Qi Liu

We investigate stochastic resonance (SR) in an ensemble of coupled overdamped bistable oscillators driven by colored noise. The network incorporates the weighted contributions of both pairwise coupling and 2-simplex coupling. Our findings reveal a suppression effect of colored noise on SR in higher-order networks, namely, that increasing the noise correlation time monotonically reduces the resonance peak. Furthermore, for a fixed noise correlation time, increasing the weight of higher-order interactions decreases the peak amplitude. Meanwhile, as both the noise correlation time and the weight of higher-order interactions increase, the optimal noise intensity shifts progressively to larger values. To clarify the underlying mechanism, we establish a close connection between SR and the four-stage variation in network synchronization level. Specifically, the effects of higher-order coupling and colored noise on SR can be understood through their impact on network synchronization, which exhibits distinct extrema. Our analysis reveals that higher-order interactions primarily promote the spatial propagation of suppression effects due to colored noise.

Topological properties play a crucial role in the collective dynamics of coupled oscillators. In this Letter, we reveal a topology-induced phenomenon, including sparsity-induced stochastic resonance (SR) and coherence resonance (CR), in coupled noisy networks. The network sparsity alters the stochastic switching rates in coupled bistable systems and modulates the mean-field coherence in coupled excitable systems. The responses achieve maxima or minima at moderate sparsity (i.e., the optimal sparsity), implying the occurrence of sparsity-induced SR and CR. In particular, we discover the existence of invariant sparsity (domain) regarding sparsity-induced SR (CR). When the system size exceeds a threshold, the optimal sparsity (domain) is invariant with respect to system size, the five types of networks, and the frequency of the periodic force. By introducing a sparsity-dependent effective coupling, mean-field theory predicts sparsity-induced SR. These findings provide new insight into the collective dynamics of brain networks, especially explaining the pruning of neural connections by astrocytes.

Tilt-rotor aircraft may be subjected to long-correlated random loads in their complex flight environments, potentially inducing dynamics distinct from those based on deterministic force or idealized white-noise assumptions in existing studies. In this paper, we explore the whirl flutter of tilt-rotor aircraft subjected to nonwhite random aerodynamic moments, modeled as two-degree-of-freedom nonlinear rotor–nacelle systems with fractional Gaussian noise. Firstly, a harmonic balance method is employed to obtain the amplitude response characteristics of the deterministic rotor–nacelle systems. Subsequently, a dimensionality reduction approach based on diffusion approximation theory is proposed for the analysis of stochastic rotor–nacelle systems. To achieve a precise and efficient calculation of system responses, a memory-dependent Fokker–Planck–Kolmogorov equation method is further introduced. Finally, numerical simulations are conducted to verify the effectiveness of the proposed solution methodology. In addition, the statistical characteristics of the responses of stochastic rotor–nacelle systems are examined in detail, and the influence of system parameters on the responses is systematically studied. We discover that the second-order central moments of the system responses increase with the decrease of the Hurst index of the FGN, while they increase with the increase of the freestream-to-blade-tip velocity ratio, the rotor angular velocity, and the noise intensity. The results reveal that both structural and noise parameters have significant impacts on the dynamic stability of the systems, further threatening the safety of tilt-rotor aircraft.

A stochastic dynamic model is proposed for a Z-shaped folding wing with random excitations. The method of multiple scales is employed to derive amplitude equations. Bistable phenomenon on the deterministic system is revealed through analyses on bifurcation and basin of attraction. Under the effect of random loads, the noise-induced transition behavior is observed, and the noise-enhanced stabilization phenomenon is examined in detail. Reliability analysis is conducted using a proposed reliability index. Reliability region is presented versus different parameters including noise intensity. The results of this study can provide guidance for the design and reliability analysis of folding wings.

Flutter suppression facilitates the improvement of structural reliability to ensure the flight safety of an aircraft. In this study, we propose a novel strategy for enlarging the amplitude death (AD) regime to enhance flutter suppression in two coupled identical airfoils with structural nonlinearity. Specifically, we introduce an intermittent mixed coupling strategy, i.e., a linear combination of intermittent instantaneous coupling and intermittent time-delayed coupling between two airfoils. Numerical simulations are performed to reveal the influence mechanisms of different coupling scenarios on the dynamic behaviors of the coupled airfoil systems. The obtained results indicate that the coupled airfoil systems experience the expected AD behaviors within a certain range of the coupling strength and time-delayed parameters. The continuous mixed coupling favors the onset of AD over a larger parameter set of coupling strength than the continuous purely time-delayed coupling. Moreover, the presence of intermittent interactions can lead to a further enlargement of the AD regions, i.e., flutter suppression enhancement. Our findings support the structural design and optimization of an aircraft wing for mitigating the unwanted aeroelastic instability behaviors.