检索结果-南通市图书馆

Size and strain rate effects in tensile strength of penta-twinned Ag nanowires

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2017年第4期33卷 792-800页

作者： Xuan Zhang Xiaoyan Li Huajian Gao centre of Advanced mechanics and Materials Department of Engineering Mechanics Tsinghua University School of Engineering Brown University

Penta-twinned Ag nanowires（pt-AgNWs） have recently attracted much attention due to their interesting mechanical and physical properties. Here we perform largescale atomistic simulations to investigate the influence of sample size and strain rate on the tensile strength of pt-AgNWs. The simulation results show an apparent size effect in that the nanowire strength（defined as the critical stress for dislocation nucleation） increases with decreasing wire diameter. To account for such size effect, a theoretical model involving the interaction between an emerging dislocation and the twin boundary has been developed for the surface nucleation of dislocations. It is shown that the model predictions are in quantitative agreement with the results from atomistic simulations and previous experimental studies in the literatures. The simulations also reveal that nanowire strength is strain-rate dependent, which predicts an activation volume for dislocation nucleation in the range of 1–10b^3,where b is the magnitude of the Burgers vector for a full dislocation.

关键词： nucleation tensile dislocation modulus apparent diameters decreasing magnitude crystalline penta

Molecular rotors with designed polar rotating groups possess mechanics-controllable wide-range rotational speed

在线全文

学校读者我要写书评

暂无评论

npj Computational Materials 2020年第1期6卷 131-139页

作者： Jian Shao Wenpeng Zhu Xiaoyue Zhang Yue Zheng State Key Laboratory of Optoelectronic Materials and Technologies Sun Yat-sen University510275 GuangzhouChina physical mechanics and biophysics Research Center School of PhysicsSun Yat-sen University510275 GuangzhouChina

Molecular rotors with controllable functions are promising for molecular machines and electronic ***,fast rotation in molecular rotor enables switchable molecular conformations and charge transport states for electronic ***,the key to molecular rotor-based electronic devices comes down to a trade-off between fast rotational speed and thermal *** rotation in molecular rotor requires a small energy barrier height,which disables its controllability under thermal excitation at room temperature.

关键词： Molecular rotation rotating

Covalent intermolecular interaction of the nitric oxide dimer (NO)_2

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics B 2015年第9期24卷 177-181页

作者：张辉郑桂丽吕刚耿轶钊纪青 School of Science Hebei University of Technology Changchun Institute of Optics Fine Mechanics and Physics Mathematical and physical Science School North China Electric Power University Institute of biophysics Hebei University of Technology State Key Laboratory of Theoretical Physics Institute of Theoretical PhysicsChinese Academy of Sciences

Covalent bonds arise from the overlap of the electronic clouds in the internucleus region, which is a pure quantum effect and cannot be obtained in any classical way. If the intermolecular interaction is of covalent character, the result from direct applications of classical simulation methods to the molecular system would be questionable. Here, we analyze the special intermolecular interaction between two NO molecules based on quantum chemical calculation. This weak intermolecular interaction, which is of covalent character, is responsible for the formation of the NO dimer,（NO）2, in its most stable conformation, a cis conformation. The natural bond orbital（NBO） analysis gives an intuitive illustration of the formation of the dimer bonding and antibonding orbitals concomitant with the breaking of the πbonds with bond order 0.5of the monomers. The dimer bonding is counteracted by partially filling the antibonding dimer orbital and the repulsion between those fully or nearly fully occupied nonbonding dimer orbitals that make the dimer binding rather weak. The direct molecular mechanics（MM） calculation with the UFF force fields predicts a trans conformation as the most stable state, which contradicts the result of quantum mechanics（QM）. The lesson from the investigation of this special system is that for the case where intermolecular interaction is of covalent character, a specific modification of the force fields of the molecular simulation method is necessary.

