Reference Quantity Research Articles

Automatic JOREK calibration via batch Bayesian optimization

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.

Multi input multi output lateral dynamics control of an electric vehicle

Full electric vehicles with multiple and independently controlled powertrains allow for an improvement of vehicle handling capabilities both in steady state and in transient manoeuvres. This paper focuses on active lateral dynamics control of an electric vehicle equipped with 4 in-wheel motors and active rear steering. An integral terminal sliding mode controller (ITSMC) is derived starting from the linearized single track model with the addition of the rear wheel steering angle. The controller has a multi-input multi-output structure and is designed to track vehicle yaw rate and sideslip angle reference quantities through torque vectoring and active rear steering actuation. A novel approach for calculating reference sideslip angle and yaw rate using a logistic function is also presented in this paper. The ITSMC relies on real time knowledge of sideslip angle which cannot be measured in the real vehicle, thus it is estimated through the addition of an extended Kalman filter to the control loop. The performance of the controller is tested with VI-CarRealTime 14 degrees of freedom nonlinear model both for steady state and transient manoeuvres. Simulation results show a good tracking of the reference value with no chattering issues and with an improved behaviour if compared to a sliding mode controller from literature.

Accurate magnification determination for cryoEM using gold

Determining the correct magnified pixel size of single-particle cryoEM micrographs is necessary to maximize resolution and enable accurate model building. Here we describe a simple and rapid procedure for determining the absolute magnification in an electron cryomicroscope to a precision of <0.5%. We show how to use the atomic lattice spacings of crystals of thin and readily available test specimens, such as gold, as an absolute reference to determine magnification for both room temperature and cryogenic imaging. We compare this method to other commonly used methods, and show that it provides comparable accuracy in spite of its simplicity. This magnification calibration method provides a definitive reference quantity for data analysis and processing, simplifies the combination of multiple datasets from different microscopes and detectors, and improves the accuracy with which the contrast transfer function of the microscope can be determined. We also provide an open source program, magCalEM, which can be used to accurately estimate the magnified pixel size of a cryoEM dataset ex post facto.

IoT-based compensation and control of power theft in weak distribution system

This paper presents a prototype model of real-time rampant power theft detection and compensating the required power current components through switching of distribution static compensator (DSTATCOM) using IoT (Internet of Things) based microcontroller via the GSM module. In this case study, an Internet of Things (IoT) application is used to wirelessly transmit data of the difference of smart meters through intelligent current sensors with ESP8266 module. Transmitted pulse sequences find out the derivatives of functions at discrete points through weight function. A weighting function includes power theft detection information in the pulse sequence series form. It computes the unknown sample of pulse in the line that identified the power theft and the quality of the power supply. The sequence error of the of energy meter units communicates microcontroller through the IoT. Microcontroller communicate to μ-PMU to addressed power quality error with a GPS receiver in the line. Based on weight function an algorithm has been developed for switching DSTATCOM for compensation of power quality. The reference and feedback quantities’ resultant errors are sampled within a time rate of the weight function. This control approach is applied with dynamic load to analyze the power quality issues. The results are implemented in MATLAB Simulink and validated experimentally for power theft detection and its compensation in low voltage distribution system.

Effect of stainless-steel substrate grain boundaries on surface graphene morphology and nano-friction behavior

The characteristics of graphene's surface morphology and frictional behavior can be significantly impacted by the underlying substrate material, particularly in the domain of nanofriction. This study observed that the grain boundaries present in polycrystalline substrates like stainless steel induce bulging in graphene, which, in turn, impacts its nanofriction behavior. While graphene exhibits low friction when tightly adsorbed on stainless steel grains, the phenomenon of graphene bulging leads to an increase in frictional force. Additionally, this study revealed that the process of contact between the tip and the bulging graphene gives rise to a two-stage frictional rise, wherein the rate of frictional rise and the underlying mechanism differs between the stages. The first stage of the frictional rise was explained using the fold theory, considering the contact area as the reference quantity. Using the tip atomic force statistics as a reference quantity, the second stage of frictional rise can be explained by quality evolution theory. Through a combination of experimental observations and theoretical analyses, this study provides a comprehensive understanding of the nano frictional behavior exhibited by graphene on stainless-steel substrates. The mechanism of action of the entire process of frictional changes caused by graphene bulging is revealed.

