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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
    Abstract267)   HTML32)    PDF(pc) (3313KB)(840)       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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    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
    Abstract160)   HTML10)    PDF(pc) (2433KB)(766)       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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    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
    Abstract378)   HTML356)    PDF(pc) (14702KB)(547)       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
    Abstract591)   HTML36)    PDF(pc) (9362KB)(496)       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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    Cost Sharing Mechanisms of Pumped Storage Stations in the New-Type Power System: Review and Prospect
    LIU Fei, CHE Yanying, TIAN Xu, XU Decao, ZHOU Huijie, LI Zhiyi
    Journal of Shanghai Jiao Tong University    2023, 57 (7): 757-768.   DOI: 10.16183/j.cnki.jsjtu.2021.516
    Abstract728)   HTML44)    PDF(pc) (2464KB)(452)       Save

    Driven by the carbon peaking and carbon neutrality goals, the power system is transforming to the new structure which is dominated by renewable energy and is facing a new supply-demand balance situation. Pumped storage, as the most mature energy storage technology at present, can provide flexible resources with different time scales to ensure the safety of the power system and promote the consumption of renewable energy. However, the operation strategy and cost sharing mechanism of the pumped storage station (PSS) are not clear, which hinders its further development under the new situation. In this context, the technical characteristics and functions of PSS are sorted out first. Then, the investment cost model is established from the perspective of the whole life cycle. After that, the evolution path of pricing mechanism and cost sharing mode are described in view of the different stages of electricity market development, providing a feasible scheme for the marketization of PSS. Finally, the future development of PSS is summarized and prospected.

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    Decoupling and Synchronization Control of Asymmetric Flexure-Linked Dual-Drive Gantry Stage
    WEI Guangyu, GU Chaochen, YANG Shusheng, GUAN Xinping
    Journal of Shanghai Jiao Tong University    2023, 57 (5): 593-600.   DOI: 10.16183/j.cnki.jsjtu.2021.456
    Abstract384)   HTML18)    PDF(pc) (5432KB)(395)       Save

    A decoupling and synchronization control strategy based on a model-compensated extended state observer is proposed in control of a dual-drive gantry positioning stage with asymmetric flexure-linked structures. A gantry dynamic model considering the features of the flexure-linked structures and the impact of load acceleration is built using Lagrangian equations. Translational and rotational control loops are designed according to this model, while extended state observers with compensation of known coupling items in the model are deployed in each control loop to estimate and attenuate the total disturbances composed of unmodeled dynamics, unknown couplings, etc. The experimental results show that the proposed control strategy, which is simple to realize and requires few parameters to be measured, can effectively decouple the dynamics of dual axes and attenuates disturbances, greatly improving the dynamic response and synchronization accuracy of the gantry stage.

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    Application of Machine Learning in Chemical Synthesis and Characterization
    SUN Jie, LI Zihao, ZHANG Shuyu
    Journal of Shanghai Jiao Tong University    2023, 57 (10): 1231-1244.   DOI: 10.16183/j.cnki.jsjtu.2023.078
    Abstract421)   HTML48)    PDF(pc) (4421KB)(346)       Save

    Automated chemical synthesis is one of the long-term goals pursued in the field of chemistry. In recent years, the advent of machine learning (ML) has made it possible to achieve this goal. Data-driven ML uses computers to learn relative information in massive chemical data, find objective connections between information, train models by using objective connections, and analyze the actual problems which can be solved according to these models. With its excellent computational prediction capabilities, ML helps chemists solve chemical synthesis problems quickly and efficiently and accelerate the research process. The emergence and development of ML has shown a strong research assistance in the field of chemical synthesis and characterization. However, there is no highly versatile ML model at present, and chemists still need to choose different models for training and learning according to actual situations. This paper aims to show chemists the best cases of common learning methods in chemical synthesis and characterization from the perspective of ML, such as supervised learning, unsupervised learning, semi-supervised learning, reinforcement learning, etc., and help them use ML knowledge to further broaden their research ideas.

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    Refined Simulation of Near-Surface Wind Field of Atmospheric Boundary Layer Based on WRF-LES Model
    LIU Dalin, TAO Tao, CAO Yong, ZHOU Dai, HAN Zhaolong
    Journal of Shanghai Jiao Tong University    2024, 58 (2): 220-231.   DOI: 10.16183/j.cnki.jsjtu.2022.415
    Abstract1537)   HTML9)    PDF(pc) (9950KB)(323)       Save

    Extreme meteorological disasters such as typhoons pose a serious threat to the safety of engineering structures. Therefore, the refined simulation on the near-surface atmospheric boundary layer (ABL) is valuable for civil engineering. Large-eddy simulation (LES) implemented in the weather research and forecating (WRF) model has the advantages of multiple options of numerical schemes and high accuracy. It is generally suitable for the refined simulation of the near-surface wind field, although the performance of simulation results is closely related to the numerical methods. This paper assesses the impacts of vital parameters regarding subfilter-scale (SFS) stress models, mesh size, and spatial difference schemes within WRF-LES to simulate the ideal ABL in order to figure out appropriate numerical schemes for the refined simulation of the near-surface wind field. The wind field characteristics are addressed and analyzed such as mean wind speed profile, turbulence intensity profile, and power of spectrum. Comparisons of simulation results among different SFS stress models indicate that the nonlinear backscatter and anisotropy one (NBA1) SFS stress model can effectively improve the accuracy of simulation in the near-surface wind profiles. Investigations of mesh resolution effects indicate that the nonuniformly refined vertical grid near the surface agrees much better with the expected profiles and reduces the expenditure of computational resources. Furthermore, the results show that the even-order spatial difference schemes produce more small-scale turbulent structures than the odd-order difference schemes. The numerical methods of WRF-LES proposed can provide a technical reference for refined simulation of the near-surface wind field and typhoon boundary layer.

