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Nonlinear constitutive models of rock structural plane and their applications

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第3期16卷 790-806页

作者： Wenlin feng Shuangjian Niu Chunsheng qiao Dujian Zou School of Civil and Environmental Engineering Harbin Institute of TechnologyShenzhenChina Shenzhen Municipal Engineering Corporation Shenzhen518000China School of Civil Engineering Beijing Jiaotong UniversityBeijing100044China

Structural planes play an important role in controlling the stability of rock engineering,and the influence of structural planes should be considered in the design and construction process of rock *** this paper,mechanical properties,constitutive theory,and numerical application of structural plane are studied by a combination method of laboratory tests,theoretical derivation,and program *** test results reveal the change laws of various mechanical parameters under different roughness and normal *** the pre-peak stage,a non-stationary model of shear stiffness is established,and threedimensional empirical prediction models for initial shear stiffness and residual stage roughness are *** nonlinear constitutive models are established based on elasto-plastic mechanics,and the algorithms of the models are developed based on the return mapping *** to a large number of statistical analysis results,empirical prediction models are proposed for model parameters expressed by structural plane characteristic ***,the discrete element method(DEM)is chosen to embed the constitutive models for practical *** running programs of the constitutive models have been compiled into the discrete element model *** comparison results between the proposed model and the Mohr-Coulomb slip model show that the proposed model can better describe nonlinear changes at different stages,and the predicted shear strength,peak strain and shear stiffness are closer to the test *** research results of the paper are conducive to the accurate evaluation of structural plane in rock engineering.

关键词： Structural plane Engineering stability Roughness Normal stress Elasto-plastic constitutive model Discrete element method

Smart Gait:A Gait Optimization Framework for Hexapod Robots

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Chinese Journal of Mechanical Engineering 2024年第1期37卷 146-159页

作者： Yunpeng Yin feng Gao qiao Sun Yue Zhao Yuguang Xiao State Key Laboratory of Mechanical System and Vibration School of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai 200240China Lenovo Corporation ShanghaiChina AI Institute School of Electronic Information and Electrical EngineeringShanghai Jiao Tong UniversityShanghai 200240China

The current gait planning for legged robots is mostly based on human presets,which cannot match the flexible characteristics of natural *** paper proposes a gait optimization framework for hexapod robots called Smart *** Gait contains three modules:swing leg trajectory optimization,gait period&duty optimization,and gait sequence *** full dynamics of a single leg,and the centroid dynamics of the overall robot are considered in the respective *** Smart Gait not only helps the robot to decrease the energy consumption when in locomotion,mostly,it enables the hexapod robot to determine its gait pattern transitions based on its current state,instead of repeating the formalistic clock-set step *** Smart Gait framework allows the hexapod robot to behave nimbly as a living animal when in 3D movements for the first *** Smart Gait framework combines offline and online optimizations without any fussy data-driven training procedures,and it can run efficiently on board in real-time after *** experiments are carried out on the hexapod robot *** results show that the energy consumption is reduced by 15.9%when in *** gait patterns can be generated spontaneously both in regular and challenge environments,and when facing external interferences.

关键词： Gait optimization Swing trajectory optimization Legged robot Hexapod robot

Tailoring the austenite characteristics via dual nanoparticles to synergistically optimize the strength-ductility in cold rolled medium Mn steel

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Journal of Materials Science & Technology 2024年第2期169卷 158-171页

作者： Qizhe ye Haokai Dong Qinyi Guo Yishuang Yu Lijie qiao Yu Yan Beijing Advanced Innovation Center for Materials Genome Engineering Corrosion and Protection CenterInstitute for Advanced Materials and TechnologyUniversity of Science and Technology BeijingBeijing 100083China School of Mechanical and Automotive Engineering South China University of TechnologyGuangzhou 510641China School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China School of Biomedical Engineering Shanghai Jiao Tong UniversityShanghai 200240China

In this work,we proposed a novel Cu/θdual nanoparticles strategy to tailor the austenite characteris-tics of a medium Mn steel via a tempering-annealing process to optimize the mechanical *** explored the effects of Cu-rich particles and cementite precipitated in the tempering process on the austenite reversion during the subsequent annealing *** experiments and numerical simula-tions verified that the austenite inherited from cementite had a finer size and a higher Mn enrichment compared with the austenite originating from the tempered martensite *** addition,quantitative evaluations revealed that the pinning effect exerted by the Cu-rich particles could significantly hinder theα/γinterface migration and the recrystallized grain growth,thereby further refining the final *** contributions from the effects of dual nanoprecipitates on the austenite reversion,the heterogeneous austenite grains inherited from varying nucleation sites ensured the sustained and gradual deformation-induced martensite and twinning ***,the Cu-added steels subjected to a tempering-annealing process achieved synergetic enhancement of the tensile strength from 1055 MPa to 1250 MPa and elongation from 33%to 45%.This strategy may provide new guidance for the development and alloy design of high-performance medium Mn steels.

