1,721,039 research outputs found
Algoritmi e Strutture di Dati
No full textL'algoritmica e' quella branca dell'informatica che riguarda la definizione e la progettazione degli algoritmi, l'analisi della loro correttezza ed efficienza, la dimostrazione delle loro inerenti limitazioni e complessita', e lo studio delle strutture di dati da essi elaborati. Il presente testo e' suddiviso in quattro parti, che corrispondono alle suddette quattro aree principali dell'algoritmica, ed e' rivolto agli studenti dei corsi di Algoritmi e Strutture di Dati dei Corsi di Laurea in Informatica. Sono presentate le principali strutture di dati (liste, pile, code, alberi, insiemi, dizionari, code con priorita', grafi). Sono descritte le tecniche basilari di progettazione (divide et impera, backtrack, greedy, programmazione dinamica, ricerca locale, randomizzazione) e i metodi per la valutazione dell'efficienza di algoritmi (risoluzione di relazioni di ricorrenza, metodo del potenziale per l'analisi ammortizzata). Sono inoltre considerate tecniche per dimostrare l'inerente intrattabilita' di problemi (riduzioni polinomiali) e per affrontare problemi intrattabili (approssimazione, branch-&-bound, euristiche)
T-Man: Gossip-based Fast Overlay Topology Construction
No full textLarge-scale overlay networks have become crucial ingredients of fully-decentralized appli- cations and peer-to-peer systems. Depending on the task at hand, overlay networks are organized into different topologies, such as rings, trees, semantic and geographic proximity networks. We argue that the central role overlay networks play in decentralized applica- tion development requires a more systematic study and effort towards understanding the possibilities and limits of overlay network construction in its generality. Our contribu- tion in this paper is a gossip protocol called T-MAN that can build a wide range of overlay networks from scratch, relying only on minimal assumptions. The protocol is fast, robust, and very simple. It is also highly configurable as the desired topology itself is a parameter in the form of a ranking method that orders nodes according to preference for a base node to select them as neighbors. The paper presents extensive empirical analysis of the protocol along with theoretical analysis of certain aspects of its behavior. We also describe a prac- tical application of T-MAN for building CHORD distributed hash table overlays efficiently from scratch
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
Jgroup/ARM: a distributed object group platform with autonomous replication management
No full textThis paper presents the design and implementation of Jgroup/ARM, a distributed object group platform
with autonomous replication management along with a novel measurement-based assessment technique
that is used to validate the fault-handling capability of Jgroup/ARM. Jgroup extends Java RMI through the
group communication paradigm and has been designed specifically for application support in partitionable
systems. ARM aims at improving the dependability characteristics of systems through a fault-treatment
mechanism. Hence, ARM focuses on deployment and operational aspects, where the gain in terms of
improved dependability is likely to be the greatest. The main objective of ARM is to localize failures
and to reconfigure the system according to application-specific dependability requirements. Combining
Jgroup and ARM can significantly reduce the effort necessary for developing, deploying and managing
dependable, partition-aware applications. Jgroup/ARM is evaluated experimentally to validate its fault-handling capability; the recovery performance of a system deployed in a wide area network is evaluated. In
this experiment multiple nearly coincident reachability changes are injected to emulate network partition
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
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