导体直流电阻测量结果的不确定度分析

本文依据国家标准提供的检测方法,对被测电线样品进行了测量,分析了测量过程各因素对测量结果的影响情况,提供了测量结果不确定度的评定过程,并对标准不确定度、合成不确定度、扩展不确定度以及测量结果的表示给予了明确的论述。     

公法线千分尺示值误差测量结果的不确定度评定

文章采用JJF1130-2005<几何量测量设备校准中的不确定度评定指南>中的方法对公法线千分尺示值误差测量结果的不确定度进行评定.给出了目标不确定度,并根据不确定度误差的来源对测量结果进行分析计算,得到合成标准不确定度.通过对目标不确定度和合成标准不确定度的大小比较来得到最终判据.     

直流电位差计示值误差测量结果的测量不确定度评定

在测量过程中,测量结果都不可避免地具有测量不确定度,直流电位差计是一种常见的测量电压的仪器,它用一个已知电压与被测电压相平衡,该已知电压可以由可调电流流过固定电阻来获得,或者由它们的组合而获得。本文主要从方法概述、确定测量中不确定度分量、建立数学模型、计算相对标准不确定度分量、合成相对标准不确定度、扩展不确定度等入手,介绍了直流电位差计测量不确定度的评定过程。     

M2等级砝码测量结果的不确定度评定

本文根据JJG99-2006砝码检定规程,分析各种测量不确定度的来源,通过输测量过程的引起不确定度、标准砝码引起的不确定度、天平显示分辨力引起的不确定度的评定,空气浮力引起的不确定度、磁性引入的不确定度、计算出砝码在各称量点的不确定度评估值。     

钢筋抗拉强度测量结果的不确定度评定

用微机控制电液伺服式万能试验机测量钢筋的抗拉强度时,为确定测量结果的分散性即测量结果的置信区间,对影响检测结果的诸多因素进行分析,确定不确定度产生的来源,并采用A类不确定度评定和B类不确定度评定的方法,对各个不确定度分量进行评定,再根据各个量的方差和协方差算得合成标准不确定度,最终用扩展不确定表示,给出钢筋抗拉强度测量的不确定度报告。     

六氟化硫中杂质含量测量不确定度评定

采用氦离子化气相色谱法和光腔衰荡法依照国家标准GB/T 18867—2014《电子工业用气体六氟化硫》测定六氟化硫中杂质气体含量和水分含量,通过分析测量过程中不确定度的来源,对各不确定度分量进行评定及结果判断。评定结果表明:六氟化硫中杂质气体含量的测量不确定度主要来源于标准气体。     

测量不确定度传播规律存在的问题及解决

通过分析GUM中不确定度传播规律推导过程所使用的三个假设;1)每次测量均使用不同测量设备;2)系统误差与随机误差不相关;3)系统误差的期望为0。本文在只假设系统误差与随机误差不相关的情况下,推导出了重复性条件下复杂数学模型测量结果的B类标准不确定度的传播公式。解决了目前测量不确定度传播规律推导过程中假设过多,以及推导过程中使用的假设在A类标准不确定度评定中不予考虑的矛盾。     

量块比较测量法的不确定度分析

1　前言长期以来 ,我们将测量结果减被测量真值定为测量误差。因而测量结果的准确度用测量误差来表示。近年来为向国际标准靠扰 ,测量结果已采用测量不确定度取而代之。因为测量误差是未知的 ,而测量不确定度是可以根据期望的置信概率来估计。因此 ,对测量结果的可靠性 ,即误差的大小的估量用不确定度比用误差来描述更确切 ,更科学。2　比较测量不确定度来源及计算方法量块比较测量不确定度来源有以下几项 :(ａ)比较测量中所用标准量块长度的不确定度 ;(ｂ)被测与标准量块的温度差 ;(ｃ)被测与标准量块的线膨胀系数差 ;(ｄ)被测量块温度偏差…     

电能表检验装置的误差测量与不确定度评定

标准电能表法常用于电能表检验装置的误差测量。本文叙述了检验电能表检验装置的测量方法,给出了方差、灵敏度和标准偏差的计算公式。并通过对电能表检验装置的误差测试来分析电能表检验装置的测量不确定度,从而给出电能表检验装置的合成标准不确定度和扩展不确定度。     

测量不确定度理解与应用(四)包含因子k的选择

当得到合成标准不确定度后．获得扩展不确定度Up的前提是确定包含因子k的数值。包含因子的确定方法取决于被测量的分布．因此当被测量Y的分布不同时，应采用不同的方法来确定包含因子。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。