简介:SomelaboratorydiffusiontestswereconductedwithdiffusiondevicetodeterminethediffusioncoefficientofCr(Ⅵ)ionpassingthroughDalianredclaysamples.TheconcentrationsofCr(Ⅵ)atdifferentplacesofthesampleswerethenmeasuredspectrophotometricallyafterastandingtimeof1000d.Aone-dimensionalsolutetransportequationwasusedtosimulatethetransportofCr(Ⅵ)throughclaysamples.Back-calculationofdiffusioncoefficientofCr(Ⅵ)wasmadewithfinitedifferencemethod.Parametricanalysiswasconductedtosimulatevariationsinsoildrydensity,temperature,pHandstandingtime.Theresultsshowthatthemethodusedinthispaperissimpleandeffective.ThediffusioncoefficientofCr(Ⅵ)inDalianredclayvariesfrom1.50×10-7cm2/sto2.08×10-7cm2/s.After1000ddiffusion,theconcentrationofthesourcesolutiondropsdownto1.27mg/Lfrom62.5mg/L,andthediffusiondistanceisonly3.5cm.Undertheassumptionthatdiffusioncoefficientisconstant,thediffusioneffectbecomesmoreobviouswithlowerdensity,lowertemperature,higherpHvalue,andmuchmoretime.
简介:海洋的循环和气候的学习要求能精确地模仿tracer旋涡散开和移流的模型。传统的Eulerian坐标能由于轴的不正确的排列介绍大人工的水平扩散性/粘性,这被显示出。因此,如此的模型能涂锋利的前面并且介绍另外的数字人工制品。为有相对低的分辨率的模拟,大侧面的散开明确地在模型被使用;因此,如此的数字散开不能是一个问题。随水平分辨率的增加,然而,在通常使用的Eulerian坐标与水平移流联系的人工的扩散性/粘性可以为精确地为海洋发行量建模成为最挑战性的障碍之一。Isopycnal旋涡散开(混合)广泛地在数字模型被使用了。普通智慧是沿着isopycnal混合是精力免费。然而,小心的考试表明这不是事实。事实上,旋涡散开能概念上被分开成二步:激动人心并且subscale散开。由于thermobaric效果,激动人心,或交换水集中,沿着isopycnal,表面处于吝啬的状态与GPE的变化被联系。这是不稳定性的一种新类型,叫了thermobaric不稳定性。另外,由于cabbelingsubscale,水包裹的散开总是导致GPE的版本。GPE的版本可以由于激动人心的isopycnal和subscale散开导致thermobaric不稳定性。
简介:ONACLASSOFANISOTROPICDIFFUSIONEQUATIONSONACLASSOFANISOTROPICDIFFUSIONEQUATIONS¥GAOHang(DepartmentofMathematics,FudanUniversit...
简介:Inthispaper,twofinitedifferencestreamlinediffusion(FDSD)schemesforsolvingtwo-dimensionaltime-dependentconvection-diffusionequationsareconstructed.Stabilityandoptimalordererrorestimati-ionsforconsideredschemesarederivedinthenormstrongerthanL~2-norm.
简介:海水热力学的二个重要非线性的性质连接了到水密度,cabbeling和弹性(压缩的可能性)的变化,被讨论。埃迪散开和移流在密度导致变化;作为结果,系统的重力的势能被改变。因此,cabbeling和弹性玩在侧面的旋涡散开和移流的energetics给角色调音。垂直旋涡散开是处于全球海洋的机械精力平衡的关键元素之一。垂直旋涡散开能概念上被分开成二步:激动人心并且subscale散开。垂直旋涡向上、温暖/轻的激动人心的推冷/稠密水向下流水;因此,重力的势能被增加。在第二步期间,来自不同地方的水群众通过subscale混合散开,和水密度由于cabbeling被增加。使用WOA01气候学并且假定垂直旋涡扩散性等于2慭楲敮瀠慨潥桰瑹獥?有洠牡湩?桲摯灯票整?ㄠ?挠汨牯灯票整?的经常的价值?挠祲瑰灯票整??栠灡潴桰瑹獥?湡?‵汧畡潣桰瑹獥眠牥?敳畱湥散?眠?獵摥愠朠湥?湡污獹獩洠瑥潨?潴愠慮祬敺琠敨倠?朠湥?敳畱湥散?湩愠杬敡愠摮挠湯楦浲琠敨攠楸瑳湥散漠?桴???敧敮椠?桴?牴湡'諛L瑰浯捩猠煥敵据湩?慤慴漠?桒摯灯票慴愠摮传档潲桰瑹吗?
