学科分类
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24 个结果
  • 简介:对于物品的度量(大小、长短、数额、重量等)的描述是人们日常生活中的常用语。这种对物品进行描述和比较的句子经常出现在一些试题中,所以掌握相关的表述是十分必要的。

  • 标签: 中等教育 英语 阅读 理解
  • 简介:Wemeasuretheelectromagneticdegreeoftemporalcoherenceandtheassociatedcoherencetimeforquasi-monochromaticunpolarizedlightbeamsemittedbyanLED,afilteredhalogenlamp,andamultimodeHe–Nelaser.ThemethodisbasedonobservingattheoutputofaMichelsoninterferometerthevisibilities(contrasts)oftheintensityandpolarization-statemodulationsexpressedintermsoftheStokesparameters.Theresultsareingoodagreementwiththosededuceddirectlyfromthesourcespectra.Themeasurementsarerepeatedafterpassingthebeamsthroughalinearpolarizersoastoelucidatetheroleofpolarizationinelectromagneticcoherence.Whilethepolarizervariestheequal-timedegreeofcoherenceconsistentlywiththetheoreticalpredictionsandalterstheinnerstructureofthecoherencematrix,thecoherencetimeremainsalmostunchangedwhenthelightvariesfromunpolarizedtopolarized.Theresultsareimportantintheareasofapplicationsdealingwithphysicalopticsandelectromagneticinterference.

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  • 简介:Accurateaerodynamicmeasurementsinthehypersonicflowoflargeaircraftmodelsintunnelshavepracticalsignificance,butposeasignificantchallenge.Novelaerodynamicforcemeasurementmethodshavebeenproposed,butlacktheoreticalsupport.Theformsoftheforcesignalstechniquesforsignalprocessingandcalculationofaerodynamicsareespeciallyproblematic.Atheoreticalstudyisconductedtoinvestigatethedynamicpropertiesbasedonmodelsofthedraw-rodsystemandslenderrods.Theresultsindicatethattheinertiaitemcanbeneglectedintherodgoverningequation;further,thesolutionsshowthatthesignalsofeachrodareacombinationofaerodynamicsignals(withaconstantvalue)andsinesignals,whichcanbeverifiedbyexperimentalshocktunnelresults.Signalprocessingandaerodynamicscalculationtechniquesarealsofoundtobeachievableviatheflatpartofthesignals.

  • 标签: 高超声速风洞 飞行器模型 气动测量 空气动力学计算 信号处理 计算技术
  • 简介:ThespinHalleffectoflight(SHEL)canbeobservedbythedarkstripresultingfromweakmeasurement.WefindthattheSHELofapartiallycoherentbeam(PCB)hasasimilarphenomenonaswell.However,thedarkstripintheSHELofaPCBcannotbeexplainedbyconsideringthebeamasanassemblanceofcoherentspeckles.Also,thedarkstripinaPCBisnotpurelydark.Byanalyzingtheautocorrelation,weshowthattheSHELofaPCBistheresultofoverlappingcoherentspeckles'SHEL.Wefurtherproveourconclusionbyadjustingconvergenceandincidentangles.Finally,wedevelopaqualitativetheorytoclarifytheSHELofaPCB.

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  • 简介:Aliquidmodifiedphotoniccrystalfiber(PCF)integratedwithanembeddeddirectionalcouplerandmulti-modeinterferometerisfabricatedbyinfiltratingthreeadjacentairholesoftheinnermostlayerwithstandard1.48refractiveindexliquids.Therefractiveindexofthefilledliquidishigherthanthatofbackgroundsilica,whichcannotonlysupportthetransmittingrodmodesbutalsothe'liquidmodifiedcore'modespropagatingbetweenthePCFcoreandtheliquidrods.Hence,thelightpropagatingintheliquidmodifiedcorecanbeefficientlycoupledintothesatellitewaveguidesunderthephase-matchingconditions,resultinginadramaticdecreaseoftheresonantwavelengthintensity.Furthermore,thereisamulti-modeinterferenceproducedbymodifiedcoremodesandrodmodes.Suchacompact(~0.91cm)deviceintegratedwithanembeddedcouplerandinterferometerisdemonstratedforhigh-sensitivitysimultaneoustemperature(~14.72nm∕℃)andstrain(~13.01pm∕με)measurement.

