Papers by Rosa Fitzgerald
Scattering of Electromagnetic Waves from One-Dimensionally Rough Surfaces Containing Resonant Structures (invited)
Asia-Pacific Radio Science Conference, 2001
ABSTRACT The elastic scattering of electromagnetic waves from a rough surface containing resonant... more ABSTRACT The elastic scattering of electromagnetic waves from a rough surface containing resonant structures is studied as a function of the frequency of the incident light. A diagrammatic perturbation theory treatment is used. The surface consists of a planar vacuum-metal or vacuum-dielectric interface upon which an array of identical cylindrical dielectric ridges are randomly placed. The axes of the ridges are parallel to one another so that the translational symmetry of the surface is maintained along one axis in the surface, and the scattering of p-polarized radiation within a scattering plane perpendicular to the axes of the ridges is treated. The ridges are composed of a medium which undergoes a dielectric resonance as a function of frequency. The frequencies of the surface shape resonance modes bound to the dielectric ridges are computed for a surface supporting a single dielectric ridge. For the surface supporting a random array of dielectric ridges the specular scattering and diffuse scattering are computed for frequencies in the neighborhood of the dielectric resonance of the dielectric material forming the Gaussian ridges.
Characterization of Aerosols in the El Paso-Juarez Airshed using the TUV Model in Conjunction with Multi-filter Rotating Shadow Band Radiometers
AAAR 28th Annual Conference., Oct 26, 2009
Determination of aerosol optical properties is vital towards a better understanding of the aeroso... more Determination of aerosol optical properties is vital towards a better understanding of the aerosols present in an urban-rural interface region, eg the El Paso-Juarez Airshed [R. Pearson, R. Fitzgerald and J. Polanco, 2007]. In this work we present sensitivity studies of optical parameters ...
S-polarized guided electromagnetic waves at a planar interface between vacuum and a graded-index dielectric
Waves in Random and Complex Media, May 1, 2013
ABSTRACT Analytic expressions for the dispersion relation and electric field profiles of guided w... more ABSTRACT Analytic expressions for the dispersion relation and electric field profiles of guided waves supported by an asymmetric graded-index dielectric waveguide are derived. The system studied consists of vacuum in the region , and a dielectric medium in the region whose dielectric permittivity decreases continuously with increasing distance into it from the interface according to . Here is the (real) index of refraction of the medium at , and it is assumed that . It is found that for frequencies below a certain critical value given by , where is the speed of light in vacuum, the dispersion curve consists of a single branch that exists in a narrow spectral range. Its electric field decays exponentially with increasing distance into each medium. For frequencies above this critical value, the dispersion curve possesses several branches. The corresponding electric field decays exponentially with increasing distance into the vacuum, and decays in an oscillatory fashion with increasing distance into the graded-index dielectric medium. The number of nodes in the latter field equals the branch number, starting with zero for the lowest frequency branch.
Journal of the Air & Waste Management Association, Dec 6, 2018
An ozone abatement strategy for the South Coast Air Basin (SoCAB) has been proposed by the South ... more An ozone abatement strategy for the South Coast Air Basin (SoCAB) has been proposed by the South Coast Air Quality Management District (SCAQMD) and the California Air Resources Board (ARB). The proposed emissions reduction strategy is focused on the reduction of nitrogen oxide (NO x ) emissions by the year 2030. Two high PM 2.5 concentration episodes with high ammonium nitrate compositions occurring during September and November 2008 were simulated with the Community Multi-scale Air Quality model (CMAQ). All simulations were made with same meteorological files provided by the SCAQMD to allow them to be more directly compared with their previous modeling studies. Although there was an overall under-prediction bias, the CMAQ simulations were within an overall normalized mean error of 50%; a range that is considered acceptable performance for PM modeling. A range of simulations of these episodes were made to evaluate sensitivity to NO x and ammonia emissions inputs for the future year 2030. It was found that the current ozone control strategy will reduce daily average PM 2.5 concentrations. However, the targeted NO x reductions for ozone were not found to be optimal for reducing PM 2.5 concentrations. Ammonia emission reductions reduced PM 2.5 and this might be considered as part of a PM 2.5 control strategy. Implications: The SCAQMD and the ARB have proposed an ozone abatement strategy for the SoCAB that focuses on NO x emission reductions. Their strategy will affect both ozone and PM 2.5 . Two episodes that occurred during September and November 2008 with high PM 2.5 concentrations and high ammonium nitrate composition were selected for simulation with different levels of nitrogen oxide and ammonia emissions for the future year 2030. It was found that the ozone control strategy will reduce maximum daily average PM 2.5 concentrations but its effect on PM 2.5 concentrations is not optimal.
