flaskwww.580hu.com

www.580hu.com  时间:2021-03-21  阅读:()
1Longopen-path,TDLbasedsystemformonitoringmethanebackgroundconcentrationfordeploymentatJungfraujochHighAltitudeResearchStation-SwitzerlandValentinSimeonov,HubertvandenBergh,andMarcParlangeEPFL-ENAC-EFLUMStation2,CH1015Lausanne,Switzerland,Tel.
+41(0)216936185,Fax.
+41(0)216936390email(valentin.
simeonov@epfl.
ch)Anew,longopen-pathinstrumentformonitoringofthebackgroundmethaneconcentrationpath-averagedover1000mwillbepresented.
Theinstrumentallowsmonitoringofwatervaporconcentrationaswell.
Theinstrumentisbuiltonthemonostaticscheme(transceiver–distantretroreflector).
AVCSELtunablediodelaser(TDL)withacentralwavelengthof1654nmisusedasalightsource.
Thereceiverisbuiltarounda20cmNewtoniantelescope.
Toavoiddistortionsintheshapeofamethaneline,causedbyatmosphericturbulences,themethanelineisscannedwithin1μs.
FastInGaAsphotodiodesanda200MHz,14bitADCareusedtoachievethisscanningrate.
Theexpectedconcentrationresolutionfortheabovementionedpath-lengthsisoftheorderof1ppbwithaccuracybetterthan5%.
TheinstrumentisdevelopedattheSwissFederalInstituteofTechnology–Lausanne(EPFL)SwitzerlandandwillbeusedwithintheGAW+CHprogramforlong-termmonitoringofbackgroundmethaneconcentrationintheSwissAlps.
AftercompletingtheongoinginitialtestsattheEPFL,theinstrumentwillbeinstalledin2012attheHighAltitudeResearchStationJungfraujoch(HARSJ).
TheHARSJislocatedat3580mASLandisoneofthe24globalGAWstationsandcarriesoncontinuousobservationsofanumberoftracegasses,includingmethane.
Oneofthegoalsoftheprojectistocomparepath-averagedtoongoingpointmeasurementsofmethaneinordertoidentifypossibleinfluenceofthestation.
FuturedeploymentsofacopyoftheinstrumentcouldincludetheColombianpartofAmazoniaandSiberianwetlands.
1.
IntroductionAnumberofgasesareinvolvedintheanthropogenicenhancementofthegreenhouseeffect.
Themostimportantofthesegreenhousegases(GHGs)arecarbondioxide(CO2);methane(CH4);nitrousoxide(N2O);halocarbons(HC);andtroposphericozone(O3).
Methanehasaspecialplaceamongthesegasessinceitsglobalwarmingpotentialis25timesoreven72timeslargerthanthepotentialofCO2in100yr.
and20yr.
timehorizonsrespectively[1].
Besidethedirectradiativeforcing(RF),estimatedto+0.
48Wm-2methanehasimportantindirecteffectbecauseofitschemicalreactivityresultinginatotalRFof+0.
7Wm-2.
TheindirectradiativeeffectsofmethaneresultmostlyfromreactionwithatmosphericOH.
Thisreaction:reducestheOHconcentration,leadingviaapositivefeedbacktoanenhancementofmethaneandsomeHClifetimes;producesadditionalCO2;enhancesstratosphericwatervapor;andincreasestroposphericozoneconcentrationthroughthemethaneproductionchain.
BecauseofconcentrationslowerthanthoseofCO2,atpresentmethanehasthesecond-largestradiativeforcing(RF)effectafterCO2.
Methaneisemittedbynaturalandanthropogenicsourceswithanthropogenicsourcesaccountingfor60%ofthetotalCH4budgetatpresent.
Themainnaturalsourcesarewetlands,termites,oceans,geologicalsources,methanehydrates,andwildfire.
Themostimportantanthropogenicsourcesareenergyproduction,(includingmining,fossilfuelproduction,distributionanduse),riceagriculture,ruminantanimals,landfills,wastetreatmentandbiomassburning.
ThemainmethanesinksaretheoxidationbytroposphericOH,oxidationinsoilsandlosstostratosphere.
Methaneconcentrationshaveincreasedalmost2.
5timessince1750reaching1774ppbin2005.
Systematicmeasurementsoverthelast25yearsshowa30%increaseinmethaneconcentrationsduringthatperiod.
