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Research on the Dynamic Compressibility of Polyurethane Microcellular Elastomer and its Application for Impact Resistance

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Chinese Journal of Polymer Science 2024年第8期42卷 1185-1197页

作者： Zhi-Ying Zhao Hao Jiang Xiao-dong Li Xu-dong Zhang Xing Su Mei-Shuai Zou School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China

The packaging materials with cushioning performance are used to prevent the internal contents from being damaged by the impact and vibration of external *** polyurethane microcellular elastomers(PUMEs)can absorb energy through cell collapse and molecular chain *** this study,PUMEs with different densities were investigated by scanning electron microscopy,dynamic mechanical analysis and dynamic compression *** exhibited significant im pact resistance and the maximum peak stress attenuation ratio reached 73.33%.The protective equipment was made by PUME with the optimal density of 600 kg/m^(3),and then the acceleration sensing device installed with the same protective equipment fell from a height of 3,5 and 10 m to evaluate the energy-absorbing property and reusability of *** results showed that PUMEs equipment reduced the peak acceleration of the device by 93.84%,with a maximum deviation of 9%between actual test and simulation,and shortened the impact time of first landing by 57.39%.In addition,the equipment PUMEs equipment could effectively reduce the stress on the protected items.

关键词： Polyurethane microcellular elastomer Impact velocity Stress attenuation ratio Impact resistance

Physical informed memory networks for solving PDEs:implementation and applications

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Communications in Theoretical Physics 2024年第2期76卷 51-61页

作者： Jiuyun Sun Huanhe dong Yong Fang College of Mathematics and Systems Science Shandong University of Science and TechnologyQingdao 266590China

With the advent of physics informed neural networks(PINNs),deep learning has gained interest for solving nonlinear partial differential equations(PDEs)in recent *** this paper,physics informed memory networks(PIMNs)are proposed as a new approach to solving PDEs by using physical laws and dynamic behavior of *** the fully connected structure of the PINNs,the PIMNs construct the long-term dependence of the dynamics behavior with the help of the long short-term memory ***,the PDEs residuals are approximated using difference schemes in the form of convolution filter,which avoids information loss at the neighborhood of the sampling ***,the performance of the PIMNs is assessed by solving the Kd V equation and the nonlinear Schr?dinger equation,and the effects of difference schemes,boundary conditions,network structure and mesh size on the solutions are *** show that the PIMNs are insensitive to boundary conditions and have excellent solution accuracy even with only the initial conditions.

关键词： nonlinear partial differential equations physics informed memory networks physics informed neural networks numerical solution

Changes in Spring Snow Cover over the Eastern and Western Tibetan Plateau and Their Associated Mechanism

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Advances in Atmospheric Sciences 2024年第5期41卷 959-973页

作者： Fangchi LIU Xiaojing JIA Wei dong Key Laboratory of Geoscience Big Data and Deep Resource of Zhejiang Province School of Earth SciencesZhejiang UniversityHangzhouZhejiang 310058China

The spring snow cover(SC)over the western Tibetan Plateau(TP)(TPSC)(W_TPSC)and eastern TPSC(E_TPSC)have displayed remarkable decreasing and increasing trends,respectively,during 1985–*** current work investigates the possible mechanisms accounting for these distinct TPSC *** results indicate that the decrease in W_TPSC is primarily attributed to rising temperatures,while the increase in E_TPSC is closely linked to enhanced *** circulation analysis shows that the essential system responsible for the TPSC changes is a significant anticyclonic system centered over the northwestern *** anomalous descending motion and adiabatic heating linked to this anticyclone leads to warmer temperatures and consequent snowmelt over the western ***,anomalous easterly winds along the southern flank of this anticyclone serve to transport additional moisture from the North Pacific,leading to an increase in snowfall over the eastern *** analysis reveals that the anomalous anticyclone is associated with an atmospheric wave pattern that originates from upstream *** warming of the subtropical North Atlantic(NA)sea surface temperature(SST)induces an atmospheric pattern resembling a wave train that travels eastward across the Eurasian continent before reaching the ***,the decline in winter sea ice(SIC)over the Barents Sea exerts a persistent warming influence on the atmosphere,inducing an anomalous atmospheric circulation that propagates southeastward and strengthens the northwest TP anticyclone in ***,an enhancement of subtropical stationary waves has resulted in significant increases in easterly moisture fluxes over the coastal areas of East Asia,which further promotes more snowfall over eastern TP.

