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Dynamic shockless compression experiments provide the ability to explore material behavior at extreme pressures but relatively low temperatures. Typically, the data from these types of experiments are interpreted through an analytic method called Lagrangian analysis. In this work, alternative analysis methods are explored using modern statistical methods. Specifically, Bayesian model calibration is applied to a new set of platinum data shocklessly compressed to 570 GPa. Several platinum equation-of-state models are evaluated, including traditional parametric forms as well as a novel non-parametric model concept. The results are compared to those in Paper I obtained by inverse Lagrangian analysis. The comparisons suggest that Bayesian calibration is not only a viable framework for precise quantification of the compression path, but also reveals insights pertaining to trade-offs surrounding model form selection, sensitivities of the relevant experimental uncertainties, and assumptions and limitations within Lagrangian analysis. The non-parametric model method, in particular, is found to give precise unbiased results and is expected to be useful over a wide range of applications. The calibration results in estimates of the platinum principal isentrope over the full range of experimental pressures to a standard error of 1.6%, which extends the results from Paper I while maintaining the high precision required for the platinum pressure standard. [ABSTRACT FROM AUTHOR]

The scarcity of cryogenic thermometers often stems from their high cost and lengthy lead times for calibration. Establishing an in-lab temperature calibration system is necessary to quickly make use of uncalibrated sensors or self-made sensors. This paper introduces a straightforward and high-accuracy thermometer calibration system. By employing copper screws as thermal links between the sensor platform and the cryogen-free refrigerator, temperature oscillation on the sensor platform is suppressed to a few millikelvins. In addition, this paper presents a data processing model based on clustering algorithms. These algorithms sort and group data based on distance, which is similar to human visual judgment of data. This paper discusses the parameter optimization process of the clustering algorithm to interpret the automated data process. The cryogenic temperature sensors calibrated by this system exhibited high accuracy, with relative errors of less than 1% compared to standard thermometers. Moreover, automatically processing calibration data from two uncalibrated thermometers takes just over 10 min, highlighting the effectiveness of this calibration system. [ABSTRACT FROM AUTHOR]

A data-driven approach to model calibration is developed to accurately obtain the input parameters for nonlinear dynamical systems. The paper focuses on the convergence properties of the proposed method, which play a significant role in understanding the validity and usefulness of any data-driven model. The input parameters of nonlinear dynamical systems are optimized to a reference solution, which can be experimental data or results from a high-fidelity computer simulation, using the Wasserstein metric and a phase-space representation of a set of time-dependent signals. Test cases shown in this paper include the Lorenz system and the discharge plasma of a Hall effect thruster to characterize the numerical uncertainties of the proposed data-driven approach, given a constructed reference solution. Distinct wells in the cost function, the Wasserstein metric, are obtained relative to the reference solution, illustrating the applicability of the proposed method to dynamical problems. The numerical uncertainties associated with the phase-space portrait and sampling time are discussed. [ABSTRACT FROM AUTHOR]

Optical second harmonic generation (SHG) can be employed to characterize the passivation quality of semiconducting material interfaces. The interface electric field (EDC) related to the existing charges at and near the interface, including the fixed oxide charges Qox, gives rise to the electric field induced second harmonic phenomenon. In this paper, we calibrate the SHG response for EDC measurement, using Al2O3/SiO2/Si(100) samples with different Qox. To perform this calibration, SHG and capacitance-voltage measurements (to access the electrical field of the samples) were made. The experimental results match well the simulated calibration curve, proving the potential of the SHG as stand-alone characterization technique for dielectric stacks on Si. [ABSTRACT FROM AUTHOR]

The Ma_MISS miniaturized spectrometer is integrated within the Drilling System of the ExoMars Rosalind Franklin Rover for Mars exploration. Here we focus on the on ground calibration campaign to obtain radiometric and linearity calibrations of the Ma_MISS instrument, while the first paper dealt with the spectral calibration [De Angelis et al., Rev. Sci. Instrum. 93, 123704 (2022)]. The experimental setup used to carry out radiometric calibration is described, as are the methods used for data processing and key parameter retrieval. In particular, the Spectrometer Transfer Function (Responsivity), Signal-to-Noise Ratio, and detector linearity are determined. In a third paper [De Sanctis et al., Planet. Sci. J. 3, 142 (2022)], validation of the Ma_MISS calibration results through spectral measurements performed on rock and synthetic targets during the radiometric calibration campaign is described. [ABSTRACT FROM AUTHOR]

Industrial robots are important components in the production and manufacturing industry. As a core component of the industrial robot, the industrial robot reducer plays a crucial role in the performance of the entire industrial robot. The error analysis and accuracy traceability of the industrial robot reducer testing instrument are of great significance in improving the quality of the precision reducer. Therefore, it is essential to calibrate the dynamic torsional moment measurement error of the instrument. The features of the dynamic torsional moment measurement error are analyzed in this paper. Based on these features, a new dynamic torsional moment measurement error calibration method is proposed based on the Bisquare curve fitting–improved Bayes particle swarm optimization–nonlinear echo state network (BCF–IBPSO–NESN) algorithm. The proposed method focuses on calibrating the dynamic torsional moment measurement error of the industrial robot reducers in real time. The experimental results show that the dynamic torsional moment measurement error of the input side torsional moment measurement module and the output side torsional moment measurement module can be reduced to ±0.05 Nm and ±1 Nm, respectively. The contribution of this paper is that the method calibrates the dynamic torsional moment measurement error. It supplies a guideline for calibrating the dynamic torsional moment measurement error of the instrument under any load. [ABSTRACT FROM AUTHOR]

