Papers by D. Chrissoulidis
Distribution of Heating Potential in an Eccentric Spheres Model of a Cranial Structure
COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, 1995
EM wave scattering from statistically inhomogeneous and periodic random rough surfaces
Iee Proceedings H Microwaves, Antennas and Propagation, 1989
First-order scatter from statistically inhomogeneous and periodic random rough surfaces is treate... more First-order scatter from statistically inhomogeneous and periodic random rough surfaces is treated by the boundary perturbation technique. The single array of rough strips on a perfectly conducting plane and the complementary arrays of rough strips are examined. Using a sampling approach, it is proved that scatter is produced through a multiple Bragg resonance mechanism. The scattering behavior of the single array of rough strips is investigated numerically. Scatter for the corresponding surface which is covered throughout by roughness is used as reference. The numerical results indicate that the incidence/scattering directions are related to the orientation of the strips while the sensing radio wavelength is related to the strips width and period. Possible applications for this class of scatterers are discussed.
The scattering behavior of a slightly rough surface moving parallel to its mean plane with uniform velocity
IEEE Transactions on Antennas and Propagation, 1985
ABSTRACT The scattering of plane electromagnetic (EM) waves from a perfectly conducting, slightly... more ABSTRACT The scattering of plane electromagnetic (EM) waves from a perfectly conducting, slightly rough surface moving in vacuum with uniform and constant velocity is examined by combining the boundary perturbation method and the special, homogeneous Lorentz transform. The direction of motion is assumed to be parallel to both the incidence plane and the mean plane of the moving rough surface. The analysis is confined to first-order scatter. The end result is the determination of the velocity-dependent expressions for the bistatic and backscatter incoherent cross sections per unit area of the scattering surface. The expressions for bistatic geometry are only valid for scattering inside the plane of incidence. A numerical example demonstrates the effect of the motion on the scattering behavior of the rough surface.
Numerical evaluation of the eigenexpansion of the electrostatic potential near a dielectric cone
2010 International Conference on Mathematical Methods in Electromagnetic Theory, 2010
ABSTRACT The purpose of this paper is to elaborate on some numerical aspects of the evaluation of... more ABSTRACT The purpose of this paper is to elaborate on some numerical aspects of the evaluation of the eigenfunction expansion for the electrostatic potential near a dielectric cone of circular cross-section. This expansion has been derived analytically by the authors in a recent article [SIAM J. Appl. Math., 70 (2010), pp. 2329-2352] with the aid of the two-interval Sturm-Liouville theory. In our effort to implement numerically the aforesaid expansion we discovered a numerical instability on the spherical surface which is centered at the vertex of the cone and passes through the point source. In this paper we present an analytical way of removing that instability. Furthermore, we propose some numerical methods for calculating the terms of the eigenfunction expansion and we present some numerical results in the form of equipotential contour plots.
Electromagnetics and optics
Applied Optics, 1993
Backscatterino from a cylinder with several eccentric cylindrical inclusions: application to multifiber cables
Trans Black Sea Region Symposium on Applied Electromagnetism, 1996
Detection of near-water ducts by the wave tilt probing method
Radio Science, 1989
ABSTRACT A theoretical study indicates that near-water ducts can be detected by airborne wave til... more ABSTRACT A theoretical study indicates that near-water ducts can be detected by airborne wave tilt measurements. Sea roughness and trapping refractivity gradients are incorporated in an iterative procedure which results in wave tilt versus frequency diagrams at low altitudes above sea level. The phase quadrature technique offers itself for duct intensity estimation through measurements of frequency shift, provided that the refractivity at sea level is accurately known.
Relativistic bistatic scattering by a uniformly moving random rough surface
IEEE Transactions on Antennas and Propagation, 1986
... a&), S3, = sin a3(t), C2, = cos a2(t), C3, = cos a3(t). In effect, (OG, XGYGZc), which fo... more ... a&), S3, = sin a3(t), C2, = cos a2(t), C3, = cos a3(t). In effect, (OG, XGYGZc), which follows the motion of the surface, is the Galilean counterpart of thesystem (0' , X' Y'Z') considered in Q' , hence the subscript G. It can be proven that Ezr is zero for a motionless scattering surface. ...
Comparison of radar reflectivity calculations to satellite measurements across the melting layer of precipitation
2011 XXXth URSI General Assembly and Scientific Symposium, 2011
Calculations of the radar reflectivity factor across the melting layer of precipitation successfu... more Calculations of the radar reflectivity factor across the melting layer of precipitation successfully reproduce measured data provided by the Precipitation Radar (PR) of the Tropical Rainfall Measurement Mission (TRMM) satellite. This work proves that calculations made by use of a proposed modeling scheme, which is based on the eccentric spheres model for melting ice particles, deviate from measurements by no more than 8%. As a side effect of the comparisons made, cases of erroneous information about the height and width of the melting layer in TRMM data sets are brought to the light.
