声学共鸣腔特征长度激光干涉法测量图像处理软件研制

圆柱形声学共鸣腔特征长度是声学法测量玻尔兹曼常数的一个重要参数。在中国计量科学研究院建立的圆柱形声学共鸣腔特征长度双波长测量系统基础上，基于图形化编程语言Labview设计开发了图像处理软件。实现了对长度测量系统输出图像的滤波去噪、CCD像素元按灰度值的软件细分、拟合法测量等倾环直径、减小了特征长度测量系统的不确定度，从而极大的提高了玻尔兹曼常数测量的精度。     

圆主形声学共鸣腔端面平行性测量

圆柱形声学共鸣腔特征长度是声学共鸣法定义玻尔兹曼常数中一个关键参数,圆柱形声学共鸣腔的端面平行性是确定圆柱形声学共鸣腔特征长度的重要因素.采用Fabry - Perot腔激光等倾干涉原理,通过旋转圆柱形声学共鸣腔,实现了圆柱形声学共鸣腔端面平行性的高精度测量.     

测量理想气体状态下单原子分子输运性质的双毛细管黏度计研究

热力学温度是客观世界真实的温度,是制定国际温标的基础,目前声学基准测温法是测量中低温区热力学温度不确定度最小的方法,中国计量科学研究院采用圆柱型定程共鸣腔建立了声学温度计,但是圆柱型共鸣腔的热边界层和黏性边界层修正是影响这种测量方法最主要因素之一,而决定边界层修正的参数是理想气体状态下气体工质的输运性质(黏度和导热系数).双毛细管黏度计测量气体介质黏度和导热系数具有很高的准确性,该方法结合了基准毛细管黏度计和量子化“从头算”的优势,可以有效地降低毛细管基准黏度计的测量不确定度与温度的依赖关系.本文介绍了作者在中国计量科学研究院开展的双毛细管黏度计测量氩气输运性质的研究,测量温度范围为240 ～400 K,测量相对标准不确定度为0.083％.     

三项创新助推我国玻尔兹曼常数测量进入国际“第一梯队”

国际计量委员会（CIPM）建议采用自然基本常数——玻尔兹曼常数kB来定义热力学温度单位开尔文（K）。准确绝对地测量玻尔兹曼常数,使其不确定度达到新定义可以接受的水平,是国际计量界面临的极大挑战。     

坐标测量机面向任务的测量不确定度评定

基于产品几何技术规范,分析了坐标测量机面向任务的测量不确定度主要来源;重点讨论了量值特性指标测量复现性的定义与特点,并针对坐标测量机的测量任务,提出引起坐标测量复现性的主要因素,研究了进行复现性指标评价的实验方案,建立了复现性评定的数学模型;通过孔径测量实例分析,介绍了坐标测量机面向任务的测量不确定度评定方法。结果表明,孔径测量结果的合成标准不确定度为3.2 μm,其中测量复现性的不确定度分量高达2.5μm,在测量结果不确定度中所占比重最大。     

双锥腔互补偿型绝对辐射计的测量不确定度分析

由双锥腔互补偿型绝对辐射计(DCICAR)的热平衡方程,推导并建立了评定测量不确定度的数学模型.讨论了主要的不确定度来源,对在航天器上测量一个太阳常数(1367 W/m2)时的各个不确定度分量分别进行了计算,包括工作腔替代加热丝电阻、加热丝所加电压、腔吸收率、视场同环境的辐射交换、日地距离校正等,最后得到的合成标准不确定度为0.77 W/m2,扩展不确定度为1.5 W/m2(ρ=0.95).     

导管对圆柱共鸣腔径向共振模式的扰动

修正进气导管的影响对声学共鸣法测量Boltzmann常数kB十分必要。基于一阶声学微扰理论研究了导管对圆柱形共鸣腔理想径向共振模式的扰动,分析了导管末端不同连接方式所带来的声阻抗差异,计算了导管对（001）径向模式的共振频率和半宽的扰动值分别为Δf/f0≈-0.04×10^-6和Δg/f0≈14.15×10^-6,同时分析了导管长度、半径以及径向安装位置的变化对理想径向共振模式扰动的影响。     

利用光学方法测量实验室标准传声器的前腔深度

实验室标准传声器的前腔深度是耦合腔互易法校准其声压灵敏度的主要不确定度分量之一.为了控制声压灵敏度校准的不确定度,利用光学三坐标自动测量系统,分别通过直测法和块规法测量3只LS1P和3只LS2P传声器的前腔深度.测量结果表明,在传声器外环面放置高精度的块规,较好匹配了传声器与平面波耦合腔进行声学耦合时的物理模型,其前腔深度测量不确定度优于3.0 μm(k=2).对于LS1P传声器20 Hz～10 kHz频率范围内的声压灵敏度,前腔深度引入的不确定度分量优于0.005 dB(k=2);对于LS2P传声器,20 Hz～25 kHz频率范围内的不确定度分量优于0.012 dB(k=2),能够实现实验室标准传声器声压灵敏度的高精度校准.     

