简介:Focusingonobstacleavoidanceinthree-dimensionalspaceforunmannedaerialvehicle(UAV),thedirectobstacleavoidancemethodindynamicspacebasedonthree-dimensionalvelocityobstaclesphericalcapisproposed,whichquantifiestheinfluenceofthreateningobstaclesthroughvelocityobstaclesphericalcapparameters.Inaddition,theobstacleavoidanceschemesofanypointonthecriticalcurveduringthemulti-obstaclesavoidancearegiven.Throughprediction,theinsertionpointfortheobstacleavoidancecanbeobtainedandtheflightpathcanbereplanned.TakingthePythagoreanHodograph(PH)curvetrajectoryre-planningasanexample,thethree-dimensionaldirectobstacleavoidancemethodindynamicspaceistested.Simulationresultsshowthattheproposedmethodcanrealizetheonlineobstacleavoidancetrajectoryre-planning,whichincreasestheflexibilityofobstacleavoidancegreatly.
简介:Aglobal-scaleglaciationoccurredatabout600Maago.Asaresult,theEarthbecamethe'SnowballEarth'.Theglaciationcametotheendabruptlywhenatmosphericcarbondioxideincreasedtosuchanextentastobeabout350timesthemodernlevelbecauseofsubaerialvolcanicdegassing.TherapidterminationofglaciationwouldhaveledtowarmingoftheSnowballEarthandextremegreenhouseconditionswouldhavebeencreated.Thetransferofatmosphericcarbondioxidetooceanswouldgiverisetotherapidprecipitationofcalciumcarbonateinwarmsurfaceseawaters,thusformingthecapcarbonaterocksasobservedworldwidetoday.Regionallypersisting,thinlayersofcarbonaterocksdirectlyandubiquitouslyoverlieProterozoicglacialdepositsalmostoneverycontinent,andarecommonlyreferredtoascapcarbonates.Theirunusuallitho-fabrics,stratigraphicallyabruptbasalandupper-levelcontactsandstronglynegativecarbonateisotopicsignatures(δ13Ccarb.valuesrangefrom-7.0‰-0‰)suggestachemicaloceanographicorigin,thedetailsofwhichremainunknown.Itisproposedthattheseenigmaticdepositsarerelatedtothedestabilizationofgaseoushydrateinterrestrialpermafrostfollowingrapidpostglacialwarmingandfloodingofwidelyexposedcontinentalshelvesandinternalbasins.Theauthorscarriedoutstudiesonthegeochemistry,sedimentologyandpalaeontologyoftheSiniancapcarbonatesinGuizhouandHunanprovinces,includingtheoccurrenceofcapcarbonatesofunusualfabrics,stronglynegativecarbonisotopicsignatures,andalotofbitumennodules.Fromtheresultsitissuggestedthatthecapcarbonateswereformedfromsolidmethaneseepage,anditisinagreementwithKennedy'sviewpoint(2001)thatthecapcarbonatesresultedfromtherapidprecipitationofcalciumcarbonateinresponsetosolidmethaneseepage.
简介:在CDQ(科克干燥熄灭)柄,有复杂结构的发泄帽子在冷却室下面在锥形的漏斗被安装。它行动介绍冷却气体并且在房间支持下降焦炭。设计和发泄帽子目的安装,到得到相对一致的煤气的分发在插头减少焦炭的温度变化并且认识到CDQ的稳定的操作仪器。在这篇论文,在1:7规模CDQ试验性的柄的发泄帽子的气体的狂暴的流动被使用CFD(计算液体动力学)数字地模仿软件,CFX。速度地,插头流动分发和在三种发泄帽子(叫的高发泄帽子,低发泄帽子和椭圆形的发泄帽子)下面的每个插头的压力落下因素被分析并且比较。结果生产椭圆形的发泄帽子的压力落下因素比另外的二发泄帽子大,并且高发泄帽子和低发泄帽子的压力落下因素几乎有一样的价值。当时为一顶指定发泄帽子,没有压,有压砖的压力落下因素比那大砖。在这篇论文的工作为为大规模CDQ柄设计发泄帽子是珍贵的。
简介:摘要:CAP1000电气贯穿件是安全壳的组成部分,安装工作涉及到测量放线、开孔、组对、焊接、无损检测、热处理以及测量等工序,过程中出现偏差,极易导致最终的焊接等质量不满足要求。本文对电气贯穿件安装工序和质量控制要点进行了总结和分析,具有一定的借鉴和参考意义。