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A daily drought index based on evapotranspiration and its application in regional drought analyses

Science China Earth Sciences 2022年第2期65卷 317-336页

作者： Xia ZHANG Yawen duan Jianping duan Dongnan JIAN Zhuguo MA Key Laboratory of Regional Climate-Environment Research for Temperate East Asia Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China University of Chinese Academy of Sciences Beijing 100049China

With climate warming, frequent drought events have occurred in recent decades, causing huge losses to industrial and agricultural production, and affecting people’s daily lives. The monitoring and forecasting of drought events has drawn increasing attention. However, compared with the various monthly drought indices and their wide application in drought research,daily drought indices, which would be much more suitable for drought monitoring and forecasting, are still scarce. The development of a daily drought index would improve the accuracy of drought monitoring and forecasting, and facilitate the evaluation of existing indices. In this study, we constructed a new daily drought index, the daily evapotranspiration deficit index(DEDI), based on actual and potential evapotranspiration data from the high-resolution ERA5 reanalysis dataset of the European Center for Medium-Range Weather Forecasts. This new index was then applied to analyze the spatial and temporal evolution characteristics of four drought events that occurred in southwest, north, northeast, and eastern northwest China in the spring and summer of 2019. Comparisons with the operationally used Meteorological Drought Composite Index and another commonly used index, the Standardized Precipitation Evapotranspiration Index, indicated that DEDI characterized the spatiotemporal evolution of the four drought events reasonably well and was superior in depicting the onset and cessation of the drought events,as well as multiple drought intensity peaks. Additionally, DEDI considers land surface conditions, such as vegetation coverage,which enables its potential application not only for meteorological purposes but also for agricultural drought warning and monitoring.

关键词： Actual evapotranspiration Potential evapotranspiration Daily drought index Meteorological drought Drought events

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Nanostructured lubricant additives for titanium alloy:Lubrication by the solid-liquid interface with Coulomb repulsion

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Friction 2024年第7期12卷 1564-1579页

作者： Linlin duan Dan JIA Jian LI Jianfang LIU Haitao duan State Key Laboratory of Special Surface Protection Materials and Application Technology Wuhan Research Institute of Materials ProtectionWuhan 430030China Hubei Longzhong Laboratory Xiangyang 441000China College of Life Science and Technology Wuhan Polytechnic UniversityWuhan 430030China

In this work,the advantage of Coulomb repulsion in the intermolecular forces experienced by molecules on the solid–liquid nanosized contact interface is taken,and the superior friction-reducing property of Cu_(3)(PO_(4))2·3H_(2)O(CuP)oil-based additives has been confirmed for titanium ***-dimensional(3D)CuP nanoflowers(CuP-Fs)with a strong capillary absorption effect are prepared to achieve the homogeneous mixing of solid CuP and lubricating *** by CuP-Fs additives for titanium alloy,friction coefficient(COF)can be reduced by 73.68%,and wear rate(WR)reduced by 99.69%.It is demonstrated that the extraordinary friction-reducing property is due to the repulsive solid–liquid interface with low viscous shear force originating from Coulomb repulsion between polar water molecules in CuP and non-polar oil ***,any steric hindrance or connection between this repulsive solid–liquid interface will trigger the adhesion and increase the viscous shear force,for example,dispersant,hydrogen bondings,and shaky adsorbed water ***,the lamellar thickness of CuP and the molecular size of lubricant both have a great influence on tribological *** the lubrication mechanism based on interface Coulomb repulsion is proposed that may help broaden the scope of the exploration in low-friction nanomaterial design and new lubricant systems.

