1,354,927 research outputs found
ANGULAR MOMENTUM IN THE STRAIGHT TKATCHEV ON HIGH BAR
No full textAngular momentum in the straddle Tkatchev was reported as part of a study by Arampatzis and Brüggemann, (2001). The Tkatchev is an interesting skill as it requires the gymnast to reverse the direction of rotation between the bar circling action (the longswing) and the flight phase from release until regrasp
ON THE WAY FROM STRADDLED TO STRETCHED TKATCHEV ON HIGH BAR
No full textReversing the direction of rotation is the main issue for the flight element Tkatchev on high bar. The principles are well described. There is a lack of knowledge to apply this to motor learning. Aim of the study is to analyse an individual gymnast’s performance and support the change from straddled to stretched Tkatchev. An instrumented high bar (force measurement) was used to give the gymnast immediately feedback about the performance. The gymnast was informed about the magnitude of the force maxima during the preparatory giant swing. After 5 training sessions with 42 trails the gymnast transferred more energy (higher forces) to the bar. But this results not in a higher angular momentum during the Tkatchev flight. Possible causes for this result where discussed. The complex demands on energy transfer and precise performance are important
Consistency of performance in the Tkatchev release and re-grasp on high bar
No full textThe Tkatchev on the high bar is a release and re-grasp skill in which the gymnast rotates in a direction during flight opposite to that of the preceding swing. Since the release window is defined as the time during which the gymnast has appropriate linear and angular momentum to ensure the bar can be re-grasped, it was speculated that the release windows for this skill would be smaller than for dismounts which are less constrained. One senior male gymnast competing at national level performed 60 Tkatchev trials. A four-segment planar simulation model of the gymnast and high bar was used to determine the release windows in 10 successful and 10 unsuccessful performances of the Tkatchev recorded using a Vicon motion analysis system. Model parameters were optimised to obtain a close match between simulations and recorded performances in terms of rotation angle (1°), bar displacements (0.01 m) and release velocities (1%). Each matched simulation was used to determine the time window around the actual point of release for which the model had appropriate release parameters to complete the Tkatchev successfully. The release windows for the successful trials were small compared to those of dismounts. The unsuccessful trials were associated with later release and later timing of the actions at the shoulders and hips
Functional phases and angular momentum characteristics of Tkatchev and Kovacs
No full textUnderstanding the technical requirements and underlying biomechanics of complex release and re-grasp skills on high bar allows coaches and scientists to develop safe and effective training programmes. The aim of this study was to examine the differences in the functional phases between the Tkatchev and Kovacs skills and to explain how the angular momentum demands are addressed. Images of 18 gymnasts performing 10 Tkatchevs and 8 Kovacs at the Olympic Games were recorded (50 Hz), digitised and reconstructed (3D Direct Linear Transformation). Orientation of the functional phase action, defined by the rapid flexion to extension of the shoulders and extension to flexion of the hips as the performer passed through the lower vertical, along with shoulder and hip angular kinematics, angular momentum and key release parameters (body angle, mass centre velocity and angular momentum about the mass centre and bar) were compared between skills. Expected differences in the release parameters of angle, angular momentum and velocity were observed and the specific mechanical requirement of each skill were highlighted. Whilst there were no differences in joint kinematics, hip and shoulder functional phase were significantly earlier in the circle for the Tkatchev. These findings highlight the importance of the orientation of the functional phase in the preceding giant swing and provide coaches with further understanding of the critical timing in this key phase
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
OPTIMISATION TO IMPROVE CONSISTENCY IN THE TKATCHEV ON HIGH BAR
No full textThe purpose of this study was to improve the consistency of performance of the Tkatchev release and re-grasp on high bar. A simulation model (Hiley & Yeadon, 2003) was used to optimise the technique in the giant circle leading up to release in order to maximise the size of the window within which the gymnast could release and successfully re-grasp the bar. The optimal simulation resulted in a release window considerably larger (93 ms) than the gymnast’s actual performances (mean 29 ms).
However, when the technique was required to be robust to small errors in timing the size of the release window was smaller. Performing the final hip and shoulder flexion and extension actions earlier and over a larger angle range than in the actual performances lead to the increase in size of release window
Variations on the Author
No full text“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
No full textWe 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
No full textWe 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
Author, publisher and bookseller : a tripartite synergy in Nigerian book industry
No full textThis work is about the roles of Author, Publisher and Bookseller in Book development in
Nigeria. The paper started by delving into the history of Book Publishing in Nigeria after
which it proceeded by defining who an author, a publisher, and a bookseller is and
expatiated on the indispensable roles of these key actors in Nigerian Book Industry and in
the emerging Information Society. Furthermore, the various constraints to book
development were identified while the paper advised on how the Book Industry can be
further promoted in Nigeria. However, the paper concluded and made recommendations
on how the Book sector can help in enhancing scholarship in the country
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