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关于矢量网络仪校准是多年来人们不断研究改进的课题。文章介绍了系统误差和校准的概念，详细讨论了在实际应用中几种不同的校准方法，根据被测件与网络仪端口连接方式不同分为3种情况：被测件可以直接连接到网络仪的两个端口；被测件经过电缆、转接头适配器与网络仪端口连接；被测件放在测试夹具里，如二极管、晶体管、微带电路等。 相似文献
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宋君萍 《实验室研究与探索》2010,29(4)
使用激光导热仪测试4种炭黑以不同体积分数填充天然橡胶复合材料的导热性能。介绍了激光导热仪的测试原理、测试前的准备工作、测试过程以及测试工作的注意事项等,给出热扩散系数、比热与导热系数随温度的变化规律和不同炭黑的导热性能对比情况,并进行合理性分析。结果表明,采用激光导热仪测试橡胶导热性能是可行的,采用的方法是可靠的。 相似文献
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1 概述 在下厂生产实践中对微电机机壳引伸次数按一般设计资料介绍计算需要二次引伸才能成形,但实际生产一次成形已安全投产。为此对理论计算作进一步分析,并予以修正。 引伸次数是制定引伸工艺和设计引伸模的主要依据,阶梯引伸件的引伸系数一般根据制件的假想引伸系数m_y与圆筒形制件第一次极限引伸系数m_1相比较,若m_y>m_1则一次成形,否则需多次。由于零件结构复杂性不同,假想引伸系数m_y不一定能确切的反映制件的变形特性,故还需分析制件的变形特点,进而确定引伸次数,使次数尽可能的少。 相似文献
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吴平 《实验室研究与探索》2014,(7):48-52
阐述了一种基于实验室激光目标运动模拟器的校准技术和测试方法,根据非扫描激光雷达探测原理,应用雪崩光电二极管(APD)单元探测器、电荷耦合器件(CCD)和面阵探测器等技术,构建双通道激光被动式非扫描测试系统。对激光实验室目标仿真区域内模拟目标三维运动信息的获取和测量并予以校准,实现对激光雷达运动目标模拟系统的计量与校准,完成当前量值正确地溯源,满足型号装备技术保障的计量技术体系需求。 相似文献
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开发了基于数字图像相关法的光学引伸计,研制了非接触的光学变形测量系统。从数字图像相关法的基本原理出发,介绍了该引伸计系统的工作原理和实验前的准备工作。实验表明,该系统能实现均匀变形场的实时测量和非均匀变形场的事后分析。 相似文献
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新课程初中数学九年级人教版,北师大版、华师大版及苏科等版都介绍了如下一道习题“三角形两边之积等于第三边上的高与外接圆直径之积”及其引伸“圆上任意一点到某切线的距离等于该点到某切线的距离与圆直径的比例中项”,应用上述习题及引伸,我发现了如下两个新的几何定理． 相似文献
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工程测量技术的最新发展 总被引：1，自引：0，他引：1
随着计算机技术、电子学、激光技术、空间技术的进步，工程测量在其内涵、技术手 段、基本理论、测量设备等方面都发生了根本性的变化。讨论了测量学内涵的变化，介绍了ＧＰＳ， ＧＩＳ技术，数字化大比例尺地形图的测绘技术；简介了电子水准仪，激光准直仪、全站仪、陀螺 仪等新型设备。 相似文献
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根据定标物和定标算法的不同,对现有的各种传统摄像机定标方法进行了总结、比较和分类,并讨论了各种传统定标方法在计算机视觉中的应用特征,提出今后有待进一步研究的方向. 相似文献
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A 2 × 2 quasi-experimental design was used to investigate the impact of extrinsic incentives and reflection on students’ calibration
of exam performance. We further examined the relationships among attributional style, performance, and calibration judgments.
Participants were 137 college students enrolled in an educational psychology course. Results differed as a function of exam
performance. Higher-performing students were very accurate in their calibration and did not show significant improvements
across a semester-length course. Attributional style did not significantly contribute to their calibration judgments. Lower-performing
students, however, were less accurate in their calibration, and students in the incentives condition showed significant increases
in calibration. Beyond exam scores, attributional style constructs were significant predictors of calibration judgments for
these students. The constructs targeting study and social variables accounted for most of the additional explained variance.
