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International Conference on Power System technology (POWERCON)

作者： Minhua Xie Lu Gao Feng Ji Chang Lin Heming Yan Junjie Lin State Key Laboratory of Advanced Transmission Technology State Grid Smart Grid Research Institute Co. Ltd Beijing China Laboratory of DC Grid Technology & Simulation State Grid Smart Grid Research Institute Co. Ltd Beijing China

In order to avoid equipment damage or valve breakdown caused by power surplus during AC system short-circuit faults in the hybrid cascaded ultra HVDC, the controllable and adaptive energy absorption device is installed parallel with the MMC converter valve. To accurately simulate the characteristics of the system and test the control and protection hardware in the loop, the small time-step real-time simulation is needed. In order to achieve the small time-step real-time simulation of the whole system including nonlinear controllable energy absorption device, a small inductor is used to separate the nonlinear network from the linear network based on equivalent transmission line method. The nonlinear subnetwork is solved using Newton-Raphson iteration method and the linear system is linearly solved. The comparison results show that the proposed method is high efficient and precise.

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Radar signal recognition based on deep residual network with attention mechanism 4

Radar signal recognition based on deep residual network with...

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4th IEEE International Conference on Electronic Information and Communication technology, ICEICT 2021

作者： Jin, Xiaolin Ma, Jing Ye, Fang College of Infomation and Communication Engineering Harbin Engineering University Harbin150001 China Key Laboratory of Advanced Marine Communication and Information Technology Ministry of Industry and Information Technology Beijing100854 China Science and Technology on Special System Simulation Laboratory Beijing100854 China

ISBN: (纸本)9781665432030

To address the problem of poor recognition success rate (RSR) of low probability of intercept (LPI) radar signals such as polyphase codes at low signal-to-noise ratio (SNR), In this paper, we propose a method of deep neural network with attention mechanism for modulation recognition of radar signals. The method first transforms the received radar signal into a two-dimensional time-frequency image(TFI), and then we obtain a binary time-frequency image by threshold segmentation，and resize TFIs through bicubic interpolation. While a deep residual network with Convolutional Block Attention Module (CBAM) is designed to recognize the radar signals. We take advantage of the attention mechanism to find the effective feature information in the noise and increase the effective information weight to further improve the recognition success rate of radar signals under low SNR. Finally, the average RSR of the method is nearly 96% for 7 signals at -6dB. © 2021 IEEE

关键词： Deep neural networks

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Research on flame classification and recognition based on object detection and similarity fusion

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The Journal of China Universities of Posts and Telecommunications 2021年第5期28卷 59-67页

作者： He Xin Zhou Junhua Liao Zhonghua Zhai Xiang Sun Siyuan School of Electronic Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China Beijing Complex Product Advanced Manufacturing Engineering Research Center Beijing Simulation CenterBeijing 100854China State Key Laboratory of Intelligent Manufacturing System Technology Beijing Institute of Electronic System EngineeringBeijing 100854China

The color, shape, and other appearance characteristics of the flame emitted by different flame engines are different. In order to make a preliminary judgment on the category of the device to which it belongs through studying exterior characteristics of the flame, this paper uses the flame of matches, lighters, and candles to simulate different types of flames. It is hoped that the flames can be located and classified by detecting the characteristics of flames using the object detection algorithm. First, different types of fire are collected for the dataset of experiments. The mmDetection toolbox is then used to build several different object detection frameworks, in which the dataset can be trained and tested. The object detection model suitable for this kind of problem is obtained through the evaluation index analysis. The model is ResNet50-based faster-region-convolutional neural network(Faster R-CNN), whose mean average-precision(mAP) is 93.6%. Besides, after clipping the detected flames through object detection, a similarity fusion algorithm is used to aggregate and classify the three types of flames. Finally, the color components are analyzed to obtain the red, green, blue(RGB) color histograms of the three flames.