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    Coupling Modeling of Humanoid Flexible Joint and Vibration Suppression at Variable Load
    SONG Chuanming, DU Qinjun, LI Cunhe, LUO Yonggang
    Journal of Shanghai Jiao Tong University    2023, 57 (5): 601-612.   DOI: 10.16183/j.cnki.jsjtu.2021.342
    Abstract183)   HTML13)    PDF(pc) (5177KB)(313)       Save

    Aimed at the joint vibration problem caused by the load change of humanoid flexible joint, a torque compensation control method based on state observer is proposed. By controlling the motor to output a torque increment equivalent to the disturbance torque, the joint torque can quickly balance the load torque and shorten the oscillation process of the elastic element passively adapting to the load change. A state observer for estimating load disturbance torque and motor speed is designed, whose convergence is proved by the Lyapunov function. The control structure of the drive system based on the proportional integral-intergral proportional (PI-IP) speed regulator is established, and the observer output feedforward link is added to the speed regulator to improve the anti-interference ability of the system. The simulation results show that compared with proportional integral differential (PID) control and joint force feedback proportional differential (PD) control, the proposed method can restore the motor speed to stability within 0.6 s after load change and realize joint vibration suppression within 1 s. Besides, the joint speed adjustment time is shortened by about 1.8 s and 0.9 s respectively, which effectively improves the dynamic adjustment ability of the system. Finally, the effectiveness of the proposed method was verified by experiments on an integrated flexible joint testing platform.

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    A CNN-LSTM Ship Motion Extreme Value Prediction Model
    ZHAN Ke, ZHU Renchuan
    Journal of Shanghai Jiao Tong University    2023, 57 (8): 963-971.   DOI: 10.16183/j.cnki.jsjtu.2022.089
    Abstract232)   HTML13)    PDF(pc) (2516KB)(312)       Save

    Aimed at the short-term extreme value prediction of ship motion, a sliding window method based on motion spectrum information is proposed to extract feature data, based on which, a series prediction model of convolutional neural networks (CNN) and long short-term memory (LSTM) is built. The CNN module aims at the local correlation characteristics of the input data, and the LSTM module aims at the time dimension characteristics of the data. The simulation test results of S175 ship show that the model has a good prediction effect on the motion extremum information in the next 1 and 2 cycles, and the evaluation indexes are significantly better than those of LSTM and gate recurrent unit (GRU) models, which has an important application value.

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    Interval Prediction Technology of Photovoltaic Power Based on Parameter Optimization of Extreme Learning Machine
    HE Zhizhuo, ZHANG Ying, ZHENG Gang, ZHENG Fang, HUANG Wandi, ZHANG Shenxi, CHENG Haozhong
    Journal of Shanghai Jiao Tong University    2024, 58 (3): 285-294.   DOI: 10.16183/j.cnki.jsjtu.2022.338
    Abstract207)   HTML6)    PDF(pc) (1907KB)(311)       Save

    This paper proposes an interval prediction technology of photovoltaic (PV) power based on parameter optimization of extreme learning machine (ELM) model. First, the weighted Euclidean distance is proposed as the evaluation index of PV power prediction interval. The historical sample units are screened and the ELM training set is optimized. Then, a hybrid optimization algorithm for ELM parameters is proposed. The hidden layer input and output weights and biases parameters of the ELM model are optimized by using the elitist strategy genetic algorithm and quantile regression, and the trained model is used to predict the PV power range. Finally, an actual calculation example is constructed based on the historical data of PV power plants and weather stations. The PV power interval is predicted, and the results are compared with those obtained by other methods. The results of the calculation example show that the method proposed can greatly improve the accuracy of interval prediction while increasing the reliability of interval prediction.

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    A Structured Pruning Method Integrating Characteristics of MobileNetV3
    LIU Yu, LEI Xuemei
    Journal of Shanghai Jiao Tong University    2023, 57 (9): 1203-1213.   DOI: 10.16183/j.cnki.jsjtu.2022.077
    Abstract371)   HTML16)    PDF(pc) (11611KB)(311)       Save

    Due to its huge amount of calculation and memory occupation, the traditional deep neural network is difficult to be deployed to embedded platform. Therefore, lightweight models have been developing rapidly. Among them, the lightweight architecture MobileNet proposed by Google has been widely used. To improve the performance, the model of MobileNet has developed from MobileNetV1 to MobileNetV3. However, the model has become more complex and its scale continues to expand, which is difficult to give full play to the advantages of lightweight model. To reduce the difficulty of deploying MobileNetV3 on embedded platform while maintaining its performance, a structured pruning method integrating the characteristics of MobileNetV3 is proposed to prune the lightweight model MobileNetV3-Large to obtain a more compact lightweight model. First, the model is trained by sparse regularization to obtain a sparse network model. Then, the product of the sparse value of convolution layer and scale factor of batch normalization layer is used to identify the redundant filter, which is structurally pruned, and experiment is conducted on CIFAR-10 and CIFAR-100 datasets. The results show that the proposed compression method can effectively compress the model parameters, and the compressed model can still ensure a good performance. While the accuracy remains unchanged, the number of parameters on CIFAR-10 in the model is reduced by 44.5% and calculation amount is reduced by 40%.

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    Improved Thermal Network Method for Fuel Transient Temperature Prediction of High-Speed Aircrafts
    CHENG Xianda, ZHENG Haoran, YANG Xuesen, DONG Wei
    Journal of Shanghai Jiao Tong University    2023, 57 (6): 728-738.   DOI: 10.16183/j.cnki.jsjtu.2021.387
    Abstract180)   HTML12)    PDF(pc) (11336KB)(310)       Save

    The low simulation efficiency of three-dimensional transient calculation makes it difficult to be applied in predicting fuel temperature during the entire fuel consumption process. In order to satisfy the requirements of fuel temperature field calculation in the rapid iterative fuel system design process, a novel efficient and accurate improved thermal network method was proposed. The mixing coefficient was introduced to the heat conduction equation to represent the heat convection inside the fuel, and the heat transfer caused by the mass transfer term was added to the heat balance equation to represent the problem of overall fuel flow. Based on the improved thermal network method, the transient thermal analysis model of the high-speed aircraft fuel tank was constructed. The results show that under different thermal boundary conditions and tank geometries, the temperature deviation between the thermal network method and the computational fluid dynamics(CFD) method is less than 5%, and the calculation efficiency of the thermal network method is much higher, which can greatly improve the computational efficiency. By combining CFD calculation with the improved thermal network method, a novel fuel transient temperature prediction method is provided for the design of the high-speed aircraft fuel storage system.

