共查询到18条相似文献，搜索用时 189 毫秒
1.
QIU Yong-you KANG Shuang-yang PENG Yun-feng YANG Ping HUANG Zi-qiang 《重庆大学学报(英文版)》2016,15(4):139-148
The purpose of the study concerns the measurement of worm’s helical angle by a coordinate measurement machine in the ambient industrial environment. The novel measurement method and sampling strategy were described firstly. This method used the coordinate measurement machine to measure both of the worm gear’s left and right surfaces. The worm surface was reconstructed based on the measured data of all the sampling points. Then a middle cylinder was established to truncate the fitted worm surfaces, and the truncated spiral lines were straightened to calculate the helical angle. The measurement uncertainty of worm’s helical angle was evaluated by taking the difference of calculated helical angles along the truncated spiral lines on both the left and right side surfaces of the worm. Twenty-four measurement experiments show that the maximum measurement error of the proposed method is 0.105, and the measurement error ratios are all less than 3.5?. The result means that the measurement method can realize the precision measurement of worm’s helical angle and can be employed in the generally industrial application. 相似文献
2.
通过对交流同步采样误差的分析,提出了一种软件补偿算法,解决被测信号工频周期变化、采样时间间隔非等分等带来的采样精度降低的问题．仿真结果表明此法切实可行、计算简单,有效地提高了测量精度． 相似文献
3.
In fringe projection profilometry, the nonlinear intensity response caused by the γ effect of a digital projector results in periodic phase error and therefore measurement error. Previous error correction methods are largely based on the calibration of single γ value. However, in practice, it is difficult to accurately model the full range of the intensity response with a one-parameter γ function. In this paper, a compensated intensity response curve is generated and fitted with the constrained cubic spline. With the compensated curve, the full range of the nonlinear intensity response can be corrected and the periodic phase errors can be removed significantly. Experimental results on a flat board confirm the average root mean square （RMS） of the phase error which can be reduced to at least 0.0049 rad. 相似文献
4.
文章首先分析了传统多周期同步测频原理及误差,然后对全同步和准全同步两种频率测量的改进方法做了讨论,分析了其原理与特点,最后,在此基础上提出了一种新的改进方法,该方法通过对标准频率计数值的修正,在不提高系统时钟频率和延长闸门时间的前提下,实现了测量精度的提高,并详细分析了其测量误差。 相似文献
5.
具有最少采样点的圆度误差测量研究 总被引：1，自引：0，他引：1
建立了采样点均匀分布情况下，圆度误差测量采样点数量与测量极限误差之间的定量关系数学模型。根据所得数学模型，对测量坐标值原则下给定圆度误差检测对象的采样点进行规划，求得具有最少采样点的测量方法，并给出了测量实例，对数学模型进行了验证。 相似文献
6.
《洛阳师范学院学报》2016,(2):37-41
为消除数控机床在长期使用中定位精度和重复定位精度降低的现象,并对机床进行精度检测及误差补偿,以ZJK7532A机床精度的检测为例,采用激光干涉仪对机床的线性误差和角度误差进行研究.通过调整光路、搭建环境补偿以及设置软件参数等完成对系统的总体调试,进而通过Laser XL软件采集测量数据.根据测量结果分析得出,该ZJK7532A华中数控钻铣床的精度已经超出机床允许的误差范围,需要进行误差方面的修整,最后分析了激光干涉仪测量误差的来源. 相似文献
7.
许胜辉 《武汉职业技术学院学报》2011,10(1):69-71,82
对交流（AC）信号进行同步采样,如电网电压和有功功率均方根值,为了测量计算的非同步交流信号（在文10-6[1]的部分）。提出了一种估值测量的数学表达式,它可测量非同步基频交流信号。用该方法测量的结果与高精密仪器测量的结果进行了比较。最后通过仿真实验证实了此方法的有效性和实用性。 相似文献
8.
Effect of the scale of quantitative trait data on the representativeness of a cotton germplasm sub-core collection 总被引：1，自引：0，他引：1
Jian-cheng WANG Jin HU Ya-jing GUAN Yan-fang ZHU 《Journal of Zhejiang University. Science. B》2013,14(2):162-170
A cotton germplasm collection with data for 20 quantitative traits was used to investigate the effect of the scale of quantitative trait data on the representativeness of plant sub-core collections.The relationship between the representativeness of a sub-core collection and two influencing factors,the number of traits and the sampling percentage,was studied.A mixed linear model approach was used to eliminate environmental errors and predict genotypic values of accessions.Sub-core collections were constructed using a least distance stepwise sampling(LDSS) method combining standardized Euclidean distance and an unweighted pair-group method with arithmetic means(UPGMA) cluster method.The mean difference percentage(MD),variance difference percentage(VD),coincidence rate of range(CR),and variable rate of coefficient of variation(VR) served as evaluation parameters.Monte Carlo simulation was conducted to study the relationship among the number of traits,the sampling percentage,and the four evaluation parameters.The results showed that the representativeness of a sub-core collection was affected greatly by the number of traits and the sampling percentage,and that these two influencing factors were closely connected.Increasing the number of traits improved the representativeness of a sub-core collection when the data of genotypic values were used.The change in the genetic diversity of sub-core collections with different sampling percentages showed a linear tendency when the number of traits was small,and a logarithmic tendency when the number of traits was large.However,the change in the genetic diversity of sub-core collections with different numbers of traits always showed a strong logarithmic tendency when the sampling percentage was changing.A CR threshold method based on Monte Carlo simulation is proposed to determine the rational number of traits for a relevant sampling percentage of a sub-core collection. 相似文献
9.
