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    Fault Detection in Power Distribution Systems Based on Gated Recurrent Attention Network
    CHEN Haolan, JIN Bingying, LIU Yadong, QIAN Qinglin, WANG Peng, CHEN Yanxia, YU Xijuan, YAN Yingjie
    Journal of Shanghai Jiao Tong University    2024, 58 (3): 295-303.   DOI: 10.16183/j.cnki.jsjtu.2022.091
    Abstract171)   HTML10)    PDF(pc) (2938KB)(2188)       Save

    To improve fault identification accuracy in power distribution systems, a model named gated recurrent attention network is proposed. First, a higher weight is put on the key cycles of fault phase based on the attention mechanism, making the model focus more on these key messages by weight assignment. Then, the gated recurrent network is adopted, which controls the memory transmission with gate signal and constructs the relationship between input waveform and probability of events at different stages to process the waveform sequence, thereby improving recognition accuracy. Experiments based on both simulation and field data show that the proposed method, under the small-sample-learning condition, is much better than other commonly-used classification models, such as support vector machine, gradient boosting decision tree, and convolutional neural network, providing new insights into fault identification technology in power distribution systems.

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    Challenges of Distributed Green Energy Carbon Trading Mechanism and Carbon Data Management
    LI Xingzhi, HAN Bei, LI Guojie, WANG Keyou, XU Jin
    Journal of Shanghai Jiao Tong University    2022, 56 (8): 977-993.   DOI: 10.16183/j.cnki.jsjtu.2021.450
    Abstract1057)   HTML893)    PDF(pc) (2604KB)(1233)       Save

    To achieve the double carbon goal of “carbon peaking and carbon neutrality”, the construction of the power system which is based on the green energy needs to be accelerated. With the growth of the system scale, the distributed green energy carbon trading mechanism and the carbon data management technology based on the blockchain technology can effectively encourage the development of green energy and become effective means for the implementation of low-carbon electricity. The accurate and real-time carbon emission calculation will further provide data support for the accuracy and security of carbon trading information. First, the current research status of green certificate trading and carbon asset management is introduced. Next, the adaptability analysis of the key technologies of the blockchain technology in the four directions of green electricity traceability, green certificate trading, carbon trading, and joint market of green certificate and carbon assets is performed. Afterwords, the specific mathematical models of carbon emission calculation is studied, and the data availability of carbon source traceability methods applicable to the blockchain architecture are discussed. Finally, some suggestions for the future development of carbon emission flow analysis are proposed.

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    Multi-Objective Optimization Strategy of Trajectory Planning for Unmanned Aerial Vehicles Considering Constraints of Safe Flight Corridors
    HUANG Yuhao, HAN Chao, ZHAO Minghui, DU Qiankun, WANG Shigang
    Journal of Shanghai Jiao Tong University    2022, 56 (8): 1024-1033.   DOI: 10.16183/j.cnki.jsjtu.2021.154
    Abstract855)   HTML41)    PDF(pc) (5684KB)(1131)       Save

    Aimed at the problem of generating a smooth, safe, and dynamically feasible continuous-time trajectory for unmanned aerial vehicles (UAV) in complex environments, a trajectory planning algorithm is proposed to minimize a multi-objective function based on safe flight corridors. The safe flight corridor represented by a collection of convex polyhedra is built based on the initial discrete waypoints generated by the improved rapidly-exploring random tree(RRT), namely the RRT* algorithm. The safety objective function is established according to the constraints of limiting the trajectory inside safe flight corridors. In combination with the flight smoothness, dynamic characteristics, and time performance, a multi-objective function is built. The gradient-based convex optimization algorithm is used to derive the continuous-time trajectory expressed as a piece-wise polynomial by optimizing the position, velocity, acceleration of waypoints, and time allocation. The effectiveness and performance of the proposed algorithm is tested and compared under complex environments such as the coal mine. The test results demonstrate that the proposed algorithm has a better comprehensive performance in comparison with existing algorithms.

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    Circulation Control of Airfoil Aerodynamic Force Under Ground Effect of Wavy Wall
    LIU Hao, SUN Jianhong, SUN Zhi, TAO Yang, WANG Dechen, LIU Guangyuan
    Journal of Shanghai Jiao Tong University    2022, 56 (8): 1101-1110.   DOI: 10.16183/j.cnki.jsjtu.2021.384
    Abstract653)   HTML34)    PDF(pc) (3280KB)(964)       Save

    The interaction of airflow and sea waves seriously affects the flight stability and cruising safety of ground effect vehicles. The influence of different sea states and different angles of attack were analyzed numerically on the aerodynamic characteristics of the airfoil under ground effect of wavy wall. The influence of the constant blowing and periodic blowing methods was further studied on the aerodynamic force of the airfoil under ground effect. The simulation results show that the lift coefficient of the airfoil changes periodically with the wave under the wavy ground wall. The amplitude of the lift coefficient fluctuation is larger with the increasing of wave height and angle of attack, or the decreasing of wavelength. Applying the circulation control method for periodic blowing in the same period as the relative motion of the waves can effectively weaken the fluctuation of the airfoil lift coefficient under wavy sea conditions and improve the flight stability and safety of ground effect vehicles.

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    Ultra-Short-Term Load Forecasting of Electric Vehicle Charging Stations Based on Ensemble Learning
    LI Hengjie, ZHU Jianghao, FU Xiaofei, FANG Chen, LIANG Daming, ZHOU Yun
    Journal of Shanghai Jiao Tong University    2022, 56 (8): 1004-1013.   DOI: 10.16183/j.cnki.jsjtu.2021.486
    Abstract1194)   HTML397)    PDF(pc) (3182KB)(872)       Save

    Accurate electric vehicle load forecasting is the basis for maintaining the safe and economical operation of charging stations, and for supporting the planning and decision-making of new and expanded charging infrastructure. In order to improve the accuracy of the ultra-short-term load forecasting of charging stations, an ultra-short-term load forecasting method based on ensemble learning is proposed. First, aimed at the prediction accuracy and the response speed, the light gradient boosting machine (LightGBM) framework is utilized to build several basic regressors. Next, the basic regressors are integrated by using the adaptive boosting (Adaboost) method. Finally, by using hyperparameter adjustment and optimization, a dual-system for ultra-short-term load forecasting of charging stations named energy ensemble boosting-light gradient boosting machine (EEB-LGBM) is generated. The analysis of the numerical examples shows that the proposed model has a higher accuracy than the back propagation neural network (BPNN), convolutional neural networks-long short term memory (CNN-LSTM), autoregressive integrated moving average (ARIMA), and other load forecasting methods, which can greatly reduce the training time and the computing power requirements of the training platform.

