1,634 research outputs found
Scaling behavior of online human activity
The rapid development of Internet technology enables human explore the web
and record the traces of online activities. From the analysis of these
large-scale data sets (i.e. traces), we can get insights about dynamic behavior
of human activity. In this letter, the scaling behavior and complexity of human
activity in the e-commerce, such as music, book, and movie rating, are
comprehensively investigated by using detrended fluctuation analysis technique
and multiscale entropy method. Firstly, the interevent time series of rating
behaviors of these three type medias show the similar scaling property with
exponents ranging from 0.53 to 0.58, which implies that the collective
behaviors of rating media follow a process embodying self-similarity and
long-range correlation. Meanwhile, by dividing the users into three groups
based their activities (i.e., rating per unit time), we find that the scaling
exponents of interevent time series in three groups are different. Hence, these
results suggest the stronger long-range correlations exist in these collective
behaviors. Furthermore, their information complexities vary from three groups.
To explain the differences of the collective behaviors restricted to three
groups, we study the dynamic behavior of human activity at individual level,
and find that the dynamic behaviors of a few users have extremely small scaling
exponents associating with long-range anticorrelations. By comparing with the
interevent time distributions of four representative users, we can find that
the bimodal distributions may bring the extraordinary scaling behaviors. These
results of analyzing the online human activity in the e-commerce may not only
provide insights to understand its dynamic behaviors but also be applied to
acquire the potential economic interest
Experimental Realization of Entanglement Concentration and A Quantum Repeater
We report an experimental realization of entanglement concentration using two
polarization-entangled photon pairs produced by pulsed parametric
down-conversion. In the meantime, our setup also provides a proof-in-principle
demonstration of a quantum repeater. The quality of our procedure is verified
by observing a violation of Bell's inequality by more than 5 standard
deviations. The high experimental accuracy achieved in the experiment implies
that the requirement of tolerable error rate in multi-stage realization of
quantum repeaters can be fulfilled, hence providing a practical toolbox for
quantum communication over large distances.Comment: 15 pages, 4 figures, submitte
Relative clock demonstrates the endogenous heterogeneity of human dynamics
The heavy-tailed inter-event time distributions are widely observed in many
human-activated systems, which may result from both endogenous mechanisms like
the highest-priority-first protocol and exogenous factors like the varying
global activity versus time. To distinguish the effects on temporal statistics
from different mechanisms is this of theoretical significance. In this Letter,
we propose a new timing method by using a relative clock, where the time length
between two consecutive events of an individual is counted as the number of
other individuals' events appeared during this interval. We propose a model, in
which agents act either in a constant rate or with a power-law inter-event time
distribution, and the global activity either keeps unchanged or varies
periodically versus time. Our analysis shows that the heavy tails caused by the
heterogeneity of global activity can be eliminated by setting the relative
clock, yet the heterogeneity due to real individual behaviors still exists. We
perform extensive experiments on four large-scale systems, the search engine by
AOL, a social bookmarking system--Delicious, a short-message communication
network, and a microblogging system--Twitter. Strong heterogeneity and clear
seasonality of global activity are observed, but the heavy tails cannot be
eliminated by using the relative clock. Our results suggest the existence of
endogenous heterogeneity of human dynamics.Comment: 6 pages 7 figures 2 Table
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