检索结果-内蒙古大学图书馆

SSRN 2023年

作者： Cui, Huimin Han, Mengjiao Zhang, Jitao Han, Zhiming Xu, Feng Liu, Qingkuan State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China Innovation Center for Wind Engineering and Wind Energy Technology of Hebei Province Shijiazhuang050043 China Department of Mathematics and Physics Shijiazhuang Tiedao University Shijiazhuang050043 China School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China School of Physical Science and Engineering Beijing Jiaotong University Beijing100044 China

Solar chimneys can induce natural ventilation through solar radiation. However, sufficient theoretical studies are needed as a basis in order to fully exploit passive design in practical green building design. In this study, the heat transfer properties of turbulent natural convective flows in a combined solar chimney with a thermal flux at the absorption wall are investigated by theoretical analysis and numerical simulations. Two different flow patterns have been discovered, one with an obvious thermal boundary layer flow pattern and the other without, based on the high Rayleigh number. For the flow development in these two flow regimes, the transient scaling analysis is performed separately and the control mechanism for each phase is presented. Scaling correlations of air flow speed, temperature, and mass flow rate have been established to describe the ventilation properties of solar chimneys. The corresponding numerical simulation data is used for scaling verification. Ventilation times are calculated for a solar chimney with aspect ratio A=7.5 to provide a basis for the devise of a solar chimney. © 2023, The Authors. All rights reserved.

关键词： Boundary layers

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A new control strategy for high speed train and its simulation analysis

A new control strategy for high speed train and its simulati...

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第八届国际振动工程会议

作者： Yiwei Zhao Shaopu Yang Yongqiang Liu Yingying Liao State Key Laboratory of Mechanical behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Department of Transportation Shijiazhuang Tiedao University Department of Mechanical Engineering Shijiazhuang Tiedao University Department of Civil Engineering Shijiazhuang Tiedao University

For a long time, the dynamic performance of high-speed train has been studied by many experts. And it will continue to be studied in the future with the rapid development of high-speed trains. The ride comfort and safety of trains which is the part of the dynamic performance is studied in this paper through applying the control method to the secondary lateral dampers and yaw dampers. Firstly, a train model is built by multi-body dynamics software UM. Then the co-simulation model is built in Simulink for the further study. The second, the multi-objective optimization for the damper damping coefficient of the secondary lateral dampers and yaw dampers is carried out in a straight track. The optimal damping coefficient that can improve the ride comfort and safety simultaneously is obtained. The objectives of optimization are the lateral acceleration and derailment coefficient. Similarly, the multi-objective optimization for the damping coefficient of the two kind of dampers is carried out in a curve track. The optimal damping coefficient is obtained. In order to keep the ride comfort and safety of the train, no matter in a straight track or in a curve track, the semi-active control method is proposed to adjust the damping coefficient. In this way, the damping coefficients of the two kinds of shock absorbers are always ***, the train model is simulated and *** results show that the control method that the two kinds of shock absorbers are controlled at the same time can significantly improve the ride comfort and safety of the train whether it's running in a straight track or a curve track. In other words,multi-point control can improve the train dynamic performance comprehensively.

关键词： high-speed train co-simulation semi-active ride comfort safety

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Erratum: ‘Scattering of SH Waves Around Circular Canyon in Inhomogeneous Wedge Space’

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Geophysical Journal International 2021年第1期226卷 345-350页

作者： Zailin Yang Xinzhu Li Yunqiu Song Guanxixi Jiang Menghan Sun Xueqian Fang College of Aerospace and Civil Engineering Harbin Engineering University Harbin China Key Laboratory of Advanced Material of Ship and Mechanics Ministry of Industry and Information Technology Harbin Engineering University Harbin China sunmenghan163@*** State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang China

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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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The Effects of Row Spacing and Ground Clearance On the Wind Load of Photovoltaic (Pv) Arrays

SSRN

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SSRN 2023年

作者： Xu, Ang Ma, Wenyong Yuan, Huanxin Lu, Lihe State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang051132 China Key Laboratory of Road and Railway Engineering Safety Ministry of Education Shijiazhuang Tiedao University Shijiazhuang Hebei050043 China Innovation Center for Wind Engineering and Wind Energy Technology of Hebei Province Hebei050043 China School of Civil Engineering Wuhan University Wuhan430072 China Inner Mongolia Electric Power Survey & Design Istitute Co. Ltd. Huhehot Inner Mongolia 010011 China

