简介：2018年4月13日,中共中央总书记、国家主席习近平在庆祝海南建省办经济特区30周年大会上宣布,在全岛建立自由贸易试验区,分步骤、分阶段建立自由贸易港。这意味着自由贸易港将迎来物流、商流、信息流、资金流、人才流的自由高效流动,全球供应链巨头也必然将跨国企业的经营触角伸到这块新大陆,国内物流企业将面临空前的竞争压力。

简介：随着全球气候变暖,北极西北航道的通航日益具有可行性。但我国在使用西北航道时,面临着加拿大严格管理措施的挑战。我国需妥善处理加拿大对西北航道的海洋主张,在＂一带一路＂倡议下推进与加拿大在西北航道的合作,以《极地规则》为契机敦促加拿大在西北航道实行更加科学合理的环保规则,维护我国在西北航道的航行自由权。

简介：Acomplianttowerismodeledasapartiallydry,partiallytapered,dampedTimoshenkobeamwiththesuperstructuremodeledasaneccentrictipmass,andanon-classicaldampedboundaryatthebase.Thefoundationismodeledasacombinationofalinearspringandatorsionalspring,alongwithparallellinearandtorsionaldampers(Kelvin-Voigtmodel).Thesuperstructureaddstothekineticenergyofthesystemwithoutaffectingthepotentialenergy,therebyreducingthenaturalfrequencies.Theweightofthesuperstructureactsasanaxialcompressiveloadonthebeam,reducingitsnaturalfrequenciesfurther.Theemptyspacefactorduetothetruss-typestructureofthetowerisincluded.Theeffectofsheardeformationandrotaryinertiaareincludedinthevibrationanalysis;withthenon-uniformbeammode-shapesbeingaweightedsumoftheuniformbeammode-shapessatisfyingtheendcondition.TheweightsareevaluatedbytheRayleigh-Ritz(RR)method,andverifiedusingfiniteelementmethod(FEM).Theweightofthesuperstructureactsasanaxialcompressiveloadonthebeam.Kelvin-Voigtmodelofstructuraldampingisincluded.Apartofthestructurebeingunderwater,thevirtualaddedinertiaisincludedtocalculatethewetnaturalfrequencies.Aparametricstudyisdoneforvariousmagnitudesoftipmassandvariouslevelsofsubmergence.ThecomputationalefficiencyandaccuracyoftheRayleigh-Ritzmethod,ascomparedtotheFEA,hasbeendemonstrated.Theadvantageofusingclosed-formtrialfunctionsisclearlyseenintheefficacyofcalculatingthevariousenergycomponentsintheRRmethod.