Relative Systematic Errors Research Articles

Experimental and Theoretical Study of the Reaction of F2 with Thiirane.

The kinetics of the F2 reaction with thiirane (C2H4S) was studied for the first time in a flow reactor combined with mass spectrometry at a total helium pressure of 2 Torr and in the temperature range of 220 to 800 K. The rate constant of the title reaction was determined under pseudo-first-order conditions, either monitoring the kinetics of F2 or C2H4S consumption in excess of thiirane or of F2, respectively: k1 = (5.79 ± 0.17) × 10-12 exp(-(16 ± 10)/T) cm3 molecule-1 s-1 (the uncertainties represent precision of the fit at the 2σ level, with the total 2σ relative uncertainty, including statistical and systematic errors on the rate constant being 15% at all temperatures). HF and CH2CHSF were identified as primary products of the title reaction. The yield of HF was measured to be 100% (with an accuracy of 10%) across the entire temperature range of the study. Quantum computations revealed reaction enthalpies ranging from -409.9 to -509.1 kJ mol-1 for all the isomers/conformers of the products, indicating a strong exothermicity. Boltzmann relative populations were then established for different temperatures.

Measurement of light absorption by chromophoric dissolved organic matter using a type-II liquid capillary waveguide: assessment of an achievable accuracy

Light absorption by chromophoric dissolved organic matter (CDOM) in the ocean is often measured using liquid waveguide capillary cells coupled to spectral array detectors. This type of optical setup is affected by several sources of uncertainties related to the waveguide and the detector. Uncertainties from the waveguide arise from errors in the effective path length and the effects of water salinity, while errors related to the detector are due to the non-linearity in the response, internal stray light, and wavelength accuracy. Here, uncertainties in the measurements of the spectral absorption coefficient of CDOM due to the optical setup itself were investigated in detail. The related systematic errors were very often significant (2–15%) and larger than expected from simple measurement uncertainty (±1%). However, they can be corrected by characterizing the detector’s response for non-linearity and stray light, regularly performing calibrations for the detector’s wavelength response, and routinely measuring the waveguide’s effective path length. Including such corrections and timely calibrations reduces the uncertainties related to the spectrophotometric measurements to about ±2%. Uncertainties related to the necessary handling of samples are not included here.

Improvement of instrumented indentation test accuracy by data augmentation with electrical contact resistance

Instrumented Indentation Test allows thorough surface multi-scale mechanical characterisation by depth-sensing the indenter penetration and correlating it with the indenter-sample contact area and the applied force. Localised plastic phenomena at the indentation edge, i.e. pile-up and sink-in, may bias the characterisation results. Current approaches attempt correcting related systematic errors by numerical simulation and AFM-based techniques. However, they require careful tuning and complex and expensive experimental procedures. This work proposes a methodology based on in-situ Electric Contact Resistance which augments information on the contact area and allows edge effect correction. The methodology is demonstrated and validated on industrially relevant metallic materials.

Effect of the Dynamic Response of a Side-Wall Pressure Measurement System on Determining the Pressure Step Signal in a Shock Tube Using a Time-of-Flight Method.

Technological progress demands accurate measurements of rapidly changing pressures. This, in turn, requires the use of dynamically calibrated pressure meters. The shock tube enables the dynamic characterization by applying an almost ideal pressure step change to the pressure sensor under calibration. This paper evaluates the effect of the dynamic response of a side-wall pressure measurement system on the detection of shock wave passage times over the side-wall pressure sensors installed along the shock tube. Furthermore, it evaluates this effect on the reference pressure step signal determined at the end-wall of the driven section using a time-of-flight method. To determine the errors in the detection of the shock front passage times over the centers of the side-wall sensors, a physical model for simulating the dynamic response of the complete measurement chain to the passage of the shock wave was developed. Due to the fact that the use of the physical model requires information about the effective diameter of the pressure sensor, special attention was paid to determining the effective diameter of the side-wall pressure sensors installed along the shock tube. The results show that the relative systematic errors in the pressure step amplitude at the end-wall of the shock tube due to the errors in the detection of the shock front passage times over the side-wall pressure sensors are less than 0.0003%. On the other hand, the systematic errors in the phase lag of the end-wall pressure signal in the calibration frequency range appropriate for high-frequency dynamic pressure applications are up to a few tens of degrees. Since the target phase measurement uncertainty of the pressure sensors used in high-frequency dynamic pressure applications is only a few degrees, the corrections for the systematic errors in the detection of the shock front passage times over the side-wall pressure sensors with the use of the developed physical dynamic model are, therefore, necessary when performing dynamic calibrations of pressure sensors with a shock tube.