关键词： snow cover Tibetan Plateau long-term changes spring

Mechanical properties and acoustic emission characteristics of soft rock with different water contents under dynamic disturbance

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International Journal of Coal Science & Technology 2024年第3期11卷 135-148页

作者： Yujing Jiang Lugen Chen dong Wang Hengjie Luan Guangchao Zhang Ling dong Bin Liang State Key Laboratory of Mining Disaster Prevention and Control Co-Founded By Shandong Province and the Ministry of Science and Technology Shandong University of Science and TechnologyQingdao266590China State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyBeijing100083China Inner Mongolia Shanghaimiao Mining Co. Ltd.Ordos016299China

Uniaxial compression tests and cyclic loading acoustic emission tests were conducted on 20%,40%,60%,80%,dry and saturated muddy sandstone by using a creep impact loading system to investigate the mechanical properties and acoustic emission characteristics of soft rocks with different water contents under dynamic *** mechanical properties and acoustic emission characteristics of muddy sandstones at different water contents were *** of experimental studies show that water is a key factor in the mechanical properties of rocks,softening them,increasing their porosity,reducing their brittleness and increasing their *** uniaxial compression,the macroscopic damage characteristics of the muddy sandstone change from mono-bevel shear damage and‘X’type conjugate bevel shear damage to a roadway bottom-drum type damage as the water content *** perturbation has a strengthening effect on the mechanical properties of samples with 60%and less water content,and a weakening effect on samples with 80%and more water content,but the weakening effect is not *** damage characteristics of dry samples remain unchanged,water samples from shear damage and tensile–shear composite damage gradually transformed into cleavage damage,until saturation transformation monoclinic shear *** evolution of acoustic emission energy and event number is mainly divided into four stages:loading stage(Ⅰ),dynamic loading stage(Ⅱ),yield failure stage(Ⅲ),and post-peak stage(Ⅳ),the acoustic emission characteristics of the stages were different for different water *** characteristic value of acoustic emission key point frequency gradually decreases,and the damage degree of the specimen increases,corresponding to low water content—high main frequency—low damage and high water content—low main frequency—high damage.

关键词： Dynamic disturbance Soft rock Cyclic loading Acoustic emission Water content

Adaptive multi-channel Bayesian graph attention network for IoT transaction security

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Digital Communications and Networks 2024年第3期10卷 631-644页

作者： Zhaowei Liu dong Yang Shenqiang Wang Hang Su School of Computer and Control Engineering Yantai UniversityYantai264005China Department of Electronics Information and BioengineeringPolitecnico di MilanoMilan20133Italy

With the rapid advancement of 5G technology,the Internet of Things(IoT)has entered a new phase of appli-cations and is rapidly becoming a significant force in promoting economic *** to the vast amounts of data created by numerous 5G IoT devices,the Ethereum platform has become a tool for the storage and sharing of IoT device data,thanks to its open and tamper-resistant ***,Ethereum account security is necessary for the Internet of Things to grow quickly and improve people's *** modeling Ethereum trans-action records as a transaction network,the account types are well identified by the Ethereum account classifi-cation system established based on Graph Neural Networks(GNNs).This work first investigates the Ethereum transaction ***,experimental metrics reveal that the Ethereum transaction network is neither optimal nor even satisfactory in terms of accurately representing transactions per *** flaw may significantly impede the classification capability of GNNs,which is mostly governed by their *** work proposes an Adaptive Multi-channel Bayesian Graph Attention Network(AMBGAT)for Ethereum account clas-sification to address this *** uses attention to enhance node features,estimate graph topology that conforms to the ground truth,and efficiently extract node features pertinent to downstream *** extensive experiment with actual Ethereum transaction data demonstrates that AMBGAT obtains competitive performance in the classification of Ethereum accounts while accurately estimating the graph topology.

关键词： Internet of things Graph representation learning Node classification Security mechanism

Investigation of high rate mechanical flow followed by ignition for high-energy propellant under dynamic extrusion loading

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Defence Technology（防务技术） 2024年第2期32卷 336-347页

作者： Liying dong Yanqing Wu Kun Yang Xiao Hou State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China

Investigating the ignition response of nitrate ester plasticized polyether(NEPE) propellant under dynamic extrusion loading is of great significant at least for two cases. Firstly, it helps to understand the mechanism and conditions of unwanted ignition inside charged propellant under accident ***, evaluates the risk of a shell crevice in a solid rocket motor(SRM) under a falling or overturning scene. In the present study, an innovative visual crevice extrusion experiment is designed using a dropweight apparatus. The dynamic responses of NEPE propellant during extrusion loading, including compaction and compression, rapid shear flow into the crevice, stress concentration, and ignition reaction, have been firstly observed using a high-performance high-speed camera. The ignition reaction is observed in the triangular region of the NEPE propellant sample above the crevice when the drop weight velocity was 1.90 m/s. Based on the user material subroutine interface UMAT provided by finite element software LS-DYNA, a viscoelastic-plastic model and dual ignition criterion related to plastic shear dissipation are developed and applied to the local ignition response analysis under crevice extrusion conditions. The stress concentration occurs in the crevice location of the propellant sample, the shear stress is relatively large, the effective plastic work is relatively large, and the ignition reaction is easy to occur. When the sample thickness decreases from 5 mm to 2.5 mm, the shear stress increases from 22.3 MPa to 28.6 MPa, the critical value of effective plastic work required for ignition is shortened from 1280 μs to 730 μs, and the triangular area is easily triggering an ignition reaction. The propellant sample with a small thickness is more likely to stress concentration, resulting in large shear stress and effective work, triggering an ignition reaction.

