某国产600MW汽轮发电机组振动故障诊断及处理

某国产600MW汽轮发电机组投产以来存在低压转子支承轴承瓦振超标的故障问题。本文针对产生该振动问题的根本原因进行了分析,在此基础上在现场进行了增加低压缸支承轴承动刚度的尝试。最后利用机组几次临停机会,在机组低压1转子、低压2转子及低发对轮上加重,进行现场精细动平衡,将机组轴振降低到了50μm以内,从而使该机组低压缸瓦振得到控制。     

从不同高度下落到不同硬度的地面上下肢关节的力学响应

本研究了人从30cm和60cm高度下落到两种不同硬度的地面，即木板地面和海绵垫上时下肢关节的力学响应。结果表明从两种高度下落到海绵垫上比落到木板地面时下肢关节的受力、力矩显减小，关节的角度变化显增加，从着地到落地停稳所用的时问显增加。各关节力矩是外力矩与肌肉力矩共同作用的结果，正确的落地技术应该是三个关节的力矩同时减小，掌握正确的落地技术的实质是掌握正确的肌肉被拉伸与收缩的顺序和大小。从30cm和60cm下落着地后，不论是何种地面条件。三个关节的力矩以髋关节力矩为最大，膝和踝关节肌肉是在髋关节控制下起互相协调作用。     

撑竿跳高运动员助跑速度与其成绩的关系研究

目前国内外对撑竿跳高的研究主要是针对各技术环节进行分析，认为影响其成绩的主要因素是握竿的高度、竿子磅数、腾起高度。本文通过文献资料法、访谈法和逻辑推理法，根据能量守衡定律，从理论和实践上证明助跑速度是撑杆跳高的首动链，由它影响后续的一个个技术环节，是制约撑杆跳高运动成绩的关键因素。     

谈英语语法的几个特性

阐述英语语法的三个特性，掌握这些特点有利于提高英语学习效果。     

The influence of shaft stiffness on potential energy and puck speed during wrist and slap shots in ice hockey

The purpose of this study was to explore the relationship between hockey stick shaft stiffness and puck speed with mechanical energy considerations during stationary wrist and slap shots. Thirty left-handed pro-model composite hockey sticks, submitted by eleven hockey stick manufacturers, were subjected to a mechanical cantilever bend test to determine the shaft stiffness of each stick. Eight sticks representing the entire spectrum of stiffnesses were then used by five elite male hockey players to perform stationary wrist and slap shots in a laboratory setting. Eight infra-red high-speed digital video cameras were used to capture shaft deformation and puck speed. A second mechanical test then replicated the loading patterns applied to each stick during shooting. Force-deformation data from this test were used to determine the shaft stiffness and potential energy storage and return associated with each stick during shooting. The results of this study suggest that shaft stiffness has an influence on puck speed in wrist but not slap shots. During a wrist shot, a given player should realise higher puck speeds with a stick in which they store increased elastic potential energy in the shaft. In general, flexible sticks were found to store the most energy. However, how the athlete loads the stick has as much influence on puck speed as stick construction. Energy considerations were unable to explain changes in puck speed for the slap shot. For this type of shot it is the athlete and not the equipment influencing puck speed, but the governing mechanisms have yet to be elucidated.     

大跨度单层工业厂房上部结构的设计

１工程概况 中国长城铝业公司新建炭素二焙车间焙烧工段厂房为单层单跨排架工业厂房，跨度３６ｍ，总长１９８ｍ，按伸缩缝区段划分为三个部分，屋面采用３６ｍ跨梯形钢屋架和１２ｍ跨钢天窗架，上铺６ｍ跨大型混凝土屋面板和天沟板，柱距６ｍ，柱子采用预制钢筋混凝土工字型柱，部分柱为现浇矩形截面柱，柱基采用钢筋混凝土灌注桩，厂房内设有两台新型多功能天车，每台自重１６８ｔ，其中小车自重５８．６ｔ，装满料后总重量达２０ｔ，工作级别为特重级，吊车梁采用钢吊车梁，其截面高度为１２４０ｍｍ。该天车自重大，使用频繁，是决定柱…     

有限元法分析平面问题的编程实现

本文通过有限单元法对弹性力学平面问题的受力分析,介绍了构建程序框图,编制通用程序的过程。     

Analysis on Dynamic Performance for Active Magnetic Bearing—Rotor System

In the application of active magnetic bearings(AMB),one of the key problems to be solved is the safety and stabiltiy in the sense of rotor dynamics,The project related to the present paper deals with the method for analyzing bearing rotor systems with high rotation speed and specially supported by active magnetic bearings,and studies its rotor dynamics performance,including calculation of the natural frequencies with their distribution characteristics,and the critical speeds of the system.one of the targets of this project is to formulate a theory and method valid for the analysis of the dynamic performance of the active magntic bearing-rotor systemby combining the traditional theory and method of rotor dynamics with the analytical theory and design method based on modern control theory of the AMB system.     

Mechanical behaviour of cross-country ski racing poles during double poling

The purpose of this study was to evaluate the behaviour of cross-country ski poles during double poling on a treadmill using three-dimensional kinematics. The results were compared with standard laboratory tests of the pole manufacturers. A total of 18 skiers were analysed at two speeds (85% and 95% of the maximal speed) at grades of 1.5% and 7%. Variables describing cycle characteristics, bending stiffness, bending behaviour, and trajectories of the pole markers were analysed. Triangular-shaped poles demonstrated the greatest stiffness and lowest variability in maximal bending. Softer poles demonstrated greater variability in bending behaviour and lost ground contact at high skiing speeds, which for some skiers resulted in failure to complete high-speed tests. Considerable variations in pole behaviour for similar poles between skiers were observed, which might be attributed to differences in technique, indicating that mechanical properties of the poles did not exclusively determine pole behaviour in the dynamic situation. The greatest magnitude of pole bending was in the middle part of the pole, which differed from the standard static pole analysis of the manufacturer. Increases in grade demonstrated the greatest effect on pole bending. Distinct differences from the pole manufacturers' laboratory measures were apparent, suggesting that basic pole testing might be adapted.