Search results for "Virtual"
showing 10 items of 1485 documents
New Insight in the $Q^2$-Dependence of Proton Generalized Polarizabilities
2019
Virtual Compton scattering on the proton has been investigated at three yet unexplored values of the four-momentum transfer $Q^2$: 0.10, 0.20 and 0.45 GeV$^2$, at the Mainz Microtron. Fits performed using either the low-energy theorem or dispersion relations allowed the extraction of the structure functions $P_{LL} -P_{TT} / \epsilon$ and $P_{LT}$, as well as the electric and magnetic generalized polarizabilities $\alpha_{E1}(Q^2)$ and $\beta_{M1}(Q^2)$. These new results show a smooth and rapid fall-off of $\alpha_{E1}(Q^2)$, in contrast to previous measurements at $Q^2$ = 0.33 GeV$^2$, and provide for the first time a precise mapping of $\beta_{M1}(Q^2)$ in the low-$Q^2$ region.
Muonic-hydrogen Lamb shift: Dispersing the nucleon-excitation uncertainty with a finite-energy sum rule
2013
We assess the two-photon exchange contribution to the Lamb shift in muonic hydrogen with forward dispersion relations. The subtraction constant (T) over bar (0, Q(2)) that is necessary for a dispersive evaluation of the forward doubly virtual Compton amplitude, through a finite energy sum rule, is related to the fixed J = 0 pole generalized to the case of virtual photons. We evaluated this sum rule using excellent virtual photoabsorption data that are available. We find that the "proton polarizability correction" to the Lamb shift in muonic hydrogen is -(40 +/- 5) mu eV. We conclude that nucleon structure-dependent uncertainty by itself is unlikely to resolve the large (300 mu eV) discrepan…
Antiscreening of the Ampère force in QED and QCD plasmas
2013
The static forces between electric charges and currents are modified at the loop level by the presence of a plasma. While electric charges are screened, currents are not. The effective coupling constant at long distances is enhanced in both cases as compared to the vacuum, and by different amounts, a clear sign that Lorentz symmetry is broken. We investigate these effects quantitatively, first in a QED plasma and secondly using non-perturbative simulations of QCD with two light degenerate flavors of quarks.
Virtual point detector: Application to coincidence-summing correction in gamma-ray spectrometry
2009
The use of an efficiency transfer method based on the virtual point detector approximation to evaluate coincidence-summing correction values for point and volume sources was examined. The method was validated by means of a comparison with experimental efficiency determinations.
A crop field modeling to simulate agronomic images
2010
In precision agriculture, crop/weed discrimination is often based on image analysis but though several algorithms using spatial information have been proposed, not any has been tested on relevant databases. A simple model that simulates virtual fields is developed to evaluate these algorithms. Virtual fields are made of crops, arranged according to agricultural practices and represented by simple patterns, and weeds that are spatially distributed using a statistical approach. Then, experimental devices using cameras are simulated with a pinhole model. Its ability to characterize the spatial reality is demonstrated through different pairs (real, virtual) of pictures. Two spatial descriptors …
ON THE “SOLAR SYSTEM SMALL BODIES” ASTROPLATE PROJECT OF THE UKRAINIAN VIRTUAL OBSERVATORY
2019
The UkrVO Joint Digital Archive of astro- plates and the newest digitized data processing services al- lowed us to form a new approach for the creation of catalogs of astrometric and photometric characteristics of the Solar System bodies. Given this, the main goal of this approach was not only to complete the processing with the best possi- ble accuracy of high-quality and unprocessed earlier photo- graphic observations of the Solar System bodies but also to find new original data from these observations. As a result, more than 6,500 new astrometric positions and stellar magnitudes of asteroids, and 3,036 positions of outer planets (Pluto, Uranus, Neptune, Saturn, Jupiter) and their satelli…
Towards an Immersive and Accessible Virtual Reconstruction of Theaters from the Early Modern
2020
This paper reports on the work being done towards achieving an immersive and accessible reconstruction of Historical and Cultural Heritage, focusing on Theaters of the Early Modern as use case. In particular, the paper presents and discusses potential possibilities to enable: 1) the acoustical reconstruction of the virtual (lost) environments – beyond the graphical reconstruction for the buildings, elements and performances; 2) effective interaction features and navigation within the virtual environment (e.g. by means of adaptive interfaces, guiding methods, insertion of Point of Interest); and 3) accessible experiences, by means of an innovative and personalized presentation modes for acce…
Se l’enunciatore non parla. Note sulla nozione ducrotiana di punto di vista.
2018
«Voice» and «Point of view» have been two of the most debated topics in some fields of linguistics and semiotics. Generally, DUCROT (1984) is considered like one of the first essays which introduced these concepts in the theoretical framework of the analysis of enunciation. As for the first one, the Author limits himself to suggest that it is connected with the notion of «discourse». In fact, by examining some topics of SPERBER & WILSON (1978), he seems to assimilate «voice» to «discourse». Indeed, you can read «j’ai substitué l’expression “faire entendre une voix” à leur expression “mentionner un discours”». As for the second concept, He seems to assimilate «point of view» to intuitive not…
Una experiencia docente: la introducción del foro en la asignatura de Informática II en Biblioteconomía y Documentación
2010
Este artículo introduce la experiencia docente que se ha llevado a cabo durante el curso académico 2008/09 con la introducción de un foro virtual como herramienta de enseñanza y aprendizaje en la asignatura de Informática II en la Diplomatura de Biblioteconomía y Documentación de la Universitat de València. Para analizar la experiencia se realiza un estudio cuantitativo sobre de la utilización del foro y del tipo de participaciones. Así mismo se valora la opinión de los alumnos sobre el foro como herramienta de trabajo para el aprendizaje.
Immersi nel futuro
2020
"Immersi nel futuro" è un volume di ricerca che affronta il tema dei contenuti "cinematici" per la realtà virtuale. "Immersi nel futuro" is a research volume that deals with the theme of "cinematic" contents for virtual reality.