The traditional multi-line laser calibration method relies primarily on calibrating the spatial plane equations of multiple laser lines and reconstructing the multi-line laser in three dimensions through the plane equation and camera parameters. In traditional methods, the multi-line laser is projected as a straight line by default, but in reality, the laser line projected by the multi-line laser is not a plane due to the Diffractive Optical Element (DOE). Instead, it is a surface with a certain curvature in space. During the production process, the multi-line laser experiences significant distortion because of the DOE projecting at a large angle. Consequently, if traditional methods are used, accurate calibration of the multi-line laser cannot be achieved. To address this issue, this paper introduces a new calibration algorithm for multi-line laser based on a spatial quadric equation. By calibrating the spatial quadric equation of the multi-line laser, the spatial characteristics of the laser can be accurately captured. The algorithm involves projecting a crossed 7-line laser onto a calibration plate and changing the position of the calibration plate while capturing images. This allows for obtaining the spatial three-dimensional coordinates of each laser line in the camera coordinate system. Next, spatial quadric equations are fitted for each laser line based on the three-dimensional coordinates. Finally, 3D reconstruction is performed using the quadratic surface parameters of the multi-line laser and camera parameters. The results from 3D reconstruction demonstrate that, compared to traditional laser calibration methods based on planes, the proposed algorithm achieves higher calibration accuracy. It also improves the number of successful binocular multi-line laser matches and overall accuracy. [ABSTRACT FROM AUTHOR]

The measurement of the reducer stiffness plays a vital role in evaluating the robot's performance. Since the angle measurement error caused by the instrument's torsional deformation is included in the angular sensor's measurement results, it cannot be used as the actual torsional deformation of the reducer. This paper analyzes the instrument's torsional deformation characteristics. Based on the features, a new method of calibration and compensation of the angle measurement error based on the improved B-spline curve fitting-gradient descent and particle swarm optimization-radial basis function neural network (IBSCF-GDPSO-RBF) method is proposed to eliminate the influence of the instrument torsional deformation. The steps of the IBSCF-GDPSO-RBF method are introduced, and the error compensation of angular measurement is carried out under load conditions. The experimental results show that the angle measurement error caused by the instrument deformation after compensation is within ± two angular seconds. The contribution of this paper is that the method calibrates and compensates for the angle measurement error based on the IBSCF-GDPSO-RBF method, which is not limited to measuring the RV reducer torsional deformation. It provides a reference for measuring and evaluating the actual RV reducer torsional rigidity under any load. [ABSTRACT FROM AUTHOR]

This paper describes the calibration of the Arrhenius Wescott–Stewart–Davis (AWSD) reactive flow model for the recently developed high explosive PBX 9701, which consists of 97% 3, 3 ′ -diamino-4, 4 ′ -azoxyfurazan (DAAF) and 3% FK-800 binder by weight. DAAF-based explosive formulations have several desirable qualities as they are relatively insensitive to non-shock insults but have higher performance than triaminotrinitrobenzene based formulations. Equations of state for the explosive reactants and products are calibrated using a combination of existing and new experimental data and theoretical calculations. The AWSD rate law calibration utilizes both one-dimensional shock-to-detonation and multidimensional rate stick experiments to capture the shock initiation and propagating detonation regimes. Validation of the calibrated model is demonstrated through comparison with recent gas-gun experiments. [ABSTRACT FROM AUTHOR]

The Ma_MISS spectrometer is integrated within the drilling system of the Rosalind Franklin ExoMars rover. This paper reports the on-ground calibration campaign performed on the spectrometer. Here, we focus on the spectral calibration of the instrument. The experimental setup used to carry out calibration is described, and the methods used for data processing and key parameters retrieval are explained. In particular, the spectral parameters such as (i) pixel central wavelengths, (ii) spectral response function, (iii) spectral resolution, (iv) sampling, and (v) range are determined. In a follow-up paper, the linearity and radiometric calibrations are described, while in De Sanctis et al. [Planet. Sci. J. 3, 142 (2022)], the validation of spectral measurements performed on synthetic and natural rock targets is presented. [ABSTRACT FROM AUTHOR]

Aiming at the distributed measurement system multi-equipment coordinated measurement, the data measured by each transmitting station are unified under a common coordinate system, which has the problems of complicated operation and high time and cost. In this paper, a fast calibration method for distributed measurement systems based on standard devices is proposed. The method designs a new type of architectural calibration board with non-coplanar measurement nodes, calculates the coordinates of the measurement nodes using geometric relations, solves the initial values of the system parameters, and substitutes the initial values into the L-M least squares algorithm for iterative optimization so that it only needs to carry out one scanning measurement for each reference position in the calibration process to complete the calibration. We designed an experiment in which a distributed measurement system consisting of four transmitting stations measured three standard rods (1650.073, 1156.704, and 875.950 mm) sequentially after calibration in a measuring space of 5 × 5 × 3 m3. The experimental results show that under the premise of ensuring that the measurement accuracy is better than 0.20 mm, the calibration of the parameters of the distributed measurement system can be completed within 20 min. [ABSTRACT FROM AUTHOR]

Aligning pedestal models and associated magnetohydrodynamic codes with experimental data is an important challenge in order to be able to generate predictions for future devices, e.g., ITER. Previous efforts to perform calibration of unknown model parameters have largely been a manual process. In this paper, we construct a framework for the automatic calibration of JOREK. More formally, we reformulate the calibration problem into a black-box optimization task, by defining a measure of the discrepancy between an experiment and a reference quantity. As this discrepancy relies on JOREK simulations, the objective becomes computationally intensive and, hence, we resort to batch Bayesian optimization methodology to allow for efficient, gradient-free optimization. We apply this methodology to two different test cases with different discrepancies and show that the calibration is achievable. [ABSTRACT FROM AUTHOR]