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  • 简介:这份报纸为numberresolved主人方程的推导论述波浪功能途径的全面评论,在mesoscopic系统为对运输和测量的描述使用。评论包含重要修正案,澄清在主人方程和他们的有效性的推导的微妙的点。这在这个题目上完成更早的工作。推导不假定弱结合,这被表明环境和水库,而是需要仅仅高偏导状况。这个条件为Markovian主人方程的有效性是很必要的,广泛地为对不同物理过程的现象学的描述使用。

  • 标签: mesoscopic 系统 量运输 主人方程 连续测量
  • 简介:Inthispaper,recentmeasurementsoftipvortexflowwithandwithoutcavitationcarriedoutinCavitationMechanismTunnelofChinaShipScientificResearchCenter(CSSRC)arepresented.TheelliptichydrofoilwithsectionNACA662-415wasadoptedastestmodel.High-speedvideo(HSV)camerawasusedtovisualizethetrajectoryoftipvortexcoreandtheformoftipvortexcavitation(TVC)indifferentcavitationsituations.LaserDopplervelocimetry(LDV)wasemployedtomeasurethetipvortexflowfieldinsometypicalsectionsalongthevortextrajectorywiththecaseofcavitationfree.Stereoparticleimagevelocimetry(SPIV)systemwasusedtomeasurethevelocityandvorticitydistributionswithandwithoutcavitation.Seriesmeasurementresultssuchasvelocityandvorticitydistributions,thetrajectoryoftipvortexcore,thevortexcoreradius,cavitysizeandcavitationinceptionnumberwereobtained.Theresultsdemonstratedthattheminimumpressurecoefficientinthevortexcoreobtainedbyflowfieldmeasurementwasquitecoincidentwiththetipvortexcavitationinceptionnumberobtainedundertheconditionofhighincomingvelocityandlowaircontent.AndTVCwoulddecreasethevortexstrengthcomparingwiththecasewithoutcavitation.

  • 标签: 旋涡流动 测量速度 水翼船 椭圆形 成穴 试验性
  • 简介:Inthisstudy,thepracticalmethodologiesaredescribedforthedeterminationofthefactorsfortheselfabsorptioneffect(Fs),spectralinterferences(Fcsi),andtruecoincidencesummingeffects(Fcoi),whichareusedindirectgamma-spectrometricmeasurementofradionuclidessuchas210Pb,238U,234Th,226Ra,214Pb,228Ac,208Tl,214Bi,137Csand40Kinsamples.Tovalidatetheappliedmethods,certifiedreferencematerials(CRMs)oflakeandstreamsedimentsweremeasuredwithann-typeGermanium(Ge)detector-calibratedusingamultinuclidereferencesource.Thehighestself-absorptioncorrectionfactorsrangedfromFs1.44-2.10for46.5keVpeak(210Pb)andFs?1.25-1.60for63.3keVpeak(234Th)lyinginthelowenergyregionofthespectrum.Thesystematicinfluencewasobservedfor186.2keV(226Ra)peakduetospectralinterferenceswiththe235Ucontribution.Forthispeak,Fcsiischangedfrom0.921to0.955.Additionally,thepresentstudysuggeststhattruecoincidencesumming(TCS)effectsarenotdominant,exceptfor208Tland214BiforwhichFcoirangedfrom1.179to1.192anrangedfrom1.140to1.151,respectively.