ДОСЛІДЖЕННЯ МЕТРОЛОГІЧНИХ ХАРАКТЕРИСТИК ТЕРМОАНЕМОМЕТРА НА ОСНОВІ ВИМІРЮВАЛЬНОГО КОНТРОЛЮ ПАРАМЕТРІВ ТЕПЛОВОГО ПОТОКУ МИКРОХВИЛЬОВОЇ КАМЕРИ

The purpose of the article is to study the rational operation of the hot-wire anemometer in accordance with the dynamic characteristics and measurement errors, when implementing the process of drying raw nuts in an industrial microwave chamber. The technique of studying the informative parameters of the heat flow was used to determine the rational mode of operation of the hot-wire anemometer and to reduce the time of heat treatment of nut raw materials. The characteristics of the thermal transient process of drying raw nut materials in a microwave chamber are investigated. Theoretical substantiation and an algorithm for determining the dynamic characteristics of the hot-wire anemometer under the external sinusoidal effect of the heat flow temperature are given, algorithms for determining the instantaneous values of the temperature increments of the hot-wire anemometer sensitive element in the process of drying nut raw materials are given. On the basis of the general theory of errors of indirect measurements in the investigated range of variation of the rate V of the heat flow, the values of the relative systematic errors of indirect measurements of the rate of heat flow in the range from 10 to 40 m / s were determined. It was found that in accordance with the dynamic characteristics and measurement errors when blowing a moving heat flow of nut raw materials, the most rational is the mode of constant resistance of the hot-wire anemometer. Solutions of the differential equation describing the dynamic heat process when the temperature of the moving heat flow changes according to the periodic law, i.e. stationary, non-stationary and complete. The results of calculating the constant times of the hot-wire anemometer thread τп and τтп of the moving heat flow, respectively, were τп = 0.59 s and τтп = 0.6 s, the time constant of the hot-wire anemometer is practically commensurate with the thermal time constant of the moving stream blowing over the nut raw material. It consists in the fact that the theoretical position of the hot-wire anemometer has been further developed in the direction of researching the characteristics of the thermal transient process of processing nut raw materials, all this makes it possible to determine the ranges of changes in the signals of the thermal device, which correspond to the ranges of change in the informative characteristics of the moving heat flow, and also allows the selection measuring equipment, establish rational operating modes of hot-wire anemometers and automated devices that use them in accordance with errors and sensitivities. The proposed algorithms for determining the informative parameters of the heat flow in the study of the transient process of heat transfer from the moving air flow to the sensitive element of the transducer, the results of the errors in measuring the velocity V of the moving heat flow, make it possible to calculate, design and create measuring automated devices that use hot-wire anemometers in food and processing industry, instrument making and chemical engineering.

Round Robin into Best Practices for the Determination of Indentation Size Effects.

The paper presents a statistical study of nanoindentation results obtained in seven European laboratories that have joined a round robin exercise to assess methods for the evaluation of indentation size effects. The study focuses on the characterization of ferritic/martensitic steels T91 and Eurofer97, envisaged as structural materials for nuclear fission and fusion applications, respectively. Depth-controlled single cycle measurements at various final indentation depths, force-controlled single cycle and force-controlled progressive multi-cycle measurements using Berkovich indenters at room temperature have been combined to calculate the indentation hardness and the elastic modulus as a function of depth applying the Oliver and Pharr method. Intra- and inter-laboratory variabilities have been evaluated. Elastic modulus corrections have been applied to the hardness data to compensate for materials related systematic errors, like pile-up behaviour, which is not accounted for by the Oliver and Pharr theory, and other sources of instrumental or methodological bias. The correction modifies the statistical hardness profiles and allows determining more reliable indentation size effects.

