1,721,040 research outputs found
An Algorithm for Real Time Estimation of the Flexible UAV Structural Motions Using a Video-based System
No full textThis paper focuses on the application of a vision based system coupled with an Inertial Measurement Unit (IMU) and several accelerometers, distributed along the aircraft structure, for estimating the structural displacements for flexible aircrafts. This sensor suite, associated with the proposed data fusion algorithm, represents an innovative approach to solve the problem of structural displacements determination for flexible aircrafts. The knowledge of the aircraft actual shape allows implementing active control techniques, Structural Health Monitoring (SHM) and moreover to determine the true position and attitude of sensors, installed on board. The effectiveness of the proposed approach is demonstrated through numerical simulations
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
An extension of integrated navigation algorithms to estimate elastic motions of very flexible aircrafts
No full textThis paper presents an algorithm for estimating the rigid and elastic motions of aircrafts showing significant elastic displacements, based on an EKF (Extended Kalman Filter) technique. The proposed algorithm can be applied to HALE (High Attitude Long Endurance Vehicle) unmanned vehicles, which typically show a configuration with high aspect ratios wings, fuselages with high length to diameter ratios and, above all, lightweight structures. The knowledge of their actual structure shape is fundamental essentially for three reasons: health monitoring of the structure, control purposes (Active Control Technologies) and finally for the determination of onboard sensors exact position and attitude, relative to a specified reference frame, to improve the accuracy of their measurements. Filter equations have been developed considering the coupling between rigid and elastic motions. The elastic motions are modeled in the assumptions of modal decomposition. Sensors budget of the presented algorithm, consists in two GPS Antennas/Receivers for speed/position measurements, an Inertial Measurement Unit with tri-axial accelerometers, gyros and magnetometers, and at least one auxiliary tri-axial accelerometer. The matrix formulation of the algorithm allows using the desired number of auxiliary accelerometers without changes to its implementation or its mathematical structure. Filter implementation also allows defining a numerical criterion to determine the better allocation of auxiliary accelerometers. The observability of the filter error state vector is also exhaustively analyzed, considering different scenarios concerning the elastic features of the structure. Finally simulation test results are reported, which demonstrate effectiveness of the proposed algorithm
A Load Alleviation Application of an Elastic Motion Estimatorfor a Flexible UAV
No full textThis work investigates the applicability of an algorithm for real time estimation of flexible structural motions, using an innovative sensors setup in the field of active control technologies (ACT), particularly, gust load alleviation (GLA). The innovative proposal, presented in this paper, is the coupling of an active control function, based on an optimal state feedback control law, with an algorithm able to elaborate onboard sensor measurements for real time estimation of structural motion. Another innovative aspect of this paper concerns the proposed setup, which integrates inertial measurements of accelerometers and gyros with the output of a vision based system with a target LED, positioned in a suitable point of the aircraft. The effectiveness and potentialities of the proposed approach are verified through numerical simulations, performed using a complete aeroelastic model of a flexible UAV, and a realistic modeling of sensors included in the proposed setup
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
The glucoregulatory response to intravenous glucose infusion in normal man: roles of insulin and glucose.
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