共查询到20条相似文献,搜索用时 62 毫秒
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依据ISO 6142和GB/T 5274标准,采用称量法制备1 μmol/mol的氮中微量氧气体标准物质.使用钢瓶清洗系统和配气系统,通过超纯气体纯化器对高纯氮中的氧杂质进行脱除,使纯化后氧含量小于3 nmol/mol.同时平行配制模拟气,确保空气中的氧对所制备的标准物质污染最小.用微量氧分析仪考察标准物质随贮存时间和压力变化的稳定性,并通过比对验证了标准物质的定值结果和不确定度,证明了该制备方法可行,定值准确可靠.气体标准物质定值扩展不确定度为2%,有效期限为12个月. 相似文献
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《中国测试》2020,(8)
介绍一种三聚甲醛挥发经过转换器加热裂解得到甲醛的新方法,通过补充适量的平衡气进行稀释,采用称量法制备得到目标浓度的高压瓶装甲醛气体标准物质。实验表明(210±5)°C为最佳的裂解温度,采用气相色谱质谱联用的方法对裂解产物进行分析,甲醛的纯度为99.525%。使用经过内壁特殊处理的铝合金气瓶对研制的氮中甲醛气体标准物质进行存储,量值水平1~5μmol/mol,成功通过国家二级标准物质定级评审,标物编号为GBW(E)083617。将研制的4.92μmol/mol氮中甲醛气体标准物质,气瓶编号L55016195,送至英国国家物理研究院进行比对,测试结果为4.81μmol/mol,采用En值进行判定,比对结果为满意,也进一步验证称量法制备定值得到的瓶装甲醛气体标准物质的准确性。 相似文献
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设计和研制了容量法多元混合标准气体简易动态配气装置,该装置漏率小于1×10-9Pa.m3.s-1,并且具备高精度称量、测温、测压系统。利用该动态配气装置,选用不同大小、不同体积的不锈钢定量环,可以一次稀释制备10-610-4(V/V)浓度范围的不同浓度、不同组分的混合标准气体,解决了微量组分标准气体配制上的困难。分析了容量法制备多元混合标准气体定值的不确定度来源,实验表明不确定度为1%2%。该方法简单、可靠,具有实际应用价值。 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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