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A numerical method based on boundary integral equations and radial basis functions for plane anisotropic thermoelastostatic equations with general variable coefficients

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Applied Mathematics and Mechanics(English Edition) 2020年第4期41卷 551-566页

作者： W.t.ang X.Wang School of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore 639798Singapore Department of Mechanical Engineering National University of SingaporeSingapore 117575Singapore

A boundary integral method with radial basis function approximation is proposed for numerically solving an important class of boundary value problems governed by a system of thermoelastostatic equations with variable coe?cients. the equations describe the thermoelastic behaviors of nonhomogeneous anisotropic materials with properties that vary smoothly from point to point in space. No restriction is imposed on the spatial variations of the thermoelastic coe?cients as long as all the requirements of the laws of physics are satis?ed. to check the validity and accuracy of the proposed numerical method, some speci?c test problems with known solutions are solved.

关键词： elliptic partial differential equation variable coefficient boundary element method radial basis function anisotropic thermoelastostatics

Cortical hem signaling center: functions, development, and potential implications for evolution and brain disorders

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Neural Regeneration Research 2025年第4期20卷 1079-1080页

作者： Victor V.Chizhikov Igor y.Iskusnykh Department of Anatomy and Neurobiology University of Tennessee Health Science CenterMemphisTNUSA

Development of the telencephalon relies upon several signaling centers-localized cellular populations that supply secreted factors to pattern the cortical *** such signaling center is the cortical hem,which arises during embryonic development at the telencephalic dorsal midline,adjacent to the choroid plexus and hippocampal primordium(Figure 1A).While the cortical hem has also been described in reptiles and birds,most of our knowledge about the developmental roles of the cortical hem is derived from the analysis in *** cortical hem produces several types of secreted molecules,including wingless-related integration site(Wnt)and bone morphogenetic(Bmp)*** cortical hem is particularly important for the development of the hippocampus,which is involved in learning and memory,and the neocortex,which is the most complex brain region that mediates multiple types of behavior and higher cognitive functions(Mangale et al.,2008;Dal-Valle-Anton and Borrell,2022).

关键词： epithelium Figure center

A micromechanical model based on hypersingular integro-differential equations for analyzing micro-crazed interfaces between dissimilar elastic materials

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Applied Mathematics and Mechanics(English Edition) 2020年第2期41卷 193-206页

作者： X.Wang W.t.ang H.FAN School of Mechanical and Aerospace Engineering Nanyang Technological University50 Nanyang AvenueSingapore 639798Singapore

the current work models a weak(soft) interface between two elastic materials as containing a periodic array of micro-crazes. the boundary conditions on the interfacial micro-crazes are formulated in terms of a system of hypersingular integro-differential equations with unknown functions given by the displacement jumps across opposite faces of the micro-crazes. Once the displacement jumps are obtained by approximately solving the integro-differential equations, the effective stiffness of the micro-crazed interface can be readily computed. the effective stiffness is an important quantity needed for expressing the interfacial conditions in the spring-like macro-model of soft interfaces. Specific case studies are conducted to gain physical insights into how the effective stiffness of the interface may be influenced by the details of the interfacial micro-crazes.

关键词： micromechanical modeling micro-crazed interface effective stiffness coefficient hypersingular integro-differential equation

Effect of thermal Refining on Mechanical Properties of Annealed SAE 4130 by Multilayer GtAW

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Journal of Iron and Steel Research International 2012年第7期19卷 71-78页

作者： I K lee C l Chung y t lee y t Chien Department of Materials Science and Engineering Da-Yeh University

