Table of Content

28 August 2022, Volume 56 Issue 8 Previous Issue    Next Issue

New Type Power System and the Integrated Energy

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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 2022, 56 (8):  977-993.  doi: 10.16183/j.cnki.jsjtu.2021.450 Abstract ( 1145 )   HTML ( 895 )   PDF (2604KB) ( 1329 )   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. Figures and Tables | References | Related Articles | Metrics

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Real-Time Detection of Insulator Drop String Based on UAV Aerial Photography LI Dengpan, REN Xiaoming, YAN Nannan 2022, 56 (8):  994-1003.  doi: 10.16183/j.cnki.jsjtu.2021.416 Abstract ( 850 )   HTML ( 398 )   PDF (28565KB) ( 848 )   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%. Figures and Tables | References | Related Articles | Metrics

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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 2022, 56 (8):  1004-1013.  doi: 10.16183/j.cnki.jsjtu.2021.486 Abstract ( 1302 )   HTML ( 398 )   PDF (3182KB) ( 943 )   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. Figures and Tables | References | Related Articles | Metrics

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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 2022, 56 (8):  1014-1023.  doi: 10.16183/j.cnki.jsjtu.2021.195 Abstract ( 974 )   HTML ( 148 )   PDF (7466KB) ( 627 )   Save 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. Figures and Tables | References | Related Articles | Metrics

Mechanical Engineering

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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 2022, 56 (8):  1024-1033.  doi: 10.16183/j.cnki.jsjtu.2021.154 Abstract ( 960 )   HTML ( 43 )   PDF (5684KB) ( 1223 )   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. Figures and Tables | References | Related Articles | Metrics

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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 2022, 56 (8):  1034-1042.  doi: 10.16183/j.cnki.jsjtu.2021.162 Abstract ( 764 )   HTML ( 33 )   PDF (20093KB) ( 789 )   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. Figures and Tables | References | Related Articles | Metrics

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A Novel Method for Evidence Conflict Identification and Adjustment ZHANG Xin, TAN Minjia 2022, 56 (8):  1043-1050.  doi: 10.16183/j.cnki.jsjtu.2021.118 Abstract ( 748 )   HTML ( 28 )   PDF (852KB) ( 495 )   Save Aimed at the shortcomings of existing methods in identifying evidence conflicts, in combination with traditional evidence conflicts, an evidence conflict identification and adjustment method is proposed. First, the weighted average of traditional evidence conflicts is used as the identification index in this method. Then, the credibility and uncertainty are introduced to determine the weight coefficients in two situations based on whether it is a conflict between different evidences. After that, the identified evidence conflicts are adjusted in combination with the traditional evidence conflicts and Jousselme information distance. This method is based on the traditional evidence conflicts, which ensures the representativeness of the identification index and the authenticity of the identification results. In addition, the weight coefficients comprehensively consider the credibility within and between the evidence, which is also more representative. Finally, the reduction degree and the average deviation are selected to analysis and verify the proposed method. The results show that the proposed method has a high recognition accuracy and can effectively adjust evidence conflicts. Figures and Tables | References | Related Articles | Metrics

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Quantitative Factors of Recovery Length of Flow Pressure Behind Orifice Plate JI Pengxiang, AI Wanzheng, DING Tianming 2022, 56 (8):  1051-1056.  doi: 10.16183/j.cnki.jsjtu.2021.138 Abstract ( 667 )   PDF (1582KB) ( 310 )   Save The orifice plate has the advantages of convenient construction, high energy dissipation efficiency, and economy, and is widely used in hydropower engineering and discharge engineering. The recovery length of the flow pressure behind the orifice plate is related to the distance arrangement between orifice plates in multi-stage orifice plate design. However, little research has been conducted on the pressure recovery length behind the orifice plate. The numerical simulation method is used to quantitatively study the influencing factors of the pressure recovery length behind the orifice plate, and the results show that the recovery length of the flow pressure behind the orifice plate is mainly dominated by the aperture ratio of orifice plate, the relative thickness of the orifice plate, and the Reynolds number of fluids flowing through orifice plate. As the Reynolds number increases to a fixed value, the pressure recovery length behind the orifice plate does not change. When the relative thickness of the aperture ratio of the orifice plate are within a certain range, the relative thickness of the orifice plate will not change, the aperture ratio of the orifice plate decreases, and the pressure recovery length behind the orifice plate increases. As the diameter ratio of orifice plate remains unchanged, the relative thickness of the orifice plate increases, and the pressure recovery length behind the orifice plate decreases. The empirical formula for the pressure recovery length behind the orifice plate is obtained by multivariate regression analysis and curve fitting, and the indoor test verification is adopted, which provide theoretical basis for distance arrangement between orifice plates in multi-stage orifice plate design. References | Related Articles | Metrics

