Combined Standard Uncertainty Research Articles

New capabilities of the PAT plutonium analysis program

The Plutonium Attribute Test (PAT) is a software program originally developed for determining the category of a plutonium sample. The premise for its development was that, to assign Pu samples to particular categories, it is not necessary to determine the abundance of all its isotopes. Rather, it is sufficient to determine only 239Pu abundance, which is universally used to establish a category assignment, i.e., >90 wt% 239Pu is low burnup (LBPu), <70 wt% is high burnup (HBPu), and the abundances in between could be considered medium burnup (MBPu) plutonium grade. In contrast to previous Pu isotopic analysis programs which analyse spectra taken with HPGe detectors, the algorithms developed in PAT analyses use spectra taken with medium resolution detectors such as LaBr3(Ce) and CZT detectors. As demonstrated by initial tests, PAT was found capable of not only assigning the material category, but also accurately determining 239Pu abundance, with several per cent typical relative combined standard uncertainty. Furthermore, an advanced algorithm (A-PAT) was added to allow full isotopic characterization of samples. This paper presents further enhancements of the PAT/A-PAT algorithms towards analysis of heavily shielded samples, samples with varied size and age, as well as mixed oxide (MOX) materials.

Uncertainty Evaluation for the Determination of Perfluorinated Compounds in Wastewater Treatment Facility Effluent

This study evaluates the sources of uncertainty in the determination of poly &amp; perfluorinated compounds(PFHxS, PFOS, PFOA) in the effluent of a wastewater treatment facility using LC-MS/MS. The uncertainty sources were identified and, numerically quantified, and the overall uncertainty of the final results was calculated through the synthesis and expansion of uncertainties. The main factors contributing to the combined standard uncertainty were identified as the construction of calibration curves, the reproducibility uncertainty from repeated tests, and the uncertainty associated with sample collection. By contrast, the effects of processes such as the volume filling of 1 mL standards after concentration and the injection of internal standards were found to be negligible. The relative expanded uncertainties for the three perfluorinated compounds were within 7.45%. The contributions to the overall uncertainty from sample collection, calibration curve construction, internal standard injection, volume filling of 1 mL standards, and reproducibility from repeat tests were 1.16~1.62%, 87.11~94.52%, 0.37~0.53%, 0.33~0.46%, 2.87~11.03%, respectively.

Measurement of tiny moment of inertia based on flexure hinge for automobile collision testing

Abstract The moment of inertia is a critical parameter for determining the motion state of an object and achieving precise control. At present, measurement techniques for the moment of inertia of large and heavy objects (greater than 0.5 kgm2) are very mature. However, it is still a challenge to achieve high precision for smaller objects (less than 0.5 kgm2). In this paper, a measuring device based on flexure hinges is proposed to achieve high-accuracy measurement of tiny moments of inertia, without additional friction. A theoretical model of measurement is developed and optimised to obtain the rotational inertia by measuring swing periods. The experimental results show that the maximum load of the device is 20 kg, and the resolution reaches 4 × 10−5 kgm2. For a 5 kg head model, the moment of inertia was measured to be 0.011 58 kgm2, with a combined standard uncertainty of 0.000 29 kgm2.

Simultaneous quantification of 2-pyrrolidone-5-carboxylic acid (PCA), urocanic acid (UCA), and histidine (His) in the stratum corneum by HPLC-PDA

Located in the epidermis, the stratum corneum is the most superficial layer of the skin, acting as a barrier against aggression from the external environment, preventing dehydration, and maintaining the water balance of the skin. The stratum corneum contains the Natural Hydration Factor (NMF), a mixture of hygroscopic molecules derived from filaggrin. The NMF includes 2-pyrrolidone-5-carboxylic acid (PCA), urocanic acid (UCA), and histidine (His), target biomarkers that were extracted by tape-stripping from the stratum corneum of participants for quantification in HPLC-PDA. By extracting the stratum corneum, we developed a protocol to optimize, through audience definition, the quantification of NMF biomarkers. Chromatographic analysis was performed using a YMC-Triart C18 chromatographic column, with a gradient elution of mobile phase composed of triethylammonium phosphate and acetonitrile mixture, and a photodiode array detector. HPLC-PDA procedure was selective, linear (in the range from 0.2 to 5.0 µg/mL), accurate (recovery from 92.7 to 115.1 %), precise (RSD from 0.3 to 12.1 %), and with proper detection and quantification limits. The measurement uncertainty was evaluated from validation data, with combined standard uncertainty values of 0.025–0.12 µg/mL (2.1–5.6 %), 0.004–0.28 µg/mL (2.4–12.6 %), and 0.016–0.16 µg/mL (3.2–7.9 %) for His, PCA, and UCA, respectively. Statistical analyses were performed using Monte Carlo simulation and the Mann-Whitney test, as our results were not homoscedastic and deviated from normality. The results indicate that the best audience for quantifying biomarkers were participants up to 35 years old, with all phototypes, and, preferably, female.