Trilateral control for LCL filter‐based system with single grid current sensor in weak grid

AbstractA trilateral control for LCL filter‐based system is introduced by the authors with a single grid current sensor in weak grid conditions. The LCL filter increases the complexity when the uncertain nature of the grid comes into the picture. Moreover, the traditional three‐loop control technique requires three current sensors on the inverter side, three voltage sensors to sense voltage across the capacitor, and three current sensors on the grid side combined for sensing. A novel trilateral control technique utilising a single sensor is implemented to sense the grid current. This technique has reduced a considerable number of current sensors and voltage sensors. The α axis of grid current is proportional to sensed ‘a’ phase grid current. The β current in the utility grid is acquired by employing the controller reference quantities of the grid current. The computation of another variable, that is, the current in the inverter side inductor and the voltage across the capacitor, is executed by an estimation algorithm. The proposed technique provides the feature of reducing implementation financial value and weight that reduces the complexity and size of hardware. The synchronisation technique is executed by a modified dual second‐order generalised integrator digital phase‐locked loop for the grid‐connected converter. The implemented system offers the advantage of ease of implementation, good performance, and high stability. The validity of the proposed scheme in the implemented system is demonstrated by the simulated waveform obtained on the MATLAB/Simulink platform. Finally, the effectiveness of the proposed system is further justified by the experimental waveform procured from a prototype developed in the laboratory.

An experiment-design methodology for the selection of optimal experimental conditions for the correlation of transport properties

In accordance with the pioneering work of Rosenfeld, our recent research activities on transport properties (viscosities, thermal conductivities, self-diffusion coefficients) lead to the conclusion that there is a univariate dependence of reduced transport properties on residual entropy where the reduced transport property is a dimensionless ratio of the transport property and a suitable reference quantity. This is the basis of the proposed entropy scaling method in which an equation of state is used not only to estimate the residual entropy of any fluid at specified temperature and pressure but also the reference quantity. The link between the residual entropy and the reduced transport property can be made through a correlation involving six component-dependent parameters that need to be fitted to experimental data to accurately correlate any given transport property throughout the whole fluid region (liquid, gas and supercritical states). Starting from this observation, the present study proposes to identify the minimum number of experimental measurements, and the corresponding temperature and pressure conditions, to fully characterize a given transport property of a specified compound through a design of experiments-like approach. In this note, it is shown that six experimental data points are sufficient to determine the six parameters of the entropy-scaling based correlation for a given property, provided that the temperatures and pressures of these six data points are properly chosen. A methodology to select the optimal temperature and pressure conditions for these six data is proposed here. Eventually, to characterize the transport property behavior of a given species, experimentalists are advised to perform measurements of the transport properties for all six sets of temperatures and pressures and then, to use our general correlation with parameters fitted to these six experimental data to estimate the transport property in other temperature and pressure conditions.

Strip Surface Defect Detection Algorithm Based on YOLOv5.

In order to improve the detection accuracy of the surface defect detection of industrial hot rolled strip steel, the advanced technology of deep learning is applied to the surface defect detection of strip steel. In this paper, we propose a framework for strip surface defect detection based on a convolutional neural network (CNN). In particular, we propose a novel multi-scale feature fusion module (ATPF) for integrating multi-scale features and adaptively assigning weights to each feature. This module can extract semantic information at different scales more fully. At the same time, based on this module, we build a deep learning network, CG-Net, that is suitable for strip surface defect detection. The test results showed that it achieved an average accuracy of 75.9 percent (mAP50) in 6.5 giga floating-point operation (GFLOPs) and 105 frames per second (FPS). The detection accuracy improved by 6.3% over the baseline YOLOv5s. Compared with YOLOv5s, the reference quantity and calculation amount were reduced by 67% and 59.5%, respectively. At the same time, we also verify that our model exhibits good generalization performance on the NEU-CLS dataset.

