Relative Standard Uncertainty Research Articles

Primary Measurement of Gaseous Elemental Mercury Concentration with a Dynamic Range of Six Decades.

We present a primary method for absolute reference material-free measurement of gaseous elemental mercury mass concentration based on laser absorption spectroscopy at wavelengths near 254 nm and anchored to the international system of units. A 76 m-long multipass cell provides a detection limit of 1 ng m-3 for an averaging time of 8 min. A dual-cell arrangement, comprising a single-pass and a multipass cell, provides a dynamic range of six decades and spans from ambient to emission levels of gaseous elemental mercury (1 ng m-3 to 1000 μg m-3). The relative standard uncertainty of the measurement is 0.5% in the 0.25 to 1000 μg m-3 range.

Gravimetric Complexometric Titration Method to Determine Mass Fraction of Ethylenediaminetetraacetic Acid Disodium Salt Dihydrate in Candidate-Certified Reference Materials

Titrations are a group of techniques that have contributed considerably to developing the chemical industry and chemistry itself. Currently, the Consultative Committee for Amount of Substance has recognized titration as one of the primary methods for determining the amount of substance. In this context, an accurate gravimetric complexometric titration method was implemented to determine the purity of ethylenediaminetetraacetic acid (EDTA) disodium salt dihydrate using a lead nitrate-certified reference material (CRM). The titration reaction was followed potentiometrically using a lead ion-selective electrode. The equivalence point was found by the inflection of a non-parametric regression line that fits the experimental data. The titrations were made in diluted ammonium hydroxide media and sodium tartrate was added to avoid the lead hydroxide precipitation that occurs at high pH. The effect of both concentrations, ammonium hydroxide and sodium tartrate, were evaluated by a Box-Behnken experimental design. A complete uncertainty statement for the measurement method is presented in terms of the International System of Units (SI). The combined relative standard uncertainty of the measurement results is 0.034 % for the purity of the EDTA disodium salt. The atomic weight of the lead that applies to the lead nitrate CRM was determined with mass spectrometry to decrease the uncertainty budget contribution of this parameter which, otherwise, would have been the most important. The main sources of uncertainty were the mass of the EDTA solution for titration blanks, the purity of the lead nitrate CRM, and the precision of the equivalence point determination. The method was evaluated using an EDTA disodium salt dihydrate CRM and no significant bias was found. Finally, the results indicated that the developed method could be used for the value assignment of the mass fraction of EDTA disodium salt dihydrate to produce CRMs.

Absorbed-dose-to-water measurement using alanine in ultra-high-pulse-dose-rate electron beams

Objective. The aim of the presented study is to evaluate the dose response of the PTB’s secondary standard system, which is based on alanine and electron spin resonance (ESR) spectroscopy measurement, in ultra-high-pulse-dose-rate (UHPDR) electron beams. Approach. The alanine dosimeter system was evaluated in the PTB’s UHPDR electron beams (20 MeV) in a range of 0.15–6.2 Gy per pulse. The relationship between the obtained absorbed dose to water per pulse and the in-beamline charge measurement of the electron pulses acquired using an integrating current transformer (ICT) was evaluated. Monte Carlo simulations were used to determine the beam quality conversion and correction factors required to perform alanine dosimetry. Main results. The beam quality conversion factor from the reference quality 60Co to 20 MeV obtained by Monte Carlo simulation, 1.010(1), was found to be within the standard uncertainty of the consensus value, 1.014(5). The dose-to-water relative standard uncertainty was determined to be 0.68% in PTB’s UHPDR electron beams. Significance. In this investigation, the dose-response of the PTB’s alanine dosimeter system was evaluated in a range of dose per pulse between 0.15 Gy and 6.2 Gy and no evidence of dose-response dependency of the PTB’s secondary standard system based on alanine was observed. The alanine/ESR system was shown to be a precise dosimetry system for evaluating absorbed dose to water in UHPDR electron beams.

