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1、Sensors&TransducersMagazine,Vol.39,Issue1,2004,pp.112-120Sensors&TransducersISSN1726-5479©2004byIFSAhttp://www.sensorsportal.comFerroelectricCeramic/PolymerCompositeforSoil-HumidityDetectionWalterKatsumiSAKAMOTO,JoséAntonioMALMONGE,SérgioHenriqueFERNANDESDepartamentodeFísicaeQuímica,FaculdadedeEn
2、genharia,UniversidadeEstadualPaulista–UNESP,Av.Brasil,56,15385-000IlhaSolteira(SP),Brasil.Fax:+551837424868,tel:+551837431081,e-mail:sakamoto@fqm.feis.unesp.brhttp://www.fqm.feis.unesp.brReceived:2December2004/Accepted:14January2004/Published:18January2004Abstract:Ferroelectricceramic+polymercomp
3、ositesusingcastoroil-basedpolyurethane(PU)asmatrixandleadzirconatetitanate(PZT)asdispersedpowderwerefabricatedinthethinfilmsformbyspin-coatingmethod.Thecompositeswerepoledwithappropriatedelectricfieldanditspiezoelectricpropertywasstudiedbyconventionalmethod.Usingtheabilityofthecompositetoresponse
4、withanelectricsignaltoavariationofpressure,adetectionsystemwasmadetosubstitutethemanometertomeasurethesoilhumidity.Keywords:composite,soilhumidity,pressuresensor,tensiometer___________________________________________________________________________________________________1.IntroductionInsoilstudy
5、measuresofsoilwatercontentareneededandinthefieldknowledgeofthewateravailableforplantgrowthrequiresameasureofsomeindexofwatercontent[1].Soilwatercanbecharacterisedbyanenergystate.Sincethesoilwatermovementisveryslowthekineticenergycanbeneglectedandtheenergystate,whichisafunctionofpositionandinterna
6、lconditionofthewater,isdefinedbypotentialenergy.TheenergystateofsoilwatercanbedescribedbytheGibbsfreeenergythermodynamicsfunction[2]thatiscalled“totalpotentialofwater”insoil-plant-atmospheresystem.120Sensors&TransducersMagazine,Vol.39,Issue1,2004,pp.112-120Thefirstthermodynamicslawassociatedwithe
7、ntropycanbewritten[3],,(1)wheredUistheinternalenergyvariation,Tisthetemperature,dStheentropyvariation,Petheexternalpressure,dVisthechangeinvolume,isthechemicalpotentialandisanyotherkindofenergy.Thedifferentialequationo
