Following a cross-sectional design, the present study investigated the acquisition of English requests by Chinese learners at three proficiency levels with open production questionnaires. It was found that L2 linguist...Following a cross-sectional design, the present study investigated the acquisition of English requests by Chinese learners at three proficiency levels with open production questionnaires. It was found that L2 linguistic proficiency, L1 pragmatic transfer and classroom instruction have interactive effect on learners' L2 pragmatic development. A range of acquisitional features were found-learners' employment of direct request strategies decreased, the employment of conventionally indirect strategies increased and the number and variety of internal modifiers increased with the increase of proficiency. It was also found that L1 pragmatic transfer worked on various aspects of learners' requestive behavior and that inadequate or inappropriate input from the teaching materials and the EFL classroom arrangements might constrain their pragmatic development.展开更多
Postbuckling behavior of the 3D braided rectangular plates subjected to uniaxial compression combined with transverse loads in thermal environments is presented.Based on a micro-macro-mechanical model,a 3D braided com...Postbuckling behavior of the 3D braided rectangular plates subjected to uniaxial compression combined with transverse loads in thermal environments is presented.Based on a micro-macro-mechanical model,a 3D braided composite may be treated as a cell system and the geometry of each cell is deeply dependent on its position in the cross-section of the plate.The material properties of the epoxy are expressed as a linear function of temperature.Uniform,linear and nonlinear temperature distributions through the thickness are involved.The lateral pressure(three types of transverse loads,i.e.transverse uniform load;transverse patch load over a central area;and transverse sinusoidal load)is first converted into an initial deflection and the initial geometric imperfection of the plate is taken into account.The governing equations are based on Reddy’s higher-order shear deformation plate theory with a von Kármán-type of kinematic nonlinearity.Two cases of the in-plane boundary conditions are also taken into account.A perturbation technique is employed to determine buckling loads and postbuckling equilibrium paths of simply supported 3D braided rectangular plates.The results reveal that the temperature rise,geometric parameter,fiber volume fraction,braiding angle,the character of the in-plane boundary conditions and different types of initial transverse loads have a significant effect on the buckling and postbuckling behavior of the braided composite plates.展开更多
文摘Following a cross-sectional design, the present study investigated the acquisition of English requests by Chinese learners at three proficiency levels with open production questionnaires. It was found that L2 linguistic proficiency, L1 pragmatic transfer and classroom instruction have interactive effect on learners' L2 pragmatic development. A range of acquisitional features were found-learners' employment of direct request strategies decreased, the employment of conventionally indirect strategies increased and the number and variety of internal modifiers increased with the increase of proficiency. It was also found that L1 pragmatic transfer worked on various aspects of learners' requestive behavior and that inadequate or inappropriate input from the teaching materials and the EFL classroom arrangements might constrain their pragmatic development.
基金supported by the National Natural Science Foundation of China(Grant Nos.50909059,51279222)
文摘Postbuckling behavior of the 3D braided rectangular plates subjected to uniaxial compression combined with transverse loads in thermal environments is presented.Based on a micro-macro-mechanical model,a 3D braided composite may be treated as a cell system and the geometry of each cell is deeply dependent on its position in the cross-section of the plate.The material properties of the epoxy are expressed as a linear function of temperature.Uniform,linear and nonlinear temperature distributions through the thickness are involved.The lateral pressure(three types of transverse loads,i.e.transverse uniform load;transverse patch load over a central area;and transverse sinusoidal load)is first converted into an initial deflection and the initial geometric imperfection of the plate is taken into account.The governing equations are based on Reddy’s higher-order shear deformation plate theory with a von Kármán-type of kinematic nonlinearity.Two cases of the in-plane boundary conditions are also taken into account.A perturbation technique is employed to determine buckling loads and postbuckling equilibrium paths of simply supported 3D braided rectangular plates.The results reveal that the temperature rise,geometric parameter,fiber volume fraction,braiding angle,the character of the in-plane boundary conditions and different types of initial transverse loads have a significant effect on the buckling and postbuckling behavior of the braided composite plates.