Half-life determination of 155Tb from mass-separated samples produced at CERN-MEDICIS

Terbium-155 has been identified for its potential for single-photon emission computed tomography (SPECT) in nuclear medicine. For activity measurements, an accurate and precise half-life of this radionuclide is required. However, the currently evaluated half-life of 5.32(6) d with a relative standard uncertainty of 1.1% determines the precision possible. Limited literature for the half-life measurements of this radionuclide is available and all reported investigations are prior to 1970. Further measurements are therefore needed to confirm the accuracy and improve the precision of the half-life for its use in the clinical setting. Two samples produced and mass separated at the CERN-MEDICIS facility have been measured at the National Physical Laboratory by two independent techniques: liquid scintillation counting and high-purity germanium gamma-ray spectrometry. A half-life of 5.2346(36) d has been determined from the weighted mean of the half-lives determined by the two techniques. The half-life reported in this work has shown a relative difference of 1.6% to the currently evaluated half-life and has vastly improved the precision.

Validation of Tritium Calibration Curve in CIEMAT/NIST Activity Measurement Using Non Linear Least Squared Fittings and Calculations of the Half-Life and Decay Constant of Potassium-40

Non-linear curve fitting of tracer efficiency is one of the uncertainty contributors in CIEMAT/NIST method for specific activity measurement and half-life evaluation of radionuclide. This study applied least squared fitting of four different polynomials to validate the tracer efficiency calibration curve for the specific activity measurements of nine Potassium Chloride samples from which half-life and decay constants were computed. All samples were measured using TR1000 Liquid Scintillation Counter and the results of the relative standard uncertainties in tracer interpolated efficiencies associated with the least square fit analysis were found to be 8.363%, 8.076%, 7.941% and 8.767% for polynomials of n = 2, n = 3, n = 4 and n = 5, respectively. The corresponding values of 40 K specific activity, from the application of empirical efficiencies generated with these polynomials were found to be (16.541, 16.540, 16.537 and 16.548) Bq/g respectively. From these measured specific activity values, the computed half-life and decay constants were found to be (1.2518, 1.2519, 1.2521 and 1.2513) ×109 y (for n = 2, n = 3, n = 4, and n = 5), respectively, and (5.365, 5.5364, 5.5354 and 5.5391) ×10-10 y-1 respectively. All values were found to be in good agreement with results of other literatures. However to minimize uncertainty associated with empirically generated tracer interpolation efficiencies, least squared fit analysis of tracer calibration curve should be done, with control trials using different polynomials so as to obtain the best fit.

The probe-format graphite calorimeter, Aerrow, for absolute dosimetry in ultrahigh pulse dose rate electron beams.

The purpose of this investigation is to evaluate the use of a probe-format graphite calorimeter, Aerrow, as an absolute and relative dosimeter of high-energy pulse dose rate (UHPDR) electron beams for in-water reference and depth-dose-type measurements, respectively. In this paper, the calorimeter system is used to investigate the potential influence of dose per pulses delivered up to 5.6Gy, the number of pulses delivered per measurement, and its potential for relative measurement (depth-dose curve measurement). The calorimeter system is directly compared against an Advanced Markus ion chamber. The finite element method was used to calculate heat transfer corrections along the percentage depth dose of a 20-MeV electron beam. Monte Carlo-calculated dose conversion factors necessary to calculate absorbed dose-to-water at a point from the measured dose-to-graphite are also presented. The comparison of Aerrow against a fully calibrated Advanced Markus chamber, corrected for the saturation effect, has shown consistent results in terms of dose-to-water determination. The measured reference depth is within 0.5mm from the expected value from Monte Carlo simulation. The relative standard uncertainty estimated for Aerrow was 1.06%, which is larger compared to alanine dosimetry (McEwen etal. https://doi.org/10.1088/0026-1394/52/2/272) but has the advantage of being a real-time detector. In this investigation, it was demonstrated that the Aerrow probe-type graphite calorimeter can be used for relative and absolute dosimetries in water in an UHPDR electron beam. To the author's knowledge, this is the first reported use of an absorbed dose calorimeter for an in-water percentage depth-dose curve measurement. The use of the Aerrow in quasi-adiabatic mode has greatly simplified the signal readout, compared to isothermal mode, as the resistance was directly measured with a high-stability digital multimeter.

