1,135 research outputs found
Followee recommendation based on text analysis of micro-blogging activity
Nowadays, more and more users keep up with news through information streams coming from real-time micro-blogging activity offered by services such as Twitter. In these sites, information is shared via a followers/followees social network structure in which a follower receives all the micro-blogs from his/her followees. Recent research efforts on understanding micro-blogging as a novel form of communication and news spreading medium, have identified three different categories of users in these systems: information sources, information seekers and friends. As social networks grow in the number of registered users, finding relevant and reliable users to receive interesting information becomes essential. In this paper we propose a followee recommender system based on both the analysis of the content of micro-blogs to detect users´ interests and in the exploration of the topology of the network to find candidate users for recommendation. Experimental evaluation was conducted in order to determine the impact of different profiling strategies based on the text analysis of micro-blogs as well as several factors that allows the identification of users acting as good information sources. We found that user-generated content available in the network is a rich source of information for profiling users and finding like-minded people.Fil: Armentano, Marcelo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Instituto Superior de Ingeniería del Software. Universidad Nacional del Centro de la Provincia de Buenos Aires. Instituto Superior de Ingeniería del Software; ArgentinaFil: Godoy, Daniela Lis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Instituto Superior de Ingeniería del Software. Universidad Nacional del Centro de la Provincia de Buenos Aires. Instituto Superior de Ingeniería del Software; ArgentinaFil: Amandi, Analia Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Instituto Superior de Ingeniería del Software. Universidad Nacional del Centro de la Provincia de Buenos Aires. Instituto Superior de Ingeniería del Software; Argentin
How Advanced Change Patterns Impact the Process of Process Modeling
Process model quality has been an area of considerable research efforts. In
this context, correctness-by-construction as enabled by change patterns
provides promising perspectives. While the process of process modeling (PPM)
based on change primitives has been thoroughly investigated, only little is
known about the PPM based on change patterns. In particular, it is unclear what
set of change patterns should be provided and how the available change pattern
set impacts the PPM. To obtain a better understanding of the latter as well as
the (subjective) perceptions of process modelers, the arising challenges, and
the pros and cons of different change pattern sets we conduct a controlled
experiment. Our results indicate that process modelers face similar challenges
irrespective of the used change pattern set (core pattern set versus extended
pattern set, which adds two advanced change patterns to the core patterns set).
An extended change pattern set, however, is perceived as more difficult to use,
yielding a higher mental effort. Moreover, our results indicate that more
advanced patterns were only used to a limited extent and frequently applied
incorrectly, thus, lowering the potential benefits of an extended pattern set
Mapping systematic errors in helium abundance determinations using Markov Chain Monte Carlo
Monte Carlo techniques have been used to evaluate the statistical and
systematic uncertainties in the helium abundances derived from extragalactic
H~II regions. The helium abundance is sensitive to several physical parameters
associated with the H~II region. In this work, we introduce Markov Chain Monte
Carlo (MCMC) methods to efficiently explore the parameter space and determine
the helium abundance, the physical parameters, and the uncertainties derived
from observations of metal poor nebulae. Experiments with synthetic data show
that the MCMC method is superior to previous implementations (based on flux
perturbation) in that it is not affected by biases due to non-physical
parameter space. The MCMC analysis allows a detailed exploration of
degeneracies, and, in particular, a false minimum that occurs at large values
of optical depth in the He~I emission lines. We demonstrate that introducing
the electron temperature derived from the [O~III] emission lines as a prior, in
a very conservative manner, produces negligible bias and effectively eliminates
the false minima occurring at large optical depth. We perform a frequentist
analysis on data from several "high quality" systems. Likelihood plots
illustrate degeneracies, asymmetries, and limits of the determination. In
agreement with previous work, we find relatively large systematic errors,
limiting the precision of the primordial helium abundance for currently
available spectra.Comment: 25 pages, 11 figure
Banning the bulb: institutional evolution and the phased ban of incandescent lighting in Germany
Much academic attention has been directed at analysing energy efficiency investments through the lens of ‘behavioural failure’. These studies have challenged the neoclassical framing of regulation which emphasises the efficiency benefits of price based policy, underpinned by the notion of rational individual self-mastery. The increasing use of a regulatory ban on electric lamps in many countries is one of the most recent and high profile flash points in this dialectic of ‘freedom-versus-the-state’ in the public policy discourse. This paper interrogates this debate through a study of electric lamp diffusion in Germany. It is argued that neoclassical theory and equilibrium analysis is inadequate as a tool for policy analysis as it takes the formation of market institutions, such as existing regulations, for granted. Further still, it may be prone to encourage idealistic debates around such grand narratives which may in practice simply serve those who benefit most from the status quo. Instead we argue for an evolutionary approach which we suggest offers a more pragmatic framing tool which focuses on the formation of market institutions in light of shifting social norms and political goals—in our case, progress towards energy efficiency and environmental goals
Making Rules to Dispose of Manifestly Unfounded Assertions: An Exorcism of the Bogy of Non-Trans-Substantive Rules of Civil Procedure
Since the concept of universal design is already extending the boundary of disabilities, it is significant to include different aspects of information technology where universal design enabled efforts can contribute towards better designed systems, products and services. Sustainability is an important and growing public concern in today’s world. Nevertheless, attempts of designing IT system that can be called sustainable in nature are not so evident at present. In this paper we propose a framework originating from sustainable IT system design principles (also described in the paper). The universal design principles are used as a foundation upon which the resultant sustainable IT system design principles were derived. The concept of ‘sustainable IT system’ addressed in this research paper is beyond the common phenomenon of sustainability like green IT, CO2 emission etc. Rather, the framework proposed in this paper incorporates more user inclusion and increased user satisfaction together towards higher usability. And an IT system designed in this manner is a sustainable IT system according to the argument of this paper which can therefore be designed by following the proposed design principles and framework
On possible interpretations of the high energy electron-positron spectrum measured by the Fermi Large Area Telescope
The Fermi-LAT experiment recently reported high precision measurements of the
spectrum of cosmic-ray electrons-plus-positrons (CRE) between 20 GeV and 1 TeV.
