1,721,048 research outputs found
A Reputation-based Approach to Tolerate Misbehaving Carriers in Delay Tolerant Networks
No full textDelay Tolerant Network (DTN) is a network paradigm used to deliver messages when network connectivity is not guaranteed. In a DTN, communication is made possible by carriers, mobile nodes that physically carry messages from a network partition to another. Selecting carriers that provide the best delivery probability is a crucial issue. However, if carriers misbehave, the integrity and availability of a DTN is endangered. In this paper we present a decentralised reputation-based system aimed at tolerating misbehaving carriers. A prototype of the system has been integrated into Context Aware Routing (CAR) [1]. Simulations show that the resulting system RCAR provides a greater delivery probability than CAR and Epidemic Routing [2] without increasing the average delivery delay
A Cryptographic Suite for Underwater Cooperative Applications
No full textAn underwater acoustic scenario raises many problems in terms of security because of the limited bandwidth provided by the underwater medium. In this paper we face with the problem of secure cooperation among underwater acoustic vehicles. We propose a cryptographic suite able to reduce at the minimum the message overhead added by security. The cryptographic suite provides vehicles authentication, confidentiality and integrity of messages and key management. A prototype has been implemented and preliminary performance evaluation tests are shown
Towards a Reputation-based Routing Protocol to Contrast Blackholes in a Delay Tolerant Network
No full textA Delay Tolerant Network (DTN) relies on the implicit assumption that nodes cooperate towards message forwarding. However, this assumption cannot be satisfied when there are malicious nodes acting as blackholes and voluntarily attracting and dropping messages.
In this paper we propose a reputation-based protocol for contrasting blackholes. Every node locally maintains the reputation of forwarding nodes it comes in touch with and, then, upon selecting the next forwarding node, the node chooses among those having the highest reputation. The proposed reputation protocol is composed of three basic mechanisms—acknowledgments, node lists, and aging—that make communication efficient and capable of adapting to the changing operating conditions of a DTN.
The protocol has been used to extend CAR [1]. The resulting protocol RCAR (reputation-based CAR) has been compared with T-ProPHET [2], a state-of-the-art reputation-based DTN routing protocol, from several standpoints. As it turns out, RCAR is more effective than T-ProPHET and outperforms it in most cases
Exact controllability to eigensolutions of the bilinear heat equation on compact networks
No full textPartial differential equations on networks have been widely investigated in the last decades in view of their application to quantum mechanics (Schrodinger type equations) or to the analysis of flexible structures (wave type equations). Nevertheless, very few results are available for diffusive models despite an increasing demand arising from life sciences such as neurobiology. This paper analyzes the controllability properties of the heat equation on a compact network under the action of a single input bilinear control. By adapting a recent method due to [F. Alabau-Boussouira, P. Cannarsa, C. Urbani, Exact controllability to eigensolutions for evolution equations of parabolic type via bilinear control, arXiv:1811.08806], an exact controllability result to the eigensolutions of the uncontrolled problem is obtained in this work. A crucial step has been the construction of a suitable biorthogonal family under a non-uniform gap condition of the eigenvalues of the Laplacian on a graph. Application to star graphs and tadpole graphs are included
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
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