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    Theoretical Modeling, Simulation Analysis, and Experimental Investigation of a Pneumatic Toothed Soft Actuator
    SU Yiyi, XU Qiping, LIU Jinyang
    Journal of Shanghai Jiao Tong University    2023, 57 (8): 1016-1027.   DOI: 10.16183/j.cnki.jsjtu.2022.039
    Abstract199)   HTML9)    PDF(pc) (17776KB)(307)       Save

    Based on the nonlinear geometric relationship of the bulging angle and the bending angle, and the principle of virtual work and nonlinear constitutive relationship of Neo-Hookean incompressible hyperelastic material, a quasi-static mechanical model for pneumatic toothed soft actuator was established, considering the strain energy of the bottom, side walls, and front and rear walls. Considering the geometric nonlinearity and material nonlinearity, the proposed model could solve the configuration of the soft actuator at different driving pressures and terminal loads precisely and efficiently. The finite element simulation of the cantilevered-free soft actuator was conducted by Abaqus, and the corresponding experimental device was established. The simulation analysis and experimental investigation were performed at different driving pressures. A comparison of the results show that there is a positive linear correlation between the driving pressure and the bending angle of the soft actuator, and the prediction of the theoretical model agrees well with the simulation and experimental results. In addition, the distribution of the strain energy was analyzed. Based on the equal-curvature model, the configuration results of the soft actuator at terminal loads are basically consistent with those obtained by Abaqus. The proposed quasi-static mechanical modeling method provides a theoretical basis for the structural optimization design, performance improvement, and motion control of similar soft actuators.

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    A Single Image Deraining Algorithm Based on Swin Transformer
    GAO Tao, WEN Yuanbo, CHEN Ting, ZHANG Jing
    Journal of Shanghai Jiao Tong University    2023, 57 (5): 613-623.   DOI: 10.16183/j.cnki.jsjtu.2022.032
    Abstract353)   HTML32)    PDF(pc) (26863KB)(304)       Save

    Single image deraining aims to recover the rain-free image from rainy image. Most existing deraining methods based on deep learning do not utilize the global information of rainy image effectively, which makes them lose much detailed and structural information after processing. Focusing on this issue, this paper proposes a single image deraining algorithm based on Swin Transformer. The network mainly includes a shallow features extraction module and a deep features extraction network. The former exploits the context information aggregation module to adapt to the distribution diversity of rain streaks and extracts the shallow features of rainy image. The latter uses Swin Transformer to capture the global information and long-distance dependencies between different pixels, in combination with residual convolution and dense connection to strengthen features learning. Finally, the derained image is obtained through a global residual convolution. In addition, this paper proposes a novel comprehensive loss function that constrains the similarity of image edges and regions synchronously to further improve the quality of derained image. Extensive experimental results show that, compared with the two state-of-the-art methods, MSPFN and MPRNet, the average peak signal-to-noise ratio of derained images of our method increases by 0.19 dB and 2.17 dB, and the average structural similarity increases by 3.433% and 1.412%. At the same time, the model parameters of the proposed network decreases by 84.59% and 34.53%, and the forward propagation time reduces by 21.25% and 26.67%.

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    Optimization Design of New Bionic Propeller
    WU Chunxiao, LU Yu, LIU Shewen, GU Zhuhao, SHAO Siyu, SHAO Wu, LI Chuang
    Journal of Shanghai Jiao Tong University    2023, 57 (11): 1421-1431.   DOI: 10.16183/j.cnki.jsjtu.2022.174
    Abstract1657)   HTML20)    PDF(pc) (10709KB)(288)       Save

    A novel method for optimal design of hydrodynamic performance of bionic propeller with a deformable leading edge is proposed. Based on the bionics principle and method of parameterized modeling, the fore-fin concave-convex structure of humpback whales is applied to the propeller leading edge, the leading edge in the propeller to meet flow region according to the exponential decay curve and the standard sine curve smooth leading edge for similar humpback fins protuberant structure of concave and convex deformation, and the leading edge of concave and convex bionic propeller. The hydrodynamic performance, the cavitation performance, and the noise performance of the exponential decay bionic propeller and the sinusoidal function bionic propeller were simulated respectively. The propeller with a better performance is selected, and the simulation based design (SBD) technology is introduced into the optimization design of the new bionic propeller. The parameters controlling the shape of the exponential attenuation curve of the guide edge deformation are taken as optimization design variables, the torque of the parent propeller is taken as the constraint condition, the open water efficiency is selected as the objective function, and the optimization algorithm of Sobol and T-Search is adopted. A bionic propeller optimization system based on the exponential decay curve is constructed. The results show that the application of the concave and convex structure of the humpback whale fore-fin to the guide edge of the propeller improves the cavitation performance and noise performance of the propeller, but the improvement of the open water performance of the propeller is not particularly significant. It is verified that the hydrodynamic performance optimization design method of the bionic propeller established in this paper is effective and reliable, which provides a certain theoretical basis and technical guidance for the performance numerical calculation and configuration optimization design of the bionic propeller.

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    Low-Carbon Operation Strategy of Integrated Energy System Based on User Classification
    ZHANG Chunyan, DOU Zhenlan, BAI Bingqing, WANG Lingling, JIANG Chuanwen, XIONG Zhan
    Journal of Shanghai Jiao Tong University    2024, 58 (1): 1-10.   DOI: 10.16183/j.cnki.jsjtu.2022.321
    Abstract2194)   HTML30)    PDF(pc) (1783KB)(282)       Save

    Integrated energy system (IES) is an important means to achieve the goal of “carbon peaking and carbon neutrality”. However, different types of users in the system have different energy consumption behaviors, which makes the coordinated optimization and low-carbon operation of the integrated energy system more difficult. In order to give full play to the subjective initiative of users, the user behavior of the integrated energy system is modelled based on user behavior analysis, and users are classified into aggressive and conservative types by convolutional neural network (CNN). Then, the decision model of integrated energy system operator is constructed to determine the supply mode of electric heating energy, and the corresponding energy package is designed for different types of users. Finally, the effectiveness of the above models and methods is analyzed based on actual data, and the value of user classification in low-carbon operation of integrated energy systems is verified.

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    A Short-Term Production Simulation Model of Wind-PV-Hydrogen-Pumped Storage Zero Carbon Power System
    GU Huijie, PENG Chaoyi, SUN Shuhao, LIU Mingtao, XIE Jun, SHI Xionghua, BAO Yong
    Journal of Shanghai Jiao Tong University    2023, 57 (5): 505-512.   DOI: 10.16183/j.cnki.jsjtu.2022.054
    Abstract371)   HTML206)    PDF(pc) (1646KB)(281)       Save

    To achieve the goal of carbon peaking and carbon neutrality, it is urgent to build a new power system with renewable energy as the main body, characterized by clean energy supply and electrification of energy consumption. Considering the intermittency and randomness of wind-solar power, as well as the energy storage and flexibility of pumped storage power stations and power-to-hydrogen, a short-term production simulation model of wind-PV-hydrogen-pumped storage zero carbon power system is established based on the stochastic programming theory. In the proposed short-term production simulation model, on the basis of meeting the total demand of flexible hydrogen load, the short-term production simulation is implemented, including electricity-hydrogen production schedule, reserve capacity, pumped storage-water discharge power output and wind-solar curtailment, with the goal of maximizing green on-grid electricity. Taking Zhangbei zero carbon power system of China as an example, many operation scenarios are established to simulate the proposed model. The simulation results show that the proposed model can effectively simulate the on-grid scheme situation of green power in which the system deals with the randomness of wind-solar output in any output scenarios of wind-solar power scene set. The flexible hydrogen load and the pumped storage power station can effectively promote wind-solar energy accommodation and increase the comprehensive benefit of the combined system.