简介:重力的势能(GPE)变化由于horizontal/isopycnal旋涡散开和移流被检验。Horizontal/isopycnal旋涡散开概念上被分开成二步:激动人心并且subscale散开。与这二步联系的GPE变化被分析。另外,GPE变化由于激动人心并且在Eulerian坐标与horizontal/isopycnal移流联系的subscale散开被分析。这些公式为世界海洋被用于SODA数据。我们的分析显示在Eulerian坐标的horizontal/isopycnal移流能在模型介绍大人工的散开。在isopycnal坐标的GPE来源/水池仔细被连接到物理性质分发,这被显示出,例如温度,咸度和速度。与z协调比较,GPE来源/水池由于与isopycnal散开/移流联系的stirring/cabbeling是小得多的。尽管isopycnal坐标可以以处理侧面的散开是一种更好的选择,在传统的Eulerian坐标的移流术语能由于与移流联系的cabbeling生产GPE的人工的来源。减少如此的数字错误仍然是宏大挑战。
简介:Inthispaper,theasymptoticbehaviorofthreetypesofpopulationmodelswithdelaysanddiffusionisstudied.ThefirstrepresentsonespeciesgrowthinthepatchΩandperiodicenvironmentandwithdelaysrecruitment,thesecondmodelsasinglespeciesdispersalamongthempatchesofaheterogeneousenvironment,andthethirdmodelsthespreadofbacterialinfections.Sufficientconditionsfortheglobalattractivityofperiodicsolutionareobtainedbythemethodofmonotonetheoryandstronglyconcaveoperators.Someearlierresultsareextendedtopopulationmodelswithdelaysanddiffusion.
简介:LetX(1)={X(1)(s),s∈R+}andX(2)={X(2)(t),t∈R+}betwoindependentnondegeneratediusionprocesseswithvaluesinRd.TheexistenceandfractaldimensionofintersectionsofthesamplepathsofX(1)andX(2)arestudied.Moregenerally,letE1,E2■(0,∞)andFRdbeBorelsets.AnecessaryconditionandasuffcientconditionforP{X(1)(E1)∩X(2)(E2)∩F=φ}>0areprovedintermsoftheBessel-RiesztypecapacityandHausdormeasureofE1×E2×Finthemetricspace(R+×R+×Rd,ρ),whereρisanunsymmetricmetricdefinedinR+×R+×Rd.Underreasonableconditions,resultsresemblingthoseofBrowianmotionareobtained.
简介:Reaction-diffusion(RD)equationwasoftenusedtoinvestigatethepatterndynamics,buttelegraphreaction-diffusion(TRD)systemwasseldomstudied.Inthispaper,theIzhikevichmodelwasmodifiedtoexplainsomebiologicalmechanismsbyRDandTRDinneuronalcluster.Thenanewconditionunderwhichthesystemlosesstabilitywasproposedandtheeffectofparameters,diffusion,memoryandsteadystatewereconsideredontheprocessofneuronalspiking.Themethodpresentedisanovelapproachtoinvestigatethepatterndynamicsofbiologicalsystems.Finally,simulationsarecarriedouttovalidateourtheoreticalresults.
简介:Theeffectofdiffusiononthermoelasticthinplatesisinvestigated.Thegoverningequationsforthinthermoelasticdiffusionplatesunderthreedifferentlawsofheatanddiffusiontransmissionarederived.BytheC0-semigrouptheory,thewell-posednessoftheproposedequationsisshown.
简介:Thesingularlyperturbedinitialboundaryvalueproblemsforreactiondiffusionequationsareconsidered.Undersuitableconditionsandbyusingthetheoryofdifferentialinequality,theasymptoticbehaviorofsolutionforinitialboundaryvalueproblemsarestudied,wherethereducedproblemspossesstwointersectingsolutions.