Peiqiang Zhang

Dynamic properties of flexural beams using a nonlocal elasticity model

In this paper, a nonlocal Bernoulli-Euler beam model is established based on the theory of nonlocal elasticity. Frequency equations and modal shape functions of beam structures with some typical boundary conditions are derived based on the model. The corresponding dynamic properties are presented and discussed in detail, which are shown to be very different from those predicted by classic elasticity theory when nonlocal effects are significant. The results can be applied to modeling and characterization of size-dependent mechanical properties of micro- or nanoelectromechanical system (MEMS or NEMS) devices.

Study on the mechanism of the squeeze-strengthen effect in magnetorheological fluids

Current magnetorheological (MR) fluids have the limitation that their yield stresses are not strong enough to meet some industrial requirements. X. Tang, X. Zhang, and R. Tao [J. App. Phys 87, 2634 (2000)] proposed a method to achieve high-efficiency MR fluids by study of squeeze-strengthen effect. But there is little report on its mechanism. This paper aims to investigate this effect through experimental and theoretical approaches. For this purpose, an apparatus is designed to experimentally study the mechanism of this squeeze-strengthen effect. Taking account of a modified magnetic dipole model and the friction effect, a semiempirical model is proposed to explain this effect. In addition, this model is expected to study the squeeze-strengthen effect in electrorheological fluids.

Spin relaxation in n-type (111) GaAs quantum wells

We investigate the spin relaxation limited by the D’yakonov–Perel’ mechanism in n-type (111) GaAs quantum wells, by means of the kinetic spin Bloch equation approach. In (111) GaAs quantum wells, the in-plane effective magnetic field from the D’yakonov–Perel’ term can be suppressed to zero on a special momentum circle under the proper gate voltage, by the cancellation between the Dresselhaus and Rashba spin-orbit coupling terms. When the spin-polarized electrons mainly distribute around this special circle, the in-plane inhomogeneous broadening is small and the spin relaxation can be suppressed, especially for that along the growth direction of quantum well. This cancellation effect may cause a peak (the cancellation peak) in the density or temperature dependence of the spin relaxation time. In the density (temperature) dependence, the interplay between the cancellation peak and the ordinary density (Coulomb) peak leads to rich features of the density (temperature) dependence of the spin relaxation time. ...

Research of Natural Frequency of Single-walled Carbon Nanotube

The modified molecular structural mechanics method (MMSMM) is extended to analyze the dynamic characteristics of single-walled carbon nanotubes (SWCNTs). In MMSMM, the deformation potential of SWCNT is decomposed and it can be easily expressed as the function of the positions of carbon atoms in molecular mechanics, and so the stiffness matrix of SWCNT can be obtained. The elemental mass matrix is a diagonal one, so the natural frequency and vibration mode of SWCNT can be calculated effectively. In this work, the form of cantilevered nanotubes is analyzed. The natural frequencies of SWCNT computed by this algorithm are discussed. The frequency dependence on the tube diameter and length of SWCNT is confirmed and, it is shown that when the diameter of tube is small the frequency can reach the the GHz level. The frequency results and the vibration modes are comparable with those of other researchers. Furthermore, a new FEM continuum-model is proposed to analyze the dynamic character of SWCNT to compare with these results by MMSMM.

Electron spin diffusion and transport in graphene

We investigate the spin diffusion and transport in a graphene monolayer on SiO

Hot-carrier transport and spin relaxation on the surface of topological insulator

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Preparation and Characterization of Nickel–poly(St-co-AA) Composite Nanoparticles

substrate by means of the microscopic kinetic spin Bloch equation approach. The substrate causes a strong Rashba spin-orbit coupling field

Electron spin relaxation in rippled graphene with low mobilities

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Voltage-controlled spin precession in InAs quantum wells

meV, which might be accounted for by the impurities initially present in the substrate or even the substrate-induced structure distortion. By surface chemical doping with Au atoms, this Rashba spin-orbit coupling is further strengthened as the adatoms can distort the graphene lattice from

Electron spin diffusion at the interface of multiferroic oxides

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