The terminal velocity has been widely used in extensive fields, but the complexity of drag coefficient expression leads to the calculation of terminal velocity in transitional flow （1 〈 Re ≤ 1000） with much more d...The terminal velocity has been widely used in extensive fields, but the complexity of drag coefficient expression leads to the calculation of terminal velocity in transitional flow （1 〈 Re ≤ 1000） with much more difficulty than those in laminar flow （Re ≤ 1） and turbulent flow （Re ≥ 1000）. This paper summarized and compared 24 drag coefficient correlations, and developed an expression for calculating the terminal velocity in transitional flow, and also analyzed the effects of particle density and size, fluid density and viscosity on terminal velocity. The results show that 19 of 24 previously published correlations for drag coefficient have good prediction performance and can be used for calculating the terminal velocity in the entire transitional flow with higher accuracy. Adapting two dimensionless parameters （w＊, d＊）, a proposed explicit correlation, w＊=-25.68654 × exp （-d＊/77.02069）＋ 24.89826, is attained in transitional flow with good performance, which is helpful in calculating the terminal velocity.展开更多
The paper regards young adult literature (YAL) as a dissolved-point between localization and globalization of English teaching, and discusses (1) whether the western YAL teaching theories, methods and teaching materia...The paper regards young adult literature (YAL) as a dissolved-point between localization and globalization of English teaching, and discusses (1) whether the western YAL teaching theories, methods and teaching materials accord with Chinese actual situation well or not, (2) if YAL reading is an effective way for creating life-long readers, and (3) why and how to teach YAL. Based on YAL learning and teaching practice, the author uses Soter's YAL theories and alternative approaches, try to clarify three relationships: YA-YAL; adult literature-YAL-children's literature; classics-YAL balance. And put forward three ways for books selection and three reading patterns to YAL teaching.展开更多
文摘The terminal velocity has been widely used in extensive fields, but the complexity of drag coefficient expression leads to the calculation of terminal velocity in transitional flow （1 〈 Re ≤ 1000） with much more difficulty than those in laminar flow （Re ≤ 1） and turbulent flow （Re ≥ 1000）. This paper summarized and compared 24 drag coefficient correlations, and developed an expression for calculating the terminal velocity in transitional flow, and also analyzed the effects of particle density and size, fluid density and viscosity on terminal velocity. The results show that 19 of 24 previously published correlations for drag coefficient have good prediction performance and can be used for calculating the terminal velocity in the entire transitional flow with higher accuracy. Adapting two dimensionless parameters （w＊, d＊）, a proposed explicit correlation, w＊=-25.68654 × exp （-d＊/77.02069）＋ 24.89826, is attained in transitional flow with good performance, which is helpful in calculating the terminal velocity.
文摘The paper regards young adult literature (YAL) as a dissolved-point between localization and globalization of English teaching, and discusses (1) whether the western YAL teaching theories, methods and teaching materials accord with Chinese actual situation well or not, (2) if YAL reading is an effective way for creating life-long readers, and (3) why and how to teach YAL. Based on YAL learning and teaching practice, the author uses Soter's YAL theories and alternative approaches, try to clarify three relationships: YA-YAL; adult literature-YAL-children's literature; classics-YAL balance. And put forward three ways for books selection and three reading patterns to YAL teaching.
