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Journal of Modern Power Systems and Clean Energy 2023年第3期11卷 980-989页

作者： Yongqing Meng Haibo Wang Ziyue Duan Feng Jia Zhengchun Du Xiuli Wang State key laboratory of Electrical Insulation and Power Equipment Shaanxi Province Key Laboratory of Smart GridXi’an Jiaotong UniversityXi’an 710049China State Grid Henan Electric Power Corporation Maintenance Company Zhengzhou 450000China IEEE

Voltage source converter based high-voltage direct current(VSC-HVDC)transmission technology has been extensively employed in power systems with a high penetration of renewable energy ***,connecting a voltage source converter(VSC)to an AC weak grid may cause the converter system to become *** this paper,a phase-shift phaselocked loop(PS-PLL)is proposed wherein a back electromotive force(BEMF)observer is added to the conventional phaselocked loop(PLL).The BEMF observer is used to observe the voltage of the infinite grid in the stationaryαβframe,which avoids the problem of inaccurate observations of the grid voltage in the dq frame that are caused by the output phase angle errors of the *** VSC using the PS-PLL can operate as if it is facing a strong grid,thus enhancing the stability of the VSC-HVDC *** proposed PS-PLL only needs to be properly modified on the basis of a traditional PLL,which makes it easy to *** addition,because it is difficult to obtain the exact impedance of the grid,the influence of shortcircuit ratio(SCR)estimation errors on the performance of the PS-PLL is also *** effectiveness of the proposed PSPLL is verified by the small-signal stability analysis and timedomain simulation.

关键词： Phase-locked loop(PLL) small-signal model stability improvement voltage source converter based high-voltage direct current(VSC-HVDC) weak grid

Establishment and Validation for the Theoretical Model of the Vehicle Airbag

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Chinese Journal of Mechanical Engineering 2015年第3期28卷 487-495页

作者： ZHANG Junyuan JIN Yang XIE Lizhe CHEN Chao State key laboratory of Automobile simulation and Control Jilin University China Automotive Technology & Research Center

The current design and optimization of the occupant restraint system（ORS） are based on numerous actual tests and mathematic simulations. These two methods are overly time-consuming and complex for the concept design phase of the ORS, though they＇re quite effective and accurate. Therefore, a fast and directive method of the design and optimization is needed in the concept design phase of the ORS. Since the airbag system is a crucial part of the ORS, in this paper, a theoretical model for the vehicle airbag is established in order to clarify the interaction between occupants and airbags, and further a fast design and optimization method of airbags in the concept design phase is made based on the proposed theoretical model. First, the theoretical expression of the simplified mechanical relationship between the airbag＇s design parameters and the occupant response is developed based on classical mechanics, then the momentum theorem and the ideal gas state equation are adopted to illustrate the relationship between airbag＇s design parameters and occupant response. By using MATLAB software, the iterative algorithm method and discrete variables are applied to the solution of the proposed theoretical model with a random input in a certain scope. And validations by MADYMO software prove the validity and accuracy of this theoretical model in two principal design parameters, the inflated gas mass and vent diameter, within a regular range. This research contributes to a deeper comprehension of the relation between occupants and airbags, further a fast design and optimization method for airbags＇ principal parameters in the concept design phase, and provides the range of the airbag＇s initial design parameters for the subsequent CAE simulations and actual tests.

关键词： occupant restraint systems airbag theoretical model concept design

Numerical and Experimental Study on Aerodynamic Performance of Small Axial Flow Fan with Splitter Blades

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Journal of Thermal Science 2013年第4期22卷 333-339页

作者： Zhu Lifu Jin Yingzi Li Yi Jin Yuzhen Wang Yanping Zhang Li The province key laboratory of Fluid Transmission Technology Zhejiang Sci-Tech University

To improve the aerodynamic performance of small axial flow fan, in this paper the design of a small axial flow fan with splitter blades is studied. The RNG k-e turbulence model and SIMPLE algorithm were applied to the steady simulation calculation of the flow field, and its result was used as the initial field of the large eddy simulation to calculate the unsteady pressure field. The FW-H noise model was adopted to predict aerodynamic noise in the six monitoring points. Fast Fourier transform algorithm was applied to process the pressure signal. Experiment of noise testing was done to further investigate the aerodynamic noise of fans. And then the results obtained from the numerical simulation and experiment were described and analyzed. The results show that the static characteristics of small axial fan with splitter blades are similar with the prototype fan, and the static characteristics are improved within a certain range of flux. The power spectral density at the six monitoring points of small axial flow fan with splitter blades have decreased to some extent. The experimental results show sound pressure level of new fan has reduced in most frequency bands by comparing with prototype fan. The research results will provide a proof for parameter optimization and noise prediction of small axial flow fans with high performance.

