scholarly journals Acoustic Performance Analysis of Bionic Coupling Multi-Layer Structure

2013 ◽  
Vol 461 ◽  
pp. 22-30
Author(s):  
Yong Hua Wang ◽  
Cheng Chun Zhang ◽  
Lu Quan Ren ◽  
Mohamed Ichchou ◽  
Marie Annick Galland ◽  
...  
Keyword(s):  
Layer Structure ◽  
Structure Model ◽  
Absorption Coefficients ◽  
Acoustic Performance ◽  
Proposed Model ◽  
Average Absorption Coefficient ◽  
Absorption Performance ◽  
Bionic Coupling ◽  
Transfer Method ◽  
Porous Fibrous Material

The interest of this paper lies in the proposition of using bionic method to develop a new sound absorption structure. Inspired by the coupling absorption structure of the skin and feather of a typical silent flying bird – owl, a bionic coupling multi-layer structure model is developed, which is composed of a micro-silt plate, porous fibrous material and a flexible micro-perforated membrane backed with airspace. The impedance transfer method is applied to calculate the absorption coefficients and analyze the influences of different parameters of each layer on absorption coefficients of this model. Based on numerical simulations, the effectiveness of this proposed model is tested. The average absorption coefficient reaches 0.85 within the frequency range from 200 Hz to 2000 Hz. The significant improvement of absorption coefficients can be mainly due to the Helmholtz effects of the micro-silt plate and flexible micro-perforated membrane, and the combination with porous materials can lead to even better absorption performance in broadband.

scholarly journals Diffuse Sound Absorptive Properties of Parallel-Arranged Perforated Plates with Extended Tubes and Porous Materials

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1091 ◽  
Author(s):  
Dengke Li ◽  
Daoqing Chang ◽  
Bilong Liu
Keyword(s):  
Boundary Condition ◽  
Porous Material ◽  
Porous Materials ◽  
Sound Absorption ◽  
Azimuthal Angle ◽  
Octave Band ◽  
Frequency Range ◽  
Absorption Coefficients ◽  
Perforated Plates ◽  
Absorption Performance

The diffuse sound absorption was investigated theoretically and experimentally for a periodically arranged sound absorber composed of perforated plates with extended tubes (PPETs) and porous materials. The calculation formulae related to the boundary condition are derived for the periodic absorbers, and then the equations are solved numerically. The influences of the incidence and azimuthal angle, and the period of absorber arrangement are investigated on the sound absorption. The sound-absorption coefficients are tested in a standard reverberation room for a periodic absorber composed of units of three parallel-arranged PPETs and porous material. The measured 1/3-octave band sound-absorption coefficients agree well with the theoretical prediction. Both theoretical and measured results suggest that the periodic PPET absorbers have good sound-absorption performance in the low- to mid-frequency range in diffuse field.

Sound absorption of a finite flexible micro-perforated panel absorber back by a rigid air cavity filled with a fibrous porous material

2021 ◽  
Vol 263 (3) ◽  
pp. 3625-3632
Author(s):  
Ho Yong Kim ◽  
Yeon June Kang
Keyword(s):  
Energy Dissipation ◽  
Porous Material ◽  
Fibrous Material ◽  
Alternative Energy ◽  
Sound Absorption ◽  
Sound Pressure ◽  
Absorption Coefficients ◽  
Air Cavity ◽  
Acoustic Cavity ◽  
Absorption Performance

Back by a rigid cavity filled with a layer of porous layer, the sound absorption performance of a micro-perforated panel (MPP) can be enhanced in comparison with other resonance based sound absorbers. In this paper, a theoretical model of a finite flexible MPP back by a rigid air cavity filled with a fibrous porous material is developed to predict normal sound absorption coefficients. Displacements of MPP and sound pressure field in fibrous porous material and acoustic cavity are expressed using a series of modal functions, and the sound absorption coefficients of MPP system are obtained. Additionally, comparison of energy dissipation by MPP and fibrous material is performed to identify effects of a fibrous material on the sound absorption of a MPP. As expected, at anti-resonance frequency of an MPP, the fibrous material provide an alternative energy dissipation mechanism.

Finite element sound field analysis on measurement of absorption coefficient in a reverberation room -Relationships between inclination of walls and measurement results-

2021 ◽  
Vol 263 (1) ◽  
pp. 5571-5577
Author(s):  
Reiji Tomiku ◽  
Noriko Okamoto ◽  
Toru Otsuru ◽  
Shun Iwamoto ◽  
Shoma Suzuki
Keyword(s):  
Finite Element ◽  
Absorption Coefficient ◽  
Sound Field ◽  
Field Analysis ◽  
Reverberation Time ◽  
Absorption Coefficients ◽  
Sound Fields ◽  
Measurement Results ◽  
Coefficient Measurement ◽  
Absorption Performance

