Search results for "BED"
showing 10 items of 1605 documents
Modelling of the thermal mechanical behaviour of a single size beryllium pebble bed
2001
The Helium Cooled Pebble Bed (HCPB) Blanket for fusion power reactors and the ITER breeding blanket are based on the use of pebble beds of lithium ceramics as breeder and beryllium as neutron multiplier. Experimental activities were performed at Forschungszentrum Karlsruhe concerning the measurement of pebble bed heat transfer parameters. At the Department of Nuclear Engineering of the University of Palermo, the experimental results have been reproduced by means of the ABAQUS finite element code. Moreover, a thermal-mechanical theoretical model has been developed for single size beryllium pebble beds. In the paper the results from the numerical and theoretical analyses and the comparison wi…
Characterization of the ESR response of alanine dosimeters to low-energy Cu-target X-tube photons
2017
Abstract This article describes Electron Spin Resonance (ESR) response measurements of Kodak BioMax alanine films exposed to low-energy X-rays from a Cu-target tube operating at 20 kV. Commercial alanine detectors were used to ensure maximum reproducibility of the results, while the choice of a film was due the low penetration of the soft X-rays. X-ray energy spectra and fluences were determined with an innovative digital semiconductor detector system. These data were used to quantify the irradiation of the alanine films in terms of absorbed dose to water. The alanine films were found to present a stable response, highly linear with dose. To our knowledge, these data have not been previousl…
Depth-dose measurement corrections for the surface electronic brachytherapy beams of an Esteya® unit: a Monte Carlo study
2020
Abstract Three different correction factors for measurements with the parallel-plate ionization chamber PTW T34013 on the Esteya electronic brachytherapy unit have been investigated. This chamber type is recommended by AAPM TG-253 for depth-dose measurements in the 69.5 kV x-ray beam generated by the Esteya unit. Monte Carlo simulations using the PENELOPE-2018 system were performed to determine the absorbed dose deposited in water and in the chamber sensitive volume at different depths with a Type A uncertainty smaller than 0.1%. Chamber-to-chamber differences have been explored performing measurements using three different chambers. The range of conical applicators available, from 10 to 30…
An EPR method for discriminating radiation beams in ammonium tartrate and tooth enamel
2008
The radiation linear energy transfer (LET), which is the energy released by ionizing radiation per path unit, arouses great scientific interest because the biological damage produced by ionizing radiation in tissues is strictly related to LET. Radiation beams with different LETs will cause different spatial energy distribution and therefore different effects inside matter. In the last twenty years the EPR spectroscopy has become a valuable dosimetric tool. This technique allows absorbed dose measurements through the detection of free radicals produced by ionizing radiation in organic and/or inorganic compounds. In this work we have analyzed the possibility of using the acquisition of two co…
PPG embedded system for blood pressure monitoring
2014
In this work, we have designed and implemented a microcontroller-based embedded system for blood pressure monitoring through a PhotoPlethysmoGraphic (PPG) technique. In our system, it is possible to perform PPG measurements via reflectance mode. Hardware novelty of our system consists in the adoption of Silicon PhotoMultiplier detectors. The signal received from the photodetector is used to calculate the instantaneous heart rate and therefore the heart rate variability. The obtained results show that, by using our system, it is possible to easily extract both the PPG and the breath signal. These signals can be used to monitor the patients during the convalescence both in hospital and at hom…
Improvement of the butyl methacrylate-paraffin embedment.
1983
The excellent butyl methacrylate-paraffin method as an embedment for light microscopy has been technically improved. More uniform and reproducible polymerization has been obtained by using a vacuum oven to degas the polymerizing mixture and to replace the air with nitrogen at 650 Torr. The amount of benzoyl peroxide required must be determined for each batch of butyl methacrylate. A teflon lined, reusable metal mold and a method of one-step blocking of tissues in preparation for sectioning are also described.
Experimental tests and thermo-mechanical analyses on the HEXCALIBER mock-up
2008
Abstract Within the framework of the R&D activities promoted by European Fusion Development Agreement on the helium-cooled pebble bed test blanket module to be irradiated in ITER, ENEA Brasimone and the Department of Nuclear Engineering of the University of Palermo performed intense research activities on the modelling of the thermo-mechanical behaviour of both beryllium and lithiated ceramics pebble beds, which are envisaged to be used, respectively, as neutron multiplier and tritium breeder. In particular, at the DIN a thermo mechanical constitutive model was developed for both lithiated ceramics and beryllium pebble beds and it was successfully implemented on a commercial finite element …
On the theoretical–numerical study of the HEXCALIBER mock-up thermo-mechanical behaviour
2010
Abstract Within the framework of the R&D activities promoted by European Fusion Development Agreement on the Helium-Cooled Pebble Bed Test Blanket Module to be irradiated in ITER, ENEA Brasimone and the Department of Nuclear Engineering of the University of Palermo (DIN) performed intense research activities on the modelling of the thermo-mechanical behaviour of both beryllium and lithiated ceramics pebble beds, that are envisaged to be used, respectively, as neutron multiplier and tritium breeder. In particular, the DIN developed a thermo-mechanical constitutive model for these pebble beds to be validated against the HEXCALIBER mock-up test campaign, carried out at the ENEA HE-FUS3 facilit…
Semi-continuous feeding and gasification of alfalfa and wheat straw pellets in a lab-scale fluidized bed reactor
2015
Abstract Small scale air-blown fluidized bed gasification of alfalfa and wheat straw pellets were conducted for semi-continuous solid feeding and range of operating conditions varied due to the modifications in equivalence ratio (ER) (0.20–0.35) achieved both by varying solid and air input. Alfalfa pellets displayed an improvement in several gasification variables such as gas lower heating value (∼4.1 MJ/Nm3), specific gas yield (1.66 Nm3/kg), cold gas efficiency (∼42%) and carbon conversion efficiency (∼72%) as ER maximized to 0.35 which was found optimum for this feedstock for the present course of experiments. Gasification parameters of wheat straw pellets on the other hand were characte…
Series expansion for the effective conductivity of a periodic dilute composite with thermal resistance at the two-phase interface
2019
We study the asymptotic behavior of the effective thermal conductivity of a periodic two-phase dilute composite obtained by introducing into an infinite homogeneous matrix a periodic set of inclusions of a different material, each of them of size proportional to a positive parameter ?. We assume that the normal component of the heat flux is continuous at the two-phase interface, while we impose that the temperature field displays a jump proportional to the normal heat flux. For ? small, we prove that the effective conductivity can be represented as a convergent power series in ? and we determine the coefficients in terms of the solutions of explicit systems of integral equations.