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Effects of orientation on the fatigue crack growth behaviors of the ZK60 magnesium alloy in air and PBS

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Journal of Magnesium and Alloys 2024年第1期12卷 281-294页

作者： Jiaqi Hu Zheng Liu Zuoliang ning hong Gao School of Chemical Engineering and Technology Tianjin UniversityTianjin 300072China Tianjin Key Laboratory of Chemical Process Safety and Equipment Technology Tianjin 300072China

Strong anisotropic corrosion and mechanical properties caused by specimen orientations greatly limit the applications of wrought magnesium *** investigate the influences of specimen orientation,the corrosion tests and(corrosion)fatigue crack growth tests were *** rolled and transverse surfaces of the materials show distinct corrosion rate differences in the stable corrosion stage,but the truth is the opposite for the initial stage of *** air,specimen orientations have a significant influence on the plastic deformation mechanisms near the crack tip,which results in different fatigue fracture surfaces and cracking *** with R-T specimens,N-T specimens show a slower fatigue crack growth(FCG)rate in air,which can be attributed to crack closure effects and deformation twinning near the crack *** corrosion environment will not significantly change the main plastic deformation mechanisms for the same type of ***,the FCG rate in phosphate buffer saline(PBS)is one order of magnitude higher than that in air,which is caused by the combined effects of hydrogen-induced cracking and anodic *** to the similar corrosion rates at crack tips,the specimens with different orientations display close FCG rates in PBS.

关键词： Magnesium alloy Orientation Corrosion Fatigue crack growth

Effect of solvent on the initiation mechanism of living anionic polymerization of styrene:A computational study

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Chinese Journal of Chemical Engineering 2024年第5期69卷 135-142页

作者： Shen Li Yin-ning Zhou Zhong-Xin Liu Zheng-hong Luo School of Chemical Engineering and Technology Hainan UniversityHaikou 570228China Department of Chemical Engineering School of Chemistry and Chemical EngineeringState Key Laboratory of Metal Matrix CompositesShanghai Jiao Tong UniversityShanghai 200240China

For living anionic polymerization(LAP),solvent has a great influence on both reaction mechanism and *** this work,by using the classical butyl lithium-styrene polymerization as a model system,the effect of solvent on the mechanism and kinetics of LAP was revealed through a strategy combining density functional theory(DFT)calculations and kinetic *** terms of mechanism,it is found that the stronger the solvent polarity,the more electrons transfer from initiator to solvent through detailed energy decomposition analysis of electrostatic interactions between initiator and solvent ***,we also found that the stronger the solvent polarity,the higher the monomer initiation energy barrier and the smaller the initiation rate ***,initiation is more favorable at lower temperatures based on the calculated results ofΔG_(TS).Finally,the kinetic characteristics in different solvents were further examined by kinetic *** is found that in benzene and n-pentane,the polymerization rate exhibits first-order ***,slow initiation and fast propagation were observed in tetrahydrofuran(THF)due to the slow free ion formation rate,leading to a deviation from first-order kinetics.

关键词： Living anionic polymerization Solvent effect Reaction kinetics Computational chemistry Mathematical modeling Kinetic modeling

Ballistic performance of spherical fragments penetrating PCrNi3MoV target plates

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Defence Technology（防务技术） 2024年第3期33卷 295-307页

作者： Dou hong Wenbin Li Yu Zheng Yiming Li ning Jiang Kebin Zhang Ministerial Key Laboratory of ZNDY Nanjing University of Science and TechnologyNanjingChina

PCrNi3MoV steel is a medium-carbon,low-alloy quenched and tempered steel that finds its applications in military gun barrels due to the high wear resistance and ablation *** study the penetration and failure modes of PCrNi3MoV plates impacted by tungsten spheres,tungsten spheres of various diameters(5 mm,8 mm,and 10 mm)were used to impact PCrNi3MoV steel plates with thicknesses of 6 mm,9 mm,and 14 *** penetration performance of the spheres was analyzed for different velocities,and the ultimate penetration velocity of the plate was *** was found that the primary failure modes of the PCrNi3MoV plate were compression pitting failure and shear *** the dimensional analysis method,a relationship between the bulge height of the steel plate and the fragment velocity,an equation for the ultimate penetration velocity,and a relationship between the target penetration energy and the fragment velocity were ***,a projectile-target action index was proposed to describe the process of tungsten spheres with different velocities impacting target *** results suggested that under the same thickness of the target plate,a larger-diameter fragment required more kinetic energy to obtain the same ultimate penetration effect as a smaller-diameter *** equations obtained through dimensional analysis predicted values that agreed well with experimental values,indicating that these equations can be applied to engineering applications.

