1,722,021 research outputs found
Feasibility of ultrasound flow measurements via non-linear wave propagation
No full textTypically, ultrasonic flow meters assume linear wave propagation. Nevertheless, if the transducers of an ultrasonic flow sensor excite a pressure wave with a high amplitude, nonlinear wave propagation effects become significant. The appearance of higher harmonics increases the bandwidth of the received signal, which may potentially lead to a more precise flow measurement. However, the question arises whether the increased bandwidth can be used in practice, since the intensity of the 2nd harmonic can be 25 dB below the fundamental. One exploit of the increased bandwidth is to filter the received signals and to obtain two components: the fundamental and the 2nd harmonic. Differences between the upstream and downstream transit times are directly related to the flow speed, and these can be computed for each component of the received signals. This paper shows that averaging the transit time differences of the fundamental signals and the 2nd harmonic signals results in a lower standard deviation compared to the standard deviation of the transit time differences of the fundamental or the 2nd harmonic signal alone. This demonstrates the feasibility of using non-linear wave propagation to improve the precision of flow measurements using ultrasound.Accepted Author ManuscriptImPhys/Acoustical Wavefield ImagingElectronic Instrumentatio
Utilization of Polarisation Diversity and Antenna Directivity to Combat Co-channel Interference for Indoor Cordless Telephony
No full text
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
Keeping features in the field of view in eye-in-hand visual servoing: A switching approach
No full textA visual servoing strategy for keeping features in the field of view is proposed which consists of a switching among position-based control strategies and backward motion. In the absence of uncertainty on the extrinsic parameters, all features are kept in the field of view. Moreover, if the intrinsic parameters are also known, the trajectory length is minimized in the rotational space and, for some cases, also minimized in the translational space. Simulation results also show a certain degree of robustness against uncertainty on the intrinsic parameters. © 2004 IEEE.link_to_subscribed_fulltex
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
A switching control law for keeping features in the field of view in eye-in-hand visual servoing
No full textIn this paper, a visual servoing strategy for dealing with the problem of keeping the observed points in the camera field of view is proposed. The approach consists of a switching control law based on camera displacement estimation and regulated from the position of the points in the image. In absence of uncertainties on the intrinsic parameters and optical axis direction, global stability is achieved and all points are kept in the field of view. Moreover, the trajectory length is minimized in the rotational space and, for some cases, also minimized in the translational one. Robustness against uncertainties is also guaranteed
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