Thisincreaseisnotmonotonic,withgreaterthan1%peryeargrowthratesinthelate1970andearly1980,slowingdowntozeroornegativevaluesduring1999-2005withsubstantialinterannualvariationsintheperiod1988-2005.
Recentdatashowrenewedgrowthofatmosphericmethane[2]duringlastyears.
ThereasonsforthedecreaseandvariabilityintheCH4growthrateandtheimplicationsforfuturechangesarenotunderstoodalthoughanumberofhypothesesweresuggested[1].
Inresponsetoanincreaseinglobalaveragetemperature,largequantitiesofmethanecanbereleasedinrelativelyshorttimescalesfromgeologicalstorage,suchasmethanehydratesandpermafrostandthroughbiogenicprocesses.
Theglobaltemperatureincreasecancausesignificantincreaseinmethaneconcentrationssince70%oftheatmosphericmethaneoriginatesfrombiogenicsources,whicharehighlysensitivetoclimatevariables.
Recentstudieshaveshownthatthepermafrostcontainsapprox.
500-900Gtcarbon,upto30%ofwhichcanbeconvertedinmethanebymicroorganismsduringthawing[3,4,5].
Inresponsetoclimatewarming,permafrosthasalreadybeguntothaw,withextremeprojectionsthatbytheendofthecenturyitwillhavethawedalmostcompletely.
Climatechangesalsoaffectthestabilityofmethanehydratesbeneaththeoceanwhere~4Ttarestored[6].
ThelatestobservationsoftheSiberianArcticshelfsuggestthat900Gtmethanearestoredthereinmethanehydratedepositsandasafreegasbelowthehydratedeposits.
Thereishighprobabilitythat50Gtmethaneofthisstoragecanbereleasedabruptlyatanytimedueto2thechangesinseawatertemperatures,relatedtothemeltingofArcticice,orasaresultofgeologicalevents[7,8,9].
DatafromSeptember2005showhigh(12000%)CH4supersaturationofsurfacewater,andhigh(upto8ppm)CH4concentrationintheatmosphericlayerabovetheseasurfaceovertheEastSiberianShelf[7].
Currentlyseveralnetworksandgovernmentalorganizationssystematicallymeasuremethaneconcentrationinsurfaceair[1].
NOAA/GMDisthemostgeographicallyextensivenetworkoperating40surfaceairflask-samplingsitesandacquiringdataalmostweeklysince1983[10].
GAGE/AGAGEnetworkoperates5+3sitesequippedwithautomaticsystemswithsamplingratesupto36samples/24hsincelate1980[11].
Allnetworksuseexclusivelythegaschromatograph(GC)techniquewithaflameionizationdetector(FID)formeasuringCH4concentration.
Withapropercalibration,thistechniquecansupplymeasurementswithrelativelygoodsensitivityandprecisionof0.
2-1%.
Sincethemeasurementprocessdependsonanumberofexternalparameters,toachievesufficientcorrelationamongmeasurementstakenwithdifferentinstrumentsandbetweenconsecutiverunstakenwiththesameinstrument,theGCrequirescalibrationwithaprecisestandardgasmixturebeforeeverysamplemeasurement.
Driftsandshiftsinthestandardscale[12]mayrequirereassessmentofthewholedataseries.
Inaddition,GCinstrumentshaverelativelyhighinitialpriceandoperationalcostsbecauseoftheneedofexpensiveconsumables(highandvery-highpuritygases),theneedofspecialenvironment(housing),andregularmaintenancebyqualifiedpersonnel.
Sincethesamplingisdoneatafixedpoint,themeasurementscanbeeasilyalteredbysampletakingandcanbeaffectedbylocalsources,sinks,orlocaltransport,particularlyinpoorlymixedatmospheresasinthecaseofwetlandswhereconcentrationcanvarybyordersofmagnitudefordistancesofseveralmeters.
Therefore,pointmeasurementslackthespatialrepresentativenessneededformodelingpurposes.
BecauseofallthesefactorsGCarenotsuitablefortheenlargementoftheexistingCH4networksasenvisagedintheGAW2008-2015strategicplanespeciallyinArcticandtropicalregions.
Infrared(IR)spectralanalysistechniquessuchasFourierTransformInfrared(FTIR)orTunableLaserAbsorptionSpectroscopy(TLAS)arewidelyusedforaccuratequantitativemeasurementsoftracegasconcentrations[13].
