Equivalent Calibration Research Articles

A view on distributed sound level sensors from the perspective of legal metrology

Paper-based calibration certificates are gradually being replaced by equivalent digital calibration certificates (DCCs). The DCC is human-readable as well as machine-readable which simplifies the administration process significantly. During calibration procedure a measurement instrument is tested on-site in a testing laboratory. However, nowadays sound level sensors are increasingly deployed as distributed systems, where they transmit measurement data from one location (e.g. a workplace in a factory) to a measurement laboratory over available networks. This data transmission process has until now not been considered during calibration procedure or type approval tests. Therefore, requirements for the data transmission process according to the regulations of the European Cooperation in Legal Metrology (WELMEC Guide) must be considered. In this project two digital sound level sensors were selected and tested when deployed as distributed systems. The data collected were used to compare the two systems in accordance with the regulations of the WELMEC guide. In this work the first example of an acoustical DCC is presented and discussed. Further, a list of requirements is proposed that should be considered in the future when developing sound level sensors intended to be used as distributed systems.

Measurement of the sodium and iodine scintillation quenching factors across multiple NaI(Tl) detectors to identify systematics

The amount of light produced by nuclear recoils in scintillating targets is strongly quenched compared to that produced by electrons. A precise understanding of the quenching factor is particularly interesting for weakly interacting massive particles (WIMP) searches and coherent elastic neutrino-nucleus scattering (CEνNS) measurements since both rely on nuclear recoils, whereas energy calibrations are more readily accessible from electron recoils. There is a wide variation among the current measurements of the quenching factor in sodium iodide (NaI) crystals, especially below 10 keV, the energy region of interest for dark matter and CEνNS studies. A better understanding of the quenching factor in NaI(Tl) is of particular interest for resolving the decades-old puzzle in the field of dark matter between the null results of most WIMP searches and the claim for dark matter detection by the DAMA/LIBRA collaboration. In this work, we measured sodium and iodine quenching factors for five small NaI(Tl) crystals grown with similar thallium concentrations and growth procedures. Unlike previous experiments, multiple crystals were tested, with measurements made in the same experimental setup to control systematic effects. The quenching factors agree in all crystals we investigated, and both sodium and iodine quenching factors are smaller than those reported by DAMA/LIBRA. The dominant systematic effect was due to the electron equivalent energy calibration originating from the nonproportional behavior of the NaI(Tl) light yield at lower energies, potentially the cause for the discrepancies among the previous measurements. Published by the American Physical Society 2024

Fast and high-accuracy collinear reflection Mueller imaging polarimeter implemented with the compound calibration method

The collinear reflection Mueller matrix imaging polarimeter is suitable for characterizing thick samples with high-scattering depolarization such as biological tissues or in-situ living organs. Achieving fast detection and high measurement accuracy is vital to prevent artifacts and accurately assess polarization characteristics in these applications. This paper demonstrates a fast collinear reflection imaging polarimeter based on liquid crystal variable retarders (LCVRs-CRMMIP). We propose a novel compound calibration method (CCM), to the best of our knowledge, which enhances measurement accuracy through light intensity correction and an improved equivalent calibration sample model. This method surpasses the double-pass eigenvalue calibration method (dp-ECM), enhancing accuracy by over 23 times. Performance evaluations with standard samples, including mirrors, linear polarizers, and wave plates, reveal that the LCVRs-CRMMIP achieves rapid measurements (about 3 s) and high accuracy with an error of less than 0.0017.

Assessing the impact of distributed snow water equivalent calibration and assimilation of Copernicus snow water equivalent on modelled snow and streamflow performance

