Spatial patterns in a network composed of neurons with different excitabilities induced by autapse

Gaussian colored noise induced spatial patterns and spatial coherence resonances in a square lattice neuronal network composed of Morris—Lecar neurons are studied. Each neuron is at resting state near a saddle-node bifurcation on invariant circle, coupled to its nearest neighbors by electronic coupling. Spiral waves with different structures and disordered spatial structures can be alternately induced within a large range of noise intensity. By calculating spatial structure function and signal-to-noise ratio (SNR), it is found that SNR values are higher when the spiral structures are simple and are lower when the spatial patterns are complex or disordered, respectively. SNR manifest multiple local maximal peaks, indicating that the colored noise can induce multiple spatial coherence resonances. The maximal SNR values decrease as the correlation time of the noise increases. These results not only provide an example of multiple resonances, but also show that Gaussian colored noise play constructive roles in neuronal network.

A study on ship performance in waves using a RANS solver, part 2: Comparison of added resistance performance in various regular and irregular waves

Regular and irregular waves were numerically generated in a wave canal to investigate hydrodynamic loads acting on a wind turbine monopile and to predict its structural response. The monopile was implemented in the canal and modeled as a flexible structure, with the turbine blades and rotors considered as a point mass situated at the top of the monopile. Fluid–structure interaction (FSI) simulations were performed by coupling a structure solver based on a finite element method (FEM) with an unsteady Reynolds-averaged Navier–Stokes (URANS) equations solver of the finite volume method (FVM). The FSI simulations considered the two-way interaction between the deformable structure and the fluid flow. The URANS equations solver was coupled with the volume of fluid (VoF) method to account for the two-phase flow. In regular waves, numerically predicted total load coefficients occurring at the monopile’s first eigenfrequency compared favorably to experimental measurements. A deviation between calculations and measurements was observed for the total loads in irregular waves. This deviation occurred due to the smaller wave energy density of the numerically predicted irregular wave. Hydroelasticity effects increased wave-induced forces by about 6% and wave induced bending moments by about 16% in regular waves. A relatively strong whipping event was observed, which characterized the hydroelasticity response bending moment of the monopile in irregular long-crested waves. This whipping event also had a significant influence on the loads on the monopile. These investigations demonstrated the favorable use of FSI simulations to predict hydroelasticity effects on a monopile.

Two-dimensional (2D) numerical simulations have been performed to investigate both regular and irregular waves past a fixed horizontally semisubmerged circular cylinder. The 2D simulations are carried out by solving Navier–Stokes equations discretized by finite volume method. Volume of fluid (VOF) method is employed to capture the free surface in the numerical wave tank (NWT). Validation studies have been performed by comparing the numerical results of free surface waves past the cylinder with the published experimental and numerical data. The present numerical results are in good agreement with both the experimental and the other numerical results in terms of hydrodynamic forces and free surface elevation. Subsequently, the effects of the wave height and the wavelength on wave–structure interaction are investigated by conducting numerical simulations on the regular and the irregular waves past a semisubmerged cylinder at different wave heights and the wavelengths. The averaged and maximum vertical wave forces on the cylinder increase with the increasing wave height. The numerical results for the irregular waves are compared with those induced by the regular waves in terms of the maximum and averaged vertical wave forces. When the significant wave height and the spectral peak period of the irregular waves are equal to the wave height and the wave period of the regular waves, the maximum vertical wave force induced by the irregular waves is larger than that induced by the regular waves, meanwhile, the average vertical wave forces have the contrary relationship.

