共查询到20条相似文献,搜索用时 562 毫秒
1.
M.B.A. Mansour 《Physica A》2007,383(2):466-472
In this paper, we consider a reaction-diffusion model for the bacterial growth. Mathematical analysis on the traveling wave solutions of the model is performed. This includes traveling wave analysis and numerical simulations of wave front propagation for a special case. Specifically, we show that such solutions exist only for wave speeds greater than some minimum speed giving wave with a sharp front. The minimum speed is estimated and the wave profile is calculated and compared with different numerical methods. 相似文献
2.
A Simplified Neuronal Model for the Instigation and Propagation of Cortical Spreading Depression
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Huaxiong Huang Robert M. Miura & Wei Yao 《advances in applied mathematics and mechanics.》2011,3(6):759-773
In this paper, we construct a simplified neuronal model that is capable
of simulating the instigation of cortical spreading depression (CSD) and
propagation of a CSD wave. Our model is a simplification and extension of
a single neuron model proposed in the literature for studying the instigation
of CSD. Using the simplified neuronal model, we construct a network of these
simplified neurons. This network model shows that the propagation of a CSD
wave occurs naturally after it is instigated electrically or chemically.
Although the model is simple, the speed of the CSD wave predicted by our
model is consistent with experimentally observed values. Finally, our model
allows us to investigate the effects of specific ion channels on the spread
of a CSD wave. 相似文献
3.
In a previous work of ours the numerical results have proved that there exists the Anderson transition zone in the Aubry model of one-dimensional incommensurate systems. In this paper, we further investigate the relation between the Anderson transition zone and the wave vector in this model. Our numerical results show that the Anderson transition zone is relative immediately to the wave vector, that is to say, the smaller the wave vector, the lower the value of the potential strength V in which the Anderson transition zone lies. 相似文献
4.
5.
单个囚禁离子的Jaynes—Cummings模型 总被引:6,自引:0,他引:6
Cirac等人证明处于驻波光场波节处的单个囚禁两能级离子的动力学由Jaynes-Cum-mings(J-C)模型描述。本文旨在推广这一结论。通过引入穿衣态描述,证明处于驻波光场中任意位置时,单个囚禁的两能级离子的动力学仍由相同模型描述。 相似文献
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7.
Materials with hysteretic non-linearity have the property of memorizing specific previous extrema in the stress/strain loading history. Because of this complexity, the analytical theory describing the non-linear evolution of acoustic waves in such materials is currently restricted to simplex wave propagation processes with a single minimum and a single maximum over a wave period. In the present paper a numerical model is presented which is valid for an arbitrary strain wave profile, and the results for the frequency-mixing process in acoustic waves composed initially of two harmonic frequency components are analyzed. The model simulations demonstrate that an initially complex wave transforms into a simplex wave during propagation. In addition, we have studied the mutual influence of the initial frequency components, and we have found regimes of induced absorption and induced transparency. 相似文献
8.
Alexander K. Hartmann 《The European Physical Journal B - Condensed Matter and Complex Systems》2014,87(5):1-10
In this study, we consider a propagating wave segment in two dimensions. A reaction diffusion system with global feedback is proposed, and spiral waves and propagating wave segments are shown. Propagating wave segments with large arc lengths can exist due to the absence of strong lateral inhibition. In order to study the properties of propagating wave segments, we propose a kinematic model with global feedback. When the elongating and shortening effects on the curve are balanced, stable propagating wave segments exist. For other cases, the initial wave segment evolves into a spiral wave or expanding wave or shrinking wave. The conditions for the propagating wave segment and the dependences of the solutions on the various relevant parameters are discussed. 相似文献
9.
《中国物理C(英文版)》2018,(11)
It is known that in supernova explosions, there might be a reverse shock wave in addition to the forward shock wave during the explosion phase, when the mass of supernova is in a certain range. In this paper, we propose to add the reverse shock wave to the previous supernova model, in which only the forward shock wave was included,and thus obtain a new model. By analyzing the resonance condition as well as the density jump in the new model and using the Landau-Zener method, an expression for the crossing probability in high density matter(PH) is given.We proceed to study how PH varies with time and with neutrino energy when both the reverse shock wave and the forward shock wave are considered. From comparison with the previous results, where only the effects of the forward shock wave were considered, it is clear that the reverse shock wave brings significant changes to PH. 相似文献
10.