Row spacing and ground clearance have a significant effect on the wind load of a photovoltaic (PV) array. Based on wind tunnel tests and numerical simulations with the self-sustainable equilibrium atmospheric boundary layer, the influences of row spacing and ground clearance on the wind load of PV arrays are analysed, and the mechanism of the wind-induced interference effect is determined by flow field analysis. The results show that the ground clearance affects the wind load distribution on the PV module, and this effect has an inconsiderable impact on the net wind pressure on the PV modules. The effect of row spacing on the wind load of PV arrays is more significant, and this effect is mainly manifested in the shielding effect. The tilt angle is the main factor that affects the size of the vortex scale which significantly influences the wind load. The ground clearance, row spacing and tilt angle all affect the torque coefficient on the PV module. The larger the ground clearance is, the larger the torque coefficient. Finally, the wind load coefficients and reduction factors are presented as a recommendation for wind resistance design of PV arrays. © 2023, The Authors. All rights reserved.

关键词： Atmospheric boundary layer

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Soft-Landing Dynamics of a Type of Four-Legged Space Lander

SSRN

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SSRN 2024年

作者： Shi, Tengfei Shi, Tengfei Yang, Yinping Zhang, Zhijuan Liu, Cuicui Liu, Caishan Ma, Daolin Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and Aerospace Engineering Southwest Jiaotong University Chengdu610031 China State Key Laboratory for Turbulence and Complex Systems College of Engineering Peking University Beijing100871 China Institute of Dynamics and Control College of Mechanical Engineering and Applied Electronics Technology Beijing University of Technology Beijing100871 China China Academy of Space Technology Beijing100094 China School of Naval Architecture Ocean and Civil Engineering Shanghai Jiao Tong University Shanghai200240 China Key Laboratory of Marine Intelligent Equipment and System Ministry of Education Shanghai200240 China

Analyzing the landing dynamics response is essential for enhancing the success rate of surface explorations on Mars, the moon, or asteroids. This paper develops a comprehensive dynamics model for a space lander equipped with four sets of buffer legs, each consisting of a primary strut, two secondary struts, and a footpad, during its soft landing process. The degrees of freedom of the main body and the footpads are defined as generalized coordinates to describe the motion of the space lander. The compression force of the buffer struts is obtained by interpolating real experimental data, and the contact force between the footpad and the ground is calculated using Archimedes law for granular media. Then, the dynamical model for the lander in terms of minimal degrees of freedom can be constructed by applying the Lagrange equations of the second kind. The proposed dynamics model is validated by the experiments of a single-legged lander vertical touchdown and a four-legged lander free touchdown. Moreover, histories of buffer force, acceleration of the main body, and other key physical quantities are computed to investigate the landing process. This highly efficient and accurate dynamics model provides a method to perform extensive simulations to design and optimize a soft landing process. © 2024, The Authors. All rights reserved.

关键词： Landing

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Research on Brake Failure Control of Heavy Commercial Vehicles Based on Turning Conditions

Research on Brake Failure Control of Heavy Commercial Vehicl...

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Conference on Vehicle Control and Intelligence (CVCI)

作者： Yongjie Lu Fahui Wang Guangfeng Zhang State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang China

ISBN: (数字)9781728184975

ISBN: (纸本)9781728184982

With the rapid rise of the transportation industry, commercial vehicles as an important means of transportation, its safety and stability are paid more and more attention. In order to improve the safety performance of heavy commercial vehicles when braking failure occurs under turning conditions. Based on the vehicle dynamics characteristics, this paper designed the stability control strategy in the case of brake failure in the above conditions, designed a fuzzy PID controller based on yurch angular velocity control, carried out the Trucksim-Simulink joint simulation and hardware in the loop experiment to jointly verify the control effect of the brake. The results show that the influence of vehicle brake failure on vehicle driving stability is reduced, the performance of vehicle brake under long and downhill conditions and turning conditions is improved, and the safety stability of vehicle brake failure in hardware loop is improved, which meets the requirements of national standards for vehicle braking.

