International Journal of Bifurcation and Chaos

We treat the problem of characterizing in a systematic way the qualitative features of two-dimensional dynamical systems. To that end, we construct a representation of the topological features of phase portraits by means of diagrams that discard their quantitative information. All codimension 1 bifurcations are naturally embodied in the possible ways of transitioning smoothly between diagrams. We introduce a representation of bifurcation curves in parameter space that guides the proposition of bifurcation diagrams compatible with partial information about the system.

We propose and experimentally demonstrate an ultra-wideband (UWB) chaos life-detection radar. The proposed radar transmits a wideband chaotic-pulse-position modulation (CPPM) signal modulated by a single-tone sinusoidal wave. A narrow-band split ring sensor is used to collect the reflected sinusoidal wave, and a lock-in amplifier is utilized to identify frequencies of respiration and heartbeat by detecting the phase change of the sinusoidal echo signal. Meanwhile, human location is realized by correlating the CPPM echo signal with its delayed duplicate and combining the synthetic aperture technology. Experimental results demonstrate that the human target can be located accurately and his vital signs can be detected in a large dynamic range through a 20-cm-thick wall using our radar system. The down-range resolution is 15cm, benefiting from the 1-GHz bandwidth of the CPPM signal. The dynamic range for human location is 50dB, and the dynamic ranges for heartbeat and respiration detection respectively are 20dB and 60dB in our radar system. In addition, the bandwidth of the CPPM signal can be adjusted from 620MHz to 1.56GHz to adapt to different requirements.

In this paper, a physical SBT memristor-based chaotic circuit is presented. The circuit dynamic behavior of dependence on the initial state of the SBT memristor and a key circuit parameter are investigated by theoretical analyses and numerical simulations. The results indicate that different initial states of the SBT memristor and the key circuit parameter can significantly impact the dynamic behavior of the chaotic circuit, such as stable sink, periodic cycle, chaos, and even some complex transient dynamics. It can guide future research on the realization of chaotic circuit based on physical SBT memristor.

Large scale networks may exhibit complicated dynamical behaviors, such as instability, bifurcation, and chaos. It is not easy to get which nodes or links need to be controlled for ensuring the desired dynamical behavior. This paper presents a detailed analysis on the dynamics and control of a delayed network by a pinning strategy. The network system is first mapped to a simple system by means of an orthogonal transformation. The control signals are then exerted only on a fraction of nodes in the transformed system. We analyze how to get the desired dynamics of the original controlled system (such as zeros solutions, periodic solutions, quasi-periodic solutions and chaos) via controlling the transformed system. It shows that the solutions of the original system can be obtained by the local dynamical behavior exhibiting in the transformed system. The results show that the proposed pinning control strategy is an effective approach for dynamics control.

In this paper, a gene regulatory network mediated by small noncoding RNA involving two time delays and diffusion under the Neumann boundary conditions is studied. Choosing the sum of delays as the bifurcation parameter, the stability of the positive equilibrium and the existence of spatially homogeneous and spatially inhomogeneous periodic solutions are investigated by analyzing the corresponding characteristic equation. It is shown that the sum of delays can induce Hopf bifurcation and the diffusion incorporated into the system can effect the amplitude of periodic solutions. Furthermore, the spatially homogeneous periodic solution always exists and the spatially inhomogeneous periodic solution will arise when the diffusion coefficients of protein and mRNA are suitably small. Particularly, the small RNA diffusion coefficient is more robust and its effect on model is much less than protein and mRNA. Finally, the explicit formulae for determining the direction of Hopf bifurcation and the stability of the bifurcating periodic solutions are derived by employing the normal form theory and center manifold theorem for partial functional differential equations. Finally, numerical simulations are carried out to illustrate our theoretical analysis.

The phenomenon of synchronization (trapping) of coming waves by the resonant water area in a coastal zone of the sea found from the observed data is considered in the paper. Edge waves with the period of about 10.7 minutes are visually observed in sea level fluctuations near the village of Okhotskoye and the cape Ostri on the southeast coast of Sakhalin Island. These waves are synchronized with the resonance water area. It becomes apparent from the unlimited increase of a phase between the bottom stations installed at distance of about 7.5km. In relation to the phenomenon found, the problem of weak and periodic impact on regular self-oscillatory system — Van der Paul’s oscillator — is considered. Good compliance between theoretical model and data of experiments is obtained.

This paper investigates the planar differential systems $ẋ=-yG(x,y)$, $ẏ=xG(x,y)$ under the perturbations of polynomials of $(x,y)$ with degree $n$, where $G(x,y)={(x-a)}^{m_1}{(y-b)}^{m_2}$ with $ab\ne 0$ and $m_1,m_2\in \mathbb{N}$. The upper bound for the number of zeros of Abelian integral from the period annulus around the center is obtained.

