1,721,070 research outputs found
Application of Tell & Go and Tell & Wait Reservation Strategies in a Optical Burst Switching Network: a Performance Comparison
No full textDesign and Analysis of an Information-Centric Protocol Architecture in Softwarized Mobile Networks
Full text linkL’Information-Centric Networking si è affermato come una delle tecnologie più promettenti dell'Internet del Futuro, in grado di abilitare la fornitura di servizi scalabili ed efficienti nelle architetture mobili. Per servire i consumatori mobili, la maggior parte dei contributi scientifici estendono le primitive di comunicazione dell’Information-Centric Networking tramite metodi basati sul pull, secondo il quale il consumatore mobile invia richieste ogni volta che raggiunge un nuovo punto di accesso alla rete. Questo approccio genera due importanti problemi. Innanzitutto, le richieste consegnate prima dell'handover genereranno percorsi obsoleti con informazioni di instradamento errate nei router di rete. Di conseguenza, alcuni nuovi contenuti verranno consegnati anche nei punti di accesso precedenti, sprecando banda ed energia. In secondo luogo, durante gli handover, i consumatori mobili potrebbero perdere alcuni contenuti rilasciati in tempo reale. Per risolvere questi problemi, questo lavoro concepisce una nuova architettura protocollare che sfrutta opportunamente le funzionalità dei paradigmi Information-Centric Networking, Multi-access Edge Computing e Software Defined Networking. L'impatto dell'architettura protocollare ideata sull'overhead di comunicazione, sulla memoria dei router e sul consumo di energia è modellato e valutato analiticamente in scenari con diverse condizioni di topologia, mobilità, natura dell’applicazione e numero di consumatori mobili. I test condotti dimostrano l'efficacia dell'architettura protocollare proposta, attraverso simulazioni al computer, in tutti gli scenari considerati.Information-Centric Networking emerged as one of the most promising technologies of the Future Internet and a powerful enabling technology for the provisioning of scalable and efficient services in mobile architectures. To serve mobile consumers, most of scientific contributions extend the information-centric communication primitives by means of a pull-based methodology, according to which the mobile consumer issues pending requests every time it reaches a new network attachment point. This approach generates two important shortcomings. First, the requests delivered before the handover will generate stale paths with wrong forwarding information in their network routers. As a consequence, some new contents will be delivered also to previous locations, thus wasting bandwidth and energy. Second, during handovers, mobile consumers may miss some contents released in real-time. In order to solve these issues, this work conceives a novel protocol architecture that properly customizes the functionalities of Information-Centric Networking, Multi-access Edge Computing, and Software Defined Networking paradigms. The impact of the devised protocol architecture on the communication overhead, router memory, and energy consumption is analytically formulated and evaluated in scenarios with different topology, mobility, application settings, and number of mobile consumers. The conducted tests demonstrate the effectiveness of the proposed protocol architecture, through computer simulations, in all the considered scenarios
Optical Burst Switching with Burst Drop(OBS/BD): An easy OBS improvement
No full textIn this paper, the Optical Burst Switching with Burst Dropping (OBS/BD) technique is proposed to be implemented in an all-optical backbone network to support IP traffic. The OBS/BD is based on two main features: i) several IP packets are assembled in a single macro-packet, called burst; ii) the burst contention in an optical switch is handled by the means of two techniques: the wavelength dimension and the "burst dropping". In the Optical Burst Switching (OBS), the entire burst is discarded when all of the output wavelengths are engaged at its arrival instant. Whereas, the OBS/BD technique discards only the initial part of the burst and forwards the final part of the burst beginning at the instant in which one wavelength becomes free. Obviously, the OBS/BD, respect to the OBS, allows to increase the switch throughput, i.e. the number of forwarded IP packets. We develop the analytical models that quantify this increase tacking into account of several system parameters
Predizione del rischio di malattie lavoro-correlate attraverso analisi di clustering e ottimizzazione genetica
