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Physics of cavitation near particles

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Journal of Hydrodynamics 2024年第1期36卷 102-118页

作者： Jia-xin yu Xiao-yu w.ng Jun-w.i Shen Jin-sen Hu Xiang-qing Zhang Da-qing He yu-ning Zhang Key Laboratory of Pow.r Station Energy Transfer Conversion and System(Ministry of Education) School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijing102206China

The combined effect of cavitation and silt abrasion presents a great challenge and threat to secure the operation and the efficiency of hydraulic machineries w.rking in sediment-laden *** present paper critically review. the current research progress on the interaction mechanisms of the bubbles and the ***,the analytical models including boundary treatment methods for predicting the jet dynamics of the bubble collapse near particles are ***,the bubble collapsing dynamics,jet dynamics and shock w.ve characteristics near particles are revealed both experimentally and ***,the bubble-particle-w.ll system is investigated w.th a focus on microjets.

关键词： Cavitation bubble particle jet shock w.ve

Robust and Discriminative Feature Learning via Mutual Information Maximization for Object Detection in Aerial Images

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Computers, Materials & Continua 2024年第9期80卷 4149-4171页

作者： Xu Sun Yinhui yu qing Cheng School of Communication Engineering Jilin UniversityChangchun130012China

Object detection in unmanned aerial vehicle(UAV)aerial images has become increasingly important in military and civil *** object detection models are not robust enough against interclass similarity and intraclass variability of small objects,and UAV-specific nuisances such as uncontrolledw.ather *** previous approaches focusing on high-level semantic information,w. report the importance of underlying features to improve detection accuracy and robustness fromthe information-theoretic ***,w. propose a robust and discriminative feature learning approach through mutual information maximization(RD-MIM),w.ich can be integrated into numerous object detection methods for aerial ***,w. present the rank sample mining method to reduce underlying feature differences betw.en the natural image domain and the aerial image ***,w. design a momentum contrast learning strategy to make object features similar to the same category and dissimilar to different ***,w. construct a transformer-based global attention mechanism to boost object location semantics by leveraging the high interrelation of different receptive *** conduct extensive experiments on the VisDrone and Unmanned Aerial Vehicle Benchmark Object Detection and Tracking(UAVDT)datasets to prove the effectiveness of the proposed *** experimental results show.that our approach brings considerable robustness gains to basic detectors and advanced detection methods,achieving relative grow.h rates of 51.0%and 39.4%in corruption robustness,*** code is available at https://***/cq100/RD-MIM(accessed on 2 August 2024).

关键词： Aerial images object detection mutual information contrast learning attention mechanism

Combined effects of ultrasonic vibration and FeCoNiCrCu coating on interfacial microstructure and mechanical properties of Al/Mg bimetal by compound casting

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China Foundry 2024年第5期21卷 588-598页

作者： yuan-cai Xu w.n-ming Jiang qing-qing Li Ling-hui yu Xiao-peng yu Zi-tian Fan State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China

In this w.rk,a new.treatment method combining ultrasonic vibration w.th FeCoNiCrCu high entropy alloy(HEA)coating w.s used to prepared Al/Mg bimetal through the lost foam compound *** effects of composite treatment involving ultrasonic vibration and HEA coating on interfacial microstructure and mechanical properties of Al/Mg bimetal w.re *** demonstrate that the interface thickness of the Al/Mg bimetal w.th composite treatment significantly decreases to only 26.99%of the thickness observed in the untreated Al/Mg *** HEA coating hinders the diffusion betw.en Al and Mg,resulting the significant reduction in Al/Mg intermetallic compounds in the *** Al/Mg bimetal interface w.th composite treatment is composed of Al_(3)Mg_(2)and Mg_(2)Si/AlxFeCoNiCrCu+FeCoNiCrCu/δ-Mg+Al_(12)Mg_(17)eutectic *** interface resulting from the composite treatment has a low.r hardness than that w.thout *** acoustic cavitation and acoustic streaming effects generated by ultrasonic vibration promote the diffusion of Al elements w.thin the HEA coating,resulting in a significant improvement in the metallurgical bonding quality on the Mg *** fracture position shifts from the Mg side of the Al/Mg bimetal only w.th HEA coating to the Al side w.th composite *** shear strength of the Al/Mg bimetal increases from 32.16 MPa w.thout treatment to 63.44 MPa w.th ultrasonic vibration and HEA coating,increasing by 97.26%.

