Information propagation in recurrent neuronal populations with mixed excitatory–inhibitory synaptic connections

Nonlinear Dynamics - Linearizing the equations of motion of a constrained multibody system is a common need in, for example, stability analyses. While the theory of modelling multibody systems is...     

Synchronization mode transitions induced by chaos in modified Morris–Lecar neural systems with weak coupling

Nonlinear Dynamics - Based on a modified Morris–Lecar neural model, the synchronization modes transitions between two coupled neurons or star-coupled neural network connected by weak...     

Population rate coding in recurrent neuronal networks consisting of neurons with mixed excitatory–inhibitory synapses

Nonlinear Dynamics - Neural coding is a key problem in neuroscience aimed to understand the information processing mechanism in brain. Among the classical theories of neural coding, population rate...     

Synchronization and chimeras in a network of photosensitive FitzHugh–Nagumo neurons

Nonlinear Dynamics - Recently, a photosensitive model has been proposed that takes into account nonlinear encoding and responses of photosensitive neurons that are subject to optical signals. In...     

Critical phenomena in laminar–turbulence transitions by a mean field model

In this work, following the papers (Cortet et al., Phys Rev Lett 105:214501, 2010; Manneville, Dissipative structures and weak turbulence, 1990), we study the turbulence behavior in a fluid as a critical phenomenon related with a continuous phase transition. So that, we use the Ginzburg–Landau equation describing the evolution of the order parameter, which control the laminar–turbulence transition. While, the velocity is represented by a sum of two terms, the normal and the rotational (or turbulence) components. As a result, the rotational term is zero in the laminar phase. Then, a hydrodynamic model is formulated, which chooses as fundamental fields the components of velocity and a phase field function f. Moreover, we study the thermodynamic restrictions, a maximum theorem for the phase field and the role of the pressure in the phase transition. In the last section, we address the study of turbulence in Helium II, where it is possible to observe many analogies with the phenomena which occur in classical fluids     

Energy harvesting in a Mathieu–van der Pol–Duffing MEMS device using time delay

This paper investigates quasi-periodic vibration-based energy harvesting in a delayed nonlinear MEMS device consisting of a delayed Mathieu–van der Pol–Duffing type oscillator coupled to a delayed piezoelectric coupling mechanism. We use the multiple scales method to approximate the quasi-periodic response and the related power output near the principal parametric resonance. The effect of time delay on the energy harvesting performance is studied. It is shown that for appropriate combination of time delay parameters, there exists an optimum range of excitation frequency beyond the resonance where quasi-periodic vibration-based energy harvesting is maximum. Numerical simulations are performed to confirm the analytical predictions.     

Z n equivariant in delay coupled dissipative Stuart–Landau oscillators

We consider a coupled dissipative Stuart?CLandau oscillator models. As the propagation time delay in the coupling varies, stability switches for the trivial solution are found. We discuss the spatio-temporal patterns of bifurcating periodic oscillations by using the symmetric bifurcation theory of delay differential equations combined with representation theory of Lie groups. The existence of multiple branches of bifurcating periodic solution is obtained. We also found that the spatio-temporal patterns of bifurcating periodic oscillations alternate according to the change of the propagation time delay in the coupling, i.e., different ranges of delays correspond to different patterns of dissipative Stuart?CLandau oscillators. Some numerical simulations support our analysis results.     

Nonlinear dynamics of a non-autonomous network with coupled discrete–continuum oscillators

A network model of a multi-modular floating platform incorporated with a runway structure, viewed as a non-autonomous network with discrete–continuum oscillators, is developed for a general purpose of dynamic analysis. Numerical analysis shows the coupling effect between the two different types of oscillators on various complex dynamics, including sudden leaps, torus motions, beating vibrations, the synergetic effect of phase lock and anti-phase synchronizations. The amplitude death phenomenon, a suppressed weak oscillation state, is studied by using the fundamental solution derived by the averaging method. The parametric domain of the onset of amplitude death is illustrated to show the great significance to the stability design of the floating platform. The effect of the flexural rigidity of the runway on the distribution of amplitude death state is also discussed.     

Coherence resonance in an autaptic Hodgkin–Huxley neuron with time delay

Autapses, synapses between a neuron and itself, are believed to serve as a regulator of information processing in the nervous system. Noise, as random or unpredictable fluctuations, affects nearly all aspects of nervous function. In this work, we studied the regulatory ability of an autapse on firing behaviors of a Hodgkin–Huxley neuron in response to synaptic-like signals in the presence of noise. For weak subthreshold synaptic input, the autaptic neuron produced the similar firing behavior governed by the noise in case of either determinate or random synaptic input. The critical noise intensity necessary to trigger the spike train slightly was decreased with determinate low-frequency input. Under a strong suprathreshold synaptic current, noise-induced frequency resonance and precise responses mostly occured with a high-frequency determinate input. With a random strong synaptic input, an increase in the autaptic delay led to a resonance-like response, but had no observable effects in cases with a short delay time under a low-frequency input.     

