Respective Measurement Uncertainties Research Articles

Metrological characterization of the longitudinal ultrasonic velocity of cylindrical rock cores

The correlation of the use of ultrasonic velocity in rock cores has been a fundamental resource in the analysis of geoscientists and rock engineers. The general rule is that ultrasonic velocities in typically heterogeneous materials, such as composites, rocks, and soils, present greater dispersion than homogeneous ones. This behaviour, although expected due to the more significant internal variation in the composition of its matrix, requires the application of a more cautious measurement protocol, mainly for samples with low parallelism. This work presents a metrological measurement protocol to determine the longitudinal ultrasonic velocities of these materials and their respective measurement uncertainties. The evaluation of the proposed protocol was applied to four samples of cylindrical migmatite rocks, each 76 mm in diameter. The frequency used was centred at 500 kHz. The determination of the transit time in each sample was made from the difference between the first internal reflection of the sample and the direct signal from the receiver. Samples with approximate heights of 51 mm, 62 mm, 77 mm and 101 mm were used. Their faces were divided into four quadrants. Measurements were taken around the geometric centre of the part and in each of the four quadrants. Fivedimensional measurements were performed for each quadrant, and ten transit time measurements were for each of the five defined regions. Due to the low parallelism of the parts, a protocol was adopted where the global uncertainty of each part was increased to that of the part with greater uncertainty. From the results of this research, it was noted that the effect of low parallelism tends to increase the dimensional uncertainty measurements and, consequently, the sample measurement uncertainty values.

Impact of Estimation Uncertainty in PMU-Based Resynchronization of Continental Europe Synchronous Areas

Power system stability is a task that every system operator (SO) is required to achieve daily to ensure an uninterruptible power supply. Especially at the transmission level, for each SO it is of utmost importance to ensure proper exchange of information with other SOs, mainly in case of contingencies. However, in the last years, two major events led to the splitting of Continental Europe into two synchronous areas. These events were caused by anomalous conditions which involved in one case the fault of a transmission line and in the other a fire outage in proximity to high-voltage lines. This work analyzes these two events from the measurement point of view. In particular, we discuss the possible impact of estimation uncertainty on control decisions based on measurements of instantaneous frequency. For this purpose, we simulate five different configurations of phasor measurement units (PMUs), as characterized by different signal models, processing routines, and estimation accuracy in the presence of off-nominal or dynamic conditions. The objective is to establish the accuracy of the frequency estimates in transient conditions, more specifically during the resynchronization of the Continental Europe area. Based on this knowledge, it is possible to set more suitable conditions for resynchronization operations: the idea is to consider not only the frequency deviation between the two areas but also to take into account the respective measurement uncertainty. As confirmed by the analysis of the two real-world scenarios, such an approach would allow for minimizing the probability of adverse or even dangerous conditions such as dampened oscillations and inter-modulations.

Winter Vertical Diffusion Rates in the Arctic Ocean, Estimated From 7Be Measurements and Dissipation Rate Profiles

AbstractOcean turbulent mixing is a key process affecting the uptake and redistribution of heat, carbon, nutrients, oxygen and other dissolved gasses. Vertical turbulent diffusivity sets the rates of water mass transformations and ocean mixing, and is intrinsically an average quantity over process time scales. Estimates based on microstructure profiling, however, are typically obtained as averages over individual profiles. How representative such averaged diffusivities are, remains unexplored in the quiescent Arctic Ocean. Here, we compare upper ocean vertical diffusivities in winter, derived from the 7Be tracer‐based approach to those estimated from direct turbulence measurements during the year‐long Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, 2019–2020. We found that diffusivity estimates from both methods agree within their respective measurement uncertainties. Diffusivity estimates obtained from dissipation rate profiles are sensitive to the averaging method applied, and the processing and analysis of similar data sets must take this sensitivity into account. Our findings indicate low characteristic diffusivities around 10−6 m2 s−1 and correspondingly low vertical heat fluxes.

