58 research outputs found
Pruning Algorithms for Low-Dimensional Non-metric k-NN Search: A Case Study
We focus on low-dimensional non-metric search, where tree-based approaches
permit efficient and accurate retrieval while having short indexing time. These
methods rely on space partitioning and require a pruning rule to avoid visiting
unpromising parts. We consider two known data-driven approaches to extend these
rules to non-metric spaces: TriGen and a piece-wise linear approximation of the
pruning rule. We propose and evaluate two adaptations of TriGen to
non-symmetric similarities (TriGen does not support non-symmetric distances).
We also evaluate a hybrid of TriGen and the piece-wise linear approximation
pruning. We find that this hybrid approach is often more effective than either
of the pruning rules. We make our software publicly available
Twitter Watch: Leveraging Social Media to Monitor and Predict Collective-Efficacy of Neighborhoods
Sociologists associate the spatial variation of crime within an urban
setting, with the concept of collective efficacy. The collective efficacy of a
neighborhood is defined as social cohesion among neighbors combined with their
willingness to intervene on behalf of the common good. Sociologists measure
collective efficacy by conducting survey studies designed to measure
individuals' perception of their community. In this work, we employ the curated
data from a survey study (ground truth) and examine the effectiveness of
substituting costly survey questionnaires with proxies derived from social
media. We enrich a corpus of tweets mentioning a local venue with several
linguistic and topological features. We then propose a pairwise learning to
rank model with the goal of identifying a ranking of neighborhoods that is
similar to the ranking obtained from the ground truth collective efficacy
values. In our experiments, we find that our generated ranking of neighborhoods
achieves 0.77 Kendall tau-x ranking agreement with the ground truth ranking.
Overall, our results are up to 37% better than traditional baselines.Comment: 10 pages, 7 figure
Co-Authorship and Bibliographic Coupling Network Effects on Citations
Climate change adaptation (CCA) has recently emerged as a new fundamental dimension to be considered in the planning and management of water resources. Because of the need to consider the already perceived changes in climate trends, variability and extremes, and their interactions with evolving social and ecological systems, water management is now facing new challenges. The research community is expected to contribute with innovative methods and tools to support to decision- and policy-makers. Decision Support Systems (DSSs), have a relatively long history in the water management sector. They are usually developed upon pre-existing hydrologic simulation models, providing interfaces for facilitated use beyond the limited group of model developers, and specific routines for decision making (e.g. optimization methods). In recent years, the traditional focus of DSS research has shifted away from the software component, towards the process of structuring problems and aiding decisions, thus including in particular robust methods for stakeholders' participation. The paper analyses the scientific literature, identifies the main open issues, and proposes an innovative operational approach for the implementation of participatory planning and decision-making processes for CCA in the water domain
Social stream classification with emerging new labels
Singapore National Research Foundation under International Research Centres in Singapore Funding Initiativ
Active Inference, Novelty and Neglect
In this chapter, we provide an overview of the principles of active inference. We illustrate how different forms of short-term memory are expressed formally (mathematically) through appealing to beliefs about the causes of our sensations and about the actions we pursue. This is used to motivate an approach to active vision that depends upon inferences about the causes of 'what I have seen' and learning about 'what I would see if I were to look there'. The former could manifest as persistent 'delay-period' activity - of the sort associated with working memory, while the latter is better suited to changes in synaptic efficacy - of the sort that underlies short-term learning and adaptation. We review formulations of these ideas in terms of active inference, their role in directing visual exploration and the consequences - for active vision - of their failures. To illustrate the latter, we draw upon some of our recent work on the computational anatomy of visual neglect
Automatic Detection of Cyberbullying in Social Media Text
While social media offer great communication opportunities, they also
increase the vulnerability of young people to threatening situations online.
Recent studies report that cyberbullying constitutes a growing problem among
youngsters. Successful prevention depends on the adequate detection of
potentially harmful messages and the information overload on the Web requires
intelligent systems to identify potential risks automatically. The focus of
this paper is on automatic cyberbullying detection in social media text by
modelling posts written by bullies, victims, and bystanders of online bullying.
We describe the collection and fine-grained annotation of a training corpus for
English and Dutch and perform a series of binary classification experiments to
determine the feasibility of automatic cyberbullying detection. We make use of
linear support vector machines exploiting a rich feature set and investigate
which information sources contribute the most for this particular task.
Experiments on a holdout test set reveal promising results for the detection of
cyberbullying-related posts. After optimisation of the hyperparameters, the
classifier yields an F1-score of 64% and 61% for English and Dutch
respectively, and considerably outperforms baseline systems based on keywords
and word unigrams.Comment: 21 pages, 9 tables, under revie
Prediction of Muscle Energy States at Low Metabolic Rates Requires Feedback Control of Mitochondrial Respiratory Chain Activity by Inorganic Phosphate
The regulation of the 100-fold dynamic range of mitochondrial ATP synthesis flux in skeletal muscle was investigated. Hypotheses of key control mechanisms were included in a biophysical model of oxidative phosphorylation and tested against metabolite dynamics recorded by 31P nuclear magnetic resonance spectroscopy (31P MRS). Simulations of the initial model featuring only ADP and Pi feedback control of flux failed in reproducing the experimentally sampled relation between myoplasmic free energy of ATP hydrolysis (ΔGp = ΔGpo′+RT ln ([ADP][Pi]/[ATP]) and the rate of mitochondrial ATP synthesis at low fluxes (<0.2 mM/s). Model analyses including Monte Carlo simulation approaches and metabolic control analysis (MCA) showed that this problem could not be amended by model re-parameterization, but instead required reformulation of ADP and Pi feedback control or introduction of additional control mechanisms (feed forward activation), specifically at respiratory Complex III. Both hypotheses were implemented and tested against time course data of phosphocreatine (PCr), Pi and ATP dynamics during post-exercise recovery and validation data obtained by 31P MRS of sedentary subjects and track athletes. The results rejected the hypothesis of regulation by feed forward activation. Instead, it was concluded that feedback control of respiratory chain complexes by inorganic phosphate is essential to explain the regulation of mitochondrial ATP synthesis flux in skeletal muscle throughout its full dynamic range
Retrieving haystacks: a data driven information needs model for faceted search.
The research aim was to develop an understanding of information need characteristics for word co-occurrence-based search result filters (facets). No prior research has been identified into what enterprise searchers may find useful for exploratory search and why. Various word co-occurrence techniques were applied to results from sample queries performed on industry membership content. The results were used in an international survey of 54 practising petroleum engineers from 32 organizations. Subject familiarity, job role, personality and query specificity are possible causes for survey response variation. An information needs model is presented: Broad, Rich, Intriguing, Descriptive, General, Expert and Situational (BRIDGES). This may help professionals to more effectively meet their information needs and stimulate new needs, improving a systems ability to facilitate serendipity. This research has implications for faceted search in enterprise search and digital library deployments
What Are People Tweeting About Zika? An Exploratory Study Concerning Its Symptoms, Treatment, Transmission, and Prevention
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