The preparatory state of ground reaction forces in defending against a dribbler in a basketball 1-on-1 dribble subphase     

Keisuke Fujii  Shinsuke Yoshioka  Tadao Isaka  Motoki Kouzaki 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(1):28-44

We previously demonstrated the relationship between sidestepping performance and the preparatory state of ground reaction forces (GRFs). The present study investigated the effect of the preparatory state of GRFs on defensive performance in 1-on-1 subphase of basketball. Ten basketball players participated in 1-on-1 dribble game of basketball. The outcomes (penetrating and guarding) and the preparatory state of GRFs (non-weighted and weighted states, i.e. vertical GRFs below and above 120% of body weight, respectively) were assessed by separating the phases. In the non-weighted state and the weighted state to determine the outcome, the probability of successful guarding was 78.8% and 29.6%, respectively. The non-weighted state prevented delay of the defensive step in the determination phase. Both the non-weighted and weighted states, immediately before the determination phase, were likely to change to the weighted state in the determination phase; during this time, the defender's preparatory state would be destabilised, presumably by the dribbler's movement. These results revealed that the preparatory GRFs before the defensive step help to explain the outcome of the 1-on-1 subphase, and suggest a better way to prevent delaying initiation of the defensive step and thereby to guard more effectively against a dribbler.  相似文献   

Biomechanical pole and leg characteristics during uphill diagonal roller skiing     

Stefan Josef Lindinger  Caroline Göpfert  Thomas Stöggl  Erich Müller  Hans-Christer Holmberg 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(4):318-333

Diagonal skiing as a major classical technique has hardly been investigated over the last two decades, although technique and racing velocities have developed substantially. The aims of the present study were to 1) analyse pole and leg kinetics and kinematics during submaximal uphill diagonal roller skiing and 2) identify biomechanical factors related to performance. Twelve elite skiers performed a time to exhaustion (performance) test on a treadmill. Joint kinematics and pole/plantar forces were recorded separately during diagonal roller skiing (9°; 11 km/h). Performance was correlated to cycle length (r = 0.77; P < 0.05), relative leg swing (r = 0.71), and gliding time (r = 0.74), hip flexion range of motion (ROM) during swing (r = 0.73) and knee extension ROM during gliding (r = 0.71). Push-off demonstrated performance correlations for impulse of leg force (r = 0.84), relative duration (r = ? 0.76) and knee flexion (r = 0.73) and extension ROM (r = 0.74). Relative time to peak pole force was associated with performance (r = 0.73). In summary, diagonal roller skiing performance was linked to 1) longer cycle length, 2) greater impulse of force during a shorter push-off with larger flexion/extension ROMs in leg joints, 3) longer leg swing, and 4) later peak pole force, demonstrating the major key characteristics to be emphasised in training.  相似文献   

Comparison of force-related performance indicators between heavyweight and lightweight rowers     

Matthew M. Doyle  Andrew Lyttle  Bruce Elliott 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(3):178-192

The aim of this study was to examine biomechanical variables relating to the force production of men's Lightweight (LW) and Heavyweight (HW) rowing pairs. Seven HW and seven LW coxless pairs were studied under a range of stroke rates, from 20 spm to race rating (average of 33.7 spm for the HWs and 33.9 spm for the LWs). Each crew was equipped with biomechanical apparatus allowing the measurement of gate force, horizontal oar angle, and boat velocity. The HW crews exhibited significantly higher (p < 0.05) values for all variables examined, at all rates. Peak handle force was 26.2% to 30.2% higher in the HW group. Average handle force ranged from 18.7% to 22.1% higher than the LW group. Work per stroke was found to be 26% to 28% higher for the HW crews, and Power Per Kilogram was also greater for the HW crews, from 24.0% to 29.2%. The LWs were observed to be consistently, but not significantly, slower than the HWs (from 96.9% at the race situation, to 98.7% at 28 spm). These observations are important when considering biomechanical performance indicators in rowing, as significant changes in performance indicators may lead to only minimal alteration in boat velocity.  相似文献   

