336 research outputs found
SURGE: Continuous Detection of Bursty Regions Over a Stream of Spatial Objects
With the proliferation of mobile devices and location-based services,
continuous generation of massive volume of streaming spatial objects (i.e.,
geo-tagged data) opens up new opportunities to address real-world problems by
analyzing them. In this paper, we present a novel continuous bursty region
detection problem that aims to continuously detect a bursty region of a given
size in a specified geographical area from a stream of spatial objects.
Specifically, a bursty region shows maximum spike in the number of spatial
objects in a given time window. The problem is useful in addressing several
real-world challenges such as surge pricing problem in online transportation
and disease outbreak detection. To solve the problem, we propose an exact
solution and two approximate solutions, and the approximation ratio is
in terms of the burst score, where is a parameter
to control the burst score. We further extend these solutions to support
detection of top- bursty regions. Extensive experiments with real-world data
are conducted to demonstrate the efficiency and effectiveness of our solutions
Predictability of conversation partners
Recent developments in sensing technologies have enabled us to examine the
nature of human social behavior in greater detail. By applying an information
theoretic method to the spatiotemporal data of cell-phone locations, [C. Song
et al. Science 327, 1018 (2010)] found that human mobility patterns are
remarkably predictable. Inspired by their work, we address a similar
predictability question in a different kind of human social activity:
conversation events. The predictability in the sequence of one's conversation
partners is defined as the degree to which one's next conversation partner can
be predicted given the current partner. We quantify this predictability by
using the mutual information. We examine the predictability of conversation
events for each individual using the longitudinal data of face-to-face
interactions collected from two company offices in Japan. Each subject wears a
name tag equipped with an infrared sensor node, and conversation events are
marked when signals are exchanged between sensor nodes in close proximity. We
find that the conversation events are predictable to some extent; knowing the
current partner decreases the uncertainty about the next partner by 28.4% on
average. Much of the predictability is explained by long-tailed distributions
of interevent intervals. However, a predictability also exists in the data,
apart from the contribution of their long-tailed nature. In addition, an
individual's predictability is correlated with the position in the static
social network derived from the data. Individuals confined in a community - in
the sense of an abundance of surrounding triangles - tend to have low
predictability, and those bridging different communities tend to have high
predictability.Comment: 38 pages, 19 figure
Seeking for a fingerprint: analysis of point processes in actigraphy recording
Motor activity of humans displays complex temporal fluctuations which can be
characterized by scale-invariant statistics, thus documenting that structure
and fluctuations of such kinetics remain similar over a broad range of time
scales. Former studies on humans regularly deprived of sleep or suffering from
sleep disorders predicted change in the invariant scale parameters with respect
to those representative for healthy subjects. In this study we investigate the
signal patterns from actigraphy recordings by means of characteristic measures
of fractional point processes. We analyse spontaneous locomotor activity of
healthy individuals recorded during a week of regular sleep and a week of
chronic partial sleep deprivation. Behavioural symptoms of lack of sleep can be
evaluated by analysing statistics of duration times during active and resting
states, and alteration of behavioural organization can be assessed by analysis
of power laws detected in the event count distribution, distribution of waiting
times between consecutive movements and detrended fluctuation analysis of
recorded time series. We claim that among different measures characterizing
complexity of the actigraphy recordings and their variations implied by chronic
sleep distress, the exponents characterizing slopes of survival functions in
resting states are the most effective biomarkers distinguishing between healthy
and sleep-deprived groups.Comment: Communicated at UPON2015, 14-17 July 2015, Barcelona. 21 pages, 11
figures; updated: figures 4-7, text revised, expanded Sec. 1,3,
Win-stay lose-shift strategy in formation changes in football
Managerial decision making is likely to be a dominant determinant of
performance of teams in team sports. Here we use Japanese and German football
data to investigate correlates between temporal patterns of formation changes
across matches and match results. We found that individual teams and managers
both showed win-stay lose-shift behavior, a type of reinforcement learning. In
other words, they tended to stick to the current formation after a win and
switch to a different formation after a loss. In addition, formation changes
did not statistically improve the results of succeeding matches.The results
indicate that a swift implementation of a new formation in the win-stay
lose-shift manner may not be a successful managerial rule of thumb.Comment: 7 figures, 11 table
Scaling in the space climatology of the auroral indices: Is SOC the only possible explanation ?
The study of the robust features of the magnetosphere is motivated both by
new "whole system" approaches, and by the idea of "space climate" as opposed to
"space weather". We enumerate these features for the AE index, and discuss
whether self-organised criticality (SOC) is the most natural explanation of the
"stylised facts" so far known for AE. We identify and discuss some open
questions, answers to which will clarify the extent to which AE's properties
provide evidence for SOC. We then suggest an SOC-like reconnection-based
scenario drawing on the result of Craig(2001) as an explanation of the very
recent demonstration by Uritsky et al(2001b) of power laws in several
properties of spatiotemporal features seen in auroral images.Comment: 24 pages including 7 figures. Based on an invited talk given at the
IAGA meeting in Hanoi, Vietnam, August 2000. Retitled v2 has revisions,
clearer statement of intent of paper i.e. part review/part critique/some new
suggestions, and 1 new figure. In press, Nonlinear Processes in Geophysic
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