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Contrasting trends of PM2.5 and surface-ozone concentrations in China from 2013 to 2017

National Science Review 2020年第8期7卷 1331-1339页

作者： Yonghong Wang Wenkang Gao Shuai Wang Tao Song Zhengyu Gong Dongsheng Ji Lili Wang Zirui Liu Guiqian Tang Yanfeng Huo Shili Tian Jiayun Li Mingge Li Yuan Yang Biwu Chu Tuukka Pet?j? Veli-Matti Kerminen Hong He Jiming Hao Markku Kulmala Yuesi Wang Yuanhang Zhang State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC) Institute of Atmospheric Physics Chinese Academy of Sciences Institute for Atmospheric and Earth System Research University of Helsinki China National Environmental Monitoring Center (CNEMC) Anhui Institute of Meteorological Sciences State Key Joint Laboratory of Environment Simulation and Pollution Control Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Center for Excellence in Regional Atmospheric Environment Institute of Urban Environment Chinese Academy of Sciences State Key Joint Laboratory of Environment Simulation and Pollution Control School of Environment Tsinghua University State Key Joint Laboratory of Environmental Simulation and Pollution Control College of Environmental Sciences and Engineering Peking University

Although much attention has been paid to investigating and controlling air pollution in China, the trends of air-pollutant concentrations on a national scale have remained unclear. Here, we quantitatively investigated the variation of air pollutants in China using long-term comprehensive data sets from 2013 to 2017, during which Chinese government made major efforts to reduce anthropogenic emission in polluted regions. Our results show a significant decreasing trend in the PM2.5concentration in heavily polluted regions of eastern China, with an annual decrease of ～7% compared with measurements in 2013. The measured decreased concentrations of SO2, NO2and CO（a proxy for anthropogenic volatile organic compounds） could explain a large fraction of the decreased PM2.5concentrations in different regions. As a consequence, the heavily polluted days decreased significantly in corresponding regions. Concentrations of organic aerosol,nitrate, sulfate, ammonium and chloride measured in urban Beijing revealed a remarkable reduction from 2013 to 2017, connecting the decreases in aerosol precursors with corresponding chemical components closely. However, surface-ozone concentrations showed increasing trends in most urban stations from 2013 to 2017, which indicates stronger photochemical pollution. The boundary-layer height in capital cities of eastern China showed no significant trends over the Beijing–Tianjin–Hebei, Yangtze River Delta and Pearl River Delta regions from 2013 to 2017, which confirmed the reduction in anthropogenic emissions. Our results demonstrated that the Chinese government was successful in the reduction of particulate matter in urban areas from 2013 to 2017, although the ozone concentration has increased significantly, suggesting a more complex mechanism of improving Chinese air quality in the future.

关键词： air pollution clean-air action particulate matter surface ozone China chemical composition

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High-performance self-powered ultraviolet to near-infrared photodetector based on WS_(2)/InSe van der Waals heterostructure

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Nano research 2023年第5期16卷 7851-7857页

作者： Jinping Chen Zhen Zhang Yi Ma Jiying Feng Xiaoyu Xie Xiaoxuan Wang Aoqun Jian Yuanzheng Li Zhuxin Li Heng Guo Yizhi Zhu Qiannan Cui Zengliang Shi Chunxiang Xu State Key Laboratory of Bioelectronics School of Biological Science and Medical EngineeringSoutheast UniversityNanjing 210096China Micro Nano System Research Center Key Laboratory of Advanced Transducers and Intelligent Control System of the Ministry of Education&College of Information Engineering and ComputerTaiyuan University of TechnologyTaiyuan 030024China Key Laboratory of UV-Emitting Materials and Technology of Ministry of Education Northeast Normal UniversityChangchun 130024China

van der Waals heterostructures(vdWHs)based on two-dimensional(2D)materials without the crystal lattice matching constraint have great potential for high-performance optoelectronic ***,a WS_(2)/InSe vdWH photodiode is proposed and fabricated by precisely stacking InSe and WS_(2)flakes through an all-dry transfer *** WS_(2)/InSe vdWH forms an n–n heterojunction with strong built-in electric field due to their intrinsic n-type semiconductor characteristics and energy-band alignments with a large Fermi level offset between WS_(2)and *** a result,the device displays excellent photovoltaic behavior with a large open voltage of 0.47 V and a short-circuit current of 11.7 nA under 520 nm light ***,a fast rising/decay time of 63/76μs,a large light on/off ratio of 105,a responsivity of 61 mA/W,a high detectivity of 2.5×10^(11) Jones,and a broadband photoresponse ranging from ultraviolet to near-infrared(325–980 nm)are achieved at zero *** study provides a strategy for developing high-performance self-powered broadband photodetectors based on 2D materials.

关键词： two-dimensional materials van der Waals heterostructure self-powered photodetector photocurrent

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Accurate tracking control of a linear fast tool servo unit for noncircular cutting

Accurate tracking control of a linear fast tool servo unit f...

