1,721,329 research outputs found
A Cloaking Metamaterial Based on an Inhomogeneous Linear Field Transformation
No full textA new type of bianisotropic metamaterial is theoretically investigated on the basis of a linear inhomogeneous field transformation applied to an arbitrary free-space Maxwellian field. This transformation does not include any space compression as predicted by transformation optics, and consists of a linear combination with space-dependent coefficients of the electric and magnetic incident fields. Duality conditions are applied to select an appropriate shape of the constituent dyads, thus resulting in a metamaterial completely defined by two real differentiable functions of space sigma and eta. When these functions satisfy the condition sigma(2) + eta(2) on the medium contour, the medium becomes globally lossless, and when imposing sigma = 0 and eta = 1 at the same boundary, the medium does not scatter for any arbitrary incident field, that is, it becomes invisible. When an additional internal boundary is introduced with boundary conditions sigma = 0 and eta = 0, the medium becomes a perfect cloak. Explicit analytical results are given for an invisible sphere and for a spherical cloak to provide additional physical insight
The European School of Antennas: Structure, results and perspectives
No full textThe European School of Antennas (ESoA) is a geographically distributed nonprofit post-graduate school on antennas, propagation, and relevant applications. The ESoA courses are distributed in the most accredited European research centers of antennas and wireless systems. In the first three year of life, the ESoA courses involved about 680 students and more than 150 different teachers, mostly university professors. This paper presents the structure of the school, the results obtained since its founding, and its future development and perspectives
Legacy of Excellence: Honoring the Leadership of Ross Stone in Editorial, Industry and Science
No full textWith his extensive experience of over 45 years in the field, Ross Stone was a towering figure and a guiding light in the Antennas and Propagation and Radio Science community. Throughout his career, he made significant contributions to industry, consulting, and research in antennas, propagation, and related technologies. Renowned for his exceptional skills and altruistic nature in supporting and fostering new initiatives, Ross became a key figure in major international societies and networks. His involvement with the IEEE Antennas and Propagation Society (AP-S), the International Union of Radio Science (URSI), and the European Association on Antennas and Propagation (EuRAAP) was profoundly influential. His active participation and leadership within these organizations was driven by his commitment to advancing the field and fostering and serving global scientific and technical communities. Through his roles, Ross not only contributed to the technical advancement of antennas and propagation but also played a pivotal role in bridging gaps between different scientific communities and enhancing international collaboration
EM Metasurfaces [Guest Editorial]
No full textMetasurfaces (MTSs) [1], [2], [3], [4], [5] are the surface equivalent of metamaterials (MTMs): artificial materials composed of subwavelength inclusions embedded in a host medium tailored to exhibit unconventional electromagnetic (EM) properties. In contrast to MTMs, which are characterized in terms of homogenized material parameters, the EM responses of MTSs are often characterized by homogenized boundary conditions (BCs). MTSs can be designed to exhibit abrupt amplitude and phase discontinuities to perform extreme wavefront transformations. Classical 'surface EMs' [3] took on fresh and exciting research directions with MTSs, revealing fascinating phenomena and new applications
Empowering Patients to Self-Care in Web-mediated Communication: A Multimodal Discourse Analysis. Nel volume Insights into Medical Communication, a cura di Gotti, M. / Maci, S. / Sala, M., Peter Lang, Berna, pp. 213-239
No full textThis study offers a multimodal discourse analytic description of online self-care communication as a dynamic and strategic medium for engaging people in their health. It does so by looking at the linguistic and visual resources used across Web-mediated texts, uncovering the potential meanings created for the social activities and purposes behind those resources. The paper breaks down as follows. First, the empirical material for corpus-driven analysis is indicated and the research method outlined. Secondly, the key findings of empirical data are analysed and discussed and, thirdly, tentative conclusions are drawn from contextualized material
An Exact Line Integral Representation of the PO Radiation Integral from a Flat Perfectly Conducting Surface Illuminated by Elementary Electric or Magnetic Dipoles
No full textIn this paper, a line integral representation for the PO radiation integral from a flat perfectly conducting surface, illuminated by an arbitrary oriented elementary either electric or magnetic dipole, is presented. No restriction is imposed on the position of the source and of the observation point. The main application of this result is the acceleration of the numerical PO integration for electrically large surfaces. The formulation is based on the application of the equivalence principle to a projecting surface which allows the analytical evaluation in closed form of one of the two-fold surface integral which define the radiated field at any space point. Although similar solutions has been suggested by other authors, our final outcome is simple, clearly interpretable, and easily applicable with respect to previous results
Theory, Analysis, and Design of Metasurfaces for Smart Radio Environments
Full text linkThe term ``metasurface'' (MTS) denotes an artificial surface constituted by a distribution of electrically small elements that collectively exhibit equivalent homogeneous boundary conditions (BCs) to an interacting electromagnetic field. MTSs are becoming increasingly popular due to the technological simplification that they offer with respect to volumetric metamaterials. In this article, we review the basic theory behind microwave MTSs seen as reconfigurable intelligent surfaces (RISs), oriented to the future visionary challenge of a smart radio environment. To this end, two different typologies of MTS are reviewed: surface-wave-based MTSs and nonspecular reflective MTSs. Both types can be effectively characterized using simplified problems that locally match the homogenized, modulated BCs. A different use of these problems allows for an accurate design of radiated and scattered fields. An accurate ray representation is also suggested, which allows for an effective description of the scattered field also in the Fresnel region and for the insertion of the MTS description in ray-tracing tools for network planning. Several examples of practical implementation are shown, and the challenges in applying electronic reconfigurability are discussed
Spatio-temporal patterns of abundance, size structure and body condition of Atherina boyeri (Pisces: Atherinidae) in a small non-tidal Mediterranean lagoon.
No full textNear-field line-integral representation of the kirchhoff-type aperture radiation for a parabolic reflector
No full textIn this letter, a line integral representation is presented for a linearly polarized Kirchhoff-type aperture radiation from a parabolic reflector antenna. The main purpose of this result is concerned with the acceleration of the numerical integration for calculating the near field of large reflector antennas. The formulation, which is rigorous for uniform aperture field, is based on the application of the equivalence principle to a projecting surface, which allows the analytical evaluation in a closed form of one of the twofold surface integral which defines the radiated field at any space point; the extension to slowly varying primary feed pattern is based on an asymptotic approximation, which is proved to be accurate in proximity of the aperture till to -30 dB of amplitude edge illumination. The present formulation is well suited to be improved by fringe diffraction contributions in the framework of edge-wave theories such as physical theory of diffraction (PTD) and incremental theory of diffraction (ITD)
Empowering patients to self-care in web-mediated communication: A multimodal discourse analysis
No full textThis study offers a multimodal discourse analytic description of online self-care communication as a dynamic and strategic medium for engaging people in their health. It does so by looking at the linguistic and visual resources used across Web-mediated texts, uncovering the potential meanings created for the social activities and purposes behind those resources. The paper breaks down as follows. First, the empirical material for corpus-driven analysis is indicated and the research method outlined. Secondly, the key findings of empirical data are analysed and discussed and, thirdly, tentative conclusions are drawn from contextualized material
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