Hip and upper extremity kinematics in youth baseball pitchers

The purpose of this study was to examine the relationship between dynamic hip rotational range of motion and upper extremity kinematics during baseball pitching. Thirty-one youth baseball pitchers (10.87 ± 0.92 years; 150.03 ± 5.48 cm; 44.83 ± 8.04 kg) participated. A strong correlation was found between stance hip rotation and scapular upward rotation at maximum shoulder external rotation (r = 0.531, P = 0.002) and at ball release (r = 0.536, P = 0.002). No statistically significant correlations were found between dynamic hip rotational range of motion and passive hip range of motion. Hip range of motion deficits can constrain pelvis rotation and limit energy generation in the lower extremities. Shoulder pathomechanics can then develop as greater responsibility is placed on the shoulder to generate the energy lost from the proximal segments, increasing risk of upper extremity injury. Additionally, it appears that passive seated measurements of hip range of motion may not accurately reflect the dynamic range of motion of the hips through the progression of the pitch cycle.     

卢瑟福模型中电子运动分析

关于卢瑟福模型中电子的运动是加速还是减速,不同文献给出不同描述,甚至是截然相反的描述.本文分别从能量和力的角度定量、定性地分析了卢瑟福模型中电子的运动情况,得出了卢瑟福模型中电子绕原子核旋转、辐射能量时作加速运动的结论.     

Validation of the Microsoft Kinect® camera system for measurement of lower extremity jump landing and squatting kinematics

Cost effective, quantifiable assessment of lower extremity movement represents potential improvement over standard tools for evaluation of injury risk. Ten healthy participants completed three trials of a drop jump, overhead squat, and single leg squat task. Peak hip and knee kinematics were assessed using an 8 camera BTS Smart 7000DX motion analysis system and the Microsoft Kinect® camera system. The agreement and consistency between both uncorrected and correct Kinect kinematic variables and the BTS camera system were assessed using interclass correlations coefficients. Peak sagittal plane kinematics measured using the Microsoft Kinect® camera system explained a significant amount of variance [Range_hip = 43.5–62.8%; Range_knee = 67.5–89.6%] in peak kinematics measured using the BTS camera system. Across tasks, peak knee flexion angle and peak hip flexion were found to be consistent and in agreement when the Microsoft Kinect® camera system was directly compared to the BTS camera system but these values were improved following application of a corrective factor. The Microsoft Kinect® may not be an appropriate surrogate for traditional motion analysis technology, but it may have potential applications as a real-time feedback tool in pathological or high injury risk populations.     

轴瓦自激振动的诊断及几点消除措施

该文分析了轴瓦自激振动的原因，并提出了怎样对该故障现象进行诊断及一些消除措施。     

解析法在机构运动分析中的应用

解析法适用于精度机构的运动分析。只要将解析结果编程上机，就可完成计算机辅助分析和设计。随着计算机的日益普及，解析法日遂受到人们的重视。     

牛顿第二定律对变质量问题的应用

从经典力学范围和相对论力学两方面,分别讨论了牛顿第二定律的应用条件,并从所导出的牛顿第二定律解决变质量问题的公式,通过具体举例说明了如何应用变质量公式来解决实际问题.     

关于MTV维权事件的法理思考

近期在我国各大城市发生的MTV维权事件,引发了人们关于MTV的法律性质及其收费方式的进一步思考。通过对MTV的特点及其与电影作品、录像制品的区别的分析和版权与邻接权的界限问题的讨论,可以得出这样的结论:著作权集体管理组织及其相应收费机制的缺失是造成MTV诉讼的主要原因。     

认知突显视阈下英汉多义动词对比研究--基于语科的“run/跑”为例

动词表征事件,涉及到事件主体、方式、结果等因素,不同因素的突显是多义性产生的动因。基于认知语言学的图形背景以及运动事件理论,以英汉多义动词“run/跑”为例,两者都在共性突显运动目的、速度和结果方面延伸出了基本相同的义项;但是英语“run”在时间、位移、状态、路线,而汉语“跑”则在方式、方向方面进行个性突显,使两者有了不同的义项。同时由于英语“run”比汉语“跑”在突显时延伸出的语义更加具体,因而比汉语有更多的义项。     

冲压成形过程中机械运动的控制与运用

在冲压过程中，机械运动贯穿始终．各种冲压工艺的实现都有其基本运动机理，这种成形运动是与模具密切相关的，各种模具的结构设计和力学设计最终都是为了满足其能够实现特定运动的要求．设计的模具能否严格完成实现冲压工艺所需的运动，直接影响到冲压件的品质，所以在模具设计中应对机械运动进行控制．同时为了达到产品形状尺寸的要求，不能拘泥或局限于各种工艺基本运动模式中，而应不断发展和创新，在模具设计中灵活运用机械运动．     

一种在MPEG-4编码过程中提高实时性的算法

本文提出了一种新的在MPEG-4编码过程中提高实时性的算法。算法采用双重筛选机制,充分利用了运动估计的结果提取运动对象。首先在运动估计过程中加入背景优先准则进行第一重筛选;然后根据运动估计后宏块的最小平均绝对差值分利用区域自适应门限进行第二重筛选,从而获得运动区域掩模;最后对掩模进行形态滤波和填充消除噪声点,最终得到运动区域。算法分别在硬件和软件平台上进行测试,结果表明提出的算法得到了理想的分割效果,较传统的在编码前进行运动对象提取的方法实时性大大提高了。