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IEEE International Conference on Mechatronics and Automation

作者： Xuefeng Chang Youping Chen Wu Ai Zude Zhou National Numerical Control System Engineering Research Center Huazhong University of Science and Technology Wuhan Hubei China

In this paper, an accurate position tracking control scheme is proposed for a moving-coil-type linear DC motor driven fast tool servo unit for noncircular cutting application. A sliding mode tracking controller is designed to ensure the system has a fast tracking characteristic to the position command. Moreover a disturbance observer is used to estimate and compensate exogenous disturbance to improve robustness and stability of the fast tool servo unit. Because the reference input is approximately periodic in noncircular cutting process. Therefore, the periodic error can he further reduced by augmenting an iterative learning controller to the existing sliding mode controller for repetitive position tracking. The experimental results of noncircular cutting adopting the proposed control method, including tracking performance and robustness of the system, are much improved.

关键词： Servomechanisms Sliding mode control control systems Error correction Robust control Three-term control DC motors Robust stability Machining Fuzzy control

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Switch Machine Fault Diagnosis Method Based on Kalman Filter and Support Vector Machines 4th

Switch Machine Fault Diagnosis Method Based on Kalman Filter...

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4th International Conference on Electrical and Information Technologies for Rail Transportation, EITRT 2019

作者： Li, Xiang Qin, Yong Wang, Zhipeng Kan, Jiayu Zhang, Xiaofeng State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong University Beijing100044 China National Research Center of System Engineering of Railway Intelligent Transport Beijing100081 China National Research Center of System Engineering of Railway Intelligent Transport Signal & Communication Research Institute Beijing100044 China

ISBN: (纸本)9789811528651

Switch machines are used for operating railway turnout;its error can cause delays, increase operating costs and may even lead to train accidents. Therefore, the fault diagnosis technology for the switch machine has received more and more attention. This paper proposes a fault diagnosis method based on the action current of switch machine. Firstly, the Kalman filter is used to preprocess the collected action current to reduce the influence of the unavoidable error of the measurement. In addition, we can further improve the accuracy of fault diagnosis by extracting the characteristics of the action current curve, like the maximum, minimum and average value, etc. Finally, we use DAG-SVMs to intelligently diagnose switch failures. Experiments show that the accuracy of classification after Kalman filter preprocessing is better than that of direct classification. © Springer Nature Singapore Pte Ltd. 2020.

关键词： Kalman filters

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A novel seam measuring method of complex tight butt joint for laser welding

A novel seam measuring method of complex tight butt joint fo...

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IEEE International Conference on Mechatronics and Automation

作者： Jiayong Wu Pingjiang Wang Xingdou Fu Biao Liu Jihong Chen National Numerical Control System Engineering Research Center Huazhong University of Science and Technology Wuhan Hubei China

Seam measuring of complex tight butt joint without misalignment for laser welding is a challenging problem. The allowable seam gap width and misalignment in laser welding process are less than 0.1 mm for thin sheet around 2 mm thickness. Current measuring methods or sensors can not stably and accurately extract 3D seam position and seam gap width, due to narrow seam gap and too little misalignment of the butt joint. Furthermore, almost all sensors can not provide seam surface normal vector directly along with seam position and seam gap width. A novel seam measuring method, integrating the 2D machine vision and 3D structured light vision techniques, is proposed. By projecting a unique pattern of three structured light stripes onto the seam surface, 3D seam position, seam gap width and seam surface normal vector can be accurately acquired from a single image, using the 2D/3D vision information fusion approach. Experimental results demonstrate that the proposed seam measuring method is capable of extracting the integrated seam features of tight butt joint without misalignment stably and accurately.

关键词： Welding Current measurement Laser fusion Position measurement Focusing Surface fitting Computer vision Laser beams Surface emitting lasers Machine vision

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Screw thermal characteristics analysis and error prediction considering the two-dimensional heat transfer structure

Research Square

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research Square 2021年

作者： Chen, Yu Chen, Jihong Xu, Guangda National Numerical Control System Engineering Research Center Huazhong University of Science and Technology Wuhan430074 China

Thermal error is a common problem in machine tool processing. It is usually proposed to take the screw as one-dimensional rod heat transfer system to solve the thermal error of screw by establishing thermal characteristic equation. This method regards the temperature on the nut as the temperature of the screw contact surface without considering the heat transfer distance between screw and the mounting point on the nut. To solve this problem, this paper takes the screw-nut feed system as a two-dimensional heat transfer structure considering both screw and nut. In addition, to solve the low convergence speed and easy fall into local optimum problem in optimal parameter identification. The improved particle swarm optimization algorithm (IPSOA) is proposed to identify the boundary parameters of thermal characteristics equations. Finally, the temperature and thermal error of the screw-nut feed system is calculated by the identified results. Experiments under different working condition show that the maximum prediction residual error of the two-dimensional method (TDM) is less than 7.2 um and the simulating prediction accuracy can reach 86.2%. Besides, compared with one-dimensional model (ODM), TDM has a higher predict accuracy which verifies the effectiveness of the proposed method. © 2021, CC BY.