Expression for uncertainty intervals handling skewness when the relative standard uncertainty is independent of the measurand level

Uncertainty intervals for many measurement results are typically reported as symmetric intervals around the measured value. However, at large standard uncertainties (> approx. 15 %–20 %), it is necessary to consider asymmetry of the uncertainty intervals. Here, an expression for calculating uncertainty intervals handling asymmetry when the relative standard uncertainty is independent of the measurand level is presented. The expression is based on implementation of a power transformation ({x}^{B}) for transformation of measurement results in order to achieve results that have a symmetric and approximate normal distribution. Uncertainty intervals are then calculated in the transformed space and back-transformed to the original space. The transformation includes a parameter, B, that needs to be optimized, and this can be based on real results, modelling of results, or on judgement. Two important reference points are B equal to 1 that corresponds to an approximate normal distribution of the original measurement results, and B approaching 0 that corresponds to an approximate log-normal distribution of the original measurement results. Comparisons are made with uncertainty intervals calculated using other expressions where it is assumed that measurement results have a normal distribution or a log-normal distribution. Implementation of the approach is demonstrated with several examples from chemical analysis.

A cross-validation study of Ge-doped silica optical fibres and TLD-100 systems for high energy photon dosimetry audit under non-reference conditions

This study compares the practicality of Ge-doped silica optical fibres as a potential remote dosimeter for radiotherapy postal dosimetry audit in non-reference conditions with a commercial thermoluminescence dosimeter (TLD-100). The optical fibre system consists of two types of fibres: cylindrical (CF) and flat fibres (FF). The dosimetric characteristics of the systems were investigated and compared, with particular attention to dose linearity, energy dependence, reproducibility, and fading. Measurements of absorbed doses of CF, FF, and TLD-100 were made, along with uncertainty budgets. A preliminary test was performed under non-reference conditions to evaluate the variations in absorbed doses measured with CF and FF versus TLD-100. For both 6 MV and 10 MV photon beams, CF, FF, and TLD-100 show a linear dose-response from 1 Gy to 3 Gy with a coefficient of determination (R2) greater than 0.99, minimal energy dependence, and good reproducibility with less than 3% deviation. The highest fading rates were 37.6%, 63.4%, and 14.2% for CF, FF, and TLD-100, respectively, at day 106 after irradiation. For irradiation with a photon beam of 6 MV, the combined relative standard uncertainty of absorbed dose determined from CF, FF, and TLD-100 measurements was estimated to be 4.3%, 5.56%, and 0.74%, respectively. Preliminary absorbed dose measurement tests under non-reference conditions showed that the mean ratios of Ge-doped silica optical fibres to TLD-100 for on-axis dose, wedge transmission, and output factor were 1.014, 0.991, and 1.013, respectively. The Ge-doped silica optical fibre systems have dosimetric performance commensurate with the TLD-100 and can be used as a potential remote dosimeter for mailed dosimetry audits if appropriate correction factors are applied to the absorbed dose measurements.

