Effect of steady-state response versus excitatory/inhibitory balance on spiking synchronization in neural networks with log-normal synaptic weight distribution

Synchronization of neural activity, especially at the gamma band, contributes to perceptual functions. In several psychiatric disorders, deficits of perceptual functions are reflected in synchronization abnormalities. Plausible cause of this impairment is an alteration in the balance between excitation and inhibition (E/I balance); a disruption in the E/I balance leads to abnormal neural interactions reminiscent of pathological states. Moreover, the local lateral excitatory-excitatory synaptic connections in the cortex exhibit excitatory postsynaptic potentials (EPSPs) that follow a log-normal amplitude distribution. This long-tailed distribution is considered an important factor for the emergence of spatiotemporal neural activity. In this context, we hypothesized that manipulating the EPSP distribution under abnormal E/I balance conditions would provide insights into psychiatric disorders characterized by deficits in perceptual functions, potentially revealing the mechanisms underlying pathological neural behaviors. In this study, we evaluated the synchronization of neural activity with external periodic stimuli in spiking neural networks in cases of both E/I balance and imbalance with or without a long-tailed EPSP amplitude distribution. The results showed that external stimuli of a high frequency lead to a decrease in the degree of synchronization with an increasing ratio of excitatory to inhibitory neurons in the presence, but not in the absence, of high-amplitude EPSPs. This monotonic reduction can be interpreted as an autonomous, strong-EPSP-dependent spiking activity selectively interfering with the responses to external stimuli. This observation is consistent with pathological findings. Thus, our modeling approach has potential to improve the understanding of the steady-state response in both healthy and pathological states.

A new perturb and observe MPPT algorithm based on two steps variable voltage control

Based on the fact that the effectiveness of perturb and observe algorithm in a maximum power point tracking maximum power point tracking (MPPT) in a photovoltaic array is a tradeoff between the tracking speed during the transient response and the oscillation around the stable level during the steady state response. To have a high tracking speed, incremental step should be high, but this high incremental step increases the oscillation level around the steady level of MPPT, whereas adopting low incremental step reduces the algorithm response time but improve the response during the steady state condition. This paper presents a new perturb and observe algorithm based on two step variable control for MPPT applications. A two variable incremental step control is proposed to gain the merit of high step for guaranteeing a fast response during tracking process, and also for guaranteeing the merit of low oscillation during the steady state working condition through adopting a low step during steady state response. The effectiveness of the proposal is proved by the analysis of the simulation results via MATLAB/Simulink software, and by the comparison of the simulation results with a conventional perturb and observe MPPT algorithm.

Steady-State Response Analysis of the Incompressible Nonlocal Saturated Poroelastic Beam under a Vertical Harmonic Load

Based on the nonlocal theory and the theory of saturated porous media, the mathematical and physical model and governing equations of the steady-state response of the incompressible nonlocal saturated poroelastic beam under vertical harmonic loading are established with assumption of the movement of the liquid-phase fluid only in the axial direction of the beam and considering the nonlocal effects such as particle size, pore size, and pore dynamic stress. The dynamic response of a saturated poroelastic cantilever beam with permeability at both ends under a vertical harmonic concentrated force at the free end is studied. In the frequency domain, the analytical expressions of deflection amplification factor and equivalent couple amplification factor of liquid fluid pressure are given. The effects of nonlocal coefficient τ, mechanical parameter α, and geometric parameter β on the deflection amplification factor and equivalent couple amplification factor at the midpoint of the nonlocal saturated poroelastic cantilever beam are studied. The results show that the steady-state vibration of the incompressible nonlocal saturated poroelastic cantilever beam has resonance. When the nonlocal effect is considered, the deflection amplification factor and the equivalent couple amplification factor are larger, so the influence of the nonlocal effect on the steady-state response of the beam should not be ignored. The geometric parameter β has significant effect on the peak positions of the curves of the deflection amplification factor and the equivalent couple amplification factor varying with frequency.

Transient Response of a Simulated Aeroengine with a Fusing Structure during a Fan-Blade Out Event

A fan-blade out (FBO) event may cause complex vibrations in an aeroengine. A fusing structure protects the structural integrity of the whole aeroengine after an extreme accident, such as a blade-loss event. In this paper, we investigate not only the transient and steady responses of a simulated aeroengine model with a fusing structure after an FBO event but also the changes made to the model because of the fusing structure. Our simulated model of an aeroengine includes two rotors, bearings, and a casing. The results for the dynamic response of the simulated model show that the fusing structure can reduce the steady-state response and the impact load on the support bearings in the rotor system. The rubbing impact between the blades and casing was accounted for. A fast method for calculating the response of fused structures was developed, which may be useful when designing the stiffness of the fusing structure.