简介:AnartificialdisturbanceisintroducedintotheboundarylayeroveraflatplatetoinvestigatetheeffectonthetransitionprocessintheMach6.5windtunnelatPekingUniversity.Alinearstabilitytheory(LST)isutilizedtopredicttheevolutionoftheeigenmodes,andthefrequencyoftheartificialdisturbanceischosenaccordingtotheLSTresults.Theartificialdisturbanceisgeneratedbyglowingdischargeonthesurfaceoftheplateclosetotheleadingedge.TheRayleigh-scatteringvisualizationandparticleimagevelocimetry(PIV)measurementsareperformed.Bycomparingtheexperimentalresultswithartificialdisturbanceswiththoseunderthenaturalcondition(withoutartificialdisturbances),thepresentpapershowsthatthesecond-modeinstabilitywavesaresignificantlystimulatedbytheartificialdisturbances,andtheboundarylayertransitioniseffectivelytriggered.
简介:通过对2014年8月3日云南鲁甸6.5级地震震害开展实地调查,对灾区破坏情况进行总体介绍,并就各烈度区特征和建筑物震害、地震地质灾害、工程结构震害进行分析,初步得出本次地震的一些震害特点.一是灾区人口密度大,人员死亡较集中.人员死亡主要集中在Ⅷ和Ⅸ度区.二是地震振动强,灾区破坏严重.本次地震震源深度12km,极震区烈度高达Ⅸ度,震源破裂在11s内集中释放.三是抗震能力弱,房屋破坏严重.灾区属国家级贫困区,农村民居抗震能力弱,且多数民房坐落在河谷陡坡上,边坡效应加重房屋震害,重灾区砖木和土木房屋成片损毁、倒塌.四是灾区条件恶劣,救灾难度大.震区活动断裂密集发育、地质破碎疏松、地形崎岖不平,又恰值雨季,诱发极其严重次生地质灾害,导致人员伤亡,造成灾区大面积交通、通信、电力中断,救援物资与救援力量无法及时发挥作用.
简介:Weproduced5-μJ,6.5-fsvisiblepulsesatarepetitionrateof1kHzusingfilamentationinagascellfilledwithkryptonfollowedbyspectralselectionandphasecompensationbyacombinationofdielectricmirrors.Thevisiblepulseshaveasmoothspectrumfrom520to650nmwithashot-to-shotstabilityineachspectralcomponentofbetterthan2%(standarddeviation).Thispulsecompressionschemeissimpleandrobust,andcanbeeasilyintegratedintointenseultrashort-pulselasersystems.
简介:TheJuly3,2015PishanM_S6.5earthquakeoccurredintheintersectionareaoftheTarimblockandWestKunlunblockwherethemoderate-strongearthquakeshavebecomeactiveinrecentyears.Thispaperhasstudiedtheseismicityparametersoftheearthquakesequencessuchastheb-valueinthePishanregionanditsvicinity.Inaddition,wealsorelocatedtheaftershocksofthePishanM_S6.5earthquakeusingtheseismicphasereportbythedouble-differencemethod.ThetemporalandspatialvariationcharacteristicsofthePishanearthquakesequenceintherupturezoneareanalyzed.Thestudyisofgreatsignificanceintheseismichazardassessmentinthisregion.