The electronic states in Thus-Morse chain （TMC） and generalized Fibonacci chain （GFC） are studied by solving eigenequation and using transfer matrix method. Two model Hamiltonians are studied. One contains the nea...The electronic states in Thus-Morse chain （TMC） and generalized Fibonacci chain （GFC） are studied by solving eigenequation and using transfer matrix method. Two model Hamiltonians are studied. One contains the nearest neighbor （n.n.） hopping terms only and the other has additionally next nearest neighbor （n.n.n.） hopping terms. Based on the transfer matrix method, a criterion of transition from the extended to the localized states is suggested for CFC and TMC. The numerical calculation shows the existence of both extended and localized states in pure aperiodic system. A random potential is introduced to the diagonal term of the Hamiltonian and then the extended states are always changed to be localized. The exponents related to the localization length as a function of randomness are calculated. For different kinds of aperiodic chain, the critical value of randomness for the transition from extended to the localized states are found to be zero, consistent with the case of ordinary one-dimensional systems.展开更多
The influence of the size distribution of particles on the viscous property of an electrorheological fluid has been investigated by the molecular dynamic simulation method.The shear stress of the fluid is found to dec...The influence of the size distribution of particles on the viscous property of an electrorheological fluid has been investigated by the molecular dynamic simulation method.The shear stress of the fluid is found to decrease with the increase of the variance σ^(2) of the Gaussian distribution of the particle size,and then reach a steady value whenσis larger than 0.5.This phenomenon is attributed to the influence of the particle size distribution on the dynamic structural evolution in the fluid as well as the strength of the different chain-like structures formed by the particles.展开更多
A hydrodynamic boundary condition for the lattice Boltzmann model at impermeable boundaries is developed.This boundary condition satisfies both the no-slip condition and the fluid conservation at boundary nodes.Poiseu...A hydrodynamic boundary condition for the lattice Boltzmann model at impermeable boundaries is developed.This boundary condition satisfies both the no-slip condition and the fluid conservation at boundary nodes.Poiseuille flow and Couette flow are calculated with this technique to demonstrate the accuracy of the present boundary condition.展开更多
Analytical studies of the effect of edge decoration on the energy spectrum of semi-infinite one-dimensional （1D） model and zigzag edged graphene （ZEG） are presented by means of transfer matrix method, in the frame...Analytical studies of the effect of edge decoration on the energy spectrum of semi-infinite one-dimensional （1D） model and zigzag edged graphene （ZEG） are presented by means of transfer matrix method, in the frame of which the conditions for the existence of edge states are determined. For 1D model, the zero-energy surface state occurs regardless of whether the decorations exist or not, while the non-zero-energy surface states can be induced and manipulated through adjusting the edge decoration. On the other hand, the case for the semi-infinite ZEG model with nearestneighbour interaction is discussed in the analogous way. The non-zero-energy surface states can be induced by the edge decoration and moreover, the ratio between the edge hopping and the bulk hopping amplitudes should be within a certain threshold.展开更多
基金The project supported by National Natural Science Foundation of China
文摘The electronic states in Thus-Morse chain （TMC） and generalized Fibonacci chain （GFC） are studied by solving eigenequation and using transfer matrix method. Two model Hamiltonians are studied. One contains the nearest neighbor （n.n.） hopping terms only and the other has additionally next nearest neighbor （n.n.n.） hopping terms. Based on the transfer matrix method, a criterion of transition from the extended to the localized states is suggested for CFC and TMC. The numerical calculation shows the existence of both extended and localized states in pure aperiodic system. A random potential is introduced to the diagonal term of the Hamiltonian and then the extended states are always changed to be localized. The exponents related to the localization length as a function of randomness are calculated. For different kinds of aperiodic chain, the critical value of randomness for the transition from extended to the localized states are found to be zero, consistent with the case of ordinary one-dimensional systems.
基金Supported by the National Natural Science Foundation of Chinathe National Education Commission under the Grant for Training Doctors.
文摘The influence of the size distribution of particles on the viscous property of an electrorheological fluid has been investigated by the molecular dynamic simulation method.The shear stress of the fluid is found to decrease with the increase of the variance σ^(2) of the Gaussian distribution of the particle size,and then reach a steady value whenσis larger than 0.5.This phenomenon is attributed to the influence of the particle size distribution on the dynamic structural evolution in the fluid as well as the strength of the different chain-like structures formed by the particles.
基金Supported in part by Exxon R&E company,the Chinese Postdoctoral Foundation,and ShanghaiPostdoctoral Foundation.
文摘A hydrodynamic boundary condition for the lattice Boltzmann model at impermeable boundaries is developed.This boundary condition satisfies both the no-slip condition and the fluid conservation at boundary nodes.Poiseuille flow and Couette flow are calculated with this technique to demonstrate the accuracy of the present boundary condition.
基金supported by the National Natural Science Foundation of China (Grant No.10847001)the National Basic Research Program of China (Grant Nos.2009CB929204 and 2011CB921803)
文摘Analytical studies of the effect of edge decoration on the energy spectrum of semi-infinite one-dimensional （1D） model and zigzag edged graphene （ZEG） are presented by means of transfer matrix method, in the frame of which the conditions for the existence of edge states are determined. For 1D model, the zero-energy surface state occurs regardless of whether the decorations exist or not, while the non-zero-energy surface states can be induced and manipulated through adjusting the edge decoration. On the other hand, the case for the semi-infinite ZEG model with nearestneighbour interaction is discussed in the analogous way. The non-zero-energy surface states can be induced by the edge decoration and moreover, the ratio between the edge hopping and the bulk hopping amplitudes should be within a certain threshold.
