4,315 research outputs found
The Directed Closure Process in Hybrid Social-Information Networks, with an Analysis of Link Formation on Twitter
It has often been taken as a working assumption that directed links in
information networks are frequently formed by "short-cutting" a two-step path
between the source and the destination -- a kind of implicit "link copying"
analogous to the process of triadic closure in social networks. Despite the
role of this assumption in theoretical models such as preferential attachment,
it has received very little direct empirical investigation. Here we develop a
formalization and methodology for studying this type of directed closure
process, and we provide evidence for its important role in the formation of
links on Twitter. We then analyze a sequence of models designed to capture the
structural phenomena related to directed closure that we observe in the Twitter
data
Network Structure, Efficiency, and Performance in WikiProjects
The internet has enabled collaborations at a scale never before possible, but
the best practices for organizing such large collaborations are still not
clear. Wikipedia is a visible and successful example of such a collaboration
which might offer insight into what makes large-scale, decentralized
collaborations successful. We analyze the relationship between the structural
properties of WikiProject coeditor networks and the performance and efficiency
of those projects. We confirm the existence of an overall
performance-efficiency trade-off, while observing that some projects are higher
than others in both performance and efficiency, suggesting the existence
factors correlating positively with both. Namely, we find an association
between low-degree coeditor networks and both high performance and high
efficiency. We also confirm results seen in previous numerical and small-scale
lab studies: higher performance with less skewed node distributions, and higher
performance with shorter path lengths. We use agent-based models to explore
possible mechanisms for degree-dependent performance and efficiency. We present
a novel local-majority learning strategy designed to satisfy properties of
real-world collaborations. The local-majority strategy as well as a localized
conformity-based strategy both show degree-dependent performance and
efficiency, but in opposite directions, suggesting that these factors depend on
both network structure and learning strategy. Our results suggest possible
benefits to decentralized collaborations made of smaller, more tightly-knit
teams, and that these benefits may be modulated by the particular learning
strategies in use.Comment: 11 pages, 5 figures, to appear in ICWSM 201
Coordination and Efficiency in Decentralized Collaboration
Environments for decentralized on-line collaboration are now widespread on
the Web, underpinning open-source efforts, knowledge creation sites including
Wikipedia, and other experiments in joint production. When a distributed group
works together in such a setting, the mechanisms they use for coordination can
play an important role in the effectiveness of the group's performance.
Here we consider the trade-offs inherent in coordination in these on-line
settings, balancing the benefits to collaboration with the cost in effort that
could be spent in other ways. We consider two diverse domains that each contain
a wide range of collaborations taking place simultaneously -- Wikipedia and
GitHub -- allowing us to study how coordination varies across different
projects. We analyze trade-offs in coordination along two main dimensions,
finding similar effects in both our domains of study: first we show that, in
aggregate, high-status projects on these sites manage the coordination
trade-off at a different level than typical projects; and second, we show that
projects use a different balance of coordination when they are "crowded," with
relatively small size but many participants. We also develop a stylized
theoretical model for the cost-benefit trade-off inherent in coordination and
show that it qualitatively matches the trade-offs we observe between
crowdedness and coordination.Comment: 10 pages, 6 figures, ICWSM 2015, in Proc. 9th International AAAI
Conference on Weblogs and Social Medi
Quantum transport through single and multilayer icosahedral fullerenes
We use a tight-binding Hamiltonian and Green functions methods to calculate
the quantum transmission through single-wall fullerenes and bilayered and
trilayered onions of icosahedral symmetry attached to metallic leads. The
electronic structure of the onion-like fullerenes takes into account the
curvature and finite size of the fullerenes layers as well as the strength of
the intershell interactions depending on to the number of interacting atom
pairs belonging to adjacent shells. Misalignment of the symmetry axes of the
concentric icosahedral shells produces breaking of the level degeneracies of
the individual shells, giving rise some narrow quasi-continuum bands instead of
the localized discrete peaks of the individual fullerenes. As a result, the
transmission function for non symmetrical onions are rapidly varying functions
of the Fermi energy. Furthermore, we found that most of the features of the
transmission through the onions are due to the electronic structure of the
outer shell with additional Fano-like antiresonances arising from coupling with
or between the inner shells.Comment: 16 pages, 5 figur
Shocking the Crowd: The Effect of Censorship Shocks on Chinese Wikipedia
Collaborative crowdsourcing has become a popular approach to organizing work
across the globe. Being global also means being vulnerable to shocks --
unforeseen events that disrupt crowds -- that originate from any country. In
this study, we examine changes in collaborative behavior of editors of Chinese
Wikipedia that arise due to the 2005 government censor- ship in mainland China.
Using the exogenous variation in the fraction of editors blocked across
different articles due to the censorship, we examine the impact of reduction in
group size, which we denote as the shock level, on three collaborative behavior
measures: volume of activity, centralization, and conflict. We find that
activity and conflict drop on articles that face a shock, whereas
centralization increases. The impact of a shock on activity increases with
shock level, whereas the impact on centralization and conflict is higher for
moderate shock levels than for very small or very high shock levels. These
findings provide support for threat rigidity theory -- originally introduced in
the organizational theory literature -- in the context of large-scale
collaborative crowds
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