Using the Greenberg-Hasting cellular automata model, we study the properties of target waves in excitable media under the no-flux boundary conditions. For the system has only one excited state, the computer simulation...Using the Greenberg-Hasting cellular automata model, we study the properties of target waves in excitable media under the no-flux boundary conditions. For the system has only one excited state, the computer simulation and analysis lead to the conclusions that, the number of refractory states does not influence the wave-front speed; the wave- front speed decreases as the excitation threshold increases and increases as the neighbor radius increases; the period of target waves is equal to the number of cell states; the excitation condition for target waves is that the wave-front speed must be bigger than half of the neighbor radius.展开更多
During the seismic wave propagation process,as for the anisotropic lower medium,the speed is a function of the propagating direction.This article focuses on solving the problem how to get the transmittance angle and s...During the seismic wave propagation process,as for the anisotropic lower medium,the speed is a function of the propagating direction.This article focuses on solving the problem how to get the transmittance angle and speed,knowing the upper seismic wave propagation velocity and the angle of incidence conditions.The main theories used Snell law,Christoffel equation and speed characteristics.Taking the HTI medium as an example,the authors give the detailed solving process and draw the space velocity characteristic curve.展开更多
Under the excitation of elastic waves,local fluid flow in a complex porous medium is a major cause for wave dispersion and attenuation.When the local fluid flow process is simulated with wave propagation equations in ...Under the excitation of elastic waves,local fluid flow in a complex porous medium is a major cause for wave dispersion and attenuation.When the local fluid flow process is simulated with wave propagation equations in the double-porosity medium,two porous skeletons are usually assumed,namely,host and inclusions.Of them,the volume ratio of inclusion skeletons is low.All previous studies have ignored the consideration of local fluid flow velocity field in inclusions,and therefore they can not completely describe the physical process of local flow oscillation and should not be applied to the situation where the fluid kinetic energy in inclusions cannot be neglected.In this paper,we analyze the local fluid flow velocity fields inside and outside the inclusion,rewrite the kinetic energy function and dissipation function based on the double-porosity medium model containing spherical inclusions,and derive the reformulated Biot-Rayleigh(BR)equations of elastic wave propagation based on Hamilton’s principle.We present simulation examples with different rock and fluid types.Comparisons between BR equations and reformulated BR equations show that there are significant differences in wave response characteristics.Finally,we compare the reformulated BR equations with the previous theories and experimental data,and the results show that the theoretical results of this paper are correct and effective.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos. 10562001 and 10765002
文摘Using the Greenberg-Hasting cellular automata model, we study the properties of target waves in excitable media under the no-flux boundary conditions. For the system has only one excited state, the computer simulation and analysis lead to the conclusions that, the number of refractory states does not influence the wave-front speed; the wave- front speed decreases as the excitation threshold increases and increases as the neighbor radius increases; the period of target waves is equal to the number of cell states; the excitation condition for target waves is that the wave-front speed must be bigger than half of the neighbor radius.
文摘During the seismic wave propagation process,as for the anisotropic lower medium,the speed is a function of the propagating direction.This article focuses on solving the problem how to get the transmittance angle and speed,knowing the upper seismic wave propagation velocity and the angle of incidence conditions.The main theories used Snell law,Christoffel equation and speed characteristics.Taking the HTI medium as an example,the authors give the detailed solving process and draw the space velocity characteristic curve.
基金supported by the National Natural Science Foundation of China(Grant No.41104066)RIPED Youth Innovation Foundation(Grant No.2010-A-26-01)+1 种基金the National Basic Research Program of China(Grant No.2014CB239006)the Open fund of SINOPEC Key Laboratory of Geophysics(Grant No.WTYJY-WX2013-04-18)
文摘Under the excitation of elastic waves,local fluid flow in a complex porous medium is a major cause for wave dispersion and attenuation.When the local fluid flow process is simulated with wave propagation equations in the double-porosity medium,two porous skeletons are usually assumed,namely,host and inclusions.Of them,the volume ratio of inclusion skeletons is low.All previous studies have ignored the consideration of local fluid flow velocity field in inclusions,and therefore they can not completely describe the physical process of local flow oscillation and should not be applied to the situation where the fluid kinetic energy in inclusions cannot be neglected.In this paper,we analyze the local fluid flow velocity fields inside and outside the inclusion,rewrite the kinetic energy function and dissipation function based on the double-porosity medium model containing spherical inclusions,and derive the reformulated Biot-Rayleigh(BR)equations of elastic wave propagation based on Hamilton’s principle.We present simulation examples with different rock and fluid types.Comparisons between BR equations and reformulated BR equations show that there are significant differences in wave response characteristics.Finally,we compare the reformulated BR equations with the previous theories and experimental data,and the results show that the theoretical results of this paper are correct and effective.
