查看更多>>摘要：? 2022 Elsevier LtdA novel intelligent scheme using the wavelet packet transform (WPT) and extreme learning machine (ELM) is proposed for fault event classification in the grid-connected photovoltaic (PV) system. The WPT is applied for preprocessing the cycle of the post-fault voltage samples at the point of common coupling (PCC) measurement to get the normalized logarithmic energy entropy (NLEE). The ELM is applied to classify the different fault cases. To enhance the performance of ELM for faults classification, a hybrid optimization mechanism based on an equilibrium optimization algorithm (EOA) is proposed to optimize the selection of input feature subset and the number of ELM hidden nodes. Furthermore, to evaluate the proposed scheme's performance, a comprehensive evaluation was conducted on a 250 kW grid-connected photovoltaic system. From simulation, the classification accuracy is recorded to be 100% under the no-noise condition, while at the signal-to-noise ratios (SNR) of 30, 35, and 40 dB, the accuracies are 98.96, 99.04, and 99.36%, respectively. Moreover, the practical performance of the EOA-ELM classifier is validated using IEEE 34 bus system. The obtained results validate the effectiveness of the proposed scheme in terms of robustness against measurement noise, computation time, and detection accuracy.
查看更多>>摘要：? 2022 Elsevier LtdThe leakage detection method based on fiber Bragg grating (FBG) sensing technology is an effective method to determine leakage points in diaphragm wall joints. However, the detection method involves cumbersome data processing which causes manual data processing errors and costs time. In this work, an intelligent leakage detection method for diaphragm wall joints based on FBG sensing signals was proposed. Firstly, a field study of the leakage detection method was carried out in a new urban expressway in Hohhot, Inner Mongolia, China. The field monitoring data were compared with test data, and characteristics of the FBG wavelength curve and mechanism of leakage detection were analyzed. In addition, four intelligent detection models including a convolutional neural network, support vector machine (SVM), decision tree, and random forest were established. Results showed that the proposed method is effective and efficient in identifying and locating leakage through diaphragm walls.
查看更多>>摘要：? 2022 Elsevier LtdKinematic chains are essential elements configurable in different topologies according to the requirements of industry. Their main components are the rotating machines and mechanical parts in which diverse faults can appear. Nowadays, infrared imaging analysis has gained attention for monitoring kinematic chains, however, the approaches for detecting and classifying faults still can be improved. Therefore, this work presents a methodology that uses a low-cost infrared measurement system and combines adequate techniques, such as infrared images preprocessing and segmenting, extraction of statistical indicators, generation of a high-dimensional matrix of features, features reduction, and categorization, for accurately detecting and classifying a wide variety of fault conditions in kinematic chains. This approach was applied to a configurable kinematic chain under the following conditions: healthy motor, misalignment, unbalance, one and two broken rotor bars, bearing faults on the outer race, healthy gearbox, and gearbox wearing. The obtained results validate the effectiveness of the proposed methodology.
查看更多>>摘要：? 2022 Elsevier LtdThe performance of the gravimetric geoid models is usually evaluated by comparison of geoid heights with the GNSS/levelling derived geoid. But the GNSS/levelling network can be infected by significant systematic biases and random errors, especially in large and uneven areas. This contribution addresses the challenging problem of the corrector surface development along with the elimination of biases. To this end, fitting an appropriate geometric surface to the GNSS/levelling geoid heights is required, which is accomplished by applying the least squares B-spline approximation theory to the GNSS/levelling data. In addition, the 3D affine transformation is used to detect systematic effects of the GNSS/levelling network compared to a global geoid model. This strategy is applied to the adjustment of the Iranian GNSS/levelling network. A significant tilt is observed across the country ranging from ?0.35 m to 0.04 m. The entire study area is divided into four zones and the corrector surfaces are obtained in each zone. The accuracy of three global geoid models, EGM2008, EIGEN-6C4 and SGG-UGM-1, along with that of the Iranian regional geoid model IRG2016, are then investigated based on the raw GNSS/levelling heights and the corrector surfaces. The evaluations show the reliable results regarding the corrector surfaces against the raw data set. All geoid models show their maximum RMSE values of discrepancies in the mountainous zones and their minimum RMSEs in the zones having lower variety in topography. This indicates that the irregular topographies are not well detected by the global models over the study area.
查看更多>>摘要：? 2022 Elsevier LtdWhen the Global Navigation Satellite System (GNSS) is used for positioning under challenging environments, including the natural occlusions and man-made buildings, the signals are easily reflected, diffracted, and even blocked. A stochastic model that conforms to reality is the prerequisite for obtaining high-precision and high-reliability positioning results. However, existing stochastic models which use indicators such as elevation angle and carrier-to-noise ratio cannot reflect the actual situation of the station very well sometimes. Therefore, in this study, in addition to the accuracy of observations, we also consider the impact of the spatial distribution of satellites on positioning accuracy, i.e., position dilution of precision (PDOP). By combining with traditional weighting schemes, the PDOP is considered stochastic modeling. Specifically, different from the previous studies that use PDOP to determine the variance factors between different systems, a new approach is proposed to quantify the contribution of each satellite to PDOP so that the observation weight of each satellite in the system can be appropriately adjusted. The new approach highlights the satellites that contribute much to PDOP and increases the weight of these satellites. Both real static and kinematic data have been tested. The results show that the proposed method is helpful under challenging environments such as high occlusion environments. In civil navigation, the accuracy and reliability of code positioning are improved.
查看更多>>摘要：? 2022 The AuthorsNanoparticles can be used in numerous therapeutic procedures, including controlled drug delivery and release, thermal therapy, and photo- and sonodynamic therapy. However, such approaches remain limited due to difficulties associated with accurately controlling their therapeutic efficiency and localized consequences. Thus, we propose the use of ultrasound transmission tomography (UTT) measurements following ultrasonic heating when using nanomaterials as mediators. We test various nanomaterials doped to agar tissue-mimicking phantoms to study how they affect the UTT imaging through improving the contrast. Simultaneously, we investigate the suitability of these mediators in relation to the process of ultrasonic heating under the guidance of UTT. The results show that UTT is sensitive to the presence of magnetic nanoparticle-based nanomaterials and induced temperature rises. The combination of an imaging modality based on generally safe and well-known ultrasound-based imaging and the use of nanomaterials as mediators represents our proposal for a new theranostic approach.
查看更多>>摘要：? 2022 Elsevier LtdThe measurement system of contact spherical actuator has the disadvantages of large friction resistance and poor rotor positioning accuracy. The structure or calculation of non-contact attitude measurement system is complicated. In order to solve the above problems, a multi-to-one wireless power transmission (WPT) spherical actuator attitude measurement method is proposed. The model of mutual inductance(MI) is built. This method effectively shortens the time of finite element analysis(FEA). Three motion states (spin, yaw and tilt) of actuator rotor are analyzed by using this measurement method. Compared with the micro electro mechanical system (MEMS) and fast complementary filter (FCF), the initial attitude error of this method is about 50% of that of the other two methods. Compared with MEMS method, the average angle error of WPT method is reduced by 35%. Experimental results show that this method has good real-time performance and repeatability.
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