简介:在多维流体动力学计算中,流体运动和计算网格的关系可以分为两种情况。一是Lagrangian方法,即网格跟随流体运动;二是Eulerian方法,即流体流过固定;下动的网格。一般计算网格的运动是任意的。这就对应于任意Lagrangian—Eulerian(ALE)方法。ALE方法的核心是通过调整网格运动,使得数值模拟的精度、效率有所提高。它的主要步骤是:显式Lagrangian步;网格重分,即得到新的计算网格;物理量重映,即将Lagrangian步的计算结果变换到新网格上。在这3步中,较少研究网格重分。数值模拟和网格重分的一个基本前提是网格是合理的,或者说网格不能发生翻转,网格应当是凸的。而Lagrangian步数值模拟会造成网格扭曲,因此在网格重分前进行网格解扭是十分必要的。文中描述了通用的网格解扭、重分算法,使得解扭、重分后的网格有较好的几何品质,同时尽可能接近Lagrangian网格。
简介:Inthispaper,weshowthatapositiverecurrentuidqueueisautomaticallyV-uniformlyergodicforsomefunctionV≥1butneveruniformlyergodic.Thisrevealsasimilarityofergodicitybetweenafluidqueueandaquasi-birth-and-deathprocess.AsabyproductofV-uniformergodicity,wederivecomputableboundsontheexponentialmomentsofthebusyperiod.
简介:Rotation in Reaction 19F+51VRotationinReaction19F+51V¥WangQi;LuJun;XuHushan;LiSonglin;ZhuYongtaiandZhangYuhuIndLssi...
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简介:Theeffectofbismuth(Bi)forbothVO2+/VO2+andV3+/V2+redoxcouplesinvanadiumflowbatteries(VFBs)hasbeeninvestigatedbydirectlyintroducingBionthesurfaceofcarbonfelt(CF).TheresultsshowthatBihasnocatalyticeffectforVO2+/VO2+redoxcouple.Duringthefirstchargeprocess,BiisoxidizedtoBi3+(neverreturnbacktoBimetalinthesubsequentcycles)duetothelowstandardredoxpotentialof0.308V(vs.SHE)forBi3+/BiredoxcouplecomparedwithVO2+/VO2+redoxcoupleandBi3+exhibitno(orneglectable)electro-catalyticactivity.Additionally,therelationshipbetweenBiloadingandelectrochemicalactivityforV3+/V2+redoxcouplewasstudiedindetail.2wt%Bi-modifiedcarbonfelt(2%-BiCF)exhibitsthehighestelectrochemicalactivity.Usingitasnegativeelectrode,ahighenergyefficiency(EE)of79.0%canbeachievedatahighcurrentdensityof160mA/cm2,whichis5.5%higherthanthepristineone.Moreover,theelectrolyteutilizationratioisalsoincreasedbymorethan30%.Eventhecelloperatedat140mA/cm2forover300cycles,theEEcanreach80.9%withoutobviousfluctuationandattenuation,suggestingexcellentcatalyticactivityandelectrochemicalstabilityinVFBs.
简介:At-hyperwheel(t≥3)oflengthl(orW(t)lforbrevity)isat-uniformhypergraph(V,E),whereE={e1,e2,...,el}andv1,v2,...,vlaredistinctverticesofV=∪eii=1lsuchthatfori=1,...,l,vi,vi+1∈eiandei∩ej=P,j∈/{i1,i,i+1},wheretheoperationonthesubscriptsismodulolandPisavertexofVwhichisdifferentfromvi,1≤i≤l.Inthispaper,theminimumcoveringproblemofMCλ(3,W(3)4,v)isinvestigated.DirectandrecursiveconstructionsonMCλ(3,W(3)4,v)arepresented.Thecoveringnumbercλ(3,W(3)4,v)isfinallydeterminedforanypositiveintegersv≥5andλ.