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    Matching Characteristics of Expansion Valve Opening and Flow Rate of High Temperature Heat Pump with Green Refrigerant HP-1
    WANG Yuehan, NAN Xiaohong, OUYANG Hongsheng, GUO Zhikai, HU Bin, WANG Ruzhu
    Journal of Shanghai Jiao Tong University    2023, 57 (10): 1367-1377.   DOI: 10.16183/j.cnki.jsjtu.2022.155
    Abstract177)   HTML7)    PDF(pc) (1421KB)(280)       Save

    The throttling process, as an important part of the heat pump system, plays a crucial role in the efficient and reliable operation of the whole system. This paper, taking the quasi two-stage compression high-temperature heat pump with green refrigerant HP-1 as the research subject, established the mathematical models of the circulatory system and electronic expansion valve by using MATLAB and considering the influence of the opening of electronic expansion valve and thermodynamic properties of the new green refrigerant. It simulated the matching characteristics of electronic expansion valve opening and flow rate under variable operating conditions, and fitted the HP-1 dimensionless flow coefficient correlation by power-law distribution using experimental data. The research results show that the electronic expansion valve with an elliptical conical body structure adapts to the throttling characteristics of the HP-1 high-temperature heat pump system under variable operating conditions. When the evaporating temperature varies from 50 ℃ to 90 ℃ and the condensing temperature varies from 60 ℃ to 120 ℃, the opening adjustment range of this type of valve body is from 49.8% to 69.8% for the main throttle valve, and from 41.5% to 56.0% for the injection throttle valve. The relative deviation of the fitted correlation results and the actual test data is between -7.8% and +7.5%, and the flow coefficient correlation can accurately predict the flow characteristics of the electronic expansion valve with a similar body structure. The selection of favorable electronic expansion valve matching refrigerant properties and the optimization of the electronic expansion valve control system are essential for the actual operating performance. This study provides a good research foundation for the selection of electronic expansion valves and the optimization of the control system for the HP-1 high temperature heat pump.

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    Support Structure Optimization of High-Pile Cap Supported Horizontal Axis Wind Turbine System Based on BESO Algorithm
    ZHAN Lingyu, HE Wenjun, ZHOU Dai, HAN Zhaolong, ZHU Hongbo, ZHANG Kai, TU Jiahuang
    Journal of Shanghai Jiao Tong University    2023, 57 (8): 939-947.   DOI: 10.16183/j.cnki.jsjtu.2022.182
    Abstract230)   HTML32)    PDF(pc) (9027KB)(278)       Save

    The study of reliable support structure is of great significance to the safety of large-scaled horizontal axis wind turbine (HAWT) system. In this paper, for cap-supported HAWT with high pile, the bidirectional evolutional structure optimization (BESO) algorithm based on inversely proportional deletion rate was used to optimize its support structure. Using computational fluid dynamics (CFD) and the principle of pile-soil interaction, the finite element model of HAWT was established, where the wind load and pile-soil interaction were taken into consideration. The reliability of the structural optimization method was verified through the comparison of the dynamic response characteristics between the initial and the optimized model. The results show that the current BESO algorithm can effectively generate a novel support structure form for high-pile HAWT, whose dynamic response is significantly reduced. The results can provide useful references for HAWTs designs.

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    Growth Rates of HFCVD Diamond Films on Silicon Carbide Substrates for Heat Dissipation Applications
    LI Weihan, QIAO Yu, SHU Da, WANG Xinchang
    Journal of Shanghai Jiao Tong University    2023, 57 (8): 1078-1085.   DOI: 10.16183/j.cnki.jsjtu.2022.043
    Abstract178)   HTML4)    PDF(pc) (18057KB)(269)       Save

    Diamond has an extremely high thermal conductivity, making it to have a great potential as a heat dissipation material. Based on the hot filament chemical vapor deposition (HFCVD) technique, diamond thick films were deposited on silicon carbide substrates by using the multi-step method in this paper. The scanning electron microscopy (SEM) and Raman spectroscopy were adopted for characterizing the samples. The influences of filament power, carbon concentration, and reactive pressure on the growth rate and quality of the diamond films were systematically studied. It is found that the diamond film with the best quality is synthesized by adopting a filament power of 1 600 W, a methane/hydrogen flux ratio of 18/300 (nucleation stage) and 14/300 (growth stage), and a reactive pressure of 4 kPa. The corresponding growth rate is 1.4 μm/h.

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    Experimental Study of Influence of Different Parameters on Flow Field Structures Around an Airfoil Covered with Rough Ice
    ZHENG Chengyi, DU Xuzhi, DONG Qiaotian, YANG Zhigang, XIONG Bing, XU Yi, WU Linghao, JIN Zheyan
    Journal of Shanghai Jiao Tong University    2023, 57 (9): 1221-1230.   DOI: 10.16183/j.cnki.jsjtu.2022.149
    Abstract113)   HTML12)    PDF(pc) (8438KB)(266)       Save

    Rough ice can change the leading edge of airfoil and affect the aerodynamic characteristics. Studying the influence of rough ice caused by supercooled water droplets can provide reference for anti-icing design of aircrafts. A detailed experimental study was conducted to measure the flow field structure of an airfoil model with rough ice in a low-speed wind tunnel by using particle image velocimetry. The parameters include Reynolds number, roughness of rough ice, and angle of attack. The results show that with the increase of Reynolds number, the range and value of spanwise vorticity at the wake of the airfoil with ice increased, while the normalized Reynolds stress decreased slightly. The presence of rough ice reduced the airflow velocity near the airfoil, increased the vorticity of wake, and seriously affected the shear stress distribution. Compared with the clean airfoil, the rough ice caused the air flow to separate earlier and the velocity in the separation bubble fluctuated more violently.

