简介：

简介：摘要  由于矩阵的初等变换和初等矩阵都有“初等”二字,所以非常容易将二者混为一谈.此文的目的在于解释这两个概念的区别,同时也介绍它们的关系.在对矩阵进行运算时,我们可对其进行类似于行列式的行（列）变换或数乘运算等,即矩阵的初等变换.为了搞清楚变换后的矩阵所具有的特性,也为了说明矩阵的初等变换的意义,我们引入初等矩阵的概念.其实初等矩阵就是单位矩阵经矩阵的初等变换后所得的矩阵.具体内容见下文简述.

简介：AftertheendoftheColdWar,therehaveemergedaseriesofnewsignificantphenomenaininternationalrelations.First,asaresultofthecollapseoftheformerSovietUnionandthedisintegrationoftheWarsawTreatyOrganization,thereisnolongeracommonenemyforWesternEuropeandtheUS.Second,con-

简介：In2011,Chanproposedanimageauthenticationmethodbyproducingtheparitycheckbitsfrompixelswhosebitshavebeenrearranged.Duetothisrearrangement,thevalueofthemost-significantbitofeachtamperedpixelcanbedeterminedaccordingtoitsparitycheckbits.Withthehelpofthemost-significantbitofthepixel,thepixelcanberecoveredbyselectingtwopossible(7,4)Hammingcodewords.However,ifthedistancebetweentwoHammingcodewordsiswithinacertainrange,incorrectselectionmayoccur.Chan'smethodaddedoneadditionalbittoindicatethecorrectone.Itistrivialthatthismaydegradethequalityoftheauthenticatedimage.Inthispaper,wegroupfourmost-significantbitsintodifferentgroupstoformamappingcodebookandthemappingcodebookisusedtoproduceauthenticationdatainsteadofthe(7,4)Hammingcodebook.Theexperimentalresultsshowthattheproposedmethodhasagreaterabilitytorecovertamperedareas.

简介：Weexploredthepossibilitiesofwhole-genomeduplication(WGD)inprokaryoticspecies,whereweperformedstatisticalanalysesoftheconfigurationsofthecentralanglesbetweenhomologoustandemrepeats(TRs)onthecircularchromosomes.Atfirst,wedetectedTRsontheirchromosomesandidentifiedequivalenttandemrepeatpairs(ETRPs);here,anETRPisdefinedasapairoftandemrepeatssequentiallysimilartoeachother.ThenwecarriedoutstatisticalanalysesofthecentralangledistributionsofthedetectedETRPsoneachcircularchromosomebywayofcomparisonsbetweenthedetecteddistributionsandthosegeneratedbynullmodels.Intheanalyses,weestimatedaPvaluebyasimulationusingtheKullback–Leiblerdivergenceasadistancemeasurebetweentwodistributions.Asaresult,thecentralangledistributionsfor8outofthe203prokaryoticspeciesshowedstatisticallysignificantdeviations(P<0.05).Inparticular,wefoundoutthecharacteristicfeatureofoneroundofWGDinPhotorhabdusluminescensgenomeandthatoftworoundsofWGDinEscherichiacoliK12.

简介：Inthispaper,weanalyzedtheOneFoundationsreliefandreconstructionactivitiesaftertheYaanearthquake.TheanalysisshowsthattheparticipationofNGOsindisasterreliefactivitieshasundergonedifferentstages.IntheJiujiangearthquake,NGOsparticipationwasintherudimentarystage.IntheWenchuanearthquake,theybecameoneoftheactiveparticipants.IntheYaanearthquake,theyplayedanactiverolethroughacooperationmechanism.ThatmeansNGOshavehadthecapabilityofresourcemobilizationandcooperationwiththemwillimprovedisastermanagementcapacities,especiallyinthenationalsignificantseismicmonitoringandprotectionregions.

简介：Forpredictionoftheextremesignificantwaveheightintheoceanareaswherelongtermwavedataarenotavailable,theempiricalmethodofextrapolatingshorttermdata(1～3years)isusedindesignpractice.Inthispapertwomethodsareproposedtopredictextremesignificantwaveheightbasedonshort-termdailymaxima.AccordingtothedaarecordedbytheOceanographicStationofLiaodongBayattheBohaiSea,itissupposedthatdailymaximumwaveheightsarestatisticallyindependent.Thedatashowthatdailymaximumwaveheightsobeylog-normaldistribution,andthatthenumbersofdailymaximavaryfromyeartoyear,obeyingbinomialdistribution.Basedonthesestatisticalcharacteristics,thebinomial-log-normalcompoundextremumdistributionisderivedforpredictionofextremesignificantwaveheights(50～100years).Forexaminationofitsaccuracyandvalidity,thepredictionofextremewaveheightsisbasedon12years′dataatthisstation,andbasedoneach3years′datarespectively.Theresultsshowthatwithconsiderationofconfidenceintervals,thepredictedwaveheightsbasedon3years′dataareveryclosetothosebasedon12years′data.TheobserveddatainsomeoceanareasintheAtlanticOceanandtheNorthSeashowitisnotcorrecttoassumethatdailymaximumwaveheightsarestatisticallyindependent;theyaresubjecttoMarkovchaincondition,obeyinglog-normaldistribution.Inthispaperananalyticalmethodisderivedtopredictextremewaveheightsinthesecases.AcomparisonofthecomputationsshowsthatthedifferencebetweentheextremewaveheightsbasedontheassumptionthatdailymaximaarestatisticallyindependentandthattheyaresubjecttoMarkovChainconditionissmallerthan10%.

