简介:AprototypeRamanlidarwasdesignedformonitoringtroposphericCO_2profileandotherscientificin-vestigations.ThethirdharmonicofNd:YAGlaser(354.7-nmwavelength)wasusedasstimulatedlightsourcetoprovidenighttimemeasurements.FilterwithhighrejectionratioperformancewasusedtoextractCO_2RamansignalsfromRayleigh-Miescatteringsignalseffectively.Toimprovetherealtimemonitoringfunction,atwo-channelsignalcollectionsystemwasdesignedtocollectCO_2andN_2Ramanscatteringsig-nalssimultaneously.TheN_2Ramanscatteringsignalswereusedtoretrieveaerosolextinctioncoefficient.TypicalfeaturesofCO_2concentrationprofileandaerosolextinctioncoefficientinHefeiwerepresented.ThemixingratioofatmosphericCO_2inHefeicanreachabout360-400ppmv.
简介:Becausepulserepetitionrateaffecteddirectlythemomentumcouplingcoefficientoftransverselyexcitedatmospheric(TEA)CO2laserpropulsion,adoublepulsetrigger,controllinghighvoltageswitchoflaserexcitationcircuit,wasdesigned.Thepulseintervalrangedbetween5and100ms.Themomentumcouplingcoefficientforair-breathingmodelaserpropulsionwasstudiedexperimentally.Itwasfoundthatthemomentumcouplingcoefficientdecreasedwiththepulserepetitionrateincreasing.
简介:Usingamicrowavegenerator,chlorinedilutedbyheliumwasdissociatedtochlorineatomsthatsubse-quentlyreactedwithhydrogenazidetoproducetheexcitedstatesofNCl(a1△).Meanwhile,moleculariodinewithcarriergasofheliumreactedwithatomicchlorinetoproduceatomiciodinewhichthenwaspumpedtoexcitedstateofI(2P1/2)byanenergytransferreactionfromNCl(a1△).Inthispaper,thechangesofNCl(a1△)andNCl(bi∑)emissionintensityispresentedwhenI2/HeisintroducedintothestreamofCl/Cl2/He/HN3/NCl(a1△)/NCl(b1∑).ThedependencesofatomiciodineI(2P1/2)onflowratesofgaseswerealsoinvestigated.TheoptimumparametersforI(2P1/2)productionaregiven.
简介:Weprovidethefirstdemonstrationofpureredemissioninthevisiblelightregionviathree-photonexcitationinmonodisperseNa_3ZrF_7:Ernanoparticles(NPs)byusingalaseroperatinginthetelecommunicationband.NPsof~22nmindiameteraresynthesizedat260°Cbythethermaldecompositionmethod.TheexperimentalresultsrevealthattheNa_3ZrF_7:ErNPsexhibitpureredemissioninthevisibleregionunder1480nmlaserexcitation,andtheemissionintensityissignificantlyinfluencedbytheEr~(3+)ionconcentration.Thedecaytimesofthe~4S_(3∕2)→~4F_(15∕2)and~4F_(9∕2)→~4F_(15∕2)transitionsoftheEr~(3+)ionsat540and655nm,respectively,arereducedbyincreasingtheEr~(3+)ionconcentrationintheNa_3ZrF_7:ErNPs.Thesuppressedemissionintensityresultfromthedefect-relatedquenchingeffect:whentrivalentEr~(3+)ionsreplactetravalentZr~(4+)ions,extraNationsandFvacanciesareformedtore-balancethechargeintheNa_3ZrF_7matrix.TheemissioncoloroftheNa_3ZrF_7:ErNPsisrelatedtothecrossrelaxationbetweenEr~(3+)ions.Theseresultsprovideanimportantsteptowardmoreeffectivebiologicalimagingandphotodynamictherapybyminimizingthescatteringoftheexcitationlightandincreasingthepenetrationdepth.
