A very large number of scientific papers have been published in the literature on wearable antennas of several types, structure and functionality. The main focus is always antenna efficiency from an engineering point of view. However,... more
A very large number of scientific papers have been published in the literature on wearable antennas of several types, structure and functionality. The main focus is always antenna efficiency from an engineering point of view. However, antenna integration into actual, realistic garments is seldom addressed. In this paper, 2D pattern and 3D virtual prototyping technology is utilized to develop regular clothing, available in the market, in which wearable antennas are incorporated in an automated manner, reducing the chances of compromising the garment elegance or comfort. The functionality of various commercial software modules is described, and particular design examples are implemented, proving the efficiency of the procedure and leading the way for more complex configurations.
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The Physical Optics approximation is employed in the derivation of a closed form expression for the Radar Cross Section (RCS) of a flat, polygonal, perfectly conducting (PEC) plate, located over a dielectric, possibly lossy half space.... more
The Physical Optics approximation is employed in the derivation of a closed form expression for the Radar Cross Section (RCS) of a flat, polygonal, perfectly conducting (PEC) plate, located over a dielectric, possibly lossy half space. The well-known "fourpath model" is invoked in a first order approximation of the half space contribution to the scattering mechanisms. Numerical results are successfully compared to a reference, Moment Method solution. The analytical expressions derived can facilitate very fast RCS calculations for realistic scatterers, such as ships in a sea environment, or aircraft flying low over the ground. INTRODUCTION Radar Cross Section (RCS) estimation of electrically large, complex targets is usually performed via high frequency techniques, such as Physical Optics (PO). A target of complex geometry is routinely decomposed into an aggregate of elementary surfaces, and the total scattered field is computed as a superposition of the elementary scatteri...
The method of auxiliary sources (MAS) is utilized in the analysis of Transverse Magnetic (TM) plane wave scattering from infinite, conducting, or dielectric cylinders, including curved wedges. The latter are defined as intersections of... more
The method of auxiliary sources (MAS) is utilized in the analysis of Transverse Magnetic (TM) plane wave scattering from infinite, conducting, or dielectric cylinders, including curved wedges. The latter are defined as intersections of circular arcs. The artificial surface, including the auxiliary sources, is shaped in various patterns to study the effect of its form on the MAS accuracy. In juxtaposition with the standard, conformal shape, several deformations are tested, where the auxiliary sources are forced to approach the tip of the wedge. It is shown that such a procedure significantly improves the accuracy of the numerical results. Comparisons of schemes are presented, and the optimal auxiliary source location is proposed.
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In this paper a numerical analysis of electromagnetic scattering from various infinite, dielectric cylindrical objects is presented using the Method of Auxiliary Sources (MAS). Several cross sections which can be considered as perturbed... more
In this paper a numerical analysis of electromagnetic scattering from various infinite, dielectric cylindrical objects is presented using the Method of Auxiliary Sources (MAS). Several cross sections which can be considered as perturbed duplicates of the circle were investigated. The computational error associated with the numerical solution of the MAS linear system, as well as the condition number of the pertinent impedance matrix are plotted and the results are discussed. Furthermore, a parametric analysis is conducted in order to examine the effect of various parameters on the accuracy of the solution and the stability of the linear system. The aim of this study is the extraction of useful conclusions on the optimum location of the auxiliary sources for arbitrarily shaped dielectric scatterers.
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Page 1. I Accuracy Analysis of the Method of Auxiliary Sources (MAS); for Scattering by a Perfectly Conducting Cylinder Hristos T. Anastassiu Institute of Communications and Computer Systems, National Technical University ...
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Page 1. The P(MMAS) Interactive Environment: An Internet Service Coupling Web Technology and HPCN to Analyse Conformal Microstrip Arrays Andy Marsh, Dimitra I. Kaklamani, Member, IEEE, Hristos T. Anastassiu, Member, IEEE, and Phridon... more
Page 1. The P(MMAS) Interactive Environment: An Internet Service Coupling Web Technology and HPCN to Analyse Conformal Microstrip Arrays Andy Marsh, Dimitra I. Kaklamani, Member, IEEE, Hristos T. Anastassiu, Member, IEEE, and Phridon Shubitidze ...
