A Model Updating Technique Based on the Constitutive Relation Error for In Situ Identification of Admittance Coefficient of Sound Absorbing Materials

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Aurélie Progneaux ◽  
Philippe Bouillard ◽  
Arnaud Deraemaeker
Keyword(s):  
Constitutive Relation ◽  
Model Updating ◽  
Test Case ◽  
Important Place ◽  
Acoustical Properties ◽  
Absorbing Materials ◽  
Absorbing Material ◽  
Constitutive Relation Error ◽  
Faulty Sensors

The development of new absorbing materials and the description of their acoustical properties take an important place in the current acoustical researches. This paper focuses on the identification of the admittance coefficient of sound absorbing material from in situ measurements, using the constitutive relation error (CRE)-based updating technique. This technique consists of a two-stage approach, allowing to regularize the inverse problem. Moreover, the technique allows the detection of faulty sensors and therefore the correction of the erroneous measurements before the updating process. The technique is developed, in a first part of this paper, for acoustical problems with generalized boundary conditions, and illustrated, in a second part, on a numerical and a physical two-dimensional (2D) test case.

scholarly journals THE EFFECT OF LOCATION OF SOUND-ABSORBING MATERIALS IN CALCULATING THE REVERBERATION TIME OF THE HALL BY DIFFERENT FORMULAS

2003 ◽  
Vol 9 (2) ◽  
pp. 83-87 ◽  
Author(s):  
Vytautas J. Stauskis
Keyword(s):  
Absorption Coefficient ◽  
Fold Increase ◽  
Acoustical Properties ◽  
Length Difference ◽  
Absorbing Materials ◽  
Absorbing Material ◽  
Insignificant Difference ◽  
The Difference ◽  
Lateral Walls ◽  
Made In

Earlier formulas used for calculating the echoing length in a hall did not make allowance for the location of sound-absorbing materials and the shape of the hall. Fitzroy in 1959 and Neubauer in 1999 tried to take these factors into account. The echoing length calculations were made in a 1018 m3 hall where sound-absorbing materials were placed on the floor and the lateral walls. Formulas produced by 6 authors were used for calculations. As the echoing length is calculated by Fitzroy's and Neubauer's formulas, with the sound-absorbing materials of different acoustical properties placed on various planes of the hall, large differences in values are obtained compared with the calculations based on Eyring's formula. When a half of the floor area is covered with a sound-absorbing material, the increase of its absorption ratio results in the increase of the difference in echoing lengths calculated by Fitzroys' and Neubauer's formulas. When only the lateral walls are covered with sound-absorbing material, the increase of their absorption coefficient from 0,1 to 0,6 results in a 3 s (or three-fold) increase in the echoing length difference when calculated by Fitzroy's formula and in a 2 s (or two-fold) increase when calculated by Eyring's formula. Calculation by other formulas gives an insignificant difference of ∼ 0,5 s. As Fitzroy's and Neubauer's formulas are used, the difference becomes more significant: the larger the average hall absorption coefficient, the larger the difference.

scholarly journals Preparation and properties of CF–Fe3O4–BN composite electromagnetic wave-absorbing materials

RSC Advances ◽  
2020 ◽  
Vol 10 (19) ◽  
pp. 11121-11131 ◽  
Author(s):  
Wei Ye ◽  
Qilong Sun ◽  
Xiaoyun Long ◽  
Yingying Cai
Keyword(s):  
Electromagnetic Wave ◽  
Carbon Fiber ◽  
Boron Nitride ◽  
Absorbing Materials ◽  
Absorbing Material

A three-layered electromagnetic (EM) wave-absorbing material was prepared by depositing a Fe3O4 and boron nitride (BN) coating onto the surface of a carbon fiber (CF) by in situ hybridization.

In-situ testing and model updating of a long-span cable-stayed railway bridge with hybrid girders subjected to a running train

2022 ◽  
Vol 253 ◽  
pp. 113823
Author(s):  
Hongye Gou ◽  
Tianqi Zhao ◽  
Shiqiang Qin ◽  
Xiaogang Zheng ◽  
Alessio Pipinato ◽  
...  
Keyword(s):  
Model Updating ◽  
Railway Bridge ◽  
In Situ Testing ◽  
Long Span

Characterization and Design of Honeycomb Absorbing Materials

2019 ◽  
Vol 294 ◽  
pp. 51-56
Author(s):  
Hui Min Sun ◽  
Le Chen ◽  
Zhao Zhan Gu
Keyword(s):  
Double Layer ◽  
Low Frequency ◽  
Single Layer ◽  
Electromagnetic Parameters ◽  
Honeycomb Sandwich ◽  
Absorbing Materials ◽  
Absorbing Material ◽  
The Difference ◽  
Free Space Method ◽  
Honeycomb Sandwich Structure

Honeycomb absorbing materials are anisotropic structural materials. Depending on the size of honeycomb lattices, the absorbent content of the impregnated layer is different, the thickness of the impregnated layer is different, and the absorbing function of the impregnated honeycomb absorbing materials is also different. For the characterization of electromagnetic parameters of honeycomb absorbing materials, this paper adopts free space method for testing, uses CST software for modeling, and inverts the electromagnetic parameters of honeycomb absorbing structures. The absorbing performance of single-layer and double-layer honeycomb sandwich structures was simulated by RAM Optimizer software. The research shows that the height of the single-layer honeycomb absorbing material is 22mm. When the absorber content is 65%, 75% and 85% respectively, the harmonic peak moves slightly to the low frequency electromagnetic wave with the increase of the absorber content, but the absorbing strength decreases with the increase of the absorber content. For the double-layer honeycomb sandwich structure, the difference of absorber content in the upper and lower honeycomb absorbing materials is smaller, and the absorbing performance is stronger. When the thickness of the wave-transparent panel is thinner, the harmonic peak of the absorbing curve moves slightly to the high frequency.

EXCAVATION OF AN OBSIDIAN CRAFT WORKSHOP AT TEOTIHUACAN, MEXICO

2019 ◽  
Vol 30 (1) ◽  
pp. 163-179 ◽  
Author(s):  
Kenneth G. Hirth ◽  
David M. Carballo ◽  
Mark Dennison ◽  
Sean Carr ◽  
Sarah Imfeld ◽  
...  
Keyword(s):  
Large Scale ◽  
Lithic Technology ◽  
Craft Production ◽  
Classic Period ◽  
Original Research ◽  
Test Case ◽  
Single Test ◽  
Production Areas ◽  
Teotihuacan Mexico

AbstractThe original research by the Teotihuacan Mapping Project (TMP) identified a large number of obsidian workshops within Teotihuacan based on surface concentrations of production debris. Clark (1986b) questioned the validity of these identifications and called for subsurface excavation to confirm the presence of in situ workshop locales. This article summarizes the results from the excavation of one of the obsidian workshops identified in the Tlajinga district of Teotihuacan at Compound 17:S3E1 (Compound 17). We describe the excavations, discuss the lithic technology, and examine the subsurface contexts in terms of what they tell us about in situ obsidian craft activity. Excavations confirm that Compound 17 was a locus of large-scale obsidian craft production during the Classic period. While only a single test case, these results suggest that surface remains at Teotihuacan can be a useful guide in identifying craft production areas when they are confirmed through subsurface testing.

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