Quantitative signal subspace imaging

2021 ◽  
Author(s):  
Pedro Gonzalez-Rodriguez ◽  
Arnold D Kim ◽  
Chrysoula Tsogka
Keyword(s):  
Quantitative Information ◽  
Signal Classification ◽  
Single Frequency ◽  
Relative Dielectric Permittivity ◽  
Imaging Method ◽  
Signal Subspace ◽  
Multiple Signal Classification ◽  
Extended Target ◽  
Resolution Analysis ◽  
Array Imaging

Abstract We develop and analyze a quantitative signal subspace imaging method for single-frequency array imaging. This method is an extension to MUSIC (multiple signal classification) which uses (i) the noise subspace to determine the location and support of targets, and (ii) the signal subspace to recover quantitative information about the targets. For point targets, we are able to recover the complex reflectivity and for an extended target under the Born approximation, we are able to recover a scalar quantity that is related to the product of the volume and relative dielectric permittivity of the target. Our resolution analysis for a point target demonstrates this method is capable of achieving exact recovery of the complex reflectivity at subwavelength resolution. Additionally, this resolution analysis shows that noise in the data effectively acts as a regularization to the imaging functional resulting in a method that is surprisingly more robust and effective with noise than without noise.

scholarly journals Bearing and Range Estimation Algorithm for Buried Object in Underwater Acoustics

2009 ◽  
Vol 2009 ◽  
pp. 1-4
Author(s):  
Dong Han ◽  
Caroline Fossati ◽  
Salah Bourennane ◽  
Zineb Saidi
Keyword(s):  
Underwater Acoustics ◽  
Classical Model ◽  
Acoustic Scattering ◽  
Estimation Algorithm ◽  
Signal Classification ◽  
Music Algorithm ◽  
Range Estimation ◽  
Multiple Signal Classification ◽  
Buried Objects ◽  
Buried Object

A new algorithm which associates (Multiple Signal Classification) MUSIC with acoustic scattering model for bearing and range estimation is proposed. This algorithm takes into account the reflection and the refraction of wave in the interface of water-sediment in underwater acoustics. A new directional vector, which contains the Direction-Of-Arrival (DOA) of objects and objects-sensors distances, is used in MUSIC algorithm instead of classical model. The influence of the depth of buried objects is discussed. Finally, the numerical results are given in the case of buried cylindrical shells.

Azimuthal multiple signal classification of dispersive and aliased surface waves recorded in 3D seismic acquisition

Geophysics ◽  
2021 ◽  
pp. 1-84
Author(s):  
Chunying Yang ◽  
Wenchuang Wang
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Body Waves ◽  
Signal Classification ◽  
Dispersion Pattern ◽  
Velocity Spectrum ◽  
Low Velocity ◽  
Surface Wave Dispersion ◽  
Multiple Signal Classification ◽  
Multiple Signal

Irregular acquisition geometry causes discontinuities in the appearance of surface wave events, and a large offset causes seismic records to appear as aliased surface waves. The conventional method of sampling data affects the accuracy of the dispersion spectrum and reduces the resolution of surface waves. At the same time, ”mode kissing” of the low-velocity layer and inhomogeneous scatterers requires a high-resolution method for calculating surface wave dispersion. This study tested the use of the multiple signal classification (MUSIC) algorithm in 3D multichannel and aliased wavefield separation. Azimuthal MUSIC is a useful method to estimate the phase velocity spectrum of aliased surface wave data, and it represent the dispersion spectra of low-velocity and inhomogeneous models. The results of this study demonstrate that mode-kissing affects dispersion imaging, and inhomogeneous scatterers change the direction of surface-wave propagation. Surface waves generated from the new propagation directions are also dispersive. The scattered surface wave has a new dispersion pattern different to that of the entire record. Diagonal loading was introduced to improve the robustness of azimuthal MUSIC, and numerical experiments demonstrate the resultant effectiveness of imaging aliasing surface waves. A phase-matched filter was applied to the results of azimuthal MUSIC, and phase iterations were unwrapped in a fast and stable manner. Aliased surface waves and body waves were separated during this process. Overall, field data demonstrate that azimuthal MUSIC and phase-matched filters can successfully separate aliased surface waves.

