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Distributed velocity-f.ee f.rmation tracking control f.r clustered UAVs under virtual leader-f.llower f.amework

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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 f.rmation control problem of.a cluster of.rotorcraf. unmanned aerial vehicles(UAVs)is investigated in this *** consensus tracking towards f.rmation centroid with f.llowing UAVs f.rming a predef.ned conf.guration around the leader is considered as the *** prior studies,the inf.rmation of.the central ref.rence trajectory,which is deemed as a virtual leader in the leader-f.llower topology,is not directly accessible f.r partial nodes through the communication ***,a novel distributed f.rmation tracking control scheme is ***,a decentralized saturation observer is employed to estimate the ref.rence acceleration signal of.the virtual *** the absence of.linear velocity measurement,two sliding manif.lds are proposed by introducing the relative discrepancy terms of.position and *** a smooth saturation operator in the f.rm of.a sigmoid f.nction is applied to generate the command f.rce ***,under the dilemma of.constrained capabilities of.the airborne sensors equipped on the rotorcraf.s,the angular velocity is dif.icult to *** cascaded auxiliary attitude error systems are established on each rotorcraf. system to synthesize the rotating torque with no need to require the angular velocity *** to the strong coupling and nonlinearity of.the rotorcraf. UAV system,the command angular velocity and the derivatives of.command input are hard to *** a continuous nonlinear dif.erentiator is proposed to work with the dif.iculties in deriving the explicit expression of.system ***,a detailed stability analysis is conducted progressively on the angular control loop,ref.rence trajectory observer loop,and the position control loop.A simulation scheme f.r a cluster of.0}ur rotorcraf. UAVs tracking sinusoidal trajectory are presented and the f.rmation control results are proven advantageous in comparison with the control protocol in previous literature.

关键词： distributed f.rmation control unmanned rotorcraf. clusters velocity-f.ee tracking nonlinear dif.erentiator

A comprehensive research on wear resistance of.GH4169 superalloy in longitudinal-torsional ultrasonic vibration side milling with tool wear and surf.ce 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 f.n ZHANG Lian duan Ji-an duan School of.Mechanical and Electrical Engineering Central South UniversityChangsha 410083China State Key Laboratory of.High Perf.rmance and Complex Manuf.cturing Central South UniversityChangsha 410083China School of.Physics and Electronics Central South UniversityChangsha 410083China

To improve the service and machining perf.rmance of.the workpiece, the tool wear mechanisms, surf.ce machining quality, and wear resistance in conventional side milling(CSM)and longitudinal-torsional ultrasonic vibration side milling(LTUVSM) of.GH4169 superalloy at dif.erent cutting lengths are investigated systematically. Tool wear mechanisms are revealed and the correlation between machined surf.ce quality with tool wear is analyzed correspondingly. Tool wear patterns mainly include adhesive wear, dif.usion wear, abrasive wear, and chipping *** surf.ce quality is achieved in LTUVSM due to a maximum reduction of.0}ank wear bandwidth and wear rate by 71.9% and 71.5%, respectively, compared to CSM. The f.iction coef.icient,initial wear stage time, and wear volume of.dry sliding wear were measured to evaluate the workpiece wear resistance. The maximum reductions in f.iction coef.icient and wear volume in LTUVSM are 18.2% and 15.8% compared to CSM. The regular ultrasonic vibration textures suppress the f.iction and the growth of.contact nodes in the contact area, decreasing the degree of.surf.ce wear, which is demonstrated by a 38.8% increase in initial wear stage time compared to *** conclusion, the workpiece in LTUVSM exhibits higher wear resistance because of.the improvement of.tool wear and the guarantee of.surf.ce quality.

关键词： Dry sliding wear Surf.ce quality Tool wear Ultrasonic vibration Wear resistance

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

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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 f.r Temperate East Asia Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China University of.Chinese Academy of.Sciences Beijing 100049China

With climate warming, f.equent drought events have occurred in recent decades, causing huge losses to industrial and agricultural production, and af.ecting people’s daily lives. The monitoring and f.recasting 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 f.r drought monitoring and f.recasting, are still scarce. The development of.a daily drought index would improve the accuracy of.drought monitoring and f.recasting, and f.cilitate the evaluation of.existing indices. In this study, we constructed a new daily drought index, the daily evapotranspiration def.cit index(DEDI), based on actual and potential evapotranspiration data f.om the high-resolution ERA5 reanalysis dataset of.the European Center f.r Medium-Range Weather f.recasts. This new index was then applied to analyze the spatial and temporal evolution characteristics of.0}ur 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 f.ur 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 surf.ce conditions, such as vegetation coverage,which enables its potential application not only f.r meteorological purposes but also f.r 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 f.r titanium alloy:Lubrication by the solid-liquid interf.ce with Coulomb repulsion

