学科分类
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337 个结果
  • 简介:Aseachtypeofsatellitenetworkhasdifferentlinkfeatures,itsdatatransmissionmustbedesignedbasedonitslinkfeaturestoimprovetheefficiencyofdatatransferring.Thetransmissionofnavigationintegratedservicesinformation(NISI)inaglobalnavigationsatellitesystem(GNSS)withinter-satellitelinks(ISLs)isstudiedbytakingtherealsituationofinter-satellitecommunicationlinksintoaccount.Anon-demandcomputingandbufferingcentralizedroutestrategyisproposedbasedondynamicgroupingandthetopologyevolutionlawoftheGNSSnetworkwithinwhichthesatellitenodesareoperatedinthemannerofdynamicgrouping.Dynamicgroupingisbasedonsatellitesspatialrelationshipsandthegrouproleofthesatellitenodechangesbyturnsduetoitsspatialrelationships.Theroutestrategyprovidessignificantadvantagesofhighefficiency,lowcomplexity,andflexibleconfiguration,bywhichtheestablishedGNSScanpossessthefeaturesandcapabilitiesoffeasibledeployment,efficienttransmission,convenientmanagement,structuralinvulnerabilityandflexibleexpansion.

  • 标签: 全球导航卫星系统 网络拓扑结构 卫星网络 路由策略 演化规律 卫星间链路
  • 简介:BasedontheresearchofChinaandabroad,thisthesiscarriedonanempiricalstudyon272EnglishmajorsusingtheinstrumentofquestionnairesandgainedsomeimportantfindingsthatEnglishmajors’BeliefsaboutTranslationandTheirUseofChineseTranslationasalearningarecloselyrelatedwitheachotherwhichprovedthefindingsofPosenLiao.

  • 标签: BELIEFS ABOUT TRANSLATION Use of Chinese
  • 简介:Manyglobalemissionreductionstrategieshavebeenproposed,butfewhavebeenassessedquantitativelyfromtheviewofequality,efficiencyandeffectiveness.Integratedassessmentmodels(IAM)isoneoftheeffectivewaystomakeclimatepolicymodeling.SointhispaperwedevelopedtheMRICES(Multi-regionalintegratedmodelofclimateandeconomywithGDPspillovers)model,whichisanIAMbutextendstoincludeGDPspillovermechanism,tomakeassessmentonseveralstrategiesforglobalemissionreduction,includingtheegalitarianismstrategy,theUNDPstrategyandtheCopenhagenAccord.Using1990asabaselineforhistoricalemissionlevels,theegalitarianstrategyarguesthatdevelopedcountriesshouldimplementurgentemissionreductions,whereasdevelopingcountriesareallowedrelativelyhigherfutureemissionquotas.TheUNDPstrategyaddressestheissueofsubstantialchangesinglobaltemperaturebutacknowledgesthatdevelopingcountriesarenotabletoaffordmorecostsformitigationmeasures,whichisinequitablefromtheperspectiveofacountry’srighttodevelop.WealsosimulatedtheCopenhagenAccordtodeterminetheconsequencesbytheyear2100ifeachcountrycontinuestheircurrentemissionmitigationactions,andresultsindicatedthattheincreaseinglobaltemperaturewillbe2.8℃by2100;consequently,muchstrongeremissionreductioneffortsmustbeimplementedafter2020.Basedonanalysisonmitigationstrategies,itisrecognizedthatthecommonbutdifferentiatedresponsibilityprinciplemustbeinsistedwhenmakingglobalmitigationstrategy.Tocomplywiththisprinciple,theemissionreductionbaselineofdevelopedanddevelopingcountriesshouldbediscriminated,so1990and2005canbetakenasthebaseyearfordevelopedanddevelopingcountriesrespectively.

  • 标签: 综合评估模型 减排 发展中国家 应用 国内生产总值 发达国家
  • 简介:Comparedwithworld’sothergreatpowers,theUnitedStatesdeservestobecalledastatethathasboththedesireandcapabilitytorebuildtheworld.Therefore,itsglobalstrategyhasbecomeveryimportant,andanynationthathasdealingswithWashingtonmusttakethisintoconsideration.However,itismuchdebatablewhethertheUnitedStateshasaglobalstrategy,andwhetheranewglobalstrategyhas

