查看更多>>摘要：? 2022 Elsevier LtdA new optimisation problem is proposed to facilitate a fast and reliable damage detection of structures with closely-spaced eigenvalues. The first stage of the proposed method identifies the most probable defective elements resulting in the elimination of healthy members from further investigation. This will further reduce the computational efforts of computing damage indices regarding the defective elements. The second stage of the proposed method exploits the proposed objective function to update the damage indices of the identified defective elements from the first stage. Two truss structures with multiple damaged elements in different damage scenarios are studied where measurements with different levels of noise are used as input to the proposed algorithm. Numerical results and comparison with previous studies demonstrate the superiority of the proposed method in damage detection of structures with closely-spaced eigenvalues.
查看更多>>摘要：? 2022 Elsevier LtdAccurate temperature measurements are essential for the proper monitoring and control of industrial furnaces. However, measurement uncertainty is a risk for such a critical parameter. Certain instrumental and environmental errors must be considered when using spectral-band radiation thermometry techniques, such as the uncertainty in the emissivity of the target surface, reflected radiation from surrounding objects, or atmospheric absorption and emission, to name a few. Undesired contributions to measured radiation can be isolated using measurement models, also known as error-correction models. This paper presents a methodology for budgeting significant sources of error and uncertainty during temperature measurements in a petrochemical furnace scenario. A continuous monitoring system is also presented, aided by a deep-learning-based measurement correction model, to allow domain experts to analyze the furnace's operation in real-time. To validate the proposed system's functionality, a real-world application case in a petrochemical plant is presented. The proposed solution demonstrates the viability of precise industrial furnace monitoring, thereby increasing operational security and improving the efficiency of such energy-intensive systems.
查看更多>>摘要：? 2022 Elsevier LtdThis work presents an improved estimation of the local measurement uncertainty of transient heat transfer experiments using Thermochromic Liquid Crystals (TLC). Additional signal analysis steps and a Monte Carlo (MC) approach are added to the evaluation routine. As a result, the local uncertainty in the indication time of the maximum green intensity is determined. All other input quantities for the heat transfer coefficient calculation are provided with their characteristic distribution function introducing additional uncertainties. As a final result, lower and upper boundaries for a confidence interval with a user defined confidence level for the heat transfer coefficient are calculated locally for single pixels. The new method is applied to own measurement data from a transient TLC experiment. The local measurement uncertainty is compared to the traditional approach based on error propagation. Hence, the advantages of taking the non-linearity and the local uncertainty in the peak detection into consideration are shown.
查看更多>>摘要：? 2022 Elsevier LtdExtraction of the fault-related periodic impulses from vibration signals with heavy background noise is fundamental but difficult for bearing fault diagnosis. In this paper, a novel fault feature extraction method based on a new sparse representation, adaptive adjacent signal difference lasso (AdaASDL) is proposed for bearing fault diagnosis. AdaASDL model is composed of l1-norm sparse regularization term and adjacent signal difference sparse regularization term, which are used to enhance the sparsity of the signal amplitude and adjacent signal difference, respectively. Moreover, a weighted method is proposed for setting the regularization parameter adaptively. The majorization–minimization (MM)-based optimization algorithm is derived to solve the objection function optimization of AdaASDL. In comparison with other state-of-the-art methods including the conventional sparse representation and spectral kurtosis (SK), AdaASDL has the better denoising performance on simulation signals and bearing vibration signals and the comparison results demonstrate the superiority of AdaASDL in bearing fault diagnosis.
查看更多>>摘要：? 2022 Elsevier LtdImpedance and vector network analyzer measurements are combined in order to measure frequency dependent conductivity and permittivity of two different saturated clays: montmorillonite and illite chlorite. In the low frequency range, the complex conductivity is determined over the 10 mHz to 45 kHz frequency range using a complex impedance analyzer with a 4-electrodes cell. In the high frequency range (50 MHz to 5 GHz), the complex permittivity is obtained from measured reflection factor of an open-ended probe. The ultrabroadband constitutive properties of the saturated clays were investigated in the temperature range 25°C down to 0°C. A mixture equation, based on a volume average approach, was applied to model the low and high frequency electrical properties based on the formation factor. The temperature dependency was considered in the following petrophysical quantities: low frequency conductivity, chargeability and high frequency permittivity. The modeled results are in reasonable agreement with measurements.