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    Numerical Simulation of Stamping-Spinning Hybrid Process for Aluminum Alloy Hemispherical Shells
    YU Xiaopeng, WANG Zimin, YU Zhongqi, LUO Yimin, YU Li
    Journal of Shanghai Jiao Tong University    2023, 57 (10): 1329-1336.   DOI: 10.16183/j.cnki.jsjtu.2022.165
    Abstract122)   HTML6)    PDF(pc) (4480KB)(247)       Save

    Aimed at the poor accuracy in traditional deep drawing of aerospace aluminum alloy hemispherical shells, and by introducing metal spinning, a stamping-spinning hybrid process strategy for aluminum alloy hemispherical shells is proposed, which can achieve the forming processing of the formed component with a high thickness uniformity and high shape accuracy. The finite element simulation model of the hybrid process of the aluminum alloy hemispherical shell is developed, which realizes the simulation. In addition, the variation law of the wall thickness and shape fitting of the hemispherical shells formed by the hybrid process are analyzed. The simulation results show that the uniformity of wall thickness of the hemispherical shells formed by 50% stamping + 50% spinning is significantly improved. The shape accuracy of the component can be obviously improved by changing the stress state of the forming component by power spinning. Meanwhile, the hybrid process is verified by using an aluminum alloy hemispherical shell with a diameter of 1 m in processing test, which improves the thickness uniformity and the shape accuracy of the hemispherical shell.

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    A Resolved CFD-DEM Approach Based on Immersed Boundary Method
    MAO Jia, XIAO Jingwen, ZHAO Lanhao, DI Yingtang
    Journal of Shanghai Jiao Tong University    2023, 57 (8): 988-995.   DOI: 10.16183/j.cnki.jsjtu.2022.095
    Abstract273)   HTML7)    PDF(pc) (11088KB)(246)       Save

    Based on the immersed boundary method, a resolved CFD-DEM algorithm is proposed to tackle fluid-solid interaction problems which widely exist. In the proposed method, the fluid filed is described by the computational fluid dynamics in the Eulerian framework, while the movement and collision of the solids are simulated by the discrete element method in the Lagrangian framework. In order to deal with the moving interfaces between the fluid and the solids, several immersed boundary points are allocated on the boundaries of the solids. Two classic test cases are calculated to verify the accuracy of the proposed method, including the vortex-induced vibration of a cylinder and the rotational galloping of a rectangular rigid body. Good agreements are achieved between the current results and those in previous references and the reliability of the present method in modelling the fluid-solid interaction problems are proved. Finally, the sedimentation of multiple solids is simulated and the ability of the proposed CFD-DEM method in solving the complex fluid field and the collision among the solids with arbitrary shapes are verified.

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    RUL Prediction Method for Quay Crane Hoisting Gearbox Bearing Based on LSTM-CAPF Framework
    SUN Zhiwei, HU Xiong, DONG Kai, SUN Dejian, LIU Yang
    Journal of Shanghai Jiao Tong University    2024, 58 (3): 352-360.   DOI: 10.16183/j.cnki.jsjtu.2022.440
    Abstract92)   HTML4)    PDF(pc) (5678KB)(243)       Save

    The health condition of hoisting gearbox bearings of quay cranes is of great importance for the safety of port production. A remaining useful life (RUL) predicting framework for lifting gearbox bearings of quay crane under time-varying operating conditions is proposed. First, the working load is discretized and the condition boundaries are determined. Then, the long short-term memory (LSTM) network model is adopted to predict the load and the corresponding operating conditions. Afterwards, considering the degradation rates and jump coefficients under different operating conditions, the state degradation function is established based on the Wiener process. Finally, the condition-activated particle filter (CAPF) is used to predict the degradation state and RUL of bearings. The proposed prediction framework is verified by the full-life data of the hoisting gearbox bearings in a port in Shanghai collected by the NetCMAS system. A comparison with the other three prediction methods shows that the proposed framework is able to obtain more accurate degradation states and RUL predictions under time-varying operating conditions.

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    Application of Improved LSTM Neural Network in Time-Series Prediction of Extreme Short-Term Wave
    SHANG Fancheng, LI Chuanqing, ZHAN Ke, ZHU Renchuan
    Journal of Shanghai Jiao Tong University    2023, 57 (6): 659-665.   DOI: 10.16183/j.cnki.jsjtu.2021.438
    Abstract289)   HTML23)    PDF(pc) (2062KB)(236)       Save

    Efficient and accurate extreme short-term prediction is of great significance for the safety of ship and marine structures in actual sea waves. Due to the stochastic of actual sea waves, short-term prediction always uses time series analysis. The neural networks, particularly long short-term memory (LSTM) neural networks, have received increasing attention for their powerful forecasting capability in time series analysis. Based on this, an improved form of LSTM combining generative adversarial ideas is proposed, in which the frequency domain characteristics are embedded in the neural network to achieve coupled time-frequency domain information forecasting. The experimental test shows that the forecasting accuracy of this method is better than the results of traditional time series analysis methods and the LSTM neural network, and it is suitable for extreme short-term time series prediction for better ship maneuvering.

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    Resilience Evaluation and Enhancement Strategy of Distribution Network Considering Impact of Seismic Attack on Transportation Networks
    YAN Wenting, YANG Long, LI Changcheng, LUO Wei
    Journal of Shanghai Jiao Tong University    2023, 57 (9): 1165-1175.   DOI: 10.16183/j.cnki.jsjtu.2022.152
    Abstract762)   HTML17)    PDF(pc) (2248KB)(236)       Save

    Serious earthquake disasters not only cause power outages in distribution network, but also destroy transportation networks, which hinders the transportation of resources for restoration of distribution network and slows down the restoration. This paper proposes an improved resilience evaluation method and a resilience enhancement strategy of distribution network considering the effects of seismic attack on transportation networks. First, a seismic attack model is established to describe the relation between earthquake disasters and failure probability of transportation-distribution networks based on peak ground acceleration. The impact of earthquake disasters on transportation-distribution networks is quantified, and the failure scenarios are generated. Then, a resilience evaluation index is proposed by introducing the waiting time for road repair of emergency repair teams. Afterwards, a bi-level optimization model for distribution network restoration considering the fault line repair, the road repair, and the emergency resource scheduling is established and solved. The upper layer aims at the minimum power loss load, while the lower layer takes the minimum waiting time of the repair team as the goal. Finally, case studies on a coupling example of a 12-node transportation network and an IEEE 33-node distribution network verify the feasibility of the improved resilience index and the effectiveness of the proposed method. The results show that the resilience index considering seismic attack on transportation networks is accurate, and the restoration strategy can effectively enhance the resilience of distribution network in earthquake disasters.

