1,721,109 research outputs found
Active vibration control unit with a flywheel inertial actuator
No full textThis paper presents simulation and experimental results on the implementation of a velocity
feedback control unit with a new flywheel inertial actuator, which can be used to
reduce flexural vibration of distributed structures. The actuator incorporates a classical coil
emagnet linear transducer and a flywheel element such that both linear and rotational
inertia effects are generated by the moving components of the actuator. The additional
rotational inertia effect shifts to lower values the fundamental resonance frequency of the
actuator without increasing the static deflection of the suspended masses. Therefore, this
actuator can be conveniently used to implement feedback control units, which are robust
to shocks, have enhanced stability properties and, thus, improved vibration control effects.
To illustrate the key features of the proposed actuator, the characteristic electromechanical
response functions of a classical actuator and of the flywheel actuator are
first presented. Then, the stability and flexural vibration control performance of velocity
feedback loops with a classical and the flywheel inertial actuators are contrasted considering
a thin rectangular plate hosting structure
Flywheel proof mass actuator for active vibration control
Full text linkThis paper presents the experimental results of a new proof mass actuator for the implementation of velocity feedback control loops to reduce the flexural vibration of a thin plate structure. Classical proof mass actuators are formed by coil–magnet linear motors. These actuators can generate constant force at frequencies above the fundamental resonance frequency of the spring–magnet system, which can be used to efficiently implement point velocity feedback control loops. However, the dynamics of the spring–magnet system limit the stability and control performance of the loops when the actuators are exposed to shocks. The proof mass actuator investigated in this paper includes an additional flywheel element that improves the stability of the velocity feedback loop both by increasing the feedback gain margin and by reducing the fundamental resonance frequency of the actuator. This paper is focused on the stability and control performance of decentralized velocity feedback control loops
Flywheel inertial vibration absorber
No full textThis paper presents a comprehensive study on the working principle and design concepts, of an inertial vibration absorber incorporating a flywheel seismic mass. The unit is formed by a seismic flywheel element, which is mounted on the base via a coupled liner-torsional suspension spring that couples the axial and rotational motions of the flywheel. In this way the axial inertia effect generated by the linear vibration of the flywheel is augmented by its rotational inertia produced by the coupled rotational vibration. The advantage of such design is twofold. Firstly, the inertia effect of the absorber can be increased without increasing the total weight of the unit. Secondly, the characteristic dimension of the device can be miniaturised. This work presents the working principles and the designs and manufacturing process based on additive 3D printing of different solutions. The paper shows that indeed the rotational inertia effect increments the vibration control performance of the absorber with now weight cost
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
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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