简介:目前汽车助力装置的主流是真空助力和气压助力。真空助力结构小巧,但存在安全隐患;气压助力安全性好,但结构庞大。高液压存储仓的日的是提供一种小巧且安全性兼顾的装置。高液压存储仓的基本工作原理是利用制冷剂的瓜力特性,用制冷剂充当储压剂来储存压力液的能量。使整罐压力液能够以高达20~25MPa的准恒压向外作功。讨论了液压仓的基本结构和工作原理、储压剂选择的难题、抑制泄漏的措施、超临界CO2的特性,在此基础上,提出了存储高液压的超临界CO2液压仓的设计思路,用超临界CO2和温控相配合,得到了准恒高压压力液,实现了小巧且安全性兼顾,由此产生新型的制动、转向、离合助力器。
简介:Nitridatedβ-Ga_2O_3(100)substratewasinvestigatedasthesubstrateforGaNepitaxialgrowth.Theeffectsofnitridationtemperatureandsurfaceroughnessofβ-Ga_2O_3wafersontheformationofGaNwerestudied.Itwasfoundthatthemostoptimizednitridationtemperaturewas900°C,andhexagonalGaNwithpreferredorientationwasproducedonthewell-polishedwafer.Thenitridationmechanismwasalsodiscussed.
简介:FourkindsofY2O3stabilizedZrO2(YSZ)thinfilmswithdifferentY2O3contents(from0to12mol%)aredepositedonBK7glasssubstratesbyelectron-beamevaporationmethod.TheeffectsofdifferentY2O3dopantcontentsonresidualstress,structure,andopticalpropertiesofZrO2thinfilmsareinvestigated.TheresultsshowthatresidualstressinYSZthinfilmsvariesfromtensiletocompressivewiththeincreaseofY2O3molarcontent.TheadditionofY2O3isbeneficialtothecrystallizationofYSZthinfilmandtransformationfromamorphoustohightemperaturephase,andtherefractiveindexdecreaseswiththeincreaseofY2O3molarcontent.Moreover,thevariationsofresidualstressandtheshiftsofrefractiveindexcorrespondtotheevolutionofstructuresinducedbytheadditionofY2O3.
简介:WhenfemtosecondlaserpulsesinterferewithchirpedfemtosecondlaserpulsesinAs2S3fiber,achirpedfibergratingisformed.Ananalyticalexpressionisgiventodescribethechirpedgrating,anditsBraggreflectivityiscalculated.BecauseofthehighphotosensitiveeffectofAs2S3material,thechirpedfibergratinghasawideBraggreflectivespectrumandhighreflectivitybychoosingproperparameters.Thisindicatesthatthechirpedfibergratingcanbeusedasastretcherinthefemtosecondchirpedpulseamplification(CPA)system.
简介:实验通过高温固相法合成了不同气氛条件下的BaZn2(BO3)2荧光粉.在空气气氛条件下制备的BaZn_2(BO_3)_2样品,发射黄色的荧光,峰位在543nm处,这是由颗粒中单个带负电荷的氧填隙离子O-i中心捕获价带上的光生空穴,与导带上落下的光生电子辐射复合产生的.在氮氢还原气氛条件下的BaZn_2(BO_3)_2样品,发射绿色的荧光,峰位在500nm处,这是由于在颗粒中光生电子经过无辐射跃迁,落入被单一电离的氧空位缺陷V*o,再由缺陷回到靠近价带,与光生空穴复合产生可见光的发射.BaZn_2(BO_3)_2荧光粉紫外波段有很强的吸收,并且荧光衰减寿命和稀土元素掺杂的荧光粉寿命相当.因此BaZn_2(BO_3)_2荧光粉在用于白光LED时,将会具有广泛的应用前景与潜在的商业价值.
简介:TheCa_2SiO_4:Dy~(3+)phosphorwassynthesizedbythehightemperaturesolid-statereactionmethodinair.TheemissionspectrumofCa_2SiO_4:Dy~(3+)phosphorshowsseveralbandsat486,575,and665nmunderthe365-nmexcitation.TheeffectsofLi~+,Na~+,andK~+ontheemissionspectrumofCa_2SiO_4:Dy~(3+)phosphorwerestudied,TheresultsshowthattheemissionspectrumintensityisgreatlyinfluencedbyLi~+,Na~+,andK~+.Thechargecompensationconcentrationcorrespondingtothemaximumemissionintensityisdifferentwithdifferentchargecompensations.