1,721,150 research outputs found
Nonlinear feedback preamplifier for optical trigger circuits
No full textA nonlinear preamplifier system to improve the performance of a zerocrossover optical trigger circuit is presented. The network is based on a low-noise operational amplifier with a Zener diode feedback. It is proposed to exploit the nonlinear characteristic of this network to reduce timing measurement uncertainty. Accordingly the circuit has been developed and tested in operation
la pinacoteca nel sistema museale dell'università degli studi di trieste
No full textSi tratta della presenza di arte contemporanea all'università di Trieste nella pinacoteca di atene
A PC-controlled nonincremental distance meter based on a comb-spectrum combined with a frequency-modulated continuous wave interferometer
No full textIn this paper, a PC-controlled nonincremental interferometer that integrates frequency-modulated continuous wave (FMCW) and dispersive comb spectrum (DCS) techniques is presented. This system takes advantage of the wide measuring range of the FMCW technique and of the high resolution of the DCS technique. The system prototype presented in this paper performs measurements over a range of 30 mm with an accuracy of about 600 nm. The proposed combined interferometer is expected to also have applications in biomedical frameworks
A true-phase polarimetric system to study bi-anisotropic media
No full textThe article describes a true-phase polarimeter designed to study bi-anisotropic media. Exploiting a simple optical setup based on two He-Ne lasers and a precise analogue phase-to-voltage converter, the measuring system exhibits high sensitivity and excellent rejection ambient ligh
Hyperbolic geometry and amplituhedra in 1+2 dimensions
Full text linkRecently, the existence of an Amplituhedron for tree level amplitudes in the bi-adjoint scalar field theory has been proved by Arkani-Hamed et al. We argue that hyperbolic geometry constitutes a natural framework to address the study of positive geometries in moduli spaces of Riemann surfaces, and thus to try to extend this achievement beyond tree level. In this paper we begin an exploration of these ideas starting from the simplest example of hyperbolic geometry, the hyperbolic plane. The hyperboloid model naturally guides us to re-discover the moduli space Associahedron, and a new version of its kinematical avatar. As a by-product we obtain a solution to the scattering equations which can be interpreted as a special case of the two well known solutions in terms of spinor-helicity formalism. The construction is done in 1 + 2 dimensions and this makes harder to understand how to extract the amplitude from the dlog of the space time Associahedron. Nevertheless, we continue the investigation accommodating a loop momentum in the picture. By doing this we are led to another polytope called Halohedron, which was already known to mathematicians. We argue that the Halohedron fulfils many criteria that make it plausible to be understood as a 1-loop Amplituhedron for the cubic theory. Furthermore, the hyperboloid model again allows to understand that a kinematical version of the Halohedron exists and is related to the one living in moduli space by a simple generalisation of the tree level map
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
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