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f.iction 2024年第7期12卷 1564-1579页

作者： Linlin duan Dan JIA Jian LI Jianf.ng LIU Haitao duan State Key Laboratory of.Special Surf.ce Protection Materials and Application Technology Wuhan Research Institute of Materials ProtectionWuhan 430030China Hubei Longzhong Laboratory Xiangyang 441000China College of.Lif. Science and Technology Wuhan Polytechnic UniversityWuhan 430030China

In this work,the advantage of.Coulomb repulsion in the intermolecular f.rces experienced by molecules on the solid–liquid nanosized contact interf.ce is taken,and the superior f.iction-reducing property of.Cu_(3)(PO_(4))2·3H_(2)O(CuP)oil-based additives has been conf.rmed f.r titanium ***-dimensional(3D)CuP nanof.owers(CuP-f.)with a strong capillary absorption ef.ect are prepared to achieve the homogeneous mixing of.solid CuP and lubricating *** by CuP-f. additives f.r titanium alloy,f.iction coef.icient(COf.can be reduced by 73.68%,and wear rate(WR)reduced by 99.69%.It is demonstrated that the extraordinary f.iction-reducing property is due to the repulsive solid–liquid interf.ce with low viscous shear f.rce originating f.om Coulomb repulsion between polar water molecules in CuP and non-polar oil ***,any steric hindrance or connection between this repulsive solid–liquid interf.ce will trigger the adhesion and increase the viscous shear f.rce,f.r example,dispersant,hydrogen bondings,and shaky adsorbed water ***,the lamellar thickness of.CuP and the molecular size of.lubricant both have a great inf.uence on tribological *** the lubrication mechanism based on interf.ce Coulomb repulsion is proposed that may help broaden the scope of.the exploration in low-f.iction nanomaterial design and new lubricant systems.

关键词： lubrication nanomaterial additive solid-liquid interf.ce wear

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

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Def.nce 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 f.ng-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 f.r the shock initiation of.melt-cast explosives based on the pore collapse hot-spot ignition mechanism.A series of.shock initiation experiments was perf.rmed f.r the Comp B melt-cast explosive to estimate ef.ects 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 f.rmula proportion greatly af.ect 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

ViTAU:基于Vision transf.rmer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(f.cial nerve paralysis,f.P),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(f.cial nerve paralysis,f.P),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 transf.rmer(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 f.cial Palsy(Yf.)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： Transf.rmer 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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Precipitation anomaly over the Tibetan Plateau af.ected by tropical sea-surf.ce 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 f.r Atmospheric Sciences and Geophysical f.uid 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 af.ected 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 ef.ects 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-surf.ce 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 ef.ects 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 ef.ects of.drivers in the tropics and mid-latitudes,providing a basis f.r more accurate simulations and predictions of.TP precipitation.

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

Robust Attitude Control f.r Reusable Launch Vehicles Based on f.actional 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 f.ight Systems(BAf.) 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 f.actional order sliding mode control and dynamic inversion approach is presented f.r the reusable launch vehicle RLV during the reentry phase. By introducing the f.actional order sliding surf.ce 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 ef.ectiveness 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

Avian contrast sensitivity inspired contour detector f.r 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 f.r autonomous landing of.unmanned aerial vehicles. Inspired by the attenuation ef.ect and surround suppression mechanism, a novel biologically computational method based on the avian contrast sensitivity is proposed f.r runway contour detection. f.r the noisy stimuli, deniosed responses of.the biologically inspired Gabor energy operator are generalized f.llowed by the denoising layer and the multiresolution f.sion layer. Moreover, two f.ctors such as contour ef.ect and texture suppression are considered in the contrast sensitivity based surround inhibition. Dif.erent f.om traditional detectors, which do not distinguish between contours and texture edges, the proposed method can respond strongly to contours and suppress the texture inf.rmation. Applying the contrast sensitivity inspired detector to noisy runway scenes yields ef.ective contours, while the non-meaningf.l texture elements are removed dramatically at the same time. Besides the superior perf.rmance over traditional detectors, the proposed method is capable to provide insight into the attenuation ef.ect of.the avian contrast sensitivity f.nction and has potential applications in computer vision and pattern recognition.

关键词： contrast sensitivity f.nction surround suppression contour perception unmanned aerial vehicle landing