排序方式: 共有17条查询结果,搜索用时 15 毫秒
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建立了一个无标度网络上带有时滞的SIRS模型,并分析了在度不相关情况下模型的动力学性态.当基本再生数R_01时,模型只有无病平衡点,运用Jacobi矩阵和Lyapunov泛函得出无病平衡点的全局稳定性;当R_01时,无病平衡点不稳定,存在唯一地方病平衡点且是持续的. 相似文献
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人工神经网络在SARS疫情分析与预测中的应用 总被引:4,自引:0,他引:4
讨论人工神经网络在 SARS疫情分析与预测中的应用 .采用三层结构的反向传播网络 ( Backpropagation network,简称 BP网络 ) ,对 SARS在中国的传播与流行趋势及控制策略建立了网络模型 .并利用实际数据拟合参数 ,针对北京、山西的疫情进行了计算仿真 .结果表明 ,该网络模型算法收敛速度较快 ,预测精度很高 相似文献
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本讨论了空间曲线x=x(t),y=y(t),x=z(t)上奇异点的性卷,结果表明:若[x^(k)(t0)]^2 [y^(k)(t0)]^2 [z^(k)(t0)]^2=0,k=1,2,…,n-1,而[x^(n)(t0)]^2 [y^(n)(t0)]^2 [z^(n)(t0)]^2 [y^(n)(t0)]^2 [z^(n)(t0)]^2≠0,则当n为奇数时,曲线在点M0(x0,y0,z0)是光滑的;当n为偶数时,曲线在点M0(x0,y0,z0)是不光滑的。 相似文献
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Pattern formation of a spatial epidemic model with nonlinear incidence rate hI^2 S/(1 + αI^2) is investigated. Our results show that strange spatial dynamics, i.e., filament-like pattern, can be obtained by both mathematical analysis and numerical simulation, which are different from the previous results in the spatial epidemic model such as stripe-like or spotted or coexistence of both pattern and so on. The obtained results well extend the finding of pattern formation in the epidemic model and may well explain the distribution of the infected of some epidemic. 相似文献
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在谣言传播过程中加入真实信息的传播者,考虑了人们对谣言的遗忘因素,建立了SITR (susceptible-infective-true-removed)谣言传播模型.利用下一代矩阵得到了谣言传播的阈值K_0,证明了K_0 1时无谣言传播者无真实信息传播者平衡点的稳定性,给出了边界平衡点(即有谣言传播者但无真实信息传播者,及无谣言传播者但有真实信息传播者平衡点)存在的条件,以及它们的稳定性,发现了两个边界平衡点出现双稳的区域,获得了不同条件下正平衡点的存在性,及其局部稳定性.最后,通过数值模拟验证了理论结果,模拟分析了真实信息传播者的初始值对谣言传播者的峰值及谣言的持续时间等的影响. 相似文献
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This paper considers the Holling-Tanner model for predator-prey with self and cross-diffusion. From the Turing theory, it is believed that there is no Turing pattern formation for the equal self-diffusion coefficients. However, combined with cross-diffusion, it shows that the system will exhibit spotted pattern by both mathematical analysis and numerical simulations. Furthermore, asynchrony of the predator and the prey in the space. The obtained results show that cross-diffusion plays an important role on the pattern formation of the predator-prey system. 相似文献
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研究了两个城市之间人口相互流动的具有出生死亡的SIR流感模型,获得了该模型基本再生数,并对基本再生数与移出率之间的关系作了敏感度分析.结果显示,人口的适当迁移可以有效控制流感爆发. 相似文献
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Pattern formation of a spatial epidemic model with both self- and cross-diffusion is investigated. From the Turing theory, it is well known that Turing pattern formation cannot occur for the equal self-diffusion coefficients. However, combined with cross-diffusion, the system will show emergence of isolated groups, i.e., stripe-like or spotted or coexistence of both, which we show by both mathematical analysis and numerical simulations. Our study shows that the interaction of self- and cross-diffusion can be considered as an important mechanism for the appearance of complex spatiotemporal dynamics in epidemic models. 相似文献
10.
Emergence of spatiotemporal chaos arising from far-field breakup of spiral waves in the plankton ecological systems 下载免费PDF全文
It has been reported that the minimal spatially extended phytoplankton-zooplankton system exhibits both temporal regular/chaotic behaviour, and spatiotemporal chaos in a patchy environment. As a further investigation by means of computer simulations and theoretical analysis, in this paper we observe that the spiral waves may exist and the spatiotemporal chaos emerge when the parameters are within the mixed Turing-Hopf bifurcation region, which arises from the far-field breakup of the spiral waves over a large range of diffusion coefficients of phytoplankton and zooplankton. Moreover, the spatiotemporal chaos arising from the far-field breakup of spiral waves does not gradually invade the whole space of that region. Our results are confirmed by nonlinear bifurcation of wave trains. We also discuss ecological implications of these spatially structured patterns. 相似文献