We present results for the estimation of the effective surface conductivity of the walls of a multimode microwave cavity applicator, based on measurements of reflected power from the cavity. During microwave thermal processing, this conductivity is a critical issue because the walls of the microwave applicator can become contaminated with evaporated material or process by-products, resulting in significantly reduced surface reflectivity from that of the bare metal. Thus, the cavity walls may absorb an increased amount of microwave energy, compared to that expected based on reflectivity data for clean metallic walls. A method based on the expansion of the total microwave fields in eigenmodes of a cylindrical waveguide is used to find the power reflection coefficient from an overmoded cylindrical applicator cavity as a function of the wall conductivity. The results of this analysis are compared with power reflection measurements from an experimental multimode applicator cavity, in order to determine a realistic value for the cavity wall loss. Because of the sensitivity of the calculated reflection spectrum to small changes in cavity geometry, a detailed comparison of the calculated reflectivity with that measured is not practical. It is found instead that a comparison of the average reflectivity over a broad frequency interval containing many cavity resonances, combined with a calculation of microwave reflectivity as a function of surface reflectivity, is the best means of determining the effective conductivity (effective surface reflectivity) of the walls of a multimode cavity applicator. The realistic surface conductivities and cavity wall loss determined by this means can be used for modeling and optimization of microwave material processing. A comparison is also shown of the calculated contours of microwave power density in the cavity with experimental measurements using thermal paper, showing reasonable agreement. This is done for various transverse and circumferential sections in the cavity and demonstrates the potential and limitations of this technique for characterizing power distributions in microwave systems. The nonlinear response of the thermal paper complicates interpretation, but image analysis techniques could extract substantial amounts of more detailed information from the thermal paper results with suitable calibration techniques. [ABSTRACT FROM AUTHOR]

Optical and visual measurement technology is used widely in fields that involve geometric measurements, and among such technology are laser and vision-based displacement measuring modules (LVDMMs). The displacement transformation coefficient (DTC) of an LVDMM changes with the coordinates in the camera image coordinate system during the displacement measuring process, and these changes affect the displacement measurement accuracy of LVDMMs in the full field of view (FFOV). To give LVDMMs higher accuracy in the FFOV and make them adaptable to widely varying measurement demands, a new calibration method is proposed to improve the displacement measurement accuracy of LVDMMs in the FFOV. First, an image coordinate system, a pixel measurement coordinate system, and a displacement measurement coordinate system are established on the laser receiving screen of the LVDMM. In addition, marker spots in the FFOV are selected, and the DTCs at the marker spots are obtained from calibration experiments. Also, a fitting method based on locally weighted scatterplot smoothing (LOWESS) is selected, and with this fitting method the distribution functions of the DTCs in the FFOV are obtained based on the DTCs at the marker spots. Finally, the calibrated distribution functions of the DTCs are applied to the LVDMM, and experiments conducted to verify the displacement measurement accuracies are reported. The results show that the FFOV measurement accuracies for horizontal and vertical displacements are better than ±15 µm and ±19 µm, respectively, and that for oblique displacement is better than ±24 µm. Compared with the traditional calibration method, the displacement measurement error in the FFOV is now 90% smaller. This research on an improved calibration method has certain significance for improving the measurement accuracy of LVDMMs in the FFOV, and it provides a new method and idea for other vision-based fields in which camera parameters must be calibrated. HIGHLIGHTS: • This paper proposes an improved DTC calibration method for LVDMMs that improves significantly the displacement measurement accuracy in the FFOV. Compared with the traditional calibration method, the improved one decreases the measurement error by more than 90%, and this is related to the measured displacement: the greater the displacement, the more obvious the effect. • The LOWESS method based on a statistical approach is used to fit the dx and dy surfaces in the FFOV, and this avoids the fitting error caused by a specified fitting method for data models with unknown distributions and incomplete data. • The coordinate systems are established and feature points are selected in the FFOV. The DTCs at the feature points are obtained by experiments based on the displacement measurement principle, and the obtained DTCs are used as the sample sets for fitting the distribution surfaces. This offers a new idea and method for calibrating camera parameters in other fields. [ABSTRACT FROM AUTHOR]

The angle misalignment error of a USBL (Ultrashort Baseline) acoustic array is one of the major error sources of the strapdown inertial navigation system/USBL positioning system, which will directly affect the positioning accuracy of the USBL positioning system. For the traditional calibration method cannot accurately estimate the angle misalignment error due to its strict trajectory requirements in the field experiment and the high-precision layout of the transceiver array elements, a new method for estimating the angle misalignment error of a USBL acoustic array based on single transponder and dual-vector reconstruction is studied in this paper. The precondition of USBL misalignment calibration is to locate the underwater transponder accurately. In this paper, the single transponder segmentation iterative long baseline method is used to locate the underwater target transponder. The dual-vector reconstruction method is studied to control the estimation accuracy of USBL misalignment error calibration based on the traditional single transponder method, which provides a theoretical basis for the determination of the iteration times to the USBL angle misalignment error estimation module. The underwater experiment results show that the positioning error could be reduced to less than 1 m after the angle misalignment error compensation. The underwater transponder positioning and the angle misalignment error estimation of USBL could be accomplished in a circle sailing. It is a new method with good performance of high estimation accuracy, simple operation, and easy realization. [ABSTRACT FROM AUTHOR]

A calibration technique with potential for low frequencies and sizeable systems of underwater transducers is being developed at the Swedish Defence Research Agency. The technique is based on the three-transducer spherical wave reciprocity method for use in an ice-covered lake with a depth of 220 m in the Swedish arctic zone. The calibration is performed at a depth of approximately 100 m with inter-transducer separations of 50 m, 86.6 m, and 100 m, allowing for frequencies down to 59 Hz using time-gated tone burst signals. In this paper, the calibration location, system, and technique are introduced, and the calibration results of an acoustical recorder in the range of 59 Hz–1 kHz are presented. The sensitivity is varying with frequency around −148 dB re 1 V/μPa, and the uncertainty budget is discussed. [ABSTRACT FROM AUTHOR]

This paper presents a joint calibration scheme for voltage (V) and current (I) probes that helps accurately resolve the voltage–current phase differences even when the difference is very close to 90°. The latter has been a major issue with V–I probes when used with miniature RF plasma devices such as the atmospheric pressure plasma jet (APPJ). Since the impedance of such miniature devices is predominantly capacitive, the phase difference between the voltage and current signals is very nearly 90°. It turns out, however, that when V–I probes are used with such devices without joint calibration, these frequently yield phase shifts over 90°. Also, since the power absorption is proportional to the resistive part of the impedance, it becomes very sensitive to the phase difference when it is close to ≈ 90 °. Thus, it is important to be able to accurately resolve the phases. Post-calibration, V–I probes would be indispensable for the electrical characterization of APPJs for determining the average RF power Pav, plasma impedance Zp, etc. Typical post-calibration V–I data yield Zp ≈ 93.6 − j 1139 Ω (81.5 − j 1173 Ω) at Pav ≈ 9.8 W ( ≈ 7.7 W) for helium (argon) gas. [ABSTRACT FROM AUTHOR]

