Controlling dynamical behavior of drive-response system through linear augmentation

Unidirectionally coupled chaotic systems give rise to driver induced bistability in response system under certain parameters setting. Such a system is studied here with augmented dynamics. A linear augmentation provides a controlled dynamical behavior of response system in two different ways: augmented drive system brings the stabilization of the steady state where as augmented response system is able to control the bistability. We present a detailed analysis of Lorenz–Rössler system with linear augmentation for controlled dynamical behavior.     

Relative stabilities and the spectral signatures of stacked and hydrogen-bonded dimers of serotonin

The O–H???N hydrogen-bonded dimer of serotonin is shown to be more stable than the stacked dimer in its ground electronic state, by using the Møller–Plesset second-order perturbation theory (MP2) and the 6–31g^** basis set. The vertical excitation energy for the lowest π?→?π* transition for the monomer as well as the dimer is predicted by time-dependent density functional theory. The experimentally observed red shift of excitation wavelength on oligomerisation is explained in terms of the change in the HOMO–LUMO energy gap due to complex formation. The impact of dimer formation on the proton magnetic resonance spectrum of serotonin monomer is also examined.     

Experimental and theoretical investigation of superharmonic resonances in a planar oscillator under angular base excitation

This paper explores the complicated dynamic behavior of a mechanical oscillator under harmonic angular excitation. The motivation behind this work comes from the nature of the actuation produced by high-performance dither motors. A lumped-mass model, which captures the primary and the 1 : 2 superharmonic resonances observed on an analogous experimental test setup, is put forward. The equations of motion governing the dynamics of the model are derived and are found to comprise both parametric and direct forcing terms. The governing equations are solved analytically using the generalized harmonic balance method and numerical integration. The method of multiple scales is utilized to obtain closed-form expressions that relate the system parameters to the oscillation amplitudes in the vicinity of the direct and the 1 : 2 superharmonic resonances. It is found that eccentricity plays a vital role in the occurrence of the resonances. Besides, the relationship between the excitation amplitudes and the resulting oscillations for the direct and the superharmonic resonances are dissimilar. A few salient differences between classical (rectilinear) and angular base excitation mechanisms are pointed out.