Setting Multivariate and Correlated Acceptance Limits for Assessing the Conformity of Items

Many industrial products, foodstuffs and environmental samples are checked for values of different chemical parameters against tolerance limits or intervals defined in a specification or legislation. In some cases, the measured values of the different parameters are correlated due to how materials are obtained, chemical constraints and/or due to the simple fact that determinations are performed by multi-analyte procedures that share analytical operations and effects. In these cases, instead of defining an acceptance criterion for each measured value on the tested item separately based on the respective measurement uncertainty, the multivariate problem should be addressed by defining multivariate criteria. These multivariate criteria are set for a maximum total risk of wrong conformity decisions that is a complex function of all particular risks of the item being rejected or accepted by comparing each measured value with its respective limit. Computational tools have been developed to estimate the total specific risk of an item being wrongly considered to conform or not to conform with tolerance limits for various components when the measured values are independent or correlated. However, these tools must be applied for each test to check if the total specific risk is acceptable. This work presents a tool for setting multivariate acceptance limits applicable to correlated measurements and referenced to a defined total specific risk. The acceptance limits allow the decision about conformity of an item based on the simple comparison of the measured values with the acceptance limits. The acceptance limits are estimated by a user-friendly and iterative tool implemented in a MS-Excel spreadsheet and available in the Supplementary Material. This tool is successfully applied to various conformity problems. Acceptance limits based on informative and non-informative prior information are compared for a critical review of the merits and problems associated with Bayesian or frequentist conformity assessments.

Data-based energy coverage measurements to discover the potentials of regional energy storage

Abstract The fluctuations of the renewable energies request storage systems as a significant part of the future energy system. Here we introduce a measurement approach regarding the regional coverage of the power demand and the influence of a storage system on it. The approach is based on measured power data with given uncertainties. The resolution is 15 minutes in the time domain and 2-digit ZIP code regions in the spatial domain. An idealized storage model is introduced, and one storage is implemented for each region. As a result, the regional coverage is measured for different storage parameters and the respective measurement uncertainty is assessed to be below the set goal of 2 %. Furthermore, the inverse problem, i. e. the storage dimensioning, is investigated by estimating the necessary storage parameters to achieve a desired regional coverage. Findings: electrical self-sufficiency can be reached in 23 out of 95 regions, in contrast in 56 regions the regional coverage is increased insignificantly regardless of the parameters of the storage system. This illustrates the necessity of power transport to enable the increase of regional coverage. Concluding, the proposed measurement approach enables the estimation of storage parameters and can be used for storage dimensioning.

Value of amniotic fluid homocysteine assay in prenatal diagnosis of combined methylmalonic acidemia and homocystinuria, cobalamin C type

BackgroundCombined methylmalonic acidemia and homocystinuria, cobalamin C type (cblC defect) is the most common inborn error of cobalamin metabolism, and different approaches have been applied to its prenatal diagnosis. To evaluate the reliability of biochemical method for the prenatal diagnosis of cblC defect, we conducted a retrospective study of our 10-year experience at a single center.Methods248 pregnancies whose probands were diagnosed as cblC defect were referred to our center for prenatal diagnosis from January 2010 to December 2019. Prenatal data of Hcy levels determined by enzymatic cycling assay, acylcarnitine analysis using liquid chromatography tandem mass spectrometry, organic acid analysis using gas chromatography mass spectrometry, and genetic analysis by direct sequencing of 248 at-risk fetuses were retrospectively reviewed.ResultsFor 2.0 and 16.0 μmol/L levels of Hcy AF samples, the relative errors were − 2.5% and 2.8%, respectively. The respective measurement uncertainties were 13.07% and 14.20%. For the 248 at-risk fetuses, 63 fetuses were affected and 185 fetuses were unaffected. Hcy level of 13.20 (6.62–43.30) μmol/L in 63 affected fetuses was significantly higher than that in 185 unaffected fetuses of 2.70 (0.00–5.80) μmol/L, and there was no overlap between the affected and unaffected groups. The diagnostic sensitivity and specificity of Hcy were 100% and 92.05%, respectively. The positive and negative predictive values of the combination of Hcy, propionylcarnitine (C3), ratio of C3 to acetylcarnitine (C2; C3/C2), methylmalonic acid (MMA), and methylcitric acid (MCA) were both 100%. Sixteen fetuses displayed inconclusive genetic results of MMACHC variants, in which seven fetuses were determined to be affected with elevated levels of Hcy, C3, C3/C2 and MMA, and their levels were 18.50 (6.70–43.30) μmol/L, 8.53(5.02–11.91) μmol/L, 0.77 (0.52–0.97), 8.96 (6.55–40.32) mmol/mol Cr, respectively. The remaining nine fetuses were considered unaffected based on a normal amniotic fluid metabolite profile.ConclusionsHcy appears to be another characteristic biomarker for the prenatal diagnosis of cblC defect. The combination of Hcy assay with acylcarnitine and organic acid analysis is a fast, sensitive, and reliable prenatal diagnostic biochemical approach. This approach could overcome the challenge of the lack of genetic analysis for families with at-risk cblC defect fetuses.

