简介：Thechemicaloxygen–iodinelaser(COIL)istheshortest-wavelengthhigh-powerchemicallaserthathasbeendemonstrated.Thecharacteristics,suchasgoodatmosphericpropagation,shortwavelengthandexcellenttransmissionthroughopticalfibers,maketheCOILagoodcandidateforhigh-powerlaserapplication.TomodelthecompleteCOILlasinginteraction,athree-dimensionalformulationofthefluiddynamics,speciescontinuityandradiationtransportequationsisnecessary.Thecomputationalefforttocalculatetheflowfieldovertheentirenozzlebankwithagridfineenoughtoresolvetheinjectionholesissolargeastoprecludedoingthecalculation.Theapproachtomodelingchemicallasersthenhasbeentoreducethecomplexityofthemodeltocorrespondtotheavailablecomputationalcapability,addingdetailsascomputingpowerincreased.ThemodelingoflasingintheCOILmediumisproposed,whichiscouplingwiththeeffectsinducedbytransverseinjectionofsecondarygases,non-equilibriumchemicalreactions,nozzletailflowandboundarylayer.ThecoupledsteadysolutionsofthefluiddynamicsandopticsinaCOILcomplexthree-dimensionalcavityflowfieldareobtainedfollowingtheproposal.Themodelingresultsshowthattheseeffectshavesomeinfluenceonthelasingproperties.Afeasiblemethodologyandatheoreticaltoolareofferedtopredictthebeamqualityforlarge-scaleCOILdevices.

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简介：TheeffectofSiO2particlesonheattransferperformanceofapulsatingheatpipe(PHP)wasinvestigatedexperimentally.DIwaterwasusedasthebasefluidandcontrastmediumforthePHP.Inordertostudyandmeasurethecharacter,thereareSiO2/H2Onanofluidswithdifferentconcentrationandapplyingwithvariousheatingpowersduringtheexperimentinvestigation.Accordingtotheexperimentalresult,thehighfractionofSiO2/H2OwilldeterioratetheperformanceofPHPcomparedwithDIwater,i.e.thethermalresistanceandthetemperatureofevaporationsectionincreases.ItisincontraryinthecaseoflowfractionofSiO2/H2O.Finally,thecomparisonofthethermalperformancesbetweenthenormaloperationsystemandthestaticsettlementsystemisgiven.ItisfoundthatboththethermalresistanceofnanofluidPHPandthetemperatureoftheevaporationsectionincreaseafterstandingforaperiod,anditisthesametrendforthetemperaturefluctuationattheidenticalheatingpowerforPHP.

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简介：Inthispaper,anexperimentalstudyonthesulphateattackresistanceofhigh-performanceconcrete(HPC)withtwodifferentwater-to-binderratios(w/b)undercompressiveloadingispresented.Thesulphateconcentration,compressivestrength,andthemasschangeintheHPCspecimensweredeterminedforimmersioninaNa2SO4solutionoverdifferentdurationsunderexternalcompressiveloadingbyself-regulatingloadingequipment.Theeffectsofthecompressivestress,thew/bratio,andtheNa2SO4solutionconcentrationontheHPCsulphateattackresistanceundercompressiveloadingwereanalysed.TheresultsshowedthattheHPCsulphateattackresistanceundercompressiveloadingwascloselyrelatedtothestresslevel,thew/bratio,andtheNa2SO4solutionconcentration.Applyinga0.3stressratioforthecompressiveloadingorreducingthew/bratioclearlyimprovedtheHPCsulphateattackresistance,whereasapplyinga0.6stressratioforthecompressiveloadingorexposingtheHPCtoamoreconcentratedNa2SO4solutionacceleratedthesulphateattackandHPCdeterioration.

简介：Thesupersonicnozzleisthemostimportantdeviceofanejector-diffusersystem.Thebestoperationconditionandoptimalstructureofsupersonicnozzlearehardlyknownduetothecomplicatedturbulentmixing,compressibilityeffectsandevenflowunsteadinesswhicharegeneratedaroundthenozzleextent.Inthepresentstudy,theprimarystreamnozzlewasredesignedusingconvergentnozzletoactivatetheshearactionsbetweentheprimaryandsecondarystreams,bymeansoflongitudinalvorticesgeneratedbetweentheChevronlobes.Exactlysamegeometricalmodelofejector-diffusersystemwascreatedtovalidatetheresultsofexperimentaldata.TheoperationcharacteristicsoftheejectorsystemwerecomparedbetweenChevronnozzleandconventionalconvergentnozzlefortheprimarystream.ACFDmethodhasbeenappliedtosimulatethesupersonicflowsandshockwavesinsidetheejector.ItisobservedthattheflowstructureandshocksystemwerechangedandprimarynumericalanalysisresultsshowthattheChevronnozzleachieveapositiveeffectonthesupersonicejector-diffusersystemperformance.TheejectorwithChevronnozzlecanentrainmoresecondarystreamwithlessprimarystreammassflowrate.