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    Real-Time Laser Speckle Imaging of Blood Flow with High Gray Level and High Resolution
    ZHANG Zelong, ZHANG Yingchao, WU Bo, DONG Wei, FAN Youben
    Journal of Shanghai Jiao Tong University    2023, 57 (5): 552-559.   DOI: 10.16183/j.cnki.jsjtu.2021.466
    Abstract217)   HTML13)    PDF(pc) (27048KB)(232)       Save

    Laser speckle contrast imaging (LSCI) is a large measurement ranging, real-time, high spatial resolution optical imaging method. Exisiting reserches show that the low gray level (8-bit) and low resolution (752×480 pixels) camera can effectively monitor the flow of scattering media such as blood, but the defects such as large noise of scattered particles and small effective imaging area are difficult to be compensated by software, which seriously affects the imaging quality. Monitoring blood flow with a camera with a high gray level (16-bit) and a high resolution (2 048×2 048 pixels) will slow down the imaging speed of a single frame, and parallel computing can reduce the image processing time by 1/3. With the aid of an animal blood flow experiment, the results of high-gray-level and high-resolution spatial laser speckle contrast imaging (sLSCI), spatial approximate laser speckle contrast imaging (sLSCIa), and temporal laser speckle contrast imaging (tLSCI) were compared and analyzed using imaging speed and imaging quality as evaluation criteria. The parallel computation of high-gray-level and high-resolution sLSCI takes into consideration both imaging quality and imaging speed, which can meet the requirements of clinical real-time monitoring of blood flow.

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    Assessment Method for Urban Energy Carbon Emission Peak Based on Mann-Kendall Trend Test
    CHEN Yun, SHEN Hao, WANG Xiaohui, ZHAO Wenkai, PAN Zhijun, WANG Jiayu, LI Siyuan, HAN Dong
    Journal of Shanghai Jiao Tong University    2023, 57 (7): 928-938.   DOI: 10.16183/j.cnki.jsjtu.2021.524
    Abstract344)   HTML14)    PDF(pc) (1541KB)(228)       Save

    Energy is an important component of urban carbon emissions. Assessing the peak of urban energy carbon is a necessary means to implement the national “double carbon” strategy. For this reason, this paper proposes an energy carbon peaking assessment method based on Mann-Kendall trend test for carbon emission of urban energy. By constructing a carbon monitoring system covering elements such as energy carbon emissions, clean energy generation, and transportation electric energy substitution, the total energy carbon emissions of the city are calculated by combining historical data. In view of the seasonality and randomness of energy carbon emissions, the Mann-Kendall trend test was used to establish a model for determining urban energy carbon peaking and to measure regional carbon emissions in different periods. Taking an administrative region in Shanghai as an example, the peak status of energy carbon in this region is judged from the perspective of year and quarter. The results show that based on the annual data, the region has reached its peak energy carbon in 2020. Based on quarterly data, peak energy carbon has been achieved in summer and autumn, while spring and winter are still in plateau. The methods proposed in this paper can be used to assess the carbon peak status in the city, and provide a reference for examining the carbon peak process in other provinces and cities.

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    Improvement and Numerical Verification of Weighting Strategy for High Precision WCNS Scheme
    YANG Qiang, LI Weipeng
    Journal of Shanghai Jiao Tong University    2023, 57 (6): 719-727.   DOI: 10.16183/j.cnki.jsjtu.2022.014
    Abstract256)   HTML19)    PDF(pc) (3360KB)(227)       Save

    In order to reveal the complex flow mechanism, a series of high-order precision schemes have been proposed at home and abroad, of which, the weighted compact nonlinear scheme (WCNS) has a good shock capture ability and has been widely used in the numerical simulation of complex flows. However, it has insufficient resolution and large dissipation in the simulation of small-scale flows. In the framework of the WCNS, by using the weighting strategy of the targeted essentially non-oscillatory (TENO) scheme for reference, this paper introduces the new methods of discontinuity detection and template weighting into the construction of the WCNS scheme, and develops a WCNS7-T scheme with a 7-order accuracy. Example tests are conducted through one-dimensional shock tube problem and two-dimensional Riemann problem. By comparing with the traditional WCNS7-Z scheme, the improved performance of the new scheme is verified. The numerical experiments show that the WCNS7-T scheme can better suppress the numerical oscillation near the discontinuity, improve the resolution and shock capture ability, and further reduce the dissipation.

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    Arc Attachment Characteristics of Carbon Fiber Reinforced Thermoplastic Materials
    XIE Minqi, XIAO Cien, BIAN Jiapeng, LIU Yakun, FAN Yin, CHEN Xiuhua, LIU Libo
    Journal of Shanghai Jiao Tong University    2023, 57 (9): 1214-1220.   DOI: 10.16183/j.cnki.jsjtu.2022.146
    Abstract129)   HTML12)    PDF(pc) (14040KB)(216)       Save

    As a promising structural material, carbon fiber reinforced thermoplastic (CFRTP) has been gradually applied on aircrafts. The lightning arc adhesion characteristics of CFRTP, however, are still unclear. Therefore, the arc adhesion characteristics of CFRTP were studied by simulating the lightning test method. Based on the finite element method, the effect of CFRTP on spatial electric field was analyzed and compared with that of metal materials. It is found that for the structure containing both CFRTP and metal materials, CFRTP is possible to be attached by the lightning discharging channel, but the probability is lower than that of the metal material by 22.5%. In the process of lightning arc adhesion, single upward leader and multiple upward leaders appear on the surface of CFRTP, resulting in the corresponding single or multiple arc attachment points. Simultaneous adhesion of lightning arc on both CFRTP and metal material also occurs. The spatial electric distribution obtained by simulation is consistent with the experimental results. This paper can provide the basis for the lightning characteristics and damage response of CFRTP.

