简介：Ultrasonicbiophysicistsandphysicianshavecontinuouslyexhibitedgreatinterestinstudyingtheultrasonicpropertiesofblood.Itisshownthatcompressibilityofredcellappearstobeinverselypropor-tionalwithitshemoglobincontent.Amongultrasonicattenuationproducedbyredcellstructurelevelinblood,absorptionofredcellplayspredominantrole,viscousrelativemotionlossaccountsforlessthan15%,andcellscatteringcontributionisnegligible.Thecoagulationprocessofbloodisaccompaniedbysignificantchangeofsoundparameters.Themarkedadvantagehasbeenfoundintestofbloodcoagula-tionprocessbyusingultrasonictechniquethanthetraditionalviscousmethod.Bloodcoagulationcausessoundattenuation,soundbackscatteringandnonlinearityparameterB/Atoincrease,buttheattenuationfrequencydependencehardlychanges.Allofthesefindingsareofanimportantrealisticsignifi-cancefordevelopingultrasonicmedicine.

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简介：Inthispaper,atwo-dimensionalprimitiveequationmodel,couplingdynamical,radiativeandphotochemicalprocesses,isusedtosimulatethequasi-biennialoscillation(QBO)inozone.TheQBOintotalozonehasbeensuccessfullysimulatedwhentheforcingofequatorialstratosphericQBOinzonalwindisimposed.ThesimulatedcharactersofQBOinozoneareincloseagreementwiththoseobserved.WefurtheranalyzedthemechanismofformationandmaintenanceofQBOinozone.InthedifferentphasesofQBOinequatorialstratosphericwindfield,theglobalcirculationhassogreatdifferencethatitmakestheeffectsofadvectiontransferandeddytransferpresentaquasi-biennialperiodicalvariation.Chemicaleffectanddynamicaleffectarebasicallyout-of-phase.TheytogetherformandmaintaintheQBOinozone.Totalvariationrateisatinydifferenceofthetwolargeamounts.Atthelowerlevelofmiddle-highlatitudes,however,ithasaphasedifferenceofabout1-2monthsbetweendynamicalandnegativechemicaleffects,wherethedynamicaleffectiscomparativelygreater.QBOinozonehasnoclearcountereffectsonatmosphericcirculation.TheexperimentresultsshowthattheeffectsofQBOinozoneontemperaturefieldandwindfieldareverysmall.

简介：Dizzinessaffectsaleutone-thirdofindividualsovertheageof65years,andisoneofthemostconmlonreasonsfortheelderlytoconsulttheirgeneralpractitioner.Syncopeaffectsatleast20%ofthepopulationatmlnetimeandaccountsforabout6%ofgeneralmedicaladmissionsintheUK.Recurrentsymptomsareparticulas-lydisablingbecausetheyaffectanindividual'sabilitytoworkandtodrive,increasesusceptibilitytofallsandassociateinju-rim,andreduceindependenceintheelderly.

简介：Thestabilityofthethinliquidfilminacapillaryisimportanttothephase-changeheattransferprocessinminiatureofmicrostructures.Fromthebasicequationsformotionandheattransferattheinterfaceofthefilm,itsstabilityistheoreticallystudied.Withevaluationoftheeffectsandrelativemagnitudesofvariousdrivingforcesandwiththeuseoflong-wavetheoryinadditiontolinearstabilityanalysis,thecontrollingequationsaresimplifiedandanevolutionequationforthefilm'sthicknessisobtained.Detailedanalysisontheevolutionequationshowsthatinstabilityoccursfirstinthemeniscusregionandtheinstabilityconditionvarieswithboundaryconditions,geometricalscalesandthermalproperties.Thenumericalresultsagreewellwithearlieroneswithsomefavorableextensionsandimprovements.

