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1、Chapter3Chapter3::FractalFractal1.FractalPhenomena2.FractalDimension3.FractalTimeSeriesAnalysisDefiningChaoticMotionChaoticmotionis:1.Irregular,notperiodic:requiresinfiniteinformationtofollowoneparticle’strajectory2.Exquisitely(敏銳地)sensitivetoinitialconditions:twonea
2、rbytrajectoriesdivergeexponentiallyfast(atraitfoundonlyinnon-linearsystems)3.Fractalinnature:self-similaratallmagnifications11-1.FractalPhenomena1-1.FractalPhenomena美籍法國數(shù)學(xué)家MandelbrotB.B(1924-)。1952年獲巴黎大學(xué)博士學(xué)位后,先后“闖入”過物理學(xué)、經(jīng)濟(jì)學(xué)、生理學(xué)、語言學(xué)和其它一些似乎毫不相關(guān)的學(xué)科(IntellectualWanderer)
3、.1982年《大自然的分形幾何學(xué)》為成名作??茖W(xué)貢獻(xiàn):①.發(fā)現(xiàn)Levy穩(wěn)定分布的重要性并應(yīng)用于經(jīng)濟(jì)學(xué)、布朗運(yùn)動(dòng)、星系分布等領(lǐng)域;②.用自相似觀點(diǎn)研噪聲與湍流的陣發(fā)過程;③.在前人基礎(chǔ)上擴(kuò)展了維數(shù)概念及提出分形概念,并使各領(lǐng)域科學(xué)家廣泛理解;④.重新發(fā)現(xiàn)M集合,推動(dòng)復(fù)迭代復(fù)興及計(jì)算機(jī)圖形學(xué)發(fā)展。HowlongiscoastofBritain?(Mandelbrot:Scinece,Vol.156,1967,pp636-638)2ConstructionoftheKochcurve(KochHelgeVon,1904,瑞典數(shù)學(xué)家)?
4、無特征尺度(長度及面積);?永遠(yuǎn)看不清的“精細(xì)結(jié)構(gòu)”,傳統(tǒng)幾何學(xué)很難研究(妖魔曲線);?具有自相似性。?局部幾何性質(zhì)很難描述,處處連續(xù)但不可微;3Self-SimilaritySierpinskistriangle(1915-1916年俄國Sierpinski構(gòu)造出“病態(tài)”圖形)AselfsimilarobjectsrepeatingitselfoverallscalesofmagnificationIteration1Iteration2Iteration…4?x"=?(y+z)??y"=x+ay??z"=b+xz?cz5Th
5、eLorenzAttractorasViewedfromEightDifferentAnglesAgeometricfigureofthissortwithaninfinitelevelofdetailiscalledafractal.Chaosalwaysresultsintheformationofafractal,butnotallfractalsareassociatedwithchaos.河流三角洲波濤洶涌雪域高原電閃雷鳴6山巒疊嶂枝條繁密Butwhataboutthesefamiliarthingsfromthena
6、turalworld?CantheybeeasilydescribedwithEuclideanshapes?ChaosandFractalsinChemistryBeluzov-ZhabotinskireactionWavesrepresentingtheconcentrationofacertainchemical(s).Thesecanassumemanypatternsandcanalsobechaotic7顆粒分布腎的動(dòng)靜脈Weierstrass函數(shù)(1872)n=+∞n(1cos?bt)wt()=∑(2?Dn)n=?
7、∞b處處連續(xù)處處不可微函數(shù)2?Dwbt()=bwt()自相似結(jié)構(gòu)8FractalfunctionsD=1.2Wierstrassfunctionisscale-invariant+∞n(1?cosbt)Ct()Re()==Wt∑(2?Dn)n=?∞bD=1.5D=1.8Mandelbrothasstated:“Cloudsarenotspheres,mountainsarenotcones,coastlinesarenotcircles,andbarkisnotsmooth,nordoeslightingtravelinastr
8、aightline”Therangeofnaturalphenomenaencompssedbyself-similarityisastonishing.Besidesmountains,cloudsandtrees,therearenumerousothers