Proofs produced by secondary school students learning geometry in a dynamic computer environment     

Ramón Marrades  Ángel Gutiérrez 《Educational Studies in Mathematics》2000,44(1-2):87-125

As a key objective, secondary school mathematics teachers seek to improve the proof skills of students. In this paper we present an analytic framework to describe and analyze students' answers to proof problems. We employ this framework to investigate ways in which dynamic geometry software can be used to improve students' understanding of the nature of mathematical proof and to improve their proof skills. We present the results of two case studies where secondary school students worked with Cabri-Géeomèetre to solve geometry problems structured in a teaching unit. The teaching unit had theaims of: i) Teaching geometric concepts and properties, and ii) helping students to improve their conception of the nature of mathematical proof and to improve their proof skills. By applying the framework defined here, we analyze students' answers to proof problems, observe the types of justifications produced, and verify the usefulness of learning in dynamicgeometry computer environments to improve students' proof skills.  相似文献   

Geological risk assessment for cultural heritage conservation in karstic caves     

Eneko Iriarte  Miguel Ángel Sánchez  Alberto Foyo  Carmen Tomillo 《Journal of Cultural Heritage》2010,11(3):250-258

The increasing awareness of some local and international authorities has promoted the appearance of new legislation and the rising of research works focused in the prevention of damage to the cultural heritage in karstic caves. Nevertheless, karstic areas usually imply complex studies, and a universal methodology is very difficult to establish. This work exposes the basic methodology for the geological risk assessment in archaeological site and/or rock art bearing karstic caves getting a strategy that provides flexibility to adjust specific methods according to the conditions of different cases. The integrated use of basic geological (mapping, petrology, stratigraphy…) and geotechnical (rock mass quality analytical methods and indexes) techniques used in engineering geology is proposed. Those techniques permit the geological characterization of the rock mass, the hazard identification and the analysis and the geological risk assessment of the research area. Obtained geological risk areas could be included in protection areas that could be used as the basis for the selection of the areas where further investigations and the application of prevention/mitigation measures would have a better cost/benefit ratio. The geological risk should be considered together with other type risk evaluations in order to define effective protection areas.  相似文献   

Identity and Otherness: Maghribi Images in the Historiography about Alfonso XI of Castile (1311–1350)     

Miguel Ángel Manzano Rodríguez 《Al-Masaq: Islam & the Medieval Mediterranean》2017,29(1):1-12

This work studies the information that the historiography on King Alfonso XI of Castile offers on the Marīnid dynasty of Fes. In spite of the confrontation between the two states in the thirteenth and fourteenth centuries for the control of the Strait of Gibraltar and the southern part of Andalusia, the Alfonsine texts (the Crónica del Rey don Alfonso el Onceno, the Gran Crónica de Alfonso XI and, to a lesser extent, the Poema of Alfonso Onceno) attempt to reconstruct the history of the rival sultanate through a verifiable and rigorous approach comparing with Arab sources from that period. In this regard, their ideological conception moves away from the usual stereotypes, which are generally negative in the way they portray the other, i.e. the Maghribi opponent. In contrast, Alfonsine historiography assumes the empathetic portrayal of the identity values of the rival as part of the task of the historian, and uses the history and deeds of the adversaries to highlight the victory of the Castilian monarch over them.  相似文献   

Exploring the effects of substituting basketball players in high-level teams     

Miguel-Ángel Gómez  Roberto Silva  Alberto Lorenzo  Rasa Kreivyte  Jaime Sampaio 《Journal of sports sciences》2017,35(3):247-254

Substituting basketball players during competition is a key process to optimise collective performance. Available research on this topic is scarce, probably due to the difficulty in isolating these effects; thus, the aim of this study was to identify the temporal effects of substitutions in basketball (Spanish professional basketball league). The sample was composed of 1118 substitutions gathered from 21 basketball games. The analysed variables were coach-controlled (player and team’s personal fouls, player in and player out roles, player’s in and out minutes on-court and timeout situation); on-court (foul committed, free throws, 2- and 3-point field-goal effectiveness) and situational variables (scoreline, quality of opposition, game location and game quarter). The results showed positive scoring performances after the substitution for all the analyses. During the first quarter, there were significant effects for fouls committed, scoreline and game location after the substitution. The player’s out personal fouls, free-throw effectiveness, player in, minutes on-court player in, timeout situation and 3-point field-goal effectiveness were significant during the second quarter. The team’s personal fouls, game location, and scoreline were identified as important in the third quarter. The fourth quarter did not show significant effects on the independent variables. Current findings allow optimising coaches’ plans and team management of on-court and bench players throughout the game.  相似文献   

Sprint kayaking and canoeing performance prediction based on the relationship between maturity status,anthropometry and physical fitness in young elite paddlers     

Daniel López-Plaza  Fernando Alacid  José María Muyor  Pedro Ángel López-Miñarro 《Journal of sports sciences》2017,35(11):1083-1090

This study aimed to identify the maturity-related differences and its influence on the physical fitness, morphological and performance characteristics of young elite paddlers. In total, 89 kayakers and 82 canoeists, aged 13.69 ± 0.57 years (mean ± s), were allocated in three groups depending on their age relative to the age at peak height velocity (pre-APHV, circum-APHV and post-APHV) and discipline (kayak and canoe). Nine anthropometric variables, a battery of four physical fitness tests (overhead medicine ball throw, countermovement jump, sit-and-reach test and 20 m multistage shuttle run test) and three specific performance tests (1000, 500 and 200 m) were assessed. Both disciplines presented significant maturity-based differences in all anthropometric parameters (except for fat and muscle mass percentage), overhead medicine ball throw and all performance times (pre > circum > post; P < 0.05). Negative and significant correlations (P < 0.01) were detected between performance times, chronological age and anthropometry (body mass, height, sitting height and maturity status), overhead medicine ball throw and sit and reach for all distances. These findings confirm the importance of maturity status in sprint kayaking and canoeing since the more mature paddlers were also those who revealed largest body size, physical fitness level and best paddling performance. Additionally, the most important variables predicting performance times in kayaking and canoeing were maturity status and chronological age, respectively.  相似文献   