Atmosphere, Dec 10, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Studies of the phase-coherent scattering of electromagnetic waves from a random array of resonant dielectric ridges placed upon a dielectric substrate
APS, Mar 1, 2004
We discuss the diffuse scattering of p-polarized electromagnetic waves from a vacuum-dielectric i... more We discuss the diffuse scattering of p-polarized electromagnetic waves from a vacuum-dielectric interface characterized by a one-dimensional disorder in the form of parallel, Gausian shaped, resonant dielectric ridges positioned at random on a planar semi-infinite dielectric substrate. The ridges are taken to be made from either NAF or ZnS. The substrate material is CdS. The light is taken to be
<title>Scattering of electromagnetic waves from one-dimensionally rough surfaces containing surface resonant structures</title>
Proceedings of SPIE, Sep 26, 2000
ABSTRACT The elastic scattering of electromagnetic waves from a rough surface containing resonant... more ABSTRACT The elastic scattering of electromagnetic waves from a rough surface containing resonant structures is studied as a function of the frequency of the incident light. A diagrammatic perturbation theory treatment is used. The surface consists of a planar vacuum-metal or vacuum-dielectric interface upon which an array of identical cylindrical dielectric ridges are randomly placed. The axes of the ridges are parallel to one another so that the translational symmetry of the surface is maintained along one axis in the surface, and the scattering of p-polarized radiation within a scattering plane perpendicular to the axes of the ridges is treated. The ridges are composed of a medium which undergoes a dielectric resonance as a function of frequency. The frequencies of the surface shape resonance modes bound to the dielectric ridges are computed for a surface supporting a single dielectric ridge. For the surface supporting a random array of dielectric ridges the specular scattering and diffuse scattering are computed for frequencies in the neighborhood of the dielectric resonance of the dielectric material forming the Gaussian ridges.
Plasmonics, Mar 12, 2015
The reduced Rayleigh equation for the scattering of a surface plasmon polariton incident non-norm... more The reduced Rayleigh equation for the scattering of a surface plasmon polariton incident non-normally on a one-dimensional ridge or groove on an otherwise planar metal surface is solved by a purely numerical approach. The solution is used to calculate the transmission, reflection, and out-of-plane scattering coefficients of the surface plasmon polariton. The angular dependence of the out-of-plane scattering is found to have a conical nature.
Transmission of light through a metal film with two corrugated surfaces
Proceedings of SPIE, Aug 18, 2005
ABSTRACT We study theoretically the transmission of p- and s-polarized light through a thin, supp... more ABSTRACT We study theoretically the transmission of p- and s-polarized light through a thin, supported, silver or gold film, both of whose surfaces are one-dimensional, periodically corrugated surfaces, as a function of the wavelength of the incident light. The calculations are carried out by the use of reduced Rayleigh equations in the form of a pair of coupled inhomogeneous matrix equations for the amplitudes of the scattered and transmitted Bragg beams. The results show that enhanced transmission occurs for both p- and s-polarized incident light for large-amplitude periodic corrugations of the two surfaces. In p polarization an additional enhancement occurs at the wavelengths of the surface plasmon polaritons supported by the film. Thus, slits that pierce the film are not necessary for enhanced transmission of light through it.
Enhancement of phase-coherent electromagnetic scattering from a random array of identical resonant dielectric ridges placed upon a dielectric substrate
Physical review, Mar 29, 2002
The elastic scattering of p-polarized electromagnetic waves from a one-dimensionally rough surfac... more The elastic scattering of p-polarized electromagnetic waves from a one-dimensionally rough surface formed as an array of identical resonant dielectric ridges randomly placed upon a dielectric substrate is studied as a function of the frequency of incident light. A diagrammatic perturbation theory is used. Emphasis is given to determining how the resonant properties, as a function of frequency, of the
IEEE Transactions on Antennas and Propagation, 2000
Atmospheric Environment, Dec 1, 2011
A light-extinction technique for monitoring aerosols was used in conjunction with a robust invers... more A light-extinction technique for monitoring aerosols was used in conjunction with a robust inverse reconstruction model to retrieve aerosol size distribution. Results for the columnar aerosol size distribution for the Paso del Norte Airshed for two different pollution scenarios and at two different seasons were presented. These are well correlated with experimental surface aerosol data for this region. It was observed that, for the clean day scenario, the summer case showed a greater columnar concentration of smaller size aerosols than the winter case. Results for the columnar aerosol size distribution in the polluted day scenario demonstrated that the concentration of aerosols were greater in the summer than in the winter. In addition, HYSPLIT backward trajectories were used to identify pollution sources.
An Improved Methodology to Calculate the Aerosol Extinction Coefficients for the El Paso-Juarez Airshed
98th American Meteorological Society Annual Meeting, Jan 11, 2018
Optics Communications, Apr 1, 2014
We study properties of a p-polarized surface plasmon polariton propagating circumferentially arou... more We study properties of a p-polarized surface plasmon polariton propagating circumferentially around a portion of a cylindrical interface between a vacuum and a metal, a situation investigated earlier by Berry (J. Phys. A: Math. Gen. 8 (1975) 1952). When the metal is convex toward the vacuum this mode is radiative and consequently is attenuated as it propagates on the cylindrical surface. An approximate analytic solution of the dispersion relation for this wave is obtained by an approach different from the one used by Berry, and plots of the real and imaginary parts of its wave number are presented. When the metal is concave to the vacuum, the resulting dispersion relation possesses a multiplicity of solutions that have the nature of waveguide modes that owe their existence to the curvature of the interface.