A Simple and Low-Cost Technique for 5G Conservative Human Exposure Assessment

The purpose of this paper is to introduce a simple, low-cost methodology for estimating a conservative value of the maximum field level that can be radiated by a 5G base station useful for human exposure assessment. The method is based on a Maximum Power Extrapolation (MPE) approach and requires the measurement of a reference quantity associated with the SS-PBCH, such as Primary Synchronization Signal (PSS), Secondary Synchronization Signal (SSS), Physical Broadcast CHannel (PBCH), or PBCH Demodulation Reference Signal (PBCH-DMRS). This step requires a simple spectrum analyzer and allows one to obtain the Resource Element (RE) power of a signal transmitted through broadcast beams. In the second phase, the RE power of the signal transmitted through the traffic beam is estimated using the Cumulative Distribution Function (CDF) of the antenna boost factor obtained from the broadcast and the traffic envelope radiation patterns made available by the base station vendor. The use of the CDF allows us to mitigate the problems related to the exact estimation of the direction of the measurement point with respect to the beam of the 5G antenna. The method is applied to a real 5G communication system, and the result is compared with the value given by other MPE methods proposed in the literature.

A Calculation Model for Vibration Effect Induced by Resonance-Free Vibratory Hammer Method

Buildings close to the ground treated by the resonance- free vibratory hammer method are often vulnerable to excessive vibrations. An in situ test of an urban soft site was carried out to investigate the resonance-free vibratory hammer induced vibration effects during construction. Vibration pickups were set at the positions with distances of 15 m, 30 m, 50 m, and 100 m away from the vibration source. On the basis of the results obtained from this investigation, vibration effects of the resonance-free vibratory hammer and safe construction distances were systematically analyzed. The testing results indicate that the vibration in the vertical direction is stronger than that in the other two horizontal directions. The vertical vibration should be the main reference quantity for the foundation treatment by using the resonance-free vibratory hammer method. The predominant frequency of each measuring point in the same direction decreased with an increase of the distance from the vibration source (DFTVS). In terms of the measuring point with a DFTVS of 30 m, the peak values of velocity in all directions were within 5 mm/s, which meet the requirements of the allowable limit of building vibration. According to the in situ testing results, a model for calculating the acceleration exponent of the vibration caused by the resonance-free vibratory hammer technology was established by comprehensively considering the amplitude of acceleration, the attenuation coefficient of THE DFTVS, and the vibration correction factor. Finally, the reliability of the calculation model was verified through the comparison between the calculated results and field vibration experimental results, in which all the correlation coefficients of validation example were above 0.9.

Energy Transfer from an Electrical Network-Connected Synchronous Machine

Any alternating electric power supply is always characterized by three reference quantities, which are voltage, electric power and frequency. The generators of power stations are synchronous machines. The present work is based on the modelling of the synchronous machine for a study of the stability of the electricity transmission network. The example considered is a thermal power station of the national network. i.e., Algiers port power station. We have developed a computer program based on MATLAB to simulate the calculations of our multi-variable system. The study presented in this article examines the static stability of a thermal power plant. To make this study a reality, it is necessary to model the synchronous machine. We present the three models of the synchronous machine by emphasizing the role of the shock absorbers and the smoothness of the model with three windings. This work is supported by a spectral analysis based on the eigenvalues of the system.

Feasibility of Photovoltaic Module Single-Diode Model Fitting to the Current–Voltage Curves Measured in the Vicinity of the Maximum Power Point for Online Condition Monitoring Purposes

Photovoltaic system condition monitoring can be performed via single-diode model fitting to measured current–voltage curves. Model parameters can reveal cell aging and degradation. Conventional parameter identification methods require the measurement of entire current–voltage curves, causing interruptions in energy production. Instead, partial curves measured near the maximum power point offer a promising option for online condition monitoring. Unfortunately, measurement data reduction affects fitting and diagnosis accuracy. Thus, the optimal selection of maximum power point neighbourhoods used for fitting requires a systematic analysis of the effect of data selection on the fitted parameters. To date, only one published article has addressed this issue with a small number of measured curves using symmetrically chosen neighbourhoods with respect to the maximum power. Moreover, no study has determined single-diode fit quality to partial curves constructed via other principles, e.g., as a percentage of the maximum power point voltage. Such investigation is justified since the voltage is typically the inverter reference quantity. Our work takes the study of this topic to a whole new scientific level by systematically examining how limiting the current–voltage curve measuring range to maximum power point proximity based on both power and voltage affects single-diode model parameters. An extensive dataset with 2400 measured curves was analysed, and statistically credible results were obtained for the first time. We fitted the single-diode model directly to experimental curves without measuring outdoor conditions or using approximations. Our results provide clear guidance on how the choices of partial curves affect the fitting accuracy. A significant finding is that the correct selection of maximum power point neighbourhoods provides promising real-case online aging detection opportunities.