复杂地理环境是电波传播不可避免的传播环境,不仅不规则地形会对电波传播产生影响,不同的地表媒质对电波传播也会产生不同的影响。为了使得电波传播特性的预测结果更加地准确有效,通过图像分割算法实现地表环境的简单分类,同时对不同的媒质赋予不同的电磁参数,并结合数字高程模型(DEM)数据,实现了既具有地形起伏信息又具有地表电磁环境参数的复杂地理环境建模。在此基础上,对地表电磁环境信息做了网格剖分处理,利用抛物方程(PE)模型对复杂地理环境下的电波传播特性进行了预测。 相似文献
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12.
In order to understand the viscoelasticity of material, this research has been conducted to study the propagation characteristics of viscoelastic Rayleigh wave theoretically. A model is presented for the pulsed laser generation of ultrasound on viscoelastic medium surface. Referred to the Kelvin model, the frequency equation and the normal displacement of viscoelastic Rayleigh wave were derived, the influence of the viscoelastic modulus on dispersion and attenuation was discussed. From the theoretical calculation, it is shown that the effect of viscoelasticity on the attenuation of Rayleigh wave is more than that on its dispersion. In the case of a weak viscosity, the attenuation of viscoelastic Rayleigh wave is directly proportional to viscosity modulus; the effect of shear viscosity on the attenuation is much more than that of bulk viscosity. The transient response of viscoelastic Rayleigh wave was also simulated using Laplace and Hankel inversion transform, which are showed in good agreement with the theoretic predictions. The model provides a useful tool for the determination of viscoelastic parameters of medium. 相似文献
13.
《Physics letters. A》2019,383(24):2903-2907
In degenerate quantum plasma the energy behavior of electrostatic modes propagating perpendicular to the external magnetic field is studied by employing the separated spin evolution quantum hydrodynamic (SSE-QHD) model. This model reveals that spin electron cyclotron wave (SECW) appears additionally with the upper hybrid wave (UHW). In case of SECW, the curves for the energy flow speed at different levels of spin polarization effect flip over at a particular value of wave number. The spin polarization effect enhances the energy flow speed before this value of wave number and then suppresses it afterward. The energy flow speed is enhanced by spin polarization effect in the entire range of wave number for the propagation of UHW. The Bohm potential effect drastically increases the energy flow speed at high wave number domain in both the waves. This study may find its applications to understand the energy behavior inspin polarized solid state plasmas 相似文献
14.
An analysis of seismic attenuation in random porous media 总被引:1,自引:0,他引:1
LIU Jiong BA Jing MA JianWei & YANG HuiZhu Institute of Seismic Exploration School of Aerospace Tsinghua University Beijing China Research Institute of Petroleum Exploration & Development PetroChina Beijing 《中国科学:物理学 力学 天文学(英文版)》2010,(4)
The attenuation of seismic wave in rocks has been one of the interesting research topics, but till now no poroelasticity models can thoroughly explain the strong attenuation of wave in rocks. In this paper, a random porous medium model is designed to study the law of wave propagation in complex rocks based on the theory of Biot poroelasticity and the general theory of stochastic process. This model sets the density of grain, porosity, permeability and modulus of frame as random parameters in space, and only one fluid infiltrates in rocks for the sake of better simulation effect in line with real rocks in earth strata. Numerical simulations are implemented. Two different inverse quality factors of fast P-wave are obtained by different methods to assess attenuation through records of virtual detectors in wave field (One is amplitude decay method in time domain and the other is spectral ratio method in frequency domain). Comparing the attenuation results of random porous medium with those of homogeneous porous medium, we conclude that the attenuation of seismic wave of homogeneous porous medium is far weaker than that of random porous medium. In random porous media, the higher heterogeneous level is, the stronger the attenuation becomes, and when heterogeneity σ = 0.15 in simulation, the attenuation result is consistent with that by actual observation. Since the central frequency (50 Hz) of source in numerical simulation is in earthquake band, the numerical results prove that heterogeneous porous structure is one of the important factors causing strong attenuation in real stratum at intermediate and low frequency. 相似文献
15.
