1,721,653 research outputs found
Entrained-flow gasification of coal under slagging conditions: Relevance of fuel-wall interaction and char segregation to the properties of solid wastes
No full textEntrained-flow slagging gasifiers are characterized by operating conditions that promote ash migration/ deposition onto the reactor walls, whence ash is drained as a molten phase. Experimental investigation on ashes generated by full-scale plants suggested that both char entrapment inside the melt and carboncoverage of the slag can occur. Because of the wide range of spatial and temporal scales involved in these phenomena, numerical simulation of the fate of the flying fine char particles is a very difficult task. This work illustrates how different numerical modeling approaches can be jointly used to understand segregation patterns of char particles in full-scale entrained-flow coal gasifiers operated in the slagging regime. A multilevel approach has been developed for this purpose. RANS-based simulations of the full-scale geometry with coal particle injection and tracking aimed to obtain the general behavior of the flow field and particle trajectories. Simulations enabled to estimate the effect of swirl and tangential flow on the bulk-to-wall char particle deposition rate. Then, RANS results were adopted in a more detailed numerical model based on the solution of the filtered Navier-Stokes equations. In this last model, a turbulence LES approach for the Eulerian gas phase was applied. The equations of particles motion were solved via a Lagrangian particle tracking algorithm with the TrackToFace method. Simulations were performed involving a level of detail that allowed to obtain a clear picture of the multiphase flow behavior responsible for char deposition phenomena. This multilevel approach enabled the assessment of the char particle deposition rates and the nature of char-slag interaction (segregation/entrapment) that are likely to occur in full-scale slagging gasifiers. Results of numerical simulations have been critically discussed in the light of experimental findings. They represent a useful source of information for the implementation of constitutive equations and parameters in design-oriented reduced compartmental models. © 2013 Elsevier Ltd. All rights reserved
A virtual prototyping platform to improve CAE analysis workflow
No full textThis paper describes an experimental software system that allows interfacing a virtual immersive environment with Computer Aided Engineering (CAE) open source software aiming for improving and simplifying design process and results evaluation. System includes a middleware to execute jobs on HPC architectures and to compare results of server-class processors with GPGPU hardware. The main innovation of the overall system is the possibility to setup the CAE job directly inside the virtual reality platform speeding-up the entire process. User evaluations on selected case studies show how the use of a virtual environment may enhance the perception of engineers ideas during the design process. In addition, the use of a system that allows reconfiguring and relaunching the job simplifies setup of job configuration. Results also show that HPC hardware based on GPGPU offers a perceivable speedup for problems with an high number of nodes. © 2015, Springer International Publishing Switzerland
Real-time Detectors for Muography
No full textDifferent types of detectors can be used for muon radiography. Common to all detectors is the ability to track the direction of the incoming muon. Emulsion detectors have very high resolution and no need for electric power, but cannot give real-time information and cannot be used in all environmental conditions. Detectors with electronic readout have generally lower resolution but are more flexible, can be operated in real-time, and can also measure the time of the muon hitting the detector with resolutions as low as few hundred ps in specific setups. Special geometries and assemblies have been used for specific applications, where the size, weight, or shape of the detector are heavily constrained
Landslide susceptibility assessment in ash-fall pyroclastic deposits covering carbonate slopes surrounding the Vesuvius: application of geophysical surveys for soil depth mapping (Abstract)
No full textDevelopment of radon transport model in different types of dwellings to assess indoor activity concentration
No full textThe influence of different building types on the activity concentration of Radon indoor is studied through transport models in soil and building materials. The numerical solutions of the relevant transport equations are solved by the finite differences method (FDM) and used to evaluate the indoor Radon activity concentration. Several boundary conditions are introduced to simulate the Radon entry into the buildings from soils and to assess the Radon activity concentration at the different floors. The types of dwelling investigated differ in the position of the lower floor respect to the ground. Comparisons are made to modeling assessments obtained considering different soil characteristics underneath the building and building materials to simulate indoor Radon activity concentration. These investigations lead to the conclusion that, in addition to the nature of the soil and building materials, the position of lower floor of dwellings plays a significant role in determining the amount of radon entry into residential buildings. This work is effective to assess the health hazards coming from the Radon accumulation in living environments