TheconcentrationisderivedfromIRabsorptionmeasuredoveranopticalpath.
Thesensitivityandtheprecisionofthesemeasurementsdependstronglyonthepath-length.
Toachievesufficientsensitivityandprecisionfortraceconcentrationmeasurements,thepathlengthisextendedeitherbyusingmultiple-pathcellsormeasuringoverlong-pathinopenair(referredtohereinas"open-path"orOP).
Themultiple-passtechniqueallowscompactinstrumentaldesignandrelativelyeasycalibrationbutbeingapointmeasurementtechniquesuffersfromthesamedrawbacksastheGCtechniquementionedabove.
IntheOPtechniquetheconcentrationmeasurementsareaveragedoveranextendedpath,andthereforearemuchlessaffectedbylocalunrepresentativefluctuationsingasconcentrationthanmeasurementstakenwithpointsensors.
Thepassiveopen-pathFTIRmethodusestheSunasalightsourceandhasbeenusedtoproducecontinuous,longtimeseriesofhighquality,totalcolumnGHGsdata[14].
TheFTIRmethod,however,islimitedtoonlydaytimeandclearweatherconditions.
TheactiveOP-FTIRcanbeoperatedaroundtheclockbuttheachievableabsorptionpathsareusuallyshort(<1000m)becauseoftheuseofnon-coherentlightsources,whichleadstolowsensitivity.
BothOP-FTIRmethodsrequiresignificantresourcesandexpertknowledgetoensureproperdeployment,operation,andfinaldataproduction.
Furthermore,FTIRinstrumentsaredelicateandhavemovingparts,whichmakesthemdifficulttodeployinfieldconditions.
Theadvancesinsemiconductorlaserscienceandtechnologyhasmadeavailabletunable,sourcesforreal-timeTLASmonitoringofalargenumberofmolecularspeciesintheIR.
TunableDiodelaser(TDL)andQuantumCascadeLaser(QCL)basedpointmeasurementsofanumberoftracegasesincludingCO2,CH4,O3N2Oandotherhavebeensuccessfullydemonstratedinrecentyears[15,16,17,18,19,20]andcommercialinstruments[21,22,23]havebecomeavailablerecently.
Themajorityoftheseexperimentsandmostcommercialinstrumentsarehowever,designedforpointobservations.
SomesuccessfulOPexperimentshavebeencarriedoutinthelate1970,butbecauseofthelackofsuitablelasersources,thesetypemeasurementsdidnotfindwideapplications.
Recentlywiththeappearanceofnewlasersources,OPmeasurementsofmethanehavebeenreportedandcommercialinstruments[24]areavailable.
Theseinstrumentshoweveraredesignedmostlyfordetectinggasleaksormeasuringhigherthanbackgroundconcentrations.
Inthispaperwedescribeanew,TDLbasedOPinstrumentformonitoringofthebackgroundmethaneconcentration.
TheinstrumentisdevelopedattheSwissFederalInstituteofTechnology–Lausanne(EPFL)SwitzerlandandwillbeusedwithintheGAW+CHprogramforlong-termmonitoringofbackgroundmethaneconcentrationintheSwissAlps.
AftercompletingtheongoinginitialtestsattheEPFL,theinstrumentwillbeinstalledin2012attheHighAltitudeResearchStationJungfraujoch(HARSJ).
TheHARSJislocatedat3580mASLandisoneofthe24globalGAWstationsandcarriesoncontinuousobservationsofanumberoftracegasses,includingmethane.
Oneofthegoalsoftheprojectistocomparepath-averagedtoongoingpointmeasurementsofmethaneinordertoidentifypossibleinfluenceofthestation.
FuturedeploymentsofacopyoftheinstrumentcouldincludetheColombianpartofAmazoniaandSiberianwetlands.
2.
TheoryofoperationTheOPTDLtechniqueemploystheabsorptionspectroscopyprincipletoobtainspeciesconcentration.
TheconcentrationCisderivedfromthemeasuredoverthesamplelengthLlighttransmittance)(νTasLTC)()(lnνσν=3where)(νσiswavelength)(νdependantabsorptioncrosssection,specificforthedetectedsubstance.
Thetransmittanceismeasuredbysweepingrepeatedlythelaserwavelengthacrossanabsorptionlineofthespeciesbeingdetected.
