42,047 research outputs found
Interactive tag maps and tag clouds for the multiscale exploration of large spatio-temporal datasets
'Tag clouds' and 'tag maps' are introduced to represent geographically referenced text. In combination, these aspatial and spatial views are used to explore a large structured spatio-temporal data set by providing overviews and filtering by text and geography. Prototypes are implemented using freely available technologies including Google Earth and Yahoo! 's Tag Map applet. The interactive tag map and tag cloud techniques and the rapid prototyping method used are informally evaluated through successes and limitations encountered. Preliminary evaluation suggests that the techniques may be useful for generating insights when visualizing large data sets containing geo-referenced text strings. The rapid prototyping approach enabled the technique to be developed and evaluated, leading to geovisualization through which a number of ideas were generated. Limitations of this approach are reflected upon. Tag placement, generalisation and prominence at different scales are issues which have come to light in this study that warrant further work
Survey and Analysis of Production Distributed Computing Infrastructures
This report has two objectives. First, we describe a set of the production
distributed infrastructures currently available, so that the reader has a basic
understanding of them. This includes explaining why each infrastructure was
created and made available and how it has succeeded and failed. The set is not
complete, but we believe it is representative.
Second, we describe the infrastructures in terms of their use, which is a
combination of how they were designed to be used and how users have found ways
to use them. Applications are often designed and created with specific
infrastructures in mind, with both an appreciation of the existing capabilities
provided by those infrastructures and an anticipation of their future
capabilities. Here, the infrastructures we discuss were often designed and
created with specific applications in mind, or at least specific types of
applications. The reader should understand how the interplay between the
infrastructure providers and the users leads to such usages, which we call
usage modalities. These usage modalities are really abstractions that exist
between the infrastructures and the applications; they influence the
infrastructures by representing the applications, and they influence the ap-
plications by representing the infrastructures
Can gravitational infall energy lead to the observed velocity dispersion in DLAs?
The median observed velocity width v_90 of low-ionization species in damped
Ly-alpha systems is close to 90 km/s, with approximately 10% of all systems
showing v_90 > 210 km/s at z=3. We show that a relative shortage of such
high-velocity neutral gas absorbers in state-of-the-art galaxy formation models
is a fundamental problem, present both in grid-based and particle-based
numerical simulations. Using a series of numerical simulations of varying
resolution and box size to cover a wide range of halo masses, we demonstrate
that energy from gravitational infall alone is insufficient to produce the
velocity dispersion observed in damped Ly-alpha systems, nor does this
dispersion arise from an implementation of star formation and feedback in our
highest resolution (~ 45 pc) models, if we do not put any galactic winds into
our models by hand. We argue that these numerical experiments highlight the
need to separate dynamics of different components of the multiphase
interstellar medium at z=3.Comment: 12 Pages, 9 Figures, accepted to ApJ, printing in colour recommende
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