基于等效合成波方法的双真空管空气折射率测量仪

在高精度测量中必须实时补偿空气折射率的影响。文中提出了等效合成波的概念,利用长度不等的两个真空管构成两个虚拟波长并推导出等效合成波测量公式,并由此建立了一种新型的双真空管空气折射率测量仪。该仪器具有结构紧凑、能实现实时测量的优点。系统测量分辨率为1×10-8,与Edlen公式方法进行的比对实验结果表明,其测量精度优于1×10-7,并具有很好的稳定性和抗干扰能力。     

试析光干涉测量几何长度的相对不确定度极限

随着稳频激光和现代干涉仪的发展，光波波长在空气中的不确定性已成为限制用光学方法测量几何长度相对不确定度的主要因素。本回顾了现代干涉测长精度的提高；探讨了用Ｅｄｌｅｎ公式修正空气中波长及其在高精度实际应用中的限制，用折射率干涉仪修正空气中波长的技术关键和可达到的精度极限；最后介绍了在真空中测长的实用性以及可能达到的精度。     

翅片管换热器空气侧换热模型在低气压环境下的适用性研究

本文总结了现具有较高认可度且具有相当预测精度的空气侧换热特性的理论预测模型,选用常规平直铝翅片铜管换热器在典型的空调工况(空气干球温度为27℃,湿球温度为19. 5℃,换热器迎面风速为1~4 m/s,入口水温为7~13℃,流速为1. 8 m/s)下,对现有模型在低气压环境(40~100 kPa)下的适用性进行分析研究。实验研究表明:在试验工况下,随着换热器所处环境压力的降低,常压模型预测值与实验值的偏差急剧增加至127. 4%^-36. 6%,且常压模型预测值普遍偏大。同时低气压环境下管排数的影响依然存在,且更加显著。基于本文实验数据对3个常压模型进行环境气压修正后,预测精度大幅提高:在试验工况下,最大偏差分别降至32. 63%、24. 91%和21. 74%,平均偏差为1. 79%、-2. 90%和-8. 59%,在±20%的误差带内修正模型预测精度比分别达到90. 97%、93. 75%和88. 96%。     

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)。     

空气折射率埃德林公式的修改

由于空气密度和水蒸汽折射率数值的更新、温标的两次改值、以及空气中二氧化碳的含量的增加，致使当前广泛采用的１９６６年埃德林（Ｅｄｌｅｎ）公式需要进行修改。本文简单介绍Ｂｉｒｃｈ和Ｄｏｗｎｓ对埃德林公式所作的修改。修改后的公式使计算值和实验值之间的一致性保持在测量不确定度３×１０－８范围内。在空气湿度较大时，新、旧公式的差异可达１×１０－７，即一米长度的修正量可相差０．１μｍ。因此，对测量不确定度要求较高的场合，应按新公式进行空气折射率的修正。     

环境对双频激光干涉仪测量不确定度的影响

双频激光干涉仪使用于不同的环境条件下时，由于空气折射率的变化，会使其测量不确定度受到影响。采用计算法进行修正时，要求正确地测定环境参数，如气压、温度、湿度等。本文对于这些参数的测定精度进行了分析，给出了具体的环境参数测定不确定度。     

爆破振动峰值速度计算的优化研究

基于非线性数值分析思想,提出一种提高爆破振动峰值速度计算精度的方法,并借助MAT-LAB编程对其内部参数进行拟合求解。工程实践证明,此种优化方法明显优越于传统的萨道夫斯基经验公式和线性分析方法修正的萨氏公式,使爆破预测精度得到提高,进而为工程的防震减灾提供了更加可靠的依据。每个工程场地都存在一个最佳的装药量与爆心距指数比,建议修正《爆破安全规程》(GB6722-2003)所采用的萨氏公式中装药量与爆心距之间固定指数比的规定。此外,文中提出了一个适用于多排孔延时爆破振动速度预测模型的依据公式。     

爆破振动峰值速度计算的优化研究

基于非线性数值分析思想,提出一种提高爆破振动峰值速度计算精度的方法,并借助MAT-LAB编程对其内部参数进行拟合求解。工程实践证明,此种优化方法明显优越于传统的萨道夫斯基经验公式和线性分析方法修正的萨氏公式,使爆破预测精度得到提高,进而为工程的防震减灾提供了更加可靠的依据。每个工程场地都存在一个最佳的装药量与爆心距指数比,建议修正《爆破安全规程》(GB6722-2003)所采用的萨氏公式中装药量与爆心距之间固定指数比的规定。此外,文中提出了一个适用于多排孔延时爆破振动速度预测模型的依据公式。     

高精度空气折射率测量系统设计与实现

针对商用空气折射率测量装置受到传感器采集性能和解算公式准确度的影响使得实际测量精度较低的问题,基于便携式多环境参数采集装置,设计了一套空气折射率测量系统,采集环境中的温湿度、大气压强状态信息,对3种折射率间接测量公式进行误差分析,并和商用环境补偿器进行性能对比。实验结果表明:在压强为100.17~100.21kPa,温度为21.1~21.9℃,湿度为45.9~58.0% RH的实验条件下,该测量系统的测量偏差比商用环境补偿器低2.69×10^-7。     

空气动力学粒径的光学修正

针对空气动力学粒径和光学等效粒径之间存在的差异,本文提出对空气动力学粒径进行光学修正的方法.该方法根据黑碳仪(AE)、浊度计(IN)和光学粒子计数器(OPC)的测量结果,对气溶胶折射率进行反演,再利用反演的折射率结合黑碳仪和浊度计的测量结果对厦门地区空气动力学粒度仪(3321)测量的空气动力学粒径数据进行光学修正,与光学粒子计数器测量结果对比表明修正的结果是合理的.最后还对引起空气动力学粒径和光学等效粒径之间差异的原因进行了分析.     

