查看更多>>摘要：? 2022 Elsevier LtdIn this research, blood samples of 47 patients infected by COVID were analyzed. The samples were taken on the 1st, 3rd and 6th month after the detection of COVID infection. Total antibody levels were measured against the SARS-CoV-2 N antigen and surrogate virus neutralization by serological methods. To differentiate COVID patients with different antibody levels, Fourier Transform InfraRed (FTIR) and Raman spectroscopy methods were used. The spectroscopy data were analyzed by multivariate analysis, machine learning and neural network methods. It was shown, that analysis of serum using the above-mentioned spectroscopy methods allows to differentiate antibody levels between 1 and 6 months via spectral biomarkers of amides II and I. Moreover, multivariate analysis showed, that using Raman spectroscopy in the range between 1317 cm?1 and 1432 cm?1, 2840 cm?1 and 2956 cm?1 it is possible to distinguish patients after 1, 3, and 6 months from COVID with a sensitivity close to 100%.
查看更多>>摘要：? 2022 Elsevier LtdThe accurate identification of tripped branch (ITB) is an essential requirement to maintain the reliability and security of modern smart grid. Most of the existing phasor angle based approaches fail to identify the tripping of parallel branches. To this end, a novel method is presented in this study using current measurements of phasor measurement unit (PMU). A new term namely Jaccard dissimilarity index (JDI) is proposed and the ITB problem is solved through JDI based novel objective function. Furthermore, a generalized mathematical model of false data injection (FDI) attack is formulated considering two types of attack such as in phase attack and angular attack. Considering the FDI attack, the proposed method is implemented on different IEEE systems in MATLAB software. The identification rate of the proposed method is found to be competitive compared to some well-established methods. Test results considering various aspects such attack factor variation and attack location variation prove the applicability and effectiveness of the proposed method.
查看更多>>摘要：? 2022 Elsevier LtdThe nonequilibrium kinetics of nitrogen metastable N2 (A3Σu+) manifold is of a high interest for the non-thermal plasma diagnostics. A review of laser induced fluorescence (LIF) diagnostic techniques of N2 (A3Σu+) metastable molecules in nitrogen discharges indicates the need to introduce single-shot LIF measurements. The main obstacle in introducing the single-shot technique is the extremely weak fluorescence of N2 (A3Σu+) species, which monitoring requires a very sensitive and fast detector. In this paper, 2-D imaging technique of metastable nitrogen molecules in a nitrogen discharge via single-shot LIF is presented. The experiments involved a sub-atmospheric pressure nitrogen afterglow of a positive-pulsed streamer discharge that was generated in a modified wire-to-plate electrode system. Using 2-D single-shot LIF technique, instantaneous images of the spatial and temporal distributions of the metastable N2 (A3Σu+, v”=2) species and streamer optical emission in the nitrogen afterglow were captured for the first time. The LIF from N2 (A3Σu+, v”=2) metastable molecules and the streamer emission from the excited nitrogen molecules had similar spatial distribution. The key factors for successful single-shot LIF measurements were the intensive streamers produced by the modified wire-to-plate electrode system with a short gap distance, and the use of an intensified charge-coupled detector (ICCD) camera equipped with a two-stage microchannel plate (MCP). The single-shot LIF measurement has the advantages of offering the instantaneous distribution of N2 (A3Σu+) species in the discharge, short measuring time, and better spatial resolution. All of this enable a deeper insight into the nonequilibrium kinetics of nitrogen discharges, making the single-shot LIF technique a powerful diagnostic tool, especially when the LIF signal is weak in stochastic discharges.
查看更多>>摘要：? 2022 The Author(s)The surface roughness of a particle monolayer is one of its fundamental characteristics, conventionally described in terms of power spectral density. We derive a general equation for this function and demonstrate its similarity to those applied in the theory of scattering. To validate our analytical results, we compare them with numerical results derived for a monolayer of 450nm spherical particles, of surface coverage 0.85. We also demonstrate a practical application of our approach on the example of spectral analysis of a SEM image of a polystyrene particle monolayer of surface coverage close to 0.5. Our theoretical model provides a general framework for a cheap and easy parametrization of particle monolayers.
查看更多>>摘要：? 2022Optoelectronic devices' organic materials and metal electrodes are highly susceptible to water vapor. The use of a thin-film encapsulation technique is an effective solution. The accurate water vapor transmission rate (WVTR) of thin films, however, is challenging to acquire because of the influence of dust particles in industrial production laboratories. We have developed a low-cost, high accurate optical and electrical combined Ca corrosion test to analyze the permeation at the defects by optical camera and Matlab software, and established a model to eliminate the influence caused by defective spots in the WVTR method for the encapsulated film. We tested the WVTR of aluminum oxide (Al2O3) with different defect spot densities to ensure the accuracy and reliability of this process. The results illustrated that regardless of the sample defect spot density, the WVTR acquired by the test method reported in this paper generally agreed with the spotless WVTR.
