System for Measuring Elevator Guide Rail Quality and Its Calibration

A system for measuring the quality parameters of elevator guide rails is developed. The quality parameters the system can measure include straightness, flatness, squareness, width and height of the rail. The system consists of six parts:main guideway, auxiliary guideway, reference rail, saddle, control casing and measured rail. The guide rail to be measured is mounted on a bed. The straightness errors of surfaces are checked by five linear displacement sensors mounted on the saddle. The deviation of readings from the sensor, which is in contact with top guiding surface, gives the straightness error of the surface and height of the rail. The other four sensors are used to measure side guiding surfaces respectively and give other parameters including flatness on the surfaces, squareness, width and height of the rail. A novel calibration method is also developed to calibrate the straightness motion error of the system in horizontal and vertical directions. The deflection deformation of the measured rail is fitted by using a fourth-order polynomial. Experimental results show that the uncertainty of the system on the side surfaces after compensating the straightness motion error is less than 0. 01 mm, and the uncertainty of the system on the top surface after compensating the straightness motion error and the deflection deformation of the rail is less than 0.03 mm.     

Temporal Error Concealment Technique for MPEG-4 Video Streams

Concerning inter4v mode employed widely in MPEG-4 video, a new temporal error concealment scheme for MPEG-4 video sequences is proposed, which can selectively interpolate one or four motion vectors (MVs) for the missing macroblock (MB) according to the estimated MB coding mode. Performance of the proposed scheme is compared with the existing schemes with multiple testing sequences at different bit error rates. Experimental results show that the proposed algorithm can mask the impairments caused by transmission errors more efficiently than 0 MV and average MV methods by consuming more time for different bit error rates. It has an acceptable image quality close to that obtained by the selective motion vector matching (SMVM) algorithm, while taking less than half of cycles of operations. The proposed concealment scheme is suitable for low complexity video real-time implementations.     

Using a Shiny app to teach the concept of power

Understanding and computing power and the relationship between sample size and power are facilitated via a Shiny app. The Shiny app allows students to solve various scenarios by entering different parameters or moving sliders.     

光杠杆放大法测量中α角产生的误差

分析了用光杠杆放大法测量长度变化量的实验中,光杠杆镜面与望远镜光轴不垂直时,对测量微小长度变化所产生的误差.     

基于MAPGIS6.6地图矢量化误差分析及校正

MAPGIS作为深受广大用户喜爱的一款国产GIS软件，已经从4．0．5．0,5．32、6．0．6．5发展到目前的6．6版本。但是在图形矢量化过程中依然不可避免各种类型误差的产生。文章对MAPGIS6．6图形处理模块在地图矢量化过程中产生误差的原因及减小误差、误差校正等问题进行了深入地分析和探讨。     

双模压缩真空态模间纠缠度的讨论

讨论了双模压缩真空态的模间纠缠度与压缩参数的关系，同时指出造成以往文献中双模压缩真空态的模间纠缠度的不同形式的图像产生差异的原因是数值计算的浮点数误差．     

机械设计中对回转体零件基准选择的分析

分析了机械设计图样中回转体类零件基准标注的三种形式,得出了以装轴承的两轴颈(或孔)的公共轴线为基准最好.应用数学演绎推理法证明了这种基准使位置误差偏移值最小,又符合实际装配工作条件,比较理想.仅在以较长的圆柱面为主要定位面时才可选择单一基准.最后探讨了实现基准统一时的基准转换问题及增加辅助基准问题.     

Visual and phonological determinants of misreadings in a transparent orthography

Growth of word reading skills was examined in first and second year Italian school children by analysis of the pattern of reading errors. The study was designed to investigate the role of visual vs phonological similarities as causes of misreadings in a transparent orthography. The selection of reading material was tailored to permit a meaningful cross-language comparison with pre-existing findings on English-speaking children. The results showed that, in Italian as in English, spatially-related errors (such as confusingb andd) constituted a minor proportion of the total errors. Errors on vowel and consonant letters that are not spatially confusable accounted for the greater proportion of the total. Moreover, the co-occurrence of spatial and phonological confusability resulted in appreciably more errors than when either occurred without the other. Vowel position in the syllable had no systematic effect on errors. In beginning readers of Italian, consonant errors outnumbered vowel errors by a wide margin; the reverse pattern was found in previous studies on English-speaking children at the same level of schooling. It is proposed that differences between Italian and English in the phonological structure of the lexicon and in the consistency of grapheme-phoneme correspondences account in large part for the differences in quantity and distribution of the errors.     

陕北地区普通话水平测试中常见声母、韵母错误类型分析

通过对若干不同等级应试测试语音材料的分析，归纳出陕北地区普通话水平测试中常见的声母错误36类，韵母错误51类，以期为测试员提供可供参考的语音评定参照框架。     

处理纸带实验数据的最佳方法

对“研究匀变速直线运动”的实验数据处理过程进行了深入的误差分析,在此基础上指出了处理纸带实验数据的最佳方法。