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Comparative Study on Perforation Resistance of Nacre-Like, Layered and Encased Ceramic/Polyurea Composite Plates Subjected to Low Velocity Impact of Different Shaped Impactors

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SSRN 2023年

作者： Xiao, Yihua Zhang, Xuan Xiao, Wei State Key Laboratory of Performance Monitoring and Protecting of Rail Transit Infrastructure East China Jiaotong University Nanchang330013 China School of Mechatronics and Vehicle Engineering East China Jiaotong University Nanchang330013 China

Ceramic and polyurea have respective advantages in impact protection. Composite structures combining ceramic with polyurea may make use of advantages of both materials. Their impact performance is dependent on structural configuration and impactor shape. In this work, perforation resistance of ceramic/polyurea composite plates of different structural configurations subjected to low velocity impact of different shaped impactors are investigated. Firstly, perforation experiment of polyurea sheet and bending fracture experiment of ceramic sheet are performed, and numerical simulations for the experiments are conducted to validate constitutive models and parameters for the polyurea and ceramic materials. Then, using the validated constitutive models and parameters, numerical models for nacre-like, layered and encased ceramic/polyurea composite plates subjected to impact of conical, hemispherical and blunt impactors are established. Numerical simulations are conducted to reveal failure modes and energy absorption characteristics of the three kinds of composite plates. Numerical results show that the nacre-like plate exhibits a similar petalling failure mode under impact of different shaped impactors, while the layered and encased plates show different failure modes as the impactor shape changes. With almost the same areal density, the nacre-like plate is superior to the other two composite plates in energy absorption, and its advantage is especially distinct for the impact of blunt impactor. Contact force histories are analyzed to enhance the understanding of perforation resistance of the composite plates. © 2023, The Authors. All rights reserved.

关键词： Failure modes

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Multi-Factor Analysis of Spatio-Temporal Stress Evolution in Shale Reservoir Based on Plackett-Burman and Central Composite Design

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SSRN 2024年

作者： Mu, Shuxing Zhao, Lianheng Liu, Yuxuan School of Civil Engineering Central South University Hunan Province Changsha410075 China School of Civil Engineering Central South University Key Laboratory of Heavy-Haul Railway Engineering Structure Ministry of Education Hunan Provincial Key Laboratory for Disaster Prevention and Mitigation of Rail Transit Engineering Structures Hunan Province Changsha410075 China State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum University Sichuan Province Chengdu610500 China

Multi-factor analysis and accurate prediction of dynamic stress in shale reservoirs are of great practical significance for designing gas well fracturing. The seepage-geomechanics of reservoirs in the development of shale gas is a multi-physical and multi-scale coupling problem. In this paper, we propose a hydro-mechanical model considering geomechanical heterogeneity and multi-scale seepage mechanisms of shale gas to simulate the spatio-temporal evolution of gas well stress. The numerical model is validated by Terzaghi's theory. The Plackett-Burman method is used for sensitivity analysis to screen the significant factors affecting reservoir stress. Then, in combination with central composite design and numerical simulation, the combined effect of significant factors on reservoir stress is studied, and a mathematical model for predicting stress is established. The results show that after considering the heterogeneity, the minimum horizontal stress fluctuation range is 20.25 MPa~44.03 MPa and the maximum horizontal stress fluctuation range is 26.46 MPa~49.77 MPa in the area controlling hydraulic fracture. The initial reservoir pressure, as well as the length and width of hydraulic fractures, are the key factors influencing reservoir stress. The proposed method is effective for predicting reservoir stress. The research results are helpful for gaining a deeper understanding of the evolution mechanism of dynamic stress fields in shale reservoirs and provide guidance for treatment design and dynamic optimization of gas wells. © 2024, The Authors. All rights reserved.

关键词： Factor analysis

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Study on axial compressive behavior of concrete-filled steel tube columns with mult-source mixed recycled coarse aggregate

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Structures 2025年 78卷

作者： Wang, Wenpeng Xu, Kaicheng Xu, Hanqi Zhang, Liqing School of Civil Engineering and Architecture East China Jiaotong University Nanchang330013 China State Key Laboratory of Performance Monitoring and Protecting of Rail Transit Infrastructure East China Jiaotong University Nanchang330013 China Zhongheng Construction Group Co. Ltd Nanchang330200 China School of Civil Engineering and Architecture Nanchang University Nanchang330031 China

