学科分类
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13 个结果
  • 简介:GeologictimeisfundamentaltotheEarthSciences,andprogressinmanydisciplinesdependscriticallyonourabilitytomeasuretimewithincreasingaccuracyandprecision.Isotopicgeochronologymakesuseofthedecayofradioactivenuclidesasahelptoquantifythehistoriesofrock,minerals,andothermaterials.Bothaccuracyandprecisionofradioisotopicagesare,atpresent,limitedbythoseofradioactivedecayconstants.Modemmassspectrometerscanmeasureisotoperatioswithaprecisionof10-4orbetter.Ontheotherhand,theuncertaintiesassociatedwithdirecthalf-lifedeterminationsare,inmostcases,stillatthepercentlevel.ThepresentshortnotebrieflysummarizesprogressandproblemsthathavebeenencounteredduringtheWorkingGroup'sactivity.

  • 标签: 地球年代学 衰变常数 地球化学 同位素
  • 简介:Areal-valuedfunctionf(x)onЖbelongstoZygmundclassA.(Ж)ffitsZygmundnorm‖f‖x=inf,|f(x+t)-2f(x)+f(x-t)/t|isfinite.Itisprovedthatwhenf∈A*(Ж),thereexistsanextensionF(z)offtoH={Imz>0}suchthat‖Э^-F‖∞≤√—1+53^2/72‖f‖z.Itisalsoprovedthatiff(0)=f(1)=0,thenmax,x∈[0,1]|f(x)|≤1/3‖f‖x.

  • 标签: 准保角变形 展开式 连续复值函数 Zygmund类
  • 简介:Withthehelpofthedeclinemethod,acomputer-aidedanalysisprogramofChristoffelequationisdes-cribedwhichmakesitpossibletocalculateelasticandviscousconstantsofcrystalspreciselyandeasily.TheelasticconstantsofLiNbO3andBi12GeO20crystalsarecalculatedwithanApple-ⅡcomputerandtheFortranprogramsuggested,andthecalculateddataarecomparedwiththevaluesachievedbyothers.

  • 标签: CONSTANTS DECLINE Apple ultrasonic VISCOUS aided
  • 简介:Elovich,parabolicdiffusion,powerfunctionandexponentialequationswereusedtodescribeKdesorptionkineticsof12soilsinaconstantelectricfieldofelectro-ultrafiltration(EUF),ResultsshowedthattheElovich,parabolicdiffusionandpowerfunctionequationscoulddescribeKdesorptionkineticswellowingtotheirhighcorrelationcoefficientsandlowstandarderrors;buttheexponentialequationwasnotsuitabletobeusedinthisstudyduetoitsrelativelylowcorrelationcoefficientsandrelativelyhighstandarderrors.Thisworkestablishedsuccessfullytherelationshipsbetweentheconstants(slopeorintercept)ofkineticequationsandthebarleyresponsestoKfertilizerinthemultiple-sitefieldexperimentsandK-supplyingstatusofsoilsk,theconstantsofElovich,parabolicdiffusionandpowerfunctionequationswereverysignificantlyorsignificantlycorrelatedtothesoilavailableK,relativeyieldofbarleyandKuptakeofbarleyinNPplot.ItwassuggestedthatthekineticequationconstantscouldbeusedtoestimateK-supplyingpowerofsoils.

  • 标签: 土壤钾 钾解吸附 动力学方程 方程常数 应用
  • 简介:IntroductionAvarietyofnewpolyaminopolycarboxylateligandsandtheirlanthanidecomplexeshavebeensynthesizedinrecentyearsbecauseoft...

  • 标签: Terbium(Ⅲ) Polyaminopolycarboxylate Complex STABILITY CONSTANT FLUORESCENCE
  • 简介:ElasticconstantsofNaandLimetalsarecalculatedsuccessfullyfortemperaturesupto350Kandpressuresupto30GPausingaschemewithoutinvolvinganyadjustableparameter.Elasticconstantsareassumedtodependonlyonaneffectivepairpotentialthatisonlydeterminedbytheaverageinteratomicdistance.Temperaturehasaneffectonelasticconstantsbywayofchargingtheequilibrium.Theelasticconstantscanbeobtainedbyfittingtherelationshipbetweentotalenergyandstraintensorusingthenewsetoflatticeparametersobtainedbycalculatingdisplacementofatomsatthefinitetemperatureandatafixedpressure.Therelationshipbetweentheeffectivepairpotentialandtheinteratiomicdistanceisfittedbyusingaseriesofdataofcohesiveenergycorrespondingtolatticeparameters.