简介：由测试melt索引(MI)，张力的力量；碎延期比率，polyoxymethylene(POM)的热变老率被分析；比较。表面形态学；POM表面的功能组的类型被观察；由SEM分析了；XPS。结果证明MI在120°C与变老的时间逐渐地珍视增加，显示热氧化分解occurrs慢慢地。在张力的力量上的20天的热变老的效果；打破POM的延期比率不是明显的，证明变老POM是相当一个长过程。在以后105天，裂开的热变老；POM表面上的搽粉的occurr。XPS决心以前显示出样品的C1s系列；在变老以后，包括C-C的二座山峰；公司，当在变老以后C-C的内容减少时；公司的内容增加，显示POM的热变老主要是碎；C-C债券分解。原来的样品的O1s/C1s比率是56.98%；在105天的热变老以后，比率是72.92%。

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简介：ThisletterintroducescolorconstancyandRetinextheoryforimageenhancement.Itclas-sifiesRetinexalgorithmsintofourcategoriesandprovidestheirprinciplesandimplementationsingeneral.TheexperimentalresultsofFrankle-McCann,MSR(Multi-ScaleRetinex)andPNSD(Pro-jectedNormalizedSteepestDescent)Retinexalgorithmsarepresentedandcompared.Moreover,varianceandaveragegradientareproposedtoevaluatetheperformanceofthedifferentalgorithms.

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简介：Toinvestigatethefeasibilityforahelicallinetobeusedasapulseformingline(PFL),thetransmissioncharacteristicsofthehelicaltransmissionlineisstudiedboththeoreticallyandexperimentally.Theresultsindicatethatitisfeasibletoemployahelicallineasalong-pulsePFL,andtheinfluenceofitsdispersionisnegligible.ComparedwithaconventionalcoaxialPFL,thehelicalPFLwiththesamesizecanproducealongerpulse.

简介：Hydrodynamiccharactersonahorizontal,thin,rigidplatelocatedbeneaththefreesurfacearenumericallyinvestigated.Assumingalinear,time-harmonicpotentialflowandutilizingGreenidentity,thegoverningLaplaceequationcanbesimplifiedintoFredholmintegralequationofthesecondkind.Supposinglinear-orderdiscontinuouselementsalongintersectingverticalboundaries,andbyuseoftheboundaryelementmethod,numericalsolutionaboutsourcestrengthdistributionontheplatecanbechangedintoaseriesofalgebraicequations.The3DGreenfunctionisintroducedtosetuptheintegralequations,andtheGMRESsolverisperformedforsolvingthelargedenselinearsystemofequations.Theadded-mass,dampingforceandexcitingforceareevaluateddirectlyfromtheequations.Itisfoundthattheadded-masscoefficientbecomesnegativeforarangeoffrequencieswhentheplateissufficientlyclosetothefreesurface.

简介：Thesurfacecoatingofgrindingballswasinvestigatedexperimentally.TheresultsshowthatacoatingmayformonthesurfaceofgrindingballswhenCrorAlpowdersaresubjectedtoballgrinding.Theplasticdeformationoftheballsurfaceplaysanimportantroleduringthecoatingformation,andthestrongbindingforcebetweenthepowdersandtheballsisanecessarypre-condition.Thethicknessofcoatingincreaseswiththeplasticityofthepowdersandtheballs.Annealingtheballswithcoatingwillresultinanobviousdiffusionoftheelementsinthebondingzoneofinter-face.

简介：Densityfunctionaltheory(DFT)calculationswerecarriedoutonthecompoundsCp2Ln-guanforLn=Y,Lu,Yb,DyandGd,[guan=(iPrN)2CN(iPr)2].TheresultswerecomparedwiththeX-raystructuresthatwereavailablefromtheliterature;thecalculationsreproducedquitewelltheexperimentalstructuralfeaturesinthesecomplexesexhibitingdistortedtetrahedrongeometry.ThecalculatedevolutionoftheLn-guanbondasafunctionofthecationshowedthatlanthanide-liganddistancesincreasedwiththeincrea...