关键词： Particle swarm optimization (PSO)

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Interoperability test data graphical capture and analysis system based on multi-resolution models for the onboard equipment of CTCS-3 train control system 11

Interoperability test data graphical capture and analysis sy...

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11th IEEE International Symposium on Autonomous Decentralized systems, ISADS 2013

作者： Liu, Yu Tang, Tao National Engineering Research Center of Rail Transportation Operation and Control System Beijing Jiaotong University Beijing China State Key Lab of Rail Traffic Control and Safety Beijing Jiaotong University Beijing China

ISBN: (纸本)9781467350686

Onboard equipment of CTCS-3 train control system has to be executed the interoperability test by the independent third-party test bench before it running on the lines. During the test, it has a large amount and higher frequency in the data transmission, test phenomenon occurs on several visible interfaces and frequently, test data should be captured and displayed graphically in real time during the test, it should also be replayed graphically after the test, the fault in the test could be analyzed repeatedly, therefore it makes the data recording and analysis easier to read and estimate, help to generate final test result. In this paper, test data capture and analysis system is built based on multi-resolution modeling, related information is organized reasonably, provide the information detail that the tester concerns maximum, improve the simulation fidelity and testing efficiency. The system is implemented using Labview tools, and verify the simulation result.

关键词： Interoperability

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Coordinated train control in a fully automatic operation system for reducing energy consumption

Coordinated train control in a fully automatic operation sys...

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作者： Xun, J. Yang, X. Ning, B. Tang, T. Wang, W. The State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong University Beijing China National Engineering Research Center of Rail Transportation Operation and Control System Beijing Jiaotong University Beijing China

Energy efficient train operation includes four levels for energy saving: energy efficient driving, real-time multi-train coordination and rescheduling, energy-saving timetabling, and energy-saving planning. For a fully automatic operation system, it provides a flexible way to coordinate trains. The coordination of trains can improve some system performances, such as the efficient use of regenerative energy. The efficient use of energy regenerated by other trains which are during braking phase can contribute to reducing energy consumption. In general, the approaches of coordinated train control for using regenerative energy can be divided into two types: train dwell time control and train running time control. This paper proposes an approach for coordinating trains in fully automatic operation system by modifying running time between adjacent stations. Simulation studies are performed and the usage of regenerative energy and average passenger waiting time is analysed by using the proposed method. It is shown that improvements in the usage of regenerative energy can be achieved by using the proposed method. © 2012 WIT Press.

关键词： Energy utilization

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Model-based test cases generation for onboard system 11

Model-based test cases generation for onboard system

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11th IEEE International Symposium on Autonomous Decentralized systems, ISADS 2013

作者： Lv, Jidong Li, Kaicheng Wei, Guodong Tang, Tao Li, Chenling Zhao, Weihui National Engineering Research Center of Rail Transportation Operation and Control System Beijing Jiaotong University Beijing China State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong University Beijing China

ISBN: (纸本)9781467350686

The Onboard system is a typical safety-critical system, in which any fault can lead to huge human injury or wealth losing. Function testing method which is mainly focus on the conformance relation between the specification and the SUT has been widely used in testing the Onboard system in the past few years. However, most of the test cases are manually generated which can't be reused and leads to repeat works when the specification is changed. To improve the testing efficiency and quality, Model-based testing method is introduced. We use a tool chain to generate test case automatically based on Timed Automata theory and apply in function testing of the Onboard system. EBD-TR timed automata network model is established using tool Uppaal. And based on the EBD-TR model, two kinds of coverage criteria (all-location coverage, and all-edge coverage) are used in tool of CoVer to generate test case automatically. Different test suits of the Onboard system are acquired and a complete model transition function test suit is derived which is proven very useful for testing the Onboard system.

关键词： Automata theory

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Three-dimensional surface topography simulation of ultra- precision milling based on point cloud

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Huazhong Keji Daxue Xuebao (Ziran Kexue Ban)/Journal of Huazhong University of Science and Technology (Natural Science Edition) 2012年第8期40卷 1-6页

作者： Peng, Fangyu Fang, Zhenglong Wu, Jing Yan, Rong State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and Technology Wuhan 430074 China National Engineering Research Center for Numerical Control System Huazhong University of Science and Technology Wuhan 430074 China

A three-dimensional surface topography simulation algorithm for ultra-precision milling was proposed. In order to illustrate the formation of surface topography, blade point clouds which were consisted by a serial of blade points according to calculating the instantaneous locations of static discrete blade points in machining process, was introduced as the research object. Meanwhile the servo bounding boxes which were constructed by meshing simulation surface were utilized to selecting sampling points. The comparison between simulation results and measurement pictures shows that the algorithm can clearly illustrate the distribution of scallop in different directions, as well as the influence on the topography caused by initial cutter phrase. Hence, it provides a method to the research the surface topography composition in the range of ultra-precision milling machining.

关键词： Surface topography

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