii) the controllability of the dynamical system modeling the acoustic wave motion implies the *** Codes 60H15, 60G10, 35L52, 35R60 Copyright © 2022, The Authors. All rights reserved.

关键词： Acoustic waves

来源：评论

学校读者我要写书评

暂无评论

Stability for nonlinear wave motions damped by time-dependent frictions

arXiv

引用

arXiv 2022年

作者： Jiao, Zhe Xu, Yong Zhao, Lijing Department of Applied Mathematics Northwestern Polytechnical University Xi’an710129 China MIIT key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Xi’an710072 China

We are concerned with the dynamical behavior of solutions to semilinear wave systems with time-varying damping and nonconvex force potential. Our result shows that the dynamical behavior of solution is asymptotically stable without any bifurcation and chaos. And it is a sharp condition on the damping coefficient for the solution to converge to some equilibrium. To illustrate our theoretical results, we provide some numerical simulations for dissipative sine-Gordon equation and dissipative Klein-Gordon *** Codes 35L70, 35B35 Copyright © 2022, The Authors. All rights reserved.

关键词： Damping

来源：评论

学校读者我要写书评

暂无评论

Precise Laplace approximation for mixed rough differential equation

arXiv

引用

arXiv 2022年

作者： Yang, Xiaoyu Xu, Yong Pei, Bin 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

This work focuses on the Laplace approximation for the rough differential equation (RDE) driven by mixed rough path (BH, W) with H ∈ (1/3, 1/2) as Ε → 0. Firstly, based on geometric rough path lifted from mixed fractional Brownian motion (fBm), the Schilder-type large deviation principle (LDP) for the law of the first level path of the solution to the RDE is given. Due to the particularity of mixed rough path, the main difficulty in carrying out the Laplace approximation is to prove the Hilbert-Schmidt property for the Hessian matrix of the Itô map restricted on the Cameron-Martin space of the mixed fBm. To this end, we imbed the Cameron-Martin space into a larger Hilbert space, then the Hessian is computable. Subsequently, the probability representation for the Hessian is shown. Finally, the Laplace approximation is constructed, which asserts the more precise asymptotics in the exponential *** Codes 60F10, 60G22, 60H10 Copyright © 2022, The Authors. All rights reserved.

关键词： Laplace transforms

来源：评论

学校读者我要写书评

暂无评论

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

SSRN

引用

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

来源：评论

学校读者我要写书评

暂无评论

基于子区域的结构拓扑优化并行策略

引用

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

来源：评论

学校读者我要写书评

暂无评论

Mechanical Properties of 3d-Printed Biomimetic Nacreous Composites: Experiments and Theory

SSRN

引用

SSRN 2024年

作者： Yan, Yi Zhao, Zheng-Ze Li, Jia Gao, Yuan Feng, Xi-Qiao Deng, Zi-Chen Department of Engineering Mechanics MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Xi’an710072 China Institute of Biomechanics and Medical Engineering AML Department of Engineering Mechanics Tsinghua University Beijing100084 China School of Mechanical Engineering Hebei University of Technology Tianjin300401 China

Nacre exhibits exceptional mechanical properties, which are attributed to its brick–mortar microstructure with an integration of stiff mineral platelets and soft organic interfaces. The rapidly developing 3D printing technique has been used to make nacre-inspired composites with similar brick–mortar structure. To date, however, there is still lack of a theoretical model to exactly predict the entire deformation and failure process of biomimetic nacreous composites consisting of various constituent phases with different geometric sizes. Based on a mesomechanical theoretical model, we derive the stress–strain response and macroscopic strength of the brick–mortar structure under uniaxial tension. The brick–mortar structure shows three typical failure modes, according to the occurrence of strain hardening and platelet fracture. Furthermore, we investigate how the mechanical properties of the brick–mortar structure depends on its geometry and constituent properties. It is found that increasing the aspect ratio of the platelets and the stiffness of the soft phase both enhance the strength of the brick–mortar structure. However, increasing the aspect ratio of the platelets promotes strain hardening, while increasing the stiffness of the soft phase leads to the disappearance of strain hardening. Finally, we utilize bi-material 3D printing technology to prepare biomimetic nacre samples and conduct uniaxial tensile mechanical tests, confirming the guiding significance of the theoretical model for the design of 3D-printed biomimetic nacreous composites. © 2024, The Authors. All rights reserved.

关键词： Biomimetics

来源：评论

学校读者我要写书评

暂无评论

Machine learning-integrated computational analysis on a blood-based ternary nanofluid flow in a stenosed artery with the artificial neural networks and modified finite difference approach

引用

Chaos, Solitons and Fractals 2025年 199卷

作者： Hussain, Mohib Lin, Du Waqas, Hassan Ali, Bagh Shah, Nehad Ali School of Mathematics and Statistics Northwestern Polytechnical University Xian710072 China MIIT Key Laboratory of Dynamics and Control Complex System Northwestern Polytechnical University Xi'an710072 China School of Naval Architecture Ocean and Energy Power Engineering Wuhan University of Technology Hubei Wuhan430063 China Department of Software Engineering Faculty of Science & Technology ILMA University 75190 Karachi Pakistan Department of Mechanical Engineering Sejong University Seoul05006 Korea Republic of

Heart failure and stroke continue to be the most common cause of global death, with atherosclerosis artery stenosis becoming a significant contributor. Although prior research has progressed in comprehending blood circulation behaviour, however, the incorporation of artificial intelligence (AI) and machine learning (ML) in the examination of ternary nanofluids for stenosed arterial diseases signifies a notable breakthrough in this domain. We proposes an integration of ML technique with computational fluid dynamics (CFD) to analyse the non-linear dynamics of thermal characterization in blood-based tri-hybrid nano-fluid flow, influenced by thermal radiation, variable heat sources and sinks, and aligned magnetic field effects within a blood artery exhibiting cosine stenosis. The investigation is based on AI approach, the Levenberg–Marquardt algorithm (LMA), with back propagation Artificial Neural Network (ANN-BP). The mathematical model is developed in the form of partial differentia equations and transformed into ordinary differential equation by similarity scaling, and then numerically evaluated by a modified finite difference approach, the Keller-Box method. The suggested ANN-LMA accuracy is compared to the ML solution for boundary layer flow. Regression values indicate an excellent fit between the predictions and the real data. It is observed that the inclined magnetic angle affects the drag force and heat transfer rate. There is a 27.9% increase in the heat transfer rate for ternary nano-fluid. Conclusively, the non-linear interaction between the magnetic field and nanofluid flow may significantly enhance heat transfer rates, which could have potential applications in biomedical sciences. © 2025 Elsevier Ltd

关键词： Magnetic levitation

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：