The absorption coefficients in a reverberation room are most representative measure for evaluating absorption performance of architectural materials. However, it is well known that measurement results of the coefficient vary according to a room shape of the measurement and area of the specimen. Numerical analyses based on wave acoustics are effective tools to investigate these factors on absorption coefficient measurement in reverberation room. In this study, sound fields for the measurement of absorption coefficient in reverberation room are analyzed by time domain finite element method (TDFEM). This study shows effectiveness of the analysis for investigation on causes of variation in the measurement results and improvement methods of the measurement. First, some measurement sound fields for absorption coefficient in reverberation rooms the walls of which are incline or decline are analyzed by the TDFEM. Next, reverberation times in each sound fields are calculated from the results obtained by TDFEM and the absorption coefficients are evaluated from the reverberation time of the room with and without specimen. Finally, the relationships among room shape, degree of inclination of the wall, the sound absorption coefficient of the specimen, frequencies and the measurement absorption coefficient are investigated.

scholarly journals Optimization and Validation of Sound Absorption Performance of 10-Layer Gradient Compressed Porous Metal

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 588 ◽  
Author(s):  
Fei Yang ◽  
Xinmin Shen ◽  
Panfeng Bai ◽  
Xiaonan Zhang ◽  
Zhizhong Li ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Sound Absorption ◽  
Search Algorithm ◽  
Theoretical Data ◽  
Porous Metal ◽  
Cuckoo Search ◽  
Absorption Coefficients ◽  
Element Simulation ◽  
Absorption Performance

Sound absorption performance of a porous metal can be improved by compression and optimal permutation, which is favorable to promote its application in noise reduction. The 10-layer gradient compressed porous metal was proposed to obtain optimal sound absorption performance. A theoretical model of the sound absorption coefficient of the multilayer gradient compressed porous metal was constructed according to the Johnson-Champoux-Allard model. Optimal parameters for the best sound absorption performance of the 10-layer gradient compressed porous metal were achieved by a cuckoo search algorithm with the varied constraint conditions. Preliminary verification of the optimal sound absorber was conducted by the finite element simulation, and further experimental validation was obtained through the standing wave tube measurement. Consistencies among the theoretical data, the simulation data, and the experimental data proved accuracies of the theoretical sound absorption model, the cuckoo search optimization algorithm, and the finite element simulation method. For the investigated frequency ranges of 100–1000 Hz, 100–2000 Hz, 100–4000 Hz, and 100–6000 Hz, actual average sound absorption coefficients of optimal 10-layer gradient compressed porous metal were 0.3325, 0.5412, 0.7461, and 0.7617, respectively, which exhibited the larger sound absorption coefficients relative to those of the original porous metals and uniform 10-layer compressed porous metal with the same thickness of 20 mm.

scholarly journals Improving and Optimizing Sound Absorption Performance of Polyurethane Foam by Prepositive Microperforated Polymethyl Methacrylate Panel

2020 ◽  
Vol 10 (6) ◽  
pp. 2103
Author(s):  
Xiaocui Yang ◽  
Xinmin Shen ◽  
Haiqin Duan ◽  
Fei Yang ◽  
Xiaonan Zhang ◽  
...  
Keyword(s):  
Polyurethane Foam ◽  
Composite Structures ◽  
Sound Absorption ◽  
Search Algorithm ◽  
Cuckoo Search ◽  
Cuckoo Search Algorithm ◽  
Absorption Model ◽  
Absorption Coefficients ◽  
Element Simulation ◽  
Absorption Performance

Sound absorption performance of polyurethane foam could be improved by adding a prepositive microperforated polymethyl methacrylate panel to form a composite sound-absorbing structure. A theoretical sound absorption model of polyurethane foam and that of the composite structure were constructed by the transfer matrix method based on the Johnson–Champoux–Allard model and Maa’s theory. Acoustic parameter identification of the polyurethane foam and structural parameter optimization of the composite structures were obtained by the cuckoo search algorithm. The identified porosity and static flow resistivity were 0.958 and 13078 Pa·s/m2 respectively, and their accuracies were proved by the experimental validation. Sound absorption characteristics of the composite structures were verified by finite element simulation in virtual acoustic laboratory and validated through standing wave tube measurement in AWA6128A detector. Consistencies among the theoretical data, simulation data, and experimental data of sound absorption coefficients of the composite structures proved the effectiveness of the theoretical sound absorption model, cuckoo search algorithm, and finite element simulation method. Comparisons of actual average sound absorption coefficients of the optimal composite structure with those of the original polyurethane foam proved the practicability of this identification and optimization method, which was propitious to promote its practical application in noise reduction.

Microwave Absorption of Double-Layer Absorber Based on Nanocomposite BaFe12O19/α–Fe and Nanocrystalline Alloy Fe0.2(Co0.2Ni0.8)0.8 Microfibers

2014 ◽  
Vol 1035 ◽  
pp. 339-343 ◽  
Author(s):  
Hao Shen ◽  
Xiang Qian Shen ◽  
Min Li ◽  
Hong Bo Liu ◽  
Zhou Wang
Keyword(s):  
Microwave Absorption ◽  
Double Layer ◽  
Layer Structure ◽  
Nanocrystalline Alloy ◽  
Magnetic Alloy ◽  
Matching Layer ◽  
Absorption Performance ◽  
Absorbing Layer ◽  
Microwave Absorption Performance ◽  
Very High

