1,720,956 research outputs found
Tecniche di virtualizzazione per lo studio di reti di emergenza
No full textLe reti di supporto agli operatori d’emergenza sono tradizionalmente basate su infrastrutture Professional Mobile Radio con capacità trasmissive alquanto limitate. Le agenzie di protezione civile palesano invece la necessità di accrescere l'efficacia e l’affidabilità delle operazioni tramite una migliore qualità delle
comunicazioni. Per questa ragione, sembra probabile che le future reti per l’emergenza possano utilizzare tecnologie eterogenee a banda larga (con modalità trasmissive diverse per le reti sensoriali, d’accesso,
metropolitane e geografiche) per collegare tra loro i soccorritori, i Centri tattici mobili e i Centri remoti di coordinamento.
Allargando lo spettro d’interesse, si può affermare che, in generale, la progettazione di un qualsivoglia sistema di telecomunicazione eterogeneo porge sempre svariate sfide. Un primo problema è capire fin
dall’inizio se l'architettura composita che si sta progettando sia idonea a offrire le prestazioni attese. In particolare, sarebbe utile disporre di uno strumento di progettazione flessibile, che consenta di
confrontare rapidamente le prestazioni di sistemi differenti al fine di selezionare subito la soluzione ottimale. A tal fine, sono disponibili svariate metodologie, dai modelli matematici puri fino all’uso di dispositivi reali. In teoria, lo strumento perfetto dovrebbe riassumere il meglio di tutti i possibili approcci: essere flessibile e conveniente come un simulatore software, modulare come un emulatore hardware, e realistico come solo i dispositivi fisici possono essere.
Per questi motivi, l’emulazione software delle reti è una tecnica di recente interesse per la comunità scientifica. L'idea di fondo è quella di puntare su di un approccio “ibrido”, in cui gli emulatori software possono essere interposti a dispositivi reali, allo scopo di accrescere il realismo delle valutazioni. Chiaramente, gli emulatori sono rapidi da configurare ed economici quanto i simulatori puri; al tempo stesso, la loro precisione è indiscutibilmente legata ai modelli simulativi in essi integrati. Diversamente da un simulatore, un emulatore però non può essere eseguito in unità di tempo virtuali, se vuole poter dialogare con sistemi reali, e occorre dotarlo di risorse computazionali certe, che gli consentano di osservare dei vincoli temporali rigorosi durante l'elaborazione dei dati in ingresso. In tal senso, l'esecuzione di una rete complessa ed eterogenea all'interno di un singolo emulatore richiederebbe una quantità enorme di risorse di calcolo. Una soluzione banale potrebbe essere quella di frazionare
l'infrastruttura in più parti ed eseguirne l’emulazione in parallelo su più calcolatori. Tuttavia, oggigiorno, le tecniche di virtualizzazione sono divenute molto efficienti e permettono di ospitare diverse entità software autonome su un unico hardware; inoltre, i sistemi di calcolo multi-processore sono ormai disponibili a costi ridotti.
Per queste ragioni, il presente lavoro è dedicato agli studi svolti per l’implementazione di un testbed modulare, NetBoxIT, basato su tecniche di virtualizzazione e di simulazione software in ambiente multi-core, in grado di emulare reti complesse su un’unica piattaforma. Utilizzando i container Linux e il simulatore di rete NS-3, è possibile creare, concatenare ed eseguire in parallelo un insieme di reti virtuali distinte che rappresentano i diversi segmenti di una rete eterogenea reale. NetBoxIT supporta la gestione del traffico in ingresso con distorsioni temporali quasi sempre trascurabili, e può essere collegato tramite interfacce standard con nodi esterni in modo semplice e trasparente. Il risultato che offriamo è costituito da un’estesa analisi delle prestazioni del testbed durante l’emulazione di vari generi di reti, con particolare riferimento alla rete d’emergenza identificata per il progetto europeo “A holistic approach towards the development of the first responder of the future”.Communications for crisis support are today based on rate-limited Professional Mobile Radio infrastructures. However, protection agencies show a rising need for a broadband approach, to increase the reliability and the quality of communications, and the effectiveness of operations. Multipart Emergency Networks, where different technologies are used at the Personal, Incident, Jurisdictional and Extended Area Networks might be employed to support first responders (FRs), mobile Emergency Operation Centers (MEOCs) and the remote Emergency Operation Center (EOC). However, the design of a heterogeneous, multi-technological telecommunication system offers several challenges.
A significant target is to understand since the beginning if a network architecture matches the expected performance. In particular, it would be helpful to have a design tool with smart configuration capabilities, for examining the performance of alternative architectures, to choose the optimal infrastructure. A broad variety of methods can be adopted, ranging from pure mathematical models to real-world testbeds. If it were possible, the perfect tool should summarize the best of all the possible practices, that is, be as flexible and cost- effective as a software simulator; modular as a hardware emulator; and, realistic as a physical testbed.
For these reasons, software network emulation has recently gained a lot of interest in the research community. The key idea behind it is to follow a hybrid approach: a software simulator is mixed with real components and applications, to increase the fidelity of results and to perform the validation of an infrastructure against real traffic. Similarly to pure simulators, software emulators are fast to configure and low-cost, and their realism depends on the network modeling accuracy. However, an emulator cannot run in a virtual simulated time, like simulators do, to coexist with real network entities, and it needs enough computing resources to respect real-time constraints when processing incoming data. If true applications exchange traffic through an emulated topology, the emulator should not introduce any extrinsic delay.
Certainly, the plain execution of several types of networks within a single, real-time emulator requires a huge amount of computing resources. Therefore, the investigation of a heterogeneous infrastructure could be performed by the execution of many emulators in parallel (one for each part of the overall network). This task can be accomplished by running the different emulators onto several PCs. However, today, virtualization techniques have become very efficient and allow different applications to be hosted onto a single hardware, as well as multi-core CPUs are widely available, even within the cheapest netbooks.
Therefore, in this work, we investigated the architecture and the implementation issues of a modular and scalable testbed (NetBoxIT) which aims at taking advantage of these available techniques (software emulation, virtualization, and multi-CPU platforms) to simulate complex networks, possibly organized with different topologies and technologies. NetBoxIT supports the creation, and interconnection of several, coexisting virtual networks (“netboxes”) onto a single, multi-core platform. In summary, using LXC containers and the NS-3 simulator, a number of distinct netboxes can run concurrently and mimic the separate portions of a heterogeneous network. NetBoxIT supports real-time data handling, with negligible timing overheads against the represented true network in many cases, and can be interfaced with external real nodes. We examined the testbed performance with several emulation trials, most of which are related to the reference Emergency Network under study within the EU 7th FP project “A holistic approach towards the development of the first responder of the future”, to verify its realism in assessing multipart networks evaluations
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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