关键词： flame classification object detection similarity fusion

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Vibration Shock Disturbance Modeling in the Rotating Machinery Fault Diagnosis ∶ a Generalized Mixture Gaussian Model

SSRN

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SSRN 2023年

作者： Wang, Ran Gu, Zhixin Wang, Chaoge Yu, Mingjie Han, Wentao Yu, Liang College of Logistics Engineering Shanghai Maritime University Shanghai201306 China School of Civil Aviation Northwestern Polytechnical University Xi’an710072 China State Key Laboratory of Airliner Integration Technology and Flight Simulation Shanghai200126 China

In real-world industrial environments, complex background noises are composed of various components, deviating from a simple Gaussian distribution like shock *** this work, a robust noise modeling method based on the mixture of exponential power (MoEP) distributions is developed to address this issue. To proficiently extract the fault characteristics, the signal's 2-D representation is attained via Fast-SC, both of the fault features' low-rankness and the complex noise are combined in a signal model. Then, a penalized function of the noise model is combined to further improve the performance of the method. The model is designated as the PMoEP enhanced low-rank model (PMoEP-LR). The Generalized Expectation-Maximization (GEM) algorithm is utilized to estimate the low-rank spectral correlation matrix and deduce all parameters of the PMoEP-LR model. Finally, the enhanced envelope spectrum (EES) is used to detect the defect characteristic. The efficacy of the proposed method is showcased by analyzing both simulated and real data. © 2023, The Authors. All rights reserved.

关键词： Rotating machinery

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Adaptive radar detection of subspace-based distributed target in power heterogeneous clutter

arXiv

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arXiv 2024年

作者： Xiao, Daipeng Liu, Weijian Liu, Jun Dai, Lingyan Fang, Xueli Ge, Jianjun Wuhan Electronic Information Institute Wuhan430019 China Department of Electronic Engineering and Information Science University of Science and Technology of China Hefei230027 China Key Laboratory of Complex Aviation Simulation System Beijing100076 China Information Science Academy China Electronics Technology Group Corporation Beijing100041 China

This paper investigates the problem of adaptive detection of distributed targets in power heterogeneous clutter. In the considered scenario, all the data share the identical structure of clutter covariance matrix, but with varying and unknown power mismatches. To address this problem, we iteratively estimate all the unknowns, including the coordinate matrix of the target, the clutter covariance matrix, and the corresponding power mismatches, and propose three detectors based on the generalized likelihood ratio test (GLRT), Rao and the Wald tests. The results from simulated and real data both illustrate that the detectors based on GLRT and Rao test have higher probabilities of detection (PDs) than the existing competitors. Among them, the Rao test-based detector exhibits the best overall detection performance. We also analyze the impact of the target extended dimensions, the signal subspace dimensions, and the number of training samples on the detection performance. Furthermore, simulation experiments also demonstrate that the proposed detectors have a constant false alarm rate (CFAR) property for the structure of clutter covariance matrix. © 2024, CC BY.

关键词： Radar clutter

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Aging Performance and Mechanism of Carbon Fiber-Reinforced Bismaleamide Composites Under Natural Aging in Marine Environments

SSRN

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SSRN 2024年

作者： Zhu, Longyu Bi, Ran Li, Weidong Obara, Evance Cai, Peipei Huang, Shuaijun Luo, Chuyang Bao, Jianwen Center for Civil Aviation Composites Donghua University Shanghai201620 China National Key Laboratory of Advanced Composites AVIC Composite Technology Center AVIC Composite Corporation Ltd. Beijing101300 China Luoyang Optoelectro Technology Development Center Luoyang471009 China

