Search results for " pattern"
showing 10 items of 2245 documents
Linear transform for simultaneous diagonalization of covariance and perceptual metric matrix in image coding
2003
Two types ofredundancies are contained in images: statistical redundancy and psychovisual redundancy. Image representation techniques for image coding should remove both redundancies in order to obtain good results. In order to establish an appropriate representation, the standard approach to transform coding only considers the statistical redundancy, whereas the psychovisual factors are introduced after the selection ofthe representation as a simple scalar weighting in the transform domain. In this work, we take into account the psychovisual factors in the de8nition of the representation together with the statistical factors, by means of the perceptual metric and the covariance matrix, res…
Physicians’ Knowledge and Application of Immunization Strategies in Patients with Inflammatory Bowel Disease: A Survey of the Italian Group for the S…
2019
<b><i>Background:</i></b> No data on European countries about knowledge and application of immunization strategies in patients with inflammatory bowel disease (IBD) are available. <b><i>Objectives:</i></b> We designed a questionnaire aimed at exploring these issues among Italian gastroenterologists dealing with adult and paediatric IBD. <b><i>Methods:</i></b> An anonymous, 24-item, questionnaire was sent via e-mail to all members of the Italian Group for the study of Inflammatory Bowel Disease. Three sets of questions were formulated: (1) Characteristics of respondents; (2) General opinions on the role of vaccines in IB…
Cross-diffusion effects on stationary pattern formation in the FitzHugh-Nagumo model
2022
<p style='text-indent:20px;'>We investigate the formation of stationary patterns in the FitzHugh-Nagumo reaction-diffusion system with linear cross-diffusion terms. We focus our analysis on the effects of cross-diffusion on the Turing mechanism. Linear stability analysis indicates that positive values of the inhibitor cross-diffusion enlarge the region in the parameter space where a Turing instability is excited. A sufficiently large cross-diffusion coefficient of the inhibitor removes the requirement imposed by the classical Turing mechanism that the inhibitor must diffuse faster than the activator. In an extended region of the parameter space a new phenomenon occurs, namely the exis…
The TES-based cryogenic anticoincidence detector for IXO: First results from large area prototypes
2010
The technique which combines high resolution spectroscopy with imaging capability is a powerful tool to extract fundamental information in X-ray Astrophysics and Cosmology. TES (Transition Edge Sensors)-based microcalorimeters match at best the requirements for doing fine spectroscopy and imaging of both bright (high count rate) and faint (poor signal-to-noise ratio) sources. For this reason they are considered among the most promising detectors for the next high energy space missions and are being developed for use on the focal plane of the IXO (International X-ray Observatory) mission. In order to achieve the required signal-to-noise ratio for faint or diffuse sources it is necessary to r…
Baseline design of the thermal blocking filters for the X-IFU detector on board ATHENA
2014
ATHENA is an advanced X-ray observatory designed by a large European consortium to address the science theme "Hot and Energetic Universe" recently selected by ESA for L2 – the second Large-class mission within the Cosmic Vision science program (launch scheduled in 2028). One of the key instruments of the mission is the X-ray Integral Field Unit (X-IFU), an array of Transition Edge Sensor (TES) micro-calorimeters with high energy resolution (2.5 eV @ 6 keV) in the energy range 0.2÷12 keV, operating at the focal plane of a large effective area high angular resolution (5" HEW) grazing incidence X-ray telescope. The X-IFU operates at temperatures below 100 mK and thus requires a sophisticated c…
Thermal modelling of the ATHENA X-IFU filters
2018
Copyright 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. The X-IFU instrument of the ATHENA mission requires a set of thermal filters to reduce the photon shot noise onto its cryogenic detector and to protect it from molecular contamination. A set of five filters, operating at different nominal temperatures corresponding to the cryostat shield temperatures, is currently baselined. The knowledge of the actual filter temperature profi…
Radio frequency shielding of thin aluminized plastic filters investigated for the ATHENA X-IFU detector
2018
Copyright 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. The X-ray Integral Field Unit (X-IFU) is one of the two detectors of the ATHENA astrophysics space mission approved by ESA in the Cosmic Vision 2015-2025 Science Programme. The X-IFU consists of a large array of transition edge sensors (TES) micro-calorimeters covering a field of view of 5' diameter, sensitive in the energy range 0.2-12 keV, and providing a spectral resolution…
The focal plane assembly for the Athena X-ray Integral Field Unit instrument
2016
This paper summarizes a preliminary design concept for the focal plane assembly of the X-ray Integral Field Unit on the Athena spacecraft, an imaging microcalorimeter that will enable high spectral resolution imaging and point-source spectroscopy. The instrument's sensor array will be a ~ 3840-pixel transition edge sensor (TES) microcalorimeter array, with a frequency domain multiplexed SQUID readout system allowing this large-format sensor array to be operated within the thermal constraints of the instrument's cryogenic system. A second TES detector will be operated in close proximity to the sensor array to detect cosmic rays and secondary particles passing through the sensor array for off…
From witnessing to recording – material objects and the epistemic configuration of science classes
2012
Drawing on concepts developed in actor-network theory and postphenomenology this article shows how material objects in the science classroom become part of epistemic configurations and thus co-shape science education. An ethnographic study on epistemic objects in science education is the basis for the analysis of two of these objects: experimental arrangements and the blackboard. While experimental arrangements configure students as witnesses of the fascinating otherness of material objects, the blackboard enacts students as recorders of semiotic representations. In the interplay of these socio-material enactments scientific knowledge receives its authority in the classroom. The perspective…
Viajeros étnicos, gestos exóticos y encuentros esporádicos: los tours mayas en Los Altos de Chiapas
2018
Este trabajo reflexiona sobre la interacción turista/anfitrión en los tours étnicos promovidos en la región Altos Tsotsil-Tseltal Chiapas, México. Las agencias turísticas promueven diferentes encuentros de los turistas con la población indígena donde se espera que los primeros cumplan con sus expectativas sobre el Otro exótico y los segundos se acoplen a los imaginarios que corren sobre sí mismos. Aquí, al contrario, interesa analizar un espacio turístico en constante construcción con la observación de tres lugares de protagonismo indígena: un mercado indígena en San Cristóbal de Las Casas, una iglesia en San Juan Chamula y una casa de tejedoras en Zinacantán, donde los roles sociales del v…