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Given the critical role of time delays in epidemic modeling, this paper delves into the dynamics and finite-time optimal stabilization of a novel epidemic system characterized by such delays. Our findings reveal that time delays significantly influence both the system's dynamics and the formulation of an optimal control strategy. Specifically, the system's endemic equilibrium point remains locally asymptotically stable under mild conditions for small time delays. However, exceeding critical delay thresholds induces Hopf bifurcation. To closely regulate the system's state towards the equilibrium point and minimize control costs, we propose an optimal control problem. We derive the explicit form of the optimal control strategy employing Pontryagin's Maximum Principle. Finally, numerical simulations further confirm the theoretical results obtained in this paper. • A time-delayed SEAIR epidemic model with a general incidence function is studied. • We focus on discussing the effects of time delays on dynamics and optimal control. • The theoretical results are well verified by the numerical simulation results. [ABSTRACT FROM AUTHOR]

We are concerned in this paper with dynamic behaviors and an optimal control problem of a new delayed epidemic model. There are three major ingredients. The first one is the dynamic behaviors of the state system. The locally asymptotic stability of the disease-free equilibrium and the endemic equilibrium are investigated and the effect of time delay on stability is also discussed. It is also found that the Hopf bifurcation appears at a specific time delay. The second, which is the main new ingredient of this paper, is an optimal control problem. Applying vaccine strategy in the system, an optimal control problem is proposed to minimize the total number of infected individuals as much as possible, maximize the total number of the uninfected individuals, and reduce the total control cost. In view of Pontryagin's maximum principle, the specific characteristics of the optimal control policy are given. The third ingredient is the numerical simulations of the theoretical results. • The model considers time delay, competition and spread of disease. • It studies dynamics and an optimal control problem of a delayed model. • Examples and numerical simulations are given to verify the theoretical results. [ABSTRACT FROM AUTHOR]

This paper serves as a continuation and expansion of the previous achievement by B. Han and D. Jiang in their article (Han and Jiang, 2024). Our initial step involves transforming the more complex stochastic Holling-II model featuring a stronger kernel into a simplified yet degenerate stochastic system composed of five interconnected equations. For the deterministic component of this model, we delve into an extensive examination of the local asymptotic stability of its positive equilibrium state. Subsequently, for the stochastic model, we derive critical conditions that determine the thresholds for exponential extinction and persistence of both predator and prey populations. Importantly, our findings not only encompass scenarios where there are no stochastic disturbances but also shed light on how environmental noise impacts the population dynamics within the predator–prey system. Through the exploration of the homologous Fokker–Planck equations, we present approximate representations characterizing the probability density function of the stochastic predator–prey model. To substantiate these theoretical advancements, several illustrative examples are provided, offering numerical elucidations of our proposed results and emphasizing the profound effects of stochastic noises and some important parameters on the behaviors of the stochastic model. • A stochastic Holling II predator–prey model with general distributed delay is investigated. • The sufficient and necessary condition for the coexistence of predator and prey populations is derived. • The approximate expression of the density function of the stochastic predator–prey model is obtained. • Several examples with simulations are presented to demonstrate the theoretical results. [ABSTRACT FROM AUTHOR]

In this paper it is exhibited the bifurcation scenario concerning a typical singularity of planar piecewise smooth vector fields in two zones. This singularity is characterized by a quadratic contact of one vector field and a quartic contact of another vector field at the same point of the switching manifold. By means of a three parameter perturbation, we observe the presence of bifurcations like: Hopf Bifurcation, Sliding Hopf Bifurcation, the birth and annihilation of chaotic scenarios, among others. The two and three dimensional bifurcation diagrams are included. • quartic–quadratic fold singularity of planar piecewise smooth vector fields. • normal form of the quartic–quadratic fold singularity. • 3-parameter bifurcation of a planar piecewise smooth vector field. • Planar bifurcation diagrams. • tridimensional bifurcation diagram. [ABSTRACT FROM AUTHOR]

