An ultrathin acoustic metasurface composed of an anisotropic three-component resonator

2022 ◽  
Author(s):  
Zhihong Xu ◽  
pan li ◽  
Meiyu Liu ◽  
QiuJiao Du ◽  
Yifan Guo ◽  
...  
Keyword(s):  
Phase Change ◽  
Mass Density ◽  
Phase Delay ◽  
Resonant Frequencies ◽  
Material Parameters ◽  
Anisotropic Resonator ◽  
Good Comparison ◽  
Homogenous Medium ◽  
Large Phase ◽  
Direction Of Polarization

Abstract An ultrathin acoustic metasurface consisting of an anisotropic three-component resonator is proposed. The resonator can induce nondegenerate dipole resonances at the same resonant frequencies. A large phase delay can be obtained based on the resonance, which can be modulated by the direction of polarization. The anisotropic resonator can be regarded as an effective homogenous medium with an anisotropic mass density, and the phase change can also be attributed to the change of the effective material parameters. A good comparison between the results for the metasurface and its effective slab is obtained.

scholarly journals On the Jump Conditions for Shock Waves in Condensed Materials

2021 ◽  
Author(s):  
R K Anand
Keyword(s):  
Stainless Steel ◽  
Mach Number ◽  
Shock Front ◽  
Particle Velocity ◽  
Mass Density ◽  
Jump Conditions ◽  
Condensed Material ◽  
Material Parameters ◽  
Stainless Steel 304 ◽  
Condensed Materials

Abstract In this article, we have proposed Rankine–Hugoniot (RH) boundary conditions at the normal shock-front which is passing through the condensed material. These RH conditions are quite general, and their convenient forms for the particle velocity, mass density, pressure and temperature have been presented in terms of the upstream Mach number, and the material parameters for the weak and the strong shocks, respectively. Finally, the effects on the mechanical quantities of the shock compressed materials e.g. titanium Ti6Al4V, stainless steel 304, aluminum 6061-T6, etc. have been discussed.

Observation of Large Photoacoustic Signal Phase Changes during a Diffusion Process

2005 ◽  
Vol 59 (11) ◽  
pp. 1420-1426
Author(s):  
Stanley J. Bajic ◽  
Roger W. Jones ◽  
John F. McClelland
Keyword(s):  
Phase Modulation ◽  
Heterogeneous Systems ◽  
Photoacoustic Signal ◽  
Phase Changes ◽  
Phase Delay ◽  
Homogeneous Sample ◽  
Heterogeneous Samples ◽  
Large Phase ◽  
Teflon Film

The phase of the photoacoustic signal is known to be a sensitive and accurate means to investigate, both qualitatively and quantitatively, static multilayer heterogeneous systems. According to theory, the maximum phase delay for a very weakly absorbing homogeneous sample should be within 45° of a very strongly absorbing sample, while for heterogeneous samples the phase delay can be greater than 45°. Here we report the observation of photoacoustic phase delays greater than 350° by extending the use of step-scan phase modulation photoacoustic spectroscopy to study a non-repetitive dynamic system in situ, in real time. These large phase delays correspond to sampling several thermal diffusion lengths into the sample. The model system used in this study consisted of a hydrocarbon grease diffusing through a porous Teflon film. The progress of the diffusion was tracked by monitoring both the photoacoustic signal magnitude and the phase of the hydrocarbon grease after isolation from the Teflon film signal contributions at two different phase modulation frequencies.

scholarly journals Tunable Two-Layer Dual-Band Metamaterial with Negative Modulus

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3229
Author(s):  
Limei Hao ◽  
Meiling Men ◽  
Yazhe Wang ◽  
Jiayu Ji ◽  
Xiaole Yan ◽  
...  
Keyword(s):  
Mass Density ◽  
Hollow Spheres ◽  
Volume Ratio ◽  
Blue Shift ◽  
Relative Volume ◽  
Hole Diameter ◽  
Dual Band ◽  
Resonant Frequencies ◽  
In Series ◽  
Simulation Results

