Broadband sound absorbers of multilayered micro-slit panels using Bayesian probabilistic inference

2021 ◽  
Vol 263 (2) ◽  
pp. 4177-4183
Author(s):  
Michael Hoeft ◽  
Cameron J. Fackler ◽  
Ning Xiang
Keyword(s):  
Probabilistic Method ◽  
Frequency Bandwidth ◽  
Individual Layer ◽  
Broadband Absorption ◽  
Design Goal ◽  
Fabrication Tolerances ◽  
Broadband Sound ◽  
Best Parameters ◽  
High Absorption ◽  
Visual Transparency

Micro-perforated panel absorbers can typically achieve either visual transparency or broadband absorption, but not both. This paper assesses the potential of Multilayer Micro-Slit panels to maintain both of these characteristics simultaneously. Micro-slit panels are similar to micro-perforated panels, and can similarly achieve high absorption coefficients without fibrous backing materials. The arrangement of slits are better suited to visual transparency than perforated holes because it provides more unobstructed panel per perforated area. However, these types of absorbers are limited to a narrow frequency bandwidth of effective absorption. By combining several panels into a multilayer assembly, broadband absorption becomes possible. The inherent complexity stemming from optimizing the parameters for multiple layers to meet a given design criteria necessitates the use of the Bayesian framework. This probabilistic method rapidly hones in on the best parameters of each individual layer so that the overall composite meets the design goal. Furthermore, Bayesian inference implemented cyclically alongside panel fabrication and testing allows for corrections of fabrication tolerances while assessing visual transparency.

APU-Noise Reduction by Novel Muffler Concepts

2018 ◽  
Author(s):  
Karsten Knobloch ◽  
Lars Enghardt ◽  
Friedrich Bake
Keyword(s):  
Noise Reduction ◽  
Operating Conditions ◽  
Acoustic Damping ◽  
Broadband Absorption ◽  
Auxiliary Power Unit ◽  
Auxiliary Power ◽  
Absorber Material ◽  
Bias Flow ◽  
Downstream Section ◽  
Broadband Sound

For a GTCP36-28 auxiliary power unit (APU), a set of mufflers has been designed and tested for some representative operating conditions. The first muffler design uses cavities of different sizes in conjunction with a bias flow for efficient broadband sound absorption. The second design — also expected to perform well over a large frequency range — makes use of a variable perforation and some porous absorber material. The acoustic damping performance of the mufflers was assessed using a downstream section of dedicated microphone probes. Individual spectra and circumferential averages have been computed and are used for a comparison to a hard-walled duct section of the same length. Results show a reasonable broadband absorption for most configurations. For one operating point, significant differences were found while comparing the performance of the cavity muffler with and without bias flow. The results suggest, that a small amount of air — less than initially expected — is sufficient to obtain the desired noise reduction.

scholarly journals Polarization-Independent Tunable Ultra-Wideband Meta-Absorber in Terahertz Regime

Electronics ◽  
2019 ◽  
Vol 8 (8) ◽  
pp. 831 ◽  
Author(s):  
Shuxiang Liu ◽  
Li Deng ◽  
Meijun Qu ◽  
Shufang Li
Keyword(s):  
Ground Plane ◽  
Bilayer Graphene ◽  
Polarization Property ◽  
Ultra Wideband ◽  
Promising Candidate ◽  
Graphene Layers ◽  
Broadband Absorption ◽  
Cylinder Arrays ◽  
Polarization Independent ◽  
High Absorption

In this paper, we demonstrate an ultra-broadband terahertz bilayer graphene-based absorption structure. It has two stacking graphene layers sandwiched by an Au cylinders array, backed by a metallic ground plane. Au cylinders are used to adjust the input impedance to be closely matched to the free space, enabling an ultra-broadband absorption. The absorption spectrum of the bilayer graphene-based absorption structure with Au cylinder arrays shows a bandwidth of 7.1 THz, with the absorption exceeding 80%. The achieved ultra-wideband THz meta-absorber has high absorption, independence of polarization property, simultaneously, illustrating to be a promising candidate for teraherz broadband absorption application.

scholarly journals Broadband Absorption Based on Thin Refractory Titanium Nitride Patterned Film Metasurface

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1092
Author(s):  
Dewang Huo ◽  
Xinyan Ma ◽  
Hang Su ◽  
Chao Wang ◽  
Hua Zhao
Keyword(s):  
Titanium Nitride ◽  
Oblique Incidence ◽  
Normal Incidence ◽  
Perfect Absorber ◽  
Size Parameter ◽  
Perfect Absorption ◽  
Broadband Absorption ◽  
Solar Energy Harvesting ◽  
Difference Time ◽  
High Absorption

In this paper, a thin metasurface perfect absorber based on refractory titanium nitride (TiN) is proposed. The size parameter of the metasurface is investigated based on the finite difference time domain method and transfer matrix method. With only a 15-nm-thick TiN layer inside the silica/TiN/silica stacks standing on the TiN substrate, the near-perfect absorption throughout the visible regime is realized. The cross-talk between the upper and lower dielectric layers enables the broadening of the absorption peak. After patterning the thin film into a nanodisk array, the resonances from the nanodisk array emerge to broaden the high absorption bandwidth. As a result, the proposed metasurface achieves perfect absorption in the waveband from 400 to 2000 nm with an average absorption of 95% and polarization-insensitivity under the normal incidence. The proposed metasurface maintains average absorbance of 90% up to 50-degree oblique incidence for unpolarized light. Our work shows promising potential in the application of solar energy harvesting and other applications requiring refractory metasurfaces.