Development and validation of an advanced electrochemical sensor for the fast and cheap determination of hydrochlorothiazide in urine samples using the Monte-Carlo method for uncertainty evaluation

This work describes the development, optimization, and validation of an electrochemical method for the determination of hydrochlorothiazide (HCTZ) in urine. The method allows fast, cheap and reliable determinations of recent administrations of this diuretic that can be used in doping control in sport. The response of the sensor was determined by differential pulse voltammetry (DPV). The glassy carbon electrode was modified with multiwall carbon nanotubes (MWCNT) and gold nanoparticles. The sensor is calibrated in the analysed sample matrix by the cumulative standard addition method. The method validation was based on the bottom-up evaluation of the measurement uncertainty were components were combined using the Monte Carlo Method (MCM) applicable with no restrictions regarding components uncertainty value and measurement function linearity. The developed metrological models were implemented in MS-Excel spreadsheets. The adequacy of the electrochemical measurements was assessed by comparing their relative standard uncertainty with a target value of 20% and by evaluating the compatibility of measurements with determinations performed by a reference procedure. The tools developed for the construction and optimization of working electrodes are applicable to measurements of other analytes and matrices. The used cumulative standard addition method and respective measurement uncertainty models are applicable to any kind of non-destructive chemical measurement of a solution.

A smartphone-based bioassay for determining relative potency estimated from sigmoidal-response curves and respective measurement uncertainty

ABSTRACT The use of smartphones in colorimetric bioassay applications is an alternative to spectrophotometric measurements. However, the development of bioassays requires the optimization of several critical analytical parameters. The aim of this work was to develop and optimize a smartphone-based colorimetric bioassay for determining relative potency of antibiotics and the respective measurement uncertainty. Analytical development was performed using an analytical quality by design (AQbD) approach. Critical analytical parameters were identified using risk assessment and optimized using a factorial design. The bioassay was accurate, precise, and robust. Relative potency values obtained from smartphone-based colorimetric measurements and spectrophotometric measurements were found to be comparable. The correlation of quantities due to shared analytical conditions significantly reduced the uncertainty multiplicative factor associated with the relative potency. AQbD approach was found to be a useful tool in developing and optimizing bioassays. In addition, the measurement uncertainty associated with the relative potency estimated from sigmoidal-response curves was successfully evaluated.

In-process workpiece displacement measurements under the rough environments of manufacturing technology

Abstract The goal-oriented manipulation of surface integrity by certain manufacturing processes requires comprehensive knowledge of the physical stresses induced into the workpiece. Properties such as the hardness are strongly influenced by mechanical stresses, induced during machining. The basic prerequisite for a comprehensive comparison of different manufacturing processes is the ability to precisely determine the stresses in the form of plastic and elastic displacements during the running manufacturing process. Due to the rough environmental conditions in many metalworking manufacturing processes, there are no non-invasive commercial methods for measuring the loads in the processed zone. For this reason, the suitability of speckle photography for in-process measurements of displacements to determine material loads in the process of single-tooth milling, rolling, grinding and laser hardening is investigated and questions regarding the respective achievable measurement uncertainty are addressed. To prevent a decorrelation of the speckle patterns within a measurement series, the images are captured with a high-speed camera and the total surface displacement is calculated from the sum of the individual image-to-image shifts. The measurement uncertainty of the image series thus adds up slowly with the number of processed images. However, by locally averaging the image series when stitching the individual displacement fields together to form a larger overall measurement field, the measurement uncertainty in the applications under consideration can be reduced to 1% of the maximum displacement. In this context, the interrelation between the cumulative uncertainty of measurement and the lateral expansion or size of the total displacement fields under consideration is investigated. In particular, the measurement uncertainty can decrease even further, if the individual measurement fields overlap more and if the displacement fields are small in relation to the measuring field. As a result, speckle photography provides a low measurement uncertainty and shows its applicability under rough environmental conditions in the examined processes.

