Calibration Method Research Articles

Improved calibration method based on phase-slope description in phase-shift deflectometry

Phase-shift deflectometry is a widely used high-precision gradient measurement method for assessing the topography of specular objects. The calibration of phase-shift deflectometry measurement systems involves establishing the phase-slope mapping relationship. This paper analyzes the causes of phase variations at different calibration points in existing phase-slope analysis models. Based on the fact that changes in height simultaneously produce phase variations in two perpendicular directions, a decoupling method is proposed to address the phase ambiguity problem to some extent. Through simulation, the variation in height phase and slope distribution were quantitatively analyzed for a unidirectional inclined plane to validate the proposed algorithm. Additionally, measurement experiments were performed on a unidirectional inclined plane with an inclination angle of −2.584° and a concave mirror with a curvature radius of 779.87 mm. Based on the findings, the decoupling method reduced the relative root-mean-square error of the gradient measurement for the inclined plane in the inclined direction by 2.206% and improved the error range of the curvature radius for the concave mirror from [0.55%, 4.1%] to [0.22%, 3.86%]. By comparing with the existed method, the decoupling method showed a certain advantage in practicality.

Spin echo small-angle neutron scattering using superconducting magnetic Wollaston prisms.

We show the implementation of superconducting magnetic Wollaston prisms for spin echo small-angle neutron scattering. Two calibration methods for the spin echo length are presented: one utilizing spin echo modulated small-angle neutron scattering and the other based on the neutron refraction by quartz wedge crystals. Our experimental results with polystyrene nano-particle colloids showcase the system's efficacy in measuring both dilute and concentrated colloidal systems. Additionally, investigations into the pore diameter and pitch of a nano-porous alumina membrane demonstrate its capability in analyzing nano-porous materials. Furthermore, we discuss potential optimizations to further extend the accessible spin echo length.

Calibration of CAMS PM2.5 data over Hungary: a machine learning approach

Air pollution is a major environmental problem, and reliable monitoring of particulate matter (PM) concentrations is critical for assessing its impact on human health and the environment. The Copernicus Atmosphere Monitoring Service (CAMS) offers vital data on PM2.5 concentrations by applying a worldwide modelling system. This study compares in situ PM2.5 measurements and raw CAMS data at 0.1° × 0.1° resolutions for 2019 and 2020 in Hungary. It proposes a calibration method to improve the accuracy of CAMS PM2.5 data at the scale of air monitoring stations. In the study, the accuracy of the raw CAMS PM2.5 data is assessed based on the chosen air quality stations. Then, to improve the precision, we employed machine learning algorithms (LightGBM, Random Forest (RF), and Multiple Linear Regression (MLR)) for calibration. Initial assessment of the raw CAMS PM2.5 data showed positive hourly Spearman correlation coefficient values (SR between 0.64 and 0.87 for the 14 air quality stations used), indicating a positive relationship between the datasets but a systemic underestimation. Our findings highlight LightGBM as the most effective method, consistently demonstrating elevated correlation SR and coefficient of determination R2 values reaching up to 0.95 and 0.93, respectively, and very good RSR (Root mean square error ratio) and NSE (Nash-Sutcliffe Efficiency) values (lower than 0.5 and higher than 0.75 for RSR and NSE, respectively). In contrast, RF yields mixed results, and MLR exhibits variable performance. By correcting underestimation and lowering modelling biases, the calibrated PM2.5 data better matches ground-based observations, which can be promising for using the obtained model for accurate estimation at individual air monitoring stations.

