简介:Background:Dependingontreeandsitecharacteristicscrownbiomassaccountsforasignificantportionofthetotalabovegroundbiomassinthetree.Crownbiomassestimationisusefulfordifferentpurposesincludingevaluatingtheeconomicfeasibilityofcrownutilizationforenergyproductionorforestproducts,fuelloadassessmentsandfiremanagementstrategies,andwildfiremodeling.However,crownbiomassisdifficulttopredictbecauseofthevariabilitywithinandamongspeciesandsites.Thustheallometricequationsusedforpredictingcrownbiomassshouldbebasedondatacollectedwithpreciseandunbiasedsamplingstrategies.Inthisstudy,weevaluatetheperformancedifferentsamplingstrategiestoestimatecrownbiomassandtoevaluatetheeffectofsamplesizeinestimatingcrownbiomass.Methods:Usingdatacollectedfrom20destructivelysampledtrees,weevaluated11differentsamplingstrategiesusingsixevaluationstatistics:bias,relativebias,rootmeansquareerror(RMSE),relativeRMSE,amountofbiomasssampled,andrelativebiomasssampled.Wealsoevaluatedtheperformanceoftheselectedsamplingstrategieswhendifferentnumbersofbranches(3,6,9,and12)areselectedfromeachtree.Treespecificloglinearmodelwithbranchdiameterandbranchlengthascovariateswasusedtoobtainindividualbranchbiomass.Results:Comparedtoallothermethodsstratifiedsamplingwithprobabilityproportionaltosizeestimationtechniqueproducedbetterresultswhenthreeorsixbranchespertreeweresampled.However,thesystematicsamplingwithratioestimationtechniquewasthebestwhenatleastninebranchespertreeweresampled.Underthestratifiedsamplingstrategy,selectingunequalnumberofbranchesperstratumproducedapproximatelysimilarresultstosimplerandomsampling,butitfurtherdecreasedRMSEwheninformationonbranchdiameterisusedinthedesignandestimationphases.Conclusions:UseofauxiliaryinformationindesignorestimationphasereducestheRMSEproducedbyasamplingstrategy.Howe
简介:Duringthelastfewdecades,photothermalradiometry(PTR)hasbeengreatlydevelopedandwidelyappliedinthefieldofnondestructivetesting.However,thetraditionalPTRsystememploysanexpensivelock-inamplifiertodetecttheweakphotothermalsignal,whichleadstohighcostandlongtesttime.Inthispaper,afasttransmissionPTRsystembasedonsamplingbyusinganinternalcomputersoundcardwasdevelopedtolowerthesystemcostandshorterthetesttime.Apieceofamorphoussilicon(a:Si)thinfilmsolarcellswithartificialdefectswaspreparedandtestedbythesystem.Theresultsshowthatthesharpeneddefectscanbeidentifiedeasilyandquicklyaccordingtothesignificantpeaksoftheoriginalinfraredsignalsampledbytheinternalcomputersoundcard.Furthermore,moredetaileddefectscanbeinvestigatedbyprocessingtheinfraredsignal.ThesevalidatetheeffectivenessoftheproposedtransmissionPTRsystemasalowcostandefficientnon-destructivetesttechnique.
简介:Background:Remotesensing-basedinventoriesareessentialinestimatingforestcoverintropicalandsubtropicalcountries,wheregroundinventoriescannotbeperformedperiodicallyatalargescaleowingtohighcostsandforestinaccessibility(e.g.REDDprojects)andaremandatoryforconstructinghistoricalrecordsthatcanbeusedasforestcoverbaselines.Giventheconditionsofsuchinventories,thesurveyareaispartitionedintoagridofimagerysegmentsofpre-fixedsizewheretheproportionofforestcovercanbemeasuredwithinsegmentsusingacombinationofunsupervised(automatedorsemi-automated)classificationofsatelliteimageryandmanual(i.e.visualon-screen)enhancements.Becausevisualon-screenoperationsaretimeexpensiveprocedures,manualclassificationcanbeperformedonlyforasampleofimagerysegmentsselectedatafirststage,whileforestcoverwithineachselectedsegmentisestimatedatasecondstagefromasampleofpixelsselectedwithinthesegment.Becauseforestcoverdataarisingfromunsupervisedsatelliteimageryclassificationmaybefreelyavailable(e.g.Landsatimagery)overtheentiresurveyarea(wall-to-walldata)andarelikelytobegoodproxiesofmanuallyclassifiedcoverdata(sampledata),theycanbeadoptedassuitableauxiliaryinformation.Methods:Thequestionishowtochoosethesampleareaswheremanualclassificationiscarriedout.Wehaveinvestigatedtheefficiencyofone-per-stratumstratifiedsamplingforselectingsegmentsandpixels,wheretocarryoutmanualclassificationandtodeterminetheefficiencyofthedifferenceestimatorforexploitingauxiliaryinformationattheestimationlevel.Theperformanceofthisstrategyiscomparedwithsimplerandomsamplingwithoutreplacement.Results:OurresultswereobtainedtheoreticallyfromthreeartificialpopulationsconstructedfromtheLandsatclassification(forest/nonforest)availableatpixellevelforastudyarealocatedincentralItaly,assumingthreelevelsoferrorratesoftheuns
简介:对于感觉细腻而又喜欢以独特视角进行观照的蔡石来说,他更希望拥有一部各方面综合素质都优秀的相机,这包括相机的防护能力、对焦表现、连拍能力等表现。暮色降临EOS5DS高像素慢门记录飘摇雨夜夜色即将来临的时候,是环境光线色彩最为丰富而明暗对比也最多的时候,在这个时间拍摄,很容易获得丰富的光影色彩效果,但要想获得丰富的明暗细节,也就对相机的动态范围宽容度提出了很高的要求。风中、桥上,我把相机固定到三脚架上,装16-35mmF4镜头,为了获得合适的视角,把焦距设置为18mm,这样视角足够宽广也有效避免了大广角端容易出现的桶形畸变,然后将光圈缩小到F6.3
简介:Afullycoherentfreeelectronlaser(FEL)seededwithahigher-orderharmonic(HH)pulsefromhigh-orderharmonicgeneration(HHG)issuccessfullyoperatedforasufficientlyprolongedtimeinpilotuserexperimentsbyusingatimingdriftfeedback.ForHHG-seededFELs,theseedinglaserpulseshavetobesynchronizedwithelectronbunches.DespiteseededFELsbeingnon-chaoticlightsourcesinprinciple,externallaser-seededFELsareoftenunstableinpracticebecauseofatimingjitterandadriftbetweentheseedinglaserpulsesandtheacceleratedelectronbunches.Accordingly,weconstructedarelativearrival-timingmonitorbasedonnon-invasiveelectro-opticsampling(EOS).TheEOSmonitormadeuninterruptedshot-to-shotmonitoringpossibleevenduringtheseededFELoperation.TheEOSsystemwasthenusedforarrival-timingfeedbackwithanadjustabilityof100fsforcontinualoperationoftheHHG-seededFEL.UsingtheEOS-basedbeamdriftcontrollingsystem,theHHG-seededFELwasoperatedoverhalfadaywithaneffectivehitrateof20%–30%.Theoutputpulseenergywas20μJatthe61.2nmwavelength.TowardsseededFELsinthewaterwindowregion,weinvestigatedourupgradeplantoseedhigh-powerFELswithHHphotonenergyof30–100eVandlaseatshorterwavelengthsofupto2nmthroughhigh-gainharmonicgeneration(HGHG)attheenergy-upgradedSPring-8CompactSASESource(SCSS)accelerator.WestudiedabenefitaswellasthefeasibilityofthenextHHG-seededFELmachinewithsingle-stageHGHGwithtunabilityofalasingwavelength.
简介:沉稳细致的付增凯,已经从事商业人像摄影多年,他更关注器材的图像画质,以及数据传输能力和闪光灯控制性能。商业摄影师最爱一次性去除摩尔纹EOS5DSR具有专门的PC闪光同步端子和快门线连接接口,并且机顶热靴可以支持各种E-TTLII自动闪光灯,这让我不用担心这部相机的补光能力。在此次富哥男装品牌广告片的拍摄过程中,5060万高像素给我和客户带来很多兴奋感,在苹果笔记本retina显示屏上,图片中服装的细节非常清晰,材料的质感也得以还原,色彩也真实且柔和。而且EOS5DSR还帮我在拍摄中就解决了服装拍摄中的摩尔纹大难题,让我省去了很多后期工作。
简介:摘要目的对支气管哮喘患者FeNO表达水平及其与FEV1%、EOS、总IgE和ACT评分的相关性。方法选取我院2013年4月至2014年9月收治的支气管哮喘患者60例作为观察组,再选择60例健康者作为对照组,对比两组的FeNO表达水平及FEV1%、EOS、总IgE,并进行ACT评分。结果观察组患者的FeNO水平高于对照组,FEV1%低于对照组,EOS评分低于对照组,差异具有统计学意义(P<0.05)。FeNO表达水平和外周血EOS计数呈正相关关系(P<0.05)。结论通过FeNO表达水平能够对哮喘患者对慢性气道炎症进行反映,而且能够反映患者的EOS炎症,从而对患者的哮喘控制水平进行评估。