This paper investigates the bifurcations of homoclinic orbits to hyperbolic saddle points in a simplified railway wheelset model with cubic and quintuple nonlinear terms. Using Melnikov's method, the sufficient conditions for the existence of the supercritical and the subcritical pitchfork bifurcations of homoclinic orbits are proven. To determine the integrability of the variational equations around homoclinic orbits in the meaning of differential Galois theory, the corresponding Fuchsian second-order differential equation for the normal variational equation and the Riemann P function are obtained. It is shown that the coefficients of the linear terms and the cubic coupling terms play a very significant role on influencing the existence of homoclinic orbits. While, the cubic coupling terms have little effect on the size of the left-hand and right-hand potential wells of homoclinic orbits. These results are beneficial to explore the key mechanism of hunting stability of a simplified railway wheelset model. • The sufficient conditions for pitchfork bifurcations of homoclinic orbits are proven. • The integrability of variational equations around homoclinic orbits is determined. • Linear and cubic coupling term coefficients affect the existence of homoclinic orbits. [ABSTRACT FROM AUTHOR]

• A Light-fueled liquid crystal elastomer self-fluttering aircraft is proposed. • The system has two motion patterns: stationary and self-fluttering. • Triggering conditions, frequency, and amplitude of self-fluttering are adjustable. • The amplitude and frequency of self-fluttering can be designed by system parameters. In response to external stimuli, active materials are able to alter their shape or motion. Nonetheless, considerable challenges remain in the effective realization and control of active machines. Conventional control methods, involving sensor-based and external device control as well as electronic control, are intricate and tough to put into practice. Conversely, self-oscillators built upon active materials exhibit remarkable properties, including steady motion and straightforward regulation. Drawing inspiration from flying organisms, this paper puts forward an innovative light-fueled self-fluttering aircraft with a liquid crystal elastomer (LCE) engine, capable of sustained flight in the presence of steady illumination. The governing equations of the self-fluttering aircraft are derived in accordance with the well-known dynamic LCE model. The system is capable of experiencing a supercritical Hopf bifurcation, transitioning from a stationary pattern to a self-fluttering pattern, and the energy compensation mechanism of the self-fluttering pattern is revealed as well. Moreover, the quantitative investigation covers how distinct system parameters influence the Hopf bifurcation conditions and the self-fluttering amplitude and frequency, as well as the average flight velocity. With the benefits of customizable size, electronics-free and dependence on ambient energy, the proposed system may generate fresh insights into the practical use of active materials-based self-oscillators in micro actuators, soft robotics, bionic devices, and energy harvesting. [ABSTRACT FROM AUTHOR]

In this paper, we delve into double Hopf bifurcation induced by memory-driven directed movement in a spatial predator–prey model with Allee effect and maturation delay of predators. We first adopt a novel technique to handle the associated characteristic equation and thus obtain the crossing curves as well as the double Hopf points. We then calculate explicit formulae of normal form regarding non-resonant double Hopf bifurcation. We thus divide the dynamics of the developed model into several categories near the double Hopf bifurcation points. Our numerical and theoretical results both demonstrate that the model can exhibit various complex phenomena when the parameters are near the double Hopf bifurcation points. For example, the transition from one stable spatially inhomogeneous periodic orbit with mode-5 to another with mode-4 and the coexistence of them can be observed. • A spatial model with delays in both reaction and diffusion terms is considered. • An innovative technique is given to obtain crossing curves and bifurcation points. • The algorithm to compute normal form of double Hopf bifurcation is generalized. • Compared with only random diffusion, memory-based movement causes complex dynamics. [ABSTRACT FROM AUTHOR]

Travel between patches and behavior changes of susceptible individuals are two crucial factors affecting the disease dynamics for any emerging infectious disease. Therefore studies of their impacts on disease dynamics are of great importance, especially to public health policy-makers. In this paper, we propose an SIR model that incorporates these two factors into consideration. For our two-patch SIR model with infection force mediated by (past) disease surveillance, we identify the basic reproduction number and show how it is related to travel modified basic reproduction numbers. We also carry out stability and Hopf bifurcation analysis and obtain conditions under which the disease persists in one patch or both patches. Numerical simulations are carried out to illustrate how travel between two patches and disease surveillance mediated infection force affect the disease dynamics and thus provide us some helpful insights on proper control of emerging infectious diseases. • Build a two-patch SIR model with infection force mediated by (past) disease surveillance. • Identify the overall basic reproduction number and related it with several travel modified basic reproduction numbers (See Table 1). • Find that the travel of susceptible individuals alone can cause an endemic even if the disease dies out in each isolated patch. • Study the effects of the past disease surveillance on the spread of the disease. [ABSTRACT FROM AUTHOR]

