36 research outputs found
Shared-per-wavelength asynchronous optical packet switching: A comparative analysis
Cataloged from PDF version of article.This paper compares four different architectures for sharing wavelength converters in
asynchronous optical packet switches with variable-length packets. The first two architectures
are the well-known shared-per-node (SPN) and shared-per-link (SPL) architectures,
while the other two are the shared-per-input-wavelength (SPIW) architecture, recently
proposed as an optical switch architecture in synchronous context only, which is extended
here to the asynchronous scenario, and an original scheme called shared-per-output-wavelength
(SPOW) architecture that we propose in the current article. We introduce novel analytical
models to evaluate packet loss probabilities for SPIW and SPOW architectures in
asynchronous context based on Markov chains and fixed-point iterations for the particular
scenario of Poisson input traffic and exponentially distributed packet lengths. The models
also account for unbalanced traffic whose impact is thoroughly studied. These models are
validated by comparison with simulations which demonstrate that they are remarkably
accurate. In terms of performance, the SPOW scheme provides blocking performance very
close to the SPN scheme while maintaining almost the same complexity of the space
switch, and employing less expensive wavelength converters. On the other hand, the SPIW
scheme allows less complexity in terms of number of optical gates required, while it substantially
outperforms the widely accepted SPL scheme. The authors therefore believe that
the SPIW and SPOW schemes are promising alternatives to the conventional SPN and SPL
schemes for the implementation of next-generation optical packet switching systems.
2010 Elsevier B.V. All rights reserved
The Large-Angle Photon Veto System for the NA62 Experiment at CERN
The branching ratio (BR) for the decay K^+ \rightarrow \pi^+ \nu \bar{\nu} is
a sensitive probe for new physics. The NA62 experiment at the CERN SPS will
measure this BR to within about 10%. To reject the dominant background from
channels with final state photons, the large-angle vetoes (LAVs) must detect
photons of energy as low as 200 MeV with an inefficiency of less than 10^-4, as
well as provide energy and time measurements with resolutions of 10% and 1 ns
for 1 GeV photons. The LAV detectors make creative reuse of lead glass blocks
recycled from the OPAL electromagnetic calorimeter barrel. We describe the
mechanical design and challenges faced during construction, the
characterization of the lead glass blocks and solutions adopted for monitoring
their performance, and the development of front-end electronics to allow
simultaneous time and energy measurements over an extended dynamic range using
the time-over-threshold technique. Our results are based on test-beam data and
are reproduced by a detailed Monte Carlo simulation that includes the readout
chain.Comment: 8 pages, 13 figures. Prepared for the Conference Record of the IEEE
Nuclear Science Symposium, Valencia, Spain, October 201
Measurement of the mass difference m(D-s(+))-m(D+) at CDF II
We present a measurement of the mass difference m(D-s(+))-m(D+), where both the D-s(+) and D+ are reconstructed in the phipi(+) decay channel. This measurement uses 11.6 pb(-1) of data collected by CDF II using the new displaced-track trigger. The mass difference is found to be m(D-s(+))-m(D+)=99.41+/-0.38(stat)+/-0.21(syst) MeV/c(2)
Potencialidades da técnica qualitativa grupo focal em investigações sobre abuso de substâncias
Hematomas intracranianos isodensos: estudo de cinco casos
Registro de 5 casos de hematomas intracranianos isodensos diagnosticados mediante tomografia computadorizada craniana, confirmados por exame angio-gráfico e cirurgia. São discutidos aspectos radiológicos encontrados e ressaltados os achados tomográficos que podem facilitar o diagnóstico