During the first welding process in manufacturing a precise seam container, the steel material must first undergo a full annealing treatment. Multilayer welding operations are conducted and then applied with refining treatment to obtain the goal by hardening. the influence of thermal refining on mechanical properties of annealed SAE 4130 by multilayer GtAW （gas tungsten arc welding） was discussed. the AW （annealing＋welding） and AWSt （annealing＋welding＋solution＋tempering） occurred with a minimum hardness value at GGHAZ （grain growth heat affected zone） due to coarse grain growth~ the hardness occurred with sudden drops between the multilayer welding, but was still larger than the minimum value at HAZ （heat affected zone）. the welded joint efficiency of the AWSt was 89.9%, with the elongation reduced to 77.2% of ASt （annealing＋solution＋tempering）. the cross section of the tensile samples both appeared with a uniform dimple-shaped structure, and however the necking for ASt was greater than that for AWSt. the impact value for AWSt was 166.5% of ASt. Moreover, from microstructure observations, it was found that AWSt had a greater tendency to ductile failure than ASt. these results can be inferred., the process of steady pressure and the initial position of the precision tube breakage HAZ. However, when stress occurs instantly, HAZ can absorb more energy, therefore the initial damage does not occur.

关键词： thermal refining SAE 4130 multilayer welding GtAW

An Overview of Self-piercing Riveting Process with Focus on Joint Failures, Corrosion Issues and Optimisation techniques

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Chinese Journal of Mechanical Engineering 2021年第1期34卷 89-113页

作者： Hua Qian ang School of Engineering RMIT UniversityBundooraVictoria 3083Australia

Self-piercing riveting(SPR)is a cold forming technique used to fasten together two or more sheets of materials with a rivet without the need to predrill a *** application of SPR in the automotive sector has become increasingly popular mainly due to the growing use of lightweight materials in transportation ***,SPR joining of these advanced light materials remains a challenge as these materials often lack a good combination of high strength and ductility to resist the large plastic deformation induced by the SPR *** this paper,SPR joints of advanced materials and their corresponding failure mechanisms are discussed,aiming to provide the foundation for future improvement of SPR joint *** paper is divided into three major sections:1)joint failures focusing on joint defects originated from the SPR process and joint failure modes under different mechanical loading conditions,2)joint corrosion issues,and 3)joint optimisation via process parameters and advanced techniques.

关键词： Self-piercing riveting Mechanical joining Joint defects Failure mechanisms Corrosion Joint optimisation

Broadband strong optical dichroism in topological Dirac semimetals with Fermi velocity anisotropy

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Chinese Physics B 2020年第7期29卷 128-134页

作者： J lim K J A Ooi C Zhang l K ang yee Sin ang Science Math and TechnologySingapore University of Technology and DesignSingapore School of Energy and Chemical Engineering Xiamen University MalaysiaSelangor Darul Ehsan 43900Malaysia College of Chemistry and Chemical Engineering Xiamen UniversityXiamen 361005China School of Physics University of WollongongNorthfields AvenueNew South Wales 2522Australia

Prototypical three-dimensional(3D)topological Dirac semimetals(DSMs),such as Cd3As2 and Na3Bi,contain electrons that obey a linear momentum-energy dispersion with different Fermi velocities along the three orthogonal momentum *** being extensively studied in recent years,the inherent Fermi velocity anisotropy has often been neglected in the theoretical and numerical studies of 3D *** this omission does not qualitatively alter the physics of light-driven massless quasiparticles in 3D DSMs,it does quantitatively change the optical coefficients which can lead to nontrivial implications in terms of nanophotonics and plasmonics *** we study the linear optical response of 3D DSMs for general Fermi velocity values along each *** the signature conductivity-frequency scaling,σ(ω)∝ω,of 3D Dirac fermion is well-protected from the Fermi velocity anisotropy,the linear optical response exhibits strong linear dichroism as captured by the universal extinction ratio scaling law,Λi j=(vi/v j)^2(where i=j denotes the three spatial coordinates x,y,z,and vi is the i-direction Fermi velocity),which is independent of frequency,temperature,doping,and carrier scattering *** Cd3As2 and Na3Bi3,an exceptionally strong extinction ratio larger than 15 and covering a broad terahertz window is *** findings shed new light on the role of Fermi velocity anisotropy in the optical response of Dirac semimetals and open up novel polarization-sensitive functionalities,such as photodetection and light modulation.

