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A novel unsupervised deep learning method for the generalization of urban form

Geo-Spatial Information Science 2022年第4期25卷 568-587页

作者： Jihong Cai Yimin Chen School of Geography and Planning Sun Yat-sen UniversityGuangzhouChina

Accurate delineation of urban form is essential to understand the impacts that urbanization has on the environment and regional climate.Conventional supervised classification of urban form requires a rigidly defined scheme and high-quality sample data with class labels.Due to the complexity of urban systems,it is challenging to consistently define urban form types and collect metadata to describe them.Therefore,in this study,we propose a novel unsupervised deep learning method for urban form delineation while avoiding the limitations of conventional super-vised urban form classification methods.The novelty of the proposed method is the Multiscale Residual Convolutional Autoencoder(MRCAE),which can learn the latent representation of differ-ent urban form types.These vectors can be further used to generalize urban form types by using Self-Organizing Map(SOM)and the Gaussian Mixture Model(GMM).The proposed method is applied in the metropolitan area of Guangzhou-Foshan,China.The MRCAE model along with SOM and GMM is used to generalize the urban form types from satellite images.The physical and functional properties of each urban form type are also analyzed using several auxiliary datasets,including building footprints,Points-of-Interests(POIs)and Tencent User Density(TUD)data.The results reveal that the urban form map generated based on the MRCAE can explain 55%of the building height distribution and 55%of the building area distribution,which are 2.1%and 3.3%higher than those derived from the conventional convolutional autoencoder.As the information of urban form is essential to urban climate models,the results presented in this study can become a basis to refine the quantification of urban climate parameters,thereby introducing the urban heterogeneity to help understand the climate response of future urbanization.

关键词： Convolutional autoencoder Self-Organizing Map(SOM) Gaussian Mixture Model(GMM) urban form clustering

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Lane-Exchanging Driving Strategy for Autonomous Vehicle via Trajectory Prediction and Model Predictive Control

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Chinese Journal of Mechanical Engineering 2022年第4期35卷 256-267页

作者： Yimin Chen Huilong Yu Jinwei Zhang Dongpu Cao School of Marine Science and Technology Northwestern Polytechnical UniversityXi’an 710072China School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China Department of Mechanical and Mechatronics Engineering University of WaterlooWaterlooCanada School of Vehicle and Mobility Tsinghua UniversityBeijing 100084China

The cooperation between an autonomous vehicle and a nearby vehicle is critical to ensure driving safety in the laneexchanging scenario.The nearby vehicle trajectory needs to be predicted,from which the autonomous vehicle is controlled to prevent possible collisions.This paper proposes a lane-exchanging driving strategy for the autonomous vehicle to cooperate with the nearby vehicle by integrating vehicle trajectory prediction and motion control.A trajectory prediction method is developed to anticipate the nearby vehicle trajectory.The Gaussian mixture model(GMM),together with the vehicle kinematic model,are synthesized to predict the nearby vehicle trajectory.A potential-feldbased model predictive control(MPC)approach is utilized by the autonomous vehicle to conduct the lane-exchanging maneuver.The potential feld of the nearby vehicle is considered in the controller design for collision avoidance.On-road driving data verifcation shows that the nearby vehicle trajectory can be predicted by the proposed method.CarSim®simulations validate that the autonomous vehicle can perform the lane-exchanging maneuver and avoid the nearby vehicle using the proposed driving strategy.The autonomous vehicle can thus safely perform the laneexchanging maneuver and avoid the nearby vehicle.

关键词： Autonomous vehicle Lane-exchanging Vehicle trajectory prediction Potential feld Model predictive control

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Stability and metastability in a chemotaxis model

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International Journal of Biomathematics 2023年第3期16卷 147-163页

作者： Yimin Chen Jicheng Tao Yazhou Han Manjun Ma Department of Mathematics School of Science Zhejiang Sci-Tech UniversityHangzhou Zhejiang 310018P.R.China Department of Mathematics College of Science China Jiliang UniversityHangzhou Zhejiang 310018P.R.China

This work studies the stability and metastability of stationary patterns in a diffusionchemotaxis model without cell proliferation.We first establish the interval of unstable wave modes of the homogeneous steady state,and show that the chemotactic flux is the key mechanism for pattern formation.Then,we treat the chemotaxis coefficient as a bifurcation parameter to obtain the asymptotic expressions of steady states.Based on this,we derive the sufficient conditions for the stability of one-step pattern,and prove the metastability of two or more step patterns.All the analytical results are demonstrated by numerical simulations.