AbstractAccuracy of the Copernicus snow water equivalent (SWE) product and the impact of SWE calibration and assimilation on modelled SWE and streamflow was evaluated. Daily snowpack measurements were made at 12 locations from 2016 to 2019 across a 4104 km2 mixed‐forest basin in the Great Lakes region of central Ontario, Canada. Sub‐basin daily SWE calculated from these sites, observed discharge, and lake levels were used to calibrate a hydrologic model developed using the Raven modelling framework. Copernicus SWE was bias corrected during the melt period using mean bias subtraction and was compared to daily basin average SWE calculated from the measured data. Bias corrected Copernicus SWE was assimilated into the models using a range of parameters and the parameterizations from the model calibration. The bias corrected Copernicus product agreed well with measured data and provided a good estimate of mean basin SWE demonstrating that the product shows promise for hydrology applications within the study region. Calibration to spatially distributed SWE substantially improved the basin scale SWE estimate while only slightly degrading the flow simulation demonstrating the value of including SWE in a multi‐objective calibration formulation. The particle filter experiments yielded the best SWE estimation but moderately degraded the flow simulation. The particle filter experiments constrained by the calibrated snow parameters produced similar results to the experiments using the upper and lower bounds indicating that, in this study, model calibration prior to assimilation was not valuable. The calibrated models exhibited varying levels of skill in estimating SWE but demonstrated similar streamflow performance. This indicates that basin outlet streamflow can be accurately estimated using a model with a poor representation of distributed SWE. This may be sufficient for applications where estimating flow is the primary water management objective. However, in applications where understanding the physical processes of snow accumulation, melt and streamflow generation are important, such as assessing the impact of climate change on water resources, accurate representations of SWE are required and can be improved via multi‐objective calibration or data assimilation, as demonstrated in this study.

Taking full advantage of ‘low-quality’ datasets in watershed modeling and management: From a perspective of parameter calibration

The quality of calibration datasets is critical for establishing well-calibrated models for reliable decision-making support. However, the analysis of the influence of calibration dataset quality and the discussion on how to use flawed and/or incomplete datasets are still far from sufficient. An evaluation framework for the impact of model calibration data on parameter identifiability, sensitivity, and uncertainty (ISU) was established. Three quantitative and normalized indicators were designed to describe the magnitude of ISU. With the case study of the upper Daqing River watershed, China and the model SWAT (Soil and Water Assessment Tool), one ideal dataset without quality flaws and 79 datasets with different types of flaws including observation error, low monitoring frequency, short data duration and low data resolution were evaluated. The result showed that 4 of 13 parameters that control canopy, groundwater and channel processes have higher ISU values, indicating the high identifiability, high sensitivity, and low uncertainty. The largest gap of parameter ISU between dataset with quality flaw and ideal dataset was 0.61 due to short data duration, while the smallest gap was −0.28 due to low monitoring data frequency. Although some defective datasets caused unacceptable calibration results and model output, some defective datasets can still be valuable for model calibration which depends on the hydrological processes of interest when applying the model. Equivalent calibration results were yielded by the datasets with similar statistical properties. When using datasets with traditional defective issues for calibration, a new step checking the consistency among decision goal, representative system process, determinative parameters and calibration datasets is suggested. Practices including process-related data selection, dataset regrouping and risk self-reporting when using low-quality datasets are encouraged to increase the reliability of model-based watershed management.

Deep-field Metacalibration

We introduce deep-field metacalibration, a new technique that reduces the pixel noise in metacalibration estimators of weak lensing shear signals by using a deeper imaging survey for calibration. In standard metacalibration, when estimating the object's shear response, extra noise is added to correct the effect of shearing the noise in the image, increasing the uncertainty on shear estimates by ~ 20%. Our new deep-field metacalibration technique leverages a separate, deeper imaging survey to calculate calibrations with less degradation in image noise. We demonstrate that weak lensing shear measurement with deep-field metacalibration is unbiased up to second-order shear effects. We provide algorithms to apply this technique to imaging surveys and describe how to generalize it to shear estimators that rely explicitly on object detection (e.g., metacalibration). For the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST), the improvement in weak lensing precision will depend on the somewhat unknown details of the LSST Deep Drilling Field (DDF) observations in terms of area and depth, the relative point-spread function properties of the DDF and main LSST surveys, and the relative contribution of pixel noise vs. intrinsic shape noise to the total shape noise in the survey. We conservatively estimate that the degradation in precision is reduced from 20% for metacalibration to ~ 5% or less for deep-field metacalibration, which we attribute primarily to the increased source density and reduced pixel noise contributions to the overall shape noise. Finally, we show that the technique is robust to sample variance in the LSST DDFs due to their large area, with the equivalent calibration error being ~ 0.1%. The deep-field metacalibration technique provides higher signal-to-noise weak lensing measurements while still meeting the stringent systematic error requirements of future surveys.

