scholarly journals Tunable Fluid-Type Metasurface for Wide-Angle and Multifrequency Water-Air Acoustic Transmission

Research ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Zhandong Huang ◽  
Shengdong Zhao ◽  
Yiyuan Zhang ◽  
Zheren Cai ◽  
Zheng Li ◽  
...  
Keyword(s):  
Incident Angle ◽  
Acoustic Energy ◽  
Wide Angle ◽  
Acoustic Metamaterials ◽  
Fluid Type ◽  
Acoustic Transmission ◽  
Interface Instability ◽  
Practical Applications ◽  
Air Interface ◽  
Transmission Enhancement

Efficient acoustic communication across the water-air interface remains a great challenge owing to the extreme acoustic impedance mismatch. Few present acoustic metamaterials can be constructed on the free air-water interface for enhancing the acoustic transmission because of the interface instability. Previous strategies overcoming this difficulty were limited in practical usage, as well as the wide-angle and multifrequency acoustic transmission. Here, we report a simple and practical way to obtain the wide-angle and multifrequency water-air acoustic transmission with a tunable fluid-type acoustic metasurface (FAM). The FAM has a transmission enhancement of acoustic energy over 200 times, with a thickness less than the wavelength in water by three orders of magnitude. The FAM can work at an almost arbitrary water-to-air incident angle, and the operating frequencies can be flexibly adjusted. Multifrequency transmissions can be obtained with multilayer FAMs. In experiments, the FAM is demonstrated to be stable enough for practical applications and has the transmission enhancement of over 20 dB for wide frequencies. The transmission enhancement of music signal across the water-air interface was performed to demonstrate the applications in acoustic communications. The FAM will benefit various applications in hydroacoustics and oceanography.

scholarly journals Research on Perfect and Tunable Metamaterial Absorber Based on Crosshair-shaped Graphene

2021 ◽  
Vol 2109 (1) ◽  
pp. 012015
Author(s):  
Yiran Guo ◽  
Yunping Qi ◽  
Chuqin Liu ◽  
Weiming Liu ◽  
Xiangxian Wang
Keyword(s):  
Relaxation Time ◽  
Chemical Potential ◽  
Incident Angle ◽  
Fdtd Method ◽  
Reference Value ◽  
Metamaterial Absorber ◽  
Selective Absorption ◽  
Perfect Absorber ◽  
Wide Angle ◽  
Perfect Absorption

Abstract Graphene, as a new nano-material, according to the physical properties of electric field localization and selective absorption on light of surface plasmon resonance (SPR), a tunable, multi-band and wide-angle perfect absorber based on crosshair-shaped graphene is devised by using the Finite Difference in Time Domain (FDTD) method. In this paper, the effects of chemical potential, relaxation time, and incident angle of light on the absorptivity of graphene are systematically discussed. The simulation experiment shows that there are two absorption peaks with perfect absorption rate appeared in the study range, and the maximum modulation index can be obtained by changing the relaxation time. Finally, it proves that the absorber is insensitive to wide-angle of light. Thus, it is able to be concluded that the absorber has a great reference value to sensor, wireless communication, biomedical and other fields.

scholarly journals An Integration Strategy for Acoustic Metamaterials to Achieve Absorption by Design

2018 ◽  
Vol 8 (8) ◽  
pp. 1247 ◽  
Author(s):  
Min Yang ◽  
Ping Sheng
Keyword(s):  
Absorption Spectrum ◽  
Perforated Plate ◽  
Design Strategy ◽  
Sample Thickness ◽  
Acoustic Metamaterials ◽  
Metamaterial Structure ◽  
Minimum Thickness ◽  
Practical Applications ◽  
Integration Strategy ◽  
Minimum Sample

As much of metamaterials’ properties originate from resonances, the novel characteristics displayed by acoustic metamaterials are a narrow bandwidth and high dispersive in nature. However, for practical applications, broadband is often a necessity. Furthermore, it would even be better if acoustic metamaterials can display tunable bandwidth characteristics, e.g., with an absorption spectrum that is tailored to fit the noise spectrum. In this article we present a designed integration strategy for acoustic metamaterials that not only overcomes the narrow-band Achilles’ heel for acoustic absorption but also achieves such effect with the minimum sample thickness as dictated by the law of nature. The three elements of the design strategy comprise: (a) the causality constraint, (b) the determination of resonant mode density in accordance with the input target impedance, and (c) the accounting of absorption by evanescent waves. Here, the causality constraint relates the absorption spectrum to a minimum sample thickness, derived from the causal nature of the acoustic response. We have successfully implemented the design strategy by realizing three structures of which one acoustic metamaterial structure, comprising 16 Fabry-Perot resonators, is shown to exhibit near-perfect flat absorption spectrum starting at 400 Hz. The sample has a thickness of 10.86 cm, whereas the minimum thickness as dictated by the causality constraint is 10.55 cm in this particular case. A second structure demonstrates the flexible tunability of the design strategy by opening a reflection notch in the absorption spectrum, extending from 600 to 1000 Hz, with a sample thickness that is only 3 mm above the causality minimum. We compare the designed absorption structure with conventional absorption materials/structures, such as the acoustic sponge and micro-perforated plate, with equal thicknesses as the metamaterial structure. In both cases the designed metamaterial structure displays superior absorption performance in the target frequency range.

