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Highly Improved Creep Resistance in Polypropylene Through Thermally Reduced Graphene Oxide and Its Creep Lifetime Prediction

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Chinese Journal of Polymer Science 2024年第2期42卷 256-266,I0010页

作者： Can-Can zhang Jun-long Yang Ya-Jiang Huang Guang-Xian Li College of Polymer Science and Engineering State Key Laboratory of Polymer Materials Engineering of ChinaSichuan UniversityChengdu610065China

Polypropylene(PP) exhibits suboptimal creep resistance due to the presence of methyl groups on its main chain, leading to irregular chain segment distribution, diminished inter-chain interaction, and crystallinity. This structural feature causes chain slippage in PP under stress,significantly constraining its service lifetime. In this study, thermally reduced graphene oxide(TrGO) nanosheets were incorporated into the PP matrix, yielding a nanocomposite with exceptional creep resistance performance. Results demonstrated that at a stress of 25 MPa, a 2.0 wt% TrGO content could enhance the creep failure lifetime of PP by 21.5 times compared to neat PP. Rheology, transmission electron microscopy(TEM),and scanning electron microscopy(SEM) characterization techniques were employed to analyze the mechanism of TrGO's influence on PP's creep behavior. It was observed that when TrGO content exceeded 1.0 wt%, an effective particle network structure formed within the PP matrix. This homogeneously dispersed TrGO-formed particle network structure restricted the migration and rearrangement of PP molecular chains, enabling prolonged stress resistance without structural failure. By combining the time-strain superposition method with the critical failure strain as a criterion, generalized creep compliance curves for PP and its composites were established, facilitating the prediction of material creep failure lifetimes, with a strong agreement between experimental and predicted lifetime values. This research proposes a novel strategy aimed at developing polypropylene materials and products with enhanced long-term stability and durability, thus extending service life, reducing failure risk, and broadening their potential across various application domains.

关键词： Thermally reduced graphene oxide Polypropylene Creep failure and lifetime prediction

Neural Dynamics for Cooperative Motion Control of Omnidirectional Mobile Manipulators in the Presence of Noises: A Distributed Approach

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IEEE/CAA Journal of Automatica Sinica 2024年第7期11卷 1605-1620页

作者： Yufeng Lian Xingtian Xiao Jiliang zhang long Jin Junzhi Yu Zhongbo Sun the Department of Control Engineering Changchun University of TechnologyChangchun 130012China IEEE the College of Information Science and Engineering Northeastern UniversityShenyang 110819 the National Mobile Communications Research Laboratory Southeast UniversityNanjing 210096China the School of Information Science and Engineering Lanzhou UniversityLanzhou 730000China the State Key Laboratory for Turbulence and Complex Systems Department of Advanced Manufacturing and RoboticsCollege of EngineeringPeking UniversityBeijing 100871China

This paper presents a distributed scheme with limited communications, aiming to achieve cooperative motion control for multiple omnidirectional mobile manipulators(MOMMs).The proposed scheme extends the existing single-agent motion control to cater to scenarios involving the cooperative operation of MOMMs. Specifically, squeeze-free cooperative load transportation is achieved for the end-effectors of MOMMs by incorporating cooperative repetitive motion planning(CRMP), while guiding each individual to desired poses. Then, the distributed scheme is formulated as a time-varying quadratic programming(QP) and solved online utilizing a noise-tolerant zeroing neural network(NTZNN). Theoretical analysis shows that the NTZNN model converges globally to the optimal solution of QP in the presence of noise. Finally, the effectiveness of the control design is demonstrated by numerical simulations and physical platform experiments.