A tunable dual-band acoustic metamaterial (AM) with nested two-layer split hollow spheres (TLSHSs) is presented here, which was achieved by adjusting the hole diameter and the ratio of the two layers’ volumes. This work comprises theoretical and numerical studies. Based on sound-force analogy (SFA), TLSHSs can be considered equivalent to a model of two spring oscillators in series. The equations of two resonant frequencies were derived, which precisely provided the relation between two resonant frequencies and the hole diameter as well as the ratio of the two layers’ volumes. The analytical formulas and simulation results by the finite element method (FEM) showed that there were two resonant frequencies for the TLSHSs, and their dynamic modulus became negative near the resonant frequencies. As the the diameter of two holes increased, both of the resonant frequencies underwent a blue shift. As the relative volume ratio increased, both of the resonant frequencies underwent a red shift. The calculation and simulation results were in good agreement. This kind of precisely controllable dual-band AM with negative modulus can easily be coupled to other structures with negative mass density, thereby achieving a double-negative AM in an expected frequency range.

scholarly journals Multi-physics adjoint modeling of Earth structure: combining gravimetric, seismic, and geodynamic inversions

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Georg S. Reuber ◽  
Frederik J. Simons
Keyword(s):  
Acoustic Wave ◽  
Mass Density ◽  
Resolving Power ◽  
Surface Velocity ◽  
Seismic Displacement ◽  
Material Parameters ◽  
Gradient Based ◽  
Geophysical Imaging ◽  
The Cost ◽  
Inversion Techniques

AbstractWe discuss the resolving power of three geophysical imaging and inversion techniques, and their combination, for the reconstruction of material parameters in the Earth’s subsurface. The governing equations are those of Newton and Poisson for gravitational problems, the acoustic wave equation under Hookean elasticity for seismology, and the geodynamics equations of Stokes for incompressible steady-state flow in the mantle. The observables are the gravitational potential, the seismic displacement, and the surface velocity, all measured at the surface. The inversion parameters of interest are the mass density, the acoustic wave speed, and the viscosity. These systems of partial differential equations and their adjoints were implemented in a single Python code using the finite-element library FeNICS. To investigate the shape of the cost functions, we present a grid search in the parameter space for three end-member geological settings: a falling block, a subduction zone, and a mantle plume. The performance of a gradient-based inversion for each single observable separately, and in combination, is presented. We furthermore investigate the performance of a shape-optimizing inverse method, when the material is known, and an inversion that inverts for the material parameters of an anomaly with known shape.

Analysis on Application Prospect of Shape-Stabilized Phase Change Materials in Asphalt Pavement

2013 ◽  
Vol 357-360 ◽  
pp. 1277-1281 ◽  
Author(s):  
Li Hong He ◽  
Jing Ruo Li ◽  
Hong Zhou Zhu
Keyword(s):  
Thermal Stability ◽  
Phase Change ◽  
Phase Change Materials ◽  
Asphalt Pavement ◽  
Driving Safety ◽  
Maintenance Cost ◽  
Chemical Compatibility ◽  
Good Thermal Stability ◽  
Large Phase ◽  
And Control

Blends of asphalt and shape-stabilized phase change materials (SSPCM) were prepared by physical blending. Heat storage and thermal stability of asphalt-SSPCM blends were investigated by DSC and TG, chemical compatibility of asphalt-SSPCM blends was characterized by FT-IR, and the application feasibility of SSPCM in asphalt pavement was explored. The results show that asphalt-SSPCM blends have large phase change enthalpy, good thermal stability and chemical compatibility. Based on phase change theoretical analysis and numerical calculation, SSPCM applied in asphalt pavement can actively regulate and control pavement temperature using solar energy conversion or storage, lighten the asphalt pavement diseases related temperatures, enhance the performance of and prolong the service life of asphalt pavement, lower repair and maintenance cost, and enhance driving safety. At the same time, it can also saving energy sources and protect environment. Therefore, SSPCM have broad application foregrounds in asphalt pavement.

