共查询到19条相似文献,搜索用时 203 毫秒
1.
2.
3.
4.
采用FitzHugh-Nagumo方程,研究了二维时空系统中螺旋波的控制问题,利用相空间压缩方法对部分系统变量的振幅进行限制从而影响螺旋波的稳定性.研究表明,控制过程可分为三个不同的阶段:在较小压缩限条件下螺旋波可以被完全消除,系统进入均匀定态;在较大的压缩限条件下螺旋波能够稳定存在,而且其振荡频率不随控制参数的改变而发生变化;当压缩限介于上述两者之间时,系统表现为时空混沌态.对上述控制过程进行了进一步的讨论,研究了不同控制参数条件下的系统斑图、变量的演化、相空间轨道等性质,并且对振幅函数和振荡频率特征进
关键词:
螺旋波
相空间压缩
FitzHugh-Nagumo方程 相似文献
5.
研究了一类二维变量描述的激发系统中漂移螺旋波的抑制问题.通过在整个系统中局部注入带随机相位的电信号,如在系统256×256格点的边界或中心区域中选取4×4或者5×5格点区域施加一个带随机相位的外部激励电信号,在系统内部产生一个持续的靶波信号,实现靶波对螺旋波的动态竞争.数值计算表明:该方法对于Barkley模型中螺旋波有很强的抑制作用,与简单的局部周期信号驱动比较,具有暂态过程比较短的特点,而且对于时空噪声具有一定的抗干扰性.在一定的噪声范围内,即使系统出现不均匀性,也可以观测到靶波,新出现的靶波对螺旋波有抑制作用.
关键词:
螺旋波
靶波
Barkley模型
随机相位 相似文献
6.
7.
采用系统中的局部不均匀性消除振荡系统中的反螺旋波. 该不均匀性在系统中成为一个波源,不断产生稳定的相波. 研究结果发现,不均匀性的尺寸大小存在一个临界值,如果低于此临界值,则系统将无法激发任何相波. 根据不均匀性形状的不同,系统分别产生靶波和行波. 此外,实验还发现靶波与反螺旋波之间以及行波与反螺旋波之间存在着不同的动态竞争. 数值计算表明,对于行波,无论是低频行波还是高频行波,都可以成功地消除系统中的反螺旋波;而对于靶波,只有低频靶波才可以消除反螺旋波. 此控制方法简单易行,且同样适用于消除向外传播的螺旋波 相似文献
8.
采用Hindmarsh-Rose(HR)神经元模型,研究了二维神经元阵列系统从一个具有随机相位分布的初态演化最终是否能自发产生螺旋波的问题.数值结果表明:系统是否出现螺旋波与单个HR神经元的状态、系统的初态和耦合强度有关,其中单个HR神经元的振荡状态起主要作用.当单个HR神经元处于一周期振荡态时,在一定的耦合强度范围内系统都会自发出现多个螺旋波和螺旋波对,出现螺旋波与系统初态无关,只要适当选择耦合强度,在系统中可以出现单个螺旋波.当耦合强度超过某一阈值后,继续增加耦合强度,系统会呈现三种不同的动力学行为,分别与三类初态有关.系统从第一类初态演化将偶尔出现单个螺旋波,系统从第二类和第三类初态演化将分别出现间歇性全局同步振荡和振荡死亡.当单个神经元处于二周期态时,只有当系统神经元的初相位比较均匀分布时,系统才能自发出现螺旋波,而且出现螺旋波的耦合强度范围大为减少.当神经元处于更高的周期态时,系统一般不容易自发出现螺旋波.这些结果有助于人们了解大脑皮层自发产生螺旋波的机制. 相似文献
9.
本文采用Luo-Rudy相I模型研究如何通过调控心肌细胞钠电流变化来控制心脏中的螺旋波和时空混沌,提出了这样的钠电流调控方案:当细胞将被激发时启动钠电流调节,若由模型方程得到的钠电流的绝对值小于钠电流控制阈值的绝对值,就让钠电流等于钠电流控制阈值,其他情况下则限制钠电流的绝对值不能高于一个给定的最大值;当膜电位上升超过-5 mV时,让钠电流自然演化.这种调节钠电流的方式保证了所有细胞几乎具有相同的钠电流幅值,从而使所有细胞具有相同的激发性,数值模拟结果表明,只要钠电流控制阈值达到一定临界值,就可以有效抑制螺旋波波头的旋转,导致螺旋波运动出系统边界而消失,以及时空混沌演化为螺旋波后消失,如果钠电流控制阈值足够大,螺旋波和时空混沌还可通过传导障碍而消失.这些结果能够为抗心律失常治疗提供新的思路. 相似文献
10.