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    An Admittance Reshaping Strategy of Three-Phase LCL Grid-Connected Inverter Based on Modified Passive Control
    WANG Han, ZHANG Jianwen, SHI Gang, ZHU Miao, CAI Xu
    Journal of Shanghai Jiao Tong University    2023, 57 (9): 1105-1113.   DOI: 10.16183/j.cnki.jsjtu.2022.120
    Abstract316)   HTML34)    PDF(pc) (3313KB)(864)       Save

    The passivity-based control (PBC) based on energy function has been studied for grid-connected converters to achieve a better performance. However, traditional PBC method relies on the accurate mathematical model of grid-connected inverter. In previous studies on PBC, the effect of digital control delay is rarely considered and the stability under grid impedance uncertainties is not discussed, especially in the capacitive grid or complex weak grid. To address these issues, this paper proposes an improved PBC method to reshape the output admittance for LCL-filtered grid-connected inverters. The system passive region is expanded up to the Nyquist frequency by adding a capacitor current feedback loop which can achieve active damping control of LCL resonant frequency under the wide range of grid impedance changes. The parameter design method is also presented for the proposed PBC control. To verify the correctness of the theoretical analysis, both simulation and experiments are conducted on a 3 kW grid-connected inverter prototype.

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    A Dual-System Reinforcement Learning Method for Flexible Job Shop Dynamic Scheduling
    LIU Yahui, SHEN Xingwang, GU Xinghai, PENG Tao, BAO Jinsong, ZHANG Dan
    Journal of Shanghai Jiao Tong University    2022, 56 (9): 1262-1275.   DOI: 10.16183/j.cnki.jsjtu.2021.215
    Abstract911)   HTML71)    PDF(pc) (4009KB)(823)       Save

    In the production process of aerospace structural parts, there coexist batch production tasks and research and development (R&D) tasks. Personalized small-batch R&D and production tasks lead to frequent emergency insertion orders. In order to ensure that the task is completed on schedule and to solve the flexible job shop dynamic scheduling problem, this paper takes minimization of equipment average load and total completion time as optimization goals, and proposes a dual-loop deep Q network (DL-DQN) method driven by a perception-cognition dual system. Based on the knowledge graph, the perception system realizes the representation of workshop knowledge and the generation of multi-dimensional information matrix. The cognitive system abstracts the scheduling process into two stages: resource allocation agent and process sequencing agent, corresponding to two optimization goals respectively. The workshop status matrix is designed to describe the problems and constraints. In scheduling decision, action instructions are introduced step by step. Finally, the reward function is designed to realize the evaluation of resource allocation decision and process sequence decision. Application of the proposed method in the aerospace shell processing of an aerospace institute and comparative analysis of different algorithms verify the superiority of the proposed method.

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    Optimal Planning of Power Systems with Flexible Resources for High Penetrated Renewable Energy Accommodation
    GUO Yongtao, XIANG Yue, LIU Junyong
    Journal of Shanghai Jiao Tong University    2023, 57 (9): 1146-1155.   DOI: 10.16183/j.cnki.jsjtu.2022.269
    Abstract201)   HTML11)    PDF(pc) (2433KB)(812)       Save

    High penetrated renewable energy has brought great challenges to the flexibility of the power system due to its volatility and intermittency. To improve the capacity of renewable energy accommodation, the flexibility reformation of thermal power units, the construction of gas-fired units, and the electrical energy storage installation are considered as effective solutions. Thus, an optimization model for power system planning scheme considering multi-type flexible resources with their different output characteristics is established. The simulation results on a modified IEEE 24-bus power system and 12-node natural gas system demonstrate the effectiveness of the proposed model. In addition, the applicability of different flexible resource planning schemes is comprehensively evaluated from the perspectives of economy, accommodation capacity, and carbon reduction, so as to meet the different planning goals.

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    Differentiated Allocation Model of Renewable Energy Green Certificates for New-Type Power System
    ZHANG Shuo, LI Wei, LI Yingzi, LIU Qiang, ZENG Ming
    Journal of Shanghai Jiao Tong University    2022, 56 (12): 1561-1571.   DOI: 10.16183/j.cnki.jsjtu.2022.150
    Abstract1379)   HTML816)    PDF(pc) (1436KB)(797)       Save

    In order to achieve China’s “30·60” decarbonization goal, the green and low-carbon transformation of the energy system is the fundamental support; the construction of new-type power system is the key step, and the green certificate is the important voucher to reflect the green value of renewable energy. Currently, the distribution mechanism of green certificates in China is oversimplified, which neither effectively measures the variability of green values generated by different types of renewable energy, nor balances the coordinated development of renewable energy. Therefore, to differentiate the exchange mechanism of green certificates by different types of renewable energy power in this paper, an evaluation index system is established, which describes the difference between green certificates, considering the comprehensive value of renewable energy, and an evaluation model is built with the criteria importance by using the intercriteria correlation (CRITIC) method, the entropy weight method, and the technique for order preference by similarity to an ideal solution (TOPSIS) method. Under the development scenario of peaking carbon emissions before 2030, the impact of the differentiated distribution model on the green incomes of centralized photovoltaic distributed photovoltaic power, onshore wind power, and offshore wind power is analyzed. Moreover, the development plan of renewable energy is modified in consideration of the effect of the differentiated distribution model, and policy suggestions on green certificates are proposed accordingly. The results show that the differentiated distribution model of green certificates is practical to provide corresponding decision-making support to the construction and improvement of green certificates trading mechanism in China.

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    Real-Time Calculation of Carbon Emissions in County-Level Administrative Regions Based on ‘Energy Brain’
    CHEN Yun, SHEN Hao, WANG Jiayu, ZHAO Wenkai, PAN Zhijun, WANG Xiaohui, XIAO Yinjing
    Journal of Shanghai Jiao Tong University    2022, 56 (9): 1111-1117.   DOI: 10.16183/j.cnki.jsjtu.2021.364
    Abstract1054)   HTML782)    PDF(pc) (851KB)(794)       Save

    Existing calculation methods of carbon emission cannot well meet the needs of gradual refinement and real-time of carbon emission regions. In order to ensure the real-time and accuracy of carbon emissions responsibility allocation, a real-time calculation method of carbon emissions in urban regions is proposed. The improved K-means clustering algorithm is used to cluster and combine the operating periods and operating scenarios of the urban area energy load,so as to obtain the typical carbon emission characteristics. The regional unit electricity carbon emission is proposed as a carbon emission indicator, the operating period and scenario are classified, and the unit electricity carbon emission and the total carbon emission of urban regions for each cluster are calculated. The proposed algorithm is verified based on part of the historical data of energy consumption in the energy brain of a certain region in eastern China. The results show that the clustering method and carbon emission indicators can effectively calculate the total carbon emission of urban regions in real-time.