Measurements of wideband acoustic immittance (WAI) rely on the calibration of an ear probe to obtain its acoustic source parameters. The clinical use of WAI and instruments offering the functionality are steadily growing, however, no international standard exists to ensure a certain reliability of the hardware and methods underlying such measurements. This paper describes a reciprocity method that can evaluate the accuracy of and identify errors in ear-probe source calibrations. By placing the ear probes of two calibrated WAI instruments face-to-face at opposite ends of a short waveguide, the source parameters of each ear probe can be measured using the opposite calibrated ear probe. The calibrated and measured source parameters of each ear probe can then be compared directly, and the influence of possible calibration errors on WAI measurements may be approximated. In various exemplary ear-probe calibrations presented here, the reciprocity method accurately identifies errors that would otherwise remain undetected and result in measurement errors in real ears. The method is likely unsuitable for routine calibration of WAI instruments but may be considered for conformance testing as part of a potential future WAI standard. [ABSTRACT FROM AUTHOR]

The magnetic diagnostics across TAE Technologies' compact toroid fusion device include 28 internal and 45 external flux loops that measure poloidal flux and axial field strength, 64 three-axis (radial, toroidal, and axial) Mirnov probes, and 22 internal and external, axial-only Mirnov probes. Imperfect construction, installation, and physical constraints required a Bayesian approach for the calibration process to best account for errors in signals. These errors included flux loops not fitted to a perfect circle due to spatial constraints, Mirnov probes not perfectly aligned against their respective axes, and flux pickup that occurred within the insert (feedthrough) of the Mirnov probes. Our model-based calibration is derived from magnetostatic theory and the circuitry of the sensors. These models predicted outputs that were compared against experimental data. Using a simple least-squares optimization, we were able to predict flux loop data within 1% of relative error. For the Mirnov probes, we utilized Bayesian inference to determine three rotation angles and three amplifier gains. The results of this work not only gave our diagnostic measurements physical meaning, but also act as a safeguard to spot when instruments have malfunctioned, or when there is an error in database maintenance. This paper will go into the details of our calibration procedure, our Bayesian modeling, and the accuracy of our results compared to experimental data. [ABSTRACT FROM AUTHOR]

In this paper, a micro-load cell utilized for the thrust measurement of a micro-resistojet is described. To improve the degree of completion of the micro-resistojet during the development process, a concept of a micro-load cell, which enables sufficient performance evaluation under space environmental conditions, was proposed through minimization and simplification of a thrust measurement stand. The piezoresistive sensing method was applied to this load cell, which was composed of a membrane, strain gauges, and a built-in Wheatstone bridge. The membrane size was designed using large-deflection theory so that the load cell could exhibit linear characteristics within the measurement range. A polysilicon strain gauge with a high gauge factor was used for the piezoresistor. The strain gauge also had very low sensitivity to temperature, allowing accurate measurement of the membrane deflection caused by thrust without requiring an additional compensation circuit. Four strain gauges were placed to form a full-bridge circuit at the edge of the membrane. The load cell was then realized by a microelectromechanical system fabrication process. The fabricated load cell was calibrated using a three-axis precision moving stage and a commercial load cell. As a result, the load cell output signal was linear in the measurement range of 1-7 mN and the measured sensitivity of the sensor was 1.566 31 × 10 -4 V/mN. The calculated nonlinearity was within 1% in the measurement range.

The increasing demand for wide-range aircraft techniques drives the development of variable Mach number test facilities. Existing tunnels can provide uniform flow at design case, but the imperfect wave-elimination at non-design cases leads to insufficient flow uniformity, limited variation range, and complex operation. By applying flowfield inverse design and elasticity inverse design, this paper designs a continuous wave-elimination variable Mach number nozzle. The nozzle is validated by the perfect nozzle theory. By a single jack, the nozzle can deform to the perfect nozzles with different Mach numbers, eliminating the Mach waves continuously and achieving the high-quality test flow. The numerical evaluation validates the design and supports the fabrication of continuous wave-elimination variable Mach number tunnel for the National University of Defense Technology. The flow visualizations by Schlieren and nanoparticle-tracer based planar laser scattering technique indicate no vortices or waves induced by imperfect nozzle geometry. The Mach number calibrations show that the maximum deviations are less than 0.6%, and the standard deviations meet the national advanced standards. These results show that the tunnel eliminates the Mach waves at different Mach numbers through simple operation, providing a wider variable Mach range and a higher flow quality. [ABSTRACT FROM AUTHOR]

MicrOmega, a miniaturized near-infrared hyperspectral microscope, has been selected to characterize in the laboratory the samples returned from Ryugu by the Hayabusa2 mission. MicrOmega has been delivered to the Extraterrestrial Samples Curation Center of the Japanese Aerospace eXploration Agency at the Institute of Space and Astronautical Science in July 2020 and then mounted and calibrated to be ready for the analyses of the samples returned to Earth on December 6, 2020. MicrOmega was designed to analyze the returned samples within a field of view of 5 × 5 mm2 and a spatial sampling of 22.5 µm. It acquires 3D near-infrared hyperspectral image-cubes by imaging the sample with monochromatic images sequentially covering the 0.99–3.65 µm spectral range, with a typical spectral sampling of 20 cm−1. This paper reports the calibration processes performed to extract scientific data from these MicrOmega image-cubes. The determination of the instrumental response and the spectral calibration is detailed. We meet or exceed the goals of achieving an accuracy of ∼20% for the absolute reflectance level, 1% for the relative wavelength-to-wavelength reflectance, and <5 nm for the peak position of the detected absorption features. For the nominal measurements of Ryugu samples with MicrOmega/Curation, the instrument performance also reaches a signal-to-noise ratio of >100 over the entire spectral range. By characterizing the entire collection of the returned samples at the microscopic scale, MicrOmega/Curation offers the potential to provide unprecedented insights into the composition and history of their asteroid parent body. [ABSTRACT FROM AUTHOR]

