Uncertainties in calibration using capacitance diaphragm gauges as reference standard

A study of the uncertainties in calibration using capacitance diaphragm gauges as reference standard in the range from 1000 mbar to 10⁻³ mbar is presented. The contributions to the expanded uncertainty are: (i) Uncertainty from the calibration certify of the reference standard; (ii) Long-term stability or shift; (iii) Uncertainties inherent to the reference standard; (iv) Uncertainties derived from the calibration chamber; and (v) Uncertainties derived from the calibration procedure. These contributions have been determined for four reference standard capacitance diaphragm gauges of 1.3 mbar, 13 mbar, 130 mbar and 1300 mbar full scale used in routine calibration. Long-term stability or shift jointly with the uncertainty displayed in the calibration certifies issued by a National Metrological Laboratory are the main contributions to the expanded uncertainty. Values of the shift for each of the reference standard for a period of several years are presented and discussed. Best-expanded uncertainties obtained from calibration of a gauge of similar characteristics to the reference standards are:

10−3-1 mbar	4-0.2% of the reading
1-13 mbar	0.2% of the reading
13-130 mbar	0.2-0.08% of the reading
130-1300 mbar	0.2-0.06% of the reading

Full-size table

     

高g值加速度传感器激光绝对法冲击校准技术研究

在详细分析反射式激光多普勒原理的基础上,研究了高g值加速度传感器的冲击校准方法。该方法利用Hopkinson杆作为加载手段,利用差动式激光多普勒干涉仪来绝对复现冲击加速度的量值。针对高g值压阻加速度传感器SIMIT-AYZ-60k进行了一系列的校准试验,利用积分运算法和最小二乘法的组合从准动态条件下的校准数据得到了准静态条件下的传感器冲击灵敏度。试验表明,这种方法实现了利用脉宽有限的激励脉冲对固有频率在20kHz以上的高g值加速度传感器的校准,校准的不确定度可以满足冲击测试的工程需求。     

Reference surface calibration of a Fizeau interferometer through even/odd synthesis

We propose an even-/odd-synthesis method for the elimination of additional aberration caused by misalignment or environmental vibration during the calibration of a Fizeau interferometer reference surface (RS). The odd and even parts of an RS can be obtained, because surface errors could be divided into rotationally symmetric and nonrotationally symmetric terms. We then propose a least-squares algorithm with a dual-objective optimization function for calibration of the measurement results at the confocal position. Finally, a complete RS can be eventually obtained by synthesizing the odd and even parts of the RS. It has been verified through experiments that the measurement repeatability of the PV value is better than 0.003λ, and the root-mean-square value is better than 0.0003λ.     

Two-color interferometer for surface characterization using two frequency doublers and a four-phase-step method

A high-accuracy, two-color interferometer for characterizing a processed surface is described. It is composed of two frequency doublers. It is not affected by air turbulence and mechanical vibration because it is a complete common-path interferometer, and the effects from different reflectivities of various materials are canceled by a four-phase-step technique that shifts the phase of the interference fringe in steps of π/2. The processed surface is measured with subnanometer resolution.     

Interplay between chemistry and statistics,with special reference to calibration and the generalized standard addition method

Ever since the beginning of this century problems in the field of chemistry and chemical engineering have played an important role in the development of statistics, and statistical models and methods have proved to be an efficient tool for planning of chemical experiments and in the analysis of chemical data. After mentioning a number of mutually important statistical methods and chemical problem areas, I will discuss in more detail the interplay and lack thereof in the field of calibration. In particular I will describe and discuss the generalized standard addition method (GSAM) with a two-fold intention: to propose statistically motivated improvements and future developments in the theory of estimation and design for this method of multicomponent analysis, as well as to illustrate how a statistician looks at the topic, for the possible benefit of chemists in their future contacts with statistics and statisticians.     

臭氧标准参考光度计一级校准周期考察

对不同量程的臭氧二级传递标准进行一级校准实验,结果显示量程分别为500 nmol/mol和1 000 nmol/mol时,所得校准曲线的斜率和截距均能够满足臭氧一级校准指标的要求。对臭氧二级传递标准开展臭氧一级校准时,应根据实际需求选择合适的量程。对于大多数的监测站点,臭氧二级传递标准量程范围选择为500 nmol/mol可满足要求。在相同实验条件下(选择串口连接模式、校准曲线浓度点个数为6个、臭氧二级传递标准量程为500 nmol/mol),考察臭氧一级校准的周期。36个月的考察结果显示臭氧一级校准曲线的斜率在0.992 7~1.010 5之间,平均斜率为1.001 9;截距在-0.437 3~-0.026 6 nmol/mol之间,平均截距为-0.211 5 nmol/mol;斜率的相对标准偏差为0.32%,截距的标准偏差为0.094 nmol/mol,均能符合臭氧一级校准指标的要求。结合国内外相关标准及我国环境空气臭氧监测质量管理需求,建议臭氧二级传递标准至少每12个月开展一次臭氧一级校准。     

