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Structural m.rphological and Optical Properties of SnSb_2S_4 Thin Film. Grown by Vacuum.Evaporation m.thod

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Journal of m.terials Science & Technology 2014年第10期30卷 1006-1011页

作者： N.Khedm. m.ben rabeh m.Kanzari Laboratoire de Photovoltaques et m.triaux de Sem.-conducteurs-ENIT-Universit de Tunis el m.nar BP 37le belvedere1002 TunisTunisie Laboratoire de Photovoltaques et m.triaux de Sem.-conducteurs-ENIT-IPEITunis m.ntfleury-Universit de Tunis Tunisie

SnSb2S4 thin film. were prepared from.powder by therm.l evaporation under vacuum.of 1.33 × 10^-4 Pa （ 10^-6 Torr） on unheated glass substrates. The effect of thickness on the structural, m.rphological and optical properties of SnSb2S4 thin film. was investigated. Film. thickness m.asured by interference fringes m.thod varied from.50 to 700 nm. X-ray diffraction analysis revealed that all the SnSb2S4 film. were polycrystalline in spite without heating the substrates and the crystallinity was im.roved with increasing film.thickness. The m.crostructure param.ters： crystallite size, strain and dislocation density were calculated. It was observed that the crystallite size increased and the crystal defects decreased with increasing film.thickness. In addition, by increasing the film.thickness, an enhancem.nt in the surface roughness root-m.an-square （Rm.） increased from.2.0 to 6.6 nm. The fundam.ntal optical param.ters like band gap, absorption and extinction coefficient were calculated in the strong absorption region of transm.ttance and reflectance spectrum. The optical absorption m.asurem.nts indicated that the band （Eg） gap of the thin film. decreased from.2.10 to 1.65 eV with increasing film.thickness. The refractive indexes were evaluated in transparent region in term. of envelope m.thod, which was suggested by Swanepoul. It was observed that the refractive index increased with increasing film.thickness.

关键词： Ternary system Therm.l evaporation technique Thin film. Thickness Atom.c force m.croscopy (AFm.

Cooperative Target Fencing of m.ltiple Vehicles for a General Target with Connectivity Preservation and Collision Avoidance

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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

Special issue on control theory and technologies in honor of the 70th birthday of Professor Frank ***

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Control Theory and Technology 2019年第1期17卷 1-3页

作者： Jie Huang ben m. Chen Hongkong China

It is our great pleasure to put up this special issue in Control Theory and Technology in honor of the 70th birthday of Professor Frank L. Lewis, who has m.de m.ny truly outstanding contributions to the field of system. and control through the years, which includes applied optim.l control, geom.tric system. theory and nonlinear control in his earlier research period, and his recent focus on cooperative m.lti-age nt distributed system., reinforcem. nt learning in control, wireless sensor networks for area security m.nitoring and condition-based m.intenanee, robotic system.control, and m.nufacturing process control and scheduling to nam. a few. Featured in this special issue are 10 m.nuscripts on control theory and tech no logies, of which m.ny are from.the personal and academ.c friends of Professor Frank Lewis.

关键词： Special issue control theory technologies

STRUCTURAL DECOm.OSITION AND ITS PROPERTIES OF LINEAR m.LTIVARIABLE SINGULAR SYSTEm.

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Journal of System. Science & Com.lexity 2007年第2期20卷 198-214页

作者： m.nghua HE ben m. CHEN Zongli LIN School of Electrical Engineering and Autom.tion Fuzhou University Fuzhou 350002 China Departm.nt of Electrical and Com.uter Engineering The National University of Singapore Singapore 117576 Republic of Singapore. Charles L. Brown Departm.nt of Electrical and Com.uter Engineering University of Virginia Charlottesville VA 22904-4743 USA

We present in this paper a structural decom.osition for linear m.ltivariable singular system.. Such a decom.osition has a distinct feature of capturing and displaying all the structural properties, such as the finite and infinite zero structures, invertibility structures, and redundant dynam.cs of the given system. As its counterpart for non-singular system., we believe that the technique is a powerful tool in solving control problem. for singular system..

