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。     

基于水中氰化物测量不确定度评定的检测质量管理

通过评定实验室检测的测量不确定度,建立以不确定度指标量化检测质量控制和质量管理效果的方法。以水中氰化物测量不确定度评定为例,采用GUM法和线性拟合法,评定其A类和B类不确定度,着重量化了标准溶液制备、校准曲线回归、检测过程等B类不确度分量,并采用电子表格的统计性能,建立起便于日常检测中快速评定不确定度的方法。实验结果表明,当水样中氰化物的质量浓度为0.125mg/L时,扩展不确定度为0.008mg/L,评定模型中比色管内氰化物的质量引入的不确定度分量最大。评定过程说明了影响实验室检测数据质量的主要因素是人员、仪器、环境、测量方法、取样和以标准物质为代表的试剂;按照RB/T 214-2017的要求对上述因素规范管理,结合本文建立的不确定度动态评定方法,能够保证检测实验室的数据质量。     

一种适用性更强的标准不确定度A类评定

测量不确定度往往由统计方法和非统计方法分别求得A类、B类标准不确定度后再合成得到。而采用统计方法一般需要一定数量的测量数据且知道其统计分布规律,这在实际中很难做到。本文给出一种求解标准差的方法,以此来评定测量不确定度,对数据量和分布规律无特殊要求,在实际应用中取得较好效果。     

测量不确定度概念的理解

本文以测量误差与测量不确定度的定义解析,了解两者的区别,在概念上加深对测量不确定度的理解;通过介绍测量不确定度A类和B类评定方法的异同点,使检测人员初步认知测量不确定度的评定方法,为今后开展测量不确定度的评定工作打下基础。     

测量不确定度概念的理解

本文以测量误差与测量不确定度的定义解析,了解两者的区别,在概念上加深对测量不确定度的理解;通过介绍测量不确定度A类和B类评定方法的异同点,使检测人员初步认知测量不确定度的评定方法,为今后开展测量不确定度的评定工作打下基础。     

测量不确定度评定及应用

对测量误差和测量不确定度的基本概念进行了分析,并举例说明了测量不确定度A类和B类评定以及测量结果给出的方法,为测量不确定度评定提供参考。     

双光束激光多普勒测速实验系统的不确定度分析

激光多普勒测速技术被广泛应用于流体速度的测量。为减小双光束激光多普勒测速实验系统的测量误差,依据计量技术规范JJF 1059—1999 中规定测量不确定度的分析步骤和方法,针对系统的测量结果,从数学模型和测量方法2个方面,分析了流速测量中不确定度的主要来源。采用不确定度的A类评定和B类评定,对测量结果的各不确定度分量进行评定,得到了测量结果的合成标准不确定度和扩展不确定度。     

测量不确定度(Uncertainty of Masurement):表征被测量的真值所处量值范围的评定。

这里的评定指的是估计或估计值,用该值表征被测量所处的量值范围。测量不确定度由A、B两部份(分量) 合成。A类通过统计分析观测列的方法获得,通常称为“标准不确定度”。B类为除了上述A类以外的所有非统计不确定度分量合成。应当指出,A类和B类不能用随机”和系统”替代(对应)。7个国际组织早已建议用测量不确定度的概念代替测量误差的概念来描述测量结果。     

水听器法的医用超声声场参数测量不确定度分析

提出了一种基于水听器法测量医用超声声场参数的测量装置,可通过扫描声场获取IEC 61157国际标准所要求的声场中峰值负声压等医用超声诊断设备的声输出参数.同时以一种B型超声诊断仪为例,对声场中声压的测量不确定度进行分析,分别给出A类、B类测量不确定度及标准不确定度,并对影响测量结果的主要因素进行了评定,得出当声压测定结果为1.456 4MHz时,其最小扩展不确定度可为0.215 0MHz.     

可燃气体检测报警器测量结果不确定度评定

为了获得满意的测量结果,依据:JJG 693—2004《可燃气体检测报警器》检定规程,用标准气体(10,40,60)%LEL(相对扩展不确定度为1%,k=2)对可燃气体检测报警器进行测量,并依据JJF 1059—1999《测量不确定度评定与表示》,通过不确定度A类和B类评定方法求得各标准不确定度分量,并通过一定的数学运算和程序求得合成标准不确定度,最后获得可燃气体检测报警器测量结果的扩展不确定度。     

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.     

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.     

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.     

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)。