Refractive index of air: 3. The roles of CO2, H2O,and refractivity virials

The author's recent studies of the refractive index of air are extended, and several assumptions made therein are further examined. It is shown that the alternative dispersion equations for CO2, which are due to Edlen [Metrologia 2, 71 (1966)] and Old et al. [J. Opt. Soc. Am. 61, 89 (1971)] result in differences of less than 2 x 10(-9) in the phase refractive index and less than 3 x 10(-9) in the group refractive index for current and predicted concentrations of CO2. However, because the dispersion equation given by Old et al. is consistent with experimental data in the near infrared, it is preferable to the equation used by Edlen, which is valid only in the ultraviolet and the visible. The classical measurement by Barrell and Sears [Philos. Trans. R. Soc. London Ser. A 238, 1 (1939)] on the refractivity of moist air is shown to have some procedural errors in addition to the one discussed by Birch and Downs [Metrologia 30, 155 (1993)]. It is shown that for normal atmospheric conditions the higher refractivity virial coefficients related to the Lorentz-Lorenz relation are adequately incorporated into the empirically determined first refractivity virial. As a guide to users the practical limits to the calculation of the refractive index of the atmosphere that result from the uncertainties in the measurement of the various atmospheric parameters are summarized.     

基于Edlén公式空气折射率测量系统的校准研究

为了检验对激光干涉仪测量精度有很大影响的空气折射率测量系统的测试性能,提出一种可用于基于Edlén公式的空气折射率测量系统的校准方法,并且设计了专门的校准装置,该装置主要由温度、气压以及湿度测量系统组成。实验证明：取包含因子k=2时,温度在(5~40)℃区间,测量不确定度U优于0.02 ℃;气压在(66~105)kPa区间,U=18 Pa;湿度在(10~90)%RH区间,U=2.0%RH,等效于整个系统对应的空气折射率测量的相对不确定度优于1×10^-7     

Validity conditions for the radiative transfer equation

We compare the radiative transfer equation for media with constant refractive index with the radiative transfer equation for media with spatially varying refractive indices [J. Opt. A Pure App. Opt. 1, L1 (1999)] and obtain approximate conditions under which the former equation is accurate for modeling light propagation in scattering media with spatially varying refractive indices. These conditions impose restrictions on the variations of the refractive index, the gradient of the refractive index, the divergence of the rays, the frequency of modulation, and the widths of light pulses, which are related to the mean refractive index, the absorption coefficient, and the reduced scattering coefficient of the medium. Each condition is geometrically interpreted. Some implications of the results are discussed.     

Refractive index of air. 2. Group index

In a previous paper [Appl. Opt. 35, 1566 (1996)] one of us presented new equations for evaluation of the phase refractive index of air over a range of wavelengths and atmospheric parameters. That paper also gave an incorrect, although sufficiently accurate, procedure for calculating the group refractive index. Here we describe the results of a more rigorous derivation of the group index that takes proper account of the Lorentz-Lorenz formula, and we demonstrate that deviations from the Lorentz-Lorenz formula are insignificant to within a foreseeable precision of dispersion measurements for atmospheric conditions. We also derive and evaluate a simplification of the resultant equation that is useful for exploratory calculations. We clarify the limits of validity of the standard equation for the group refractive index and correct some minor errors in the previous paper.     

玻璃材料折射率及色散的高准确度测量

使用德国Triotics公司生产的SpectroMaster HR UV-VIS-IR型折射率测量设备,对FK5玻璃块的e、d、g、F′和C′谱线的折射率值进行高准确度测量,并修正至标准环境条件下的折射率值。用得到的折射率值进行曲线拟合,验证Cauchy色散公式和Sellmeier色散公式。     

Active suppression of air refractive index fluctuation using a Fabry-Perot cavity and a piezoelectric volume actuator

Air refractive index fluctuation (Δn(air)) is one of the largest uncertainty sources in precision interferometry systems that require a resolution of nanometer order or less. We introduce a method for the active suppression of Δn(air) inside a normal air-environment chamber using a Fabry-Perot cavity and a piezoelectric volume actuator. The temporal air refractive index (n(air)) at a local point is maintained constant with an expanded uncertainty of ~4.2 × 10(-9) (k = 2), a sufficiently low uncertainty for precise measurements unaffected by Δn(air) to be made inside a chamber.     

An optical technique forin situ density determination in electrolyte solutions under hydrothermal conditions

We report on a technique which determines the density of hydrothermal solutions through the relationship between density and refractive index given by the Lorentz Lorenz equation. An optical cell is described which allows the refractive index of fluids to be measured at temperatures up to 823 K and pressures up to 1200 bar. The validity of the Lorentz-Lorenz equation is demonstrated for pure water and water/NaCl solutions. New experimental results are presented for the density of water/NaNO₃ solutions at high temperature and pressure. The use of density data to derive other properties such as compressibility, thermal expansion coefficient, and apparent molar volume is demonstrated.