Evaluation of the temporal reconstruction methods for MODIS-based continuous daily actual evapotranspiration estimation

Monitoring continuous daily actual evapotranspiration (ET) is very useful for managing regional water resources and understanding vegetation water consumption and water use efficiency. However, the research on remote sensing-based temporal reconstruction methods for mapping continuous daily ET is still limited, lacking comparative evaluations and mechanism discussions. In the study, four reconstruction methods, including two interpolation methods (the reference evaporative fraction (ETrF) and evaporative fraction (EF) method) and two calibration methods (the advection-aridity (AA) and modified Katerji-Perrier (KP) method), were systematically evaluated to reconstruct continuous daily ET from discrete daily ET based on MODIS products and atmospheric data. Meanwhile, an additional test using in situ measurements as a perfect proxy for the retrievals on satellite overpass dates was added as a baseline case that is independent of remotely sensed ET error. The internal coupling mechanism between each model’s simulations and the underlying surface physical and atmospheric driving factors were also analyzed using the sensitivity and uncertainty analysis methods. The results demonstrated that the interpolation methods performed better and had a higher potential for improvement as the quality of remote sensing ET inputs improved. Although the underestimation errors in the remote sensing-based ET estimates propagated to subsequent reconstructions and caused underestimation to a certain extent, the four methods could still effectively simulate continuous daily ET. Among them, the EF method with a simple calculation process, which used reference quantity directly related to solar radiation, had the best performance based on in situ with an R2 of 0.8233 and an NRMSE of 0.0889. Given remote sensing estimates, the AA method was the best due to the compensation effects, with an R2 of 0.7267 and an NRMSE of 0.1442. As all methods showed high sensitivity to ET of satellite overpass days, its accuracy should be a top priority for continuous daily ET reconstruction work.

On the Validity of a Linearity Axiom in Diffusion and Heat Transfer

In this work, the linearity axiom of irreversible thermodynamics for diffusion and heat transfer has been re-examined. It is shown that this axiom is compatible with the entropy production invariance principle with respect to a reference quantity for diffusion and heat transfer in the Euclidean space. Moreover, the underlying relations of the other principles of irreversible thermodynamics for multi-component diffusion and heat transfer, such as the quasi-equilibrium and the Onsager reciprocal relations (ORR) with the entropy production invariance, are re-examined. It was shown that the linearity principle postulates for diffusion and heat transfer and could be directly derived from the entropy production invariance axiom. It is believed that this work could not only be used for the drying of polymer coatings but also for pedagogical purposes. It may also be generalized; thus, leading to a generalized framework for irreversible thermodynamics.

A Model of Consumer Choice With Bounded Rationality and Reference Quantity

The authors consider the economic problem of consumers' demand under the assumption of bounded rationality. They move from the hypothesis that the consumer does not know the amount of the good maximizing the utility but he/she is able to understand, at each time period, if the current consumption is above or below than the optimal choice and decide consequently for the next period. Moreover, they also take into consideration the role of a reference amount of consumption that can influence the consumption choice of the consumer. They show that this assumption led to a failure in the convergence process towards the rational choice because the equilibrium of the model, even when locally stable, is located on an intermediate value between the rational choice and the reference quantity.

Flamelet modeling of thermo-diffusively unstable hydrogen-air flames

In order to reduce CO2 emissions, hydrogen combustion has become increasingly relevant for technical applications. In this context, lean H2-air flames show promising features but, among other characteristics, they tend to exhibit thermo-diffusive instabilities. The formation of cellular structures associated with these instabilities leads to an increased flame surface area which further promotes the flame propagation speed, an important reference quantity for design, control, and safe operation of technical combustors. While many studies have addressed the physical phenomena of intrinsic flame instabilities in the past, there is also a demand to predict such flame characteristics with reduced-order models to allow computationally efficient simulations. In this work, a H2-air spherical expanding flame, which exhibits thermo-diffusive instabilities, is studied with flamelet-based modeling approaches both in a-priori and a-posteriori manner. A recently proposed Flamelet/Progress Variable (FPV) model, with a manifold based on unstretched planar flames, and a novel FPV approach, which takes into account a large curvature variation in the tabulated manifold, are compared to detailed chemistry (DC) calculations. Both flamelet approaches account for differential diffusion utilizing a coupling strategy which is based on the transport of major species instead of transporting the control variables of the manifold. First, both FPV approaches are assessed in terms of an a-priori test with the DC reference dataset. Thereafter, the a-posteriori assessment contains two parts: a linear stability analysis of perturbed planar flames and the simulation of the spherical expanding flame. Both FPV models are systematically analyzed considering global and local flame properties in comparison to the DC reference data. It is shown that the new FPV model, incorporating large curvature variations in the manifold, leads to improved predictions for the microstructure of the corrugated flame front and the formation of cellular structures, while global flame properties are reasonably well reproduced by both models.

