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Mesoscale Damage Analysis of UHTCC under Seawater Dry-Wet Cycles Using Particle Flow Theory

Mechanics Research Communications 2025年

作者： Ruiqing Chang Zhanyou Yan Li Zhao Shuo Xu Xiya Zhao Yiqing Yan School of Traffic and Transportation Shijiazhuang Tiedao University Hebei China School of Civil Engineering Shijiazhuang Tiedao University Hebei China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Hebei China

This study investigates the effects of seawater dry-wet cycling on the dynamic compressive properties of Ultra-High Toughness Cementitious Composites (UHTCC) using a discrete element model developed with Particle Flow Code (PFC2D). Five sets of controlled laboratory dynamic compression tests with varying dry-wet cycles were conducted alongside numerical simulations to examine force chain evolution, crack propagation, and acoustic emission characteristics at the mesoscale level. Results demonstrate good agreement between numerical simulations and experimental data. The peak stress of UHTCC exhibited a non-monotonic response to increasing dry-wet cycles, initially rising before declining after reaching its maximum at 90 days. Acoustic emission events showed strong correlation with crack development, where increased crack density corresponded to higher signal intensity and event frequency. The developed discrete element model successfully captured the complete internal fracture process at microscopic scales, demonstrating its effectiveness for analyzing complex mechanical behaviors in cementitious composites.

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Reinforcement Learning-based Token Pruning in Vision Transformers: A Markov Game Approach

arXiv

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arXiv 2025年

作者： Lu, Chenglong Liang, Shen Wang, Xuewei Wang, Wei School of Computer Science Fudan University China LIPADE Université Paris Cité Paris France State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Shijiazhuang Tiedao University Shijiazhuang China

Vision Transformers (ViTs) have computational costs scaling quadratically with the number of tokens, calling for effective token pruning policies. Most existing policies are handcrafted, lacking adaptivity to varying inputs. Moreover, they fail to consider the sequential nature of token pruning across multiple layers. In this work, for the first time (as far as we know), we exploit Reinforcement Learning (RL) to data-adaptively learn a pruning policy. Formulating token pruning as a sequential decision-making problem, we model it as a Markov Game and utilize Multi-Agent Proximal Policy Optimization (MAPPO) where each agent makes an individualized pruning decision for a single token. We also develop reward functions that enable simultaneous collaboration and competition of these agents to balance efficiency and accuracy. On the well-known ImageNet-1k dataset, our method improves the inference speed by up to 44% while incurring only a negligible accuracy drop of 0.4%. The source code is available at https://***/daashuai/rl4evit. © 2025, CC BY.

关键词： Reinforcement learning

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Research on hunting stability and bifurcation characteristics of nonlinear stochastic wheelset system

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Applied Mathematics and Mechanics(English Edition) 2023年第3期44卷 431-446页

作者： Peng WANG Shaopu YANG Yongqiang LIU Pengfei LIU Xing ZHANG Yiwei ZHAO State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversityShijiazhuang 050043China School of Traffic and Transportation Shijiazhuang Tiedao UniversityShijiazhuang 050043China School of Mechanical Engineering Shijiazhuang Tiedao UniversityShijiazhuang 050043China

A stochastic wheelset model with a nonlinear wheel-rail contact relationship is established to investigate the stochastic stability and stochastic bifurcation of the wheelset system with the consideration of the stochastic parametric excitations of equivalent conicity and suspension *** wheelset is systematized into a onedimensional(1D)diffusion process by using the stochastic average method,the behavior of the singular boundary is analyzed to determine the hunting stability condition of the wheelset system,and the critical speed of stochastic bifurcation is *** stationary probability density and joint probability density are derived *** on the topological structure change of the probability density function,the stochastic Hopf bifurcation form and bifurcation condition of the wheelset system are *** effects of stochastic factors on the hunting stability and bifurcation characteristics are analyzed,and the simulation results verify the correctness of the theoretical *** results reveal that the boundary behavior of the diffusion process determines the hunting stability of the stochastic wheelset system,and the left boundary characteristic value cL=1 is the critical state of hunting ***,stochastic D-bifurcation and P-bifurcation will appear in the wheelset system,and the critical speeds of the two kinds of stochastic bifurcation decrease with the increase in the stochastic parametric excitation intensity.

关键词： stochastic wheelset system stochastic average method singular boundary hunting stability stochastic Hopf bifurcation

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Speed following control of truck based on driver intention recognition 4

Speed following control of truck based on driver intention r...

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4th CAA International Conference on Vehicular Control and Intelligence, CVCI 2020

作者： Wang, Guiyang Li, Shaohua Wang, Hesen State Key Laboratory of Mechanical Behavior in Traffic Engineering Structure and System Safety Dept. Name of Organization Shijiazhuang050043 China

ISBN: (纸本)9781728184968

Autonomous emergency braking (AEB) system enables vehicles to avoid collisions or mitigate the damage. Due to large braking distance, a safety distance model on the basis of the vehicles driving state and the process of vehicle braking is established. The driver's reaction time and early warning vehicle speed following controller are established, and the predictive AEB algorithm based on the driver's operation intention is established. Finally, TruckSim-Matlab/Simulink co-simulation for the AEB control strategy is conducted. The simulation result shows that the proposed control strategy can hierarchically warn and automatically brake, which is effective. © 2020 IEEE.

