Spectral Amplification Factor Research Articles

Two and Half Dimensional Simulation of Ridge Effects on the Ground Motion Characteristics

— Seismic responses of weathered and non-weathered ridge models were simulated to study the ridge effects on the ground motion characteristics. The range of ridge slope from 19.98° to 45° was considered to produce a possible set of generalized results. 2.5-D modeling based on parsimonious staggered grid approximation of elastodynamic wave equations was adopted in simulations. Computed results reveal an increase of amplitude of incoming waves with both elevation and the slope of the ridge. Further, the characteristics of surface waves are highly ridge slope dependent. The analysis of responses of weathered and non-weathered ridge models reveals that ridge has caused a strong generation of surface waves near its top. The surface waves are not dominating on the top of the ridge but at some lower elevation. The increase of weathering of ridge further intensified the ridge effect. Analysis in frequency domain, based on spectral ratio method, does not indicate a ny pattern in the spectral amplification factor and is very much sensitive to slope, source focal mechanism and location. However, on an average there is a continuous decrease of amplification with slope in the vertical component and increase in the transverse component, and it is increasing in the radial component up to slope =38.0° and thereafter decreasing.

Relaxation rate and stochastic resonance of a single-mode nonlinear optical syst em

The variational method is applied to a single-mode stochastic nonlinear optical system and the dependence of its relaxation rate and spectral amplification factor on the noise intensity based on the linear response theory is investigated.The investigation shows that when the biased input is vanishing,the relaxation rate has different dependence in monostable and multistable cases.The investigation also shows that the stochastic resonance occurs in one-dimensional symmetric monostable potential,and the possible condition for it is pointed out.

On the influence of noise on the critical and oscillatory behavior of a predator–prey model: coherent stochastic resonance at the proper frequency of the system

Noise-induced changes in the critical and oscillatory behavior of a prey–predator system are studied using power spectrum density and spectral amplification factor (SAF) analysis. In the absence of external noise, the population densities exhibit three kinds of asymptotic behavior, namely: absorbing state, fixed point (FP) and an oscillatory regime with a well defined proper (natural) frequency. The addition of noise destabilizes the FP phase inducing a transition to a new OR. Surprisingly, it is found that when a periodic signal is added to the control parameter, the system responds robustly, without relevant changes in its behavior. Nevertheless, the coherent stochastic resonance phenomenon is found only at the proper frequency. Also, a method based on SAF allows us to locate very accurately the transition points between the different regimes.