Image plates (IPs) are a popular detector in the field of laser driven ion acceleration, owing to their high dynamic range and reusability. An absolute calibration of these detectors to laser-driven protons in the routinely produced tens of MeV energy range is, therefore, essential. In this paper, the response of Fujifilm BAS-TR IPs to 1–40 MeV protons is calibrated by employing the detectors in high resolution Thomson parabola spectrometers in conjunction with a CR-39 nuclear track detector to determine absolute proton numbers. While CR-39 was placed in front of the image plate for lower energy protons, it was placed behind the image plate for energies above 10 MeV using suitable metal filters sandwiched between the image plate and CR-39 to select specific energies. The measured response agrees well with previously reported calibrations as well as standard models of IP response, providing, for the first time, an absolute calibration over a large range of proton energies of relevance to current experiments. [ABSTRACT FROM AUTHOR]

Measuring ear-canal absorbance and compensating for effects of the ear-canal acoustics on otoacoustic-emission measurements using an ear probe rely on accurately determining its acoustic source parameters. Using pressure measurements made in several rigid waveguides and models of their input impedances, a conventional calibration method estimates the ear-probe Thévenin-equivalent source parameters via a least-squares fit to an over-determined system of equations. Such a calibration procedure involves critical considerations on the geometry and number of utilized calibration waveguides. This paper studies the effects of calibration-waveguide geometry on achieving accurate ear-probe calibrations and measurements by systematically varying the lengths, length ratios, radii, and number of waveguides. For calibration-waveguide lengths in the range of 10–60 mm, accurate calibrations were generally obtained with absorbance measurement errors of approximately 0.02. Longer waveguides resulted in calibration errors, mainly due to coincident resonance frequencies among waveguides in the presence of mismatches between their assumed and actual geometries. The accuracy of calibrations was independent of the calibration-waveguide radius, except for an increased sensitivity of wider waveguides to noise. Finally, it is demonstrated how reformulating the over-determined system of equations to return the least-squares reflectance source parameters substantially reduces calibration and measurement errors. [ABSTRACT FROM AUTHOR]

The ultrashort baseline system is widely used in ships and underwater navigation and positioning. The misalignment and level arm with the inertial measurement unit are the two sources of positioning inaccuracy. The accuracy of calibration is usually affected by measurement noise and linearization of the observation equation. In order to improve the calibration accuracy, the variational Bayesian unscented Kalman filter (VBUKF) method is proposed for the calibration of the ultrashort baseline installation error in the paper. The detailed derivation of VBUKF for the calibration is presented in the paper. Simulation experiments and field experiments were carried out, respectively, to verify the algorithm. The simulation results show that the proposed method can calibrate the installation error of the sensors in real time on line. The field experiment verified that the algorithm improves the calibration accuracy of the installation error under the large misalignment. The positioning accuracy is also improved compared with the traditional method. [ABSTRACT FROM AUTHOR]

DC offsets in a quadrature mixing structure will affect the system performance. This paper proposes a Hilbert transform-based algorithm to blindly calibrate the DC offsets by filtering the inphase and quadrature signals with the same Hilbert filters. Compared with the traditional averaging-based method, this method consumes less time and resources. Moreover, the proposed method need not interrupt analog-to-digital converter's conversion, featuring the characteristics of high efficiency and good real-time performance. The Matlab simulation results verify the correctness of the proposed algorithm, and finally, an experimental platform is designed in detail to verify the practicability of this blind calibration algorithm. [ABSTRACT FROM AUTHOR]

This paper presents a high-stability and low-jitter Arbitrary Timing Generator (ATG) design based on the Xilinx Field Programmable Gate Array (FPGA) and its special integrated delay line. In recent years, FPGA-based or application specific integrated circuit-based delay lines have been used to achieve picosecond-level timing resolution. Devices with pure digital delay methods can only acquire triggers at the clock rising edges when triggered externally. Therefore, there is a large time irregularity caused by the uncertainty of the entry time of the trigger, which is difficult to compensate and leads to a large time jitter of outputs. We describe the design of an ATG that includes jitter self-measurement and calibration methods, which is available for both internal and external trigger modes. This structure is completely based on the FPGA's own resources and has the advantages of being simple and flexible. Experimental results show a sub-nanosecond timing resolution of 78 ± 20 ps with a minimum of 120 ps and a time jitter of 160 ± 20 ps in the external trigger mode after compensation. [ABSTRACT FROM AUTHOR]

This paper is about the development of a copper sulphate based aqueous-electrolytic voltage divider for the measurement of high voltage pulses, 100 kV, with pulse widths of 1-2 ns and rise time <1 ns. Novel features are incorporated in the design of the divider, to meet the performance requirements for the application. Analytical calculations to justify design are described. Structural simulation of the divider is carried out using field wave simulation software to verify the effectiveness. A calibration procedure has been developed to calibrate the divider. Results obtained during calibration are subjected to statistical analysis to determine the confidence of measurement. Details of design, analysis, and simulation are described in this paper. [ABSTRACT FROM AUTHOR]

In recent years, there has been rapid growth in demand for precision grade micro-electromechanical system microphones (MEMSMs). While new applications are increasingly demanding in terms of MEMSM performance, research and development of the technology is thus far keeping pace. To calibrate all these new MEMSMs, a reliable and cost-efficient method for bulk calibration of MEMSMs is urgently required. This paper describes a pilot version of such a method, carried out at the United Kingdom's National Physical Laboratory. The method was intended for use by MEMSM manufacturers themselves for bulk calibration. It may also be usable by manufacturers of devices that incorporate multiple MEMSMs for bulk calibration of these MEMSMs, provided that they are detachable from the devices' circuit-boards. The uncertainty of the method has been compared to that of the coupler comparison calibration which is a technique for acoustic pressure calibration of precision microphones. It is concluded that the pilot method is promising as the basis of a method for the bulk calibration of precision MEMSMs. [ABSTRACT FROM AUTHOR]