Crystallization Characteristics of Ge-Sb Phase Change Materials

2009 ◽  
Vol 1160 ◽  
Author(s):  
Simone Raoux ◽  
Cyril Cabral ◽  
Lia Krusin-Elbaum ◽  
Jean L. Jordan-Sweet ◽  
Martin Salinga ◽  
...  
Keyword(s):  
Phase Change ◽  
Phase Change Materials ◽  
Mass Density ◽  
Large Change ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Time Resolved ◽  
X Ray ◽  
Diffraction Peaks ◽  
Low X

AbstractThe crystallization behavior of Ge-Sb phase change materials with variable Ge:Sb ratio X between 0.079 and 4.3 was studied using time-resolved x-ray diffraction, differential scanning calorimetry, x-ray reflectivity, optical reflectivity and resistivity vs. temperature measurements. It was found that the crystallization temperature increases with Ge content from about 130 °C for X = 0.079 to about 450 °C for X = 4.3. For low X, Sb x-ray diffraction peaks occurred during a heating ramp at lower temperature than Ge diffraction peaks. For X = 1.44 and higher, Sb and Ge peaks occurred at the same temperature. Mass density change upon crystallization and optical and electrical contrast between the phases show a maximum for the eutectic alloy with X = 0.17. The large change in materials properties with composition allows tailoring of the crystallization properties for specific application requirements.

Three-Dimensional Sonic Band Gaps Tunned by Material Parameters

2010 ◽  
Vol 29-32 ◽  
pp. 1797-1802 ◽  
Author(s):  
Xiao Zhou Zhou ◽  
Yue Sheng Wang ◽  
Chuan Zeng Zhang
Keyword(s):  
Bulk Modulus ◽  
Mass Density ◽  
Density Ratio ◽  
Three Dimensional ◽  
Expansion Method ◽  
Small Mass ◽  
Band Gaps ◽  
Face Centered Cubic ◽  
Modulus Ratio ◽  
Material Parameters

In this paper, band gaps tunned by material parameters in three-dimensional fluid-fluid sonic crystals are studied. From the basic wave equation, it is found that the material parameters directly determining the three-dimensional sonic band gaps are the mass density ratio and bulk modulus ratio. The calculation of the sonic band gaps is completed by the plane-wave expansion method. The effects of these parameters on sonic band gaps are discussed in details for the simple-cubic (sc), face-centered cubic (fcc) and body-centered cubic (bcc) lattices. The results show that the first potential sonic band gap easily appears at both small mass density ratio and bulk modulus ratio, and becomes wider with both of these two parameters decreasing. The bulk modulus ratio plays a more important role than the mass density ratio in tuning the sonic band gaps. The present analysis can be applied to artificially design band gaps.

Shielding performance of T-shaped periodic barrier for surface waves in transversely isotropic soil

2021 ◽  
pp. 146442072110130
Author(s):  
De-Xin Ji ◽  
Gui-Lan Yu
Keyword(s):  
Finite Element Method ◽  
Surface Waves ◽  
Floquet Theory ◽  
Vibration Isolation ◽  
Mass Density ◽  
Density Ratio ◽  
Transversely Isotropic ◽  
Band Gaps ◽  
Modulus Ratio ◽  
Material Parameters

Aiming at the vibration isolation in transversely isotropic soil, a T-shaped partially embedded periodic barrier for surface waves is proposed, and its shielding performance is explored by using finite element method combined with Bloch-Floquet theory. Seven independent dimensionless material parameters are derived and their influences on band gaps are discussed numerically. The results show that the band gaps exhibit strong sensitivity to the three parameters out of seven, and the band gaps are far wider in transversely isotropic soils than that in the isotropic. The mass density ratio and the shear modulus ratio of the barrier to the soil, as well as the length ratio of the barrier above the ground to that below, can be used to adjust band gaps effectively to meet the shielding requirements for different frequency ranges under different anisotropic soils. As a case of study, the El Centro seismic wave is considered and found that it can be considerably attenuated by the designed periodic barrier.

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