Thetransmittancemeasuredoutsideoftheabsorptionlineisusedtocorrectforlightlossesotherthanspeciesabsorption.
Toachievesufficientsensitivity(oftheorderofppbv),theopen-pathmonitoringuseslongopticalpathsthroughtheatmosphere.
Thisgivesapath-averagedvalueofthespeciesconcentration.
ThemainfeaturesoftheOPTDLmethod,whichmakeitavaluabletechniqueforatmosphericmeasurements,canbesummarizedas:-Asahigh-resolutionspectroscopictechniqueitisvirtuallyimmunetointerferencesbyotherspecies,aproblemthatplaguesmostcompetingmethods.
-Asadifferentialspectroscopictechniquethemethodallowsstraightforwardcalibrationandcancelationofbackgroundabsorption-Concentrationmeasurementsareaveragedoveranextendedpath,andthereforearemuchlessaffectedbylocalunrepresentativefluctuationsingasconcentrationthanmeasurementstakenwithpointsensors.
-Itofferscontinuousmeasurementsattime-constantsoftensofsecondsorsowithppborsub-ppblowdetectionlimit.
Thetime-constantofthetechniquecanbetradedoffagainstsensitivityandthiscanallowfluxmeasurementsofrelativelyabundantspeciesbytheeddy-fluxcorrelationtechnique.
-Measurementscanbemadeinregionsofdifficultaccess,especiallyabovegroundlevel.
-Thereisnomaterialcontactbetweengasandsensorandthusthereisnodegradationofthegasbeingmeasuredor"poisoning"ofthesensor.
-Severalspeciescanbemeasuredsimultaneouslywithasinglelaser-Itisageneraltechnique.
Thesameinstrumentcaneasilybeconvertedfromonespeciestoanotherbychangingthelaserorthelasertemperature.
Furthermore,thenumberofsimultaneouslymeasuredspeciescanbeextendedbymultiplexingtheoutputsofseverallasers.
3.
InstrumentdesignanddeploymentTheinstrumentconsistsofatransmitter-receiveranddistantretroreflectoroperatedinmonostaticconfigurationasshowninFig.
1.
Thetransmitter-receiverisdesignedasacompactblockbuiltaroundthereceivingtelescope.
ThetransmitterusesaVerticalCavitySurfaceEmittingLaser(VCSEL)withacentralwavelength1.
654μm,current-tunedover3nm.
Therelativelywidetuningrangeofthelaserallowssimultaneousmeasurementsofwatervaporusingawatervaporabsorptionbandcenteredatapprox.
6047.
8cm-1.
Thelaserradiationiscollimatedbyanoff-axisparabolicmirroranddirectedtotheretroreflectoralongthetelescopeopticalaxis.
ForalignmentpurposesagreentracinglaserbeamistransmittedcoaxiallytotheIRlaserbeam.
ThetelescopeisNewtoniantypewith20cmdiameterofthemainmirror.
PeltiercooledInGaAsphotodiodeandalow-noisetransimpedanceamplifierareusedinthereceiver.
Toavoiddistortionsinthelineshape,causedbyatmosphericturbulences,themethanelineisscannedwithin1μs.
Theacquisitioniscarriedoutbyafast14bit,200MHzADCcardinstalledinaPC.
Thelaser,thecollimatingoptics,andthereceiverdetectorarefixedonthetelescope.
Aretroreflectorwith15cmclearaperturewasassembledfromflatmirrorsusingthetechnologyforbuildingandalignmentdevelopedatEPFL.
TheinstrumentiscontrolledviaLabViewbasedsoftware.
Toensurebetterthan1ppbaccuracythedatatreatmentsoftwarewilltakeintoaccounttheactualatmosphericpressureandtemperaturemeasuredatthetwoendsoftheopticalpathandlaserpowervariations.
Fig.
1.
Opticalschemaoftheinstrument.
Theenclosuresofthetransceiverandtheretroreflectorarenotshownhereforsimplicity.
4.
Fig.
2LeftAphotographoftheopen-pathinstrumentformonitoringbackgroundmethaneconcentration.
Rightpane;lInstrumenttransceiver.
Leftpanel.
ThemeasuringsiteatEPFLshowingthepositionoftheretroreflector.
Theinsetshowsaclosepictureoftheretroreflector.
Theinstrumenthasalreadybeenbuiltandextensivetestsmeasurementsover1000mopticalpathhasbeencarriedout.