The quality of recycled coarse aggregate (RCA) is highly effected by the strength of original concrete. However, it is hard to confirm the source and strength of original concrete of mixed recycled coarse aggregate (MRCA) used in the actual engineering. In order to study the effects of multi-sources MRCA on the axial compressive behavior of concrete confined by steel tubes and use easily measured parameters to build a stress-strain model, 6 different types of MRCA were collected and the axial compressive tests and analysis of 63 plain mixed recycled concrete (PMRC) columns and 21 mixed recycled concrete-filled steel tube (MRCFST) columns were carried out. The results show that there are more cracks and holes in the microstructure of mixed recycled concrete (MRC), which results in a lower compressive capacity of PMRC than plain ordinary concrete (POC). The constraint of steel tube weakens the negative influence of MRCA on the compressive capacity of MRCFST, especially for the circular cross-section. The peak strain of MRCFST is smaller than that of ordinary CFST, and the reduction of peak strain of circular MRCFST is the smallest in different cross sections. Meanwhile, the peak strains of MRCFST columns in circular, square, and rectangular sections are all approximately linearly related to the apparent density (ρ), water absorption (ω) and crushing index (δ) of MRCA. The confinement coefficient has no obvious influence on the σ-Ε curves of MRCFST with different sections, and the curves all exhibited the characteristic of "strain softening". The predicted curves of the stress-strain model considering the effects of ρ, ω and δ parameters agree well with the experimental curves. © 2025

关键词： Stress-strain curves

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A Coord-Aware Transformer for Pedestrian Fall Detection

A Coord-Aware Transformer for Pedestrian Fall Detection

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2023 China Automation Congress, CAC 2023

作者： Zheng, Haoyuan Hou, Enguang Jiang, Yuyi Shen, Zhen Xiong, Gang Li, Chuanfu Han, Tao The College of Rail Transit of Shandong Jiaotong University Jinan China Qingdao Academy of Intelligent Industries Qingdao China Institute of Automation Chinese Academy of Sciences Beijing Engineering Research Center of Intelligent Systems and Technology Beijing China Institute of Automation Chinese Academy of Sciences State Key Laboratory of Multimodal Artificial Intelligence Systems Beijing China Shandong Hi-Speed Qingdao Development Company Group Qingdao China

ISBN: (纸本)9798350303759

The detection of fallen pedestrians is one of the key problems in automatic driving. Due to complex road conditions, the detection of fallen pedestrians during driving is still challenging for occlusion and small targets. Usually, existing methods such as convolutional networks have low detection accuracy for these cases. Therefore, in this paper we propose to apply the Coord-Aware Transformer YOLOv7 (T-YOLOv7) method to the detection of fallen pedestrians. The CoordConv Feature Pyramid Networks (C-FPN) and the CoordConv perception Detect (C-Detect) are designed. By introducing feature coordinate channels, the network can perceive the spatial information of the feature map, improve the detection of occluded targets. Add the Biformer module to the C-FPN to improve the detection accuracy of small targets. In addition, we use the Wise-IoU to replace the original network CIoU, it can focus on ordinary prediction boxes. The improved network model achieved 87.45% mAP on the open source data set Fall detection Database, which increased by 3.72%mAP and 5.25%mAP compared with YOLOv7 and PDD-FCOS, respectively. © 2023 IEEE.

关键词： Fall detection

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A systematic evaluation of helicopter cabin noise:Case study of Robinson R44 RAVEN Ⅱ

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Chinese Journal of Aeronautics 2025年第5期 168-183页

作者： Dan YAO Jie ZHANG Ruiqian WANG Chang CHEN Yumei ZHANG Yue ZHAO Jie PANG College of Aviation Engineering Civil Aviation Flight University of China State Key Laboratory of Polymer Materials Engineering/Polymer Research Institute Sichuan University School of Mechanical Engineering and Rail Transit Changzhou University Key Laboratory of Aerodynamic Noise Control China Aerodynamics Research and Development Centre

This paper presents a comprehensive test and systematic evaluation analysis of cabin noise in the Robinson R44 RAVEN II ***,microphones were placed within the cabin to conduct systematic assessments of noise levels under various flight conditions,including takeoff,climbing,level flight,landing,hovering,***,time–frequency analysis was conducted on the test data utilizing traditional A-weighted sound pressure levels,which was followed by quantitative comparisons across different flight ***,detailed evaluation and discussion were conducted,taking into account the subjective perceptions and communication challenges of cabin crew *** assessment incorporated the use of aviation noise indicators,speech interference levels,and metrics related to sound ***,potential noise reduction measures and their effects were preliminarily *** results indicate that helicopter cabin noise exhibited variations across different flight states or positions within the same state,ranging from 87.6 d B(A) to 92.6 dB(A).Discrepancies between A-weighted sound pressure level and psychoacoustic parameters were observed,particularly during hovering states,which indicate that there is a necessity for the combination of multiple evaluation ***,damping measure can serve as a pivotal factor in mitigating cabin noise.