关键词： lubrication nanomaterial additive solid-liquid interface wear

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A melt-cast duan-Zhang-Kim mesoscopic reaction rate model and experiment for shock initiation of melt-cast explosives

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Defence Technology（防务技术） 2021年第5期17卷 1753-1763页

作者： Shu-rui Li Zhuo-ping duan Lian-sheng Zhang Zhuo-cheng Ou Feng-lei Huang State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China

A melt-cast duan-Zhang-Kim(DZK)mesoscopic reaction rate model is developed for the shock initiation of melt-cast explosives based on the pore collapse hot-spot ignition mechanism.A series of shock initiation experiments was performed for the Comp B melt-cast explosive to estimate effects of the loading pressure and the particle size of granular explosive component,and the mesoscopic model is validated against the experimental *** numerical simulations indicate that the initial density and formula proportion greatly affect the hot-spot ignition of melt-cast explosives.

关键词： Melt-cast explosive Shock initiation Mesoscopic reaction rate model Hot-spot ignition Shock sensitivity

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ViTAU:基于Vision transformer和面部动作单元的面瘫识别与分析

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工程科学学报 2025年第2期47卷 351-363页

作者：高嘉蔡文浩赵俊莉段福庆青岛大学计算机科学技术学院青岛266071 北京师范大学人工智能学院北京100875

面部神经麻痹(Facial nerve paralysis,FNP),通常称为贝尔氏麻痹或面瘫,对患者的日常生活和心理健康产生显著影响,面瘫的及时识别和诊断对于患者的早期治疗和康复至关重要.随着深度学习和计算机视觉技术的快速发展,面瘫的自动识别变得可... 详细信息

面部神经麻痹(Facial nerve paralysis,FNP),通常称为贝尔氏麻痹或面瘫,对患者的日常生活和心理健康产生显著影响,面瘫的及时识别和诊断对于患者的早期治疗和康复至关重要.随着深度学习和计算机视觉技术的快速发展,面瘫的自动识别变得可行,为诊断提供了一种更准确和客观的方式.目前的研究主要集中关注面部的整体变化,而忽略了面部细节的重要性.面部不同部位对识别结果的影响力并不相同,这些研究尚未对面部各个区域进行细致区分和分析.本项研究引入结合Vision transformer(ViT)模型和动作单元(Action unit,AU)区域检测网络的创新性方法用于面瘫的自动识别及区域分析.ViT模型通过自注意力机制精准识别是否面瘫,同时,基于AU的策略从StyleGAN2模型提取的特征图中,利用金字塔卷积神经网络分析受影响区域.这一综合方法在YouTube Facial Palsy(YFP)和经过扩展的Cohn Kanade(CK+)数据集上的实验中分别达到99.4%的面瘫识别准确率和81.36%的面瘫区域识别准确率.通过与最新方法的对比,实验结果展示了所提的自动面瘫识别方法的有效性.

关键词： Transformer 面部动作单元多分辨率特征图生成器热力图回归

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Robust Attitude Control for Reusable Launch Vehicles Based on Fractional Calculus and Pigeon-inspired Optimization

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IEEE/CAA Journal of Automatica Sinica 2017年第1期4卷 89-97页

作者： Qiang Xue Haibin duan Bio-inspired Autonomous Flight Systems(BAFS) Research Group the Science and Technology on Aircraft Control Laboratory School of Automation Science and Electrical Engineering Beihang University (BUAA) IEEE

In this paper, a robust attitude control system based on fractional order sliding mode control and dynamic inversion approach is presented for the reusable launch vehicle RLV during the reentry phase. By introducing the fractional order sliding surface to replace the integer order one, we design robust outer loop controller to compensate the error introduced by inner loop controller designed by dynamic inversion approach. To take the uncertainties of aerodynamic parameters into account, stochastic robustness design approach based on the Monte Carlo simulation and Pigeon-inspired optimization is established to increase the robustness of the controller. Some simulation results are given out which indicate the reliability and effectiveness of the attitude control system. © 2014 Chinese Association of Automation.