关键词： Dual nanoparticles Medium Mn steel Tempering-annealing process Austenite reversion Mechanical properties

Atomic-Scale Insights into Damage Mechanisms of GGr15 Bearing Steel Under Cyclic Shear Fatigue

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Acta Metallurgica Sinica(English Letters) 2024年第7期37卷 1265-1278页

作者： qiao-Sheng Xia Dong-Peng Hua Qing Zhou ye-Ran Shi Xiang-Tao Deng Kai-Ju Lu Hai-feng Wang Xiu-Bing Liang Zhao-Dong Wang State Key Laboratory of Solidification Processing Center of Advanced Lubrication and Seal MaterialsNorthwestern Polytechnical UniversityXi’an710072China State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang110819China Defense Innovation Institute Academy of Military ScienceBeijing100071China

Alternating shear stress is a critical factor in the accumulation of damage during rolling contact fatigue,severely limiting the service life of ***,the specific mechanisms responsible for the cyclic shear fatigue damage in bearing steel have not been fully *** the mechanical response and microstructural evolution of a model GGr15 bearing steel under cyclic shear loading are investigated through the implementation of molecular dynamics *** samples undergo 30 cycles under three different loading conditions with strains of 6.2%,9.2%,and 12.2%,*** findings indicate that severe cyclic shear deformation results in early cyclic softening and significant accumulation of plastic damage in the bearing ***,samples subjected to higher strain-controlled loading exhibit higher plastic strain energy and shorter fatigue ***,strain localization is identified as the predominant damage mechanism in cyclic shear fatigue of the bearing steel,which accumulates and ultimately results in fatigue ***,simulation results also revealed the microstructural reasons for the strain localization(e.g.,BCC phase transformation into FCC and HCP phase),which well explained the formation of white etching *** study provides fresh atomic-scale insights into the mechanisms of cyclic shear fatigue damage in bearing steels.

关键词： Cyclic shear fatigue Molecular dynamic simulation Bearing steels Plastic damage accumulation

Estimation of the anisotropy of hydraulic conductivity through 3D fracture networks using the directional geological entropy

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International Journal of Mining Science and Technology 2024年第2期34卷 137-148页

作者： Chuangbing Zhou Zuyang ye Chi Yao Xincheng Fan feng Xiong School of Infrastructure Engineering Nanchang UniversityNanchang 330031China b School of Resource and Environmental Engineering Wuhan University of Science and TechnologyWuhan 430081China School of Engineering China University of GeosciencesWuhan 430074China

With an extension of the geological entropy concept in porous media,the approach called directional entrogram is applied to link hydraulic behavior to the anisotropy of the 3D fracture networks.A metric called directional entropic scale is used to measure the anisotropy of spatial order in different *** with the traditional connectivity indexes based on the statistics of fracture geometry,the directional entropic scale is capable to quantify the anisotropy of connectivity and hydraulic conductivity in heterogeneous 3D fracture *** to the numerical analysis of directional entrogram and fluid flow in a number of the 3D fracture networks,the hydraulic conductivities and entropic scales in different directions both increase with spatial order(i.e.,trace length decreasing and spacing increasing)and are independent of the dip *** a result,the nonlinear correlation between the hydraulic conductivities and entropic scales from different directions can be unified as quadratic polynomial function,which can shed light on the anisotropic effect of spatial order and global entropy on the heterogeneous hydraulic behaviors.

关键词： 3D fracture network Geological entropy Directional entropic scale Anisotropy Hydraulic conductivity

Ultralow friction PTFE/PEEK heterolayer:A new solid lubrication approach toward simplicity

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Friction 2024年第1期12卷 120-135页

作者： Wei SUN Jiaxin ye Qingrui SONG Yi feng Xiaojun LIU School of Materials Science and Engineering Hefei University of TechnologyHefei 230009China Institute of Tribology School of Mechanical EngineeringHefei University of TechnologyHefei 230009China

Tribological applications of polytetrafluoroethylene(PTFE)are often limited by technological complexity to overcome its poor wear ***,a PTFE/polyetheretherketone(PEEK)heterolayer(HL)was proposed and evaluated as a new solid lubrication ***-on-disk tribometry found the lowest friction coefficient(μ)of 0.031 and ultralow wear for the PEEK/HL under typical *** friction coefficient of the HL surpasses those of the state-of-the-art polymeric coatings/composites by at least 200%,and approaches that of highly lubricated *** investigations revealed multi-length physical and chemical heterogeneity of the HL that best facilitates a tribofilm with high subsurface stability and surface *** technological simplicity and robustness of the HL’s high lubricity make it a promising new type of solid lubrication toward greater reliability and longevity.