Equivalent Calibration Method Based on a Blackbody Baffle Substitution for a Large External Surface-Source Blackbody.

Highly accurate measurements of infrared systems cannot be achieved without precise radiometric calibrations. In order to correctly interpret and process infrared images and monitor the performance of infrared cameras, their radiometric calibration is also required periodically. In this paper, an equivalent calibration method is proposed based on an internal blackbody baffle. It is used for the replacement of a large surface-source blackbody covering the aperture for the field calibration of large-aperture equipment. Subsequently, the expressions of the equivalent calibration conversion function (ECCF) are derived based on the grayscale response of the camera and the calibration models of the two methods, and experimental measurements and fits are performed using a cooled mid-wave infrared camera. The results show that the measured functional form is consistent with the physical meaning. Moreover, in the target imaging experiments, the results of the inversion using the equivalent calibration conversion function and the results of the direct calibration of the external blackbody are largely consistent with the average error of 0.198% between the two, and the maximum error is within 1%. The maximum error between the inversion result of radiation brightness and the actual value of the target is 6.29%, and the accuracy fully meets the radiometric measurement requirements.

A Technique for Rapid Bacterial-Density Enumeration through Membrane Filtration and Differential Pressure Measurements.

In this article, we present a microfluidic technique for the rapid enumeration of bacterial density with a syringe filter to trap bacteria and the quantification of the bacterial density through pressure difference measurement across the membrane. First, we established the baseline differential pressure and hydraulic resistance for a filtration membrane by fully wetting the filter with DI water. Subsequently, when bacteria were infused and trapped at the pores of the membrane, the differential pressure and hydraulic resistance also increased. We characterized the infusion time required for the bacterial sample to achieve a normalized hydraulic resistance of 1.5. An equivalent electric-circuit model and calibration data sets from parametric studies were used to determine the general form of a calibration curve for the prediction of the bacterial density of a bacterial sample. As a proof of concept, we demonstrated through blind tests with Escherichia coli that the device is capable of determining the bacterial density of a sample ranging from 7.3 × 106 to 2.2 × 108 CFU/mL with mean and median accuracies of 87.21% and 91.33%, respectively. The sample-to-result time is 19 min for a sample with lower detection threshold, while for higher-bacterial-density samples the measurement time is further shortened to merely 8 min.

Research on Calibration Method of Infrared Temperature Measurement System Near Room Temperature Field

The calibration accuracy of the infrared temperature measurement system near room temperature field is easily affected by the calibration environment. In this paper, an equivalent blackbody calibration method is proposed for this problem. In this method, the target radiation and ambient radiation superimposed in calibration data are separated by two calibration functions at different ambient temperatures, and an equivalent blackbody calibration function is constructed. The experimental verification of the proposed method is carried out, and the results show that the proposed method has a better calibration effect for the surface blackbody than the commonly used environmental compensation methods. This method can effectively improve the calibration accuracy of infrared temperature measurement system near room temperature field, and further improve the infrared temperature measurement theory.

Fatigue life analysis of aero-engine blades for abrasive belt grinding considering residual stress

Abrasive belt grinding technology is widely used in the processing of aero-engine blades. Residual stress is used as an indicator of grinding gauge integrity, which has a significant impact on the fatigue performance of aero-engine blades. In fatigue life research, experiments are mainly used to explore the influence of residual stress on fatigue life. Restricted by factors such as experimental efficiency and cost, it is necessary to simulate the influence of residual stress in the process of fatigue failure. Based on the theory of crack initiation and propagation, this paper proposes a life prediction algorithm considering residual stress; carries out a bending vibration fatigue experiment and simulation fatigue life analysis of aero-engine blade grinding with abrasive belt; compares the results of experiments and simulations and proposes a residual stress equivalent calibration method. Used theory, simulation, and experiment to verify the effectiveness of the method, and uses this equivalent calibration method to analyze the effect of residual stress on the fatigue life of aero-engine blades ground by abrasive belts. The experimental results show that the surface residual compressive stress will optimize the size and distribution of the surface stress during the service process of the aero-engine blade. Under the same external load and surface roughness conditions, a larger surface residual compressive stress will increase the aero-engine blade stiffness, reduce the aero-engine blade’s vibration amplitude, and reduce Surface stress, which in turn, has a beneficial effect on fatigue life. The proposed calibration method considering residual stress can accurately predict the fatigue life of aero-engine blades with a prediction accuracy up to 90%.