An original three-dimensional (3D) smooth continuous chaotic system and its mirror-image system with eight common parameters are constructed and a pair of symmetric chaotic attractors can be generated simultaneously. Basic dynamical behaviors of two 3D chaotic systems are investigated respectively. A double-scroll chaotic attractor by connecting the pair of mutual mirror-image attractors is generated via a novel planar switching control approach. Chaos can also be controlled to a fixed point, a periodic orbit and a divergent orbit respectively by switching between two chaotic systems. Finally, an equivalent 3D chaotic system by combining two 3D chaotic systems with a switching law is designed by utilizing a sign function. Two circuit diagrams for realizing the double-scroll attractor are depicted by employing an improved module-based design approach.

In this study, the dynamic behavior and chaos control of a chaotic fractional incommensurate-order financial system are investigated. Using well-known tools of nonlinear theory, i.e. Lyapunov exponents, phase diagrams and bifurcation diagrams, we observe some interesting phenomena, e.g. antimonotonicity, crisis phenomena and route to chaos through a period doubling sequence. Adopting largest Lyapunov exponent criteria, we find that the system yields chaos at the lowest order of $2.15$. Next, in order to globally stabilize the chaotic fractional incommensurate order financial system with uncertain dynamics, an adaptive fractional sliding mode controller is designed. Numerical simulations are used to demonstrate the effectiveness of the proposed control method.

Memristor is a nonlinear “missing circuit element”, that can easily achieve chaotic oscillation. Memristor-based chaotic systems have received more and more attention. Research shows that fractional-order systems are more close to real systems. As an important parameter, the order can increase the flexibility and degree of freedom of the system. In this paper, a fractional-order generalized memristor, which consists of a diode bridge and a parallel circuit with an equivalent unit circuit and a linear resistance, is proposed. Frequency and electrical characteristics of the fractional-order memristor are analyzed. A chain structure circuit is used to implement the fractional-order unit circuit. Then replacing the conventional Chua’s diode by the fractional-order generalized memristor, a fractional-order memristor-based chaotic circuit is proposed. A large amount of research work has been done to investigate the influence of the order on the dynamical behaviors of the fractional-order memristor-based chaotic circuit. Varying with the order, the system enters the chaotic state from the periodic state through the Hopf bifurcation and period-doubling bifurcation. The chaotic state of the system has two types of attractors: single-scroll and double-scroll attractor. The stability theory of fractional-order systems is used to determine the minimum order occurring Hopf bifurcation. And the influence of the initial value on the system is analyzed. Circuit simulations are designed to verify the results of theoretical analysis and numerical simulation.

In this paper, a novel version of nonlinear model, i.e. a complex-valued love model with two time delays between two individuals in a love affair, has been proposed. A notable feature in this model is that we separate the emotion of one individual into real and imaginary parts to represent the variation and complexity of psychophysiological emotion in romantic relationship instead of just real domain, and make our model much closer to reality. This is because love is a complicated cognitive and social phenomenon, full of complexity, diversity and unpredictability, which refers to the coexistence of different aspects of feelings, states and attitudes ranging from joy and trust to sadness and disgust. By analyzing associated characteristic equation of linearized equations for our model, it is found that the Hopf bifurcation occurs when the sum of time delays passes through a sequence of critical value. Stability of bifurcating cyclic love dynamics is also derived by applying the normal form theory and the center manifold theorem. In addition, it is also shown that, for some appropriate chosen parameters, chaotic behaviors can appear even without time delay.

This paper mathematically investigates the process equation. The process equation is a one-dimensional map $A_{k+1}=A_k+g\mathrm{\text{sin}}(A_k)$. It can show multistable attractors and various dynamics such as period doubling, unifurcation, chaos, bios, unstable windows and bio-periodic windows with respect to the changing of its control parameter, $g$. Different dynamics and the reasons for their occurrence are investigated in this note.

We aim to investigate bifurcation behaviors in a stochastic birhythmic van der Pol (BVDP) system subjected to delay self-control feedback. First, the harmonic approximation is adopted to drive the delay self-control feedback to state variables without delay. Then, Fokker–Planck–Kolmogorov (FPK) equation and stationary probability density function (SPDF) for amplitude are obtained by applying stochastic averaging method. Finally, dynamical scenarios of the change of delay self-control feedback as well as noise that markedly influence bifurcation performance are observed. It is found that: the big feedback strength and delay will suppress the large amplitude limit cycle (LC) while the relatively big noise strength facilitates the large amplitude LC, which imply the proposed regulation strategies are feasible. Interestingly enough, the inner LC is never destroyed due to noise. Furthermore, the validity of analytical results was verified by Monte Carlo simulation of the dynamics.