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  • 简介:Inthispaper,anonlineardynamicMIMOmodelofa6-DOFunderactuatedquadrotorrotorcraftisderivedbasedonNewton-Eulerformalism.Thederivationcomprisesdeterminingequationsofmotionofthequadrotorinthreedimensionsandseekingtoapproximatetheactuationforcesthroughmodelingoftheaerodynamiccoefficientsandelectricmotordynamics.Thederivedmodelisdynamicallyunstable,soasequentialnonlinearcontrolstrategyisimplementedforthequadrotor.Thecontrolstrategyincludesexactfeedbacklinearizationtechnique,usingthegeometricmethodsofnonlinearcontrol.Theperformanceofthenonlinearcontrolalgorithmisevaluatedusingsimulationandtheresultsshowtheeffectivenessoftheproposedcontrolstrategyforthequadrotorrotorcraftnearquasi-stationaryflight.

  • 标签: 飞行控制系统 飞行器 技术性能 模型设计
  • 简介:Overthepastdecade,theChinesegovernmenthasdevelopedseveralplansregulationsandpolicymeasuresrelatedtothedevelopmentofrenewableenergytechnologiesandhasimplementedaseriesofpilotprojects.ChinesepolicymakershavespentseveralyearsstudyinghowrenewableenergypolicymodelsthathavebeenusedinternationallycouldbeimplementedinChina.Programsarecurrentlyunderwaytoimplementpilotrenewableportfoliostandards,ormandatorymarketshares(MMS)forrenewableenergy,inseveralprovinces.ThispaperexaminestheprimaryinstitutionsthatareinvolvedinpromotingrenewablepoliciesinChina,thestructureofthepoliciesthatcurrentlyarebeingdrafted,andthestatusofthecomplementary,national-levelrenewableenergylawbeingdraftedtoprovidealegalbasisforongoinglocalandnational-levelpolicies.ItthenexaminesthelegalrequirementsforpromotingrenewableenergylegislationundertheChineselaw-makingsystem.Finally,itprovidesrecommendationsfor

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  • 简介:Code-switchingisasocio-linguisticterm,whichreferstotheswitchingfromonelanguagetoanother.Thispaperattemptstoshowthatcode-switchingcanbeusedasateachingstrategyforsecondlanguageteachingbyillustratingthepossiblereasonsfortheswitching.Italsoexploresthepossibilityofviewingcode-switchingaslanguageinterferenvefromateachingperspective.Inaccordancewiththeseanalysisthispapermakesaconclusionthatwhencode-switchingistocompensateforalanguagecifficultyitmaybeviewedasinterfernceandwhenitisusedasasocio-linguistictoolitbecomesastrategy.

  • 标签: 语码转换 社会语言学 教学方法 语言障碍 第二语言教学
  • 简介:Inthethree-phasetrafficflowstudies,thetrafficflowcharacteristicatthebottlenecksectionisahotspotintheacademicfield.Thecontroversyaboutthecharacteristicsofthesynchronizedflowatbottleneckisalsothemaincontradictionbetweenthethree-phasetrafficflowtheoryandthetraditionaltrafficflowtheory.Undertheframeworkofthree-phasetrafficflowtheory,thispapertakestheon-rampasanexampletodiscussthetrafficflowcharacteristicsatthebottlenecksection.Inparticular,thispapermainlyconductsthemicro-analysistotheeffectoflanechangeunderthetwolaneconditions,aswellastheeffectoftheon-ramponthemainlinetrafficflow.Itisfoundthatwhenthemainroadflowislow,thegreatertheon-rampinflowrate,thehighertheaveragespeedofthewholeroadsection.Astheprobabilityofvehiclesenteringfromtheon-rampincreases,theflowandtheaveragespeedofthemainroadaregraduallystabilized,andthentheon-rampinflowvehiclesnolongerhaveasignificantimpactonthetrafficflow.Inaddition,thispaperfocusesonthevelocitydisturbancegeneratedattheon-ramp,andproposesthecorrespondingon-rampcontrolstrategybasedonit,andthesimulationverifiedthatthecontrolstrategycanreasonablycontrolthetrafficflowbytheon-ramp,whichcanmeetthecontrolstrategyrequirementstosomeextent.

