The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Vadim Backman - One of the best experts on this subject based on the ideXlab platform.
-
structural length scale sensitivities of reflectance measurements in continuous random media under the Born Approximation
Optics Letters, 2012Co-Authors: Andrew J Radosevich, Jeremy D Rogers, Vadim BackmanAbstract:Which range of structures contributes to light scattering in a continuous random media, such as biological tissue? In this Letter, we present a model to study the structural length-scale sensitivity of scattering in continuous random media under the Born Approximation. The scattering coefficient μs, backscattering coefficient μb, anisotropy factor g, and reduced scattering coefficient μs* as well as the shape of the spatial reflectance profile are calculated under this model. For media with a biologically relevant Henyey–Greenstein phase function with g∼0.93 at wavelength λ=633 nm, we report that μs* is sensitive to structural length-scales from 46.9 nm to 2.07 μm (i.e., λ/13 to 3λ), μb is sensitive from 26.7 to 320 nm (i.e., λ/24 to λ/2), and the spatial reflectance profile is sensitive from 30.8 nm to 2.71 μm (i.e., λ/21 to 4λ).
-
modeling spectral dependence of reduced scattering coefficient for continuous random media with the Born Approximation
IEEE Transactions on Biomedical Engineering, 2010Co-Authors: Jeremy D Rogers, Ilker R Capoglu, Valentina Stoyneva, Vladimir Turzhitsky, Vadim BackmanAbstract:The power law dependence of reduced scattering coefficient (μs′) on wavelength (λ) is derived for continuous random media using a three parameter model of index correlation function by applying the Born Approximation.
-
accuracy of the Born Approximation in calculating the scattering coefficient of biological continuous random media
Optics Letters, 2009Co-Authors: Ilker R Capoglu, Jeremy D Rogers, Allen Taflove, Vadim BackmanAbstract:A rigorous error analysis is presented for the scattering coefficient of biological random continuous media in the Born (or single-scattering) Approximation. The analysis is done in two dimensions (2-D) for simplicity of numerical computation. Scattering coefficients of various tissue-like random media are numerically calculated via statistical finite-difference-time-domain analysis. The results are then checked against analytical formulas for the scattering coefficient in the Born Approximation. The validity ranges for the correlation length and the refractive index fluctuation strength of the medium are clearly identified. These 2-D results show promise for future 3-D investigations.
-
nonscalar elastic light scattering from continuous random media in the Born Approximation
Optics Letters, 2009Co-Authors: Jeremy D Rogers, Ilker R Capoglu, Vadim BackmanAbstract:A three-parameter model based on the Whittle-Matern correlation family is used to describe continuous random refractive-index fluctuations. The differential scattering cross section is derived from the index correlation function using nonscalar scattering formulas within the Born Approximation. Parameters such as scattering coefficient, anisotropy factor, and spectral dependence are derived from the differential scattering cross section for this general class of functions.
-
tissue self affinity and polarized light scattering in the Born Approximation a new model for precancer detection
Physical Review Letters, 2006Co-Authors: Martin Hunter, Vadim Backman, Gabriel Popescu, Maxim Kalashnikov, Charles W Boone, Adam Wax, V Gopal, Kamran Badizadegan, Gary D Stoner, Michael S FeldAbstract:Light scattered from biological tissues can exhibit an inverse power law spectral component. We develop a model based on the Born Approximation and von Karman (self-affine) spatial correlation of submicron tissue refractive index to account for this. The model is applied to light scattering spectra obtained from excised esophagi of normal and carcinogen-treated rats. Power law exponents used to fit dysplastic tissue site spectra are significantly smaller than those from normal sites, indicating that changes in tissue self-affinity can serve as a potential biomarker for precancer.
Jeremy D Rogers - One of the best experts on this subject based on the ideXlab platform.