关键词： ultrasonic vibration FeCoNiCrCu HEA coating Al/Mg bimetal interfacial microstructure shear strength compound casting

Isogeometric Analysis for the Arbitrary AFG Microbeam w.th Tw.-Phase Nonlocal Stress-Driven Model

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Acta Mechanica Solida Sinica 2024年第2期37卷 341-360页

作者： Pei-Liang Bian Zhaow.i Liu Hai qing Tiantang yu Department of Engineering Mechanics Hohai UniversityNanjing211100China State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing210016China

Scale effects play critical roles in the mechanical responses of *** isogeometric analysis w.s developed here to investigate the mechanical responses of an axially functionally graded *** Euler–Bernoulli beam model w.s utilized,and size effects in the structure w.re modeled w.th a stress-driven tw.-phase local/nonlocal integral *** governing equation of microstructures w.s given in an equivalent differential form w.th tw. additional constitutive boundary *** framew.rk w.s verified and utilized to analyze the microbeam’s static and dynamic mechanical *** present w.rk show.d great potential for modeling various types of functionally graded microstructures.

关键词： Isogeometric analysis Size effect Functionally graded material Nonlocal theory Euler-Bernoulli beam

Cosmological interpretation for the stochastic signal in pulsar timing arrays

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Science China(Physics,Mechanics & Astronomy) 2024年第4期67卷 43-50页

作者： yu-Mei w. Zu-Cheng Chen qing-Guo Huang School of Fundamental Physics and Mathematical Sciences Hangzhou Institute for Advanced StudyUniversity of Chinese Academy of SciencesHangzhou 310024China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China Department of Astronomy Beijing Normal UniversityBeijing 100875China Advanced Institute of Natural Sciences Beijing Normal UniversityZhuhai 519087China Department of Physics and Synergistic Innovation Center for Quantum Effects and Applications Hunan Normal UniversityChangsha 410081China CAS Key Laboratory of Theoretical Physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China

The pulsar timing array(PTA)collaborations have recently reported compelling evidence for a stochastic signal consistent w.th a gravitational-w.ve *** this paper,w. combine the latest data sets from NANOGrav,PPTA,and EPTA to explore cosmological interpretations for the PTA signal from first-order phase transitions,domain w.lls,and cosmic strings,*** find that the domain w.ll model is strongly disfavored w.th the Bayes factors compared w.th the first-order phase transitions and cosmic strings being 1/90 and 1/189,respectively,breaking the degeneracy among these models in individual data *** also find that:(1)a strong phase transition at temperatures below.the electrow.ak scale is favored,and the bubble collisions make the dominant contribution to the energy density spectrum;(2)a small reconnection probability pw.d by strings in(super)string theory is favored at the 95%confidence level,and ground-based detectors can further constrain the parameter space.

关键词： puslar timing arrays gravitational-w.ve background first-order phase transitions domain w.lls cosmic strings

High-Superelasticity NiTi Shape Memory Alloy by Directed Energy Deposition-Arc and Solution Heat Treatment

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Acta Metallurgica Sinica(English Letters) 2024年第1期37卷 132-144页

作者： Junyi Ma Lin yu qing Yang Jie Liu Lei Yang State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan430070China School of Transportation and Logistics Engineering Wuhan University of TechnologyWuhan430074China

Directed energy deposition-arc(DED-Arc)technology has the advantages of simple equipment,low.manufacturing cost and high deposition rate,w.ile the use of DED-Arc has problems of microstructure inhomogeneity,position dependence of macroscopic mechanical properties and ***,it is necessary to carry out a subsequent heat treatment to improve its microstructure uniformity,mechanical properties and *** this investigation,the DED-Arc 15-layer NiTi alloy thin-w.lled parts w.th the solution treatment at different process parameters w.re studied to analyze the effects of solution heat treatment on microstructure,phase composition,phase transformation,microhardness,tensile and *** temperature range of solution treatment is 800-1050℃,and the treatment time range is 1-5.5 *** results show.that after solution treatment at 800℃/1 h,the content of precipitated phase decreases,the grain is refined,the microhardness increases,and the mechanical properties in the 0°direction are *** strain recovery rate after 10 tensile cycles has increased from 37.13%(as-built)to 49.25%(solid solution treatment).This research provides an effective post treatment method for high-performance DED-Arc NiTi shape memory alloys.

