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Seasonal prediction of extreme high-temperature days over the Yangtze River basin

Science China Earth Sciences 2024年第7期67卷 2137-2147页

作者： Shifeng PAN Zhicong YIN mingkeng duan Tingting HAN Yi FAN Yangyang HUANG Huijun WANG Key Laboratory of Meteorological Disaster Ministry of Education/Joint International Research Laboratory of Climate and Environment Change/Collaborative Innovation Center on Forecast and Evaluation of Meteorological DisastersNanjing University of Information Science and TechnologyNanjing 210044China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519080China

Extreme high temperatures occur frequently over the densely populated Yangtze River basin(YRB)in China during summer,significantly impacting the local economic development and ecological system.However,accurate prediction of extreme high-temperature days in this region remains a challenge.Unfortunately,the Climate Forecast System Version 2(CFSv2)exhibits poor performance in this regard.Thus,based on the interannual increment approach,we develop a hybrid seasonal prediction model over the YRB(HM_(YRB))to improve the prediction of extreme high-temperature days in summer.The HM_(YRB)relies on the following four predictors:the observed preceding April-May snowmelt in north western Europe;the snow depth in March over the central Siberian Plateau;the CFSv2-forecasted concurrent summer sea surface temperatures around the Maritime Continent;and the 200-hPa geopotential height over the Tibetan Plateau.The HM_(YRB)indicates good capabilities in predicting the interannual variability and trend of extreme high-temperature days,with a markable correlation coefficient of 0.58 and a percentage of the same sign(PSS)of 76% during 1983-2015 in the one-year-out cross-validation.Additionally,the HM_(YRB) maintains high PSS skill(86%)and robustness in the independent prediction period(2016-2022).Furthermore,the HM_(YRB) shows a good performance for years with high occurrence of extreme high-temperature days,with a hit ratio of 40%.These predictors used in HM_(YRB)are beneficial in terms of the prediction skill for the average daily maximum temperature in summer over the YRB,albeit with biases existing in the magnitude.Our study provides promising insights into the prediction of 2022-like hot extremes over the YRB in China.

关键词： Hot extremes Yangtze River basin CFSv2 Seasonal prediction One-year-out cross-validation

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Distinct influential mechanisms of the warm pool Madden-Julian Oscillation on persistent extreme cold events in Northeast China

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Atmospheric and Oceanic Science Letters 2022年第5期15卷 36-42页

作者： Yitian Qian Pang-Chi Hsu Huijun Wang mingkeng duan Key Laboratory of Meteorological Disaster Ministry of EducationNanjing University of Information Science&TechnologyNanjing 210044China

本文利用高分辨率气温数据和热带季节内振荡(MJO)实时指数,研究了1979-2015年冬季MJO活动对中国东北持续性极端低温事件(PECE)的影响特征和机理.结果表明:当MJO对流分别位于暖池地区的东印度洋(位相3)和西太平洋(位相5)时,中国东北PECE... 详细信息

本文利用高分辨率气温数据和热带季节内振荡(MJO)实时指数,研究了1979-2015年冬季MJO活动对中国东北持续性极端低温事件(PECE)的影响特征和机理.结果表明:当MJO对流分别位于暖池地区的东印度洋(位相3)和西太平洋(位相5)时,中国东北PECE的发生频率显著增加.利用温度方程诊断分析发现MJO两个位相所导致的冷却过程不同:当MJO处于位相3时,中国东北地区为低压异常,上升运动引起绝热冷却作用;而位相5所形成的气旋性环流为中国东北地区带来西北风冷平流,降温过程更强且持续更长时间.

关键词：持续性极端低温事件中国东北地区季节内振荡

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Two-dimensional ballistic transistors for advanced-node integrated circuits

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National Science Review 2024年第3期11卷 9-10页

作者： Jia Li Xidong duan Hunan Provincial Key Laboratory of Two-Dimensional Materials State Key Laboratory for Chemo/Biosensing and Chemometrics College of Chemistry and Chemical Engineering Hunan University

As the feature size of metal-oxide-semiconductor-field-effect-transistors(MOSFETs) in integrated circuits(ICs)is reduced to sub-10-nm, the traditional channel materials are plagued by enhanced scattering and short-cha... 详细信息

关键词： CONTACT

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A FAS approach for stabilization of generalized chained forms: part 1. Discontinuous control laws

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Science China(Information Sciences) 2024年第2期67卷 118-143页

作者： Guang-Ren duan Center for Control Theory and Guidance Technology Harbin Institute of Technology Center for Control Science and Technology Southern University of Science and Technology

In this paper, a type of general nonholonomic systems is proposed, which contains both the Brockett’s two example systems, and their extended n-dimensional chained forms, as special cases. For the stabilization of such systems, a stabilizing controller is proposed based on the fully actuated system(FAS)approach, which is discontinuous at the origin but time-invariant when the open-loop system is time-invariant,and drives the feasible trajectories of the system to the origin exponentially. Furthermore, the proposed FAS approach is also extended to the sub-normal system case and the time-delay system case.