The qualitative data also revealed differences by performance level in open-ended explanations for calibration judgments. 相似文献
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赵晓东 《邢台职业技术学院学报》2010,27(1):31-32
运动精度限制了并联机器人的应用,而运动学标定是提高并联机器人运动精度的有效手段。并联机器人的运动学标定方法有三种：传统标定方法、自标定方法和第三类标定方法。这三种标定方法各有特色,在应用这些方法对并联机器人进行运动学标定时需要充分考虑具体机构的特点。 相似文献
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在深入计量校准机构进行调查和分析现有远程校准系统的基础上,设计了一种普遍通用的远程校准系统。该校准系统投入较少,适应能力强,能提高校准机构的工作效率,为各企事业单位的器具送检节省了大量的时间。 相似文献
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Educational psychologists have found that metacognitive calibration predicts learning outcomes in self‐regulated learning. In this research the authors apply theories of metacognition from educational psychology and postulate that metacognitive calibration influences learning time and performance in online learning. Data gathered from 230 college students who completed online self‐regulated assignments in an introductory information systems course confirms that higher calibration accuracy leads to better performance on assignments, which contributes to higher exam grades. In addition, higher calibration accuracy also reduces the amount of time students spent on the online assignments. However, time spent on the assignments is not a mediator of the effect of calibration on learning performance. This research presents pioneering work in examining a holistic model that assesses the impact of metacognition in online learning on both assignment and exam level learning outcomes using field data collected through a natural learning setting. The findings highlight the need to include metacognitive calibration as one of the learner characteristics in research models addressing student performance in online learning. 相似文献
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《天津大学学报(英文版)》2017,(6)
Conventional camera calibration that employs calibration targets is a commonly used method to acquire a camera's intrinsic and/or extrinsic parameters. The calibration targets are usually designed as periodic arrays of simple high-contrast patterns that provide highly accurate world coordinate system points and the corresponding image pixel coordinate system points. The existing pixel coordinate extraction algorithms can reach a sub-pixel level; however, they treat each single pattern in one image as an independent individual, which makes it difficult to further improve extraction accuracy. In this paper, a novel method is proposed by utilizing the periodic arrangement characteristics of the calibration target pattern as a global constraint to improve the calibration accuracy. Based on a camera's pinhole model, the intersection point of two fitted curves is used as an optimized pixel point to replace the initial one. Following the pixel coordinate optimization procedures, experiments were performed using real data from a 3D laser line scanner and a dynamic precision calibration target. Our results show that the relative errors of camera homography matrix elements obtained by the proposed optimization method were reduced compared with the commonly used method. The average coordinate measurement accuracy can be improved by nearly 0.05 mm. It is shown that the proposed optimization method can enhance the camera calibration accuracy,especially when the extracted pixels are of poorer precision. 相似文献
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The present study used multiple calibration indices to capture the complex picture of fifth graders' calibration of feeling of confidence in mathematics. Specifically, the effects of gender, type of mathematical problem, instruction method, and time of measurement (before and after problem solving) on calibration skills were investigated. Fourteen classes (N = 389 fifth graders) were randomly selected from two school mathematics programs, namely the gradual program design and the realistic program design. Students completed two different types of mathematical problems (a set of computation problems and a set of application problems) and reported their feeling of confidence (that they would find the right solution) when first reading the problem statement and again after they had produced the solution of each of the problems. Students' calibration skills were measured using three indices of calibration. Effects on the calibration of feeling of confidence due to gender, instruction method, type of mathematical problem, and time of measurement were found and are discussed. 相似文献
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Accurate judgment of performance, or calibration, is an important element of self-regulated learning (SRL) and itself has been an area of growing study. The current study contributes to work on calibration by presenting practical and predictive results of varying calibration measures from authentic educational data: elementary-aged students' interactions with a year-long digital mathematics curriculum. Comparison of predictive validity of measures show only small differences in explained variance in models predicting posttest performance while controlling for pretest. A combined model including Sensitivity and Specificity outperforms other single measures, confirming results in Schraw, Kuch, & Gutierrez (2013); however, results show that student patterns of calibration within these data differ from those assumed in simulation studies and these differences have implications for the calculability of popular calibration measures. 相似文献
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Various applications of item response theory often require linking to achieve a common scale for item parameter estimates obtained from different groups. This article used a simulation to examine the relative performance of four different item response theory (IRT) linking procedures in a random groups equating design: concurrent calibration with multiple groups, separate calibration with the Stocking-Lord method, separate calibration with the Haebara method, and proficiency transformation. The simulation conditions used in this article included three sampling designs, two levels of sample size, and two levels of the number of items. In general, the separate calibration procedures performed better than the concurrent calibration and proficiency transformation procedures, even though some inconsistent results were observed across different simulation conditions. Some advantages and disadvantages of the linking procedures are discussed. 相似文献
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Classificationofaircleanlinessinanykindofclean roomsandcleanzoneswillbeaccomplishedintermsofconcentrationofairborneparticles .Alightdiscreteair borneparticlecounter (hereafterreferringtoasAPC)isusedtodeterminetheconcentrationofairborneparticlesequaltoandlargerthanthespecifiedsizesatdesignatedsamplinglocation[1,2 ] .Inthepracticalmeasurementofparticleconcentrationincleanrooms,itisfoundthetest ingresultsofparticlenumberinthesameareacountedbydifferentparticlecountersarequitedifferentanduptoanord… 相似文献