关键词： Cooperative motion control noise-tolerant zeroing neural network(NTZNN) omnidirectional mobile manipulator(OMM) repetitive motion planning

High-entropy materials:Excellent energy-storage and conversion materials in the field of electrochemistry

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Particuology 2024年第9期92卷 42-60页

作者： Jincan Li Huiyu Duan Qi long Bianjiang zhang Changyun Chen Huan Pang Key Laboratory of Advanced Functional Materials of Nanjing School of Environmental ScienceNanjing Xiaozhuang UniversityNanjing211171China School of Chemical Engineering Institute for Innovative Materials and EnergyYangzhou UniversityYangzhou225009China

High-entropy materials(heMs),a new type of materials,have attracted significant attention in the field of electrocatalytic reactions,batteries and energy-storage materials over the past few years owing to their unique structure,controllable elementary composition,and adjustable *** excellent characteristics result from four major factors:high entropy,sluggish-diffusion,severe lattice distortion,and cocktail effect,and are used widely in energy-energy *** review aims to summarize the recent progress of heMs in electrochemical *** begin with the concept,structure,and four core effects of heMs that provide the basic information on ***,we discuss the major properties of heMs and analyze the relationship between their structures and ***,we highlight the outstanding performance of heMs in hydrogen storage,electrode materials of batteries,catalysis,and supercapacitors,and briefly explain the mechanisms of these materials that are crucial in energy storage and *** review will assist in understanding the excellent energy-storage properties,intricacies of the phase structures,elemental interactions,and reaction mechanisms associated with ***,challenges and future development prospects are *** work will provide insight into the factors that are crucial for designing heMs with energy storage properties.

关键词： High-entropy materials Hydrogen storage Electrode materials of batteries Catalyst Supercapacitor

Room-temperature ferroelectricity in van der Waals SnP_(2)S_(6)

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Frontiers of physics 2024年第4期19卷 113-123页

作者： Chaowei he Jiantian zhang Li Gong Peng Yu State Key Laboratory of Optoelectronic Materials and Technologies Guangzhou Key Laboratory of Flexible Electronic Materials and Wearable Devices Nanotechnology Research Center School of Materials Science and EngineeringSun Yat-sen UniversityGuangzhou 510275China Instrumental Analysis and Research Center Sun Yat-sen UniversityGuangzhou 510275China

Two-dimensional(2D)ferroelectric materials,which possess electrically switchable spontaneous polarization and can be easily integrated with semiconductor technologies,is of utmost importance in the advancement of high-integration low-power *** the experimental discovery of certain 2D ferroelectric materials such as CuInP2S6 and In2Se3,achieving stable ferroelectricity at room temperature in these materials continues to present a significant ***,stable ferroelectric order at room temperature in the 2D limit is demonstrated in van der Waals SnP_(2)S_(6) atom layers,which can be fabricated via mechanical exfoliation of bulk SnP_(2)S_(6) *** polarization is observed in thin SnP_(2)S_(6) of~7 ***,a van der Waals ferroelectric field-effect transistor(Fe-FET)with ferroelectric SnP_(2)S_(6) as top-gate insulator and ptype WTe0.6Se1.4 as the channel was designed and fabricated successfully,which exhibits a clear clockwise hysteresis loop in transfer characteristics,demonstrating ferroelectric properties of SnP_(2)S_(6) atomic *** addition,a multilayer graphene/SnP_(2)S_(6)/multilayer graphene van der Waals vertical heterostructure phototransistor was also fabricated successfully,exhibiting improved optoelectronic performances with a responsivity(R)of 2.9 A/W and a detectivity(D)of 1.4×10^(12) *** results show that SnP_(2)S_(6) is a promising 2D ferroelectric material for ferroelectric-integrated low-power 2D devices.

