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Multiscale observation in wide-spatial radar surveillance based on coherent FDA design

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science china(Information sciences) 2024年第2期67卷 232-252页

作者： Lei YU Feng HE Yi SU College of Electronics science National University of Defense Technology

Wide-spatial radar surveillance missions are challenging tasks, requiring an increased power budget and agility in transmission aimed at extracting information from multiple targets in different environments. These requirements necessitate high transmitting degrees of freedom(DOF) to achieve the objective of multiscale observation for specific tasks in specialized regions of interest. Herein, we exploit the multiscale observation ability in wide-spatial radar surveillance based on frequency diverse array(FDA)radar. The proposed method facilitates spatial anisotropic control of multiple radar resources, including the transmitting waveforms, beampattern, and bandwidth. By utilizing a coherent FDA radar, we offer principles for the selection of baseband waveforms, in addition to the quantitative design of the beampattern gain and optimal bandwidth from the perspective of detection. The feasibility of the proposed method is validated through numerical experiments, thus indicating the potential in wide-spatial radar surveillance. Moreover,this work can be regarded as a preliminary attempt to gauge the efficacy of the computational array, a novel academic concept.

关键词： multi-scale observation wide-spatial surveillance frequency diverse array (FDA) beampattern synthesis frequency diversity gain computational array

Multi-spherical interactions and mechanisms of hydrocarbon enrichment in the Southeast Asian archipelagic tectonic system

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science china Earth sciences 2024年第2期67卷 566-583页

作者： Rixiang ZHU Hongjun WANG Huajian WANG Xiaomei WANG Bo WAN Wang ZHANG Houqin ZHU Yuke LIU Junlai LIU Qingren MENG Fang HAO Zhijun JIN State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing100029China State Key Laboratory of Enhanced Oil and Gas Recovery PetroChina Research Institute of Petroleum Exploration and DevelopmentBeijing100083China School of Earth sciences and Resources China University of GeosciencesBeijing100083China State Key Laboratory of Deep Oil and Gas China University of Petroleum(East China)Qingdao266580China Institute of Energy Peking UniversityBeijing100871China

Global cooling began since 50 Ma,but a warm climate was maintained in the archipelagic tectonic system in Southeast Asia where a wealth of Cenozoic oil and gas resources was formed and *** the perspective of Earth system,this study analyzes Cenozoic tectonic activities,climatic and environmental evolution,and petroleum enrichment in Southeast Asia,and provides the following insights:(1)Subduction of oceanic plates and the extension of overlying continental lithosphere resulted in widespread volcanic eruptions as well as the formation of rift basins and shallow marine shelves,leading to complex interactions between deep tectonic processes and Earth’s surface including mountains,basins,and seas.(2)Microcontinental accretion and prolonged stay in equatorial low-latitude regions have changed trade winds into monsoons,altered ocean current pathways and flow rates,and profoundly affected rainfall and climate.(3)The archipelagic tectonic system,coupled with a hot and rainy climate,fostered tropical rainforests,mangroves,and phytoplankton,providing abundant organic matter and promoting the development of petroleum resources.(4)Combinations of rift basin development and marine transgression and regression led to an effective superposition of source-reservoir-seal combinations from multiplepetroleum *** deep burial of organic matter and high geothermal gradients facilitated the generation and large-scale accumulation of oil and gas.(5)Multi-spherical(such as atmosphere,biosphere,hydrosphere and lithosphere)interactions on the Earth,which resulted from the convergence of multiple tectonic plates,are believed as the primary driver for exceptional enrichments of Cenozoic oil and gas resources in Southeast *** understandings are significant for developing theories of oil and gas enrichment under the guidance of Earth System *** order to continue making significant oil and gas exploration discoveries in the deep-layers,deep-waters,and unconventio

关键词： Southeast Asia Archipelagic tectonic system Interactions of Earth’s spheres Oil and gas resources Cenozoic

Direct observation of shock-induced phase transformation in polycrystalline iron via in situ x-ray diffraction

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Chinese Physics B 2024年第10期33卷 337-342页

作者： Fan Zhang Jia-Qin Dong Zhi-Yong Xie Zhi-Yu He Hua Shu Rui-Rong Wang Jun Xiong Guo Jia Zhi-Heng Fang Wei Wang Da-Wu Xiao An-Le Lei Jie Chen Xiu-Guang Huang Collaborative Innovation Center of IFSA(CICIFSA) School of Physics and AstronomyCenter for Ultrafast Science and TechnologyKey Laboratory for Laser Plasmas(Ministry of Education)Shanghai Jiao Tong UniversityShanghai 200240China Shanghai Institute of Laser Plasma China Academy of Engineering PhysicsShanghai 201800China Institute of Materials China Academy of Engineering PhysicsMianyang 621700China