A nN[formula omitted]m level micromotor holding torque measurement method

Efficient and high-precision torque measurement methods for micromotors are globally critical, impeding the advancement of microsystems, particularly ultrasonic micromotors, known for their small size, high speed and high resolution. This paper proposes a novel torque measurement method for ultrasonic micromotors, establishing a torque measurement device that utilizes a parallelogram flexible hinge as the force transmission element. This approach can measure torque at the nano-Newton-meter (nN⋅m) level. The system demonstrates high measurement accuracy, robust anti-interference capability, and a wide measurement range. When the 18 V voltage is applied to the motor, the holding torque is 234.66 nN⋅m, the repeatability error of the system is 1.25%, and the combined standard uncertainty is 5.36 nN⋅m. The proposed method is a pivotal step towards filling the existing technological void, offering a substantial impact on the development of ultrasonic micromotors and the broader field of microsystems.

Calibrating the global network of gravitational wave observatories via laser power calibration at NIST and PTB

Current gravitational wave (GW) observatories rely on photon calibrators that use laser radiation pressure to generate displacement fiducials used to calibrate detector output signals. Reducing calibration uncertainty enables optimal extraction of astrophysical information such as source distance and sky position from detected signals. For the ongoing O4 observing run that started on 24 May 2023, the global GW detector network is employing a new calibration scheme with transfer standards calibrated at both the National Institute of Standards and Technology (NIST) and the Physikalisch-Technische Bundesanstalt (PTB). These transfer standards will circulate between the observatories and the metrology institutes to provide laser power calibration traceable to the International System of Units (SI) and enable assessment and reduction of relative calibration errors for the observatory network. The Laser Interferometer Gravitational-Wave Observatory (LIGO) project and the Virgo project are currently participating in the new calibration scheme. The Large-scale Cryogenic Gravitational-wave Telescope project (KAGRA) is expected to join in 2024, with the LIGO Aundha Observatory in India joining later. Before implementing this new scheme, a NIST-PTB bilateral comparison was conducted. It validated the scale representation by both laboratories, with a degree of equivalence of −0.2% and an associated expanded uncertainty of 0.32% (k = 2) which is significantly lower than previous studies. We describe the transfer of power sensor calibration, including detailed uncertainty estimates, from the transfer standards calibrated by NIST and PTB to the sensors operating continuously at the interferometer end stations. Finally, we discuss the ongoing calibration of Pcal-induced displacement fiducials for the O4 observing run. Achieved combined standard uncertainty levels as low as 0.3% facilitate calibrating the interferometer output signals with sub-percent accuracy.

Accurate characterisation of optical diffuse transmission—primary facility and extension to translucent samples

To perform accurate, high-quality and traceable measurement of optical diffuse transmission, which is quantified using the bidirectional transmittance distribution function (BTDF), a new primary facility has been developed at the Physikalisch–Technische Bundesanstalt (PTB), the German metrology institute. This newly developed reference facility will complement the available calibration services and research facilities at PTB for regular reflectance and transmittance and diffuse reflectance. The performance of the new BTDF setup has been investigated in an internal comparison, where consistency of the results was achieved. A thorough uncertainty analysis results in a minimum combined standard (k = 1) uncertainty of about 0.8 %. Research on the accurate characterisation of the BTDF of samples with non-negligible lateral scattering is being carried out on this new setup. Some first results have shown that the measured BTDF value depends on the applied irradiation area size. An empirical model has been found to describe the diffuse transmission of such translucent samples with different scattering parameters.

