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This study investigates the optimization of the process parameters in the development of ecofriendly brakepads from wastes nko-nko (Thais Coronata L.) seashell (NSS) reinforcement materials by central composite face-centered (CCF) design. The brakepad composites were developed by compression moulding. NSS brakepads samples were developed based on 3-levels of 3-factors: curing time Ct, curing temperature CT, and moulding pressure MP. Multivariate quadratic models, signal-to-noise ratio, and ANOVA were used for optimization. The determined optimal process parameters of the developed NSS brakepads were MP = 13MPa, CT = 165°C, and Ct = 3h. The properties of the developed NSS samples were comparable with those of 2 control samples. EDX spectroscopy showed toxic heavy metals (7-40% Sb, 6.44-12.88%Ti) presence in the control samples, unlike the NSS samples. Comparatively, the green NSS samples showed superior mechanical and tribological performance. [ABSTRACT FROM AUTHOR]

A generalized oscillator model for nonlinear vibration analysis of various mechanical systems was proposed and solved using the quasi-static cubication method. The proposed generalized oscillator model is useful for introducing and discussing the nonlinear vibration models of several oscillatory systems. To establish the accuracy of the quasi-static cubication method for the generalized oscillator model, a number of simulations were carried out for the nonlinear vibration models of common mechanical systems derived from the generalized oscillator model. The results obtained were found to be in good agreement with exact solutions and other approximate solutions found in the literature. Furthermore, the quasi-static cubication method was found to be accurate for a wide range of oscillation amplitudes. A significant feature of the quasi-static cubication method is its simplicity and accuracy; hence, it is considered an efficient technique for nonlinear vibration analysis in undergraduate and post-graduate courses on dynamics. [ABSTRACT FROM AUTHOR]