Novel negative mass density resonant metamaterial unit cell

2015 ◽  
Vol 379 (1-2) ◽  
pp. 33-36 ◽  
Author(s):  
Norbert Cselyuszka ◽  
Milan Sečujski ◽  
Vesna Crnojević-Bengin
Keyword(s):  
Mass Density ◽  
Unit Cell ◽  
Negative Mass

An elastic metamaterial with simultaneously negative mass density and bulk modulus

2011 ◽  
Vol 98 (25) ◽  
pp. 251907 ◽  
Author(s):  
X. N. Liu ◽  
G. K. Hu ◽  
G. L. Huang ◽  
C. T. Sun
Keyword(s):  
Bulk Modulus ◽  
Mass Density ◽  
Negative Mass

A design of active elastic metamaterials with negative mass density and tunable bulk modulus

2018 ◽  
Vol 230 (3) ◽  
pp. 1003-1008 ◽  
Author(s):  
Sheng Sang ◽  
Anwer Mhannawee ◽  
Ziping Wang
Keyword(s):  
Bulk Modulus ◽  
Mass Density ◽  
Negative Mass ◽  
Elastic Metamaterials

Silicon Pillars as Resonators in an Acoustical Metamaterial

2014 ◽  
Author(s):  
Bernard Bonello ◽  
Rémi Marchal ◽  
Rayisa Moiseyenko ◽  
Yan Pennec ◽  
Bahram Djafari-Rouhani ◽  
...  
Keyword(s):  
Thin Plate ◽  
Lamb Waves ◽  
Mass Density ◽  
Resonant Mode ◽  
Ultrasonic Technique ◽  
Frequency Range ◽  
Negative Mass ◽  
Laser Ultrasonic ◽  
Compressional Mode ◽  
Bending Modes

We have investigated the propagation of Lamb waves in structures made of either an isolated resonant pillar or a set of pillars arranged in a line on a thin plate. The resonators as well as the plate are made of silicon. FEM computations show that two bending modes and one compressional mode are unambiguously identified in the frequency range of interest (0–10 MHz). We used a laser ultrasonic technique to map both the amplitude and the phase of the normal displacements on top of the pillars and at the surface of the sample. When the frequency is tuned to a resonant mode, either compressional or bending, the pillars vibrate 180° out-of-phase with respect to the Lamb waves, resulting in a negative modulus or negative mass density respectively.

Dynamic Behavior of a Metamaterial Beam With Embedded Membrane-Mass Structures

2017 ◽  
Vol 84 (12) ◽  
Author(s):  
Jung-San Chen ◽  
I-Ting Chien
Keyword(s):  
Mass Density ◽  
Elastic Membrane ◽  
Circular Membrane ◽  
Negative Mass ◽  
Propagation Behavior ◽  
Resonant Behavior ◽  
Structural Periodicity ◽  
Theoretical Results ◽  
Base Structure ◽  
Good Agreement

Flexural propagation behavior of a metamaterial beam with circular membrane-mass structures is presented. Each cell is comprised of a base structure containing circular cavities filled by an elastic membrane with a centrally loaded mass. Numerical results show that there exist two kinds of bandgaps in such a system. One is called Bragg bandgap caused by structural periodicity; the other is called locally resonant (LR) bandgap caused by the resonant behavior of substructures. By altering the properties of the membrane-mass structure, the location of the resonant-type bandgap can be easily tuned. An analytical model is proposed to predict the lowest bandgap location. A good agreement is seen between the theoretical results and finite element (FE) results. Frequencies with negative mass density lie in the resonant-type bandgap.

Multi-cavity coupling acoustic metamaterials with low-frequency broad band gaps based on negative mass density

2016 ◽  
Vol 30 (23) ◽  
pp. 1650317
Author(s):  
Chuanhui Yang ◽  
Jiu Hui Wu ◽  
Songhua Cao ◽  
Li Jing
Keyword(s):  
Band Gap ◽  
Mass Density ◽  
Resonant Cavity ◽  
Broad Band ◽  
Low Frequency ◽  
Band Gaps ◽  
Acoustic Metamaterials ◽  
Negative Mass ◽  
Closed Cavity ◽  
Cavity Coupling

This paper studies a novel kind of low-frequency broadband acoustic metamaterials with small size based on the mechanisms of negative mass density and multi-cavity coupling. The structure consists of a closed resonant cavity and an open resonant cavity, which can be equivalent to a homogeneous medium with effective negative mass density in a certain frequency range by using the parameter inversion method. The negative mass density makes the anti-resonance area increased, which results in broadened band gaps greatly. Owing to the multi-cavity coupling mechanism, the local resonances of the lower frequency mainly occur in the closed cavity, while the local resonances of the higher frequency mainly in the open cavity. Upon the interaction between the negative mass density and the multi-cavity coupling, there exists two broad band gaps in the range of 0–1800 Hz, i.e. the first-order band gap from 195 Hz to 660 Hz with the bandwidth of 465 Hz and the second-order band gap from 1157 Hz to 1663 Hz with the bandwidth of 506 Hz. The acoustic metamaterials with small size presented in this paper could provide a new approach to reduce the low-frequency broadband noises.

scholarly journals On the ignition of small thermonuclear assemblies

2018 ◽  
Vol 36 (2) ◽  
pp. 232-235 ◽  
Author(s):  
Friedwardt Winterberg
Keyword(s):  
Mass Density ◽  
Particle Beam ◽  
Natural Uranium ◽  
Inertial Confinement ◽  
Theory Of Relativity ◽  
General Theory Of Relativity ◽  
Positive Mass ◽  
Negative Mass ◽  
Novel Concept ◽  
Thermonuclear Target

AbstractA novel way for igniting small thermonuclear assemblies by inertial confinement is proposed, by replacing the positive mass of an imploding dense star with the negative mass in the reference frame of a rapidly rotating thermonuclear target. According to Einstein's general theory of relativity, this negative mass can be orders of magnitude larger than the positive mass density of a neutron star. This novel concept also replaces the Plutonium 239 “spark plugs” of large thermonuclear devices with a shell of natural uranium surrounding a target composed of DT or Li6D.Unlike the ignition by a laser – or particle beam – induced spherical implosion, this configuration, similar to that of an imploding star is not only Rayleigh–Taylor stable, but it can be realized with intense relativistic electron or ion beams, with an energy of about 100 MJ, having a short range in the dense high Z natural uranium shell.

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