简介:Green-Naghdi(G-N)theoryisafullynonlineartheoryforwaterwaves.SomeresearcherscallitafullynonlinearBoussinesqmodel.DifferentdegreesofcomplexityofG-Ntheoryaredistinguishedby"levels"wherethehigherthelevel,themorecomplicatedandpresumablymoreaccuratethetheoryis.IntheresearchpresentedhereacomparisonwasmadebetweentwodifferentlevelsofG-Ntheory,specificallylevelIIandlevelIIIG-Nrestrictedtheories.AlinearanalyticalsolutionforlevelIIIG-Nrestrictedtheorywasgiven.WavesonaplanarbeachandshoalingwaveswerebothsimulatedwiththesetwoG-Ntheories.ItwasshownforthefirsttimethatlevelIIIG-Nrestrictedtheorycanalsobeusedtopredictfluidvelocityinshallowwater.AlevelIIIG-NrestrictedtheoryisrecommendedinsteadofalevelIIG-Nrestrictedtheorywhensimulatingfullynonlinearshallowwaterwaves.
简介:根据IMF的最新预测,发达经济体2018和2019年的经济增速为2.3%和2.2%,2018年的增速预测比之前上调了0.3个百分点,2019年上调了0.4个百分点。这是2010年1月以来最大幅度的持续上调。波罗的海国际航运公会(BIMCO)首席分析师PeterSand表示,如果这一预测实现,将十分利好集运业,因为发达经济体的增长将带来更高的“贸易˙GDP乘数”(=贸易增速/GDP增速)。PeterSand指出,各国抓住全球经济增长这一“窗口期”带来的机会,开展关键领域改革就显得尤为重要。因为从长期看,全球经济将只能实现温和增