The dispersion relation is derived for three-dimensional dust-acoustic waves in a current-driven dusty plasmas with both positively and negatively charged dust particles. The dependencies of the frequency and the grow...The dispersion relation is derived for three-dimensional dust-acoustic waves in a current-driven dusty plasmas with both positively and negatively charged dust particles. The dependencies of the frequency and the growth rate on the wave number K, the intensity of magnetic field B, and the inclination angle θ have been numerically shown in this paper. The growth rate is negative for the laboratory dusty plasma, but it is positive for the cosmic dusty plasma. It is found that when the inclination angle θ = π/2, there is no instability. The effect of the electrostatic field Eo has also been studied in this paper.展开更多
To study the damage evolution of the metal plate in elastic and plastic deformation stages, an improved micropolar peridynamic model is proposed to simulate the deformation process and damage evolution of metal materi...To study the damage evolution of the metal plate in elastic and plastic deformation stages, an improved micropolar peridynamic model is proposed to simulate the deformation process and damage evolution of metal materials with variable Poisson’s ratios in the elastic-plastic stages. Firstly, both the stretching and bending moments of the bonds between the material points are added to peridynamic pairwise force functions, and the coordinate transformation of the micro-beam made up of bonds is deduced. Therefore, the numerical calculation implementation of the improved micropolar peridynamic model is obtained. Then, the strain values are obtained by solving the difference equation based on the displacement values of material points, and the stress values can be calculated according to generalized Hook’s law. The elastic and plastic deformation stages can be estimated based on the von Mises yield criterion, and different constitutive equations are adopted to simulate the damage evolution. Finally, the proposed micropolar peridynamic model is applied to simulate the damage evolution of a metal plate with a hole under velocity boundary conditions, and the effectiveness of the model is verified through experiments. In the experiments, the displacement and strain distributions in the stretching process are analyzed by the digital image correlation(DIC) method. By comparing the results, the proposed model is more accurate than the bond-based peridynamic model and the error of the proposed model is 7.2% lower than that of the bond-based peridynamic model. By loading different velocity boundary conditions, the relationship between the loads and damage evolution is studied.展开更多
Since the 1980s,single-crystal Pt electrodes with well-defined surface structures have been deemed stable under mild electrochemical conditions(e.g.,in the potential region of electric double layers,underpotential dep...Since the 1980s,single-crystal Pt electrodes with well-defined surface structures have been deemed stable under mild electrochemical conditions(e.g.,in the potential region of electric double layers,underpotential deposition of hydrogen,or mild hydrogen evolution/OH adsorption)and have served as model electrodes for unraveling the structure-performance relation in electrocatalysis.With the advancement of in situ electrochemical microscopy/spectroscopy techniques,subtle surface restructuring under mild electrochemical conditions has been achieved in the last decade.Surface restructuring can considerably modify electrocatalytic properties by generating/destroying highly active sites,thereby interfering with the deduction of the structure-performance relation.In this review,we summarize recent progress in the restructuring of well-defined Pt(-based)electrode surfaces under mild electrochemical conditions.The importance of the meticulous structural characterization of Pt electrodes before,during,and after electrochemical measurements is demonstrated using CO adsorption/oxidation,hydrogen adsorption/evolution,and oxygen reduction as examples.The implications of present findings for correctly identifying the reaction mechanisms and kinetics of other electrocatalytic systems are also briefly discussed.展开更多
The propagators of pion and sigma meson at a finite nuclear density and zero temperature are studied in chiral σ model. Their dispersion relations are calculated numerically in one-loop approximation. In order to avo...The propagators of pion and sigma meson at a finite nuclear density and zero temperature are studied in chiral σ model. Their dispersion relations are calculated numerically in one-loop approximation. In order to avoid the so-called tachyon pole appearing in the one-loop propagators of pion and sigma meson, we regard the mass of sigma meson mσ as a free parameter and adjust it to fit the nuclear saturation properties. For mσ equal to 3075 MeV, the tachyonpole does not appear at the normal nuclear density. Thus the dispersion relation can be calculated in chiral σ model in one-loop level for the first time.展开更多
In this paper,a phenomenological continuum theory of surface piezoelectricity accounting for the linear superficial interplay between electricity and elasticity is formulated primarily for elastic dielectric materials...In this paper,a phenomenological continuum theory of surface piezoelectricity accounting for the linear superficial interplay between electricity and elasticity is formulated primarily for elastic dielectric materials.This theory is inspired by the physical idea that once completely relaxed,an insulating free dielectric surface will sustain a nontrivial spontaneous surface polarization in the normal direction together with a tangential self-equilibrated residual surface stress field.Under external loadings,the surface Helmholtz free energy density is identified as the characteristic function of such surfaces,with the in-plane strain tensor of surface and the surface free charge density as the independent state variables.New boundary conditions governing the surface piezoelectricity are derived through the variational method.The resulting concepts of charge-dependent surface stress and deformationdependent surface electric field reflect the linear electromechanical coupling behavior of nanodielectric surfaces.As an illustrative example,an infinite radially polarizable piezoelectric nanotube with both inner and outer surfaces grounded is investigated.The novel phenomenon of possible surface-induced polarity inversion is predicted for thin enough nanotubes.展开更多
文摘The dispersion relation is derived for three-dimensional dust-acoustic waves in a current-driven dusty plasmas with both positively and negatively charged dust particles. The dependencies of the frequency and the growth rate on the wave number K, the intensity of magnetic field B, and the inclination angle θ have been numerically shown in this paper. The growth rate is negative for the laboratory dusty plasma, but it is positive for the cosmic dusty plasma. It is found that when the inclination angle θ = π/2, there is no instability. The effect of the electrostatic field Eo has also been studied in this paper.
