Analysis of an epidemic model with density-dependent birth rate,birth pulses

In this paper, we propose an SIS epidemic model for which population births occur during a single period of the year. Using the discrete map, we obtain exact periodic solutions of system which is with Ricker function. The existence and stability of the infection-free periodic solution and the positive periodic solution are investigated. The Poincaré map, the center manifold theorem and the bifurcation theorem are used to discuss flip bifurcation and bifurcation of the positive periodic solution. Numerical results imply that the dynamical behaviors of the epidemic model with birth pulses are very complex, including small-amplitude periodic 1 solution, large-amplitude multi-periodic cycles, and chaos. This suggests that birth pulse, in effect, provides a natural period or cyclicity that allow for a period-doubling route to chaos.     

Dynamical behaviors of a prey-predator system with impulsive control

In this paper, we study dynamics of a prey-predator system under the impulsive control. Sufficient conditions of the existence and the stability of semi-trivial periodic solutions are obtained by using the analogue of the Poincaré criterion. It is shown that the positive periodic solution bifurcates from the semi-trivial periodic solution through a transcritical bifurcation. A strategy of impulsive state feedback control is suggested to ensure the persistence of two species. Furthermore, a steady positive period-2 solution bifurcates from the positive periodic solution by the flip bifurcation, and the chaotic solution is generated via a cascade of flip bifurcations. Numerical simulations are also illustrated which agree well with our theoretical analysis.     

Flip bifurcations of an SIR epidemic model with birth pulse and pulse vaccination

In this paper, we study an SIR epidemic model with birth pulse and pulse vaccination. We present a new constructor method of Poincaré maps. Using this method, we construct a Poincaré map. However, for this Poincaré map, we can’t directly use the bifurcation theorem to discuss the existence of flip bifurcations. We use a new method to investigate the existence of flip bifurcations. We establish that the system undergoes flip bifurcation when the maximum birth rate passes some critical values. Furthermore, some numerical simulations are given to illustrate our results.     

Hopf-flip bifurcations of vibratory systems with impacts

Two vibro-impact systems are considered. The period n single-impact motions and Poincaré maps of the vibro-impact systems are derived analytically. Stability and local bifurcations of single-impact periodic motions are analyzed by using the Poincaré maps. A center manifold theorem technique is applied to reduce the Poincaré map to a three-dimensional one, and the normal form map associated with Hopf-flip bifurcation is obtained. It is found that near the point of codim 2 bifurcation there exists not only Hopf bifurcation of period one single-impact motion, but also Hopf bifurcation of period two double-impact motion. Period doubling bifurcation of period one single-impact motion is commonly existent near the point of codim 2 bifurcation. However, no period doubling cascade emerges due to change of the type of period two fixed points and occurrence of Hopf bifurcation associated with period two fixed points. The results from simulation shows that there exists an interest torus doubling bifurcation occurring near the value of Hopf-flip bifurcation. The torus doubling bifurcation makes the quasi-periodic attractor associated with period one single-impact motion transit to the other quasi-periodic attractor represented by two attracting closed circles. The torus bifurcation is qualitatively different from the typical torus doubling bifurcation occurring in the vibro-impact systems.     

Impulsive state feedback control of a predator–prey model

The dynamics of a predator–prey model with impulsive state feedback control, which is described by an autonomous system with impulses, is studied. The sufficient conditions of existence and stability of semi-trivial solution and positive period-1 solution are obtained by using the Poincaré map and analogue of the Poincaré criterion. The qualitative analysis shows that the positive period-1 solution bifurcates from the semi-trivial solution through a fold bifurcation. The bifurcation diagrams of periodic solutions are obtained by using the Poincaré map, and it is shown that a chaotic solution is generated via a cascade of period-doubling bifurcations.     

A delayed SIRS epidemic model with pulse vaccination

A delayed SIRS epidemic model with pulse vaccination and saturated contact rate is investigated. By using the discrete dynamical system determined by the stroboscopic map, we obtain the exact infection-free periodic solution of the system. Further, by using the comparison theorem, we prove that under the condition that R₀ < 1 the infection-free periodic solution is globally attractive, and that under the condition that R′ > 1 the disease is uniformly persistent, which means that after some period of time the disease will become endemic.     

The differential susceptibility SIR epidemic model with stage structure and pulse vaccination

The differential susceptibility SIR epidemic model with stage structure and pulse vaccination is introduced. By the comparison theorem, some sufficient conditions for the globally attractivity of an infection-free periodic solution and the permanence of this system are presented. Two numerical simulations are also given to illustrate our main results.     

Complex dynamics of a Holling type II prey–predator system with state feedback control

The complex dynamics of a Holling type II prey–predator system with impulsive state feedback control is studied in both theoretical and numerical ways. The sufficient conditions for the existence and stability of semi-trivial and positive periodic solutions are obtained by using the Poincaré map and the analogue of the Poincaré criterion. The qualitative analysis shows that the positive periodic solution bifurcates from the semi-trivial solution through a fold bifurcation. The bifurcation diagrams, Lyapunov exponents, and phase portraits are illustrated by an example, in which the chaotic solutions appear via a cascade of period-doubling bifurcations. The superiority of the state feedback control strategy is also discussed.     

Impulsive control in a stage structure population model with birth pulses

The dynamical behavior of a stage structure population model with birth pulses and impulsive pest management strategy is discussed analytically and numerically. It is assumed that birth pulse and impulsive pest management strategy act with the same period, but not simultaneously. The existence and stability of the positive 2T-period solution are investigated. By using center manifold theorem and bifurcation theorem, the conditions of existence for flip bifurcation are derived. Moreover, some detailed numerical results for phase portraits, periodic solutions, bifurcation diagram, and chaotic attractors, which are illustrated with two examples, are in good agreement with the theoretical analysis.     

