Nonlocal acoustic metasurface absorber for ultra-broadband sound absorption

2021 ◽  
Vol 263 (1) ◽  
pp. 5409-5414
Author(s):  
Yifan Zhu ◽  
Badreddine Assouar
Keyword(s):  
Sound Absorption ◽  
Coupling Effect ◽  
Analytical Models ◽  
Bandwidth Efficiency ◽  
Specific Effects ◽  
Fabry Perot ◽  
Unit Cells ◽  
Non Local ◽  
Broadband Sound ◽  
Adjacent Unit

Classical designs of acoustic meta-absorber usually have a trade-off between bandwidth, efficiency and thickness. Here, we introduce the concept of nonlocal acoustic metasurface absorber by using a bridge structure connecting resonating unit cells to improve the performances of the meta-absorber. By utilizing the coupling effect between the adjacent unit cells, ultra-broadband sound absorption is achieved with deep-wavelength thickness. The physical mechanism of the nonlocal acoustic metasurface absorber is investigated by developing analytical models. We theoretically and numerically study the nonlocal metasurface with connecting bridge and the traditional metasurface without bridge. The nonlocality can introduce three specific effects: 1. Optimizing of effective acoustic impedances. 2. Shift of Fabry-Perot resonant frequencies. 3. Strengthening of the coupling effects between adjacent unit cells. These effects help to improve the bandwidth and the efficiency of the acoustic meta-absorber. We numerically and experimentally achieve an averaged absorption coefficient larger than 0.9 within the ultra-broadband bandwidth from about 600 Hz to 2600 Hz, with a sample thickness of 6.8 cm, , /9 for the lowest frequency. Our finding demonstrates the advantage of non-local acoustic metasurface to conceive subwavelength sound meta-absorber.

Sequence Specificity Despite Intrinsic Disorder: How a Disease-Associated Val/Met Polymorphism Shifts Tertiary Interactions in a Long Disordered Protein

2019 ◽  
Author(s):  
Ruchi Lohia ◽  
Reza Salari ◽  
Grace Brannigan
Keyword(s):  
Secondary Structure ◽  
Electrostatic Interactions ◽  
Intrinsically Disordered Proteins ◽  
Disordered Proteins ◽  
Sequence Specificity ◽  
Intrinsically Disordered ◽  
Specific Effects ◽  
Heterogeneous Polymer ◽  
Non Local ◽  
Dynamics Simulations

<div>The role of electrostatic interactions and mutations that change charge states in intrinsically disordered proteins (IDPs) is well-established, but many disease-associated mutations in IDPs are charge-neutral. The Val66Met single nucleotide polymorphism (SNP) encodes a hydrophobic-to-hydrophobic mutation at the midpoint of the prodomain of precursor brain-derived neurotrophic factor (BDNF), one of the earliest SNPs to be associated with neuropsychiatric disorders, for which the underlying molecular mechanism is unknown. Here we report on over 250 μs of fully-atomistic, explicit solvent, temperature replica exchange molecular dynamics simulations of the 91 residue BDNF prodomain, for both the V66 and M66 sequence.</div><div>The simulations were able to correctly reproduce the location of both local and non-local secondary changes due to the Val66Met mutation when compared with NMR spectroscopy. We find that the local structure change is mediated via entropic and sequence specific effects. We show that the highly disordered prodomain can be meaningfully divided into domains based on sequence alone. Monte Carlo simulations of a self-excluding heterogeneous polymer, with monomers representing each domain, suggest the sequence would be effectively segmented by the long, highly disordered polyampholyte near the sequence midpoint. This is qualitatively consistent with observed interdomain contacts within the BDNF prodomain, although contacts between the two segments are enriched relative to the self-excluding polymer. The Val66Met mutation increases interactions across the boundary between the two segments, due in part to a specific Met-Met interaction with a Methionine in the other segment. This effect propagates to cause the non-local change in secondary structure around the second methionine, previously observed in NMR. The effect is not mediated simply via changes in inter-domain contacts but is also dependent on secondary structure formation around residue 66, indicating a mechanism for secondary structure coupling in disordered proteins. </div>

Highly Efficient Low‐Frequency Broadband Sound Absorption with a Composite Hybrid Metasurface

2021 ◽  
Author(s):  
Qingxuan Liang ◽  
Yutao Wu ◽  
Peiyao Lv ◽  
Jin He ◽  
Fuyin Ma ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Low Frequency ◽  
Highly Efficient ◽  
Broadband Sound

The Structure and Acoustic Properties of Aluminum Foams by Gas Injection Method

2010 ◽  
Vol 146-147 ◽  
pp. 1049-1055
Author(s):  
Xue Liu Fan ◽  
Xiang Chen ◽  
Yan Xiang Li
Keyword(s):  
Sound Absorption ◽  
Gas Injection ◽  
Optical Microscope ◽  
Absorption Efficiency ◽  
Absorption Capacity ◽  
Acoustic Properties ◽  
Analytical Models ◽  
Aluminum Foams ◽  
Injection Method ◽  
Membrane Vibrations

The acoustic properties of aluminum foams by gas injection method were studied experimentally. The micro and macro structure of aluminum foam with closed cells were observed by optical microscope (OM) and scanning electron microscope (SEM). The special structure of the closed-pores of the aluminum foams have leaded to good performance of the sound absorption based on three mechanisms: Helmholtz resonance, cell wall vibration and viscous and thermal effects. The effect of cell sizes, thickness of aluminum foams has been investigated and the cavity set at the back of the foam samples on the sound absorption efficiency of the foams has been measured. Analytical models of membrane vibrations were used to explain the sound absorption capacity of the foams.

