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Effect of negative permeability on elastic wave propagation in magnetoelastic multilayered composites

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Theoretical & Applied Mechanics Letters 2017年第3期7卷 126-133页

作者： w. wang Y.q. Guo w.q. chen Key Laboratory of Mechanics on Disaster and Environment in western China Ministry of Education and School of Civil Engineering and MechanicsLanzhou University Lanzhou 730000 China Department of Engineering Mechanics Yuquan Campus Zhejiang University Hangzhou 310027 China Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Zhejiang University Hangzhou 310027 China

with the advent of left-handed magnetic materials, it is desirable to develop high-performance wave devices based on their novel properties of wave propagation. This letter reports the special properties of elastic wave propagation in magnetoelastic multilayered composites with negative permeability as compared to those in counterpart structures with positive permeability. These novel properties of elastic waves are discerned from the diversified dispersion curves, which represent the propagation and attenuation characteristics of elastic waves. To compute these dispersion curves, the method of reverberation-ray matrix is extended for the analysis of elastic waves in magnetoelastic multilayered composites. Although only the results of a single piezomagnetic and a binary magnetoelastic layers with mechanically free and magnetically short surfaces as well as perfect interface are illustrated in the numerical examples, the analysis is applicable to magnetoelastic multilayered structures with other kinds of boundaries/interfaces.

关键词： Magnetoelastic multilayered composites Elastic wave propagation Method of reverberation-ray matrix Negative permeability wave mode conversion

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弹性地基上功能分级梁的二维弹性解

钢结构(中英文) 2008年第12期 87-88页

作者： J Ying , C F Land w.q. chen

基于二维弹性理论,提出了winkler-Paster-nak弹性地基上功能分级梁弯曲和自由振动的精确解。假设梁是正交各向异性,沿厚度方向材料性能指数变化。通过扩展状态变量为无穷三角级数,调节偏微分方程系统,最终采用状态空间法使这一问题得到... 详细信息

基于二维弹性理论,提出了winkler-Paster-nak弹性地基上功能分级梁弯曲和自由振动的精确解。假设梁是正交各向异性,沿厚度方向材料性能指数变化。通过扩展状态变量为无穷三角级数,调节偏微分方程系统,最终采用状态空间法使这一问题得到解决。对几个参数的影响,如梯度指数、纵横比和功能梯度材料梁基本参数的力学性能进行研究。所提出的数值结果,为这类梁的分析提供了依据。

关键词：精确解功能梯度材料梁 winkler-Paster-nak弹性地基状态空间方法

Topological phase transitions and Majorana zero modes induced by the periodic potential in an antiferromagnetic chain

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Communications in Theoretical Physics 2023年第8期75卷 156-162页

作者： K w Shen q chen College of Physics and Mechanical&Electrical Engineering Jishou UniversityJishou 416000China School of Computational Science and Electronics Hunan Institute of EngineeringXiangtan 411104China

we investigate the topological properties of an antiferromagnetic(AFM)chain with an on-site periodic potential,considering the intrinsic spin–orbit coupling and an external Zeeman field along with the *** results indicate that Majorana zero modes(MZMs)can be observed by adjusting the strength of the periodic *** have calculated the energy spectrum,the wave-function and transport properties,and all these results support the existence of MZMs in the AFM ***,multiple topological phase transitions occur as the strength of the periodic potential changes,and several regions support MZMs.

关键词： AFM chain Majorana zero modes topological phase transitions periodic potential

The Novel Mechanical Property of Tongue of a woodpecker

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Journal of Bionic Engineering 2009年第3期6卷 214-218页

作者： P Zhou X q Kong C w wu Z chen National Key Laboratory for Structural Analysis of Industrial Equipment Dalian University of Technology Department of Civil and Environmental Engineering University of Missouri

Biomaterials such as bone,teeth,nacre and silk are known to have superior mechanical properties due to their specific nanocomposite *** we report that the woodpecker's tongue exhibits a novel strength and flexibility due to its special composite micro/*** tongue consists of a flexible cartilage-and-bone skeleton covered with a thin layer tissue of high strength and *** the interface between the cartilage-and-bone skeleton and the tissue layer,there is a hierarchical fiber-typed *** is this special design of the tongue that makes the woodpeckers efficient in catching the insects inside *** special micro/nanostructures of the woodpecker's tongue show us a potential method to enhance the interfacial connection between soft and hard material layers for bio-inspired composite system designs.