简介：Overthepastfewdecades,extremechangeshaveoccurredinthecharactersofexploitedfishpopulations.Themajorityofthesechangeshaveaffectedthegrowthtraitsoffishlifehistory,whichincludeasmallersize-at-age,anearlierage-at-maturationandamongothers.Currently,thecausesoftheselifehistorytraitschangesstillrequiresystematicanalysesandempiricalstudies.Theexplanationsthathavebeencitedaremerelyexpressedintermsoffishphenotypicadaptation.Ithasbeenclaimedthattheoriginaltraitsoffishcanberecoveredoncetheintensityofexploitationofthefishiscontrolled.Sustainedenvironmentalandfishingpressurewillchangethelifehistorytraitsofmostfishspecies,sothefishindividual’straitsarestillinsmallsize-at-ageandatearlierage-at-maturationinexploitedfishpopulations.Inthispaper,weexpressedourviewofpointsthatfishinggearhasimposedselectivityonfishpopulationsandindividualsasvariousotherenvironmentalfactorshavedoneandsuchchangesareunrecoverable.Accordingtotheexistingtendofexploitedfishindividual’slifehistorytraits,wesuggestedfurtherresearchesinthisfieldandprovidedbettermethodsoffisherymanagementandtherebyfisheryresourcesprotectionthanthoseavailableearly.

简介：基于专业、分工与运作统一化的考虑，许多大型、项目型组织纷纷采用矩阵管理，能否完善运作的关键在于互补，以及对本身专业的坚持、对他人的尊重支援。

简介：讨论了n（n≥2）阶方阵A与其伴随矩阵A^＊的特征值之间的关系，利用A的特征值λ0及其代数余子式Aij给出了A^＊的特征值的表达式．

简介：TherapidpopulationgrowthhasbeenamajorproblemofBeijing.Itaffectedontransportation,schoolingandhousing.On26thSeptember2011,BeijingPopulationandFamilyPlanningCommissionannouncedthattheywoulddraftpopulationassessmentprovisions.Governmentpolicieswouldbeissuedaccordingtopopulationplansforassessingtheireffectsonpopulationcontrol.

简介：将文[1,4]中定义广义正定矩阵的概念再作推广,并讨论各种不同定义下的广义正定矩阵间的包含关系,给出M-矩阵等价的四种新定义.

简介：给出基本初等矩阵的定义，得出任何方阵都可分解为有限个基本初等矩阵的乘积的结论．

简介：本文根据矩阵的初等变换，提出一种简便的分解矩阵的方法。

简介：系统内部要素之间的相互联系由可达矩阵表示，骨架矩阵是它的最简化表示。在相似关系下．一个可达矩阵的，骨架矩阵是唯一的（即所有骨架矩阵相似且具有相同个数的＂１＂元素）。

简介：首先介绍求二元对称循环矩阵逆矩阵的简便方法,然后用这种方法给出两类二元对称循环矩阵的求逆公式.

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简介：本文讨论了对合矩阵的一些性质。

简介：文讨论了循环矩阵的对角化问题。本文讨论推广了的一类循环矩阵——广义循环矩阵。首先确定了复数域上由U确定的一类广义循环矩阵所组成的空间的最大维数;然后给出了复广义循环矩阵与对角阵西相似的充要条件。

简介：Genesarecontinuallybeingcreatedbytheprocessesofgenomeduplication(ohnolog)andgeneduplication(paralog)Whole-genomeduplicationshavebeenfoundtobewidespreadinplantspeciesandplayanimportantroleinplantevolution.Clearlyun-overlappingduplicatedblocksofwhole-genomeduplicationscanbedetectedinthegenomeofsequencedrice(Oryzasativa).Syntenicohnologpairs(ohnologues)ofthewhole-genomeduplicationsinricewereidentifiedbasedontheirsyntenicduplicatelines.Theparalogsofohnologueswerefurtherscannedusingmulti-roundreciprocalBLASTbest-hitsearching(E＜e-14).Theresultsindicatedthatanaverageof0.55sisterparalogscouldbefoundforeveryohnologueinrice.Theseresultssuggestthatsmall-scaleduplications,aswellaswhole-genomeduplications,playasignificantroleinthetwoduplicatedricegenomes.