87,590 research outputs found
Santuari d'Italia - Umbria
No full textCensimento e schedatura dei principali luoghi di culto di carattere santuariale esistenti in Umbria, con alcuni saggi introduttivi (saggi di M. Tosti, L. Pellegrini, C. Coletti, M.L. Proietti, F. Troiani
Parole in prova per il Dizionario della Lingua Italiana 2008
No full textUna rassegna ragionata di neologismi pronti ad entrare nel Dizionario Sabatini Coletti 2008. Ricerca e redazione delle voci a cura di Manuela Manfredini (pp. 13-32
Hollow cathode life-time prediction from low work function surface coverage evolution
No full textIn this paper a procedure to update the plasma parameters relatively to changes of the hollow cathode surface work function has been developed. This procedure has been validated with experimental results and then coupled with the deposition/desorption model already developed by the authors. The evolution of the surface of the cathode tested for 28,000 hours by Sarver-Verhey has been simulated and from the data obtained an end of life criterion has been developed. Then using this criterion the ELT NSTAR discharge cathode has been simulated for various throttle conditions deriving the lifetime at TH0 (200,000 h), TH8 (100,000 h) and TH15 (25,000 h). The lifetimes found are in agreement with the theoretical expectation. The lifetime of the ELT NSTAR cathode under the throttling conditions used during the Deep Space 1 Spare Ion Engine life test has been found to be in excess of 30,000 hours and in particular 100,000 or more if the cathode is run at TH8 or lower from 30,000 hours onward
Hemodynamics in a giant intracranial aneurysm characterized by in vitro 4D flow MRI
No full textThe attached file "giant_ane_velocity_pressure_public_release.tar.gz" contains the processed data for the associated paper.Experimental and computational data suggest that hemodynamics play a critical role in the development, growth, and rupture of cerebral aneurysms. The flow structure, especially in aneurysms with a large sac, is highly complex and three-dimensional. Therefore, volumetric and time-resolved measurements of the flow properties are crucial to fully characterize the hemodynamics. In this study, phase-contrast Magnetic Resonance Imaging is used to assess the fluid dynamics inside a 3D-printed replica of a giant intracranial aneurysm, whose hemodynamics was previously simulated by multiple research groups. The physiological inflow waveform is imposed in a flow circuit with realistic cardiovascular impedance. Measurements are acquired with sub-millimeter spatial resolution for 16 time steps over a cardiac cycle, allowing for the detailed reconstruction of the flow evolution. Moreover, the three-dimensional and time-resolved pressure distribution is calculated from the velocity field by integrating the fluid dynamics equations, and is validated against differential pressure measurements using precision transducers. The flow structure is characterized by vortical motions that persist within the aneurysm sac for most of the cardiac cycle. All the main flow statistics including velocity, vorticity, pressure, and wall shear stress suggest that the flow pattern is dictated by the aneurysm morphology and is largely independent of the pulsatility of the inflow, at least for the flow regimes investigated here. Comparisons are carried out with previous computational simulations that used the same geometry and inflow conditions, both in terms of cycle-averaged and systolic quantities.Winston and Maxine Wallin Neuroscience Discovery FundAmili, Omid; Schiavazzi, Daniele; Moen, Sean; Jagadeesan, Bharathi; Van de Moortele, Pierre-François; Coletti, Filippo. (2017). Hemodynamics in a giant intracranial aneurysm characterized by in vitro 4D flow MRI. Retrieved from the University Digital Conservancy, https://doi.org/10.13020/D6WX0S
Morphological properties of the conducting human airways by in vivo CT
No full textData files are tables saved in xlsx format. README.txt has information regarding the format of these.Branch by branch morphometric data of human airways as presented in the article "Morphological and functional properties of the conducting human airways investigated by in vivo CT and in vitro MRI." We investigate the airway tree structure obtained by CT from a cohort of subjects with normal lung function, from 36 healthy non-smoking subjects from the COPDGene study (Regan et al. 2010).National Science Foundation (CBET-1453538)National Institutes of Health (NHLBI-R21HL129906)Van de Moortele, Tristan; Coletti, Filippo; Wendt, Christine. (2017). Morphological properties of the conducting human airways by in vivo CT. Retrieved from the University Digital Conservancy, https://doi.org/10.13020/D6J38F
Hollow cathode life time modelling
No full textHollow Cathodes (HCs) are of primary importance in the field of electric space propulsion, being used as electron sources in ion and Hall-effect thrusters. Hence, their lifetime is a key factor in all these applications.HCs have demonstrated the capability of providing up to 30,000 hours of operation, whereas no direct experimental data exist above this limit.The importance of HC lifetime is a growing issue for deep space missions usingpropulsive systems based on ion or Hall-effect thrusters that may require longerlifetimes than those demonstrated up to now. To address these concerns about HCs andto prove the suitability of an ion thrusters based solar electric propulsion subsystem forfuture high-impulse missions (such as Bepi Colombo), a model able to predict the HClifetime is needed.The model that has been developed in this thesis consists of three parts: a barium oxidedepletion model, a low work function surface coverage model and a plasma updateprocedure to calculate the effects that a change in the insert surface work function willproduce on the cathode plasma.The barium-oxide depletion model has been validated by comparing its results withexperimental measurements performed at QinetiQ and NASA, showing a goodquantitative agreement.The low-work function surface coverage model is the first of its kind to include theeffect of ion bombardment. The plasma update procedure, even if semi-empirical, isable to produce results that are in good agreement with the measurements.Using these three models the lifetime of the NSTAR hollow cathode has beensimulated, yielding predictions that are in good agreement with the theoreticalexpectations
La figura e l'opera di Francesco Coletti
No full textData l’ampiezza e la varietà dei temi trattati negli scritti di Coletti, il lavoro di ricerca è diviso tra diversi studiosi.
Gli obiettivi sono:
- riordino e apertura al pubblico del fondo bibliotecario Francesco Coletti presso la Biblioteca Comunale “F. Antolisei” di San Severino Marche
- convegno presso l’Università di Macerata
- pubblicazione di un volume di atti
- collaborazione scientifica con gli storici dell'Università di Montreal esperti di storia dell statistica
- pubblicazione di articoli su riviste internazional
Spectroscopic temperature measurement in a applied field MPD
No full textIn this paper the temperature of the plasma inside an MPD thruster has been measured with and without applied magnetic field using spectroscopic measurement. The obtained spectra show the presence of C++, C+ and F atoms while the lines relative to C, F+ and F++ are out of scope. Using the measured line intensities, formulating three different sets of hypotheses and assuming that the corona equilibrium is valid for this plasma the temperature values have been calculated. The temperatures found are around 3 eV and show small variations with the application of magnetic field confirming
A chemical model for barium oxide depletion from hollow cathode’s insert
No full textIn this paper a chemical model to predict barium oxide depletion from hollow cathode insert is developed. This model is based on the knowledge of the ternary diagram that exists in the BaO-CaO-Al2O3 system. This model takes also into account the diffusive motion of barium oxide inside the insert. A comparison between numerical and experimental data is made to determine the diffusion coefficient inside the insert. The diffusion coefficient presents an Arrhenius trend with activation energy similar to the one of barium oxide evaporation. A two dimensional model is used to demonstrate how temperature profile along the insert is a key parameter to calculate barium depletion
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