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    Mechanism of Forced Subsynchronous Oscillation of Large-Scale Photovoltaic Power Generation Grid-Connected System with Series Compensation Tranmmission Lines
    LIN Yong, KANG Jiale, YU Hao, CHEN Honglin, YANG Yanji, CHEN Wuhui
    Journal of Shanghai Jiao Tong University    2022, 56 (9): 1118-1127.   DOI: 10.16183/j.cnki.jsjtu.2021.415
    Abstract722)   HTML132)    PDF(pc) (1463KB)(785)       Save

    There exists the subsynchronous oscillation (SSO) instability risk in large-scale photovoltaic(PV) grid-connected systems with series compensation, which is generally explained by the negative damped oscillation theory. In this paper, the inter-photovoltaic harmonics due to maximum power point tracking (MPPT) control are used as the disturbance source and the large-scale PV grid-connected system with series compensation as the forced system. The forced oscillation theory is used to reveal the SSO mechanism of PV power generation based on the interaction between the perturbed MPPT and the series compensation grid-connected system, and verified in the PSCAD/EMTDC simulation platform. The results show that the perturbed MPPT-based PV inverter outputs interharmonic currents to the system due to the modulation coupling on the AC-DC side, which may lead to serious forced SSO problems when the interharmonic frequency is close to the frequency of inherent weakly damped mode of the system, causing a shock to the system stability. The simulation results verify the correctness of the proposed theory.

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    Inertial Control Strategy for Wind Farm with Distributed Energy Storage System Based on Model Predictive Control
    SHEN Yangwu, SONG Xingrong, LUO Ziren, SHEN Feifan, HUANG Sheng
    Journal of Shanghai Jiao Tong University    2022, 56 (10): 1285-1293.   DOI: 10.16183/j.cnki.jsjtu.2022.134
    Abstract941)   HTML1099)    PDF(pc) (1641KB)(776)       Save

    Distributed energy storage (DES) wind turbine is an effective means to solve the problem of system frequency stability caused by large-scale wind power connection. In this paper, an inertial control method for DES wind farms based on model predictive control (MPC) is proposed.First, the linearized prediction model of the DES wind farm is established. Then, on this basis, in combination with the control framework of MPC, an optimization model and strategy of MPC inertial control are proposed considering the cost of energy storage loss and the balanced change of wind turbine rotor speed,in order to achieve the balanced change of wind turbine rotor speed during inertia control. The simulation results show that the proposed control strategy can effectively coordinate the active power output of the wind power generation unit and the energy storage system unit in the DES wind turbine, reduce the cost of charging and discharging loss of the energy storage system, and ensure that the rotational speed of all wind turbines in the wind farm tends to be average during the inertial control period, avoiding the problem of wind turbines exiting frequency regulation due to excessive reduction of the rotational speed of wind turbines. The inertial control strategy of the DES wind farm is beneficial to improve the frequency stability of the power grid, which is of great significance to ensure the safe operation of the power grid.

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    Real-Time Detection of Insulator Drop String Based on UAV Aerial Photography
    LI Dengpan, REN Xiaoming, YAN Nannan
    Journal of Shanghai Jiao Tong University    2022, 56 (8): 994-1003.   DOI: 10.16183/j.cnki.jsjtu.2021.416
    Abstract779)   HTML397)    PDF(pc) (28565KB)(774)       Save

    It is of great significance for unmanned aerial vehicle(UAV) to replace manual inspection of power insulators. Aimed at the problem of limited computing power and storage resources of the UAV, an improved real-time target detection algorithm suitable for insulator drop string failure detection is proposed. Based on the YOLOv5s detection network, first, the PANet networks in neck are replaced with bi-directional feature pyramid network(BiFPN) to improve the feature fusion ability. Next, DIoU is used to optimize the loss function to optimize the model. The channel pruning and fine tuning of the γ coefficient generally improve the accuracy, speed, and deployment ability of the detection network. Finally, the image is enhanced at the network output to improve the availability of the algorithm. The proposed algorithm is tested under a specially expanded insulator fault data set. The results show that compared with the original YOLOv5s algorithm, the average accuracy of the proposed algorithm is improved by 3.91%, the detection speed is improved by 25.6%, and the model volume is reduced by 59.1%.

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    An LC Inverter Based on Novel Dual-Loop Control
    LI Shuang, SHI Jianqiang
    Journal of Shanghai Jiao Tong University    2022, 56 (9): 1139-1147.   DOI: 10.16183/j.cnki.jsjtu.2021.275
    Abstract938)   HTML129)    PDF(pc) (1553KB)(754)       Save

    To improve the voltage tracking and anti-disturbance performance of the LC inverter, a novel voltage-current dual-loop control strategy is proposed. First, the voltage loop is tuned to first-order inertia link by zero-pole cancellation based on virtual resistance, which restrains the overshoot during voltage tracking. Next, the hypo-time-optimal current-loop is adopted to enhance the response speed of the current loop, which suppresses the sudden change of transient voltage. Finally, the cause of overshoot during the voltage recovery period is analyzed and the overshoot is eliminated by the adaptive integrator initial value, which modifies the voltage waveform distortion under loading disturbance. Based on the traditional double-loop control, the voltage loop and the current loop are improved respectively by the proposed novel control strategy, which overcomes the shortcomings of step response and anti-load disturbance performance. The feasibility and effectiveness of this method are validated through simulations on MATLAB/Simulink.

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    Experiment on Wedge-Shaped Latticework Channel Cooling Applied in Aero Engine Gas Turbine Blade Trailing Edge
    XIAO Kehua, LUO Jiahao, RAO Yu
    Journal of Shanghai Jiao Tong University    2022, 56 (8): 1034-1042.   DOI: 10.16183/j.cnki.jsjtu.2021.162
    Abstract693)   HTML33)    PDF(pc) (20093KB)(738)       Save

    In order to study the flow and heat transfer performance of wedge-shaped latticework channels in the turbine blade trailing edge, this paper conducted an experimental study by employing the transient liquid crystal (TLC) technique to investigate the local heat transfer characteristics of the upper and lower main surfaces and applying the pressure scanning valve to mesure the pressure loss of the channels at different Reynolds numbers. The experiment shows that there is a significant difference between the upper and lower main surfaces under the turning flow configuration condition at the trailing edge section. The average Nusselt number of the lower main surface is over 30% higher than that of the upper main surface. In heat transfer coefficient, the wedge-shaped latticework channel is over 46% higher than that of the needle rib channel. There is a strong mass exchange at the interface between the upper and lower channels of the latticework channel. The intermittent high heat transfer areas on the upper and lower main surfaces are corresponding to the interface. As the inlet Reynolds number increases, the channel pressure drop increases rapidly. The pressure drop of the wedge-shaped latticework channel is 5 to 7 times that of the needle ribs, but the heat transfer area of latticework channel is 107.4% higher than the needle ribs channel, and the overall thermal performance of the wedge-shaped latticework channel is still approximately 66% higher than that of the needle ribs channel.

