1,721,020 research outputs found
Area Throughput and Energy Efficiency for Clustered Wireless Sensor Networks Deployed in Bounded Regions
No full textIn this paper we present a mathematical approach to evaluate the area throughput and the energy consumption of a multi-sink Wireless Sensor Network (WSN). The WSN is organised into clusters, with one sink per cluster collecting data from sensors. A small variation of the Thomas point process is used to model sensors and sinks positions in the
target area. We denote as area throughput the amount of data per unit of time successfully transmitted to the
sinks. Both area throughput and energy consumption are strictly related to connectivity and MAC issues. The
aim of this work is to devise a mathematical model that takes MAC and connectivity issues into account, under a common
framework. We also explicitly include border effects induced by deployment into a finite region into our framework.
We study the behavior of these two performance metrics when varying the target rate, defined as the
maximum data rate the network was deployed to deliver. Results show that a tradeoff between the area
throughput and the energy consumption must be found, when considering two different scenarios, namely, a field and a
building
Multimedia Video-Based Surveillance Systems: from User Requirements to Research Solutions
No full textOpportunistic Networking for Sensor Data Collection in Urban Environment
No full textIn this paper we present the preliminary results from a work dealing with opportunistic networking in urban context. In particular we consider a set of sensors deployed in a city center, aimed at sampling e.g. environmental parameters. Such sensors then opportunistically exploit the urban vehicular mobility to transfer their measurements to one of data fusion centers, located at chosen points in the city. Both the sensor nodes and the vehicles are equipped with radio transceivers having a fixed transmission range and data storage capability (which is assumed to be limited). Here we present simulations based study conducted in the particular case of the city of Seattle, WA, since we had access to the actual mobility traces of the city bus fleet, collected by [1]. Some of the performance metrics that can be evaluated in our simulator environment are the delivery rate of packets originated from each sensor node,
the statistics of the transport delay and the fraction of packet drops due to limited storage buffer capability. We also highlight the role played by the number of sensors and fusion centers, and the effect of transmitting power. Possible extensions of this preliminary work include comparison to the results obtained when using (theoretical and measured) mobility traces
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
Area throughput and energy consumption for clustered wireless sensor networks
No full textIn this paper we present a mathematical approach to evaluate the area throughput and the energy consumption of a multi-sink Wireless Sensor Network (WSN). The WSN is organised into clusters, with one sink per cluster collecting data from sensors. A small variation of the Thomas point process is used to model sensors and sinks positions in the target area. We denote as area throughput the amount of samples per second successfully transmitted to the sinks. Both area throughput and energy consumption are strictly related to connectivity and MAC issues. The aim of this work is to devise a mathematical model that takes MAC and connectivity issues into account, under a common framework. We study the behavior of these two performance metrics when varying the target rate, defined as the maximum number of samples the network was deployed to deliver. Results show that a tradeoff between the area throughput and the energy consumption must be found. Finally, the impact of different sensors and sinks distributions on the area throughput is evaluated
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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