Near infrared spectroscopic analysis of total alkaloids as nicotine, total nitrogen and total ash in Cuban cigar tobacco

Three models using partial least squares regression of near infrared reflectance spectroscopy were developed for the first time to evaluate the concentration of total alkaloids as nicotine, total nitrogen and total ash in powdered samples of Cuban cigar tobacco. They had lower standard error of cross-validation (SECV) and standard error of prediction (SEP) than those using: (1) principal components regression; (2) multiple linear regression and (3) other partial least squares models previously published for this and other tobacco types. SECV values in mass fraction units were: 0.0010, 0.0011 and 0.0048, respectively. The coefficients of determination (R2) in calibration were: 0.99, 0.94 and 0.96, respectively. Standard error of prediction values were: 0.0011, 0.0012 and 0.0049, respectively. The r2 obtained when comparing the predicted values using the validation set with the reference data was nearly the same as in calibration. The equation for total alkaloids as nicotine was good for quantification, and for process control, development and applied research according to the quotients range/standard error of prediction and standard deviation/standard error of prediction, respectively. Equations for the other analytes were as good as the one for alkaloids, but suitable only for screening purposes. Joint F-tests on the regression coefficients from ordinary least squares and iterative reweighted least squares fittings among predicted and reference data indicated slopes and intercepts enclosing 1 and 0, respectively. The relative systematic errors between the near infrared spectroscopy predicted values and the reference methods are close to the same figures reported previously for traditional analytical procedures under intermediate precision and reproducibility conditions; hence, the models are suitable for this industrial context.

PyAmpli: an amplicon-based variant filter pipeline for targeted resequencing data

BackgroundHaloplex targeted resequencing is a popular method to analyze both germline and somatic variants in gene panels. However, involved wet-lab procedures may introduce false positives that need to be considered in subsequent data-analysis. No variant filtering rationale addressing amplicon enrichment related systematic errors, in the form of an all-in-one package, exists to our knowledge.ResultsWe present pyAmpli, a platform independent parallelized Python package that implements an amplicon-based germline and somatic variant filtering strategy for Haloplex data. pyAmpli can filter variants for systematic errors by user pre-defined criteria. We show that pyAmpli significantly increases specificity, without reducing sensitivity, essential for reporting true positive clinical relevant mutations in gene panel data.ConclusionspyAmpli is an easy-to-use software tool which increases the true positive variant call rate in targeted resequencing data. It specifically reduces errors related to PCR-based enrichment of targeted regions.

Measurement uncertainty limit analysis of biased estimators in RFID multiple tags system

In the measurement of real radio frequency identification (RFID) system, due to the relative and absolute systematic errors, biased estimators do happen in the practical measurement, which are difficult to be analysed. In order to get effective biased estimators, the linear and nonlinear functions in the measurement of RFID tags are taken as a paradigm to study the equivalence between the bias-corrected estimators and biased estimators. The measurement curve of optimum distribution angles of multiple tags is analysed in particular based on Fisher information determinant (FID), which could be used to evaluate the optimum performance of multiple RFID tags system. The results demonstrate the bias-corrected estimators of the single tag’s reading distance and multiple tags’ measurement curve of optimum distribution angles in RFID system could be obtained by calculating the corresponding biased estimators. Particularly, the biased estimator of multiple tags’ measurement curve of optimum distribution angles reaches the CRB when and only when the bias-corrected estimator reaches its corresponding CRB. Finally, the general expression of the biased CRB case in UHF RFID measurement is obtained. This study could be used as an evaluation tool for the measurement uncertainty limit of biased estimators.

An effective stiffness model for GFRP RC cracked flexural members

Abstract There is no complete consensus of researchers on the problem of evaluating tension stiffening phenomena in cracked flexural glass fibre-reinforced polymer reinforced concrete members and, therefore, various empirical correction factors are used in the existing weighted averaging techniques for obtaining consistent estimates of experimental deflection of traditional steel bars reinforced concrete cross-sections. This paper presents an alternative method for deformational analysis of cracked GFRP RC flexural members based on constitutive modeling, taking into account the direct or inverse approach to evaluating the post-cracking stress-strain response of concrete in tension. The effect of tension stiffening is defined analytically by the derived formula for the effective moment of inertia, omitting the empirical correction of the moments of inertia of the uncracked or fully cracked RC cross-sections. Analytical formulae are also proposed to derive the parameters of tension stiffening based on the test data of GFRP RC beams subjected to bending. The relative systematic and random errors of the method are considered in the statistical analysis, involving the experimental sample of deflections for 42 beams. The case studies of manual calculation of the mid-span deflection of the beams by using the proposed technique and the inverse analysis for deriving tension stiffening parameters based on of the experimental data are also provided.

