7,451 research outputs found
Estado atual das bibliotecas digitais no Brasil
O presente capítulo "Estado atual das bibliotecas digitais no Brasil" compõe o livro "Bibliotecas digitais: saberes e práticas", 2ª edição, organizado por Carlos H. Marcondes, Helio Kuramoto, Lidia Brandão Toutain e Luis Sayão.O Brasil possui uma tradição de serviços bibliotecários, funcionando na maioria das cidades de médio e grande porte, que, geralmente, contam com sistemas de automação de bibliotecas (McCARTHY, 1990; McCARTHY; SCHMIDT, 1994; CORTE e outros, 2003). As bibliotecas suportam os programas educacionais, especialmente os de segundo e terceiro graus. Na última década, as bibliotecas digitais tiveram um significativo impacto no setor de biblioteca e informação, notadamente na América do
Norte, onde atraíram enorme atenção (CHOWDHUR; CHOWDHURX 1999). O rápido avanço da Internet no Brasil, conforme já apontado no item anterior, e a existência de uma base razoável de bibliotecas automatizadas naturalmente irão redundar na ampliação do número de bibliotecas digitais. No contexto atual, as maiores iniciativas brasileiras se enquadram em quatro categorias: ciência e tecnologia, educação, literatura e humanidades, história e política. Neste capítulo, serão analisados os
principais projetos institucionais de bibliotecas digitais
The experience of enchantment in human-computer interaction
Improving user experience is becoming something of a rallying call in human–computer interaction but experience is not a unitary thing. There are varieties of experiences, good and bad, and we need to characterise these varieties if we are to improve user experience. In this paper we argue that enchantment is a useful concept to facilitate closer relationships between people and technology. But enchantment is a complex concept in need of some clarification. So we explore how enchantment has been used in the discussions of technology and examine experiences of film and cell phones to see how enchantment with technology is possible. Based on these cases, we identify the sensibilities that help designers design for enchantment, including the specific sensuousness of a thing, senses of play, paradox and openness, and the potential for transformation. We use these to analyse digital jewellery in order to suggest how it can be made more enchanting. We conclude by relating enchantment to varieties of experience.</p
Em Memória de Eavan Boland
“In Memory of Eavan Boland” by Thomas MacCarthy. Written for “Eavan Boland — In Her Many Images”, ABEI Journal 23.2 (2021).“In Memory of Eavan Boland”, de Thomas MacCarthy. Tradução para o português por Marina Bertani Gazola e Rafael Teles da Silva. Escrito para “Eavan Boland — In Her Many Images”, ABEI Journal 23.2 (2021)
Barrier and internal wave contributions to the quantum probability density and flux in light heavy-ion elastic scattering
We investigate the properties of the optical model wave function for light
heavy-ion systems where absorption is incomplete, such as Ca
and O around 30 MeV incident energy. Strong focusing effects
are predicted to occur well inside the nucleus, where the probability density
can reach values much higher than that of the incident wave. This focusing is
shown to be correlated with the presence at back angles of a strong enhancement
in the elastic cross section, the so-called ALAS (anomalous large angle
scattering) phenomenon; this is substantiated by calculations of the quantum
probability flux and of classical trajectories. To clarify this mechanism, we
decompose the scattering wave function and the associated probability flux into
their barrier and internal wave contributions within a fully quantal
calculation. Finally, a calculation of the divergence of the quantum flux shows
that when absorption is incomplete, the focal region gives a sizeable
contribution to nonelastic processes.Comment: 16 pages, 15 figures. RevTeX file. To appear in Phys. Rev. C. The
figures are only available via anonynous FTP on
ftp://umhsp02.umh.ac.be/pub/ftp_pnt/figscat
I-mode studies at ASDEX Upgrade: L-I and I-H transitions, pedestal and confinement properties
The I-mode is a plasma regime obtained when the usual L-H power threshold is high, e.g.
with unfavourable ion
B
∇
direction. It is characterised by the development of a temperature
pedestal while the density remains roughly as in the L-mode. This leads to a confinement
improvement above the L-mode level which can sometimes reach H-mode values. This
regime, already obtained in the ASDEX Upgrade tokamak about two decades ago, has
been studied again since 2009 taking advantage of the development of new diagnostics
and heating possibilities. The I-mode in ASDEX Upgrade has been achieved with different
heating methods such as NBI, ECRH and ICRF. The I-mode properties, power threshold,
pedestal characteristics and confinement, are independent of the heating method. The power
required at the L-I transition exhibits an offset linear density dependence but, in contrast
to the L-H threshold, depends weakly on the magnetic field. The L-I transition seems to be
mainly determined by the edge pressure gradient and the comparison between ECRH and
NBI induced L-I transitions suggests that the ion channel plays a key role. The I-mode often
evolves gradually over a few confinement times until the transition to H-mode which offers
a very interesting situation to study the transport reduction and its link with the pedestal
formation. Exploratory discharges in which
n
=
2 magnetic perturbations have been applied
indicate that these can lead to an increase of the I-mode power threshold by flattening the edge
pressure at fixed heating input power: more heating power is necessary to restore the required
edge pressure gradient. Finally, the confinement properties of the I-mode are discussed in
detail.European Commission (EUROfusion 633053
Cluster scaling relations from cosmological hydrodynamic simulations in dark energy dominated universe
Clusters are potentially powerful tools for cosmology provided their observed
properties such as the Sunyaev-Zel'dovich (SZ) or X-ray signals can be
translated into physical quantities like mass and temperature. Scaling
relations are the appropriate mean to perform this translation. It is
therefore, important to understand their evolution and their modifications with
respect to the physics and to the underlying cosmology. In this spirit, we
investigate the effect of dark energy on the X-ray and SZ scaling relations.