-
structural length scale sensitivities of reflectance measurements in continuous random media under the Born Approximation
Optics Letters, 2012Co-Authors: Andrew J Radosevich, Jeremy D Rogers, Vadim BackmanAbstract:Which range of structures contributes to light scattering in a continuous random media, such as biological tissue? In this Letter, we present a model to study the structural length-scale sensitivity of scattering in continuous random media under the Born Approximation. The scattering coefficient μs, backscattering coefficient μb, anisotropy factor g, and reduced scattering coefficient μs* as well as the shape of the spatial reflectance profile are calculated under this model. For media with a biologically relevant Henyey–Greenstein phase function with g∼0.93 at wavelength λ=633 nm, we report that μs* is sensitive to structural length-scales from 46.9 nm to 2.07 μm (i.e., λ/13 to 3λ), μb is sensitive from 26.7 to 320 nm (i.e., λ/24 to λ/2), and the spatial reflectance profile is sensitive from 30.8 nm to 2.71 μm (i.e., λ/21 to 4λ).
-
modeling spectral dependence of reduced scattering coefficient for continuous random media with the Born Approximation
IEEE Transactions on Biomedical Engineering, 2010Co-Authors: Jeremy D Rogers, Ilker R Capoglu, Valentina Stoyneva, Vladimir Turzhitsky, Vadim BackmanAbstract:The power law dependence of reduced scattering coefficient (μs′) on wavelength (λ) is derived for continuous random media using a three parameter model of index correlation function by applying the Born Approximation.
-
accuracy of the Born Approximation in calculating the scattering coefficient of biological continuous random media
Optics Letters, 2009Co-Authors: Ilker R Capoglu, Jeremy D Rogers, Allen Taflove, Vadim BackmanAbstract:A rigorous error analysis is presented for the scattering coefficient of biological random continuous media in the Born (or single-scattering) Approximation. The analysis is done in two dimensions (2-D) for simplicity of numerical computation. Scattering coefficients of various tissue-like random media are numerically calculated via statistical finite-difference-time-domain analysis. The results are then checked against analytical formulas for the scattering coefficient in the Born Approximation. The validity ranges for the correlation length and the refractive index fluctuation strength of the medium are clearly identified. These 2-D results show promise for future 3-D investigations.
-
nonscalar elastic light scattering from continuous random media in the Born Approximation
Optics Letters, 2009Co-Authors: Jeremy D Rogers, Ilker R Capoglu, Vadim BackmanAbstract:A three-parameter model based on the Whittle-Matern correlation family is used to describe continuous random refractive-index fluctuations. The differential scattering cross section is derived from the index correlation function using nonscalar scattering formulas within the Born Approximation. Parameters such as scattering coefficient, anisotropy factor, and spectral dependence are derived from the differential scattering cross section for this general class of functions.
Carlos Torresverdin - One of the best experts on this subject based on the ideXlab platform.
-
efficient numerical simulation of axisymmetric electromagnetic induction measurements using a high order generalized extended Born Approximation
IEEE Transactions on Geoscience and Remote Sensing, 2006Co-Authors: Carlos TorresverdinAbstract:This paper develops a high-order generalized extended Born Approximation (Ho-GEBA) for the numerical simulation of electromagnetic scattering due to rock formations that exhibit axial symmetry around a wellbore. The resulting equations of Ho-GEBA are solved with a numerical procedure that is as efficient as the extended Born Approximation (EBA). With the acceleration of a fast Fourier transform, the operation count is proportional to O(CN), where N is the total number of spatial discretization cells and CLtN is a constant that depends on the number of discretization cells in the radial direction. Ho-GEBA remains accurate in the near-source scattering region and accounts for multiple scattering in the presence of large conductivity contrasts and relatively large frequencies. Numerical exercises conclusively indicate that the accuracy of Ho-GEBA is superior to that of EBA and the first-order Born Approximation while maintaining the same level of algorithmic efficiency. These exercises are carried out on a variety of source-receiver configurations and frequencies typical of single-well borehole induction measurements
-
high order generalized extended Born Approximation for electromagnetic scattering
IEEE Transactions on Antennas and Propagation, 2006Co-Authors: Guozhong Gao, Carlos TorresverdinAbstract:Previous work on the subject of electromagnetic scattering has shown that the extended Born Approximation (EBA) is more accurate than the first-order Born Approximation with approximately the same operation count. However, the accuracy of the EBA degrades in cases when the source is very close to the scatterer, or when the electric field exhibits significant spatial variations within the scatterer. This paper introduces a generalized extended Born Approximation (GEBA) and its high-order variants (Ho-GEBA) to efficiently and accurately simulate electromagnetic scattering problems. We make use of a generalized series expansion of the internal electric field to construct high-order terms of the generalized extended Born Approximation (Ho-GEBA). A salient feature of the Ho-GEBA is its enhanced accuracy over the Born Approximation and the EBA, even when only the first-order term of the series expansion is considered in the Approximation. This behavior is not conditioned by either the source location or the spatial distribution of the internal electric field. A unique feature of the Ho-GEBA is that it can be used to simulate electromagnetic scattering due to electrically anisotropic media. Such a feature is not possible with Approximations of the internal electric field that are based on the behavior of the background electric field. Three-dimensional (3-D) models of electromagnetic scattering are used to benchmark the efficiency and accuracy of the Ho-GEBA, including comparisons against the first-order Born Approximation and the EBA.