PRACTICAL RECOMMENDATION FOR CALIBRATION OF RADIATION SOURCES USED FOR CONTACT RADIOTHERAPY

Relevance: This paper presents two methods for calibrating ionizing radiation sources in brachytherapy. The first method involves measuring the radiation activity using a well chamber, while the second method involves measuring the air kerma using an ionization chamber. Additionally, the application and measurement method of radiochromic film is demonstrated. The relevance of the above calibration methods of the ionizing radiation source in brachytherapy is explained by the need to ensure high accuracy and reliability of treatment. All calibration methods provide a multilevel approach to quality control and safety of brachytherapy. Combining an ionization chamber, air kerma power measurement, and radiochromic film allows for high dosimetry accuracy, which is critical for successfully treating patients and minimizing side effects. The study aimed to analyze primary calibration methods and their applicability in medical institutions. Methods: The data from the radiation source provided by the manufacturer is compared with the measurements obtained using the method proposed in the article. Radiochromic film was exposed to radiation to assess the initial dose distribution in the phantom. This scientific research was carried out within the framework of the PCF scientific program “Metrological support of dosimetric measurements in contact radiation therapy,” IRN BR12967832. Results: It has been established that the measurement accuracy is approximately 1.2% at a 95% confidence interval. The activity of the radiation source and the field distribution around it were measured using methods recommended by the IAEA. Conclusion: In our case, the difference between the data measured by these two methods is 1.2%. Using the third method, which involves radiochromic film, it has been established that the radiation source distribution matches the treatment plan. The user has the right to choose any of the calibration methods mentioned above for the eye, taking into account the technical capabilities of their medical facility.

Experimentally calibrated viscoelastic phase-field fracture method of thermoplastic resins

In the past few years, there has been considerable emphasis on investigating fracture behavior in composite materials using the phase-field fracture (PFF) method. However, accurately characterizing the viscoelasticity of the matrix necessitates employing the viscoelastic PFF method, and there remains an ongoing debate regarding the precise determination of the viscous driving force introduced in this methodology. This study aims to propose a feasible calibration method for quantifying the viscous driving force. To achieve this goal, benchmark experiments utilizing Polyetheretherketone (PEEK), a typical thermoplastic resin, are carried out by designing uniaxial tension tests, three-point bending tests, as well as compression tests at various strain rates. Through employing the viscoelastic PFF method, we discuss the effect of strain rate and viscous driving force on mechanical response. Our findings reveal a non-linear relationship between the influence of viscous driving force and strain rate with an initial increase followed by a subsequent decrease. By combining simulation results with experimental data analysis, the viscous driving force value is determined. The results demonstrate that our proposed approach is reliable for quantifying the viscous driving force in the viscoelastic PFF method, laying a foundation for investigating the mechanical response of composite materials.

Calibration measurement and application of a dual-probe acoustic measurement method for seafloor sediments

The laboratory measurement of the acoustic attenuation coefficient of seafloor sediment poses a significant challenge as it is more difficult to measure with the same precision and convenience as the sound velocity. A novel dual-probe acoustic measurement method (DPAMM) addresses this challenge by simultaneously obtaining the sound velocity and acoustic attenuation coefficient of seafloor sediments, enabling stratified measurements with minimal disturbances. However, issues related to the sensitivity difference between the probes, the diameter of the sample pipe, and the inter-probe blockage can affect the accuracy of the measurement. To address these influencing factors, water was used as a reference standard for calibrating DPAMM. Experimental investigations were conducted to examine the effects of factors such as the diameter of the sample pipe, probe spacing, probe distance from the acoustic source, and probe sensitivity differences. The results revealed a positive correlation between the diameter of the sample pipe and the effective measurement distance, as well as the correction factor for probe blockage. Based on the calibration method described above, sensitivity calibration coefficients and blocking correction coefficients were derived from the experiments. The application of the stratified acoustic measurement of seafloor sediment samples demonstrates the effectiveness of the DPAMM.

Handheld In Situ Methods for Soil Organic Carbon Assessment

Soil organic carbon (SOC) assessment is crucial for evaluating soil health and supporting carbon sequestration efforts. Traditional methods like wet digestion and dry combustion are time-consuming and labor-intensive, necessitating the development of non-destructive, cost-efficient, and real-time in situ measurements. This review focuses on handheld in situ methodologies for SOC estimation, underscoring their practicality and reasonable accuracy. Spectroscopic techniques, like visible and near-infrared, mid-infrared, laser-induced breakdown spectroscopy, and inelastic neutron scattering each offer unique advantages. Preprocessing techniques, such as external parameter orthogonalization and standard normal variate, are employed to eliminate soil moisture content and particle size effects on SOC estimation. Calibration methods, like partial least squares regression and support vector machine, establish relationships between spectral reflectance, soil properties, and SOC. Among the 32 studies selected in this review, 14 exhibited a coefficient of determination (R2) of 0.80 or higher, indicating the potential for accurate SOC content estimation using in situ approaches. Each study meticulously adjusted factors such as spectral range, pretreatment method, and calibration model to improve the accuracy of SOC content, highlighting both the methodological diversity and a continuous pursuit of precision in direct field measurements. Continued research and validation are imperative to ensure accurate in situ SOC assessment across diverse environments. Thus, this review underscores the potential of handheld devices for in situ SOC estimation with good accuracy and leveraging factors that influence its precision. Crucial for optimizing carbon farming, these devices offer real-time soil measurements, empowering land managers to enhance carbon sequestration and promote sustainable land management across diverse agricultural landscapes.

