1,721,491 research outputs found
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
Identification of viscous friction coefficients for a pneumatic system model using optimization methods
No full textPneumatic actuators are often used in industrial automation for reasons related to their good power/weight ratio, easy maintenance
and assembly operations, clean operating conditions and low cost. This set of advantages, is, however, made up for by the difficulties
met during the design.
Indeed, the presence of the air along with its natural compressibility introduces further complexities to those already existing:
friction forces, losses and time delays in the cylinder and transmission lines. In particular friction is very difficult to estimate using
specially designed experiments [E. Richer, Y. Urmuzlu, A high performance pneumatic force actuator system part 1—nonlinear
mathematical model, ASME J. Dyn. Syst. Meas. Control 122 (3) (2000) 416–425], and equivalent parameters are used in modelling
pneumatic systems [K. Hamiti, A. Voda-Besancon, H. Roux-Buisson, Position control of a pneumatic actuator under the
influence of stiction, Control Eng. Pract. 4 (8) (1996) 1079–1088]. It is commonly described [K. Hamiti, A. Voda-Besancon,
H. Roux-Buisson, Position control of a pneumatic actuator under the influence of stiction, Control Eng. Pract. 4 (8) (1996)
1079–1088] as linear viscous damping, coulomb friction, stiction [D. Karnopp, Computer simulation of stick-slip friction in
mechanical dynamic system, J. Dyn. Syst. Meas. Control, 107 (1986) 100–103] or some combination of these. In linear control
theory, it is assumed that the friction is linear viscous. Unfortunately attempts to ignore significant coulomb friction or stiction
may lead to erroneous predictions of a system’s behaviour [K. Hamiti, A. Voda-Besancon, H. Roux-Buisson, Position control
of a pneumatic actuator under the influence of stiction, Control Eng. Pract. 4 (8) (1996) 1079–1088]. As a result, the analytical
models, describing the dynamics of the pneumatic system, are not only non-linear but several tuning parameters can also be
involved.
In this paper a complete mathematical model [D. Ben-Dov, S.E. Salcudan, A force controlled pneumatic actuator, J. Dyn.
Syst. Meas. Control 113 (1991) 267–272; D. Karnopp, Computer simulation of stick-slip friction in mechanical dynamic
system, J. Dyn. Syst. Meas. Control, 107 (1986) 100–103; A. Messina, N.I. Giannoccaro, A. Gentile, Experimenting and
modelling PWM-based pneumatic actuators, Mechatronics 15 (7) (2005) 859–881; E. Richer, Y. Urmuzlu, A high performance
pneumatic force actuator system part 1—nonlinear mathematical model, ASME J. Dyn. Syst. Meas. Control 122
(3) (2000) 416–425] of a pneumatic actuator driven by two on/off two ways valves (with Pulse Width Modulation technique)
is validated by tuning a number of geometric and functional characteristics and parameters by means of non-linear
optimization algorithms. The experimental data were obtained driving the on/off valves with five different duty cycles:
10, 25, 50, 75 and 90% over a period of 20 ms and measuring the actuator position with a potentiometer. In particular
experimental apparatus [J.L. Shearer, Study of pneumatic processes in the continuous control of motion with compressed
air-I, Trans. ASME 78 (2) (1956) 233–249] was realised in order to measure valve coefficients in all operative
conditions
Investigazione teorica e sperimentale su un attuatore pneumatico con controllo in posizione realizzato con valvole ON/OFF e modulazione PWM
No full textDispelling 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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