The study is based on the first hydro-simulations of cluster formation for
diferent models of dark energy. We present results for four dark energy models
which differ from each other by their equations of state parameter, .
Namely, we use a cosmological constant model (as a reference), a perfect
fluid with constant equation of state parameter and one with and a scalar field model (or quintessence) with varying . We generate
N-body/hydrodynamic simulations that include radiative cooling with the public
version of the Hydra code, modified to consider an arbitrary dark energy
component. We produce cluster catalogues for the four models and derive the
associated X-ray and SZ scaling relations. We find that dark energy has little
effect on scaling laws making it safe to use the CDM scalings for
conversion of observed quantities into temperature and masses.Comment: 9 pages, 7 figures, submitted to A&
The Large Quasar Reference Frame (LQRF) - an optical representation of the ICRS
The large number and all-sky distribution of quasars from different surveys,
along with their presence in large, deep astrometric catalogs,enables the
building of an optical materialization of the ICRS following its defining
principles. Namely: that it is kinematically non-rotating with respect to the
ensemble of distant extragalactic objects; aligned with the mean equator and
dynamical equinox of J2000; and realized by a list of adopted coordinates of
extragalatic sources. Starting from the updated and presumably complete LQAC
list of QSOs, the initial optical positions of those quasars are found in the
USNO B1.0 and GSC2.3 catalogs, and from the SDSS DR5. The initial positions are
next placed onto UCAC2-based reference frames, following by an alignment with
the ICRF, to which were added the most precise sources from the VLBA calibrator
list and the VLA calibrator list - when reliable optical counterparts exist.
Finally, the LQRF axes are inspected through spherical harmonics, contemplating
to define right ascension, declination and magnitude terms. The LQRF contains
J2000 referred equatorial coordinates for 100,165 quasars, well represented
across the sky, from -83.5 to +88.5 degrees in declination, and with 10 arcmin
being the average distance between adjacent elements. The global alignment with
the ICRF is 1.5 mas, and the individual position accuracies are represented by
a Poisson distribution that peaks at 139 mas in right ascension and 130 mas in
declination. It is complemented by redshift and photometry information from the
LQAC. The LQRF is designed to be an astrometric frame, but it is also the basis
for the GAIA mission initial quasars' list, and can be used as a test bench for
quasars' space distribution and luminosity function studies.Comment: 23 pages, 23 figures, 6 tables Accepted for publication by Astronomy
& Astrophysics, on 25 May 200
The color gradients of spiral disks in the Sloan Digital Sky Survey
We investigate the radial color gradients of galactic disks using a sample of
about 20,000 face-on spiral galaxies selected from the fourth data release of
the Sloan Digital Sky Survey (SDSS-DR4). We combine galaxies with similar
concentration, size and luminosity to construct composite galaxies, and then
measure their color profiles by stacking the azimuthally averaged radial color
profiles of all the member galaxies. Except for the smallest galaxies (R_{50}<3
kpc), almost all galaxies show negative disk color gradients with mean g-r
gradient G_{gr}=-0.006 mag kpc^{-1} and r-z gradient G_{rz}=-0.018 mag
kpc^{-1}. The disk color gradients are independent of the morphological types
of galaxies and strongly dependent on the disk surface brightness \mu_{d}, with
lower surface brightness galactic disks having steeper color gradients. We
quantify the intrinsic correlation between color gradients and surface
brightness as G_{gr}=-0.011\mu_{d}+0.233 and G_{rz}=-0.015\mu_{d}+0.324. These
quantified correlations provide tight observational constraints on the
formation and evolution models of spiral galaxies.Comment: 20 pages, 5 figures, Accepted for publication in RAA (Research in
Astronomy and Astrophysics
Stellar over-densities in the halo: the extent of the Virgo over-density
We map the three dimensional extent of the Virgo Over-density by combining
distance information from RR Lyrae variables and projected spatial information
from SEKBO (Keller et al. 2008) and Sloan Digital Sky Survey (SDSS) DR6
photometry. The Virgo Over-density is seen to comprise two filaments 14.5 x 3
degrees and 10 x 3 degrees and a circular structure 3 degrees in diameter.
Together the three features span 38 degrees of right ascension and declinations
of +2 to -15 degrees. RR Lyrae variables place the two filamentary features at
heliocentric distances of 20 and 17 kpc respectively, with projected dimensions
of 5 x 1 kpc and 3 x 1 kpc.Comment: 6 pages, 5 figures, MNRAS accepte
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