Fuzzy PID control of epileptiform spikes in a neural mass model

In this paper, the problem of controlling epileptiform spikes in a neural mass model is addressed. Considering the complication and nonlinearity of the neural mass model, a fuzzy PID controller is designed so that epileptiform spikes are quenched and the output waveform tracks an expected one. The tracking effect is analyzed by numerical simulation for a regular network of coupled neural populations. The effect of important model parameters on the control energy and the effect of the types of controlled populations on the ability to realize the tracking purpose are analyzed for the same network.     

Fuzzy adaptive unscented Kalman filter control of epileptiform spikes in a class of neural mass models

A new closed-loop control method based on the fuzzy adaptive unscented Kalman filter (FAUKF) is proposed to suppress epileptiform spikes in a class of neural mass models with uncertain measurement noise. The FAUKF is used to estimate the nonlinear system states of the underlying models and amend measurement noise adaptively. The control law is constructed via the estimated states. Numerical simulations illustrate the efficiency of the proposed method.     

Analysis of self-sustained oscillation sources in segmented flows

The analysis of self-sustained oscillations in segmented flow generated through porous walls has been carried out over a wide range of velocity levels; in fact, we studied a cold gas flow induced by injection through different wall injecting blocks. We have attempted in this study to analyse the potential unstable development occurring in solid propellant rocket motors. We lay emphasis upon the phenomenon of wall vortex shedding insofar as it conduces to acoustic mode resonance in the whole chamber, within whose confines impingement of such structures generates a source of noise. It is on account of segmented flow that the thin shear layer develops and that the aforementioned vortex shedding comes to induce aero-acoustic coupling. Subsequent experimental results highlight a link in such flows between these two noise sources - they also allow one to observe a pronounced form of selectivity in the energy transfer, i.e. in longitudinal acoustic mode amplification, which has an attested effect upon all of the pressure oscillations in the chamber.     

A review of computational models for gamma oscillation dynamics: from spiking neurons to neural masses

Nonlinear Dynamics - Gamma oscillations (30–90 Hz) in the brain are known to have an evident relationship with many cognitive processes. Computational models are promising tools for...     

The study of self-sustained oscillating plane jet flow impinging upon a small cylinder

 Experimental studies of a plane jet impinging upon a small circular cylinder are conducted by hot-wire measurements. The cylinder is located on the jet centerline within the potential-core region. The jet–cylinder interactions on the instability shear layer frequency, the cylinder wake shedding frequency, and the induced self-sustained oscillation phenomenon are carefully investigated. Test data indicate that the self-sustained flow oscillation is mainly generated by the resonant effect of the flow between the jet exit and the cylinder. Its resonant frequency is found to vary linearly and exhibits jump-stage pattern as a function of the distance between the jet exit and the cylinder. The feedback mechanism and the hydrodynamic instability theorem are proposed to predict correctly the frequency jump position, wave number and the convection speed of the self-sustained oscillating flow for different jet exit velocities. Received: 15 July 1998/Accepted: 9 December 1998     

Strength characteristics of the self-sustained wave in grooved channels with different groove length

The self-sustained oscillations arising in a series of grooved channels are investigated experimentally. Pressure drop, time-averaged and time-various local pressure in the grooved channels with six kinds of groove length are measured with the differential transducer and the pressure sensor, respectively, and the flow structures are visualized using the aluminum dust method. The local pressure signal shows that the self-sustained wave appears in the first or second frequency, and the Strouhal number, based on the nature frequency of the self-sustained wave, is almost equivalent for the first or second frequency in the same channel. Meanwhile, the Strouhal number for each channel decreases monotonously with the groove length. Furthermore, it is found that increasing pressure will result in higher amplitude of the self-sustained wave, this behavior is significant for the efficient heat transfer in practical engineering.     

Measurements of balmer line radiation from self-sustained Townsend discharges in hydrogen

Summary Absolute radiation intensities of the H and H lines emitted from self-sustained Townsend discharges in hydrogen have been measured by means of interference filters and a photomultiplier tube. The radiation intensity was in all cases found to be proportional to the discharge current, i.e., the radiation has been produced in single encounter electronic excitation processes. The excitation coefficient, corrected for quenching of the radiation, has been determined absolutely forE/p=65–250 v/Torr×cm. Finally, some possible production mechanisms have been discussed.This work is part of the author's licentiatus technicae thesis submitted to the Norwegian Institute of Technology, Trondheim, Norway.     

脉动型神经元网络的联想记忆与分割

以广泛讨论的Hodgk in-Hux ley神经元节点组成脉动神经元网络,从神经系统空时模式编码理论研究网络的记忆(或模式)存储与时间分割问题。给定一个输入模式,它是几种模式的叠加,网络能够以一部分神经元同步发放的形式一个接一个地在时间域分割出每一种模式。如果输入的模式是缺损的,系统能够把它们恢复成完好的原型,即神经网络的联想记忆功能。     

Suppressing the spiking of a synchronized array of Izhikevich neurons

Nonlinear Dynamics - The aim of this research work is to investigate the synchronization and desynchronization of an array of non-identical Izhikevich neurons in a star-like configuration. Both...     

