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Shifting agricultural land use and its unintended water consumption in the North China Plain

science Bulletin 2024年第24期69卷 3968-3977页

作者： Liang Dong Di Long Caijin Zhang Yingjie Cui Yanhong Cui Yiming Wang Luoqi Li Zhongkun Hong Ling Yao Jinling Quan Liangliang Bai Hao Wang Bridget R.Scanlon Department of Hydraulic Engineering Tsinghua UniversityBeijing 100084China Key Laboratory of Hydrosphere Sciences of the Ministry of Water Resources Beijing 100084China State Key Laboratory of Resources and Environmental Information System Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China Science and Technology Advisory Center Haihe River Water Resources CommissionMinistry of Water ResourcesTianjin 300170China State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower ResearchBeijing 100038China Bureau of Economic Geology Jackson School of GeosciencesUniversity of Texas at AustinAustin TX78712USA

Agricultural land use(ALU)critically influences food production and water resource *** study examines the dynamics of ALU in the North China Plain(NCP),a region characterized by intensive agri-culture and severe groundwater over-exploitation,focusing on the multidimensional drivers and their implications for water resource *** employing an elaborate classification scheme based on satellite imagery and extensive first-hand field data,we identified significant shifts in crop *** 2013 to 2017,there was a notable transition from double crops(primarily wheat-maize)to single crops(primarily maize),covering 4600 km^(2)and accounting for 42%of single crops in *** 2017 to 2022,there was a shift from single crops to economic forests,encompassing 3600 km^(2)and 22%of eco-nomic forests in 2017,including orchards,timber trees,and shelter forest *** shifts resulted in an 11%decrease in grain acreage(6800 km^(2))but an 11%increase in crop water consumption(6.3 km^(3))during ***,water consumption by economic forests increased by 126%(9.4 km^(3))during this *** study highlights the critical need to balance competing demands for food and water security,providing valuable insights applicable to other agriculturally intensive regions worldwide.

关键词： Agricultural land use Remote sensing imagery Random forest classification Shifts in crop patterns Water consumption

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Machine Learning-Based Channel Power Analysis inside Aircraft Cabin

Machine Learning-Based Channel Power Analysis inside Aircraf...

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Intelligent Computing and Control (IC&C), International Conference on

作者： Xijuan Ye Kai Mao Jian Ma Lixin Song Yuxin Liu Qiuming Zhu The Key Laboratory of Dynamic Cognitive System of Electromagnetic Spectrum Space Ministry of Industry and Information Technology Nanjing University of Aeronautics and Astronautics Nanjing China Nanjing Mechanical and Electrical Hydraulic Engineering Research Center of Aviation Industry Aeronautical Key Laboratory of Aeronautical Science and Technology Nanjing China

Communication inside aircraft cabin has gained more and more attentions to provide in-flight connectivity for high-quality user experience and enable the wireless communication of electromechanical equipment. In this paper, a power prediction method considering the coordinates of transceiver, propagation distance and carrier frequency based on the parameterized channel model and machine learning (ML) framework is proposed for wireless communication inside the aircraft cabin. In the proposed channel model, a random forest (RF) network is trained for channel characteristics based on ray tracing (RT) simulation data and applied to estimate the power parameters. The proposed method is verified inside a typical aircraft cabin at 1GHz and compared with traditional model and background propagation neural network (BPNN). The simulation results show that RF can accurately predict the power parameter and reproduce the channel environment. The prediction results of power distribution can provide valuable reference for the layout and optimization of communication nodes inside the aircraft cabin.

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Experimental study of thermal and hydraulic characteristics of pressurizertype heating container during blowdown process

Experimental study of thermal and hydraulic characteristics ...

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2020 International Conference on Nuclear Engineering, ICONE 2020, collocated with the ASME 2020 Power Conference

作者： Ke, Bingzheng Gao, Puzhen Wang, Bo Chen, Bowen Li, Ru Tian, Ruifeng Cheng, Kun Lu, Chuan Fundamental Science on Nuclear Safety and Simulation Technology Laboratory Harbin Engineering University Harbin China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China

ISBN: (纸本)9780791883785

Blowdown process is an important process in LOCA. Studying the internal thermal hydraulic characteristics of the pressurizer during LOCA blowdown process can help to accurately analyze the process of the whole LOCA, which is of great significance to reduce the hazard of accidents and improve the safety of nuclear power plants. An experiment system of blowdown process under low pressure conditions is built, and it uses a pressure gauge and a differential pressure level gauge to measure the pressure and liquid level in the pressurizer-type heating container, and uses a thermocouple to measure the temperature in the pressurizer-type heating container at different heights and distances from the centerline. The changes of pressure, liquid level and temperature characteristics during the blowdown process were obtained. The research results show that the higher the heating power, the greater the slope of pressure change in the heating container, and the pressure changes from negative to positive growth;The greater the heating power is, the faster the liquid level decreases, and the liquid level decreases sharply after the blowdown inflection point. The greater the heating power is, the greater the rate of temperature change, from negative growth to positive growth. The temperature change rate after the blowdown inflection point is reduced. As the height increases, the temperature inside the container first increases and then decreases;the further away from the container's centerline, the higher the measured temperature. © 2020 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Containers

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Experimental investigation on temperature characteristics of direct contact condensation in a natural circulation system

Experimental investigation on temperature characteristics of...

