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Acta Mechanica Sinica 2015年第4期31卷 494-499页

作者： Manrui Ren Ze l.u Quan-shui zheng jefferson zhe l.u Department of Engineering Mechanics and Center for Nano and Micro Mechanics Tsinghua University Department of Mechanical and Aerospace Engineering Monash University

Mechanical exfoliation is a widely used method to isolate high quality graphene layers from bulk graphite. In our recent experiments, some ordered microstructures, consisting of a periodic alternation of kinks and stripes, were observed in thin graphite flakes that were mechanically peeled from highly oriented pyrolytic graphite. In this paper, a theoretical model is presented to attribute the formation of such ordered structures to the alternation of two mechanical processes during the exfoliation：（1） peeling of a graphite flake and （2） mechanical buckling of the flake being sub- jected to bending. In this model, the width of the stripes l is determined by thickness h of the flakes, surface energy Y, and critical buckling strain ecr. using some appropriate values of y and ecr that are within the ranges determined by other inde- pendent experiments and simulations, the predicted relations between the stripe width and the flake thickness agree reason- ably well with our experimental measurements. Conversely, measuring the l-h relations of the periodic microstructures in thin graphite flakes could help determine the critical mechan- ical buckling strain εcr and the interface energy γ.

关键词： HOPG Mechanical exfoliation Periodic microstructures Kinking Mechanical buckling

Van der Waals force-induced intralayer ferroelectric-to-antiferroelectric transition via interlayer sliding in bilayer group-Ⅳmonochalcogenides

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npj Computational Materials 2022年第1期8卷 446-454页

作者： Bo Xu Junkai Deng Xiangdong Ding Jun Sun jefferson zhe l.u State Key laboratory for Mechanical Behavior of Materials Xi’an Jiaotong University710049Xi’anChina Department of Mechanical Engineering The University of MelbourneParkvilleVIC3010Australia

Two-dimensional materials with ferroelectric properties break the size effect of conventional ferroelectric materials and unlock unprecedented potentials of ferroelectric-related application at small length *** first-principles cal.ulations,a sliding-induced ferroelectric-to-antiferroelectric behavior in bilayer group-IV monochalcogenides(MX,with M=Ge,Sn and X=S,Se)is *** this mechanism,the top layer exhibits a reversible intralayer ferroelectric switching,leading to a reversible transition between the ferroelectric and antiferroelectric states in the bilayer *** results show that the interlayer van der Waals interaction,which is usually considered to be weak,can actually generate an in-plane lattice distortion and thus cause the breaking/forming of intralayer covalent bonds in the top layer,leading to the observed anomal.us *** unique property has advantages for energy harvesting over existing piezoelectric and triboelectric *** interlayer sliding-induced big polarization change(40μC cm^(−2))and ultrahigh polarization changing rate generate an open-circuit voltage two orders of magnitude higher than that of MoS_(2)-based *** theoretical prediction of power output for this bilayer MXs at a moderate sliding speed 1 m s^(−1)is four orders of magnitude higher than the MoS_(2)nanogenerator,indicating great potentials in energy harvesting applications.

关键词： ferroelectric interlayer layer

An equivalent 1D nanochannel model to describe ion transport in multilayered graphene membranes

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Progress in Natural Science:Materials International 2018年第2期28卷 246-250页

作者： Gengping Jiang Peiyao Wang Chi Cheng Dan li jefferson zhe l.u College of Science Wuhan University of Science and Technology Department of Materials Science and Engineering Monash University Department of Mechanical Engineering The University of Melbourne 4. Department of Chemical Engineering The University of Melbourne Department of Mechanical and Aerospace Engineering Monash University

Multilayered graphene-based membranes are promising for a variety of applications related to ion or molecule transport, such as energy storage and water treatment. However, the complex three-dimensional cascading nanoslit-like structure embedded in the membrane makes it difficult to interpret and rationalize experimental results, quantitatively compare with the traditional membrane systems, and quantitatively design new membrane structures. In this paper, systematic numerical simulations were performed to establish an equivalent onedimensional(1 D) nanochannel model to represent the structure of multilayered graphene membranes. We have established a quantitative relationship between effective diffusion length leffand cross-section area Aeffof the1 D model and our recently developed two dimensional(2 D) representative microstructure for graphene membranes. We find that only in the cases of a relatively large lateral size l(> ~100 nm) and a small slit size h(usion length leffand Aeffcan be cal.ulated by an over-simplified but often used model. Otherwise, they show complex dependence on all three structural parameters of the 2 D structural *** equivalent 1 D nano-channel model can reproduce experimental results very well except for h uld be attributed to the anomal.us behaviour of molecules under nano-confinement that is not considered in our simulations. This model can also be extended to multilayered membranes assembled by other2 D materials.

