754 research outputs found
Smart Highway : ITS-G5 and C2VX based testbed for vehicular communications in real environments enhanced by edge/cloud technologies
A liquid Xenon Positron Emission Tomograph for small animal imaging : first experimental results of a prototype cell
A detector using liquid Xenon (LXe) in the scintillation mode is studied for
Positron Emission Tomography (PET) of small animals. Its specific design aims
at taking full advantage of the Liquid Xenon scintillation properties. This
paper reports on energy, time and spatial resolution capabilities of the first
LXe prototype module equipped with a Position Sensitive Photo- Multiplier tube
(PSPMT) operating in the VUV range (178 nm) and at 165 K. The experimental
results show that such a LXe PET configuration might be a promising solution
insensitive to any parallax effect.Comment: 34 pages, 18 pages, to appear in NIM
Alternative networks: toward global access to the Internet for all
It is often said that the Internet is ubiquitous in our daily lives, but this holds true only for those who can easily access it. In fact, billions of people are still digitally disconnected, as bringing connectivity to certain zones does not make a good business case. The only solution for these unsatisfied potential users is to directly undertake the building of the infrastructure required to obtaining access to the Internet, typically forming groups in order to share the corresponding cost. This article presents a global classification and a summary of the main characteristics of different Alternative Network deployments that have arisen in recent years with an aim to provide Internet services in places where mainstream network deployments do not exist or are not adequate solutions. The Global Access to the Internet for All Research Group of the Internet Research Task Force, where all authors actively participate, is interested in documenting these emerging deployments. As an outcome of this work, a classification has converged by consensus, where five criteria have been identified and, based on them, four different types of Alternative Networks have been identified and described with real-world examples. Such a classification is useful for a deeper understanding of the common characteristics behind existing and emerging Alternative Networks
A threshold imaging Cerenkov detector with CsI photocathodes
A Threshold Imaging Cherenkov (TIC) detector, in conjunction with a tracking device and a time-of-flight system, has been developed to allow pion, kaon and proton identification in the 3--8 GeV/ range of momenta. The system allows spatial identification of the photons of particles above the Cherenkov threshold and their correlation to a particular track. The TIC detector uses a MWPC detector with a CsI coated photocathode for photon conversion. The results obtained in ultrarelativistic lead--lead collisions at the CERN SPS accelerator are presented
Imaging with the invisible light
We describe a UV photo-detector with single photon(electron) counting and
imaging capability. It is based on a CsI photocathode, a GEM charge multiplier
and a self triggering CMOS analog pixel chip with 105k pixels at 50 micron
pitch. The single photoelectron produced by the absorption of a UV photon is
drifted to and multiplied inside a single GEM hole. The coordinates of the GEM
avalanche are reconstructed with high accuracy (4 micron rms) by the pixel
chip. As a result the map of the GEM holes, arranged on a triangular pattern at
50micron pitch, is finely imaged.Comment: 6 pages, 14 figures, presented at the 11th Vienna Conference on
Instrumentation VIC 2007, submitted to Nuclear Instruments and Methods
Hadron beam test of a scintillating fibre tracker system for elastic scattering and luminosity measurement in ATLAS
A scintillating fibre tracker is proposed to measure elastic proton
scattering at very small angles in the ATLAS experiment at CERN. The tracker
will be located in so-called Roman Pot units at a distance of 240 m on each
side of the ATLAS interaction point. An initial validation of the design
choices was achieved in a beam test at DESY in a relatively low energy electron
beam and using slow off-the-shelf electronics. Here we report on the results
from a second beam test experiment carried out at CERN, where new detector
prototypes were tested in a high energy hadron beam, using the first version of
the custom designed front-end electronics. The results show an adequate
tracking performance under conditions which are similar to the situation at the
LHC. In addition, the alignment method using so-called overlap detectors was
studied and shown to have the expected precision.Comment: 12 pages, 8 figures. Submitted to Journal of Instrumentation (JINST
Novel geometrical concept of a high-performance brain PET scanner. Principle, design and performance estimates
We present the principle, a possible implementation and performance estimates of a novel geometrical concept for a high-resolution positron emission tomograph. The concept, which can be for example implemented in a brain PET device, promises to lead to an essentially parallax-free 3D image reconstruction with excellent spatial resolution and constrast, uniform over the complete field of view. The key components are matrices of long axially oriented scintillator crystals which are read out at both extremities by segmented Hybrid Photon Detectors. We discuss
the relevant design considerations for a 3D axial PET camera module, motivate parameter and material choices, and estimate its performance in terms of spatial and energy resolution. We support these estimates by Monte Carlo simulations and in some cases by first experimental results. From the performance of a camera module, we extrapolate to the reconstruction resolution of a 3D axial PET scanner in a semi-analytical way and compare it to an existing state-of-the art brain PET device. We finally describe a dedicated data acquisition system, capable to fully exploit the advantages of the proposed concept. We conclude that the proposed 3D axial concept and the discussed implementation is a competitive approach for
high-resolution brain PET. Excellent energy resolution and Compton enhanced sensitivity are expected to lead to high-quality reconstruction and reduced scanning times
The acquisition of Sign Language: The impact of phonetic complexity on phonology
Research into the effect of phonetic complexity on phonological acquisition has a long history in spoken languages. This paper considers the effect of phonetics on phonological development in a signed language. We report on an experiment in which nonword-repetition methodology was adapted so as to examine in a systematic way how phonetic complexity in two phonological parameters of signed languages — handshape and movement — affects the perception and articulation of signs. Ninety-one Deaf children aged 3–11 acquiring British Sign Language (BSL) and 46 hearing nonsigners aged 6–11 repeated a set of 40 nonsense signs. For Deaf children, repetition accuracy improved with age, correlated with wider BSL abilities, and was lowest for signs that were phonetically complex. Repetition accuracy was correlated with fine motor skills for the youngest children. Despite their lower repetition accuracy, the hearing group were similarly affected by phonetic complexity, suggesting that common visual and motoric factors are at play when processing linguistic information in the visuo-gestural modality
Determinacy analysis for logic programs using mode and type information
We propose an analysis for detecting procedures and goals
that are deterministic (i.e. that produce at most one solution), or predicates whose clause tests are mutually exclusive (which implies that at most one of their clauses will succeed) even if they are not deterministic (because they cali other predicates that can produce more than one solution). Applications of such determinacy information include detecting programming errors, performing certain high-level program transformations for improving search efñciency, optimizing low level code generation and parallel execution, and estimating tighter upper bounds on the computational costs of goals and data sizes, which can be used for program debugging, resource consumption and granularity control, etc. We have implemented the analysis and integrated it in the CiaoPP system, which also infers automatically the mode and type information that our analysis takes as input. Experiments performed on this implementation show that the analysis is fairly accurate and efncient
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