Vibrational resonance in globally coupled bistable systems under the noise background

Effects of system size,coupling strength,and noise on vibrational resonance(VR)of globally coupled bistable systems are investigated.The power spectral amplifications obtained by the three methods all show that the VR exists over a wide range of parameter values.The increase in system size induces and enhances the VR,while the increase in noise intensity suppresses and eventually eliminates the VR.Both the stochastic resonance and the system size resonance can coexist with the VR in different parameter regions.This research has potential applications to the weak signal detection process in stochastic multi-body systems.

Mantis Shrimp-Inspired Underwater Striking Device Generates Cavitation

Different from direct impact damage exerted by limbs of most organisms,mantis shrimps’appendages can carry out ultra-fast,powerful underwater strikes with cavitation superimposed damage to harvest hard-shelled prey.The power amplification systems and cavitation generation of mantis shrimp have attracted vast attention of researchers.Much effort has been paid to developing mantis shrimp-inspired striking robots;however,none of them are capable of generating cavitation during impacting hard objects yet.In this paper,an underwater striking robot named Shrimpbot was developed to reproduce the cavitation phenomenon when striking hard objects.Shrimpbot incorporates a Latch-Mediated Spring Actuation(LaMSA)to slowly store energy and release it instantaneously.A Diamond-Shaped Four-bar Linkage(DSFL)stretches springs to more effectively store elastic energy by reducing the maximum torque requirement of the motor.This design promised an average power amplification of over 30 times of the motor.Shape optimization and hydrophobic coating on the hammerhead and hand of Shrimpbot helped to reduce the water drag.The accomplished Shrimpbot reached an impact speed of over 12 m/s,at an acceleration of 2×10^(3) m/s^(2),an impact force of more than 1200 N in water,very close to the performance of mantis shrimp.More importantly,cavitation bubbles accompanied with the impacts were observed for the first time in mantis shrimp-inspired robots.Shrimpbot ingeniously employs only one motor to accomplish the striking automatically and repeatedly for practical purposes.Shrimpbot mimics the cavitation generation skills of mantis shrimp,which could facilitate the understanding of its mechanical principles and fluid dynamics of ultra-fast power-amplified systems of mantis shrimp and even those energy storage mechanisms of jumping robots or exoskeleton robots.