Coordination pattern of baseball pitching among young pitchers of various ages and velocity levels     

Hsiu-Hui Chen  Chiang Liu  Wen-Wen Yang 《Journal of sports sciences》2016,34(17):1682-1690

This study compared the whole-body movement coordination of pitching among 72 baseball players of various ages and velocity levels. Participants were classified as senior, junior, and little according to their age, with each group comprising 24 players. The velocity levels of the high-velocity (the top eight) and low-velocity (the lowest eight) groups were classified according to their pitching velocity. During pitching, the coordinates of 15 markers attached to the major joints of the whole-body movement system were collected for analysis. Sixteen kinematic parameters were calculated to compare the groups and velocity levels. Principal component analysis (PCA) was conducted to quantify the coordination pattern of pitching movement. The results were as follows: (1) five position and two velocity parameters significantly differed among the age groups, and two position and one velocity parameters significantly differed between the high- and low-velocity groups. (2) The coordination patterns of pitching movement could be described using three components, of which the eigenvalues and contents varied according to age and velocity level. In conclusion, the senior and junior players showed greater elbow angular velocity, whereas the little players exhibited a wider shoulder angle only at the beginning of pitching. The players with high velocity exhibited higher trunk and shoulder rotation velocity. The variations among groups found using PCA and kinematics parameter analyses were consistent.  相似文献   

互相关测速虚拟仿真的实验方法     

蔡少川  施文康  毕浩然 《实验室研究与探索》2006,25(10):1197-1198,1207

介绍利用相关技术对运动物体速度进行测量的原理和实验方法,通过相关测速实验装置及其软件操作界面的介绍,进一步阐明“软件即仪器”的思想。  相似文献   

球坐标系中速度与加速度的转动参考系求法     

罗兴垅  罗颖 《赣南师范学院学报》2002,(3):28-30

应用转动参考系 ,给出了一种求解球坐标系中速度和加速度的简捷方法。该方法不仅图像清晰 ,简明直观 ,而且可应用到矢量力学教学中去  相似文献   

智能转矩转速测量仪     

朱维怡 《昆明师范高等专科学校学报》1988,(1)

本文叙述了用微型计算机和相应的接口构成智能转矩转速测量仪。它与同类仪器相比,具有精度高、构造简单、体积小,能自动测量、显示、打印、绘图等特点。  相似文献   

Flow Field of Circulating Fluidized Bed Reactor with Venturi Inlet Configuration     

胡金榜李艳平  陈安新 《天津大学学报(英文版)》2005,11(2):106-109

Different two-equation k-ε models were used to simulate the gas flow field generated by a new type of circulating fluidized bed reactor with venturi gas distributor. The numerical results were compared with the experimental data. It has been shown that the simulation results from the standard k-ε model have the best match with the experimental data. Based on this model, the gas flow field in the venturi diffuser and riser was analyzed by the concept of velocity nonuniformity and dead zone percentage. Both the nonuniformity of gas velocity and the dead zone percentage reach the maximum at the venturi outlet due to the effect of the vortex. At the same time, it provides a good platform for the further optimization of the inlet configuration of circulating fluidized bed reactor.  相似文献   

电磁波穿过DNG媒质时的传播特性分析     

包永芳  吕英华  韩春元 《滨州学院学报》2005,21(6):53-56

针对广泛关注的DNG媒质(负折射率媒质),以有损耗的Drude型媒质为模型,对电磁波穿过DNG媒质的平行板时的传播特性做了理论分析;采用FDTD方法对正弦电磁波穿过DNG媒质的平行板的传播过程进行了数值建模,数值模拟的结果证明了正弦电磁波在穿过DNG媒质的平行板时仍然具有相速度与群速度方向相反的特性,为DNG媒质的广泛应用提供了理论基础.  相似文献   

Effect of Air Velocity on Thermal Comfort under Thermal Environment Ramp Changing   总被引：1，自引：0，他引：1  

嵇赟喆  涂光备  孙琳 《天津大学学报(英文版)》2004,10(4):291-296

Set points of the indoor air temperature and relative humidity in short-term staying location were studied. In this condition, the thermal reaction of human body varied with the ramp changes of the environmental thermal parameters. The change rules of about 60 subjects‘ thermal reaction to the ramp change of environment were surveyed, and the effect of air movement on the thermal reaction during transient condition was considered by using a questionnaire. With the experimental results and research findings under stable condition, a way to set environmental parameters of short-time staying location was recommended.  相似文献   

砂土地震液化的不确定性判别法综述     

张红敏 《山西广播电视大学学报》2003,8(1):73-74

通过对不同自由场地液化势估计的方法和公式进行总结和比较 ,发现剪切波速比其它波的波速更能反映地基岩土层的工作性能 ,现已为全国地基勘察规范所采用  相似文献   

真空-堆载联合预压法加固软土地基     

范新荣  叶海霞 《洛阳工业高等专科学校学报》2004,14(4):33-35

真空-堆载联合预压法是加固饱和软粘土的理想方法，通过试验，观测路基的表面沉降和水平位移，说明真空预压能使地基产生较大的沉降速率，同时提高路基的稳定性，侧向位移量和位移速率与荷载大小的相关性比较明显。  相似文献   

从阳离子树脂的交换速率与质量的关系谈实验教学法     

周庆华  范卓文  甄捷 《哈尔滨学院学报》2003,24(8):135-136

本文从阳离子树脂的交换速率与质量的关系，探讨了物理化学实验教学法改革的必要性，阐明了正确的教学法对实现教学目标、落实人才培养模式、提高教学质量的重要性。  相似文献