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    Frequency Control Strategy for Interconnected Power Systems with Time Delay Considering Optimal Energy Storage Regulation
    FU Yang, DING Zhiyin, MI Yang
    Journal of Shanghai Jiao Tong University    2022, 56 (9): 1128-1138.   DOI: 10.16183/j.cnki.jsjtu.2022.145
    Abstract795)   HTML128)    PDF(pc) (3139KB)(709)       Save

    Aimed at the problem of large frequency deviation caused by the source load uncertainty and the communication delay in the interconnected power system, a frequency control strategy for interconnected power systems with time-delay considering energy storage regulation is proposed. An interconnected power grid model with time delay which includes a steam turbine generator, a wind turbine generator, and energy storage equipment is established. According to the area control error (ACE), the energy storage device coordinates the steam turbine generator to participate in the frequency control, and the modified particle swarm optimization (MPSO) algorithm is used to optimize the proportional integral derivative (PID) load frequency controller to realize the secondary frequency adjustment, which improves the frequency stability of the load frequency control (LFC) system in a certain time-delay interval. A fractional order PID (FOPID) controller is designed for the energy storage device to adjust the output power and smooth the source load fluctuation. The frequency control performance of the energy storage system is improved to further control the frequency deviation of the interconnected power system. Different working conditions are compared and analyzed on the MATLAB/Simulink platform to verify the effectiveness of the proposed frequency control strategy.

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    Linear Parameter-Varying Integrated Control Law Design for a Hypersonic Vehicle
    YANG Shu, QIAN Yunxiao, YANG Ting
    Journal of Shanghai Jiao Tong University    2022, 56 (11): 1427-1437.   DOI: 10.16183/j.cnki.jsjtu.2022.190
    Abstract962)   HTML352)    PDF(pc) (2903KB)(706)       Save

    A linear parameter-varying (LPV) integrated control law is designed for a hypersonic vehicle to achieve trajectory control based on an altitude-horizontal trajectory control concept. The LPV output-feedback control theory and pole placement techniques are employed to design parameters of the control law within a Mach number envelope. Such a control law performs integrated control for longitudinal and lateral-directional dynamics of the vehicle, free from the scheme of inner and outer control loops of classical flight controls and ensuring robust and optimal control performance in the sense of L2-induced norm. A mathematical model of the hypersonic vehicle is developed in the Earth-centered-Earth-fixed reference frame. Earth rotation, Earth oblateness, and the second order harmonic perturbations of Earth are considered in the model. Numerical simulations are conducted to examine the performance of the LPV controller. The simulation results indicate that the closed-loop system of the hypersonic vehicle achieves D-stability. The LPV control law achieves a good performance in vehicle trajectory control and has sufficient robustness with respect to perturbations and sensor noise.

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    “Window Effect” and Protective Measures of Exogenous Pulsed Electromagnetic Field on Implantable Cardiac Pacemaker
    LU Wu, DING Ranran, ZHAO Wenbin, HUANG Dong, WANG Zheming
    Journal of Shanghai Jiao Tong University    2022, 56 (11): 1518-1531.   DOI: 10.16183/j.cnki.jsjtu.2021.326
    Abstract923)   HTML14)    PDF(pc) (24935KB)(676)       Save

    The electromagnetic interference (EMI) from pulsed electromagnetic field (PEMF) on pacemakers is unignorable in modern power grids and healthcare environments, but there is limited study on the interaction mechanisms and protective measures. In this paper, an in-vitro human chest model for pacemaker implantation is made by using pork tissues immersed in 0.9% sodium chloride solution. The effect of PEMFs generated by the switching actions of common electrical equipment and low-frequency medical equipment on pacemakers is simulated by using fast-front current sources. The pulse forming line theory is employed for analyzing the waveform compression of PEMFs in human thoracic cavity. Further, the parameterized bio-electromagnetic transient model of pacemaker in combination with biological tissues is established in finite element software. The results show that pacemaker malfunctions including pacing inhibition and P pulmonale occur under PEMF. The “Window effect” in subcutaneous pouch under PEMF is found by changing the winding of pacemaker leads in the pouch. Based on the research finding, a protective strategy by using composite materials to shield the window area is proposed. The theoretical feasibility of this protective measure is confirmed by simulation, where the intensity of pacemaker EMI could be reduced by 80 dB when the composite materials shielding is used. Finally, a safe distance is developed for pacemaker wearers in electrical and medical environments.

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    Off-Axis Tensile Test and Numerical Simulation of Unidirectional Thermoplastic Composite Laminates
    ZHANG Jian, CHEN Xiuhua, CHEN Yong, FANG Yin
    Journal of Shanghai Jiao Tong University    2023, 57 (2): 201-212.   DOI: 10.16183/j.cnki.jsjtu.2021.352
    Abstract507)   HTML102)    PDF(pc) (13908KB)(675)       Save

    As a high-performance thermoplastic composite material, AS4/PEEK has been widely used in aerospace, military, automotive, and other fields. After conducting the off-axial tensile test of unidirectional AS4/PEEK laminates with different angles, the relevant stress-strain curves and tensile strengths, as well as fracture plane angles are obtained. In simulation, a 3D elastic-plastic model where the parameters are determined by trust-region reflective algorithm is used to describe the nonlinear mechanical behavior of AS4/PEEK laminates. In combination with the LaRC05 criterion and the crack zone theory, a user material subroutine VUMAT based on Abaqus is developed and applied to the numerical simulation of off-axis tensile test. The numerical results show that the 3D elastic-plastic damage constitutive model can accurately simulate the plastic effect of AS4/PEEK laminates and the tensile strength predicted by the numerical method agrees well with those from the test. The proposed 3D elastic-plastic damage model provides an accurate and effective method for the comprehensive analysis of plastic deformation and damage of thermoplastic composites.

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    Aerodynamic Drag Characteristics of Ultra-Low Orbit Satellites
    WANG Xiaoliang, YAO Xiaosong, GAO Shuang, LIU Guohua
    Journal of Shanghai Jiao Tong University    2022, 56 (8): 1089-1100.   DOI: 10.16183/j.cnki.jsjtu.2021.014
    Abstract707)   HTML26)    PDF(pc) (7210KB)(664)       Save

    Taking the 180~300 km ultra-low orbit satellite as the research object, the aerodynamic drag characteristics of the typical shapes were studied by using the direct simulation Monte Carlo (DSMC) method in the free molecular flow simulation method, which can accurately simulate the three-dimensional complex shapes. By comparing the theoretical drag coefficients of spheres and plates at different velocity rates and the aerodynamic experimental data of 70° bluff body shapes at different velocity rates with the DSMC calculation results, the adaptability of the three-dimensional DSMC method to shape and mesh is verified. The drag characteristics of several typical satellite shapes were calculated and compared, and the pressure difference drag, shear drag, total drag and dimensionless drag coefficients with altitude and shape were obtained. The optimized design of the shape of the ultra-low orbit satellite can reduce the drag by about 10%, which can effectively improve its on-orbit operation characteristics and reduce the design requirements of the own related systems of the satellite.

