Time evolution of the probability density is investigated for initially quiescent dynamical systems exposed suddenly to random excitations. A variety of dynamical systems is considered, including the usual linear oscillator, and nonlinear oscillators of hardening spring, of softening spring, and of the van del Pol type. The random excitations are assumed to be stationary stochastic processes, s...

An analytical method is proposed to get the amplitude-frequency and the phase-frequency characteristics of free/forced oscillators with nonlinear restoring force. The nonlinear restoring force is expressed as a spring with varying stiffness that depends on the vibration amplitude. That is, for stationary vibration, the restoring force linearly depends on the displacement, but the stiffness of t...

In human and animal running spring-like leg behavior is found. In a spring-mass model, running proves to be self-stable in terms of external perturbations or variations in leg properties (e.g. landing angle). However, biological limbs are not made of springs but, rather, consist of segments where springlike behavior can be localized at joint level. Here, we use a two-segment leg model to invest...

malian animals, i.e. that of a cat. It was also influenced by the spring-mass model representation [2]. Compliant prismatic legs show an intrinsic robustness for their angle of attack [2], they have a stability region. If the leg design is changed into a two segmented leg with a specific linear torsional spring, the leg stiffness kleg becomes nonlinear (Fig. 2(b) blue line), similar to that of ...

The analysis of smart spring vibration isolation system is analyzed through MATLAB simulation. The results show suppressing dominant vibration mode of platform. In the paper controllers developed for the smart spring are linear and nonlinear. This paper deals with MIMO system analysis of low frequency dominant modes, which are critical, examined first by linear controller techniques and then wi...

This work is conducted to obtain mechanical properties of microtubule. For this aim, interaction energy in alpha-beta, beta-alpha, alpha-alpha, and beta-beta dimers was calculated using the molecular dynamic simulation. Force-distance diagrams for these dimers were obtained using the relation between potential energy and force. Afterwards, instead of each tubulin, one sphere with 55 KDa weight ...

Classical linear wavelet representations of images have the drawback that they are not well-suited to represent edge information. To overcome this problem, nonlinear multiresolution decompositions are being designed that can take into account the characteristics of the input signal/image. In our previous work [1, 2] we have introduced an adaptive lifting framework, that does not require bookkee...

In this work, a four-dimensional lattice spring model is developed for studying the mechanical responses of solids. Our results indicate that the Poisson's ratio limitation of the classical lattice spring model defined in three-dimensional space can be released by introducing an extra fourth-dimensional interaction. The fourth-dimensional lattice spring model adopts central interactions only, a...

We report the capacitive spring softening effect observed in single-walled carbon nanotube (SWNT) nanoelectromechanical (NEM) resonators. The nanotube resonators adopt a dual-gate configuration with both bottom-gate and end-gate capable of tuning the resonance frequency through capacitive coupling. Interestingly, downward resonance frequency shifting is observed with increasing end-gate voltage...