Design and Analysis of High Absorber Based on Sub-Wavelength Grating Structure

2017 ◽  
Vol 872 ◽  
pp. 89-93
Author(s):  
Kun Li ◽  
Yu Qing Xiong ◽  
Sheng Zhu Cao ◽  
Kai Feng Zhang ◽  
Hu Wang ◽  
...  
Keyword(s):  
Finite Difference Time Domain ◽  
Electric Field Distribution ◽  
Layer Structure ◽  
Single Layer ◽  
Double Layers ◽  
Broadband Absorption ◽  
Grating Structure ◽  
Difference Time ◽  
High Absorption ◽  
Sub Wavelength

Two kinds of high absorber were designed based on sub-wavelength grating structure for aluminum substrate. The absorption and electric field distribution of these two structures were calculated by using the finite difference time domain method. One absorber was obtained by using Al2O3/SiO2 double layers and Al rectangular sub-wavelength layer which has high absorption peaks both in TE polarization and TM polarization in infrared spectrum. Another absorber was a single layer structure with a triangular sub-wavelength grating structure which had a broadband absorption in TE polarization at spectral range of 300-1000nm.Simulation results showed that the absorption of this absorber increase and then decreases with the increasing of the height of sub-wavelength grating. The average absorption reached the maximum when the height of grating was 800nm.

scholarly journals Ultra-broadband metamaterial absorbers from long to very long infrared regime

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Yu Zhou ◽  
Zheng Qin ◽  
Zhongzhu Liang ◽  
Dejia Meng ◽  
Haiyang Xu ◽  
...  
Keyword(s):  
Surface Plasmon Resonances ◽  
Absorption Bandwidth ◽  
Broadband Absorption ◽  
Intrinsic Absorption ◽  
Thermal Emitters ◽  
Plasmon Resonances ◽  
Potential Applications ◽  
Metamaterial Absorbers ◽  
Lossy Material ◽  
High Absorption

AbstractBroadband metamaterials absorbers with high absorption, ultrathin thickness and easy configurations are in great demand for many potential applications. In this paper, we first analyse the coupling resonances in a Ti/Ge/Ti three-layer absorber, which can realise broadband absorption from 8 to 12 μm. Then we experimentally demonstrate two types of absorbers based on the Ti/Ge/Si3N4/Ti configuration. By taking advantage of coupling surface plasmon resonances and intrinsic absorption of lossy material Si3N4, the average absorptions of two types of absorbers achieve almost 95% from 8 to 14 μm (experiment result: 78% from 6.5 to 13.5 μm). In order to expand the absorption bandwidth, we further propose two Ti/Si/SiO2/Ti absorbers which can absorb 92% and 87% of ultra-broadband light in the 14–30 μm and 8–30 μm spectral range, respectively. Our findings establish general and systematic strategies for guiding the design of metamaterial absorbers with excellent broadband absorption and pave the way for enhancing the optical performance in applications of infrared thermal emitters, imaging and photodetectors.

Multilayer treatment for subwavelength and broad absorption

2021 ◽  
Vol 263 (4) ◽  
pp. 2219-2227
Author(s):  
Josué Costa Baptista ◽  
Edith Roland-Fotsing ◽  
Jacky Mardjano ◽  
Daniel Therriault ◽  
Annie Ross
Keyword(s):  
Resonance Frequency ◽  
Characteristic Impedance ◽  
Single Layer ◽  
Bottom Layer ◽  
Wave Number ◽  
Perfect Absorption ◽  
Broadband Absorption ◽  
Wave Resonance ◽  
Quarter Wave ◽  
High Absorption

Single layer optimized microchannels (268µm channels size) present high absorption at the quarter-wave resonance frequency (2460Hz for 30mm-thick treatment) but cannot provide significant absorption at lower frequencies. In this work, the absorption coefficient of multilayer treatments with 2, 5, 10- and 30-layers of channels with size varying from 50µm to 15mm was numerically optimized. The equivalent fluid wave number and characteristic impedance of each layer were predicted using the JCAL model. The Double-scale Asymptotic Method (DAM) was used to obtain the JCAL parameters. The multilayer treatment absorption was modelled with the Transfer Matrix Method (TMM). It was shown that multilayer treatments present superior absorption than single layer. For instance, bilayer treatment made of a 1mm-thick top layer (facing incident wave) of channels of 58µm and a 29mm-thick bottom layer of channels with 8.1mm provides perfect absorption around 1200Hz (i.e. 1260Hz below the quarter-wave resonance frequency of 30mm-thick single layer treatment). Alternatively, a 30-layer treatment with channels size varying from 100µm to 9.6mm provides absorption higher than 0.8 between 1350 and 6270Hz (i.e. 54% higher than single layer treatment with same thickness). These results pave the way to the fabrication of new multilayer treatments with interesting subwavelength and broadband absorption capabilities.