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2020 International Conference on Nuclear Engineering, ICONE 2020, collocated with the ASME 2020 Power Conference

作者： Sun, Jianchuang Ding, Ming Mi, Zhengpeng Zhang, Zhuohua Fundamental Science on Nuclear Safety and Simulation Technology Laboratory Harbin Engineering University Harbin China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China

ISBN: (纸本)9780791883785

Direct contact condensation (DCC) is a common physical phenomenon appearing in the nuclear power plants and other industrial applications. The current research on DCC focuses on steam-water counterflow or jet flow under forced flow conditions. For some natural-circulation passive safety systems in floating nuclear power plants, the heated section is connected with the heat sink by the horizontal pipes. The heat sink is usually the ocean. In such natural circulation systems (NCSs), the steam produced in the heated section will inevitably contact the subcooled water in the ocean and result in DCC event. In this paper, the fundamental characteristics of two-phase flow were described in detail. In addition, the influences of the subcooled water temperature on the flow rate, outlet temperature, steam bubble behaviors, and pressure surge were emphatically discussed. The experimental results revealed that the subcooled water in the water tank could reversely flow into the pipe, which was able to cause condensation induced water hammer (CIWH) event and flow oscillation. Further research showed that the subcooled water was evidently prevented from reversely flowing into the pipe with the increase in the subcooled water temperature. The position where the DCC event occurs transferred from the pipe to the water tank, and the pressure peak obviously reduced, even disappear when the subcooled water temperature is larger than 61 oC. © 2020 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Water temperature

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Synergetic roadmap of carbon neutrality and clean air for China

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Environmental science and Ecotechnology 2023年第4期16卷 1-25页

作者： Qiang Zhang Zhicong Yin Xi Lu Jicheng Gong Yu Lei Bofeng Cai Cilan Cai Qimin Chai Huopo Chen Hancheng Dai Zhanfeng Dong Guannan Geng Dabo Guan Jianlin Hu Cunrui Huang Jianing Kang Tiantian Li Wei Li Yongsheng Lin Jun Liu Xin Liu Zhu Liu Jinghui Ma Guofeng Shen Dan Tong Xuhui Wang Xuying Wang Zhili Wang Yang Xie Honglei Xu Tao Xue Bing Zhang Da Zhang Shaohui Zhang Shaojun Zhang Xian Zhang Bo Zheng Yixuan Zheng Tong Zhu Jinnan Wang Kebin He Ministry of Education Key Laboratory for Earth System Modelling Department of Earth System ScienceTsinghua UniversityBeijing100084China Key Laboratory of Meteorological Disaster Ministry of Education/Joint International Research Laboratory of Climate and Environment Change(ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD)Nanjing University of Information Science&TechnologyNanjing210044China State Key Joint Laboratory of Environment Simulation and Pollution Control School of EnvironmentTsinghua UniversityBeijing100084China Institute for Carbon Neutrality Tsinghua UniversityBeijing100084China State Key Joint Laboratory for Environment Simulation and Pollution Control College of Environmental Sciences and Engineering and Center for Environment and HealthPeking UniversityBeijing100871China Center of Air Quality Simulation and System Analysis Chinese Academy of Environmental PlanningBeijing100012China Center for Carbon Neutrality Chinese Academy of Environmental PlanningBeijing100012China National Center for Climate Change Strategy and International CooperationBeijing100035China Nansen-Zhu International Research Centre Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing100029China College of Environmental Sciences and Engineering Peking UniversityBeijing100871China Institute of Environmental Policy Management Chinese Academy of Environmental PlanningBeijing100012China Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control School of Environmental Science and EngineeringCollaborative Innovation Center of Atmospheric Environment and Equipment TechnologyNanjing University of Information Science and TechnologyNanjing210044China Vanke School of Public Health Tsinghua UniversityBeijing100084China Center for Energy and Environmental Policy Research Beijing Institute of TechnologyBeijing100081China China CDC Key Laboratory of Environment and Population Health National Institute of En

It is well recognized that carbon dioxide and air pollutants share similar emission sources so that synergetic policies on climate change mitigation and air pollution control can lead to remarkable co-benefits on greenhouse gas reduction,air quality improvement,and improved *** the context of carbon peak,carbon neutrality,and clean air policies,this perspective tracks and analyzes the process of the synergetic governance of air pollution and climate change in China by developing and monitoring 18 *** 18 indicators cover the following five aspects:air pollution and associated weather-climate conditions,progress in structural transition,sources,inks,and mitigation pathway of atmospheric composition,health impacts and benefits of coordinated control,and synergetic governance system and *** tracking the progress in each indicator,this perspective presents the major accomplishment of coordinated control,identifies the emerging challenges toward the synergetic governance,and provides policy recommendations for designing a synergetic roadmap of Carbon Neutrality and Clean Air for China.