A compact and low-frequency acoustic energy harvester using layered acoustic metamaterials

2019 ◽  
Vol 28 (2) ◽  
pp. 025035 ◽  
Author(s):  
Xiaole Wang ◽  
Jiajie Xu ◽  
Jingjing Ding ◽  
Chunyu Zhao ◽  
Zhenyu Huang
Keyword(s):  
Energy Harvester ◽  
Low Frequency ◽  
Acoustic Energy ◽  
Acoustic Metamaterials

A dynamically tunable and wide-angle terahertz absorber based on graphene-dielectric grating

2020 ◽  
Vol 34 (27) ◽  
pp. 2050292
Author(s):  
Chunyan Wu ◽  
Yiqiang Fang ◽  
Linbao Luo ◽  
Kai Guo ◽  
Zhongyi Guo
Keyword(s):  
Chemical Potential ◽  
Incident Angle ◽  
Near Field ◽  
Absorption Efficiency ◽  
Multilayer Graphene ◽  
Wide Angle ◽  
Terahertz Absorber ◽  
Tunable Range ◽  
Magnetic Components ◽  
Dielectric Grating

We theoretically and numerically demonstrate a tunable and wide-angle terahertz absorber, which is composed of multilayer graphene-dielectric grating and bottom metal substrate. Numerical simulation shows that the proposed absorber has the advantage of dynamically tunable range from 1.015 THz to 1.165 THz when the chemical potential of graphene increases from 10 meV to 150 meV. The absorption efficiency can reach a high value of 99%. To show the working mechanism of absorption, the near field distributions of magnetic components are presented at the absorption wavelength. We also demonstrate that the tunable range of absorption can be engineered by designing the geometry parameters. In addition, it is shown that the designed absorber can maintain the good performance of absorption over a wide incident angle from [Formula: see text] to [Formula: see text] under TM-polarization.

Acoustic transmission enhancement through a soft interlayer with a reactance boundary

2015 ◽  
Vol 138 (2) ◽  
pp. 782-790 ◽  
Author(s):  
Li Quan ◽  
Feng Qian ◽  
Xiaozhou Liu ◽  
Xiufen Gong
Keyword(s):  
Acoustic Transmission ◽  
Soft Interlayer ◽  
Transmission Enhancement

scholarly journals Fast Direct Solution of Electromagnetic Scattering from Left-Handed Materials Coated Target over Wide Angle

2016 ◽  
Vol 2016 ◽  
pp. 1-7
Author(s):  
Guo-hua Wang ◽  
Ying-bao Geng
Keyword(s):  
Electromagnetic Scattering ◽  
Incident Angle ◽  
Linear Equations ◽  
Computation Time ◽  
Wide Angle ◽  
Memory Consumption ◽  
Scattering Problems ◽  
Left Handed ◽  
Computation Process ◽  
Systems Of Linear Equations

When solving the electromagnetic scattering problems over wide angle, the traditional method of moments (MoM) needs to repeat the solving process of dense systems of linear equations using the iteration method at each incident angle, which proved to be quite inefficient. To circumvent this problem, a fast numerical method based on block LDLT factorization accelerated by adaptive cross approximation (ACA) algorithm is presented to analyze the electromagnetic scattering of left-handed materials (LHM) coated target. The ACA algorithm is applied to impedance matrix filling and all steps of block LDLT factorization process, which can accelerate the computation process and reduce the memory consumption. The numerical results proved that the proposed method is efficient in calculating monostatic RCS of LHM coated target with many required sampling angles. Compared with the traditional MoM, computation time and memory consumption are reduced effectively.

scholarly journals Budgets of Disturbances Energy for Nozzle Flows at Subsonic and Choked Regimes

2017 ◽  
Author(s):  
Maxime Huet
Keyword(s):  
Acoustic Energy ◽  
Energy Budgets ◽  
Acoustic Transmission ◽  
Test Rig ◽  
Transmission And Reflection Coefficients ◽  
Energetic Approach ◽  
Acoustic Fluctuations ◽  
Nozzle Flows ◽  
Transmission And Reflection ◽  
Good Agreement

The noise generated by the passage of acoustic and entropy perturbations through subsonic and choked nozzle flows is investigated numerically using an energetic approach. Low-order models are used to reproduce the experimental results of the Hot Acoustic Test rig (HAT) of DLR and energy budgets are performed to characterize the reflection, transmission and dissipation of the fluctuations. Because acoustic and entropy perturbations are present in the flow in the general case, classical acoustic energy budgets cannot be used and the disturbances energy budgets proposed by Myers (J. Fluid Mech. 226 (1991) 383–400) are used instead. Numerical results are in very good agreement with the experiments in terms of acoustic transmission and reflection coefficients. The normal shock present in the diffuser for choked regimes is shown to attenuate the scattered acoustic fluctuations, either by pure dissipation effect or by converting a part of the acoustic energy into entropy fluctuations.

scholarly journals Wide-Angle Transmission Enhancement of Metamaterial-Doped Fiber-Reinforced Polymers

IEEE Access ◽  
2019 ◽  
Vol 7 ◽  
pp. 76042-76048 ◽  
Author(s):  
Yongzhi Li ◽  
Lin Zheng ◽  
Jiafu Wang ◽  
Xinmin Fu ◽  
Mingde Feng ◽  
...  
Keyword(s):  
Fiber Reinforced Polymers ◽  
Wide Angle ◽  
Fiber Reinforced ◽  
Reinforced Polymers ◽  
Transmission Enhancement
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