Quantification of linear alkylbenzene sulphonates in complex sludge samples: Influence of matrix effects in calibration methods

Linear Alkylbenzene Sulfonates (LAS) are among the priority organic pollutants in sludge owing to their high concentrations, due to its use as a major cleaning agent (surfactant) in laundry detergents and household cleaning products, and to the concentration limits of 2,600 mg/kg outlined in the EU directive draft for land application of sludge. In this work, a method has been optimized and validated for the accurate quantification of LAS homologues C10-C13 in different types of samples in the sludge treatment and disposal process including primary, secondary, and digested sludge, compost, and soil. The type of matrix had a significant impact on the method’s validation process, resulting in the need of the use of distinct dilution factors for each matrix. Overall, the procedure propose involves a cost-effective and user-friendly technique that combines both extraction and clean-up in a single step (ultrasound-assisted extraction and dispersive solid phase extraction). Analytical determination is conducted using liquid chromatography-tandem mass spectrometry. The method demonstrated excellent accuracy (relative recoveries exceeding 84.5 % across all types of sludge samples) and the limit of quantification enables the measurement of LAS concentrations up to 1000 times lower than the concentration limits stipulated in the EU directive draft. For an accurate quantification, three calibration approaches were tested (external calibration, standard addition, and matrix-matched calibration). Standard addition was the preferred method for quantitative analysis. It helps mitigate matrix effects that could otherwise distort the accuracy of analyte measurements, making it crucial for quality control, especially in monitoring applications where matrix effects may introduce bias into concentration calculations.

Components of the development of methods for calibrating rollers for rolling channels based on changed non-uniformsty of deformation

Introduction. In metallurgy, the final stage of production is metal processing in rolling shops. The main component of the development of technologies for rolling graded profiles is the calibration of rolls. 90% of the steel that is smelted is processed by rolling. Rolling mill calibration methods are constantly being improved. Calibration methods are used in which there is a significant uneven deformation of the profile elements, which leads to rapid wear of the rolls and an increase in costs. Formulation of the problem. It is necessary to develop a method of calibrating rolls in the production of channels based on the reduction of deformation unevenness. Goal. The purpose of the article is to analyze the methods of calibrating rolls for the production of channels with an indication of their advantages and disadvantages and to justify the application of the components of the developed method of calibrating rolls based on the reduction of unevenness of deformation. The results. The analysis of various methods of calibrating channel rolls showed that the smallest unevenness of deformation is present in the method of rolling by the bending method. The greatest uniformity of deformation along the width of the profile is achieved, the wear of the rolls is reduced in connection with ensuring a minimum difference in the diameters of the rolls in the gauge, and energy costs are reduced. To reduce the uneven deformation of the metal, it is suggested to use a rectangular blank or strip. Scientific novelty. For the first time, the methods of calibrating rolls for channel rolling were analyzed in detail. To reduce uneven deformation of shelves and flanges in the center of deformation in the gauge, it is proposed to use the bending calibration method. It is proposed to use strips as a blank for the first time. Practical meaning. The application of channel rolling technology based on the developed method of calibrating rolls with reduced unevenness of deformation in the first passes allows to reduce the cost of products and give an economic effect

Improving the accuracy of interferometer testing with absolute surface calibration and power spectral density analysis

A novel absolute surface calibration method for interferometer testing based on power spectral density analysis has been proposed. The method involves obtaining the loss of signal at different frequencies as a function of various rotation angles by signal analysis to choose the rotation angle for calibration. A model is developed to evaluate the calibration method by creating random surface shapes based on the Power Spectral Density. Using this algorithm, the precision of the absolute testing method during the testing process exceeds 0.28 %. Error propagation during the experimental process, such as testing optic clamping, angular errors, eccentricity, vibrations and airflow disturbances, were calibrated. Ultimately, the absolute detection test results were verified using high-precision flat mirrors. The experimental result indicates an RMS of 4.275 nm, 4.263 nm, and 4.265 nm in different rotation angle, and the calibrated result shows an RMS of 4.880 nm. The shape of surface errors in the absolute test results and calibration results is consistent.