关键词： two-dimensional ferroelectric materials ferroelectric fieldeffect transistors photodetectors

Research on the Asymmetric Effect of Fixed-Asset Investment on China's Primary Energy Production in the Context of Energy Transformation

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Journal of Systems Science & Complexity 2024年第3期37卷 1163-1183页

作者： CHAI Jian he Peng zhang Xiaokong HOU Yamin School of Economics and Management Xidian UniversityXi'an 710126China

Under China’s“Dual Carbon”target(DCT),“clean replacement”on the energy supply side and“electric energy replacement”on the energy consumption side are the ways to achieve energy ***,energy projects have a long construction period,complex technology categories,and investment risks that greatly affect the development of energy *** judging the effect of investment changes on primary energy production is of great practical significance to the realization of the *** on this,NARDL and TVP-SV-VAR models are innovatively used to reveal the nonlinear effect of fixed-asset investment on China’s primary energy *** results show that the marginal effect of investment growth on coal production is about 1.44 times that of investment ***,the marginal effect of oil and gas investment growth is about 1.21times that of investment *** to the influence of resource constraints,China’s traditional fossil energy still has varying degrees of path dependence on the investment-driven development *** non-fossil energy,investment in hydropower and nuclear power has an inverse correlation with the change in *** marginal efficiency and diseconomies of scale have hindered the development of the hydropower and nuclear power *** addition,the asymmetric effect is not yet significant for the short development time and technical constraints of wind and solar *** the impulse response results,the impact curves of investment in wind and solar power are generally positive,and investment has different degrees of time-delay and time-varying effects on various energy production,which verifies the heterogeneity of investment adjustment mechanisms in different energy industries.

关键词： "Dual Carbon"target fixed-asset investment primary energy NARDL nonlinearity

Semi-analytical solution for drained expansion analysis of a hollow cylinder of critical state soils

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第6期16卷 2326-2340页

作者： he Yang Jialiang zhang Haisui Yu Peizhi Zhuang School of Qilu Transportation Shandong UniversityJinan250002China School of Civil Engineering University of LeedsLeedsLS29JTUK

The expansion of a thick-walled hollow cylinder in soil is of non-self-similar nature that the stress/deformation paths are not the same for different soil material *** a result,this problem cannot be solved by the common self-similar-based similarity *** paper proposes a novel,exact solution for rigorous drained expansion analysis of a hollow cylinder of critical state *** stress-dependent elastic moduli of soils,new analytical stress and displacement solutions for the nonself-similar problem are developed taking the small strain assumption in the elastic *** the plastic zone,the cavity expansion response is formulated into a set of first-order partial differential equations(PDEs)with the combination use of Eulerian and Lagrangian descriptions,and a novel solution algorithm is developed to efficiently solve this complex boundary value *** solution is presented in a general form and thus can be useful for a wide range of *** the new solution,the non-self-similar nature induced by the finite outer boundary is clearly demonstrated and highlighted,which is found to be greatly different to the behaviour of cavity expansion in infinite soil *** present solution may serve as a benchmark for verifying the performance of advanced numerical techniques with critical state soil models and be used to capture the finite boundary effect for pressuremeter tests in small-sized calibration chambers.

关键词： Cavity expansion Drained analysis Boundary effect Critical state soil Non-self-similar Eulerian-Lagrangian approach

Dynamic Update Scheme of Spectrum Information Based on Spectrum Opportunity Incentive in the Database-Assisted Dynamic Spectrum Management

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China Communications 2024年第3期21卷 75-90页

作者： zhang Yu Chen Yong he Panfeng Cai Yueming Sixty-third Research Institute National University of Defense TechnologyNanjing 210007China College of Communications Engineering Army of Engineering UniversityNanjing 210007China

To solve the problem of delayed update of spectrum information(SI) in the database assisted dynamic spectrum management(DB-DSM), this paper studies a novel dynamic update scheme of SI in DB-DSM. Firstly, a dynamic update mechanism of SI based on spectrum opportunity incentive is established, in which spectrum users are encouraged to actively assist the database to update SI in real time. Secondly, the information update contribution(IUC) of spectrum opportunity is defined to describe the cost of accessing spectrum opportunity for heterogeneous spectrum users, and the profit of SI update obtained by the database from spectrum allocation. The process that the database determines the IUC of spectrum opportunity and spectrum user selects spectrum opportunity is mapped to a Hotelling model. Thirdly, the process of determining the IUC of spectrum opportunities is further modelled as a Stackelberg game by establishing multiple virtual spectrum resource providers(VSRPs) in the database. It is proved that there is a Nash Equilibrium in the game of determining the IUC of spectrum opportunities by VSRPs. Finally, an algorithm of determining the IUC based on a genetic algorithm is designed to achieve the optimal IUC. The-oretical analysis and simulation results show that the proposed method can quickly find the optimal solution of the IUC, and ensure that the spectrum resource provider can obtain the optimal profit of SI update.