AFM interlaboratory comparison for nanodimensional metrology on silicon nanowires

Abstract Silicon nanowires (NWs) with a cylindrical form are fabricated by means of nanospheres lithography and metal-assisted chemical etching to obtain high aspect ratio nanostructures (diameter of about 100 nm and length of more than 15 µm) on cm2 area.&amp;#xD;The nanodimensional characterization of individual NWs is performed by using several techniques, because dimensions at the nanoscale strictly relate to functional performances. In this study, we report the results of an interlaboratory comparison between measurements from a metrological atomic force microscope (AFM) and research AFMs located in different national metrology institutes (NMIs) across Europe and in a university.&amp;#xD;The purpose of this study is to characterize two measurands: (i) sidewall roughness (Ra, Rq, Rz, Rsk, Rku parameters), extracted from the top profile measured along the nanowire length, and (ii) diameter of the nanowires measured as top-height. To this goal, the nanowires are spread horizontally on a silicon substrate, which has several areas labelled with a pattern of crosses and letters facilitating the measurement of the same NW, in order to study the reproducibility due to different instruments.&amp;#xD;Measurements show a good agreement between the different NMIs, with a combined standard uncertainty of top-height diameter less than 3%, and with a combined standard uncertainty of roughness parameters well within 5% for Ra and Rq values.

Measurement Uncertainty and Risk of False Compliance Assessment Applied to Carbon Isotopic Analyses in Natural Gas Exploratory Evaluation.

The concept of uncertainty in an isotopic analysis is not uniform in the scientific community worldwide and can compromise the risk of false compliance assessment applied to carbon isotopic analyses in natural gas exploratory evaluation. In this work, we demonstrated a way to calculate one of the main sources of this uncertainty, which is underestimated in most studies focusing on gas analysis: the δ13C calculation itself is primarily based on the raw analytical data. The carbon isotopic composition of methane, ethane, propane, and CO2 was measured. After a detailed mathematical treatment, the corresponding expanded uncertainties for each analyte were calculated. Next, for the systematic isotopic characterization of the two gas standards, we calculated the standard uncertainty, intermediary precision, combined standard uncertainty, and finally, the expanded uncertainty for methane, ethane, propane, and CO2. We have found an expanded uncertainty value of 1.8‰ for all compounds, except for propane, where a value of 1.6‰ was obtained. The expanded uncertainty values calculated with the approach shown in this study reveal that the error arising from the application of delta calculation algorithms cannot be neglected, and the obtained values are higher than 0.5‰, usually considered as the accepted uncertainty associated with the GC-IRMS analyses. Finally, based on the use of uncertainty information to evaluate the risk of false compliance, the lower and upper acceptance limits for the carbon isotopic analysis of methane in natural gas are calculated, considering the exploratory limits between -55‰ and -50‰: (i) for the underestimated current uncertainty of 0.5‰, the lower and upper acceptance limits, respectively, are -54.6‰ and -50.4‰; and (ii) for the proposed realistic uncertainty of 1.8‰, the lower and upper acceptance limits would be more restrictive; i.e., -53.5‰ and -51.5‰, respectively.

Uncertainty Evaluation of the TGA Oxidation Data

Thermogravimetric analysis (TGA) involves the measurement of the changes in mass that occur when a constant heat is applied to an unknown specimen as a function of time or temperature. It is used to evaluate thermal stability, oxidative stability, composition, and estimated lifetime, among other parameters. Given that accurate TGA data is important information for lifetime and stability evaluation of parts and products, an uncertainty evaluation procedure is required to ensure the reliability of the data. In this study, the uncertainty evaluation procedure was established according to the Guide to the Expression of Uncertainty in Measurement (GUM). The mathematically expression of the relationship between the measurand and the input quantities, evaluation of the standard uncertainty of each input estimate, determination of the combined standard uncertainty, and calculation of the expanded uncertainty were performed. The biggest factor affecting the uncertainty of TGA data is the uncertainty of correction factor caused by system calibration

ISO 4037 narrow spectrum X-ray reference field: Simulation and measurement

The paper presents the characteristics of the ISO-4037 narrow spectrum X-ray reference fields in 02 different manners: simulation using the SpekPy and measurement using a calibrated ionization chamber. The physical (air Kerma rate) and radiation (X-ray fluence-spectrum-averaged energy, the first and the second half value layers, as well as the beam homogeneity coefficient) quantities were simulated using the SpekPy web-based simulation toolkit. In addition, air Kerma rates were measured by the ionization chamber. The characteristics of the ISO-4037 narrow spectrum X-ray reference fields were determined for various X-ray beam qualities (i.e., N-40, 60, 80, 100, 120, and 150) at 250 cm from the X-ray focal spot. The air Kerma rate tendency was deduced by comparing simulation and measurement data. The combined standard uncertainty of measured air Kerma rate was investigated and presented.