Extending Noble Gas Solubilities in Water to Higher Temperatures for Environmental Application

Noble gas concentrations in natural waters are widely used to determine ambient temperature conditions during the last intensive contact with the atmosphere (equilibration). Such applications require accurate solubility functions, which so far are available only for the common environmental temperature range between (0 and 35) °C. Nonetheless, environmental scenarios that generate higher surface-water temperatures (such as volcanism) exist. Previous solubility measurements beyond ∼35 °C are sparse or outdated and were determined through equilibration of water with pure noble gases. This can potentially render them not suitable for environmental applications where equilibration with atmospheric air is considered. We therefore conducted new measurements for the solubilities of helium, neon, argon, krypton, and xenon in deionized water equilibrated with atmospheric air at ∼1 bar for temperatures ranging from (25 to 80) °C. These measurements were combined with data from the literature that were obtained in a similar manner and fitted with a commonly used function to determine new noble gas solubility functions valid from (0 to 80) °C. We estimate relative standard uncertainties with a 0.99 level of confidence between 0.015 and 0.030 for the new functions, which are thus suitable for the investigation of environmental high-temperature equilibration scenarios. For temperatures beyond 35 °C, the new functions deviate significantly from previous studies.

First metrological validation of TwOGaSt, a new, absolute dTDLAS-trace-hygrometer, using the primary, coulometric, trace water vapour generator at PTB

Abstract We report the first realization of a TwOGaSt, a trace water optical gas standard (OGS) based on direct tunable diode laser absorption spectroscopy (dTDLAS). The TwOGaSt (Trace water Optical Gas Standard) hygrometer is equipped with a fiber-coupled DFB-laser emitting at 1.37 µm, a 36 m multi-pass astigmatic Herriott gas cell and a room-temperature InGaAs photo detector. TwOGaSt is capable of directly measuring absolute H2O concentration without any previous calibration of the spectrometer with reference gas mixtures. Water vapour amount fraction (= concentration) results delivered by TwOGaSt covering the concentration range from 10 to 350 µmol/mol (µmol/mol = ppm) were demonstrated and showed an optimum precision of 0.023 µmol/mol at a time resolution of 2 s. Further, we demonstrate the first metrological validation of this new OGS for absolute “calibration free” trace H2O amount fraction measurements in N2 and air, by comparing it with the primary coulometric trace water standard (CSFG) of PTB. The TwOGaSt results were in excellent agreement with the CSFG, PTB’s primary trace water vapor standard [1]. The relative standard uncertainty of the laser-hygrometer was determined to be is 1.2 %. This demonstrates that after SEALDH [2] and HAI [3], we now realized with TwOGaSt a laser-based, calibration-free, first-principles, optical gas standard (OGS) for the trace water vapor range, which is highly relevant for the upper troposphere and lower stratosphere (UT/LS) i. e. below 100 µmol/mol down to 4 µmol/mol (the tropopause H2O minimum).

The measurement uncertainty of air object spatial coordinates by rho-theta fixing

The features of measurement uncertainty evaluation of the coordinates of an air object by the rho-theta fixing are discussed. Measurement models are presented that link its coordinates in the local rectangular coordinate system with the spherical coordinates of air object, found using a rangefinder and a goniometer. The models include a correction for determining the location of the base station, a correction for determining the angle of elevation due to inaccuracies in the leveling of the station platform and azimuth, and a correction related to the inaccuracy of the station’s reference to the north. The measurement uncertainty budgets of rectangular coordinates which can be a basis for creation of software for automation of calculation of measurement uncertainties are resulted. Estimates of expanded uncertainties are found by the method of kurtosis. Expressions for the relative standard uncertainties of coordinate measurements are written and an example of their estimation for real data is given.

The Effect of Mouse Size on Dose from an X-Rad320 Irradiator.

Irradiation protocols for murine experiments often use standardized dose rate estimates for calculating dose delivered, regardless of physical variations between mouse subjects. This work sought to determine the significance of mouse size on absorbed dose. Five mouse-like phantoms of various sizes based on the mouse whole-body (MOBY) model were 3D printed. The phantoms were placed in an X-Rad320 biological irradiator and a standard irradiation protocol was used to deliver dose. Dose was measured using thermoluminescent dosimeter (TLD) microcubes inside each phantom, and the relative readings were used to calculate output factors (OFs), normalized to the phantom of median volume. Additionally, the OF for each mouse was simulated in Monte Carlo N-Particle (MCNP) code. For both the TLD measurements and MCNP simulations, the OF for each mouse was determined by both experiments and calculations to be unity within the relative standard uncertainties (k = 1). This work supports comparing results across various studies using the X-Rad320 irradiator without need for corrections based on mouse size.

