Modeling perturbation of scattering coefficients by using dominating noise subspace

The scattering phenomena of the fundamental antisymmetric Lamb wave mode with a horizontal notch enabling the partial energy transfer (PET) option is addressed in this paper. The PET functionality for a given waveguide is realized using the material interface. The energy scattering coefficients are identified using two methods, namely, a hybrid approach, which utilizes the finite element method (FEM) and the general orthogonality relation, and the semi-analytical approach, which combines the modal expansion technique with the orthogonal property of Lamb waves. Using the stress and displacement continuity conditions on the present (sub)waveguide interfaces, one can explicitly derive the global scattering matrix, which allows detailed analysis of the scattering process across the considered interfaces. Both methods are then adopted on a simple representation of a surface breaking crack in the form of a vertical notch, of which a certain section enables not only the reflection of the incident energy, but also its nonzero transfer. The presented results show very good conformity between both utilized approaches, thus leading to further development of an alternative technique.

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Sensitivity Analysis of Bistatic Scattering for Soil Moisture Retrieval

Remote Sensing ◽

10.3390/rs13020188 ◽

2021 ◽

Vol 13 (2) ◽

pp. 188

Author(s):

Tingting Li ◽

Irena Hajnsek ◽

Kun-Shan Chen

Keyword(s):

Sensitivity Analysis ◽

Soil Moisture ◽

Quality Index ◽

High Sensitivity ◽

Bare Soil ◽

Sensitivity Index ◽

Scattering Coefficients ◽

Observation Systems ◽

Bistatic Scattering ◽

Scattering Response

Soil moisture is one of the vital environmental variables in the land–atmosphere cycle. A study of the sensitivity analysis of bistatic scattering coefficients from bare soil at the Ku-band is presented, with the aim of deepening our understanding of the bistatic scattering features and exploring its potential in soil moisture retrieval. First, a well-established advanced integral method was adopted for simulating the bistatic scattering response of bare soil. Secondly, a sensitivity index and a normalized weight quality index were proposed to evaluate the effect of soil moisture on the bistatic scattering coefficient in terms of polarization and angular diversity, and the combinations thereof. The results of single-polarized VV data show that the regions with the maximum sensitivity and high quality index, simultaneously, to soil moisture are in the forward off-specular direction. However, due to the effect of surface roughness and surface autocorrelation function (ACF), the single-polarized data have some limitations for soil moisture inversion. By contrast, the results of two different polarization combinations, as well as a dual-angular simulation of one transmitter and two receivers, show significant estimation benefits. It can be seen that they all provide better ACF suppression capabilities, larger high-sensitivity area, and higher quality indices compared to single-polarized estimation. In addition, dual polarization or dual angular combined measurement provides the possibility of retrieving soil moisture in backward regions. These results are expected to contribute to the design of future bistatic observation systems.

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Waveform Optimization for Target Scattering Coefficients Estimation Under Detection and Peak-to-Average Power Ratio Constraints in Cognitive Radar

Circuits Systems and Signal Processing ◽

10.1007/s00034-015-0048-y ◽

2015 ◽

Vol 35 (1) ◽

pp. 163-184 ◽

Cited By ~ 10

Author(s):

Peng Chen ◽

Lenan Wu ◽

Chenhao Qi

Keyword(s):

Average Power ◽

Power Ratio ◽

Cognitive Radar ◽

Scattering Coefficients ◽

Waveform Optimization

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Optical and Physical Properties of Atmospheric Aerosols over the Bay of Bengal during ICARB

Journal of the Atmospheric Sciences ◽

10.1175/2009jas3032.1 ◽

2009 ◽

Vol 66 (9) ◽

pp. 2640-2658 ◽

Cited By ~ 34

Author(s):

Vijayakumar S. Nair ◽

K. Krishna Moorthy ◽

S. Suresh Babu ◽

S. K. Satheesh

Keyword(s):

Atmospheric Aerosols ◽

Bay Of Bengal ◽

Radiative Forcing ◽

Latitudinal Gradients ◽

Back Trajectory ◽

Western India ◽

Size Distributions ◽

Average Mass ◽

Scattering Coefficients ◽

Vertical Heterogeneity

Abstract Simultaneous and collocated measurements of total and hemispherical backscattering coefficients (σ and β, respectively) at three wavelengths, mass size distributions, and columnar spectral aerosol optical depth (AOD) were made onboard an extensive cruise experiment covering, for the first time, the entire Bay of Bengal (BoB) and northern Indian Ocean. The results are synthesized to understand the optical properties of aerosols in the marine atmospheric boundary layer and their dependence on the size distribution. The observations revealed distinct spatial and spectral variations of all the aerosol parameters over the BoB and the presence of strong latitudinal gradients. The size distributions varied spatially, with the majority of accumulation modes decreasing from north to south. The scattering coefficient decreased from very high values (resembling those reported for continental/urban locations) in the northern BoB to very low values seen over near-pristine environments in the southeastern BoB. The average mass scattering efficiency of BoB aerosols was found to be 2.66 ± 0.1 m2 g−1 at 550 nm. The spectral dependence of columnar AOD deviated significantly from that of the scattering coefficients in the northern BoB, implying vertical heterogeneity in the aerosol type in that region. However, a more homogeneous scenario was observed in the southern BoB. Simultaneous lidar and in situ measurements onboard an aircraft over the ocean revealed the presence of elevated aerosol layers of enhanced extinction at altitudes of 1 to 3 km with an offshore extent of a few hundred kilometers. Back-trajectory analyses showed these layers to be associated with advection from west Asia and western India. The large spatial variations and vertical heterogeneity in aerosol properties, revealed by the present study, need to be included in the regional radiative forcing over the Bay of Bengal.

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