Effects on the bifurcation and chaos in forced Duffing oscillator due to nonlinear damping

In this communication, the two-well Duffing oscillator with non-linear damping term proportional to the power of velocity is considered. We mainly focus our attention on how the damping exponent affects the global dynamical behaviour of the oscillator. In particular, we obtain analytically the threshold condition for the occurrence of homoclinic bifurcation using Melnikov technique and compare the results with the computational results. We also identify the major route to chaos and the regions of the 2D parameter space (consists of external forcing amplitude and damping coefficient) corresponding to the various types of asymptotic dynamics under linear (viscous or friction like) and nonlinear (drag like) damping. We also attempt to analyze how the basins of attraction patterns change with the introduction of nonlinear damping. We also present our analysis for the physically less-interesting cases where damping is proportional to the 3rd and 4th power of velocity for the sake of generalizing our findings and establishing firm conclusion.     

Design and Development of Ultrafast Sinapic Acid Sensor Based on Electrochemically Nanotuned Gold Nanoparticles and Solvothermally Reduced Graphene Oxide

We report for the first time sinapic acid (SA) sensing based on nanocomposite comprising electrochemically tuned gold nanoparticles (EAuNPs) and solvothermally reduced graphene oxide (rGO). The synthesized EAuNPs, rGO, and EAuNPs‐rGO nanocomposite were characterized using X‐ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), particle size analysis, and Raman spectroscopy. A proof‐of‐concept electrochemical sensor for SA was developed based on synthesized EAuNPs‐rGO nanocomposite, which was characterized by electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The developed sensor detected SA with a linear dynamic range (LDR) between 20 μM and 200 μM and detection limit (DL) of 33.43 (±0.21) nM (RSD<3.32 %). To show the useful purpose of the sensor probe in clinical applications, SA was detected in human urine samples, which showed the percentage recovery between 82.6 % and 92.8 %. Interferences due to various molecules such as L‐cystine, glycine, alanine, serum albumin, uric acid, citric acid, ascorbic acid, and urea were tested. Long‐term stability of the sensor probe was examined, which was found to be stable up to 6 weeks. The sensor fabricated using EAuNPs‐rGO nanocomposite has many attractive features such as; simplicity, rapidity, and label‐free detection; hence, it could be a method of choice for SA detection in various matrices.