A multilayer microperforated panel prototype for broadband sound absorption at low frequencies

2019 ◽  
Vol 146 ◽  
pp. 134-144 ◽  
Author(s):  
F. Bucciarelli ◽  
G.P. Malfense Fierro ◽  
M. Meo
Keyword(s):  
Sound Absorption ◽  
Low Frequencies ◽  
Broadband Sound

Multiple slow waves in metaporous layers for broadband sound absorption

2016 ◽  
Vol 50 (1) ◽  
pp. 015301 ◽  
Author(s):  
Jieun Yang ◽  
Joong Seok Lee ◽  
Yoon Young Kim
Keyword(s):  
Sound Absorption ◽  
Slow Waves ◽  
Broadband Sound

scholarly journals Design of non-circular membranes metasurfaces for broadband sound absorption

2020 ◽  
Vol 59 (SK) ◽  
pp. SKKA06
Author(s):  
Keita Watanabe ◽  
Mikiya Fujita ◽  
Kenji Tsuruta
Keyword(s):  
Sound Absorption ◽  
Broadband Sound

Two analytical models for the study of periodic fibrous elastic composite with different unit cells

2011 ◽  
Vol 93 (2) ◽  
pp. 709-714 ◽  
Author(s):  
Reinaldo Rodríguez-Ramos ◽  
P. Yan ◽  
Juan C. López-Realpozo ◽  
Raúl Guinovart-Díaz ◽  
Julián Bravo-Castillero ◽  
...  
Keyword(s):  
Analytical Models ◽  
Elastic Composite ◽  
Unit Cells

A non-local implicit gradient-enhanced model for thermomechanical behavior of shape memory alloys

2018 ◽  
Vol 29 (9) ◽  
pp. 1818-1834 ◽  
Author(s):  
Hojjat Badnava ◽  
Mohammad Mashayekhi ◽  
Mahmoud Kadkhodaei ◽  
Ahmad Amiri-Rad
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Coupling Effect ◽  
Three Dimensional ◽  
Finite Element Software ◽  
Non Local ◽  
Niti Shape Memory Alloys ◽  
Temperature Responses ◽  
Fully Coupled ◽  
Good Agreement

A three-dimensional, implicit gradient-enhanced, fully coupled thermomechanical constitutive model is developed within the framework of thermodynamic principles for NiTi shape memory alloys. This work focuses on unstable behaviors of NiTi samples under different thermomechanical loading conditions. Temperature variation and its coupling effect on non-local behavior of a shape memory alloy during a loading–unloading cycle at different strain rates are considered. The proposed constitutive equations are implemented into the finite element software ABAQUS, and the numerical investigations indicate that the used procedure is an effective computational tool for simulation of several behaviors of NiTi samples including phase front nucleation and propagation, stress–strain–temperature responses, and transformation-induced stress relaxation. The obtained results are shown to be in a good agreement with available experimental and numerical findings in the literature. The effectiveness of the model in removing mesh sensitivity is evaluated by investigating the mesh-dependence issue for the low strain rate problems through numerical examples.

scholarly journals Sequence specificity despite intrinsic disorder: how a disease-associated Val/Met polymorphism rearranges tertiary interactions in a long disordered protein

2019 ◽  
Author(s):  
Ruchi Lohia ◽  
Reza Salari ◽  
Grace Brannigan
Keyword(s):  
Electrostatic Interactions ◽  
Intrinsically Disordered Proteins ◽  
Tertiary Structure ◽  
Protein A ◽  
Md Simulations ◽  
Disordered Proteins ◽  
Sequence Specificity ◽  
Intrinsically Disordered ◽  
Specific Effects ◽  
Non Local

<p>The role of electrostatic interactions and mutations that change charge states in intrinsically disordered proteins (IDPs) is well-established, but many disease-associated mutations in IDPs are charge-neutral. The Val66Met single nucleotide polymorphism (SNP) in precursor brain-derived neurotrophic factor (BDNF) is one of the earliest SNPs to be associated with neuropsychiatric disorders, and the underlying molecular mechanism is unknown. Here we report on over 250 μs of fully-atomistic, explicit solvent, temperature replica exchange molecular dynamics (MD) simulations of the 91 residue BDNF prodomain, for both the V66 and M66 sequence. The simulations were able to correctly reproduce the location of both local and non-local secondary changes due to the Val66Met mutation when compared with NMR spectroscopy. We find that the change in local structure is mediated via entropic and sequence specific effects. We developed a hierarchical sequence-based framework for analysis and conceptualization, which first identifies “blobs” of 5-15 residues representing local globular regions or linkers. We use this framework within a novel test for enrichment of higher-order (tertiary) structure in disordered proteins; the size and shape of each blob is extracted from MD simulation of the real protein (RP), and used to parameterize a self-avoiding heterogenous polymer (SAHP). The SAHP version of the BDNF prodomain suggested a protein segmented into three regions, with a central long, highly disordered polyampholyte linker separating two globular regions. This effective segmentation was also observed in full simulations of the RP, but the Val66Met substitution significantly increased interactions across the linker, as well as the number of participating residues. The Val66Met substitution replaces β-bridging between Val66 and Val94 (on either side of the linker) with specific side-chain interactions between Met66 and Met95.The protein backbone in the vicinity of Met95 is then free to form β-bridges with residues 31-41 near the N-terminus, which condenses the protein. A significant role for Met/Met interactions is consistent with previously-observed non-local effects of the Val66Met SNP, as well as established interactions between the Met66 sequence and a Met-rich receptor that initiates neuronal growth cone retraction.</p>

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