Medium change based image estimation from application of inverse algorithms to coda wave measurements

2018 ◽  
Author(s):  
Hanyu Zhan ◽  
Hanwan Jiang ◽  
Ruinian Jiang
Keyword(s):  
Coda Wave ◽  
Image Estimation ◽  
Wave Measurements ◽  
Medium Change

scholarly journals Comparative Study of Three-Dimensional Stress and Crack Imaging in Concrete by Application of Inverse Algorithms to Coda Wave Measurements

Sensors ◽  
2020 ◽  
Vol 20 (17) ◽  
pp. 4899
Author(s):  
Hanwan Jiang ◽  
Hanyu Zhan ◽  
Ziwei Ma ◽  
Ruinian Jiang
Keyword(s):  
Concrete Beam ◽  
Three Dimensional ◽  
Real Life ◽  
Reinforced Concrete Beam ◽  
Great Sensitivity ◽  
Coda Wave ◽  
Wave Measurements ◽  
Stress Changes ◽  
Real Life Situation ◽  
Load Tests

The intrinsic heterogeneity property of concrete causes strong multiple scatterings during wave propagation, forming coda wave that follows very complex trajectories. As a superposition of multiply scattered waves, coda wave shows great sensitivity to subtle changes, but meanwhile lose spatial resolution. To make use of its sensitivity and turn the limitation into advantage, this paper presents an experimental study of three-dimensionally imaging local changes in concrete by application of inverse algorithms to coda wave measurements. Load tests are performed on a large reinforced concrete beam that contains multiple pre-existing millimeter-scale cracks in order to match real life situation. The joint effects of cracks and stresses on coda waves have been monitored using a network of fixed transducers placed at the surface. The global waveform decorrelations and velocity variations are firstly quantified through coda wave interferometry technique. Subsequently, two inverse algorithms are independently applied to map the densities of changes at each localized position. Using this methodology, the stress changes and subtle cracks in the concrete beam are detected and imaged for both temporal and spatial domains.

scholarly journals Source Separation and Medium Change of Contained Chemical Explosions from Coda Wave Interferometry

2021 ◽  
Vol 1 (1) ◽  
pp. 3-10
Author(s):  
Sean R. Ford ◽  
William R. Walter
Keyword(s):  
Coda Wave ◽  
Velocity Perturbation ◽  
Spherical Region ◽  
Seismic Coda ◽  
Chemical Explosions ◽  
Medium Change ◽  
Physics Experiment ◽  
Coda Wave Interferometry ◽  
Source Physics ◽  
Chemical Explosion

Abstract Differences in the seismic coda of neighboring events can be used to investigate source location offsets and medium change with coda wave interferometry (CWI). We employ CWI to infer the known relative location between two chemical explosions in Phase I of the Source Physics Experiment (SPE). The inferred displacement between the first, SPE-1, and second, SPE-2, chemical explosion is between 6 and 18 m, with an expectation of 9.2 m, where the known separation is close to 9.4 m. We also employ CWI to find any velocity perturbation due to damage from SPE-2, by comparing its coda with the collocated third SPE chemical explosion, SPE-3. We find that damage due to SPE-2 must be confined to a spherical region with radius less than 10 m and velocity perturbation less than 25%.

Density Wave Measurements in a Rectangular Clarifier

1983 ◽  
Vol 18 (1) ◽  
pp. 129-150 ◽  
Author(s):  
Mark K. Watson ◽  
R.R. Hudgins ◽  
P.L. Silveston
Keyword(s):  
Power Spectrum ◽  
Internal Wave ◽  
Internal Waves ◽  
Wave Motion ◽  
Wave Amplitude ◽  
Suspended Solids ◽  
Small Volume ◽  
Density Wave ◽  
Measure Concentration ◽  
Wave Measurements

Abstract Internal wave motion was studied in a laboratory rectangular, primary clarifier. A photo-extinction device was used as a turbidimeter to measure concentration fluctuations in a small volume within the clarifier as a function of time. The signal from this device was fed to a HP21MX minicomputer and the power spectrum plotted from data records lasting approximately 30 min. Results show large changes of wave amplitude as frequency increases. Two distinct regions occur: one with high amplitudes at frequencies below 0.03 Hz, the second with very small amplitudes appears for frequencies greater than 0.1 Hz. The former is associated with internal waves, the latter with flow-generated turbulence. Depth, velocity in the clarifier and inlet suspended solids influence wave amplitudes and the spectra. A variation with position or orientation of the probe was not detected. Contradictory results were found for the influence of flow contraction baffles on internal wave amplitude.

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