International Journal of Bifurcation and Chaos

In the last decade, researchers, who work in the field of nonlinear circuits, have the “dream” to use a real memristor, which is the only nonlinear fundamental circuit element, in a new or other reported nonlinear circuit in literature, in order to experimentally investigate chaos. With this intention, for the first time, a well-known nonlinear circuit, in which its nonlinear element has been replaced with a commercially available memristor (KNOWM memristor), is presented in this work. Interesting phenomena concerning chaos theory, such as period-doubling route to chaos, coexisting attractors, one-scroll and double-scroll chaotic attractors are experimentally observed.

In the past few years, chaotic systems with megastability have gained more attention in research. However, megastability behavior is mostly seen in chaotic systems. In this paper, a new 4D autonomous hyperjerk hyperchaotic system with megastability is reported.The new system has two modes of operation. The first mode considers one of its parameters $c\ne 0$ and the second mode is $c=0$. In the first mode, i.e. $c\ne 0,$ the proposed system exhibits self-excited attractors. But, in the second mode, i.e. $c=0,$ the system has a line of equilibria. The new system has various dynamical behaviors. The chaotic nature of the proposed system is validated by circuit simulation using NI Multisim simulation software.

Digital bifurcation analysis is a new algorithmic method for exploring how the behavior of a parameter-dependent discrete system varies with a change in its parameters and, in particular, for the identification of bifurcation points where such variation becomes dramatic. We have developed the method in an analogy with the traditional bifurcation theory and have successfully applied it to models taken from systems biology.

In this paper, we report on the application of the digital bifurcation analysis for analyzing the stability of internet congestion control protocols by inspecting their attractor bifurcations. In contrast to the analytical methods, our approach allows fully automated analysis.

We compared the robustness of the basic Random Early Drop (RED) approach with four substantially different extensions, namely gentle, adaptive, gradient descent, and integral feedback RED. The basic RED protocol is well known to exhibit unstable behavior when parameters are varied. In the case of adaptive and gradient descent RED protocol, the analysis showed significant improvements in stability, whereas in the results for gentle and integral feedback RED protocols the improvement was negligible. We performed a series of model simulations, the results of which were in accordance with our bifurcation analysis. Based on our results, we can recommend both adaptive and gradient descent RED to improve the robustness of the RED protocol.

In this paper, we show how the global bifurcation theory for nonlinear Fredholm operators (Theorem 4.3 of [Shi & Wang, 2009]) and for compact operators (Theorem 1.3 of [Rabinowitz, 1971]) can be used in the study of the nonconstant stationary solutions for a volume-filling chemotaxis model with logistic growth under Neumann boundary conditions. Our results show that infinitely many local branches of nonconstant solutions bifurcate from the positive constant solution $(u_c,\frac{\alpha }{\beta }{u}_c)$ at $\chi ={\overline{\chi }}_k$. Moreover, for each $k\ge 1$, we prove that each ${\mathrm{\Gamma }}_k$ can be extended into a global curve, and the projection of the bifurcation curve ${\mathrm{\Gamma }}_k$ onto the $\chi$-axis contains $({\overline{\chi }}_k,\infty )$.

In this paper, we investigate coexisting strange nonchaotic attractors (SNAs) in a quasiperiodically forced system. We also describe the basins of attraction for coexisting attractors and identify the mechanism for the creation of coexisting attractors. We find three types of routes to coexisting SNAs, including intermittent route, Heagy–Hammel route and fractalization route. The mechanisms for the creation of coexisting SNAs are investigated by the interruption of coexisting torus-doubling bifurcations. We characterize SNAs by the largest Lyapunov exponents, phase sensitivity exponents and power spectrum. Besides, the SNAs with extremely fractal basins exhibit sensitive dependence on the initial condition for some particular parameters.

Locally active memristors with multiple coexisting pinched hysteresis loops have attracted the attention of researchers. However, the currently reported multiple coexisting pinched hysteresis loops memristors are obtained by adding additional piecewise-linear terms into the original Chua corsage memristor. This paper proposes a novel locally active memristor by introducing a polynomial characteristic function into the state equation. The novel memristor has three coexisting pinched hysteresis loops, large relative range of active region and simple emulator circuit. The characteristics of the novel memristor such as power-off plot, coexisting pinched hysteresis loops and DC $V$–$I$ plot are studied. The memristor is used in a Chua chaotic system to investigate the effects of locally active characteristic on the chaotic oscillation system. Furthermore, the memristor emulator and chaotic system are designed and implemented by commercial circuit elements. The hardware experiments are consistent with numerical simulations.