Circadian rhythm effect on physical tennis performance in trained male players     

Álvaro López-Samanes  Diego Moreno-Pérez  José L. Maté-Muñoz  Raúl Domínguez  Jesús G. Pallarés  Ricardo Mora-Rodriguez 《Journal of sports sciences》2017,35(21):2121-2128

To determine the effect of circadian rhythm on neuromuscular responses and kinematics related to physical tennis performance, after a standardised warm-up, 13 highly competitive male tennis players were tested twice for serve velocity/accuracy (SVA), countermovement vertical jump (CMJ), isometric handgrip strength (IS), agility T-test (AGIL) and a 10-m sprint (10-m RUN). In a randomised, counter-balance order, tennis players underwent the test battery twice, either in the morning (i.e., AM; 9:00 h) and in the afternoon (i.e., PM; 16:30 h). Paired t-tests were used to analyse differences due to time-of-day in performance variables. Comparison of morning versus afternoon testing revealed that SVA (168.5 ± 6.5 vs. 175.2 ± 6.1 km · h^?1; P = 0.003; effect size [ES] = 1.07), CMJ (32.2 ± 0.9 vs. 33.7 ± 1.1 cm; P = 0.018; ES = 1.46), AGIL (10.14 ± 0.1 vs. 9.91 ± 0.2 s; P = 0.007; ES = 1.23) and 10-m RUN time (1.74 ± 0.1 vs. 1.69 ± 0.1 s; P = 0.021; ES = 0.67) were significantly blunted during the morning testing. However, IS was not affected by time-of-day (P = 0.891). Thus, tennis performance may be reduced when competing in the morning in comparison to early evening. Therefore, coaches and tennis players should focus on schedule the SVA, power, speed and agility training sessions in the afternoon.  相似文献   

Measuring allocative efficiency in Cultural Economics: the case of “Fundación Princesa de Asturias” (The Princess of Asturias Foundation)     

Víctor Fernández-Blanco  Ana Rodríguez-Álvarez 《Journal of Cultural Economics》2018,42(1):91-110

The literature on Cultural Economics provides us with some examples for the measurement of technical efficiency. However, there are few case studies dedicated to the analysis of allocative efficiency. The aim of this paper is to fill this gap by incorporating a methodology that analyses both technical and allocative efficiency. We use the Shephard’s distance function, particularly suitable when affronted with non-profit-making firms or institutions that are not interested in cost minimization. As an empirical application, we analyse the efficiency of Fundación Princesa de Asturias (PAF), a Spanish non-governmental organization devoted to promoting the cultural, scientific and humanistic values of universal heritage, the period of study being 1988–2012. Our findings suggest that PAF could have used 7% less inputs to achieve the same level of output. On the other hand, we have found allocative inefficiency. Concretely, the input for other expenditures appears to have been over-utilized in relation to both the inputs for labour and current assets, with labour in turn being over-utilized in relation to current assets. Moreover, our results indicate that both technical and allocative efficiency have clearly improved during the period analysed. In summary, our empirical application shows how distance function methodology can be successfully implemented to measure allocative efficiency in cultural firms and institutions.  相似文献   

Aerobic fitness and academic achievement: A systematic review and meta-analysis     

Celia Álvarez-Bueno  Charles H Hillman  Mairena Sánchez-López  Diana P. Pozuelo-Carrascosa  Vicente Martínez-Vizcaíno 《Journal of sports sciences》2020,38(5):582-589

ABSTRACT

This study aims to quantify the association between aerobic fitness and academic achievement, and determine how different aerobic fitness tests and individual demographic characteristics may modify this association. It includes 41 cross-sectional and 7 longitudinal studies focusing on children and adolescents, from MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Cochrane Database and Web of Science. Pooled effect sizes (ES) were estimated for the association between aerobic fitness and specific domains of academic achievement. Subgroup analyses and meta-regressions were based on aerobic fitness tests and demographic characteristics. The ES for the association between aerobic fitness with language/reading-skills, mathematics-related skills and composite scores, were 0.23 (95% CI: 0.12; 0.34); 0.27 (95% CI: 0.19; 0.36) and 0.28 (95% CI: 0.12; 0.45), respectively. Subgroup analyses by aerobic fitness test modified these associations; additionally, analyses by sex or age showed differences between boys and girls as well as between children and adolescents. Finally, meta-regressions revealed a slight effect of body mass index on these associations. Cardiorespiratory fitness is positively associated with academic achievement. Associations were dependent on demographic and aerobic fitness test characteristics, being stronger in boys than in girls, and in children than in adolescents.

Systematic review registration: PROSPERO CRD42017069677  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   

What counts as science? Expansive learning actions for teaching and learning science with bilingual children     

Martínez-Álvarez  Patricia 《Cultural Studies of Science Education》2019,14(4):799-837

Cultural Studies of Science Education - Science education should help children acquire sophisticated understandings about science, how it is done, and how they can be scientists. Consequently,...  相似文献