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  • 简介:Considerasystemofnonlinearwaveequations(e)2t-c2i△xui=Fi(u,(e)u,(e)x(e)u)in(0,∞)×(R)3fori=1,┈,m,whereFi(i=1,┈,m)aresmoothfunctionsofdegree2neartheoriginoftheirarguments,andu=(u1,┈,um),while(e)uand(e)x(e)urepresentthefirstand(secondderivativesofu,respectively.Inthispaper,theauthorpresentsanewclassofnonlinearityforwhichtheglobalexistenceofsmallsolutionsisensured.Forexample,globalexistenceofsmallsolutionsfor((e)2t-c21Δx)u1=u2((e)tu2)+arbitrarycubicterms,((e)2t-c22Δx)u2=u1((e)tu2)+((e)tu1)u2+arbitrarycubictermswillbeestablished,providedthatc21≠c22.

  • 标签: 波动方程 倍数 处处存在 偏微分方程 非线性
  • 作者: Xu Zhi-Wei Li Zhong-Jie Hu Wen-Biao
  • 学科: 医药卫生 >
  • 创建时间:2020-08-10
  • 出处:《贫困所致传染病(英文)》 2020年第01期
  • 机构:School of Public Health and Social Work & Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia; Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia; School of Public Health, Faculty of Medicine, University of Queensland, Brisbane, Australia,Division of Infectious Disease, Key Laboratory of Surveillance and Early-warning on Infectious Disease, Chinese Center for Disease Control and Prevention, Beijing, China,School of Public Health and Social Work & Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia; Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia
  • 简介:AbstractBackground:Understanding the global spatiotemporal pattern of seasonal influenza is essential for influenza control and prevention. Available data on the updated global spatiotemporal pattern of seasonal influenza are scarce. This study aimed to assess the spatiotemporal pattern of seasonal influenza after the 2009 influenza pandemic.Methods:Weekly influenza surveillance data in 86 countries from 2010 to 2017 were obtained from FluNet. First, the proportion of influenza A in total influenza viruses (PA) was calculated. Second, weekly numbers of influenza positive virus (A and B) were divided by the total number of samples processed to get weekly positive rates of influenza A (RWA) and influenza B (RWB). Third, the average positive rates of influenza A (RA) and influenza B (RB) for each country were calculated by averaging RWA, and RWB of 52 weeks. A Kruskal-Wallis test was conducted to examine if the year-to-year change in PA in all countries were significant, and a universal kriging method with linear semivariogram model was used to extrapolate RA and RB in all countries.Results:PA ranged from 0.43 in Zambia to 0.98 in Belarus, and PA in countries with higher income was greater than those countries with lower income. The spatial patterns of high RB were the highest in sub-Saharan Africa, Asia-Pacific region and South America. RWA peaked in early weeks in temperate countries, and the peak of RWB occurred a bit later. There were some temperate countries with non-distinct influenza seasonality (e.g., Mauritius and Maldives) and some tropical/subtropical countries with distinct influenza seasonality (e.g., Chile and South Africa).Conclusions:Influenza seasonality is not predictable in some temperate countries, and it is distinct in Chile, Argentina and South Africa, implying that the optimal timing for influenza vaccination needs to be chosen with caution in these unpredictable countries.

  • 标签: Influenza a Influenza B Seasonality Spatial pattern Vaccination
  • 简介:WiththeERA40reanalysisdailydatafor1958-2001,theglobalatmosphericseasonal-meandiabaticheatingandtransientheatingarecomputedbyusingtheresidualdiagnosisofthethermodynamicequation.Thethree-dimensionalstructuresforthetwotypesofheatingaredescribedandcompared.Itisdemonstratedthatthediabaticheatingisbasicallycharacterizedbystronganddeepconvectiveheatinginthetropics,shallowheatinginthemidlatitudesanddeepcoolinginthesubtropicsandhigh-latitudes.Thetropicaldiabaticheatingalwaysshiftstowardsthesummerhemisphere,butthemidlatitudeheatingandhigh-latitudecoolingtendtobestronginthewinterhemisphere.Ontheotherhand,thetransientheatingduetotransienteddytransferischaracterizedbyameridionaldipolepatternwithcoolinginthesubtropicsandheatinginthemid-andhigh-latitudes,aswellasbyaverticaldipolepatterninthemidlatitudeswithcoolingatlowerlevelsandheatinginthemid-andhigher-levels,whichgivesrisetoaslopedstructureinthetransientheatingorientedfromthelowerlevelsinthehighlatitudesandhigherlevelsinthemidlatitudes.Thetransientheatingiscloselyrelatedtoastormtrackalongwhichthetransienteddyactivityismuchstrongerinthewinterhemispherethaninthesummerhemisphere.InNorthernHemisphere,thetransientheatinglocatesinthewesternoceanicbasin,whileitiszonally-orientedinSouthernHemisphere,forwhichthetransientheatingandcoolingarefarseparatedoverSouthPacificduringthecoldseason.Thetransientheatingtendstocancelthediabaticheatingovermostoftheglobe.However,itdominatesthemid-troposphericheatinginthemidlatitudes.Therefore,theatmospherictransientprocessesacttohelptheatmospheregainmoreheatinthehigh-latitudesandinthemid-troposphereofmidlatitudes,reallocatingtheatmosphericheatobtainedfromthediabaticheating.

