简介:ThreesamplingcrosssectionsalongthesouthpathstartingfromtheTropicsthroughthevaporpassageintheYunnan-GuizhouPlateautothemiddle-lowreachesoftheYangtzeRiver,thenorthpathfromWestChina,viaNorthChina,toJapanunderthewesterlies,andtheplateaupathfromSouthAsiaovertheHimalayastothenorthernTibetanPlateau,aresetup,basedontheIAEA(InternationalAtomicEnergyAgency)/WMOglobalsurveynetworkandsamplingsitesontheTibetanPlateau.Thevariations,andtherelationshipwithprecipitationandtemperature,oftheδ18Oinprecipitationalongthethreecrosssectionsareanalyzedandcompared.Alongthesouthpath,theseasonaldifferencesofmeanδ18OinprecipitationaresmallatthestationslocatedintheTropics,butincreasemarkedlyfromBangkoktowardsthenorth,withtheδ18Ointherainyseasonsmallerthaninthedryseason.Theδ18Ovaluesinprecipitationfluctuateonthewhole,whichshowsthattherearedifferentvaporsources.Alongthenorthpath,theseasonaldifferencesofthemeanδ18OinprecipitationforthestationsinthewestofZhengzhouareallgreaterthanintheeastofZhengzhou.Duringthecoldhalfoftheyear,themeanδ18OinprecipitationreachesitsminimumatUrumqiwiththelowesttemperatureduetothewide,coldhighpressureoverMongolia,thenincreasesgraduallywithlongitude,andremainsatroughlythesamelevelatthestationseastwardfromZhengzhou.Duringthewarmhalfoftheyear,theδ18Ovaluesinprecipitationarelowerintheeastthaninthewest,markedlyinfluencedbythesummermonsoonoverEastAsia.Alongtheplateaupath,themeanδ18OvaluesinprecipitationintherainyseasonarecorrespondinglyhighinthesouthernpartsoftheIndiansubcontinent,andthendecreasegraduallywithlatitude.Asharpdepletionofthestableisotopiccompositionsinprecipitationtakesplaceduetotheverystrongrainoutofthestableisotopiccompositionsinvaporintheprocessofliftingoverthesouthernslopeo
简介:金属氧化物压敏电阻(MOV)在防止电力系统免受雷电过电压侵扰时起至关重要的作用。文中基于MOV仿真模型IEEE模型,建立了一种新的MOV仿真模型F-D模型,并利用ATP-EMTP电磁暂态仿真软件进行仿真模拟,进而对比分析IEEE模型和F-D模型在残压误差上的优缺点。相比于IEEE模型,在波形为8/20μs和峰值为10kA的雷电电流冲击下,FD模型能更好地再现雷电电流冲击后的残压值。F-D模型中的电感参数对仿真结果影响较大,其值与残压误差值呈负相关关系。在波形为8/20μs和峰值分别为5、7、10kA的雷电电流冲击下,优化后的F-D模型残压误差均可忽略不计,因此优化后的F-D模型能很好地反映出实际的MOV动作特性。
简介:根据GNIP所提供的长江流域多年月平均降水中δD、δ^18O料以及NOAA-CIRES提供的NCEP/NCAR再分析资料,研究了长江流域降水稳定同位素与降水量、水汽压、温度和水汽来源之间的关系。结果表明:在平均季节尺度下,长江流域大气降水中δ^18O降水量、水汽压和温度均存在显著的负相关关系,说明该流域降水中δ^18O化存在显著的降水量效应、湿度效应和反温度效应。基于降水中过量氘示踪水汽来源原理,分析了中国长江流域季风区降水中过量氘与阿拉伯海、孟加拉湾和南印度洋3个海区相对湿度的关系,表明中国长江流域的水汽主要来源于上述3个海区,而昆明和成都可能受到其他水汽作用,使其与水汽源区的相对湿度呈正相变化。