简介:针对沉垫自升式平台在下放过程中四角系有锚链且处于漂浮状态,在风、浪、流的作用下会产生六个自由度的运动响应,若响应过大,会影响平台的正常安装甚至危及平台安全。采用三维势流理论和Morison公式,运用大型水动力计算分析软件SESAM,分别在频域和时域范围内对平台就位过程的运动响应进行了分析,并通过锚链的张力时历曲线对锚链的强度进行校核。结果表明,波浪的入射角和周期对平台运动有很大的影响,且纵摇和横摇对波浪的入射方向更加敏感,时域范围内考虑平台和锚链耦合作用影响下平台的运动响应和频域范围内短期预报的最大值相差不多,平台在此工况下具有良好的运动性能,在频域和时域范围内平台的运动均满足施工要求,锚链受到的张力符合强度要求。
简介:Inordertominimizetheharmcausedbytheinstabilityofaplaningcraft,amotionpredictionmodelisessential.ThispaperanalyzedthefeasibilityofusinganMGM(1,N)modelingreysystemtheorytopredictplaningcraftmotionandcarriedoutthenumericalsimulationexperiment.Accordingtothecharacteristicsofplaningcraftmotion,arecurrenceformulawasproposedoftheparametermatrixofanMGM(1,N)model.Usingthisformula,datacanbeupdatedinreal-timewithoutincreasingcomputationalcomplexitysignificantly.TheresultsofnumericalsimulationshowthatusinganMGM(1,N)modeltopredictplaningmotionisfeasibleandusefulforprediction.Sothemethodproposedinthisstudycanreflecttheplaningcraftmotionmechanismsuccessfully,andhasrationalandeffectivefunctionsofforecastingandanalyzingtrends.
简介:Stronghydrodynamicinteractionsduringtheside-by-sideoffloadingoperationbetweenfloatingliquefiednaturalgas(FLNG)andliquefiednaturalgascarrier(LNGC)caninducehighrisksofcollision.Theweathervaneeffectofasingle-pointmooringsystemnormallyresultsinthesatisfactoryhydrodynamicperformanceoftheside-by-sideconfigurationinheadseas.Nevertheless,thechangesinwavedirectionsinrealseaconditionscansignificantlyinfluencetherelativemotions.Thisarticlestudiestherelativemotionsoftheside-by-sidesystembyusingthetheoreticalanalysismethodandthenumericalcalculationmethod.Basedonthethree-dimensionalpotentialtheorymodifiedbyartificialdamping-lidmethod,thefrequency-domainhydrodynamiccoefficientscanbeimprovedtocalculatetheretardationfunctionsforthemulti-bodyproblem.Anin-housecodeisthendevelopedtoperformthetime-domainsimulationoftwovessels,throughwhichtherelativemotionsaresubsequentlyobtained.Arangeofobliquewavesarechosenfortheextensivecalculationofrelativemotionsbetweenthetwovessels,whicharefurtheranalyzedintermsofthephaseshiftofmotionresponsesinducedbyspecificresonantwavepatterns.Investigationresultsshowthatwavedirectionshaveasignificantinfluenceontherelativesway,roll,andyawmotions.Underthecircumstancethattheabsolutephaseshiftbetweentherollmotionsoftwovesselsapproaches180°,strongerrelativemotionsareinducedwhenLNGCisontheweatherside.Moreover,thegapwaterresonancesathighfrequenciestendtocausethedangerousopposedoscillationoftwovesselsintheswayandyawmodes,whereasFLNGreducesthegapwaterresonancesandrelativemotionswhenlocatedontheweatherside.
简介:分析了几种数字梳状滤波器在进行视频信号的亮、色分离时的优、缺点。针对现有的1D、2D数字梳状滤波器的局限性,通过引入图像前后场内容的相关性,实现了基于图像内容的BD运动自适应数字梳状滤波器的算法。通过与实际图像比对,证明了采用这种处理方法的滤波器能够达到非常好的亮、色分离效果。
简介:由本刊策划并组织的“纪念中国摩托车运动50周年万里行签名活动”.自4月25日启动以来,得到了广大车迷和读者的热情支持和积极参与。随着本次活动的不断推进.越来越多的车迷开始关注越野摩托车运动、关注中国摩托车运动。5月21日.“嘉陵杯”全国越野摩托车锦标赛第二站(浙江站)比赛.在著名的横店影视城赛车场拉开战幕。本次“万里行签名”活动也由北京一路南行来到了浙江横店。