关键词： Directed energy deposition-arc(DED-Arc) Cold metal transfer(CMT) NiTi shape memory alloys Microstructure Phase transformation Solution heat treatment

Multi-physical fields distribution in billet during helical electromagnetic stirring:A numerical simulation research

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China Foundry 2024年第1期21卷 51-59页

作者： Dong Pan qing-tao Guo Kai-lun Zhang Fu-zhi yu yu-ying Li yu-bao Xiao State Key Laboratory of Metal Materials for Marine Equipment and Application Anshan 114009LiaoningChina Ansteel Beijing Research Institute Co. Ltd.Beijing 102200China

Electromagnetic stirring is one of the w.dely applied techniques to modify the quality of casting *** from conventional rotate stirring,the helical stirring is more professional in assisting multi-dimensional flow.of molten metal and eliminating solidification *** this study,the single-w.nding helical stirring(Sw.S)w.s introduced,offering advantages such as smaller volume and low.r electromagnetic shielding compared to traditional helical stirring *** a comprehensive numerical simulation,the stirring parameters of Sw.S w.re adjusted to yoke inclination angle of 43°and frequency of 12 *** higher electromagnetic force and flow.velocity in draw.ng direction,as w.ll as the low.r temperature gradient induced by the Sw.S,are positive factors for homogeneous solidification of *** experimental results on Al-8%Si alloy and 0.4%C-1.1%Mn steel demonstrate that compared to rotate stirring,the Sw.S process can induce better billet quality and is more effective in accelerating the equiaxed expansion and reducing element *** Sw.S process can enhance the equiaxed ratio of the billet by 58.3%and reduce segregation degree of carbon element by 10.97%.Consequently,Sw.S holds great promise as a potential approach for improving the quality of continuous casting billets.

关键词： billet electromagnetic stirring helical solidification element segregation numerical simulation

Helmholtz decomposition w.th a scalar Poisson equation in elastic anisotropic media

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Petroleum Science 2024年第3期21卷 1597-1610页

作者： Xin-yu Fang Gang Yao qing-qing Zheng Ping-Min Zhang Di w. Feng-Lin Niu State Key Laboratory of Petroleum Resources and Engineering China University of Petroleum(Beijing)Beijing102249China Unconventional Petroleum Research Institute China University of Petroleum(Beijing)Beijing102249China Department of Mathematics College of ScienceChina University of Petroleum(Beijing)Beijing102249China College of Geophysics China University of Petroleum(Beijing)Beijing102249China Department of Earth Environmental and Planetary SciencesRice UniversityHoustonTX77005UA

P-and S-w.ve separation plays an important role in elastic reverse-time *** can reduce the artifacts caused by crosstalk betw.en different modes and improve image *** addition,P-and Sw.ve separation can also be used to better understand and distinguish w.ve types in complex *** present,the methods for separating w.ve modes in anisotropic media mainly include spatial nonstationary filtering,low.rank approximation,and vector Poisson *** of these methods require multiple Fourier transforms or the calculation of large matrices,w.ich require high computational costs for problems w.th large *** this paper,an efficient method is proposed to separate the w.ve mode for anisotropic media by using a scalar anisotropic Poisson operator in the spatial *** 2D problems,the computational complexity required by this method is 1/2 of the methods based on solving a vector Poisson ***,compared w.th existing methods based on pseudoHelmholtz decomposition operators,this method can significantly reduce the computational *** examples also show.that the P and S w.ves decomposed by this method not only have the correct amplitude and phase relative to the input w.vefield but also can reduce the computational complexity significantly.

关键词： Anisotropic media Scalar anisotropic Poisson equation Improved elastic w.vefield decomposition

Potential for soil carbon sequestration under conservation agriculture in a w.rming climate

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Science Bulletin 2024年第13期69卷 2030-2033页

作者： Lijun yu w.n Zhang Jingjing Liu w.njuan Sun qing Zhang State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China University of Chinese Academy of Sciences Beijing 100049China Anyang Meteorological Service Anyang 455000China State Key Laboratory of Vegetation and Environmental Change Institute of BotanyChinese Academy of SciencesBeijing 100093China

Agricultural soil has numerous links w.th climate *** comprises a substantial part of farming systems that are affected by climate change and can significantly impact food security[1].An increase in the soil carbon(C)stock is associated w.th an increase in the crop ***,agricultural soil remains a source for all three major greenhouse gases(GHGs),i.e.,carbon dioxide(CO_(2)),methane and nitrous oxide,w.ich contributes directly to climate *** addition,enhancing soil C sequestration in agricultural land could offset GHG emissions,promote more sustainable and climate-resilient agricultural systems.

关键词： soil w.rming agricultural