Phase transition of polycrystalline iron compressed along the Hugoniot is studied by combining laser-driven shock with in situ x-ray diffraction *** is suggested that polycrystalline iron changes from an initial body-centered cubic structure to a hexagonal close-packed structure with increasing pressure(i.e.,a phase transition fromαtoε).The relationship between density and pressure for polycrystalline iron obtained from the present experiments is found to be in good agreement with the gas-gun Hugoniot *** results show that experiments with samples at lower temperatures under static loading,such as in a diamond anvil cell,lead to higher densities measured than those found under dynamic *** means that extrapolating results of static experiments may not predict the dynamic responses of materials *** addition,neither the face-centered cubic structure seen in previous molecular-dynamics simulations or twophase coexistence are found within our experimental pressure range.

关键词： in situ x-ray diffraction phase transition polycrystalline iron

Scaling laws governing the elastic properties of 3D graphenes

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science china(Technological sciences) 2024年第6期67卷 1748-1756页

作者： LI Ming LU Guo YU HaoDong LI MengLei ZHENG FaWei Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement(MOE)School of PhysicsBeijing Institute of TechnologyBeijing100081China Beijing Key Lab of Nanophotonics&Ultrafine Optoelectronic Systems School of PhysicsBeijing Institute of TechnologyBeijing100081China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing100088China Department of Physics Capital Normal UniversityBeijing100048China

In this study,we comprehensively investigated the scaling law for elastic properties of three-dimensional honeycomb-like graphenes(3D graphenes)using hybrid neural network potential-based molecular dynamics simulations and theoretical *** elastic constants were obtained as functions of honeycomb hole size,denoted by the graphene wall length *** five independent elastic constants in the large-L limit are proportional to L^(-1).The associated coefficients are combinations of elastic constants of two-dimensional ***-order terms including L^(-2)and L^(-3)emerge for finite L *** have three origins,the distorted areas close to the joint lines of 3D graphenes,the variation in solid angles between graphene plates,and the bending distortion of graphene ***,the chirality becomes essential with decreasing L because the joint line structures are different between the armchair and zigzag-type 3D *** findings provide insights into the elastic properties of graphene-based superstructures and can be used for further studies on graphene-based materials.

关键词： scaling law neural network elastic properties 3D graphene

Optimization of the co-closing law of guide vanes and blades for bulb turbines based on CFD

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Journal of Hydrodynamics 2024年第2期36卷 363-377页

作者： Hui Liu Yun-fa Lin Yong-guang Cheng Song Xue Mao-jia Tang Jian Zhang Jia-yi Fan State Key Laboratory of Water Resources Engineering and Management Wuhan UniversityWuhan430072China Dongfang Electric Machinery Co. Ltd.Deyang618000China

The load rejection transient process of bulb turbine units is critical to safety of hydropower stations,and determining appropriate closing laws of guide vanes(GVs)and runner blades(RBs)for this process is of *** this study,we proposed a procedure to optimize the co-closing law of GVs and RBs by using computational fluid dynamics(CFD),combined with the design of experiment(DOE)method,approximation model,and genetic optimization *** sensitivity of closing law parameters on the histories of head,speed,and thrust was analyzed,and a two-stage GVs’closing law associating with a linear RBs’closing law was *** results show that GVs dominate the transient characteristics by controlling the change of *** GVs’first-stage closing speed while shortening first-stage closing time can not only significantly reduce the maximum rotational speed but also suppress the water hammer pressure;slowing GVs’second-stage closing speed is conducive to controlling the maximum reverse axial *** directly affect the runner *** RBs’closing speed can further reduce the rotational speed and the maximum reverse axial *** safety margin of each control parameter,flow patterns,and pressure pulsations of a practical hydropower station were all improved after optimization,demonstrating the effectiveness of this method.

关键词： Bulb turbine load rejection transient process double regulation closing law optimization computational fluid dynamics(CFD)

Band structures of strained kagome lattices

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Chinese Physics B 2024年第2期33卷 456-463页

作者：徐露婷杨帆 Center for Joint Quantum Studies and Department of Physics School of ScienceTianjin UniversityTianjin 300354China Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology Department of PhysicsTianjin UniversityTianjin 300354China

Materials with kagome lattices have attracted significant research attention due to their nontrivial features in energy *** theoretically investigate the evolution of electronic band structures of kagome lattices in response to uniaxial strain using both a tight-binding model and an antidot model based on a periodic muffin-tin *** is found that the Dirac points move with applied ***,the flat band of unstrained kagome lattices is found to develop into a highly anisotropic shape under a stretching strain along y direction,forming a partially flat band with a region dispersionless along ky direction while dispersive along kx *** results shed light on the possibility of engineering the electronic band structures of kagome materials by mechanical strain.

