激光计米器垂直对准装置的设计

激光计米器测量应用的准确度要达到0.05%,其安装定位尤为关键。在确定安装距离后,需控制仪器定位的垂直角度偏差在1°以内。针对安装定位的要求,本文设计了一款对准装置,其垂直定位测量的测量不确定度可达0.04°,能确保仪器测量应用的准确度。     

游乐设备坑道内安装工程导线测量法运用浅析

本文介绍在安装工程中,由于场地条件受限,全站仪无法直接与现场已知的控制点通视情况下,采取导线测量法。解决了特定安装区域内控制网络的建立,及根据新建立的控制网络进行安装基准线的测量定位。     

钢丝绳隔振器动态特性试验研究

目的 研究钢丝绳隔振器的静态、动态特性.方法 模拟隔振器的实际安装情况,利用正弦扫频激励方法,测量其动态特性.结果 获得了加载和卸载变形曲线、频响函数曲线和振动传递率曲线.结论 所得结果对分析该隔振器性能有实际应用价值.     

卧式活套带钢跑偏控制技术

本文主要阐述一种针对取向硅钢超长多轨卧式活套带钢跑偏控制的方法,以冶金系统非标类设备安装方法为基础,其主要控制点为硅钢直线机组安装基准线精度控制、多轨卧式活套轨道的安装精度控制和多辊卧式活套设备的安装精度控制。卧式活套带钢跑偏控制技术具有针对性强、测量精度高和校正速度快、实用性强的优点。     

如何做好地铁盾构洞内控制测量分析

地下控制网是盾构掘进、管片施工、设备安装等任务最基础性的工作,建立和完善高精度控制网的重要性不言而喻。基于此,本文首先对测量人员与仪器设备进行分析,对洞外控制网复测进行研究,对联系测量以及地下控制测量进行探讨,又提出盾构施工测量方式,以期对于地铁盾构洞内控制测量的提升,起到一定的促进作用。     

钢丝绳隔振器动态特性试验研究

目的 研究钢丝绳隔振器的静态,动态特性。方法 模拟隔振器的实际安装情况,利用正弦扫频激励方法,测量其动态特性。结果 获得了加载和卸载变形曲线,频响函数曲线和振动传递率曲线。结论所得结果对分析该隔振器性能有实际应用价值。     

复杂钢结构杆件预拼装与施工误差控制技术

针对复杂钢结构杆件安装问题,本文提出了基于全站仪测量数据的虚拟预拼装技术,该技术可以提前预知杆件安装误差是否可以控制在规范要求之内,同时针对现场安装问题,分别提出了截面误差和径向误差的控制方法和纠正措施,相关安装施工方法和经验可为类似大型钢结构工程安装提供参考。     

测定圆轮廓曲线的理论

一、概述由于科研的进步和需要,例如要研究机床主轴跳动对加工精度的影响,又如对工件形状的评价等等,均迫切需要测定圆形工件的轮廓曲线。可是,现通行的用圆度仪测量,因圆度仪转轴跳动的不可避免性,和各次测量时安装工件的位置的任意性,而可肯定圆度仪所测得的曲线理论上并非工件的轮廓曲线;实际上同一工件,各次测量所得曲线(圆图)也不相同。现有的其他测量理论和方法(如平板测量法,或V形块测量法等等)也有类似情况。总之,现有的测量方案从理论到设备、方法均未解决     

基于AMDF和DTS的洗衣机脱水阶段振动信号转速提取

国标GB/T4288—2018要求将传感器安装在洗衣机箱体上进行振动量检测,而转速测量要求传感器安装在洗涤筒外,效率较低。因此,提出采取利用外箱体的加速度传感器来进行脱水转速提取,可实现不拆卸状态下的转速及振动量的同时检测。根据洗衣机脱水阶段的上升控制段与自由衰减段转速曲线的不同特点,提出采用平均幅度差函数(Average Magnitude Difference Function, AMDF)和差分阈值分段(Differential Threshold Segmentation, DTS)处理相结合的算法来提取脱水阶段振动信号对应的转速,判断并截除衰减段信噪比和能量过低信号对应的转速曲线,修正完整转速曲线中的少数奇异点。采用某型波轮洗衣机的三种不同的脱水时间模式进行实验,实验表明:实测的平稳段和目标段转速曲线和理论转速曲线相比较,误差满足国标精度要求。     