This paper presents an electromagnetic modeling of a grounded metallic truncated cone to be used for calibration purposes of a microwave imaging system. The basic idea is to demonstrate the equivalence between the cone and a cylinder having a suitable radius, in order to simplify the computation of its capacity with respect to ground. A mathematical expression for the capacitance of the uniform cylinder is presented, and its validity is confirmed by comparing the data provided by this formula with numerical values given by a commercial simulator. Starting from this analytic result, the model of the cone is presented, and a procedure for the choice of the cylinder radius is discussed in detail. This methodology can be applied to calculate the contribution to the stray capacitance of a metallic tip used for scanning probe microscopy, and specifically for microwave sensing applications. In particular, the capacitance due to the conic part of the probe can be quantified, an operation that is usually a difficult task when trying to separate it from contribution of the experimental setup. In our opinion, this issue is very important to improve the accuracy of system calibration in the scanning microwave microscopy technique. [ABSTRACT FROM AUTHOR]

X-ray framing cameras (XRFCs) are routinely used at the Laser MegaJoule facility in x-ray imaging plasma diagnostics around the target chamber. Most of these diagnostics are based on multilayer x-ray toroidal mirrors under grazing incidence. The absolute calibration of the XRFCs is expressly expected both to optimize the signal-to-noise ratio for the dynamic range for specific experiments and to quantitatively process the data. The purpose of this paper is to describe our technique to routinely calibrate these instruments in the sub-keV spectral range. The calibration presented in this work was carried out using the XRFC enclosed in a sealed "airbox" structure. This calibration relies on a Manson source recently upgraded to operate at high emission current (5 mA) with 10 kV accelerating voltage to work with a 1-m grazing-incidence Rowland circle monochromator. The framing camera sensitivity was absolutely determined over the 0.1–1.2 spectral range with an average uncertainty of 2.4% rms while operating in DC mode. Finally, we compare the results with a synchrotron source calibration previously obtained and a theoretical model. [ABSTRACT FROM AUTHOR]

A simple systematic calibration method based on acceleration and angular rate measurements is introduced for the fiber-optic gyro strapdown inertial navigation system in this paper. Meanwhile, a unified mathematical framework and an iterative calculation method are designed for the systematic calibration method. Using this method, one can estimate the fiber-optic gyro inertial measurement unit (FOG IMU) parameters both at a manufacturer's facility and in the field. In order to get all FOG IMU parameters, a procedure adopted based on this approach consists of two stages: First, FOG IMU raw data (accelerometer and gyro readouts) are accumulated in 19 specified FOG IMU positions. Second, the accumulated data are processed by special software to estimate all FOG IMU parameters. In addition, observability analysis of the method in 19 specified FOG IMU positions is done without the limitation of FOG IMU's initial orientation, and this analysis provides theoretical support for the application in a complex terrain. Moreover, the influence of gravity disturbance is analyzed for the first time. The analysis and experiment results show that the systematic calibration method provided by this work can meet the requirement of FOG IMU calibration. [ABSTRACT FROM AUTHOR]

Measuring stress levels in loaded structures is crucial to assess and monitor structure health and to predict the length of remaining structural life. Many ultrasonic methods are able to accurately predict in-plane stresses inside a controlled laboratory environment but struggle to be robust outside, in a real-world setting. That is because these methods rely either on knowing beforehand the material constants (which are difficult to acquire) or require significant calibration for each specimen. This paper presents an ultrasonic method to evaluate the in-plane stress in situ directly, without knowing any material constants. The method is simple in principle, as it only requires measuring the speed of two angled shear waves. It is based on a formula that is exact for incompressible solids, such as soft gels or tissues, and is approximately true for compressible "hard" solids, such as steel and other metals. The formula is validated by finite element simulations, showing that it displays excellent accuracy, with a small error on the order of 1%. [ABSTRACT FROM AUTHOR]

An important device for modulation and frequency translation in the field of circuit quantum electrodynamics is the in-phase and quadrature mixer, an analog component for which calibration is necessary to achieve optimal performance. In this paper, we introduce techniques originally developed for wireless communication applications to calibrate upconversion and downconversion mixers. A Kalman filter together with a controllable carrier frequency offset calibrates both mixers without removing them from the embedding measurement infrastructure. These techniques can be embedded into room temperature control electronics and hopefully find widespread use as circuit quantum electrodynamics devices continue to grow in complexity. [ABSTRACT FROM AUTHOR]

Charge sensitive amplifiers (CSAs) are electronic integrating circuits frequently used for detecting quick charge pulses such as those produced in semiconductor detector devices and electron multipliers. One of the limitations of highly sensitive CSA circuits is the accuracy with which they can be calibrated due to the necessity of using injection capacitors on the order of a few pF, which are difficult to calibrate and to disentangle from other stray capacitance in calibration circuits. This paper presents an alternate method for calibrating the electronics for CSAs with conductive detectors, referred to as the “external conductor” method, using the detector itself to form the injection circuit. The external conductor method is compared to the traditional injection capacitor method for an example detector. The new method results in an increase to the calibration factor of up to 70% over the value derived from a traditional injection capacitor, with an uncertainty in the new value of 2%. Finally, the results from the external conductor method are compared to a third, independent approach, which uses reference charged particles as calibration sources in the Colorado dust accelerator. The results of the charged particle approach corroborate the external conductor calibration to within the stated uncertainty. [ABSTRACT FROM AUTHOR]

Straightness error is a parasitic translation along a perpendicular direction to the primary displacement axis of a linear stage. The parasitic translations could be coupled into other primary displacement directions of a multi-axis platform. Hence, its measurement and compensation are critical in precision multi-axis metrology, calibration, and manufacturing. This paper presents a two-dimensional (2D) straightness measurement configuration based on 2D optical knife-edge sensing, which is simple, light-weight, compact, and easy to align. It applies a 2D optical knife-edge to manipulate the diffraction pattern sensed by a quadrant photodetector, whose output voltages could derive 2D straightness errors after a calibration process. This paper analyzes the physical model of the configuration and performs simulations and experiments to study the system sensitivity, measurement nonlinearity, and error sources. The results demonstrate that the proposed configuration has higher sensitivity and insensitive to beam’s vibration, compared with the conventional configurations without using the knife-edge, and could achieve ±0.25 μm within a ±40 μm measurement range along a 40 mm primary axial motion. [ABSTRACT FROM AUTHOR]

