333 research outputs found
Understanding spatial data usability
In recent geographical information science literature, a number of researchers have made passing reference to an apparently new characteristic of spatial data known as 'usability'. While this attribute is well-known to professionals engaged in software engineering and computer interface design and testing, extension of the concept to embrace information would seem to be a new development. Furthermore, while notions such as the use and value of spatial information, and the diffusion of spatial information systems, have been the subject of research since the late-1980s, the current references to usability clearly represent something which extends well beyond that initial research. Accordingly, the purposes of this paper are: (1) to understand what is meant by spatial data usability; (2) to identify the elements that might comprise usability; and (3) to consider what the related research questions might be
Solar ions in the heliosheath: a possible new source of heavy neutral atoms
We show that multiply ionized coronal C, N, O, Mg, Si, S ions carried by the
solar wind and neutralized by consecutive electron captures from neutral
interstellar atoms constitute an important new source of neutral atoms in the
inner heliosheath, with energies up to ~ 1 keV/n. In the model we developed,
the heavy ions are treated as test particles carried by hydrodynamic plasma
flow (with a Monte-Carlo description of interstellar neutrals) and undergoing
all relevant atomic processes determining the evolution of all charge-states of
considered species (radiative and dielectronic recombination, charge exchange,
photo-, and electron impact ionization). The total strength of the source is
from ~10^6 g/s for S to ~10^8 g/s for O, deposited as neutrals below the
heliopause. These atoms should provide, as they drift to supersonic wind
region, important sources of PUIs and eventually ACRs, especially for species
that are excluded from entering the heliosphere because of their ionization in
the LISM. The expected corresponding ENA fluxes at 1 AU are in the range 10^-4
- 10^0 at./(cm^2 s sr), depending on the species and direction (Table 2).Comment: Submitted for IGGP Astrophysics Conference, March 2006; 6 page
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Geovisualization of dynamics, movement and change: key issues and developing approaches in visualization research
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
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