考虑环境因素的血吸虫传染病模型

研究了环境制约条件下人体内血吸虫传染的数学模型,分析了人体内易感细菌、受传染细菌和环境污染水平的变化规律,对模型进行了定性和稳定性分析,讨论了模型无病平衡点和地方病平衡点的存在条件,得到了各个平衡点渐近稳定的充分条件.结合实际血吸虫病感染数据,对模型进行数值模拟,并绘制出模型的变化趋势图.     

环境制约条件下含两菌株寄生虫的传染模型

研究了环境制约条件下含两菌株寄生虫的传染模型,结合流感病毒的传播规律,考虑同一亚型不同毒株之间的传染病模型.讨论了模型各个平衡点的存在条件,局部渐近稳定的条件,并对模型进行了数值模拟,很好的验证了模型的相关性质和特点.     

年龄结构CD4~+T-细胞模型复杂动力学分析

研究了一类年龄结构的CD4~+T-细胞模型.得到了控制HIV病毒扩散的阈值R_0.当R_01时,无病平衡点全局渐近稳定,病毒在人体内消除;当R_01,且-r+(2αrT~*)/(T_(max))0,地方病平衡点局部渐近稳定,病毒在人体内繁殖;当R_01,且-r+(2αrT~*)/(T_(max))0,系统由感染年龄而产生的复杂动力学行为,如Hopf分支,四周期解及混沌等.最后对模型的复杂动力学行为进行了数值模拟.     

公共教育影响的SIR传染病斑块模型性态分析

建立了考虑公共卫生教育影响的SIR斑块模型.通过分析模型动力学性态,给出模型平衡点存在条件,并证明了无病平衡点和地方病平衡点的稳定性.通过数值模拟分析公共卫生教育和斑块间的传播对模型疾病传播的影响,发现媒体的传播和公众之间的交流可以促进疾病防护意识,进而降低传染及传播疾病的几率.当疾病爆发时,应尽量减少人口流通,当疾病爆发后,应加强疾病防护意识的传播,尤其是医疗水平较低的地区.     

具有常数迁入率和非线性传染率βI~pS~q的SI模型分析

对一种具有种群动力和非线性传染率的传染病模型进行了研究,建立了具有常数迁入率和非线性传染率βI~pS~q的SI模型.与以往的具有非线性传染率的传染病模型相比,这种模型引入了种群动力,也就是种群的总数不再为常数,因此,该类模型更精确地描述了传染病传播的规律.还讨论了模型的正不变集,运用微分方程稳定性理论分析了模型平衡点的存在性及稳定性,得出了疾病消除平衡点和地方病平衡点的全局渐进稳定的充分条件.进一步的,得出了在某些参数范围内会出现Hopf分支现象,并对上述模型进行了生物学讨论.     

具有常数输入的SEIR模型的稳定性分析

讨论了易感者类和潜伏者类均为常数输入,潜伏期、染病期和恢复期均具有传染力,且传染率为一般传染率的SEIR传染病模型.利用Hurwitz判据证明了地方病平衡点的局部渐近稳定性,进一步利用复合矩阵理论得到了地方病平衡点全局渐近稳定的充分条件.     

一类具有双线性传染率的HIV/AIDS病毒动力学改进模型

针对HIV/AIDS传播的具有常数移民和指数出生的SI型模型,为了更加符合实际意义,对具有双线性传染率的模型进行局部改进,并对改进后的动力学模型进行了简化.对于改进后的模型,证明了平衡点的存在与局部稳定性,并证明了传染病毒的灭绝与持续性,得到了传染病毒的基本再生数.结果表明:当单位时间内从外界迁入人口中染病者的比例系数c近似等于零时,基本再生数小于1时,传染病毒最终灭绝;当基本再生数大于1时,模型存在唯一的正平衡点,且是局部渐近稳定的,说明传染病毒一致持续存在.     