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Two versions of a preconditioning procedure are described for a class of two-dimensional scattering problems, when the latter are solved via the Method of Auxiliary Sources (MAS). The method is useful for the case of shrinking auxiliary... more
Two versions of a preconditioning procedure are described for a class of two-dimensional scattering problems, when the latter are solved via the Method of Auxiliary Sources (MAS). The method is useful for the case of shrinking auxiliary surfaces, i.e. when the linear system may become ill-conditioned. If the cross sectional boundary can be regarded as a deformation of a circle,
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... Hristos T. Anastassiu, Member, IEEE, Dimitra I. Kaklamani, Member, IEEE, Dimitrios P. Economou, and Olav Breinbjerg, Member, IEEE ... investigated above, RCS convergence was generally achieved with a minimum auxiliary source den-sity... more
... Hristos T. Anastassiu, Member, IEEE, Dimitra I. Kaklamani, Member, IEEE, Dimitrios P. Economou, and Olav Breinbjerg, Member, IEEE ... investigated above, RCS convergence was generally achieved with a minimum auxiliary source den-sity equal to 5 per wavelength. ...
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Research Interests: Physics, Modeling, Method of Moments, Integral Equations, Antenna arrays, and 11 moreFourier Analysis, Implementation, Linear System, Linear Systems, Scattering, Antenna Array, Integral Equation, Numerical Inversion, Elementary Functions, Electrical And Electronic Engineering, and Circulant matrices
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Fundamental properties of certain popular integral equations for thin-wire circular-loop antennas with nonsingular kernels are studied. The cornerstone of our study is a large-asymptotic formula for the... more
Fundamental properties of certain popular integral equations for thin-wire circular-loop antennas with nonsingular kernels are studied. The cornerstone of our study is a large-asymptotic formula for the n'th Fourier coefficient of the nonsingular kernel. Four different methods of driving the circular loop are considered; namely, the delta-function generator, the finite-gap generator, a certain type of frill generator, and the case
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... of Auxiliary Sources (MAS) for Scattering by a Circular Cylinder Hristos T. Anastassiu, Member, IEEE, Dimitrios G. Lymperopoulos, and Dimitra I. Kaklamani, Member, IEEE ... Dimitrios G.Lymperopoulos was born in Athens, Greece, on... more
... of Auxiliary Sources (MAS) for Scattering by a Circular Cylinder Hristos T. Anastassiu, Member, IEEE, Dimitrios G. Lymperopoulos, and Dimitra I. Kaklamani, Member, IEEE ... Dimitrios G.Lymperopoulos was born in Athens, Greece, on December 8, 1978. ...
Research Interests: Data Analysis, Optimization, Geometry, Boundary Conditions, Error Analysis, and 12 moreEigenvalues, Linear System, Linear Systems, Matrix Decomposition, Scattering, Cylinder, Boundary Condition, Circular Cylinder, Electrical And Electronic Engineering, Condition number, Optimal location, and Accuracy analysis
ABSTRACT Errors were identified in the above titled paper (ibid., vol. 56, no. 1, pp. 151-157, Jan. 08), including several numerical errors on Table I. The errors do not affect the discussions. Corrections are presented here.
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Research Interests: Mathematics, Antennas & Radio Wave Propagation, Computational Electromagnetics, Numerical Analysis, Message Oriented Middleware, and 11 moreGeometry, Antenna Theory, Electromagnetic Scattering, Electromagnetic Radiation, Electromagnetic modeling, Boundary Conditions, Electromagnetic field theory, Boundary Value Problems, Integral Equation, Boundary Value Problem, and Electrical And Electronic Engineering
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ABSTRACT The analytic inversion of the Method of Auxiliary Sources (MAS) matrix plays an important role in the rigorous investigation of the accuracy of the method. In this paper we investigate the accuracy of MAS when the method is... more
ABSTRACT The analytic inversion of the Method of Auxiliary Sources (MAS) matrix plays an important role in the rigorous investigation of the accuracy of the method. In this paper we investigate the accuracy of MAS when the method is applied to plane wave scattering under oblique incidence by an infinite, dielectric circular cylinder. For this scattering configuration, we prove that the MAS matrix is analytically invertible and hence obtain a concrete expression for the discretization error. A basic contribution of this paper lies in the analytic determination of the auxiliary sources’ locations, for which the corresponding system’s matrix becomes singular. Furthermore, we calculate the computational error resulting from numerical matrix inversion, and compare it to the analytical error. The dependence of both types of errors on the angle of incidence and on the dielectric permittivity is investigated. Finally, error minimization indicates the auxiliary sources’ optimal location.