In this paper, the qualitative properties of the fixed points in the non-hyperbolic cases, codimension-one bifurcations and weak resonances of a Cournot-Bertrand duopoly mixed competition model are explored. The two firms adopt different decision variables and different objective functions, which are more consistent with the actual economic market situation. The qualitative properties of all the fixed points in the non-hyperbolic cases are investigated using the reduction principle and the center manifold theorem. After that, all the potential codimension-one bifurcations, including transcritical bifurcation, supercritical or subcritical flip bifurcation and Neimark–Sacker bifurcation are analyzed using the bifurcation theory and the center manifold theorem. The direction, stability, and even the explicit approximate expression are derived for each type of bifurcation. By perturbing the closed invariant curve caused by the Neimark–Sacker bifurcation, the 2 : 5 weak resonance associated with Arnold's tongue is theoretically proved, and the absence of 1 : 6 and 5 : 6 weak resonances is further analyzed. A large number of numerical simulations show complete consistency with all theoretical analyses. Moreover, the continuation method is used to conduct numerical bifurcation analyses, further verifying the correctness of theoretical analyses, and testing more codimension 2 bifurcations, such as fold-flip bifurcation, generalized flip bifurcation and 1 : 2 strong resonance. In addition, the economic implications of these bifurcations are also explained accordingly. [ABSTRACT FROM AUTHOR]

In this paper, we present a complete parametric analysis on a nonlinear predator–prey system with the generalized Holling type III functional response and a strong Allee effect. We apply the hierarchical parametric analysis to derive explicit conditions for the existence and stability of equilibrium solutions in a 5-dimensional parameter space. Specifically, a detailed study on Hopf bifurcation is given to show bifurcation of multiple limit cycles, and complex dynamics of multistable states including bistable, tristable and tetrastable phenomena. We also conduct simulations and provide a biological interpretation of the multistable states under various conditions. • A predator–prey generalized Holling type III functional response and a strong Allee effect is investigated. • The hierarchical parametric analysis is applied to study the existence and stability of equilibrium solutions in a 5-dimensional parameter space. • A detailed study on Hopf bifurcation is given to show bifurcation of multiple limit cycles. • Complex dynamics of multistable states including bistable, tristable and tetrastable phenomena are explored. [ABSTRACT FROM AUTHOR]

This paper focuses on a general Gause-Kolmogorov-Type predator–prey model with direct predator-taxis and indirect prey-taxis. The global existence and boundedness of solutions to the system are proved. Our approach is applicable to more general situation. Some measures of success for the constant coexistence steady state are rigorously calculated, such as decreasing the indirect prey-taxis sensitivity or the release rate of stimulus, and increasing the predator-taxis sensitivity or the decay rate of stimulus. By choosing the indirect prey-taxis coefficient as the bifurcation parameter, the existence of Hopf and double-Hopf bifurcations is established. We find that both indirect prey-taxis and direct predator-taxis can promote the complexity of the spatiotemporal pattern, e.g. spatially nonhomogeneous periodic patterns with different spatial frequency, spatially nonhomogeneous quasi-periodic patterns. Finally, we apply our theoretical analyses to a Rosenzweig–MacArthur model with indirect prey-taxis and direct predator-taxis, spatially homogeneous periodic patterns. • We bond the effects of direct and indirect taxis in a predator-prey system. • We prove the global well-posedness of a predator-prey system with direct and indirect taxis. • We determine several beneficial strategies of success about the indirect and direct taxis. • We establish double-Hopf bifurcations and pattern formations for a general predator-prey system. • In an application, complex nonhomgeneous periodic and quasi-periodic patterns emerge. [ABSTRACT FROM AUTHOR]