1,721,056 research outputs found
Guest Editorial: Special issue on metamaterials and special materials for electromagnetic applications and telecommunications
No full text3-D printed THz q-plate with a fixed rate of change of the optical axis
No full textWe report the design and test of a THz dielectric q-plate realizing a fixed rate of change of the optical axis. The device consists of space-variant birefringent slabs manufactured by 3D printing using melt extruded ABS (Acrylonitrile Butadiene Styrene). The full position-dependent electric field of the THz beam propagating through the g-plate is obtained by measuring the THz time domain signal with a standard raster scan imaging routine. The E-field azimuthal and radial wave front patterns are successfully acquired from the realized q-plate
Geometrical Dependence on the Onset of Surface Plasmon Polaritons in THz Grid Metasurfaces
Full text linkThe transmission response of metallo-dielectric grid metasurfaces is experimentally investigated
through Terahertz Time Domain Spectroscopy and the corresponding effective dielectric function is retrieved. Using a lumped element model we can determine the dependence of the effective plasma frequency (the transition frequency) on the metasurface filling factor F. The change of the transition frequency vs. F spans over one order of magnitude and sets the threshold between the metamaterial (homogeneous) and the photonic crystal (diffraction-like) regime, ruling the onset of two different Surface Plasmon Polaritons, spoof and high order. Field symmetry and spatial extension of such excitations are investigated for the possible applications of THz grid metasurfaces in bio- and chemical sensing and sub-wavelength imaging
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Two-gap superconductivity and microwave properties of YBCO
No full textThe YBa2Cu3O7-x compound contains two conductive subsystem and as a result displays a two-gap structure. The Cu-O2 planes are characterized by intrinsic pairing, whereas the superconducting state of the Cu-O chains is induced by two different charge-transfer channels (intrinsic proximity effect and phonon-mediated transfer). Oxygen ordering affects the value of the induced energy gap. Such spectrum along with a short coherence length lead to peculiar microwave properties of YBCO thin films. The large residual microwave losses are explained in the framework of the two-gap model. © 1992 Plenum Publishing Corporation
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