关键词： nonholonomic systems feedback stabilization exponential convergence sub-fully actuated systems time-delay systems

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Comparing the Arctic climate in Chinese and other CMIP6 models

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Atmospheric and Oceanic Science Letters 2023年第6期16卷 8-15页

作者： Ruilian He mingkeng duan Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters/Key Laboratory of Meteorological Disaster Ministry of EducationNanjing University of Information Science&TechnologyNanjingChina

本研究采用来自耦合模式相互比较项目第六阶段(CMIP6)模式,评估和对比了10个中国模式和27个其他国际模式对北极冬季气候的历史模拟性能.本文的主要目的是展现中国模式对北极气候的模拟能力,并了解其在国际上的模拟水平.结果表明,对于气... 详细信息

本研究采用来自耦合模式相互比较项目第六阶段(CMIP6)模式,评估和对比了10个中国模式和27个其他国际模式对北极冬季气候的历史模拟性能.本文的主要目的是展现中国模式对北极气候的模拟能力,并了解其在国际上的模拟水平.结果表明,对于气候态的模拟,中国模式在模拟北极温度场和大气场这些气候学方面与其他国际模式相当.而在趋势方面,中国模式同样和其他国际模式都能很好地模拟出北极变暖的特征.此外,与观测到的环流相比,CMIP6多模式集合平均值(MME)并没有显著的正趋势,这可能是因为外部强迫的作用.

关键词：北极气候北极增暖 CMIP6 模式评估

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Stabilization Controller of An Extended Chained Nonholonomic System With Disturbance:An FAS Approach

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IEEE/CAA Journal of Automatica Sinica 2024年第5期11卷 1262-1273页

作者： Zhongcai Zhang Guangren duan School of Engineering Qufu Normal UniversityRizhao 276826China Center for Control Science and Technology Southern University of Science and TechnologyShenzhen 518055 Center for Control Theory and Guidance Technology Harbin Institute of TechnologyHarbin 150001China

This study examines the stabilization issue of extended chained nonholonomic systems(ECNSs)with external disturbance.Unlike the existing approaches,we transform the considered system into a fully actuated system(FAS)model,simplifying the stabilizing controller design.We implement a separate controller design and propose exponential stabilization controller and finite-time stabilization controller under finite-time disturbance observer(FTDO)for the two system inputs.In addition,we discuss the specifics of global stabilization control design.Our approach demonstrates that two system states exponentially or asymptotically converge to zero under the provided switching stabilization control strategy,while all other system states converge to zero within a finite time.

关键词： design stabilization system

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A comprehensive research on wear resistance of GH4169 superalloy in longitudinal-torsional ultrasonic vibration side milling with tool wear and surface quality

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Chinese Journal of Aeronautics 2024年第4期37卷 556-573页

作者： Baoqi CHANG Zhaoxi YI Fen ZHANG Lian duan Ji-an duan School of Mechanical and Electrical Engineering Central South UniversityChangsha 410083China State Key Laboratory of High Performance and Complex Manufacturing Central South UniversityChangsha 410083China School of Physics and Electronics Central South UniversityChangsha 410083China

To improve the service and machining performance of the workpiece, the tool wear mechanisms, surface machining quality, and wear resistance in conventional side milling(CSM)and longitudinal-torsional ultrasonic vibration side milling(LTUVSM) of GH4169 superalloy at different cutting lengths are investigated systematically. Tool wear mechanisms are revealed and the correlation between machined surface quality with tool wear is analyzed correspondingly. Tool wear patterns mainly include adhesive wear, diffusion wear, abrasive wear, and chipping sticking.Better surface quality is achieved in LTUVSM due to a maximum reduction of flank wear bandwidth and wear rate by 71.9% and 71.5%, respectively, compared to CSM. The friction coefficient,initial wear stage time, and wear volume of dry sliding wear were measured to evaluate the workpiece wear resistance. The maximum reductions in friction coefficient and wear volume in LTUVSM are 18.2% and 15.8% compared to CSM. The regular ultrasonic vibration textures suppress the friction and the growth of contact nodes in the contact area, decreasing the degree of surface wear, which is demonstrated by a 38.8% increase in initial wear stage time compared to CSM.In conclusion, the workpiece in LTUVSM exhibits higher wear resistance because of the improvement of tool wear and the guarantee of surface quality.

