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Cost management : 2nd ed.

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Trajectory Generation for Autonomous Soaring UAS

2002年

作者： Edward J. Bloch.r Kung h. chen Th.mas W. Lin.

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International Journal of Automation and computing 2012年第3期9卷 248-256页

作者： J. h. A. Clarke W. h. chen Department of Aeronautical and Automotive Engineering Loughborough University

As unmanned aerial veh.cles are expected to do more and more advanced tasks, improved range and persistence is required. Th.s paper presents a meth.d of using sh.llow layer cumulus convection to extend th. range and duration of small unmanned aerial veh.cles. A simulation model of an X-models XCalubur electric motor-glider is used in combination with.a refined 4D parametric th.rmal model to simulate soaring fligh.. Th. parametric th.rmal model builds on previous successful models with.refinements to more accurately describe th. weath.r in north.rn Europe. Th. implementation of th. variation of th. MacCready setting is discussed. Meth.ds for generating efficient trajectories are evaluated and recommendations are made regarding implementation.

关键词： Unmanned aerial veh.cles (UAV) unmanned aerial systems (UAS) soaring trajectory th.rmal optimal h.uristic

Effects of diurnal adjustment on biases and trends derived from inter-sensor calibrated AMSU-A data

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Frontiers of Earth.Science 2018年第1期12卷 1-16页

作者： h. chen X. ZOU Z. QIN Department of Atmosph.ric and Oceanic Sciences University of Colorado Boulder Colorado CO 80309 USA Earth.System Science Interdisciplinary Center (ESSIC) University of Maryland College Park Maryland MD 20742 USA Joint Center for Data Assimilation Research.and Applications Nanjing University of Information Science and Technology Nanjing 210044 China

Measurements of brigh.ness temperatures from Advanced Microwave Sounding Unit-A （AMSU-A） temperature sounding instruments onboard NOAA Polar- orbiting Operational Environmental Satellites （POES） h.ve been extensively used for studying atmosph.ric temperature trends over th. past several decades. Inter- sensor biases, orbital drifts and diurnal variations of atmosph.ric and surface temperatures must be considered before using a merged long-term time series of AMSU-A measurements from NOAA- 15, - 18, - 19 and MetOp-A. We study th. impacts of th. orbital drift and orbital differences of local equator crossing times （LECTs） on temperature trends derivable from AMSU-A using near-nadir observa- tions from NOAA-15, NOAA-18, NOAA-19, and MetOp-A during 1998 - 2014 over th. Amazon rainforest. Th. double difference meth.d is firstly applied to estimation of inter-sensor biases between any two satellites during th.ir overlapping time period. Th. inter-calibrated observations are th.n used to generate a month.y mean diurnal cycle of brigh.ness temperature for each.AMSU-A ch.nnel. A diurnal correction is finally applied each.ch.nnel to obtain AMSU-A data valid at th. same local time. Impacts of th. inter-sensor bias correction and diurnal correction on th. AMSU-A derived long-term atmosph.ric temperature trends are separately quantified and compared with.th.se derived from original data. It is sh.wn th.t th. orbital drift and differences of LECT among different POESs induce a large uncertainty in AMSU-A derived long-term warming/cooling trends. After applying an inter-sensor bias correction and a diurnal correction, th. warming trends at different local times, wh.ch.are approximately th. same, are smaller by h.lf th.n th. trends derived with.ut applying th.se corrections.

关键词： AMSU-A diurnal adjustment decadal tem-perature trend

Electronic and magnetic structures of ch.in structured ironselenide compounds

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Frontiers of ph.sics 2014年第4期9卷 465-471页

作者： Wei Li Ch.ndan Setty X. h. chen Jiangping h. State Key Laboratory of Functional Materials for Informatics and Sh.ngh.i Center for Superconductivity Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai 200050 China Department of Ph.sics and State Key Laboratory of Surface Ph.sics Fudan University Shanghai 200433 China Department of Ph.sics Purdue University West Lafayette IA 47907 USA h.fei National Laboratory for Ph.sical Science at Microscale and Department of Ph.sics University of Science and Technology of China Hefei 230026 China Beijing National Laboratory for Condensed Matter Ph.sics and Institute of Physics Chinese Academy of Sciences Beijing 100190 China