Effect of position of temperature sensors on the resulting volumetric accuracy of the machine tool

This work focuses on the evaluation of the volumetric accuracy of a machine tool depending on temperature measurement errors to improve manufacturing quality. The measurement of the volumetric accuracy of the machine tool and its results is, as with each measurement, subjected to a respective measurement uncertainty. In particular, this article describes the effect of measuring the temperatures necessary to correctly evaluate the volumetric error on machine tools. From the methodical procedure of measuring the volumetric accuracy of machine tools, the most suitable requirements for positions of the temperature sensors are as close as possible to the axes of motion of the machine tool and their linear encoders. This article describes the effect of measurement errors caused by inappropriate positioning of temperature sensors on the resulting volumetric accuracy by means of a case study on a three-axis machining centre.

Using image analysis to determine gentamicin potency by agar diffusion microbiological assay and its measurement uncertainty

The inhibition zone sizes used to calculate the potency of antibiotics are often measured using calipers, which is laborious, time-consuming and provide a limited traceability audit. This work aims to propose determining potency and respective measurement uncertainty using free-based image analyzer software. Analytical conditions were optimized using design of experiments. Optimal analytical conditions were achieved using antibiotic concentrations in a range from 20 to 80 µg mL−1, 0.3% of microbial suspension, and 5 mL of inoculated culture medium. A larger signal-to-noise ratio was obtained using images obtained from a distance of about 15 cm from the camera, using triphenyl tetrazolium solution as viability dye, with image contrast enhanced, and defined edges. The potency values obtained from inhibition zone sizes measured using image analyses and regular calipers were similar (103.4% and 104.8%); however, the measurement uncertainty obtained using the image analyses measurements was significantly reduced compared to the regular caliper (1.038 and 1.124).

Quantitative analysis of cefquinome considering different matrix compositions of bovine colostrum and raw milk

A robust liquid chromatography-tandem mass spectrometry method was developed and comprehensively validated for the quantification of cefquinome considering the changing matrix composition from bovine colostrum to raw milk. Sample preparation consisted of addition of isotopically labeled cefquinome internal standard prior to protein precipitation of 2g colostrum or milk followed by solid-phase extraction. A wide concentration range from 1 to 5000ng cefquinome per gram of colostrum or milk was quantified using a 3200 QTRAP tandem mass spectrometer in positive ionization mode with electrospray ionization. Validation was performed according to the European Commission Decision 2002/657/EC guidelines. Matrix-comprehensive in-house validation included analytical limits CCα and CCβ, recovery, precision and calibration curves with prediction intervals, storage conditions, and evaluation of robustness based on factorial effect analysis. The detection limit was 0.2ng cefquinome per gram of colostrum or milk. Recovery was between 98.4 and 99.4% for cefquinome concentrations from 4 to 240ng/g. None of the investigated validation factors (matrix, storage of extracts, lot of SPE cartridges, and operators) exerted an influence higher than ± 3.2%, indicating that these factors make relatively low contributions to the respective combined measurement uncertainties. The comprehensively validated method enables routine residue control purposes and to monitor the pharmacokinetics of cefquinome in bovine colostrum and raw milk. In particular, residue depletion curves of cefquinome from high concentrations in first milking after treatment to concentrations far below the maximum residue limit can be measured.

Experimental Validation of a Boundary Layer Convective Heat Flux Measurement Technique

If a steady thermal boundary layer is sufficiently thick, wall heat fluxes and associated convective heat transfer coefficients can be directly calculated from measured temperature distributions taken within it using a traversing thermocouple probe. The boundary layer can be laminar, turbulent, or transitional and on a surface of arbitrary surface temperature distribution and geometry. Herein, this technique is presented and validated in a steady, turbulent, two-dimensional boundary layer on a flat, uniform-heat-flux wall. Care is taken to properly account for radiation from the wall and conduction within the thermocouple wire. In the same setting, heat flux measurements are made for verification purposes using an energy balance on a segment of the test wall carefully designed to minimize and include radiation and conduction effects. Heat flux values measured by the boundary layer measurement technique and by the energy balance measurement agree to within 4.4% and the difference between the two lie completely within their respective measurement uncertainties of 5.74% and 0.6%.

