Distance education courses: re‐discovered tools for small secondary schools     

John E. Davis 《Distance Education》1983,4(2):195-202

  相似文献   

Helping behavior among normal and retarded children   总被引：1，自引：0，他引：1  

L J Severy  K E Davis 《Child development》1971,42(4):1017-1031

  相似文献   

The influence of moment of inertia on baseball/softball bat swing speed   总被引：1，自引：1，他引：0  

Keith?KoenigEmail author  Nan?Davis?Mitchell  Thomas?E.?Hannigan  J.?Keith?Clutter 《Sports Engineering》2004,7(2):105-117

The speed at which a player can swing a bat is central to the games of baseball and softball, determining, to a large extent, the hit speed of the ball. Experimental and analytical studies of bat swing speed were conducted with particular emphasis on the influence of bat moment of inertia on swing speed. Two distinct sets of experiments measured the swing speed of colege baseball and fast-pitch softball players using weighted rods and modified bats. The swing targets included flexible targets, balls on a tee and machine pitched balls. Internal mass alterations provided a range of inertial properties. The average measured speeds, from 22 to 31 m s⁻¹, are consistent with previous studies. Bat speed approximately correlates with the moment of inertia of the bat about a vertical axis of rotation through the batter's body, the speed generally decreasing as this moment of inertia increases. The analytical model assumes pure rotation of the batter/bat system about a vertical axis through the batter's body. Aerodynamic drag of the batter's arms and the bat is included in the model. The independent variable is bat moment of inertia about the rotation axis. There is reasonable agreement between the model and the measured speeds. Detailed differences between the two suggest the importance of additional degrees of freedom in determining swing speed.  相似文献   

Analysis of postural stability in collegiate soccer players before and after an acute bout of heading multiple soccer balls     

Mangus BC  Wallmann HW  Ledford M 《Sports biomechanics / International Society of Biomechanics in Sports》2004,3(2):209-220

The aim of our study was to determine if any immediate changes in balance were discernable in college soccer players after a specially designed heading session. Eight male and two female skilled collegiate soccer players had a baseline balance pre-test using the Balance Master, followed by heading 20 balls kicked consecutively by a teammate from the touchline to a point near the goal, which was followed by a post-test using the same testing technique. Paired t-tests were used to compare balance ability between pre- and post-test conditions. There was no difference in balance pre- to post-test (85.3% and 86.2% respectively). No significant difference was noted from pre- to post-test in the mean equilibrium scores for conditions three through six on the Sensory Organization Test, with the exception of condition four, which revealed a significant increase from pre- to post-test. We concluded that an acute session of heading soccer balls may not result in balance changes in collegiate soccer players.  相似文献   

Physical fitness and cardiac risk factors of professional firefighters across the career span     

Davis SC  Jankovitz KZ  Rein S 《Research quarterly for exercise and sport》2002,73(3):363-370

  相似文献   

The motor core of speech: a comparison of serial organization patterns in infants and languages     

MacNeilage PF  Davis BL  Kinney A  Matyear CL 《Child development》2000,71(1):153-163

Comparison of serial organization of infant babbling and early speech with that of 10 languages reveals four movement-related design features reflecting a deep evolutionary heritage: (1) the cyclical consonant-vowel alternation underlying the syllable, a "Frame" for speech consisting of mandibular oscillation, possibly evolving from ingestive cyclicities (e.g., chewing) via visuofacial communicative cyclicities (e.g., lipsmacks); (2) three intracyclical consonant-vowel co-occurrence preferences reflecting basic biomechanical constraints-coronal consonants-front vowels, dorsal consonants-back vowels, and labial consonants-central vowels; (3) a developmental progression from above-chance to below-chance levels of intercyclical consonant repetition; (4) an ease-related labial consonant-vowel-coronal consonant sequence preference for word initiation. These design features presumably result from self-organizational responses to selection pressures, primarily determined by motor factors. No explanation for these design features is available from Universal Grammar, and, except for feature 3, perceptual-motor learning seems to have only a limited causal role in acquisition of any design feature.  相似文献   

Quiet     

Norman M. Davis 《The Educational forum》2013,77(2)

  相似文献   

The Nicaragua canal     

Geo.W. Davis 《Journal of The Franklin Institute》1892,134(2):109-131

  相似文献   

Cardiorespiratory and perceptual responses to arm crank and wheelchair exercise using various handrims in male paraplegics     

G W Gayle  R L Pohlman  R M Glaser  G M Davis 《Research quarterly for exercise and sport》1990,61(3):224-232

The purpose of the present study was to determine the effects of 10-in [0.25-m] versus 16-in [0.41-m] wheelchair handrims on cardiorespiratory and psychophysiological exercise responses during wheelchair propulsion at selected velocities. Fifteen male paraplegics (27.0 +/- 5.5 yrs) performed three discontinuous exercise tests (ACE = arm crank ergometer; WERG = wheelchair roller ergometer) and two 1600-m performance-based track trials (TRACK) under simulated race conditions. There were no significant differences in HR, VO2, VE, HLa, or category-ratio ratings of perceived exertion (RPE) using different handrims during wheelchair propulsion at 4 km.h-1. In contrast, at 8 km.h-1 subjects demonstrated a 13% lower steady state VO2 (p less than .05) using the 10-in handrims, coincident with a 23% lower VE. Steady state HR during WERG at 8 km.h-1 using the 10-in (124.4 +/- 3.9 b.min-1) or 16-in (130.6 +/- 4.6 b.min-1) handrims were not significantly different. There were also no significant differences between ACE or WERG conditions during maximal effort for VO2 or VE. However, HRpeak during ACE was 7% higher than HRpeak during WERG16 (183 +/- 15 b.min-1 vs. 171 +/- 12 b.min-1, p less than .05), and whole blood HLa during ACE was also significantly higher (by 2.3-2.5 mmol; p less than .05) compared to WERG. There were no significant differences for HR, performance time, or RPE between trials using different handrim diameters during the 1600-m event.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

5. Implications for Assessment     

Andrew Davis 《Journal of Philosophy of Education》1998,32(1):67-74

  相似文献