2,053 research outputs found
Formigoni (Guido). La scelta occidentale della CISL. Giulio Pastore e l'azione sindacale tra guerra fredda e ricostruzione. (1947-1951)
No full textDurand Jean-Dominique. Formigoni (Guido). La scelta occidentale della CISL. Giulio Pastore e l'azione sindacale tra guerra fredda e ricostruzione. (1947-1951). In: Archives de sciences sociales des religions, n°90, 1995. p. 93
Tethers for Deorbit of Objects in High Eccentricity Orbits at the End-of-Life
No full textThe present PhD research investigates the removal from orbit (i.e. deorbit) of inactive objects in high eccentricity orbits, considering as specific target Sylda, a large dual-payload adapter used onboard Ariane 5 heavy launches to Geostationary Earth Orbit (GEO), and released in Geostationary Transfer Orbit (GTO). The population of space debris always increased since the start of space activities, due to the fact that deorbit procedures were never implemented so far. The adoption of a deorbit system, onboard payloads or other objects delivered into space in the future, is an effective solution to significantly attenuate the otherwise exponentially increasing debris density and consequent collision risk in space. The deorbit is performed with a dedicated system that dissipates orbital energy, causing a gradual decrease of orbital altitude until the
object degrades while reentering the Earth’s atmosphere. Deorbit from Low Earth Orbits (LEO) has been widely studied in literature, whereas very little is present regarding deorbit from GTO or other high eccentricity orbits, even if such objects are very important targets for removal since the cross continuously both highly valuable zones of LEO and GEO. International guidelines for space debris attenuation set 25 years as maximum time for removal from orbit. The present research employs a Bare Electrodynamic Tether (BET) as deorbit device: such tape tether creates a Lorentz drag from the interaction between the current circulating along the tether, from the collection of electrons from space plasma, and the geomagnetic field. Sylda is a major threat from the collision risk standpoint, given its very large exposed area and high mass, and therefore it is an optimal candidate for deorbit implementation, also due to the high rate of dual-payload launches to GEO. The research covers both the numerical simulation and analysis of deorbit and of pre-deorbit procedures. Regarding deorbit,
two main simulation campaigns are performed: the first simulates the deorbit on the orbital plane, neglecting the out-of-plane oscillations of the system. One of the main outcomes from this first batch of analyses is that the optimal configuration for the tethered system is having one electrodynamic tether subdivided in two segments deployed along opposite directions from Sylda: this is called butterfly configuration. A second phase of deorbit analysis follows, with a different computational model, adopting the butterfly configuration, and including also the out-of-plane dynamics of
the system. Before starting the deorbit from GTO, two procedures must be performed: at first the detumbling of Sylda, i.e. the minimization of the residual angular velocity of rotation of Sylda around its center of mass. This procedure is analyzed proposing a set of magnetic torquers to accomplish this task. After detumbling is complete, the deployment of the tethers can start. The deployment is then simulated, accounting for three different options: deployment at apogee, at perigee, or at mid-way along the initial orbit, the last resulting as the most favorable location. Another part of research is dedicated to the study of the attitude detection of the two tether segments of the butterfly configuration, during deployment, using a vision system that tracks the tipmass at the end of each tether. An analysis is performed to estimate the uncertainty affecting the measure, considering two main configurations for the vision system, i.e. a monocular system and a stereo system
Glassy dynamics of a polymer monolayer on a heterogeneous disordered substrate
No full textWe present molecular dynamics simulations of a polymer monolayer on randomly functionalized
surfaces that are characterized by different fractions of weakly and strongly attractive sites. We show
that the dynamics slow-down upon cooling resembles that of a strong glass-forming liquid. Indeed, the
mean-square displacements show an increasingly lasting subdiffusive behaviour before the diffusive
regime, with signs of Fickian yet not Gaussian diffusion, and the dynamic correlation functions exhibit a
stretched exponential decay. The glassy dynamics of this relatively dilute system is dominated by the
interaction of the polymer with the substrate and becomes more marked when the substrate composition is
heterogeneous. Accordingly, the estimated glass transition temperature shows a non-monotic dependence
on surface composition, in agreement with previous results for the activation energy and with an analysis
of the potential energy landscape experienced by the polymer beads. Our findings are relevant to the
description of polymer–surface adhesion and friction and the development of polymer nanocomposites with
tailored structural and mechanical properties
don Guido Beltrame. Pastore e ricercatore
No full textVolume a più mani, commemorativo di don Guido Beltrame (1918-2002), figura di sacerdote e studioso assai noto a Padova, nel decennale della scompars
"La materia quando inizia a soffrire": Denial Figures in Guido Morselli's Work
No full textopenIl presente lavoro si propone di indagare la questione della crisi del soggetto così come discussa dall'autore italiano Guido Morselli, nelle diverse sedi dei romanzi, della produzione saggistica e del diario personale. Da qui si analizzeranno temi quali il solipsismo e gli interrogativi esistenziali, fin dai loro primi riverberi nella filosofia centro-europea di fine Ottocento, inizio Novecento.The present work aims yo investigate the issue of the crisis of the subject, as it is discussed by the Italian author Guido Morselli, on his novels, essays and personal diary. We will also analyze topics such as solipsism and existential questions from their first reverberations on the late eighteen century and early nineteen century middle European philosophy
Circulating immune complexes in sera of patients infected with Echinococcus granulosus
No full textCirculating immune complexes (CIC) were investigated by the C1q binding assay in sera of 23 patients infected with Echinococcus granulosus. For the 23 sera studied, nine were found to be positive in the test. When the samples were grouped according to the cyst localization, the highest rate of CIC positivity was found in the group of sera from patients with pulmonary cyst; in this group, double diffusion (DD) and indirect haemagglutination (IHA) tests gave a low rate of positivity for antibodies directed against parasitic antigens. Rheumatoid factor, anti-nuclear and anti-mitochondria autoantibodies were not detectable in patients' sera by indirect immunofluorescence technique (IIF). Anti-smooth muscle autoantibodies, detectable by IIF, were present in 56% of the sera and this positivity was higher in the hepatic (83%) than in the pulmonary form (40%)
Deorbit with Bare Tether System from High Eccentricity Initial Orbit: Analyses and Numerical Simulations
No full textVision system for tether tip-mass detection during deployment on high-eccentricity orbit
No full text
Influence of wall heterogeneity on nanoscopically confined polymers
No full textWe investigate via molecular dynamics simulations the behaviour of a polymer melt confined between surfaces with increasing spatial correlation (patchiness) of weakly and strongly interacting sites. Beyond a critical patchiness, we find a dramatic dynamic decoupling, characterized by a steep growth of the longest relaxation time and a constant diffusion coefficient. This arises from dynamic heterogeneities induced by the walls in the adjacent polymer layers, leading to the coexistence of fast and slow chain populations. Structural variations are also present, but they are not easy to detect. Our work opens the way to a better understanding of adhesion, friction, rubber reinforcement by fillers, and many other open issues involving the dynamics of polymeric materials on rough, chemically heterogeneous and possibly "dirty" surfaces
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