Accelerated k‐space shift calibration for free‐breathing stack‐of‐radial MRI quantification of liver fat and

To develop an accelerated k-space shift calibration method for free-breathing 3D stack-of-radial MRI quantification of liver proton-density fat fraction (PDFF) and . Accelerated k-space shift calibration was developed to partially skip acquisition of k-space shift data in the through-plane direction then interpolate in processing, as well as to reduce the in-plane averages. A multi-echo stack-of-radial sequence with the baseline calibration was evaluated on a phantom versus vendor-provided reference-standard PDFF and values at 1.5T, and in 13 healthy subjects and 5 clinical subjects at 3T with respect to reference-standard breath-hold Cartesian acquisitions. PDFF and maps were calculated with different calibration acceleration factors offline and compared to reference-standard values using Bland-Altman analysis. Bias and uncertainty were evaluated using normal distribution and Bayesian probability of difference (P < .05 considered significant). Bland-Altman plots of phantom and in vivo data showed that substantial acceleration was highly feasible in both through-plane and in-plane directions. Compared to the baseline calibration without acceleration, Bayesian analysis revealed no significant differences on biases and uncertainties of PDFF and measurements with all acceleration methods in this study, except the method with through-plane acceleration equaling slices and averages equaling 20 for PDFF and (both P < .001) for the phantom. A six-fold reduction in equivalent calibration acquisition time (time saving ≥25 s and ≥80.7%) was achieved using recommended acceleration factors for the in vivo protocols in this study. This proposed method may allow accelerated calibration for free-breathing stack-of-radial MRI PDFF and mapping.

External validation of the Memorial Sloan Kettering Cancer Centre and Briganti nomograms for the prediction of lymph node involvement of prostate cancer using clinical stage assessed by magnetic resonance imaging.

To evaluate the impact of using clinical stage assessed by multiparametric magnetic resonance imaging (mpMRI) on the performance of two established nomograms for the prediction of pelvic lymph node involvement (LNI) in patients with prostate cancer. Patients undergoing robot-assisted extended pelvic lymph node dissection (ePLND) from 2015 to 2019 at three teaching hospitals were retrospectively evaluated. Risk of LNI was calculated four times for each patient, using clinical tumour stage (T-stage) assessed by digital rectal examination (DRE) and by mpMRI, in the Memorial Sloan Kettering Cancer Centre (MSKCC; 2018) and Briganti (2012) nomograms. Discrimination (area under the curve [AUC]), calibration, and the net benefit of these four strategies were assessed and compared. A total of 1062 patients were included, of whom 301 (28%) had histologically proven LNI. Using DRE T-stage resulted in AUCs of 0.71 (95% confidence interval [CI] 0.70-0.72) for the MSKCC and 0.73 (95% CI 0.72-0.74) for the Briganti nomogram. Using mpMRI T-stage, the AUCs were 0.72 (95% CI 0.71-0.73) for the MSKCC and 0.75 (95% CI 0.74-0.76) for the Briganti nomogram. mpMRI T-stage resulted in equivalent calibration compared with DRE T-stage. Combined use of mpMRI T-stage and the Briganti 2012 nomogram was shown to be superior in terms of AUC, calibration, and net benefit. Use of mpMRI T-stage led to increased sensitivity for the detection of LNI for all risk thresholds in both models, countered by a decreased specificity, compared with DRE T-stage. T-stage as assessed by mpMRI is an appropriate alternative for T-stage assessed by DRE to determine nomogram-based risk of LNI in patients with prostate cancer, and was associated with improved model performance of both the MSKCC 2018 and Briganti 2012 nomograms.