China’s participation in the international RRT for Ic measurement of superconducting cables organized by IEC/TC90

Currently, IEC/TC90 is working on standardizing the method for measuring critical current ( I c ) in superconducting cables. At the end of 2020, an international round robin test (RRT) was organized, in which five Chinese institutions participated, and four accomplished the test. The electric-field versus current ( E - I ) curves obtained by each institution are highly repeatable. Those obtained by different institutions are nearly identical after appropriate curve averaging, indicating high reproducibility, except the last participant's inner core curves. The discrepancy was later determined to be the result of sample cable damage. After excluding highly deviated data, it is determined that the maximum relative standard uncertainty in I c is 0.7%, and the maximum relative standard uncertainty in n -value is 12.8%. The I c values are comparable to Japan's domestic RRT results, but the n -values are significantly different. The test results support the DC four-terminal method as a recommended test method, with a target relative uncertainty of less than 2% for the I c value.

Standard measurement method for normal state resistance and critical current of resistively shunted Josephson junctions

An important parameter of Josephson junctions (JJs) is the product of normal state resistance (R n) and critical current (I c) for designing superconductor analogue devices or digital circuits. Determination of R n and I c from voltage–current (U–I) characteristic curves often faces difficulties; in particular I c is considerably reduced by intrinsic thermal or extrinsic electrical noises. Here, we propose a standard measurement method of R n and intrinsic critical current (I ci) for high-T c superconductor (HTS) grain boundary JJs operated in liquid nitrogen and low-T c superconductor (LTS) multilayer superconductor/normal-conductor/superconductor (SNS) JJs in liquid helium. The applicable condition of this method is that both HTS and LTS JJs have U–I curves compatible with resistively-shunted junction (RSJ) model. Both R n and I ci values are extracted by combining a geometric mean criterion to select a data set and a least-squares fitting method with the RSJ model, eliminating two distortion effects on U–I curves: noise-rounding and self-heating. The combined method ensures relative standard uncertainty values of 1.9% for R n and 8% for I ci or better, when the users follow the standard protocol. It is demonstrated that the combined method is valid for d-wave HTS JJs near 77 K, regardless of peculiarities such as 0–π junction transition in d-wave superconductors at lower temperatures, and s-wave LTS SNS JJs with a wide range of junction parameters. This work is the first step to facilitate standardization for superconductor electronics with JJs.

Risk Assessment and Determination of Heavy Metals in Home Meal Replacement Products by Using Inductively Coupled Plasma Mass Spectrometry and Direct Mercury Analyzer.

This study quantified six heavy metals (Pb, Cd, As, Sn, Hg, and Me-Hg) in home meal replacement products. Satisfactory linearity (R2 > 0.99), recovery (80.65–118.02%), limits of detection (0.02–2.81 μg/kg), limits of quantification (0.05–8.51 μg/kg), accuracy (80.49–119.87%), precision (0.26–14.93%), standard uncertainty (0.082–0.321%) and relative standard uncertainty (0.084–0.320%) of the six heavy metals were obtained. The average concentration of the six heavy metals was 8.87 μg/kg. Heavy metal concentrations were converted to food intake data of 0.009 μg/kg to recalculate the 95th percentile food intake data (g/day) of individual heavy metals. These were then divided by age group to evaluate the average exposure to heavy metals and determine the 95th percentile of exposure from daily intake and for the whole population, of home meal replacement products. The chronic daily intake amount of six heavy metals was 1.60 × 10−2 μg/kg/day. Based on total chronic daily intake values, the risk and margin of exposure of each of the heavy metals was 9.13 × 107, demonstrating that intake associated with home meal replacement products is negligible.