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DMI Image Information Recognition Based on Improved YOLOv4 with Focal Loss 5

DMI Image Information Recognition Based on Improved YOLOv4 w...

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5th International Conference on Traffic engineering and Transportation System, ICTETS 2021

作者： He, Han Li, Kaicheng Yuan, Lei Wang, Fei National Engineering Laboratory for Urban Rail Transit Communication and Operation Control Beijing Jiaotong University Beijing100044 China State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong University Beijing100044 China Signal & Communication Research Institute of CARS Beijing100081 China

ISBN: (纸本)9781510649910

In the ATP function test project of train control system, the image information recognition of driver machine interface (DMI) is an important part of realizing test automation, because of the reason the real-time detection of DMI image information is very important. In the process of realizing DMI image information recognition based on machine vision, aiming at the problem of low generalization of the model caused by small amount of training data and single background of training image in machine vision system, combined with a variety of data enhancement strategies, a data set construction scheme of the system is proposed. In order to solve the problem of low attention to hard samples when using YOLOv4 model for small target detection, based on the idea of focus loss, a weighted fusion loss function of focus loss + CIoU loss is proposed, and the optimal parameters are obtained through experiments. The results show that the average accuracy of this method for DMI image information recognition is 98.76%, which is 2.6% higher than the traditional YOLOv4 detection model, and the single detection time is 76.9ms, which has a certain engineering application value. © 2021 SPIE

关键词： Object detection

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Modeling ground vibration excited by a high-speed train running along a viaduct railway using a new structure-soil interaction method

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Science of the Total Environment 2024年 956卷 177136页

作者： He, Yuanpeng Sheng, Xiaozhen Han, Jian Zhang, Yang Xiao, Xinbiao School of Mechanical Engineering Southwest Jiaotong University Sichuan Chengdu610031 China School of Urban Railway Transportation Shanghai University of Engineering Science Shanghai201620 China Department of Civil and Environmental Engineering Hong Kong Polytechnic University Kowloon100872 Hong Kong State Key Laboratory of Rail Transit Vehicle System Southwest Jiaotong University Sichuan Chengdu610031 China

Ground vibrations generated by high-speed trains running along railways either at grade or on viaduct bridges, are greatly concerned by the railway industry. Considering the train-track-bridge-abutment-pile-soil interactions involved, modeling the problem in an analytical manner is almost impossible, while conventional numerical methods struggle to accurately simulate the dynamic properties of infinitely large soils. Therefore, this study introduces a new substructure methodology for train-track-bridge-abutment-pile-soil interactions that leverages an ingenious combination of the 2.5-dimensional finite element-boundary element method (2.5D FE-BE) for dynamics of infinitely long periodic structures, and a local 3-dimensional finite element model for pile-soil interaction. This innovative method allows for the consideration of detailed pile-soil coupling using a local finite element model, all while retaining the ability to account for the infinite size of the soil structure using the 2.5-dimensional finite element-boundary elements. After a comparison between model prediction and field measurement, the model is employed to explore the environmental vibration characteristics of on-viaduct high-speed railways and analyze the vibration reduction effects of various measures, including rail fasteners, track slab pads, and bridge bearings. © 2024

关键词： Piles

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Numerical Simulation and Multi-Factor Optimization of Spatio-Temporal Stress Evolution in Shale Reservoir Based on Plackett-Burman and Central Composite Design

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SSRN 2024年

作者： Mu, Shuxing Zhao, Lianheng Liu, Yuxuan School of Civil Engineering Central South University Hunan Province Changsha410075 China Key Laboratory of Heavy-Haul Railway Engineering Structure Ministry of Education Hunan Province Changsha410075 China Hunan Provincial Key Laboratory for Disaster Prevention and Mitigation of Rail Transit Engineering Structures Hunan Province Changsha410075 China State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum University Sichuan Province Chengdu610500 China