简介：Ultrasonicattenuationinliquidhydrogenhasbeenmessuredwiththepulse-echotechniqueasafunctionoftemperaturefrom13.84Kto20.50K,at45MHz.Theresultsindicatethatthetemperaturedependenceofultrasonicattenuationinliquidhydrogenismainlydeterminedbyvolumeviscosityeffect.Ultrasonicattenuatinduetovolumeviscosityisgettingmoreandmorewithcooling.Theratiobetweenvolumeviscouscoefficientandshearviscouscoefficientisfrom1.4to4.2withinthemeasuredtempera-tureregion.

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简介：ByapplyinganewvortexdetectionmethodtotheECMWF40-yrreanalysis(ERA40)datafrom1985to2002,theclimatologyofsummervorticeshasbeeninvestigatedinfivesubtropicalregions,i.e.,thenorthwesternPacific,northeasternPacific,northwesternAtlantic,northeasternAtlantic,andAustralia-SouthPacific,followedbyvalidationwithNCEP/NCARreanalysisdata.Resultsareasfollows:(1)ThespatialdistributionsofERA40vortexactivities(VAC)werewellconsistentwiththoseofNCEP/NCARreanalysis(NRA)resultsinallregions,especiallyinnorthwesternPacific.(2)Becauseofdifferentmodelresolutions,boththenumberandintensityofvorticesobtainedfromNRAweresignificantlyweakerthanERA40's.(3)Vorticesmainlycruisedincoastsandtheadjacentseas,fromwheretothelandortheopenseavortexactivitiesweregraduallydecreased.(4)ThereweretwoactivecentersinthenorthwesternPacific:onewaslocatedinSouthChinaSeaandtheother,asthelargestcenterofthefiveregions,spreadfromtheeastsideofthePhilippinestoJapan.(5)OverthenorthwesternAtlantic,mostvorticesoccurredinPanamaanditswest-sideoffshore.(6)ThespatialdistributionsofvorticeswerealikebetweenthenortheasternPacificandnortheasternAtlantic,bothspreadingfromcoaststothewest-sideseaat5°-20°N.(7)IntheAustralia-SouthPacific,vorticeswerenotasactiveasthoseintheotherfourregions,andmostlytookplaceintheequator-sideofnearoceanareas.(8)ExceptthenorthwesternPacificandnorthwesternAtlantic,theVACinterannualvariationsintheotherthreeregionsweredifferentbetweenERA40andNRAdata.(9)InthenorthwesternPacificandnorthwesternAtlantic,theVACinterannualvariationcouldbeseparatedtoseveraldistinctstages.(10)Sincethemid1980s,meanvortexintensitywasgettingincreasedinthenorthwesternPacific,whichwasmostsignificantinthesubtropicalareasonaglobalbasis.InthewesternNorthAtlantic,therewasadecreasing(increasing)trendofthemeanvortexintensitybefo

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简介：Thepinchpointisimportantforanalyzingheattransferinthermodynamiccycles.Withtheaimtorevealtheimportanceofdetenniningtheaccuratepinchpoint,theresearchonthepinchpointpositioniscarriedoutbytheoreticalmethod.Theresultsshowthatthepinchpointpositiondependsontheparametersoftheheattransferfluidsandthemajorfluidproperties.Inmostcases,thepinchpointlocatesatthebubblepointfortheevaporatorandthedewpointforthecondenser.However,thepinchpointshiftstothesupercooledliquidstateinthenearcriticalconditionsfortheevaporator.Similarly,itshiftstothesuperheatedvaporstatewiththecondensingtemperatureapproachingthecriticaltemperatureforthecondenser.Itevencanshifttotheworkingfluidentranceoftheevaporatororthesupercriticalheaterwhentheheatsourcefluidtemperatureisveryhighcomparedwiththeabsorbingheattemperature.Awrongpositionforthepinchpointmaygenerateseriousmistake.Inbrief,thepinchpointshouldbefoundedbytheiterativemethodinallconditionsratherthantakingforgranted.

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