  • 标签: Correction factor SELF-ABSORPTION Spectral interference TRUE
  • 简介:有表面结果的supercooled水微滴的碰撞一个目标在表面上创造冰生长。在任何冷环境的糖衣问题在预防和预言技术上在飞机,和很多研究上导致严重损坏因为糖衣到目前为止被进行了。因此,知道冻结supercooled水微滴的机制改进反的详细是很重要的--并且除冰的设备和糖衣模拟代码。影响目标表面的单个supercooled水微滴的糖衣机制将为目的给我们大卓见。在现在的学习,我们开发一种双光的成像技术测量在不同温度条件下面影响表面的supercooled水微滴的解决时间的温度。我们使用这种技术测量水微滴的准确温度,并且讨论结冰过程的详细。

  • 标签: 饱和温度 技术测量 过冷 结冰 发光 成像法
  • 简介:Anonlinearitymeasurementofthecharge-coupleddevice(CCD)arrayspectrometerusingfluxadditionandcomparisonmethodisdescribed.Thelightwithvariouscolorsfromthecolorfullightemittingdiode(LED)lightsourceisappliedtomeasurethenonlinearityofthespectrometeratdifferentwavelengths,respectively.Anhigh-endCCDarrayspectrometeristested.ForcolorfulLEDlightsources,thenonlinearityfactorsoftheCCDarrayspectrometer(absolutevalue)areasfollows:k<0.8%forwhitelight,k<1.1%forredlight,k<2.2%forgreenlightandk<4.7%forbluelight.Byusingthosequasi-monochromaticlightsources,itisshownthatthenonlinearitydependsonthewavelength.Itisimportanttobewarinessaboutthespectralnonlinearityandrelateduncertaintyevaluationwhenthenarrow-bandlightsourceistested.

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  • 简介:Thestressintensityfactor(SIF)isacriticalparameterassociatedwiththefracturebehaviourofmaterials.Inthispaper,weselectthedisplacementfunctionaroundacracktipastheshapefunctionofthedigitalimagecorrelation(DIC),whichmakesitpossibletodirectlycalculatetheSIFbythecorrelationscheme.Moreover,weuseanon-rectangularsubset,whichcanreducetheinfluenceofplasticdeformationandcrackwidthontheDICmeasurementaccuracy.WemeasuredtheSIFofamodeIcrackinasuper-hardaluminiumalloyspecimentoverifytheperformanceoftheproposedmethod.OurexperimentalresultsshowthataDICwithaspecificshapefunctioncanbeusedtoaccuratelyandefficientlycalculatetheSIF.Furthermore,wealsopresentapracticalapplicationofourproposedmethodfordeterminingtheSIF,crackpropagationangleandcracktipdisplacement.

  • 标签: Digital image CORRELATION (DIC) SHAPE function
  • 简介:在这份报纸,data-based控制问题在反馈和前面的隧道象包退学学生一样与测量噪音为联网的非线性的系统的一个类被调查。测量噪音和在两条隧道的连续的包退学学生的数字被假定随机却围住。data-based联网了预兆的控制方法被建议,在哪个控制增长预言的一个序列基于测量产量错误,并且基于致动器收到的控制增长预言在控制器被计算,一个合适的控制行动被获得并且在每采样片刻根据连续的包退学学生的即时数字适用于植物。然后,稳定性分析为联网的closedloop系统被执行。最后,建议方法的有效性被一个数字例子说明。

  • 标签: 预测控制 非线性系统 测量噪声 网络化 丢包 前向信道
  • 简介:生物织物的吸收系数是在biomedicine的一个重要参数,但是它的决心仍然是挑战。在这份报纸,我们用集中photoacoustic成像技术和圆柱的扩散纤维(CDF)的内部轻照耀确定建议一个方法目标光吸收系数。为墨水吸收器的吸收系数第一在一样的刺激通过photoacoustic和spectrophotometric大小被决定,它表明这个方法的可行性。另外,有几集中的墨水吸收器的光吸收系数被测量。最后,二维的扫描photoacoustic图象被获得。光吸收系数测量和吸收器的同时的photoacoustic成像non-invasively是方法的典型特征。这个方法能为血氧浸透,基于吸收的成像和治疗的非侵略的决心起一个重要作用。