关键词： Graphene 2D materials Equivalent 1D nanochannel Time-lag method Continuum modelling

Diverse electronic and magnetic properties of CrS_(2) enabling strain-controlled 2D lateral heterostructure spintronic devices

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npj Computational Materials 2021年第1期7卷 704-712页

作者： Kaiyun Chen Junkai Deng Yuan Yan Qian Shi Tieyan Chang Xiangdong Ding Jun Sun Sen Yang jefferson zhe l.u MOE Key laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter State Key Laboratory for Mechanical Behavior of MaterialsXi’an Jiaotong UniversityXi’an 710049China Department of Mechanical Engineering The University of MelbourneParkvilleVIC 3010Australia

lateral heterostructures of two-dimensional(2D)materials,integrating different phases or materials into a single piece of nanosheet,have attracted intensive research interests for electronic *** the 2D lateral heterostructures to spintronics demands more diverse electromagnetic properties of 2D *** this paper,using density functional theory cal.ulations,we survey all IV,V,and VI group transition metal dichalcogenides(TMDs)and discover that CrS_(2)has the most diverse electronic and magnetic properties:antiferromagnetic(AFM)metallic 1T phase,non-magnetic(NM)semiconductor 2H phase,and ferromagnetic(FM)semiconductor 1T′phase with a Curie temperature of~1000 ***,we find that a tensile or compressive strain can turn the 1T′phase into a spin-up or spin-down *** strain tunability can be attributed to the lattice deformation under tensile/compressive strain that selectively promotes the spin-up/spin-down VBM(valence band bottom)orbital *** diverse electromagnetic properties and the strain tunability enable strain-controlled spintronic devices using a single piece of CrS_(2)nanosheet with improved energy *** a demo,a prototypical design of the spin-valve logic device is *** offers a promising solution to address the challenge of high energy consumption in miniaturized spintronic devices.

关键词： strain electronic magnetic

Critical Exponent for the Parabolic Equation u_t=Δu^m + h(t)u^p in a Cone

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Acta Mathematica Sinica,English Series 2012年第8期28卷 1623-1632页

作者： Chang Chun l.u Song zhe lIAN Department of Mathematics Jilin University

In this paper, we study the initial-boundary value problem of porous medium equationut = △um ＋ h（t）up in a cone D = （0, ） Ω, where h（t） - t. let wl denote the smallest Dirichlet eigenvalue for the laplace-Beltrami operator on Ω and let l denote the positive root cf l2＋（n-2）l = wl. 2（＋1）＋（rn- 1）, then the problem has no global nonnegative solutions We prove that if m 〈 p 〈 m ＋ for any nonnegative u0 unless u0 -= 0; if p 〉 m ＋＋ a（m - 1）, then the problem has global n4-1 solutions for some uo 〉 O.

关键词： Porous medium equation cone critical exponent

种植方式对华北平原典型农田土壤微形态特征的影响

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农业机械学报 2017年第5期48卷 282-289页

作者：孙增慧韩霁昌刘哲吕贻忠陕西省土地工程建设集团有限责任公司西安710075 中国农业大学资源与环境学院北京100093

以华北平原曲周18年长期定位试验的农田土壤为研究对象,利用偏光显微镜观察常规种植、无公害种植和有机种植3种种植方式下的土壤薄片,研究种植方式对土壤微形态特征的影响。结果表明:3种种植方式下的土壤和土壤粗颗粒的矿物组合基本一致... 详细信息

以华北平原曲周18年长期定位试验的农田土壤为研究对象,利用偏光显微镜观察常规种植、无公害种植和有机种植3种种植方式下的土壤薄片,研究种植方式对土壤微形态特征的影响。结果表明:3种种植方式下的土壤和土壤粗颗粒的矿物组合基本一致,主要由石英和长石组成,但颗粒的形态和粒径有一定差别;有机种植下,土壤表层结构由中度分离的块状和板状结构为主变为团粒结构为主,发育良好的团聚体含量明显增加,土壤容重显著下降,有机质显著增加;表层土壤容重为1.19 g/cm^3,有机质含量为22.67 g/kg,总孔隙度高达32%。常规种植条件下,土壤表层结构以中度分离的块状结构为主,土壤结构较为紧实,发育程度较低;表层土壤容重为1.30 g/cm^3,有机质含量为18.42 g/kg,表层的总孔隙度为30%。无公害种植条件下,土壤表层结构以中度分离的团块状结构和少量的高度分离的粒状结构为主,土壤结构发育程度居于有机种植和常规种植二者之间。因此,有机种植条件下土壤结构疏松,土壤透气性良好,有利于作物生长。

关键词：土壤微形态土壤结构种植方式农田土壤华北平原

掺杂TEOS的YAG透明陶瓷相转变、烧结及微观组织

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中国有色金属学报 2010年第6期20卷 1220-1225页

