The indigenous worldview of Yupiaq culture: Its scientific nature and relevance to the practice and teaching of science

Is science an invention of European thought, or have legitimate scientific bodies of knowledge and scientific ways of thinking emerged separately in other cultures? Can indigenous knowledge systems contribute to contemporary science teaching? Here we describe evidence from the Yupiaq culture in southwestern Alaska which demonstrates a body of scientific knowledge and epistemology that differs from that of Western science. We contend that drawing from Yupiaq culture, knowledge, and epistemology can provide not only a more culturally relevant frame of reference for teaching science concepts to Yupiaq students, but also a potentially valuable context for more effectively addressing many of the recommendations of U.S. science education reform initiatives. © 1998 John Wiley & Sons, Inc. J Res Sci Teach 35: 133–144, 1998.     

The relationship between homework and the academic progress of children in Spain during compulsory elementary education: A twin fixed-effects approach

Homework has traditionally been considered positive for students’ academic achievement, to the extent that it makes children more responsible while learning. Nevertheless, making students do a large amount of homework has been one of the most criticised practices in recent years. Parental associations have long held the view that Spanish elementary school pupils spend too much time on homework. This situation is so alarming that it has recently caused a ‘homework strike’, which has been supported by many children's parents. Furthermore, being assigned an excessive amount of homework is a serious problem which extends well beyond Spain. In light of this context, this article aims to provide new evidence on the relationship between homework and academic performance. To carry out this research, rich longitudinal census data, together with a twin fixed-effects approach and value-added models, have been used. In this way, we can control for variables that are the same within twins, allowing us to generate a better understanding of the association between homework time and primary children's academic achievement. Our main finding is that homework is not associated with young people's academic achievement (at least within this specific country context).     

Biomechanics,energetics and coordination during extreme swimming intensity: effect of performance level

The present study aimed to examine how high- and low-speed swimmers organise biomechanical, energetic and coordinative factors throughout extreme intensity swim. Sixteen swimmers (eight high- and eight low-speed) performed, in free condition, 100-m front crawl at maximal intensity and 25, 50 and 75-m bouts (at same pace as the previous 100-m), and 100-m maximal front crawl on the measuring active drag system (MAD-system). A 3D dual-media optoelectronic system was used to assess speed, stroke frequency, stroke length, propelling efficiency and index of coordination (IdC), with power assessed by MAD-system and energy cost by quantifying oxygen consumption plus blood lactate. Both groups presented a similar profile in speed, power output, stroke frequency, stroke length, propelling efficiency and energy cost along the effort, while a distinct coordination profile was observed (F_{(3, 42)} = 3.59, P = 0.04). Speed, power, stroke frequency and propelling efficiency (not significant, only a tendency) were higher in high-speed swimmers, while stroke length and energy cost were similar between groups. Performing at extreme intensity led better level swimmers to achieve superior speed due to higher power and propelling efficiency, with consequent ability to swim at higher stroke frequencies. This imposes specific constraints, resulting in a distinct IdC magnitude and profile between groups.     

Cognitive and language correlates of hyperlexia: evidence from children with autism spectrum disorders

Two studies were conducted to investigate the correlates of hyperlexia in Brazilian Portuguese-speaking children with the diagnosis of autism spectrum disorder (ASD). Study 1 involved 3 groups of school age children individually matched for word reading ability: 6 ASD hyperlexic children, 6 ASD non-hyperlexic children, and 6 typically developing children. Study 2 involved 2 ASD preschool hyperlexic boys, and a group of 21 typical children of similar word reading ability. In both studies, participants were administered several reading measures as well as measures of cognitive and linguistic abilities that have been associated with variations in typical and dyslexic reading, namely, vocabulary, phonological processes, and rapid naming. Results suggest that ASD hyperlexic reading differs from both typical and ASD non-hyperlexic reading. In particular, they suggest that hyperlexics learn to compute letter-sound relations implicitly, on the basis of statistical learning. Although the hyperlexic children could read nonwords as well as the typical and the ASD non-hyperlexic children, they performed significantly worse than these groups of children on a letter-sound knowledge task. They also performed relatively poorly on a phonological awareness task. It is suggested that hyperlexics’ indifference to language as a meaningful, communicative device may be the key to their exceptionally good and precocious development of word reading ability.     