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    Resistance Element Welding of Carbon Fiber Reinforced Thermoplastic Composites to High-Strength Steel
    WANG Yecheng, LI Yang, ZHANG Di, YANG Yue, LUO Zhen
    Journal of Shanghai Jiao Tong University    2022, 56 (10): 1349-1358.   DOI: 10.16183/j.cnki.jsjtu.2021.271
    Abstract744)   HTML138)    PDF(pc) (47715KB)(643)       Save

    The high strength joining of carbon fiber reinforced nylon 6 composites (CF/PA6) to TWIP980 steel was achieved by resistance element welding (REW). A 304 stainless steel rivet was used as an assistant element. The effect of welding current and welding time on the joint mechanical property was studied. Four joint failure modes with different strengths were identified, and the microstructures of joints, and the interfaces between CF/PA6 and the steel were analyzed. As the melting point and thermal conductivity of CF/PA6 are lower than those of the high-strength steel, it is prone to overheat and decompose during welding. While ensuring the formation of a certain size of weld nugget, avoiding or reducing the decomposition of CF/PA6 is the key to the successful implementation of CF/PA6 high-strength steel REW. By using a hard welding process such as high welding current and short welding time, high strength joints can be obtained while reducing the decomposition of CF/PA6. Based on the failure load of the joint, the weld lobe under the conditions of this study was determined. The process is sensitive to the change of welding time, and the allowable welding time range is narrow. The decomposition of CF/PA6 cannot be avoided completely even when the welding parameters in the weld lobe are employed. Therefore, it is necessary to conduct further research on the temperature field and the nugget formation mechanism of the REW process.

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    Numerical Simulation and Flow Pattern Evolution of Gas-Liquid Two-Phase Flow Passing Through a 90° Pipe Bend Based on CFD
    WANG Zhiwei, HE Yanping, LI Mingzhi, QIU Ming, HUANG Chao, LIU Yadong
    Journal of Shanghai Jiao Tong University    2022, 56 (9): 1159-1167.   DOI: 10.16183/j.cnki.jsjtu.2021.185
    Abstract836)   HTML30)    PDF(pc) (11131KB)(641)       Save

    In order to investigate the evolution characteristics of gas-liquid two-phase flow passing through a 90° pipe bend, the volume of fluid (VOF) multiphase flow model and the Realizable k-ε turbulence model are used to conduct numerical simulations. The evolution of velocity, pressure distribution, gas void fraction, and flow pattern passing through a 90° pipe bend is studied in detail. The results show that different gas-liquid two-phase flow patterns will produce different degrees of secondary flow phenomenon after passing through the 90° pipe bend, and the tangential velocity presents a bimodal distribution, which eventually dissipates into a unimodal distribution in the horizontal pipe. The pressure on the outer wall of the pipe bend increases as the inlet velocity increases. The change of gas void fraction is related to the transformation of the flow pattern, the bubbly flow evolves into a slender slug flow in the horizontal pipe after passing through the 90° pipe bend, and the gas void fraction will decrease. The slug flow, the churn flow, and the annular flow evolve into the stratified-wave flow in the horizontal pipe after passing through the pipe bend, and the variation of the gas void fraction is relatively low. The research results can provide certain theoretical support for the design and development of gas-liquid two-phase flow conveying elbows and the prediction of induced stress.

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    Review of Single Blade Installation and Docking Technology of Large Offshore Wind Turbine
    XIE Sihong, ZHAO Yongsheng, XU Yiqing, HE Yanping, HAN Zhaolong, XU Yuwang
    Journal of Shanghai Jiao Tong University    2023, 57 (6): 631-641.   DOI: 10.16183/j.cnki.jsjtu.2022.237
    Abstract476)   HTML359)    PDF(pc) (14702KB)(639)       Save

    In recent years, offshore wind turbines show the trend of large-scale development, the installation area of which has been expanding to the deep and far-reaching ocean. However, due to the harsh environmental conditions in the far-reaching ocean region, the traditional rotor-lifting method is facing many limitations. In contrast, the single blade installation technology has significant advantages in installation efficiency and safety, and has gradually become a new research hotspot. Based on the characteristics and difficulties of the offshore single blade installation technology, this paper investigates and summarizes the lifting equipment and key technologies involved in single blade installation section, including blade yokes, the single blade installation dynamic simulation model, and the active control technology. Among them, the research and development of novel single blade installation equipment and methods with active control technology are essential for large-scale offshore wind turbine installation in the far-reaching ocean region. Additionally, based on the development trend and prospect of offshore blade installation and the docking technology, it introduces some technical ideas, including single blade yoke with dynamic positioning function, and double hoop blade vertical installation auxiliary device, which are expected to solve the installation problem of large-scale offshore wind turbines.

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    UConvTrans:A Dual-Flow Cardiac Image Segmentation Network by Global and Local Information Integration
    LI Qing, HUANGFU Yubin, LI Jiangyun, YANG Zhifang, CHEN Peng, WANG Zihan
    Journal of Shanghai Jiao Tong University    2023, 57 (5): 570-581.   DOI: 10.16183/j.cnki.jsjtu.2022.088
    Abstract704)   HTML42)    PDF(pc) (9362KB)(639)       Save

    Cardiac magnetic resonance image (MRI) segmentation has the features such as there is a lot of noise, the target areas are indistinguishable from the background, and the shape of the right ventricle is irregular. Although convolution operations are good at extracting local features, the U-shaped convolutional neural networks (CNN) structure hardly models long-distance dependency between pixels and can not achieve ideal segmentation results on cardiac MRI. To solve these problems, UConvTrans is proposed with a dual-flow U-shaped network by global and local information integration. First, the network applies the CNN branch to extract local features and capture global representations by Transformer branch, which retains local detailed features and suppresses the interference of noise and background features in cardiac MRI. Next, the bidirectional fusion module is proposed to fuse the features extracted by CNN and the Transformer with each other, enhancing the feature expression capability and improving the segmentation accuracy of the right ventricle. Besides, the parameters of network can be set flexibly because the transformer structure in the proposed method does not require pre-trained weights. The proposed method also strikes a better balance between precision and efficiency, which is evaluated on the MICCAI 2017 ACDC dataset. The results show that the network outperforms U-Net by 1.13% average dice coefficient while the parameter amount and the floating point operations are only 10% and 8% of the U-Net. Finally, the proposed method achieves a dice coefficient of 92.42% for the right ventricle, 91.64% for the myocardium, and 95.06% for the left ventricle respectively and wins the first place in the myocardium and left ventricle on test set.

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    Numerical Analysis of Influence of Blade Icing on Dynamic Response of Integrated Wind Turbine Structure
    CHUANG Zhenju, LI Chunzheng, LIU Shewen
    Journal of Shanghai Jiao Tong University    2022, 56 (9): 1176-1187.   DOI: 10.16183/j.cnki.jsjtu.2021.258
    Abstract765)   HTML20)    PDF(pc) (10181KB)(612)       Save

    Based on the integrated jacket-support offshore wind turbine model of the National Renewable Energy Laboratory (NREL), the computational fluid dynamics (CFD) method is coupled with the wind turbine integrated analysis method to study the blade icing process and its influence on the overall dynamic performance of the wind turbine. First, the blade motion attitude calculated by the integrated analysis method is input into CFD. The discrete multiphase model and melting solidification model are used to simulate the icing growth of three-dimensional wind turbine blades. The k-ε turbulence model is used to calculate the aerodynamic performance before and after icing. Finally, the aerodynamic results after blade icing are returned to the integrated analysis method to analyze the influence of blade icing on the overall response of the wind turbine. The results show that the blade icing increases linearly along the blade span. The icing is mainly concentrated on the leading edge of the blade with the thickest ice accumulation at the tip. The lift coefficient decreases and the drag coefficient increases after icing. Blade icing will reduce the power of the whole machine, the torque, and the rotor speed. At the same time, it will lead to additional vibration response at the blade tip and tower top, and increase the wind speed required by the wind turbine to reach the rated power.

