Signs and meanings in students' emergent algebraic thinking: A semiotic analysis     

Luis Radford 《Educational Studies in Mathematics》2000,42(3):237-268

The purpose of this article, which is part of a longitudinal classroom research about students' algebraic symbolizations, is twofold: (1) to investigate the way students use signs and endow them with meaning in their very first encounter with the algebraic generalization of patterns and(2) to provide accounts about the students' emergent algebraic thinking. The research draws from Vygotsky's historical-cultural school of psychology, on the one hand, and from Bakhtin and Voloshinov's theory of discourse on the other, and is grounded in a semiotic-cultural theoretical framework in which algebraic thinking is considered as a sign-mediated cognitive praxis. Within this theoretical framework, the students' algebraic activity is investigated in the interaction of the individual's subjectivity and the social means of semiotic objectification. An ethnographic qualitative methodology, supported by historic, epistemological research, ensured the design and interpretation of a set of teaching activities. The paper focuses on the discussion held by a small group of students of which an interpretative, situated discourse analysis is provided. The results shed some light on the students' production of (oral and written) signs and their meanings as they engage in the construction of expressions of mathematical generality and on the social nature of their emergent algebraic thinking. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The Non-monetary Benefits of Education   总被引：1，自引：0，他引：1  

Luis E. Vila 《European Journal of Education》2000,35(1):21-32

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A survey of talent identification and development processes in the youth academies of professional soccer clubs from around the world     

Paul R. Ford  Juan Luis Delgado Bordonau  Daniele Bonanno  José Tavares  Corne Groenendijk  Cristina Fink 《Journal of sports sciences》2020,38(11-12):1269-1278

ABSTRACT

Talent identification (TID) and development (TDE) are large fields in professional soccer and in science. However, TID and TDE processes in youth academies have not been assessed in detail. As such, our aim was to survey professional clubs from around the world about their youth academy TID and TDE processes, with 29 clubs responding to the survey. TID and TDE processes changed as a function of player age. TID processes involved finding the best players locally and regionally, but for older players the search widened to nationally and internationally for the needs of the first team. Clubs used a multidisciplinary approach to TID, but more so with older players. Median number of academy players was 80, 100, and 66 players at 8–11 years, 12–16 years, and 17–21 years, respectively. Annual player turnover in the most recent season (selections/de-selections) was 29% across all age groups, with competition from other clubs cited as a limitation to TID. TDE processes involved weekly matches and 3–5 training sessions per week led by experienced, well-qualified coaches, with most clubs providing players with academic education, residency and transportation services. Our findings extend previous research assessing professional soccer youth academy TID and TDE processes by quantifying worldwide practices.  相似文献   

Introduction to the open file     

Luis Albala-Bertrand 《Prospects》1996,26(4):643-650

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A change in outlook: From work to school     

Luis Reguera 《Prospects》1995,25(2):245-259

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Preventive Conservation Applied to Wallpaintings in a Desert Environment in Mexico     

Denise Charua-Ayala  Rosario Guerra  Clotilde Lemoine  Federico Cambieri  Nora A. Pérez  José Luis Ruvalcaba-Sil 《文物保护研究》2018,63(5):51-57

ABSTRACT

The church of San Diego de Alcalá, located in Pitiquito, Sonora , in Mexico, lies on a missionary road founded by the Jesuit Eusebio F. Kino, which, with the expulsion of the Jesuit order in 1767, passed into the care of the Franciscans. It contains wallpaintings which presented deterioration problems whose cause was not easy to determine, since the damage appeared to be inconsistent with the techniques used and the environmental conditions. With an interdisciplinary team, a methodology was designed for a combined study of the environment of the church and its wallpaintings. Thermal imaging of the exterior and interior walls indicated that the building was made up of different materials, and the junctions between them explained the different deterioration pathologies between one zone and another. Hydrological maps for groundwater in the locality were studied, to elucidate the presence of water in a desert zone; abundant sources of water in the subsoil were identified, which, because of overexploitation of the land, have been diminishing over time. This allowed the elaboration of a plan for site management, through the identification of those deterioration factors that can be mitigated by simple maintenance actions that are inherent to the environment and the materials, which enabled a scheduled maintenance scheme to be implemented. This improved the condition of the building and its wallpaintings, while reducing the resource invested to achieve this goal.  相似文献   

Influence of football match time–motion parameters on recovery time course of muscle damage and jump ability     

Moisés de Hoyo  Daniel Dylan Cohen  Borja Sañudo  Luis Carrasco  Alejandro Álvarez-Mesa  Juan José del Ojo 《Journal of sports sciences》2016,34(14):1363-1370

