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简介：2000年8月16-17日,环北京地区出现较大范围暴雨天气过程.利用NCEP再分析资料并结合地面、高空观测资料,对本次暴雨过程的成因进行了初步的分析,结果表明：在高空西来槽和东北冷涡的环流形势下,高空辐散强迫抽吸作用和低层辐合共同作用造成强上升运动、低层有向北京地区的水汽输送,在以上两个条件成熟的情况下,前期对流不稳定能量的聚集和适时释放,也是造成此次强降水的主要原因之一.

简介：基于其体积小、重量轻、一致性好等特点,单片微波集成电路的低噪声放大器在射电天文中有着重要作用。本文采用稳懋公司150nm和100nm赝高电子迁移率晶体管(pseudomorphichighelectronmobilitytransistor,pHEMT)工艺设计了两款低噪声放大器电路,成功流片,并进行比较。两款放大器的工作频率范围均为8-20GHz,增益约为23~28dB,噪声温度低于150K,输入输出回波损耗大于10dB。

简介：ThegreatSanhe-PingguM8earthquakeoccurredin1679wasthelargestsurfaceruptureeventrecordedinhistoryinthenorthernpartofNorthChinaplain.Thisstudydeterminesthefaultgeometryofthisearthquakebyinvertingseismologicaldataofpresent-daymoderate-smallearthquakesinthefocalarea.Werelocatedthoseearthquakeswiththedouble-differencemethod.Basedontheassumptionthatclusteredsmallearthquakesoftenoccurinthevicinityoffaultplaneoflargeearthquake,andreferringtothemorphologyofthelongaxisoftheisoseismallineobtainedbythepredecessors,weselectedastrip-shapedzonefromtherelocatedearthquakecatalogintheperiodfrom1980to2009toinvertfaultplaneparametersofthisearthquake.Theinversionresultsareasfollows:thestrikeis38.23°,thedipangleis82.54°,theslipangleis-156.08°,thefaultlengthisabout80km,thelower-boundarydepthisabout23kmandtheburieddepthofupperboundaryisabout3km.ThisshowsthattheseismogenicfaultisaNNE-trendingnormaldip-slipfault,southeastwalldownwardandnorthwestwalluplift,withtheright-lateralstrike-slipcomponent.Moreover,thesurfacerupturezone,intensitydistributionoftheearthquakeandseismic-wavevelocityprofileinthefocalareaallverifiedourstudyresult.