Biomedical Engineering

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Design and Implementation of a New Type of Gastrointestinal Robot Wireless Power Transmission System FU Wenhao, JIANG Pingping, YAN Guozheng, PENG Yuqi, FEI Qian, ZHUANG haoyu 2022, 56 (8):  1057-1066.  doi: 10.16183/j.cnki.jsjtu.2021.228 Abstract ( 786 )   HTML ( 27 )   PDF (21129KB) ( 558 )   Save In order to ensure the stable operation of the miniature gastrointestinal robot inside the human body, a new type of wireless power transmission (WPT) system is presented. To fulfill the requirements of the work energy consumption, posture stability, energy supply stability, and size limitation of the intestinal robot, the design refers to the calculation of electromagnetic field theory and the optimization results of the spindle-shaped three-dimensional receiving coil model which based on the principle of electromagnetic field resonance. Accordingly, the transmitting coil adopts four sets of solenoid coils to generate a uniform alternating magnetic field. With the receiving coil integrated inside, the optimized transmitting coil can generate a stable energy greater than 500 mW for a robot to work through mutual inductance. Relevant experimental verification indicates that performance of the wireless energy supply system satisfies the working requirements of the robot in the complex environment inside the intestine. Figures and Tables | References | Related Articles | Metrics

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Admission Control of Multi-Level Emergency Patients with Time-Varying Demands XU Jie, WANG Zixiang, LIU Yuxin, LIU Ran, YANG Zhitao 2022, 56 (8):  1067-1077.  doi: 10.16183/j.cnki.jsjtu.2021.122 Abstract ( 763 )   HTML ( 19 )   PDF (1212KB) ( 449 )   Save The Markov decision process (MDP) model is developed for the patient admission control problem and is extended based on the uniformization method to realize a real-time period-by-period decision process. The classical MDP iterative method is extended, and the two-way iteration algorithm and the two-way threshold iteration algorithm are proposed to solve the new model. Numerical experiments are conducted based on the data from the resuscitation room of a large hospital in Shanghai. The results show that the proposed method can improve the admission rate of critical patients and enhance the medical service level of the hospital compared with the existing decision method. Figures and Tables | References | Related Articles | Metrics

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Multi-Feature Extraction of Pulmonary Nodules Based on LSTM and Attention Structure NI Yangfan, YANG Yuanyuan, XIE Zhe, ZHENG Dezhong, WANG Weidong 2022, 56 (8):  1078-1088.  doi: 10.16183/j.cnki.jsjtu.2021.113 Abstract ( 809 )   HTML ( 30 )   PDF (3831KB) ( 577 )   Save The accurate classification of shape, edge, and internal features of pulmonary nodules can not only assist the radiologists in their daily diagnosis, but also improve the writing efficiency of imaging reports. This paper proposes a multi-task classification model based on long-short term memory (LSTM) and attention structure, which merges the shared features among different classification tasks through attention mechanism to improve the feature extraction performance of the current task. The classifier based on temporal sequence LSTM structure can effectively screen the shared features and improve the efficiency of information transmission in the multi-task model. Experimental results show that compared with the traditional multi-task structure, the proposed model can achieve better classification results on the public dataset LIDC-IDRI, and assist doctors to quickly obtain nodule characteristics. Figures and Tables | References | Related Articles | Metrics

Aeronautics and Astronautics

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Aerodynamic Drag Characteristics of Ultra-Low Orbit Satellites WANG Xiaoliang, YAO Xiaosong, GAO Shuang, LIU Guohua 2022, 56 (8):  1089-1100.  doi: 10.16183/j.cnki.jsjtu.2021.014 Abstract ( 777 )   HTML ( 27 )   PDF (7210KB) ( 747 )   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. Figures and Tables | References | Related Articles | Metrics

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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 2022, 56 (8):  1101-1110.  doi: 10.16183/j.cnki.jsjtu.2021.384 Abstract ( 698 )   HTML ( 34 )   PDF (3280KB) ( 1020 )   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. Figures and Tables | References | Related Articles | Metrics