elizabeth bleszynski - Academia.edu (original) (raw)

Papers by elizabeth bleszynski

2019 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2019

We consider new developments in the analytical evaluation of the near-field contribution to the m... more We consider new developments in the analytical evaluation of the near-field contribution to the matrix elements of the electric and magnetic field operators for planar conducting structures embedded in a layered medium. The method is applicable to Rao-Wilton-Glisson (RWG) basis functions supported on parallel interfaces in the layered medium. The method uses suitably constructed representations of the mixed potential formulation integral kernels in terms of two-dimensional Laplacian of auxiliary functions. Such Laplacian representations can be obtained for the asymptotic forms of the Green functions, which are being subtracted in order to regularize the behavior of the Sommerfeld-type integrals. Matrix elements resulting from these asymptotic forms, given originally as quadruple surface integrals with singular integrands, are then reduced to double contour integrals over the perimeters of the surface elements, involving simple closed-form non-singular auxiliary functions MMM. The new developments include: •Derivation of relations between elements of the asymptotic dyadic Green functions and the kernels of the mixed-potential representation of the fields. •Inclusion of additional terms introduced in [1], which improve convergence of the Sommerfeld integrals. These additional kernel components, related to half-line source potentials, were not included in our previous paper [1]; they constitute non-leading asymptotic contributions to the mixed-potential kernels mathcalKPhi\mathcal{K}^{\Phi}mathcalKPhi and mathcalKPsi\mathcal{K}^{\Psi}mathcalKPsi. •Construction of two additional auxiliary functions needed to represent the above-mentioned additional terms. The resultant auxiliary functions are expressed as integrals of the previously obtained [1] functions for the leading asymptotic kernel terms. •Construction of simplified analytical expressions for the matrix elements of the asymptotic parts of the pertinent dyadic Green functions. The asymptotic matrix elements, given in terms of quadruple surface integrals with singular integrands, are subsequently converted, by using suitably constructed Laplacian representations of the Green function, to double contour integrals over the perimeters of the surface elements, with simple, non-singular, smoothly varying integrands. The line integrals can be either evaluated analytically or by means of low order numerical quadratures. We discuss the relative merits of the direct numerical and analytic evaluation if these line integrals.

Physical Review Letters, 1984

The first complete measurement of the polarization transfer observables in the (p,p') reacti... more The first complete measurement of the polarization transfer observables in the (p,p') reaction at intermediate energies is reported. Data are presented for the reaction ¹²C(p,p') ¹²C to the 1/sup +/, T = 0 (12.71-MeV) and 1/sup +/, T = 1 (15.11-MeV) states at 500 MeV for laboratory scattering angles of 3.5°, 5.5°, 7.5°, and 12.0°. Linear combinations of these observables are shown to exhibit a very selective dependence on the isoscalar and isovector spin-dependent components of the nucleon interaction.

2016 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2016

This presentation describes an ongoing work by the authors on the solution of the time-dependent ... more This presentation describes an ongoing work by the authors on the solution of the time-dependent radiative transfer equation (RTE) and its application to propagation of short pulses through dilute scattering media (in particular, atmospheric obscurants, such as clouds, fog, or aerosols). It concentrates on exploitation of the “early-time diffusion” phenomenon arising for media in which scatterers are significantly larger than the pulse wavelength. The early time diffusion signature is a sharply rising structure in the time-resolved intensity, immediately following the ballistic (coherent) signal; its rise time is, typically, orders of magnitude shorter than that of the usual “late-time” diffusion and its decay with the propagation distance is significantly slower than for the coherent intensity contribution. Two subjects are discussed in more detail: (i) spectrum and eigensolutions of the RTE in its integral form and in a discretized integro-differential form; and (ii) a possible wa...