具有免疫接种且总人口规模变化的SIR传染病模型的稳定性

讨论一类具有预防免疫接种且有效接触率依赖于总人口的SIR传染病模型,给出了决定疾病灭绝和持续生存的基本再生数σ的表达式,在一定条件下证明了疾病消除平衡点的全局稳定性,得到了唯一地方病平衡点的存在性和局部渐近稳定性条件.最后研究了具有双线性传染率和标准传染率的两个具体模型,并证明了当σ>1时该模型地方病平衡点的全局渐近稳定性.     

一类具有阶段结构和接种的SIR传染病模型

根据不同程度的感染者有不同的传染率,建立了一个具有阶段结构和双线性传染率的S IR流行病模型,得到了模型的阈值参数R0,证明了模型平衡点的全局性态完全由R0的值确定.并进行了数值模拟.     

一类具有感染时滞的HIV模型的稳定性分析

在基本病毒动力学模型的基础上,建立了一个具有HollingⅡ型感染率且带有时滞的HIV模型.通过稳定性分析,讨论了模型无病平衡点以及正平衡点的稳定性态.最后借助Matlab对模型进行了数值模拟.     

Dynamics analysis of an HTLV‐1 infection model with mitotic division of actively infected cells and delayed CTL immune response

In this paper, we propose an improved human T‐cell leukemia virus type 1 infection model with mitotic division of actively infected cells and delayed cytotoxic T lymphocyte immune response. By constructing suitable Lyapunov functional and using LaSalle invariance principle, we investigate the global stability of the infection‐free equilibrium of the system. Our results show that the time delay can change stability behavior of the infection equilibrium and lead to the existence of Hopf bifurcations. Finally, numerical simulations are conducted to illustrate the applications of the main results.     

Analysis of a viral infection model with delayed immune response

It is well known that the immune response plays an important role in eliminating or controlling the disease after human body is infected by virus. In this paper, we investigate the dynamical behavior of a viral infection model with retarded immune response. The effect of time delay on stability of the equilibria of the system has been studied and sufficient condition for local asymptotic stability of the infected equilibrium and global asymptotic stability of the infection-free equilibrium and the immune-exhausted equilibrium are given. By numerical simulating,we observe that the stationary solution becomes unstable at some critical immune response time, while the delay time and birth rate of susceptible host cells increase, and we also discover the occurrence of stable periodic solutions and chaotic dynamical behavior. The results can be used to explain the complexity of the immune state of patients.     

Maintenance of diversity in a hierarchical host–parasite model with balancing selection and reinfection

Inspired by DNA data of the human cytomegalovirus we propose a model of a two-type parasite population distributed over its hosts. The parasite is capable to persist in its host till the host dies, and to reinfect other hosts. To maintain type diversity within a host, balancing selection is assumed.For a suitable parameter regime we show that in the limit of large host and parasite populations the host state frequencies follow a dynamical system with a globally stable equilibrium, guaranteeing that both types are maintained in the parasite population for a long time on the host time scale.     

Chaos in delay-induced Leslie–Gower prey–predator–parasite model and its control through prey harvesting

In this paper we analyze a delay-induced predator–prey–parasite model with prey harvesting, where the predator–prey interaction is represented by Leslie–Gower type model with type II functional response. Infection is assumed to spread horizontally from one infected prey to another susceptible prey following mass action law. Spreading of disease is not instantaneous but mediated by a time lag to take into account the time required for incubation process. Both the susceptible and infected preys are subjected to linear harvesting. The analysis is accomplished in two phases. First we analyze the delay-induced predator–prey–parasite system in absence of harvesting and proved the local & global dynamics of different (six) equilibrium points. It is proved that the delay has no influence on the stability of different equilibrium points except the interior one. Delay may cause instability in an otherwise stable interior equilibrium point of the system and larger delay may even produce chaos if the infection rate is also high. In the second phase, we explored the dynamics of the delay-induced harvested system. It is shown that harvesting of prey population can suppress the abrupt fluctuations in the population densities and can stabilize the system when it exceeds some threshold value.     