关键词： woodpeckcr hyoid cartllage multilevel structure tensile strength

Synthesis and Properties of Layered Oxides LiCo_(1-x)Ni_xO_2

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Journal of Materials Science & Technology 1997年第5期13卷 405-408页

作者： Lin, q chen, N Ye, w Liu, RM Luo, JS GEN RES INST NONFERROUS MET BEIJING 100088PEOPLES R CHINA

The mechanism of LiCo1－xNixO2(x=0, 0.5, 1) synthesis from carbonates or hydrates was studied by thermogravimetric analysis and X-ray diffraction to identify the medium and final products. The synthesis process from carbonates can be divided into two steps. Below 300℃cobalt carbonate and/or nickel carbonate decompose forming oxides. Over 300℃ Li2CO3 decomposes and reacts with Co and/or Ni oxides gradually, as a result Co++ and/or Ni++ areoxidized to Co+++ and/or Ni+++, finally LiCo1-xNixO2 forms. The proportion of cobalt tonickel in the starting mixture and atmosphere during synthesis affects the structure of ***1-xNixO2(x≤0.5) can be synthesized in air or oxygen and characterized by solid solutionof LiCoO2 and LiNiO2. LiNiO2 can be obtained only from hydrates and in oxygen *** and LiCo0.5Ni0.5O2 have higher first charge capacity than that of LiCoO2. Their discharge capacity reaches a level with that of LiCoO2 and has reasonable reversibility.

关键词： Lithium batteries

Localized space-tim e method of fundamental solutions for three-dimensional transient diffusion problem

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Acta Mechanica Sinica 2020年第5期36卷 1051-1057,I0002页

作者： L.qiu J.Lin q.-H.qin w.chen International Center for Simulation Software in Engineering and Sciences College of Mechanics and MaterialsHohai UniversityNanjing 210098China College of Engineering and Computer Science Australian National UniversityCanberraACT 2601Australia State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversityShijiazhuang 050043China State Key Laboratory of Acoustic Institute of AcousticsChinese Academy of SciencesBeijing 100190China

A localized space-time method of fundamental solutions(LSTMFS)is extended for solving three-dimensional transient diffusion problems in this *** interval segmentation in temporal direction is developed for the accurate simulation of long-time-dependent diffusion *** the LSTMFS,the whole space-time domain with nodes arranged i divided into a series of overlapping subdomains with a simple *** each subdomain,the conventional method of fundamental solutions is utilized and the coefficients associated with the considered domain can be explicitly *** calculating a combined sparse matrix system,the value at any node inside the space-time domain can be *** experi-ments demonstrate that high accuracy and efficiency can be simultaneously achieved via the LSTMFS,even for the problems defined on a long-time and quite complex computational domain.

关键词： Localized spacetime method of fundamental solutions Meshless method Long-time evolution Transient diffusion

Plasticity-induced stacking fault behaviors ofγ'precipitates in novel CoNi-based superalloys

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Journal of Materials Science & Technology 2021年第31期90卷 20-29页

作者： w.-w.Xu G.H.Yin Z.Y.Xiong q.Yu T.q.Gang L.J.chen School of Aerospace Engineering Xiamen UniversityXiamen 361005China

Implementation of novelγ/γ'Co-based superalloys with higher strength and improved creep durability is a challenging task for *** lack of atomic-level understanding of plastic deformation behavior has seriously limited the exploration of the full capacity of Co-based *** put forward a comprehensive study of generalized stacking fault energies by first principles to explore the effect of Ni and Al/w on the plastic deformation mechanism ofγ'precipitates in Co-based *** is found that alloying Ni and adjusting Al/w obviously change the dislocation glide and twinning nucleation in theγ'precipitates by altering the stable fault energies and the unstable fault energy *** addition of either Ni or w deteriorates the strength even the stability of *** ratio of effective planar fault energy(ΔEp)bridges intrinsic energy barriers and various deformation mechanisms of superalloys at elevated *** for alloying effects,the grain orientation also significantly governs the operation of the plastic deformation of *** theoretical results agree with the available measurements and well capture the observed phenomena in experiments.

