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274 个结果
  • 简介:InthispaperthemeteorologicalbackgroundfortheformationofplumefromtheforestfireinNortheastChinaon7—8May1987isstated.Thelong-rangeinstantaneousdiffusionparametersarecalculatedbyusingthesatellitephotographoftheplumeswithvisiblelengthrangingfrom100toover500kin.Theresultsofcal-culationshowthattherelationsbetweeninstantaneousdiffusionparameterandtraveltime(upto60000sec.)obeythelawoflinearor3/2power.Inaddition,heatreleasefromthefireonMay7—8estimatedbypuffrisingformulacanmeet,inrespecttotheorderofmagnitude,thevaluegainedonthefieldsurvey.

  • 标签: FIRE PHOTOGRAPH VISIBLE instantaneous METEOROLOGICAL stated
  • 简介:这研究是为冷却高温度汽轮机翼和片的先进调查。在片的表面附近交换的有效的热可以被强迫从在结构的高力量金属上被粘贴的多孔的金属的薄层射出的冷却空气流动完成。内容通过多孔的材料,具体建模和模型,的分析的层在热转移的计算模型上包括考虑为二层的多孔的材料和热转移的关键参数的数字调查通过模型隧道的液体流动。结果表明构造系统是合理的。为多孔的材料热转移效率建议了一个评估公式。

  • 标签: 高热负荷 多孔多层冷却系统 涡轮机叶片 传热 参数
  • 简介:Inthispaper,wehaveinvestigatedtheproblemoftheconvergencerateofthemultipleintegralwheref∈Cn+1([0,T]n)isagivenfunction,πisapartitionoftheinterval[0,T]and{BtHi,π}isafamilyofinterpolationapproximationoffractionalBrownianmotionBtHwithHurstparameterH<1/2.ThelimitprocessisthemultipleStratonovichintegralofthefunctionf.Inviewofknownresults,theconvergencerateisdifferentfordifferentmultiplicityn.Undersomemildconditions,weobtainthattheuniformconvergencerateis2Hinthemeansquaresense,whereisthenormofthepartitiongeneratingtheapproximations.

  • 标签: HURST参数 分数布朗运动 收敛速度 积分函数 CH型 BTH
  • 简介:3-degree-of-freedom(3-DOF)的一个新分析模型旋转罗盘加速表系统由一个1-DOF驱动器和2-DOF感觉模式组成被介绍。模型构造微分方程由向量分析与系统的每DOF联系了的lumped。因此建立的联合微分方程是为他们在时间和频率领域的回答的解决的经分解。就这些频率反应方程而言,新奇设备设计概念被强迫感觉阶段到零导出,它导致在结构的频率之间的某个关系,从而在系统的表演上引起抑制效果的最小化。而且,现在的旋转罗盘加速表结构的可行性在他们的事件为旋转罗盘行动和线性加速的察觉用一个唯一的差别对待的计划被学习。这个计划把旋转罗盘加速表的提出的解决的短暂解决方案与同步解调和过滤的进程相结合,它导致同相并且系统输出的照部件发信号。这二个部件能在尖运动和线性加速的察觉被利用。获得的分析结果被模拟在MATLAB/Simulink环境验证,并且结果在对对方的优秀同意,这被发现。

  • 标签: 陀螺加速度计 三自由度 解析模型 行为模拟 MEMS 集总参数
  • 简介:Thisarticleprovestheexistenceanduniquenessofsolutiontotwo-parameterstochasticVolterraequationwithnon-LipschitzcoefficientsanddrivenbyBrowniansheet,wherethemaintoolisBihari'sinequalityintheplane.Moreover,wealsodiscussthetimeregularitypropertyofthesolutionbyKolmogorov'scontinuitycriterion.

  • 标签: VOLTERRA方程 LIPSCHITZ系数 随机 双参数 正解 柯尔莫哥洛夫
  • 简介:Ananalysisisperformedtostudytransientfreeconvectiveboundarylayerflowofacouplestressfluidoveraverticalcylinder,intheabsenceofbodycouples.Thesolutionofthetime-dependentnon-linearandcoupledgoverningequationsiscarriedoutwiththeaidofanunconditionallystableCrank–Nicolsontypeofnumericalscheme.Numericalresultsforthesteady-statevelocity,temperatureaswellasthetimehistoriesoftheskin-frictioncoefcientandNusseltnumberarepresentedgraphicallyanddiscussed.Itisseenthatforallflowvariablesasthecouplestresscontrolparameter,Co,isamplified,thetimerequiredforreachingthetemporalmaximumincreasesbutthesteady-statedecreases.