Актуальные проблемы или «национальные особенности» радиационного контроля питьевой воды

Relevant metrological problems of monitoring radiation in water, as well as other types of radiation measurements, are mainly related to insufficient status of measures of specific activity (standard solutions of radionuclides) and limited calibration capabilities in laboratories and standardization organizations in different regions of Russia. If there are no certified reference materials and measurement standards adequate for a measurement task, then metrological traceability of measurements can be carried out according to calibration procedures regulated by measuring methods using calibration standards prepared as certified mixtures from calibrated solutions of radionuclides, as well as pure uranium and potassium compounds. Regular interlaboratory comparisons with control samples having reference quantity values of the measured parameters allow laboratories to confirm their technical competence and the metrological traceability of measurement results.

An Optical Algorithm for Relative Thickness of Each Monochrome Component in Multilayer Transparent Mixed Films

A modification of the two-flux Kubelka-Munk (K-M) model was proposed to describe the energy conservation of scattered light in colored mixed material with a defined scattered photometric, which is applied for the relative quantity distribution of each colored monochrome component in mixed material. A series of systematical experiments demonstrated a higher consistency with the reference quantity distribution than the common Lambert-Beer (L-B) law. Its application in the fibrogram of each component for measuring the cotton fiber’s length was demonstrated to be good, extending its applicability to white and dark colored blended fibers, the length of which is harder to measure using L-B law.

Defining relative humidity in terms of water activity: III. Relations to dew-point and frost-point temperatures

Relative humidity (RH) is a fundamental quantity used in many fields of engineering and science, and in particular in meteorology and climate research. Relative fugacity (RF) and, equivalently, relative activity of water vapour in humid air have recently been proposed as a physically well-founded, unambiguous common metrological reference quantity for several conventional but mutually inconsistent definitions of RH. The RF definition is valid is valid under real-gas conditions and above boiling and sublimation temperatures. While differences between RH and RF mostly remain within uncertainties of typical present-day RH measurements, such systematic discrepancies are expected to be of substantial climatological relevance. Consequently, interdisciplinary harmonisation of RH definitions is overdue within the SI framework. Dew-point and frost-point temperatures are preferred measurands in humidity metrology using, for example, chilled-mirror hygrometers. Here, relations are presented for estimating RF from those temperatures, based on equations of state of the 2011 IUGG 5IUGG: International Union of Geodesy and Geophysics, https://iugg.org/. standard TEOS-10, the ‘international thermodynamic equation of seawater—2010’. Recommendations are given for numerically computing RF using the open-source TEOS-10 SIA library 6 6SIA Library: Sea-Ice-Air Library of TEOS-10, http://teos-10.org.. The asymptotic limiting laws of RF for nearly saturated humid air exhibit the familiar form of Clausius–Clapeyron-like equations, despite departing from ideal-gas assumptions. Under various practical conditions, these simple equations may cover the full humidity range with only minor residuals compared to the full numerical TEOS-10 solution for RF.

Finite Element Discretization Methods for Velocity-Pressure and Stream Function Formulations of Surface Stokes Equations

In this paper we study parametric trace finite element (TraceFEM) and parametric surface finite element (SFEM) discretizations of a surface Stokes problem. These methods are applied both to the Stokes problem in velocity-pressure formulation and in stream function formulation. A class of higher order methods is presented in a unified framework. Numerical efficiency aspects of the two formulations are discussed and a systematic comparison of TraceFEM and SFEM is given. A benchmark problem is introduced in which a scalar reference quantity is defined and numerically determined.