简介：Inthisstudy,amulti-relaxationtimelatticeBoltzmannmodelforshallowwaterinacurvilinearcoordinategridisdevelopedusingthegeneralizedformoftheinterpolationsupplementedlatticeBoltzmannmethod.TheTaylor-Coletteflowtestsshowthattheproposedmodelenjoysasecondorderaccuracyinspace.Theproposedmodelisappliedtothreetypesofmeanderingchannelswith180°,90°and60°consecutivebends.Thenumericalresultsdemonstratethatthesimulatedresultsagreewellwithpreviouscomputationalandexperimentaldata.Inaddition,themodelcanachievetheacceptableaccuracyintermsofthewaterdepthandthedepth-averagedvelocitiesforshallowwaterflowsincurvedandmeanderingchannelsoverawiderangeofbendangles.

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简介：Waveguideinvariantiswidelyusedinunderwatertargetpassiveranging.Inshallowwaterwithuniformsoundspeedprofile,thevalueofwaveguideinvariantisapproximatelyaconstant,whileinshallowwaterwiththermocline,itvariesinawiderange.Thewaveguideinvariantdistributionsandstriationsinthesetwoconditionsareanalyzedrespectively.Onthebasisofwavenumberdifferencebetweenreflectedmodesandrefractedmodes,awavenumber-frequencydomainfilteringtechniqueisproposedtoseparatethetwogroupsofmodes.Therequiredrelationshipbetweenarrayelementspace,totalarraylengthandtargetazimuthforeffectiveapplicationisdiscussed.Finally,thesimulationresultsindicatethatinshallowwaterwithathermocline,refractedmodescanbeeffectivelyfilteredoutusingthewavenumber-frequencydomainfilteringtechniqueandthetarget’srangeisestimatedaccurately.

简介：ResistanceanalysisisanimportantanalyticalmethodusedtoevaluatethehydrodynamicperformanceofHighSpeedCraft(HSC).AnalysisofmultihullresistanceinshallowwaterisessentialtotheperformanceevaluationofanytypeofHSC.Shipsoperatinginshallowwaterexperienceincreasesinresistancebecauseofchangesinpressuredistributionandwavepattern.Inthispaper,theshallowwaterperformanceofanHSCdesignconcept,thesemi-SmallWaterplaneAreaTwinHull(semi-SWATH)form,isstudied.Thehullisinstalledwithfinstabilizerstoreducedynamicmotioneffects,andtheresistancecomponentsofthehull,hulltrimcondition,andmaximumwaveamplitudearoundthehullaredeterminedviacalmwaterresistancetestsinshallowwater.Thesecriteriaareimportantinanalyzingsemi-SWATHresistanceinshallowwateranditsrelationtoflowaroundhull.Theforefinangleisfixedtozerodegrees,whiletheaftfinangleisvariedto0o,5o,10o,and15o.Foreachconfiguration,investigationsareconductedwithdepthFroudenumbers(FrH)rangingfrom0.65to1.2,andtheresistancetestsareperformedinshallowwateratthetowingtankofUTM.Analysisresultsindicatethattheresistance,wavepattern,andtrimofthesemi-SWATHhullformareaffectedbythefinangle.Theresistanceisamplifiedwhereasthetrimandsinkagearereducedasthefinangleincreases.IncreasesinfinanglecontributetoseakeepingandstabilitybutaffectthehullresistanceofHSCs.

简介：Theresearchofpropagationcharacteristicsofair-to-watersoundtransmissionisofgreatimportancetothedetectionofaerialtargetsfromunderwater.Inordertostudythepropagationcharacteristicsofair-to-watersoundtransmissioninshallowwater,StateKeyLaboratoryofAcoustics,InstituteofAcoustics,conductedanexperimentintheSouthChinaSeainMarch,2013.Duringtheexperiment,multi-frequencysignalstransmittedbyahooterhungonaresearchshipwerereceivedbyanunderwaterhydrophone,andthedistancebetweenthehooterandthehydrophonewasfrom2.4kmto9.8kmapproximately.Throughanalyzingexperimentaldatainthiswork,theexperimentalair-to-watertransmissionlossatfrequencies128Hzand256Hzisestimatedupto9.8kminrange,anditsoscillationstructureisevident.Thewave-numberintegrationapproachisusedtosimulatetheoreticalair-to-watertransmissionlosses,whichareingoodagreementwithexperimentalvaluesandtoexplaintheexperimentalair-to-watersoundtransmissioncharacteristics.

简介：Background:WecomparetheclimatesensitivityofEuropeanbeech(FagussylvaticaL)intwoforestnaturereservesinnortheasternGermany.Theonereserve,Schlossberg,ischaracterizedbyshallowchalksoils,whereasintheotherreserve,Eldena,soilsaredeeperandmoredeveloped.Littleisknownaboutthedroughtsensitivityofbeechonshallowchalksoils.Methods:Wecollectedincrementcoresatbothresearchsitesandestablishedclimate-growthrelationships.Intertreevariabilitywasassessedbyemployinglinearmixed-effectmodels.Results:WeexpectedtofinddistinctivelyhigherdroughtsensitivityatSchlossbergduetolimitedwateravailability,butfindonlymarginaldifferencesingrowthresponses.Atbothsites,droughtisthemajorclimaticfactordrivingtreegrowth.Adaptationsintreearchitectureandanunderestimationofthewaterholdingcapacityofshallowchalksoilsarediscussedaspossiblereasonsfornotfindingmoredistinctclimateresponses.Inanalyzingclimate-growthrelationships,wespecificallyfocusedongrowthresponsesofindividualtreesbutobservedonlylowinter-treevariabilityatbothsites.Evidentisashiftinclimateresponsepatternsfromthefirsttothesecondhalfofthetwentiethcenturywithprevious-yeardroughtconditionsbecomingmoreimportantthancurrent-yeardrought.Thisshiftisdiscussedinrelationtoawarmingtrendoverthatsameperiod,aswellaspossibletrendsinmastingbehaviorofbeech.Conclusion:Theinvestigatedbeechtreesontheshallowchalksoilareonlyslightlymoredroughtsensitivethanbeechtreesonthereferencesitewithdeeperandmoredevelopedsoils.

简介：Dongsha区域是为在华南海(SCS)的煤气的水合物探索的最有希望的目标区域之一。毛孔水地球化学的学习在中国煤气的水合物探索起了一个关键作用。Br/Cl，I/Cl和37毛孔水里的Cl在在低温度沉积环境跟踪煤气的水合物出现，毛孔液体的化学进化和水/岩石相互作用这里被使用。样品在2004在Dongsha区域从地点HD255PC和HD309PC被收集。在地点HD255PC，我们发现了提高的Br/Cl，I/Cl并且那么减少了在4-5m的深度的4/Cl，可能从煤气的水合物出现产生的旁边地移植的液体暗示。37Clis-0.54到+0.96，和积极37在4-5m间隔的Cl应该与在35Cl和37Cl。在地点HD309PC，旁边地移植的液体也在3-4m的深度被发现，与Br/Cltwotimes到，显示海水和减少的I/Cl，液体没有与煤气的水合物的关系。在这个地点，氯同位素的作文改变from-0.7到+1.9。额外的高Br/Cl可能与深产生的液体联系。在更高的温度和压力，液体的Br/Cl在含水的硅酸盐形成期间被提高，当时积极37Cl也与一样的机制被联系。