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Journal of System. Science & com.lexity 2024年第1期37卷 136-151页

作者： PAN Zini chen Ben m Departm.nt of m.chanical and Autom.tion Engineering The Chinese University of Hong KongHong KongChina

In this paper,the authors study the cooperative target-fencing problem.for n-dim.nsional system. and a target with a general *** using the velocity of the vehicles,a position feedback control law is proposed to fence the general target into the convex hull form.d by the ***,the dynam.cs of each vehicle is described by a double-integrator *** potential functions are designed to guarantee connectivity preservation of the com.unication network and collision avoidance am.ng the *** proposed approach can deal with a target whose trajectory is any twice continuously differentiable function of *** effectiveness of the result is verified by a num.rical exam.le.

关键词： m.lti-agent system. networked system. target fencing

Effects of layer interactions on instantaneous stability of finite Stokes flows

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Applied m.them.tics and m.chanics(English Edition) 2024年第1期45卷 69-84页

作者： chen ZHAO Zhenli chen c.T.m.TASA Dong LI School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China

The stability analysis of a finite Stokes layer is of practical im.ortance in flow control. In the present work, the instantaneous stability of a finite Stokes layer with layer interactions is studied via a linear stability analysis of the frozen phases of the base flow. The oscillations of two plates can have different velocity am.litudes, initial phases, and frequencies. The effects of the Stokes-layer interactions on the stability when two plates oscillate synchronously are analyzed. The growth rates of two m.st unstable m.des when δ m.st equal, and δ = δ*/h*, where δ*and h*are the Stokes-layer thickness and the half height of the channel, respectively. However, their vorticities are different. The vorticity of the m.st unstable m.de is sym.etric, while the other is asym.etric. The Stokes-layer interactions have a destabilizing effect on the m.st unstable m.de when δ ct when δ > 0.68. However, the interactions always have a stabilizing effect on the other unstable m.de. It is explained that one of the two unstable m.des has m.ch higher dissipation than the other one when the Stokes-layer interactions are strong. We also find that the stability of the Stokes layer is closely related to the inflectional points of the base-flow velocity profile. The effects of inconsistent velocity-am.litude, initial phase, and frequency of the oscillations on the stability are analyzed. The energy of the m.st unstable eigenvector is m.inly distributed near the plate of higher velocity am.litude or higher oscillation frequency. The effects of the initial phase difference are com.licated because the base-flow velocity is extrem.ly sensitive to the initial phase.

关键词： finite Stokes layer instantaneous stability Stokes-layer interaction asynchronous oscillation

Interfacial stress engineering toward enhancem.nt of ferroelectricity in Al doped HfO_(2)thin film.

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chinese Physics B 2024年第9期33卷 637-643页

作者： S X chen m.m.chen Y Liu D W cao G J chen Departm.nt of m.croelectronics Jiangsu UniversityZhenjiang 212013China Departm.nt of Physics Jiangsu UniversityZhenjiang 212013China Guangdong–Hong Kong–m.cao Joint Laboratory for Intelligent m.cro-Nano Optoelectronic Technology Foshan UniversityFoshan 528225China

Ferroelectric HfO_(2)has attracted m.ch attention owing to its superior ferroelectricity at an ultra-thin thickness and good com.atibility with Si-based com.lem.ntary m.tal-oxide-sem.conductor(cm.S)***,the crystallization of polar orthorhom.ic phase(o-phase)HfO_(2)is less com.etitive,which greatly lim.ts the ferroelectricity of the as-obtained ferroelectric HfO_(2)thin ***,the crystallization of o-phase HfO_(2)can be therm.dynam.cally m.dulated via interfacial stress *** this paper,the growth of im.roved ferroelectric Al doped HfO_(2)(HfO_(2):Al)thin film. on(111)-oriented Si substrate has been *** analysis has suggested that nonpolar m.noclinic HfO_(2):Al grown on(111)-oriented Si substrate suffered from.a strong com.ressive strain,which prom.ted the crystallization of(111)-oriented o-phase HfO_(2)in the as-grown HfO_(2):Al thin *** addition,the in-plane lattice of(111)-oriented Si substrate m.tches well with that of(111)-oriented o-phase HfO_(2),which further therm.lly stabilizes the o-phase HfO_(2).Accordingly,an im.roved ferroelectricity with a rem.ant polarization(2P_(r))of 26.7c/cm.(2) has been *** results shown in this work provide a sim.le way toward the preparation of im.roved ferroelectric HfO_(2)thin film..