  • 标签: 直圆柱 自然对流 普朗特数 应力参数 瞬态 时间变化
  • 简介:A3DfiniteelementmodelfortheTaizhouYangtzeRiverBridge,thefirsttriple-towerlong-spansuspensionbridgeinChina,isestablishedbasedonthenonlinearfiniteelementsoftwareABAQUS,andthedynamiccharacteristicsofthebridgeareanalyzedusingtheLANCZOSeigenvaluesolutionmethod.Thestudyfocusesontheeffectsofthevertical,lateralandtorsionalstiffnessofthesteelboxgirder,therigidcentralbuckleandtheelasticrestraintsconnectingthetowersandthesteelboxgirderonthedynamiccharacteristicsofthetriple-towersuspensionbridge.Ourresultsshowthat,ingeneral,thedynamiccharacteristicsofthetriple-towersuspensionbridgearesimilartothoseoftwo-towersuspensionbridges.Thevertical,lateralandtorsionalstiffnessofthesteelboxgirderhavedifferenteffectsonthedynamiccharacteristicsoftriple-towersuspensionbridges.Theelasticre-straintshaveamoresignificanteffectonthedynamiccharacteristicsthanthecentralbuckle,anddecreasingthestiffnessoftheelasticrestraintsresultsintheappearanceofalongitudinalfloatingvibrationmodeofthebridge.Also,rigidcentralbuckleshaveagreaterinfluenceonthedynamiccharacteristicsoftriple-towersuspensionbridgesthanonthoseoftwo-towersuspensionbridges.Theresultsobtainedcouldserveasavaluablenumericalreferenceforanalyzinganddesigningsuper-long-spantriple-towersuspensionbridges.

  • 标签:
  • 简介:Westudytheleastsquaresestimationofdriftparametersforaclassofstochasticdifferentialequationsdrivenbysmallα-stablenoises,observedatnregularlyspacedtimepointsti=i/n,i=1,···,non[0,1].Undersomeregularityconditions,weobtaintheconsistencyandtherateofconvergenceoftheleastsquaresestimator(LSE)whenasmalldispersionparameterε→0andn→∞simultaneously.TheasymptoticdistributionoftheLSEinoursettingisshowntobestable,whichiscompletelydifferentfromtheclassicalcaseswhereasymptoticdistributionsarenormal.

  • 标签: 随机微分方程 驱动方程 稳态噪声 参数估计 离散性 最小二乘估计
  • 简介:AbstractBackground:Male sex workers are at high-risk for acquisition of sexually transmitted infections (STIs), including human immunodeficiency virus (HIV). We quantified incidence rates of STIs and identified their time-varying predictors among male sex workers in Mexico City.Methods:From January 2012 to May 2014, male sex workers recruited from the largest HIV clinic and community sites in Mexico City were tested for chlamydia, gonorrhea, syphilis, hepatitis, and HIV at baseline, 6-months, and 12-months. Incidence rates with 95% bootstrapped confidence limits were calculated. We examined potential time-varying predictors using generalized estimating equations for a population averaged model.Results:Among 227 male sex workers, median age was 24 and baseline HIV prevalence was 32%. Incidence rates (per 100 person-years) were as follows: HIV [5.23; 95% confidence interval (CI): 2.15-10.31], chlamydia (5.15; 95% CI: 2.58-9.34), gonorrhea (3.93; 95% CI: 1.88-7.83), syphilis (13.04; 95% CI: 8.24-19.94), hepatitis B (2.11; 95% CI: 0.53-4.89), hepatitis C (0.95; 95% CI: 0.00-3.16), any STI except HIV (30.99; 95% CI: 21.73-40.26), and any STI including HIV (50.08; 95% CI: 37.60-62.55). In the multivariable-adjusted model, incident STI (excluding HIV) were lower among those who reported consistently using condoms during anal and vaginal intercourse (odds ratio= 0.03, 95% CI: 0.00-0.68) compared to those who reported inconsistently using condoms during anal and vaginal intercourse.Conclusions:Incidence of STIs is high among male sex workers in Mexico City. Consistent condom use is an important protective factor for STIs, and should be an important component of interventions to prevent incident infections.

  • 标签: Male sex worker Men who have sex with men HIV Sexually transmitted infection Transmission Risk factor Mexico
  • 简介:Theproblemoftherobustfaultdetectionfilterdesignfortime-varyingdelaysswitchedsystemsisconsideredintheframeworkofmixedH_-/H_∞.Firstly,theweightedH_∞performanceindexisutilizedastherobustnessperformance,andtheH_-indexisusedasthesensitivityperformanceforobtainingtherobustfaultdetectionfilter.ThenanovelmultipleLyapunov-Krasovskiifunctionisproposedforderivingsufficientexistenceconditionsoftherobustfaultdetectionfilterbasedontheaveragedwelltimetechnique.Byintroducingslackmatrixvariable,thecouplingbetweentheLyapunovmatrixandsystemmatrixisremoved,andtheconservatismofresultsisreduced.Basedontherobustfaultdetectionfilter,residualisgeneratedandevaluatedfordetectingfaults.Inaddition,theresultsofthispaperaredependentontimedelays,andrepresentedintheformoflinearmatrixinequalities.Finally,thesimulationexampleverifiestheeffectivenessoftheproposedmethod.