Study on the effect of TBAB and THF on the hydrate dissociation conditions for H2O + CO2 + C6H14 + C14H30 systems

In this study, hydrate dissociation conditions for the carbon dioxide + hexane + tetradecane + water systems were experimentally determined with or without Tetra-n-Butyl Ammonium (TBAB) or Tetrahydrofuran (THF), two water-soluble thermodynamic hydrate promoters. The equilibrium conditions were measured using the pressure-search method at constant volume in the temperature range from 274.8 to 291.5 K and pressure range from 1.45 to 3.97 MPa at (0, 0.1, 0.2 and 0.3) mass fraction of TBAB or THF in liquid solution. In order to verify the viability of the method used, the three-phase hydrate equilibria H-Lw-V of binary (CO2 + H2O) and ternary (CO2 + H2O + THF) systems were also measured and compared with the literature. Experimental measurements show that the addition of TBAB or THF expands the hydrate stability region significantly to a higher temperature at a specified pressure. The combined standard uncertainties were determined for temperature and pressure and are 0.19 K and 0.07 MPa, respectively. The relative standard uncertainty in composition was estimated to be 0.0013.

Assessing the accuracy of electronic portal imaging device (EPID)‐based dosimetry: II. Evaluation of a dosimetric uncertainty budget and development of a new film‐in‐EPID absorbed dose calibration methodology

The aim of this study is to reduce the uncertainty associated with determining dose-to-water using an amorphous silicon electronic portal imaging detector (EPID) under reference conditions by developing a direct calibration formalism based on radiochromic film measurements made within the EPID panel and detailed Monte Carlo simulations. To our knowledge, this is the first EPID-based dosimetry study reporting an uncertain budget METHODS: Pixel sensitivity and relative off-axis response were mapped by simultaneously irradiating film contained within the imager panel and acquiring an EPID image set. The detector panel was disassembled for the purpose of modeling the EPID in detail using the EGSnrc DOSXYZnrc usercode, which was in turn used to calculate dose-to-film in the EPID and dose-to-water in water conversion factors RESULTS: A direct comparison of the two correction methodologies investigated in this work, the previously established empirical method and the proposed simultaneous measurement approach involving in-EPID film dosimetry, produced an agreement with an RMS deviation of 1.4% overall. A combined standard relative uncertainty of 3.3% (k=1) was estimated for the determination of absorbed dose to water at the position of the EPID using the proposed calibration methodology CONCLUSIONS: This work describes a direct method of calibrating EPID response in terms of absorbed dose to water requiring fewer measurements than other empirical approaches, and without 2D spatial interpolation of correction factors.

Evaluation of uncertainty in measuring thin crystal thickness and extinction distance by Kossel-Möllenstedt pattern analysis