关键词： Impact damage Ultimate penetration velocity Bulge height Target penetration energy Failure modes

Insights into postural orthostatic tachycardia syndrome after COVID-19 in pediatric patients

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World Journal of Pediatrics 2024年第3期20卷 201-207页

作者： Ya-Xi Cui Jun-bao Du hong-Fang Jin Department of Pediatrics Peking University First HospitalNo.1 Xi-an Men StreetWest DistrictBeijing 100034China State Key Laboratory of Vascular Homeostasis and Remodeling Peking UniversityBeijing 100191China

The pandemic caused by the novel severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)profoundly threatened human health globally and greatly impacted the world economy[1].While most patients recovered,some suff... 详细信息

关键词： acute patients tachycardia

Attaining synergetic equilibrium of electrical conductivity and tensile strength in GQDs@GN/Cu composites through multi-scale intragranular and intergranular reinforcements

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Rare Metals 2024年第1期43卷 366-379页

作者： Shuang-Yin Zhang Liang Liu Rui bao Jian-hong Yi Sheng-Da Guo Faculty of Materials Science and Engineering Kunming University of Science and TechnologyKunming 650093China Key Laboratory of Advanced Materials of Yunnan Province Kunming University of Science and TechnologyKunming 650093China Faculty of Materials Metallurgy and Chemistry Jiangxi University of Science and TechnologyGanzhou 341000China

The configuration and quality of reinforcements, as well as the robustness of interfacial bonding,holding a critical significance in determining the concurrence between electrical conductivity and mechanical strength in metal matrix composites. In this study, citric acid was employed as the precursor for synthesizing multiscale carbon nanomaterials(graphene quantum dots and graphene, abbreviated as GQDs and GN). The GQDs@GN/Cu composites were fabricated through a segmented ball milling process in conjunction with subsequent spark plasma sintering(SPS). The intragranular GQDs and intergranular GQDs@GN had synergistically reinforced Cu composites through Orowan strengthening, load transfer strengthening and refinement strengthening. Furthermore,the robust interface bonding between GQDs@GN and Cu effectively mitigated interfacial impedance stemming from electron-boundary scattering. The yield strength and ultimate tensile strength of the GQDs@GN/Cu composites were recorded as 270 and 314 MPa, respectively, representing an improvement of 92 and 28% over pure Cu, while maintaining electrical conductivity at a level comparable to that of pure Cu. This study advances the understanding of the possibility of realizing a synergistic compatibility between electrical conductivity and mechanical strength in Cu composites.

关键词： Cu matrix composites Interface bonding Mechanical property Graphene quantum dots(GQDs) Electrical conductivity

Multiplicity of solutions for the semilinear subelliptic Dirichlet problem

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Science China Mathematics 2024年第3期67卷 475-504页

作者： Hua Chen hong-Ge Chen Jin-ning Li Xin Liao School of Mathematics and Statistics Wuhan UniversityWuhan 430072China Wuhan Institute of Physics and Mathematics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430071China

In this paper,we study the semilinear subelliptic equation{−△Xu=f(x,u)+g(x,u)inΩ,u=0 on∂Ω,where△X=−∑m i=1 Xi∗Xi is the self-adjoint Hormander operator associated with the vector fields X=(X_(1),X_(2),...,X_(m))satisfying the Hormander's condition,f(x,u)∈C(Ω×R),g(x,u)is a Carathéodory function onΩ×R,andΩis an open bounded domain in R~n with smooth *** the perturbation from the symmetry method with the approaches involving the eigenvalue estimate and the Morse index in estimating the minimax values,we obtain two kinds of existence results for multiple weak solutions to the problem ***,we discuss the difference between the eigenvalue estimate approach and the Morse index approach in degenerate *** with the classical elliptic cases,both approaches here have their own strengths in the degenerate *** new phenomenon implies that the results in general degenerate cases would be quite different from the situations in classical elliptic cases.

关键词： degenerate elliptic equations Hormander operators perturbation method Morse index

Study on the flow structure in curved open channels with suspended vegetation using multi relaxation time lattice Boltzmann method

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Journal of Hydrodynamics 2024年第2期36卷 300-315页

作者： He-fang Jing Qiao-ling Zhang Wei-hong Wang Zong-ning Zhang School of Mathematics and Information Science North Minzu UniversityYinchuan750021China School of Civil Engineering North Minzu UniversityYinchuan750021China Department of Basic Courses Zhengzhou University of Science and TechnologyZhengzhou450064China