关键词： Pattern formation stability and metastability chemotaxis model

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Study on the Driving Style Adaptive Vehicle Longitudinal Control Strategy

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IEEE/CAA Journal of Automatica Sinica 2020年第4期7卷 1107-1115页

作者： Jing Huang Yimin Chen Xiaoyan Peng Lin Hu Dongpu Cao the State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan UniversityChangsha 410082China the Department of Mechanical and Mechatronics Engineering University of WaterlooWaterlooON N2L3G1Canada the College of Mechanical&Vehicle Engineering Hunan UniversityChangsha 410082China the School of Automotive and Mechanical Engineering and Hunan Province Key Laboratory of Safety Design and Reliability Technology for Engineering VehicleChangsha University of Science and TechnologyChangsha 410114China

This paper presents a fusion control strategy of adaptive cruise control(ACC) and collision avoidance(CA),which takes into account a driver’s behavioral style. First, a questionnaire survey was performed to identify driver type, and the corresponding driving behavioral data were collected via driving simulator experiments, which served as the template data for the online identification of driver type. Then, the driveradaptive ACC/CA fusion control strategy was designed, and its effect was verified by virtual experiments. The results indicate that the proposed control strategy could achieve the fusion control of ACC and CA successfully and improve driver adaptability and comfort.

关键词： Adaptive cruise control collision avoidance driving simulator experiment driving style fusion control

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Synergetic strengthening mechanism of ultrasound combined with calcium fluoride towards vanadium extraction from low-grade vanadium-bearing shale

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International Journal of Mining Science and Technology 2021年第6期31卷 1095-1106页

作者： Bo chen Shenxu Bao yimin Zhang School of Resources and Environmental Engineering Wuhan University of TechnologyWuhan 430070China Hubei Key Laboratory of Mineral Resources Processing and Environment Wuhan 430070China State Environmental Protection Key Laboratory of Mineral Metallurgical Resources Utilization and Pollution Control Wuhan University of Science and TechnologyWuhan 430081China Hubei Collaborative Innovation Center for High Efficient Utilization of Vanadium Resources Wuhan University of Science and TechnologyWuhan 430081China

The effect and mechanism of ultrasound and CaF_(2) on vanadium leaching from vanadium-bearing shale were investigated systematically.In consideration of the enhancement for vanadium recovery,the combination of ultrasound and CaF_(2)(66.28%) exerts more evident effects than ultrasound(26.97%) and CaF_(2)(60.35%) alone,demonstrating the synergetic effect of ultrasound and CaF_(2).Kinetic analysis manifests that the product layer diffusion controls vanadium leaching in ultrasound system without CaF_(2),however product layer diffusion and interfacial reaction is the rate-controlling step for vanadium leaching in other three leaching systems.The combination of ultrasound and CaF_(2) notably decreases the activation energy(E_(a)) from 62.03 to 27.61 kJ/mol,nevertheless individual CaF_(2) only reduces the E_(a) to 50.70 kj/mol.X-ray diffraction and fourier transform infrared spectrometer analyses show that the decomposition degree of the vanadium-bearing mica structure is the most significant in ultrasound and CaF_(2) system,proving the highest release degree of vanadium.Specific surface area and pore distribution combined with scanning electron microscope analyses reveal that the action of ultrasound and CaF_(2) would provide higher specific surface area,more abundant pores structure and cracks for the particles,which further prompts the rapid diffusion of H^(+),F^(-)and HF,and achieves the conspicuous improvement of vanadium leaching recovery.

