On nonlinear systems diagnosis using differential and algebraic methods     

Juan C. Cruz-Victoria  Rafael Martínez-Guerra 《Journal of The Franklin Institute》2008,345(2):102-118

In this paper we tackle the diagnosis problem in nonlinear systems under failure using differential algebra. Three examples are presented in order to apply the proposed methodology. Numerical simulations of these examples are presented to illustrate the effectiveness of the suggested approach.  相似文献   

Determinants of possession of the ball in soccer   总被引：1，自引：0，他引：1  

Lago C  Martín R 《Journal of sports sciences》2007,25(9):969-974

In research on the importance of the possession of the ball in soccer, little attention has been paid to its determinants. Using data from 170 matches of the 2003 - 2004 Spanish Soccer League, we explain why differences in the possession of the ball among teams are so great. In particular, four variables are examined: evolving match status (i.e. whether the team is winning, losing or drawing), venue (i.e. playing at home or away), and the identities of the team and the opponent in each match. Results of linear regression analysis show that these four variables are statistically significant and together explain most of the variance in possession. In short, home teams have more possession than away teams, teams have more possession when they are losing matches than when winning or drawing, and the identity of the opponent matters - the worse the opponent, the greater the possession of the ball. Combinations of these variables could be used to develop a model that predicts possession in soccer.  相似文献   

高水平乒乓球运动员有力臂最大等长收缩力的评估     

Francisco Pradas　Carlos de Teresa　Maricarmen Vargas　Rafael Herrero 《体育科研》2005,26(3):86-89

乒乓球是使用单侧上肢的一项运动,其特征是要进行重复多次高速且具爆发力的动作,无氧乳酸酵解代谢能力占有重要作用.研究对象与方法男女高水平乒乓球运动员(n=31).采用Takei5101握力计测量单侧上肢有力型和非单侧上肢有力型运动员的上肢最大等长收缩力.18名男运动员(平均年龄23.5±5.4岁)和13名女运动员(平均年龄21.3±3.3岁)均为西班牙乒乓球协会的国家联盟成员.采用SPSS v12.0 for windows和Excel v10.2软件包进行数据统计分析.研究结果发现无论男女运动员单侧上肢有力型的最大等长收缩力均高于非单侧上肢有力型,而左势手女运动员与右势手女运动员相比、右势手男运动员与左势手男运动员相比,单侧上肢有力型的最大等长收缩力均高于非单侧上肢有力型.研究还发现进攻型运动员与防守型运动员相比,单侧上肢有力型的最大等长收缩力高于非单侧上肢有力型.分析与讨论无论男女,单侧上肢有力型运动员手握力高于非单侧上肢有力型运动员.男性运动员比女性运动员的等长收缩力高,一个可以解释的事实是男性有更高的睾酮水平.肌肉力量不平衡可能发展成为脊柱侧弯姿态,这应该通过适当的力量和柔韧性训练来避免,以防止将来的运动损伤和运动成绩的下降.  相似文献   

Conducting a Cultural Audit: A Case Study in Service Learning for the Dominican Republic     

J. Nicholls Eastmond  Gisela Martiz  Rafael Gutierrez  Kevin Shanley 《TechTrends》2010,54(2):16-18

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Impact sports and bone fractures among adolescents     

Kyle R. Lynch  Han C. G. Kemper  Bruna Turi-Lynch  Ricardo R. Agostinete  Igor H. Ito  Rafael Luiz-De-Marco 《Journal of sports sciences》2017,35(24):2421-2426

