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500 个结果
  • 简介:利用声光偏折效应,设计了一种测量球壳型换能器辐射聚焦声场焦点峰值声压的简便实验方法.基于焦点峰值声压与最大光偏折量之间的理论关系,通过测定聚焦声场焦域的最大光偏折量,获得球壳型聚焦换能器的焦点峰值声压;采用有限元方法对聚焦换能器辐射声场进行数值分析.对比实验测量结果,发现二者相对误差为7.33%,符合较好.该实验方法在医疗超声快速校准方面具有广泛的应用前景.

  • 标签: 聚焦声场 声光偏折 定量测量
  • 简介:摘要目的分析脑梗塞的发病与血压高峰值控制情况的相关性。方法在高血压患者中,使用偶测血压或24小时动态血压调整降压药物后,随访脑梗塞的发病情况。结果经过24小时动态血压监测后调整用药的患者,其脑梗塞的发病率低于经过诊室血压监测后调整用药的患者。结论控制高峰时段的血压有助于减少脑梗塞的发生率。

  • 标签: 高血压 脑梗塞 动态血压监测
  • 简介:本文在研究了数百个工程场地钻孔资料的基础上,选取和构造了209个有代表性的典型场地剖面,利用目前工程上广泛应用的一维等效线性化波动方法,进行了6种输入强度下(30gal、50gal、100gal、150gal、200gal、300gal)的场地土层地震反应分析。在计算时对每种工况均采用9条互不相关的基岩加速度时程作为输入地震波,同时用均方差来定量评估所得到的地面加速度峰值的离散性,发现计算结果离散性很大,其最大均方差为0.206,最小均方差为0.138,且离散性随基岩地震动输入强度的增大而变大,随场地类别的变差也变大。

  • 标签: 场地条件 地震反应 地面加速度峰值 离散性
  • 简介:Asimpleandefficientmethodhasbeendeveloped;benzil/benzoinundergoessmoothcondensationwithvarioussubstitutedaldehydeandammoniumacetateinthepresenceofpotassiumdihydrogenphosphate(KH_2PO_4)undermildreactionconditionstoaffordthecorrespondingtrisubstitutedimidazoleinexcellentyields.Themethodforsynthesisofproduct,thereactionmixturewasrefluxinethanolfor40-90min.Thepresentmethodissimple,efficient,andcost-effective.

  • 标签: 钾 dihydrogen 磷酸盐(KH2PO4 ) 2 4 5-Triaryl-1H 鈥搃m idazole BENZIL 安息香 铵醋酸盐
  • 简介:New[1+1]and62-membered[2+2]Schiffbasemacrocyclescontaininga2,6-diamidopyridinesubunithavebeensynthesizedbycondensationreactionoftheprecursorspyridine-2,6-dicarboxamideand1,10-bis(20-formylphenyloxy)decaneinthepresenceofphosphoricacidviaaone-potprocess.Thecyclocondensedproductswereeffectivelyisolatedbygelcolumnchromatographyandcharacterizedby~1HNMR,FTIR,massspectrometryandX-rayanalysis.Thetwomacrocycleshaveatwistedstructure,andnotanopen‘circular’conformationinthesolidstate.

  • 标签: 大环化合物 一锅法合成 凝胶柱层析 X射线分析 反应合成 FTIR
  • 简介:为新奇分子的clefts的合成的一个快速、安全、有效的方法基于deoxycholic被报导。七新分子的clefts在好收益被综合了(8998%)。这个方法证明了极其简单、高度有效。这些受体的结构被1HNMR,红外,MS系列和元素的分析证实。

  • 标签: 去氧胆酸 合成 微波照射 手征分子
  • 简介:那些对于是否能活着度过2012年持悲观态度的人,TG给你个活下去的理由。明年SSCTuatara将推出龙年版。中国地区第一位Tuatara车主也有望在2013年提车,至于售价尚不明朗。而龙年版我们似乎听到一个比阿斯顿·马丁One-77更高的报价,99%的人已经没兴趣往下听了吗?好吧.下面说点技术活儿。

  • 标签: 轿车 车型 品牌 汽车测试
  • 简介:Inapreviouspaper,amethodhasbeendevelopedtostudythestabilitycharacteristicsoflaminarboundarylayersovercompliantwalls.Inthispaper,theeffectofdoublelayeredcompliantwallandKramertypecompliantwallondelayingthetransitionisinvestigated,anditisshownthattheredoesexistthepossibilitytode-laythetransitionbyapplyingsuchcompliantwalls.

  • 标签: TRANSITION compliant WALL STABILITY
  • 简介:TheimpactoforbitalparametersontheclimateofChinaintheHoloceneissimulatedfrom11kaBPto0kaBPwithanintervalof1kausingNationalCenterforAtmosphericResearch(NCAR)CommunityAtmosphereModelversion2(CAM2).Thegeographicdistributionsofsummerprecipitationaroundboth9kaBPand4kaBPwererealisticallycapturedbyCAM2,comparedtotheproxydatacollectedfrom80stations.Amongallorbitalparameters,theprecessionplaysamajorroleincomputingsolarradiation,whichdominatesthevariationsofsummerprecipitationoverChinaduringtheHolocene.Thesummersaround9kaBPwerethewettestinChina.Lateron,theprecipitationgraduallyreducedtotheminimumaround0kaBPbyabout10%.ThistremendouschangeoccurredfromtheNortheastChinaandtheeasternInnerMongoliaextendingsouthwestwardstotheQinghai-TibetPlateau,especiallyovertheQinghai-TibetPlateau.

