A method of providing accurate velocity feedback of performance on an instrumented kayak ergometer     

Mickaël Begon  Olivier Mourasse  Patrick Lacouture 《Sports Engineering》2009,11(2):57-65

On a kayak ergometer, an accurate simulation of the athlete-paddle-kayak system kinematics is essential for analysing the relationship between technique and performance. The purpose of this study was to establish a strong relationship between performances on flatwater and performances on an ergometer by means of propulsive force measurement and drag models. Two trials were performed by 12 kayakers in which they were first timed over 250 m of flatwater kayaking (the reference test) and were then asked to perform a trial of the same duration on the ergometer with the same perceived physical exertion. Three techniques for measuring propulsive force and three drag models generated nine combinations, which were all evaluated for their ability to estimate kayak velocity. For each combination, the distance covered by the athlete on the ergometer was simulated. A kayakers’ ergometer ranking was based on the average velocity in the ergometer trial. Both distance and ranking were compared to the on-water results. The simulation with the best combination of force measurement and drag model gave an accurate estimate of distance (253 ± 10.5 vs. 250 m) and ranking compared to the reference test.  相似文献   

Habituation of 10-year-old hockey players to treadmill skating     

Lockwood KL  Frost G 《Sports biomechanics / International Society of Biomechanics in Sports》2007,6(2):145-154

This study assessed changes in selected physiological and kinematic variables over 6 weeks of treadmill skating in an effort to understand the process of habituation to this novel training modality. Seven male, Atom-A hockey players who were injury-free and had no previous treadmill skating experience participated in the study. Players performed four 1-min skating bouts at progressively increasing speeds, each week, for 6 weeks. One speed (10.5 km/h) was repeated weekly to allow for assessment of the habituation process. Our criteria for habituation were: a decrease in stride rate, heart rate and rating of perceived exertion, and an increase in stride length, trunk angle and vertical movement of the centre of mass, leading to a plateau, over the course of the 6-week study. Significant decreases were seen in stride rate, heart rate and ratings of perceived exertion, and significant increases were found in stride length. Some of these changes were evident after only one week of training and all were present by week 4. After 6 weeks (24 min) of exposure to treadmill skating, all participants displayed a visibly more efficient skating style.  相似文献   

Geographic clustering of economic activity: The case of prominent western visual artists   总被引：1，自引：1，他引：0  

Elish Kelly  John O’Hagan 《Journal of Cultural Economics》2007,31(2):109-128

This article compiles original data relating to artists’ place of birth and work migration patterns using various art history dictionaries. The broad historic pattern, from the 13th to the 20th century, of the birth locations of prominent artists is examined, followed by a detailed study of the work migration patterns of prominent artists in two important situations, namely Renaissance Italy and France in part of the 19th century. The evidence indicates a marked clustering of activity of prominent artists, both arising from birth location and migration patterns. Some possible explanations for the observed patterns are briefly outlined.

John O’HaganEmail:

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Heart rates of high school physical education students during team sports, individual sports, and fitness activities     

Laurson KR  Brown DD  Cullen RW  Dennis KK 《Research quarterly for exercise and sport》2008,79(1):85-91

This study examined how activity type influenced heart rates and time spent in target heart rate zones of high school students participating in physical education classes. Significantly higher average heart rates existed for fitness (142 +/- 24 beats per minute [bpm]) compared to team (118 +/- 24 bpm) or individual (114 +/- 18) activities. Similar results occurred for the percentage of activity time spent within a target heart rate zone (fitness 81.7 +/- 15.9%, individual 68.4 +/- 30.5%, and team 60.6 +/- 30.5%). Boys attained higher heart rates during team activities, while female students had higher rates during individual activities indicating male and female adolescents respond differently to activity types. The highest mean heart rates were observed during fitness activities.  相似文献   

Student achievement and differential reinforcement of incompatible behavior: Hand raising     

Michael Bryan Kelly  Donald Bushell 《Psychology in the schools》1987,24(3):273-281

Workbook reading achievement of five second-grade girls was assessed under two teacher-contact contingencies. Under one contingency, teacher contacts were made during on-task behavior. Under the other contingency, differential reinforcement of an incompatible behavior (DRI) was in effect, with teacher contacts contingent on students' hand-raising behavior. Both reading achievement and time on task were greater under the on-task contingency than under DRI for hand raising.  相似文献   

