In the process of rock breaking, the conical pick bears great cutting force and wear, as a result, high-pressure water jet technology is used to assist with cutting. However, the effect of the water jet position has n...In the process of rock breaking, the conical pick bears great cutting force and wear, as a result, high-pressure water jet technology is used to assist with cutting. However, the effect of the water jet position has not been studied for rock breaking using a pick. Therefore, the models of rock breaking with different configuration modes of the water jet are established based on SPH combined with FEM. The effect of the water jet pressure, distance between the jet and the pick bit, and cutting depth on the rock breaking performance as well as a comparison of the tension and compression stress are studied via simulation; the simulation results are verified by experiments. The numerical and experimental results indicate that the decrease in the rates of the pick force obviously increases from 25 MPa to 40 MPa, but slowly after 40 MPa, and the optimal distance between the jet and the pick bit is 2 mm under the JFP and JSP modes. The JCP mode is proved the best, followed by the modes of JRP and JFP, and the worst mode is JSP. The decrease in the rates of the pick force of the JCP, JRP, JFP, and JSP modes are up to 30.96%, 28.96%, 33.46%, 28.17%, and 25.42%, respectively, in experiment. Moreover, the JSP mode can be regarded as a special JFP model when the distance between the pick-tip and the jet impact point is 0 mm. This paper has a dominant capability in introducing new numerical and experimental method for the study of rock breaking assisted by water jet and electing the best water jet position from four different configuration modes.展开更多
Self-modeling(SM)and self-control(SC)feedback can be presented as two solutions for learning improvement.Therefore,the aim of the present study was to investigate the effects of SM and SC feedback on 100-m freestyle p...Self-modeling(SM)and self-control(SC)feedback can be presented as two solutions for learning improvement.Therefore,the aim of the present study was to investigate the effects of SM and SC feedback on 100-m freestyle performance of professional swimmers and waterpolo players.25 elite male swimmers and waterpolo players,were randomly assigned to four groups:swimmer group with SM,swimmer group with SM and SC feedback,waterpolo players group with SM,and waterpolo players group with SM and SC feedback.100-m freestyle times and performance were recorded.SM and SC feedback for the participants were utilized at the acquisition stage.The device used included a Lenovo B570 laptop and an Exilim ZR200 canon camcorder.SM and SC feedback presented to the swimmers and waterpolo players led to improved speed and results,and the effect of presenting SM with SC feedback to swimmers had better results.In conclusion,the present study indicates that SC modeling of watching video is a suitable method for professional swimmers.Water polo trainers can also use SM and SC feedback to enhance their players'swimming technique.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.51375478)the Fundamental Research Funds for the Central Universities,China(Grant No.2014ZDPY12)the Priority Academic Program Development of Jiangsu High Education Institute of China
文摘In the process of rock breaking, the conical pick bears great cutting force and wear, as a result, high-pressure water jet technology is used to assist with cutting. However, the effect of the water jet position has not been studied for rock breaking using a pick. Therefore, the models of rock breaking with different configuration modes of the water jet are established based on SPH combined with FEM. The effect of the water jet pressure, distance between the jet and the pick bit, and cutting depth on the rock breaking performance as well as a comparison of the tension and compression stress are studied via simulation; the simulation results are verified by experiments. The numerical and experimental results indicate that the decrease in the rates of the pick force obviously increases from 25 MPa to 40 MPa, but slowly after 40 MPa, and the optimal distance between the jet and the pick bit is 2 mm under the JFP and JSP modes. The JCP mode is proved the best, followed by the modes of JRP and JFP, and the worst mode is JSP. The decrease in the rates of the pick force of the JCP, JRP, JFP, and JSP modes are up to 30.96%, 28.96%, 33.46%, 28.17%, and 25.42%, respectively, in experiment. Moreover, the JSP mode can be regarded as a special JFP model when the distance between the pick-tip and the jet impact point is 0 mm. This paper has a dominant capability in introducing new numerical and experimental method for the study of rock breaking assisted by water jet and electing the best water jet position from four different configuration modes.
文摘Self-modeling(SM)and self-control(SC)feedback can be presented as two solutions for learning improvement.Therefore,the aim of the present study was to investigate the effects of SM and SC feedback on 100-m freestyle performance of professional swimmers and waterpolo players.25 elite male swimmers and waterpolo players,were randomly assigned to four groups:swimmer group with SM,swimmer group with SM and SC feedback,waterpolo players group with SM,and waterpolo players group with SM and SC feedback.100-m freestyle times and performance were recorded.SM and SC feedback for the participants were utilized at the acquisition stage.The device used included a Lenovo B570 laptop and an Exilim ZR200 canon camcorder.SM and SC feedback presented to the swimmers and waterpolo players led to improved speed and results,and the effect of presenting SM with SC feedback to swimmers had better results.In conclusion,the present study indicates that SC modeling of watching video is a suitable method for professional swimmers.Water polo trainers can also use SM and SC feedback to enhance their players'swimming technique.