We consider local and global bifurcations in a HIV model with cell-to-cell transmission and vectored immunoprophylaxis. Both theoretical and numerical analyses are conducted to explore various dynamical behaviors including backward bifurcation, Hopf bifurcation, homoclinic bifurcation, Bogdanov–Takens bifurcation, hysteresis and isola bifurcation. The isola bifurcation of periodic orbits was first detected numerically in HIV model, which means that there is a parameter interval with the same oscillations. It is shown that the effect of vectored immunoprophylaxis in this model is the main cause of the periodic symptoms of HIV disease. Moreover, it is shown that the increase of cell-to-cell transmission may be the main factor causing Hopf bifurcation to disappear, and thus eliminating oscillation behavior. Also, several patterns of dynamical behaviors are found in different parameter intervals including the bistability.

This paper introduces a new chaotic system model that could generate multi-direction multi-scroll (MDMS) chaotic attractors. The fundamental dynamics characteristics of this model are investigated, and the feasibility of the proposed method is confirmed by numerical simulation based on MATLAB. Additionally, the new chaotic system is implemented in FPGA-based platform. Implementation results are the same in MATLAB and FPGA, which indicates that they are suitable for practical applications. To investigate the cryptographic application of the new chaotic system, the chaotic sequences generated by the proposed system are used to encrypt images. The key space of the algorithm as well as key sensitivity, plain image sensitivity, plaintext histogram, correlation and information entropy are simulated and analyzed. In contrast to several encryption schemes, the proposed algorithm is very sensitive to plaintext and the key.

In this paper, we present a 6D generalized Lorenz model for magnetoconvection of an electrically conducting viscous fluid layer subjected to horizontally imposed uniform magnetic field. It generalizes the 4D generalized Lorenz model of Macek and Strumik [Phys. Rev. E 82, 027301 (2010)] taking into account high-wavenumber vertical Fourier modes of the temperature profile. These additional modes not only increase the feedback loop of the system but also subsequently affect the transitional processes. The boundedness, stability of solutions, bifurcation patterns enroute to chaos for the new 6D model are explored. Studies reveal that the stability of the quiescent state does not alter. But the stability of the steady convective state differs in comparison to the 4D model. The regions of aperiodic oscillation are suppressed which results in stabilization of the convective motion. Some new organized periodic structures embedded in chaotic domain appear in parameter space of the 6D model, and the transitional route to hyperchaos is altered owing to the inclusion of the high-order modes.

The inherent random-like behavior and one-way property of iteration in chaotic systems provide a good basis for designing Hash function. In the era of big data, due to the increasing data capacity in applications, fast Hash functions with parallel mode are highly desirable when authenticating data integrity. We analyze the issue of how to parallelize Hash function with iterative structure. Some security requirements on parallel Hash function are presented. In addition, using chaotic map and block cipher, we construct a keyed parallel Hash function. The message blocks are firstly processed in parallel by a DM-like structure. Furthermore, a tree mode with chaotic map is utilized to combine the outputs of the hash round function in parallel. The proposed Hash function is analyzed by theory and tested by computer simulations. The test results show that the proposed scheme can resist the various common attacks against Hash functions. It satisfies the secure performance requirements of Hash function. Owing to the usage of the parallel mode to process messages, the proposed chaos-based Hash function possess high efficiency and has high potential in applications to guarantee data integrity on a parallel computing platform.

In [Molaie et al., 2013] the authors provided the expressions of 23 quadratic differential systems in ${ℝ}^3$ with the unusual feature of having chaotic dynamics coexisting with one stable equilibrium point. In this paper, we consider 23 classes of quadratic differential systems in ${ℝ}^3$ depending on a real parameter $a$, which, for $a=1$, coincide with the differential systems given by [Molaie et al., 2013]. We study the dynamics and bifurcations of these classes of differential systems by varying the parameter value $a$. We prove that, for $a=0$, all the 23 considered systems have a nonisolated zero–Hopf equilibrium point located at the origin. By using the averaging theory of first order, we prove that a zero–Hopf bifurcation takes place at this point for $a=0$, which leads to the creation of three periodic orbits bifurcating from it for $a>0$ small enough: an unstable one and a pair of saddle type periodic orbits, that is, periodic orbits with a stable and an unstable manifold. Furthermore, we numerically show that the hidden chaotic attractors which exist for these systems when $a=1$ are obtained by period-doubling route to chaos.