The scattering behavior of a slightly rough surface moving parallel to its mean plane with uniform velocity
ABSTRACT The scattering of plane electromagnetic (EM) waves from a perfectly conducting, slightly... more ABSTRACT The scattering of plane electromagnetic (EM) waves from a perfectly conducting, slightly rough surface moving in vacuum with uniform and constant velocity is examined by combining the boundary perturbation method and the special, homogeneous Lorentz transform. The direction of motion is assumed to be parallel to both the incidence plane and the mean plane of the moving rough surface. The analysis is confined to first-order scatter. The end result is the determination of the velocity-dependent expressions for the bistatic and backscatter incoherent cross sections per unit area of the scattering surface. The expressions for bistatic geometry are only valid for scattering inside the plane of incidence. A numerical example demonstrates the effect of the motion on the scattering behavior of the rough surface.
[IEEE 2010 International Conference on Mathematical Methods in Electromagnetic Theory (MMET) - Kyiv, Ukraine (2010.09.6-2010.09.8)] 2010 International Conference on Mathematical Methods in Electromagnetic Theory - Numerical evaluation of the eigenexpansion of the electrostatic potential near a di...
ABSTRACT The purpose of this paper is to elaborate on some numerical aspects of the evaluation of... more ABSTRACT The purpose of this paper is to elaborate on some numerical aspects of the evaluation of the eigenfunction expansion for the electrostatic potential near a dielectric cone of circular cross-section. This expansion has been derived analytically by the authors in a recent article [SIAM J. Appl. Math., 70 (2010), pp. 2329-2352] with the aid of the two-interval Sturm-Liouville theory. In our effort to implement numerically the aforesaid expansion we discovered a numerical instability on the spherical surface which is centered at the vertex of the cone and passes through the point source. In this paper we present an analytical way of removing that instability. Furthermore, we propose some numerical methods for calculating the terms of the eigenfunction expansion and we present some numerical results in the form of equipotential contour plots.
Focusing of Electromagnetic Waves by Non-Spherical, Au-Si Nano-particles
IFMBE Proceedings, 2014
Electromagnetics and Optics
Two-Interval Sturm–Liouville Theory for the Electrostatic Potential of a Point Charge near a Dielectric Cone
SIAM Journal on Applied Mathematics, 2010
ABSTRACT This paper provides the electrostatic potential of a point charge near a dielectric cone... more ABSTRACT This paper provides the electrostatic potential of a point charge near a dielectric cone of circular cross section. Our theory applies to any pair of dielectrics on either side of the conical interface and any cone angle. Separation of variables yields two associated Legendre differential equations which are coupled through boundary conditions on the surface of the cone. We solve this boundary value problem by consideration of a two-interval Sturm-Liouville operator which acts on the direct sum of two L² spaces, as suggested by Wang, Sun, and Zettl [J. Math. Anal. Appl., 328 (2007), pp. 390-399]. We proceed further to determine the inverse—integral—operator, we prove that it is compact and symmetric, we determine its eigenvectors, which form an orthogonal basis, and we use that basis, along with a classical Fourier series, to formulate the solution of the aforesaid electrostatic problem. Our analytical solution confirms van Bladel's prediction for the field at the tip of the cone, an outcome of his numerical investigation [IEEE Trans. Antennas and Propagation, 33 (1985), pp. 893-895]. As for the far field, we show that it is as if generated by the very same point charge in an unbounded homogenous medium with an effective dielectric constant wherein the media occupying the exterior and interior of the cone contribute according to the cone angle. Finally, we present briefly the formal derivation of our solution via the classical Mellin transform method and discuss its disadvantages over our proposed method.
Wave tilt calculations in the layered troposphere above a slightly rough sea
Radio Science, 1982
ABSTRACT The tilt of an EM wave propagating above the sea in a direction parallel to its mean sur... more ABSTRACT The tilt of an EM wave propagating above the sea in a direction parallel to its mean surface is theoretically calculated in an attempt to investigate the possibility to use the wave tilt probing method for the approximate determination of the sea state. A layered tropospheric slab having a typical index profile is considered above the slightly rough sea; the effective surface impedance of the sea is calculated according to a known model for a number of characterisitc wind speeds in the band 10-50 MHz. These models are combined for the calculation of the wave tilt for both horizontally and vertically polarized electromagnetic waves at various altitudes in the troposphere. Results show that the effect of the roughness of the sea surface on the wave tilt in the lower troposphere is not negligible and can also be measured at certain frequencies by using ordinary airborne wave tilt measurement methods. The tilt of an electromagnetic wave that is propagated along a surface is closely related to the electrical properties of the underlying subsurface medium. The wave tilt probing method has been applied in various geophysical surveys involving both earthbound and airborne sensors. The remote sensing of water, oil and gravel deposits as well as ore bodies below typical grounds, deserts, and in the permafrost could be mentioned among the more successful applications of this method. The theory for the determination of the tilt of an EM wave incident on a planar layered earth model has been developed by Wait [1962]. Calculations over two- and three-layer models simulating typical earth or planetary crust regions have been carried out by various authors. We refer the reader to the works of Lytle et al. [1976] and Warne et al. [1976b]. An investigation of the wave tilt characteristics over a homogeneous earth model from VLF to HF was performed by Singh and Lal [1980]. The measurement techniques currently used for the determination of the electrical properties of the uppermost layer of the ground by the wave tilt probing method are briefly reviewed by King [1976], while
Radio Science, 1987
The physical optics approach and Lorentz transformations are combined to formulate scatter from a... more The physical optics approach and Lorentz transformations are combined to formulate scatter from a random rough surface in uniform motion.