2021 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2021

We report new developments in the analytical evaluation of the near-field contribution to the mat... more We report new developments in the analytical evaluation of the near-field contribution to the matrix elements of the electric and magnetic field operators for planar conducting structures embedded in a layered medium. The method is applicable to Rao-Wilton-Glisson (RWG) basis functions supported on parallel interfaces in the medium. Our method is an extension of the approach described in [1] of representing a Green function as a two-dimensional Laplacian of an auxiliary function. Such Laplacian representations can be obtained for the asymptotic forms of the Green functions, which are being subtracted in order to regularize the behavior of the Sommerfeld-type integrals. Matrix elements resulting from these asymptotic forms, given originally as quadruple surface integrals with singular integrands, are then reduced to double contour integrals over the perimeters of the surface elements, involving simple closed-form non-singular auxiliary functions.

Physical Review Letters, 1981

The spin rotation parameter Q has been measured for p-40 Ca elastic scattering at 497 MeV for 0.0... more The spin rotation parameter Q has been measured for p-40 Ca elastic scattering at 497 MeV for 0.01<~-t<~0.15 (GeV/c) 2 with use of the new high-resolution spectrometer focalplane polarimeter. In conjunction with analyzing power and differential cross section, this ...

Results of a numerical simulation of an acoustic wave that propagates in a spherical object fille... more Results of a numerical simulation of an acoustic wave that propagates in a spherical object filled with insulating oil are presented in the paper. The sinusoidal acoustic wave is generated by an electro-acoustic transducer mounted in the middle of the object. Presented results depict acoustic pressure distribution within the transient and the steady states in a two-dimensional object. Furthermore, comparison of short time simulations adapting different mesh element size is presented.

Public Reporting burden for this collection of information is estimated to average 1 hour per res... more Public Reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comment regarding this burden estimates or any other aspect of this collection of

OMB NO. 0704-0188 Public Reporting burden for this collection of information is estimated to aver... more OMB NO. 0704-0188 Public Reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comment regarding this burden estimates or any other aspect of this collection of information,

Public Reporting burden for this collection of information is estimated to average I hour per res... more Public Reporting burden for this collection of information is estimated to average I hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comment regarding this burden estimates or any other aspect of this collection of

Journal of the Optical Society of America A

A short pulse propagating through a medium consisting of randomly distributed scatterers, large c... more A short pulse propagating through a medium consisting of randomly distributed scatterers, large compared to the wavelength, is expected to develop an "early-time diffusion" (ETD) behavior: a sharply rising structure in the time-resolved intensity, immediately following the coherent (ballistic) component. Since the ETD signal is attenuated at a rate substantially lower than the coherent wave, it offers a possibility of application in imaging through diverse scattering media, such as atmospheric obscurants (clouds, fog, mist), dust, aerosols, fuel sprays, or biological tissues. We describe here a two-way (reflection) imaging scenario utilizing the ETD phenomenon, and propose a specific image formation technique. We evaluate, by using the radiative transport theory, the resulting point-spread function (PSF) characterizing the image resolution. We show that the directly formed image has an angular resolution comparable to the width of the forward peak in the ensemble-averaged scattering cross section of the medium constituents. Subsequently, we show that, through the application of a regularized deconvolution technique enhancing higher Fourier components of the PSF, the resolution can be further significantly improved-at least by a factor of sim4{\sim}4sim4 for a medium layer of optical thickness of the order of 20. Such an improvement can be reached even if the noise level is a few orders of magnitude higher than the coherent (ballistic) image component.

