1,721,092 research outputs found
Highly Sensitive Polarization Rotation Measurement through a High-Order Vector Beam Generated by a Metasurface
Get PDFThe precise determination of the polarization state of light is fundamental for a vast variety of applications in remote sensing, astronomy, optics and terahertz technology, to name just a few. Typically, polarization characterization is performed by using a combination of multiple optical devices such as beam splitters, polarizers, and waveplates. Moreover, to achieve high-precision, balanced photodetectors and lock-in amplifiers are employed, thus contributing to increasing system complexity. Here, a technique for polarization rotation measurements with a dynamic range of 180° and a sensitivity of about 10−2 degrees is realized using a properly designed metasurface. Such device generates a vector beam with an azimuthally-dependent polarization distribution, as a result of the superposition of two vortex beams carrying opposite orbital angular momenta (l = ±30). After propagation through a linear polarizer, the spatial intensity profile of such a beam turns into 60 lobes. By tracking the displacement of only two of these lobes on a camera, the rotation of the input polarization state can be retrieved with high resolution. The proposed approach offers a new route toward the development of compact high-precision polarimeters and can also be exploited in quantum information processing, optical communications, as well as nonlinear and chiral optics
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Polarization rotation measurements via a high-order vector beam generated by a metasurface
No full textA technique for polarization rotation measurements with a dynamic range of 180° and sensitivity of about 10-2 degrees is realized using a properly designed metasurface
Terahertz compressive imaging directly in the time domain
No full textWe exploit a single-pixel imaging approach to obtain multi-dimensional (space, time/frequency) images at terahertz frequencies by reconstructing the temporal waveform in each pixel. Moreover, we apply compressive sensing to reduce the acquisition time
A scanless method for terahertz time-domain imaging
No full textTerahertz (THz) time-domain imaging can uncover the spectral fingerprints of materials, detect changes in both refractive index and absorption, and reveal the inner structure of complex objects through time-of-flight measurements. Despite its potential, the lengthy acquisition typically required to spatially raster-scan the object and record the terahertz temporal waveforms for each spatial point limits practical applications. Our scanless imaging method sets the path for an unprecedented reduction of both system complexity and acquisition time, by addressing this crucial bottleneck. By judiciously exploiting natural wave diffraction, time-to-space encoding is applied to THz point detection and enables a nearly instantaneous capture of the terahertz waveforms. Multidimensional images are then reconstructed through a computational method. This approach opens the route for next-generation fast and compact THz imagers that are well-suited for high-repetition-rate laser sources
Plasmonic heating and temperature-sensing in the terahertz regime-thermometry and imaging
No full textResonant near-infrared excitation induces localized heating of colloidal gold nanorod dispersions. We show that detection and imaging are possible using Terahertz (THz) waves, which possess absorption and refractive indices sensitive to water temperature change. © 2014 OSA
Custom measurement system for memristor characterisation
Get PDFA cheap, compact and customisable characterisation system for memristor devices, working between ±10 V, is presented. SPICE (Simulation Program with Integrated Circuit Emphasis) simulations are performed to verify the circuit feasibility and a proper software is developed to drive the system. The potentiality of the realised system is tested by performing several electrical measurements on both Cu/HfO2/Pt memristors and two-terminals commercial devices
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