On the singularity of Green's tensor for a perfectly conducting semi-infinite cone
The Quarterly Journal of Mechanics and Applied Mathematics, 2007
ABSTRACT The paper is concerned with the problem of diffraction of electromagnetic waves by a per... more ABSTRACT The paper is concerned with the problem of diffraction of electromagnetic waves by a perfectly conducting cone. Having in mind that some literature reports differences on the known solutions of this problem [see C.-T. Tai, “Dyadic Green functions in electromagnetic theory”, Oxford: Oxford Univ. Press, New York, NY: IEEE Press (1994; Zbl 0913.73002) and D. S. Jones, Q. J. Mech. Appl. Math. 50, No. 4, 499–523 (1997; Zbl 0958.78014)], the authors: (i) reconstruct Tai’s solution in view of an analysis of the corresponding electric Green’s tensor (for a perfectly conducting semi-infinite cone); (ii) perform an expansion of Jones’s formula in series of eigenfunctions; (iii) use differentiation to obtain Jones’s solution in the expanded form. This allows the authors to compare Tai’s and Jones’s formulas. In addition, an appendix is included where the authors conclude that the closed-form solutions derived by Jones and Smyshlyaev [cf. V. P. Smyshlyaev, SIAM J. Appl. Math. 53, No. 3, 670–688 (1993; Zbl 0778.35104)] coincide as far as the magnetic field is concerned but differ by a singular term in the expression for the electric field.
Journal of the Optical Society of America A, 1995
A compact extended Mie solution to electromagnetic scattering from a cluster of spheres is obtain... more A compact extended Mie solution to electromagnetic scattering from a cluster of spheres is obtained through indirect mode matching. Our interest is focused on interactions among member spheres, as manifested in multiple scattering from the cluster. We therefore define and investigate the interactive-backscattering cross section of the cluster and the interaction length of member spheres. Numerical results are presented to probe the effect of sphere spacing as well as the effect of look direction and incident polarization on interactive backscattering from silicate clusters. Moreover, we present a brief extinction and absorption study of a soot particle near a cloud droplet.
Indirect mode-matching solution to scattering from a dielectric sphere with an eccentric inclusion
Journal of the Optical Society of America A, 1994
ABSTRACT The analytical formulation of electromagnetic wave scattering from an eccentrically stra... more ABSTRACT The analytical formulation of electromagnetic wave scattering from an eccentrically stratified dielectric sphere is greatly simplified through the indirect mode-matching technique. The resulting exact solution is the most compact available and hence the least prone to analytical or numerical errors. After some checks we present a comparison between our solution and two previous solutions that were obtained through direct mode matching. Our numerical investigation is focused on an acrylic sphere with an eccentric cavity. All four elements of the scattering matrix are available, and specific information about the possibility of detecting the scatterer's internal asymmetry is given.
Analytical study of the changes in the color of daylight due to sulfate droplets and soot grains in the atmosphere
Journal of Quantitative Spectroscopy and Radiative Transfer, 2004
ABSTRACT Absorption of daylight by an atmospheric layer that comprises non-interacting water and ... more ABSTRACT Absorption of daylight by an atmospheric layer that comprises non-interacting water and sulfate droplets, interstitial soot grains, and composite sulfate-soot particles is determined by use of exact theories of Mie or extended-Mie scattering from all types of suspended particles. Interest is in the color of the sky, as observed from the ground underneath a light-absorbing atmospheric layer which has been synthesized as above. The end-result of the theory presented in this paper is the spectral radiant power distribution and the colorimetric features of daylight at ground level. The numerical application manifests that microlensing by sulfate droplets gives rise to enhanced absorption by soot grains, which results in attenuation and redshifts of daylight. An investigation is made of the changes in the color of the sky, as observed from the ground, due to pollution of the air by sulfuric acid and carbon.
Uploads
Papers by D. Chrissoulidis