141 research outputs found
A Dynamical Model of Twitter Activity Profiles
The advent of the era of Big Data has allowed many researchers to dig into
various socio-technical systems, including social media platforms. In
particular, these systems have provided them with certain verifiable means to
look into certain aspects of human behavior. In this work, we are specifically
interested in the behavior of individuals on social media platforms---how they
handle the information they get, and how they share it. We look into Twitter to
understand the dynamics behind the users' posting activities---tweets and
retweets---zooming in on topics that peaked in popularity. Three mechanisms are
considered: endogenous stimuli, exogenous stimuli, and a mechanism that
dictates the decay of interest of the population in a topic. We propose a model
involving two parameters and describing the tweeting
behaviour of users, which allow us to reconstruct the findings of Lehmann et
al. (2012) on the temporal profiles of popular Twitter hashtags. With this
model, we are able to accurately reproduce the temporal profile of user
engagements on Twitter. Furthermore, we introduce an alternative in classifying
the collective activities on the socio-technical system based on the model.Comment: 10 pages, 5 figure
Simulating Congestion Dynamics of Train Rapid Transit using Smart Card Data
Investigating congestion in train rapid transit systems (RTS) in today's
urban cities is a challenge compounded by limited data availability and
difficulties in model validation. Here, we integrate information from travel
smart card data, a mathematical model of route choice, and a full-scale
agent-based model of the Singapore RTS to provide a more comprehensive
understanding of the congestion dynamics than can be obtained through
analytical modelling alone. Our model is empirically validated, and allows for
close inspection of the dynamics including station crowdedness, average travel
duration, and frequency of missed trains---all highly pertinent factors in
service quality. Using current data, the crowdedness in all 121 stations
appears to be distributed log-normally. In our preliminary scenarios, we
investigate the effect of population growth on service quality. We find that
the current population (2 million) lies below a critical point; and increasing
it beyond a factor of leads to an exponential deterioration in
service quality. We also predict that incentivizing commuters to avoid the most
congested hours can bring modest improvements to the service quality provided
the population remains under the critical point. Finally, our model can be used
to generate simulated data for analytical modelling when such data are not
empirically available, as is often the case.Comment: 10 pages, 5 figures, submitted to International Conference on
Computational Science 201
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