Cost efficiency comparison of four video-based techniques for assessing upper arm postures

Many video-based techniques for assessing postures at work have been developed. Choosing the most appropriate technique should be based on an evaluation of different alternatives in terms of their ability to produce posture information at low input costs, i.e. their cost efficiency. This study compared four video-based techniques for assessing upper arm postures, using cost and error data from an investigation on hairdressers. Labour costs associated with the posture assessments from the video recordings were the dominant factor in the cost efficiency comparison. Thus, a work sampling technique associated with relatively large errors appeared, in general, to be the most cost-efficient because it was labour-saving. Measurement bias and other costs than labour cost for posture assessment influenced the ranking and economic evaluation of techniques, as did the applied measurement strategy, i.e. the numbers of video recordings and repeated assessments of them. PRACTITIONER SUMMARY: The cost efficiency of four video-based techniques for assessing upper arm postures was compared. Work sampling techniques were in general more cost efficient than continuous observations since they were labour-saving. Whilst a labour cost dominated the comparison, 'hidden costs', bias and measurement strategy also influenced this dominance.     

共振仪共振相位差测量系统设计

针对波尔共振仪的共振相位差测量,提出了同步跟随相位测量方法.设计了一套跟随振动系统摆盘的受控刻度盘系统,刻度盘以振动系统的摆盘的最大转速为转动速度,刻度盘上的任意一点在水平方向的投影与振动系统摆盘的摆动为等效的振动.完整的同步跟随相位测量系统由振动系统摆盘测量系统、受控刻度盘系统和驱动同轴盘测量系统组成.同步跟随刻度盘根据振动系统摆盘测量系统所采集的数据取代摆盘,并与驱动同轴盘同轴,当同步跟随的刻度盘与振动系统摆盘达到同步时,在共振发生时同步跟随的刻度盘和驱动同轴盘也几乎同步转动,所以驱动同轴盘零指针总指向同步跟随的刻度盘一个相位值,驱动同轴盘与刻度盘之间给出相位差.同步跟随相位测量方法将不受环境因素影响,便于在不同照明条件下布置多台实验仪器.     

基于全站仪组网测量系统的测量方法研究

全站仪测量系统是由一台计算机和数台全站仪组成的一种测量系统。可以完成在工业测量中的单点坐标的测量,特别是大尺寸结构件的测量。根据坐标拟合测量原理,使多台全站仪更精确地统一到同一用户坐标系下进行测量,消除大型结构件单站测量的盲点,提高测量精度,实现大型结构件的加工及装配的在线检测。     

Train-induced vibration on elevated railway station

Results of in-situ vibration measurement carried out at Tianjin West Elevated Railway Station which has the trains running on the station structure were reported. The main excitation source is the train passing through the station. Vibration measurements were recorded in the vertical direction of the supporting track beam, the platform and the steel truss beam of the waiting hall, as well as in the vertical, longitudinal and transverse directions of the roof arch base of the station. Acceleration time responses were obtained. The maximum value, vibration level and one-third octave band RMS spectra of the measured accelerations were studied. The propagation of vibration in different structural floors was discussed. The influence of train speed, distance to the vibration source and the type of train on the structural vibration were analyzed. Results show that the vibration level increases with the train speed, while it attenuates with the distance to the track. Furthermore, the vibration responses of different structural floors were compared, and it is noted that the vertical vibration of the bottom slab of the platform is most severe and the transverse vibration of the roof arch base is the smallest. The results provide reference on the vibration characteristics and vibration energy distribution of this type of ＂Train on building frame＂ system used as an elevated railway station.     

Trace amounts of impurities in electrolytic manganese metal by sector field inductively coupled plasma mass spectrometry

An analytical method, using sector field inductively coupled plasma mass spectrometry （SF-ICP-MS） for rapid simultaneous determination of Be, Na, Mg, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, As, Sn, Sb, Pb and Bi in electrolytic manganese metal, was described. At the beginning, the samples were decomposed by HNO3 and H2504, and then analyzed by SF-ICP-MS. Most of the spectral interferences could be avoided by measuring in different mass resolution modes. The matrix effects due to the excess of sulfuric acid and Mn were evaluated. Correction of matrix effects was conducted by using the internal standard elements. The optimum condition for the determination was investigated and discussed. The detection limit is in the range of 0.001-0.169 gg/L. The current method is applied to the determination of trace impurities in electrolytic manganese metal. And experiments show that good results can be obtained much faster, more accurately and conveniently by current method.     

在运动参考系内如何正确测量时间膨胀

讨论并论证了如何正确测量时间膨胀的方法,指出了在相对于新以太运动的参考系内人们只能正确测量往返运动钟发生的时间膨胀,但却不能正确测量单向运动钟发生的时间膨胀,并以此解释了狭义相对论难以解释的一些现象,消除了人们在分析实验时所出现的多重标准.     

孤岛油田聚合物后续水驱井下注水工艺

针对聚合物后续水驱井下注水工艺存在层窜、吐聚、吐砂严重以及地层压力测试成功率较低、分层注水方案难以实施、大部分主力油层不吸水、作业频繁、后续水驱效果不理想等问题,设计了后续水驱配套工艺,制定了新的作业施工方案,优化了分层测调方法。该技术在孤岛油田B19断块、东区注水示范区进行了试验和推广应用。结果表明,地层压力场重新分布,改善了吸水剖面,地层平均吸水率为105．5％,测试平均成功率达到92．2％,有效防止了关井后地层返吐造成的出砂现象,提高注水层段的合格率,平均达到70．15％,防止了因停注或压降造成的吐聚现象。     

长春市粉煤灰蒸压加气混凝土围护结构传热系数现场检测分析

本文分析了传热系数现场检测方法的原理及适用条件,用热流计法检测粉煤灰蒸压加气混凝土围护结构的传热系数,并将实测数据与设计值、理论计算值进行了分析与研究．     

Peirce机织物几何结构模型的探讨

织物几何结构就是纱线在织物内部的屈曲状态,它影响织物的外观效应和物理机械性能,必须精确计算.在被普遍使用的Peirce机织物几何结构模型中,暗含如下假设:1织物中经纬纱屈曲波高无论怎样变化,其和均等于经纬纱理论直径之和乘以压扁系数;2同一浮长覆盖下的纱线中心在同一水平面上,屈曲波高仅与织物密度和织造缩率有关.从两个方面对此进行验证,一是以经典教材多块织物样品为例,用Peirce公式计算结果评估自身的精确性;二是用Nedgraphics纹织系统设计同一经纬密度的各种结构的机织物,在电子提花机上织造后利用Keyence 3D共聚焦显微镜对织物正反面进行非破坏性测量,得到不同浮长织物的屈曲波高并进行分析.结果表明,Peirce机织物的几何结构模型存在不足,需进一步改进.     

路堤下盖板涵的竖向土压力分布

由于盖板在填土压力作用下发生挠曲变形,针对盖板涵对竖向土压力分布的影响,推导了盖板涵竖向土压力分布计算公式.假设盖板发生弹性挠曲变形,填土服从Winkler弹性地基条件,对盖板上修正的Marston填土涵洞竖向土压力分布进行了分析.结果表明,该修正公式考虑了盖板涵内外土柱差异沉降的应力集中效应,可计算由于盖板挠曲变形而引起的土压力重分布.通过对鹤大高速公路某盖板涵进行现场测试以及有限元数值模拟分析,结果显示盖板涵土压力的分布特点与本文理论分析相一致,且理论公式计算结果值与现场实测值吻合较好.