Numerical simulation of terrain-induced severe slugging coupled by hydrodynamic slugs in a pipeline–riser system

A numerical study based on a one-dimensional two-fluid model is carried out to describe the transient hydrodynamic slugging and terrain-induced severe slugging in a pipeline–riser system. The system of equations is rendered well-posed by interfacial pressure model for the riser. The selected flow conditions are restricted in the well-posed region for the horizontal and the downward inclined pipes to ensure the hydrodynamic slug characteristics are predicted correctly. The validity of the model is examined by water faucet problem and horizontal slug flow experiments. Simulations with and without slug capturing are conducted to address the effect of hydrodynamic slugs on severe slugging. It has been found that more accurate predictions are obtained by taking hydrodynamic slugs into account. At low superficial gas velocity, the simulation without slug capturing tends to overestimate the severe slugging period. When hydrodynamic slugs are captured, the upstream gas expansion is suppressed by the hydrodynamic slugs. At relatively high superficial gas velocity, the simulation without slug capturing tends to underestimate the severe slugging period. When hydrodynamic slugs are captured, the upstream compressible volume is greatly enlarged by the blowout of the hydrodynamic slugs. In both situations, the influences of the hydrodynamic slugs can reduce the errors of the predicted severe slugging characteristics.     

Multiple scales and normal forms in a ring of delay coupled oscillators with application to chaotic Hindmarsh–Rose neurons

We study the appearance and stability of spatiotemporal periodic patterns like phase-locked oscillations, mirror-reflecting waves, standing waves, in-phase or antiphase oscillations, and coexistence of multiple patterns, in a ring of bidirectionally delay coupled oscillators. Hopf bifurcation, Hopf–Hopf bifurcation, and the equivariant Hopf bifurcation are studied in the viewpoint of normal forms obtained by using the method of multiple scales which is a kind of perturbation technique, thus a clear bifurcation scenario is depicted. We find time delay significantly affects the dynamics and induces rich spatiotemporal patterns. With the help of the unfolding system near Hopf–Hopf bifurcation, it is confirmed in some regions two kinds of stable oscillations may coexist. These phenomena are shown for the delay coupled limit cycle oscillators as well as for the delay coupled chaotic Hindmarsh–Rose neurons.     

Stability and bifurcation in a generalized delay prey–predator model

The present paper considers a generalized prey–predator model with time delay. It studies the stability of the nontrivial positive equilibrium and the existence of Hopf bifurcation for this system by choosing delay as a bifurcation parameter and analyzes the associated characteristic equation. The researcher investigates the direction of this bifurcation by using an explicit algorithm. Eventually, some numerical simulations are carried out to support the analytical results.     

Soliton interactions in a generalized inhomogeneous coupled Hirota–Maxwell–Bloch system

In this paper, via the Darboux transformation, with symbolic computation, the bright one- and two-soliton solutions for a generalized inhomogeneous coupled Hirota–Maxwell–Bloch system are obtained in an inhomogeneous nonlinear dispersive fiber doped with two-level resonant atoms. The study on the bright soliton collision shows that in this system, there exists the complete or partial energy exchange. Through the asymptotic analysis, some physical quantities are discussed. Energy transfer in the two-soliton collision might have potential applications in the study of pulse amplification. In addition, the conservation laws for the system are also constructed.     

Turing patterns induced by self-diffusion in a predator–prey model with schooling behavior in predator and prey

Nonlinear Dynamics - This article considers a reaction–diffusion predator–prey model with schooling behavior both in predator and prey species and subject to the homogeneous Neumann...     

Hopf and Bogdanov�CTakens bifurcations in a coupled FitzHugh�CNagumo neural system with delay

In this paper, Hopf bifurcation and Bogdanov?CTakens bifurcation with codimension 2 in a coupled FitzHugh?CNagumo neural system with gap junction are investigated. At first, a general bifurcation diagram on the plane of coupling strength and delay is derived. Then, explicit algorithms due to Hassard and Faria are applied to determine the normal forms of Hopf and Bogdanov?CTakens bifurcations, respectively. Next, we analyze the codimension-2 unfolding for Bogdanov?CTakens bifurcation, and give complete bifurcation diagrams and phase portraits. Furthermore, we also consider the spatio-temporal patterns of bifurcating periodic solutions by using the symmetric bifurcation theory of delay differential equations combined with representation theory of Lie groups. By the results of theoretical analysis, we obtain that the values of coupled strength, which make the transmission and received signals be synchronous and anti-phase, are opposite. And universal unfolding of Bogdanov?CTakens bifurcation indicates that the neuron signals can transit between resting and spiking.     

Visualization of deflagration-to-detonation transitions in a channel with repeated obstacles using a hydrogen–oxygen mixture

The deflagration-to-detonation transition in a 100 mm square cross-section channel was investigated for a highly reactive stoichiometric hydrogen oxygen mixture at 70 kPa. Obstacles of 5 mm width and 5, 10, and 15 mm heights were equally spaced 60 mm apart at the bottom of the channel. The phenomenon was investigated primarily by time-resolved schlieren visualization from two orthogonal directions using a high-speed video camera. The detonation transition occurred over a remarkably short distance within only three or four repeated obstacles. The global flame speed just before the detonation transition was well below the sound speed of the combustion products and did not reach the sound speed of the initial unreacted gas for tests with an obstacle height of 5 and 10 mm. These results indicate that a detonation transition does not always require global flame acceleration beyond the speed of sound for highly reactive combustible mixtures. A possible mechanism for this detonation initiation was the mixing of the unreacted and reacted gas in the vicinity of the flame front convoluted by the vortex present behind each obstacle, and the formation of a hot spot by the shock wave. The final onset of the detonation originated from the unreacted gas pocket, which was surrounded by the obstacle downstream face and the channel wall.     

Dynamical stability in a delayed neural network with reaction–diffusion and coupling

Nonlinear Dynamics - In this paper, a delayed neural network with reaction–diffusion and coupling is considered. The network consists of two sub-networks each with two neurons. In the first...