关键词： small axial flow fan splitter blades noise frequency

Influence of Blade Outlet Angle on Performance of Low-specific-speed Centrifugal Pump

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Journal of Thermal Science 2013年第2期22卷 117-122页

作者： Cui Baoling Wang Canfei Zhu Zuchao Jin Yingzi The province key laboratory of Fluid Transmission Technology Zhejiang Sci-Tech University

In order to analyze the influence of blade outlet angle on inner flow field and performance of low-specific-speed centrifugal pump, the flow field in the pump with different blade outlet angles 32.5°and 39° was numerically calculated. The external performance experiment was also carried out on the pump. Based on SIMPLEC algorithm, time-average N-S equation and the rectified k-ε turbulent model were adopted during the process of computation. The distributions of velocity and pressure in pumps with different blade outlet angles were obtained by calculation. The numerical results show that backflow areas exist in the two impellers, while the inner flow has a little improvement in the impeller with larger blade outlet angle. Blade outlet angle has a certain influence on the static pressure near the long-blade leading edge and tongue, but it has little influence on the distribution of static pressure in the passages of impeller. The experiment results show that the low-specific-speed centrifugal pump with larger blade outlet angle has better hydraulic performance.

关键词： centrifugal pump blade outlet angle numerical simulation external characteristic

Research on Performance of Centrifugal Pump with Different-type Open Impeller

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Journal of Thermal Science 2013年第6期22卷 586-591页

作者： CUI Baoling CHEN Desheng WANG Canfei ZHU Zuchao JIN Yingzi JIN Yuzhen The province key laboratory of Fluid Transmission Technology Zhejiang Sci-Tech University

To investigate the influence of impeller type on the performance and inner flow of centrifugal pump, the numeri- cal simulation and experimental research were carried out on the same centrifugal pump with straight-blade and curved-blade open impeller. Based on SIMPLEC algorithm, time-averaged N-S equation and the standard k-e turbulence model, the numerical results are obtained. The pressure distribution in the different type impellers is uniform, while the low pressure area in straight-blade inlet is larger. The vortexes in the passage of impeller exist in both cases. Relative to curved-blade impeller, there are larger vortexes in most of the flow passages except the passage near the tongue in straight-blade impeller. Also some small backflow regions are found at the blade inlet of two impellers. The characteristic curves achieved by numerical simulation basieaUy agree with those by experiment, and straight-blade open impeller centrifugal pump has a better hydraulic performance.

关键词： open impeller centrifugal pump numerical simulation experiment

Hierarchical Parking Path Planning Based on Optimal Parking Positions

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Automotive Innovation 2023年第2期6卷 220-230页

作者： Yaogang Zhang Guoying Chen Hongyu Hu Zhenhai Gao State key laboratory of Automotive simulation and Control Jilin UniversityChangchunJilinChina

Automated valet parking(AVP)has attracted the attention of industry and academia in recent ***,there are still many challenges to be solved,including shortest path search,optimal time efficiency,and applicability of algorithm in complex *** this paper,a hierarchical AVP path planner is proposed,which divides a complete AVP path planning into the guided layer and the planning layer from the perspective of global *** guided layer is mainly used to divide a complex AVP path planning into several simple path plannings,which makes the hybrid A*algorithm more applicable in a complex parking *** planning layer mainly adopts different optimization methods for driving and parking path *** proposed method is verified by a large number of simulations which include the verification of the optimal parking position,the performance of the planner for perpendicular parking,and the scalability of the planner for parallel parking and inclined *** simulation results reveal that the efficiency of the algorithm is increased by more than 20 times,and the average path length is also shortened by more than 20%.Furthermore,the planner overcomes the problem that the hybrid A*algorithm is not applicable in complex parking scenarios.

关键词： Automated valet parking Path planning Hybrid A* Visibility graph Shortest path

Human-Machine Shared Lateral Control Strategy for Intelligent Vehicles Based on Human Driver Risk Perception Reliability

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Automotive Innovation 2024年第1期7卷 102-120页

作者： Dongjian Song Bing Zhu Jian Zhao Jiayi Han State key laboratory of Automotive simulation and Control Jilin UniversityChangchun 130022China

Intelligent vehicle(Ⅳ)technology has developed rapidly in recent ***,achieving fully unmanned driving still presents numerous challenges,which means that human drivers will continue to play a vital role in vehicle operation for the foreseeable ***-machine shared driving,involving cooperation between a human driver and an automated driving system(AVS),has been widely regarded as a necessary stage for the development of *** onⅣdriving safety,this study proposed a human-machine shared lateral control strategy(HSLCS)based on the reliability of driver risk *** HSLCS starts by identifying the effective areas of driver risk perception based on eye *** establishes an anisotropic driving risk field,which serves as the foundation for the AVS to assess risk *** upon the cumulative and diminishing effects of risk perception,the proposed approach leverages the driver's risk perception effective area and converts the risk field into a representation aligned with the driver's ***,it quantifies the reliability of the driver's risk perception by using area-matching ***,based on the driver’s risk perception reliability and dif-ferences in lateral driving operation between the human driver and the AVS,the dynamic distribution of driving authority is achieved through a fuzzy rule-based system,and the human-machine shared lateral control is completed by using model predictive *** HSLCS was tested across various scenarios on a driver-in-the-loop test *** results show that the HSLCS can realize the synergy and complementarity of human and machine intelligence,effectively ensuring the safety ofⅣoperation.

