Analysis of vibrational resonance in an oscillator with exponential mass variation

This study investigated vibrational resonance (VR) in a Duffing-type oscillator with position-dependent mass (PDM) distribution defined by spatially varying exponential function. The role of two PDM parameters, the fixed rest mass and nonlinear strength on observed resonances was investigated from the analytical and numerical computation of response amplitude, which is a measure of the amplification of a low-frequency (LF) signal through the introduction and modulation of a high-frequency (HF) signal in a weakly driven nonlinear system. The method of direct separation of motion was used to analytically compute the response amplitude, while the numerically computed response amplitude was obtained from the Fourier spectrum of the output signal. Single resonance peaks with good agreement between the numerically and the analytically computed responses were observed for the traditional HF-induced VR and the PDM-induced resonances. The results demonstrated that spatial mass perturbation can play the roles of HF signals typically used in traditional VR setups. The results of this investigation corroborate earlier reports that stated PDM parameters can complement the HF signal to control the observed resonance peaks. However, the exponentially varying PDM parameters did not initiate double or multiple resonances as reported for other mass distributions such as the regular mass function and the doubly-singular mass function. This study communicates that the nature of the PDM distribution actually determines the possibility of generating new peaks from observed resonances

Physico-Chemical Characterization Of Water Samples At Egbin Thermal Station In Ijede And Its Environs In Lagos State Of Nigeria.

With the view to determining the effect of industrial effluents on the water quality of the river at Ijede in Ikorodu, Lagos state of Nigeria as a result of the panicking situation within the community, the physicochemical parameters which include PH, Turbidity, Dissolved Oxygen, Salinity and Electrical conductivity were measured to ascertain the level of pollution in the river and the Environment. The result  shows  that the pollutions of this river, if any, were not really from the effluent coming out of the Plant, but attributed to other sources since the effluents from the Plant were well managed and the physico-chemical parameters are in good agreement with World Health Organization guidelines before it is discharged into the main river. It is therefore recommended that the control on the effluents management should be controlled and enforced by the Environmentalists to protect the activities of the residents at Egbin in Ijede and its environs. Key words:         Physico-chemical, Pollution, Discharged-water, WHO

Vibrational resonance of ammonia molecule with doubly singular position-dependent mass

Abstract: We examine vibrational resonance (VR) in a position-dependent mass (PDM) oscillator with doubly singular mass distribution function describing the vibrational inversion mode of NH3 molecule. The impacts of the PDM parameters (m, a, η) on VR were studied by computing the response amplitudes as functions of the amplitude of high-frequency component of the dual-frequency driving forces and the PDM parameters. We show for the first time that, beside the significant roles played by the parameters of the variable mass in inducing and controlling resonances similar to the forcing parameters, the variable mass parameters impact on the resonance characteristics by leading the system from single resonance into double resonance

Acoustic vibrational resonance in a Rayleigh-Plesset bubble oscillator

The phenomenon of vibrational resonance (VR) has been investigated in a Rayleigh-Plesset oscillator for a gas bubble oscillating in an incompressible liquid while driven by a dual-frequency force consisting of high-frequency, amplitude-modulated, weak, acoustic waves. The complex equation of the Rayleigh-Plesset bubble oscillator model was expressed as the dynamics of a classical particle in a potential well of the Li´enard type, thus allowing us to use both numerical and analytic approaches to investigate the occurrence of VR. We provide clear evidence that an acoustically-driven bubble oscillates in a time-dependent single or double- well potential whose properties are determined by the density of the liquid and its surface tension. We show both theoretically and numerically that, besides the VR effect facilitated by the variation of the parameters on which the high-frequency depends, amplitude modulation, the properties of the liquid in which the gas bubble oscillates contribute significantly to the occurrence of VR. In addition, we discuss the observation of multiple resonances and their origin for the double-well case, as well as their connection to the low frequency, weak, acoustic force field