查看更多>>摘要：This article is a continuation of previous research in which we analysed the effect of deflections and elastic deformations caused by unsupervised support conditions on the measurements of geometrical deviations of large crankshafts. Supporting the shaft using a set of rigid supports at the same height limited the ability to detect deviations in the pin axis position and pin profile. Formula for supporting crankshaft measurements was proposed using the results and metrology fundamentals, which allowed the accurate assessment of the geometric state under such conditions. The results provide solutions for measuring large crankshafts while eliminating the imperfections of current shaft measurement techniques. In result a high correlation (correlation coefficent at level 0.9935) with datum-based method was obtained. Therefore it was stated than proposed formula largely eliminates the disadvantages of shaft measurements using V-blocks with rigid supports.
查看更多>>摘要：Fasteners are critical components of railways that maintain the rail tracks in a fixed position. Their failure can lead to serious accidents such as train derailments, so their condition needs to be inspected periodically. Conventional image-based inspection methods fail to take full advantage of the structural features of fasteners, making them less robust in real-world environments. This paper presents a new approach for real-time fastener inspection by (1) extracting fastener regions using the YOLOv3-tiny network (2) proposing and pruning a lightweight and encoder-decoder network architecture for inferring depth information from a single RGB image of fasteners (3) fusing the RGB-D features for inspection. Compared with the image-based SVM, the F-1 of RGB-D fusion-based SVM increases from 94.34% to 95.83%, illustrating the improvement of additional depth information for fastener defect inspection. The inspection system runs at 11.9 FPS, which enables real-time inspection of railway fasteners.
Vijayalakshmi, P.Nguyen, Tu N.Dinakaran, J. AbrahamCengiz, Korhan...
12页
查看更多>>摘要：The minimal energy-efficiency in ad-hoc environment usually selects path with minimal energy path cost in multi hop communications. Choosing a path with minimal energy path cost does not guarantee in link stability and reliability of individual nodes in the network. A novel energy-efficient routing protocol named as Link Error Recovery Max-Min Path (LER-MMP) has been proposed. This protocol includes total energy spent on reliable transmission forl optimized paths in dynamic network. The link error rate that affects re-transmission with increased transmission error rate and therefore LER-MMP protocol selects an efficient path that has less number of long-distance hops for reliable network connectivity. The simulation result proves that LER-MMP can adapt reliable re-transmission with less link error rate and outperforms than existing protocols. The statistical result shows that LER-MMP protocol is efficient during link disconnections for concurrent communications in dynamic smart city environment.
查看更多>>摘要：By capturing the micro-crack signals of rock mass structure, the microseismic (MS) monitoring technology is a good candidate for the forecasting and early warning of dynamic disaster. In this paper, MS sensors based on fiber optic interferometric scheme are studied and fabricated, and authors develop an 8-channel highly sensitive fiber optic MS system based on space division multiplexing technology to monitor the whole process of rock mass from micro-fracture to macro-damage. Field test of the system is carried out in Hanjiang River to Weihe River Water Diversion Project. The results show that it can realize continuously monitored with high accuracy and reliability in the tunnel and obtain the characteristic of temporal-spatio-strong of MS events, which are superior to the commercialized electrical monitoring equipment. This work shows that using fiber optic interference technology to develop accelerometer for MS monitoring system is both advantageous and feasible with the character of intrinsically safe.
查看更多>>摘要：BeiDou Navigation Satellite System (BDS) has got the global service capability after the launch of the 55th BDS-3 satellite on June 23, 2020. Currently, BDS is operated based on both the second generation BDS (BDS-2, with 15 satellites transmitting triple frequency signals) and the third generation BDS (BDS-3, with 30 satellites providing services from five frequency signals). To make full use of BDS-2 + BDS-3 signals (B1I, B2I, B3I, B1C, and B2a), this paper introduces an undifferenced and uncombined Precise Point Positioning (PPP) model by using single/ dual/triple frequencies BDS-2/BDS-3 data. Results illustrate that the Root Mean Square (RMS) values of BDS-3 PPP based on new signals are better than BDS-2 (B1I + B3I), but worse than BDS-3 (B1I + B3I). Generally, triple-frequency PPP is close to that of dual-frequency PPP, but it is improved significantly in the north, east and vertical components comparing with single-frequency PPP. Compared to the positioning accuracy of GPS + BDS2 PPP, those of GPS + BDS-3 PPP are improved obviously, especially in the horizontal components. While using BDS-2 and BDS-3 together, the positioning performance of GPS + BDS-2 + BDS-3 is upgraded significantly in both horizontal and vertical directions. Moreover, the convergence time of BDS-3 (especially B1C + B2a) and BDS-2 + BDS-3 PPP are accelerated visibly comparing with that of BDS-2 PPP.