2021 XXXIVth General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS)

We describe a concept of a system for detecting laser radiation in the presence of other (backgro... more We describe a concept of a system for detecting laser radiation in the presence of other (background) radiation sources. Unlike most existent laser-warning methods, which detect laser beams based on their intensity and monochromaticity, the proposed approach uses a high degree of coherence as the distinguishing property of laser radiation. Further, in contrast to previously considered coherence detection systems, based on amplitude interferometry (AI), we propose to utilize intensity interferometry (II), pioneered by Hanbury Brown and Twiss and originally applied to thermal radiation sources, but here generalized to coexisting high- and low-coherence radiation. In this contribution we concentrate on a possible application of the proposed system in detection of off-axis laser beam radiation scattered on atmospheric medium particles (water droplets and aerosols, especially dust). A particular design, which may operate in the visible and infrared regions, utilizes a small array of photodetectors (such as PIN photodiodes) and electronic correlator circuits identifying correlations in photocurrent fluctuations of neighboring detectors. It is shown that the normalized cross-correlation coefficients will be significant, even in the presence of a strong incoherent (e.g., solar radiation) background, provided the coherent radiation degeneracy parameter (number of photoelectrons generated by the detector during the coherence-time interval) exceeds the ratio of the background to signal intensities. This condition, which should not be difficult to achieve in realistic situations, ensures that the coherent signal is larger than the shot noise due to the background.

2018 International Workshop on Computing, Electromagnetics, and Machine Intelligence (CEMi)

We consider extensions and selected applications of the recently proposed method of evaluating Ga... more We consider extensions and selected applications of the recently proposed method of evaluating Galerkin matrix elements of electromagnetic volume and surface integral equations with the help of suitably constructed Laplacian-type representations of singular kernels (Green functions) in terms of non-singular auxiliary functions.

2018 International Conference on Electromagnetics in Advanced Applications (ICEAA)

The radiative transport theory predicts that a short pulse propagating through a random medium co... more The radiative transport theory predicts that a short pulse propagating through a random medium consisting of discrete scatterers of sizes large compared to the wavelength develops to develop an "early-time diffusion" (ETD) component: a sharply rising structure in the time-resolved intensity, immediately following the coherent (ballistic) signal, but attenuated at a rate substantially lower than the coherent attenuation. This phenomenon offers a possibility of application in imaging through obscuring (e.g., atmospheric) media. We describe here an imaging scenario utilizing the ETD signal, evaluate the resulting point-spread function characterizing the image resolution, and show how that resolution can be significantly improved by means of regularized deconvolution techniques.

2019 International Conference on Electromagnetics in Advanced Applications (ICEAA)

We consider the method of evaluating matrix elements of electromagnetic volume integral equations... more We consider the method of evaluating matrix elements of electromagnetic volume integral equations with the help of suitably constructed Laplacian-type representations of singular kernels (Green functions) appearing in electromagnetic volume and surface integral equations. The method consists of representing the singular kernels (Green functions) in terms of a generalized Laplacian operator acting on some auxiliary functions. Such a representations allow us, by using Gauss divergence theorem, to convert volumetric and surface integrals representing matrix elements to integrals always involving only non-singular integrands. The task of of finding particular Laplacian representation of different kernels amounts to solving appropriate ordinary or partial inhomogeneous differential equations. We apply the Laplacian method to analytic evaluation of matrix elements of the volume integral equation by employing two different Laplacian representations of the integral equation kernels. The first representation allows us to reduce 6-dimensional volume integrals over tetrahedra to 2-dimensional surface integrals over tetrahedra faces. The second representation is subsequently used reducing surface integrals over tetrahedra faces to pairs of of 1-dimensional line integrals over tetrahedra edges. We also derive analytic expressions for the resulting line integrals given in terms of elementary functions.

IEICE Transactions on Electronics, 2004

ABSTRACT We propose a fast integral equation solver for large periodic and non-periodic finite an... more ABSTRACT We propose a fast integral equation solver for large periodic and non-periodic finite antenna array systems. A key element of the algorithm is the rigorous block-Toeplitz method with an FFT-based matrix-vector product accelerator, which can be used in conjunction with either the conventional MoM, or with the AIM (adaptive integral method) or FMM (fast multipole method) compression techniques. We refer to the resulting algorithms as the Toeplitz-MoM, Toeplitz-AIM, or Toeplitz-FMM matrix compressions. For a periodic distribution of array elements, the algorithm exploits the block-Toeplitz structure of the impedance matrix in three dimensions and allows the implementation of matrix-vector multiplication in terms of discrete fast Fourier transforms (FFTs) in spatial variables associated with distances between the array elements. This approach generalizes to antenna arrays with boundaries, arrays located on substrates, and similar not entirely periodic systems.