Electronic and magnetic structures of iron selenide compounds Ce2O2FeSe2 （2212＊） and BaFe2Se3 （123＊） are studied by th. first-principles calculations. We find th.t wh.le all th.se compounds are composed of one-dimensional （1D） Fe ch.in （or ladder） structures, th.ir electronic structures are not close to be quasi-lD. Th. magnetic exch.nge couplings between two nearest-neigh.or （NN） ch.ins in 2212＊ and between two NN two-leg-ladders in 123＊ are both.antiferromagnetic （AFM）, wh.ch.is consistent with.th. presence of significant th.rd NN AFM coupling, a common feature sh.red in oth.r iron-ch.lcogenides, FeTe （11＊） and KyFe2-xSe2 （122＊）. In magnetic ground states, each.Fe ch.in of 2212＊ is ferromagnetic and each.two-leg ladder of 123＊ form a block-AFM structure. We suggest th.t all magnetic structures in iron-selenide compounds can be unified into an extended J1-J2-J3 model. Spin-wave excitations of th. model are calculated and can be tested by future experiments on th.se two systems.

关键词： first-principles calculations magnetism spin-wave excitations

Estimating Critical Clearing Time of Grid Faults Using DA of State-Reduction Model of Power Systems

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 807-820页

作者： Yang Liu Zh.ngyang chen h.anjin Yao Lin Yi Q.h.Wu Sch.ol of Electric Power Engineering South China University of TechnologyGuangzhou 510640China Ch.na South.rn Power Grid Research.Institute Guangzhou 510663China

Th.s paper proposes a critical clearing time (CCT) estimation meth.d by th. domain of attraction (DA) of a state-reduction model of power systems using sum of squares (SOS) programming. By exploiting th. property of th. Jacobian matrix and th. structure of th. boundary of th. DA, it is found th. DA of th. state-reduction model and th.t of th. full model of a power system are topological isomorph.sm. Th.re are one-to-one correspondence relationsh.ps between th. number of equilibrium points, th. type of equilibrium points, and solutions of th. two system models. Based on th.se findings, an expanding interior algorith. is proposed with.SOS programming to estimate th. DA of th. state-reduction model. State trajectories of th. full model can be transformed to th.se of th. state-reduction model by orth.gonal or equiradius projection. In th.s way, CCT of a grid fault is estimated with.th. DA of th. state-reduction model. Th. calculational burden of SOS programming in th. DA estimation using th. state-reduction model is rath.r small compared with.using th. full model. Simulation results sh.w th. proposed expanding interior algorith. is able to provide a tigh. estimation of DA of power systems with.h.gh.r accuracy and lower time costs.

关键词： Critical clearing time domain of attraction expanding interior algorith. state-reduction model SOS programming

A pre-compensation meth.d of th. systematic contouring error for repetitive command path.

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Frontiers of Mech.nical Engineering 2015年第4期10卷 367-372页

作者： D. L. Zh.NG Y. h. chen Y. P. chen State Key Laboratory of Digital Manufacturing Equipment andTech.ology School of Mechanical Science and Engineering HuazhongUniversity of Science and Technology Wuhan 430074 China

For a repetitive command path. pre-compen- sating th. contouring error by modifying th. command path.is practical. To obtain th. pre-compensation value with.better accuracy, th.s paper proposes th. use of a back propagation neural network to extract th. function of systematic contouring errors. Furth.rmore, by using th. extracted function, th. contouring error can be easily pre- compensated. Th. experiment results verify th.t th. proposed compensation meth.d can effectively reduce contouring errors.

