Narrow Results

This paper addresses the finite-time synchronization problem for fractional-order memristor-based neural networks (FMNNs) with discontinuous activations, in which multiple delays are considered. Firstly, on the basis of set-valued mapping as well as differential inclusions theory, the synchronization issue of drive-response systems is considered as the stabilization of the error system. Then, the state feedback controllers, which contain both discontinuous part and time-delayed part, are designed to analyze the finite-time synchronization of the concerned network model. Making use of the stability theorem of fractional-order systems with multiple time delays, some fractional derivative inequalities and comparison theorem, several sufficient criteria are established for confirming that the synchronization error of the concerned system can reach zero within a limited time. Additionally, the settling time can be optimized by adjusting controller parameter. Finally, the effectiveness of synchronization strategies is validated through the simulation results.

In this paper, an inertial two-neuron system with multiple delays is analyzed to exhibit the effect of time delays on system dynamics. The parameter region with multiple equilibria is obtained employing the pitchfork bifurcation of trivial equilibrium. The stability analysis illustrates that two nontrivial equilibria are both stable for any delays. It implies that the neural system exhibits a stability coexistence of two resting states. Further, due to the existence of multiple delays, the neural system has a periodic activity around the trivial equilibrium via Hopf bifurcation. Finally, numerical simulations are employed to illustrate many richness coexistence for multitype activity patterns. Employing the period-adding route and fold bifurcation of periodic orbit, the neural system may have multistability coexistence of two resting states, two ASP-3s (anti-symmetric periodic activity with period three), one SSP-1 (self-symmetric periodic activity with period one), and one quasi-periodic spiking. Additionally, with increasing delay, quasi-periodic spiking evolves into chaos behavior.

This paper considers the time-delayed feedback control for Maglev system with two discrete time delays. We determine constraints on the feedback time delays which ensure the stability of the Maglev system. An algorithm is developed for drawing a two-parametric bifurcation diagram with respect to two delays τ₁ and τ₂. Direction and stability of periodic solutions are also determined using the normal form method and center manifold theory by Hassard. The complex dynamical behavior of the Maglev system near the domain of stability is confirmed by exhaustive numerical simulation.

A diffusive logistic population model with multiple delays and Dirichlet boundary condition is considered in this paper. The stability/instability of the positive equilibrium and delay induced Hopf bifurcation are investigated. Moreover, we show which kind of delay could actually affect the dynamics.

Research on the output game behavior of oligopoly has greatly advanced in recent years. But many unknowns remain, particularly the influence of consumers’ willingness to buy green products on the oligopoly output game. This paper constructs a triopoly output game model with multiple delays in the competition of green products. The influence of the parameters on the stability and complexity of the system is studied by analyzing the existence and local asymptotic stability of the equilibrium point. It is found that the system loses stability and increases complexity if delay parameters exceed a certain range. In the unstable or chaotic game market, the decisions of oligopoly will be counterproductive. It is also observed that the influence of weight and output adjustment speed on the firm itself is obviously stronger than the influence of other firms. In addition, it is important that weight and output adjustment speed cannot increase indefinitely, otherwise it will bring unnecessary losses to the firm. Finally, chaos control is realized by using the variable feedback control method. The research results of this paper can provide a reference for decision-making for the output of the game of oligopoly.

It is already well-understood that many delay differential equations with only a single constant delay exhibit a change in stability according to the value of the delay in relation to a critical delay value. Finding a formula for the critical delay is important to understanding the dynamics of delayed systems and is often simple to obtain when the system only has a single constant delay. However, if we consider a system with multiple constant delays, there is no known way to obtain such a formula that determines for what values of the delays a change in stability occurs. In this paper, we present some single-delay approximations to a multidelay system obtained via a Taylor expansion as well as formulas for their critical delays which are used to approximate where the change in stability occurs in the multidelay system. We determine when our approximations perform well and we give extra analytical and numerical attention to the two-delay and three-delay settings.

Competing populations within an ecosystem often release chemicals during the interactions and diffusion processes. These chemicals can have diverse effects on competitors, ranging from inhibition to stimulation of species’ growth. This work constructs a competition model that incorporates stimulatory substances, spatial effects, and multiple time lags to investigate the combined impact of these phenomena on competitors’ growth. When the stimulation rate from the produced chemicals falls within a suitable threshold interval, all species within the system can coexist. Under the species’ coexistence, their diffusive phenomenon leads to a spatially heterogeneous distribution, resulting in patchy structures (Turing patterns) within their habitat. As the parameter values exceed their thresholds, species begin to exhibit spatially periodic oscillations (spatial Hopf bifurcation). The presence of multiple delays and competitors’ diffusion contributes to spatially complex and heterogeneous behaviors (Turing–Hopf bifurcation). The results help us understand the underlying mechanisms behind these heterogeneous behaviors and enable us to mitigate their negative impact on species’ growth and harvest. Numerical simulations are used to measure the dynamics of competitors under different parameter conditions.

A mathematical model describing the dynamics of toxin producing phytoplankton–zooplankton interaction with instantaneous nutrient recycling is proposed. We have explored the dynamics of plankton ecosystem with multiple delays; one due to gestation period in the growth of phytoplankton population and second due to the delay in toxin liberated by TPP. It is established that a sequence of Hopf bifurcations occurs at the interior equilibrium as the delay increases through its critical value. The direction of the Hopf bifurcation and the stability of the bifurcating periodic solutions are determined using the theory of normal form and center manifold. Meanwhile, effect of toxin on the stability of delayed plankton system is also established numerically. Finally, numerical simulations are carried out to support and supplement the analytical findings.

In this article we consider the generalized problem of Bolza with different time varying delays appearing in the state and velocity variables. We derive existence of solutions and prove a natural extension of a decoupling theorem, which was originally introduced by Clarke in the non delay case² and was previously extended⁷ to the neutral case when both of the delays appearing are given by one function.