作者：吕光哲孙旭东东北大学材料与冶金学院材料各向异性与织构教育部重点实验室沈阳110004 辽宁科技学院冶金系本溪117004

分别添加0.3%～3.0%(质量分数)的正硅酸乙酯(TEOS)为烧结助剂,利用液相烧结合成钇铝石榴石(Y3Al5O12,YAG)透明陶瓷。结果表明:液相生成是一种动态过程,最低形成温度约为1400℃。烧结体相对密度随着烧结温度的升高而明显增大,且烧结助剂... 详细信息

分别添加0.3%～3.0%(质量分数)的正硅酸乙酯(TEOS)为烧结助剂,利用液相烧结合成钇铝石榴石(Y3Al5O12,YAG)透明陶瓷。结果表明:液相生成是一种动态过程,最低形成温度约为1400℃。烧结体相对密度随着烧结温度的升高而明显增大,且烧结助剂对致密化过程的促进作用与其含量有关。当w(TEOS)≤0.5%时,TEOS能够更明显地促进烧结,TEOS含量对真空烧结后烧结体内残留硅酸盐相的数量、分布和显微结构产生很大的影响。当w(TEOS)≤0.5%时,Y2Si2O7与Al2O3·SiO2(Mul)固溶于YAG晶粒内,晶界处没有残留第二相;当w(TEOS)为2%和3%时,过量的Y2Si2O7与Mul在晶界析出而成为散射源,严重损害陶瓷的光学性能。

关键词： YAG透明陶瓷液相烧结液相含量 Y2Si2O7 3Al2O3·2SiO2

logcf: An Efficient Tool for Real Root Isolation

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Journal of Systems Science & Complexity 2019年第6期32卷 1767-1782页

作者： DAI liyun FAN zhe XIA Bican ZHANG Hanwen RISE&School of Computer and Information Science Southwest UniversityChongqing 400700China lMAM&School of Mathematical Science Peking UniversityBeijing 100871China

Computing upper bounds of the positive real roots of some polynomials is a key step of those real root isolation algorithms based on continued fraction expansion and Vincent's *** authors give a new algorithm for computing an upper bound of positive roots in this *** complexity of the algorithm is O(n log(uH-l))additions and multiplications where u is the optimal.upper bound satisfying Theorem 3.1 of this paper and n is the degree of the *** method together w辻h some tricks have been implemented as a software package logcf using C *** on many benchmarks show that logcf is competitive with Root Intervals of Mathematica and the function realroot of Maple averagely and it is much faster than existing open source real root solvers in many test cases.

关键词： Computer algebra continued fractions real root isolation univariate polynomial vincent's theorem

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组织蛋白酶D在人椎间盘细胞表达的研究

中国医科大学学报 2006年第3期35卷 328-329页

作者：金哲吕刚中国医科大学附属第一医院骨科辽宁沈阳110001

探讨组织蛋白酶D(Cath-D)在正常和退变间盘中表达及其意义。结果,正常组和退变组间盘中均有Cath-D表达,退变组表达水平明显高于正常组,差异显著(P<0.05)。Cath-D参与了椎间盘退变的病理改变。

关键词：椎间盘退变基质组织蛋白酶

Machine learning for deep elastic strain engineering of semiconductor electronic band structure and effective mass

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npj Computational Materials 2021年第1期7卷 694-703页

作者： Evgenii Tsymbalov zhe Shi Ming Dao Subra Suresh Ju li Alexander Shapeev Skolkovo Institute of Science and Technology MoscowRussia Department of Materials Science and Engineering and Department of Nuclear Science and Engineering Massachusetts Institute of TechnologyCambridgeMAUSA Nanyang Technological.university SingaporeRepublic of Singapore

The controlled introduction of elastic strains is an appealing strategy for modulating the physical properties of semiconductor *** the recent discovery of large elastic deformation in nanoscale specimens as diverse as silicon and diamond,employing this strategy to improve device performance necessitates first-principles computations of the fundamental electronic band structure and target figures-of-merit,through the design of an optimal straining *** simulations,however,call for approaches that combine deep learning algorithms and physics of deformation with band structure cal.ulations to custom-design electronic and optical *** by this challenge,we present here details of a machine learning framework involving convolutional neural networks to represent the topology and curvature of band structures in *** cal.ulations enable us to identify ways in which the physical properties can be altered through“deep”elastic strain engineering up to a large fraction of the ideal *** capable of active learning and informed by the underlying physics were presented here for predicting the bandgap and the band *** training a surrogate model with ab initio computational data,our method can identify the most efficient strain energy pathway to realize physical property *** power of this method is further demonstrated with results from the prediction of strain states that influence the effective electron *** il.ustrate the applications of the method with specific results for diamonds,although the general deep learning technique presented here is potentially useful for optimizing the physical properties of a wide variety of semiconductor materials。

关键词： strain deformation electronic