Vibration Reduction Index of a T-Junction With a Flexible Interlayer

This paper describes the procedure followed to evaluate the vibration reduction index for T-junctions with inserted flexible elements and proposes new equations to complement the standard EN 12354-1:2000. The experiment described in this work is based on a 1:3 scale model of a T-junction with a flexible interlayer. It was used to obtain a significant reduction in the cost of the configurations under study. We chose to carry out vibration measurements by near-field acoustic holography (NAH) in order to avoid the risk of accelerometer interference. Flanking transmission was determined for different elastic layers with the objective of quantifying the effect of the flexible interlayer and to compare the results obtained with predictive formulas. The results enabled us to propose new equations to complement EN 12354-1:2000 for the reliable prediction of the apparent sound reduction index. The uncertainty associated with the different average velocity levels is determined according to the Guide for the Expression of Uncertainty of Measurement (GUM).

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On the Uncertainty of the EN12354-1: Estimate of the Flanking Sound Reduction Index Due to the Uncertainty of the Input Data

Building Acoustics ◽

10.1260/135101009789877059 ◽

2009 ◽

Vol 16 (3) ◽

pp. 199-231 ◽

Cited By ~ 5

Author(s):

Jeffrey Mahn ◽

John Pearse

Keyword(s):

Monte Carlo ◽

Probability Density Function ◽

Monte Carlo Simulations ◽

Input Data ◽

Vibration Reduction ◽

Uncertainty In Measurement ◽

Sound Reduction ◽

Expression Of Uncertainty ◽

Lognormal Probability ◽

Reduction Index

Equations to calculate the uncertainty of the EN12354-1 estimate of the flanking sound reduction index due to the uncertainty of the input data are derived using the method of the ISO Guide to the Expression of Uncertainty in Measurement (GUM). The uncertainty equations have been validated using Monte Carlo simulations. It is shown that the magnitude of the uncertainty depends on the uncertainty of the resonant sound reduction indices of the elements, the uncertainty of the vibration reduction index and the uncertainty of the equivalent absorption lengths and areas of the elements. However, equations could not be derived to calculate the uncertainty of the EN12354 estimate of the apparent sound reduction index which has a lognormal probability density function and is therefore outside of the scope of the method of GUM. Monte Carlo simulations must be used to calculate the uncertainty of the apparent sound reduction index. It is recommended that guidance for calculating and declaring the uncertainty is included in future versions of EN12354, ISO10848 and ISO15712.

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Assessment of the sound reduction index of building elements by near field excitation through an array of loudspeakers and structural response measurements by laser Doppler vibrometry

Applied Acoustics ◽

10.1016/j.apacoust.2018.06.002 ◽

2018 ◽

Vol 140 ◽

pp. 225-235 ◽

Cited By ~ 3

Author(s):

N.B. Roozen ◽

Q. Leclère ◽

D. Urbán ◽

L. Kritly ◽

C. Glorieux

Keyword(s):

Near Field ◽

Structural Response ◽

Laser Doppler ◽

Laser Doppler Vibrometry ◽

Field Excitation ◽

Sound Reduction ◽

Reduction Index ◽

Building Elements

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Prediction of sound reduction index of plenum window by the surface impedance approach

Applied Acoustics ◽

10.1016/j.apacoust.2020.107851 ◽

2021 ◽

Vol 175 ◽

pp. 107851

Author(s):

Liangfen Du ◽

Siu-Kit Lau ◽

Siew Eang Lee

Keyword(s):

Surface Impedance ◽

Sound Reduction ◽

Reduction Index

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Demonstration of an integrated nanophotonic chip-scale alkali vapor magnetometer using inverse design

Light Science & Applications ◽

10.1038/s41377-021-00499-5 ◽

2021 ◽

Vol 10 (1) ◽

Author(s):

Yoel Sebbag ◽

Eliran Talker ◽

Alex Naiman ◽

Yefim Barash ◽

Uriel Levy

Keyword(s):