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    Numerical Study of Stern Vibration of a Self-Propulsion Ship in Propeller Induced Pressure Fluctuation
    QIN Guangfei, YAO Huilan, ZHANG Huaixin
    Journal of Shanghai Jiao Tong University    2022, 56 (9): 1148-1158.   DOI: 10.16183/j.cnki.jsjtu.2021.175
    Abstract807)   HTML21)    PDF(pc) (15563KB)(612)       Save

    To study the stern vibration characteristics of the ship sailing in still water under the action of propeller induced pressure fluctuation, the propeller self-propulsion numerical simulation was conducted based on the Reynolds-averaged Navier-Stokes (RANS) method, in combination with the shear-stress transport (SST) k-ω model. Taking the obtained fluctuating pressure on the hull surface as the external excitation, the acoustic-structure coupling calculation was performed through the structural finite element model coupled with the flow field boundary element model, and a numerical prediction method for the stern vibration of the self-propulsion ship excited by the propeller surface force was established. By analyzing the fluctuating pressure characteristics in the time domain and frequency domain, it is found that the amplitude of the blade frequency component is much larger than that of other frequency components. For the right-handed propeller, the starboard side pressure amplitude above the propeller is higher than that on the port side. The analysis of the corresponding relationship between the propeller fluctuating pressure, the structural inherent characteristics, and the vibration response shows that the coupled mode natural frequency should be far away from the propeller excitation force frequency to reduce the vibration response. The exploration of the effect of modifying stern structure on the vibration response at the same excitation indicates that increasing the plate thickness or installing stiffeners can change the inherent characteristics of the structure, thus avoiding resonance and achieving the vibration reduction effect.

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    Unmanned Aerial Vehicle Situation Assessment Based on Cumulative Prospect Theory and Three-Way Decision
    LI Weiwei, GAO Peixue, CHEN Jin, LU Yuqing
    Journal of Shanghai Jiao Tong University    2022, 56 (11): 1479-1490.   DOI: 10.16183/j.cnki.jsjtu.2021.400
    Abstract666)   HTML12)    PDF(pc) (1395KB)(598)       Save

    General uninhabited aerial vehicle (UAV) situation assessment methods do not consider the influence of complex external environment on the decision-maker, and usually only get the ranking results of the evaluation. Since the decision-maker needs to make decisions in a short period of time, misjudgments or missing strike windows often occur. To address this problem, a three-way decision model based on the cumulative prospect theory is proposed. First, the method the utilizes intuitionistic fuzzy technique for order preference by similarity to an ideal solution to estimate the conditional probability of each target and obtains the situation assessment result. Next, the method calculates the intuitionistic fuzzy situation information obtained by the UAV based on the cumulative prospect theory, and obtains the corresponding cumulative prospect value when each target performs different actions. Finally, based on the principle of maximizing the cumulative prospect value, a new three-way decision rule is derived to divide the situational assessment results into three regions. The experimental analysis shows that the method not only obtains the target threat ranking, but also classifies the target threat level objectively. At the same time, it considers the psychology of the decision-maker in the assessment process, and obtains the target threat assessment results that meet the traits of the decision-maker, providing a reasonable decision support for the complex and changing air combat.

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    Dual Modular Soft Robot with Multi-Terrain Movement Ability
    WANG Yuxuan, LIU Zhaoyu, WANG Jiangbei, FEI Yanqiong
    Journal of Shanghai Jiao Tong University    2022, 56 (10): 1388-1396.   DOI: 10.16183/j.cnki.jsjtu.2021.290
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    Aimed at the problems of limited application range, single movement scene, inability of climbing, and limited space movement of the multi-terrain movement robot, a novel dual module soft robot with the multi-terrain movement ability is proposed. Each soft module is composed of a four-chamber omnidirectional bending soft pneumatic actuator. By establishing the bending model of the omnidirectional bending soft actuator, the variation law of the omnidirectional bending soft actuator is analyzed. A new rotary movement mode is proposed, which enables the robot to move in a variety of complex environments in the rotary movement mode. A gait control method based on pulse width modulation (PWM) is proposed to make the robot realize the multi-terrain movement function more simply and quickly, and its feasibility is verified by experiments. The experimental results show that the dual modular soft robot based on the four-chamber omnidirectional bending soft actuator can climb vertically along circular pipes, square pipes, and irregular rods (human forearms), and the crawling speed can reach 11.7 mm / s. It can also move rapidly in complex terrain such as flat ground, artificial turf, rugged road surface, and slope, and the crawling speed can reach 14.0 mm/s, which overcomes the shortcomings of the existing pipe climbing robot and multi-terrain movement robot. The modular soft robot can move stably and quickly in a variety of terrain, and has a strong adaptability. It has a potential application value in pipeline detection and complex terrain detection.

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    Cooperative Navigation of UAV Formation Based on Relative Velocity and Position Assistance
    GUO Pengjun, ZHANG Rui, GAO Guangen, XU Bin
    Journal of Shanghai Jiao Tong University    2022, 56 (11): 1438-1446.   DOI: 10.16183/j.cnki.jsjtu.2022.232
    Abstract943)   HTML29)    PDF(pc) (1260KB)(591)       Save

    Because the navigation errors of inertial navigation system accumulate with time, the unmanned aerial vehicle (UAV) formation that only relies on inertial navigation system for positioning cannot obtain precision navigation information in long time flight. To solve this problem, this paper proposes a cooperative navigation scheme for master-slave UAV formation. First, the UAV is equipped with relative navigation sensors to measure the relative velocity and position information between the members of the master-slave UAV formation. Then, considering the relative pose of formation members, the spatial unified transformation scheme is studied. The absolute navigation information measured by each member of UAV formation by inertial navigation system and the relative navigation information measured by relative sensors is unified into the same navigation coordinate system. Finally, a cooperative navigation scheme based on relative velocity and relative position assistance is given. The 30 min simulation results show that the speed and position errors of each cluster converge to 0.1 m/s and 5 m respectively under this scheme, which is more suitable than the inertial navigation system.