关键词： Vanadium-bearing shale Ultrasound CaF_(2)addition Synergetic effect Leaching kinetics

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PM2.5 over North China based on MODIS AOD and effect of meteorological elements during 2003-2015

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Frontiers of Environmental Science & Engineering 2020年第2期14卷 27-40页

作者： Youfang chen yimin Zhou Xinyi Zhao College of Urban and Environmental Sciences Peking UniversityBeijing 100871China Key Laboratory for Earth Surface Processes of the Ministry of Education Peking UniversityBeijing 100871China

Over the past 40 years,PM2.5 pollution in North China has become increasingly serious and progressively exposes the densely populated areas to pollutants.However,due to limited ground data,it is challenging to estimate accurate PM2.5 exposure levels,further making it unfavorable for the prediction and prevention of PM2.5 pollutions.This paper therefore uses the mixed effect model to estimate daily PM2.5 concentrations of North China between 2003 and 2015 with ground observation data and MODIS AOD satellite data.The tempo-spatial characteristics of PM2.s and the influence of meteorological elements on PM25 is discussed with EOF and canonical correlation analysis respectively.Results show that overall R2 is 0.36 and the root mean squared predicted error was 30.1μg/m^3 for the model prediction.Our time series analysis showed that,the Taihang Mountains acted as a boundary between the high and low pollution areas in North China;while the northern part of Henan Province,the southern part of Hebei Province and the western part of Shandong Province were the most polluted areas.Although,in 2004,2009 and dates after 2013,PM25 concentrations were relatively low.Meteorological/topography conditions,that include high surface humidity of area in the range of 34°-40°N and 119°-124°E,relatively low boundary layer heights,and southerly and easterly winds from the east and north area were common factors attributed to haze in the most polluted area.Overall,the spatial distribution of increasingly concentrated PM2.5 pollution in North China are consistent with the local emission level,unfavorable meteorological conditions and topographic changes.

关键词： Aerosol optical depth PM2.5 MODIS Mixed effect model Canonical correlation analysis

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Grinding/Cutting Technology and Equipment of Multi-scale Casting Parts

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Chinese Journal of Mechanical Engineering 2022年第5期35卷 38-46页

作者： Meng Wang yimin Song Panfeng Wang Yuecheng chen Tao Sun Key Laboratory of Mechanism Theory and Equipment Design Ministry of EducationTianjin UniversityTianjin 300350China State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China Tianjin Zhongyiming Technology Co. Ltd.Tianjin 300400China

Multi-scale casting parts are important components of high-end equipment used in the aerospace,automobile manufacturing,shipbuilding,and other industries.Residual features such as parting lines and pouring risers that inevitably appear during the casting process are random in size,morphology,and distribution.The traditional manual processing method has disadvantages such as low efficiency,high labor intensity,and harsh working environment.Existing machine tool and serial robot grinding/cutting equipment do not easily achieve high-quality and high-efficiency removal of residual features due to poor dexterity and low stiffness,respectively.To address these problems,a five-degree-of-freedom(5-DoF)hybrid grinding/cutting robot with high dexterity and high stiffness is proposed.Based on it,three types of grinding/cutting equipment combined with offline programming,master-slave control,and other technologies are developed to remove the residual features of small,medium,and large casting parts.Finally,the advantages of teleoperation processing and other solutions are elaborated,and the difficulties and challenges are discussed.This paper reviews the grinding/cutting technology and equipment of casting parts and provides a reference for the research on the processing of multi-scale casting parts.

关键词： Multi-scale casting parts Residual features 5-DoF hybrid grinding/cutting robot Teleoperation processing

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Expression of PD-1/PD-L1 in lung adenocarcinoma and its clinical significance

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Oncology and Translational Medicine 2021年第1期7卷 15-19页

作者： Jian Li Yimin Chen Department of Respiration Emeishan People's HospitalEmeishan 614200China

