265 research outputs found
Crisis Communication Patterns in Social Media during Hurricane Sandy
Hurricane Sandy was one of the deadliest and costliest of hurricanes over the
past few decades. Many states experienced significant power outage, however
many people used social media to communicate while having limited or no access
to traditional information sources. In this study, we explored the evolution of
various communication patterns using machine learning techniques and determined
user concerns that emerged over the course of Hurricane Sandy. The original
data included ~52M tweets coming from ~13M users between October 14, 2012 and
November 12, 2012. We run topic model on ~763K tweets from top 4,029 most
frequent users who tweeted about Sandy at least 100 times. We identified 250
well-defined communication patterns based on perplexity. Conversations of most
frequent and relevant users indicate the evolution of numerous storm-phase
(warning, response, and recovery) specific topics. People were also concerned
about storm location and time, media coverage, and activities of political
leaders and celebrities. We also present each relevant keyword that contributed
to one particular pattern of user concerns. Such keywords would be particularly
meaningful in targeted information spreading and effective crisis communication
in similar major disasters. Each of these words can also be helpful for
efficient hash-tagging to reach target audience as needed via social media. The
pattern recognition approach of this study can be used in identifying real time
user needs in future crises
A Simple Method for Finding Optimal Paths of Hot and Cold Streams inside Shell and Tube Heat Exchangers to Reduce Pumping Cost in Heat Exchanger Network Problems
In this paper, a simple method is presented for the synthesis and retrofit of heat exchanger networks (HENs) by considering pressure drop as well as finding proper path of streams inside heat exchangers (HEs) to reduce the pumping cost of network. Generally, HEN problems lead to MINLP models which have convergence difficulties due to the existence of both continuous and integer variables. In this study, instead of solving these variables simultaneously, a combination of Genetic Algorithm (GA) with Quasi Linear Programming (QLP) and Integer Linear Programming (ILP) was used for solving the problem. GA was used to find optimal HENs structure and streams paths, whereas continuous variables were solved by QLP. For the retrofit of HENs, a modified ILP model was used. Results show that the proposed method has the ability to reduce the cost of
annual pumping due to considering optimal paths for streams in the HEs compared to the literature.
This work is licensed under a Creative Commons Attribution 4.0 International License
Efficient Enumeration of Non-Equivalent Squares in Partial Words with Few Holes
International audienceA partial word is a word with holes (also called don't cares: special symbols which match any symbol). A p-square is a partial word matching at least one standard square without holes (called a full square). Two p-squares are called equivalent if they match the same sets of full squares. Denote by psquares(T) the number of non-equivalent p-squares which are subwords of a partial word T. Let PSQUARES k (n) be the maximum value of psquares(T) over all partial words of length n with k holes. We show asympthotically tight bounds: c1 · min(nk 2 , n 2) †PSQUARES k (n) †c2 · min(nk 2 , n 2) for some constants c1, c2 > 0. We also present an algorithm that computes psquares(T) in O(nk 3) time for a partial word T of length n with k holes. In particular, our algorithm runs in linear time for k = O(1) and its time complexity near-matches the maximum number of non-equivalent p-squares
Best Practices for Maximizing Driver Attention to Work Zone Warning Signs
Studies have shown that rear-end crashes in the advance warning area for a work zone are the most common type of work zone crashes. Driver inattention (or distraction) is reported as the most common issue and a major contributing factor to those types of crashes. As such, there is a need to identify the technologies that are successful in alerting drivers when approaching work zones
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