616 research outputs found
Information filtering in complex weighted networks
Many systems in nature, society and technology can be described as networks,
where the vertices are the system's elements and edges between vertices
indicate the interactions between the corresponding elements. Edges may be
weighted if the interaction strength is measurable. However, the full network
information is often redundant because tools and techniques from network
analysis do not work or become very inefficient if the network is too dense and
some weights may just reflect measurement errors, and shall be discarded.
Moreover, since weight distributions in many complex weighted networks are
broad, most of the weight is concentrated among a small fraction of all edges.
It is then crucial to properly detect relevant edges. Simple thresholding would
leave only the largest weights, disrupting the multiscale structure of the
system, which is at the basis of the structure of complex networks, and ought
to be kept. In this paper we propose a weight filtering technique based on a
global null model (GloSS filter), keeping both the weight distribution and the
full topological structure of the network. The method correctly quantifies the
statistical significance of weights assigned independently to the edges from a
given distribution. Applications to real networks reveal that the GloSS filter
is indeed able to identify relevantconnections between vertices.Comment: 9 pages, 7 figures, 1 Table. The GloSS filter is implemented in a
freely downloadable software (http://filrad.homelinux.org/resources
A Model of Collaboration Network Formation with Heterogenous Skills
Collaboration networks provide a method for examining the highly
heterogeneous structure of collaborative communities. However, we still have
limited theoretical understanding of how individual heterogeneity relates to
network heterogeneity. The model presented here provides a framework linking an
individual's skill set to her position in the collaboration network, and the
distribution of skills in the population to the structure of the collaboration
network as a whole. This model suggests that there is a non-trivial
relationship between skills and network position: individuals with a useful
combination of skills will have a disproportionate number of links in the
network. Indeed, in some cases, an individual's degree is non-monotonic in the
number of skills she has--an individual with very few skills may outperform an
individual with many. Special cases of the model suggest that the degree
distribution of the network will be skewed, even when the distribution of
skills is uniform in the population. The degree distribution becomes more
skewed as problems become more difficult, leading to a community dominated by a
few high-degree superstars. This has striking implications for labor market
outcomes in industries where production is largely the result of collaborative
effort
Systematic comparison of trip distribution laws and models
Trip distribution laws are basic for the travel demand characterization
needed in transport and urban planning. Several approaches have been considered
in the last years. One of them is the so-called gravity law, in which the
number of trips is assumed to be related to the population at origin and
destination and to decrease with the distance. The mathematical expression of
this law resembles Newton's law of gravity, which explains its name. Another
popular approach is inspired by the theory of intervening opportunities which
argues that the distance has no effect on the destination choice, playing only
the role of a surrogate for the number of intervening opportunities between
them. In this paper, we perform a thorough comparison between these two
approaches in their ability at estimating commuting flows by testing them
against empirical trip data at different scales and coming from different
countries. Different versions of the gravity and the intervening opportunities
laws, including the recently proposed radiation law, are used to estimate the
probability that an individual has to commute from one unit to another, called
trip distribution law. Based on these probability distribution laws, the
commuting networks are simulated with different trip distribution models. We
show that the gravity law performs better than the intervening opportunities
laws to estimate the commuting flows, to preserve the structure of the network
and to fit the commuting distance distribution although it fails at predicting
commuting flows at large distances. Finally, we show that the different
approaches can be used in the absence of detailed data for calibration since
their only parameter depends only on the scale of the geographic unit.Comment: 15 pages, 10 figure
Data-driven modeling of systemic delay propagation under severe meteorological conditions
The upsetting consequences of weather conditions are well known to any person
involved in air transportation. Still the quantification of how these
disturbances affect delay propagation and the effectiveness of managers and
pilots interventions to prevent possible large-scale system failures needs
further attention. In this work, we employ an agent-based data-driven model
developed using real flight performance registers for the entire US airport
network and focus on the events occurring on October 27 2010 in the United
States. A major storm complex that was later called the 2010 Superstorm took
place that day. Our model correctly reproduces the evolution of the
delay-spreading dynamics. By considering different intervention measures, we
can even improve the model predictions getting closer to the real delay data.
