105 research outputs found
Experience versus Talent Shapes the Structure of the Web
We use sequential large-scale crawl data to empirically investigate and
validate the dynamics that underlie the evolution of the structure of the web.
We find that the overall structure of the web is defined by an intricate
interplay between experience or entitlement of the pages (as measured by the
number of inbound hyperlinks a page already has), inherent talent or fitness of
the pages (as measured by the likelihood that someone visiting the page would
give a hyperlink to it), and the continual high rates of birth and death of
pages on the web. We find that the web is conservative in judging talent and
the overall fitness distribution is exponential, showing low variability. The
small variance in talent, however, is enough to lead to experience
distributions with high variance: The preferential attachment mechanism
amplifies these small biases and leads to heavy-tailed power-law (PL) inbound
degree distributions over all pages, as well as over pages that are of the same
age. The balancing act between experience and talent on the web allows newly
introduced pages with novel and interesting content to grow quickly and surpass
older pages. In this regard, it is much like what we observe in high-mobility
and meritocratic societies: People with entitlement continue to have access to
the best resources, but there is just enough screening for fitness that allows
for talented winners to emerge and join the ranks of the leaders. Finally, we
show that the fitness estimates have potential practical applications in
ranking query results
Let Your CyberAlter Ego Share Information and Manage Spam
Almost all of us have multiple cyberspace identities, and these {\em
cyber}alter egos are networked together to form a vast cyberspace social
network. This network is distinct from the world-wide-web (WWW), which is being
queried and mined to the tune of billions of dollars everyday, and until
recently, has gone largely unexplored. Empirically, the cyberspace social
networks have been found to possess many of the same complex features that
characterize its real counterparts, including scale-free degree distributions,
low diameter, and extensive connectivity. We show that these topological
features make the latent networks particularly suitable for explorations and
management via local-only messaging protocols. {\em Cyber}alter egos can
communicate via their direct links (i.e., using only their own address books)
and set up a highly decentralized and scalable message passing network that can
allow large-scale sharing of information and data. As one particular example of
such collaborative systems, we provide a design of a spam filtering system, and
our large-scale simulations show that the system achieves a spam detection rate
close to 100%, while the false positive rate is kept around zero. This system
has several advantages over other recent proposals (i) It uses an already
existing network, created by the same social dynamics that govern our daily
lives, and no dedicated peer-to-peer (P2P) systems or centralized server-based
systems need be constructed; (ii) It utilizes a percolation search algorithm
that makes the query-generated traffic scalable; (iii) The network has a built
in trust system (just as in social networks) that can be used to thwart
malicious attacks; iv) It can be implemented right now as a plugin to popular
email programs, such as MS Outlook, Eudora, and Sendmail.Comment: 13 pages, 10 figure
Preferential survival in models of complex ad hoc networks
There has been a rich interplay in recent years between (i) empirical
investigations of real world dynamic networks, (ii) analytical modeling of the
microscopic mechanisms that drive the emergence of such networks, and (iii)
harnessing of these mechanisms to either manipulate existing networks, or
engineer new networks for specific tasks. We continue in this vein, and study
the deletion phenomenon in the web by following two different sets of web-sites
(each comprising more than 150,000 pages) over a one-year period. Empirical
data show that there is a significant deletion component in the underlying web
networks, but the deletion process is not uniform. This motivates us to
introduce a new mechanism of preferential survival (PS), where nodes are
removed according to a degree-dependent deletion kernel. We use the mean-field
rate equation approach to study a general dynamic model driven by Preferential
Attachment (PA), Double PA (DPA), and a tunable PS, where c nodes (c<1) are
deleted per node added to the network, and verify our predictions via
large-scale simulations. One of our results shows that, unlike in the case of
uniform deletion, the PS kernel when coupled with the standard PA mechanism,
can lead to heavy-tailed power law networks even in the presence of extreme
turnover in the network. Moreover, a weak DPA mechanism, coupled with PS, can
help make the network even more heavy-tailed, especially in the limit when
deletion and insertion rates are almost equal, and the overall network growth
is minimal. The dynamics reported in this work can be used to design and
engineer stable ad hoc networks and explain the stability of the power law
exponents observed in real-world networks.Comment: 9 pages, 6 figure
Intelligent evacuation management systems: A review
Crowd and evacuation management have been active areas of research and study in the recent past. Various developments continue to take place in the process of efficient evacuation of crowds in mass gatherings. This article is intended to provide a review of intelligent evacuation management systems covering the aspects of crowd monitoring, crowd disaster prediction, evacuation modelling, and evacuation path guidelines. Soft computing approaches play a vital role in the design and deployment of intelligent evacuation applications pertaining to crowd control management. While the review deals with video and nonvideo based aspects of crowd monitoring and crowd disaster prediction, evacuation techniques are reviewed via the theme of soft computing, along with a brief review on the evacuation navigation path. We believe that this review will assist researchers in developing reliable automated evacuation systems that will help in ensuring the safety of the evacuees especially during emergency evacuation scenarios
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