通过让心肌细胞钠离子通道的触发门变量延迟打开, 使介质具有激发延迟能力, 介质延迟激发时间随控制电压和刺激频率增加而增加, 当控制电压超过一个阈值时, 延迟激发介质具有低通滤波作用:低频波可以连续通过, 而高频波不能连续通过. 本文用Luo-Rudy相I模型研究了介质延迟激发对螺旋波和时空混沌的影响, 数值模拟结果表明: 当控制电压超过阈值时, 介质的延迟激发可有效消除螺旋波和时空混沌; 从小逐渐增大控制电压, 在钙最大电导率较小情况下, 延迟激发会导致介质激发性降低, 使螺旋波漫游幅度增大, 直至传导障碍导致螺旋波消失; 当钙最大电导率较大时, 延迟激发会导致螺旋波失稳变弱, 这样当控制电压增加到一定值时, 时空混沌可以演化成漫游螺旋波, 当控制参数被适当选取时, 观察到漫游幅度大的螺旋波漫游出系统边界消失现象, 继续增大控制电压将导致时空混沌直接消失. 相似文献
11.
研究了一类参数时变的反应扩散系统中螺旋波和湍流对外电场的响应问题.在数值模拟中,以一类改进的Fitzhugh-Nagumo模型为研究对象(在恰当参数值下可分别描述激发介质和振荡介质),考虑随机和不确定因素(如内外噪声、气压、温度梯度分布和介质形变等)所引起的系统参数涨落对斑图演化的影响,在模拟中选取的参数涨落范围确保系统可以观测到稳定旋转的螺旋波、漫游的螺旋波和湍流,经历一定的暂态过程后,对介质施加极化电场,研究螺旋波和湍流在外电场中的演化.数值计算结果表明:在系统参数发生涨落和外电场强度比较小情况下,主
关键词:
螺旋波
湍流
时变系统
Fitzhugh-Nagumo模型 相似文献
12.
实验发现大脑皮层内出现螺旋波且螺旋波对神经元电信号传递有积极作用.利用细胞网络方法从对大脑皮层观察到的螺旋波进行数值模拟.以包含温度因子的热敏神经元模型在二维空间构造规则网络,研究了神经元膜片温度参数对神经元网络中螺旋波演化影响;定义了一类统计同步因子来刻画温度因子引起螺旋波相变(破裂和死亡)的临界条件.发现在规则网络下,当温度超过一定值后螺旋波会死亡和消失而导致整个网络达到均匀同步;在考虑了弱通道噪声情况下,螺旋波温度超越一定临界值则引起螺旋波的破裂.进一步分析了暂时性发烧昏迷的可能机制在于神经系统某些功能区螺旋波传播电信号的中断. 相似文献
13.
Development and transition of spiral wave in the coupled Hindmarsh--Rose neurons in two-dimensional space 总被引:1,自引:0,他引:1 下载免费PDF全文
The dynamics and the transition of spiral waves in the coupled
Hindmarsh--Rose (H--R) neurons in two-dimensional space are
investigated in the paper. It is found that the spiral wave can be
induced and developed in the coupled HR neurons in two-dimensional
space, with appropriate initial values and a parameter region given.
However, the spiral wave could encounter instability when the
intensity of the external current reaches a threshold value of
1.945. The transition of spiral wave is found to be affected by
coupling intensity D and bifurcation parameter r. The spiral
wave becomes sparse as the coupling intensity increases, while the
spiral wave is eliminated and the whole neuronal system becomes
homogeneous as the bifurcation parameter increases to a certain
threshold value. Then the coupling action of the four sub-adjacent
neurons, which is described by coupling coefficient D’, is also
considered, and it is found that the spiral wave begins to breakup
due to the introduced coupling action from the sub-adjacent neurons
(or sites) and together with the coupling action of the
nearest-neighbour neurons, which is described by the coupling
intensity D. 相似文献
14.
Stabilization of spiral wave and turbulence in the excitable media using parameter perturbation scheme 下载免费PDF全文
This paper proposes a scheme of parameter perturbation to suppress the stable rotating spiral wave, meandering spiral wave and turbulence in the excitable media, which is described by the modified Fitzhug-Nagumo (MFHN) model. The controllable parameter in the MFHN model is perturbed with a weak pulse and the pulse period is decided by the rotating period of the spiral wave approximatively. It is confirmed that the spiral wave and spiral turbulence can be suppressed greatly. Drift and instability of spiral wave can be observed in the numerical simulation tests before the whole media become homogeneous finally. 相似文献
15.