关键词： ultralow friction anti-wear polytetrafluoroethylene(PTFE) heterolayer(HL)

An Efficient Reliability-Based Optimization Method Utilizing High-Dimensional Model Representation and Weight-Point Estimation Method

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Computer Modeling in Engineering & Sciences 2024年第5期139卷 1775-1796页

作者： Xiaoyi Wang Xinyue Chang Wenxuan Wang Zijie qiao feng Zhang School of Mechatronic Engineering Lanzhou Jiaotong UniversityLanzhou730070China School of Electronic and Information Engineering Lanzhou Jiaotong UniversityLanzhou730070China School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’anChina

The objective of reliability-based design optimization(RBDO)is to minimize the optimization objective while satisfying the corresponding reliability ***,the nested loop characteristic reduces the efficiency of RBDO algorithm,which hinders their application to high-dimensional engineering *** address these issues,this paper proposes an efficient decoupled RBDO method combining high dimensional model representation(HDMR)and the weight-point estimation method(WPEM).First,we decouple the RBDO model using HDMR and ***,Lagrange interpolation is used to approximate a univariate ***,based on the results of the first two steps,the original nested loop reliability optimization model is completely transformed into a deterministic design optimization model that can be solved by a series of mature constrained optimization methods without any additional *** numerical examples of a planar 10-bar structure and an aviation hydraulic piping system with 28 design variables are analyzed to illustrate the performance and practicability of the proposed method.

关键词： Reliability-based design optimization high-dimensional model decomposition point estimation method Lagrange interpolation aviation hydraulic piping system

A Blockchain and CP-ABE Based Access Control Scheme with Fine-Grained Revocation of Attributes in Cloud Health

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Computers, Materials & Continua 2024年第2期78卷 2787-2811页

作者： ye Lu Tao feng Chunyan Liu Wenbo Zhang School of Computer&Communication Lanzhou University of TechnologyLanzhou730000China School of Economics&Management Lanzhou University of TechnologyLanzhou730000China School of Computer Science Baoji University of Arts and ScienceBaoji721000China

The Access control scheme is an effective method to protect user data *** access control scheme based on blockchain and ciphertext policy attribute encryption(CP–ABE)can solve the problems of single—point of failure and lack of trust in the centralized ***,it also brings new problems to the health information in the cloud storage environment,such as attribute leakage,low consensus efficiency,complex permission updates,and so *** paper proposes an access control scheme with fine-grained attribute revocation,keyword search,and traceability of the attribute private key distribution *** technology tracks the authorization of attribute private *** credit scoring method improves the Raft protocol in consensus ***,the interplanetary file system(IPFS)addresses the capacity deficit of *** the premise of hiding policy,the research proposes a fine-grained access control method based on users,user attributes,and file *** optimizes the data-sharing *** the same time,Proxy Re-Encryption(PRE)technology is used to update the access *** proposed scheme proved to be *** analysis and experimental results show that the proposed scheme has higher efficiency and more *** can meet the needs of medical institutions.

关键词： Blockchain access-control CP-ABE cloud health

Agronomic performances of biodegradable and non-biodegradable plastic film mulching on a maize cropping system in the semi-arid Loess Plateau,China

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Pedosphere 2024年第1期34卷 88-96页

作者： Hao ZHANG Mengqiong CHEN Ruiquan qiao Fan DING Hao feng Rui JIANG Research Center for Cultural Landscape Protection and Ecological Restoration China-Portugal Belt and Road Cooperation Laboratory of Cultural Heritage Conservation ScienceGold Mantis School of ArchitectureSoochow UniversitySuzhou 215006China Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China Ministry of AgricultureCollege of Natural Resources and EnvironmentNorthwest A&F UniversityYangling 712100China College of Land and Environment Shenyang Agricultural UniversityShenyang 110866China Institute of Soil and Water Conservation Northwest A&F UniversityYangling 712100China

Biodegradable plastic film mulch (PFM) is considered an alternative to non-biodegradable PFM to mitigate the negative impacts of residual ***,the agronomic performance of biodegradable PFM in comparison to non-biodegradable PFM still needs to be *** this study,we evaluated the effects of biodegradable and non-biodegradable PFM on soil physicochemical properties,microbial community,and enzyme activities,as well as maize growth *** and non-biodegradable PFM both increased soil temperature,water content,N content,and microbial biomass and maize yield by up to 30%,but decreased soil enzyme activities as compared to no mulching (control,CK).Most soil physicochemical properties,microbial community,and enzyme activities were similar under non-biodegradable and biodegradable PFM at the early stages of maize ***,at the late stages,soil temperature,water content,mineral N,NO_(3)^(-)-N,ammonia monooxygenase (AMO) activity,and total phospholipid fatty acids (PLFAs) decreased under biodegradable PFM owing to film *** PFM increased soil temperature,water content,and total PLFAs at the early stages of maize growth but decreased soil mineral N and total PLFAs at the late stages,as compared to black *** soil temperature and N availability were the major factors affecting soil microbial community,microbial activity decreased after the fragmentation of biodegradable PFM,owing to the decreased soil temperature,water content,and mineral ***,biodegradable PFM could decrease NO_(3)^(-)-N accumulation in topsoil by decreasing N transformation due to the lower microbial and N-related enzyme (e.g.,AMO) activities,compared with non-biodegradable PFM,which may avoid negative environmental impacts,such as NO_(3)^(-)-N leaching or gas emission after *** yield,height,aboveground biomass,and N uptake under biodegradable PFM were similar to those under non-biodegradable PFM during maize growth,implying that biodegrad

关键词： black plastic film mulching enzyme activity film fragmentation microbial community phospholipid fatty acid white plastic film mulching