关键词： Attitude control Calculations Communication satellites Control systems Intelligent systems Launch vehicles Launching Monte Carlo methods Nonlinear control systems Reusability Reusable rockets Robustness (control systems) Sliding mode control Stochastic systems Vehicles

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Science China Earth Sciences 2017年第1期60卷 156-172页

作者： FENG Rong duan WanSuo State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

This study explored the spatial patterns of winter predictability barrier(WPB)-related optimal initial errors and optimal precursors for positive Indian Ocean dipole(IOD)events,and the associated physical mechanisms for their developments were analyzed using the Simple Ocean Data Assimilation *** consideration of the effects of model errors on"predictions,"it was assumed that different"predictions"are caused by different initial *** two types of WPB-related optimal initial errors are almost opposite for the start months of July(-1)and July(0),although they both present a west-east dipole pattern in the tropical Indian Ocean,with the maximum errors located at the thermocline *** feedback and ocean waves play important roles in the growth of prediction *** two physical mechanisms compete during July-December and ocean waves dominate during *** spatial patterns of optimal precursors and the physical mechanisms for their developments are similar to those of WPB-related optimal initial *** is worth noting that large values of WPB-related optimal initial errors and optimal precursors are concentrated within a few locations,which probably represent the sensitive areas of targeted observations for positive IOD *** great similarities between WPB-related optimal initial errors and optimal precursors suggest that were intensive observations performed over these areas,this would not only reduce initial errors and thus,prediction errors,but it would also permit the detection of the signal of IOD events in advance,greatly improving the forecast skill of positive IOD events.

关键词： Optimal precursors Initial errors Winter predictability barrier Indian Ocean dipole

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Avian contrast sensitivity inspired contour detector for unmanned aerial vehicle landing

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Science China(Technological Sciences) 2017年第12期60卷 1958-1965页

作者： DENG YiMin duan HaiBin State Key Laboratory of Virtual Reality Technology and Systems School of Automation Science and Electrical Engineering Beihang University Beijing 100191 China

Runway detection is a demanding task for autonomous landing of unmanned aerial vehicles. Inspired by the attenuation effect and surround suppression mechanism, a novel biologically computational method based on the avian contrast sensitivity is proposed for runway contour detection. For the noisy stimuli, deniosed responses of the biologically inspired Gabor energy operator are generalized followed by the denoising layer and the multiresolution fusion layer. Moreover, two factors such as contour effect and texture suppression are considered in the contrast sensitivity based surround inhibition. Different from traditional detectors, which do not distinguish between contours and texture edges, the proposed method can respond strongly to contours and suppress the texture information. Applying the contrast sensitivity inspired detector to noisy runway scenes yields effective contours, while the non-meaningful texture elements are removed dramatically at the same time. Besides the superior performance over traditional detectors, the proposed method is capable to provide insight into the attenuation effect of the avian contrast sensitivity function and has potential applications in computer vision and pattern recognition.

关键词： contrast sensitivity function surround suppression contour perception unmanned aerial vehicle landing

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Precipitation anomaly over the Tibetan Plateau affected by tropical sea-surface temperatures and mid-latitude atmospheric circulation in September

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Science China Earth Sciences 2023年第3期66卷 619-632页

作者： Ping ZHANG Anmin duan 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 Science University of Chinese Academy of SciencesBeijing 100049China State Key Laboratory of Marine Environmental Science College of Ocean and Earth SciencesXiamen UniversityXiamen 361102China

