Biomedical subjects

Edwin A Marengo

Publications and source records attributed to Edwin A Marengo.

4 recordsLinked to original sources

PubMed2006

Generalized power-spectrum Larmor formula for an extended charged particle embedded in a harmonic oscillator.

The nonrelativistic Larmor radiation formula, giving the power radiated by an accelerated charged point particle, is generalized for a spatially extended particle in the context of the classical charged harmonic oscillator. The particle is modeled as a spherically symmetric rigid charge distribution that possesses both translational and spinning degrees of freedom. The power spectrum obtained exhibits a structure that depends on the form factor of the particle, but reduces, in the limit of an infinitesimally small particle and for the charge distributions considered, to Larmor's familiar result. It is found that for finite-duration small-enough accelerations as well as perpetual uniform accelerations the power spectrum of the spatially extended particle reduces to that of a point particle. It is also found that when the acceleration is violent or the size parameter of the particle is very large compared to the wavelength of the emitted radiation the power spectrum is highly suppressed. Possible applications are discussed.

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PubMed2006

Noniterative analytical formula for inverse scattering of multiply scattering point targets.

This paper derives, in the exact framework of multiple scattering theory for point targets, a noniterative analytical formula for the nonlinear inversion of the target scattering strengths from the scattering or response matrix that can be applied after the target positions have been estimated in a previous step via, e.g., time-reversal multiple signal classification or another approach. The new formula provides a noniterative analytical alternative to the iterative numerical solution approach for the same problem presented in a recent paper [A. J. Devaney, E. A. Marengo, and F. K. Gruber, "Time-reversal-based imaging and inverse scattering of multiply scattering point targets," J. Acoust. Soc. Am. 118, 3129-3138 (2005)]. The two methods (noniterative versus iterative) are comparatively investigated with two numerical examples.

Humans↗

PubMed2006

Observations on "nonradiating surface sources": comment.

The proof, established in a recent paper [A. J. Devaney, "Nonradiating surface sources," J. Opt. Soc. Am. A 21, 2216 (2004)], of the existence of nonradiating surface sources formed by singlet-plus-doublet components whose generated fields vanish in either of the regions separated by a closed or infinite surface where the source resides is corroborated by means of an equivalent but slightly different formalism based on treatment of partial differential operators in a weak derivative or distributional sense. This approach yields a construction procedure applicable to a broad class of singular nonradiating sources. A fundamental question raised in that paper concerning the nonexistence of nontrivial nonradiating infinite planar sources that generate vanishing fields at both associated half-spaces is re-examined, with the conclusion that it is actually possible to mathematically construct such singular nonradiating sources as long as one allows for higher-order singularities such as certain combinations of singlet and triplet components.

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PubMed2004

Nonradiating sources with connections to the adjoint problem.

A general description of localized nonradiating (NR) sources whose generated fields are confined (nonzero only) within the source's support is developed that is applicable to any linear partial differential equation (PDE) including the usual PDEs of wave theory (e.g., the Helmholtz equation and the vector wave equation) as well as other PDEs arising in other disciplines. This description, which holds for both formally self-adjoint and non-self-adjoint linear partial differential operators (PDOs), is derived in the context of both the governing PDE and the corresponding adjoint PDE of the associated adjoint problem. It is shown that a necessary and sufficient condition for a source to be NR is that it obeys an orthogonality relation with respect to any solution in the source's support of the corresponding homogeneous adjoint PDE. For real linear PDOs, this description takes on a more relaxed form where, in addition to the previous necessary and sufficient condition, the obeying of a complementary orthogonality relation with respect to any solution in the source's support of the homogeneous form of the same governing PDE is also both necessary and sufficient for the source to be NR.

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