关键词： MATLAB

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Integrated Active Suspension and Anti-Lock Braking Control for Four-Wheel-Independent-Drive Electric Vehicles

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Chinese Journal of mechanical engineering 2024年第1期37卷 87-98页

作者： Ze Zhao Lei Zhang Xiaoling Ding Zhiqiang Zhang Shaohua Li Liang Gu National Engineering Research Center for Electric Vehicles Beijing Institute of TechnologyBeijing 100081China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversityShijiazhuang 050043China

This paper presents an integrated control scheme for enhancing the ride comfort and handling performance of a four-wheel-independent-drive electric vehicle through the coordination of active suspension system(ASS)and anti-lock braking system(ABS).First,a longitudinal-vertical coupled vehicle dynamics model is established by integrating a road input *** the coupling mechanisms between longitudinal and vertical vehicle dynamics are *** ASS-ABS integrated control system is proposed,utilizing an H∞controller for ASS to optimize load transfer effect and a neural network sliding mode control for ABS ***,the effectiveness of the proposed control scheme is evaluated through comprehensive tests conducted on a hardware-in-loop(HIL)test *** HIL test results demonstrate that the proposed control scheme can significantly improve the braking performance and ride comfort compared to conventional ABS control methods.

关键词： Four-wheel-independent-drive electric vehicles Active suspension system(ASS) Anti-lock braking system(ABS) Vertical-longitudinal vehicle dynamics

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Influence of vehicle-road coupled vibration on tire adhesion based on nonlinear foundation

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Applied Mathematics and Mechanics(English Edition) 2021年第5期42卷 607-624页

作者： Junning ZHANG Shaopu YANG Shaohua LI Yongjie LU Hu DING School of Traffic and Transportation Shijiazhuang Tiedao UniversityShijiazhuang 050043China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang 050043China Shanghai Institute of Applied Mathematics and Mechanics Shanghai Key Laboratory of Mechanics in Energy EngineeringShanghai UniversityShanghai 200072China

The influence of pavement vibration on tire adhesion is of great significance to the structure design of vehicle and *** adhesion between tire and road is the key to studying vehicle dynamics,and the precise description of tire adhesion affects the accuracy of dynamic vehicle ***,in most models,only road roughness is considered,and the pavement vibration caused by vehicle-road interaction is *** this paper,a vehicle is simplified as a spring-mass-damper oscillator,and the vehicle-pavement system is modeled as a vehicle moving along an Euler-Bernoulli beam with finite length on a nonlinear *** road roughness is considered as a sine wave,and the shear stress is ignored on the *** to the contact form between tire and road,the LuGre tire model is established to calculate the tire adhesion *** Galerkin method is used to simplify the partial differential equations of beam vibration into finite ordinary differential equations.A product-to-sum formula and a Dirac delt function are used to deal with the nonlinear term caused by the nonlinear foundation,which realizes the fast and accurate calculation of super-high dimensional nonlinear ordinary differential *** addition,the dynamic responses between the coupled system and the traditional uncoupled system are compared with each *** obtained results provide an important theoretical basis for research on the influence of vehicle-road coupled vibration on tire adhesion.

关键词： vehicle system dynamics vehicle-road coupled vibration LuGre tire model Galerkin method

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Love Waves in a Piezoelectric Semiconductor Thin Film on an Elastic Dielectric Half-Space

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固体力学学报（英文版） 2023年第1期36卷 45-54页

作者： Ru Tian Guoquan Nie Jinxi Liu Ernian Pan Yuesheng Wang State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversityShijiazhuang 050043China Department of Mathematics and Physics Shijiazhuang Tiedao UniversityShijiazhuang 050043China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversityShijiazhuang 050043China School of Mechanical Engineering Shijiazhuang Tiedao UniversityShijiazhuang 050043China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversityShijiazhuang 050043China College of Engineering and Institute of Pioneer Semiconductor Innovation National Yang Ming Chiao Tung UniversityTaiwanChina Department of Mechanics Beijing Jiaotong UniversityBeijing 100044China

In this paper,Love waves propagating in a piezoelectric semiconductor(PSC)layered structure are investigated,where a PSC thin film is perfectly bonded on an elastic dielectric *** dispersion equations are derived *** influence of semiconducting properties on the propagation characteristics is examined in *** results show that the semiconducting effect reduces the propagation speed,and that the Love waves can propagate with a speed slightly higher than the shear wave speed of the elastic dielectric *** wave speed and attenuation significantly depend on the steady-state carrier density and the thickness of the PSC thin *** is also found that when the horizontal biasing electric field is larger than the critical value(corresponding to the zero attenuation),the wave amplitude is *** findings are useful for the analysis and design of various surface wave devices made of PSC.