In this paper, we investigate chaos and adaptive control of the magnetic-field electromechanical transducer wherein the electric characteristics of the capacitor contain the fractional-order derivative. The phase diagrams for different values of the fractional-order exhibit chaotic characteristics of the magnetic-field electromechanical transducer. In the process of controller design, a continuous frequency distributed model is utilized to construct the indirect Lyapunov stability criterion and a Chebyshev neural network with weight, and fractional-order adaptive law is introduced to approximate the complicated unknown function. To suppress chaotic oscillation, an adaptive control scheme by fusing Chebyshev neural network and backstepping is presented to guarantee that the closed-loop system is globally asymptotically stable. To illustrate the feasibility of the proposed approach, simulation studies are done in the end.

Chaotic systems have been widely used in digital image encryption algorithms because of their characteristics of deterministic randomness, extreme sensitivity to initial values, etc. Although these chaos-based algorithms are good at performance in general, most of them are ineffective when confronting attacks such as the chosen plain image attack. So, this paper proposes a new digital image encryption algorithm based on orbit variation of phase diagram (AOVPD), which modifies the iterative sequence of chaotic system with the pixel values of plain image. Theoretical analysis proves that the proposed AOVPD has the ability to resist chosen plain image attack within two rounds of operation, while the existing algorithms could be cracked in the same situation. To be specific, AOVPD is effective when confronting various attacks including chosen plain image attack. Also, simulation results show that the proposed algorithm has an outstanding safety performance.

This paper considers a class of three-dimensional systems constructed by a rotating planar symmetric cubic vector field. To study its periodic orbits including homoclinic orbits, which may be knotted in space, we classify the types of periodic orbits and then calculate their exact parametric representations. Our study shows that this class of systems has infinitely many distinct types of knotted periodic orbits, which lie on three families of invariant tori. Numerical examples of $(m,n)$-torus knot periodic orbits have also been provided to illustrate our theoretical results.

Motivated by the Silk Road Economic Belt and the 21st-Century Maritime Silk Road project, i.e. the Belt and Road (B&R), more goods will flow around the world. With this trading platform, people can buy products at relatively cheap prices, and it is easier for people to buy various goods. The quality and quantity of products thus attract more and more attention in the supply chains. This paper discusses the quantity decision by considering the product quality in parallel supply chains where two manufacturers produce substitute products and then sell them to their downstream retailers separately. In terms of the changing quantity, as well as the different quality, this paper establishes a dynamic game model to explore the dynamic behavior when the optimal profits of two retailers have been calculated. The dynamic behaviors of the system, such as stable region, bifurcation and chaos, strange attractors and the largest Lyapunov exponents (LLE) are analyzed. The effect of the quantity adjustment parameter on the stability of the supply chain system is investigated through numerical simulations. Furthermore, a dynamic game model is established based on the quality delay decision, to investigate the influence of the quality delay parameter on the dynamic game model and the profits. Finally, the optimal decisions are obtained and analyzed.

Little seems to be known about the chaotification problem in the framework of fractional order nonlinear systems. Based on the negative damping instability mechanism and fractional calculus technique, this paper reports the onset of chaos in fractional order Lorenz system with periodic system parameters via asymptotically period-doubling cascade. To further understand the complex dynamics of the system, some basic properties such as the largest Lyapunov exponents, bifurcation diagram, routes to chaos, asymptotically periodic windows, possible chaotic and asymptotically periodic window parameter regions, and the compound structure of the system are analyzed and demonstrated with careful numerical simulations. Of particular interest is a striking finding that fractional derivative can chaotify the globally stable periodic system without feedback control.

A problem on the analysis of the noise-induced transitions in stochastically forced tritrophic population systems is considered. We study this problem on the basis of the conceptual “prey–predator-top predator” model which possesses coexisting attractors (limit cycles) and exhibits noise-induced transitions between them. For the parametric analysis of noise-induced phenomena in this nonlinear 3D model, we suggest a constructive approach combining the stochastic sensitivity function technique and confidence domain method. We show how increasing noise causes stochastic bifurcations, generation of mixed-mode oscillations, and transitions from order to chaos.

In this paper, the problems of stability and Hopf bifurcation in a class of fractional-order complex-valued single neuron model with time delay are addressed. With the help of the stability theory of fractional-order differential equations and Laplace transforms, several new sufficient conditions, which ensure the stability of the system are derived. Taking the time delay as the bifurcation parameter, Hopf bifurcation is investigated and the critical value of the time delay for the occurrence of Hopf bifurcation is determined. Finally, two representative numerical examples are given to show the effectiveness of the theoretical results.