2,596 research outputs found
Test beam measurement of the first prototype of the fast silicon pixel monolithic detector for the TT-PET project
The TT-PET collaboration is developing a PET scanner for small animals with
30 ps time-of-flight resolution and sub-millimetre 3D detection granularity.
The sensitive element of the scanner is a monolithic silicon pixel detector
based on state-of-the-art SiGe BiCMOS technology. The first ASIC prototype for
the TT-PET was produced and tested in the laboratory and with minimum ionizing
particles. The electronics exhibit an equivalent noise charge below 600 e- RMS
and a pulse rise time of less than 2 ns, in accordance with the simulations.
The pixels with a capacitance of 0.8 pF were measured to have a detection
efficiency greater than 99% and, although in the absence of the
post-processing, a time resolution of approximately 200 ps
Characterization of conductive polyprrole coated wool yarns
Wool yarns were coated with conducting polypyrrole by chemical synthesis methods. Polymerization of pyrrole was carried out in the presence of wool yarn at various concentrations of the monomer and dopant anion. The changes in tensile, moisture absorption, and electrical properties of the yarn upon coating with conductive polypyrrole are presented. Coating the wool yarns with conductive polypyrrole resulted in higher tenacity, higher breaking strain, and lower initial modulus. The changes in tensile properties are attributed to the changes in surface morphology due to the coating and reinforcing effect of conductive polypyrrole. The thickness of the coating increased with the concentration of p-toluene sulfonic acid, which in turn caused a reduction in the moisture regain of the wool yarn. Reducing the synthesis temperature and replacing p-toluenesulfonic acid by anthraquinone sulfonic acid resulted in a large reduction in the resistance of the yarn. <br /
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A monolithic ASIC demonstrator for the Thin Time-of-Flight PET scanner
Time-of-flight measurement is an important advancement in PET scanners to improve image reconstruction with a lower delivered radiation dose. This article describes the monolithic ASIC for the TT-PET project, a novel idea for a high-precision PET scanner for small animals. The chip uses a SiGe Bi-CMOS process for timing measurements, integrating a fully-depleted pixel matrix with a low-power BJT-based front-end per channel, integrated on the same 100 µm thick die. The target timing resolution of the scanner is 30 ps RMS for electrons from the conversion of 511 keV photons. The system will include 1.6 million channels across almost 2000 different chips. A full-featured demonstrator chip with a 3×10 matrix of 500×500 µm2 pixels was fabricated to validate each block. Its design and experimental results are presented here. © 2019 CERN
Non-conformal Hydrodynamics in Einstein-dilaton Theory
In the Einestein-dilaton theory with a Liouville potential parameterized by
, we find a Schwarzschild-type black hole solution. This black hole
solution, whose asymptotic geometry is described by the warped metric, is
thermodynamically stable only for . Applying the gauge/gravity
duality, we find that the dual gauge theory represents a non-conformal thermal
system with the equation of state depending on . After turning on the
bulk vector fluctuations with and without a dilaton coupling, we calculate the
charge diffusion constant, which indicates that the life time of the quasi
normal mode decreases with . Interestingly, the vector fluctuation with
the dilaton coupling shows that the DC conductivity increases with temperature,
a feature commonly found in electrolytes.Comment: 27 pages and 2 figures, published in JHE
Time resolution and power consumption of a monolithic silicon pixel prototype in SiGe BiCMOS technology
SiGe BiCMOS technology can be used to produce ultra-fast, low-power silicon
pixel sensors that provide state-of-the-art time resolution even without an
internal gain mechanism. The development of such sensors requires the
identification of the main factors that may degrade the timing performance and
the characterisation of the dependance of the sensor time resolution on the
amplifier power consumption. Measurements with a source of
a prototype sensor produced in SG13G2 technology from IHP Microelectronics,
shows a time resolution of 140 ps at an amplifier current of 7 A and 45 ps at higher power consumption. A full simulation shows that the
resolution on the measurement of the signal time-over-threshold, used to
correct for time walk, is the main factor affecting the timing performance
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Characterization of the demonstrator of the fast silicon monolithic ASIC for the TT-PET project
The TT-PET collaboration is developing a small animal TOF-PET scanner based on monolithic silicon pixel sensors in SiGe BiCMOS technology. The demonstrator chip, a small-scale version of the final detector ASIC, consists of a 03 × 1 pixel matrix integrated with the front-end, a 50 ps binning TDC and read out logic. The chip, thinned down to 100 µm and backside metallized, was operated at a voltage of 180 V. The tests on a beam line of minimum ionizing particles show a detection efficiency greater than 99.9% and a time resolution down to 110 ps. © 2019 CERN
Isometric Embeddings and Noncommutative Branes in Homogeneous Gravitational Waves
We characterize the worldvolume theories on symmetric D-branes in a
six-dimensional Cahen-Wallach pp-wave supported by a constant Neveu-Schwarz
three-form flux. We find a class of flat noncommutative euclidean D3-branes
analogous to branes in a constant magnetic field, as well as curved
noncommutative lorentzian D3-branes analogous to branes in an electric
background. In the former case the noncommutative field theory on the branes is
constructed from first principles, related to dynamics of fuzzy spheres in the
worldvolumes, and used to analyse the flat space limits of the string theory.
The worldvolume theories on all other symmetric branes in the background are
local field theories. The physical origins of all these theories are described
through the interplay between isometric embeddings of branes in the spacetime
and the Penrose-Gueven limit of AdS3 x S3 with Neveu-Schwarz three-form flux.
The noncommutative field theory of a non-symmetric spacetime-filling D-brane is
also constructed, giving a spatially varying but time-independent
noncommutativity analogous to that of the Dolan-Nappi model.Comment: 52 pages; v2: References adde
International Standard ISO 9001–A Soft Computing View
In order to add value to ISO 9001, a Quality Management Systems that assess, measure, documents, improves, and certify processes to increase productivity, i.e., that transforms business at any level. On the one hand, this work focuses on the development of a decision support system, which will allow companies to be able to meet the needs of customers by fulfilling requirements that reflect either the effectiveness or the non-effectiveness of an organization. On the other hand, many approaches for knowledge representation and reasoning have been proposed using Logic Programming (LP), namely in the area of Model Theory or Proof Theory. In this work it is followed the proof theoretical approach in terms of an extension to the LP language to knowledge representation and reasoning. The computational framework is centered on Artificial Neural Networks to evaluate customer’s satisfaction and the degree of confidence that one has on such a happening
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