Systematic Measurement Errors Research Articles

IMPROVING THE ACCURACY OF AUTOMATIC CONTROL WITH MATHEMATICAL METER MODEL IN ON-BOARD CONTROLLER

Context. The article discusses the issues of increasing the accuracy of automatic control of a moving object using a mathematical model of a meter and a device observing measurement errors in the on-board controller of the control system. The object of the research is the processes of automatic control of a moving object with a mathematical model of a meter and a device observing measurement errors in the on-board controller of the control system. The subject of the research is a method and algorithms for increasing the accuracy of automatic control of a moving object with a mathematical model of a meter and a device observing measurement errors in the on-board controller of the control system.Objective. The aim of research is an improving the accuracy of automatic control of a moving object.Method. This aim is achieved through the use in the on-board controller of the control system of the mathematical meter model and the observing device built on its basis, the estimation of the useful component and the systematic error, depending on the motion parameters of the controlled object, using only the useful component for control, without systematic error.Results. A method and algorithms for increasing the control accuracy of a moving object through the use in the on-board controller of a mathematical meter model and an observer of systematic measurement errors, built on its basis, have been developed. The efficiency and effectiveness of the developed method and algorithms were confirmed by mathematical modeling in the MATLAB environment of the control processes of a moving object in a closed circuit with a control system.Conclusions. The results of mathematical modeling confirmed the operability and efficiency of the proposed method and algorithms and allow them to be used for practical purposes in the development of mathematical support for high – precision automatic control systems.

Quantum tomography of noisy ion-based qudits

Quantum tomography makes it possible to obtain a comprehensive information about certain logical elements of a quantum computer. In this regard, it is a promising tool for debugging quantum computers. The practical application of tomography, however, is still limited by systematic measurement errors. Their main source are errors in the quantum state preparation and measurement procedures. In this work, we investigate the possibility of suppressing these errors in the case of trapped-ion-based qudits. First, we will show that one can construct a quantum tomography protocol that contains no more than a single quantum operation in each measurement circuit. Such a protocol is more robust to errors than the measurements in mutually unbiased bases, where the number of operations increases in proportion to the square of the qudit dimension. After that, we will demonstrate the possibility of determining and accounting for the state initialization and readout errors. Together, the measures described can significantly improve the accuracy of quantum tomography of real ion-based qudits.

Uncertainty analysis of wireless temperature measurement (WTM) in borehole heat exchangers

The reliability of temperature measurements in open and closed geothermal systems is closely related to their design, quality control and performance evaluation. Thus, wireless and miniaturized probes, which provide highly resolved temperature profiles in borehole heat exchangers (BHEs), experience a growing interest in research. To ensure quality assurance and reliability of these emerging technologies, errors and uncertainties relating to wireless temperature measurements (WTMs) must be determined. Thus, we provide a laboratory analysis of random, systematic and dynamic measurement errors, which lead to the measurement uncertainties of WTMs. For the first time, we subsequently transfer the calculated uncertainties to temperature profiles of the undisturbed ground measured at a BHE site in Karlsruhe, Germany. The resulting precision of 0.011 K and accuracy of -0.11 K ensure a high reliability of the WTMs. The largest uncertainty is obtained within the first five meters of descent and results from the thermal time constant of 4 s. The fast and convenient measurement procedure results in substantial advantages over Distributed Temperature Sensing (DTS) measurements using fiber optics, whose recorded temperature profiles at the site serve as qualitative comparison. We additionally provide recommendations for technical implementations of future measurement probes. Our work will contribute to an improved understanding and further development of WTMs.

Error analysis of cross-shaped magnetic gradient full tensor measurement system

The structural characteristics of the magnetic gradient full tensor measurement system are important factors affecting the accuracy of the magnetic gradient full tensor measurement. In order to analyze the measurement error of the cross-shaped magnetic gradient full tensor measurement system, the theoretical framework and structural configuration of the tensor system that is based on the magnetic dipole model are introduced. Four factors including the resolution, baseline length, target distance, and magnetic moment direction that cause measurement errors are simulated and analyzed. The simulation results show that the resolution, baseline length, and target distance have a great influence on the error of the measurement system. In contrast, the influence caused by the change in the magnetic moment direction is not significant. In a certain area, the resolution increases from 1 nT to 1 fT, and the error percentage of the tensor component Byy decreases the most, reaching 2.1370%. When designing the system structure, it is necessary to comprehensively consider the measurement purpose, design cost, measurement error, and other factors. It is important to select the fluxgate according to actual needs and coordinate the relationship between the baseline length and the measurement distance, which can be effective to decrease the error. The research conclusion can provide theoretical guidance for the design of the cross-shaped magnetic gradient full tensor measurement system.

