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Shale oil reservoirs are usually developed by horizontal wells completed with multi-stage hydraulic fractures. The fracture interference between clusters in a single stage and between consecutive stages has an impact on the stimulation quality in terms of fracture geometries and fracture widths. This study introduces a non-planar hydraulic fracture model based on the extended finite element method and its use in quantifying the effects of relevant parameters on multi-stage fracture quality in a realistic shale oil scenario. The numerical model is validated with field diagnostics based on vertical seismic profiling. Relevant parameters including stress contrast, fracturing fluid viscosity, cluster density, and fracturing in consecutive stages are quantitatively analyzed in the numerical study. Results show that effects of stress contrast on fracture quality are greater than those of fracturing fluid viscosity, while the effects are more significant in outer fractures instead of the inner fracture. Denser cluster design leads to greater inhibition for the growth of inner fractures which eventually divert them transversely. In fracturing for consecutive stages, the opening of fractures in the subsequent stages is inhibited and the fracture geometries are also altered by the inter-stage interference caused by the previous stage. Based on field data and numerical modeling, this study identifies key parameters and quantifies their effects on inter-fracture and inter-stage interference in multi-stage hydraulic fracturing in horizontal wells. [ABSTRACT FROM AUTHOR]

Acquiring scientific knowledge about physical activity is necessary for students to become physically literate for life, and cognitive engagement and cognitive levels of tasks are two components that often determine the effectiveness of knowledge acquisition. This study sought to determine the extent to which students' cognitive engagement in descriptive, relational and reasoning learning tasks contributed to their acquisition of knowledge and the extent to which cognitive engagement on lower-level tasks contributed to higher-level tasks (e.g. descriptive to relational to reasoning). The performance of students in descriptive, relational and reasoning tasks and knowledge acquisition was measured in 992 middle school students in active physical education lessons. The results revealed that students' performance in relational (regression coefficient = 0.09, p < 0.01) and reasoning (regression coefficient = 0.06, p < 0.01) tasks directly contributed to their acquisition of knowledge (R2 = 0.14). The performance of students in descriptive tasks indirectly contributed to knowledge acquisition through influencing their performance in relational and reasoning tasks (indirect effect = 0.09, p < 0.01). [ABSTRACT FROM AUTHOR]

There are substantial differences between the Chinese and US education systems. One difference is in the design and use of assessment due to differences in educational policies. This study described the differences in student learning outcomes, instructional approaches, and learner motivation in physical education as consequences of the policies in the two countries. Objectively measured data on skill and knowledge achievement and instructional procedures, and self-report data on student motivation were collected from a random sample of 870 students in 24 whole classes from eight Chinese middle schools and 1213 students in 39 classes from 15 US middle schools. Multivariate analyses of variance on class means revealed that Chinese students outperformed their US peers in skills, perhaps because skills were part of the high-stake tests for advancement in schooling. They were outperformed by the US students in a fitness knowledge test, perhaps because knowledge was not part of the high-stake tests. The differences in learning outcomes, instructional approaches, and motivation seem to suggest strong differentiated influences from the two countries' respective educational environments and assessment policies. [ABSTRACT FROM AUTHOR]

In physical education, it has become necessary for children to learn kinesiological knowledge for understanding the benefits of physical activity and developing a physically active lifestyle. This study was conducted to determine the extent to which cognitive assignments about healthful living and fitness contributed to knowledge growth on cardiorespiratory fitness and health. Fourth grade students (N = 616) from 15 randomly sampled urban elementary schools completed 34 cognitive assignments related to the cardiorespiratory physical activities they were engaged in across 10 lessons. Performance on the assignments were analyzed in relation to their knowledge gain measured using a standardized knowledge test. A multivariate discriminant analysis revealed that the cognitive assignments contributed to knowledge gain but the contribution varied assignment by assignment. A multiple regression analysis indicated that students’ assignment performance by lesson contributed positively to their knowledge growth scores. A content analysis based on the constructivist learning framework showed that observing–reasoning assignments contributed the most to knowledge growth. Analytical and analytical–application assignments contributed less than the constructivist theories would predict. [ABSTRACT FROM PUBLISHER]

Motivation to learn is a disposition developed through exposure to learning opportunities. Guided by the expectancy-value theory of Eccles and Wigfield (1995), this study examined the extent to which expectancy belief and task value influenced elementary school students’ physical activity and knowledge learning in physical education (PE). Students (N = 753) from 15 US public schools contributed student-level and class-level data. With a 2-level design, the data were analyzed using hierarchical linear modeling. Physical activity (t = 3.18; p < .01) positively predicted fitness knowledge. Attainment value (i.e. perception of importance) as the only expectancy-value construct, significantly predicted fitness knowledge (t = 3.07; p < .01), when physical activity was held constant. As the physical activity intensity increased, the positive prediction of attainment value to knowledge attenuated and then turned negative (t = –3.10; p < .01). The study indicated that although a physically-active context helps students to make sense of fitness knowledge, a vigorous context shifts their motivation away from cognitive learning, toward physical participation. To resolve the difficulty of attaining learning objectives both physically and cognitively, PE teachers may want to maintain an active learning context with moderate physical intensity. Future research should address the effect of learner motivation on dual or multiple learning outcomes in PE. [ABSTRACT FROM AUTHOR]