An Efficient Neumann Series–Based Algorithm for Thermoacoustic and Photoacoustic Tomography with Variable Sound Speed

2011 ◽  
Vol 4 (3) ◽  
pp. 850-883 ◽  
Author(s):  
Jianliang Qian ◽  
Plamen Stefanov ◽  
Gunther Uhlmann ◽  
Hongkai Zhao
Keyword(s):  
Sound Speed ◽  
Neumann Series ◽  
Photoacoustic Tomography

scholarly journals A direct method for photoacoustic tomography with inhomogeneous sound speed

2016 ◽  
Vol 32 (4) ◽  
pp. 045005 ◽  
Author(s):  
Zakaria Belhachmi ◽  
Thomas Glatz ◽  
Otmar Scherzer
Keyword(s):  
Sound Speed ◽  
Direct Method ◽  
Photoacoustic Tomography ◽  
A Direct Method

scholarly journals Full Field Inversion in Photoacoustic Tomography with Variable Sound Speed

2019 ◽  
Vol 9 (8) ◽  
pp. 1563 ◽  
Author(s):  
Gerhard Zangerl ◽  
Markus Haltmeier ◽  
Linh V. Nguyen ◽  
Robert Nuster
Keyword(s):  
Pressure Distribution ◽  
Speed Of Sound ◽  
Sound Speed ◽  
Photoacoustic Tomography ◽  
Reconstruction Method ◽  
Inversion Problem ◽  
Final Time ◽  
Full Field ◽  
Field Detection ◽  
Wave Inversion

To accelerate photoacoustic data acquisition, in [R. Nuster, G. Zangerl, M. Haltmeier, G. Paltauf (2010). Full field detection in photoacoustic tomography. Optics express, 18(6), 6288–6299] a novel measurement and reconstruction approach has been proposed, where the measured data consist of projections of the full 3D acoustic pressure distribution at a certain time instant T. Existing reconstruction algorithms for this kind of setup assume a constant speed of sound. This assumption is not always met in practice and thus can lead to erroneous reconstructions. In this paper, we present a two-step reconstruction method for full field detection photoacoustic tomography that takes variable speed of sound into account. In the first step, by applying the inverse Radon transform, the pressure distribution at the measurement time is reconstructed point-wise from the projection data. In the second step, a final time wave inversion problem is solved where the initial pressure distribution is recovered from the known pressure distribution at time T. We derive an iterative solution approach for the final time wave inversion problem and compute the required adjoint operator. Moreover, as the main result of this paper, we derive its uniqueness and stability. Our numerical results demonstrate that the proposed reconstruction scheme is fast and stable, and that ignoring sound speed variations significantly degrades the reconstruction.

Effect of Nada Yoga on Hypertension & Anxiety Level

GIS Business ◽  
2019 ◽  
Vol 14 (6) ◽  
pp. 1-16
Author(s):  
Naveen Kumar ◽  
Kuldeep singh
Keyword(s):  
Sound Speed ◽  
Anxiety Level ◽  
Hatha Yoga ◽  
Significant Difference ◽  
The Subject ◽  
Level Of Significance

In Nada yoga the sound speed of an object vibrates (as well as its size, however infinitesimal) contributes to its particular sound. Different tone and frequencies contains the subject of meditation in Nada Yoga, which also takes into consideration the musical intervals used in music and in the musical recitation of mantras, is brought together with meditation techniques and certain Hatha Yoga practices that are conducive to sonic exploration. Recently a study conducted on anxiety and hypertension level in Raigarh entitled as “The effect of Nada Yoga on Hypertension and anxiety level”.  The outcome of the study shows that Nada Yoga significantly reduces Anxiety as well as Hypertension. Results founds were surprisingly shows a significant difference between the two means, at .01 level of significance. It shows how Nada Yoga can effectively help to reduce anxiety and hypertension as well as many improves in health also.

ANALYSIS OF SOUND SPEED IN LONGITUDINAL DIRECTION AT REFERENCE MOISTURE CONTENT (w = 12 %) IN SAWMILL ASSORTMENTS (FAGUS SYLVATICA, L.)

Akustika ◽  
2020 ◽  
pp. 45-50
Author(s):  
Alena Rohanová
Keyword(s):  
Moisture Content ◽  
Modulus Of Elasticity ◽  
Dynamic Modulus ◽  
Sound Speed ◽  
Longitudinal Direction ◽  
Structural Timber ◽  
Sound Speeds ◽  
Dynamic Modulus Of Elasticity ◽  
Round Timber

This paper explores the analysis of sound speeds in the longitudinal direction and their reduction to the reference moisture content w = 12 %. The sound speed cw was determined with Sylvatest Duo device. Moisture content of beech sawmill assortments (round timber: N = 16, logs: N = 2 × 16, structural boards: N = 54) in the range of 12 – 72 % was measured. For the analysis purposes, the sound speed was converted to reference conditions (c12, uref = 12%). A second-degree polynomial (parabola) with a regression equation of the form: c// = 5649 - 27,371 × w + 0.0735 × w2 was used to convert cw to c12, and correction of measured and calculated values was used as well. The sound speeds c12 in sawmill assortments (c12,round, c12,log, c12,board) were evaluated by linear dependences. Dependence was not confirmed for c12,round and c12,board1 (r = 0.168), in contrast for c12,round and c12,log2 the dependence is statistically very significant (r = 0.634). The results of testing showed that the most suitable procedure for predicting quality of structural timber is the first step round timber – log2, the second step: log2 - board2. More exact results of the construction boards were obtained from log2 than from log1. The sound speed is used in the calculation of dynamic modulus of elasticity (Edyn). EN 408 mentions the possibility of using dynamic modulus of elasticity as an alternative method in predicting the quality of structural timber.

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