Contactless Pneumoelectric Fluid Viscosity Measurement Device

We review a variety of contactless techniques for fluid viscosity measurement. We discuss contactless aero-hydrodynamic techniques capable of providing high-accuracy viscosity measurements for non-homogeneous and non-transparent fluids over the range 2–100 Pa·s. We describe a very promising approach in need of additional work–a contactless aero-hydrodynamic technique that involves using a pulsed gas jet to distort the surface of the fluid being measured and determining the viscosity based on the time required to reach a specified deformation level after the gas jet comes on. We have developed a contactless aero-hydrodynamic device with a laser triangulation detector to measure the range to the surface of the liquid; this viscosity measurement device supports full automation, while providing a significant increase in measurement accuracy. We studied four possible options for implementation of the device, and selected the best option to improve the measurement accuracy and reduce the sensitivity of the device to external effects. We describe the design and operating principle for the device, and describe how device design parameters affect systematic and random measurement error. The relative measurement error in fluid viscosity was 2% or less over the entire range from 2 to 100 Pa·s. This contactless aero-hydrodynamic device will be useful for measurement of viscous fluids in a wide variety of industrial fields.

How Well Do Automated Linking Methods Perform? Lessons from U.S. Historical Data.

This paper reviews the literature in historical record linkage in the U.S. and examines the performance of widely-used record linking algorithms and common variations in their assumptions. We use two high-quality, hand-linked datasets and one synthetic ground truth to examine the direct effects of linking algorithms on data quality. We find that (1) no algorithm (including hand-linking) consistently produces representative samples; (2) 15 to 37 percent of links chosen by widely-used algorithms are classified as errors by trained human reviewers; and (3) false links are systematically related to baseline sample characteristics, showing that some algorithms may induce systematic measurement error into analyses. A case study shows that the combined effects of (1)-(3) attenuate estimates of the intergenerational income elasticity by up to 20 percent, and common variations in algorithm assumptions result in greater attenuation. As current practice moves to automate linking and increase link rates, these results highlight the important potential consequences of linking errors on inferences with linked data. We conclude with constructive suggestions for reducing linking errors and directions for future research.

Identifying health correlates of intimate partner violence against pregnant women.

Violence against women during pregnancy is a serious public health concern due to its significant adverse health consequences for both the mother and the baby. This study aims to systematically identify common health problems and synergistic health correlates of intimate partner violence (IPV) that specifically affect pregnant women. We mine large-scale electronic health record (EHR) data from the IBM Explorys database to identify health problems that are prevalent in both IPV and pregnancy populations, as well those that are synergistically associated with the presence of IPV during pregnancy. For this purpose, we develop methods that enhance the statistical reliability of identified patterns by constructing confidence intervals that take into account systematic bias and measurement errors in addition to the variance in estimation. We identify with high confidence 668 and 2750 terms that are respectively prevalent in respectively IPV and pregnancy populations. Of these terms, 279 are common. We also identify 16 synergistic health correlates with high confidence. Our results suggest that mental health, substance abuse, and genitourinary complications are prevalent among pregnant women exposed to IPV. The synergistic terms we identify reveal potential conditions that can be direct consequences of trauma (e.g., tibial fracture), long-term health consequences (e.g., chronic rhinitis), markers associated with the demograhics of affected populations (e.g., acne), and risk factors that potentially increase vulnerability during pregnancy (e.g., disorders of attention and motor control). Our results indicate that IPV significantly affects the well-being of pregnant women in multiple ways. The findings of this study can be useful for screening of IPV in pregnant women. Finally, the methodology presented here can also be useful for investigating the synergy between other medical conditions using EHR databases with privacy constraints.

Influence of the Estimation Accuracy of the Frequency Characteristics of Radar Targets on the Results of the Geometric Shape Identification of Local Reflectors

This article discusses the issues of introducing broadband technologies to civil and special-purpose radar systems. The popularity of these technologies in terms of solving numerous practical problems determines the relevance of research related to a detailed analysis of long-range portraits of objects observed at a new qualitative level. Using the results of broadband radar sounding, this study analyzes the influence of the systematic error of the measuring channel on the reliability of the identification of the geometric shape of the local reflectors of observation objects. A broadband radar-measuring channel with a linear frequency modulation of the signal is created on the basis of the generalized heterodyning method. Then, a technique for compensating systematic measurement errors for a given type of channel is proposed using calibration spheres. The systematic error in measuring the frequency characteristics (FCs) of the sphere is estimated, and an error indicator for estimating the FCs of objects is proposed. Furthermore, the dependence of the statistical indicators of the identification results of the geometric shape of local reflectors on the specified indicator is presented. The possibility of identifying the geometric shape of local reflectors through the parameters of their FCs is confirmed experimentally. The results obtained can be used to assess the reliability of the identification of the geometric shape of local reflectors at the calibration stage of the measuring channel and to make a decision on the feasibility of implementing algorithms for the identification of the geometric shape of local reflectors on an existing radiolocation station.

