1,721,016 research outputs found
Optimizing the finger table in Chord-like DHTs
No full textThe Chord protocol is the best known example of implementation of logarithmic complexity routing for
structured peer-to-peer networks. Its routing algorithm, however, does not provide an optimal trade-off
between resources exploited (the size of the ‘finger table’) and performance (the average or worst-case
number of hops to reach destination). Cordasco et al. showed that a finger table based on Fibonacci
distances provides lower number of hops with fewer table entries. In this paper we generalize this result,
showing how to construct an improved finger table when the objective is to reduce the number of hops,
possibly at the expense of an increased size of the finger table. Our results can also be exploited to
guarantee low routing time in case a fraction of nodes fails
Non-uniform deterministic routing on F-Chord(α)
No full textIn this paper, we present a family of novel P2P routing schemes based on Chord (and its variation F-Chord(α) that trades off uniformity with efficiency without using any additional overhead. We prove that H-F-Chord(α)'s routing is more efficient than in F-Chord(α) in terms of its average path length that is O(log n/ log log n). We also show, by simulations, that H-F-Chord(α) is more efficient than the corresponding F-Chord(α) by a percentage that goes from 15% to 22% even for small n
Navigable Small-World Networks with Few Random Bits
No full textWestudy Small-World graphs in the perspective of their use in the development of efficient
as well as easy to implement network infrastructures. Our analysis starts from the Small-
World model proposed by Kleinberg: a grid network augmented with directed long-range
random links. The choices of the long-range links are independent from one node to
another. In this setting greedy routing and some of its variants have been analyzed and
shown to produce paths of polylogarithmic expected length. We start from asking whether
all the randomness, used in Kleinberg's model for establishing the long-range contacts of
the nodes, is indeed necessary to assure the existence of short paths. In order to deal with
the above question, we impose (stringent) restrictions on the choice of long-range links and
we show that such restrictions do not increase the average path length of greedy routing
and its variations.
We are able to decrease the number of random bits, required to establish each node's
long-range link to O(log log n) on a network of size n. Diminishing the
randomness in the choice of random links has several benefits; in particular, it implies an
increase in the clustering of the graph, thus increasing the resilience of the network
A proportional correlation index for space analysis in mixed dentition derived from an italian population sample
No full textAim. The aim of this study was to establish a specific
proportional correlation method for space analysis in
mixed dentition applicable to the Italian population.
Material and Methods. A retrospective analysis
was performed on 300 plaster models taken from
Italian subjects, 156 females and 144 males, aged between
12 and 25 years.
Results. The variance analysis (ANOVA) showed a high
correlation between the dimension of the mesio-distal
diameters of the four mandibular incisor and those of the
upper canine and premolars. The correlation coefficient
showed the existence of a directly proportional, positive
intra-dependence between the two groups.
Discussion. The correlation tables used in the present
study appear to be much more accurate if applied to
groups of patients with similar ethnic backgrounds, thus
explaining the differences between the various prediction
indexes found in previous publications.
Conclusion. This study highlights the need to develop
specific values to fit the features of the different ethnic
group
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
Overlay networks with class
No full textWe define a family of distributed hash table systems whose aim is to combine routing efficiency of the randomized networks - i.e. average path length O(log n/log log n) vs. the O(log n) average path length of the deterministic system - with the programmability and startup efficiency of a uniform system - that is a system in which the overlay network is transitive, and greedy routing is optimal. It is known that Ω(logn) is a lower bound to the average path length for uniform systems with O(log n) degree. The proposed family is parameterized with a positive integer c which measures the amount of randomness that is used. Indeed, edges are partitioned into c equivalence classes. Varying the value c, the system goes from the deterministic case (c=1) to an "almost uniform" system. Increasing c to relatively low values allows routing with optimal average path length while retaining most of the advantages of a uniform system, such as easy programmability and quick bootstrap of the nodes entering the system. We also provide a matching lower bound for the average path length of the family of routing schemes for any c. Moreover, we show how to extend the result to other overlay networks
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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