查看更多>>摘要：? 2022 Elsevier LtdA sensing probe based on fiber side-open cavity structure is proposed for the measurement of seawater temperature, which is mainly composed of a lead-in single mode fiber (SMF), a side-open cavity C-type microstructure fiber (SOCTF), a multimode fiber (MMF), a lead-out SMF, and a layer of polydimethylsiloxane (PDMS). It could effectively reduce the transmission loss, and promote the temperature sensitivity, with a micron-level sensing area. The relative simulations and experiments were carried out to verify the feasibility. The sensitivity could be up to 12.32 nm/°C with a temperature resolution of 0.0016 °C. Considering comprehensively, the sensing structure proposed in this paper could provide an effective measurement method for seawater temperature measurement.
查看更多>>摘要：? 2022Reflection characteristic is the law of specular and diffuse reflection after receives light of the surface, usually expressed by the ratio of irradiance of incident direction to the emissivity of observation direction, namely bidirectional reflection distribution function (BRDF). A method to measure BRDF for hole inner surface based on the endoscope image and morphology is proposed, which established the relationship between BRDF and morphology. Taking stainless steel and galvanized internal threaded as an example, the axial images in the holes are collected, and the BRDF of internal surface is calculated through the image brightness and the normal direction. The distribution characteristics of BRDF on the inner surface of different materials are analyzed. Based on the Phong model, the inBRDF parameter model of the inner surface is established. Research shows that the inBRDF model is consistent with measured results, and the average fitting error of the two materials is only 6.22%. The inBRDF method of hole inner surface proposed in this paper has high measurement efficiency and strong universality of equipment, and it is preferred to be applied on hole inner surface quality detection accordingly.
查看更多>>摘要：? 2022 Elsevier LtdUltrasonic-based technologies could provide light-independent and high-resolution solutions in no-contact human–machine interaction. This paper proposed a gesture recognition system on the basis of ultrasonic frequency modulated continuous wave (FMCW) and ConvLSTM model. It employed a hardware layout of one transmitter and three receivers spatially installed at different directions. An FMCW signal emitted by the transmitter would be detected by the receivers after reflecting from the hand. Then, the range-Doppler maps (RDMs) of the received signal were obtained by processing 2D fast Fourier transform. The spatio-temporal features of the hand were extracted from RDMs by the ConvLSTM model, to facilitate the gesture classification. Experiments showed that a fine resolution of 0.005 m in distance and 0.03 m/s in velocity for hand movement, and an accuracy of 85.7% with a small size of 50 samples training for finger-movement gestures can be achieved, which verified the feasibility of the proposed system.
查看更多>>摘要：? 2022 Elsevier LtdRegional Augmented Precise Point Positioning (RA-PPP) is a method used to support PPP-Real Time Kinematic (PPP-RTK) based on state space representation. In case of RA-PPP, uncalibrated phase delays and undifferenced ionospheric and tropospheric corrections generated by the reference station network are interpolated at the rover in real time. This study proposes a set of algorithms for estimating the uncertainties of atmospheric corrections that are compatible for use with the RA-PPP model. There are two different error sources of interpolated atmospheric corrections: one relates to the error propagation law and the other to the systematic bias of the interpolation model. We discuss the spatial changes in systemic errors of the interpolation model and present a new interpolation method and its use in calculating the uncertainties of interpolated atmospheric corrections. In addition, we verify the existence of systematic errors in the interpolation model and discuss the correlation between zenith tropospheric delay and slant ionospheric corrections. The results of PPP ambiguity resolution experiments using GPS/Galileo observations are presented. For a reference station network with an interstation distance of more than 110 km, when the proposed method is used, the rate of successfully fixing ambiguities reaches 67.8% in 5 min, and the fixing rate is higher than 90%. It is considered that our method has enhanced applicability for use with large networks and in complex environments.
查看更多>>摘要：? 2022This study proposes a rotating excitation magnetic field detection method to identify in-service cladding steel pipeline damage. A ring of uniformly arranged excitation coils generates excitation magnetic fields under the action of a three-phase current, which synthesize in the pipe as a rotating magnetic excitation field based on the principle of vector synthesis. Tunneling magneto-resistive (TMR) sensors work as detection probes for measuring magnetic induction strength. The induced current flows circularly in the pipe's body under the influence of a rotating excitation field. Therefore, this excitation method has a high sensitivity to defects in different length directions and can detect damage information in the whole circumference of the pipe body. The TMR sensors are uniformly arranged along the pipe's rim and measure the magnetic field in the radial direction with high sensitivity and low background noise (10 pT/Hz@1 kHz). The finite element method investigated the operating principle and performance of two excitation coils probe structures. The specimen probe and signal acquisition setup was developed and examined, with which artificial damages in the pipeline with cladding were inspected. The test result indicates that the proposed probe can penetrate the surface cladding of the pipe, effectively identifying defects in the pipeline.
