1,720,977 research outputs found
Information Fusion e sorveglianza
No full textUno degli ambiti maggiormente interessati dall???aumento del rapporto tra numero di elaboratori e numero di utenti è quello dei sistemi di monitoraggio distribuito per applicazioni di supervisione, diagnostica e sorveglianza. In tali sistemi, infatti, pochi operatori sono chiamati a
controllare un elevato numero di sensori e sottosistemi, spesso distribuiti ed eterogenei. In questo articolo verranno illustrate tecniche automatiche di integrazione ed interpretazione dei dati per consentire di gestire una mole potenzialmente elevata di informazioni ed adottare decisioni efficaci in tempi rapidi
A robust approach for on-line and off-line threat detection based on event tree similarity analysis
No full textThe security of railway and mass-transit systems is increasingly dependant on the effectiveness of integrated Security Management Systems (SMS), which are meant to detect threats and to provide operators with information required for alarm verification purposes. In order to lower the false alarm rate and improve the detection reliability of threat scenarios, event correlation capabilities need to be integrated into the SMS. In this paper an existing approach based on a-priori defined event patterns is extended using a heuristic situation recognition approach which is more robust to both imperfect scenario modeling (human faults) and missed detections (sensor faults). The approach is based on similarity analysis between the event trees representing scenarios and it is effective both on-line and off-line. Applied on-line, it allows for an earlier and more fault-tolerant threat detection, since scenario matching is not required to be complete nor exact. Applied off-line, its effectiveness is twofold: first, it allows for detecting redundancies when updating the scenario repository; secondly, it enhances the post-event forensic search of suspicious behaviors not previously stored in the scenario repository. The strategy is being experimented in the context of railway protection
Improving the dependability of distributed surveillance systems using diverse redundant detectors
No full textSensor networks nowadays employed in critical monitoring and surveillance applications represent a relevant case of complex information infrastructures whose dependability needs to be carefully assessed. Detection models based on Event Trees provide a simple and effective mean to correlate events in Physical Security Information Management (PSIM) systems. However, as a deterministic modeling approach, Event Trees are not able to address uncertainties in practical applications, like: 1) imperfect threat modelling; 2) sensor false alarms. Regarding point (1), it is quite obvious that real-world threat scenarios can be very variable and it is nearly impossible to consider all the possible combinations of events characterizing a threat. Point (2) addresses the possibility of missed detections due to sensor faults and the positive/nuisance false alarms that any real sensor can generate. In this chapter we describe two techniques that can be adopted to deal with those uncertainties. The first technique is based on Event Tree heuristic distance metrics. It allows to generate warnings whenever a threat scenario is detected and it is similar to the ones in the knowledge base repository. The second technique allows to measure in real-time the estimated trustworthiness of event detection based on: a) sensors false alarm rates; b) uncertainties indices associated to correlation operators. We apply those techniques to case-studies of physical security for metro railways. © Springer International Publishing Switzerland 201
Towards Wireless Sensor Networks for Railway Infrastructure Monitoring
No full textIn recent years, there has been an increasing interest in the adoption of emerging sensing technologies for instrumentation within a variety of structural systems. Structural health monitoring systems are widely adopted to monitor the behavior of structures during forced vibration testing or natural excitation (e.g. earthquakes, winds, live loading). They can be found in a number of civil structures, including bridges and viaducts, and also in applications of vehicle health monitoring. Moreover, since infrastructures can be damaged by human originated threats, the adoption of security measures is also essential. This paper presents a proposal of an early warning system based on Wireless Sensor Networks (WSN) for railway infrastructure monitoring. It exploits already available research results and tools for WSN management, integration and data fusion. The aim is to hedge detection capabilities in a complete framework for structural failures as well as security threats, including both natural hazards and intentional attacks
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
Influence of Rotation Speed of Mtwo Files on Root Canal Instrumentation Time with Different Canal Curvatures
Full text linkIntroduction: The aim of this study was to analyze the effect of rotation speed on the instrumentation time of root canals with different curvatures using Mtwo NiTi rotary instruments. Methods and Materials: Forty root canals were selected and divided into 2 groups, according to the angle of curvature (group A>30°, group B<30°). Both groups were divided into 2 subgroups (n=10), according to the rotational speed used for root canal instrumentation (150 rpm: group A1 and B1; 250 rpm: group A2 and B2). The total instrumentation time and the total number of instrumentation cycles (NCI) required to complete root canal preparation were registered for each canal. The mean and standard deviation were then calculated. Data were then statistically analyzed using two-way ANOVA and interaction effect P-values (P<0.05). Results: During root canal instrumentation, there were no file fractures. Total instrumentation time of the low speed groups A1 (150 rpm) and B1 (150 rpm) were significantly higher (P<0.05) than that of the high speed groups, A2 (250 rpm) and B2 (250 rpm); however, there was no statistically significant difference in terms of NCI between the different groups (P>0.05). Statistical difference was not found between the different angles of curvature, group A1 vs B1 and A2 vs B2 in terms of total instrumentation time (P>0.05) and NCI (P>0.05). Conclusions: This ex-vivo study showed that canal preparation with Mtwo rotary files could be completed safely with an increase of the instrumentation time at low rotational speed independently of the root canal curvature
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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