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:Thetitlepolymerwaspreparedfrom5-diethylamino-3-thia-pentylglycidyletheranddiethyleneglycolbisglycidyletherviaring-openingcopolymerization.Itwasfoundthatthisreactioncouldbecatalyzedbysodium,butnotLewisacid.Theobtainedpolymercancoordinatewithplatinumcompound,andtheplatinumcomplexisanewkindofcatalystforthehydrosilylationofolefinswithtriethoxysilane.
简介:Variousmethodsforsynthesisof2-methyl-5,6-(1,4,7,10,13-pentaoxatridecamethyl-ene)benzotellurazole(8)aredescribed.Underdifferentconditions,alkylationofcompound8withmethyliodidegavetelluroniumsalt1,2-dimethyl-5,6-(1,4,7,10,13-pentaoxatridecamethylene)benzo-tellurazoliumiodide(15)orquaternaryammoniumsalt2,3-dimethyl-5,6-(1,4,7,10,13-pentaoxatri-decamethylene)benzotellurazoliumiodide(14)inhighyields,repectively.Thecyaninedye3,3’-dimethyl-5,6,5’,6’-bis(1,4,7,10,13-pentaoxatridecamethylene)telluracarbocyanineiodide(16)isobtainedbycondensationof14withethylorthoformateinaceticanhydride.Thevisibleabsorptionofthecyaninedyeisalsodiscussed.
简介:Networkcrownetherpolymerwithpendantsulfidesidechaininthenetworkstructureunitshasbeensynthesizedviaring-openingcopolymerizationofβ-ethylthioethylglycidyletheranddiethyleneglycolbisglycidylether.Akindofactivecatalystsuitableforthisreactionwassuggested.Thetitlepolymerwasfoundtobeagoodligandforplatinouschloride,andtheplatinouscomplexcouldcatalyzethehydrosilylationofolefinswithtriethoxysilaneefficiently.
简介:Thenovelcomplex[K(18-C-6)]2[Cd(mnt)2][18-C-6-18-crown-6,nmt=1,2-dicyanoethene-1,2-dithiolate,C2S2-(CN)2^2-]wassynthesizedandcharacterizedbyelementalanalysis,IRspectrumandX-raydiffractionanalysis.Thecomplexdisplaystwo-dimensionalnetworkstructureof[K(18-C-6)]complexsegmentsand[Cd(nmt)2]complexsegmentbridgedbyS-K-S,S-K-NandN-K-Ninteractionsbetweenadjacent[K(18-C-6)]and[Cd(mnt)2]units.
简介:Thesinglecrystalofthecomplex[Sc(NO3)3(H2O)2]·(15C5)hasbeenpreparedinacetonitrile.Thenewcomplexhasbeencharacterizedbyelementalanalysis,IRspectra,solubilityandmolarconductancemeasurements.ThestructureofthecomplexisdeterminedbysinglecrystalX-raydiffractionanalysis.
简介:The4-hicoldmillisoneofthekeywidestriptandemcoldrollingmillsandhasmanyadvantagesandcharacteristics.Themilltypeisthemostimportant,fundamentalandlong-termeffectivefactorforthestripshapecontrol.ManyadvancedmilltypessuchasCVC-4,HCWandPC-4,etcarecreatedbasedontheconventionalfour-rollmill.Thefactorsofmilltypewhichaffectthedeformationofrollsystem,suchasstripwidth,rollingforce,bendingforce,workrolldiameter,backupdiameterandsoon,arestudiedhowtoaffectrollgapcrown.Itprovidesagoodfoundationforimprovingtheshapeperformanceofmill.
简介:Thesynthesisofanewtypeofhetero-macrocyclicpolyether2,3-henzo-1,4,7,13-tetraoxa-10-selenacyclopentadeca-2-eneisdeseribed.
简介:Thepredictionofthedistributionofquantitativevariablesinaforeststandisofgreatinteresttoforestmanagers,fortheevaluationofforestresourcesandschedulingoffuturesilviculturaltreatments.TheaimofthisresearchwastomodelthedistributionofquantitativevariablesforQuercuspersicainopenforestsinIran.Toinvestigatetheprobabilitydistributionoftreesinnaturalstands,642treeswereselectedformeasurementusingasystematicrandomsamplingmethod.Selectedtreesweremeasuredanddatawereanalyzed.Gamma,beta,normal,lognormal,exponentialandWeibullprobabilitydistributionswerefittedtotheheightdistributionoftrees.Variablesofdistributionfunctionswereestimatedusingthemaximumlikelihoodestimationmethod.ActualprobabilityandprobabilitywhichderivedfromfunctionswascomparedusingKolmogorov–SmirnovandAnderson–Darlingtests.Beta,WeibullandWeibullprobabilitydistributionsexplainedthedistributionsoftreeheight,DBHandcrownarea.