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

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

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Electrical activities of neural systems exposed to sinusoidal induced electric field with random phase

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Science China(Technological Sciences) 2019年第7期62卷 1141-1150页

作者： DU Lin CAO ZiLu LEI YouMing DENG ZiChen School of Natural and Applied Science Northwestern Polytechnical University Xi'an 710129 China MIIT Key Laboratory of Dynamics and Control of Complex Systems Xi'an 710129 China School of Mechanics Civil Engineering and Architecture Northwestern Polytechnical University Xi 'an 710129 China

The brain neural system is often disturbed by electromagnetic and noise environments, and research on dynamic response of its interaction has received extensive attention. This paper investigates electrical activity of Morris-Lecar neural systems exposed to sinusoidal induced electric field(IEF) with random phase generated by electromagnetic effect. By introducing a membrane depolarization model under the effect of random IEF, transition state of firing patterns, including mixed-mode oscillations(MMOs) with layered inter-spike intervals(ISI) and intermittency with a power law distribution in probability density function of ISI, is obtained in a single neuron. Considering the synergistic effects of frequency and noise, coherence resonance is performed by phase noise of IEF under certain parameter conditions. For the neural network without any internal coupling, we demonstrate that synchronous oscillations can be induced by IEF coupling, and suppression of synchronous spiking is achieved effectively by phase noise of IEF. Results of the study enrich the dynamical response to electromagnetic induction and provide insights into mechanisms of noise affecting information coding and transmission in neural systems.

关键词： induced electric field random phase electrical activity transition coherence resonance synchronous suppression

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Rotating machinery fault diagnosis based on convolutional neural network and infrared thermal imaging

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Chinese Journal of Aeronautics 2020年第2期33卷 427-438页

作者： Yongbo LI Xiaoqiang DU Fangyi WAN Xianzhi WANG Huangchao YU MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversityXi’an 710072China School of Mechanical Engineering Northwestern Polytechnical UniversityXi’an 710072China Institute of Unmanned System National University of Defense TechnologyChangsha 410073China

Rotating machinery is widely applied in industrial *** diagnosis of rotating machinery is vital in manufacturing system,which can prevent catastrophic failure and reduce financial ***,Deep Learning(DL)-based fault diagnosis method becomes a hot *** Neural Network(CNN)is an effective DL method to extract the features of raw data *** paper develops a fault diagnosis method using CNN for InfRared Thermal(IRT)***,IRT technique is utilized to capture the IRT images of rotating ***,the CNN is applied to extract fault features from the IRT *** the end,the obtained features are fed into the Softmax Regression(SR)classifier for fault pattern *** effectiveness of the proposed method is validated using two different experimental *** show that the proposed method has a superior performance in identification various faults on rotor and bearings comparing with other deep learning models and traditional vibration-based method.

关键词： Convolutional neural network Feature extraction Infrared thermography(IRT) Intelligent fault diagnosis Rotating machinery

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Particle swarm optimization-based algorithm of a symplectic method for robotic dynamics and control

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Applied Mathematics and Mechanics(English Edition) 2019年第1期40卷 111-126页

作者： Zhaoyue XU Lin DU Haopeng WANG Zichen DENG School of Natural and Applied Science Northwestern Polytechnical University School of Aeronautics Northwestern Polytechnical University Ministry of Industry and Information Technology(MIIT) Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Department of Engineering Mechanics Northwestern Polytechnical University

Multibody system dynamics provides a strong tool for the estimation of dynamic performances and the optimization of multisystem robot design. It can be described with differential algebraic equations(DAEs). In this paper, a particle swarm optimization(PSO) method is introduced to solve and control a symplectic multibody system for the first time. It is first combined with the symplectic method to solve problems in uncontrolled and controlled robotic arm systems. It is shown that the results conserve the energy and keep the constraints of the chaotic motion, which demonstrates the efficiency, accuracy, and time-saving ability of the method. To make the system move along the pre-planned path, which is a functional extremum problem, a double-PSO-based instantaneous optimal control is introduced. Examples are performed to test the effectiveness of the double-PSO-based instantaneous optimal control. The results show that the method has high accuracy, a fast convergence speed, and a wide range of *** the above verify the immense potential applications of the PSO method in multibody system dynamics.