2018 International Workshop on Computing, Electromagnetics, and Machine Intelligence (CEMi), 2018

We consider extensions and selected applications of the recently proposed method of evaluating Ga... more We consider extensions and selected applications of the recently proposed method of evaluating Galerkin matrix elements of electromagnetic volume and surface integral equations with the help of suitably constructed Laplacian-type representations of singular kernels (Green functions) in terms of non-singular auxiliary functions.

: The objective of the effort was to develop a methodology which would allow enhanced signal tran... more : The objective of the effort was to develop a methodology which would allow enhanced signal transmission, high resolution range imaging and/or target detection through optically obscuring, dilute, discrete-scatterer media such as clouds, fog, dust and other aerosols. (A) Properties of chirped-train waveforms such as their multi-band power spectra and the resulting point spread and ambiguity functions were analyzed. Advantages of the utilization of chirped trains in multi-spectralimaging (i.e., imaging based on frequency sub-bands of the chirped train signal) allowing extraction of frequency dependent information with improved signal-to-noise ratio was observed. (B) Propagation of short infrared/optical pulses in dilute random media consisting of large, compared to the wavelength, scatterers was analyzed. A rigorous approach based on analytic complex-contour integration of numerically determined cut and pole singularities of the radiative transport equation solution in the Fourier s...

2015 9th European Conference on Antennas and Propagation (EuCAP), 2015

We discuss here propagation of short electromagnetic pulses through dilute particulate random med... more We discuss here propagation of short electromagnetic pulses through dilute particulate random media consisting of scatterers in situations where the wave attenuation is dominated by scattering, rather than absorption. Examples of such phenomena include propagation of laser pulses through atmospheric clouds or through sprays in combustion processes. In such scenarios the coherent wave attenuation is controlled by the mean free path ℓt = 1/(n0 σt), where n0 is the medium number density and σt is the total cross-section for scattering of the wave on a single medium particle. The incoherent intensity is attenuated at a lower rate, but, typically, develops a long temporal tail due to multiple scattering in the medium and the ensuing diffusion. In both cases the medium effects cause serious deterioration of image quality in pulse-based imaging and bandwidth in communication; we propose here an approach for alleviating these difficulties.

2018 International Applied Computational Electromagnetics Society Symposium (ACES), 2018

We present an approach to calculation of matrix elements for arbitrarily oriented planar surface ... more We present an approach to calculation of matrix elements for arbitrarily oriented planar surface elements, based on reduction of the surface integrals to line integrals over perimeters of the elements. The described method is a generalization of our previous developments applicable to parallel geometry elements; it utilizes a representation of the Helmholtz-equation Green function in terms of an auxiliary function acted upon by a differential operator involving tangential gradients in two different planes. Integration by parts allows then reduction of surface-to line integrals with nonsingular integrands. The latter integrals can be either evaluated as standard quadratures or expressed analytically, in every order of expansion in the wave number k, in closed form. The method can be applied to all operators arising in Maxwell equations and in similar problems in acoustics and elastodynamics, offering significant advantages in accuracy and the computational cost.

2019 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2019

We consider the method of evaluating matrix elements of electromagnetic volume integral equations... more We consider the method of evaluating matrix elements of electromagnetic volume integral equations with the help of suitably constructed Laplacian-type representations of singular kernels (Green functions) appearing in electromagnetic volume and surface integral equations. The method consists of representing the singular kernels (Green functions) in terms of a generalized Laplacian operator acting on some auxiliary functions. Such a representations allow us, by using Gauss divergence theorem, to convert volumetric and surface integrals representing matrix elements to integrals always involving only non-singular integrands. The task of of finding particular Laplacian representation of different kernels amounts to solving appropriate ordinary or partial inhomogeneous differential equations. We apply the Laplacian method to analytic evaluation of matrix elements of the volume integral equation by employing two different Laplacian representations of the integral equation kernels. The fir...