查看更多>>摘要：? 2022 The AuthorsThis paper describes a test for the determination of damage function limits. The proposed test consists of skew rolling of conical specimens. The test is carried out under real conditions to determine the crack initiation point, and then it is modelled numerically to determine the limit values of the damage function at the determined crack initiation point. This paper presents a methodology for the determination of limit values of the damage function on the example of C45 steel at three different temperatures, i.e. 950 °C, 1050 °C and 1150 °C. The research was carried out using the Oyane criterion as an example. The limit value of the damage function at 1000 °C was determined by regression using the calculated damage function values. The value of the damage function was adapted to a numerical model of a skew-rolling process of a bar with the deletion of elements, which took place when the limit value of the damage function determined in the test was exceeded. The numerically simulated skew rolling case was also realised in real conditions. Based on the results obtained from the skew rolling of bars, a quantitative and qualitative validation of the new damage function limit test was carried out.
查看更多>>摘要：? 2022 Elsevier LtdThe strong backscattering of smoke limits the adaptability of Gm-APD Lidar for depth imaging through dense smoke. In this paper, a dual-parameter estimation algorithm based on Gamma function is proposed. Aiming at the characteristics of small number of Bins and large Bin width, this algorithm uses continuous wavelet transform to extract scale parameter and maximum likelihood method to extract shape parameter. Based on the estimated two parameters, this study helps to distinguish between background photons reflected from the smoke and target signal photons. The experimental results show that when the smoke density is high or the acquisition time is 0.15 s, the reconstructed object shape is more complete. The distance error of short-range (30 cm) and long-range (75 cm) targets is 1 and 0 Bin respectively, which is at least 6 Bins less than the traditional algorithms. Our algorithm improves the weather adaptability of Gm-APD Lidar.
查看更多>>摘要：? 2022 The AuthorsAcicular grindable thermocouples represent an interesting and prospective technique of temperature measurements at sliding contacts. This study aimed at the investigation of their reliability and accuracy as applied to the friction materials of various classes in contact with steel. The tests were conducted on a pin-on-disc tribometer under stationary and transient regimes. The experimental results were validated by comparing the temperature data obtained by the acicular thermocouple, conventional thermocouples and infrared thermography. It was found that the measurements conducted with the acicular thermocouples are test-retest reliable for copper and a brake pads material, whereas they are not reliable for a polyamide. The temperature rise measured with the acicular thermocouple deviates from that registered by infrared thermography by 7–15% for copper and 10–19% for the brake pads material.
查看更多>>摘要：? 2022 Elsevier LtdThe dynamic calibration of pressure sensors with shock tube system are inevitably affected by the non-ideal shock wave characteristics and complex noise interferences, which limits the achievable accuracy of the dynamic pressure measurements. This paper proposes an improved shock tube (IST) method for identifying the sensitivity characteristic of piezoresistive pressure sensors. The incident shock wave (ISW) velocity attenuation model is first established by a distributed ISW velocity measurement combined with least squares fitting to compensate the shock wave pressure in shock tube. Besides, a signal correction method based on the hybrid adaptive mode decomposition is presented to eliminate the effects of complex noise on the response signals of pressure sensor. An accurate dynamic calibration result of the sensitivity characteristic is finally achieved with the compensated shock wave pressure and corrected response signal. A series of dynamic calibration experiments for a piezoresistive pressure sensor are carried out to verify the performance of the IST method. Results show that the IST method is able to effectively reduce the effects of the non-ideal shock wave and complex noises on the sensitivity calibration results. The mean relative error of sensitivity calibration results with the IST method is only 0.55%, which is about 1/7 times of the results obtained by the usual shock tube method. Furthermore, the sensitivity calibration uncertainty is evaluated and the smaller uncertainty results further verify the superiority of the IST method in high-accuracy dynamic calibration of piezoresistive pressure sensors.
查看更多>>摘要：? 2022 Elsevier LtdDue to the low spatial resolution of spectrometer and low spectral resolution of CCD, a multi-wavelength radiation thermometry method employing multispectral imaging technology was proposed to measure flame temperature and emissivity. The calculated radiation intensity lines were obtained by the Hottel emissivity model and the least square method. The temperature and flame absorption capacity with the calculated spectral line closest to the measured spectral line were considered as the optimum results. The experimental results showed that maximum temperature of the flame was 1943 K appeared in the thin-wick paraffin. At any position, the emissivity of the thin-wick paraffin flame was lower than that of the thick-wick, but the emissivity of the biomass candle flame near the flame center was the highest. The measured temperature distribution was validated by employing a spectrometer system and the relative error was 2.66%.
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