Before integration aboard European Space Agency BepiColombo mission to Mercury, the visible and near infrared hyperspectral imager underwent an intensive calibration campaign. We report in Paper I about the radiometric and linearity responses of the instrument including the optical setups used to perform them. Paper II [F. Altieri et al., Rev. Sci. Instrum. 88, 094503 (2017)] will describe complementary spectral response calibration. The responsivity is used to calculate the expected instrumental signal-to-noise ratio for typical observation scenarios of the BepiColombo mission around Mercury. A description is provided of the internal calibration unit that will be used to verify the relative response during the instrument’s lifetime. The instrumental spatial response functions as measured along and across the spectrometer’s slit direction were determined by means of spatial scans performed with illuminated test slits placed at the focus of a collimator. The dedicated optical setup used for these measurements is described together with the methods used to derive the instrumental spatial responses at different positions within the 3.5° field of view and at different wavelengths in the 0.4–2.0 μm spectral range. Finally, instrument imaging capabilities and Modulated Transfer Function are tested by using a standard mask as a target. [ABSTRACT FROM AUTHOR]

Corona cage approaches are crucial for research on the corona characteristics of conductors. Calibration is an indispensable task for determining excitation functions, which are used to predict corona performance of long transmission lines through extrapolation from measurements of short lines in corona cages. In this paper, the amplification factor G is calculated through a frequently adopted method, propagation analysis of high-frequency corona current along a short line. Another convenient calibration method, based on distributed parameter equivalent circuits, is established. The results for G obtained through propagation analysis and equivalent circuits are compared. To verify the rationality of calculation parameters in propagation analysis and equivalent circuits, a calibration experiment based on the excitation caused by a simulated monopulse current was performed. The results of the proposed calibration method and the calibration experiment are in good agreement. [ABSTRACT FROM AUTHOR]

Nanoindentation technology is developing toward the in situ test which requires miniaturization of indentation instruments. This paper presents a miniaturization nanoindentation device based on the modular idea. It mainly consists of macro-adjusting mechanism, x-y precise positioning platform, z axis precise driving unit, and the load-depth measuring unit. The device can be assembled with different forms and has minimum dimensions of 200 mm × 135 mm × 200 mm. The load resolution is about 0.1 mN and the displacement resolution is about 10 nm. A new calibration method named the reference-mapping method is proposed to calibrate the developed device. Output performance tests and indentation experiments indicate the feasibility of the developed device and calibration method. This paper gives an example that combining piezoelectric actuators with flexure hinge to realize nanoindentation tests. Integrating a smaller displacement sensor, a more compact nanoindentation device can be designed in the future. [ABSTRACT FROM AUTHOR]

Previous work has indicated that a limitation on the performance of a circular microphone array for holographic sound field recording at low frequencies is phase mismatch between the microphones in the array. At low frequencies these variations become more significant than at mid-range and high frequencies because the high order phase mode responses at low frequencies are lower in amplitude. This paper demonstrates the feasibility of a “self-calibration” method. The basis of the calibration is to estimate the location of one or more wide-band sources using mid-range frequencies and to use this source location information to perform correction to the array at low frequencies. In its simplest form the calibration must be performed in an anechoic environment, since multipath effects at widely differing frequencies are uncorrelated. The approach is first demonstrated in such an environment using recordings from an array of high quality microphones. The technique is then extended to an adaptive calibration that can be used in an environment that is somewhat reverberant. The validity of the adaptive approach is demonstrated using recordings from an array of inexpensive microphones. [ABSTRACT FROM AUTHOR]

This paper presents a dynamic calibration method for the dynamic sensitivity coefficient of a free-field pressure sensor working in liquid. In this method, an oil-filled auxiliary tool has been designed and the free-field pressure sensor sealed in the tool was loaded by a Hopkinson bar that could generate a stress wave with known amplitude. The strain signal of the Hopkinson bar and the output signal of the sensor were collected and processed based on the Hopkinson experimental principle and the dynamic sensitivity coefficient of the sensor was calibrated. A calibrated PCB W138A10 pressure sensor was re-calibrated and its dynamic sensitivity coefficient was obtained. Compared with the parameters from the calibration certificate of this sensor, this experimental result is reliable. This method can obtain the more accurate result and can be widely used in the dynamic calibration of free-field pressure sensors that work in liquid. [ABSTRACT FROM AUTHOR]

Commercial charge-coupled device (CCD) cameras are used widely in industrial applications. This paper uses a commercial CCD camera to develop a spectral band CCD-based pyrometer. To improve the calibration accuracy, a thermometry model based on the extended effective wavelength is introduced to describe the pyrometer. The Tikhonov regularization method is employed to acquire the stabilized solutions for the model parameters considering their sensitivities to the perturbations in the calibration data. Therefore, the relationships between the temperature measurement performances and the system parameters, namely, the electron gain and F-number, are analyzed in terms of the temperature measurement range and sensitivity. Meanwhile, the error and uniformity of the temperature measurements are also investigated using a blackbody furnace. The experimental results show that the temperature measurement range for the designed pyrometer is 800–1203 °C, in which the sensitivity is 0.4906–35.64 °C−1 and the average relative error and non-uniformity of the temperature measurements are 2.5‰ and 1.36%, respectively. [ABSTRACT FROM AUTHOR]

This paper describes a novel method to measure the temporal latency of electroencephalography (EEG) systems using a customized photosensitive phantom. The system was evaluated with three different EEG devices, a medical grade (g.Tec), a consumer grade (Emotiv), and a low-cost device (Arduino SpikerShield). The temporal latencies of the three EEG devices were measured. The proposed method can be easily adapted to assess other EEG devices. The measurements obtained in this experiment provided concrete data for future experiments where accurate timing data are critical. [ABSTRACT FROM AUTHOR]