Spatial Resolution ◽

Near Field ◽

Computer Assisted ◽

Experimental Characterization ◽

Optical Isolation ◽

New Concepts ◽

On Chip ◽

The Cost ◽

Micrometer Scale

AbstractRecently, there has been growing interest in the miniaturization and integration of atomic-based quantum technologies. In addition to the obvious advantages brought by such integration in facilitating mass production, reducing the footprint, and reducing the cost, the flexibility offered by on-chip integration enables the development of new concepts and capabilities. In particular, recent advanced techniques based on computer-assisted optimization algorithms enable the development of newly engineered photonic structures with unconventional functionalities. Taking this concept further, we hereby demonstrate the design, fabrication, and experimental characterization of an integrated nanophotonic-atomic chip magnetometer based on alkali vapor with a micrometer-scale spatial resolution and a magnetic sensitivity of 700 pT/√Hz. The presented platform paves the way for future applications using integrated photonic–atomic chips, including high-spatial-resolution magnetometry, near-field vectorial imaging, magnetically induced switching, and optical isolation.

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AMPLITUDE-PHASE DISTRIBUTION MEASUREMENT PLANE DIMENSIONS INFLUENCE ON THE HOLOGRAPHIC METHOD ANTENNA ARRAY RADIATION PATTERN RECONSTRUCTION ERRORS

Doklady BGUIR ◽

10.35596/1729-7648-2020-18-1-5-13 ◽

2020 ◽

pp. 5-13

Author(s):

O. A. Yurtsev ◽

R. Ch. Shimanouski

Keyword(s):

Antenna Array ◽

Radiation Pattern ◽

Phase Distribution ◽

Near Field ◽

Amplitude Distribution ◽

Holographic Method ◽

Longitudinal Zone ◽

Measurement Plane ◽

Measurement Surface ◽

The Cost

The article explores the holographic method of measuring the antenna pattern. A flat antenna array is used as the antenna under test, and a planar rectangular surface is used as the surface on which the amplitudephase distribution in the near field is measured. Using the example of a flat antenna array, we consider the influence of the size of the measurement surface of the amplitude-phase distribution of the field in a plane orthogonal to the reconstruction plane of the radiation pattern. Antenna emitters are excited with a combined amplitude distribution and linear phase distribution. The field in the longitudinal zone of the lattice is determined using the Kirchhoff integral. The reconstructed radiation patterns are estimated using the amplitude-phase distribution over the entire measurement plane in comparison with the array radiation pattern in the far zone. A numerical analysis of the influence on the errors in determining the parameters of the lattice radiation pattern using the holographic method is also carried out: the number of columns of the amplitude-phase distribution on the measurement plane, the position of this plane in three coordinates relative to the plane of the aperture of the lattice. It is shown that if the spacing of the points of measurement of the amplitude-phase distribution and the pitch of the lattice are equal, to restore the radiation pattern using the holographic method, it is sufficient to use one column of the amplitude-phase distribution on the measurement plane. This greatly simplifies and reduces the cost of the measurement process and the necessary equipment. Examples of determining errors in measuring the parameters of the antenna array when shifting the plane of measurement of the amplitude-phase distribution in three coordinates are given.

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Dual-solver hybrid computational approaches for design and analysis of vertical lift vehicles

The Aeronautical Journal ◽

10.1017/aer.2021.108 ◽

2021 ◽

pp. 1-22

Author(s):

M.J. Smith ◽

A. Moushegian

Keyword(s):

Hybrid Methods ◽

Near Field ◽

Cost Effective ◽

Navier Stokes ◽

Computational Approaches ◽

Turbulent Environments ◽

Vertical Lift ◽

Reynolds Averaged Navier Stokes ◽

The Cost

Abstract The cost of Reynolds-Averaged Navier-Stokes simulations can be restrictive to implement in aeromechanics design and analysis of vertical lift configurations given the cost to resolve the flow on a mesh sufficient to provide accurate aerodynamic and structural loads. Dual-solver hybrid methods have been developed that resolve the configuration and the near field with the Reynolds-Averaged Navier-Stokes solvers, while the wake is resolved with vorticity-preserving methods that are more cost-effective. These dual-solver approaches can be integrated into an organisation’s workflow to bridge the gap between lower-fidelity methods and the expensive Reynolds-Averaged Navier-Stokes when there are complex physics present. This paper provides an overview of different dual-solver hybrid methods, coupling approaches, and future efforts to expand their capabilities in the areas of novel configurations and operations in constrained and turbulent environments.

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