关键词： Love wave Piezoelectric semiconductor Layered structure Dispersion Attenuation

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Dimension reduction graph-based sparse subspace clustering for intelligent fault identification of rolling element bearings

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International Journal of mechanical system Dynamics 2021年第2期1卷 207-219页

作者： Le Zhao Shaopu Yang Yongqiang Liu State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversityShijiazhuangHebeiChina School of Traffic and Transportation Shijiazhuang Tiedao UniversityShijiazhuangHebeiChina

Sparse subspace clustering(SSC)is a spectral clustering *** high-dimensional data are often dispersed over the union of many low-dimensional subspaces,their representation in a suitable dictionary is ***,SSC is an effective technology for diagnosing mechanical system *** main purpose is to create a representation model that can reveal the real subspace structure of high-dimensional data,construct a similarity matrix by using the sparse representation coefficients of high-dimensional data,and then cluster the obtained representation coefficients and similarity matrix in ***,the design of SSC algorithm is based on global expression in which each data point is represented by all possible cluster data *** leads to nonzero terms in nondiagonal blocks of similar matrices,which reduces the recognition performance of *** improve the clustering ability of SSC for rolling bearing and the robustness of the algorithm in the presence of a large number of background noise,a simultaneous dimensionality reduction subspace clustering technology is provided in this *** the feature extraction of envelope signal,the dimension of the feature matrix is reduced by singular value decomposition,and the Euclidean distance between samples is replaced by correlation distance.A dimension reduction graph-based SSC technology is *** and bearing data of Western Reserve University show that the proposed algorithm can improve the accuracy and compactness of clustering.

关键词： correlation distance dimension reduction sparse subspace clustering

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Periodic-phase-diagram similarity method for weak signal detection

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International Journal of mechanical system Dynamics 2021年第2期1卷 248-255页

作者： Ruilan Tian Yangkun Zhang Shaopu Yang Kai Yuan Qiang Xue Quanrong Ren State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversityShijiazhuangChina Department of Engineering Mechanics Shijiazhuang Tiedao UniversityShijiazhuangChina

The periodic-phase-diagram similarity method is proposed to identify the frequency of weak harmonic *** key technology is to find a set of optimal coefficients for Duffing system,which leads to the periodic motion under the influence of weak signal and strong *** the phase diagram similarity,the influences of strong noise on the similarity of periodic phase diagram are *** principle of highest similarity of periodic phase diagram with the same frequency is detected by discussing the persistence of similarity of periodic motion phase diagram under the strong noise and the periodic-phase-diagram similarity method is *** weak signals of early fault and strong noise are input into Duffing system to obtain the identified *** stochastic subharmonic Melnikov method is extended to obtain the conditions of the optimal coefficients for the identified *** on the results,the constructed frequency conversion harmonic weak signals are considered to form a datum periodic *** the change of frequency in the datum periodic system,the phase diagram similarity of the two constructed systems can be *** on the periodic-phase-diagram similarity method,the frequency of weak harmonic signals can be identified by the principle of highest similarity of periodic phase diagram with the same *** results of numerical simulation and the early fault diagnosis results of actual bearings verify the feasibility of the periodic-phase-diagram similarity *** accuracy of the detection effect is 97%,and the minimum signal-to-noise ratio is−80.71 dB.

关键词： periodic system signal-to-noise ratio stochastic subharmonic Melnikov method strong noise weak signal

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The Scheme to Determine the Convergence Term of the Galerkin Method for Dynamic Analysis of Sandwich Plates on Nonlinear Foundations

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Acta Mechanica Solida Sinica 2021年第1期34卷 1-11页

作者： Hong-Yan Chen Hu Ding Shao-Hua Li Li-Qun Chen Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai Institute of Applied Mathematicsand MechanicsSchool of Mechanics and Engineering ScienceShanghai UniversitygShanghai 200444China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversitxyShiyiazhuang 050043China

The vibration of a plate resting on elastic foundations under a moving load is of great significance in the design of many engineering fields,such as the vehicle-pavement system and the aircraft-runway *** or runways are always laminated *** Galerkin truncation method is widely used in the research of *** number of truncation terms directly affects the convergence and accuracy of the response ***,the selection of the number of truncation terms has not been clearly stated.A nonlinear viscoelastic foundation model under a moving load is *** on the natural frequency of linear undisturbed derivative systems,the truncation terms are used to determine the convergence of vibration *** criterion for the convergence of the Galerkin truncation term is *** scheme is related to the natural frequency with high efficiency and *** the dynamic response of the sandwich beam under a moving load,the feasibility of the scheme is *** effects of different system parameters on the scheme and the truncation convergence of dynamic response are *** research in this paper can be used as a reference for the study of the vibration of elastic foundation ***,the model established and the truncation analysis method proposed are helpful for studying the vibration of vehicle-pavement system and related systems.

关键词： ndwich plate Galerkin method Convergence Nonlinear foundation

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