简介：Inthisletter,capacityestimationforMobileAdhocNETworks(MANETs)usingdirec-tionalantennasarestudied.TwoMatrix-basedFastCalculationAlgorithms(MFCAs)areproposedtoestimatethenetworkcapacityinanetworkscenarioinwhichthereisnochannelsharingamongmultiplesessionsandtrafficissensitivetodelaywithanend-to-enddelayconstraint.Thefirstalgo-rithmMFCA-1isusedtoestimatenetworkcapacityinasituationwherealllinkshavethesamedelay.Itestimatesthemaximumnumberofk-hopsessionsinanetworkbasedonthek-hopadjacencymatrixofthenetwork.ThesecondalgorithmMFCA-2isusedtoestimatenetworkcapacityinasituationwheredifferentlinksmayhavedifferentdelays.Itcalculatesthemaximumnumberofsessionsinanetworkwithanend-to-enddelayconstraintbasedontheadjacencymatrixandthelink-delaymatrixofthenetwork.NumericalandsimulationresultsshowthatbothMFCA-1andMFCA-2cancalculatenetworkcapacitymuchfasterthanthewell-knownBrute-ForceSearchAlgorithm(BFSA)butwiththesameaccuracy.

简介：Usingatriangularlatticemodeltostudythedesignabilityofproteinfolding,weovercametheparityproblemofpreviouscubiclatticemodelandenumeratedallthesequencesandcompactstructuresonasimpletwo-dimensionaltriangularlatticemodelofsize4+5+6+5+4.Weusedtwotypesofaminoacids,hydrophobicandpolar,tomakeupthesequences,andachieved223+212differentsequencesexcludingthereversesymmetrysequences.Thetotalstringnumberofdistinctcompactstructureswas219,093,excludingreflectionsymmetryintheself-avoidingpathoflength24triangularlatticemodel.Basedonthismodel,weappliedafastsearchalgorithmbyconstructingaclustertree.Thealgorithmdecreasedthecomputationbycomputingtheobjectiveenergyofnon-leafnodes.Theparallelexperimentsprovedthatthefasttreesearchalgorithmyieldedanexponentialspeed-upinthemodelofsize4+5+6+5+4.Designabilityanalysiswasperformedtounderstandthesearchresult.

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简介：Inthispaper,anewcoveringalgorithmcalledFCV1ispresented.FCV1comprisestwoalgorithms,oneofwhichisabletofastsearchforapartialruleandexcludethelargeportionofneggativeexamples,theotheralgorithmincorporatesthemoreoptimizedgreedyset-coveringalgorithm,andrunsonasmallportionoftrainingexamples.Hence,thetrainingprocessofFCV1ismuchfasterthanthatofAQ15.

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简介：Arraycalibrationisimportantinengineeringpractice.Inthispaper,fastcalibrationmethodsforaULA'sgainandphaseerrorsbothinfarandnearfieldsareproposed.Inthefarfield,usingasinglesoundsourcewithoutexactorientation,thismethodhorizontallyrotatesthearrayexactlyonce,performseigenvaluedecompositionforthecovariancematrixofreceiveddata,thencomputesthegainandphaseerroraccordingtotheformulas.Inthenearfield,usingthesamesinglesoundsource,itisnecessarytorotatethearrayhorizontallyatmostthreetimes,buildequationsaccordingtogeometricrelations,thensolvethem.Usingtheformulaproposedinthispaper,sphericalwavesaremodifiedintoplanewaves.Theneigenvaluesdecompositionisperformed.Thesetwocalibrationmethodswereshowntobevalidbysimulationandarefast,accurateandeasytouse.Finally,ananalysisoffactorsinfluencingestimationprecisionisgiven.

简介：AccordingaleadingpersonofChinaInstituteofAtomicEnergy(CIAE),thefirstexperimentalfastneutronreactorunderconstructionwiththermalpowerof65MWisproceedingsmoothly,andtheconstructiondesignhasbeenfinishedcompletely.ItisexpectedthatthereactorwillbefinishedandgocriticalinSeptember2009,andgenerateelectricityontrialinSeptember2010.

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简介：Inremotesensingorlasercommunicationspacemissions,spacecraftneedfastmaneuverandfaststabilizationinordertoaccomplishagileimagingandattitudetrackingtasks.However,fastattitudemaneuverscaneasilycauseelasticdeformationsandvibrationsinflexibleappendagesofthespacecraft.Thispaperfocusesonthisproblemanddealswiththecombinedcontroloffastattitudemaneuverandstabilizationforlargecomplexspacecraft.Themathematicalmodelofcomplexspacecraftwithflexibleappendagesandmomentumbiasactuatorsonboardispresented.Basedontheplantmodelandcombinedwiththefeedbackcontroller,modalparametersoftheclosed-loopsystemarecalculated,andamultiplemodeinputshaperutilizingthemodalinformationisdesignedtosuppressvibrations.Aimingatreducingvibrationsexcitedbyattitudemaneuver,aquinticpolynomialformrotationpathplanningisproposedwithconstraintsontheactuatorsandtheangularvelocitytakenintoaccount.Attitudemaneuversimulationresultsofthecontrolsystemswithinputshaperorpathplanninginloopareseparatelyanalyzed,andbasedontheanalysis,acombinedcontrolstrategyispresentedwithbothpathplanningandinputshaperinloop.Simulationresultsshowthatthecombinedcontrolstrategysatisfiesthecomplexspacecraft’srequirementoffastmaneuverandstabilizationwiththeactuators’torquelimitationsatisfiedatthesametime.