简介：Toimprovetheaerodynamicperformanceofsmallaxialflowfan,inthispaperthedesignofasmallaxialflowfanwithsplitterbladesisstudied.TheRNGk-εturbulencemodelandSIMPLEalgorithmwereappliedtothesteadysimulationcalculationoftheflowfield,anditsresultwasusedastheinitialfieldofthelargeeddysimulationtocalculatetheunsteadypressurefield.TheFW-Hnoisemodelwasadoptedtopredictaerodynamicnoiseinthesixmonitoringpoints.FastFouriertransformalgorithmwasappliedtoprocessthepressuresignal.Experimentofnoisetestingwasdonetofurtherinvestigatetheaerodynamicnoiseoffans.Andthentheresultsobtainedfromthenumericalsimulationandexperimentweredescribedandanalyzed.Theresultsshowthatthestaticcharacteristicsofsmallaxialfanwithsplitterbladesaresimilarwiththeprototypefan,andthestaticcharacteristicsareimprovedwithinacertainrangeofflux.Thepowerspectraldensityatthesixmonitoringpointsofsmallaxialflowfanwithsplitterbladeshavedecreasedtosomeextent.Theexperimentalresultsshowsoundpressurelevelofnewfanhasreducedinmostfrequencybandsbycomparingwithprototypefan.Theresearchresultswillprovideaproofforparameteroptimizationandnoisepredictionofsmallaxialflowfanswithhighperformance.

简介：Bimetalliccobalt-rutheniumnanocatalystssupportedoncarbonnanotubes(CNTs)arepreparedusingmicroemultiontechniquewithwater-to-surfactantratiosof0.5—1.5.ThenanocatalystswereextensivelycharacterizedbydifferentmethodsandtheiractivityandselectivityinFischer-Tropschsynthesis(FTS)havebeenassessedinafixed-bedmicroreactor.Thephysicochemicalpropertiesandperformanceofthenanocatalystswerecomparedwiththecatalystpreparedbyimpregnationmethod.Verynarrowparticlesizedistributionhasbeenproducedbythemicroemulsiontechniqueatrelativelyhighloadingsofactivemetals(15wt%Coand1wt%Ru).AccordingtoTEMimages,smallCoparticles(2—7nm)weremostlyconfinedinsidetheCNTs.Comparingwiththecatalystpreparedbyimpregnation,theuseofmicroemulsiontechniquewithwatertosurfactantratioof0.5decreasedtheaveragecobaltoxideparticlesizeto4.8nm,thedispersionwasalmostdoubledandthereductionincreasedby28%.Activityandselectivitywerefoundtobedependentonthecatalystpreparationmethodandwater-to-surfactantratio(aswellascobaltparticlesizes).COconversionincreasedfrom59.1%to75.1%andtheFTSrateincreasedfrom0.291to0.372gHC/(gcath).C5+liquidhydrocarbonsselectivitydecreasedfrom92.4%to87.6%.

简介：Micro-mesoporouscompositemolecularsievesH-ZSM-5/MCM-41werepreparedbythehydrothermaltechniquewithalkali-treatedH-ZSM-5zeoliteasthesourceandcharacterizedbyscanningelectronmicroscopy,transmissionelectronmicroscopy,energydispersivespectroscopy,X-raydiffraction,N2adsorption-desorptionmeasurementandNH3temperature-programmeddesorption.ThecatalyticperformancesforthemethanoldehydrationtodimethyletheroverH-ZSM-5/MCM-41wereevaluated.Amongthesecatalysts,H-ZSM-5/MCM-41preparedwithNaOHdosage(nNa/nSi)varyingfrom0.4to0.47presentedexcellentcatalyticactivitywithmorethan80%methanolconversionand100%dimethyletherselectivityinawidetemperaturerangeof170—300℃,andH-ZSM-5/MCM-41preparedwithnNa/nSi=0.47showedconstantmethanolconversionofabout88.7%,100%dimethyletherselectivityandexcellentlifetimeat220℃.Theexcellentcatalyticperformanceswereduetothehighlyactiveanduniformacidicsitesandthehierarchicalporosityinthemicro-mesoporouscompositemolecularsieves.ThecatalyticmechanismofH-ZSM-5/MCM-41forthemethanoldehydrationtodimethyletherprocesswasalsodiscussed.