查看更多>>摘要：? 2022 Elsevier LtdAutomatic detection of the cutting tool breakage plays a vital role in the automation of machining operations. However, up to now, few artificial intelligence (AI) models in the detection of cutting tool breakage have been practically applied in manufacturing. There are technological gaps between the research and practice. This systematic review comprehensively analyzed all the relevant studies to promote the practical application of AI models in the automatic detection of cutting tool breakage. Twenty-one studies were included in the qualitative analysis, and nine studies were included in the quantitative analysis. The most used AI model was the support vector machine, and the most used input signal was cutting force. The results showed that AI had good accuracy in the detection of cutting tool breakage. In future studies, the application of AI needs to be further confirmed by more cutting experiments conducted in real-time on various cutting conditions.
查看更多>>摘要：? 2022 Elsevier LtdThe article presents a method of assessing the condition of a measurement system equipped with a Rogowski coil using the response of the coil to the unit voltage jump in the secondary circuit. The method is based on a direct sensor-microcontroller interface and has been tested on the STM32F745 microcontroller. Unlike traditional direct sensor-microcontroller methods described in literature a Fully Convolutional Neural Network (FCN) is used to extract signal features and estimate the state of the system. The microcontroller is responsible for capturing the coil responses, which are used by the FCN for time series classification. This method allows creating smart sensor with self-testing and identification capabilities. The Class Activation Map (CAM) is used to define class specific contribution regions and verify the performance of the FCN network. The proposed framework is suitable for remote assessment of the system condition in high voltage areas where Rogowski coils are used. Because of the presence of voltages dangerous for humans and the frequent inability to switch off the voltage in a power facility, this method significantly speeds up the location of damage in the measurement system.
查看更多>>摘要：? 2022 Elsevier LtdThis paper numerically and experimentally investigates guided wave propagation in a steel plate with one side partly exposed to water. The fundamental anti-symmetric Lamb wave (A0) is excited on the dry plate section and travels to the water-immersed plate section, where the generated A0 wave is mode converted to quasi-Scholte (QS) wave. The results demonstrate that the energy of QS wave converted by A0 wave decreases when the excitation frequency increases. In addition, it is revealed that the guided wave energy can shift in the frequency domain if the phase velocity of the incident A0 wave is larger than the sound speed of water. The frequency shift phenomenon should be noticed in practical applications because the behaviors of guided waves vary with frequency. Finally, discussions are provided on the frequency selection for exciting guided waves to detect damage on partially immersed structures and assess liquid properties.
查看更多>>摘要：? 2022 Elsevier LtdIn this paper, we propose a transmission method, analysis, and implementation of an ultrasound touchscreen system based on Lamb waves. The basic principle of this system is to use the signals reflected from the fingertip contact. The inverted phase transmission method, which alternately transmits two opposite phases of input signals, was proposed to improve the signal contrast of the reflected signal from the fingertip. Experimental validation of this system was demonstrated on a 40-inch glass plate (800 mm × 600 mm) containing eight pairs of sensors. For imaging and localization, a simple and common method is used: the delay and sum method for imaging and the center of mass for localization. Compared with existing ultrasound technology, the proposed system is implemented in a large panel without using the training or prepared database. The system also provides reliable contact detection, simplicity, and other advantages of the present acoustic techniques.
查看更多>>摘要：? 2022 Elsevier LtdThis paper proposes a semisupervised algorithm for detecting foreign objects in ballastless beds based on the improved deep SVDD (Support Vector Data Description) algorithm. First, we use the improved Mask R-CNN algorithm to extract the rail and fastener areas in images, assuming that no foreign object exists in the rail and fastener areas. Second, we deepen the backbone network of the deep SVDD to enhance its ability to extract deep semantics from complex images. We perform pure color coverage processing with different colors and mean blur processing with different blur kernels on the rails and fastener regions extracted by the improved Mask R-CNN. The results show that the AUC (Area Under the Curve) of our improved deep SVDD algorithm is 89.23% and improves the AUC compared to that of the original model by 11.09%.
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