In this paper, the prepared nanocomposite BaFe12O19/α-Fe microfibers and nanocrystalline magnetic alloy Fe0.2(Co0.2Ni0.8)0.8 microfibers are used as absorbents in the double layer structure for microwave absorption. The double layer absorbers with a total thickness of 2.0 mm, in which various matching and absorbing layers are designed, and their absorption properties are estimated. The results show that the absorbers with the matching layer of nanocomposite BaFe12O19/α-Fe microfibers have a very high microwave absorption performance. The absorption bandwidth (the reflection loss (RL) less than-20 dB) reaches 5.8 GHz ranging from 12.2 to 18 GHz, and the minimum RL value is-61.2 dB at about 15.2 GHz with 0.9 mm matching layer and 1.1mm absorbing layer respectively.

scholarly journals Understanding Saturn’s interior from the Cassini Grand Finale gravity measurements

2020 ◽  
Vol 639 ◽  
pp. A10 ◽  
Author(s):  
Dongdong Ni
Keyword(s):  
Rotation Rate ◽  
Mass Fraction ◽  
Heavy Element ◽  
Equations Of State ◽  
Layer Structure ◽  
Element Abundance ◽  
Structure Model ◽  
Core Mass ◽  
Induced Gravity ◽  
Gravity Measurements

Context. Measurements of Saturn’s gravity field by Cassini Grand Finale have been acquired with high precision. It has been demonstrated that the even gravitational harmonics J6–J10 have larger absolute values than the predictions by typical rigid-body interior models. A four-layer structure model, proposed to interpret Juno’s gravity measurements for Jupiter, has been applied to Saturn, but great attention was paid to the depth of zonal flows in order to interpret the large absolute values of J6–J10. Aims. We aim to understand the internal structure and interior composition of Saturn with a similar model for Jupiter. The additional uncertainties in Saturn’s structure and composition are investigated in detail, such as rotation periods, atmospheric helium mass fractions, and flow-induced gravity corrections. Also, we investigate the effect of equations of state for hydrogen and helium on the predictions of the core mass and heavy element abundance. Methods. In the four-layer structure model, we adjusted the heavy element abundances in the outer two envelopes and the mass of the compact core in order to reproduce Saturn’s equatorial radius as well as the Cassini Grand Finale gravity measurements corrected by the flow-induced gravity signals. Different four-layer interior models are specified in terms of the rotation period, the atmospheric helium mass fraction, and the flow-induced gravity corrections. Two different ab initio equations of state for hydrogen and helium were used in interior structure calculations. Optimized calculations were then performed to explore Saturn’s internal structure and composition. Results. It is found that the absolute values of J6–J10 tend to increase with increasing deep rotation rate and depend on the equations of state adopted in interior calculations. Saturn’s deep rotation rate and atmospheric helium mass fraction are important to determine the distribution of helium and heavy elements in the outer envelopes. We also show that the core mass and heavy element abundance in Saturn are dependent upon the deep rotation rate, the atmospheric helium mass fraction, the flow-induced gravity corrections, and the equations of state for hydrogen and helium.

Determination of Anisotropic Absorption and Extinction Coefficients of a Tomographed Real Porous Medium

2004 ◽  
Author(s):  
Barbar Zeghondy ◽  
Jean Taine ◽  
Estelle Iacona
Keyword(s):  
Solid Phase ◽  
Fluid Phase ◽  
Radiative Properties ◽  
High Porosity ◽  
Absorption Coefficients ◽  
Extinction Coefficients ◽  
X Ray ◽  
Isotropic Media ◽  
Transfer Method

The direct general identification method of the radiative properties of high porosity media, developed and validated for virtual statistically isotropic media in [1], has been applied to a real statistically anisotropic medium. This medium has a transparent fluid phase and an opaque gray diffuse solid phase. It is modelled by a semi-transparent equivalent medium characterized by extinction and absorption coefficients β and κ. These quantities are directly determined from the morphology data obtained by X-ray tomography and from the absorptivity of the solid phase. The application of this approach to a mullite sample has established that β and κ are homogeneous but depend on direction. This last feature has to be accounted for by a radiative transfer method for this type of medium.

Research of Cloud Storage and Data Read-Write Technology

2013 ◽  
Vol 347-350 ◽  
pp. 3555-3559
Author(s):  
Hong Jun Chen ◽  
Tao Tan ◽  
Xue Qin Wu
Keyword(s):  
Disaster Recovery ◽  
Cloud Storage ◽  
Layer Structure ◽  
Structure Model ◽  
Reading And Writing ◽  
Cloud Data ◽  
Storage Technology ◽  
Model Cloud ◽  
Data Reading

Cloud storage is a promising market. In this paper, cloud storage technology and cloud data read-write technology is researched. Cloud storage has a four-layer structure model. Cloud storage uses disaster recovery and backup technology to improve the availability and reliability of the system. The request of data read-write in cloud storage is a temporary URL, which is constructed according to the algorithm. Send read-write request through push sequentially, and write by transfer between the primary chunks with the copies. The efficiency of cloud storage depends on the number of serves and clients. In order to improve the efficiency of data reading and writing, there is proposed three envisaged.

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