1,720,963 research outputs found
LoRaWAN Transmissions in Salt Water for Superficial Marine Sensor Networking: Laboratory and Field Tests
Full text linkIn this paper, the authors present the results of a set of measurements carried out to analyze the transmission capabilities of the LoRaWAN technology for underwater to above water transmission in saline water. A theoretical analysis was used to model the link budget of the radio channel in the considered operative conditions and to estimate the electrical permittivity of salt water. Preliminary measurements were performed in the laboratory at different salinity levels to confirm the application boundaries of the technology, then field tests were conducted in the Venice lagoon. While these test are not focused on demonstrating the usability of LoRaWAN to collect data underwater, the achieved results demonstrate that LoRaWAN transmitters can be used in all those conditions when they are expected to be partially or totally submerged below a thin layer of marine water, in accordance with the prediction of the proposed theoretical model. This achievement paves the way for the deployment of superficial marine sensor networks in the Internet of Underwater Things (IoUT) context, as for the monitoring of bridges, harbor structures, water parameters and water sport athletes and for the realization of high-water or fill-level alarm systems
A Collaborative Reputation Mechanism for Underwater Acoustic Networks
No full textDistributed trust mechanisms can be used to protect Underwater Acoustic Networks (UANs) against a variety of Denial of Service (DoS) attacks. Several UAN trust systems have been proposed in the recent years, but only a few of them exploit Trust-Related Data (TRD) dissemination to improve the knowledge that a node has about its neighbors. Without TRD sharing, nodes can only form an opinion about their 1-hop neighbors, which might also be inaccurate due to packet losses being mistaken for actual malicious behavior. This paper presents a collaborative reputation algorithm for UANs that performs reputation sharing, propagation and aggregation allowing distant nodes in the network to form an opinion about each other and increasing the overall reliability of the trust metric. The proposed security mechanism is then implemented and tested as a DESERT Underwater module to verify its quality. Results show that trust values resulting from the aggregation of second-hand opinions are more reliable than the first-hand evaluations obtained through direct experience, effectively extending the knowledge that each node has about the trustworthiness of the others
Field Tests of the Software Defined Modem Prototype for the MODA Project
No full textUnderwater acoustic communications has developed to such a stage that new applications and functionalities emerged in various fields of the human activities, from military missions to commercial operations. A new field of application is the use of underwater vehicles in swarms, operating in a coordinated fashion to perform tasks that would be harder, or dangerous, for humans or single vehicles. Swarms of underwater drones require the use of very flexible and high-performance wireless modems: in the context of a national funded project we developed a Software Defined Modem (SDM) to be employed in lightweight underwater vehicles. This work presents the tests of the communications capability of the modem in a very shallow environment. The tests proved the validity of the modem design, still at the prototype stage, and shed light on the areas that are worth investigating to further improve its performance. Additionally, we demonstrate that it is possible to build an SDM, capable of real-time communications, using only off-the-shelf and easily accessible hardware and software tools
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
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