3,301 research outputs found
Contextual impacts on industrial processes brought by the digital transformation of manufacturing: a systematic review
The digital transformation of manufacturing (a phenomenon also known as "Industry 4.0" or "Smart Manufacturing") is finding a growing interest both at practitioner and academic levels, but is still in its infancy and needs deeper investigation. Even though current and potential advantages of digital manufacturing are remarkable, in terms of improved efficiency, sustainability, customization, and flexibility, only a limited number of companies has already developed ad hoc strategies necessary to achieve a superior performance. Through a systematic review, this study aims at assessing the current state of the art of the academic literature regarding the paradigm shift occurring in the manufacturing settings, in order to provide definitions as well as point out recurring patterns and gaps to be addressed by future research. For the literature search, the most representative keywords, strict criteria, and classification schemes based on authoritative reference studies were used. The final sample of 156 primary publications was analyzed through a systematic coding process to identify theoretical and methodological approaches, together with other significant elements. This analysis allowed a mapping of the literature based on clusters of critical themes to synthesize the developments of different research streams and provide the most representative picture of its current state. Research areas, insights, and gaps resulting from this analysis contributed to create a schematic research agenda, which clearly indicates the space for future evolutions of the state of knowledge in this field
Linear Perturbation constraints on Multi-coupled Dark Energy
The Multi-coupled Dark Energy (McDE) scenario has been recently proposed as a
specific example of a cosmological model characterized by a non-standard
physics of the dark sector of the universe that nevertheless gives an expansion
history which does not significantly differ from the one of the standard
CDM model. In this work, we present the first constraints on the McDE
scenario obtained by comparing the predicted evolution of linear density
perturbations with a large compilation of recent data sets for the growth rate
, including 6dFGS, LRG, BOSS, WiggleZ and VIPERS. Confirming
qualitative expectations, growth rate data provide much tighter bounds on the
model parameters as compared to the extremely loose bounds that can be obtained
when only the background expansion history is considered. In particular, the
confidence level on the coupling strength is reduced from
(background constraints only) to
(background and linear perturbation constraints). We also investigate how these
constraints further improve when using data from future wide-field surveys such
as supernova data from LSST and growth rate data from Euclid-type missions. In
this case the confidence level on the coupling further reduce to . Such constraints are in any case still consistent with a scalar
fifth-force of gravitational strength, and we foresee that tighter bounds might
be possibly obtained from the investigation of nonlinear structure formation in
McDE cosmologies.[Abridged]Comment: 24 pages, 12 figure
Supernova constraints on Multi-coupled Dark Energy
The persisting consistency of ever more accurate observational data with the
predictions of the standard LCDM cosmological model puts severe constraints on
possible alternative scenarios, but still does not shed any light on the
fundamental nature of the cosmic dark sector.As large deviations from a LCDM
cosmology are ruled out by data, the path to detect possible features of
alternative models goes necessarily through the definition of cosmological
scenarios that leave almost unaffected the background and -- to a lesser extent
-- the linear perturbations evolution of the universe. In this context,the
Multi-coupled DE (McDE) model was proposed by Baldi 2012 as a particular
realization of an interacting Dark Energy field characterized by an effective
screening mechanism capable of suppressing the effects of the coupling at the
background and linear perturbation level. In the present paper, for the first
time, we challenge the McDE scenario through a direct comparison with real
data, in particular with the luminosity distance of Type Ia supernovae. By
studying the existence and stability conditions of the critical points of the
associated background dynamical system, we select only the cosmologically
consistent solutions, and confront their background expansion history with
data. Confirming previous qualitative results, the McDE scenario appears to be
fully consistent with the adopted sample of Type Ia supernovae, even for
coupling values corresponding to an associated scalar fifth-force about four
orders of magnitude stronger than standard gravity. Our analysis demonstrates
the effectiveness of the McDE background screening, and shows some new
non-trivial asymptotic solutions for the future evolution of the universe. Our
results show how the background expansion history might be highly insensitive
to the fundamental nature and to the internal complexity of the dark sector.
[Abridged]Comment: 10 pages, 7 figures. Matches version accepted for publication in JCA
Oscillating nonlinear large scale structure in growing neutrino quintessence
Growing Neutrino quintessence describes a form of dynamical dark energy that
could explain why dark energy dominates the universe only in recent
cosmological times. This scenario predicts the formation of large scale
neutrino lumps which could allow for observational tests. We perform for the
first time N-body simulations of the nonlinear growth of structures for cold
dark matter and neutrino fluids in the context of Growing Neutrino cosmologies.
