共查询到18条相似文献,搜索用时 633 毫秒
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在对Logistic映象数值计算的基础上,我们分析了一维单峰映象的逆轨道结构,证明了不同参数处逆轨道总数N(n)随求逆次数n而变化的递推公式。借此解析地求得了在倍周期区中h(f)≡0;在U序列RLR21的m=3+2l周期点上h(f)=logαmp,其中αmp为方程αm-2αm-2-1=0的最大实根;在2j-1常和2j带交界处hj(f)=(1/2)jlog2,由此可得聚点μ∞处拓扑熵的标度指数t=0.449806…。在此基础上,我们还求得了混沌区的周期窗口,U序列RLaRb所对应的各点处的拓扑熵,以及hR*Q(f)=(1/2)hQ(f)的关系。证明是在M.S.S.规则和“*”乘法则的基础上进行的。所以本文的结果对一维单峰映象是普适的。
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讨论了描述一类电子张弛振子的分段光滑映象中的两种不连续性导致激变的特性.一种激变发生的机理是一个混沌吸引子吸引域内的不稳定周期轨道与映象的不连续区碰撞;而另一种激变的机理是一个混沌吸引子与两个映象的不连续区构成的“映孔”碰撞.发现第一种激变的平均层流相长度的标度律为〈τ〉∝-1.8,层流相长度分布的标度律为P(τ)=1〈τ〉·exp-τ〈τ〉,而第二种激变的标度律分别为〈τ〉∝exp(k-1/2)和P(τ)=1〈τ〉exp-τ〈τ〉.
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我们在Oregonator模型的基础上,取速率常数k6、理想配比系数f及波数k为参变量,首先讨论了B-Z反应体系的稳定性,并得到了下列各量的表达式:空间周期结构的临界速率常数k6c、短波临界波数ksc与长波临界波数kLc,时空周期结构的临界速率常数k6c及临界波数kc等。而后,我们给出了B-Z反应体系的临界频率λc,讨论了体系在临界状态附近的行为,并得到了触发波速度uT及相位波速度uP的表达式。本文的结论是,在一定条件下,不搅拌的B-Z反应体系能在临界状态附近呈现稳定的波群或者波包,触发波是均匀体系中的波包,相位波是有微小梯度的非均匀体系中的波包。uT=2ηDkc,D为HBrO2的扩散系数,η为[H+]的缓变函数(在实验观测范围内,η≈0.1);uP=v,v为相速度。
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一个既不可微(或不连续)又不可逆的一维映象可以展示一种新型的阵发。它的机制是稳定不动点与映象不可微或不连续点碰撞而消失。这种阵发可以在该不动点附近的线性化映象本征值绝对值在阵发前为小于1的任何值的情况发生,因而可能突然出现在倍周期分岔序列中途任一部分,使序列中断进入混沌。在稳定不动点消失后映象产生的阵发时间序列中,层流相长度呈现与外控参数距临界值距离的对数依赖关系。这种新型标度规律不依赖于映象的细节。作者认为这种阵发应广泛存在于许多实际系统之中。
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快速算法结合推广的Bethe公式,可以为应用研究提供便于使用的偶极激发碰撞强度和速率系数.用准相对论平面波Born(QRPB)近似计算高能区Au50+离子n0l0→nl偶极激发的碰撞强度,给出Bethe公式中动量转移截断参数k0,从而确定激发过程的高能行为.快速计算方法中采用了Cowan所发展的准相对论方法,用统一的Hartree-Fock-Slater势计算束缚和连续态电子波函数.用准相对论扭曲波(QRDW)近似计算阈值附近的碰撞强度并外推阈值处的碰撞强度Ω0,然后拟合到高能碰撞强度上.对于特殊情况还需增加三倍阈值点a的计算,用三个参数Ω0,Ωa和k0拟合出全能域(出射电子能量εb=0—∞)的碰撞强度.由此可以得到全部温度范围(电子温度Te=0—∞)的速率系数<σv>.这样得到的Ω和<σv>,在相应的感兴趣的能量和温度范围内有合理的精度.
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11.
Tassos C. Bountis 《Physica D: Nonlinear Phenomena》1981,3(3):577-589
We have studied numerically a sequence of period doubling bifurcations of periodic orbits of Hénon's conservative two-dimensional mapping. In agreement with other recent studies, we also find evidence that such sequences possess universality properties, similar to the ones observed for dissipative systems. The corresponding universal constants, however, have significantly different values in each case. We suggest that a possible explanation for this discrepancy may be the fact that conservative systems, owing to their measure preserving property, do not become asymptotically one-dimensional, as dissipative systems do. 相似文献
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Cascades of period doubling bifurcations are found in one parameter families of differential equations in ℝ3. When varying a second parameter, the periodic orbits in the period doubling cascade can disappear in homoclinic bifurcations.