-
rapid numerical simulation of axisymmetric single well induction data using the extended Born Approximation
Radio Science, 2001Co-Authors: Carlos Torresverdin, Tarek M HabashyAbstract:We derive an extended Born Approximation for electromagnetic scattering due to rock formations that exhibit axial symmetry around a well bore. An alternative formulation is also developed to improve the accuracy of the Approximation when scattering takes place in close prroximity with the source. The resulting equations are solved via a numerical procedure that is as efficient as the first-order Born Approximation but substantially more accurate. This conclusion follows from studies carried out on a variety of source-receiver configurations and frequencies typical of single-well induction measurements.
A J R Puckett - One of the best experts on this subject based on the ideXlab platform.
-
search for effects beyond the Born Approximation in polarization transfer observables in e p elastic scattering
Physical Review Letters, 2011Co-Authors: M Meziane, E Brash, R Gilman, M K Jones, W Luo, L Pentchev, C F Perdrisat, A J R PuckettAbstract:Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton electric to magnetic form factor ratio, $$G_{E}/G_{M}$$, obtained separately from cross section and polarization transfer measurements. One possible explanation for this difference is a two-photon-exchange (TPEX) contribution. In an effort to search for effects beyond the one-photon-exchange or Born Approximation, we report measurements of polarization transfer observables in the elastic $$H(\vec{e},e'\vec{p})$$ reaction for three different beam energies at a fixed squared momentum transfer $Q^2 = 2.5$ GeV$^2$, spanning a wide range of the virtual photon polarization parameter, $$\epsilon$$. From these measured polarization observables, we have obtained separately the ratio $R$, which equals $$\mu_p G_{E}/G_{M}$$ in the Born Approximation, and the longitudinal polarization transfer component $$P_\ell$$, with statistical and systematic uncertainties of $$\Delta R \approx \pm 0.01 \mbox{(stat)} \pm 0.013 \mbox{(syst)}$$ and $$\Delta P_\ell/P^{Born}_{\ell} \approx \pm 0.006 \mbox{(stat)}\pm 0.01 \mbox{(syst)}$$. The ratio $R$ is found to be independent of $$\epsilon$$ at the 1.5% level, while the $$\epsilon$$ dependence of $$P_\ell$$ shows an enhancement of $$(2.3 \pm 0.6) %$$ relative to the Born Approximation at large $$\epsilon$$.