查看更多>>摘要：? 2021A methodology relying on relating terms of a two-port error network to the scattering (S-) parameters of a two-port network or device is applied to extract its full S-parameters. The new methodology has only one sign ambiguity problem (two solutions) in evaluation of S11 (and thus S22) while the similar methodology in the literature has two sign ambiguity problems (4 solutions). This ambiguity problem of our method is shown to be eliminated by applying an approach based on continuity of the argument of S11 in the frequency domain. On the other hand, our methodology, as compared with the thru-reflect-line calibration technique, does not necessitate usage of any reflection standard in determining full S-parameters of a two-port network or device. Finally, it gives information about error networks. For its validation, S-parameters of a microwave phase shifter and a polyethylene sample flushed with the left/bottom terminal of the coaxial cell were extracted.
查看更多>>摘要：? 2021 The AuthorsThe paper presents a noise measurement system particularly suited for the investigation of the low frequency noise in advanced infrared (IR) detectors characterized by low shunt resistance. By combining the performances of ultra-low noise amplifiers with the advantages that can be obtained by transformer input coupling and cross-correlation between two nominally identical channels, we were able to obtain excellent noise performances in the low frequency region (below 10 Hz). Indeed, the equivalent input background noise that can be obtained with the approach we propose can be as low as 1 × 10-20 V2/Hz (≈100 pV/√Hz) at 1 Hz. The system was tested using source resistances in the range from 1 to 10 Ω as well as actual advanced IR detectors to demonstrate its ability to provide information about the noise generated at very low frequencies.
查看更多>>摘要：? 2022 Elsevier LtdThe paper presents the methodology of assessing the degree of differentiation of machined technical surfaces based on the empirical probability distribution of the roughness parameters. The methodology allowed to determine the differentiation level of the analysed surfaces morphology based on the influence of the machining process features on the variability of roughness parameters. The minimum sample size necessary to obtain a statistically significant differentiation level in roughness parameters of the compared surfaces was also determined. The conducted analyses made it possible to determine the information content (indicating the ability to differentiate the features of the analysed surfaces) of the roughness parameters. The robustness of the methodology has been demonstrated. The described methodology was used to evaluate the information content on the example of the grinding process of 100Cr6 bearing steel and Ti-6Al-4V titanium alloy.
查看更多>>摘要：? 2022 Elsevier LtdA new method for measuring 3D rotation angle of precision spherical joint based on eddy current sensors is proposed in this study. A pseudorandom code is used to generate a 2D plane absolute code and then mapped to the sphere. The 3D absolute code is formed on the ball head through precision cutting, and an eddy current sensor array is arranged in the ball socket to identify the code. The experimental tests were conducted on the parameter-optimized prototype, and the experimental results showed that the mean squared error of the 3D rotation angle measurement was approximately 25′ in the range. The proposed new measurement principle provides a new approach to the precision measurement of spherical rotary motion, which is expected to produce a breakthrough in the theory and technology of spherical-angle sensor measurement. The proposed new principle also provides a theoretical basis and technical experience for the integration and development of intelligent devices.
查看更多>>摘要：? 2021Learning 3D shape representations from structured-light images for 3D reconstructions has become popular in many fields. This paper presents a new approach integrating a fringe-to-phase network with a fringe projection profilometry (FPP) technique to achieve 3D reconstructions with superior accuracy and speed performance. The proposed fringe-to-phase network has a UNet-like architecture, capable of retrieving three wrapped phase maps directly from a color image comprising three fringe patterns with designated frequencies. Because the phase maps contain the 3D shape representations of the measurement target, they serve as an intermediary to transform the single-shot fringe-pattern image into the 3D shapes of the target. The datasets with ground-truth phase labels are generated by using a tri-frequency FPP method. Unlike the existing techniques, the proposed approach yields both high-accuracy and fast-speed 3D reconstructions. Experiments have been accomplished to validate the proposed technique, which provides a promising tool for numerous scientific research and industrial applications.
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