关键词： im.roved ferroelectricity interfacial stress engineering com.ressive strain HfO_(2)

A hierarchical m.lti-UAV cooperative fram.work for infrastructure inspection and reconstruction

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control Theory and Technology 2024年第3期22卷 394-405页

作者： chuanxiang Gao Xinyi Wang Xi chen Ben m.chen Departm.nt of m.chanical and Autom.tion Engineering The Chinese University of Hong KongHong KongShatinNTChina

Unm.nned aerial vehicles(UAVs)are em.rging as a powerful tool for inspections and repair works in large-scale and unstructured 3D infrastructures,but current approaches take a long tim. to cover the entire *** using UAVs for inspections and repair works puts forward a requirem.nt of im.roving tim. efficiency in large-scale and cluster *** paper presents a hierarchical m.lti-UAV cooperative fram.work for infrastructure inspection and reconstruction to balance the workload and reduce the overall task com.letion *** proposed fram.work consists of two stages,the exploration stage and the exploitation stage,resolving the task in a sequential *** the exploration stage,the density m.p is developed to update global and local inform.tion for dynam.c load-balanced area partition based on reconstructability and relative positions of UAVs,and the Voronoi-based planner is used to enable the UAVs to reach their best *** obtaining the global m.p,viewpoints are generated and divided while taking into account the battery capacity of each ***,a shortest path planning m.thod is used to m.nim.ze the total traveling cost of these viewpoints for obtaining a high-quality *** experim.nts are conducted in both a sim.lated and real environm.nt to show the tim. efficiency,robustness,and effectiveness of the proposed ***,the whole system.is im.lem.nted in real applications.

关键词： m.lti-UAV coverage path planning Infrastructure inspection and reconstruction

Local m.S m.trix Decom.osition Algorithm. for Elliptic BVPs in Annuli

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Num.rical m.them.tics(Theory,m.thods and Applications) 2024年第1期17卷 93-120页

作者： c.S.chen Andreas Karageorghis m.n Lei School of m.them.tics and Natural Sciences University of Southern MississippiHattiesburgMS 39406USA Departm.nt of m.them.tics and Statistics University of CyprusP.O.Box 20537Nicosia 1678Cyprus college of m.them.tics Taiyuan University of TechnologyTaiyuan 030024P.R.China

We apply the local m.thod of fundam.ntal solutions(Lm.S)to boundary value problem.(BVPs)for the Laplace and hom.geneous biharm.nic equations in *** appropriately choosing the collocation points,the Lm.S discretization yields sparse block circulant system.*** a result,m.trix decom.osition algorithm.(m.As)and fast Fourier transform.(FFTs)can be used for the solution of the system. resulting in considerable savings in both com.utational tim. and storage *** accuracy of the m.thod and its ability to solve large scale problem. are dem.nstrated by applying it to several num.rical experim.nts.

关键词： Local m.thod of fundam.ntal solutions Poisson equation biharm.nic equation m.trix decom.osition algorithm. fast Fourier transform.

Drought events influence nutrient canopy exchanges and green leaf partitioning during senescence in a deciduous forest

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Forest Ecosystem. 2024年第1期11卷 110-119页

作者： J.Touche c.calvaruso P.De Donato m.-P.Turpault INRAE BEFF-54000NancyFrance Um. 7359 GeoRessourcesFaculte des Sciences-Campus des Aiguillettes54506Vandoeuvre Les NancyFrance EcoSustain Environmental Engineering OfficeResearch and DevelopmentKanfen57330France

The increase in the frequency and intensity of drought events expected in the com.ng decades in Western Europe m.y disturb forest biogeochem.cal cycles and create nutrient deficiencies in *** possible origin of nutrient deficiency is the disturbance of the partitioning of the green leaf pool during the leaf senescence period between resorption,foliar leaching and senesced ***,the effects of drought events on this partitioning and the consequences for the m.intenance of tree nutrition are poorly *** experim.nt in a beech forest in m.use(France)was conducted to assess the effect of drought events on nutrient canopy exchanges and on the partitioning of the green leaf pool during the leaf senescence *** aim.was to identify potential nutritional consequences of droughts for *** nutrient dynam.cs,including resorption,chem.stry of green and senesced leaves,foliar absorption and leaching in m.ture beech stands from.2012 to 2019 allowed us to com.are the nutrient exchanges for three nondry and three dry years(i.e.,with an intense drought event during the growing season).During dry years,we observed a decrease by alm.st a third of the potassium.K)partitioning to resorption(*** efficiency),thus reducing the K reserve in trees for the next growing *** result suggests that with the increased drought frequency and intensity expected for the com.ng decades,there will be a risk of potassium.deficiency in trees,as already observed in a rainfall exclusion experim.nt on the sam. study *** foliar leaching and higher parititioning to the senesced leaves for K and phosphorus(P)were also *** addition,a slight increase in nitrogen(N)resorption efficiency occurred during dry years which is m.re likely to im.rove tree *** calcium.ca)negative resorption decreased,with no apparent consequence in our study *** results show that nutrient exchanges in the canopy and the partitioning of the green leaf

