简介：

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.

简介：

简介：Fromtheviewpointsofenvironmentalprotection,supportfortheagedandensuringtherighttomobility,thereisaneedtodevelopanewtypeofmobilityvehiclethatprovidesmoreeffectivetransportation.Theauthorsproposeaninvertedpendulumvehiclewithpedalsasoneoftheformsofpersonalmobilityvehicles(PMVs).Inthispaper,thesteeringperformanceoftheinvertedpendulumvehiclewithpedalsisdiscussedbasedonexperimentsonaprototype.Fromtheexperimentalresults,itwasconfirmedthattheerrorsfromthefivesubjectsforthetargettrajectoryandthefive-gradeevaluationofthemaneuverabilityweresimilar.Finally,wecreatedaninvertedpendulumvehiclewithpedalstowhichwasaddedareactionactuatorforthesteeringsystem.Fromtheexperimentalresults,itwasfoundthatsettingappropriatefeedbackgainsforthehandlesteeringangleanditsrateofrotation,whichcontroltherightandleftwheeldrivingtorques,resultedingreatlyimprovedmaneuverability.

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

简介：

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：Carbonnanofiberswithapolygonalcrosssection(P-CNFs)synthesizedusingacatalyticchemicalvapordeposition(CCVD)technologyhavebeeninvestigatedforpotentialapplicationsinlithiumbatteriesasanodematerials.P-CNFsexhibitexcellenthigh-ratecapabilities.Atacurrentdensityashighas3.7and7.4A/g,P-CNFscanstilldeliverareversiblecapacityof198.4and158.2mAh/g,respectively.Toimprovetheirfirstcoulombicefficiency,carbon-coatedP-CNFswerepreparedthroughthermalvapordeposition(TVD)ofbenzeneat900℃.Theelectrochemicalresultsdemonstratethatappropriateamountofcarboncoatingcanimprovethefirstcoulombicefficiency,thecyclingstabilityandtherateperformanceofP-CNFs.Aftercarboncoating,P-CNFsgainaweightincreaseapproximatelyby103wt%,withitsfirstcoulombicefficiencyincreasingfrom63.1to78.4%,anddeliverareversiblecapacityof197.4mAh/gatacurrentdensityof3.7A/g.Afterdozensofcycles,thereisnosignificantcapacitydegradationatbothlowandhighcurrentdensities.

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：这份报纸为为敏化染料的太阳能电池(DSSC)经由一起沉淀为TiO2nanoparticles准备建模并且优化作为一条有效途径论述反应表面方法论(RSM)性能。钛(IV)二度--(acetylacetonate)di-isopropoxide(DIPBAT)，isopropanol和水分别地被用作先锋，溶剂和合作溶剂。象准备因素与的水，老化温度和锻烧温度的臼齿的比率主要并且粒子特征和表演上的相互作用效果被调查。粒子特征被X光检查diffractometry(XRD)以主要、第二等的尺寸，晶体取向和形态学决定并且扫描电子显微镜学(SEM)。乐队差距精力和DSSC的力量变换效率被用于表演研究。根据在反应表面方法论(RSM)的变化(ANOVA)的分析，所有三个独立参数是统计上重要的，最后的模型是精确的。模型在1:10:500的DIPBAT-to-isopropanol-to-water的臼齿的比率的最佳的条件下面预言了最大的力量变换效率(0.14%)，变老36潰獳獥楳湯的温度吗？

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.

简介：

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.