ANALYSIS BY SCANNER OF TRACKS PRODUCED BY RADON ALPHA PARTICLES IN CR-39 DETECTORS
No full textThe most used passive detectors for Radon measurement are the CR39s, both for the good stability of the material and for the practicality of use. But, commercial reading systems are expensive and not always fast. The aim of the present work was the development of a method for a rapid, efficient and economic evaluation of the result of the indoor Radon measurement performed with CR39 detectors. The analysis and acquisition of detector images were performed using a photo scanner and the free ImageJ software. Several groups of CR-39 detectors were exposed, developed and analysed. Calibration curve was obtained in a wide range of exposure values (200-12 000 kBq·h·m -3) to allow the procedure to be applied in all possible measurement environments. Furthermore, a statistical study was carried out on the shape and size of nuclear tracks after chemical development. The dependence of the track size on Radon exposure was effective in showing the trace saturation effect as well
Landslide susceptibility assessment in ash-fall pyroclastic deposits covering carbonate slopes surrounding the Vesuvius: application of geophysical surveys for soil depth mapping (Abstract)
No full textANALYSIS by SCANNER of TRACKS PRODUCED by RADON ALPHA PARTICLES in CR-39 DETECTORS
No full textThe most used passive detectors for Radon measurement are the CR39s, both for the good stability of the material and for the practicality of use. But, commercial reading systems are expensive and not always fast. The aim of the present work was the development of a method for a rapid, efficient and economic evaluation of the result of the indoor Radon measurement performed with CR39 detectors. The analysis and acquisition of detector images were performed using a photo scanner and the free ImageJ software. Several groups of CR-39 detectors were exposed, developed and analysed. Calibration curve was obtained in a wide range of exposure values (200–12 000 kBq·h·m −3) to allow the procedure to be applied in all possible measurement environments. Furthermore, a statistical study was carried out on the shape and size of nuclear tracks after chemical development. The dependence of the track size on Radon exposure was effective in showing the trace saturation effect as well
Landslide susceptibility assessment in ash-fall pyroclastic deposits surrounding Somma-Vesuvius: application of geophysical surveys for soil thickness mapping
No full textAlong the steep slopes of the carbonate mountains that surround the Campanian Plain and Mount Somma-Vesuvius, rainfalltriggered debris slides occur in unconsolidated ash-fall pyroclastic deposits. The initial debris slides evolve into debris flows that often cause significant property damage and loss of human life in the towns located at the foot of the slopes. In this particular geological situation, the pyroclastic soil thickness, the slope angle, and the morphological variations of the slope profile are the most important factors that contribute to landslide susceptibility. In this paper, the results of an experimental application of shallow resistivity and refraction seismic soundings in mapping the thickness of pyroclastic soils are presented. These geophysical methods are proposed as low-cost and versatile methods to be used in the difficult morphological conditions of the steep slopes in which debris-slides initiate. The methods have been used experimentally in a sample area located on the upper slope of Mount Pizzo d’Alvano, from which debris flows initiated that dramatically hit the town of Sarno on 5–6 May 1998. The inversion of geoelectrical soundings has been calibrated with resistivity values measured directly on pyroclastic outcrops and with soil thickness estimations derived from refraction seismic soundings and from the application of a mobile dynamic penetrometer. The results of the field experimentation can be summarised as follows: (i) unconsolidated ash-fall pyroclastic deposits, ranging in particle size from fine ash to lapilli, can be differentiated from fractured carbonate bedrock by means of electrical resistivity and velocity values of longitudinal seismic waves; (ii) thickness of ash-fall pyroclastic soils can be empirically related to the slope angle using an inverse relationship; and (iii) the empirical model has been applied to Digital Elevation Model data, allowing pyroclastic soil thickness mapping in the sample area
Measurement of sigma(e+e- -> pi+pi) from threshold to 0.85 GeV^2 using initial state radiation with the KLOE detector
No full text"We have measured the cross section of the radiative process e(+)e(-) -> pi(+)pi(-)gamma with the KLOE detector at the Frascati phi-factory DA(1)NE, from events taken at a CM energy W =1 GeV. Initial state radiation allows us to obtain the cross section for e(+)e(-) -> pi(+)pi(-), the pion form factor vertical bar F-pi vertical bar(2) and the dipion contribution to the muon magnetic moment anomaly, Delta alpha(pi pi)(mu) = (478.5 +\/- 2.0(stat) +\/- 5.0(syst) +\/- 4.5(th)) x 10(-10) in the range 0.1 < M-pi pi(2) <0.85 GeV2, where the theoretical error includes a SU(3) chi PT estimate of the uncertainty on photon radiation from the final pions. The discrepancy between the Standard Model evaluation of alpha(mu) and the value measured by the Muon g-2 collaboration at BNL is confirmed. (C) 2011 Elsevier B.V. All rights reserved. RI Fiore, Salvatore\/C-9722-2011; Di Domenico, Antonio\/G-6301-2011; De Lucia, Erika\/D-2250-2011; branchini, paolo\/A-4857-2011
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