In this paper, a planktonic resource–consumer system with two delays is investigated and the coefficients depend on $\tau$ one of the two delays. Firstly, the property of solution and the existence of equilibrium are given. The dynamical analysis of the system including stability and Hopf bifurcation by using the delays as parameters is carried out. Both the single delay and two delays can cause the system to produce Hopf bifurcation and the stable switching phenomena may exist. Furthermore, using the crossing curve methods, we obtain the stable changes of equilibrium in two-delay parameter plane, which generalizes the results of the system that the coefficients do not depend on delay. Furthermore, the numerical simulation results show that the theoretical analyses are correct when the delays change.

This paper investigates the nonlinear vibrations of the rotating pretwisted cylindrical panel under higher-frequency primary resonance and lower-frequency primary resonance for the case of 1:2 internal resonances. An accurate strain-displacement relationship is derived by the Green strain tensor. First-order shear deformation theory and Hamilton principle are utilized to establish the partial differential governing equation of the rotating cylindrical panel. Galerkin approach is employed to obtain the two-degree-of-freedom nonlinear system, which contains coupling between linear stiffness terms of the two transverse modes. The method of multiple scales is used to obtain the modulation equations for the amplitudes and phases. Numerical simulations are performed to show amplitude-frequency responses and bifurcation behaviors of the system. Two types of numerical methods are compared to describe the amplitude-frequency responses of the system. The results show the accuracy of our proposed method. The effects of the detuning parameter, the damping coefficient and the excitation amplitude on amplitude-frequency responses and bifurcation behaviors are fully discussed.

A variety of firing rhythms can be generated spontaneously in the pre-Bötzinger complex. External stimuli can cause changes in the pattern of the firing rhythm, which may cause different physiological effects in the body. In this study, by the fast and slow time scale dynamics, with one- and two-parameter bifurcation analysis, we study the bursting patterns and their transition mechanisms of the pre-Bötzinger complex under washout filter controller. The results may help us understand the relationship between different firing patterns of neurons and external stimuli, and further reveal the mechanisms of disease due to external stimuli.

Since the traditional detection methods cannot accurately detect, determine and extract weak signals, the extreme sensitivity of chaotic systems to initial values is used for weak signal detection using a memristor-based chaotic system. Then, in order to find out all kinds of static nonlinear circuits suitable for Chua’s circuit with identical parameters, a comparative research platform is designed to generate five kinds of nonlinearity by taking advantage of the active short-circuit line method using the memristor-involved chaotic Chua’s circuit. The comparative research platform consists of three parts: a linear circuit unit, multiple nonlinear static function circuits and a nonlinear characteristic curve measurement unit connected by an electronic switch. By pressing the space bar, the switch between the active short-circuit line and the physical short-circuit line can be realized. The diffeomorphism between them is proved by comparing the memristive nonlinearity shape and the trilinear amplitude limiting the nonlinearity in the chaotic systems. Accordingly, hardware circuit experiments are carried out to verify the effectiveness and feasibility of the comparative research platform with various nonlinearity for Chua’s circuit. A good agreement is shown between the numerical simulations and the experimental results.

This article describes the dynamics of a predator–prey model with disease in predator population and prey population subject to Allee effect. The positivity and boundedness of the solutions of the system have been determined. The existence of equilibria of the system and the stability of those equilibria are analyzed when Allee effect is present. The main objective of this study is to investigate the impact of Allee effect and it is observed that the system experiences Hopf bifurcation and chaos due to Allee effect. The results obtained from the model may be useful for analyzing the real-world ecological and eco-epidemiological systems.

