12,934 research outputs found
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
A Method of Drusen Measurement Based on the Geometry of Fundus Reflectance
BACKGROUND: The hallmarks of age-related macular degeneration, the leading cause of blindness in the developed world, are the subretinal deposits known as drusen. Drusen identification and measurement play a key role in clinical studies of this disease. Current manual methods of drusen measurement are laborious and subjective. Our purpose was to expedite clinical research with an accurate, reliable digital method. METHODS: An interactive semi-automated procedure was developed to level the macular background reflectance for the purpose of morphometric analysis of drusen. 12 color fundus photographs of patients with age-related macular degeneration and drusen were analyzed. After digitizing the photographs, the underlying background pattern in the green channel was leveled by an algorithm based on the elliptically concentric geometry of the reflectance in the normal macula: the gray scale values of all structures within defined elliptical boundaries were raised sequentially until a uniform background was obtained. Segmentation of drusen and area measurements in the central and middle subfields (1000 ÎĽm and 3000 ÎĽm diameters) were performed by uniform thresholds. Two observers using this interactive semi-automated software measured each image digitally. The mean digital measurements were compared to independent stereo fundus gradings by two expert graders (stereo Grader 1 estimated the drusen percentage in each of the 24 regions as falling into one of four standard broad ranges; stereo Grader 2 estimated drusen percentages in 1% to 5% intervals). RESULTS: The mean digital area measurements had a median standard deviation of 1.9%. The mean digital area measurements agreed with stereo Grader 1 in 22/24 cases. The 95% limits of agreement between the mean digital area measurements and the more precise stereo gradings of Grader 2 were -6.4 % to +6.8 % in the central subfield and -6.0 % to +4.5 % in the middle subfield. The mean absolute differences between the digital and stereo gradings 2 were 2.8 +/- 3.4% in the central subfield and 2.2 +/- 2.7% in the middle subfield. CONCLUSIONS: Semi-automated, supervised drusen measurements may be done reproducibly and accurately with adaptations of commercial software. This technique for macular image analysis has potential for use in clinical research
Two semi-automated computational approaches for spectroscopic analysis of stellar photospheres: detailed characterization at high resolution and abundance determination at medium resolution
We report on two distinct computational approaches to self-consistently
measure photospheric properties of large samples of stars. Both procedures
consist of a set of several semi-integrated tasks based on shell and Python
scripts, which efficiently run either our own codes or open source software
commonly adopted by the astronomical community. One approach aims to derive the
main stellar photospheric parameters and abundances of a few elements by
analysing high-resolution spectra from a given public library homogeneously
constructed. The other one is applied to recover the abundance of a single
element in stars with known photospheric parameters by using mid-resolution
spectra from another open homogeneous database and calibrating derived
abundances. Both semi-automated computational approaches provide homogeneity
and objectivity to every step of the process and represent a fast way to reach
partial and final results as well as to estimate measurement errors, making
possible to systematically evaluate and improve the distinct steps.Comment: 7 pages, 4 figures, conference paper (I Workshop of Computacao
Cientifica em Astronomia, Brazil, 2011) to appear in the Journal of
Computational Interdisciplinary Sciences - JCI
Robots for Exploration, Digital Preservation and Visualization of Archeological Sites
Monitoring and conservation of archaeological sites
are important activities necessary to prevent damage or to
perform restoration on cultural heritage. Standard techniques,
like mapping and digitizing, are typically used to document the
status of such sites. While these task are normally accomplished
manually by humans, this is not possible when dealing with
hard-to-access areas. For example, due to the possibility of
structural collapses, underground tunnels like catacombs are
considered highly unstable environments. Moreover, they are full
of radioactive gas radon that limits the presence of people only
for few minutes. The progress recently made in the artificial
intelligence and robotics field opened new possibilities for mobile
robots to be used in locations where humans are not allowed
to enter. The ROVINA project aims at developing autonomous
mobile robots to make faster, cheaper and safer the monitoring of
archaeological sites. ROVINA will be evaluated on the catacombs
of Priscilla (in Rome) and S. Gennaro (in Naples)
Performance and evaluation of real-time multicomputer control systems
Three experiments on fault tolerant multiprocessors (FTMP) were begun. They are: (1) measurement of fault latency in FTMP; (2) validation and analysis of FTMP synchronization protocols; and investigation of error propagation in FTMP
Training Future Engineers to Be Ghostbusters: Hunting for the Spectral Environmental Radioactivity
Although environmental radioactivity is all around us, the collective public
imagination often associates a negative feeling to this natural phenomenon. To
increase the familiarity with this phenomenon we have designed, implemented,
and tested an interdisciplinary educational activity for pre-collegiate
students in which nuclear engineering and computer science are ancillary to the
comprehension of basic physics concepts. Teaching and training experiences are
performed by using a 4" x 4" NaI(Tl) detector for in-situ and laboratory
{\gamma}-ray spectroscopy measurements. Students are asked to directly assemble
the experimental setup and to manage the data-taking with a dedicated Android
app, which exploits a client-server system that is based on the Bluetooth
communication protocol. The acquired {\gamma}-ray spectra and the experimental
results are analyzed using a multiple-platform software environment and they
are finally shared on an open access Web-GIS service. These all-round
activities combining theoretical background, hands-on setup operations, data
analysis, and critical synthesis of the results were demonstrated to be
effective in increasing students' awareness in quantitatively investigating
environmental radioactivity. Supporting information to the basic physics
concepts provided in this article can be found at
http://www.fe.infn.it/radioactivity/educational
- …