The aging performance and mechanisms of carbon fiber reinforced bismaleimide composites under natural aging in marine environments are comprehensively investigated in this study. The prepared samples were exposed to aging under natural sunlight testing for one and a half years at the sea shores. Quasi-static tests were performed to evaluate the tensile, compressive, and in-plane shear strengths of the unaged and aged specimens. The fracture morphologies were characterized in order to reveal the aging mechanisms. The results show that the aging and decomposition of resin led to the reduction of mechanical properties. The 0° tensile, 0° compressive, 90° tensile and in-plane shear properties compared with unaged samples decreased by 4.6 %, 24.3 %, 24.7 % and 8.5 %, respectively. The microscopic, spectroscopic, and gravimetric analyses indicated that aging process mainly occurred on the surface of the specimen;the matrix degraded due to water hydrolysis, and the heat resistance of the samples decreased after aging. It was concluded that the autoclave molding method tightly combines the fibers with resin, making it more difficult for moisture to diffuse into the interior of the specimen. Based on the findings of this study, valuable insights can be made to guide the design, manufacture, and long-term durability of carbon fiber-reinforced bismaleimide composites in marine applications. © 2024, The Authors. All rights reserved.

关键词： Shear strength

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Electronic Correlations and Hund’s Rule Coupling in Trilayer Nickelate La4Ni3O10

arXiv

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arXiv 2024年

作者： Huo, Zihao Zhang, Peng Zhang, Zihan Duan, Defang Cui, Tian Key Laboratory of Material Simulation Methods & Software of Ministry of Education State Key Laboratory of Superhard Materials College of Physics Jilin University Changchun130012 China MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter Shaanxi Province Key Laboratory of Advanced Functional Materials and Mesoscopic Physics School of Physics Xi’an Jiaotong University Xi’an710049 China Institute of High Pressure Physics School of Physical Science and Technology Ningbo University Ningbo315211 China

Trilayer Ruddlesden–Popper phase La4Ni3O10 has been observed with Tc of ~ 30 K at high pressure in recent experiment, which further expanded the family of nickelate superconductors. In this study, we explored the effects of electronic correlations in La4Ni3O10 using density function theory plus dynamical mean–field theory at ambient and high pressures. Our derived spectral functions and Fermi surface of ambient pressure phase are nicely consistent with the experimental results by angle–resolved photoemission spectroscopy, which emphasized the importance of electronic correlations in La4Ni3O10. We also found the electronic correlations in pressured La4Ni3O10 are both orbital–dependent and layer–dependent due to the presence of Hund’s rule coupling. There is a competition between the Hund’s rule coupling and the crystal–field splitting, and therefore the Ni–O layers with weaker crystal-field splitting energy would have stronger electronic correlations. Copyright © 2024, The Authors. All rights reserved.

关键词： Photoacoustic spectroscopy

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Stability Control and Trajectory Optimization of Tail-Sitter VTOL UAV Takeoff / Landing Incorporating Bionic technology

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Transactions of Nanjing University of Aeronautics and Astronautics 2024年第3期41卷 263-277页

作者： Qi, Hao Li, Qingyang Wu, Jiayue Peng, Yiming Nie, Hong Wei, Xiaohui State Key Laboratory of Mechanics and Control for Aerospace Structures Nanjing University of Aeronautics and Astronautics Nanjing210016 China Key Laboratory of Fundamental Science for National Defense Advanced Design Technology of Flight Vehicle Nanjing University of Aeronautics and Astronautics Nanjing210016 China China Aviation Power Plant Research Institute Zhuzhou412002 China School of Automation Science and Electrical Engineering Beihang University Beijing100191 China

The tail-sitter vertical takeoff / landing(VTOL)unmanned aerial vehicle(UAV)exhibits poor stability and limited compatibility with traditional landing gears. To address the aforementioned issues, a novel landing gear incorporating free-tail technology is proposed. The landing gear adopts a tandem multi-stage structure, which can ensure the length of the tail force arm in cruise condition while lowering the fuselage altitude. Furthermore, the dynamic landing process is regulated through the employment of virtual centroid force distribution techniques, streamlining the control process and facilitating seamless trajectory optimization during mode transition. Based on the single-point dataset of the cat center point, a neural network is used to train the landing gear control, which makes the landing gear adaptive takeoff and landing speed and accuracy effectively improved. Subsequently, multi-objective optimization and similarity conversion are executed in conjunction with parameter requirements of different modes of the UAV, effectively enhancing landing adaptability and stability of the tail-sitter VTOL UAV. © 2024 Nanjing University of Aeronautics an Astronautics. All rights reserved.