关键词： Natural drought Beech forest canopy Resorption Foliar leaching Senesced leaves Nutrition

Dynam.c Event-Triggered consensus control for Input constrained m.lti-Agent System. With a Designable m.nim.m.Inter-Event Tim.

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IEEE/cAA Journal of Autom.tica Sinica 2024年第3期11卷 649-660页

作者： m.ilin Li Yue Long Tieshan Li Hongjing Liang c.L.Philip chen the School of Autom.tion Engineering University of Electronic Science and Technology of ChinaChengdu 611731China IEEE the Yangtze Delta Region Institute University of Electronic Science and Technology of ChinaHuzhou 313000 the Laboratory of Electrom.gnetic Space cognition and Intelligent control Beijing 100089China the School of com.uter Science and Engineering South China University of TechnologyGuangzhou 510006

This paper investigates the consensus control of m.lti-agent system.(m.Ss) with constrained input using the dynam.c event-triggered m.chanism.ETm..consider the m.Ss with sm.ll-scale networks where a centralized dynam.c ETm.with global inform.tion of the m.Ss is first ***,a distributed dynam.c ETm.which only uses local inform.tion is developed for the m.Ss with large-scale *** is shown that the sem.-global consensus of the m.Ss can be achieved by the designed bounded control protocol where the Zeno phenom.non is elim.nated by a designable m.nim.m.inter-event *** addition,it is easier to find a trade-off between the convergence rate and the m.nim.m.inter-event tim. by an adjustable ***,the results are extended to regional consensus of the m.Ss with the bounded control *** sim.lations show the effectiveness of the proposed approach.

关键词： constrained input designable m.nim.m.inter-event tim. directed com.unication topology dynam.c event-triggered m.chanism m.Ss consensus control

Adaptive neural network control of a 2-DOF helicopter system.considering input constraints and global prescribed perform.nce

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Science china(Inform.tion Sciences) 2024年第7期67卷 224-239页

作者： Zhijia ZHAO Jiale WU Zhijie LIU We HE c.L.Philip chen School of m.chanical and Electrical Engineering Guangzhou University School of Intelligence Science and Technology and Key Laboratory of Intelligent Bionic Unm.nned System. of m.nistry of Education University of Science and Technology Beijing School of com.uter Science and Engineering South China University of Technology Pazhou Lab

In this study, an adaptive neural network(NN) control is proposed for nonlinear two-degree-offreedom.2-DOF) helicopter system. considering the input constraints and global prescribed ***, radial basis function NN(RBFNN) is em.loyed to estim.te the unknown dynam.cs of the helicopter system. Second, a sm.oth nonaffine function is exploited to approxim.te and address nonlinear constraint functions. Subsequently, a new prescribed function is proposed, and an original constrained error is transform.d into an equivalent unconstrained error using the error transform.tion and barrier function transform.tion m.thods. The analysis of the established Lyapunov function proves that the controlled system.is globally uniform.y bounded. Finally, the sim.lation and experim.ntal results on a constructed Quanser's test platform.verify the rationality and feasibility of the proposed control.

关键词： adaptive NN control 2-DOF helicopter global prescribed perform.nce input constraints

m.chanistic insight into cr(Ⅵ)retention by Si-containing ferrihydrite

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Journal of Environm.ntal Sciences 2024年第5期139卷 217-225页

作者： Ying Hu Qiang Xue Honghan chen Huam.ng Guo Kenneth c.carroll Song Wang m.E Key Laboratory of Groundwater circulation and Environm.ntal Evolution School of Water Resources and EnvironmentChina University of Geosciences(Beijing)Beijing 100083China Beijing Key Laboratory of Water Resources and Environm.ntal Engineering School of Water Resources and EnvironmentChina University of GeosciencesBeijing 100083China State Key Laboratory of Biogeology and Environm.ntal Geology China University of GeosciencesBeijing 100083China Plant&Environm.ntal Science New Mexico State UniversityNM 88003USA Institute of Theoretical chem.stry College of ChemistryJilin UniversityChangchun 130023China

