1,721,047 research outputs found
All optical 2R regeneration systems for broadband agile dense wavelength division multiplexing transparent optical networks
Full text linkRecentemente è stata notata una crescita dei servizi multimediali richiesti dagli utenti finali; in tal modo numerose soluzioni sono state implementate per garantire elevati bit rate e qualità del servizio necessari per questo tipo di applicazioni. Le reti completamente ottiche sono state stese in molte nazioni (Giappone, Corea, Cina) per fornire servizi a banda larga fino a casa dell'utente.
Conseguentemente, sono richiesti dispositivi in grado di operare nel dominio ottico in modo tale da evitare il noto “collo di bottiglia” derivante dalle conversioni di formato O/E/O (ottico/elettrico/ottico). In questo modo, nuovi tipi di sistemi (per esempio: optical processing e passive optical network) in grado di operare nel dominio completamente ottico sono richiesti poiché solo questo tipo di soluzione è la miglior strada per offrire alte prestazioni in termini di servizi, rate e riduzione dei costi per bit.
Il lavoro eseguito durante questo dottorato di ricerca è stato incentrato sull'evoluzione di dispositivi per la rigenerazione ottica in grado di operare al contempo una Ri-amplificazione e Ri-sagomatura (2R) dei segnali ottici. Studi ed esperimenti sono stati effettuati nei laboratori dell’ ISCOM sfruttando la possibilità di rigenerazione completamente ottica di un dispositivo 2R multi-canale in grado di lavorare e gestire più clients nel medesimo istante temporale. Il sistema è stato implementato in uno scenario DWDM (Dense Wavelegth Division Multiplexing); inoltre, lavorando nel dominio completamente ottico sono state eliminate le conversioni di formato (O/E/O).
Il sistema di rigenerazione è basato sulla modulazione di fase presente all'interno della fibra ottica usata per ottenere, sotto particolari condizioni, la generazione di nuove repliche del segnale originario che si vuole rigenerare. Queste nuove repliche, essendo posizionate a nuove lunghezze d’onda, possono essere usate sia per ottenere una conversione di lunghezza d’onda sia per ottenere una rigenerazione ottica dei segnali. Ciascuna replica, infatti, è caratterizzata dall’ avere un andamento simile alle funzioni di Bessel in grado di eliminare il rumore accumulatosi durante la trasmissione dei segnali.
L’idea di questo lavoro è basato su un approccio multi-lunghezza d’onda in modo tale da poter usare un solo dispositivo per fornire una rigenerazione 2R completamente ottica ai numerosi utenti operanti a 10 Gbps.
La capacità dei sistemi, implementati nei laboratori ISCOM, di risagomare i segnali, è stata confermata sperimentalmente in termini di misurazioni di diagramma ad occhio dei segnali di uscita e dalle curve di BER (Bit Error Rate).A recent increase of multimedia service demand from end-users has been noticed, thus several solutions have been implemented to guarantee the high rate and relative QoS (Quality of Service) needed for these kind of services. All optical networks have been deployed in many countries (Japan, Korea, China, at all) in order to supply broadband services to the home.
Consequently, devices able to operate in optical domain are requested in order to avoid the so called “bottle-neck” coming from the O/E/O data conversion format. Thus, new kind of systems (optical processing and passive optical networks, at all) able to operate in photonic domain are requested because only this kind of solution is the better way to offer high performances in term of services, rate and low cost per bit.
The work performed during this PhD program has been focused on the evolution of regeneration devices able to perform Re-amp and Re-shaping also know as 2R. Studies and experiments have been carried out at the ISCOM labs exploiting the possibility to a multi-channel 2R all optical regeneration device which is able to work with different client signals at the same time. The system has been implemented in a dense WDM (Wavelength Division Multiplexing) scenario. Moreover, working completely in optical domain, the format conversion (O/E/O) is avoided. The regeneration system is based on phase modulation present in the fiber and used to obtain, under particular conditions, the generation of new signal replica.
These new replica, being placed at new different wavelengths can be used both to reach a wavelength conversion and to obtain an all optical regeneration effect. Each replica, in fact, is characterized by a Bessel like transfer function able to clean the noise accumulated along the signal transmission.
The idea of this work is based on a multi-wavelength approach, thus only one device can be used to provide all optical 2R regeneration to several client signals at 10 Gbps at the same time.
The ability of the systems, implemented at the ISCOM labs, to reshape the signals, has been experimentally confirmed in terms of eyes diagrams and BER (Bit Error Rate) measurements
Overhead crane subjected to impulse loading
Full text linkOverhead cranes are machines designed to lift and transport heavy equipment and materials. For this reason, their design is regulated by rigorous standards (for example, the series EN13000 in Europe). However, the standards do not take into account the effect of cyclic loading due to, for example, rapid successions of short commands to place heavy machines and structures in a required position. Therefore, the aim of this research is to study the structural effect of rapid successions of command impulses. The preliminary results show that the displacement of the structure over time increases when the command impulses have a frequency equal or close to the natural frequency of the structure
Handcycling Assessment Through a Bench Simulator: Preliminary Analysis of IMUs Positioning on an Artificial Upper Limb Mechanism (AULM)
No full textUn piano per Firenze. Conversazione con Gianfranco Di Pietro, Pietro Giorgieri e Angelo Sampieri
No full text
Assessing the effects of microbial diversity on litter decomposition dynamics using synthetic microbial communities
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dynamic Analysis of a Quay Crane Using Lumped Parameter Models
No full textThe objective of this research activity is to evaluate the extent to which models with lumped parameters might be appropriate for the development of lifting devices. The models we used have only one or two degrees of freedom, but the parameters of the crane were derived by a FEM analysis of its structure, while the viscoelastic parameters of the ropes took into account their time-varying behavior. The results showed that it is useful to consider the length of the ropes in order to calculate more accurately the dynamics of the crane, since the stiffness and the damping change during the load movement. According to the results, higher stress values were also obtained using the model with one degree of freedom for the ropes. This implies that the model can be useful for rope selection as it ensures a conservative estimate of their coefficient of safety. In the case of the two-degree-of-freedom model, the same is true for the structure
Why intraspecific positive interactions are so rare? A comparison between terrestrial and aquatic environments
No full text- …