关键词： nitric oxide dimer intermolecular interaction natural orbital covalent bond

Collective migrations in an epithelial-cancerous cell monolayer

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2021年第5期37卷 773-784,I0001页

作者： Jian‑Qing Lv Peng‑Cheng Chen Liu‑Yuan Guan Wojciech T.Góźdź Xi‑Qiao Feng Bo Li Institute of Biomechanics and Medical Engineering Applied Mechanics LaboratoryDepartment of Engineering MechanicsTsinghua UniversityBeijing 100084China Institute of physical Chemistry Polish Academy of SciencesKasprzaka 44/5201‑224 WarsawPoland

Collective cell migration is extensively observed in embryo development and cancer *** these processes,the interactions between cells with distinct identities and fates are of importance for boundary formation and host defense against *** this paper,we explore the collective dynamics of a two-dimensional cell mixing monolayer consisting of non-tumorigenic mammary epithelial cells and breast cancer *** show that the epithelial-cancerous cell mixing system displays unique sorting *** epithelial cells aggregate to form scattered clusters,which perform random motion with simultaneous translation and rotation,strikingly distinct from the classical persistent random walk of individual migratory *** motility of cancer cells is markedly promoted by the epithelial clusters,exhibiting remarkable contact enhancement of locomotion.A discrete model based on the Johnson-Kendall-Roberts contact mechanics is proposed to identify the influence of intercellular interactions,active migration forces and cell-substrate friction forces on the collective cell *** findings could advance our understanding of many biological processes,such as cancer metastasis and tissue morphogenesis.

关键词： Collective cells Cell mixing Dynamics Cell-cell interaction

Stokes flow before plane boundary with mixed stick-slip boundary conditions

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Applied Mathematics and mechanics(English Edition) 2011年第6期32卷 795-804页

作者： N.AKHTAR G.A.H.CHOWDHURY S.K.SEN Department of Mathematics Shahjalal University of Science and Technology Research centre for Mathematical and physical Sciences University of Chittagong

A general theorem for the Stokes flow over a plane boundary with mixed stick-slip boundary conditions is established. This is done by using a representation for the velocity and pressure fields in the three-dimensional Stokes flow in terms of a biharmonic function and a harmonic function. The earlier theorem for the Stokes flow due to fundamental singularities before a no-slip plane boundary is shown to be a special case of the present theorem. Furthermore, in terms of the Stokes stream function, a corollary of the theorem is also derived, providing a solution to the problem of the axisymmetric Stokes flow along a rigid plane with stick-slip boundary conditions. The formulae for the drag and torque exerted by the fluid on the boundary are established. An illustrative example is given.

关键词： Stokes flow Stokes stream function stick-slip boundary conditions,harmonic function biharmonic function

The Unified Coordinate System in Computational Fluid Dynamics

在线全文

学校读者我要写书评

暂无评论

Communications in Computational Physics 2007年第4期2卷 577-610页

作者： W.H.Hui Division of mechanics Research Centre for Applied SciencesAcademia SinicaNankangTaipei 115Taiwan.

A fundamental issue in CFD is the role of coordinates and,in particular,the search for“optimal”*** paper reviews and generalizes the recently developed unified coordinate system(UC).For one-dimensional flow,UC uses a material coordinate and thus coincides with Lagrangian *** two-dimensional flow it uses a material coordinate,with the other coordinate determined so as to preserve mesh othorgonality(or the Jacobian),whereas for three-dimensional flow it uses two material coordinates,with the third one determined so as to preserve mesh skewness(or the Jacobian).The unified coordinate system combines the advantages of both Eulerian and the Lagrangian system and ***,the followings are shown in this paper.(a)For 1-D flow,Lagrangian system plus shock-adaptive Godunov scheme is superior to Eulerian system.(b)The governing equations in any moving multi-dimensional coordinates can be written as a system of closed conservation partial differential equations(PDE)by appending the time evolution equations–called geometric conservation laws–of the coefficients of the transformation(from Cartesian to the moving coordinates)to the physical conservation laws;consequently,effects of coordinate movement on the flow are fully accounted for.(c)The system of Lagrangian gas dynamics equations is written in conservation PDE form,thus providing a foundation for developing Lagrangian schemes as moving mesh schemes.(d)The Lagrangian system of gas dynamics equations in two-and three-dimension are shown to be only weakly hyperbolic,in direct contrast to the Eulerian system which is fully hyperbolic;hence the two systems are not equivalent to each other.(e)The unified coordinate system possesses the advantages of the Lagrangian system in that contact discontinuities(including material interfaces and free surfaces)are resolved sharply.(f)In using the UC,there is no need to generate a body-fitted mesh prior to computing flow past a body;the mesh is automatically

关键词： Unified coordinates Eulerian coordinates Lagrangian coordinates contact discontinuities automatic mesh generation moving mesh conservation form.