Development and implementation of an automated four-terminal-pair Josephson impedance bridge

The four-terminal-pair impedance bridge using pulse-driven Josephson voltage standards at PTB has been fully automated. The same bridge configuration was employed to determine R:R and C:C ratios over the frequency range between 53 Hz to 50 kHz. Only minor changes are needed to cover this large frequency range: amplifiers to increase the sensitivity of the current detections for low frequencies and signal generators with higher resolution at high frequencies to reach 50 kHz. Furthermore, the bridge can be operated for quadrature R:(1/ωC) measurements. The combined standard uncertainties (k = 1) for the new bridge were evaluated for all operating frequencies. They reach 2 nF F−1 and 4 nΩ Ω−1 at 1233.15 Hz. At this frequency, the 10 nF:10 nF ratio matched the ratio of PTB’s bridge employing inductive voltage dividers within 1 nF F−1 ± 3 nF F−1 (k = 1). Over 45 days, the 10 nF:10 nF ratio deviated less than −2 nF F−1 ± 3 nF F−1 (k = 1). The 12.9 kΩ:10 kΩ ratio at 53 Hz differed −2 nΩ Ω−1 ± 5 nΩ Ω−1 (k = 1) from the DC ratio measured by the PTB’s cryogenic current comparator bridge. Using a 12.9 kΩ resistance standard and a graphene AC quantum Hall resistance, the 10 nF:10 nF ratios derived from quadrature measurements agreed with the PTB’s inductive voltage divider bridge better than 9 nF F−1 ± 13 nF F−1 (k = 1).

239Pu[sbnd]Be neutron reference field: Physical and dosimetric parameters

This paper presents the establishment of a 239PuBe neutron reference field at the Military Institute for Chemical and Environmental Engineering, Hanoi, Viet Nam. The evaluation of the field parameters due to neutrons of the total component was performed using an in-house developed Bonner sphere spectrometer in combination with the output data from the FRUIT unfolding code. As results, these following field parameters were obtained for neutrons of the total component, at several points of interest: (i) neutron fluence spectrum; (ii) integral neutron fluence rate - ϕ, unit in cm−2s−1; (iii) neutron ambient dose rate (a new operational quantity) - Ḣ∗, unit in μSvh−1; (iv) neutron ambient dose equivalent rate (an old operational quantity) - Ḣ∗(10), unit in μSvh−1; (v) neutron fluence-to-ambient dose conversion coefficient - h∗, unit in pSvcm2; (vi) fluence-averaged neutron energy - E¯, unit in MeV; and (vii) ambient dose-averaged neutron energy - E˜, unit in MeV. The standard combined uncertainties of Ḣ∗ and Ḣ∗(10) due to the total neutron component were estimated within 10%, considered as acceptable for measurements of Ḣ∗ and/or Ḣ∗(10) less than 50 μSvh−1. In addition, the fluence-to-ambient dose equivalent conversion coefficient (h) for the direct neutron component was also deduced. The standard deviation of h between those obtained from this work and from published data was calculated as within 5.7%, acceptable for radiation protection purpose.

Densities and excess molar volumes of thiophene + heptane and thiophene + octane at temperatures between (313 K and 363) K and pressures up to 25 MPa using three calibration methods

New compressed liquid densities (ρ) of thiophene + heptane and thiophene + octane are reported in the temperature range from (313 to 363) K, with pressure up to 25 MPa. The compositions are x(1) = 0.1049, 0.2471, 0.5097, 0.7494, and 0.8994 for thiophene (1) + heptane (2), and x(1) = 0.1042, 0.2530, 0.5037, 0.7516, and 0.8988 for thiophene (1) + octane (2). The experimental system uses a vibrating tube densimeter (VTD) and three calibration methods (the first uses hexane and water, the second uses nitrogen and water, and the third uses water and applying vacuum to the VTD as calibration reference fluids). The reported density data are determined using the third method, which notifies the lowest uncertainty and estimates a maximum relative expanded uncertainty (k=2) of 0.21 % in the temperature range from (313 to 363) K and pressures up to 25 MPa. The pure compound densities were calculated from previous density measurements represented by the Pimentel-Galicia model. This empirical correlation of the pure compounds was used before for the excess molar volume calculation. The experimental data of the mixtures reported in this work were modeled by the Pimentel-Galicia model at each composition with deviations not higher than 0.07 %. The combined standard uncertainty for composition (considering the purities of the samples) is ucx= 0.0026. Finally, the isothermal compressibility and isobaric thermal expansivity were evaluated from density data.

