Biomedical subjects

Cesar Monzon

Publications and source records attributed to Cesar Monzon.

10 recordsLinked to original sources

PubMed2006

Rough ocean surface and sunglint region characteristics.

The sunglint geometrical optics equations of a statistically faceted sea, supported by the so-called interaction probability density and employing an averaging hybrid of the Cox-Munk and Mermelstein slope statistics, was successful in simulating 0.5 microm sunglint region characteristics. The results match independent experimental data, and good agreement is reported for various sea conditions and Sun locations, on sunglint amplitude, sunglint location, and azimuth range. In particular, the peak reflectance shift from the specular direction toward the horizon is correctly predicted, and it is found that the physical mechanism responsible for the shift is the accumulation of contributing facets near the horizon.

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PubMed2006

Retroreflective effect on a right angle left-handed media prism.

A different retroreflective effect which parallels that encountered with dihedral corner reflectors is found in the scattering response of a penetrable left-handed media epsilon= mu= -1 right angle prism. More significantly, no diffraction from the vertex is found to exist and hence no field singularity for the right angle wedge. Although the results are illustrated with microwaves, the concept finds applications in optics, acoustics, elasticity, and other media characterized by negative index wave propagation.

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PubMed2006

Bandpass left-handed material optical filter with enhanced stop band rejection.

It is shown that a layer of left-handed media can act as a bandpass filter with a roll factor that far exceeds those of state-of-the-art spectral filters. The conditions for enhanced stop band rejection are presented and are deemed feasible, as the models used correspond to physically realizable materials. Roll factors of the order of 10(4)-10(6) dB/GHz are found, together with acceptable insertion losses of the order of 10 dB.

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PubMed2006

Exact solution to plane-wave scattering by an ideal "left-handed" wedge.

An exact analytical solution to the problem of plane-wave diffraction by a penetrable left-handed medium (LHM) epsilon = micro = -1 wedge of arbitrary angle (subject to valid physical constraints) is presented. Standard analysis involving discontinuous angular eigenfunctions and even/odd symmetry decomposition resulted in a discrete spectrum leading to a series solution resembling the traditional perfect electric conductor wedge solution but exhibiting the expected negative refraction phenomenology. Numerical results are presented, some of which seemed paradoxical but are explainable by classical means. A new type of illusory edge radiation is observed and explained. Also, a novel edge-launched interface standing wave is observed on the directly illuminated side. The exact analytical solution is verified by comparison with finite-difference time-domain simulation on causal LHM materials.

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PubMed2006

Complex source description of focal regions.

Closed-form solutions of the two-dimensional homogeneous wave equation are presented that provide focal-region descriptions corresponding to a converging bundle of rays. The solutions do have evanescent wave content and can be described as a source-sink pair or particle-antiparticle pair, collocated in complex space, with the complex location being critical in the determination of beam shape and focal region size. The wave solutions are not plagued by singularities, have a finite energy, and have a limitation on how small the focal size can get, with a penalty for limiting small spot sizes in the form of impractically high associated reactive energy. The electric-field-defined spot-size limiting value is 0.35lambda x 0.35lambda, which is about 38% of the Poynting-vector-defined minimum spot size (0.8lambda x 0.4lambda) and corresponds to a condition related to the maximum possible beam angle. A multiple set of solutions is introduced, and the elementary solutions are used to produce new solutions via superposition, resulting in fields with chiral character or with increased depth of focus. We do not claim generality, as the size of focal regions exhibited by the closed-form solutions has a lower bound and hence is not able to account for Pendry's "ideal lens" scenario.

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PubMed2005

Exact solution to line source scattering by an ideal left-handed wedge.

A wedge or prism is a common geometry used in experiments involving left-handed media (LHM). It is shown that an exact analytical solution to the canonical problem of scattering by a LHM wedge or prism is feasible in the limit of no losses. The solution reproduces the ideal point image announced by Pendry which has not been observed experimentally. The analysis also results in the introduction of a new kind of resonator or photon localization device.

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PubMed2005

Negative refraction and focusing of circularly polarized waves in optically active media.

Analysis indicates that certain types of optically active media are capable of producing negative refraction and focusing of circularly polarized waves. It is established that a slab of such material acts just as Veselago's hypothetical left-handed media lens, providing subwavelength resolution as Sir Pendry's ideal lens, but for circularly polarized waves.

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PubMed2005

Effect of rotational invariance on the monostatic characteristics of matched bodies.

It is shown analytically and numerically that a matched epsilon = mu reciprocal object with rotational symmetry will not produce any backscattering when illuminated along the axis of symmetry unless the body is invariant un der a rotation by 180 degrees. The purpose of this work is to generalize the monostatic theorem of Weston to arbitrary rotational symmetry, thereby providing a basic rule for scattering by complex bodies. The theory is illustrated by application to a few selected scatterers.

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PubMed2004

Two theorems on electromagnetic bistatic scattering.

For an axially incident plane wave, two theorems are stated in which sufficient conditions are imposed on the constitutive parameters epsilon and mu of a three-dimensional scatterer to ensure the identity of scattering patterns in orthogonal planes, both near and far zone, such as E and H planes. The theorems represent an extension of existing scattering theorems that apply to bodies of revolution. The theorems are proven analytically, and the results are validated through detailed finite-difference-time-domain and method-of-moments computer simulations on a few noncanonical complex shapes characterized by quite general causal permittivity epsilon and permeability mu functions. The selected materials have Lorentzian functional forms and encompass ordinary materials as well as left-handed materials as special cases.

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PubMed2004

Scattering properties of an impedance-matched, ideal, homogeneous, causal "left-handed" sphere.

The plane-wave scattering properties of a sphere of material having an ideal, homogeneous, and causal permittivity epsilon(f), and permeability mu(f) were investigated through detailed three-dimensional finite-difference time-domain, method-of-moments, and series-solution simulations. A Lorentzian functional form was chosen for epsilon(f) and mu( f), as it yields causal responses and allows us to study the physics of the left-handed-medium (LHM) regime. Our interest lies mainly in the frequency range where negative refraction [Re(n) < 0] is observed. We found that when operating in the LHM regime, an impedance-matched sphere responds with scattering features strikingly different from those found in ordinary materials. In particular, we found zero back-scattering and forward scattering that exceeds that of a metal sphere of similar size. The equality of E- and H-plane patterns was proved analytically and numerically, and the possibility of internal subwavelength focusing with a zero index sphere is also reported.

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