  • 标签: 晶体 高压 有限温度 弹性常数计算法
  • 简介:TheISMbandat2.4GHzhasmostlybeenusedorplannedforindoorsystems.Thisbandisalsoattractiveforoutdoorsystemsowingtotheeaseofthesystemdeployment,asnofrequencylicensesarerequired.Inthispaper,amultiplesuccessiveinternalmultireflectionmodelisusedtoestimatethecomplexelectricpermittivityat2.4GHzband.Toobtainthedata,measurementsareperformedat160MHzbandwidthcenteredabout2.4GHzusingavectornetworkanalyzer,whichprovidesinformationabouttheamplitudeandphaseoftransmissioncoefficient.Severalsamplesofeachmaterialaremeasuredandtheresultsvaryfromsampletosample.Ithasalsobeenfoundthatsomeobstacleshavepolarizationbehaviour.

  • 标签: 透射系数 多反射模型 电介质常数 损耗因数 ISM 无线网络
  • 简介:在这个工作,我们试着为Mumford-Shah分割模型使用所谓的Piecewise经常的水平集合方法(PCLSM)。为图象分割,Mumford-Shah模型需要为分割发现这些区域和在内的经常的价值这些区域。以便为这个目的使用PCLSM,我们需要作为最小化变量用水平集合函数和经常的值解决一个最小化问题。在这个工作,我们在一个模型上测试以便我们仅仅需要关于水平集合功能最小化,即,我们不需要关于经常的价值最小化。坡度降下方法和牛顿方法被用来为最小化问题解决theEuler-Lagrange方程。数字实验被给显示出新模型和算法的效率和优点。

  • 标签: PCLSM 图像分割 MUMFORD-SHAH模型 图论
  • 简介:Thispaperpresentsanexactsolutionofthecracktipfieldinfunctionallygradientmaterialwithexponentialvariationofelasticconstants.ThedimensionlessPoisson'sratiosv0oftheengineeringmaterials(iron,glass...)arefarlessthanone;therefore,neglectingthem,onecansimplifythebasicequationandtheexactsolutioniseasytoobtain.Althoughtheexactsolutionforthecasev0≠0isalsoobtained,itisverycomplicatedandthemainresultisthesamewiththecasev0=0(itwillbedealtwithinAppendixⅦ).Ithasbeenfoundthattheexponentialtermexp(ax+by)intheconstitutiveequationsbecomesexp(ax/2+by/2-kr/2)intheexactsolution.

  • 标签: 弹性常数 指数变化 功能梯度材料 弹性力学 材料力学
  • 简介:Theopticalparametersforthreesamplesofintrinsic,dopedSianddopedMg(AlxGa1-x)yIn1-yPpreparedbytheMOCVDonGaAssubstrateweremeasuredbyusingellipsometryandwerecalculatedbythetwo-layerabsorptionfilmmodel.Theresultsobtainedwerediscussed.Thegrownratesandthicknessofoxidiclayerontheintrinsic(AlxGa1-x)yIn1-yPsurfaceexposedintheatmospherewerestudied.Alineardependenceofoxidiclayerthicknessonthetimewasobtained.

  • 标签: 椭圆光度法 光参数 氧化层 二层吸收薄膜 半导体 铝镓铟磷
  • 简介:Anewapproachtodeterminealltheelectro-elasticconstantsofthepiezoelectriccrystalsinclass4mmhasbeenputforward.Asanexample,alltheconstantsofLithiumTetraborate(Li2B4O7)crystalhavebeenmeasuredbymeansoftheapproach.Theoutstandingadvantageoftheapproachisthatiton-lyneedstoemployinmeasurementthreecrystalplatesdifferentlyoriented.

  • 标签: CONSTANTS lithium PIEZOELECTRIC outstanding INFINITE RESONANT