Bilateral comparison of 1.018 V and 10 V standards between INRIM (Italy) and the BIPM, November to December 2023 (part of the ongoing BIPM key comparison BIPM.EM-K11.a and b)

Main textAs part of the ongoing BIPM key comparison BIPM.EM-K11.a and b, a comparison of the 1.018 V and 10 V voltage reference standards of the BIPM and the INRIM (Italy), from November to December 2023. Two BIPM Zener diode-based travelling standards (Fluke 732B), BIPM_7 (Z7) and BIPM_9 (Z9), were transported by freight to the INRIM and back to the BIPM. In order to keep the Zeners powered during their transportation phase, two additional external batteries were connected in parallel to the internal battery. At the INRIM and the BIPM, the reference standard for DC voltage is a Programmable Josephson Voltage Standard (PJVS). The output electromotive force (EMF) of each travelling standard was measured by direct comparison with the primary standard. The final result of the comparison is presented as the difference between the values assigned to DC voltage standards by the INRIM, at the level of 1.018 V and 10 V, at the INRIM, UINRIM, and those assigned by the BIPM, at the BIPM, UBIPM, at the reference date of the 1st of December 2023. U INRIM - U BIPM = -0.04 µV; u c = 0.03 µV, at 1.018 V U INRIM - U BIPM = -0.18 µV; u c = 0.19 µV, at 10 Vwhere uc is the combined standard uncertainty associated with the measured difference, including the uncertainty of the realisation of the volt at the BIPM and at the INRIM, and the uncertainty related to the comparison.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Key comparison BIPM.RI(I)-K5 of the air-kerma standards of the BEV, Austria and the BIPM in 137Cs gamma radiation

Main textA new comparison of the standards for air kerma of the Bundesamt für Eich- und Vermessungswesen (BEV), Austria, and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 137Cs radiation beam using the radiation protection facility of the International Atomic Energy Agency (IAEA) in Seibersdof, Austria in April 2023. The comparison was done using the BEV and the BIPM primary standards and a transfer instrument belonging to the BEV. The direct comparison result, evaluated as a ratio of the BEV and the BIPM standards for air kerma, is 1.0043 with a combined standard uncertainty of 2.7 parts in 103. The result for the indirect comparison is in agreement with the direct result at the level of 3 parts in 104. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database, to update the 2009 comparison result.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Key comparison BIPM.RI(I)-K8 of high dose-rate 192Ir brachytherapy standards for reference air kerma rate of the LNE-LNHB and the BIPM

Main textAn indirect comparison of the standards for reference air kerma rate for 192Ir high dose rate (HDR) brachytherapy sources of the Laboratoire National Henri Becquerel (LNE-LNHB), France, and of the Bureau International des Poids et Mesures (BIPM) was carried out at the LNE-LNHB in May 2024. The comparison result, based on the calibration coefficients for a transfer standard and expressed as a ratio of the LNE-LNHB and the BIPM standards for reference air kerma rate, is 0.9990 with a combined standard uncertainty of 0.0071.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Key comparison BIPM.RI(I)-K8 of high dose-rate 192Ir brachytherapy standards for reference air kerma rate of the PTB and the BIPM

Main textAn indirect comparison of the standards for reference air kerma rate for 192Ir high dose rate (HDR) brachytherapy sources of the Physikalisch-Technische Bundesanstalt (PTB), Germany, and of the Bureau International des Poids et Mesures (BIPM) was carried out at the PTB in May 2023. The comparison result, based on the calibration coefficients for a transfer standard and expressed as a ratio of the PTB and the BIPM standards for reference air kerma rate, is 1.0022 with a combined standard uncertainty of 0.0101.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

MEASUREMENT UNCERTAINTY EVALUATION OF THE WIND SPEED IN THE ATMOSPHERIC BOUNDARY LAYER

A method for measuring wind speed by the trajectory of an acoustic package under the influence of air flows in the boundary atmospheric layer is developed. Model equations for measurement components of wind speed evaluation are ob- tained. For each of the components, an equation for the combined standard uncertainty is written, sensitivity coefficients are calcu- lated for input quantities, and uncertainty budgets are constructed. The last can serve as the basis for creating a software tool for measurement uncertainty evaluation.

Key comparison BIPM.RI(I)-K8 of high dose-rate 192Ir brachytherapy standards for reference air kerma rate of the VSL and the BIPM

Main textA new key comparison of the standards for reference air kerma rate for 192Ir high dose rate (HDR) brachytherapy sources of the Dutch Metrology Institute (VSL), The Netherlands, and the Bureau International des Poids et Mesures (BIPM) was carried out at the VSL in May 2019. The comparison result, based on the calibration coefficients for a transfer standard and expressed as a ratio of the VSL and the BIPM standards for reference air kerma rate, is 0.9926 with a combined standard uncertainty of 0.0055.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).