65 research outputs found
Heterogeneous network with distance dependent connectivity
Abstract.: We investigate a network model based on an infinite regular square lattice embedded in the Euclidean plane where the node connection probability is given by the geometrical distance of nodes. We show that the degree distribution in the basic model is sharply peaked around its mean value. Since the model was originally developed to mimic the social network of acquaintances, to broaden the degree distribution we propose its generalization. We show that when heterogeneity is introduced to the model, it is possible to obtain fat tails of the degree distribution. Meanwhile, the small-world phenomenon present in the basic model is not affected. To support our claims, both analytical and numerical results are obtaine
How to project a bipartite network?
The one-mode projecting is extensively used to compress the bipartite
networks. Since the one-mode projection is always less informative than the
bipartite representation, a proper weighting method is required to better
retain the original information. In this article, inspired by the network-based
resource-allocation dynamics, we raise a weighting method, which can be
directly applied in extracting the hidden information of networks, with
remarkably better performance than the widely used global ranking method as
well as collaborative filtering. This work not only provides a creditable
method in compressing bipartite networks, but also highlights a possible way
for the better solution of a long-standing challenge in modern information
science: How to do personal recommendation?Comment: 7 pages, 4 figure
Recommendation model based on opinion diffusion
Information overload in the modern society calls for highly efficient
recommendation algorithms. In this letter we present a novel diffusion based
recommendation model, with users' ratings built into a transition matrix. To
speed up computation we introduce a Green function method. The numerical tests
on a benchmark database show that our prediction is superior to the standard
recommendation methods.Comment: 5 pages, 2 figure
Heterogeneous network with distance dependent connectivity
We investigate a network model based on an infinite regular square lattice
embedded in the Euclidean plane where the node connection probability is given
by the geometrical distance of nodes. We show that the degree distribution in
the basic model is sharply peaked around its mean value. Since the model was
originally developed to mimic the social network of acquaintances, to broaden
the degree distribution we propose its generalization. We show that when
heterogeneity is introduced to the model, it is possible to obtain fat tails of
the degree distribution. Meanwhile, the small-world phenomenon present in the
basic model is not affected. To support our claims, both analytical and
numerical results are obtained.Comment: 6 pages, 4 figures, minor clarifications and references adde
Small world yields the most effective information spreading
Spreading dynamics of information and diseases are usually analyzed by using
a unified framework and analogous models. In this paper, we propose a model to
emphasize the essential difference between information spreading and epidemic
spreading, where the memory effects, the social reinforcement and the
non-redundancy of contacts are taken into account. Under certain conditions,
the information spreads faster and broader in regular networks than in random
networks, which to some extent supports the recent experimental observation of
spreading in online society [D. Centola, Science {\bf 329}, 1194 (2010)]. At
the same time, simulation result indicates that the random networks tend to be
favorable for effective spreading when the network size increases. This
challenges the validity of the above-mentioned experiment for large-scale
systems. More significantly, we show that the spreading effectiveness can be
sharply enhanced by introducing a little randomness into the regular structure,
namely the small-world networks yield the most effective information spreading.
Our work provides insights to the understanding of the role of local clustering
in information spreading.Comment: 6 pages, 7 figures, accepted by New J. Phy
Breakdown of the mean-field approximation in a wealth distribution model
One of the key socioeconomic phenomena to explain is the distribution of
wealth. Bouchaud and M\'ezard have proposed an interesting model of economy
[Bouchaud and M\'ezard (2000)] based on trade and investments of agents. In the
mean-field approximation, the model produces a stationary wealth distribution
with a power-law tail. In this paper we examine characteristic time scales of
the model and show that for any finite number of agents, the validity of the
mean-field result is time-limited and the model in fact has no stationary
wealth distribution. Further analysis suggests that for heterogeneous agents,
the limitations are even stronger. We conclude with general implications of the
presented results.Comment: 11 pages, 3 figure
Solving the apparent diversity-accuracy dilemma of recommender systems
Recommender systems use data on past user preferences to predict possible
future likes and interests. A key challenge is that while the most useful
individual recommendations are to be found among diverse niche objects, the
most reliably accurate results are obtained by methods that recommend objects
based on user or object similarity. In this paper we introduce a new algorithm
specifically to address the challenge of diversity and show how it can be used
to resolve this apparent dilemma when combined in an elegant hybrid with an
accuracy-focused algorithm. By tuning the hybrid appropriately we are able to
obtain, without relying on any semantic or context-specific information,
simultaneous gains in both accuracy and diversity of recommendations.Comment: 10 pages, 9 figures, 4 tables (final version with supporting
information included
General coevolution of topology and dynamics in networks
We present a general framework for the study of coevolution in dynamical
systems. This phenomenon consists of the coexistence of two dynamical processes
on networks of interacting elements: node state change and rewiring of links
between nodes. The process of rewiring is described in terms of two basic
actions: disconnection and reconnection between nodes, both based on a
mechanism of comparison of their states. We assume that the process of rewiring
and node state change occur with probabilities Pr and Pc respectively,
independent of each other. The collective behavior of a coevolutionary system
can be characterized on the space of parameters (Pr, Pc). As an application,
for a voterlike node dynamics we find that reconnections between nodes with
similar states lead to network fragmentation. The critical boundaries for the
onset of fragmentation in networks with different properties are calculated on
this space. We show that coevolution models correspond to curves on this space
describing functional relations between Pr and Pc. The occurrence of a
one-large-domain phase and a fragmented phase in the network is predicted for
diverse models, and agreement is found with some earlier results. The
collective behavior of system is also characterized on the space of parameters
for the disconnection and reconnection actions. In a region of this space, we
find a behavior where different node states can coexist for very long times on
one large, connected network.Comment: 6 pages, 6 figure
Heterogeneity, quality, and reputation in an adaptive recommendation model
Recommender systems help people cope with the problem of information
overload. A recently proposed adaptive news recommender model [Medo et al.,
2009] is based on epidemic-like spreading of news in a social network. By means
of agent-based simulations we study a "good get richer" feature of the model
and determine which attributes are necessary for a user to play a leading role
in the network. We further investigate the filtering efficiency of the model as
well as its robustness against malicious and spamming behaviour. We show that
incorporating user reputation in the recommendation process can substantially
improve the outcome
Enhancing topology adaptation in information-sharing social networks
The advent of Internet and World Wide Web has led to unprecedent growth of
the information available. People usually face the information overload by
following a limited number of sources which best fit their interests. It has
thus become important to address issues like who gets followed and how to allow
people to discover new and better information sources. In this paper we conduct
an empirical analysis on different on-line social networking sites, and draw
inspiration from its results to present different source selection strategies
in an adaptive model for social recommendation. We show that local search rules
which enhance the typical topological features of real social communities give
rise to network configurations that are globally optimal. These rules create
networks which are effective in information diffusion and resemble structures
resulting from real social systems
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