A novel phase-type quantum-dot-array diffraction grating (QDADG) is reported. In contrast to an earlier amplitude-type QDADG [C. Wang et al., Rev. Sci. Instrum. 78, 053503 (2007)], the new phase-type QDADG would remove the zeroth order diffraction at some certain wavelength, as well as suppressing the higher-order diffractions. In this paper, the basic concept, the fabrication, the calibration techniques, and the calibration results are presented. Such a grating can be applied in the research fields of beam splitting, laser probe diagnostics, and so on. [ABSTRACT FROM AUTHOR]

Calibration-quality ab initio adiabatic potential energy surfaces (PES) have been determined for all isotopologues of the molecular ion H3+. The underlying Born-Oppenheimer electronic structure computations used optimized explicitly correlated shifted Gaussian functions. The surfaces include diagonal Born-Oppenheimer corrections computed from the accurate electronic wave functions. A fit to the 41 655 ab initio points is presented which gives a standard deviation better than 0.1 cm-1 when restricted to the points up to 6000 cm-1 above the first dissociation asymptote. Nuclear motion calculations utilizing this PES, called GLH3P, and an exact kinetic energy operator given in orthogonal internal coordinates are presented. The ro-vibrational transition frequencies for H3+, H2D+, and HD2+ are compared with high resolution measurements. The most sophisticated and complete procedure employed to compute ro-vibrational energy levels, which makes explicit allowance for the inclusion of non-adiabatic effects, reproduces all the known ro-vibrational levels of the H3+ isotopologues considered to better than 0.2 cm-1. This represents a significant (order-of-magnitude) improvement compared to previous studies of transitions in the visible. Careful treatment of linear geometries is important for high frequency transitions and leads to new assignments for some of the previously observed lines. Prospects for further investigations of non-adiabatic effects in the H3+ isotopologues are discussed. In short, the paper presents (a) an extremely accurate global potential energy surface of H3+ resulting from high accuracy ab initio computations and global fit, (b) very accurate nuclear motion calculations of all available experimental line data up to 16 000 cm-1, and (c) results suggest that we can predict accurately the lines of H3+ towards dissociation and thus facilitate their experimental observation. [ABSTRACT FROM AUTHOR]

Two methods for spatially resolved measurement of the bulk minority carrier lifetime on the side faces of block cast silicon bricks, both based on photoluminescence imaging, are presented. The first method uses a single photoluminescence image which is normalized for variations in the background doping density. The second method is based on the measurement of the ratio of two photoluminescence images taken with different spectral filters in front of the CCD camera. This second method is advantageous over the first method since it is not dependent on an absolute measurement of the luminescence intensity and does not require a separate resistivity measurement. It is further demonstrated, that the measurement of an intensity ratio image and comparison of the latter with an individual luminescence image also allow obtaining the doping density gradient within silicon bricks. This paper presents an in-depth analysis of the underlying models, demonstrates experimental results and discusses the calibration and uncertainties of the techniques. Practical limitations and dependencies on various experimental parameters are discussed. [ABSTRACT FROM AUTHOR]

Sonic infrared is potentially a very attractive nondestructive evaluation technique offering the possibility of rapid testing of complex components. However, at present it is difficult to be sure that sufficient excitation has been applied so that a null (no defect present) result can be trusted. This paper presents a calibration method to improve the reliability of the technique. The method uses a measurement of the vibration of the component during the test, the vibration signal being processed to give a “heating index” which is a measure of the ability of the vibration field to generate heat at any defects of interest that are present. The calculation of the heating index and the rationale for its formulation are described. The method is then applied on two sets of beamlike specimens with cracks of different sizes. The maximum temperature rise in successive tests on a given specimen is shown to correlate well with the maximum heating index, so validating the method. The threshold heating index required to reliably detect cracks as a function of crack size is discussed and practical calibration and test procedures are proposed. [ABSTRACT FROM AUTHOR]

Optical and electrical characteristics of power light-emitting diodes (LEDs) are strongly dependent on the diode junction temperature. However, direct junction temperature determination is not possible and alternative methods must be developed. Current-voltage characteristics of commercial high power LEDs have been measured at six different temperatures ranging between 295 and 400 K. Modeling these characteristics, including variation in the bandgap with temperature, revealed a linear temperature dependence of the forward voltage if the drive current is chosen within a rather limited current range. Theoretically, the voltage intercept can be deduced from the bulk semiconductor bandgap. However, accurate junction temperature determination is only possible if at least two calibration measurements at a particular drive current are performed. The method described in this paper can be applied to calculate the thermal resistance from the junction to any other reference point for any particular LED configuration. [ABSTRACT FROM AUTHOR]

A dual-axis micromechanical probe that combines a double cantilever and torsion beams is presented. This probe can reduce the mechanical cross-talk between the lateral and vertical force detections. In addition, dual-axis forces can be detected by measuring the dual-axis displacement of the probe end using the optical lever-based method used in conventional friction force microscopes (FFMs). In this paper, the mechanical design of the probe, the details of the fabrication method, FFM performance, and calibration of the friction force are discussed. The mechanical design and the microfabrication method for probes that can provide a force resolution of the order of 1 nN without mechanical cross-talk are presented. Calibration of the lateral force signal is possible by using the relationship between the lateral force and the piezodisplacement at the onset of the probe scanning. The micromechanical probe enables simultaneous and independent detection of atomic and friction forces. This leads to accurate investigation of nanotribological phenomena and visualization of the distribution of the friction properties, which helps the identification of the material properties. [ABSTRACT FROM AUTHOR]

In this paper, the small scaling parameter e0 of the nonlocal Timoshenko beam theory is calibrated for the free vibration problem of single-walled carbon nanotubes (SWCNTs). The calibration exercise is performed by using vibration frequencies generated from molecular dynamics simulations at room temperature. It was found that the calibrated values of e0 are rather different from published values of e0. Instead of a constant value, the calibrated e0 values vary with respect to length-to-diameter ratios, mode shapes, and boundary conditions of the SWCNTs. In addition, the physical meaning of the scaling parameter is explored. The results show that scaling parameter assists in converting the kinetic energy to the strain energy, thus enabling the kinetic energy to be equal to the strain energy. The calibrated e0 presented herein should be useful for researchers who are using the nonlocal beam theories for analysis of micro and nano beams/rods/tubes. [ABSTRACT FROM AUTHOR]