ApictureoftheinstrumentisshownontheleftpanelofFig.
2.
TherightpanelofthesamefigureshowsthedeployedattheEPFLcampusindicatingthepositionoftheretroreflector.
Acomparisonbetweenasimulated(usingHITRANdatabase)andexperimentallymeasuredatmosphericabsorptiontakenduringthetestsisshowninFig.
3.
Well-expressedmethaneandwatervaporspectralfeaturesareclearlyseeninthefigure.
ThesignallevelandsignaltonoiseratioallowustoestimatethatthemeasurementofambientCH4concentrationswithaccuracyandprecisionbetterthan1ppbisfeasiblewiththecurrentconfigurationforacquisitiontimesoftheorderoftensofseconds.
Thelowerdetectionlimitforwatervaporisexpectedtobeoftheorderoftensofppb.
Laser(VCSEL)ColimationopticsTracinggreenlaserTelescopeDetectorFTAmGcpaTFig.
3.
Atmospsimulation;1.
7ThesignalisaAftercAltitudeReseamostofthetimGAWstationschromatographpossiblepositisurroundingsoaltitudeof380TheMnchsjoFig.
4.
Pstphericabsorpti79ppmCH4,4averagedover2completingthearchStationJunmeinthefreesandcarrieshandanFTIRionsoftheretofMnchsjohh00mASLandhhüttehutisloPossibleopticPTTtationionspectrumi4%H2O,10002000laserpulsongoinginitingfraujoch(HAtroposphereaoncontinuousRsystem.
Thetroreflectorarehüttehutataphassuitableinocatedat3627alpathsfromH1.
1kmHARSJinthevicinitymopticalpathses(0.
5s),timealtestsattheARSJ).
Duetoallowingbackgsobservationstransceiverwieenvisaged;approx2.
3kmnfrastructurealmASLandisHARSJ2yof6047cm-h.
LowerpaneeforscanningEPFL,theinoitshigh-altitudgroundtracegofanumberillbeinstalledaPTTstationNEfromHAllowingeasyinaccessibleparMhu2.
3km1CH4line.
Upl,MeasuredovtheCH4line1nstrumentwilldelocation(35gasmonitoringroftracegasdintheSphinxatapprox.
1.
ARSJ(Fig.
5).
nstallationandrtoftheyear.
MnchsjohhüutUpperpanel,Hver1000mpaμs.
beinstalledi580mASL)th.
HARSJisoses,includingxobservatoryo1kmwestfroThePTTstatdmaintenanceütteHITRAN[25]athlengthspecn2012attheheHARSJissitoneofthe24gmethanebyofHARSJanomHARSJanionislocatedoftheretroreflbasedctrum.
Hightuatedglobalagasndtwondtheatanlector.
6Thenextphaseoftheprojectisdueforexperimentalmeasurements,comparisonwiththeoperationalatJungfraujochpointandremotemeasurementsandanalysisoftheresults.
Todefinetheweatherdependencemeasurementswillbecarriedoutindifferentweatherconditions.
Becauseoftheshortacquisitiontimeoftheopen-pathmidIRsystem,measurementswillbepossibleinscatteredcloudsinshorttimeintervals.
ThecomparisonwiththeregularpointgaschromatographandTDLmulti-passcellmeasurementsandwiththeFTIRspace-averagedmeasurementswillbecarriedout.
ThegoaloftheintercomparisonisnotonlytoverifytheTDL-open-pathdatabutalsotoidentifypossibleinfluenceoftheemissionsfromtheJungfraujochstationandtouristsitesonthepointGHGsmeasurements.
TheJungfraujochisaverybusytouristsitewithahighlysophisticatedinfrastructureandupto8'000visitorsperday;thereforetherealwaysexiststhepossibilitythatemissionsfromtheJungfraujochtouristfacilitiescanaffectthepointmeasurementsofCH4andwatervaportoamuchlargerextentthanthelongopenpathmeasurements.
SincetheTDLinstrumentwillsupplydataaveragedoverone(two)kilometersthiscouldpossiblyallowtheidentificationoftheJungfraujochstation'sinfluenceontheGHGsmeasurementsbystudyingthedifferencesbetweenthepointandspatiallyaverageddata,andvisitorstatisticsandmeteorologicalconditions.
4.