Atmospheric Environment, 2012
A methodology to retrieve Single Scattering Albedo (SSA) values employing the ratio of Direct to ... more A methodology to retrieve Single Scattering Albedo (SSA) values employing the ratio of Direct to Diffuse Irradiances (DDR) is used and applied to the El Paso-Juarez Airshed, a challenging region where air masses interact. The TUV model was used to obtain the calculated DDR irradiances, and the experimental irradiances were obtained from a UV-MFRSR instrument located in the city of El Paso, Texas. The wavelengths used were 332 nm and 368 nm. The retrieved SSA values at both 332 nm and 368 nm were higher in a lightly polluted day (0.66e0.81 at 332 nm, and 0.61 to 0.80 at 368 nm) than in a heavier polluted day (0.56e0.70 at 332 nm and 0.53e0.66 at 368 nm). A sensitivity study of the ground albedo and the asymmetry parameter was performed, which indicated that the variation of the asymmetry parameter is a secondary effect in the retrievals of SSA. In addition, the variation of SSA values during the day was also analyzed for the El Paso-Juarez Airshed and linked to the flow of air masses into the region using HYSPLIT trajectories. A presence of absorptive aerosols was observed during the late morning and the middle of the day. This methodology can be applied in any area, and is particularly useful for cities that experience episodes of high PM concentrations.
A dominant part of the circulation in nearly enclosed bays, estuaries, or sounds is dictated by t... more A dominant part of the circulation in nearly enclosed bays, estuaries, or sounds is dictated by tidal inflow at its mouth, called co-oscillatory forcing. The remaining flow component is usually due to winds. HF radar measurements across the region at the entrance can be used to extract the sinusoidal tidal velocity constituents along a line across the mouth. We use this complex (i.e., amplitude and phase) spatial profile at different times of the tidal cycle as the boundary excitation condition to solve a scalar second-order partial differential equation (PDE) for tide height. For the boundary condition over the remaining enclosing coast, the flow normal to the shore is taken to be zero. The bathymetry of the bay is included in this scalar PDE. This is then solved by a powerful finite-element code, PDE2D. From the tide height distribution, the velocity circulation is simply calculated as its gradient.
Bulletin of the American Physical Society, Mar 23, 2012
referred to, as the "weekend effect." If the ozone standard is exceeded more frequently on weeken... more referred to, as the "weekend effect." If the ozone standard is exceeded more frequently on weekends, then this phenomenon must be considered in the design of ozone control strategies. In this work we investigate some of the most representative weekend ozone episodes at El Paso, TX, during the years 2009, 2010 and 2011 using the ozone photolysis rates. In this research the TUV radiative-transfer model is used to calculate the local photolysis rates and a UV MFRSR instrument is used to obtain experimental parameters. Seasonal variations and the weekday-weekend effect is studied. The results of this research will help to understand the underlying behavior of the photolysis rate constants when different atmospheric conditions are present.
Theory of Diatomic Molecules Scattering from a Non-Rigid Surface: Application to HYDROGEN-COPPER(111) System
ABSTRACT
Computer Physics Communications, Feb 1, 2000
A general purpose partial differential equation solver, PDE2D, which is useful on a wide range of... more A general purpose partial differential equation solver, PDE2D, which is useful on a wide range of computational physics applications, including 1D, 2D and 3D, time-dependent, steady-state and eigenvalue problems, is described. This program has the advantages of being both accurate and very easy to use. Its wide applicability is illustrated by solving three representative quantum mechanics problems.
A reciprocal phase-perturbation theory for rough-surface scattering
Waves in Random Media, Jul 1, 1994
We study the scattering of a scalar plane wave from a two-dimensional, randomly rough surface, on... more We study the scattering of a scalar plane wave from a two-dimensional, randomly rough surface, on which the Dirichlet boundary condition is satisfied. The scattering amplitude is obtained in the form of the Fourier transform of an exponential, in which the exponent is written as an expansion in powers of the surface profile function. It is shown that the latter expansion can be written in such a way that the corresponding scattering matrix is manifestly reciprocal. Numerical results for the reflectivity, and for the contribution to the mean differential reflection coefficient from the incoherent component of the scattered field, are obtained and compared with the predictions of small-amplitude perturbation theory and the Kirchhoff approximation. As the wavelength of the incident wave is varied continuously the results of the phase-perturbation theory change continuously from those of the small-amplitude perturbation theory to those of the Kirchhoff approximation.
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Papers by Rosa Fitzgerald