simulatori di sistemi di comunicazione su fibra ottica

La tesi rappresenta una ricerca accurata in rete dei principali e più sofisticati software di simulazione di sistemi di comunicazione ottica. Lo sviluppo sempre maggiore e a basso costo di reti di telecomunicazionie, basate su tecniche di trasmissione ottica su fibra, ha spinto le aziende a investire sulla creazione di sistemi software sempre piu’ avanzati in grado di progettare,simulare e analizzare sistemi di comunicazione ottica anche molto complessi. Esistono software in grado di simulare sia l’intero sistema ottico che i singoli dispositivi ottici che lo compongono,come generatori di segnale,laser,modulatori,fibre,ricevitori ottici,amplificatori ottici,multiplatori e altri ancora. In un progetto di sistema di trasmissione,il cui scopo fondamentale è il trasferimento da una sorgente ad un utilizzatore di un segnale portatore di informazione,bisogna sfruttare al massimo e quindi ottimizzare le risorse caratteristiche del mezzo fisico,cioe’ del mezzo portante. E’ proprio grazie a questi software di simulazione che riusciamo ad effettuare previsioni su un particolare collegamento ottico,riuscendo cosi’ ad ottimizzare le risorse a nostra disposizione,diminuendo notevolmente i costi,che invece si avrebbero con delle prove sperimentali. Quindi questa tesi vuole essere una guida,per chiunque fosse interessato,ai principali software di simulazione di questo tipo di sistemi presenti sul mercato. L’uso del linguaggio html rende tale guida di facile utilizzo e di rapida consultazione

INTEGRAL and Swift observations of the hard X-ray transient MAXI J1828-249

In this paper we report on the observations performed with INTEGRAL and Swift of the first outburst detected from the hard X-ray transient MAXI J1828-249. During the first about two days of the outburst, the source was observed by MAXI to undergo a very rapid transition from a hard to a softer spectral state. While the hard state was not efficiently monitored because the transition occurred so rapidly, the evolution of the source outburst in the softer state was covered quasi-simultaneously in a broad energy range (0.6-150 keV) by the instruments on-board INTEGRAL and Swift. During these observations, the spectra measured from the source displayed both a prominent thermal emission with temperature kT 0.7 keV and a power-law hard component with a photon index gamma 2.2 extending to 200 keV. The properties of the source in the X-ray domain are reminiscent of those displayed by black hole transients during the soft intermediate state, which supports the association of MAXI J1828-249 with this class of objects.Comment: 5 pages, 5 figures, 2 tables. Accepter for publication in A&

Zacharias Calliergis, la première imprimerie grecque de Rome et le rôle du banquier du pape: Les enjeux éducatifs et économiques du marché des savoirs au XVIe siècle

The invention of printing had a profound impact on access to knowledge, extended the readership, and transformed information into a consumer product. The publishing industry, already in full expansion in the early 16th century, was attracting numerous investors. Typesetter-printers and businessmen worked together to develop new commercial activities. With the establishment of the first Greek print shop in Rome, many key issues (technical, educational, economic, etc.) emerged and provide new insights into the emergence of a new economic system, new practices in acquiring knowledge, and transformations to the university model. This context allows us to revisit the role of the merchant banker in the new market for information.L'avènement de l'imprimerie change les voies d'accès à la connaissance, élargit le lectorat et fait du savoir un produit consommable. Le secteur éditorial, en plein essor durant le début du xvi e siècle, attire de nombreux investisseurs. Typographes-imprimeurs et hommes d'affaires s'associent alors dans un objectif commercial commun. La fondation de la première imprimerie grecque de Rome cristallise plusieurs enjeux (technique, éducatif, économique…) et permet d'observer la mise en place d'un nouveau système économique, de nouvelles pratiques d'acquisitions des connaissances et les transformations du milieu universitaire. Ce contexte nous invite à ce nous interroger sur le rôle du marchand-banquier dans le nouveau marché des savoirs.L'avvento della stampa cambia i percorsi di accesso alla conoscenza, allargando il lettorato e facendo dei saperi un prodotto di consumo. Il settore dell'editoria, in forte espansione nel corso del xvi secolo, attira molti investitori. Tipografi e uomini d'affari si associano in un obiettivo aziendale comune. La fondazione della prima stampa greca di Roma cristallizza molti problemi (tecnici, educativi, economici ...) e permette di osservare lo sviluppo di un nuovo sistema economico, nuove pratiche di acquisizione di conoscenza e trasformazione dell'ambiente universitario. Tale contesto ci invita ad interrogarci sul ruolo del mercante banchiere nel nuovo mercato del sapere

Missing hard states and regular outbursts: the puzzling case of the black hole candidate 4U 1630-472