Multi-factor analysis and accurate prediction of dynamic stress in shale reservoirs are of great practical significance for designing gas well fracturing. The seepage-geomechanics of reservoirs in the development of shale gas is a multi-physical and multi-scale coupling problem. In this paper, we propose a hydro-mechanical model considering geomechanical heterogeneity and multi-scale seepage mechanisms of shale gas to simulate the spatio-temporal evolution of gas well stress. The numerical model is validated by Terzaghi's theory. The Plackett-Burman method is used for sensitivity analysis to screen the significant factors affecting reservoir stress. Then, in combination with central composite design and numerical simulation, the combined effect of significant factors on reservoir stress is studied, and a mathematical model for predicting stress is established. The results indicate that the initial reservoir pressure, as well as the length and width of hydraulic fractures, are the key factors influencing reservoir stress. The proposed method is effective for predicting reservoir stress. The research results are helpful for gaining a deeper understanding of the evolution mechanism of dynamic stress fields in shale reservoirs and provide guidance for treatment design and dynamic optimization of gas wells. © 2024, The Authors. All rights reserved.

关键词： Gases

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A Novel Sliding Mode Control for Dual Three-phase PMSM System 7

A Novel Sliding Mode Control for Dual Three-phase PMSM Syste...

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7th IEEE International Conference on Power and Renewable Energy, ICPRE 2022

作者： Peng, Weifa Lin, Tao Liu, Annan Chen, Yumeng Liu, Jun Xu, Xiaoling East China Jiaotong University School of Electrical and Automation Engineering Nanchang China East China Jiaotong University School of Tianyou Nanchang China East China Jiaotong University State Key Laboratory of Performance Monitoring and Protecting of Rail Transit Infrastructure Seae Nanchang China East China Jiaotong University School of Electrical and Automation Engineering Nanchang China

ISBN: (数字)9781665450638

ISBN: (纸本)9781665450638

The speed control problem of dual three-phase permanent magnet synchronous motor has the characteristics of nonlinearity, parameter perturbation and load disturbance. To solve this problem, a new sliding mode approach law is proposed. The saturation function is used to replace the sign function to suppress chattering, and the approach law is used to design a sliding mode speed controller for dual three-phase permanent magnet synchronous motor. According to the established mathematical model, the vector control model of the sliding mode speed controller based on the new approach law is established. Under three states of motor starting, steady state and sudden load, the new sliding mode approach law has less phase current impact , almost no buffeting, fast response of speed and torque, no overshoot of speed. The simulation results show that the speed controller can effectively improve the static and dynamic characteristics of the dual three-phase permanent magnet synchronous motor drive system. © 2022 IEEE.

关键词： Sliding mode control

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Ni Mesh-Reinforced Ultrasonic-Assisted Cu/Sn58Bi/Cu Joint Performance: Experiments and First-Principles Calculations

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SSRN 2024年

作者： Huang, Xi Zhang, Liang Chen, Yu-Hao Sun, Lei Yu, Xin-Quan Lu, Quan-Bin School of Materials Science and Engineering Xiamen University of Technology Xiamen361000 China School of Mechanical Engineering and Rail Transit Changzhou University Changzhou213164 China State Key Laboratory of Advanced Brazing Filler Metals & Technology Zhengzhou Research Institute of Mechanical Engineering Co. Ltd. Zhengzhou450001 China

The Ni mesh was incorporated into the Cu/Sn58Bi/Cu bonding as a reinforcing skeleton to achieve an enhancement effect analogous to steel reinforcement in concrete. Ultrasonic-assisted soldering (UAS) improved the metallurgical bond among the solder, Ni mesh, and substrate. It facilitated the formation of (Cu, Ni)6Sn5 intermetallic compounds (IMCs) layers, increasing the joint strength. Observations indicated that ultrasonic treatment effectively refined the (Cu, Ni)6Sn5 grains and induced a uniform preferred orientation of β-Sn and Bi grains in the joint matrix adjacent to the Ni mesh. The shear strength of the joint reached 72.23 MPa when the ultrasonic application was sustained for 15 seconds, achieving the fabrication of a high-strength point with low energy consumption. First-principles calculations have confirmed that changes in the Ni content within (Cu, Ni)6Sn5 IMCs improved the stability of the crystal structure. Furthermore, the variations in content could potentially improve the mechanical and electrical properties of the (Cu, Ni)6Sn5. Enhancements in ultrasonic efficiency and the reinforcement of IMC structures offer new avenues for research in green and high-performance electronic packaging material joining technologies. © 2024, The Authors. All rights reserved.

关键词： Mesh generation

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