简介:Inconsideringthetheoryofstructuraldynamicoptimizationdesign,adesignmethodofthestructuralstyleofshipcompositebracewithrigidvibrationisolationmasswasstudied.Twokindsofstructuraldynamicoptimizationformulationsminimizingthevibrationaccelerationofthenon-pressurehullontherestrainingconditionofthegrossweightoftheshipcabinwereestablished:1)dynamicoptimizationofthesectionaldimensionsoftherigidvibrationisolationmassinthecompositebrace;2)dynamicoptimizationofthearrangingpositionoftherigidvibrationisolationmass.Throughtheoptimizationresults,sectionaldimensionsandthearrangingpositionoftherigidvibrationisolationmasswithbetterperformanceinreducingvibrationweregained,andsomereferencewasprovidedforpracticalengineeringdesignsaswellasenrichmentofthedesignmethodofanovelshipvibration-isolationbrace.
简介:Basedontheprincipleofimpedancemismatching,theperformanceofrigidvibrationisolationmassinimpedingvibrationwavepropagationwasdiscussedfromtheperspectiveofwaveapproach.BasedonFEM,theinfluenceofitsweightaswellasthecross-sectionshapeparametersontheisolationperformanceofrigidvibrationisolationmasswasstudiedthroughnumericalsimulation.Theresultsshowthatrigidvibrationisolationmasscaneffectivelyimpedethepropagationofthemediumandhighfrequencyvibrationwaves,andtheheavierthevibrationisolationmass,thebettertheisolationperformance.Forlowfrequencywaves,thevibrationisolationeffectisnotsoobvious;forarectangularvibrationisolationmass,theisolationperformancecouldbeeffectivelyimprovedbyincreasingthecross-sectionheightandreducingthecross-sectionwidth.Ausefulreferencewasprovidedfortheapplicationofrigidvibrationisolationmassestothevibrationisolationandnoisereductionofshipstructure.
简介:Rigidblockingmassesarelocatedinthetypicalbasestructureofapowercabinbasedontheimpedancemismatchprinciple.Bycombiningtheacoustic-structuralcouplingmethodandstatisticalenergyanalysis,thefull-bandvibrationandsoundradiationreductioneffectofvibrationisolationmasseslocatedinabasestructurewasresearched.Theinfluenceoftheblockingmass’cross-sectionsizeandshapeparametersandthelayoutlocationofthebaseisolationperformancewasdiscussed.Furthermore,theeffectivenessofrigidvibrationisolationdesignofthebasestructurewasvalidated.Theresultsshowthatthemediumandhighfrequencyvibrationandsoundradiationofapowercabinareeffectivelyreducedbyablockingmass.Concerningweightincrementandsectionrequirement,suitablyincreasingtheblockingmasssizeandsectionheightandreducingsectionwidthcanresultinanefficiency-costratio.
简介:税收是共和国的血脉,然而税法在社会上刚性不足,致使许多企业存在欠税问题,并且相当一部分人借改制之机逃避税收管理,使许多经营者偷税严重,甚至以逃税为荣,也使得一些政府部门习惯于随意干预税收执法,近年来,涉税案件有增无减也与此不无关系。追其根源是因为:没有税收基本法。现有的税收法规层次低,许多由国务院制定颁布的税收行政性法规,其效力低于税收法律,缺乏应有的权威性,规范性和稳定性,另外,现行税制存在着不足之处,有避税的黑洞、重复征税的弊端等。没有强有力的司法保卫体系,导致很多税收违法行为得不到及时制裁。经济活动日益频繁,涉税案件逐年增加,但移送司法机关处置较少,有的即使移送处置,但对于偷税案件的取证
简介:<正>一、原始主义是一股世界性文化思潮。它是以推崇原始状态下的本真、批判文明带来的痼疾为其特征的。在现代社会,人们普遍信仰进化论的社会观,认为历史是沿着直线发展的。从原始的采集——狩猎社会到农业社会再到工业社会,每一个历史阶段的跨越都意味着一次进步。在这种世界观的支配下,“原始”不啻是“野蛮”与“愚昧”的同义语。然而,原始主义却从截然不同的思路进行文化反省,力图证明人类在得到的同时也失去了什么,每一次进步的同时也隐伏着某种更大的危险。因此,原始阶段并非一片混沌与黑暗,相反,返朴归真倒是补救现代文明种种缺陷的药方。早在十八世纪,法国的启蒙思想家卢梭在其名著《论人类不平等的起源和基础》里,