关键词： Co-based superalloys Stacking fault energy Creep resistance First-principles method

Active{1121}and{1012}extension twinning in a wE43 Mg alloy

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Journal of Materials Science & Technology 2023年第13期144卷 93-101页

作者： w.q.chen S.Deng X.J.Zhao S.N.Luo Key Laboratory of Advanced Technologies of Materials Ministry of EducationSouthwest Jiaotong UniversityChengdu 610031China The Peac Institute of Multiscale Sciences Chengdu 610031China

Deformation twinning in a wE43 alloy subjected to uniaxial compression at room temperature is ***{1121}and{1012}extension twinning is *** activation of{1121}twinning in a certain grain is influenced not only by its own Schmid factor,but also by that of the basal ***-twin interactions of the co-zone{1121}twin variants are commonly observed and systematically studied,including the crystallographic characteristics of the four typically observed twin-twin junctions(TTJs)and the associated twin-twin *** the quilted-looking TTJs formed by the interaction of co-zone{1012}twin variants,crossing-like TTJs of co-zone{1121}twin variants are observed and their formation mechanisms are ***-like TTJs are also formed by the interaction of{1121}and{10¯12}*** morphology and thickening rate of{1121}and{1012}twins vary markedly due to the difference in twinning *** needle-like{1121}twins thicken more slowly than the lenticular{1012}*** nucleation is observed on the previously formed{1121}twin boundary due to the relatively large strain concentration on such interface,while twin nucleation on{1012}twin boundary is rarely observed.

关键词： Mg alloy Plastic deformation Twinning Twin-twin interaction Twin-twin junction

Precipitation on stacking faults in Mg–9.8wt%Sn alloy

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Journal of Materials Science & Technology 2020年第10期42卷 230-240页

作者： C.q.Liu C.He H.w.chen J.F.Nie International Joint Laboratory for Light Alloys(Ministry of Education) College of Materials Science and EngineeringChongqing UniversityChongqing400044China Department of Materials Science and Engineering Monash UniversityVictoria3800Australia Electron Microscopy Center Chongqing UniversityChongqing400044PR China

In this work,we have systematically investigated precipitation ofβ’-Mg3Sn phase on intrinsic stacking faults I1 and I2 in a Mg-9.8 wt%Sn alloy using aberration-corrected scanning transmission electron *** observed I1 faults are generated by the dissociation of c+a perfect dislocations and bounded by Frank partial dislocations having a Shockley *** ofβ’on I1 involves a shear of 1/3α,similar to its formation directly from theα-Mg ***β’phase often nucleates at one end of an I1 fault due to the interaction between shear strain fields ofβ’and the Shockley component of the Frank partial at that end,and subsequently grows towards the other end of the *** theβ’reaches to the other end,the Shockley partial bounding the lengthening end of theβ’reacts with the Frank partial bounding the fault,generating an a perfect dislocation that can glide away from the precipitate and the *** observed I2 faults are generated by the dissociation of a perfect dislocations and bounded by Shockley *** ofβ’on I2 does not need a shear of 1/3α,since the pre-existing I2 fault already provides an ABCA four-layer structure ofβ’.Thickening of theβ’that has already formed on the I2 involves the successive occurrence of three crystallographically equivalent shears of 1/3αon every second(0002)αplane of theα-Mg *** this thickening mechanism is similar to that of theβ’formed directly from theα-Mg matrix,an a perfect dislocation will be produced when theβ’is thickened to eight layers,and it can again glide away from the precipitate and the fault.

关键词： Heterogeneous precipitation HAADF-STEM Shockley partial dislocation Frank partial dislocation Dislocation reaction