国内对温度单位重新定义的研究

鉴于有同期论文介绍了中国计量科学研究院量子电压噪声原级法测量玻尔兹曼常数的研究,故本文概述性地介绍了定程圆柱声学原级法测量玻尔兹曼常数的研究,同时介绍了应用该原级方法达到当前国际上最先进的测量水平所面临的技术难点问题,以及我们的解决方法,及其对国际单位制基本单位重新定义的贡献和未来研究的展望。     

化妆品中新补骨脂异黄酮、补骨脂二氢黄酮、补骨脂素和异补骨脂素含量的测量不确定度评定

用高效液相色谱法测定化妆品中新补骨脂异黄酮、补骨脂二氢黄酮、补骨脂素和异补骨脂素含量,建立数学模型,分析检测过程中不确定度的来源,给出量化结果,得到标准不确定度和扩展不确定度。结果表明,当取95%置信概率,包含因子k为2,被测样品中新补骨脂异黄酮、补骨脂二氢黄酮、补骨脂素和异补骨脂素的含量分别为42.61μg/g、44.04μg/g 、42.94μg/g和41.90μg/g时,相应的扩展不确定度为1.65μg/g、1.82μg/g、1.66μg/g和1.61μg/g。分析了测量不确定度的主要来源,并提出了改进建议。     

Length Determination of a Fixed-Path Cylindrical Resonator with the Dual Wavelength Laser Interference Method

The length is one of the key parameters for a cylindrical acoustic resonator used for measurement of the Boltzmann constant. A research project has been conducted in the National Institute of Metrology (NIM), China, for the re-determination of the Boltzmann constant with a fixed-path cylindrical acoustic resonator. This paper describes the procedure for the length determination. The excess fraction method was applied to accurately obtain the length of the resonator. This method is performed in a two-step procedure. First, the length is coarsely determined as L ₁ with an uncertainty of 1.5 ??m in the length division of NIM. Second, the result of the coarse measurement is further interpolated by the dual wavelength laser interferometer with a resolution of 1 nm, which is composed of a 633 nm He?CNe laser and a 657 nm semiconductor laser. A Michelson wavemeter has been constructed for calibration of the wavelength of the semiconductor laser. The length variation of the resonator has to be measured from room temperature to the triple point of water (TPW). As a result, the laser interferometer can be also used as a precise dilatometer. The result and the measurement uncertainty of the length measurement are given in this paper.     

Assessment of Uncertainty in the Determination of the Boltzmann Constant by an Acoustic Technique

NPL is currently carrying out acoustic resonator experiments with the aim of determining the Boltzmann constant k _B with an uncertainty below 1 part in 10⁶. In this article, the progress in our efforts to assess the uncertainty in our determination is described. The uncertainty contributions arising from dimensional, chemical, isotopic, thermal, and acoustical considerations are assessed, and it is concluded that a measurement with an uncertainty below 1 part in 10⁶ is achievable.     

多边法坐标测量系统中解算方式对测量精度的影响研究

为了研究多边法坐标测量系统中解算方式对测量精度的影响,建立了多边法坐标测量模型,分析了两种目标点坐标解算方式的差异,并针对典型的4台测站多边法坐标测量系统进行了两种解算方式的仿真测量实验。仿真结果表明:预先准确标定系统参数方式能有效提升测量精度,测量精度依次改善了69.5%、64.6%、46.3%。进行了坐标测量精度验证实验,实验结果表明:与同步解算方式相比较,预先准确标定系统参数取模后的3组实验平均测量误差由203.0μm降至23.8μm,且3组实验的测量误差与测量距离的平均相关系数由99.8%降至37.8%,验证了仿真实验结果。     