  • 标签: HOLOCENE 气候模拟 轨道的参数 气候湿度
  • 简介:Inthispaper,onlynarrow-senseprimitiveBCHcodesoverGF(q)areconsidered.Aformula,thatcanbeusedinmanycases,isfirstpresentedforcomputingthedimensionofBCHcodes.ItimprovestheresultgivenbyMacWilliamsandSloanein1977.AnewmethodforfindingthedimensionofalltypesofBCHcodesisproposed.Insecondpart,itisprovedthattheBCHboundistheleaderofsomecyclotomiccoset,andweguessthattheminimumdistanceforanyBCHcodeisalsotheleaderofsomecyclotomiccoset.

  • 标签: BCH CODE Cyclotomic COSET DIMENSION Minimum
  • 简介:ThispaperintroducesaunifiedoperatortheoryapproachtotheabstractFourieranalysisoverhomogeneousspacesofcompactgroups.LetGbeacompactgroupandHbeaclosedsubgroupofG.LetG/HbetheleftcosetspaceofHinGandμbethenormalizedG-invariantmeasureonG/HassociatedtotheWeil'sformula.Then,wepresentageneralizedabstractframeworkofFourieranalysisfortheHilbertfunctionspaceL~2(G/H,μ).

  • 标签: 傅立叶分析 陪集空间 齐次 紧致 算子理论 不变测度
  • 简介:AbstractGlobally, rabies remains a serious threat to public health. In particular, large number of cases continue to be detected in Africa and Asia. China has experienced three major outbreaks with the current epizootic starting in 1990s, peaking in 2007 with 3,300 cases, and consistently decreasing since this point. A key factor of the success in keeping the rabies outbreak under control is the National Public Health Reporting Program that was introduced to coordinate surveillance at provincial and regional levels. Through this program, it is possible to obtain an integrated overview of how rabies was spreading and how various factors were contributing to the outbreak. At the same time, samples have been collected from suspected rabies cases and a subset of positive samples selected for sequencing. In this way, it is possible to investigate the outbreak from a phylogenetic perspective, providing the comprehensive description of a rabies outbreak to date. In this work, we review rabies control efforts over the last 20 years, and show how this integrated approach has led to a deeper characterization of the outbreak and a better understanding of the factors driving the spread of the disease.

  • 标签: Rabies Rabies virus China Surveillance Lineage
  • 简介:CharacteristicsoftheMeanWaterVaporTransportoverMonsoonAsiaYiLan(伊兰)(InshtuteofAtmosphericPhysics,ChineseAcademyofSciences,Bei...

  • 标签: WATER vapor transport EAST ASIAN MONSOON
  • 简介:OptimisinguseoftheWeb(WWW)forLHCdataanalysisisacomplexproblemandillustratesthechallengesarisingfromtheintegrationofandcomputationacrossmassiveampuntsofinformationdistributedworldwide.Findingtherightpieceofinformationcan,attimes,beextremelytime-consuming,ifnotimpossible,SO-calledGridshavebeenproposedtofacilitateLHCcomputingandmanygroupshaveembarkedonstudiesofdatareplication,datamigrationandnetwrokingplhilosophies.Otheraspectssuchastheroleofmoddleware'forGridsareemergingasrequiringresearch.Thispaperpositionstheneedforappropriatemiddlewarethatenablesuserstoresolvephysicsqueriesacrossmassivedatasets.Itidentifiestheroleofmeta-dataforqueryresolutionandtheimportanceofInformationGridsforhigh-energyphysicsanalysisratherthanjustcomputationalorDataGrids,ThispaperidentifiessoftwarethatisbeingimplementedatCERNtoenablethequeryingofverylargecollaboratingHEPdata-sets,initiallybeingemployedfortheconstructionofCMSdetectors.

  • 标签: 高能物理 物理数据库 信息网络
  • 简介:WHATHASTHEDALAIDONEOVERTHEPAST36YEARS?¥//InApril1959,theDataiLamaissuedthe"statementoftheDalaiLama"whichadvocated"Tibetindepe...

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  • 简介:TheabruptchangesofzonalcirculationintheTibetanPlateau(TP)regionandtheirlikelycausesarederivedfromNationalCentersforEnvironmentalPredictionandtheNationalCenterforAtmosphericResearchreanalysisdata.ThezonalcirculationovertheTPabruptlychangedinsummer(31stpentad)andwinter(59thpentad).Theswitchfromsummertowintercirculationischaracterizedbyasuddennorthwardshiftofthewesterliesandthezero-velocitycurveanddisappearanceofthewesterlyjet.Thewinter-summerswitchischaracterizedbythereversepattern.Therefore,thecirculationconversionbetweensummerandwintercanbejudgedfromthepositionofthezero-velocitycurve.Curveslocatednorthof20°NindicatesummercirculationovertheTPandviceversa.TheabruptchangeofzonalcirculationismainlycausedbythethermodynamiceffectoftheTP.InJune,thiseffectcausesahugemonsooncirculationcellextendingfromtheTPtolowlatitudes.Consequently,thewesterliesjumptothenorthaseasterliesdevelop.Thisprocess,whichisenhancedbythestrongnortherlyinCoriolis,establishesthesummercirculation.InOctober,theHadleycellrecursasthethermaleffectsoftheTPdiminish,thewesterliesrushsouthward,andthewintercirculationisestablished.

  • 标签: TIBETAN Plateau ZONAL CIRCULATION ABRUPT change