关键词： Intelligent vehicle Human-machine shared driving Risk perception Driving authority distribution

Mapping winter rapeseed in South China using Sentinel-2 data based on a novel separability index

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Journal of Integrative Agriculture 2023年第6期22卷 1645-1657页

作者： TAO Jian-bin ZHANG Xin-yue WU Qi-fan WANG Yun key laboratory for Geographical Process Analysis&simulation of Hubei province/School of Urban and Environmental Sciences Central China Normal UniversityWuhan 430079P.R.China

Large-scale crop mapping using remote sensing data is of great significance for agricultural production, food security and the sustainable development of human societies. Winter rapeseed is an important oil crop in China that is mainly distributed in the Yangtze River Valley. Traditional winter rapeseed mapping practices are insufficient since they only use the spectral characteristics during the critical phenological period of winter rapeseed, which are usually limited to a small region and cannot meet the needs of large-scale applications. In this study, a novel phenology-based winter rapeseed index(PWRI) was proposed to map winter rapeseed in the Yangtze River Valley. PWRI expands the date window for distinguishing winter rapeseed and winter wheat, and it has good separability throughout the flowering period of winter rapeseed. PWRI also improves the separability of winter rapeseed and winter wheat, which traditionally have been two easily confused winter crops. A PWRI-based method was applied to the Middle Reaches of the Yangtze River Valley to map winter rapeseed on the Google Earth Engine platform. Time series composited Sentinel-2 data were used to map winter rapeseed with 10 m resolution. The mapping achieved a good result with overall accuracy and kappa coefficients exceeding 92% and 0.85, respectively. The PWRI-based method provides a new solution for high spatial resolution winter rapeseed mapping at a large scale.

关键词： phenology-based winter rapeseed index winter rapeseed mapping Sentinel-2 Google Earth Engine

Mapping winter wheat using phenological feature of peak before winter on the North China Plain based on time-series MODIS data

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Journal of Integrative Agriculture 2017年第2期16卷 348-359页

作者： TAO Jian-bin WU Wen-bin ZHOU Yong WANG Yu JIANG Yan key laboratory of Agri-informatics Ministry of Agriculture/Institute of Agricultural Resources and Regional PlanningChinese Academy of Agricultural Sciences key laboratory for Geographical Process Analysis & simulation of Hubei province/School of Urban and Environmental Sciences Central China Normal University

By employing the unique phenological feature of winter wheat extracted from peak before winter （PBW） and the advantages of moderate resolution imaging spectroradiometer （MODIS） data with high temporal resolution and intermediate spatial resolution, a remote sensing-based model for mapping winter wheat on the North China Plain was built through integration with Landsat images and land-use data. First, a phenological window, PBW was drawn from time-series MODIS data. Next, feature extraction was performed for the PBW to reduce feature dimension and enhance its information. Finally, a regression model was built to model the relationship of the phenological feature and the sample data. The amount of information of the PBW was evaluated and compared with that of the main peak （MP）. The relative precision of the mapping reached up to 92% in comparison to the Landsat sample data, and ranged between 87 and 96% in comparison to the statistical data. These results were sufficient to satisfy the accuracy requirements for winter wheat mapping at a large scale. Moreover, the proposed method has the ability to obtain the distribution information for winter wheat in an earlier period than previous studies. This study could throw light on the monitoring of winter wheat in China by using unique phenological feature of winter wheat.

关键词： time-series MODIS data phenological feature peak before wintering winter wheat mapping

Denitrification Potential of Marsh Soils in Two Natural Saline-alkaline Wetlands

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Chinese Geographical Science 2014年第3期24卷 279-286页

作者： BAI Junhong ZHAO Qingqing WANG Junjing LU Qiongqiong YE Xiaofei GAO Zhaoqin State key laboratory of Water Environment simulation School of EnvironmentBeijing Normal University

Little information is available on denitrification potential of marsh soils in natural saline-alkaline wetlands. The denitrification potentials of an open wetland in the floodplain(Erbaifangzi wetland) and a closed wetland(Fulaowenpao wetland) in backwater areas in Jilin province of Northeast China were monitored by an anaerobic incubation at 30℃ for 25 days. Our results showed that the relative denitrification index(RDI) increased gradually with incubation time, and showed a rapid increase in the first 5 days of incubation. The RDI values declined quickly from surface soils to subsurface soils and then kept a small change in deeper soils along soil profiles over the incubation time. Denitrification proceeded much faster in the top 20 cm soils of open wetland than in the closed wetland, whereas no significant differences in RDI values were observed in deeper soils between both wetlands. The RDIs were significantly negatively correlated with bulk density and sand content, while a significantly positive correlation with clay content, soil organic matter, total nitrogen and phosphorous. The maximum net NO–3-N loss through denitrification in 1 m depth were higher in the open wetland than the closed wetland with higher soil pH values. Future research should be focused on understanding the influencing mechanisms of soil alkalinity.

关键词： relative denitrification index potential net denitrification rate marsh soil saline-alkaline wetland