  • 标签: three-phase TRAFFIC flow theory lane change
  • 简介:ThispaperpresentsgeneralizedCAPP(G-CAPP)methodwhichdealswithmacroprocessplanningformulti-objectiveintheplanningstageofproductionlineofaccuracywelding(PLAW)basedonthefeaturesofaccuracyweldingproduction(AWP).G-CAPPoffersfoundationsforprototypedesignandgeneralequipmentsorting,productioncapacitypredicationandproductionanalysisbymeansofsimulationandoptimization.Asynthetichierarchyevaluation(SHE)modelforG-CAPPestablishedaccordingtotheplanningobjectiveisutilizedtoestimatethealternateprocessingplansbyusingmembershipfunctionandanalytichierarchyprocess(AHP)ofoperationaltheory.Theassemblyweldinglineofhydraulictorqueconverter(HTC)isasanexampleoftypicalAWPtoexplicateG-CAPPandsyntheticevaluatingstrategyofPLAW.ThefeasibleandrationalprocessconfigurationstrategiesofHTCassemblyweldinglinearepointedoutunderdifferentplanningobjective.

  • 标签: 精度焊接 生产线 广义CAPP 综合评估策略
  • 简介:TheSeptember11eventupsetJapan’sdiplomaticagendaandusheredinastrategicrestructuringwiththefocusonanti-terrorismandthetopprioritygiventotieswithWashington.Itsnewdiplomacyagainstterrorstressesthreeaspects:policytowardsWashingtonforensuringstrategiccenterof

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  • 简介:Chinaisoneofthecountrieswiththemostseriousfloodingdisasters.InChina,above70%ofbigcities,50%ofpopulationand75%ofindustrialandagriculturaloutputvaluearedistributedineasterncoastalareaswithseriousflooding.Therefore,enhancementoftheoreticalstudyandexperiencesummarizationofurbanfloodcontrolisofgreattheoreticalandpracticalsignificance.Aseconomyisdevelopingrapidly,urbanscaleisexpandingfast,andurbanfloodcontrolstandispromoted.Urbanfloodcontrolcallsfornewconceptandmethods.Thispapermakesasystematicsummarizationofconceptevolutionandadvancedmethodsconcerningurbanfloodcontrolathomeandabroad.Theconceptofurbanfloodcontrolhastransformedfromsimplefloodcontrolanddrainagetocoexistencewithanduseofflood.Floodcontrolmeasureshavetransferredformemphasisuponengineeringonestoprioritytobothengineeringandnon-engineeringones,withspecialattentiontoecologicalfloodcontrol,suchasmakingfulluseofecologicalrevetment,ecologicalrealignmentofariver,multi-objectivemanagementofurbanflooddetentionregion,turningfloodintoresourcesandutilizationofwetlands.

  • 标签: 防洪策略 大城市 城市防洪 洪水 人力 基础
  • 简介:AbstractA novel bat-origin coronavirus emerged in Wuhan, China in December 2019 and continues to spread across China and the world. At the time of writing, a massive global response has been implemented to control the disease as it spreads from person to person. Yet the high-risk human-wildlife interactions and interfaces that led to the emergence of SARS-CoV and of 2019-nCoV continue to exist in emerging disease hotspots globally. To prevent the next epidemic and pandemic related to these interfaces, we call for research and investment in three areas: 1) surveillance among wildlife to identify the high-risk pathogens they carry; 2) surveillance among people who have contact with wildlife to identify early spillover events; and 3) improvement of market biosecurity regarding the wildlife trade. As the emergence of a novel virus anywhere can impact the furthest reaches of our connected world, international collaboration among scientists is essential to address these risks and prevent the next pandemic.

  • 标签: Novel coronavirus Disease emergence SurveillanceRisk reductionMarket biosecurity 2019-nCoV
  • 简介:Mobileplatformdevelopsrapidlyinrecentyears,withitsperformanceandcapacityincreasing.Alargenumberofvirtualrealityapplicationssuchas3Dsimulationandvisualizationhaveappearedonmobileplatform.However,duetorestrictions,suchasthelackofcomputingresourcesandthelimitednetworkbandwidth,thevirtualrealitysystemsonmobileplatformcouldnothavecomparableperformanceastheirpeersondesktopplatform.Takingresourcerestrictionsintoconsideration,trade-offshavebeenmaderegardingthedisplayofvirtualrealitysystems.Weproposeaunifiednetworkschedulingstrategybasedonasynchronousmulti-thread,databasecache,prioritizationandeliminationofoverduerequests.ThisstrategyhasbeentestedontheprototypesystemofvirtualrealitysystemonAndroid.Theresultsdemonstratehighernetworkresourceutilizationandbetteruserexperience.

  • 标签: 虚拟现实系统 网络带宽 调度策略 网络资源利用率 移动平台 计算资源