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We examine the existence of multiple vibrational resonance (VR) and antiresonance in two coupled overdamped anharmonic oscillators where each one is individually driven by a monochromatic sinusoidal signal with widely separated frequencies ( $$\Omega \gg \omega $$ ). In contemporary VR, superposed periodic waves are adopted to infer resonance, but herein we employ non-superposed periodic waves to acquire the elevated response. We study two coupling schemes namely, unidirectional and bidirectional, to substantiate the occurrence of multiple VR and antiresonance. Such occurrences have been shown and the results were ascertained with supportive numerical and experimental outcomes. We also illustrate the effect of coupling strength on the observed phenomenon.

This paper investigates the dynamics of four-dimensional autonomous oscillator with antiparallel diodes. A rare phenomenon of volume-expanding phase space is observed from the proposed model, and the only equilibrium point at the origin is found to be a repeller. Systems of this kind pave the way for the better understanding of repellers. In addition, the oscillator possesses extremely rich dynamical behaviors, including 2-tori, 3-tori (triple tori), limit cycles, chaos and hyperchaos. These dynamical behaviors are characterized with the help of the Lyapunov spectrum, bifurcation diagram, recurrence analysis, Poincare surface of section, 0–1 test etc., Period doubling and torus breakdown to chaos are the predominant routes observed in the system for different parametric choices. The results of the real-time circuit are quite compatible with the numerical predictions.

We wish to report the occurrence of vibrational resonance in certain discrete systems like sine square map and sine circle map, in a unique fashion, comprising of multiple resonant peaks which pave the way for enrichment. As the systems of our choice are capable of exhibiting vibrational resonance behaviour unlike the earlier reports, they are taken for investigation and the necessary numerical and analytical results are presented. Further, we study the effect of external forcing on various attractors of these systems with appropriate bifurcation and Lyapunov exponent diagrams.

Tannery effluent was collected from Common Effluent Treatment Plant, Dindigul, Tamil Nadu and used for analysis for physico-chemical, heavy metals and biological properties. Soil samples were collected from the field and Aspergillus sp. and Pseudomonas sp. were isolated and pure cultured. The pH of the tannery waste water was around 8.50 and electrical conductivity was 2.89 dS/m indicating the alkalinity of the effluent. Total dissolved solids(TSS) was found to be 1460 mg/L and BOD showed 2346 mg/l. The AAS reading of chromium in the effluent indicated 205 mg/L which means the effluent can not be released into the environment without proper treatment. The metal tolerance capacity of the organisms was tested at different concentrations of chromium salts dissolved in tannery effluent viz., 25 to 200 ppm with 25 ppm of increment for each of the treatment. Pseudomonas sp.tested tolerated upto 100 ppm,while the Aspergillus sp could resist upto 75 ppm of chromium concentration. It was also found that the Pseudomonas sp. had potentially removed chromium from aqueous spiked solution with effluent, hence it could be a good biosorbent for the removal of chromium from tannery effluent contaminated agricultural fields.

This paper addresses the problem of sharing common nonlinearity among nonautonomous and autonomous oscillators. By choosing a suitable common nonlinear element with the driving point characteristics capable of bringing out chaotic motion in a combined system, we obtain identical chaotic states. The dynamics of the coupled system is explored through numerical and experimental studies. Employing the concept of common nonlinearity, a simple chaotic communication system is modeled and its performance is verified through Multisim simulation.