Oscillation mode linewidths and heights of 23 main-sequence stars observed byKepler

Solar-like oscillations have been observed by Kepler and CoRoT in many solar-type stars, thereby providing a way to probe the stars using asteroseismology. We provide the mode linewidths and mode heights of the oscillations of various stars as a function of frequency and of effective temperature. We used a time series of nearly two years of data for each star. The 23 stars observed belong to the simple or F-like category. The power spectra of the 23 main-sequence stars were analysed using both maximum likelihood estimators and Bayesian estimators, providing individual mode characteristics such as frequencies, linewidths, and mode heights. We study the source of systematic errors in the mode linewidths and mode heights, and we present a way to correct these errors with respect to a common reference fit. Using the correction, we could explain all sources of systematic errors, which could be reduced to less than $\pm$15% for mode linewidths and heights, and less than $\pm$5% for amplitude, when compared to the reference fit. The effect of a different estimated stellar background and a different estimated splitting will provide frequency-dependent systematic errors that might affect the comparison with theoretical mode linewidth and mode height, therefore affecting the understanding of the physical nature of these parameters. All other sources of relative systematic errors are less dependent upon frequency. We also provide the dependence of the so-called linewidth dip, in the middle of the observed frequency range, as a function of effective temperature. We show that the depth of the dip decreases with increasing effective temperature. The dependence of the dip on effective temperature may imply that the mixing length parameter $\alpha$ or the convective flux may increase with effective temperature.

Controlling the non-linear intracavity dynamics of large He–Ne laser gyroscopes

A model based on Lamb's theory of gas lasers is applied to a He–Ne ring laser (RL) gyroscope to estimate and remove the laser dynamics contribution from the rotation measurements. The intensities of the counter-propagating laser beams exiting one cavity mirror are continuously observed together with a monitor of the laser population inversion. These observables, once properly calibrated with a dedicated procedure, allow us to estimate cold cavity and active medium parameters driving the main part of the non-linearities of the system. The quantitative estimation of intrinsic non-reciprocal effects due to cavity and active medium non-linear coupling plays a key role in testing fundamental symmetries of space–time with RLs. The parameter identification and noise subtraction procedure has been verified by means of a Monte Carlo study of the system, and experimentally tested on the G-PISA RL oriented with the normal to the ring plane almost parallel to the Earth's rotation axis. In this configuration the Earth's rotation rate provides the maximum Sagnac effect while the contribution of the orientation error is reduced to a minimum. After the subtraction of laser dynamics by a Kalman filter, the relative systematic errors of G-PISA reduce from 50 to 5 parts in 103 and can be attributed to the residual uncertainties on geometrical scale factor and orientation of the ring.

Empirical assessment of uncertainties of meteorological parameters and turbulent fluxes in the AmeriFlux network

Terrestrial ecosystem‐atmosphere exchange of carbon, water vapor, and energy has been measured for over a decade at many sites globally. To minimize measurement and analysis errors, quality assurance data have been collected over short periods along‐side tower instruments at AmeriFlux research sites. Theoretical and empirical error and uncertainty values have been reported for various aspects of the eddy covariance technique but until recently it has not been possible to constrain network level variation based on direct comparison of side‐by‐side measurements. Paired observations, although rare in practice, offer a possibility to obtain real‐world error estimates for flux observations and corresponding uncertainties. In this study, we report the relative instrumental errors from the AmeriFlux quality assurance and quality control (QA/QC) site intercomparisons of 84 site visits (2002–2012). Relative errors, including random and systematic instrumental errors, are presented for meteorological and radiation variables, gas concentrations, and the turbulent fluxes. The lowest relative errors (<2%) were found for the meteorological parameters, while the largest relative errors were found for latent heat and CO2 fluxes. The mean relative instrumental error for CO2 flux averaged −8.2% (underestimation by the tower instruments). Sensible and latent heat fluxes exhibited mean errors of −1.7% and −5.2%, respectively. Deviation around the mean was also largest for the turbulent fluxes, approaching 20%. Because the data collected during QA/QC site visits are used to identify and correct errors, our results represent a conservative estimate of instrumental errors in the AmeriFlux database. Overall, the presented results confirm the high quality of the network data and underline its status as a valuable data source for the research community.

