简介:Ananalyticalstudywaspresentedonactivecontrolofsoundtransmissionintoavibro-acousticenclosurecomprisingtwoflexibleplates.Twotypesofactuatorswereused,i.e.acousticactuatoranddistributedleadzirconatetitanatepiezoelectric(PZT)actuatorinsteadofpointforceactuator.Usingthemodalacoustictransferimpedance-mobilitymatrices,theexcitationandinteractioninthecoupledsoundtransmissionsystemcanbedescribedwithclearphysicalsignificance.Withthecontrolsystemdesignedtogloballyreducethesoundfield,differentcontrolsystemconfigurationswereconsidered,includingthestructuralactuatorontheincidentplate,actuatoronthereceivingplate,acousticactuatoronthecavity,andtheircombinations.Theeffectivenessandperformanceofthecontrolstrategycorrespondingtoeachsystemconfigurationwerecomparedanddiscussed.Theroleandcontrolmechanismofeachtypeofactuatorwereofparticularinterest.Itwasshownthattheincidentplateactuatoriseffectiveincontrollingthecavity-dominatedmodesandthestructuralmodesdominatedbytheincidentplateandreceivingplate.Twomaincontrolmechanismsareinvolvedinthiscontrolconfiguration,i.e.,modalsuppressingandmodalrearrangement.Forcontrolsystemconfigurationwithonlyacousticactuatorintheenclosure,themechanisminvolvedinthisarrangementispurelymodalsuppression.Desirableplacementsofstructuralactuatorsintermsoftotalpotentialenergyreductionwerealsodiscussed.
简介:针对噪声同时依赖于状态和控制的It8型离散随机奇异系统,讨论其在有限时域内的非零和博弈问题.首先,讨论了单人博弈问题(离散随机奇异系统最优控制问题),即双人博弈的特殊情形,借鉴连续随机奇异系统的相关研究,利用配方法,得到了离散随机奇异系统单人博弈最优策略存在的充分条件等价于相应的差分方程存在解.在此基础上,通过转换方法,由单人博弈推广到两人博弈,得到了有限时间离散随机奇异系统非零和博弈问题的均衡解.该均衡解存在的充分条件等价于其相应耦合Riccati差分方程存在解,并给出了最优策略及最优值的表达式.
简介:Themainchallengeforcontainerportsistheplanningrequiredforberthingcontainershipswhiledockedinport.Growthofcontainerizationiscreatingproblemsforportsandcontainerterminalsastheyreachtheircapacitylimitsofvariousresourceswhichincreasinglyleadstotrafficandportcongestion.Goodplanningandmanagementofcontainerterminaloperationsreduceswaitingtimeforlinerships.Reducingthewaitingtimeimprovestheterminal’sproductivityanddecreasestheportdifficulties.Twoimportantkeystoreducingwaitingtimewithberthallocationaredeterminingsuitableaccesschanneldepthsandincreasingthenumberofberthswhichinthispaperarestudiedandanalyzedaspracticalsolutions.Simulationbasedanalysisistheonlywaytounderstandhowvariousresourcesinteractwitheachotherandhowtheyareaffectedintheberthingtimeofships.WeusedtheEnterpriseDynamicssoftwaretoproducesimulationmodelsduetothecomplexityandnatureoftheproblems.WefurtherpresentcasestudyforberthallocationsimulationofthebiggestcontainerterminalinIranandtheoptimumaccesschanneldepthandthenumberofberthsareobtainedfromsimulationresults.Theresultsshowasignificantreductioninthewaitingtimeforcontainershipsandcanbeusefulformajorfunctionsinoperationsanddevelopmentofcontainershipterminals.
简介:以厦门国际航运中心为对象,从共生理论的视角探讨了航运服务要素集聚的内涵、特征和现状,研究了航运服务要素集聚的共生关系,建立了航运服务要素集聚共生系统的Lotka-Volterra模型,分析了航运服务要素集聚发展的共生模式和共生效应.分析结果表明,厦门航运服务要素集聚表现为偏利共生和非对称性互惠共生,共生单元发展不协调、不平衡,需加快改善共生环境、优化共生单元,积极引导高端航运服务要素集聚共生,促进航运服务要素向对称性互惠共生和一体化共生关系发展,进而提高厦门国际航运中心的综合竞争力.