关键词： Dry sliding wear Surface quality Tool wear Ultrasonic vibration Wear resistance

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Distributed velocity-free formation tracking control for clustered UAVs under virtual leader-follower framework

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Science China(Technological Sciences) 2024年第5期67卷 1538-1552页

作者： ZHANG ZhaoYu duan HaiBin School of Automation Science and Electrical Engineering Beihang UniversityBeijing100083China

The collective formation control problem of a cluster of rotorcraft unmanned aerial vehicles(UAVs)is investigated in this article.The consensus tracking towards formation centroid with following UAVs forming a predefined configuration around the leader is considered as the objective.Unlike prior studies,the information of the central reference trajectory,which is deemed as a virtual leader in the leader-follower topology,is not directly accessible for partial nodes through the communication network.Therefore,a novel distributed formation tracking control scheme is promoted.Besides,a decentralized saturation observer is employed to estimate the reference acceleration signal of the virtual leader.In the absence of linear velocity measurement,two sliding manifolds are proposed by introducing the relative discrepancy terms of position and velocity.Then a smooth saturation operator in the form of a sigmoid function is applied to generate the command force input.Moreover,under the dilemma of constrained capabilities of the airborne sensors equipped on the rotorcrafts,the angular velocity is difficult to acquire.Two cascaded auxiliary attitude error systems are established on each rotorcraft system to synthesize the rotating torque with no need to require the angular velocity measurement.Due to the strong coupling and nonlinearity of the rotorcraft UAV system,the command angular velocity and the derivatives of command input are hard to obtain.Then a continuous nonlinear differentiator is proposed to work with the difficulties in deriving the explicit expression of system derivatives.Thereafter,a detailed stability analysis is conducted progressively on the angular control loop,reference trajectory observer loop,and the position control loop.A simulation scheme for a cluster of four rotorcraft UAVs tracking sinusoidal trajectory are presented and the formation control results are proven advantageous in comparison with the control protocol in previous literature.

关键词： distributed formation control unmanned rotorcraft clusters velocity-free tracking nonlinear differentiator

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Predicting climate anomalies:A real challenge

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Atmospheric and Oceanic Science Letters 2022年第1期15卷 2-11页

作者： Huijun Wang Yongjiu Dai Song Yang Tim Li Jingjia Luo Bo Sun mingkeng duan Jiehua Ma Zhicong Yin Yanyan Huang Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters/Key Laboratory of Meteorological Disaster Ministry of EducationNanjing University of Information Science and TechnologyNanjingChina School of Atmospheric Sciences Sun Yat-sen University&Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)ZhuhaiChina International Pacific Research Center and Department of Atmospheric Sciences School of Ocean and Earth Science and TechnologyUniversity of Hawaii at ManoaHonoluluUSA Nansen‐Zhu International Research Center Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina Climate Change Research Center Chinese Academy of SciencesBeijingChina

过去几十年,气候变化和极端气候事件造成的经济损失和灾害显著增加.虽然全球的科学家在理解和预测气候变异方面做出了巨大的努力,但当前在气候预测领域仍然存在几个重大难题.2020年,依托于国家自然科学基金基础科学中心项目的气候系统... 详细信息

过去几十年,气候变化和极端气候事件造成的经济损失和灾害显著增加.虽然全球的科学家在理解和预测气候变异方面做出了巨大的努力,但当前在气候预测领域仍然存在几个重大难题.2020年,依托于国家自然科学基金基础科学中心项目的气候系统预测研究中心(CCSP)成立了,该中心旨在应对和处理气候预测领域的三大科学难题:厄尔尼诺-南方涛动(ENSO)预测,延伸期天气预报,年际-年代际气候预测,并为更加准确的气候预测和更加有效的灾害防御提供科学依据.因此,本文介绍了CCSP的主要目标和面对的科学挑战,回顾了CCSP在季风动力过程,陆-气相互作用和模式开发,ENSO变率,季节内振荡,气候预测等方面已取得的重要研究成果.未来CCSP将继续致力于解决上述领域的关键科学问题.

关键词：气候系统预测研究中心季风动力学陆面过程模式 ENSO动力学延伸期天气预报年际-年代际气候预测

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Fabrication of porous adsorbents from eco-friendly aqueous foam for high-efficient removal of cationic dyes and sustainable utilization assessment

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Journal of Environmental Sciences 2024年第3期137卷 395-406页

作者： Fangzhi duan Yongfeng Zhu Yan Liu Aiqin Wang Key Laboratory of Clay Mineral Applied Research of Gansu Province Center of Eco-material and Green ChemistryLanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China

Porous materials applied in environmental remediation have received researchers'extensive attention recently,but the related green and convenient preparation method is rarely reported.Here,we recommended a green and convenient strategy for the fabrication of porous material via aqueous foam templates,which was synergistically stabilized by Codonopsis pilosula(CP)and clay minerals of attapulgite(APT).The characterization results revealed that the APT was modified by organic molecules leached from CP and anchored at the air-water interface,which improved the foam stability significantly.The novel porous material of polyacrylamide/Codonopsis pilosula/attapulgite(PAM/CP/APT)templated from the aqueous foam via a polymerization reaction had excellent adsorption capacity for the cationic dyes methyl violet(MV)and methylene blue(MB),and the adsorption capacity can reach 755.85 mg/g and557.64 mg/g,respectively.More importantly,the adsorption capacity of spent adsorbent material was still over 200 mg/g after being recycled five times through a simple carbonization process,and then it was added to the plant pot,the total biomass was increased by about86.42%.This study provided a green and sustainable pathway for the preparation,application and subsequent processing of porous materials.

关键词： Porous material Aqueous foam Atapulgite Adsorption Cationic dyes Sustainable utilization

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