基于MAX125的多通道同步采样数据采集系统 总被引：2，自引：0，他引：2
涂水林 《常熟理工学院学报》2004,18(2):56-58
介绍了一种基于MAX125的多通道同步采样数据采集系统.该系统由89C51单片机作为控制核心完成控制功能.文中较详细地介绍了本系统的硬件电路设计和软件设计方法. 相似文献
10.
黄磊 《淮北职业技术学院学报》2006,5(5):72-72
多周期同步测量是实现频率等精度测量的一种有效的方法.本文提出了用单片机实现频率的多周期同步测量的原理,并对该方法的测量精度进行了分析. 相似文献
11.
石梅香 《实验室研究与探索》2011,30(2):70-73
根据铁路检测信号的特点论述了基于AD7657数据采集系统。AD7657是真正的多通道双极性ADC转换器,该系统用单片机控制对振动信号进行同步采集,并将采集到的数据经过处理。文中对系统的硬件组成结构予以详细介绍,并给出了软件流程。 相似文献
12.
本讨论稀土永磁同步电动机空载反电动势R的取值是电磁设计的关键所在．它关系列永磁同步电动机运行性能的效率和功率因数的大小，采用变压变频(VVVF)交流调遣系统，可以保持电源的频率f与电源的电压U以及与空载反电动势E0的对应关系，结合稀土永磁同步电动机的设计值和试验实测值。阐明变压变频(VVVF)交流调速系统是稀土永磁同步电动机的最佳调速方法。 相似文献
13.
高河福 《韩山师范学院学报》2011,(6):49-53
本文分析了B／S结构的应用系统中表单重复提交的原因,并在深入研究同步令牌核心工作原理和应用过程的基础上,将同步令牌的机制用于解决表单重复提交的问题,让需要避免重复提交的页面在每次提交页面时携带同步令牌,通过初始化令牌、校验令牌、销毁令牌等步骤,解决了表单重复提交的问题．并对其实现的过程进行了分析和阐述． 相似文献
14.
苗童玲 《晋城职业技术学院学报》2012,5(6):62-63,78
本文研究目标是油田企业的永磁同步电动机抽油机的变频控制方案,介绍了目前抽油机的技术发展现状以及应用领域,给出了永磁同步电动机在抽油机上应用的控制方案,结果表明,将永磁同步电动机应用于抽油机能够明显提高其工作性能和节能指标。 相似文献
15.
＂机械制图＂与＂AutoCAD＂课程教学当前存在一些问题。＂机械制图＂融入＂AutoCAD＂课程同步教学具有优越性。轮机工程专业的＂机械制图＂与＂AutoCAD＂同步教学方案,明显提高课程的教学效果,能更好地实现教学目标。 相似文献
16.
相位差校正法是连续两次加窗截断时域信号并进行两次FFT变换,然后利用其对应离散谱线的相位差校正出谱峰处的准确频率和相位的新校正方法,通过利用插值fft算法的窗谱函数公式还可以校正其幅值,用以解决离散频谱分析中由于不能做到同步采样带来的较大误差。由于加Blackman-harris窗函数的频谱泄漏影响小、计算精度高,所以本文采用加Blackman-harris窗截断。 相似文献
17.
Lanqin Zheng Panpan Cui Xin Li Ronghuai Huang 《Assessment & Evaluation in Higher Education》2018,43(3):500-514
Research on peer assessment in higher education has been conducted for decades. However, ways to improve the quality of peer feedback and optimise student’ benefits through peer assessment remain a puzzle. The present study aimed to examine the impacts of synchronous discussion between assessors and assessees on writing performance, qualitative feedback quality, meta-cognitive awareness and self-efficacy in web-based peer assessment. A total of 64 undergraduate students participated in the study and were randomly assigned into either the experimental or control group. Participants in the experimental group conducted synchronous discussion after the first round of peer assessment, while students in the control group did not conduct any synchronous discussion. The results revealed that synchronous discussion between the assessors and assessees significantly improved the students’ writing performance, especially content writing skills, affective and meta-cognitive feedback quality, meta-cognitive awareness and self-efficacy. Practical implications, limitations and future directions are discussed based on these findings. 相似文献
18.
This study examined differences in student satisfaction and perceptions of online teamwork in two cohorts of an undergraduate educational technology course: one delivered fully asynchronously and the other incorporating synchronous Google Hangouts sessions in student online teamwork. Participants included 50 undergraduate students at a large university in the northeastern United States. Results indicated that the cohort that used synchronous Google Hangouts as a tool supplementary to the asynchronous communication components such as discussion boards and e-mails had a higher level of satisfaction with online teamwork when compared with the cohort that used only asynchronous communication tools. In addition, students reported that synchronous communication using Google Hangouts helped them develop a sense of community. Implications of the results are discussed. 相似文献