Joint estimation of SOC and SOH for lithium-ion batteries based on EKF multiple time scales

PurposeThe operation state of lithium-ion battery for vehicle is unknown and the remaining life is uncertain. In order to improve the performance of battery state prediction, in this paper, a joint estimation method of state of charge (SOC) and state of health (SOH) for lithium-ion batteries based on multi-scale theory is designed.Design/methodology/approachIn this paper, a joint estimation method of SOC and SOH for lithium-ion batteries based on multi-scale theory is designed. The venin equivalent circuit model and fast static calibration method are used to fit the relationship between open-circuit voltage and SOC, and the resistance and capacitance parameters in the model are identified based on exponential fitting method. A battery capacity model for SOH estimation is established. A multi-time scale EKF filtering algorithm is used to estimate the SOC and SOH of lithium-ion batteries.FindingsThe SOC and SOH changes in dynamic operation of lithium-ion batteries are accurately predicted so that batteries can be recycled more effectively in the whole vehicle process.Originality/valueA joint estimation method of SOC and SOH for lithium-ion batteries based on multi-scale theory is accurately predicted and can be recycled more effectively in the whole vehicle process.

Evaluation of patient tissue selection methods for deriving equivalent density calibration for femoral bone quantitative CT analyses.

Osteoporosis affects an increasing number of people every year and patient specific finite element analysis of the femur has been proposed to identify patients that could benefit from preventative treatment. The aim of this study was to demonstrate, verify, and validate an objective process for selecting tissues for use as the basis of phantomless calibration to enable patient specific finite element analysis derived hip fracture risk prediction. Retrospective reanalysis of patient computed tomography (CT) scans has the potential to yield insights into more accurate prediction of osteoporotic fracture. Bone mineral density (BMD) specific calibration scans are not typically captured during routine clinical practice. Tissue-based BMD calibration can therefore empower the retrospective study of patient CT scans captured during routine clinical practice. Together the method for selecting tissues as the basis for phantomless calibration coupled with the post-processing steps for deriving a calibration equation using the selected tissues provide an estimation of quantitative equivalent density results derived using calibration phantoms. Patient tissues from a retrospective cohort of 211 patients were evaluated. The best phantomless calibration resulted in a femoral strength (FS) [N] bias of 0.069±0.07% over FS derived from inline calibration and a BMD [kg/cm3] bias of 0.038±0.037% over BMD derived from inline calibration. The phantomless calibration slope for the best method presented was within the range of patient specific calibration curves available for comparison and demonstrated a small bias of 0.028±0.054 HU/(mg/cm3), assuming the Mindways Model 3 BMD inline calibration phantom as the gold standard. The presented method of estimating a calibration equation from tissues showed promise for CT-based femoral fracture analyses of retrospective cohorts without readily available calibration data.

Multiparameter Modeling of Piezoelectric Six-Degree-of-Freedom Accelerometer About Sensitivity Characteristics

In order to realize the active design of six-degree-of-freedom (6-DOF) accelerometer based on sensitivity characteristics, it is necessary to develop the multi-parameter modeling of accelerometer sensitivity characteristics. Based on (6-DOF) piezoelectric accelerometer sensitivity characteristics of parametric modeling, the multi-parameter model is deduced through the analysis of (6-DOF) piezoelectric accelerometer static structure and the measuring principle of sensitivity features. The ANSYS software is used for the numerical simulation of multiple sets of models, and the (6-DOF) accelerometer prototype is fabricated. Equivalent static calibration experiments are proposed, and the experimental results show that the multi-parameter model and numerical simulation of sensitivity characteristics have the same rule and the same trend as the test results of the accelerometer experimental prototype, which verifies the effectiveness of the proposed multi-parameter model and method. This study lays a theoretical foundation for further research on active design method of piezoelectric (6-DOF) accelerometer.

Study of equivalent efficiency calibration method for radioactive gas source measured on HPGe detectors

ABSTRACT In view of the complexity of current detection efficiency calibration of radioactive gas sources, a method using solid planar sources to be equivalent to gas sources was studied. For the 50 mL gas source box, an optimal equivalent scheme was selected by Monte Carlo Simulations. Then, the full-energy-peak efficiency curve of gas sources at the measurement position of 25 cm, with source-to-detector distance of 25 cm, was fitted by measuring solid planar sources with known activity. To verify the accuracy of the efficiency curve, 41Ar, 133Xe and 87Kr gases were produced and determined by length-compensated method. Then, their full-energy-peak efficiencies at 25 cm position away from the detector were directly calibrated. The percentage efficiency deviations between interpolation from the efficiency curve and direct calibration are all less than 2.5%, which proves the accuracy of the equivalent method. This calibration method is a general one and can be also used for some other radioactive sample measurements, such as non-destructive analysis of gaseous fission product samples with a suitable source-to-detector distance.