ABSTRACT

We analysed the time course of recovery of creatine kinase (CK) and countermovement jump (CMJ) parameters after a football match, and correlations between changes in these variables and match time–motion parameters (GPS-accelerometry) in 15 U-19 elite male players. Plasma CK and CMJ height (CMJ_H), average concentric force (CMJ_CON) and average eccentric force (CMJ_ECC) were assessed 2 h before and 30 min, 24 h and 48 h post-match. There were substantially higher CK levels 30 min, 24 h and 48 h (ES: 0.43, 0.62, 0.40, respectively), post-match. CMJ_ECC (ES: ?0.38), CMJ_H (ES: ?0.35) decreased 30 min post, CMJ_CON (ES: ?0.35), CMJ_ECC (ES: ?0.35) and CMJ_H (ES: ?1.35) decreased 24 h post, and CMJ_CON (ES: ?0.41) and CMJ_H (ES: ?0.53) decreased 48 h post. We found correlations between distance covered at velocities ≤21 km · h^?1 and changes in CK at 24 h (r = 0.56) and at 48 h (r = 0.54) and correlations between CK and distance covered >14 km · h^?1 (r = 0.50), accelerations (r = 0.48), and decelerations (r = 0.58) at 48 h. Changes in CMJ_CON 30 min and 24 h post (both r = ?0.68) correlated with impacts >7.1·G. Decelerations >2 m · s^?2 correlated with changes CMJ_CON (r = ?0.49) at 48 h and CMJ_ECC (r = ?0.47) at 30 min. Our results suggest that match GPS-accelerometry parameters may predict muscle damage and changes in components of neuromuscular performance immediately and 24–48 h post-match.  相似文献   

Attacking and defensive styles of play in soccer: analysis of Spanish and English elite teams     

Javier Fernandez-Navarro  Luis Fradua  Asier Zubillaga  Paul R. Ford  Allistair P. McRobert 《Journal of sports sciences》2016,34(24):2195-2204

ABSTRACT

The aim of this study was to define and categorise different styles of play in elite soccer and associated performance indicators by using factor analysis. Furthermore, the observed teams were categorised using all factor scores. Data were collected from 97 matches from the Spanish La Liga and the English Premier League from the seasons 2006–2007 and 2010–2011 using the Amisco® system. A total of 19 performance indicators, 14 describing aspects of attacking play and five describing aspects of defensive play, were included in the factor analysis. Six factors, representing 12 different styles of play (eight attacking and four defensive), had eigenvalues greater than 1 and explained 87.54% of the total variance. Direct and possession styles of play, defined by factor 1, were the most apparent styles. Factor analysis used the performance indicators to cluster each team’s style of play. Findings showed that a team’s style of play was defined by specific performance indicators and, consequently, teams can be classified to create a playing style profile. For practical implications, playing styles profiling can be used to compare different teams and prepare for opponents in competition. Moreover, teams could use specific training drills directed to improve their styles of play.  相似文献   

The effect of different foot and hand set-up positions on backstroke start performance     

Karla de Jesus  Kelly de Jesus  J. Arturo Abraldes  Luis Mourão  Márcio Borgonovo-Santos  Alexandre I. A. Medeiros 《Sports biomechanics / International Society of Biomechanics in Sports》2016,15(4):481-496

Foot and hand set-up position effects were analysed on backstroke start performance. Ten swimmers randomly completed 27 starts grouped in trials (n = 3) of each variation, changing foot (totally immersed, partially and totally emerged) and hand (lowest, highest horizontal and vertical) positioning. Fifteen cameras recorded kinematics, and four force plates collected hands and feet kinetics. Standardised mean difference and 95% confidence intervals were used. Variations with feet immersed have shown lower vertical centre of mass (CM) set-up position (0.16 m), vertical impulse exerted at the hands, horizontal and vertical impulse exerted at the feet (0.28, 0.41, 0.16 N/BW.s, respectively) than feet emerged with hands horizontal and vertically positioned. Most variations with feet partially emerged exhibited higher and lesser vertical impulse exerted at hands than feet immersed and emerged (e.g. vertical handgrip, 0.13, 0.15 N/BW.s, respectively). Variation with feet emerged and hands on the lowest horizontal handgrip depicted shorter horizontal (0.23, 0.26 m) and vertical CM positioning at flight (0.16, 0.15 m) than the highest horizontal and vertical handgrip, respectively. Start variations have not affected 15-m time. Variations with feet partially or totally emerged depicted advantages, but focusing on the entry and underwater biomechanics is relevant for a shorter start time.  相似文献   

Supporting computer-mediated learning: A case study in online staff development and classroom learning environment assessment     

Luis Miguel Villar Angulo  Olga María Alegre de la Rosa 《Learning Environments Research》2008,11(3):211-226

The rapid growth of online learning has led to the development of staff inservice evaluation models that are geared towards improving degree programs. Based on best practices in student online assessment, the Online Faculty Development and Classroom Learning Environment Assessment course was designed to serve the dual purpose of staff development and classroom learning environment assessment. Results of analyses showed that the course maximised the potential of online staff development for encouraging staff to reflect on Curriculum and Teaching Capacities (CTC). Implications are discussed in terms of emphasising the process of online CTC learning and incorporating perspectives to capture a comprehensive view of staff teaching attitudes and their association with student perceptions of the classroom learning environment.  相似文献