Creation of twistless circles in a model of stellar pulsations

In the present paper, we study the Poincaré map associated to a periodic perturbation, both in space and time, of a linear Hamiltonian system. The dynamical system embodies the essential physics of stellar pulsations and provides a global and qualitative explanation of the chaotic oscillations observed in some stars. We show that this map is an area preserving one with an oscillating rotation number function. The nonmonotonic property of the rotation number function induced by the triplication of the elliptic fixed point is superposed on the nonmonotonic character due to the oscillating perturbation. This superposition leads to the co-manifestation of generic phenomena such as reconnection and meandering, with the nongeneric scenario of creation of vortices. The nonmonotonic property due to the triplication bifurcation is shown to be different from that exhibited by the cubic Hénon map, which can be considered as the prototype of area preserving maps which undergo a triplication followed by the twistless bifurcation. Our study exploits the reversibility property of the initial system, which induces the time-reversal symmetry of the Poincaré map.     

具饱和传染率的脉冲免疫接种SIRS模型

研究了具饱和传染率的脉冲免疫接种SIRS模型的一致持续生存和周期解,得到了无病周期解全局渐近稳定的充分条件和系统一致持续生存的充分条件,并应用分支理论得到了正周期解存在的分支参数.     

An SIRS epidemic model with pulse vaccination and non-monotonic incidence rate

An SIRS epidemic model with pulse vaccination and non-monotonic incidence rate is introduced. Some sufficient conditions for the global attractivity of the infection-free periodic solution and permanence of this system are presented. Two numerical simulations are also given to illustrate our main results.     

Dynamic analysis of an SIR epidemic model with state dependent pulse vaccination

An SIR epidemic model with state dependent pulse vaccination is proposed in this paper. Using the Poincaré map, the differential inequality and the method of qualitative analysis, we prove the existence and the stability of positive order-1 or order-2 periodic solution for this model. Moreover, we show that there is no periodic solution with order larger than or equal to three. Numerical simulations are carried out to illustrate the feasibility of our main results and the suitability of state dependent pulse vaccination is also discussed.     

The differential susceptibility SIR epidemic model with time delay and pulse vaccination

The differential susceptibility SIR epidemic model with time delay and pulse vaccination is introduced. Some sufficient conditions for the globally attractivity of infection-free periodic solution and permanence of this system are presented. Two numerical simulations are also given to illustrate our main results.     

具脉冲两阶段结构的自治SIS传染病模型

讨论了具有脉冲两阶段结构的自治SIS传染病模型,得到了该模型无病周期解存在性和稳定性的充分条件,并利用分支理论研究了正周期解的存在性.     

Pulse vaccination on SEIR epidemic model with nonlinear incidence rate

In this paper, we consider an SEIR epidemic model with two time delays and nonlinear incidence rate, and study the dynamical behavior of the model with pulse vaccination. By using the Floquet theorem and comparison theorem, we prove that the infection-free periodic solution is globally attractive when R^*<1, and using a new modelling method, we obtain a sufficient condition for the permanence of the epidemic model with pulse vaccination when R_*>1.     

A delay SIR epidemic model with pulse vaccination and incubation times

In this paper, a new delay SIR epidemic model with pulse vaccination and incubation times is considered. We obtain an infection-free semi-trivial periodic solution and establish the sufficient conditions for the global attractivity of the semi-trivial periodic solution. By use of new computational techniques for impulsive differential equations with delay, we prove that the system is permanent under appropriate conditions. The results show that time delay, pulse vaccination and nonlinear incidence have significant effects on the dynamics behaviors of the model. Our results are illustrated and corroborated with some numerical experiments.     

Hopf bifurcations, Lyapunov exponents and control of chaos for a class of centrifugal flywheel governor system

In this paper, complex dynamical behavior of a class of centrifugal flywheel governor system is studied. These systems have a rich variety of nonlinear behavior, which are investigated here by numerically integrating the Lagrangian equations of motion. A tiny change in parameters can lead to an enormous difference in the long-term behavior of the system. Bubbles of periodic orbits may also occur within the bifurcation sequence. Hyperchaotic behavior is also observed in cases where two of the Lyapunov exponents are positive, one is zero, and one is negative. The routes to chaos are analyzed using Poincaré maps, which are found to be more complicated than those of nonlinear rotational machines. Periodic and chaotic motions can be clearly distinguished by all of the analytical tools applied here, namely Poincaré sections, bifurcation diagrams, Lyapunov exponents, and Lyapunov dimensions. This paper proposes a parametric open-plus-closed-loop approach to controlling chaos, which is capable of switching from chaotic motion to any desired periodic orbit. The theoretical work and numerical simulations of this paper can be extended to other systems. Finally, the results of this paper are of practical utility to designers of rotational machines.     

Dynamics of a discretized SIR epidemic model with pulse vaccination and time delay

We derive a discretized SIR epidemic model with pulse vaccination and time delay from the original continuous model. The sufficient conditions for global attractivity of an infection-free periodic solution and permanence of our model are obtained. Improving discretization, our results are corresponding to those in the original continuous model.     

Dynamics of a discretized SIR epidemic model with pulse vaccination and time delay

We derive a discretized SIR epidemic model with pulse vaccination and time delay from the original continuous model. The sufficient conditions for global attractivity of an infection-free periodic solution and permanence of our model are obtained. Improving discretization, our results are corresponding to those in the original continuous model.