1,720,966 research outputs found
Clamp-and-Forget: A self-sustainable non-invasive wireless sensor node for smart metering applications
No full textMeasuring andmanagingthepowerconsumptionofhouseholdappliances,aswellasthatofindustrial
machineries, isbecomingmoreandmoreimportanttoimprovethedistributionandusageofthe
electrical energyandtoreducetheenergybill.Wepresentthedesignofanon-invasivewirelesscurrent
meter whichcanmeasureACcurrentupto60ARMS exploitingasmallclamp-oninductivesensor.The
noveltyofthedesignisasubsystemconsistingofaharvestingcircuitdesignedtoextractenergyfrom
the samecurrenttransducerusedformeasurements.Experimentshavebeenconductedtovalidatethe
approach, toassesstheaccuracyofthesensingsystemanddeviationsduetotheenergyharvester,andto
determine theconditionwhichpermitsustoachievetheenergyneutralityandthus,aself-sustainable
smart meter
Applications in Electronics Pervading Industry, Environment and Society
No full textEnergy availability and long term operation are key challenges for wireless sensor networks and for all the applications where the devices are battery operated. For this reason energy harvesting is becoming very important for powering ubiquitously deployed sensor networks and mobile electronics. One of most important goal for the next generation of power supply units for standalone embedded systems is to power nearly perpetually the devices when the scavenger is exposed to reasonable environmental energy conditions. However, due to the unpredictable nature of the environmental sources, prolonged lacks of energy intake usually happen. The last frontiers of perpetual operating systems is combining different energy harvesters in a single unit and using green energy supply with high energy density as micro hydrogen fuel cells. In this paper we introduce a Smart Power Unit (SPU) for embedded system which incorporates energy harvesters from sun and wind and uses hydrogen fuel cell as alternative energy storage. The power unit can work as a long-term battery or providing serial communication to exchange power information and to perform power management. In fact the core of the SPU is an ultra low power micro controller which is in charge to do the power activities such as Maximum Power Point Tracking for the harvesters, fuel cell activation, energy prediction, adaptive power management on board, battery monitoring and communications with powered systems. Experimental results and simulations shows the high efficiency (up to 90 %) of the power conversion subsystem. Finally a real deployment in a structural health monitoring site in Switzerland shows as the energy neutral condition is achieved on field
InfiniTime: A multi-sensor energy neutral wearable bracelet
No full textWearable technology is gaining popularity, with people wearing everything "smart" from clothing to glasses and watches. Nowadays wearables are battery-powered and a critical issue is the limited lifetime. So most devices have to be recharged every few days or even hours and thus they miss the expectations for a truly unobtrusive user experience. This paper presents InfiniTIME, a novel sensor-rich smart bracelet powered by small photovoltaic cells, designed to achieve energy neutrality even with modest indoor light levels. Experimental characterization of the fully operational prototype demonstrates a wide range of energy optimization techniques used to achieve the neutrality target. Simulations using energy intake measurements from various deployment scenarios confirm that the InfiniTIME achieves energy neutrality with indoor lighting levels in an office for several realistic application scenarios featuring data acquisition from the on-board camera and multiple sensors, visualization and radio connectivity
Adaptive rectifier driven by power intake predictors for wind energy harvesting sensor networks
No full textThis paper presents a power management technique for improving the efficiency of harvesting energy from air-flows in wireless sensor networks (WSNs) applications. The proposed architecture consists of a two-stage energy conversion circuit: an ac-dc converter followed by a dc-dc buck-boost regulator with maximum power point tracking capability. The key feature of the proposed solution is the adaptive hybrid voltage rectifier, which exploits both passive and active topologies combined with power prediction algorithms. The adaptive converter significantly outperforms other solutions, increasing the efficiency between 10% and 30% with respect to the only passive and the only active topologies. To assess the performance of this approach in a real-life scenario, air-flow data have been collected by deploying WSN nodes interfaced with a wind microturbine in an underground tunnel of the Metro B1 line in Rome. It is shown that, using the adaptive ac-dc converter combined with power prediction algorithms, nodes deployed in the tunnel can harvest up to 22% more energy with respect to previous methods. Finally, it is shown that using power management techniques optimized for the specific scenario, the overall system overhead, in terms of average number of sampling performed per day by a node, is reduced of up to 93%
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
Design and implementation of a multi sensors self sustainable wearable device
Full text linkWearable electronics is increasingly attracting researchers and manufacturers for the application opportunities it opens. Chip makers are responding to the hot wearable-computer trend with new components, microcontrollers and sensors. The most critical challenge is the autonomy of the systems. Even if battery management can help in extending the lifetime, the trade-off between features given by a multisensory platforms and autonomy can determine if a platform will win or not in the marketplace. In this paper we present a bracelet device, which attempts to maximize the capability of sensors on board, while still keeping the energy consumption low. Aggressive power management and an accurate selection of the sensors are addressed in this paper to demonstrate the effectiveness of our design
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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