关键词： Stability criteria Turning Hardware safety Brakes Acceleration Standards

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Experimental Investigations on the Wind Load Interference Effects of Single-Axis Solar Tracker Arrays

SSRN

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SSRN 2022年

作者： Ma, Wenyong Zhang, Weida Zhang, Xiaobin Chen, Wei Tan, Qiang School of Civil Engineering Shijiazhuang Tiedao University Hebei 050043 China Innovation Center for Wind Engineering and Wind Energy Technology of Hebei Province Hebei 050043 China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China School of Mechanical Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China Jiangsu Guoqiang Singsun Energy Co. Ltd 213300 China

Aiming at the interference effect of wind loads on single-axis solar tracker arrays, this study conducts rigid-model pressure measurement wind tunnel tests on a single-row solar tracker and solar tracker arrays. The effects of the tilt angle and wind direction on aerodynamic characteristics are examined. The basic characteristics of the wind-induced interference effects of a single-axis solar tracker array are clarified. The results reveal that when the tilt angle is small, the interference effect is small, the tilt angle increases, the interference effect becomes stronger. From the mean pressure and torque coefficients, the interference effect is mainly manifested as a shielding effect. Based on the fluctuating pressure and torque coefficients, the interference effect appears as a shielding effect and an amplification effect in small- and large-tilt angle ranges, respectively. The wind load power spectrum of the solar modules in the rear-row of the solar tracker arrays presents remarkable frequency peaks, and experiences stronger wind-induced vibrations than the front-row modules. The influence of the wind direction results in nonuniform distributions of wind loads along the length of the solar tracker. Thus, the enhancement in wind loads on the edge areas of solar arrays caused by the wind direction should be considered. © 2022, The Authors. All rights reserved.

关键词： Wind stress

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Periodically stable vibration of homogeneous rod-shaped double pendulum under parametric excitation

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Zhendong yu Chongji/Journal of Vibration and Shock 2020年第16期39卷 231-235页

作者： Zhang, Hongqiao Tian, Ruilan Chen, Enli Guo, Xiuying School of Mechanical Engieering Shijiazhuang Tiedao University Shijiazhuang050043 China State Key Laboratory of Mechanical Behavior in Transfertation Engineering Structure and System Safety Shijiazhuang Tiedao University Shijiazhuang050043 China

Based on the motion of both legs in the walking process of a robot, a homogeneous rod-shaped pendulum motion model under parametric was designed. The motion differential equation of the system was established by the Lagrange method, and its dimensionless treatment was carried out. Nonlinear dynamic analysis of the system with two natural frequencies ratio of 1:3, the relationship curve between length ratio and mass ratio of double pendulum was obtained by theoretical deduction, the mass ratio of two rods could be determined according to the length ratio. On this basis, the differential equation was linearized and decoupled into two Mathieu equations. Finally, the stability interval of the system was determined by the Lindstede-Poincare perturbation method (L-P), and the correctness of the results was verified by numerical simulation with Matlab. © 2020, Editorial Office of Journal of Vibration and Shock. All right reserved.

关键词： Equations of motion

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Experimental and calculation of flexuralmechanical properties of reinforced reactive powder concrete simply supported beams

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Gongcheng Lixue/engineering Mechanics 2020年第6期37卷 131-139页

作者： Li, Hai-Yan Zhang, Bo-Yang Li, Jin-Shu State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University ShijiazhuangHebei050043 China Mechanics Engineering Department Shijiazhuang Tiedao University ShijiazhuangHebei050043 China

Reactive powder concrete (RPC) has superior strength, high toughness and excellent durability compared with ordinary concrete (OC). The calculation method of the strength and stiffness of components of RPC is inevitably different from ordinary concrete components. A full-scale test on the bending performance of four reinforced RPC simply supported beams is conducted. The cracking moment, ultimate bending moment and mid-span load-deformation curve of the beam are obtained. The bending deformation characteristics and failure modes of RPC simply supported beams are revealed, and the calculation formulas for the cracking moment and the bending strength of the RPC simply supported beams are derived. The ultimate compressive strain of steel fiber reinforced RPC is 4394 μΕ~5200 μΕ, and the cracking strain is 690 μΕ~820 μΕ, which are much larger than those of OC. Due to the addition of steel fibers, the influence of the tensile stress of the RPC tension zone must be considered. The derived cracking moment, the normal section bending capacity and the calculated value of the stiffness are in good agreement with the experimental values. The calculation formula has high precision and can be used for the design calculation of reinforced RPC beams. © 2020, engineering Mechanics Press. All right reserved.

关键词： Stiffness

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