Publications from our Researchers
Several of our current PhD candidates and fellow researchers at the Data Science Institute have published, or in the proccess of publishing, papers to present their research.
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Journal articleCreswell A, Bharath AA, 2016,
Task Specific Adversarial Cost Function
The cost function used to train a generative model should fit the purpose ofthe model. If the model is intended for tasks such as generating perceptuallycorrect samples, it is beneficial to maximise the likelihood of a sample drawnfrom the model, Q, coming from the same distribution as the training data, P.This is equivalent to minimising the Kullback-Leibler (KL) distance, KL[Q||P].However, if the model is intended for tasks such as retrieval or classificationit is beneficial to maximise the likelihood that a sample drawn from thetraining data is captured by the model, equivalent to minimising KL[P||Q]. Thecost function used in adversarial training optimises the Jensen-Shannon entropywhich can be seen as an even interpolation between KL[Q||P] and KL[P||Q]. Here,we propose an alternative adversarial cost function which allows easy tuning ofthe model for either task. Our task specific cost function is evaluated on adataset of hand-written characters in the following tasks: Generation,retrieval and one-shot learning.
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Journal articleTaquet M, Quoidbach J, de Montjoye Y-A, et al., 2016,
Hedonism and the choice of everyday activities
, Proceedings of the National Academy of Sciences, Vol: 113, Pages: 9769-9773, ISSN: 0027-8424Most theories of motivation have highlighted that human behavior is guided by the hedonic principle, according to which our choices of daily activities aim to minimize negative affect and maximize positive affect. However, it is not clear how to reconcile this idea with the fact that people routinely engage in unpleasant yet necessary activities. To address this issue, we monitored in real time the activities and moods of over 28,000 people across an average of 27 d using a multiplatform smartphone application. We found that people’s choices of activities followed a hedonic flexibility principle. Specifically, people were more likely to engage in mood-increasing activities (e.g., play sports) when they felt bad, and to engage in useful but mood-decreasing activities (e.g., housework) when they felt good. These findings clarify how hedonic considerations shape human behavior. They may explain how humans overcome the allure of short-term gains in happiness to maximize long-term welfare.
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Journal articleMcGinn D, Birch DA, Akroyd D, et al., 2016,
Visualizing Dynamic Bitcoin Transaction Patterns
, Big Data, Vol: 4, Pages: 109-119, ISSN: 2167-647XThis work presents a systemic top-down visualization of Bitcoin transaction activity to explore dynamically generated patterns of algorithmic behavior. Bitcoin dominates the cryptocurrency markets and presents researchers with a rich source of real-time transactional data. The pseudonymous yet public nature of the data presents opportunities for the discovery of human and algorithmic behavioral patterns of interest to many parties such as financial regulators, protocol designers, and security analysts. However, retaining visual fidelity to the underlying data to retain a fuller understanding of activity within the network remains challenging, particularly in real time. We expose an effective force-directed graph visualization employed in our large-scale data observation facility to accelerate this data exploration and derive useful insight among domain experts and the general public alike. The high-fidelity visualizations demonstrated in this article allowed for collaborative discovery of unexpected high frequency transaction patterns, including automated laundering operations, and the evolution of multiple distinct algorithmic denial of service attacks on the Bitcoin network.
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Journal articleBertone G, Calore F, Caron S, et al., 2016,
Global analysis of the pMSSM in light of the Fermi GeV excess: prospects for the LHC Run-II and astroparticle experiments
, Journal of Cosmology and Astroparticle Physics, Vol: 2016, ISSN: 1475-7516 -
Journal articleMa ZB, Yang Y, Liu YX, et al., 2016,
Recurrently decomposable 2-D convolvers for FPGA-based digital image processing
, IEEE Transactions on Circuits and Systems, Vol: 63, Pages: 979-983, ISSN: 1549-7747Two-dimensional (2-D) convolution is a widely used operation in image processing and computer vision, characterized by intensive computation and frequent memory accesses. Previous efforts to improve the performance of field-programmable gate array (FPGA) convolvers focused on the design of buffering schemes and on minimizing the use of multipliers. A recently proposed recurrently decomposable (RD) filter design method can reduce the computational complexity of 2-D convolutions by splitting the convolution between an image and a large mask into a sequence of convolutions using several smaller masks. This brief explores how to efficiently implement RD based 2-D convolvers using FPGA. Three FPGA architectures are proposed based on RD filters, each with a different buffering scheme. The conclusion is that RD based architectures achieve higher area efficiency than other previously reported state-of-the-art methods, especially for larger convolution masks. An area efficiency metric is also suggested, which allows the most appropriate architecture to be selected.