Adaptive Weighted Data Fusion for Line Structured Light and Photometric Stereo Measurement System.

Line structured light (LSL) measurement systems can obtain high accuracy profiles, but the overall clarity relies greatly on the sampling interval of the scanning process. Photometric stereo (PS), on the other hand, is sensitive to tiny features but has poor geometrical accuracy. Cooperative measurement with these two methods is an effective way to ensure precision and clarity results. In this paper, an LSL-PS cooperative measurement system is brought out. The calibration methods used in the LSL and PS measurement system are given. Then, a data fusion algorithm with adaptive weights is proposed, where an error function that contains the 3D point cloud matching error and normal vector error is established. The weights, which are based on the angles of adjacent normal vectors, are also added to the error function. Afterward, the fusion results can be obtained by solving linear equations. From the experimental results, it can be seen that the proposed method has the advantages of both the LSL and PS methods. The 3D reconstruction results have the merits of high accuracy and high clarity.

Proton CT on biological phantoms for x-ray CT calibration in proton treatment planning

Objective. To present and characterize a novel method for x-ray computed tomography (xCT) calibration in proton treatment planning, based on proton CT (pCT) measurements on biological phantoms. Approach. A pCT apparatus was used to perform direct measurements of 3D stopping power relative to water (SPR) maps on stabilized, biological phantoms. Two single-energy xCT calibration curves—i.e. tissue substitutes and stoichiometric—were compared to pCT data. Moreover, a new calibration method based on these data was proposed, and verified against intra- and inter-species variability, dependence on stabilization, beam-hardening conditions, and analysis procedures. Main results. Biological phantoms were verified to be stable in time, with a dependence on temperature conditions, especially in the fat region: (−2.5 土 0.5) HU °C−1. The pCT measurements were compared with standard xCT calibrations, revealing an average SPR discrepancy within ±1.60% for both fat and muscle regions. In the bone region the xCT calibrations overestimated the pCT-measured SPR of the phantom, with a maximum discrepancy of about +3%. As a result, a new cross-calibration curve was directly extracted from the pCT data. Overall, the SPR uncertainty margin associated with this curve was below 3%; fluctuations in the uncertainty values were observed across the HU range. Cross-calibration curves obtained with phantoms made of different animal species and anatomical parts were reproducible with SPR discrepancies within 3%. Moreover, the stabilization procedure did not affect the resulting curve within a 2.2% SPR deviation. Finally, the cross-calibration curve was affected by the beam-hardening conditions on xCTs, especially in the bone region, while dependencies below 2% resulted from the image registration procedure. Significance. Our results showed that pCT measurements on biological phantoms may provide an accurate method for the verification of current xCT calibrations and may represent a tool for the implementation of a new calibration method for proton treatment planning.

A machine learning-based calibration method for strength simulation of self-piercing riveted joints

A machine learning-based calibration method for strength simulation of self-piercing riveted joints

Designing optimal sensor arrays: leveraging hard modeling for improved performance.

In a sensor array system with the ability to design multiple sensor elements, selecting the optimal sensor elements can maximize the efficiency of the sensor array in responding to various analytes. This paper proposes the application of hard chemical modeling as a means to identify the optimal subset of indicator displacement assay (IDA)-based sensors in the array, aiming to achieve maximum performance for detection or quantification. The model governing all reactions in the IDA sensor and the model of the pure spectrum of active species are first determined. Next, by applying the model of the pure spectrum of active species (including the indicator and indicator-receptor complex) to each sensor element and taking into account the system's nonlinearity, corrected concentration profiles of active species are derived using the generalized classical least square (G-CLS) method. These corrected concentration profiles are utilized as the output signal for each sensor element. Finally, the dynamic ranges (DR) of each sensor element and subsequently the DR for all possible sensor arrays are determined.To assess the effectiveness of the sensor array through dynamic range analysis, an IDA-based sensor system comprising five different elements was designed. It was observed that sensors with a larger dynamic range, when arranged together in an array, are more efficient for the quantitative identification of analytes. However, simply increasing the number of elements in the sensor array may not necessarily enhance its effectiveness; instead, it could amplify the noise within the system. Additionally, multivariate fitting regression with Gaussian function (MFRG), a nonlinear calibration method, was applied to assess the prediction ability of all possible designed sensor arrays.