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    Unmanned Aerial Vehicle Path Planning Algorithm Based on Improved Informed RRT* in Complex Environment
    LIU Wenqian, SHAN Liang, ZHANG Weilong, LIU Chenglin, MA Qiang
    Journal of Shanghai Jiao Tong University    2024, 58 (4): 511-524.   DOI: 10.16183/j.cnki.jsjtu.2022.442
    Abstract732)   HTML18)    PDF(pc) (11075KB)(589)       Save

    To address the problems of long planning time, redundant planning path, and even planning failure caused by local constraints in narrow spaces in the rapid exploring random trees (RRT) algorithm when unmanned aerial vehicle is planning a path in a complex environment, an improved Informed RRT* algorithm is proposed. First, the artificial potential field (APF) method is used to make the sampling points move to the target point in the way of potential field descending, which improves the purpose and directionality of RRT tree expansion. Considering the complexity of the global environment during tree expansion, an adaptive step size is introduced to accelerate the expansion speed of the RRT tree in an unobstructed environment. Then, relevant constraints are added in the process of random tree expansion to ensure the feasibility of the generated paths. After the first reachable path is found, variable elliptic or ellipsoidal sampling domain is used to limit the selection of sampling points and the expansion range of adaptive step size, so as to accelerate the convergence of the algorithm to the asymptotic optimization. Finally, the original algorithm and the improved algorithm are compared in two-dimensional and three-dimensional complex environment. The simulation results show that the improved algorithm can find a better reachable path with a small number of iterations, lock the elliptic or ellipsoidal sampling domain faster and leave more time for path optimization. The improved algorithm performs better in path planning.

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    Characteristics of Droplet Transmission in Buses in Different Air Supply Modes
    CHEN Zhixin, WANG Yiping, YANG Yafeng, SU Jianjun, YANG Bin
    Journal of Shanghai Jiao Tong University    2022, 56 (11): 1532-1540.   DOI: 10.16183/j.cnki.jsjtu.2021.318
    Abstract546)   HTML9)    PDF(pc) (32872KB)(588)       Save

    In order to study the spread characteristics of virus droplets in the bus and predict the risk probability of airborne virus infecting passengers in the bus, a numerical model of the bus with the refrigeration and air conditioning on in summer is established based on the numerical simulation of computational fluid dynamics (CFD) in combination with the Wells-Riley equation. Through the analysis of the characteristics of the flow field in the bus in combination with the Lagrangian method, the spread process of the droplets produced by the cough of the virus carrier in the bus is calculated. The infection risk of virus-carrying droplets to the passengers in the bus in the four ventilation mades is analyzed. It is found that the longitudinal airflow in the bus is a key factor affecting the spread of droplets. Compared with the asymmetrically arranged circular air outlets, the longitudinal airflow in the bus can be reduced by the use of slit-type air outlets. Only 6% of passengers have a higher than 5% probability of contracting diseases in the bus with displacement ventilation, which is more effective in reducing the risk of droplet-borne infection. The research results can provide guidance for the structural design of bus air supply systems and reduce the risk of droplet-borne infections.

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    Multiscale Calculation of Elastic Modulus of Cement Paste Based on Grid Nanoindentation Technology
    CHEN Xiaowen, HAN Yudong, DING Xiaoping, HOU Dongwei
    Journal of Shanghai Jiao Tong University    2022, 56 (9): 1199-1207.   DOI: 10.16183/j.cnki.jsjtu.2021.089
    Abstract754)   HTML16)    PDF(pc) (1695KB)(581)       Save

    The calculation of multiscale elastic parameters of cementitious materials based on micromechanical tests and the composite material theory is one of the key theoretical bases for precise design of cementitious materials performance. In this paper, grid nanoindentation tests of microscopic elastic modulus and the mercury intrusion test were conducted on hardened cement paste specimens at different water-cement ratios, to establish a multiscale homogenization calculation method for the elastic modulus of cement paste considering the influence of pores. Besides, the applicability of the dilute method, the self-consistent method, the Mori-Tanaka method, the interaction direct derivation (IDD) method, and the multilevel homogenization method was compared. The results show that the multi-phase and multi-scale calculations considering the effect of pores is in good agreement with experimental values. Except the multi-level homogenization method, the calculation results of several commonly used composite homogenization methods are similar.

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    Clustering Separation Method Based on Multi-Source Partial Discharge Signal Data Stream
    CHEN Changchuan, LIU Kai, LIU Renguang, FENG Xiaozong, QIN Yanjia, DAI Shaosheng, ZHANG Tianqi
    Journal of Shanghai Jiao Tong University    2022, 56 (8): 1014-1023.   DOI: 10.16183/j.cnki.jsjtu.2021.195
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    In partial discharge(PD) detection, due to the simultaneous and constantly changing phenomenon of multiple discharge sources and on-site interference sources, it is difficult to effectively separate and identify multiple PD sources. An efficient adaptive efficient adaptive online data stream clustering algorithm (EAOStream) is proposed. The algorithm uses natural neighborhoods to create K-dimensional (KD) trees to improve the efficiency of querying neighbors. That is, the adaptive neighborhood radius and the area density are obtained through the characteristics of the flow data, which can search locally and form clusters, and realize the real-time online separation of multiple local discharge sources. The superiority of EAOStream is verified in the artificial data set and the real data set. After comparing EAOStream with the traditional DenStream and SE-Stream algorithms, it is applied to the pattern recognition of gas-insulated substation faults. Experimental test results show that the clustering accuracy of EAOStream in the real network intrusion detection, the forest cover type, and the multi-source PD signal data sets reaches 95.28%, 98.47%, and 97.23%, verifying the practicability and effectiveness of the algorithm in fault diagnosis of gas-insulated substations.

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    Numerical Simulation of Crashback Condition of a Propeller Based on OpenFOAM
    GUO Haipeng, ZOU Zaojian, LI Guangnian
    Journal of Shanghai Jiao Tong University    2023, 57 (2): 168-176.   DOI: 10.16183/j.cnki.jsjtu.2021.305
    Abstract487)   HTML24)    PDF(pc) (14061KB)(556)       Save

    The hydrodynamic characteristics of a propeller under the crashback condition are closely related to the crash stopping ability of a ship, which directly affect the ship navigational safety. In this paper, a numerical study on the hydrodynamic characteristics of a propeller and the flow field around the propeller under the crashback condition is conducted based on the Reynolds-averaged Navier-Stokes solver in the open source computational fluid dynamics platform OpenFOAM. Taking the 5-blade propeller DTMB4381 model as the study object, the ahead and crashback conditions are numerically simulated. The numerical results are compared with international open model test data to validate the effectiveness of the numerical method in the prediction of the hydrodynamic characteristics of the propeller under different conditions. Based on the obtained hydrodynamic loads and flow field details, the local flow field characteristics changing with the advance velocity and the relation between the local flow fields and the global hydrodynamic forces are explored, which provides theoretical basis for the evaluation of ship crash stopping ability.