关键词： database-assisted dynamic spectrum management Hotelling information updating contribution spectrum information updating Stackelberg

Investigations of the mechanical response of dummy HTPB propellant grain under ultrahigh acceleration overload conditions using onboard flight-test measurements

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Defence Technology（防务技术） 2024年第2期32卷 473-484页

作者： Yiming zhang Ningfei Wang Weihua Ma Ran Wang long Bai Yi Wu School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China Beijing System Design Institute of Electro-mechanic Engineering Beijing 100854China Xi'an Changfeng Research Institute of Mechanism and Electricity Xi'an 710065China

In this paper,to study the mechanical responses of a solid propellant subjected to ultrahigh acceleration overload during the gun-launch process,specifically designed projectile flight tests with an onboard measurement system were *** projectiles containing dummy HTPB propellant grains were successfully recovered after the flight tests with an ultrahigh acceleration overload value of 8100 *** onboard-measured time-resolved axial displacement,contact stress and overload values were successfully obtained and *** compression tests of the dummy HTPB propellant used in the gunlaunched tests were carried out at low and intermediate strain rates to characterize the propellant's dynamic properties.A linear viscoelastic constitutive model was employed and applied in finite-element simulations of the projectile-launching *** the launch process,the dummy propellant grain exhibited large deformation due to the high acceleration overload,possibly leading to friction between the motor case and propellant *** calculated contact stress showed good agreement with the experimental results,though discrepancies in the overall displacement of the dummy propellant grain were *** dynamic mechanical response process of the dummy propellant grain was analysed in *** results can be used to estimate the structural integrity of the analysed dummy propellant grain during the gun-launch process.

关键词： Gun-launched flight test Dummy HTPB propellant Onboard measurements Utrahigh overload Mechanical response

Independent and Combined Associations of Sleep Duration, Bedtime, and Polygenic Risk Score with the Risk of hearing Loss among Middle-Aged and Old Chinese: The Dongfeng–Tongji Cohort Study

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Research 2024年第1期2023卷 721-733页

作者： Miao Liu Haiqing zhang Zhichao Wang Tingting Mo Xuefeng Lai Yaling he Minghui Jiang Meian he Weijia Kong Tangchun Wu Xiaomin zhang Department of Occupational and Environmental health Ministry of Education Key Laboratory of Environment and Healthand State Key Laboratory of Environmental Health(Incubating)School of Public HealthTongji Medical CollegeHuazhong University of Science and TechnologyWuhanHubeiChina Department of Otorhinolaryngology Union HospitalTongji Medical CollegeHuazhong University of Science and TechnologyWuhanHubeiChina Department of Epidemiology and Biostatistics School of Public HealthTongji Medical CollegeHuazhong University of Science and TechnologyWuhanHubeiChina

Evidence available on the independent and combined associations of sleep duration,bedtime,and genetic predisposition with hearing loss was *** present study included 15,827 participants from the Dongfeng–Tongji cohort *** risk was characterized by polygenic risk score(PRS)based on 37 genetic loci related to hearing *** conducted multivariate logistic regression models to assess the odds ratio(OR)for hearing loss with sleep duration and bedtime,as well as the joint association and interaction with *** showed that hearing loss was independently associated with sleeping≥9 h/night compared to the recommended 7 to9:00 *** 10:00 *** to those with bedtime>10:00 *** 11:00 p.m.,with estimated ORs of 1.25,1.27,and 1.16,respectively.

关键词： Middle hearing fen