计入脉动风速非线性项的随机稳定性分析

将脉动风速及其非线性项引入到桥梁的自激力公式中 ,运用随机微积分理论与矩方程理论 ,得到双方向运动的桥梁断面的一阶矩与二阶矩的微分方程组。通过微分方程的数值方法 ,得到扭转驱动的桥梁断面随机振动的时程曲线 ,从而得到随机失稳的临界风速。研究表明 ,脉动风速非线性项使得扭转驱动的桥梁趋于稳定     

浅谈材料力学中简易法快速画梁的剪力图和弯矩图

文章以作用于梁上的横向分布力集度与剪力、弯矩的微分关系为基础,归纳总结了几种荷载作用下剪力图、弯矩图的特征.掌握这些特征就能不写内力方程而根据外力直接画出相应的剪力图和弯矩图.     

Identification of twist-angle-dependent excitons in WS2/WSe2 heterobilayersOA

Stacking atomically thin films enables artificial construction of van der Waals heterostructures with exotic functionalities such as superconductivity, the quantum Hall effect, and engineered light-matter interactions.In particular, heterobilayers composed of monolayer transition metal dichalcogenides have attracted significant interest due to their controllable interlayer coupling and trapped valley excitons in moiré superlattices. However, the identification of twist-angle-modulated optical tr...     

机械与机电系统中力学量的Saber仿真分析探讨

通过对Saber仿真软件在机械与机电系统中的力学量仿真分析探讨,说明了sabet仿真不仅可以代替许多有关力学实验,而且可以在建立准确模型的基础上对机械及机电混合系统的力学应用和分析发挥作用。     

基于灰色关联分析的作者相似度算法对比研究

[目的/意义]作者相似度研究是探测学科知识结构、挖掘潜在合作关系的重要基础.[方法/过程]本文拟构建作者的关键词—文献2模矩阵,通过研究矩阵对应的灰度图像之间的相似性来判定作者相似性,并利用灰色关联理论计算基于合著关系和基于关键词的作者相似度,最后进行实证分析,对比三种作者相似性结果.[结果/结论]实验表明:基于关键词...     

我国高水平手枪慢射运动员瞄准技术的生物力学研究

本研究采用瑞典生产的高精度红外光点记录系统（ＳＥＬＳＰＯＴＳＹＳＴＥＭ），对我国四名优秀手枪慢射运动员瞄准阶段的身体环节和枪支的运动进行了测量，经研究发现：瞄准时间、击发前枪口的晃动量、击发瞬间枪口位置的差异三指标是瞄准阶段的重要技术指标，与射击精度有关，存在一定的规律性。通过测试分析，发现维持枪管左右方向（Ｙ方向）的平衡稳定难于其它两个方向，左右方向的晃动量对射击成绩有较大影响，同时，瞄准时间、击发前枪口的晃动量、击发瞬间枪口位置的差异几个技术指标之间存在着一定的相互制约关系。同时，还发现我国优秀射手在动作的一致性方面都还存在着一定差距；在瞄准时间、枪口晃动量、击发瞬间枪口位置三者的配合上不是很完善。     

关于磁电系电表的放置问题

文章根据力矩平衡条件初步分析了磁电系电表的放置问题,为仪表的工作原理提供了理论基础。     

考虑半轴齿轮摩擦力矩条件下的差速器转矩分配原理

在考虑差速器半轴齿轮摩擦力矩条件下，根据对半轴齿轮的受力分析，重新确定了差速器内摩擦力矩所含内容，进一步论述了差速器转矩分配原理。     

深埋软硬互层地质的长距离隧道TBM施工方法

为了提高深埋软硬互层地质的长距离隧道施工效率和质量,提出基于隔离桩盾构隧道开挖技术的深埋软硬互层地质长距离隧道TBM施工方法,采用模糊约束控制方法进行长距离隧道TBM施工的盾构参数优化设计,对弯矩、水平位移、轴力等参数进行准确计算,针对深埋软硬互层地质土体的各向异性和复杂边界条件进行长距离隧道施工过程中的地基土层基本物理力学指标优化设计,实现隔离桩盾构隧道开挖施工优化设计。测试结果表明,采用该方法进行深埋软硬互层地质的长距离隧道施工的弯矩控制性能较好,水平位移和沉降的效能较好,提高了深埋软硬互层地质的长距离隧道施工的质量。     

The effects of baseball bat mass properties on swing mechanics,ground reaction forces,and swing timing

Swing trajectory and ground reaction forces (GRF) of 30 collegiate baseball batters hitting a pitched ball were compared between a standard bat, a bat with extra weight about its barrel, and a bat with extra weight in its handle. It was hypothesised that when compared to a standard bat, only a handle-weighted bat would produce equivalent bat kinematics. It was also hypothesised that hitters would not produce equivalent GRFs for each weighted bat, but would maintain equivalent timing when compared to a standard bat. Data were collected utilising a 500 Hz motion capture system and 1,000 Hz force plate system. Data between bats were considered equivalent when the 95% confidence interval of the difference was contained entirely within ±5% of the standard bat mean value. The handle-weighted bat had equivalent kinematics, whereas the barrel-weighted bat did not. Both weighted bats had equivalent peak GRF variables. Neither weighted bat maintained equivalence in the timing of bat kinematics and some peak GRFs. The ability to maintain swing kinematics with a handle-weighted bat may have implications for swing training and warm-up. However, altered timings of kinematics and kinetics require further research to understand the implications on returning to a conventionally weighted bat.