A lesson in communication: The GPO access model gateway program at UIC     

Maurie Caitlin Kelly   《Government Information Quarterly》1995,12(4)

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Coordination of perspective by sixth graders and teacher trainees     

Gwendolyn N. Kelly  Joseph T. Kelly  Wallace S. Johnson 《Contemporary educational psychology》1988,13(4)

Sixth grade students were compared by sex for their performance on two perspective coordination tasks. Responses were compared with understanding of the principle that still water remains invariantly horizontal. Forty-eight randomly selected sixth grade students (24 girls and 24 boys) and 12 college women were individually shown a standardized three-dimensional scene. While seated in a single position, subjects completed two tasks: (1) selecting from a set of 12 pictures (displayed together) the one which could be seen from each of eight positions marked on the displayed scene and (2) choosing the positions from which could be seen eight of the 12 pictures (shown one at a time). Four of the 12 pictures were mirror images which were impossible views. Males outperformed females on both of the coordination-of-perspective tasks. For both males and females, choosing the place was more difficult than choosing the picture. Strong relationships were found between understanding of horizontality and performance on the perspective tasks. Selection of mirror images (impossible views) indicated more understanding of perspective than other, less systematic errors. Finally, female teacher trainees performed only marginally better than sixth grade students, suggesting possible remediation needs.  相似文献   

Preparation time influences ankle and knee joint control during dynamic change of direction movements     

Patrick Fuerst  Albert Gollhofer  Dominic Gehring 《Journal of sports sciences》2017,35(8):762-768

The influence of preparation time on ankle joint biomechanics during highly dynamic movements is largely unknown. The aim of this study was to evaluate the impact of limited preparation time on ankle joint loading during highly dynamic run-and-cut movements. Thirteen male basketball players performed 45°-sidestep-cutting and 180°-turning manoeuvres in reaction to light signals which appeared during the approach run. Both movements were executed under (1) an easy condition, in which the light signal appeared very early, (2) a medium condition and (3) a hard condition with very little time to prepare the movements. Maximum ankle inversion angles, moments and velocities during ground contact, as well as EMG signals of three lower extremity muscles, were analysed. In 180°-turning movements, reduced preparation time led to significantly increased maximum ankle inversion velocities. Muscular activation levels, however, did not change. Increased inversion velocities, without accompanying changes in muscular activation, may have the potential to destabilise the ankle joint when less preparation time is available. This may result in a higher injury risk during turning movements and should therefore be considered in ankle injury research and the aetiology of ankle sprains.  相似文献   

The international political economy of the hack: A closer look at markets for cybersecurity software     

Patrick Burkart  Tom McCourt 《Popular Communication》2017,15(1):37-54

This article examines the development of hacking and cybersecurity software packages as commodities, based on an international political economy of vendors and clients operating in the interstices of international law. Offensive hacking and defensive cybersecurity tools offer new means for surveillance of critics, journalists, and human rights workers, especially in corrupt or authoritarian political systems. The article provides a case study of the Hacking Team, an international “cybersecurity” firm offering spyware and surveillance systems to government security agencies, which was itself hacked and “doxed” in 2015. The leak of documents contributes new knowledge of an international political economy for software products, which exploits the digital rights of targets and which could further undermine general Internet security.  相似文献   

Developing Culturally Competent Preservice Teachers     

Calli Lewis Chiu  Donna Sayman  Kelly M. Carrero  Thomas Gibbon  Staci M. Zolkoski  Mandy E. Lusk 《Multicultural Perspectives》2017,19(1):47-52

An unfortunate, yet persistent, truth in U.S. public schools is the large achievement gap existing between children from culturally and linguistically diverse backgrounds and their White, middle-class counterparts. The potential for cultural dissonance between contemporary teachers and their students necessitates that educators must persistently seek culturally responsive practices. Much has been written regarding strategies for culturally responsive pedagogy; therefore, this article moves beyond a review of culturally responsive pedagogy. Rather than providing teacher candidates with more suggestions for culturally responsive teaching activities, the authors provide teacher educators with specific resources for facilitating the development of cultural competence among preservice teachers.  相似文献