绝对重力仪落体光心与质心空间距离测量

为了准确测量重力仪落体光心与质心距离,减少落体光心与质心不重合引起的旋转对重力加速度测量的影响,设计了落体光心与质心空间距离测量装置。提出了1种光心与质心间距的计算方法,并仿真验证了计算方法的可行性。使用设计的测量装置对落体进行测试,结果表明:激光干涉仪在信号频率为0.3~0.5Hz时的测量精度为0.1nm,提出的计算方法可以使测量系统的A类不确定度优于10μm,最大调校测量误差为1μm。     

常温黑体光谱发射率校准技术研究

为了能够实现常温状态下的黑体光谱发射率的准确测量,基于连续可调激光器,搭建了一套中红外波段黑体光谱发射率测量装置。采用自行设计10 mA恒流源对MCT探测器进行驱动,测量结果的动态范围从7.29×10⁴提高到4.32×10⁵,有效提升了探测系统的动态范围。该装置实现了覆盖光谱范围7.5～10.6μm,发射率测量量值范围0.01～0.999 9的高精度测量,最优不确定度为4.0×10^-5(k=2)。     

Measurement of the Boltzmann Constant <Emphasis Type="Italic">k</Emphasis><Subscript>B</Subscript> Using a Quasi-Spherical Acoustic Resonator

There is currently great interest in the international metrological community for new accurate determinations of the Boltzmann constant k _B, with the prospect of a new definition of the unit of thermodynamic temperature, the kelvin. In fact, k _B relates the unit of energy (the joule) to the unit of the thermodynamic temperature (the kelvin). One of the most accurate ways to access the value of the Boltzmann constant is from measurements of the velocity of the sound in a noble gas. In the method described here, the experimental determination has been performed in a closed quasi-spherical cavity. To improve the accuracy, all the parameters in the experiment (purity of the gas, static pressure, temperature, exact shape of the cavity monitored by EM microwaves, etc.) have to be carefully controlled. Correction terms have been computed using carefully validated theoretical models, and applied to the acoustic and microwave signals. We report on two sets of isothermal acoustic measurements yielding the value k _B = 1.380 647 74(171) × 10⁻²³ J · K⁻¹ with a relative standard uncertainty of 1.24 parts in 10⁶. This value lies 1.9 parts in 10⁶ below the 2006 CODATA value (Mohr et al., Rev. Mod. Phys. 80, 633 (2008)), but, according to the uncertainties, remains consistent with it.     

基于传感器阵列的野外基线环境参数自动测量系统研制

为了保证野外测距精度,研制了一套环境参数自动测量系统,该系统通过在野外基线沿线布置密集的气温、气压与湿度传感器阵列,精确测量光路气温、气压及湿度等环境参数,进行空气折射率修正。采用μ-base测距仪在不同气候条件下进行验证实验,测量距离为144 m。实验结果表明,采用该系统测量环境参数,进行空气折射率修正,其修正误差引入的距离测量不确定度优于3.0×10^-7(k=2)。     

Cylindrical Acoustic Resonator for the Re-determination of the Boltzmann Constant

The progress towards re-determining the Boltzmann constant k _B using two fixed-path, gas-filled, cylindrical, acoustic cavity resonators is described. The difference in the lengths of the cavities is measured using optical interferometry. Thus, a literature value for the density of mercury is not used, in contrast with the presently accepted determination of k _B. The longitudinal acoustic resonance modes of a cylindrical cavity have lower quality factors Q than the radial modes of gas-filled, spherical cavities, of equal volume. The lower Qs result in lower signal-to-noise ratios and wider, asymmetric resonances. To improve signal-to-noise ratios, conventional capacitance microphones were replaced with 6.3 mm diameter piezoelectric transducers (PZTs) installed on the outer surfaces of each resonator and coupled to the cavity by diaphragms. This arrangement preserved the shape of the cylindrical cavity, prevented contamination of the gas inside the cavity, and enabled us to measure the longitudinal resonance frequencies with a relative standard uncertainty of 0.2 × 10⁻⁶. The lengths of the cavities and the modes studied will be chosen to reduce the acoustic perturbations due to non-zero boundary admittances at the endplates, e.g., from endplate bending and ducts and/or transducers installed in the endplates. Alternatively, the acoustic perturbations generated by the viscous and thermal boundary layers at the gas–solid boundary can be reduced. Using the techniques outlined here, k _B can be re-determined with an estimated relative standard uncertainty of 1.5 × 10⁻⁶.