基于G7工艺印刷质量控制方法的研究

分析了基于G7工艺印刷质量控制的关键参数,即亮调范围HR中性灰密度值的控制以及中性灰密度曲线NPDC。在保证设备性能稳定且印刷材料符合标准的情况下,使用G7工艺进行了印刷测试实验,然后测量相关数据并绘制了NPDC曲线,进行灰平衡校正。最后进行了验证特性化测试,应用校正补偿曲线重新出版印刷,测量灰平衡数据,再次绘制了NPDC曲线,发现结果基本符合标准曲线的趋势。     

Bridge Engineering for the Elementary Grades

A one hour presentation was developed to get elementary school students interested in engineering. The presentation begins with the students building a six feet long, structurally sound bridge which they can crawl across. A pictorial presentation helps them learn to identify some of the different types of bridges: truss, stone arch, steel arch, concrete girder, cable-stayed, and suspension. They are introduced to the fundamental engineering concepts of tension and compression. These concepts are reinforced by demonstrating that if a tension member is replaced with a chain then the bridge is still strong, but if a compression member is replaced with a chain the bridge will collapse. The presentation was integrated into the engineering curriculum by having senior design groups develop new bridge concepts and introduce new ideas into the presentation. This project provides a good senior design problem and helps keep the program fresh and interesting for the grade school children.     

Optimization of the Wheatstone Bridge Sensitivity

Analysis of the Wheatstone bridge has shown that the optimization of the maximum normalized bridge sensitivity can be achieved if the power dissipation in two of the four bridge elements approaches infinity for a given source voltage. Results also indicate that the power input to the bridge can be minimized as a function of maximum normalized bridge sensitivity.     

交流电桥的误差因素分析

交流电桥是由电阻、电容或电感等元件组成的桥式电路,交流电桥路的平衡还与电桥交流电源的频率有关,因此影响交流电桥的测量误差因数较多。     

Bridge over broadway

Abstract

In the middle of the 19th century, traffic congestion on the streets of New York City's commercial districts was, as it remains today, a major problem. Getting around town was especially difficult for pedestrians. Numerous solutions to ease the situation were proposed. One popular idea that had been discussed for years was finally tried in 1867. A bridge for pedestrians was built spanning the intersection of Broadway and Fulton Street in the heart of crowded lower Manhattan. Officially called the Broadway Bridge it became more commonly known as the ‘Loew Bridge’ after City Alderman Charles E. Loew, a major proponent of the project. As successful and practical as the bridge might have been it was removed a year following its erection. Its short life has been attributed to Knox, the famous hatter, who, with a store on one corner of the intersection and competition all around him, apparently felt it was a deterrent to business. According to one newspaper account, a sign was hung on the bridge just before its demolition that read, ‘This bridge has been Loew for some time, Hard Knox killed it.’     

Wheatstone Bridge Sensitivity

One of the important properties of a bridge is the sensitivity of the unbalance voltage to changes in some bridge parameter. In the self-balancing bridge, the uniformity of the null sensitivity, as well as the peak value of sensitivity, is relevant. The sensitivity of the four-arm Wheatstone bridge is reexamined from this point of view, with particular regard to the problem of the interchange of the generator and detector. It is shown that a single parameter set of universal curves suffices to describe the sensitivity variation of both configurations.     

Load Testing of an FRP Bridge Deck on a Truss Bridge

New York State has constructed a fiber reinforced polymer (FRP) bridge deck as an experimental project. The goal of the project was to improve the load rating of a 50-yr old truss bridge located in Wellsburg, New York. The FRP deck weighs approximately 80-percent less than the deteriorated concrete bridge deck it replaced. Reducing the dead load increased the allowable live load capacity of the bridge without significant repair work to the existing superstructure, thus lengthening its service life. Load testing was conducted after installation of the FRP deck to study the conservativeness of the design, ascertain the assumptions made on composite action between the deck and the superstructure, and examine the effectiveness of joints in load transfer. This report describes the testing and discusses the results. The results indicate that the design was conservative. The design assumed no composite action between the deck and the superstructure, and the experimental data confirms that assumption. The study also shows that the joints are only partially-effective in load transfer between panels. Peak strains under the test loads were only a very small fraction of the ultimate strength of the FRP deck.     

栈桥桁架的施工方案与实施

文章介绍了在3×104t/a甲醇法甲烷氯化物建设工程(以下简称CMS工程)产品贮运工段栈桥桁架"异地制作、铁路运输、旋转就位"的整体施工吊装技术,在特殊现场条件下,充分利用铁路运输设施进行施工.