关键词： robotic dynamics multibody system symplectic method particle swarm optimization(PSO)algorithm instantaneous optimal control

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A novel electron-phonon coupling thermoelasticity with Burgers electronic heat transfer

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Applied Mathematics and Mechanics(English Edition) 2023年第11期44卷 1927-1940页

作者： Hua WU Xinyi LI Yajun YU Zichen DENG School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi'an 710072China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversityXi'an 710072China State Key Laboratory for Strength and Vibration of Mechanical Structures Xi'an Jiaotong UniversityXi'an 710049China

The electron-phonon interaction can reveal the microscopic mechanism of heat transfer in *** two-step heat conduction considering electron-phonon interaction has become an effective theoretical model for extreme environments,such as micro-scale and ultrafast *** this work,the two-step heat transfer model is further extended by considering the Burgers heat conduction model with the secondorder heat flux rate for ***,a novel generalized electron-phonon coupling thermoelasticity is proposed with the Burgers electronic heat ***,the problem of one-dimensional semi-infinite copper strip subject to a thermal shock at one side is studied by the Burgers two-step(BTS)*** thermoelastic analytical solutions are systematically derived in the Laplace domain,and the numerical Laplace inversion method is adopted to obtain the transient *** new model is compared with the parabolic two-step(PTS)model and the hyperbolic two-step(HTS)*** results show that in ultrafast heating,the BTS model has the same wave front jump as the HTS *** present model has the faster wave speed,and predicts the bigger disturbed regions than the HTS *** deeply,all two-step models also have the faster wave speeds than one-step *** work may benefit the theoretical modeling of ultrafast heating of metals.

关键词： Burgers heat transfer electron-phonon coupling two-step generalized thermoelasticity

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Parallel solution of model predictive control using the alternating direction multiplier method

Parallel solution of model predictive control using the alte...

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4th IFAC Conference on Nonlinear Model Predictive control, NMPC'12

作者： Kögel, Markus Findeisen, Rolf Laboratory for Systems Theory and Automatic Control Otto-von-Guericke-University Magdeburg Germany Max Planck Institute for Dynamics of Complex Technical Systems Magdeburg Germany

ISBN: (纸本)9783902823076

In this work a parallel solution method for model predictive control is presented based on the alternating direction multiplier method. Our approach solves the overall problem by decomposing it along the time-axis into smaller subproblem. The resulting subproblems can be solved efficiently in parallel and are coupled by the multiplier update. We specifically considers box constraints, since this allows to use tailored methods to solve the subproblems. We outline the applicability of the approach and the performance using a multi-core systems. © 2012 IFAC.

关键词： Model predictive control

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Moiré ferroelectricity modulates light emission from a semiconductor monolayer

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Science Advances 2025年第19期11卷 eadt7789页

作者： Kim, Dong Seob Xiao, Chengxin Dominguez, Roy C. Liu, Zhida Abudayyeh, Hamza Lee, Kyoungpyo Mayorga-Luna, Rigo Kim, Hyunsue Watanabe, Kenji Taniguchi, Takashi Shih, Chih-Kang Miyahara, Yoichi Yao, Wang Li, Xiaoqin Department of Physics and center for complex Quantum Systems University of texas at Austin AustintX78712 United States Center for dynamics and control of Materials and texas Materials institute University of texas at Austin AustintX78712 United States New cornerstone Science laboratory Department of Physics University of Hong Kong Hong Kong Hong Kong Department of Physics Texas State University San MarcostX78666 United States Research center for electronic and Optical Materials National institute for Materials Science 1-1 namiki tsukuba305-0044 Japan Re-search center for Materials nanoarchitectonics National institute for Materials Science 1-1 namiki tsukuba305-0044 Japan Texas State University San MarcostX78666 United States

Semiconductor moiré superlattices, characterized by their periodic spatial light emission, unveil a new paradigm of engineered photonic materials. Here, we show that ferroelectric moiré domains formed in a twisted hexagonal boron nitride (t-hBN) substrate can modulate light emission from an adjacent semiconductor MoSe2 monolayer. The electrostatic potential at the surface of the t-hBN substrate provides a simple way to confine excitons in the MoSe2 monolayer. The excitons confined within the domains and at the domain walls are spectrally separated because of a pronounced Stark shift. Moreover, the patterned light emission can be dynamically controlled by electrically gating the ferroelectric domains, introducing a functionality beyond other semiconductor moiré superlattices. Our findings chart an exciting pathway for integrating nanometer-scale moiré ferroelectric domains with various optically active functional layers, paving the way for advanced nanophotonics and metasurfaces. copyright © 2025 the Authors, some rights reserved

