简介：本文以语言学、认知心理学和学习论等理论为指导,根据中国学生在非目标语交际环境中对某些词素习得序列的研究成果,探讨词素习得在目标语与非目标语交际环境中的异同特点。作者提出,语言习得和语言学习是一个互为依托的认知过程,只要在语言课堂里能给学生提供有效而丰富的语言理解输入,语言习得是一种渐进而有序的必然现象。比较研究证明,学习与习得过程要受语言内部规律的制约。国内外词素习得序列的研究成果对语言教学和教材编写有积极意义。

简介：ThispapershowsthatXisuniformlynon-squareiffP(η_o)>0forsomeη_o∈(0,2).ThusXissuper-reflexiveifandonlyifforXthereexistsanequivalentnormwhichmeetstheabovecondition.Byvirtueofthebeforementionedresult,theauthorderivesthenecessary,andsuffi-cientconditionsforXandl~p(X_j)beinguniformlynon-square,respectively,andgivesacharacterizationoffinite-dimensionalspaceswhichareuniformlynon-square.

简介：片断杆射弹的设计经常为它的表演当模特儿的便利在理论分析被简化进理想的。但是在在实际应用的影响速度范围上的非理想的片断杆射弹的实际表演很少被探索。AUTODYN数字代码被用来在大量影响速度上在非理想的片断杆射弹的穿入性能之上调查部件设计的影响，它能被用来指导武器片断杆射弹的最佳的设计。

简介：Amulti-objectiveoptimizationofnon-uniformbeamsispresentedforminimumradiatedsoundpowerandweight.Thetransfermatrixmethodisusedtocomputethestructuralandacousticresponsesofanon-uniformbeamaccuratelyandefficiently.Themulti-objectiveparticleswarmoptimizationtechniqueisappliedtosearchtheParetooptimalsolutionsthatrepresentvariouscompromisesbetweenweightandsoundradiation.Severalconstraintsareimposed,whichsubstantiallyreducethevolumefractionoffeasiblesolutionsinthedesignspace.Twononuniformbeamswithdifferentboundaryconditionsarestudiedtodemonstratethemulti-objectiveoptimaldesignsofthestructure.

简介：Theparallelspectral-domainopticalcoherencetomography(PSDOCT)isdescribedforhigh-speedopticalcoherencetomography(OCT)withoutlateralscanning.Inthissetup,theself-eliminationofauto-correlation(AC)interferencealgorithmwasusedforeradicatingtheACinterferenceandghostimages.However,whenperformedinfreespaceOCT,thisalgorithmstillgeneratedaweakDCcomponent.Thealgorithmwasimprovedbyaddingthebackgroundintensityparttocompensateforthemutualinterferencebetweenobjectandreferencearms.TheresultsdemonstratethattheDCcomponentcanbeeradicated.ComparedwithconventionalOCTandcomplexFourier-domainopticalcoherencetomography,theadvantagesofPSDOCTwiththeimprovedalgorithminfreespacearethatithasnomovingpartstogenerateconsecutivephaseshift,thestructureoftheobjectcanbereconstructedimmediatelyandautomatically,andthespeedisapproximately16timesfasterthanthoseoftheothertwointhesamecase.

简介：INTRODUCTIONForChinesestudentsofEnglish,grammarlearningissoimportantthattheirtextbooksinevitablyentailgrammarsectionsorganizedinalinearway.ThesestudentstreatgrammarlearningasthesteppingstoneontheirwayofEnglishlearning.Theyhopetohaveagoodcommandofgrammarbothfortheirpresentlearningandfortheirfurtherstudies.Fortheirpresentlearning,theirlinguisticknowledgeistestedandassessedthroughexaminations

简介：AmodifiedLindstedt-Poincaré(LP)methodforobtainingtheresonanceperiodicsolutionsofnonlinearnon-autonomousvibrationsystemsisproposedinthispaper.Inthemodifiedmethod,nonlinearnon-autonomousequationsareconvertedintoagroupoflinearordinarydifferentialequationsbyintroducingasetofsimpletransformations.Anapproximateresonancesolutionfortheoriginalequationcanthenbeobtained.Theperiodicsolutionsofprimary,super-harmonic,sub-harmonic,zero-frequencyandcombinationresonancescanbesolvedeffectivelyusingthemodifiedmethod.Someexamples,suchasdampedcubicnonlinearsystemsundersingleanddoublefrequencyexcitation,anddampedquadraticnonlinearsystemsunderdoublefrequencyexcitation,aregiventoillustrateitsconvenienceandeffectiveness.UsingthemodifiedLPmethod,thefirst-orderapproximatesolutionsforeachequationareobtained.Bycomparison,themodifiedmethodproposedinthispaperproducesthesameresultsasthemethodofmultiplescales.

简介：ToovercomethedeficienciesoftheexistingVerhulstGM(1,1)model,basedontheexistinggreytheory,anon-equal-intervaldirectoptimumVerhulstGM(1,1)modelisbuiltwhichchoosesamodifiedn-thcomponentx(n)ofX(0)asthestartingconditionofthegreydifferentialmodel.Itoptimizesamodifiedβvalueandthebackgroundvalue,andtakestwotimesfittingoptimization.Thenewmodelextendsequalintervalstonon-equal-intervalsandissuitableforgeneraldatamodellingandestimatingparameters...