scholarly journals A Fano-based acoustic metamaterial for ultra-broadband sound barriers

2021 ◽  
Vol 477 (2248) ◽  
Author(s):  
H. Q. Nguyen ◽  
Q. Wu ◽  
H. Chen ◽  
J. J. Chen ◽  
Y. K. Yu ◽  
...  
Keyword(s):  
Transmission Loss ◽  
Normal Incidence ◽  
Sound Insulation ◽  
Fano Resonances ◽  
Working Mechanism ◽  
Acoustic Metamaterial ◽  
Broadband Absorption ◽  
Sound Barriers ◽  
Sound Reduction ◽  
Broadband Sound

Ultra-broadband sound reduction schemes covering living and working noise spectra are of high scientific and industrial significance. Here, we report, both theoretically and experimentally, on an ultra-broadband acoustic barrier assembled from space-coiling metamaterials (SCMs) supporting two Fano resonances. Moreover, acoustic hyper-damping is introduced by integrating additional thin viscous foam layers in the SCMs for optimizing the sound reduction performance. A simplified model is developed to study sound transmission behaviour of the SCMs under a normal incidence, which sets forth the basis to understand the working mechanism. An acoustic barrier with 220 mm thickness is then manufactured and tested to exhibit ultra-broadband transmission loss overall above 10 dB across the range 0.44–3.85 kHz, covering completely nine third-octave bands. In addition, unconventional broadband absorption in the dampened barrier (65%) is experimentally observed as well. We believe this work paves the way for realizing effective broadband sound insulation, absorption and sound wave controlling devices with efficient ventilation.

scholarly journals Broadband absorption with gradient metasurfaces

2018 ◽  
Vol 5 ◽  
pp. 4 ◽  
Author(s):  
Hoyeong Kwon ◽  
Hamidreza Chalabi ◽  
Andrea Alù
Keyword(s):  
Incident Wave ◽  
Light Propagation ◽  
Incident Angle ◽  
Dielectric Materials ◽  
Broadband Absorption ◽  
Spatial Inhomogeneities ◽  
High Absorption

A metasurface with appropriately designed transverse spatial inhomogeneities can provide the desired phase redistribution in response to an incident wave with arbitrary incident angle. This property of gradient metasurfaces has been used to modify light propagation in unusual manners, to transform the impinging optical wavefront with large flexibility. In this work, we show how gradient metasurfaces can be tailored to offer high absorption in thin absorptive layers, and how to design realistic metasurfaces for this purpose using dielectric materials.

Autómatas Celulares Aplicados al Comportamiento de Células de Cáncer Cervicouterino

2019 ◽  
Vol 6 (1) ◽  
pp. 44-49
Author(s):  
Tania Muñoz Jiménez ◽  
Aurora Torres Soto ◽  
María Dolores Torres Soto
Keyword(s):  
Cellular Automaton ◽  
Medical Model ◽  
Research Process ◽  
Simulation Algorithm ◽  
Stages Of Development ◽  
Literary Research ◽  
Migration Dynamics ◽  
Three Stages ◽  
And Migration ◽  
Best Parameters

En este documento se describe el desarrollo e implementación de un modelo para simular computacionalmente la dinámica del crecimiento y migración del cáncer cervicouterino, considerando sus principales características: proliferación, migración y necrosis, así como sus etapas de desarrollo. El modelo se desarrolló mediante un autómata celular con enfoques paralelo y secuencial. El autómata celular se basó en el modelo de Gompertz para simular las etapas de desarrollo de este cáncer, el cual se dividió en tres etapas cada una con diferentes comportamientos durante la simulación. Se realizó un diseño experimental con parámetros de entrada que se seleccionaron a partir de la investigación literaria y su discusión con médicos expertos. Al final del proceso de investigación, se logró obtener un algoritmo computacional de simulación muy bueno comparado con el modelo médico de Gompertz y se encontraron los mejores parámetros para su ejecución mediante un diseño factorial soportado estadísticamente. This paper describes the development and implementation of a model to computationally simulate the growth and migration dynamics of cervical cancer, considering its main characteristics: proliferation, migration and necrosis, as well as its stages of development. The model was developed by means of a cellular automaton with parallel and sequential approaches. The cellular automaton was based on the model of Gompertz to simulate the stages of development of this cancer, which was divided into three stages, each with different behaviors during the simulation. An experimental design was carried out with input parameters that were selected from literary research and its discussion with expert physicians. At the end of the research process, a very good simulation algorithm was obtained compared to the Gompertz medical model and the best parameters for its execution were found by means of a statistically supported factorial design.

MID-INFRARED BROADBAND ABSORPTION BASED ON HBN/METAL HETEROSTRUCTURES

2018 ◽  
Author(s):  
Y. H. Kan ◽  
Changying Zhao ◽  
Zhuomin M. Zhang
Keyword(s):  
Mid Infrared ◽  
Broadband Absorption
Sign in / Sign up

Export Citation Format

Share Document