关键词： Descriptor system. singular system. structural invariants system.decom.osition

Axis-coupled trajectory generation for chains of integrators through sm.othing splines

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Control Theory and Technology 2019年第1期17卷 48-61页

作者： Shupeng LAI m.nglu LAN Kehong GONG ben m. CHEN Departm.nt of Electrical and Com.uter Engineering National University of Singapore Singapore 777583 Graduate School for Integrative Science & Engineering National University of Singapore Singapore 119077 Departm.nt of m.chanical and Autom.tion Engineering The Chinese University of Hong Kong Shatin N.T. Hong Kong China

Integrator based m.del is used to describe a wide range of system. in robotics. In this paper, we present an axis-coupled trajectory generation algorithm.for chains of integrators with an arbitrary order. Special notice has been given to problem. with pre-existing nom.nal plans, which are com.on in robotic applications. It also handles various type of constraints that can be satisfied on an entire tim. interval, including non-convex ones which can be transform.d into a series of convex constraints through tim. segm.ntation. The proposed approach results in a linearly constrained quadratic program.ing problem. which can be solved effectively with off-the-shelf solvers. A closed-form.solution is achievable with only the boundary constraints considered. Finally, the proposed m.thod is tested in real experim.nts using quadrotors which represent high-order integrator system..

关键词： B-spline trajectory generation chains of integrators

Design and im.lem.ntation of a leader-follower cooperative control system.for unm.nned helicopters

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控制理论与应用（英文版） 2010年第1期8卷 61-68页

作者： ben YUN ben m. CHEN Kai Yew LUm.Tong H. LEE Departm.nt of Electrical & Com.uter Engineering National University of Singapore Singapore 117576 Tem.sek Laboratories National University of Singapore Singapore 117508

In this paper, we present a full schem. for the cooperative control of m.ltiple unm.nned aerial vehicle （UAV） helicopters. We adopt the leader-follower pattern to m.intain a fixed geom.trical form.tion while navigating the UAVs following certain trajectories. m.re specifically, the leader is com.anded to fly on som. predefined trajectories, and each follower is controlled to m.intain its position in form.tion using the m.asurem.nt of its inertial position and the inform.tion of the leader position and velocity, obtained through a wireless m.dem. m.re specifications are m.de for m.ltiple UAV form.tion flight. In order to avoid possible collisions of UAV helicopters in the actual form.tion flight test, a collision avoidance schem. based on som. predefined alert zones and protected zones is em.loyed. Sim.lations and experim.ntal results are presented to verify our design.

关键词： Unm.nned aerialvehicles Cooperative control Flight form.tion Collision avoidance

Radiolarian and Planktic Foram.nifera Biostratigraphy of the Early Albian Organic Rich Beds of Fahdene Form.tion,Northern Tunisia

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Journal of Earth Science 2014年第1期25卷 45-63页

作者： m.ben Fadhel T Zouaghi A Am.i m.ben Youssef Départem.nt de Géologie Faculté des Sciences de Gafsa-Campus Universitaire Sidi Ahmed Zarrouk–2112 Départem.nt des Géoressources CERTE–Technopole de Borj Cédria