关键词： contouring error pre-compensation motioncontrol system back propagation (BP) neural network

Network Embedding Algorith. for Vulnerability Assessment of Power Transmission Lines Using Integrated Structure and Attribute Information

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CSEE Journal of Power and Energy Systems 2024年第1期10卷 351-360页

作者： Xianglong Lian Tong Qian Zepeng Li Xingyu chen Wenh. Tang Q.h.Wu Sch.ol of Electric Power Engineering South China University of TechnologyGuangzhou 510640China

In power systems,failures of vulnerable lines can trigger large-scale cascading failures,and vulnerability assessment is dedicated to locating th.se lines and reducing th. risks of such.*** on a structure and attribute network embedding(SANE)algorith.,a novel quantitative vulnerability analysis meth.d is proposed to identify vulnerable lines in th.s ***,a two-layered random walk network with.topological and electrical properties of transmission lines is ***,based on th. weigh.ed degree of nodes in th. two-layered network,th. inter-layer and intra-layer walking transition probabilities are developed to obtain walk ***,a Word2Vec algorith. is applied to obtain lowdimension vectors representing transmission lines,according to obtained walk sequences for calculating th. vulnerability index of transmissions ***,th. proposed meth.d is compared with.th.ee widely used meth.ds in two test *** sh.w th. network embedding based meth.d is superior to th.se comparison meth.ds and can provide guidance for identifying vulnerable lines.

关键词： Network embedding random walk transmission lines vulnerability assessment

MICROSTRUCTURAL FORMATION MECh.NISM OF SEMI-SOLID AZ91D ALLOY

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Acta Metallurgica Sinica(English.Letters) 2005年第4期18卷 539-546页

作者： W.M. Mao Z.S. Zh.n h. T. chen X. Y. Zh.ng Sch.ol of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

With.th. h.lp of an electromagnetic stirring device and alloy melt quench.ng tech.ology, th. microstntcture of semi-solid AZqlD magnesium alloy slurry stirred by a rotationally electromagnetic fieM was studied and th. experimental results are sh.wn as th. following. Th. primary α-Mg grains are refined obviously wh.n th. slurry is stirred by a rotational electromagnetic field during continuously cooling and th.y are eventually ch.nged to fine rosette grains or sph.rical grains. If th. above semi-solid slurty is furth.r stirred isoth.rmally for some time, much.more sph.rical primary α-Mg grains can be obtained. If th. melt is first cooled down to a given semi-solid temperature and th.n starts being stirred by th. rotational electromagnetic field, th. primary α-Mg dendrites will be large, and a longer time will be taken and a larger stirring power will be needed for th. secondary army of th. dendrites to be remelted on th. roots to prepare an ideal semiolid slurry. Th.oretical analysis indicates th.t th. strong flow motion leads to a more even temperature field and a solute field and stronger man-made temperature fluctuation in th. AZglD magnesium alloy melt so th.t th. sph.rical primary α-Mg grains are increased in th. slurry. Moreover, all th. measures promoting th. temperature fluctuation will be favorable to th. formation of sph.rical primary α-Mg grains and all th. factors increasing th. arm＇s root remelting difficulty will be favorable to th. formation of rosette-type primary α-Mg grains.

关键词： AZ91D magnesium alloy electromagnetic stirring microstructure semi-solid

3-D FINITE ELEMENT ANALYSIS OF Th. EFFECT OF WELDING RESIDUAL STRESS ON h.DROGEN DIFFUSION IN h.DROGEN CONTAINED ENVIRONMENT

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Acta Metallurgica Sinica(English.Letters) 2007年第5期20卷 347-354页

作者： W.C. Jiang J.M. Gong J.Q. Tang h. chen S.T. Tu College of Mech.nical and Power Engineering Nanjing University of Technology Nanjing 210009 China

Th. h.drogen distribution of 16MnR steel weldment in h.drogen contained environment was calculated using th. finite element meth.d （ FEM）. Th. effect of welding residual stress on h.drogen diffusion h.s been discussed using a 3-D sequential coupling finite element analysis procedure complied by Abaqus code. Th. h.drogen diffusion coefficient in weld metal, th. h.at affected zone （h.Z）, and th. base metal of th. 16MnR steel weldment were measured using th. electroch.mical permeation tech.ique. Th. h.drogen diffusion with.ut th. effect of stress was also calculated and compared. Owing to th. existence of welding residual stress, th. h.drogen concentration was obviously increased and th. h.drogen wouM diffuse and accumulate in th. h.gh.r stress region.

关键词： 16MnR steel h.drogen diffusion welding residual stress finite element analysis