The objective of the present study was to investigate the effects of different sports on stress fractures among adolescents during a 9-month follow-up period. The sample was composed of 184 adolescents divided into three groups (impact sports [n = 102]; swimming [n = 35]; non-sports [n = 47]). The occurrence of stress fracture was reported by participants and coaches. As potential confounders we considered age, sex, resistance training, body composition variables and age at peak of height velocity. There were 13 adolescents who reported fractures during the 9-month period. Bone mineral density values were higher in adolescents engaged in impact sports (P-value = 0.002). Independently of confounders, the risk of stress fracture was lower in adolescents engaged in impact sports than in non-active adolescents (hazard ratio [HR] = 0.23 [95% confidence interval (CI) = 0.05 to 0.98]), while swimming practice was not associated to lower risk of fracture (HR = 0.49 [95% CI = 0.09 to 2.55]). In conclusion, the findings from this study indicate the importance of sports participation among adolescents in the reduction of stress fracture risk, especially with impact sports. More importantly, these results could be relevant for recognising adolescents in danger of not reaching their potential for peak bone mass and later an increased risk of fractures.  相似文献   

Designing a Tool to Support Critical Web Reading     

Rafael Pastor  Timothy Read  Salvador Ros  Roberto Hernandez  Rocael Hernández 《TechTrends》2009,53(1):23-28

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Determination of a quantitative parameter to evaluate swimming technique based on the maximal tethered swimming test     

Rafael Soncin  Bruno Mezêncio  Jacielle Carolina Ferreira  Sara Andrade Rodrigues  Rudolf Huebner  Julio Cerca Serrão 《Sports biomechanics / International Society of Biomechanics in Sports》2017,16(2):248-257

The aim of this study was to propose a new force parameter, associated with swimmers’ technique and performance. Twelve swimmers performed five repetitions of 25 m sprint crawl and a tethered swimming test with maximal effort. The parameters calculated were: the mean swimming velocity for crawl sprint, the mean propulsive force of the tethered swimming test as well as an oscillation parameter calculated from force fluctuation. The oscillation parameter evaluates the force variation around the mean force during the tethered test as a measure of swimming technique. Two parameters showed significant correlations with swimming velocity: the mean force during the tethered swimming (r = 0.85) and the product of the mean force square root and the oscillation (r = 0.86). However, the intercept coefficient was significantly different from zero only for the mean force, suggesting that although the correlation coefficient of the parameters was similar, part of the mean velocity magnitude that was not associated with the mean force was associated with the product of the mean force square root and the oscillation. Thus, force fluctuation during tethered swimming can be used as a quantitative index of swimmers’ technique.  相似文献   

Some Challenges in the Empirical Investigation of Conceptual Mappings and Embodied Cognition in Science Education: Commentary on Dreyfus,Gupta and Redish; and Close and Scherr     

Rafael Núñez 《International Journal of Science Education》2015,37(5-6):867-875

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The impact of professional learning on in-service teachers’ pedagogical delivery of literacy-infused science with middle school English learners: a randomised controlled trial study in the U.S     

Fuhui Tong  Beverly J. Irby  Rafael Lara-Alecio  Cindy Guerrero  Shifang Tang  Kara L. Sutton-Jones 《Educational studies》2019,45(5):533-553

ABSTRACT

Research in the United States show that professional learning (PL) can improve classroom instruction. However, teachers, especially educators in the content areas, receive insufficient training specific to meeting the language and academic needs of English learners (ELs). The purpose of the current randomized controlled trial (RCT) study was to introduce a high-quality PL program for supporting middle school teachers in teaching science to ELs through classroom observations, so as to evaluate whether in-service science teachers’ instructional delivery can be shaped by intensive, structured, and ongoing PL. Results indicated that after receiving PL, treatment teachers allocated a significantly higher portion of their instructional time in teaching content language, developing students’ expressive language skills, small group and pair activities, implementing strategies evidenced to effective with ELs, and providing more opportunities for students to participate in hands-on activities that were content-related and grade-appropriate. Practical implications for PL were discussed for an international audience.  相似文献   

Exploring pre-service primary teachers’ progression towards inquiry-based science learning     

Soraya Hamed  Ángel Ezquerra  Rafael Porlán  Ana Rivero 《Educational research; a review for teachers and all concerned with progress in education》2020,62(3):357-374

ABSTRACT