关键词： III-V semiconductors

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On Klein tunneling of low-frequency elastic waves in hexagonal topological plates

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Applied Mathematics and Mechanics(English Edition) 2024年第7期45卷 1139-1154页

作者： Yuxin YAO Yuansheng MA Fang HONG Kai ZHANG Tingting WANG Haijun PENG Zichen DENG School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an710072China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversityXi’an710072China State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of TechnologyDalian116024Liaoning ProvinceChina

Incident particles in the Klein tunnel phenomenon in quantum mechanics can pass a very high potential *** the concept of tunneling into the analysis of phononic crystals can broaden the application *** this study,the structure of the unit cell is designed,and the low frequency(<1 k Hz)valley locked waveguide is realized through the creation of a phononic crystal plate with a topological phase transition *** defect immunity of the topological waveguide is verified,that is,the wave can propagate along the original path in the cases of impurities and ***,the tunneling phenomenon is introduced into the topological valley-locked waveguide to analyze the wave propagation,and its potential applications(such as signal separators and logic gates)are further explored by designing phononic crystal *** research has broad application prospects in information processing and vibration control,and potential applications in other directions are also worth exploring.

关键词： topological metamaterial elastic wave Klein tunneling valley-locked waveguide

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Navigation and guidance strategy planning for UAV urban operation

Navigation and guidance strategy planning for UAV urban oper...

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AIAA Infotech @ Aerospace Conference, 2016

作者： Watanabe, Yoko Veillard, Aurélien Chanel, Caroline ONERA - The French Aerospace Laboratory Systems Control and Flight Dynamics Department Toulouse31000 France ISAE-SUPAERO Complex Systems Engineering Department Toulouse31000 France

ISBN: (数字)9781624103889

ISBN: (纸本)9781624103889

This paper proposes a concept of navigation and guidance strategy planner for urban operation of a VTOL-type UAV. One of major challenges of UAV autonomous navigation in an urban environment is to deal with the risk of GPS signal occlusion. In order to address this issue, various approaches have been proposed for GPS-independent UAV navigation and guidance such as visual odometry and visual servoing control. In this context, this work supposes that different navigation and guidance modes using different set of sensors are available onboard an UAV. An idea of the proposed planner is to anticipate the navigation and guidance performance degradation (or amelioration) due to unavailability (or availability) of certain mode in the path planning task. The planning problem is formulated as a 5D (3D position + selection of navigation and guidance modes) graph search problem, where the localization and path execution uncertainties are propagated according to a model of corresponding modes for each node transition. Node transition is denied if the path execution uncertainty ellipsoid intersects with any obstacle. A minimizing cost function is defined by a volume of the path execution uncertainty corridor, as it implies minimizing path distance and execution accuracy at the same time. A deterministic graph search algorithm is applied to find a flight path with specified navigation and guidance mode transitions which minimizes the defined cost function. Simulations are performed by using path planning configurations given in an existing UAV obstacle field navigation benchmark, and the results are presented to prove the proposed navigation and guidance strategy planning concept. © 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Unmanned aerial vehicles (UAV)

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Surface deformation-dependent mechanical properties of bending nanowires:an ab initio core-shell model

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Applied Mathematics and Mechanics(English Edition) 2022年第2期43卷 219-232页

作者： Ye XIAO J.SHANG L.Z.KOU Chun LI School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an710072China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversityXi’an710072China School of Mechanical Medical and Process EngineeringQueensland University of TechnologyBrisbaneQLD4000Australia

An ab initio core-shell model is proposed to evaluate the surface effect in bending nanowires,in which the elastic modulus depends on the surface relaxation and deformation induced by external *** using first-principles calculations based on the density functional theory(DFT),the surface and bulk properties are calculated for Ag,Pb,and Si *** obtained theoretical predictions of the effective Young’s modulus of nanowires agree well with the experimental data,which shows that the fixed-fixed nanowire is stiffened and the cantilevered nanowire is softened as the characteristic size of the cross section ***,the contrastive analysis on the two kinds of nanowires demonstrates that increasing the nanowire aspect ratio would enhance the surface *** present results could be helpful for understanding the size effect in nanowires and designing nanobeam-based devices in nanoelectromechanical systems(NEMSs).

关键词： surface effect density functional theory(DFT) surface relaxation surface stress nanowire

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