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Recent advances in the field of computational electromagnetics, as well as the increasing availability of processing power in computer systems, have enabled the analysis of complex antennas, which are often used in wireless and personal... more
Recent advances in the field of computational electromagnetics, as well as the increasing availability of processing power in computer systems, have enabled the analysis of complex antennas, which are often used in wireless and personal communications. Modern CAD tools permit the rapid analysis of such antenna systems and the visualization of their radiation characteristics. The ability to visualize two- and three-dimensional radiation patterns is a key to the understanding of basic antenna principles. Therefore, the study of the electromagnetic fields and their interaction with antennas therefore benefits tremendously by the introduction of advanced visualization tools. Additionally, current Web technologies provide unprecedented opportunities for making antenna analysis and design software packages accessible through standard browsers, removing often complicated interfaces. This article describes an integrated, World-Wide-Web-based asynchronous simulation environment for analyzing conformal microstrip antenna arrays. By coupling Web technology with visualization languages that offer interactivity and are suited to a web environment, such as the Virtual Reality Modelling Language (VRML), we can achieve the development of realistic visualization applications that offer a number of unique features over traditional visualization techniques.
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Een vindplaats van Polyommatus (Neolysandra) coelestina (Eversmann, 1843) werd ontdekt op
Multi-layer structures of single-walled carbon nanotubes mixtures with epoxy resin at different weight percentages are studied for maximizing the absorption of incident waves over X-Band. A short survey is also performed in 1-5 GHz. A... more
Multi-layer structures of single-walled carbon nanotubes mixtures with epoxy resin at different weight percentages are studied for maximizing the absorption of incident waves over X-Band. A short survey is also performed in 1-5 GHz. A plane wave from various elevation angles is illuminating the structure. Comparison with reference results shows satisfactory agreement. An optimization method is adopted for minimizing both the Reflection and Transmission Coefficient with respect to the optimum thickness of each layer for structures with and without perfect electric conducting substrates. A drastically increased absorption greater than 90% is achieved with the presence of carbon nanotubes even without the use of perfect electric conducting substrates. Total thickness is similar to structures with perfect electric conducting substrates promising thus innovative and interesting components for both electromagnetic compatibility and radar absorbing material applications.
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ABSTRACT
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A thriving colony of Cacyreus marshalli (Butler, 1898) is reported for the first time from Greece. The butterflies appeared in large numbers in late summer and throughout autumn of 2009 in parkland and gardens in the northern suburbs of... more
A thriving colony of Cacyreus marshalli (Butler, 1898) is reported for the first time from Greece. The butterflies appeared in large numbers in late summer and throughout autumn of 2009 in parkland and gardens in the northern suburbs of Athens. Introduced Pelargonium plants in a particular park were identified as the most probable explanation of this sudden occurrence. Moreover, the authors' persistent, yet unsuccessful efforts to locate Zizeeria karsandra (Moore, 1865) on the island of Crete are discussed. Samenvatting. Eerste vermelding van Cacyreus marshalli in Griekenland, en bemerkingen over het mogelijke voorkomen van Zizeeria karsandra op het Griekse eiland Kreta (Lepidoptera: Lycaenidae) Een succesvolle kolonie Cacyreus marshalli (Butler, 1898) wordt voor het eerst uit Griekenland vermeld. De vlinders vlogen talrijk in de nazomer en de herfst van 2009 in parken en tuinen van de noordelijke buitenwijken van Athene. De meest waarschijnlijke oorzaak van dit plotse voorkomen...