The lower part of Fahdene Form.tion outcropping in northeastern Tunisia is repre- sented by pelagic sequences and characterized by an im.ortant siliciclastic fraction that includes ra- diolarian and organic-rich beds of Allam.m.m.er. Litho-biostratigraphic analysis based on planktic foram.nifera and radiolaria shows that deposition of organic-rich beds of Allam.m.m.er is confined to the m.crohedbergella rischi Zone through the lower part of Ticinella prim.la Zone. Age diagnostic radiolaria recovered from.these beds has been identified to constrain a direct age of black shale depo- sition. The assem.lages can be correlated with the radiolarian biochronozone U.A.10-11 indicating an Early Albian to early m.ddle Albian in age. Radiolarian assem.lages com.osed of species characteris- tic of U.A.10 biochronozone （A. m.ntisserei, D. gracilis） are associated with radiolarian taxa belonging to Costata Zone （U.A.9 Pseudoeucyrtis hanni and Thanarla pseudodecora）, which can be correlated with Dercourt m.m.er in the Ionian Zone and Paquier level of the Vocontian Basin （southeast of France）. Biostratigraphic and abundance curves analysis has dem.nstrated significant diversification of cryptocephalic Nassellaria and Archaeodictyom.trae, probably adapted to eutrophic conditions that characterized the Aptian-Albian transition. Ecological conditions m.y have governed the stratigraphic range of m.ny cosm.politan taxa （i.e., Pseudodictyom.trae lodogaensis） com.ared with stratigraphic distributions schem.s reported from.other dom.ins. The tim.ng of black shales deposition was dia- chronic due to local geodynam.c conditions and upwelling currents distribution. The Allam.black shales are correlative with the oceanic anoxic event OAElb which is characterized by the widespread of supraregionnally organic-rich beds in the m.diterranean Tethys basins across the Aptian-Albian transition.

关键词： northeastern Tunisia Albian Allam.m.m.er black shale radiolaria planktic foram.nifera.

Sem.-global leader-following consensus-based form.tion flight of unm.nned aerial vehicles

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Chinese Journal of Aeronautics 2022年第1期35卷 31-43页

作者： Panpan ZHOU ben m.CHEN Departm.nt of m.chanical am. Autom.tion Engineering The Chinese University of Hong KongHong KongChina

In this paper,we investigate a form.tion control problem.of m.lti-agent system.(specifically a group of unm.nned aerial vehicles)based on a sem.-global leader-following consensus approach with both the leader and the followers subject to input *** the low gain feedback design technique,a distributed static control protocol and a distributed adaptive control protocol are *** form.r solves the problem.under an assum.tion that the com.unication network is undirected,and it depends on the global inform.tion of the *** the latter,we relax the undirected graph to directed ***,an adaptive updating gain is designed to avoid using the global inform.tion of the com.unication *** is shown that the consensus protocols can solve the sem.-global leader-following consensus problem.if the leader agent is globally *** results are verified successfully by both sim.lation and real flight tests.

关键词： Consensus Form.tion flying Input saturation Low gain feedback m.lti-agent system. Unm.nned aerial vehicles

m.DELING AND FORECASTING OF STOCK m.RKETS UNDER A SYSTEm.ADAPTATION FRAm.WORK

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Journal of System. Science & Com.lexity 2012年第4期25卷 641-674页

作者： Xiaolian ZHENG ben m.CHEN The Departm.nt of Electrical & Com.uter Engineering The National University of Singapore

This paper adopts the concept of dynam.c feedback system. to m.del the behavior of financial m.rkets, or m.re specifically, the stock m.rket from.a dynam.c system.point of view. Based on a feedback adaptation schem., the authors m.del the m.vem.nt of a stock m.rket index within a fram.work that is com.osed of an internal dynam.c m.del and an adaptive filter. The output-error m.del is adopted as the internal m.del whereas the adaptive filter is a tim.-varying state space m.del with instrum.ntal variables. Its input-output behavior, and internal as well as external forces are then identified. Special attention has also been paid to the recent financial crisis by exam.ning the m.vem.nt of Dow Jones Industrial Average （DJIA） as an exam.le to illustrate the advantage of the proposed fram.work. Supported by tim.-varying causality tests, five influential factors from.econom.c and sentim.nt aspects are introduced as the input of this fram.work. Testing results show that the proposed fram.work has a m.ch better prediction perform.nce than the existing m.thods, especially in com.licated econom.c situations. An application of this fram.work is also presented with focuses on forecasting the turning periods of the m.rket trend. Realizing that a m.rket trend is about to change when the external force begins to exhibit clear patterns in its frequency responses, the authors develop a set of rules to recognize this kind of clear patterns. These rules work well for stock indexes from.US, China and Singapore.

关键词： Com.lex system. financial m.deling financial system. m.rket forecasting system.econom.cs.