Our analysis shows a pulsation - increase and subsequent decrease - of the
neutrino density contrast. This could lead to interesting observational
signatures, as an enhanced bulk flow in a situation where the dark matter
density contrast only differs very mildly from the standard LCDM scenario. We
also determine for the first time the statistical distribution of neutrino
lumps as a function of mass at different redshifts. Such determination provides
an essential ingredient for a realistic estimate of the observational
signatures of Growing Neutrino cosmologies. Due to a breakdown of the
non-relativistic Newtonian approximation our results are limited to redshifts z
> 1.Comment: 17 pages, 1 table, 10 figures; MNRAS in pres
Structure formation in Multiple Dark Matter cosmologies with long-range scalar interactions
(Abridged) An interaction between Cold Dark Matter (CDM) and a classical
scalar field playing the role of the cosmic dark energy (DE) might provide
long-range dark interactions without conflicting with solar system bounds.
Although presently available observations allow to constrain such interactions
to a few percent of the gravitational strength, some recent studies have shown
that if CDM is composed by two different particle species having opposite
couplings to the DE field, such tight constraints can be considerably relaxed,
allowing for long-range scalar forces of order gravity without significantly
affecting observations both at the background and at the linear perturbations
level. In the present work, we extend the investigation of such Multiple Dark
Matter scenarios to the nonlinear regime of structure formation, by presenting
the first N-body simulations ever performed for these cosmologies. Our results
highlight some characteristic footprints of long-range scalar forces that arise
only in the nonlinear regime for specific models that would be otherwise
practically indistinguishable from the standard LCDM scenario both in the
background and in the growth of linear density perturbations. Among these
effects, the formation of "mirror" cosmic structures in the two CDM species,
the suppression of the nonlinear matter power spectrum at k > 1 h/Mpc, and the
fragmentation of collapsed halos, represent peculiar features that might
provide a direct way to constrain this class of cosmological models.Comment: 11 pages, 4 figures. Submitted to MNRA
Entity set expansion from the Web via ASP
Knowledge on the Web in a large part is stored in various semantic resources that formalize, represent and organize it differently.
Combining information from several sources can improve results of tasks such as recognizing similarities among objects.
In this paper, we propose a logic-based method for the problem of entity set expansion (ESE), i.e. extending a list of named entities given a set of seeds.
This problem has relevant applications in the Information Extraction domain, specifically in automatic lexicon generation for dictionary-based annotating tools.
Contrary to typical approaches in natural languages processing, based on co-occurrence statistics of words, we determine the common category of the seeds by analyzing the semantic relations of the objects the words represent.
To do it, we integrate information from selected Web resources.
We introduce a notion of an entity network that uniformly represents the combined knowledge and allow to reason over it.
We show how to use the network to disambiguate word senses by relying on a concept of optimal common ancestor
and how to discover similarities between two entities.
Finally, we show how to expand a set of entities,
by using answer set programming with external predicates
Early massive clusters and the bouncing coupled dark energy
The abundance of the most massive objects in the Universe at different epochs
is a very sensitive probe of the cosmic background evolution and of the growth
history of density perturbations, and could provide a powerful tool to
distinguish between a cosmological constant and a dynamical dark energy field.
In particular, the recent detection of very massive clusters of galaxies at
high redshifts has attracted significant interest as a possible indication of a
failure of the standard LCDM model. Several attempts have been made in order to
explain such detections in the context of non-Gaussian scenarios or interacting
dark energy models, showing that both these alternative cosmologies predict an
enhanced number density of massive clusters at high redshifts, possibly
alleviating the tension. However, all the models proposed so far also
overpredict the abundance of massive clusters at the present epoch, and are
therefore in contrast with observational bounds on the low-redshift halo mass
function. In this paper we present for the first time a new class of
interacting dark energy models that simultaneously account for an enhanced
number density of massive clusters at high redshifts and for both the standard
cluster abundance at the present time and the standard power spectrum
normalization at CMB. The key feature of this new class of models is the
"bounce" of the dark energy scalar field on the cosmological constant barrier
at relatively recent epochs. We present the background and linear perturbations
evolution of the model, showing that the standard amplitude of density
perturbations is recovered both at CMB and at the present time, and we
demonstrate by means of large N-body simulations that our scenario predicts an
enhanced number of massive clusters at high redshifts without affecting the
present halo abundance. (Abridged)Comment: 11 pages, 6 figures, 2 tables. Minor changes, references added.
Accepted for publication in MNRA
- …