关键词： Carbon neutrality Clean air Synergetic roadmap

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General Impedance Modeling for Modular Multilevel Converter with Grid-forming and Grid-following Control

arXiv

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arXiv 2024年

作者： Sun, Chu Zhang, Fei Xiao, Huafeng Wang, Na Chen, Jikai The School of Electrical Engineering and Computer Science KTH Royal Institute of Technology Stockholm11428 Sweden The School of Electrical Engineering Southeast University Nanjing210096 China The School of Automation Science and Electrical Engineering Beihang University Beijing100191 China The Key Laboratory of Modern Power System Simulation and Control & Renewable Energy Technology Ministry of Education Northeast Electric Power University Jilin132012 China

Modular multilevel converter (MMC) has complex topology, control architecture and broadband harmonic spectrum. For this, linear-time-periodic (LTP) theory, covering multi-harmonic coupling relations, has been adopted for MMC impedance modeling recently. However, the existing MMC impedance models usually lack explicit expressions and general modeling procedure for different control strategies. To this end, this paper proposes a general impedance modeling procedure applicable to various power converters with grid-forming and grid-following control strategies. The modeling is based on a unified representation of MMC circuit as the input and output relation between the voltage or current on the AC side and the exerted modulation index, while the control part vice versa, thereby interconnected as closed-loop feedback. With each part expressed as transfer functions, the final impedance model keeps the explicit form of harmonic transfer function matrix, making it convenient to directly observe and analyze the influence of each part individually. Thereby the submodule capacitance is found as the main cause of difference between MMC impedance compared to two-level converter, which will get closer as the capacitance increases. Effectiveness and generality of the impedance modeling method is demonstrated through comprehensive comparison with impedance scanning using electromagnetic transient simulation. Copyright © 2024, The Authors. All rights reserved.

关键词： Harmonic analysis

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Air-Ground Integrated Online Federated Learning Under Unreliable Communication

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IEEE Transactions on Cognitive Communications and Networking 2025年

作者： Jing, Yuqian Qu, Yuben Wu, Tao Dong, Chao Guo, Song Wu, Qihui Ministry of Industry and Information Technology Key Laboratory of Dynamic Cognitive System of Electromagnetic Spectrum Space China Nanjing University of Aeronautics and Astronautics College of Electronic and Information Engineering Nanjing211106 China Hong Kong Polytechnic University Department of Computing Hong Kong Hong Kong National University of Defense Technology Anhui Hefei230009 China Hong Kong University of Science and Technology Department of Computer Science and Engineering Hong Kong999077 Hong Kong

In recent years, unmanned aerial vehicles (UAVs) equipped with intelligent computing modules for machine learning (ML) have garnered attention. Federated learning (FL), as an emerging distributed learning paradigm, aligns seamlessly with this scenario. UAVs train local models while a terrestrial base station (BS) aggregates the global model, forming an air-ground integrated federated learning (AGIFL) system. However, under air-ground integrated networks with unreliable wireless links, the online retraining of ML models with new samples is promising but challenging in AGIFL. To this end, we study how to enhance the performance of air-ground integrated online FL (AGIOFL) considering packet transmission error. Specifically, we formulate a joint optimization problem for sample selection and client scheduling, aiming to minimize the loss function that maximizes the performance of AGIOFL. To solve the aforementioned problem without explicit expression, we first derive a closed-form expression for the expected convergence rate of the FL algorithm to quantify the impact of AGIOFL and unreliable wireless transmission. Based on this relationship, we reformulate the optimization problem into a mixed-integer nonlinear programming problem. Subsequently, we develop an alternating iterative optimization algorithm (OFL-PE) combining branch-and-bound with the Dinkelbach algorithm to solve this problem. simulations indicate that OFL-PE converges within 10 iterations only, with a maximum error of less than 7% compared to the exhaustive brute force approach. In addition, we construct a proof-of-concept system based on widely used UAV embedded computers, and experimental results show that OFL-PE demonstrates superior accuracy, convergence, and robustness compared to three existing FL algorithms. © 2015 IEEE.