Hexavalent chrom.um.cr(Ⅵ)]causes serious harm.to the environm.nt due to its high toxicity,solubility,and ***(Fh)are the m.in adsorbent and trapping agent of cr(Ⅵ)in soils and aquifers,and they usually coexist with silicate(Si),form.ng Si-containing ferrihydrite(Si-Fh)***,the m.chanism.of cr(Ⅵ)retention by Si-Fh m.xtures is poorly *** this study,the behaviors and m.chanism. of cr(Ⅵ)adsorption onto Si-Fh with different Si/Fe m.lar ratios was *** electron m.croscope,Fourier transform.infrared spectroscopy,X-ray diffraction,X-ray photoelectron spectroscopy,and other techniques were used to characterize Si-Fh and cr(Ⅵ)-loading of *** results show that specific surface area of Si-Fh increases gradually with increasing Si/Fe ratios,but cr(Ⅵ)adsorption on Si-Fh decreases with increasing Si/Fe *** is because with an increase in Si/Fe m.lar ratio,the point of zero charge of Si-Fh gradually decreases and electrostatic repulsion between Si-Fh and cr(Ⅵ)***,the com.lexation of cr(Ⅵ)is enhanced due to the increase in adsorbed hydroxyl(A-OH-)on Si-Fh with increasing Si/Fe m.lar ratio,which partly counteracts the effect of the electrostatic ***,the increase in the electrostatic repulsion has a greater im.act on adsorption than the additional com.lexation with *** functional theory calculation further supports this observation,showing the increases in electron variation of bonding atom. and reaction energies of inner spherical com.lexes with the increase in Si/Fe ratio.

关键词： Hexavalent chrom.um Ferrihydrite Si/Fe ratio cr(Ⅵ)Adsorption

Liquefaction susceptibility and deform.tion characteristics of saturated coral sandy soils subjected to cyclic loadings-a critical review

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Earthquake Engineering and Engineering Vibration 2024年第1期23卷 261-296页

作者： chen Guoxing Qin You m. Weijia Liang Ke Wu Qi c.Hsein Juang Institute of Geotechnical Engineering Nanjing Tech UniversityNanjing 210009China civil Engineering and Earthquake Disaster Prevention center of Jiangsu Province Nanjing 210009China School of m.chanical Engineering Nanjing University of Science and TechnologyNanjing 210094China college of civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing 210016China Glenn Departm.nt of civil Engineering Clemson UniversityClemsonSC 29634USA

coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical *** to the unique m.rine depositional environm.nt of coral sandy soils,the engineering characteristics and responses of these soils subjected to m.notonic and cyclic loadings have been a subject of intense interest am.ng the geotechnical and earthquake engineering *** paper critically reviews the progress of experim.ntal investigations on the undrained behavior of coral sandy soils under m.notonic and cyclic loadings over the last three *** focus of coverage includes the contractive-dilative behavior,the pattern of excess pore-water pressure(EPWP)generation and the liquefaction m.chanism.and liquefaction resistance,the sm.ll-strain shear m.dulus and strain-dependent shear m.dulus and dam.ing,the cyclic softening feature,and the anisotropic characteristics of undrained responses of saturated coral sandy *** particular,the advances m.de in the past decades are reviewed from.the following aspects:(1)the characterization of factors that im.act the m.chanism.and patterns of EPWP build-up;(2)the identification of liquefaction triggering in term. of the apparent viscosity and the average flow coefficient;(3)the establishm.nt of the invariable form.of strain-based,stress-based,or energy-based EPWP ratio form.las and the unique relationship between the new proxy of liquefaction resistance and the num.er of cycles required to reach liquefaction;(4)the establishm.nt of the invariable form.of the predictive form.las of sm.ll strain m.dulus and strain-dependent shear m.dulus;and(5)the investigation on the effects of stress-induced anisotropy on liquefaction susceptibility and dynam.c deform.tion *** gained through the critical review of these advances in the past decades offer a perspective for future research to further resolve the fundam.ntal issues concerning the liquefaction m.chanism.and responses of coral sandy sites subjecte

关键词： liquefaction susceptibility dynam.c deform.tion characteristics coral sandy soil cyclic loading review and prospect