关键词： NEPE propellant Crevice extrusion Shear flow Sample thickness Ignition reaction

Study on the force chain characteristics with coal dust layer and the three-body contact stiffness

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Particuology 2024年第9期92卷 288-304页

作者： Xinwei Yang dongxuan Wu Hongyue Chen dong Wang School of Mechanical Engineering Liaoning Technical UniversityFuxin123000China Ordos Institute of Liaoning Technical University Ordos017000China School of Mining Liaoning Technical UniversityFuxin123000China China National Coal Association Dynamic Research for High-end Complete Integrated Coal Mining Equipment and Big Data Analysis CentreFuxin123000China

To explore the influence of the meso-mechanical behaviors of the wet coal dust layers on the contact stiffness of mechanical bonding surfaces,a three-body contact model incorporating an interface with wet coal dust was constructed based on breakage *** model considered the mechanical surface morphology and contact characteristics of the wet coal *** force chain evolution laws of the wet coal dust layer were elucidated under the effects of gap filling and the cover layer,and the bearing characteristics of the three-body contact bonding surfaces were revealed by quantitative analyses of the number,length,collimation coefficient,and coordination number of the force chains within the wet coal dust ***,the three-body normal contact stiffness under various preload forces was computed and experimentally *** results demonstrate that the external load transfer path of the three-body contact bonding surfaces was from mechanical surface(macroscopic stress)to wet coal dust layer(mesoscopic force chains)and then to mechanical surface(peaks and valleys).The interactions among these three elements contributed to transforming the distributions of the macroscopic stresses and mesoscopic force chains to the locations at the peaks and valleys of the mechanical *** them,the proportion of short force chains in the wet coal dust layer increased from approximately 0.8%–91%,while the proportion of long force chains exhibited an opposite changing *** force chain collimation coefficient initially increased and subsequently stabilized,reaching a maximum value of 0.93.A large number of broken,small particles in the wet coal dust layer mainly served to fill the gaps among large *** maximum relative error between the experimental and simulated values on the three-body contact stiffness is 7.26%,indicating that the simulation results can be an approximate substitute for the experimental results with a certain degree of accuracy and practic

关键词： Wet coal dust Force chain Three-body contact stiffness Gap flling effect Cover layer effect

Brain Cognition Mechanism-Inspired Hierarchical Navigation Method for Mobile Robots

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Journal of Bionic Engineering 2024年第2期21卷 852-865页

作者： Qiang Zou Chengdong Wu Ming Cong dong Liu Faculty of Robot Science and Engineering Northeastern UniversityShenyang110819China School of Mechanical Engineering Dalian University of TechnologyDalian116024China

Autonomous navigation is a fundamental problem in *** methods generally build point cloud map or dense feature map in perceptual space;due to lack of cognition and memory formation mechanism,traditional methods exist poor robustness and low cognitive *** a new navigation technology that draws inspiration from mammal’s navigation,bionic navigation method can map perceptual information into cognitive space,and have strong autonomy and environment *** improve the robot’s autonomous navigation ability,this paper proposes a cognitive map-based hierarchical navigation ***,the mammals’navigation-related grid cells and head direction cells are modeled to provide the robots with location *** then a global path planning strategy based on cognitive map is proposed,which can anticipate one preferred global path to the target with high efficiency and short ***,a hierarchical motion controlling method is proposed,with which the target navigation can be divided into several sub-target navigation,and the mobile robot can reach to these sub-targets with high confidence ***,some experiments are implemented,the results show that the proposed path planning method can avoid passing through obstacles and obtain one preferred global path to the target with high efficiency,and the time cost does not increase extremely with the increase of experience nodes *** motion controlling results show that the mobile robot can arrive at the target successfully only depending on its self-motion information,which is an effective attempt and reflects strong bionic properties.

关键词： Bionic navigation Spatial localization cells Global path planning Hierarchical motion controlling

Production of linear alkylbenzene over Ce containing Beta zeolites

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Chinese Journal of Chemical Engineering 2024年第3期67卷 220-227页

作者： Shiqi Zhang Shengzhi Gan Baoyu Liu Jinxiang dong School of Chemical Engineering and Light Industry Guangdong Provincial Key Laboratory of Plant Resources BiorefineryGuangzhou Key Laboratory of Clean Transportation Energy ChemistryGuangdong University of TechnologyGuangzhou 510006China Jieyang Branch of Chemistry and Chemical Engineering Guangdong Laboratory(Rongjiang Laboratory) Jieyang 515200China

Ce-encapsulated Beta zeolite was synthesized by a one-pot hydrothermal method with citric acid complexing Ce in the absence of Na *** citric acid can effectively prevent the deposition of Ce species during the hydrothermal synthesis of zeolites,leading to uniform distribution of Ce cluster in the framework of Beta ***,the sodium-free synthesis system resulted that the Brønsted acid sites were mainly located on the straight channels and external surface of Beta zeolites,improving the utilization of Brønsted acid *** addition,Ce encapsulated Beta zeolites showed enhanced activity and robust stability in the alkylation of benzene with 1-dodecene based on the synergistic effect between Ce species and Brønsted acid sites,which pave the way for its practical application in the production of alkylbenzene.

关键词： Beta zeolites Catalysis Alkylation Long-chain olefins