简介：Leaderpropagationisafundamentalissueinlightningphysics.Thepropagationcharacteristicsofpositiveleadersandnegativeleadersaresummarizedandcomparedbasedondatafromhigh-speedcameraandelectromagneticfieldinrocket-triggeredlightningandtower-initiatedlightningdischarges;availablechannelbasecurrentdatarecordedinrocket-triggeredlightningarealsoused.Thenegativeleaderspropagateinasteppedfashionaccompaniedbymanybranches.Thestemsaheadofthenegativeleadertipdeterminethemanneranddirectionoftheleaderpropagation,andeventhebranchingandwindingofthelightningchannel.Theimpulsivecurrent,electromagneticfield,andrelatedopticalimagessuggestthatthepositiveleadermaydevelopinastep-likefashionatitsinitialstageoftriggeredlightning.However,thesteppingprocessesofthepositiveleaderareobviouslydifferentfromthoseofthenegativeleader.Tower-initiatedlightningrevealedthatthemostconspicuouscharacteristicsofthestepwisepositiveleaderinvolvetheintermittentbrush-likecoronazoneinfrontoftheleadertipandtheluminosityenhancementofthechannelbehindthetip.Inrockettriggeredlightningflashes,thechargetransferredduringanindividualstepforthenegativeleaderwasnearlyanordergreaterthanforthepositivecounterpart.Thesuccessivestreamersaheadoftheleadertipareessentialforbothnegativeandpositiveleaderpropagation,andthestemscouldbeformedfromoneormorestreamersinthepreviousnegativestreamerzonewiththemainleaderchanneldim.High-resolutionobservationoftowerlightningalsorevealedanewtypeofbidirectionalrecoilleader,withpolaritycontrarytothetraditionalone,traversinginnegativechannelsassociatedwithtower-initiatedandrocket-triggeredlightning.

简介：INTRODUCTIONItiscommonknowledgethatthedevelopmentandoccurrenceofanearthquakeisaverycomplicatedgeophysicalprocess.Anearthquakeiscausedbythelocalfailureoftheearthcrustmedium,andearthquakesaredistributedinhomogeneouslyinspace.Seismicactivities,however,arearealreflectionoftheinteractionofthefaults,whichprovidesussomeinformationconcerningtheearthcrustmediumandmayhelpuspredicttheearthquake.Therefore,thestudyoftheseismicitypatterncanbecomeameansofearthquakeprediction.Inordertoreflectdirectlythespacialdistributionofseismicactivities,thesketchofepicentraldistributionhasbeenwidetyusedinthestudy

简介：Anewlightninglocatingtechnology,calledLightningMappingArray(LMA),hasbeendeveloped.ThesystemtakesadvantageofGPStechnologytomeasurethetimesofarrival(TOA)oflightningimpulsiveveryhighfrequency(VHF)radiationeventsateachremotelocation.Thespatiotemporaldevelopmentprocessesoflightningaredescribedinthree-dimensionbymeasurementofthesystemwithhightimeresolution(50ns)andspaceprecision(50-100m).Thechargestructuresinthunderstormandtheirrelationshipwithlightningdischargeprocessesarerevealed.Thetemporalandspatialcharacteristicsofpreliminarybreakdownprocessinvolvedinnegativecloud-to-ground(CG)lightningdischargesareanalyzedbasedonthedataoflightningVHFradiationevents.TheeffectofpositivechargeregioninlowerpartofthunderstormontheoccurrenceofnegativeCGlightningdischargeisdiscussed.TheresultsindicatethatthepreliminarybreakdownprocesswithlongerdurationinnegativeCGlightningdischargesisanintraclouddischargeprocess.Itoccursbetweennegativeandpositivechargeregionslocatedinmiddleandlowerpartsofthunderstormrespectively.Itinitiatesfromthenegativechargeregionandpropagatesdownward.Afterpropagatingintothepositivechargeregion,thelightningchanneldevelopshorizontally.Thecharacteristicsofthepreliminarybreakdownprocessareconsistentwiththatofintracloudlightningdischarges.ThesteppedleadersareinitiatedbytheKtypebreakdownwhichoccursinthelaststageofthepreliminarybreakdownprocessanddevelopsdownwardthroughthepositivechargeregion.TheexistenceofpositivechargeregioninlowerpartofthunderstormresultsintheoccurrenceofpreliminarybreakdownprocesswithlongerdurationbeforethereturnstrokeofnegativeCGlightningdischarges.

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简介：在华南的Dajiangbian形成是统治siliciclastic的沉积继任，低档变态在卡赛西亚·布洛克的西方的边缘上扔了，并且被glaciogenicdiamictite(Sizhoushan形成)盖住。Sizhoushanglaciogenic阶层能被归因于Jiangkou冰川(Sturtian冰川)他们在华南与Jiangkou阶层分享stratigraphic和lithological类似的事件。在整个Dajiangbian形成的上面的部分的一些碳酸盐，燧石和页岩单位为碳酸盐碳同位素被取样(13Ccarb)和器官的碳同位素(13Corg)分析。geochemical的一个范围索引包括氧同位素(18O)并且Mn/Sr(Fe/Sr)比率建议主要的碳同位素价值在上面的Dajiangbian形成被保存。上面的Dajiangbian形成表演13C向上减少向的-0.1,的carb到-5.4。我们建议否定13在Sizhoushandiamictite下面的C旅行是有Pre-SturtianIslay13Ccarb异例并且与全球Neoproterozoic同位素地层学允许关联。我们发现碳酸盐和上面的Dajiangbian形成的器官的碳同位素数据被联合，与13Ccarb-13C在多重大陆上观察的org模式。