腾空时间的长与短是竞走技术训练成败的关键之一,也是竞走裁判员观察的难点。本文采用文献资料法、运动生物力学方法和灰色系统理论方法,对1995年国际田联/锐步世界杯竞赛女子10 km、男子20 km和男子50 km 3个项目前8名运动员的技术进...腾空时间的长与短是竞走技术训练成败的关键之一,也是竞走裁判员观察的难点。本文采用文献资料法、运动生物力学方法和灰色系统理论方法,对1995年国际田联/锐步世界杯竞赛女子10 km、男子20 km和男子50 km 3个项目前8名运动员的技术进行了定量和定性分析研究。结果表明,在24项运动学参数中。展开更多
G821.19 9904456对我国部分现役竞走运动员技术分析=TheanalysIs of the shIlls of elIre ChInese maleFace walkers[刊,中,A]/林宏伟,倪晓萍,邱学志//体育与科学.-1999.-20(3).-24-27,39图1表6参2(XG)竞走//技术//腿部动作//支撑//膝关...G821.19 9904456对我国部分现役竞走运动员技术分析=TheanalysIs of the shIlls of elIre ChInese maleFace walkers[刊,中,A]/林宏伟,倪晓萍,邱学志//体育与科学.-1999.-20(3).-24-27,39图1表6参2(XG)竞走//技术//腿部动作//支撑//膝关节//角度依据高速摄影及国际田联竞走规则,对第5届全国大学生运动会男子20公里竞走比赛的运动员进行技术分析,结论如下:1、摆动腿摆动时间长于支撑腿支撑时间;2、摆动腿方向和线路应低平,增加髋绕入体垂直轴的扭转幅度;3、应控制摆动腿的膝角的最小角度;4、为了减少摆动时间应提高髋和踝的水平速度:5、减少后蹬角提高重心水平移动速度,提高单步效率。展开更多
By using an instrumented impact pendulum, the force versus time curves of 7075-T651 aluminum welds were obtained from standard Charpy-V samples. Considering the force-time curves and constant impact velocity, the frac...By using an instrumented impact pendulum, the force versus time curves of 7075-T651 aluminum welds were obtained from standard Charpy-V samples. Considering the force-time curves and constant impact velocity, the fracture energies for different zones were quantified. A fracture energy improvement for the HAZ(33.6 J) was observed in comparison with the weld metal(7.88 J), and base metal(5.37 J and 7.37 J for longitudinal and transverse directions, respectively). This toughness increment was attributed to the microstructural transformation caused by the thermodynamic instability of η′ precipitates during the welding. Fracture energy for weld metal was higher than that for base metal, probably due to pores created during solidification. Regarding the dynamic yielding force obtained from the force-time curves, an approximation to the dynamic yield strength for weld, HAZ and base metal was determined. Fracture surfaces revealed an intergranular failure for base metal in longitudinal direction, whereas a predominately brittle failure(cleavage) with some insights of ductile characteristics was observed for the transverse direction. In contrast, a ductile failure was observed for weld metal and HAZ.展开更多
Under condition of four potential fields, equations of motion and fluctuations in imaginary time are utilized to analytically derive the basic and fluctuating periodic instantons. It is shown that the basic instantons...Under condition of four potential fields, equations of motion and fluctuations in imaginary time are utilized to analytically derive the basic and fluctuating periodic instantons. It is shown that the basic instantons satisfy the elliptic or simple pendulum equations and their solutions are Jacobi elliptic functions, and fluctuating periodic instantons satisfy the Lam′e equation and their solutions are Lame functions. These results indicate that there exists the common solution family for different potential fields which are called the super-symmetry family.展开更多
文摘G821.19 9904456对我国部分现役竞走运动员技术分析=TheanalysIs of the shIlls of elIre ChInese maleFace walkers[刊,中,A]/林宏伟,倪晓萍,邱学志//体育与科学.-1999.-20(3).-24-27,39图1表6参2(XG)竞走//技术//腿部动作//支撑//膝关节//角度依据高速摄影及国际田联竞走规则,对第5届全国大学生运动会男子20公里竞走比赛的运动员进行技术分析,结论如下:1、摆动腿摆动时间长于支撑腿支撑时间;2、摆动腿方向和线路应低平,增加髋绕入体垂直轴的扭转幅度;3、应控制摆动腿的膝角的最小角度;4、为了减少摆动时间应提高髋和踝的水平速度:5、减少后蹬角提高重心水平移动速度,提高单步效率。
基金CONACy T (project CB 177834)SIP-IPN for the funds given to conduct this research
文摘By using an instrumented impact pendulum, the force versus time curves of 7075-T651 aluminum welds were obtained from standard Charpy-V samples. Considering the force-time curves and constant impact velocity, the fracture energies for different zones were quantified. A fracture energy improvement for the HAZ(33.6 J) was observed in comparison with the weld metal(7.88 J), and base metal(5.37 J and 7.37 J for longitudinal and transverse directions, respectively). This toughness increment was attributed to the microstructural transformation caused by the thermodynamic instability of η′ precipitates during the welding. Fracture energy for weld metal was higher than that for base metal, probably due to pores created during solidification. Regarding the dynamic yielding force obtained from the force-time curves, an approximation to the dynamic yield strength for weld, HAZ and base metal was determined. Fracture surfaces revealed an intergranular failure for base metal in longitudinal direction, whereas a predominately brittle failure(cleavage) with some insights of ductile characteristics was observed for the transverse direction. In contrast, a ductile failure was observed for weld metal and HAZ.
基金Supportted by the National Natural Science Foundation of China under Grant No.40975027
文摘Under condition of four potential fields, equations of motion and fluctuations in imaginary time are utilized to analytically derive the basic and fluctuating periodic instantons. It is shown that the basic instantons satisfy the elliptic or simple pendulum equations and their solutions are Jacobi elliptic functions, and fluctuating periodic instantons satisfy the Lam′e equation and their solutions are Lame functions. These results indicate that there exists the common solution family for different potential fields which are called the super-symmetry family.