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    Influence of Aerodynamic Characteristics of Airfoil Forward Flight Considering Step-Type Ground
    XU Xiaogang, ZHANG Yang, CHANG Min, CHEN Gang
    Journal of Shanghai Jiao Tong University    2023, 57 (6): 747-756.   DOI: 10.16183/j.cnki.jsjtu.2021.380
    Abstract161)   HTML14)    PDF(pc) (6339KB)(212)       Save

    The aerodynamic influence of ground effects during forward flight is difficult to ignore, especially when there is a sudden change in the ground structure. The aerodynamic performance of the airfoil during forward flight is investigated using the NACA4412 airfoil, the correlation between two factors, i.e., height and angle of attack, and the aerodynamic performance of the airfoil are analyzed. The results show that under the effect of step-type ground, the wing forward flight causes a steep drop in lift-to-drag ratio when the ground effect is absent, and there is a linear relationship with the height above the ground. The angle of attack from the ground has an inverse relationship with the sudden change in aerodynamic performance, i.e., the airfoil needs to maintain a large angle of attack when it leaves the ground in order to reduce the steep change in aerodynamic performance. The take-off and landing process of a shipboard aircraft is typical of a step-type ground. This paper provides a reference for the aerodynamic design of an airfoil under the influence of ground effects.

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    Evaluation of Thermal Insulation Performance of EB-PVD YSZ Thermal Barrier Coatings by Phosphorescence Lifetime Online Measurement
    LIU Zhenghong, YU Yali, CHENG Weilun, LI Muzhi, YANG Lixia, ZHAO Xiaofeng, PENG Di, MOU Rende, LIU Delin
    Journal of Shanghai Jiao Tong University    2023, 57 (9): 1186-1195.   DOI: 10.16183/j.cnki.jsjtu.2022.252
    Abstract116)   HTML11)    PDF(pc) (10690KB)(211)       Save

    Precise measurement of the thermal insulation performance of thermal barrier coatings (TBCs) under the thermal gradient environment is important for the design and development of TBCs. A phosphorescent sensor TBC which contains an Eu doped yttria-stabilized zirconia (YSZ:Eu) surface layer, a YSZ intermediate layer, and a YSZ:Dy bottom layer, is designed and prepared by electron beam physical vapor deposition (EB-PVD). Based on the thermal quenching characteristics of phosphorescence signal, the surface temperature of the YSZ coating and the interface temperature of the bond-coat/YSZ layer are measured online in a temperature gradient environment, and the real thermal insulation effect of the EB-PVD YSZ thermal barrier coating is evaluated. The results show that the EB-PVD YSZ coating with a thickness of 113 μm can achieve an average temperature decrease of 66.5 ℃. The average thermal conductivity of the coating is (0.87±0.15) W/(m·K) in the temperature range between 400 and 700 ℃, which is slightly lower than the value (0.95±0.02) W/(m·K) obtained by using the traditional laser flash method. The above results validate the reliability of online phosphorescence temperature measurement technique, and provide an effective method to monitor the thermal insulation effect of TBCs in real time.

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    Experimental Investigation of Dynamic Response of Pile-Supported Wharf in Liquefiable Ground Under Wave Action
    BI Jianwei, SU Lei, XIE Libo, ZHANG Yu, LING Xianzhang
    Journal of Shanghai Jiao Tong University    2023, 57 (11): 1442-1454.   DOI: 10.16183/j.cnki.jsjtu.2022.163
    Abstract1580)   HTML9)    PDF(pc) (8259KB)(204)       Save

    Pile-supported wharf (PSW) is widely used in the deep-water port engineering construction, most of which are located in liquefiable ground. The effect of wave action on the working performance of PSW in liquefiable ground cannot be ignored, but few studies have been reported. This study performs the wave flume test of PSW in liquefiable ground considering the soil-structure-wave interaction. This test really reproduces the operating condition of PSW, and explores the internal response difference of wharf structure under wave. The influence of wave height on dynamic response of the PSW system is discussed systematically. The result shows that the acceleration and displacement of the PSW deck gradually increase first and finally remain relatively stable with the increase of wave action. The hydrodynamic pressure and deformation of each pile in pile group are obviously different, and the response variation is related to the pile position. The pore pressure of the soil layer in the free field and around the pile decreases with the increase of depth, and the existence of the pile group can reduce the pore pressure in the soil layer around the pile, and increase the acceleration of the soil layer. The effect of wave height on the soil layer decreases with the increase of depth. The above results can provide reference for the similar PSW test under wave and the support for the design and wave protection of PSW.

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    Remaining Useful Life Prediction of IGBT Modules Across Working Conditions Based on ProbSparse Self-Attention
    ZHONG Zhiwei, WANG Yuxiang, HUANG Yixiang, XIAO Dengyu, XIA Pengcheng, LIU Chengliang
    Journal of Shanghai Jiao Tong University    2023, 57 (8): 1005-1015.   DOI: 10.16183/j.cnki.jsjtu.2021.538
    Abstract297)   HTML9)    PDF(pc) (5921KB)(202)       Save

    In order to improve the accuracy of remaining useful life (RUL) prediction of insulated gate bipolar transistor(IGBT) modules across working conditions to enhance their reliability, an RUL prediction method based on the ProbSparse self-attention mechanism and transfer learning was proposed based on the transient thermal resistance features of IGBT modules under different working conditions. An accelerated aging test bench of the IGBT module was designed ang built to perform power cycling experiments in different temperature ranges, and state data of full life-time under different working conditions were collected. Transient thermal resistance change data during the IGBT module degradation were calculated, and the transient thermal features that can accurately reflect the aging state of the IGBT module were extracted and selected. These features were used to predict the RUL of IGBT modules across different working conditions based on the proposed method. The experimental result shows that the accuracy of the proposed RUL prediction method of IGBT modules across working conditions outperforms other compared methods. Particularly, the RUL prediction accuracy during the early degradation stage has been significantly improved.

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    Segmentation and Evaluation of Continuous Rehabilitation Exercises
    HU Mingxuan, QIAO Jun, ZHANG Zhinan
    Journal of Shanghai Jiao Tong University    2023, 57 (5): 533-544.   DOI: 10.16183/j.cnki.jsjtu.2021.458
    Abstract246)   HTML14)    PDF(pc) (17320KB)(201)       Save

    To provide an accurate and objective feedback on rehabilitation training movements and to improve the motivation of rehabilitation patients in rehabilitation training, a motion evaluation method capable of processing continuous human rehabilitation training movement data is proposed. First, a motion segmentation method based on the Gaussian mixture model (GMM) is developed to extract single motion repetition from continuous repetitive motion sequences of the same motion. Then, based on relevant a priori knowledge, a multi-feature fusion motion evaluation method combining significant motion feature dynamic time warping (DTW) distance evluation and Gaussian mixture model likelihood evaluation is proposed to perform motion evaluation in both the overall motion feature and local joint information of rehabilitation exercises. The results show that the motion segmentation method can segment the motion data of continuous repetitive motions well, and the correct rate of segmented motions on the dataset reaches more than 95%. The multi-feature fusion motion evaluation method effectively improves the differentiation of motion evaluation between healthy samples and rehabilitation patient samples, so that the motion scores of healthy samples are mainly distributed in the range of 0.93—0.94 on a scale of 0—1, while the motion scores of patient samples are mainly distributed in the range of 0.81—0.89.