The influence of temperature on the speed of sound of cortical bone phantom: a metrological view

This paper presents an experimental study to estimate the group velocity of ultrasound longitudinal propagation in a cortical bone phantom for the temperature range of 19 °C to 37 °C, and respective measurement uncertainty estimates. The group velocity was measured using the pulse/echo method. The uncertainty model was proposed based on the BIPM JCGM:100 – Guide of the Expression of Uncertainty in Measurements. The velocity results show a tendency to decrease linearly as the temperature increases, considering the uncertainty estimated.

An evaluation of three methods for measuring black carbon in Alert, Canada

Abstract. Absorption of sunlight by black carbon (BC) warms the atmosphere, which may be important for Arctic climate. The measurement of BC is complicated by the lack of a simple definition of BC and the absence of techniques that are uniquely sensitive to BC (e.g., Petzold et al., 2013). At the Global Atmosphere Watch baseline observatory in Alert, Nunavut (82.5° N), BC mass is estimated in three ways, none of which fully represent BC: conversion of light absorption measured with an Aethalometer to give equivalent black carbon (EBC), thermal desorption of elemental carbon (EC) from weekly integrated filter samples to give EC, and measurement of incandescence from the refractory black carbon (rBC) component of individual particles using a single particle soot photometer (SP2). Based on measurements between March 2011 and December 2013, EBC and EC are 2.7 and 3.1 times higher than rBC, respectively. The EBC and EC measurements are influenced by factors other than just BC, and higher estimates of BC are expected from these techniques. Some bias in the rBC measurement may result from calibration uncertainties that are difficult to estimate here. Considering a number of factors, our best estimate of BC mass in Alert, which may be useful for evaluation of chemical transport models, is an average of the rBC and EC measurements with a range bounded by the rBC and EC combined with the respective measurement uncertainties. Winter-, spring-, summer-, and fall-averaged (± atmospheric variability) estimates of BC mass in Alert for this study period are 49 ± 28, 30 ± 26, 22 ± 13, and 29 ± 9 ng m−3, respectively. Average coating thicknesses estimated from the SP2 are 25 to 40 % of the 160–180 nm diameter rBC core sizes. For particles of approximately 200–400 nm optical diameter, the fraction containing rBC cores is estimated to be between 10 and 16 %, but the possibility of smaller undetectable rBC cores in some of the particles cannot be excluded. Mass absorption coefficients (MACs) ± uncertainty at 550 nm wavelength, calculated from light absorption measurements divided by the best estimates of the BC mass concentrations, are 8.0 ± 4.0, 8.0 ± 4.0, 5.0 ± 2.5 and 9.0 ± 4.5 m2 g−1, for winter, spring, summer, and fall, respectively. Adjusted to better estimate absorption by BC only, the winter and spring values of MACs are 7.6 ± 3.8 and 7.7 ± 3.8 m2 g−1. There is evidence that the MAC values increase with coating thickness.

Improvements in world-wide intercomparison of PV module calibration

Abstract The calibration of the electrical performance of seven photovoltaic (PV) modules was compared between four reference laboratories on three continents. The devices included two samples in standard and two in high-efficiency crystalline silicon technology, two CI(G)S and one CdTe module. The reference value for each PV module parameter was calculated from the average of the results of all four laboratories, weighted by the respective measurement uncertainties. All single results were then analysed with respect to this reference value using the En number approach. For the four modules in crystalline silicon technology, the results agreed in general within ±0.5%, with all values within ±1% and all En numbers well within [−1, 1], indicating further scope for reducing quoted measurement uncertainty. Regarding the three thin-film modules, deviations were on average roughly twice as large, i.e. in general from ±1% to ±2%. A number of inconsistent results were observable, although within the 5% that can be statistically expected on the basis of the En number approach. Most inconsistencies can be traced to the preconditioning procedure of one participant, although contribution of other factors cannot be ruled out. After removing these obvious inconsistent results, only two real outliers remained, representing less than 2% of the total number of measurands. The results presented show improved agreement for the calibration of PV modules with respect to previous international exercises. For thin-film PV modules, the preconditioning of the devices prior to calibration measurements is the most critical factor for obtaining consistent results, while the measurement processes seem consistent and repeatable.