Calibration and Inter-Unit Consistency Assessment of an Electrochemical Sensor System Using Machine Learning.

This paper addresses the challenges of calibrating low-cost electrochemical sensor systems for air quality monitoring. The proliferation of pollutants in the atmosphere necessitates efficient monitoring systems, and low-cost sensors offer a promising solution. However, issues such as drift, cross-sensitivity, and inter-unit consistency have raised concerns about their accuracy and reliability. The study explores the following three calibration methods for converting sensor signals to concentration measurements: utilizing manufacturer-provided equations, incorporating machine learning (ML) algorithms, and directly applying ML to voltage signals. Experiments were performed in three urban sites in Greece. High-end instrumentation provided the reference concentrations for training and evaluation of the model. The results reveal that utilizing voltage signals instead of the manufacturer's calibration equations diminishes variability among identical sensors. Moreover, the latter approach enhances calibration efficiency for CO, NO, NO2, and O3 sensors while incorporating voltage signals from all sensors in the ML algorithm, taking advantage of cross-sensitivity to improve calibration performance. The Random Forest ML algorithm is a promising solution for calibrating similar devices for use in urban areas.

Hybrid calibration method for a single camera stereo digital image correlation system

In single camera stereo digital image correlation systems, the existing calibration methods have problems with poor accuracy and violation of theoretical constraints, so we have proposed a hybrid calibration method. In this study, we first explain the principles of the existing single camera stereo measurement calibration methods. Then, on the basis of the classical camera calibration method combined with the characteristics of planar mirror reflection imaging, a hybrid calibration method is proposed that not only satisfies the constraints of the same intrinsic parameters but also has higher accuracy. Next, we complete the mathematical model of the hybrid calibration method and explain the specific calibration process. Finally, the experimental results of point distance reconstruction and static displacement measurement show that, compared with the existing calibration methods, the hybrid calibration method has lower error and higher reconstruction accuracy.

An analysis of laser distance measuring by different laser rangefinders

Laser rangefinders have emerged as indispensable tools in various fields, enabling accurate distance measurements through the utilization of laser technology. This paper provides a comprehensive overview of laser rangefinders, including the principle of laser rangefinders, classification, practical applications, and calibration methods. Different types of laser rangefinders are discussed based on their operating principles, while the various fields in which laser rangefinders are widely used are highlighted. The importance of accurate calibration is also discussed in depth, and the various techniques used to calibrate laser rangefinders are explored. In addition, accuracy and measuring range of each kind of laser rangefinder will also be discussed. This paper aims to provide a comprehensive understanding of laser rangefinders, including their classification, practical applications, and calibration methods. It also highlights the importance of accurate distance measurements in various industries and the role of laser rangefinders in meeting these requirements.

THE SIMULTANEOUS SPECTRAL DETERMINATION OF CANDESARTAN CILEXETIL AND HYDROCHLOROTHIAZIDE IN TABLETS USING THE TRIVARIATE CLASSICAL LEAST SQUARES METHOD