2019 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2019

We consider new developments in the analytical evaluation of the near-field contribution to the m... more We consider new developments in the analytical evaluation of the near-field contribution to the matrix elements of the electric and magnetic field operators for planar conducting structures embedded in a layered medium. The method is applicable to Rao-Wilton-Glisson (RWG) basis functions supported on parallel interfaces in the layered medium. The method uses suitably constructed representations of the mixed potential formulation integral kernels in terms of two-dimensional Laplacian of auxiliary functions. Such Laplacian representations can be obtained for the asymptotic forms of the Green functions, which are being subtracted in order to regularize the behavior of the Sommerfeld-type integrals. Matrix elements resulting from these asymptotic forms, given originally as quadruple surface integrals with singular integrands, are then reduced to double contour integrals over the perimeters of the surface elements, involving simple closed-form non-singular auxiliary functions MMM. The new developments include: •Derivation of relations between elements of the asymptotic dyadic Green functions and the kernels of the mixed-potential representation of the fields. •Inclusion of additional terms introduced in [1], which improve convergence of the Sommerfeld integrals. These additional kernel components, related to half-line source potentials, were not included in our previous paper [1]; they constitute non-leading asymptotic contributions to the mixed-potential kernels mathcalKPhi\mathcal{K}^{\Phi}mathcalKPhi and mathcalKPsi\mathcal{K}^{\Psi}mathcalKPsi. •Construction of two additional auxiliary functions needed to represent the above-mentioned additional terms. The resultant auxiliary functions are expressed as integrals of the previously obtained [1] functions for the leading asymptotic kernel terms. •Construction of simplified analytical expressions for the matrix elements of the asymptotic parts of the pertinent dyadic Green functions. The asymptotic matrix elements, given in terms of quadruple surface integrals with singular integrands, are subsequently converted, by using suitably constructed Laplacian representations of the Green function, to double contour integrals over the perimeters of the surface elements, with simple, non-singular, smoothly varying integrands. The line integrals can be either evaluated analytically or by means of low order numerical quadratures. We discuss the relative merits of the direct numerical and analytic evaluation if these line integrals.

Physical Review Letters, 1984

The first complete measurement of the polarization transfer observables in the (p,p') reacti... more The first complete measurement of the polarization transfer observables in the (p,p') reaction at intermediate energies is reported. Data are presented for the reaction ¹²C(p,p') ¹²C to the 1/sup +/, T = 0 (12.71-MeV) and 1/sup +/, T = 1 (15.11-MeV) states at 500 MeV for laboratory scattering angles of 3.5°, 5.5°, 7.5°, and 12.0°. Linear combinations of these observables are shown to exhibit a very selective dependence on the isoscalar and isovector spin-dependent components of the nucleon interaction.

2016 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2016

This presentation describes an ongoing work by the authors on the solution of the time-dependent ... more This presentation describes an ongoing work by the authors on the solution of the time-dependent radiative transfer equation (RTE) and its application to propagation of short pulses through dilute scattering media (in particular, atmospheric obscurants, such as clouds, fog, or aerosols). It concentrates on exploitation of the “early-time diffusion” phenomenon arising for media in which scatterers are significantly larger than the pulse wavelength. The early time diffusion signature is a sharply rising structure in the time-resolved intensity, immediately following the ballistic (coherent) signal; its rise time is, typically, orders of magnitude shorter than that of the usual “late-time” diffusion and its decay with the propagation distance is significantly slower than for the coherent intensity contribution. Two subjects are discussed in more detail: (i) spectrum and eigensolutions of the RTE in its integral form and in a discretized integro-differential form; and (ii) a possible wa...