-
search for effects beyond the Born Approximation in polarization transfer observables in e p elastic scattering
Physical Review Letters, 2011Co-Authors: M Meziane, R Gilman, M K Jones, W Luo, L Pentchev, C F Perdrisat, A J R Puckett, E J BrashAbstract:Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton electric to magnetic form factor ratio, $$G_{E}/G_{M}$$, obtained separately from cross section and polarization transfer measurements. One possible explanation for this difference is a two-photon-exchange (TPEX) contribution. In an effort to search for effects beyond the one-photon-exchange or Born Approximation, we report measurements of polarization transfer observables in the elastic $$H(\vec{e},e'\vec{p})$$ reaction for three different beam energies at a fixed squared momentum transfer $Q^2 = 2.5$ GeV$^2$, spanning a wide range of the virtual photon polarization parameter, $$\epsilon$$. From these measured polarization observables, we have obtained separately the ratio $R$, which equals $$\mu_p G_{E}/G_{M}$$ in the Born Approximation, and the longitudinal polarization transfer component $$P_\ell$$, with statistical and systematic uncertainties of $$\Delta R \approx \pm 0.01 \mbox{(stat)} \pm 0.013 \mbox{(syst)}$$ and $$\Delta P_\ell/P^{Born}_{\ell} \approx \pm 0.006 \mbox{(stat)}\pm 0.01 \mbox{(syst)}$$. The ratio $R$ is found to be independent of $$\epsilon$$ at the 1.5% level, while the $$\epsilon$$ dependence of $$P_\ell$$ shows an enhancement of $$(2.3 \pm 0.6) %$$ relative to the Born Approximation at large $$\epsilon$$.
Andrea Randazzo - One of the best experts on this subject based on the ideXlab platform.
-
electromagnetic subsurface prospecting by a multifocusing inexact newton method within the second order Born Approximation
Journal of The Optical Society of America A-optics Image Science and Vision, 2014Co-Authors: Marco Salucci, Matteo Pastorino, Andrea Randazzo, Giacomo Oliveri, Andrea MassaAbstract:In this paper the reconstruction of a shallow buried object is addressed by an electromagnetic inverse scattering method based on combining different imaging modalities. In particular, the proposed approach integrates the inexact Newton (IN) method with an iterative multiscaling approach. Moreover, the use of the second-order Born Approximation is exploited. A numerical validation is provided concerning the potentialities arising by combining the regularization capabilities of the IN method and the effectiveness of the multifocusing strategy to mitigate the nonlinearity and ill-posedness of the inversion problem. Comparisons with the standard “bare” approach in terms of accuracy, robustness, noise levels, and computational efficiency are also included.
-
imaging buried objects within the second order Born Approximation through a multiresolution regularized inexact newton method
International Symposium on Electromagnetic Theory, 2013Co-Authors: Marco Salucci, Andrea Randazzo, Davide Sartori, Nicola Anselmi, Giacomo Oliveri, Andrea MassaAbstract:The inspection of 2-D scatterers buried in a lossy half-space from field measurements is formulated within the framework of the second-order Born Approximation (SOBA) of the inverse scattering problem. An iterative multi-scaling approach (IMSA) is combined with a two-step inexact-Newton (IN) algorithm to solve the arising problem. A set of preliminary numerical results is presented to assess the features and potentialities of the considered approach also in comparison with state of the art IN-SOBA techniques.
-
application of an inexact newton method within the second order Born Approximation to buried objects
IEEE Geoscience and Remote Sensing Letters, 2007Co-Authors: G Bozza, Claudio Estatico, Matteo Pastorino, Andrea RandazzoAbstract:The imaging of buried objects is a challenging topic in electromagnetic research. In this letter, a method previously proposed for imaging of scatterers in free-space is extended to the case of objects buried in a lossy half-space. The proposed approach is based on the solution of the underlying inverse-scattering problem within the second-order Born Approximation by means of a two-step inexact-Newton algorithm. The capabilities and limitations of the method are evaluated by means of some numerical simulations. Furthermore, comparisons with the free-space approach are also reported
-
an inexact newton method for short range microwave imaging within the second order Born Approximation
IEEE Transactions on Geoscience and Remote Sensing, 2005Co-Authors: Claudio Estatico, Matteo Pastorino, Andrea RandazzoAbstract:A new approach to noninvasive inspection of dielectric targets at microwave frequencies is proposed. Cylindrical dielectric objects are reconstructed under the second-order Born Approximation. A multi-illumination configuration is considered. The continuous model is discretized by the moment method and an efficient inexact-Newton method is applied. The dielectric profile is iteratively reconstructed starting from the measured scattered data, which are related to the unknown target through the inverse scattering equations written in a variational setting. Several numerical results are reported, which are aimed at assessing the capabilities of the approach in dealing with the nonlinear ill-posed inverse problem associated to the short-range microwave imaging. Single, multilayer, and separate cylinders are reconstructed in noiseless and noisy environments.