  • 标签: 光吸收系数 声测量 分光光度法测定 无损伤 内照射 光纤
  • 简介:为紧张和温度测量的一个光纤维传感器与纤维基于长时期纤维栅栏(LPFG)串联了布拉格栅栏(FBG)结构理论上并且试验性地被建议了并且认识到。有类似的敏感的二微观结构不能被用于的理论分析表演加倍参数测量。LPFG是由CO2激光的micromachined,并且FBG是由excimer激光的micromachined。为确认和比较,二FBG和一LPFG与三条传播山谷被串联,也就是在1536.3nm,在1551.2nm的LPFG山谷,和在1577.3nm的FBG2山谷的FBG1山谷。建议传感器的温度和紧张特征在4570椠歮愠獢牯敢獲愠敲映物瑳祬搠瑥牥業敮?桴潲杵?桰瑯慯潣獵楴?湡?灳'虪沟茲滀髷疇罐鏇V畳敲敭瑮?瑡琠敨猠浡?被测量硥楣慴楴湯?桷捩?敤潭獮牴瑡獥琠敨映慥楳楢楬祴漠?桴獩洠瑥潨d

  • 标签: 长周期光纤光栅 光纤传感器 参数测量 光纤布拉格光栅 准分子激光 灵敏度矩阵
  • 简介:TheprecisionofplasmaelectrondensityandFaradayrotationanglemeasurementisakeyindicatorforfar-infraredlaserinterferometer/polarimeterplasmadiagnosis.Toimprovetheprecision,anewmulti-channelhighsignal-to-noiseratioHCOOHinterferometer/polarimeterhasbeendevelopedontheHL-2Atokamak.Ithasahigherlevelrequirementforphasedemodulationprecision.Thispaperintroducesanimprovedreal-timefastFouriertransformalgorithmbasedonthefieldprogrammablegatearray,whichsignificantlyimprovestheprecision.Wealsoapplyareal-timeerrormonitoringmodule(REMM)andastableerrorinhibitingmodule(SEIM)forprecisioncontroltodealwiththeweaksignal.Wetesttheinterferometer/polarimetersystemwiththisimprovedprecisioncontrolmethodinplasmadischargeexperimentsandsimulationexperiments.Theexperimentalresultsconfirmthattheplasmaelectrondensityprecisionisbetterthan1/3600fringeandtheFaradayrotationanglemeasurementprecisionisbetterthan1/900fringe,whilethetemporalresolutionis80ns.ThisperformancecanfullymeettherequirementsofHL-2A.

  • 标签: HL-2A装置 等离子体诊断 电子密度 转角测量 控制处理 高精度
  • 简介:WeinvestigatethesensitivityoftheangularrotationmeasurementwiththemethodofhomodynedetectioninSU(2)andSU(1,1)interferometersbyemployingorbitalangularmomentum(OAM).BycombiningacoherentbeamwithavacuumbeaminanSU(2)interferometer,wegetthesensitivityoftheangularrotationmeasurementas1/(2N1/2l).WecansurpassthelimitoftheangularrotationmeasurementinanSU(1,1)interferometerbycombiningacoherentbeamwithavacuumbeamorasqueezedvacuumbeamwhentheprobebeamhasOAM.Withoutinjection,thesensitivitycanreach1/(2N1/2l).Inaddition,byemployinganotherconstructionofanSU(1,1)interferometerwherethepumpbeamhasOAM,withthesameinjectionofanSU(1,1)interferometer,thesensitivityoftheangularrotationmeasurementcanbeimprovedbyafactorof2,reaching1/(4Nl).Theresultsconfirmthepotentialofthistechnologyforprecisionmeasurementsinangularrotationmeasurements.

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