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ABSTRACT http://deepblue.lib.umich.edu/bitstream/2027.42/21483/2/rl2460.0001.001.pdf http://deepblue.lib.umich.edu/bitstream/2027.42/21483/1/rl2460.0001.001.txt
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Samenvatting. Polyommatus (Neolysandra) coelestina uit Centraal-Griekenland (Lepidoptera: Lycaenidae) Een vindplaats van Polyommatus (Neolysandra) coelestina (Eversmann, 1843) werd ontdekt op het Griekse vasteland, wat aantoont dat deze... more
Samenvatting. Polyommatus (Neolysandra) coelestina uit Centraal-Griekenland (Lepidoptera: Lycaenidae) Een vindplaats van Polyommatus (Neolysandra) coelestina (Eversmann, 1843) werd ontdekt op het Griekse vasteland, wat aantoont dat deze soort niet uitsluitend op de Peloponnesos voorkomt. Resume. Polyommatus (Neolysandra) coelestina (Eversmann, 1843) de Grece centrale (Lepidoptera: Lycaenidae) Une nouvelle localite de Polyommatus (Neolysandra) coelestina (Eversmann, 1843) fut decouverte en Grece continentale, ce qui montre que cette espece n'existe pas seulement sur le Peloponnese.
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... MEMO: April 19, 1995 TO: Jet Engine Analysis Team FROM: Dan Ross RE: Interfacing Exact Methods to Xpatch CC: In order to make use of the exact methods (FEM, Mode Matching) in Xpatch, it is necessary to add more sophistication into the... more
... MEMO: April 19, 1995 TO: Jet Engine Analysis Team FROM: Dan Ross RE: Interfacing Exact Methods to Xpatch CC: In order to make use of the exact methods (FEM, Mode Matching) in Xpatch, it is necessary to add more sophistication into the existing interfacing software. ...
A restricted colony of Clossiana selene ([Denis & Schiffermuller], 1775) is reported for the first time from Greece. The species appeared to be locally common in mid-July 2011, however its known distribution so far is extremely limited,... more
A restricted colony of Clossiana selene ([Denis & Schiffermuller], 1775) is reported for the first time from Greece. The species appeared to be locally common in mid-July 2011, however its known distribution so far is extremely limited, encompassing only a small marshland area surrounded by coniferous forest in the West Rhodopi mountain range, NE Greece, very close to the Bulgarian border. The small size of its habitat, which is of unusual nature in Greece, in conjunction with the general rarity of this butterfly in SE Europe, call for immediate environmental protection by the authorities. Samenvatting. Eerste melding van Clossiana selene in Griekenland (Lepidoptera: Nymphalidae) Een erg lokale kolonie van Clossiana selene ([Denis & Schiffermuller], 1775) wordt hier voor het eerst uit Griekenland gemeld. De soort bleek plaatselijk gewoon te zijn midden juli 2011, maar ze komt uiterst lokaal voor, nl. in een klein moerassig gebied omgeven door pijnbomen in de westelijke Rhodopen, N.-...
Several colonies of Pseudochazara graeca (Staudinger, 1870) are reported for the first time from north-central Greece, geographically connecting the hitherto known as disjunct northern and southern populations of this species, and clearly... more
Several colonies of Pseudochazara graeca (Staudinger, 1870) are reported for the first time from north-central Greece, geographically connecting the hitherto known as disjunct northern and southern populations of this species, and clearly showing that the wing coloration exhibits a clinal variation from north to south, casting doubt about the validity of ssp. coutsisi Brown, 1977 (= zagoriensis Aussem, 1978). The generally held notion regarding Satyrinae, and as far as Europe is concerned, especially regarding the genera Hipparchia, Pseudochazara and Hyponephele, that the HW underside ground colour adapts to the geological character of the habitat by mimicking the colour of rock surfaces, is shown to be inapplicable both to P. graeca, as well as to Hyponephele lycaon (Rottemburg, 1775). Samenvatting. Nieuwe gegevens betreffende de geografische verspreiding van Pseudochazara graeca in Griekenland, met bemerkingen over de kleur van de vleugels, de status van ssp. coutsisi (= zagoriens...
Like all branches of physics and engineering, electromagnetics relies on mathematical methods for modeling, simulation, and design procedures in all of its aspects (radiation, propagation, scattering, imaging, etc [...]