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Journal articlede Montjoye YKJV,
Privacy by design in big data: An overview of privacy enhancing technologies in the era of big data analytics
, arXivThe extensive collection and processing of personal information in big data analytics has given rise to serious privacy concerns, related to wide scale electronic surveillance, profiling, and disclosure of private data. To reap the benefits of analytics without invading the individuals' private sphere, it is essential to draw the limits of big data processing and integrate data protection safeguards in the analytics value chain. ENISA, with the current report, supports this approach and the position that the challenges of ...
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Book chapterde Montjoye YKJV, 2015,
Modeling and UnderstandingIntrinsic Characteristics of Human Mobility
, Social Phenomena From Data Analysis to Models, Publisher: Springer, ISBN: 9783319140117Humans are intrinsically social creatures and our mobility is central to understanding how our societies grow and function. Movement allows us to congregate with our peers, access things we need, and exchange information. Human mobility has huge impacts on topics like urban and transportation planning, social and biologic spreading, and economic outcomes. So far, modeling these processes has been hindered by a lack of data. This is radically changing with the rise of ubiquitous devices. In this chapter, we discuss recent progress deriving insights from the massive, high resolution data sets collected from mobile phone and other devices. We begin with individual mobility, where empirical evidence and statistical models have shown important intrinsic and universal characteristics about our movement: we, as human, are fundamentally slow to explore new places, relatively predictable, and mostly unique. We then explore methods of modeling aggregate movement of people from place to place and discuss how these estimates can be used to understand and optimize transportation infrastructure. Finally, we highlight applications of these findings to the dynamics of disease spread, social networks, and economic outcomes.
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Journal articleRivera-Rubio J, Alexiou I, Bharath AA, 2015,
Appearance-based indoor localization: a comparison of patch descriptor performance
, Pattern Recognition Letters, Vol: 66, Pages: 109-117, ISSN: 1872-7344Vision is one of the most important of the senses, and humans use it extensively during navigation. We evaluated different types of image and video frame descriptors that could be used to determine distinctive visual landmarks for localizing a person based on what is seen by a camera that they carry. To do this, we created a database containing over 3 km of video-sequences with ground-truth in the form of distance travelled along different corridors. Using this database, the accuracy of localization—both in terms of knowing which route a user is on—and in terms of position along a certain route, can be evaluated. For each type of descriptor, we also tested different techniques to encode visual structure and to search between journeys to estimate a user’s position. The techniques include single-frame descriptors, those using sequences of frames, and both color and achromatic descriptors. We found that single-frame indexing worked better within this particular dataset. This might be because the motion of the person holding the camera makes the video too dependent on individual steps and motions of one particular journey. Our results suggest that appearance-based information could be an additional source of navigational data indoors, augmenting that provided by, say, radio signal strength indicators (RSSIs). Such visual information could be collected by crowdsourcing low-resolution video feeds, allowing journeys made by different users to be associated with each other, and location to be inferred without requiring explicit mapping. This offers a complementary approach to methods based on simultaneous localization and mapping (SLAM) algorithms.
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Conference paperKarpathiotakis M, Alagiannis I, Heinis T, et al., 2015,
Just-In-Time Data Virtualization: Lightweight Data Management with ViDa
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Conference paperHeinis T, Ailamaki A, 2015,
Reconsolidating Data Structures
, Pages: 665-670 -
Conference paperTauheed F, Heinis T, Ailamaki A, 2015,
THERMAL-JOIN: A Scalable Spatial Join for Dynamic Workloads
, Pages: 939-950 -
Conference paperRivera-Rubio J, Alexiou I, Bharath AA, 2015,
Associating Locations Between Indoor Journeys from Wearable Cameras
, 13th European Conference on Computer Vision (ECCV), Publisher: SPRINGER-VERLAG BERLIN, Pages: 29-44, ISSN: 0302-9743- Author Web Link
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- Citations: 1
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Journal articleHeinis T, Ham DA, 2015,
On-the-Fly Data Synopses: Efficient Data Exploration in the Simulation Sciences
, SIGMOD Record, Vol: 44, Pages: 23-28 -
Conference paperRivera-Rubio J, Alexiou I, Bharath AA, 2015,
Indoor Localisation with Regression Networks and Place Cell Models.
, Publisher: BMVA Press, Pages: 147.1-147.1 -
Journal articleWang S, Pandis I, Johnson D, et al., 2014,
Optimising Correlation Matrix Calculations on Gene Expression Data
, BMC Bioinformatics, Vol: 15, ISSN: 1471-2105
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