Studio e progetto di sistema per la misura della velocità in veicoli

La misura della velocità in un veicolo, rispetto al riferimento rappresentato dal terreno, è generalmente ricavata dalla misura della velocità di rotazione delle ruote, utilizzando vari tipi di sensori (magnetici, ottici ecc) applicati direttamente alle ruote o su organi meccanici rigidamente collegati alle ruote stesse. Quello che interessa conoscere è la velocità del mezzo rispetto al terreno: il modello fisico che descrive il sistema terreno-ruota ha dei parametri che hanno una certa varianza rispetto al loro valor medio conosciuto (si pensi alle tolleranze di lavorazione) e inoltre è tempovariante sia nel lungo periodo (mesi), sia nel medio periodo (ore), che nel breve periodo (secondi): si pensi alle usure dei pneumatici, al cambiamento della loro pressione con la temperatura o addirittura al caso di slittamento fra ruota e terreno. La misura della velocità rispetto al terreno (detta comunemente TSOG, True Speed Over Ground) è utile anche per rilevare se, e di quanto, una ruota stia muovendosi slittando. Pertanto argomento di questa tesi sarà quello di studiare un sistema di misura della velocità che non utilizzi un contatto fra il mezzo di cui si vuol misurare la velocità e il terreno (un sistema di misura siffatto è detto “contactless”), realizzato inoltre con componentistica idonea a ottenere un sistema di basso costo

«Da la cuna a la tomba è un breve passo»: una lettura di due "rime morali" di Marino

In queste pagine si intende rivolgere lo sguardo alle scaturigini dellapoesia sacra mariniana, in particolare alle Rime morali contenute delle Rime del1602. Attraverso la lettura di due tessere esemplari, si propone un’indagine chedelinei alcune costanti della poesia morale del giovane Marino. Nell’analisi sicontestualizzano i testi all’interno del panorama letterario dell’epoca e della tradizioneclassica del genere morale, mettendo in luce, oltre alla disinvoltura nel riusoe nell’intarsio delle fonti, il grado d’innovazione dell’operazione mariniana

Improving the Protectiveness of 3-Mercaptopropyl-Trimethoxysilane Coatings on Bronze by Addition of Oxidic Nano- and Microparticles

The protectiveness of coatings based on 3-mercaptopropyl-trimethoxysilane (PropS-SH) applied on bronze artworks was enhanced by investigating and tuning a variety of factors. In particular, the coating performances were optimized by proper additive choice among oxide nanoparticles (CeO2, La2O3, TiO2) and microparticles (fly ash (FA)), and by varying the aging time of the nanoparticle suspensions before coating application and the RT curing time of the coatings. Moreover, the possibility of conservation of the silane solution under refrigerated conditions was assessed. The aggressive environment was a tenfold concentrated synthetic acid rain (AR × 10). The techniques adopted comprised electrochemical tests (polarization curve recording and EIS tests) and SEM-Energy Dispersion Spectroscopy (EDS) observations. In the case of FA microparticles, never used before as additives in silane coatings, further tests were performed in FA suspensions in AR × 10 to clarify the contribution of these particles to PropS-SH coating protectiveness. The tests included pH measurements, elemental chemical analyses, and electrochemical tests on bare bronze. Improved performances of PropS-SH coatings were achieved by La2O3, CeO2, and FA addition, with La2O3 affording the best results during 20 days of immersion. The positive influence of FA was connected to its alkaline character and to the release of soluble silicates

The chemical evolution of self-gravitating primordial disks

Numerical simulations show the formation of self-gravitating primordial disks during the assembly of the first structures in the Universe, in particular during the formation of Pop.~III and supermassive stars. Their subsequent evolution is expected to be crucial to determine the mass scale of the first cosmological objects, which depends on the temperature of the gas and the dominant cooling mechanism. Here, we derive a one-zone framework to explore the chemical evolution of such disks and show that viscous heating leads to the collisional dissociation of an initially molecular gas. The effect is relevant on scales of 10 AU (1000 AU) for a central mass of 10 M_sun (10^4 M_sun) at an accretion rate of 10^{-1} M_sun yr^{-1}, and provides a substantial heat input to stabilize the disk. If the gas is initially atomic, it remains atomic during the further evolution, and the effect of viscous heating is less significant. The additional thermal support is particularly relevant for the formation of very massive objects, such as the progenitors of the first supermassive black holes. The stabilizing impact of viscous heating thus alleviates the need for a strong radiation background as a means of keeping the gas atomic.Comment: 13 pages, 5 figures, 6 tables, accepted at A&

The two-machine one-buffer continuous time model with restart policy

This paper deals with the performance evaluation of production lines in which well defined machine start/stop control policies are applied. A modeling approach has been developed in order to reduce the complexity of a two-machine one-buffer line where a specific control policy, called “restart policy”, is adopted. The restart policy exercises control over the start/stop condition of the first machine: when the buffer gets full and, as a consequence, the first machine is forced to stop production (i.e., it is blocked), the control policy keeps the first machine in an idle state until the buffer becomes empty again. The rationale behind this policy is to reduce the blocking frequency of the first machine, i.e. the probability that a blockage occurs on the first machine due to the buffer filling up. Such a control policy is adopted in practice when outage costs (e.g., waste production) are related to each restart of the machine. The two-machine one-buffer line with restart policy (RP line) is here modeled as a continuous time Markov process so as to consider machines having different capacities and working in an asynchronous manner. The mathematical RP model is described along with its analytical solution. Then, the most critical line performance measures are derived and, finally, some numerical examples are reported to show the effects of such a policy on the blocking frequency of the first machine

Ieri come oggi, oggi come domani: la dimensione temporale e linguistica in Finale di partita di Samuel Beckett

Endgame (1957), considered by many as Samuel Beckett’s major work, stands out as a “terminal” play, a play in which the characters live in an absolute present, devoid of any idea of future and completely disconnected from the world of memories, which are so far away as to seem mere hallucinations. How, then, should these characters live in a universe that is so close to its end? By waiting, Beckett suggests; by waiting, paradoxically, for things to take their own course