4U 1630-472 is a recurrent X-ray transient classified as a black-hole candidate from its spectral and timing properties. One of the peculiarities of this source is the presence of regular outbursts with a recurrence period between 600 and 730 d that has been observed since the discovery of the source in 1969. We report on a comparative study on the spectral and timing behaviour of three consecutive outbursts occurred in 2006, 2008 and 2010. We analysed all the data collected by the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) and the Rossi X-ray timing Explorer (RXTE) during these three years of activity. We show that, in spite of having a similar spectral and timing behaviour in the energy range between 3 and 30 keV, these three outbursts show pronounced differences above 30 keV. In fact, the 2010 outburst extends at high energies without any detectable cut-off until 150-200 keV, while the two previous outbursts that occurred in 2006 and 2008 are not detected at all above 30 keV. Thus, in spite of a very similar accretion disk evolution, these three outbursts exhibit totally different characteristics of the Compton electron corona, showing a softening in their evolution rarely observed before in a low mass X-ray binary hosting a black hole. We argue the possibility that the unknown perturbation that causes the outbursts to be equally spaced in time could be at the origin of this particular behaviour. Finally we describe several possible scenarios that could explain the regularity of the outbursts, identifying the most plausible, such as a third body orbiting around the binary system.Comment: April 2015: accepted for publication in MNRAS. May 2015: in pres

A new model for the X-ray continuum of the magnetized accreting pulsars

Accreting highly magnetized pulsars in binary systems are among the brightest X-ray emitters in our Galaxy. Although a number of high statistical quality broad-band (0.1-100 keV) X-ray observations are available, the spectral energy distribution of these sources is usually investigated by adopting pure phenomenological models, rather than models linked to the physics of accretion. In this paper, a detailed spectral study of the X-ray emission recorded from the high-mass X-ray binary pulsars Cen X-3, 4U 0115+63, and Her X-1 is carried out by using BeppoSAX and joined Suzaku+NuStar data, together with an advanced version of the compmag model. The latter provides a physical description of the high energy emission from accreting pulsars, including the thermal and bulk Comptonization of cyclotron and bremsstrahlung seed photons along the neutron star accretion column. The compmag model is based on an iterative method for solving second-order partial differential equations, whose convergence algorithm has been improved and consolidated during the preparation of this paper. Our analysis shows that the broad-band X-ray continuum of all considered sources can be self-consistently described by the compmag model. The cyclotron absorption features, not included in the model, can be accounted for by using Gaussian components. From the fits of the compmag model to the data we inferred the physical properties of the accretion columns in all sources, finding values reasonably close to those theoretically expected according to our current understanding of accretion in highly magnetized neutron stars. The updated version of the compmag model has been tailored to the physical processes that are known to occur in the columns of highly magnetized accreting neutron stars and it can thus provide a better understanding of the high energy radiation from these sources.Comment: 19 pages, 10 figures, accepted for publication in A&

Raffaello e Agostino Chigi, nascita di un nuovo stile pittorico: L'influsso del mecenate sulla pittura del maestro

International audienceA Roma Raffaello è circondato da numerosi mecenati, i Papi Giulio II e Leone X, ma anche uno dei banchieri più potenti d’Europa, temibile uomo d’affari e tesoriere della Curia: Agostino Chigi. Chiaramente, Chigi non è un mecenate qualsiasi per il pittore, prima di tutto, perché non rientra nella categoria tradizionale dei mecenati, ma appartiene a una nuova tipologia sociale, quella proveniente dalla borghesia mercantile

Investigating Supergiant Fast X-ray Transients with LOFT

Supergiant Fast X-ray Transients (SFXT) are a class of High-Mass X-ray Binaries whose optical counterparts are O or B supergiant stars, and whose X-ray outbursts are ~ 4 orders of magnitude brighter than the quiescent state. LOFT, the Large Observatory For X-ray Timing, with its coded mask Wide Field Monitor (WFM) and its 10 m^2 class collimated X-ray Large Area Detector (LAD), will be able to dramatically deepen the knowledge of this class of sources. It will provide simultaneous high S/N broad-band and time-resolved spectroscopy in several intensity states, and long term monitoring that will yield new determinations of orbital periods, as well as spin periods. We show the results of an extensive set of simulations performed using previous observational results of these sources obtained with Swift and XMM-Newton. The WFM will detect all SFXT flares within its field of view down to a 15-20 mCrab in 5ks. Our simulations describe the outbursts at several intensities (F_(2-10keV)=5.9x10^-9 to 5.5x10^-10 erg cm^-2 s^-1), the intermediate and most common state (10^-11 erg cm^-2 s^-1), and the low state (1.2x10^-12 to 5x10^-13 erg cm^-2 s^-1). We also considered large variations of N_H and the presence of emission lines, as observed by Swift and XMM-Newton.Comment: Proceedings of the 5th International Symposium on High-Energy Gamma-Ray Astronomy (Gamma2012), Heidelberg. 4 pages, 3 figures, 1 tabl