查看更多>>摘要：Product quality control of large-sized components with complex supports requires automatic and accurate 3D shape measurement. For accurate and efficient measurements of key local features (KLFs) on the mounting surface of multiple supports, we propose a flexible measurement method combining a laser tracker, a 3D scanner, and a mobile robot system. As for improving the overall measurement accuracy, we also introduce a calibration method based on a multidimensional combined collaboration target (MCCT) to establish correlation constraints between global and local calibration. Specifically, a global calibration method based on multidimensional geometric constraints provides a global measurement field. Additionally, a local calibration method derived from combination optimization model achieves accurate calibration of extrinsic parameters. We constructed the corresponding mobile robotic measurement system (MRMS) and conducted experiments. The experimental results demonstrate that the maximum and mean calibration errors are reduced from 0.045/0.0261 mm to 0.0231/ 0.0122 mm within 7 m, which features high accuracy.
查看更多>>摘要：Magnetic field sensing plays vital role in vast range of areas such as navigation, military, and biomedical sciences. In recent times, optical sensors have made great advances, resulting in the development of magnetic field sensors based on optical principles due to their non-susceptibility to electromagnetic interference. Here, a simple and inexpensive approach for sensing magnetic field, that converts the magnetic field into a mechanical translation (of the sensing element) and then change into optical signals is presented. These optical signals are speckle patterns generated using a laser beam reflected off an optically rough metal cantilever which is exposed to the magnetic field. Magnetic field is quantified by measuring the changes in the speckle pattern using the intensity correlation technique. The approach can measure the static and time varying magnetic fields. The proposed system has a resolution of 2.2 mu T and can measure magnetic fields with less than a 2% error.
查看更多>>摘要：The phase velocity matching Lamb waves are considered as an effective solution to excitation in the detection of nonlinear ultrasound early fatigue damage. In general, it is difficult to meet the phase velocity matching in real world measurement. In this paper an approach to approximate phase velocity matching early fatigue damage detection is proposed. With the third harmonic approximate phase velocity matching modes treated as excitation frequencies by the Lamb wave dispersion curve, an analysis is conducted with regard to the time-frequency diagrams of the response signals at different frequencies. The change in the third harmonic amplitude with crack growth is analyzed by Fast Fourier Transform (FFT), which leads to the results suggesting that the third harmonic amplitude declines with crack growth. Moreover, a comparison is performed in the normalized relative third order nonlinear parameters (NRTNP) of phase velocity matching and approximate phase velocity matching, with the relative deviation falling within 0.12.
查看更多>>摘要：In this study, we developed a novel DNA sensor exploiting Carbon/La3+/CuO (C/La3+/CuO) nanocomposites for the determination of isoniazid (INZ). After modification of sensor by C/La3+/CuO, the electrode showed an excellent conductivity, and carbon possesses a large specific surface area, thereby enabling a significant improvement in the sensor sensitivity. Since no DNA probe modification or chemical labeling was required in this approach, this sensor could be employed to detect INZ. The present biosensor was selectively and sensitively able to detect INZ, with a wide linear range (1.0-165.0 mu M) and a low limit of detection (0.035 mu M). The fabricated biosensor was also used to detect INZ in the real samples successfully. Good recovery values were obtained, showing the excellent analytical potential of the electrochemical biosensor based on ds-DNA/C/La3+/CuO. Moreover, electrochemical, spectroscopic and docking methods showed an effective interaction between INZ and ds-DNA.
查看更多>>摘要：A spectral-domain optical coherence tomography (SD-OCT) system with 1555 nm center wavelength is tested for stability and accuracy from the micron level to the sub-micron level. The energy centrobaric correction method is used to extract the sub-axial-resolution information as the optical path difference, i.e., the topographic height. We compared the used algorithm with the widely applied phase slope method. The stability of a point scanning OCT system in Michelson style is experimentally compared with that of a system in Fizeau style. Several simple and complicated samples are measured and compared. Finally, we compare the topographic performance of the OCT system with a commercial confocal microscope and white-light interferometer (WLI).
NSTL
Elsevier