1,721,594 research outputs found
A strong zero-one law for connectivity in one-dimensional geometric random graphs with non-vanishing densities
Get PDFWe consider the geometric random graph where n points are distributed independently on the unit interval [0,1] according to some probability distribution function F. Two nodes communicate with each other if their distance is less than some transmission range. When F admits a continuous density f which is strictly positive on [0,1], we show that the property of graph connectivity exhibits a strong critical threshold and we identify it. This is achieved by generalizing a limit result on maximal spacings due to Levy for the uniform distribution
On the critical communication range under node placement with vanishing densities
Get PDFWe consider the random network where n points are placed independently on the unit interval [0, 1] according to some probability distribution function F. Two nodes communicate with each other if their distance is less than some transmission range. When F admits a continuous density f with f = inf (f(x), x [0, 1]) > 0, it is known that the property of graph connectivity for the underlying random graph admits a strong critical threshold. Through a counterexample, we show that only a weak critical threshold exists when f = 0 and we identify it. Implications for the critical transmission range are discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Connectivity in one-dimensional geometric random graphs: Poisson approximations, zero-one laws and phase transitions
Get PDFConsider n points (or nodes) distributed uniformly and independently on the unit interval [0,1]. Two nodes are said to be adjacent if their distance is less than some given threshold value.For the underlying random graph we derive zero-one laws for the property of graph connectivity and give the asymptotics of the transition widths for the associated phase transition. These results all flow from a single convergence statement
for the probability of graph connectivity under a particular class of scalings. Given the importance of this result, we give two separate proofs; one approach relies on results concerning maximal spacings, while the other one exploits a Poisson convergence result for the number of breakpoint users.This work was prepared through collaborative participation in the Communications and Networks Consortium sponsored by the U. S. Army Research Laboratory under the Collaborative Technology Alliance Program,
Cooperative Agreement DAAD19-01-2-0011
Consistency analysis and evaluation of TTL-based Internet caches
Get PDFConsistency algorithms have been proposed for a wide range of applications that include distributed shared memories (DSM), distributed file systems, and databases. Fundamental definitions and operational constraints that are specific for each system do not necessarily translate well to Internet caches. A Web object is consistent if it is identical to the master document at the origin server, at the time it is served to users, therefore cached objects become stale immediately after the master is modified. Stale cache copies remain served to users until the cache is refreshed, subject to the network transmit delays. However, the performance of Internet consistency algorithms is evaluated through the corresponding cache hit rate and network traffic load that do not inform on the service of stale data, and are therefore inadequate, as outlined in numerous studies. To date, neither an analytical framework nor a suitable measure are available to model the service of stale data to users. In this paper we seek to remedy this state of affairs by formalizing both a framework and the novel hit* rate consistency measure, which captures non-stale downloads from the cache. To demonstrate this new methodology, we analyze and evaluate the consistency performance of a well studied TTL algorithm, under both zero and non-zero download latency. We conclude that data consistency can be significantly degraded even when a high hit rate is achieved, by calculating the incurred hit and hit* rates. The proposed procedure can be used to evaluate additional TTL and other (e.g., polling and invalidation) Web consistency protocols, as well as those retained by other applications (e.g., virtual shared memories)
Variations on the Author
Get PDF“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
Get PDFWe 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
Very sharp transitions in one-dimensional MANETs
Get PDFWe investigate how quickly phase transitions can occur in one-dimensional geometric random graph models of MANETs. In the case of graph connectivity, we show that the transition width behaves like 1/n (when the number n of users is large), a significant improvement over general asymptotic bounds given recently by Goel et al. for monotone graph properties. We also discuss a similar result for the property that there exists no isolated user in the network. The asymptotic results are validated by numerical computations. Finally we outline how the approach sed here could be applied in higher dimensions and or other graph properties
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