Our model can thus be of help to managers as a tool to assess different
intervention measures in order to diminish the impact of disruptive conditions
in the air transport system.Comment: 9 pages, 5 figures. Tenth USA/Europe Air Traffic Management Research
and Development Seminar (ATM2013
Transport on weighted Networks: when correlations are independent of degree
Most real-world networks are weighted graphs with the weight of the edges
reflecting the relative importance of the connections. In this work, we study
non degree dependent correlations between edge weights, generalizing thus the
correlations beyond the degree dependent case. We propose a simple method to
introduce weight-weight correlations in topologically uncorrelated graphs. This
allows us to test different measures to discriminate between the different
correlation types and to quantify their intensity. We also discuss here the
effect of weight correlations on the transport properties of the networks,
showing that positive correlations dramatically improve transport. Finally, we
give two examples of real-world networks (social and transport graphs) in which
weight-weight correlations are present.Comment: 8 pages, 8 figure
Consideración social de la profesión enfermera en España
Trabajo fin de grado en EnfermerÃaEste trabajo surge por la necesidad de reflexionar acerca de la consideración social de la profesión enfermera en España. A partir de la justificación del objeto de estudio se plantearon como objetivos especÃficos describir los estereotipos institucionalizados que determinan el rol profesional de la enfermera, identificar las barreras que limitan la construcción de la identidad profesional de la enfermerÃa y determinar la autopercepción social sobre la imagen de la profesión enfermera. Se ha realizado una revisión narrativa en las bases de datos PubMed, Cinalh, Scielo, Cuiden y buscadores como Google académico y Encuentra.
Los resultados obtenidos muestran la necesidad de crear una conciencia social acerca de un problema que atañe a los profesionales de enfermerÃa, como es el reconocimiento de la enfermerÃa como profesión. Para ello el colectivo enfermero debe aumentar la visibilidad de los cuidados y la conciencia pública mediante los medios de comunicación y el marketing personal, registrar su actividad, reivindicar la reducción de cargas de trabajo, trabajar en la educación continua, el trabajo interdisciplinar y las cooperación intensiva con los médicos, entre otras muchas cosas.This work arises from the need to reflect on the social status of the nursing profession in Spain. From the justification under study raised specific objectives describe the institutionalized stereotypes that determine the professional role of the nurse, identify barriers that limit the construction of the professional identity of nursing and determine the social perception on the image of the nursing profession. A narrative review has been done based in PubMed, Cinalh, Scielo, Cuiden and search engines like Google Scholar and Encuentra.
The results show the need to create a social awareness of a problem that concerns nurses, as is the recognition of nursing as a profession. Nursing should increase the visibility of care and public awareness through media and marketing staff, record activity, claiming reducing workload, work in continuing education, interdisciplinary work and intensive cooperation with physicians, among others many
Tweets on the road
The pervasiveness of mobile devices, which is increasing daily, is generating
a vast amount of geo-located data allowing us to gain further insights into
human behaviors. In particular, this new technology enables users to
communicate through mobile social media applications, such as Twitter, anytime
and anywhere. Thus, geo-located tweets offer the possibility to carry out
in-depth studies on human mobility. In this paper, we study the use of Twitter
in transportation by identifying tweets posted from roads and rails in Europe
between September 2012 and November 2013. We compute the percentage of highway
and railway segments covered by tweets in 39 countries. The coverages are very
different from country to country and their variability can be partially
explained by differences in Twitter penetration rates. Still, some of these
differences might be related to cultural factors regarding mobility habits and
interacting socially online. Analyzing particular road sectors, our results
show a positive correlation between the number of tweets on the road and the
Average Annual Daily Traffic on highways in France and in the UK. Transport
modality can be studied with these data as well, for which we discover very
heterogeneous usage patterns across the continent.Comment: 15 pages, 17 figure
Prominence and Control: The Weighted Rich-Club Effect
Published in Physical Review Letters PRL 101, 168702 (2008)http://link.aps.org/doi/10.1103/PhysRevLett.101.168702. Copyright American Physical Society (APS).Publisher's note: Erratum in Phys Rev Lett. 2008 Oct 31;101(18):189903 http://link.aps.org/doi/10.1103/PhysRevLett.101.18990
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