Global stability of a virus infection model with two delays and two types of target cells

In this paper, incorporating the delay of viral cytopathicity within target cells, we first presented a basic model of viral infection with delay, and then extended it into a model with two delays and two types of target cells. For the models proposed here, both their basic reproduction numbers are found. By constructing Lyapunov functionals, necessary and sufficient conditions ensuring the global stability of the models with delays are given. The obtained results show that, when the basic reproduction number is not greater than one, the infection-free equilibrium is globally stable in the feasible region, which implies that the virus infection goes extinct eventually; when it is greater than one, the infection equilibrium is globally stable in the feasible region, which implies that the virus infection persists in the body of host.     

A schistosomiasis compartment model with incubation and its optimal control

A new mathematical model included an exposed compartment is established in consideration of incubation period of schistosoma in human body. The basic reproduction number is calculated to illustrate the threshold of disease outbreak. The existence of the disease free equilibrium and the endemic equilibrium are proved. Studies about stability behaviors of the model are exploited. Moreover, control measure assessments are investigated in order to seek out effective control interventions for anti‐schistosomiasis. Then, the corresponding optimal control problem according to the model is presented and solved. Theoretical analyses and numerical simulations induce several prevention and control strategies for anti‐schistosomiasis. At last, a discussion is provided about our results and further work. Copyright © 2017 John Wiley & Sons, Ltd.     

Dynamics of an HIV‐1 virus model with both virus‐to‐cell and cell‐to‐cell transmissions,general incidence rate,intracellular delay,and CTL immune responses

Direct cell‐to‐cell transmission of HIV‐1 is a more efficient means of virus infection than virus‐to‐cell transmission. In this paper, we incorporate both these transmissions into an HIV‐1 virus model with nonlinear general incidence rate, intracellular delay, and cytotoxic T lymphocyte (CTL) immune responses. This model admits three types of equilibria: infection‐free equilibrium, CTL‐inactivated equilibrium, and CTL‐activated equilibrium. By using Lyapunov functionals and LaSalle invariance principle, it is verified that global threshold dynamics of the model can be explicitly described by the basic reproduction numbers.     

Dynamics of an intra-host model of malaria with a constant drug efficiency

In this paper, we investigate the dynamics of an intra-host model of malaria with logistic red blood growth, treatment and immune response. We provide a theoretical study of the model. We derive the basic reproduction number $\mathcal R_f$ which determines the extinction and the persistence of malaria within the body of a host. We compute equilibria and study their stability. More precisely, we show that there exists a threshold parameter $\zeta$ such that if $\mathcal R_f\leq\zeta\leq1$, the disease-free equilibrium is globally asymptotically stable. However, if $\mathcal R_f>1$, there exist two malaria infection equilibria which are locally asymptotically stable: one malaria infection equilibrium without immune response and one malaria infection equilibrium with immune response. The sensitivity analysis of the model has been performed in order to determine the impact of related parameters on outbreak severity. The theory is supported by numerical simulations. We also derive a spatio-temporal model, using Diffusion-Reaction equations to model parasites dispersal. Finally, we provide numerical simulations for parasites spreading, and test different treatment scenarios.     

博弈方的行动集合变化的博弈运动研究——以稀土出口贸易为例

文章以稀土出口贸易为背景,分析了博弈方的行动集合随时间变化的博弈运动。首先定义了行动集合的三种变化情形:集合变大、集合变小和集合变化不确定。然后针对单个博弈方行动集合的三种变化情形,分别讨论了均衡解的运动轨迹,分析表明:在行动集合变大和变小两种情形下,均衡解的轨迹呈现互逆的运动特性;在行动集合变化不确定的情形下,保守和冒险策略等价,固定策略严格优于保守、冒险策略。在此基础上,将模型推广到博弈双方的行动集合均发生变化的博弈运动模型,分析表明上述结论仍然成立。最后,以中国同马来西亚在2012年6月到2013年3月间的稀土出口贸易为例,验证了本文模型和求解方法的合理性与可行性。     

人力资本投资的随机内生增长模型

本文假设人力资本是宏观经济的一部分 ,由此建立一个随机内生增长模型 ,把人力资本作为宏观经济变量并进入个人效用 .分析了经济达到均衡时个体偏好 ,不确定性对均衡增长率的影响 .同时分析了财政政策 ,税率对经济增长的影响 ,还求出了最优的增长率和人力资本投入与物质资本比 .