In this paper, the local thickness of single crystal Si film sample and the extinction distance <inline-formula><tex-math id="M11">\begin{document}$ {\xi }_{400} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20212271_M11.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20212271_M11.png"/></alternatives></inline-formula> of the (400) plane of Si crystal are obtained by analyzing the double-beam converging beam diffraction (CBED) pattern of single crystal Si film sample under the 200 kV of accelerated voltage. The factors affecting the measurement uncertainty are analyzed, and the influence coefficients of each factor on the measurement uncertainty are discussed by using the concept of first-order partial derivative. The measurement uncertainty of thin crystal thickness and extinction distance are evaluated and expressed according to national standards GB/T 27418-2017. The conclusions are as follows. The local thickness of the measured Si crystal is estimated at 239 nm, the combined standard uncertainty is 5 nm, and the relative standard uncertainty is 2.2%. With the inclusion probability being 0.95, the coverage factor is 2.07 and the expanded uncertainty is 11 nm. With the accelerated voltage being 200 kV, the extinction distance of Si crystal (400) plane is estimated at 194 nm, the combined standard uncertainty of the extinction distance is 20 nm, and the relative standard uncertainty of the extinction distance is 10%. With the inclusion probability being 0.85, the coverage factor is 1.49 and the expanded uncertainty is 30 nm. The main factors that can affect the combined standard uncertainty of sample thickness <i>t</i><sub>0</sub> are camera constant, accelerating voltage and sample thickness, while the factors that influence the combined standard uncertainty of extinction distance are camera constant, accelerating voltage and extinction distance. The influence of the uncertainties of the measurement data of the Kossel-Möllenstedt pattern on the uncertainty of the extinction distance is <inline-formula><tex-math id="M12">\begin{document}${n}_{i}{\left( {\xi }/{t}\right)}^{3}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20212271_M12.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20212271_M12.png"/></alternatives></inline-formula> times that on the sample thickness, and their influence on the slope of the fitting line is about <inline-formula><tex-math id="M13">\begin{document}$ {n}_{i} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20212271_M13.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20212271_M13.png"/></alternatives></inline-formula> times that on the intercept of the line, where <inline-formula><tex-math id="M14">\begin{document}$ {n}_{i} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20212271_M14.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20212271_M14.png"/></alternatives></inline-formula> is a positive integer and greater than or equal to 1. If the sample is not too thin, that is, <inline-formula><tex-math id="M15">\begin{document}$ {n}_{i} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20212271_M15.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20212271_M15.png"/></alternatives></inline-formula> is greater than 1, then the uncertainty of crystal thickness will be smaller than the uncertainty of extinction distance.

Accurate Stereo-Vision-Based Flying Droplet Volume Measurement Method

Accurate volume measurement of flying droplets in the Mura-free manufacturing of inkjet printed organic light-emitting diodes (IJP OLEDs) remains a challenge due to the micrometer scale and high speeds of the droplets. Most existing vision-based methods pay little attention to image segmentation and estimate the droplet volume based on a symmetry assumption, which yields poor accuracy, especially for droplets with an unknown shape. In this article, an accurate measurement method for flying droplet volume based on stereo vision is proposed. First, an image acquisition technique based on stereo vision and synchronous triggering is used to obtain multiview high-resolution droplet images. Then, an accurate binocular droplet image segmentation algorithm is proposed to segment the images with different degrees of blur to achieve similar accuracy. Finally, a polar-coordinate-Hermite-interpolation-based droplet reconstruction (PHDR) algorithm is proposed to reconstruct droplets and to calculate volume on the basis of the contours obtained by the binocular droplet image segmentation algorithm without any symmetry assumptions. The droplet measurement system (DMS) is set up, and a series of experiments are conducted to verify the performance of the proposed method. The results show the advantages of our algorithms, that the volume measurement accuracy is ±3%, and that the relative standard uncertainty is better than 2.1%.

Comparison of a 100-pF Capacitor With a 12 906-Ω Resistor Using a Digital Impedance Bridge.

We tested a digital impedance bridge in a hybrid structure for comparison of a capacitor with a resistor where the impedance ratio was measured in two separate parts. The modulus of the impedance ratio was matched arbitrarily close to the input-to-output ratio, in magnitude, of a two-stage inductive voltage divider by adjusting the operating frequency of the bridge; the residual deviation between the two together with the phase factor of the impedance ratio was measured using a custom detection system based on a four-channel 24-bit digitizer. The ratio of the inductive voltage divider was calibrated, in situ, using a conventional four-arm bridge with two known capacitors. Fluctuations of the source voltages were largely removed through postprocessing of the digitized data, and the measurement results were limited by the digitizer error. We have achieved an overall bridge resolution and stability of 0.02 μF/F in 2 h for measuring a 100-pF capacitor relative to a 12 906-Ω resistor at 1233 Hz. The relative combined standard uncertainty (k = 1) is 0.13 μF/F, dominated by the digitizer error.