  • 标签: 热带气象 气象学 天气学 气团
  • 简介:Thispaperfirstanalyzesthefeaturesoftwoclassesofnumericalmethodsforglobalanalysisofnonlineardynamicalsystems,whichregardstatespacerespectivelyascontinuousanddiscreteones.Onbasisofthisunderstandingitthenpointsoutthatthepreviouslyproposedmethodofpointmappingundercellreference(PMUCR),haslaidaframeworkforthedevelopmentofatwoscalednumericalmethodsuitablefortheglobalanalysisofhighdimensionalnonlinearsystems,whichmaytaketheadvantagesofb...

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  • 简介:Wedeveloptheinterpolatedfiniteelementmethodtosolvesecond-orderhy-perbolicequations.Thestandardlinearfiniteelementsolutionisusedtogenerateanewsolutionbyquadraticinterpolationoveradjacentelements.Weprovethatthisinterpo-latedfiniteelementsolutionhassuperconvergence.Thismethodcaneasilybeappliedtogeneratingmoreaccurategradienteitherlocallyorglobally,dependingontheapplications.Thismethodisalsocompletelyvectorizableandparallelizabletotaketheadvantagesofmoderncomputerstructures.Severalnumericalexamplesarepresentedtoconfirmourtheoreticalanalysis.

  • 标签: Interpolated FINITE ELEMENT methods HYPERBOLIC EQUATIONS
  • 简介:<正>LetMbeacompactminimalsurfaceinS3.Y.J.Hsuprovedthatif‖S‖2≤2(21/2π,thenMiseithertheequatorialsphereortheCliffordtorus,where5"isthesquareofthelengthofthesecondfundamentalformofM,‖·‖2denotestheL2-normonM.Inthispaper,wegeneralizeHsu’sresulttoanycompactsurfacesinS3withconstantmeancurvature.

  • 标签: COMPACT surface CONSTANT mean CURVATURE GLOBAL
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  • 简介:卫星运营商SESGlobal公司的转发器利用率在2006年期间提高到74.5%,到2006年底,在1019个可商用的转发器中有760个在使用中。

  • 标签: SES 业绩 转发器 运营商 利用率 卫星
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  • 简介:Adiscrepancyremainsinthefirsttwoleadingempiricalorthogonalfunction(EOF)modesofthetropicalPacificseasurfacetemperatureanomaly(SSTA)basedonobservationssincethe1980s.TheEOF1mode,representingtheElNino-SouthernOscillation(ENSO),isarobustresult.However,theEOF2featureseitherElNinoModoki(EM)orENSOevolutionduringdifferentperiods,whichisprobablyassociatedwiththeimpactsofglobalwarming.TheunderlyingquestioniswhattheEOF2modeofthetropicalPacificwouldbewithoutglobalwarming.UsingtheCMIP5preindustrialscenariotoexcludetheinfluenceofglobalwarming,wefindthattheEOF1modeofthetropicalPacificSSTArepresentsENSOandthattheEOF2modeisnotEM.Accordingtothelead–lagcorrelationbetweentheENSOandEOF2modes,thelinkagebetweenthesetwomodesisasfollows:…ElNino→EOF2→LaNina→–EOF2→ElNino….Byanalyzingtheevolutionofseasurfacetemperature,surfacewind,andsubsurfaceoceantemperatureanomalies,wefindthemechanismlinkingtheENSOandEOF2modesistheair–seainteractionassociatedwiththeENSOcycle.ThisresultsuggeststhattheEOF2moderepresentsanaspectofENSOevolutionunderpreindustrialconditions.Therefore,thisstudyfurtherindicatesthattheEMisprobablyduetotheinfluenceofglobalwarming.

  • 标签: El Nino-Southern Oscillation(ENSO) ENSO evolution global
  • 简介:Climatechangeisagreatconcernofvariouscountries,thepublicandsciencecommunity,andforestplaysanimportantroleinmitigatingclimatechange.ThepapermadeacomprehensiveanalysisregardingthepolicyselectionsofChinatopromoteforestryresponsetotheglobalclimatechange,andelaboratedtheconcreteactionsandachievementsinthisregard.Policyselectionsinclude:1)Reinforcetreeplantingandafforestation,increasetheforestedareaandenhancethecapacityofcarbonsequestration...

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  • 简介:Inthispaper,wepresentanovelregion-basedactivecontourmodelbasedonglobalin-tensityfittingenergyinavariationallevelsetframework.Meanwhile,aninternalenergytermisin-troduced,anditforcesthelevelsetfunctiontobeclosetoasigneddistancefunction.Imageglobalinformationutilizedefficientlymakestheproposedmodelinsensitivetonoise,andtheintroducedpenaltytermcanavoidthecostlyre-initializationfortheevolvinglevelsetfunction,whichnotonlyspeedsupthecontourevolvement,butalsoimprovesaccuracyofthefinalcontour.Comparisonswithotherclassicalregion-basedmodels,suchasChan-VesemodelandRegion-ScalableFitting(RSF)model,showtheadvantagesofourmodelintermsofefficiencyandaccuracy.Moreover,themodelisrobusttonoise.

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