基金The National Natural Science Foundation of China(No.51575101)
文摘To study the damage evolution of the metal plate in elastic and plastic deformation stages, an improved micropolar peridynamic model is proposed to simulate the deformation process and damage evolution of metal materials with variable Poisson’s ratios in the elastic-plastic stages. Firstly, both the stretching and bending moments of the bonds between the material points are added to peridynamic pairwise force functions, and the coordinate transformation of the micro-beam made up of bonds is deduced. Therefore, the numerical calculation implementation of the improved micropolar peridynamic model is obtained. Then, the strain values are obtained by solving the difference equation based on the displacement values of material points, and the stress values can be calculated according to generalized Hook’s law. The elastic and plastic deformation stages can be estimated based on the von Mises yield criterion, and different constitutive equations are adopted to simulate the damage evolution. Finally, the proposed micropolar peridynamic model is applied to simulate the damage evolution of a metal plate with a hole under velocity boundary conditions, and the effectiveness of the model is verified through experiments. In the experiments, the displacement and strain distributions in the stretching process are analyzed by the digital image correlation(DIC) method. By comparing the results, the proposed model is more accurate than the bond-based peridynamic model and the error of the proposed model is 7.2% lower than that of the bond-based peridynamic model. By loading different velocity boundary conditions, the relationship between the loads and damage evolution is studied.
文摘Since the 1980s,single-crystal Pt electrodes with well-defined surface structures have been deemed stable under mild electrochemical conditions(e.g.,in the potential region of electric double layers,underpotential deposition of hydrogen,or mild hydrogen evolution/OH adsorption)and have served as model electrodes for unraveling the structure-performance relation in electrocatalysis.With the advancement of in situ electrochemical microscopy/spectroscopy techniques,subtle surface restructuring under mild electrochemical conditions has been achieved in the last decade.Surface restructuring can considerably modify electrocatalytic properties by generating/destroying highly active sites,thereby interfering with the deduction of the structure-performance relation.In this review,we summarize recent progress in the restructuring of well-defined Pt(-based)electrode surfaces under mild electrochemical conditions.The importance of the meticulous structural characterization of Pt electrodes before,during,and after electrochemical measurements is demonstrated using CO adsorption/oxidation,hydrogen adsorption/evolution,and oxygen reduction as examples.The implications of present findings for correctly identifying the reaction mechanisms and kinetics of other electrocatalytic systems are also briefly discussed.
文摘The propagators of pion and sigma meson at a finite nuclear density and zero temperature are studied in chiral σ model. Their dispersion relations are calculated numerically in one-loop approximation. In order to avoid the so-called tachyon pole appearing in the one-loop propagators of pion and sigma meson, we regard the mass of sigma meson mσ as a free parameter and adjust it to fit the nuclear saturation properties. For mσ equal to 3075 MeV, the tachyonpole does not appear at the normal nuclear density. Thus the dispersion relation can be calculated in chiral σ model in one-loop level for the first time.
基金supports from the National Natural Science Foundation of China(Grant Nos. 10772093,10972121,and 10732050)the National Basic Research Program of China(Grant Nos. 2007CB936803 and 2010CB-631005)
文摘In this paper,a phenomenological continuum theory of surface piezoelectricity accounting for the linear superficial interplay between electricity and elasticity is formulated primarily for elastic dielectric materials.This theory is inspired by the physical idea that once completely relaxed,an insulating free dielectric surface will sustain a nontrivial spontaneous surface polarization in the normal direction together with a tangential self-equilibrated residual surface stress field.Under external loadings,the surface Helmholtz free energy density is identified as the characteristic function of such surfaces,with the in-plane strain tensor of surface and the surface free charge density as the independent state variables.New boundary conditions governing the surface piezoelectricity are derived through the variational method.The resulting concepts of charge-dependent surface stress and deformationdependent surface electric field reflect the linear electromechanical coupling behavior of nanodielectric surfaces.As an illustrative example,an infinite radially polarizable piezoelectric nanotube with both inner and outer surfaces grounded is investigated.The novel phenomenon of possible surface-induced polarity inversion is predicted for thin enough nanotubes.