Ultrasonic study of adsorption in polysaccharide (starch) metabolism

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Chemistry in China 2011年第2期6卷 147-152页

作者： S.NITHIYANANTHAM L.PALANIAPPAN D.Raja biophysics/Ultrasonics Division School of Physical Sciences and Nano TechnologySRM UniversityKattankulathur 603203India Department of Physics Annamalai UniversityAnnamalainagar 602008India Bio/Fluid mechanics Devision SRM UniversityKattankulathur 603203India

Starch metabolism due to adsorption of enzyme amylase on the starch substrate is outlined *** explore the necessary conditions required for effective adsorption in biological media,ultrasonic techniques have been applied to elucidate the structural variations and component destruction in the considered *** ability of the enzyme amylase to break the linkages in starch(substrate)was determined from the observed ultrasonic velocity,which highlights the deciding factors of *** is concluded that the phenomenon of adsorption is decided by the surface area,the number of subunits held by the substrate,and the structure existing in the adsorbent,and above all,a relatively higher quantity of enzyme and the substrate.

关键词： acoustic parameters molecular interaction adsorption starch

Visible-light driven room-temperature coupling of methane to ethane by atomically dispersed Au on WO_(3)

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2021年第10期30卷 195-202,I0006页

作者： Xing Yang Wu Zhiyuan Tang Xiaoxu Zhao Xin Luo Stephen John Pennycook Song Ling Wang China-UK Low Carbon College Shanghai Jiao Tong UniversityShanghai 201306China School of Environmental Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory of Optoelectronic Materials and Technologies Centre for Physical Mechanics and BiophysicsSchool of PhysicsSun Yat-sen UniversityGuangzhou 510275GuangdongChina Institute Department of Materials Science and Engineering National University of SingaporeSingapore 117575Singapore Shanghai Institute of Pollution Control and Ecological Security Shanghai 200092China

Gold(Au)as co-catalyst is remarkable for activating methane(CH4),especially atomically dispersed Au with maximized exposing active sites and specific electronic ***,singlet oxygen(^(1)O_(2))typically manifests a mild redox capacity with a high selectivity to attack organic ***(PMS)favors to produce oxidative species 102 during the photocatalytic ***,combining atomic Au as co-catalyst and ^(1)O_(2) as oxidant is an effective strategy to selectively convert ***,we synthesized atomically dispersed Au on WO_(3)(Au/WO_(3)),where Au was in the forms of single atoms and *** room temperature,such Au/WO_(3) exhibited enhanced photocata lytic conversion of CH4 to CH3 CH3 with a selectivity,up to 94%,under visible *** radicals-pathway mechanism of CH4 coupling has also been investigated through detection and trapping experiment of active *** calculations further interpret the electronic structure of Au/WO_(3) and tip-enhanced local electric field at the Au sites for promoting CH4 conversion.

关键词： Photocatalysis Single-atom Au Methane Ethane Visible light

Bidirectional mechanical switching window in ferroelectric thin films predicted by first-principle-based simulations

在线全文

学校读者我要写书评

暂无评论

npj Computational Materials 2022年第1期8卷 1291-1299页

作者： Jianyi Liu Weijin Chen Mengjun Wu Fei Sun Xiang Huang Yue Zheng College of Physics Qingdao UniversityQingdao266071China Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices School of PhysicsSun Yat-sen UniversityGuangzhou510275China centre for physical mechanics and biophysics School of PhysicsSun Yat-sen UniversityGuangzhou510275China State Key Laboratory of Optoelectronic Materials and Technologies School of PhysicsSun Yat-sen UniversityGuangzhou510275China School of Materials Sun Yat-sen UniversityShenzhen518107China

Mechanical control of ferroelectric domain evolution has attracted much interest over the past ***,bidirectional 180°mechanical switching,i.e.,a complete cycle of mechanical writing and then erasing of a ferroelectric nanodomain,has not yet been realized in tip-film ***,via first-principles-based molecular dynamics simulations,we demonstrate that bidirectional 180°mechanical switching is possible in tip-film architectures when screening condition of ferroelectric films and tip loading force are within an appropriate *** switching utilizes a delicate competition between the flexoelectric field and an overlooked effective dipolar *** effective dipolar field dominates at small tip force and trigger switching from a downward single-domain state to an upward poly-domain state,whereas the flexoelectric field dominates at relatively large tip force and enables a *** mechanical switching is achieved by applying tip force pulses with alternatively varying *** dipole-dipole interaction dynamics play important roles in mechanical switching.

关键词： ferroelectric dipole utilize