Multi-resonant piezoelectric metamaterials for broadband isolation of elastic wave transmission

This paper proposes a general method to design multi-resonant piezoelectric metamaterials. Such metamaterials contain periodically distributed piezoelectric patches bonded on the surfaces of a host structure. The patches are assumed to be shunted with digital circuits. A transfer function is designed to realize multi-resonance. The transfer function is derived only using the parameters of the patches. Consequently, it can be used to realize any type of multi-resonant metamaterial structures, like beams, plates and shells. The mechanism of generating multi-bandgaps by the transfer function is explained by analytically studying the effective bending stiffness of a multi-resonant piezo-metamaterial plate. It is shown that the transfer function induces multiple frequency ranges in which the effective bending stiffness becomes negative, consequently results in multiple bandgaps. The characteristics of these bandgaps are investigated, coupling and merging phenomena between them are observed and analyzed. Isolation effects of vibration transmission (elastic wave) in the metamaterials at multiple line frequencies or within a broad frequency band are numerically verified. The proposed multi-resonant piezoelectric metamaterials may open new opportunities in vibration mitigation of transport vehicles and underwater equipment.

Isolation effects of vehicle-induced vibration tested by integral floating method

A set of integral floating vibration isolation methods was developed in this study to remedy the lack of effective measures for over-track buildings. The effect of vibration isolation pads was investigated experimentally; the resulting field measurements were used to determine the time-frequency dynamic responses of vehicle-induced vibration and isolation effects. The characteristics of the vibration source appear to significantly affect the frequency domain distribution of vibration inside the building. When no vibration isolation measures are taken, the internal vibration of the cultural center exceeds the limit. BSW vibration isolation pads R480, R550, and R800 are effective in the frequency range of 16–80 Hz. The vibration isolation level in the Z direction is between 5.6 and 7.3 dB. After floating vibration isolation treatment, the maximum Z vibration level of the cultural center is 56.4 dB in daytime hours and 52.9 dB at night, which satisfies the relevant standard. The proposed method is shown to effectively hinder the structural vibration caused by subways on surrounding buildings.

Failure behavior of multi-state system considering functional and physical isolation effects

The multi-state system (MSS) is a system that may exhibit multiple states or performance levels. Most existing studies assumed that the transition probabilities from states to states are known. However, in practical engineering, the complex stress conditions lead to great difficulty of collecting the statistical data of state transitions. In this paper, based on physics-of-failure theory, we consider different levels of damages caused by failure mechanisms (FMs) are the main reasons to components’ multiple states. Besides, the physical isolation (PI) effect on degradations of FMs is also studied, which is neglected in the existing studies about the MSS with functional dependence groups. Decision-diagram based methods are used for modeling the failure behavior of the MSS. An automatic collision avoidance system is analyzed for illustrating the proposed modeling and analyzing methods. The results show that comparing to the results without the consideration of PI effect, the probabilities of different states with PI effect of multi-state components and system may decrease or increase, which depends on the actual PI effects to the stress conditions.

Orthogonally Integrated Hybrid Antenna for Intelligent Transportation Systems

The aim of this paper is to design an orthogonally integrated hybrid antenna to address 5G/Wi-Fi/C-V2X communication simultaneously in one device. The proposed antenna consists of three planar monopoles and a defected ground plane with a dimension of 55x30x1.2mm3. High Frequency Structure Simulator (HFSS) is employed to design the proposed antenna, which resonates at three distinct frequencies 2.45 GHz (Wi-Fi), 3.5 GHz (5G), and 5.9 GHz. Further, the prototype antenna is fabricated and experimentally validated in comparing with simulation results. The excellent agreement among the simulation and measured results shows that the designed antenna operates simultaneously at 5G/Wi-Fi/C-V2X frequency bands and the isolation effects between the elements is less than 15dB.

Le abitudini al tempo del Coronavirus

Introduction: The COVID-19 pandemic that hit the humankind in December 2019, is steering quick and drastic changes to our habits. The goal of our research is the analysis of the emotional, healthy and physiological effects of this radical routine disruption, in a sample of 3000 Italian people. Methods: We made use of a 5-days flash survey in an anonymous way, available from April the 5th until April the 10th. Results: As expected, results show a healthy decrease, after just one month of lockdown, at several stages: emotional, relational, nutritional and physical. Conclusions: This quarantine period can be considered as an extreme example of immediate sedentary and isolation effects on people. Home habits such as basic physical activity, circadian rhythm routine, proper diet, and correct information consumption can be useful to increase our resilience in difficult times like the current one, but also in our next future.