关键词： kagome lattice strain band structure engineering

Mechanical responses and crystal plasticity model of CoCrNi medium-entropy alloy under ramp wave compression

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Matter and Radiation at Extremes 2024年第5期9卷 93-108页

作者： Jinlei Dong Xuping Zhang Guiji Wang Xianqian Wu Binqiang Luo Xuemiao Chen Fuli Tan Jianheng Zhao Chengwei Sun Institute of Fluid Physics China Academy of Engineering PhysicsMianyang 621999China Institute of Mechanics Chinese Academy of SciencesBeijing 100190China Institute of Applied Electronics China Academy of Engineering PhysicsMianyang 621999China

It is of substantial scientific significance and practical value to reveal and understand the multiscale mechanical properties and intrinsic mechanisms of medium-entropy alloys(MEAs)under high strain rates and *** this study,the mechanical responses and deformation mechanisms of an equiatomic CoCrNi MEA are investigated utilizing magnetically driven ramp wave compression(RWC)with a strain rate of 105 s^(−1).The CoCrNi MEA demonstrates excellent dynamic mechanical responses and yield strength under RWC compared with other advanced *** characterizations reveal that grain refinement and abundant micromechanisms,including dislocation slip,stacking faults,nanotwin network,and Lomer–Cottrell locks,collectively contribute to its excellent performance during ***,dense deformation twins and shear bands intersect,forming a weave-like microstructure that can disperse deformation and enhance *** the basis of these observations,we develop a modified crystal plasticity model with coupled dislocation and twinning mechanisms,providing a relatively accurate quantitative description of the multiscale behavior under *** results of simulations indicate that the activation of multilevel microstructures in CoCrNi MEA is primarily attributable to stress inhomogeneities and localized strain during *** research offers valuable insights into the dynamic mechanical responses of CoCrNi MEA,positioning it as a promising material for use under extreme dynamic conditions.

关键词： deformation alloy microstructure

Design and evaluation of the traveling wave piezoelectric beam actuators

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Acta Mechanica Sinica 2024年第7期40卷 152-163页

作者： Yuanshuai Ding Zengyao Lv Hangyu Li Yuyang Lin Yongmao Pei Department of Mechanics and Engineering science College of EngineeringPeking UniversityBeijing100871China Department of Civil and Environmental Engineering Northwestern UniversityEvanstonIL60208USA

Traveling wave piezoelectric beam actuators(TWPBAs)present an advantageous structural configuration for self-moving actuators and hold significant promise for operation in confined ***,current research on TWPBAs faces several limitations,including deficient design methods of excitation and structural parameters,inadequate evaluation metrics,and lack of a quantitative relationship between these parameters and evaluation *** study presents a systematic approach to determining TWPBAs'structure and excitation parameters,proposes criteria for determining the excitation parameters through an established analytical model,and introduces an effective evaluation method for TWPBAs'*** the analytical model and evaluation metrics,we reveal:(1)the coupling relationship between excitation parameters and structural parameters,(2)the influence of participating mode pairs on vibration response,(3)the quantitative relationship between the evaluation metrics and excitation parameters is also *** conclusions are substantiated by the results of finite element analysis,laser vibration measurements,and motion test ***,the practical application of TWPBAs in pipeline operations underscores their potential for use in endoscopy and precision instruments.

关键词： Piezoelectric actuator Exciter-Exciter method Wave propagation Vibration control

Target layer state estimation in multi-layer complex dynamical networks considering nonlinear node dynamics

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Chinese Physics B 2024年第4期33卷 245-252页

作者：吴亚勇王欣伟蒋国平 College of Automation and College of Artificial Intelligence Nanjing University of Posts and TelecommunicationsNanjing 210023China Jiangsu Engineering Laboratory for IOT Intelligent Robots Nanjing 210023China

In many engineering networks, only a part of target state variables are required to be *** the other hand,multi-layer complex network exists widely in practical *** this paper, the state estimation of target state variables in multi-layer complex dynamical networks with nonlinear node dynamics is studied.A suitable functional state observer is constructed with the limited *** parameters of the designed functional observer are obtained from the algebraic method and the stability of the functional observer is proven by the Lyapunov *** necessary conditions that need to be satisfied for the design of the functional state observer are *** from previous studies, in the multi-layer complex dynamical network with nonlinear node dynamics, the proposed method can estimate the state of target variables on some layers directly instead of estimating all the individual ***, it can greatly reduce the placement of observers and computational *** simulations with the three-layer complex dynamical network composed of three-dimensional nonlinear dynamical nodes are developed to verify the effectiveness of the method.

关键词： multi-layer complex dynamical network nonlinear node dynamics target state estimation functional state observer