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Abstract: In this paper, we study the dynamical behaviors of a three-node recurrent neural network model with four discrete time delays. We study several types of bifurcation, and use the method of multiple time scales to derive the normal forms associated with Hopf-zero bifurcation, non-resonant and resonant double Hopf bifurcations. Moreover, bifurcations are classified in two-dimensional parameter space near these critical points, and numerical simulations are presented to demonstrate the applicability of the theoretical results. [Copyright &y& Elsevier]

Abstract: The complex dynamics is explored in a prey predator system with multiple delays. Holling type-II functional response is assumed for prey dynamics. The predator dynamics is governed by modified Leslie–Gower scheme. The existence of periodic solutions via Hopf-bifurcation with respect to both delays are established. An algorithm is developed for drawing two-parametric bifurcation diagram with respect to two delays. The domain of stability with respect to τ 1 and τ 2 is thus obtained. The complex dynamical behavior of the system outside the domain of stability is evident from the exhaustive numerical simulation. Direction and stability of periodic solutions are also determined using normal form theory and center manifold argument. [Copyright &y& Elsevier]

Abstract: The dynamics of bacteria and bacteriophage coexistence in the presence of bacterial debris, in a marine environment, was studied using a system of delay differential equations (DDE). The system exhibits a rich variety of behavior in terms of two control parameters values: the bacteriophage burst size β, and the lysing time delay τ. Limit cycles of various periodicity, quasiperiodicity, period doubling, chaotic bands and toroidal chaos were identified using basic tools of non-linear dynamics analysis: first return maps, Poincaré sections, Fourier spectrum, and largest Lyapunov exponents. [Copyright &y& Elsevier]

Abstract: A ring of three coupled advertising oscillators with delay is considered. Using the symmetric functional differential equation theories, the multiple Hopf bifurcations of the equilibrium at the origin are demonstrated. The existence of multiple branches of bifurcating periodic solution is obtained. Numerical simulation supports our analysis results. [ABSTRACT FROM AUTHOR]

Abstract: We investigate the stability of the in-phase mode in a system of two delay-coupled bubble oscillators. The bubble oscillator model is based on a 1956 paper by Keller and Kolodner. Delay coupling is due to the time it takes for a signal to travel from one bubble to another through the liquid medium that surrounds them. Using techniques from the theory of differential-delay equations as well as perturbation theory, we show that the equilibrium of the in-phase mode can be made unstable if the delay is long enough and if the coupling strength is large enough, resulting in a Hopf bifurcation. We then employ Lindstedt’s method to compute the amplitude of the limit cycle as a function of the time delay. This work is motivated by medical applications involving noninvasive localized drug delivery via microbubbles. [Copyright &y& Elsevier]

Abstract: This paper investigates the dynamics of a new model of two coupled relaxation oscillators. The model replaces the usual DDE (differential-delay equation) formulation with a discrete-time approach with jumps. Existence, bifurcation and stability of in-phase periodic motions is studied. Simple periodic motions, which involve exactly two jumps per period, are found to have large plateaus in parameter space. These plateaus are separated by regions of complicated dynamics, reminiscent of the Devil’s Staircase. Stability of motions in the in-phase manifold are contrasted with stability of motions in the full phase space. [Copyright &y& Elsevier]

Abstract: In this paper, the Bautin bifurcation of synchronous solution of a coupled FHN neural system with delay is investigated. Firstly, the method of Lyapunov functional is used to obtain the synchronization conditions of the neural system, and then distributions of the roots of the characteristic equation associated with the linearization of the synchrosystem are discussed. Center manifold and normal form are employed to calculate its Lyapunov coefficients. A group of sufficient conditions are given to present Bautin bifurcation of the synchrosystem by applying the Bautin bifurcation theorem of delay differential equations developed by Anca-Veronica Ion. The Bautin bifurcation diagram in the physical parameter space is provided to illustrate the correctness of our theoretical analysis. [Copyright &y& Elsevier]

Abstract: A forced scalar delay dynamical system is analyzed from the perspective of bifurcation and synchronization. In general first order differential equations do not exhibit chaos, but introduction of a delay feedback makes the system infinite dimensional and shows chaoticity. In order to study the dynamics of such a system, Galerkin projection technique is used to obtain a finite dimensional set of ordinary differential equations from the delay differential equation. We compare the results of simulation with those obtained from direct numerical simulation of the delay equation to ascertain the accuracy of the truncation process in the Galerkin approximation. We have considered two cases, one with five and the other with eight shape functions. Next we study two types of synchronization by considering coupling of the above derived equations with a forced dynamical system without delay. Our analysis shows that it is possible to have synchronization between two such systems. It has been shown that the chaotic system with delay feedback can drive the system without delay to achieve synchronization and the opposite case is also equally valid. This is confirmed by the evaluation of the conditional Lyapunov exponents of the systems. [Copyright &y& Elsevier]

Abstract: This work presents an explicit formula for determining the radius of a limit cycle which is born in a Hopf bifurcation in a class of first order constant coefficient differential-delay equations. The derivation is accomplished using Lindstedt’s perturbation method. [Copyright &y& Elsevier]

• Using tools from control and bifurcation theory, we study whether the queue size feedback in Rate Control Protocol (RCP) is useful. • We conduct stability, convergence, and bifurcation analysis for RCP with and without queue size feedback. • Removal of queue size feedback could enhance both the stability and convergence properties of RCP. • The presence of queue size feedback in RCP can lead to a sub-critical Hopf bifurcation, which is undesirable. • Queue size feedback is detrimental to the performance of the RCP protocol. The Rate Control Protocol (RCP) uses explicit feedback from routers to control network congestion. RCP estimates it's fair rate from two forms of feedback: rate mismatch and queue size. An important design question that remains open in RCP is whether the presence of queue size feedback is helpful, given the presence of feedback from rate mismatch. The feedback from routers to end-systems is time-delayed, and may introduce instabilities and complex nonlinear dynamics. Delay dynamical systems are often modeled using delay differential equations to facilitate a mathematical analysis of their performance and dynamics. The RCP models with and without queue size feedback give rise to two distinct nonlinear delay differential equations. Earlier work on this design question was based on methods of linear systems theory. For further progress, it is quite natural to employ nonlinear techniques. In this study, we approach this design question using tools from control and bifurcation theory. The analytical results reveal that the removal of queue feedback could enhance both stability and convergence properties. Further, using Poincaré normal forms and center manifold theory, we investigate two nonlinear properties, namely, the type of the Hopf bifurcation and the asymptotic stability of the bifurcating limit cycles. We show that the presence of queue feedback in the RCP can lead to a sub-critical Hopf bifurcation, which would give rise either to the onset of large amplitude limit cycles or to unstable limit cycles. Whereas, in the absence of queue feedback, the Hopf bifurcation is always super-critical, and the bifurcating limit cycles are stable. The analysis is complemented with computations and some packet-level simulations as well. In terms of design, our study suggests that the presence of both forms of feedback may be detrimental to the performance of RCP. [ABSTRACT FROM AUTHOR]