简介：Generallyspeaking,mainflowpathofgasturbineisassumedtobeperfectforstandard3Dcomputation.Butinrealengine,theturbineannulusgeometryisnotcompletelysmoothforthepresenceoftheshroudandassociatedcavityneartheendwall.Besides,shroudleakageflowisoneofthedominantsourcesofsecondaryflowinturbomachinery,whichnotonlycausesadeteriorationofusefulworkbutalsoapenaltyonturbineefficiency.Ithasbeenfoundthatneglectshroudleakageflowmakesthecomputedvelocityprofilesandlossdistributionsignificantlydifferenttothosemeasured.Evenso,theinfluenceofshroudleakageflowisseldomtakenintoconsiderationduringtheroutineofturbinedesignduetoinsufficientunderstandingofitsimpactonendwallflowsandturbineperformance.Inordertoevaluatetheimpactoftipshroudgeometryonturbineperformance,a3Dcomputationalinvestigationfor1.5-stageturbinewithshroudedbladeswasperformedinthispaper.Thefollowinggeometryparameterswerevariedrespectively:-Inletcavitylengthandexitcavitylength,-Shroudoverhangupstreamoftherotorleadingedgeanddownstreamofthetrailingedge,-Shroudradialtipclearance,Theaimofthispaperistoisolatetheinfluenceofshroudandcavitygeometrymodificationsonturbineaerodynamicperformanceandtoobtaincleartrendsofefficiencychangescausedbydifferenttipshroudgeometry.Moreover,interactionbetweenleakageflowandmainstreamfordifferentshroudconfigurationisalsohighlightedinordertopenetrateintothephysicalmechanismsproducingthem.Duetothelimitationsofthemodelselectedinthispaper,theaimofresearchisnottoputforwardthedesignrulesofturbineshroud.However,theresultsobtainedfromthisworkwillbeusefultotheintegrateddesignandoptimizationofturbinewithshroudedblades.

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简介：TheHongKongObservatory(HKO)provideslow-levelturbulencealertingservicefortheHongKongInternationalAirport(HKIA)throughthewindshearandturbulencewarningsystem(WTWS).IntheWTWS,turbulenceintensitiesalongtheflightpathsoftheairportareestimatedbaseduponcorrelationequationsestablishedbetweenthesurfaceanemometerdataandtheturbulencedatafromresearchaircraftbeforetheopeningoftheairport.Theresearchaircraftdataarenotavailableonday-to-daybasis.Theremotesensingmeteorologicalinstruments,suchastheDopplerlightdetectionandranging(LIDAR)andradar,maybeusedtoprovidedirectmeasurementsofturbulenceintensitiesovertherunwaycorridors.TheperformancesofLIDAR-andradar-basedturbulenceintensitydataarestudiedinthispaperbasedonactualturbulenceintensitymeasurementsmadeon423commercialjetsforatypicalcaseofterrain-inducedturbulenceinassociationwithatyphoon.Itturnsoutthat,withthetuningoftherelativeoperatingcharacteristic(ROC)curvebetweenhitrateandfalsealarmrate,theLIDAR-basedturbulenceintensitymeasurementperformsbetterthantheanemometer-basedestimationofWTWSforturbulenceintensityatmoderatelevelorabove.Ontheotherhand,theradar-basedmeasurementdoesnotperformaswellwhencomparedwithWTWS.BycombiningLIDAR-andradar-basedmeasurements,theperformanceisslightlybetterthanWTWS,mainlyasaresultofcontributionfromLIDAR-basedmeasurement.Asaresult,theLIDAR-basedturbulenceintensitymeasurementcouldbeusedtoreplaceanemometer-basedestimatefornon-rainyweatherconditions.Furtherenhancementsofradar-basedturbulenceintensitymeasurementinrainwouldbenecessary.