Neutron Decay with PERC: a Progress Report

The PERC collaboration will perform high-precision measurements of angular correlations in neutron beta decay at the beam facility MEPHISTO of the Forschungs-Neutronenquelle Heinz Maier-Leibnitz in Munich, Germany. The new beam station PERC, a clean, bright, and versatile source of neutron decay products, is designed to improve the sensitivity of neutron decay studies by one order of magnitude. The charged decay products are collected by a strong longitudinal magnetic field directly from inside a neutron guide. This combination provides the highest phase space density of decay products. A magnetic mirror serves to perform precise cuts in phase space, reducing related systematic errors. The new instrument PERC is under development by an international collaboration. The physics motivation, sensitivity, and applications of PERC as well as the status of the design and preliminary results on uncertainties in proton spectroscopy are presented in this paper.

Incurred Sample Accuracy Assessment: Design of Experiments Based on Standard Addition

It is commonly acknowledged that random and systematic analytical errors contribute to poor data quality, and moreover, to imprecise and inaccurate pharmacokinetic parameters. To investigate the random errors in GLP bioanalysis, common ground has been found in today's bioanalysis to assess the reproducibility of the method by reanalyzing part of the incurred samples. The undesired systematic errors in bioanalysis affecting the trueness of the method and leading to inaccurate data remain relatively unattended so far. In order to obtain both precise and accurate data it is suggested in this paper to apply standard addition experiments to calculate the relative systematic errors as an estimate for the incurred sample accuracy. This approach, which can be seen as an important extension to current guidelines in GLP bioanalysis, is illustrated by assessing the accuracy of the bioanalytical results for a bioequivalence study for alendronate.

A near-infrared method for the assay of cineole in eucalyptus oil as an alternative to the official BP method.

Thirty different eucalyptus oil samples were scanned on the FOSS NIRSystems 6500 Rapid Content Sampler using a reflectance vessel as sample presentation method. The cineole content of each sample was determined by the BP method and these reference data were used to construct two calibration equations for cineole content in the oils using Vision software. The mean accuracy for the NIR method differed by 1.01% or less, and the mean bias by +/-0.33% or less, compared with the BP method. Calculation of the 95% confidence intervals for the slope and intercept of plots of NIR predicted values against BP method reference values showed that there was no evidence of fixed or relative systematic errors. Tests for short-term and intermediate repeatability were conducted. The standard deviation was 0.83% w/w or less and the coefficient of variation was 1.11% or less. The confidence intervals for both short-term and intermediate repeatability overlapped with that for the BP method, suggesting that there was no evidence for a difference in values obtained by the BP and NIR methods. The range of cineole contents used in the calibrations was extended by incorporating five samples of eucalyptus oil spiked with cineole, and five samples of two essential oils known to have a lower cineole content than eucalyptus oil, to give a range of 52.5 to 99.0% w/w. The mean accuracy decreased to an error of 1.26% or less and the bias to +/-0.50% or less. Again, confidence intervals suggested there was no evidence for fixed or systematic errors in the NIR calibrations. We propose that NIR spectroscopy could be used as an alternative method for the determination of cineole content in eucalyptus oils.

