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简介：Insub-tropicalcoastalwatersaroundHongKong,algalbloomsandredtidesareusuallyfirstsightedintheMirsBay,intheeasternwatersofHongKong.Acalibratedthree-dimensionalhydrodynamicmodelforthePearlRiverEstuary(Delft3D)hasbeenappliedtothestudyofthephysicalhydrographyofHongKongwatersanditsrelationshipwithalgalbloomtransportpatternsinthedryandwetseasons.Thegeneral3Dhydrodynamiccirculationandsalinitystructureinthepartially-mixedestuaryarepresented.ExtensivenumericalsurfacedroguetrackingexperimentsareperformedforalgalbloomsthatareinitiatedintheMirsBayunderdifferentseasonal,windandtidalconditions.TheprobabilityofbloomimpactontheVictoriaHarbourandnearbyurbancoastalwatersisestimated.Thecomputationsshowthat:I)Inthewetseason(May～August),algalbloomsinitiatedintheMirsBaywillmoveinaclockwisedirectionoutofthebay,andbetransportedawayfromHongKongduetoSWmonsoonwindswhichdrivetheSWtoNEcoastalcurrent;ii)Inthedryseason(November～April),algalbloomsinitiatedinthenortheastMirsBaywillmoveinananti-clockwisedirectionandbecarriedawayintosouthernwatersduetotheNEtoSWcoastalcurrentdrivenbytheNEmonsoonwinds;thebloomtypicallyflowspasttheeastedgeoftheVictoriaHarbourandnearbywaters.Finally,theroleofhydrodynamictransportinanimportantepisodicevent-thespring1998massiveredtide-isquantitativelyexamined.ItisshownthatthestrongNEtoEwindduringlateMarchtoearlyApril,coupledwiththediurnaltideatthebeginningofApril,significantlyincreasedtheprobabilityofbloomtransportintothePortShelterandEastLammaChannel,resultinginthemassivefishkill.Theresultsprovideabasisforriskassessmentofharmfulalgalbloom(HAB)impactonurbancoastalwatersaroundtheVictoriaHabour.

简介：Accuratedeterminationofflushingtimeiscrucialformaintainingsustainableproductioninfishculturezones(FCZs),asitrepresentsthephysicalself-purificationcapabilityviatidalexchangewithcleanwaterintheoutersea.However,owingtothetemporalandspatialcomplexityofthecoastalflushingprocess,existingmethodsfordeterminingflushingtimemaynotbegenerallyapplicable.Inthispaper,asystematicmethodfordeterminingtheflushingtimeinFCZsispresented,inwhichbathymetry,runoff,tidalrangeandstratificationareproperlyaccountedfor.Wedeterminetheflushingtimevianumericaltracerexperiments,usingrobust3Dhydrodynamicandmasstransportmodels.ForFCZslocatedinshelteredandland-lockedtidalinlets,thesystemboundarycanbenaturallydefinedattheconnectionwiththeopensea.ForFCZslocatedinopenwaters,hydrodynamictrackingisfirstusedtoassesstheextentoftidalexcursionandthusdelimittheinitialboundarybetweencleanwaterandpollutedwater.ThisgeneralmethodisappliedtoalldesignatedmarineFCZsinHongKongforboththedryandwetseasons,including20shelteredFCZs(insemi-enclosedwatersofToloHarbour,MirsBay,andPortShelter)and6FCZsinopenwaters.OurresultsshowthatflushingtimeisthelongestininnerPortShelter(about40daysindryseason),andtheshortestfortheFCZsinopenwaters(lessthanoneweekindryseason).Inaddition,theflushingtimeindryseasoniscommonlylongerthanthatinwetseason:20%~40%formostwell-shelteredFCZs;2.6~4timesfortheothers.Ourresultsindicateapositivecorrelationbetweentheflushingtimeanddistancetoopenboundary,supportingtheviewthattheflushingtimeofaFCZiscloselyrelatedtoitslocation.ThisstudyprovidesasolidbasisformariculturemanagementsuchasthedeterminationofcarryingcapacityofFCZs.

简介：ThenorthernmarginoftheSouthChinaSea,asatypicalextensionalcontinentalmargin,hasrelativelystrongintraplateseismicity.ComparedwiththeactivezonesofNanaoIsland,Yangjiang,andHeyuan,seismicityinthePearlRiverEstuaryisrelativelylow.However,aML4.0earthquakein2006occurrednearDanganIsland(DI)offshoreHongKong,andthissitewasadjacenttothesourceofthehistoricalM5.8earthquakein1874.TorevealtheseismogenicmechanismofintraplateearthquakesinDI,wesystematicallyanalyzedthestructuralcharacteristicsinthesourceareaofthe2006DIearthquakeusingintegrated24-channelseismicprofiles,onshore–offshorewide-angleseismictomography,andnaturalearthquakeparameters.WeascertainedthelocationsofNW-andNE-trendingfaultsintheDIseaandfoundthattheNE-trendingDIfaultmainlydippedsoutheastatahighangleandcutthroughthecrustwithanobviouslow-velocityanomaly.TheNW-trendingfaultdippedsouthwestwithasimilarhighangle.The2006DIearthquakewasadjacenttotheintersectionoftheNE-andNW-trendingfaults,whichsuggestedthattheintersectionofthetwofaultswithdifferentstrikescouldprovideafavorableconditionforthegenerationandtriggeringofintraplateearthquakes.Crustalvelocitymodelshowedthatthehigh-velocityanomalywasimagedinthewestofDI,butadistinctentitywithlow-velocityanomalyintheuppercrustandhigh-velocityanomalyinthelowercrustwasfoundinthesouthofDI.Boththe1874and2006DIearthquakesoccurredalongtheedgeofthedistinctentity.Twoverticalcross-sectionsnearlyperpendiculartothestrikesoftheintersectingfaultsrevealedgoodspatialcorrelationsbetweenthe2006DIearthquakeandthelowtohighspeedtransitioninthedistinctentity.Thisresultindicatedthatthetransitionalzonemightbeaweaklystructuralbodythatcanstorestrainenergyandreleaseitasabrittlefailure,resultinginanearthquake-pronearea.

简介：ImmersedtunnelisanimportantpartoftheHongKong–Zhuhai–MacaoBridge(HZMB)project.Inimmersedtunnelfloating,translationwhichincludesstraightandtransversemovementsisthemainworkingmode.Todecidethemagnitudeanddirectionofthetowingforceforeachtug,aparticleswarm-basedtranslationcontrolmethodispresentedfornon-powerimmersedtunnelelement.Asortoflinearweightedlogarithmicfunctionisexploitedtoavoidweaksubgoals.Insimulation,theparticleswarm-basedcontrolmethodisevaluatedandcomparedwithtraditionalempiricalmethodinthecaseoftheHZMBproject.Simulationresultsshowthatthepresentedmethoddeliversperformanceimprovementintermsoftheenhancedsurplustowingforce.