Calibration method of Risley-prism imaging System

In this paper, a Risley-prism imaging system is proposed, which incorporates a camera and two coaxial Risley prisms to capture various scenes, namely images captured by equivalent cameras. An equivalent camera calibration method is established to obtain the extrinsic parameters of the equivalent cameras from rectified images captured by the system. To improve calibration accuracy, a geometric method is applied to rectify the degraded images over the whole scanning area. Such opto-electronmechanical configuration makes possible an agile and compact imaging system suitable for boresight adjustment. Experiments that apply imaging system located in different positions are conducted to validate the proposed method, and results are compared to verify its efficiency and accuracy.

A Comparative Study of On-Wafer and Waveguide Module S-Parameter Measurements at D-Band Frequencies

In this paper, we present a comparative study of S-parameter measurements of electronic components on planar substrates performed with a waveguide module and in a conventional on-wafer probing environment. Measurements were conducted at three well-established measurement laboratories for the investigation of reproducibility at frequencies from 110 to 170 GHz. For the comparison, we fabricated waveguide modules for six passive structures, including devices under test (DUTs). Four of these structures are related to using a second tier calibration to achieve the same reference planes for the waveguide module measurements as used for the on-wafer probing measurements. Additionally, we processed three complete on-wafer calibration sets, including DUTs, equipped with different probe-to-pad interfaces. In this comparison, the DUT measurement from the waveguide module acts as a reference standard, with reduced crosstalk behavior in comparison to the on-wafer measurement. With the waveguide reference, we are able to assess the ability of two techniques to compensate for crosstalk and higher order modes influencing the on-wafer S-parameter measurements. On the one hand, we use a shielded probe-to-pad transition and on the other hand, we use an algorithm-based crosstalk correction scheme. To the best of our knowledge, this is the first time that such a comparison has been undertaken, comparing well-established waveguide calibrations with an equivalent on-wafer calibration.

Framework for Photon Counting Quantitative Material Decomposition.

In this paper, the accuracy of material decomposition (MD) using an energy discriminating photon counting detector was studied. An MD framework was established and validated using calcium hydroxyapatite (CaHA) inserts of known densities (50 mg/cm3, 100 mg/cm3, 250 mg/cm3, 400 mg/cm3), and diameters (1.2, 3.0, and 5.0 mm). These inserts were placed in a cardiac rod phantom that mimics a tissue equivalent heart and measured using an experimental photon counting detector cone beam computed tomography (PCD-CBCT) setup. The quantitative coronary calcium scores (density, mass, and volume) obtained from the MD framework were compared with the nominal values. In addition, three different calibration techniques, signal-to-equivalent thickness calibration (STC), polynomial correction (PC), and projected equivalent thickness calibration (PETC) were compared to investigate the effect of the calibration method on the quantitative values. The obtained MD estimates agreed well with the nominal values for density (mass) with mean absolute percent errors (MAPEs) 8 ± 11% (9 ± 15%) and 4 ± 6% (9 ± 14%) for STC and PETC calibration methods, respectively. PC displayed large MAPEs for density (27 ± 9%), and mass (25 ± 12%). Volume estimation resulted in large deviations between true and measured values with notable MAPEs for STC (40 ± 90%), PC (40 ± 80%), and PETC (40 ± 90%). The framework demonstrated the feasibility of quantitative CaHA mass and density scoring using PCD-CBCT.

Noise equivalent radiance calibration system for infrared Fourier spectrometer at low-temperature and vacuum environment

The equivalent noise radiance (NESR) of infrared Fourier spectrometer is not only a reflection of its ultimate detection ability to infrared target signal, but also a core technical index of instrument. Limited by the current technical conditions in China, there is no relevant capability of calibration system testing and specification verification yet. Based on the standard transmission method of infrared radiation metering devices at home and abroad, a scheme of NESR high-precision testing device was proposed. The traceability chain of this device was put forward, its overall structure and optical path were also described, while a suppression system with low-temperature and vacuum background was designed. This designing scheme of radiation source on infrared integrating sphere with wide dynamic range, equivalent optical path and vacuum cryogenic environment were introduced in detail. The proposed technical solution provides a basic reference for NESR high-precision measurement, which also supports the condition of NESR quantity traceability for Fourier spectrometer in China.