The spectrum shows no prominent spectral features, and is significantly harder
than that inferred from several previous experiments. Here we discuss several
interpretations of the Fermi results based either on a single large scale
Galactic CRE component or by invoking additional electron-positron primary
sources, e.g. nearby pulsars or particle Dark Matter annihilation. We show that
while the reported Fermi-LAT data alone can be interpreted in terms of a single
component scenario, when combined with other complementary experimental
results, specifically the CRE spectrum measured by H.E.S.S. and especially the
positron fraction reported by PAMELA between 1 and 100 GeV, that class of
models fails to provide a consistent interpretation. Rather, we find that
several combinations of parameters, involving both the pulsar and dark matter
scenarios, allow a consistent description of those results. We also briefly
discuss the possibility of discriminating between the pulsar and dark matter
interpretations by looking for a possible anisotropy in the CRE flux.Comment: 29 pages, 12 figures. Final version accepted for publication in
Astroparticle Physic
The Japanese model in retrospective : industrial strategies, corporate Japan and the 'hollowing out' of Japanese industry
This article provides a retrospective look at the Japanese model of industrial development. This model combined an institutional approach to production based around the Japanese Firm (Aoki's, J-mode) and strategic state intervention in industry by the Japanese Ministry of International Trade and Industry (MITI). For a long period, the alignment of state and corporate interests appeared to match the wider public interest as the Japanese economy prospered. However, since the early 1990s, the global ambitions of the corporate sector have contributed to a significant 'hollowing out' of Japan's industrial base. As the world today looks for a new direction in economic management, we suggest the Japanese model provides policy-makers with a salutary lesson in tying the wider public interest with those of the corporate sector
Implications of the Fermi-LAT diffuse gamma-ray measurements on annihilating or decaying Dark Matter
We analyze the recently published Fermi-LAT diffuse gamma-ray measurements in
the context of leptonically annihilating or decaying dark matter (DM) with the
aim to explain simultaneously the isotropic diffuse gamma-ray and the PAMELA,
Fermi and HESS (PFH) anomalous data. Five different DM
annihilation/decay channels , , , , or (the latter
two via an intermediate light particle ) are generated with PYTHIA. We
calculate both the Galactic and extragalactic prompt and inverse Compton (IC)
contributions to the resulting gamma-ray spectra. To find the Galactic IC
spectra we use the interstellar radiation field model from the latest release
of GALPROP. For the extragalactic signal we show that the amplitude of the
prompt gamma-emission is very sensitive to the assumed model for the
extragalactic background light. For our Galaxy we use the Einasto, NFW and
Isothermal DM density profiles and include the effects of DM substructure
assuming a simple subhalo model. Our calculations show that for the
annihilating DM the extragalactic gamma-ray signal can dominate only if rather
extreme power-law concentration-mass relation is used, while more
realistic relations make the extragalactic component comparable or
subdominant to the Galactic signal. For the decaying DM the Galactic signal
always exceeds the extragalactic one. In the case of annihilating DM the PFH
favored parameters can be ruled out only if power-law relation is
assumed. For DM decaying into or the PFH favored DM parameters
are not in conflict with the Fermi gamma-ray data. We find that, due to the
(almost) featureless Galactic IC spectrum and the DM halo substructure,
annihilating DM may give a good simultaneous fit to the isotropic diffuse
gamma-ray and to the PFH data without being in clear conflict with the
other Fermi-LAT gamma-ray measurements.Comment: Accepted for publication in JCAP, added missing references, new Figs.
9 \& 10, 35 page
Magnetic Field Amplification in Galaxy Clusters and its Simulation
We review the present theoretical and numerical understanding of magnetic
field amplification in cosmic large-scale structure, on length scales of galaxy
clusters and beyond. Structure formation drives compression and turbulence,
which amplify tiny magnetic seed fields to the microGauss values that are
observed in the intracluster medium. This process is intimately connected to
the properties of turbulence and the microphysics of the intra-cluster medium.
Additional roles are played by merger induced shocks that sweep through the
intra-cluster medium and motions induced by sloshing cool cores. The accurate
simulation of magnetic field amplification in clusters still poses a serious
challenge for simulations of cosmological structure formation. We review the
current literature on cosmological simulations that include magnetic fields and
outline theoretical as well as numerical challenges.Comment: 60 pages, 19 Figure
Modulational instability of matter waves under strong nonlinearity management
We study modulational instability of matter-waves in Bose-Einstein
condensates (BEC) under strong temporal nonlinearity-management. Both BEC in an
optical lattice and homogeneous BEC are considered in the framework of the
Gross-Pitaevskii equation, averaged over rapid time modulations. For a BEC in
an optical lattice, it is shown that the loop formed on a dispersion curve
undergoes transformation due to the nonlinearity-management. A critical
strength for the nonlinearity-management strength is obtained that changes the
character of instability of an attractive condensate. MI is shown to occur
below(above) the threshold for the positive (negative) effective mass. The
enhancement of number of atoms in the nonlinearity-managed gap soliton is
revealed
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