This communication examines, in digital computer simulated network, input signals and response patterns established at excitatory neurons' level i.e. the membrane potential of neuron soma. It is restricted to spatial patterns of the auditory neuron networks and time factor for nervous conduction and transmission is neglected compared with long maintained membrane potentials of neuron somas. The model analyzes the change in the spatial patterns of the membrane potential in the two dimensional networks of the auditory system. In order to evaluate the contribution of the various parameters, it is started that the simplest model has only one parameter, lateral inhibition. The other parameters are then added, one at a time, to successive models. The lateral inhibition is a necessary condition in the auditory nervous system if any sharpening of the response areas in the single neurons is to occur. A necessary condition for the validity of the model is that is should be applicable to the other senses such as vision and chemical patterns, taste. The threshold feature of auditory neurons aids in producing a sharpening in the neuron of the auditory relay nuclei. It does this clipping the spatial response patterns in one dimensional arrays of excitatory neurons. Recurrent inhibition seems a necessary condition in the sensory nervous system that any kinds of input signals are to be preserved over a wide range of stimulus intensity. In other words, this network has a wide dynamic range against any kinds of input signals. A simple self-recurrent negative feedback does not contribute to the sharpening, but more complex socalled averaged type does. A neuron network is capable of responding stably to stimuli with a wide range of intensity and with any kind of spatial patterns if there is a simple negative feedback mechanism. When there is no negative feedback, input signals soon disappear or saturate in the neuron network. Therefore, recurrent inhibition is the most important mechanism. Spontaneous activity appears to aid in the sharpening by providing a kind of contrast, that is by reducting the amount of activity in neurons adjacent to the excitatory area. Moreover, the effect of spontaneous activity in the model seems to make repples around the excitatory area and suggests that an introduction of activity at any stage of the networks, from whatever source for example reticulum formation and thalamus, might appreciably alter the response patterns at subsequent neuron network. This suggests that the mechanism of the consciousness that might be controlled by the thalamus and or reticular formation. These two dimensional neuron networks may be expanded to three dimensional neuron networks. The former might simulate the auditory nervous system while the latter might simulate the visual system.

Application of complex network method to spatiotemporal patterns in a neuronal network

An application of Boussinesq equations to Bragg reflection of irregular waves

Researches on the motion and flooding process of a damaged passenger ship in regular and irregular beam waves

Study on wave-induced motions of a turning ship in regular and long-crest irregular waves

This study numerically analyzes a submerged horizontal plate (SHP) device subjected to both regular and irregular waves. This device can be used either as a breakwater or a wave energy converter (WEC). The WaveMIMO methodology was applied for the numerical generation and wave propagation of the sea state of the Rio Grande coast in southern Brazil. The finite volume method was employed to solve conservation equations for mass, momentum, and volume fraction transport. The volume of fluid model was employed to handle the water-air mixture. The SHP length (Lp) effects were carried out in five cases. Results indicate that relying solely on regular waves in numerical studies is insufficient for accurately determining the real hydrodynamic behavior. The efficiency of the SHP as a breakwater and WEC varied depending on the wave approach. Specifically, the SHP demonstrates its highest breakwater efficiency in reducing wave height at 2.5Lp for regular waves and 3Lp for irregular waves. As a WEC, it achieves its highest axial velocity at 3Lp for regular waves and 2Lp for irregular waves. Since the literature lacks studies on SHP devices under the incidence of realistic irregular waves, this study significantly contributes to the state of the art.

Nonlinear computational methods for hydroelastic effects of ships in extreme seas

Spiral waves are particular spatiotemporal patterns connected to specific phase singularities representing topological wave dislocations or nodes of zero amplitude, witnessed in a wide range of complex systems such as neuronal networks. The appearance of these waves is linked to the network structure as well as the diffusion dynamics of its blocks. We report a novel form of the Hindmarsh-Rose neuron model utilized as a square neuronal network, showing the remarkable multistructure of dynamical patterns ranging from characteristic spiral wave domains of spatiotemporal phase coherence to regions of hyperchaos. The proposed model comprises a hyperbolic memductance function as the monotone differentiable magnetic flux. Hindmarsh-Rose neurons with an external electromagnetic excitation are considered in three different cases: no excitation, periodic excitation, and quasiperiodic excitation. We performed an extensive study of the neuronal dynamics including calculation of equilibrium points, bifurcation analysis, and Lyapunov spectrum. We have found the property of antimonotonicity in bifurcation scenarios with no excitation or periodic excitation and identified wide regions of hyperchaos in the case of quasiperiodic excitation. Furthermore, the formation and elimination of the spiral waves in each case of external excitation with respect to stimuli parameters are investigated. We have identified novel forms of Hindmarsh-Rose bursting dynamics. Our findings reveal multipartite spiral wave formations and symmetry breaking spatiotemporal dynamics of the neuronal model that may find broad practical applications.

Spiking Irregularity and Frequency Modulate the Behavioral Report of Single-Neuron Stimulation

Elementary theory of the gyroscope

Wave induced motions of partially submerged bodies near a fixed structure