In this manuscript, we consider an extended version of the prey–predator system with nonlinear harvesting [Gupta et al., 2015] by introducing a top predator (omnivore) which feeds on more than one trophic levels. Consideration of third species as omnivore makes the system a food web of three populations. We have guaranteed positivity as well as the boundedness of solutions of the proposed system. We observed that the presence of third species complicates the dynamical behavior of the system. It is also observed that multiple positive steady states exist for the proposed system which makes the problem more interesting compared to the similar models studied previously. Sotomayor’s theorem is being utilized to study the saddle-node bifurcation. The persistence conditions are discussed for the proposed model. The local existence of periodic solution through Hopf bifurcations is also guaranteed numerically. It is observed that the proposed model is capable to exhibit more complicated dynamics in the form of chaos in both the cases when there are unique and multiple coexisting steady states. Bifurcation diagrams and Lyapunov exponents have been drawn to ensure the existence of chaotic dynamics of the system.

In this work, we demonstrate a new chaotic signal-induced phenomenon that the output of a chaotic signal-driven bistable system can be consistently mapped to specific logic gate operation in an optimal window of chaotic signal intensity. We term this phenomenon logical chaotic resonance (LCR). Then, an intuitive interpretation for LCR phenomenon is given based on potential well map and mean first-passage time. Through LCR mechanism, the chaotic signal with proper intensity is used to obtain reliable logical gate in the bistable system. Besides, appropriately increasing the chaotic signal intensity can effectively improve the response speed of the bistable system to the change of input signal. Finally, the role of chaotic signal in enhancing the capacity of resisting disturbance of parameters is demonstrated.

We examine the orbital dynamics in a new Hénon–Heiles system with an additional gravitational potential, by classifying sets of starting conditions of trajectories. Specifically, we obtain the results on how the total orbital energy along with the transition parameter influence the overall dynamics of the massless test particle, as well as the respective time of escape/collision. By using modern diagrams with color codes we manage to present the different types of basins of the system. We show that the character of the orbits is highly dependent on the energy and the transition parameter.

Connected branches of periodic orbits originating at a Hopf bifurcation point of a differential system are considered. A computable estimate for the range of amplitudes of periodic orbits contained in the branch is provided under the assumption that the nonlinear terms satisfy a linear estimate in a ball. If the estimate is global, then the branch is unbounded. The results are formulated in an equivariant setting where the system can have multiple branches of periodic orbits characterized by different groups of symmetries. The nonlocal analysis is based on the equivariant degree method, which allows us to handle both generic and degenerate Hopf bifurcations. This is illustrated by examples.

Chimera states — the coexistence of synchrony and asynchrony in a nonlocally-coupled network of identical oscillators — are often used as a model framework for epileptic seizures. Here, we explore the dynamics of chimera states in a network of modified Hindmarsh–Rose neurons, configured to reflect the graph of the mesoscale mouse connectome. Our model produces superficially epileptiform activity converging on persistent chimera states in a large region of a two-parameter space governing connections (a) between subcortices within a cortex and (b) between cortices. Our findings contribute to a growing body of literature suggesting mathematical models can qualitatively reproduce epileptic seizure dynamics.

This research shows a structural voltage stability analysis of a distribution network incorporating large-scale solar photovoltaic power plant. Detailed modeling of the transmission network and photovoltaic systems is presented and a differential-algebraic equations model is developed. The resulting system state and load-flow Jacobian matrix are reorganized according to the type of the bus system in place of the standard injected complex power equations arrangement. The interactions among system buses for loading tests and solar photovoltaic power penetration are structurally scrutinized. Two-bus bifurcations are revealed to be a predecessor to system voltage collapse. The investigation is carried out by using bifurcation diagrams of photovoltaic generation margin, load-flow analysis, short-circuits, photovoltaic farm disconnections and loading conditions. Furthermore, evaluation of voltage stability reveals that the dynamic component of the voltage strongly depends on fault short-circuit capacity of the power system at the bus, where, the solar system is integrated. The overall result, which encompasses the views from the presented transmission network integration studies, is a positive outcome for future grid integration of solar photovoltaic in the Tunisian system. Tunisia’s utilities policies on integration of solar photovoltaic in distribution network is expected to benefit from the results of the presented study. Moreover, given the huge potential and need for solar photovoltaic penetration into the transmission network, the presented comprehensive analysis will be a valuable guide for evaluating and improving the performances of national transmission networks of other countries too.