In this paper, a spatial perturbation scheme is proposed to suppress
the spiral wave in the modified Orengonator model, which is used to
describe the chemical reaction in the light-sensitive media. The
controllable external illumination Φ is perturbed with a spatial linear function. In our numerical simulation, the scheme is investigated by imposing the external controllable illumination
on the space continuously and/or intermittently. The numerical
simulation results confirm that the stable rotating spiral wave
still can be removed with the scheme proposed in this paper even if
the controllable Φ changed vs. time and space synchronously. Then the scheme is also used to control the spiral wave and turbulence in the modified Fitzhugh-Nagumo model. It is
found that the scheme is effective to remove the sable rotating and
meandering spiral wave but it costs long transient period and intensity of the gradient parameter to eliminate the spiral turbulence. 相似文献
16.
We discuss the reliability of hadronic wave functions (quark distribution amplitudes) determined by a finite number of QCD sum-rule moments. Although the expansion coefficients for polynomial models of the wave function are uniquely determined by the moments, the inherent uncertainty in such moments leads to a considerable indeterminacy in the wave functions because minimal changes of the moments can lead to large oscillations of the model function. In particular, the freedom in the moments left by QCD sum rules leads to a nonconverging polynomial expansion. This remains true even if additional constraints on the wave functions are used. As a consequence of this, the widely used procedure of constructing polynomial models of hadronic wave function from QCD sum rule moments does not guarantee even a reasonable approximation to the true wave function. The differences among the model wave functions persist also in the calculations of physical observables like hadronic form factors. This implies that physical observables calculated by means of such model wave functions are in general very unreliable. As specific examples, we examine the pion and nucleon wave functions and show that Gegenbauer as well as Appell polynomial expansions constructed from QCD sum rule moments are ruled out. The implications for the wave functions which are generally used in the literature are discussed. 相似文献
17.
HUANG Shou-Jun CHEN Chun-Li 《理论物理通讯》2007,48(5):773-780
In this paper, we employ the bifurcation method of dynamical systems to study the solitary waves and periodic waves of a generalized Boussinesq equations. All possible phase portraits in the parameter plane for the travelling wave systems are obtained. The possible solitary wave solutions, periodic wave solutions and cusp waves for the general Boussinesq type fluid model are also investigated. 相似文献
18.
WANG JinHua & SHEN YongMing State Key Laboratory of Coastal Offshore Engineering Dalian University of Technology Dalian China 《中国科学:物理学 力学 天文学(英文版)》2011,(1)
Using unstructured meshes provides great flexibility for modeling the flow in complex geomorphology of tidal creeks,barriers and islands,with refined grid resolution in regions of interest and not elsewhere.In this paper,an unstructured three-dimensional fully coupled wave-current model is developed.Firstly,a parallel,unstructured wave module is developed.Variations in wave properties are governed by a wave energy equation that includes wave-current interactions and dissipation representative of wave breaki... 相似文献
19.
In a one-dimensional reaction-diffusion model of an active medium, stable steady-state wave pulses of a new type are described. They are called multihumped because their waveforms contain several maxima of similar size. Presumably, the multihumped pulses arise via a bifurcation at which an unstable trigger wave disappears. The parameter governing this bifurcation is the diffusion coefficient for the model inhibitor. The model is analyzed by varying this parameter to determine the conditions for the emergence of multihumped pulses. The results of this analysis show how their waveform and dynamics of excitation depend on the inhibitor diffusion coefficient. 相似文献
20.
Recently, Deser, Jackiw and Pi have shown that three-dimensional conformal gravity with a source given by a conformally coupled scalar field admits pp wave solutions. In this paper, we consider this model with a self-interacting potential preserving the conformal structure. A pp wave geometry is also supported by this system and, we show that this model is equivalent to topologically massive gravity with a cosmological constant whose value is given in terms of the potential strength. 相似文献