用于换能器校准的激光干涉测振技术

本文介绍了用激光干涉仪对换能器表面振动位移进行绝对测量的原理,对不同情况下的信号处理方法进行了探讨,分别给出了低频及高频时的实验及进行信号处理后的结果。从实验结果及信号处理的结果可以看出,记系纹数的处理方法比较简单直观,而最大频率法则可解决小数条纹的测量。     

Rationalizing the calibration method of reference telescopic radiation pyrometers

Conclusions An equation which was derived in this work provides with sufficient accuracy the relationship between the thermal emf and the measured radiation temperature for two types of TERA-50 radiation pyrometer telescopes.Optimum temperatures have been found for plotting a curve (2) through three points, at 600, 900 and 1200°C for telescopes type TERA-50/(600–1400°C), and at 1300, 1600 and 1900°C for telescopes type TERA-50/(1200–2500°C).Thus, it becomes possible to recommend a new and more efficient, three-point calibration technique for 2nd grade telescopes type TERA-50/(600–1400°C) and TERA-50/(1200–2500°C).     

Measurement of profiles along a circle on two flat surfaces by use of a Fizeau interferometer with no standard

A method for measuring profiles along a circle on a flat surface with no standard is described. For the measurement, two unknown surfaces are placed almost parallel, and the distance between them is measured many times along a circle by rotation of one of the surfaces. Profiles of the two surfaces can be determined from the distance data. In this study the measuring method is explained: The space between two surfaces measured with a Fizeau interferometer. Four measuring experiments are carried out for determining the profile of a precision-grade half-mirror; in each experiment a different ordinary mirror with unknown profile is used as the second mirror. Profiles of the precise mirrors obtained by these experiments agree closely, with deviations of approximately 2 nm. A similar experiment with many concentric circles was carried out with a precise half-mirror and another precise mirror. Although the profiles of many concentric circles were independent of one another, the result shows that the high-frequency component of a whole plane can be estimated.     

Fabrication of flat capped carbon nanotubes using an arc-discharge method assisted with a Sm-Co catalyst

In this study, carbon nanotubes (CNTs) were fabricated using an arc-discharge method assisted with samarium-cobalt (Sm-Co) chloride as a catalyst. The optimal fabrication condition was determined through a series of experiments on various ambient conditions. Observations were completed using scanning electron microscopy (SEM), Raman spectroscopy, and tunneling electron microscopy (TEM); the main products we observed are well-structured multi-walled carbon nanotubes. By identifying the radial breathing modes (RBMs) of the Raman spectra with a TEM micrograph, we also observed a small number of single-walled carbon nanotubes. With the assistance of the Sm-Co chloride catalyst, the RBMs of the Raman spectra were measured in the ambient pressure of 760 torr. The TEM observations revealed that our nanotubes have good graphitic structures and almost no bamboo defects, which agrees with their Raman measurements with a high I_G/I_D ratio (~88). A perfect graphitic flat cap was found to be attached at the end of the nanotube. Simulation shows that by incorporating 5 carbon pentagons, it is possible to construct a flat capped carbon nanotube. The results of our experiment offer a unique approach to growing high quality CNTs. Such a flat capped structure may useful for further advanced application in nano-electronics and nano-optics.     

On-orbit vicarious calibration of ocean color sensors using an ocean surface reflectance model

Recent advances in global biogeochemical research demonstrate a critical need for long-term ocean color satellite data records of consistent high quality. To achieve that quality, spaceborne instruments require on-orbit vicarious calibration, where the integrated instrument and atmospheric correction system is adjusted using in situ normalized water-leaving radiances, such as those collected by the marine optical buoy (MOBY). Unfortunately, well-characterized time-series of in situ data are scarce for many historical satellite missions, in particular, the NASA coastal zone color scanner (CZCS) and the ocean color and temperature scanner (OCTS). Ocean surface reflectance models (ORMs) accurately reproduce spectra observed in clear marine waters, using only chlorophyll a (C(a)) as input, a measurement for which long-term in situ time series exist. Before recalibrating CZCS and OCTS using modeled radiances, however, we evaluate the approach with the Sea-viewing Wide-Field-of-view Sensor (SeaWiFS). Using annual C(a) climatologies as input into an ORM, we derive SeaWiFS vicarious gains that differ from the operational MOBY gains by less than +/-0.9% spectrally. In the context of generating decadal C(a) climate data records, we quantify the downstream effects of using these modeled gains by generating satellite-to-in situ data product validation statistics for comparison with the operational SeaWiFS results. Finally, we apply these methods to the CZCS and OCTS ocean color time series.     