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    Fast Construction of a Circuit Model for Via-Hole Transition Based on Liquid Crystal Polymer Multilayer Substrate
    LIU Weihong, LIU Ye
    Journal of Shanghai Jiao Tong University    2022, 56 (11): 1547-1553.   DOI: 10.16183/j.cnki.jsjtu.2021.308
    Abstract781)   HTML9)    PDF(pc) (2713KB)(546)       Save

    Liquid crystal polymer (LCP) with excellent microwave and millimeter-wave properties is widely applied in high frequency multilayer substrates. The design of an excellent via-hole transition in multilayer circuits board is important to employ as an interconnect to route signal traces on different layers or connect components. Recently, with the operating frequency increasing, the problem of discontinuity in the via-hole transition structure has become increasingly prominent. Therefore, electromagnetic modeling of via-plate-pair structures is essential for the design of microwave and millimeter-wave circuits. In this paper, an efficient and fast via-hole transition modeling method for the ground coplanar waveguide-strip line-ground coplanar waveguide(GCPW-SL-GCPW) structure based on the four-layer LCP circuit board is proposed. By segmented modeling of the multilayer structure and introducing a fast convergence algorithm in the parasitic parameter calculation process, a via-hole lumped parameter equivalent circuit structure is established. Finally, the equivalent circuit model of the GCPW-SL-GCPW structure is quickly constructed based on the microwave network cascade method. Compared with the full-wave simulation results of HFSS high frequency structure simulator, which is a 3D high-frequency electromagnetic software, it is found that this modeling process is simple and fast. The GCPW-SL-GCPW circuit structure has been fabricated using the LCP multilayer process. The test results show that the test results and the equivalent circuit analysis results are highly consistent in the wide frequency range of 10 MHz—40 GHz, which verifies the effectiveness of the via-hole transition modeling method.

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    A Sensing Method Based of Floating Photovoltaic Grids to Sudden Changes in Marine Weather
    JIANG Haoyu, WANG Peilun, GE Quanbo, XU Jinqiang, LUO Peng, YAO Gang
    Journal of Shanghai Jiao Tong University    2022, 56 (12): 1584-1597.   DOI: 10.16183/j.cnki.jsjtu.2021.526
    Abstract853)   HTML205)    PDF(pc) (8866KB)(540)       Save

    Currently, the application of floating photovoltaics in the ocean is mainly restricted by the cost of submarine cables and special buoys. It will show a high degree of applicability if the energy is consumed by the unmanned management systems on ocean farms and in other scenarios. The grid system formed by the floating photovoltaics can satisfy the early warning requirements of the sudden weather changes on ocean farms. Due to the strong follow-up of the photovoltaic output model to random weather changes, based on the spatial-temporal correlation analysis of large-area photovoltaics, hardware, distance, time delay, and weather, a similar power station fusion estimation relationship is established. Based on the long short-term memory (LSTM) algorithm, the ultra-short-term prediction value of the time sequence tracking of similar power stations can be used to estimate the early warning of the status of target similar power stations. The city-scale data was used to verify the feasibility of the proposed idea, which shows that the framework can complement traditional research deficiencies.

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    Discrete Element Simulation and Analysis of Ice-Inclined Structure Interaction
    WANG Yanlin, GUO Qi, SUN Shanshan, WEI Sihao, XU Ning
    Journal of Shanghai Jiao Tong University    2022, 56 (9): 1168-1175.   DOI: 10.16183/j.cnki.jsjtu.2021.182
    Abstract661)   HTML19)    PDF(pc) (4028KB)(539)       Save

    Inclined structure is an important marine structure in the iced area. The change of the inclined angle will change the main failure mode of sea ice and affect the peak ice force acted on the structure. In order to simulate the random breaking characteristics of level ice, an irregular distributed dilated disk element model with bond-break function is constructed, and the dynamic process of interaction between the level ice and the inclined structure is simulated based on this model, which is verified by comparing the peak ice forces obtained by numerical simulation with the peak ice forces measured in the field. The influence law of the inclined angle on the ice force and the ice failure mode is analyzed. It shows that the variation of ice load with the changes of inclined angles simulated by the numerical method is basically consistent with the variation calculated by the two-dimensional theoretical model. With the increase of the incline angle, the proportion of bending failure decreases and the peak ice force and its occurrence probability increase. The inclined angle is an important factor in the change of sea ice failure modes and the peak ice force. This paper can be used as a reference for discrete element numerical simulation of sea ice and ice-resist design of inclined marine structures.

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    Material Model of Membrane Structure in Rainstorm
    PANG Yan, QING Qiang, WANG Shasha, ZHANG Xiangyu, GONG Jinghai
    Journal of Shanghai Jiao Tong University    2023, 57 (2): 213-220.   DOI: 10.16183/j.cnki.jsjtu.2021.365
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    When encountering heavy rain, the membrane surface with a relatively small slope is easy to accumulate water. Accurately simulating the deformation of the membrane surface at this time will help ensure the safety of the structure. The linear constitutive model of membrane material used in existing research is not suitable for simulating the deformation of membrane structure in rainstorm. This study conducts a uniform load test on a membrane structure to simulate the mechanical behavior of the membrane surface in rainstorm and obtains the deformation form of the structure when water is accumulated. The linear constitutive model and the double broken line constitutive model of membrane material are used in the finite element model of the membrane structure for load analysis. By comparing the deformation of the finite element model and the actual structure, it selects the constitutive model suitable for simulating the deformation of the membrane structure in heavy rain. The numerical simulation results show that the structural deformation simulated by the double broken line constitutive model is closer to the deformation measured in the experiment than the linear constitutive model. The research results can provide a reference for the selection of the membrane constitutive model and the analysis of membrane structure in rainstorm.

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    Energy Consumption Prediction of Office Buildings Based on CNN-RNN Combined Model
    ZENG Guozhi, WEI Ziqing, YUE Bao, DING Yunxiao, ZHENG Chunyuan, ZHAI Xiaoqiang
    Journal of Shanghai Jiao Tong University    2022, 56 (9): 1256-1261.   DOI: 10.16183/j.cnki.jsjtu.2021.192
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    In order to accurately reflect the operation characteristics of office buildings, a convolutional neural network(CNN)-recurrent neural network(RNN)combined model for energy consumption prediction of office buildings is proposed by using the good feature extraction ability of CNN and the good time series learning ability of RNN. Besides, a two-dimensional matrix data input structure suitable for the deep learning model is designed. The case study results show that compared with the simple recurrent neural network and long short term memory network, both the prediction accuracy and computational efficiency of CNN-RNN combined model are significantly improved, and the generalization of the model is also good.

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    Loop Closure Detection Method of Laser SLAM Based on Global Feature Descriptor
    HAN Chao, CHEN Min, HUANG Yuhao, ZHAO Minghui, DU Qiankun, LIANG Qinhua
    Journal of Shanghai Jiao Tong University    2022, 56 (10): 1379-1387.   DOI: 10.16183/j.cnki.jsjtu.2021.202
    Abstract855)   HTML73)    PDF(pc) (5130KB)(533)       Save

    To solve the problem that localization error of the underground inspection system continues to accumulate over time, a loop closure detection algorithm based on point cloud global feature descriptor is proposed, which is suitable for laser simultaneous localization and mapping (SLAM). The feature vector of each point in point cloud is calculated by curvature, then the global feature descriptor of point cloud is constructed based on the angle distribution and scale distribution relationship between the feature vector and center point coordinate system. In addition, the pose transformation of two similar frames is calculated by feature point registration to improve computing efficiency. The proposed algorithm is verified by simulation experiments and open-source data experiments. The experimental results show that the proposed algorithm has a significant improvement in localization accuracy and real-time performance, which can effectively solve the problems of increased cumulative error and poor global consistency of the localization algorithm during long-term inspections.

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