Objective: Candesartan cilexetil (CDS) is a member of the sartan group of drugs and is widely used to lower blood pressure. Hydrochlorothiazide (HCT) is the most commonly used diuretic group of drugs and is prescribed together with candesartan cilexetil in cases where blood pressure cannot be reduced. Pharmaceutical preparations containing these two active compounds in combination are preferred today to provide a more effective pharmacological effect. Therefore, it is of great importance to determine the quantities of these combined pharmaceutical preparations with new analytical methods that are fast, easy, and sensitive in quality control and routine analysis. In this study, a new trivariate classical least squares calibration method (TCLS) was developed for the simultaneous quantification of candesartan cilexetil (CDS) and hydrochlorothiazide (HCT) in binary mixtures and commercial tablets without using a preliminary separation step. Material and Method: CDS and HCT compounds were kindly donated by National Pharm Ind., Turkey. HPLC-grade methanol (J.T. Baker, Netherlands) was used as a solvent for the spectrophotometric analysis. In the application of the TCLS method, the determination and quantification of CDS and HCT were carried out using UV spectrophotometric measurements with 1 cm quartz cells in the 200-310 nm spectral region (slit range 2 nm). The newly developed TCLS method was tested using a validation set consisting of eight synthetic mixture solutions within the working ranges of 4.0-20.0 μg/ml for CDS and HCT. Simultaneous quantification analyses of CDS and HCT were performed on ATACAND PLUS® Tablet supplied by Astra Zeneca İlaç Ltd Şti. Result and Discussion: The method is based on the application of TCLS to the absorbance measurements at three different wavelength points (223.5, 240.0, and 268.5 nm). The absorptivity values (µg-1mlcm-1) of pure CDS and pure HCT were 6.67x10-2, 2.76x10-2, 2.33x10-2, and 11.41x10-2, 0.46x10-2, 6.42x10-2 at the selected wavelengths, respectively. Recovery values and relative standard deviation values were calculated as 97.2% and 1.61% for CDS and 99.7% and 3.67% for HCT, respectively. This method was successfully applied to the spectrophotometric quantitative analysis of tablets containing CDS and HCT, and then, a good agreement was reported.

Accurate extrinsic calibration for the invisible-light 1D laser rangefinder and camera

Abstract A combined sensor, comprising a camera and a one-dimensional laser rangefinder (1D LRF), has wide application across engineering sectors, notably in aerospace. This combined sensor is pivotal for earth observation and deep space exploration. To achieve precise and stable external parameters for this combined sensor, an accurate external calibration method is proposed. Initially, a technique for localized registration of laser spots is introduced to ensure precise determination of their positions, addressing the challenge of laser invisibility in a 1D LRF. Subsequently, a data evaluation criterion known as the data synthesis criterion is presented, addressing the issue of limited constraints in traditional calibration methods. This criterion evaluates relative errors encompassing 1D LRF ranging values, camera external parameters, and laser spot positions. Finally, based on the proposed criteria, a robust extrinsic calibration method is introduced that automatically filters observation data with significant errors and utilizes the growth rate of camera spatial resolution as the termination condition. The efficacy of the proposed method is confirmed through simulation experiments and real-world data experiments.

Studying Different Mechanisms of Seismo-to-Acoustic Coupling Using Ground Motion Local to Seismoacoustic Sensors

ABSTRACT The correlation between seismic and acoustic signals can be used to quantify the influence of earthquake ground motion on the output signals of infrasound sensors and thus evaluate the performance of infrasound sensors under field conditions. However, there have been relatively few studies, and earthquakes considered in those studies are large magnitude events. There remains a need to quantify correlation mechanisms at high frequencies using small earthquakes. In this study, we utilize a collocated seismoacoustic station BJT and a six-element infrasound array DQS to study different coupling mechanisms for infrasound sensors. From 2019 to 2021, 11 and 37 small magnitude earthquakes were detected by BJT and DQS, respectively. Seismoacoustic signals from these small magnitude earthquakes are used to compute the seismoacoustic spectral ratio and the observed spectral ratios are then compared with theoretical estimates. For local seismic-to-acoustic coupling (local infrasound), the highly local pressure field induced by high-frequency ground motion and the separation between seismoacoustic sensors reduce seismic and acoustic signal correlation, which prevents the use of small earthquakes in current studies. The seismic sensitivity of the infrasound sensor, MB3a is shown to be 30f0.75 for ground acceleration or 60πf1.75 for ground velocity and may be an important source of high-frequency noise for an infrasound station using this sensor. Furthermore, an empirical relation is developed to constrain the characteristics of earthquakes that can generate coupled signals on the infrasound sensor. Our study complements previous work and provides insight into the improved interpretation of infrasound signals and methods of seismoacoustic station calibration.