In one of the possible scenarios one finds cascades of homoclinic doubling bifurcations. Relevant aspects of this scenario
can be understood from a study of interval maps close to x↦p+r(1 −x
β)2, β∈ (?,1). We study a renormalization operator for such maps. For values of β close to ?, we prove the existence of a fixed
point of the renormalization operator, whose linearization at the fixed point has two unstable eigenvalues. This is in marked
contrast to renormalization theory for period doubling cascades, where one unstable eigenvalue appears. From the renormalization
theory we derive consequences for universal scalings in the bifurcation diagrams in the parameter plane.
Received: 16 June 1999 / Accepted: 24 April 2001 相似文献
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Tohru Kai 《Journal of statistical physics》1982,29(2):329-343
A stochastic one-dimensional map which produces a sequence of period doubling bifurcations is theoretically studied. We obtain analytic expressions, to a second-order approximation, of the local distribution function of fluctuating orbital points and the Lyapunov number for a noisy 2
n
cycle. The expressions satisfy scaling laws and well agree with the results of numerical experiments when the external noise is weak. A scaling factor for the noise level is formulated in terms of the derivatives of a deterministic map. From it, the scaling factor is refined to be 6.6190 .... The Lyapunov number shows that, when the external noise is weaker than some extent, the noisy orbit is more stable rather than the deterministic one. 相似文献
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在电磁流体力学范围内研究了与磁辫相联系的反常电子粘滞性效应所驱动的双撕裂模的线性行为。采用分区处理方法得到了该模式的一个近似色散关系。如果在x=±xs处的两个有理面间的距离足够小[xs/α《(kyα)-11/15R-11/15],则所得增长率的变化规律为τv-1/5,随着该距离的增大,增长率过渡为τr-1/3定标。τv-1/5定标被证明为与撕裂层中不变φ近似的失效有关。
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We study the characteristic features of certain statistical quantities near critical bifurcations such as onset of chaos,
sudden widening and band-merging of chaotic attractor and intermittency in a periodically driven Duffing-van der Pol oscillator.
At the onset of chaos the variance of local expansion rate is found to exhibit a self-similar pattern. For all chaotic attractors
the variance Σn(q) of fluctuations of coarse-grained local expansion rates of nearby orbits has a single peak. However, multiple peaks are
found just before and just after the critical bifurcations. On the other hand, Σn (q) associated with the coarse-grained state variable is zero far from the bifurcations. The height of the peak of Σn(q) is found to increase as the control parameter approached the bifurcation point. It is maximum at the bifurcation point.
Power-law variation of maximal Lyapunov exponent and the mean value of the state variablex is observed near sudden widening and intermittency bifurcations while linear variation is seen near band-merging bifurcation.
The standard deviation of local Lyapunov exponent λ(X,L) and the local mean valuex(L) of the coordinatex calculated after everyL time steps are found to approach zero in the limitL → ∞ asL
-Β. Β is sensitive to the values of control parameters. Further weak and strong chaos are characterized using the probability
distribution of ak-step difference quantity δxk = xi+k
x
i. 相似文献
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M.F.H. Schuurmans 《Optics Communications》1980,34(2):185-189
The emission from a high gain pencil-shaped volume of inhomogeneously broadened (T12) and initially completely inverted two-level atoms is described fully quantum-mechanically taking into account propagation along the pencil axis. The emission is shown to be superfluorescence for T12 ? √τRτD and amplified spontaneous emission for τR ? T12 ? √τRτD, where τR and τD are the collective decay time and the delay time of pure (T12 = ∞) superfluorescence, respectively. 相似文献
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A new universal empirical function that depends on a single critical exponent (acceleration exponent) is proposed to describe the scaling behavior in a dissipative kicked rotator. The scaling formalism is used to describe two regimes of dissipation: (i) strong dissipation and (ii) weak dissipation. For case (i) the model exhibits a route to chaos known as period doubling and the Feigenbaum constant along the bifurcations is obtained. When weak dissipation is considered the average action as well as its standard deviation are described using scaling arguments with critical exponents. The universal empirical function describes remarkably well a phase transition from limited to unlimited growth of the average action. 相似文献