基于数值信息法的煤巷支护综合设计研究

针对山西大同某煤矿辅助巷道支护结构的锚杆与锚索的设计,采用理论设计、数值模拟、观测设计、工程类比几种方法的综合设计进行方案选择、设计优化。此方案不仅在经济方面,而且在技术、安全方面都满足要求,对类似的工程起到借鉴的作用。     

引入多QoS开销适应度的云计算任务权衡调度

提出一种引入QoS开销适应度运算的云计算任务权衡调度算法,首先进行了支持多QoS因素任务调度问题描述与网格拓扑结构构建,进行云计算任务权衡调度对多用户QoS偏好的影响力数学度量,通过多QoS开销适应度运算的引入,根据计算资源的成本和数据传输时间,来确定分配任务的位置。为了适应云存储中的多QoS偏好,重新定义PSO的适应度函数,实现任务权衡调度算法的改进。通过仿真实验研究得出,采用该算法对云计算任务节点的聚类准确性较高,进行任务调度中的实时性好。通过多QoS偏好分析,引入QoS开销适应度运算,用户满意率有明显上升,适应度函数随不同类别任务变化,有效地反映不同类型任务的QoS偏好。展示了较好的云计算任务权衡调度性能。     

网球高压球技术的运动学分析

运用三维立体摄影解析法,获取了网球高压球技术动作的运动学参数,并对数据进行统计学处理。结果表明:击球蹬离地面过程中,大腿、小腿和足的运动顺序为自上而下用力;整个击打过程肩、肘、腕三关节移动速度基本保持同步,肩关节角速度峰值最先出现,肘关节和腕关节角速度峰值出现时间基本同步;网球高压球技术动作采用"棍打"式为主,旨在指明网球高压球技术的运动学特征,并为网球教学和训练提供定量的科学依据。     

无形资产摊销不该一律计入"管理费用"

《企业会计制度》规定:摊销无形资产价值时,借记“管理费用──无形资产摊销”科目。本文认为无形资产摊销不该一律计入“管理费用”科目,在社会主义市场经济条件下,无形资产的规模、作用、经济效益空前发达,所以应该区别不同情况分别计入各受益对象的生产经营成本或期间费用。     

变频技术在桥式起重机上的应用研究

阐述采用变频器对起重机的控制系统进行改造设计,介绍变频器和变频系统中电机的选择方法、接线原理和功能设置;在对提升机变频控制线路和制动器的接法进行设计和分析的基础上,对变频运行时防溜钩方法进行说明。     

Multivariate isokinetic asymmetry of the knee and shoulder in elite volleyball players

Abstract

Muscle strength asymmetries have been investigated in athletes under the assumption of their connection to functional discrepancies and injuries. In volleyball, which is a highly asymmetric sport, this assumption becomes a well established research hypothesis. Given the almost complete lack of scientific evidence on this hypothesis, the present study focused on the detailed multivariate quantification of muscle asymmetries in offensive volleyball players. Twenty-four elite athletes (age 24.71±4.44 years, weight 84.62±6.24, height 190.08±5.58) were tested for concentric isokinetic muscle strength (a) of the internal and external rotators of the shoulder and (b) of the quadriceps and hamstrings of the knee at 60^o/s. Significant multivariate results were found for absolute (Max-Min) asymmetry in the upper (Hotteling's T ²=8.801, F=7.447, P=0.001) and the lower limbs (Hotteling's T ²=16.382, F=13.862, P=0.000), for fluctuating asymmetry (Dominant-Non Dominant) in the upper limbs (Hotteling's T ²=5.584, F=4.296, P=0.013) and for directional asymmetry (Left-Right) in the lower limbs (Hotteling's T ²=3.593, F=3.041, P=0.036). It appears that the upper and lower limbs of offensive volleyball players present significant composite muscle strength asymmetries, which should be taken into consideration in training and rehabilitation.     

Electromyography activities for shoulder muscles over various movements on different torque changes

Abstract

The aim of the present study was to investigate the patterns of shoulder muscle activation and joint torques during maximal effort eccentric contractions with shoulder extension, abduction, and diagonal movements on the isokinetic device. Participants in this investigation were nine men and four women with no history of shoulder injury or disorders. They all participated in overhead sports at least three days a week, and volunteered to participate in this study for shoulder isokinetic muscle strength testing. They performed eccentric muscle action with shoulder flexion, abduction, and diagonal movements at velocities of 60 rad·s^?1 and 180 rad· s^?1, which was followed alternately by passive shoulder flexion, abduction and diagonal movement at a velocity of 30 rad· s^?1, and total range of motion was standardised to 90°. Electromyography (EMG) and torque values were calculated to every 10°, except for the start and end 5° during each task. During each test, the isokinetic force output and muscle activation were synchronised. EMG data were normalised by percentage of maximum voluntary isometric contraction (%MVIC). EMG signals were recorded by surface EMG from the anterior deltoid (AD), middle deltoid (MD), posterior deltoid (PD), upper trapezius (UT), middle trapezius (MT), and biceps brachii (BB) muscles during this test. All of the muscle patterns were significantly decreased at the last compared with the initial part during eccentric shoulder flexion movement, except for the BB muscle (P < 0.05). AD and BB muscles played a similar role when peak torque was generated under load during eccentric muscle action with varying shoulder movements. PD and UT muscle activities were significantly lower than the other muscle activities during eccentric contraction with shoulder flexion and abduction movements, and the PD and UT muscles played a significant role in conjunction with MD and MT muscles in varying degrees during eccentric contraction with shoulder diagonal movements at 180 rad·s^?1 (P < 0.05). Our study demonstrated that MT muscle activity was greatly influenced when torque values showed a peak moment under load during maximum effort, eccentric contraction with shoulder abduction and diagonal movements. However, the MD, PD, UT, and MT muscle activities had no great influence when peak torque was generated under load during eccentric muscle action with shoulder diagonal movement at high velocity. The present study suggested that varying eccentric muscle activity patterns may be needed to investigate proper training and functional contributions of upper extremity muscles to stabilisation of the shoulder joint when peak torque was generated under load.     

双回路高压供电线路并列经济运行分析

在架空输电线路总损耗的基础上,用数学极值方法推导出单回路和双回路架空输电线路经济负荷功率的计算公式,并推导双回路架空输电线路并列运行的临界投切功率的计算公式,举例说明了公式的应用。     

多媒体投影教学在课堂互动中的问题及对策

本文基于建构主义学习理论,探讨了多媒体投影在促进大学英语课堂互动方面的优劣势,着重指出大学英语教师利用多媒体投影在课堂互动方面容易出现的问题,并提出了相应的教学对策。     

毽球倒勾球技术教学球感练习法研究

依据毽球倒勾球动作技术的时间与空间特征,结合教学实践经验,运用运动心理学有关球感的理论,在分析与探讨球感练习对毽球倒勾球动作技能形成的作用的基础上,对毽球倒勾球动作技术教学中球感练习选择的依据、练习顺序、练习手段及基本要求、运用球感练习的基本原则等问题进行了分析与讨论。