孙太凤掷铁饼最后用力阶段运动学参数与投掷成绩的相关分析

本文采用三维录像解析法、Person相关分析等方法,以2007年全国田径锦标赛中孙太凤的5次有效投掷技术为研究对象,对孙太凤掷铁饼最后用力技术阶段的运动学参数与投掷成绩进行相关分析,结果显示：在左脚着地瞬间以及铁饼出手瞬间存在着与投掷成绩密切相关的运动学参数,同时,在最后用力的初始加速阶段、最后用力的最后加速阶段以及整个最后用力阶段也存在着与投掷成绩密切相关的运动学参数。     

一种GPS网络RTK整周模糊度解算方法(英文)

提出了一种适用于GPS多参考站网络的RTK模糊度固定方法. 首先, 以参与模糊度解算的参考站三角形重心为参考点, 将与其形成高度角最大的卫星选作参考卫星, 进而提供了载波观测值权阵构造的参数以及模糊度网解正确性的检验条件. 然后, 通过双频线性观测数据组合计算双差宽巷模糊度, 并利用无电离层观测数据组合计算L1模糊度浮点解, 引入卡尔曼滤波进行精化, 并实时估计对流层延迟参数. 最后, 通过Z变换对模糊度协因素阵进行去相关, 从而减小模糊度整数解的搜索空间, 提高LABMDA算法固定模糊度的效率. 实验结果表明, 该方法能在40个历元内可靠实现多个参考站间整周模糊度解算.     

基于灰色系统理论的绝对关联度图像边缘检测方法研究

边缘检测主要是对图像的灰度变化进行度量、检测.解决图像边缘的有无、真假、定向和定位.基于边缘检测的灰色系统理论中的绝对关联度方法对处理非典型规律的图像数据与其它一些方法相比,具有明显的优势.根据绝对关联度分析方法,将仿射变换和最小二乘法原理与绝对关联度模型相结合的边缘检测方法在克服绝对关联度分析方法的规范性和序数效应问题上有一定效果.     

一类特殊点、线段的包含测度

本文讨论了由各种特殊图形蜕化为点或直线的包含测度的一般公式。由此通过比较它们蜕化为同一图形结果上的差异,从本质上加深认识包含测度的意义。     

Fatigue-related changes in technique emerge at different timescales during repetitive training

Training consisting of numerous repetitions performed as closely as possible to ideal techniques is common in sports and every-day tasks. Little is known about fatigue-related technique changes that emerge at different timescales when repeating complex actions such as a karate front kick. Accordingly, 15 karatekas performed 600 kicks (1 pre-block and 9 blocks). The pre-block comprised 6 kicks (3 with each leg) at maximum intensity (K-100%). Each block comprised 60 kicks (10 with each leg) at 80% of their self-perceived maximum intensity (K-80%) plus 6 K-100%. In between blocks, the participants rested for 90 seconds. Right leg kinematics (peak joint angles, peak joint angular velocities, peak joint linear resultant velocities, and time of occurrence of peaks) and kick duration corresponding to the K-80% were measured resulting in numerous variations with fatigue. At the timescale of tens of seconds, the changes involved variables that were related to velocity of execution (slowed down), while variables related to movement form were hardly affected. At the timescale of tens of minutes, the opposite results were observed. These findings challenge the long-standing rationale underlying repetitive training, suggesting instead that such involuntary variations in technique might play a crucial role in motor skill training     

Comparison of two methodological approaches for the mechanical analysis of single-joint isoinertial movement using a customised isokinetic dynamometer*

Compared to isokinetic and isometric tests, isoinertial movements have been poorly used to assess single-joint performance. Two calculation procedures were developed to estimate mechanical performance during single-joint isoinertial movements performed on a customised isokinetic dynamometer. The results were also compared to appreciate the effects of measurement systems and calculation procedures. Five participants performed maximal knee extensions at four levels of resistance (30, 50, 70 and 90% of the one-repetition maximum, 1-RM). Joint angular velocity and torque were assessed from customised isokinetic dynamometer measures (method A) and from weight stack kinematic (method B). Bland–Altman plots and mean percent differences (M_diff) were used to assess the level of agreement for mean and peak angular velocity and torque. A Passing–Bablok regression was performed to compare the angular velocity-angle and torque-angle relationships computed from the two analysis methods. The results showed a high level of agreement for all mechanical parameters (M_diff < 6% for all parameters). No statistically significant differences were observed between methods A and B in terms of angular velocity-angle and torque-angle relationships except at 30% of 1-RM for the torque-angle relationship. Both methodologies provide comparable values of angular velocity and torque, offering alternative approaches to assess neuromuscular function from single-joint isoinertial movements.     

2007年田径冠军赛男子跳高运动员起跳技术的运动学分析

对2007年全国田径冠军赛男子跳高项目前六名运动员最好一次试跳起跳技术进行三维运动学分析,结果表明：被试H2远低于世界优秀选手;根据起跳时运动员质心降低的方式,将本次跳高运动员起跳技术分为三类：低-高型、高-低型、低-平型;助跑平均水平速度和起跳垂直速度分量小;起跳阶段水平速度损失值与起跳离地瞬间重心垂直速度呈显著性正相关性;起跳腿离地瞬间膝关节蹬伸较充分。     

中外优秀女排运动员四号位强攻扣球三维运动学研究

通过文献资料法、三维高速录像解析法、数理统计法、对比分析法等对2010年世界女排大奖赛总决赛三名中外优秀选手四号位强攻扣球进行系统分析研究。结果显示,中外女排选手都采用并步两脚依次蹬地起跳方式,中国选手起跳时间长、外国选手起跳时间短,起跳时间越短扣球成功率越高。扣球是以转体、伸肩和收腹带动挥臂击球的三维动作构成,转体和伸肩动作对扣球具有重要作用,击球瞬间肘关节呈146°左右稍屈肘能充分发挥前臂内旋加速功能。     

Ground reaction force characteristics of Tai Chi push hand

Abstract

Push Hand is an advanced training technique for the Yang-style old frame 108 forms Tai Chi Chuan. It is performed by two practitioners. To clarify how people use forces during Push Hand training, it is important to review the ground reaction force (GRF). Here, we quantify the characteristics of the GRF during Push Hand training. Kinematic data and GRF data from 10 Tai Chi Chuan practitioners (29.9 ± 7.87 years) were synchronously recorded using a three-dimensional motion analysis system (200 frames · s^?1) and three-dimensional force plates (1000 Hz). The resultant GRF for both feet for the 0%, 50% and 100% phases of attack and defence were compared to body weight using a paired-samples t-test. The differences in the resultant GRF between the 0%, 50% and 100% phases of attack and defence were tested by one-way repeated-measures ANOVA. The significance level was set to 0.05. The total resultant GRF was almost equal to the participant’s body weight in push hand. This result was consistent throughout the entire push hand process. Our results revealed that the GRF was comparable to the body weight, implying that practitioners do not push or resist their opponents during the push hand process.     

高校心理普查危机因子检测系统的构建

当代高校心理普查中危机因子检测系统存在严重的弊端,学校应当从心理普查前、中、后续的访谈与跟踪过程三个阶段入手,对高校心理普查中的心理危机因子检测系统进行重新构建,以提高心理普查的针对性与实效性。