An autofocus method to reduce acoustic inhomogeneity in microwave-induced thermo-acoustic tomography based on basis pursuit

2021 ◽  
Vol 119 (2) ◽  
pp. 023702
Author(s):  
Haoyang Yu ◽  
Yiming Lv ◽  
Zhiqin Zhao ◽  
Zaiping Nie ◽  
Qinghuo Liu
Keyword(s):  
Acoustic Tomography ◽  
Basis Pursuit

MAPPING TIDAL CURRENTS AND RESIDUAL CURRENTS BY USE OF COASTAL ACOUSTIC TOMOGRAPHY

2017 ◽  
Author(s):  
Xiao-Hua Zhu ◽  
Xiao-Hua Zhu ◽  
Ze-Nan Zhu ◽  
Ze-Nan Zhu ◽  
Xinyu Guo ◽  
...  
Keyword(s):  
Shallow Water ◽  
Shallow Water Equations ◽  
Mean Amplitude ◽  
Momentum Equation ◽  
Tidal Currents ◽  
Acoustic Tomography ◽  
Mean Values ◽  
Residual Currents ◽  
Water Depths ◽  
Deep Area

A coastal acoustic tomography (CAT) experiment for mapping the tidal currents in the Zhitouyang Bay was successfully carried out with seven acoustic stations during July 12 to 13, 2009. The horizontal distributions of tidal current in the tomography domain are calculated by the inverse analysis in which the travel time differences for sound traveling reciprocally are used as data. Spatial mean amplitude ratios M2 : M4 : M6 are 1.00 : 0.15 : 0.11. The shallow-water equations are used to analyze the generation mechanisms of M4 and M6. In the deep area, velocity amplitudes of M4 measured by CAT agree well with those of M4 predicted by the advection terms in the shallow water equations, indicating that M4 in the deep area where water depths are larger than 60 m is predominantly generated by the advection terms. M6 measured by CAT and M6 predicted by the nonlinear quadratic bottom friction terms agree well in the area where water depths are less than 20 m, indicating that friction mechanisms are predominant for generating M6 in the shallow area. Dynamic analysis of the residual currents using the tidally averaged momentum equation shows that spatial mean values of the horizontal pressure gradient due to residual sea level and of the advection of residual currents together contribute about 75% of the spatial mean values of the advection by the tidal currents, indicating that residual currents in this bay are induced mainly by the nonlinear effects of tidal currents.

Acoustic Tomography Applied to Water Flow in Unsaturated Soils

2004 ◽  
Vol 3 (1) ◽  
pp. 288
Author(s):  
Andreas Blum ◽  
Ivo Flammer ◽  
Thomas Friedli ◽  
Peter Germann
Keyword(s):  
Water Flow ◽  
Unsaturated Soils ◽  
Acoustic Tomography

Using acoustic tomography to monitor deep ocean currents in the eastern Gulf of Mexico

OCEANS 2009 ◽  
2009 ◽  
Author(s):  
D. A. Rosenfield ◽  
J. W. Caruthers ◽  
D. A. Nechaev ◽  
G. E. Ioup ◽  
J. W. Ioup ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Deep Ocean ◽  
Ocean Currents ◽  
Acoustic Tomography ◽  
Eastern Gulf Of Mexico ◽  
Deep Ocean Currents

scholarly journals ECG Signal Denoising and Reconstruction Based on Basis Pursuit

2021 ◽  
Vol 11 (4) ◽  
pp. 1591
Author(s):  
Ruixia Liu ◽  
Minglei Shu ◽  
Changfang Chen
Keyword(s):  
Signal To Noise Ratio ◽  
Heart Diseases ◽  
Gaussian White Noise ◽  
Basis Pursuit ◽  
Signal Denoising ◽  
Ecg Signal ◽  
Penalty Term ◽  
Ecg Signals ◽  
Alternating Direction ◽  
Low Pass

The electrocardiogram (ECG) is widely used for the diagnosis of heart diseases. However, ECG signals are easily contaminated by different noises. This paper presents efficient denoising and compressed sensing (CS) schemes for ECG signals based on basis pursuit (BP). In the process of signal denoising and reconstruction, the low-pass filtering method and alternating direction method of multipliers (ADMM) optimization algorithm are used. This method introduces dual variables, adds a secondary penalty term, and reduces constraint conditions through alternate optimization to optimize the original variable and the dual variable at the same time. This algorithm is able to remove both baseline wander and Gaussian white noise. The effectiveness of the algorithm is validated through the records of the MIT-BIH arrhythmia database. The simulations show that the proposed ADMM-based method performs better in ECG denoising. Furthermore, this algorithm keeps the details of the ECG signal in reconstruction and achieves higher signal-to-noise ratio (SNR) and smaller mean square error (MSE).

Basis Pursuit Anisotropic Inversion Based on the L₁-L₂-Norm Regularization

2021 ◽  
pp. 1-5
Author(s):  
Cong Luo ◽  
Jing Ba ◽  
Jose M. Carcione ◽  
Qiang Guo
Keyword(s):  
Basis Pursuit
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