共查询到20条相似文献,搜索用时 93 毫秒
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ISO导则35《标准物质定值及通用统计学原则》中要求,采取称量法制备、定值的标准物质,需评估由称量法制备、均匀性、稳定性及核验四个分量引入的不确定度.对于称量法制备的校准用溶液标准物质,制备过程中由天平和容量器具引入的不确定度往往较小且易于评估,而制备过程中其它来源不确定度以及核验、均匀性、稳定性不确定度的评估方法会对该类标准物质的总体量值不确定度水平产生显著影响.本文以导则35及GUM原则为基础,提出了针对该类标准物质量值不确定度评定的新型改进方法,以达到既确保评估的全面性,又通过适当的方案设计,去除各不确定度分量中的交叉重叠成分,避免不确定度评定结果盲目扩大的目的. 相似文献
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为了满足新疆地区对黏度标准物质的需求,研制了三种常用的标准黏度液。标准黏度液以精制甲基硅油为原料配制。使用MCR302流变仪分析甲基硅油的流动性和黏温性。使用标准毛细管黏度计对配制的黏度液进行均匀性、稳定性考察和定值,采用方差分析法和趋势分析法进行统计检验。评定了运动黏度值的不确定度并与国家一级标准物质比对,结果表明研制的黏度液量值准确可靠,相对扩展不确定度U=(0. 33~0. 40)%(k=2),均匀性和稳定性符合二级标准物质的要求,有效期1年,可以用于检定或校准工作用黏度计。 相似文献
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本文介绍了氮中乙烷气体标准物质制备的原理和过程,运用气相色谱仪对该气体标准物质进行比较法定值,同时对研制气体标准物质的压力变化均匀性以及储存时间稳定性考察,以及对引入的不确定度进行计算评估.试验结果表明研制的气体标准物质量值准确可靠,在浓度范围内具备良好的均匀性和稳定性,技术指标达到了项目预期目标. 相似文献
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标准样品的稳定性检验 总被引:4,自引:0,他引:4
1.标准样品的稳定性概念在第5讲中我们知道:根据标准样品技术的基本理论,在测量、确定标准样品特性值时,该值的测量不确定度是由三个互相独立的分量合成的。这就是:测量方法引入的测量不确定度分量、瓶-瓶之间非均匀性引入的测量不确定度分量和随时间变化样料不稳定性引入的测量不确定度分量。那么什么是标准样品的稳定性?由于标准样品在运输过程中或贮存在仓库期间内时,标准样品的特性值可能会随运输条件的变化或在规定的贮存条件下随时间的改变而变化。在标准样品技术领域内,我们把在合适的运输条件下,在运输期间标准样品特性的变化程度称… 相似文献
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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. 相似文献
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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. 相似文献
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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)。 相似文献
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Liebert A Wabnitz H Grosenick D Möller M Macdonald R Rinneberg H 《Applied optics》2003,42(28):5785-5792
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. 相似文献
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