Measurement of the surface profile of an axicon lens with a polarization phase-shifting shearing interferometer

We present a Twyman-Green interferometer (TGI)-based polarization phase-shifting shearing interferometric technique for testing the conical surface of an axicon (AX) lens. In this technique, the annular beam generated due to the passing of an expanded collimated laser beam traveling along the axis of revolution of the transparent glass AX element is split up into its reflected and transmitted components, having the plane of polarization in the orthogonal planes, by the polarization beam splitter (PBS) cube of the TGI-based optical setup. The split-up components are made to travel unequal paths along the two arms of the TGI and are recombined by the PBS. Because of the difference in path lengths traveled by the annular conical beams, a linear shear is introduced along the radial direction between the interfering components. Thus, the resulting interference pattern gives a map of the optical path difference (OPD) between two successive close points along a radial direction on the conical surface of the AX lens. The OPD map along radial directions, and hence the slopes/profiles of the conical surface, are obtained by applying polarization phase-shifting interferometry. Results obtained for an AX lens are presented.     

Accurate wavelength calibration in the near-infrared for multielement analysis without the need for reference spectra

A new technique has been developed for an instant, precise, and accurate wavelength calibration over a wide pixel array for simultaneous, multielement spectral analysis based on an inverse numerical solution to the grating dispersion function. This technique is applicable to multielement analytical applications such as laser-induced breakdown spectroscopy (LIBS), particularly when using high-density gratings in the upper visible and in the near-infrared, where nonmetallic elements are detected. This application overcomes the need to use reference spectra for each window of observation and is tested on a commercially available LIBS instrument.     

Investigation of heat transfer during boiling on a flat surface by a nonstationary method

A nonstationary method of investigating heat transfer during boiling on a flat surface is described. The heat flux is determined from the reduction in the intrinsic energy of a massive bar over a definite time interval by graphic integration of the temperature field over the bar length.     

Photoacoustic tomography using a Mach-Zehnder interferometer as an acoustic line detector

A three-dimensional photoacoustic imaging method is presented that uses a Mach-Zehnder interferometer for measurement of acoustic waves generated in an object by irradiation with short laser pulses. The signals acquired with the interferometer correspond to line integrals over the acoustic wave field. An algorithm for reconstruction of a three-dimensional image from such signals measured at multiple positions around the object is shown that is a combination of a frequency-domain technique and the inverse Radon transform. From images of a small source scanning across the interferometer beam it is estimated that the spatial resolution of the imaging system is in the range of 100 to about 300 mum, depending on the interferometer beam width and the size of the aperture formed by the scan length divided by the source-detector distance. By taking an image of a phantom it could be shown that the imaging system in its present configuration is capable of producing three-dimensional images of objects with an overall size in the range of several millimeters to centimeters. Strategies are proposed how the technique can be scaled for imaging of smaller objects with higher resolution.     

一种检测平晶和透镜面形的方法

介绍了数字式激光平面干涉仪的测量优势,阐述了利用其进行平面和球面面形的测量方法,弥补了传统平面等厚干涉仪只能测量平面平晶的不足。同时分析了影响测量结果的几个因素,并利用ZEMAX软件模拟平晶位置,观察干涉条纹。     

A method of determining temperature fields with an interferometer

A method of determining temperature fields using an interferometer is described. A new formula is presented for calculating temperatures from interferograms. Data obtained on the interferometer are compared with data obtained by other methods.     

Converting an unstructured quadrilateral mesh to a standard T-spline surface

This paper presents a novel method for converting any unstructured quadrilateral mesh to a standard T-spline surface, which is C ²-continuous except for the local region around each extraordinary node. There are two stages in the algorithm: the topology stage and the geometry stage. In the topology stage, we take the input quadrilateral mesh as the initial T-mesh, design templates for each quadrilateral element type, and then standardize the T-mesh by inserting nodes. One of two sufficient conditions is derived to guarantee the generated T-mesh is gap-free around extraordinary nodes. To obtain a standard T-mesh, a second sufficient condition is provided to decide what T-mesh configuration yields a standard T-spline. These two sufficient conditions serve as a theoretical basis for our template development and T-mesh standardization. In the geometry stage, an efficient surface fitting technique is developed to improve the geometric accuracy. In addition, the surface continuity around extraordinary nodes can be improved by adjusting surrounding control nodes. The algorithm can also preserve sharp features in the input mesh, which are common in CAD (Computer Aided Design) models. Finally, a Bézier extraction technique is used to facilitate T-spline based isogeometric analysis. Several examples are tested to show the robustness of the algorithm.