Activity optimization method in SPECT： A comparison with ROC analysisActivity optimization method in SPECT： A comparison with ROC analysis

A discriminant method for optimizing activity in nuclear medicine studies is validated by comparison with ROC （received operating characteristic）-curves. The method is tested in 21 single photon emission computerized tomography （SPECT）, performed with a cardiac phantom. Three different lesions （Lb L2 and L3） were placed in the myocardium-wall by pairs fbr each SPECT. Three activities （84, 37 or 18.5 MBq） of 99mTc were used as background. Linear discriminant analysis was used to select the parameters that characterize image quality among the measured variables in the images [（Background-to-Lesion （B/Li） and Signal-to-Noise （S/N） ratios）]. Two clusters with different image quality （P=0.021 ） were obtained. The ratios B/Lj, B/L2 and B/L3 are the parameters used to construct the function with 100% of cases correctly classified into the clusters. The value of 37 MBq was the lowest tested activity for which good results for the B/Li ratios were obtained. The result coincides with the applied ROC-analysis （r=0.89）.     

Analysis of the interplay between knowledge and performance management in industrial clusters

The concept of industrial clustering has been studied in-depth by policy makers and researchers from many fields, mainly due to the competitive advantages it may bring to regional economies. Companies often take part in collaborative initiatives with local partners while also taking advantage of knowledge spillovers to benefit from locating in a cluster. Thus, Knowledge Management (KM) and Performance Management (PM) have become relevant topics for policy makers and cluster associations when undertaking collaborative initiatives. Taking this into account, this paper aims to explore the interplay between both topics using a case study conducted in a collaborative network formed within a cluster. The results show that KM should be acknowledged as a formal area of cluster management so that PM practices can support knowledge-oriented initiatives and therefore make better use of the new knowledge created. Furthermore, tacit and explicit knowledge resulting from PM practices needs to be stored and disseminated throughout the cluster as a way of improving managerial practices and regional strategic direction.     

Physical activity and school recess time: Differences between the sexes and the relationship between children's playground physical activity and habitual physical activity

The aims of this study were: (1) to observe participation in moderate-to-vigorous physical activity (MVPA) during school recess periods; (2) to determine the relative importance of physical activity during recesses to overall daily physical activity; and (3) to examine differences in physical activity between the sexes during unstructured recess periods. The participants were 22 school children (10 boys, 12 girls) aged 8?–?10 years (mean = 8.9, s = 0.7) in the third and fourth grades. Daily totals for the physical activity variables were calculated by summing the values for each hour of 14?h of physical activity measurements (08:00 to 22:00?h). Recess times (minutes) were as follows: morning 10:30 to 11:00?h and afternoon 15:30 to 16:00?h. We did not differences between boys and girls in daily total accelerometer counts or the overall time spent in MVPA. However, girls were significantly (P <?0.05) more involved (38%) in MVPA during recess time than boys (31%). Participation in MVPA during recess contributes significantly more (P <?0.05) for girls (19%) than boys (15%) to the total amount of physical activity suggested by international health-related physical activity guidelines, while the percentage of time engaged in MVPA during recess time at school accounts for a small amount of the daily MVPA (6% for boys and 8% for girls). The results of this study suggest that school recess time is an important setting to promote MVPA and contributes to daily physical activity in young children, especially in girls.     

A real-time estimation and control scheme for induction motors based on sliding mode theory

In this paper a sliding mode position control for high-performance real-time applications of induction motors is developed. The design also incorporates a sliding mode rotor flux estimator in order to avoid the flux sensors. The proposed control scheme presents a low computational cost and therefore can be implemented easily in a real-time applications using a low cost Digital Signal Processor (DSP). The stability analysis of the observer and the controller, under parameter uncertainties and load torque disturbances, is provided using the Lyapunov stability theory. Finally simulated and experimental results show that the proposed controller with the proposed observer provides a good trajectory tracking and that this scheme is robust with respect to plant parameter variations and external load disturbances.     

Real time observer and control scheme for a wind turbine system based on a high order sliding modes

The introduction of advanced control algorithms may improve considerably the efficiency of wind turbine systems. This work proposes a high order sliding mode (HOSM) control scheme based on the super twisting algorithm for regulating the wind turbine speed in order to obtain the maximum power from the wind. A robust aerodynamic torque observer, also based on the super twisting algorithm, is included in the control scheme in order to avoid the use of wind speed sensors. The presented robust control scheme ensures good performance under system uncertainties avoiding the chattering problem, which may appear in traditional sliding mode control schemes. The stability analysis of the proposed HOSM observer is provided by means of the Lyapunov stability theory. Experimental results show that the proposed control scheme, based on HOSM controller and observer, provides good performance and that this scheme is robust with respect to system uncertainties and external disturbances.