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    Defect Classification of Weld Metallographic Structure Based on Data Augmentation of Poisson Fusion
    BAI Xiongfei, GONG Shuicheng, LI Xuesong, XU Bo, YANG Xiaoli, WANG Mingyan
    Journal of Shanghai Jiao Tong University    2023, 57 (10): 1316-1328.   DOI: 10.16183/j.cnki.jsjtu.2022.202
    Abstract221)   HTML10)    PDF(pc) (10332KB)(199)       Save

    The classification of the defects in welding applications based on the metallographic structure images plays an important part in industrial welding quality inspections. In order to improve the classification performance of defects in the weld metallographic structure images with a small sample dataset available (the amount of samples being less than 30), a Poisson fusion method is used for data augmentation of the defect images and the ResNet18_PRO network is proposed. Both of the methods notably improve the defects classification performance. During data augmentation, the defect area is extracted from original defect samples via digital image processing, and the defect area is fused with normal samples by the Poisson fusion method to generate new defect samples, thus increasing the number of defect samples. The model in this paper is improved based on the ResNet18 network. The downsampling structure is improved to reduce the information loss in the original downsampling structure, and an improved space pyramid pooling structure is added at the end of the network to integrate multi-scale feature information. The classification performance before and after data augmentation is compared by different classification models, which verifies the significant effect of the data augmentation on the classification performance. Meanwhile, the ablation experiment of the ResNet18_PRO is conducted to verify the effectiveness of the improved network structure and the training strategy. It is found that the average classification accuracy of ResNet18_PRO reaches 98.83% and the average F1-score reaches 98.76%, which greatly improves the classification accuracy of metallographic structure defects. Finally, the network is trained and tested with another industrial defect dataset and obtains good classification results. These results show that the proposed network has a good robustness and practical application value.

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    Characteristics of a Hybrid Three-Dimensional Transmitting Coil for Wireless Power Transmission of Intestinal Robot
    ZHUANG Haoyu, YAN Guozheng, FEI Qian, WANG Wei, ZHAO Kai
    Journal of Shanghai Jiao Tong University    2023, 57 (5): 545-551.   DOI: 10.16183/j.cnki.jsjtu.2021.356
    Abstract220)   HTML14)    PDF(pc) (6114KB)(194)       Save

    In order to meet the needs of the intestinal robot to obtain power stably through wireless methods in different positions and postures, and to reduce the volume of the intestinal robot as much as possible, the transmitting coil is required to have the ability to generate spatial multi-dimensional magnetic fields. A hybrid transmitting coil structure is proposed, which combines Helmholtz coil pair and saddle-shaped coil pair. The structure is compact, and its symmetry can be used to generate a three-dimensional magnetic field without dead zone through rotation. The characteristics of the two types of coils and the combined characteristics are analyzed separately. The simulation and experimental results show that at the excitation of 2 A current, the minimum transmission efficiency of 3.44% and the received power of 1 204 mW can be obtained at the center of the coil. The minimum positional uniformity is 88.1%, and the three-dimensional power coverage can be achieved.

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    Two Dimensional Nonlinear Consolidation Analysis of Saturated Soft Soil Around Tunnel
    HU Anfeng, GONG Zhaoqi, XIAO Zhirong, CHEN Yuan
    Journal of Shanghai Jiao Tong University    2023, 57 (12): 1631-1638.   DOI: 10.16183/j.cnki.jsjtu.2022.228
    Abstract83)   HTML5)    PDF(pc) (2636KB)(191)       Save

    Considering the nonlinear changes of compressibility and permeability of soft soil around the tunnel, a two-dimensional nonlinear seepage consolidation control equation is established, which is solved by an alternating implicit difference method, and the development law of the average degree of consolidation with time under the three conditions of complete permeability, complete impermeability, and semi permeability of the tunnel is obtained. By comparing the degenerate solution with the existing analytical solution, the correctness of the difference solution is verified. In addition, the effects of compression index Cc and permeability index Ck on the consolidation degree of soft soil around the tunnel are analyzed. The results show that the permeability of tunnel is an important factor affecting the development and change of consolidation degree. The influence of compression index Cc on the development of degree of consolidation is less than that of permeability index Ck. Seepage consolidation will change the effective stress field of the soil around the tunnel, and the average degree of consolidation decreases with the increase of permeability index Ck. If the nonlinearity of soil is not considered, there will be a large error in the calculation of degree of consolidation.

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    Simulation Study of Reentry Dynamics of a Deep-Water Drilling Riser System Based on Model Predictive Control
    ZHANG Chenyu, MENG Shuai
    Journal of Shanghai Jiao Tong University    2023, 57 (11): 1389-1399.   DOI: 10.16183/j.cnki.jsjtu.2022.235
    Abstract1337)   HTML25)    PDF(pc) (2622KB)(191)       Save

    A marine drilling riser at normal operation condition is required to disconnect the lower marine riser package (LMRP) and blow-out preventer (BOP) in case of severe weather. When the weather gets fine, it must reconnect the LMRP and the BOP. This process is called riser reentry. Marine drilling operations have been driven into extreme deep-waters characterized by severe weather which inevitably leads to a much higher incidence of disconnection. In addition, it requires to accomplish the reentry in a fast way owing to the capricious ocean environment. This study tries to develop a novel reentry control system based on model predictive control (MPC). First, the transverse governing equation of the hanging-off riser system with an end-mass is established based on the modified Hamilton’s principle. The optimization function and constraints in MPC are designed by use of the riser prediction model and the target location. A nonlinear disturbance observer is established for compensation of the model uncertainties and ocean environment disturbances. Finally, simulations are conducted after introducing the dynamic position system (DPS). The riser dynamics employing MPC are compared with that when adopting proportional-integral-derivative (PID) controller. It has found that the drilling riser system based on MPC has a higher response speed, which can complete the reentry process in a faster and more stable manner. It can handle the hydrodynamic force model uncertainties well and has a good robustness for current velocity disturbances. As the flexibility of the riser system is notably enhanced with the significant increase of aspect ratio, the higher-order mode of the flexible hanging-off riser can be triggered in the fast reentry process subjected to the excitations of the mother vessel and ocean environment.

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