简介:D·B·库珀是世界航空史上大名鼎鼎的传奇人物,而他这个知名度的得来并不是因为他对航空科技做出过什么贡献,更不是因为他有多么高超的飞行技艺,而是因为他制造了航空史上第一个劫机案.同时,该案也是唯一至今未破的劫机案。劫机案已经过去四十多年。作为劫机犯,库珀本来应该是臭名昭著的。但是在时间的发酵下。公众对他最初的痛恨早已烟消云散。而他在劫机过程中,从精心策划到顺利实施,再到成功逃脱。反倒使他拥有了无数粉丝。四十多年中。数以千计的人声称自己就是库珀,但是经联邦调查局一一确认,没有一个人是真正的库珀,这更增加了库珀的神秘性和公众的热情。
简介:Athree-dimensionalrigidbodyontheshapeofaparallelepipedismodelledinordertorockonasideoravertexofthebase,inordertoevaluatetheseismicresponseofrigidblockslyingonahorizontalsupport.Thecenterofmassofthebodyisconsideredaseccentricwithrespecttoitsgeometriccenter.Asseismicinput,threeItalianrecordedaccelerograms,withdifferentspectralcontent,areused.Thestudyismainlyconductedtohighlightthedifferencesbetweentheseismicresponseof2Dand3Dmodelsofrigidblocks,withtheaimtounderstandif,insomecases,theuseofthe3Dmodelofrigidblockisrequiredtoobtainsaferresults.Infact,theoutcomesshowthatinsomerangesofthegeometricalandmechanicalparametersthatcharacterizetheexcitationandthebody,atwo-dimensionalmodel,whichisnotabletoconsiderthe3Drockingonavertex,canprovideunsaferesults.Inparticular,itisfoundthattheoverturningprocessofthethree-dimensionalblockcanoccurunderexcitationswhicharelowerthanthosewhichoverturnacorrespondingtwo-dimensionalblock.
简介:祸福的降临真的是没有一点儿预兆?不需要理由?也不讲究时间吗?秋天到来的时候,我的心情就像一个瘪蔫的气球重又被吹得圆满起来。我在等待着那种重复过数次的喜悦的到来。蜷缩在壁脚的大黄狗突然站起来,龇牙咧嘴地从我背后跑过去,对着山湾里的下坡路狂叫起来,以为又是陌生人进村。
简介:Thehumanvisionsystemcanreconstructa3Dobjecteasilyfromsingle2Dlinedrawingsevenifthehiddenlinesoftheobjectareinvisible.Now,therearemanymethodshaveemulatedthisability,butwhenthehiddenlinesoftheobjectareinvisible,thesemethodscannotreconstructacomplete3Dobject.Therefore,weputforwardanewalgorithmtosettlethishardproblem.Ourapproachconsistsoftwosteps:(1)infertheinvisibleverticesandedgestocompletethelinedrawing,(2)proposeavertex-basedoptimizationmethodtoreconstructa3Dobject.