On the extraction of yield stresses from micro-compression experiments

It is widely stated that yield stress extraction from micro-compression testing can be unreliable due to factors such as the pillar taper, pillar-punch misalignment and lateral displacement for example through discrete slip events. This study reports on how these factors can be eradicated when using digital image correlation based strain mapping. This approach is demonstrated through a conventional micropillar compression experiment using the hexagonal MAX phase system Cr2AlC. The use of this approach enables the uncertainty of the extracted yield stress values to be significantly reduced and effectively increases the precision of critical resolved shear stress extraction for basal plane slip from ±52% to ±4% of the mean value. The findings suggest that the statistical variations commonly observed in micro-compression tests may frequently be linked to systematic errors in the stress measurements taken, and that precise evaluation of deformation statistics can only be facilitated if the pillar deformation morphology is closely monitored.

Development and application of online load measurement system for hanger and support

It was difficult to monitor the load and evaluate the performance of the hanger and support of power plant. The online load measurement system for hanger and support was developed and some experiments had been carried out. Compared with the offline bench performance testing machine, the experimental results showed that the average measurement error of the online measurement system was less than 1%. It can effectively measure the performance parameters of the hanger, conveniently and reliably monitor the real-time load of the hanger, which is important for the safe operation of the hanger and the steam/water pipeline in the power plant.

An Approach for Data Treatment of Solar Photovoltaic Generation

A good solar power photovoltaic generation forecast depends on good quality time series data from measurements of Global Horizontal Irradiance and Solar Power Generation. However, measurement system failures and errors in data handling can corrupt data records with gaps and outliers that undermine forecasting accuracy. Therefore, it is important that the fitting of solar energy prediction models must be preceded by a data analysis in order to detect and correct measurement errors. Given that Global Horizontal Irradiance and Solar Power Generation are correlated variables, this paper aims to present the main characteristics of an offline approach developed for the joint treatment of hourly data values of both variables in a photovoltaic plant. In the proposed methodology, the measurements of Global Horizontal Irradiance and Solar Power Generation are analyzed by using reanalysis data and statistical and data mining techniques for the correction of outliers and the filling of data gaps. The application of the approach is illustrated by the analysis of measurements from a real solar PV system.

An Accurate Calibration Method of Large-Scale Reference System

The large-scale reference system (LRS) based on multiple measuring stations is widely used to estimate the position and orientation of the aligned components of aircraft. The reference system consists of some enhanced reference system (ERS) points. However, the calibration accuracy of the reference system is prone to be degraded due to measurement systematic errors and environmental disturbance in the workshop. A novel nonlinear optimization method has been developed to reduce the overall calibration error of the LRS. First, the method focuses on analyzing the inhomogeneity and anisotropy of measurement errors of ERS points and establishing an improved weighting model for optimizing the coordinates of the points. Then, the measurement errors of each measuring station can be greatly reduced through a nonlinear unconstraint optimization method with redundant measurements. Thus, a more accurate LRS can be established. Finally, a field measurement experiment of ERS points in the reference system was conducted, and the results showed that the mean registration error of all ERS points was reduced from 0.058 to 0.014 mm and the standard deviation of registration error was reduced from 0.021 to 0.012 mm. Meanwhile, the measurement errors of each measuring station were also greatly reduced.

Temporal Matrices Mapping-Based Calibration Method for Event-Driven Structured Light Systems

Strong ambient illumination severely degrades the performance of conventional structured light 3D imaging systems due to the limited sensor bandwidth and light source power. In contrast, event-driven structured light techniques fully take advantage of laser-galvanometer scanning and event-detection property, which can achieve robust 3D reconstruction under such challenging scenarios. However, the low measurement accuracy of such systems severely hinders their extensive applications, as no accurate calibration method has yet been developed for them. In this work, we propose a novel Temporal Matrices Mapping (TMM) based calibration algorithm for event-driven structured light systems. The crucial step of our method is establishing the pixel correspondences between the galvanometer and event camera image planes with two temporal matrices. Specifically, we 1) scan a front-parallel plane vertically and horizontally to attain two temporal matrices; 2) estimate the coordinates of feature points on the galvanometer image plane through the temporal matrices and corresponding scanning speeds. In order to make the most of our calibration method, we present a disparity correction approach for depth calculation. We developed a prototype system to validate the proposed algorithms. Experimental results demonstrate that the calibration algorithm can reach sub-pixel precision, and the system's measurement error can achieve 0.2%, which outperforms the typical 1.0% of the state-of-the-art.