Full text linkIl lavoro di questa tesi è stato condotto attraverso le tecniche di intelligenza computazionale per uno studio sulla predizione dei rischi per la salute nei posti di lavoro. Il dataset disponibile è stato popolato da parte delle Aziende Sanitarie Locali (ASL) nell’ambito di un programma per la realizzazione del Sistema Nazionale di Sorveglianza per le malattie professionali e gli infortuni mortali. Lo scopo principale di questo lavoro è la progettazione di un’applicazione software capace di evidenziare situazioni di maggior criticità per la manifestazione di Malattie Professionali che possa essere usata agevolmente da parte dei medici del lavoro come strumento di supporto nella loro attività di prevenzione e sorveglianza della salute dei lavoratori. Gli algoritmi proposti, utilizzano tecniche di clustering e l’ottimizzazione genetica per determinare in maniera automatica sia i pesi delle caratteristiche prese in considerazione nel calcolo della distanza interindividuale che il numero di cluster per la sintesi del classificatore finale. In particolare, si propone un nuovo approccio che consiste nel definire il classificatore generale come un insieme di classificatori specifici per ciascuna classe di patologia, ciascuno addestrato a riconoscere le condizioni di rischio che caratterizzano una singola patologia. I primi risultati sono incoraggianti e suggeriscono interessanti temi di ricerca per un ulteriore sviluppo del sistema.The study of this research deals with the health risk prediction problem in workplaces through computational intelligence techniques. The available dataset has been collected from the Italian Local Health Authority (ASL) as part of the Surveillance National System. The main aim of this work is the design of a software application that can be used by occupational physicians in monitoring workers, performing a risk assessment of contracting some particular occupational diseases. The proposed algorithms, based on clustering techniques, includes a genetic optimization in order to automatically determine the weights of the adopted distance measure between patterns and the number of clusters for the final classifier’s synthesis. In particular, we propose a novel approach, consisting in defining the overall classifier as an ensemble of class-specific ones, each trained to recognize patterns of risk conditions characterizing a single pathology. First results are encouraging and suggest interesting research tasks for further system development
Performance evaluation of a new technique for IP support in a WDM optical network: Optical composite burst switching (OCBS)
No full textIn this paper, the optical composite burst switching (OCBS) technique is proposed to be implemented in an all-optical backbone network to support Internet protocol (IP) traffic. The OCBS is based on two main features. First, several IP packets are assembled in a single macropacket, called burst. Second, the burst contention in an optical switch is handled by means of two techniques, the wavelength dimension and the burst-dropping (BD) technique. Different from traditional optical burst switching, where an entire burst is discarded when all of the output wavelengths are engaged at the arrival instant of the burst, a switch adopting the BD technique discards only the initial part of a burst finding all of the engaged output wavelengths while forwarding the final part of the burst, beginning at the instant in which one wavelength becomes free. The OCBS allows an increase in the switch throughput in terms of number of accepted IP packets because a burst contains a given number of IP packets. We introduce the analytical model that allows us to evaluate the effectiveness of the technique and, in particular, the obtained saving; furthermore, a sensitivity analysis of the saving, with respect to both the optical burst switch parameters and the traffic load, is carried out
Impact of segments aggregation on tcp reno flows in optical burst switching networks
No full textAbstract-- In this paper we study the Optical Burst Switching (OBS) paradigm for the support of the TCP flows in an All Optical Network (AON). We analyze the TCP send rate, i.e. the amount of data sent per time unit, taking into account of: i) the burst assembly mechanism, called burstification process; ii) the burst loss events inside the OBS network. The goals of the paper are to investigate the effect of the variation of the burstification period and to derive some general guidelines about the dimensioning of the burstification period. With respect to the case in which any assembly mechanism is missing, the results show that an accurate dimensioning of the burstification period yields negligible penalties with regard to the low speed sources and significant benefits with regard to the high speed sources. Index terms—burst switching, optical network, performance modeling, TCP/IP. A
Going 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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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