ConclusionAnew,longopen-pathinstrumentformonitoringofatmosphericwatervaporandbackgroundmethaneconcentrationpath-averagedover1000mwasdevelopedattheSwissFederalInstituteofTechnology–Lausanne(EPFL)Switzerland.
Theinstrumentisbuiltonthemonostaticscheme(transceiver–distantretroreflector).
UsinganIRVerticalCavitySurfaceEmittingLaserinthetransmitter.
Thereceiverisbuiltarounda20cmNewtoniantelescope.
Toavoiddistortionsintheshapeofamethaneline,causedbyatmosphericturbulences,themethanelineisscannedwithin1μs.
FastInGaAsphotodiodesanda200MHz,14bitADCareusedtoachievethisscanningrate.
TheinstrumentwillbeusedwithintheGAW+CHprogramforlong-termmonitoringofbackgroundmethaneconcentrationintheSwissAlps.
AftercompletingtheongoinginitialtestsattheEPFL,theinstrumentwillbedeployedin2012attheHighAltitudeResearchStationJungfraujoch(3580mASL).
FuturedeploymentsofacopyoftheinstrumentcouldincludetheColombianpartofAmazoniaandSiberianwetlands.
References:1.
IPCCFourthassessmentreport,WorkingGroupIReport"ThePhysicalScienceBasis",2007,Ch2andCh7,availablefromhttp://www.
ipcc.
ch/ipccreports/ar4-wg1.
htm2.
S.
Zymovetal.
"PermafrostandtheGlobalCarbonBudget",ScienceV312,pp.
1612-1613,20063.
M.
Rigbyatal,Renewedgrowthofatmosphericmethane,Geophys.
Res.
Lett.
,35,L22805,doi:10.
1029/2008GL036037,20084.
K.
M.
Walter,MethanebubblingfromSiberianthawlakesasapositivefeedbacktoclimatewarming,NatureVol443|7September2006|doi:10.
1038/nature05040,pp.
71-75,20065.
M.
Mastepanovatal,Largetundramethaneburstduringonsetoffreezing,NatureLett.
Vol456|4December20086.
Buffett,B.
,andD.
Archer,2004:Globalinventoryofmethaneclathrate:sensitivitytochangesinthedeepocean.
EarthPlanet.
Sci.
Lett.
,227,185–199.
7.
N.
Shakhovaatal.
AnomaliesofmethaneintheatmosphereovertheEastSiberianshelf:IsthereanysignofmethaneleakagefromshallowshelfhydratesGeophysicalResearchAbstractsVol.
10,EGU2008-A-01526,20088.
N.
Shakhovaatal.
MethanereleaseandcoastalenvironmentintheEastSiberianArcticshelf,JournalofMarineSystemsv.
66,pp.
227–243,20079.
A.
Mascarelli,"Asleepinggiant",NaturereportsclimatechangeV.
3April,200910.
E.
J.
Dlugokenckyatal,"Thegrowthrateanddistributionofatmosphericmethane",JGRV,.
99,NO.
D8,pp17,021-17,043A,199411.
D.
M.
Cunnoldatal,InsitumeasurementsofatmosphericmethaneatGAGE/AGAGEsitesduring1985–2000andresultingsourceinferences",JGRV.
107,NO.
D14,pp.
ACH20-1-ACH20-18,200212.
E.
J.
Dlugokencky,ConversionofNOAAatmosphericdryairCH4molefractionstoagravimetricallypreparedstandardscale,JGR,V.
.
110,D18306,doi:10.
1029/2005JD006035,200513.
Airmonitoringbyspectroscopictechniquesed.
MSigrist,JohnWiley&sons.
Inc.
NeyYork,199414.
L.
Delbouille,andG.
Roland,High-resolutionsolarandatmosphericspectroscopyfromtheJungfraujochhigh-altitudestation,Opt.
Eng,34,pp.
2736-2739,199515.
F.
Titel,etal,Mid-InfraredLaserApplicationsinSpectroscopy,inSolid-StateMid-InfraredLaserSources,I.
T.
SorokinaandK.
L.
Vodopyanov,2003,Springer,Verlag:BerlinHeidelberg.
p.
445-51016.
P.
Werle,Near-andmid-infraredlaser-opticalsensorsforgasanalysis,OptandLasersEng.
,37,101-114,200217.
M.
Taslakov,V.
Simeonov,andH.
vandenBergh,"Open-pathozonedetectionbyQuantumCascadeLaser",AppliedPhysicsB,82,501-506,(2006)718.