关键词： Federated learning

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Revealing the Onset Condition of Li Plating on Graphite Electrodes Under Fast Charging

SSRN

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SSRN 2023年

作者： Xiong, Ruoyu Yu, Yue Lv, Taolin Zhou, Mengyuan Li, Longhui Li, Maoyuan Xie, Jingying Zhang, Yun Zhou, Huamin State Key Laboratory of Material Processing and Die & Mould Technology School of Materials Science and Engineering Huazhong University of Science and Technology Wuhan430074 China School of Materials Science and Engineering Peking University Beijing100871 China Space Power Technology State Key Laboratory Shanghai Institute of Space Power-Sources Shanghai200245 China Shanghai Power & Energy Storage Battery System Engineering Tech Co.Ltd Shanghai200245 China

Li plating on graphite-based electrodes is the primary issue hindering the fast charging of electric vehicle batteries. Although wide attention has been paid to this topic, the fundamental understanding of Li plating onset is still under debate (concentration control or potential control?) due to overpotential coupling and highly localized deposition in porous electrodes. Here, the single-layer particle electrode structure combined with time-resolved potential measurements is applied to isolate the local Li plating overpotential and surface equilibrium potential from the global (over)potential. It is found that Li plating overpotential ≤0 V, rather than surface concentration saturation triggers Li plating on graphite electrodes under fast charging. Based on the overpotential criterion, electrochemical simulation well predicts Li plating/stripping behavior on porous graphite electrodes and reveals different limiting processes leading to Li plating which can be reconciled by this overpotential-control mechanism. Experimental demonstration is given by the cases of regulating interface charge transfer and liquid-phase ion transport. This work clarifies the onset condition of Li plating and indicates the optimization directions of fast-charging graphite electrodes. © 2023, The Authors. All rights reserved.

关键词： Plating

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The Analysis and Compensation of Elastic Unbalance Torque of the Three-axis Air-bearing Simulator

The Analysis and Compensation of Elastic Unbalance Torque of...

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作者： Zhanxin Li Zizhen Cao Wenjie Duan Yikang Du Haiteng Liu Tianjin Key Laboratory of Microgravity Environment Simulation Technology Beijing Institute of Control Engineering Science and Technology on Space Intelligent Control Laboratory

The most important interfering torque of a three-axis air-bearing simulator is the displacement of the center of mass in the gravity field caused by structural *** order to characterize the torque,a mathematical model of the interference moment was *** on the model,it is suggested that the vertical stiffness and horizontal stiffness of the structure should be equal as far as possible during the structural design,and the elastic unbalance moment can be compensated by the vertical offset of the center of mass of the air floating platform relative to the rotation center after the initial attitude *** was used to build a simulation model of the air floating platform,and the changes of the structure's centroid before and after the gravitational field was applied were extracted by software to simulate the centroid deviation caused by the elastic deformation of the structure,which was used as the characterization to conduct discrete optimization of the *** optimal structural parameters were *** the disturbance torque curve and the corresponding initial centroid offset after initial centroid compensation were calculated by mathematical *** results are of positive guiding significance to the design of three-axis air-bearing simulator.

关键词： Three-axis air-bearing simulator Unbalance torque Mass-center compensation

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A Multi-Point Two-Hop Neighbor Relay Based OLSR Routing Protocol Design Method for Self-organized Multi-agent Communication*

A Multi-Point Two-Hop Neighbor Relay Based OLSR Routing Prot...

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Control Conference (ANZCC), Australian and New Zealand

作者： Zhenlei Wang Chunfeng Li Xiongjun Wu The 54th Research Institute of China Electronics Technology Group Corporation (CETC54) Hebei Province China The 802 Institute of Shanghai Academy of Space Flight Technology The Eighth Academy of China Aerospace Science and Technology Corporation National Defense Key Laboratory of Science and Technology on Electromagnetic Scattering Shanghai Department of Automation Key Laboratory of System Control and Information Processing Ministry of Education of China Shanghai Jiao Tong University Shanghai China

The OLSR routing protocol is a proactive Linkstate routing protocol in Ad hoc networks. It uses MPR nodes to spread TC messages across the network, reducing the flooding of protocol control messages in the network. However, all MPR nodes used to propagate a TC message in the whole network are not optimal, and there are a lot of redundancy, which results in unnecessary forwarding of TC messages and increases the overhead of control protocol. To overcome this limitation, the concepts of multi-point one hop neighbor relay (MPOHNR) and multi-point two hop neighbor relay (MPTHNR) are proposed, and the node selection algorithms of MPOHNR and MPTHNR are given. By using MPOHNR and MPTHNR to forward TC messages alternately, the number of forwarding nodes is reduced, the control protocol overhead is reduced, the effective bandwidth of the link is greatly increased, and the end-to-end average delay is reduced. Numerical simulations by using the EXATA software verifies that, the improved OLSR routing protocol is a potential design method for optimizing OLSR routing protocol.

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