Objective This study aimed to investigate PD-1/PD-L1 expression in lung adenocarcinoma and its relationship with EGFR/KRAS mutation.Methods The expression levels of PD-1 and PD-L1 in lung adenocarcinoma were detected.Clinicopathological parameters were collected and followed up.The effects of PD-1 and PD-L1 expression on clinicopathological parameters and prognosis of patients with lung adenocarcinoma were statistically analyzed.Results PD-L1 and PD-1 were mainly located in the membrane and cytoplasm of tumor cells.The positive expression rates of PD-1 and PD-L1 were 53%and 40%,respectively.Positive PD-1 expression had a significant effect on the incidence of KRAS mutation(P0.05).EGFR gene mutation,high PD-1 expression,high PD-L1 expression,N stage,and AJCC stage were independent risk factors of DFS(P<0.05).Conclusion High PD-1/PD-L1 expression is closely related to the occurrence of lung adenocarcinoma and can be used as an independent factor to assess the prognosis of patients with lung adenocarcinoma.There were negative correlations between PD-L1 expression and EGFR mutation and between PD-1 expression and KRAS mutation.

关键词： lung adenocarcinoma PD-1 PD-L1 gene mutation

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Interannual Influences of the Surface Potential Vorticity Forcing over the Tibetan Plateau on East Asian Summer Rainfall

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Advances in Atmospheric Sciences 2022年第7期39卷 1050-1061页

作者： chen SHENG Bian HE Guoxiong WU yimin LIU Shaoyu ZHANG State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China

The influences of interannual surface potential vorticity forcing over the Tibetan Plateau(TP)on East Asian summer rainfall(EASR)and upper-level circulation are explored in this study.The results show that the interannual EASR and associated circulations are closely related to the surface potential vorticity negative uniform leading mode(PVNUM)over the TP.When the PVNUM is in the positive phase,more rainfall occurs in the Yangtze River valley,South Korea,Japan,and part of northern China,less rainfall occurs in southern China,and vice versa.A possible mechanism by which PVNUM affects EASR is proposed.Unstable air induced by the positive phase of PVNUM could stimulate significant upward motion and a lower-level anomalous cyclone over the TP.As a result,a dipole heating mode with anomalous cooling over the southwestern TP and anomalous heating over the southeastern TP is generated.Sensitivity experiment results regarding this dipole heating mode indicate that anomalous cooling over the southwestern TP leads to local and northeastern Asian negative height anomalies,while anomalous heating over the southeastern TP leads to local positive height anomalies.These results greatly resemble the realistic circulation pattern associated with EASR.Further analysis indicates that the anomalous water vapor transport associated with this anomalous circulation pattern is responsible for the anomalous EASR.Consequently,changes in surface potential vorticity forcing over the TP can induce changes in EASR.

关键词： surface potential vorticity East Asian summer monsoon rainfall the Tibetan Plateau

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Plasmon-mediated photodecomposition of NH3 via intramolecular charge transfer

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Nano Research 2022年第5期15卷 3894-3900页

作者： yimin Zhang Weite Meng Daqiang chen Lili Zhang Shunfang Li Sheng Meng Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of SciencesBeijing 100190China Key Laboratory of Material Physics Ministry of EducationSchool of Physics and MicroelectronicsZhengzhou UniversityZhengzhou 450001China School of Chemical Engineering Anhui University of Science and TechnologyHuainan 232000China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100190China

As an excellent clean medium for hydrogen storage and fuel cell applications,the photolysis of ammonia via localized surface plasmon could be invoked as a promising route towards significantly reducing the temperature for conventional thermolysis.Here,we explore the underlying microscopic mechanism of ultrafast carrier dynamics in plasmon-mediated NH3 photodecomposition at the single-molecular level using real-time time-dependent density functional theory.The NH_(3)molecule adsorbed on the tip of archetypal magic metal clusters represented by tetrahedral Ag_(2)0 and icosahedral Ag147,splits within a hundred femtoseconds upon laser pulse illumination.We found that the splitting of the first N-H bond is dominated by the intramolecular charge transfer driven by localized surface plasmon.Surprisingly,the phase of laser pulse could modulate the dynamics of charge transfer and thus affect the plasmon-induced bond breaking.These findings offer a new avenue for NH3 decomposition and provide in-depth insights in designing highly efficient plasmon-mediated photocatalysts.

关键词： ammonia photodecomposition localized surface plasmon intramolecular charge transfer time-dependent density functional theory

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