关键词： Drones

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DISCRIMINATION METHOD OF HVDC COMMUTATION FAILURE BASED ON VALVE VOLTAGE AND VALVE CURRENT

DISCRIMINATION METHOD OF HVDC COMMUTATION FAILURE BASED ON V...

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2021 Annual Meeting of CSEE Study Committee of HVDC and Power Electronics, HVDC 2021

作者： Fan, Zheng Zhu, Lin Wei, Xiaoguang Liu, Dong State Key Laboratory of Advanced Power Transmission Technology Global Energy Interconnection Research Institute Co. Ltd. Beijing China Beijing Key Laboratory of Dc Grid Technology and Simulation Global Energy Interconnection Research Institute Co. Ltd. Beijing China

ISBN: (纸本)9781839537035

Commutation failure is one of the most common faults on the inverter side of HVDC transmission system. Rapid and accurate discrimination of commutation failure is the premise of resisting commutation failure. In this paper, a method for discriminating HVDC commutation failure based on valve voltage and valve current is proposed. According to the process and development of commutation failure, combined with the two waveform information of valve voltage and valve current, the most direct information characteristics of commutation failure are extracted for discrimination. Compared with the discrimination method of single use of converter valve voltage or converter valve current, this method not only accurately discriminates the commutation failure, but also improves the discrimination speed and shortens the discrimination time. Taking CIGRE HVDC benchmark model as simulation example, the logic module of HVDC commutation failure discrimination method based on valve voltage and valve current is built in PSCAD/EMTDC to verify the effectiveness of the proposed method. © 2021 IET Conference Proceedings. All rights reserved.

关键词： Logic devices

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Composition-dependent micro-structure and photocatalytic performance of g-C_(3)N_(4) quantum dots@SnS2 heterojunction

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Nano Research 2021年第11期14卷 4188-4196页

作者： Sheng-Qi Guo Haijun Zhang Zhenzhong Hu Mengmeng Zhen Bo Yang Boxiong Shen Fan Dong Tianjin Key Laboratory of Clean Energy and Pollutant Control School of Energy and Environmental EngineeringHebei University of TechnologyTianjin300401China Center for Aircraft Fire and Emergency Department of Safety EngineeringCivil Aviation University of ChinaTianjin300300China Yangtze Delta Region Institute(Huzhou) &Institute of Fundamental and Frontier SciencesUniversity of Electronic Science and Technology of ChinaHuzhou313001China Institute of Advanced Technology University of Science and Technology of ChinaHefei230088China

Semiconductor combination is one of the most common strategies to obtain high-efficiency photocatalysts;however, the effect mechanism of composition ratio on micro-structure and photocatalytic activity is remaining unclear. In this study, a case of g-C_(3)N_(4) quantum dots@SnS_(2) (CNQDn@SnS_(2)) heterojunction with different ratio of CNQD is used to uncover the origin of optimum and excess composition for photocatalysts. Research on the functional mechanism of the optimum composition shows that 0.8 wt.% CNQD are completely attached to the non-(001) facets of SnS_(2), which benefits the formation of type-II heterojunction, resulting in an optimal pollutant degradation and mineralization efficiency. For the excess composition, both experiments and theoretical calculations confirm that excess CNQD (the part exceeding of 0.8 wt.%) located on the (001) facet of SnS_(2), leading to the type-I band alignment of this heterojunction, which severely restricts the separation of photo-induced charge carriers, and thus reduces their lifetime. This work makes the functional mechanism of composition ratio on micro-structure and photocatalytic activity clearer. Related research results provide a new insight into semiconductor combination study and take an important step toward the rational design of highly active photocatalysts.

关键词： heterojunction semiconductor combination composition ratio photocatalyst functional mechanism

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