简介：1.IntroductionInthispaperweconsidertheCauchyproblemforthefastdiffusionequationwheremaxandpositivefunction.Thistypeofequationhasbeenextensivelystudiedasamathematicalmodelofalotofphysicalproblems(see[1-3]).Amajortopicofstudyistheexistenceandnonexistenc...

简介：Reconstructionofabsorptioncoefficientμ_aandscatteringcoefficientμ_aisveryimportantforapplicationsofdiffuseopticaltomographyandnearinfraredspectroscopy.Aimingattheearlycancerdetectionofcervixandstomach,wepresentafastinverseMonte-Carloschemeforextractingμ_aandμ_sofatubulartissuefromthemeasurementonfrequencydomain.Resultsshowthatthecomputationtimeforreconstructingonesetofμ_aandμ_sislessthan1minandtherelativeerrorsinreconstructionarelessthan±10%fortheopticalpropertiesofnormalcervicaltissueandprecancerouslesions.

简介：Usingfinite-timecontrolapproach,thispaperproposesanewdesignmethodfornonlinearrobustexcitationcontrolofawidelyused5th-ordermodelofsynchronousgenerators.Thefinite-timeexcitationcontrollerachievedherecanimprovethesystem'sbehaviorsinsomeaspectssuchasquickconvergenceandrobustnessforuncertainties.Simulationsdemonstratethatthefinite-timeexcitationcontrollerismoreeffectivethansomeotherexcitationcontrollers.

简介：Asimpleandeffectivegreedyalgorithmforimageapproximationisproposed.Basedonthematchingpursuitapproach,itischaracterizedbyareducedcomputationalcomplexitybenefitingfromtwomajormodifications.First,ititerativelyfindsanapproximationbyselectingMatomsinsteadofoneatatime.Second,theinnerproductcomputationsareconfinedwithinonlyafractionofdictionaryatomsateachiteration.Themodificationsareimplementedveryefficientlyduetothespatialincoherenceofthedictionary.Experimentalresultsshowthatcomparedwithfullsearchmatchingpursuit,theproposedalgorithmachievesaspeed-upgainof14.4～36.7timeswhilemaintainingtheapproximationquality.

简介：最近中国完成了世界上最大的射电望远镜的组装，该望远镜将被用于探索太空，追寻外星生命。

简介：Efficientdatavisualizationtechniquesarecriticalformanyscientificapplications.CentroidalVoronoitessellation(CVT)basedalgorithmsofferaconvenientvehicleforperformingimageanalysis,segmentationandcompressionwhileallowingtooptimizeretainedimagequalitywithrespecttoagivenmetric.InexperimentalsciencewithdatacountsfollowingPoissondistributions,severalCVT-baseddatatessellationalgorithmshavebeenrecentlydeveloped.Althoughtheysurpasstheirpredecessorsinrobustnessandqualityofreconstructeddata,timeconsumptionremainstobeanissueduetoheavyutilizationoftheslowlyconvergingLloyditeration.Thispaperdiscussesonepossibleapproachtoacceleratingdatavisualizationalgorithms.ItreliesonamultidimensionalgeneralizationoftheoptimizationbasedmultilevelalgorithmforthenumericalcomputationoftheCVTsintroducedin[1],wherearigorousproofofitsuniformconvergencehasbeenpresentedin1-dimensionalsetting.Themultidimensionalimplementationemploysbarycentriccoordinatebasedinterpolationandmaximalindependentsetcoarseningprocedures.Itisshownthatwhencoupledwithbinaccretionalgorithmaccountingforthediscretenatureofthedata,thealgorithmoutperformsLloyd-basedschemesandpreservesuniformconvergencewithrespecttotheproblemsize.Althoughnumericaldemonstrationsprovidedarelimitedtospectroscopydataanalysis,themethodhasacontext-independentsetupandcanpotentiallydeliversignificantspeeduptootherscientificandengineeringapplications.

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简介：Thispaperproposesatree-basedbackoff(TBB)protocolthatreducesthenumberofiterationsimplementedintheprocedureoftagcollisionarbitrationinradiofrequencyidentification(RFID)systems.Thisisachievedbyemployingthefollowingmechanisms:oneissendtherequestcommanditerativelytoalltagsintheinterrogationzoneuntilasingletagisidentified.Theotherisbackwardtotheparentnodeinsteadofrootnodetoobtaintherequestparametersandsendtherequestcommandagainuntilalltagsareidentified.Comparedwiththetraditionaltree-basedprotocol,onaverage,simulatedresultsshowthattheTBBprotocolreducesthenumberoftheiterationsby72.3%andtheidentificationdelayby58.6%andachievesthegoaloffasttagidentification.

简介：作者与快可逆反应考虑一个反应散开系统的有限体积近似。它从priori被推出估计近似答案收敛到反应散开问题的弱答案并且满足不取决于运动的率的估计。因而，解决方案收敛到一个非线性的散开问题的解决方案，作为当运动的率趋于到无穷时，元素和时间步集成到零的卷的尺寸。

简介：Thefinancialcrisisishavingagreatimpactontheworldeconomicandpoliticalstructure.Atthesametime,ithasbroughtimportantopportunitiestoChina,acountryinacrucialstageofdevelopment.ThecrisishasdemonstratedChina'simportance