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:Theprogressofeconomicglobalization,therapidgrowthofinternationaltrade,andthemaritimetransportationhasplayedanincreasinglysignificantroleintheinternationalsupplychain.Asaresult,worldwideseaportshavesufferedfromacentralproblem,whichappearsintheformofmassiveamountsoffuelconsumedandexhaustgasfumesemittedfromtheshipswhileberthed.Manyportshavetakenthenecessaryprecautionstoovercomethisproblem,whileothersstillsufferduetothepresenceoftechnicalandfinancialconstraints.Inthispaper,thebarriers,interconnectionstandards,rules,regulations,powersources,andeconomicandenvironmentalanalysisrelatedtoships,shore-sidepowerwerestudiedineffortstofindasolutiontoovercomehisproblem.Asacasestudy,thispaperinvestigatesthepracticability,costsandbenefitsofswitchingfromonboardshipauxiliaryenginestoshore-sidepowerconnectionforhigh-speedcraftscalledAlkaherawhileberthedattheportofSafaga,Egypt.Theresultsprovidethenationalelectricitygridconceptasthebesteconomicalselectionwith49.03percentofannualcostsaving.Moreover,environmentally,itcouldachieveanannualreductioninexhaustgasemissionsofCO2,CO,NOx,P.M,andSO2by276,2.32,18.87,0.825and3.84tons,respectively.