MA Jun CHEN Yong JIN Wu-Yin 《理论物理通讯》2007,47(4):675-678
Evolution of spiral wave generated from the excitable media within the Barkley model is investigated. The external gradient electric field modulated by the logistic map is imposed on the media (along x- and y-axis). Drift and break up of spiral wave are observed when the amplitude of the electric field is modulated by the chaotic signal from the logistic map, and the whole system could become homogeneous finally and the relevant results are compared when the gradient electric field is modulated by the Lorenz or Rossler chaotic signal. 相似文献
16.
Jun Ma Chun-Ni Wang Jun Tang Ya-Feng Xia 《International Journal of Theoretical Physics》2009,48(1):150-157
Periodical forcing is used to control the spiral wave and turbulence in the modified Fithzhugh-Nagumo equation (MFHNe) when
excitability is changed. The decisive parameter ε of (MFHNe), which describes the ratio of time scales of the fast activator u and the slow inhibitor variable v, is supposed to increase linearly to simulate the excitability modulation in the media. In the numerical simulation, a local
periodical stimulus is imposed on the left border of the media and the periods of external forcing are adjusted according
to the approximate formula ω
∝1/ε
1/3 so that using the most appropriate frequency for the external forcing can approach a shorter transient period. It is found
that the spiral wave and turbulence can be removed successfully by using an appropriate periodical forcing on the left border
of the media. The mean activator and distribution of frequency of all the sites are also used to analyze the transition of
spiral wave. 相似文献
17.
In this paper, an intermittent local electric shock scheme is proposed to
suppress stable spiral waves in the Barkley model by a weak electric shock
(about 0.4 to 0.7) imposed on a random selected n×n grids (n=1-5,
compared with the original 256×256 lattice) and monitored
synchronically the evolutions of the activator on the grids as the sampled
signal of the activator steps out a given threshold (i.e., the electric
shock works on the n×n grids if the activator
u\leq0.4 or u \geq 0.8). The numerical
simulations show that a breakup of spiral is observed in the media
state evolution to finally obtain homogeneous states if the electric
shock
with appropriate intensity is imposed. 相似文献
18.
Suppression of spiral wave and turbulence in the complex Ginzburg-Landau equation (CGLE) plays a prominent role in nonlinear science and complex dynamical system. In this paper, the nonlinear behavior of the proposed drive-response system, which consists of two coupled CGLEs, is investigated and controlled by a state error feedback controller with the lattice Boltzmann method. First, spiral wave and turbulence are, respectively, generated by selecting appropriate parameters of the response system under the no-flux boundary and perpendicular gradient initial conditions. Then, based on the random initial condition, the target wave yielded by introducing spatially localized inhomogeneity into the drive system is applied on the above response system. The numerical simulation results show that the spiral wave and turbulence existing in the response system could be successfully eliminated by the target wave in the drive system during a short evolution time. Furthermore, it turns out that the transient time for the drive course is related to the control intensity imposed on the whole media. 相似文献
19.
本文采用Bär-Eiswirth模型研究了两层可激发介质中螺旋波的动力学, 两层介质采用抑制和兴奋性非对称耦合. 数值模拟结果表明: 兴奋性非对称耦合可以促进两个不同频率的螺旋波锁频, 即使初始频率相差大, 两螺旋波也能实现锁频, 这种耦合使两个螺旋波具有最强的锁频能力; 当两层介质采用抑制性非对称耦合时, 只有当两个初始螺旋波的频率差比较小才能实现锁频, 而且比一般扩散耦合的锁频范围窄, 两螺旋波锁频能力达到最低水平; 当耦合强度和控制参数适当选取时, 抑制性和兴奋性非对称耦合既可以使其中一层介质维持螺旋波态, 使另一层介质中的螺旋波演化到静息态或低频靶波态, 也可以使两层介质中的螺旋波都漫游, 或都转变成靶波, 最后这两个靶波要么消失, 要么转变成平面波状的振荡斑图, 而且两层介质振荡是反相的, 此外在模拟中还观察到两螺旋波局部间歇锁频现象, 这些结果有助于人们理解在心脏系统中出现的复杂现象. 相似文献