Flow stress correction for hot compression of titanium alloys considering temperature gradient induced heterogeneous deformation

Uniaxial compression is widely employed to investigate the constitutive behavior and microstructural developments of metallic materials at elevated temperatures. However, the heat exchange between work-piece and anvils leads to temperature gradient and inhomogeneous deformation within the work-piece, which weakens the reliability of the testing method. The problem is more serious for titanium alloys due to the poor thermal conductivity and high sensitivity of deformation resistance on temperature. To quantify the effect of temperature gradient, a coupled thermo-electric-mechanical FE model is developed for hot compression of TA15 titanium alloy with a Gleeble thermal simulator. The precise temperature control is achieved via a negative feedback control algorithm. It is found that the temperature gradient prior to deformation is sensitive to the electrical contact conductance between specimen and anvils as well as the heat transfer between the anvil and anvil base. Bulging is sensitive to temperature gradient rather than interfacial friction. The measured flow stress is smaller than the true value at large strain for the titanium alloy, which is contrary to conventional perception. Thus, the traditional flow stress correction method degrades the accuracy of flow stress measurement. A correction procedure is developed based on inverse analysis of the FE simulation. The results can reduce the systematic error of flow stress measurement of titanium alloys with Gleeble system.

Research on Error and Compensation of Volume Measurement System for Nondestructive Testing

In order to improve the measurement accuracy of the three-dimensional non-destructive testing device for slice volume, the experimental error caused by the hydraulic loss of the experimental container is analyzed and compensated. Through the analysis of the overflow characteristics, the weir flow model of the overflow is established, the profile curve of the overflow and the overflow round tube are optimized to reduce local losses, and verified by experiment. The results show that the measurement accuracy of the liquid volume is improved by about 54.85%, and this optimization scheme is effective. By optimizing the experimental device, the error is compensated to ensure the accuracy of data collection.

Accuracy of interproximal enamel reduction during clear aligner treatment

AimThe aim of the present study was to compare the accuracy of the actual space obtained through interproximal enamel reduction (IPR) compared to the amount of IPR planned through the digital setup during clear aligner treatment (CAT).Materials and methodsA total of 10 clinicians were randomly recruited using the Doctor Locator by Align Technology (California). For each clinician, four consecutive patients treated with CAT and manual stripping were selected for a total of 40 subjects and 80 dental arches. For each patient, the amount of planned IPR and the amount of actual IPR performed were recorded. Each arch was considered individually. For each arch, the mesio-distal tooth measurements were obtained from second to second premolars.ResultsNo systematic measurement errors were identified. In 25 cases, stripping was planned and performed in both arches; in 4 cases only in the upper arch and in the remaining 7 cases only in the lower arch. The difference between planned IPR and performed IPR was on average 0.55 mm (SD, 0.67; P = 0.022) in the upper arch and 0.82 mm (SD, 0.84; P = 0.026) in the lower arch. The accuracy of IPR in the upper arch was estimated to be 44.95% for the upper arch and 37.02% for the lower arch.ConclusionOverall, this study showed that the amount of enamel removed in vivo did not correspond with the amount of IPR planned. In most cases, the performed IPR amount was lower than planned. When considering the actual amount in millimeter, these differences may not be considered clinically relevant.

Investors' Misweighting of Firm‐Level Information and the Market's Expectations of Earnings

ABSTRACTPrior studies use fundamental earnings forecasts to proxy for the market's expectations of earnings because analyst forecasts are biased and are available for only a subset of firms. We find that as a proxy for market expectations, fundamental forecasts contain systematic measurement errors analogous to those in analysts' biased forecasts. Therefore, these forecasts are not representative of investors' beliefs. The systematic measurement errors from using fundamental forecasts to proxy for market expectations occur because investors misweight the information in many firm‐level variables when estimating future earnings, but fundamental forecasts are formed using the historically efficient weights on firm‐level variables. Thus, we develop an alternative ex ante proxy for the market's expectations of future earnings (“the implied market forecast”) using the historical (and inefficient) weights, as reflected in stock returns, that the market places on firm‐level variables. A trading strategy based on the implied market forecast error, which is measured as the difference between the implied market forecast and the fundamental forecast, generates excess returns of approximately 9 percent per year. These returns cannot be explained by investors' reliance on analysts' biased forecasts. Overall, our results reveal that market expectations differ from both fundamental forecasts and analysts' forecasts.

