118,241 research outputs found
BIOMECHANICS OF LONGSWINGS PRECEDING TKACHEV ON UNEVEN BARS
No full textChanges in the rules governing the separation of uneven bars have allowed female gymnasts to perform the Tkachev in both directions. The aim of this study was to compare the similarities in the preparatory longswing during the outward (O) and inward (I) Tkachevs. Video recordings of the Tkachevs (O=5, I=5) were collected from the 2000 Sydney Olympic Games. A 37° greater range of movement was found at the hips during the I Tkachev. In the more conventional O technique changes in the hip angle were smaller (23°) and occurred over a greater circle angle. This study has identified differences in what appear to be very similar skills. Further inter-segmental coordination and joint kinetic analyses may provide insight into the performance of these release and regrasp skills
KINEMATICS AND ANGULAR MOMENTUM CONTRIBUTIONS TO THE TOE-ON TKACHEV ON UNEVEN BARS IN FEMALE GYMNASTICS
No full textThe purpose of this study was to explain the mechanics of the Toe-on Tkachev on Uneven Bars, and identify whether this variant creates the release characteristics needed to perform more complex aerial body positions (e.g. straight). Images of 5 Toe-on Tkachev’s performed at the 2007 World Championships were recorded with twin video cameras (50Hz). Digitising and 3D DLT techniques were combined with inertia modelling to develop customised profiles for the gymnasts. Greater flight time and angular momentum (L) suggest this variant may provide the gymnast with the opportunity to perform more complex aerial shapes. The dominant roll of the hip in the creation of L was highlighted
Influence of longswing technique on the kinematics and key release parameters of the straddle Tkachev on uneven bars
No full textTkachev on uneven bars is a release and re-grasp skill performed using variations of preparatory longswing techniques; the reasons why different techniques are chosen remains unclear. This study examined kinematic and key release parameters specific to three distinct techniques with the aim of understanding the relative benefits of each. During two international artistic gymnastics competitions six arch, straddle and pike longswings preceding the straddle Tkachev were recorded using twin video cameras. Calibration and movement images were digitised and reconstructed using 3D DLT. Shoulder and hip angular kinematics, angular momentum and key release parameters were compared between techniques. In the arch longswing, the first and second hip functional phases began significantly earlier than the straddle or pike. No significant differences were established for release parameters although large effect sizes for horizontal release velocity and angular momenta about the mass centre and bar were reported between the arch and other two variants. Therefore, the arch variant may provide the opportunity to develop more complex combinations following the Tkachev. Providing insight into mechanical advantages of specific longswing techniques, and highlighting those that elicit desirable characteristics offers the potential to provide coaches with objective data on technique selection and ultimately skill development
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
Square Dancing with the Stars to Enhance Dynamic Hirschman Linkages?
No full textIn this Presidential Address, the author takes the reader on a reconnaissance of his life and time as a regional scientist. He points out scenery he found scintillating along the way, hoping that some may pick up the banner and chew on a few of the ideas for a while. He suggests a revisit to Albert O. Hirschman’s notion of key sectors and more empirical analysis related to Marcus Berliant’s and Masahisa Fujita’s notion of knowledge creation and transfer.Presidential Address, San Antonio, Texas, March 29, 2014 (53rd Meetings of the Southern Regional Science Association
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
Biomechanical evolution of the Tkachev on uneven bars in female gymnastics
No full textThe development of joint kinematics and kinetics is fundamental to the successful performance of complex flight skills
in gymnastics bar routines. Biomechanical understanding of these skills can provide coaches and scientists with key
information to make training safe and effective. The Tkachev is a complex and popular gymnastics skill with many different variations. Recently, a new version has been performed, which has become popular with elite female performers.
This study examined the key biomechanical characteristics of this skill and contrasted these to the earlier versions
reported. Elite female gymnasts (n = 5) were recorded and manually digitised using twin video cameras (50 Hz) at the
2007 World Gymnastics Championships. Three-dimensional (3D) DLT was used to reconstruct the real world coordinates. Individualised inertia characteristics were calculated and used to determine mass centre kinematics. Inverse
dynamics analysis was used to calculate joint kinetics at the hips and shoulders from the known values at the toes. The
results of this study showed an increased flight time and rotational capacity during the aerial phase for the toe-on Tkachev, as well as a more simple movement pattern and joint kinetic demand with single power impulses at the hips and
shoulders compared with previous versions. The key finding of this study was that the toe-on version appeared to be less
physically demanding than that the inward and outward techniques, and provide the opportunity to perform more complex aerial phase body positions. These results can help coaches to physically prepare their gymnasts and biomechanists
in terms of understanding the demands of these skills
Letter from unknown writer to Jesse L. Boyce
No full textLetter to Jesse L. Boyce from unknown author (possibly Jack) about the investigation into the powder magazine located in the Grand Canyon. Some personal news is included in the letter such as the writer's marriage to the daughter of C.A. Taylor, former Supervisor of Cochise County
Biomechanical evolution of the Tkachev on uneven bars in female gymnastics
No full text The development of joint kinematics and kinetics is fundamental to the successful performance of complex flight skills in gymnastics bar routines. Biomechanical understanding of these skills can provide coaches and scientists with key information to make training safe and effective. The Tkachev is a complex and popular gymnastics skill with many different variations. Recently, a new version has been performed, which has become popular with elite female performers. This study examined the key biomechanical characteristics of this skill and contrasted these to the earlier versions reported. Elite female gymnasts (n = 5) were recorded and manually digitised using twin video cameras (50 Hz) at the 2007 World Gymnastics Championships. Three-dimensional (3D) DLT was used to reconstruct the real world coordinates. Individualised inertia characteristics were calculated and used to determine mass centre kinematics. Inverse dynamics analysis was used to calculate joint kinetics at the hips and shoulders from the known values at the toes. The results of this study showed an increased flight time and rotational capacity during the aerial phase for the toe-on Tkachev, as well as a more simple movement pattern and joint kinetic demand with single power impulses at the hips and shoulders compared with previous versions. The key finding of this study was that the toe-on version appeared to be less physically demanding than that the inward and outward techniques, and provide the opportunity to perform more complex aerial phase body positions. These results can help coaches to physically prepare their gymnasts and biomechanists in terms of understanding the demands of these skills. </p
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
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