Experimental and numerical POD study of the Coanda effect used to reduce self-sustained tones

The two-dimensional flow along an inclined plate may be detached or reattached to the plate by Coanda effect. Experimentally, we explore the influence of the inclination angle and of the Reynolds number on the attachment and detachment phenomena, and on the hysteresis loop. A proper orthogonal decomposition (POD) of the flow is applied to a LES simulation resulting data. A low-dimensional dynamical model is obtained using by Galerkin projection of the Navier–Stokes equations upon the POD basis functions. We show that this model represents qualitatively the characteristics of the flow.     

Effect of parameters of the discharge circuit on the mode of energy input into the gas in a self-sustained discharge

A model is proposed for calculating the characteristics of volumetric gas discharges used in the pumping of electric-discharge lasers. The dependence of the mode of energy input into the plasma of the gas discharge on the parameters of the discharge circuit is discussed.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 2, pp. 42–46, March–April, 1976.In conclusion, the authors thank Yu. D. Korolev for useful discussions.     

Stationary and non-stationary chimeras in an ensemble of chaotic self-sustained oscillators with inertial nonlinearity

We study spatial structures arising in an ensemble of Anishchenko–Astakhov chaotic self-sustained oscillators with non-local coupling. Diagrams of the regimes realizing in this system are constructed numerically. The peculiarities of formation of chimera states appearing with decreasing the coupling strength are analyzed. A new type of the chimera state which is born from the traveling wave regime is demonstrated.

     

Influence of periodic excitation on self-sustained vibrations of one disk rotors in arbitrary length journals bearings

Interaction of forced and self-sustained vibrations of one disk rotor is described by nonlinear finite-degree-of-freedom dynamical system. The shaft of the rotor is supported by two journal bearings. The combination of the shooting technique and the continuation algorithm is used to study the rotor periodic vibrations. The Floquet multipliers are calculated to analyze periodic vibrations stability. The results of periodic motions analysis are shown on the frequency response. The quasi-periodic motions are investigated. These nonlinear vibrations coexist with the periodic forced vibrations.     

Probability of rebound and eject of sand particles in wind-blown sand movement

When incident particles impact into a sand bed in wind-blown sand movement, rebound of the incident particles and eject of the sand particles by the incident particles affect directly the development of wind sand flux. In order to obtain rebound and eject lift-off probability of the sand particles, we apply the particle-bed stochastic collision model presented in our pervious works to derive analytic solutions of velocities of the incident and impacted particles in the post-collision bed. In order to describe randomness inherent in the real particle-bed collision, we take the incident angle, the impact position and the direction of resultant action of sand particles in sand bed on the impacted sand particle as random variables, and calculate the rebound and eject velocities, angles and coefficients (ratio of rebound and eject velocity to incident velocity). Numerical results are found in accordance with current experimental results. The rebound and eject lift-off probabilities versus the incident and creeping velocities are predicted. The project was supported by the National Natural Science Foundation of China (10532040, 10601022). The English text was polished by Yunming Chen.     

Effects of internal noise on the spiking regularity of a clustered Hodgkin-Huxley neuronal network

Spiking regularity in a clustered Hodgkin–Huxley (HH) neuronal network has been studied in this letter. A stochastic HH neuronal model with channel blocks has been applied as local neuronal model. Effects of the internal channel noise on the spiking regularity are discussed by changing the membrane patch size. We find that when there is no channel blocks in potassium channels, there exist some intermediate membrane patch sizes at which the spiking regularity could reach to a higher level. Spiking regularity increases with the membrane patch size when sodium channels are not blocked. Namely, depending on different channel blocking states, internal channel noise tuned by membrane patch size could have different influence on the spiking regularity of neuronal networks.     

The role of convergence in the theory of shells

Similarly to what happens in the finite element method, the concept of convergence can be used for justifying the use of the virtual work and variational theorems in the derivation of the equations of the theory of shells.It is proved that the two-dimensional solution becomes more and more near the three-dimensional ones as the thickness tends to zero, provided the relative values of the bending and membrane stiffness coefficients are not changed when the shell becomes thinner and thinner.Such condition can be respected only if the shell is a generalized one, i.e. if the couple-stresses are not supposed to vanish.The analysis gives a upper bound to the order of magnitude of the distance between the exact and approximate solution and thus provides a powerful method for testing the efficiency and consistency of any particular theory of shells.     

液滴撞击超疏水壁面反弹及破碎行为研究

液滴撞击壁面时,壁面亲水性对液滴撞击壁面后的变化历程具有重要的影响。利用相界面追踪的复合Level Set-VOF方法对液滴撞击超疏水壁面的运动进行了研究。研究结果表明,撞击速度较小时,液滴撞壁后发生反弹;撞击速度较大时,液滴撞壁后会发生破碎现象;初始粒径的增大和表面张力的减小,有利于液滴撞壁后产生铺展破碎现象;撞击角度对撞壁后的液滴行为具有较大的影响。通过数值模拟,给出了一定条件下液滴垂直及倾斜撞击超疏水壁面反弹及破碎的临界条件。