遮帘式板桩码头三维地震动响应   总被引：1，自引：0，他引：1  

蒋建平  刘春林  蒋宏鸣 《上海海事大学学报》2013,34(1):28-35

为研究遮帘式板桩码头在地震作用下板桩结构与土的相互作用,及前墙弯矩、遮帘桩弯矩和拉杆拉力的变化情况,运用ABAQUS软件研究京唐港32#遮帘式板桩码头在不同加速度峰值的地震载荷作用下的动态响应.结果表明,不同加速度峰值地震波对码头结构有重要影响,地震加速度峰值每增大0.1g,前墙最大弯矩增大约10%,遮帘桩最大弯矩增大约21%,后拉杆拉力增大约25%.地震动土压力对海底标高以上的前墙结构作用不明显,对海底标高以下前墙部分影响较大,对遮帘桩沿桩身分布的动土压力显著;在地震作用下遮帘桩依然发挥前墙挡土的作用.  相似文献   

从一个佯谬对电磁场动量守恒的理论推证     

赵彦杰 《德州学院学报》2012,28(6):31-32,36

从一个佯谬问题出发,利用数学计算的方法,得出了稳态电磁场动量守恒的结论.目的是加深对电磁场具有物质属性概念的理解.  相似文献   

仿人机器人步行运动控制研究     

柯文德  陈珂  李家兰 《茂名学院学报》2012,22(4):30-33

针对仿人机器人多自由度的复杂机械连杆特征,详细分析了机器人运动构型以及步行规划约束、ZMP控制、奇异位姿控制、二维倒立摆等运动模型,提出单双腿交替运动序列并采用离线生成双足步行运动轨迹和在线调整的方法。实验验证了方法有效性。  相似文献   

商业银行ATM机混凝土机房改造设计     

罗东远  赖建文 《闽西职业技术学院学报》2012,14(1):114-116

自动存取款机混凝土机房一般在原有商业银行营业网点内改造而成.因其具有较大集中荷载,同时由于防盗防抢的要求需新增墙体作为维护结构,墙体线荷载也比较大,因此有必要对新增荷载进行分析,进而对楼板、次梁、框架梁进行内力分析、结构验算并进行结构加固.  相似文献   

Deflection analysis of reinforced concrete beams strengthened with carbon fibre reinforced polymer under long-term load action     

Mykolas DAUGEVIIUS  Juozas VALIVONIS  Gediminas MAR IUKAITIS 《浙江大学学报(A卷英文版)》2012,13(8):571-583

This paper presents the results of an experimental research on reinforced concrete beams strengthened with an external carbon fibre reinforced polymer(CFRP) layer under long-term load action that lasted for 330 d.We describe the characteristics of deflection development of the beams strengthened with different additional anchorages of the external carbon fibre composite layer during the period of interest.The conducted experiments showed that the additional anchorage influences the slip of the external layer with respect to the strengthened element.Thus,concrete and carbon fibre composite interface stiffness decreases with a long-term load action.Therefore,the proposed method of analysis based on the built-up-bars theory can be used to estimate concrete and carbon fibre composite interface stiffness in the case of long-term load.  相似文献   

《哈姆雷特》中主人公语言的语用模糊现象     

童晓燕  刘书梅 《湖北第二师范学院学报》2012,(1):15-17

本文首先简要介绍Austin言语行为理论尤其是言外行为和言外之力的定义,并据此引出语用模糊的概念,接着尝试从语用模糊的角度探讨了《哈姆雷特》主人公哈姆雷特的语言,从而发现了其语言魅力的部分原因在于灵活地运用了语用模糊。因而发现语用模糊在《哈姆雷特》中是一个行之有效的会话策略,这也为莎翁戏剧语言巨大魅力找到了一个新的语用学依据。  相似文献   

采煤机滚筒齿座开裂分析     

朱忠文 《鸡西大学学报》2012,(2):46-47

齿座开裂是我厂采煤机生产中存在的一大问题,齿座开裂直接影响到采煤机的产品质量,保证齿座在采煤机生产中安全使用,与采煤机滚筒设计,生产各个环节有密切的关系。拟对各个环节存在的问题做一分析。  相似文献