RJimenez,M.
Taslakov,V.
Simeonov,B.
Calpini,F.
Jeanneret,D.
Hofstetter,M.
Beck,J.
Faist,andH.
vandenBergh,Ozonedetectionbydifferentialabsorptionspectroscopyatambientpressurewitha9.
6mpulsedquantum-cascadelaser,Appl.
Phys.
B,78,pp.
249-256,(2003)19.
P.
Werle,Areviewofrecentadvancesinsemiconductorlaserbasedgasmonitors,SpectrochimicaActaPartA54,pp197–236,199820.
R.
Wainner,"Handheld,battery-powerednear-IRTDLsensorforstand-offdetectionofgasandvaporplumes",Appl.
Phys.
B75,249–254,200221.
http://www.
aerodyne.
com/Tunablediodelasertracegasdetectors,andQuantumcascadelasertracegasdetectors.
22.
http://www.
lgrinc.
com/index.
aspsubid=ps&ProductCategoryID=1523.
http://www.
picarro.
com/markets/greenhouse/24.
http://www.
boreal-laser.
comTheannounced(webpage)maximumpathis1000m.
Accordingtoacompanyengineertherealmaximumpathis400mwithapossibilitytoextendthepathlengthto1000musingamulti-retroreflectorarraythathastobedevelopedspecially.
Ourexperienceofusingmulti-reflectorarrayswithQCLandTDLsystemsshowsthatmulti-reflectorconfigurationwhenusedwithcoherentsourcesproducesdynamicinterferencefringeswhichcompromisethemeasurement.
Thefringesarecausedbytheinterferenceofthemodulatedbyatmosphericturbulencebeamsthatoriginatefromindividualretroreflectors.
Paperonthissubjectisonpreparation.

spinservers:圣何塞10Gbps带宽服务器月付$109起,可升级1Gbps无限流量

spinservers是Majestic Hosting Solutions LLC旗下站点,主营国外服务器租用和Hybrid Dedicated等,数据中心在美国达拉斯和圣何塞机房。目前,商家针对圣何塞部分独立服务器进行促销优惠,使用优惠码后Dual Intel Xeon E5-2650L V3(24核48线程)+64GB内存服务器每月仅109美元起,提供10Gbps端口带宽,可以升级至1Gbp...

美国200G美国高防服务器16G,800元

美国高防服务器提速啦专业提供美国高防服务器,美国高防服务器租用,美国抗攻击服务器,高防御美国服务器租用等。我们的海外高防服务器带给您坚不可摧的DDoS防护,保障您的业务不受攻击影响。HostEase美国高防服务器位于加州和洛杉矶数据中心,均为国内访问速度最快最稳定的美国抗攻击机房,带给您快速的访问体验。我们的高防服务器配有最高层级的DDoS防护系统,每款抗攻击服务器均拥有免费DDoS防护额度,让您...

CloudCone月付$48,MC机房可小时付费

CloudCone商家在前面的文章中也有多次介绍,他们家的VPS主机还是蛮有特点的,和我们熟悉的DO、Linode、VuLTR商家很相似可以采用小时时间计费,如果我们不满意且不需要可以删除机器,这样就不扣费,如果希望用的时候再开通。唯独比较吐槽的就是他们家的产品太过于单一,一来是只有云服务器,而且是机房就唯一的MC机房。CloudCone 这次四周年促销活动期间,商家有新增独立服务器业务。同样的C...

www.580hu.com为你推荐
.cn域名cn域名和com域名有啥区别?各有啥优点?sherylsandberg这个文章什么意思 给个翻译好吗 谢谢了硬盘的工作原理简述下硬盘的工作原理?22zizi.com福利彩双色球22号开奖号百度关键词价格查询百度竞价关键词价格查询,帮忙查几个词儿点击一次多少钱,thankswww.119mm.comwww.993mm+com精品集!百度指数词什么是百度指数javbibinobibi的中文意思是?lcoc.toptop weenie 是什么?www.diediao.com这是什么电影
域名代理 云网数据 vultr美国与日本 国外空间 java空间 阿里云浏览器 炎黄盛世 工信部icp备案号 91vps 环聊 360云服务 域名与空间 视频服务器是什么 我的世界服务器ip 工信部网站备案查询 apnic 阿里云个人邮箱 hdsky 九零网络 美国主机侦探 更多