Tibetan Plateau(TP)precipitation is affected by anomalous circulation systems in both the tropics and mid-latitudes,due to the TP’s unique geographical *** using observational,reanalysis,and CMIP6 model datasets,this study reveals the individual and joint effects of the Indian Ocean Dipole(IOD)and Silk Road pattern(SRP)on the interannual variability of TP precipitation in *** the positive IOD phase,the zonal gradient of the sea-surface temperature anomalies(SSTAs)drives a Gill-type response with an anticyclonic anomaly over the Indian subcontinent and Bay of *** the north,anomalous westerlies induce a shallow trough,and the associated anomalous southwesterlies transport moisture to the southeastern TP,resulting in surplus precipitation ***,the westerly jet disturbances over the North Atlantic excite an SRP-like pattern,resulting in a baroclinic structure in northern India with the upper(lower)tropospheric anomalous anticyclone(cyclone)over west-central Asia(northern India).The anomalous southwesterlies to the east of the low-level cyclone transport abundant moisture to the southeastern TP,which results in increased precipitation *** joint effects of IOD and SRP can explain nearly 52%of the TP precipitation anomaly,exceeding the contribution of IOD(19%)and SRP(27%)*** results highlight the necessity of considering the joint effects of drivers in the tropics and mid-latitudes,providing a basis for more accurate simulations and predictions of TP precipitation.

关键词： Tibetan Plateau precipitation Interannual variability Indian Ocean Dipole Silk Road pattern

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The application of the orthogonal conditional nonlinear optimal perturbations method to typhoon track ensemble forecasts

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Science China Earth Sciences 2019年第2期62卷 376-388页

作者： Zhenhua HUO Wansuo duan National Meteorological Center China Meteorological Administration State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of Sciences University of Chinese Academy of Sciences

The orthogonal conditional nonlinear optimal perturbations (CNOPs) method, orthogonal singular vectors (SVs)method and CNOP+SVs method, which is similar to the orthogonal SVs method but replaces the leading SV (LSV) with the first CNOP, are adopted in both the Lorenz-96 model and Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) Fifth-Generation Mesoscale Model (MM5) for ensemble forecasts. Using the MM5, typhoon track ensemble forecasting experiments are conducted for strong Typhoon Matsa in 2005. The results of the Lorenz-96 model show that the CNOP+SVs method has a higher ensemble forecast skill than the orthogonal SVs method, but ensemble forecasts using the orthogonal CNOPs method have the highest forecast skill. The results from the MM5 show that orthogonal CNOPs have a wider horizontal distribution and better describe the forecast uncertainties compared with SVs. When generating the ensemble mean forecast, equally averaging the ensemble members in addition to the anomalously perturbed forecast members may contribute to a higher forecast skill than equally averaging all of the ensemble members. Furthermore, for given initial perturbation amplitudes, the CNOP+SVs method may not have an ensemble forecast skill greater than that of the orthogonal SVs method, but the orthogonal CNOPs method is likely to have the highest forecast skill. Compared with SVs, orthogonal CNOPs fully consider the influence of nonlinear physical processes on the forecast results; therefore, considering the influence of nonlinearity may be important when generating fast-growing initial ensemble perturbations. All of the results show that the orthogonal CNOP method may be a potential new approach for ensemble forecasting.

关键词： Ensemble forecasts Initial perturbation Conditional nonlinear optimal perturbation Singular vector Typhoon track

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Multi-objective pigeon-inspired optimization for brushless direct current motor parameter design

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Science China(Technological Sciences) 2015年第11期58卷 1915-1923页

作者： QIU HuaXin duan HaiBin Bio-inspired Autonomous Flight Systems(BAFS) Research Group Science and Technology on Aircraft Control Laboratory School of Automation Science and Electrical Engineering Beihang University

Pigeon-inspired optimization(PIO) is a new swarm intelligence optimization algorithm, which is inspired by the behavior of homing pigeons. A variant of pigeon-inspired optimization named multi-objective pigeon-inspired optimization(MPIO) is proposed in this paper. It is also adopted to solve the multi-objective optimization problems in designing the parameters of brushless direct current motors, which has two objective variables, five design variables, and five constraint variables. Furthermore, comparative experimental results with the modified non-dominated sorting genetic algorithm are given to show the feasibility, validity and superiority of our proposed MIPO algorithm.

关键词： brushless direct current (BLDC) motor multi-objective pigeon-inspired optimization (MPIO) electromagnetics mul-ti-objective optimization

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