具有媒体效应和时滞的反应扩散传染病模型的控制与预测

针对媒体效应的传染病建立相应的反应扩散模型,研究平衡点的稳定性、Hopf分岔以及重要参数如时滞、传染率和媒体效应等对模型Turing结构的影响.最后,给出精确Turing失稳的参数条件,并给出相应的数值模拟,得到条状和点状共存的斑图.理论分析与数值模拟揭示了空间动力学复杂性机理,为控制疾病的传播提供了有力理论依据.     

具时滞效应的多商品蛛网模型及其稳定性分析

构建一类具有时滞效应的多商品非均衡蛛网模型.然后建立一个广义时滞差分不等式,在此基础上讨论该蛛网模型的平衡点存在性,并着重对其稳定性进行分析.     

时滞反馈作用下ENSO充电振子模型的分岔分析

通过数学变换将一类含有时滞反馈机制的ENSO充电振子模型转换成时滞Van der PolDuffing方程,并以此为基础来研究该ENSO系统的零解稳定性、Hopf分岔和极限环等动力学特征.用平均法分析了其零解的稳定性与时滞效应的强度,其和时间都有关系,讨论了时滞负反馈对ENSO振荡的影响并通过简单数值模拟验证理论分析的结果.     

时滞机床颤振模型的稳定性和Hopf分支分析

研究了时滞机床模型平衡点的局部稳定性和Hopf分支的存在性,得到了模型平衡点局部稳定的充分条件以及产生Hopf分支的充分条件.并发现当模型中时滞较大时,出现混沌现象.用Matlab进行数值模拟,验证了理论分析的结果.     

具有营养循环和时滞的浮游生物系统的稳定性及Hopf分支

建立并研究了具有营养循环和时滞的浮游动植物模型,模型中描述浮游动植物间的相互作用函数是Holling-Ⅲ型功能反应函数.首先讨论了模型解的正性及有界性,然后分析了系统在无时滞和有时滞两种情况下边界平衡点和正平衡点的局部稳定性,并通过建立适当的Lyapunov函数,讨论了平衡点的全局稳定性.研究表明,随着时滞的增加,系统会出现Hopf分支.     

具有固定时滞的经济周期模型的动态分析

在经济活动中,投资行为和资本存量存在一定的时滞效应,这会影响经济周期模型的动态行为,进而使得投资政策对经济的稳定调整复杂化.考虑到资本存量的预期时间以及投资时滞对经济活动的影响,采用Hopf分岔理论,研究具有固定时滞的经济周期模型的均衡点的稳定性以及形成经济周期的条件.研究发现,投资过程中的投资时滞,以及投资决策中对于资本存量的预测时间构成经济周期产生的诱因;同时可通过政府投资政策调整达到预期均衡目标,这对保持经济周期稳定及经济政策制定有一定的指导作用.     

一类时滞分数阶计算机病毒模型的稳定性研究

本文研究一类改进的时滞分数阶计算机病毒模型正平衡点的稳定性问题.利用线性化方法和拉普拉斯变换获得模型对应的线性化系统的特征方程,通过讨论特征方程的根以及横截条件研究时滞和正平衡点稳定性之间的关系,推导了Hopf分支出现时时滞临界值的计算公式,并选择恰当的系统参数进行数值模拟以验证理论分析的合理性.     

一类时滞病毒动力学模型的稳定性分析

建立并分析了一类带有两个时滞的病毒动力学模型.通过讨论,获得了有时滞情况下无病平衡点以及正平衡点的稳定性态.     

多重时滞富营养化生态模型的稳定性与分支分析

本文研究了多重时滞富营养化生态模型的稳定性与分支问题.利用特征值方法,分别研究了具有单时滞和双时滞模型的线性稳定性.发现当模型中的时滞经过一系列临界值时,模型在平衡点附近经历了Hopf分支和Hopf-zero分支,并给出Hopf分支和Hopf-zero分支存在的充分条件.最后数值模拟验证了理论结果.     

含有时滞的CES生产函数的资产投资模型解的稳定性

研究含有非局部和时滞边界条件的投资控制模型在解的存在唯一性基础上,讨论了模型解的稳定性,得到解的渐进稳定性.     

Dynamic behaviour of a discrete-time SIR model with information dependent vaccine uptake

This paper proposes and analyzes a discrete-time deterministic SIR model with information dependent immunization behaviour, where vaccination coverage at birth during any period of time is a general phenomenological function of the risk of infection that is perceived at the beginning of the period. Results on existence of equilibria, their local stability, and system persistence are proved. Then, by considering the noteworthy subcase of a piecewise linear ‘prevalence-dependent’ coverage function, the local stability of the endemic state is proved and conditions for its global asymptotic stability are given. Some insight on both Neimarck-Sacher and period-doubling bifurcations are provided. Overall we show that prevalence-dependent coverage is an essentially stabilising force. However period-doubling bifurcations are possible though under stressed parameter constellations.     

Stochastic logistic equation with infinite delay

This paper perturbs the famous logistic equation with infinite delay into the corresponding stochastic system This study shows that the above stochastic system has a global positive solution with probability 1 and gives the asymptotic pathwise estimation of this solution. In addition, the superior limit of the average in time of the sample path of the solution is estimated. This work also establishes the sufficient conditions for extinction, nonpersistence in the mean, and weak persistence of the solution. The critical value between weak persistence and extinction is obtained. Then these results are extended to n‐dimensional stochastic Lotka–Volterra competitive system with infinite delay. Finally, this paper provides some numerical figures to illustrate the results. The results reveal that, firstly, different types of environmental noises have different effects on the persistence and extinction of the population system; secondly, the delay has no effect on the persistence and extinction of the stochastic system.Copyright © 2012 John Wiley & Sons, Ltd.     