Suspended vegetation in rivers,lakes,reservoirs and canals can change flow structure,which will in turn affect the sediment transport and cause the variation of water ecological *** order to study the characteristics of bend flow through suspended vegetation,three-dimensional numerical simulations are carried out by using the multi-relaxation-time lattice Boltzmann method(MRT-LBM).The drag force induced by vegetation is added in the velocity correction in the equilibrium distribution and a hybrid format combined bounce and specular reflection scheme is applied in the solid-fluid *** the validation of this model,six cases are designed to conduct the numerical simulations according to the root depth and the arrangement of *** simulated results show that the suspended vegetation can redistribute the flow structure in curved open *** the arrangement of suspended vegetation,the main flow moves to the side without vegetation,and the distribution of velocity tends to be balanced when vegetation is arranged on the entire cross section,the range of circulating current is reduced from the whole cross section to the local position without vegetation,however,the circulating current can still exist in the curve where the suspended vegetation enters less than half of the water *** addition,it can also be concluded that the suspended vegetation can affect the lateral gradient of flow velocity,and the bed shear stress in the curved channel.

关键词： Multi-relaxation-time lattice Boltzmann method(MRT-LBM) suspended vegetation curved open channel circulating current bed shearstress

A robust viscoelastic surfactant tolerating 20% HCl up to 150℃ for oil well stimulation

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Petroleum Science 2024年第3期21卷 1865-1874页

作者： Ji Wang ning Qi hong-Yao Yin Yu-Jun Feng Polymer Research Institute State Key Laboratory of Polymer Materials EngineeringSichuan UniversityChengdu610065SichuanPR.China Tianfu Yongxing Laboratory New Theory and Technology of CO_(2) Capture Research CenterChengdu610065SichuanPR China School of Petroleum Engineering China University of Petroleum(East China)Qingdao266580ShandongPR China

Viscoelastic surfactants(VES)are often used as viscous diverters in acidizing stimulation to prolong the acid consumption time and maximize zonal coverage of the acid for improving well ***,the ceiling temperature of commercial VES cannot exceed 120℃in practical use because of the poor thermal stability and fragile molecular structure,hindering their implementation in hightemperature oil reservoirs,i.e.,≥150℃.Here we synthesized a novel C22-tailed diamine,N-erucaminopropyl-N,N-dimethylamine(EDPA),and examined comparatively its rheological behavior,assemblies morphology and molecular stability in 20 wt%HCl with a commercial VES,erucyl dimethyl amidopropyl betaine(EDAB).The feasibility of EDPA for acidizing stimulation was assessed by acid etching of carbonate rock with its HCl solution at 150℃.Rheological results showed that the 2.5 wt%EDPA—20 wt%HCl solution maintains stable viscosity of 90 m Pa s at 150℃for 60 min,while that of 2.0 wt%EDAB HCl solution is just 1 m Pa s under identical conditions.1H NMR spectra and cryo-TEM observations revealed that the chemical structure and self-assembled architectures of EDPA remained intact in such context,but the EDAB suffered from degradation due to the hydrolysis of the amide group,accounting for the poor heat-resistance and *** reaction rate of 2.5 wt%EDPA HCl solution with carbonate rock was one order of magnitude lower than that of 20 wt%HCl solution at 150℃,underpinning the potential of EDPA to be used in the high-temperature reservoirs *** work improved the thermal tolerance of VES in highly concentrated HCl solution,paving a feasible way for the acidization of high-temperature reservoir environments(~150℃).

关键词： Viscoelastic surfactants Thermal stability Self-diverting acid Wormlike micelles Acidizing stimulation

A stable one-point quadrature rule for three-dimensional numerical manifold method

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Science China(Technological Sciences) 2024年第5期67卷 1401-1416页

作者： ZHANG ning ZHENG hong YANG Liang WU WenAn YUAN Chi School of Civil Engineering Qinghai UniversityQinghai810016China Key Laboratory of Urban Security and Disaster Engineering Ministry of EducationBeijing University of TechnologyBeijing100124China Faculty of Engineering China University of GeoscienceWuhan430074China

We present a numerically stable one-point quadrature rule for the stiffness matrix and mass matrix of the three-dimensional numerical manifold method(3D NMM).The rule simplifies the integration over irregularly shaped manifold elements and overcomes locking issues,and it does not cause spurious modes in modal *** essential idea is to transfer the integral over a manifold element to a few moments to the element center,thereby deriving a one-point integration rule by the moments and making modifications to avoid locking *** the stiffness matrix,after the virtual work is decomposed into moments,higher-order moments are modified to overcome locking issues in nearly incompressible and bending-dominated *** the mass matrix,the consistent and lumped types are derived by *** particular,the lumped type has the clear advantage of *** proposed method is naturally suitable for 3D NMM meshes automatically generated from a regular *** tests justify the accuracy improvements and the stability of the proposed procedure.

关键词： three-dimensional numerical manifold method quadrature rule locking mass lumping