  • 标签: 故障检测滤波器 切换系统 时变时滞 滤波器设计 线性矩阵不等式 LYAPUNOV
  • 简介:这份报纸处理一二维(2D)为厚板有热采购的transverselyisotropic和身体的问题强迫。板的上面的表面是与规定表面温度免费的应力,当板的更低的表面在一个僵硬基础上休息时并且热地被绝缘。学习在格林和Naghdi建议的概括thermoelasticity的上下文被执行。为排水量和温度领域的管理方程被使用Laplace和Fourier变换在Laplace-Fourier变换领域获得。双变换的倒置数字地被做。Laplace变换的数字倒置基于Fourier系列扩大被做。数字计算为镁(Mg)被执行,并且结果图形地被介绍。各向同性的材料(Cu)的结果数字地被获得并且图形地介绍了与横着各向同性的材料(Mg)的那些相比。身体力量的效果也被学习。

  • 标签: 横观各向同性材料 动态响应 体力 厚板 热源 二维
  • 简介:二种反复的方法被设计解决方程的线性系统,我们以一个几何概念获得新解释。因此,我们有更好的卓见进反复的方法的本质并且为进一步的学习和设计提供一本参考书。最后,一个新反复的方法被设计作为特别地,表明几何特征的SOR方法的多样的松驰参数说出。许多例子证明方法是相当有效的。

  • 标签: SOR方法 迭代方法 线性系统 参数方程 几何解释 松弛
  • 简介:在这篇论文,为orthotropic板的飞机裂缝问题的压力紧张因素的评估相等参数用一个分数维的二水平的有限元素方法(F2LFEM)被调查。一个orthotropic裂缝问题的一般答案被与各向同性的裂缝问题吸收这个问题获得,并且在F2LFEM作为全球插值功能被采用。在裂缝板的裂缝尖端的邻居,分数维的几何学概念被介绍完成有类似比率的类似的网孔不到一个并且产生一个无穷小的网孔以便在二邻近的层的僵硬矩阵之间的关系是相等的。在裂缝尖端附近的自由的很多度被转变到概括坐标的一个小集合。数字例子证明这个方法在评估压力紧张因素(SIF)有效、精确。

  • 标签: 平面裂缝 分形有限元 应力密度因子 固体力学
  • 简介:Thecalculationofsettlingspeedofcoarseparticlesisfirstlyaddressed,withacceleratedStokesiandynamicswithoutadjustableparameters,inwhichfarfieldforceactingontheparticleinsteadofparticlevelocityischosenasdependentvariablestoconsiderinter-particlehydrodynamicinteractions.Thesedimentationofasimplecubicarrayofsphericalparticlesissimulatedandcomparedtotheresultsavailabletoverifyandvalidatethenumericalcodeandcomputationalscheme.TheimprovedmethodkeepsthesamecomputationalcostoftheorderO(NlogN)asusualacceleratedStokesiandynamicsdoes.Then,morerealisticrandomsuspensionsedimentationisinvestigatedwiththehelpofMontCarlomethod.Thecomputationalresultsagreewellwithexperimentalfitting.Finally,thesedimentationoffinercohesiveparticle,whichisoftenobservedinestuaryenvironment,ispresentedasafurtherapplicationincoastalengineering.

  • 标签: 速度计算 可调参数 粗颗粒 加速 多尺度 粒子沉积
  • 简介:不可思议地使不安的传送对流散开方程的Acoupled系统被考虑。每个方程的领先的条款被一个小积极参数乘,但是这些参数可以有不同大小。系统的答案有重叠并且交往的边界层。这些层的结构被分析,并且这导致是平常的Shishkin网孔的变体的一个piecewise制服网孔的构造。在一个迎风的差别计划被证明几乎一阶精确的这个网孔上,一致地在两个小参数。我们在场数字实验到的结果证实我们的理论结果。

  • 标签: 对流扩散方程 扰动理论 分析解 SHISHKIN网格 逆向有限微分
  • 简介:Thispaperpresentstheresultsofaluminumsurfacetreatmentbydiffusecoplanarsurfacebarrierdischarge.Thegoalsaretostudytheeffectivenessoftheplasmatreatmentandthedependenceofitsefficiencyonoperationparameters,suchassample-to-electrodedistance,treatmenttimeorgasatmosphere.Threetypesofaluminummaterials(bricks,sheetsandthinfilms)weretestedtoensurethereliabilityofthetreatment.Thechangesinthesurfacepropertieswerecharacterizedbythesurfacefreeenergy,atomicforcemicroscopy,attenuatedtotalreflectanceFouriertransforminfraredspectroscopy(ATRFTIR)andX-rayphotoelectronspec-troscopy(XPS).Theinfluenceofagingeffectonthetreatmentwasalsomeasuredanddiscussed.

  • 标签: 等离子体处理 表面处理 操作参数 铝材料 参数优化 放电