2021 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2021

We report new developments in the analytical evaluation of the near-field contribution to the mat... more We report new developments in the analytical evaluation of the near-field contribution to the matrix elements of the electric and magnetic field operators for planar conducting structures embedded in a layered medium. The method is applicable to Rao-Wilton-Glisson (RWG) basis functions supported on parallel interfaces in the medium. Our method is an extension of the approach described in [1] of representing a Green function as a two-dimensional Laplacian of an auxiliary function. Such Laplacian representations can be obtained for the asymptotic forms of the Green functions, which are being subtracted in order to regularize the behavior of the Sommerfeld-type integrals. Matrix elements resulting from these asymptotic forms, given originally as quadruple surface integrals with singular integrands, are then reduced to double contour integrals over the perimeters of the surface elements, involving simple closed-form non-singular auxiliary functions.

Physical Review Letters, 1981

The spin rotation parameter Q has been measured for p-40 Ca elastic scattering at 497 MeV for 0.0... more The spin rotation parameter Q has been measured for p-40 Ca elastic scattering at 497 MeV for 0.01<~-t<~0.15 (GeV/c) 2 with use of the new high-resolution spectrometer focalplane polarimeter. In conjunction with analyzing power and differential cross section, this ...

Results of a numerical simulation of an acoustic wave that propagates in a spherical object fille... more Results of a numerical simulation of an acoustic wave that propagates in a spherical object filled with insulating oil are presented in the paper. The sinusoidal acoustic wave is generated by an electro-acoustic transducer mounted in the middle of the object. Presented results depict acoustic pressure distribution within the transient and the steady states in a two-dimensional object. Furthermore, comparison of short time simulations adapting different mesh element size is presented.

Public Reporting burden for this collection of information is estimated to average 1 hour per res... more Public Reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comment regarding this burden estimates or any other aspect of this collection of

OMB NO. 0704-0188 Public Reporting burden for this collection of information is estimated to aver... more OMB NO. 0704-0188 Public Reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comment regarding this burden estimates or any other aspect of this collection of information,

Public Reporting burden for this collection of information is estimated to average I hour per res... more Public Reporting burden for this collection of information is estimated to average I hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comment regarding this burden estimates or any other aspect of this collection of

Journal of the Optical Society of America A

A short pulse propagating through a medium consisting of randomly distributed scatterers, large c... more A short pulse propagating through a medium consisting of randomly distributed scatterers, large compared to the wavelength, is expected to develop an "early-time diffusion" (ETD) behavior: a sharply rising structure in the time-resolved intensity, immediately following the coherent (ballistic) component. Since the ETD signal is attenuated at a rate substantially lower than the coherent wave, it offers a possibility of application in imaging through diverse scattering media, such as atmospheric obscurants (clouds, fog, mist), dust, aerosols, fuel sprays, or biological tissues. We describe here a two-way (reflection) imaging scenario utilizing the ETD phenomenon, and propose a specific image formation technique. We evaluate, by using the radiative transport theory, the resulting point-spread function (PSF) characterizing the image resolution. We show that the directly formed image has an angular resolution comparable to the width of the forward peak in the ensemble-averaged scattering cross section of the medium constituents. Subsequently, we show that, through the application of a regularized deconvolution technique enhancing higher Fourier components of the PSF, the resolution can be further significantly improved-at least by a factor of sim4{\sim}4sim4 for a medium layer of optical thickness of the order of 20. Such an improvement can be reached even if the noise level is a few orders of magnitude higher than the coherent (ballistic) image component.

2021 XXXIVth General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS)

We describe a concept of a system for detecting laser radiation in the presence of other (backgro... more We describe a concept of a system for detecting laser radiation in the presence of other (background) radiation sources. Unlike most existent laser-warning methods, which detect laser beams based on their intensity and monochromaticity, the proposed approach uses a high degree of coherence as the distinguishing property of laser radiation. Further, in contrast to previously considered coherence detection systems, based on amplitude interferometry (AI), we propose to utilize intensity interferometry (II), pioneered by Hanbury Brown and Twiss and originally applied to thermal radiation sources, but here generalized to coexisting high- and low-coherence radiation. In this contribution we concentrate on a possible application of the proposed system in detection of off-axis laser beam radiation scattered on atmospheric medium particles (water droplets and aerosols, especially dust). A particular design, which may operate in the visible and infrared regions, utilizes a small array of photodetectors (such as PIN photodiodes) and electronic correlator circuits identifying correlations in photocurrent fluctuations of neighboring detectors. It is shown that the normalized cross-correlation coefficients will be significant, even in the presence of a strong incoherent (e.g., solar radiation) background, provided the coherent radiation degeneracy parameter (number of photoelectrons generated by the detector during the coherence-time interval) exceeds the ratio of the background to signal intensities. This condition, which should not be difficult to achieve in realistic situations, ensures that the coherent signal is larger than the shot noise due to the background.