The Influence of Thermal Comfort on the Quality of Life of Nursing Home Residents

ABSTRACTThermal comfort (TC) parameters were measured in 130 rooms from nursing homes (NH), following ISO 7730:2005 in order to evaluate the influence of winter season TC indices on quality of life (QoL) in older individuals. Mean radiant temperature (mrT), predicted mean vote (PMV) and predicted percent of dissatisfied people (PPD) indices, and the respective measurement uncertainties were calculated using Monte Carlo Method. The WHOQOL-BREF questionnaire was conducted from September 2012 to April 2013, during the winter season TC sampling campaign. Winter PMV and PPD indices showed significant differences between seasons in median values for comfort. There were also significant differences between seasons for air temperature, air velocity, mrT, and relative humidity. The winter PMV index displayed a “slightly cool” [≤−1] to “cool” [≤−2] in thermal sensation scale [−3 to 3]. PPD index reflected this discomfort as evidenced by a high rate of predicted dissatisfied occupants (64%). The influence of winter season TC on older individual QoL results demonstrated that values of PMV above −0.7 had higher mean score of QoL (coefficient estimate: 11.13 units) compared with values of PMV below −0.7. These findings are of relevance to public health and may be useful for understanding NH indoor environment variables thus implementing preventive policies in terms of standards and guidelines for these susceptible populations.

Measurement of titanium in hip-replacement patients by inductively coupled plasma optical emission spectroscopy.

Background Patients with metal-on-metal hip replacements require testing for cobalt and chromium. There may also be a need to test for titanium, which is used in the construction of the femoral stem in total hip replacements. It is not possible to use quadrupole inductively coupled plasma mass spectrometry due to interferences. Methods Titanium was measured using inductively coupled plasma optical emission spectroscopy using the emission line at 336.1 nm and Y (internal standard) at 371.0 nm. Internal quality control materials were prepared for blood and serum and concentrations assigned using a sector field-inductively coupled plasma mass spectrometer. A candidate whole blood certified reference material was also evaluated. Results The method had detection and quantitation limits of 0.6 and 1.9 µg/L, respectively. The respective bias (%) and measurement uncertainty ( U) (k = 2) were 3.3% and 2.0 µg/L (serum) and - 1.0% and 1.4 µg/L (whole blood). The respective repeatability and intermediate precision (%) were 5.1% and 10.9% (serum) and 2.4% and 8.6% (whole blood). The concentration of titanium was determined in patients' samples, serum (median = 2.4 µg/L, n = 897) and whole blood (median = 2.4 µg/L, n = 189). Serum is recommended for monitoring titanium in patients, since the concentration is higher than in whole blood and the matrix less problematic. In hip fluid samples, the concentrations were much higher (mean 58.5 µg/L, median 5.1 µg/L, n = 83). Conclusions A method based on inductively coupled plasma optical emission spectroscopy was developed and validated for measuring titanium in clinical samples.

Speed of sound as a function of temperature for ultrasonic propagation in soybean oil

Ultrasound has been used for characterization of liquid in several productive sectors and research. This work presents the studied about the behavior of the speed of sound in soybean oil with increasing temperature. The pulse echo technique allowed observing that the speed of sound decreases linearly with increasing temperature in the range 20 to 50 °C at 1 MHz. As result, a characteristic function capable to reproduce the speed of sound behavior in soybean oil, as a function of temperature was established, with the respective measurement uncertainty.

A Monte Carlo-Based Method for Assessing the Measurement Uncertainty in the Training and Use of Artificial Neural Networks

Abstract When an artificial neural network is used to determine the value of a physical quantity its result is usually presented without an uncertainty. This is due to the difficulty in determining the uncertainties related to the neural model. However, the result of a measurement can be considered valid only with its respective measurement uncertainty. Therefore, this article proposes a method of obtaining reliable results by measuring systems that use artificial neural networks. For this, it considers the Monte Carlo Method (MCM) for propagation of uncertainty distributions during the training and use of the artificial neural networks.