Global dynamics for an age-structured epidemic model with media impact and incomplete vaccination

Some studies show that the efficacy of vaccines may decline and the vaccine-induced immunity wanes with time elapsed since vaccination (e.g., BCG, HBV vaccines). Meanwhile, the use of media can effectively contain the emerging epidemics. In our work, an SVEIR epidemic model with media impact, age-dependent vaccination and latency is proposed, where the efficacy of vaccines depends on the time since vaccination. Uniform persistence and the sharp threshold dynamics are established, that is, the vaccination reproduction number completely determines the global dynamics of the model system. Our main results established can be extended to the SVEIR model with the general nonlinear infectious force function of monotonicity and concavity.     

An Infectious Disease Model With Media Coverage and Limited Medical Resources北大核心CSCD

该文建立和分析了一类具有媒体报道效应和有限医疗资源的传染病动力学模型,定义了疾病的基本再生数,分析了平衡点的存在性和稳定性,给出了系统发生前向分支、后向分支和Hopf分支的条件.通过数值模拟发现：提高媒体报道的信息覆盖率或医院对病人的最大容纳量,可以显著降低疾病流行的峰值或稳态时的感染人数;随着参数变化,系统不仅可能会产生后向分支或前向分支,还可能会出现鞍结点分支、Hopf分支以及地方病平衡点稳定性随参数变化而变化等动力学行为.     

Mathematical Modeling and Analysis of an Epidemic Model with Quarantine, Latent and Media Coverage

Epidemic models are very important in today''s analysis of diseases. In this paper, we propose and analyze an epidemic model incorporating quarantine, latent, media coverage and time delay. We analyze the local stability of either the disease-free and endemic equilibrium in terms of the basic reproduction number $\mathcal{R}_{0}$ as a threshold parameter. We prove that if $\mathcal{R}_{0}<1,$ the time delay in media coverage can not affect the stability of the disease-free equilibrium and if $\mathcal{R}_{0}>1$, the model has at least one positive endemic equilibrium, the stability will be affected by the time delay and some conditions for Hopf bifurcation around infected equilibrium to occur are obtained by using the time delay as a bifurcation parameter. We illustrate our results by some numerical simulations such that we show that a proper application of quarantine plays a critical role in the clearance of the disease, and therefore a direct contact between people plays a critical role in the transmission of the disease.     

Analyzing the dynamics of a stochastic rumor propagation model incorporating media coverage

In the age of information globalization, research on the mechanism of propagation will help mitigate the bad influence of rumors. Based on the classical rumor propagation model, this paper further analyzes the internal mechanism of the stochastic rumor propagation model incorporating media coverage with white noise. We investigate the existence of a unique global positive solution to the model and study the dynamic properties of the solutions around the rumor-free and local equilibrium points of the deterministic model. Furthermore, we establish sufficient conditions for the existence of traversal static distribution in the model. Numerical simulation shows that the role of media coverage is crucial to reduce the rumor propagation scale. The larger the coverage rate is, the smaller the rumor propagation scale is.     

媒体报道对一类具有潜伏期的传染病控制的影响

针对媒体报道产生的信息对一类具有潜伏期的传染病控制的影响问题,建立了一类带时滞的传染病模型.计算得到模型的基本再生数R_0并证明了当R0<1时,无病平衡点局部渐近稳定.通过分析模型正平衡点处对应的特征方程,得到了模型在正平衡点处稳定的条件,给出了正平衡点处会出现Hopf分支的临界条件并得到相关结论.     

一类带时滞的阶段结构捕食模型的定性分析

研究了一类具有时滞和阶段结构的捕食模型系统,给出了系统持续生存的充分条件.利用比较定理和构造适当的Lyapunov泛函得到了该系统正平衡态全局渐近稳定的充分条件.     

CONSIDERATION OF STOCHASTIC DEMOGRAPHY IN THE DESIGN AND MANAGEMENT OF BIOLOGICAL RESERVES

A generalized birth–and–death process serves as a simple, flexible model for computing the expected persistence time of a small population in a random world. We may reparametrize the model in ways that allow explicit incorporation of density dependence, random differences in events experienced by different individuals, and random environmental variation experienced by all individuals in concert. This model seems to capture the important features of real population dynamics for purposes of computing the mean persistence time, even though the underlying mechanisms presumed in the mathematics of the model are decidedly unrealistic. The lack of isomorphism between birth and death rates, as they feature in the model, and vital rates of real biological populations can lead to extremely misleading results, if the classic formulation, rather than the reparametrization is applied without due circumspection. Using the reparametrized model, we find that environmental variation poses a greater problem for population persistence than does individual variation. In particular, with purely individual variation, the expected persistence time increases approximately with the power of the ceiling on population size; but with purely environmental variation, the expected persistence time increases somewhat less than linearly with the size of the population ceiling. The birth–and–death process model can also be applied to calculating the persistence time of a population on an ensemble of reserves which are linked by natural migration or by deliberate reintroduction programs. Results of this model, for an idealized ensemble, show that multiple independent reserves with a sufficient recolonization rate (natural or otherwise) will confer a longer persistence time than a single reserve with the same total carrying capacity, but in the absence of recolonization, the system of smaller separate reserves confers a shorter persistence time than the single large reserve.     

Persistence of wavefronts in delayed nonlocal reaction-diffusion equations

We develop a perturbation argument based on existing results on asymptotic autonomous systems and the Fredholm alternative theory that yields the persistence of traveling wavefronts for reaction-diffusion equations with nonlocal and delayed nonlinearities, when the time lag is relatively small. This persistence result holds when the nonlinearity of the corresponding ordinary reaction-diffusion system is either monostable or bistable. We then illustrate this general result using five different models from population biology, epidemiology and bio-reactors.