2018 International Workshop on Computing, Electromagnetics, and Machine Intelligence (CEMi)

We consider extensions and selected applications of the recently proposed method of evaluating Ga... more We consider extensions and selected applications of the recently proposed method of evaluating Galerkin matrix elements of electromagnetic volume and surface integral equations with the help of suitably constructed Laplacian-type representations of singular kernels (Green functions) in terms of non-singular auxiliary functions.

2018 International Conference on Electromagnetics in Advanced Applications (ICEAA)

The radiative transport theory predicts that a short pulse propagating through a random medium co... more The radiative transport theory predicts that a short pulse propagating through a random medium consisting of discrete scatterers of sizes large compared to the wavelength develops to develop an "early-time diffusion" (ETD) component: a sharply rising structure in the time-resolved intensity, immediately following the coherent (ballistic) signal, but attenuated at a rate substantially lower than the coherent attenuation. This phenomenon offers a possibility of application in imaging through obscuring (e.g., atmospheric) media. We describe here an imaging scenario utilizing the ETD signal, evaluate the resulting point-spread function characterizing the image resolution, and show how that resolution can be significantly improved by means of regularized deconvolution techniques.

2019 International Conference on Electromagnetics in Advanced Applications (ICEAA)

We consider the method of evaluating matrix elements of electromagnetic volume integral equations... more We consider the method of evaluating matrix elements of electromagnetic volume integral equations with the help of suitably constructed Laplacian-type representations of singular kernels (Green functions) appearing in electromagnetic volume and surface integral equations. The method consists of representing the singular kernels (Green functions) in terms of a generalized Laplacian operator acting on some auxiliary functions. Such a representations allow us, by using Gauss divergence theorem, to convert volumetric and surface integrals representing matrix elements to integrals always involving only non-singular integrands. The task of of finding particular Laplacian representation of different kernels amounts to solving appropriate ordinary or partial inhomogeneous differential equations. We apply the Laplacian method to analytic evaluation of matrix elements of the volume integral equation by employing two different Laplacian representations of the integral equation kernels. The first representation allows us to reduce 6-dimensional volume integrals over tetrahedra to 2-dimensional surface integrals over tetrahedra faces. The second representation is subsequently used reducing surface integrals over tetrahedra faces to pairs of of 1-dimensional line integrals over tetrahedra edges. We also derive analytic expressions for the resulting line integrals given in terms of elementary functions.

IEICE Transactions on Electronics, 2004

ABSTRACT We propose a fast integral equation solver for large periodic and non-periodic finite an... more ABSTRACT We propose a fast integral equation solver for large periodic and non-periodic finite antenna array systems. A key element of the algorithm is the rigorous block-Toeplitz method with an FFT-based matrix-vector product accelerator, which can be used in conjunction with either the conventional MoM, or with the AIM (adaptive integral method) or FMM (fast multipole method) compression techniques. We refer to the resulting algorithms as the Toeplitz-MoM, Toeplitz-AIM, or Toeplitz-FMM matrix compressions. For a periodic distribution of array elements, the algorithm exploits the block-Toeplitz structure of the impedance matrix in three dimensions and allows the implementation of matrix-vector multiplication in terms of discrete fast Fourier transforms (FFTs) in spatial variables associated with distances between the array elements. This approach generalizes to antenna arrays with boundaries, arrays located on substrates, and similar not entirely periodic systems.