Abstract 116: Single-synapse Analysis Of Synaptic Remodeling In The Post-stroke Rodent Brain

Stroke ◽  
2012 ◽  
Vol 43 (suppl_1) ◽  
Author(s):  
Takeshi Hiu ◽  
Tonya M Bliss ◽  
Andrew Olson ◽  
Kristina D Micheva ◽  
Kevin Tran ◽  
...  
Keyword(s):  
Quantitative Information ◽  
Artery Occlusion ◽  
Cortical Lesion ◽  
Imaging Method ◽  
Functional Changes ◽  
Post Stroke ◽  
Array Tomography ◽  
Synaptic Markers ◽  
Gabaergic Synapses ◽  
Synaptic Circuitry

Introduction: The mechanisms of functional recovery after stroke are thought to be based on structural and functional changes in brain circuits adjacent to or connected with the stroke site. Deciphering these changes at the synaptic level is key to understanding the re-organization of the synaptic circuitry (i.e. the connectome). Quantitative information about such synapse rearrangements after stroke has been inadequate however, due to the technical limitations of available methodologies. Here we describe the use of array tomography, a new high-resolution proteomic imaging method, to determine the composition of glutamate and GABA synapses in the post-stroke mouse brain. Methods: A cortical lesion was induced in 12-week-old C57BL/6J male mice using the distal middle cerebral artery occlusion model of ischemia. Small tissue sections were removed from the peri-infarct cortex and ribbons of serial ultrathin (70 nm) sections were obtained using an ultramicrotome. Ribbons were stained with antibodies for the synaptic markers SynapsinI, VGlut1, VGlut2, PSD-95, GAD, VGAT. Analysis of the resultant staining pattern was used to identify subtypes of glutamatergic and GABAergic synapses. Results: At 1 week post-stroke, an increase in GABAergic synapses was observed in layer 5 of the peri-infarct cortex. A sub-analysis of the type of inhibitory interneurons (e.g. parvalbumin, somatostatin) expressing these synapses is pending. In addition, a trend for an increase of VGlut1+2 synapses was also observed. However, there were no detectable differences in total synapse number between stroke-injured and naïve animals, thus suggesting that VGluT2 expression may be upregulated in existing glutamatergic VGluT1 synapses after stroke. Further analysis will be extended to cortical layers 2/3 and 4. Conclusion: These results provide new information about the organization of synaptic circuitry and its plasticity after stroke. Furthermore, it demonstrates how array tomography enables a previously unobtainable level of volumetric visualization and quantification of synapses.

Experimental study of single vs. two-close-frequency heating impact on confinement and losses dynamics in ECR Ion Sources plasmas by means of X-ray spectroscopy and imaging

2021 ◽  
Author(s):  
David Mascali ◽  
Eugenia Naselli ◽  
Richard Racz ◽  
Sándor Biri ◽  
Luigi Celona ◽  
...  
Keyword(s):  
Ion Source ◽  
Single Frequency ◽  
Specific Power ◽  
Imaging Method ◽  
X Ray ◽  
Plasma Chamber ◽  
X Ray Imaging ◽  
Close Frequency ◽  
The Impact ◽  
Frequency Heating

Abstract We hereby report the study of confinement and electron losses dynamics in the magnetic trap of an Electron Cyclotron Resonance Ion Source (ECRIS) using a special multi-diagnostic setup that has allowed the simultaneous collection of plasma radio-self-emission and X-ray images in the range 500 eV - 20 keV. Argon plasmas were generated in single and two close frequency heating (TCFH) modes. Evidences of turbulent regimes have been found: for stable and unstable configurations quantitative characterizations of the plasma radio self-emission have been carried out, then compared with local measurement of plasma energy content evaluated by X-ray imaging. This imaging method is the only one able to clearly separate X-ray radiation coming from the plasma from the one coming from the plasma chamber walls. X-ray imaging has been also supported and benchmarked by volumetric spectroscopy performed via SDD and HPGe detectors. The obtained results in terms of X-ray intensity signal coming from the plasma core and from the plasma chamber walls have permitted to estimate the average ratio: plasma vs. walls (i.e., plasma losses) as a function of input RF power and pumping wave frequency, showing an evident increase (above the experimental errors) of the intensity in the 2-20 keV energy range due to the plasma losses in case of unstable plasma. This ratio was well correlated with the strength of the instabilities, in single frequency heating (SFH) operation mode; in TCFH mode, under specific power balance conditions and frequency combinations, it was possible to damp the instabilities, thus the plasma losses were observed to decrease and a general reconfiguration of the spatial plasma structure occurred (the X-ray emission was more concentrated in the center of the plasma chamber). In the end, a simplified model has been used to simulate electron heating under different pumping frequencies, discussing the impact of velocity anisotropy vs. the onset of the instability, and the mechanism of particles diffusion in the velocity space in stable and unstable regimes.

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