A Measurement Method Based on RF Deflector for Particle Bunch Longitudinal Parameters in Linear Accelerators

In high-brightness electron linear accelerators (LINACs), the particle bunch length is measured by a radio frequency deflector (RFD). The electron bunch is deflected vertically toward a screen and its length can be obtained using vertical spot size measurements after a proper calibration, e.g., measuring the vertical bunch centroid while varying the deflecting voltage phase. The energy parameters of the bunch (the energy chirp and the energy spread) and the correlation between particle positions, divergences, and energies contribute to the bunch vertical dimension at the screen position after the RFD and so far were considered as a source of systematic errors in a bunch length measurement. The measurement theory and production model for bunch length, energy spread and chirp, as well as correlations are described. As usual in particle accelerators physics, the method is validated using numerical simulations of state-of-the-art LINACs with a reference simulation code showing a typical accuracy in the few percent levels.

Combining eddy covariance measurements with process-based modelling to enhance understanding of carbon exchange rates of dairy pastures

Many temperate grasslands are used for dairying, and ongoing research aims to better understand these systems in order to increase animal production and soil organic carbon (SOC) stocks. However, it is difficult to fully understand management effects on SOC because most changes are slow and difficult to distinguish from natural variability, even if changes are important over years to decades. Eddy covariance (EC) measurements can overcome this problem by continuously measuring net carbon exchange from pastures, but net balances are very sensitive to even small systematic measurement errors. Combining EC measurements with detailed process-based modelling can reduce the risks inherent in total reliance on EC measurements. Modelling can also reveal information about the underlying processes that drive observed fluxes.Here, we describe carbon exchange patterns of five paddocks situated at four different locations in New Zealand and France where EC data and detailed physiological modelling were available. The work showed that respiration by grazing animals was often only incompletely captured in EC measurements. This was most problematic when fluxes were based on gap-filling, which could have estimated incorrect fluxes during grazing periods based on observations from periods without grazing. We then aimed to extract plant physiological insights from these studies. We found appreciable carbon uptake rates even at temperatures below 0 °C. After grazing, carbon uptake was reduced for up to 2 weeks. This reduction was larger than expected from reduced leaf area after grazing, but the factors contributing to that difference have not yet been identified.Detailed physiological models can also extrapolate findings to new management regimes, environmental conditions or plant attributes. This overcomes the limitation of experimental studies, which are necessarily restricted to actual site and weather conditions allowing models to make further progress on predicting management effects on SOC.

Pregnancy-induced changes in serum concentrations of perfluoroalkyl substances and the influence of kidney function

BackgroundEpidemiological associations between maternal concentrations of perfluoroalkyl substances (PFAS) and birth weight are inconsistent. There is concern that studies based on samples collected in late pregnancy may be confounded by kidney function but studies of the relation between pregnancy-induced changes in PFAS and kidney function are lacking. Our aims were to investigate changes in serum concentrations of perfluorononanoic acid (PFNA), perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonate (PFHxS) from early to late pregnancy and to explore relations to changes in glomerular filtration rate (GFR) and glomerular pore size.MethodsWe conducted the study in a cohort of 73 pregnancies of normal-weight Swedish women without gestational diabetes and preeclampsia, enrolled 2009–2014. Blood was collected in median weeks 11 and 36, respectively, and analysed PFAS using liquid chromatography-tandem-mass-spectrometry. We estimated GFR based on creatinine and cystatin C and used the ratio eGFRcystatin C/eGFRcreatinine to indicate glomerular pore size. We used Wilcoxon signed-rank test to compare early and late measures and partial Spearman rank correlations to explore relations between changes in PFAS and kidney function.ResultsMedian concentrations of PFNA, PFOA and PFOS decreased by 15–21% but changes were uncorrelated to changes in kidney function (partial R = − 0.06–0.11). The observed increase in median PFHxS concentration of 69% was likely an artefact of systematic measurement error caused by coeluting endogenous inferences.ConclusionsSerum concentrations of PFNA, PFOA and PFOS decrease during pregnancy but the magnitudes of change are unrelated to parallel changes in eGFR and glomerular pore size, suggesting that changes in these indicators of kidney function are not important confounders in studies of PFAS and birth weight in pregnancies without gestational diabetes and preeclampsia.