2018 International Workshop on Computing, Electromagnetics, and Machine Intelligence (CEMi), 2018

We consider extensions and selected applications of the recently proposed method of evaluating Ga... more We consider extensions and selected applications of the recently proposed method of evaluating Galerkin matrix elements of electromagnetic volume and surface integral equations with the help of suitably constructed Laplacian-type representations of singular kernels (Green functions) in terms of non-singular auxiliary functions.

: The objective of the effort was to develop a methodology which would allow enhanced signal tran... more : The objective of the effort was to develop a methodology which would allow enhanced signal transmission, high resolution range imaging and/or target detection through optically obscuring, dilute, discrete-scatterer media such as clouds, fog, dust and other aerosols. (A) Properties of chirped-train waveforms such as their multi-band power spectra and the resulting point spread and ambiguity functions were analyzed. Advantages of the utilization of chirped trains in multi-spectralimaging (i.e., imaging based on frequency sub-bands of the chirped train signal) allowing extraction of frequency dependent information with improved signal-to-noise ratio was observed. (B) Propagation of short infrared/optical pulses in dilute random media consisting of large, compared to the wavelength, scatterers was analyzed. A rigorous approach based on analytic complex-contour integration of numerically determined cut and pole singularities of the radiative transport equation solution in the Fourier s...

2015 9th European Conference on Antennas and Propagation (EuCAP), 2015

We discuss here propagation of short electromagnetic pulses through dilute particulate random med... more We discuss here propagation of short electromagnetic pulses through dilute particulate random media consisting of scatterers in situations where the wave attenuation is dominated by scattering, rather than absorption. Examples of such phenomena include propagation of laser pulses through atmospheric clouds or through sprays in combustion processes. In such scenarios the coherent wave attenuation is controlled by the mean free path ℓt = 1/(n0 σt), where n0 is the medium number density and σt is the total cross-section for scattering of the wave on a single medium particle. The incoherent intensity is attenuated at a lower rate, but, typically, develops a long temporal tail due to multiple scattering in the medium and the ensuing diffusion. In both cases the medium effects cause serious deterioration of image quality in pulse-based imaging and bandwidth in communication; we propose here an approach for alleviating these difficulties.

2018 International Applied Computational Electromagnetics Society Symposium (ACES), 2018

We present an approach to calculation of matrix elements for arbitrarily oriented planar surface ... more We present an approach to calculation of matrix elements for arbitrarily oriented planar surface elements, based on reduction of the surface integrals to line integrals over perimeters of the elements. The described method is a generalization of our previous developments applicable to parallel geometry elements; it utilizes a representation of the Helmholtz-equation Green function in terms of an auxiliary function acted upon by a differential operator involving tangential gradients in two different planes. Integration by parts allows then reduction of surface-to line integrals with nonsingular integrands. The latter integrals can be either evaluated as standard quadratures or expressed analytically, in every order of expansion in the wave number k, in closed form. The method can be applied to all operators arising in Maxwell equations and in similar problems in acoustics and elastodynamics, offering significant advantages in accuracy and the computational cost.

2019 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2019

We consider the method of evaluating matrix elements of electromagnetic volume integral equations... more We consider the method of evaluating matrix elements of electromagnetic volume integral equations with the help of suitably constructed Laplacian-type representations of singular kernels (Green functions) appearing in electromagnetic volume and surface integral equations. The method consists of representing the singular kernels (Green functions) in terms of a generalized Laplacian operator acting on some auxiliary functions. Such a representations allow us, by using Gauss divergence theorem, to convert volumetric and surface integrals representing matrix elements to integrals always involving only non-singular integrands. The task of of finding particular Laplacian representation of different kernels amounts to solving appropriate ordinary or partial inhomogeneous differential equations. We apply the Laplacian method to analytic evaluation of matrix elements of the volume integral equation by employing two different Laplacian representations of the integral equation kernels. The fir...