关键词： topological Dirac semimetal optical anisotropy linear dichroismn linear response theory

Frequency Veering of Rotating Metal Porous twisted Plate with Cantilever Boundary Using Shell theory

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Acta Mechanica Solida Sinica 2022年第2期35卷 282-302页

作者： y.y.liu y.X.Hao W.Zhang l.t.liu S.W.yang y.t.Cao College of Mechanical Engineering Beijing Information Science and Technology UniversityBeijing 100192China College of Mechanical Engineering Beijing University of TechnologyBeijing 100124China

the frequency veering of a metal porous rotating cantilever twisted plate with twist angle and stagger angle is *** porous materials may have the characteristics of gradient or uniform distribution along the thickness *** on the classical shell theory,considering the influence of centrifugal force produced by high-speed rotation,the free vibration equations of a rotating cantilever twisted plate are *** the polynomial function and Rayleigh-Ritz method,the natural frequencies and mode shapes of the metal porous cantilever twisted plate in both static and rotating states are *** accuracy of the present theory and calculation results is confirmed by a comparison between them and the results available from the literature and those obtained from *** influences of the thickness ratio,porosity,twist angle,stagger angle and rotational velocity on the frequency veering and mode shape shift of the rotating cantilever twisted plate with porous material under three different distributions are *** should be mentioned that the frequency veering accompanied by mode shape shift occurs in both static and dynamic states.

关键词： Frequency veering Rotating twisted plate Cantilever boundary Metal porous

Combined approach for analysing evolutionary power spectra of a track-soil system under moving random loads

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Acta Mechanica Sinica 2019年第3期35卷 674-690页

作者： y.Zhao l.t.Si H.Ouyang State Key laboratory of Structural Analysis for Industrial Equipment Department of Engineering MechanicsInternational Center for Computational MechanicsDalian University of TechnologyDalian 116023Chin School of Engineering University of LiverpoolLiverpool L69 3GHUK

the pseudo-excitation method combined with the integral transform method (PEM-ItM) is presented to investigate the ground vibration of a coupled track-soil system induced by moving random loads. Commonly in the track model, the rail, sleepers, rail pads, and ballast are modelled as an infinite Euler beam, discretely distributed masses, discretely distributed vertical springs, and a viscoelastic layer, respectively. the soil is regarded as a homogenous isotropic half-space coupled with the track using the boundary condition at the surface of the ground. By introducing a pseudo-excitation, the random vibration analysis of the coupled system is converted into a harmonic analysis. the analytical form of evolutionary power spectral density responses of the simplified coupled track-soil system under a random moving load is derived in the frequency/wavenumber domain by PEM-ItM. In the numerical examples, the effects of different parameters, such as the moving speed, the soil properties, and the coherence of moving loads, on the ground response are investigated.

关键词： track-soil system Moving random loads Evolutionary power spectrum Pseudo-excitation method Integral transform method Vibration transmission

Role of interstitial flow in tumor migration through 3D ECM

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Acta Mechanica Sinica 2020年第3期36卷 768-774页

作者： ang li Ren Sun MOE Key laboratory of Hydrodynamics School of Naval ArchitectureOcean&Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China

Cancer invasion in tissue is simultaneously regulated by chemical and mechanical *** suggest that interstitial flow plays a critical role in tumor *** one hand,the distribution of chemokines around cell is influenced by *** the other hand,interstitial flow may reconfigure the alignment of fiber matrix,which greatly changes the contact force between cell and extracellular *** this study,we have upgraded a model by which we can quantitatively investigate the influence of flow on tumor cell migration.A hydrodynamic analysis of shear stress on a slender body is introduced to simulate the fiber *** such as subtle flow and cell-matrix interaction which dominate tumor migration are integrated in this novel *** results show interstitial flow facilitates tumor cell migration in the flow ***,the flow-related chemical and mechanical cues have a synergistic effect on the *** model provides better understanding on cancer metastasis and helps design vitro experiment precisely.

关键词： Interstitial flow tumor cell migration Extracellular matrix