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Full Duplex (FD) wireless communications is considered to be the next big step for future Wireless Local Area Networks (WLANs). Old (IEEE 802.11ac) and new (IEEE 802.11ax) WLAN features are expected to co-exist with FD operation. Some of... more
Full Duplex (FD) wireless communications is considered to be the next big step for future Wireless Local Area Networks (WLANs). Old (IEEE 802.11ac) and new (IEEE 802.11ax) WLAN features are expected to co-exist with FD operation. Some of these features include Downlink Multi-User (DL MU) transmissions at the physical layer while at the Medium Access Control (MAC) layer techniques such as the Transmission Opportunity (TXOP) sharing mechanism facilitates these multiuser transmissions. The traditional Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol is inadequate to support full duplex communications efficiently. A very promising adaptation of CSMA/CA and a powerful candidate as the basic channel access method for future WLANs is the Carrier Sense Multiple Access with Enhanced Collision Avoidance (CSMA/ECA). In this paper, we provide an analytical model to assess the performance of resource sharing techniques in full duplex WLANs operating with the CSMA/ECA pro...
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In the geometry considered, a finite-size parabolic reflector in two- and three- dimensions is illuminated by a two or three-dimensional Gaussian beam (GB), respectively. The aim of the study is to evaluate analytically the reflected and... more
In the geometry considered, a finite-size parabolic reflector in two- and three- dimensions is illuminated by a two or three-dimensional Gaussian beam (GB), respectively. The aim of the study is to evaluate analytically the reflected and the edge diffracted field. In particular, the relatively general 3-D problem of the reflection of an incident electromagnetic GB by a perfectly conducting parabolic surface whose principal directions may not coincide with the plane of incidence is considered.<<ETX>>
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ABSTRACT Several well-known computational methods, based on various mathematical concepts, are applied to the electromagnetic scattering analysis of a benchmark cavity structure. Specifically, a simplified jet engine inlet configuration... more
ABSTRACT Several well-known computational methods, based on various mathematical concepts, are applied to the electromagnetic scattering analysis of a benchmark cavity structure. Specifically, a simplified jet engine inlet configuration is defined, constructed and used as reference, whereas predicted numerical results for the radar cross-section are compared with measurements. The merits and drawbacks of each method are highlighted and quantified, with respect to accuracy, efficiency, resource requirements, reliability and robustness. Conclusions may be exploited in the near future in the construction of reliable classifiers, used in non-cooperative target identification.
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The results of two days' collecting on the Greek Island of Simi are being presented together with an account of the island's previous lepidopterological records. Gegenes pumilio and Nymphalis polychloros are reported from Simi for... more
The results of two days' collecting on the Greek Island of Simi are being presented together with an account of the island's previous lepidopterological records. Gegenes pumilio and Nymphalis polychloros are reported from Simi for the first time and Jordanita anatolica is reported as new to the Greek fauna. Moreover, unusual FW upperside and HW underside colour features in male Satyrium ilicis are being presented and discussed. Samenvatting. Vlinders waargenomen op het Griekse eiland Simi einde april 2010 (Lepidoptera: Hesperioidea, Papilionoidea, Zygaenidae) De resultaten van een tweedaagse trip naar het Griekse eiland Simi worden opgesomd samen met een verslag van de reeds bekende vlindersoorten van dit eiland. Gegenes pumilio en Nymphalis polychloros worden voor het eerst van Simi vermeld en Jordanita anatolica is nieuw voor de Griekse fauna. Verder worden ongewone kleurvormen op de bovenkant van de voorvleugels en de onderkant van de achtervleugels bij het maantje van Sa...
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... MEMO: April 19, 1995 TO: Jet Engine Analysis Team FROM: Dan Ross RE: Interfacing Exact Methods to Xpatch CC: In order to make use of the exact methods (FEM, Mode Matching) in Xpatch, it is necessary to add more sophistication into the... more
... MEMO: April 19, 1995 TO: Jet Engine Analysis Team FROM: Dan Ross RE: Interfacing Exact Methods to Xpatch CC: In order to make use of the exact methods (FEM, Mode Matching) in Xpatch, it is necessary to add more sophistication into the existing interfacing software. ...
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The aim of this paper is to present an extension over a novel three dimensional high frequency method for the calculation of the scattered electromagnetic (EM) field from a Perfect Electric Conductor (PEC) plate, which is based on the... more
The aim of this paper is to present an extension over a novel three dimensional high frequency method for the calculation of the scattered electromagnetic (EM) field from a Perfect Electric Conductor (PEC) plate, which is based on the Physical Optics (PO) approximation and the Stationary Phase Method (SPM). This method has been presented only recently, showing fast and satisfactory