Lax sphygmomanometer standard causes overdetection and underdetection of hypertension: a computer simulation study

To quantify overdetection and underdetection of hypertension caused by systematic sphygmomanometer errors permitted by the current European standard (EN 1060 'noninvasive sphygmomanometers'). We carried out Monte Carlo simulation of measurement of blood pressure (BP) of the adult Australian population using sphygmomanometers showing systematic errors compliant with the EN 1060 standard. We repeated the simulations limiting systematic sphygmomanometer errors to +/-1 mmHg. Simulated BP measurements included systematic sphygmomanometer error, random intraindividual BP variability and random measurement error. After three visits, underdetection of hypertension is common owing to variability of BP measurements and systematic errors of sphygmomanometers. After three visits, the wide tolerances of EN 1060 are responsible for approximately 4.9 and 11% of underdetection of systolic and diastolic hypertension, respectively. Underdetection is worse in some groups, for example, permitted sphygmomanometer error causes 20% of all undetected systolic hypertension in 18-24 year-old women. The current standard also results in overdetection of hypertension. Permitted sphygmomanometer error causes 5.8 and 14% of the overdetection of systolic and diastolic hypertension, respectively, after three visits. Overdetection is worse in some groups, for example, after three visits, permitted sphygmomanometer error causes 19% of falsely detected diastolic hypertension in 18-24 year-old men. For all adults, reduction of permitted sphygmomanometer error to +/-1 mmHg achieves approximately the same improvement in hypertension detection as at least one additional visit to the clinician. Systematic sphygmomanometer errors permitted by the current standard are a preventable cause of clinically significant overdetection and underdetection of hypertension. The standard should be revised to make the effects of equipment related systematic errors negligible compared with the effects of physiological variability.

SU‐FF‐T‐369: Propagation of Linac Output and Fluence Discretization Error to Dose Distributions in IMRT

Purpose: Linac output variation and the fluence discretization from MLC leaf sequencing are sources of IMRT delivery error. We investigate a theory describing the propagation of fluence errors to dose distributions. Method and Materials: We assume that the fluence from each beam port is the planned fluence plus a gantry angle dependent error. We assume linac output variation contributes to systematic and random error whereas fluence discretization error is purely random. Expressions for the random and systematic dose error distributions were derived with standard error propagation theory. We investigated hepatocellular carcinoma (HCC) and prostate cases planned with step‐and‐shoot IMRT and tomotherapy. Linac output errors were estimated from measurements from a linac with a malfunctioning magnetron, thus representing higher‐than‐normal output errors. The maximum relative random and systematic linac output errors were both around 2%. Results: For both patients and both modalities, the relative dose error in the PTV due to systematic linac output variations was around 1% and the random component was negligible. The dose error in the PTV due to fluence discretization was between 0.1% and 0.2% for tomotherapy and about 1% for step‐and‐shoot. The relative dose error threshold such that 90% of the voxels in the PTV had a 90% chance of error less than the threshold was 1.5% for step‐and‐shoot and 0.5% for tomotherapy. Conclusions: The relative random dose error at a point decreases as the inverse square root of the number of beams that affect that point, making the relative random dose error orders of magnitude lower than the relative systematic error. Systematic dose error changes little with the number of beams used in the treatment since it is not propagated in quadrature. The dose errors from the malfunctioning magnetron had little effect on the treatment. Conflict of Interest: TR Mackie has financial interest in TomoTherapy Inc.

Weak absorption in ATR spectroscopy: Systematic errors of Harrick’s formulas

A method for the determination of the systematic errors of Harrick’s formulas is proposed. The method is based on the expansion of the expressions for the optical density into a Maclaurin series in terms of the extinction coefficient of the medium under study. Using numerical calculations, it is shown that, under conditions of weak absorption, it is sufficient to consider only the first two terms of this series, with the relative systematic errors of Harrick’s formulas being determined in this case by dividing the first term of the series by the second. The behavior of the relative systematic errors for perpendicular and parallel polarizations is compared. These errors are shown to decrease monotonically with an increase in the angle of incidence and have finite limits both for angles of incidence tending to the critical value and at grazing incidence of probe radiation.

Determination of Neodymium and Ytterbium by Isotope Dilution Laser Mass Spectrometry

The experimental conditions for minimizing errors in the laser mass spectrometric (LMS) analysis of isotopic ratios for Nd and Yb were found, and the optimum isotope pairs for determining these elements with the use of isotope dilution (ID) were chosen. The precision and accuracy of LMS data, which are characterized by relative random errors (RSD) and relative systematic errors (δ), can be improved using ID. The values for Nd or Yb were no higher than RSD = 2.9% and δ = 0.024 or RSD = 5% and δ = 0.097, respectively.