Inferring Unusual Crowd Events From Mobile Phone Call Detail Records

The pervasiveness and availability of mobile phone data offer the opportunity of discovering usable knowledge about crowd behaviors in urban environments. Cities can leverage such knowledge in order to provide better services (e.g., public transport planning, optimized resource allocation) and safer cities. Call Detail Record (CDR) data represents a practical data source to detect and monitor unusual events considering the high level of mobile phone penetration, compared with GPS equipped and open devices. In this paper, we provide a methodology that is able to detect unusual events from CDR data that typically has low accuracy in terms of space and time resolution. Moreover, we introduce a concept of unusual event that involves a large amount of people who expose an unusual mobility behavior. Our careful consideration of the issues that come from coarse-grained CDR data ultimately leads to a completely general framework that can detect unusual crowd events from CDR data effectively and efficiently. Through extensive experiments on real-world CDR data for a large city in Africa, we demonstrate that our method can detect unusual events with 16% higher recall and over 10 times higher precision, compared to state-of-the-art methods. We implement a visual analytics prototype system to help end users analyze detected unusual crowd events to best suit different application scenarios. To the best of our knowledge, this is the first work on the detection of unusual events from CDR data with considerations of its temporal and spatial sparseness and distinction between user unusual activities and daily routines.Comment: 18 pages, 6 figure

Від редакційної колегії

No abstract

Ultrafast time-resolved spectroscopy of 1D metal-dielectric photonic crystals

We study the all-optical switching behavior of one-dimensional metal-dielectric photonic crystals due to the nonlinearity of the free metal electrons. A polychromatic pump-probe setup is used to determine the wavelength and pump intensity dependence of the ultrafast transmission suppression as well as the dynamics of the process on a subpicosecond timescale. We find ultrafast (sub-picosecond) as well as a slow (millisecond) behavior. We present a model of the ultrafast dynamics and nonlinear response which can fit the measured data well and allows us to separate the thermal and the electronic response of the system.Comment: 7 pages, 5 figure

Shifting new media: from content to consultancy, from heterarchy to hierarchy

This is a detailed case history of one of London’s iconic new media companies, AMX Studios. Some of the changes in this firm, we assume, are not untypical for other firms in this sector. Particularly we want to draw attention to two transformations. The first change in AMX and in London’s new media industry more generally refers to the field of industrial relations. What can be observed is a shift from a rather heterarchical towards a more hierarchical organized new media industry, a shift from short-term project networks to long-term client dependency. The second change refers to new media products and services. We want to argue for a shift from cool content production towards consultancy and interactive communications solutions

A new approach for the limit to tree height using a liquid nanolayer model

Liquids in contact with solids are submitted to intermolecular forces inferring density gradients at the walls. The van der Waals forces make liquid heterogeneous, the stress tensor is not any more spherical as in homogeneous bulks and it is possible to obtain stable thin liquid films wetting vertical walls up to altitudes that incompressible fluid models are not forecasting. Application to micro tubes of xylem enables to understand why the ascent of sap is possible for very high trees like sequoias or giant eucalyptus.Comment: In the conclusion is a complementary comment to the Continuum Mechanics and Thermodynamics paper. 21 pages, 4 figures. Continuum Mechanics and Thermodynamics 20, 5 (2008) to appea

Identifying Appropriate Nursing Home Resources to Reduce Fall-Related Emergency Department Transfers.

OBJECTIVES To describe potentially avoidable fall-related transfers to the emergency department (ED), and to identify infrastructure, training needs, and resources deemed appropriate for implementation in nursing homes (NHs) to decrease fall-related transfers to EDs. DESIGN A multi-method design, including (1) in-depth case review by an expert panel, (2) structured discussion with NH stakeholders, and (3) appropriateness rating. SETTING AND PARTICIPANTS Fall-related transfers were identified from the prospective reporting of every unplanned hospital transfer occurring within 21 months, collected during the INTERCARE study in 11 Swiss NHs. METHODS Eighty-one fall-related transfers were rated for avoidability by a 2-round expert panel. NH stakeholders were consulted to discuss key implementable resources for NHs to mitigate potentially avoidable fall-related transfers. A questionnaire composed of 21 contextually adapted resources was sent to a larger group of stakeholders, to rate the appropriateness for implementation in NHs. χ2 tests were used to assess whether avoidability was associated with an ED visit and to describe transfers. The RAND/UCLA method for appropriateness was used to determine appropriate resources. RESULTS One of 4 fall-related transfers were rated as potentially avoidable. A positive association was found between an ED visit and a rating of avoidability (χ2 (1, N = 81) = 18.0, P < .001). Fourteen resources, including developing partnerships with outpatient clinics to access imaging services and strengthening geriatric expertise in nursing homes through clinical training and advanced nurse practitioners, were rated as appropriate by NH stakeholders for NH implementation to reduce potentially avoidable fall-related ED transfers. CONCLUSIONS AND IMPLICATIONS Access to diagnostic equipment, geriatric expertise, and clinical training is essential to reduce fall-related potentially avoidable transfers from NHs. Implementing and supporting advanced practice nurses or nurses in extended roles provides NH directors, policymakers, and health care institutions with the possibility of re-engineering resources to limit unnecessary transfers, which are detrimental for resident quality of care and costly for the health system