40,419 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
Interactive visual exploration of a large spatio-temporal dataset: Reflections on a geovisualization mashup
Exploratory visual analysis is useful for the preliminary investigation of large structured, multifaceted spatio-temporal datasets. This process requires the selection and aggregation of records by time, space and attribute, the ability to transform data and the flexibility to apply appropriate visual encodings and interactions. We propose an approach inspired by geographical 'mashups' in which freely-available functionality and data are loosely but flexibly combined using de facto exchange standards. Our case study combines MySQL, PHP and the LandSerf GIS to allow Google Earth to be used for visual synthesis and interaction with encodings described in KML. This approach is applied to the exploration of a log of 1.42 million requests made of a mobile directory service. Novel combinations of interaction and visual encoding are developed including spatial 'tag clouds', 'tag maps', 'data dials' and multi-scale density surfaces. Four aspects of the approach are informally evaluated: the visual encodings employed, their success in the visual exploration of the clataset, the specific tools used and the 'rnashup' approach. Preliminary findings will be beneficial to others considering using mashups for visualization. The specific techniques developed may be more widely applied to offer insights into the structure of multifarious spatio-temporal data of the type explored here
Quantum Zeno effect with a superconducting qubit
Detailed schemes are investigated for experimental verification of Quantum
Zeno effect with a superconducting qubit. A superconducting qubit is affected
by a dephasing noise whose spectrum is 1/f, and so the decay process of a
superconducting qubit shows a naturally non-exponential behavior due to an
infinite correlation time of 1/f noise. Since projective measurements can
easily influence the decay dynamics having such non-exponential feature, a
superconducting qubit is a promising system to observe Quantum Zeno effect. We
have studied how a sequence of projective measurements can change the dephasing
process and also we have suggested experimental ways to observe Quantum Zeno
effect with a superconducting qubit. It would be possible to demonstrate our
prediction in the current technology
Recommended from our members
Mashup cartography: cartographic issues of using Google Earth for tag maps
Quantum phase slip interference device based on superconducting nanowire
We propose a transistor-like circuit including two serially connected
segments of a narrow superconducting nanowire joint by a wider segment with a
capacitively coupled gate in between. This circuit is made of amorphous NbSi
film and embedded in a network of on-chip Cr microresistors ensuring a
sufficiently high external electromagnetic impedance. Assuming a virtual regime
of quantum phase slips (QPS)in two narrow segments of the wire, leading to
quantum interference of voltages on these segments, this circuit is dual to the
dc SQUID. Our samples demonstrated appreciable Coulomb blockade voltage (analog
of critical current of the SQUIDs) and periodic modulation of this blockade by
an electrostatic gate (analog of flux modulation in the SQUIDs). The model of
this QPS transistor is discussed.Comment: 5 pages including 3 figures; in v2 the title was updated, typos were
fixed and 4 references adde
Magnetically modulated accretion in T Tauri stars
We examine how accretion on to T Tauri stars may be modulated by a
time-dependent `magnetic gate' where the inner edge of the accretion disc is
disrupted by a varying stellar field. We show that magnetic field variations on
time-scales shorter than 10^5 yr can modulate the accretion flow, thus
providing a possible mechanism both for the marked photometric variability of T
Tauri stars and for the possible conversion of T Tauri stars between classical
and weak line status. We thus suggest that archival data relating to the
spectrophotometric variability of T Tauri stars may provide an indirect record
of magnetic activity cycles in low-mass pre-main-sequence stars.Comment: LaTeX file (requires mn.sty), 4 pages, no figures or tables. To
appear in MNRAS
Periodic photometric variability of the brown dwarf Kelu-1
We have detected a strong periodicity of 1.80+/-0.05 hours in photometric
observations of the brown dwarf Kelu-1. The peak-to-peak amplitude of the
variation is ~1.1% (11.9+/-0.8 mmag) in a 41nm wide filter centred on 857nm and
including the dust/temperature sensitive TiO & CrH bands. We have identified
two plausible causes of variability: surface features rotating into- and
out-of-view and so modulating the light curve at the rotation period; or,
elliposidal variability caused by an orbiting companion. In the first scenario,
we combine the observed vsin(i) of Kelu-1 and standard model radius to
determine that the axis of rotation is inclined at 65+/-12 degrees to the line
of sight.Comment: 7 pages, 9 figures. Accepted for publication in MNRA
Standardized field testing of assistant robots in a Mars-like environment
Controlled testing on standard tasks and within standard environments can provide meaningful performance comparisons between robots of heterogeneous design. But because they must perform practical tasks in unstructured, and therefore non-standard, environments, the benefits of this approach have barely begun to accrue for field robots. This work describes a desert trial of six student prototypes of astronaut-support robots using a set of standardized engineering tests developed by the US National Institute of Standards and Technology (NIST), along with three operational tests in natural Mars-like terrain. The results suggest that standards developed for emergency response robots are also applicable to the astronaut support domain, yielding useful insights into the differences in capabilities between robots and real design improvements. The exercise shows the value of combining repeatable engineering tests with task-specific application-testing in the field
Group study of an 'undercover' test for visuospatial neglect: Invisible cancellation can reveal more neglect than standard cancellation
Visual neglect is a relatively common deficit after brain damage, particularly strokes. Cancellation tests provide standard clinical measures of neglect severity and deficits in daily life. A recent single-case study introduced a new variation on standard cancellation. Instead of making a visible mark on each target found, the patient made invisible marks (recorded with carbon paper underneath, for later scoring). Such invisible cancellation was found to reveal more neglect than cancellation with visible marks. Here we test the generality of this. Twenty three successive cases with suspected neglect each performed cancellation with visible or invisible marks. Neglect of contralesional targets was more pronounced with invisible marks. Indeed, about half of the patients only showed neglect in this version. For cases showing more neglect with invisible marks, stronger neglect of contralesional targets correlated with more revisits to ipsilesional targets for making additional invisible marks upon them. These results indicate that cancellation with invisible marks can reveal more neglect than standard cancellation with visible marks, while still providing a practical bedside test. Our observations may be consistent with recent proposals that demands on spatial working memory (required to keep track of previously found items only when marked invisibly) can exacerbate spatial neglect
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